JPH0474938B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to an electric brush used in a rotating electric machine such as a motor or a generator. This invention particularly relates to electric brushes used in motors for automobile electrical equipment, such as motors for fuel injection pumps. [Prior art] Electric brushes used in rotating electric machines are those that use a graphite electric brush body made of natural graphite or artificial graphite, or those that use a metal graphite electric brush body that is a mixture of metal and graphite. things are known. When the electric brush is assembled to the rotating electric machine and slid on the commutator, the graphite in the electric brush body transfers to the surface of the commutator, forming a graphite film to maintain the lubrication between the two. It will be done. However, if the graphite film is not formed in an appropriate state, the electric brush body and commutator will wear out significantly, causing maintenance problems. Various studies have already been conducted on improving the abrasion resistance of electric brush bodies. For example, it is known to add molybdenum disulfide, tungsten disulfide, or boron nitride to assist the lubricity of graphite and form a mixed film with graphite (Japanese Patent Publication No. 60-42595
issue). It is also known to add copper sulfide or zinc sulfide instead of molybdenum disulfide. Furthermore, it is known to add fine particles of an abrasive substance such as silica or alumina to remove excess graphite film on the commutator. However, despite these studies, the abrasion resistance characteristics of the electric brush body have not been sufficiently improved. [Object of the Invention] An object of the present invention is to improve the wear resistance of an electric brush body. [Structure of the Invention] The present invention provides an electric brush using a graphite or metal graphite electric brush body, in which the electric brush body contains spherical particles of a thermosetting synthetic resin with a particle size of 1 to 800 μm or particles thereof. Carbonized spherical particles from 1 to
It is characterized by adding 30% by weight and firing it to contain carbonized spherical particles. If spherical particles of a thermosetting synthetic resin or carbonized spherical particles thereof are added to the electric brush body and fired, the wear resistance of the electric brush body can be significantly improved. This effect is particularly remarkable when the electric brush is immersed in liquid fuel, such as when used in a motor for a fuel injection pump. The thermosetting synthetic resin particles used are obtained, for example, by emulsion polymerization or suspension polymerization,
Thereafter, it is separated from the dispersion medium and used. The shape of the particles is spherical. The degree of condensation of the particles can be any desired degree, from an initial condensation state to a completed condensation state, and any degree of condensation can be used as long as the particles are hardened to the extent that a spherical shape can be maintained. When such spherical particles of thermosetting synthetic resin are heat-treated in a neutral or reducing atmosphere, the resin is carbonized and spherical carbonized particles are obtained. Such carbonized spherical particles can also be used. As the thermosetting resin, for example, a phenol resin, a furan resin, a xylene resin, or a thermosetting polyimide resin may be used. Among these, inexpensive and easily available resins include Univex (Univex is a trade name, manufactured by Unitika Co., Ltd.) and Bell Pearl (Bell Pearl is a trade name, manufactured by Kanebo Co., Ltd.). These are spherical particles of phenolic resin. Regarding the material of the resin, it is preferable that the resin has a large amount of residual carbon when fired in a neutral or reducing atmosphere. The amount of residual carbon is preferably 50% or more. Note that the amount of residual carbon here means the weight ratio of the amount of carbon after firing to the resin. The amount of residual carbon is determined from the value obtained when resin particles are fired under the same firing conditions as the electric brush body. Next, the resin is fired in a reducing atmosphere to prevent oxidation, and then the resin is made into glassy carbon, that is, dense and shiny carbon.
Those that convert into are preferred. Many thermosetting resins such as phenol resins, furan resins, and xylene resins are converted into glassy carbon by firing. The particle size of the resin particles is 1 to 800 μm, and either those with a small particle size distribution or those with a large particle size distribution can be used. The particle size is more preferably 10 to 500 μm, still more preferably 10 to 250 μm. If the particle size is 1 μm or less, the effect of improving wear resistance is small, and if a large amount is added to enhance the effect, the specific resistance of the electric brush increases. On the other hand, particles with a particle size of 800 μm or more are easily separated from graphite powder and metal powder during molding, making it difficult to obtain a homogeneous electric brush. Furthermore, particles with a particle size of 800 μm or more may cause large scratches on the commutator etc. during use, damaging the commutator etc. The amount of resin particles or carbonized resin particles to be added is 1 to 30% by weight, more preferably 2 to 20% by weight, still more preferably 3 to 15% by weight, based on the total material of the electric brush body. In addition, below, the proportion of each material in the total amount of the main body material of the electric brush is expressed as weight%.
The unit is simply displayed as %. The product of the amount of resin particles added and the amount of residual carbon, or if the resin is carbonized from the beginning and used, the amount of carbonized resin particles is the actual amount of resin carbon added to the electric brush body. . If the amount of added resin or particles made of carbonized resin is less than 1%, hardly any improvement in wear resistance properties will be obtained. Even if 30% or more is added, the effect is saturated, increasing the resistivity of the electric brush body and reducing the output of rotating electrical machines such as motors. Furthermore, according to experiments conducted by the inventors, there were cases in which the addition of 30% or more resin accelerated wear of the commutator. The resin particles used in this invention or carbonized particles thereof are spherical. On the other hand, in the manufacture of electric brush bodies, phenolic resin varnish is often used as a binder for graphite. These binders are used by being dissolved in a solvent, and after the electric brush body is fired, they turn into a very thin film of carbon. Such carbon film does not contribute to the wear resistance of the electric brush body. The present invention can be applied to either graphite or metal graphite electric brush bodies. The metal powder here is preferably a metal powder with excellent conductivity such as copper powder or silver powder, and lead powder, tin powder, etc. may be used in combination as necessary. The amount of metal powder used is preferably 0 to 80%, and may be determined as appropriate depending on the type of motor, required output, durability, etc. For example, 50 to 80% is preferable for a starter motor of an automobile engine, and 30% for a blower motor or wiper motor.
~60% is preferable, and 0~40% is preferable for motors for fuel injection pumps such as gasoline. 80 metal powder
% or more will promote wear of the commutator when the current density is increased. As the graphite powder, natural graphite powder is preferable, but artificial graphite powder can also be used. These graphite powders are usually used after being treated in advance with a binder such as phenolic resin varnish in an amount of about 1 to 30% by weight based on the weight of graphite. However, it is not necessary to use a binder. In addition, the amount of graphite powder used is, for example, 15 to 99%, and metal powder, thermosetting resin particles, carbonized particles thereof, and other materials such as boron nitride, molybdenum disulfide, tungsten disulfide, etc. are used as necessary. Including additives, the total amount is 100%. In addition, the content of graphite powder is 15%.
If it is less than that, the abrasion resistance of the electric brush will deteriorate significantly, which is not preferable. For example, the electric brush body may be manufactured in the following order: mixing materials, molding, and firing in a neutral or reducing atmosphere. Here, resin particles or carbonized particles thereof may be mixed with graphite powder in advance and then metal powder may be mixed therein, or all materials may be mixed at once. [Example] Example 1 70% copper powder, 23% natural graphite powder treated with phenolic resin varnish, and spherical particles of phenolic resin with a particle size of 100 to 200 μm (trade name: Univex N,
5% (manufactured by Unitika Co., Ltd.) and 2% molybdenum disulfide were mixed, press-molded into the shape of an electric brush body with embedded pigtails, and then fired to obtain an electric brush for a starter motor. The residual carbon content of the phenolic spherical particles is 63%, and the composition of the electric brush body after firing is 71.4% copper, 23.4% graphite, 3.2% spherical carbon particles made by carbonizing phenolic resin,
Molybdenum disulfide is 2%. As a comparative example, an electric brush prepared in exactly the same manner except that phenolic resin-based spherical particles were not added was used. These electric brushes were assembled into a starter motor with an output of 2.0KW, attached to a 3000cc diesel engine, and used for 10,000 cycles, with one cycle consisting of 2 seconds of operation and 13 seconds of rest. The amount of wear of the electric brush after use was evaluated. The amount of wear in the example is 1.6mm
However, in the comparative example, it was 2.7 mm. In the example, the wear rate is reduced by about 40%. Example 2 30% copper powder, 60% natural graphite powder treated with phenolic resin varnish, and hardened phenolic resin spherical particles with a particle size of 1 to 20 μm (trade name Bell Pearl R-
900 (manufactured by Kanebo Co., Ltd.) at 10%, a pigtail was embedded therein, press molding and firing were performed to obtain an electric brush. The residual carbon content of this resin is 62%, and the composition of the electric brush body is 31.2% copper, 62.4% graphite, and 6.4% spherical carbonized particles. As a comparative example, a sample prepared in exactly the same manner except that spherical particles of phenolic resin were not added was used. These electric brushes were attached to a small automobile blower motor, and the voltage was 12V and the current density was 25A/ ^cm2.
They were used for 500 hours and the amount of wear was compared. The amount of wear in the example was 2.5 mm, while in the comparative example
It was 3.75mm. In the example, the wear rate is reduced by 2/3. Example 3 Natural graphite powder treated with phenolic resin varnish 72
% and 28% of cured phenolic resin spherical particles with a particle size of 500 to 750 μm (product name Univex C, manufactured by Unitika Co., Ltd.) were mixed and heated at 700°C after press molding.
An electric brush was obtained by firing it. The amount of residual carbon is 63%,
Composition: 80.3% graphite, 19.7% spherical resin-based carbon particles
It is. Example 4 The phenolic resin spherical particles used in Example 3 were
It was heated to 700°C for an hour and carbonized into spherical carbon particles. The amount of residual carbon in this process was 63%. 3% of these carbonized particles and 97% of natural graphite powder treated with phenolic resin varnish were mixed, molded, and fired at 700°C to make an electric brush. Example 5 20% copper powder and 70% natural graphite powder treated with phenolic resin varnish were mixed with phenolic resin spherical particles (trade name: Univex WA-S,
(Manufactured by Unitika Co., Ltd.) 10% and after molding
It was fired at 700℃ and made into an electric brush. The composition of the electric brush body calculated from the amount of residual carbon is 21% copper and 72.5% graphite.
%, spherical carbon particles 6.5%. Example 6 20% copper powder and 70% natural graphite powder treated with phenolic resin varnish were mixed with hardened phenolic resin spherical particles (trade name: Bell Pearl R-
900, manufactured by Kanebo Co., Ltd.) 10% and after molding.
It was fired at 700℃ and made into an electric brush. The composition of the electric brush body calculated from the amount of residual carbon is 20.8% copper and graphite.
72.8%, resin-based spherical carbon particles 6.4%. Comparative Example 1 A comparative example for Examples 3 and 4, prepared in exactly the same manner except that no phenolic resin spherical particles were added. Comparative Example 1. Comparative Example 2 A comparative example for Examples 5 and 6. Comparative Example 2 was prepared in exactly the same manner except that no phenolic resin spherical particles were added. These electric brushes were attached to a motor for a gasoline injection pump of an automobile engine, and used while being immersed in gasoline. The motor was used under conditions of a voltage of 12 V and a current of 4.5 A, and the amount of wear on the electric brush was measured after driving for 500 hours.

【table】

[Table] As is clear from Table 1, when spherical particles of thermosetting resin or carbonized spherical particles are added, the amount of wear on electric brushes is reduced to less than 1/10. As described above, the effect of adding spherical carbonized particles is particularly remarkable when an electric brush is immersed in liquid fuel, such as in a motor for a fuel injection pump. This effect can be obtained regardless of whether the resin is cured, uncured, or carbonized. Furthermore, the amount of resin added was varied over a wide range of 3 to 28%, and the wear resistance properties were sufficiently improved regardless of the amount added. [Effects of the Invention] In this invention, spherical particles of thermally effective resin or spherical particles obtained by carbonizing the same are added to a graphite or metal graphite electric brush and fired, thereby improving the abrasion resistance of the electric brush. Improve wear characteristics.

Claims (1)

[Scope of Claims] 1. In an electric brush using a graphite or metal graphite electric brush body, the electric brush body includes spherical particles of thermosetting synthetic resin with a particle size of 1 to 800 μm or carbonized particles thereof. An electric brush characterized by adding 1 to 30% by weight of carbonized spherical particles and firing the carbonized spherical particles.