Electric motor

Abstract

This electric motor comprises: a rotor having a rotary shaft that extends in the axial direction in which the axis stretches; a commutator attached to the rotary shaft; brushes that contact the commutator; brush springs that press the brushes against the commutator; and a cover plate that covers the brushes and the brush springs. The cover plate is provided with through-holes. The appearance of a brush viewed from the through holes when the brush is in a first orientation looks different from the appearance of the brush viewed from the through holes when the brush is in a second orientation that is on the side opposite from the first orientation in the axial direction.

Description

electric motor

[0001] The present disclosure relates to electric motors.

[0002] Electric motors are widely used in the fields of household electrical appliances such as electric vacuum cleaners, as well as in the field of electrical equipment mounted on vehicles, etc. For example, electric motors are used in two-wheeled or four-wheeled vehicles to drive cooling fans that cool the radiators or batteries.

[0003] 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, a rotor that rotates due to the magnetic force of the stator, a commutator attached to the rotating shaft of the rotor, and brushes that contact the commutator.

[0004] In brush motors, brush springs are used to press the brushes against the commutator. The brush springs apply a spring load (pressing force) to the brushes using their spring elasticity. Conventionally, coil springs or torsion springs have been used as brush springs in brush motors.

[0005] However, when a coil spring or a torsion spring is used as the brush spring, the spring load on the brush is not constant, but gradually decreases as the brush wears. As a result, the surface pressure between the brush and the commutator changes as the brush wears. As a result, the reliability of the motor decreases.

[0006] To address this issue, a technique has been proposed in which a constant force spring having a spiral portion formed by winding a strip of wire as a brush spring has been used (see Patent Document 1). When using a constant force spring as a brush spring, the spiral portion of the constant force spring is brought into contact with the rear end surface of the brush. This makes it possible to suppress changes in spring load due to brush wear.

[0007] In a brush motor, the brushes are placed in a brush storage compartment provided in a brush holder or the like. In this case, the brushes must be placed in the brush storage compartment in the correct orientation. However, the brushes may be placed in the brush storage compartment in the wrong orientation. In other words, the motor may be assembled with the brushes in an incorrectly assembled state. As a result, the brushes may not slide correctly when the motor is driven.

[0008] Microfilm of Utility Model Application No. 59-4563 (Utility Model Application No. 60-117675)

[0009] The present disclosure has been made to solve such problems, and an object of the present disclosure is to provide an electric motor that can prevent brushes from being assembled incorrectly.

[0010] In order to achieve the above object, a first aspect of the electric motor according to the present disclosure comprises a rotor having a rotating shaft extending in an axial direction in which an axis extends, a commutator attached to the rotating shaft, a brush in contact with the commutator, a brush spring that presses the brush against the commutator, and a cover plate that covers the brush and the brush spring, wherein the cover plate has a through hole, and the appearance of the brush seen from the through hole when the brush is in a first position is different from the appearance of the brush seen from the through hole when the brush is in a second position in which the brush is facing opposite to the first position in the axial direction.

[0011] A second aspect of the electric motor according to the present disclosure comprises a rotor having a rotating shaft extending in an axial direction in which an axis extends, a commutator attached to the rotating shaft, brushes in contact with the commutator, brush springs that press the brushes against the commutator, and a cover plate that covers the brushes and the brush springs, wherein the cover plate has a through hole, and the brush has a display portion that is visible through the through hole when the brush is in a first position, and is not visible through the through hole when the brush is in a second position in which it is facing opposite to the first position in the axial direction.

[0012] According to the present disclosure, incorrect assembly of the brush can be prevented.

[0013] FIG. 1 is a perspective view of an electric motor according to an embodiment, as seen from above. FIG. 2 is a perspective view of the electric motor according to the embodiment, as seen from below. FIG. 3 is a cross-sectional view of the electric motor according to the embodiment, taken along a plane passing through the axis of the rotating shaft and the brushes. FIG. 4 is an exploded perspective view of the electric motor according to the embodiment. FIG. 5 is an exploded perspective view of a brush holder and various components arranged in the brush holder shown in FIG. 4. FIG. 6 is a perspective view of a brush used in the electric motor according to the embodiment. FIG. 7 is an enlarged cross-sectional view of an area VII surrounded by a dashed line in FIG. 3. FIG. 8 is a side view of a brush spring used in the electric motor according to the embodiment. FIG. 9A is a perspective view of a cover plate used in the electric motor according to the embodiment, as seen from the outside. FIG. 9B is a perspective view of a cover plate used in the electric motor according to the embodiment, as seen from the inside. FIG. 10 is a cross-sectional view showing a state in which the brush is correctly assembled to the brush holder and a state in which the brush is incorrectly assembled to the brush holder when assembling an electric motor of a comparative example. Fig. 11 is a cross-sectional view showing a state in which the brush is correctly assembled to the brush holder and a state in which the brush is incorrectly assembled to the brush holder when the electric motor according to the embodiment is assembled. Fig. 12 is a plan view showing a state in which the brush is correctly assembled to the brush holder and a state in which the brush is incorrectly assembled to the brush holder when the electric motor according to the embodiment is assembled. Fig. 13 is a diagram showing a state in which an incorrect assembly occurs when the electric motor according to the embodiment is actually assembled. Fig. 14 is an exploded perspective view showing the brush holder and various parts arranged on the brush holder in another electric motor according to the embodiment. Fig. 15 is a diagram showing the configuration of a portion of an electric motor according to a modified example.

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Each of the embodiments described below represents a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, arrangement positions and connection forms of the components, 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 the independent claims that represent the highest concept of the present disclosure will be described as optional components.

[0015] In this specification and the drawings, the X-axis, Y-axis, and Z-axis represent the three axes of a three-dimensional Cartesian coordinate system. The X-axis and Y-axis are perpendicular to each other and perpendicular to the Z-axis. In this embodiment, the Z-axis direction is the direction in which the axis C of the rotation shaft 21 extends.

[0016] Each drawing is a schematic diagram and is not necessarily a precise illustration. In all drawings, substantially the same components are denoted by the same reference numerals, and redundant explanations will be omitted or simplified.

[0017] In this embodiment, the radial direction of the stator 10 and the rotor 20 is referred to as the "radial direction," and the rotation direction of the rotor 20 is referred to as the "circumferential direction." In other words, the direction spreading from the axis C of the rotating shaft 21 as the center is the "radial direction," and the direction going around the axis C of the rotating shaft 21 as the center is the "circumferential direction." Therefore, the "radial direction" is a direction perpendicular to the direction of the axis C of the rotating shaft 21 (also simply referred to as the "axial direction"). In this specification, the terms "up" and "down" do not necessarily refer to the up direction (vertically upward) and the down direction (vertically downward) in absolute spatial recognition.

[0018] (Embodiment) The configuration of an electric motor 1 according to an embodiment will be described with reference to Figs. 1 to 5. Fig. 1 is a perspective view of the electric motor 1 according to the embodiment as seen from above. Fig. 2 is a perspective view of the electric motor 1 according to the embodiment as seen from below. Fig. 3 is a cross-sectional view of the electric motor 1 according to the embodiment when cut along a plane that passes through the axis C of the rotating shaft 21 and the brushes 40. Fig. 4 is an exploded perspective view of the electric motor 1 according to the embodiment. Fig. 5 is an exploded perspective view of the brush holder 60 and various components arranged in the brush holder 60 shown in Fig. 4.

[0019] As shown in FIG. 3 , 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 further includes a commutator 30 attached to a rotating shaft 21 of the rotor 20, at least one brush 40 in contact with the commutator 30, a brush spring 50 for pressing the brush 40 against the commutator 30, a brush holder 60 for holding the brush 40, and a cover plate 70 for covering the brush 40. As shown in FIGS. 3 to 5 , the electric motor 1 further includes a power supply terminal 80 electrically connected to the brush 40, a capacitor 90 connected to the power supply terminal 80, a bearing 100, a first bracket 111, and a second bracket 112. As shown in FIGS. 1 and 2 , a power supply line 2 for supplying power to the electric motor 1 is connected to the electric motor 1.

[0020] The electric motor 1 is a type of direct current motor (DC (Direct Current) motor) driven by direct current. For this reason, as shown in FIG. 3 , the electric motor 1 uses a magnet as the stator 10. The electric motor 1 uses an armature having a coil 22 as the rotor 20. In this embodiment, the electric motor 1 is a flat-type (flat-type) brushed coreless motor (flat motor) 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 has a thin and lightweight configuration overall. Specifically, the electric motor 1 is a small motor used in a cooling fan for a radiator in a vehicle. The outer diameter (diameter) φ of the electric motor 1 is 120 mm or less. For example, the outer diameter φ of the electric motor 1 is φ60 mm, φ70 mm, φ90 mm, or the like. The electric motor 1 is driven by power supplied from an external power source such as a battery. For example, the electric motor 1 is driven by an input voltage of DC 12V supplied via a power supply line 2 connected to an external power source.

[0021] Each component of the electric motor 1 will now be described in detail.

[0022] As shown in FIG. 3 , the stator 10 is disposed between the rotor 20 and the stator 10 via a small air gap. 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, together with the rotor 20, which is an armature, forms a magnetic circuit. Specifically, the stator 10 is substantially donut-shaped as a whole. The stator 10 is configured so that north and south poles alternate evenly 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 generates magnetic flux for generating torque. In this embodiment, the stator 10 is composed of multiple magnets. The magnets that make up the stator 10 are, for example, permanent magnets. The direction of the main magnetic flux generated by the stator 10 (magnets) is aligned with the extension direction of the rotating shaft 21. The stator 10 is fixed to a first bracket 111.

[0023] 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.

[0024] The rotor 20 rotates around the axis C along which the rotating shaft 21 extends. 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 along the axis C along which the rotating shaft 21 extends.

[0025] The rotor 20 is disposed opposite the stator 10. The rotor 20 faces the stator 10 in the direction of the axis C along which the rotating shaft 21 extends. Specifically, the coil 22 of the rotor 20 and the stator 10 face each other in the direction of the axis C along which the rotating shaft 21 extends. In other words, the coil 22 and the stator 10 are aligned in the direction of the axis C of the rotating shaft 21.

[0026] 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 Use Stainless Steel). The axis C included in the rotating shaft 21 serves as the center of rotation when the rotor 20 rotates. The longitudinal direction of the rotating shaft 21, i.e., the direction in which the rotating shaft 21 extends (extension direction), is the direction of the axis C.

[0027] The rotating shaft 21 is supported by a bearing 100. In this embodiment, there is only one bearing 100. That is, the rotating shaft 21 is supported by only one bearing 100. The bearing 100 supports the rotating shaft 21 so that it can rotate freely. The rotating shaft 21 is press-fitted into the bearing 100. The bearing 100 is held by a first bracket 111. Specifically, the bearing 100 is press-fitted and fixed into a recess provided in the first bracket 111. As an example, the bearing 100 is a ball bearing. Specifically, the bearing 100 is a deep groove ball bearing. Other types of bearings may also be used for the bearing 100. For example, a plain bearing may be used as the bearing 100.

[0028] The first end 21a of the rotating shaft 21 is the end on the output side (output shaft). The first end 21a protrudes from the first bracket 111 and the bearing 100. The first end 21a is the end of the rotating shaft 21 that is closer to the bearing 100 than the bearing 100 and the commutator 30. A load such as a rotary fan is attached to the first end 21a. The electric motor 1 with a rotary fan attached to the rotating shaft 21 can be used as, for example, a cooling fan or an electric blower. The second end 21b of the rotating shaft 21 is the end on the counter-output side (counter-output shaft) and does not protrude from the second bracket 112.

[0029] The first bracket 111 and the second bracket 112 are made of, for example, a metal material. For example, the first bracket 111 and the second bracket 112 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 first bracket 111 and the second bracket 112 form a housing. The stator 10 and the rotor 20 are arranged in this housing.

[0030] 1 and 2 , in this embodiment, the first bracket 111 is an outer shell member of the electric motor 1. The first bracket 111 is formed in a cylindrical shape with a bottom and a cylindrical side wall. The magnets that make up the stator 10 are fixed to the bottom of the first bracket 111. The coils 22 of the rotor 20 are surrounded by the side wall of the first bracket 111.

[0031] The second bracket 112 is arranged to cover the brush holder 60. Specifically, the second bracket 112 is arranged to cover the opening of the brush holder 60. The second bracket 112 has a flat plate shape. In other words, the second bracket 112 is a flat plate-shaped cover that is arranged to cover the opening of the brush holder 60. The second bracket 112 is arranged between the first bracket 111 and the brush holder 60. Specifically, the second bracket 112 is sandwiched between the first bracket 111 and the brush holder 60.

[0032] The material of the first bracket 111 and the second bracket 112 is not limited to a metal material and may be a resin material. From the viewpoint of suppressing noise generated from the electric motor 1, it is preferable that the first bracket 111 and the second bracket 112 are made of a metal material. Specifically, the first bracket 111 and the second bracket 112 are made of a metal plate. The first bracket 111 is formed into a predetermined three-dimensional shape by performing a predetermined press process or the like on the metal plate. The second bracket 112 is a flat, planar metal plate.

[0033] The coils 22 of the rotor 20 shown in Fig. 3 are wound coils. The rotor 20 has a plurality of coils 22. Each of the plurality of coils 22 is an armature winding made of electric wire. Each of the plurality of coils 22 is wound so as to generate a magnetic force acting on the stator 10 when a current flows through it. The direction of the main magnetic flux generated by each coil 22 is along the axis C along which the rotating shaft 21 extends. Specifically, each of the plurality of coils 22 is wound in a flat shape, and is arranged with the coil surface facing in the direction along the axis C along which the rotating shaft 21 extends.

[0034] Each coil 22 is formed of an insulating-coated wire having a core wire made of a metal such as copper or aluminum and an insulating film coating the core wire. Each of the multiple coils 22 is a thin wound coil having a coil layer in which the insulating-coated wire is wound in a planar shape. Specifically, each of the multiple coils 22 is formed, for example, of one or more coil layers in which the insulating-coated wire is wound in a substantially fan-like shape in a planar view. The multiple coils 22 thus formed are arranged to surround the rotating shaft 21 when viewed from the direction of the axis C along which the rotating shaft 21 extends.

[0035] Each of the plurality of coils 22 is electrically connected to the commutator 30. Specifically, each of the plurality of coils 22 is electrically connected to one of the plurality of commutator segments 31 of the commutator 30. Therefore, a current flows through each of the plurality of coils 22 via the commutator segment 31 with which the brush 40 is in contact.

[0036] The multiple coils 22 are covered with molded resin 23. That is, the multiple coils 22 are resin-molded. Therefore, the multiple coils 22 are molded integrally with the molded resin 23 by being covered with the molded resin 23. The external shape of the molded resin 23 after molding the multiple coils 22 is circular in a plan view. The molded resin 23 may be made of an insulating resin material such as phenolic resin or unsaturated polyester (BMC (Bulk Molding Compound)). The molded resin 23 may be made of either a thermosetting resin or a thermoplastic resin.

[0037] In this way, the electric motor 1 is a coreless motor in which the rotor 20 does not have a core. In the electric motor 1, the rotor 20 has a plurality of thin coils 22 molded from resin. This makes it possible to realize a flat, thin electric motor 1 with low inductance.

[0038] 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 is attached to the second end 21b of the rotating shaft 21. The commutator 30 attached to the rotating shaft 21 may be a part of the rotor 20.

[0039] The commutator 30 has a plurality of commutator bars 31 (commutator segments) arranged along the rotation direction of the rotating shaft 21. Specifically, the plurality of commutator bars 31 are arranged in an annular shape along the rotation direction of the rotating shaft 21 so as to surround the rotating shaft 21. Each commutator bar 31 is shaped as an elongated member extending in the longitudinal direction of the rotating shaft 21.

[0040] Each of the plurality of commutator segments 31 is a conductive terminal made of a metal material such as copper. Each of the plurality of commutator segments 31 is electrically connected to a coil 22 of the rotor 20. The plurality of commutator segments 31 are arranged insulated and separated from one another, but are electrically connected by the coil 22 of the rotor 20.

[0041] As an example, the commutator 30 is a molded commutator. The commutator 30 has a configuration in which a plurality of commutator segments 31 are molded in the molded resin 23. In this case, the plurality of commutator segments 31 are embedded in the molded resin 23 so that their surfaces are exposed. The molded resin 23 is the commutator body. The molded resin 23 is a substantially cylindrical member having a through hole into which the rotating shaft 21 is inserted. The molded resin 23 is a resin molded body made of an insulating resin material such as a thermosetting resin.

[0042] At least one brush 40 is in contact with the commutator 30. Specifically, a front end 41 of the brush 40 is in contact with the commutator segments 31 of the commutator 30. As the commutator 30 rotates due to the rotation of the rotary shaft 21, the brush 40 continues to come into contact with all of the commutator segments 31 in sequence.

[0043] The brushes 40 are power supply brushes for supplying power to the coils 22. Specifically, the brushes 40 supply power to the coils 22 by contacting the commutator segments 31 of the commutator 30. When the brushes 40 contact the commutator segments 31, the armature current supplied to the brushes 40 from the power supply terminals 80 flows to the coils 22 via the commutator segments 31.

[0044] As an example, the brush 40 is a conductive carbon brush made of carbon. In this case, the brush 40 is preferably a carbon brush containing a metal such as copper. This reduces the contact resistance between the brush 40 and the commutator segments 31. Such a brush 40 can be produced, for example, by crushing a mixture of graphite powder, copper powder, binder resin, and hardener, compression-molding the mixture into a rectangular parallelepiped, and then firing the mixture.

[0045] In this embodiment, a plurality of brushes 40 are provided. Specifically, as shown in FIGS. 3 to 5 , the electric motor 1 is provided with two brushes 40. The two brushes 40 are arranged opposite each other with the commutator 30 sandwiched therebetween. That is, the two brushes 40 are arranged at 180° intervals along the rotation direction of the rotor 20. Therefore, the two brushes 40 are arranged on a single straight line. The angle between the longitudinal directions of the two brushes 40 is 180°. Therefore, the commutator 30 is pressed in a single axial direction by the two brushes 40 arranged in a straight line. In this embodiment, the electric motor 1 is a DC (Direct Current) motor. Therefore, one of the two brushes 40 is a positive-side brush 40. The other of the two brushes 40 is a negative-side brush 40.

[0046] As shown in Figures 4 and 5, a pigtail wire 45, through which current supplied from a power supply terminal 80 flows, is connected to each brush 40. The pigtail wire 45 is connected to the side of the brush 40 and fixed to the brush 40. Specifically, one end of the pigtail wire 45 is embedded in the brush 40. As shown in Figure 4, the other end of the pigtail wire 45 is connected to the power supply terminal 80. As a result, when the brush 40 comes into contact with the commutator segments 31, current from the power supply terminal 80, which is supplied to the brush 40 via the pigtail wire 45, flows through the commutator segments 31 to the coil 22 of the rotor 20.

[0047] 6 is a perspective view of the brush 40 used in the electric motor 1 according to the embodiment. As shown in FIGS. 3 and 6, the brush 40 includes a front end portion 41 that contacts the commutator 30 and a rear end portion 42 that is located on the opposite side to the front end portion 41.

[0048] The front end portion 41 of the brush 40 is one end portion in the longitudinal direction of the brush 40. The front end portion 41 of the brush 40 is the tip portion of the brush 40 on the rotating shaft 21 side (radially inner side). As shown in Fig. 3, the front end surface of the front end portion 41 is one end surface in the longitudinal direction of the brush 40. The front end surface of the front end portion 41 is a contact surface that comes into contact with the commutator segments 31 of the commutator 30.

[0049] The rear end 42 of the brush 40 is the other end in the longitudinal direction of the brush 40. The rear end 42 of the brush 40 is the tip end on the opposite side (radially outward) of the brush 40 from the rotary shaft 21 side. The rear end surface of the rear end 42 is the other end surface in the longitudinal direction of the brush 40. The rear end surface of the rear end 42 is the contact surface that comes into contact with the brush spring 50. Specifically, the rear end surface of the rear end 42 comes into contact with the spiral portion 51 of the brush spring 50.

[0050] Fig. 7 is an enlarged cross-sectional view of region VII surrounded by a dashed line in Fig. 3. As shown in Fig. 3 and Fig. 7, the rear end 42 of the brush 40 is provided with a spring contact surface 42a that contacts the spiral portion 51 of the brush spring 50, and a protruding portion 42b that protrudes rearward from the spring contact surface 42a.

[0051] As shown in FIG. 7 , a protrusion 42b is provided on the rear end 42 of the brush 40, thereby forming a recess in the rear end 42 of the brush 40. The spring contact surface 42a forms the bottom surface of this recess. The spring contact surface 42a is part of the rear end surface of the rear end 42 of the brush 40. The spring contact surface 42a is a plane perpendicular to the sliding direction of the brush 40. In other words, the spring contact surface 42a is a plane perpendicular to the unwinding direction D of the wire material constituting the brush spring 50. The unwinding direction D of the wire material constituting the brush spring 50 is the sliding direction of the brush 40 (i.e., the radial direction). Therefore, the spring contact surface 42a is a plane perpendicular to the sliding direction of the brush 40. As a result, the spring contact surface 42a is a plane parallel to the extension direction of the axis C of the rotation shaft 21.

[0052] The protrusion 42b of the brush 40 is formed only on the end of the brush 40 facing the cover plate 70 (upper surface side). The protrusion 42b is located between the spiral portion 51 of the brush spring 50 and the inner surface of the brush box BX. This allows a gap to be formed between the spiral portion 51 and the inner surface of the brush box BX. Specifically, the protrusion 42b is located between the spiral portion 51 and the cover plate 70 that constitutes the brush box BX. In other words, a gap exists between the spiral portion 51 and the inner surface of the cover plate 70. The gap is located closer to the cover plate 70 at the rear end 42 of the brush 40. Therefore, the contact portion between the spiral portion 51 and the spring contact surface 42a is located closer to the rear end 42 of the brush 40 than the cover plate 70.

[0053] The side of the protruding portion 42b on the spiral portion 51 side is a curved surface having an arc-shaped cross section. This side is formed continuously with the spring contact surface 42a. This side, together with the spring contact surface 42a, forms a continuous rear end surface at the rear end portion 42 of the brush 40. The radius of curvature of the arc of this side (curved surface) is larger than the radius of curvature of the outermost arc of the spiral portion 51. However, this is not limited to this.

[0054] Protrusion 42b has the function of restricting movement of spiral portion 51 in a direction perpendicular to the unwinding direction D of the wire material constituting brush spring 50. In other words, when spiral portion 51 moves in a direction perpendicular to the unwinding direction D of the wire material, spiral portion 51 abuts against protrusion 42b, preventing further movement of spiral portion 51. As a result, when the wire material constituting brush spring 50 tries to unwind, spiral portion 51 does not come into contact with the inner surface of brush box BX. In other words, protrusion 42b has the function of preventing spiral portion 51 from coming into contact with the inner surface of brush box BX when the wire material constituting brush spring 50 tries to unwind.

[0055] In this way, the spring contact surface 42a that contacts the spiral portion 51 of the brush spring 50 is a plane that is perpendicular to the unwinding direction D of the wire that constitutes the brush spring 50, so that the direction of the vector B of the spring load from the spiral portion 51 can be set to the unwinding direction D of the wire. This makes it possible to suppress loss of spring load compared to the original spring load of the brush spring 50, which is a constant force spring.

[0056] The protruding portion 42b of the brush 40 is located between the spiral portion 51 and the cover plate 70. Therefore, when the front end portion 41 of the brush 40 wears and the wire that makes up the brush spring 50 tries to unwind, the spiral portion 51 can be prevented from coming into contact with the inner surface of the cover plate 70. In other words, even if the brush 40 wears, the gap between the spiral portion 51 and the inner surface of the brush box BX is maintained.

[0057] The brushes 40 are subjected to a pressing force (spring load) from the brush springs 50 and are constantly in contact with the commutator segments 31 of the commutator 30. In other words, the brushes 40 are pressed against the commutator 30 by the brush springs 50. In this way, the brushes 40 are in sliding contact with the commutator 30 due to the pressing force from the brush springs 50, and are arranged so as to be movable in a direction (radial direction) intersecting the direction of the axis C along which the rotating shaft 21 extends due to wear with the commutator 30.

[0058] The number of brush springs 50 provided corresponds to the number of brushes 40. In this embodiment, the electric motor 1 is provided with two brushes 40. Therefore, two brush springs 50 are also provided. The brushes 40 and the brush springs 50 are housed in a brush holder 60 and covered with a cover plate 70.

[0059] The brush spring 50 applies a pressure (spring pressure) to the brush 40 by means of its spring elastic force (spring restoring force), urging the brush 40 toward the commutator 30. In this embodiment, the brush spring 50 is a constant-load spring. Therefore, the spring load of the brush spring 50 does not change with wear (stroke) of the brush 40. As a result, the brush spring 50 applies a uniform spring load to the brush 40 from the initial stage, before the brush 40 is worn, to the final stage, when the brush 40 has worn and the electric motor 1 has reached the end of its life.

[0060] The brush spring 50, which is a constant force spring, is made of a strip-shaped wire material. Fig. 8 is a side view of the brush spring 50 used in the electric motor 1 according to this embodiment. As shown in Figs. 5, 7, and 8, the brush spring 50 is a spiral spring having a spiral portion 51 (coil portion) in which a strip-shaped wire material is wound in a spiral shape. In Fig. 8, the solid line indicates a state in which the strip-shaped wire material constituting the brush spring 50 is pulled out from the spiral portion 51. The dashed line indicates a state in which the strip-shaped wire material constituting the brush spring 50 is pulled back into the spiral portion 51.

[0061] The brush spring 50 is formed, for example, from a single strip-shaped wire material made of a metal material such as a steel plate. Specifically, the brush spring 50 is formed from a long, strip-shaped metal plate. The spiral portion 51 of the brush spring 50 is a portion in which the long, strip-shaped metal plate is wound in a spiral shape multiple times in only one direction. By pulling out one end of the wire material from the spiral portion 51, a force (spring restoring force) that causes the wire material to return to its original spiral shape to the spiral portion 51 can be generated in the brush spring 50.

[0062] 3 and 7 , by bringing the spiral portion 51, in a state in which the wire is pulled out and a spring restoring force is applied, into contact with the rear end portion 42 of the brush 40, a pressing force (spring load) can be applied to the brush 40. In other words, the brush spring 50 applies a pressing force to the brush 40 by the spiral portion 51, pressing the brush 40 against the commutator 30.

[0063] The brush spring 50 is disposed so that the spiral axis of the spiral portion 51 and the axis C of the rotary shaft 21 are in a twisted position. In other words, the brush spring 50 is disposed so that the spiral portion 51 is in a vertical position. The spiral surface (coil surface) of the spiral portion 51 of the brush spring 50 is parallel to the axis C of the rotary shaft 21.

[0064] The spiral portion 51 of the brush spring 50 contacts the spring contact surface 42a at the rear end 42 of the brush 40. As shown in Fig. 7, the diameter of the spiral portion 51 of the brush spring 50 is larger than the thickness of the brush 40. Therefore, a portion of the spiral portion 51 protrudes from the rear end 42 of the brush 40. Specifically, the portion of the spiral portion 51 protrudes from the rear end 42 of the brush 40 on the side opposite to the protruding portion 42b side (the side opposite to the cover plate 70 side) in the direction in which the axis C of the rotary shaft 21 extends.

[0065] Electric power is supplied to the brushes 40 from an external power supply disposed outside the electric motor 1 via a power supply terminal 80 shown in Figures 4 and 5. 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 12 V to the electric motor 1.

[0066] As shown in Figures 3 and 4, the brushes 40 are arranged in a brush holder 60. The brush holder 60 is a holding member that holds the brushes 40. The brush holder 60 holds not only the brushes 40, but also the brush springs 50, the cover plate 70, the power terminals 80, and the capacitor 90. As shown in Figures 1 to 3, the brush holder 60 is also an outer shell member that forms the outer shell of the electric motor 1. The brush holder 60 covers the second bracket 112 from the outside.

[0067] The brush holder 60 is made of an insulating resin material. In this embodiment, the brush holder 60 is a resin-molded product integrally formed from an insulating resin material. As an example, the resin material constituting the brush holder 60 is phenolic resin. However, the present invention is not limited to this.

[0068] 3 and 5, the brush holder 60 has a brush storage section 61 in which the brushes 40 are stored. The brush storage section 61 is a brush case that contains the brushes 40. The brush storage sections 61 are formed according to the number of brushes 40. In this embodiment, the brush holder 60 has two brush storage sections 61 formed therein.

[0069] The brush storage section 61 is elongated in a direction perpendicular to the axial center C of the rotary shaft 21 (i.e., in the radial direction). The brush storage section 61 has a rectangular concave cross-sectional shape. Specifically, the brush storage section 61 has a bottom 61a and a pair of side walls 61b extending from the bottom 61a. In other words, the bottom 61a and the pair of side walls 61b form a recess with a concave cross-sectional shape. The bottom 61a of the brush storage section 61 supports the bottom surface of the brush 40. The pair of side walls 61b of the brush storage section 61 sandwich the brush 40. The pair of side walls 61b may be in contact with the side surfaces of the brush 40. However, it is preferable to provide a gap between the pair of side walls 61b and the side surfaces of the brush 40 to facilitate sliding of the brush 40 within the brush storage section 61.

[0070] As shown in FIG. 3 , the brush storage section 61 accommodates the brush 40 and the brush spring 50. Therefore, the longitudinal length of the brush storage section 61 is longer than the length of the brush 40. Specifically, the spiral portion 51 of the brush spring 50 is disposed rearward of the rear end portion 42 of the brush 40. In other words, the spiral portion 51 is disposed in the brush storage section 61 so as to be located on the opposite side of the brush 40 from the side on which the commutator 30 is located within the brush storage section 61. As shown in FIG. 3 , the brush spring 50 is fixed to the brush storage section 61 by supporting a portion of the wire drawn from the spiral portion 51 by the brush holder 60. Specifically, the wire drawn from the spiral portion 51 passes below the brush 40 (the side opposite the cover plate 70) and is extended toward the commutator 30, and is fixed in a recess 61 c formed in the front of the brush storage section 61. The wire drawn out from the spiral portion 51 is arranged in a groove 61d formed in the bottom portion 61a of the brush storage portion 61. The groove 61d extends along the longitudinal direction of the brush 40.

[0071] The brush 40 stored in the brush storage section 61 slides within the brush storage section 61. Specifically, the brush 40 pressed against the brush spring 50 moves toward the commutator 30 within the brush storage section 61 due to the pressing force from the brush spring 50 as the front end 41 of the brush 40 wears due to friction with the commutator segments 31. In other words, as the brush 40 wears, the rear end surface of the rear end 42 of the brush 40 moves in the direction (radial direction) toward the axis C of the rotary shaft 21. As a result, the spiral portion 51 of the brush spring 50 in contact with the rear end 42 of the brush 40 also moves, together with the rear end 42 of the brush 40, in the direction toward the axis C of the rotary shaft 21.

[0072] As shown in FIGS. 3 to 5 , a cover plate 70 is provided to cover the brush 40 stored in the brush storage section 61. The cover plate 70 is arranged to cover the brush storage section 61. The cover plate 70 covers not only the brush 40 but also the brush spring 50. The cover plate 70 covering the brush 40 may or may not be in contact with the upper surface of the brush 40. The protruding portion 42b of the brush 40 is present between the spiral portion 51 of the brush spring 50 and the cover plate 70. Therefore, the cover plate 70 and the brush spring 50 do not come into contact with each other. Therefore, even if the brush 40 wears, a gap is maintained between the spiral portion 51 and the inner surface of the cover plate 70, and the cover plate 70 and the spiral portion 51 of the brush spring 50 do not come into contact with each other.

[0073] FIG. 9A is a perspective view of a cover plate 70 used in the electric motor 1 according to the embodiment, as seen from the outside. FIG. 9B is a perspective view of the cover plate 70 used in the electric motor 1 according to the embodiment, as seen from the inside. The cover plate 70 is a metal member made of a metal material. The cover plate 70 is made of, for example, brass or stainless steel (SUS). In the present embodiment, the cover plate 70 is made of a plate-shaped metal plate. The cover plate 70 having the shape shown in FIGS. 9A and 9B can be obtained by subjecting a single metal plate formed into a predetermined shape to sheet metal processing such as bending or pressing.

[0074] As shown in FIGS. 4, 5, 9A and 9B, the cover plate 70 has a cover portion 71, a first leg portion 72a and a second leg portion 72b.

[0075] The cover portion 71 covers the brush 40. The cover portion 71 is formed in an elongated shape along the longitudinal direction of the brush 40. The cover portion 71 covers not only the brush 40 but also the brush spring 50. The cover portion 71 is a top plate that serves as the main body (cover main body) of the cover plate 70. The cover portion 71 is arranged to cover the brush storage portion 61 of the brush holder 60.

[0076] The first leg 72a and the second leg 72b are formed to protrude from the side of the cover portion 71. Each of the first legs 72a extends in a direction perpendicular to the main surface of the cover portion 71. The first legs 72a are formed by bending a portion of the metal plate that constitutes the cover plate 70. Both of the two first legs 72a are provided on one side of the cover portion 71. The second leg 72b extends in a direction parallel to the main surface of the cover portion 71. The second leg 72b is provided on the other side of the cover portion 71. The second leg 72b is provided in a position facing one of the two first legs 72a.

[0077] The first leg portion 72a is inserted into a first insertion hole 62a provided in the brush holder 60. In this embodiment, the first leg portion 72a is press-fitted into the first insertion hole 62a. The second leg portion 72b is inserted into a second insertion hole 62b provided in the brush holder 60. The second leg portion 72b is also press-fitted into the second insertion hole 62b. The press-fit directions of the first leg portion 72a and the second leg portion 72b are the same, which are both the Z-axis direction. Therefore, the first leg portion 72a is inserted into the first insertion hole 62a along the direction in which the first leg portion 72a extends (the protruding direction). Meanwhile, the second leg portion 72b is pressed into the second insertion hole 62b along a direction perpendicular to the direction in which the second leg portion 72b extends (the protruding direction). The cover plate 70 is fixed to the brush holder 60 by press-fitting the first leg portion 72 a into the first insertion hole 62 a and press-fitting the second leg portion 72 b into the second insertion hole 62 b.

[0078] The brush 40 is surrounded on all four sides by the brush storage section 61 and the cover plate 70. In other words, the brush storage section 61 and the cover plate 70 form a brush box (brush box) BX that stores the brush 40. Specifically, the brush 40 is surrounded by the bottom 61a and pair of side wall sections 61b that form the brush storage section 61, and the cover plate 70. In this way, the brush box BX is formed by the brush storage section 61 made of resin and the cover plate 70 made of metal.

[0079] In this embodiment, as described above, the cover plate 70 covers not only the brushes 40 but also the brush springs 50. Therefore, the brush box BX accommodates not only the brushes 40 but also the brush springs 50. In other words, the brush springs 50 are surrounded by the cover plate 70 and the bottom 61a and pair of side walls 61b that constitute the brush accommodation section 61.

[0080] A through hole 70a is provided in the cover plate 70. The through hole 70a is provided in the cover portion 71. That is, the through hole 70a penetrates the cover portion 71. In this embodiment, the through hole 70a is provided at a position that overlaps with the brush 40 when the cover plate 70 is viewed in a plan view (when viewed from the Z-axis direction). Therefore, the brush 40 can be seen through the through hole 70a. The opening shape of the through hole 70a is circular. However, this is not limited to this.

[0081] 4 and 5 , the brush holder 60 is provided with two insertion holes 63 through which the power supply lines 2 are inserted. Each insertion hole 63 is formed in a tunnel shape to connect the outside and inside of the brush holder 60. Each insertion hole 63 extends to the position of the power supply terminal 80. When the power supply lines 2 are inserted into the insertion holes 63, the power supply lines 2 and the power supply terminals 80 are connected to each other. In other words, the power supply lines 2 and the power supply terminals 80 are electrically and mechanically connected to each other.

[0082] The power supply terminals 80 receive power from an external power supply via the power supply line 2 to supply power to the brushes 40. Therefore, the power supply terminals 80 are electrically connected to the brushes 40. The power supply power supplied to the brushes 40 is then supplied to the coils 22 of the rotor 20. In this embodiment, the external power supply is a DC power supply, so the power supply terminals 80 receive a DC voltage as an input voltage via the power supply line 2. Therefore, two power supply terminals 80 are provided. One of the two power supply terminals 80 is a positive power supply terminal connected to the positive side of the DC power supply. The other of the two power supply terminals 80 is a negative power supply terminal connected to the negative side of the DC power supply. The two power supply terminals 80 are fixed to the brush holder 60.

[0083] 4 , the power supply terminal 80 and the brush 40 are electrically connected by a pigtail wire 45. The pigtail wire 45 and the power supply terminal 80 are joined by, for example, soldering. When power is supplied from an external power supply to the power supply terminal 80 via the power supply line 2, a current is supplied to the brush 40 via the pigtail wire 45 connected to the power supply terminal 80.

[0084] A capacitor 90 housed in the brush holder 60 is connected to the two power supply terminals 80. The capacitor 90 is connected to the two power supply terminals 80 so as to be connected in parallel with the two power supply terminals 80. This makes it possible to suppress noise generated from the electric motor 1. In other words, the capacitor 90 is a capacitor for noise reduction.

[0085] In the electric motor 1 configured as described above, when power is supplied to the power supply terminals 80 via the power supply line 2, the power is supplied to the brushes 40 via the power supply terminals 80. As a result, an armature current (drive current) flows through the coils 22 via the commutator 30, which is in contact with the brushes 40, and magnetic flux is generated in the rotor 20 (coils 22). A magnetic force generated by the interaction between the magnetic flux generated in the rotor 20 and the magnetic flux generated by the stator 10 becomes torque that rotates the rotor 20. At this time, the direction of the current flowing through the coils 22 is switched depending on the positional relationship when the commutator segments 31 and the brushes 40 are in contact. By switching the direction of the current flow in this way, a rotational force in a fixed direction is generated by the magnetic repulsive and attractive forces generated between the stator 10 and the rotor 20, and the rotor 20 rotates around the axis C of the rotating shaft 21.

[0086] Here, the features of the electric motor 1 according to the present embodiment will be described with reference to FIGS. 10 to 12 , including how the technology of the present disclosure was developed. FIG. 10 is a cross-sectional view showing a state in which the brush 40 is correctly assembled to the brush holder 60 (properly assembled state) and a state in which the brush 40 is incorrectly assembled to the brush holder 60 (misassembled state) when an electric motor 1X of a comparative example is assembled. FIG. 11 is a cross-sectional view showing a state in which the brush 40 is correctly assembled to the brush holder 60 (properly assembled state) and a state in which the brush 40 is incorrectly assembled to the brush holder 60 (misassembled state) when an electric motor 1 according to the embodiment is assembled. FIG. 12 is a plan view showing a state in which the brush 40 is correctly assembled to the brush holder 60 (properly assembled state) and a state in which the brush 40 is incorrectly assembled to the brush holder 60 (misassembled state) when an electric motor 1 according to the embodiment is assembled. In each of FIGS. 10 and 11 , (a) shows the properly assembled state, and (b) and (c) show the misassembled states. In FIG. 12, (a) shows a state of correct assembly, and (b) shows a state of incorrect assembly.

[0087] The brush 40 used in the electric motor 1X of the comparative example has a shape in which a protrusion 42b is provided at a biased position on the rear end 42, similar to the electric motor 1 in the above-described embodiment. In other words, a brush 40 with a distinctive shape is used. In this case, if a brush 40 with a pigtail wire 45 connected to its side is used, the two brushes 40 to which the pigtail wire 45 is connected will have different shapes. In other words, one brush 40 (e.g., the positive side brush) and the other brush 40 (e.g., the positive side brush) of the two brushes 40 to which the pigtail wire 45 is connected will be dedicated (non-common) parts.

[0088] Therefore, it is necessary to correctly combine one brush and the other brush of the pair 40 and place them in the brush storage section 61 of the brush holder 60. Specifically, as shown in Figure 10(a), the brush 40 needs to be placed in the brush storage section 61 so that the spring contact surface 42a of the brush 40 contacts the spiral portion 51 of the brush spring 50.

[0089] However, misassembly may occur in which one brush 40 of the pair of brushes 40 is placed in the brush storage section 61 where the other brush 40 should be placed, or the other brush 40 of the pair of brushes 40 is placed in the brush storage section 61 where one brush 40 should be placed. In other words, the brushes 40 may not be placed in the brush storage section 61 in the correct orientation.

[0090] For example, as shown in FIG. 10B , one brush 40 (the left brush 40) of the pair of brushes 40 may be positioned in the correct orientation, but the other brush 40 (the right brush 40) of the pair of brushes 40 may be positioned in the incorrect orientation. In this case, for the left brush 40 positioned in the correct orientation, the spiral portion 51 of the brush spring 50 is in contact with the spring contact surface 42 a. On the other hand, for the right brush 40 positioned in the incorrect orientation, the spiral portion 51 of the brush spring 50 does not contact the spring contact surface 42 a, but rather contacts the tip of the protruding portion 42 b of the brush 40. As a result, the right brush 40 positioned in the incorrect orientation is positioned with the front end 41 protruding further than the predetermined position.

[0091] Alternatively, as shown in FIG. 10( c), one brush 40 (the right brush 40) of the pair of brushes 40 may be positioned in the correct orientation, but the other brush 40 (the left brush 40) of the pair of brushes 40 may be positioned in the incorrect orientation. In this case, for the right brush 40 positioned in the correct orientation, the spiral portion 51 of the brush spring 50 is in contact with the spring contact surface 42 a. On the other hand, for the left brush 40 positioned in the incorrect orientation, the spiral portion 51 of the brush spring 50 does not contact the spring contact surface 42 a, but rather contacts the tip of the protruding portion 42 b of the brush 40. As a result, the left brush 40 positioned in the incorrect orientation is positioned with the front end 41 protruding further than the predetermined position.

[0092] The brush 40 in the correct posture (first posture) and the brush 40 in the incorrect posture (second posture) are in opposite orientations in the direction of the axis C of the rotating shaft 21. In other words, the brush 40 in the correct posture (first posture) and the brush 40 in the incorrect posture (second posture) are upside down in the direction of the axis C of the rotating shaft 21.

[0093] As described above, one of the pair of brushes 40 may be placed in the brush storage section 61 in an incorrect orientation. However, even in such a case, the motor may still be assembled. That is, when assembling the rotor 20 to the brush holder 60 in which the pair of brushes 40 are placed, the commutator 30 fixed to the rotating shaft 21 is placed in the brush holder 60. However, the brush 40 with its front end 41 protruding may be pushed in by the commutator 30, causing the commutator 30 to be forcibly set in the brush holder 60. In other words, the motor may be assembled without noticing that the brush 40 has been misassembled. As a result, the brush 40 may not slide correctly when the motor is driven.

[0094] Although not shown, misassembly may occur when both brushes 40 are placed in the brush storage section 61 in the wrong orientation. In this case, the front ends 41 of both brushes 40 protrude from their designated positions. Therefore, even if an attempt is made to place the commutator 30 in the brush holder 60, the commutator 30 and the front ends 41 of the pair of brushes 40 may come into contact with each other when assembling the rotor 20 to the brush holder 60, making it highly likely that the commutator 30 cannot be set in the brush holder 60. In other words, if both brushes 40 are placed in the brush storage section 61 in the wrong orientation, the commutator 30 cannot be forcibly set in the brush holder 60, and the user is highly likely to notice the misassembly. The cover plate 70X used in the electric motor 1X of the comparative example has a structure similar to that of the cover plate 70 used in the present embodiment, but without the through-holes 70a.

[0095] As a result of intensive research into this problem, the inventors discovered a technology that involves providing a through hole 70a in the cover plate 70 and detecting whether the brush 40 is misassembled based on how the brush 40 appears through the through hole 70a.

[0096] Specifically, in the electric motor 1 according to this embodiment, a through hole 70a is provided in the cover plate 70, and the appearance of the brush 40 seen through the through hole 70a when the brush 40 is in the correct posture (first posture) is different from the appearance of the brush 40 seen through the through hole 70a when the brush 40 is in the incorrect posture (second posture).

[0097] More specifically, when the brush 40 is placed in the brush storage section 61 in the correct posture (first posture), in a plan view of the cover plate 70 (viewed from the direction of the axis C of the rotary shaft 21), the brush 40 is close to the cover plate 70 near the through-hole 70a of the cover plate 70, and therefore the surface of the brush 40 is visible through the through-hole 70a. In this embodiment, the brush 40 is a carbon brush, and therefore the glossy black surface of the brush 40 is visible through the through-hole 70a. In other words, light incident on the through-hole 70a is reflected by the surface of the brush 40.

[0098] On the other hand, when the brush 40 is placed in the brush storage compartment 61 in the incorrect position (second position), the through-hole 70a of the cover plate 70 overlaps with the protruding portion 42b of the brush 40 when the cover plate 70 is viewed from above. That is, the recess formed by the protruding portion 42b overlaps with the through-hole 70a. As a result, the surface of the brush 40 (the surface of the recess) is recessed near the through-hole 70a. This makes it difficult to see the brush 40 through the through-hole 70a. In other words, light entering the through-hole 70a is less likely to reach the surface of the brush 40, and the inside of the through-hole 70a appears dark. That is, the through-hole 70a appears black to the user's eyes.

[0099] Therefore, when both of the pair of brushes 40 are placed in the brush storage section 61 in the correct position (first position) as shown in Fig. 11(a), the surfaces of the brushes 40 are visible from the through-holes 70a of each cover plate 70 as shown in Fig. 12(a). In other words, the view of the through-holes 70a of one cover plate 70 is the same as the view of the through-holes 70a of the other cover plate 70. As a result, the user can see that both of the pair of brushes 40 are placed correctly in the brush storage section 61.

[0100] On the other hand, as shown in (b) of Figure 11, if one brush 40 (the left brush 40) of the pair of brushes 40 is positioned in the correct posture, but the other brush 40 (the right brush 40) of the pair of brushes 40 is positioned in the incorrect posture, the through hole 70a will look different on one of the two cover plates 70 and the other, as shown in (b) of Figure 12.

[0101] Specifically, as shown in Figures 11(b) and 12(b), the surface of the brush 40 is visible through the through-hole 70a of one of the two cover plates 70 (the left cover plate 70), but the surface of the brush 40 is difficult to see through the through-hole 70a of the other of the two cover plates 70 (the right cover plate 70), and the through-hole 70a appears black. This is because, as described above, for the brush 40 covered by the right cover plate 70, the recess in the rear end 42 of the brush 40 formed by the protrusion 42b overlaps with the through-hole 70a, making the through-hole 70a appear black. This indicates that the right brush 40 is misassembled.

[0102] Fig. 13 is a diagram showing a state in which an incorrect assembly occurs when the electric motor 1 according to the embodiment is actually assembled. As shown in Fig. 13, the glossy surface of the brush 40 is visible through the through-hole 70a of the left cover plate 70 covering the brush 40 in the correct posture (first posture), while the through-hole 70a of the right cover plate 70 covering the brush 40 in the incorrect posture (second posture) appears black.

[0103] As shown in (c) of Figure 11, even if one brush 40 (the right brush 40) of the pair of brushes 40 is positioned in the correct posture but the other brush 40 (the left brush 40) of the pair of brushes 40 is positioned in the incorrect posture, the through hole 70a will look different on one of the two cover plates 70 and the other.

[0104] Specifically, the surface of the brush 40 is visible through the through-hole 70a of one of the two cover plates 70 (the right cover plate 70). On the other hand, the surface of the brush 40 is difficult to see through the through-hole 70a of the other of the two cover plates 70 (the left cover plate 70), and the through-hole 70a appears black. In this case, as described above, for the brush 40 covered by the left cover plate 70, the recess in the rear end 42 of the brush 40 formed by the protrusion 42b overlaps with the through-hole 70a, so the through-hole 70a appears black. This indicates that the left brush 40 is misassembled.

[0105] As described above, according to the electric motor 1 of this embodiment, a through hole 70a is provided in the cover plate 70 that covers the brush 40, and the appearance of the brush 40 seen through the through hole 70a when the brush 40 is in the first position is different from the appearance of the brush 40 seen through the through hole 70a when the brush 40 is in the second position.

[0106] This makes it possible to easily detect whether the brush 40 is improperly assembled at the stage of assembling the brush 40 to the brush holder 60. Therefore, it is possible to prevent the brush 40 from being assembled improperly.

[0107] The configuration of another electric motor 101 according to the embodiment will now be described with reference to Fig. 14. Fig. 14 is an exploded perspective view showing the brush holder 60 and various components arranged on the brush holder 60 in the other electric motor 101 according to the embodiment.

[0108] The electric motor 101 shown in Fig. 14 differs from the above-described electric motor 1 in that it has a brush 140. Specifically, the brush 140 shown in Fig. 14 has a display portion 142 that is visible through the through-hole 70a when the brush 140 is in a first position, but is not visible through the through-hole 70a when the brush 140 is in a second position in which the brush 140 is oriented opposite to the first position in the axial direction.

[0109] In other words, the display portion 142 is formed on the surface facing the through-hole 70a when the brush 140 is inserted into the brush storage portion 61 in the correct posture. On the other hand, the display portion 142 is not formed on the surface facing the through-hole 70a when the brush 140 is inserted into the brush storage portion 61 in the wrong posture.

[0110] The display unit 142 may be formed on the entire surface where the brush 140 and the cover plate 70 face each other, or as shown in Fig. 14, the display unit 142 may be formed in a main portion facing the through-hole 70a on the surface where the brush 140 and the cover plate 70 face each other. Specifically, in Fig. 14, the display unit 142 is not formed on the front end 41 of the brush 140, but is provided only on the upper surface of the rear end 42.

[0111] With this configuration, it is possible to easily detect whether the brush 140 is improperly assembled at the stage of assembling the brush 140 to the brush holder 60. Therefore, it is possible to prevent the brush 140 from being assembled improperly.

[0112] (Modification) The electric motor 1 according to the present disclosure has been described above based on the embodiment, but the present disclosure is not limited to the above embodiment.

[0113] For example, in the above embodiment, when the brush 40 is in the incorrect position (second position), the through-hole 70a and the protruding portion 42b of the brush 40 overlap, so that the brush 40 looks different when viewed from the through-hole 70a depending on whether the brush 40 is in the correct position (first position) or the incorrect position (second position). However, the present invention is not limited to this.

[0114] FIG. 15 is a diagram illustrating a partial configuration of an electric motor 1 according to a modified example. Specifically, the through-hole 70a of the cover plate 70A may be positioned so that when the brush 40 is in the correct position (first position) as shown in FIG. 15A , the through-hole 70a overlaps the pigtail wire 45 in a plan view of the cover plate 70A. Furthermore, when the brush 40 is in the incorrect position (second position) as shown in FIG. 15B , the through-hole 70a does not overlap the pigtail wire 45 and the brush 40 is visible in a plan view of the cover plate 70A. In this case, too, the appearance of the brush 40 as seen through the through-hole 70a of the cover plate 70A differs between the correct position (first position) and the incorrect position (second position). This allows for easy detection of improper assembly of the brush 40. Therefore, incorrect assembly of the brush 40 can be prevented.

[0115] Alternatively, the surface of the brush 40 visible through the through hole 70a when the brush 40 is in the correct position (first position) may be defined as the first surface, and the surface of the brush 40 visible through the through hole 70a when the brush 40 is in the incorrect position (second position) may be defined as the second surface. Surface treatment may be applied to only one of the first and second surfaces of the brush 40 to make it appear different from the other. In this case, the appearance of the brush 40 as seen through the through hole 70a differs between the correct position (first position) and the incorrect position (second position). Possible surface treatments for the brush 40 include coloring the surface of the brush 40 (e.g., a conspicuous color such as yellow or white) or forming minute irregularities on the surface by embossing or the like. In this case, incorrect assembly of the brush 40 can be easily detected. Therefore, incorrect assembly of the brush 40 can be prevented.

[0116] In the above embodiment, the brush box BX that houses the brushes 40 is composed of a resin brush storage section 61 and a metal cover plate 70. However, this is not limited to this. Specifically, the entire brush box BX may be made of a resin material or a metal material. As an example, the brush box BX may be a metal rectangular cylinder that surrounds the four sides of the brushes 40, or a resin rectangular cylinder that surrounds the four sides of the brushes 40. The brush box BX may be a metal L-shaped plate that surrounds two sides of the brushes 40 and a resin block that surrounds the other two sides of the brushes 40.

[0117] Furthermore, in the above embodiment, the electric motor 1 includes only one bearing 100. However, this is not limited to this. Specifically, the electric motor 1 may include two bearings. In this case, for example, one of the two bearings may be attached to the first end 21a of the rotating shaft 21, and the other of the two bearings may be attached to the second end 21b of the rotating shaft 21. In this way, by using two bearings 100, it is possible to suppress misalignment of the rotating shaft 21 itself, and it is also possible to further suppress misalignment of the brush 40 relative to the rotating shaft 21.

[0118] Furthermore, in the above embodiment, the electric motor 1 is a coreless motor in which the stator 10 and the rotor 20 do not have cores. However, this is not limiting. For example, the electric motor 1 may be an electric motor in which the stator 10 and the rotor 20 have cores. However, by using a coreless motor as in the above embodiment, it is possible to realize an electric motor 1 that has low inductance and is thin.

[0119] In the above embodiment, the stator 10 is composed of only permanent magnets. However, this is not limiting. For example, the stator 10 may be a stator composed of permanent magnets and an iron core, or an armature composed of a stator winding and an iron core without using permanent magnets.

[0120] In the above embodiment, the electric motor 1 is a flat motor having an outer size in which the thickness is smaller than the outer diameter. However, this is not limited to this. The technology of the present disclosure can also be applied to, for example, a cylindrical electric motor having a cylindrical housing having an outer size in which the thickness is larger than the outer diameter.

[0121] Furthermore, in the above embodiment, the direction of the main magnetic flux generated by the stator 10 and the rotor 20 is the direction in which the axis C of the rotating shaft 21 extends. 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 in which the axis C of the rotating shaft 21 extends (the radial direction of rotation of the rotating shaft 21). For example, the technology disclosed herein may also be applied to an inner rotor type motor in which the rotor 20 is arranged inside the stator 10.

[0122] In the above embodiment, the electric motor 1 is a vehicle motor used in a vehicle. However, the present disclosure is not limited to this. The technology of the present disclosure 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.

[0123] In addition, the present disclosure also includes forms obtained by applying various modifications to the above-described embodiments that a person skilled in the art would conceive, or forms realized by arbitrarily combining the components and functions of the embodiments within the scope of the present disclosure. The present disclosure also includes any combination of two or more claims from the multiple claims set forth in the claims at the time of filing, provided that there is no technical contradiction. For example, when a dependent claim set forth in the claims at the time of filing is made into a multiple claim or multiple multiple claims that cite all of the superordinate claims within the scope of the technical contradiction, the present disclosure also includes all combinations of claims included in that multiple claim or multiple multiple multiple claims.

[0124] The technology disclosed herein can be widely used in electric motors and various products equipped with electric motors, including products in the electrical equipment field such as automobiles and the field of household electrical appliances.

[0125] DESCRIPTION OF SYMBOLS 1, 1X, 101 Electric motor 2 Power supply line 10 Stator 20 Rotor 21 Rotating shaft 21a First end 21b Second end 22 Coil 23 Molded resin 30 Commutator 31 Commutator segment 40, 140 Brush 41 Front end 42 Rear end 42a Spring contact surface 42b Protrusion 45 Pigtail wire 50 Brush spring 51 Spiral portion 60 Brush holder 61 Brush storage portion 61a Bottom 61b Side wall portion 61c Recess 61d Groove 62a First insertion hole 62b Second insertion hole 63 Insertion hole 70, 70A, 70X Cover plate 70a Through hole 71 Cover portion 72a First leg portion 72b Second leg portion 80 Power terminal 90 Capacitor 100 Bearing 111 First bracket 112 Second bracket 142 Display unit BX Brush box

Claims

1. An electric motor comprising: a rotor having a rotating shaft extending in an axial direction in which an axis extends; a commutator attached to the rotating shaft; brushes in contact with the commutator; brush springs that press the brushes against the commutator; and a cover plate that covers the brushes and the brush springs, wherein the cover plate has a through hole, and the appearance of the brush seen from the through hole when the brush is in a first position is different from the appearance of the brush seen from the through hole when the brush is in a second position in which it is facing opposite to the first position in the axial direction.

2. An electric motor comprising: a rotor having a rotating shaft extending in an axial direction in which an axis extends; a commutator attached to the rotating shaft; brushes in contact with the commutator; brush springs that press the brushes against the commutator; and a cover plate that covers the brushes and the brush springs, wherein the cover plate has a through hole, and the brush has a display part that is visible through the through hole when the brush is in a first position and is not visible through the through hole when the brush is in a second position in which it is facing opposite to the first position in the axial direction.

3. An electric motor as claimed in claim 1 or 2, wherein the brush spring is a constant force spring having a spiral portion around which a strip-shaped wire is wound, and the brush is subjected to an elastic force by the constant force spring so as to move towards the commutator, and includes a front end that contacts the commutator and a rear end located opposite the front end, and the rear end is provided with a spring contact surface with which the spiral portion contacts and a protrusion that protrudes rearward beyond the spring contact surface, and when the cover plate is viewed in a plane with the brush in the second position, the through hole and the protrusion overlap.

4. An electric motor as described in claim 1 or 2, wherein a pigtail wire is connected to a side surface of the brush, and when the cover plate is viewed in a plane with the brush in the first position, the through hole is positioned so as to overlap with the pigtail wire.

5. An electric motor as claimed in claim 1 or 2, wherein the surface of the brush visible through the through hole when the brush is in the first position is defined as a first surface, and the surface of the brush visible through the through hole when the brush is in the second position is defined as a second surface, and only one of the first surface and the second surface is surface treated.

Images