JPH10172812A - Variable resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a slider from spring out of a fitting space provided to a slider supporting part of a slider operating member in assembling, without requiring bonding, welding, etc. SOLUTION: A first wall part 15 and a second wall part 19 whose cross sectional form is L-shaped are formed on a slider supporting part 7 of a slider operating member 1 in an integrally formed body. A rectangular fitting space 27 is formed between the first wall part 15 and the second wall part 19. A pair of bite protrusions 61 and 63 are formed at a center part 39 of a slider 37 provided with a first arm 45 and a second arm 47. The bite protrusions 61 and 63 are made to bite inner wall parts of the first wall part 15 and the second wall part 19 to fit the slider 37 into the fitting space 27.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable resistor.

[0002]

2. Description of the Related Art As a high-voltage variable resistor, a circuit board having a variable resistance pattern is arranged inside an opening of an insulating case, and slides on a slider operating member which can be operated from outside the insulating case. A type in which a slider is supported and a slider is slid in an insulating case is known. In this type of variable resistor, when assembling, first, an insulating case is arranged on a jig with the opening facing upward. Next, the assembled part, in which the supported part of the slider is fitted, is inserted into the fitting space formed in the slider supporting part of the slider operating member, and then the circuit board is moved to the inner periphery of the opening of the insulating case. It is joined to the fixing rib provided in the portion using an adhesive. The input terminals and output terminals are soldered and connected to the circuit board in advance.

[0003]

Conventionally, in order to reduce the number of working steps and the manufacturing cost by omitting the work of fixing the slider which requires bonding or welding, the supported portion of the slider has been replaced with a slider. Only the fitting is performed in the fitting space provided in the slider supporting portion of the operation member, and the slider is not particularly fixed to the slider supporting portion. For this reason, when unnecessary vibration is applied to the insulating case when the assembly is performed in a flow operation, the slider slides out of the fitting space, or the slider is inclined inside the fitting space. However, in the automatic assembly line, even in such a state, since the circuit board is attached to the insulating case, there is a problem that the occurrence rate of defective products is increased (yield is reduced).

An object of the present invention is to provide a variable resistor that can solve the above-mentioned problems.

Another object of the present invention is to provide a variable resistor which is unlikely to cause assembly failure.

Another object of the present invention is to prevent the slider from dancing during the assembly from the fitting space provided in the slider support portion of the slider operating member without the need for adhesion or welding. It is an object of the present invention to provide a variable resistor which can be prevented.

[0007]

SUMMARY OF THE INVENTION In the variable resistor to be improved by the present invention, a circuit board having a variable resistor circuit pattern and an output circuit pattern on its surface is housed in an insulating case. More specifically, the circuit board is joined to a fixing rib provided on the inner peripheral portion of the opening of the insulating case. An operation knob that penetrates a wall portion of the insulating case facing the surface of the circuit board and a slider operation member made of insulating resin having a slider support portion connected to the operation knob and arranged in the insulating case. A metal slider is supported. A slider supported by a slider supporting portion of the slider operating member; a first arm having a first contact in contact with a variable resistance circuit pattern; and the output circuit pattern. And a second arm portion having a second contact portion that makes contact with the second arm portion. The slider supporting portion of the slider operating member is provided with a fitting space which opens toward the surface of the circuit board and into which the supported portion of the slider is fitted. More specifically, the slider supporting portion is continuous with the operation knob, and has a base portion having an end surface facing the surface of the circuit board, and a slider protruding from the end surface of the base portion toward the surface of the circuit board. And a wall portion for forming a fitting space which forms a fitting space in which the supported portion is fitted. The slider is supported by the supported portion in a state where the supported portion is fitted in the fitting space.

In such a variable resistor, in the present invention, at least one biting projection that bites into a wall surrounding the fitting space is formed in the supported portion of the slider. In the assembling stage, in the process of fitting the supported portion of the slider to the fitting space, one or more biting projections bite into the wall surrounding the fitting space. As a result, the slider slides out of the fitting space when vibration is applied during the assembly stage, without having to fix the slider to the slider operating member by performing a troublesome operation such as bonding or welding. Can be prevented.

The one or more biting projections may be basically provided anywhere on the supported portion of the slider, but have the first and second contact portions with the biting projections biting into the wall. It is preferable that the first arm and the second arm are provided at positions where the movement of the first and second arms is not affected as much as possible. If the supported portion of the slider bends significantly with the biting projection biting into the wall, the bending affects the movement of the first and second arms. Therefore, in order to suppress the bending of the supported portion, it is preferable to provide a well-balanced biting projection on the supported portion of the slider. For example, when two biting projections are provided, the two biting projections are arranged at symmetrical positions with the center of the supported portion therebetween. With this configuration, the amount of deflection of the supported portion of the slider can be reduced.

If the amount of the biting projection biting into the wall is too large, the amount of cutting of the wall portion cut by the biting projection increases, and the cut portion becomes an obstacle to be supported by the slider. The possibility that the portion is greatly inclined and the supported portion is greatly bent increases. Therefore, in order to prevent this, the shape of the biting projection is adjusted so that the biting projection bites into the wall while shaving the wall while the supported part of the slider is fitted into the fitting space, and the supported part is fitted. It is preferable that the supported portion is set so as not to be substantially bent in the state located at the innermost portion of the joint space. More preferably, the at least one biting projection should be formed such that the supported portion can entirely contact the end face of the base portion in a state where the supported portion is fitted in the fitting space.

In one example of the slider, the supported portion has a substantially rectangular central portion, a first protruding portion extending from one end of the central portion in a direction orthogonal to the longitudinal direction of the central portion, A second projection extending from the other end in a direction perpendicular to the longitudinal direction of the central portion and opposite to the direction in which the first projection extends. A base is provided continuously with the first protrusion and the second protrusion. In the case of using such a slider, for example, the wall portion for forming the fitting space is formed so as to surround the first and second protrusions at the center of the supported portion of the slider from the outside. First and second L-shaped cross sections are formed.
And third and fourth wall portions formed so as to sandwich two sides extending along the longitudinal direction of the central portion. In this case, two biting portions may be formed on the first and second protrusions or two sides.
Further, the fitting space forming wall-like portion forming the fitting space is formed by two corner portions where the first and second protrusions at the center of the supported portion of the slider do not extend, and the two corner portions. The first and second walls are formed so as to respectively surround two sides continuous with the portion and have an L-shaped cross section. Then, the two biting portions may be formed so as to extend from sides located at both ends in the longitudinal direction of the central portion to both sides in the longitudinal direction. With such a configuration, the two biting portions can be arranged in a well-balanced manner.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an assembled perspective view of a slider operating member 1 and a slider 37 used in the variable resistor according to the present invention, and FIG. 2 is a perspective view of an assembled state.

The slider operating member 1 is integrally formed of insulating resin, and has a small-diameter cylindrical operation knob 5 having a knurl 3 formed at one end (the lower end in the drawing), and the operation knob 5. And a slider supporting portion 7 integrally formed on the other end side (the upper end side in the drawing). A driver groove 9 is formed at the lower end of the operation knob 5, and the slider support portion 7 is formed.
Is a large-diameter disc-shaped portion 1 formed concentrically with the operation knob 5.
1 is extended radially outward to form a rectangular extension 1
3 is provided. In addition, the disk-shaped part 11 and the extension part 13 comprise a base part.

The main body 1 of the first wall portion 15 having an L-shaped cross section is provided at both ends of the front end surface of the slider supporting portion 7.
7 and the main body portion 21 of the second wall portion 19 are disc-shaped portions 11
To the extension portion 13. The first wall portion 15 has a short curved portion 23 which is curved short of the center position of the disc-shaped portion 11, and the second wall portion 19 also has a curved portion which is curved at the distal end position of the extended portion 13. 25. The rectangular space surrounded by the first wall portion 15 and the second wall portion 19 forms a fitting space 27 for fitting the slider.
The first wall portion and the second wall portion constitute a wall portion for forming a fitting space. In this fitting space 27, a first positioning projection 29 (third wall) is provided so as to extend in parallel with the main body portion 17 of the first wall 15, and a second wall 19 is provided. A second positioning projection 31 (fourth wall) is provided so as to extend in parallel with main body portion 21. The rear end of the first positioning projection 29 and the curved portion 2 of the first wall 15
3 and between the tip of the second positioning projection 31 and the second
There is an interval between the curved portion 25 of the wall portion 19 of FIG.

The slider 37 is formed by pressing a single metal plate and then bending it. The slider 37 has a central portion 39 constituting a main portion of the rectangular supported portion, and a first protrusion extending outward from one end of the central portion 39 in a width direction (a direction orthogonal to the longitudinal direction). A second protrusion 43 extending outward in the width direction (a direction orthogonal to the longitudinal direction) so as to protrude from the other end of the central portion 39 in the opposite direction to the first protrusion 41;
A first arm 45 extending from the first protrusion 41;
And a second arm 47 extending from the projecting portion 43. The first arm 45 has a base 49 extending obliquely upward from a first protrusion 41 provided at one end of the central portion 39, and the other end of the central portion 39 curved from the base 49 in the width direction. It comprises an end portion and a contact portion 51 extending at a predetermined interval. The distal end portion of the contact portion 51 is bifurcated, and is curved so as to protrude upward to form a contact 53. Second arm 4
7 is a second projection 4 provided at the other end of the central portion 39.
A base 55 extending obliquely upward from the base 3;
5 and a contact portion 57 which is curved in the width direction and extends at one end of the central portion 39 at a predetermined interval. The tip portion of the contact portion 57 is also divided into a crotch shape, and the contact portion 59 is formed to be curved so as to protrude upward.

The length dimension of the central portion 39 is the first wall portion 1.
5 and the curved portion 2 of the second wall 19
The width of the central portion 39 is set to be slightly shorter than the distance between the inner surface of the first positioning protrusion 29 and the inner surface of the second positioning protrusion 31. It is set to be slightly shorter than. The dimension between the outer edge of the base 49 of the first arm 45 and the outer edge of the base 55 of the second arm 47 is determined by the inner surface of the main body 17 of the first wall 15 and the main body 21 of the second wall 19. Is set so as to be slightly shorter than the distance from the inner surface.

The first protrusion 41 is formed so as to be continuous with the central portion 39, and the outer edge of the first protrusion 41 has a bite slightly projecting outward in the surface direction of the first protrusion 41. A projection 61 is provided. Similarly, the second protrusion 43 is formed so as to be continuous with the central portion 39, and the outer edge of the second protrusion 43 has a biting protrusion slightly projecting outward in the surface direction of the second protrusion 43. 63 are provided. The straight line connecting the biting projections 61 and 63 passes through the center of the central portion 39.

FIG. 2 is a perspective view showing a state in which the slider 37 is attached to the slider operating member 1. The bite protrusion 61 is located on the inner surface side of the curved portion 23 of the first wall portion 15, and the slider 37 is operated by the slider so that the bite protrusion 63 is located on the inner surface of the curved portion 25 of the second wall portion 19. The first arm 45 and the second arm 47 are fitted into the fitting space 27 of the member 1 with the first arm 45 and the second arm 47 facing upward until they come into contact with the outer end surface of the slider supporting portion 7. In this fitting process, the biting projections 61, 6
3 descends while slightly shaving the inner surface of the curved portion 23 of the first wall portion 15 and the inner surface of the curved portion 25 of the second wall portion 19 (see reference numeral 65). As a result, the slider 37 is supported by the slider. Part 7
When they come into contact with the outer end surfaces of the first wall 15, the biting projections 61, 63 form the inner surface of the curved portion 23 of the first wall 15 and the second wall 19
Is in a state of being cut into the 25 wall portions of the curved portion.

A first positioning projection 29 fits between the central portion 39 and the first arm 45, and a second positioning projection 31 fits between the central portion 39 and the second arm 47. The slider 37 is stably fitted in the fitting space 27 by being fitted. The contact point 59 of the second arm 47 is located on the center of the disk-shaped portion 11 of the slider support 7, that is, on the rotation center of the slider operating member 1. The variable resistor is configured by disposing the slider operating member 1 to which the slider 37 is attached in an insulating case.

FIG. 3 is a schematic sectional view of a variable resistor according to the present invention using the slider operating member 1 and the slider 37. The variable resistor 67 has a structure in which a circuit board 79 is housed in an insulating case 73 made of an insulating resin having an open end.
In a space between the insulating case 73 and the circuit board 79, a part of the slider operating member 1 and the slider 37 are housed. A through-hole 71 into which the operation knob 5 of the slider operation unit is rotatably inserted is formed in a wall 69 of the insulating case 73 facing the surface of the circuit board 79. When assembling, the insulating case 73 is placed on the jig so that the opening faces upward, and the operation knob 5 of the slider operating member 1 having the slider 37 is inserted into the through hole 71. . And the circuit board 7
9 is joined to a fixing rib 81 provided in the opening of the insulating case 73. The circuit board 79 includes a variable resistance circuit pattern 75 on which the contact 53 of the first arm 45 of the slider 37 slides.
And an output circuit pattern 77 in which the contact point 59 of the second arm 47 slides. The circuit board 79 is an insulating case 7
3 is fixed to a fixing rib 81 formed on an inner wall of the circuit board 79 by using an adhesive, and an insulating layer is formed by filling an insulating resin on the back surface of the circuit board 79. In the figure, 83 and 85 are input / output terminals.

FIG. 4 is a perspective view of another slider operating member and another slider used in the variable resistor according to the present invention, and FIG. 5 is another slider mounted on another slider operating member. FIG. This slider operating member 87 is obtained by changing the configuration of the slider supporting portion 7 of the slider operating member 1. On the slider supporting portion 89 of the slider operating member 87, the position of the large-diameter disc-shaped portion 91 formed concentrically with the operation knob 5 is extended outward to provide a larger diameter than the disc-shaped portion 91. An extension 93 having an arcuate outer edge is provided. Note that the disc-shaped portion 91 and the extension portion 93 constitute a base portion. At one end of the slider supporting portion 89, a first wall portion 95 having an L-shaped cross section extending from the surface of the disk-shaped portion 91 to the outer edge of the extension portion 93 is integrally formed. At the other end of the support portion 87, a second wall portion 99 having an L-shaped cross section is integrally formed from the disc-shaped portion 91 to the outer edge of the extension portion 93. The first wall portion 95 has a short curved portion 103 which is curved before the center position of the disc-shaped portion 91, and the second wall portion 99 has a short curved portion 105 which is curved at a position on the extension portion 93 side. Have. This first wall 95
And a rectangular fitting space 1 surrounded by the second wall 99
07 is formed. Curved portion 10 of first wall 95
A first positioning projection 109 having a height lower than that of the main body portion 97 extends from the end of the third wall 3 in a direction orthogonal to the main body portion 97, and also extends from the tip of the curved portion 105 of the second wall portion 99. A second positioning projection 111 having a height lower than that of the main body portion 101 extends in a direction orthogonal to the main body portion 101. The tip of the first positioning projection 109 and the second wall 99
And the second positioning projection 1
The widthwise intervals between the front end of the first wall portion 95 and the body portion 97 of the first wall portion 95 are equal.

The slider 113 is also formed by pressing a single metal plate and then bending it. The slider 113 has a rectangular central portion 115, a first protrusion 117 extending from one end of the central portion 115 in a direction orthogonal to the longitudinal direction, and a first protruding portion 117 extending from the other end of the central portion 115. The second projection 1 extending in a direction orthogonal to the longitudinal direction so as to project in the opposite direction to the first projection 117
19 and the first arm 1 extending from the first protrusion 117
21 and a second arm 1 extending from the second protrusion 119
23. The first arm 121 has a base 125 and a contact 129. The base 125 is formed with a slit extending along the longitudinal direction of the base 125, and is almost entirely divided into two branches. The contact portion 129 has two contacts 127 that are curved so as to protrude upward at the distal end. The second arm 123 also includes a base 131 and a contact 135. Base 13
1, a slit extending along the longitudinal direction of the base 131 is formed, and the whole is divided into two parts. The contact portion 135 has two contacts 133 curved at the tip so as to protrude upward.

The length of the central portion 115 in the longitudinal direction is determined to be slightly shorter by the distance between the inner surface of the main body portion 97 of the first wall portion 95 and the inner surface of the main body portion 101 of the second wall portion 99. The width dimension is determined so as to be slightly shorter than the distance between the inner surface of the first positioning protrusion 109 and the inner surface of the second positioning protrusion 111. And the central part 1
A biting projection 137 slightly projecting outward in the surface direction of the central portion 115 is provided at one longitudinal edge of the central portion 115, and a biting projection slightly projecting outward in the surface direction at the other longitudinal edge. 139 are provided. An imaginary straight line connecting the biting projections 137 and 139 passes through the center of the central portion 115.

FIG. 5 shows a state in which the slider 113 is connected to the slider operating member 87.
It is a perspective view showing the case where it was attached to. Biting protrusion 1
29 is located on the inner surface of the main body portion 97 of the first wall portion 95,
The biting projection 139 is formed on the main body 101 of the second wall 99.
The slider 113 is placed on the outer surface of the slider support 89 with the first arm 121 and the second arm 123 facing upward in the fitting space 107 of the slider operating member 87 so as to be positioned on the inner surface of the slider support member 89. It is fitted until it touches. In this fitting process, the biting projections 129 and 139 are attached to the first wall 9.
5 while slightly shaving the inner surface of the main body portion 97 and the inner surface of the main body portion 101 of the second wall portion 99 (FIG. 137).
As a result, when the slider 113 comes into contact with the outer surface of the slider supporting portion 87, the biting projections 129 and 139 become the inner surface of the main body portion 97 of the first wall portion 95 and the second wall portion 99.
Is in a state of being cut into the inner surface of the main body portion 101.

A second positioning projection 111 is fitted between the central portion 115 and the first arm 121, and a first positioning projection 109 is provided between the central portion 115 and the second arm 123. The slider 113 is fitted into the fitting space 1
07 in a stable manner. The contact portion 133 of the second arm 123 is located on the center of the disk-shaped portion 91 of the slider supporting portion 87, that is, on the rotation center of the slider operating member 87. A variable resistor is formed by disposing the slider operating member 87 to which the slider 113 is attached in the insulating case 73 (see FIG. 3).

In the above embodiment, the one or more biting projections (61, 63, 129, 139) may be basically provided anywhere on the supported portion of the sliders 37, 113. It is preferable that the first arm and the second arm having the first and second contact portions be provided at a position where the movement of the first and second arm portions having the first and second contact portions is not affected as much as possible.
When the center portions 39 and 115 of the slider are largely bent with the biting projections (61, 63, 129 and 139) biting into the wall portion, the bending is caused by the first and second arm portions (4).
5, 47, 121, 123) to suppress the bending of the central portions 39, 115,
It is preferable to provide a well-balanced biting projection at the center of the slider.

The biting projections (61, 63, 129,
139), if the amount of bite into the wall (projection dimension of the bite protrusion) is too large, the amount of cut of the wall portion cut by the bite protrusion becomes large, and the cut portion becomes an obstacle and becomes a slider. Of the central portions 39 and 115 are greatly inclined, and the possibility that the central portions 39 and 115 are greatly bent increases.
Therefore, in order to prevent this, the shape of the biting projection is adjusted by adjusting the center portions 39 and 115 of the slider to the fitting spaces 27 and 10.
In the process of being fitted to 7, the biting projections bite into the wall while shaving the wall, and the central portions 39, 115 are substantially in a state where the central portions 39, 115 are located at the deepest portion of the fitting space. It is preferable that the angle is determined so as not to bend. More preferably, the one or more biting projections should be formed such that the central portions 39, 115 can entirely contact the end surface of the base portion with the central portions 39, 115 fitted in the fitting spaces. .

[0028]

According to the variable resistor of the present invention, at least one biting projection that cuts into the wall surrounding the fitting space is formed in the supported portion of the slider, so that the supported portion of the slider is formed. In the process of fitting the fitting into the fitting space, one or more biting projections bite into the wall surrounding the fitting space, and the slider can be removed from the fitting space without any troublesome work such as bonding or welding. It can be prevented from dancing.

[Brief description of the drawings]

FIG. 1 is a perspective view of a slider operating member and a slider used in a variable resistor according to the present invention.

FIG. 2 is a perspective view showing a case where a slider is attached to a slider operating member.

FIG. 3 is a sectional view of a variable resistor according to the present invention using a slider operating member and a slider.

FIG. 4 is a perspective view of another slider operating member and another slider used in the variable resistor according to the present invention.

FIG. 5 is a perspective view showing a case where another slider is attached to another slider operating member.

[Explanation of symbols]

 1,87 Slider operating member 5 Operation knob 7,89 Slider support 15,95 First wall 19,99 Second wall 27,107 Fitting space 29 First positioning convex (first 3 wall portion 31 31 second positioning convex portion (fourth wall portion) 37, 113 slider 39, 115 central portion 41, 117 first protruding portion 43, 119 second protruding portion 45, 121 1st arm 47,123 2nd arm 51,57,129,135 Contact part 67 Variable resistor 73 Insulating case 75 Variable resistance circuit pattern 77 Output circuit pattern 79 Circuit board

Claims (6)

[Claims] A circuit board having a variable resistance circuit pattern and an output circuit pattern on a surface thereof; an insulating case for housing the circuit board; and a wall of the insulating case facing the surface of the circuit board. A slider operating member made of insulating resin having an operation knob and a slider supporting portion connected to the operating knob and arranged in the insulating case; and a slider operating portion of the slider operating member. A supported arm, a first arm having a first contact in contact with the variable resistance circuit pattern, and a second arm having a second contact in contact with the output circuit pattern; The slider supporting member of the slider operating member opens toward the surface of the circuit board, and the supported portion of the slider fits into the slider supporting portion. Has a mating space that is A variable resistor in which the slider is supported by the supported part in a state where the supported part is fitted in a fitting space, wherein the fitting is performed on the supported part of the slider. A variable resistor, wherein at least one biting projection is formed in a wall surrounding the joint space. 2. The supported portion is formed with two of the biting protrusions, and the two biting protrusions are arranged at symmetrical positions with the center of the supported portion therebetween. 3. The variable resistor according to item 1. 3. The shape of the biting projection is such that the biting projection bites into the wall while shaving the wall in a process in which the supported portion of the slider is fitted into the fitting space. The variable resistor according to claim 2, wherein the variable resistor is set so that the supported portion does not substantially bend when the supported portion is located at the deepest portion of the fitting space. 4. A circuit board having a variable resistance circuit pattern and an output circuit pattern on its surface, and said circuit board is bonded to a fixing rib that houses said circuit board and is provided on an inner peripheral portion of an opening. An insulating case, an operation knob penetrating a wall portion of the insulating case facing the surface of the circuit board, and a slider supporting portion connected to the operation knob and arranged in the insulating case; A slider operating member, a supported portion supported by the slider supporting portion of the slider operating member, a first arm portion having a first contact portion that contacts the variable resistance circuit pattern, and A metal slider having a second arm portion having a second contact portion that comes into contact with the output circuit pattern, wherein the slider support portion of the slider operation member is Continuing with the operation knob and in front of the circuit board A base portion having an end surface facing the front surface, and a fitting space protruding from the end surface of the base portion toward the surface of the circuit board so as to fit the supported portion of the slider. A variable resistor comprising: a fitting space forming wall-shaped portion; and the slider is supported by the supported portion in a state where the supported portion is fitted in the fitting space. The supported portion of the slider has one or more biting projections that bite into the inner wall of the wall portion for forming the fitting space, and the one or more biting projections cover the fitting space. The variable resistor, wherein the supported portion is formed so as to be entirely in contact with the end face of the base portion in a state where the support portion is fitted. 5. The supported portion of the slider has a substantially rectangular central portion, a first protruding portion extending from one end of the central portion in a direction perpendicular to a longitudinal direction of the central portion, and A second protruding portion extending from the other end of the portion perpendicular to the longitudinal direction of the central portion and opposite to the direction in which the first protruding portion extends, the first arm portion and the second The base of the arm portion is continuous with the first protrusion and the second protrusion, and the fitting space forming wall-shaped portion is configured to connect the first and second protrusions of the central portion. First and second wall portions each having an L-shaped cross-sectional shape formed so as to surround from the outside, and are formed so as to sandwich the two sides extending along the longitudinal direction of the central portion therebetween. Third and fourth wall portions, and the two biting portions are The variable resistor according to claim 4, wherein the variable resistor is formed on the first and second protrusions or on the two sides. 6. The supported portion of the slider has a substantially rectangular central portion, a first protruding portion extending from one end of the central portion in a direction perpendicular to a longitudinal direction of the central portion, and A second protruding portion extending from the other end of the portion perpendicular to the longitudinal direction of the central portion and opposite to the direction in which the first protruding portion extends, the first arm portion and the second The base of the arm portion is continuous with the first protrusion and the second protrusion, and the fitting space forming wall-shaped portion has the first and second protrusions of the central portion. The first and second wall portions are formed to have an L-shaped cross section formed so as to surround two corner portions that do not extend and two sides continuous with the two corner portions, respectively. The biting portion extends from the side located at both ends in the longitudinal direction of the central portion to the longitudinal direction. Variable resistor according to claim 4 which is formed to extend in the direction both sides.