JP2000152538A - Motor with embedded permanent magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To materialize high output and high efficiency at low cost by embedding a permanent magnet in a rotor core, and also, forming slits inside and outside the permanent magnet. SOLUTION: A rotor 11 is constituted by embedding a permanent magnet in a stacked rotor core 12. That is, the rotor core 12 is equipped with circular slits convex inward in a plurality of layers, and a permanent magnet 13 is embedded in axial direction in one of that slits. Then, it takes such a form that plural lines each of slits remain inside and outside the permanent magnet 13. These slits 16 weaken the magnetic flux of the permanent magnet 13, so they are provided less on the periphery side and more on the center side of the rotor. Hereby, in the case of using the rotor 11, the difference between the inductance in the direction of d axis 14 and the inductance in the direction of q axis 15 becomes large, so the reluctance torque can be made larger. Accordingly, in the case of designing a motor, the magnet torque can be made small, so the cost can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet embedded motor having a rotor with improved reluctance torque.

[0002]

2. Description of the Related Art Conventionally, there is a motor using a permanent magnet as a high-efficiency motor, and one of them is an IPM (permanent magnet embedded) motor in which a permanent magnet is embedded in a rotor core.

[0003] The structure of a rotor of a conventional IPM motor will be described below with reference to the drawings.

In FIG. 2, a rotor 21 of an IPM motor is used.
Has a structure in which a permanent magnet 23 is embedded in a rotor core 22, and has an inductance Ld in a d-axis direction 24.
And a difference in the inductance Lq in the q-axis direction 25 and the saliency, the reluctance torque is generated, and the motor is more efficient than the surface magnet type motor.

Further, since the permanent magnet 23 is embedded in the rotor core 22 and the permanent magnet 23 can be held inside the rotor core 22 even during high-speed rotation, the rotor 21 has a highly rigid structure. For these reasons, IPM motors have become more prevalent than surface magnet type motors.

On the other hand, there is a synchronous reluctance motor as a low-cost motor that does not use a permanent magnet. Hereinafter, the structure of a rotor of a conventional synchronous reluctance motor will be described with reference to the drawings.

In FIG. 3, a rotor 31 of a synchronous reluctance motor has a structure in which a number of slits 35 are provided inside a rotor core 32. Like the above-described IPM motor, the inductance Ld in the d-axis direction 33 and the q-axis Since the inductance Lq in the direction 34 has a difference and has saliency, a reluctance torque is generated to rotate.

[0008] This synchronous reluctance motor is:
Since only reluctance torque is generated, the efficiency is lower than that of the IPM motor. However, since there is no winding in the rotor, no secondary copper loss occurs, and the efficiency is higher than that of the same low-cost induction machine. In recent years, it has been put to practical use as a changing low-cost motor.

[0009]

However, in the case of the above-described conventional IPM motor, although it is an excellent motor having high efficiency and high rigidity, there is a problem that the cost is increased because a permanent magnet is used for the rotor. On the other hand, a synchronous reluctance motor has an advantage that it is lower in cost and more efficient than an induction motor, but it is still not enough from the viewpoint of high efficiency.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a low-cost, high-output, and high-efficiency permanent magnet embedded motor.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention embeds a permanent magnet in a rotor core and forms slits inside and outside the permanent magnet to increase saliency. , With improved reluctance torque.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a permanent magnet is embedded in a rotor core, and slits are formed inside and outside the permanent magnet.

The permanent magnet and the slit are set in an arc shape that protrudes toward the center. Further, a permanent magnet having a small residual magnetic flux density was used.

Further, an electric vehicle having a permanent magnet embedded in the rotor core and a permanent magnet embedded motor having slits formed inside and outside the permanent magnet as a driving source is obtained.

According to the above, the saliency can be increased and the reluctance torque can be improved. Further, even if a permanent magnet having a small residual magnetic flux density is used as the permanent magnet because the saliency can be increased, the output does not decrease.

Since the induced voltage can be further reduced, if the field-weakening control is performed using the drive source of an electric vehicle, a wide range of rotation speed control can be realized.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings.

In FIG. 1, 11 is a rotor, and 12 is its rotor core. 13 is a permanent magnet, 14 is a d-axis direction,
Reference numeral 15 denotes a q-axis direction, and reference numeral 16 denotes a slit.

The rotor 11 is constructed by embedding permanent magnets 13 in a laminated rotor core 12. That is, the rotor core 12 has a plurality of arc-shaped slits 1 whose central sides are convex.
The permanent magnet 13 is embedded in one of the slits in the axial direction. A plurality of slits 16 are left inside and outside the permanent magnet 13, respectively. Since the slits 16 weaken the magnetic flux of the permanent magnets 13, the slits 16 are provided less on the outer peripheral side of the rotor 11 and more on the central side. The slit 16 may be an air layer, or may be filled with a non-magnetic material such as a resin.

According to the above structure, the magnetic flux is difficult to pass because the slit crosses in the d-axis direction, and the inductance in the d-axis direction is further reduced. On the other hand, in the q-axis direction, the magnetic flux becomes easier because the slit is inserted along the q-axis direction, and the inductance in the q-axis direction becomes larger.

Here, the motor torque is expressed by the following (Equation 1).
As shown in (1), it is the sum of the magnet torque and the reluctance torque. The reluctance torque increases as the difference between the d-axis inductance and the q-axis inductance increases, and the magnet torque increases as the magnetic flux of the permanent magnet increases.

[0022]

(Equation 1)

In the case of the motor using the rotor of this embodiment,
Since the difference between the d-axis inductance and the q-axis inductance becomes larger, the reluctance torque can be made larger.

Therefore, when designing a motor, when trying to output the same torque as the conventional one, the magnet torque can be reduced by an amount corresponding to the increase in the reluctance torque. For example, a low-cost permanent magnet having a small residual magnetic flux density is used. be able to.

Further, since the cost of the permanent magnet accounts for a large portion of the cost of the motor, a low cost and highly efficient motor can be designed.

Further, since the induced voltage can be reduced, it is advantageous for the field weakening control, and the high speed rotation can be improved.

When a permanent magnet having the same residual magnetic flux density as that of the conventional one is used, a motor having a higher output than the conventional IPM motor can be obtained.

[0028]

As is apparent from the above embodiment, according to the present invention, a low-cost, high-output, and high-efficiency motor can be obtained.

Further, since the induced voltage can be reduced, it is advantageous for the field-weakening control, and is particularly effective when used as a drive source for an electric vehicle requiring a wide speed range.

[Brief description of the drawings]

FIG. 1 is a front view of a rotor according to an embodiment of the present invention.

FIG. 2 is a front view of a rotor of a conventional IPM motor.

FIG. 3 is a front view of a rotor of a conventional synchronous reluctance motor.

[Explanation of symbols]

 Reference Signs List 11 rotor 12 rotor core 13 permanent magnet 14 d-axis direction 15 q-axis direction 16 slit

Claims (4)

[Claims] 1. A permanent magnet embedded motor in which permanent magnets are embedded in a rotor core and slits are formed inside and outside the permanent magnets. 2. The motor with embedded permanent magnets according to claim 1, wherein the permanent magnets and the slits are set in an arc shape protruding toward the center. 3. The permanent magnet motor according to claim 1, wherein a permanent magnet having a small residual magnetic flux density is used. 4. An electric vehicle using a permanent magnet embedded motor having a permanent magnet embedded in a rotor core and slits formed inside and outside the permanent magnet as a driving source.