JP6386859B2 - heater - Google Patents

Description

  The present invention relates to a heater used for a liquid heating heater, a powder heating heater, a gas heating heater, an oxygen sensor heater, and the like.

  As a heater used for a liquid heating heater, a powder heating heater, a gas heating heater, an oxygen sensor heater, and the like, for example, a heater device disclosed in Patent Document 1 is known. The heater device disclosed in Patent Document 1 includes a metal case, a ceramic heater inserted into the metal case, and a metal layer formed by casting between the inner surface of the metal case and the surface of the ceramic heater. I have.

  As a ceramic heater, for example, a ceramic heater disclosed in Patent Document 2 is known. The ceramic heater disclosed in Patent Document 2 has a groove along the length direction of the ceramic heater.

Japanese Patent Laid-Open No. 9-22774 JP 2001-257062 A

  When the ceramic heater disclosed in Patent Document 2 is used as the ceramic heater used in the heater device disclosed in Patent Document 1, it is difficult to improve the long-term reliability of the heater device. Specifically, when the metal layer is formed by casting, the metal layer may enter the groove portion of the ceramic heater. When the heater device is used in this state, there is a possibility that a large thermal stress is generated between the metal layer located inside the groove and the groove. As a result, there is a possibility that a crack starting from the groove portion may occur in the ceramic heater.

  This invention is made | formed in view of this problem, The objective is to improve long-term reliability in a heater apparatus.

A heater according to an aspect of the present invention includes a columnar or cylindrical ceramic body having a groove portion along a length direction on an outer peripheral surface, a heating resistor provided inside the ceramic body, and the ceramic body among the ceramic bodies. A metal cylinder in which a portion provided with a heating resistor is inserted, and a filler made of a metal material filled between the outer peripheral surface of the ceramic body and the inner peripheral surface of the metal cylinder, There is a gap between the ceramic body and the filler, and the thermal expansion coefficient of the filler is higher than the thermal expansion coefficient of the metal cylinder .

  According to the heater of one embodiment of the present invention, long-term reliability of the heater can be improved.

It is sectional drawing which shows one Embodiment of the heater of this invention. It is a perspective view which shows a ceramic body among the heaters of this invention. It is a fragmentary sectional view which shows the groove part vicinity of a ceramic body among the heaters of this invention.

  The heater 10 according to an embodiment of the present invention will be described in detail.

  FIG. 1 is a cross-sectional view showing an example of an embodiment of a heater 10 of the present invention. As shown in FIG. 1, the heater 10 is provided with a columnar or cylindrical ceramic body 1, a heating resistor 2 provided inside the ceramic body 1, and a heating resistor 2 of the ceramic body 1. A metal cylinder 3 in which a portion is inserted and a filler 4 made of a metal material filled between the outer peripheral surface of the ceramic body 1 and the inner peripheral surface of the metal cylinder 3 are provided.

  The ceramic body 1 is a member provided to protect the heating resistor 2. The shape of the ceramic body 1 is columnar or cylindrical. Examples of the columnar shape include a columnar shape or a prismatic shape. In addition, the column shape here includes, for example, a plate shape extending long in a specific direction. Examples of the cylindrical shape include a cylindrical shape and a rectangular tube shape. In the heater 10 shown in FIG. 1, the ceramic body 1 has a cylindrical shape.

  The ceramic body 1 is made of an insulating ceramic material. Examples of the insulating ceramic material include alumina, silicon nitride, and aluminum nitride. From the viewpoint of excellent thermal conductivity, it is preferable to use aluminum nitride. In particular, when aluminum nitride is used, the thermal conductivity of the ceramic body 1 can be increased to 150 W / (m · K), so the heat generated in the heating resistor 2 formed inside the ceramic body 1 can be used as the filler 4. Can communicate efficiently. Accordingly, the heater 10 can be rapidly heated. From the viewpoint of ease of production, it is preferable to use alumina. When the ceramic body 1 is cylindrical, the dimensions of the ceramic body 1 can be set, for example, to a length of 100 mm and an outer diameter of 20 mm. When the ceramic body 1 is plate-shaped, the dimensions of the ceramic body 1 can be set, for example, to a length of 80 mm, a width of 50 mm, and a thickness of 2 mm. When the ceramic body 1 is cylindrical, the dimensions of the ceramic body 1 can be set, for example, to a length of 100 mm, an outer diameter of 20 mm, and an inner diameter of 14 mm.

  As shown in FIG. 2, the ceramic body 1 has a groove portion 11 along the length direction on the outer peripheral surface. In the present embodiment, a groove 11 is provided from one end of the ceramic body 1 to the other end. As shown in FIG. 3, the cross-sectional shape of the groove part 11 is formed so that the bottom face 12 becomes circular arc shape, for example. The dimensions of the groove 11 in such a case can be set, for example, to a depth of about 0.2 to 0.8 mm and a width of about 0.4 to 2.4 mm.

  The heating resistor 2 is a resistor that generates heat when a current flows. The heating resistor 2 is provided inside the ceramic body 1. That is, the heating resistor 2 is embedded in the ceramic body 1. The heating resistor 2 in the heater 10 of the present embodiment has a folded shape. Both ends of the heating resistor 2 are connected to the extraction electrode 21. The extraction electrode 21 is extracted to one end portion of the ceramic body 1, and is extracted to the outer peripheral surface of the ceramic body 1 at the end portion. In the present embodiment, the extraction electrode 21 is extracted to the outside at a portion of the ceramic body 1 located outside the metal cylinder 3.

  In the present embodiment, the folded portion of the heating resistor 2 is provided at the other end of the ceramic body 1. That is, the extraction electrode 21 is provided in a region of the ceramic body 1 opposite to the folded portion of the heating resistor 2. Both end portions of the heating resistor 2 are electrically connected to the electrode layer 6 provided on the outer peripheral surface of the ceramic body 1 via the extraction electrode 21.

The heating resistor 2 is made of a metal material. Examples of the metal material include tungsten, molybdenum, rhenium, and the like. The dimensions of the heating resistor 2 can be set, for example, to a width of 1 mm, a total length of 3000 mm, and a thickness of 0.02 mm. The extraction electrode 21 can be formed simultaneously with the heating resistor 2 by using the same metal material as that of the heating resistor 2. The extraction electrode 21 can also be formed separately using a material different from that of the heating resistor 2.

  The electrode layer 6 is formed on the surface of the ceramic body 1. In the present embodiment, the electrode layer 6 is formed in a portion of the ceramic body 1 that is located outside the metal cylinder 3. The electrode layer 6 is formed on the outer peripheral surface when the ceramic body 1 has a cylindrical or prismatic shape. On the other hand, when the ceramic body 1 has a cylindrical shape or a rectangular tube shape, it can also be formed on the inner peripheral surface thereof. In this case, the electrode layer 6 can also be formed in a portion of the ceramic body 1 located inside the metal tube 3. Further, the extraction electrode 21 can be drawn out to the outer peripheral surface of the ceramic body 1 inside the metal cylinder 3. The electrode layer 6 is made of a metal material. Examples of the metal material include tungsten, molybdenum, rhenium, and the like. The dimensions of the electrode layer 6 can be set, for example, to a length of 9 mm, a width of 5 mm, and a thickness of 0.02 mm.

  The metal cylinder 3 is a member used in contact with an object to be heated. The metal cylinder 3 is a cylindrical member. Examples of the cylindrical shape include a cylindrical shape and a rectangular tube shape. In the heater 10 shown in FIG. 1, the metal cylinder 3 has a cylindrical shape having a bottom. In the heater 10 of the present embodiment, at least the entire portion of the ceramic body 1 where the heating resistor 2 is formed is inserted into the metal cylinder 3. That is, the inner diameter of the metal cylinder 3 is larger than the outer diameter of the ceramic body 1, and a gap that allows the filler 4 to be filled between the inner peripheral surface of the metal cylinder 3 and the outer peripheral surface of the ceramic body 1. Is formed. In the present embodiment, a gap is also formed between the bottom of the metal tube 3 and the ceramic body 1. By filling the filler 4 between the bottom of the metal cylinder 3 and the ceramic body 1, it is possible to reduce the bias of heat transmitted from the ceramic body 1 to the metal cylinder 3 via the filler 4. Therefore, the heat uniformity on the surface of the metal cylinder 3 can be improved.

  The metal cylinder 3 is made of a metal material. Examples of the metal material include stainless steel, aluminum, brass, bronze, and titanium. From the viewpoint of weight reduction, it is preferable to use aluminum as the metal material. From the viewpoint of corrosion resistance, it is preferable to use titanium as the metal material. In particular, stainless steel is preferably used from the viewpoint of workability, durability, and heat resistance. When stainless steel is used, the thermal conductivity of the metal tube 3 is, for example, about 16 W / (m · K). When the metal cylinder 3 is cylindrical, the dimensions of the metal cylinder 3 can be set, for example, to a length of 120 mm, an outer diameter of 25 mm, and an inner diameter of 23 mm.

  The metal cylinder 3 can be produced by a method such as cutting or casting. If desired, the surface of the metal tube 3 can be provided with unevenness or heat radiation fins for improving the heat transfer to the object to be heated. When unevenness is provided, the unevenness can be formed by cutting the surface of the metal tube 3. Moreover, when providing a radiation fin, a radiation fin can be formed by cutting, welding, or casting.

  The filler 4 is a member for improving the heat conduction between the ceramic body 1 and the metal cylinder 3. The filler 4 is filled between the outer peripheral surface of the ceramic body 1 and the inner peripheral surface of the metal cylinder 3. The filler 4 is filled so as to cover at least a portion of the ceramic body 1 where the heating resistor 2 is provided. As the filler 4, for example, a material obtained by casting and adding a metal such as aluminum, zinc, or tin with copper, magnesium, silicon, or the like can be used. Compared with the case where the metal powder is filled, since the filling rate is high and the thermal conductivity is excellent, the time required for the temperature rise of the outer peripheral surface of the metal tube 3 can be shortened.

As shown in FIG. 3, the heater 10 of the present embodiment has a gap 41 between the ceramic body 1 and the filler 4 in the groove 11. As a result, even when the filler 4 undergoes a large thermal expansion when the heater 10 is used, the filler 4 can be thermally expanded so as to fill the gap 41, so that the gap between the groove 11 and the filler 4 can be reduced. The generated thermal stress can be reduced. Therefore, it is possible to reduce the risk of cracks occurring in the ceramic body 1. As a result, the long-term reliability of the heater 10 can be improved.

  Furthermore, it is preferable to have the space | gap part 41 in the part which the wall surface 13 and the bottom face 12 continue. More specifically, in the present embodiment, a portion where the wall surface 13 and the bottom surface 12 are continuous is a corner portion, and a void portion 41 is provided at the corner portion. Thereby, the thermal stress which arises in the part between the wall surface 13 and the bottom face 12 in which a thermal stress tends to concentrate especially among the groove parts 11 can be reduced. Therefore, the long-term reliability of the heater 10 can be improved. In the case where the depth of the groove 11 is 0.4 mm and the width is 0.8 mm, for example, the gap 41 is 0. 0 along the direction of the wall 13 and the bottom 12 as viewed from the boundary between the wall 13 and the bottom 12. It preferably has a length of 05 mm or more. In addition, in this embodiment, although the shape of the part which the wall surface 13 and the bottom face 12 continue was a corner | angular part, it is not restricted to this. Specifically, the portion where the wall surface 13 and the bottom surface 12 are continuous may be a gentle curve.

  Furthermore, it is preferable that the gap 41 extends in the length direction of the groove 11. Thereby, the thermal uniformity of the groove part 11 vicinity in the length direction of the groove part 11 can be improved. Thereby, the possibility that thermal stress concentrates in a specific part of the groove 11 can be reduced. As a result, the long-term reliability of the heater 10 can be improved. Furthermore, it is preferable that the gap portion 41 is formed in the entire length direction of the groove portion 11. Thereby, the concentration of thermal stress can be further reduced.

  Furthermore, it is preferable that the gap 41 extends along the wall surface 13 and the bottom surface 12. In other words, the filler 4 enters the groove 11 other than the portions along the wall surface 13 and the bottom surface 12. Thereby, heat transfer from the ceramic body 1 to the metal tube 3 can be performed satisfactorily while reducing the generation of thermal stress in the groove 11.

  Furthermore, it is preferable that the thermal expansion coefficient of the filler 4 is higher than the thermal expansion coefficient of the metal cylinder 3. Thereby, the adhesiveness of the filler 4 and the metal cylinder 3 can be improved. Thereby, heat transfer from the ceramic body 1 to the metal cylinder 3 can be performed satisfactorily.

When alumina is used as the ceramic body 1, tin alloy is used as the filler 4, and stainless steel is used as the metal cylinder 3, the thermal expansion coefficient of the ceramic body 1 is 7 × 10 ⁶ / ppm, and the thermal expansion coefficient of the filler 4 is Can be 20 × 10 ⁶ / ppm, and the coefficient of thermal expansion of the metal cylinder 3 can be 16 × 10 ⁶ / ppm.

  Furthermore, in the groove part 11, it is preferable to have the space | gap part 41 in the edge part by the side of an opening among the wall surfaces 13. FIG. Since the end portion on the opening side is formed with a corner portion by the outer peripheral surface of the ceramic body 1 and the wall surface 13 of the groove portion 11, thermal stress tends to concentrate under a heat cycle. By providing the gap 41 at the end on the opening side, the thermal stress generated in the corner can be reduced. In addition, in this embodiment, although the space | gap part 41 is provided from the bottom face 12 and the wall surface 13 of the groove part 11 to the edge part of an opening part, it is not restricted to this. Specifically, the gap 41 may not be provided on the bottom surface 12 but may be provided only at the end of the opening.

The bonding material 7 is used for attaching the lead terminal 5 on the electrode layer 6. As the bonding material 7, a conductive material is selected that has an adhesive force sufficient to fix the lead terminal 5 for power feeding and durability that can withstand temperature changes. As such a material, for example, a conductive adhesive, solder, brazing material, or the like can be used. From the viewpoint of excellent heat resistance, it is desirable to use a brazing material made of silver and copper as the bonding material 7.

  The lead terminal 5 is a member for passing a current through the electrode layer 6 or taking out a current. As the lead terminal 5, a wire or plate made of nickel or copper metal can be used. The lead terminal 5 can be attached on the surface of the electrode layer 6 using the bonding material 7. When the lead terminal 5 is a wire, a single wire or a stranded wire can be used. The material and shape of the wire or plate are determined in consideration of the current value when the heater 10 is used.

  The sealing material 8 is filled so as to fill a gap between the ceramic body 1 and the metal cylinder 3 generated in the opening of the metal cylinder 3 into which the ceramic body 1 is inserted. The sealing material 8 is provided in order to block the filler 4 from the outside air. As the sealing material 8, for example, an adhesive such as silicone or epoxy, an inorganic adhesive obtained by mixing ceramic powder such as alumina and an inorganic polymer, cement, or the like can be used. In view of having the appropriate elasticity and heat resistance necessary to cope with temperature changes, it is desirable to use an adhesive made of silicone. By providing the sealing material 8, the filler 4 can be shielded from the outside air and corrosion of the filler 4 due to the outside air can be suppressed, so that the long-term reliability of the heater 10 can be improved.

  In the above-described embodiment, a part of the ceramic body 1 is located outside the metal cylinder 3, but the present invention is not limited to this. Specifically, the entire ceramic body 1 may be located inside the metal cylinder 3. In such a case, the insulating property between the filler 4 and the filler 4 may be ensured by covering the electrode layer 6 and the lead terminal 5 with an insulating sheet. Thereby, the possibility that electric leakage may occur through the filler 4 can be reduced.

  A method for manufacturing the heater 10 of the present embodiment will be described.

First, an alumina ceramic green sheet having Al ₂ O ₃ as a main component and prepared so that SiO ₂ , CaO, MgO, and ZrO ₂ are within 10 mass% in total is produced.

  A predetermined pattern to be the heating resistor 2 is formed on the surface of the alumina ceramic green sheet. As a method for forming the heating resistor 2, there are a screen printing method, a transfer method, a resistor embedding method, and other methods such as a method of forming a metal foil by an etching method, a method of embedding a nichrome wire in a coil shape, and the like. However, it is desirable to use a screen printing method in consideration of manufacturing cost and quality stability. Further, the extraction electrode 21 can be integrally formed simultaneously with the heating resistor 2.

  A predetermined pattern to be the electrode layer 6 is formed on the surface of the ceramic green sheet opposite to the surface on which the heating resistor 2 is formed in the same manner as in the case of forming the heating resistor 2. Further, in order to electrically connect the heating resistor 2 and the electrode layer 6 formed on different surfaces of the ceramic green sheet, a hole is formed in the ceramic green sheet and a conductive paste that becomes a through-hole conductor is filled.

  As a material for forming the heating resistor 2, the electrode layer 6, and the through-hole conductor, for example, a conductive paste mainly composed of a refractory metal such as tungsten, molybdenum or rhenium can be used.

  On the other hand, a cylindrical alumina ceramic molded body is formed by extrusion molding. Then, the alumina ceramic green sheet is wound around the cylindrical alumina ceramic molded body, and an adhesive liquid in which the alumina ceramic of the same composition is dispersed is applied and brought into close contact, whereby alumina that becomes the ceramic body 1 is obtained. A quality-integrated molded body can be obtained.

  By firing the alumina integrated molded body thus obtained in a reducing atmosphere (nitrogen atmosphere) at 1500 to 1600 ° C., an alumina integrated sintered body (ceramic body 1) can be produced.

  As described above, the cylindrical ceramic body 1 can be obtained. And the chemical | medical agent for the filler 4 to become difficult to get wet to the groove part 11 is apply | coated to the bottom face 12 and the wall surface 13 of the groove part 11 formed when the alumina ceramic green sheet was wound among the ceramic bodies 1. Specifically, when a metal material such as a tin alloy is used as the filler 4, it is preferable to apply a boron nitride-based chemical. Thereby, when the filler 4 is filled, the gap portion 41 along the bottom surface 12 and the wall surface 13 of the groove portion 11 can be formed.

  Then, the ceramic body 1 is inserted into the metal cylinder 3 so that the gaps in the same diameter direction are uniform. As a material of the metal cylinder 3 into which the ceramic body 1 is inserted, for example, stainless steel, aluminum, bronze, titanium, or the like can be selected depending on the application. A tin alloy is poured into the gap between the ceramic body 1 and the metal cylinder 3 as a filler 4 by casting. At this time, the filler 4 spreads between the outer peripheral surface of the ceramic body 1 and the inner peripheral surface of the metal cylinder 3, but boron nitride based chemicals are applied to the wall surface 13 and the bottom surface 12 of the groove 11. For this reason, the filler 4 is less likely to wet the bottom surface 12 and the wall surface 13 of the groove 11. As a result, the gap 41 along the bottom surface 12 and the wall surface 13 of the groove 11 can be formed.

  Moreover, the sealing material 8 is filled so that the opening part of the metal cylinder 3 in which the ceramic body 1 is inserted may be closed. As the sealing material 8, for example, an adhesive such as silicone or epoxy, an inorganic adhesive obtained by mixing ceramic powder such as alumina and an inorganic polymer, cement, or the like can be used. It is desirable to use a silicone adhesive from the viewpoint of having an appropriate elasticity and heat resistance corresponding to a temperature change.

  As described above, the heater 10 of the present invention can be obtained.

  Examples of the method for confirming the gap 41 formed in the groove 11 include the following methods. Specifically, imaging is performed with X-ray CT while the heater 10 is sandwiched and rotated by a jig, and this is subjected to image processing to be three-dimensional. By confirming this three-dimensional image, the presence or absence of voids can be confirmed.

1: Ceramic body 11: Groove portion 2: Heating resistor 21: Extraction electrode 3: Metal tube 4: Filler 41: Gap portion 5: Lead terminal 6: Electrode layer 7: Bonding material 8: Sealing material 10: Heater

Claims (5)

A columnar or cylindrical ceramic body having a groove along the length direction on the outer peripheral surface, a heating resistor provided in the ceramic body, and a portion of the ceramic body where the heating resistor is provided An inserted metal cylinder, and a filler made of a metal material filled between the outer peripheral surface of the ceramic body and the inner peripheral surface of the metal cylinder, and in the groove portion, the ceramic body and the filler With a gap between them,
The heater characterized in that the thermal expansion coefficient of the filler is higher than the thermal expansion coefficient of the metal cylinder .   The heater according to claim 1, wherein in the groove portion, the gap portion is provided in a portion where the wall surface and the bottom surface are continuous.   The heater according to claim 1, wherein the gap portion extends in a length direction of the groove portion. The heater according to claim 2 , wherein the gap portion extends along the wall surface and the bottom surface.   The heater according to claim 1, wherein the groove portion has the gap portion at an end portion on the opening side of the wall surface.

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