JP7347229B2 - dc motor - Google Patents

Description

The present invention relates to a DC motor used in a starter or the like as an engine starting device.

In the starter motor, two or more positive side brushes and two or more negative side brushes are arranged so as to be in contact with the outer periphery of a cylindrical commutator. This brush is housed in a brush holder, and a brush spring that biases the brush toward the commutator is provided in the brush holder (for example, Patent Document 1).

International Publication 2017/033655

By the way, water may enter a DC motor used in a vehicle starter from the outside. If water entering from the outside stays in the brush holder, the brushes and brush springs may deteriorate due to rust, and there is a risk that the commutator may not be properly energized.

The present invention has been made in view of the above problems, and its main purpose is to provide a DC motor that can properly drain water.

In the first means, a commutator provided coaxially with the rotor;
brushes on the positive electrode side and negative electrode side that are provided so as to be able to come into contact with the commutator;
a brush holder that accommodates and holds each of the brushes;
an urging member disposed within the brush holder between the rear end of the holder opposite to the commutator and the brush, and urging the brush toward the commutator;
a housing having a cylindrical portion and accommodating the brush holder with the rear end portion of the holder facing the inner circumferential surface of the housing;
The rear end portion of the holder includes a convex portion whose surface facing the inner circumferential surface of the cylindrical portion extends convexly outward in the radial direction along the inner circumferential surface of the cylindrical portion, and the convex portions on both sides in the circumferential direction. and a spaced apart part in which the opposing surface is provided further away from the inner peripheral surface of the cylindrical part than the convex part,
A through hole that penetrates inside and outside of the brush holder is provided in the spaced apart portion of the rear end of the holder.

A convex portion is provided at the rear end of the brush holder on the opposite side of the commutator, the surface facing the inner circumferential surface of the cylindrical portion of the housing extending convexly outward in the radial direction along the inner circumferential surface of the cylindrical portion. It is being By providing the convex portion, the housing position of the biasing member can be moved closer to the cylindrical portion, and the dimension of the brush in the wear direction can be increased. However, if the entire rear end of the holder is made into a convex portion extending along the inner circumferential surface, drainage performance by the through hole provided in the rear end of the holder will be impaired. Therefore, at the rear end of the holder, a spaced part is provided between the convex parts on both sides in the circumferential direction, and the facing surface is further away from the inner circumferential surface of the cylindrical part than the convex part. The structure is such that a through hole is provided. Thereby, water that has entered the brush holder can be suitably discharged from the through hole provided in the spaced portion.

In the second means, the biasing member is a coil spring, and the through hole is located at a position inside the coil spring in the spaced apart portion of the rear end of the holder and has a diameter smaller than the inner diameter of the coil spring. It is provided as a hole.

At the rear end of the holder, a through hole smaller than the inner diameter of the coil spring is provided at a position inside the coil spring. Thereby, it is possible to suppress contact between the coil spring and the housing through the through hole while improving drainage performance in the brush holder. In this case, since a long creepage distance can be ensured between the coil spring and the housing, it is possible to suppress short circuits between the brush and the housing via the coil spring.

In the third means, in the separated part of the rear end of the holder, a thin wall is provided at a position inside the coil spring and around the through hole by being recessed toward the brush side. A section has been established.

A thin wall portion is provided in the spaced apart portion of the rear end of the holder, which is recessed toward the brush side and becomes thinner. This thin portion is provided inside the coil spring, that is, inside the portion where the coil spring comes into contact. Thereby, in the brush holder, the contact portion of the coil spring can be thickened to ensure strength, while the thin inner portion can improve drainage performance.

In the fourth means, the cylindrical portion is formed in a tapered shape whose diameter increases toward one side in the motor axial direction.

Since the cylindrical portion surrounding each brush holder is formed in a tapered shape, water discharged from the through hole at the rear end of the brush flows in the motor axial direction along the inner peripheral surface of the cylindrical portion. Thereby, water discharged from the brush holder can be prevented from staying between the housing and the brush holder.

In the fifth means, the through hole is provided in the rear end portion of the holder on the side where the diameter of the cylindrical portion is expanded in the motor axial direction.

The cylindrical portion is formed in a tapered shape whose diameter is expanded in the motor axial direction, and the through hole is provided on the side where the cylindrical portion is expanded in diameter in the motor axial direction. This increases the distance between the through hole and the inner peripheral surface of the housing. Therefore, drainage performance can be improved.

In the sixth means, the convex portion of the rear end portion of the holder is in contact with the inner circumferential surface of the cylindrical portion.

Since the convex portion at the rear end of the holder is in contact with the inner peripheral surface of the cylindrical portion, the biasing force of the biasing member can also be received by the housing via the brush holder. Thereby, the strength required at the position where the biasing member of the brush holder contacts can be reduced, and the wall thickness at the position where the brush holder contacts can be reduced. Therefore, the distance in the wear direction of the brush can be increased, and the life of the brush can be extended.

Schematic configuration diagram of the starter in the first embodiment Perspective view of brush assembly Perspective view of brush assembly Perspective view of positive electrode side plate and brush Perspective view of positive plate Top view of brush assembly Front view of the brush assembly in a modified example Front view of the brush assembly in a modified example Top view of the brush assembly in a modified example A partially enlarged sectional view of the brush assembly in the second embodiment Cross-sectional view of brush and brush holder Cross-sectional view of a brush and brush holder in a modified example A cross-sectional view of a portion of a brush assembly in a third embodiment A cross-sectional view of a portion of the brush assembly in a modified example Longitudinal cross-sectional view of a portion of the brush assembly in a modified example

<First embodiment>
Hereinafter, a specific configuration of a DC motor used in a starter for starting an engine will be described based on the drawings. Note that in each of the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals in the drawings, and the explanations thereof will be referred to for the parts with the same reference numerals.

FIG. 1 is a schematic diagram of the starter 10. As shown in FIG. The starter 10 includes a DC motor 20, a speed reducer 12 that decelerates the rotation of the DC motor 20 and transmits it to the pinion gear 11, and a magnetic switch 13 that serves as a switch for supplying power to the DC motor 20. The speed reducer 12 is configured by, for example, a planetary gear mechanism.

The magnet switch 13 serves as a switch for an energizing circuit between a battery outside the starter 10 and the DC motor 20. For example, when the IG switch is turned on by a user's key operation, the magnet switch 13 closes the energization circuit between the external battery of the starter 10 and the DC motor 20, and power is supplied to the DC motor 20. Then, when the DC motor 20 is energized, the rotation of the DC motor 20 is transmitted to the pinion gear 11 via the speed reducer 12 and the one-way clutch 15. Further, when the IG switch is turned on, the magnet switch 13 causes the shift lever 14 to push the pinion gear 11 to the side opposite to the DC motor 20, so that the ring gear of the engine and the pinion gear 11 mesh with each other. When the IG switch is turned on in this manner, the starter 10 rotates the ring gear of the engine.

The DC motor 20 is, for example, of a magnet field type, and includes a magnet 21, a rotor 22 rotatably disposed on the inner periphery of the magnet 21, a commutator 24 provided coaxially with the rotor 22, and a commutator 24. The brush 30 is arranged around the outer periphery of the brush 30. In the following description, the direction in which the rotating shaft 20A of the DC motor 20 extends is referred to as the axial direction (motor axial direction), the direction extending radially from the center of the rotating shaft 20A is referred to as the radial direction, and the direction in which the rotating shaft 20A is the center is referred to as the radial direction. The direction in which it extends circumferentially is defined as the circumferential direction.

A yoke 23 is provided around the outer periphery of the magnet 21, and the cylindrical yoke 23 accommodates the magnet 21 and the rotor 22. The brush assembly A and the commutator 24 are housed in a cylindrical housing 80 with a bottom. The yoke 23 and the housing 80 are combined to form a motor case of the DC motor 20. Note that a field coil may be used instead of the magnet 21.

The brush assembly A includes positive and negative brushes 30, a brush holder 40 that accommodates the brushes 30, a positive plate 50, a negative plate 70 facing the positive plate 50, and a positive plate 50. A power supply line 60 to be connected is provided. The brush assembly A is provided with the positive plate 50 facing the rotor 22 in the motor axial direction, and the negative plate 70 facing the rotor 22.

2 is a perspective view of the brush assembly A viewed from the positive plate 50 side, and FIG. 3 is a perspective view of the brush assembly A viewed from the negative plate 70 side. In the brush assembly A, three positive and negative brushes 30 are arranged alternately in the circumferential direction at predetermined intervals in the circumferential direction. In the following, when distinguishing between the positive electrode side and the negative electrode side of the brush 30, they will be referred to as a positive electrode side brush 30A and a negative electrode side brush 30B. Further, the number of brushes 30 may be plural on the positive electrode side and on the negative electrode side, and the number of positive electrode side brushes 30A and negative electrode side brushes 30B may be different.

The brush 30 will be explained using the positive electrode side brush 30A as an example. Although the positive electrode side brush 30A will be explained as an example, the negative electrode side brush 30B has the same structure. FIG. 4 is a perspective view of the positive plate 50 and the positive brush 30A of the brush assembly A.

The brush 30 can come into contact with the sliding surface of the commutator 24, and a lead wire 32 is connected to the brush 30. The brush 30 has a prismatic shape. A lead wire 32 extends in the circumferential direction from one side of the brush 30 in the circumferential direction. The lead wire 32 is connected to the end of the brush 30 on the opposite side to the contact surface 31A that contacts the commutator 24. The end of the connecting portion 32A of the lead wire 32 of the brush 30 on the contact surface 31A side is the wear limit position of the brush 30. (See FIG. 10) In other words, the brush 30 can be worn down to the connecting portion 32A of the lead wire 32. Further, a coil spring 45 is in contact with the rear end surface 31B of the brush 30 on the opposite side from the contact surface 31A (see FIG. 10). The brush 30 is provided with a positioning portion 33 that protrudes rearward from the rear end surface 31B of the brush 30 and positions the coil spring 45.

The lead wire 32 is an electric wire called a pigtail made by braiding or bundling conductive copper wires, and has flexibility. Further, the lead wire 32 is an electric wire that is not covered with an insulating coating or the like. The tip of the lead wire 32 is joined to the positive plate 50 or the negative plate 70 by welding or the like. That is, the lead wire 32 is mechanically fixed to each plate 50, 70 and electrically connected to the plate.

As shown in FIGS. 2 and 3, the brushes 30 are housed in brush holders 40, respectively. The brush holder 40 is made of an insulating material such as resin, and is formed in a box shape that opens inward in the radial direction perpendicular to the axial direction, that is, toward the commutator 24 side. The brush holder 40 has a brush accommodating portion 42 that accommodates the brush 30.

In the brush holder 40, a spring accommodating portion 46 for accommodating a coil spring 45 is provided on the radially outer side of the brush accommodating portion 42 (on the opposite side from the commutator 24). The spring accommodating portion 46 partially bulges outward along the outer shape of the coil spring 45 and has a cylindrical shape. Further, a circumferential side wall of the brush holder 40 partially bulges outward along the outer shape of the coil spring 45.

The brush accommodating portion 42 of the brush holder 40 is provided with openings 41 on both side walls in the circumferential direction thereof, through which the lead wire 32 can be drawn out. Since the opening 41 is formed to extend in the radial direction, the brush 30 can be moved in the radial direction while the lead wire 32 remains pulled out. Note that the opening 41 may be provided only on one side wall in the circumferential direction from which the lead wire 32 is drawn out.

Further, the brush accommodating portion 42 of the brush holder 40 projects further toward the rotor 22 than the positive electrode side plate 50 . Further, a part of the brush 30 is accommodated in a portion of the brush accommodating portion 42 that protrudes beyond the positive electrode side plate 50. In other words, the brush 30 and the positive plate 50 partially overlap in the axial direction. Moreover, the brush holder 40 and the positive electrode side plate 50 are positioned with respect to each other in the axial direction, the circumferential direction, and the radial direction.

A positioning convex portion 43 is provided on the negative side plate 70 side of the brush holder 40 in the axial direction, which projects toward the side opposite to the rotor 22 and positions the brush holder 40 with respect to the negative side plate 70. The brush 30 is not accommodated in the positioning convex portion 43, and the brush 30 does not overlap the negative electrode side plate 70 in the axial direction. The brush holder 40 and the negative plate 70 are positioned relative to each other in the axial direction, circumferential direction, and radial direction.

Further, the positive electrode side plate 50 and the negative electrode side plate 70 are formed of conductive metal plates having a predetermined thickness, and have an annular shape with a round hole through which the commutator 24 can be inserted in the center in the radial direction. It has become. The positive electrode side plate 50 and the negative electrode side plate 70 are arranged parallel to each other in the axial direction and spaced apart from each other. The brush 30 and the brush holder 40 are held in a sandwiched state between the positive electrode side plate 50 and the negative electrode side plate 70.

Slits 71 are formed in the negative electrode side plate 70 at equal intervals in the circumferential direction. By fitting the positioning convex portion 43 into the slit 71, the negative electrode side plate 70 and the brush holder 40 are positioned. Further, a plurality of bolt insertion holes 72 are formed in the negative electrode side plate 70. The negative plate 70 is fixed to the housing 80 by bolts B inserted into the bolt insertion holes 72 (see FIG. 1). Further, the negative plate 70 is electrically connected to the housing 80 via this bolt B. Thereby, the negative electrode side plate 70 is grounded.

FIG. 5 is a perspective view of the positive electrode side plate 50. As shown in FIGS. 2 and 5, the positive electrode side plate 50 has a flat intermediate portion 51 interposed between the brush holders 40 arranged in the circumferential direction, and a transition portion 52 that connects the intermediate portions 51. ing. The intermediate portion 51 is provided in a substantially trapezoidal shape so as to be interposed between the brush holders 40 adjacent to each other in the circumferential direction. The intermediate portion 51 has a radial dimension that is the same as or slightly smaller than the radial dimension of the brush accommodating portion 42 . Furthermore, the space between the intermediate portions 51 becomes a fitting groove 53 in which the brush accommodating portion 42 of the brush holder 40 is disposed. The fitting groove 53 is open on both sides in the radial direction on the same plane as the intermediate portion 51 .

The transition portion 52 connects the intermediate portions 51 disposed on both sides of the fitting groove 53 in the circumferential direction. The transition portion 52 is formed by bending in the axial direction a portion that is formed to wrap around the outside in the radial direction of the brush accommodating portion 42 . In other words, the transition portion 52 is formed as a bent portion that is bent in a direction that crosses the current-carrying path. Corners arranged on both circumferential sides of the fitting groove 53 in the transition portion 52 and bent from the intermediate portion 51 serve as bent corner portions 54, respectively. The transition portion 52 is formed to avoid the brush holder 40.

The transition portion 52 is bent from the intermediate portion 51 at 90 degrees with a predetermined bending radius, and extends in the axial direction. The transition portion 52 extends in the axial direction while maintaining a predetermined distance from the housing 80 and the rotor 22. Note that the bending angle between the transition portion 52 and the intermediate portion 51 is desirably 90 degrees or less. The bending angle is the angle between the intermediate portion 51 and the transition portion 52, and the smaller the bending angle, the larger the residual stress. Further, the bending radius between the intermediate portion 51 and the transition portion 52 is desirably smaller because the residual stress increases. The bending radius is arbitrary as long as residual stress is generated in the bending corner 54, and specifically, it is preferably smaller than three times the thickness of the positive plate 50, for example. Further, the bending radius is preferably determined based on the minimum radius that does not cause cracks in the material due to bending, and is preferably larger than one quarter of the thickness of the positive electrode side plate 50, for example.

As shown in FIGS. 1 and 4, a power supply line 60 for supplying electric power is connected to the positive plate 50 at a power line joint 55. Further, the lead wire 32 of the positive electrode brush 30A is joined to the positive electrode side plate 50 at a lead joint portion 56. The power line joint portion 55 and the lead joint portion 56 are provided on opposing surfaces of the positive plate 50 that face the negative plate 70 . By joining the lead wire 32 to the surface of the positive electrode side plate 50 facing the negative electrode side plate 70, it is possible to suppress the lead wire 32 from becoming long. Furthermore, when welding the power supply line 60 and the lead wire 32, the power line joint 55 and the lead joint 56 are provided on the same plane, and all welding processes can be performed simultaneously, resulting in high productivity. Become.

Further, the power line joint portion 55 is provided in the intermediate portion 51 of the plurality of intermediate portions 51 of the positive electrode side plate 50 where the lead joint portion 56 to which the lead wire 32 of the positive electrode side brush 30A is connected is not provided. . The intermediate portion 51 where the power line joint portion 55 is provided is provided with a protrusion piece 51B that protrudes outward in the radial direction to ensure an area for joining the power supply line 60. The power supply line 60 is an electric wire that connects the magnet switch 13 and the positive plate 50 to supply power to the positive plate 50.

The power supply line 60 is held by a power line holding member 65 for ensuring insulation from the housing 80 and the yoke 23. The power line holding member 65 is made of an insulating material such as rubber, and is assembled into a notch provided in the housing 80 through which the power supply line 60 is inserted. Furthermore, since the power line holding member 65 is disposed at the boundary between the housing 80 and the yoke 23, it is also assembled at the end of the yoke 23. The power supply line 60 is held by the power line holding member 65 by inserting the power supply line 60 through the through hole provided in the power line holding member 65 .

By the way, when the DC motor 20 is abnormally continuously energized or when an overcurrent flows, it is necessary to stop the power supply to the rotor 22 in order to prevent burnout of the coils of the rotor 22. Therefore, the positive electrode side plate 50 is provided with a path blocking function. Specifically, the configuration is such that the power supply to the positive brush 30A is cut off by fusing a portion of the positive electrode side plate 50.

When the positive plate 50 is fused, it is desirable that the positive plate 50 be fused at a position where power supply to all of the positive brushes 30A on the positive plate 50 can be cut off. Specifically, the power line joint 55 is connected between the lead joint 56 of the positive brush 30A adjacent to the power line joint 55 in the circumferential direction on the positive plate 50 and the power line joint 55, that is, on the energization path. It is desirable that the positive electrode side plate 50 be fused between the lead joint portion 56 and the power line joint portion 55 that are adjacent in the circumferential direction. However, if the lead joint of the positive brush 30A of the two brushes 30 adjacent to the power line joint 55 is provided on the power line joint 55 side of the positive brush 30A, the lead joint will be It is close to the power line joint portion 55 in this direction, and a space for providing a fusing portion cannot be secured. Therefore, in order to fuse the positive electrode side plate 50 between the power line joint part 55 and the lead joint part 56, the distance in the circumferential direction (space for providing the fusing part) between the power line joint part 55 and the lead joint part 56 is ) must be ensured.

FIG. 6 is a plan view of the brush assembly A viewed from the positive plate 50 side. As shown in FIGS. 2 and 6, the positive and negative brushes 30A and 30B are arranged alternately in the circumferential direction. The lead wire 32 of the positive electrode side brush 30A and the lead wire 32 of the negative electrode side brush 30B are pulled out in the same direction in the circumferential direction, and the lead wire 32 of the positive electrode side and the lead wire of the negative electrode side are pulled out in the same direction in the circumferential direction. The lines 32 are arranged alternately.

In the positive electrode side plate 50, each intermediate portion 51 is provided sandwiched between a brush holder 40 that accommodates the positive electrode side brush 30A and a brush holder 40 that accommodates the negative electrode side brush 30B. A power supply line 60 is joined to the portion 51, and the joined portion serves as a power line joint portion 55. In FIG. 6, for convenience, the intermediate portion 51 where the power line joint portion 55 is located is hatched, and the intermediate portion 51 is referred to as an “intermediate portion 51A”.

In the brush 30A on the positive electrode side which is adjacent to the intermediate portion 51A in the circumferential direction, the lead wire 32 is pulled out to the opposite side to the intermediate portion 51A, and the lead wire 32 of the brush 30A on the positive electrode side is drawn out to the intermediate portion 51 on the opposite side. A lead joint portion 56 is provided to which the lead joint portion 56 is joined. That is, in the positive plate 50, the lead joint 56 of the lead wire 32 of the positive brush 30A closest to the power line joint 55 is provided on the opposite side of the power line joint 55 across the positive brush 30A. There is. As a result, at least one brush holder 40 and one brush 30 are disposed between the power line joint portion 55 and the lead joint portion 56 on the positive electrode side plate 50. Therefore, a distance in the circumferential direction between the power line joint portion 55 and the lead joint portion 56 can be secured.

In the positive electrode side plate 50, a fusing portion 57 is provided between the power line joint portion 55 and the lead joint portion 56 adjacent to the power line joint portion 55 in the circumferential direction. Specifically, the bent corner portion 54 of the transition portion 52 that connects to the intermediate portion 51A, that is, the bent corner portion 54 of the transition portion 52 that is on the side of the positive electrode side brush 30A in the circumferential direction, and the bent corner portion 54 of the transition portion 52 that is on the side of the negative electrode side brush 30B in the circumferential direction. The bent corner portion 54 of the portion 52 serves as a fusing portion 57 . A plurality of transition portions 52 are provided in the circumferential direction, and among the plurality of transition portions 52, a bent corner portion 54 of the transition portion 52 connected to the intermediate portion 51A is used as a fusing portion 57.

Each transition portion 52 has two bent corners 54, but in the transition portion 52 connected to the intermediate portion 51A, the bent corner 54 on the intermediate portion 51A side is preferably a fusing portion 57. However, in the transition portion 52 that connects to the intermediate portion 51A, the two bent corners 54 may have fusing portions 57 in both directions, or the bent corner on the opposite side from the intermediate portion 51A among the two bent corners 54. 54 may be a fusing portion 57.

The fusing portions 57 are provided in the transition portions 52 on both sides of the intermediate portion 51A where the power line joint portion 55 is provided. This is because the power path starting from the power line joint 55 is an annular path that conducts current in both directions, that is, it is necessary to interrupt these two paths.

In the fusing portion 57, the residual stress generated by the bending process acts as a force in the direction of separating the transition portion 52 and the intermediate portion 51. Therefore, due to the residual stress, when the temperature of the fusing portion 57 increases, the timing at which the fusing occurs is brought forward. As a result, the cross-sectional area of the fusing part 57 can be made larger in the configuration in which the bent corner part 54 is the fusing part 57 than in the configuration in which the fusing part is formed in a flat area, and the path resistance during normal operation can be increased. Can be lowered. At this time, as described above, it is preferable to increase the residual stress at the fusing portion 57 by making the bending angle 90 degrees or less or making the bending radius small. Furthermore, by bending, the mechanical strength of the fusing portion 57 can be improved. Furthermore, by using the bent corner portion 54 of the transition portion 52 bent in the axial direction as the fusing portion 57, it becomes possible to achieve radial miniaturization and the desired path blocking function with the transition portion 52. ing.

In addition, among the plurality of bent corners 54, the two closest to the power line joint portion 55 on both sides in the circumferential direction are the fusing portions 57, so that after the positive electrode side plate 50 is fused, the power is removed from the power supply line 60. The range of the positive electrode side plate 50 to be supplied can be minimized. Further, by increasing the distance between the position of the fusing part 57 and the lead joint part 56 of the positive electrode side brush 30A, heat generated at the fusing part 57 is transferred to the positive electrode side brush 30A via the lead wire 32. can be suppressed. Therefore, damage to other components due to heat generated by the fusing portion 57 can be suppressed.

The plurality of transition portions 52 include a first bent portion in which the bent corner portion 54 has a small width dimension, and a second bent portion in which the bent corner portion 54 has a large width dimension. The first bent part is the transition part 52 functioning as the fusing part 57, and the second bent part is the other transition part 52. The bent corner portion 54 of the first bent portion serves as a fusing portion 57 . In other words, the cross-sectional area of the bent corner 54 of the first bent portion in the direction perpendicular to the current-carrying path is set to be smaller than the cross-sectional area of the bent corner 54 of the second bent portion in the direction perpendicular to the current-carrying path. This is a fusing portion 57. As a result, the path resistance at the bent corner 54 that becomes the fusing portion 57 becomes higher than the path resistance at the other bent corners 54 . Therefore, when an overcurrent occurs, the temperature at the fusing portion 57 increases, and the positive electrode side plate 50 is fused at the fusing portion 57 . Moreover, the cross-sectional area of the fusing part 57 at this time can be made larger than the cross-sectional area when the fusing part is formed in a planar shape due to residual stress due to bending. Furthermore, the strength of each bent corner portion 54 is improved by work hardening due to bending. Thereby, even if the width dimension of the fusing portion 57 is reduced, mechanical strength can be ensured.

Further, the lead wire 32 of the negative electrode side brush 30B is drawn out into the space between the brush holders 40 where the power supply line 60 is arranged, and is joined to the negative electrode side plate 70. Thereby, the power line joint portion 55 and a portion of the lead wire 32 of the negative electrode side brush 30B are arranged at a position where they overlap in the axial direction. Therefore, there is a possibility that the power supply line 60 and the lead wire 32 of the negative brush 30B come into contact with each other.

Therefore, as shown in FIGS. 2 and 4, the power line holding member 65 has a power line holding member 65 arranged between the end portion 60A of the power supply line 60 joined to the positive side plate 50 and the lead wire 32 of the negative side brush 30B. An insulating section 66 is provided. The insulating portion 66 is provided in the power line holding member 65 so as to protrude inward in the radial direction, and covers the opposite side of the positive electrode side plate 50 of the end portion 60A of the power supply line 60. The insulating portion 66 is slightly larger than the end portion 60A of the power supply line 60. As a result, contact between the power supply line 60 and the lead wire 32 of the negative brush 30B can be suppressed without providing an axial distance between the power line joint 55 and the lead wire 32 of the negative brush 30B. This allows the DC motor 20 to be downsized in the axial direction. In this embodiment, the insulating part 66 is provided integrally with the power line holding member 65, but it is also possible to provide the insulating part 66 separately from the power line holding member 65.

According to this embodiment described in detail above, the following actions and effects can be obtained.

A lead wire 32 extending from the positive brush 30A is connected to the annular positive plate 50, and power is supplied to the positive brush 30A via the positive plate 50. This positive electrode side plate 50 is provided with a transition portion 52 that is bent in a direction that crosses the energization path of the positive electrode side plate 50. For example, when the transition portion 52 is formed by press working, residual stress will be generated at the bent corner portion 54 of the transition portion 52. In the positive electrode side plate 50, when an overcurrent flows, the bent corner 54 is fused earlier than other parts due to this residual stress. As a result, the bent corner portion 54 becomes a fusing portion 57 that is fused when an overcurrent occurs. Since the fusing part 57 is formed by bending, the path cross-sectional area at the fusing part 57 is larger than when the fusing part is formed by a cutout, etc., and the path resistance of the positive plate 50 during normal energization is reduced. can be lowered. Therefore, it is possible to provide a desired path-blocking function while appropriately performing energization during normal energization.

The positive electrode side plate 50 has an intermediate portion 51 interposed between the brush holders 40 arranged in the circumferential direction, and a transition portion 52 that connects the intermediate portions 51 to each other. In the configuration in which the transition portion 52 avoids the brush holder 40, since the transition portion 52 is formed by bending in the axial direction from the intermediate portion 51, the positive electrode side plate 50 is suppressed from increasing in the radial direction. The transition portion 52 is defined as a bent portion, and the bent corner portion 54 obtained by bending the transition portion 52 from the intermediate portion 51 is defined as a fusing portion 57. Thereby, the portion bent for miniaturization can be used as the fusing portion 57 that interrupts the current flow path. Therefore, it is possible to provide a desired route blocking function while achieving miniaturization.

The magnitude of residual stress varies depending on the bending angle during press working. Since the bending angle of the transition portion 52 is 90 degrees or less, the residual stress can be increased. Therefore, the bent corner portion 54 can function appropriately as the fusing portion 57.

In this embodiment, in the brush 30A located next to the power line joint 55 and on the positive side, the lead wire 32 is pulled out to the side opposite to the power line joint 55 in the circumferential direction across the positive side brush 30A. And so. Thereby, in the positive electrode side plate 50, the fusing part 57 can be provided at a desired position near the power line joint part 55. Therefore, while achieving miniaturization, it is possible to optimize the fusing position of the positive electrode side plate 50 and cut off current to all the positive electrode side brushes 30A.

The positive electrode side plate 50 is provided with a transition portion 52 for each brush 30, and the positive electrode side plate 50 is configured to be fused at a bent corner portion 54 adjacent to the power line joint portion 55 in the circumferential direction. In other words, the structure is such that the fuse is fused between the brush 30 adjacent to the power line joint 55 and the power line joint 55 . Thereby, the range of the positive plate 50 to which power is supplied from the power supply line 60 after the positive plate 50 is fused can be minimized. Therefore, it is possible to suppress the occurrence of a short circuit or the like due to contact of the positive electrode side plate 50 on the side of the power line joint portion 55 after blowing out with other members.

In the fusing portion 57, the residual stress generated by the bending process acts as a force in the direction of separating the transition portion 52 and the intermediate portion 51. Therefore, due to the residual stress, when the temperature of the fusing portion 57 increases, the timing at which the fusing occurs is brought forward. As a result, the cross-sectional area of the fusing part 57 can be made larger in the configuration in which the bent corner part 54 is the fusing part 57 than in the configuration in which the fusing part is formed in a flat area, and the path resistance during normal operation can be increased. Can be lowered. At this time, as described above, it is preferable to increase the residual stress at the fusing portion 57 by making the bending angle 90 degrees or less or making the bending radius small. Furthermore, by bending, the mechanical strength of the fusing portion 57 can be improved. Furthermore, by using the bent corner portion 54 of the transition portion 52 bent in the axial direction as the fusing portion 57, it becomes possible to achieve radial miniaturization and the desired path blocking function with the transition portion 52. ing.

In this embodiment, an insulating part 66 is provided between the lead wire 32 of the negative electrode side brush 30B and the power supply line 60 in the space where the power supply line 60 is arranged among the spaces between the brushes 30 arranged in the circumferential direction. The structure is as follows. This prevents contact between the power supply line 60 and the lead wire 32 of the negative brush 30B without providing an axial space to avoid contact between the lead wire 32 of the negative brush 30B and the power supply line 60. This makes it possible to reduce the size of the DC motor 20 in the axial direction.

<Example of change>
The first embodiment may be modified and implemented as follows. Note that the following configurations may be applied individually to the configuration of the first embodiment, or may be applied in any combination.

- In the positive electrode side plate 50, the fusing portion 57 is provided only in a specific transition portion 52 (first bent portion) among the plurality of transition portions 52, and the width dimension of the bent corner portion 54 of the specific transition portion 52 is In addition to or in place of the configuration in which the transition portion 52 is made smaller than the other transition portions 52 (second bent portions), the bending angle or bending radius of the specific transition portion 52 may be made larger than the other transition portions 52 .

- The configuration of the transition portion 52 of the positive electrode side plate 50 may be changed. FIG. 7 is a front view showing a schematic structure of the brush assembly A developed in plan, and the left-right direction in the drawing is the circumferential direction. In FIG. 7, the positive electrode side plate 50 is provided with a transition portion 52 for each brush holder 40, which is bent and formed with the plate surface facing the side and top surfaces of the brush holder 40. The transition portion 52 is provided so as to avoid the brush holder 40 by being bent in a convex shape in the axial direction. In this case, the transition portion 52 has a plurality of bent corner portions 54, and the bent corner portions 54 are configured to be used as a fusing portion 57. Note that the ease with which the bent corner portions 54 of each transition portion 52 are fused and cut due to bending is adjusted by appropriately setting at least one of the radial plate width dimension, bending angle, and bending radius. It has become.

- The positive electrode side plate 50 may have a configuration in which a bent portion is formed at a location other than the transition portion 52. FIG. 8 is a front view showing a schematic structure of the brush assembly A developed in plan, and the left-right direction in the drawing is the circumferential direction. In FIG. 8, a bent portion 58 is formed at a position between the brush holders 40 arranged in the circumferential direction on the positive electrode side plate 50, and a bent corner of the bent portion 58 serves as a fusing portion 59.

- FIG. 9 is a plan view of the brush assembly A1 in a modified example. In this brush assembly A1, the fusing portion 157 of the positive electrode side plate 150 is formed by a method other than bending. Specifically, in this modification, the fusing portion 157 is formed by making the path cross-sectional area smaller than other positions of the positive electrode side plate 150. Also in this modification, the lead wire 32 of the negative electrode side brush 30B is placed on the power line joint portion 55 side while the power line joint portion 55 and the lead joint portion 56 are provided on the same plane of the positive electrode side plate 50. Since the lead wire 32 of the negative electrode side brush 30B and the power supply line 60 may come into contact with each other, an insulating portion 66 is provided.

The positive electrode side plate 150 has a flat intermediate portion 151 interposed between the brush holders 40 and a transition portion 152 that connects the intermediate portions 151 to each other. The transition portion 152 is formed so as to wrap around the outside of the brush accommodating portion 42 in the radial direction, and is connected to the intermediate portion 151 on both sides in the circumferential direction. The transition portion 152 is formed to avoid the brush holder 40.

In the positive electrode side plate 150, a fusing portion 157 is provided between the power line joint portion 55 and the lead joint portion 56 of the positive electrode brush 30A adjacent to the power line joint portion 55 in the circumferential direction. More specifically, a fusing portion 157 is provided between the brush 30 and adjacent brushes 30A and 30B in the circumferential direction. In the fusing part 157, two slits are provided from the outer peripheral side of the positive electrode side plate 150 toward the radially inward side, and the radially inner part of the positive electrode side plate 150 after the slits are formed becomes the fusing part 157. . In the fusing portion 157, the dimension in the direction across the current-carrying path (radial direction dimension) is smaller than in other parts of the positive electrode side plate 150, and the path cross-sectional area is smaller. In other words, the path resistance at the fusing portion 157 is higher than at other positions on the positive electrode side plate 150. Thereby, when an overcurrent occurs, the positive electrode side plate 150 is fused at the fused portion 157 .

- The positive electrode side plate 50, 150 may be a C-shaped plate. If the C-shaped cut is arranged between the power line joint 55 and the lead joint 56 of the positive electrode brush 30A adjacent in the circumferential direction, there may be only one fusing part. .

<Second embodiment>
In the second embodiment, as shown in FIGS. 10 and 11, a part of the first embodiment is changed, and the transition portion 252 is configured to overlap the brush holder 240 in the axial direction. FIG. 10 is a partially enlarged sectional view of the brush assembly A1 in the second embodiment. FIG. 11 is a cross-sectional view of the brush 230 and brush holder 240. In FIGS. 10 and 11, the vertical direction of the drawings is the axial direction (motor axial direction), and the left-right direction of the drawings is the radial direction. In the following description, the radially inner side (commutator 24 side) of the brush holder 240 will be referred to as the front, and the radially outer side (the side opposite to the commutator 24) will be referred to as the rear. Further, a configuration in which the transition portion 252 of the second embodiment overlaps the brush holder 240 in the axial direction may be used in the first embodiment.

The brush assembly A1 of the second embodiment includes brushes 230 on the positive and negative sides, a brush holder 240 that accommodates the brushes 230, a positive plate 250, and a negative plate 70 facing the positive plate 250. The power supply line 60 (see FIG. 3) is connected to the positive electrode side plate 250. Regarding the brush 230, brush holder 240, brush accommodating portion 242 of the brush holder 240, positive electrode side plate 250, and transition portion 252 of the positive electrode side plate 250 of the second embodiment, the brush 30, the brush holder 40 of the first embodiment, The brush accommodating portion 42, the positive electrode side plate 50, and the transition portion 52 are substantially the same except for the points described below. In the following description, only points different from the first embodiment and points not explained in detail in the first embodiment will be explained.

In the brush holder 240, the brush 230 is housed in the brush housing part 242, and the coil spring 45 that urges the brush 230 toward the commutator 24 is housed in the spring housing part 46 on the rear side. The coil spring 45 is a compression spring formed by spirally winding a wire rod, and presses the rear end surface 231B of the brush 230. The diameter of the coil spring 45 is smaller than the axial dimension of the brush 230 and larger than the circumferential dimension. The brush 230 is provided with a positioning portion 33 that positions the coil spring 45 with respect to the brush 230.

The positive electrode side plate 250 has an intermediate portion 51 and a transition portion 252. The transition portion 252 is bent at approximately 90 degrees from the intermediate portion 51 on the side away from the brush holder 240 (rotor 22 side). That is, the transition portion 252 extends so as to protrude from the brush holder 240 side to the rotor 22 side. Therefore, the transition portion 252 protrudes further in the axial direction than the axial end surface of the brush holder 240, which may increase the size of the DC motor 20 in the axial direction.

Therefore, the brush holder 240 is formed with a holder reduction portion 247 that reduces the axial dimension of the rear end of the brush holder 240 on the positive electrode side plate 250 side. Specifically, in the brush holder 240, a portion rearward from a position radially overlapping with the transition portion 252 is reduced in the axial direction, thereby forming a holder reduced portion 247. In the holder reduction portion 247, the rear end portion of the brush holder 240 is reduced in the axial direction to the outer diameter position of the coil spring 45. Note that a rear portion of the brush accommodating portion 242 is also reduced in the axial direction and becomes a part of the holder reduction portion 247 .

Further, at the end of the brush 230, a brush reduction portion 234 is formed at a position corresponding to the holder reduction portion 247, with a reduced axial dimension of the brush 230. Thereby, a portion corresponding to the brush reduction portion 234 in the radial direction can be inserted into the area within the holder reduction portion 247 . Further, like the brush reduction portion 234, the brush 230 also has a stepped shape on the negative electrode side plate 70 side in which the axial dimension of the rear end portion of the brush 230 is reduced. As a result, the brush 230 has a line-symmetrical shape with the connecting portion 32A of the lead wire 32 interposed therebetween. Note that the rear end portion of the brush holder 240 on the side of the negative electrode side plate 70 is also made smaller in axial direction, similarly to the holder reduction portion 247. This reduces the gap between the brush holder 240 and the rear end of the brush 230 at the initial position.

The transition portion 252 overlaps the holder reduction portion 247 both in the radial direction and in the axial direction. In other words, the spanning portion 252 is arranged to face the step surface 247A facing rearward, which is formed by providing the holder reduction portion 247. Further, the transition portion 252 overlaps the brush reduction portion 234 in the axial direction. That is, the transition portion 252 overlaps the holder reduction portion 247 and the brush reduction portion 234 in the axial direction. Thereby, the protrusion amount L1 by which the transition portion 252 protrudes from the axial end surface of the brush holder 240 can be reduced. Therefore, the DC motor 20 can be made smaller in the axial direction.

Further, a connecting portion 32A of the lead wire 32 is provided at a portion of the brush 230 corresponding to the brush reduction portion 234 in the radial direction. The brush reduction portion 234 of the brush 230 and the connection portion 32A of the lead wire 32 partially or completely overlap in the radial direction. Since the contact area of the brush 230 with the commutator 24 becomes small in the portion corresponding to the brush reduction portion 234 in the radial direction, the brush reduction portion 234 cannot be included in the effective length of the brush 230. By connecting the lead wire 32 at a dead portion that is not included in the effective length, the dead portion can be effectively utilized. In other words, the brush reduction portion 234 is formed on the rear side of the front end of the connecting portion 32A of the brush 230 (the end of the connecting portion 32A on the commutator 24 side). The portion of the brush 230 up to the connection portion 32A of the lead wire 32 is included in the effective length of the brush 230, and the brush reduced portion 234 is formed in a portion that is not included in the effective length.

By the way, since the brush holder 240 and the brush 230 have different linear expansion coefficients, a predetermined clearance is provided between the brush holder 240 and the brush 230 so that the brush 230 and the brush holder 240 do not interfere with each other during use. ing. When the brush 230 wears out and the radial opposing range between the brush holder 240 and the brush 230 (the radial dimension where the axial inner surface of the brush holder 240 and the axial end surface of the brush 230 face each other) becomes shorter, the brush 230 becomes shorter. The brush holder 240 tends to wobble in the axial direction, making sliding contact with the commutator 24 unstable. When the brush 230 is provided with the brush reduction portion 234, the range in which it faces the brush holder 240 in the radial direction is shortened, and the sliding contact between the brush 230 and the commutator 24 tends to become unstable.

Therefore, an uneven shape 24A parallel to the sliding direction of the brush 230 is provided on the sliding surface of the commutator 24 with the brush 230. As a result, the uneven shape 24A of the commutator 24 forms a groove on the contact surface 31A of the brush 230 that matches the uneven shape 24A, and the groove of the brush 230 fits into the uneven shape 24A on the commutator 24 side. Thereby, the state of contact between the brush 230 and the commutator 24 can be stabilized. Therefore, even if the brush 230 is provided with the brush reduction portion 234 and the radially opposing range is shortened, excessive wear of the brush 230 can be suppressed.

According to this embodiment described in detail above, the following actions and effects can be obtained.

A configuration in which a holder reduction part 247 that is reduced in the axial direction is formed at the end (rear end) on the radially opposite side of the commutator 24 in the brush holder 240, and the transition part 252 is overlapped with the holder reduction part 247 in the axial direction. And so. In this case, due to the overlap between the brush holder 240 and the transition portion 252 in the axial direction, the protrusion amount L1 by which the transition portion 252 projects from the axial end surface of the brush holder 240 can be reduced. Therefore, the DC motor 20 can be made smaller in the axial direction.

A brush reduction portion 234 that becomes smaller in the axial direction is formed at a position corresponding to the holder reduction portion 247 of the brush 230. By providing the brush reduction portion 234, a portion corresponding to the brush reduction portion 234 can be inserted into the area within the holder reduction portion 247 in the radial direction. Further, a lead wire 32 is connected to a portion corresponding to this brush reduction portion 234 in the radial direction. Since the contact area of the brush 230 with the commutator 24 is small at the portion corresponding to the brush reduction portion 234, the portion where the brush reduction portion 234 is provided is not included in the effective length of the brush 230. By connecting the lead wire 32 at a dead portion that is not included in the effective length, the dead portion can be effectively utilized. Thereby, the effective length of the brush 230 can be increased.

The sliding surface of the commutator 24 with the brush 230 is provided with an uneven shape 24A parallel to the sliding direction of the brush 230. Thereby, the brush 230 and the commutator 24 are brought into a state of engagement with the uneven shape 24A, and it is possible to suppress the brush 230 from wobbling during sliding. Therefore, even if the brush 230 is provided with the brush reduction portion 234 and the range in which the brush holder 240 and the brush 230 face each other in the radial direction is shortened, excessive wear of the brush 230 can be suppressed.

<Example of change>
The second embodiment may be modified and implemented as follows. Note that the following configurations may be applied individually to the configuration of the second embodiment, or may be applied in any combination.

- FIG. 12 is a sectional view of a brush and a brush holder in a modified example. In this brush holder, the holder reduction portion 247 is formed obliquely from the rotor 22 side to the spring housing portion 46 side. In this case, the transition portion 252 overlaps the holder reduction portion 247 in the radial and axial directions. Thereby, the amount L1 of protrusion of the transition portion 252 from the brush holder 240 can be suppressed. Further, when the holder reduction portion 247 is formed diagonally, the brush reduction portion 234 may also be formed diagonally in accordance with the shape of the holder reduction portion 247.

- The board thickness of the transition part 252 may be thicker than the board thickness of the intermediate part 51. Since the plate thickness of the transition part 252 is thicker than the plate thickness of the intermediate part 51, it becomes easier to ensure the cross-sectional area of the transition part 252 in the current supply direction. Thereby, the dimension in which the transition portion 252 protrudes from the brush holder 240 toward the rotor 22 can be reduced. Therefore, it is possible to further reduce the size while ensuring the necessary cross-sectional area of the current-carrying path.

<Third embodiment>
In the third embodiment, as shown in FIG. 13, the first embodiment and the second embodiment are partially modified. In the third embodiment, a configuration is provided for appropriately discharging water that has entered the brush holder 340. FIG. 13 is a cross-sectional view of a portion of the brush assembly A2 in the third embodiment. In the following description, the radially inner side (commutator 24 side) of the brush holder 340 will be referred to as the front, and the radially outer side (the side opposite to the commutator 24) will be referred to as the rear. Further, the configuration for drainage of the third embodiment may be combined with the first embodiment and the second embodiment.

The brush assembly A2 of the third embodiment includes positive and negative brushes 30, a brush holder 340 that accommodates the brushes 30, a positive plate 50, and a negative plate 70 facing the positive plate 50. , and a power supply line 60 joined to the positive electrode side plate 50. The brush assembly A2 is housed in a housing 80. The brush holder 340 is almost the same as the brush holder 40 of the first embodiment except for the points explained below, and the coil spring 345 is explained below as the coil spring 45 of the first embodiment and the second embodiment. They are almost the same except for this point. In the following description, only points that are different from the first embodiment and the second embodiment and points that are not explained in detail in the first embodiment will be explained.

The housing 80 has a cylindrical shape with a bottom, and includes a cylindrical portion 81 and a bottom portion 82 that covers an axial end portion of the DC motor 20 (see FIG. 1). The inner circumferential surface 81A of the cylindrical portion 81 faces the holder rear end portion 348 of the brush holder 340 (the wall portion of the brush holder 340 on the opposite side of the commutator 24). Note that the housing 80 and the yoke 23 may be integrated, or the yoke 23 may extend to the brush assembly A2 and have a cylindrical portion.

The brush 30 is housed in the brush housing portion 42 of the brush holder 340, and a coil spring 345, which is a biasing member that biases the brush 30 toward the commutator 24, is housed on the rear side. The coil spring 345 is a compression spring formed by spirally winding a wire rod, and presses the rear end surface 31B of the brush 30. The inner diameter of the coil spring 345 is the same as or smaller than the circumferential dimension of the brush 30. Note that instead of the coil spring 345, an elastic member such as an annular rubber member having elasticity in the radial direction or a disc spring may be used as the biasing member.

The radial dimension (dimension in the wear direction) of the brush 30 housed in the brush holder 340 is preferably long in order to extend the life of the brush 30. The radial dimensions of the brush 30 are determined by the inner diameter of the cylindrical portion 81 of the housing 80, the outer diameter of the commutator 24, the wall thickness of the holder rear end 348, the dimensions of the coil spring 345, and the facing surface 348A of the brush holder 340. and the dimension between the inner circumferential surface 81A of the cylindrical portion 81. Generally, the opposing surface of the brush holder (the outer surface of the rear end of the holder facing the housing) is a flat surface, so the circumferential end of the brush holder comes into contact with the inner peripheral surface 81A of the housing 80. A space (dead space) is formed between the brush holder and the inner peripheral surface 81A of the cylindrical portion 81.

Therefore, in order to reduce the dead space between the brush holder and the inner circumferential surface 81A of the cylindrical portion 81, the opposing surface of the rear end of the brush holder is aligned in the radial direction along the inner circumferential surface 81A of the cylindrical portion 81. It is conceivable to extend it outward in a convex shape. That is, it is conceivable that the opposing surface of the rear end of the holder be a curved surface along the inner circumferential surface 81A of the cylindrical portion 81. As a result, the coil spring 345 can be moved closer to the cylindrical portion 81 than when the rear end of the holder is flat.

However, if the entire rear end portion of the holder is made into a convex portion extending along the inner circumferential surface 81A, the drainage performance of the through hole provided at the rear end portion of the holder will be impaired. If drainage from the rear end of the holder is impaired, the coil spring 345 and the like may deteriorate due to rust or the like due to water that has entered the brush holder.

Therefore, in this embodiment, the holder rear end portion 348 of the brush holder 340 has a convex portion 348B and a separating portion 348C provided between the convex portions 348B on both sides in the circumferential direction. The holder rear end portion 348 has a uniform wall thickness over its entire circumferential length, and the inner surface of the holder rear end portion 348 is also formed in shape along the shape of the opposing surface 348A. Note that the inner surface of the holder rear end portion 348 may be an inclined surface that slopes toward a through hole 349, which will be described later.

The convex portions 348B are provided at both ends of the holder rear end portion 348 in the circumferential direction, and the opposing surfaces 348A extend radially outward along the inner circumferential surface 81A of the cylindrical portion 81. Specifically, the convex portion 348B protrudes rearward (toward the cylindrical portion 81 side) from the rear end position of the circumferential side wall of the brush holder 340. As a result, the position where the coil spring 345 is disposed is moved closer to the cylindrical portion 81 side. Therefore, the coil spring 345 can be disposed on the outside in the radial direction, and the distance in the wear direction of the brush 30 can be increased. At this time, the coil spring 345 may be in contact with the convex portion 348B of the holder rear end portion 348, or may be in contact with the separating portion 348C.

Note that the convex portion 348B may be in contact with the inner peripheral surface 81A of the cylindrical portion 81. Since the convex portion 348B follows the shape of the inner circumferential surface 81A, the convex portion 348B can make surface contact with the inner circumferential surface 81A. Thereby, the compression reaction force of the coil spring 345 can also be received by the cylindrical portion 81 via the brush holder 340. Therefore, the wall thickness of the brush holder 340 at the position where the coil spring 345 comes into contact can be made thinner.

The spacing portion 348C is provided between the convex portions 348B on both circumferential sides of the holder rear end portion 348 so that the opposing surface 348A is spaced further from the inner circumferential surface 81A than the convex portion 348B. The opposing surface 348A in the spacing portion 348C is a flat surface, and the center side of the surface in the circumferential direction is further away from the inner peripheral surface 81A. A through hole 349 passing through the inside and outside of the brush holder 340 is provided in the separating portion 348C. The through hole 349 is provided at the center in the circumferential direction of the spacing portion 348C. Therefore, water that has entered the brush holder 340 can be discharged into the space provided between the opposing surface 348A and the inner peripheral surface 81A.

Further, the through hole 349 is provided at a position inside the coil spring 345 as a hole smaller than the inner diameter of the coil spring 345. As a result, the holder rear end portion 348 is arranged between the coil spring 345 and the cylindrical portion 81 without overlapping the positions of the through hole 349 and the coil spring 345. In other words, it is possible to prevent the coil spring 345 from coming into contact with the housing 80 through the through hole 349 while ensuring good drainage performance in the brush holder 340 . In this case, a sufficient creepage distance between the coil spring 345 and the cylindrical portion 81 can be ensured. Note that it is desirable that the through hole 349 be made as large as possible within the range of the inner diameter of the coil spring 345.

According to this embodiment described in detail above, the following actions and effects can be obtained.

In this embodiment, the holder rear end portion 348 is provided with a spacing portion 348C between the convex portions 348B on both sides in the circumferential direction, in which the opposing surface 348A is further away from the inner circumferential surface 81A of the cylindrical portion 81 than the convex portion 348B. A through hole 349 passing through the inside and outside of the brush holder 340 is provided in this spaced portion 348C. Thereby, water that has entered the brush holder 340 can be suitably discharged from the through hole 349 provided in the separation part 348C.

In the holder rear end portion 348 , a through hole 349 is provided at a position inside the coil spring 345 as a hole smaller than the inner diameter of the coil spring 345 . Thereby, while improving drainage performance in the brush holder 340, contact between the coil spring 345 and the housing 80 via the through hole 349 can be suppressed. In this case, since a long creepage distance can be ensured between the coil spring 345 and the housing 80, short circuits between the brush 30 and the housing 80 via the coil spring 345 can be suppressed.

Since the convex portion 348B of the holder rear end portion 348 comes into contact with the inner circumferential surface 81A of the cylindrical portion 81, the compression reaction force of the coil spring 345 can also be received by the housing 80 via the brush holder 340. Thereby, the strength required at the position where the coil spring 345 of the brush holder 340 contacts can be reduced, and the wall thickness of the brush holder 340 at the position where the coil spring 345 contacts can be reduced. Therefore, the distance in the wear direction of the brush 30 can be increased, and the life of the brush 30 can be extended.

<Example of change>
The third embodiment may be modified and implemented as follows. Note that the following configurations may be applied individually to the configuration of the third embodiment, or may be applied in any combination.

- Like the first embodiment and the second embodiment, the coil spring 345 may be larger than the width of the brush 30 in the circumferential direction. In this case, the coil spring 345 is in contact with the inner surface of the convex portion 348B. The position of the coil spring 345 is slightly shifted toward the cylindrical portion 81 side by the convex portion 348B. Furthermore, it is desirable that the separating portion 348C be as large as possible inside the contact position of the coil spring 345. By increasing the size of the separating portion 348C, the space between the inner peripheral surface 81A of the cylindrical portion 81 and the inner circumferential surface 81A can be increased.

- As shown in FIG. 14, a thin wall portion 348D is further provided at a position around the through hole 349 in the spaced apart portion 348C of the rear end portion 348 of the holder. It's okay. The thin portion 348D is recessed so that the side facing the inner circumferential surface 81A of the cylindrical portion 81 (opposing surface 348A) is spaced apart from the inner circumferential surface 81A of the cylindrical portion 81. Further, the thin portion 348D is provided at a position inside the coil spring 345, that is, inside a portion where the coil spring 345 contacts the holder rear end portion 348. Thereby, in the holder rear end portion 348, the abutting portion of the coil spring 345 is made thick to ensure strength, and the thin portion 348D is provided on the inner side, thereby improving drainage performance.

- As shown in FIG. 15, the cylindrical portion 81 surrounding each brush holder 340 is preferably formed in a tapered shape. More specifically, the inner circumferential surface 81A of the cylindrical portion 81 of the housing 80 may be formed in a tapered shape such that the diameter increases on the rotor 22 side. This inner circumferential surface 81A may have a tapered shape having an angle comparable to a so-called draft angle. As a result, as shown by the broken line arrow in FIG. 15, water discharged from the through hole 349 flows toward the rotor 22 (in the axial direction) along the slope of the inner circumferential surface 81A. Thereby, it is possible to suppress the discharged water from staying inside the housing 80, more specifically, between the housing 80 and the brush holder 340.

The through hole 349 is provided on the side where the diameter of the cylindrical portion 81 is expanded in the axial direction, that is, on the rotor 22 side. Specifically, a through hole 349 is provided outside the coil spring 345 and at a position closest to the rotor 22 in the axial direction. This increases the distance between the through hole 349 and the inner circumferential surface 81A of the cylindrical portion 81. Therefore, drainage performance can be improved. Note that it may be provided within the inner range of the coil spring 345 at a position closer to the rotor 22 than the center in the axial direction.

20... DC motor, 22... Rotor, 24... Commutator, 30... Brush, 80... Housing, 81... Cylindrical part, 81A... Inner peripheral surface, 340... Brush holder, 345... Coil spring, 348... Rear end part, 348A ...Opposing surface, 348B...Convex portion, 348C...Separated portion, 348D...Thin wall portion, 349...Through hole.

Claims (6)

a commutator (24) provided coaxially with the rotor (22);
brushes (30) on the positive and negative electrode sides that are provided so as to be able to come into contact with the commutator;
a brush holder (340) that accommodates and holds each of the brushes;
a biasing member (345) disposed within the brush holder between the holder rear end (348) on the side opposite to the commutator and the brush, and biasing the brush toward the commutator;
A housing (80) having a cylindrical part (81) and accommodating the brush holder with the rear end of the holder facing the inner peripheral surface (81A),
The rear end portion of the holder includes a convex portion (348B) in which a surface (348A) facing the inner circumferential surface of the cylindrical portion extends convexly outward in the radial direction along the inner circumferential surface of the cylindrical portion; between the convex portions on both sides, the opposing surface has a spacing portion (348C) provided farther from the inner circumferential surface of the cylindrical portion than the convex portion;
A DC motor in which a through hole (349) penetrating inside and outside of the brush holder is provided in the spaced apart portion of the rear end of the holder. The biasing member is a coil spring,
2. The DC motor according to claim 1, wherein the through hole is provided at a position inside the coil spring in the separated portion of the rear end of the holder and has a diameter smaller than the inner diameter of the coil spring. In the spaced apart portion of the rear end of the holder, a thin wall portion (348D) that is recessed toward the brush side is provided at a position that is inside the coil spring and around the through hole. The DC motor according to claim 2, wherein: The DC motor according to any one of claims 1 to 3, wherein the cylindrical portion is formed in a tapered shape whose diameter increases toward one side in the axial direction of the motor. 5. The DC motor according to claim 4, wherein the through hole is provided in the rear end portion of the holder on the side where the diameter of the cylindrical portion is enlarged in the motor axial direction. The DC motor according to any one of claims 1 to 5, wherein the convex portion of the rear end portion is in contact with an inner circumferential surface of the cylindrical portion.

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