JP2002119027A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor in which local concentration of magnetic flux is relieved and cogging torque is small, taking into consideration the magnetic flux concentration in a magnetic path in the front surface of a slit, in which a permanent magnet is embedded, so that the conventional constitution where cogging torque is large, and vibration and noise are increased are solved. SOLUTION: This motor is provided with a rotor body, having multilayered slits arranged in the radial direction, and a magnet 6 is embedded only in parts of the multilayer slits. Rotational drive is performed by magnet torque and reluctance torque. With respect to the magnetic flux path width outside the slit in which the magnet 6 is embedded, by making the end portion of the outer peripheral side of the rotor body is made widest, the cogging torque is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reluctance motor utilizing reluctance torque.

[0002]

2. Description of the Related Art Reluctance motors have attracted attention as driving motors for electric vehicles, machine tools, and the like because they have the characteristic that secondary copper loss of a rotor does not occur as compared with inductance motors. However, this type of motor generally has a poor power factor, and for industrial use, it is necessary to improve the rotor core structure or the driving method. In recent years, a technique has been developed to improve the power factor by providing a multilayer flux barrier on the core sheet of the rotor core (1996, National Institute of Electrical Engineers of Japan, 1029, Honda et al., “Multi-flux barrier type synchronous reluctance motor Considerations ”).

FIG. 4 shows an example of the rotor core structure of the conventional improved reluctance motor. In FIG. 4A, a multilayer flux barrier 162 is formed in an inverted arc shape with respect to a shaft core 163 of the core sheet 161 in a disk-shaped core sheet 161 made of an electromagnetic steel sheet. The flux barrier 162 is formed of a slit (through groove) having a width of about 1 mm, and is formed by press working. In addition, core sheet 1
The outer periphery of the slit 61 is provided with a slit outer peripheral end 164 having a constant width in order to have strength against centrifugal force applied during rotation. By laminating several tens of core sheets 161 in the direction of the rotor shaft 165, a rotor core 166 as shown in FIG. 4B is completed. And, this rotor core 166
Is set in the stator 167 as shown in FIG. 4C, a rotating magnetic field is applied to the rotor core 166 from the plurality of field portions 168 of the stator 167, thereby generating a reluctance torque T. This reluctance torque T is expressed by the following equation.

T = Pn (Ld−Lq) idiq (1) where Pn is the number of pole pairs, Ld and Lq are d and q-axis inductances, and id and iq. Is the d- and q-axis currents. The above (1)
It can be seen from the equation that the performance of the motor depends on the difference Ld-Lq between the d and q axis inductances. Therefore, in order to increase the difference Ld-Lq, the flux barrier is provided to provide resistance to the magnetic path in the q-axis direction crossing the slit, while securing the magnetic path in the d-axis direction sandwiched between the slits. Was.

However, in this configuration, since the rotary drive is performed only by the reluctance torque, the drive torque generated by the electric motor is inevitably reduced.

For this reason, as shown in FIG. 3, a permanent magnet is embedded in the slit to utilize not only the reluctance torque but also the magnet torque, so that the electric motor has a large driving torque.

[0007]

In the conventional configuration, the magnetic flux concentrates on the magnetic path in front of the slit in which the permanent magnet is embedded, so that the cogging torque is large and the vibration and noise are increased.

The present invention has been made in view of the above-mentioned problems, and has as its object to provide an electric motor in which local concentration of magnetic flux is reduced and cogging torque is small.

[0009]

According to the present invention, there is provided a rotor body having a multilayer slit arranged in a radial direction, a permanent magnet is embedded in only a part of the multilayer slit, and the rotor is rotated by a magnet torque and a reluctance torque. In the driving motor, the cogging torque can be reduced by making the width of the magnetic flux path outside the slit in which the permanent magnet is embedded widest at the outer peripheral end of the rotor body.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention comprises a rotor body having multilayer slits arranged in a radial direction, a permanent magnet is embedded only in some of the slits in the multilayer slit, and driven to rotate by magnet torque and reluctance torque. In the electric motor, the magnetic flux path width outside the slit in which the permanent magnet is embedded is made wider at the outer peripheral end portion of the rotor body, thereby alleviating magnetic saturation and reducing the distribution of magnetic flux appearing on the rotor surface. Smoothness and reduction of cogging torque can be achieved.

Further, by reducing the width of the slit outside the slit in which the permanent magnet is embedded so that the converging end outside the rotor body becomes the narrowest, magnetic saturation can be reduced.
The distribution of the magnetic flux appearing on the rotor surface can be smoothed, and the cogging torque can be reduced.

In addition, the width of the slit adjacent to the outside of the slit in which the permanent magnet is embedded is made narrower at the converging end outside the rotor main body, thereby alleviating the magnetic saturation and increasing the width of the rotor surface. The distribution of the magnetic flux that appears can be smoothed, and the cogging torque can be reduced.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that the following embodiments are merely examples embodying the present invention, and do not limit the technical scope of the present invention.

In FIG. 1, reference numeral 1 denotes a disc-shaped core sheet made of a material having a high magnetic permeability such as an electromagnetic steel sheet. Curved arc-shaped magnetic flux paths 2 are arranged in a row in the radial direction with a slit 3 interposed therebetween. Such a core sheet 1 is formed by press working or laser processing. Magnetic flux path 2
Is preferably an arc shape in consideration of the shape of the magnetic path, the processing of the core sheet 1, and the like. Where V
Needless to say, the shape may be a letter shape or an I shape. After stacking several tens of core sheets 1 in the axial direction to form a laminate, the rotor shaft is inserted to complete the rotor core. Such core sheets 1 are integrally fixed with an adhesive or the like as necessary.

When the completed rotor core is set in the stator 4, a rotating magnetic field is applied to the rotor core from a field portion including a plurality of teeth of the stator, thereby generating reluctance torque. The stator 4 is a stator having a core portion formed by a distributed winding method, and a winding (not shown) is wound so as to straddle a plurality of teeth.

In the reluctance motor having such a rotor core, the inductance Lq in the q-axis direction crossing the magnetic flux path 2 and the inductance Ld in the d-axis direction along the magnetic flux path 2 are compared as follows. That is, the magnetic permeability in the q-axis direction is about 1 /
Since resistance is given to the magnetic path by the slit 3 of the air layer of 1000, the magnetic flux hardly passes, and the inductance Lq decreases. On the other hand, since the magnetic flux path 2 forms a magnetic path in the d-axis direction, the magnetic flux easily passes through and the inductance Ld increases.

The feature of the electric motor of this embodiment is that not only the reluctance torque but also the magnet torque is used to rotate and drive the permanent magnet 6 in the slit 7 at the most central side of the rotor core with gaps at both ends. And the magnetic flux generated by the permanent magnet 6 adds not only the reluctance torque but also the magnet torque to the driving torque of the electric motor, so that the driving torque can be increased.

At this time, the magnetic flux path 5 between the slit 7 closest to the center, in which the permanent magnet is embedded, and the adjacent slit.
Are wider than the other magnetic flux paths 2. The reason why the magnetic flux path 5 is widened is that the permanent magnet magnetic flux generated by the permanent magnet 6 is blocked by the slit 3 located outside the permanent magnet 6 and flows into the magnetic flux path 5. Therefore, not only the magnetic flux from the stator but also the permanent magnet magnetic flux passes through the magnetic flux path, so that magnetic saturation easily occurs. Therefore, the magnetic flux path on the most central side is made thicker than the other magnetic flux paths so that magnetic saturation does not easily occur in the magnetic flux path.

Further, the magnetic flux path 5 between the slit 7 on the most central side in which the permanent magnet is embedded and the adjacent slit is
The end portion on the outer peripheral side of the rotor body is the widest, so that magnetic saturation is eased, the distribution of magnetic flux appearing on the rotor surface is smoothed, and cogging torque is reduced.

In the rotor of the embodiment described above, the permanent magnet is embedded only in one layer in one pole slit, but may be embedded in a plurality of layers.

The shape of the magnetic flux path is V-shaped,
It may have a linear shape.

Further, the rotor performance may be further improved by reducing the torque ripple caused by the skew of the rotor and the non-uniform magnetic flux.

As shown in FIG. 2, the stator side is not a stator 4 having a coil portion formed by a distributed winding method, but a stator 14 having a coil portion formed by a concentrated winding method as shown in FIG. Is also good.

It should be noted that the motor shown in the above embodiment is preferably used for a drive unit of a compressor provided in a refrigerator or an air conditioner.

[0025]

According to the first and second aspects of the present invention, the cogging torque can be reduced in a motor using not only reluctance torque but also magnet torque.

According to the third aspect of the present invention, the cogging torque can be reduced by making the width of the slit adjacent to the outside of the slit in which the permanent magnet is embedded narrowest at the outer peripheral end of the rotor body. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an electric motor according to the present embodiment.

FIG. 2 is a cross-sectional view of a motor having a concentrated winding type stator.

FIG. 3 is a diagram showing a conventional magnet embedded type reluctance motor.

FIG. 4 is a diagram showing a conventional reluctance motor.

[Explanation of symbols]

 1,161 Core sheet 2,5 Magnetic flux path 3,7 Slit 4,167 Stator 6 Magnet 162 Flux barrier 163,165 axis 164 Slit outer peripheral end 166 Rotor core 168 Coil winding part

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Murakami 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 72) Inventor Shinichiro Kawano 1006 Kadoma, Kazuma, Osaka Pref.F-term in Matsushita Electric Industrial Co., Ltd. (reference)

Claims (4)

[Claims] 1. An electric motor comprising a rotor body having multilayer slits arranged in a radial direction, a permanent magnet embedded in only some of the multilayer slits, and rotationally driven by magnet torque and reluctance torque. An electric motor having the widest magnetic flux path width outside the slit in which the permanent magnet is embedded, the outer peripheral end of the rotor body. 2. The electric motor according to claim 1, wherein a slit width outside the slit in which the permanent magnet is embedded is narrowest at an outer peripheral end of the rotor body. 3. The electric motor according to claim 1, wherein the width of the slit adjacent to the outside of the slit in which the permanent magnet is embedded is narrowest at the outer peripheral end of the rotor body. 4. A compressor using the electric motor according to claim 1.