CN111247407A - Temperature sensor and method of making the same - Google Patents

Abstract

This invention relates to a temperature sensor and its manufacturing method that uses resin molding of a thermistor element. It provides a temperature sensor and its manufacturing method that improve the airtightness of the thermistor element, enhance the stability of performance during manufacturing, and increase yield. The temperature sensor and its manufacturing method include a sensor portion (A) consisting of a thermistor element (1) and a connecting terminal (2), a cable portion (B) connected to the connecting terminal (2), and a covering portion (C) covering the entire sensor portion (A) and the front end of the cable portion (B). The covering portion (C) includes: a sensor housing (5) having a hollow portion (5a) that tapers towards the center of the front end of the thermistor element (1); an elastic resin coating layer (6) covering the entire surface of the thermistor element (1); and a filling resin layer (7) filling the space between the inner surface of the sensor housing (5) and the elastic resin coating layer (6).

Description

Temperature sensor and method of making the same

technical field

The present invention relates to a temperature sensor in which a thermistor element is resin-molded and a method for manufacturing the same.

Background technique

A temperature sensor is known to have a sensor portion in which a thermistor element and a connection terminal (copper wire or copper beryllium-iron-nickel alloy wire, etc.) are connected by lead wires are inserted into a metal case, and a resin molded portion formed of a molded resin is passed through. The structure which seals the opening part of a case (for example, refer following patent document 1).

Such a temperature sensor may cause disconnection or short-circuit of the sensor portion due to corrosion of the metal alloy due to infiltration of moisture, etc. Therefore, it is extremely important to ensure the airtightness in the sensor portion.

Therefore, it has been proposed to insert an insulating cap made of resin into the opening of a metal case, insert a sensor portion into the opening of the insulating cap, and mold the opening of the case and the insulating cap with resin in this state. and sealed structure.

In this example, by using the same resin for the insulating cap and the resin mold portion, the interface is welded during molding, and the water penetration path is blocked.

Such a temperature sensor usually uses a thermistor element, but the thermistor surface is sometimes covered with a very brittle protective film.

prior art literature

Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2014-77678

SUMMARY OF THE INVENTION

The problem to be solved by the invention

However, if such a temperature sensor is to be miniaturized, the creepage distance of the welded portion that blocks the penetration path of moisture is shortened, and there is a problem that the airtightness with respect to the thermistor element decreases.

In addition, when the mold resin is cured, it expands in a limited space, which causes damage to the protective film of the thermistor element, and reduces the yield at the time of manufacture.

In addition, such a mold-type temperature sensor has a problem that the sensitivity and characteristics of the sensor change due to the difference in the molding position of the thermistor element in the housing, and the quality is not stable.

The present invention has been made in view of the above-mentioned actual conditions, and relates to a temperature sensor in which a thermistor element is resin-molded and a method for manufacturing the same, and aims to provide a temperature sensor with improved airtightness to the thermistor element and improved performance during manufacturing. A temperature sensor for stability and yield and a method for manufacturing the same.

solutions to problems

In order to solve the above-mentioned problems, the temperature sensor of the present invention includes: a sensor part composed of a thermistor element and a connection terminal; a cable part connected to the connection terminal; and a covering part covering the entire sensor part and the cable part The front end portion of the cladding portion, wherein the covering portion includes: a sensor case having a hollow portion that tapers toward the center of the front end portion where the thermistor element is accommodated; and an elastic resin coating layer covering the thermistor element the entire surface; and a filling resin layer filling between the inner surface of the sensor housing and the elastic resin coating layer.

The temperature sensor may be provided with a primer layer covering the front end portion of the cable portion.

In addition, a structure in which the elastic resin coating layer is continuously provided on the entire surface of the thermistor element and the region from the entire surface of the thermistor element to the distal end portion of the cable portion may be employed.

In addition, the primer is a structure normally used as an adhesion promoter or a primer treatment agent, and has the effect of improving the adhesiveness between members.

In the method for manufacturing a temperature sensor of the present invention, which has been devised to solve the above-mentioned problems, the temperature sensor includes: a sensor part composed of a thermistor element and a connection terminal; a cable part connected to the connection terminal; and a covering part, Covering the entire sensor portion and the front end portion of the cable portion, the temperature sensor manufacturing method includes the following steps: a connecting step of connecting a lead wire of the cable portion to a connection terminal of the sensor portion; a coating step of applying heat to the sensor portion. The elastic resin coating layer is attached to the entire surface of the thermistor element; the base forming step is to attach a primer layer to the front end of the cable part; The front end of the hollow part of the housing is inserted, and the hollow part becomes thinner toward the center of the front end part where the thermistor element is accommodated; in the filling process, the filling resin layer fills the inner surface of the sensor housing and the elastic resin coating layer. and a curing process to cure the filled resin layer.

Invention effect

According to the temperature sensor and the method for manufacturing the same of the present invention, the shape of the hollow portion of the sensor case is provided with the hollow portion that becomes thinner toward the center of the front end portion where the thermistor element is accommodated, whereby the thermistor When the element comes into contact with the front end of the inner surface of the case, the positioning to the center of the front end portion of the sensor case is automatically performed, so that the position of the thermistor element can be more easily and accurately determined.

In addition, since the front end of the hollow portion is tapered, the amount of the filling resin existing in the vicinity of the thermistor element is reduced, and the pressure caused by the expansion of the filling resin is directed toward the opening of the sensor case, thereby reducing the amount of heat applied to the sensor case. The stress exerted by the varistor element.

In addition, by providing the elastic resin coating layer covering the entire surface of the thermistor element, it is possible to avoid the inconvenience that the protective film provided on the surface of the thermistor element is damaged due to the pressure generated when the filling resin is cured due to its cushioning effect.

In addition, by adopting a structure in which the elastic resin coating layer is continuously provided in the region up to the front end of the cable portion, it is also possible to prevent a short circuit due to deformation of the connection terminal when the sensor portion is mounted on the covering portion.

On the other hand, if a material with high thermal conductivity, such as PPS containing reinforcing materials such as glass fibers or inorganic fillers, is used as the material for the sensor case, the thickness of the filling resin existing near the thermistor element is reduced, so that it is possible to improve the thermal conductivity. Thermal responsiveness of hollow-packed thermistor elements.

In addition, through the base forming step of attaching the primer layer to the front end of the cable portion, the adhesion between the coating of the cable and the filling resin is improved, and the infiltration of air, moisture or oil along the surface of the cable is avoided, A good temperature detection can be performed for a long time.

Description of drawings

FIG. 1 is a cross-sectional view showing an example of a temperature sensor of the present invention.

2(A), (B) and (C) are exploded views showing an example of the constituent elements of the temperature sensor of the present invention.

FIG. 3 is an explanatory diagram showing one step of the manufacturing method of the temperature sensor of the present invention.

FIG. 4 is an explanatory diagram showing one step of the method of manufacturing the temperature sensor of the present invention.

FIG. 5 is an explanatory diagram showing one step of the method of manufacturing the temperature sensor of the present invention.

6 is a cross-sectional view showing examples (A) and (B) of the sensor housing of the temperature sensor of the present invention in comparison with an example (C) of a conventional temperature sensor.

Detailed ways

Hereinafter, an embodiment of the temperature sensor of the present invention and its manufacturing method will be described in detail based on the drawings.

The temperature sensor of the present invention includes: a sensor part A consisting of a thermistor element 1 and a connection terminal 2; a cable part B consisting of a lead wire 3 connected to the connection terminal 2 and a sheath 4 for insulating and protecting each copper wire and a covering portion C, covering the entire sensor portion A and the front end portion of the cable portion B.

The sensor unit A includes a glass-sealed thermistor element 1 whose surface is covered with a protective film 1a made of glass, and a pair of connection terminals 2 and 2 for energizing between the thermistor element 1 and the temperature control circuit.

The cable portion B includes a pair of lead wires 3 and 3 and a sheath 4 made of fluororubber or the like covering the side surfaces thereof, and the pair of lead wires 3 and 3 are welded to the pair of connection terminals 2 and 2 , respectively.

The covering portion C includes a sensor case 5 including a hollow portion 5 a that is tapered toward the center of the front end portion where the thermistor element 1 is housed, and an elastic resin coating layer 6 that covers the thermistor element 1 The entire surface of the sensor housing 5 is filled with the resin layer 7 and between the inner surface of the sensor housing 5 and the elastic resin coating layer 6 .

The sensor case 5 is a protective case made of synthetic resin or the like having relatively high thermal conductivity and insulating properties, and in this example, PPS (polyphenylene sulfide) is used.

The sensor case 5 of this example has an outer shape of a rectangular parallelepiped that is convenient for installation, and includes a hollow portion 5 a with a tapered tip in its central portion.

The hollow portion 5a is provided with a planar, spherical or pyramid-shaped support surface 5b capable of holding the thermistor element 1 at a substantially fixed position of the distal end portion of the sensor case 5, and is provided with a continuous or intermittent support surface 5b from the support surface 5b. The gradually expanding guide surface 5c (for example, refer to FIG. 6(A) or (B)).

Due to the relationship between the outer shape of the sensor case 5 and the shape of the hollow portion 5a, the thickness of the front end portion of the sensor case 5 is increased in the left and right directions, and the thickness in the front-rear direction of the front end portion of the sensor case 5 is reduced.

In this way, it is undeniable that the sensitivity of the thermistor element 1 varies depending on the direction due to the environment in which the thermistor element 1 is wound. However, PPS, which is a material of the sensor case 5, is an insulating material with relatively high thermal conductivity. The difference due to the directivity of the sensitivity of the thermistor element 1 can be alleviated.

It should be noted that, when higher responsiveness is required, it is only necessary to include glass fibers, inorganic fillers, etc. to improve thermal conductivity, or to orient the front end portion of the sensor case 5 that can reduce the thickness of the sensor case 5 toward the temperature detection device. direction.

The elastic resin coating layer 6 of this example is formed on the entire surface of the thermistor element 1 and the front end portion of the cable portion B using, for example, a low-hardness resin material such as silicone resin.

In addition, the filled resin layer 7 of this example is formed so that the gap between the inner surface of the sensor case 5 and the primer layer 8 may be filled with epoxy resin.

<Manufacturing method>

The above-mentioned temperature sensor is manufactured through the following steps: a connection step (refer to FIG. 2 ), by a manufacturing method in which each component of the temperature sensor is assembled in the molding space while suppressing the disposition variation of the thermistor element 1 . The lead wires 3 and 3 are welded to the connection terminals 2 and 2 of the sensor part A by methods such as laser, ultrasonic wave, soldering, etc.; The elastic resin coating layer 6 is adhered to the entire surface of the thermistor element 1 by dipping and curing in silicone resin; The primer layer 8 is adhered to the entire surface of the thermistor element 1 and the front end of the cable part B by dipping and drying in the primer; the loading process (refer to FIG. 5 ), the thermistor that has undergone the above steps is placed The element 1 is inserted into the support surface 5b at the front end of the hollow portion 5a of the sensor case 5; the filling step is to fill the space between the inner surface of the sensor case 5 and the primer layer 8 with a filling resin composed of epoxy resin; and curing In the step (refer to FIG. 1 ), the sensor case 5 that has undergone the filling step is heated while maintaining the position of the thermistor element 1 , and the filling resin is cured (the filling resin layer 7 is formed).

According to this manufacturing method, through the coating process, the elasticity of the elastic resin coating layer 6 complements the gradual expansion of the hollow portion 5a of the sensor case 5, and it is possible to prevent high temperature loads during the curing process or during use. The case where the protective film 1a made of glass is damaged due to the expansion of the filling resin at the time.

In addition, before the filling step, through the base forming step of adhering the primer layer 8 to the entire surface of the thermistor element 1 and the front end portion of the cable portion B, the resin 7 and the cable portion B are filled at the time of the curing step. The affinity of the sheath 4 is improved, and the airtightness around the sensor portion A is not to mention, and the front end portion of the sensor portion A can secure a moisture barrier structure using a filling process that does not go through the conventional substrate forming process. Higher air tightness.

Label description

A sensor part, B cable part, C covering part,

1 thermistor element, 1a protective film,

2 connection terminals,

3 wires, 4 sheaths,

5 sensor housing, 5a hollow portion, 5b support surface, 5c guide surface,

6 elastic resin coating layer,

7 filling resin layer, 8 primer layer.

Claims (4)

1. A temperature sensor is provided with: a sensor unit including a thermistor element and a connection terminal; a cable portion connected to the connection terminal; and a covering part covering the entire sensor part and the front end part of the cable part,

the coating portion includes:

a sensor case having a hollow portion that becomes thinner toward the center of a distal end portion that houses the thermistor element;

an elastic resin coating layer covering the entire surface of the thermistor element; and

and the filling resin layer is filled between the inner surface of the sensor shell and the elastic resin coating layer.

2. The temperature sensor according to claim 1,

the temperature sensor is provided with a primer layer covering the front end portion of the cable portion.

3. The temperature sensor according to claim 1 or 2,

the elastic resin coating layer is continuously provided over the entire thermistor element and over a region from the entire thermistor element to the tip end of the cable portion.

4. A method for manufacturing a temperature sensor, the temperature sensor comprising: a sensor unit including a thermistor element and a connection terminal; a cable portion connected to the connection terminal; and a covering portion that covers the entire sensor portion and a distal end portion of the cable portion, wherein the method for manufacturing the temperature sensor includes:

a connection step of connecting a lead wire of the cable portion to a connection terminal of the sensor portion;

a coating step of attaching an elastic resin coating layer to the entire surface of the thermistor element of the sensor unit;

a base forming step of attaching a primer layer to the front end portion of the cable portion;

a loading step of inserting the thermistor element having undergone the above-described steps into a front end of a hollow portion of a sensor case having the hollow portion, the hollow portion being tapered toward a center of a front end portion in which the thermistor element is housed;

a filling step of filling a space between the inner surface of the sensor case and the elastic resin coating layer with a filling resin layer; and

and a curing step of curing the filled resin layer.

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