JP7217205B2 - Outer-rotating surface magnet rotating electric machine - Google Patents

Description

The present invention relates to an outer rotor type surface magnet rotating electric machine.

Rotating electric machines, which are electric/mechanical energy conversion devices, are built in various devices, and along with the miniaturization of devices, miniaturization of rotating electric machines is also required. As one means for miniaturizing rotating electric machines, outer rotor type permanent magnet rotating electric machines are used. An outer rotor type permanent magnet rotating electric machine has a configuration in which a rotor with permanent magnets is arranged on the outer peripheral side of a stator with coils. Compared to the inner rotor type permanent magnet rotating electric machine, the outer rotor type permanent magnet rotating electric machine has a larger rotor-stator gap (gap) radius, and because the rotor is located on the outer side, the perimeter of one pole is longer. Therefore, there is a feature that a magnet having a large area when viewed from the radial direction can be arranged. This makes it possible to increase the output and reduce the size of the rotary electric machine.

Since the outer rotor type permanent magnet rotating electric machine has a rotor iron core on the outer peripheral side of the magnet, there is little problem in holding the magnet against centrifugal force, so the surface magnet type is often used. Since the surface magnet type reduces short-circuiting of the magnetic flux in the rotor core, the effective magnetic flux can be increased and the output can be increased.

One of the problems of rotary electric machines is the reduction of torque ripple. Torque ripple is torque pulsation. Torque ripple causes vibration and noise in the drive system.

Japanese Patent Application Laid-Open No. 2002-200002 discloses a technique for reducing torque ripple. A rotor of a rotary electric machine includes a substantially annular rotor core having a plurality of magnet insertion holes formed at predetermined intervals in the circumferential direction, and permanent magnets inserted into the magnet insertion holes. The rotor core is formed by laminating a large number of electromagnetic steel sheets, and is characterized by having a hole substantially on the d-axis of each magnetic pole formed by a permanent magnet on the outer peripheral side of the magnet insertion hole of the rotor core.

Further, there is a technique described in Patent Document 2 for reducing torque ripple. A magnet holding portion having a multipolar magnetized cylindrical magnet and a back yoke provided in contact with a radially one side surface of the magnet, and a magnetic field generating portion positioned opposite to the other side surface of the magnet. In the spindle motor in which either one of the magnet holding portion and the magnetic field generating portion is rotatably provided, the back yoke has, on the surface of the side in contact with the magnet, the adjacent magnetic poles of the magnet. It is characterized by providing a concave portion along the boundary line.

JP 2018-137924 JP 2001-57752

In Patent Document 1, the torque ripple is reduced by providing an air gap on the gap side with respect to the magnet. However, the surface magnet type is difficult to adapt because the magnet faces the gap.

In Patent Document 2, the torque ripple is reduced by providing grooves (non-magnetic portions) on the outer shape side of the magnet end portion. However, since the magnetic resistance increases due to the non-magnetic portion, the magnetic flux at the ends of the magnet cannot be effectively used. In addition, if the magnet is subjected to an impact for some reason, there is a high possibility that the magnet will be damaged due to the small number of members that hold the magnet.

SUMMARY OF THE INVENTION An object of the present invention is to provide an epitaxial surface magnet rotating electric machine that reduces demerits such as magnet breakage and an increase in magnetic resistance and reduces torque ripple.

A preferred example of the present invention includes a rotor having a rotor core, permanent magnets arranged on the inner diameter side of the rotor core, and a stator core arranged on the inner diameter side of the rotor with a gap therebetween. , and a coil attached to the stator core, and the rotor core is an epitaxial type having a plurality of air gaps per pole on the outer diameter side of the surface on which the permanent magnets are attached. It is a surface magnet rotating electric machine.

ADVANTAGE OF THE INVENTION According to this invention, while reducing the demerit of a magnet breakage and an increase in magnetic resistance, it becomes possible to reduce a torque ripple.

FIG. 2 is a diagram showing a radial cross section of the outer-rotating surface magnet rotating electric machine in Embodiment 1; FIG. 4 is a diagram showing a radial cross section with an enlarged gap in Example 1; FIG. 10 is a diagram showing a radial cross section with an enlarged gap in Example 2; FIG. 8 is a diagram showing torque ripple with respect to the number of air gaps in Example 2; FIG. 11 is a diagram showing a radial cross section with an enlarged gap in Example 3; FIG. 11 is a diagram showing torque ripple with respect to the gap position in Example 3; The figure which shows the cross section of the axial direction in Example 4. FIG. The figure which shows the cross section of the axial direction of the winding machine for elevators in Example 5. FIG.

An embodiment will be described below with reference to the drawings.

FIG. 1 shows Embodiment 1 of the epitaxial surface magnet rotating electric machine of the present invention. FIG. 1 is a radial cross-sectional view of an outer rotor type surface magnet rotating electric machine. The radial direction refers to the outer peripheral direction from the center of FIG. An outer-rotating surface magnet rotating electric machine 1 of this embodiment includes a rotor 4 composed of a rotor core 2 and permanent magnets 3, and a rotor 4 which is arranged with a predetermined gap on the inner diameter side of the rotor 4, and a stator core. 5 and a stator 7 composed of a coil 6 .

Here, it is desirable that the permanent magnets 3 are surface magnet type arranged on the surface of the rotor core 2 . As a result, by arranging the permanent magnets 3 on the surface of the rotor core 2, it is possible to reduce the leakage magnetic flux that short-circuits the magnet magnetic flux in the rotor and increase the effective magnetic flux, so that the output can be increased.

Moreover, it is desirable that the coil 6 be attached to the stator core 5 by concentrated winding. As a result, the length of the axial end portion of the coil 6 is shortened, and the axial length of the outer rotor type surface magnet rotating electric machine 1 is shortened, thus enabling miniaturization. Furthermore, it is desirable that the portion (slot 8) in which the coil 6 of the stator core 5 is arranged be an open slot. This facilitates the insertion of the coil 6 and improves the ease of assembly.

Furthermore, it is desirable that the radius of curvature near the gap side of the stator core 5 (tips of the teeth) be smaller than the radius of the stator 7 . As a result, the rate of change in magnetic resistance in the circumferential direction can be reduced, and torque ripple can be reduced.

Here, an air gap 9 is provided on the outer diameter side of the mounting surface of the rotor core 2 on which the permanent magnets 3 are mounted. FIG. 2 shows an enlarged view of the vicinity of the gap 9. FIG. By providing an air gap, changes in magnetic resistance seen from the stator side are leveled, harmonic components superimposed on the magnetic flux are reduced, and torque ripple can be reduced. In FIG. 2, two air gaps 9 are arranged per magnet.

In the case of a single air gap 9, the air gap may be large in order to achieve the air gap position that gives optimum torque ripple reduction. Since the air gap 9 is a non-magnetic portion, it becomes magnetic resistance when viewed from the magnet. As the number of air gaps increases, the magnetic resistance also increases, resulting in deterioration of the electrical properties. On the other hand, when two or more air gaps that do not contact each other are formed, the air gaps are made of a magnetic material and magnetic flux can pass through them, so that deterioration in electrical characteristics can be reduced.

In addition, by using air gaps instead of dents and grooves, the shape of the magnet placement part is constant, so there is no need to change the manufacturing method, and the risk of magnet damage due to impact remains the same as before, so it is easy to use. structure can be applied.

Although FIG. 1 shows a 40-pole, 48-slot outer-rotating surface magnet rotating electric machine, the shape is not limited to this, and similar effects can be obtained with other slot combinations. Moreover, when the outer rotor rotating electric machine rotates in both directions, it is desirable that the two gap positions are symmetrical with respect to the central axis of the permanent magnet 3 as shown in FIG.

Furthermore, the gap need not be filled with air, and may be made of a non-magnetic material such as resin. Regarding the shape of the gap, although it is semicircular in FIG. 2, it may be circular, triangular, trapezoidal, etc., and the shape is not limited. In addition, it is not necessary to uniform the size and shape of the air gap within one magnetic pole, and the size, shape and position of the air gap may be changed for each magnetic pole. Moreover, one or more permanent magnets 3 may be arranged for each pole, and may be arranged in the circumferential direction with a substantially constant space between the permanent magnets of the adjacent magnetic poles.

According to the first embodiment, the air gap 9 is arranged inside the rotor core 2 on the outer diameter side of the mounting surface of the rotor core 2 to which the permanent magnets 3 are mounted, so that the members holding the magnets are not affected. This reduces the possibility of damage to the magnet. Furthermore, torque ripple can be reduced while reducing the demerit of increased magnetic resistance.

FIG. 3 is a diagram showing an outer rotor type surface magnet rotating electric machine according to a second embodiment. In Example 1, the number of air gaps per pole was considered to be two, but the number of air gaps may be two or more. FIG. 4 shows the 6th order torque ripple with respect to the number of air gaps. The 6th order torque ripple is a pulsation that is a multiple of 6 of the fundamental frequency.

As described above, the torque ripple reduction effect differs depending on the position of the air gap. Therefore, the position and size of the voids were defined on the same basis by an optimization method. From FIG. 4, it can be seen that by increasing the number of air gaps from 2 to 4, the torque ripple is reduced and the effect of reducing the torque ripple is greatly increased.

However, even if the number of air gaps is changed from 4 to 6, the change in the torque ripple reduction effect is small. Increasing the voids increases the number of processes and may increase the cost, so it is inappropriate to increase the voids unnecessarily. Therefore, it is preferable to set the number of voids to four.

According to the second embodiment, the effect of reducing torque ripple can be increased by setting the number of air gaps per pole to four.

FIG. 5 is a diagram showing an epitaxial surface magnet rotating electric machine according to a third embodiment. In the second embodiment, the effect of reducing the torque ripple of the 6th order was examined, but the effect of reducing the torque ripple due to the irregularity of the rotating electric machine will be examined.

In the case of a 10-pole, 12-slot outer-rotating surface magnet rotating electric machine, secondary and 2.4-order torque ripples are generated due to irregularities in the rotating electric machine. As shown in FIG. 5, the shortest distance between the center of the permanent magnet 3 and the air gap is W1, and the shortest distance between the end of the permanent magnet 3 and the air gap is W2.

FIG. 6 shows a comparison between the torque ripple when W1>W2 and the torque ripple when W1<W2. When there are a plurality of gaps, the largest gap is targeted, and when there are a plurality of gaps of the same size, the gap closest to the center of the magnet is targeted.

As shown in FIG. 6, it can be seen that when W1<W2, the effect of reducing the torque ripple caused by irregularities in the rotating electric machine is greater. Therefore, W1<W2 is preferable in order to reduce the torque ripple caused by the irregularity of the rotating electric machine.

According to the third embodiment, the effect of reducing torque ripple can be increased by adjusting the positional relationship between the permanent magnet and the air gap.

FIG. 7 is a diagram showing an outer rotor type surface magnet rotating electric machine according to a fourth embodiment. FIG. 7 is a cross-sectional view in the axial direction, and describes half the radial direction. Incidentally, the hatched parts in FIG. 7 indicate that they are rotating structures. Rotor 4 is arranged in rotor frame 10 and stator 7 is arranged in stator frame 11 .

Rotor frame 10 is connected to shaft 12 and to stator frame 11 via bearing 13 . The axial direction is the longitudinal direction of the shaft 12 . Here, an auxiliary bearing 14 may be provided to hold the shaft.

A high thermal conductivity member 15 such as a heat pipe is placed in the gap shown in Examples 1 to 3, and the high thermal conductivity member 15 extends outside the rotor 4 . Permanent magnets have a limited operating temperature, and their performance deteriorates due to irreversible demagnetization at high temperatures. Also, the temperature of the permanent magnet is not constant but distributed in the axial direction.

Therefore, it is desirable that the magnet temperature be uniform, since only the hottest part of the permanent magnet can be irreversibly demagnetized.

Therefore, according to the fourth embodiment, by providing the high thermal conductivity member 15 in the air gap, the thermal resistance in the axial direction of the permanent magnet is reduced, and the magnet temperature can be made uniform.

Further, by attaching fins or the like to the ends of the high thermal conductive member 15, the heat radiation area is increased, and furthermore, the heat transfer coefficient is improved by the peripheral speed due to the rotation, making it possible to effectively reduce the magnet temperature.

Although FIG. 7 shows a structure in which the shaft rotates, the same effect can be obtained with a structure in which a bearing is connected between the rotor frame 10 and the shaft 12 and the shaft does not rotate.

FIG. 8 is a diagram showing a sixth embodiment in which the epitaxial surface magnet rotating electric machine of the fourth embodiment is applied to an elevator hoist. In addition, FIG. 8 shows only 1/2 of the radial cross section, and the rotating portion is hatched.

As shown in FIG. 8, an external rotor type surface magnet rotating electric machine 1 is provided as a power source for hoisting a rope 16 connected to a car. It is attached.

According to the fifth embodiment, since the torque pulsation of the epitaxial surface magnet rotating electric machine is reduced, the ride comfort of the elevator can be improved.

REFERENCE SIGNS LIST 1 outer-rotating surface magnet rotating electric machine, 2 rotor core, 3 permanent magnet, 4 rotor, 5 stator core, 6 coil, 7 stator, 8 slot, 9 air gap, 10 ... rotor frame, 11 ... stator frame, 12 ... shaft, 13 ... bearing, 14 ... auxiliary bearing, 15 ... high heat conduction member, 16 ... rope, 17 ... sheave, 18 ... brake

Claims (11)

a rotor having a rotor core and permanent magnets arranged on the inner diameter side of the rotor core;
A stator having a stator core disposed on the inner diameter side of the rotor with a gap therebetween and a coil attached to the stator core,
The rotor core has a plurality of air gaps per pole on the outer diameter side of the surface on which the permanent magnets are mounted ,
Where W1 is the shortest distance between the center of the permanent magnet and the air gap, and W2 is the shortest distance between the end of the permanent magnet and the air gap, W1<W2. rotating electric machine. In the epitaxial surface magnet rotating electric machine according to claim 1,
An outer-rotating surface magnet rotating electric machine, wherein one or more permanent magnets are arranged per pole, and are arranged in a circumferential direction with a substantially constant space from the permanent magnets of adjacent magnetic poles. In the epitaxial surface magnet rotating electric machine according to claim 1,
An outer-rotating surface magnet rotating electric machine, wherein the air gaps are not in contact with each other. In the epitaxial surface magnet rotating electric machine according to claim 1,
An epitaxial surface magnet rotating electric machine, wherein the air gap per pole is arranged symmetrically with respect to the center of the permanent magnet. In the epitaxial surface magnet rotating electric machine according to claim 1,
An outer-rotating surface magnet rotating electric machine, wherein the air gap is filled with a non-magnetic material. In the epitaxial surface magnet rotating electric machine according to claim 1,
An epitaxial surface magnet rotating electric machine, wherein the number of said air gaps per pole is four. In the epitaxial surface magnet rotating electric machine according to claim 1,
An outer-rotating surface magnet rotating electric machine, wherein a high thermal conductivity member such as a heat pipe is arranged in the air gap. An elevator hoist comprising the epitaxial surface magnet rotating electric machine according to claim 1 as power for hoisting a rope connected to a car. In the epitaxial surface magnet rotating electric machine according to claim 1,
The outer-rotating surface magnet rotating electric machine, wherein the air gap has a semicircular, circular, or trapezoidal shape. In the epitaxial surface magnet rotating electric machine according to claim 1,
An epitaxial surface magnet rotating electric machine, wherein the radius of curvature of the stator core on the side of the gap is smaller than the radius of the stator. In the epitaxial surface magnet rotating electric machine according to claim 1,
An epitaxial surface magnet rotating electric machine, wherein the coils are arranged in the slots of the stator core.

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