JP2000050543A - Permanent magnet embedded motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize output of a drive torque by embedding a permanent magnet in a slit extended at its end to the vicinity of an outer periphery, and providing a non-magnetic part between the outer periphery of a rotor core and an end of the magnet, thereby suppressing demagnetization generated at the end of the magnet. SOLUTION: A rotor 13 is obtained by embedding four sets of permanent magnets 11, 12 disposed at an interval at two layers per one pole in a radial direction of the rotor at a rotor core 14 made of laminated magnetic steel sheets. The magnets 11, 12 of the respective sets are disposed so that S-poles and N-poles are alternately adjacent, and the magnets 11, 12 of the two layer relation are adjacently disposed so that polarities of the outer peripheral side become the same. At this time, the magnets 11, 12 are embedded in a slit extended to the vicinity of the outer periphery of the rotor 13, and an air gap of a non-magnetic part is provided at an end (at a position near the outermost periphery of the rotor of the slot) of the slot. Thus, since a magnetic flux flowing to adjacent tees passes the air gap, a demagnetized magnetic field applied to the magnets can be alleviated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a permanent magnet embedded motor realizing miniaturization and an apparatus using the same.

[0002]

2. Description of the Related Art Conventionally, distributed motors have been employed in permanent magnet embedded motors in consideration of the utilization efficiency of magnetic flux and the balance of magnetic flux due to armature current.

[0003] In the distributed winding, the winding pitch can be close to the full pitch, and the magnetic poles can be formed in a wide range and in a well-balanced manner on the stator. FIG. 8 is a cross-sectional view of a conventional permanent magnet embedded motor (Japanese Patent Application Laid-Open No. 8-331783). The rotor 3 has a structure in which four sets of permanent magnets 1 and 2 arranged at intervals in two layers per pole in the rotor radial direction are embedded in a rotor core 7 made of laminated electromagnetic steel sheets,
The permanent magnets 1 and 2 of each set are arranged adjacent to each other so that the S pole and the N pole are alternately arranged, and have a two-layer relationship.
Are arranged adjacent to each other so that the polarity on the outer peripheral side is the same. Each of the permanent magnets 1 and 2 is formed in a circular arc shape convex on the inner peripheral side of the rotor, and the outer peripheral permanent magnet 1 and the inner peripheral side permanent magnet 2 in a two-layer relationship are substantially concentrically parallel to each other. Are arranged, and the interval between them is substantially constant. The rotor 3 configured as described above has a magnet torque generated by the relationship between the rotating magnetic field generated by the current flowing through the windings 9 provided between the teeth 6 on the stator 5 side and the magnetic fields of the permanent magnets 1 and 2. In addition, the magnetic path is rotated in the direction of R in FIG. 1 by combining with a reluctance torque generated by a magnetic path formed by the rotating magnetic field being formed on the surface side of the rotor 3 or at a space between the inner and outer permanent magnets 1 and 2. With the above configuration,
The reluctance torque can be effectively used, and high efficiency can be realized.

[0004] In such a permanent magnet embedded motor, in order to reduce the size, the winding around the teeth portion is performed by concentrated winding, and the winding is performed at a high density, so that the permanent magnet embedded motor can be downsized. Is considered.

[0005]

However, in a permanent magnet embedded motor, if the windings of the teeth are concentrated windings, when three phases are energized at 120 °, the magnetic poles of adjacent teeth become opposite magnetic poles. In addition, since the winding of one pole and one phase is concentrated on one tooth, the magnetizing force is twice or more as compared with the distributed winding, the magnetic flux flows between adjacent teeth, and the magnetic flux is embedded. The permanent magnet is demagnetized.

[0006]

According to the present invention, there is provided a stator core comprising a plurality of teeth, a yoke connecting the teeth, a winding wound on the teeth by a concentrated winding method,
A rotor core having a reverse salient polarity or a forward salient polarity having a slit portion whose end extends to the vicinity of the outer periphery, a permanent magnet is embedded in the slit portion, and a nonmagnetic material is provided between the outer periphery of the rotor core and the end of the permanent magnet. This is a permanent magnet embedded motor characterized in that a magnetic flux due to a demagnetizing field passes through a non-magnetic part, so that demagnetization generated at an end of the permanent magnet can be suppressed. In particular, the demagnetization is likely to occur in the slit portion close to the outer periphery of the rotor core, so that the magnetic flux from the teeth does not easily reach the permanent magnet, so that demagnetization hardly occurs.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a plurality of teeth,
A stator core consisting of a yoke connecting the teeth, a winding applied to the teeth in a concentrated winding manner, and a rotor core having a salient polarity having a slit part whose end extends to the vicinity of the outer periphery, A permanent magnet embedded motor in which a permanent magnet is embedded and a non-magnetic portion is provided between an outer periphery of a rotor core and an end of the permanent magnet, wherein the end of the permanent magnet is a portion where the permanent magnet is easily demagnetized. Is provided with a non-magnetic portion. By providing a shielding wall between the end portion of the permanent magnet and the outer peripheral end of the rotor, the magnetic flux leaking between adjacent teeth passes through the non-magnetic portion, so that the demagnetizing field applied to the permanent magnet is reduced.

It is preferable that the shape of the slit is convex at the center of the rotor. Further, the permanent magnet may be a rare earth magnet. In addition, the number of rotor magnetic poles is four, the magnetic attraction force is balanced, and a highly efficient motor with less iron loss can be provided.

Further, by using this permanent magnet embedded motor for a compressor of an electric vehicle air conditioner having a limited installation space, it is possible to provide a small compressor that consumes less electricity.

[0010] Further, an electric bicycle equipped with the permanent magnet embedded motor as a driving power or an auxiliary power can be provided, and it is possible to provide an electric bicycle which is small and lightweight and has a long running distance per charge.

[0011]

(Embodiment 1) A permanent magnet embedded motor according to an embodiment of the present invention includes a rotor 13 and a stator 15. The stator 15 includes a stator core 16 including a plurality of teeth 18, a yoke 17 connecting the teeth 18, and a concentrated winding type winding 19 applied to the teeth 18. The rotor 13 has a rotor core 14 made of laminated electromagnetic steel sheets.
And four sets of permanent magnets 11 and 12 arranged at intervals in two layers per pole in the radial direction of the rotor are embedded, and each set of permanent magnets 11 and 12 has an S pole and an N pole alternately. Permanent magnets 1 which are arranged adjacent to each other and have a two-layer relationship.
Reference numerals 1 and 12 are arranged adjacently so that the polarities on the outer peripheral side are the same. The permanent magnet used here is a ferrite magnet which is easy to mold because the shape of the magnet is an arc. At this time, the permanent magnets 11 and 12 are embedded in a slit portion extending to near the outer peripheral portion of the rotor 13,
The end of the slot (the position of the slot closest to the outer periphery of the rotor) has a gap 40. At this time, the air gap 40 has a configuration in which the air gap 40 is provided only at the end of the slot portion, and the side surface portion is in contact with the electromagnetic steel sheet forming the rotor core so that the magnetic flux from the permanent magnet can easily flow. Each of the permanent magnets 11 and 12 is formed in a circular arc shape convex on the inner peripheral side of the rotor, and the outer peripheral permanent magnet 11 and the inner peripheral side permanent magnet 12 in a two-layer relationship are substantially concentrically parallel to each other. Are arranged, and the interval between them is substantially constant. End plates (not shown) and the like are arranged on both end surfaces of the rotor, and are fastened by rivet pins 20 and the like.

The rotor 13 constructed as described above has a rotating magnetic field generated by a current flowing through a group of windings 19 provided between the teeth 18 on the stator 15 side and the permanent magnet 11,
The magnetic torque generated by the relationship with the magnetic field of the rotor 12 and the magnetic path by the rotating magnetic field
It rotates in the direction of R in the figure by combining with a1 and the reluctance torque generated by being formed in the gap Pa2 between the inner and outer permanent magnets 11 and 12 and the gap Pa3 between the poles. Since the reluctance torque at this time is used as an aid to the magnet torque, the magnet torque is usually larger than the reluctance torque.

Since the concentrated winding reduces the effective utilization rate of the magnetic flux by about 10% as compared with the distributed winding, it is necessary to increase the number of turns by about 10% in the concentrated winding as compared with the distributed winding. However, the coil end height is about 40% of the distributed winding,
In the case of the distributed winding, the length of the coil transition 19a is one-fourth of the circumference of the central portion of the stator in the case of four poles. However, since the width is equivalent to one tooth, the winding resistance is greatly reduced.
Therefore, since the installation space is particularly limited, the copper loss is greatly reduced and the efficiency is improved in applications where the thickness is reduced.

In this embodiment, a gap 40, which is a non-magnetic portion, is arranged at the end of the permanent magnet where the permanent magnet is easily demagnetized. Thus, by providing the air gap 40 between the end of the permanent magnet and the outer periphery of the rotor, the air gap 40 serves as a shielding wall for a short-circuit magnetic path between adjacent magnetic poles of the rotor, and the magnetic flux flowing to the adjacent teeth is The passage through the gap 40 alleviates the demagnetizing field applied to the permanent magnet. Note that a non-magnetic material such as a resin material may be embedded instead of the space 40.

A conventional permanent magnet embedded motor driven by using a magnet torque and a reluctance torque is as follows.
In order to make effective use of the reluctance torque, the end of the permanent magnet is brought close to the outer periphery of the rotor, so that the magnetic flux from the teeth easily flows along the side surface of the permanent magnet.

Further, as shown in FIG. 2, the stator core is divided for each tooth, and after winding the teeth, the stator is formed by press-fitting, welding, or the like, so that the winding is easy. High-density winding becomes possible. Thus, a thick line can be used regardless of the status lot open width, and the winding resistance is greatly reduced.

In order to realize the same induced voltage, when the number of windings per phase is increased by about 10% as compared with the distributed winding and the diameter of the winding is increased by about 3%, the line resistance of the winding becomes It was about 3/5 compared to the distributed winding.

Further, in the motor having a core thickness of about half the outer diameter of the stator, the length of the motor including the coil end is reduced by about 25% as compared with the distributed winding. The miniaturization of the motor is more remarkable for a motor having a smaller thickness. In addition,
The number of teeth: the number of magnetic poles is preferably 3: 2.

The permanent magnet embedded motor of this embodiment has a non-magnetic portion between the permanent magnets 11 and 12 and the outer periphery of the rotor 13 so that a large amount of magnetic flux due to a demagnetizing field flowing between adjacent teeth can be generated. It can be prevented from flowing to the end. Further, by providing the non-magnetic portion, the permanent magnet is separated from the outer periphery of the rotor, and the effect of the magnetic flux flowing between the adjacent teeth can be suppressed. The non-magnetic portion is located between the permanent magnet and the outer periphery of the rotor, and has the same salient pole ratio as the rotor in which the permanent magnet extends to the vicinity of the outer periphery of the rotor without extending the permanent magnet to the vicinity of the outer periphery of the rotor.

That is, comparing the permanent magnet of the embodiment of the present application in which a non-magnetic portion is provided at the end with the permanent magnet of the conventional example extended to the outer periphery of the rotor, the conventional motor has a permanent magnet. Is affected by demagnetization at the end, and the amount of magnetic flux decreases as use is repeated from the time of initial shipment, making it difficult to adjust the torque of the permanent magnet. On the other hand, in the present embodiment, by providing a non-magnetic portion at the end of the permanent magnet, the permanent magnet is not affected by demagnetization, generates a constant magnetic flux, and outputs a stable torque.

Embodiment 2 FIG. 3 is a sectional view of a permanent magnet embedded motor according to Embodiment 2 of the present invention. Rotor 23
Is formed by embedding four sets of plate-shaped permanent magnets 21 in a rotor core 24 made of laminated electromagnetic steel sheets perpendicular to the rotor radial direction, and each set of permanent magnets 21 has an S pole and an N pole alternately. Are arranged adjacent to each other. A non-magnetic layer 22 is provided at an end of the magnetic pole surface of the permanent magnet 21 in order to suppress demagnetization due to magnetic flux flowing between adjacent teeth. As the permanent magnet, a rare earth magnet having Br of about 1.1 to 1.4 T (tesla) is used. The rotor 23 configured as described above has a magnet torque generated by a relationship between a rotating magnetic field generated by a current flowing through a group of windings 19 provided between the teeth 18 on the stator 15 side and a magnetic field of the permanent magnet 11, and The magnetic path by the rotating magnetic field is rotated in the direction of R in the figure by combining with the reluctance torque generated by forming the magnetic path at the surface Pa4 and the gap Pa5 of the rotor 13.

Since a rare earth magnet is used, the amount of magnetic flux is large, and the thickness can be reduced by 20 to 60% as compared with a ferrite magnet. Furthermore, since the coil end height is reduced by the concentrated winding type winding, a motor small in the axial direction can be realized. The permanent magnet is inexpensive because it is plate-shaped.

FIG. 4 shows a motor using a distributed winding stator designed to realize the same induced voltage and the same core magnetic flux density using the same rotor, and the rotation of the motor in this embodiment at the same torque. 9 shows the relationship between speed and motor efficiency. FIG. 5 similarly shows the relationship between the rotation speed and the iron loss and the copper loss. In the motor of the second embodiment, the efficiency is improved by 0.5 to 2% as compared with the distributed winding, and the efficiency difference is larger at a low rotation speed. In the case of the same torque, the copper loss is almost constant irrespective of the rotation speed, but the iron loss increases almost in proportion to the rotation speed. Therefore, the efficiency difference becomes larger at the time of low-speed rotation where the iron loss ratio is small. Note that the power supply frequency for realizing the same rotation speed increases in proportion to the number of poles. On the other hand, iron loss is the eddy current loss of frequency 2
Since the power and the hysteresis loss are proportional to the first power of the frequency, in this embodiment, if the number of poles is 6 or more, the increase in the iron loss becomes
Efficiency is reduced because it exceeds the reduction in copper loss. On the other hand, in the case of the two poles, the electric angle between the N pole and the S pole generated in the stator by the current is 120 ° and 240 °, so that the attraction force acting on the rotor is biased in the direction adjacent to the N pole and the S pole. Therefore, the eccentricity of the rotor becomes severe. N for four poles
There are two pairs of poles and south poles, and two pairs of north poles and south poles balance each other. Therefore, in consideration of efficiency, sound and vibration, etc., four poles are the best. Further, if the shape of the permanent magnet is an arc or the like, more magnetic flux can be generated, and further downsizing can be achieved.

(Embodiment 3) FIG. 6 is a sectional view of a compressor equipped with a permanent magnet embedded motor according to Embodiment 1.

An arc-shaped permanent magnet 1 convex on the inner peripheral side of the rotor
The rotor cores 14 are divided into two layers in the radial direction per pole.
The rotor 13 having a gap between the permanent magnets 11 and 12 and the outer periphery of the rotor 13 and a stator 15 having a concentrated winding winding are provided inside the compressor shell 30.
Mounted inside.

The structure and operation of the motor are the same as in the first embodiment, and a description thereof will be omitted. In the case of the concentrated winding method, particularly in the case of a sealed brushless motor such as a compressor that requires sensorless driving, a large current flows at the time of startup, and a large demagnetizing field may be applied to the rotor. Therefore, by embedding the permanent magnet inside the rotor core, it is possible to prevent a demagnetizing field from being applied to the permanent magnet.

Further, since the length of the motor including the coil end is small and the efficiency is high, it is particularly suitable for an air-conditioner compressor for an electric vehicle, which has limited power consumption and storage space.

If the rare earth magnet is used, the thickness can be further reduced and the size can be further reduced. (Embodiment 4) FIG. 7 is a sectional view of a drive unit of an electric bicycle equipped with a permanent magnet embedded motor according to Embodiment 2.

The structure and operation of the motor are the same as in the second embodiment, and a description thereof will be omitted. The rotation of the shaft 4 of the motor
1 to the output shaft 32. The output shaft 32 is connected to a bicycle pedal (not shown). In the case of an electrically assisted bicycle, torque is generated according to the pedaling force. Therefore, a large torque is required, and the rotation speed is 2,000 to 2,000.
The motor to be used is about 5000 r / min, and the motor to be used is a permanent magnet embedded motor having a large output, and four poles are optimal. In addition, since it is a bicycle, it is required to be thin and lightweight. Furthermore, efficiency must be high in order to increase the mileage per charge. For the above reasons,
The permanent magnet embedded motor of the present invention is most suitable for the electric bicycle driving motor. In addition, it is effective to embed a permanent magnet in order to prevent a demagnetizing field from being applied to the permanent magnet when rowing out or when a large assist amount suddenly acts on an uphill.

The present invention is not limited to the above embodiment, and various modifications can be made to the shape and specifications of the motor and the combination of the device and the motor in accordance with the purpose of the present invention. They are not excluded from the scope of the present invention.

[0031]

As is apparent from the above description, claim 1
According to the described invention, demagnetization occurring at the end of the permanent magnet can be suppressed, and a stable driving torque can be output.

According to the second aspect of the present invention, since the Br of the permanent magnet is high, a large amount of magnetic flux is generated with a small amount of magnet, and furthermore, the permanent magnet is embedded in the rotor core, so that the vortex inside the permanent magnet is reduced. Since the current can be significantly reduced, a small and highly efficient motor can be provided. In particular, it is suitable as a motor driven by a moving power supply.

According to the third aspect of the present invention, the winding is easy and the space factor is improved by the aligned winding, so that the efficiency is high,
A motor having a small axial length can be manufactured with good productivity.

According to the fourth aspect of the present invention, it is possible to provide a highly efficient motor with a good balance of magnetic attraction force and small iron loss.

According to the fifth aspect of the present invention, it is possible to provide a small-sized compressor that uses less electricity.

According to the sixth aspect of the present invention, it is possible to provide an electric bicycle which is small and lightweight and has a long running distance per charge.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a permanent magnet embedded motor shown in a first embodiment.

FIG. 2 is an assembly diagram of a stator of the permanent magnet embedded motor.

FIG. 3 is a cross-sectional view of the permanent magnet embedded motor shown in the second embodiment.

FIG. 4 is a diagram showing a relationship between rotation speed and motor efficiency.

FIG. 5 is a diagram showing a relationship between a rotation speed and iron loss and copper loss.

FIG. 6 is a cross-sectional view of the compressor of the electric vehicle air conditioner according to the third embodiment.

FIG. 7 is a cross-sectional view of the electric bicycle drive unit according to the third embodiment.

FIG. 8 is a sectional view of a conventional permanent magnet embedded motor.

[Explanation of symbols]

 11, 12 permanent magnet 13 rotor 14 rotor core 15 stator 16 stator core 17 yoke 18 teeth 19 winding 19a coil end 20 rivet pin

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H02K 21/16 H02K 21/16 M (72) Inventor Toshio Yamamoto 1006 Odakadoma, Kadoma City, Osaka Matsushita Electric Industrial In-house F term (reference) 3H003 AA05 AB04 AC03 AD01 CF04 CF05 3H029 AA04 AA13 AB03 BB00 CC07 CC38 5H621 AA03 BB07 GA01 GA04 GB06 HH03 5H622 AA03 AA04 CA02 CA07 CA10 CA13 CB04 CB05 DD02 PP03 PP11

Claims (6)

[Claims] 1. A salient pole having a stator core comprising a plurality of teeth, a yoke connecting the teeth, a winding wound on the teeth by a concentrated winding method, and a slit having an end extending near the outer periphery. A permanent magnet is embedded in the slit portion, and a non-magnetic portion is provided between an outer periphery of the rotor core and an end of the permanent magnet. 2. A permanent magnet embedded motor in which the shape of a slit is convex at the center of the rotor. 3. The permanent magnet embedded motor according to claim 1, wherein the permanent magnet is a rare earth magnet. 4. The permanent magnet embedded motor according to claim 1, wherein the number of rotor magnetic poles is four. 5. A compressor for an electric vehicle air conditioner, comprising the permanent magnet embedded motor according to claim 1. 6. An electric bicycle equipped with the permanent magnet embedded motor according to claim 1 for driving.