JP3709827B2 - Variable resistor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable resistor, and more particularly to a variable resistor in which a slider attached to a rotatable rotating shaft slides on a resistor and a current collector on a substrate to adjust the resistance value.
[0002]
[Prior art]
Conventionally, as a rotary variable resistor having a slider, one disclosed in Japanese Patent Application Laid-Open No. 2000-138109 is known. In this variable resistor, as shown in FIGS. 9 to 11, a substrate 100 made of a resin molded product has a central hole 101, and first and second terminals 112 and 113 are embedded therein. The end portions 112 a and 113 a of the terminals 112 and 113 protrude from the side surface of the substrate 100, and the other end portions 112 b and 113 b are exposed on the upper surface of the substrate 100. On the substrate 100, a current collector 104 is formed in an annular shape, and a resistor 105 is formed in a substantially annular shape on a concentric circle. The current collector 104 is connected to the other end portion 112 b of the terminal 112, and the opposite end portions 105 a of the resistor 105 are connected to the other end portion 113 b of the terminal 113 through the extraction electrode 106.
[0003]
A rotation shaft 107 made of a resin molded product having a slider 108 made of a conductive material is rotatably mounted in the center hole 101 of the substrate 100. A contact piece 108a that slides on the resistor 105 and a contact piece 108b that slides on the current collector 104 are formed on the slider 108, and a terminal 112 is formed according to the rotational position of the contact pieces 108a and 108b. , 113 is adjusted. A cover 109 made of a resin molded product is attached on the substrate 100.
[0004]
[Problems to be solved by the invention]
In the variable resistor shown in FIGS. 9 to 11, the current collector 104 is formed on the substrate 100 by applying and baking a paste containing a good conductive material such as silver, and the other end of the first terminal 112. 112b has a physical predetermined bonding strength. However, this joining is a joining between different kinds of objects such as a metal material (terminal 112) and a fired paste (current collector 104), and is not necessarily strong. That is, the joint is easily peeled off due to a load generated when the terminal 112 is cut or bent, or a stress generated due to a difference in thermal expansion coefficient between the substrate 100 and the current collector 104. Had problems with sex. Further, silver has a problem in quality that it is sulfurized to increase contact resistance.
[0005]
Further, since the current collector 104 is formed by applying and baking a paste on the substrate 100, the number of facilities and processes is increased, resulting in an increase in cost.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to provide a variable resistor that has a high connection reliability between a terminal and a current collector and can reduce costs.
[0007]
[Means and Actions for Solving the Problems]
In order to achieve the above object, a variable resistor according to the present invention includes a current collector and a resistor that are electrically connected to a first terminal and a second terminal on a substrate made of a resin material. A variable resistor in which the slider is attached to the substrate so that the slider is slidable on the current collector and the resistor. The current collector is the first terminal. Made of a ring-shaped or substantially ring-shaped metal material formed integrally with the substrate, exposed on the surface of the substrate, and on the current collector, having a conductivity equal to or smaller than the width of the current collector A lubrication layer is provided, and a resistance value between the first and second terminals is adjusted by changing a length of the extended surface of the current collector and the resistor according to a rotational position of the slider. It is characterized by that.
[0008]
In the variable resistor according to the present invention, the first terminal and the current collector are made of one metal material, and there is no joint portion. Therefore, even if a load is applied to the terminal or a thermal stress is applied to the current collector, a malfunction such as deterioration of electrical characteristics, malfunction, or inability occurs between the first terminal and the current collector. Never do. Further, the current collector may be handled integrally with the terminal to cut a metal material or insert it into a resin molded product (substrate), and it is not necessary to form the current collector by a paste application step and a firing step.
[0009]
In particular, the conductive lubricating layer is provided on the current collector. When the current collector is a metal material, wear is promoted by sliding of the slider. However, if a lubrication layer is provided, wear is reduced and the life can be extended. If the conductive lubricating layer is made of the same material as the resistor, it can be applied (for example, screen printing) in the same process as the resistor.
[0010]
The width dimension of the conductive lubricating layer has a width dimension the same as or smaller of the current collector. In this way, the lubrication layer is formed only on the current collector and is not subjected to stress due to the difference in thermal expansion coefficient between the metal material (current collector) and the resin material (substrate), and cracks are generated in the lubrication layer. Is prevented.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a variable resistor according to the present invention will be described with reference to the accompanying drawings.
[0012]
(Refer 1st Embodiment and FIGS. 1-6)
First, a configuration of a variable resistor according to a first embodiment of the present invention will be described with reference to FIGS.
[0013]
This variable resistor includes a substrate 10 made of a resin molded product, a cover 20 made of a resin molded product, and a rotary shaft 30 made of a resin molded product provided with a slider 35. The substrate 10 has a center hole 11 in which the first terminal 12 and the second terminals 13 and 13 are embedded.
[0014]
Ends 12a and 12a of the first terminal 12 protrude from the side surface of the substrate 10, and the central portion is exposed on the surface of the substrate 10 as an annular current collector 12b. The first terminal 12 is obtained by integrally cutting the end portions 12a and 12a and the current collector 12b from a single metal material. The end portions 13 a of the second terminals 13 and 13 protrude from the side surface of the substrate 10, and the other end portions 13 b are exposed on the surface of the substrate 10.
[0015]
As shown in FIG. 4, the terminals 12 and 13 are formed by punching a long hoop material 40 into a predetermined shape, and are inserted into a molding die (not shown) to mold the substrate 10. After this resin molding, the resistor 15 is formed in a substantially annular shape on the surface of the substrate 10 by applying a conductive resin material, and both ends 15a of the resistor 15 facing each other are the other ends of the terminals 13. 13b. The current collector 12 b and the resistor 15 are provided concentrically on the surface of the substrate 10, and the current collector 12 b is located inside the resistor 15.
[0016]
The rotating shaft 30 has a center hole 31, and a slider 35 is attached around the flange portion 32. The rotating shaft 30 is rotatably mounted in the center hole 11 of the substrate 10. The slider 35 is made of a conductive metal material, and the brush-like first contact piece 35a that slides on the resistor 15 in an elastically pressed state and the current collector 12b slides on the current collector 12b in an elastically pressed state. And a moving brush-like second contact piece 35b.
[0017]
As shown in FIG. 1A, the center hole 31 of the rotating shaft 30 has a shape in which a part of the circular hole is embedded. By inserting an operation shaft (not shown) into the center hole 31 and rotating in either the left or right direction, the slider 35 is rotated together with the rotating shaft 30, and the resistor 15 and the current collector of the contact pieces 35 a and 35 b are collected. By changing the contact position with respect to the body 12b, the extended surface lengths of the resistor 15 and the current collector 12b are changed, and the resistance value between the terminals 12 and 13 is adjusted.
[0018]
The cover 20 has a center hole 21 for positioning the upper portion of the rotary shaft 30 and is attached to the substrate 10 by a so-called snap-in method. Specifically, as shown in FIG. 6, an engaging protrusion 10 a whose upper side is inclined is formed on the side surface of the substrate 10, and the first protrusion 22 provided on the side of the cover 20 is engaged with the protrusion 10 a. The mating through hole 20a is formed in the thickness direction of the projecting piece 22, and the through hole 20a is engaged with the projecting part 10a by a snap-in method. Further, the cover 20 is formed with a second protruding piece 23 located on the side surface 10 c of the substrate 10. The second projecting piece 23 is formed in a comb-like shape to avoid interference with the terminals 12, 13, and 13, and only comes into surface contact with the side surface 10c and does not engage with it.
[0019]
By the way, in the variable resistor of the first embodiment, the current collector 12b is formed integrally with the first terminal 12 from a single metal material, and between the current collector 12b and the terminal 12 is formed. There are no joints. Therefore, even if a load is applied to the terminal 12 or a thermal stress is applied to the current collector 12b, a functional failure such as deterioration of electrical characteristics, malfunction, or inability occurs between the terminal 12 and the current collector 12b. There is nothing. Further, providing the current collector on the substrate 10 does not require a separate process such as application of paste or firing, and the current collector 12b is cut integrally with the terminal 12 and inserted into a mold to insert the substrate 10. The manufacturing cost can be reduced. Furthermore, since a paste containing silver is not used, there is no problem that contact resistance increases due to silver sulfidation.
[0020]
(Refer to the second embodiment, FIGS. 7 and 8)
Next, a second embodiment of the variable resistor according to the present invention will be described. This variable resistor has basically the same configuration as that of the first embodiment, and is different in that a conductive lubricating layer 14 is provided on a current collector 12b as shown in FIG. The lubricant layer 14 is made of a material mainly composed of carbon or graphite that reduces the frictional resistance with the slider 35, and is mainly composed of a resin approximate to the resin component of the resistor 15. Alternatively, the lubricating layer 14 may be the same material as the resistor 15. If the lubricating layer 14 and the resistor 15 are made of the same material, they can be applied simultaneously by screen printing or the like, and workability is improved.
[0021]
If the conductive lubricating layer 14 is provided on the current collector 12b as in the second embodiment, the wear generated between the current collector 12b is remarkably reduced and the life of the current collector 12b is extended. it can. In order to improve the slidability, in addition to providing the lubricating layer 14 as described above, the contact pieces 35a and 35b may be surface-treated so as to reduce the sliding resistance in accordance with the resistor 15 and the current collector 12b. Conceivable. However, making the processing specifications of two portions (contact pieces 35a, 35b) of one member called the slider 35 different is not preferable because it increases the manufacturing cost. In the second embodiment, the lifetime of the current collector 12b can be extended to almost the same as that of the resistor 15 by an inexpensive method of providing the conductive lubricating layer 14 on the current collector 12b.
[0022]
By the way, as shown in FIG. 8, the width dimension B of the lubricated layer 14 with hatching is the same as or smaller than the width dimension A of the current collector 12b. In other words, the lubricant layer 14 protrudes from the current collector 12b. It is preferable not to hang on the substrate 10. The metal material (current collector 12b) and the resin material (substrate 10) have different coefficients of thermal expansion, and if the lubricating layer 14 is formed over both the current collector 12b and the substrate 10, There is a risk that cracks may occur in the lubricating layer 14 due to stress. Therefore, by satisfying the condition of B ≦ A, it is possible to prevent a problem that a crack occurs in the lubricating layer 14 and adversely affects the contact piece 35b.
[0023]
In addition, even if it applies with respect to the electrical power collector 104 of the variable resistor shown in FIGS. 9-11 which is a prior art example, the effect by providing the lubrication layer 14 will show | play similarly.
[0024]
(Other embodiments)
The variable resistor according to the present invention is not limited to the above embodiment, and can be variously modified within the scope of the gist. In particular, the current collector may not be a complete annular shape, but may be a substantially annular shape with a part missing.
[0025]
【The invention's effect】
As is clear from the above description, according to the present invention, since the current collector is formed integrally with the first terminal and exposed on the surface of the substrate, the connection between the current collector and the first terminal is reliable. Therefore, it is not necessary to separately form a current collector on the substrate, and the variable resistor can be manufactured at low cost. Further, since the current collector does not use silver-containing paste, there is no problem of increased contact resistance due to silver sulfidation.
[0026]
In the present invention, if a conductive lubricating layer is provided on the current collector, the life of the current collector can be extended. Furthermore, if this lubricating layer is made of the same material as the resistor, the lubricating layer and the resistor can be formed in the same process. Furthermore, if the width dimension of the lubricating layer is the same as or smaller than the width dimension of the current collector, it is possible to avoid the possibility of cracks occurring in the lubricating layer due to the influence of thermal stress.
[Brief description of the drawings]
1A and 1B show a variable resistor according to a first embodiment of the present invention, in which FIG. 1A is a plan view and FIG. 1B is a side view.
FIG. 2 is a cross-sectional view showing a state where the variable resistor is mounted on a printed board.
FIG. 3 is a plan view showing a substrate of the variable resistor.
FIG. 4 is a plan view showing a molding state of the substrate.
FIG. 5 is a perspective view showing a cover of the variable resistor.
FIG. 6 is a sectional view showing an example of an engagement structure between the substrate and the cover.
FIG. 7 is a plan view showing a substrate of a variable resistor according to a second embodiment of the present invention.
FIG. 8 is an explanatory view showing the relationship of the width dimension between the current collector and the lubricating layer.
9A and 9B show a conventional variable resistor, in which FIG. 9A is a plan view and FIG. 9B is a side view.
10 is a cross-sectional view of the variable resistor shown in FIG.
11 is a plan view showing a substrate of the variable resistor shown in FIG. 9;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Board | substrate 12 ... 1st terminal 12b ... Current collector 13 ... 2nd terminal 14 ... Conductive lubricating layer 15 ... Resistor 30 ... Rotating shaft 35 ... Slider

Claims (2)

A current collector and a resistor, which are electrically connected to the first and second terminals, are provided on a concentric circle on a substrate made of a resin material, and a rotary shaft to which the slider is attached is provided on the slider. In the variable resistor attached to the substrate slidably on the current collector and the resistor,
The current collector is made of an annular or substantially annular metal material that is formed integrally with the first terminal, is exposed on the surface of the substrate, and is on the current collector. A conductive lubricating layer that is the same as or smaller than the width of the body is provided,
The resistance value between the first and second terminals is adjusted by changing the extended surface length of the current collector and the resistor according to the rotational position of the slider,
A variable resistor. Variable resistor according to claim 1, wherein said electrically conductive lubricating layer, which is a same material as the resistor.

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