Electric motor

Abstract

This electric motor comprises: a rotor having a rotary shaft that extends in an axial direction in which an axial center extends; a commutator attached to the rotary shaft; a brush that is in contact with the commutator; a brush spring for pressing the brush against the commutator; and a brush box that stores the brush and the brush spring, and that is covered by a cover plate. The brush spring is a constant load spring having a spiral portion around which a belt-like wire material is wound. The brush includes a front-end portion contacting the commutator, and a rear-end portion located on the side opposite the front-end portion. The rear-end portion is provided with a spring contact surface that is contacted by the spiral portion of the brush spring, and a protruding portion that protrudes rearward from the spring contact surface. The spring contact surface is a plane that is perpendicular to an unwinding direction of the wire material. The protruding portion is positioned between the spiral portion and the cover plate, and maintains a state in which the spiral portion does not come into contact with an inner surface of the brush box when the wire material is beginning to unwind.

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] However, a constant force spring is designed so that the spiral portion of the unwound wire contacts the brush, causing the wire to rewind around the spiral portion, thereby applying a spring load to the brush. As a result, when the brush wears and the wire attempts to unwind, the spiral portion moves in a direction perpendicular to the direction in which the wire rewinds. Therefore, if the spiral portion of the constant force spring is housed in the brush box together with the brush, the spiral portion may move and come into contact with the inner surface of the brush box. If the spiral portion comes into contact with the brush box, friction between the spiral portion and the brush box reduces the spring load generated by the spiral portion, resulting in a loss of spring load. Furthermore, if the part of the brush box that the spiral portion comes into contact with is made of a metal material, the spiral portion may become stuck to the brush box and move.

[0008] Therefore, as in the electric motor described in Patent Document 1, it is conceivable to form an inclined surface at the rear end of the brush and have the spiral portion of the constant force spring contact this inclined surface to prevent the spiral portion from moving in a direction perpendicular to the unwinding direction of the wire. However, with this method, the direction of the spring load vector from the spiral portion becomes oblique to the unwinding direction of the wire. This results in a loss of spring load compared to the original spring load of the constant force spring.

[0009] Microfilm of Utility Model Application No. 59-4563 (Utility Model Application No. 60-117675)

[0010] The present disclosure has been made to solve these problems, and aims to provide an electric motor that can prevent the spiral portion of the constant force spring from contacting the brush box while aligning the vector direction of the spring load from the spiral portion of the constant force spring with the unwinding direction of the wire.

[0011] In order to achieve the above object, one 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 brush box that houses the brushes and the brush springs and is covered by a cover plate, wherein the brush springs are constant-force springs having a spiral portion around which a strip-shaped wire is wound, and the brushes include a front end that contacts the commutator and a rear end that is located opposite the front end, and the rear end is provided with a spring contact surface that contacts the spiral portion of the brush spring and a protrusion that protrudes rearward beyond the spring contact surface, the spring contact surface is a plane perpendicular to the unwinding direction of the wire, and the protrusion is located between the spiral portion and the cover plate, and maintains the spiral portion out of contact with the inner surface of the cover plate when the wire tries to unwind.

[0012] According to the present disclosure, in an electric motor using a constant load spring as a brush spring, the vector direction of the spring load from the spiral portion of the constant load spring can be set to the direction in which the wire rewinds, while preventing the spiral portion of the constant load spring from coming into contact with the cover plate.

[0013] FIG. 1 is a perspective view of an electric motor according to an embodiment, as viewed from above. FIG. 2 is a perspective view of the electric motor according to an embodiment, as viewed from below. FIG. 3 is a cross-sectional view of the electric motor according to an embodiment, cut along a plane passing through the axis of the rotating shaft and passing through the brushes. FIG. 4 is an exploded perspective view of the electric motor according to an 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 an embodiment. FIG. 7 is a side view of a brush spring used in the electric motor according to an embodiment. FIG. 8 is an enlarged cross-sectional view of an area VIII surrounded by a dashed line in FIG. 3. FIG. 9A is a diagram for explaining an issue when a constant force spring is used as the brush spring. FIG. 9B is a diagram for explaining an issue when a constant force spring is used as the brush spring. FIG. 10 is a diagram for explaining an issue when the rear end surface of the brush is an inclined surface. FIG. 11 is an enlarged cross-sectional view of an electric motor according to a first modification. FIG. 12 is an enlarged cross-sectional view of an electric motor according to a second modification. FIG. 13 is an enlarged cross-sectional view of an electric motor according to a third modification.

[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"). Furthermore, 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 overall configuration of an electric motor 1 according to an embodiment will be described with reference to FIGS. 1 to 7. FIG. 1 is a perspective view of the electric motor 1 according to the embodiment, as viewed from above. FIG. 2 is a perspective view of the electric motor 1 according to the embodiment, as viewed from below. FIG. 3 is a cross-sectional view of the electric motor 1 according to the embodiment, taken along a plane passing through the axis C of the rotating shaft 21 and the brush 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. FIG. 6 is a perspective view of the brush 40 used in the electric motor 1 according to the embodiment. FIG. 7 is a side view of the brush spring 50 used in the electric motor 1 according to the embodiment. In FIG. 7, 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.

[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, at least one brush 40, a brush spring 50, a brush holder 60, and a cover plate 70. The commutator 30 is attached to a rotating shaft 21 of the rotor 20. The at least one brush 40 is in contact with the commutator 30. The brush spring 50 presses the brush 40 against the commutator 30. The brush holder 60 holds the brush 40. The cover plate 70 covers 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] As shown in FIG. 3 , the electric motor 1 is a type of direct current motor (DC motor) driven by direct current. 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. The electric motor 1 is a 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 cores (iron cores). As a result, the electric motor 1 is 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 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, or φ90 mm. 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 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 rotor 20 forms a magnetic circuit together with the stator 10, which is an armature. Specifically, the stator 10 is essentially donut-shaped as a whole. The stator 10 is configured so that north and south poles alternate and exist 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 creates magnetic flux to generate torque. 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 along 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 made of 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). 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. There is only one bearing 100. In other words, 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 can be used to obtain the same effects.

[0028] The first end 21a of the rotating shaft 21 is the end on the output side (output shaft). The first end 21a of the rotating shaft 21 protrudes from the first bracket 111 and the bearing 100. The first end 21a of the rotating shaft 21 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, for example, as 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). The second end 21b of the rotating shaft 21 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, 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. The plurality of coils 22 are armature windings made of electric wire. The plurality of coils 22 are wound so as to generate a magnetic force acting on the stator 10 when a current flows through them. The direction of the main magnetic flux generated by each coil 22 is along the axis C to which the rotating shaft 21 extends. Specifically, the plurality of coils 22 are wound in a flat shape. The coil surface is arranged in a position facing the direction along the axis C to 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. In other words, 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 planar external shape of the molded resin 23 after the multiple coils 22 are molded is circular. 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 an elongated member extending in the longitudinal direction of the rotating shaft 21.

[0040] Each of the plurality of commutator bars 31 is a conductive terminal made of a metal material such as copper. The plurality of commutator bars 31 are electrically connected to the coils 22 of the rotor 20. The plurality of commutator bars 31 are arranged insulated and separated from one another. However, the plurality of commutator bars 31 are electrically connected by the coils 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, the front end 41 of each brush 40 is in contact with at least one commutator segment 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 the commutator segments 31 in sequence.

[0043] As shown in FIGS. 3, 5 and 6, each brush 40 includes a front end 41 that contacts the commutator 30 and a rear end 42 located opposite the front end 41.

[0044] The front end portion 41 of the brush 40 is one end portion in the longitudinal direction of the brush 40, and is the tip portion on the rotating shaft 21 side (radially inner side) of the brush 40. The front end surface of the front end portion 41 is one end surface in the longitudinal direction of the brush 40, and is the contact surface that comes into contact with the commutator segments 31 of the commutator 30.

[0045] The rear end 42 of the brush 40 is the other longitudinal end of the brush 40 and is the tip end of the brush 40 on the opposite side (radially outward) from the rotary shaft 21 side. The rear end surface of the rear end 42 is the other longitudinal end surface of the brush 40 and is the contact surface that comes into contact with the brush spring 50. Specifically, the spiral portion 51 of the brush spring 50 comes into contact with the rear end surface of the rear end 42. The detailed configuration of the rear end 42 of the brush 40 will be described later.

[0046] 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, an armature current supplied to the brushes 40 from the power supply terminals 80 flows through the commutator segments 31 to the coils 22.

[0047] As an example, the brush 40 is a conductive carbon brush made of carbon. The brush 40 is a long, substantially rectangular parallelepiped. 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.

[0048] A plurality of brushes 40 are provided. Specifically, as shown in FIGS. 3 to 5, two brushes 40 are provided in the electric motor 1. 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. Therefore, the two brushes 40 are arranged so as to be positioned on a single straight line. The angle formed by 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. However, the number of brushes 40 is not limited to two.

[0049] 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.

[0050] The number of brush springs 50 provided corresponds to the number of brushes 40. Since the electric motor 1 is provided with two brushes 40, it is also provided with two brush springs 50. The brushes 40 and the brush springs 50 are housed in a brush holder 60 and covered with a cover plate 70.

[0051] The brush spring 50 applies a pressure (spring pressure) to the brush 40 by its spring elastic force (spring restoring force), urging the brush 40 toward the commutator 30. 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, and applies a uniform spring load to the brush 40 from the initial period before the brush 40 is worn to the final period when the brush 40 has worn and the electric motor 1 has reached the end of its life.

[0052] The brush spring 50, which is a constant force spring, is made of a strip-shaped wire material. As shown in Figures 3, 5, and 7, the brush spring 50, which is a constant force spring, is a spiral spring having a spiral portion 51 (coil portion) in which a strip-shaped wire material is wound in a spiral shape. The brush spring 50, which is a constant force spring, is made of a single strip-shaped wire material made of a metal material such as a steel plate.

[0053] Specifically, brush spring 50, which is a constant force spring, is made of a long, strip-shaped metal plate. Spiral portion 51 of 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. Pulling out one end of the wire from spiral portion 51 generates a force (spring restoring force) in brush spring 50 that causes the wire to return to its original spiral shape.

[0054] 3 and 5 , 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.

[0055] 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.

[0056] 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, for example, DC 12 V to the electric motor 1.

[0057] 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.

[0058] The brush holder 60 is made of an insulating resin material. The brush holder 60 is a resin-molded product integrally formed from the 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.

[0059] 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.

[0060] 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) and 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. That is, 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 have 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.

[0061] 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 to 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.

[0062] 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 face of the rear end 42 of the brush 40 moves in a direction (radial direction) toward the axis C of the rotating 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 toward the axis C of the rotating shaft 21 together with the rear end 42 of the brush 40.

[0063] 3 and 4 , 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 is fixed to the brush holder 60 by press-fitting legs 71 provided on the cover plate 70 into insertion holes 62 provided in the brush holder 60. 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 cover plate 70 and the brush spring 50 are not in contact with each other, and a gap exists between the cover plate 70 and the spiral portion 51 of the brush spring 50.

[0064] The cover plate 70 is a metal plate made of a metal material such as brass or stainless steel (SUS). In this embodiment, the cover plate 70 is made of a plate-shaped metal plate. The cover plate 70 is formed by performing sheet metal processing such as bending or pressing on a single metal plate that has been punched into a predetermined shape.

[0065] 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 BX (brush box) 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.

[0066] The cover plate 70 covers not only the brushes 40 but also the brush springs 50. Therefore, the brush box BX stores 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 storage section 61.

[0067] 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. The power supply line 2 is inserted into the insertion hole 63, thereby connecting the power supply line 2 and the power supply terminal 80. In other words, the power supply line 2 and the power supply terminal 80 are electrically and mechanically connected.

[0068] 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.

[0069] As shown in FIG. 4 , the power supply terminal 80 and the brush 40 are electrically connected by a pigtail wire 45. The pigtail wire 45 is fixed to the brush 40. Specifically, one end of the pigtail wire 45 is embedded and fixed in the brush 40. The other end of the pigtail wire 45 is connected to the power supply terminal 80. The pigtail wire 45 is drawn out from the side surface of the brush 40. 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.

[0070] 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.

[0071] 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 in contact with the brushes 40, generating magnetic flux 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 come into 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 about the axis C of the rotating shaft 21.

[0072] Here, the detailed configuration of the rear end portion 42 of the brush 40 will be described using Fig. 8 while also referring to Fig. 6. Fig. 8 is an enlarged cross-sectional view of an area VIII surrounded by a dashed line in Fig. 3.

[0073] 6 and 8, 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 protrusion 42b that protrudes rearward from the spring contact surface 42a. By providing the protrusion 42b at the rear end 42 of the brush 40, a recess is formed at the rear end 42 of the brush 40. The spring contact surface 42a forms the bottom surface of this recess. The protrusion 42b is formed only at the end of the brush 40 on the cover plate 70 side (upper surface side). By providing the protrusion 42b, a step is formed at the rear end 42 of the brush 40.

[0074] The spring contact surface 42a is a part of the rear end surface of the rear end portion 42 of the brush 40. As shown in FIG. 8 , the spring contact surface 42a is a plane (flat surface) perpendicular to the unwinding direction D of the wire material constituting the brush spring 50. Specifically, the unwinding direction D of the wire material constituting the brush spring 50 is the direction in which the brush 40 slides (i.e., the radial direction). Therefore, the spring contact surface 42a is a plane perpendicular to the sliding direction of the brush 40. The spring contact surface 42a is a plane parallel to the direction in which the axis C of the rotation shaft 21 extends. Because the unwinding direction D of the wire material constituting the brush spring 50 is the X-axis direction, the spring contact surface 42a is a plane perpendicular to the X-axis direction and parallel to the YZ plane.

[0075] 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 provided 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.

[0076] The side surface 42b1 of the protrusion 42b on the spiral portion 51 side is a curved surface having an arc-shaped cross section. The side surface 42b1 is formed continuously with the spring contact surface 42a. The side surface 42b1 and the spring contact surface 42a form a continuous rear end surface at the rear end 42 of the brush 40. In this case, the spiral portion 51 of the brush spring 50 is in contact with the spring contact surface 42a in a vertically placed position. Therefore, the spiral portion 51 is arranged along the curved side surface 42b1. In other words, the spiral portion 51 is arranged so as to fit into a recess formed in the rear end 42 by the protrusion 42b.

[0077] The radius of curvature of the arc of the curved side surface 42b1 is larger than the radius of curvature of the outermost arc of the spiral portion 51. Therefore, as shown in Figure 8, the spiral portion 51 does not contact the top of the protrusion 42b. The spiral portion 51 and the rear end portion 42 of the brush 40 contact each other only at one point on the spring contact surface 42a. Therefore, there is a small gap between the spiral portion 51, which has a circular cross section, and the side surface 42b1, which has a circular cross section, that gradually increases with increasing distance from the contact point between the spiral portion 51 and the spring contact surface 42a.

[0078] The protrusion 42b is located closer to the cover plate 70 at the rear end 42 of the brush 40 in the direction in which the axis C of the rotary shaft 21 extends. Therefore, the contact portion between the spiral portion 51 and the spring contact surface 42a is located on the opposite side of the rear end 42 of the brush 40 from the cover plate 70 in the direction in which the axis C of the rotary shaft 21 extends.

[0079] 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 portion 42 of the brush 40. Specifically, the portion of the spiral portion 51 protrudes from the rear end portion 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.

[0080] 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 that constitutes 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. In this way, protrusion 42b functions as a stopper that restricts movement of spiral portion 51 in a direction perpendicular to the unwinding direction D of the wire material.

[0081] In the present embodiment, the unwinding direction D of the wire material constituting brush spring 50 is the direction in which brush 40 slides. Therefore, protrusion 42b restricts movement of spiral portion 51 in a direction perpendicular to the direction in which brush 40 slides. Specifically, protrusion 42b restricts movement of spiral portion 51 in the direction in which axis C of rotating shaft 21 extends (Z-axis direction). More specifically, protrusion 42b is located between spiral portion 51 and cover plate 70. Therefore, protrusion 42b restricts movement of spiral portion 51 toward cover plate 70 in the direction in which axis C of rotating shaft 21 extends.

[0082] In this way, the protrusion 42b restricts the movement of the spiral portion 51, so that the spiral portion 51 is kept out of contact with the inner surface of the brush box BX when the wire material constituting the brush spring 50 tries to unwind. In other words, the protrusion 42b has the function of preventing the spiral portion 51 from contacting the inner surface of the brush box BX when the wire material constituting the brush spring 50 tries to unwind. The protrusion 42b is located between the spiral portion 51 and the cover plate 70. Therefore, the protrusion 42b prevents the spiral portion 51 from contacting the inner surface of the cover plate 70. By providing the protrusion 42b, the spiral portion 51 is kept out of contact with the inner surface of the cover plate 70 when the wire material constituting the brush spring 50 tries to unwind.

[0083] Furthermore, the provision of the protrusion 42b can also prevent the spiral portion 51 of the brush spring 50 from tilting. For example, even if the brush 40 tilts in the rotational direction at the contact surface with the commutator 30, the spiral portion 51 of the brush spring 50 itself can be prevented from tilting.

[0084] The effects of the electric motor 1 according to this embodiment, including the background to the development of the technology of the present disclosure, will be described with reference to Figures 9A and 9B. Figures 9A and 9B are diagrams for explaining the issues that arise when a constant force spring is used as the brush spring 50.

[0085] 9A , when a constant force spring having a spiral portion 51 in which a strip-shaped wire is wound in a spiral shape is used as the brush spring 50, the spiral portion 51 of the brush spring 50 is disposed in contact with the rear end portion 42X of the brush 40X, and the spiral portion 51 applies a spring load to the brush 40X. Specifically, when the wire is pulled out from the spiral portion 51, the force of the wire trying to rewind into the original spiral portion 51 applies a spring load to the brush 40X.

[0086] As shown in Fig. 9A , before the brush 40X is worn, there is a gap between the spiral portion 51 of the brush spring 50 and the cover plate 70 that constitutes the brush box BX. However, as shown in Fig. 9B , as the brush 40X wears and the wire that constitutes the brush spring 50 unwinds, the spiral portion 51 of the brush spring 50 moves in a direction perpendicular to the unwinding direction D of the wire (upward in Fig. 9B ), and the spiral portion 51 of the brush spring 50 comes into contact with the inner surface of the brush box BX. Specifically, the spiral portion 51 and the cover plate 70 come into contact with each other. As a result, the spring load of the spiral portion 51 decreases due to frictional resistance between the spiral portion 51 and the cover plate 70, resulting in a loss of spring load.

[0087] In particular, since the cover plate 70 is made of a metal material, contact between the spiral portion 51 and the cover plate 70 may result in the spiral portion 51 adhering to the cover plate 70 and moving. In this case, the loss of spring load becomes significantly large.

[0088] FIG. 10 illustrates the problems that arise when the rear end surface of the brush 40Y is inclined. As shown in FIG. 10 , it is possible to prevent the spiral portion 51 from moving perpendicular to the unwinding direction D of the wire by making the entire rear end 42Y of the brush 40Y an inclined surface and contacting this inclined surface. However, with this approach, the direction of the spring load vector B of the spiral portion 51 is normal to the inclined surface, so the spring load vector B of the spiral portion 51 is oblique to the unwinding direction D of the wire. This results in a loss of spring load relative to the original spring load of the brush spring 50. For example, with the inclination of the inclined surface of the rear end 42Y of the brush 40Y shown in FIG. 10 , the spring load vector of the brush spring 50 is directed upward and leftward. This results in not only a spring load being generated in the leftward direction, which is the unwinding direction D of the wire, but also a large spring load being generated upward, which is perpendicular to the unwinding direction D of the wire. As a result, the spring load in the originally desired left direction (the rewinding direction D of the wire) decreases, resulting in sliding loss.

[0089] As a result of intensive research by the inventors into these issues, they discovered a shape for the brush 40 that can prevent the spiral portion 51 of the brush spring 50 from coming into contact with the brush box BX while aligning the direction of the spring load vector B from the spiral portion 51 of the brush spring 50, which is a constant load spring, with the rewinding direction D of the wire.

[0090] Specifically, in the electric motor 1, the rear end 42 of the brush 40 is provided with a spring contact surface 42a that comes into contact with the spiral portion 51 of the brush spring 50, and a protrusion 42b that protrudes rearward from the spring contact surface 42a. The spring contact surface 42a is a plane that is perpendicular to the unwinding direction D of the wire that constitutes the brush spring 50. Furthermore, the protrusion 42b is located between the spiral portion 51 and the inner surface of the brush box BX, and prevents the spiral portion 51 from contacting the inner surface of the brush box BX when the wire that constitutes the brush spring 50 tries to unwind.

[0091] In this way, the spring contact surface 42a of 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 by 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 from the original spring load of the brush spring 50, which is a constant force spring.

[0092] Furthermore, the provision of the protrusion 42b on the rear end 42 of the brush 40 prevents the spiral portion 51 from coming into contact with the inner surface of the brush box BX when the front end 41 of the brush 40 wears and the wire that makes up the brush spring 50 tries to unwind. 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 can be maintained.

[0093] As described above, according to the electric motor 1 of this embodiment, the direction of the spring load vector B due to the spiral portion 51 of the brush spring 50, which is a constant load spring made of wire, is set to the rewinding direction D of the wire, while preventing the spiral portion 51 of the brush spring 50 from coming into contact with the brush box BX.

[0094] Furthermore, in the electric motor 1 according to this embodiment, the protrusion 42 b of the brush 40 restricts the movement of the spiral portion 51 in a direction perpendicular to the unwinding direction D of the wire that constitutes the brush spring 50 .

[0095] This configuration makes it possible to easily prevent the spiral portion 51 from coming into contact with the inner surface of the brush box BX when the wire constituting the brush spring 50 tries to unwind.

[0096] Specifically, the protrusion 42b of the brush 40 restricts the movement of the spiral portion 51 toward the metal cover plate 70, preventing the spiral portion 51 from contacting 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 cover plate 70 can be maintained.

[0097] With this configuration, even if a metal cover plate 70 is used for part of the brush box BX, it is possible to prevent the metal cover plate 70 and the spiral portion 51 of the brush spring 50 from adhering to each other.

[0098] In addition, in electric motor 1 according to this embodiment, side surface 42b1 of protruding portion 42b on the side of spiral portion 51 is a curved surface having a cross-sectional shape of an arc surface.

[0099] With this configuration, the protrusion 42b allows the circular spiral portion 51 to be fitted into the recess 61c formed in the rear end portion 42 of the brush 40. Therefore, the brush spring 50 can be stably held in the rear end portion 42 of the brush 40.

[0100] In this case, in the electric motor 1 according to the present embodiment, the radius of curvature of the arc of the curved surface of the side surface 42 b 1 of the protruding portion 42 b is greater than the radius of curvature of the arc of the outermost portion of the spiral portion 51 .

[0101] With this configuration, the spiral portion 51 and the rear end 42 of the brush 40 contact each other at only one point on the spring contact surface 42a. This allows the vector B of the spring load applied to the brush 40 by the spiral portion 51 of the brush spring 50 to be limited to the unwinding direction D of the wire constituting the brush spring 50. In other words, if the spiral portion 51 of the brush spring 50 and the rear end 42 of the brush 40 contact each other at two or more points, the vector of the spring load applied to the brush 40 by the spiral portion 51 would have not only a component in the unwinding direction D of the wire, but also a component in a direction different from the unwinding direction D of the wire. However, by having the spiral portion 51 and the rear end 42 of the brush 40 contact each other at only one point on the spring contact surface 42a, the vector of the spring load applied to the brush 40 by the spiral portion 51 of the brush spring 50 can be limited to the unwinding direction D of the wire. This allows the brush 40 to be pressed against the commutator 30 with the maximum spring load inherent to the brush spring 50.

[0102] FIG. 11 is an enlarged cross-sectional view of an electric motor 1 according to Modification 1. As shown in FIG. 11 , the radius of curvature of the arc of the curved surface of the side surface 42b1 of the protrusion 42b may be smaller than the radius of curvature of the outermost arc of the spiral portion 51. In this case, the spiral portion 51 and the rear end 42 of the brush 40 contact each other at two points: the spring contact surface 42a and the protrusion 42b. This allows the spiral portion 51 to be stably held. However, the brush spring 50 can be stably held at the rear end 42 of the brush 40. However, in this case, the spring load of the spiral portion 51 on the brush 40 occurs not only at the contact point between the spring contact surface 42a and the spiral portion 51 but also at the contact point between the protrusion 42b and the spiral portion 51. However, the spring load at the contact point between the spring contact surface 42a and the spiral portion 51 is the main spring load, while the spring load at the contact point between the protrusion 42b and the spiral portion 51 is slight. Therefore, in this modification as well, the vector B of the spring load applied to the brush 40 by the spiral portion 51 is substantially in the direction D of the unwinding of the wire.

[0103] In the above embodiment, the side surface 42b1 of the protrusion 42b facing the spiral portion 51 is a curved surface. However, this is not limited to this. Fig. 12 is an enlarged cross-sectional view of the electric motor 1 according to Modification 2. Fig. 13 is an enlarged cross-sectional view of the electric motor 1 according to Modification 3. For example, as in the brush 40B shown in Fig. 12, the side surface 42b1 of the protrusion 42b facing the spiral portion 51 may be a flat surface that is inclined with respect to the spring contact surface 42a. As in the brush 40C shown in Fig. 13, the side surface 42b1 of the protrusion 42b facing the spiral portion 51 may be a flat surface that is perpendicular to the spring contact surface 42a.

[0104] (Modification) Although the electric motor 1 according to the present disclosure has been described above based on the embodiment, the present disclosure is not limited to the above embodiment.

[0105] For example, in the above embodiment, the brush box BX that stores the brushes 40 is composed of a resin brush storage portion 61 and a metal cover plate 70. However, this is not limited to this. Specifically, the brush box BX may be entirely 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 block composed of a metal L-shaped plate that surrounds two sides of the brushes 40 and a resin L-shaped plate that surrounds the other two sides of the brushes 40.

[0106] 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, the other of the two bearings can be attached to the first end 21a of the rotating shaft 21, and one of the two bearings can 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. Therefore, it is possible to further suppress misalignment of the brush 40 relative to the rotating shaft 21.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] In addition, the present disclosure also includes forms obtained by applying various modifications to the above-described embodiments and variations that would occur to a person skilled in the art, or forms realized by arbitrarily combining the components and functions of each embodiment 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 claims.

[0113] 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.

[0114] REFERENCE SIGNS LIST 1 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 segments 40, 40A, 40B, 40C, 40X, 40Y brush 41 front end 42, 42X, 42Y rear end 42a spring contact surface 42b protrusion 42b1 side surface 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 62 insertion hole 63 insertion hole 70 cover plate 71 leg portion 80 power terminal 90 capacitor 100 bearing 111 First bracket 112 Second bracket BX Brush box

Claims

1. An electric motor comprising: a rotor having a rotating shaft extending in the axial direction of an axis; a commutator attached to the rotating shaft; brushes in contact with the commutator; brush springs that press the brushes against the commutator; and a brush box that houses the brushes and the brush springs and is covered by a cover plate, wherein the brush springs are constant-force springs having a spiral portion around which a strip-shaped wire is wound, and the brushes have a front end that contacts the commutator and a rear end that is located opposite the front end, and the rear end is provided with a spring contact surface with which the spiral portion of the brush spring contacts, and a protrusion that protrudes rearward beyond the spring contact surface, the spring contact surface is a plane that is perpendicular to the unwinding direction of the wire, and the protrusion is located between the spiral portion and the cover plate, and maintains the spiral portion out of contact with the inner surface of the cover plate when the wire tries to unwind.

2. The electric motor according to claim 1, wherein the protrusion restricts movement of the spiral portion in a direction perpendicular to the unwinding direction of the wire.

3. The electric motor according to claim 2, wherein the spiral portion is in contact with the spring contact surface in a vertical position along the axial direction.

4. An electric motor as set forth in claim 3, wherein the contact portion between the spiral portion and the spring contact surface is located on the opposite side of the rear end of the brush from the inner surface of the brush box in the axial direction.

5. The electric motor according to any one of claims 1 to 4, wherein the side surface of the protrusion on the side of the spiral portion is a curved surface having a cross-sectional shape of an arc.

6. The electric motor according to claim 5, wherein the radius of curvature of the arc of said curved surface is greater than the radius of curvature of the outermost arc of said spiral portion.

7. The electric motor according to claim 5, wherein the radius of curvature of the arc of said curved surface is smaller than the radius of curvature of the outermost arc of said spiral portion.

8. The electric motor according to any one of claims 1 to 4, wherein the side surface of the protrusion on the side of the spiral portion is a flat surface inclined relative to the spring contact surface.

9. An electric motor according to any one of claims 1 to 4, wherein the diameter of the spiral portion is greater than the thickness of the brush.

10. An electric motor as claimed in any one of claims 1 to 4, further comprising a resin brush holder for holding the brushes, the brush holder having a brush storage section for storing the brushes, the brush storage section having a bottom and a pair of side walls erected on the bottom, and the brush box being constituted by the brush storage section and the metal cover plate.

Images