JPH11234990A - Permanent magnet motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively transmit magnetic flux change caused by rotor rotation of a permanent magnet motor to the winding of a stator salient. SOLUTION: A rotor which is provided with a permanent magnet 2 forming a field system of a motor and has a pole pitch FP of the rotor surface of the field system, stator salients SAT of each phase which are arranged on a stator and have salient width SP of inner periphery of the stator which width is nearly equal to the magnetic pole pitch, windings U, V, W of each phase wound around each stator salient SAT, and bypass magnetic paths BPT which are arranged between the stator salients SAT of each phase and pass magnetic flux on the rotor surface positioned between the rotor salients to a yoke part of the stator are installed. Harmful magnetic flux on the rotor surface is introduced from the rotor surface to a yoke part SA of the stator by the bypass magnetic paths BAT.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a motor using a permanent magnet.

[0002]

2. Description of the Related Art Brushless servomotors using permanent magnets are widely used as industrial and consumer servo control motors. As the stator structure of the motor, a stator structure having a three-phase AC winding wound in a distributed manner similar to the stator of a general-purpose induction motor, or one salient pole of the stator corresponds to a one-phase stator, For example, there is a stator structure including a plurality of salient poles in which windings of the phase are wound. In particular, the latter is often adopted in recent years because of its ease of winding work and mounting advantages such as high-density mounting of the winding, and is commercially available. For specific technologies, see, for example, the technical magazine “Nikkei Mechanical”, 1994.
March 21, pp. 36-49, "Reducing the size and weight by 1/3 with the innovation of the new generation AC servo motor construction method" describes some comparatively new examples of the structure of permanent magnet motors and their features. ing.

FIG. 8 shows an example of a sectional view of a conventional permanent magnet motor.

[0004] Reference numeral 1 denotes a shaft of the rotor, which also functions as a magnetic path of a field magnetic flux.

[0005] Reference numeral 2 denotes a permanent magnet, and recently, Nd-F
EB (neodymium, iron, boron) -based cylindrical sintered magnets are often used. The permanent magnet 2 of the rotor is magnetized to eight poles.

[0006] SC is a yoke portion of the stator. SCT
Numerals are stator teeth, in which magnetic paths and windings are not distributed unlike a general-purpose induction motor, and have a concentrated salient pole shape. Six salient poles SCT of the stator are arranged uniformly over the entire circumference. A winding of each phase is wound around each salient pole SCT of the stator. In FIG. 8, a U-phase winding U1C is wound around the rightmost salient pole SCT, and a U-phase winding U2C is wound around the leftmost salient pole.
Counterclockwise rotation CCW of the salient pole on which winding U1C is wound
A V-phase winding V1C is wound around the adjacent salient pole, and a V-phase winding V2C is also wound around the salient pole 180 ° opposite to the salient pole. A W-phase winding W1C is wound on a salient pole adjacent to the salient pole in which the winding V1C is wound in the counterclockwise direction CCW, and a W-phase winding V2C is also wound on the salient pole 180 ° opposite to the salient pole. It is wound.

The connection of each winding is such that the suffix A of the name of the winding is changed to C in the connection diagram of FIG.
It is a Y connection. A small circle at the end of each winding symbol indicates the beginning of winding.

[0008] The permanent magnet motor of FIG.
The motor is a phase, 8 pole, 6 salient pole, 6 winding motor. The operation principle of this permanent magnet motor is the same as the operation principle of a general brushless motor, and the rate of change in the rotor rotation of the interlinkage magnetic flux of each winding, that is, the rotation of the rotor to the winding having a large dΦ / dθ, When a current is applied accordingly, a rotational torque is generated. At the time of constant rotation, a torque of any magnitude can be obtained in principle by applying a three-phase alternating current to each winding of the U, V, and W phases. The magnitude of the three-phase alternating current is proportional to the magnitude of the desired torque at that time. Is the magnetic flux passing through the salient pole of interest, and θ is the rotational angle position RA of the rotor.

Next, the torque generated by the motor shown in FIG. 8, the magnetic flux distribution, and the harmonic component of the back induced voltage will be described.

The torque T generated by each salient pole in the permanent magnet motor shown in FIG.

T = KT · I · NT · dΦ / dθ (1) Here, KT is a torque constant,
I is the conduction current, and NT is the number of turns of the winding. dΦ /
dθ is the rate of change of rotation of the magnetic flux linked to the winding, and dΦ
/ Dθ is obtained.

Considering the magnetic flux existing in one stator salient pole when the rotor is rotated in FIG. 8, the salient pole width SP of the stator is 60 mechanical degrees, 240 electrical degrees, and Since the magnetic pole pitch FP is 45 degrees in mechanical angle and 180 degrees in electrical angle, while the rotor rotates 180 degrees in electrical angle, the magnetic flux existing in the stator salient poles changes with the rotation. The magnetic flux existing in the stator salient pole does not change with the rotation during the rotation. Therefore, when the rotation speed is constant and rotating, FIG.
A reverse induced voltage as shown in FIG. Here, the horizontal axis represents the rotor rotation angle RA in electrical angle. 9A shows the voltage UN between the U-phase terminal and the winding neutral point N, and FIG. 9B shows the voltage between the V-phase terminal and the winding neutral point N. VN, and FIG.
This is the voltage UV between the phase terminal and the V-phase terminal. The W-phase voltage has a phase delayed by 120 degrees from the V-phase voltage, but the description is omitted.

When actually controlling the motor, the voltage between the terminals of the motor is a problem regardless of the internal voltage of the motor. In this sense, when the motor terminal voltage UV shown in FIG. 9C, which is the motor terminal voltage, is represented by a Fourier series, the following equation is obtained.

[0013]

## EQU2 ## UV = 0.95493 · (sin θ + ／ · sin 5θ + ／ · sin 7θ + 1/11 · sin 11θ + 1/13 · sin 13θ +...) (2) where tertiary Harmonics, such as harmonics, that are integral multiples of three have already been eliminated because the three-phase winding of the stator is Y-connected as shown in FIG. Voltage UN, V
The waveform of −N includes a third harmonic component. When controlling the three-phase current of the motor with a three-phase AC sine wave, (2)
These harmonic components represented by the equations become the torque ripple components of the motor. When actually designing a motor, measures such as skewing the rotor or devising the magnet shape of the rotor are usually taken to reduce these harmonic components.

In addition to the torque ripple that generates a motor current, there is a so-called cogging torque ripple due to a change in magnetic energy inside the motor accompanying rotation of the rotor.

Normally, in such a permanent magnet motor, a rotary encoder for detecting a rotational position of a rotor is attached to a rear portion of the motor in order to control a current and to control a speed and a position. Also, researches on detecting and controlling the rotational position and speed of the rotor of the permanent magnet motor from the current or voltage of the motor and eliminating the need for a rotary encoder have been actively conducted.

[0016]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a motor capable of generating a larger torque, thereby providing a motor with good efficiency and inexpensiveness. It is to realize a motor that can perform the following.

In this sense, the problems of the prior art are, as shown in FIGS. 9A and 9B, the motor phase voltages UN,
There is a problem that there is a 33% section where VN is zero, and the magnetic flux generated by the permanent magnet cannot be used efficiently.

Further, by devising the stator structure, the coercive force required for the permanent magnet of the rotor can be reduced, specifically, the thickness of the magnet can be reduced, and the magnet volume can be reduced to reduce the magnet cost. is there.

Further, the conventional torque ripple reduction technique is a method of making the magnetic flux distribution generated by the rotor in the rotation direction of the rotor more sinusoidal, or the least common multiple of the number of rotor poles and the number of salient poles of the stator. There is a method of making the back induced voltage of the generated motor more sinusoidal as a result, but in any case, there is a problem that the motor output torque is reduced.

As for the cogging torque ripple, a method of making the magnetic flux distribution in the rotational direction of the rotor generated by the rotor more sinusoidal, and a method of skew of the rotor are known, but they are still insufficient.

Usually, in such a permanent magnet motor, a rotary encoder for detecting a rotational position of a rotor is attached to a rear portion of the motor in order to control an electric current and to control a speed and a position. There is a cost and size challenge. Also, sensorless control that does not require a rotary encoder has been studied, but its performance is insufficient and there is a problem.

[0022]

In order to increase the torque generated by a permanent magnet motor, increase efficiency, and reduce costs, a permanent magnet for forming a field of the motor is provided, and the magnetic pole pitch on the rotor surface of the field is FP. And a salient pole of each phase, which is disposed on the stator and has a salient pole width SP on the inner periphery of the stator having a value substantially equal to the magnetic pole pitch FP, and a salient pole of each phase wound around the stator salient pole. A winding is provided between the stator salient poles of the respective phases, and a bypass magnetic path is provided between the salient poles of the phase and passes magnetic flux on the rotor surface positioned between the salient poles of the stator to the yoke portion of the stator.

The thickness of the permanent magnet is determined by calculating from the coercive force of the permanent magnet so that the permanent magnet is not demagnetized by the magnetomotive force generated by the current of the motor. In that sense, for the purpose of reducing the magnetomotive force of the motor to reduce the volume of the permanent magnet and reduce the cost of the motor, stator salient poles of the same phase are adjacent to each other in the direction of rotor rotation, and their respective windings. Is supplied with a current in the opposite direction.

In order to reduce the torque ripple, the phase of the salient stator poles of the same phase with respect to the rotor magnetic poles is 60 degrees in electrical angle so that harmonic components such as the third, fifth, seventh and eleventh harmonics can be removed. Alternatively, it is shifted in the rotation direction of the rotor by 36 degrees, 25.7 degrees, or 16.36 degrees.

Also, the axial direction of the stator or the rotor is divided into two, and their electromagnetic characteristics are relatively 3, 5,
An electrical angle of 60 degrees, 36 degrees, 25.7 degrees, or 1 so that harmonic components such as the 7th and 11th orders can be removed.
6.36 degrees in the direction of rotation of the rotor.

Further, in the plurality of stator salient poles of the same phase, the width of the stator salient poles in the rotor rotation direction is made different to reduce torque ripple.

The shape of the end of the salient pole of the stator in the rotor rotation direction is a smooth curve with respect to a circle drawn from the center of rotation of the rotor to the inner periphery of the salient pole of the stator.

A magnetic flux detecting means for detecting a magnetic flux formed by the rotor is provided in a part of the bypass magnetic path for the purpose of detecting the rotational position of the rotor and realizing a reduction in size and cost of the motor.

[0029]

[Function] Increased torque generated by a permanent magnet motor, increased efficiency,
For the purpose of cost reduction, salient pole width SP on the inner circumference of the stator
Is substantially equal to the magnetic pole pitch FP of the rotor. As a result, the change in the magnetic flux that the rotor moves with the rotation substantially changes the magnetic flux of each stator salient pole, and the magnetic flux of the rotor can be used more efficiently. The arrangement of the stator salient poles of each phase with respect to the rotor is arranged at an appropriate position with a phase difference of 120 degrees in electrical angle, thereby enabling efficient three-phase AC driving.

On the other hand, each stator salient pole is electrically
When they are arranged with a phase difference of 12 degrees, 12
A space of 0 degree is created, during which the permanent magnet generates a harmful magnetic flux to the nearby stator poles for torque generation. This harmful magnetic flux on the rotor surface is passed from the rotor surface to the yoke of the stator by the bypass magnetic path, thereby enabling efficient torque generation.

In order to reduce the amount of permanent magnets by reducing the magnetomotive force of the motor and reduce the cost of the motor,
The same torque can be generated by allowing the stator salient poles of the same phase to be adjacent to each other in the direction of rotation of the rotor and the currents flowing in the respective windings to flow in opposite directions. doing.

For the purpose of reducing the torque ripple, the phase of the salient pole of the same phase with respect to the rotor magnetic pole is 60 degrees in electrical angle so that harmonic components such as the third, fifth, seventh and eleventh harmonics can be removed. Alternatively, a specific harmonic component is canceled by shifting in the rotation direction of the rotor by 36 degrees, 25.7 degrees, or 16.36 degrees.

The axial direction of the stator or the rotor is divided into two, and their electromagnetic characteristics are relatively 3, 5,
An electrical angle of 60 degrees, 36 degrees, 25.7 degrees, or 1 so that harmonic components such as the 7th and 11th orders can be removed.
A specific harmonic component is canceled by shifting in the rotation direction of the rotor by 6.36 degrees.

In a plurality of stator salient poles of the same phase, the width of the stator salient poles in the rotor rotation direction is set to be different from each other, and the locations where the respective torque ripples are generated are shifted in the rotor rotation direction. A torque effect can be reduced by obtaining an effect of forming and canceling.

In particular, for a high-order torque ripple component, the shape of the inner periphery of the stator salient pole in the direction of rotor rotation is changed by a smooth curve with respect to a circle drawn from the center of rotation of the rotor to the inner periphery of the stator salient pole. And to slightly skew the rotor or stator to reduce higher order torque ripple components.

For the purpose of detecting the rotational position of the rotor and realizing miniaturization and cost reduction of the motor, a magnetic flux detecting means for detecting a magnetic flux formed by the rotor is provided in a part of the bypass magnetic path. It is used as a position detection sensor to realize inexpensive rotation position detection that does not require encoder space.

[0037]

FIG. 1 shows an embodiment of the present invention.
1 shows an example of a sectional view of a permanent magnet motor.

Reference numeral 1 denotes a rotor shaft, which also serves as a magnetic path of a field magnetic flux. 2 is a permanent magnet, and recently, Nd-F
An eB (neodymium, iron, boron) -based cylindrical sintered magnet is often used. The permanent magnet 2 of the rotor is magnetized to eight poles. SA is a yoke portion of the stator. SAT
Numerals are stator teeth, in which magnetic paths and windings are not distributed unlike a general-purpose induction motor, and have a concentrated salient pole shape. Six salient poles SAT of the stator are arranged evenly over the entire circumference. A winding of each phase is wound around each salient pole SAT of the stator. In FIG. 1, a U-phase winding U1A is wound around the rightmost salient pole SCT, and a U-phase winding U2A is wound around the leftmost salient pole.
CCW direction of the salient pole around which winding U1A is wound
A V-phase winding V1A is wound on the salient pole of the same shape adjacent to the side, and a V-phase winding V2 is also wound on the salient pole 180 ° opposite thereto.
A is wound. A W-phase winding W1A is wound around a salient pole of the same shape adjacent to the salient pole around which the winding V1A is wound in the counterclockwise rotation direction CCW, and a W-phase winding is also wound on the salient pole 180 ° opposite thereto. The line V2C is wound.

The permanent magnet motor shown in FIG. 1 differs from the conventional permanent magnet motor shown in FIG. 8 in that the width SP of the salient stator pole SAT facing the inner periphery of the stator is substantially equal to the magnetic pole width FP of the rotor. A bypass magnetic path BPT for bypassing a part of the magnetic flux generated by the rotor between the salient poles SAT to the yoke portion SA of the stator is provided, and a sensor MS for detecting the rotational position of the rotor is provided with one of the bypass magnetic paths BPT. That is, it is fixedly arranged on the part.

Since the salient pole width SP of the stator shown in FIG. 8 is 4/3 times the magnetic pole width FP of the rotor, a part of the magnetic flux is closed between the N pole and the S pole in the salient poles of the stator. The maximum magnetic flux passing through the salient poles is 2 times the magnetic flux of one magnetic pole of the rotor.
/ 3. In this regard, the maximum magnetic flux that passes through the stator salient pole SAT of the permanent magnet motor of FIG. 1 is the magnetic flux of one magnetic pole of the rotor, and is 倍 of the maximum magnetic flux of the stator salient pole of FIG. Large torque can be generated by the presence of the large magnetic flux.

Next, the arrangement of the salient poles of the stator will be described. In order to perform three-phase AC control, the arrangement of the salient poles of each phase is, as shown in FIG. Must be shifted in the rotor rotation direction. With such a stator salient pole shape and a stator salient pole arrangement, a space corresponding to an electrical angle of 60 degrees is generated between stator salient poles having a width SP substantially equal to the magnetic pole width FP of the rotor. Considering the case where the bypass magnetic path BPT does not exist in such an arrangement, the magnetic flux generated by the permanent magnet of the rotor facing the space between the salient poles of the stator leaks through the space and causes the stators on both sides to leak. Supplied to salient poles. Particularly when a permanent magnet having a large coercive force such as a rare earth magnet is used, the effect is great. The characteristics of the permanent magnet motor are close to those of the permanent magnet motor shown in FIG. 8, and the effect of reducing the salient pole width SP is small. Become. In other words, the magnetic flux generated by the permanent magnet located between the salient stator poles leaks and is supplied to the nearby stator salient poles, which closes with the effective magnetic flux in the stator salient poles and does not function effectively as a motor. It has harmful effects. By arranging the bypass magnetic path BPT in the space between the stator salient poles and guiding harmful magnetic flux from the rotor surface to the yoke portion SA of the stator, the effective magnetic flux existing on the stator salient poles is increased and a large torque is generated. Is what you do.

Next, consider the case where the permanent magnet motor of the present invention is driven by a three-phase sinusoidal current. The permanent magnet motor shown in FIG. 1 is a motor having three phases, eight poles, six salient poles and six windings. The connection of each winding is shown in the connection diagram of FIG. 2 and is Y connection. A small circle at the end of each winding symbol indicates the beginning of winding. The operating principle of this permanent magnet motor is the same as that of a general brushless motor, and the rotor rotation change rate of the interlinkage magnetic flux of each winding, that is, to the winding having a large dΦ / dθ,
When a current is supplied according to the rotation of the rotor, a rotation torque is generated. At constant rotation, U, V,
By applying a three-phase alternating current to each winding of the W phase,
In principle, torque of any magnitude can be obtained.
The magnitude of the three-phase alternating current is proportional to the magnitude of the desired torque at that time. Is the magnetic flux passing through the salient pole of interest, and θ is the rotational angular position RA of the rotor.
It is.

Next, the generated torque of the motor shown in FIG. 1, the magnetic flux distribution, and the harmonic component of the back induced voltage will be described. The torque T generated by each salient pole in the permanent magnet motor of FIG.
It can be expressed by the above equation (1).

Considering the case where the motor is rotating at a constant rotational speed, a counter-induced voltage as shown in FIG. 3 appears at each motor terminal. Here, the horizontal axis represents the rotor rotation angle RA in electrical angle. 3A shows the voltage UN between the U-phase terminal and the winding neutral point N, and FIG. 3B shows the voltage between the V-phase terminal and the winding neutral point N. VN, and FIG.
(C) is a voltage UV between the U-phase terminal and the V-phase terminal. The W-phase voltage has a phase delayed by 120 degrees from the V-phase voltage, but the description is omitted.

When actually controlling the motor, the voltage between the terminals of the motor is a problem regardless of the internal voltage of the motor. In this sense, when the motor terminal voltage UV shown in FIG. 3C, which is the motor terminal voltage, is represented by a Fourier series, the following equation is obtained.

[0046]

## EQU3 ## UV = 1.12666 · (sin θ− ／ · sin 5θ−1 / 7 · sin 7θ + 1/11 · sin 11θ + 1/13 · sin 13θ +...) (3) The harmonics of an integral multiple of 3, including the third harmonic, have already been eliminated because the three-phase winding of the stator is Y-connected as shown in FIG. Voltage UN, V
The waveform of −N includes a third harmonic component. When controlling the three-phase current of the motor with a three-phase AC sine wave, (3)
These harmonic components represented by the equations become the torque ripple components of the motor.

Compared with the characteristic of the conventional permanent magnet motor of the formula (2), the amplitude of the fundamental wave component is 1.1547 times, and the harmonic component may have different positive and negative polarities, but the component ratio is completely different. Is the same. Therefore, assuming that the harmonic component is removed by a similar technique and the reduction of the fundamental component is also the same,
Compared with the conventional permanent magnet motor shown in FIG. 8, the permanent magnet motor of the present invention shown in FIG. 1 can generate torque of 1.1547 times.

As a simple motor drive example, the current of each phase has the same shape as the voltage waveform of each phase,
When a three-phase rectangular wave current is applied so that the positive constant value is maintained during 80 degrees and the negative constant value is maintained during 180 degrees, the permanent magnet motor shown in FIG. On the other hand, in the permanent magnet motor shown in FIG. 1A, since the average magnetic flux of each stator salient pole is 1.5 times, it is possible to generate a torque 1.5 times as large as the average torque. However, in this case, since the torque ripple is large and the total value of the three-phase AC currents does not become zero, a normal three-phase AC control circuit cannot be used for the driving device, and electric wires for supplying the motor current to the permanent magnet motor are not provided. A total of six tubes are required, two for each phase.

Further, by supplying a trapezoidal wave current to each phase, it is possible to perform a control more improved than a rectangular wave current.

Next, another embodiment of the present invention is shown in FIG.

This is an example in which the number of poles of the rotor is increased from eight to fourteen in FIG. The width SP of the stator salient pole SAT is narrowed similarly to the magnetic pole pitch FP of the rotor, and the width of the bypass magnetic path BPT is widened accordingly. The number of turns of the motor winding is the same, and substantially the same torque is generated. However, when the rotor rotates at the same rotation speed, the frequency of the current needs to be increased by an amount corresponding to the increase in the number of poles.

Next, another embodiment of the present invention is shown in FIG.

The rotor is composed of the same 14-pole permanent magnet as in FIG. The number of stator salient poles SAT is 2 in FIG.
There are 12 times as many. The U-phase windings and the U-phase stator salient poles are four U-phase windings U1B, U2B, U3B, and U4B and four stator salient poles each wound.
FIG. 6 shows the connection relationship between the respective U-phase windings. The adjacent U-phase windings U1B and U2B have the opposite magnetic characteristics of the N and S poles of the opposing rotors, so that the winding connections are also reversed. U phase winding U
The same applies to 3B and U4B. The number of windings wound around the U-phase winding U1B is the winding U1 shown in FIG.
A is と し て of A, and the other windings are the same. However, since the number of U-phase windings is doubled,
The total number of turns of the U phase is the same as the total number of turns of the U phase winding in FIG. V-phase winding and V-phase stator salient pole
There are four V-phase windings V1B, V2B, V3B, V4B and four stator salient poles each wound. The connection relation is the same as in the case of the U phase. The W-phase winding and the W-phase stator salient pole are four W-phase windings of W1B, W2B, W3B, and W4B and four stator salient poles each wound. The connection relation is the same as in the case of the U phase.

The generated torque of the permanent magnet motor of FIG. 5 is the same as compared with the motor of FIG. 4 if the current of each phase is the same. However, the magnetomotive force generated by each winding of each stator salient pole in FIG. 5 is half of the magnetomotive force of the permanent magnet motor in FIG. Normally, the thickness of the permanent magnet is designed so that the permanent magnet is not demagnetized by the magnetomotive force generated by the winding current of the motor. Therefore, the permanent magnet motor of FIG. 5 is about half of the permanent magnet motor of FIG. The thickness is good. As a result, the amount of relatively expensive permanent magnets can be reduced, so that a low-cost permanent magnet motor can be realized.

In the permanent magnet motor shown in FIG. 5, since the stator salient poles SAT of the same phase are arranged next to each other, such as V-phase windings VIB and V2B, permanent magnets of the rotor are generated. The angle of the bypass magnetic path BPT for absorbing magnetic flux harmful to the torque generation of the motor is narrowed to 8.57 degrees as shown in the drawing. The ratio of harmful magnetic flux to effective magnetic flux is 8.5
7 / 51.428 = 0.166. On the other hand, the angle of the bypass magnetic path of the permanent magnet motor shown in FIG.
The ratio between the harmful magnetic flux and the effective magnetic flux is 15/45 = 0.3
33. Therefore, by arranging a plurality of stator salient poles SAT of the same phase in the rotation direction as in the permanent magnet motor shown in FIG. 5, the ratio of harmful magnetic flux can be reduced. The performance of the motor in which the harmful magnetic flux is reduced and the bypass magnetic path BPT is removed from the permanent magnet motor shown in FIG. 5 is qualitatively determined by comparing the conventional permanent magnet motor shown in FIG. 8 with the present invention shown in FIG. It has intermediate characteristics with the motor. That is, even if there is no bypass magnetic path BPT, it is possible to improve the torque output performance of the motor by arranging a plurality of stator salient poles SAT of the same phase in the rotation direction.

Next, a technique for reducing torque ripple will be described. The torque ripple of the permanent magnet motor having this structure includes a so-called cogging torque ripple caused by a change in magnetic energy inside the motor due to rotation of the rotor and a torque ripple generating a motor current. If the harmonic component represented by the equation (3) can be reduced in the torque ripple generated by the motor current, the torque ripple will also be reduced.

As a method of canceling the fifth harmonic, a stator salient pole of a certain phase is divided into two parts, and each phase is relatively shifted by 360 / (2 × 5) = 36 degrees in electrical angle in the rotor rotation direction. If shifted, the fifth harmonic should be theoretically completely eliminated. If the shape shown by the broken line in FIG. 7 is the shape when the stator salient poles are arranged at equal intervals, the shape shifts in the rotor rotation direction as shown by the solid line. In the case of the U phase in FIG. 1, the stator salient poles of U1A and U2A may be relatively shifted in the rotational direction. In the case of the U phase in FIG. 5, U1B, U2B, U3B, U4
There are three ways to choose two from B salient poles,
In any case, it is sufficient to relatively shift in the rotation direction.
At this time, the reduction of the fundamental wave component, that is, the reduction of the output torque is sin (90−36 / 2) = 0.9613,
This is about a 4% reduction. Of course, this harmonic reduction measure can be applied to other than the fifth harmonic. In the case of the motor of FIG. 5, two harmonic components can be eliminated by superimposing the same method.

As another torque ripple reduction method, the rotor or the stator is bisected in the axial direction, and one of them is relatively shifted in the rotational direction by half of the pitch of the harmonic to be eliminated. Wave components can be eliminated. Since the rotation direction of the rotor may be shifted magnetically, it is only necessary to change the magnetized shape of the permanent magnet.

As another torque ripple reduction method, a method of slightly changing the width SP of the salient stator poles is also effective. Further, it is also effective to make the rotation end of the inner peripheral shape of each salient pole of the stator into a smooth shape gradually moving away from the rotor surface, and to further smooth the change in magnetic flux due to rotation. A method of skewing the stator or the rotor is also effective for reducing the torque ripple. It is also effective to make the surface shape of each magnetic pole of the rotor a sector shape and to make the magnetic flux distribution on each magnetic pole surface of the rotor approximate a sine wave.

In the overall torque ripple reduction, the above-described torque ripple reduction measure is applied to each harmonic component in a complex manner, and a permanent magnet motor with small torque ripple can be realized.

Normally, in such a permanent magnet motor, a rotary encoder for detecting a rotational position of a rotor is attached to a rear portion of the motor in order to control an electric current and to control a speed and a position. This rotary encoder has a problem of reliability due to the size problem of the motor system, the problem of cost, and the necessity of many elements. According to the present invention, the position of the rotor is detected by providing a rotor position detecting unit in a part of the bypass magnetic path. Specifically, it is a Hall element or a magnetoresistive element capable of detecting a magnetic flux density.

It is also possible to detect a change in magnetic flux in the bypass magnetic path by winding a detection winding around the bypass magnetic path, or to detect a change in inductance by applying an exciting current to detect the rotational state of the rotor. It is. Further, in order to avoid the influence of the magnetomotive force of the stator winding current applied to the rotor position detecting means on the bypass magnetic path or the influence of noise components generated by the winding current, the sensor is disposed on the bypass magnetic path on the side surface of the rotor. Is also effective.

The rotor position and speed of the permanent magnet motor are detected and controlled based on the current or voltage of the motor.
Although researches on the necessity of a rotary encoder are being actively conducted, there are other problems such as performance problems.

The present invention has been described above, and the rotor structure in which the permanent magnets are arranged on the rotor surface has been introduced. However, the present invention is also applicable to a motor having a structure in which the permanent magnets are arranged inside the rotor. For the structure of the stator, various splitting methods and joining methods such as welding have been proposed for the convenience of the winding work of the motor, the convenience of assembly, and the like. The present invention can be applied to the case. Although the case of the three-phase AC motor has been described, the present invention is also applicable to a multi-phase AC other than the three-phase. Although the rotary motor has been described, the present invention is also applicable to a linear motor developed on a straight line.

[0065]

As an effect of the present invention, by effectively utilizing the magnetic flux of the rotor, it is possible to increase the generated torque of the permanent magnet motor, increase the efficiency, and reduce the cost.

By reducing the magnetomotive force of the stator winding current acting on the permanent magnet, the thickness of the expensive permanent magnet can be reduced, and the cost can be reduced.

According to the torque ripple reduction method of the present invention,
A low torque ripple permanent magnet motor can be realized, and high-precision motor control with low vibration and low noise can be realized.

By incorporating means for detecting the rotational position of the rotor inside the motor, the overall shape including the encoder for detecting the rotational position can be reduced in size, and at the same time, the cost can be reduced. Since the number of parts can be reduced, reliability is also improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a permanent magnet motor of the present invention.

FIG. 2 is a connection diagram of windings of the permanent magnet motor of FIG.

FIG. 3 is a diagram showing voltage waveforms induced in windings of the permanent magnet motor of the present invention.

FIG. 4 is a sectional view of another permanent magnet motor of the present invention.

FIG. 5 is a sectional view of another permanent magnet motor of the present invention.

6 is a wiring diagram of windings of the permanent magnet motor of FIG.

FIG. 7 is a diagram showing a shift of a position of a stator salient pole in a rotation direction.

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

FIG. 9 is a diagram showing voltage waveforms induced in windings of the permanent magnet motor of FIG.

[Description of Signs] 1 Rotor shaft, 2 permanent magnet, SAT stator salient pole, FP rotor magnetic pole width, SA stator yoke, BPT bypass magnetic path, MS sensor, SP stator salient pole width.

Claims (7)

[Claims] 1. A rotor having a permanent magnet for forming a field of a motor and having a magnetic pole pitch of FP on the rotor surface of the field, and a salient pole width SP on the inner periphery of the stator having a magnetic pole pitch of FP. Stator salient poles of each phase having a value substantially equal to the above, windings of the respective phases wound around the stator salient poles, and disposed between the stator salient poles of the respective phases, and located between the stator salient poles. And a bypass magnetic path for passing a magnetic flux on the rotor surface to a yoke portion of the stator. 2. A rotor having a permanent magnet for forming a field of a motor, the rotor having a magnetic pole pitch of FP on the rotor surface of the field, and a salient pole width SP on the inner periphery of the stator having a magnetic pole pitch FP. And a winding of each phase wound around each of the stator salient poles, the stator salient poles of the same phase being adjacent to each other in the direction of rotor rotation, and A current in the opposite direction is supplied to the winding of the permanent magnet motor. 3. A plurality of stator salient poles having the same phase, and a phase of the stator salient poles with respect to a rotor magnetic pole is three.
The electrical angle is shifted by 60 degrees, 36 degrees, 25.7 degrees, or 16.36 degrees in the rotation direction of the rotor so that harmonic components such as the fifth, seventh, and eleventh harmonic components can be removed. The permanent magnet motor according to claim 1. 4. The stator or the rotor is bisected in the axial direction, and one of the electromagnetic characteristics is relatively 3, 5, 7,
In order to remove the 11th and other harmonic components, the
0 degrees or 36 degrees or 25.7 degrees or 16.
3. The permanent magnet motor according to claim 1, wherein the motor is shifted by 36 degrees in the rotation direction of the rotor. 5. In a plurality of stator salient poles having the same phase,
The torque ripple is reduced by setting the width of the stator salient poles in the rotor rotation direction to be different from each other.
The permanent magnet motor according to the item. 6. The rotor according to claim 1, wherein the shape of the end of the salient pole of the stator in the direction of rotation of the rotor is a smooth curve with respect to a circle drawn from the center of rotation of the rotor to the inner periphery of the salient pole of the stator. Item 3. The permanent magnet motor according to item 1 or 2. 7. A permanent magnet motor according to claim 1, further comprising: a magnetic flux detecting means for detecting a magnetic flux formed by a rotor in a part of said bypass magnetic path.