Temperature sensor

Abstract

In a temperature sensor 1, conductive patterns 11 are gradually changed in length in the longitudinal direction of a base film 14 from each of both edges in the short direction of the base film 14 toward the central part, become the longest at the central part thereof, and are formed symmetrical with respect to the central part in the short direction. Furthermore, conductive patterns positioned at the central part, among the conductive patterns 11, are formed so as to extend, in the longitudinal direction of the base film 14, beyond a line segment obtained by connecting connection portions 15a, 15b between linear patterns 12a, 12b and electrodes 8a, 8b in the short direction of the base film 14. Thus, disconnection of the conductive patterns 11 formed on an insulating film can be prevented.

Description

Temperature Sensor

[0001] The present invention relates to a temperature sensor having a temperature sensor portion with a film as a base material.

[0002] Temperature sensors with various shapes and thicknesses have been developed depending on the object to be measured, the location to be measured, etc. For example, Patent Document 1 discloses a temperature sensor film in which a metal thin film is formed on a resin film substrate by a sputtering method or the like, and the metal thin film is patterned to form multiple lead portions and resistance temperature measuring portions within the substrate surface.

[0003] Patent Document 2 discloses a thin temperature sensor that can be inserted between battery cells and that uses etching to form a conductive pattern on a metal foil to improve strength, since thin films formed by sputtering or vapor deposition on a thin film-like substrate have low strength and are likely to break when bent, etc.

[0004] Japanese Patent No. 7345341 Japanese Patent Application Laid-Open No. 2023-7041

[0005] In the conventional temperature sensors described above, the end portion of the wiring pattern, which is made of a resistor that serves the function of measuring temperature, is extended as is and connected to the sensor electrode, which causes the problem that the connection (joint) between the wiring pattern and the electrode cannot adapt to bending or thermal expansion, and may break.

[0006] In the case of the temperature sensor film of Patent Document 1, the sensor wiring has a zigzag pattern consisting of multiple vertical and horizontal wires formed by patterning a thin metal film into fine lines. However, in addition to the substrate being flexible (film), the edges of the sensor wiring on the electrode (lead portion) side are formed to be aligned horizontally. Therefore, bending and expansion cause stress to concentrate at the connection (boundary) between the sensor wiring pattern and the lead portion, making that portion prone to breakage.

[0007] Furthermore, in Patent Document 1, the lead portion has a wide line width (area), and when plated, there is a problem that stress is more likely to be applied to the connecting portion between the wiring pattern and the lead portion.

[0008] This problem also applies to a configuration such as the temperature sensor in Patent Document 2, in which a terminal portion, which is an electrode, extends directly from a predetermined conductive pattern serving as a temperature-sensing element portion, and the conductive pattern and the terminal portion are connected.

[0009] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a temperature sensor that can prevent disconnection of the conductive pattern that is the measurement portion pattern.

[0010] As a means for achieving the above object and solving the above problem, the temperature sensor according to the present invention has the following configuration: That is, a temperature sensor having a temperature sensor part using an insulating film that is rectangular in a plan view as a base material, the temperature sensor having a meandering conductive pattern formed on the insulating film, a first electrode that is arranged on one edge in the lateral direction of the insulating film and connected to one end of the conductive pattern, and a second electrode that is arranged on the other edge in the lateral direction of the insulating film and connected to the other end of the conductive pattern, the length of the conductive pattern in the longitudinal direction of the insulating film being such that the length of the conductive pattern is 1 / 2 .0 ... The conductive pattern is formed so as to gradually change toward the center, become longest at the center, and be symmetrical in the short direction with respect to the center, and when the connecting portion between one end of the conductive pattern and the first electrode is defined as a first connecting portion and the connecting portion between the other end of the conductive pattern and the second electrode is defined as a second connecting portion, the conductive pattern located in the central portion is formed so as to exceed the line segment connecting the first connecting portion and the second connecting portion in the short direction in the direction toward the lower end in the longitudinal direction.

[0011] For example, the conductive pattern located in the central portion is formed at a position not exceeding the edge portions of the plating layers applied to the first electrode and the second electrode in the direction toward the lower end of the longitudinal direction of the insulating film, and the length of the conductive pattern in the longitudinal direction of the insulating film is characterized by changing in a step-like manner in the longitudinal direction from each of the both short-side edge portions of the insulating film toward the central portion.

[0012] Furthermore, for example, the length of the conductive pattern in the longitudinal direction of the insulating film may change in an arc shape in the longitudinal direction from each of both edges in the lateral direction of the insulating film toward the center thereof, and the conductive pattern having a predetermined shape may be formed in a region sandwiched between the first connecting portion and the second connecting portion in the lateral direction of the insulating film.

[0013] Furthermore, for example, the present invention is characterized in that through holes of a predetermined shape are provided in a region of the first electrode near the first connecting portion and a region of the second electrode near the second connecting portion.Furthermore, for example, the present invention is characterized in that the conductive patterns located on both short edge portions of the insulating film are folded back on the way to the upper end portion of the insulating film in the long direction, and the ends of the folded back conductive patterns are connected to adjacent conductive patterns.Furthermore, for example, the present invention is characterized in that the conductive patterns are patterned by etching a metal foil made of titanium (Ti) on the insulating film.

[0014] According to the present invention, it is possible to provide a temperature sensor that has a flexible structure using a film as a base material, prevents disconnection of the conductive pattern formed on the film, and is capable of highly accurate and stable temperature measurement.

[0015] FIG. 1 is a perspective view of the appearance showing the overall configuration of a temperature sensor according to the present embodiment. FIG. 2 is a cross-sectional view of the temperature sensor of FIG. 1 cut along the line of the arrows AA'. FIG. 3 is a plan view of a temperature sensor portion of a temperature sensor according to Example 1. FIG. 4 is a plan view of a temperature sensor portion of a temperature sensor according to Example 2. FIG. 5 is a plan view of a temperature sensor portion of a temperature sensor according to Example 3. FIG. 6 is a plan view of a temperature sensor portion of a temperature sensor according to Example 4. FIG. 7 is a plan view of a temperature sensor portion of a temperature sensor according to Example 8.

[0016] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Fig. 1 is an external perspective view showing the overall configuration of a temperature sensor according to this embodiment. Fig. 2 is a cross-sectional view of the temperature sensor shown in Fig. 1 taken along the line AA'.

[0017] The temperature sensor 1 according to this embodiment includes a temperature sensor unit 3 and a cable unit 5 electrically and mechanically connected to the temperature sensor unit 3. The temperature sensor unit 3 is composed of a temperature sensor element 7, which is a resistor having a wiring pattern (described later), and other components. The cable unit 5 extracts, as an electrical signal, a change in resistance value in response to a temperature change detected by the temperature sensor unit 3.

[0018] The temperature sensor element 7 is a thermosensitive element in which a metal foil is bonded to a base film 2 via an adhesive layer 4, and then etched to form a predetermined wiring pattern (conductive pattern). The metal foil is, for example, titanium (Ti) or a titanium (Ti)-based, iron (Fe)-based, or nickel (Ni)-based alloy. In addition to metal foil, a metal thin film (Ti, Ni, Pt, etc.) can be deposited by sputtering or the like and then etched to form the predetermined wiring pattern. Taking processability into consideration, the thickness of the metal foil is preferably 2 μm or more and 10 μm or less.

[0019] The base film 2 is an insulating film made of thermoplastic resin, and has a thickness of, for example, 20 to 80 μm. The film is made of PET, polyimide, polyester, or the like. The cable portion 5 is a flexible flat cable (FFC). The tip portion of the cable portion 5 is connected to one end of the sensor element 7 via a solder layer 9 or the like.

[0020] 2, the entire upper surface of the temperature sensor element 7 and a part of the cable part 5 (the connection part with the temperature sensor element 7) may be covered with an insulating protective film 6. Alternatively, only the entire upper surface of the temperature sensor element 7 may be covered with a protective film.

[0021] Next, the temperature sensor according to this embodiment will be described in detail, including features of the conductive pattern of the temperature sensor portion.

[0022] 3 is a plan view of a temperature sensor unit of a temperature sensor according to Example 1 of the present embodiment. The temperature sensor unit 13 of the temperature sensor according to Example 1 measures temperature using a temperature coefficient of resistance (TCR) change in resistance value caused by a temperature change of a conductive pattern 11 serving as a temperature-sensitive film formed on a base film 14.

[0023] By using titanium (Ti), a single metal, for the conductive pattern 11, the temperature-resistance characteristics of the temperature sensor portion 13 are stabilized, and the variation in the TCR value is suppressed, thereby making it possible to obtain a highly accurate temperature sensor.

[0024] The conductive pattern 11 is composed of a plurality of linear patterns 11a patterned by etching a titanium (Ti) metal foil, and a plurality of folded patterns 11b and 11c. The linear patterns 11a are patterns that extend linearly for a predetermined length in the longitudinal direction (y direction) of the base film 14, while being spaced apart from each other by a predetermined distance in the lateral direction (x direction) of the base film 14. The folded patterns 11b and 11c have a hairpin shape, and each of them connects the upper ends and lower ends of adjacent linear patterns 11a.

[0025] Of the linear patterns 11a, linear pattern 12a located on the left edge in the width direction of base film 14 has its upper end in the longitudinal direction connected to linear pattern 11a by folded pattern 11b and its lower end connected to electrode 8a. Similarly, linear pattern 12b located on the right edge in the width direction of base film 14 has its upper end in the longitudinal direction connected to linear pattern 11a by folded pattern 11b and its lower end connected to electrode 8b. As a result, conductive pattern 11 becomes a single, continuous conductive pattern that meanders between electrodes 8a and 8b.

[0026] The linear patterns 11a are formed so that the length in the longitudinal direction of the base film 14 increases from each of the two short-side edges of the base film 14 toward the center (the central region indicated by the symbol CL in FIG. 3).

[0027] More specifically, the straight line patterns 11a are formed so that they are aligned in the longitudinal direction of the base film 14 on the side where they are connected to each other by the folded pattern 11b (the longitudinal upper end side of the base film 14), and on the side where they are connected to each other by the folded pattern 11c (the longitudinal lower end side of the base film 14), they are formed so that they become longer in a stepped manner in the direction toward the longitudinal lower end of the base film 14 as they move from each of the two short edge portions (both end regions) of the base film 14 toward the center (indicated by the symbol CL).

[0028] As a result, the conductive pattern 11 is symmetrical with respect to the center (center line CL), i.e., symmetrical in the short direction. Making the conductive pattern 11 symmetrical eliminates bias in the change in TCR in the conductive pattern 11, improving the temperature measurement accuracy of the temperature sensor unit 13 acting as a temperature sensing element. Furthermore, making the conductive pattern 11 meandering allows a resistance pattern with a long path to be formed in a limited area on the base film 14, thereby enabling the conductive pattern 11 to have a high resistance.

[0029] Furthermore, by changing the conductive pattern 11 stepwise, the proximity distance between the conductive pattern 11 and the electrodes 8a, 8b on the base film 14 can be kept constant, preventing the occurrence of short circuits and the like.

[0030] Furthermore, if the connection portion between the linear pattern 12a and the electrode 8a on the base film 14 is defined as the connecting portion 15a, and the connection portion between the linear pattern 12b and the electrode 8b is defined as the connecting portion 15b, the conductive pattern located in the center of the above-mentioned step-like changing conductive pattern 11, i.e., the conductive pattern having the longest portion, is formed so as to extend beyond the line segment connecting the connecting portion 15a and the connecting portion 15b in the short direction of the base film 14 in the direction toward the bottom end of the longitudinal direction of the base film 14.

[0031] By forming the conductive pattern 11 in this way so that the central portion, which is the longest portion of the conductive pattern 11, has a length that exceeds the connecting portions 15a, 15b between the linear patterns 12a, 12b and the electrodes 8a, 8b, respectively, in the longitudinal direction of the base film 14, the conductive pattern is also provided between the connecting portions 15a, 15b on the base film 14. This eliminates weak portions in the conductive pattern 11 that are vulnerable to bending and thermal expansion, and prevents stress from concentrating on the connecting portions between the linear patterns and the electrodes, thereby preventing breakage of the conductive pattern.

[0032] In order to increase the strength of the linear patterns 12a and 12b located at the edges of the base film against breakage, the linear patterns 12a and 12b are formed wider than the conductive pattern 11. If the line width of the linear patterns 12a and 12b is W1 and the line width of the conductive pattern 11 is W2, then, for example, W1≈W2×2.

[0033] The number of stages when the length of the conductive pattern 11 changes in the longitudinal direction of the base film 14 is not limited to two stages as in the first embodiment shown in FIG. 3, but may be three stages, four stages, or the like.

[0034] Plated layers 17a, 17b made of, for example, nickel (Ni) are formed on the electrodes 8a, 8b of the temperature sensor unit 13 so as to cover the regions marked in Fig. 3. If the line segment connecting the upper edges of the plated layers 17a, 17b in the longitudinal direction of the base film 14 to the short side of the temperature sensor unit 13 is indicated by dashed line B as shown in Fig. 3, the longest portion of the conductive pattern 11 described above is formed at a position not exceeding dashed line B in the direction toward the bottom end of the base film 14 in the longitudinal direction.

[0035] In other words, by preventing plating from covering the longest part of the conductive pattern 11, which is formed so as to extend in a stepped manner in the longitudinal direction of the base film 14, it is possible to prevent temperature measurement errors caused by changes in TCR in the conductive pattern 11.

[0036] <Example 2> In the temperature sensor of this embodiment, the conductive pattern of the temperature sensor portion is not limited to being step-like as in the temperature sensor portion of Example 1, as long as the length of the base film in the longitudinal direction changes stepwise from each of the two short edge portions of the base film toward the center and is formed so as to be symmetrical with respect to the center line CL.

[0037] 4 is a plan view of the temperature sensor portion of a temperature sensor according to Example 2 of this embodiment. As in the temperature sensor portion 23 shown in FIG. 4, the linear pattern 21a of the conductive pattern 21 may be formed so that it gradually changes in an arc shape (preferably a circular arc shape) rather than a stepped shape when it is lengthened in the direction from the short-side edge of the base film 24 toward the center toward the lower end of the long-side direction of the base film 24. Even in this case, the conductive pattern 21 is symmetrical with respect to the center line CL.

[0038] In addition, in the temperature sensor portion 23 shown in Figure 4, the central portion having the longest part of the conductive pattern 21 that changes gently into an arc shape is formed so as to exceed the line segment B that connects the connecting portions 15a and 15b in the short direction of the base film 24 in the direction toward the lower end of the longitudinal direction of the base film 24.

[0039] Furthermore, in the temperature sensor section 23, the conductive pattern 21 changes smoothly into an arc shape, so that the proximity distance between the conductive pattern 21 and the electrodes 8a, 8b on the base film 24 is maintained constant, thereby preventing the occurrence of short circuits, etc.

[0040] As in the first embodiment, the second embodiment is also configured such that the plating layers 17 a and 17 b applied to the electrodes 8 a and 8 b on the base film 24 do not cover the longest portion of the conductive pattern 21 .

[0041] As mentioned above, stress is concentrated at the connection points between the linear patterns of the conductive pattern formed on the base film of the temperature sensor section and the electrodes, making the conductive pattern prone to breakage. Therefore, a reinforcing pattern may be formed in the area sandwiched between these connection points in the short direction of the base film.

[0042] 5 is a plan view of a temperature sensor portion of a temperature sensor according to Example 3 of this embodiment. In the temperature sensor portion 33 shown in Fig. 5, a reinforcing pattern 35 is formed in an area sandwiched between connecting portions 15a and 15b of the linear patterns 12a and 12b and the electrodes 8a and 8b in the short-side direction of the base film 34.

[0043] The reinforcing pattern 35 is made of titanium (Ti), the same material as the conductive pattern 31, and has a shape that conforms to the stepped shape of the lower end of the conductive pattern 31 and the shape of the inclined portions of the outer peripheries of the electrodes 8a and 8b.

[0044] 6 is a plan view of a temperature sensor portion of a temperature sensor according to Example 4 of the present embodiment. The temperature sensor portion 43 shown in Fig. 6 is an example in which a pair of reinforcing patterns 45a, 45b are formed in an area sandwiched between connecting portions 15a, 15b of linear patterns 12a, 12b and electrodes 8a, 8b in the short-side direction of base film 44.

[0045] The reinforcing patterns 45a and 45b are made of titanium (Ti), are thin wire-like in their entirety, and are formed so as to be inclined along the inclined outer peripheral portions of the electrodes 8a and 8b.

[0046] 7 is a plan view of a temperature sensor part of a temperature sensor according to Example 5 of this embodiment, showing a temperature sensor part 53 provided with a reinforcing pattern 55 between electrodes 8 a and 8 b. The reinforcing pattern 55 has a thin line shape extending in the longitudinal direction of the base film 54, and is composed of three bar-shaped patterns in this example.

[0047] The presence of the reinforcing pattern 55 increases the proportion of metal (titanium (Ti)) between the electrodes 8 a and 8 b in the temperature sensor unit 53, making it possible to accommodate thermal expansion in the region between the electrodes 8 a and 8 b. The shape of the reinforcing pattern 55 is not limited to a thin line shape, and may be, for example, a rectangular pattern.

[0048] 8 is a plan view of a temperature sensor portion of a temperature sensor according to Example 6 of this embodiment. Here, attention was paid to the fact that, in the temperature sensor portion according to Examples 1, 2, etc. described above, of the linear patterns located on both edges in the short direction of the base film, for example, the portions indicated by dashed circles 65a and 65b in Fig. 8 are most vulnerable to bending or the like and are therefore susceptible to breakage.

[0049] Since titanium (Ti) has a relatively high hardness, the conductive pattern formed by extending titanium foil into thin wires becomes more prone to breakage the longer it is. Therefore, in the temperature sensor unit 63 according to Example 6 shown in Figure 8, the linear patterns 62a and 62b located on both short-side edges of the base film 64 and connected to the electrodes 8a and 8b are shortened in the longitudinal direction of the base film 64.

[0050] 3 and 4, the linear patterns 62a and 62b do not extend to the upper end of the base film 64 in the longitudinal direction, but are connected to the conductive pattern 61 by a folded pattern at the midpoint. This improves the resistance of the shortened linear patterns 62a and 62b to bending and the like.

[0051] 9 is a plan view of the temperature sensor part of a temperature sensor according to Example 7 of this embodiment. One of the reasons why the linear patterns formed on both short-side edges of the base film in the temperature sensor part are likely to break is the distribution of the metal material (titanium) that constitutes the linear patterns.

[0052] In the temperature sensor unit 73 shown in Fig. 9, when the amounts of metal material constituting the linear patterns 12a, 12b and the electrodes 8a, 8b connected thereto are compared, the amount of metal material used for the electrodes 8a, 8b, which have larger areas, is greater. This means that when the linear patterns 12a, 12b and the electrodes 8a, 8b are viewed as a single unit, the amount of metal material varies greatly in the portions indicated by dashed circles 75a, 75b in Fig. 9.

[0053] Therefore, in the temperature sensor part 73 according to Example 7 shown in Figure 9, through holes 77a and 77b, which are areas without metal material, are provided in the areas of the electrodes 8a and 8b near the portions connected to the linear patterns 12a and 12b, thereby adjusting the amount of metal material in the electrodes 8a and 8b.

[0054] By providing the through holes in this way and adjusting the amount of metal per unit area, areas where the amount of metal material changes significantly are eliminated, and the amount of metal material changes gradually. As a result, there are no areas in the temperature sensor part 73 that are extremely vulnerable to bending, etc., as indicated by the dashed circles 75a and 75b, so the linear patterns 12a and 12b are more resistant to bending, thermal expansion, etc., and breakage can be prevented.

[0055] The shape of the through holes 77a, 77b is not limited to the triangle shown in Fig. 9, but may be a round hole, a triangle without corners, etc. The number of through holes may be either one or more. Furthermore, the through holes 77a, 77b are formed so as to avoid the plated regions of the electrodes 8a, 8b.

[0056] 10 is a plan view of a temperature sensor unit of a temperature sensor according to Example 8 of this embodiment. Here, in the temperature sensor unit 83, the pattern shapes of the connection portions 85a, 85b between the linear patterns 12a, 12b and the electrodes 8a, 8b are circular in plan view, which is larger than the line width of the linear patterns. In this way, by increasing the pattern area of ​​the connection portions between the linear patterns and the electrodes, it is possible to prevent disconnection of the conductive patterns 12a, 12b.

[0057] 3, 4, 5, etc., which show the temperature sensor portions of the temperature sensors according to Examples 1 to 8 of this embodiment described above, the conductive patterns 11, 21, 31, etc. are depicted as serpentine patterns spaced apart by a predetermined distance for convenience of illustration. However, the serpentine conductive patterns 11, 21, 31, etc. are not shown in the drawings. However, if the arc-shaped first and second turn portions alternately folded back on both ends of the conductive patterns are arranged with a phase difference, high resistance can be achieved, which contributes to high sensitivity and miniaturization.

[0058] The distance between adjacent opposing main pattern portions connecting these first turn portions and second turn portions is set to gradually narrow with the inner diameter dimensions of the first turn portion, second turn portion, etc. as the maximum width.

[0059] As described above, the temperature sensors according to Examples 1 to 8 of this embodiment prevent breakage of the conductive pattern, which is the measurement part pattern made of metal foil, due to expansion caused by heat generation of the object to be measured in a high-temperature environment, and provide a temperature sensor that is flexible to bending and can be used for a long period of time.

[0060] REFERENCE SIGNS LIST 1 Temperature sensor 2, 14, 24, 34, 44, 54, 64, 74, 84 Base film 3, 13, 23, 33, 43, 53, 63, 73, 83 Temperature sensor section 4 Adhesive layer 5 Cable section 6 Protective film 7 Temperature sensor element 8a, 8b Electrode 9 Solder layer 11, 21, 31, 41, 51, 61 Conductive pattern 11a, 11b, 62a, 62b Linear pattern 11b, 11c Folded pattern 15a, 15b, 85a, 85b Connecting section 17a, 17b Plating layer 45a, 45b, 55 Reinforcement pattern 77a, 77b Through hole

Claims

1. A temperature sensor having a temperature sensor portion whose base material is an insulating film that is rectangular in plan view, comprising: a meandering conductive pattern formed on the insulating film; a first electrode disposed on one edge in the lateral direction of the insulating film and connected to one end of the conductive pattern; and a second electrode disposed on the other edge in the lateral direction of the insulating film and connected to the other end of the conductive pattern, wherein the length of the conductive pattern in the longitudinal direction of the insulating film changes stepwise from each of the lateral edge portions of the insulating film toward the center, becoming longest at the center, and being symmetrical in the lateral direction with respect to the center, A temperature sensor characterized in that, when a connection portion between one end of the conductive pattern and the first electrode is defined as a first connection portion and a connection portion between the other end of the conductive pattern and the second electrode is defined as a second connection portion, the conductive pattern located in the central portion of the conductive pattern is formed so as to exceed, in a direction toward the lower end portion of the longitudinal direction, a line segment connecting the first connection portion and the second connection portion in the short direction.

2. A temperature sensor as described in claim 1, characterized in that the conductive pattern located in the central portion is formed at a position that does not extend beyond the edges of the plating layers applied to the first electrode and the second electrode in the direction toward the lower end of the longitudinal direction of the insulating film.

3. A temperature sensor as described in claim 1 or 2, characterized in that the length of the conductive pattern in the longitudinal direction of the insulating film changes stepwise in the longitudinal direction from each of the two short edge portions of the insulating film toward the center.

4. A temperature sensor as described in claim 1 or 2, characterized in that the length of the conductive pattern in the longitudinal direction of the insulating film changes in an arc shape in the longitudinal direction from each of the two short edges of the insulating film toward the center.

5. A temperature sensor according to claim 1 or 2, characterized in that a conductive pattern of a predetermined shape is formed in the area sandwiched between the first connecting portion and the second connecting portion in the short direction of the insulating film.

6. A temperature sensor as described in claim 1 or 2, characterized in that a through hole of a predetermined shape is provided in the area of ​​the first electrode near the first connecting portion and in the area of ​​the second electrode near the second connecting portion.

7. A temperature sensor as described in claim 1 or 2, characterized in that the conductive patterns located on both short edge portions of the insulating film are folded back on the way to the top end of the insulating film in the long direction, and the ends of the folded back conductive patterns are connected to adjacent conductive patterns.

8. A temperature sensor according to claim 1 or 2, characterized in that the conductive pattern is a conductive pattern formed by etching a metal foil made of titanium (Ti) on the insulating film.

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