JPH02106150A - Brush device for electrical rotary machine - Google Patents

Abstract

PURPOSE:To form oxidation film uniformly on positive and negative pole brushes by employing different type of metal brushes so that the resistivity of the positive pole brush will be higher than that of the negative pole brush. CONSTITUTION:Positive and negative pole brushes are made of different material such that the content of copper in the positive brush 12 will be lower than that in the negative pole brush 13 and the resistivity of the positive pole brush will be higher than that of the negative pole brush. Furthermore, the positive pole brush is prepared by baking a metal graphite brush with the temperature prevailing before annealing of copper while the negative pole brush is prepared through low pressure molding with coarse graphite treating viscosity. By such arrangement, oxidation film is formed uniformly on the sliding face of commutator brush at the positive and negative pole sides, and thereby commutation noise is reduced and the service life of brush is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a brush device for a rotating electrical machine, and particularly to a brush device for a rotating electrical machine suitable for a blower motor of an automobile air conditioner.

[Conventional technology]

Regarding metal graphite brushes used in conventional small electric motors, as described in Japanese Patent Publication No. 58-18978, metal graphite brushes with compositions that meet the requirements for wear resistance, impact resistance, corrosion resistance, low electrical loss, etc. It is mentioned that a brush is used. The above-mentioned Japanese Patent Publication No. 58-18978 specifically describes the materials and components of the metal graphite brush, the weight percentages of the materials and components, and the method for molding the materials.

On the other hand, as methods for improving the noise level of brush devices, Japanese Patent Application Laid-Open No. 57-65250 and Japanese Patent Application Laid-Open No. 62-23034
No. 0 is known.

Normally, in an electric motor, current flows from the positive brush to the commutator, passes through the rotating armature winding, and from the commutator to the negative brush. Looking at this from the perspective of electron movement, the flow is completely opposite to the above direction. In other words, electrons move from the negative brush to the commutator, pass through the rotating armature winding, and move from the commutator to the positive brush.

The electrical polarity of the brush is closely related to boundary layer formation.

Oxidation is prevented under the positive electrode brush, but the polarity of the brush material is such that it accumulates, and under the negative electrode brush, the potential gradient of the conductive point is in the direction of drawing out metal ions, and oxidation of copper is likely to be accelerated. It is polar, including the graphite layer, which is removed by brush friction. In other words, the film under the positive electrode brush is mainly characterized by the accumulation of black T (1F!), and the copper oxide layer underneath is in a protected state even if the formation rate is low, and the ring surface under the negative brush is oxidized. The oxide layer is removed because the equilibrium between the formation and removal of the graphite layer is such that the latter prevails.

That is, the positive electrode brush is more likely to form an oxide film, and the negative electrode brush is less likely to have an oxide film than the positive electrode brush, resulting in an imbalance between the positive and negative electrode brushes. When an oxide film is formed in an unbalanced manner, current concentrates in thin parts of the film, increasing local current.An oxide film is similar in nature to an insulator, but because it is extremely thin, it can cause dielectric breakdown when applied with voltage. Therefore, even if a uniform film is initially formed, if the current distribution becomes non-uniform due to unstable brush sliding characteristics or other causes, the film will be locally destroyed and become non-uniform.

[Problem to be solved by the invention]

Since the above-mentioned conventional technology does not take into account the properties of the brush device, there is a problem that the oxide film formed on the brush sliding surface of the commutator is locally destroyed, and the noise and lifespan have not been improved.

One of the objects of the present invention is to provide a brush device for a rotating electrical machine that is suitable for reducing noise and has a long life.

An object of the present invention is to provide a brush device for a rotating electric machine in which the oxide film on the rectifying surface can be adjusted by varying the resistivity of the positive and negative brushes.

One of the objects of the present invention is to provide a method for molding a brush that can easily satisfy required characteristics.

[Means to solve the problem]

One of the above objects is achieved by constructing the positive and negative brushes from different materials, and by increasing the volume of the positive brush to the negative brush.

One of the above objects is achieved by making the resistivity of the positive brush greater than that of the negative brush.

One of the above objects is achieved by firing the positive electrode brush at a temperature before copper annealing and softening the metal graphite brush, and by treating the negative electrode brush to roughen the graphite viscosity and forming it by low pressure molding.

[Effect]

The metal brushes are made of different materials such that the resistivity of the positive electrode brush is greater than the resistivity of the negative electrode brush. As a result, the oxide film on the positive electrode brush is less likely to be formed than on the negative electrode brush and is made uniform, so that the oxide film is not locally destroyed and the sliding characteristics of the brush are stabilized.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Figure 1 shows an automobile blower device using the brush device of the present invention, in which a mounting plate 1 is fixed on the outer periphery, a field magnetic pole 2 is fixed on the inner periphery, and a front cover 3 and a rear cover 4 are fixed on the sides. This forms the stator 5.

On the other hand, the rotor 6 includes a rotating shaft 7 that passes through the front cover 3 and is rotatably supported by the rear cover 4, and a rotating shaft 7 that passes through the front cover 3 and is rotatably supported by the rear cover 4.
an armature core 8 fixed to and provided with a winding; and the rotating shaft 7.
The commutator 9 is fixed to the winding and connected to the winding.

10 is a sirocco fan made of synthetic resin, and the central boss portion 10A is fixed to the rotating shaft 7 (11). 11 is a brush device equipped with a positive electrode brush 12 and a negative electrode brush 13, details of which are shown in FIG. As shown, each brush has a base of 14
Reference numeral 617, which is slidably held by brush holders 15 and 16 fixed at target positions, is a power supply connector for the brushes.

Table 1 shows an example of the materials, components, and physical properties of the positive electrode brush 10 and negative electrode brush 11. The components of the positive electrode brush are a mixture of 34% by weight of copper (Cu), 63% by weight of graphite (C), and 3% by weight of other components. The components of the negative electrode brush are 40% by weight of copper (Cu) and graphite Jl (C).
A brush was made using a mixture containing 59% by weight of the following ingredients and 1% by weight of other components. The physical property values obtained with the above brush are as follows. First, the apparent density of the positive electrode brush is 2.52~
2.60 (g/aI?) + hardness is 11-16 (Hs)
, resistivity is 370-460 (μΩ・traction), bending strength is 115-140 (kg/1-n), elastic modulus is 112
0 to 1290 (kg/m112). On the other hand, the physical properties of the negative electrode brush have an apparent density of 2.57 to 2.63 (g/
cXj), hardness 16-20 (Hs), resistivity 40
5 to 525 (μΩ・■) 1 bending strength is 130 to 150 (
kg/a+f), the elastic modulus is 1300 (kg/mn
Use a brush rated +2).

Table 1 Table 2 A manufacturing method for forming the above brush will be described.

The negative electrode brush is based on the current brush (lower row of Table 1).
The viscosity of the treated graphite was made coarser, and the elastic modulus was further suppressed by low-pressure molding. In addition, the positive electrode brush was baked at a temperature (300° C.) before the copper was annealed and softened, thereby suppressing a decrease in hardness. As is widely known in the Cu softening curve with respect to the normal annealing temperature, copper suddenly softens at around 300°C.

Therefore, the positive electrode brush was molded at 300° C. to suppress the decrease in the hardness of copper and to have a hardness of 16 to 20 Hs.

The operating principle of a small electric motor equipped with both positive and negative brushes will now be explained.

First, the relationship between commutator surface roughness and noise will be explained with reference to FIG. This experiment was the result of intentionally changing the surface roughness of the commutator and measuring the noise of a single unit using a slip ring. According to this data, the noise changes as the tel of the commutator changes. On the contrary, always
If the surface roughness of the commutator is kept at 6 μm, the noise will always be
It is possible to maintain it at a low value. This is one of the major reasons for using positive and negative brushes with different resistivities, which will be explained later.
It is one.

On the other hand, there are generally minute pits on the commutator and brush sliding surfaces, an oxide film and graphite fine powder layer on the commutator 4 surface, and water around the graphite and oxide film deposited on the brush surface due to wear. It is adsorbed and forms a water film, providing lubricity. After cutting a piece of copper, it becomes thin C11 after a few seconds.
It is said that a film of No. 20 is formed, which turns into brown CuzO after a few hours, and then becomes black (CaO) as oxidation progresses further. The commutator surface film differs depending on the current direction, and is thicker for positive brushes (current direction is brush → commutator) and thinner for negative brushes (current direction is commutator → brush). Due to this imbalance phenomenon,
Non-uniformity of the film occurs, which causes current to concentrate in thinner parts of the film, increasing local current and causing dielectric breakdown of the film.

Therefore, the surface roughness of the commutator surface can change, and the noise is not constant due to the relationship between surface roughness and noise. In other words, the noise will increase.

A film tends to form on the positive electrode of the brush described above, and a film does not easily form on the negative electrode. In order to solve this problem, it was unsuccessful to use brushes made of different materials for the positive electrode brush and the negative electrode brush described above. This principle takes advantage of the fact that a film is easier to form when the amount of copper in a metal-graphite brush is reduced and the amount of graphite is increased.
5% by weight, and the negative electrode has a copper content of 30% to 40% by weight.
Uses unsold metal graphite. As described above, this example is an example in which the positive electrode brush has a copper content of 34% by weight, and the negative electrode brush has a copper content of 40% by weight.

Here, the reason why the copper amount is specified in the range of 30% by weight to 55% by weight will be explained.

When the amount of copper increases, the bonding strength of the structure weakens, resulting in poor wear resistance and shortened life. On the other hand, if the amount of copper is too small, the wear resistance will be excellent, but the noise performance will be poor. For the above reasons, the appropriate amount of copper was determined from the sample product.
The weight percentage was reduced to 55% by weight.

Next, a method for manufacturing and molding the metal graphite brush used in the small electric motor of this embodiment will be described.

As mentioned above, the positive electrode brush was fired at a temperature before Cu softening to suppress the decrease in hardness (16 to 20 Hs).
. That is, the weight percent of Cu is increased and the amount of graphite is decreased to prevent a decrease in hardness.

The negative electrode brush has more graphite and coarser treated graphite viscosity.
Furthermore, the elastic modulus is suppressed by low pressure molding (1120 ~
1290 kg/m+"). The reason for suppressing this elastic modulus is to obtain stable sliding characteristics and to improve rectification performance, etc.

The mainstream hardness of commutators currently used is 25 to 30°.
Hs, and since the brush on the positive electrode side wears out faster, the brush hardness on the positive electrode side may be made higher.

For this purpose, it is necessary to consider the annealing temperature of Cu.

Graphite is a semimetal, and considering the brush as a metal composite, it is important to maintain the initial state of the brush by having a soft, lubricating thin metal film between the metals of the same hardness. Based on this, by firing at a Cu annealing temperature of around 300°C, it becomes possible to bring the hardness close to that of a commutator.

On the other hand, the negative electrode side brush has a low specific gravity by roughening the graphite viscosity and is easy to mold under low pressure, thereby suppressing the elastic modulus.

The measurement results of the noise frequency characteristics (noise frequency of 3 (Oct)) in the actual machine of 6 small electric motors using the above positive electrode brush and negative electrode brush are shown.

The measurement method is to drive a small electric motor with a power supply and set the rotation speed to 15.
Set it to 0Orpm, and set it to 100 rpm from the rear end of the small electric motor.
A microphone was set at a distance of mm1l, and the noise frequency was analyzed and measured. The results are shown in FIG. (A)
The curve shows the case where conventional materials are used for the positive and negative electrodes, (B
) The curve is a noise frequency analysis when different materials are used for the positive and negative brushes.

From this frequency analysis, IK (Hz) to 16K [Hz
] The effect is noticeable.

Comparing the product of the present invention with the conventional product, the noise of the product of the present invention was 4 (dB) lower in overall value (0 A). It can be seen that noise reduction in the vicinity of Hz is expected.

Although the above embodiment describes a brush device of a direct current machine of an automobile blower device, the same can be said of a current collecting ring device of an automobile alternating current generator, etc., and by adopting the present invention, It can contribute to noise reduction.

〔Effect of the invention〕

According to the present invention, the positive and negative electrode brushes are made of metal graphite brushes made of different materials, and the oxide film formed on the brush sliding surface of the commutator can be made uniform on the positive and negative electrode sides.
It has the effect of reducing noise during rectification and extending the life of the brush.

[Brief explanation of the drawing]

The drawings show an embodiment of the brush device for a rotating electrical machine according to the present invention, and FIG. 1 is a half-longitudinal sectional view of a blower device for an automobile, FIG. 2 is an enlarged perspective view of the brush 'A'ft in FIG. 1, and FIG. Figure 3 is a characteristic diagram showing the relationship between rectifying surface roughness and noise, Figure 4 is a characteristic diagram showing the relationship between noise and brush wear amount with respect to the amount of brush copper, and Figure 5 is a characteristic diagram showing the relationship between noise and brush wear amount.
The figure is a comparison diagram of noise frequencies between the present invention and a conventional example. 511. Stator, 6... Rotor, 9... Commutator, 1
1... Brush device, 12... Positive electrode brush, 13...
negative electrode brush. ] Nmita Tsuki Rōmen Shou l 2 (μ weight) = 4! A blending amount (y,)

Claims (1)

[Claims] 1. A commutator connected to one end of a rotating armature winding or a rotating field winding and fixedly disposed on a rotating shaft, and a positive electrode in sliding contact with the commutator. In a brush device for a rotating electric machine including a negative electrode brush, the positive electrode and the negative electrode of the brush are
A brush device for a rotating electric machine characterized by being made of different materials. 2. The brush device for a rotating electric machine according to claim 1, wherein each of the brushes is made of metal graphite, and the positive electrode side brush contains a larger amount of copper than the negative electrode side brush. 3. In claim 2, the amount of copper in the positive electrode brush is from 40 to 5.
A brush device for a rotating electric machine, characterized in that the amount of copper in the negative electrode brush is in the range of 30 to 40% by weight. 4. In claim 1, the positive electrode brush has a copper content of 40 to 5.
A brush device for a rotating electric machine, characterized in that it is a metal graphite brush containing 0% by weight. 5. A commutator connected to one end of a rotating armature winding or a rotating field winding and fixedly disposed on a rotating shaft, and positive and negative brushes in sliding contact with the commutator. 1. A brush device for a rotating electrical machine, characterized in that the positive electrode brush is a metal graphite brush whose hardness is higher than that of the negative electrode brush. 6. In claim 5, the positive electrode brush has a hardness of 16 to 20.
HS, the elastic modulus is 1300 kg/mm^2 or more, and the negative electrode brush has a hardness of 11 to 16 HS and an elastic modulus of 1120 to 12.
A brush device for a rotating electric machine characterized by having a brushing capacity of 90 kg/mm or more. 7. A commutator connected to one end of a rotating armature winding or a rotating field winding and fixedly disposed on a rotating shaft, and positive and negative brushes in sliding contact with the commutator. A brush device for a rotating electrical machine, wherein the positive electrode brush has a resistance value set to be larger than at least the negative electrode brush. 8. In claim 7, each of the brushes is made of a metal graphite brush, and the positive electrode brush has a resistivity of 405 to 525;
A brush device for a rotating electric machine, characterized in that the negative electrode brush has a resistance in the range of 370 to 460 μΩ-cm. 9. A commutator connected to one end of a rotating armature winding or a rotating field winding and fixedly disposed on a rotating shaft, and positive and negative brushes in sliding contact with the commutator. A brush device for a rotating electrical machine, characterized in that the resistivity of the positive electrode and negative electrode brushes is varied to adjust an oxide film formed on a commutating surface of a commutator. 10. In the brush forming method, the brush is fired at a temperature (about 300 ° C.) before copper annealing and softening of the metal graphite brush,
Hardness 16-20HS, elastic modulus 1300kg/mm^
A brush forming method characterized by obtaining two or more positive electrode brushes. 11. In the brush molding method, the treated graphite viscosity of the metal graphite brush is made rough, and the hardness is made 11~11 by low pressure molding.
16HS, elastic modulus 1120-1290kg/mm^2
A brush forming method characterized by obtaining a negative electrode brush.