JP2002267540A - Temperature sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure capable of preventing water from intruding the boundary surface between a metal case and a resin part without complicating a manufacturing process in a temperature sensor having a thermistor sealed in the metal case with resin. SOLUTION: The metal case 2 is provided with a cylindrical part 24 projected to be enclosed in the resin part 5 at the end part 28 of an opening part, and the cylindrical part 24 has a projecting part 24a on the inside of its forward end part. In this arrangement, even if the metal case 2 or the resin case 5 expands or shrinks due to an environmental temperature change, a difference in coefficient of expansion between them causes one face of the cylindrical part 24 having the projecting part 24 to closely adhere to the resin part 5, so that no air layer is formed on the boundary surface 10. Thus, entering of water from the boundary surface 10 between the metal case 2 and the resin part 5 can be prevented without specially providing a process of forming a waterproof structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature sensor, and more particularly, to a temperature sensor in which a temperature detecting element is sealed in a metal case with a resin.

[0002]

2. Description of the Related Art Conventionally, a thermistor having a lead wire at the bottom of a bottomed cylindrical metal case disposed in an object to be measured, such as cooling water, has been used as a temperature sensor for measuring the temperature of cooling water for automobiles. There is known a temperature sensor having a structure in which a metal case is filled with a resin and a thermistor is sealed with the resin portion.

In the case of this type of temperature sensor, a metal case or a resin portion having a different coefficient of thermal expansion expands and contracts due to a change in environmental temperature such as a change in cooling water temperature, so that air is applied to the interface between the metal case and the resin portion. A layer was formed, and air or water droplets having humidity sometimes entered along the boundary surface.

When water enters from the boundary surface to reach the portion where the thermistor is arranged, a leak occurs at the base of the lead wire on the thermistor side, and an accurate resistance value cannot be output, or the lead wire is broken due to electrolytic corrosion. There is a problem that occurs.

As a countermeasure, a thermistor having a waterproof structure formed by sealing the root of the lead wire on the thermistor side with a resin or the like, as in a temperature sensor described in Utility Model Registration Publication No. 2520903, for example, is used. 2. Description of the Related Art A temperature sensor having a structure in which a resin portion is formed on a bottom portion is known.

[0006]

However, in the above-mentioned prior art, there is a problem that the manufacturing process is complicated because the waterproof structure is formed.

[0007] The present invention has been made in view of the above points,
It is an object of the present invention to provide a temperature sensor that can prevent moisture from entering from a boundary surface between a metal case and a resin portion without complicating a manufacturing process.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, a metal case (2) having a bottomed cylindrical shape having an opening and a lead wire (4) are connected to the opening side. And a temperature detecting element (3) housed in the bottom of the metal case (2) and a metal case (2) so as to seal the temperature detecting element (3). In the temperature sensor having the resin portion (5) filled and extended to the end (28) of the opening, the metal case (2) projects in the axial direction from the end (28) of the opening. And a resin part (5) having an annular protrusion (24)
Is characterized in that it covers so as to surround the surface of the protrusion (24).

According to this, the protruding portion (24) of the metal case (2) is located in the resin portion (5) and is surrounded by the resin portion (5). Therefore, even if the metal case (2) or the resin portion (5) expands and contracts due to a change in environmental temperature, any of the surfaces (24) of the protruding portion (24) of the metal case (2) differs due to the difference in their expansion coefficients. 24b, 24c, 24d, 2
4e) is in close contact with the resin portion (5) and does not form an air layer on the boundary surface (10).

In this way, it is possible to prevent water from entering from the boundary surface (10) between the metal case (2) and the resin portion (5) without providing a special step of forming a waterproof structure.

According to the second aspect of the present invention, the protrusion (24) has an annular protrusion (24a) projecting in the radial direction of the metal case (2), and the resin portion (5) has a protrusion. Part (24
a) is coated.

According to this, a cylindrical metal case (2)
Metal case (2) due to environmental temperature change in the axial direction
Even if the resin part (5) expands and contracts, any of the surfaces (24d, 24e) of the annularly provided convex part (24a) is in close contact with the resin part (5) because of their different expansion coefficients. No air layer is formed on the boundary surface (10). When a corner is formed at the tip of the projection (24a), the surface pressure of the corner increases when the metal case (2) and the resin portion (5) are in close contact with each other. Therefore, it is more difficult to form an air layer.

In this way, it is possible to reliably prevent water from entering from the boundary surface between the metal case (2) and the resin portion (5) without specially providing a step of forming a waterproof structure.

The reference numerals in parentheses attached to the respective means indicate the correspondence with specific means described later in the embodiments.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a temperature sensor 1 to which the present invention is applied.

As shown in FIG. 1, the temperature sensor 1
A cylindrical metal case 2 having an opening on the middle right side is provided. The metal case 2 has a thin protective tube portion 21 on the bottom side, and a hexagonal portion 22 serving as a receiving portion for a tightening tool when the temperature sensor is attached is formed on the outer periphery on the right side in the drawing.

On the left outer periphery of the hexagonal portion 22 of the metal case 2, for example, a male screw portion 23 for screwing into a screw hole of a cooling water outflow pipe of a water-cooled engine is formed. In FIG. 1, illustration of the screw shape of the male screw portion 23 is omitted. At the end (right end in the drawing) 28 of the opening of the metal case 2, a cylindrical portion 24, which is an annular protrusion, is formed. The cylindrical portion 24 will be described later in detail.

In this embodiment, the metal case 2 is a case made of brass. The material of the metal case 2 is not limited to brass, but may be any metal material having desired thermal conductivity, strength, environmental resistance and the like.

A well-known glass-sealed thermistor 3 serving as a temperature detecting element is disposed in the protective tube portion 21 of the metal case 2. The glass-sealed thermistor 3 is sealed by a resin portion 5 together with a pair of lead wires 4 connected to a thermistor element (not shown) constituting the same and fixed to the metal case 2. ing.

In this embodiment, the lead wire 4 employs a lead wire having a polyimide tube coating on the outer periphery of a metal conductor. The covering of the lead wire 4 may be a fluororesin tube or the like as long as it has desired insulation properties, heat resistance, and the like.

Further, on the right side of the glass-sealed thermistor 3 in the drawing, two lead wire through holes are provided to protect the vicinity of the root of the lead wire 4 from the glass-sealed thermistor 3 from external force. A ceramic member 7 is fused to the glass sealing thermistor 3.

The resin portion 5 itself forms a connector portion 61 on the opening side of the metal case 2, and a socket insertion space 62 of the connector portion 61 is spot-welded with the above-described lead wire 4. A pair of terminals 6 connected by the terminal protrude.

In the temperature sensor 1 having the above-described structure, the resistance value of the thermistor element in the glass-sealed thermistor 3 changes depending on the temperature. The voltage drop between the terminals 6 changes according to the temperature of the measured object (in this example, engine cooling water). By converting from this voltage drop value, the temperature of the device under test can be known.

In order to manufacture the temperature sensor 1 having the above-described configuration, first, the metal case 2 processed into the above-described shape by cutting and the glass-sealed thermistor 3 are connected to the terminal 6 via the lead wire 4. Are set in the mold cavity. Then, after clamping the mold, a resin is injected into the cavity to obtain the temperature sensor 1. In the present embodiment, a 66 nylon resin containing 30% glass fiber is used as a resin material for forming the resin portion 5. The resin material is not limited to this, but may be any material having desired strength and environmental resistance.

Next, the cylindrical portion 24 which is a main part of the present invention will be described.

FIG. 2 is an enlarged sectional view of the portion A shown in FIG.

The cylindrical portion 24 is formed at the end 28 of the opening of the metal case 2, and is provided in the resin portion 5 so as to protrude in the axial direction of the metal case 2. In addition, cylindrical part 2
Reference numeral 4 has a circumferentially continuous convex portion 24a protruding inward in the radial direction of the metal case 2 at the distal end thereof. Therefore, as shown in FIG. 2, all surfaces of the cylindrical portion 24 are in contact with the resin portion 5, and the cylindrical portion 24 is formed so as to be surrounded by the resin portion 5.

In this structure, since the coefficient of thermal expansion of the resin forming the resin portion 5 is larger than the coefficient of thermal expansion of the metal forming the metal case 2, when the temperature of the temperature sensor 1 becomes high, 2, the resin portion 5 expands more than the metal case 2, and the resin portion 5 is
4b and the inner flat surface 24d. When the temperature of the temperature sensor 1 becomes low, the metal case 2
The resin portion 5 is more contracted than the resin portion 5, and the resin portion 5 surely adheres to the outer peripheral surface 24c and the end surface 24e of the cylindrical portion 24 shown in FIG.

Further, when the resin portion 5 is in close contact with the inner peripheral surface 24b and the inner flat surface 24d of the cylindrical portion 24 at a high temperature,
The surface pressure of the corner 24f between the closely contacted surfaces tends to be higher than that of each of the closely adhered surfaces 24b and 24d. When the temperature is low, the resin portion 5 is connected to the outer peripheral surface 24 c and the end surface 2 of the cylindrical portion 24.
4e, the surfaces 24c, 24e in close contact with each other
The surface pressure at the corners 24g between the closely contacted surfaces tends to be higher than the surface pressure.

According to the above configuration and mechanism, even if the metal case 2 and the resin portion 5 having different thermal expansion coefficients expand and contract due to a change in environmental temperature, the boundary surface 10 between the metal case 2 and the resin portion 5 Water can be prevented from entering the boundary surface end 10a.

The inventors immerse the temperature sensor 1 of this embodiment in a liquid colored with the left side downward as shown in FIG. 1 until the edge 10a of the boundary surface is hidden. A cooling / heating cycle test at 120 ° C. and 120 ° C. was performed to confirm that the colored liquid did not enter the inside of the metal case 2.

Further, there is no need to provide a dedicated member for forming the waterproof structure. Further, since there is no need to provide a dedicated manufacturing process for forming the waterproof structure, the manufacturing process does not become complicated.

(Other Embodiments) In the above embodiment, the convex portions 24a are provided inside the distal end portion of the cylindrical portion 24. However, as shown in FIG. Alternatively, as shown in FIG.
May be provided only on the outside of the distal end portion 24 of the second member. In addition, the inventors conducted a cooling / heating cycle test similar to that of the above-described embodiment in these two examples, and confirmed that the colored liquid did not enter the inside of the metal case 2.

In the above embodiment, the projection 24
a is provided inside the distal end portion of the cylindrical portion 24.
It may be provided on the inner surface of the metal case 2 other than the above.

In the above embodiment, the temperature sensor 1 detects the temperature of the cooling water of the engine.
It goes without saying that the present invention can be applied to temperature detection of other objects to be measured such as oil.

[Brief description of the drawings]

FIG. 1 is a sectional view of a temperature sensor 1 according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of the temperature sensor 1 according to the embodiment of the present invention.

FIG. 3 is an enlarged sectional view of a main part of a temperature sensor according to another embodiment.

FIG. 4 is an enlarged sectional view of a main part of a temperature sensor according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Temperature sensor 2 Metal case 3 Glass sealing thermistor (temperature detection element) 4 Lead wire 5 Resin part 6 Terminal 10 Boundary surface 21 Protective tube part 24 Cylindrical part (projection part) 24a Convex part 28 End of opening 61 Connector part

Claims (2)

[Claims] 1. A metal case (2) having a bottomed cylindrical shape having an opening, and a lead wire (4) is connected so as to be led out from the opening side, and a metal case (2) in the metal case (2) is provided. A temperature detecting element (3) housed in a bottom portion, and filled in the metal case (2) so as to seal the temperature detecting element (3), and extend to an end (28) of the opening. The metal case (2) has an annular protrusion (24) that protrudes in the axial direction from an end (28) of the opening; The resin part (5) is covered so as to surround the surface of the protruding part (24). 2. The protruding portion (24) has an annular protruding portion (24a) protruding in a radial direction of the metal case (2), and the resin portion (5) has the protruding portion (24a). The temperature sensor according to claim 1, wherein the temperature sensor is coated.