WO2019189313A1

WO2019189313A1 - Rotor, motor, and electric power steering device

Info

Publication number: WO2019189313A1
Application number: PCT/JP2019/013098
Authority: WO
Inventors: 児玉　光生; 明一円; 秀幸金城
Original assignee: 日本電産株式会社
Priority date: 2018-03-30
Filing date: 2019-03-27
Publication date: 2019-10-03
Also published as: JP7275436B2; CN111919361B; JPWO2019189313A1; CN111919361A

Abstract

In one embodiment of the rotor of the present invention, the rotor is provided with: a shaft having a center axis; a rotor core affixed to the shaft; and a magnet section provided on the radially outer surface of the rotor core. The rotor core has a plurality of recesses which are recessed radially inward from the radially outer surface of the rotor core and which radially face the magnet section. The plurality of recesses include a first recess and a second recess, which are arranged at different axial positions so as to be circumferentially offset from each other.

Description

Rotor, motor and electric power steering device

The present invention relates to a rotor, a motor, and an electric power steering device.

A configuration is known in which the rotor is skewed for the purpose of reducing the cogging torque. For example, International Publication No. 2011/114574 describes a configuration in which a continuous skew is applied to a ring magnet of a rotor.

International Publication No. 2011/114574

However, when the continuous skew as described above is applied, it is necessary to make the magnet of the ring magnet slanted, which may be troublesome. On the other hand, as in another example described in International Publication No. 2011/114574, a step skew may be applied to the rotor by dividing the magnet in the axial direction and shifting the magnetic pole in the circumferential direction. However, in this case, it is necessary to shift the plurality of magnets in the circumferential direction, which may be troublesome. As described above, when a skew is applied to the rotor, there is a case where labor for manufacturing the rotor increases.

In view of the above circumstances, an object of the present invention is to provide a rotor having a structure capable of reducing cogging torque and suppressing an increase in manufacturing effort. Another object is to provide a motor including such a rotor. Another object is to provide an electric power steering apparatus including such a motor.

One aspect of the rotor of the present invention includes a shaft having a central axis, a rotor core fixed to the shaft, and a magnet portion provided on a radially outer surface of the rotor core. The rotor core has a plurality of recesses that are recessed radially inward from the radially outer surface of the rotor core and that face the magnet portion in the radial direction. The plurality of recesses include, as the recesses, a first recess and a second recess that are arranged so as to be shifted in the circumferential direction at different positions in the axial direction.

One aspect of the motor of the present invention includes the above-described rotor and a stator facing the rotor with a gap in the radial direction.

One aspect of the electric power steering apparatus of the present invention includes the motor described above.

According to one aspect of the present invention, the cogging torque in the rotor can be reduced, and an increase in labor for manufacturing the rotor can be suppressed. Further, since the cogging torque in the rotor is reduced, vibration and noise of the motor and the electric power steering device can be suppressed.

FIG. 1 is a cross-sectional view showing the motor of the first embodiment. FIG. 2 is a perspective view showing a part of the rotor core of the first embodiment. FIG. 3 is a view showing a part of the rotor according to the first embodiment, and is a cross-sectional view taken along the line III-III in FIG. FIG. 4 is a graph showing an example of a cogging torque waveform in the motor of the first embodiment. FIG. 5 is a perspective view showing a part of a rotor core that is a modification of the first embodiment. FIG. 6 is a perspective view showing a part of the rotor core of the second embodiment. FIG. 7 is a cross-sectional view showing a part of the rotor of the second embodiment. FIG. 8 is a graph showing an example of a cogging torque waveform in the motor of the second embodiment. FIG. 9 is a graph showing an example of a motor torque waveform in the motor of the second embodiment. FIG. 10 is a schematic diagram showing a schematic configuration of the electric power steering apparatus of the present embodiment.

The Z-axis direction shown in each figure as appropriate is the vertical direction with the positive side on the top and the negative side on the bottom. A central axis J shown as appropriate in each drawing is an imaginary line extending in a direction parallel to the vertical direction. In the following description, the axial direction of the central axis J, that is, the direction parallel to the vertical direction is simply referred to as “axial direction”, and the radial direction around the central axis J is simply referred to as “radial direction”. The circumferential direction centered on is simply referred to as the “circumferential direction”. In each drawing, the circumferential direction is appropriately indicated by an arrow θ.

The side that proceeds counterclockwise when viewed from the upper side to the lower side in the circumferential direction, that is, the side that proceeds in the direction of the arrow θ is called “one side in the circumferential direction”. The side proceeding clockwise when viewed from the upper side to the lower side in the circumferential direction, that is, the side proceeding in the direction opposite to the direction of the arrow θ is referred to as “the other side in the circumferential direction”. In the present embodiment, the upper side corresponds to one side in the axial direction. The vertical direction, the upper side, and the lower side are simply names for explaining the relative positional relationship of each part, and the actual layout relationship is a layout relationship other than the layout relationship indicated by these names. May be.

<First Embodiment>
As shown in FIG. 1, the motor 10 of the present embodiment includes a rotor 20, a stator 30, a housing 11, a plurality of

bearings

15 and 16, and a bearing holder 40. The rotor 20 includes a shaft 21 having a central axis J, a rotor core 22, and a plurality of magnet portions 23.

The shaft 21 extends in the vertical direction along the central axis J. In the example of the present embodiment, the shaft 21 has a cylindrical shape extending in the axial direction. The shaft 21 is supported by a plurality of

bearings

15 and 16 so as to be rotatable around the central axis J. The plurality of

bearings

15, 16 are arranged at intervals in the axial direction and are supported by the housing 11. The bearing 15 is held by the bearing holder 40 and supported by the housing 11 through the bearing holder 40. The housing 11 is cylindrical.

The shaft 21 is fixed to the rotor core 22 by press-fitting or bonding. That is, the rotor core 22 is fixed to the shaft 21. The shaft 21 may be fixed to the rotor core 22 via a resin member or the like. That is, the shaft 21 is fixed directly or indirectly to the rotor core 22. The shaft 21 is not limited to the cylindrical shape, and may be a cylindrical shape, for example.

The rotor core 22 is a magnetic member. The rotor core 22 is, for example, a laminated steel plate configured by laminating a plurality of electromagnetic steel plates in the axial direction. The rotor core 22 is cylindrical. As shown in FIGS. 2 and 3, the rotor core 22 has a polygonal outer shape when viewed from the axial direction. The radially outer surface of the rotor core 22 has a plurality of flat portions 22a arranged in the circumferential direction. Although illustration is omitted, in the example of this embodiment, the outer shape of the rotor core 22 is an octagonal shape. The outer surface in the radial direction of the rotor core 22 has eight flat portions 22a arranged in the circumferential direction. The planar portion 22a has a planar shape extending in a direction perpendicular to the radial direction. The flat portion 22 a extends in the axial direction on the radially outer surface of the rotor core 22. The flat portion 22 a is disposed on the radially outer surface of the rotor core 22 over the entire axial direction. In the example of the present embodiment, the axial length of the planar portion 22a is larger than the circumferential length of the planar portion 22a. The flat portion 22a has a rectangular shape when viewed from the outside in the radial direction.

The rotor core 22 has a through hole 22h, a hole 22b, and a groove 22c. When viewed from the axial direction, the through hole 22 h is disposed at the center of the rotor core 22. The through hole 22h penetrates the rotor core 22 in the axial direction. As shown in FIG. 1, the shaft 21 is inserted into the through hole 22h.

The hole 22b penetrates the rotor core 22 in the axial direction. As shown in FIGS. 2 and 3, a plurality of holes 22 b are arranged in the rotor core 22 at intervals in the circumferential direction. Although illustration is omitted, in the example of this embodiment, the holes 22b are arranged in the rotor core 22 at equal intervals in the circumferential direction. The plurality of hole portions 22b are respectively located on the inner side in the radial direction of each plane portion 22a. When viewed from the axial direction, the hole 22b has a circular shape. According to this embodiment, the rotor core 22 is thinned by the hole 22b, and the weight of the rotor core 22 and the material cost can be reduced.

The groove 22c is recessed from the radially outer surface of the rotor core 22 radially inward and extends in the axial direction. The groove portion 22c is disposed on the radially outer surface of the rotor core 22 over the entire length in the axial direction. The groove portion 22c is disposed between a pair of planar portions 22a adjacent to each other in the circumferential direction on the radially outer surface of the rotor core 22 and opens radially outward. A plurality of the groove portions 22c are arranged in the rotor core 22 at intervals in the circumferential direction. Although illustration is omitted, the groove portions 22 c are arranged in the rotor core 22 at equal intervals in the circumferential direction. The groove portion 22c has a groove width that decreases as it extends radially outward. When viewed from the axial direction, the groove 22c has a wedge shape.

The rotor core 22 further has a plurality of recesses 24. The plurality of recesses 24 are recessed radially inward from the radially outer surface of the rotor core 22. In the present embodiment, the plurality of recesses 24 are recessed radially inward from the planar portion 22a. As shown in FIG. 3, the plurality of recesses 24 face the magnet part 23 in the radial direction. In the present embodiment, the plurality of recesses 24 include a first recess 24 a, a second recess 24 b, and a third recess 24 c as the recesses 24.

As shown in FIG. 2, a plurality of first recesses 24a, second recesses 24b, and third recesses 24c are provided along the circumferential direction. The 1st recessed part 24a, the 2nd recessed part 24b, and the 3rd recessed part 24c are provided for every plane part 22a, respectively. That is, in the present embodiment, eight first recesses 24a, second recesses 24b, and third recesses 24c are provided. The first recess 24a, the second recess 24b, and the third recess 24c have a rectangular shape when viewed from the outside in the radial direction.

1st recessed part 24a, 2nd recessed part 24b, and 3rd recessed part 24c are mutually shifted | deviated to the circumferential direction in the position where an axial direction differs. The 1st recessed part 24a is located in the edge part of the circumferential direction other side among the lower parts of the plane part 22a. The first recess 24 a opens on the lower surface of the rotor core 22.

The second recess 24b is located above the first recess 24a and on one side in the circumferential direction from the first recess 24a. The 2nd recessed part 24b is located in the center part of the circumferential direction among the center parts of the axial direction of the plane part 22a. The end portion on the other circumferential side of the second recess 24b is located at substantially the same position in the circumferential direction as the end portion on the one circumferential side of the first recess 24a. The lower end of the second recess 24b is located at substantially the same position in the axial direction as the upper end of the first recess 24a.

The third recess 24c is located on the upper side of the second recess 24b and on the one side in the circumferential direction of the second recess 24b. The 3rd recessed part 24c is located in the edge part of the circumferential direction one side among the upper part of the plane part 22a. The third recess 24 c opens on the upper surface of the rotor core 22. The end portion on the other circumferential side of the third recess 24c is located at substantially the same position in the circumferential direction as the end portion on the one circumferential side of the second recess 24b. The lower end of the third recess 24c is located at substantially the same position in the axial direction as the upper end of the second recess 24b.

In the present embodiment, the first concave portion 24a, the second concave portion 24b, and the third concave portion 24c are arranged along the diagonal line of the rectangular planar portion 22a in each planar portion 22a. The 1st recessed part 24a and the 3rd recessed part 24c are arrange | positioned at the corner | angular part of the plane part 22a. When viewed from the outside in the radial direction, the first concave portion 24a and the third concave portion 24c are arranged at positions that are point-symmetric about the second concave portion 24b. In the present embodiment, the shape of the first recess 24a and the shape of the third recess 24c are the same.

In this embodiment, the circumferential dimension of the second recess 24b is larger than the circumferential dimension of the first recess 24a and the circumferential dimension of the third recess 24c. In the present embodiment, the axial dimension of the first recess 24a, the axial dimension of the second recess 24b, and the axial dimension of the third recess 24c are the same. The interior of the first recess 24a, the interior of the second recess 24b, and the interior of the third recess 24c are separated from each other.

As shown in FIG. 3, the concave portion 24 is filled with an adhesive 28. The adhesive 28 contacts the bottom surface of the recess 24 and the radially inner side surface of the magnet portion 23 to fix the rotor core 22 and the magnet portion 23. Thereby, the fixing strength of the magnet part 23 with respect to the rotor core 22 can be improved.

As shown in FIG. 2, a portion of the rotor core 22 that has the same axial position as the first recess 24a is referred to as a first portion 27a. A portion of the rotor core 22 that has the same axial position as the second recess 24b is referred to as a second portion 27b. A portion of the rotor core 22 having the same axial position as the third recess 24c is referred to as a third portion 27c. The first portion 27a, the second portion 27b, and the third portion 27c are arranged in this order from the lower side to the upper side. Arranged side by side. The first portion 27 a is a lower portion of the rotor core 22. The second portion 27 b is a central portion in the axial direction of the rotor core 22. The third portion 27 c is an upper portion of the rotor core 22.

In this embodiment, the magnet part 23 is a permanent magnet, for example. As shown in FIGS. 1 and 3, the magnet portion 23 has a columnar shape extending in the axial direction. As shown in FIG. 3, the cross-sectional shape orthogonal to the axial direction of the magnet part 23 is a substantially square shape long in the circumferential direction. The radially inner surface of the magnet part 23 is a flat surface orthogonal to the radial direction. The radially outer surface of the magnet part 23 is a curved surface that is convex outward in the radial direction when viewed from the axial direction.

The magnet part 23 is provided on the radially outer surface of the rotor core 22. In this embodiment, the magnet part 23 is provided for every plane part 22a. That is, in the present embodiment, for example, eight magnet portions 23 are provided. Although illustration is omitted, the plurality of magnet parts 23 are arranged at equal intervals over the entire circumference in the circumferential direction. Each magnet portion 23 provided for each flat portion 22a is a single separate member.

Each of the magnet parts 23 is fixed such that the radially inner side surface is in contact with the flat part 22a. The circumferential dimension on the radially inner side surface of the magnet part 23 is smaller than the circumferential dimension of the flat part 22a. As shown in FIG. 1, the axial dimension of the magnet part 23 is the same as the axial dimension of the plane part 22a.

Each magnet part 23 opposes the some recessed part 24 provided for every plane part 22a in radial direction. In this embodiment, each magnet part 23 opposes the 1st recessed part 24a, the 2nd recessed part 24b, and the 3rd recessed part 24c which were each provided in each plane part 22a in radial direction. The radially inner side surface of the magnet part 23 closes the radially outer opening of each recess 24.

FIG. 4 is a graph showing an example of the waveform of the cogging torque CT in the motor 10 of the present embodiment. In FIG. 4, the horizontal axis indicates the circumferential rotation angle φ, and the vertical axis indicates the cogging torque CT. 4, the cogging torque CT1 generated in the first portion 27a, the cogging torque CT2 generated in the second portion 27b, the cogging torque CT3 generated in the third portion 27c, and the cogging torque CTta generated in the entire rotor 20 are shown. . The cogging torque CTta generated in the entire rotor 20 is a value obtained by adding the cogging torque CT1, the cogging torque CT2, and the cogging torque CT3.

As shown in FIG. 4, the cogging torques CT1, CT2 and CT3 generated in each part are out of phase with each other. This is considered to be because the concave portions 24 that are shifted in the circumferential direction are provided in the respective portions. Specifically, in the first portion 27a, a first recess 24a is provided on the other circumferential side. Therefore, the circumferential center of the magnetic flux density distribution in the magnetic flux that exits radially outward from the magnet portion 23 or the magnetic flux that enters the magnet portion 23 from the radially outer side is shifted to one side in the circumferential direction from the circumferential center of the flat portion 22a. In the following description, “the magnetic flux density distribution in the magnetic flux that exits radially outward from the magnet portion 23 or the magnetic flux that enters the magnet portion 23 from the radially outer side” is simply referred to as “magnetic flux density distribution”.

In the second portion 27b, a second recess 24b is provided at the center in the circumferential direction of the flat portion 22a. Therefore, the circumferential center of the magnetic flux density distribution coincides with the circumferential center of the flat portion 22a. In the 3rd part 27c, the 3rd recessed part 24c is provided in the circumferential direction one side. Therefore, the circumferential center of the magnetic flux density distribution is shifted to the other circumferential side from the circumferential center of the flat portion 22a. Thereby, in each part of the 1st part 27a, the 2nd part 27b, and the 3rd part 27c from which an axial direction position mutually differs, the circumferential direction center of magnetic flux density distribution is mutually shifted | deviated and arrange | positioned in the circumferential direction. Therefore, the phases of the cogging torque CT generated in each portion are offset from each other and cancel each other, and the cogging torque CTta generated in the entire rotor 20 can be reduced.

As described above, according to the present embodiment, the plurality of recesses 24 that are shifted from each other in the circumferential direction at different positions in the axial direction are provided on the radially outer surface of the rotor core 22, thereby generating the entire rotor 20. The cogging torque CTta can be reduced. Therefore, there is no need to skew the rotor 20. Therefore, the cogging torque CTta generated in the entire rotor 20 can be reduced, and an increase in labor for manufacturing the rotor 20 can be suppressed.

Moreover, according to this embodiment, the magnet part 23 and each recessed part 24 are provided for every plane part 22a. Therefore, the cogging torque CT can be reduced in each plane portion 22a, and the cogging torque CTta generated in the entire rotor 20 can be further reduced.

Moreover, according to this embodiment, the magnet part 23 provided for every plane part 22a is a single member, respectively, and opposes the some recessed part 24 provided for every plane part 22a in radial direction. Therefore, the number of the magnet parts 23 can be reduced compared with the case where the magnet parts 23 are divided in the axial direction and skewed. Thereby, it can suppress that the number of parts of the rotor 20 increases, and can suppress further that the effort which manufactures the rotor 20 increases.

Thus, in this embodiment, since the cogging torque CT can be reduced by providing the recess 24, it is not necessary to divide the magnet part 23, and it is not necessary to make the magnet part 23 magnetized obliquely. Therefore, it is possible to easily manufacture the magnet part 23 and attach the magnet part 23 to the rotor core 22.

Further, according to the present embodiment, the first concave portion 24a, the second concave portion 24b, and the third concave portion 24c whose circumferential positions are sequentially shifted from the other circumferential side to the one circumferential side are provided as the concave portion 24. Therefore, the center in the circumferential direction of the magnetic flux density distribution can be gradually changed along the axial direction, and the cogging torque CTta can be more preferably reduced.

In the central portion in the axial direction of the flat portion 22a, the magnetic flux density of the magnetic flux passing through the portions on both sides in the circumferential direction of the second concave portion 24b is larger than the magnetic flux density of the magnetic flux passing through the second concave portion 24b. And the part of the circumferential direction both sides of the 2nd recessed part 24b is connected with the part of the circumferential direction one side of the 1st recessed part 24a, and the part of the circumferential direction other side of the 3rd recessed part 24c, respectively. For this reason, the magnetic flux density passing through the portion on one side in the circumferential direction of the second recess 24b can easily bring the magnetic flux density distribution in the portion on one side in the circumferential direction of the first recess 24a toward the one side in the circumferential direction. Further, the magnetic flux density passing through the other circumferential portion of the second recess 24b tends to bring the magnetic flux density distribution in the other circumferential portion of the third recess 24c toward the other circumferential side. Thereby, in the 1st part 27a and the 3rd part 27c, the circumferential direction center of magnetic flux density distribution can be suitably shifted in the circumferential direction. Therefore, the phase of the cogging torque CT in each part can be suitably shifted, and the cogging torque CTta of the entire rotor 20 can be further reduced.

According to this embodiment, when viewed from the outside in the radial direction, the first recess 24a and the third recess 24c are arranged at positions that are symmetric with respect to the second recess 24b. Therefore, it is easy to shift the circumferential center of the magnetic flux density distribution in the first portion 27a, the second portion 27b, and the third portion 27c at equal intervals in the circumferential direction. Thereby, cogging torque CTta can be reduced more suitably. It is easy to make the shape of the first portion 27a and the shape of the third portion 27c symmetrical to each other in the axial direction. Therefore, when making the rotor core 22 by laminating the electromagnetic steel plates, the first portion 27a and the third portion 27c can be made by inverting and using the same shape of the electromagnetic steel plates in the axial direction. Therefore, the cost for producing the rotor core 22 can be reduced.

According to this embodiment, the circumferential dimension of the second recess 24b is larger than the circumferential dimension of the first recess 24a and the circumferential dimension of the third recess 24c. Therefore, in the flat portion 22a of the second portion 27b, the portions on both sides in the circumferential direction of the second recess 24b can be arranged further apart in the circumferential direction. Thereby, the magnetic flux density distribution in the part of the circumferential direction one side of the 1st recessed part 24a can be more easily brought to the circumferential direction one side with the magnetic flux which passes through the part of the circumferential direction one side of the 2nd recessed part 24b. The magnetic flux density passing through the other circumferential part of the second recess 24b makes it easier to bring the magnetic flux density distribution in the other circumferential part of the third recess 24c closer to the other circumferential side. Thereby, in the 1st part 27a and the 3rd part 27c, the circumferential direction center of magnetic flux density distribution can be shifted to the circumferential direction more suitably. Therefore, the cogging torque CTta of the entire rotor 20 can be further reduced.

As shown in FIG. 3, the rotor 20 further includes a resin mold portion 26. The resin mold part 26 covers at least a part of the rotor core 22 and at least a part of the magnet part 23. The resin mold part 26 is located at least partially between the magnet parts 23 adjacent in the circumferential direction. The resin mold part 26 is made by insert molding using the rotor core 22 and the magnet part 23 as insert members.

The resin mold part 26 has the anchor part 26a and the movement suppression part 26b. The anchor part 26a is a part provided in each groove part 22c. The anchor part 26a is made by filling the melted resin into the groove part 22c and solidifying it. The anchor part 26a extends in the axial direction. The circumferential width of the anchor portion 26a increases as it goes inward in the radial direction.

The movement restraining part 26b is located radially outside the anchor part 26a and is connected to the anchor part 26a. The movement restraining part 26 b is disposed at the radially outer end of the resin mold part 26. The movement suppressing part 26b protrudes toward both sides in the circumferential direction with respect to the anchor part 26a. The movement restraining part 26b has a plate shape whose plate surface faces the radial direction. The movement suppression unit 26b extends in the axial direction. The movement suppressing part 26b is arranged on the outer side in the radial direction of the flat part 22a with a space between the flat part 22a. When viewed from the radial direction, the movement restraining portion 26b and the flat portion 22a are disposed so as to overlap each other. The movement restraining part 26 b contacts the radially outer surface of the magnet part 23.

According to the present embodiment, the wedge-shaped groove portion 22 c is provided on the radially outer surface of the rotor core 22. Thereby, the anchor part 26a can be hooked to the groove part 22c in the radial direction. Therefore, the resin mold portion 26 can be prevented from coming out radially outward with respect to the rotor core 22. And the magnet part 23 can be hold | suppressed from the radial direction outer side by the movement suppression part 26b. Therefore, the resin mold part 26 can prevent the magnet part 23 from being detached from the rotor core 22.

As shown in FIG. 1, the stator 30 has a stator core 31, an insulator 30Z, and a plurality of coils 30C. The stator core 31 has an annular shape centered on the central axis J. The stator core 31 surrounds the rotor 20 on the radially outer side of the rotor 20. The stator core 31 faces the rotor 20 with a gap in the radial direction. That is, the stator 30 faces the rotor 20 with a gap in the radial direction. The stator core 31 is, for example, a laminated steel plate configured by laminating a plurality of electromagnetic steel plates in the axial direction.

The stator core 31 has a substantially annular core back 31a and a plurality of teeth 31b. Although illustration is omitted, in the present embodiment, the core back 31a has an annular shape centered on the central axis J. The teeth 31b extend radially inward from the radially inner side surface of the core back 31a. The outer peripheral surface of the core back 31 a is fixed to the inner peripheral surface of the peripheral wall portion of the housing 11. The plurality of teeth 31b are arranged on the radially inner side surface of the core back 31a at intervals in the circumferential direction. Although illustration is omitted, in the present embodiment, the plurality of teeth 31b are arranged at equal intervals in the circumferential direction.

The insulator 30Z is attached to the stator core 31. Insulator 30Z has a part which covers teeth 31b. The material of the insulator 30Z is an insulating material such as a resin. The coil 30 </ b> C is attached to the stator core 31. The plurality of coils 30C are attached to the stator core 31 via the insulator 30Z. The plurality of coils 30 </ b> C are configured by winding a conductive wire around each tooth 31 b via the insulator 30 </ b> Z.

(Modification of the first embodiment)
As shown in FIG. 5, in the rotor core 122 of this modification, the shape of the first recess 124a and the shape of the third recess 124c are the same as the shape of the second recess 24b. That is, the shape of the plurality of recesses 124 is the same as each other. According to this configuration, the plurality of recesses 124 can be easily manufactured. In the rotor core 122, the recesses 124 that are displaced in the circumferential direction have the same circumferential position. A portion on one side in the circumferential direction of the first recess 124a and a portion on the other side in the circumferential direction of the second recess 24b overlap each other when viewed in the axial direction. The portion on the one circumferential side of the second recess 24b and the portion on the other circumferential side of the third recess 124c overlap each other when viewed from the axial direction. In the rotor core 122, the interior of the first recess 124a and the interior of the second recess 24b are connected to each other. The inside of the second recess 24b and the inside of the third recess 124c are connected to each other. According to this configuration, it is easy to increase the circumferential dimension of each recess 124. Therefore, it is easier to shift the circumferential center of the magnetic flux density distribution in the circumferential direction.

Second Embodiment
As shown in FIG. 6, the rotor core 222 of this embodiment differs in the shape and arrangement | positioning of the recessed part 224 with respect to 1st Embodiment. The rotor core 222 has a first portion 227a and a second portion 227b. The first portion 227 a is a lower portion of the rotor core 222. The second portion 227 b is an upper portion of the rotor core 222. The second part 227b is located above the first part 227a. In the present embodiment, the rotor core 222 includes only the first portion 227a and the second portion 227b. The first portion 227a and the second portion 227b have the same shape and the same dimension in the axial direction, and are stacked with a 45 ° shift in the circumferential direction. Therefore, according to this embodiment, each of the 1st part 227a and the 2nd part 227b can be made by laminating | stacking the same number of electromagnetic steel plates of the same shape. Thereby, the electromagnetic steel plate which comprises the rotor core 222 can be made into 1 type, and the effort and cost which manufacture the rotor core 222 can be reduced.

In the present embodiment, each planar portion 222a is configured by connecting the radially outer surface of the first portion 227a and the radially outer surface of the second portion 227b in the axial direction. In the example of the present embodiment, the length in the axial direction of the plane portion 222a is smaller than the length in the circumferential direction of the plane portion 222a. In the present embodiment, each flat surface portion 222a is provided with only one of the first recess 224a and the second recess 224b. That is, in the present embodiment, the plurality of planar portions 222a include, as the planar portions 222a, a first planar portion 222d provided with the first recess 224a and a second planar portion 222e provided with the second recess 224b. . The first flat surface portions 222d and the second flat surface portions 222e are provided alternately along the circumferential direction.

1st recessed part 224a is provided in the radial direction outer surface of 1st part 227a among the 1st plane parts 222d. The 2nd recessed part 224b is provided in the radial direction outer surface of the 2nd part 227b among the 2nd plane parts 222e. As a result, a plurality of first recesses 224a are provided on the radially outer surface of the first portion 227a at intervals from one another along the circumferential direction. A plurality of the second recesses 224b are provided on the radially outer surface of the second portion 227b at intervals from one another along the circumferential direction. The first recesses 224a and the second recesses 224b are alternately provided along the circumferential direction when viewed from the axial direction. That is, when the plurality of recesses 224 are viewed from the axial direction, the recesses 224 adjacent to both sides in the circumferential direction of the first recesses 224a are the second recesses 224b, and the recesses 224 that engage with both sides in the circumferential direction of the second recesses 224b are the first One recess 224a.

Each of the 1st recessed part 224a and the 2nd recessed part 224b is a rectangular shape long in the circumferential direction seeing from the radial direction outer side. The first recess 224a opens downward. In this embodiment, the 1st recessed part 224a is provided in the whole surface except the edge part of the circumferential direction both sides among the 1st plane parts 222d in the 1st part 227a. As shown in FIG. 7, the circumferential dimension of the first recess 224a is substantially the same as the circumferential dimension of the magnet part 23 provided on the first flat surface part 222d. In the present embodiment, the dimension in the circumferential direction of the first recess 224a is slightly smaller than the dimension in the circumferential direction of the magnet part 23 provided on the first flat surface part 222d. The dimension of the first recess 224a in the radial direction is uniform over the entire first recess 224a.

The second recess 224b opens upward. As shown in FIG. 6, in the present embodiment, the second recess 224 b is provided on the entire surface of the second flat portion 222 e in the second portion 227 b except for the edges on both sides in the circumferential direction. As shown in FIG. 7, the circumferential dimension of the second recess 224b is substantially the same as the circumferential dimension of the magnet part 23 provided on the second flat surface part 222e. In the present embodiment, the dimension in the circumferential direction of the second recess 224b is slightly smaller than the dimension in the circumferential direction of the magnet part 23 provided on the second plane part 222e. The dimension in the radial direction of the second recess 224b is uniform over the entire second recess 224b.

The circumferential dimension of the first recess 224a and the circumferential dimension of the second recess 224b are the same. The radial dimension of the first recess 224a and the radial dimension of the second recess 224b are the same. As shown in FIG. 6, the axial dimension of the first recess 224a and the axial dimension of the second recess 224b are the same. The upper end of the first recess 224a and the lower end of the second recess 224b are located at the same position in the axial direction. As shown in FIG. 7, in the present embodiment, the inside of the second recess 224b is a gap. Although illustration is omitted, the inside of the first recess 224a is also a gap.

FIG. 8 is a graph showing an example of the waveform of the cogging torque CT in the motor of the present embodiment. In FIG. 8, the horizontal axis represents the circumferential rotation angle φ, and the vertical axis represents the cogging torque CT. FIG. 8 shows the cogging torque CT4 generated in the first portion 227a, the cogging torque CT5 generated in the second portion 227b, and the cogging torque CTtb generated in the entire rotor 220. The cogging torque CTtb generated in the entire rotor 220 is a value obtained by adding the cogging torque CT4 and the cogging torque CT5.

FIG. 9 is a graph showing an example of a waveform of the motor torque MT in the motor of the present embodiment. In FIG. 9, the horizontal axis indicates the circumferential rotation angle φ, and the vertical axis indicates the motor torque MT. FIG. 9 shows motor torque MT4 generated in the first portion 227a, motor torque MT5 generated in the second portion 227b, and motor torque MTt generated in the entire rotor 220. Motor torque MTt generated in the entire rotor 220 corresponds to an average value of motor torque MT4 and motor torque MT5 for each rotation angle φ.

As shown in FIG. 8, the cogging torques CT4 and CT5 generated in each part are out of phase with each other. This is presumably because, as in the first embodiment, each portion is provided with a recess 224 that is shifted in the circumferential direction. As a result, the phases of the cogging torque CT generated in each portion are offset from each other and cancel each other, and the cogging torque CTtb generated in the entire rotor 220 can be reduced. Therefore, there is no need to skew the rotor 220. Therefore, the cogging torque CTtb generated in the entire rotor 220 can be reduced, and an increase in labor for manufacturing the rotor 220 can be suppressed.

According to the present embodiment, the first recesses 224a and the second recesses 224b provided at mutually different axial positions are alternately provided along the circumferential direction when viewed from the axial direction. For this reason, the phase of the cogging torque CT4 and the phase of the cogging torque CT5 are likely to be opposite in phase by a half cycle. As a result, the cogging torque CT4 and the cogging torque CT5 are easily offset appropriately, and the cogging torque CTtb generated in the entire rotor 220 can be more suitably reduced.

According to this embodiment, the first flat surface portions 222d provided with the first concave portions 224a and the second flat surface portions 222e provided with the second concave portions 224b are alternately provided along the circumferential direction. The first recess 224a is provided in the first flat portion 222d of the first portion 227a, and the second recess 224b is provided in the second flat portion 222e of the second portion 227b. Therefore, in the 1st part 227a, the part in which the 1st recessed part 224a was provided, and the part in which the recessed part 224 is not provided are provided alternately along the circumferential direction. Here, the magnetic flux is less likely to pass through the first recess 224a than the rotor core 222, which is a magnetic member. Therefore, in the first flat portion 222d where the first concave portion 224a is provided in the first portion 227a, the gap between the magnet portion 23 and the stator 30 is larger than in the second flat portion 222e where the concave portion 224 is not provided in the first portion 227a. Less magnetic flux passes through. Thereby, in the 1st part 227a, the magnetic flux which passes between the magnet part 23 and the stator 30 increases / decreases for every plane part 222a and the magnet part 23 along the circumferential direction. Therefore, as shown in FIG. 9, the motor torque MT4 in the first portion 227a periodically increases and decreases according to the rotation angle φ.

On the other hand, in the second portion 227b, the portion where the second recess 224b is provided and the portion where the recess 224 is not provided are alternately provided along the circumferential direction. Here, like the inside of the first recess 224a, the magnetic flux is less likely to pass through the second recess 224b than the rotor core 222, which is a magnetic member. Therefore, similarly to the motor torque MT4 of the first portion 227a described above, the motor torque MT5 of the second portion 227b also periodically increases or decreases according to the rotation angle φ.

The first planar portions 222d and the second planar portions 222e are alternately provided along the circumferential direction, and the first concave portions 224a and the second concave portions 224b are alternately provided along the circumferential direction when viewed from the axial direction. It is done. Therefore, a portion where the magnetic flux between the magnet portion 23 and the stator 30 is reduced in the first portion 227a and a portion where the magnetic flux between the magnet portion 23 and the stator 30 is reduced in the second portion 227b are from the axial direction. As seen, they are provided alternately along the circumferential direction. Thereby, the phase of motor torque MT4 and the phase of motor torque MT5 are shifted from each other by a half cycle and are likely to be opposite to each other, and the fluctuation range of motor torque MT4 and the fluctuation range of motor torque MT5 cancel each other. Therefore, the fluctuation range of the motor torque MTt of the entire rotor 220 can be reduced, and the torque ripple can be reduced.

Note that the decrease in motor torque MT due to the provision of the recess 224 described above is that the radial distance between the magnet portion 23 and the stator 30 is substantially increased in the portion where the recess 224 is provided. Equivalent to. In other words, according to the present embodiment, the radial distance between the magnet part 23 and the stator 30 can be increased by appropriately providing the recess 224 without changing the radial distance between the magnet part 23 and the stator 30. An effect equivalent to the change can be obtained.

Further, according to the present embodiment, the first recess 224a is provided on the entire surface of the first flat portion 222d of the first portion 227a except for the edges on both sides in the circumferential direction. Therefore, in the first portion 227a, the circumferential dimension of the first recess 224a in the first plane portion 222d and the circumferential dimension of the second plane portion 222e where the recess 224 is not provided can be made substantially the same. Thereby, in the waveform of the motor torque MT4 of the first portion 227a, the cycle width in which the motor torque MT4 increases and the cycle width in which the motor torque MT4 decreases can be made substantially the same.

Also, the second recess 224b is provided on the entire surface of the second portion 227b excluding the edges on both sides in the circumferential direction of the second flat portion 222e. Therefore, in the second portion 227b, the circumferential dimension of the second recess 224b in the second planar portion 222e and the circumferential dimension of the first planar portion 222d where the recess 224 is not provided can be made substantially the same. Thereby, in the waveform of the motor torque MT5 of the second portion 227b, the cycle width in which the motor torque MT5 increases and the cycle width in which the motor torque MT5 decreases can be made substantially the same. Therefore, when the waveform of the motor torque MT4 and the waveform of the motor torque MT5 are shifted by a half cycle, they are more likely to be in opposite phases, and the torque ripple can be reduced more suitably.

Further, in the waveforms of the cogging torques CT4 and CT5, the period width in which the cogging torque CT has a positive value and the period width in which the cogging torque CT has a negative value can be made substantially the same. Therefore, when the waveform of the cogging torque CT4 and the waveform of the cogging torque CT5 are shifted by a half cycle, they are more likely to be in opposite phases, and the cogging torque CTtb can be more preferably reduced.

In addition, the first concave portion 224a is not provided at the edges on both sides in the circumferential direction of the first flat portion 222d in the first portion 227a. Therefore, the magnet part 23 provided in the 1st plane part 222d can be supported from the radial inside by the edge part of the circumferential direction both sides of the 1st recessed part 224a. Thereby, the magnet part 23 can be hold | maintained to the 1st plane part 222d more stably.

In addition, the second concave portion 224b is not provided at the edges on both sides in the circumferential direction of the second flat portion 222e in the second portion 227b. Therefore, the magnet part 23 provided in the 2nd plane part 222e can be supported from the radial inside by the edge part of the circumferential direction both sides of the 2nd recessed part 224b. Thereby, the magnet part 23 can be hold | maintained to the 2nd plane part 222e more stably.

Further, according to the present embodiment, the first portion 227a and the second portion 227b have the same shape and the same dimension in the axial direction, and are stacked while being shifted in the circumferential direction. For this reason, the waveform and the amplitude of the cogging torque CT in each part are substantially the same. Thereby, the waveform of cogging torque CT4 and the waveform of cogging torque CT5 become an antiphase, and can reduce cogging torque CTtb more suitably. Similarly, the waveform of the motor torque MT in each part has substantially the same period and amplitude. As a result, the torque ripple can be reduced more suitably by the motor torque MT4 waveform and the motor torque MT5 waveform being in opposite phases.

The present invention is not limited to the above-described embodiment, and other configurations can be adopted. The configuration of the recess is not particularly limited as long as at least one first recess and two second recesses are provided that are shifted in the circumferential direction at different positions in the axial direction. The concave portions arranged at different positions in the axial direction need only be shifted from each other in the axial direction, and some axial positions may be the same. For example, in the example of the first embodiment described above, the upper part of the

first recesses

24a and 124a and the lower part of the second recess 24b may be located at the same position in the axial direction. The upper part of the second recess 24b and the lower part of the

third recesses

24c, 124c may be located at the same position in the axial direction.

Further, in the first embodiment, the third recess 24c may not be provided. In this case, for example, in the plane portion, the first recess may be provided on the other circumferential side, and the second recess may be provided on the one circumferential side. Further, for example, in the first embodiment described above, the second recess 24b may not be provided, and only the first recess 24a and the third recess 24c may be provided. In this case, for example, the third recess 24c corresponds to the second recess. A concave portion may not be provided in some of the flat portions. The number of the recessed portions provided for each plane portion may be different.

The shape of the plurality of recesses is not particularly limited. The shape of the recess may be a circular shape or a polygonal shape other than a square shape. The inside of the recess may be filled with a nonmagnetic member other than an adhesive or may be a gap. For example, in the first embodiment, the inside of the

recesses

24 and 124 may be a gap. In the second embodiment, the recess 224 may be filled with a nonmagnetic member such as an adhesive.

The rotor core may have any number of steps as long as the first recess and the second recess are provided. For example, in the first embodiment, the

rotor cores

22 and 122 may have a two-stage configuration or a four-stage or more configuration. For example, in the second embodiment, the rotor core 222 may have three or more stages. In the case of the three-stage configuration in the second embodiment, for example, a portion where the first concave portion is provided in the first flat portion is stacked on the upper side of the second portion 227b, similarly to the first portion 227a. In the case of the configuration of four or more steps in the second embodiment, for example, a portion where the first concave portion is provided in the first flat portion on the upper side of the second portion 227b, and the same as the second portion 227b. The portions where the second concave portions are provided in the second plane portion are alternately laminated. In the case of the configuration of three or more steps in the second embodiment, the sum of the dimensions in the axial direction of the portion where the first concave portion is provided in the first plane portion and the axial direction of the portion where the second concave portion is provided in the second plane portion By making the sum of the dimensions the same, the cogging torque CT and the motor torque MT in each part can be suitably canceled out, and the cogging torque CT and the torque ripple can be suitably reduced.

The magnet part provided in each plane part may be divided into a plurality in the axial direction. The shape of the rotor core is not particularly limited. The rotor core may be cylindrical, for example. In this case, the magnet part may be a cylindrical single member. In this case, for example, a plurality of recesses may be provided at positions facing each magnetic pole of the magnet unit in the radial direction.

The application of the motor of the above-described embodiment is not particularly limited. The motor of the above-described embodiment can be used for various devices such as a pump, a brake, a clutch, a cleaner, a dryer, a ceiling fan, a washing machine, and a refrigerator. As an example, an example in which the motor 10 of the above-described embodiment is mounted on an electric power steering apparatus will be described.

As shown in FIG. 10, the electric power steering device 1 is mounted on a steering mechanism of a vehicle wheel. The electric power steering device 1 is a device that reduces the steering force by hydraulic pressure. The electric power steering apparatus 1 of the present embodiment includes a motor 10, a steering shaft 314, an oil pump 316, and a control valve 317. The steering shaft 314 transmits the input from the steering 311 to the axle 313 having the wheels 312. The oil pump 316 generates hydraulic pressure in the power cylinder 315 that transmits the driving force by hydraulic pressure to the axle 313. The control valve 317 controls the oil of the oil pump 316. In the electric power steering apparatus 1, the motor 10 is mounted as a drive source for the oil pump 316. The electric power steering apparatus 1 according to the present embodiment includes the motor 10 according to the present embodiment. For this reason, the electric power steering apparatus 1 which has an effect similar to the above-mentioned motor 10 is obtained. The motor mounted on the electric power steering apparatus 1 may be a motor including the rotor core 122 illustrated in FIG. 5 or a motor including the rotor core 222 illustrated in FIG.

The above configurations can be appropriately combined within a range that does not contradict each other.

Claims

A shaft having a central axis;
A rotor core fixed to the shaft;
A magnet portion provided on a radially outer surface of the rotor core;
With
The rotor core has a plurality of recesses that are recessed radially inward from the radially outer surface of the rotor core and facing the magnet portion in the radial direction;
The plurality of concave portions include a first concave portion and a second concave portion, which are arranged as being shifted from each other in the circumferential direction at different positions in the axial direction as the concave portions.
The rotor core has a polygonal outer shape when viewed from the axial direction,
The radially outer surface of the rotor core has a plurality of flat portions arranged in the circumferential direction,
The rotor according to claim 1, wherein the magnet portion, the first recess, and the second recess are provided for each of the planar portions.
The rotor according to claim 2, wherein each of the magnet portions provided for each of the planar portions is a single member and is opposed to the plurality of concave portions provided for each of the planar portions in a radial direction.
The rotor core has a groove that extends in the radial direction from the radially outer surface of the rotor core and extends in the axial direction,
The groove portion is disposed between a pair of the planar portions adjacent in the circumferential direction on the radially outer side surface of the rotor core and opens radially outward, and the groove width decreases toward the radially outer side. The rotor according to claim 2 or 3.
The plurality of recesses further include a third recess as the recess,
The third recess is provided for each of the planar portions,
The second recess is located on one side in the axial direction from the first recess and on the one side in the circumferential direction from the first recess,
The rotor according to any one of claims 2 to 4, wherein the third recess is located on one axial side of the second recess and on one circumferential side of the second recess.
6. The rotor according to claim 5, wherein the first recess and the third recess are arranged in a point-symmetric position with respect to the second recess as viewed from the outside in the radial direction.
The rotor according to claim 5 or 6, wherein a circumferential dimension of the second recess is larger than a circumferential dimension of the first recess and a circumferential dimension of the third recess.
The rotor according to any one of claims 5 to 7, wherein the inside of the second recess and the inside of the third recess are connected to each other.
The rotor core is
A first part;
A second portion located on one axial side of the first portion;
Have
A plurality of the first recesses are provided on the radially outer surface of the first portion at intervals from one another along the circumferential direction.
A plurality of the second recesses are provided on the radially outer side surface of the second portion at intervals from one another along the circumferential direction.
The rotor according to claim 1, wherein the first recesses and the second recesses are alternately provided along a circumferential direction when viewed from the axial direction.
The rotor core has a polygonal outer shape when viewed from the axial direction,
The radially outer surface of the rotor core has a plurality of flat portions arranged in the circumferential direction,
The magnet part is provided for each flat part,
The plurality of flat portions include, as the flat portion, a first flat portion in which the first concave portion is provided on a radially outer surface of the first portion, and a second concave portion on a radially outer surface of the second portion. A second plane portion provided with,
The rotor according to claim 9, wherein the first planar portion and the second planar portion are alternately provided along a circumferential direction.
The first recess is provided on the entire surface excluding edges on both sides in the circumferential direction of the first flat portion in the first portion,
11. The rotor according to claim 10, wherein the second recess is provided on the entire surface of the second portion of the second portion excluding edges on both sides in the circumferential direction.
The rotor according to any one of claims 9 to 11, wherein the first portion and the second portion have the same shape and axial dimensions, and are stacked while being shifted in the circumferential direction.
The rotor according to any one of claims 1 to 12, wherein the inside of the first recess and the inside of the second recess are connected to each other.
The rotor according to any one of claims 1 to 13, wherein the plurality of recesses have the same shape.
The rotor according to any one of claims 1 to 14, wherein the concave portion is filled with an adhesive.
The rotor core has a hole that penetrates the rotor core in the axial direction;
The rotor according to any one of claims 1 to 15, wherein the hole portions are arranged in the rotor core at intervals in a circumferential direction.
The rotor according to any one of claims 1 to 16, and
A stator facing the rotor with a gap in the radial direction;
Comprising a motor.
An electric power steering apparatus comprising the motor according to claim 17.