JP2021118553A - DC motor - Google Patents

Abstract

To provide a DC motor comprising an appropriate electrification cutoff function.SOLUTION: A DC motor comprises: a commutator 24 provided coaxially with a rotor 22; positive electrode side and negative electrode side brushes 30 provided in a contactable manner with the commutator 24; an annular positive electrode side plate 50 in which the positive electrode side and negative electrode side brushes 30 are disposed at predetermined intervals in a circumferential direction and to which a lead wire 32 extending from a positive electrode side brush 30A is joined. A bent part 54 which is bent in a direction across an electrification path is provided in the positive electrode side plate 50, and the bent corner part 54 of a crossover part 52 becomes a fusible part 57 which is fused with occurrence of overcurrent.SELECTED DRAWING: Figure 2

Description

The present invention relates to a DC motor used for 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 circumference of the cylindrical commutator. A plate-shaped connecting member is used to supply power to the brush on the positive side. For example, Patent Document 1 discloses a DC motor in which power is supplied to a positive brush by connecting a pigtail provided on the positive brush to a positive plate. Further, in this DC motor, a notch portion in which the cross-sectional area of the plus plate is partially reduced is provided in order to suppress burning when the DC motor is abnormally continuously energized. When an abnormal energization occurs, the notch becomes red and blows, so that the notch functions as a fuse.

German Patent Application Publication No. 102010063688

In the structure of Patent Document 1, since the cross-sectional area of the plus plate is partially reduced at the notch, the path resistance at the notch becomes high. Therefore, there is room for improvement.

The present invention has been made in view of the above problems, and a main object thereof is to provide a DC motor having an appropriate power cutoff function.

In the first means, a commutator provided coaxially with the rotor and
Brushes on the positive electrode side and the negative electrode side provided so as to be in contact with the commutator,
The brushes on the positive electrode side and the negative electrode side are arranged at predetermined intervals in the circumferential direction, and an annular positive electrode side plate to which the lead wires extending from the brushes on the positive electrode side are joined is provided.
The positive electrode side plate is provided with a bent portion that is bent in a direction that crosses the current-carrying path.
The bent corner portion of the bent portion is a fusing portion that is fusing when an overcurrent is generated.

A lead wire extending from the brush is joined to the annular positive electrode side plate, and power is supplied to the positive electrode side brush via the positive electrode side plate. The positive electrode side plate is provided with a bent portion that is bent in a direction crossing the current-carrying path of the positive electrode side plate. For example, when a bent portion is formed by press working, residual stress is generated at a bent corner portion of the bent portion. In the positive electrode side plate, when an overcurrent flows, the bent corner portion is blown faster than other places due to residual stress. That is, the bent corner portion is a fusing portion that is fusing when an overcurrent is generated. Since the fusing part is formed by bending, the path cross-sectional area at the fusing part is larger than when the fusing part is formed by a notch or the like, and the path resistance of the positive electrode side plate during normal energization can be reduced. can. Therefore, it is possible to impart a desired route blocking function while appropriately performing energization during normal energization.

In the second means, a brush holder for holding each of the brushes is provided, and the positive electrode side plate has an intermediate portion interposed between the brush holders arranged in the circumferential direction and the intermediate portion in the circumferential direction. The crossover portion is formed by bending from the intermediate portion in the motor axial direction, and is provided as the bent portion.

The positive electrode side plate has an intermediate portion interposed between the brush holders arranged in the circumferential direction, and a crossover portion connecting the intermediate portions. In the configuration in which the crossover avoids the brush holder, the crossover is formed by bending from the intermediate portion in the motor axial direction, so that the positive electrode side plate is suppressed from becoming large in the radial direction. This crossover portion is used as a bent portion, and the bent corner portion obtained by bending the crossover portion from the intermediate portion is used as a fusing portion. As a result, it is possible to use the bent portion for miniaturization to form a fusing portion that cuts off the energization path. Therefore, it is possible to provide a desired route blocking function while reducing the size.

In the third means, the bending angle of the bent portion is 90 degrees or less.

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

In the fourth means, a power supply line for supplying power to the brush on the positive electrode side is joined to the positive electrode side plate at a power line joint portion, and the positive electrode side plate is joined to the power line joint portion. The fusing portion is provided between the lead wire of the brush on the positive electrode side adjacent to the power line joint in the circumferential direction and the lead joint of the brush.

A power supply line for supplying power to the brush on the positive electrode side is joined to the positive electrode side plate at a power line joint portion. In the positive electrode side plate, a fusing portion is provided between the power line joint portion and the lead joint portion to which the lead wire of the brush on the positive electrode side adjacent to the power line joint portion in the circumferential direction is joined. As a result, the positive electrode side plate is blown between the power line joint portion and the lead joint portion of the positive electrode side brush adjacent to the power supply line due to the occurrence of the overcurrent. Therefore, it is possible to cut off the energization of all the brushes on the positive electrode side.

In the fifth means, a power supply line for supplying power to the brush on the positive electrode side is joined to the positive electrode side plate at a power line joining portion, and the positive electrode side plate is connected to the positive electrode side plate for each brush. A bent portion is provided, and the bent corner portion of the bent portion adjacent to the power line joint portion in the circumferential direction is the fusing portion.

A power supply line for supplying power to the brush on the positive electrode side is joined to the positive electrode side plate at a power line joint portion. A bent portion is provided for each brush on the positive electrode side plate, and the positive electrode side plate is blown at a bent corner portion of the bent portion adjacent to the power line joint in the circumferential direction. This makes it possible to minimize the range of the positive electrode side plate to which power is supplied from the power supply line after fusing. Therefore, it is possible to prevent the positive electrode side plate on the power line joint side after fusing from coming into contact with other members and causing a short circuit or the like.

In the sixth means, the positive electrode side plate is provided with a plurality of the bent portions, and the plurality of bent portions have the same width as the first bent portion having a small width dimension of the bent corner portion. It includes a large second bent portion, of which the bent corner portion of the first bent portion is the fusing portion.

In the positive electrode side plate, of the plurality of bent portions, the bent corner portion of the first bent portion having a small width dimension of the bent corner portion, that is, a small cross-sectional area of the bent corner portion was used as a fusing portion. As a result, even if a plurality of bent portions are bent and formed on the positive electrode side plate, the path resistance at a specific bent corner portion (fusing portion) becomes higher than the path resistance at the other bending corner portions, and the fusing portion It is possible to appropriately block the route of. Further, the bent corner portion of the first bent portion is a portion that functions as a fusing portion by bending and narrowing the cross section, and has a cross-sectional area as compared with the conventional configuration in which the fusing portion is provided by narrowing the cross section without being bent. The degree of narrowing can be reduced. Therefore, it is possible to impart a desired route blocking function to a predetermined position while appropriately performing energization during normal energization.

In the seventh means, a commutator provided coaxially with the rotor and
Brushes on the positive electrode side and the negative electrode side provided so as to be in contact with the commutator,
An annular positive electrode side plate in which the positive electrode side and negative electrode side brushes are arranged at predetermined intervals in the circumferential direction and lead wires extending from the positive electrode side brushes are joined.
A negative electrode side plate which is arranged at a position facing the positive electrode side plate so as to sandwich the brush between the positive electrode side plate and to which a lead wire extending from the brush on the negative electrode side is joined.
It is provided with a power supply line that is joined to the positive electrode side plate and supplies power to the brush on the positive electrode side.
Among the brushes, in the brush located next to the power line joining portion to which the power supply line is joined in the positive electrode side plate and on the positive electrode side, the lead wire sandwiches the brush with the power line joining portion. It is pulled out to the opposite side in the circumferential direction,
In the positive electrode side plate, fusing is performed between the power line joint and the lead joint of the brush on the positive electrode side which is adjacent to the power line joint in the circumferential direction in the circumferential direction due to the generation of an overcurrent. A part is provided.

A power supply line for supplying power to the brush on the positive electrode side is joined to the positive electrode side plate at a power line joint portion. In order to cut off the power supply to all the positive electrode side brushes when the positive electrode side plate is blown, in the positive electrode side plate, the power line joint and the positive electrode side brush adjacent to the power line joint in the circumferential direction are used. It is desirable to provide a fusing portion between the lead wire and the lead joint. However, in this case, if the lead wire of the brush on the positive electrode side is joined on the power line joint side in the positive electrode side plate, it is difficult to provide a fusing part between the lead joint portion and the power line joint portion. become.

Therefore, in the brush located next to the power line joint and on the positive electrode side, the lead wire is pulled out to the opposite side in the circumferential direction with the brush sandwiched from the power line joint. As a result, the fusing portion can be provided at a desired position in the vicinity of the power line joint portion on the positive electrode side plate. Therefore, it is possible to optimize the fusing position of the positive electrode side plate and cut off the energization of all the positive electrode side brushes while reducing the size.

In the eighth means, the fusing portion is provided between the power line joint portion and the brush adjacent to the power line joint portion in the circumferential direction in the positive electrode side plate.

When an overcurrent occurs, the brush next to the power line joint and the power line joint are blown, thereby minimizing the range of the positive electrode side plate to which power is supplied from the power supply line after the blow. be able to. Therefore, it is possible to prevent the positive electrode side plate on the power line joint side after fusing from coming into contact with other members and causing a short circuit or the like.

In the ninth means, the lead wires are drawn out from the brushes on the positive electrode side and the negative electrode side in the same direction in the circumferential direction between the positive electrode side plate and the negative electrode side plate, respectively, and are arranged in the circumferential direction. The lead wire extending from the brush on the negative electrode side is drawn out from the space between the brushes where the power supply wire is arranged, and is insulated between the lead wire and the power supply wire. Members are provided.

In the configuration in which the lead wires are drawn out from the brushes on the positive electrode side and the negative electrode side in the same circumferential direction between the positive electrode side plate and the negative electrode side plate, interference between the lead wires extending from each brush can be suppressed. However, as described above, the lead wire extending from the brush on the positive electrode side is pulled out to the opposite side (opposite side of the power supply line) of the power line joint in the circumferential direction, and the lead wire extending from the brush on the negative electrode side is on the side of the power supply line. In the drawn configuration, the lead wire of the brush on the negative electrode side and the power supply wire may come into contact with each other. Therefore, in the space where the power supply line is arranged among the spaces between the brushes arranged in the circumferential direction, an insulating member is provided between the lead wire of the brush on the negative electrode side and the power supply line. As a result, contact between the power supply wire and the lead wire of the brush on the negative electrode side can be suppressed without providing a space in the motor axial direction for avoiding contact between the lead wire of the brush on the negative electrode side and the lead wire of the power supply wire. The DC motor can be miniaturized in the axial direction of the motor.

Schematic configuration 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 the positive electrode side plate Top view of brush assembly Front view of the brush assembly in the modified example Front view of the brush assembly in the modified example Top view of the brush assembly in the modified example Partially enlarged cross-sectional view of the brush assembly in the second embodiment Cross section of brush and brush holder Cross-sectional view of the brush and brush holder in the modified example A cross-sectional view of a part of the brush assembly according to the third embodiment. Cross-sectional view of a part of the brush assembly in the modified example Vertical section of a part of the brush assembly in the modified example

<First Embodiment>
Hereinafter, a configuration embodied as a DC motor used for a starter for starting an engine will be described with reference to the drawings. In each of the following embodiments, parts that are the same or equal to each other are designated by the same reference numerals in the drawings, and the description thereof will be incorporated for the parts having the same reference numerals.

FIG. 1 is a schematic configuration diagram of the starter 10. The starter 10 includes a DC motor 20, a reduction unit 12 that decelerates the rotation of the DC motor 20 and transmits it to the pinion gear 11, and a magnet switch 13 that serves as a switch for supplying electric power to the DC motor 20. The speed reduction unit 12 is composed of, for example, a planetary gear mechanism or the like.

The magnet switch 13 is a switch for an energizing circuit between the 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 energizing circuit between the battery outside the starter 10 and the DC motor 20 is closed by the magnet switch 13, 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 reduction gear 12 and the one-way clutch 15. When the IG switch is turned on, the magnet switch 13 causes the shift lever 14 to push the pinion gear 11 to the opposite side of the DC motor 20, and the ring gear of the engine and the pinion gear 11 mesh with each other. When the IG switch is turned on in this way, the starter 10 rotates the ring gear of the engine.

The DC motor 20 is, for example, a magnet field type, and has a magnet 21, a rotor 22 rotatably arranged on the inner circumference of the magnet 21, a commutator 24 provided coaxially with the rotor 22, and a commutator 24. It is provided with a brush 30 arranged on the outer periphery of the magnet. In the following description, the direction in which the rotary shaft 20A of the DC motor 20 extends is the axial direction (motor axial direction), the direction extending radially from the center of the rotary shaft 20A is the radial direction, and the circle is centered on the rotary shaft 20A. The direction extending in a circumferential shape is the circumferential direction.

A yoke 23 is provided on the outer circumference 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 bottomed cylindrical housing 80. The yoke 23 and the housing 80 are combined to form a motor case for the DC motor 20. A field coil may be used instead of the magnet 21.

The brush assembly A includes a brush 30 on the positive electrode side and a negative electrode side, a brush holder 40 for accommodating the brush 30, a positive electrode side plate 50, a negative electrode side plate 70 facing the positive electrode side plate 50, and a positive electrode side plate 50. It includes a power supply line 60 to be joined. The brush assembly A is provided with the positive electrode side plate 50 facing the rotor 22 side in the motor axial direction and the negative electrode side plate 70 facing the opposite side to the rotor 22.

FIG. 2 is a perspective view of the brush assembly A viewed from the positive electrode side plate 50 side, and FIG. 3 is a perspective view of the brush assembly A viewed from the negative electrode side plate 70 side. In the brush assembly A, three brushes 30 on the positive electrode side and three brushes on the negative electrode side are arranged alternately in the circumferential direction and 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, the positive electrode side brush 30A and the negative electrode side brush 30B will be described. Further, the number of brushes 30 may be a plurality of each on the positive electrode side and the negative electrode side, and the numbers of the positive electrode side brush 30A and the negative electrode side brush 30B may be different.

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

The brush 30 can come into contact with the sliding surface of the commutator 24, and the 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 surface of the brush 30 in the circumferential direction. The lead wire 32 is connected to an end portion of the brush 30 opposite to the contact surface 31A in contact with the commutator 24. The end of the connection 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) That is, the brush 30 can be worn up to the connection portion 32A of the lead wire 32. Further, the coil spring 45 is in contact with the rear end surface 31B on the side opposite to the contact surface 31A of the brush 30 (see FIG. 10). The brush 30 is provided with a positioning portion 33 that projects rearward from the rear end surface 31B of the brush 30 to position the coil spring 45.

The lead wire 32 is an electric wire called a pigtail that is bundled by knitting a conductive copper wire or the like, and has flexibility. 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 electrode side plate 50 or the negative electrode side plate 70 by welding or the like. That is, the lead wire 32 is mechanically fixed to each of the plates 50 and 70 and is electrically connected.

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

In the brush holder 40, a spring accommodating portion 46 accommodating the coil spring 45 is provided on the radial side (opposite side of the commutator 24) of the brush accommodating portion 42. The spring accommodating portion 46 has a cylindrical shape that partially bulges outward along the outer shape of the coil spring 45. Further, the side wall in the circumferential direction 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 so that the lead wire 32 can be pulled out. Since the opening 41 is formed so as to extend in the radial direction, the brush 30 can be moved in the radial direction while the lead wire 32 is pulled out. The opening 41 may be provided only on one side wall in the circumferential direction on the side where the lead wire 32 is drawn out.

Further, the brush accommodating portion 42 of the brush holder 40 projects toward the rotor 22 side with respect to the positive electrode side plate 50. Further, a part of the brush 30 is housed in a portion of the brush housing part 42 that protrudes from the positive electrode side plate 50. That is, the brush 30 and the positive electrode side plate 50 partially overlap in the axial direction. Further, the brush holder 40 and the positive electrode side plate 50 are positioned with each other in the axial direction, the circumferential direction, and the radial direction.

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

Further, the positive electrode side plate 50 and the negative electrode side plate 70 are formed of a conductive metal plate having a predetermined plate thickness, and have an annular shape provided with a round hole through which the commutator 24 can be inserted in the central portion in the radial direction. It has become. The positive electrode side plate 50 and the negative electrode side plate 70 are arranged so as to be parallel to each other in the axial direction. The brush 30 and the brush holder 40 are held in a state of being sandwiched 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. The negative electrode side plate 70 and the brush holder 40 are positioned by fitting the positioning convex portion 43 into the slit 71. Further, a plurality of bolt insertion holes 72 are formed in the negative electrode side plate 70. The negative electrode side plate 70 is fixed to the housing 80 by the bolt B inserted through the bolt insertion hole 72 (see FIG. 1). Further, the negative electrode side plate 70 is electrically connected to the housing 80 via the bolt B. As a result, 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 plate-shaped intermediate portion 51 interposed between the brush holders 40 arranged in the circumferential direction, and a crossover portion 52 connecting the intermediate portions 51 to each other. 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. Further, between the intermediate portion 51 and the intermediate portion 51, there is a fitting groove 53 in which the brush accommodating portion 42 of the brush holder 40 is arranged. The fitting groove 53 is open on both sides in the radial direction on the same plane as the intermediate portion 51.

The crossover 52 connects the intermediate portions 51 arranged on both sides of the fitting groove 53 in the circumferential direction. The crossover portion 52 is formed by bending a portion formed so as to wrap around the brush accommodating portion 42 radially outward in the axial direction. That is, the crossover portion 52 is formed as a bent portion that is bent in a direction that crosses the current-carrying path. The crossing portions 52 are arranged on both sides of the fitting groove 53 in the circumferential direction, and the corner portions bent from the intermediate portion 51 are bent corner portions 54, respectively. The crossover 52 is formed so as to avoid the brush holder 40.

The crossover portion 52 is formed by bending at a predetermined bending radius at 90 degrees from the intermediate portion 51, and extends in the axial direction. The crossover 52 extends in the axial direction while maintaining a predetermined distance from the housing 80 and the rotor 22. The bending angle between the crossover portion 52 and the intermediate portion 51 is preferably 90 degrees or less. The bending angle is the angle between the intermediate portion 51 and the crossover portion 52, and the smaller the bending angle, the larger the residual stress. Further, the smaller the bending radius between the intermediate portion 51 and the crossover portion 52, the larger the residual stress, which is desirable. The bending radius is arbitrary as long as it causes residual stress in the bending angle portion 54, and specifically, it is desirable that the bending radius is smaller than, for example, three times the plate thickness of the positive electrode side plate 50. Further, the bending radius is preferably set based on the minimum radius at which the material is not cracked by bending, and is preferably larger than one-fourth of the plate 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 joined to the positive electrode side plate 50 at a power line joining portion 55. Further, the lead wire 32 of the positive electrode side brush 30A is joined to the positive electrode side plate 50 at the lead joining portion 56. The power line joining portion 55 and the lead joining portion 56 are provided on the facing surface of the positive electrode side plate 50 facing the negative electrode side plate 70. Since the lead wire 32 is joined to the surface of the positive electrode side plate 50 facing the negative electrode side plate 70, it is possible to prevent the lead wire 32 from becoming long. Further, when the power supply line 60 and the lead wire 32 are welded, the power line joint portion 55 and the lead wire joint portion 56 are provided on the same plane, and all the welding processes can be performed at the same time, so that the productivity is high. Become.

Further, the power line joining portion 55 is provided in the intermediate portion 51 of the plurality of intermediate portions 51 of the positive electrode side plate 50, which is not provided with the lead joining portion 56 to which the lead wire 32 of the positive electrode side brush 30A is joined. .. The intermediate portion 51 provided with the power line joining portion 55 is provided with a protruding piece 51B protruding outward in the radial direction to secure 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 electrode side plate 50 to supply electric power to the positive electrode side plate 50.

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

By the way, when an abnormal continuous energization of the DC motor 20 or an overcurrent flows, it is necessary to stop the power supply to the rotor 22 in order to suppress the burning of the coil of the rotor 22. Therefore, the positive electrode side plate 50 is provided with a path blocking function. Specifically, the power supply to the positive electrode side brush 30A is cut off by fusing a part of the positive electrode side plate 50.

When the positive electrode side plate 50 is blown, it is desirable that the positive electrode side plate 50 is blown at a position where the power supply to all the positive electrode side brushes 30A in the positive electrode side plate 50 can be cut off. Specifically, the power line joint 55 is formed between the lead joint 56 of the positive electrode side brush 30A adjacent to the power line joint 55 in the circumferential direction of the positive electrode side plate 50 and the power line joint 55, that is, on the energization path. It is desirable that the positive electrode side plate 50 is blown between the lead joint portion 56 adjacent to each other in the circumferential direction and the power line joint portion 55. However, if the lead joint of the positive electrode side 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 electrode side brush 30A, the lead joint will be peripheral. It is not possible to secure a space for providing the fusing portion because it is close to the power line joint portion 55 in the direction. Therefore, in order to fusing the positive electrode side plate 50 between the power line joint 55 and the lead joint 56, the distance between the power line joint 55 and the lead joint 56 in the circumferential direction (a space for providing the fusing portion). ) Need to be secured.

FIG. 6 is a plan view of the brush assembly A as viewed from the positive electrode side plate 50 side. As shown in FIGS. 2 and 6, the brushes 30A and 30B on the positive electrode side and the negative electrode side are alternately arranged 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 on the positive electrode side and the lead wire 32 on the negative electrode side are drawn between the brush holders 40 arranged in the circumferential direction. The lines 32 are arranged so as to alternate with each other.

In the positive electrode side plate 50, each intermediate portion 51 is provided in a state of being sandwiched between a brush holder 40 accommodating the positive electrode side brush 30A and a brush holder 40 accommodating the negative electrode side brush 30B, and one of them is intermediate. A power supply line 60 is joined to the portion 51, and the joint portion is 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 the “intermediate portion 51A”.

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

Then, 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 bending angle portion 54 of the crossover portion 52 connected to the intermediate portion 51A, that is, the crossover portion 54 on the side of the positive electrode side brush 30A in the circumferential direction and the side of the negative electrode side brush 30B. The bent corner portion 54 of the portion 52 is used as a fusing portion 57. A plurality of crossover portions 52 are provided in the circumferential direction, and among the plurality of crossover portions 52, the bent corner portion 54 of the crossover portion 52 connected to the intermediate portion 51A is used as the fusing portion 57.

Each crossover 52 has two bending corners 54, but in the crossover 52 connected to the intermediate 51A, the bending corner 54 on the intermediate 51A side may be the fusing portion 57. However, in the crossover portion 52 connected to the intermediate portion 51A, both directions of the two bending corner portions 54 are set as the fusing portions 57, or the bending corner portion of the two bending corner portions 54 on the opposite side to the intermediate portion 51A. The configuration may be such that 54 is a fusing portion 57.

The fusing portion 57 is provided at each of the crossover portions 52 on both sides of the intermediate portion 51A provided with the power line joint portion 55. This is because the power path starting from the power line junction 55 is an annular path that energizes in both directions, that is, in two directions, and it is necessary to cut off the 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 crossover portion 52 and the intermediate portion 51. Therefore, the residual stress accelerates the timing of fusing when the temperature of the fusing portion 57 rises. As a result, in the configuration in which the bending angle portion 54 is used as the fusing portion 57, the cross-sectional area of the fusing portion 57 can be made larger than that in the configuration in which the fusing portion has a flat cross-sectional 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 reducing the bending angle to 90 degrees or less or reducing the bending radius. Further, the mechanical strength of the fusing portion 57 can be improved by bending the fusing portion 57. Further, by using the bending corner portion 54 of the crossover portion 52 bent in the axial direction as the fusing portion 57, it is possible to realize miniaturization in the radial direction and a desired path blocking function by the crossover portion 52. ing.

Further, of the plurality of bending angle portions 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 the power is supplied from the power supply line 60 after the positive electrode side plate 50 is fusing. The range of the positive electrode side plate 50 supplied can be minimized. Further, when the position of the fusing portion 57 and the lead joining portion 56 of the positive electrode side brush 30A are separated from each other, the heat generated at the fusing portion 57 is transferred to the positive electrode side brush 30A via the lead wire 32. Can be suppressed. Therefore, it is possible to prevent damage to other parts due to heat generated by the fusing portion 57.

The plurality of crossovers 52 include a first bent portion having a small width dimension of the bent corner portion 54 and a second bent portion having a large width dimension of the bent corner portion 54. The first bent portion is a crossover portion 52 functioning as a fusing portion 57, and the second bent portion is a crossover portion 52 other than that. The bending angle portion 54 of the first bending portion is the fusing portion 57. That is, the cross-sectional area in the direction orthogonal to the energization path of the bending angle portion 54 of the first bending portion is set to be smaller than the cross-sectional area in the direction orthogonal to the energizing path of the bending angle portion 54 of the second bending portion. Therefore, the fusing portion 57 is used. As a result, the path resistance at the bending angle portion 54, which is the fusing portion 57, becomes higher than the path resistance at the other bending angle portions 54. Therefore, when an overcurrent occurs, the temperature at the fusing portion 57 rises, and the positive electrode side plate 50 is fusing at the fusing portion 57. Further, the cross-sectional area of the fusing portion 57 at this time can be made larger than the cross-sectional area when the fusing portion is formed in a planar shape due to the residual stress due to bending. Further, the strength of each bending corner portion 54 is improved by work hardening by bending. As a result, mechanical strength can be ensured even if the width dimension of the fusing portion 57 is reduced.

Further, the lead wire 32 of the negative electrode side brush 30B is pulled out from the space between the brush holders 40 in which the power supply line 60 is arranged, and is joined to the negative electrode side plate 70. As a result, the power line joint 55 and a part 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, the power supply line 60 and the lead wire 32 of the negative electrode side brush 30B may come into contact with each other.

Therefore, as shown in FIGS. 2 and 4, the power line holding member 65 is arranged between the end portion 60A of the power supply line 60 joined to the positive electrode side plate 50 and the lead wire 32 of the negative electrode side brush 30B. The insulating portion 66 is provided. The insulating portion 66 is provided in the power line holding member 65 so as to project 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 electrode side brush 30B can be suppressed without providing an axial distance between the power line joint portion 55 and the lead wire 32 of the negative electrode side brush 30B. The DC motor 20 can be miniaturized in the axial direction. In the present embodiment, the insulating portion 66 is integrally provided with the power line holding member 65, but it is also possible to provide the insulating portion 66 separately from the power line holding member 65.

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

A lead wire 32 extending from the positive electrode side brush 30A is joined to the annular positive electrode side plate 50, and power is supplied to the positive electrode side brush 30A via the positive electrode side plate 50. The positive electrode side plate 50 is provided with a crossover portion 52 bent in a direction crossing the current-carrying path of the positive electrode side plate 50. For example, when the crossover portion 52 is formed by press working, residual stress is generated at the bending angle portion 54 of the crossover portion 52. In the positive electrode side plate 50, when an overcurrent flows, the bent corner portion 54 is blown faster than other places due to this residual stress. As a result, the bending angle portion 54 becomes a fusing portion 57 that is fusing due to the generation of an overcurrent. Since the fusing portion 57 is formed by bending, the path cross-sectional area at the fusing portion 57 is larger than when the fusing portion is formed by a notch or the like, and the path resistance of the positive electrode side plate 50 during normal energization. Can be lowered. Therefore, it is possible to impart a desired route 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 crossover portion 52 connecting the intermediate portions 51 to each other. In the configuration in which the crossover portion 52 avoids the brush holder 40, the crossover portion 52 is formed by being bent in the axial direction from the intermediate portion 51, so that the positive electrode side plate 50 is suppressed from becoming large in the radial direction. The crossover portion 52 is used as a bent portion, and the bent corner portion 54 obtained by bending the crossover portion 52 from the intermediate portion 51 is used as a fusing portion 57. As a result, the fusing portion 57 that cuts off the energization path can be formed by utilizing the bent portion for miniaturization. Therefore, it is possible to provide a desired route blocking function while reducing the size.

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

In the present embodiment, in the brush 30A located next to the power line joint 55 and on the positive electrode side, the lead wire 32 is pulled out to the opposite side in the circumferential direction with the positive electrode side brush 30A sandwiched from the power line joint 55. And said. As a result, the fusing portion 57 can be provided at a desired position in the vicinity of the power line joining portion 55 on the positive electrode side plate 50. Therefore, it is possible to optimize the fusing position of the positive electrode side plate 50 and cut off the energization of all the positive electrode side brushes 30A while trying to reduce the size.

The positive electrode side plate 50 is provided with a crossover portion 52 for each brush 30, and the positive electrode side plate 50 is blown at a bent corner portion 54 adjacent to the power line joint portion 55 in the circumferential direction. That is, the brush 30 adjacent to the power line joint 55 and the power line joint 55 are blown together. As a result, the range of the positive electrode side plate 50 to which power is supplied from the power supply line 60 after the positive electrode side plate 50 is blown can be minimized. Therefore, it is possible to prevent the positive electrode side plate 50 on the power line joint 55 side after fusing from coming into contact with other members and causing a short circuit or the like.

In the fusing portion 57, the residual stress generated by the bending process acts as a force in the direction of separating the crossover portion 52 and the intermediate portion 51. Therefore, the residual stress accelerates the timing of fusing when the temperature of the fusing portion 57 rises. As a result, in the configuration in which the bending angle portion 54 is used as the fusing portion 57, the cross-sectional area of the fusing portion 57 can be made larger than that in the configuration in which the fusing portion has a flat cross-sectional 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 reducing the bending angle to 90 degrees or less or reducing the bending radius. Further, the mechanical strength of the fusing portion 57 can be improved by bending the fusing portion 57. Further, by using the bending corner portion 54 of the crossover portion 52 bent in the axial direction as the fusing portion 57, it is possible to realize miniaturization in the radial direction and a desired path blocking function by the crossover portion 52. ing.

In the present embodiment, an insulating portion 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. It was configured. As a result, the contact between the power supply wire 60 and the lead wire 32 of the negative electrode side brush 30B can be maintained without providing an axial space for avoiding contact between the lead wire 32 of the negative electrode side brush 30B and the power supply wire 60. It can be suppressed and the DC motor 20 can be miniaturized in the axial direction.

<Change example>
The first embodiment may be modified as follows. The following configurations may be applied individually to the configurations of the first embodiment, or may be applied in any combination.

In the positive electrode side plate 50, the width dimension of the bending angle portion 54 of the specific crossing portion 52 is set so that the fusing portion 57 is provided only in the specific crossing portion 52 (first bent portion) among the plurality of crossing portions 52. In addition to or instead of making the crossover portion 52 (second bent portion) smaller than the other crossover portion 52, the bending angle or bending radius of the specific crossover portion 52 may be made larger than the other crossover portion 52.

-The configuration of the crossover 52 of the positive electrode side plate 50 may be changed. FIG. 7 is a front view showing the schematic configuration of the brush assembly A in a plan view, 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 crossover portion 52 formed by bending each brush holder 40 with the plate surface facing the side surface and the upper surface of the brush holder 40. The crossover portion 52 is provided so as to avoid the brush holder 40 by being formed by bending in a convex shape in the axial direction. In this case, the crossover portion 52 has a plurality of bending corner portions 54, and the bending corner portion 54 is used as the fusing portion 57. The bending angle portion 54 of each crossover portion 52 can be adjusted for ease of fusing due to bending by appropriately setting at least one of the radial plate width dimension, the bending angle, and the bending radius. It has become.

-The positive electrode side plate 50 may have a configuration in which a bent portion is formed at a portion other than the crossover portion 52. FIG. 8 is a front view showing the schematic configuration of the brush assembly A in a plan view, 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 the bent corner portion of the bent portion 58 is a fusing portion 59.

FIG. 9 is a plan view of the brush assembly A1 in the 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 the 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 on the power line joint 55 side in a state where the power line joint 55 and the lead joint 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, the insulating portion 66 is provided.

The positive electrode side plate 150 has a flat plate-shaped intermediate portion 151 interposed between the brush holders 40 and a crossover portion 152 connecting the intermediate portions 151 to each other. The crossover portion 152 is formed so as to wrap around the radially outer side of the brush accommodating portion 42, and both sides in the circumferential direction are connected to the intermediate portion 151. The crossover 152 is formed so as to avoid the brush holder 40.

In the positive electrode side plate 150, a fusing portion 157 is provided between the lead joint portion 56 of the positive electrode side brush 30A adjacent to the power line joint portion 55 in the circumferential direction and the power line joint portion 55. More specifically, a fusing portion 157 is provided between the brush 30 and the brushes 30A and 30B adjacent to the brush 30 in the circumferential direction. The fusing portion 157 is provided with two slits from the outer peripheral side of the positive electrode side plate 150 toward the inside in the radial direction, and the radial inner portion of the positive electrode side plate 150 after forming the slits is the fusing portion 157. .. In the fusing portion 157, the dimension in the direction crossing the energization path (dimension in the radial direction) is smaller than the other portion of the positive electrode side plate 150, and the path cross-sectional area is smaller. That is, the path resistance at the fusing portion 157 is higher than at other positions on the positive electrode side plate 150. As a result, when an overcurrent occurs, the positive electrode side plate 150 is blown at the fusing portion 157.

-The positive electrode side plates 50 and 150 may be C-shaped plates. When a C-shaped cut is arranged between the power line joint 55 and the lead joint 56 of the positive electrode side brush 30A adjacent to each other 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 modified so that the crossover 252 overlaps the brush holder 240 in the axial direction. FIG. 10 is a partially enlarged cross-sectional view of the brush assembly A1 according to the second embodiment. FIG. 11 is a cross-sectional view of the brush 230 and the brush holder 240. In FIGS. 10 and 11, the vertical direction in the figure is the axial direction (motor axial direction), and the horizontal direction in the figure is the radial direction. In the following description, the radial inside (commutator 24 side) of the brush holder 240 will be referred to as the front, and the radial outside (opposite to the commutator 24) will be referred to as the rear. Further, in the first embodiment, a configuration in which the crossover portion 252 of the second embodiment overlaps with the brush holder 240 in the axial direction may be used.

The brush assembly A1 of the second embodiment includes a brush 230 on the positive electrode side and a negative electrode side, a brush holder 240 accommodating the brush 230, a positive electrode side plate 250, and a negative electrode side plate 70 facing the positive electrode side plate 250. It is provided with a power supply line 60 (see FIG. 3) joined to the positive electrode side plate 250. Regarding the brush 230, the brush holder 240, the brush accommodating portion 242 of the brush holder 240, the positive electrode side plate 250, and the crossing 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 crossing portion 52 are almost the same except for the points described below. In the following description, only the points different from the first embodiment and the points not described in detail in the first embodiment will be described.

In the brush holder 240, the brush 230 is accommodated in the brush accommodating portion 242, and the coil spring 45 for urging the brush 230 toward the commutator 24 is accommodated in the spring accommodating portion 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 for positioning the coil spring 45 with respect to the brush 230.

The positive electrode side plate 250 has an intermediate portion 51 and a crossover portion 252. The crossover portion 252 is formed on the side away from the brush holder 240 (rotor 22 side) by being bent at approximately 90 degrees from the intermediate portion 51. That is, the crossover portion 252 extends so as to project from the brush holder 240 side to the rotor 22 side. Therefore, the crossover portion 252 may protrude in the axial direction from 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 having a reduced axial dimension on the positive electrode side plate 250 side at the rear end portion of the brush holder 240. Specifically, in the brush holder 240, the portion rearward from the position where it overlaps the crossover portion 252 in the radial direction is reduced in the axial direction, so that the holder reduction portion 247 is formed. 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. A part of the rear part of the brush accommodating portion 242 is also reduced in the axial direction to become a part of the holder reducing portion 247.

Further, at the end of the brush 230, a brush reduction portion 234 having a reduced axial dimension of the brush 230 is formed at a position corresponding to the holder reduction portion 247. As a result, a portion corresponding to the brush reduction portion 234 can be inserted into the region inside the holder reduction portion 247 in the radial direction. Further, the brush 230 has a stepped shape in which the axial dimension of the rear end portion of the brush 230 is reduced on the negative electrode side plate 70 side as well as the brush reduction portion 234. As a result, the brush 230 has a line-symmetrical shape with the connecting portion 32A of the lead wire 32 interposed therebetween. The rear end portion of the brush holder 240 on the negative electrode side plate 70 side also has a smaller axial dimension as in the holder reduction portion 247. As a result, the gap between the brush holder 240 and the rear end portion of the brush 230 at the initial position is reduced.

The crossover portion 252 overlaps with the holder reduction portion 247 in both the radial direction and the axial direction. That is, the crossover portion 252 is arranged so as to face the stepped surface 247A facing the rear formed by providing the holder reduction portion 247. Further, the crossover portion 252 overlaps with the brush reduction portion 234 in the axial direction. That is, the crossover portion 252 overlaps with the holder reduction portion 247 and the brush reduction portion 234 in the axial direction. As a result, the amount of protrusion L1 of the crossover portion 252 protruding from the axial end surface of the brush holder 240 can be reduced. Therefore, the DC motor 20 can be miniaturized in the axial direction.

Further, a connection portion 32A of the lead wire 32 is provided at a portion corresponding to the brush reduction portion 234 in the radial direction of the brush 230. 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 is small at 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 with the dead portion 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 (the end of the connection portion 32A on the commutator 24 side) of the connection portion 32A of the brush 230. Up to the connecting portion 32A of the lead wire 32 in the brush 230 is a portion included in the effective length of the brush 230, and the brush reduction portion 234 is formed in a portion 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 in the used state. ing. Then, when the brush 230 is worn and the radial facing range between the brush holder 240 and the brush 230 (the radial dimension in which the axial inner surface of the brush holder 240 and the axial end face of the brush 230 face each other) becomes shorter, the brush 230 becomes short. The brush holder 240 tends to wobble in the axial direction, and the sliding contact with the commutator 24 becomes unstable. When the brush 230 is provided with the brush reduction portion 234, the radial facing range with the brush holder 240 is shortened, and the sliding contact between the brush 230 and the commutator 24 tends to be unstable.

Therefore, a concave-convex 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 concave-convex shape 24A of the commutator 24 forms a groove matching the uneven shape 24A on the contact surface 31A of the brush 230, and the groove of the brush 230 and the concave-convex shape 24A on the commutator 24 side are fitted to each other. As a result, the contact state of the brush 230 with the commutator 24 can be stabilized. Therefore, even if the brush 230 is provided with the brush reduction portion 234 and the radial facing range is shortened, excessive wear of the brush 230 can be suppressed.

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

A holder reduction portion 247 that shrinks in the axial direction is formed at an end (rear end) opposite to the commutator 24 in the brush holder 240 in the radial direction, and the crossover portion 252 overlaps the holder reduction portion 247 in the axial direction. And said. In this case, the overlap between the brush holder 240 and the crossover portion 252 in the axial direction makes it possible to reduce the amount of protrusion L1 of the crossover portion 252 protruding from the axial end surface of the brush holder 240. Therefore, the DC motor 20 can be miniaturized 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 region inside the holder reduction portion 247 in the radial direction. Further, a lead wire 32 is connected to a portion corresponding to the 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 with the dead portion not included in the effective length, the dead portion can be effectively utilized. As a result, the effective length of the brush 230 can be increased.

A concave-convex 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 brush 230 and the commutator 24 are in a state of being meshed with each other in the concave-convex shape 24A, and it is possible to prevent the brush 230 from wobbling during sliding. Therefore, even if the brush 230 is provided with the brush reduction portion 234 and the radial facing range between the brush holder 240 and the brush 230 is shortened, excessive wear of the brush 230 can be suppressed.

<Change example>
The second embodiment may be modified as follows. The following configurations may be applied individually to the configurations of the second embodiment, or may be applied in any combination.

FIG. 12 is a cross-sectional view of the brush and the brush holder in the modified example. In this brush holder, the holder reduction portion 247 is formed so as to be oblique from the rotor 22 side to the spring accommodating portion 46 side. In this case, the crossover portion 252 overlaps the holder reduction portion 247 in the radial and axial directions. As a result, the amount of protrusion L1 of the crossover portion 252 from the brush holder 240 can be suppressed. When the holder reduction portion 247 is formed diagonally, the brush reduction portion 234 may also be formed obliquely according to the shape of the holder reduction portion 247.

The plate thickness of the crossover portion 252 may be thicker than the plate thickness of the intermediate portion 51. Since the plate thickness of the crossover portion 252 is thicker than the plate thickness of the intermediate portion 51, it becomes easy to secure the cross-sectional area of the crossover portion 252 in the energizing direction. As a result, the dimension in which the crossover portion 252 protrudes from the brush holder 240 toward the rotor 22 side can be reduced. Therefore, it is possible to further reduce the size while securing the required cross-sectional area of the energization path.

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

The brush assembly A2 of the third embodiment includes a brush 30 on the positive electrode side and a negative electrode side, a brush holder 340 for accommodating the brush 30, a positive electrode side plate 50, and a negative electrode side plate 70 facing the positive electrode side plate 50. , A power supply line 60 joined to the positive electrode side plate 50 is provided. The brush assembly A2 is housed in the housing 80. The brush holder 340 is substantially the same as the brush holder 40 of the first embodiment except for the points described below, and the coil spring 345 will be described below with the coil spring 45 of the first embodiment and the second embodiment. It is almost the same except for the points. In the following description, only the points different from the first embodiment and the second embodiment and the points not described in detail in the first embodiment will be described.

The housing 80 has a bottomed cylindrical shape, and has a cylindrical cylindrical portion 81 and a bottom portion 82 that covers an axial end portion of the DC motor 20 (see FIG. 1). The inner peripheral surface 81A of the cylindrical portion 81 faces the holder rear end portion 348 of the brush holder 340 (the wall portion on the brush holder 340 opposite to the commutator 24). 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 accommodated in the brush accommodating portion 42 of the brush holder 340, and a coil spring 345, which is an urging member for urging the brush 30 toward the commutator 24 side, is accommodated on the rear side thereof. 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. Instead of the coil spring 345, an elastic member such as an annular rubber member or a disc spring having elasticity in the radial direction may be used as the urging member.

It is desirable that the radial dimension (wearing direction dimension) of the brush 30 housed in the brush holder 340 is long in order to extend the life of the brush 30. The radial dimensions of the brush 30 are 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 portion 348, the dimensions of the coil spring 345, and the facing surface 348A of the brush holder 340. It is determined based on the dimension between the inner peripheral surface 81A of the cylindrical portion 81 and the inner peripheral surface 81A. Generally, the facing surface of the brush holder (the outer surface of the rear end of the holder on the housing side) is a flat surface, so that the end of the brush holder on the circumferential direction 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 peripheral surface 81A of the cylindrical portion 81, the facing surface of the holder rear end portion of the brush holder is radially along the inner peripheral surface 81A of the cylindrical portion 81. It is conceivable to extend it in a convex shape to the outside. That is, it is conceivable that the facing surface of the rear end portion of the holder is a curved surface along the inner peripheral surface 81A of the cylindrical portion 81. As a result, the coil spring 345 can be moved closer to the cylindrical portion 81 side as compared with the case where the rear end portion of the holder has a flat shape.

However, if the entire area of the rear end of the holder is a convex portion extending along the inner peripheral surface 81A, the drainage property of the through hole provided at the rear end of the holder is impaired. If the drainage property from the rear end of the holder is impaired, the coil spring 345 or the like may be deteriorated by rust or the like due to the water that has entered the brush holder.

Therefore, in the present embodiment, the holder rear end portion 348 of the brush holder 340 has a convex portion 348B and a separation 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 the entire length in the circumferential direction, and the shape of the inner surface of the holder rear end portion 348 is also formed along the shape of the facing surface 348A. The inner surface of the rear end portion 348 of the holder may be an inclined surface that is inclined toward the through hole 349 described later.

The convex portions 348B are provided at both ends in the circumferential direction of the rear end portion 348 of the holder, and the facing surfaces 348A extend radially outward along the inner peripheral surface 81A of the cylindrical portion 81. Specifically, the convex portion 348B protrudes rearward (on the cylindrical portion 81 side) from the rear end position of the side wall in the circumferential direction of the brush holder 340. As a result, the position where the coil spring 345 is arranged is moved toward the cylindrical portion 81 side. Therefore, the coil spring 345 can be arranged on the outer side 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 rear end portion 348 of the holder, or may be in contact with the separating portion 348C.

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 peripheral surface 81A, the convex portion 348B can come into contact with the inner peripheral surface 81A in a plane. As a result, 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 at the position where the coil spring 345 of the brush holder 340 comes into contact can be reduced.

The separating portion 348C is provided so that the facing surface 348A is separated from the inner peripheral surface 81A than the convex portion 348B between the convex portions 348B on both sides in the circumferential direction at the rear end portion 348 of the holder. The facing surface 348A in the separating portion 348C is a flat surface, and is separated from the inner peripheral surface 81A toward the center side in the circumferential direction. The separation portion 348C is provided with a through hole 349 that penetrates inside and outside the brush holder 340. The through hole 349 is provided at the center of the separation portion 348C in the circumferential direction. Therefore, the water that has entered the brush holder 340 can be discharged into the space provided between the facing 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 in a state where the positions of the through hole 349 and the coil spring 345 do not overlap. That is, it is possible to prevent the coil spring 345 and the housing 80 from coming into contact with each other through the through hole 349 while improving the drainage property of the brush holder 340. In this case, a sufficient creepage distance between the coil spring 345 and the cylindrical portion 81 can be secured. The through hole 349 is preferably made as large as possible within the range of the inner diameter of the coil spring 345.

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

In the present embodiment, the rear end portion 348 of the holder is provided with a separating portion 348C in which the facing surface 348A is separated from the inner peripheral surface 81A of the cylindrical portion 81 than the convex portion 348B between the convex portions 348B on both sides in the circumferential direction. The separation portion 348C is provided with a through hole 349 penetrating inside and outside the brush holder 340. As a result, the water that has entered the brush holder 340 can be suitably discharged from the through hole 349 provided in the separation portion 348C.

At the rear end portion 348 of the holder, a through hole 349 is provided as a hole smaller than the inner diameter of the coil spring 345 at a position inside the coil spring 345. As a result, it is possible to prevent the coil spring 345 and the housing 80 from coming into contact with each other through the through hole 349 while improving the drainage property of the brush holder 340. In this case, since the creepage distance between the coil spring 345 and the housing 80 can be secured, it is possible to prevent a short circuit between the brush 30 and the housing 80 via the coil spring 345.

When the convex portion 348B of the rear end portion 348 of the holder abuts on the inner peripheral 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. As a result, the strength required at the position where the coil spring 345 of the brush holder 340 comes into contact can be reduced, and the wall thickness at the position where the coil spring 345 of the brush holder 340 comes into contact 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.

<Change example>
The third embodiment may be modified as follows. The following configurations may be applied individually to the configurations of the third embodiment, or may be applied in any combination.

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

As shown in FIG. 14, in the separating portion 348C of the rear end portion 348 of the holder, a thin-walled portion 348D which is thinned by being recessed toward the brush 30 is further provided at a position around the through hole 349. You may. The thin-walled portion 348D is recessed so that the side of the cylindrical portion 81 facing the inner peripheral surface 81A (opposing surface 348A) is separated from the inner peripheral surface 81A of the cylindrical portion 81. Further, the thin-walled portion 348D is provided at a position inside the coil spring 345, that is, inside a portion where the coil spring 345 comes into contact with the rear end portion 348 of the holder. As a result, in the rear end portion 348 of the holder, the contact portion of the coil spring 345 is thickened to ensure strength, and the thin-walled portion 348D is provided inside the contact portion, so that the drainage property can be improved.

As shown in FIG. 15, it is preferable that the cylindrical portion 81 surrounding each brush holder 340 is formed in a tapered shape. More specifically, the inner peripheral surface 81A of the cylindrical portion 81 of the housing 80 may be formed in a tapered shape so that the rotor 22 side has an enlarged diameter. The inner peripheral surface 81A may have a tapered shape having an angle of about a so-called draft. As a result, as shown by the broken line arrow in FIG. 15, the water discharged from the through hole 349 flows toward the rotor 22 side (axial direction) along the inclination of the inner peripheral surface 81A. As a result, it is possible to prevent the discharged water from staying in 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 side in the axial direction. As a result, the separation distance between the through hole 349 and the inner peripheral surface 81A of the cylindrical portion 81 becomes large. Therefore, the drainage property can be improved. It should be noted that the coil spring 345 may be provided at a position closer to the rotor 22 side than the center in the axial direction within the range inside the coil spring 345.

20 ... DC motor, 22 ... Rotor, 24 ... Commuter, 30 ... Brush, 32 ... Lead wire, 50 ... Positive electrode side plate, 52 ... Crossing part, 54 ... Bending angle part, 57 ... Fusing part, 58 ... Bending part, 59 ... Fusing part, 150 ... Positive electrode side plate, 157 ... Fusing part.

Claims (9)

A commutator (24) provided coaxially with the rotor (22),
Brushes (30) on the positive electrode side and the negative electrode side provided so as to be in contact with the commutator, and
The brushes on the positive electrode side and the negative electrode side are arranged at predetermined intervals in the circumferential direction, and an annular positive electrode side plate (50) to which a lead wire (32) extending from the brush on the positive electrode side is joined is provided.
The positive electrode side plate is provided with a bent portion (52,58) bent in a direction crossing the current-carrying path.
A DC motor (20) in which the bending angle portion (54) of the bent portion is a fusing portion (57, 59) that is fusing due to the generation of an overcurrent. A brush holder (40) for holding each of the brushes in a housed state is provided.
The positive electrode side plate has an intermediate portion (51) interposed between the brush holders arranged in the circumferential direction and a crossover portion (52) connecting the intermediate portions in the circumferential direction while avoiding the brush holder. Have,
The DC motor according to claim 1, wherein the crossover portion is formed by bending from the intermediate portion in the motor axial direction, and is provided as the bent portion. The DC motor according to claim 1 or 2, wherein the bending angle of the bent portion is 90 degrees or less. A power supply line (60) for supplying power to the brush on the positive electrode side is joined to the positive electrode side plate at a power line joint portion (55).
In the positive electrode side plate, the fusing portion is formed between the power line joint portion and the lead joint portion (56) to which the lead wire of the brush on the positive electrode side adjacent to the power line joint portion in the circumferential direction is joined. The DC motor according to any one of claims 1 to 3, which is provided. A power supply line (60) for supplying power to the brush on the positive electrode side is joined to the positive electrode side plate at a power line joint portion (55).
The positive electrode side plate is provided with the bent portion for each brush.
The DC motor according to any one of claims 1 to 4, wherein the bent corner portion of the bent portion adjacent to the power line joint portion in the circumferential direction is the fusing portion. The positive electrode side plate is provided with a plurality of the bent portions.
The plurality of bent portions include a first bent portion having a small width dimension of the bent corner portion and a second bent portion having a large width dimension, and the bent corner portion of the first bent portion is the fusing portion. The DC motor according to any one of claims 1 to 5. A commutator (24) provided coaxially with the rotor (22),
Brushes (30) on the positive electrode side and the negative electrode side provided so as to be in contact with the commutator, and
An annular positive electrode side plate (50, 150) in which the positive electrode side and negative electrode side brushes are arranged at predetermined intervals in the circumferential direction and lead wires (32) extending from the positive electrode side brush are joined.
A negative electrode side plate (70) which is arranged at a position facing the positive electrode side plate so as to sandwich the brush between the positive electrode side plate and to which a lead wire extending from the brush on the negative electrode side is joined.
It is provided with a power supply line (60) that is joined to the positive electrode side plate and supplies power to the brush on the positive electrode side.
Among the brushes, in the brush located next to the power line joining portion to which the power supply line is joined in the positive electrode side plate and on the positive electrode side, the lead wire sandwiches the brush with the power line joining portion. It is pulled out to the opposite side in the circumferential direction,
In the positive electrode side plate, fusing is performed between the power line joint and the lead joint of the brush on the positive electrode side which is adjacent to the power line joint in the circumferential direction in the circumferential direction due to the generation of an overcurrent. A DC motor provided with parts (57, 59, 157). The DC motor according to claim 7, wherein in the positive electrode side plate, the fusing portion is provided between the brush adjacent to the power line joint portion in the circumferential direction and the power line joint portion. Between the positive electrode side plate and the negative electrode side plate, the lead wires are drawn out from the positive electrode side and the negative electrode side brushes in the same direction in the circumferential direction, and between the brushes arranged in the circumferential direction. The lead wire extending from the brush on the negative electrode side is drawn out from the space in which the power supply wire is arranged, and an insulating member (66) is provided between the lead wire and the power supply wire. The DC motor according to claim 7 or 8.

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