Rotor and electric motor

Abstract

To provide a rotor capable of increasing average torque while suppressing electric motor torque ripple, and an electric motor.SOLUTION: In a rotor 3, a rotating shaft 13 is placed on the inner circumference side of a rotor core 11 with an axis X1 as the center of rotation. A resin member 14 is placed between the rotor core 11 and the rotating shaft 13 to fix the rotor core 11 and the rotating shaft 13. The rotor core 11 has multiple recesses 17. The multiple recesses 17 are formed between multiple permanent magnets 12 in the circumferential direction Y1. The multiple recesses 17 are recessed on the side away from the axis X1 from the inner periphery of the rotor core 11 when viewed from the axial direction along which axis X1 extends or the rotor core 11 is recessed in the axial direction. The resin member 14 is filled in the multiple recesses 17. The volume of the multiple recesses 17 is in the range of 15% to 32% of the sum of the volume of the rotor core 11 and the volume of the multiple recesses 17.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a rotor and an electric motor, and more particularly to a rotor having a permanent magnet and an electric motor including the rotor. [Background technology]

[0002] A rotor used in a motor (electric motor) generally has a plurality of permanent magnets arranged in the circumferential direction (see, for example, Patent Document 1).

[0003] In the motor described in Patent Document 1, a plurality of permanent magnets are disposed between a plurality of core piece parts (rotor cores), and the core piece parts are fixed to a shaft (rotating shaft) via an annular molded resin part (resin member). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-163409 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the electric motor described in Patent Document 1, each core piece has a recess that is open to the shaft side. These recesses make it possible to reduce leakage magnetic flux that leaks radially inward from the permanent magnets.

[0006] In this case, the rotating shaft, the core piece, and the permanent magnets are fixed by a resin member. Therefore, the resin member needs to have high strength against centrifugal force. However, the rotor described in Patent Document 1 does not pay attention to or propose any solution to the above problem.

[0007] The present disclosure has been made in consideration of the above-mentioned points, and has an object to provide a rotor and an electric motor that can increase average torque while suppressing torque ripple. [Means for solving the problem]

[0008] A rotor according to an embodiment of the present disclosure includes a rotor core, a plurality of permanent magnets, a rotating shaft, and a resin member. The plurality of permanent magnets are arranged in the rotor core in a circumferential direction of the rotor. The rotating shaft is arranged on the inner periphery side of the rotor core, and has the axis as a rotation center. The resin member is arranged between the rotor core and the rotating shaft to fix the rotor core and the rotating shaft. The rotor core has a plurality of recesses. The plurality of recesses are formed between the plurality of permanent magnets in the circumferential direction. The plurality of recesses are recessed on the side away from the axis when viewed from the axis direction in which the axis extends at the inner periphery of the rotor core, or are recessed in the axis direction within the rotor core. The resin member is filled in the plurality of recesses. The volume of the plurality of recesses is in the range of 15% to 32% of the sum of the volume of the rotor core and the volume of the plurality of recesses.

[0009] An electric motor according to one aspect of the present disclosure includes the rotor and a stator. Effect of the Invention

[0010] According to the rotor and electric motor according to one aspect of the present disclosure, it is possible to increase the average torque while suppressing torque ripple. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a partial cross-sectional view of an electric motor according to a first embodiment. [Diagram 2] FIG. 2 is a partial plan view of the rotor core of the electric motor. [Diagram 3] FIG. 3 is a partial plan view of a rotor core in which no recesses are formed. [Figure 4] FIG. 4 is a graph showing the change in average torque and torque ripple versus the recess volume ratio. [Diagram 5] FIG. 5 is a graph showing the change in average stress versus the recess volume ratio. [Figure 6] FIG. 6 is a partial plan view of a rotor core of an electric motor according to the second embodiment. [Figure 7] FIG. 7 is a partial plan view of a rotor core of an electric motor according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (Embodiment) Hereinafter, the rotor and the electric motor according to the embodiment of the present disclosure will be described in detail with reference to the drawings. However, each figure described in the following embodiment is a schematic diagram, and the ratio of the size and thickness of each component does not necessarily reflect the actual dimensional ratio. Note that the configuration described in the following embodiment is merely one example of the present disclosure. The present disclosure is not limited to the following embodiment, and various modifications are possible depending on the design, etc., as long as the effects of the present disclosure can be achieved.

[0013] (First embodiment) (1) Overview of the motor An electric motor 1 according to an embodiment of the present disclosure will be described with reference to Fig. 1. The electric motor 1 is an inner rotor type motor.

[0014] As shown in Fig. 1, electric motor 1 has a stator 2 and a rotor 3. In the following description, the direction in which axis X1 of a rotating shaft 13 (described later) extends (the direction perpendicular to the plane of Fig. 1) is referred to as the axial direction, and the circumferential direction of rotor 3 is referred to as the circumferential direction Y1. Also, the case viewed from the axial direction is referred to as "in a plan view."

[0015] The stator 2 is a stator having a stator core 4 and a plurality of (12 in total) coils 6. The stator core 4 is a laminated core in which a plurality of electromagnetic steel sheets are laminated in the thickness direction. The stator core 4 has an annular core back 7 and a plurality of (12 in total) teeth 8, and is formed in a generally cylindrical columnar shape as a whole. The teeth 8 are arranged at regular intervals along the circumferential direction Y1 on the inner peripheral surface of the core back 7, and extend radially inward. The coils 6 correspond to the teeth 8, and each coil 6 is formed by winding a conductive wire 34 around the corresponding tooth 8. In detail, the teeth 8 include a teeth main body 9 and two flange portions 10. The teeth main body 9 extends in the radial direction and is, for example, rectangular parallelepiped. The two flange portions 10 protrude from the inner end of the teeth main body 9 along the circumferential direction Y1. A slot 31 is provided between adjacent teeth 8 in the circumferential direction Y1. The coil 6 is disposed in the slot 31 and wound around the tooth body 9 of the tooth 8.

[0016] The rotor 3 is an IPM (Interior Permanent Magnet) type rotor in which a permanent magnet is embedded inside the rotor core. More specifically, the rotor 3 has a so-called spoke-type rotor structure in which a pair of magnetic pole faces of the magnets are arranged so as to face the circumferential direction. Specifically, the rotor 3 is arranged radially inside the stator 2, and includes a rotor core 11, a rotating shaft 13, and a plurality of (10 in total) permanent magnets 12. The permanent magnets 12 are members that generate magnetic flux that serves as the driving force for the rotor 3, and are magnetized so that the direction of the magnetic poles is along the circumferential direction Y1 of the rotor core 11.

[0017] The electric motor 1 operates as follows: Three-phase currents having a phase difference of 120° electrical angle from each other are supplied to the coils 6 through a power supply connection unit (not shown), exciting the stator 2 and generating a rotating magnetic field. This rotating magnetic field interacts with a magnetic field generated by a permanent magnet 12 provided in the rotor 3, generating a rotational torque in the rotor 3, causing the rotor 3 to rotate around the axis X1.

[0018] (2) Rotor (2-1) Rotor core The rotor core 11 is a laminated core in which a plurality of electromagnetic steel sheets are laminated along the axial direction.

[0019] 1, a shaft hole is formed in the center of rotor core 11, passing through rotor core 11 along the axial direction and opening at both end faces.

[0020] (2-1-1) Magnet placement hole As shown in Fig. 1, the rotor core 11 is provided with a plurality of magnet arrangement holes 16 (10 in total). The magnet arrangement holes 16 are provided radially, specifically at 10 locations equally spaced apart in the circumferential direction Y1. Each magnet arrangement hole 16 extends along the axial direction and penetrates the plurality of electromagnetic steel plates in the axial direction. Each magnet arrangement hole 16 has a rectangular opening shape in a plan view, specifically with its longitudinal direction aligned with the radial direction. Each magnet arrangement hole 16 is formed so as to open toward the axial center X1 side along the inner circumferential edge of the rotor core 11.

[0021] (2-1-2) Recess As shown in Figs. 1 and 2, the rotor core 11 is provided with a plurality of recesses 17 (10 in total). The recesses 17 are provided radially, specifically at 10 locations at equal intervals in the circumferential direction Y1. Each recess 17 is formed along the inner periphery of the rotor core 11 and opens toward the axis X1. In other words, in a plan view, it is a portion recessed radially outward from the innermost periphery 18 of the rotor core 11. In a plan view, each recess 17 has an opening shape of a rectangle, specifically, the longitudinal direction is along the radial direction. Each recess 17 is provided between two adjacent magnet arrangement holes 16 in the circumferential direction Y1. As a result, the rotor core 11 is a cylindrical member in which the magnet arrangement holes 16 and the recesses 17 are alternately arranged in the circumferential direction Y1.

[0022] As shown in FIG. 1, the recess 17 is filled with a filling portion 21 of a resin member 14, which will be described later.

[0023] The recesses 17 have the function of restricting the flow of magnetic flux from the permanent magnets 12. In other words, since the recesses 17 are provided so as to extend from the inner surface of the rotor core 11, collision between the magnetic fluxes of the permanent magnets 12 adjacent in the circumferential direction Y1 is suppressed in the portion where the recesses 17 are provided, i.e., the portion closer to the radially inner side of the rotor core 11. In other words, a magnetic path passing through the radially inner sides of the permanent magnets 12 adjacent in the circumferential direction is less likely to occur, and as a result, leakage magnetic flux is reduced.

[0024] 2, each recess 17 is symmetrical with respect to a straight line 25 that connects the axis X1 and the circumferential center of the recess 17 in a plane normal to the axis X1. Therefore, the same characteristics can be obtained when the rotor 3 rotates on both sides in the rotation direction.

[0025] (2-2) Rotation axis The rotating shaft 13 is a cylindrical member having an axis X1 which is the center of rotation. The rotating shaft 13 is inserted into an axial hole of the rotor core 11 and fixed via a resin member 14 which will be described later.

[0026] (2-3) Plastic materials The resin member 14 is disposed between the rotor core 11 and the rotating shaft 13 to fix the rotor core 11 and the rotating shaft 13. Specifically, the resin member 14 has an annular portion 20 disposed between the rotor core 11 and the rotating shaft 13, and a plurality of filling portions 21 provided on the outer periphery of the annular portion 20.

[0027] (2-4) Permanent magnets The multiple permanent magnets 12 are each inserted into and fixed in a corresponding one of the multiple magnet arrangement holes 16 in the rotor core 11. A sintered ferrite magnet is used as the permanent magnet 12. The permanent magnet 12 may also be a samarium-cobalt based permanent magnet, a neodymium magnet, or the like.

[0028] The permanent magnet 12 has approximately the same shape and dimensions as the magnet arrangement hole 16. The permanent magnet 12 has a roughly rectangular parallelepiped shape, and has a spoke shape that is long in the radial direction when viewed from above.

[0029] The magnetization direction of the permanent magnets 12 is parallel to the circumferential direction Y1 of the rotor 3, that is, two permanent magnets 12 adjacent to each other in the circumferential direction Y1 are magnetized so that the two magnetic pole faces facing each other in the circumferential direction Y1 have the same polarity.

[0030] The radially inner surface of the permanent magnet is in contact with the outer circumferential surface of the annular portion 20 of the resin member 14. As a result, the permanent magnet 12 is fixed to the rotor core 11.

[0031] (2-5) Effects 3 shows the shape of the rotor core 11 without the multiple recesses 17. In this case, the radially inner edge 19 of the rotor core 11 has an arc shape that continues in the circumferential direction Y1.

[0032] The volume of the multiple recesses 17 is in the range of 15% to 32% of the sum of the volume of the rotor core 11 and the volume of the multiple recesses 17 (for example, the volume of the rotor core 11 before the recesses 17 are formed). Within this range, as shown in Fig. 4, the reduction rate of the average torque is less than 5%, and the torque ripple is 1.0% or less. In other words, in this embodiment, the average torque can be increased by increasing the strength of the resin member 14 against the centrifugal force acting during rotation while suppressing the torque ripple.

[0033] Next, the reason why the strength of the resin member 14 can be increased will be further explained. As shown in Fig. 5, when the volume of the recesses 17 is in the range of 15% to 32% of the sum of the volume of the rotor core 11 and the volume of the recesses 17, the rate of decrease in the average stress acting on the resin member 14 is large. This means that the rotational fracture strength of the resin member 14 is high.

[0034] Second embodiment In the first embodiment, the recesses 17 penetrate the rotor core 11 in the axial direction. However, the recesses 17 do not have to penetrate the rotor core 11 in the axial direction.

[0035] A second embodiment in which the recess does not penetrate the rotor core in the axial direction will be described with reference to Fig. 6. Note that the basic structure and basic operation of the second embodiment are the same as those of the first embodiment, so the following description will focus on the differences.

[0036] As shown in Fig. 6, the rotor core 11A is provided with a plurality of magnet arrangement holes 16A (10 in total). The magnet arrangement holes 16A are provided radially, specifically at 10 locations equally spaced apart in the circumferential direction Y1. Each magnet arrangement hole 16A extends along the axial direction and penetrates the plurality of electromagnetic steel sheets in the axial direction. Each magnet arrangement hole 16A has a rectangular opening shape in a plan view, specifically with its longitudinal direction aligned with the radial direction. Each magnet arrangement hole 16A is formed to open toward the axial center X1 side along the inner circumferential edge of the rotor core 11A.

[0037] As shown in FIG. 6, the rotor core 11A is provided with a plurality of recesses 17A (10 in total). The recesses 17A are provided radially, specifically at 10 locations at equal intervals in the circumferential direction Y1. In plan view, each recess 17A is a portion recessed radially outward from the innermost circumferential edge 18A of the rotor core 11A, in other words, a portion that opens toward the axis X1 side. In plan view, each recess 17A has a rectangular opening shape, specifically, the longitudinal direction is along the radial direction. Each recess 17A is provided between two adjacent magnet arrangement holes 16A in the circumferential direction Y1. As a result, the rotor core 11A is a cylindrical member in which the magnet arrangement holes 16A and the recesses 17A are alternately arranged in the circumferential direction Y1, as shown in FIG. 6.

[0038] The multiple permanent magnets 12A are each inserted into and fixed in a corresponding one of the multiple magnet arrangement holes 16A in the rotor core 11A.

[0039] As shown in FIG. 6, for example, the bottom lamination plate of rotor core 11A has shielding portion 32A that blocks recess 17A in the axial direction.

[0040] In this case, too, if the volume of the multiple recesses 17A is in the range of 15% to 32% of the sum of the volume of the rotor core 11A and the volume of the multiple recesses 17A, the average torque can be increased by increasing the strength of the resin member against the centrifugal force acting during rotation while suppressing torque ripple.

[0041] Third embodiment In the above-described second embodiment, the rotor core 11A further includes a plurality of shielding portions 32A that shield one side in the axial direction of each of the recesses 17A.

[0042] In the third embodiment, the rotor core 11A further includes a plurality of shielding portions 32A that shield both sides in the axial direction of the plurality of recesses. That is, the shielding portions 32A are arranged on both axial sides of each recess.

[0043] In this case too, if the volume of the multiple recesses is in the range of 15% to 32% of the sum of the volume of the rotor core 11A and the volume of the multiple recesses, the average torque can be increased by increasing the strength of the resin member against the centrifugal force acting during rotation while suppressing torque ripple.

[0044] (Fourth embodiment) In the first embodiment, the recesses 17 are open toward the axis X1 at the inner circumferential edge of the rotor core 11. However, the recesses 17 do not have to be open toward the axis X1.

[0045] 7, a fourth embodiment will be described as an embodiment in which the recess is recessed in the axial direction within rotor core 11. Note that the basic structure and basic operation of the fourth embodiment are the same as those of the first embodiment, so the following description will focus on the differences.

[0046] As shown in Fig. 7, the rotor core 11B is provided with a plurality of magnet arrangement holes 16B (10 in total). The magnet arrangement holes 16B are provided radially, specifically at 10 locations equally spaced apart in the circumferential direction Y1. Each magnet arrangement hole 16B extends along the axial direction and penetrates the plurality of electromagnetic steel sheets in the axial direction. Each magnet arrangement hole 16B has a rectangular opening shape in a plan view, specifically with its longitudinal direction aligned with the radial direction. Each magnet arrangement hole 16B is formed to open toward the axial center X1 side along the inner circumferential edge of the rotor core 11B.

[0047] As shown in FIG. 7, the rotor core 11B is provided with a plurality of recesses 17B (10 in total). The recesses 17B are provided radially, specifically at 10 locations at equal intervals in the circumferential direction Y1. In plan view, each recess 17B is recessed in the axial direction near the innermost circumferential edge 18B of the rotor core 11B. That is, each recess 17B penetrates a plurality of electromagnetic steel sheets. In plan view, each recess 17B has an opening shape of a rectangle, specifically, the longitudinal direction is along the radial direction. Each recess 17B is provided between two adjacent magnet arrangement holes 16B in the circumferential direction Y1. As a result, the rotor core 11B is a cylindrical member in which the magnet arrangement holes 16B and the recesses 17B are alternately arranged in the circumferential direction Y1, as shown in FIG. 7.

[0048] The multiple permanent magnets 12B are each inserted into and fixed in a corresponding one of the multiple magnet arrangement holes 16B of the rotor core 11B.

[0049] In this case, too, if the volume of the multiple recesses 17B is in the range of 15% to 32% of the sum of the volume of the rotor core 11B and the volume of the multiple recesses 17B, the average torque can be increased by increasing the strength of the resin member against the centrifugal force acting during rotation while suppressing torque ripple.

[0050] In the fourth embodiment, the recess 17B may or may not be filled with a resin member.

[0051] (Modification) The above-described embodiment is merely one of various embodiments of the present disclosure. The above-described embodiment can be modified in various ways depending on the design and the like as long as the object of the present disclosure can be achieved. Below, modified examples of the above-described embodiment are listed. The modified examples described below can be applied in appropriate combination.

[0052] (1) Modifications of the electric motor The rotor core and the stator core may be dust cores whose main component is a dust material obtained by compressing a powdered magnetic body.

[0053] (2) Modifications of permanent magnets The permanent magnet may be a bonded magnet made by mixing and kneading magnet powder, which is a hard magnetic material, with a binder such as resin or rubber and molding it into a molded magnet, or it may be a sintered magnet made by baking magnet powder at high temperature.

[0054] (3) Modification of the recess The shape, number and position of the recesses are not limited.

[0055] The shape of the recess in plan view is not limited to a rectangle. For example, the shape of the recess in plan view may be a trapezoid, a parallelogram, a pentagon, or another polygon. Furthermore, the recess may have a shape including a circular arc.

[0056] (4) Modified rotor core The rotor core may have a through hole in addition to the magnet arrangement holes and recesses.

[0057] (Aspect) The present specification discloses the following aspects.

[0058] The rotor (3) according to the first aspect includes a rotor core (11, 11A, 11B), a plurality of permanent magnets (12, 12A, 12B), a rotating shaft (13), and a resin member (14). The plurality of permanent magnets (12, 12A, 12B) are arranged in a line in the circumferential direction (Y1) of the rotor core (11, 11A, 11B) and are arranged on the rotor core (11, 11A, 11B). The rotating shaft (13) is arranged on the inner peripheral side of the rotor core (11, 11A, 11B) and has a rotation center at the axis (X1). The resin member (14) is arranged between the rotor core (11, 11A, 11B) and the rotating shaft (13) to fix the rotor core (11, 11A, 11B) and the rotating shaft (13). The rotor core (11, 11A, 11B) has a plurality of recesses (17, 17A, 17B). The recesses (17, 17A, 17B) are formed between the permanent magnets (12, 12A, 12B) in the circumferential direction (Y1). The recesses (17, 17A, 17B) are recessed on the side away from the axis (X1) when viewed from the axial direction in which the axis (X1) extends on the inner peripheral edge of the rotor core (11, 11A, 11B), or are recessed in the axial direction within the rotor core (11, 11A, 11B). The resin member (14) is filled in the recesses (17, 17A, 17B). The volume of the plurality of recesses (17, 17A, 17B) is in the range of 15% to 32% of the sum of the volume of the rotor core (11, 11A, 11B) and the volume of the plurality of recesses (17, 17A, 17B).

[0059] According to this embodiment, the average torque can be increased by increasing the strength of the resin member (14) against the centrifugal force acting during rotation while suppressing torque ripple.

[0060] In the rotor (3) according to the second aspect of the present disclosure, in the first aspect, each of the multiple recesses (17, 17A, 17B) is symmetrical with respect to a straight line (25) connecting the axis (X1) and the circumferential center of the recess (17) in a plane normal to the axis (X1).

[0061] According to this embodiment, the same characteristics can be obtained when the rotor (3) rotates in both directions of rotation.

[0062] In a rotor (3) according to a third aspect of the present disclosure, in the first or second aspect, the rotor core (11A) further has a plurality of shielding portions (32A) that each shield one side in the axial direction of the plurality of recesses (17A).

[0063] According to this embodiment, the average torque can be increased by increasing the strength of the resin member (14) against the centrifugal force acting during rotation while suppressing torque ripple.

[0064] In a rotor (3) according to a fourth aspect of the present disclosure, in any of the first to third aspects, the rotor core (11A) further has a plurality of shielding portions (32A) that shield both sides in the axial direction of the plurality of recesses (17A).

[0065] According to this embodiment, the average torque can be increased by increasing the strength of the resin member (14) against the centrifugal force acting during rotation while suppressing torque ripple.

[0066] An electric motor (1) according to a fifth aspect of the present disclosure includes a rotor (3) according to any one of the first to fourth aspects, and a stator (2).

[0067] According to this embodiment, the average torque can be increased by increasing the strength of the resin member (14) against the centrifugal force acting during rotation while suppressing torque ripple. [Explanation of symbols]

[0068] 1: Electric motor 2: Stator 3: Rotor 4: Stator core 6: Coil 11, 11A, 11B: Rotor core 12, 12A, 12B: Permanent magnet 13: Rotation axis 14: Resin material 17, 17A, 17B: recess 32A: Shielding part X1: Axial center Y1: Circumferential direction

Claims

1. A rotor core; A plurality of permanent magnets arranged in a circumferential direction of the rotor core; a rotating shaft disposed on an inner circumferential side of the rotor core and having a rotation center at the axis of the rotor core; a resin member disposed between the rotor core and the rotating shaft to fix the rotor core and the rotating shaft, the rotor core has a plurality of recesses formed between the plurality of permanent magnets in the circumferential direction, the plurality of recesses are recessed on an inner circumferential edge of the rotor core toward a side away from the axis when viewed from the axis direction in which the axis extends, or recessed in the rotor core toward the axis direction, The resin member is filled in the plurality of recesses, a volume of the plurality of recesses is in a range of 15% to 32% of a sum of a volume of the rotor core and a volume of the plurality of recesses, Rotor.

2. Each of the plurality of recesses is symmetrical with respect to a straight line connecting the axis and a circumferential center of the recess in a plane normal to the axis. The rotor according to claim 1 .

3. The rotor core further includes a plurality of shielding portions each shielding one side of the recess in the axial direction. A rotor according to claim 1 or 2.

4. The rotor core further includes a plurality of shielding portions that shield both sides of the recesses in the axial direction. A rotor according to claim 1 or 2.

5. A rotor according to claim 1 or 2; A stator; Electric motor.

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