JP2930789B2 - Metal graphite brush - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metallic graphite brush,
In particular, the present invention relates to a metal graphite brush suitably used for a small DC motor for an automobile.

[0002]

2. Description of the Related Art In general, for a rotating electric machine used for an automobile, for example, a small DC motor, a metal graphite brush is used as a brush for performing a rectifying action. The basic performance of metal graphite brushes includes steady noise, self-excited vibration abnormal noise generation rate, life (wear resistance), and specific resistance. Various methods have been used to obtain brushes with excellent performance. Used. The most basic ones are metal /
Selection of a graphite component ratio, addition of a special component, for example, an inorganic material such as lead or molybdenum sulfide, and adoption of a brush material having a small friction coefficient and a small frictional change are performed.

[0003]

However, when the mixing ratio of metal / graphite and the addition of a special component such as an inorganic material in the above-mentioned prior art tend to conflict with each other in terms of noise and current-carrying life, they are excellent in both performances. It was difficult to manufacture the brush and the effect of suppressing the self-excited vibration noise was not expected. That is, for example, when the compounding ratio of the metal component is increased,
Although the contact resistance with the commutator can be improved, there is a disadvantage that the brush noise increases.
Also, addition of a special component such as an inorganic substance can improve noise and life (wear resistance), but causes a problem in conductivity.

As described above, in the selection of the metal / graphite component ratio, the addition of special components such as inorganic materials, and the adoption of brush materials having a small friction coefficient and friction variation, all of the basics required for brushes are required. There is a tendency to conflict with the performance, and the effect of suppressing self-excited vibration noise cannot be expected.

Accordingly, the present inventors have paid attention to the relationship between the size of the metal particles blended in the metal graphite brush and the steady noise, self-excited vibration noise generation rate, life (wear resistance), specific resistance, and the like. As a result of intensive research, the particle size of the metal powder to be blended is varied, and the powder of the metal having the different particle size is set to a predetermined blending ratio, whereby the basics of the contradictory metal graphite brush are obtained. The inventors have found that performance requirements can be achieved, and have led to the present invention.

An object of the present invention is to provide a metal graphite brush by using at least two kinds of blended powders of a fine particle powder and a large particle powder as a metal powder as one of brush materials. Provided is a metal graphite brush which suppresses a sliding noise and a self-excited vibration noise generated by friction sliding with a sliding member, for example, a commutator, and is excellent in specific resistance and life (abrasion resistance). It is in.

[0007]

SUMMARY OF THE INVENTION A metal graphite brush according to the present invention is formed by pressing a graphite powder and a metal powder mixed in a predetermined blending ratio into a predetermined shape and then firing. In the metal graphite brush, for copper of the metal, a powder of fine particles, and a powder of large particles having a particle diameter of 20 to 150 times the particle diameter of the powder of fine particles, And a ratio of 4: 6 to 6: 4 in the mixing ratio of the fine particles and the large particles. The fine particles have an average particle size of about 2.8 μm, and the large particles have the average particle size. Diameter is about 100
It is preferable to set it to μm.

[0008]

With respect to copper constituting the metallic graphite brush, fine particles of powder and 20 to 1 times the particle diameter of the fine particles are used.
When two copper powders having greatly different particle diameters are mixed with a 50-fold large-particle powder, and the mixing ratio of the fine-particle powder and the large-particle powder is 4: 6 to 6: 4, In addition, a metal graphite brush excellent in steady noise, self-excited vibration generation rate and life, and specific resistance can be obtained.

This will be described with reference to FIG. 3 which shows an example of sliding between a metal graphite brush and a commutator which slides with the metal graphite brush. FIG. 3 is an explanatory view showing a sliding state of the commutator and the metal graphite brush. As shown in FIG. 3, the effect of the copper powder having a large particle diameter makes it easier for the current to flow in the metal graphite brush, lowers the contact resistance with the commutator, reduces the calorific value, and reduces the life of the metal graphite brush. Is improved. In addition, the copper powder of fine particles causes a rolling friction between the metal graphite brush and the commutator, which causes a reduction in frictional force and a decrease in spring constant, thereby suppressing self-excited vibration noise and reducing steady noise. This is effective in reducing the amount of brush friction.

[0010] That is, the copper powder having a large particle size improves the wear resistance and extends the life greatly, and the current flows through the large particle size to improve the specific resistance. Regarding the steady noise, self-excited vibration noise generation rate, and contact resistance, copper powder with a small particle size is generated by the sliding between the metallic graphite brush and the commutator, and interposed between the contact surfaces of the metallic graphite brush and the commutator. And be improved.

[0011]

An embodiment of the present invention will be described below with reference to the drawings. The members, arrangements, and the like described below do not limit the present invention, and can be variously modified within the scope of the present invention. In this example, a description will be given of an example in which a metal graphite brush slides with a commutator of a small DC motor.

FIG. 1 shows the relationship between the particle size of copper and the basic characteristics of the brush, ie, a: life (wear resistance, unit: hours), steady noise (unit: dB · A), generation of self-excited vibration noise. Rate (unit:
%) And resistivity (unit: μΩ · cm). FIG. 2 is a graph showing the copper particle diameter (μm) on the horizontal axis and the numerical values on the vertical axis. A: life (abrasion resistance), b: steady noise,
c is a graph showing the self-excited vibration noise generation rate, and d is the resistivity. The horizontal axis represents the mixture ratio between large particles and fine particles, and the vertical axis represents FIG.
The figure shows the respective numerical values of the same brush basic characteristics. The measurements in FIGS. 1 and 2 were performed under the following conditions. That is, a: For the life, a motor (not shown, the same applies hereinafter) is operated continuously at 12 V and 15 A, and calculated from the time until the motor fails. B: For the steady noise, a constant distance ( 5 mm), a microphone for sound collection is arranged at a position of 1500R. P. M. The time is calculated from the overall value at a frequency of 0 to 20 KHz. C: The self-excited vibration abnormal noise generation rate is calculated from the abnormal noise generation rate during the continuous operation of the motor at 5 V, 1 A for 3000 hours. , D: The resistivity was calculated from a voltage drop value by applying a current to a test piece of a metallic graphite brush.

In this embodiment, a metal graphite brush 10 is obtained by firing graphite powder 11 and copper powder 12 as a metal. In this example, the graphite powder 11 and the copper powder 12 are used in a ratio of 85:15. The copper powder 12 is a fine particle having a mean particle size of about 2.8 μm and a powder having a mean particle diameter of about 100 μm, which is 20 to 150 times larger than the fine particle powder 12 a. Two kinds of powders having different particle diameters from the particles 12b are used.
The two types of copper powders 12a and 12b are in a weight ratio of 4: 6 to 10 when the total amount of copper to be mixed is 10.
It is blended at a ratio of 6: 4.

In this manner, as shown in FIG. 3, the contact resistance with the commutator 13 is reduced by the large-diameter powder 12b of copper constituting the metallic graphite brush 10, and at the same time, the calorific value is reduced. The wear resistance is good and the life is greatly extended. Then, the current A flows through the powder 12.
b, and the specific resistance is improved. Further, the powder 12a having a small particle size of copper is interposed between the contact surface 13a of the metal graphite brush 10 and the commutator 13 due to sliding between the metal graphite brush 10 and the commutator 13 to generate a rolling friction state, thereby causing a frictional force. And the spring constant is reduced, thereby improving steady noise, self-excited vibration noise generation rate, and contact resistance. As described above, by reducing the particle size of copper, the occurrence rate of steady noise and self-excited vibration noise of the metal graphite brush 10 is improved. Conversely, by increasing the particle size of copper, the metal graphite brush 10 The contact resistance and life of the device are improved. In the above example, the mixing ratio of copper and graphite was set to 1
Although the ratio is 5:85, it can be applied to other compounding ratios.

The metal graphite brush having the above structure can be manufactured as follows. That is, a graphite pretreatment step,
It comprises a compounding step, a forming step, a firing step, and a finishing step.

In the graphite pretreatment step of this embodiment, the graphite 11 is purified to a high degree of purity. First, graphite as a raw material and a binder (not shown) are stirred and mixed by a mixer and dried by a dryer. And pulverize to predetermined particles by a pulverizer. Then, it is sieved by a sieving machine to make graphite particles constant.

In the compounding and mixing step of this embodiment, the graphite 11 and the copper powders 12a and 12b are mixed. Copper powder having two kinds of particle diameters is used in advance. That is, two types of copper powder, a powder 12a having an average particle size of approximately 2.8 μm and a powder 12b having an average particle size of approximately 100 μm, are mixed with copper powder 1.
Copper powder 12a having an average particle size of about 2.8 μm is 40% and the average particle size is about 10% by weight relative to the total amount of 2a and 12b.
0 μm copper powder 12b is blended so as to be 60%, and mixed by a mixer. At this time, a known additive or the like may be added.

In the molding step of this embodiment, a mixture of the graphite 11 and the copper powders 12a and 12b is molded into a predetermined shape of a metallic graphite brush, and pressure molding is performed by a powder molding machine. At this time, pigtail (not shown)
Is embedded in a predetermined position to perform integral molding. A connection terminal is formed at the end of the pigtail by a spot welder. In the firing step of the present example, the molded product is fired in a firing furnace. This firing step is performed at a known temperature and other conditions. The finishing step in this example is for processing a brush fired by a firing furnace, and is for cutting, cutting, dusting, and other processing. At this time, finishing such as spot welding and mounting of a solder terminal is also performed at the same time.

FIG. 4 shows the copper 1 constituting the metallic graphite brush 10.
2 is an explanatory view showing another example of the powder 12b having a large particle size among the powders 12; FIG. In the above embodiment, the fine powder 12a and the large-particle copper powder 12b are used. However, as the large-particle copper powder 12b (that is, instead of the large-particle-size copper powder), FIG. 4
Using the copper foil 14 as shown by the above, the same effect as when the copper powder 12b is used can be obtained. The powder 14 used in this example has a thickness of about 1 to 2 μm and a vertical and horizontal XY dimension of about 50 to 300 μm.

[0020]

As described above, the metallic graphite brush according to the present invention is characterized in that the copper powder of the metal used in the brush has a fine powder and a fine powder having a particle diameter of 20%. Since the ratio of the fine particles to the large particles is set at a ratio of 4: 6 to 6: 4 in terms of the mixing ratio of the fine particles to the large particles, the fine particles can be used as a brush. As a result, the sliding surface of the roller becomes in a rolling frictional state, and a reduction in frictional resistance and a reduction in spring constant can reduce the occurrence of steady noise and abnormal noise of self-excited vibration of the brush. At the same time, the flow of current in the brush can be improved by the large-particle powder, and the contact resistance of the brush can be reduced, and the amount of heat generated can be reduced to extend the life.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a copper particle diameter and a brush basic characteristic.

FIG. 2 is a graph showing the relationship between the mixing ratio of copper particles having different particle diameters and the brush basic characteristics.

FIG. 3 is an explanatory view showing a sliding state between a commutator and a metal graphite brush.

FIG. 4 is an explanatory diagram showing another example of a particle having a large particle diameter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Metal graphite brush 11 Graphite 12 Copper 12a Copper fine particle size powder 12b Copper large particle size powder 13 What slides with a metal graphite brush (commutator) 13a Sliding contact surface 14 Copper large particle size powder Body (copper foil)

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shoichi Yoshikawa 390 Umeda, Kosai-shi, Shizuoka Asumo Co., Ltd. (72) Inventor Takio Oya 2-27-2 Sakaiminamicho, Musashino-shi, Tokyo (56) References JP-A-62-61284 (JP, A) JP-A-50-122611 (JP, A) JP-A-58-222760 (JP, A) JP-A-3-164048 (JP, A) JP-A-1-295642 (JP, A) JP-A-5-190240 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01R 39/29 H02K 13/00 H01R 43/12

Claims (2)

(57) [Claims] 1. A metal graphite brush formed by press-molding a graphite powder and a metal powder mixed at a predetermined compounding ratio to form a predetermined shape, and then firing the metal graphite brush, A fine particle powder, and a large particle powder having a particle size of 20 to 150 times the particle size of the fine particle powder,
4: 6 to 6: in the mixing ratio of the fine particle powder and the large particle powder
Metal graphite brush with a ratio of 4. 2. The fine particle powder has an average particle diameter of about 2.
8 μm, and the large-particle powder has an average particle diameter of about 100 μm.
The metal graphite brush according to claim 1, wherein