JP2001078401A - Permanent magnet synchronous motor - Google Patents

Abstract

(57) [Problem] To provide a permanent magnet having a capacity sufficient to generate a sufficient torque even when a starting secondary conductor is skewed. SOLUTION: A secondary conductor 26 including a skewed bar 26a and an end ring 26b is manufactured by aluminum die casting. The permanent magnet 2 is formed by compression-molding a bonded magnet made of a mixture of a neodymium-based magnetic powder and a nylon resin with the secondary conductor 26 set in a molding die.
5 and the secondary conductor 26 are integrally formed. This integrally molded product is fitted into the rotor core 23 from the direction of the rotation axis, and both are fixed and magnetized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet type synchronous motor comprising a stator having a stator winding and a rotor having a rotor core provided with a permanent magnet and a starting secondary conductor. Related to electric motors.

[0002]

2. Description of the Related Art A permanent magnet type synchronous motor of this type operates as an induction motor in an asynchronous rotation state in which the rotation frequency and the frequency of a driving power supply are different from each other, such as at the time of starting, and the magnetic flux generated by the current of the stator windings is reduced. The torque is generated by the electromagnetic action with the current flowing through the starting secondary conductor of the rotor. On the other hand, the permanent magnet type synchronous motor operates as an original synchronous motor in the synchronous rotation state, and generates torque by the interaction between the magnetic flux generated by the current of the stator winding and the magnetic flux of the permanent magnet. As described above, the permanent magnet synchronous motor having the secondary conductor for starting can self-start without using a variable voltage variable frequency power supply such as an inverter device.
Commercial power supply (for example, three-phase 200V, 50Hz / 60Hz)
Can be supplied directly. Further, since there is no loss due to the circuit, the synchronous motor is inherently highly efficient.

FIG. 10 shows a cross-sectional structure (a) and a longitudinal cross-sectional structure (b) of a permanent magnet synchronous motor having a three-phase four-pole structure. And a rotor 3 rotatably provided on the inner peripheral side of the stator 2. The stator 2 is inserted into a cylindrical stator core 4 formed by laminating a large number of annular thin plates made of electromagnetic steel plates in the direction of the rotation axis, and a slot 5 formed on the inner peripheral surface side of the stator core 4. And the stator winding 6. The stator winding 6 includes three-phase (U-phase, V-phase, and W-phase) windings.

On the other hand, the rotor 3, which is disposed opposite to the tip end surface of the teeth portion 7 formed between the slots 5 and 5 of the stator 2 with a certain gap 8 therebetween, is made of a circular thin plate made of an electromagnetic steel plate. A rotor core 9 formed by laminating a large number in the rotation axis direction,
Four storage units 10 provided inside the rotor core 9
The permanent magnet 11 includes four permanent magnets 11 having a rectangular cross section which are inserted and fixed in the direction of the rotation axis, and a secondary conductor 12 incorporated in the outer peripheral portion of the rotor core 9. A rotating shaft 13 (not shown in FIG. 10B) is fixed through the shaft of the rotor core 9. The four permanent magnets 11 are arranged uniformly around the axis, and the N pole and the S pole are alternately arranged.

[0005] A plurality of slots 14 extending in the direction of the rotation axis are formed on the outer periphery of the rotor core 9 at equal intervals over the entire circumference. The secondary conductor 12 is composed of a bar 12a housed in the slot 14 and an annular end ring 12b at both ends in the rotation axis direction of the rotor core 9 to end-wrap the bar 12a. This secondary conductor 12
For example, it is formed by aluminum die casting.

[0006]

By the way, the permanent magnet type synchronous motor 1 having the above-described structure generates large vibrations and shocks when starting as an induction motor, and generates electromagnetic noise as it rotates. In order to reduce the vibration and noise, a structure is conceivable in which the slot 5 of the stator core 4 or the slot 14 (that is, the bar 12a) of the rotor core 9 is skewed in the rotation axis direction. When the skew is applied to the slot 5 of the stator core 4, it is difficult to automate the winding operation of winding the stator winding 6 in the slot 5, and the occupation of the stator winding 6 in the slot 5 is difficult. The motor characteristic is deteriorated due to a decrease in the product moment or an increase in the coil circumference. Therefore, a structure in which the slot 14 (bar 12a) of the rotor core 9 is skewed is usually used.

However, a circular hole corresponding to the slot 14,
When the rotor iron core 9 is formed by laminating electromagnetic steel plates having a rectangular hole corresponding to the storage part 10 and a circular hole of the axial center part while skewing, the rotor core 9 is shown in FIG. As shown in (b), the storage unit 10 has a shape twisted with respect to the rotation axis direction, and the rectangular plate-shaped permanent magnet 11 cannot be inserted into the storage unit 10.

In this case, as shown by hatching in FIG. 11 (a), only the rhombic region 10a of the storage portion 10 which can be seen in the direction of the rotation axis of the rotor core 9 has the shape of the region 10a. It is possible to insert a permanent magnet formed in the same rhombus. However, in this case, the storage unit 10
In the state where the diamond-shaped permanent magnet is inserted, the gap in the storage portion 10 becomes large, the magnetic resistance of the rotor core 9 increases, and the magnetic flux of the permanent magnet decreases. there were.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a motor having a secondary conductor for starting, and having a sufficient torque even when the secondary conductor for starting is skewed. It is an object of the present invention to provide a permanent magnet type synchronous motor in which permanent magnets having a capacity sufficient to cause the problem can be easily arranged.

[0010]

According to a first aspect of the present invention, there is provided a permanent magnet type synchronous motor comprising: a stator having a stator winding; In a permanent magnet type synchronous motor including a rotor provided with a conductor, the starting secondary conductor is formed in a skewed state in a rotation axis direction, and the permanent magnet is formed of magnetic powder and heat. It is characterized by being formed integrally with the secondary conductor for starting by using a mixture with a plastic resin.

According to this configuration, since the starting secondary conductor is skewed in the direction of the rotation axis, the non-uniform structure and the teeth structure on the rotor side which are repeated at the pitch of the starting secondary conductor are fixed. The magnetically non-uniform structure on the stator side is substantially uniformized, and the torque generated by the electromagnetic action of the magnetic flux due to the current flowing through the stator winding and the current flowing through the secondary conductor for starting the rotor is stabilized. . As a result, vibrations and shocks can be reduced at the time of starting operation as the induction motor, and deterioration due to vibrations of the permanent magnet synchronous motor itself and its mounting device can be prevented. In addition, electromagnetic noise during rotation can be reduced, and noise can be reduced.

In this case, a mixture of a magnetic powder and a thermoplastic resin is used as the permanent magnet, and the permanent magnet is molded integrally with the starting secondary conductor. Therefore, even if a skewed secondary conductor for starting is used, a permanent magnet having a sufficient capacity to generate a predetermined torque can be easily provided.

It is preferable that magnetic poles having different polarities are alternately generated along the circumferential direction in the permanent magnet, and that the thickness in the radial direction is larger at the center portion than at the end portions of the magnetic pole. 2). According to this configuration, the air gap magnetic flux at the center of the magnetic pole increases, so that the air gap magnetic flux generated by the permanent magnet approaches a sine wave, and the harmonic components contained in the air gap magnetic flux decrease. As a result, cogging torque is reduced, and vibration and noise are reduced.

On the other hand, the secondary conductor for starting may be provided only near the end of each magnetic pole (the invention according to claim 3). According to this configuration, the air gap magnetic flux generated by the permanent magnet is mainly controlled by a non-magnetic material (aluminum, copper, etc.).
Since the air gap magnetic flux near the ends of the magnetic poles on which the starting secondary conductors are arranged is reduced, the air gap magnetic flux approaches a sine wave as a whole, thereby reducing vibration and noise.

Further, it is preferable that the permanent magnet is configured to be skew-magnetized in the rotation axis direction (the invention according to claim 4). According to this configuration, the air gap magnetic flux near the magnetic pole end portion is effectively reduced, so that the air gap magnetic flux generated by the permanent magnet approaches a sine wave as a whole, and vibration and noise are reduced.

In each of these cases, a groove may be provided along the circumferential direction on the surface of the permanent magnet facing the stator (the invention according to claim 5), or the permanent magnet may be divided into a plurality in the rotation axis direction. It is a preferable configuration to mold (the invention according to claim 6). According to this configuration, since the magnetic resistance of the permanent magnet increases and eddy current hardly flows, eddy current loss in the permanent magnet is reduced. Further, since the inside of the permanent magnet is cooled through the groove or the divided portion, the temperature rise of the permanent magnet is suppressed in addition to the reduction of the eddy current loss.

[0017]

FIG. 1 shows a first embodiment in which the present invention is applied to a three-phase four-pole permanent magnet type synchronous motor.
This will be described with reference to FIG. Note that the stator of the permanent magnet type synchronous motor of this embodiment has the same configuration as the stator 2 of the prior art shown in FIG. 10A, and therefore, the rotor will be mainly described here.

FIG. 1 shows a cross sectional structure (a) of a permanent magnet type synchronous motor 21 (hereinafter, referred to as a permanent magnet type motor 21) and a longitudinal sectional structure (b) of a rotor 22 of this embodiment. . In FIG. 1, a rotor core 23 of a rotor 22 is shown.
Is formed by laminating a large number of circular thin plates made of, for example, a silicon steel plate in the rotation axis direction. A shaft hole 23a is formed in the center of the rotor core 23, and a rotation shaft 24 (not shown in FIG. 1B) is inserted and fixed in the shaft hole 23a.

On the outer peripheral surface of the rotor core 23, an inner peripheral surface of a cylindrical permanent magnet 25 having an axial dimension substantially equal to that of the rotor core 23 and a constant radial thickness is bonded. . The permanent magnet 25 is, for example, a bonded magnet made of a mixture of neodymium-based magnetic powder and a thermoplastic resin, for example, a nylon resin. The permanent magnet 25 is configured such that N poles and S poles are alternately arranged along the circumferential direction. It is magnetized to four poles.

In the peripheral wall portion of the permanent magnet 25, a large number of bars 26 constituting the secondary conductor 26 for starting are arranged at equal intervals (this interval corresponds to one slot pitch) over the entire circumference.
a is stored. The secondary conductor 26 has a cage shape as shown in the perspective view of FIG.
and an annular end ring 26 for connecting the bar 26a at both ends in the rotation axis direction of the rotor core 23.
b. The bar 26a and the end ring 26b constituting the secondary conductor 26 are integrally formed by, for example, aluminum die casting. All the bars 26a are skewed by a pitch of 1 to 2 slots in the rotation axis direction. FIG. 1 shows a state in which skew is omitted for convenience. The number of the bars 26a (30 in this embodiment) is empirically determined by the stator 2
Is set to 0.8 times to 1.25 times (1.25 times in this embodiment) the number of slots (24 in this embodiment), but this range is set to improve the starting characteristics and electromagnetic noise. Outside setting values may be used.

The rotor 22 having the above configuration is manufactured as follows. First, the secondary conductor 26 is manufactured by aluminum die casting. At this time, the bar 26a is skewed as described above. Subsequently, the permanent magnet 25 is integrally formed with the secondary conductor 26 by compression-molding the bond magnet with the secondary conductor 26 set in a molding die. Then, this integrally molded product is fitted into the rotor core 23 from the direction of the rotation axis, and both are fixed with an adhesive or the like. Then, for example, using a magnetizing jig,
The permanent magnet 25 is magnetized into four poles so that N poles and S poles are alternately arranged along the circumferential direction.

As another manufacturing method, first, the secondary conductor 26 is manufactured by aluminum die casting, and both the secondary conductor 26 and the rotor core 23 are set in a molding die. You may. In this case, the permanent magnet 25 includes the rotor core 23 and the secondary conductor 2.
6, and the bonding work between the rotor core 23 and the permanent magnet 25 becomes unnecessary.

The permanent magnet type motor 21 having the above configuration
Can be driven using a constant frequency power supply such as a commercial power supply without using a variable frequency power supply device such as an inverter device. That is, the permanent magnet type motor 21 is
In an asynchronous rotation state in which the rotation frequency and the power supply frequency are different, such as at the time of starting, the motor operates as an induction motor, and accelerates, for example, from a stopped state to near a synchronous rotation speed. And
When the permanent magnet type motor 21 approaches the synchronous rotational speed, it is pulled down to the synchronous rotational speed, and thereafter rotates at a synchronous speed as a synchronous motor. Further, the permanent magnet type motor 21 has a characteristic that it is inherently highly efficient because there is no loss due to the excitation circuit.

As described above, according to the present embodiment, the permanent magnet type motor 21 has the non-uniform structure and the teeth on the rotor 22 side repeated at the pitch of the secondary conductor 26 because the secondary conductor 26 is skewed. The magnetically non-uniform structure on the stator side due to the shape of the portion 7 is substantially uniform, and the magnetic flux due to the current flowing through the stator winding 6 and the secondary conductor 26 of the rotor 22
The amount of torque ripple generated by the electromagnetic action with the current flowing through the motor decreases.

As a result, vibrations and shocks can be reduced at the time of starting operation as an induction motor, and deterioration and failures caused by the vibrations and shocks in the permanent magnet type motor 21 itself and its mounting device can be prevented. . In addition, electromagnetic noise during rotation is reduced and noise is reduced.

In particular, as a feature of the present invention, the permanent magnet 25
, A permanent magnet 25 is used as the secondary conductor 2
6 (or the secondary conductor 26 and the rotor core 23) are integrally formed, so that even if the secondary conductor 26 is skewed, it is not necessary to process the permanent magnet 25 into a complicated shape, and the productivity is remarkably improved. And, regardless of the shape of the secondary conductor 26 (for example, the presence or absence of skew), the permanent magnet 25 having a capacity required for generating a predetermined torque can be easily arranged on the rotor core 23.

Further, since the bar 26a made of aluminum is housed inside the permanent magnet 25, the heat radiation of the permanent magnet 25 is improved and the temperature of the permanent magnet 25 can be prevented from rising. As a result, it is possible to suppress a decrease in magnetic properties due to a rise in the temperature of the permanent magnet 25.

Next, a second embodiment obtained by modifying the first embodiment will be described with reference to FIGS. 3 and 4. FIG. In FIG. 3 showing the cross-sectional structure of the rotor 27, the rotor 27 is composed of a rotor core 28 and an integrally formed product of a secondary conductor 26 and a permanent magnet 29 arranged around the core. The permanent magnet 29 is formed so that the thickness in the radial direction becomes larger near the center of the magnetic pole near the center of the magnetic pole, and the thickness in the radial direction becomes constant near the magnetic pole end. I have. A shaft hole 28a is formed in the center of the rotor core 28, and the rotating shaft 24 is inserted and fixed in the shaft hole 28a. With this configuration, the same operation and effect as those of the first embodiment can be obtained.

FIG. 4 (b) shows the developed transverse cross section, the developed air gap surface, and the magnetic flux (hereinafter referred to as air gap magnetic flux) of the air gap 8 (see FIG. 1) in association with each other. . FIG. 4A similarly shows the permanent magnet 25 used in the first embodiment (see FIG. 1).
When these two are compared, FIG.
In the case shown in (a), the air gap magnetic flux has a trapezoidal wave shape, and it can be seen that the generation of the cogging torque is slightly large.
On the other hand, in the case shown in FIG. 4B using the permanent magnet 29, the thickness of the permanent magnet 29 increases and the magnetic flux increases nearer the center of the magnetic pole, so that the air gap magnetic flux approaches a sine wave distribution. As a result, in the present embodiment, the cogging torque becomes smaller, and the vibration and noise are further reduced.

FIGS. 5 and 6 show a third embodiment of the present invention. FIG. 5 showing a cross-sectional structure of the rotor 30.
In the above, a large number of bars 32a constituting a secondary conductor 32 for starting are accommodated in a permanent magnet 31 disposed around the rotor core 23. Both ends of the bar 32a are end-wrapped by an annular end ring 32b. In the bar 32a of the secondary conductor 32, sparse portions and dense portions are alternately formed along the circumferential direction. In the case of the present embodiment, the bars 32a are not arranged in the sparse portion, and the bars 32a are arranged in the dense portion at equal intervals.

According to such a configuration, the air gap magnetic flux at the magnetic pole tip where the bar 32a, which is a non-magnetic material, is disposed is reduced, so that the air gap magnetic flux approaches a sine wave distribution as shown in FIG. As a result, the cogging torque becomes smaller, and vibration and noise during driving can be further reduced.

FIGS. 7 and 8 show a fourth embodiment of the present invention. In FIG. 7, the permanent magnet 34 made of a bonded magnet provided on the outer periphery of the rotor 33 is the same as the permanent magnet 2 of the rotor 22 shown in the first embodiment.
5 and is integrally formed with the secondary conductor 26.
Further, the permanent magnet 34 is skew-magnetized in the rotation axis direction. Even with such a configuration, the first
The same operation and effect as those of the embodiment can be obtained. In addition, as shown in FIG. 8, the change of the air gap magnetic flux at the magnetic pole end portion becomes gentle and the air gap magnetic flux approaches a sinusoidal waveform, so that the cogging torque is reduced and the vibration and noise are further reduced.

Further, a fifth embodiment obtained by modifying the first embodiment will be described with reference to FIG. FIG. 9 is an enlarged view of a part of the longitudinal sectional structure of the rotor 22.
On the outer peripheral surface of the permanent magnet 35, that is, the surface facing the stator 2 (see FIG. 1), a plurality of narrow grooves 35a formed over one circumference are provided at equal intervals in the rotation axis direction. .

According to such a configuration, the eddy current flowing in the permanent magnet 35 during rotation is blocked by the groove 35a, so that the eddy current loss is reduced and the motor efficiency is improved.
Further, since the surface area of the permanent magnet 35 is increased by the groove 35a, the permanent magnet 35 is easily cooled, and the temperature rise of the permanent magnet 35 is suppressed. Thereby, the permanent magnet 3
5 can be kept small, and the motor characteristics can be maintained in a good state.

The present invention is not limited to the above embodiments, but can be modified or expanded as follows. In each embodiment, a three-phase four-pole inner rotor type permanent magnet synchronous motor has been described. However, the present invention can be similarly applied to other phases, other poles, or outer rotor type. Also, the number of slots of the stator 2 and the rotors 22, 27,
The number of slots 30 and 33 may be different from that in the above embodiment.

In each of the above embodiments, the permanent magnets 25, 29,
Bond magnets made by mixing neodymium-based magnetic powder and nylon resin were used as 31, 34 and 35, but bonded magnets mixed with other magnetic powders such as ferrite and samarium or other resins were used. Is also good.

In the fifth embodiment, the groove 35a is formed on the outer peripheral surface of the permanent magnet 35. However, the permanent magnet may be formed into a structure in which the permanent magnet is divided into a plurality in the rotation axis direction. According to this configuration as well, the eddy current is blocked by the divided portion (for example, the slit), and the heat generation of the permanent magnet can be suppressed.

After the bar 26a and the end ring 26b constituting the secondary conductor 26 are integrally formed by aluminum die casting, the secondary conductor 26 and the bond magnet are integrally formed. May be welded with copper end rings 26b at both ends of the bar 26a. The same applies to the secondary conductor 32.

[0039]

As described above, in the permanent magnet type synchronous motor of the present invention, the starting secondary conductor is formed in a skewed state in the direction of the rotation axis, so that the torque is stabilized and the starting motor operates as an induction motor. Vibration and shock at the time are reduced, and electromagnetic noise during rotation is reduced. Further, since the permanent magnet is formed integrally with the starting secondary conductor by using a mixture of the magnetic powder and the thermoplastic resin, the productivity is good regardless of the shape of the starting secondary conductor, and the skew is improved. Even with the use of the starting secondary conductor described above, it is possible to dispose a permanent magnet having a sufficient capacity to generate a predetermined torque.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a permanent magnet type synchronous motor according to a first embodiment of the present invention, and FIG.

FIG. 2 is a perspective view showing a secondary conductor.

FIG. 3 is a cross-sectional view of a rotor showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a cross section of a permanent magnet and a relationship between a gap surface and a gap magnetic flux.

FIG. 5 is a view corresponding to FIG. 3, showing a third embodiment of the present invention.

FIG. 6 is a diagram corresponding to FIG. 4;

FIG. 7 is a perspective view of a rotor showing a fourth embodiment of the present invention.

FIG. 8 is a diagram corresponding to FIG. 4;

FIG. 9 is an enlarged view of a longitudinal sectional structure of a rotor showing a fifth embodiment of the present invention.

FIG. 10 is a diagram corresponding to FIG. 1 showing a conventional configuration.

FIGS. 11A and 11B are a cross-sectional view and a perspective view, respectively, of a rotor when a secondary conductor is skewed.

[Explanation of symbols]

2 is a stator, 6 is a stator winding, 21 is a permanent magnet synchronous motor, 22, 27, 30, 33 is a rotor, 23, 28 is a rotor core, 24 is a rotating shaft, 25, 29, 31,. 34,
35 is a permanent magnet, 26 and 32 are secondary conductors for starting, 35a
Is a groove.

Claims (6)

[Claims] 1. A permanent magnet type synchronous motor comprising: a stator having a stator winding; and a rotor having a rotor core provided with a permanent magnet and a starting secondary conductor. The secondary conductor is formed in a skewed state with respect to the rotation axis direction, and the permanent magnet is a mixture of a magnetic powder and a thermoplastic resin, and is formed integrally with the starting secondary conductor. Features a permanent magnet synchronous motor. 2. The permanent magnet has magnetic poles of different polarities alternately along the circumferential direction, and is configured such that the thickness in the radial direction is thicker at the center than at the ends of the magnetic poles. The permanent magnet type synchronous motor according to claim 1, wherein: 3. The permanent magnet has magnetic poles of different polarities alternately along the circumferential direction, and the starting secondary conductor is provided only near the end of each magnetic pole. A permanent magnet synchronous motor as described. 4. The permanent magnet synchronous motor according to claim 1, wherein the permanent magnet is skew-magnetized in the direction of the rotation axis. 5. The permanent magnet type synchronous motor according to claim 1, wherein the permanent magnet is provided with a groove along a circumferential direction on a surface facing the stator. 6. The permanent magnet type synchronous motor according to claim 1, wherein the permanent magnet is formed in a state divided into a plurality in the direction of the rotation axis.