WO2024084845A1

WO2024084845A1 - Electric motor

Info

Publication number: WO2024084845A1
Application number: PCT/JP2023/032159
Authority: WO
Inventors: 圭策中野; 和雄遠矢
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2022-10-19
Filing date: 2023-09-01
Publication date: 2024-04-25

Abstract

This electric motor comprises: a rotary shaft, the axial direction of which is the direction in which the axis thereof extends; a commutator that is attached to the rotary shaft; at least one brush that is in contact with the commutator; a brush holder that holds the brush; a terminal that is attached to the brush holder; and a conductive wire that has one end connected to the brush and the other end electrically connected to the terminal. The brush has an arc shape, and the angle formed by the brush tangent and the electric-motor rotation direction is less than 90 degrees at the site where the commutator and the leading end surface of the brush are in contact.

Description

Electric motor

This disclosure relates to electric motors.

Electric motors are widely used in household electrical appliances such as vacuum cleaners, as well as in the electrical equipment field of automobiles. For example, electric motors are used in two-wheeled and four-wheeled vehicles to drive cooling fans such as radiators.

Known electric motors include brushed motors (commutator motors) that use brushes, and brushless motors that do not use brushes. Of these, brushed motors include a stator, rotor, commutator, brushes, a brush holder, and a brush spring. The rotor rotates due to the magnetic force of the stator. The commutator is attached to the rotating shaft of the rotor. The brushes are in sliding contact with the commutator. The brush holder holds the brushes. The brush spring presses the brushes against the commutator.

In brushed motors, it is possible to lengthen the brushes in order to extend the life of the motor. However, simply lengthening the straight brushes increases the diameter of the motor, resulting in a larger motor. Therefore, technology has been proposed that uses arc-shaped brushes in order to achieve both a longer life and a more compact motor (see, for example, Patent Documents 1 and 2).

In order to further extend the life of electric motors equipped with arc-shaped brushes, it is possible to increase the diameter of the circle that forms the arc of the arc-shaped brush (arc diameter).

However, simply increasing the arc diameter of the brush will increase the external size of the motor, which will result in a larger motor.

JP 2006-149154 A JP 2010-35272 A

This disclosure has been made to solve these problems. The purpose of this disclosure is to provide an electric motor that uses arc-shaped brushes and has a long life without increasing the outer diameter size.

In order to achieve the above object, one embodiment of the electric motor according to the present disclosure comprises a rotating shaft whose axial direction is the direction in which the shaft extends, a commutator attached to the rotating shaft, at least one brush in contact with the commutator, a brush holder that holds the brush, a terminal attached to the brush holder, and a conductive wire whose one end is connected to the brush and whose other end is electrically connected to the terminal, the brush is arc-shaped, and at the point where the front end face of the brush contacts the commutator, the angle between the tangent of the brush and the direction of rotation of the electric motor is less than 90°.

According to this disclosure, a motor using arc-shaped brushes can be realized with a long life without increasing the outer diameter size.

FIG. 1 is an external perspective view of an electric motor according to a first embodiment of the present invention, as viewed obliquely from above. FIG. 2 is an external perspective view of the electric motor according to the first embodiment as viewed obliquely from below. FIG. 3 is a cross-sectional perspective view of the electric motor according to the first embodiment. FIG. 4 is an exploded perspective view of the electric motor according to the first embodiment. FIG. 5 is a top view showing a brush holder in which various components are arranged and a commutator in the electric motor according to the first embodiment. FIG. 6 is an enlarged view of region VI enclosed by a dashed line in FIG. FIG. 7 is a perspective view showing a brush holder in which various components are arranged and a commutator in the electric motor according to the first embodiment. FIG. 8 is a perspective view showing the positional relationship between the pair of brushes, the pair of brush springs, and the commutator in FIG. FIG. 9 is a perspective view of a brush holder in the electric motor according to the first embodiment. FIG. 10 is a perspective view of the brush spring in a state where the strip-shaped wire is housed in the spiral portion. FIG. 11 is a diagram showing a state in which the brush spring and the brush in the state shown in FIG. 10 are set in the brush holder. FIG. 12 is a diagram for explaining a state in which the brush and the brush spring are fixed to the brush holder. FIG. 13 is a diagram showing how the brush slides due to wear. FIG. 14 is a perspective view of a brush holder in which brushes and brush springs are arranged in the electric motor according to the second embodiment. FIG. 15 is an enlarged view of the rear end portion of the brush and its surrounding area in FIG. FIG. 16 is a perspective view of a brush and conductive wires included in the electric motor according to the second embodiment. FIG. 17 is a diagram for explaining the arrangement of brushes in an electric motor according to a modified example.

Below, embodiments of the present disclosure will be described with reference to the drawings. Each embodiment described below shows a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, arrangement positions of the components, connection forms, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Therefore, among the components in the following embodiments, components that are not described in an independent claim that shows the highest concept of the present disclosure will be described as optional components.

Each figure is a schematic diagram and is not necessarily a precise illustration. In each figure, the same reference numerals are used for configurations that are substantially the same as in other figures, and duplicate explanations are omitted or simplified. In this specification, the terms "upper" and "lower" do not necessarily refer to the upper direction (vertically upward) and the lower direction (vertically downward) in an absolute spatial sense.

(Embodiment 1)
First, the overall configuration of the electric motor 1 according to the first embodiment will be described with reference to Figs. 1 to 7. Fig. 1 is an external perspective view of the electric motor 1 according to the first embodiment when viewed obliquely from above. Fig. 2 is an external perspective view of the electric motor 1 according to the first embodiment when viewed obliquely from below. Fig. 3 is a cross-sectional perspective view of the electric motor 1 according to the first embodiment. Fig. 4 is an exploded perspective view of the electric motor 1 according to the first embodiment. Fig. 5 is a top view showing the brush holder 60 and the commutator 30 on which various components are arranged in the electric motor 1 according to the first embodiment. Fig. 6 is an enlarged view of an area VI surrounded by a dashed line in Fig. 5. Fig. 7 is a perspective view showing the brush holder 60 and the commutator 30 on which various components are arranged in the electric motor 1 according to the first embodiment.

As shown in Figs. 1 to 7, the electric motor 1 includes a stator 10 and a rotor 20 that rotates due to the magnetic force of the stator 10. The electric motor 1 is a brushed electric motor. The electric motor 1 includes a commutator 30, at least one brush 40, a brush spring 50, and a brush holder 60. The commutator 30 is attached to a rotating shaft 21 of the rotor 20. At least one brush 40 contacts the commutator 30. The brush spring 50 presses the brush 40 against the commutator 30. The brush holder 60 holds the brush 40. The electric motor 1 includes a terminal 70 that receives power from an external power source, and a conductive wire 80 that is electrically connected to the terminal 70 and the brush 40. The electric motor 1 further includes a first bearing 91, a second bearing 92, a first bracket 101, and a second bracket 102.

The electric motor 1 is a type of direct current motor (DC motor) that is driven by direct current. In the electric motor 1, a magnet is used as the stator 10. In the electric motor 1, an armature having a coil 22 is used as the rotor 20. The electric motor 1 is a flat type (flat type) brushed coreless motor (flat motor) that is mounted on a vehicle such as a two-wheeled or four-wheeled vehicle. Therefore, the stator 10 and the rotor 20 do not have a core (iron core). The electric motor 1 is configured to be thin and lightweight overall. Specifically, the electric motor 1 is a small motor used in a cooling fan for a radiator in a vehicle. The electric motor 1 is driven by an input voltage of, for example, DC 12V.

The components of the electric motor 1 are described in detail below.

As shown in FIG. 3, the stator 10 is disposed with a small air gap between it and the rotor 20. The stator 10 generates a magnetic force acting on the rotor 20. The stator 10 is configured to generate magnetic flux on the air gap surface with the rotor 20. The stator 10 forms a magnetic circuit together with the rotor 20, which is an armature. As shown in FIG. 4, the stator 10 is generally annular. The stator 10 is magnetized so that N poles and S poles are alternately and evenly present on the air gap surface with the rotor 20 along the circumferential direction of the rotating shaft 21. The stator 10 is a field magnet that creates magnetic flux to generate torque. The stator 10 is composed of, for example, a permanent magnet. The direction of the main magnetic flux generated by the stator 10 (magnet) is the direction in which the rotating shaft 21 extends. As shown in FIG. 3, the stator 10 is fixed to a first bracket 101.

As shown in FIG. 3, the rotor 20 has a rotating shaft 21 and a coil 22. The rotor 20 is a coreless rotor that does not have a core.

The rotor 20 rotates around the axis C of the rotating shaft 21. The rotor 20 generates a magnetic force that acts on the stator 10. The direction of the main magnetic flux generated by the rotor 20 is the direction in which the rotating shaft 21 extends.

The rotor 20 is disposed opposite the stator 10. The rotor 20 faces the stator 10 in the direction in which the rotating shaft 21 extends. Specifically, the coil 22 of the rotor 20 and the stator 10 face each other in the direction in which the rotating shaft 21 extends.

The rotating shaft 21 is a shaft having an axis C. The rotating shaft 21 is a long rod-shaped member. As an example, the rotating shaft 21 is a metal rod made of a metal material such as SUS (Steel special use stainless steel). The axis C of the rotating shaft 21 is the center when the rotor 20 rotates. The longitudinal direction of the rotating shaft 21, i.e., the direction in which the rotating shaft 21 extends, is the direction of the axis C (axial direction).

The first end 21a, which is one end of the rotating shaft 21, is supported by a first bearing 91. The second end 21b, which is the other end of the rotating shaft 21, is supported by a second bearing 92. As an example, the first bearing 91 and the second bearing 92 are bearings such as ball bearings.

The first end 21a of the rotating shaft 21 is the output side end (output shaft). The first end 21a of the rotating shaft 21 protrudes from the first bracket 101 and the first bearing 91. A load such as a rotating fan is attached to the first end 21a. The second end 21b of the rotating shaft 21 is the anti-output side end (anti-output shaft). The first end 21a of the rotating shaft 21 does not protrude from the second bracket 102 and the second bearing 92.

The first bearing 91 is held by the first bracket 101. Specifically, the first bearing 91 is fixed to a recess provided in the center of the first bracket 101. The second bearing 92 is held by the brush holder 60. Specifically, the second bearing 92 is fixed to a recess provided in the center of the brush holder 60.

The first bracket 101 and the second bracket 102 are made of, for example, a metal material. For example, the first bracket 101 and the second bracket 102 are made of an iron-based material such as cold-rolled steel plate (SPC (Steel Plate Cold) material) or a metal such as aluminum. The material of the first bracket 101 and the second bracket 102 is not limited to a metal material and may be a resin material. However, from the viewpoint of suppressing noise generated from the electric motor 1, it is preferable that the first bracket 101 and the second bracket 102 are made of a metal material.

As shown in Figures 1 to 4, the first bracket 101 is an outer shell member of the electric motor 1. The first bracket 101 is a thin, flat cylinder having a bottom and a cylindrical side wall. The second bracket 102 is a flat plate with a through hole. The first bracket 101 and the brush holder 60 form an outer shell housing. The stator 10 and rotor 20 are arranged inside this outer shell housing.

As shown in FIG. 3, the rotor 20 has a rotating shaft 21, multiple coils 22, and molded resin 23.

The multiple coils 22 are wound coils. Specifically, the multiple coils 22 are armature windings made of electric wire. The multiple coils 22 are wound so that a magnetic force acting on the stator 10 is generated when a current flows through them. The direction of the main magnetic flux generated by the coils 22 is along the axis C to which the rotating shaft 21 extends. Specifically, the multiple coils 22 are wound in a flat shape. The coil surfaces of the multiple coils are arranged in a position facing in a direction along the axis C to which the rotating shaft 21 extends.

The coils 22 are composed of an insulated wire having a core wire made of a metal such as copper or aluminum and an insulating film coating the core wire. The multiple coils 22 are thin wound coils having a coil layer in which the insulated wire is wound in a planar shape. Specifically, the multiple coils 22 are composed of, for example, one layer or multiple coil layers in which the insulated wire is wound in a substantially fan-like shape in a planar view. The multiple coils 22 thus configured are arranged in a ring shape surrounding the rotating shaft 21 when viewed from the direction of the axis C along which the rotating shaft 21 extends.

The multiple coils 22 are electrically connected to the commutator 30. Specifically, the multiple coils 22 are electrically connected to one of the multiple commutator segments 31 that the commutator 30 has. Therefore, current flows through the multiple coils 22 via the commutator segment 31 that the brush 40 contacts.

The multiple coils 22 are molded integrally with the molded resin 23 by being covered with the molded resin 23. In other words, the multiple coils 22 are resin molded. Therefore, as shown in FIG. 4, the external shape of the molded resin 23 after the multiple coils 22 are molded is circular in a plan view. As the molded resin 23, for example, an insulating resin material such as phenolic resin or unsaturated polyester (BMC (Bulk Molding Compound)) can be used. The molded resin 23 may be either a thermosetting resin or a thermoplastic resin. As shown in FIG. 3, the molded resin 23 is fixed to the rotating shaft 21 via a cylindrical member 24.

In this way, the electric motor 1 is a coreless motor in which the rotor 20 does not have a core. The multiple coils 22 of the rotor 20 of the electric motor 1 are thin and molded from resin. This makes it possible to realize a thin electric motor 1 with low inductance.

As shown in FIG. 3, the commutator 30 is attached to the rotating shaft 21. Therefore, the commutator 30 rotates together with the rotating shaft 21 as the rotor 20 rotates. The commutator 30 attached to the rotating shaft 21 may be a part of the rotor 20.

As shown in FIG. 5, the commutator 30 has a plurality of commutator pieces 31 (commutator segments) arranged along the rotational direction of the rotating shaft 21. Specifically, the plurality of commutator pieces 31 are arranged in an annular shape along the rotational direction of the rotating shaft 21 so as to surround the rotating shaft 21. Each commutator piece 31 is shaped as an elongated member extending in the longitudinal direction of the rotating shaft 21. Each commutator piece 31 is formed so as to have a step on its surface.

The multiple commutator segments 31 are conductive terminals made of a metal material such as copper. The multiple commutator segments 31 are electrically connected to the coils 22 of the rotor 20. The multiple commutator segments 31 are arranged insulated and separated from each other. The multiple commutator segments 31 are electrically connected via the coils 22 of the rotor 20.

The commutator 30 is a molded commutator. The commutator 30 is configured with multiple commutator segments 31 molded with resin. In this case, the multiple commutator segments 31 are embedded in the resin so that their surfaces are exposed. The multiple commutator segments 31 are fixed to the rotating shaft 21 by fixing the resin that molds the multiple commutator segments 31 to the rotating shaft 21. The molded resin that covers the multiple commutator segments 31 and the molded resin 23 that covers the coil 22 are integrated. The molded resin that covers the multiple commutator segments 31 and the molded resin 23 that covers the coil 22 may be made of the same resin material, or may be separate bodies made of different resin materials or the same resin material.

At least one brush 40 is in contact with the commutator 30. Specifically, the tip of the brush 40 is in contact with the commutator segments 31 of the commutator 30. The brush 40 is in contact with the commutator segments 31 in a direction (radial direction) perpendicular to the direction of the axis C of the rotating shaft 21. Since the commutator 30 rotates due to the rotation of the rotating shaft 21, the brush 40 continues to come into contact with all the commutator segments 31 in sequence.

Brush 40 is a power supply brush for supplying power to coil 22. Brush 40 is connected to conductive wire 80, which is electrically connected to terminal 70. When brush 40 comes into contact with commutator segments 31, the current (armature current) supplied to brush 40 via conductive wire 80 flows through commutator segments 31 to coil 22 of rotor 20.

Brush 40 is a conductive carbon brush whose main component is carbon. In this case, brush 40 is preferably a carbon brush containing a metal such as copper. This can reduce the contact resistance between brush 40 and commutator segments 31. As an example, brush 40 is a sintered brush made of a sintered body. In this case, brush 40, which is a sintered body, can be produced, for example, by putting a mixture of graphite powder, copper powder, binder resin, and hardener into a mold, compression molding, and sintering. In this embodiment, brush 40 is produced without cutting. In other words, brush 40 is produced after graphite powder and copper powder are put into a mold, compression molding, and sintering, and then no cutting is performed.

As shown in FIG. 5, the brush 40 is arc-shaped. Specifically, the cross-sectional shape of the brush 40 is substantially rectangular. The brush 40 has a shape that forms an arc when viewed from above. When viewed from above, the width of the brush 40 is constant. The top view shape of the arc-shaped brush 40 does not have to be strictly an arc, but may be approximately an arc.

As shown in Figures 4 and 5, the brush 40 has a pair of opposite side surfaces, a first side surface 41 and a second side surface 42. The first side surface 41 is the side surface on the outer periphery of the arc that constitutes the brush 40. The second side surface 42 is the side surface on the inner periphery of the arc that constitutes the brush 40.

Since the width of the brush 40 is constant, the curvature of the arc of the first side surface 41 on the outer periphery is smaller than the curvature of the arc of the second side surface 42 on the inner periphery. The first side surface 41 and the second side surface 42 are cylindrical surfaces. Therefore, the circle that forms the arc of the first side surface 41 has one center point. Similarly, the circle that forms the arc of the second side surface 42 also has one center point. The center point of the circle that forms the arc of the first side surface 41 and the center point of the circle that forms the arc of the second side surface 42 are the same. In other words, the circle that forms the arc of the first side surface 41 and the circle that forms the arc of the second side surface 42 are concentric circles. Note that the center point of the circle that forms the arc of the first side surface 41 and the center point of the circle that forms the arc of the second side surface 42 do not have to be the same.

The brush 40 has a front end face 43 which is a surface that contacts the commutator 30, and a rear end face 44 which is a surface opposite to the front end face 43. The front end face 43 is an end face at the front end, which is one end in the longitudinal direction of the brush 40. The front end face 43 is a sliding surface that comes into sliding contact with the commutator pieces 31 of the commutator 30. The rear end face 44 is an end face at the rear end, which is the other end in the longitudinal direction of the brush 40. The rear end face 44 is a surface that comes into contact with the spiral portion 51 of the brush spring 50.

The front end surface 43 and the rear end surface 44 are substantially rectangular flat surfaces. However, this is not limited thereto. For example, the front end surface 43 may be a concave curved surface that curves along the surface shape of the commutator piece 31. The rear end surface 44 may be a concave curved surface that curves along the surface shape of the spiral portion 51 so that a part of the spiral portion 51 of the brush spring 50 is accommodated therein.

As shown in FIG. 5, the front end surface 43 of the brush 40 contacts the commutator 30 so that the center line of the front end surface 43 is oblique to the surface of the commutator 30. Specifically, as shown in FIG. 6, at the point where the front end surface 43 of the brush 40 contacts the commutator 30, the angle θ between the tangent line of the brush 40 and the direction of rotation of the motor 1 is less than 90° (θ<90°). It is preferable that the angle θ be greater than 45°. In other words, it is preferable that the angle θ be 45°<θ<90°.

The brushes 40 include multiple brushes. In this case, it is preferable that multiple brushes 40 are arranged at equal intervals along the rotation direction of the rotor 20. Specifically, two brushes 40 are arranged. The two brushes 40 are arranged opposite each other with the commutator 30 in between. In other words, the two brushes 40 are arranged at 180° intervals along the rotation direction of the rotor 20. Specifically, the front end face 43 of one brush 40 and the front end face 43 of the other brush 40 face each other with the rotation shaft 21 in between.

Each of the two brushes 40 is elongated. If the center of the circle forming the arc of the brush 40 is taken as the center point, the angle between the line connecting this center point to the front end surface 43 of the brush 40 and the line connecting the center point to the rear end surface 44 of the brush 40 is 90° or more. In other words, the central angle of the arc of the brush 40 of both of the two brushes 40 is 90° or more. Specifically, in both of the two brushes 40, the first side surface 41 and the second side surface 42 both have a central angle of the arc of 90° or more. The two brushes 40 have the same shape. However, this is not limited to this.

The brush 40 is constantly in contact with the commutator segments 31 of the commutator 30 due to the pressing force of the brush spring 50. Specifically, as shown in FIG. 5, the brush 40 is pressed against the commutator 30 by the brush spring 50, so that the front end surface 43 of the brush 40 is in contact with the commutator segments 31. The brush 40 wears out as it continues to come into contact with the rotating commutator segments 31. In this way, the brush 40 is in sliding contact with the commutator 30 due to the pressing force of the brush spring 50. At the same time, the brush 40 becomes shorter due to wear caused by the commutator 30.

The brush springs 50 are provided according to the number of brushes 40. Since the electric motor 1 is provided with two brushes 40, two brush springs 50 are also provided. The brushes 40 and brush springs 50 are held in the brush holder 60.

The brush spring 50 applies a pressure (spring pressure) to the brush 40 by the spring elastic force. The brush spring 50 biases the brush 40 toward the commutator 30. The brush spring 50 is a constant load spring. Therefore, the brush spring 50 applies a uniform load to the brush 40. In other words, the brush spring 50 applies a uniform pressure to the brush 40 from the initial stage before the brush 40 wears out to the final stage when the brush 40 wears out and the motor 1 reaches the end of its life.

The brush spring 50, which is a constant-load spring, is made of a strip-shaped wire material. As shown in Figures 4 and 5, the brush spring 50 is a spiral spring. The brush spring 50 has a spiral portion 51 (coil portion) in which a strip-shaped wire material is wound in a spiral shape. The brush spring 50 is made of a single strip-shaped wire material made of a metal material such as a steel plate.

Specifically, the wire that constitutes brush spring 50 is a long, band-shaped metal plate. Thus, spiral portion 51 is the portion of the constant-load spring in which the long, band-shaped metal plate is wound in a spiral shape multiple times in only one direction. Brush spring 50 generates a force (spring restoring force) that returns the wire to its original spiral state by stretching one end of the wire from spiral portion 51. As an example, brush spring 50 is made of a stainless steel metal plate.

As shown in FIG. 5, the brush spring 50 has an outer end 50a which is one end of a strip of metal plate, and an inner end 50b which is the other end of the strip of metal plate. The outer end 50a is one end of the strip of metal plate that is pulled outward from the outermost periphery of the spiral portion 51. The inner end 50b is the other end of the strip of metal plate that is located at the innermost periphery of the spiral portion 51.

As shown in Figures 5 and 7, the brush spring 50 presses the brush 40 against the commutator 30 with the spiral portion 51. Specifically, the spiral portion 51 of the brush spring 50 contacts the rear end surface 44 of the brush 40. The brush spring 50 applies a pressing load to the brush 40 with the spring restoring force of the spiral portion 51. In other words, the brush spring 50 applies a pressing force (spring pressure) to the brush 40 with the spiral portion 51. This biases the brush 40 towards the commutator 30.

FIG. 8 is a perspective view showing the positional relationship between the pair of brushes 40, the pair of brush springs 50, and the commutator 30 in FIG. 7. As shown in FIG. 8, the brush springs 50 are arranged so as to contact the first side surface 41, which is the side surface on the outer periphery side of the brushes 40.

Specifically, a strip of wire (metal plate) pulled out from the spiral portion 51 of the brush spring 50 extends along the first side surface 41 of the brush 40. Therefore, the strip of wire pulled out from the spiral portion 51 of the brush spring 50 is curved in an arc, just like the brush 40. The width of the wire constituting the brush spring 50 should be between 1/3 and 2/3 of the width of the first side surface 41 of the brush 40. This improves the sliding properties between the brush spring 50 and the brush 40, while allowing the brush spring 50 to apply a stable pressure load to the brush 40.

As shown in Figures 5 and 7, the brush 40 is held by the brush holder 60. As shown in Figures 2 and 3, the brush holder 60 is also an outer shell member that constitutes the outer shell of the electric motor 1. The brush holder 60 covers the second bracket 102 from the outside.

The brush holder 60 is made of, for example, an insulating resin material. The brush holder 60 is a resin molded product formed by integral molding using a resin material. As an example, the resin material that makes up the brush holder 60 is phenolic resin. However, this is not limited to this.

As shown in Figures 3 to 5, the brush holder 60 has a brush storage section 60a, which is a spatial area in which the brush 40 is stored. As shown in Figure 3, the brush storage section 60a is a recessed portion formed in a concave shape. As shown in Figure 5, the brush storage section 60a is formed in an elongated shape that conforms to the shape of the brush 40. In other words, the brush storage section 60a is curved in an arc shape. Figure 9 is a perspective view of the brush holder 60 in the electric motor 1 according to the first embodiment. As shown in Figure 9, both ends of the brush storage section 60a in the longitudinal direction are both open. In other words, the brush storage section 60a is not only open at the front end on the front end surface 43 side of the brush 40, but also at the rear end on the rear end surface 44 side of the brush 40.

As shown in Figures 5 and 7, the brush storage section 60a stores the brush spring 50 together with the brush 40. Therefore, the longitudinal length of the brush storage section 60a is longer than the length of the brush 40. Specifically, the brush spring 50 is arranged in the brush storage section 60a so that the spiral portion 51 is located rearward of the rear end of the brush 40. In this case, the strip-shaped wire material (metal plate) constituting the brush spring 50 is pulled out from the spiral portion 51 toward the commutator 30 along the arc shape of the brush storage section 60a. Specifically, as shown in Figures 7 and 8, the strip-shaped wire material constituting the brush spring 50 is pulled out from the spiral portion 51 along the first side surface 41 of the brush 40.

The outer end 50a of the strip-shaped wire pulled out from the spiral portion 51 of the brush spring 50 is fixed to a fixing portion 60b formed near the opening at the front end of the brush storage portion 60a in the brush holder 60. The fixing portion 60b to which the outer end 50a of the brush spring 50 is fixed is a notched groove. In this case, as shown in FIG. 5, the outer end 50a of the brush spring 50 is fixed to the fixing portion 60b by engaging the V-shaped bent portion formed at the outer end 50a of the brush spring 50 with the fixing portion 60b.

As shown in FIG. 3, the brush 40 stored in the brush storage section 60a is covered by a cover plate 110. In addition to the brush 40, the brush spring 50 is also stored in the brush storage section 60a. Therefore, the cover plate 110 not only covers the brush 40, but also the brush spring 50. The cover plate 110 is, for example, a metal cover made of a metal plate. The cover plate 110 is arranged so as to cover the brush storage section 60a. As shown in FIG. 4, the cover plate 110 is provided with a locking claw. By inserting this locking claw into a locking hole formed in the brush holder 60, the cover plate 110 can be fixed to the brush holder 60.

The brush storage sections 60a are formed according to the number of brushes 40. Since there are two brushes 40, two brush storage sections 60a are formed in the brush holder 60. The two brush storage sections 60a are long in the direction in which the brushes 40 extend. Furthermore, the two brush storage sections 60a are formed with a rectangular concave cross-sectional shape.

As shown in FIG. 4, the brush storage section 60a has a first side wall 61, a second side wall 62, and a bottom wall 63. The first side wall 61 faces the first side surface 41 of the brush 40. The second side wall 62 faces the second side surface 42 of the brush 40. The bottom wall 63 supports the bottom surface of the brush 40.

As shown in Figures 5 and 7, the first side wall 61 and the second side wall 62 are a pair of side walls that sandwich the brush 40. The first side wall 61 and the second side wall 62 are formed in an arc shape, similar to the arc shape of the brush 40. A fixing portion 60b (locking hole) to which the outer end portion 50a of the brush spring 50 is fixed is formed at the end portion of the first side wall 61 on the commutator 30 side.

The first side wall 61 has an arc-shaped side wall surface that faces the first side surface 41, which is the side surface on the outer periphery of the brush 40. The second side wall 62 has an arc-shaped side wall surface that faces the second side surface 42, which is the side surface on the inner periphery of the brush 40.

The brush storage section 60a has a shape that allows the brush 40 to rotate once along the brush storage section 60a. In other words, even if the arc-shaped brush 40 rotates once along the brush storage section 60a, there is no obstacle in the brush holder 60 that the brush 40 comes into contact with. Since the brush 40 is arc-shaped, the brush storage section 60a is formed to form at least a part of the circle that constitutes the arc of the brush 40. Specifically, the shape of the first side wall 61 and the second side wall 62 when viewed from above is an arc of the circle that constitutes the arc of the brush 40.

The distance between the first side wall 61 and the second side wall 62 is constant. Therefore, the curvature of the arc of the first side wall 61 on the outer periphery side is smaller than the curvature of the arc of the second side wall 62 on the inner periphery side. The side wall surfaces of the first side wall 61 and the second side wall 62 are cylindrical surfaces. Therefore, the circle forming the arc of the first side wall 61 has one center point. Similarly, the circle forming the arc of the second side wall 62 also has one center point. The center point of the circle forming the arc of the side wall surface of the first side wall 61 and the center point of the circle forming the arc of the side wall surface of the second side wall 62 are concentric.

The brush storage section 60a is formed so that the brush 40 can rotate once along the brush storage section 60a. Therefore, the arc circle of the side wall surface of the first side wall 61, the arc circle of the side wall surface of the second side wall 62, the arc circle of the first side surface 41 of the brush 40, and the arc circle of the second side surface 42 of the brush 40 are concentric circles.

A gap (clearance) exists between the first side wall 61 and the first side surface 41 of the brush 40. A strip-shaped wire material drawn out from the spiral portion 51 of the brush spring 50 is in contact with the first side surface 41 of the brush 40. A gap exists between the wire material of the brush spring 50 and the first side wall 61. A gap may exist between the second side wall 62 and the second side surface 42 of the brush 40. The gap between the first side wall 61 and the first side surface 41 of the brush 40, and the gap between the second side wall 62 and the second side surface 42 of the brush 40 are, for example, 100 μm or more.

As shown in Figures 5, 7 and 9, the brush holder 60 has a third side wall 64. The third side wall 64 is a wall provided along the commutator 30. The third side wall 64 has an arc shape when viewed from above. The third side wall 64 is provided in a portion of the commutator 30 facing the second side surface 42 (the side surface on the inner circumference side) of the brush 40. The third side wall 64 is not provided in a portion of the commutator 30 that does not face the second side surface 42 of the brush 40. In other words, the third side wall 64 is provided on the inner circumference side of the brush 40, but not on the outer circumference side of the brush 40.

A terminal 70 is attached to the brush holder 60. As shown in FIG. 4, the terminal 70 is formed so as to have a pair of legs and a cross-sectional shape that is substantially U-shaped. As shown in FIG. 9, the brush holder 60 is provided with a pair of slit-shaped through holes 65. The terminal 70 is fixed to the brush holder 60 by pressing the pair of legs of the terminal 70 into the pair of through holes 65 provided in the brush holder 60. The terminal 70 is a conductive terminal made of a conductive metallic material. The terminal 70 is a metal terminal made of a metal plate.

The terminal 70 receives the power passed through the coil 22 of the rotor 20 via the brush 40. The terminal 70 is a power supply terminal. The terminal 70 is electrically connected to an external power supply arranged outside the electric motor 1, and receives power supply power from the external power supply. Therefore, power is supplied to the terminal 70 from the external power supply. The external power supply is a power supply that exists outside the electric motor 1. The external power supply supplies a predetermined input voltage to the electric motor 1.

The external power supply is a DC power supply that supplies an input voltage of DC 12V to the electric motor 1. Therefore, the terminal 70 receives the DC voltage as the input voltage. For this reason, as shown in Figures 5 to 7, the electric motor 1 is provided with two terminals 70 as a pair of power supply terminals. In this case, one of the two terminals 70 is a positive terminal (plus terminal) that is connected to the positive side of the DC power supply. The other of the two terminals 70 is a negative terminal (minus terminal) that is connected to the negative side of the DC power supply.

The terminal 70 is located inside the arc-shaped brush 40. In other words, the terminal 70 is located between the second side surface 42 of the brush 40 and the commutator 30. Specifically, the terminal 70 is disposed in the space surrounded by the second side surface 42 of the brush 40 and the third side wall 64.

The terminal 70 is disposed in the center of the area surrounded by the brush 40. Specifically, when viewed from above, at least a portion of the terminal 70 overlaps with the center of the circle that constitutes the arc of the brush 40, which has an arc-shaped shape when viewed from above.

The pair of terminals 70 and the pair of brushes 40 are in one-to-one correspondence. In other words, one of the pair of terminals 70 is located inside one of the pair of brushes 40, and the other of the pair of terminals 70 is located inside the other of the pair of brushes 40.

Although not shown, electronic components such as a capacitor and a choke coil may be arranged in the brush holder 60. Such electronic components are electrically connected to the brush 40 and the terminal 70.

For example, one or more capacitors may be connected in parallel to the two terminals 70. This allows the capacitors to suppress noise generated by the motor 1. In this case, one lead of the capacitor is electrically connected to one of the two terminals 70, and the other lead of the capacitor is electrically connected to the other of the two terminals 70.

A choke coil may be inserted in the current path between the brush 40 and the terminal 70. This allows the choke coil to remove noise contained in the current flowing in the current path between the brush 40 and the terminal 70. The choke coil is inserted, for example, between the terminal 70 and the conductive wire 80. In this case, one end of the choke coil is electrically connected to the terminal 70, and the other end of the choke coil is electrically connected to the conductive wire 80.

The electronic components electrically connected to the brush 40 and the terminal 70 may be arranged inside the arc-shaped brush 40 in the brush holder 60, similar to the terminal 70. Specifically, the electronic components are arranged in the space surrounded by the second side surface 42 and the third side wall 64 of the brush 40. The electronic components do not have to be arranged inside the brush 40. For example, the electronic components may be arranged in the space between two brushes 40. The electronic components arranged in the brush holder 60 are not limited to noise removal elements such as choke coils or capacitors.

As shown in Figs. 5 to 8, the brush 40 and the terminal 70 are electrically connected by a conductive wire 80. A current supplied from the terminal 70 flows through the conductive wire 80. In other words, the conductive wire 80 is a power supply line for supplying power to the brush 40. For example, a pigtail wire can be used as the conductive wire 80.

As shown in FIG. 8, the first end 80a, which is one end of the conductive wire 80, is connected to the brush 40. Specifically, the first end 80a of the conductive wire 80 is fixed to the rear end of the brush 40. A step portion having a step surface that is one step lower is formed on the upper surface of the rear end of the brush 40. The first end 80a of the conductive wire 80 is fixed to the step surface of this step portion. In this case, the first end 80a of the conductive wire 80 is fixed to the brush 40 by being embedded in the brush 40.

The other end of the conductive wire 80, the second end 80b, is electrically connected to the terminal 70. As shown in FIG. 8, the second end 80b of the conductive wire 80 is directly connected to the terminal 70. In this case, the second end 80b of the conductive wire 80 and the terminal 70 are joined by welding, soldering, or the like.

The conductive wire 80 is pre-twisted before the brush 40 wears. The conductive wire 80 is configured so that the twist is relaxed as the brush 40 wears. Therefore, when joining the conductive wire 80 to the terminal 70, the conductive wire 80 is twisted multiple times and the second end 80b of the conductive wire 80 is joined to the terminal 70. Specifically, the conductive wire 80 is configured so that the twist is eliminated when the brush 40 wears down to its shortest length.

Here, a method for fixing the brush 40 and brush spring 50 to the brush holder 60 will be described with reference to Figures 10 to 12. Figure 10 is a perspective view of the brush spring 50 in a state in which the strip-shaped wire is stored in the spiral portion 51 (before the wire is pulled out). Figure 11 is a diagram showing the brush spring 50 in the state shown in Figure 10 and the brush 40 when set in the brush holder 60. Figure 12 is a diagram for explaining the state when the brush 40 and brush spring 50 are fixed to the brush holder 60. The brush spring 50 has been omitted from Figure 12.

As shown in Figure 11, the brush spring 50 and the brush 40 in the state shown in Figure 10 are set in the brush holder 60. Specifically, the wire that constitutes the brush spring 50 is inserted into the fixing portion 60b (notched groove) of the brush holder 60, and the tip of the V-shaped bent portion formed on the outer end portion 50a of the brush spring 50 is engaged with the outer surface of the first side wall 61 of the brush storage portion 60a, and the brush spring 50 is set in the brush storage portion 60a.

The brush 40 with the conductive wire 80 connected thereto is prepared, and the brush 40 is set in the brush storage section 60a with the rear end surface 44 of the brush 40 abutting against the spiral portion 51 of the brush spring 50. At this time, part of the brush 40 protrudes from the brush storage section 60a. Specifically, part of the brush 40 is present in the area where the commutator 30 is located (the area closer to the center than the third side wall 64). At this time, the conductive wire 80 connected to the brush 40 is joined to the terminal 70. As described above, the conductive wire 80 is twisted and joined to the terminal 70.

Next, as shown in (a) to (d) of Figure 12, the brush 40 is moved from the state shown in Figure 11. Specifically, as shown in (d) of Figure 12, the brush 40 is moved until the front end surface 43 of the brush 40 is positioned at the front end of the brush storage section 60a.

In this embodiment, the brush storage section 60a is formed so that the brush 40 can rotate once along the brush storage section 60a. As a result, by rotating the brush 40, the rear end surface 44 of the brush 40 can be moved sequentially toward the back side of the brush storage section 60a (in the direction of the arrow in Figure 12).

At this time, although not shown, the spiral portion 51 of the brush spring 50, which abuts against the rear end surface 44 of the brush 40, moves toward the rear side of the brush storage section 60a as the brush 40 moves. At that time, because the outer end portion 50a of the brush spring 50 is fixed to the fixed portion 60b of the brush holder 60, as the brush 40 rotates, the strip-shaped wire that constitutes the brush spring 50 is pulled out from the spiral portion 51 along the arc shape of the brush storage section 60a. In other words, the brush 40 rotates while receiving a gradually increasing spring elastic force from the spiral portion 51 of the brush spring 50.

In this way, there is no obstacle that comes into contact with the brush 40 even when the brush 40 rotates once along the brush storage section 60a. Therefore, by adopting this configuration that combines the arc-shaped brush 40 with a constant load spring, the assembly of the electric motor 1 can be improved.

Then, although not shown, the two brushes 40 and the two brush springs 50 are set in the brush holder 60, and then the two brushes 40 and the two brush springs 50 are attached to the second bracket 102. In this way, the brush holder 60 and the second bracket 102 are separate entities. Therefore, even when multiple brushes 40 are placed on the brush holder 60, the brushes 40 can be attached to the second bracket 102 while being held by the brush holder 60. This makes it possible to easily set multiple brushes 40 in the brush holder 60, even when multiple arc-shaped brushes 40 are used.

In the electric motor 1 configured as described above, the current (drive current) supplied to the brushes 40 flows through the coils 22 via the commutator segments 31 of the commutator 30. This generates magnetic flux in the rotor 20 (coils 22). The magnetic force generated by the interaction between the magnetic flux generated in the rotor 20 and the magnetic flux generated from the stator 10 becomes torque that rotates the rotor 20. At this time, the direction of the current flow is switched depending on the positional relationship when the commutator segments 31 of the commutator 30 come into contact with the brushes 40. In this way, by switching the direction of the current flow, a rotational force in a fixed direction is generated by the repulsive and attractive forces of the magnetic forces generated between the stator 10 and the rotor 20. This causes the rotor 20 to rotate around the rotating shaft 21.

Figure 13 shows how the brush 40 slides due to wear. As shown in Figure 13, the brush 40 stored in the brush storage section 60a of the brush holder 60 is pressed against the commutator 30 by the brush spring 50. Therefore, when the rotor 20 rotates, the front end portion is worn down due to friction with the commutator segments 31 of the commutator 30. In other words, as shown by the arrow in Figure 13, the brush 40 becomes shorter due to wear. Therefore, the rear end surface 44 of the brush 40 moves toward the commutator 30 inside the brush storage section 60a. At this time, the wire that constitutes the brush spring 50, which is a constant-load spring, is wound up into a spiral portion 51 as the brush 40 becomes shorter due to wear. In other words, the spiral portion 51 approaches the outer end portion 50a.

In this way, the brush 40 slides within the brush storage section 60a toward the commutator 30 as the front end wears. In this embodiment, the brush storage section 60a is composed of a first side wall 61 and a second side wall 62. Therefore, the brush 40 moves between the first side wall 61 and the second side wall 62 while being guided by the first side wall 61 and the second side wall 62. In other words, the first side wall 61 and the second side wall 62 function as guide walls that guide the brush 40.

As shown in FIG. 13, as the brush 40 slides between the first side wall 61 and the second side wall 62, the spiral portion 51 of the brush spring 50 pressing against the brush 40 also moves between the first side wall 61 and the second side wall 62 toward the commutator 30. Specifically, the spiral portion 51 of the brush spring 50 moves between the first side wall 61 and the second side wall 62 while being guided by the first side wall 61 and the second side wall 62. In this way, the first side wall 61 and the second side wall 62 also function as guide walls that guide the spiral portion 51 of the brush spring 50.

As described above, in the electric motor 1, the brush 40 is arc-shaped. At the point where the front end surface 43 of the brush 40 contacts the commutator 30, the angle θ between the tangent of the brush 40 and the direction of rotation of the electric motor 1 is less than 90°.

With this configuration, the diameter (arc diameter) of the circle that forms the arc of the arc-shaped brush 40 can be made larger than when the angle θ between the tangent of the brush 40 and the direction of rotation of the motor 1 is 90° (θ = 90°). This makes it possible to extend the life of the motor 1. In this case, by arranging the longer brush 40 to effectively utilize the internal space of the motor 1, it is possible to extend the life of the motor 1 without increasing the external size of the motor 1. In other words, it is possible to achieve a motor 1 with a long life without increasing the external diameter size. In this way, a compact motor 1 with a long life can be easily achieved.

If a torsion spring is used as the brush spring for pressing the arc-shaped brush 40 against the commutator 30, the load will be strong on the second side 42 (inner peripheral surface) of the brush 40, and the load on the brush 40 will be biased. However, as in this embodiment, by using a constant load spring as the brush spring 50, the load will be biased on the first side 41 (outer peripheral surface) of the brush 40. Therefore, by making the angle θ between the tangent of the brush 40 and the direction of rotation of the electric motor 1 less than 90°, the load on the front and rear ends of the brush 40 can be made closer to constant. This makes it possible to apply a load appropriate for the commutator 30 to the commutator 30.

When a torsion spring is used as a brush spring, the difference between the pressure (initial pressure) before the brush wears out and the pressure (final pressure) when the motor reaches the end of its life due to brush wear becomes large. In other words, the difference in the pressing load on the commutator becomes large between the initial and final stages of the brush's life. Furthermore, when a torsion spring presses an arc-shaped brush, the arc-shaped brush is pressed outward by the pressing load of the torsion spring. As a result, the pressing load when the brush presses the commutator by the torsion spring is reduced. Furthermore, when a torsion spring is used as a brush spring for pressing an arc-shaped brush against a commutator, the torsion spring is positioned inside the arc-shaped brush. This leaves no free space inside the brush. This makes it difficult to position terminals inside the brush.

In contrast, by using a constant load spring as the brush spring 50 as in this embodiment, a constant pressure load can be applied to the brush 40 by the brush spring 50 even if the brush 40 wears. This makes it possible to reduce the difference between the pressure (initial pressure) before the brush 40 wears and the pressure (final pressure) when the motor 1 reaches the end of its life due to wear of the brush 40.

By using a constant load spring as the brush spring 50, it is possible to provide an empty space inside the brush 40. This makes it possible to easily place the terminals 70 inside the arc-shaped brush 40. In this case, not only the terminals 70 but also electronic components (such as a choke coil or a capacitor) electrically connected to the brush 40 can be placed inside the brush 40.

In this way, by arranging the terminal 70 inside the brush 40, the length of the conductive wire 80 electrically connecting the terminal 70 and the brush 40 can be shortened. This prevents the conductive wire 80 from interfering with the uneven structure of the brush holder 60, etc., and reducing the load stability of the brush 40, even if the conductive wire 80 moves as the brush 40 wears. Therefore, a highly reliable, long-life electric motor 1 can be realized.

Furthermore, at least a portion of the terminal 70 overlaps with the center of the circle that constitutes the arc of the brush 40.

This configuration allows the length of the conductive wire 80 to be minimized. This further prevents the load stability of the brush 40 from decreasing.

Furthermore, when a constant force spring is used as the brush spring 50, as in this embodiment, the brush spring 50 is positioned so that the strip-shaped wire pulled out from the spiral portion 51 contacts the arc-shaped side of the brush 40. As a result, the brush 40 not only receives the pressing load from the brush spring 50 at the rear end surface 44 where the spiral portion 51 contacts, but also at the contact point between the strip-shaped wire pulled out from the spiral portion 51 and the arc-shaped side of the brush 40. Therefore, it is possible to eliminate the reduction in the pressing load when the brush presses the commutator, as occurs when a torsion spring is used as the brush spring.

Specifically, the brush spring 50 is arranged so that the strip-shaped wire material (metal plate) that constitutes the brush spring 50 is in contact with the first side surface 41 on the outer periphery of the brush 40.

As a result, a pressure load is generated in the direction toward the commutator 30 from the contact point between the band-shaped wire of the brush spring 50 and the arc-shaped first side surface 41 of the brush 40. Therefore, even with an arc-shaped brush 40, a stable pressure load can be applied from the brush 40 to the commutator 30. In other words, a stable pressure from the brush 40 can be achieved.

In addition, the strip-shaped wire pulled out from the spiral portion 51 of the brush spring 50 and the arc-shaped first side surface 41 of the brush 40 are in close contact with each other. Therefore, wear powder from the brush 40 cannot get between the strip-shaped wire of the brush spring 50 and the first side surface 41 of the brush 40. As a result, even when the brush spring 50 is used, the wear powder from the brush 40 does not reduce the sliding properties between the brush spring 50 and the brush 40.

In addition, when the terminal 70 is placed inside the brush 40, the conductive wire 80 connected to the terminal 70 and brush 40 moves with the joint between the conductive wire 80 and the terminal 70 as a fixed end as the brush 40 wears. Specifically, the conductive wire 80 rotates with the joint between the conductive wire 80 and the terminal 70 as a fixed end. At this time, the conductive wire 80 twists as the brush 40 wears, which may cause the load of the brush 40 to decrease.

Therefore, in the electric motor 1, the conductive wire 80 is twisted in advance before the brush 40 wears. This allows the twist to be relaxed as the brush 40 wears.

With this configuration, when the conductive wire 80 rotates around the joint between the conductive wire 80 and the terminal 70 as the brush 40 wears, the twist in the conductive wire 80 is relaxed as the conductive wire 80 rotates. This effectively prevents the load of the brush 40 from decreasing even if the conductive wire 80 rotates.

In addition, when the brush 40 wears, brush wear powder is generated, and in particular, the arc-shaped brush 40 generates more brush wear powder than a straight brush. In this regard, in this embodiment, a third side wall 64 is provided along the commutator 30. This makes it possible for the third side wall 64 to prevent brush wear powder from scattering. In other words, the third side wall 64 functions as a protective wall that prevents brush wear powder from scattering. In this way, by providing the third side wall 64 on the brush holder 60, it is possible to prevent the load of the brush 40 from decreasing due to clogging with brush wear powder.

In particular, the third side wall 64 is provided in the portion facing the second side surface 42 of the brush 40 (the inner peripheral portion of the brush 40), and is not provided in the portion not facing the second side surface 42 of the brush 40 (the outer peripheral portion of the brush 40). This can encourage the scattering of brush wear powder to the portion not facing the second side surface 42 of the brush 40. This makes it difficult for brush wear powder to scatter to the portion facing the second side surface 42 of the brush 40. In other words, the brush wear powder can be selectively collected to the outer peripheral portion of the brush 40. Therefore, it is possible to prevent the insulation reliability of the terminals 70 and electronic components arranged in the inner peripheral portion of the brush 40 from being reduced by the brush wear powder. For example, it is possible to prevent the electronic components from shorting out, etc., and thereby reducing the electromagnetic compatibility (EMC).

In addition, in this embodiment, the arc-shaped brush 40 is made without cutting. To process the arc-shaped brush 40 with high dimensional accuracy, a sintered body obtained by compressing and sintering powder is cut. However, it is difficult to cut an arc-shaped sintered body. For this reason, the manufacturing costs are high to make an arc-shaped brush 40 with high dimensional accuracy. Therefore, in this embodiment, the arc-shaped brush 40 is made without cutting. This allows the brush 40 to be made at low cost. Therefore, a low-cost electric motor 1 can be realized.

The motor 1 also uses a long, arc-shaped brush 40. Specifically, the angle between the line connecting the center point of the circle that forms the arc of the brush 40 to the front end surface 43 of the brush 40 and the line connecting the center point of the circle that forms the arc of the brush 40 to the rear end surface 44 of the brush 40 is 90° or more.

If a torsion spring is used as the brush spring for such a long, arc-shaped brush 40, the pressing load applied to the brush 40 by the brush spring may not be stable, resulting in a reduced lifespan and quality. However, by using a constant-load spring as the brush spring 50 as in the case of the electric motor 1, the pressing load on the brush 40 can be stabilized even when a long, arc-shaped brush 40 is used. This makes it possible to realize an electric motor 1 with a long lifespan and high quality.

As described above, the electric motor 1 according to this embodiment includes the rotating shaft 21 whose axial direction is the direction in which the axis C extends, the commutator 30 attached to the rotating shaft 21, at least one brush 40 in contact with the commutator 30, a brush holder 60 that holds the brush 40, a terminal 70 attached to the brush holder 60, and a conductive wire 80 whose one end, the first end 80a, is connected to the brush 40 and whose other end, the second end 80b, is electrically connected to the terminal 70. The brush 40 is arc-shaped. At the point where the front end surface 43 of the brush 40 contacts the commutator 30, the angle between the tangent of the brush 40 and the direction of rotation of the electric motor 1 is less than 90°.

As a result, in an electric motor 1 using arc-shaped brushes 40, it is possible to extend the life of the electric motor 1 without increasing the external size of the electric motor 1.

(Embodiment 2)
Next, an electric motor 1A according to a second embodiment will be described with reference to Figs. 14, 15 and 16. Fig. 14 is a perspective view of a brush holder 60 in which a brush 40A and a brush spring 50 are arranged in the electric motor 1A according to the second embodiment. Fig. 15 is an enlarged view of a rear end portion of the brush 40A and its surrounding area in Fig. 14. Fig. 16 is a perspective view of the brush 40A and conductive wire 80 provided in the electric motor 1A according to the second embodiment.

The electric motor 1A differs from the electric motor 1 according to the first embodiment in the shape of the brush 40A and the connection structure between the brush 40A and the brush spring 50.

Specifically, as shown in Figures 14 to 16, brush 40A has protrusion 45 and groove 46. Spiral portion 51 of brush spring 50 is inserted into protrusion 45. The wound portion of wire in spiral portion 51 inserted into protrusion 45 (laminated portion of wire) is inserted into groove 46. In other words, spiral portion 51 of brush spring 50 is wound around protrusion 45 of brush 40A.

The protrusion 45 of the brush 40A is formed on the upper surface of the rear end of the brush 40A. The protrusion 45 is formed in a cylindrical shape. The shape of the protrusion 45 when viewed from above is circular. The central axis of the cylindrical protrusion 45 is parallel to the axis C of the rotating shaft 21. The conductive wire 80 is fixed to the center of the protrusion 45. Therefore, when viewed from above, the connection portion between the brush 40A and the conductive wire 80 is located inside the spiral portion 51 of the brush spring 50. The groove 46 is formed on the front side of the protrusion 45.

The brush spring 50 thus arranged on the brush 40A applies pressure to the brush 40A on the inner circumferential surface of the spiral portion 51. Specifically, the brush spring 50 applies pressure to the brush 40A on the inner circumferential surface of the spiral portion 51 on the rear end surface 44 side of the brush 40A.

Other than that, the configuration of the electric motor 1A is basically the same as that of the electric motor 1 in the first embodiment described above.

Therefore, the electric motor 1A has the same effect as the electric motor 1 in the first embodiment. For example, in the electric motor 1A, the angle θ between the tangent of the brush 40A and the direction of rotation of the electric motor 1 is less than 90° at the point where the front end surface 43 of the brush 40A contacts the commutator 30. This provides the effect of realizing an electric motor 1A with a long life without increasing the outer diameter size.

In the electric motor 1A of this embodiment, the brush spring 50, which is a constant force spring, is also positioned so that it contacts the first side surface 41 (the side surface on the outer periphery) of the brush 40A.

If the brush spring 50 were arranged so as to contact the second side surface 42 (the side surface on the inner circumference) of the brush 40A, the amount of plastic deformation would be more than doubled when the outer diameter of the spiral portion 51 increases as the brush 40A wears and the band-shaped wire material constituting the brush spring 50 undergoes plastic deformation. Therefore, it is possible to increase the width W of the groove 46 of the brush 40A. However, if the width W of the groove 46 is made too large, the effective wear length of the brush 40A will be reduced. Therefore, as in this embodiment, by arranging the brush spring 50 so as to contact the first side surface 41 of the brush 40A, the amount of plastic deformation of the band-shaped wire material constituting the brush spring 50 can be reduced without making the width W of the groove 46 of the brush 40A too large.

In the case of a stainless steel brush spring 50 with an outer diameter of the spiral portion 51 of 4 mm, the width W of the groove 46 should be between 1.3 and 2 times the thickness of the portion of the spiral portion 51 where the wire is wound. This allows the amount of plastic deformation of the strip-shaped wire that makes up the brush spring 50 to be about 1.5 times larger.

In addition, in the electric motor 1A, the brush spring 50, which is a constant-load spring, applies pressure to the brush 40A with the inner circumferential surface of the spiral portion 51. When viewed from above, the connection between the brush 40A and the conductive wire 80 is located inside the spiral portion 51.

This configuration maximizes the effective wear length of the brush 40A. It also stabilizes the pressure (spring load) applied by the brush 40A to the commutator 30. Moreover, the brush spring 50 can be connected to the brush 40A by inserting and fitting the spiral portion 51 of the brush spring 50 into the protrusion 45 of the brush 40A. This allows the brush 40A to be easily set in the brush holder 60.

(Modification)
The electric motor according to the present disclosure has been described above based on the first and second embodiments. However, the present disclosure is not limited to the first and second embodiments.

For example, in the above-mentioned first and second embodiments, two

brushes

40 and 40A are arranged. However, this is not limited to this. FIG. 17 is a diagram for explaining the arrangement of the brushes 40 in the electric motor 1B according to the modified example. As in the electric motor 1B shown in FIG. 17, the arc-shaped brush 40 may include four brushes. When a torsion spring is used as the brush spring, it is difficult to arrange four arc-shaped brushes due to space issues unless the external size of the electric motor is increased. However, as in the above-mentioned first and second embodiments, by using a constant-load spring as the brush spring 50 and arranging the terminal 70 inside the arc-shaped brush 40, as shown in FIG. 17, it is possible to arrange four arc-shaped brushes 40 without increasing the external size of the electric motor 1B. In other words, the space of the electric motor 1 can be effectively utilized to further extend the life of the electric motor 1. As an example, it is preferable to arrange the four brushes 40 at equal intervals (0°, 90°, 180°, 270°) in the rotation direction. This allows the space of the electric motor 1B to be used as effectively as possible. The longest-lasting motor 1B can be achieved by using four brushes 40. When using four brushes 40, the number of poles of the motor 1B can be 4n (n is an integer equal to or greater than 1).

In the above embodiments 1 and 2, the electric motors 1 and 1A are coreless motors in which the stator 10 and the rotor 20 do not have cores. However, this is not limited to this. For example, the electric motor 1 may be an electric motor in which the stator 10 and the rotor 20 have cores.

In the above embodiments 1 and 2, the stator 10 is composed of only permanent magnets. However, this is not limited to this. For example, the stator 10 may be a stator composed of a permanent magnet and an iron core, or an armature composed of a stator winding and an iron core without using permanent magnets.

In the above-mentioned embodiments 1 and 2, the electric motors 1 and 1A are flat motors with an outer size whose thickness is smaller than the outer diameter. However, this is not limited to this. The technology disclosed herein can also be applied to, for example, a cylindrical electric motor having a cylindrical housing with an outer size whose thickness is larger than the outer diameter.

In the above-mentioned first and second embodiments, the direction of the main magnetic flux generated by the stator 10 and the rotor 20 is the direction of the axis C of the rotating shaft 21. However, this is not limited to this. Specifically, the direction of the main magnetic flux generated by the stator 10 and the rotor 20 may be a direction perpendicular to the direction of the axis C of the rotating shaft 21 (the radial direction of the rotation of the rotating shaft 21). For example, the technology disclosed herein can also be applied to an inner rotor type motor in which the rotor 20 is arranged inside the stator 10.

In the above-mentioned embodiments 1 and 2, the electric motors 1 and 1A are vehicle motors used in vehicles. However, this is not limited to this. The technology disclosed herein can also be applied to electric motors used in various other electrical devices, such as electric motors used in electric blowers mounted on electric vacuum cleaners, etc.

In addition, this disclosure also includes forms obtained by applying various modifications that a person skilled in the art would conceive of to the above-mentioned embodiments 1 and 2 and the modifications, or forms realized by arbitrarily combining the components and functions of embodiments 1 and 2 and the modifications without departing from the spirit of this disclosure. In addition, this disclosure also includes any combination of one or more components in each of the multiple claims described in the claims at the time of filing this application. In addition, when a cited-form claim described in the claims at the time of filing this application is made into a multiple claim or multiple-multi claim so as to cite any multiple claims, this disclosure also includes inventions of combinations of all claims included in that multiple claim or multiple-multi claim.

The technology disclosed herein can be widely used in a variety of products equipped with electric motors, including products in the electrical equipment field such as automobiles and in the field of household electrical appliances.

1, 1A, 1B Electric motor 10 Stator 20 Rotor 21 Rotating shaft 21a First end 21b Second end 22 Coil 23 Molded resin 24 Cylindrical member 30 Commutator 31

Commutator segment

40, 40A Brush 41 First side surface 42 Second side surface 43 Front end surface 44 Rear end surface 45 Protrusion 46 Groove 50 Brush spring

50a Outer end

50b Inner end 51 Spiral portion 60 Brush holder 60a Brush storage portion 60b Fixing portion 61 First side wall 62 Second side wall 63 Bottom wall 64 Third side wall 65 Through hole 70 Terminal 80 Conductive wire 80a First end 80b Second end 91 First bearing 92 Second bearing 101 First bracket 102 Second bracket 110 Cover plate

Claims

A rotation axis having an axial direction in a direction in which the axis extends;
A commutator attached to the rotating shaft;
At least one brush in contact with the commutator;
A brush holder for holding the brush;
A terminal attached to the brush holder;
a conductive wire having one end connected to the brush and the other end electrically connected to the terminal;
The brush is arc-shaped,
At a point where the front end surface of the brush contacts the commutator, an angle between a tangent of the brush and a rotation direction of the motor is less than 90°.
Electric motor.
a brush spring for pressing the brush against the commutator;
The brush spring is a constant force spring.
2. The electric motor according to claim 1.
The constant force spring is disposed so as to contact the outer peripheral side surface of the brush.
3. The electric motor according to claim 2.
The brush holder has a wall provided along the commutator,
the wall is provided at a portion of the commutator facing the inner peripheral side surface of the brush, and is not provided at a portion of the commutator not facing the inner peripheral side surface of the brush;
The electric motor according to any one of claims 1 to 3.
The brush holder has a brush storage portion that stores the brush,
The brush housing has a shape that allows the brush to rotate once along the brush housing.
The electric motor according to any one of claims 1 to 3.
The at least one brush comprises a plurality of brushes.
The electric motor according to any one of claims 1 to 3.
The plurality of brushes includes four brushes.
7. The electric motor according to claim 6.
The number of poles of the motor is 4n (n is an integer equal to or greater than 1).
8. The electric motor according to claim 7.
A bracket separate from the brush holder is further provided,
The brush holder is configured to be attachable to the bracket while holding the at least one brush.
7. The electric motor according to claim 6.
The constant force spring has a spiral portion in which a strip-shaped wire is wound in a spiral shape,
The constant force spring applies a pressure to the brush via an inner circumferential surface of the spiral portion.
4. The electric motor according to claim 2 or 3.
When viewed from above, a connection portion between the brush and the conductive wire is located inside the spiral portion.
11. The electric motor according to claim 10.
The brush has a protrusion into which the spiral portion is inserted, and a groove into which a portion of the spiral portion around which the wire is wound is inserted when the protrusion is inserted.
11. The electric motor according to claim 10.
The width of the groove is 1.3 times or more and 2 times or less the thickness of the portion of the spiral portion around which the wire is wound.
13. The electric motor according to claim 12.