JPWO2019123952A1 - Rotor and motor - Google Patents

Abstract

The rotor is a rotor used in an inner rotor type motor, and includes a shaft centered on a central axis extending in the vertical direction, a rotor core fixed to the shaft, and a rotor magnet supported by the rotor core. The rotor core is provided with a central hole into which the shaft is press-fitted. The inner peripheral surface of the central hole is provided with a plurality of fitting convex portions that are arranged along the circumferential direction, project inward in the radial direction, and come into contact with the shaft at the tip surface. A groove extending along the axial direction and facing the tip surface in the radial direction is provided on the outer peripheral surface of the shaft.

Description

The present invention relates to a rotor and a motor.

In motors, rotors with shafts and rotor cores fixed to each other are known. As the fastening structure between the shaft and the rotor core, a structure fixed by key fitting, a structure fixed by press fitting, and the like are known. For example, Patent Document 1 discloses a structure in which a shaft and a rotor core are key-fitted.

Japanese Unexamined Patent Publication No. 2011-259689

When a fixed structure by key fitting is adopted, a gap is provided in the circumferential direction at the fitting portion between the shaft and the rotor core. Therefore, vibration may occur during high-speed rotation. Further, when a fixed structure in which the shaft is press-fitted into the rotor core is adopted, it is required to take measures against slipping between the shaft and the rotor core.

One aspect of the present invention is one aspect of the present invention, one of which is to provide a rotor capable of suppressing idling between a rotor core and a shaft.

The rotor according to one aspect of the present invention is a rotor used in an inner rotor type motor, and is supported by a shaft centered on a central axis extending in the vertical direction, a rotor core fixed to the shaft, and the rotor core. It is equipped with a rotor magnet. The rotor core is provided with a central hole into which the shaft is press-fitted. The inner peripheral surface of the central hole is provided with a plurality of fitting convex portions that are arranged along the circumferential direction, project inward in the radial direction, and come into contact with the shaft at the tip surface. The outer peripheral surface of the shaft is provided with a groove portion extending along the axial direction and facing the tip surface in the radial direction.

According to one aspect of the present invention, it is possible to provide a rotor capable of suppressing idling between the rotor core and the shaft.

FIG. 1 is a schematic cross-sectional view taken along the central axis of the motor of one embodiment. FIG. 2 is a plan view of the rotor core of one embodiment. FIG. 3 is a partial cross-sectional view of the rotor of one embodiment. FIG. 4 is an enlarged view of region IV of FIG. FIG. 5 is a plan view of the rotor core of the modified example.

Hereinafter, the rotor and the motor according to the embodiment of the present invention will be described with reference to the drawings. In the drawings below, the scale and number of each structure may differ from the actual structure in order to make each configuration easy to understand.

Each figure shows the Z axis as appropriate. The Z-axis direction of each figure is a direction parallel to the axial direction of the central axis J shown in FIG. Further, in the following description, the positive side (+ Z side) in the Z-axis direction is referred to as "upper side", and the negative side (-Z side) in the Z-axis direction is referred to as "lower side". The upper side and the lower side are directions used only for explanation, and do not limit the actual positional relationship or direction. Unless otherwise specified, the direction parallel to the central axis J (Z-axis direction) is simply referred to as "axial direction" or "vertical direction", and the radial direction centered on the central axis J is simply referred to as "radial direction". The circumferential direction centered on the central axis J, that is, the circumference of the central axis J is simply referred to as the "circumferential direction". Further, in the following description, the "planar view" means a state viewed from the axial direction.

<Motor>

FIG. 1 is a schematic cross-sectional view taken along the central axis J of the motor 1 of the embodiment. The motor 1 includes a rotor 3, a stator 10, a housing 2, a bearing holder 5, an upper bearing 6A, and a lower bearing 6B. The motor 1 of the present embodiment is an inner rotor type motor in which the rotor 3 is arranged inside the stator 10 in the radial direction.

The housing 2 has a tubular shape that opens upward. The housing 2 houses the rotor 3, the stator 10, and the bearing holder 5. The housing 2 has a tubular portion 2a and a bottom portion 2b. The tubular portion 2a surrounds the stator 10 from the outside in the radial direction. The bottom portion 2b is located at the lower end of the tubular portion 2a. A lower bearing holding portion 2c for holding the lower bearing 6B is provided at the center of the bottom portion 2b in a plan view.

The bearing holder 5 is located above the stator 10. The bearing holder 5 is held on the inner peripheral surface of the housing 2. The bearing holder 5 holds the upper bearing 6A in the upper bearing holding portion 5a.

The stator 10 is arranged in an annular shape around the central axis J. The stator 10 is located on the radial outer side of the rotor 3. The stator 10 faces the rotor 3 in the radial direction through a gap. The stator 10 is fixed to the inner peripheral surface of the housing 2. The stator 10 has an annular stator core 11, a pair of insulators 14 mounted on the stator core 11 from above and below, and a coil 13 mounted on the stator core 11 via the insulator 14.

<Rotor>

The rotor 3 is used for the inner rotor type motor 1. The rotor 3 rotates around a central axis J extending in the vertical direction. The rotor 3 has a shaft 90, a plurality of rotor cores 30, and a plurality of rotor magnets 3b. The shaft 90 extends in the vertical direction about a central axis J extending in the vertical direction (axial direction). The shaft 90 has a circular cross-sectional shape orthogonal to the central axis J. The shaft 90 is rotatably supported around the central axis J by the upper bearing 6A and the lower bearing 6B.

The rotor core 30 is fixed to the outer peripheral surface 90a of the shaft 90. The rotor 3 of the present embodiment is provided with two rotor cores (first rotor core 30A and second rotor core 30B) arranged along the axial direction. The first rotor core 30A and the second rotor core 30B have the same shape. In the present specification, when the first rotor core 30A and the second rotor core 30B are not distinguished, they are simply referred to as the rotor core 30.

Rotor magnets 3b are fixed to the outer peripheral surfaces of the first rotor core 30A and the second rotor core 30B, respectively. That is, the rotor magnet 3b is supported by the rotor core 30.

The first rotor core 30A and the second rotor core 30B are fixed to the shaft 90 in a state where the magnetic poles of the rotor magnet 3b are displaced in the circumferential direction. That is, the first rotor core 30A and the second rotor core 30B are arranged so as to be displaced from each other in the rotational direction at a predetermined skew angle. As a result, the cogging torque of the motor 1 can be reduced. In the present embodiment, the case where the rotor 3 has two rotor cores 30 is illustrated, but the rotor 3 may have three or more rotor cores arranged with a skew angle.

The rotor core 30 is formed by laminating a plurality of electromagnetic steel plates 39 along the axial direction. The plurality of electromagnetic steel sheets 39 have the same shape. Therefore, the shape of the rotor core 30 seen from the axial direction matches the shape seen from the axial direction of each of the electrical steel sheets 39.

FIG. 2 is a plan view of the rotor core 30 of one embodiment. The rotor core 30 extends in a uniform cross section along the axial direction. The outer shape of the rotor core 30 is substantially polygonal when viewed from the axial direction. In this embodiment, the rotor core 30 is octagonal when viewed from the axial direction. That is, the rotor core 30 of the present embodiment is an octagonal pillar.

The rotor core 30 has eight holding surfaces 30a facing outward in the radial direction. The eight holding surfaces 30a form an outer peripheral surface of the rotor core 30. The holding surfaces 30a are arranged along the circumferential direction. The holding surface 30a is a surface orthogonal to the radial direction. The rotor magnets 3b are fixed to the holding surface 30a via an adhesive or the like. Further, the rotor magnet 3b may be fixed by a tubular rotor cover. Therefore, the rotor 3 of the present embodiment is provided with eight rotor magnets 3b. The eight rotor magnets 3b are arranged so that the directions of the magnetic poles are alternately arranged along the circumferential direction. The number of holding surfaces 30a of the rotor core 30 and the number of rotor magnets 3b provided on the rotor 3 are examples, and are not limited to this embodiment.

The rotor core 30 is provided with a plurality of through holes 35. In the present embodiment, the rotor core 30 is provided with eight through holes 35. The through hole 35 penetrates in the axial direction. Further, the plurality of through holes 35 are arranged at equal intervals along the circumferential direction. The inside of the through hole 35 is hollow.

The rotor core 30 is provided with a central hole 31 located at the center in a plan view. The central hole 31 penetrates in the axial direction. The central hole 31 has a substantially circular shape centered on the central axis J. The shaft 90 is press-fitted into the central hole 31.

A plurality of fitting convex portions 32 are provided on the inner peripheral surface of the central hole 31. In the present embodiment, eight fitting convex portions 32 are provided on the inner peripheral surface of the central hole 31. The number of fitting protrusions 32 matches the number of rotor magnets 3b and the number of through holes 35. Further, one rotor magnet 3b is provided on the radial outer side of the one fitting convex portion 32. In the present specification, the "inner peripheral surface of the central hole" means a surface forming the central hole in the rotor core.

The plurality of fitting protrusions 32 are arranged at equal intervals along the circumferential direction. The fitting convex portion 32 projects inward in the radial direction. The fitting convex portion 32 has a tip surface 32a facing inward in the radial direction. The tip surface 32a has an arc shape centered on the central axis J and extends uniformly along the axial direction. The fitting convex portion 32 comes into contact with the shaft 90 on the tip surface 32a.

In the present embodiment, one through hole 35 is provided on the radial outer side of one fitting convex portion 32. As a result, when the shaft 90 is press-fitted into the central hole 31, the rotor core 30 is easily elastically deformed. As a result, the fitting convex portion 32 can be easily displaced outward in the radial direction. As a result, the stress generated when the shaft 90 is press-fitted into the rotor core 30 is reduced, and the assembly process can be facilitated. In addition, the elastic deformation of the rotor core 30 is promoted between the fitting convex portion 32 and the through hole 35, so that the pressure generated when the fitting convex portion 32 comes into contact with the tip surface 32a is stabilized. As a result, the holding of the shaft 90 in the central hole 31 can be stabilized.

According to this embodiment, the inside of the through hole 35 is a cavity. Therefore, as compared with the case where the inside of the through hole 35 is filled with a resin material or the like, the fitting convex portion 32 located inside the through hole 35 in the radial direction can be easily deformed. The inside of the through hole 35 may be filled with a resin material or the like that is more easily elastically deformed than the material constituting the rotor core 30. In such a case, the fitting convex portion 32 is likely to be deformed radially outward due to the difference in elastic modulus between the material constituting the rotor core 30 and the material filled in the through hole 35.

FIG. 3 is a partial cross-sectional view of the rotor 3. Further, FIG. 4 is an enlarged view of region IV of FIG. As shown in FIG. 3, a plurality of (four in the present embodiment) groove portions 91 are provided on the outer peripheral surface 90a of the shaft 90. The plurality of groove portions 91 are arranged at equal intervals along the circumferential direction. The groove 91 extends linearly along the axial direction. The groove portion 91 faces the tip surface 32a of the fitting convex portion 32 in the radial direction.

The eight fitting convex portions 32 include four first fitting convex portions 32A and four second fitting convex portions 32B. The first fitting convex portion 32A faces the groove portion 91 on the tip surface 32a. On the other hand, the second fitting convex portion 32B does not face the groove portion 91 on the tip surface 32a. That is, the second fitting convex portion 32B contacts the outer peripheral surface 90a of the shaft 90 over the entire area of the tip surface 32a. In the state before press fitting of the shaft 90, the first fitting convex portion 32A and the second fitting convex portion 32B have the same shape. That is, in the state before the shaft 90 is press-fitted, the first fitting convex portion 32A and the second fitting convex portion 32B have the same protrusion height and width dimension along the circumferential direction.

As shown in FIG. 4, the groove 91 has a V shape in which the width in the circumferential direction becomes narrower toward the inside in the radial direction. The groove 91 has a pair of side surfaces 91b and a bottom surface 91a. The pair of side surfaces 91b extend radially outward from the bottom surface 91a. The pair of side surfaces 91b extend in a direction away from each other toward the outer side in the radial direction. The bottom surface 91a faces outward in the radial direction. The bottom surface 91a smoothly connects the lower ends of the pair of side surfaces 91b. The cross-sectional shape of the groove 91 is not limited to this embodiment. For example, the cross-sectional shape of the groove 91 may be rectangular or arcuate.

The groove 91 can be formed, for example, by pressing a tool having a V-shaped tip against the outer peripheral surface 90a of the shaft 90 and moving it in the axial direction. As a result, the outer peripheral surface 90a of the shaft 90 pressed against the tool is plastically deformed to form a V-shaped groove 91. Further, when the groove portion 91 is formed through such a process, convex portions due to plastic deformation are formed on both sides of the groove portion 91 in the circumferential direction. Therefore, after forming the groove 91, it is preferable to polish the outer peripheral surface of the shaft 90 to remove the convex portions on both sides in the circumferential direction of the groove 91. The above-mentioned molding method of the groove portion 91 is an example. The groove 91 may be formed by another forming method such as cutting.

The tip surface 32a of the first fitting convex portion 32A facing the groove portion 91 is located on both sides of the deformed convex portion 32b in the circumferential direction, which is deformed by contact with the shaft 90 and penetrates into the groove portion 91. It has a pair of contact portions 32c. The tip surface 32a of the first fitting convex portion 32A comes into contact with the outer peripheral surface 90a of the shaft 90 at the contact portion 32c.

When the shaft 90 is press-fitted into the central hole 31, the fitting convex portion 32 elastically deforms outward in the radial direction. The tip surface 32a of the first fitting convex portion 32A is not stressed by the outer peripheral surface 90a of the shaft 90 in the region facing the groove portion 91. Therefore, in the tip surface 32a of the first fitting convex portion 32A, the region facing the groove portion 91 has a smaller rate of elastic deformation than the other regions. As a result, the deformed convex portion 32b is provided on the tip surface 32a of the first fitting convex portion 32A.

In addition, in FIG. 4, for the purpose of emphasizing the deformed convex portion 32b, the ratio of the radial dimension (height dimension) of the deformed convex portion 32b to the depth dimension of the groove portion 91 is made larger than the actual one. is there. In the present embodiment, the depth dimension of the groove 91 is, for example, 10% or less of the diameter of the shaft 90. On the other hand, the height dimension of the deformed convex portion is, for example, 1 μm or more and 30 μm or less.

Surface pressure is generated in the region (contact portion 32c) of the tip surface 32a of the first fitting convex portion 32A that comes into contact with the outer peripheral surface 90a of the shaft 90. On the other hand, no surface pressure is generated in the region (deformed convex portion 32b) of the tip surface 32a of the first fitting convex portion 32A that faces the groove portion 91. As described above, the groove 91 extends along the axial direction. According to the present embodiment, the tip surface 32a is provided with a boundary portion where the surface pressure changes extremely in a straight line along the axial direction. By providing the tip surface 32a with a boundary portion where the surface pressure changes extremely, the shaft 90 is deformed at the boundary portion, and the tip surface 32a of the first fitting convex portion 32A is relative to the outer peripheral surface 90a of the shaft 90. It is possible to suppress slipping, and the idling of the rotor core 30, the shaft, and 90 is suppressed.

Further, according to the present embodiment, the tip surface 32a of the first fitting convex portion 32A has a deformed convex portion 32b that penetrates into the groove portion 91. The deformed convex portion 32b comes into contact with the side surface 91b of the groove portion 91 at the root portion. The deformed convex portion 32b functions as an anchor when the first fitting convex portion 32A tries to move relative to the outer peripheral surface 90a of the shaft 90 in the circumferential direction. Therefore, it is possible to prevent the tip surface 32a of the first fitting convex portion 32A from slipping with respect to the outer peripheral surface 90a of the shaft 90, and the idling of the rotor core 30, the shaft and 90 is suppressed.

According to this embodiment, a gap is provided between the tip of the deformed convex portion 32b and the bottom surface 91a of the groove portion 91. Therefore, the tip surface 32a of the first fitting convex portion 32A can be sufficiently deformed inward in the radial direction to provide the deformed convex portion 32b.

According to the present embodiment, the rotor core 30 comes into contact with the outer peripheral surface 90a of the shaft 90 at the tip surface 32a of the fitting convex portion 32 provided on the inner peripheral surface of the central hole 31. Therefore, the surface pressure of the contact surface is higher than that in the case where the entire inner peripheral surface of the central hole 31 is in contact with the outer peripheral surface 90a of the shaft 90. As a result, a part of the tip surface 32a of the first fitting convex portion 32A facing the groove portion 91 easily penetrates into the groove portion 91 as the deformed convex portion 32b, and the rotor core 30 and the shaft 90 slip. Can be effectively suppressed.

In the present embodiment, it is preferable that the circumferential lengths d2 and d2 of the pair of contact portions 32c located on both sides of the deformed convex portion 32b in the circumferential direction are equal to each other. As a result, it is possible to effectively prevent the rotor core 30 from idling with respect to the shaft 90 regardless of the rotation direction of the shaft 90. Further, the circumferential length d1 of the deformed convex portion 32b is preferably shorter than the sum of the circumferential lengths d2 and d2 of the pair of contact portions 32c. When the sum of the circumferential lengths d2 and d2 of the pair of contact portions 32c is lengthened, the positioning accuracy of the rotor core 30 with respect to the shaft 90 is improved. That is, according to the present embodiment, it is possible to improve the positioning accuracy of the rotor core 30 while suppressing the rotor core 30 from idling with respect to the shaft 90. Further, the circumferential length d1 of the deformed convex portion 32b may be longer than the sum of the circumferential lengths d2 and d2 of the pair of contact portions 32c. In this case, the slip suppression effect of the deformed convex portion 32b can be enhanced.

As shown in FIG. 3, the first fitting convex portion 32A and the second fitting convex portion 32B are alternately arranged along the circumferential direction. As described above, the tip surface 32a of the first fitting convex portion 32A is deformed inward in the radial direction in the region facing the groove portion 91 to form the deformed convex portion 32b. Along with this, the tip surface 32a of the first fitting convex portion 32A is distorted in the arc shape in contact with the outer peripheral surface 90a of the shaft 90. Therefore, when the tip surfaces 32a of all the fitting convex portions 32 face the groove portions 91, the coaxiality between the shaft 90 and the rotor core 30 may decrease. However, according to the present embodiment, the fitting convex portion 32 includes a first fitting convex portion 32A facing the groove portion 91 on the tip surface 32a and a second fitting convex portion 32B not facing the groove portion 91. .. Therefore, in the first fitting convex portion 32A, the idling of the rotor core 30 and the shaft 90 can be suppressed, and in the second fitting convex portion 32B, the coaxiality between the rotor core 30 and the shaft 90 can be ensured. it can.

According to the present embodiment, the plurality of first fitting convex portions 32A are arranged at equal intervals in the circumferential direction. Therefore, the symmetry of the rotor core 30 can be maintained, and the variation in the coaxiality between the rotor core 30 and the shaft 90 can be effectively suppressed. Further, according to the present embodiment, the first fitting convex portion 32A and the second fitting convex portion 32B are alternately arranged in the circumferential direction. Therefore, the effect of suppressing the variation in the coaxiality between the rotor core 30 and the shaft 90 can be enhanced.

In this embodiment, the case where four groove portions 91 are provided on the outer peripheral surface 90a of the shaft 90 and one groove portion 91 faces one fitting convex portion 32 is illustrated. However, the relationship between the groove portion 91 and the fitting convex portion 32 is not limited to this embodiment. For example, the plurality of groove portions 91 may face one fitting convex portion 32 in the radial direction. Further, at least one groove portion 91 may be provided on the outer peripheral surface 90a of the shaft 90. That is, the plurality of fitting convex portions 32 may include at least one first fitting convex portion 32A facing the groove portion 91.

(Modification example)

FIG. 5 is a plan view of a modified rotor core 130 that can be used in the motor 1 of the above-described embodiment. In FIG. 5, the rotor magnet 103b fixed to the outer peripheral surface 130a of the rotor core 130 is illustrated by a chain double-dashed line. The components having the same aspects as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The rotor core 130 of the modified example extends in a uniform cross section along the axial direction. The rotor core 130 has a circular shape centered on the central axis J when viewed from the axial direction. That is, in the present embodiment, the rotor core 130 is cylindrical. The rotor core 130 has an outer peripheral surface 130a facing outward in the radial direction. The rotor magnet 103b is fixed to the outer peripheral surface 130a via an adhesive or the like. The rotor magnet 103b may be fixed by a tubular rotor cover.

The rotor magnet 103b of this modification is annular. Further, the rotor magnet 103b is magnetized with a plurality of N poles and S poles alternately arranged side by side along the circumferential direction. That is, the rotor magnet 103b is an annular shape in which magnetic poles are arranged along the circumferential direction. The north and south poles of the rotor magnet 103b may be magnetized in a spiral shape. By magnetizing in this way, the cogging torque of the motor can be reduced.

Although various embodiments of the present invention and modified examples thereof have been described above, the respective configurations and combinations thereof in the respective embodiments and the modified examples are examples, and are within the scope not deviating from the gist of the present invention. , Configuration can be added, omitted, replaced and other changes are possible. Moreover, the present invention is not limited to the embodiments.

Motors with rotors and rotors of the various embodiments and variants thereof described above are mounted on electric power steering devices. Further, these rotors and motors are not limited to the electric power steering device, and may be mounted on any device.

1 ... Motor, 3 ... Rotor, 3b, 103b ... Rotor magnet, 10 ... Stator, 30, 130 ... Rotor core, 31 ... Central hole, 32 ... Fitting convex part, 32A ... First fitting convex part, 32B ... First 2 fitting convex portion, 32a ... tip surface, 32b ... deformed convex portion, 35 ... through hole, 90 ... shaft, 90a ... outer peripheral surface, 91 ... groove portion, 91a ... bottom surface, J ... central axis

Claims (11)

A rotor used for inner rotor type motors.

A shaft centered on a central axis extending in the vertical direction,

The rotor core fixed to the shaft and

A rotor magnet supported by the rotor core is provided.

The rotor core is provided with a central hole into which the shaft is press-fitted.

The inner peripheral surface of the central hole is provided with a plurality of fitting convex portions that are arranged along the circumferential direction, project inward in the radial direction, and come into contact with the shaft at the tip surface.

A rotor having a groove extending along the axial direction and facing the tip surface in the radial direction on the outer peripheral surface of the shaft. The rotor according to claim 1, wherein the tip surface facing the groove has a deformed convex portion that is deformed by contact with the shaft and penetrates into the groove. The rotor according to claim 2, wherein a gap is provided between the bottom surface of the groove portion and the tip end of the deformed convex portion. The plurality of fitting protrusions

A first fitting convex portion facing the groove portion on the tip surface,

Includes a second fitting protrusion that contacts the outer peripheral surface of the shaft over the entire tip surface.

The plurality of first fitting protrusions are arranged at equal intervals in the circumferential direction.

The rotor according to any one of claims 1 to 3. The rotor according to claim 4, wherein the first fitting convex portion and the second fitting convex portion are alternately arranged in the circumferential direction. The rotor core has

Multiple through holes are provided that penetrate in the axial direction and line up along the circumferential direction.

Each of the through holes is located radially outward of one of the fitting protrusions.

The rotor according to any one of claims 1 to 5. The rotor according to claim 6, wherein the inside of the through hole is hollow. Equipped with a plurality of the rotor magnets

The number of the rotor magnets and the number of the fitting protrusions match.

The rotor according to any one of claims 1 to 7. The rotor according to any one of claims 1 to 7, wherein the rotor magnet is an annular shape in which magnetic poles are arranged along the circumferential direction. The rotor according to any one of claims 1 to 9, wherein the rotor magnet is fixed to an outer peripheral surface of the rotor core. The rotor according to any one of claims 1 to 10, and the rotor.

A motor having a stator located on the radial outer side of the rotor.

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