Electric motor

Abstract

To provide an electric motor which can press a commutator with a stable load from an initial stage to a terminal stage of a brush even if an arc-like brush is used for the electric motor.SOLUTION: An electric motor 1 comprises: a rotating shaft 21; a commutator 30 attached to the rotating shaft 21; a brush 40 in contact with the commutator 30; and a brush spring 50 for pressing the brush 40 against the commutator 30. The brush 40 has an arc shape, and the brush spring 50 is a constant load spring.SELECTED DRAWING: Figure 5A

Description

[Technical Field]

[0001] The present disclosure relates to electric motors. [Background technology]

[0002] Electric motors are widely used in a wide range of applications, including household electrical appliances such as electric vacuum cleaners, as well as in electrical equipment for automobiles, etc. For example, electric motors are used to rotate rotary fans in electric blowers mounted on electric vacuum cleaners, and electric motors are also used to drive cooling fans for radiators and other components in two-wheeled and four-wheeled vehicles.

[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, brushes that slide against the commutator, a brush holder with a brush storage section that stores the brushes, and a brush spring that presses the brushes against the commutator.

[0004] Increasing the length of the brushes is one way to extend the life of the motor. However, simply lengthening a straight brush increases the diameter of the motor, resulting in a larger motor. Therefore, technology using arc-shaped brushes has been proposed to achieve both a longer life and a more compact motor (e.g., Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-149154 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-35272 Summary of the Invention [Problem to be solved by the invention]

[0006] 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.

[0007] However, when a coil spring or torsion spring is used to press an arc-shaped brush, the difference between the pressure (initial pressure) before the brush wears and the pressure (final pressure) when the motor reaches the end of its life due to brush wear becomes large. In other words, the difference in the pressing load on the commutator between the initial and final stages of brush use becomes large. For this reason, even if the brush is made arc-shaped and the brush length is increased, it is difficult to maintain the optimal pressing load on the commutator, and the brush will not be able to achieve a sufficient lifespan.

[0008] Furthermore, if a torsion spring is used as the brush spring to apply a pressure load to the arc-shaped brush, the brush spring reduces the pressure load when the brush presses against the commutator. Furthermore, if a torsion spring is used to apply a pressure load to the arc-shaped brush, the brush may come into contact with the side wall of the brush housing portion in the brush holder. In other words, the pressure load from the brush spring may be applied to the contact point between the brush and the side wall of the brush housing portion.

[0009] In particular, when the arc-shaped brush is long, the pressing load from the brush spring is likely to be applied to the contact point between the side wall of the brush housing and the brush. When the brush comes into contact with the side wall of the brush housing, wear powder from the brush accumulates in the gap between the side wall of the brush housing and the brush, significantly reducing the smoothness of the brush in the brush housing.

[0010] As such, in conventional electric motors equipped with arc-shaped brushes, it was difficult to press the commutator with a stable load from the initial to final stages of the brush life, making it difficult to achieve the long life that would be expected from arc-shaped brushes.

[0011] The present disclosure has been made to solve such problems, and aims to provide an electric motor that can press the commutator with a stable load from the initial to final stages of the brush operation, even in a motor that uses arc-shaped brushes. [Means for solving the problem]

[0012] In order to achieve the above object, one aspect of the electric motor according to the present disclosure comprises a rotating shaft, a commutator attached to the rotating shaft, a brush in contact with the commutator, and a brush spring for pressing the brush against the commutator, wherein the brush is arc-shaped and the brush spring is a constant force spring. [Effects of the Invention]

[0013] According to the present disclosure, even in an electric motor using arc-shaped brushes, the brushes can press the commutator with a stable load from the initial stage to the final stage. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a perspective view of an electric motor according to an embodiment of the present invention, viewed obliquely from above; [Figure 2] 1 is an external perspective view of an electric motor according to an embodiment, as viewed obliquely from below; [Figure 3] 1 is a cross-sectional view of an electric motor according to an embodiment. [Figure 4] FIG. 1 is an exploded perspective view of an electric motor according to an embodiment. [Figure 5A] FIG. 2 is a rear view of the electric motor according to the embodiment. [Figure 5B] 3 is a diagram showing the relationship between a commutator, brushes, and brush springs in the electric motor according to the embodiment; FIG. [Figure 6] FIG. 2 is a perspective view showing a rotor, a brush, and a brush spring in the electric motor according to the embodiment. [Figure 7] 7 is a side view showing the brush and the brush spring when viewed from the direction of arrow A in FIG. 6. FIG. [Figure 8]FIG. 10 is a diagram showing how a brush slides due to wear. [Figure 9] FIG. 10 is a diagram illustrating the configuration of an electric motor of a comparative example. [Figure 10] 1 is a diagram illustrating a configuration of an electric motor according to an embodiment; [Figure 11] FIG. 10 is a perspective view of the electric motor according to the first modification when viewed from the rear side. [Figure 12] FIG. 10 is a rear view of the electric motor according to the first modification. [Figure 13] 10 is a diagram showing the relationship between the brushes and the brush springs in the electric motor according to the second modification. FIG. [Figure 14] FIG. 11 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 a third modification. [Figure 15] FIG. 15 is a top view showing the positional relationship between one brush, one brush spring, and the commutator in FIG. [Figure 16] FIG. 10 is a diagram for explaining the arrangement of brushes in an electric motor according to a fourth modification. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that 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.

[0016] Note that each figure is a schematic diagram and is not necessarily a precise illustration. Furthermore, in each figure, substantially the same configuration is assigned the same reference numeral, and duplicate explanations are omitted or simplified. Furthermore, in this specification, the terms "up" and "down" do not necessarily refer to the upward direction (vertically upward) and downward direction (vertically downward) in absolute spatial recognition.

[0017] (Embodiment) First, the overall configuration of electric motor 1 according to the embodiment will be described with reference to Figs. 1 to 5B. Fig. 1 is an external perspective view of electric motor 1 as seen obliquely from above, and Fig. 2 is an external perspective view of electric motor 1 as seen obliquely from below. Fig. 3 is a cross-sectional view of electric motor 1, and Fig. 4 is an exploded perspective view of electric motor 1. Fig. 5A is a rear view of electric motor 1. Fig. 5B is a diagram showing the relationship between commutator 30, brushes 40, and brush springs 50 in Fig. 5A.

[0018] As shown in FIGS. 1 to 5B, electric motor 1 includes stator 10 and rotor 20 that rotates due to the magnetic force of stator 10. Electric motor 1 in this embodiment is a brushed electric motor, and further includes commutator 30 attached to rotating shaft 21 of rotor 20, at least one brush 40 in contact with commutator 30, brush spring 50 for pressing brush 40 against commutator 30, and brush holder 60 for holding brush 40. Electric motor 1 further includes first bearing 71, second bearing 72, first bracket 81, and second bracket 82.

[0019] The electric motor 1 in this embodiment is a type of direct current motor (DC motor) driven by direct current, and uses a magnet as the stator 10 and an armature having coils 22 as the rotor 20. In this embodiment, the electric motor 1 is a flat-type (flat-type) brushed coreless motor (flat motor) mounted on a vehicle such as a two-wheeled or four-wheeled vehicle. Therefore, the stator 10 and the rotor 20 do not have a core (iron core), and the electric motor 1 has a thin and lightweight configuration overall. Specifically, the electric motor 1 in this embodiment is a small motor used in a cooling fan for a radiator in a vehicle. The electric motor 1 is driven by an input voltage of, for example, DC 12V.

[0020] Each component of the electric motor 1 will be described in detail below.

[0021] 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 between the stator 10 and the rotor 20, and forms a magnetic circuit together with the rotor 20, which is an armature. As shown in FIG. 4, the stator 10 is generally donut-shaped overall and is magnetized so that N poles and S poles are alternately and evenly present on the air gap surface between the stator 10 and the rotor 20 along the circumferential direction of the rotating shaft 21. The stator 10 is a field magnet that generates magnetic flux for generating torque. The stator 10 is formed, for example, of a permanent magnet. In this embodiment, the direction of the main magnetic flux generated by the stator 10 (magnet) is the extension direction of the rotating shaft 21. As shown in FIG. 3, the stator 10 is fixed to a first bracket 81.

[0022] 3, rotor 20 has a rotating shaft 21 and coils 22. Rotor 20 in this embodiment is a coreless rotor that does not have a core.

[0023] Rotor 20 rotates around axis C of rotating shaft 21. Rotor 20 generates a magnetic force that acts on stator 10. In this embodiment, the direction of the main magnetic flux generated by rotor 20 is the direction in which rotating shaft 21 extends.

[0024] Rotor 20 is disposed opposite stator 10. In this embodiment, rotor 20 faces stator 10 in the direction in which rotation axis 21 extends. Specifically, coils 22 included in rotor 20 and stator 10 face each other in the direction in which rotation axis 21 extends.

[0025] The rotating shaft 21 is a shaft having an axis C and is a long rod-shaped member. As an example, the rotating shaft 21 is a metal rod made of a metal material such as SUS. The axis C of the rotating shaft 21 is the center around which the rotor 20 rotates. The longitudinal direction of the rotating shaft 21, i.e., the direction in which the rotating shaft 21 extends, is the direction of the axis C (axial direction).

[0026] A first end 21a, which is one end of the rotating shaft 21, is supported by a first bearing 71. On the other hand, a 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.

[0027] In this embodiment, the first end 21a of the rotating shaft 21 is the output side end (output shaft) and protrudes from the first bracket 81 and the first bearing 71. A load such as a rotary fan is attached to the first end 21a. The second end 21b of the rotating shaft 21 is the counter-output side end (counter-output shaft) and does not protrude from the second bracket 82 and the second bearing 72.

[0028] The first bearing 71 is held by a 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.

[0029] 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 cold-rolled steel plate (SPC material) or a metal such as aluminum. The first bracket 81 and the second bracket 82 form a housing, and the stator 10 and the rotor 20 are arranged in this housing.

[0030] 1 to 3, in this embodiment, first bracket 81 is an outer shell member of electric motor 1, and is formed in a bottomed cylindrical shape having a bottom and a cylindrical sidewall. Stator 10 is fixed to the bottom of first bracket 81. Note that the material of first bracket 81 and second bracket 82 is not limited to metal material and may be resin material, but from the perspective of suppressing noise generated from electric motor 1, it is preferable that first bracket 81 and second bracket 82 be made of metal material.

[0031] As shown in FIG. 3, rotor 20 includes a rotating shaft 21, a plurality of coils 22, and a molding resin .

[0032] Each of the plurality of coils 22 is a wound coil. Specifically, each of the plurality of coils 22 is an armature winding made of electric wire, and is wound so as to generate a magnetic force acting on the stator 10 when a current flows through it. In this embodiment, the direction of the main magnetic flux generated by each coil 22 is along the axis C along which the rotating shaft 21 extends. Specifically, each of the plurality of coils 22 is wound in a flat shape, and is disposed with the coil surface facing in the direction along the axis C along which the rotating shaft 21 extends.

[0033] 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. In this embodiment, 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 layer or multiple 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 in a ring shape surrounding the rotating shaft 21 when viewed from the direction of the axis C along which the rotating shaft 21 extends.

[0034] 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.

[0035] The multiple coils 22 are covered with the molded resin 23 and are molded integrally with the molded resin 23. In other words, the multiple coils 22 are resin-molded. Therefore, as shown in FIG. 4, the external shape of the molded resin 23 after the multiple coils 22 are molded is circular in a plan view. The molded resin 23 may be made of an insulating resin material such as phenolic resin or unsaturated polyester (BMC). The molded resin 23 may be made of either a thermosetting resin or a thermoplastic resin. The molded resin 23 is fixed to the rotating shaft 21 via a cylindrical member 24.

[0036] As described above, the electric motor 1 in this embodiment is a coreless motor in which the rotor 20 does not have a core, and the multiple coils 22 of the rotor 20 are thin and molded from resin. This makes it possible to realize a thin electric motor 1 with low inductance.

[0037] 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.

[0038] 4 and 5B, 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. Each commutator bar 31 is formed so as to have steps on its surface.

[0039] Each of the plurality of commutator segments 31 is a conductive terminal made of a metal material such as copper, and is electrically connected to the coil 22 of the rotor 20. The plurality of commutator segments 31 are arranged insulated and separated from one another, but are electrically connected by the coil 22 of the rotor 20.

[0040] In this embodiment, the commutator 30 is a molded commutator, and is configured such that a plurality of commutator segments 31 are molded with resin. In this case, the plurality of commutator segments 31 are embedded in resin so that their surfaces are exposed. The plurality of commutator segments 31 are fixed to the rotating shaft 21 by fixing the resin that molds the plurality of commutator segments 31 to the rotating shaft 21. Note that the molded resin that covers the plurality of commutator segments 31 and the molded resin 23 that covers the coil 22 are separate bodies made of different resin materials, but this is not a limitation. In other words, the molded resin that covers the plurality of commutator segments 31 and the molded resin 23 that covers the coil 22 may be integrated.

[0041] At least one brush 40 is in contact with the commutator 30. Specifically, the tip of the brush 40 is in contact with the commutator segments 31 of the commutator 30. In this embodiment, the brush 40 is in contact with the commutator segments 31 in a direction (radial direction) perpendicular to the direction of the axis C of the rotating shaft 21. As the commutator 30 rotates with the rotation of the rotating shaft 21, the brush 40 continues to come into contact with all the commutator segments 31 in sequence.

[0042] The brush 40 is a power supply brush for supplying power to the coil 22. Specifically, the brush 40 contacts the commutator segments 31 of the commutator 30, and an armature current supplied to the brush 40 via a power supply terminal (not shown) fixed to the brush holder 60 flows to the coil 22 via the commutator segments 31. The brush 40 and the power supply terminal are connected by a pigtail wire (not shown). Specifically, one end of the pigtail wire is connected to the brush 40, and the other end of the pigtail wire is connected to the power supply terminal. Note that 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 supply is a power supply that exists outside the electric motor 1 and supplies a predetermined input voltage to the electric motor 1. In this embodiment, the external power supply is a DC power supply that supplies an input voltage of DC 12 V to the electric motor 1.

[0043] 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 a metal such as copper. This reduces the contact resistance between the brush 40 and the commutator segments 31. As an example, the brush 40 is a sintered brush made of a sintered body. In this case, the sintered brush 40 can be produced by, for example, placing a mixture of graphite powder, copper powder, binder resin, and hardener in a mold, compression-molding the mixture, and sintering the mixture. In addition, in this embodiment, the brush 40 is produced without cutting. In other words, the brush 40 is produced by placing a powder of graphite powder and copper powder in a mold, compression-molding the mixture, and sintering the mixture, without cutting the mixture.

[0044] 5A and 5B, the brush 40 is arc-shaped. Specifically, the cross-sectional shape of the brush 40 is substantially rectangular, and the shape in top view is arc-shaped. In this embodiment, the width of the brush 40 is constant when viewed from above. Note that the shape of the arc-shaped brush 40 in top view does not have to be strictly arc-shaped, as long as it is roughly arc-shaped.

[0045] The brush 40 has a pair of opposing side surfaces, a first side surface 41 and a second side surface 42. The first side surface 41 is a side surface on the outer periphery of the arc constituting the brush 40, and the second side surface 42 is a side surface on the inner periphery of the arc constituting the brush 40.

[0046] In this embodiment, since the width of the brush 40 is constant, the curvature of the arc of the first side surface 41 on the outer periphery is smaller than the curvature of the arc of the second side surface 42 on the inner periphery. The first side surface 41 and the second side surface 42 are cylindrical surfaces. Therefore, the circle forming the arc of the first side surface 41 has a single center point. Similarly, the circle forming the arc of the second side surface 42 also has a single center point. Furthermore, 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 are the same. In other words, 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 do not have to be the same.

[0047] The brush 40 has a front end face 43 that is a surface that contacts the commutator 30, and a rear end face 44 that is a surface opposite to the front end face 43. The front end face 43 is an end face at the front end, which is one end in the longitudinal direction of the brush 40. The rear end face 44 is an end face at the rear end, which is the other end in the longitudinal direction of the brush 40. The front end face 43 is a sliding contact surface that comes into sliding contact with the commutator segments 31 of the commutator 30. The rear end face 44 is a surface that contacts the spiral portion 51 of the brush spring 50. The front end face 43 and the rear end face 44 are flat surfaces that are approximately rectangular.

[0048] In this embodiment, a plurality of brushes 40 are provided. In this case, it is preferable that the plurality of brushes 40 are provided at equal intervals along the rotation direction of the rotor 20. Specifically, two brushes 40 are provided. The two brushes 40 are arranged opposite each other with the commutator 30 in between. In other words, the two brushes 40 are arranged at 180° intervals along the rotation direction of the rotor 20. Specifically, the front end face 43 of one brush 40 and the front end face 43 of the other brush 40 face each other with the rotation shaft 21 in between.

[0049] Each of the two brushes 40 is elongated. As shown in FIG. 5B , in this embodiment, when the center of the circle forming the arc of each brush 40 is taken as the center point, the angle θ formed by the line connecting the center point to the front end surface 43 of the brush 40 and the line connecting the center point to the rear end surface 44 of the brush 40 is 90° or more (θ≧90°). That is, in each of the two brushes 40, the central angle of the arc of each brush 40 is 90° or more. Specifically, in each of the two brushes 40, the first side surface 41 and the second side surface 42 both have central angles of 90° or more. Note that the two brushes 40 have the same shape, but this is not limited to this.

[0050] The brush 40 receives a pressing force from the brush spring 50 and is constantly in contact with the commutator segments 31 of the commutator 30. Specifically, as shown in Figures 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 contacts the commutator segments 31. The brush 40 wears out due to continuous contact with the rotating commutator segments 31. In this way, the brush 40 is in sliding contact with the commutator 30 due to the pressing force from the brush spring 50, and becomes shorter due to wear with the commutator 30.

[0051] The brush springs 50 are provided in accordance with the number of brushes 40. In this embodiment, the electric motor 1 is provided with two brushes 40, and therefore, two brush springs 50 are also provided. The brushes 40 and the brush springs 50 are held by a brush holder 60.

[0052] The brush spring 50 applies a pressing force (spring pressure) to the brush 40 by its spring elasticity, urging the brush 40 toward the commutator 30. In this embodiment, the brush spring 50 is a constant-force spring. Therefore, the brush spring 50 applies a uniform load to the brush 40. In other words, the brush spring 50, which is a constant-force spring, applies a uniform pressing force to the brush 40 from the initial stage before the brush 40 is worn to the final stage when the brush 40 has worn and the electric motor 1 has reached the end of its life.

[0053] The brush spring 50, which is a constant force spring, is made of a strip-shaped wire material. In this embodiment, the brush spring 50, which is a constant force spring, is a spiral spring and has a spiral portion 51 (coil portion) in which the 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.

[0054] Specifically, the wire material constituting brush spring 50, which is a constant force spring, is a long, strip-shaped metal plate. Therefore, spiral portion 51 is a portion of the constant force spring in which the long, strip-shaped metal plate is wound in a spiral shape multiple times in only one direction. Brush spring 50, which is a constant force spring, generates a force (spring restoring force) that returns it to its original spiral shape by stretching one end of the wire material from spiral portion 51.

[0055] 5A and 5B, the brush spring 50 presses the brush 40 against the commutator 30 by 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 as the spiral portion 51 comes into contact with the rear end surface 44 of the brush 40.

[0056] Brush spring 50, which is a constant force spring, has an outer end 50a, which is one end of a strip-shaped metal plate, and an inner end 50b, which is the other end of the strip-shaped metal plate. Outer end 50a is one end of the strip-shaped metal plate pulled outward from the outermost periphery of spiral part 51, and inner end 50b is the other end of the strip-shaped metal plate located at the innermost periphery of spiral part 51.

[0057] The brush spring 50 presses the brush 40 against the commutator 30 with the spiral portion 51. Specifically, the spiral portion 51 of the brush spring 50 contacts the rear end surface 44 of the brush 40, and the spring restoring force of the spiral portion 51 applies a pressing load to the brush 40. In other words, the brush spring 50 applies a pressing force (spring pressure) to the brush 40 with the spiral portion 51. As a result, the brush 40 is urged toward the commutator 30.

[0058] As shown in Fig. 6, brush spring 50 is arranged so as to contact first side surface 41, which is the side surface on the outer periphery of brush 40. Specifically, a strip-shaped wire material (metal plate) drawn out from spiral portion 51 of brush spring 50 extends along first side surface 41 of brush 40. Therefore, the strip-shaped wire material drawn out from spiral portion 51 of brush spring 50 is curved in an arc shape, similar to brush 40. Note that Fig. 6 is a perspective view showing rotor 20, brush 40, and brush spring 50 in electric motor 1 according to the embodiment.

[0059] 7, if the height of brush 40 is H1 and the height of brush spring 50 is H2 in the direction of axis C of rotating shaft 21, then height H2 of brush spring 50 should be between 1 / 3 and 2 / 3 of height H1 of brush 40 (1 / 3≦H2 / H1≦2 / 3). Height H2 of brush spring 50 is the width of the strip-shaped wire material (metal plate) that constitutes brush spring 50. Note that FIG. 7 is a side view showing brush 40 and brush spring 50 as viewed from the direction of arrow A in FIG. 6.

[0060] As shown in Figures 3 and 5A, the brush 40 is held by the brush holder 60. As shown in Figures 2 and 3, the brush holder 60 is also an outer shell member that constitutes the outer shell of the electric motor 1, and covers the second bracket 82 from the outside. In this embodiment, the brush holder 60 and the second bracket 82 are separate bodies. Therefore, even when multiple brushes 40 are arranged in the brush holder 60, the brushes 40 can be attached to the second bracket 82 while being held by the brush holder 60. This makes it possible to easily set multiple brushes 40 in the brush holder 60, even when multiple arc-shaped brushes 40 are used.

[0061] The brush holder 60 is made of, for example, an insulating resin material. In this embodiment, the brush holder 60 is a resin molded product formed by integral molding using a resin material. As an example, the resin material constituting the brush holder 60 is phenolic resin, but is not limited to this.

[0062] As shown in Figures 3 to 5A, the brush holder 60 has a brush storage section 60a, which is a spatial region in which the brush 40 is stored. As shown in Figure 3, the brush storage section 60a is a recessed portion formed in a concave shape. Also, as shown in Figure 5A, the brush storage section 60a is formed in an elongated shape that follows the shape of the brush 40. In other words, the brush storage section 60a is curved in an arc shape. The front and rear portions of the brush storage section 60a are open.

[0063] As shown in FIGS. 5A and 5B, the brush storage section 60a stores the brush 40 and the brush spring 50. Therefore, the longitudinal length of the brush storage section 60a is longer than the length of the brush 40. Specifically, the brush spring 50 is disposed in the brush storage section 60a so that the spiral portion 51 is located rearward of the rear end of the brush 40. In this case, the strip-shaped wire material (metal plate) constituting the brush spring 50 is drawn from the spiral portion 51 toward the commutator 30 along the arc shape of the brush storage section 60a. Specifically, the strip-shaped wire material constituting the brush spring 50 is drawn from the spiral portion 51 along the first side surface 41 of the brush 40.

[0064] The outer end 50a of the strip-shaped wire pulled out from the spiral portion 51 of the brush spring 50 is fixed to a fixing portion 60b formed near the opening in the front portion of the brush storage portion 60a in the brush holder 60. In this embodiment, the fixing portion 60b to which the outer end 50a of the brush spring 50 is fixed is a locking hole. In this case, the outer end 50a of the brush spring 50 is fixed to the fixing portion 60b by locking a V-shaped bent portion formed on the outer end 50a of the brush spring 50 into the fixing portion 60b (locking hole).

[0065] The brush storage sections 60a are formed according to the number of brushes 40. In this embodiment, since there are two brushes 40, two brush storage sections 60a are formed in the brush holder 60. Each of the two brush storage sections 60a is elongated in the direction in which the brushes 40 extend, and has a rectangular concave cross-sectional shape.

[0066] As shown in Figure 4, the brush storage section 60a has a first side wall 61 facing the first side surface 41 of the brush 40, a second side wall 62 facing the second side surface 42 of the brush 40, and a bottom wall 63 supporting the bottom surface of the brush 40.

[0067] 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, similar to the arc-shaped brush 40. In this embodiment, a fixing portion 60b (locking hole) to which the outer end portion 50a of the brush spring 50 is fixed is formed at the end portion of the first side wall 61 on the commutator 30 side.

[0068] The first side wall 61 has an arc-shaped side wall surface facing the first side surface 41, which is the side surface on the outer periphery 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 arc-shaped side wall surface facing the second side surface 42, which is the side surface on the inner periphery 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.

[0069] In this embodiment, the distance between the first side wall 61 and the second side wall 62 is constant, so the curvature of the arc of the first side wall 61 on the outer periphery side is smaller than the curvature of the arc of the second side wall 62 on the inner periphery side. The side wall surfaces of the first side wall 61 and the second side wall 62 are cylindrical surfaces. Therefore, the circle forming the arc of the first side wall 61 has a single center point. Similarly, the circle forming the arc of the second side wall 62 also has a single center point. Furthermore, the center point of the circle forming the arc of the side wall surface of the first side wall 61 and the center point of the circle forming the arc of the side wall surface of the second side wall 62 are coincident. In other words, 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. In this embodiment, the arc-shaped circle of the side wall surface of the first side wall 61, the arc-shaped circle of the side wall surface of the second side wall 62, the arc-shaped circle of the first side surface 41, and the arc-shaped circle of the second side surface 42 are concentric circles. Note that the center point of the arc-shaped circle of the first side wall 61 and the center point of the arc-shaped circle of the second side wall 62 do not have to coincide with each other.

[0070] A gap (clearance) exists between the first side wall 61 and the first side surface 41 of the brush 40. In the present embodiment, a strip-shaped wire drawn out from the spiral portion 51 of the brush spring 50 contacts the first side surface 41 of the brush 40, and a gap exists between the wire of the brush spring 50 and the first side wall 61. A gap also 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.

[0071] In the electric motor 1 configured as described above, the current (drive current) supplied to the brushes 40 flows through the coils 22 via the commutator segments 31 of the commutator 30. This generates magnetic flux in the rotor 20 (coils 22). The magnetic flux generated in the rotor 20 interacts with the magnetic flux generated from the stator 10, generating a magnetic force that serves as torque to rotate the rotor 20. At this time, the direction of the current flow is switched depending on the positional relationship between the commutator segments 31 of the commutator 30 and the brushes 40 when they 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, causing the rotor 20 to rotate around the rotation axis 21.

[0072] As the rotor 20 rotates, as shown in FIG. 8, the brush 40 housed in the brush housing portion 60a of the brush holder 60 is pressed against the commutator 30 by the brush spring 50, and the front end portion thereof is worn away by friction with the commutator segments 31 of the commutator 30. In other words, the brush 40 shortens due to wear. As a result, the rear end surface 44 of the brush 40 moves toward the commutator 30 within the brush housing portion 60a. At this time, the wire constituting the brush spring 50, which is a constant force spring, is wound up into a spiral portion 51 as the brush 40 shortens due to wear. In other words, the spiral portion 51 approaches the outer end portion 50a.

[0073] In this way, as the front end of the brush 40 wears, the brush 40 slides within the brush housing portion 60a toward the commutator 30. In the present embodiment, the brush housing portion 60a is formed by the first side wall 61 and the second side wall 62, and the brush 40 moves between the first side wall 61 and the second side wall 62 while being guided by the first side wall 61 and the second side wall 62. In other words, the first side wall 61 and the second side wall 62 function as guide walls that guide the brush 40.

[0074] 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 between the first side wall 61 and the second side wall 62 toward the commutator 30. Specifically, the spiral portion 51 of the brush spring 50 moves between the first side wall 61 and the second side wall 62 while being guided by the first side wall 61 and the second side wall 62. In this way, the first side wall 61 and the second side wall 62 also function as guide walls that guide the spiral portion 51 of the brush spring 50.

[0075] Next, the effects of the electric motor 1 according to the present embodiment will be described in comparison with an electric motor 1X of a comparative example with reference to Figures 9 and 10. Figure 9 is a diagram showing the configuration of the electric motor 1X of the comparative example. Figure 10 is a diagram showing the configuration of the electric motor 1 according to the embodiment.

[0076] 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 pressure 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 segments 31 of the commutator 30.

[0077] However, when the brush 40 is pressed by the brush spring 50X, which is a torsion spring, there is a large difference between the pressing force (initial pressure) before the brush 40 wears and the pressing force (final pressure) when the motor 1X reaches the end of its life due to wear of the brush 40. In other words, there is a large difference in pressing load on the commutator 30 between the initial and final stages of the brush 40.

[0078] Furthermore, when the torsion spring presses the arc-shaped brush 40, the pressing load of the brush spring 50X presses the arc-shaped brush 40 outward, as shown by the black arrow in Fig. 9. As a result, the pressing load when the brush 40 presses the commutator 30 by the brush spring 50X is reduced.

[0079] Furthermore, the pressing load of the brush spring 50X may cause contact between the brush storage section 60a and the brush 40. 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 first side surface 41 of the brush 40 may come into contact with the inner surface of the first side wall 61, which is located on the outer side, of the first side wall 61 and the second side wall 62 of the brush storage section 60a.

[0080] In particular, as shown in Figure 9, when the arc-shaped brush 40 is long (for example, when the angle between the line connecting the center point of the circle forming the arc of the brush 40 to the front end surface 43 of the brush 40 and the line connecting the center point of the circle forming the arc of the brush 40 to the rear end surface 44 of the brush 40 is 90° or more), the pressing load of the brush spring 50X makes it easier for the brush 40 to come into contact with the first side wall 61.

[0081] When the first side wall 61 and the brush 40 come into contact in this way, the slipperiness of the brush 40 in the brush storage section 60a is significantly reduced when wear powder from the brush 40 accumulates in the gap between the first side wall 61 and the brush 40. Furthermore, if the slipperiness of the brush 40 is reduced and the load pressing the brush 40 against the commutator 30 is lost, the electric motor 1X may stop.

[0082] On the other hand, it is possible to increase the gap between the first side wall 61 and the brush 40 so that the first side wall 61 and the brush 40 do not come into contact even when the arc-shaped brush 40 is pressed outward by the pressure load of the brush spring 50X. However, if the gap between the first side wall 61 and the brush 40 is increased, the brush 40 becomes more likely to vibrate when the rotor 20 rotates, which ultimately reduces the lifespan of the electric motor 1X.

[0083] In particular, since arc-shaped brush 40 is difficult to machine and therefore difficult to manufacture with high dimensional accuracy, when arc-shaped brush 40 is used, the gap between first side wall 61 and brush 40 tends to become unstable and large. As a result, brush 40 tends to vibrate when rotor 20 rotates, shortening the life of electric motor 1X.

[0084] 10, in the electric motor 1 of this 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, the brush spring 50 can apply a constant pressure load to the brush 40. This makes it possible to reduce the difference between the pressure (initial pressure) before the brush 40 wears and the pressure (final pressure) when the electric motor 1 reaches the end of its life due to wear of the brush 40.

[0085] Furthermore, when a constant force spring is used as the brush spring 50, as in this embodiment, the brush spring 50 is arranged so that the strip-shaped wire pulled out from the spiral portion 51 contacts the arc-shaped side surface of the brush 40. As a result, the brush 40 receives the pressing load from the brush spring 50 not only at the rear end surface 44 where the spiral portion 51 contacts, but also at the contact point between the strip-shaped wire pulled out from the spiral portion 51 and the arc-shaped side surface of the brush 40. 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 in FIG. 9.

[0086] In particular, in the electric motor 1 according to this embodiment, the brush spring 50 is arranged so that the strip-shaped wire material (metal plate) constituting the brush spring 50 contacts the first side surface 41 on the outer periphery of the brush 40. As a result, as shown by the black arrow in FIG. 10 , a pressing load is generated in the direction from the contact point between the strip-shaped wire material of the brush spring 50 and the arc-shaped first side surface 41 of the brush 40 toward the commutator 30. Therefore, even with the arc-shaped brush 40, a stable pressing load can be applied from the brush 40 to the commutator 30. In other words, a stable pressing force by the brush 40 can be achieved.

[0087] Furthermore, because the strip-shaped wire material drawn out from the spiral portion 51 of the brush spring 50 and the arc-shaped first side surface 41 of the brush 40 are in close contact with each other, wear powder from the brush 40 cannot get in between the strip-shaped wire material of the brush spring 50 and the first side surface 41 of the brush 40. As a result, even when the brush spring 50 is used, wear powder from the brush 40 does not reduce the sliding properties between the brush spring 50 and the brush 40.

[0088] As described above, with the electric motor 1 according to this embodiment, even if arc-shaped brushes 40 are used, the brushes 40 can press the commutator 30 with a stable load from the beginning to the end of their life. This makes it possible to realize an electric motor 1 with a long life and high quality.

[0089] Furthermore, in this embodiment, the arc-shaped brush 40 is manufactured without cutting. To manufacture the arc-shaped brush 40 with high dimensional accuracy, a sintered body obtained by compressing and sintering powder is subjected to cutting, but it is difficult to perform cutting on an arc-shaped sintered body. For this reason, manufacturing an arc-shaped brush 40 with high dimensional accuracy requires high manufacturing costs. Therefore, in this embodiment, the arc-shaped brush 40 is manufactured without cutting. This allows the brush 40 to be manufactured at low cost, thereby realizing a low-cost electric motor 1.

[0090] Furthermore, electric motor 1 in this embodiment uses long, arc-shaped brush 40. Specifically, similar to the embodiment shown in Fig. 5B, the angle θ formed by the line connecting the center point of the circle forming the arc of brush 40 to front end surface 43 of brush 40 and the line connecting the center point of the circle forming the arc of brush 40 to rear end surface 44 of brush 40 is 90° or more (θ≧90°).

[0091] If a torsion spring is used as the brush spring 50X for such a long, arc-shaped brush 40, as in the comparative electric motor 1X shown in Fig. 9, the pressing load on the brush 40 by the brush spring 50X may become unstable, resulting in a risk of reduced lifespan and quality. 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. 10, the pressing load on the brush 40 can be stabilized even when a long, arc-shaped brush 40 is used. Therefore, a long-life, high-quality electric motor 1 can be realized.

[0092] Furthermore, in the electric motor 1 according to this embodiment, as shown in FIG. 7, the height H2 of the brush spring 50, which is a constant force spring, is greater than or equal to 1 / 3 and less than or equal to 2 / 3 of the height H1 of the brush 40 in the direction of the axis C of the rotating shaft 21.

[0093] The strip-shaped wire pulled out from the spiral portion 51 of the brush spring 50 contacts the first side surface 41 of the brush 40. Therefore, the lower the height H2 of the brush spring 50 (i.e., the smaller the plate width of the strip-shaped wire), the smaller the contact area between the wire of the brush spring 50 and the first side surface 41 of the brush 40. Therefore, by making the height H2 of the brush spring 50 equal to or less than two-thirds of the height H1 of the brush 40, it is possible to improve the sliding properties between the brush spring 50 and the brush 40 when the wire constituting the brush spring 50 is wound into the spiral portion 51 as the brush 40 becomes shorter. Meanwhile, the rear end surface 44 of the brush 40 is pressed 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, allowing the brush spring 50 to stably apply a pressing load to the brush 40. In this way, by setting the height H2 of the brush spring 50 to be between 1 / 3 and 2 / 3 of the height H1 of the brush 40, the sliding property between the brush spring 50 and the brush 40 is improved, and the brush spring 50 can apply a stable pressing load to the brush 40. This further increases the life span and makes it possible to realize a high-quality electric motor 1.

[0094] Furthermore, in the electric motor 1 according to this embodiment, the brush holder 60 has a guide wall facing the side of the brush 40, and 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, and 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.

[0095] In this embodiment, the arc-shaped brush 40 is manufactured without cutting. This allows the brush 40 to be manufactured at low cost, but the dimensional accuracy of the brush 40 is not as high as when the brush 40 is machined. Therefore, for the arc-shaped brush 40 that has not been machined, the gap between the brush 40 and the guide walls (first side wall 61, second side wall 62) of the brush storage compartment 60a is unstable, so the gap between the brush 40 and the guide walls of the brush storage compartment 60a must be made relatively large. Therefore, in this embodiment, the gap between the brush 40 and the guide walls (first side wall 61, second side wall 62) of the brush holder 60 is set to 100 μm or more. This allows for a margin in the gap between the brush 40 and the guide walls, even when using an arc-shaped brush 40 that has not been machined, and therefore allows for sufficient tolerance of dimensional variations in the arc-shaped brush 40. From the viewpoint of allowing for dimensional variations in the brush 40, it is more preferable that the gap between the brush 40 and the guide walls (first side wall 61, second side wall 62) of the brush holder 60 be 200 μm or more.

[0096] (Variation) 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.

[0097] In the above embodiment, the guide wall of the brush holder 60 is provided to face both the first side surface 41 on the outer periphery side of the brush 40 and the second side surface 42 on the inner periphery side of the brush 40, but this is not limited thereto. Specifically, in the above embodiment, the brush holder 60 has, as guide walls, a first side wall 61 that faces the entire surface of the first side surface 41 on the outer periphery side of the brush 40 and a second side wall 62 that faces the entire surface of the second side surface 42 on the inner periphery side of the brush 40, but this is not limited thereto. For example, the guide wall of the brush holder 60 that holds the brush 40 may be provided 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.

[0098] Specifically, the electric motor 1A can be configured as shown in FIGS. 11 and 12. In the electric motor 1A, a brush holder 60A that holds the brush 40 has only a 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. In other words, the brush holder 60A does not have a guide wall that faces the entire first side surface 41 of the brush 40. Therefore, the first side surface 41 on the outside of the brush 40 is open. Note that the brush holder 60A does not have a guide wall that guides the brush 40, but does have a first side wall 61A on which a fixing portion 60b for fixing the brush spring 50 is formed. In other words, in this modification, the brush storage portion 60aA of the brush holder 60A is formed by the first side wall 61A on which the fixing portion 60b is formed and the elongated arc-shaped second side wall 62 that serves as a guide wall. The tip of the wire drawn 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 brush 40, which has an outer peripheral first side surface 41 and an inner peripheral second side surface 42.

[0099] As described above, in the electric motor 1A according to this modified example, of the first side surface 41 and the second side surface 42 of the brush 40, there is no guide wall facing the first side surface 41 on the wire side (the outer side in this modified example) drawn out from the spiral portion 51 of the brush spring 50. As a result, even if an arc-shaped brush 40 having dimensional variations that is manufactured without cutting is used, 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, and the brush 40 can be stored accurately in the brush storage portion 60aA.

[0100] Furthermore, the electric motor 1A according to this modification does not have a guide wall facing the first side surface 41 of the brush 40 on the brush spring 50 side (outside), but the electric motor 1A still functions without any problems. That is, the brush 40 slides in the brush storage section 60aA. By eliminating the guide wall on the brush spring 50 side in this way, the structure of the brush holder 60A can be simplified. Therefore, an even lower-cost electric motor 1A can be realized. Moreover, since there is no guide wall facing the entire first side surface 41 of the brush 40, it is possible to prevent wear powder from the brush 40 from getting between the first side surface 41 of the brush 40 and the guide wall. This prevents wear powder from the brush 40 from reducing the sliding property between the brush spring 50 and the brush 40, thereby stabilizing the quality of the electric motor 1A.

[0101] Furthermore, in the electric motor 1 according to the above embodiment, the brush spring 50 is arranged so as to contact the first side surface 41 on the outer periphery side of the brush 40, but this is not limiting. For example, as in the electric motor 1B shown in FIG. 13, the brush spring 50 may be arranged so as to contact the second side surface 42 on the inner periphery side of the brush 40. In other words, the strip-shaped wire drawn out from the spiral portion 51 of the brush spring 50 may extend so as to contact the second side surface 42 of the brush 40.

[0102] In addition, in the electric motor 1 according to the above embodiment, the pigtail wire and power terminal connected to the brush 40 are arranged at any position on the brush holder 60, but as in the electric motor 1C shown in Figures 14 and 15, the pigtail wire 90 and power terminal 100 may be arranged inside the arc-shaped brush 40.

[0103] The pigtail wire 90 is a conductive wire for electrically connecting the brush 40 and the power terminal 100. One end, a first end 90a, is connected to the brush 40, and the other end, a second end 90b, 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. The second end 90b of the pigtail wire 90 and the power terminal 100 are joined by welding, soldering, or the like. The power terminal 100 is formed so as to have a pair of legs and a substantially U-shaped cross section. The power terminal 100 is fixed to the brush holder 60 by press-fitting the pair of legs of the power terminal 100 into a pair of through-holes provided in the brush holder 60.

[0104] 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. In this modification, the power terminal 100 is located in the center of the area surrounded by the brush 40. Specifically, in a top view, at least a portion of the power terminal 100 overlaps the center of the circle that constitutes the arc of the brush 40, whose top view shape is an arc. Because the power terminal 100 is located inside the brush 40, the joint between the power terminal 100 and the pigtail wire 90 is also located inside the brush 40. This configuration allows the length of the pigtail wire 90 to 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, etc., and thereby prevent a decrease in the load stability of the brush 40.

[0105] Furthermore, while the electric motor 1 in the first embodiment is provided with two brushes 40, this is not limiting. For example, as in the electric motor 1D shown in FIG. 16, four arc-shaped brushes 40 may be provided. When torsion springs are used as the brush springs, it is difficult to provide four arc-shaped brushes due to space limitations unless the external size of the electric motor is increased. However, as shown in FIGS. 14 and 15, by using constant-force springs as the brush springs 50 and positioning the power terminals 100 inside the arc-shaped brushes 40, as shown in FIG. 16, it is possible to provide four arc-shaped brushes 40 without increasing the external size of the electric motor 1D. In other words, the space in the electric motor 1D can be effectively utilized to further extend its lifespan. As an example, it is recommended that the four brushes 40 be arranged at equal intervals (0°, 90°, 180°, and 270°) in the rotational direction. This allows for maximum space utilization within the electric motor 1D, and the electric motor 1D with four brushes 40 can have the longest lifespan. When four brushes 40 are used, the number of poles of the electric motor 1D can be set to 4n (n is an integer equal to or greater than 1).

[0106] 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, but 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.

[0107] In the above embodiment, the stator 10 is composed of only permanent magnets, but 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.

[0108] 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, but this is not limiting. 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.

[0109] In addition, in the above embodiment, the direction of the main magnetic flux generated by the stator 10 and the rotor 20 is the direction of the axis C of the rotating shaft 21, but this is not limited to this. Specifically, the direction of the main magnetic flux generated by the stator 10 and the rotor 20 may be a direction perpendicular to the direction of the axis C of the rotating shaft 21 (the radial direction of the rotation of the rotating shaft 21). For example, the technology 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.

[0110] In the above embodiment, the electric motor 1 is a vehicle motor used in a vehicle, but 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 blowers mounted on electric vacuum cleaners.

[0111] In addition, this disclosure also includes forms obtained by making various modifications to the above embodiments that a person skilled in the art would think of, and forms realized by arbitrarily combining the components and functions in each embodiment within the scope of the present disclosure. [Industrial Applicability]

[0112] The technology disclosed herein can be widely used in a variety of products equipped with electric motors, including products in the electrical equipment field such as automobiles and the household electrical appliance field. [Explanation of symbols]

[0113] 1, 1A, 1B, 1C, 1D electric motor 10 Stator 20 rotor 21 Rotation axis 21a First end 21b Second end 22 coils 23 Molding resin 24 Cylindrical member 30 commutator 31 Commutator piece 40 brushes 41 First aspect 42 Second aspect 43 Front end surface 44 Rear end surface 50 Brush spring 50a outer end 50b Inner edge 51 Spiral part 60, 60A Brush Holder 60a, 60aA brush storage compartment 60b Fixed part 61, 61A 1st 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 1st end 90b 2nd end 100 Power terminal

Claims

1. a rotation axis whose axial direction is the direction in which the axis 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 is arc-shaped, The brush spring is a constant force spring. Electric motor.

2. When the center of the circle forming the arc of the brush is taken as the center point, the angle formed by the line connecting the center point to the front end surface of the brush and the line connecting the center point to the rear end surface of the brush is 90° or more.

2. The electric motor according to claim 1.

3. The constant force spring is disposed in contact with the outer peripheral side surface of the brush.

3. The electric motor according to claim 1 or 2.

4. a height of the constant force spring in the axial direction of the rotation shaft is equal to or greater than one-third and equal to or less than two-thirds of a height of the brush; 3. The electric motor according to claim 1 or 2.

5. a brush holder for holding 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.

3. The electric motor according to claim 1 or 2.

6. a brush holder for holding the brush; the brush holder has a guide wall that guides the brush, the guide wall is provided so as to face only one of the outer peripheral side surface and the inner peripheral side surface of the brush, The other of the outer peripheral side surface and the inner peripheral side surface of the brush is open.

3. The electric motor according to claim 1 or 2.

7. the constant force spring has a spiral portion in which a strip-shaped wire is wound in a spiral shape, the brush holder is located on a front end surface side of the brush and has a fixing portion to which a tip end of the wire drawn out from the spiral portion is fixed, the fixing portion is located on the front end surface side of the other of the inner peripheral side surface and the outer peripheral side surface of the brush, 7. The electric motor according to claim 6.

8. The fixing portion is provided facing the outer peripheral side surface of the brush, The guide wall is provided facing the inner peripheral side surface of the brush.

8. The electric motor according to claim 7.

9. The brushes are arranged in plurality.

3. The electric motor according to claim 1 or 2.

10. The brushes are arranged in four pieces.

10. The electric motor according to claim 9.

11. The number of poles of the motor is 4n (n is an integer equal to or greater than 1).

11. The electric motor according to claim 10.

12. The brush holder further includes a brush holder for holding a plurality of the brushes, and a bracket separate from the brush holder. The brush holder is configured to be attachable to the bracket while holding a plurality of the brushes.

10. The electric motor according to claim 9.

Images