JPS63283449A - Carbon brush for rotating electrical machine - Google Patents

Abstract

PURPOSE:To improve the electric conductivity, abrasion resistance and mechanical strength of a carbon brush through simple means by including a given amount of solid epoxy compound in graphite powder and by heating, compressing and forming the obtained mixture at a given temperature and under. CONSTITUTION:2-30pts.wt. of solid epoxy compound are included in 100pts.wt. graphite powder and their mixture is pressure-molded at 300 deg.C and under to obtain a carbon brush. Said graphite powder is the powder of natural graphite such as flake graphite, crystalline graphite and earthy graphite kish graphite or artificial graphite, and it is possible to use a single kind of said graphites or a combination of two kinds or more thereof. Also, said solid epoxy compound is a general term given to such compound which is solid in a service condition and has an epoxy radical.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a carbon brush for rotating electric machines, and more specifically, a carbon brush that exhibits excellent mechanical strength without impairing the electrical conductivity essential for rotating electric machines. This relates to carbon brushes.

[Conventional technology]

Conventional carbon brushes are disclosed in Japanese Patent Application Laid-Open No. 52-3851, for example.
As seen in the description of the prior art on page 1 of Publication No. 6, graphite is used as the main raw material, tar, pitch, or thermosetting resin is used as the binder, and after pressure molding, it is fired at a relatively high temperature and further heated to 2500°C. Graphitization is carried out at different temperatures, or, as shown in the description of the prior art on page 1 of Japanese Patent Publication No. 17915, graphite is mixed with a thermosetting resin such as phenol resin and then molded, followed by thermosetting. It is molded by heating and curing a synthetic resin.

However, with the former method of forming using high-temperature firing and graphitization, although a carbon brush with excellent conductivity and mechanical strength can be obtained, it takes a long time for firing and graphitization, and high temperatures are required during firing and graphitization. However, there are problems with dimensional accuracy due to thermal expansion of the material, etc., and there are large variations in mechanical strength, making it difficult to obtain products of constant quality.

In addition, the latter method of mixing graphite with a thermosetting resin and curing it by heating generally has the drawback that the density of the molded product is low and mechanical strength such as bending strength and Charpy impact value is low. Naturally, in order to increase this mechanical strength, it is sufficient to increase the content of the thermosetting resin, but as the graphite content decreases, the resistivity and friction coefficient become high, making it impossible to put it into practical use.

Therefore, as an improvement technique for the former, a method has been proposed to select a special combination of carbon materials to be used, and as an improvement technique for the latter, a means has been proposed for selecting a special combination of resins to be used. . However, even in these improved techniques, the adjustment of each main raw material is quite complicated, and it is difficult to say that it is a practical means.

[Problem that the invention seeks to solve]

The purpose of the present invention is to solve all of the above-mentioned problems, and to improve electrical conductivity, frictional properties, wear resistance, and mechanical strength by simple means without performing high-temperature firing at 100°C or higher. The purpose of this invention is to provide an excellent carbon brush for rotating electric machines.

[Means for solving problems]

The inventors of the present invention have conducted various studies to solve the above-mentioned problems, and have found that a solid epoxy compound within a specific range is blended into graphite powder, and when compression molding is carried out at 300°C.
By maintaining the following, it satisfies the resistivity of 15 x 10 Ω-G or less and the friction coefficient of 0.3 or less, which are essential for carbon brushes for rotating electric machines, and also has a room temperature bending strength of 500 kg.
The present invention was completed based on the completely new knowledge that a carbon brush for a rotating electric machine can be obtained which exhibits extremely excellent mechanical strength with a Charpy impact value of 1.5 kgc++/- or higher.

That is, the gist of the present invention is that the rotary epoxy compound contains 2 to 30 parts by weight of a solid epoxy compound based on 100 parts by weight of graphite powder, and the mixture thereof is heated and compression molded at 300°C or less. Found in carbon brushes for electrical equipment.

The present invention will be explained in detail below.

First, an important feature of the present invention is that a limited amount of a solid epoxy compound is used as a thermosetting compound when graphite powder is molded in a mixture with a thermosetting compound.

In other words, molded products made by simply heating and compression molding a mixture of graphite powder and thermosetting resin such as phenolic resin generally have low density and mechanical strength such as bending strength and Charpy impact value. On the other hand, when a mixture of graphite powder and a solid epoxy compound in a specific range is used according to the present invention, a carbon brush can be obtained which has extremely high mechanical strength while satisfying resistivity and friction coefficient.

The reason for this is that epoxy compounds have superior adhesion to graphite and carbon materials compared to other general resins and can provide high-strength composite materials, and unlike phenolic resins, they can be used under the heat compression molding conditions described below. The resistivity,
This is because various mechanical strengths can be improved without impairing the friction coefficient or the like. In addition, the reason why the epoxy compound is in a solid state is that when the epoxy compound is in a liquid state, the amount used when mixed with graphite powder is smaller than that of graphite powder, so the mixture cannot be made homogeneous unless a solvent is used. However, in the case of a solid product, it is difficult to make the mixture homogeneous by simple mixing using a ball mill, etc. This is because the molded product after hot compression has small variations in physical properties such as mechanical strength.

In this case, the amount of solid epoxy compound used is 100% graphite powder.
It is important that the amount is 2 to 30 parts by weight; if it is less than 2 parts by weight, the mechanical strength of the carbon brush as a molded product will be low, while if it exceeds 30 parts by weight, the resistivity and friction will decrease. This is because not only the coefficient becomes large, but also the coefficient of thermal expansion becomes thick, making it impossible to put it to practical use as a carbon brush.

In addition, the graphite powder referred to in the present invention is a powder of natural graphite such as flaky graphite, phosphorous graphite, earthy graphite, quiche graphite, or artificial graphite, and these may be used alone or in combination of two or more types. be able to. The average particle size of these graphite powders is preferably 1 to 150 μm.

In addition, solid epoxy compounds are a general term for compounds that are solid in use and have epoxy groups; examples thereof include:
Epoxy resins such as bisphenol A epoxy resin, bisphenol F epoxy resin, orthocresol novolac epoxy resin, and phenol novolak epoxy resin, glycidyl ester compounds such as phthalic acid glycidyl ester and terephthalic acid glycidyl ester, triglycidyl isocyanurate, etc. Examples include glycidyl-modified compounds. These epoxy compounds may be used alone or in combination of two or more. However, if two or more epoxy compounds are used in combination, even if one or more is a solid epoxy compound and the other is a liquid epoxy compound, as long as the mixed epoxy compound is solid in the state of use, it falls within the scope of the present invention. It is.

In this case, solid means that the softening point or melting point is above room temperature, and powder is most desirable from the viewpoint of mixing with graphite powder.

Note that these epoxy compounds are usually used in combination with a curing agent and/or curing accelerator. Examples of curing agents include amine compounds such as aliphatic polyamines such as diethylenetriamine, aromatic polyamines such as 4.4'-diaminodiphenylmethane and 4-4'-diaminodiphenylsulfone, and hydrazides such as isophthalic acid dihydrazide. Examples of the compound include aliphatic acid anhydrides such as oxalic anhydride and maleic anhydride, aromatic acid anhydrides such as phthalic anhydride, pyromellitic acid, and trimellitic acid, and curing agents other than those listed above. Other examples include dicyandiamide polysulfide. Examples of the curing accelerator include Lewis acids such as boron trifluoride, boron trifluoride amine complexes, and imidazoles such as ethylimidazole.

The curing agent and/or curing accelerator for this epoxy compound is also preferably in powder form from the viewpoint of use.

In the present invention, in addition to the above-mentioned main raw materials, solid lubricants such as molybdenum disulfide, boron tinide, and calcium fluoride may be used to further reduce the coefficient of friction, and carbon may be used to improve mechanical strength. Short fibers such as fibers and graphite fibers, woven fabrics such as carbon cloth, and one or more types of carbon black such as acetylene black for the purpose of improving conductivity can be appropriately blended within the range that does not impair the above-mentioned characteristics. be.

Next, when blending the above components and molding them into a carbon brush, it is appropriate to mix each component in the powder state by tri-blending, but it is also appropriate to perform wet blending using other solvents, etc. The mixture may be dried, or the components other than graphite may be mixed in advance and melted, then cooled and solidified, pulverized, and mixed with graphite.

Furthermore, it is preferable that the epoxy compound other than graphite and the curing agent and/or curing accelerator be ground to a particle size as fine as possible, usually 0.5 mm or less, before mixing with graphite powder.

Next, in the present invention, the heating compression molding temperature of the mixture is set to 30
The reason why the heating temperature is set to be 0°C or lower is that when the heating temperature exceeds 300°C, the cured resin begins to deteriorate. Note that a desirable heating range is 100°C to 250°C. The pressure during compression molding is 10~2゜000kg/cj, especially 100~2゜000kg/cj.
2,000 kg/- is desirable.

Furthermore, when the powder mixture exhibits appropriate fluidity or plasticity, methods such as injection molding and ram molding can be used.

The carbon brush obtained in this way has a resistivity of 15×1
It is possible to achieve a mechanical strength of 0-3 Ω-1 or less, a friction coefficient of 0.3 or less, a room-temperature bending strength of 500 kg/cj or more, and a Charpy impact value of 1.51+rcm/- or more.

〔Example〕

The effects of the present invention will be explained in more detail with reference to Examples below.

The physical property test conditions for the carbon brush test materials used in the Examples and Comparative Examples are as follows.

a) Room temperature bending strength (gift/-) Test piece: 10M (width) x 60mm (length) XIO fin (thickness) Using a universal strength testing machine, the bending strength in the direction of the molded pressurized surface was determined at a distance between fulcrums of 401 m.

b) Charpy impact value (kg cs / cll) test piece: 10mm (width) x 60u (length) x 10m (thickness) weighing 5k
Using Z-ELL's Charpy impact tester, the distance between fulcrums was 4.
The impact value in the direction of the molding pressurized surface was determined at 0u.

C) Resistivity (Ω-(J) Test piece: 10 mm (width) x 60 um (mm) x 10 mm (thickness) Using a four-probe resistor, the molding was determined as the volume resistivity value in the direction perpendicular to the pressurizing surface direction.

d) Friction coefficient test piece: A lead wire is attached to a molded body measuring 16 mm (width) x 30 u (length) x 10 u (thickness), and the terminal shape is JIS-C28.
T-1-5 according to 02.

Using a tester consisting of a brush dynamic friction measuring device and a triangular wave generator, a current of 5 A was applied and the brush pressure was 1 kg.

Example 1 63 parts by weight of natural scaly graphite with an average particle size of 7 μm and 62 μm
Orthocresol novolak type epoxy resin (
6.3 parts by weight of epoxy equivalent (211, softening point 69°C) and 1.3 parts by weight of diaminodiphenylmethane as a hardening agent were dry-pulverized and mixed in a ball mill to obtain a homogeneously dispersed mixed powder.

Note that, prior to mixing the epoxy resin and the curing agent with the graphite, both compounds were ground together in a pot mill and used as a powder having a particle size of 35 mesh (0.42 u+) or less.

Put the above mixed powder into a mold and press under a pressure of 34
Under a pressure of 0 kg/-, the mold was heated externally from room temperature to 220° C. over 2.5 hours using a heater to perform molding. The test results of the molded bodies are shown in Table 1.

Although not shown in Table 1, when the friction fluctuation value and dynamic voltage-current characteristic (Ω) were measured using this molded article, good results of 0.010 and 0.047 were obtained, respectively.

Example 2 The same graphite powder and epoxy compound as in Example 1 were used, and 10 parts by weight of the epoxy compound and 23 parts by weight of diaminodiphenylsulfur as a hardening agent were used for 100 parts by weight of graphite powder.

The heating and pressure molding was carried out in the same manner as in Example 1, by increasing the temperature from room temperature to 240° C. over 3 hours. The test results of the molded bodies are shown in Table 1.

Although not shown in Table 1, when the friction fluctuation value and the dynamic voltage ii flow characteristics Ω) were measured using this molded article, good results of 0.0095 and 0.045 were obtained, respectively.

Example 3 100 parts by weight of the same graphite powder as in Example 1 was used, 9.2 parts by weight of a brominated phenol novolac type epoxy resin (epoxy weight 1276, softening point 84°C) as an epoxy compound, and diaminodiphenylmethane as a hardening agent. 1.
6 parts by weight was used.

Heat and pressure molding was performed in the same manner as in Example 1, starting at room temperature.
It was heated to 80° C. over 2 hours and molded. The test results of the molded bodies are shown in Table 1.

Example 4 100 parts by weight of the same graphite powder as in Example 1 was used, 11.4 parts by weight of bisphenol A type epoxy resin (epoxy equivalent: 475, softening point 68'C) was used as the epoxy compound, and 1.5 parts by weight of diaminodiphenylmethane was used as the softener. 2 parts by weight was used. The heating and pressure molding was carried out in the same manner as in Example 1, by increasing the temperature from room temperature to 180° C. over 2 hours. The test results of the molded bodies are shown in Table 1.

Example 5 For 100 parts by weight of natural flaky graphite with an average particle size of 7 μm,
The same epoxy compound and curing agent as in Example 2 were used, 1 part by weight and 3 parts by weight, respectively. The heating and pressure molding was carried out in exactly the same manner as in Example 2. The results are shown in Table 1.

Comparative Example 1 The same epoxy compound and curing agent for graphite powder as in Example 1 were used, and 33 parts by weight of the epoxy compound and 7.8 parts by weight of the curing agent were used for 100 parts by weight of graphite powder, and heat and pressure were applied. Molding was carried out in exactly the same manner as in Example 1. The test results of the molded product are shown in Table 1, and the resistivity was 20XlO-'Ω-1, making it unsuitable as a brush material.

Comparative Example 2 The same graphite powder as in Example 5 was used, and 15 parts by weight of resol type phenol resin was mixed in the same manner as in Example 1, followed by heating and pressure molding to obtain a molded product. The test results of the molded product are shown in Table 1, and the bending strength and Charpy impact value are very low, making it unsuitable as a brush material.

Comparative Example 3 The same graphite powder as in Example 5 was used, and novolac-type phenol fat (phenol equivalent: 105, softening point: 80°C) 1
5 parts by weight and 1. hexamethylenetetramine as a curing agent.
Using 5 parts by weight, the mixture was mixed in the same manner as in Example 1, and molded under heat and pressure to obtain a molded product. The test results of the molded product are shown in Table 1, and the bending strength and Charpy impact value are very low, making it unsuitable as a brush material. (Leaving space below) Table 1 Physical property test results [Effects of the invention] As is clear from the above examples, according to the present invention, the carbon material has excellent mechanical strength while satisfying resistivity and friction coefficient. It is possible to obtain a brush that achieves physical property values that were thought to be extremely difficult with the conventional combination of graphite and thermosetting resin, and it is an extremely significant contribution to the development of industry. There is.

Claims (1)

[Claims] 2 to 30 parts of solid epoxy compound to 100 parts by weight of graphite powder
1. A carbon brush for a rotating electric machine, which contains a carbon brush containing parts by weight, and is formed by heating and compressing a mixture thereof at 300° C. or less.