WO2023248586A1 - Electric motor - Google Patents

Abstract

This electric motor comprises: a rotating shaft the axial direction of which is the direction in which the axis extends; a commutator that is attached to the rotating shaft; a brush that adjoins the commutator; and a brush spring for pushing the brush against the commutator. The brush has an arc shape, and the brush spring is a fixed load spring.

Description

Electric motor

The present disclosure relates to an electric motor.

Electric motors are widely used not only in the field of household electrical equipment such as vacuum cleaners, but also in the field of electrical equipment such as automobiles. For example, an electric blower mounted on a vacuum cleaner uses an electric motor to rotate a rotary fan. Two-wheel or four-wheel vehicles use electric motors to drive cooling fans such as radiators.

As electric motors, brushed electric motors (commutator motors) that use brushes and brushless electric motors that do not use brushes are known. Among these, the brushed electric motor includes a stator, a rotor, a commutator, a brush, a brush holder, and a brush spring. The rotor is rotated by the magnetic force of the stator. The commutator is attached to the rotating shaft of the rotor. The brush is in sliding contact with the commutator. The brush holder is provided with a brush storage section that stores the brushes. The brush spring is used to press the brush against the commutator.

In order to extend the life of the electric motor, it is possible to increase the length of the brush. However, if the linear brush is simply made longer, the diameter of the motor becomes larger, resulting in an increase in the size of the motor. Therefore, in order to extend the life of the electric motor and reduce its size at the same time, a technique using an arc-shaped brush has been proposed (see, for example, Patent Documents 1 and 2).

In conventional electric motors equipped with arc-shaped brushes, coil springs or torsion springs are used as brush springs for pressing the brushes against the commutator.

However, in conventional electric motors, when an arc-shaped brush is pressed using a coil spring or torsion spring, there is a pressing force (initial pressure) before the brush wears out, and a pressing force (final pressure) when the motor reaches the end of its life due to brush wear. ) becomes larger. In other words, in the conventional electric motor, there is a large difference in the pressing load applied to the commutator between the initial stage and the final stage of the brush. For this reason, in conventional electric motors, even if the brushes are made arcuate and the length of the brushes is increased, it is difficult to maintain an optimal pressing load on the commutator by the brushes. Therefore, conventional electric motors cannot provide sufficient service life.

Furthermore, when a torsion spring is used as the brush spring to apply a pressing load to the arc-shaped brush, the brush spring reduces the pressing load when the brush presses against the commutator. When a pressing load is applied to the arc-shaped brush using a torsion spring, the brush may come into contact with the side wall of the brush storage portion in the brush holder. In other words, a pressing load by the brush spring may be applied to the contact portion between the side wall of the brush storage portion and the brush.

In particular, when the arc-shaped brush is long, the pressing load from the brush spring is likely to be applied to the contact area between the brush and the side wall of the brush housing. In this way, when the side wall of the brush storage section and the brush come into contact, the slipperiness of the brush in the brush storage section is significantly reduced when wear particles of the brush accumulate in the gap between the side wall of the brush storage section and the brush. do.

As described above, in conventional electric motors equipped with arc-shaped brushes, it is difficult to press the commutator with a stable load from the initial stage to the final stage of the brush. Therefore, with conventional electric motors, it is difficult to achieve a long life when arc-shaped brushes are used.

Japanese Patent Application Publication No. 2006-149154 Japanese Patent Application Publication No. 2010-35272

The present disclosure has been made to solve such problems. An object of the present disclosure is to provide an electric motor that can press a commutator with a stable load from the initial stage to the final stage of the brush even if the motor uses arc-shaped brushes.

In order to achieve the above object, one aspect of the electric motor according to the present disclosure includes a rotating shaft whose axial direction is the direction in which the axial center extends, a commutator attached to the rotating shaft, and a commutator that is in contact with the commutator. The apparatus includes a brush and a brush spring for pressing the brush against the commutator, the brush having an arc shape, and the brush spring being a constant force spring.

If the center of the circle forming the arc of the brush is the center point, the angle between the line connecting the center point and the front end surface of the brush and the line connecting the center point and the rear end surface of the brush is 90°. It is preferable that it is above.

It is preferable that the constant force spring is placed in contact with a side surface on the outer peripheral side of the brush.

In the axial direction of the rotating shaft, the height of the constant force spring is preferably 1/3 or more and 2/3 or less of the height of the brush.

The electric motor may further include a brush holder that holds the brush, and the brush holder may have a guide wall that guides the brush, and a gap between the brush and the guide wall may be 100 μm or more. preferable.

The electric motor further includes a brush holder that holds the brush, and the brush holder has a guide wall that guides the brush. It is preferable that the brush is provided so as to face only one side surface thereof, and that the other of the outer peripheral side surface and the inner peripheral side surface of the brush is open.

The constant force spring has a spiral portion in which a band-shaped wire is spirally wound, and the brush holder is located on the front end surface side of the brush, and the brush holder is located on the front end side of the brush, and the brush holder has a tip portion of the wire pulled out from the spiral portion. It is preferable that the brush has a fixing part to which the brush is fixed, and the fixing part is located on the front end surface side of the other of the inner circumferential side surface and the outer circumferential side surface of the brush.

The fixing portion may be provided facing an outer peripheral side surface of the brush, and the guide wall may be provided facing an inner peripheral side surface of the brush.

A plurality of brushes may be arranged.

Four brushes may be arranged.

The number of poles of the electric motor may be 4n (n is an integer of 1 or more).

The electric motor further includes a brush holder that holds the plurality of brushes, and a bracket separate from the brush holder, and the brush holder is configured to be attachable to the bracket while holding the plurality of brushes. may have been done.

According to the present disclosure, even in an electric motor using an arcuate brush, the commutator can be pressed with a stable load from the initial stage to the final stage of the brush.

FIG. 1 is an external perspective view of an electric motor according to an embodiment as viewed obliquely from above. FIG. 2 is an external perspective view of the electric motor according to the embodiment as viewed diagonally from below. FIG. 3 is a sectional view of the electric motor according to the embodiment. FIG. 4 is an exploded perspective view of the electric motor according to the embodiment. FIG. 5A is a rear view of the electric motor according to the embodiment. FIG. 5B is a diagram showing the relationship between a commutator, a brush, and a brush spring in the electric motor according to the embodiment. FIG. 6 is a perspective view showing a rotor, brushes, and brush springs in the electric motor according to the embodiment. FIG. 7 is a side view showing the brush and brush spring when viewed from the direction of arrow A in FIG. 6. FIG. FIG. 8 is a diagram showing how the brush slides due to wear. FIG. 9 is a diagram showing the configuration of an electric motor of a comparative example. FIG. 10 is a diagram showing the configuration of the electric motor according to the embodiment. FIG. 11 is a perspective view of the electric motor according to Modification 1 when viewed from the back side. FIG. 12 is a rear view of the electric motor according to Modification 1. FIG. 13 is a diagram showing the relationship between the brush and the brush spring in the electric motor according to Modification 2. FIG. 14 is a perspective view showing the positional relationship between a pair of brushes, a pair of brush springs, and a commutator in an electric motor according to modification 3. FIG. 15 is a top view showing the positional relationship between one brush, one brush spring, and a commutator in FIG. 14. FIG. 16 is a diagram for explaining the arrangement of brushes in an electric motor according to modification 4.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The embodiments described below are all specific examples 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 do not limit the present disclosure. Therefore, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims representing the most important concept of the present disclosure will be described as arbitrary constituent elements.

Each figure is a schematic diagram and is not necessarily strictly illustrated. In each figure, components that are substantially the same as those in other figures are denoted by the same reference numerals, and overlapping explanations will be omitted or simplified. In this specification, the terms "upper" and "lower" do not necessarily refer to the upper direction (vertically upward) and the downward direction (vertically downward) in absolute spatial recognition.

(Embodiment)
First, the overall configuration of the electric motor 1 according to the embodiment will be described using FIGS. 1 to 5B. FIG. 1 is an external perspective view of an electric motor 1 according to an embodiment as viewed obliquely from above. FIG. 2 is an external perspective view of the electric motor 1 according to the embodiment as viewed diagonally from below. FIG. 3 is a sectional view of the electric motor 1 according to the embodiment. FIG. 4 is an exploded perspective view of the electric motor 1 according to the embodiment. FIG. 5A is a rear view of the electric motor 1 according to the embodiment. FIG. 5B is a diagram showing the relationship among the commutator 30, the brush 40, and the brush spring 50 in the electric motor 1 according to the embodiment.

As shown in FIGS. 1 to 5B, the electric motor 1 includes a stator 10 (stator) and a rotor 20 (rotor) that rotates by the magnetic force of the stator 10. The electric motor 1 is a brushed electric motor. The electric motor 1 includes a commutator 30, at least one brush 40, a brush spring 50, and a brush holder 60. Commutator 30 is attached to rotating shaft 21 that rotor 20 has. At least one brush 40 contacts commutator 30 . The brush spring 50 is for pressing the brush 40 against the commutator 30. Brush holder 60 holds brush 40. The electric motor 1 further includes a first bearing 71 and a second bearing 72, and a first bracket 81 and a second bracket 82.

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

Hereinafter, each component of the electric motor 1 will be explained in detail.

As shown in FIG. 3, the stator 10 is arranged with a small air gap between it and the rotor 20. Stator 10 generates magnetic force that acts on rotor 20. The stator 10 is configured to generate magnetic flux on the air gap surface with the rotor 20. The stator 10 constitutes a magnetic circuit together with the rotor 20, which is an armature. As shown in FIG. 4, stator 10 has a substantially toroidal overall shape. The stator 10 is magnetized so that north poles and south poles are alternately and evenly present on the air gap surface with the rotor 20 along the circumferential direction of the rotating shaft 21. The stator 10 is a magnetic field that creates magnetic flux for generating torque. The stator 10 is made of, for example, a permanent magnet. The direction of the main magnetic flux generated by the stator 10 (magnet) is the direction in which the rotating shaft 21 extends. As shown in FIG. 3, the stator 10 is fixed to a first bracket 81.

As shown in FIG. 3, the rotor 20 has a rotating shaft 21 and a coil 22. The rotor 20 is a coreless rotor without a core.

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

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

The rotating shaft 21 is a shaft having an axis C. The rotating shaft 21 is an elongated rod-shaped member. As an example, the rotating shaft 21 is a metal rod made of a metal material such as SUS (Steel Special Use Stainless). The axis C of the rotating shaft 21 becomes the center when the rotor 20 rotates. The longitudinal direction of the rotating shaft 21, that is, the direction in which the rotating shaft 21 extends is the direction of the axial center C (axial center direction).

A first end 21a, which is one end of the rotating shaft 21, is supported by a first bearing 71. The second end 21b, which is the other end of the rotating shaft 21, is supported by a second bearing 72. As an example, the first bearing 71 and the second bearing 72 are bearings such as ball bearings.

The first end 21a of the rotating shaft 21 is an output side end (output shaft). The first end 21a of the rotating shaft 21 protrudes from the first bracket 81 and the first bearing 71. A load such as a rotating fan is attached to the first end 21a. The second end 21b of the rotating shaft 21 is an end on the opposite output side (anti-output shaft). The second end 21b of the rotating shaft 21 does not protrude from the second bracket 82 and the second bearing 72.

The first bearing 71 is held by the first bracket 81. Specifically, the first bearing 71 is fixed to a recess provided in the first bracket 81. The second bearing 72 is held by a second bracket 82. Specifically, the second bearing 72 is fixed to a recess provided in the second bracket 82.

The first bracket 81 and the second bracket 82 are made of, for example, a metal material. For example, the first bracket 81 and the second bracket 82 are made of an iron-based material such as a cold rolled steel plate (SPC (Steel Plate Cold) material) or a metal such as aluminum. Note that the first bracket 81 and the second bracket 82 constitute a housing, and the stator 10 and the rotor 20 are arranged within this housing.

As shown in FIGS. 1 to 3, the first bracket 81 is an outer shell member of the electric motor 1. The first bracket 81 is formed into a bottomed cylindrical shape having a bottom portion and a cylindrical side wall portion. The stator 10 is fixed to the bottom of the first bracket 81. The material of the first bracket 81 and the second bracket 82 is not limited to metal material. The material of the first bracket 81 and the second bracket 82 may be a resin material. However, from the viewpoint of suppressing noise generated from the electric motor 1, the first bracket 81 and the second bracket 82 are preferably made of a metal material.

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

The plurality of coils 22 are wire-wound coils. Specifically, the plurality of coils 22 are armature windings made of electric wire. The plurality of coils 22 are wound so as to generate magnetic force acting on the stator 10 when current flows therethrough. The direction of the main magnetic flux generated by the coil 22 is along the axis C along which the rotating shaft 21 extends. Specifically, the plurality of coils 22 are wound in a flat shape. The coil surfaces of the plurality of coils 22 are arranged so as to face in the direction along the axis C along which the rotating shaft 21 extends.

The coil 22 is composed of an insulated wire having a core wire made of metal such as copper or aluminum and an insulating film covering the core wire. The plurality of coils 22 are thin wire-wound coils having a coil layer in which the insulated wire is wound in a planar shape. Specifically, the plurality of coils 22 are constituted by, for example, one or more coil layers in which insulated wires are wound in a substantially fan shape in a plan view. The plurality of coils 22 configured in this manner are arranged in an annular shape surrounding the rotating shaft 21 when viewed from the direction of the axis C along which the rotating shaft 21 extends.

The plurality of coils 22 are electrically connected to the commutator 30. Specifically, the plurality of coils 22 are electrically connected to any one of the plurality of commutator pieces 31 that the commutator 30 has. Therefore, current flows through the plurality of coils 22 via the commutator pieces 31 that are in contact with the brushes 40 .

The plurality of coils 22 are integrally molded together with the mold resin 23 by being covered with the mold resin 23. That is, the plurality of coils 22 are resin molded. Therefore, as shown in FIG. 4, the outer shape of the molded resin 23 after molding the plurality of coils 22 in plan view is circular. As the mold resin 23, an insulating resin material such as phenol resin or unsaturated polyester (BMC (Bulk Molding Compound)) can be used. The mold resin 23 may be either a thermosetting resin or a thermoplastic resin. The molded resin 23 is fixed to the rotating shaft 21 via a cylindrical member 24.

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

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

As shown in FIGS. 4 and 5B, the commutator 30 has a plurality of commutator pieces 31 (commutator segments) provided along the rotational direction of the rotating shaft 21. Specifically, the plurality of commutator pieces 31 are arranged in an annular shape along the rotation direction of the rotation shaft 21 so as to surround the rotation shaft 21 . The shape of each commutator piece 31 is a long member extending in the longitudinal direction of the rotating shaft 21 . Each commutator piece 31 is formed to have a step on its surface.

The plurality of commutator pieces 31 are conductive terminals made of a metal material such as copper. The plurality of commutator pieces 31 are electrically connected to the coil 22 that the rotor 20 has. The plurality of commutator pieces 31 are arranged to be insulated and separated from each other. The plurality of commutator pieces 31 are electrically connected by the coil 22 of the rotor 20.

The commutator 30 is a molded commutator. The commutator 30 has a structure in which a plurality of commutator pieces 31 are molded with resin. In this case, the plurality of commutator pieces 31 are embedded in the resin so that their surfaces are exposed. The plurality of commutator pieces 31 are fixed to the rotating shaft 21 by fixing resin for molding the plurality of commutator pieces 31 to the rotating shaft 21 . The mold resin covering the plurality of commutator pieces 31 and the mold resin 23 covering the coil 22 are separate bodies. The mold resin covering the plurality of commutator pieces 31 and the mold resin 23 covering the coil 22 are made of different resin materials. However, it is not limited to this. That is, the mold resin covering the plurality of commutator pieces 31 and the mold resin 23 covering the coil 22 may be integrated.

At least one brush 40 is in contact with the commutator 30. Specifically, the tip of the brush 40 is in contact with the commutator piece 31 of the commutator 30. The brush 40 is in contact with the commutator piece 31 in a direction (radial direction) perpendicular to the direction of the axis C of the rotating shaft 21 . The commutator 30 of the brush 40 rotates as the rotating shaft 21 rotates. Therefore, the brush 40 continues to be in contact with all the commutator pieces 31 in sequence.

The brush 40 is a power supply brush for supplying power to the coil 22. Specifically, when the brush 40 comes into contact with the commutator piece 31 of the commutator 30, the armature current supplied to the brush 40 via the power terminal (not shown) fixed to the brush holder 60 is transferred to the commutator piece 31 of the commutator 30. It flows to the coil 22 via the piece 31. The brush 40 and the power terminal are connected by a pigtail wire (not shown). Specifically, one end of the pigtail wire is connected to the brush 40. The other end of the pigtail wire is connected to the power terminal. Power is supplied to the power supply terminal fixed to the brush holder 60 from an external power supply arranged outside the electric motor 1. The external power source is a power source that exists outside the electric motor 1. The external power supply supplies the electric motor 1 with a predetermined input voltage. The external power supply is a DC power supply that supplies the motor 1 with an input voltage of DC12V.

The brush 40 is a conductive carbon brush whose main component is carbon. In this case, the brush 40 is preferably a carbon brush containing metal such as copper. Thereby, the contact resistance between the brush 40 and the commutator piece 31 can be reduced. As an example, the brush 40 is a sintered brush made of a sintered body. In this case, the brush 40, which is a sintered body, may be produced by, for example, putting a kneaded mixture of graphite powder, copper powder, binder resin, and hardening agent into a mold, compression molding, and firing. Can be done. In this embodiment, the brush 40 is manufactured without cutting. In other words, the brush 40 is not cut after putting graphite powder and copper powder into a mold, compression molding, and firing.

As shown in FIGS. 5A and 5B, the brush 40 has an arc shape. Specifically, the brush 40 has a substantially rectangular cross-sectional shape. The brush 40 has an arcuate shape when viewed from above. When the brush 40 is viewed from above, the width of the brush 40 is constant. The top view shape of the brush 40, which is arc-shaped, is not limited to a strictly circular arc. The shape of the brush 40 when viewed from above may be approximately an arc.

The brush 40 has a first side surface 41 and a second side surface 42 as a pair of opposing side surfaces. The first side surface 41 is a side surface on the outer circumferential side of the arc that constitutes the brush 40 . The second side surface 42 is a side surface on the inner circumferential side of the arc that constitutes the brush 40 .

Since the width of the brush 40 is constant, the curvature of the arc of the first side surface 41 on the outer circumference side is smaller than the curvature of the arc of the second side surface 42 on the inner circumference side. The first side surface 41 and the second side surface 42 are cylindrical surfaces. Therefore, the center point of the circle forming the arc of the first side surface 41 is one. Similarly, the center point of the circle forming the arc of the second side surface 42 is also one. The center point of the circle forming the arc of the first side surface 41 and the center point of the circle forming the arc of the second side surface 42 coincide. That is, the circle forming the arc of the first side surface 41 and the circle forming the arc of the second side surface 42 are concentric circles. Note that the center point of the circle forming the arc of the first side surface 41 and the center point of the circle forming the arc of the second side surface 42 may not coincide with each other.

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

A plurality of brushes 40 are provided. In this case, a plurality of brushes 40 may be provided at equal intervals along the rotation direction of the rotor 20. Specifically, two brushes 40 are provided. The two brushes 40 are arranged to face each other with the commutator 30 in between. That is, the two brushes 40 are arranged at 180° intervals along the rotational direction of the rotor 20. Specifically, the front end surface 43 of one brush 40 and the front end surface 43 of the other brush 40 face each other with the rotating shaft 21 in between.

The two brushes 40 are both elongated. As shown in FIG. 5B, when the center of the circle forming the arc of the brush 40 is set as the center point, a line connecting the center point and the front end surface 43 of the brush 40 and a line connecting the center point and the rear end surface 44 of the brush 40 The angle θ between the two is 90° or more (θ≧90°). That is, in both of the two brushes 40, the central angle of the arc of the brush 40 is 90° or more. Specifically, in the two brushes 40, both the first side surface 41 and the second side surface 42 have central arc angles of 90° or more. The two brushes 40 have the same shape, but the shape is not limited to this.

The brush 40 is constantly in contact with the commutator piece 31 of the commutator 30 under pressure from the brush spring 50. Specifically, as shown in FIGS. 5A and 5B, the brush 40 is pressed against the commutator 30 by the brush spring 50, so that the front end surface 43 of the brush 40 is in contact with the commutator piece 31. The brush 40 wears out due to continued contact with the rotating commutator piece 31. In this way, the brush 40 receives the pressing force from the brush spring 50 and comes into sliding contact with the commutator 30 . At the same time, the brush 40 becomes shorter due to wear with the commutator 30.

The brush springs 50 are provided according to the number of brushes 40. In this embodiment, since the electric motor 1 is provided with two brushes 40, two brush springs 50 are also provided. The brush 40 and brush spring 50 are held in a brush holder 60.

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

The brush spring 50, which is a constant force spring, is made of a band-shaped wire rod. The brush spring 50, which is a constant force spring, is a spiral spring. The brush spring 50 has a spiral portion 51 (coil portion) in which a band-shaped wire is spirally wound. The brush spring 50 is constituted by a single strip-shaped wire rod made of a metal material such as a steel plate, for example.

Specifically, the wire that constitutes the brush spring 50 is a long and band-shaped metal plate. Therefore, the spiral portion 51 is a portion of a constant force spring in which a long, band-shaped metal plate is spirally wound multiple times in only one direction. In the brush spring 50, by stretching one end of the wire from the spiral spiral part 51, a force (spring restoring force) to return to the original spiral state is generated.

As shown in FIGS. 5A and 5B, the brush spring 50 presses the brush 40 against the commutator 30 using the spiral portion 51. Specifically, the brush spring 50 applies a load to the brush 40 by the spring restoring force of the spiral portion 51 when the spiral portion 51 contacts the rear end surface 44 of the brush 40 .

The brush spring 50 has an outer end 50a that is one end of a band-shaped metal plate, and an inner end 50b that is the other end of the band-shaped metal plate. The outer end portion 50a is one tip of a band-shaped metal plate drawn out from the outermost periphery of the spiral portion 51. The inner end portion 50b is the other tip of the band-shaped metal plate located at the innermost periphery of the spiral portion 51.

The brush spring 50 presses the brush 40 against the commutator 30 by the spiral portion 51. Specifically, the spiral portion 51 of the brush spring 50 is in contact with the rear end surface 44 of the brush 40 . The brush spring 50 applies a pressing load to the brush 40 by the spring restoring force of the spiral portion 51. That is, the brush spring 50 applies a pressing force (spring pressure) to the brush 40 by the spiral portion 51. Thereby, the brush 40 is urged toward the commutator 30.

FIG. 6 is a perspective view showing the rotor 20, brush 40, and brush spring 50 in the electric motor 1 according to the embodiment. As shown in FIG. 6, the brush spring 50 is arranged so as to be in contact with a first side surface 41, which is a side surface on the outer peripheral side of the brush 40. Specifically, a band-shaped wire rod (metal plate) pulled out from the spiral portion 51 of the brush spring 50 extends along the first side surface 41 of the brush 40 . Therefore, the band-shaped wire pulled out from the spiral portion 51 of the brush spring 50 is curved in an arc shape, similarly to the brush 40.

FIG. 7 is a side view showing the brush 40 and brush spring 50 when viewed from the direction of arrow A in FIG. 6. As shown in FIG. 7, when the height of the brush 40 is H1 and the height of the brush spring 50 is H2 in the direction of the axis C of the rotating shaft 21, the height H2 of the brush spring 50 is equal to the height of the brush 40. It is preferable that it is 1/3 or more and 2/3 or less of H1 (1/3≦H2/H1≦2/3). The height H2 of the brush spring 50 is the width of the band-shaped wire rod (metal plate) that constitutes the brush spring 50.

As shown in FIGS. 3 and 5A, the brush 40 is held by a brush holder 60. As shown in FIGS. 2 and 3, the brush holder 60 is also an outer shell member that constitutes the outer shell of the electric motor 1. The brush holder 60 covers the second bracket 82 from the outside. The brush holder 60 and the second bracket 82 are separate bodies. Therefore, even when a plurality of brushes 40 are arranged in the brush holder 60, the brushes 40 can be attached to the second bracket 82 while being held in the brush holder 60. Thereby, even when using a plurality of arc-shaped brushes 40, the plurality of brushes 40 can be easily set in the brush holder 60.

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

As shown in FIGS. 3 to 5A, the brush holder 60 has a brush storage section 60a that is a spatial area in which the brush 40 is stored. As shown in FIG. 3, the brush storage portion 60a is a recessed portion formed in a concave shape. As shown in FIG. 5A, the brush storage section 60a is formed in an elongated shape along the shape of the brush 40. In other words, the brush storage portion 60a is curved in an arc shape. The front portion and the rear portion of the brush storage portion 60a are open.

As shown in FIGS. 5A and 5B, a brush spring 50 is also accommodated in the brush accommodating portion 60a together with the brush 40. Therefore, the length of the brush storage section 60a in the longitudinal direction is longer than the length of the brush 40. Specifically, the brush spring 50 is arranged in the brush storage part 60a so that the spiral part 51 is located on the rear side of the rear end part of the brush 40. In this case, the band-shaped wire rod (metal plate) constituting the brush spring 50 is pulled out from the spiral portion 51 toward the commutator 30 along the arc shape of the brush storage portion 60a. Specifically, the band-shaped wire that constitutes the brush spring 50 is pulled out from the spiral portion 51 along the first side surface 41 of the brush 40 .

The outer end portion 50a of the band-shaped wire pulled out from the spiral portion 51 of the brush spring 50 is fixed to a fixing portion 60b formed near the opening of the front portion of the brush storage portion 60a in the brush holder 60. The fixing part 60b to which the outer end 50a of the brush spring 50 is fixed is a locking hole. In this case, by locking the V-shaped bent portion formed on the outer end 50a of the brush spring 50 to the fixing portion 60b (locking hole), the outer end 50a of the brush spring 50 is fixed to the fixing portion 60b. be done.

The brush storage portion 60a is formed according to the number of brushes 40. Since the number of brushes 40 is two, the brush holder 60 is formed with two brush storage sections 60a. Each of the two brush storage parts 60a is elongated in the direction in which the brush 40 extends. Moreover, each of the two brush storage parts 60a is formed in a concave shape with a rectangular cross-sectional shape.

As shown in FIGS. 3 and 4, the brush storage section 60a has a first side wall 61, a second side wall 62, and a bottom wall 63. The first side wall 61 faces the first side surface 41 of the brush 40 . The second side wall 62 faces the second side surface 42 of the brush 40 . The bottom wall 63 supports the bottom surface of the brush 40.

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

The first side wall 61 has an arc-shaped side wall surface that faces the first side surface 41 that is the outer peripheral side surface of the brush 40. Specifically, the first side wall 61 is provided in an elongated shape so as to face the entire surface of the first side surface 41. The second side wall 62 has an arcuate side wall surface facing the second side surface 42 that is the inner peripheral side surface of the brush 40 . Specifically, the second side wall 62 is provided in an elongated shape so as to face the entire surface of the second side surface 42 .

The distance between the first side wall 61 and the second side wall 62 is constant. Therefore, the curvature of the circular arc of the first side wall 61 on the outer peripheral side is smaller than the curvature of the circular arc of the second side wall 62 on the inner peripheral side. The side wall surface of the first side wall 61 and the side wall surface of the second side wall 62 are cylindrical surfaces. Therefore, the center point of the circle forming the arc of the first side wall 61 is one. Similarly, the center point of the arc of the second side wall 62 is also one. The center point of the circle forming the arc of the side wall surface of the first side wall 61 and the center point of the circle forming the arc of the side wall surface of the second side wall 62 coincide. That is, the circle forming the arc of the first side wall 61 and the circle forming the arc of the second side wall 62 are concentric circles. What are the circles forming the arc of the side wall surface of the first side wall 61, the circle forming the arc of the side wall surface of the second side wall 62, the circle forming the arc of the first side surface 41, and the circle forming the arc of the second side surface 42? , are concentric circles. However, the center point of the circle forming the arc of the first side wall 61 and the center point of the circle forming the arc of the second side wall 62 may not coincide.

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

In the electric motor 1 configured as described above, the current (driving current) supplied to the brush 40 flows to the coil 22 via the commutator piece 31 of the commutator 30. As a result, magnetic flux is generated in the rotor 20 (coil 22). The magnetic force generated by the interaction between the magnetic flux generated in the rotor 20 and the magnetic flux generated from the stator 10 becomes a torque that rotates the rotor 20. At this time, the direction in which the current flows is switched depending on the positional relationship when the commutator piece 31 of the commutator 30 and the brush 40 are in contact with each other. In this way, by switching the direction in which the current flows, a rotational force in a certain direction is generated by the repulsion and attraction of the magnetic force generated between the stator 10 and the rotor 20, and the rotor 20 rotates. It rotates around an axis 21.

FIG. 8 is a diagram showing how the brush 40 slides due to wear. When the rotor 20 rotates, the brush 40 housed in the brush housing part 60a of the brush holder 60 is pressed against the commutator 30 by the brush spring 50, as shown in FIG. Therefore, the front end portion of the commutator 30 wears out due to friction with the commutator pieces 31. In other words, the length of the brush 40 becomes shorter due to wear. Therefore, the rear end surface 44 of the brush 40 moves toward the commutator 30 within the brush storage portion 60a. At this time, the wire constituting the brush spring 50, which is a constant force spring, is wound into a spiral portion 51 as the brush 40 becomes shorter due to wear. In other words, the spiral portion 51 approaches the outer end portion 50a.

In this way, the brush 40 slides within the brush storage portion 60a toward the commutator 30 as the front end portion thereof becomes worn. The brush storage section 60a is configured by a first side wall 61 and a second side wall 62. Therefore, the brush 40 moves between the first side wall 61 and the second side wall 62 while being guided by the first side wall 61 and the second side wall 62. That is, the first side wall 61 and the second side wall 62 function as guide walls that guide the brush 40.

As shown in FIG. 8, as the brush 40 slides between the first side wall 61 and the second side wall 62, the spiral portion 51 of the brush spring 50 that presses the brush 40 also moves toward the first side wall 61 and the commutator 30. 61 and the second side wall 62. Specifically, the spiral portion 51 of the brush spring 50 moves between the first side wall 61 and the second side wall 62 while being guided by the first side wall 61 and the second side wall 62. In this way, the first side wall 61 and the second side wall 62 also function as guide walls that guide the spiral portion 51 of the brush spring 50.

Next, the effects of the electric motor 1 according to the present embodiment will be described in comparison with the electric motor 1X of a comparative example using FIGS. 9 and 10. FIG. 9 is a diagram showing the configuration of an electric motor 1X of a comparative example. FIG. 10 is a diagram showing the configuration of the electric motor 1 according to the embodiment.

As shown in FIG. 9, the electric motor 1X of the comparative example uses a torsion spring as the brush spring 50X. In this case, as shown by the white arrow in FIG. 9, by applying a pressing load to the rear end surface 44 of the brush 40 by the brush spring 50X, the front end surface 43 of the brush 40 can be pressed against the commutator piece 31 of the commutator 30. Can be done.

However, when the brush 40 is pressed by the brush spring 50X, which is a torsion spring, the pressure (initial pressure) before the brush 40 wears out and the pressure (final pressure) when the motor 1X reaches the end of its life due to wear of the brush 40 are different. The difference becomes large. In other words, the difference in the pressing load applied to the commutator 30 becomes large between the initial stage and the final stage of the brush 40.

Moreover, when the arc-shaped brush 40 is pressed by the torsion spring, the arc-shaped brush 40 is pressed outward by the pressing load of the brush spring 50X, as shown by the black block arrow in FIG. As a result, the pressing load when the brush 40 presses the commutator 30 is reduced by the brush spring 50X.

Furthermore, the brush storage portion 60a and the brush 40 may come into contact with each other due to the pressing load caused by the brush spring 50X. Specifically, as shown in FIG. 9, when the arc-shaped brush 40 is pressed outward by the pressing load of the brush spring 50X, the outer side of the first side wall 61 and the second side wall 62 in the brush storage portion 60a The first side surface 41 of the brush 40 may come into contact with the inner surface of the first side wall 61 located at.

Particularly, as shown in FIG. 9, when the arc-shaped brush 40 is long (for example, a line connecting the center point of the circle forming the arc of the brush 40 and the front end surface 43 of the brush 40 and a circle forming the arc of the brush 40) When the angle between the center point of the brush 40 and the line connecting the rear end surface 44 of the brush 40 is 90° or more, the brush 40 tends to come into contact with the first side wall 61 due to the pressing load of the brush spring 50X.

In this way, when the first side wall 61 and the brush 40 come into contact with each other, the slipperiness of the brush 40 in the brush storage section 60a decreases when wear powder of the brush 40 accumulates in the gap between the first side wall 61 and the brush 40. decreases significantly. Furthermore, if the slipperiness of the brush 40 decreases and the load with which the brush 40 presses against the commutator 30 disappears, the electric motor 1X may stop.

On the other hand, the gap between the first side wall 61 and the brush 40 is maintained so that the first side wall 61 and the brush 40 do not come into contact even if the arc-shaped brush 40 is pushed outward by the pressing load of the brush spring 50X. It is possible to make it larger. However, if the gap between the first side wall 61 and the brush 40 is increased, the brush 40 will easily vibrate when the rotor 20 rotates. As a result, the life of the electric motor 1X will be reduced.

In particular, the arc-shaped brush 40, which is difficult to cut, is difficult to manufacture with high dimensional accuracy. Therefore, when the arc-shaped brush 40 is used, the gap between the first side wall 61 and the brush 40 is unstable and tends to become large. As a result, the brushes 40 tend to vibrate when the rotor 20 rotates, reducing the lifespan of the electric motor 1X.

On the other hand, as shown in FIG. 10, in the electric motor 1 according to the present embodiment, a constant force spring is used as the brush spring 50 for pressing the arc-shaped brush 40 against the commutator 30. With this configuration, even if the brush 40 wears out, a constant pressing load can be applied to the brush 40 by the brush spring 50. Thereby, the difference between the pressing force (initial pressure) before the brush 40 wears out and the pressing force (final pressure) when the electric motor 1 reaches the end of its life due to the brush 40 wearing out can be reduced.

Moreover, when a constant force spring is used as the brush spring 50, the brush spring 50 is arranged so that the band-shaped wire pulled out from the spiral portion 51 contacts the arcuate side surface of the brush 40. As a result, the brush 40 not only receives a pressing load from the brush spring 50 at the rear end surface 44 in contact with the spiral portion 51, but also contacts the band-shaped wire pulled out from the spiral portion 51 with the arc-shaped side surface of the brush 40. The pressing load from the brush spring 50 can also be received at this location. Therefore, it is possible to prevent the pressing load from being reduced when the brush 40 presses the commutator 30 as in the electric motor 1X of the comparative example shown in FIG.

In particular, in the electric motor 1, the brush spring 50 is arranged so that a band-shaped wire rod (metal plate) constituting the brush spring 50 and the first side surface 41 on the outer peripheral side of the brush 40 are in contact with each other. As a result, a pressing load is generated in the direction toward the commutator 30 from the contact point between the strip-shaped wire of the brush spring 50 and the arc-shaped first side surface 41 of the brush 40, as shown by the black block arrow in FIG. Therefore, even if the brush 40 is arc-shaped, a stable pressing load can be applied from the brush 40 to the commutator 30. In other words, stable pressing by the brush 40 can be achieved.

The band-shaped wire pulled out from the spiral portion 51 of the brush spring 50 and the arc-shaped first side surface 41 of the brush 40 are in close contact. Therefore, abrasion powder of the brush 40 cannot enter between the band-shaped wire of the brush spring 50 and the first side surface 41 of the brush 40. As a result, even if the brush spring 50 is used, the slipperiness between the brush spring 50 and the brush 40 will not deteriorate due to abrasion powder of the brush 40.

As described above, the electric motor 1 according to the present embodiment includes a rotating shaft 21 whose axial center direction is the direction in which the axial center extends, a commutator 30 attached to the rotating shaft 21, and a commutator 30 that is in contact with the commutator 30. It includes a brush 40 and a brush spring 50 for pressing the brush 40 against the commutator 30. The brush 40 has an arc shape. The brush spring 50 is a constant force spring.

Thereby, even if the arc-shaped brush 40 is used, the commutator 30 can be pressed with a stable load from the initial stage to the final stage of the brush 40. Therefore, a long-life and high-quality electric motor 1 can be realized.

The electric motor 1 uses an arc-shaped brush 40 that is manufactured without cutting. In order to process the arc-shaped brush 40 with high dimensional accuracy, cutting is performed on a sintered body obtained by compression molding and firing powder. However, it is difficult to cut an arc-shaped sintered body. Therefore, manufacturing cost is high in order to manufacture the arc-shaped brush 40 with high dimensional accuracy. Therefore, in the electric motor 1, the arc-shaped brush 40 is manufactured and used without cutting. Thereby, the brush 40 can be manufactured at low cost. Therefore, a low-cost electric motor 1 can be realized.

The electric motor 1 uses a long arc-shaped brush 40. Specifically, similar to the form shown in FIG. 5B, a line connecting the center point of the circle forming the arc of the brush 40 and the front end surface 43 of the brush 40, and a line connecting the center point of the circle forming the arc of the brush 40. The angle θ between the center point and the line connecting the rear end surface 44 of the brush 40 is 90° or more (θ≧90°).

If a torsion spring is used as the brush spring 50X for the long arc-shaped brush 40 as shown in the comparative example electric motor 1X shown in FIG. There is a risk that the product life and quality will deteriorate. However, by using a constant force spring as the brush spring 50 as in the electric motor 1 according to the present embodiment shown in FIG. Pressure load can be stabilized. Therefore, a long-life and high-quality electric motor 1 can be realized.

In the electric motor 1, as shown in FIG. 7, the height H2 of the brush spring 50, which is a constant force spring, is 1/3 or more and 2/3 or less of the height H1 of the brush 40 in the direction of the axis C of the rotating shaft 21. It has become.

The band-shaped wire pulled out from the spiral portion 51 of the brush spring 50 is in contact with the first side surface 41 of the brush 40. Therefore, the lower the height H2 of the brush spring 50 (that is, the smaller the plate width of the band-shaped wire rod), the smaller the contact area between the wire rod of the brush spring 50 and the first side surface 41 of the brush 40 becomes. Therefore, by setting the height H2 of the brush spring 50 to 2/3 or less of the height H1 of the brush 40, when the wire forming the brush spring 50 is wound as the spiral portion 51 as the brush 40 becomes shorter, The slipperiness between the brush spring 50 and the brush 40 can be improved. On the other hand, the rear end surface 44 of the brush 40 is pushed by the spiral portion 51 of the brush spring 50. Therefore, the higher the height H2 of the brush spring 50, the larger the contact area between the rear end surface 44 of the brush 40 and the spiral portion 51. Therefore, the brush spring 50 can stably apply a pressing load to the brush 40. In this way, by setting the height H2 of the brush spring 50 to 1/3 or more and 2/3 or less of the height H1 of the brush 40, the sliding property between the brush spring 50 and the brush 40 can be improved, and the brush spring 50 can stabilize the brush spring 50. A pressing load can be applied to the brush 40. Thereby, it is possible to further realize a long-life and high-quality electric motor 1.

In the electric motor 1, the brush holder 60 has a guide wall facing the side surface of the brush 40. The gap between the brush 40 and the guide wall of the brush holder 60 is 100 μm or more. Specifically, the brush holder 60 has a first side wall 61 and a second side wall 62 as guide walls. The gap between the first side wall 61 and the first side surface 41 of the brush 40 and the gap between the second side wall 62 and the second side surface 42 of the brush 40 are 100 μm or more.

In this embodiment, the arc-shaped brush 40 is manufactured without cutting. Therefore, the brush 40 can be manufactured at low cost. On the other hand, the brush 40 does not have high dimensional accuracy compared to a case where the brush 40 is machined. For this reason, for the arc-shaped brush 40 that has not been subjected to cutting, the gap between the brush 40 and the guide wall (first side wall 61, second side wall 62) of the brush storage portion 60a is not stable. For this reason, it is necessary to increase the gap between the brush 40 and the guide wall of the brush storage section 60a to some extent. Therefore, in this embodiment, the gap between the brush 40 and the guide wall (first side wall 61, second side wall 62) of the brush holder 60 is set to 100 μm or more. Thereby, even when using an arc-shaped brush 40 that has not been subjected to cutting, a margin can be provided in the gap between the brush 40 and the guide wall. Therefore, dimensional variations in the arc-shaped brush 40 can be sufficiently tolerated. In addition, from the viewpoint of allowing dimensional variations in the brush 40, it is more preferable that the gap between the brush 40 and the guide wall (first side wall 61, second side wall 62) of the brush holder 60 is 200 μm or more.

(Modified example)
The electric motor 1 according to the present disclosure has been described above based on the embodiments. However, the present disclosure is not limited to the above embodiments.

In the embodiment described above, the guide wall of the brush holder 60 is provided so as to face both the first side surface 41 on the outer peripheral side and the second side surface 42 on the inner peripheral side of the brush 40. However, it is not limited to this. Specifically, in the above embodiment, the brush holder 60 has a first side wall 61 facing the entire first side surface 41 on the outer circumferential side of the brush 40 and a second side wall 61 on the inner circumferential side of the brush 40 as guide walls. It has a second side wall 62 facing the entire surface of the side surface 42. However, it is not limited to this. For example, the guide wall of the brush holder 60 that holds the brush 40 may be provided so as to face only one of the first side surface 41 and the second side surface 42 of the brush 40. In this case, the other of the first side surface 41 and the second side surface 42 of the brush 40 is open.

Specifically, it can be configured as the electric motor 1A shown in FIGS. 11 and 12. FIG. 11 is a perspective view of the electric motor 1A according to Modification Example 1 when viewed from the back side. FIG. 12 is a rear view of the electric motor 1A according to the first modification. In the electric motor 1A, the brush holder 60A that holds the brush 40 has only the second side wall 62 that faces the entire second side surface 42 of the brush 40 as a guide wall that guides the brush 40. That is, the brush holder 60A does not have a guide wall that faces the entire first side surface 41 of the brush 40. Therefore, the outer first side surface 41 of the brush 40 is open. The brush holder 60A is not a guide wall that guides the brush 40. The brush holder 60A has a first side wall 61A in which a fixing portion 60b for fixing the brush spring 50 is formed. That is, the brush accommodating portion 60aA of the brush holder 60A is configured by a first side wall 61A in which a fixing portion 60b is formed, and a long arc-shaped second side wall 62 that is a guide wall. The tip of the wire pulled out from the spiral portion 51 of the brush spring 50 is fixed to the fixing portion 60b formed on the first side wall 61A. The first side wall 61A has the sole function of fixing the brush spring 50. The fixing portion 60b is located on the front end surface side of the brush 40. Specifically, the fixing portion 60b is located on the front end surface side of the first side surface 41 of the first side surface 41 on the outer peripheral side and the second side surface 42 on the inner peripheral side of the brush 40.

As described above, according to the electric motor 1A, of the first side surface 41 and the second side surface 42 of the brush 40, the first side surface 41 on the wire rod side (outside in this modification example) pulled out from the spiral portion 51 of the brush spring 50 There is no guide wall to face. As a result, even if an arcuate brush 40 with varying dimensions is used, which is manufactured without cutting, there is no need to provide a margin in the gap between the first side surface 41 of the brush 40 and the guide wall. Therefore, the brush 40 can be stored in the brush storage portion 60aA with high precision.

In the electric motor 1A, there is no guide wall that faces the first side surface 41 of the brush 40 on the brush spring 50 side (outside). However, the electric motor 1A functions without any problem. In other words, the brush 40 slides in the brush storage section 60aA. In this way, by eliminating the guide wall on the brush spring 50 side, the structure of the brush holder 60A can be simplified. Therefore, it is possible to realize the electric motor 1A at even lower cost. Furthermore, since there is no guide wall facing the entire first side surface 41 of the brush 40, it is possible to prevent abrasion powder of the brush 40 from entering between the first side surface 41 of the brush 40 and the guide wall. Thereby, it is possible to suppress the sliding property between the brush spring 50 and the brush 40 from decreasing due to wear powder of the brush 40. Therefore, the quality of the electric motor 1A can be stabilized.

In the electric motor 1 according to the embodiment described above, the brush spring 50 is arranged so as to be in contact with the first side surface 41 on the outer peripheral side of the brush 40. However, it is not limited to this. FIG. 13 is a diagram showing the relationship between the brush 40 and the brush spring 50 in the electric motor 1B according to the second modification. For example, as in the electric motor 1B shown in FIG. 13, the brush spring 50 may be arranged so as to be in contact with the second side surface 42 on the inner peripheral side of the brush 40. That is, the band-shaped wire pulled out from the spiral portion 51 of the brush spring 50 may extend so as to come into contact with the second side surface 42 of the brush 40.

In the electric motor 1 according to the embodiment described above, the pigtail wire and the power terminal connected to the brush 40 are arranged at arbitrary positions on the brush holder 60. However, as in the electric motor 1C shown in FIGS. 14 and 15, the pigtail wire 90 and the power terminal 100 may be arranged inside the arc-shaped brush 40. FIG. 14 is a perspective view showing the positional relationship between a pair of brushes 40, a pair of brush springs 50, and a commutator 30 in an electric motor 1C according to modification 3. FIG. 15 is a top view showing the positional relationship between one brush 40, one brush spring 50, and commutator 30 in FIG.

The pigtail wire 90 is a conductive wire for electrically connecting the brush 40 and the power terminal 100. A first end 90a, which is one end of the pigtail wire 90, is connected to the brush 40. A second end 90b, which is the other end of the pigtail wire 90, is electrically connected to the power terminal 100. Specifically, the first end 90a of the pigtail wire 90 is fixed to a stepped surface formed at the rear end of the brush 40, which is lowered by one step. The second end 90b of the pigtail wire 90 and the power terminal 100 are joined by welding, soldering, or the like. The power supply terminal 100 is formed to have a substantially U-shaped cross section so as to have a pair of legs. The power terminal 100 is fixed to the brush holder 60 by press-fitting a pair of legs of the power terminal 100 into a pair of through holes provided in the brush holder 60.

As shown in FIGS. 14 and 15, the power terminal 100 is located between the second side surface 42 of the arc-shaped brush 40 and the commutator 30. The power terminal 100 is arranged at the center of the area surrounded by the brush 40. Specifically, when viewed from above, at least a portion of the power supply terminal 100 overlaps with the center of a circle forming an arc of the brush 40, which has an arc shape when viewed from above. A power terminal 100 is arranged inside the brush 40. Therefore, the joint portion between the power terminal 100 and the pigtail wire 90 is also arranged inside the brush 40. With this configuration, the length of the pigtail wire 90 can be shortened. Therefore, even if the pigtail wire 90 moves as the brush 40 wears, it is possible to prevent the pigtail wire 90 from interfering with the uneven structure of the brush holder 60 and reducing the load stability of the brush 40.

In the electric motor 1 in the first embodiment described above, two brushes 40 are arranged. However, it is not limited to this. FIG. 16 is a diagram for explaining the arrangement of brushes 40 in electric motor 1D according to modification 4. For example, like the electric motor 1D shown in FIG. 16, four arc-shaped brushes 40 may be arranged. When a torsion spring is used as the brush spring, it is difficult to arrange four arc-shaped brushes due to space issues unless the external size of the electric motor is increased. However, as shown in FIGS. 14 and 15, by using a constant force spring as the brush spring 50 and arranging the power terminal 100 inside the arc-shaped brush 40, as shown in FIG. Four arc-shaped brushes 40 can be arranged without increasing the size. In other words, it is possible to effectively utilize the space of the electric motor 1D and further extend its life. As an example, the four brushes 40 may be arranged at equal intervals (0°, 90°, 180°, 270°) in the rotation direction. Thereby, the space of the electric motor 1D can be utilized as effectively as possible. Moreover, when four brushes 40 are used, the electric motor 1D with the longest life can be realized. When using four brushes 40, the number of poles of the electric motor 1D can be 4n (n is an integer of 1 or more).

In the above embodiment, the electric motor 1 is a coreless motor in which the stator 10 and rotor 20 do not have a core. However, it is not limited to this. For example, the electric motor 1 may be an electric motor in which the stator 10 and the rotor 20 have cores.

In the above embodiment, the stator 10 is composed only of permanent magnets. However, it is not limited to this. For example, the stator 10 may be a stator composed of a permanent magnet and an iron core. The stator 10 may be an armature made of stator windings and an iron core without using permanent magnets.

In the above embodiment, the electric motor 1 is a flat motor with an external size and a thickness smaller than the outer diameter. However, it is not limited to this. The technology of the present disclosure can be applied to, for example, a compact electric motor having a cylindrical casing with an outer size larger in thickness than the outer diameter.

In the embodiment described above, the direction of the main magnetic flux generated by the stator 10 and the rotor 20 is in the direction of the axis C of the rotating shaft 21. However, it 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 axis C direction of the rotating shaft 21 (radial direction of rotation of the rotating shaft 21). For example, the technology of the present disclosure can also be applied to an inner rotor type motor in which the rotor 20 is arranged inside the stator 10.

In the above embodiment, the electric motor 1 is a vehicle motor used in a vehicle. However, it is not limited to this. The technology of the present disclosure can also be applied to motors used in various other electrical devices, such as motors used in electric blowers installed in vacuum cleaners and the like.

Other embodiments may be obtained by making various modifications to the above-described embodiments that those skilled in the art would think of, or by arbitrarily combining the components and functions of the embodiments without departing from the spirit of the disclosure. Forms are also included in this disclosure.

The technology of the present disclosure can be widely used in various products equipped with electric motors, including products in the field of electrical equipment such as automobiles and household electrical equipment.

1, 1A, 1B, 1C, 1D Electric motor 10 Stator 20 Rotor 21 Rotating shaft 21a First end 21b Second end 22 Coil 23 Mold resin 24 Cylindrical member 30 Commutator 31 Commutator piece 40 Brush 41 First side 42 Second side surface 43 Front end surface 44 Rear end surface 50 Brush spring 50a Outer end 50b Inner end 51 Spiral section 60, 60A Brush holder 60a, 60aA Brush storage section 60b Fixing section 61, 61A First side wall 62 Second side wall 63 Bottom wall 71 First bearing 72 Second bearing 81 First bracket 82 Second bracket 90 Pigtail wire 90a First end 90b Second end 100 Power terminal

Claims (12)

1. a rotating shaft whose axial direction is the direction in which the axial center extends;
   a commutator attached to the rotating shaft;
   a brush in contact with the commutator;
   a brush spring for pressing the brush against the commutator,
   The brush has an arc shape,
   The brush spring is a constant force spring.
   Electric motor.
2. If the center of the circle forming the arc of the brush is the center point, the angle between the line connecting the center point and the front end surface of the brush and the line connecting the center point and the rear end surface of the brush is 90°. That's all,
   The electric motor according to claim 1.
3. The constant force spring is arranged in contact with a side surface on the outer peripheral side of the brush.
   The electric motor according to claim 1 or 2.
4. In the axial direction of the rotating shaft, the height of the constant force spring is 1/3 or more and 2/3 or less of the height of the brush.
   The electric motor according to claim 1 or 2.
5. further comprising a brush holder that holds the brush,
   The brush holder has a guide wall that guides the brush,
   The gap between the brush and the guide wall is 100 μm or more,
   The electric motor according to claim 1 or 2.
6. further comprising a brush holder that holds the brush,
   The brush holder has a guide wall that guides the brush,
   The guide wall is provided so as to face only one side of the outer peripheral side and the inner peripheral side of the brush,
   The other of the outer circumferential side and inner circumferential side of the brush is open;
   The electric motor according to claim 1 or 2.
7. The constant force spring has a spiral portion in which a band-shaped wire is spirally wound,
   The brush holder has a fixing part located on the front end surface side of the brush, to which the tip of the wire pulled out from the spiral part is fixed,
   The fixing portion is located on the front end surface side of the other of the inner circumferential side surface and the outer circumferential side surface of the brush.
   The electric motor according to claim 6.
8. The fixing part is provided facing an outer peripheral side surface of the brush,
   The guide wall is provided facing an inner peripheral side surface of the brush.
   The electric motor according to claim 7.
9. A plurality of brushes are arranged.
   The electric motor according to claim 1 or 2.
10. The brushes are arranged in four pieces,
    The electric motor according to claim 9.
11. The number of poles of the electric motor is 4n (n is an integer of 1 or more)
    The electric motor according to claim 10.
12. Further comprising a brush holder that holds a plurality of the brushes, and a bracket separate from the brush holder,
    The brush holder is configured to be able to be attached to the bracket while holding a plurality of brushes.
    The electric motor according to claim 9.

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