WO2014156678A1

WO2014156678A1 - Electric motor

Info

Publication number: WO2014156678A1
Application number: PCT/JP2014/056648
Authority: WO
Inventors: 夏樹渡辺; 貞一郎千葉; 敦誉小柴
Original assignee: 株式会社小松製作所
Priority date: 2013-03-29
Filing date: 2014-03-13
Publication date: 2014-10-02
Also published as: JP6133657B2; JP2014197971A

Abstract

An electric motor provided with an annular stator that is mounted in a housing and a rotor that is disposed within the stator, is rotatably supported by the housing, and has a rotor core (41) having a plurality of permanent magnets (43) embedded therein, wherein the rotor core (41) is provided with flux barriers (41C, 41D) at which the end faces of the permanent magnets (43) are positioned, side bridges (44) that are formed between the flux barriers (41C) that are positioned closer to the periphery of the rotor core (41) and the outer peripheral surface of the rotor core (41), and first recesses (61) and second recesses (62) that are recessed from the ends, in the peripheral direction, of the side bridges (44) toward the inside of the rotor core (41).

Description

Electric motor

The present invention relates to an electric motor, and more particularly to an improvement in a rotor of an embedded permanent magnet type synchronous motor.

Conventionally, in an embedded permanent magnet type synchronous motor, it is known that a concave portion is provided on the outer peripheral surface of a rotor core constituting a rotor for the purpose of reducing torque pulsation, iron loss, magnetic flux harmonics, or cogging torque ( For example, see Patent Documents 1 and 2). When using an electric motor as a driving source for running an electric vehicle or a hybrid vehicle, such characteristics greatly affect vibration and noise generation in the electric motor, miniaturization of the electric motor, fuel consumption in the hybrid vehicle, etc. In addition to

Patent Documents

1 and 2, many proposals have been made regarding the shape and position of the recesses. And such a recessed part will be located in the edge part vicinity of the permanent magnet embedded in a rotor core.

On the other hand, the rotor core is provided with a gap at a position corresponding to the end portion of the permanent magnet to reduce the leakage magnetic flux from the end portion. Since this air gap is located near the outer peripheral surface of the rotor, a portion between the air gap and the outer peripheral surface of the rotor core is formed in a bridge shape having a predetermined thickness. Such a part will be referred to as a side bridge.

Japanese Patent Laid-Open No. 2004-328956 JP 2009-278860 A

However, in the above-mentioned side bridge, depending on the shape of the air gap, due to the centrifugal force generated by the rotation of the rotor, stress concentrates on the base end portion of the bridge, and the side bridge may be damaged during the rotation of the rotor, etc. There is a problem with durability.
On the other hand, in order to prevent breakage of the side bridge, it is conceivable to increase the thickness of the base end portion of the side bridge, but in such a case, the leakage magnetic flux from the permanent magnet increases, There is a concern that the characteristics brought about by the recess may be affected.

An object of the present invention is to provide an electric motor capable of improving durability while maintaining good characteristics as an electric motor.

An electric motor according to a first aspect of the present invention includes an annular stator mounted in a housing, a rotor disposed in the stator and rotatably supported by the housing, and a plurality of permanent magnets in a rotor core of the rotor. Embedded in the rotor core, formed on the rotor core between the flux barrier where the end face of the permanent magnet is located, the flux barrier located near the outer periphery of the rotor core, and the outer peripheral surface of the rotor core. And a first concave portion and a second concave portion that are recessed from the both ends in the circumferential direction of the side bridge toward the inner side of the rotor core.

In the electric motor according to the second aspect of the present invention, it is desirable that the side bridge is formed in a curved arch shape so as to protrude outward in the radial direction of the rotor core.
In the generator according to the third aspect of the invention, it is desirable that the side bridge has a substantially uniform thickness in the circumferential direction of the rotor core.
In the electric motor according to the fourth aspect of the present invention, the pair of permanent magnets are arranged in a V shape when viewed from the axial center of the rotor, and the flux barrier on which the inner end surfaces of the pair of permanent magnets are located is It is desirable that they are adjacent to each other via a center bridge.

An electric motor according to a fifth aspect of the present invention includes an annular stator mounted in a housing, and a rotor disposed in the stator and rotatably supported by the housing. The rotor core of the rotor has a plurality of rectangular cross sections. An electric motor in which a permanent magnet having a shape is embedded, and one magnetic pole is formed by a pair of the permanent magnets arranged in a V shape when viewed from the axial center of the rotor, and the rotor core has the permanent magnet One end face on the short side of the outer peripheral side is located near the outer periphery of the rotor core, and the other end face on the short side of the permanent magnet is located on the inner side of the flux barrier. An inner flux barrier located on the outer side, a side bridge formed between the outer peripheral flux barrier and the outer peripheral surface of the rotor core, A center bridge formed between a pair of adjacent inner-side flux barriers, and a first recess and a second recess recessed from the circumferential ends of the side bridge toward the inner side of the rotor core. And the side bridge is formed in an arch shape curved so as to protrude outward in the radial direction of the rotor core, and has a substantially uniform thickness in the circumferential direction of the rotor core, The outer peripheral flux barrier is provided between a line connecting the first recess and the axis center of the rotor core and a line connecting the second recess and the axis center of the rotor core.

According to the first invention, since the first and second recesses are provided at both ends of the side bridge, the stress caused by the centrifugal force at the time of rotation of the rotor is applied to the three centers in the circumferential direction of the first and second recesses and the side bridge The amount of stress at each location can be reduced and the durability can be improved. Moreover, it is possible to make any one of a 1st, 2nd recessed part function as a conventional recessed part, and can maintain the characteristic which a recessed part brings to an electric motor favorably. The side bridge is formed to be thin so that stress is generated at the center in the circumferential direction. By doing so, leakage magnetic flux from the permanent magnet can be reduced.

According to the second invention, since the side bridge is curved and protrudes outward, the first and second recesses formed at both ends of the side bridge can be made into a clearer shape recessed inward, Various characteristics such as torque pulsation and iron loss can be maintained satisfactorily.
According to the third invention, since the side bridge has a uniform thickness in the circumferential direction, the stress generated in the middle of the circumferential direction can be distributed along the circumferential direction, and is generated in a concentrated manner at the minimal part. Can be suppressed.
According to the fourth invention, since the center bridge is provided between the adjacent flux barriers, it is possible to more reliably cope with the centrifugal force during the rotation of the rotor, and the durability can be further improved.
According to the fifth aspect, the effects of the first to fourth aspects can be obtained similarly.

A sectional view showing the whole electric motor concerning one embodiment of the present invention. The figure which shows the rotor core of the said electric motor. The enlarged view which expands and shows the principal part of the said rotor core. The figure which shows the modification of this invention.

[Overall configuration of electric motor]
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing the entire electric motor 1 of the present embodiment. FIG. 2 is a view showing the rotor core 41 of the electric motor 1.

1, an electric motor 1 includes an annular stator 3 mounted in a housing 2 and a rotor 4 that is disposed in the stator 3 and is rotatably supported in the housing 2. Such an electric motor 1 is configured as an embedded permanent magnet type synchronous motor in which a permanent magnet 43 is embedded in a rotor core 41 of a rotor 4.

[Stator]
Although not clearly shown in the figure, the stator 3 includes a stator core 31 formed by laminating a large number of electromagnetic steel plates along the axial direction. The stator core 31 includes an outer peripheral yoke 32 continuous in the circumferential direction and a plurality of teeth 33 protruding from the yoke 32 toward the central rotor 4 side. The plurality of teeth 33 are provided at equal intervals along the circumferential direction of the yoke 32. An electromagnetic coil 34 is wound around such a tooth 33.

[Rotor]
The rotor 4 includes an annular rotor core 41 configured by laminating a large number of electromagnetic steel plates along the axial direction in the same manner as the stator core 31, and a rotor shaft 42 inserted through an insertion hole 41A provided in the center of the rotor core 41. And a total of 16 prismatic permanent magnets 43 fitted into the embedded holes 41B of the rotor core 41.

2, the embedded hole 41B of the rotor core 41 is provided in a V shape so as to be symmetric when viewed from the axial center side. A pair of such embedded holes 41B is taken as one set, and one magnetic pole is formed by a pair of permanent magnets 43 embedded in the set of embedded holes 41B. That is, the number of poles of the rotor 4 of this embodiment is eight. The polarities of adjacent magnetic poles are different from each other. The magnetic poles are formed at equal intervals along the circumferential direction of the rotor core 41.

In the rotor core 41, one end in the longitudinal direction of the embedded hole 41B whose opening shape is a long hole is a flux barrier 41C made of a gap. Of the pair of

end surfaces

43B, 43B on the short side of the permanent magnet 43 having a rectangular cross section, one end surface 43B (see FIG. 3) is positioned on the flux barrier 41C. Similarly, the other end in the longitudinal direction of the embedded hole 41B is a similar flux barrier 41D on which the other end face 43B of the permanent magnet 43 is located. That is, a pair of side surfaces 43A (see FIG. 3) on the long side of the permanent magnet 43 are in contact with the inner surface of the embedded hole 41B except for a part of an end surface 43B that comes into contact with

support portions

71 and 72 described later. is doing.

Among the flux barriers 41 C and 41 D, the flux barrier 41 C located on the outer peripheral side of the rotor core 41 is provided in order to reduce the leakage magnetic flux from the permanent magnet 43. The flux barrier 41D located on the inner side far from the outer peripheral surface of the rotor core 41 is provided to reduce leakage magnetic flux from the permanent magnet 43 and to constitute a part of a cooling structure described later. A side bridge 44 is provided between the flux barrier 41C and the outer peripheral surface of the rotor core 41, and a center bridge 45 is provided between the flux barriers 41D adjacent to each other on the center side of the magnetic pole. The side bridge 44 will be described later.

The

annular end plates

46 and 47 are attached to both sides of the rotor core 41 in the axial direction. On the side of the output portion 42A (left side in FIG. 1) of the rotor shaft 42, the end plate 46 attached to the rotor core 41 communicates the portion corresponding to the flux barrier 41D of the rotor core 41 and the rotor shaft 42 side. A path 46A is provided along the radial direction. A discharge hole 46B opened in the housing 2 is provided at the end of the oil passage 46A. The other end plate 47 is provided with a discharge opening 47A at a position corresponding to the flux barrier 41D, and the flux barrier 41D communicates with the inside of the housing 2. In the present embodiment, the horizontal electric motor 1 in which the axial direction of the rotor shaft 42 is substantially horizontal is described. However, in the present invention, the vertical electric motor in which the axial direction of the rotor shaft is substantially vertical is described. An electric motor may be used. And when set vertically, the discharge hole 46B may be omitted.

At the center of the rotor shaft 42, there is provided an oil passage 42B that opens on the opposite side to the output part 42A and extends toward the output part 42A along the axial direction. The end portion on the output portion 42A side of the oil passage 42B communicates with the oil passage 42C penetrating in the radial direction. The oil passage 42 C communicates with the oil passage 46 A of the end plate 46.

As the permanent magnet 43, a rare earth permanent magnet such as neodymium or dysprosium is preferably used. Such a permanent magnet 43 is fixed by an adhesive in a state of being fitted in the embedded hole 41B of the rotor core 41. The fixing structure of the permanent magnet 43 will be described later.

(Cooling structure)
In the electric motor 1, the stator core 31, the electromagnetic coil 34, the rotor core 41, and the permanent magnet 43 are in a high temperature state due to heat generation caused by hysteresis loss and eddy current loss. For this reason, in the present embodiment, a structure in which the cooling oil circulates between the inside of the housing 2 and the external cooling oil tank 51 to cool the electric motor 1 is adopted.

In this structure, the supply flow path 52 from the cooling oil tank 51 is connected to the opening side of the oil path 42B provided in the rotor shaft 42 of the electric motor 1. On the other hand, a drain passage 53 to the cooling oil tank 51 is connected to a drain opening 2 A provided in the bottom portion of the housing 2 constituting the electric motor 1. The supply passage 52 is provided with a hydraulic pump 54, and the drain passage 53 is provided with an oil cooler 55.

The cooling oil sucked up by the hydraulic pump 54 from the cooling oil tank 51 enters the oil passage 42B of the rotor shaft 42, flows in the oil passage 42B from one end side to the other end side along the axial direction, and the other end. It flows into the oil passage 46A of the end plate 46 through the radial oil passage 42C provided on the side.

A portion of the cooling oil that has entered the oil passage 46A is injected into the housing 2 from the discharge hole 46B, thereby cooling the rotor core 41 and the electromagnetic coil 34. Further, the other cooling oil that has entered the oil passage 46A enters the flux barrier 41D of the rotor core 41 and cools the rotor core 41 and the permanent magnet 43 by flowing in the flux barrier 41D along the axial direction. The cooling oil that has finished flowing through the flux barrier 41D is injected into the housing 2 from the discharge opening 47A of the end plate 47, and also cools the rotor core 41 and the electromagnetic coil 34.

The cooling oil sprayed from the discharge hole 46B and the discharge opening 47A cools the rotor core 41 and the electromagnetic coil 34, and cools the bearings 21 and 22 that support the rotation of the rotor shaft 42. The cooling oil that has cooled them is dropped into the housing 2 and collected in the oil reservoir 23 at the bottom. The collected cooling oil flows from the oil reservoir 23 through the drain opening 2 A through the drain passage 53, is cooled by the oil cooler 55, and then returns to the cooling oil tank 51.

[Side Bridge]
FIG. 3 is an enlarged view showing a main part of the rotor core 41 in an enlarged manner. In FIG. 3, two adjacent poles are shown.
As shown in FIG. 3, the outer peripheral surface of the rotor core 41 is provided with a first recess 61 and a second recess 62 that are recessed inward in the vicinity of the flux barrier 41 C located near the outer periphery. In each magnetic pole, the first recesses 61 are provided at positions on the outer side in the circumferential direction with respect to the center of the magnetic pole, and the second recesses 62 are provided at positions on the inner side in the circumferential direction with respect to the center of the magnetic pole. And the space | interval of the circumferential direction of the 1st recessed part 61 and the 2nd recessed part 62 is a magnitude | size of the grade which straddles the flux barrier 41C in the circumferential direction. That is, when the line connecting the first recess 61 and the axis center of the rotor core 41 is L1, and the line connecting the second recess 62 and the axis center of the rotor core 41 is L2, the flux barrier 41C is between the lines L1 and L2. Is provided. As a result, the side bridge 44 that connects the first recess 61 and the second recess 62 is formed by the thin portion between the flux barrier 41 C and the outer peripheral surface of the rotor core 41.

The side bridge 44 has a substantially uniform thickness (a radial thickness) in the circumferential direction of the rotor core 41 in relation to the opening shape of the flux barrier 41C, and protrudes outward in the radial direction of the rotor core. It is formed in a curved arch shape. That is, the first recess 61 and the second recess 62 are provided on the base end side of the arched side bridge 44. The curvature radius of the side bridge 44 is smaller than the radius of the outer periphery of the rotor core 41.

In the side bridge 44 having such a shape, stress concentration occurs due to the centrifugal force accompanying the rotation of the rotor 4, but the places where the side bridges 44 occur are near both ends in the circumferential direction and the center in the circumferential direction. Specifically, stress is generated by being dispersed at three locations, that is, the bottom portions of the first recess portion 61 and the second recess portion 62 and the inner surface side portion of the side bridge 44 (flux barrier 41C). Therefore, compared with the conventional case where stress concentration occurs at one point, the stress generated at each point can be reduced, and the durability is improved. Of the first recess 61 and the second recess 62, in the present embodiment, the second recess 62 can function as a conventional recess, and the characteristics of the electric motor 1 can be maintained well. .

[Permanent magnet fixing structure]
Below, based on FIG. 3, the fixed structure of the permanent magnet 43 is demonstrated.
As shown in FIG. 3,

support portions

71 and 72 projecting toward two diagonal positions of the permanent magnet 43 are provided at portions where the flux barriers 41 C and 41 D of the steel plate 7 are formed. The support portion 71 on the flux barrier 41 C side is in contact with the edge farther from the outer peripheral surface of the rotor core 41 in one end face 43 B of the permanent magnet 43. The support portion 72 on the flux barrier 41D side is provided at the base end portion on the outer side of the center bridge 45, and the other end surface 43B of the permanent magnet 43 is on the edge closer to the outer peripheral surface of the rotor core 41. It is in contact. Thus, the permanent magnet 43 is supported by the rotor core 41 at two diagonal positions on the opposite short side edge.

Here, the contact width at which the

support portions

71 and 72 are in contact with the end surface 43B of the permanent magnet 43 is approximately 1/5 (5 minutes) with respect to the entire width on the short side of the permanent magnet 43 provided with the end surface 43B. It is desirable to be shorter than 1). By being shorter than 1/5, the leakage magnetic flux from the end face 43B can be reduced. Further, the contact portion of the

support portions

71 and 72 on the end surface 43 B may be separated from the end portion in the width direction of the end surface 43 B that is a corner portion of the permanent magnet 43.

And in the part which forms the embedding hole 41B of the steel plate 7, the extended part 73 is provided in the position on the opposite side to the

support parts

71 and 72 across the corner part of the permanent magnet 43. The extended portion 73 is provided by extending a part of the embedded hole 41 B in order to form a slight gap with the side surface 43 A of the permanent magnet 43. The extension part 73 is also provided in all the steel plates 7 to be laminated. The laminated steel plates 7 all have the same shape, and by aligning each, an embedded hole 41B communicating with the lamination direction (same as the axial direction of the rotor core 41) is formed, and the permanent magnet 43 is formed in the embedded hole 41B. Can be incorporated.

By all the extended portions 73 communicating in the stacking direction, a filling hole 48 penetrating the rotor core 41 along the axial direction is formed at two positions at different diagonal positions of the permanent magnet 43 in the embedded hole 41B. . That is, such a filling hole 48 is formed between the permanent magnet 43 and the extended portion 73 in a state where the permanent magnet 43 is incorporated in the embedded hole 41B. By filling the axially continuous filling hole 48 with the adhesive, the two diagonal positions of the opposing long side edges of the permanent magnet 43 are fixed to the rotor core 41. A resin material such as a molding material may be used as the adhesive.

Therefore, in this embodiment, it is not necessary to rotate and fix the adhesive on the entire side surface 43A of the permanent magnet 43, and the labor for filling the adhesive can be greatly reduced, and the assembling work can be facilitated. Moreover, the permanent magnet 43 is fitted in the embedded hole 41B, and the side surfaces 43A on both sides of the permanent magnet 43 are in contact with the inner surface of the embedded hole 41B. Therefore, the permanent magnet 43 can be reliably held in the embedded hole 41B with at least an adhesive filling amount.

[Modification]
It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
In the embodiment, the permanent magnet 43 is fixed to the rotor core 41 with the adhesive filling the filling hole 48, but the fixing structure of the permanent magnet 43 is not limited to this. For example, the size of the embedded hole 41B is set so that the permanent magnet 43 can be loosely fitted, and an adhesive is filled in the gap formed between the inner surface of the embedded hole 41B and the side surface 43A of the permanent magnet 43. The permanent magnet 43 may be fixed to the rotor core 41, or both end surfaces of the permanent magnet 43 in the axial direction may be fixed to the

end plates

46 and 47 with an adhesive.

In the embodiment, a pair of permanent magnets 43 arranged in a V shape is used as one set to form one magnetic pole. For example, as shown in FIG. A magnet 43 may be provided, and one magnetic pole may be formed by each permanent magnet 43.
In such a configuration, the flux barrier 41C is provided in a line-symmetric shape at both ends of each permanent magnet 43, and the side bridge 44 and the first and

second recesses

61, 62 are provided corresponding to each flux barrier 41C.

The present invention is used for vehicles such as an electric vehicle, a hybrid vehicle, an electric construction machine, and a hybrid construction machine, and can be preferably used as an electric motor for running these construction machines.

DESCRIPTION OF SYMBOLS 1 ... Electric motor, 2 ... Housing, 3 ... Stator, 4 ... Rotor, 41 ... Rotor core, 41C, 41D ... Flux barrier, 43 ... Permanent magnet, 43B ... End face, 44 ... Side bridge, 45 ... Center bridge, 61 ... 1st Recess, 62 ... second recess.

Claims

An electric motor comprising an annular stator mounted in a housing and a rotor disposed in the stator and rotatably supported by the housing, and a plurality of permanent magnets embedded in a rotor core of the rotor. And
In the rotor core,
A flux barrier in which an end face of the permanent magnet is located;
A side bridge formed between the flux barrier located near the outer periphery of the rotor core and the outer peripheral surface of the rotor core;
An electric motor comprising a first recess and a second recess that are recessed from both ends in the circumferential direction of the side bridge toward the inside of the rotor core.
The electric motor according to claim 1,
The electric motor according to claim 1, wherein the side bridge is formed in a curved arch shape so as to protrude outward in a radial direction of the rotor core.
The electric motor according to claim 1 or 2,
The electric motor according to claim 1, wherein the side bridge has a substantially uniform thickness in a circumferential direction of the rotor core.
The electric motor according to any one of claims 1 to 3,
The pair of permanent magnets are arranged in a V shape when viewed from the axial center of the rotor,
Flux barriers in which end faces on the inner side of the rotor core of the pair of permanent magnets are located adjacent to each other via a center bridge.
An annular stator mounted in the housing, and a rotor disposed in the stator and rotatably supported by the housing, and a plurality of rectangular permanent magnets embedded in the rotor core of the rotor An electric motor,
One magnetic pole is formed by the pair of permanent magnets arranged in a V shape when viewed from the axial center of the rotor,
In the rotor core,
One end face on the short side of the permanent magnet is located, and the outer peripheral flux barrier located near the outer periphery of the rotor core,
The other end face on the short side of the permanent magnet is located, and the inner flux barrier located on the inner side of the flux barrier;
A side bridge formed between the outer peripheral flux barrier and the outer surface of the rotor core;
A center bridge formed between a pair of inner flux barriers adjacent to each other;
A first recess and a second recess recessed from both ends in the circumferential direction of the side bridge toward the inside of the rotor core;
The side bridge is formed in an arch shape curved so as to protrude outward in the radial direction of the rotor core, and has a substantially uniform thickness in the circumferential direction of the rotor core,
The outer peripheral flux barrier is provided between a line connecting the first recess and the axis center of the rotor core and a line connecting the second recess and the axis center of the rotor core. .