JP4708123B2 - Brushed rotating electrical machine and method for manufacturing the same - Google Patents

Description

  The present invention relates to a rotary electric machine with a brush and a method for manufacturing the same.

  In a brushed electric motor, which is a general rotating electrical machine with a brush, a pair of brushes 2 are brought into contact with a commutator 1 and power is supplied from a DC power source 3 as shown in FIG. In such a conventional rotating electrical machine with a brush, it is generally known that the wear life of the brush 2 and the commutator 1 is extended by forming an appropriate oxide film on the surface of the commutator 1.

  However, depending on conditions such as the temperature and humidity of the surface of the commutator 1, an excessive oxide film may be formed on the surface of the commutator 1. In this case, an excessive oxide film becomes resistance, and the contact resistance between the brush 2 and the commutator 1 increases. This increase in contact resistance becomes a factor that destabilizes the contact voltage drop that occurs when a minute current flows through the brush. This unstable contact voltage drop generates an unstable rectifying spark. The rectifying spark generates brush noise.

  Recently, in a rotary electric machine with a brush, such as a motor with a brush, there is a case where a reduction in noise is strongly required depending on the use situation.

  Therefore, the present inventors examined the structure of the brush 2 in order to obtain a solution that meets this requirement. Recently, the brush 2 generally used is constituted by a sintered body obtained by stirring and sintering granulated particles of particles such as graphite and silver and a binder (for example, a phenol resin) (for example, (See Patent Document 1).

FIG. 4 is a photomicrograph showing the sintered state of the cross section of the conventional brush 2. In this photograph, the white portion is a sintered portion of a metal made of silver, the black portion is a sintered portion of graphite, and the intermediate portion of white and black is a sintered portion of a portion where a binder and graphite are mixed. Conventionally, in the case of the brush 2 used for the rotating electrical machine, the silver content is about 50% in mass ratio at most.
Japanese Patent Laid-Open No. 4-8145

  However, the noise of the motor using the conventional brush 2 having such a blending ratio and sintered structure often exceeds 50 dB (A).

  An object of the present invention is to provide a brushed rotating electrical machine that can reduce noise compared to a conventional brushed rotating electrical machine and a method for manufacturing the same.

  Since graphite is softer than silver, if the state where the brush 2 is in contact with the commutator 1 continues to some extent, the sintered portion of the graphite is worn and the sintered portion of the silver is exposed, and It is expected that the joints reduce the contact resistance by polishing the oxide film on the surface of the commutator 1. However, in a conventionally used brush, as shown in FIG. 4, the dispersion of the sintered portion of silver is not uniform and is not uniform. Also, with the silver content of the conventional brush, the polishing effect of the oxide film by the silver sintered part is low, and when the part where the dispersion ratio of the silver sintered part is low is the contact part, the silver sintered part The polishing effect of the oxide film on the surface of the commutator 1 due to can not be expected. For this reason, it is considered that there was a limit to reducing the noise of rotating electrical machines.

  Therefore, in the present invention, a brushed rotary electric machine that includes a plurality of brushes that come into contact with a commutator and is configured by a sintered body of graphite and metal particles that are granulated is improved as follows. . That is, in the rotating electrical machine with a brush of the present invention, as a plurality of brushes to be used, the metal content with respect to the weight of the brush is 70 ± 5 wt%, and the sintered portion of the metal is evenly distributed throughout the brush. Use what you have.

  When such a brush is used for all of a plurality of brushes used in a rotating electrical machine with a brush, the dispersion ratio of the sintered portion of the metal in the brush is larger than before, so the tips of all the brushes in use In addition to increasing the number of exposed metal sintered portions at the portion, the exposure ratio of the metal sintered portions at the tips of all the brushes can always be maintained in the same state. As a result, according to the present invention, more metal sintered parts than the metal sintered parts at the tip of the conventional brush bite into the oxide film on the surface of the commutator to polish the oxide film, thereby reducing the contact resistance. In addition, the generation of unstable rectifying sparks can be suppressed and the noise of the rotating electrical machine can be reduced. In particular, all the brushes used in the rotating electrical machine satisfy the above conditions, whereby the noise generated from the brushes can be minimized and minimized. When the metal content with respect to the weight of the brush exceeds 75% by weight, the surface of the commutator becomes rough and noise increases, which is not preferable. Further, when the metal content relative to the weight of the brush is less than 65% by weight, the ratio of the oxide film remaining on the surface of the commutator is increased, and noise due to commutator failure increases, which is not preferable.

  The plurality of brushes used are cut out from a sintered matrix obtained by sintering granulated graphite and metal particles. The sintered base includes a surface portion in which the sintered portion of the metal is biased toward the surface side, and a core portion in which a plurality of sintered portions made of the metal located inside the surface portion are evenly dispersed. ing. Therefore, in the present invention, a plurality of brushes used are all cut out from the core. In the core part of the sintered base, the content rate of the sintered part of the metal is generally high, and since the sintered part of the metal is evenly dispersed throughout the brush, if the brush is cut out from this core part Satisfies the conditions of the present invention. In addition, the size of the sintered part of the plurality of metals is a size that exhibits the ability to grind the oxide film of the commutator so that the average thickness of the oxide film formed on the surface of the commutator is 10 μm to 50 μm. It is preferable to have it.

  The metal is preferably gold, silver or copper in view of conductivity. Since these metals have high conductivity and are harder than graphite, they are easily exposed due to wear of the graphite, and the oxide film on the surface of the commutator can be easily polished.

  When silver is used as the metal, a brush having a high polishing ability can be obtained at a reasonable price, so that the price of the rotating electrical machine can be reduced.

  Moreover, this invention makes the object of improvement the manufacturing method of the rotary electric machine with a brush formed by forming the several brush which contacts a commutator with the sintered compact of all the granulated graphite and a metal particle.

  In the method for manufacturing a rotating electrical machine with a brush according to the present invention, a plurality of brushes are mixed with graphite and metal particles granulated at a blending ratio of 70 ± 5 wt% of metal content with respect to the weight of the brush. A step of making a mixture, a step of sintering the mixture into a predetermined shape to form a sintered base, and removing the surface portion where the sintered portion of the metal is biased to the surface side from the sintered base Further, it is characterized in that it is formed by a process of cutting out the raw material of the sintered body from the core part in which the sintered parts of the metal are uniformly distributed and a process of finishing the raw material into a predetermined shape.

  According to such a method of manufacturing a rotating electrical machine with a brush, the content of the sintered portion of the metal is high overall for all brushes, and the sintered portion of the metal is uniformly distributed throughout the brush. Can be manufactured stably and easily.

  In this case, when the metal is silver and the silver particles having an under 200 mesh (passing through a 200 mesh sieve) particle size are used, the oxide film on the surface of the commutator is polished well. Can be manufactured.

  Moreover, the silver particle can manufacture the brush which can grind | polish the oxide film on the surface of a commutator satisfactorily as the average particle diameter dimension is 50 micrometers-200 micrometers.

  In the rotating electrical machine with a brush of the present invention, all the plurality of brushes have a metal content of 70 ± 5% by weight with respect to the weight of the brush, and the sintered parts of the metal are uniformly distributed throughout the brush. The dispersion ratio of the sintered part of the metal for all brushes of the rotating electrical machine is higher than before, and the sintered part of the metal is evenly distributed throughout the brush. The number of exposed metal sintered parts increases, and these bite into the oxide film on the surface of the commutator to polish the oxide film, reduce the contact resistance, suppress the generation of unstable rectifying sparks, and reduce the noise of rotating electrical machinery. Reduction can be achieved.

  In the method of manufacturing a rotating electrical machine with a brush according to the present invention, a rotating electrical machine having a brush with a high content of the sintered portion of the metal as a whole, and the metal sintered portion distributed evenly throughout the brush, It can be manufactured stably and easily.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  First, a brushed motor which is a kind of brushed rotating electrical machine according to the present invention will be described. This motor with brushes includes a plurality of brushes 2 (in this example, a pair) in contact with the commutator 1, as shown in FIG. 3. The point that these brushes 2 are composed of a sintered body of granulated graphite and metal particles is also the same as in the past.

  The pair of brushes 2 used in the brushed motor of this example all have a metal content of 70 ± 5% by weight with respect to the weight of the brush 2, and the sintered portion of the metal is evenly distributed throughout the brush. ing. The metal is silver in this example, and the size of the sintered portion of the silver is such that the average thickness of the oxide film formed on the surface of the commutator 1 is 10 μm to 50 μm. Each has a size that demonstrates its ability to grind.

  Such a pair of brushes 2 is cut out from a sintered base formed by sintering granulated graphite and silver particles. The sintered base has a surface portion in which silver sintered portions are biased to the surface side, and a core portion in which a plurality of sintered portions made of silver located inside the surface portion are evenly dispersed. I have. Each brush 2 is cut out from the core part.

  FIG. 1 is a photomicrograph showing the sintered state of the cross section of the brush 2 cut out from the core of the sintered base used in the motor with brushes of this example. In this photograph, the white portion is a sintered portion of a metal made of silver, the black portion is a sintered portion of graphite, and the intermediate portion of white and black is a sintered portion of a portion where a binder and graphite are mixed. As is apparent from this photograph, the brush used in the present embodiment has a higher dispersion ratio of the sintered portion of silver than the conventional brush shown in FIG. Moreover, the sintered part of silver is evenly dispersed throughout the brush.

  In the motor with a brush of this example, the silver content with respect to the weight of the brush 2 is 70 ± 5% by weight, and the sintered parts of silver are uniformly distributed throughout the brush. Therefore, the dispersion ratio of the silver sintered portion is increased as compared with the conventional brush 2 for all the brushes 2 of the motor, and the silver sintered portion is uniformly distributed throughout the brush. Therefore, as schematically shown in FIG. 2, when the brush 2 is used in contact with the commutator 1, the brush 2 contacts the oxide film 1b on the surface of the commutator body 1a constituting the commutator 1. To supply power. In such a use state, the relatively soft graphite sintered portion 2a constituting the brush 2 is worn, and a plurality of relatively hard silver sintered portions 2b are exposed. Each exposed silver sintered portion 2b bites into the oxide film 1b of the commutator 1 to polish the oxide film 1b. Thereby, the contact resistance with respect to the commutator 1 of the brush 2 reduces, generation | occurrence | production of an unstable commutation spark can be suppressed, and the noise reduction of a motor with a brush can be aimed at.

  When all the brushes 2 used in the brushed motor satisfy these conditions, the brush noise generated from the brush 2 used can be minimized, and the noise of the brushed motor can be easily reduced. Can do.

  When the noise level was compared with a brushed motor using a conventional brush and a brushed motor using the brush of this example, the following results were obtained.

Silver content ratio by mass of conventional brush: 50%
Brush noise level of a DC motor using a conventional brush: 52 dB (A)
Silver content mass ratio of the brush of this example: 70%
Brush noise level of DC motor using brush of this example: 39 dB (A)
From this experiment, it was confirmed that the noise ratio can be reduced most in the vicinity of 70% mass specific silver content. When the silver content with respect to the weight of the brush 2 is more than 75% by weight, the commutator surface becomes rough and noise increases. When the silver content with respect to the weight of the brush 2 is less than 65% by weight, the commutator is reduced. It has been confirmed by tests that the rate at which an oxide film remains on the surface of 1 increases and noise due to commutator failure increases. Therefore, the numerical range described later has a critical meaning.

  Since silver has a high conductivity and is harder than graphite, it is easily exposed due to abrasion of the graphite, and the oxide film 1b on the surface of the commutator can be easily polished.

  Next, the manufacturing method of each brush 2 which is the feature point of the manufacturing method of the motor with a brush is demonstrated.

  An example of the manufacturing method of each brush 2 in this example is as follows.

  First, graphite and silver particles granulated at a blending ratio of 70 ± 5% by weight with respect to the weight of the brush 2 are mixed to make a mixture. Silver particles having an under 200 mesh size (passing through a 200 mesh screen) are used. In addition, the silver particle can manufacture the brush 2 which can grind | polish the oxide film 1b on the surface of the commutator 1 favorably that the average particle diameter dimension is 50 micrometers-200 micrometers. The granulated graphite particles are those having a particle size of under 100 to 200 mesh (passing through a 100 to 200 mesh sieve).

  Next, the mixture is sintered into a predetermined shape to produce a sintered matrix. The firing temperature when firing the sintered matrix was about 800 ° C.

  Next, the raw material of the sintered body is removed from the core portion where the silver sintered portion is dispersed evenly by removing the surface portion where the silver sintered portion is biased to the surface side from the sintered base. Cut out.

  Thereafter, the obtained raw material is finished into a predetermined brush shape to obtain the brush 2.

  In this way, all the brushes 2 are manufactured in the same manner.

  According to such a method for manufacturing a motor with a brush, the content of the silver sintered portion 2b is generally high for all the brushes 2 required by the motor (a pair in this example), and the brush 2 It is possible to stably and easily manufacture a material in which the silver sintered parts 2b are uniformly distributed.

  In the above example, an example using silver as a metal has been described. However, the present invention is not limited to this, and gold, copper, or the like can also be used. Again, the content may be the same as silver.

  Moreover, although the motor with a brush was demonstrated as a rotary electric machine with a brush, this invention is not limited to this. For example, it can be applied to a DC motor with a tachometer generator. In this case, if a plurality of brushes in each of the motor unit and the tachometer generator unit have the same performance as that of the brush 2 described above, brush noise can be greatly reduced. Product value can be improved. Of course, the present invention can also be applied to a generator.

It is a microscope picture which shows the sintering state of the cross section of the brush cut out from the core part of the sintered base in the motor with a brush of this invention. It is an expanded sectional view which shows the state which used the brush used by this invention in contact with the commutator. It is explanatory drawing which shows the state which made the brush contact the commutator with the motor with a brush. It is a microscope picture which shows the sintering state of the cross section of a brush with the conventional motor with a brush.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Commutator 1a Commutator body 1b Oxide film 2 Brush 2a Sintered part of graphite 2b Sintered part of silver 3 DC power supply

Claims (6)

A rotating electrical machine with a brush comprising a plurality of brushes in contact with a commutator, wherein the plurality of brushes are constituted by a sintered body of granulated graphite and metal particles,
In the plurality of brushes, the content of the metal with respect to the weight of the brush is 70 ± 5 wt%, and the sintered portion of the metal is uniformly distributed throughout the brush ,
The plurality of brushes are cut out from a sintered base formed by sintering the granulated graphite and the metal particles,
The sintered base has a core in which a sintered portion of the metal is present on the surface side and a plurality of sintered portions made of the metal located inside the surface portion are evenly dispersed. Department and
The plurality of brushes are all cut from the core portion, and the rotary electric machine with brushes is characterized in that: The rotating electrical machine with a brush according to claim 1 , wherein the metal is gold, silver, or copper. The metal is silver;
The plurality of sintered portions of the silver each have a size that exhibits an ability to grind the oxide film such that an average thickness of the oxide film formed on the surface of the commutator is 10 μm to 50 μm. The brushed rotary electric machine according to claim 1. A method of manufacturing a rotating electrical machine with a brush, wherein a plurality of brushes in contact with a commutator are formed by a sintered body of all granulated graphite and metal particles,
A step of mixing the plurality of brushes with the granulated graphite and the metal particles at a blending ratio of 70 ± 5% by weight of the metal with respect to the weight of the brush; and Sintering the mixture into a predetermined shape to form a sintered base, and removing the surface portion where the sintered portion of the metal is biased to the surface side is removed from the sintered base. A method of manufacturing a rotating electrical machine with a brush characterized by forming all of a process of cutting out the raw material of the sintered body from a core part in which the knots are uniformly distributed and a process of finishing the raw material into a predetermined shape. The metal is silver;
The method for manufacturing a rotating electrical machine with a brush according to claim 4 , wherein the silver particles have an under 200 mesh particle size. The method for manufacturing a rotating electrical machine with a brush according to claim 5 , wherein the silver particles have an average particle size of 50 μm to 200 μm.