JP4996196B2 - THERMISTOR ELEMENT, TEMPERATURE SENSOR USING SAME, AND METHOD FOR PRODUCING THERMISTOR ELEMENT - Google Patents

Description

  The present invention relates to a thermistor element whose resistance value changes with a temperature change, a temperature sensor using the thermistor element, and a thermistor element manufacturing method.

Conventionally, an NTC thermistor element that conducts temperature measurement using a conductive oxide sintered body (metal oxide ceramic) that has electrical conductivity and whose resistance value (specific resistance) varies with temperature. Temperature sensors using elements are known (Patent Documents 1 and 2).
One of the uses of such a temperature sensor is to attach to an exhaust pipe or a catalyst device of an automobile or the like and measure the temperature of exhaust gas or catalyst.
Moreover, as a form example of the thermistor element, for example, as shown in FIG. 2 of Patent Document 1, there is one in which a part of two conductive wires are inserted in parallel to each other in the thermistor element body.

JP 2006-30025 A JP 2000-88673 A

  A temperature sensor (thermistor element) for such applications may be required to be able to measure temperature in a very wide temperature range from a low temperature range of −40 ° C. to a high temperature range of 900 ° C. By the way, the NTC type thermistor element has a high resistance value when the temperature is low, and the resistance value decreases as the temperature rises.

However, when the resistance value of the thermistor element is too high or too low, it is difficult to appropriately measure the resistance value with a simple circuit. For example, when a linearize circuit (resistance voltage dividing circuit) or the like often used for temperature measurement using a thermistor element is used, the resistance value of the thermistor element is roughly in the range of about 20Ω to 700 kΩ in the temperature measurement range. It has turned out to be preferable. More preferably, it has been found that it is generally preferable to be in the range of 50Ω to 500 kΩ.
It has also been found that the B constant of the thermistor element body needs to be about 2000K to 3000K in order to be within such a resistance value range in the temperature range of -40 to 900 ° C.

  However, in order to keep the resistance value of the thermistor element within the above range in the temperature range of −40 to 900 ° C., not only the value of the B constant of the thermistor element body but also other elements such as dimensions of each part. In order to manufacture a thermistor element having appropriate characteristics, further studies have been required.

Then, when the inventors further investigated, the thermistor element comprising a conductive oxide sintered body having a B constant of B (−40 to 900) = 2.00 × 10 ^{3 to} 3.00 × 10 ³ K Among the thermistor elements using the main body, a first electrode line having a first electrode portion having a circular cross section and extending linearly through the thermistor element main body, and a second electrode line paired with the first electrode line And a thermistor element including a second electrode line having a second electrode part having a circular cross section and extending in a straight line and penetrating the thermistor body in parallel to the electrode part. The thickness t in the direction perpendicular to the imaginary plane perpendicular to the imaginary plane connecting the first electrode section and the second electrode section passing through the imaginary midpoint between the first electrode section and the second electrode section of the main body is t = 0.50 to 1.2 mm, and the diameter φ of the first electrode portion and the second electrode portion is φ = 0. In the range of 25 to 0.40 mm, the length of the first electrode portion and the second electrode portion is L (mm), and the distance between the electrodes between the first electrode portion and the second electrode portion is D (mm). ), The resistance value of the thermistor element is proportional to the electrode dimension ratio D / L, and it has been found that the resistance value increases as the electrode dimension ratio D / L increases.

Furthermore, the influence of the diameter φ on the resistance value, the influence of the thickness t on the resistance value, and the influence of using the first and second electrode portions having a circular cross section have been found.
The present invention has been made based on such knowledge, and thermistor element capable of taking an appropriate resistance value in the temperature range of −40 to 900 ° C., temperature sensor using the thermistor element, and manufacture of the thermistor element. It aims to provide a method.

The solution includes a thermistor element body made of a conductive oxide sintered body having a B constant of B (-40 to 900) = 2.00 × 10 ^{3 to} 3.00 × 10 ³ K, and the thermistor element body. A first electrode line having a first electrode portion that penetrates and extends linearly and has a circular cross section, and a second electrode line that forms a pair with the first electrode line, wherein the thermistor element body is the first electrode. A second electrode wire having a second electrode portion having a circular cross section, extending in a straight line, extending in a straight line, and having the same diameter and length as the first electrode portion, and the thermistor element body includes: A thickness t in a direction perpendicular to a virtual plane passing through a virtual midpoint between the first electrode portion and the second electrode portion and orthogonal to a virtual plane connecting the first electrode portion and the second electrode portion is t = 0. .500 to 1.20 mm, and the diameter of the first electrode portion and the second electrode portion is φ = 0.250 to 0.4. 00 mm, the length of the first electrode part and the second electrode part is L (mm), the distance between the first electrode part and the second electrode part is D (mm), and the remaining element thickness is A thermistor element in which the electrode dimension ratio D / L is in the range of the following formula (1) when Y (mm) = t−φ / √2.
[(2.00 × 10 ^-2 × 0.410) / (7.00 × 10 ² × exp (B × -3.44 × 10 ^-3 ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)]
≦ D / L ≦
[(7.00 × 10 ² × 0.410) / (2.00 × 10 ⁻² × exp (B × 3.44 × 10 ⁻³ ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)] (1)

In the thermistor element of the present invention, if the electrode dimension ratio D / L of the thermistor element is within the range defined by the equation (1) according to the B constant (= 2000 to 3000 K), the diameter φ, and the thickness t, − The resistance value Rs (−40) between the first electrode line and the second electrode line of the thermistor element at 40 ° C. can be set to Rs (−40) ≦ 7.00 × 10 ² kΩ. Furthermore, the resistance value Rs (900) between the first electrode line and the second electrode line of the thermistor element at 900 ° C. can be set to Rs (900) ≧ 2.00 × 10 ⁻² kΩ. That is, when the temperature is in the range of −40 to 900 ° C., the resistance value Rs between the first electrode line and the second electrode line of the thermistor element is Rs = 2.00 × 10 ^{−2 to} 7.00 × 10 ^2. It can be set to kΩ. Therefore, a constant voltage is applied to a resistance voltage dividing circuit in which a thermistor element and a detection resistor are connected in series, and a simple circuit such as a circuit for measuring a divided voltage value is used, but a range of −40 to 900 ° C. Thus, a thermistor element capable of appropriately detecting the resistance value Rs can be obtained.
Moreover, according to the equation (1), since it is given as a range of the electrode dimension ratio D / L, D is fixed to a convenient value and L is changed, or L is fixed to a convenient value. In addition, the resistance value Rs can be easily adjusted by adjusting D or the like.
The B constant B (−40 to 900) is a B constant obtained from the resistance values at −40 ° C. and 900 ° C.

Here, Formula (1) is demonstrated. In this formula (1), [(2.00 × 10 ⁻² × 0.410) / (7.00 × 10 ² × exp (B × −3.44 × 10 ⁻³ ))] is represented by the term A1, [(7.00 × 10 ² × 0.410 ) / (2.00 × 10 ⁻² × exp (B × 3.44 × 10 ⁻³ ))]. [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)] is the B term, (φ / 0.300) is the C term, and [0.278 / (0.474Y ² -0.919Y + 0.698)] and the D term. The terms B, C and D are common to the left and right terms (upper limit and lower limit terms) of Equation (1).

First, the A1 term will be described.
The resistance-temperature characteristic of the NTC thermistor element, that is, the resistance value Rs at the temperature Ts (K) is approximately given by Rs = R0 · exp [B (1 / Ts−1 / T0)]. Here, the initial resistance value R0 is a resistance value at the initial temperature T0 (K), and B is a B constant (= B (−40 to 900)).
By the way, as described above, a thermistor using a thermistor element body made of a conductive oxide sintered body having a B constant of B (−40 to 900) = 2.00 × 10 ^{3 to} 3.00 × 10 ³ K. Of these, a first electrode line having a first electrode part having a circular cross section and extending linearly through the thermistor element body and a second electrode line paired with the first electrode line, the thermistor element body being Consider a thermistor element comprising a second electrode line that penetrates in parallel with the electrode part and extends linearly and has a second electrode part having a circular cross section. For this thermistor element, at least a virtual plane that passes through a virtual midpoint between the first electrode portion and the second electrode portion of the thermistor element body and is orthogonal to a virtual plane connecting the first electrode portion and the second electrode portion. In the range where the thickness t in the direction perpendicular to the plane is t = 0.50 to 1.2 mm and the diameter φ of the first electrode portion and the second electrode portion is φ = 0.25 to 0.40 mm, When the length of one electrode part and the second electrode part is L (mm) and the distance between the first electrode part and the second electrode part is D (mm), the resistance value Rs of the thermistor element is It has been found that there is a proportional relationship with the electrode dimension ratio D / L.
The reason for this is that the first and second electrode portions pass through the thermistor element main body in parallel with each other, so that when viewed in the direction along the length L, the first and second electrode portions occur between the first and second electrode portions. The state of the electric field is considered to be almost the same in any part. Therefore, if the length L is doubled, the resistance value Rs of the thermistor element is ½, so that the relationship is inversely proportional. On the other hand, if the interelectrode distance D between the first electrode portion and the second electrode portion is doubled, the resistance value Rs of the thermistor element is also doubled. Therefore, it is considered that the resistance value Rs of the thermistor element is directly proportional to the electrode dimension ratio D / L.

Here, a reference thermistor element in which the reference electrode distance Db = 0.410 mm, the reference electrode portion length Lb = 1.00 mm, and the reference electrode dimension ratio Db / Lb = 0.410 is considered. The B constant of the thermistor element is B (−40 to 900) = B.
It is assumed that the initial resistance value R0 (-40) at the initial temperature T0 = 233K (= −40 ° C.) is R0 (−40) = 7.00 × 10 ² (kΩ). When the temperature of this thermistor element is changed to a temperature Ts = 1173K (= 900 ° C.), the resistance value Rs is Rs = 7.00 × 10 ² × exp [B (1 / 1733-1 / 233)] = It is given by 7.00 × 10 ² × exp (B × −3.44 × 10 ⁻³ ). That is, the resistance value Rs at the temperature Ts (= 900 ° C.) of the reference thermistor element having the B constant B and the reference electrode size ratio Db / Lb = 0.410 is given by the above equation.
On the other hand, since the resistance value Rs of the thermistor element is directly proportional to the electrode dimension ratio D / L, Rs = a1 · (Db / Lb), where a1 can be expressed by a proportional coefficient. Further, when the electrode size ratio at which the minimum resistance value 2.00 × 10 ⁻² (kΩ) (= 20.0Ω) allowed for the thermistor element at temperature Ts (= 900 ° C.) is (D / L) min, In this case, the relationship of 2.00 × 10 ⁻² = a1 × (D / L) min is satisfied. Accordingly, the relationship of proportionality coefficient a1 = (D / L) min / 2.00 × 10 ⁻² = (Db / Lb) / (7.00 × 10 ² × exp (B × −3.44 × 10 ⁻³ )) is satisfied. From this, (D / L) min = (2.00 × 10 ⁻² ) × (Db / Lb) / (7.00 × 10 ² × exp (B × −3.44 × 10 ⁻³ )) = (2.00 × 10 ⁻² × 0.410) / (7.00 × 10 ² × exp (B × -3.44 × 10 ⁻³ )). Since this electrode dimension ratio (D / L) min is the smallest allowable value among the electrode dimension ratios D / L, the electrode dimension ratio D / L is D / L ≧ [(2.00 × 10 ^-2 × 0.410) / (7.00 × 10 ² × exp (B × −3.44 × 10 ⁻³ )) is selected.
Thereby, the relationship between A1 term and electrode size ratio D / L was obtained.

Next, the A2 term will be described.
First, it is assumed that the initial resistance value R0 (900) at the initial temperature T0 = 1173K (= 900 ° C.) is R0 (900) = 2.00 × 10 ⁻² (kΩ) contrary to the above A1 term. To do. When the temperature of the thermistor element is changed to a temperature Ts = 233K (= −40 ° C.), the resistance value Rs is Rs = 2.00 × 10 ⁻² × exp [B (1 / 233−1 / 1733) ] = 2.00 × 10 ⁻² × exp (B × 3.44 × 10 ⁻³ ). That is, the resistance value Rs at the temperature Ts (= −40 ° C.) of the reference thermistor element having the reference electrode size ratio Db / Lb = 0.410 is given by the above equation.
On the other hand, since the resistance value Rs of the thermistor element is directly proportional to the electrode dimension ratio D / L as described above, it can be expressed by Rs = a2 · (Db / Lb). Further, assuming that the electrode dimension ratio at which the maximum resistance value allowed for the thermistor element is 7.00 × 10 ² (kΩ) at the temperature Ts (= −40 ° C.) is (D / L) max, in this case also 7.00 The relationship x10 ² = a2 × (D / L) max is satisfied. Therefore, the relationship of proportionality coefficient a2 = (D / L) max / 7.00 × 10 ² = (Db / Lb) / (2.00 × 10 ⁻² × exp (B × −3.44 × 10 ⁻³ )) is satisfied. From this, (D / L) max = (7.00 × 10 ² ) × (Db / Lb) / (2.00 × 10 ⁻² × exp (B × −3.44 × 10 ⁻³ )) = (7.00 × 10 ² × 0.410 ) / (2.00 × 10 ⁻² × exp (B × −3.44 × 10 ⁻³ )). Since this electrode dimension ratio (D / L) max is the largest allowable value among the electrode dimension ratios D / L, the electrode dimension ratio D / L is D / L ≦ [(2.00 × 10 ^{A value of −2} 7.00 × 10 ² × 0.410) / (2.00 × 10 ⁻² × exp (B × −3.44 × 10 ⁻³ )) may be selected.
Thereby, the relationship between A2 term and electrode size ratio D / L was obtained.

Next, the term B will be described.
The thermistor element of the present invention uses a first electrode part and a second electrode part extending in a straight line and having a circular cross section. The diameters of the first electrode portion and the second electrode portion are φ (mm). What contributes to the resistance value Rs between the first electrode part and the second electrode part is not only a part of the first and second electrode parts, which is the closest to each other, forming the interelectrode distance D. Therefore, it is necessary to consider the surface shapes (cylindrical surfaces) of the first electrode portion and the second electrode portion. In this case, the effective distance between the first electrode portion and the second electrode portion that contributes to the resistance value Rs should be larger than the inter-electrode distance D.
Therefore, as shown in FIG. 1, the effective distance Deff between the first electrode portion 2a and the second electrode portion 3a is set to D + (1-1 / √2) × φ / 2 × 2 = D + (1-1 / √2 ) φ.
By the way, in the reference thermistor element, since the reference interelectrode distance Db = 0.410 mm and the reference electrode portion diameter φb = 0.300 mm, the reference effective distance Deffb is Deffb = (0.410+ (1-1 / √). 2) × 0.300) = 0.498
The term B is a correction term for correcting the influence of the effective distance Deff on the thermistor element under consideration with respect to the A1 term or the A2 term on the basis of the effective distance Deffb of the reference. As with the inter-electrode distance D, the effective distance Deff increases (proportional) as the resistance value Rs of the thermistor element increases as the value increases. Therefore, when a value different from the reference effective distance Deffb is employed as the effective distance Deff of the thermistor element, the B term: Deffb / Deff = [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)].

Next, the C term will be described.
As shown in FIG. 1, the first and second electrode portions have the inter-electrode distance of the effective distance Deff described above, and the electrode portions having the width of the effective width Weff are opposed to each other. Can think. The effective width Weff is given by Weff = 2 × 1 / √2 × φ / 2 = φ / √2.
Incidentally, in the reference thermistor element, since the diameter φb of the reference electrode portion is 0.300 mm, the effective width Weffb of the reference is Weffb = 0.300 / √2 = 0.212 mm.
The term C is a correction term for correcting the influence of the effective width Weff on the thermistor element under consideration with respect to the A1 term or the A2 term on the basis of the effective width Weffb of the reference. As the effective width Weff increases, the resistance value Rs of the thermistor element decreases (inversely proportional). Therefore, when a value different from the reference effective width Weffb is adopted as the effective width Weff of the thermistor element, the C term: Weff / Weffb = φ / 0.300 ( = ((Φ / √2) / (0.300 / √2))).

Next, the term D will be described.
As shown in FIG. 2, the electric field lines EF generated between the thermistor element first electrode portion 2a and the second electrode portion 3a have an effective width Weff of the surfaces of the first electrode portion 2a and the second electrode portion 3a. It does not occur only in the range (see FIG. 1), but extends more than that. Specifically, it passes through a virtual midpoint CP between the first electrode portion 2a and the second electrode portion 3a, and is orthogonal to a virtual plane P passing through the center line 2ac of the first electrode portion 2a and the center line 3ac of the second electrode portion 3a. Of the thickness t of the thermistor element main body 1 in the imaginary plane orthogonal direction DR1 (up and down direction in FIG. 2), the portion excluding the effective width Weff (the portions of the thickness t1, t2) also has the electric lines of force EF. Pass through. Therefore, the resistance value Rs of the thermistor element also changes depending on the thicknesses t1 and t2 of these portions. Therefore, the remaining element thickness Y is defined as Y = t1 + t2 = t−Weff = t−φ / √2.
When the reference thermistor element (Db = 0.410 mm, φb = 0.300 mm, Weffb = 0.212 mm) using the thermistor body 1 having a predetermined composition is changed, when the remaining element thickness Y, and hence the thickness t, is changed, Each example of the resistance value Rs obtained at Ts = 350 ° C. is plotted in FIG.
Furthermore, from this result, a quadratic approximate curve formula: Rs = 0.474Y ² −0.919Y + 0.698 was obtained.
Further, the reference resistance value Rsb when the thickness t is the reference thickness tb = 0.950 mm and the reference element remaining thickness Yb is Yb = tb−φb / √2 = 0.950−0.300 / √2 = 0.338 mm. Is obtained from the above equation, Rsb = 0.278 (kΩ).
The term D is a resistance value when the remaining element thickness of the thermistor element under consideration is Y, based on the resistance value Rsb when the reference element remaining thickness Yb is relative to the A1 or A2 term. This is a correction term that corrects the influence of changing values. Therefore, when a value different from the reference element remaining thickness Yb is adopted as the element remaining thickness Y of the thermistor element, the correction of the resistance value by changing the element remaining thickness Y cancels the influence. , A1 term or A2 term is multiplied by D term: [0.278 / (0.474Y ² −0.919Y + 0.698)].

  As described above, the A1 term that gives the lower limit of the electrode dimension ratio D / L and the A2 term that gives the upper limit are respectively multiplied by the B, C, and D terms for correction based on the respective dimensions of the reference thermistor element. In addition, a more appropriate range (lower limit and upper limit) of the electrode dimension ratio D / L can be given by correcting the difference in each dimension.

Other solutions include a thermistor element body made of a conductive oxide sintered body having a B constant of B (−40 to 900) = 2.00 × 10 ^{3 to} 2.50 × 10 ³ K, and the thermistor element body. A first electrode line having a first electrode portion having a circular cross section and extending in a straight line, and a second electrode line paired with the first electrode line, wherein the thermistor element body is the first electrode line. A second electrode line having a second electrode part that penetrates in parallel with the electrode part and extends linearly, has a circular cross section, and has the same diameter and length as the first electrode part. The thickness t in the direction perpendicular to the imaginary plane orthogonal to the imaginary plane connecting the first electrode section and the second electrode section passing through the imaginary midpoint between the first electrode section and the second electrode section is t = The first electrode portion and the second electrode portion have a diameter φ of φ = 0.250 to 0.4. 00 mm, the length of the first electrode part and the second electrode part is L (mm), the distance between the first electrode part and the second electrode part is D (mm), and the remaining element thickness is A thermistor element in which the electrode dimension ratio D / L is in the range of the following formula (2) when Y (mm) = t−φ / √2.
[(5.00 × 10 ^-2 × 0.410) / (5.00 × 10 ² × exp (B × -3.44 × 10 ^-3 ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)]
≦ D / L ≦
[(5.00 × 10 ² × 0.410) / (5.00 × 10 ⁻² × exp (B × 3.44 × 10 ⁻³ ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)] (2)

In the thermistor element of the present invention, when the electrode dimension ratio D / L of the thermistor element is set to a range defined by the equation (2) according to the B constant (= 2000 to 2500 K), the diameter φ, and the thickness t, − The resistance value Rs (−40) between the first electrode line and the second electrode line of the thermistor element at 40 ° C. can be set to Rs (−40) ≦ 5.00 × 10 ² kΩ. Furthermore, the resistance value Rs (900) between the first electrode line and the second electrode line of the thermistor element at 900 ° C. can be set to Rs (900) ≧ 5.00 × 10 ⁻² kΩ. That is, when the temperature is in the range of −40 to 900 ° C., the resistance value Rs between the first electrode line and the second electrode line of the thermistor element is Rs = 5.00 × 10 ^{−2 to} 5.00 × 10 ^2. It can be set to kΩ. Therefore, it is possible to provide a thermistor element capable of more appropriately detecting the resistance value Rs in the range of −40 to 900 ° C. while using a simple circuit such as a resistance voltage dividing circuit.
Moreover, according to the equation (2), since it is given as a range of the electrode dimension ratio D / L, D is fixed to a convenient value and L is changed, or L is fixed to a convenient value. In addition, the resistance value Rs can be easily adjusted by adjusting D or the like.

In equation (2), the A3 term: [(5.00 × 10 ⁻² × 0.410) / (5.00 × 10 ² × exp (B × −3.44 × 10 ⁻³ ))] is the above-mentioned A1 term, Since the values of 5.00 × 10 ⁻² and 5.00 × 10 ² are different, they can be considered in the same way, and the description is omitted. Similarly, the A4 term: [(5.00 × 10 ² × 0.410) / (5.00 × 10 ⁻² × exp (B × 3.44 × 10 ⁻³ ))] is also the above-mentioned A2 term, 5.00 × 10 ⁻² and 5.00 Since only the value of × 10 ² is different, it can be considered in the same way, and the description is omitted.
Furthermore, the terms B, C, and D are the same as those in the above-described equation (1), and are common to the left and right terms (upper and lower limit terms) in the equation (2).

  Further, in the thermistor element according to claim 1 or 2, when the correlation between the B constant of the thermistor element body and the thickness t is observed for a number of thermistor elements having the same product number, The thermistor element having a larger B constant of the thermistor element body is preferably a thermistor element having a correlation obtained by reducing the thickness t.

As described above, one of the uses of the thermistor element is a temperature sensor for a vehicle. Some of these temperature sensors are exposed to a temperature of about 400 to 900 ° C. during operation of the vehicle and the like, and it is desired to detect the temperature change with high accuracy by changing the resistance value of the thermistor element near this temperature.
By the way, the B constant of the thermistor element body (conductive oxide sintered body) is difficult to form completely the same, even if it is thermistor element of the same product number, fluctuation of raw materials, fluctuation in the preparation stage, etc. Therefore, when a large number of thermistor elements are viewed, for example, when a thermistor element (thermistor element body) having a different production lot manufactured at different times is subjected to a sampling inspection, it is inevitable that the B constant varies. Specifically, regarding the raw material powder for the thermistor element body, as a result of the preceding test, when a certain lot is fired, the B constant is slightly higher even if it is within a predetermined allowable range. . On the other hand, when another lot is baked, a state occurs in which the B constant is slightly lower even if it is within a predetermined allowable range.
In addition, by adjusting the firing conditions, it may be possible to correct the tendency of the B constant of the raw material powder, it is possible to influence the other characteristics of the thermistor element body by changing the firing conditions, There are many cases where adoption is difficult.

  On the other hand, even if the thickness t of the thermistor element main body is changed, the B constant cannot be changed. However, by forming the thermistor element main body with the thickness t changed, between the first and second electrode portions of the thermistor element. It is possible to change the magnitude of the resistance value generated in the above. Specifically, the resistance value decreases as the thickness t increases.

Since the thermistor element of the present invention has a smaller thickness t as the B constant of the thermistor element body is larger, the resistance value of the thermistor element is relatively higher than that of a larger thermistor t.
Accordingly, when the B constant is large, the resistance value of each thermistor element tends to be lower in the temperature range of 400 to 900 ° C., particularly in the high temperature range where the resistance value is low, in the temperature range of −40 to 900 ° C. Can be suppressed by reducing the thickness t.
On the contrary, if the B constant is small, the resistance value of each thermistor element tends to be high in this high temperature range can be suppressed by increasing the thickness t.
In this way, each thermistor element can suppress the variation in the resistance value actually taken in this high temperature range, and can detect the temperature more appropriately and accurately.

Furthermore, it is the thermistor element of any one of Claims 1-3, Comprising: The said electroconductive oxide sintered compact which makes the said thermistor element main body is at least 1 sort (s) among 3A group elements except La Where M1 is at least one element out of Group 2A elements and M2 is at least one element among Group 4A, 5A, 6A, 7A and Group 8 elements excluding Cr, M1 are written in _{a M2 b M3 c Al d Cr} e O f, a, b, c, d, e, f satisfies the following condition, a conductive perovskite phase having a perovskite crystal structure, from the perovskite phase lower conductivity, when at least one metal element selected from metal elements constituting the perovskite phase and Me, at least one having a crystal structure and represented by a composition formula MeO _x And a metal oxide phase, may be a thermistor element is a conductive oxide sintered body containing.
0.600 ≦ a ≦ 1.000
0 ≦ b ≦ 0.400
0.150 ≦ c <0.600
0.400 ≦ d ≦ 0.800
0 <e ≦ 0.050
0 <e / (c + e) ≦ 0.18
2.80 ≦ f ≦ 3.30

  In the thermistor element of the present invention, the above-described conductive oxide sintered body (hereinafter also simply referred to as a sintered body) is used for the thermistor element body. Among the sintered bodies, the conductive perovskite phase in which a, b, c, d, e, and f satisfy the above-described conditional expression is a temperature gradient constant (B constant: B in a temperature range of −40 ° C. to + 900 ° C. (-40 to 900)) is 2000 to 3000K. Further, the conductive oxide sintered body also includes a metal oxide phase having lower conductivity (higher insulation and higher specific resistance) than the perovskite phase. For this reason, it is possible to shift the specific resistance value of the entire conductive oxide sintered body while maintaining the B constant by appropriately changing the ratio of the metal oxide phase in the conductive oxide sintered body. it can. Therefore, the thermistor element using this conductive oxide sintered body can be adjusted to have an appropriate resistance value in the temperature range of −40 ° C. to + 900 ° C. while having a desired form. . Thus, the thermistor element using the conductive oxide sintered body for the thermistor element body can appropriately measure the temperature in such a wide temperature range. In addition, the circuit configuration for resistance value measurement (temperature measurement) can be simplified, or resistance value measurement with high accuracy can be performed.

Moreover, in this conductive oxide sintered body, the metal element Me constituting the metal oxide phase MeOx is selected from the metal elements constituting the perovskite phase. Therefore, there is no possibility that an unexpected by-product is generated in the sintered body in which the perovskite phase and the metal oxide phase coexist, and there is no possibility that the characteristics are changed due to the formation of the by-product.
In addition, when the metal element Me is not a metal element forming a perovskite phase, the metal element Me may be dissolved in the perovskite phase, so that a perovskite phase composed of an element different from that before solid solution may be generated. However, in the sintered body of the present invention, such composition fluctuations are unlikely to occur, a stable composition can be maintained, and fluctuations in various characteristics of the sintered body are suppressed.

In the conductive oxide sintered body, the perovskite phase has a perovskite type (ABO ₃ ) crystal structure, and the A site is usually (M1 _a M2 _b ) and the B site is (M3 _c Al _d). Cr _e ) (M1 _a M2 _b ) (M3 _c Al _d Cr _e ) O ₃ . However, a, b, c, d, and e satisfy the above-described conditions.
In the case of such a crystal structure, the elements M1 and M2 occupying the A site have close ionic radii and can be easily replaced with each other, and there are few by-products formed of these elements. Exist stably in the substituted composition. Similarly, the elements M3, Al, and Cr occupying the B site have close ionic radii and can be easily replaced with each other, and the generation of by-products composed of these elements is small and replaced. Stable in composition. Therefore, the specific resistance value of the conductive oxide sintered body and its temperature gradient constant (B constant) can be adjusted by continuously changing the composition ratio in a wide composition range.

In addition, the firing conditions (the firing atmosphere such as oxidation and reduction, the firing temperature, and the like) at the time of producing the conductive oxide sintered body described above, and the amount ratio of substitution of elements at the A site and B site of the perovskite phase As a result, excess or deficiency of oxygen may occur, so f takes a value of around 3. Thus, the molar ratio of the oxygen atom (M1 _a M2 _b) in the above composition formula, and the molar ratio of the oxygen atoms and (M3 _c Al _d Cr _e) are each exactly 3: has become 1 Even if not, it is only necessary to maintain a perovskite crystal structure.

Further, the metal oxide phase has a lower conductivity than the perovskite phase, and when at least one metal element selected from the metal elements constituting the perovskite phase is Me, a crystal structure represented by MeO _x What is necessary is just to have. Specifically, oxides of a single metal element, for example, Y ₂ O ₃ , SrO, CaO, MnO ₂ , Al ₂ O ₃ , Cr ₂ O _{3 and the} like can be mentioned. In addition, double oxides composed of a plurality of metal elements, for example, Y-Al-based oxides (YAlO ₃ , Y ₃ Al ₅ O _12, etc.), Sr-Al-based oxides (SrAl ₂ O ₄ ), and the like are also included. Further, a plurality of these oxides may be mixed.

  In addition, the average particle diameter which shows the magnitude | size of the crystal particle which comprises an electroconductive oxide sintered compact becomes like this. Preferably it is 7 micrometers or less, More preferably, it is 0.1-7 micrometers, More preferably, it is 0.1-3 micrometers. This is because if the average particle diameter of the crystal particles becomes too large, the characteristics of the sintered body or the thermistor element using the sintered body tend to be unstable.

Furthermore, the thermistor element described above is preferably a thermistor element in which the a and b of the conductive oxide sintered body satisfy the following conditional expression.
0.600 ≦ a <1.000
0 <b ≦ 0.400

  In this thermistor element, 0.600 ≦ a <1.000 and 0 <b ≦ 0.400, that is, a <1.000, b> 0 are set for the conductive oxide sintered body. That is, in this sintered body, the perovskite phase contains at least one element M1 of the 3A group elements excluding La, and at least one element M2 of the 2A group as essential components, and a and b Has a composition satisfying the above conditional expression. In the thermistor element using this conductive oxide sintered body, each of the conductive oxides is also produced in the case where a large number of the perovskite phases are produced as compared with those in which the element M2 is not included (b = 0). There is an advantage that it is possible to reduce the characteristic variation between the individual sintered thermistor bodies (thermistor element main body) and the individual thermistor elements and between the firing lots.

Furthermore, it is preferable that the thermistor element is a thermistor element in which a, b, c, d, e, and f satisfy the following conditional expressions.
0.820 ≦ a ≦ 0.950
0.050 ≦ b ≦ 0.180
0.181 ≦ c ≦ 0.585
0.410 ≦ d ≦ 0.790
0.005 ≦ e ≦ 0.050
0 <e / (c + e) ≦ 0.18
2.91 ≦ f ≦ 3.27

  In the thermistor element of the present invention in which a to f satisfy the above-mentioned conditional expression, the B constant in the temperature range of −40 ° C. to 900 ° C. is more reliably set to 2000 to 3000 K for the thermistor element body formed by the conductive oxide sintered body. Can be adjusted within the range. Further, in this conductive oxide sintered body in which a to f satisfy the above-described conditional expression, each of the conductive oxides is also used when a plurality of thermistor elements using the conductive sintered body in which a to f are specified to a certain numerical value are manufactured. Characteristic sintered body (thermistor element main body), and therefore, characteristic variation among individual thermistor elements and characteristic variation between firing lots can be further reduced.

Furthermore, it is preferable that the thermistor element is a thermistor element in which a, b, c, d, e, and f satisfy the following conditional expressions.
0.850 ≦ b ≦ 0.940
0.060 ≦ b ≦ 0.150
0.181 ≦ c ≦ 0.545
0.450 ≦ d ≦ 0.780
0.005 ≦ e ≦ 0.050
0 <e / (c + e) ≦ 0.18
2.92 ≦ f ≦ 3.25

  Furthermore, in the thermistor element according to any one of the above, in the conductive oxide sintered body, the element M1 is one or more elements selected from Y, Nd, and Yb, and the element M2 is The thermistor element is preferably one or more elements selected from Mg, Ca and Sr, and the element M3 is one or more elements selected from Mn and Fe.

  In the conductive oxide sintered body used for the thermistor element, the element M1 is one or more elements selected from Y, Nd, and Yb, and the element M2 is one or more elements selected from Mg, Ca, and Sr. The element M3 is one or more elements selected from Mn and Fe. By selecting these elements, it is easy to obtain the B constant in the above range stably.

  Alternatively, the thermistor element according to any one of the above, wherein the element M1 is Y, the element M2 is Sr, and the M3 is Mn in the conductive oxide sintered body. Is preferred.

  In this conductive oxide sintered body used for the thermistor element, in particular, the element M1 is Y, the element M2 is Sr, and the element M3 is Mn. Thereby, the B constant in the above-mentioned range is easily obtained stably.

Furthermore, in the above-described thermistor element, when the total cross-sectional area of the perovskite phase that appears in the cross-section (cross-sectional area S) of the conductive oxide sintered body in the conductive oxide sintered body is SP. , S and SP are preferably thermistor elements satisfying the following formula.
0.20 ≦ SP / S ≦ 0.80

Since the sintered body contains a perovskite phase and a metal oxide phase, a perovskite phase and a metal oxide phase also appear in the cross section. In the sintered body used for the thermistor element of the present invention, the cross-section (cross-sectional area S) of the sintered body and the total cross-sectional area SP of the perovskite phase appearing in the sintered body satisfy the above-described formula. Specifically, the lower limit of the ratio of the total cross-sectional area SP of the perovskite phase in the cross-sectional area S of the sintered body was set to 0.20 (20%).
When the total cross-sectional area of the perovskite phase exhibiting relatively high conductivity with respect to the metal oxide phase is less than 20%, the conductivity of the sintered body is reduced and the specific resistance is increased. This is because it becomes difficult to use a sintered body having such a specific resistance value.

Similarly, the upper limit of the ratio of the total cross-sectional area SP of the perovskite phase in the cross-sectional area S of the sintered body was set to 0.80 (80%) or less. When the total cross-sectional area of the perovskite phase exceeds 80%, the decrease in conductivity of the sintered body is slight and the increase in specific resistance is small. For this reason, there are few advantages by adding the metal oxide phase whose specific resistance is larger than the perovskite phase.
The ratio of the total cross-sectional area SP of the perovskite phase in the cross-sectional area S of the sintered body is equal to the volume fraction of the perovskite phase contained in the sintered body.

  Furthermore, it is preferable that the thermistor element described in any of the above is a thermistor element including a double oxide in the metal oxide phase of the conductive oxide sintered body.

In the thermistor element of the present invention, the metal oxide phase of the sintered body contains a double oxide. The double oxide is an oxide composed of two or more metal elements.
Only one of the two elements forming the double oxide moves from the double oxide to the perovskite phase and dissolves in the sintered body or in a high temperature environment such as 900 ° C. Is considered to be less likely to occur from a single element oxide as compared to the case where the metal element (M1 or M2) forming the oxide moves to the perovskite phase and dissolves. Therefore, it is considered that the inclusion of the double oxide in the metal oxide phase can suppress the deviation of the composition of the perovskite phase in a high temperature environment and can improve the heat resistance.

Furthermore, in the above thermistor element, the conductive oxide sintered body satisfies the following conditional expression:
0.600 ≦ a <1.000
0 <b ≦ 0.400
It is preferable that the thermistor element in which the metal oxide phase includes a double oxide composed of the element M1 and the element M2.

In this thermistor element, in the sintered body, 0.600 ≦ a <1,000, and 0 <b ≦ 0.400, that is, a <1,000, b> 0. That is, in this sintered body, the perovskite phase has a composition containing the 2A group element M2 as an essential component in addition to the 3A group element M1. In addition, the metal oxide phase includes a double oxide composed of the elements M1 and M2 as the double oxide. These elements M1 and M2 are both elements arranged at the A site in the perovskite phase.
At the time of firing the sintered body or in a high temperature environment such as 900 ° C., only one of the two elements M1 and M2 forming the double oxide moves from the double oxide to the A site of the perovskite phase and is solidified. It is considered that dissolution is less likely to occur than when a metal element (M1 or M2) that forms a single element oxide moves to the A site of the perovskite phase and dissolves. Therefore, by including a double oxide composed of the elements M1 and M2 in the metal oxide phase, it is possible to further suppress the deviation of the composition of the perovskite phase in a high temperature environment and improve the heat resistance.
Examples of such a double oxide include SrY ₂ O ₄ and SrY ₄ O ₇ when the perovskite phase is represented by (Y, Sr) (Mn, Al, Cr) O _3. It is done.

Furthermore, in the above-described thermistor element, in the conductive oxide sintered body, the element M1 contains Y, the element M2 contains Sr, and the metal oxide phase has a composition formula SrY ₂ O ₄ . It is preferable that the thermistor element includes the indicated double oxide.

In this thermistor element, the sintered body contains SrY ₂ O ₄ as a double oxide in the metal oxide phase. By doing in this way, the heat resistance of a sintered compact and high temperature stability can be improved.

  Further, in the above-described thermistor element, in the conductive oxide sintered body, the metal oxide phase includes at least one of the elements M1 and M2 and at least one of the elements M3, Al, and Cr. A thermistor element containing a double oxide is preferable.

In this thermistor element, the sintered body is a composite oxide in which the metal oxide phase is composed of elements (M1, M2) forming the A site of the perovskite phase and elements (M3, Al, Cr) forming the B site. Contains. As described above, it is considered that the deviation of the composition of the perovskite phase in a high temperature environment can be further suppressed by using a double oxide composed of an element selected from the elements forming the A site and the B site of the perovskite phase. It is done.
Examples of such double oxides include SrAl ₂ O ₄ , YAlO ₃ , Y ₃ Al ₅ O ₁₂ when the perovskite phase is (Y, Sr) (Mn, Al, Cr) O _3. It is done.

Furthermore, in the above-described thermistor element, in the conductive oxide sintered body, the element M2 contains Sr, and the metal oxide phase is a complex oxide represented by a composition formula SrAl ₂ O ₄ A thermistor element containing is preferable.

In the thermistor element of the present invention, the sintered body contains Sr in the perovskite phase, and SrAl ₂ O ₄ in the metal oxide phase. By doing in this way, there exists an advantage which heat resistance improves.

  Furthermore, it is the thermistor element of any one of the above-mentioned, Comprising: The said electroconductive oxide sintered compact and the reduction-resistant reduction-resistant film which coat | covers the said electroconductive oxide sintered compact are provided. A thermistor element is preferable.

  This thermistor element has a conductive oxide sintered body and a reduction-resistant film covering the conductive oxide sintered body. For this reason, even when the thermistor element is exposed to a reducing atmosphere, the sintered body is protected by the reduction-resistant coating, and the sintered body is prevented from being reduced. Therefore, the thermistor element (sintered body) The resistance value indicated by can be maintained.

  Furthermore, a temperature sensor using the thermistor element described in any one of the above is preferable.

  In the temperature sensor of the present invention, a thermistor element having an appropriate resistance value of 20 to 700 kΩ or within 50 to 500 kΩ is used over a wide temperature range of −40 to 900 ° C. The temperature sensor can appropriately measure the temperature over the temperature range. In addition, a temperature sensor that can simplify the circuit configuration for resistance value measurement (temperature measurement) or enable resistance value measurement with high accuracy can be obtained.

Still another solution is a thermistor element body made of a conductive oxide sintered body having a B constant of B (−40 to 900) = 2.00 × 10 ^{3 to} 3.00 × 10 ³ K, and the thermistor element A first electrode line having a first electrode portion having a circular cross section and extending linearly through the body, and a second electrode line paired with the first electrode line, wherein the thermistor element body is the first electrode line. A thermistor element manufacturing method comprising: a second electrode line penetrating in parallel to one electrode portion and extending in a straight line, having a circular cross section and having a second electrode portion having a diameter and a length equal to that of the first electrode portion. In the thermistor element, a virtual connecting the first electrode part and the second electrode part passing through a virtual midpoint between the first electrode part and the second electrode part in the thermistor element body. The thickness in the direction perpendicular to the imaginary plane perpendicular to the surface is t (mm), the first electrode portion and the second The diameter of the pole part is φ (mm), the lengths of the first electrode part and the second electrode part are L (mm), and the inter-electrode distance between the first electrode part and the second electrode part is D (mm). ), When the remaining thickness of the element is Y (mm) = t−φ / √2, the powder for pressing that becomes the conductive oxide sintered body after sintering, the first electrode wire, and the second electrode wire Is used to press-mold an unsintered thermistor element, and when the unsintered thermistor element is fired, the thickness t is t = 0.500 to 1.20 mm, and the diameter φ is φ = 0.250-0.400 mm, Electrode size ratio D / L is the manufacturing method of a thermistor element provided with the press process of shape | molding the said unsintered thermistor element of the form which becomes in the range of following formula (1).
[(2.00 × 10 ^-2 × 0.410) / (7.00 × 10 ² × exp (B × -3.44 × 10 ^-3 ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)]
≦ D / L ≦
[(7.00 × 10 ² × 0.410) / (2.00 × 10 ⁻² × exp (B × 3.44 × 10 ⁻³ ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)] (1)

In the thermistor element manufacturing method of the present invention, in the thermistor element after firing, the thickness t and the diameter φ are within a predetermined range, the electrode dimension ratio D / L is a B constant (= 2000 to 3000 K), the diameter The unfired thermistor element is press-molded so as to be in the range defined by the formula (1) according to φ and thickness t.
Then, in the thermistor element obtained by firing this, the resistance value Rs (−40) between the first electrode line and the second electrode line at −40 ° C. is set to Rs (−40) ≦ 7.00 × 10 ² kΩ. It can be. Furthermore, the resistance value Rs (900) between the first electrode line and the second electrode line of the thermistor element at 900 ° C. can be set to Rs (900) ≧ 2.00 × 10 ⁻² kΩ. That is, when the temperature is in the range of −40 to 900 ° C., the resistance value Rs between the first electrode line and the second electrode line of the thermistor element is Rs = 2.00 × 10 ^{−2 to} 7.00 × 10 ^2. It can be set to kΩ.
Thus, by using the thermistor element manufacturing method of the present invention, a thermistor element capable of appropriately detecting the resistance value Rs in the range of −40 to 900 ° C. while using a simple circuit such as a resistance voltage dividing circuit. Can do.
Moreover, according to the equation (1), since it is given as a range of the electrode dimension ratio D / L, D is fixed to a convenient value and L is changed, or L is fixed to a convenient value. In addition, a thermistor element resistance value Rs can be easily adjusted by adjusting D or the like.

Still another solution is a thermistor element body made of a conductive oxide sintered body having a B constant of B (−40 to 900) = 2.00 × 10 ^{3 to} 2.50 × 10 ³ K, and the thermistor element A first electrode line having a first electrode portion having a circular cross section and extending linearly through the body, and a second electrode line paired with the first electrode line, wherein the thermistor element body is the first electrode line. A thermistor element manufacturing method comprising: a second electrode line penetrating in parallel to one electrode portion and extending in a straight line, having a circular cross section and having a second electrode portion having a diameter and a length equal to that of the first electrode portion. In the thermistor element, a virtual connecting the first electrode part and the second electrode part passing through a virtual midpoint between the first electrode part and the second electrode part in the thermistor element body. The thickness in the direction perpendicular to the imaginary plane perpendicular to the surface is t (mm), the first electrode portion and the second The diameter of the pole part is φ (mm), the lengths of the first electrode part and the second electrode part are L (mm), and the inter-electrode distance between the first electrode part and the second electrode part is D (mm). ), When the remaining thickness of the element is Y (mm) = t−φ / √2, the powder for pressing that becomes the conductive oxide sintered body after sintering, the first electrode wire, and the second electrode wire Is used to press-mold an unsintered thermistor element, and when the unsintered thermistor element is fired, the thickness t is t = 0.500 to 1.20 mm, and the diameter φ is φ = 0.250-0.400 mm, It is a manufacturing method of a thermistor element provided with the press process which shape | molds the said unbaking thermistor element of the form from which electrode dimension ratio D / L becomes in the range of following formula (2).
[(5.00 × 10 ^-2 × 0.410) / (5.00 × 10 ² × exp (B × -3.44 × 10 ^-3 ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)]
≦ D / L ≦
[(5.00 × 10 ² × 0.410) / (5.00 × 10 ⁻² × exp (B × 3.44 × 10 ⁻³ ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)] (2)

In the thermistor element manufacturing method of the present invention, in the thermistor element after firing, the thickness t and the diameter φ are within the predetermined ranges, the electrode dimension ratio D / L is the B constant (= 2000 to 2500 K), the diameter The unfired thermistor element is press-molded so as to be in the range defined by the formula (2) according to φ and thickness t.
Then, in the thermistor element fired, the resistance value Rs (−40) can be set to Rs (−40) ≦ 5.00 × 10 ² kΩ. Further, the resistance value Rs (900) can be set to Rs (900) ≧ 5.00 × 10 ⁻² kΩ. That is, when the temperature is in the range of −40 to 900 ° C., the resistance value Rs between the first electrode line and the second electrode line of the thermistor element is Rs = 5.00 × 10 ^{−2 to} 5.00 × 10 ^2. It can be set to kΩ.
Thus, by using the thermistor manufacturing method of the present invention, a thermistor element capable of more appropriately detecting the resistance value Rs in the range of −40 to 900 ° C. while using a simple circuit such as a resistance voltage dividing circuit. Can do.
Moreover, according to the equation (2), since it is given as a range of the electrode dimension ratio D / L, D is fixed to a convenient value and L is changed, or L is fixed to a convenient value. In addition, a thermistor element resistance value Rs can be easily adjusted by adjusting D or the like.

  Furthermore, it is a manufacturing method of the thermistor element of Claim 6 or Claim 7, Comprising: When the said press process manufactures the thermistor element of the same product number, the said B constant of the said thermistor element main body after sintering is The larger the pressed powder, the better the thermistor element manufacturing method is to mold the unfired thermistor element with the thickness t decreasing.

  In the method for manufacturing the thermistor element of the present invention, the unsintered thermistor element is formed so that the thickness t becomes smaller as the press powder in which the B constant of the sintered thermistor element body (conductive oxide sintered body) becomes larger is used. Is molded.

As described above, the B constant of the thermistor element body (conductive oxide sintered body) is difficult to form completely the same, even if the thermistor elements have the same product number. Therefore, when a large number of thermistor elements are observed, for example, when a thermistor element having a different production lot is subjected to a sampling inspection, the B constant varies.
In addition, by adjusting the firing conditions, it may be possible to correct the tendency of the B constant of the raw material powder, but there may be an influence on other characteristics of the thermistor element body due to the change of the firing conditions, There are many cases where adoption is difficult.

  On the other hand, even if the thickness t of the thermistor element main body is changed, the B constant cannot be changed. However, by forming the thermistor element main body with the thickness t changed, between the first and second electrode portions of the thermistor element. It is possible to change the magnitude of the resistance value generated in the above. Specifically, the resistance value decreases as the thickness t increases.

In the manufacturing method of the thermistor element of the present invention, the unsintered thermistor element is formed in a form in which the thickness t becomes smaller as the press powder having a larger B constant is used in the pressing step. Compared to the case, the resistance value of the thermistor element after firing can be made relatively high.
By manufacturing in this way, when the B constant is large, the resistance value of each thermistor element is in the high temperature range of 400 to 900 ° C., where the resistance value is low, in the temperature range of −40 to 900 ° C. The tendency to be lower can be suppressed by reducing the thickness t.
On the contrary, if the B constant is small, the resistance value of each thermistor element tends to be high in this high temperature range can be suppressed by increasing the thickness t.
Thus, according to the manufacturing method of the present invention, it is possible to manufacture a thermistor element capable of suppressing temperature variation actually taken in this high temperature range and detecting temperature more appropriately and accurately.

Furthermore, it is a manufacturing method of the thermistor element of any one of Claims 6-8, Comprising: The said electroconductive oxide sintered compact which makes the said thermistor element main body is 3A group elements except La. When at least one element is M1, at least one element of group 2A is M2, and at least one element of group 4A, 5A, 6A, 7A and group 8 elements except Cr is M3, is expressed by the composition formula _{M1 a M2 b M3 c Al d} Cr e O f, a, b, c, d, e, f satisfies the following condition, a conductive perovskite phase having a perovskite crystal structure, the It has a conductivity lower than that of the perovskite phase and has a crystal structure represented by the composition formula MeO _x when Me is at least one metal element selected from the metal elements constituting the perovskite phase. Both methods may be a method for manufacturing a thermistor element which is a conductive oxide sintered body containing one kind of metal oxide phase.
0.600 ≦ a ≦ 1.000
0 ≦ b ≦ 0.400
0.150 ≦ c <0.600
0.400 ≦ d ≦ 0.800
0 <e ≦ 0.050
0 <e / (c + e) ≦ 0.18
2.80 ≦ f ≦ 3.30

  In the method for manufacturing a thermistor element of the present invention, a sintered body that satisfies the above-described condition is used for a conductive oxide sintered body (hereinafter, also simply referred to as a sintered body) forming the thermistor element body. Among the sintered bodies, the conductive perovskite phase in which a, b, c, d, e, and f satisfy the above-described conditional expression is a temperature gradient constant (B constant: B in a temperature range of −40 ° C. to + 900 ° C. (-40 to 900)) is 2000 to 3000K. Further, the conductive oxide sintered body also includes a metal oxide phase having lower conductivity (higher insulation and higher specific resistance) than the perovskite phase. For this reason, it is possible to shift the specific resistance value of the entire conductive oxide sintered body while maintaining the B constant by appropriately changing the ratio of the metal oxide phase in the conductive oxide sintered body. it can. Therefore, the thermistor element using this conductive oxide sintered body can be adjusted to have an appropriate resistance value in the temperature range of −40 ° C. to + 900 ° C. while having a desired form. . Thus, in manufacturing the thermistor element, by using this conductive oxide sintered body for the thermistor element body, it is possible to manufacture a thermistor element capable of appropriately measuring the temperature in such a wide temperature range. it can. Further, a thermistor element capable of simplifying a circuit configuration for resistance value measurement (temperature measurement) or capable of measuring a resistance value with high accuracy can be manufactured.

  A thermistor element 10 according to the present invention will be described with reference to the drawings. As shown in FIG. 4, the thermistor element 10 is a hexagonal plate having a thickness t (mm), and is formed of a conductive oxide sintered body having a predetermined composition, and the thermistor element body. A first electrode line 2 and a second electrode line 3 that are linear and have a diameter φ pass between the opposing surfaces 1A and 1B facing each other in parallel. Of the first electrode wire 2, a portion that is located in the thermistor element body 1 and that penetrates the first electrode wire 2 is a first electrode portion 2 a, and a portion that protrudes downward from the facing surface 1 A in FIG. The part which protrudes upward in FIG.4 (b) from the part 2b and the opposing surface 1B is made into the 1st protrusion part 2c. Similarly, a portion of the second electrode wire 3 that is located in the thermistor element body 1 and that penetrates the second electrode wire 3 extends downward from the opposing electrode 1a in FIG. 4B. The part which protrudes upwards in FIG.4 (b) from the 2nd connection part 3b and the opposing surface 1B is made into the 2nd protrusion part 3c. These first and second electrode wires 2 and 3 are both made of a Pt—Rh alloy.

Next, the relationship between the dimension of each part of the thermistor element 10 and the resistance value will be examined.
The interelectrode distance between the first electrode portion 2a and the second electrode portion 3a is D (mm), the lengths of the first electrode portion 2a and the second electrode portion 3a are L (mm), and the diameters thereof are Let φ (mm) be the thermistor element body 1 thickness t (mm).
Here, it is assumed that the thickness t is in a range of t = 0.500 to 1.20 mm and the diameter φ is in a range of φ = 0.250 to 0.400 mm.
The length L is preferably L ≧ 0.3 mm. The interelectrode distance D is preferably D ≧ 0.1 mm.

As described above, the resistance-temperature characteristic of the NTC thermistor element, that is, the resistance value Rs at the temperature Ts (K) is approximately given by Rs = R0 · exp [B (1 / Ts−1 / T0)]. It is done. Here, the initial resistance value R0 is the resistance value at the initial temperature T0 (K), and B is the B constant (K).
By the way, as described above, a thermistor element using a thermistor element body made of a conductive oxide sintered body having a B constant of B (−40 to 900) = 2.00 × 10 ^{3 to} 3.00 × 10 ³ K. Among these, in the thermistor element 10 according to the above-described embodiment, it has been found that the resistance value Rs is proportional to the electrode size ratio D / L.
That is, a first electrode line 2 that penetrates the thermistor element body 1 and extends linearly and has a first electrode portion 2 a having a circular cross section, and a second electrode line 3 that forms a pair with the first electrode line 2. Consider a thermistor element 10 comprising a second electrode line 3 having a second electrode part 3a having a circular cross section and extending in a straight line through the thermistor element body 1 in parallel with the first electrode part 2a. As shown in FIG. 1, the thermistor element 10 passes through at least a virtual midpoint CP between the first electrode portion 2a and the second electrode portion 3a of the thermistor element body 1, and the first electrode portion 2a and the second electrode portion 2a. The thickness t in the imaginary plane orthogonal direction DR1 perpendicular to the imaginary plane P connecting to the electrode section 3a is t = 0.50 to 1.2 mm, and the diameter φ of the first electrode section 2a and the second electrode section 3a However, in the range where φ = 0.25 to 0.40 mm, the resistance value Rs of the thermistor element 10 is found to be proportional to the electrode dimension ratio D / L.

The reason for this is considered to be as follows. That is, since the first electrode portion 2a and the second electrode portion 3a penetrate the thermistor element body 1 in parallel to each other, when viewed in the direction along the length L (virtual plane orthogonal direction DR1), The state of the electric field and the lines of electric force generated between the electrode part 2a and the second electrode part 3a are considered to be almost the same in any part. Therefore, the resistance value Rs of the thermistor element 10 has an inversely proportional relationship, such that if the length L is doubled, it is 1/2 times.
On the other hand, regarding the interelectrode distance D, if the interelectrode distance D between the first electrode portion 2a and the second electrode portion 3a is doubled, the resistance value Rs of the thermistor element is also doubled. It becomes a direct proportional relationship.
Therefore, it is considered that the resistance value Rs of the thermistor element is directly proportional to the electrode dimension ratio D / L.

Here, as the thermistor element 10, a reference thermistor element in which the reference electrode distance Db = 0.410 mm, the reference electrode portion length Lb = 1.00 mm, and the reference electrode dimension ratio Db / Lb = 0.410 is considered. The B constant of the thermistor element 10 is B (−40 to 900) = B.
It is assumed that the initial resistance value R0 (-40) at the initial temperature T0 = 233K (= −40 ° C.) is R0 (−40) = 7.00 × 10 ² (kΩ). When the temperature of the thermistor element 10 is changed to a temperature Ts = 1173K (= 900 ° C.), the resistance value Rs is Rs = 7.00 × 10 ² × exp [B (1 / 1733-1 / 233)] = 7.00 × 10 ² × exp (B × −3.44 × 10 ⁻³ ). That is, the resistance value Rs at the temperature Ts (= 900 ° C.) of the reference thermistor element having the B constant B and the reference electrode size ratio Db / Lb = 0.410 is given by the above equation.
On the other hand, since the resistance value Rs of the thermistor element 10 is directly proportional to the electrode dimension ratio D / L, Rs = a1 · (Db / Lb), where a1 can be expressed by a proportional coefficient.
Also, when the temperature ratio Ts (= 900 ° C.) and the electrode size ratio at which the minimum resistance value allowed for the thermistor element 10 is 2.00 × 10 ⁻² (kΩ) (= 20.0Ω) is (D / L) min. In this case, the relationship of 2.00 × 10 ⁻² = a1 × (D / L) min is satisfied.
Accordingly, the relationship of proportionality coefficient a1 = (D / L) min / 2.00 × 10 ⁻² = (Db / Lb) / (7.00 × 10 ² × exp (B × −3.44 × 10 ⁻³ )) is satisfied. From this, (D / L) min = (2.00 × 10 ⁻² ) × (Db / Lb) / (7.00 × 10 ² × exp (B × −3.44 × 10 ⁻³ )) = (2.00 × 10 ⁻² × 0.410) / (7.00 × 10 ² × exp (B × -3.44 × 10 ⁻³ )). Since this electrode dimension ratio (D / L) min is the smallest allowable value among the electrode dimension ratios D / L, the electrode dimension ratio D / L is D / L ≧ [(2.00 × 10 ^-2 × 0.410) / (7.00 × 10 ² × exp (B × −3.44 × 10 ⁻³ )) is selected.
This relationship gives the relationship between the term A1 in the above-described formulas (1) and (2) and the electrode dimension ratio D / L.

Next, contrary to the above case, it is assumed that the initial resistance value R0 (900) at the initial temperature T0 = 1173K (= 900 ° C.) is R0 (900) = 2.00 × 10 ⁻² (kΩ). . When the temperature of the thermistor element 10 is changed to a temperature Ts = 233 K (= −40 ° C.), the resistance value Rs is Rs = 2.00 × 10 ⁻² × exp [B (1 / 233−1 / 1733 )] = 2.00 × 10 ⁻² × exp (B × 3.44 × 10 ⁻³ ). That is, the resistance value Rs at the temperature Ts (= −40 ° C.) of the reference thermistor element having the reference electrode size ratio Db / Lb = 0.410 is given by the above equation.
On the other hand, since the resistance value Rs of the thermistor element 10 is directly proportional to the electrode dimension ratio D / L as described above, it can be expressed by Rs = a2 · (Db / Lb). If the electrode size ratio at which the maximum resistance value allowed for the thermistor element is 7.00 × 10 ² (kΩ) at temperature Ts (= −40 ° C.) is (D / L) max, this is also 7.00 × 10 ² = a2 × (D / L) max is satisfied.
Therefore, the relationship of proportionality coefficient a2 = (D / L) max / 7.00 × 10 ² = (Db / Lb) / (2.00 × 10 ⁻² × exp (B × −3.44 × 10 ⁻³ )) is satisfied. From this, (D / L) max = (7.00 × 10 ² ) × (Db / Lb) / (2.00 × 10 ⁻² × exp (B × −3.44 × 10 ⁻³ )) = (7.00 × 10 ² × 0.410 ) / (2.00 × 10 ⁻² × exp (B × −3.44 × 10 ⁻³ )). Since this electrode dimension ratio (D / L) max is the largest allowable value among the electrode dimension ratios D / L, the electrode dimension ratio D / L is D / L ≦ [(2.00 × 10 ^{A value of −2} 7.00 × 10 ² × 0.410) / (2.00 × 10 ⁻² × exp (B × −3.44 × 10 ⁻³ )) may be selected.
This relationship gives the relationship between the term A2 in the above-described formulas (1) and (2) and the electrode dimension ratio D / L.

From the above, the following basic relational expression (3) between the electrode dimension ratio D / L and the resistance value Rs was obtained.
[(2.00 × 10 ^-2 × 0.410) / (7.00 × 10 ² × exp (B × -3.44 × 10 ^-3 ))]
≦ D / L ≦
[(7.00 × 10 ² × 0.410) / (2.00 × 10 ⁻² × exp (B × 3.44 × 10 ⁻³ ))]… (3)

Similarly, by setting R0 (-40) = 5.00 × 10 ² (kΩ) and R0 (900) = 5.00 × 10 ⁻² (kΩ), the following electrode dimension ratio D / L and resistance value A basic relational expression (4) with Rs is also obtained.
[(5.00 × 10 ^-2 × 0.410) / (5.00 × 10 ² × exp (B × -3.44 × 10 ^-3 ))]
≦ D / L ≦
[(5.00 × 10 ² × 0.410) / (5.00 × 10 ⁻² × exp (B × 3.44 × 10 ⁻³ ))]… (4)

However, in the expressions (3) and (4), the influence on the resistance value Rs such as the diameter φ of the first and second electrode portions 2a and 3a and the thickness t of the thermistor element body 1 is not considered.
Therefore, in order to effectively use the above basic relational expression (3) in consideration of the influences thereof, a standard value is determined for each dimension of the thermistor element, and the deviation of the resistance value Rs that occurs when a different value is used. Is corrected by a correction term.

First, the distance between the electrode parts will be examined.
As already described with reference to FIG. 1, the interelectrode distance D is given by the size of the gap between the first electrode portion 2a and the second electrode line 3a. The diameters of the first electrode portion and the second electrode portion are φ (mm). What contributes to the resistance value Rs between the first electrode part 2a and the second electrode part 3a is the smallest part of the first and second electrode parts 2a, 3a, which forms the inter-electrode distance D. It's not just near. Therefore, it is necessary to consider the surface shapes (cylindrical surfaces) of the first electrode portion 2a and the second electrode portion 3a. In this case, the distance between the first electrode part 2a and the second electrode part 3a should be larger than the inter-electrode distance D.
In this example, since the first electrode portion 2a and the second electrode portion 3a have a circular cross section, the effective distance Def is a distance that contributes to the resistance value Rs between the first electrode portion 2a and the second electrode portion 3a. Is given as shown in FIG. That is, lines extending in directions inclined by 45 degrees (45 degrees) from the center line 2ac and the center line 3ac, respectively, with respect to a line connecting the center line 2ac of the first electrode portion 2a and the center line 3ac of the second electrode portion 3a. The points intersecting with the outer peripheral surfaces of the first electrode portion 2a and the second electrode portion 3a are denoted as L1, L2, N1, and N2, respectively. The distance (gap) between the line segment L1-L2 connecting the points L1 and L2 and the line segment N1-N2 connecting the points N1 and N2 is defined as an effective distance Deff. This effective distance Deff is given by Deff = D + (1-1 / √2) × φ / 2 × 2 = D + (1-1 / √2) φ.

On the other hand, in the reference thermistor element, the reference electrode distance Db = 0.410 mm and the reference electrode portion diameter φb = 0.300 mm. Then, the reference effective distance Deffb is Deffb = (0.410+ (1-1 / √2) × 0.300) = 0.498.
Therefore, as a B term, a correction term for correcting the influence of the effective distance Deff on the thermistor element under consideration with respect to the A1 term or the A2 term on the basis of the effective distance Deffb of the reference is considered. As with the inter-electrode distance D, the effective distance Deff increases (proportional) as the resistance value Rs of the thermistor element increases as the value increases. Therefore, when a value different from the reference effective distance Deffb is employed as the effective distance Deff of the thermistor element, the B term: Deffb / Deff = [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)].

Next, the width at which the first electrode portion and the second electrode portion face each other will be examined.
As shown in FIG. 1, the first electrode portion 2a and the second electrode portion 3a effectively have the inter-electrode distance of the effective distance Deff described above, and the electrode portions having the effective width Weff face each other. You can also think that The effective width Weff is given by Weff = 2 × 1 / √2 × φ / 2 = φ / √2.
By the way, in the reference thermistor element, the diameter φb of the reference electrode portion is set to 0.300 mm. Then, the reference effective width Weffb is Weffb = 0.300 / √2 = 0.212 mm.
Therefore, a correction term for correcting the influence of the effective width Weff on the thermistor element under consideration with respect to the effective width Weffb of the reference is considered as the C term with respect to the A1 term or the A2 term. As the effective width Weff increases, the resistance value Rs of the thermistor element decreases (inversely proportional). Therefore, when a value different from the reference effective width Weffb is adopted as the effective width Weff of the thermistor element, the C term: Weff / Weffbφ / 0.300 (= ( (φ / √2) / (0.300 / √2))).

Further, the thickness of the thermistor element body 1 will be examined.
As shown in FIG. 2, the electric field lines EF generated between the thermistor element first electrode portion 2a and the second electrode portion 3a have an effective width Weff of the surfaces of the first electrode portion 2a and the second electrode portion 3a. It does not occur only in the range (see FIG. 1), but extends more than that. Specifically, it passes through a virtual midpoint CP between the first electrode portion 2a and the second electrode portion 3a, and is orthogonal to a virtual plane P passing through the center line 2ac of the first electrode portion 2a and the center line 3ac of the second electrode portion 3a. Of the thickness t of the thermistor element main body 1 in the imaginary plane orthogonal direction DR1 (up and down direction in FIG. 2), the portion excluding the effective width Weff (the portions of the thickness t1, t2) also has the electric lines of force EF. Pass through. Therefore, the resistance value Rs of the thermistor element also changes depending on the thicknesses t1 and t2 of these portions. Therefore, the remaining element thickness Y is defined as Y = t1 + t2 = t−Weff = t−φ / √2.
When the reference thermistor element (Db = 0.410 mm, φb = 0.300 mm, Weffb = 0.212 mm) using the thermistor body 1 having a predetermined composition is changed, when the remaining element thickness Y, and hence the thickness t, is changed, Each example of the resistance value Rs obtained at Ts = 350 ° C. is plotted in FIG.
Furthermore, from this result, a quadratic approximate curve equation: Rs = 0.474Y ² −0.919Y + 0.698 can be obtained.

Here, the reference resistance value when the thickness t is the reference thickness tb = 0.950 mm and the reference element remaining thickness Yb is Yb = tb−φb / √2 = 0.950−0.300 / √2 = 0.338 mm When Rsb is obtained from the above equation of the approximate curve, Rsb = 0.278 (kΩ).
When the resistance value Rsb when the reference element residual thickness Yb is used as a reference with respect to the A1 term or the A2 term as the D term, the resistance is obtained when the residual thickness of the thermistor element under consideration is Y. Consider a correction term that corrects the effect of changing values. Therefore, when a value different from the reference element remaining thickness Yb is adopted as the element remaining thickness Y of the thermistor element, the correction of the resistance value by changing the element remaining thickness Y cancels the influence. , the A1 paragraphs or A2 wherein, D ^{claim: [0.278 / (0.474Y 2 -0.919Y} + 0.698)] by multiplying the be carried out.

From the above, the above-described formula (1) was obtained regarding the relationship between the electrode dimension ratio D / L and the resistance value Rs, further taking into account the influence of the diameter φ and the thickness t (element remaining thickness Y).
[(2.00 × 10 ^-2 × 0.410) / (7.00 × 10 ² × exp (B × -3.44 × 10 ^-3 ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)]
≦ D / L ≦
[(7.00 × 10 ² × 0.410) / (2.00 × 10 ⁻² × exp (B × 3.44 × 10 ⁻³ ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)] (1)

Thus, for the thermistor element 10 of the present embodiment according to the above-described embodiment, the resistance value Rs is 20.0 in the range of −40 to 900 ° C. by keeping the electrode dimension ratio D / L within the range of the formula (1). It can be kept within the range of Ω to 700 kΩ.
Further, according to the equation (1), the electrode dimension ratio D / L to be adopted is given as a certain range. For example, the distance D between the electrodes is fixed to a convenient value, and the length L is The resistance value Rs of the thermistor element 10 can be easily adjusted by adjustment to change or by fixing the length L to a convenient value and changing the distance D between the electrodes.

Similarly, with respect to the relationship between the electrode dimension ratio D / L and the resistance value Rs, the above-described formula (2) is obtained in consideration of the influence of the diameter φ and the thickness t (element remaining thickness Y).
[(5.00 × 10 ^-2 × 0.410) / (5.00 × 10 ² × exp (B × -3.44 × 10 ^-3 ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)]
≦ D / L ≦
[(5.00 × 10 ² × 0.410) / (5.00 × 10 ⁻² × exp (B × 3.44 × 10 ⁻³ ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)] (2)

Accordingly, for the thermistor element 10 of the present embodiment, the resistance value Rs is reduced from 50.0Ω to -40 to 900 ° C. by keeping the electrode dimension ratio D / L within the range of the formula (2). It can be kept within the range of 500kΩ.
Further, according to this equation (2), the electrode dimension ratio D / L to be adopted is given as a certain range. For example, the distance D between the electrodes is fixed to a convenient value, and the length L is The resistance value Rs of the thermistor element 10 can be easily adjusted by adjustment to change or by fixing the length L to a convenient value and changing the distance D between the electrodes.

By the way, as already described with reference to FIG. 2, the electric lines of force EF pass through a portion (thickness t 1, t 2) of the thermistor element body 1 except for the range of the effective width Weff. . Therefore, the resistance value Rs of the thermistor element also changes depending on the size of the thicknesses t1 and t2 of this portion, and hence the thickness t.
That is, even if the thickness t of the thermistor element body 1 is changed, the B constant cannot be changed. However, by forming the thermistor element body 1 with the thickness t changed, the first electrode portion 2a of the thermistor element 10 is formed. The resistance value Rs generated between the first electrode portion 3a and the second electrode portion 3a can be changed. Specifically, the resistance value Rs can be reduced as the thickness t is increased.

On the other hand, the B constant of the thermistor element body (conductive oxide sintered body) is difficult to form completely the same, even though the thermistor elements have the same product number. When a large number of thermistor elements are seen due to fluctuations in raw materials or changes in the preparation stage, for example, if the thermistor elements (thermistor element bodies) of different production lots manufactured at different times are sampled, the B constant will vary. It is inevitable that this will occur.
Specifically, regarding the raw material powder for the thermistor element body, as a result of the preceding test, when a certain lot is fired, the B constant is slightly higher even if it is within a predetermined allowable range. . On the other hand, when another lot is baked, a state occurs in which the B constant is slightly lower even if it is within a predetermined allowable range.
In addition, by adjusting the firing conditions, it may be possible to correct the tendency of the B constant of the raw material powder, it is possible to influence the other characteristics of the thermistor element body by changing the firing conditions, There are many cases where adoption is difficult.

  In such a case, even if the thermistor elements have the same product number, it is inevitable that the B constant will vary. However, there is a case where there is a demand for suppressing variation in resistance value of each thermistor element in a certain temperature range. For example, one use of the thermistor element 10 is a vehicle temperature sensor 100. Some of the temperature sensors 100 are exposed to a temperature of about 400 to 900 ° C. when the vehicle is operated. Among them, the resistance value of the thermistor element changes, particularly in this high temperature range. Therefore, there is a demand for detecting a temperature change with high accuracy.

In the case where there is such a requirement, the thickness t of the thermistor element 10 is preferably decreased as the B constant of the thermistor element body 1 is increased. In this way, the resistance value Rs of the thermistor element 10 can be made relatively higher than that with a large thickness t.
As a result, when the B constant of the thermistor element body 1 is large, the resistance value Rs of each thermistor element 10 is particularly in the high temperature range of 400 to 900 ° C. where the resistance value is low in the temperature range of −40 to 900 ° C. Tends to be lower. However, a decrease in the resistance value Rs can be suppressed by reducing the thickness t of the thermistor element body 1.
Conversely, when the B constant is small, the resistance value Rs of each thermistor element tends to be high at this high temperature range. However, an increase in the resistance value Rs can be suppressed by increasing the thickness t.
Thus, even if the B constant varies for each thermistor element 10, variations in the resistance value Rs actually taken by the thermistor element 10 at this high temperature range can be suppressed, and temperature detection can be performed more appropriately and accurately. Can do.

Next, the manufacture of the thermistor element 10 of this embodiment will be described.
First, a powder for pressing that becomes a conductive oxide sintered body having a B constant of B (−40 to 900) = 2.00 × 10 ^{3 to} 3.00 × 10 ³ K after sintering is manufactured. The composition of the conductive oxide sintered body (thermistor element body) and the production of the pressing powder (granulated powder) will be described later. Thereafter, in the pressing step, this pressing powder is press-molded into a hexagonal plate shape by a mold molding method.
At that time, as shown in FIG. 4, a pair of first and second electrode wires 2 and 3 made of a Pt—Rh alloy having a diameter φ of φ = 0.250 to 0.400 mm are arranged in parallel. Both ends protrude and an intermediate portion is buried so that an unfired thermistor element 10M is obtained. Thereafter, the thermistor element 10 was manufactured by firing at 1500 ° C. in the atmosphere for 2 hours.
However, in this pressing step, when the unsintered thermistor element 10M is fired, the thickness t is t = 0.500 to 1.20 mm, and the electrode dimension ratio D / L is the above-described formula (1). An unfired thermistor element having a form within the range is formed.

In the thermistor element 10 manufactured as described above, the resistance value Rs (−40) at −40 ° C. can be set to Rs (−40) ≦ 7.00 × 10 ² kΩ. Furthermore, the resistance value Rs (900) at 900 ° C. can be set to Rs (900) ≧ 2.00 × 10 ⁻² kΩ. That is, the resistance value Rs of the thermistor element 10 can be set to Rs = 2.00 × 10 ^{−2 to} 7.00 × 10 ² kΩ in the temperature range of −40 to 900 ° C.
Thus, with this manufacturing method, it is possible to manufacture the thermistor element 10 capable of appropriately detecting the resistance value Rs in the range of −40 to 900 ° C. while using a simple circuit such as a resistance voltage dividing circuit.

More preferably, use is made of a powder for pressing which becomes a conductive oxide sintered body having a B constant of B (−40 to 900) = 2.00 × 10 ^{3 to} 2.50 × 10 ³ K after sintering. Then, an unfired thermistor element having an electrode dimension ratio D / L within the range of the above-described formula (2) is formed and fired.

Then, in this thermistor element 10, the resistance value Rs (−40) can be set to Rs (−40) ≦ 5.00 × 10 ² kΩ. Further, the resistance value Rs (900) can be set to Rs (900) ≧ 5.00 × 10 ⁻² kΩ. That is, at temperature of between -40～900 ° C., the resistance value Rs of the thermistor element 10 can be a ^{Rs = 5.00 × 10 -2 ~5.00 ×} 10 2 kΩ.
Thus, a thermistor element capable of more appropriately detecting the resistance value Rs can be manufactured in the range of −40 to 900 ° C. while using a simple circuit such as a resistance voltage dividing circuit.

  Moreover, according to the formula (1) or (2), since it is given as a range of the electrode dimension ratio D / L, D is fixed to a convenient value and L is changed, or L is This is a manufacturing method in which the thermistor element resistance value Rs can be easily adjusted by adjusting such as fixing D to a good value and changing D.

  Further, in the pressing step, when the thermistor element of the same product number is manufactured, the unsintered thermistor element 10M having a form in which the thickness t decreases as the press powder that increases the B constant of the sintered thermistor element body is used. It is good to mold. Specifically, by adjusting the movement stroke of the mold in the pressing process, the dimension corresponding to the thickness t of the unfired thermistor element 10M becomes smaller as the press powder that increases the B constant of the thermistor element body is used. Adjust so that

By manufacturing the thermistor element 10 (unfired thermistor element 10M) in this way, when the B constant is large, the temperature range of −40 to 900 ° C., in particular, the high temperature range 400 to 900 ° C. at which the resistance value decreases. In this range, it is possible to suppress the resistance value Rs of each thermistor element 10 from becoming lower by reducing the thickness t.
Conversely, if the B constant is small, the resistance value Rs of each thermistor element 10 tends to be high in this high temperature range can be suppressed by increasing the thickness t.
Thus, according to this manufacturing method, it is possible to manufacture the thermistor element 10 which can suppress the variation of the resistance value actually taken in this high temperature range and can detect the temperature more appropriately and accurately.

Next, the production, composition, and characteristics of the conductive oxide sintered body used for the thermistor element 10 (thermistor element body 1) of this example will be described.
In the above description, as the thermistor element 10, the first and second electrode lines 2 and 3 are penetrated through the thermistor element main body 10. Therefore, the first and second electrode portions 2 a and 3 a are both first , Thermistor elements in a form in which a part of the second electrode lines 2 and 3 (first and second connecting portions 2b and 3b and first and second projecting portions 2c and 3c) protrudes (hereinafter also referred to as a penetration type). showed that. On the other hand, in the following description, unlike the above-described penetration type thermistor element 10, the embodiment of the present invention deviates. However, as shown in FIG. 1. Thermistor element 210 (reference examples 1 to 18 and comparative reference examples) in which the end portions on the facing surface 201B side of the first and second electrode portions 202a and 203a are positioned in the thermistor element body 201 (hereinafter also referred to as insertion type) Based on the results obtained by using 1 and 2), the characteristics and the like of the conductive oxide sintered body will be described.
Accordingly, the B constant and the like which are not related to the form of the thermistor element but related to the characteristics of the conductive oxide sintered body can be directly applied to the thermistor element 10 of the present invention (Example). . On the other hand, the resistance value (initial resistance value Rs (-40), Rs (900)) of the thermistor element 210 depends on the form of the thermistor element, and cannot be applied to the thermistor element of the present invention as it is. Is.

First, manufacture of the thermistor elements 210 and 220 having the conductive oxide sintered body and the thermistor element body 201 made of the conductive oxide sintered bodies according to Reference Examples 1 to 18 and Comparative Reference Examples 1 and 2 shown in Table 1 will be described.
First, a calcined powder for the perovskite phase is obtained as follows. That is, Y ₂ O ₃ , Nd ₂ O ₃ , Yb ₂ O ₃ , SrCO ₃ , MgO, CaCO ₃ , MnO ₂ , Fe ₂ O ₃ , Al ₂ O ₃ , Cr ₂ O ₃ (all purity 99) % or more of a commercially available product.) using the formula (when a composition _{formula) M1 a M2 b M3 c Al} d Cr e O 3, elements M1, M2, M3 becomes the combination shown in Table 1 In addition, each a, b, c, d, e is weighed so as to have the number of moles shown in Table 1. Furthermore, the raw material powder mixture for the perovskite phase was prepared by wet mixing and drying these raw material powders. Next, this raw material powder mixture was calcined for 2 hours at 1400 ° C. in an air atmosphere to obtain a calcined powder for the perovskite phase having an average particle diameter of 1 to 2 μm.

On the other hand, the calcined powder for the metal oxide phase according to Reference Examples 1 to 15, 17, 18 and Comparative Reference Example 1 is obtained as follows. That is, SrCO ₃ , Al ₂ O ₃ (all commercially available products with a purity of 99% or more) were used as raw material powders, and weighed so as to have a chemical formula (composition formula) SrAl ₂ O _4. The raw material powder mixture for the metal oxide phase was prepared by wet mixing and drying the raw material powder. Next, this raw material powder mixture was calcined for 2 hours at 1200 ° C. in an air atmosphere to obtain a calcined powder for a metal oxide phase having an average particle diameter of 1 to 2 μm.
In addition, in order to form the reduction-resistant film of Reference Example 17, a binder and a dispersion medium were added to the calcined powder of SrAl ₂ O ₄ and kneaded to separately prepare a slurry for dip coating.

Moreover, the calcined powder for the metal oxide phase according to Reference Example 16 is obtained as follows. That is, as raw material powders, Y ₂ O ₃ and SrCO ₃ (all commercially available products having a purity of 99% or more were used) were weighed so as to have a chemical formula (composition formula) SrY ₂ O _4. The raw material powder mixture for the metal oxide phase was prepared by wet mixing and drying the raw material powder. Next, this raw material powder mixture was calcined for 2 hours at 1200 ° C. in an air atmosphere to obtain a calcined powder for a metal oxide phase having an average particle diameter of 1 to 2 μm.

Next, the calcined powder for the perovskite phase and the calcined powder for the metal oxide phase are weighed, and the calcined powder is used with a resin pot and high-purity Al ₂ O ₃ boulder, with ethanol as the dispersion medium, Wet mixed grinding was performed.

Next, the obtained slurry was dried at 80 ° C. for 2 hours to obtain a thermistor synthetic powder. Thereafter, 20 parts by weight of a binder mainly composed of polyvinyl butyral is added to 100 parts by weight of the thermistor synthetic powder, mixed and dried. Furthermore, it granulated through the sieve of a 250 micrometers mesh, and the granulated powder (powder for press) was obtained.
In addition, as a binder which can be used, it is not specifically limited to the above-mentioned polyvinyl butyral, For example, polyvinyl alcohol, an acrylic binder, etc. are mentioned. The amount of the binder is usually 5 to 20 parts by weight, preferably 10 to 20 parts by weight, based on the total amount of the calcined powder.
Moreover, when mixing with a binder, it is preferable that the average particle diameter of the thermistor synthetic powder is 2.0 μm or less, whereby uniform mixing is possible.

Next, as a pressing step, the above granulated powder (pressing powder) is used and press-molded (pressing pressure: 4500 kg / cm ² ) by a die molding method, and as shown in FIG. 5, Pt-Rh A hexagonal plate-shaped green body (thickness: 1.24 mm) in which one end side of the pair of alloy electrode wires 202 and 203 is embedded is obtained. Then, thermistor element 210 of Reference Examples 1 to 16 and 18 was manufactured by firing at 1500 ° C. in the atmosphere for 2 hours. The thermistor elements according to Comparative Reference Examples 1 and 2 were manufactured in the same manner.
The thermistor element 210 has a hexagonal shape with a side of 1.15 mm, a thickness of 1.00 mm, a diameter φ0.3 mm of the electrode wires 202 and 203, an interelectrode distance of 0.44 mm, and an electrode insertion amount of 1.10 mm.

  In the above description, it was explained that the thermistor element 210 was manufactured by performing press molding and firing by a die molding method using a pressing powder having a predetermined composition and manufacturing method. Also in the manufacture of the thermistor element 10 (unfired thermistor element 10M), a pressing process is performed using the same pressed powder.

Moreover, about the thermistor element of the reference example 17, after immersing the above-mentioned unbaking molded object in the slurry for the above-mentioned dip coating, it pulled up and dried, and the film was formed on the surface of this unbaking molded object. Next, the unfired molded body with a film was fired at 1500 ° C. for 2 hours in the atmosphere, and as shown in FIG. 6, the sintered body 201 and a SrAl ₂ O ₄ anti-resistance comprising the surface densely covered. A thermistor element 220 of Reference Example 17 having a reducing reduction resistant coating 201b was manufactured.

Next, B constants (temperature gradient constants) were measured for the thermistor elements 210 and 220 of Reference Examples 1 to 18 and Comparative Reference Examples 1 and 2 as follows. That is, first, the thermistor elements 210 and 220 are left in an environment where the absolute temperature T (−40) = 233 K (= −40 ° C.), and the initial resistance value Rs (−40) of the thermistor element 10 in that state is determined. It was measured. Next, the thermistor elements 210 and 220 were left in an environment of absolute temperature T (900) = 1173K (= 900 ° C.), and the initial resistance value Rs (900) of the thermistor elements 210 and 220 in that state was measured. And B constant: B (-40-900) was computed according to the following formula | equation (5).
B (-40 to 900) = ln [Rs (900) / Rs (-40)] / [1 / T (900) -1 / T (-40)] (5)
Rs (-40): initial resistance value (kΩ) of the thermistor element at −40 ° C., Rs (900): initial resistance value (kΩ) of the thermistor element at 900 ° C.

The method for measuring the B constant is the same for the thermistor element 10 of this embodiment.
Further, the initial resistance values Rs (-40) and Rs (900) are the same in the thermistor element body in the insertion type thermistor elements 210 and 220 and the penetration type thermistor element 10 of the present embodiment. Even if it exists, since the form of the 1st, 2nd electrode part differs, it becomes a mutually different value. However, since the B constant B (−40 to 900) is a value unique to the conductive oxide sintered body, the thermistor may be used if the composition, manufacturing conditions, firing conditions, etc. of the conductive oxide sintered body are the same. The same value is shown regardless of the form of the element body.

Further, the thermistor elements 210 and 220 according to Reference Examples 1, 2, 3, 6, and 17 are incorporated into the temperature sensor 100 as described later, and the initial resistance values of the thermistor elements 210 and 220 in the state of the temperature sensor 100 are described. Rt (-40) and Rt (900) were measured. Next, the temperature is maintained at 1050 ° C. × 50 Hr in the atmosphere, and thereafter, the resistance values Rt ′ (− 40) after the heat treatment of the thermistor elements 210 and 220 in the state of the temperature sensor 100 at −40 ° C. and 900 ° C., as described above Rt ′ (900) was measured respectively.
Then, from the comparison between the initial resistance value Rt (-40) at -40 ° C. and the post-heat treatment resistance value Rt ′ (-40), the temperature change converted value CT (-40) of the resistance change due to the heat treatment (unit: deg) ) Was calculated by the following formula (6). From the comparison between the initial resistance value Rt (900) at 900 ° C. and the post-heat treatment resistance value Rt ′ (900), the temperature change conversion value CT (900) was calculated by the same equation (7). In addition, the larger one of the temperature change converted values CT (-40) and CT (900) is shown in Table 1 as the temperature change converted value CT (deg).
CT (-40) = [(B (-40 ~ 900) × T (-40)) / [ln (Rt '(-40) / Rt (-40)) × T (-40) + B (-40 ~ 900)]] − T (-40)… (6)
CT (900) = [(B (-40 to 900) × T (900)) / [ln (Rt '(900) / Rt (900)) × T (900) + B (-40 to 900)]] −T (900)… (7)
In the temperature sensor 100, an oxide film is formed in advance on the inner peripheral surface of the metal tube 9 and the metal outer cylinder constituting the sheath member 8. Thereby, even when the thermistor element 10 vicinity of this temperature sensor 100 is made into high temperature, the oxidation of the outer cylinder of the metal tube 9 and the sheath member 8 is suppressed, and the atmosphere in this metal tube 9 is prevented from becoming a reducing atmosphere. Has been. Therefore, it is prevented that the thermistor element 10 is reduced and its resistance value changes.

Further, the thermistor elements 210 and 220 (single unit) according to each reference example and comparative reference example were evaluated for resistance change when a temperature change was repeatedly applied in the atmosphere. Specifically, it is cooled from room temperature (25 ° C.) to −40 ° C. at a temperature decrease rate of −80 deg / Hr, and left at −40 ° C. for 2.5 hours, and the resistance value R1 (−40) of the thermistor element is taking measurement. Thereafter, the temperature is increased to 900 ° C. at a temperature increase rate of +300 deg / Hr, maintained at 900 ° C. for 2 hours, and the resistance value R1 (900) is measured. Next, the temperature is cooled again to −40 ° C. at a temperature drop rate of −80 deg / Hr, maintained at −40 ° C. for 2.5 hours, and the resistance value R 2 (−40) of the thermistor element is measured. Thereafter, the temperature is further increased to 900 ° C. at a temperature increase rate of +300 deg / Hr, maintained at 900 ° C. for 2 hours, and the resistance value R2 (900) is measured.
Based on the comparison between the resistance value R1 (-40) and resistance value R2 (-40) at -40 ° C, the temperature change conversion value DT (-40) (unit: deg) It was calculated by the following formula (8). Further, from the comparison between the resistance value R1 (900) and the resistance value R2 (900) at 900 ° C., the temperature change converted value DT (900) was calculated by the same equation (5). In addition, the larger one of the temperature change converted values DT (-40) and DT (900) is shown in Table 1 as the temperature change converted value DT (deg).
DT (-40) = [(B (-40 ~ 900) x T (-40)) / [ln (R2 (-40) / R1 (-40)) x T (-40) + B (-40 ~ 900)]] − T (-40)… (8)
DT (900) = [(B (-40 to 900) × T (900)) / [ln (R2 (900) / R1 (900)) × T (900) + B (-40 to 900)]] − T (900)… (9)
These results are also shown in Table 1.

The above-described methods for measuring the temperature change converted values CT (-40) and CT (900) and the temperature change converted values DT (-40) and DT (900) are the same for the thermistor element 10 of this embodiment.
Moreover, the temperature change conversion values CT (-40) and CT (900) and the temperature change conversion values DT (-40) and DT (900) are indicators showing the stability of the characteristics of the conductive oxide sintered body. Yes, it is considered to be a value unique to the conductive oxide sintered body. For this reason, if the composition, manufacturing conditions, firing conditions, and the like of the conductive oxide sintered body are the same, the same value is exhibited regardless of the form of the thermistor element body.

Moreover, the cross-sectional structure | tissue photograph of the sintered compact (thermistor element main body 201) was image | photographed as follows, and area fraction SP / S was computed.
First, a sample was prepared by embedding the sintered body in a resin and performing a buffing treatment using a 3 μm diamond paste to polish the cross section. Thereafter, the cross section is photographed at a magnification of 3000 times with a scanning electron microscope (trade name: JSM-6460LA, manufactured by JEOL). FIG. 7 shows a cross-sectional photograph of the sintered body according to Reference Example 6. From the composition analysis by EDS, the white portion is the perovskite phase and the dark gray portion is the metal oxide phase (specifically, SrAl ₂ O ₄ ). The black part is a pore. A 40 μm × 30 μm field of view of the photographed tissue photograph was analyzed with an image analyzer, and the ratio (area fraction) SP / S of the phase area SP of the perovskite phase to the field of view (cross-sectional area S) was determined.
The measuring method of the area fraction SP / S is the same for the thermistor element 10 of this embodiment. The area fraction SP / S is an index that does not depend on the form of the thermistor element body.

  In a sintered body composed of a composite phase, the area fraction occupied by a specific phase in an arbitrary cross section is equal to the volume fraction occupied by the specific phase in the sintered body. That is, this area fraction SP / S is equal to the volume fraction of the perovskite phase in the thermistor element body (sintered body) 201. Further, as can be seen with reference to FIG. 7, the thermistor element body (sintered body) 201 of the present reference example is composed of two phases of a perovskite phase and a metal oxide phase. The rate SP / S substantially indicates the area ratio and volume ratio of the perovskite phase and the metal oxide phase.

First, Reference Examples 1 to 7 and 18 will be described. According to Table 1, M1 = Y, M2 = Sr, and M3 = Mn. Formula _{Y a Sr b Mn c Al d} Cr e O f values a, b, c, d, e, f are conductive satisfies the following conditional expression and perovskite phase, of electrically conductive than the perovskite phase In the thermistor element 10 using the thermistor element body 201 made of the conductive oxide sintered body of Reference Examples 1 to 7 and 18, which is made of a low metal oxide phase (SrAl ₂ O _{4 in} this reference example), B Constant: B (−40 to 900) is a conductive oxide sintered body (thermistor element 210) having a relatively low value of B (−40 to 900) = 2000 to 3000 K as compared with the prior art.
0.600 ≦ a ≦ 1.000
0 ≦ b ≦ 0.400
0.150 ≦ c <0.600
0.400 ≦ d ≦ 0.800
0 <e ≦ 0.050
0 <e / (c + e) ≦ 0.18
2.80 ≦ f ≦ 3.30

Although the value f is not described in Table 1, the composition ratio of each element of Y, Sr, Mn, Al, Cr, O using fluorescent X-ray analysis and the area calculated by the above-described method. From the rate or presence / absence ratio of the crystal phase identified by powder X-ray diffraction analysis, it is confirmed that f is in the range of 2.80 to 3.30. Specifically, in this reference example, the abundance ratio of the perovskite phase and the metal oxide phase (SrAl ₂ O ₄ ) is specified, and the amount of each metal element is distributed to the perovskite phase and the metal oxide phase. Then, after determining that the number of O contained in the metal oxide phase (SrAl ₂ O ₄ ) is 4 (that is, SrAl ₂ O ₄ has no oxygen deficiency), By calculating the amount of O used, the number f of O in the perovskite phase is calculated.

In addition to the perovskite phase, the sintered body also contains a metal oxide phase (SrAl ₂ O ₄ ) having a lower conductivity than the perovskite phase. Compared with Comparative Reference Example 2), the resistance value indicated by the thermistor element 210 such as the initial resistance values Rs (-40) and Rs (900) can be increased while maintaining the B constant, and the perovskite phase The resistance value can be adjusted to an appropriate value depending on the amount ratio of the metal oxide phase.

This will be specifically described. In the sintered body of Comparative Reference Example 2 in which no metal oxide phase (SrAl ₂ O ₄ ) is present, the B constant (B (−40 to 900) = 2553 K) is appropriate, but the thermistor element in the form of this Reference Example In the case of 210, since the sintered body is composed of only the perovskite phase having a relatively high conductivity, the initial resistance values Rs (-40) = 39 kΩ, Rs (900) = 0.006 kΩ (= 6Ω), the resistance value of the thermistor element 10 is low, and the resistance value measurement tends to be difficult.

  On the other hand, the composition of the perovskite phase (values a to e) is the same as that of Comparative Reference Example 2, but a metal oxide phase having relatively low conductivity is generated, and the area fraction of the perovskite phase is 30 to 30%. In the sintered bodies of Reference Examples 1, 2, and 3 set to about 40%, the resistance value can be made higher than that of Comparative Reference Example 2 by the amount of the metal oxide phase increased (therefore, the amount of the perovskite phase decreased). . For example, in the sintered body of the reference example 1 (thermistor element 210), the initial resistance values Rs (-40) = 423 kΩ and Rs (900) = 0.088 kΩ are obtained, and it can be seen that the resistance value can be set to an easy resistance value.

  In addition, in Reference Example 7 in which a large amount of metal oxide phase having lower conductivity is generated and the area fraction of the perovskite phase is about 16%, the resistance value is further increased. Specifically, the initial resistance values Rs (-40) = 41400 kΩ and Rs (900) = 5.92 kΩ. From this, the proportion of the metal oxide phase in the sintered body, and accordingly, by appropriately adjusting the area fraction of the perovskite phase, the specific resistance value is shifted, and the resistance value of the thermistor element 210 is changed to the resistance value. It can be seen that the resistance value can be set easily.

  On the other hand, in the sintered bodies of Reference Examples 1, 2, 3 and Reference Example 7, the B constant is a value around 2500 K, which is almost the same as the B constant of Comparative Reference Example 2. That is, it can be seen that the B constant does not change even when a metal oxide phase is generated.

Also, according to Table 1, Reference Examples 1 to 7 and 18 using Y as the element M1, Reference Examples 8 and 9 using Nd as the element M1, and Reference examples using Y and Yb as the element M1 Similarly, 10 and 11 are conductive oxide sintered bodies (thermistor element 210) having a B constant of B (−40 to 900) = 2000 to 3000K, which is a relatively low value as compared with the prior art. I can see that Further, as in Reference Examples 1 to 7 and 18 as well, the resistance value of the thermistor element 210 is appropriately adjusted by changing the quantitative ratio between the perovskite phase and the metal oxide phase (SrAl ₂ O _{4 in} this example). Can be adjusted to the value.

Furthermore, according to Table 1, in contrast to Reference Examples 1 to 7 using Sr as the element M2, Sr and Mg as the element M2, or Reference Examples 12, 13, and 14 using Sr and Ca are similarly used. It can be seen that the conductive oxide sintered body (thermistor element 210) having a B constant of B (−40 to 900) = 2000 to 3000 K, which is a relatively low value compared to the conventional one. Further, as in Reference Examples 1 to 7, these also change the resistance ratio of the thermistor element 10 to an appropriate value by changing the quantitative ratio between the perovskite phase and the metal oxide phase (SrAl ₂ O _{4 in} this example). Can be adjusted.
The same applies to Reference Examples 1 to 7 using Mn as the element M3 and Example 15 using Fe as the element M3.

Further, in Reference Examples 16 using SrY ₂ O ₄ as opposed to Reference Examples 1 to 7 using SrAl ₂ O ₄ as the metal oxide phase, similarly, a perovskite phase and a metal oxide phase (in this example, SrY The resistance value of the thermistor element 10 can be set to an appropriate value by changing the quantity ratio with ₂ O ₄ ).

In Reference Example 18, a conductive oxide sintered body (thermistor element 10) having a perovskite phase not containing Sr (b = 0) is shown. However, in addition to Y, a conductive oxide containing Sr is also shown. It is preferable to use a sintered body (thermistor element 10).
That is, as shown in Reference Examples 1 to 17, it is preferable that a <1.000, b> 0. In the sintered body according to Reference Example 18 having a perovskite phase that does not contain Sr or the like (Group A element M2) (b = 0), when a large number of these sintered bodies (thermistor elements 210 and 220) are produced, There is a tendency that the characteristic variation and the characteristic variation between firing lots tend to be large. In comparison, for example, in the sintered bodies of Reference Examples 1 to 17 containing Sr and the like (Group 2A element M2) in addition to Y and the like (Group 3A element M1), the characteristics between the individual members are relatively large. Variations and variation in characteristics between firing lots can be reduced.

  Further, the thermistor element 220 according to Reference Example 17 having the reduction-resistant film 201b can be similarly formed as the thermistor element 220 having the B constant and the resistance value in an appropriate range as in Examples 1-7. Further, the thermistor element 220 according to this reference example 17 has a reduction resistant coating 201b. For this reason, for example, when the thermistor element 220 according to the reference example 17 is assembled to the temperature sensor 100 described later, a part of the oxide film formed on the outer tube of the metal tube 9 or the sheath member 8 is damaged for some reason. Even if the periphery of the thermistor element 220 becomes a reducing atmosphere due to oxidation of the outer tube of the metal tube 9 or the sheath member 8 due to a defect in the oxide film, the internal sintered body (thermistor) Since the element main body 201 is prevented from being reduced, the resistance value can be further stably maintained.

  The sintered body of Comparative Reference Example 1 was d = 0, that is, the perovskite phase did not contain Al. The sintered body (thermistor element body) according to Comparative Reference Example 1 has an appropriate B constant (B (-40 to 900) = 2137K), but generates a large amount of a metal oxide phase, resulting in a perovskite phase. In this case, the initial resistance values Rs (-40) = 14 kΩ and Rs (900) = 0.09 kΩ. This is because the conductivity of the perovskite phase is high (specific resistance is low), and the resistance value of the thermistor element 210 cannot be sufficiently high even by the presence of a large amount of metal oxide phase. Thus, in a sintered body having a perovskite phase in which a to f are out of the range of the conditional expression described above, the specific resistance (and hence the resistance value of the thermistor element) and the B constant are not appropriate.

  Thus, the thermistor elements 210 and 220 using the conductive oxide sintered bodies (thermistor element body 201) having the respective compositions of this reference example have resistance over a wide range from a low temperature of −40 ° C. to a high temperature of 900 ° C. It can have a B constant of 2000-3000K, suitable for performing measurements. Furthermore, the thermistor elements 210 and 220 have a resistance value by appropriately adjusting the number of metal oxide phases in the sintered body, that is, the area fraction of the perovskite phase, according to the shape, the distance between the electrode wires, and the like. The size can be adjusted, and an appropriate resistance value can be obtained over a wide range from a low temperature of −40 ° C. to a high temperature of 900 ° C. Thereby, according to the thermistor elements 210 and 220 of this reference example, temperature measurement can be appropriately performed over a wide range from a low temperature of −40 ° C. to a high temperature of 900 ° C.

  The range of the B constant is preferably B (-40 to 900) = 2000 to 2900K, and more preferably B (-40 to 900) = 2000 to 2800K. . More preferably, B (−40 to 900) = 2000 to 2500K.

Furthermore, in Table 1, in the temperature sensor 100 in which the thermistor elements 210 and 220 using the conductive oxide sintered bodies (thermistor element body 201) shown in the columns of Reference Examples 1, 2, 3, 6, and 17 are assembled, The temperature change conversion value CT (deg) was a good value within ± 10 deg. A standard for determining whether or not the sintered body (thermistor elements 210 and 220, temperature sensor 100) has a characteristic that the resistance change with respect to the thermal history is small is considered that the temperature change conversion value CT is ± 10 deg. It is done. This is because the sintered bodies (thermistor elements 210 and 220) of each reference example are included in the range of this standard. In particular, in the sintered bodies (Thermistor elements 210 and 22 and the temperature sensor 100) of Reference Examples 2, 3, 6, and 17, CT is a value within ± 3 deg. It turns out that it becomes a sintered compact (thermistor element) with a small resistance change with respect to a thermal history.
In addition, about the sintered compact of other reference examples 4, 5, 7-16, 18, the measurement result of temperature change conversion value CT is not specified.

However, the temperature change conversion value DT measured by the above-described method is measured for any of the reference examples and the comparative reference example. In any reference example, the temperature change conversion value DT was within ± 10 deg.
The temperature change conversion value DT is ± 10 deg as a guideline for determining whether or not the sintered body 1 (thermistor element 10) has the characteristic that the resistance change with respect to the thermal history is small even with this temperature change conversion value DT. it is conceivable that. Since the sintered bodies (thermistor elements 210 and 220) of the reference examples 1 to 18 are all included in the range of this guideline, the thermistor elements 210 and 220 of the reference examples 1 to 18 are both heated. It can be seen that the resistance change with respect to the history is small, and that the sintered body (thermistor element) can be used without any practical problem.

  Next, the configuration of the temperature sensor 100 using the thermistor element 10 according to the present embodiment will be described with reference to FIG. The same applies to the temperature sensor 100 using the thermistor elements 210 and 220 according to the reference example described above. The temperature sensor 100 uses the thermistor element 10 (210, 220) as a temperature-sensitive element. The temperature sensor 100 is mounted on a mounting portion of an exhaust pipe of an automobile, and the exhaust gas flows through the thermistor element 10. It is arranged in a pipe and used for temperature detection of exhaust gas.

  In the temperature sensor 100, the metal tube 9 extending in the direction along the axis AX (hereinafter also referred to as the axis direction) has a bottomed cylindrical shape with the tip 91 side (downward in FIG. 2) closed. The thermistor element 10 of this embodiment is housed inside the tip 91. The metal tube 9 is heat-treated in advance, and the outer side surface and inner side surface thereof are oxidized and covered with an oxide film. A cement 14 is filled around the thermistor element 10 inside the metal tube 9 to fix the thermistor element 10. The rear end 92 of the metal tube 9 is open, and the rear end 92 portion is press-fitted and inserted into the flange member 4.

  The flange member 4 is positioned on the distal end side (downward in FIG. 2) of the cylindrical sheath portion 42 extending in the axial direction, and has a larger outer diameter than the sheath portion 42 and has a radial direction. And a flange portion 41 protruding outward. On the distal end side of the flange portion 41, there is a tapered seating surface 45 that seals with the attachment portion of the exhaust pipe. Moreover, the sheath part 42 has comprised the two-stage shape which consists of the front end side sheath part 44 located in the front end side, and the rear end side sheath part 43 smaller in diameter than this.

  The metal tube 9 press-fitted into the flange member 4 is firmly fixed to the flange 4 by laser welding of the outer peripheral surface thereof at the portion L1 over the entire circumference in the circumferential direction with the rear end side sheath portion 43. Yes. Moreover, the substantially cylindrical metal cover member 6 is press-fitted into the distal end side sheath portion 44 of the flange member 4, and is laser-welded at the portion L2 over the entire circumference in the circumferential direction and joined in an airtight state.

  An attachment member 5 having a hexagon nut 51 and a screw 52 is rotatably fitted around the flange member 4 and the metal cover member 6. The temperature sensor 100 of the present embodiment is configured so that the seat surface 45 of the flange portion 41 of the flange member 4 is brought into contact with the attachment portion of the exhaust pipe (not shown) and the nut 5 is screwed into the attachment portion, thereby Fix it.

Inside the metal tube 9, the flange member 4, and the metal cover member 6, a sheath member 8 that includes a pair of core wires 7 is disposed. The sheath member 8 includes a metal outer tube, a pair of conductive core wires 7, and an insulating powder that fills the outer tube and holds the core wire 7 while insulating between the outer tube and each core wire 7. It is configured. An oxide film is also formed in advance on the outer cylinder of the sheath member 8 by heat treatment.
The first and second electrode wires 2 and 3 of the thermistor element 10 are connected by laser welding to the core wire 7 protruding from the tip of the outer cylinder of the sheath member 8 inside the metal tube 9 (downward in the figure). .
On the other hand, the core wire 7 protruding from the sheath member 8 toward the rear end side is connected to a pair of lead wires 12 via a crimping terminal 11. The core wires 7 and the crimping terminals 11 are insulated from each other by an insulating tube 15.

  The pair of lead wires 12 are drawn out from the inside of the metal cover member 6 to the outside through the lead wire insertion holes of the elastic seal member 13 inserted inside the rear end portion of the metal cover member 6, (It is not shown. For example, it is connected to the terminal member of the connector 21 for connecting with ECU.). As a result, the output of the thermistor element 10 is extracted from the core wire 7 of the sheath member 8 to the external circuit (not shown) via the lead wire 12 and the connector 21, and the temperature of the exhaust gas is detected. The lead wire 12 is covered with a glass braided tube 20 for protection from external forces such as stepping stones, and the glass braided tube 20 is fixed by crimping to the metal cover member 6 with its elastic end member 13 together with the elastic seal member 13. Has been.

As described above, the temperature sensor 100 having such a structure is made of a conductive oxide sintered body having a predetermined composition, and has an appropriate B constant (B (−40 to 900) = 2.00 × 10 ^3. -3.00 × 10 ³ K, or 2.00 × 10 ^{3 to} 2.50 × 10 ³ K), and a suitable electrode satisfying the formula (1) or (2) A thermistor element 10 having a dimension such as a dimension ratio D / L is used. For this reason, the magnitude of the resistance value Rs of the thermistor element 10 can fall within a range of 20Ω to 700 kΩ (or 50Ω to 500 kΩ) over a wide range from a low temperature of −40 ° C. to a high temperature of 900 ° C. This is a temperature sensor that can appropriately measure the temperature of the exhaust gas of an automobile engine by using a resistance voltage dividing circuit having a simple configuration.

  In addition, about manufacture of the temperature sensor 100, since it should just be based on the above-mentioned description and a well-known method, description is abbreviate | omitted.

In the above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the above-described embodiments, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof. .
For example, the thermistor element 10 of the embodiment illustrated in FIG. 4 is configured to have first and second electrode lines 2 and 3 penetrating between the opposing surfaces 1A and 1B of the hexagonal plate-like thermistor body 1.
However, for example, as shown in FIG. 9A, a linear thermistor element main body 61 and a linear first electrode penetrating in parallel between the opposing parallel opposing surfaces 61A and 61B of the thermistor element main body 61. The thermistor element 60 having the first electrode line 62 and the second electrode line 63 having the part 62a, the second electrode part 63a may be used. Further, as shown in FIG. 9B, a disc-shaped thermistor element main body 71 and a linear first electrode portion penetrating in parallel between opposing parallel facing surfaces 71A and 71B of the thermistor element main body 71. The thermistor element 70 having the first electrode line 72 having the second electrode part 73a and the second electrode line 73 having the second electrode part 73a may be used.

In the production of the thermistor element, the powder of the compound containing each element exemplified in the examples can be used as the raw material powder of the conductive oxide sintered body constituting the thermistor element body. In addition, compounds such as oxides, carbonates, hydroxides, and nitrates can be used. In particular, oxides and carbonates are preferably used.
In addition, when required for conductive oxide sintered bodies, thermistor elements, or temperature sensors, such as the sinterability of conductive oxide sintered bodies, the B constant, and the high temperature durability of temperature characteristics, the characteristics are not impaired. The conductive oxide sintered body may contain other components such as Na, K, Ga, Si, C, Cl, and S.

It is explanatory drawing which shows the relationship between a 1st electrode part and a 2nd electrode part, and uses for description of B, C, D term in Formula (1), (2). It is explanatory drawing which shows the relationship between a 1st electrode part and a 2nd electrode part, and the electric force line | wire which generate | occur | produces between these, and uses for description of D term in Formula (1), (2). It is the graph which plotted the change of resistance value Rs when changing element remaining thickness Y in a standard thermistor element. It is applied to the thermistor element of an example, (a) is the perspective view, and (b) is a top view. It is a top view which shows the structure of the thermistor element of the reference example shown in Table 1, and a comparative reference example. It is a fragmentary sectional view which shows the structure of the thermistor element concerning the reference example 17 shown in Table 1. FIG. It is a scanning electron microscope (SEM) photograph which shows the structural example (Example 6) in the cross section of an electroconductive oxide sintered compact. FIG. 5 is a partially broken sectional view showing a structure of a temperature sensor using the thermistor element of FIG. 4. It is a perspective view which shows the other form of the thermistor element of this invention.

Explanation of symbols

10, 60, 70, 210, 220 Thermistor element 10M Unfired thermistor element 100 Temperature sensor 1, 61, 71, 201 Thermistor element body 1A, 1B Opposing surface 2 First electrode line 2a First electrode part 2ac (first electrode part) Center line 2b first connection portion 2c first projection portion 3 second electrode line 3a second electrode portion 3ac center line 3b (second electrode portion) 21st connection portion 3c second projection portion φ (first electrode portion) , Diameter D of the second electrode part) distance L between the first electrode part and the second electrode part D length of the first electrode part and the second electrode part D / L electrode size ratio Deff effective distance Weff Effective width CP Virtual midpoint P (between first electrode portion and second electrode portion) Virtual plane DR1 Virtual plane orthogonal direction t Thickness t1, t2 (in the direction perpendicular to the virtual plane passing through the virtual midpoint of the thermistor element body) Thickness Y Element remaining thickness Ts (Thermistor element) temperature Rs (thermistor element) (thermistor element) resistance value T0 initial temperature R0 (thermistor element) initially resistance

Claims (9)

A thermistor element body made of a conductive oxide sintered body having a B constant of B (−40 to 900) = 2.00 × 10 ^{3 to} 3.00 × 10 ³ K;
A first electrode line having a first electrode portion that has a circular cross section and extends linearly through the thermistor element body;
A second electrode line paired with the first electrode line,
A second electrode wire penetrating the thermistor element body in parallel to the first electrode portion and extending in a straight line, having a circular cross section and having a second electrode portion having the same diameter and length as the first electrode portion; With
The thermistor element main body passes through a virtual midpoint between the first electrode portion and the second electrode portion, and has a thickness in a virtual plane orthogonal direction orthogonal to a virtual plane connecting the first electrode portion and the second electrode portion. t is t = 0.500 to 1.20 mm;
The first electrode portion and the second electrode portion have a diameter φ of φ = 0.250 to 0.400 mm,
The length of the first electrode part and the second electrode part is L (mm),
The inter-electrode distance between the first electrode part and the second electrode part is D (mm),
When the remaining element thickness is Y (mm) = t−φ / √2,
A thermistor element having an electrode dimension ratio D / L in the range of the following formula (1).
[(2.00 × 10 ^-2 × 0.410) / (7.00 × 10 ² × exp (B × -3.44 × 10 ^-3 ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)]
≦ D / L ≦
[(7.00 × 10 ² × 0.410) / (2.00 × 10 ⁻² × exp (B × 3.44 × 10 ⁻³ ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)] (1) A thermistor element body made of a conductive oxide sintered body having a B constant of B (−40 to 900) = 2.00 × 10 ^{3 to} 2.50 × 10 ³ K;
A first electrode line having a first electrode portion that has a circular cross section and extends linearly through the thermistor element body;
A second electrode line paired with the first electrode line,
A second electrode wire penetrating the thermistor element body in parallel to the first electrode portion and extending in a straight line, having a circular cross section and having a second electrode portion having the same diameter and length as the first electrode portion; With
The thermistor element main body passes through a virtual midpoint between the first electrode portion and the second electrode portion, and has a thickness in a virtual plane orthogonal direction orthogonal to a virtual plane connecting the first electrode portion and the second electrode portion. t is t = 0.500 to 1.20 mm;
The first electrode portion and the second electrode portion have a diameter φ of φ = 0.250 to 0.400 mm,
The length of the first electrode part and the second electrode part is L (mm),
The inter-electrode distance between the first electrode part and the second electrode part is D (mm),
When the remaining element thickness is Y (mm) = t−φ / √2,
A thermistor element having an electrode dimension ratio D / L within the range of the following formula (2).
[(5.00 × 10 ^-2 × 0.410) / (5.00 × 10 ² × exp (B × -3.44 × 10 ^-3 ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)]
≦ D / L ≦
[(5.00 × 10 ² × 0.410) / (5.00 × 10 ⁻² × exp (B × 3.44 × 10 ⁻³ ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)] (2) The thermistor element according to claim 1 or 2,
For many thermistor elements of the same product number, when the correlation between the B constant of the thermistor element body and the thickness t is viewed,
A thermistor element having a correlation in which the thermistor element having a larger B constant of the thermistor element body has a smaller thickness t. The thermistor element according to any one of claims 1 to 3,
The conductive oxide sintered body forming the thermistor element body is,
At least one of the 3A group elements excluding La is M1,
At least one of the 2A group elements is M2,
When at least one element of 4A, 5A, 6A, 7A and group 8 elements excluding Cr is M3,
Is expressed by the composition formula _{M1 a M2 b M3 c Al d} Cr e O f,
a, b, c, d, e, f satisfy the following conditional expression,
A conductive perovskite phase having a perovskite crystal structure;
Less conductive than the perovskite phase,
When at least one metal element selected from the metal elements constituting the perovskite phase is Me,
A thermistor element, which is a conductive oxide sintered body, comprising at least one metal oxide phase having a crystal structure represented by a composition formula MeO _x .
0.600 ≦ a ≦ 1.000
0 ≦ b ≦ 0.400
0.150 ≦ c <0.600
0.400 ≦ d ≦ 0.800
0 <e ≦ 0.050
0 <e / (c + e) ≦ 0.18
2.80 ≦ f ≦ 3.30 The temperature sensor which uses the thermistor element of any one of Claims 1-4. A thermistor element body made of a conductive oxide sintered body having a B constant of B (−40 to 900) = 2.00 × 10 ^{3 to} 3.00 × 10 ³ K;
A first electrode line having a first electrode portion that has a circular cross section and extends linearly through the thermistor element body;
A second electrode line paired with the first electrode line,
A second electrode wire penetrating the thermistor element body in parallel to the first electrode portion and extending in a straight line, having a circular cross section and having a second electrode portion having the same diameter and length as the first electrode portion; A thermistor element manufacturing method comprising:
In the thermistor element,
Of the thermistor element body, passing through a virtual midpoint between the first electrode portion and the second electrode portion, in a virtual plane orthogonal direction orthogonal to a virtual plane connecting the first electrode portion and the second electrode portion. The thickness is t (mm),
The diameter of the first electrode part and the second electrode part is φ (mm),
The length of the first electrode part and the second electrode part is L (mm),
The inter-electrode distance between the first electrode part and the second electrode part is D (mm),
When the remaining element thickness is Y (mm) = t−φ / √2,
A pressing step of press-molding an unfired thermistor element using the pressing powder that becomes the conductive oxide sintered body after sintering, the first electrode wire, and the second electrode wire,
When firing the unfired thermistor element,
The thickness t is t = 0.500 to 1.20 mm,
The diameter φ is φ = 0.250-0.400 mm,
A method for manufacturing a thermistor element comprising a pressing step of forming the unfired thermistor element having an electrode dimension ratio D / L within the range of the following formula (1).
[(2.00 × 10 ^-2 × 0.410) / (7.00 × 10 ² × exp (B × -3.44 × 10 ^-3 ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)]
≦ D / L ≦
[(7.00 × 10 ² × 0.410) / (2.00 × 10 ⁻² × exp (B × 3.44 × 10 ⁻³ ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)] (1) A thermistor element body made of a conductive oxide sintered body having a B constant of B (−40 to 900) = 2.00 × 10 ^{3 to} 2.50 × 10 ³ K;
A first electrode line having a first electrode portion that has a circular cross section and extends linearly through the thermistor element body;
A second electrode line paired with the first electrode line,
A second electrode wire penetrating the thermistor element body in parallel to the first electrode portion and extending in a straight line, having a circular cross section and having a second electrode portion having the same diameter and length as the first electrode portion; A thermistor element manufacturing method comprising:
In the thermistor element,
Of the thermistor element body, passing through a virtual midpoint between the first electrode portion and the second electrode portion, in a virtual plane orthogonal direction orthogonal to a virtual plane connecting the first electrode portion and the second electrode portion. The thickness is t (mm),
The diameter of the first electrode part and the second electrode part is φ (mm),
The length of the first electrode part and the second electrode part is L (mm),
The inter-electrode distance between the first electrode part and the second electrode part is D (mm),
When the remaining element thickness is Y (mm) = t−φ / √2,
A pressing step of press-molding an unfired thermistor element using the pressing powder that becomes the conductive oxide sintered body after sintering, the first electrode wire, and the second electrode wire,
When firing the unfired thermistor element,
The thickness t is t = 0.500 to 1.20 mm,
The diameter φ is φ = 0.250-0.400 mm,
A method for manufacturing a thermistor element comprising a pressing step of forming the unfired thermistor element having an electrode dimension ratio D / L within the range of the following formula (2).
[(5.00 × 10 ^-2 × 0.410) / (5.00 × 10 ² × exp (B × -3.44 × 10 ^-3 ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)]
≦ D / L ≦
[(5.00 × 10 ² × 0.410) / (5.00 × 10 ⁻² × exp (B × 3.44 × 10 ⁻³ ))]
× [(0.410+ (1-1 / √2) × 0.300) / (D + (1-1 / √2) φ)]
× (φ / 0.300)
× [0.278 / (0.474Y ² −0.919Y + 0.698)] (2) A thermistor element manufacturing method according to claim 6 or 7,
The pressing step includes
When manufacturing thermistor elements of the same part number,
When using a press powder that increases the B constant of the thermistor element body after sintering,
A method for manufacturing a thermistor element, wherein the green thermistor element is formed in a form in which the thickness t is reduced. It is a manufacturing method of the thermistor element given in any 1 paragraph of Claims 6-8,
The conductive oxide sintered body forming the thermistor element body is,
At least one of the 3A group elements excluding La is M1,
At least one of the 2A group elements is M2,
When at least one element of 4A, 5A, 6A, 7A and group 8 elements excluding Cr is M3,
Is expressed by the composition formula _{M1 a M2 b M3 c Al d} Cr e O f,
a, b, c, d, e, f satisfy the following conditional expression,
A conductive perovskite phase having a perovskite crystal structure;
Less conductive than the perovskite phase,
When at least one metal element selected from the metal elements constituting the perovskite phase is Me,
A method for producing a thermistor element, which is a conductive oxide sintered body, comprising at least one metal oxide phase having a crystal structure represented by a composition formula MeO _x .
0.600 ≦ a ≦ 1.000
0 ≦ b ≦ 0.400
0.150 ≦ c <0.600
0.400 ≦ d ≦ 0.800
0 <e ≦ 0.050
0 <e / (c + e) ≦ 0.18
2.80 ≦ f ≦ 3.30