CN116868480A - Rotary electric machine - Google Patents

Abstract

A rotating electrical machine (1) is provided with: a rotatable rotor (10), wherein a plurality of permanent magnets (13) are embedded in the outer peripheral portion of the rotor (10); a stator (20), wherein the stator (20) is fixedly arranged around the rotor (10), and a plurality of coils (22) are arranged on a stator core (21); and a motor case (30), wherein the motor case (30) accommodates the rotor (10) and the stator (20) therein, wherein the rotating electrical machine (1) is configured by fixing the stator (20) to the motor case (30) by bolts (fasteners) (23), wherein the fasteners (23) are inserted through a plurality of fixing portions (24) protruding radially outward from the outer periphery of the stator core (21), and wherein a magnetic flux barrier (25) penetrating in the axial direction is formed in the stator core (21) on the q-axis other than the q-axis passing through the center of the fixing portion (24) in a state in which the q-axis of the rotor (10) passes through the center of the fixing portion (24).

Description

Rotary electric machine

Technical Field

The present application relates to a rotary electric machine configured to fix a stator housed in a motor casing to the motor casing by a fastener such as a bolt.

The present application claims priority based on japanese patent application No. 2021-142395, filed on 1/9/2021, the contents of which are incorporated herein by reference.

Background

In a rotary electric machine configured by housing a rotatable rotor and a stator disposed on the outer periphery of the rotor in a motor housing, the stator is fixed to the motor housing, and the fixing method of the stator to the motor housing includes a press-fit method and a bolt-fastening method or a combination of both methods.

In the case of using the bolt fastening method as the method of fixing the stator to the motor housing, a plurality of fixing portions protruding radially outward are formed on the outer periphery of the stator, and the stator is fixed to the motor housing by fastening fasteners such as bolts inserted into the fixing portions.

However, although the stator core constituting the stator is formed in a cylindrical shape by stacking a plurality of annular electromagnetic steel plates in the axial direction and connecting the plurality of electromagnetic steel plates to each other by caulking or the like, in patent document 1, in order to suppress eddy current loss generated in the stator core to a low level, a circumferential distance between a connecting portion of the electromagnetic steel plates constituting the stator core by caulking or the like and a fixing portion is defined. Specifically, when the number of fastening portions is an odd number, the fixing portions are formed at a circumferential pitch equal to or corresponding to a divisor of the circumferential pitch of the fastening portions with respect to the rotor rotation center, and when the number of fastening portions is an even number, the fixing portions are formed at a circumferential pitch corresponding to a divisor of the circumferential pitch of the fastening portions with respect to the rotor rotation center or a divisor of 180 °.

In addition, patent document 2 proposes a structure in which a recess is formed in a root portion of a fixing portion (protruding portion) of a stator in order to improve a fastening force of the stator to a motor case and to suppress deformation of the stator due to fastening in a rotating electric machine adopting a shrink fit system and a bolt fastening system as a fixing system of the stator.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication No. 2017-060326

Patent document 2: WO2014/046101

Disclosure of Invention

Technical problem to be solved by the application

However, in the case of using the bolt fastening method as the fixing method of the stator to the motor case, a plurality of fixing portions, which are formed with insertion holes through which bolts are inserted, are integrally protruded toward the radial outside at the outer peripheral edge of the stator core, but in the stator core provided with these fixing portions, the distribution of the magnetic flux density in the vicinity of the fixing portions is not uniform in the circumferential direction with respect to the stator core not provided with the fixing portions. Therefore, in a rotating electrical machine employing a bolt fastening method as a fixing method of a stator, there is a problem that torque pulsation (fluctuation width of output torque) becomes large, and vibration and noise become large.

The present application has been made in view of the above-described problems, and an object thereof is to provide a rotary electric machine capable of suppressing torque pulsation to be small and suppressing vibration and noise to be low.

Technical proposal adopted for solving the technical problems

In order to achieve the above object, the present application provides a rotary electric machine including: a rotatable rotor having a plurality of permanent magnets buried in an outer peripheral portion thereof; a stator fixedly arranged around the rotor and provided with a plurality of coils at a stator core; and a motor case that accommodates the rotor and the stator therein, wherein the rotating electrical machine is configured by fixing the stator to the motor case by means of a fastener that is inserted into a plurality of fixing portions that protrude radially outward from an outer peripheral edge of the stator core, wherein a magnetic flux barrier that penetrates in an axial direction is formed in the stator core on a q-axis other than the q-axis that penetrates a center of the fixing portion in a state where the q-axis of the rotor penetrates the center of the fixing portion.

Effects of the application

According to the present application, in a state where a part of the magnetic flux that has emerged from the N pole of the permanent magnet of the rotor and entered the S pole flows through the fixed portion of the stator core, the magnetic circuit expands, and the magnetic resistance decreases, and the torque increases, but since a flux barrier is provided in the middle of the magnetic flux, the magnetic circuit narrows and the magnetic resistance increases due to the flux barrier. Therefore, the decrease in magnetic resistance due to the magnetic flux flowing through the fixed portion is offset by the increase in magnetic resistance due to the magnetic flux barrier, and the torque fluctuation of the rotor, that is, the torque ripple is suppressed to be small, and the vibration and noise of the rotating electrical machine are suppressed to be low.

Drawings

Fig. 1 is a longitudinal sectional view of a rotary electric machine of the present application.

Fig. 2 is a cross-sectional view taken along line A-A of fig. 1.

Fig. 3 is an enlarged detail view of the portion B of fig. 2.

Fig. 4 is an enlarged detail view of section C of fig. 2.

Fig. 5 is a top half view of a rotor and a stator showing magnetic fluxes generated in a stator core at a predetermined electrical angle, (a) is a view showing magnetic fluxes of a rotating electrical machine according to the present application, and (b) is a view showing magnetic fluxes of a conventional rotating electrical machine.

Fig. 6 is a top half view of a rotor and a stator showing magnetic fluxes generated in a stator core at a predetermined electrical angle, (a) is a view showing magnetic fluxes of a rotating electrical machine according to the present application, and (b) is a view showing magnetic fluxes of a conventional rotating electrical machine.

Fig. 7 is a diagram showing a comparison between torque fluctuation with respect to an electrical angle of the rotating electrical machine according to the present application and torque fluctuation of a conventional rotating electrical machine.

Detailed Description

Hereinafter, embodiments of the present application will be described with reference to the drawings.

Fig. 1 is a longitudinal sectional view of a rotary electric machine according to an embodiment of the present application, fig. 2 is a sectional view taken along line A-A of fig. 1, fig. 3 is an enlarged detail B of fig. 2, and fig. 4 is an enlarged detail C of fig. 2.

[ Structure of rotating Electrical machine ]

The rotary electric machine 1 according to the present embodiment is a three-phase synchronous motor generator, and functions as a motor or a generator, and is used as a drive source for an electric vehicle (EV vehicle), a hybrid electric vehicle (HEV vehicle), or the like. As shown in fig. 1, the rotary electric machine 1 is configured such that a rotor 10 that is rotatable and a stator 20 fixedly provided around the rotor 10 are housed in a motor case 30. Hereinafter, the motor case 30, the rotor 10, and the stator 20 constituting the rotary electric machine 1 will be described.

(Motor housing)

The motor case 30 is formed by covering an opening of a bottomed tubular body 30A having one end face opened with a disc-shaped cover 30B, and is molded by die casting of aluminum, aluminum alloy, or the like, for example.

(rotor)

The rotor 10 includes a cylindrical rotor core 11, a shaft (motor shaft) 12 having a circular shaft shape penetrating the center of the rotor core 11 in the axial direction (left-right direction in fig. 1), and a plurality of permanent magnets 13 (see fig. 2) embedded in the outer peripheral portion of the rotor core 11, and both axial end portions of the shaft 12 are rotatably supported by bearings (ball bearings) 14, 15 provided in a main body 30A and a cover 30B of a motor housing 30, respectively. Accordingly, the rotor 10 can rotate around the shaft center (rotation center) of the shaft 12.

The rotor core 11 is formed by stacking a plurality of thin electromagnetic steel plates 11a in the shape of a plate of iron, iron alloy, or the like, and each electromagnetic steel plate 11a is formed into a circular shape by punching, for example, by punching. Here, the plurality of electromagnetic steel plates 11a are integrally connected to each other by caulking, welding, or the like, and the rotor core 11 formed by stacking the electromagnetic steel plates 11a is fixed to the outer periphery of the shaft 12 by caulking, press-fitting, nut tightening, or the like. Therefore, the rotor core 11 can rotate integrally with the shaft 12.

As shown in fig. 2, the plurality of permanent magnets 13 are rectangular plates long in the axial direction (the direction perpendicular to the paper surface in fig. 2), and a total of 8 sets of magnetic pole portions 40 each formed by arranging three permanent magnets 13 in a triangular shape are arranged at equal angular intervals (45 ° intervals) in the circumferential direction on the outer peripheral portion of the rotor core 11. Further, hollow portions 16 (see fig. 3 and 4) each having a rectangular cross section are provided at both longitudinal end portions of each permanent magnet 13 of the rotor core 11 so as to penetrate in the axial direction (the direction perpendicular to the paper surface in fig. 2).

Here, the plurality of (8 sets of) magnetic pole portions 40 are constituted by N-pole magnetic pole portions 40N and S-pole magnetic pole portions 40S alternately arranged in the circumferential direction, and among the three permanent magnets 13 (13 a, 13b, 13 c) arranged in a triangular shape in each of the N-pole magnetic pole portions 40N, as shown in fig. 3, 1 permanent magnet 13a arranged in the circumferential direction is arranged with the N-pole facing the outer circumferential side, and two permanent magnets 13b, 13c arranged obliquely in the radial direction are arranged with the N-pole facing the opposite inner surface side.

On the other hand, in each S pole magnetic pole portion 40S, as shown in fig. 4, among the three permanent magnets 13 (13 a, 13b, 13 c) arranged in a triangular shape, 1 permanent magnet 13a arranged in the circumferential direction is arranged with the S pole facing the outer circumferential side, and two permanent magnets 13b, 13c arranged obliquely in the radial direction are arranged with the S pole facing the opposite inner surface side.

In the rotating electrical machine 1 of the present embodiment, 8 d (direct) axes and 8 q (quadrature) axes are alternately arranged in the circumferential direction at an angular interval of 22.5 ° in each of the rotating electrical machine 1, each d (direct) axis being an axis orthogonal to the d (quadrature) axis (axis between the N pole 40N and the S pole 40S) axes, each d pole 40N and each S pole 40S being a magnetic pole center line showing the main magnetic flux direction of each S pole 40S.

(stator)

As shown in fig. 2, the stator 20 is configured to include a cylindrical stator core 21 and a plurality of coils 22. Here, the stator core 21 is formed by stacking a plurality of thin electromagnetic steel plates 21a in the shape of a plate of iron, iron alloy, or the like, and each electromagnetic steel plate 21a is formed into a circular shape by punching, for example, by punching. Here, the plurality of electromagnetic steel plates 21a are integrally connected to each other by caulking, welding, or the like.

The stator core 21 includes an annular yoke 21A and a plurality of (48 in the example of the figure) teeth 21B extending radially inward on the inner peripheral side of the yoke 21A. Here, a plurality of (48) teeth 21B are formed at equal angular intervals (7.5 ° intervals) in the circumferential direction, and grooves 21C penetrating in the axial direction are formed between adjacent teeth 21B, respectively. Therefore, the stator core 21 is formed with the same number (48) of slots 21C as the teeth 21B at equal angular intervals (7.5 ° intervals) in the circumferential direction, and the rotary electric machine 1 of the present embodiment takes the form of 8-pole 48 slots.

Further, in the stator core 21, coils 22 are provided around each tooth 21B, and the coils 22 are configured by winding, for example, insulated wires. Here, the plurality of coils 22 are constituted by U-phase coils, V-phase coils, and W-phase coils, and when alternating currents are applied to the coils 22 constituted by the U-phase coils, the V-phase coils, and the W-phase coils, alternating magnetic fields are generated in directions penetrating the U-phase coils, the V-phase coils, and the W-phase coils, respectively, in the coils 22.

As shown in fig. 1, the stator 20 configured as described above is fixed to the motor case 30 by 4 bolts (only 1 is shown in fig. 1) 23 as fasteners. Specifically, as shown in fig. 2, four fixing portions 24, which are substantially triangular when viewed in the axial direction, are integrally provided on the outer periphery of the stator core 21 (yoke 21A) on four q-axes orthogonal to each other so as to protrude radially outward. That is, the four fixing portions 24 are integrally provided so as to protrude at equal angular intervals (90 ° intervals) in the circumferential direction on the outer peripheral portion of the stator core 21, and circular hole-shaped bolt insertion holes 24a are provided in each fixing portion 24 so as to penetrate in the axial direction (the direction perpendicular to the plane of the drawing of fig. 2). In addition, in the shape formed by each fixing portion 24, that is, the shape of a substantially triangle when viewed in the axial direction, the top of the triangle forms a convex circular arc curved surface, and the two hypotenuse portions of the triangle form a concave circular arc curved surface smoothly continuous with the outer periphery of the annular stator core 21 (yoke 21A). By setting the shape of each fixing portion 24 in this way, stress concentration at both base end portions (connection portions with the yoke 21A) of the fixing portion 24 can be avoided, and occurrence of cracks or the like at both base end portions can be prevented.

As shown in fig. 1, the stator 20 is fixed to the motor housing 30 by screwing a total of 4 bolts (only 1 is shown in fig. 1) 23 into a main body 30A of the motor housing 30, and the bolts 23 are respectively inserted into bolt insertion holes 24a penetrating four fixing portions 24 (see fig. 2).

However, in the rotating electrical machine 1 of the present embodiment, as shown in fig. 2, when the q-axis of the rotor 10 is in a state of passing through the center of the fixed portion 24, circular hole-shaped flux barriers 25 penetrating in the axial direction are formed in the stator core portions 21 on the 4 q-axes other than the 4 q-axes passing through the center of the four fixed portions 24, respectively. Here, as described above, four fixed portions 24 are formed at equal angular intervals (90 ° intervals) on the outer circumferences of the mutually orthogonal q-axes of the stator core 21, and four flux barriers 25 are formed on each q-axis (circumferentially intermediate positions (positions at an angle of 45 ° with respect to the q-axis passing through the center of the fixed portion 24) of two fixed portions 24 adjacent in the circumferential direction) other than the total of four q-axes passing through the center of each fixed portion 24. That is, in the present embodiment, four flux barriers 25 are formed in the stator core 21 at equal angular intervals (90 ° intervals) in the circumferential direction.

In the present embodiment, four fixing portions 24 are provided so as to protrude at equal angular intervals (90-degree intervals) in the circumferential direction on the outer periphery of the stator core 21, but the number of fixing portions 24 is arbitrary. However, in the case where the number of fixing portions 24 is two, there is a possibility that the mounting strength of the stator 20 to the motor case 30 is insufficient, and in the case where the number of fixing portions 24 is six, although the mounting strength of the stator 20 to the motor case 30 is improved, there is a problem that the shape of the stator core 21 is complicated and the manufacturing cost thereof is high. Therefore, in the present embodiment, the number of the fixing portions 24 is set to four.

In the present embodiment, the shape of the magnetic flux barrier 25 is a circular hole, but the shape is not limited to this, and the shape may be an elliptical hole, a polygonal hole, or the like, and the size of the magnetic flux barrier 25 may be arbitrarily set within a range that achieves the object of the present application.

[ Effect of rotating Electrical machine ]

Next, the operation and effects of the rotary electric machine 1 according to the present embodiment will be described.

For example, when the rotating electrical machine 1 of the present embodiment mounted in an electric vehicle (EV vehicle), a hybrid vehicle (HEV vehicle), or the like (hereinafter, simply referred to as "vehicle") functions as a motor (motorr) for driving and rotating wheels, a direct current output from a direct current power source such as a battery (not shown) is converted into an alternating current by an inverter (not shown). When the alternating current is supplied to a plurality of coils (U-phase, V-phase, and W-phase) 22 provided in the stator 20 of the rotating electric machine 1, a rotating magnetic field is generated by the coils 22. Specifically, the magnetic fluxes of the coils (U-phase, V-phase, and W-phase) 22 become combined rotating magnetic fluxes, and the rotor 10 in which the plurality of permanent magnets 13 arranged in the region where the rotating magnetic fluxes are generated are buried rotates in synchronization with the rotating magnetic fluxes.

That is, the electric energy supplied from the battery is converted into rotational energy (mechanical energy) of the rotor 10 by the rotary electric machine 1, and is output as rotation of the shaft 12. The rotation of the shaft 12 is transmitted to an axle, not shown, via a transmission, a differential device, or the like, not shown, and wheels, not shown, mounted on the axle are driven to rotate, whereby the vehicle runs at a predetermined speed.

However, in the stator core 21 of the rotary electric machine 1 according to the present embodiment, as shown in fig. 2, in a state in which the q-axis of the rotor 10 passes through each of the four fixing portions 24, four flux barriers 25 are formed in total at equal angular intervals (90 ° intervals) in the circumferential direction on q-axes other than the four q-axes passing through each of the four fixing portions 24 (at circumferentially intermediate positions of two fixing portions 24 adjacent in the circumferential direction), so that variation in torque (torque ripple) output to the rotor 10 (shaft 12) in the case where the rotary electric machine 1 functions as a motor (motor) can be suppressed to be small. The reason for this will be described below with reference to fig. 5 to 7.

Fig. 5 and 6 are upper half views of a rotor and a stator showing magnetic fluxes generated in a stator core at a predetermined electrical angle, (a) is a view showing magnetic fluxes of a rotating electrical machine according to the present application, (b) is a view showing magnetic fluxes of a conventional rotating electrical machine, and fig. 7 is a view showing torque fluctuations of the rotating electrical machine according to the present application with respect to the electrical angle compared with torque fluctuations of the conventional rotating electrical machine.

As shown in fig. 5 (a), in a state where the d-axis of the rotor 10 passes through the centers of the four fixed portions 24, the magnetic fluxes f1, f2, which are opposite to each other, coming out from the N-pole magnetic pole portions 40N provided on the rotor 10 and entering the S-pole magnetic pole portions 40S flow through the stator core 21, but since the fixed portions 24 are located at positions where the magnetic fluxes f1 and f2 diverge, these magnetic fluxes f1, f2 do not flow through the fixed portions 24. Further, since each of the flux barriers 25 is located at a position where the fluxes f1 and f2 diverge, the fluxes f1 and f2 are not obstructed by the flux barrier 25. Therefore, in the motor angular range a shown in fig. 7, the magnetic flux resistance is the same as that in the conventional rotating electrical machine shown in fig. 5 (b) without the magnetic flux barrier 25. As a result, as shown in fig. 7, the waveform of the torque in the predetermined electric angle range a is the same as that in the conventional rotary electric machine 1 of the present application. In fig. 5 (b) and 6 (b), 110 is a rotor, 111 is a rotor core, 140N is an N-pole magnetic pole portion, 140S is an S-pole magnetic pole portion, 120 is a stator, 121 is a stator core, 122 is a coil, and 124 is a fixed portion.

On the other hand, in the conventional rotating electrical machine shown in fig. 6 (b), when the q-axis of the rotor 110 passes through each center of the four fixed portions 124, a part f3 of the magnetic flux f2 flows through each fixed portion 124. This corresponds to the expansion of the magnetic circuit, so that the magnetic resistance decreases, and in the electrical angle range b shown in fig. 7, as shown by the broken line, the torque waveform increases, and the torque shows the maximum value.

In contrast, in the rotating electrical machine 1 of the present application, as shown in fig. 6 (a), a part f3 of the magnetic flux f2 also flows through each of the fixing portions 24, but since the magnetic flux barrier 25 is provided midway in the magnetic flux f1, the magnetic path is narrowed by the magnetic flux barrier 25, and the magnetic resistance is increased. Accordingly, the decrease in magnetic resistance due to the flow of the magnetic flux f3 through the fixed portion 24 is offset by the increase in magnetic resistance due to the magnetic flux barrier 25, and the rise in torque waveform in the electrical angle range b of fig. 7 is prevented, and the torque waveform takes on substantially the same shape over the entire electrical angle range as shown by the solid line in fig. 7. As a result, torque fluctuation, that is, torque ripple of the rotor 10 (shaft 12) is suppressed to be small, and vibration and noise of the rotary electric machine 1 are suppressed to be low. The torque ripple shows the fluctuation amount of the output torque of the rotor 10 (shaft 12) as a percentage relative to the average torque.

On the other hand, the rotating electrical machine 1 mounted on the vehicle functions as a generator (generator) when the vehicle decelerates by regenerative braking. That is, when the rotor 10 is driven to rotate by rotational power input from the wheel side to the shaft 12 of the rotary electric machine 1, electric power generation is performed by generating an alternating current in the coil 22 of the stator 20 by the rotational magnetic flux of the permanent magnet 13 embedded in the rotor 10. The alternating current generated by the power generation is converted into direct current by a converter not shown, and the battery not shown is charged by the direct current.

The above description has been given of the embodiment of the present application applied to a rotating electrical machine mounted in an electric vehicle (EV vehicle), a hybrid electric vehicle (HEV vehicle), or the like, but the present application is also applicable to a rotating electrical machine for any other application.

The above description has been given of the embodiment of the present application applied to a rotating electrical machine (motor generator) that functions as a motor (motorr) and a generator (generator), but the present application can be similarly applied to a rotating electrical machine that functions as a motor (motorr) alone.

The present application is not limited to the above-described embodiments, and it is obvious that various modifications are possible within the scope of the technical ideas described in the claims, the specification, and the drawings.

(symbol description)

1 rotating electric machine

10 rotor

11 stator core

12-axis

13 permanent magnet

20 stator

21 stator core

21A yoke of stator core

21B teeth of stator core

21C stator core slots

22 coil

23 bolt (fastener)

24 fixing portion

24a bolt inserting hole (through hole)

25 flux barrier

30 motor housing

40 magnetic pole part

40N N pole part

40S S pole portions.

Claims (4)

1. A rotating electrical machine is provided with:

a rotatable rotor having a plurality of permanent magnets buried in an outer peripheral portion thereof;

a stator fixedly arranged around the rotor and provided with a plurality of coils at a stator core; and

a motor housing that houses the rotor and the stator inside,

the rotating electric machine is configured by fixing the stator to the motor housing by means of a fastener inserted through a plurality of fixing portions protruding radially outward from an outer periphery of the stator core,

it is characterized in that the method comprises the steps of,

in a state where the q-axis of the rotor passes through the center of the fixed portion, a flux barrier penetrating in the axial direction is formed on the stator core portion on the q-axis other than the q-axis passing through the center of the fixed portion.

2. The rotating electrical machine according to claim 1, wherein,

the N-pole portions and the S-pole portions are alternately arranged in the circumferential direction on the outer periphery of the rotor, and each of the N-pole and the S-pole portions is configured such that three permanent magnets are arranged in a triangular shape when viewed in the axial direction.

3. The rotating electrical machine according to claim 2, wherein,

the N pole and the S pole are alternately provided with four poles respectively at equal angular intervals in the circumferential direction,

the fixing portions are formed four at equal angular intervals in the circumferential direction of the stator core, and the magnetic flux barriers are formed at circumferentially intermediate positions of two adjacent fixing portions in the circumferential direction, respectively.

4. A rotary electric machine according to any one of claim 1 to 3, wherein,

the fixing portion is a substantially triangular portion that protrudes radially outward from an outer peripheral edge of the stator, and a through hole through which the fastener is inserted is formed in a center portion of the fixing portion.