JP4337617B2 - Variable resistor and resistor paste - Google Patents

Description

  The present invention relates to a variable resistor and a resistor paste, and more particularly to a variable resistor in which a slider slides on a resistor, and a resistor paste used as a resistor of the variable resistor.

  Generally, as a variable resistor, one using a thick film resistor obtained by kneading carbon black in a resin and a brush (slider) sliding on the thick film resistor is known. . However, in this type of variable resistor, when the brush continuously slides on the thick film resistor, the surface of the thick film resistor is fatigued and cracks are generated. There was a problem that the carbon black in the film resistor dropped off. For this reason, in conventional variable resistors, the electrical contact between the brush and the thick film resistor becomes unstable due to cracks on the surface of the thick film resistor or the reattachment of carbon black or resin dropping particles. There was a problem of becoming.

  For example, Patent Document 1 and Patent Document 2 disclose variable resistors that solve the above problems. Patent Document 1 discloses that a diamond-like carbon film or the like is formed on the thick film resistor side or the brush side sliding on the thick film resistor side. Patent Document 2 discloses one using a thick film resistor made of a carbon film having a hardness equal to or higher than the hardness of the brush.

In both of Patent Documents 1 and 2, it is possible to maintain the stability of electrical conductivity while reducing the wear of the thick film resistor and the brush. However, the diamond-like carbon film and the carbon film with high hardness have a problem that the cost of the material itself and the processing cost are high, and thus the product cost of the variable resistor is high.
Japanese Patent Laid-Open No. 3-115868 JP 2002-289411 A

  Therefore, an object of the present invention is to provide a low-cost variable resistor that is highly reliable and has excellent electrical characteristics by using an inexpensive material.

  Another object of the present invention is to provide a low-cost resistor paste having high wear resistance and excellent electrical characteristics.

  In order to achieve the above object, a variable resistor according to the present invention includes a resistor disposed on a main surface of a substrate and a slider that slides on the resistor, and the resistor is made of graphite. It contains a coated diamond.

  The graphite-coated diamond can be manufactured at a low cost, for example, by a technique called an explosion impact method described later. In the variable resistor according to the present invention, the resistor contains the graphite-coated diamond ultrafine particles, so that the lubricity and toughness of the resistor are greatly improved. As a result, the plastic deformation and fatigue wear of the resistor are drastically reduced, and not only the resistance value change is reduced, but also the generation of cracks due to fatigue wear is reduced, and the wear powder is further refined. Moreover, since the graphite-coated diamond ultrafine particles have surface conductivity, resistance value fluctuations due to reattachment of wear powder are not induced. Therefore, it is possible to obtain a variable resistor that is inexpensive, reliable, and excellent in electrical characteristics.

  In the variable resistor according to the present invention, it is preferable that the content of the graphite-coated diamond in the resistor is 2 weight percent or more and 15 weight percent or less. When the resistor contains such a graphite-coated diamond ultrafine particle with such a content, the resistance value change within 30 million rotation tests of the slider is ± 1.0% or less, and the sliding resistance noise is 0.3% or less. Thus, a variable resistor that is inexpensive, reliable, and excellent in electrical characteristics can be obtained.

  The resistor paste according to the present invention is characterized in that graphite-coated diamond, carbon black, graphite, and thermosetting resin are kneaded into a paste, and the content of the graphite-coated diamond is 2 to 15 percent by weight. And

  In the resistor paste according to the present invention, the content of the graphite-coated diamond is not less than 2 weight percent and not more than 15 weight percent. Therefore, if the resistor paste is used as a resistor material of a variable resistor, it is low-cost and reliable. A high variable resistor can be obtained, and a change in resistance value during 30 million rotation tests of the slider can be ± 1.0% or less, and a sliding resistance noise can be 0.3% or less.

  Hereinafter, embodiments of a variable resistor and a resistor paste according to the present invention will be described with reference to the accompanying drawings.

  First, the configuration of an embodiment of a variable resistor according to the present invention will be described with reference to FIGS.

  This variable resistor includes a resistor 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 central hole 11 in which terminals 12 and 13 are embedded. An end 12a of the terminal 12 protrudes from the side surface of the substrate 10, and a central portion is exposed on the surface of the substrate 10 as an annular current collector 12b. The terminal 13 has an end 13a (see FIG. 4) protruding from the side surface of the substrate 10 and the other end 13b exposed at the surface of the substrate 10.

  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, a resistor 15 (see FIG. 3) is formed in a substantially annular shape on the surface of the substrate 10, and both end portions 15a of the resistor 15 facing each other are connected to the other end portion 13b of the terminal 13. The The resistor 15 is made of a resistor paste containing graphite-coated diamond, and details thereof will be described later.

  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.

  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.

  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. The resistance value between the terminals 12 and 13 is adjusted by changing the contact position with the body 12b.

  In the variable resistor, the resistor 15 is prepared by mixing 5 weight percent of graphite-coated diamond, 25 weight percent of carbon black, 5 weight percent of graphite, 65 weight percent of thermosetting phenolic resin, and a solvent, and using a roll. The resistor paste is printed on the resistor substrate 10 and cured.

  Graphite-coated diamond exists in outer space, but is manufactured at a low cost by a technique called an explosion impact method as disclosed in, for example, Russian Chemical Reviews 70 (2001) 607 Can do. The graphite-coated diamond thus produced has an average particle diameter of 5 nm, and some of the graphite (graphite) covering the diamond may be amorphous carbon.

  In the present embodiment, the lubricity and toughness of the resistor 15 are greatly improved by adding a small amount of the graphite-coated diamond ultrafine particles. Thereby, the plastic deformation and fatigue wear of the resistor 15 are drastically reduced, and the resistance value change is reduced. In addition, the generation of cracks due to fatigue wear is reduced, the wear powder becomes finer, and the graphite-coated diamond ultrafine particles have surface conductivity, so resistance fluctuation due to wear powder reattachment is not induced. . Furthermore, since the average particle diameter of the graphite-coated diamond ultrafine particles is as fine as 5 nm, the contact pieces 35a and 35b of the slider 35 are rarely worn, and the wear resistance and corrosion resistance of the slider 35 are improved. Is also effective.

  In the present embodiment, since the graphite-coated diamond is used as a part of the raw material of the resistor 15, a conventional variable resistor manufacturing process can be used, and a technique called an explosion impact method is used. Combined with the use of an inexpensive material called graphite-coated diamond that can be manufactured in large quantities, the product cost of the variable resistor can be greatly reduced.

  Examples of the variable resistor according to the present invention will be described below. 5 weight percent of graphite-coated diamond, 25 weight percent of carbon black, 5 weight percent of graphite, 65 weight percent of thermosetting phenol resin and a solvent were added and mixed, and a resistor paste was formed using a roll. The resistor paste was printed on the resistor substrate 10 in the shape shown in FIG. 3 and cured to prepare a sample S1. This sample S1 was subjected to a rotation test 30 million times, and the resistance value change and sliding resistance noise were measured.

  In addition, samples S2 to S13 were prepared by changing the mixing ratio of graphite-coated diamond, carbon black, graphite, and thermosetting phenol resin by the same method as described above, and the same rotation test was performed as described above to determine the resistance value change and the sliding resistance. Dynamic resistance noise was measured. The results are shown in Table 1 below.

  From the results shown in Table 1, in the samples S1, S4, S5, and S13 in which the content of the graphite-coated diamond in the resistor 15 is 2 weight percent or more and 15 weight percent or less, the resistance of the slider 35 in 30 million rotation tests is shown. It was possible to suppress the value change to ± 1.0% or less and the sliding resistance noise to 0.3% or less. It can be seen that the resistance value change and the sliding resistance noise are greatly improved as compared with the other comparative examples (samples S2, S3 and samples S6 to S12).

  The variable resistor and resistor paste according to the present invention are not limited to the above-described embodiments and examples, and can be variously modified within the scope of the gist.

  In particular, the variable resistor according to the present invention is not limited to the variable resistor having the structure described as the embodiment, but can be applied to variable resistors having other structures.

The variable resistor which is one Embodiment of this invention is shown, (A) is a top view, (B) is a side view. It is sectional drawing which shows the said variable resistor. It is a top view which shows the resistor board | substrate of the said variable resistor. It is a top view which shows the molding state of the said board | substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Resistor board 15 ... Resistor 35 ... Slider

Claims (3)

  A variable resistor comprising a resistor disposed on a main surface of a substrate and a slider sliding on the resistor, wherein the resistor includes a graphite-coated diamond.   2. The variable resistor according to claim 1, wherein the content of the graphite-coated diamond in the resistor is 2 weight percent or more and 15 weight percent or less.   A resistor paste, wherein graphite-coated diamond, carbon black, graphite, and thermosetting resin are kneaded in a paste, and the content of the graphite-coated diamond is 2 to 15 percent by weight.

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