JP2024080053A - Rotating Electric Machine - Google Patents

Abstract

[Problem] To provide a rotating electric machine that can effectively utilize the magnetic flux of the overhanging portion of a permanent magnet and efficiently achieve high torque. [Solution] The rotating electric machine includes a rotor 9 that is rotatable about a rotation axis Cr, and a stator 8 that surrounds the outer periphery of the rotor. The stator 8 has a stator core 20 around which a coil 24 is wound. The rotor 9 has a shaft 31 whose axis is the rotation axis Cr, a rotor core 32 that is fitted and fixed to the shaft 31, and a permanent magnet 33 that is arranged on the outer periphery of the rotor core 32. The permanent magnet 33 has an overhanging portion 33e that protrudes outward in the axial direction beyond both end faces 20a, 20b of the stator core 20 in the axial direction. A cylindrical portion 72 made of a magnetic material is provided on the inner periphery of the radially inner side of the overhanging portion 33e. [Selected Figure] Figure 2

Description

The present invention relates to a rotating electric machine.

An example of a rotating electric machine is an electric motor. The electric motor includes a stator and a rotor that is rotatable around the axis of rotation relative to the stator. The stator includes a stator core around which a coil is wound. The rotor includes a shaft whose center is the axis of rotation, a rotor core that is fitted and fixed to the shaft, and a number of permanent magnets for a field magnet that are provided on the rotor core. With this configuration, when power is supplied to the coil, a magnetic flux linkage is formed in the stator core. Magnetic attraction and repulsion are generated between this magnetic flux linkage and the permanent magnets, causing the rotor to rotate continuously.

Among rotors, there are so-called surface permanent magnet (SPM) type rotors in which permanent magnets are arranged on the outer peripheral surface of the rotor core. In order to increase the effective magnetic flux in these surface magnet type rotors and achieve high torque, the length of the permanent magnet in the direction of the rotation axis may be made longer than the length of the stator core and rotor core in the direction of the rotation axis.

By having both ends of the permanent magnet in the direction of the rotation axis protrude outward beyond both end faces of the stator core in the direction of the rotation axis, the amount of effective magnetic flux of the rotor can be increased. This allows the interlinked magnetic flux formed in the stator core to contribute efficiently to the rotational force of the rotor, increasing the torque of the electric motor. Hereinafter, the portions of the permanent magnet that protrude outward beyond both end faces of the stator core in the direction of the rotation axis are referred to as overhanging portions.

JP 2021-168575 A

However, in the above-mentioned conventional technology, the magnetic flux on the radially outer peripheral surface of the overhanging portion of the permanent magnet contributes to the rotational force of the rotor. In contrast, the magnetic flux on the radially inner peripheral surface of the overhanging portion of the permanent magnet simply becomes leakage magnetic flux. As a result, the effective magnetic flux of the permanent magnet is reduced, making it difficult to efficiently increase the torque of the electric motor.

Therefore, the present invention provides a rotating electric machine that can effectively utilize the magnetic flux in the overhanging part of the permanent magnet and efficiently achieve high torque.

In order to solve the above problems, in a first aspect of the present invention, a rotating electric machine includes a rotor that is rotatable about a rotation axis and a stator that surrounds the outer periphery of the rotor, the stator having a stator core around which a coil is wound, the rotor having a shaft centered on the rotation axis, a rotor core that is fitted and fixed to the shaft, and a permanent magnet arranged on the outer periphery of the rotor core, the permanent magnet having an overhang portion that protrudes outward beyond both end faces of the rotation axis of the stator core in the direction of the rotation axis, and a magnetic body is provided on the inner periphery radially inward of the overhang portion.

By configuring it in this way, a magnetic path can be formed on the inner circumferential surface side of the overhang portion, through which magnetic flux flows to the rotor core via the magnetic material. This reduces the magnetic flux that leaks into the air at the overhang portion, and makes effective use of the magnetic flux at the overhang portion. This increases the effective magnetic flux of the entire permanent magnet, and efficiently increases the torque of the rotating electric machine.

In a second aspect of the present invention, in the rotating electric machine of the first aspect, the magnetic body is a magnet holder that holds the permanent magnet, and the magnet holder is disposed on the inner peripheral surface of the overhang portion and includes a cylindrical portion that abuts against the rotor core, and an end wall that protrudes radially outward from the end of the cylindrical portion opposite the rotor core, and the end wall abuts against the end of the overhang portion in the direction of the rotation axis.

This configuration allows the permanent magnets to be fixed to the rotor core and ensures that the permanent magnets are positioned relative to the rotor core. In addition, the magnetic flux on the inner peripheral surface of the overhang portion can be reliably passed through the cylindrical portion to the rotor core.

In a third aspect of the present invention, in the rotating electric machine of the second aspect, the rotor core is formed by laminating steel plates, and the magnet holder is formed by pressure molding soft magnetic powder.

This configuration increases the magnetic permeability of the rotor core while making it easier to form the magnet holder.

In a fourth aspect of the present invention, in the rotating electric machine of the second or third aspect, the magnet holder is provided with an engagement claw formed on the cylindrical portion and engaged with the rotor core, and a positioning portion formed on the end wall for positioning the magnet holder relative to other devices.

By configuring it in this way, for example when magnetizing a permanent magnet, it is easy to position the permanent magnet relative to the magnetizing device. This makes it easier to manufacture the rotor.

In a fifth aspect of the present invention, in the rotating electric machine of the fourth aspect, the positioning portion is an opening formed in the end wall.

This configuration makes it easy to form a positioning portion on the end wall. For example, a pin can be provided on another device, and the rotor can be positioned relative to the other device simply by fitting the opening onto the pin.

In a sixth aspect of the present invention, in a rotating electric machine according to any one of the second to fifth aspects, when the circle passing through the outermost radial area of the outer peripheral surface of the overhang portion is defined as the outermost circle of the overhang portion with the axis of rotation as the center, and the center between the outermost circle and the inner peripheral surface is defined as the center of the overhang portion, the outer peripheral edge of the end wall is located between the inner peripheral surface of the overhang portion and the center.

This configuration makes it possible to prevent the formation of a magnetic flux flow that is shortcutted through the end wall at the end of the overhang portion in the direction of the rotation axis. This flow becomes leakage magnetic flux that does not contribute to the torque of the rotor. By reducing the leakage magnetic flux, the effective magnetic flux of the entire permanent magnet can be increased, and the rotating electric machine can be efficiently made to have high torque.

According to the present invention, the magnetic flux in the overhanging part of the permanent magnet can be effectively utilized, and the rotating electric machine can be efficiently made to have high torque.

1 is a perspective view of a motor with a reducer according to an embodiment of the present invention. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 2 is an exploded perspective view of a rotor according to an embodiment of the present invention. FIG. 2 is a perspective view of a rotor with a magnet cover removed in an embodiment of the present invention. 2 is a perspective view of a magnet holder according to an embodiment of the present invention, seen from the opposite side to a rotor core. FIG. 2 is a perspective view of a magnet holder according to an embodiment of the present invention, seen from the rotor core side. FIG. 2 is a partially enlarged view of a cross section along an axial direction of a rotor according to an embodiment of the present invention. FIG. 5A to 5C are diagrams illustrating the operation of the magnet holder according to the embodiment of the present invention. 11 is a graph showing a change in the overall effective magnetic flux of a permanent magnet when the protruding length of an overhang portion is changed in an embodiment of the present invention, comparing the case with and without a cylindrical portion. 11 is a graph showing the change in the total effective magnetic flux of a permanent magnet when the outer diameter of the outer peripheral edge of an end wall is changed in an embodiment of the present invention. FIG. 11 is an exploded perspective view of a rotor according to a modified example of the embodiment of the present invention.

Next, an embodiment of the present invention will be described with reference to the drawings.

<Motor with reduction gear>
Fig. 1 is a perspective view of a geared motor 1. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1.
The motor 1 with a reduction gear is used, for example, as a drive source for a wiper device of a vehicle.
As shown in Figures 1 and 2, a motor with a reducer 1 includes an electric motor 2, a reduction unit 3 that reduces the rotation of the electric motor 2 and outputs it, and a controller unit 4 that controls the drive of the electric motor 2.

In the following description, when we simply refer to the "axial direction," we mean the direction parallel to the central axis of the shaft 31 of the electric motor 2 (the rotation axis Cr of the electric motor 2). When we simply refer to the "circumferential direction," we mean the circumferential direction (rotation direction) of the shaft 31. When we simply refer to the "radial direction," we mean the radial direction of the shaft 31 that is perpendicular to the axial and circumferential directions.

<Electric motor>
The electric motor 2 includes a motor case 5, a cylindrical stator 8 housed in the motor case 5, and a rotor 9 provided radially inside the stator 8 and rotatably relative to the stator 8. The electric motor 2 is a so-called brushless motor that does not require brushes when supplying power to the stator 8.

<Motor case>
The motor case 5 is made of a material with excellent heat dissipation properties, such as aluminum die-casting. The motor case 5 is made up of a first motor case 6 and a second motor case 7, which are configured to be separable in the axial direction. The first motor case 6 and the second motor case 7 are each formed in a cylindrical shape with a bottom.
The first motor case 6 is molded integrally with the gear case 40 of the reduction gear unit 3 so that the bottom portion 10 is joined to the gear case 40. A through hole 10a, through which the shaft 31 of the rotor 9 is inserted, is formed in the radial center of the bottom portion 10.

The opening 6a of the first motor case 6 is formed with an outer flange portion 16 that protrudes radially outward. The opening 7a of the second motor case 7 is formed with an outer flange portion 17 that protrudes radially outward. These outer flange portions 16, 17 are butted together to form the motor case 5 having an internal space. The stator 8 is arranged in the internal space of the motor case 5 so as to fit into the first motor case 6 and the second motor case 7.

<Stator>
The stator 8 has a stator core 20. The stator core 20 is integrally formed with a cylindrical back yoke portion 21 having a circular cross-sectional shape along the radial direction, and a plurality of (for example, six in this embodiment) teeth portions 22 protruding radially inward from the back yoke portion 21. The stator core 20 is formed by stacking a plurality of steel plates 20p in the axial direction. For example, an electromagnetic steel plate is used as the steel plate 20p. However, this is not limited to this, and various steel plates can be used. In addition, the stator core 20 is not limited to being formed by stacking a plurality of steel plates 20p in the axial direction, and may be formed by, for example, stacking rolled steel plates in the axial direction and molding them, or by pressure molding soft magnetic powder.

The inner circumferential surface of the back yoke portion 21 and the teeth portion 22 are covered with an insulator 23 made of insulating resin. A coil 24 is wound around each of the teeth portions 22 from above the insulator 23. Each coil 24 generates a magnetic flux linkage for rotating the rotor 9 when power is supplied from the controller portion 4.

<Rotor>
Fig. 3 is an exploded perspective view of the rotor 9. Fig. 4 is a perspective view of the rotor 9 with the magnet cover 71 removed.
2 to 4 , the rotor 9 is rotatably disposed radially inside the stator 8 with a small gap therebetween. The rotor 9 includes a shaft 31 integrally molded with a worm shaft 44 constituting the reduction gear unit 3, a rotor core 32 fitted and fixed to the shaft 31, four permanent magnets 33 provided on an outer circumferential surface 32a of the rotor core 32, magnet holders 70 provided on both axial end faces 32b, 32c of the rotor core 32 (both axial end faces of the shaft fixing portion 37), and a magnet cover 71 that covers the permanent magnets 33 and the magnet holder 70.

<Rotor core>
The rotor core 32 is formed by stacking a plurality of steel plates 32p in the axial direction. As the steel plates 32p, for example, electromagnetic steel plates are used. However, the steel plates 32p are not limited to this, and various steel plates can be used. The axial thickness of the rotor core 32 is the same as the axial thickness of the stator core 20.
The rotor core 32 is formed integrally with a cylindrical shaft fixing portion 37 having a radial center coincident with the axial center (rotation axis Cr) of the shaft 31, and four salient pole portions 35 formed to protrude radially outward from an outer circumferential surface 37a of the shaft fixing portion 37. The outer circumferential surface 37a of the shaft fixing portion 37 is the outer circumferential surface 32a of the rotor core 32.

A shaft insertion hole 37b is formed in the radial center of the shaft fixing portion 37, penetrating in the axial direction. The shaft 31 is press-fitted into the shaft insertion hole 37b. The shaft 31 may be inserted into the shaft insertion hole 37b, and the rotor core 32 may be fixed to the shaft 31 using adhesive or the like. The shaft insertion hole 37b has four escape grooves 37c that extend radially outward.

Each of the escape grooves 37c is formed to penetrate the shaft fixing portion 37 in the axial direction and communicates with the shaft insertion hole 37b. Each of the escape grooves 37c is arranged at equal intervals in the circumferential direction. The radial outer end of the escape groove 37c is formed in a semicircular shape. Both side surfaces of the escape groove 37c that face each other in the circumferential direction are formed flat and parallel. In other words, the escape groove 37c is formed so that the circumferential width dimension is uniform in the radial direction. Each of the escape grooves 37c has the role of adjusting the press-fit strength of the shaft 31 into the shaft insertion hole 37b, and also has the role of positioning the magnet holder 70 (details will be described later).

The four salient pole portions 35 are disposed at equal intervals in the circumferential direction. Each salient pole portion 35 is disposed on the same straight line as each relief groove 37c in the radial direction. In other words, each salient pole portion 35 faces a corresponding relief groove 37c in the radial direction.
The salient pole portion 35 is formed so as to extend over the entire axial direction of the rotor core 32. The salient pole portion 35 is formed so that both side surfaces facing each other in the circumferential direction are parallel to each other. In other words, the salient pole portion 35 is formed so that the width dimension in the circumferential direction is uniform in the radial direction.
A single groove 91 is formed over the entire axial direction in the radial outer end 35b of the salient pole portion 35. The groove 91 is disposed in the circumferential center of the outer end 35b.

The groove portion 91 is formed in a V-groove shape so that the circumferential groove width gradually narrows toward the inside in the radial direction. On the outer circumferential surface 32a of the rotor core 32 (the outer circumferential surface 37a of the shaft fixing portion 37) formed in this manner, and between two adjacent salient pole portions 35 in the circumferential direction, each is configured as a magnet storage portion 36.

<Permanent magnet>
A permanent magnet 33 is disposed over each magnet storage portion 36 and fixed to the rotor core 32 by, for example, an adhesive.
The permanent magnet 33 is formed in an arc shape when viewed from the axial direction. In other words, the permanent magnet 33 is formed in a tile-like shape. More specifically, for example, the inner peripheral surface 33a of the permanent magnet 33 is formed in an arc shape (an arc shape that approximately matches the outer peripheral surface 37a of the shaft fixing portion 37) centered on the rotation axis Cr. In contrast, the outer peripheral surface 33b of the permanent magnet 33 is formed in an arc shape with a smaller radius of curvature than the inner peripheral surface 33a, for example.

As a result, the outer peripheral surface 33b of the permanent magnet 33 bulges outward in the radial direction most at the circumferential center position 33p. The distance between the circumferential center position 33p of the outer peripheral surface 33b of the permanent magnet 33 and the rotation axis Cr is approximately the same as the distance between the outer end portion 35b of each salient pole portion 35 and the rotation axis Cr. The outer peripheral surface 33b of the permanent magnet 33 gradually moves away from the teeth portion 22 from the circumferential center toward both sides in the circumferential direction.

Both circumferential sides of the permanent magnet 33 have an inner side surface 33c located radially inward and an outer side surface 33d located radially outward of the inner side surface 33c. The inner side surface 33c is formed to follow the side surface 35a of the salient pole portion 35. In other words, the inner side surface 33c and the side surface 35a of the salient pole portion 35 are substantially parallel to each other.
The outer surface 33d is formed to be inclined and flat so as to gradually move away from the side surface 35a of the salient pole portion 35 in the circumferential direction from the connection portion with the inner surface 33c toward the outside in the radial direction. In one permanent magnet 33, the two outer surfaces 33d on both sides in the circumferential direction are parallel to each other.

The axial length of each permanent magnet 33 is longer than the axial length of the rotor core 32. Therefore, when assembled to the rotor core 32, each permanent magnet 33 has an overhang portion 33e that protrudes axially outward from both axial end faces 32b, 32c of the rotor core 32. The protruding lengths of each overhang portion 33e from both axial end faces 32b, 32c of the rotor core 32 are approximately the same. Since the axial thickness of the rotor core 32 is the same as the axial thickness of the stator core 20, it can be said that the overhang portion 33e protrudes axially outward from both axial end faces 20a, 20b of the stator core 20.

The permanent magnets 33 are desirably magnetized so that the orientation of the magnetization (magnetic field) is parallel along the radial direction (thickness direction). The permanent magnets 33 are arranged so that the magnetic poles are staggered in the circumferential direction. Therefore, the salient poles 35 of the rotor core 32 are located at the boundaries of the magnetic poles (pole boundaries).
For example, a ferrite bonded magnet is used as the permanent magnet 33. However, this is not limited to this, and instead of the ferrite bonded magnet, a ferrite sintered magnet, a neodymium bonded magnet, a neodymium sintered magnet, or the like can also be used as the permanent magnet 33.

<Magnet cover>
The magnet cover 71 is formed by pressing a metal plate and includes a cylindrical portion 71a that covers the outer peripheral surfaces of the rotor core 32 and the permanent magnets 33, a protruding portion 71b integrally molded at one axial end (upper end in FIG. 3 ) of the cylindrical portion 71a, an inner flange portion 71c integrally molded at a radially inner end of the protruding portion 71b, and a crimping portion 71d integrally molded at the other axial end (lower end in FIG. 3 ) of the cylindrical portion 71a.

The protruding portion 71b is formed so as to be convex from one axial end of the cylindrical portion 71a toward the outside in the axial direction and bent back toward the inside in the radial direction. The protruding portion 71b is formed around the entire circumference of the cylindrical portion 71a.
An inner flange portion 71c extends from the folded-back radially inner end of the overhanging portion 71b. The extending direction of the inner flange portion 71c is along the radial direction.
The crimped portion 71d is formed by disposing the rotor core 32 and the permanent magnets 33 together with the pair of magnet holders 70 inside the cylindrical portion 71a, and then plastically deforming the rotor core 32 and the permanent magnets 33 by crimping.

<Magnet holder>
Fig. 5 is a perspective view of the magnet holder 70 as viewed from the opposite side to the rotor core 32. Fig. 6 is a perspective view of the magnet holder 70 as viewed from the rotor core 32 side.
3 to 6, the magnet holders 70 provided on both end faces 32b, 32c of the rotor core 32 have the same configuration. Both are assembled to the rotor core 32 in an inverted upside-down state.

The magnet holder 70 is made of a magnetic material, for example, by pressure molding soft magnetic powder.
The magnet holder 70 comprises a cylindrical portion 72 arranged on the inner surface 33a of the overhang portion 33e of the permanent magnet 33, four leg portions 73 protruding radially outward from the outer peripheral surface 72a of the cylindrical portion 72, and disk-shaped end walls 74 protruding radially outward from the ends of the cylindrical portion 72 and the leg portions 73 opposite both end faces 32b, 32c of the rotor core 32.

The outer peripheral surface 72a of the cylindrical portion 72 contacts the inner peripheral surface 33a of the overhang portion 33e of the permanent magnet 33. The rotor core 32 side end 72b of each cylindrical portion 72 abuts against both end faces 32b, 32c of the rotor core 32. Four recesses 76 are formed in the end 72b of the cylindrical portion 72. The four recesses 76 are arranged at equal intervals in the circumferential direction. By forming the recesses 76, the contact area of the cylindrical portion 72 (end 72b) with both end faces 32b, 32c of the rotor core 32 is reduced. Therefore, the molding die can be easily adjusted to accurately abut the end 72b of the cylindrical portion 72 against both end faces 32b, 32c of the rotor core 32.

Four engagement claws 75 are formed to protrude from the end 72b of the cylindrical portion 72. The four engagement claws 75 are arranged at equal intervals in the circumferential direction so as to avoid the recesses 76. The four engagement claws 75 are arranged on the inner peripheral edge side of the cylindrical portion 72. The engagement claws 75 are formed so that their cross sections along the radial direction are semicircular. When the magnet holder 70 is arranged on both end faces 32b, 32c of the rotor core 32, the engagement claws 75 are fitted into the radially outer side of the escape grooves 37c of the rotor core 32. This positions the magnet holder 70 relative to the rotor core 32.

The four legs 73 are arranged at equal intervals in the circumferential direction. Each leg 73 is arranged in the same straight line as each engagement claw 75 in the radial direction. In other words, each leg 73 faces the corresponding engagement claw 75 in the radial direction. The end 73a of each leg 73 on the rotor core 32 side is abutted against both end faces 32b, 32c of the rotor core 32.

The axial length of the cylindrical portion 72 and each leg portion 73 is slightly longer than the axial length of the overhang portion 33e of the permanent magnet 33. Therefore, the position of the end wall 74 is slightly outward in the axial direction from the axial end portion 33f of the overhang portion 33e. As a result, the magnet holder 70 on the crimping portion 71d side of the magnet cover 71 receives the crimping load during the crimping operation of the crimping portion 71d.

FIG. 7 is a partially enlarged view of a cross section of the rotor 9 taken along the axial direction.
4 to 7, an opening 74a is formed in the radial center of the end wall 74. The inner diameter of the opening 74a is the same as the inner diameter of the cylindrical portion 72. In other words, the opening 74a of the end wall 74 and the inner circumferential surface of the cylindrical portion 72 are smoothly connected.
The radius of the end wall 74 is equal to the distance from the rotation axis Cr to the radially outer end 73b of the leg 73. In other words, the outer peripheral edge 74b of the end wall 74 and the radially outer end 73b of the leg 73 are smoothly connected.

As shown in detail in FIG. 7, the outermost circle Co is the circle that is centered on the rotation axis Cr and passes through the radially outermost part of the outer peripheral surface 33b of the overhang portion 33e, i.e., the center position 33p. The center between this outermost circle Co and the inner peripheral surface 33a of the overhang portion 33e is the center portion 33g. In this case, the outer peripheral edge 74b of the end wall 74 and the radially outer end portion 73b of the leg portion 73 are positioned between the inner peripheral surface 33a of the overhang portion 33e and the center portion 33g.

Furthermore, four openings 77 are formed in the outer peripheral edge 74b of the end wall 74. The openings 77 are located in the center between adjacent leg portions 73 in the circumferential direction. When viewed from the axial direction, the openings 77 have a shape that approximates a circle. The openings 77 are open on the radially outer side and are formed in a dovetail shape.

The opening 77 is used, for example, to position the rotor 9 relative to a magnetizing device (not shown). For example, a positioning pin is provided on the magnetizing device, and the opening 77 is fitted onto this pin. This positions the magnet holder 70 relative to the magnetizing device. The magnet holder 70 is positioned relative to the rotor core 32 by the engagement claws 75. As a result, the rotor 9 can be positioned by the opening 77. The permanent magnet 33 is also positioned relative to the magnetizing device. This makes it possible to magnetize the permanent magnet 33 with high precision.

A number of reinforcing ribs 78 are formed to protrude from the inner surface 74c of the end wall 74 facing the rotor core 32. The reinforcing ribs 78 are formed along the radial direction of the inner surface 74c of the end wall 74 and across the entire radial direction of the inner surface 74c. Two reinforcing ribs 78 are disposed between each pair of legs 73 adjacent in the circumferential direction. These two reinforcing ribs 78 are disposed on either side of the corresponding opening 77 in the circumferential direction.

The reinforcing rib 78 has the function of suppressing the occurrence of deformation such as dents and waves around the periphery of the end wall 74 during molding of the magnet holder 70, and also has the function of increasing the mechanical strength of the end wall 74. Furthermore, when the magnet holder 70 is assembled into the magnet cover 71 together with the rotor core 32 holding the permanent magnet 33, the reinforcing rib 78 abuts against the end 33f of the overhang portion 33e. As a result, when an excessive load acts on the permanent magnet 33 in the axial direction, the reinforcing rib 78 (end wall 74) limits the axial displacement of the permanent magnet 33.

<Reduction section>
1 and 2, the reduction unit 3 includes a gear case 40 to which the motor case 5 is attached, and a worm reduction mechanism 41 housed in the gear case 40. The gear case 40 is made of a material with excellent heat dissipation properties, such as aluminum die casting. The gear case 40 is formed in a box shape with an opening 40a on one side. The gear case 40 has a gear housing portion 42 that houses the worm reduction mechanism 41. An opening 43 that communicates between the through hole 10a of the first motor case 6 and the gear housing portion 42 is formed in a portion of the side wall 40b of the gear case 40 where the first motor case 6 is integrally molded.

A cylindrical bearing boss 49 protrudes from the bottom wall 40c of the gear case 40. The bearing boss 49 is for supporting the output shaft 48 of the worm reduction mechanism 41 so that it can rotate freely. A plain bearing (not shown) is provided on the inner peripheral surface of the bearing boss 49. An O-ring (not shown) is attached to the inner peripheral edge of the tip of the bearing boss 49. This prevents dust and water from entering the inside from the outside through the bearing boss 49. A number of ribs 52 are provided on the outer peripheral surface of the bearing boss 49. This ensures the rigidity of the bearing boss 49.

The worm reduction mechanism 41 housed in the gear housing 42 is composed of a worm shaft 44 and a worm wheel 45 meshed with the worm shaft 44. The worm shaft 44 is arranged coaxially with the shaft 31 of the electric motor 2. Both ends of the worm shaft 44 are rotatably supported by bearings 46, 47 provided in the gear case 40. The end of the worm shaft 44 on the electric motor 2 side protrudes through the bearing 46 to the opening 43 of the gear case 40. The protruding end of the worm shaft 44 and the end of the shaft 31 of the electric motor 2 are joined, and the worm shaft 44 and the shaft 31 are integrated. The worm shaft 44 and the shaft 31 may be integrally formed by molding the worm shaft portion and the shaft portion from one base material.

The worm wheel 45 that meshes with the worm shaft 44 has an output shaft 48 provided at the radial center of the worm wheel 45. The output shaft 48 is arranged coaxially with the rotational axis of the worm wheel 45. The output shaft 48 protrudes to the outside of the gear case 40 via a bearing boss 49 of the gear case 40. A spline 48a that connects to an electrical component (not shown) is formed at the protruding tip of the output shaft 48.

A sensor magnet (not shown) is provided in the radial center of the worm wheel 45, opposite the side from which the output shaft 48 protrudes. The sensor magnet constitutes one side of a rotational position detection unit 60 that detects the rotational position of the worm wheel 45. A magnetic detection element 61 that constitutes the other side of the rotational position detection unit 60 is provided in the controller unit 4 that is disposed opposite the worm wheel 45 on the sensor magnet side of the worm wheel 45 (the opening 40a side of the gear case 40).

<Controller section>
The controller unit 4 that controls the drive of the electric motor 2 has a controller board 62 on which a magnetic detection element 61 is mounted, and a cover 63 provided to close the opening 40a of the gear case 40. The controller board 62 is disposed opposite the sensor magnet side of the worm wheel 45 (the opening 40a side of the gear case 40).

The controller board 62 is a so-called epoxy board on which multiple conductive patterns (not shown) are formed. The terminals of the coils 24 drawn from the stator core 20 of the electric motor 2 are connected to the controller board 62, and the terminals (not shown) of the connector 11 provided on the cover 63 are also electrically connected to the controller board 62.

In addition to the magnetic detection element 61, the controller board 62 is also equipped with a power module (not shown) consisting of switching elements such as a FET (field effect transistor) that controls the current supplied to the coil 24. The controller board 62 is also equipped with a capacitor (not shown) that smoothes the voltage applied to the controller board 62.

The cover 63 that covers the controller board 62 configured in this manner is made of resin. The cover 63 is formed so as to bulge outward slightly. The inner surface of the cover 63 is configured as the controller housing portion 56 that houses the controller board 62 and the like.
The connector 11 is integrally molded on the outer periphery of the cover 63. A connector extending from an external power supply (not shown) is fitted into the connector 11. The controller board 62 is electrically connected to the terminals of the connector 11. This allows power from the external power supply to be supplied to the controller board 62.

A fitting portion 81 that fits with the end of the side wall 40b of the gear case 40 is formed protruding from the opening edge of the cover 63. The fitting portion 81 is composed of two walls 81a, 81b along the opening edge of the cover 63. The end of the side wall 40b of the gear case 40 is inserted (fitted) between these two walls 81a, 81b. This forms a labyrinth portion 83 between the gear case 40 and the cover 63. The labyrinth portion 83 prevents dust and water from entering between the gear case 40 and the cover 63. The gear case 40 and the cover 63 are fixed by tightening bolts (not shown).

<Operation of a motor with a reducer>
Next, the operation of the geared motor 1 will be described.
In the motor 1 with a speed reducer, power is supplied to the controller board 62 via the connector 11, and is selectively supplied to each coil 24 of the electric motor 2 via a power module (not shown). Then, a predetermined interlinkage magnetic flux is formed in the stator 8 (teeth portion 22), and a magnetic attraction force or a repulsion force is generated between this interlinkage magnetic flux and an effective magnetic flux formed by the permanent magnets 33 of the rotor 9.

Here, the rotor 9 is a so-called SPM (Surface Permanent Magnet) type rotor in which permanent magnets 33 are arranged on the outer circumferential surface 32a of the rotor core 32. For this reason, the inductance value in the d-axis direction is small.
In addition, the rotor 9 is provided with salient pole portions 35 between the circumferentially adjacent permanent magnets 33. Therefore, the interlinkage magnetic flux J of the stator 8 flows through the salient pole portions 35.

This flux linkage J flows in the circumferential direction from one salient pole portion 35 to the adjacent salient pole portion 35 via the shaft fixing portion 37. As a result, the inductance value in the q-axis direction due to the flux linkage J1 of the stator 8 becomes larger compared to a case in which the salient pole portion 35 is not present. In this manner, the rotor 9 is rotated also by utilizing the difference in reluctance torque between the d-axis direction and the q-axis direction. The reluctance torque rotates the rotor 9 so as to reduce the magnetic resistance (reluctance) of the magnetic path of the flux linkage J.
In this way, the rotor 9 rotates continuously due to the magnetic torque caused by the magnetic attractive and repulsive forces due to the permanent magnets 33 and the reluctance torque described above.

When the rotor 9 rotates, the worm shaft 44 that is integrated with the shaft 31 rotates, which in turn rotates the worm wheel 45 that is meshed with the worm shaft 44. The output shaft 48 that is connected to the worm wheel 45 then rotates, driving the desired electrical equipment (for example, a wiper drive device mounted on the vehicle).

The rotational position detection result of the worm wheel 45 detected by the magnetic detection element 61 mounted on the controller board 62 is output as a signal to an external device (not shown). The external device (not shown) controls the switching timing of the switching elements of the power module (not shown) based on the rotational position detection signal of the worm wheel 45, and controls the drive of the electric motor 2. The output of the drive signal of the power module and the drive control of the electric motor 2 may be performed by the controller unit 4.

<Function of the magnet holder>
Next, the operation of the magnet holder 70 will be described with reference to FIGS.
FIG. 8 is a diagram illustrating the operation of the magnet holder 70. As shown in FIG.
As described above, the rotor 9 has the overhang portion 33e, which increases the effective magnetic flux of the permanent magnet 33.
If no magnetic body is disposed on the inner circumferential surface 33a side of the overhang portion 33e, the magnetic flux on the inner circumferential surface 33a side will leak into the air and become leakage magnetic flux, which means that the magnetic flux of the overhang portion 33e cannot be effectively utilized.

In contrast, in this embodiment, the overhang portion 33e is provided with a magnet holder 70 formed by pressure molding soft magnetic powder. A cylindrical portion 72 of the magnet holder 70 is disposed on the inner circumferential surface 33a of the overhang portion 33e.
8, the cylindrical portion 72 functions as a magnetic path such that the magnetic flux on the inner circumferential surface 33a side of the overhanging portion 33e flows toward the rotor core 32 (see arrow J1 in FIG. 8). This allows the magnetic flux of the overhanging portion 33e to be effectively utilized, and the overall effective magnetic flux of the permanent magnet 33 can be increased.

Figure 9 is a graph showing the change in effective magnetic flux when the vertical axis represents the overall effective magnetic flux [μWb] of the permanent magnet 33 and the horizontal axis represents the protruding length [mm] of the overhang portion 33e from both end faces 32b, 32c of the rotor core 32 (hereinafter simply referred to as the protruding length of the overhang portion 33e), comparing the case with and without the cylindrical portion 72.
As shown in FIG. 9, when the cylindrical portion 72 is provided, as compared with the case where the cylindrical portion 72 is not provided, it can be seen that the overall effective magnetic flux of the permanent magnet 33 increases as the protruding length of the overhang portion 33e increases.

The magnet holder 70 also has an end wall 74. The end wall 74 has the role of limiting the axial displacement of the permanent magnet 33 and of bearing the load during the crimping operation of the crimping portion 71d of the magnet cover 71. On the other hand, the end wall 74 may allow magnetic flux from the outer peripheral surface 33b side of the overhang portion 33e to flow into it, forming a shortcut magnetic path at the end 33f of the overhang portion 33e (see arrow J2 in Figure 8).

However, the outer peripheral edge 74b of the end wall 74 and the end 73b of the leg 73 are located between the inner peripheral surface 33a of the overhang portion 33e and the central portion 33g. This prevents the formation of a shortcut magnetic path via the end wall 74 (indicated by an x in FIG. 8). As a result, the magnetic flux of the overhang portion 33e can be effectively utilized, and the overall effective magnetic flux of the permanent magnet 33 can be increased.

Figure 10 is a graph showing the change in effective magnetic flux when the vertical axis represents the overall effective magnetic flux [μWb] of the permanent magnet 33 and the horizontal axis represents the ratio (outer diameter ratio) of the outer diameter of the outermost circle Co to the outer diameter of the outer peripheral edge 74b of the end wall 74.
As shown in FIG. 10, when the outer peripheral edge 74b of the end wall 74 is located radially outward of the central portion 33g, it can be seen that the overall effective magnetic flux of the permanent magnet 33 is rapidly reduced.

Thus, in the above embodiment, the permanent magnet 33 has an overhang portion 33e that protrudes axially outward from both axial end faces 20a, 20b of the stator core 20. The cylindrical portion 72 of the magnet holder 70, which is a magnetic body, is provided on the inner peripheral surface 33a of the overhang portion 33e. Therefore, a magnetic path through which the magnetic flux of the overhang portion 33e flows to the rotor core 32 can be formed on the inner peripheral surface 33a side of the overhang portion 33e. Therefore, the magnetic flux leaking into the air at the overhang portion 33e can be reduced, and the magnetic flux of the overhang portion 33e can be effectively utilized. Therefore, the overall effective magnetic flux of the permanent magnet 33 can be increased, and the electric motor 2 can be efficiently made to have high torque.

The magnet holder 70 is made of a magnetic material to provide a magnetic body on the inner circumferential surface 33a of the overhang portion 33e. The end wall 74 of the magnet holder 70 abuts against the end 33f of the overhang portion 33e. In this way, the permanent magnet 33 can be positioned and fixed to the rotor core 32 by the magnet holder 70. In addition, there is no need to provide a separate magnetic body on the inner circumferential surface 33a of the overhang portion 33e, and the magnetic flux of the inner circumferential surface 33a of the overhang portion 33e can be reliably passed through the cylindrical portion 72 to the rotor core 32. The end wall 74 of the magnet holder 70 may abut against only one of the ends 33f of the overhang portion 33e, rather than against each end 33f, 33f of the overhang portion 33e.

The rotor core 32 is formed by stacking a plurality of steel plates 32p in the axial direction. The magnet holder 70 is formed by pressure molding soft magnetic powder. This makes it possible to easily form the magnet holder 70 while increasing the magnetic permeability of the rotor core 32.
An engagement claw 75 is formed on the cylindrical portion 72 of the magnet holder 70. The engagement claw 75 allows the magnet holder 70 to be positioned relative to the rotor core 32. An opening 77 is also formed in the end wall 74. This opening 77 is used to position the magnet holder 70 relative to a magnetizing device (not shown), for example, and as a result, the rotor 9 is positioned relative to the magnetizing device (not shown). With this configuration, the rotor 9 (permanent magnet 33) can be easily positioned relative to other devices such as the magnetizing device. This makes it easier to manufacture the rotor 9.

The outer peripheral edge 74b of the end wall 74 and the end 73b of the leg 73 in the magnet holder 70 are positioned between the inner peripheral surface 33a of the overhang portion 33e and the central portion 33g. This prevents the formation of a shortcut magnetic path in the overhang portion 33e via the end wall 74. As a result, the magnetic flux in the overhang portion 33e can be effectively utilized, and the overall effective magnetic flux of the permanent magnet 33 can be increased. This allows the electric motor 2 to efficiently produce high torque.

The present invention is not limited to the above-described embodiment, and includes various modifications to the above-described embodiment without departing from the spirit of the present invention.
For example, in the above embodiment, the reduction gear motor 1 is used as a drive source for a wiper device of a vehicle. However, the present invention is not limited to this, and the reduction gear motor 1 can be used for various purposes such as a drive source for electrical equipment (e.g., power windows, sunroofs, power seats, etc.) mounted on a vehicle other than the wiper device.

In the above embodiment, the rotor 9 configuration is used in the electric motor 2 as a rotating electric machine. However, this is not limited to this, and the rotor 9 configuration can be used in various rotating electric machines. For example, the rotor 9 configuration can be used in a generator instead of the electric motor 2.

In the above embodiment, the outer peripheral surface 33b of the permanent magnet 33 is formed in an arc shape with a smaller radius of curvature than the inner peripheral surface 33a. The outer peripheral surface 33b of the permanent magnet 33 is formed such that the center in the circumferential direction bulges outward in the radial direction to the greatest extent. However, this is not limited to the above, and the outer peripheral surface 33b of the permanent magnet 33 may be formed to follow a circle centered on the rotation axis Cr. The radius of curvature of the outer peripheral surface 33b of the permanent magnet 33 and the radius of curvature of the inner peripheral surface 33a may be the same. The radius of curvature of the inner peripheral surface 33a of the permanent magnet 33 may be smaller than the radius of curvature of the outer peripheral surface 33b.

When the radius of curvature of the inner peripheral surface 33a of the permanent magnet 33 is smaller than the radius of curvature of the outer peripheral surface 33b, the central portion 33g between the outermost circle Co (see FIG. 7) and the inner peripheral surface 33a is the center between the point on the inner peripheral surface 33a where the inner diameter is smallest and the outermost circle Co. This is because the end wall 74 of the magnet holder 70 is formed in a circular shape.

The shape of the outer peripheral edge 74b of the end wall 74 may be deformed in response to the shape of the inner peripheral surface 33a and the outer peripheral surface 33b of the permanent magnet 33. The position of the radially outer end 73b of the leg 73 may also be changed in response to the shape of the outer peripheral edge 74b of the end wall 74. By configuring in this way, the positions of the outer peripheral edge 74b of the end wall 74 and the radially outer end 73b of the leg 73 may be set to be between the inner peripheral surface 33a of the overhang portion 33e and the central portion 33g, regardless of the arc shape (radius of curvature) of the inner peripheral surface 33a of the permanent magnet 33 or the arc shape (radius of curvature) of the outer peripheral surface 33b.

In the above embodiment, the cylindrical portion 72 of the magnet holder 70 is disposed as the magnetic body on the inner peripheral surface 33a of the permanent magnet 33. However, this is not limited to the above, and it is sufficient if a magnetic body is disposed on the inner peripheral surface 33a of the permanent magnet 33. For example, the axial thickness of the rotor core 32 may be made thicker than the axial thickness of the stator core 20. In this way, the rotor core 32 may be disposed as the magnetic body on the inner peripheral surface 33a of the permanent magnet 33.

In the above embodiment, an opening 77 is formed in the outer peripheral edge 74b of the end wall 74 of the magnet holder 70. The opening 77 is used to position the rotor 9, for example, in a magnetizing device (not shown). However, this is not limited to the above, and it is sufficient if a positioning portion is formed in the end wall 74 for positioning with respect to another device. For example, a protrusion may be formed in the end wall 74 instead of the opening 77. The rotor 9 may be positioned with respect to another device using this protrusion.

FIG. 11 is an exploded perspective view of the rotor 9 in the modified example.
In the above embodiment, the rotor core 32 is formed by stacking a plurality of steel plates 32p in the axial direction. However, this is not limited to the above, and as shown in Fig. 11, the rotor core 32 may be formed by stacking rolled steel plates in the axial direction or by pressure molding soft magnetic powder. By configuring in this way, the rotor core 32 and the magnet holder 70 can be integrated. This reduces the number of parts of the rotor 9.

1...motor with reducer, 2...electric motor (rotating electric machine), 3...reduction section, 4...controller section, 5...motor case, 6...first motor case, 6a...opening, 7...second motor case, 7a...opening, 8...stator, 9...rotor, 10...bottom, 10a...through hole, 11...connector, 16...outer flange section, 17...outer flange section, 20...stator core, 20a...end face, 20b...end face, 20p...steel plate, 21...back yoke section, 22...teeth section, 23... Insulator, 24... coil, 31... shaft, 32... rotor core, 32a... outer circumferential surface, 32b... end surface, 32c... end surface, 32p... steel plate, 33... permanent magnet, 33a... inner circumferential surface, 33b... outer circumferential surface, 33c... inner side surface, 33d... outer side surface, 33e... overhang portion, 33f... end portion, 33g... central portion, 33p... central position, 35... salient pole portion, 35a... side surface, 35b... outer end portion, 36... magnet storage portion, 37... shaft fixing portion, 37a... outer circumferential surface, 37b... shaft through hole, 37c...groove, 40...gear case, 40a...opening, 40b...side wall, 40c...bottom wall, 41...worm reduction mechanism, 42...gear accommodating section, 43...opening, 44...worm shaft, 45...worm wheel, 46...bearing, 47...bearing, 48...output shaft, 48a...spline, 49...bearing boss, 52...rib, 56...controller accommodating section, 60...rotational position detection section, 61...magnetic detection element, 62...controller board, 63...cover, 70...magnet holder, 71...Magnet cover, 71a...Cylindrical part, 71b...Protruding part, 71c...Inner flange part, 71d...Crimped part, 72...Cylindrical part, 72a...Outer surface, 72b...End part, 73...Leg part, 73a...End part, 73b...End part, 74...End wall, 74a...Opening, 74b...Outer edge, 74c...Inner surface, 75...Engagement claw, 76...Recess, 77...Opening, 78...Reinforcing rib, 81...Fitting part, 81a...Wall, 81b...Wall, 83...Labyrinth part, 91...Groove part, Cr...Rotation axis, Co...Outermost circle

Claims (6)

A rotor that is rotatably provided around a rotation axis;
a stator surrounding the outer periphery of the rotor;
Equipped with
The stator has a stator core around which a coil is wound,
The rotor is
A shaft having the rotation axis as its axis;
a rotor core that is fitted and fixed to the shaft;
A permanent magnet disposed on an outer peripheral surface of the rotor core;
having
the permanent magnet has an overhang portion that protrudes outward from both end surfaces of the rotation axis of the stator core in the direction of the rotation axis,
A magnetic body is provided on an inner peripheral surface of the overhang portion in the radial direction.
A rotating electric machine characterized by: the magnetic body is a magnet holder that holds the permanent magnet,
The magnet holder includes:
a cylindrical portion that is disposed on the inner circumferential surface of the overhang portion and that is in contact with the rotor core;
an end wall extending radially outward from an end of the cylindrical portion opposite to the rotor core;
Equipped with
The end wall abuts against an end of the overhang portion in the direction of the rotation axis.
2. The rotating electric machine according to claim 1 . The rotor core is formed by laminating steel plates,
The magnet holder is formed by pressure molding soft magnetic powder.
3. The rotating electric machine according to claim 2. The magnet holder includes:
an engagement claw formed on the cylindrical portion and adapted to engage with the rotor core;
a positioning portion formed on the end wall for positioning the magnet holder relative to another device;
Equipped with
4. The rotating electric machine according to claim 2 or 3. The positioning portion is an opening formed in the end wall.
5. The rotating electric machine according to claim 4. When a circle passing through the outermost part in the radial direction of the outer peripheral surface of the overhang portion is defined as an outermost circle of the overhang portion, the circle being centered on the rotation axis, and the center between the outermost circle and the inner peripheral surface is defined as a center portion of the overhang portion,
The outer peripheral edge of the end wall is located between the inner peripheral surface of the overhang portion and the central portion.
3. The rotating electric machine according to claim 2.

Images