JP2002369457A - Brush device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brush device which can suppress loosening of a brush in a brush holder, in the rotating direction of a commutator. SOLUTION: This brush device 4 has brushes 6, which are housed and held in brush holders 5 extending in a direction perpendicular to an axis of a commutator 3 with gaps, so as to have their tips pressed against the commutator 3. The rear end parts of the brushes 6 are pressed against sidewalls 5b of the brush holders 5 in the rotating direction of the commutator 3 by the slopes 6a of the brushes 6 and coil springs 7. The tip end parts of the brushes 6 are pressed against the sidewalls 5b in the rotating direction of the commutator 3 by pressing parts 8a of pressing springs 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brush device for bringing a brush into contact with a commutator of a motor.

[0002]

2. Description of the Related Art Conventionally, a DC motor is provided with a pair of brush devices as shown in FIG. In this brush device, a brush 53 is housed and held in a brush holder 52 extending in a direction perpendicular to the axis of a commutator 51 provided on an armature (rotor) (not shown), and a rear end of the brush 53 is attached by a coil spring 54. The leading end of the brush 53 is pressed against the commutator 51 by being urged.

In the brush device configured as described above, when the rotor rotates, the brush 53 comes into sliding contact with the commutator 51, so that an external driving current is applied to the rotor by the brush 53.
And supplied through a commutator 51.

In the above-described brush device, the inside (inside surface) of the brush holder 52 is a brush 53.
The brush 5 in a cooled state (normal temperature) in consideration of the thermal expansion of the brush 5
3 is set so as to have a gap when it is stored. Therefore, when the rotor is rotated for a long time, the brush 53
The brush holder 52 becomes a brush 53
Is prevented from moving in the front-rear direction.

[0005]

However, in such a brush device as described above, for example, when the rotor (commutator 51) starts rotating (at the time of starting), the brush 5 is moved.
Due to the frictional force between the commutator 51 and the commutator 51, the front end and the rear end may rattle in the rotation direction of the commutator 51. In this case, one end of the end of the brush 53 in the rotation direction of the commutator 51 is connected to the commutator 51.
Is separated (gets up) from the brush 5
3 and the contact area between the commutator 51 and the commutator 51 become small. Then, the drive current does not flow normally from the brush 53 to the commutator 51. Therefore, in the above-described motor, there is a possibility that desired rotation characteristics cannot be obtained, especially at the time of starting. For example, when a driving current is supplied to the rotor, the rotor is in a stopped state while generating a predetermined torque, and when the rotor starts rotating by satisfying some condition, the predetermined torque is temporarily reduced. There is a problem that it is reduced.

In some brush holders, the back end of the brush is pressed against the rotating side wall of the commutator in the brush holder to reduce the rattling of the brush in the rotating direction. The rattling causes a problem similar to that of the brush device.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a brush device capable of suppressing the rattle of the brush holder against the brush holder in the rotation direction of the commutator. Is to do.

[0008]

According to a first aspect of the present invention, a brush is accommodated and held in a brush holder extending in a direction perpendicular to the axis of a commutator with a gap therebetween, and a tip of the brush is attached to the commutator. In a brush device that is pressed and contacted, a first pressing unit that presses a rear end side of the brush against a rotation side wall of the commutator of the brush holder, and a second pressing unit that presses a front end side of the brush against the rotation side wall. 2 pressing means.

According to a second aspect of the present invention, in the brush device according to the first aspect, the first pressing means urges a rear end of the brush toward the commutator to move a tip end of the brush. It also serves as a commutator direction urging means for pressing the commutator.

According to a third aspect of the present invention, in the brush device according to the second aspect, the first pressing means is formed at a rear end of the brush and has an inclined surface inclined in a rotation direction of the commutator. And a biasing means for abutting against the inclined surface from behind the brush and biasing the brush toward the commutator.

[0011] The invention according to claim 4 is the invention according to claims 1 to 3.
In the brush device according to any one of the above, the second
The pressing means is a pressing piece provided at an end of the brush holder on the commutator side.

According to a fifth aspect of the present invention, in the brush device according to the fourth aspect, the pressing piece is formed integrally with the brush holder. The invention according to claim 6 is the brush device according to claim 4 or 5, wherein the pressing piece is
A pressing portion that is directed in the direction of rotation of the commutator toward the commutator side and has a leading end portion pressing the leading end side of the brush, and a guide that is further away from the brush as the tip portion of the pressing portion further moves toward the commutator side. Unit.

[0013] The invention according to claim 7 is the invention according to claims 1 to 6.
In the brush device according to any one of the above, the second
The pressing load A of the pressing means is F, the frictional load between the brush and the commutator and the frictional coefficient between the brush and the rotation side wall are μ, and the frictional coefficient between the brush and the commutator is μ. Assuming that the minimum required load on the connec- tion-side load is B, (FB) / μ> A
> ΜF.

(Operation) According to the first aspect of the present invention,
The rear end of the brush is pressed by the first pressing means against the rotating side wall of the commutator of the brush holder, and the tip end is pressed by the second pressing means against the rotating side wall of the commutator of the brush holder. Therefore, for example, when the commutator starts rotating, it is possible to prevent the leading end and the rear end of the brush from rattling in the rotating direction of the commutator.

According to the second aspect of the present invention, the first pressing means urges the rear end of the brush toward the commutator and presses the tip of the brush against the commutator in the commutator direction. Since it also serves as a means, the number of parts can be reduced.

According to the third aspect of the present invention, the first pressing means is formed at the rear end of the brush, and has a slope inclined in the rotation direction of the commutator, and the slope from behind the brush. And a biasing means for abutting against the commutator and biasing toward the commutator side. With this configuration, it is possible to press the tip of the brush against the commutator with a simple configuration while pressing the rear end side of the brush against the rotation direction side wall of the brush holder.

According to the fourth aspect of the present invention, since the second pressing means is a pressing piece provided at the end of the brush holder on the commutator side, the tip of the brush can be rotated with a simple configuration. It can be pressed against the direction side wall.

According to the fifth aspect of the present invention, since the pressing piece is formed integrally with the brush holder, the number of components is not increased by the second pressing means. According to the invention as set forth in claim 6, the pressing piece is directed in the rotation direction of the commutator toward the commutator side, and the tip portion presses the tip side of the brush, and the tip of the pressing portion. And a guide part which is further away from the brush toward the commutator side from the part. Therefore, the tip side of the brush is pressed against the rotation side wall by the pressing portion of the pressing piece. When the brush is inserted into the brush holder from the commutator side when the brush is assembled, the brush is guided by the guide portion. Therefore, with a simple configuration, the tip side of the brush can be pressed against the side wall in the rotation direction, and the brush can be easily assembled.

According to the seventh aspect of the present invention, the pressing load A of the second pressing means is F, the load on the contiguous side for pressing the brush toward the commutator, the coefficient of friction between the brush and the commutator, and (F−B) / μ>A> μ, where μ is the friction coefficient between the brush and the rotation direction side wall, and B is the minimum load that is the minimum required load on the cement side.
F is set. By doing so, the rattle of the brush tip in the rotating direction of the commutator is suppressed, and the pressing load A of the second pressing means can be easily determined so that the brush is preferably pressed against the commutator. it can.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment in which the present invention is embodied in a DC motor will be described below with reference to FIGS.

As shown in FIG. 1, a DC motor 1 is provided with a rotating shaft 2, a substantially columnar commutator 3 fixed to the rotating shaft 2, and a vicinity of the commutator 3. And a pair of brush devices 4. Each brush device 4 includes a brush holder 5, a brush 6, and a coil spring 7 as urging means.

The brush holder 5 is made of a resin material and is fixed to a motor case (not shown). The brush holder 5 has a brush 6 and a coil spring 7 inside.
Is formed so as to extend in the radial direction of the commutator 3 so as to accommodate and hold the same. More specifically, the brush holder 5 extends in the radial direction of the commutator 3 and has a pair of rotating side walls 5a, 5b arranged in parallel on the rotating direction side of the commutator 3 and a rear end side of the pair of rotating side walls 5a, 5b. (Radially outward of the commutator 3), and upper and lower parts formed to cover the upper and lower ends of the rotation direction side walls 5a, 5b and the rear end wall 5c. Have been. Here, the distance between the pair of rotation side walls 5a and 5b is set to a distance between the brush 6 when the brush 6 in a cooled state (normal temperature) is housed in consideration of the thermal expansion of the brush 6 to be housed. Is set to have a gap. In FIG. 1, the gap is schematically shown in an exaggerated manner. or,
One end of a pigtail (not shown) is embedded in the brush 6, and the pigtail is connected to a controller (power supply) (not shown) outside the DC motor 1.

As shown in FIG. 1 and FIG. 2, the diameter of the commutator 3 is set on the tip side (radially inside of the commutator 3) of one (clockwise in FIG. 1) rotation side wall 5a. A notch 5d extending outward in the direction is formed. Then, the notch 5 of the rotation side wall 5a is formed.
Tip part where d is formed (commutator 3 side end part)
, A pressing piece 8 as a second pressing means is fixed. This pressing piece 8 is made of an elastic metal plate material,
It is formed by bending a metal plate material. This pressing piece 8
The pressing portion 8a is directed toward the forward rotation direction of the commutator 3 (the counterclockwise direction in FIG. 1 and the direction of the other rotation side wall 5b) toward the commutator 3, and the tip of the pressing portion 8a. And a guide portion 8b that moves in the reverse rotation direction (clockwise direction in FIG. 1) of the commutator 3 further toward the commutator 3 side.

The coil spring 7 is housed in the brush holder 5 so as to be supported by the rear end wall 5c, and the brush 6 is housed and held in contact with the coil spring 7. Specifically, an inclined surface 6 a inclined in the rotation direction of the commutator 3 is formed at the rear end of the brush 6. The inclined surface 6a is formed so as to be more toward the rear end side of the brush holder 5 as it goes in the forward rotation direction of the commutator 3 (in the counterclockwise direction in FIG. 1 and in the direction of the other rotation side wall 5b). Have been. In this embodiment, the inclined surface 6a and the coil spring 7 are the first type.
The pressing means and the commutator-direction biasing means are included. The brush 6 has an inclined surface 6a at its rear end.
Abuts against the coil spring 7, the leading end contacts the commutator 3, and the leading end of the one side surface 6 b contacts the leading end of the pressing portion 8 a of the pressing piece 8.
a) It is inserted and arranged in the brush holder 5 from the side. At this time, the dimensions of each member are set such that the coil spring 7 is compressed in the radial direction of the commutator 3 and the pressing piece 8 is bent (the pressing portion 8a is bent clockwise in FIG. 1). Is set. Therefore, the rear end of the brush 6 has the inclined surface 6 a and the coil spring 7.
As a result, while being pressed against the other side wall 5b in the rotation direction, the tip portion is urged toward the commutator 3 and the leading end thereof is pressed against the commutator 3. The brush 6 has its tip end pressed by the pressing portion 8a of the pressing piece 8 against the other rotation direction side wall 5b. In addition, a pair of brush devices 4
Are arranged such that the brushes 6 face each other (at an interval of 180 degrees) in a state where the brushes 6 are both pressed against the other rotation side wall 5b.

Here, a method of determining the pressing load A which is the pressing force of the pressing piece 8 (the pressing portion 8a) of the present embodiment will be described below. Assuming that the load at the side of pressing the brush 6 toward the commutator 3 is F and the coefficient of friction between the brush 6 and the commutator 3 is μ, the tip of the brush 6 is prevented from rotating with the commutator 3 when rotating. A), it is necessary that A> μF. That is, in FIG. 3, it is necessary that A is above (left side) the μF.

Further, if the friction coefficient between the brush 6 and the rotation side wall 5b is μ, and the minimum load which is the minimum necessary condensate side load for pressing the brush 6 against the commutator 3 is B, F−μA> B That is, A <(FB) / μ. That is, in FIG. 3, A = (FB) / μ
Must be lower (right side).

For the above reason, the range (indicated by a range S in FIG. 3) of the pressing load A of the pressing piece 8 (the pressing portion 8a) is determined so as to satisfy (FB) / μ>A> μF. Have been.

In the present embodiment, the load on the side of pressing the brush 6 toward the commutator 3 is F, and the brush 6
And the commutator 3 and the friction coefficient between the brush 6 and the rotation side wall 5b are both 0.2, and the minimum load, which is the minimum necessary commissible load, is 1 [N], and the pressing piece 8 (pressing The range (indicated by a range S in FIG. 3) of the pressing load A of the portion 8a) is determined so as to satisfy 5 (F-1)>A> 0.2F.

In the DC motor 1 (brush device 4) configured as described above, since the brush 6 is in sliding contact with the commutator 3, the brush 6 and the commutator 3 are controlled by the control device (power supply device) even when the rotor rotates. , A drive current is supplied to a rotor, specifically a winding wound around an armature core (not shown).

The space between the pair of rotation side walls 5a and 5b of the brush holder 5 is set so as to have a gap between the brush 6 and the brush 6 when the brush 6 is cooled (normal temperature). This prevents the brush holder 5 from hindering the movement of the brush 6 in the front-rear direction even when the brush 6 becomes hot and expands, such as when the rotor rotates for a long time.

Next, the characteristic operation and effect of the above embodiment will be described below. (1) The rear end of the brush 6 is pressed against the other rotation side wall 5b by the inclined surface 6a and the coil spring 7, and the front end of the brush 6 is pressed by the pressing portion 8a of the pressing piece 8.
It is pressed against the other side wall 5b in the rotation direction. Therefore, for example, when the commutator 3 starts rotating (at startup)
For example, it is possible to prevent the front end and the rear end of the brush 6 from rattling in the rotation direction of the commutator 3. As a result, the contact area between the tip of the brush 6 and the commutator 3 is always maintained, and the supply of the drive current to the rotor, specifically, the winding wound around the armature core (not shown) is maintained. As a result, this DC motor 1 can obtain desired rotational characteristics, especially at the time of startup. For example, when a driving current is supplied to the rotor and the rotor is in a stopped state while generating a predetermined torque, and when the rotor starts rotating when some condition is satisfied, the predetermined torque Is maintained.

(2) The inclined surface 6a of the brush 6 and the coil spring 7 press the rear end of the brush 6 against the other side wall 5b in the rotation direction (first pressing unit), and the tip of the brush 6 Is also used as a commutator direction urging means that presses against the commutator 3. By doing so, the tip of the brush 6 can be pressed against the commutator 3 while pressing the rear end of the brush 6 against the rotation side wall 5b of the brush holder 5 with a simple configuration with a small number of parts. .

(3) Rotational side wall 5 of brush holder 5
Since the pressing piece 8 for pressing the tip side of the brush 6 against the other side wall 5b in the rotation direction is provided at the tip end of the portion where the notch 5d of a is formed, the tip end of the brush 6 can be formed with a simple configuration. It can be pressed against the rotation side wall 5b.

(4) As the pressing piece 8 moves toward the commutator 3, the pressing portion 8a moves in the forward rotation direction of the commutator 3 (the counterclockwise direction in FIG. 1 and the direction of the other rotation side wall 5b). And a guide portion 8b that moves in the reverse rotation direction (clockwise direction in FIG. 1) of the commutator 3 as it goes further toward the commutator 3 from the tip of the pressing portion 8a. Therefore, the tip side of the brush 6 is pressed against the rotation side wall 5 b by the pressing portion 8 a of the pressing piece 8. And
When the brush 6 is inserted into the brush holder 5 from the commutator 3 side when the brush 6 is assembled, the brush 6 is guided by the guide portion 8b. In other words, when inserting the brush 6 into the brush holder 5, it is not necessary to bend the pressing piece 8 by other means to widen the opening of the brush holder 5. Therefore, with a simple configuration, the brush 6
Can be pressed against the rotation side wall 5b, and the brush 6 can be easily assembled.

(5) The holding load A of the pressing piece 8 (the pressing portion 8a) is F, the frictional force between the brush 6 and the commutator 3 and the rotational direction of the brush 6 and the commutator 3 that press the brush 6 toward the commutator 3. Assuming that the coefficient of friction with the side wall 5b is μ, and the minimum load that is the minimum necessary condensate side load for pressing the brush 6 against the commutator 3 is B, (F−
B) / μ>A> μF is determined. In this way, the tip end of the brush 6 is prevented from rattling in the rotation direction of the commutator 3 and the pressing load of the pressing piece 8 (pressing portion 8a) is set so that the brush 6 can be satisfactorily pressed into contact with the commutator 3. A can be easily determined.

The above embodiment may be modified as follows. In the above embodiment, the inclined surface 6a of the brush 6 and the coil spring 7 press the rear end side of the brush 6 against the other rotation side wall 5b (first pressing unit), and the tip of the brush 6 Although the commutator direction biasing means configured to press the portion against the commutator 3 is configured, if the rear end side of the brush 6 can be pressed against the other rotation side wall 5b, and if the tip end of the brush 6 can be pressed against the commutator 3, You may change to another structure. Further, the first pressing means and the commutator direction biasing means may be independent means. For example, the rear end of the brush is a flat surface that is not inclined,
The flat surface is urged by a coil spring to press the leading end of the brush against the commutator 3, and a pressing member is provided on one side surface of the rear end side of the brush to press the one side wall 5a in the rotation direction. May be changed so as to be pressed against the other rotation side wall 5b. Even in this case, the contact area between the tip of the brush and the commutator is always maintained, and the supply of the drive current to the rotor, specifically the winding wound around the armature core (not shown) is maintained.

In the above embodiment, the pressing piece 8 is formed by bending a metal plate material. However, the condition of the pressing load A of the pressing piece 8 (the pressing portion 8a) ((FB) /
The shape may be appropriately changed to satisfy μ>A> μF). For example, when the holding load A is smaller than in the above embodiment, the pressing piece 21 is changed to the pressing piece 21 shown in FIG. The pressing piece 21 has a guide portion 21b and a pressing portion 21a.
Two slits 21c extending up to the end are formed. Thus, the condition of the holding load A ((FB) / μ>A> μ)
Even if the pressing piece is changed to satisfy F), the same effect as that of the above embodiment can be obtained. Pressing piece 2
In FIG. 1, the slit 21c extending from the guide portion 21b to the pressing portion 21a is formed so that the pressing load A is smaller than that in the above-described embodiment, so that the range in which the pressing portion 21a presses the brush 6 (in the axial direction of the commutator 3). range)
And the brush 6 can be pressed in a well-balanced manner.

In the above-described embodiment, the tip end of the brush 6 is pressed against the other side wall 5b in the direction of rotation of the brush holder 5 where the cutout 5d is formed in the side wall 5a in the direction of rotation. The pressing piece 8 made of a metal plate is fixed, but another configuration may be used as long as the tip end of the brush 6 can be pressed against the other rotation direction side wall 5b.

For example, the pressing piece 8 (second pressing means) may be changed to a pressing piece 31c shown in FIG. A brush 6 is provided on one rotation side wall 31a of the brush holder 31.
A pressing piece 31c for pressing the front end side of the base against the other rotation side wall 31b is integrally formed. This pressing piece 31c is
A pressing portion 31d that moves in the forward rotation direction of the commutator 3 (the counterclockwise direction in FIG. 5 and the direction of the other rotation side wall 31b) toward the commutator 3, and further from the tip of the pressing portion 31d. A guide portion 31e is provided in the direction of reverse rotation of the commutator 3 (clockwise direction in FIG. 1) toward the commutator 3 side. Even in this case, the same effect as that of the above embodiment can be obtained. Moreover, since the pressing piece 31c is integrally formed with the brush holder 31, the number of components is reduced and the number of assembling steps is reduced.

For example, the configuration may be such that the guide portion 8b of the pressing piece 8 is deleted. Even in this case, effects similar to the effects (1) to (3) and (5) of the above embodiment can be obtained. Further, in this case, the tip of the pressing portion 8a of the pressing piece 8 can be arranged to a position closer to the commutator 3 than in the above embodiment, and the tip of the brush 6 is more effectively suppressed from rattling in the rotation direction of the commutator 3. be able to. The commutator 3 is connected to the other side wall 5 in the rotation direction.
The distance from the commutator 3 to the tip of the pressing piece 8 is designed to be, for example, 0.6 mm or less while also taking into account manufacturing variations. If designed below, brush 6
Rattling in the rotation direction of the commutator 3 can be effectively suppressed.

The pressing piece 8 (pressing portion 8) of the above embodiment
The holding load A of a) is F, where the load on the contiguous side for pressing the brush 6 toward the commutator 3 is F, and the brush 6 and the commutator 3
And the friction coefficient between the brush 6 and the rotation side wall 5b are both μ, and the minimum load, which is the minimum necessary condensate load for pressing the brush 6 against the commutator 3, is B, (F− B) / μ>A> μF is determined, but the tip side of the brush 6 is prevented from rattling in the rotation direction of the commutator 3, and the brush 6 is pressed against the commutator 3 satisfactorily. If it can be determined, it may be determined by another method. For example, the holding load A may be determined by further adding details (in consideration of the details). Even in this case, the effects (1) to the effects of the above-described embodiment can be obtained.
The same effect as (4) can be obtained.

In the above embodiment, the brush device 4 is embodied as a pair (two) of motors.
(For example, a wiper motor) provided with another number (for example, three). Even in this case, the same effect as that of the above embodiment can be obtained.

The technical ideas that can be grasped from the above embodiment will be described below together with their effects. (A) A motor comprising the brush device (4) according to any one of claims 1 to 7. With this configuration, it is possible to provide a motor that can prevent the brush from rattling with respect to the brush holder in the rotation direction of the commutator.

[0044]

As described in detail above, according to the present invention,
It is possible to provide a brush device that can prevent the brush from rattling with respect to the brush holder in the rotation direction of the commutator.

[Brief description of the drawings]

FIG. 1 is a schematic view of a brush device according to an embodiment viewed from a rotation axis direction.

FIG. 2 is a schematic view of the brush device according to the embodiment when viewed from a direction perpendicular to the rotation axis.

FIG. 3 is an explanatory diagram for explaining a method of determining a pressing load of a pressing piece.

FIG. 4 is a schematic view of another example of a brush device viewed from a direction perpendicular to a rotation axis.

FIG. 5 is a schematic view of another example of a brush device as viewed from a rotation axis direction.

FIG. 6 is a schematic view of a conventional brush device as viewed from a rotation axis direction.

[Explanation of symbols]

Reference numeral 3: commutator, 5, 31: brush holder, 6: brush, 7: coil spring (biasing means) constituting a part of the first pressing means and commutator direction biasing means, 8, 2
1, 31c ... pressing pieces (second pressing means), 5b, 31b ...
Rotational side wall 6a: inclined surfaces forming a part of the first pressing means and the commutator direction urging means, 8a, 21a, 3
1d: Pressing portion, 8b, 21b, 31e: Guide portion.

Continued on the front page (72) Inventor Kazuma Moriya 390 Umeda, Kosai-shi, Shizuoka Prefecture Asmo Co., Ltd. (72) Inventor Yasuhide Ito 390 Umeda, Kosai-shi, Shizuoka Prefecture Asmo Co., Ltd. F-term (reference) 5H605 AA04 AA05 BB05 BB09 CC07 DD03 EA05 EA11 EA12 EA23 FF06 5H613 AA02 AA03 BB15 BB27 BB30 GA10 GA15 GB01 PP02

Claims (7)

[Claims] A brush (6) is accommodated and held in a brush holder (5, 31) extending in a direction perpendicular to the axis of a commutator (3) with a gap, and a tip of the brush (6) is connected to the commutator. In the brush device, which is in contact with (3), the rear end of the brush (6) is pressed against the rotational side wall (5b, 31b) of the commutator (3) in the brush holder (5, 31). 1 pressing means (6
a, 7), and the tip side of the brush (6) is connected to the rotation side wall (5).
b, 31b) for pressing the second pressing means (8, 21, 31)
c) a brush device comprising: 2. The brush device according to claim 1, wherein the first pressing means (6a, 7) urges a rear end side of the brush (6) toward the commutator (3) to make the brush. The brush device according to (6), which also functions as a commutator-direction urging means for pressing the tip portion of the commutator (3). 3. The brush device according to claim 2, wherein the first pressing means (6a, 7) is formed at a rear end of the brush (6), and is inclined in a rotation direction of the commutator (3). And a biasing means (7) for contacting the inclined surface (6a) from behind the brush (6) and biasing the commutator (3). Brush equipment. 4. The brush device according to claim 1, wherein the second pressing means (8, 21, 31c) is an end of the brush holder (5, 31) on the commutator side. A brush device characterized in that it is a pressing piece provided in the brush device. 5. The brush device according to claim 4, wherein the pressing piece (31c) is formed integrally with the brush holder (31). 6. The brush device according to claim 4, wherein the pressing piece (8, 21, 31c) moves in a direction of rotation of the commutator (3) toward the commutator (3). Pressing portions (8a, 21a, 31) whose tip portions press the tip side of the brush (6)
d), and a guide portion (8b, 21b, 31e) further away from the brush (6) toward the commutator (3) from the tip of the pressing portion (8a, 21a, 31d). Characteristic brush device. 7. The brush device according to claim 1, wherein a pressing load A of said second pressing means (8, 21, 31c).
The load on the side of the commutator that presses the brush (6) toward the commutator (3) is F, the coefficient of friction between the brush (6) and the commutator (3), and the side wall of the brush (6) and the rotational direction. The coefficient of friction with (5b, 31b) is μ,
A brush device characterized in that the minimum load that is the minimum necessary connec- tive-side load is set to B and (FB) / μ>A> μF.