WO2023032406A1

WO2023032406A1 - Rotary electrical machine

Info

Publication number: WO2023032406A1
Application number: PCT/JP2022/023595
Authority: WO
Inventors: 真弘北野
Original assignee: 日本電産株式会社
Priority date: 2021-09-01
Filing date: 2022-06-13
Publication date: 2023-03-09
Also published as: CN116868480A

Abstract

A rotary electrical machine 1 comprises: a rotatable rotor 10 having a plurality of permanent magnets 13 buried in an outer circumferential part thereof; a stator 20 that is fixed around the rotor and that is provided with a plurality of coils 22 at a stator core 21; and a motor housing 30 for housing the rotor 10 and the stator 20. The stator 20 is fixed to the motor housing 30 by bolts (fasteners) 23 inserted through a plurality of fixed parts 24 projecting radially outward from the outer circumferential edge of the stator core 21. In a state where a q-axis of the rotor 10 passes through centers of the fixed parts 24, a flux barrier 25 penetrating in an axial direction is formed in the stator core 21 on a q-axis other than the q-axis passing through the centers of the fixed parts 24.

Description

Rotating electric machine

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotating electric machine that employs a structure in which a stator housed in a motor housing is fixed to the motor housing with fasteners such as bolts.
This application claims priority based on Japanese Patent Application No. 2021-142395 filed on September 1, 2021, the contents of which are incorporated herein.

In a rotating electrical machine constructed by housing a rotatable rotor and a stator arranged on the outer periphery of the rotor in a motor housing, the stator is fixed to the motor housing. Methods include a shrink fitting method, a bolt fastening method, or a combination of both methods.

When a bolt fastening method is adopted as a method of fixing the stator to the motor housing, a plurality of fixing portions projecting radially outward are formed on the outer periphery of the stator, and the stator is inserted through each of the fixing portions. It is fixed to the motor housing by tightening fasteners such as bolts.

By the way, a stator core that constitutes a stator is formed into a cylindrical shape by laminating a plurality of ring-shaped electromagnetic steel sheets in the axial direction and connecting the plurality of electromagnetic steel sheets to each other by caulking or the like. defines the circumferential pitch between the connecting portion and the fixed portion by caulking or the like of the electromagnetic steel sheets forming the stator core in order to suppress the eddy current loss generated in the stator core. Specifically, when the number of fastening portions is an odd number, the fixed portions are formed at a circumferential pitch equal to or a divisor of the circumferential pitch of the fastening portions with respect to the rotation center of the rotor. When the number is an even number, the fixed portions are formed at a circumferential pitch corresponding to a divisor of the circumferential pitch of the fastening portion with respect to the rotor rotation center or a divisor of 180°.

Further, in Patent Document 2, in a rotating electric machine that adopts a shrink fitting method and a bolt fastening method as fixing methods of the stator, in order to increase the fastening force of the stator to the motor housing and to suppress deformation of the stator due to fastening, A configuration has been proposed in which a recess is formed at the base of the fixing portion (protruding portion) of the stator.

JP 2017-060326 A WO2014/046101

By the way, when a bolt fastening method is adopted as a method of fixing the stator to the motor housing, a plurality of fixing portions having through-holes for inserting bolts are formed on the outer peripheral edge of the stator core, extending radially outward. However, in the stator core provided with these fixed portions, the distribution of the magnetic flux density in the vicinity of the fixed portions is uneven in the circumferential direction with respect to the stator core in which the fixed portions are not provided. . For this reason, in a rotating electric machine that employs a bolt fastening method as a stator fixing method, torque ripple (fluctuation range of output torque) increases, causing a problem of increased vibration and noise.

The present invention has been made in view of the above problems, and its object is to provide a rotating electric machine that can suppress torque ripple to a low level, thereby suppressing vibration and noise.

In order to achieve the above object, the present invention provides a rotatable rotor having a plurality of permanent magnets embedded in its outer peripheral portion, a stator fixed around the rotor and having a stator core provided with a plurality of coils, and A rotor and a motor housing that accommodates the stator therein are provided, and the stator is fixed to the motor housing by fasteners that are inserted through a plurality of fixing portions projecting radially outward from the outer peripheral edge of the stator core. wherein the stator core on the q-axis other than the q-axis passing through the center of the fixed portion is axially provided with the q-axis of the rotor passing through the center of the fixed portion A penetrating flux barrier is formed.

According to the present invention, when part of the magnetic flux that exits the N pole of the permanent magnet of the rotor and enters the S pole flows through the fixed portion of the stator core, the magnetic path widens, reducing magnetic resistance and increasing torque. However, since a flux barrier is provided in the middle of the magnetic flux, the flux barrier narrows the magnetic path and increases the magnetic resistance. For this reason, the decrease in magnetic resistance caused by the magnetic flux flowing through the fixed part is offset by the increase in magnetic resistance due to the flux barrier, and the torque fluctuation of the rotor, that is, the torque ripple, is kept small, and the vibration and noise of the rotating electric machine are reduced. be kept low.

1 is a vertical cross-sectional view of a rotary electric machine according to the present invention; FIG. FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1; FIG. 3 is an enlarged detailed view of a B portion of FIG. 2; FIG. 3 is an enlarged detailed view of a C portion of FIG. 2; FIG. 2 is an upper half view of a rotor and a stator showing the magnetic flux generated in the stator core at a predetermined electrical angle, where (a) shows the magnetic flux of the rotating electrical machine according to the present invention and (b) shows the magnetic flux of the conventional rotating electrical machine. is. FIG. 2 is an upper half view of a rotor and a stator showing the magnetic flux generated in the stator core at a predetermined electrical angle, where (a) shows the magnetic flux of the rotating electrical machine according to the present invention and (b) shows the magnetic flux of the conventional rotating electrical machine. is. FIG. 4 is a diagram showing a comparison of torque fluctuation with respect to electrical angle of a rotating electric machine according to the present invention with torque fluctuation of a conventional rotating electric machine;

Embodiments of the present invention will be described below based on the accompanying drawings.

1 is a vertical cross-sectional view of a rotating electric machine according to an embodiment of the present invention, FIG. 2 is a cross-sectional view along line AA of FIG. 1, FIG. 3 is an enlarged detailed view of B part of FIG. 2, and FIG. It is a partial enlarged detail view.

[Configuration of rotating electric machine]
The rotary electric machine 1 according to the present embodiment is a three-phase synchronous motor generator, functions as an electric motor (motor) or a generator (generator), and can be used, for example, as an electric vehicle (EV vehicle) or a hybrid vehicle (HEV vehicle). It is used as a driving source such as As shown in FIG. 1 , the rotating electric machine 1 is constructed by housing a rotatable rotor 10 and a stator 20 fixed around the rotor 10 in a motor housing 30 . The motor housing 30, the rotor 10, and the stator 20, which constitute the rotary electric machine 1, will be described below.

(motor housing)
The motor housing 30 is constructed by covering the opening of a bottomed cylindrical main body 30A with one end face opened with a disc-shaped cover 30B, and is formed by die casting of aluminum, aluminum alloy, or the like, for example. there is

(rotor)
The rotor 10 includes a cylindrical rotor core 11, a round shaft (motor shaft) 12 passing through the center of the rotor core 11 in the axial direction (horizontal direction in FIG. Both ends of the shaft 12 in the axial direction are connected to bearings (ball bearings) 14 and 15 provided in the main body 30A and the cover 30B of the motor housing 30, respectively. is rotatably supported by Therefore, the rotor 10 is rotatable around the axis (rotational center) of the shaft 12 .

The rotor core 11 is formed in a columnar shape by laminating a plurality of plate-shaped thin electromagnetic steel sheets 11a such as iron or iron alloys. Here, the plurality of electromagnetic steel sheets 11a are integrated by being connected to each other by caulking, welding, or the like. It is fixed to the outer circumference of the shaft 12 by a technique such as fastening. Therefore, the rotor core 11 can rotate together with the shaft 12 .

As shown in FIG. 2, the plurality of permanent magnets 13 are configured as rectangular plates elongated in the axial direction (perpendicular to the paper surface of FIG. 2). are arranged in a triangular shape, and a total of eight pairs of magnetic pole portions 40 are arranged at equal angular pitches (45° pitches) in the circumferential direction. Cavities 16 each having a rectangular cross-section are provided axially (perpendicular to the paper surface of FIG. 2) through both longitudinal ends of each permanent magnet 13 of the rotor core 11 (see FIGS. 3 and 4).

Here, the plurality (eight sets) of magnetic pole portions 40 are composed of N magnetic pole portions 40N and S magnetic pole portions 40S that are alternately arranged in the circumferential direction. 3, of the three permanent magnets 13 (13a, 13b, 13c) arranged in a triangular shape, one permanent magnet 13a arranged along the circumferential direction is oriented so that the N pole faces the outer circumference. The two

permanent magnets

13b and 13c, which are arranged obliquely along the radial direction, are arranged so that their north poles face the inner surfaces facing each other.

On the other hand, in each S pole magnetic pole portion 40S, as shown in FIG. 4, one of the three permanent magnets 13 (13a, 13b, 13c) arranged in a triangular shape is arranged along the circumferential direction. The magnet 13a is arranged so that the S pole faces the outer peripheral side, and the two

permanent magnets

13b and 13c arranged obliquely along the radial direction are arranged so that the S pole faces the opposing inner surface side. ing.

The d (direct) axis shown in FIG. 2 is the magnetic pole center line indicating the main magnetic flux direction of each N pole magnetic pole portion 40N and each S pole magnetic pole portion 40S, and the q (quadrature) axis is the d axis. The d-axis and the q-axis are magnetically orthogonal axes (axis between the N pole magnetic pole portion 40N and the S pole magnetic pole portion 40S), and in the rotating electric machine 1 according to the present embodiment, these d-axis and q-axis are in the circumferential direction. 8 are alternately arranged at an angular pitch of 22.5°.

(stator)
The stator 20 includes a cylindrical stator core 21 and a plurality of coils 22, as shown in FIG. Here, the stator core 21 is configured in a columnar shape by laminating a plurality of plate-shaped thin electromagnetic steel sheets 21a such as iron or iron alloy. there is Here, the plurality of electromagnetic steel sheets 21a are integrated by being connected to each other by caulking, welding, or the like.

The stator core 21 has a ring-shaped yoke 21A and a plurality of (48 in the illustrated example) teeth 21B extending radially inward on the inner peripheral side of the yoke 21A. Here, a plurality of (48) teeth 21B are formed at an equal angular pitch (7.5° pitch) in the circumferential direction, and axially penetrating slots 21C are formed between adjacent teeth 21B. formed. Therefore, the same number (48) of slots 21C as the teeth 21B are formed in the stator core 21 at an equal angular pitch (7.5° pitch) in the circumferential direction. It takes the form of pole 48 slots.

In the stator core 21, coils 22 are provided around each tooth 21B, each coil 22 being formed by, for example, winding an insulating-coated conductive wire. Here, the plurality of coils 22 are composed of a U-phase coil, a V-phase coil, and a W-phase coil. is applied, an AC magnetic field is generated in each coil 22 in a direction penetrating through the U-phase coil, the V-phase coil, and the W-phase coil.

By the way, the stator 20 configured as described above is fixed to the motor housing 30 by four bolts (only one bolt is shown in FIG. 1) 23, which are fasteners, as shown in FIG. Specifically, as shown in FIG. 2, on the outer circumference of the stator core 21 (yoke 21A), four fixed portions 24 which form a substantially triangular shape when viewed in the axial direction are arranged on four orthogonal q-axes. It protrudes integrally toward the outside. That is, the four fixing portions 24 are integrally protruding from the outer peripheral portion of the stator core 21 at an equal angular pitch (90° pitch) in the circumferential direction, and each fixing portion 24 has a circular bolt insertion hole. 24a are pierced in the axial direction (perpendicular to the paper surface of FIG. 2). In addition, in the shape formed by each fixed portion 24, that is, the shape of a substantially triangle when viewed in the axial direction, the top of the triangle forms a convex arc curved surface, and the two oblique sides of the triangle form the ring-shaped stator core 21 (yoke). 21A), forming a concave curved surface that smoothly connects to the outer circumference. By setting the shape of each fixing portion 24 in this way, stress concentration at both base end portions (connecting portions with the yoke 21A) of the fixing portion 24 can be avoided, and cracks at both base end portions can be prevented. can be prevented.

As shown in FIG. 1, the stator 20 includes a total of four bolts (one bolt in FIG. 1) that are respectively inserted into bolt insertion holes 24a provided through the four fixing portions 24 (see FIG. 2). (only shown) 23 is screwed into the main body 30A of the motor housing 30 to be fixed to the motor housing 30 .

By the way, in the rotary electric machine 1 according to the present embodiment, when the q-axis of the rotor 10 passes through the centers of the fixed portions 24 as shown in FIG. Circular hole-shaped flux barriers 25 penetrating in the axial direction are formed in the stator cores 21 on four q-axes other than the first q-axis. Here, as described above, four fixed portions 24 are formed at an equal angular pitch (90° pitch) on the outer circumference of the stator core 21 on the q-axis perpendicular to each other. On each q-axis other than a total of four q-axes passing through the center of each fixed portion 24 (circumferentially intermediate position of two fixed portions 24 adjacent in the circumferential direction (an angle to the q-axis passing through the center of the fixed portion 24 In other words, in the present embodiment, the four flux barriers 25 are formed in the stator core 21 at equal angular pitches (90° pitches) in the circumferential direction. there is

In the present embodiment, the four fixed portions 24 are protruded on the outer circumference of the stator core 21 at equal angular pitches (90-degree pitches) in the circumferential direction, but the number of fixed portions 24 is arbitrary. However, if the number of fixing portions 24 is two, the mounting strength of the stator 20 to the motor housing 30 may be insufficient. Although the mounting strength to the stator core 21 can be increased, there is a problem that the shape of the stator core 21 becomes complicated and the manufacturing cost increases. Therefore, in this embodiment, the number of fixing portions 24 is set to four.

In the present embodiment, the shape of the flux barrier 25 is a circular hole, but it is not limited to this, and may be an elliptical hole shape or a polygonal hole shape. It can be set arbitrarily within the achievable range.

[Action and effect of rotating electric machine]
Next, the action and effect of the rotary electric machine 1 according to this embodiment will be described.

For example, the electric rotating machine 1 according to the present embodiment mounted in an electric vehicle (EV vehicle), a hybrid vehicle (HEV vehicle), etc. (hereinafter simply referred to as "vehicle") serves as an electric motor (motor) that drives wheels to rotate. When it works, a DC current output from a DC power supply such as a battery (not shown) is converted into an AC current by an inverter (not shown). When this alternating current is supplied to each of the plurality of coils (U-phase, V-phase and W-phase coils) 22 provided in the stator 20 of the rotary electric machine 1, these coils 22 generate rotating magnetic fields. Specifically, the magnetic flux of each coil (U-phase, V-phase, and W-phase coils) 22 becomes a combined rotating magnetic flux. 10 rotates in synchronization with the rotating magnetic flux.

That is, electrical energy supplied from the battery is converted by the rotating electric machine 1 into rotational energy (mechanical energy) of the rotor 10 and output as rotation of the shaft 12 . The rotation of the shaft 12 is transmitted to an axle (not shown) through a transmission, a differential device, etc. (not shown), and wheels (not shown) attached to the axle are driven to rotate, thereby driving the vehicle at a predetermined speed. run.

By the way, in the stator core 21 of the rotary electric machine 1 according to the present embodiment, when the q-axis of the rotor 10 passes through the centers of the four fixed portions 24 as shown in FIG. A total of four flux barriers 25 are arranged at equal angular pitches (90° pitches) in the circumferential direction on q-axes other than the four q-axes passing through the center (intermediate positions in the circumferential direction between two fixing portions 24 adjacent in the circumferential direction). Since it is formed, the fluctuation (torque ripple) of the torque output to the rotor 10 (shaft 12) when the rotary electric machine 1 functions as an electric motor (motor) is suppressed. The reason will be described below with reference to FIGS. 5 to 7. FIG.

5 and 6 are upper half views of the rotor and stator showing the magnetic flux generated in the stator core at a predetermined electrical angle, where (a) is the magnetic flux of the rotating electric machine according to the present invention, and (b) is the conventional rotating electric machine. and FIG. 7 is a diagram showing the torque fluctuation with respect to the electrical angle of the rotary electric machine according to the present invention in comparison with the torque fluctuation of the conventional rotary electric machine.

As shown in FIG. 5A, in a state where the d-axis of the rotor 10 passes through the centers of the four fixed portions 24, each N pole magnetic pole portion 40N provided on the rotor 10 is followed by each S pole magnetic pole portion. The magnetic fluxes f1 and f2 entering 40S in opposite directions flow through the stator core 21. Since each fixed portion 24 is located at the position where the magnetic fluxes f1 and f2 diverge, these magnetic fluxes f1 and f2 are Not flowing. Moreover, since each flux barrier 25 is located at a position where the magnetic fluxes f1 and f2 diverge, the flux barriers 25 do not block the magnetic fluxes f1 and f2. Therefore, in the electrical angle range a shown in FIG. 7, the magnetic flux resistance is the same as the magnetic flux resistance in the conventional rotating electrical machine without the flux barrier 25 shown in FIG. As a result, as shown in FIG. 7, the torque waveforms in the predetermined electrical angle range a are the same between the rotating electrical machine 1 according to the present invention and the conventional rotating electrical machine. 5(b) and 6(b), 110 is a rotor, 111 is a rotor core, 140N is an N magnetic pole portion, 140S is an S magnetic pole portion, 120 is a stator, 121 is a stator core, 122 is a coil, 124 is the fixed part.

On the other hand, in the conventional rotating electric machine shown in FIG. 6(b), when the q-axis of the rotor 110 passes through the centers of the four fixed portions 124, a portion f3 of the magnetic flux f2 flows through each fixed portion 124. This corresponds to the expansion of the magnetic path, so that the magnetic resistance decreases, and in the electrical angle range b shown in FIG.

On the other hand, in the rotary electric machine 1 according to the present invention, as shown in FIG. 6A, a part f3 of the magnetic flux f2 flows through each fixed portion 24, but the flux barrier 25 is formed in the middle of the magnetic flux f1. Since the flux barrier 25 is provided, the flux barrier 25 narrows the magnetic path and increases the magnetic resistance. Therefore, the decrease in magnetic resistance caused by the flow of the magnetic flux f3 through the fixed portion 24 is offset by the increase in magnetic resistance due to the flux barrier 25, preventing the torque waveform from rising in the electrical angle range b in FIG. The waveform has substantially the same shape over the entire electrical angle range, as indicated by the solid line in FIG. As a result, the torque fluctuation of the rotor 10 (shaft 12), that is, the torque ripple is kept small, and the vibration and noise of the rotary electric machine 1 are kept low. Note that the torque ripple indicates the amount of fluctuation in the output torque of the rotor 10 (shaft 12) as a percentage of the average torque.

On the other hand, the rotating electrical machine 1 mounted on the vehicle functions as a generator during deceleration due to regenerative braking of the vehicle. That is, when the rotor 10 is rotationally driven by the rotational power input to the shaft 12 of the rotary electric machine 1 from the wheel side, alternating current is applied to the coils 22 of the stator 20 by the rotating magnetic flux of the permanent magnets 13 embedded in the rotor 10 . Generates power generation. The alternating current generated by the power generation is converted into a direct current by a converter (not shown), and the direct current charges a battery (not shown).

In the above description, the present invention is applied to a rotating electric machine mounted on an electric vehicle (EV vehicle) or a hybrid vehicle (HEV vehicle). It is also applicable to a rotating electrical machine with

In the above description, the present invention is applied to a rotating electric machine (motor generator) that functions as both a motor and a generator. It is also applicable to electric machines in the same way.

In addition, the application of the present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the technical ideas described in the claims, the specification, and the drawings. is of course.

1 rotating electrical machine 10 rotor 11 stator core 12 shaft 13 permanent magnet 20 stator 21 stator core 21A stator core yoke 21B stator core disk 21C stator core slot 22 coil 23 bolt (fastener)
24 Fixed portion 24a Bolt insertion hole (through hole)
25 flux barrier 30 motor housing 40 magnetic pole portion 40N N magnetic pole portion 40S S magnetic pole portion

Claims

a rotatable rotor having a plurality of permanent magnets embedded in its outer periphery;
a stator fixed around the rotor and having a stator core provided with a plurality of coils;
a motor housing housing the rotor and the stator therein;
wherein the stator is fixed to the motor housing by fasteners that are inserted into a plurality of fixing portions projecting radially outward from the outer peripheral edge of the stator core,
In a state in which the q-axis of the rotor passes through the center of the fixed portion, a flux barrier that penetrates in the axial direction is formed in the stator core on a q-axis other than the q-axis passing through the center of the fixed portion. Rotating electric machine.
On the outer circumference of the rotor, N magnetic pole portions and S magnetic pole portions are alternately arranged in the circumferential direction. 2. The electric rotating machine according to claim 1, which is arranged and configured.
Four each of the N pole magnetic poles and the S pole magnetic poles are provided alternately at equal angular pitches in the circumferential direction,
Four fixed portions are formed at equal angular pitches in the circumferential direction of the stator core, and the flux barriers are formed at intermediate positions in the circumferential direction between the two fixed portions that are adjacent in the circumferential direction. The rotary electric machine according to claim 2, wherein
The fixed portion is a substantially triangular portion that bulges outward in the radial direction from the outer peripheral edge of the stator, and is characterized in that a through hole through which the fastener is inserted is provided in the central portion of the fixed portion. The electric rotating machine according to any one of claims 1 to 3.