JPH11164501A - Permanent magnet rotating electric machine and electric vehicle using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the cogging torque of a permanent magnet rotating electric machine. SOLUTION: Trenches 10 or holes stretching in the axial direction are formed in the outer peripheral part of a rotor core 2. Through the trenches 10 or the holes, cogging torque for canceling the cogging torque generated by magnetic fluctuations of the magnetic field for permanent magnets 8 and a stator 1 is generated. Thereby the cogging torque of the rotating electric machine as a whole is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a permanent magnet rotating electric machine and an electric vehicle using the same.

[0002]

2. Description of the Related Art In a permanent magnet rotating electric machine, there is a problem that "cogging torque" is generated due to magnetic fluctuations of a stator and a rotor, thereby preventing smooth rotation.

As an attempt to reduce the cogging torque, Japanese Unexamined Patent Publication No. 3-45140 discloses a method in which a groove is formed in a permanent magnet to generate a cogging torque of the same order as the generated cogging torque and substantially in the opposite phase. There is described a permanent magnet rotating electric machine in which a magnetic fluctuation component to be provided is provided in a permanent magnet field.

In addition, instead of providing the permanent magnet field with a magnetically fluctuating component, a variable component such as a hole or a groove is provided on the surface of the rotor core located on the outer periphery of the permanent magnet. As a permanent magnet rotating electric machine having the configuration,
-103453, JP-A-7-103453
Some are described in -336917.

The former (Japanese Patent Application Laid-Open No. 5-103453) has a rotor core having holes extending in the axial direction at positions corresponding to electrical angles of 60 degrees and 120 degrees. By reducing the torque at the peak position of the torque ripple and making the torque as a whole uniform, vibration and noise are reduced.

The latter (Japanese Patent Application Laid-Open No. 7-336917) is a rotor core in which arc-shaped permanent magnets are evenly arranged so that the projections face the center of rotation of the rotor, and are located on the concave side of the permanent magnets. A slit extending in the radial direction is formed in the portion. The slit increases the reluctance of the portion, reduces the magnetic flux passing therethrough, and reduces the inductance of the stator winding, thereby suppressing torque reduction.

In an electric vehicle using a permanent magnet rotating electric machine, it is difficult to smoothly decelerate and stop the vehicle due to the cogging torque of the permanent magnet rotating electric machine. Therefore, a mechanism for cutting off the connection between the rotating shaft of the rotating electric machine and the wheel or the wheel drive shaft and a mechanism for absorbing vibration are required.

[0008]

The technique described in Japanese Patent Application Laid-Open No. 3-45140 can reduce the cogging torque, but has the following problems because the grooves are provided in the permanent magnet itself.

First, when a permanent magnet is machined, a crack or a crack is easily generated depending on the material, and the mechanical strength is reduced.
Second, since grooves are formed on the surface of the permanent magnet, it is necessary to form large grooves in order to sufficiently reduce cogging torque. Third, magnetize the magnet after the rotor is formed,
In the case of so-called post-magnetization, if there is a groove on the magnet surface, it is difficult to perform uniform magnetization, so that the performance as a magnet is reduced.

The technique described in Japanese Patent Application Laid-Open No. 5-103453 is capable of equalizing the entire torque, but if holes are provided at electrical angles of 60 degrees and 120 degrees,
Cogging torque cannot be effectively reduced.

The technique described in Japanese Patent Application Laid-Open No. 7-336917 relates to a permanent magnet rotating electric machine in which a convex portion of an arc type permanent magnet is arranged so as to face the center of the rotor. The purpose is not to effectively reduce the cogging torque of the rotating electric machine having such an arrangement.

In view of the above, the present invention provides a permanent magnet rotating electric machine having a block shape, a trapezoidal shape, or an arc shape in which a convex portion faces the stator, without providing a groove on the surface of the permanent magnet and having a very small cogging torque. A first object is to provide a permanent magnet rotating electric machine.

In an electric vehicle using a permanent magnet rotating electric machine, there is provided a mechanism for cutting the connection between the rotating shaft and the wheel or the wheel drive shaft for suppressing cogging torque, or a mechanism for absorbing vibration. Equipment has resulted in reduced efficiency, reduced assemblability, and increased cost.

Accordingly, a second object of the present invention is to increase the efficiency of the electric vehicle as a whole in an electric vehicle using a permanent magnet rotating electric machine, by eliminating the need for equipment for reducing the influence of cogging torque on the vehicle. .

[0015]

A first object of the present invention is to provide a permanent magnet rotating electric machine having a permanent magnet embedded in a rotor core, wherein the permanent magnet has a block shape or a trapezoidal shape, or an arc whose convex portion faces the stator. A groove or hole extending in the axial direction is provided on the outer periphery of the rotor core, and the groove or hole is generated by generating a cogging torque that cancels a cogging torque generated by magnetic fluctuation of the stator and the rotor. Is done.

The second object is achieved by using these permanent magnet rotating electric machines, and the permanent magnet rotating electric machines directly drive wheels or wheel drive shafts.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is applied to a three-phase 8-pole / 48-slot 50 kW permanent magnet rotating electric machine will be described below with reference to FIG. 1 showing one pole pair. First, in FIG. 1, a stator 1 includes a U-phase stator winding U1, a V-phase stator winding V1, and a W-phase stator winding 48 in 48 slots 3 formed in a substantially annular stator core 2.
A phase stator winding W1 is inserted and arranged. An opening 4 corresponding to each slot is provided on the inner peripheral portion of the stator core.
Are formed.

On the other hand, the rotor 6 has the rotor core 7 fitted and fixed to the rotating shaft 9, and N-poles and S-poles are alternately provided in the punching receiving portion formed in the rotor core. The permanent magnet 8 is formed by inserting eight permanent magnets 8 made of neodymium which are magnetized so as to be embedded in the axial direction and embedded therein. And is rotatably arranged. The rotor core 7 is formed by laminating a large number of silicon steel plates having holes for forming a storage portion, and a groove 10 for reducing cogging torque is formed on the surface of the rotor core 7 by rotation per magnetic pole of the permanent magnet 8. It is provided on the outer periphery of the child core 7. The groove 10 extends in the axial direction of the rotor core 7, is disposed between the outer peripheral portion of the rotor core 7 and the outer surface of the permanent magnet 8 in the circumferential direction, and corresponds to the center of the magnetic pole of the permanent magnet 8. Is located.

FIG. 2 shows a magnetic field analysis result for one pole without a groove in order to compare the effect of the presence or absence of a groove on the surface of the rotor core in the present invention, and FIG. 3 shows the shape of FIG. 2 shows the cogging torque of one pole (electrical angle 180 degrees).

FIG. 4 shows a surface of the rotor core of the present invention having a depth of 1 mm.
FIG. 5 shows a magnetic field analysis result for one pole in the case where there is a groove of FIG.
(Degree) of cogging torque.

3 and 5 that the cogging torque from peak to peak when the rotor core surface has no grooves is 1
In contrast to 1.4 Nm, the cogging torque of the present invention having a groove on the rotor surface is 4.6 Nm, and the formation of the groove can reduce the cogging torque to 40%.

On the other hand, FIG. 6 shows a magnetic field analysis result for one pole when there is no groove in order to compare the effect of the presence or absence of a groove on the magnet surface in the conventional example, and FIG. 7 shows the shape of FIG. 2 shows the cogging torque of one pole (electrical angle 180 degrees).

FIG. 8 shows a conventional example in which the magnet surface has a depth of 1 mm.
FIG. 9 shows a magnetic field analysis result of one pole in the case where there is a groove of FIG.
(Degree) of cogging torque.

7 and 9 that the cogging torque from peak to peak when there is no groove on the magnet surface is 21.6N.
In contrast, the cogging torque when the groove is formed on the surface of the permanent magnet is 18.5 Nm, and the cogging torque can be reduced to 85% by providing the groove.

FIG. 10 shows a change in the value of the cogging torque according to the present invention and the conventional example depending on the presence or absence of the groove. Despite having grooves of the same depth, cogging torque can be greatly reduced when grooves are formed on the rotor core surface of the present invention, compared to grooves formed on the magnet surface of the conventional example. I understand. This is because the change in magnetic energy due to the presence or absence of the groove in the rotor core is greater than the change in magnetic energy due to the presence or absence of the groove in the permanent magnet.

In the present invention and the conventional example, in order to obtain the same cogging torque, the groove on the surface of the magnet must be deepened in the conventional example. Increases and efficiency decreases.

In the present invention, since a groove is formed on the surface of the stator core, a grooved die may be used in cutting the laminated steel sheet, and the production is easy. The mechanical strength is stronger than the conventional example, the windage loss can be reduced and the efficiency is improved.

The principle of generation of cogging torque in this type of rotating electric machine will be described below with reference to FIG. Generally, the cogging torque is caused by the movement of the permanent magnet magnetic pole (b),
This is caused by a change in magnetic energy in the gap 5. The cause of this change in magnetic energy is in the winding groove.

FIG. 11A shows the gap magnetic flux density,
(c) is a circumferential development of the stator part, and (d) is a stator part having θ.
Shows the stator part when it has just moved. In the figure, for convenience,
The following description is based on the assumption that the armature portion (c) moves with respect to the permanent magnet magnetic pole (b), contrary to the actual case.

In the figure, the cogging torque _Tc is represented by θ, the moving angle of the armature portion (c) with respect to the permanent magnet magnetic pole (b),
When E (θ) is the magnetic energy of the entire gap, it can be expressed by the following equation.

[0031]

(Equation 1)

On the other hand, the magnetic energy ΔE (θ) per micro physique dφ at an arbitrary angle in the gap is represented by μ ₀ as the magnetic permeability of air, B _g (φθ) as the magnetic flux density of the gap, and K ₁ as a constant. Then, it is expressed by equation (2).

[0033]

(Equation 2)

Therefore, the magnetic energy E (θ) of the entire gap is expressed by the following equation (3), where P is the number of permanent magnet poles.

[0035]

(Equation 3)

In general, the gap magnetic flux density B (φ) when there is no winding groove is decomposed into harmonics, and if _Bn is the peak value of the harmonic of B (φ), it can be expressed by the following equation.

[0037]

(Equation 4)

In the gap, the energy function S
As (φ), S _n (φ) is a harmonic component of S (φ), and K _n is S
_The following equation is defined when the DC component of _n (φ) and S _an are the peak components of harmonics of S _n (φ) (FIG. 11 (f)).

[0039]

(Equation 5)

Here, it is considered that the influence of the winding groove on the magnetic flux density is such that the gap magnetic flux density on the groove decreases or becomes zero. Therefore, the following function using only the position of the groove as a unit is defined as W as the winding groove width (FIG. 11).
(e)).

[0041]

(Equation 6)

[0042]

(Equation 7)

By using the above function, the existence of the winding groove can be represented by the following ut (θ) using α ₁ , α ₂ ,..., Α _n as the winding groove position and nα as the number of winding grooves. .

[0044]

(Equation 8)

Therefore, the distribution of the magnetic flux density including the winding groove is

[0046]

B _g (φ, θ) = (1−ut (θ)) B (φ) (8), and substituting equation (8) into equation (3),

[0047]

(Equation 10)

Is as follows. By the way, since the first term of the equation (9) does not become a function of θ, it does not clearly affect the cogging torque than the equation (1). Therefore, the cogging torque T _c
Is

[0049]

[Equation 11]

Where S (φ) represents an energy function when there is no winding groove, and is expressed by the following equation.

[0051]

(Equation 12)

Therefore, the cogging torque will be described with reference to FIG. 11, and the positional relationship before the movement ((e) in FIG. 11 (f)) in the energy function E (θ) shown in FIG. And the energy function E2 indicating (d) after the movement.

Since it is difficult to find the fluctuation directly from FIG. 11 (f), when the expression (11) is further expanded, the following is obtained.

[0054]

(Equation 13)

Therefore, according to equation (12), the cogging torque can be decomposed into each harmonic component. This indicates that each harmonic component of the cogging torque is given as a variation in the sum of the winding groove positions of the energy function of the same harmonic component.

A permanent magnet rotating electric machine that generates cogging torque according to the above-described theory. In this embodiment, as shown in FIG. 1, a permanent magnet 8 and a stator 1 are attached to a rotor core 7.
And a groove 10 for generating a cogging torque having substantially the same order as the cogging torque generated by the above-described steps. By doing so, the cogging torque generated between the permanent magnet 8 and the stator 1 is reduced by the groove 10 provided in the rotor core 7. In particular, when the grooves 10 are arranged so that the pulsating component of ΣB ² in the pulsating component of the cogging torque is reduced, the effect is large.

In an electric vehicle using a permanent magnet rotating electric machine as a drive motor, vibration occurs due to cogging torque of the rotating electric machine when starting and stopping. By using the present invention, the cogging torque of the rotating electric machine can be reduced, and a comfortable electric vehicle with small vibration at the start and stop of the electric vehicle can be obtained.

On the other hand, by providing the groove 10 on the surface of the rotor core, the gap 5 becomes non-uniform, so that the induced voltage waveform changes. The induced voltage waveform is usually a sine wave, but by using a trapezoidal wave, the peak value and the effective value of the induced voltage can be made closer to those of a sine wave. Therefore, the groove 10
Is provided so that the induced voltage waveform becomes a trapezoidal wave, the effective value of the induced voltage can be increased, and the efficiency and size of the rotating electric machine can be increased. FIG. 12 shows the analysis values of the induced voltage waveform.

In the present invention, the shape of the magnet is not limited to the arc type shown in the first embodiment, but can be realized in various shapes. FIG.
FIG. 9 shows a second embodiment in which the magnet shape is a block shape (rectangle). Also in this case, similarly to the first embodiment, the cogging torque can be reduced by forming a groove in the rotor core.

The magnetic fluctuation component may be other than the groove 10 on the rotor surface, and may be present inside the rotor. FIG. 14 shows a third embodiment in which the magnetic fluctuation component is in the punched hole 11 inside the rotor. This hole 11 is for the permanent magnet 1
One per magnetic pole is provided on the rotor core 7, and is installed on the outer surface of the outer peripheral portion of the rotor core 7 and the circumferential width of the magnetic pole of the permanent magnet 8. Also in this case, the same cogging torque reduction effect as described above can be obtained, and further, there is an effect that windage loss can be reduced. The shape of the punched hole 11 is not limited to a circle but may be an ellipse, a block (rectangular), or the like as long as the mechanical strength of the rotor permits.

The permanent magnet 8 may be other than a neodymium magnet, and the number of permanent magnets (the number of poles) may be other than eight.
The number of slots of the stator may be other than 48. Furthermore, a plurality of grooves 10 on the surface of the rotor core may be provided per pole in the circumferential direction of the magnetic poles of the permanent magnet. Further, the depth of the grooves 10 on the surface of the rotor core provided in the circumferential direction of the magnetic poles of the permanent magnet can be reduced by increasing the number. Those requiring a reduction in cogging torque can be applied not only to rotary electric machines such as an internal rotation type and an external rotation type but also to a linear motor and the like.

As a fourth embodiment of the present invention, the grooves 12 are arranged on both sides of the magnetic pole of the permanent magnet 8. FIG. 15 shows a magnetic field analysis result in this case, and FIG. 16 shows a cogging torque waveform. For comparison, FIG. 17 shows a magnetic field analysis result without a groove, and FIG. 18 shows a cogging torque waveform. A comparison between FIG. 16 and FIG. 18 shows that the cogging torque from peak to peak does not change much, but FIG.
In this case, the electrical angle of 30 degrees is half the electrical angle of 15 degrees when there is a groove. Since the frequency band of the vibration that can be sensed by a person is constant, the frequency (the number of rotations) at which the vibration is sensed is reduced to half by providing the groove. Vibration due to cogging torque originally poses a problem in an extremely low speed region, so that the speed is almost zero at half the speed.

In this case, leakage of magnetic flux can be prevented by making the grooves arranged on both sides of the magnetic pole of the permanent magnet 8 deep.

[0064]

According to the present invention, a groove or a hole extending in the axial direction is provided in the outer peripheral portion of the rotor core to generate a cogging torque for canceling the cogging torque, thereby providing a groove in the permanent magnet field. As compared with the above, a cogging torque can be effectively reduced with a small groove or hole, and a permanent magnet rotating electric machine excellent in workability and mechanical strength can be provided.

Further, by using the rotating electric machine and directly driving the wheels or the wheel drive shafts, smooth deceleration and stop can be realized, and the efficiency of the electric vehicle as a whole can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a magnetic field analysis without a groove for comparison with the first embodiment of the present invention.

FIG. 3 is a graph showing cogging torque in the shape of FIG. 2;

FIG. 4 is a diagram showing a magnetic field analysis according to the first embodiment of the present invention.

FIG. 5 is a graph showing cogging torque in the shape of FIG.

FIG. 6 is a diagram showing a magnetic field analysis when there is no groove for comparison with a conventional example.

FIG. 7 is a graph showing cogging torque in the shape of FIG. 6;

FIG. 8 is a diagram showing a magnetic field analysis of a conventional example.

FIG. 9 is a graph showing cogging torque in the shape of FIG. 8;

FIG. 10 is a graph showing the effect of the presence or absence of a groove in the first embodiment of the present invention and the conventional example.

FIG. 11 is an explanatory diagram showing the principle of generation of cogging torque.

FIG. 12 is a graph showing analysis values of a rotating electric machine having a trapezoidal induced voltage waveform in the present invention.

FIG. 13 is a diagram showing a second embodiment of the present invention.

FIG. 14 is a diagram showing a third embodiment of the present invention.

FIG. 15 is a diagram showing a magnetic field analysis of an example in which two grooves are provided between poles.

FIG. 16 is a diagram showing cogging torque in the shape of FIG.

FIG. 17 is a diagram showing a magnetic field analysis when there is no groove for comparison with an example in which two grooves are provided between poles.

FIG. 18 is a diagram showing cogging torque in the shape of FIG. 17;

[Explanation of symbols]

1 ... stator, 2 ... stator core, 3 ... stator slot, 4
... stator opening, 5 ... gap, 6 ... rotor, 7 ... rotor core, 8 ... permanent magnet, 9 ... rotating shaft, 10 ... groove, 11
… A punched hole.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Suetaro Shibukawa 2520 Oji Takaba, Hitachinaka-shi, Ibaraki Co., Ltd.Automotive Equipment Division, Hitachi, Ltd. (72) Inventor Osamu Koizumi 2520 Odaiba-Koba, Hitachinaka-shi, Ibaraki Co., Ltd. Hitachi, Ltd. Automotive Equipment Division

Claims (8)

[Claims] 1. A permanent magnet rotating electric machine comprising a stator and a rotor, wherein a permanent magnet is embedded in a rotor core, wherein the permanent magnet has a block shape, a trapezoidal shape, and an arc shape in which a convex portion faces the stator side. At least one groove extending in the axial direction of the rotor core per one magnetic pole of the permanent magnet is provided on an outer peripheral portion of the rotor core, and the at least one groove is provided by the rotor core. And the at least one groove generates a cogging torque that cancels a cogging torque generated by magnetic fluctuations of the stator and the rotor. A permanent magnet rotating electric machine characterized by: 2. The permanent magnet rotating electric machine according to claim 1, wherein the one groove is located near a center of the one magnetic pole of the permanent magnet. 3. The permanent magnet rotating electric machine according to claim 1, wherein the plurality of grooves are located corresponding to the one magnetic pole of the permanent magnet. 4. A permanent magnet rotating electric machine comprising a stator and a rotor, wherein a permanent magnet is embedded in a rotor core, wherein the permanent magnet has a block shape, a trapezoidal shape, and an arc shape in which a convex portion faces the stator side. At least one hole is provided in the rotor core for each magnetic pole of the permanent magnet, and the at least one hole is provided between an outer peripheral portion of the rotor core and the one magnetic pole of the permanent magnet. A permanent magnet rotating electric machine disposed between the outer surface having a circumferential width and the at least one hole generating a cogging torque for canceling a cogging torque generated by magnetic fluctuations of the stator and the rotor. 5. The permanent magnet rotating electric machine according to claim 4, wherein the one hole is located near a center of the one magnetic pole of the permanent magnet. 6. The permanent magnet rotating electric machine according to claim 4, wherein the plurality of holes are located corresponding to the one magnetic pole of the permanent magnet. 7. A permanent magnet rotating electric machine comprising a stator and a rotor, wherein a permanent magnet is embedded in a rotor core, wherein the permanent magnet has a block shape, a trapezoidal shape, and an arc shape in which a convex portion faces the stator. A plurality of sections extending in the axial direction of the rotor core are provided on an outer peripheral portion of the rotor core, and the plurality of grooves are arranged on both sides of one magnetic pole of the permanent magnet; The plurality of grooves generate a cogging torque that cancels a cogging torque generated by magnetic fluctuations of the stator and the rotor. 8. A permanent magnet rotating electric machine according to claim 1, wherein said permanent magnet rotating electric machine directly connects a wheel or a wheel drive shaft of an electric vehicle. An electric vehicle characterized in that the electric vehicle is driven.