JPH11251113A - Sliding resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sliding resistor having a long sliding lifetime and superior sliding resistance stability with respect to charges in passage of time. SOLUTION: A sliding resistor 2 is made of carbon black and a binder resin, and the carbon black is a mixture of acetylene black having a pH of 9-10 and a furnace black having a pH of 6-8. The primary particle diameters of the acetylene black and furnace black are adjusted to 40-60 nm, and the DBP oil absorption of the acetylene black and furnace black are adjusted to 100-200ml/100 g. In addition, the volatile components of the acetylene black and furnace black are respectively adjusted to be within the ranges of 0.3-1.5% and 0.05-0.2% respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a sliding resistor used for a potentiometer or the like.

[0002]

2. Description of the Related Art As a sliding resistor used in a potentiometer of an automobile, a resistor substrate provided with a sliding resistor serving as a fixed contact on a surface thereof, and a resistor substrate including the surface of the sliding resistor Is configured to slide on the surface of the element while maintaining electrical continuity with the sliding resistor, and includes a contact serving as a movable contact.

When the contact moves on the sliding resistor, the position of an object connected to the contact can be detected from a change in the electric resistance value in a circuit connected to the sliding resistor. Most of the above-mentioned sliding resistors are made of a conductive resin composed of carbon and a binder resin.

Conventionally, with respect to the improvement of the sliding life of a sliding resistor, measures have been taken to reduce the generation of abrasion powder of the resistor, which causes sliding noise that determines the sliding life of the sliding resistor. Is well known. As a specific example of a known technique relating to such a reduction measure, a technique of adding an inorganic filler such as alumina or silica to a sliding resistor to reinforce the strength of the sliding resistor (for example, JP-A-2-158657) is known. Are known. For this reason, wear of the sliding resistor hardly occurs. It is also known to add a solid lubricant such as Teflon or graphite to a sliding resistor (for example, Japanese Patent Publication No. 58-50003). As a result, the slidability of the resistor surface is improved,
The amount of resistor wear powder generated is reduced.

A constant current is applied between the sliding resistor and the contact, and the voltage between the predetermined terminals is converted into a resistance. The contact resistance (value) is the sliding noise. When the contact resistance (value) is large, the sliding noise is high, and when the contact resistance (value) is small, the sliding noise is low.

[0006]

However, the above prior art has the following problems. First, the wear of the resistor is certainly reduced by the addition of the inorganic filler. However,
Conversely, since the hardness of the sliding resistor increases, the wear of the contact sliding with the sliding resistor increases, and the life of the contact may be shortened.

Further, there is a possibility that the wear particles of the resistor adhere to the surface of the inorganic filler deposited on the surface of the sliding resistor, and the wiping performance of the wear particles of the resistor is deteriorated. In this case, the sliding noise may be increased. Further, when a solid lubricant such as Teflon is added, the solid lubricant dropped from the sliding resistor itself may be a source of sliding noise.

It is also important that the resistance value, which is the original performance of the sliding resistor, is stable over a long period of time, as a requirement of the sliding resistor. However, there are no known sliding resistors that sufficiently satisfy such requirements. In particular, when a conductive filler such as graphite is added as an inorganic filler,
The temporal stability of the resistance value may be reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a sliding resistor having a long sliding life and excellent resistance stability with time.

[0010]

The invention according to claim 1 is a sliding resistor comprising carbon black and a binder resin, wherein the carbon black is a mixture of acetylene black having a pH of 9 to 10 and furnace black having a pH of 6 to 8. The acetylene black and the furnace black each have a primary particle diameter of 40 to 60 nm, the acetylene black and the furnace black have a DBP oil absorption of 100 to 200 ml / 100 g, respectively. The volatile resistor is in a range of 0.3 to 1.5%, and the volatile component of the acetylene black is in a range of 0.05 to 0.2%.

In general, carbon black can be roughly classified according to its production method and raw materials, and further classified according to its basic characteristics such as shape (size) and surface chemical state. Regarding the above-mentioned shape, since a structure in which primary particles are aggregated is used as the minimum unit of carbon black, it can be classified based on the primary particle diameter and the DBP oil absorption indicating the structure size. In addition, the chemical state of the surface can be classified by pH and volatile content, which are the measures of the amount of residual functional groups on the carbon surface.

[0012] The carbon black constituting the sliding resistor of the present invention comprises furnace black produced by an oil furnace method and acetylene black produced by an acetylene method. The carbon shape is a factor that governs the specific resistance and strength of the sliding resistor. In the present invention, both acetylene black and furnace black have a primary particle diameter of 40 to 60 nm and a DBP oil absorption of 1%.
It is in the range of 00-200 ml / 100 g.

When the primary particle diameter and the DBP lubrication amount deviate from the above ranges, the blending amount of carbon black for obtaining a predetermined resistance value increases or decreases, so that the hardness of the sliding resistor may deviate from an appropriate value. There is.

Further, the chemical condition of the carbon surface is a factor that governs the wettability with the binder resin and the stability over time.
-8, volatile content 0.3-1.5%, acetylene black pH 9-10, volatile content 0.05-0.2%.

When the pH and the volatile content deviate from the above ranges, the rheological properties of the uncured resistance paste (see Embodiment 1) are deteriorated by mixing carbon black and the binder resin. In addition, there is a possibility that the stability with time of the resistance value after being cured to form a sliding resistor may deteriorate. The volatile content is a value obtained by subtracting moisture from the mass loss rate when the sample is heated without contact with air.

As the binder resin, novolak phenol resin, resol phenol resin,
Epoxy resins and the like can be mentioned. As described below, the most preferred of these is a novolak phenolic resin.

In the sliding resistor according to the present invention, the mixing ratio (weight) of the carbon black and the binder resin is preferably 25/75 to 35/65. Thereby, the effect of the present invention can be reliably obtained. If the mixing ratio of carbon black is less than 25, the specific resistance of the sliding resistor may be too large or the hardness may be low because the amount of the binder resin is too large. On the other hand, when the mixing ratio of carbon black is larger than 35, the binder resin is too small, so that the specific resistance of the sliding resistor may be too small or the hardness may be high.

The mixing ratio (weight) of acetylene black and furnace black is 25/75 to 75/2.
It is preferably set to 5. Thereby, the effect of the present invention can be reliably obtained. If the mixing ratio of acetylene black is less than 25, the resistance value may increase with time because the amount of furnace black is too large.
On the other hand, when the mixing ratio of acetylene black is larger than 75, the resistance value may decrease with time because the amount of furnace black is too small.

The sliding resistor according to the present invention may contain a dispersant, a coupling agent and the like as components other than the above-described carbon black and the binder resin.

Next, the operation of the present invention will be described. The sliding resistor according to the present invention comprises carbon black and a binder resin, and the carbon black comprises acetylene black and furnace black as described above. The surface microhardness of such a sliding resistor is, for example, 50.
A preferred range of not too hard, not too soft, such as in the range of ６０60. Therefore, it is possible to obtain a sliding resistor having a small amount of resistor wear powder, a small sliding noise, and a long sliding life.

Further, in the sliding resistor provided with the sliding resistor according to the present invention, the contact sliding on the sliding resistor hardly wears. Therefore, according to the present invention, the life of the contact can be extended together with the sliding life of the sliding resistor, and the life of the sliding resistor itself can be extended.

Further, since the resistor wear powder generated from the sliding resistor according to the present invention is composed of the above-mentioned carbon black and binder resin, the resistor wear powder is aggregated on the surface of the inorganic filler, and the surface of the sliding resistor is exposed. It does not hinder the wiping of the resistor abrasion powder by contact, such as sticking to the contact. Therefore, the resistor wear powder is easily wiped off by the contact, and the contact hardly gets on the resistor wear powder. Therefore, a sliding resistor having a small sliding noise and a long sliding life of, for example, 2,000,000 times or more (see Table 1 described later) can be obtained.

Further, the carbon black in the sliding resistor of the present invention comprises acetylene black and furnace black. By the optimal blending of the surface chemistry of these carbons, the wettability with the binder resin can be improved,
The change rate of the sliding resistance applied to the sliding resistor is, for example, -10%.
It is possible to obtain an excellent sliding resistor that is suppressed to a narrow range of up to + 10% (see Table 1). In other words, it is possible to obtain a sliding resistor excellent in stability of sliding resistance with time.

As described above, according to the present invention, it is possible to provide a sliding resistor having a long sliding life and excellent stability over time of sliding resistance.

Next, as in the second aspect of the present invention, the binder resin is a novolak type phenol resin, and its melting point is preferably in the range of 90 to 100 ° C.
This makes it possible to maintain good rheological properties in the paste state when carbon is added. If the melting point is lower than 90 ° C., the viscosity ratio, which is an index of the leveling property, is too high, and the surface of the sliding resistor may be rough. When the temperature is higher than 100 ° C., the viscosity ratio is too low, and there is a possibility that the printing property is deteriorated.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A sliding resistor according to an embodiment of the present invention and a sliding resistor constituted by the sliding resistor will be described with reference to FIGS. The sliding resistor according to the present example is made of carbon black and a binder resin. The carbon black is a mixture of acetylene black and furnace black, each of which has a primary particle diameter of 40 nm, the DBP oil absorption of acetylene black is 180 ml / 100 g, and the DBP oil absorption of furnace black is 180 ml / 100 g. It is.

The chemical state of the surface of acetylene black is pH 10, and the chemical state of the surface of furnace black is pH 6.3. Further, the volatile content of acetylene black is 0.10%, and the volatile content of furnace black is 0.70%. The binder resin is a novolak phenol resin, and its melting point is 98 ° C.

Next, a method of manufacturing the sliding resistor according to this embodiment will be described. A mixed solvent composed of butyl carbitol acetate and acetone was prepared, and a novolak phenol resin was dissolved in the mixed solvent. Thereafter, acetylene black and furnace black were added. If necessary, a dispersing agent such as a phosphoric acid ester and a coupling agent such as a titanate type and an aluminum type were added.
Thereafter, these were stirred by a ball mill means to uniformly disperse acetylene black and furnace black in the solvent. Thereafter, the viscosity of the obtained dispersion solvent was adjusted using an automatic mortar to obtain a resistance paste.

This resistive paste was patterned by, for example, a screen printing method on the surface of a resistive substrate (refer to FIGS. 1 to 3 described later) on which electrodes had been provided in advance. Thereafter, the printed resistor substrate was put into a hot air circulating furnace and heated at a temperature of 230 to 250 ° C. for 1 to 2 hours. As described above, the resistance paste was cured to form a sliding resistor.

Next, a description will be given of a sliding resistor and a potentiometer incorporating the sliding resistor according to the present embodiment.
As shown in FIGS. 1 to 3, the sliding resistor 1 of the present embodiment constitutes a potentiometer 10 of an automobile. Resistor substrate 20 of potentiometer 10 for detecting rotational position
A sliding resistor 2 made of acetylene black, furnace black, and a novolak phenol resin is provided above. Reference numeral 101 denotes a case forming the outer shell of the potentiometer.

As shown in FIGS. 2 and 3, the sliding resistor 2
Is the resistance substrate 2 of the rotation center protrusion 302 of the rotary cylinder 30.
A first sliding resistor 21 (for inner current collection) formed concentrically around the 0-side fitting hole 202 and a second sliding resistor formed on the outer periphery of the first sliding resistor 21. Body 22 (for outside output). In other words, the sliding resistor 2 has a circular arc shape corresponding to a movement locus of two contacts 3 described later.
It comprises an inner first sliding resistor 21 and an outer second sliding resistor 22 arranged in a row.

One end of the inner first sliding resistor 21 and both ends of the outer second sliding resistor 22 are
A contact portion 23 for establishing electrical continuity with the three electric terminals 12 arranged in the first position is formed.

As shown in FIGS. 3 (a) and 3 (b), the contact 3 is fixedly provided on the surface of the rotary cylinder 30 facing the resistor substrate 20. A voltage corresponding to the position of the contact 3 is output from the terminal 23 by sliding on the sliding resistor 2 with the rotation of the rotary cylinder 30.

As shown in FIGS. 1 and 2, a potentiometer 10 to which the sliding resistor 1 for an automobile of this embodiment is applied.
Is a resistor substrate 2 on which a case 11 and a sliding resistor 2 are attached.
A contact chamber 4 is provided in the area surrounded by 0.

As shown in FIG. 2, a rotary cylinder 30 having the contacts 3 is rotatably disposed in the case 11 of the potentiometer 10. As shown in FIG. 3A, the contact 3 is divided into a first contact 31 and a second contact
2 and is fixed to the upper part of the rotary cylinder 30.

The rotating cylinder 30 has a rotation center protrusion 302 at the upper center thereof, and a corresponding center hole 202 (see FIG. 3A) is formed at the center of the resistor substrate 20. It is provided in. The rotary cylinder 30 is always urged upward by a spring 18 disposed below the flange portion 301, and is configured to maintain a contact state between the contact 3 and the sliding resistor 2. I have.

Next, using the potentiometer 10 comprising the sliding resistor according to the present embodiment, the sample 1 according to the present embodiment was used.
The performance of the sliding resistors according to Nos. 1 to 3 was evaluated together with Comparative Samples C1 and C2. Details of the samples 1 to 3 and the comparative samples C1 and C2 are described in Table 1. The primary particle size of acetylene black and furnace black in the table is 40 nm. The DBP oil absorption of acetylene black and furnace black is 180 ml / 100 g.

The chemical state of the surface of acetylene black is pH 10, and the chemical state of the surface of furnace black is pH 6.3. Further, the volatile matter of acetylene black is 0.1%, and the volatile matter of furnace black is 1.
0%. Note that the comparative sample C1 and the comparative sample C2 contain only one of acetylene black and furnace black, and also contain an inorganic filler.

In the evaluation of the performance, each value as shown in Table 1 was measured. First, the sliding life will be described. A potentiometer 10 according to FIGS. 1 to 3 constituted by a sliding resistor made of each sample is prepared, and the contact 3 is connected to the sliding resistor 2 at an ambient temperature of 120 ° C.
Was slid against. The sliding noise in the potentiometer 10 was monitored, and the number of times of sliding when the value became 10 kΩ or more was defined as the sliding life.

At an ambient temperature of 120 ° C., the contact 3 of the potentiometer 10 is
2 million times. After that, the depth of wear marks on the sliding resistor and the contact was measured by a surface profiler. These measured values are the resistance wear amount and the contact wear amount.

The resistance value stability was measured as follows. The resistor substrate and the sliding resistor in the potentiometer were left at a temperature of 130 ° C. for 1000 hours. The resistance value of the sliding resistor before leaving was compared with the resistance value after leaving, and the change rate was evaluated. The results are shown in Table 1.

As can be seen from the table, with respect to the sliding life, samples 1 to 3 showed no particular abnormality even when the number of sliding operations exceeded 2 million. However, for the comparative samples C1 and C2, it was found that the sliding noise became 10 kΩ or more after 500 to 1,000,000 times. That is, it was found that the sliding life of the comparative samples C1 and C2 was shorter than that of the sample according to the present example.

The resistance wear of each of the sample and the comparative sample was 1 μm or less, and it was found that the sample according to the present example was a sliding resistor having the same hardness as the conventional product. The contact wear amount was 5 μm for samples 1 to 3.
m, and Comparative Samples C1 and C2 were larger than 10 μm. As a result, it was found that the sliding resistor of the comparative sample was too hard, and even the contact was worn away, possibly shortening its life. Further, the resistance value stability of Samples 1 to 3 was in the range of -10% to + 10%, but Comparative Samples C1 and C2 were out of this range. That is, it was found that the resistance values of the comparative samples C1 and C2 were more likely to fluctuate than those of the samples 1 to 3.

Next, the operation and effect of the sliding resistor according to this embodiment will be described. The sliding resistor according to the present embodiment is made of carbon black as a conductive material and a binder resin, and the carbon black is made of acetylene black and furnace black as described above. The surface microhardness of such a sliding resistor can be in a preferable range of not too hard or not too soft. For this reason,
The amount of abrasion powder generated by the resistor is small, the sliding noise is small,
A sliding resistor having a long sliding life can be obtained.

Further, in the sliding resistor provided with the sliding resistor according to the present embodiment, the contact sliding with respect to the sliding resistor hardly wears. For this reason, according to this example, the life of the contact can be extended together with the sliding life of the sliding resistor, and the life of the sliding resistor itself can be extended.

The resistor wear powder generated from the sliding resistor according to the present embodiment is composed of the above-mentioned acetylene black, furnace black and binder resin. The wiping property of such a resistor abrasion powder does not agglomerate on the surface of the inorganic filler and does not adhere to the surface of the sliding resistor. Therefore, sliding noise is small, for example, 2 million times or more (Table 1).
), A sliding resistor having a long sliding life can be obtained.

The carbon black in the sliding resistor of this embodiment is composed of acetylene black and furnace black. The wettability with the binder resin is good depending on the particle size and the chemical state of the surface. Therefore, the rate of change of the sliding resistance applied to the sliding resistor is -10% to + 10%.
%, It is possible to obtain an excellent sliding resistor that is suppressed to a narrow range such as within% (see Table 1). In other words, it is possible to obtain a sliding resistor excellent in stability of sliding resistance with time.

As described above, according to this embodiment, it is possible to provide a sliding resistor having a long sliding life and excellent stability with time of sliding resistance.

[0049]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a plan view of a potentiometer incorporating a sliding resistor according to an embodiment.

FIG. 2 is a sectional view of a potentiometer incorporating a sliding resistor according to the embodiment;

3A is a plan view of a sliding resistor, FIG. 3B is a cross-sectional view taken along line AA, and FIG. 3C is a side view of the sliding resistor according to the embodiment.

[Explanation of symbols]

 1. . . 9. sliding resistor; . . Potentiometer, 20. . . 1. resistor substrate, . . Sliding resistor,

Claims (2)

[Claims] 1. A sliding resistor comprising carbon black and a binder resin, wherein the carbon black is p
It is a mixture of acetylene black of H9-10 and furnace black of pH 6-8, and the primary particle size of the acetylene black and furnace black is 40
And the DBP oil absorption of the acetylene black and the furnace black is 100 to 200, respectively.
The volatile content of the furnace black is in the range of 0.3 to 1.5%, and the volatile content of the acetylene black is in the range of 0.05 to 1.5%.
A sliding resistor characterized by being in the range of 0.2%. 2. The sliding resistor according to claim 1, wherein the binder resin is a novolak type phenol resin having a melting point in the range of 90 to 100 ° C.