Temperature sensor and manufacturing method of the same

Abstract

To provide a temperature sensor achieving a higher degree of freedom of material selection of a case and high adhesion between the case and filler resin.SOLUTION: A temperature sensor comprises: a resin case 2 closed at one end side and serving as opening end 2a at the other end side; a heat sensitive element 3 stored on the one end side in the case; a pair of lead wires 4 connected at one end to the heat sensitive element; and a filler resin part 5 filling the case and encapsulating the heat sensitive element and the pair of lead wires at least one end side with resin. An inner surface of the case is embossed with protrusions and recesses rougher than an outside surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a temperature sensor in which a heat-sensitive element is sealed with resin in a resin case, and a method for manufacturing the same. [Background technology]

[0002] Conventionally, a temperature sensor has been known in which a chip thermistor or the like is inserted into a case made of PPS (polyphenylene sulfide) resin and filled with epoxy resin or the like. For example, Patent Document 1 describes a temperature sensor in which a filler is contained in a PPS resin, thereby forming unevenness due to the filler on the surface of the case, thereby exerting an anchor effect. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-151805 Summary of the Invention [Problem to be solved by the invention]

[0004] The above conventional techniques still have the following problems. That is, the temperature sensor described in Patent Document 1 has the disadvantage of limiting the flexibility of material selection because the anchoring effect varies depending on the shape and content of the filler. Therefore, it is not possible to prioritize thermal conductivity, moldability, etc. when selecting materials. Furthermore, depending on the shape and content of the selected filler, the filler may create irregularities on the outer surface of the case. In this case, even if an attempt is made to closely contact the outer surface of the case with the object to be measured, the irregularities may leave an air gap between the case and the object to be measured, hindering heat conduction and reducing temperature measurement performance. Furthermore, if the anchoring effect is weak, there is a risk of peeling at the interface between the case and the filled resin during temperature cycling, which could lead to the case coming loose or water intrusion, as well as reduced thermal responsiveness.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a temperature sensor that allows greater freedom in selecting case materials and achieves high adhesion between the case and the filling resin. [Means for solving the problem]

[0006] The present invention employs the following configuration to solve the above problems: That is, a temperature sensor according to a first aspect of the invention includes a resin case having one closed end and the other open end, a heat-sensitive element housed in one end of the case, a pair of lead wires each having one end connected to the heat-sensitive element, and a resin filling portion that fills the case and seals the heat-sensitive element and at least one end of the pair of lead wires with resin, and the inner surface of the case is textured with irregularities that are rougher than the outer surface.

[0007] In this temperature sensor, the inner surface of the case is textured with unevenness that is rougher than the outer surface. The resin penetrates into the gaps created by the textured surface, creating an anchoring effect that increases the contact area between the inner surface of the case and the internal filled resin portion, improving adhesion between the case and the filled resin portion. This reduces the likelihood of separation between the case and the filled resin portion, maintaining high thermal responsiveness and preventing case removal and water infiltration. Furthermore, restrictions on material selection, such as filler content and shape, are reduced, increasing the freedom of material selection. This allows the use of general-purpose materials for the case, and even if the case does not contain filler or the filler content is reduced, high adhesion between the case and the filled resin portion can be achieved. Therefore, even if the outer surface of the case that comes into contact with the object to be measured is made smooth with few irregularities by not including filler or by reducing the filler content, the inner surface of the case can be made rough with rough irregularities. This makes it possible to achieve both high adhesion between the inner surface of the case and the filled resin portion and high adhesion between the object to be measured and the outer surface of the case, and to obtain high thermal conductivity inside and outside the case.

[0008] The temperature sensor according to the second invention is the same as that of the first invention, and is characterized in that the inner surface of the case near the heat-sensitive element is embossed with rougher irregularities than the area near the opening edge. In this temperature sensor, the inner surface of the case near the thermal element is textured with coarser irregularities than the area near the open end, allowing the draft angle near the open end of the case to be set smaller. In other words, if the entire inner surface of the case were textured with coarse irregularities, a large draft angle would be required for the entire inner surface when transferring the texture using a mold, resulting in an increased case size. However, in this invention, by textured with coarse irregularities near the thermal element inside the case, the draft angle at one end of the case can be set larger, making it easier to remove the mold, and by textured with fine irregularities near the open end, the draft angle at the other end of the case can be reduced, allowing the overall size to be reduced.

[0009] The manufacturing method of a temperature sensor according to the third invention is a manufacturing method of a temperature sensor according to the first or second invention, and comprises a case molding process in which the case is molded with resin by injection molding, a resin filling process in which resin is filled into the case to form the filled resin portion, and an insertion process in which the heat-sensitive element and the pair of lead wires connected to the heat-sensitive element are inserted into the case, and is characterized in that the case molding process comprises a mold surface treatment process in which irregularities are formed on the surface of the mold that forms the inner surface of the case by sandblasting, and an embossing process in which the irregularities of the mold are transferred to the inner surface of the case during the injection molding.

[0010] That is, in the case molding process of this temperature sensor manufacturing method, the mold surface treatment process is performed in which unevenness is formed on the surface of the mold that forms the inner surface of the case by sandblasting, and the embossing process is performed in which the unevenness of the mold is transferred to the inner surface of the case during injection molding. Therefore, unevenness with controlled roughness can be formed on the mold surface by sandblasting, and the inner surface of the case can be easily embossed during injection molding.

[0011] The manufacturing method of a temperature sensor according to the fourth invention is characterized in that, in the mold surface treatment process, rougher irregularities are formed on one end side of the surface of the mold than on the other end side, and the draft angle on one end side of the mold is set to be larger than that on the other end side. That is, in this temperature sensor manufacturing method, the mold surface treatment step forms rougher irregularities on one end of the mold surface than on the other end, allowing one end of the case's inner surface to be embossed with rougher irregularities than the other end. Furthermore, the one end with the rougher irregularities has a larger draft angle than the other end, making it easier to remove from the mold, and the other end with the finer irregularities has a smaller draft angle than the one end, making it possible to miniaturize the case. By thus embossing different areas of the inner surface of the case with different roughness, it is possible to achieve both good adhesion to the filled resin and ease of removal from the mold. The draft angle is the angle of inclination of the surface relative to the direction in which the mold is drawn (the axial direction of the mold), and one end of the mold is tapered at an angle of, for example, 2 to 3 degrees. Therefore, one end of the inner surface of the case after molding is inclined at an angle of 2 to 3 degrees relative to the axis of the case. The other end of the mold has a smaller angle of inclination than the one end, set at an angle of less than 2 degrees. [Effects of the Invention]

[0012] According to the present invention, the following effects are achieved. In other words, according to the temperature sensor and manufacturing method of the present invention, the inner surface of the case is embossed with rougher irregularities than the outer surface, which improves adhesion between the case and the filled resin part and makes the outer surface of the case, which is the contact surface with the object to be measured, a smooth surface with fewer irregularities, thereby achieving high thermal conductivity. Therefore, in the temperature sensor of the present invention, high temperature measurement characteristics are obtained due to the high adhesion between the case and the filled resin part and the smooth outer surface of the case with few irregularities, and the case can be prevented from coming loose or water can be prevented from entering, resulting in high reliability. [Brief explanation of the drawings]

[0013] [Figure 1]1 is an enlarged cross-sectional view of a main part showing an embodiment of a temperature sensor according to the present invention. [Figure 2] 1 is a cross-sectional view showing an entire temperature sensor according to the present embodiment. [Figure 3] FIG. 2 is a perspective view showing a temperature sensor in the present embodiment. [Figure 4] In this embodiment, (a) is a conceptual enlarged cross-sectional view showing the unevenness of one end side (area A1) of the inner surface of the case, and (b) is a conceptual enlarged cross-sectional view showing the unevenness of the other end side (area A2). DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of a temperature sensor according to the present invention will be described with reference to FIGS.

[0015] As shown in Figures 1 to 3, the temperature sensor 1 of this embodiment comprises a resin case 2 having one closed end and the other open end 2a, a heat-sensitive element 3 housed at one end of the case 2, a pair of lead wires 4 having one end connected to the heat-sensitive element 3, and a filled resin section 5 filled in the case 2 and sealing at least one end of the heat-sensitive element 3 and the pair of lead wires 4 with resin.

[0016] The inner surface of the case 2 is textured to have rougher irregularities than the outer surface. Furthermore, the inner surface of the case 2 near the heat-sensitive element 3 is textured with rougher irregularities than the area near the opening end 2a. That is, on the inner surface of the case 2, as shown in Figures 1 and 4(a), one end side near the thermal element 3 is an area A1 with rough irregularities, and the other end side near the opening end 2a is an area A2 with fine irregularities, as shown in Figures 1 and 4(b). For example, the arithmetic surface roughness Ra of the area A2 with fine irregularities is set to about 10 μm, but the surface roughness Ra of the area A1 with coarse irregularities is set to a surface roughness exceeding 10 μm.

[0017] The case 2 has an insertion hole 2b with a rectangular cross section into which the thermal element 3 is inserted, and is formed by injection molding from PPS resin into a rectangular parallelepiped shape as a whole. The inner surface of the case 2 is provided with a draft angle to facilitate removal of the mold during injection molding. The draft angle at one end of the inner surface of the case 2 is set to be larger than that at the other end. That is, the draft angle is the inclination angle of the surface relative to the direction in which the mold is removed (the axial direction of the case 2), and the insertion hole 2b is tapered at an inclination angle θ of, for example, 2 to 3° at one end side (area A1) of the inner surface of the case 2. Furthermore, the inclination angle at the other end side (area A2) of the inner surface of the case 2 is smaller than that at the one end side, and is set to an angle of less than 2°.

[0018] The heat-sensitive element 3 is, for example, a flake-type thermistor, and is sealed with a sealing resin 3a made of epoxy resin or the like. The heat-sensitive element 3 may be a chip thermistor, a thin film thermistor, or the like. The case is formed from, for example, a general-purpose PPS resin or a material in which a filler such as a thermally conductive filler is contained in the resin to an extent that the smoothness of the outer surface is not affected.

[0019] One end of the pair of lead wires 4 is connected to the heat-sensitive element 3 with a solder material, a metal paste, or the like (both not shown). The other ends of the pair of lead wires 4 are connected by soldering 6c or welding to the core wires 6a of the pair of electric wires 6. The core wires 6a are covered with insulating covering material 6b except for the one end to be connected. The connection portion (including the solder material 6c) between the lead wire 4 and the core wire 6a is also sealed with the filled resin portion 5 inside the case 2. The filling resin portion 5 is, for example, an epoxy resin.

[0020] The manufacturing method of the temperature sensor of this embodiment includes a case molding process in which the case 2 is molded from resin (such as PPS resin) by injection molding, a resin filling process in which resin (such as epoxy resin) is filled into the case 2 to form a filled resin portion 5, and an insertion process in which a thermal element 3 and a pair of lead wires 4 connected to the thermal element 3 are inserted into the case 2. The case molding process includes a mold surface treatment process in which irregularities are formed on the surface of the mold (not shown) that forms the inner surface of case 2 by sandblasting, and a embossing process in which the irregularities of the mold are transferred to the inner surface of case 2 during injection molding. The inserting step may be performed after the resin filling step, or may be performed after the inserting step. However, if the inserting step is performed after the resin filling step, the thermal element 3 and the pair of lead wires 4 are inserted before the resin filled in the case 2 hardens.

[0021] In the mold surface treatment step, one end of the mold surface is formed with rougher irregularities than the other end. Furthermore, the draft angle at one end of the mold is set larger than that at the other end. The draft angle is the angle of inclination of the surface relative to the direction in which the mold is drawn (the axial direction of the mold), and one end of the mold is tapered at an angle of inclination of, for example, 2 to 3 degrees. The mold has a rectangular parallelepiped shape with a rectangular cross section corresponding to the shape of the insertion hole 2b of the case 2 to be molded.

[0022] As described above, in the temperature sensor 1 of this embodiment, the inner surface of the case 2 is textured with unevenness that is coarser than the outer surface, and the resin seeps into the gaps in the textured unevenness, creating an anchor effect that increases the contact area between the inner surface of the case 2 and the internal filled resin portion 5, improving adhesion between the case 2 and the filled resin portion 5. Therefore, separation between the case 2 and the filled resin portion 5 is unlikely to occur, and high thermal responsiveness can be maintained while preventing the case from coming off or water intrusion.

[0023] Furthermore, restrictions on material selection that take into consideration filler content, shape, etc. are reduced, increasing the degree of freedom in material selection. This allows general-purpose materials to be used as the material for case 2, and even if no filler is contained or the filler content is reduced, the adhesion between case 2 and filled resin portion 5 can be increased. Therefore, even if the outer surface of the case 2, which comes into contact with the object to be measured, is made smooth with few irregularities by not including filler or by reducing the filler content, it is possible to make the inner surface of the case 2 a rough surface with rough irregularities. This makes it possible to achieve both high adhesion between the inner surface of the case 2 and the filled resin portion 5 and high adhesion between the object to be measured and the outer surface of the case 2, and to obtain high thermal conductivity inside and outside the case 2.

[0024] Furthermore, the inner surface of the case 2 near the thermal element 3 is textured with coarser irregularities than the area near the opening edge 2a, making it possible to set a smaller draft angle near the opening edge 2a of the case 2. In other words, if the entire inner surface of the case 2 were textured with coarse irregularities, a large draft angle would be required for the entire inner surface when transferring the texture using a mold, resulting in an increase in the size of the case 2. However, in this embodiment, by texturing the area near the thermal element 3 inside the case 2 with coarse irregularities, it is possible to set a larger draft angle at one end of the case 2, making it easier to remove the mold, and by texturing the area near the opening edge 2a with fine irregularities, it is possible to reduce the draft angle at the other end of the case 2, thereby making the entire case more compact.

[0025] Furthermore, in the manufacturing method of the temperature sensor 1 of this embodiment, the case molding process includes a mold surface treatment process in which unevenness is formed on the surface of the mold that forms the inner surface of the case 2 by sandblasting, and a texturing process in which the unevenness of the mold is transferred to the inner surface of the case 2 during injection molding.Therefore, unevenness with controlled roughness can be formed on the mold surface by sandblasting, and texturing can be easily applied to the inner surface of the case 2 during injection molding.

[0026] Furthermore, in the mold surface treatment process, one end of the mold surface is formed with rougher irregularities than the other end, allowing one end of the inner surface of case 2 to have a rougher texture than the other end. Furthermore, since the one end with the rougher irregularities has a larger draft angle than the other end, the mold can be easily removed, and since the other end with the finer irregularities has a smaller draft angle than the one end, case 2 can be made smaller. In this way, by dividing the inner surface of the case 2 into areas A1 and A2 with different roughness, it is possible to achieve both adhesion to the filled resin portion 5 and ease of removal from the mold.

[0027] The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. [Explanation of symbols]

[0028] 1...Temperature sensor, 2...Case, 2a...Open end, 3...Thermal element, 4...Lead wire, 5...Filled resin portion

Claims

1. a resin case having one closed end and the other open end; a heat-sensitive element housed at one end of the case; a pair of lead wires each having one end connected to the thermal element; a resin filling portion that is filled in the case and seals the heat-sensitive element and at least one end of the pair of lead wires with resin; The temperature sensor is characterized in that the inner surface of the case is textured with unevenness that is coarser than the outer surface.

2. 2. The temperature sensor according to claim 1, A temperature sensor characterized in that the inner surface of the case near the heat-sensitive element is textured with rougher irregularities than the area near the open end.

3. 3. A method for manufacturing the temperature sensor according to claim 1 or 2, comprising the steps of: a case molding step of molding the case from resin by injection molding; a resin filling step of filling the case with resin to form the filled resin portion; an insertion step of inserting the heat-sensitive element and the pair of lead wires connected to the heat-sensitive element into the case, a mold surface treatment step of forming irregularities on the surface of a mold that forms the inner surface of the case by sandblasting in the case molding step; and a texturing step of transferring the irregularities of the mold onto the inner surface of the case during the injection molding.

4. 4. The method for manufacturing a temperature sensor according to claim 3, In the mold surface treatment step, roughness is formed on one end side of the surface of the mold so that it is rougher than the other end side, A method for manufacturing a temperature sensor, characterized in that the draft angle at one end of the mold is set larger than that at the other end.

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