Electric motors and electric blowers

Abstract

The present invention provides an electric motor, etc., that can stably support a rotating shaft with a single ball bearing in an electric motor having a coreless rotor. The electric motor comprises: a rotor having a rotating shaft and a coil extending in the axial direction; a commutator attached to the rotating shaft; at least one brush in sliding contact with the commutator; a brush spring for pressing at least one brush against the commutator; and one bearing that supports the rotating shaft. The bearing is a ball bearing, and the brush spring is a constant load spring.

Description

Technical Field

[0001] The present disclosure relates to an electric motor and an electric blower.

Background Art

[0002] Electric motors are widely used not only in the field of household electrical appliances, but also in the field of electrical equipment such as automobiles. For example, in vehicles such as two-wheeled motor vehicles or four-wheeled motor vehicles, electric motors are used for cooling fans that cool radiators, condensers, and the like.

[0003] In-vehicle electric motors used in vehicles are required to be reduced in size and thickness in order to be arranged in a limited space. However, in addition to this, high efficiency and weight reduction may be required in order to achieve low fuel consumption. For this reason, it has been proposed to use a flat brushed coreless motor having a bearing structure that cantilever-supports the rotating shaft of a coreless rotor without a core as an in-vehicle electric motor (see, for example, Patent Document 1 and Patent Document 2).

[0004] In a conventional electric motor having a bearing structure that cantilever-supports the rotating shaft (shaft) of a rotor, as disclosed in Patent Document 2, the rotating shaft is supported by one bearing. For this reason, sintered bearings are used as the bearing.

[0005] However, when a sintered bearing is used as the bearing, the sliding area between the bearing and the rotating shaft increases, which reduces efficiency, there is a risk of oil leakage at high temperatures, and insufficient starting torque occurs at low temperatures.

[0006] Therefore, one might consider using ball bearings instead of sintered bearings to support the rotating shaft with a single bearing. However, because ball bearings have a small sliding surface area with the rotating shaft, it is difficult to stably support the rotating shaft with them. In other words, it is difficult to simply replace sintered bearings with ball bearings and support the rotating shaft with a single ball bearing. For this reason, conventionally, when using ball bearings, it was necessary to use two ball bearings, such as supporting both ends of the rotating shaft with ball bearings or connecting two ball bearings together. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 61-49646 [Patent Document 2] Japanese Patent Publication No. 2014-36452 [Overview of the project]

[0008] This disclosure was made to solve these problems. The purpose of this disclosure is to provide an electric motor and an electric blower that have a coreless rotor and can stably support the rotating shaft with a single ball bearing.

[0009] To achieve the above objective, one embodiment of the electric motor according to the present disclosure comprises a rotor having a rotating shaft and coils extending in the axial direction, a commutator attached to the rotating shaft, at least one brush sliding against the commutator, a brush spring for pressing the at least one brush against the commutator, and a bearing supporting the rotating shaft, wherein the bearing is a ball bearing and the brush spring is a constant load spring.

[0010] Furthermore, the rotor is a coreless rotor that does not have a core. ru . The coil consists of multiple winding coils, each wound in a flattened shape. The multiple winding coils are arranged to surround the axis of rotation, with each coil surface facing the axial direction. The bearing is a deep groove ball bearing. The constant-load spring has a spiral section formed by winding a metal plate in a spiral shape. The constant-load spring is arranged such that the spiral axis of the spiral section is perpendicular to the axial direction. Furthermore, one embodiment of the electric motor according to this disclosure includes a magnet as the stator. The stator and the coils face each other in the axial direction.

[0011] One embodiment of the electric blower according to the present disclosure comprises the above-mentioned electric motor and a rotating fan attached to the rotating shaft of the electric motor, wherein the rotating fan is attached to the bearing and the end of the commutator on the bearing side of the rotating shaft.

[0012] According to this disclosure, even a single ball bearing can stably support a rotating shaft. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is an external perspective view of an electric motor according to an embodiment. [Figure 2] Figure 2 is a cross-sectional view (XZ cross-sectional view) of an electric motor according to an embodiment. [Figure 3] Figure 3 is a cross-sectional view (XY cross-sectional view) of an electric motor according to an embodiment. [Figure 4] Figure 4 is a partially enlarged cross-sectional view of an electric motor according to an embodiment. [Figure 5] Figure 5 shows the arrangement of the brush springs of an electric motor according to a modified example. [Figure 6] Figure 6 is a conceptual diagram of an electric blower according to an embodiment. [Modes for carrying out the invention]

[0014] The embodiments of this disclosure will be described below with reference to the drawings. The embodiments described below are all specific examples of this disclosure. Therefore, the numerical values, shapes, materials, components, arrangement positions of components, and connection configurations shown in the following embodiments are examples and are not intended to limit this disclosure. Accordingly, any components in the following embodiments that are not described in the independent claims representing the highest-level concepts of this disclosure will be described as optional components.

[0015] Also, in the present specification and the drawings, the X-axis, Y-axis and Z-axis represent the three axes of a three-dimensional orthogonal coordinate system. The X-axis and the Y-axis are axes orthogonal to each other, and both are axes orthogonal to the Z-axis. In the present embodiment, the Z-axis direction is the direction of the axis center C of the rotating shaft 21.

[0016] Note that each figure is a schematic diagram, and is not necessarily strictly illustrated. Also, in each figure, substantially the same configuration is denoted by the same reference numeral, and overlapping description is omitted or simplified. Also, in the present specification, the terms "upper" and "lower" do not necessarily refer to the upward direction (vertically upward) and downward direction (vertically downward) in absolute spatial perception, respectively.

[0017] (Embodiment) First, the configuration of the electric motor 1 according to the embodiment will be described with reference to FIGS. 1 to 4. FIG. 1 is an external perspective view of the electric motor 1 according to the embodiment. FIGS. 2 and 3 are cross-sectional views of the electric motor 1. FIG. 2 shows a cross-section (XZ cross-section passing through the brush 40) when cut along a plane passing through the axis center C of the rotating shaft 21 and passing through the brush 40. FIG. 3 shows a cross-section (XY cross-section passing through the brush 40) when cut along a plane where the axis center C of the rotating shaft 21 is a vertical line and passing through the brush 40. FIG. 4 is an enlarged cross-sectional view of a region IV surrounded by a broken line in FIG. 2. FIG. 6 is a conceptual diagram of the electric blower 90 according to the embodiment.

[0018] The electric blower 90 includes the electric motor 1 and a rotating fan 91. The rotating fan 91 is attached to the rotating shaft 21 of the electric motor 1. The rotating fan 91 is attached to an end on the bearing side among the bearing and the commutator on the rotating shaft 21.

[0019] The electric motor 1 is a commutator motor with brushes. The electric motor 1 comprises a stator 10, a rotor 20, a commutator 30, at least one brush 40, a brush spring 50, and a bearing 60. The rotor 20 is rotated by the magnetic force of the stator 10. The commutator 30 is attached to a rotating shaft 21 of the rotor 20. The brush 40 is in sliding contact with the commutator 30. The brush spring 50 is for pressing the brush 40 against the commutator 30. The bearing 60 supports the rotating shaft 21 of the rotor 20. In the following description, a pair of brushes 40 will be taken as an example for explanation.

[0020] The electric motor 1 further comprises a motor case 70 forming the outer casing of the electric motor 1, and a cover plate 80 covering the brushes 40. The motor case 70 has a first member 71, a second member 72, a third member 73, and a fourth member 74.

[0021] 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.

[0022] The electric motor 1 is a flat-type coreless motor with brushes that is mounted on vehicles such as two-wheeled motor vehicles or four-wheeled motor vehicles. Therefore, the stator 10 and the rotor 20 do not have a core, and the electric motor 1 has a thin and lightweight configuration as a whole. Specifically, the electric motor 1 is a small motor used for a radiator cooling fan in a vehicle. The outer diameter (diameter) of the electric motor 1 is φ120 mm or less. As an example, the outer diameter of the electric motor 1 is φ60 mm, φ70 mm, φ90 mm, or the like.

[0023] The stator 10 is positioned between it and the rotor 20 with a small air gap between them. The stator 10 generates a magnetic force that acts on the rotor 20. The stator 10 is configured to generate magnetic flux on the air gap surface with the rotor 20. The stator 10, together with the armature rotor 20, constitutes a magnetic circuit. Specifically, the stator 10 as a whole is essentially donut-shaped. The stator 10 is configured such that north poles and south poles are alternately and evenly distributed on the air gap surface with the rotor 20 along the circumferential direction of the rotating shaft 21. The stator 10 is a field magnet that creates magnetic flux for generating torque. The stator 10 is composed of multiple magnets. The magnets that make up the stator 10 are, for example, permanent magnets. The direction of the main magnetic flux generated by the stator 10 (magnets) is along the axis C direction in which the rotating shaft 21 extends. The stator 10 is fixed to the first member 71 of the motor case 70.

[0024] The rotor 20 has a rotating shaft 21 and a coil 22. The rotor 20 is a coreless rotor that does not have a core.

[0025] The rotor 20 rotates with the axis C, to which the rotation shaft 21 extends, as its center of rotation. The rotor 20 generates a magnetic force that acts on the stator 10. The direction of the main magnetic flux generated by the rotor 20 is along the axis C, to which the rotation shaft 21 extends.

[0026] The rotor 20 is positioned opposite the stator 10. The rotor 20 faces the stator 10 in the direction of the axis C along which the rotation shaft 21 extends. Specifically, the coils 22 of the rotor 20 and the stator 10 face each other in the direction of the axis C along which the rotation shaft 21 extends. In other words, the coils 22 and the stator 10 are aligned in the direction of the axis C along the rotation shaft 21.

[0027] The rotating shaft 21 is a shaft having an axis C. The rotating shaft 21 is a long, rod-shaped member. For example, the rotating shaft 21 is a metal rod made of a metal material such as SUS (Stainless Used Steel). The axis C contained within the rotating shaft 21 is 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 (extension direction), is the direction of the axis C (also simply called the "axis direction").

[0028] The rotating shaft 21 is supported by a single bearing 60. In other words, there is only one bearing 60 supporting the rotating shaft 21. The bearing 60 rotatably supports the rotating shaft 21. The bearing 60 is a ball bearing. Specifically, the bearing 60 is a deep groove ball bearing.

[0029] The first end 21a of the rotating shaft 21 is the output end (output shaft). The first end 21a protrudes from the first member 71 and the bearing 60 of the motor case 70. The first end 21a is the end of the rotating shaft 21 on the bearing 60 side of the commutator 30. A load such as a rotating fan can be attached to the first end 21a. An electric motor 1 with a rotating fan attached to the rotating shaft 21 can be used, for example, as a cooling fan. The second end 21b of the rotating shaft 21 is the non-output end (non-output shaft). The second end 21b does not protrude from the motor case 70.

[0030] The coils 22 of the rotor 20 are wound coils. The rotor 20 has multiple coils 22. The multiple coils 22 are armature windings made of electric wires. The multiple coils 22 are wound in such a way that they generate a magnetic force that acts on the stator 10 when current flows through them. The direction of the main magnetic flux generated by each coil 22 is in the direction of the axis C, from which the rotation shaft 21 extends. Specifically, the multiple coils 22 are wound in a flattened shape and are arranged so that their coil surfaces face the direction of the axis C, from which the rotation shaft 21 extends.

[0031] Each coil 22 is composed of an insulated wire having a core wire made of a metal such as copper or aluminum and an insulating film covering the core wire. Multiple coils 22 are thin wound coils having coil layers in which this insulated wire is wound in a planar manner. Specifically, multiple coils 22 are composed of, for example, one or more coil layers in which the insulated wire is wound in a substantially fan shape when viewed from a planar perspective. Multiple coils 22 configured in this way are arranged to surround the rotation axis 21 when viewed from the direction of the axis C from which the rotation axis 21 extends.

[0032] Multiple coils 22 are electrically connected to the commutator 30. Specifically, each of the multiple coils 22 is electrically connected to one of the multiple commutator segments 31 of the commutator 30. Therefore, current flows through each of the multiple coils 22 via the commutator segment 31 that the brush 40 is in contact with.

[0033] Multiple coils 22 are covered with molded resin 23. In other words, the multiple coils 22 are integrally molded together with the molded resin 23 by being covered with the molded resin 23. The plan view shape of the molded resin 23 after the multiple coils 22 have been molded is circular. The molded resin 23 is made of an insulating resin material such as phenolic resin or unsaturated polyester (Bulk Molding Compound, BMC). The molded resin 23 may be either a thermosetting resin or a thermoplastic resin.

[0034] The commutator 30 is attached to the rotating shaft 21. Therefore, the commutator 30 rotates together with the rotating shaft 21 as the rotor 20 rotates. The commutator 30 is attached to the second end 21b of the rotating shaft 21. The commutator 30 attached to the rotating shaft 21 may be part of the rotor 20.

[0035] The commutator 30 and the bearing 60 are located on opposite sides of the axis C in which the rotating shaft 21 extends, with reference to the position of the coil 22 on the rotating shaft 21. Since the rotor 20 does not have a core, the commutator 30 and the bearing 60 are located in close proximity. Furthermore, the bearing 60 is located in the central part of the rotating shaft 21, including the portion that protrudes from the motor case 70.

[0036] The commutator 30 has a plurality of commutator segments 31 arranged along the rotational direction of the rotating shaft 21. Specifically, the plurality of commutator segments 31 are arranged in a ring shape along the rotational direction of the rotating shaft 21 so as to surround the rotating shaft 21. The shape of each commutator segment 31 is an elongated member that extends in the longitudinal direction of the rotating shaft 21.

[0037] The multiple commutator segments 31 are conductive terminals made of a metal material such as copper. The multiple commutator segments 31 are electrically connected to the coils 22 of the rotor 20. The multiple commutator segments 31 are arranged in an insulated manner from each other. However, the multiple commutator segments 31 are electrically connected by the coils 22 of the rotor 20.

[0038] As an example, the commutator 30 is a molded commutator. The commutator 30 is constructed by molding multiple commutator segments 31 with a molding resin. In this case, the multiple commutator segments 31 are embedded in the molding resin so that their surfaces are exposed. The molding resin is the commutator body. The molding resin is a substantially cylindrical member having a through hole into which the rotating shaft 21 is inserted. The molding resin is a resin molded body made of an insulating resin material such as a thermosetting resin.

[0039] 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 segment 31 of the commutator 30. As the commutator 30 rotates due to the rotation of the rotating shaft 21, the brush 40 continues to make sequential contact with all of the commutator segments 31.

[0040] The brush 40 is a power supply brush for supplying power to the coil 22. Specifically, the brush 40 supplies power to the coil 22 by contacting the commutator segment 31 of the commutator 30. The brush 40 is connected to a power terminal fixed to the motor case 70 by a pigtail wire. When the brush 40 contacts the commutator segment 31, the armature current supplied from the power terminal to the brush 40 flows to the coil 22 through the commutator segment 31. As an example, the brush 40 is a conductive carbon brush made of carbon. The brush 40 is a long, essentially rectangular parallelepiped.

[0041] In this embodiment, multiple brushes 40 are provided. In this case, it is preferable that multiple brushes 40 are provided at equal intervals along the rotation direction of the rotor 20. In this embodiment, two brushes 40 are provided. The two brushes 40 are arranged opposite each other, sandwiching the commutator 30. That is, as shown in Figure 3, the two brushes 40 are arranged at 180-degree intervals along the rotation direction of the rotor 20.

[0042] The brush 40 is constantly in contact with the commutator segment 31 of the commutator 30 due to the pressing force from the brush spring 50. In other words, the brush 40 is pressed against the commutator 30 by the brush spring 50. Thus, the brush 40 slides against the commutator 30 due to the pressing force from the brush spring 50. The brush 40 is positioned to be movable in a direction (radial direction) that intersects the axial direction C in which the rotating shaft 21 extends due to wear with the commutator 30.

[0043] The brush spring 50 presses the brush 40 against the commutator 30 by applying pressure to the brush 40. Specifically, the brush spring 50 applies pressure (spring pressure) to the brush 40 by its spring elastic force (spring restoring force), biasing the brush 40 toward the commutator 30. A brush spring 50 is provided for each brush 40. In this embodiment, since two brushes 40 are used, two brush springs 50 are also used.

[0044] The brush spring 50 is a constant-load spring. Therefore, the brush spring 50 applies a uniform load to the brush 40. In other words, the brush spring 50, being a constant-load spring, applies a uniform pressing force to the brush 40.

[0045] The brush spring 50, which is a constant-load spring, is made of a strip-shaped wire. The brush spring 50, which is a constant-load spring, is a spiral spring. The brush spring 50, which is a constant-load spring, has a spiral section 51 (coil section) in which the strip-shaped wire is wound in a spiral shape. The brush spring 50, which is a constant-load spring, is made of a single strip-shaped wire made of, for example, a metal material.

[0046] Specifically, the brush spring 50, which is a constant-load spring, is made up of a long, strip-shaped metal plate. Therefore, the spiral section 51 is the part of the constant-load spring in which the long, strip-shaped metal plate is wound spirally multiple times in only one direction. When one end of the wire is stretched from the spiral section 51 of the brush spring 50, a force (spring restoring force) is generated that returns it to its original spiral shape.

[0047] The brush spring 50 presses the brush 40 against the commutator 30 with its 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 contacts the rear end of the brush 40. In this case, the load applied by the brush spring 50 to the commutator 30 by the brush 40 should be at least 1 times the radial load generated during the rotation of the rotor 20.

[0048] The brush spring 50 is positioned so that the spiral axis of the spiral section 51 and the direction of the axis C from which the rotation axis 21 extends are perpendicular. In other words, the brush spring 50 is installed so that the spiral section 51 is oriented vertically. The spiral surface (coil surface) of the spiral section 51 is parallel to the axis C contained in the rotation axis 21.

[0049] The motor case 70 houses the stator 10, the coils 22 of the rotor 20, the commutator 30, the brushes 40, the brush springs 50, and the bearings 60. As described above, the motor case 70 has a first member 71, a second member 72, a third member 73, and a fourth member 74. The first member 71, the second member 72, the third member 73, and the fourth member 74 may be made of an iron-based material such as cold-rolled steel plate (Steel Plate Cold Commercial, SPC material) or a metal material such as aluminum, or they may be made of an insulating resin material. In this embodiment, the first member 71, the second member 72, and the third member 73 are made of a metal material. The third member 73 is made of an insulating resin material.

[0050] The first member 71 is an outer casing member that forms part of the outer casing of the electric motor 1. The first member 71 is formed in a flattened, substantially bottomed cylindrical shape having a circular bottom and thin cylindrical side walls. The first member 71 also functions as a bracket for holding the stator 10 and the bearing 60.

[0051] The stator 10 is fixed to the bottom of the first member 71. The bearing 60 is fixed to a recess 71a provided in the center of the bottom of the first member 71. Specifically, the bearing 60 is press-fitted into the recess 71a of the first member 71 (bracket). The rotating shaft 21 is press-fitted into the bearing 60. In other words, both the inner and outer rings of the bearing 60 are press-fitted. In this case, the bearing 60 is fixed to the first member 71 by press-fitting it into the recess 71a of the first member 71. After that, the rotating shaft 21, to which the commutator 30 and the resin-molded coil 22 are attached, is press-fitted into the bearing 60 fixed to the first member 71.

[0052] The second member 72 is a thin plate-shaped member. The second member 72 is positioned between the first member 71 and the third member 73 in the direction of the axis C of the rotation shaft 21. The stator 10 and the rotor 20 coil 22 are positioned between the first member 71 and the second member 72.

[0053] The third member 73 is an outer casing member that forms part of the outer casing of the electric motor 1. The third member 73 is formed in a flattened, substantially bottomed cylindrical shape having a circular bottom and thin cylindrical side walls. A through hole is formed in the center of the bottom of the third member 73.

[0054] The third member 73 also functions as a brush holder for holding the brush 40. Specifically, the third member 73 is provided with a brush storage section 73a in which the brush 40 is housed.

[0055] The brush spring 50 is also housed in the brush housing portion 73a of the third member 73. Specifically, the brush spring 50 is positioned in the brush housing portion 73a such that the spiral portion 51 is located behind the rear end of the brush 40. In this case, the outer end portion 52 of the brush spring 50 is pulled out towards the commutator 30, passing along the side of the brush 40, and is fixed near the front opening of the brush housing portion 73a. Specifically, as shown in Figure 4, a through hole 52a is provided in the outer end portion 52 of the brush spring 50. The third member 73 is provided with a key-shaped projection as a locking portion 73b. The outer end portion 52 of the brush spring 50 is fixed to the third member 73 by locking the through hole 52a formed in the outer end portion 52 of the brush spring 50 with the locking portion 73b.

[0056] Furthermore, a cover plate 80 is provided so as to cover the brush 40 housed in the brush housing section 73a. The cover plate 80 covers the brush 40 and brush spring 50 housed in the brush housing section 73a. The cover plate 80 also has the function of guiding the spiral portion 51 of the brush spring 50 as it moves toward the commutator 30 side as the brush 40 wears down.

[0057] The fourth member 74 is an outer enclosure member that forms part of the outer casing of the electric motor 1. The fourth member 74 is a thin plate-shaped member. The fourth member 74 is provided so as to cover the through hole of the third member 73. The fourth member 74 and the third member 73 may be a single unit rather than separate.

[0058] In the electric motor 1 configured as described above, the current supplied to the brushes 40 flows as armature current (driving current) to the coils 22 of the rotor 20 via the commutator segments 31 of the commutator 30. This generates a magnetic flux in the rotor 20 (coils 22). The magnetic force generated by the interaction between the magnetic flux generated in the rotor 20 and the magnetic flux generated from the stator 10 becomes the 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 segments 31 of the commutator 30 and the brushes 40 come into contact. In this way, by switching the direction in which the current flows, a rotational force in a constant direction is generated by the repulsive and attractive magnetic forces between the stator 10 and the rotor 20, causing the rotor 20 to rotate around the rotation axis 21.

[0059] As the rotor 20 rotates, the front end of the brush 40 that contacts the commutator 30 wears down. At this time, the brush 40 is constantly pressed against the commutator 30 by a constant pressing force (load) from the brush spring 50, which is a constant-load spring. As a result, the brush 40 slides toward the commutator 30 as its front end wears down due to friction with the commutator segments 31. At this time, the wire material constituting the brush spring 50 is wound more as the brush 40 gets shorter. In other words, the spiral portion 51 of the brush spring 50 moves closer to the outer end 52.

[0060] Thus, in this embodiment, in the electric motor 1 which uses a rotor 20 that is a coreless rotor without a core, a constant-load spring is used as the brush spring 50 for pressing the brush 40 against the commutator.

[0061] This configuration allows for stable support of the rotor shaft 21, even though only one ball bearing is used as bearing 60. This point will be explained below.

[0062] If a torsion spring or compression coil spring is used as the brush spring 50, and a single ball bearing is used as the bearing 60 supporting the rotating shaft 21, the ball bearing has a small sliding surface area with the rotating shaft 21. As a result, the load applied by the brush spring 50 to the commutator 30 decreases as the brushes 40 wear down. Consequently, axial runout occurs in the rotating shaft 21 when the rotor 20 rotates, reducing the stability of the rotating shaft 21.

[0063] In contrast, by using a constant-load spring as the brush spring 50, a constant pressure is always applied to the brush 40 by the brush spring 50 even as the brush 40 wears down. The pressure from the brush spring 50 keeps the surface pressure that the brush 40 applies to the commutator 30 constant. In other words, even as the brush 40 wears down, the load applied by the brush spring 50 to the commutator 30 does not decrease. As a result, it is possible to suppress the occurrence of axial runout of the rotating shaft 21 when the rotor 20 rotates. Therefore, the stability of the rotating shaft 21 is improved.

[0064] As described above, the electric motor 1 according to this embodiment makes it possible to realize a bearing structure that supports the rotating shaft 21 of the coreless rotor in a cantilevered manner. Furthermore, the rotating shaft 21 can be stably supported even with a single ball bearing. This makes it possible to make the electric motor 1 thinner and more efficient compared to the case where multiple bearings are used. For example, in order to prevent axial runout of the rotating shaft, a conventional coreless flat motor using a compression spring required the use of at least two ball bearings with a thickness of 4 mm. However, in this embodiment, axial runout of the rotating shaft was not generated with a single ball bearing that had a thickness of 6 mm.

[0065] In the electric motor 1 according to this embodiment, the bearing 60 is a deep groove ball bearing.

[0066] Deep groove ball bearings are among the least expensive types of ball bearings. Therefore, by using deep groove ball bearings as bearing 60, it is possible to realize a low-cost electric motor 1 while achieving a thinner profile and higher efficiency.

[0067] In the electric motor 1 according to this embodiment, multiple brushes 40 are provided at equal intervals along the rotational direction of the rotor 20. Specifically, two brushes 40 are arranged at 180-degree intervals along the rotational direction of the rotor 20. In other words, the two brushes 40 are arranged facing each other, sandwiching the commutator 30.

[0068] In this way, by providing multiple brushes 40 at equal intervals along the rotational direction of the rotor 20, the load exerted by the brush springs 50 on the commutator 30 by the brushes 40 becomes uniform in the rotational direction of the rotor 20. This further suppresses the occurrence of axial runout of the rotating shaft 21.

[0069] In this case, the load exerted by the brush spring 50 on the commutator 30 by the brush 40 should be at least 1 times the radial load generated during the rotation of the rotor 20.

[0070] This effectively suppresses the occurrence of axial runout in the rotating shaft 21.

[0071] In the electric motor 1 according to this embodiment, the commutator 30 and the bearing 60 are located on opposite sides of the axis C of the rotating shaft 21, with reference to the position of the coil 22 on the rotating shaft 21.

[0072] This configuration allows the rotating shaft 21 to which the commutator 30 is attached to be stably held, even if the bearing 60 is a single ball bearing. Therefore, axial runout of the rotating shaft 21 can be effectively suppressed. Thus, the stability of the rotating shaft 21 can be further improved.

[0073] As described above, the electric motor 1 of this embodiment comprises a rotor 20 having a rotating shaft 21 and coils 22 extending in the axial direction, a commutator 30 attached to the rotating shaft 21, at least one brush 40 slidingly in contact with the commutator 30, a brush spring 50 for pressing at least one brush 40 against the commutator 30, and a bearing 60 supporting the rotating shaft 21, wherein the bearing 60 is a ball bearing and the brush spring 50 is a constant load spring.

[0074] The rotor 20 may be a coreless rotor that does not have a core.

[0075] This allows even a single ball bearing to stably support the rotating shaft.

[0076] Furthermore, the coil 22 is preferably a plurality of winding coils, each wound in a flattened shape, and the plurality of winding coils are arranged to surround the rotation axis 21 with each coil surface facing in the axial direction.

[0077] Furthermore, it is preferable that the electric motor 1 is further equipped with a magnet as a stator 10, and that the stator 10 and the coil 22 face each other in the axial direction.

[0078] The electric blower 90 comprises an electric motor 1 and a rotary fan 91 attached to the rotating shaft 21 of the electric motor 1. The rotary fan 91 is attached to the bearing 60 side of the commutator 30, which is part of the bearing 60 on the rotating shaft 21.

[0079] (modified version) The electric motor 1 and electric blower related to this disclosure have been described above based on embodiments. However, this disclosure is not limited to the embodiments described above.

[0080] For example, in the above embodiment, the brush spring 50 is arranged so that the spiral axis of the spiral section 51 and the axis C direction of the rotation axis 21 are perpendicular to each other. However, it is not limited to this. Figure 5 shows the arrangement of the brush spring 50 in an electric motor 1A according to a modified example. For example, as in the electric motor 1A shown in Figure 5, the brush spring 50 may be arranged so that the spiral axis of the spiral section 51 and the axis C direction of the rotation axis 21 are parallel to each other. In other words, the brush spring 50 may be installed so that the spiral section 51 is oriented horizontally.

[0081] However, as shown in Figure 2, it is preferable that the brush spring 50 be positioned such that the spiral axis of the spiral section 51 and the axis C of the rotation axis 21 are perpendicular to each other (i.e., the spiral section 51 is oriented vertically).

[0082] This is because, when the brush spring 50, which is a constant-load spring, is positioned, the wires constituting the brush spring 50 are drawn out so as to pass to the side of the brush 40, and the brush spring 50 is positioned in an offset state. When the brush spring 50 is in this offset state, as the wear of the brush 40 causes the spiral portion 51 to move toward the commutator 30, the direction of the load on the brush 40 by the spiral portion 51 will not be perfectly parallel to the longitudinal direction of the brush 40, but will be slightly tilted toward the outer end 52. In this case, as shown in Figure 5, if the spiral portion 51 is positioned horizontally, and the direction of the load on the brush 40 by the spiral portion 51 is tilted toward the outer end 52, the load will act in the radial direction, and the load on the brush 40 that the brush 40 presses against the commutator 30 by the brush spring 50 will deviate from the direction perpendicular to the direction of the axis C of the rotating shaft 21, reducing the stability of the rotating shaft 21.

[0083] On the other hand, as shown in Figure 2, when the spiral section 51 is oriented vertically, even if the direction of the load on the brush 40 by the spiral section 51 is tilted towards the outer end 52, the load acts in the thrust direction but not in the radial direction. In other words, the tilt of the direction of the load on the brush 40 by the brush spring 50 does not affect the rotation direction of the rotor 20. Therefore, even if the brush spring 50 is offset, it does not affect the stability of the rotating shaft 21. Consequently, arranging the brush spring 50 so that the spiral section 51 is oriented vertically (Figure 2) rather than horizontally (Figure 5) will allow the rotating shaft 21 to rotate stably without axial runout during rotation. In other words, by arranging the brush spring 50 so that the spiral section 51 is oriented vertically, the rotating shaft 21 can be stably supported even if a single ball bearing is used as the bearing 60.

[0084] 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 rotor 20 have a core.

[0085] In the above embodiment, the stator 10 is composed solely of permanent magnets. However, it is not limited to this. For example, the stator 10 may be a stator composed of permanent magnets and an iron core. The stator 10 may also be an armature consisting of stator windings and an iron core without using permanent magnets.

[0086] In the above embodiment, the electric motor 1 is a flat motor with an external size having a thickness smaller than its outer diameter. However, it is not limited to this. The technology of this disclosure can also be applied to, for example, a cylindrical electric motor having an external size having a cylindrical housing with a thickness larger than its outer diameter.

[0087] In the above embodiment, the direction of the main magnetic flux generated by the stator 10 and rotor 20 is in the direction of the axis C of the rotation axis 21. However, it is not limited to this. Specifically, the direction of the main magnetic flux generated by the stator 10 and rotor 20 may be in a direction perpendicular to the direction of the axis C of the rotation axis 21 (the radial direction of rotation of the rotation axis 21). For example, the technology of this disclosure can also be applied to an inner rotor type motor in which the rotor 20 is arranged inside the stator 10.

[0088] In the above embodiment, the electric motor 1 is exemplified as an example of an electric blower applied to a cooling fan for a vehicle. However, it is not limited to this. The technology of this disclosure can also be applied to electric blowers other than those for vehicles, such as electric blowers mounted on vacuum cleaners. The technology of this disclosure can also be applied to electric motors other than those used in electric blowers. In other words, the technology of this disclosure can be applied to electric motors mounted on various electrical devices.

[0089] Furthermore, this disclosure also includes forms obtained by applying various modifications to the above embodiments that a person skilled in the art could conceive, or forms realized by arbitrarily combining the components and functions of each embodiment without departing from the spirit of this disclosure. [Industrial applicability]

[0090] The technology disclosed herein can be widely used in various products that incorporate electric motors, including products in the fields of automotive electrical systems and household electrical appliances. [Explanation of Symbols]

[0091] 1, 1A electric motor 10 Stator 20 rotors 21 Rotation axis 21a First end 21b Second end 22 coils 23 Mold resin 30 commutator 31 Commutator piece 40 brushes 50 Brush springs 51 Spiral section 52 Outer edge 52a through hole 60 bearings 70 Motor Case 71 First Member 71a Recess 72 Second Member 73 Third Member 73a Brush storage section 73b Locking part 74 Fourth member 80 Cover Plate 90 Electric blower 91 Rotating Fan

Claims

1. A rotor having a rotating shaft and coils extending in the axial direction, A commutator attached to the aforementioned rotating shaft, At least one brush that slides against the commutator, A brush spring for pressing at least one of the brushes against the commutator, The rotating shaft is supported by one bearing, The rotor is a coreless rotor that does not have a core. The aforementioned coil is a plurality of winding coils, each wound in a flattened shape. The plurality of winding coils are arranged so as to surround the rotation axis, with each coil surface facing the axial direction. The bearing is a ball bearing, specifically a deep groove ball bearing. The brush spring is a constant-load spring having a spiral portion in which the metal plate is wound spirally in only one direction, and the spiral axis of the spiral portion is arranged to be perpendicular to the axial direction, so that the spiral portion contacts the rear end of the brush. Equipped with a magnet as a stator, The stator and the coil are opposite each other in the axial direction. Electric motor.

2. The at least one brush is provided in multiple locations at equal intervals along the rotational direction of the rotor. The electric motor according to claim 1.

3. The aforementioned at least one brush is two, The at least one brush is arranged opposite to the commutator, The electric motor according to claim 2.

4. The commutator and the bearing are located on opposite sides in the axial direction with reference to the position of the coil on the rotating shaft. The electric motor according to any one of claims 1 to 3.

5. The load exerted by the brush spring on the commutator by at least one brush is at least one times the radial load generated during the rotation of the rotor. The electric motor according to any one of claims 1 to 3.

6. An electric motor according to any one of claims 1 to 3, The electric motor comprises a rotating fan attached to the rotating shaft, The rotating fan is attached to the bearing and the commutator on the bearing side of the rotating shaft. Electric blower.

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