Method for manufacturing temperature detector

Abstract

To provide a method for manufacturing a temperature detector that can comparatively easily manufacture a temperature detector while remarkably reducing usage amounts of internal insulative synthetic resin and also position at least a portion from a thermistor chip coated with thermosetting synthetic resin to a connection end part of a lead wire at a predetermined site, sufficiently easily and sufficiently accurately, without needing cumbersome positioning operation.SOLUTION: The method for manufacturing a temperature detector includes: a storing step in which at least portions from a thermistor chip coated with insulative thermosetting synthetic resin 30 in an uncured state to connection end parts of lead wires 28a and 28b are at least partially stored in receiving grooves 6 and 14 arranged on one inner surfaces of plate members 2 and 4; an overlapping step in which one sides of the plate members are overlapped with the other sides of the plate members after the storing step; and a pressing / hearing step in which inner surface of the one sides of the plate member are pressed on inner surface of the other sides of the plate members and the insulative thermosetting synthetic resin is heated and then cured, after the overlapping step.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a temperature detector, and more particularly to a method for manufacturing a temperature detector having a thermistor chip, a pair of lead wires connected to the thermistor chip directly or via a lead wire, and an insulating coating that covers at least the area from the thermistor chip to the connection end of the lead wires. [Background technology]

[0002] As is well known to those skilled in the art, temperature detectors having a thermistor chip, a pair of lead wires connected to the thermistor chip directly or via a lead wire, and an insulating coating covering at least the thermistor chip to the connection end of the lead wires are widely used. When such a temperature detector is used as a temperature detector for a secondary battery mounted in an automobile, for example, it is desired that the temperature detector has excellent heat resistance and mechanical strength, can contact the object to be measured over a relatively wide area, and is sufficiently thin. The following Patent Document 1 discloses a method for manufacturing a temperature detector that satisfies such a requirement, in which the thermistor chip, a pair of lead wires connected to the thermistor chip via a lead wire, and at least the thermistor chip to the connection end of the lead wires are disposed between a pair of inner insulating synthetic resin sheets and a pair of outer insulating synthetic resin sheets, and the pair of inner insulating synthetic resin sheets and the pair of outer insulating synthetic resin sheets are pressurized and heated in a direction approaching each other and perpendicular to their planes. Each of the pair of inner insulating synthetic resin sheets is made of fluorinated ethylene propylene, which is a fluorine-based synthetic resin with a relatively low melting point, and each of the pair of outer insulating synthetic resin sheets is made of polytetrafluoroethylene, which is a fluorine-based synthetic resin with a relatively high melting point. The pair of inner synthetic resin sheets and the pair of outer synthetic resin sheets are rectangular in plan view and have the same dimensions and the same plan view. Heating is performed at a temperature higher than the melting point of fluorinated ethylene propylene but lower than the melting point of polytetrafluoroethylene, so that the pair of outer insulating synthetic resin sheets do not melt, but the pair of inner insulating synthetic resin sheets melt and then harden. The melted and hardened inner insulating synthetic resin sheet and outer insulating synthetic resin sheet constitute the insulating coating. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Republished Patent WO2019 / 087755 Summary of the Invention [Problem to be solved by the invention]

[0004] The method disclosed in Patent Document 1 has the following problems to be solved: (1) it is necessary to position the pair of outer insulating synthetic resin sheets together with the pair of inner insulating synthetic resin sheets with sufficient precision when applying pressure and heat, making the operation complicated; and (2) the use of the pair of inner insulating synthetic resin sheets results in the amount of inner insulating synthetic resin used being greater than necessary, resulting in increased manufacturing costs.

[0005] In view of the above facts, the present inventor previously proposed a method in Japanese Patent Application No. 2022-166278 in which an uncured insulating thermosetting synthetic resin is applied at least from the thermistor chip to the connection end of the lead wire, and then at least the thermistor chip to which the thermosetting synthetic resin is applied is interposed between a pair of insulating synthetic resin sheets, and the pair of sheets is pressed in a direction approaching each other and in a direction perpendicular to their planes while heating the thermosetting synthetic resin. According to this method, instead of using a pair of inner insulating synthetic resin sheets, an uncured thermosetting synthetic resin is applied at least from the thermistor chip to the connection end of the lead wire, so that a temperature detector can be manufactured relatively easily and with a significantly reduced amount of inner insulating synthetic resin used compared to conventional methods.

[0006] However, the method proposed by the inventor as described above is still not fully satisfactory. When positioning at least the thermistor chip, which is coated with thermosetting synthetic resin between a pair of insulating synthetic resin sheets, to the connection end of the lead wire, it is not always easy to position it accurately with respect to the pair of insulating synthetic resin sheets, the positioning operation is complicated, and there is a tendency for errors to occur in the positioning with respect to the pair of insulating synthetic resin sheets.

[0007] The present invention has been made in view of the above-mentioned facts, and its main technical object is to provide a method for manufacturing a new and improved temperature detector which can be manufactured relatively easily and with a significantly reduced amount of inner insulating synthetic resin used compared to conventional methods, and which can also position at least the thermistor chip to the connection end of the lead wire, on which the thermosetting synthetic resin is applied, in a predetermined position sufficiently easily and accurately without the need for complicated positioning operations. [Means for solving the problem]

[0008] As a result of extensive research and experimentation, the inventors have found that the above-mentioned main technical object can be achieved by preparing a pair of plate members formed from insulating synthetic resin, at least one of which has a receiving groove extending in a predetermined direction on its inner surface, and at least partially accommodating, within the receiving groove provided on the inner surface of one of the plate members, at least the thermistor chip to the connection end of the lead wire, on which uncured insulating thermosetting synthetic resin is applied.

[0009] That is, according to the present invention, a method for manufacturing a temperature detector that achieves the above-mentioned main technical object includes the following steps: A method for manufacturing a temperature detector including a thermistor chip, a pair of lead wires connected to the thermistor chip directly or via a lead wire, and an insulating coating covering at least an area extending from the thermistor chip to a connection end of the lead wires, comprising the steps of: a preparation step of preparing a pair of plate members formed from an insulating synthetic resin, at least one of which has a receiving groove extending in a predetermined direction on an inner surface thereof; a coating step of coating an uncured insulating thermosetting synthetic resin at least from the thermistor chip to the connection end of the lead wire; a housing step of at least partially housing, after the preparing step and the applying step, the thermistor chip to which the uncured insulating thermosetting synthetic resin has been applied, and the connection end of the lead wire, in the receiving groove provided on the inner surface of the one of the plate members; a superposing step of superposing the one of the plate members on the other of the plate members after the accommodating step; a pressing and heating step of pressing the inner surface of the other plate member against the inner surface of the one plate member and heating the insulating thermosetting synthetic resin to harden the insulating thermosetting synthetic resin after the overlapping step; A method is provided comprising:

[0010] Preferably, the receiving groove disposed on the inner surface of the one of the plate members extends from near one edge of the one of the plate members to the other edge of the one of the plate members. A receiving groove is also disposed on the inner surface of the other of the plate members, and it is preferable that when the other of the plate members is placed on the one of the plate members, the receiving groove disposed on the inner surface of the one of the plate members and the receiving groove disposed on the inner surface of the other of the plate members are aligned and positioned. It is preferable that the receiving groove disposed on the inner surface of the other of the plate members extends from near one edge of the other of the plate members to the other edge of the other of the plate members, and the cross-sectional shape of the portion from near the other edge to the other edge is two concave arcs arranged in parallel corresponding to the outer shapes of a pair of lead wires. In the coating step, it is convenient to coat at least the thermistor chip to the connection end of the lead wire by immersing at least the thermistor chip to the connection end of the lead wire in uncured insulating thermosetting synthetic resin and then removing the resin from the insulating thermosetting synthetic resin. The insulating thermosetting synthetic resin is preferably an epoxy-based synthetic resin mixed with silica particles to impart thixotropy. Each of the plate members is preferably made of a polyamide-based synthetic resin. Each of the plate members preferably has a thickness of 0.7 to 1.0 mm. Preferably, the outer shape of the one plate member and the outer shape of the other plate member are the same rectangular shape. It is preferable that the receiving groove disposed on the inner surface of one of the plate members extends longitudinally through the widthwise center of the inner surface of one of the plate members. Preferably, the one and the other of the plate members are connected via a flexible thin-walled connecting piece, and the one and the other of the pair of plate members and the flexible thin-walled connecting piece are integrally formed. It is convenient that the flexible thin-walled connecting piece connects one end edge of the one of the plate members to one end edge of the other of the plate members. Two through holes or protrusions extending to a recess or outer surface are formed at a predetermined interval on the inner surface of the one of the plate members, and two through holes extending to a protrusion, recess, or outer surface are formed at a predetermined interval on the inner surface of the other of the pair of plate members, and the other of the pair of plate members is preferably positioned relative to the one of the pair of plate members as required by engaging the protrusions with the recesses or through holes. Effect of the Invention

[0011] The method of the present invention not only enables relatively simple manufacturing compared to conventional methods and with a significantly reduced amount of inner insulating synthetic resin used, but also makes it possible to position at least the thermistor chip, on which the thermosetting synthetic resin is applied, to the connection end of the lead wire in the specified position with sufficient ease and accuracy without the need for complicated positioning operations. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a perspective view showing a preferred embodiment of a pair of plate members used in the method of the present invention. [Diagram 2] FIG. 2 is a perspective view showing a thermistor chip used in the method of the present invention and a pair of lead wires connected to the thermistor chip via lead wires. [Diagram 3] 3 is a perspective view showing a state in which an insulating thermosetting synthetic resin is applied to the connection ends of the thermistor chip shown in FIG. 2 and a pair of lead wires connected to the thermistor chip via lead wires. FIG. [Figure 4] FIG. 4 is a perspective view showing a state in which the thermistor chip coated with the insulating thermosetting synthetic resin shown in FIG. 3, the connection ends of a pair of lead wires connected to the thermistor chip via lead wires, and portions adjacent to the connection ends of the lead wires are partially accommodated in a receiving groove arranged on the inner surface of one of the pair of plate members shown in FIG. 1. [Diagram 5] 5 is a perspective view showing a state in which one of the pair of plate members is placed on the other in the state shown in FIG. 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The invention will now be described in further detail with reference to the accompanying drawings, in which preferred embodiments of the invention are shown.

[0014] Preparation process With reference to FIG. 1 showing a preferred embodiment of a pair of plate members used in the method of the present invention, it is important to prepare a pair of plate members 2 and 4 in the method of the present invention. One of the pair of plate members 2 and 4, i.e., the plate member 2, is composed of a plate-like member having a rectangular outer shape. It is important that a receiving groove 6 extending in a predetermined direction is arranged on the inner surface of this plate member 2. In the illustrated embodiment, the receiving groove 6 extends continuously in the longitudinal direction in the center of the width direction of the plate member 2 from the vicinity of one end edge 8 of the plate member 2 to the other end edge 10. The portion of the receiving groove 6 excluding both end edges is approximately an elongated rectangle in a plan view, and one end edge of the receiving groove 6 is arc-shaped in a plan view. The cross-sectional shape of the receiving groove 6 may be an elongated rectangle. The plate member 2 further has two through holes 12 formed at a center in the longitudinal direction at a distance in the width direction. One of the through holes 12 is located at a distance on one side of the receiving groove 6, and the other is located at a distance on the other side of the receiving groove 6. The through hole 12 extending from the inner surface to the outer surface of the plate member 2 may have a circular cross-sectional shape. If desired, the through hole 12 may be replaced by a recess, preferably having a circular cross-sectional shape.

[0015] The other of the pair of plate members 2 and 4, that is, the plate member 4, is also composed of a plate-like member having a rectangular outer shape. It is preferable that the outer shape of the plate member 2 and the outer shape of the plate member 4 are substantially the same. A receiving groove 14 is also formed on the inner surface of the plate member 4. In the illustrated embodiment, the receiving groove 14 extends continuously in the longitudinal direction in the widthwise center of the plate member 4 from the vicinity of one end edge 16 of the plate member 4 to the other end edge 18. The main portion 14a of the receiving groove 14 is an elongated rectangular shape in a plan view except for the one end edge, and the one end edge is an arc shape in a plan view. The cross-sectional shape of the receiving groove 14 may be an elongated rectangle. On the other hand, the portion 14b of the receiving groove 14 from the vicinity of the other end edge 18 of the plate member 4 to the other end edge 18 is a rectangle in a plan view, but has two concave arc shapes arranged in parallel in the cross section. The two concave arc shapes arranged in parallel in the cross section correspond to the cross-sectional shape of a pair of lead wires described later. Two protrusions 20 are further formed on the inner surface of the plate member 4 at the center in the longitudinal direction, spaced apart in the width direction. The locations of the protrusions 20 correspond to the locations of the through holes 12 in the plate member 2, and the cross-sectional shape of the protrusions 20 is substantially the same as the cross-sectional shape of the through holes 12 formed in the plate member 2, and is preferably circular. One of the protrusions 20 is located on one side of the receiving groove 14 with a space therebetween, and the other is located on the other side of the receiving groove 14 with a space therebetween.

[0016] Continuing with the explanation with reference to Fig. 1, in the illustrated embodiment, a pair of plate members 2 and 4 are connected by a flexible thin connecting piece 22. The flexible thin connecting piece 22 is composed of a narrow strip that connects one end edge 8 of the plate member 2 and one end edge 16 of the plate member 4. The plate members 2 and 4 can pivot relative to each other by bending the flexible thin connecting piece 22.

[0017] The plate members 2 and 4 and the flexible thin-walled connecting piece 22 described above are conveniently molded integrally from a suitable insulating synthetic resin. A suitable example of the insulating synthetic resin is polyamide-based synthetic resin, which has high mechanical strength. The thickness of the plate members 2 and 4 may be about 0.7 to 1.0 mm, and the thickness of the flexible thin-walled connecting piece 22 may be about 0.1 to 0.2 mm.

[0018] Thus, in the above-described embodiment, the plate members 2 and 4 are connected by the flexible thin-walled connecting piece 22, but if desired, the plate members 2 and 4 can be separate members. Also, in the above-described embodiment, the receiving groove 14 is also provided on the inner surface of the plate member 4, but such receiving groove 14 can be omitted. When the receiving groove 14 is omitted, it is desirable to somewhat increase the depth of the receiving groove 6 provided on the inner surface of the plate member 2. Furthermore, in the illustrated embodiment, the through hole 12 (or recess) is formed in the plate member 2 and the protrusion 20 is formed in the plate member 4, but it is also possible to form the protrusion 20 in the plate member 2 and the through hole 12 (or recess) in the plate member 4.

[0019] Coating process FIG. 2 shows the thermistor chip 24 and a pair of lead wires 28a and 28b connected to the thermistor chip 24 via lead wires 26a and 26b. Although not shown, the thermistor chip 24 is composed of a thermistor, an element electrode layer laminated on both surfaces of the thermistor, and a cover electrode layer laminated on the element electrode layer. Such a thermistor chip 24 itself is a well-known form and is described, for example, in JP 2020-21861 A, so its details will not be described in this specification. The tips of a pair of lead wires 26a and 26b are connected to the thermistor chip 24 by appropriate connecting means such as welding or soldering, and the tips of the lead wires 28a and 28b are connected to the rear ends of the lead wires 26a and 26b by appropriate connecting means such as welding or soldering. The lead wires 26a and 26b may be made of copper-nickel alloy wire, and the lead wires 28a and 28b may be made of a core material made of many twisted copper wires and a coating made of insulating synthetic resin. The coating is removed from the tip end, i.e., the connection end, of the lead wires 28a and 28b, and the core material is connected to the lead wires 26a and 26b. In the illustrated embodiment, the thermistor element to which the tip end of the lead wires 26a and 26b is connected is further sealed with synthetic resin or glass. In the illustrated embodiment, the lead wires 28a and 28b are connected to the thermistor element via the lead wires 26a and 26b, but the method of the present invention can also be applied to a form in which the lead wires 28a and 28b are directly connected to the thermistor element.

[0020] In the method of the present invention, as shown in Fig. 3, at least the thermistor chip 24, the lead wires 26a and 26b, and the connection ends of the lead wires 28a and 28b, i.e., at least from the thermistor chip 24 to the connection ends of the lead wires 28a and 28b, are coated with an insulating thermosetting synthetic resin 30. Such coating can be suitably performed by immersing the thermistor chip 24 to the connection ends of the lead wires 28a and 28b (including the connection ends from which the coating has been removed and the adjacent portions of the lead wires 28a and 28b where the coating is present) in the uncured insulating thermosetting synthetic resin, and then removing them from the insulating thermosetting synthetic resin. The amount of the thermosetting synthetic resin 30 applied can be appropriately adjusted by adjusting the speed at which the thermistor chip 24 to the connection ends of the lead wires 28a and 28b (and the adjacent portions of the lead wires 28a and 28b where the coating is present) are removed from the thermosetting synthetic resin. A relatively large amount of thermosetting synthetic resin can be applied by removing the area from the thermistor chip 24 to the connection ends of the lead wires 28a and 28b (and the adjacent portions of the lead wires 28a and 28b where the coating is present) at a relatively slow speed, whereas a relatively small amount of thermosetting synthetic resin can be applied by removing the area at a relatively high speed (the amount of thermosetting synthetic resin to be applied will be described later). A suitable example of the thermosetting synthetic resin to be applied is an epoxy synthetic resin mixed with silica particles to impart thixotropy to a thixotropy index of about 3.0 to 3.9.

[0021] If desired, instead of applying the thermosetting synthetic resin 30 by dip coating, a suitable applicator such as a paintbrush may be used to apply the uncured thermosetting synthetic resin at least from the thermistor chip 24 to the connection ends of the leads 28a and 28b (and adjacent portions of the leads 28a and 28b where the coating is present).

[0022] Storage process In the method of the present invention, the accommodation step is performed after the preparation step and the application step. In this accommodation step, as shown in Fig. 4, at least the thermistor chip 24, the lead wires 26a and 26b, and the connection ends of the lead wires 28a and 28b, which are coated with the uncured thermosetting synthetic resin 30, are at least partially accommodated in the receiving groove 6 arranged on the inner surface of one of the pair of plate members, i.e., the plate member 2. In the illustrated embodiment, the thermistor chip 24, the connection ends of the lead wires 26a and 26b, and the lead wires 28a and 28b, which are coated with the uncured thermosetting synthetic resin 30, and the portions adjacent to the connection ends of the lead wires 28a and 28b, as well as the portions of the lead wires 28a and 28b not coated with the uncured thermosetting synthetic resin 30, are accommodated in the receiving groove 6 up to about halfway in the cross section. The positioning of at least the thermistor chip 24, the lead wires 26a and 26b, and the connection ends of the lead wires 28a and 28b, which are coated with uncured thermosetting synthetic resin 30, against the inner surface of the plate member 2 can be achieved sufficiently easily and accurately by accommodating them in the receiving groove 6.

[0023] Layering process After the above-mentioned accommodating step, as shown in Fig. 5, the other of the pair of plate members, i.e., plate member 4, is rotated relative to one of the pair of plate members, i.e., plate member 2, so that plate member 4 is superimposed on plate member 2. In this way, the receiving groove 14 formed on the inner surface of plate member 4 is aligned with the receiving groove 6 formed on the inner surface of plate member 2, and at least the thermistor chip 24, the connection ends of the lead wires 26a and 26b, and the lead wires 28a and 28b, which are coated with the uncured thermosetting synthetic resin 30, the portions adjacent to the connection ends of the lead wires 28a and 28b, and the upper halves of the portions of the lead wires 28a and 28b where the coating is present, protruding upward from the receiving groove 6, are accommodated in the receiving groove 14. The upper halves of the portions of the lead wires 28a and 28b where the uncured thermosetting synthetic resin 30 is not coated are accommodated in the receiving groove 14 in the portions 14b which have a cross section of two concave arcs arranged in parallel.

[0024] Following the above overlapping step, the inner surface of the plate member 4 is pressed against the inner surface of the plate member 2. The amount of the thermosetting synthetic resin 30 applied to at least the thermistor chip 24, the lead wires 26a and 26b, and the connection ends of the lead wires 28a and 28b (and also the portions adjacent to the connection ends of the lead wires 28a and 28b in the illustrated case) is preferably such that the thermosetting synthetic resin 30 protrudes somewhat from the receiving grooves 6 and 14 when the inner surface of the plate member 4 is pressed against the inner surface of the plate member 2. Simultaneously with or following the pressing of the inner surface of the plate member 4 against the inner surface of the plate member 2, the thermosetting synthetic resin 30 is heated and hardened, and the plate members 2 and 4 are joined to each other by the hardened thermosetting synthetic resin. The heating of the thermosetting synthetic resin 30 can be accomplished by heating the plate members 2 and 4 with an appropriate heating means at a temperature higher than the hardening temperature of the thermosetting synthetic resin 30 but lower than the melting temperature of the plate members 2 and 4. If desired, the thermosetting synthetic resin 30 itself can be directly heated by an appropriate heating means without passing through the plate members 2 and 4. Thus, a temperature detector is obtained in which at least the thermistor chip 24, the lead wires 26a and 26b, and the connection ends of the lead wires 28a and 28b (and further the portions adjacent to the connection ends of the lead wires 28a and 28b in the illustrated case) are covered with an insulating coating made of the hardened thermosetting synthetic resin 30 and the plate members 2 and 4. [Explanation of symbols]

[0025] 2: Plate material 4: Plate material 6: Receiving groove 8:One edge 10:Other edge 12:Through hole 14: Receiving groove 16:One edge 18:Other edge 20: Protrusion 22: Flexible thin-walled connection piece 24: Thermistor 26a:Leader line 26b:Leader line 28a: Lead wire 28b: Lead wire 30: Insulating thermosetting synthetic resin

Claims

1. A method for manufacturing a temperature detector including a thermistor chip, a pair of lead wires connected to the thermistor chip directly or via a lead wire, and an insulating coating covering at least an area extending from the thermistor chip to a connection end of the lead wires, comprising the steps of: a preparation step of preparing a pair of plate members formed from an insulating synthetic resin, at least one of which has a receiving groove extending in a predetermined direction on an inner surface thereof; a coating step of coating an uncured insulating thermosetting synthetic resin at least from the thermistor chip to the connection end of the lead wire; a housing step of at least partially housing, after the preparing step and the applying step, the thermistor chip to which the uncured insulating thermosetting synthetic resin has been applied, and the connection end of the lead wire, in the receiving groove provided on the inner surface of the one of the plate members; a superposing step of superposing the one of the plate members on the other of the plate members after the accommodating step; a pressing and heating step of pressing the inner surface of the other plate member against the inner surface of the one plate member and heating the insulating thermosetting synthetic resin to harden the insulating thermosetting synthetic resin after the overlapping step; The method according to claim 1, further comprising:

2. 2. The method of claim 1, wherein the receiving groove disposed on the inner surface of the one of the plate members extends from adjacent one edge of the one of the plate members to the other edge of the one of the plate members.

3. 3. The method according to claim 2, wherein a receiving groove is also provided on the inner surface of the other of the plate members, and when the other of the plate members is superimposed on the one of the plate members, the receiving groove provided on the inner surface of the one of the plate members and the receiving groove provided on the inner surface of the other of the plate members are aligned and positioned.

4. 4. The method according to claim 3, wherein the receiving groove disposed on the other inner surface of the plate member extends from the vicinity of one end edge of the other of the plate member to the other end edge, and the cross-sectional shape at the portion from the vicinity of the other end edge to the other end edge is two concave arc shapes arranged in parallel to correspond to the outer shapes of a pair of lead wires.

5. 2. The method according to claim 1, wherein in the coating step, the insulating thermosetting synthetic resin is coated on at least the area from the thermistor chip to the connection end of the lead wire by immersing the area from the thermistor chip to the connection end of the lead wire in uncured insulating thermosetting synthetic resin and then removing the area from the insulating thermosetting synthetic resin.

6. 2. The method according to claim 1, wherein the insulating thermosetting synthetic resin is an epoxy-based synthetic resin having thixotropy imparted thereto by mixing silica particles therein.

7. 2. The method of claim 1, wherein each of said plate members is formed from a polyamide type synthetic resin.

8. 2. The method of claim 1, wherein each of said plate members has a thickness of 0.7 to 1.0 mm.

9. 2. The method of claim 1, wherein the outer shape of said one of said plate members and the outer shape of said other of said plate members are the same rectangular shape.

10. 10. The method of claim 9, wherein the receiving groove disposed on the inner surface of the one of the plate members extends longitudinally through a central portion in a width direction of the inner surface of the one of the plate members.

11. 2. The method according to claim 1, wherein the one and the other of the pair of plate members are connected via a flexible thin-walled connecting piece, and the one and the other of the pair of plate members and the flexible thin-walled connecting piece are integrally formed.

12. 2. The method of claim 1, wherein said flexible thin-walled connecting piece connects said one edge and said other edge of said plate member.

13. 2. The method according to claim 1, wherein the inner surface of said one of said plate members has two through holes or protrusions at a predetermined interval, which extend to the recess or outer surface, and the inner surface of the other of said pair of plate members has two through holes at a predetermined interval, which extend to the protrusions, recesses or outer surface, and the other of said pair of plate members is positioned as required relative to said one of said pair of plate members by engaging said protrusions with said recesses or through holes.

Images