JP2008312297A - Multiple-phase claw-pole type motor and rotor for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make cogging torque into a sine-wave shape in a multiple-phase claw-pole type motor. <P>SOLUTION: In a multiple-phase claw-pole type motor, each magnet constituting a rotor is molded so that a gap in-between a magnetic-pole face has a narrow central part and wide circumferential both sides while a gap is provided between each magnet. By this, it suppresses the occurrence of cogging torque due to manufacturing errors between phases. Consequently, it is possible to obtain a smoothly rotating motor that has a small torque pulsation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a motor structure of a multi-phase claw pole type motor used in the industrial, home appliance, automobile field and the like.

  A motor is used as a drive device that converts electrical energy into mechanical output for industrial, household, and automotive fields. The claw pole type motor is used for OA equipment, automobile equipment, etc. because of its inexpensive structure and simplicity of drive circuit, and is usually used as a two-phase stepping motor as disclosed in JP-A-2002-359938. It is configured. There are single-phase, two-phase, and three-phase motor types, depending on the application. Among them, the three-phase motor has the advantage of good controllability and can be driven with a small number of transistors.

  Normally, a claw pole type motor as described above is made of a rolled steel plate such as SPCC as shown in JP-A-2002-359938, and a claw pole portion is formed by bending, and the core is cylindrical. It is structured to sandwich a coil wound in a shape.

  However, since this structure uses SPCC which is inferior in magnetic properties, there is a problem that iron loss generated in the core becomes large. Further, since the SPCC is bent, residual stress is generated in the bent portion of the core, and the magnetic characteristics are further deteriorated by the strain. Since the bent part is a part where the magnetic flux is particularly concentrated, a large iron loss occurs and the motor is inefficient. In addition, the magnetic pole core on the inner diameter side that is plastically processed by bending has a cantilever structure and has a very poor roundness. For this reason, there is a problem that the cogging torque is large due to the influence of the roundness, and at present, it is used for applications in which efficiency, torque pulsation, vibration, noise, etc. are not a problem.

  In order to solve these problems, a method of forming the claw magnetic poles by compressing magnetic powder has been devised as disclosed in JP-A-2006-296188. When this method is used, the degree of freedom in forming the claw magnetic pole and the accuracy are greatly improved as compared with the conventional method, and therefore, it is expected as a technique for dramatically expanding the application range of the claw pole type motor. In addition, as described in the publication, a high-efficiency motor can be obtained by using magnetic powder having good magnetization characteristics. Further, the permanent magnet has a gap between the magnetic pole surface and the central portion. By forming it so that both sides in the circumferential direction are narrow, the inter-pole leakage magnetic flux can be reduced and the magnetic flux can be used effectively without reducing the effective value of the interlinkage magnetic flux.

JP 2002-359938 A JP 2006-296188 A

  The problem to be solved is to establish a motor structure for reducing cogging torque and a method for reducing the same in a multiphase claw pole motor in which magnetic pole claws are formed using a dust core. Since the claw pole type motor described in Japanese Patent Laid-Open No. 2006-296188 has a structure in which the stator is independent for each phase, the positional relationship between the independent phases changes due to an assembly error or the like. In the case of a three-phase motor, it is essential that the positional relationship be deviated every 120 degrees in electrical angle. However, the positional relationship changes slightly due to the error during assembly described above, and the cogging torque due to the error. Will occur. The cogging torque due to this error is characterized by a longer period and a larger absolute value of several to several tens of times than the cogging torque determined by the original design. The cogging torque contributes to torque ripple at the time of motor rotation and smoothness of rotation, and causes vibration and noise. Therefore, cogging torque is a characteristic that is regarded as important in all areas where motors such as precision machines, home appliances, and automobiles are applied, and reduction thereof is desired. In addition, the permanent magnet is formed so that the gap with the magnetic pole surface is narrow in the center and wide on both sides in the circumferential direction, thereby reducing the leakage flux between the poles without reducing the effective value of the flux linkage. The magnetic flux can be used effectively, but on the other hand, since the magnetic flux is used effectively, the harmonic component of the magnetic flux density of the gap increases, and a large cogging torque is generated due to manufacturing errors such as the magnet mounting position. There was a problem.

  In the multiphase claw pole type motor, the magnet constituting the rotor is formed such that the gap with the magnetic pole surface is narrow at the center and wide on both sides in the circumferential direction, and a gap is provided between the magnets. .

  The multiphase claw pole type motor of the present invention can make the cogging torque sinusoidal. Thereby, generation of cogging torque due to manufacturing errors between phases can be suppressed, and a smoothly rotating motor with small torque pulsation can be obtained.

  The contents of the present invention will be described below with reference to the drawings.

  FIG. 1 is a sectional view showing the structure of a three-phase claw pole motor having 16 poles. The rotor of this embodiment has a rotor structure in which bowl-shaped magnets are arranged with a gap and the magnets are fixed to the shaft 1 by bonding or the like. The rotor has a structure in which both axial ends are rotatably held by bearings 8 </ b> A and 8 </ b> B held by the housing 7. The stator is held by the housing, and the surface on the inner diameter side opposes the surface on the outer diameter side of the rotor via a gap. The stator of this motor has a structure in which one phase exists independently, and is arranged in the axial direction as an A phase, a B phase, and a C phase to constitute a three-phase motor.

  The magnets are arranged with an electrical angle shifted by 120 degrees for each phase, and each phase is composed of a 16-pole magnet. The stator cores arranged in the axial direction are arranged so that their rotational directions are different every 120 degrees in electrical angle. In the 16-pole motor of this embodiment, the electrical angle of 120 degrees is a mechanical angle of 15 degrees, and A, B, and C are shifted by 15 degrees. Assuming that the positions of the magnet poles in the circumferential direction are as shown in the figure, the positions of the poles of the rotor magnet in the cross sections A to C are the same. In the A section, the center of the claw magnetic pole coincides with the center of the pole of the magnet. The section B is configured so that the position of the claw magnetic pole is deviated by 15 degrees, and the position of the claw magnetic pole is shifted by 30 degrees from the position A in the C section.

  The cogging torque for one phase of the claw pole motor is determined by the magnitude of the magnetomotive force of the rotor and the shape of the claw magnetic pole, and can be grasped to some extent at the time of design.

  Hereinafter, in FIG. 2 and FIG. 3, it will be described that the cogging torque increases when an assembly error between phases occurs.

  FIG. 2 shows an example in which the cogging torque of the claw pole type motor is calculated using FEM (electromagnetic field analysis). The shape of the claw magnetic pole and the core shape for one phase are shown. FIG. 2A shows an FEM mesh model for one electrical angle period (mechanical angle 30 °) of a 24-pole claw motor. FIG. 2B shows the result of calculating the cogging torque of the motor using this mesh model and using the magnetic characteristics of the magnet and the claw magnetic pole as input conditions. It can be seen that when the rotor magnet is rotated from 0 ° to 30 °, the gap magnetic flux density changes depending on the relationship between the magnet pole and the claw magnetic pole, and a sinusoidal two-cycle torque is generated. As for the cogging torque generated in one phase, the same cogging torque is generated in any phase, but as shown in FIG. 1, the position of the magnet pole is the same in the axial direction, but the position of the claw magnetic pole of the stator is The cogging torque generated in the B-phase and C-phase is shifted by 120 degrees in electrical angle. Therefore, the cogging torque in FIG. Will do. The cogging torque for each phase is shown in FIG. The cogging torque waveform (amplitude, period) is the same, and only the phase is shifted by 120 degrees. The cogging torque when viewed as a three-phase motor is a composite of three phases. FIG. 2 (d) shows the resultant torque waveform. It can be seen that by synthesizing the three phases, the cogging torque as a motor can be reduced to 1/30 of the amplitude of the cogging torque for one phase.

  In manufacturing this motor, an error during assembly occurs. That is, there is a problem that the positional relationship is deviated within the allowable dimensional tolerance. In the case of the 24-pole motor shown in FIG. 2, if the electrical angle for one cycle is 30 ° in mechanical angle and the tolerance for assembly is designed to be about ± 0.5 °, the deviation in electrical angle is assumed. The amount will be ± 6 degrees. FIG. 3 shows an example in which one phase is shifted by 0.5 degrees in mechanical angle due to an assembly error. As shown in FIG. 3 (a), it is assumed that the A and B phases are assembled with a mechanical angle shifted by 10 degrees, and the C phase should be shifted by 10 degrees from the B phase. Assume that it is assembled at 9.5 degrees. At this time, as shown in FIG. 3B, the cogging torque of each phase is a relationship in which the A phase and B phase torques are shifted by 120 degrees in electrical angle, and the B phase and C phase are shifted by 114 degrees. It becomes. The result of synthesizing the three phases of cogging torque is shown in FIG. As a result, the amplitude of the cogging torque becomes as large as 10 times or more than the design value. The cycle is also secondary to one electrical angle cycle and larger than the 6th order which is the cogging torque of the original three-phase motor, and causes low-frequency vibration and noise during rotation.

  In order to reduce the cogging torque due to this assembly error, it is essential to improve the assembly accuracy. However, considering the accuracy of each part, variation in material characteristics, integration error, etc., the error is zero every time. It can be easily guessed that it is very difficult to do.

  As described above, in FIGS. 2 and 3, it has been described that the cogging torque of each phase is close to a sine wave, and even in that case, a cogging torque having a magnitude that cannot be ignored is generated due to an assembly error. However, in general, the waveform of the cogging torque depends on the shape of the claw magnetic pole and the magnet, and it has been difficult in practice to convert the cogging torque of each phase into a sine wave. Therefore, in the following embodiment, a motor structure is proposed in which the cogging torque of each phase is converted into a sine wave and the generation of the cogging torque is suppressed even if an assembly error occurs.

  FIG. 4 is a cross-sectional view of a multiphase claw pole type motor according to an embodiment of the present invention. A permanent magnet 15 is attached to the surface of the rotor core 14, and the claw magnetic poles 16 and 17 sandwich the annular coil 18 through the gap 19. The permanent magnet is characterized in that the gap between the stator and the rotor is formed so as to be narrow at the center and wide at both sides in the circumferential direction (in a bowl shape), and a gap is provided between the magnets. Further, as shown in the figure, the radius of curvature of the outer periphery of the magnet is characterized by being smaller than the radius of a circle 20 in contact with each magnet constituting the rotor from the claw magnetic pole side. By arranging the magnet in such a shape, the distribution of the magnetic flux density in the gap in the angular direction can be made sinusoidal, and the harmonic component can be reduced. Such an arrangement and shape are uniquely determined by optimization calculation. When the mounting error in the circumferential direction of the magnet is Δθ in electrical angle, cogging torque is generated at the magnitude of nΔθ due to interference with the nth-order harmonic, and the higher the order of the harmonic component, the higher the cogging torque is generated. Although there is a phenomenon, as in the present invention, by making the circumferential distribution of the magnetic flux density of the gap into a sine wave and suppressing harmonic components, a robust design that reduces the generation of cogging torque against magnet mounting errors is made. I can do it.

  FIG. 5A shows the initial shape of the magnet 21 before optimizing the magnet shape, and FIG. 5B shows the shape of the magnet 15 after optimization (the present invention). Thus, in the initial shape, no gap is provided between the magnets, and the outer peripheral shape of the magnet is a cylindrical shape.

  FIG. 6 shows the cogging torque for one phase in the initial shape before optimizing the magnet shape and in the magnet shape after optimization. When the line 22 is shown in FIG. 5A, the line 23 is the cogging torque waveform in the case shown in FIG. 5B. As shown in FIGS. 5 (a) and 5 (b), when the cogging torque is converted into a sine wave, a gap is formed between the magnets, and the radius of curvature of the outer periphery of the magnet constitutes the rotor. It can be seen that j is smaller than the radius of the circle 20 in contact with each magnet from the claw magnetic pole side. Such a shape is uniquely determined by solving the optimization problem by numerical calculation, and the result is what the present invention claims.

  As described above, the multiphase claw pole type motor of the present invention can make the cogging torque sinusoidal. Thereby, generation of cogging torque due to manufacturing errors between phases can be suppressed, and a smoothly rotating motor with small torque pulsation can be obtained. Further, by reducing the cogging torque and torque pulsation, the vibration and noise of the motor can be reduced, and the effect of improving the quietness of the system to which this motor is applied can be expected.

Sectional drawing which showed the structure of the multiphase claw pole type motor. It is a figure which shows the result of having analyzed the cogging torque using the mesh model for claw pole type | mold motor FEM analysis, and its model. It is a perspective view which shows the motor core positional relationship when there is an error in the positional relationship between the B phase and the C phase of the claw pole type motor, and a diagram showing the cogging torque calculation result in the FEM analysis in that case. Sectional drawing of the multiphase claw pole type motor of this invention. The figure which showed the magnet shape of the rotor. The figure which showed the waveform of the cogging torque.

Explanation of symbols

1 axis 2 rotor 3, 14 rotor core 4 permanent magnet 5 stator 6U, 6V, 6W stator core 7 housing 15 magnets 16, 17 claw magnetic pole 19 gap

Claims (8)

A stator in which a ring-shaped coil is sandwiched between an upper claw magnetic pole and a lower claw magnetic pole to constitute one phase, and at least two phases having the same shape are arranged in the axial direction;
In a multiphase claw pole type motor having a rotor with a magnet,
The magnet is formed such that the gap between the stator and the rotor is narrow at the center and wide on both sides in the circumferential direction, and a gap is provided between the magnets. In claim 1,
The surface shape of the magnet has a substantially single radius of curvature. In claim 2,
The multiphase claw pole motor, wherein the radius of curvature is smaller than the radius of a circle in contact with each magnet constituting the rotor from the claw magnetic pole side. In claim 1,
The multiphase claw pole motor, wherein the magnet is disposed on a surface of the rotor. In claim 1,
A multiphase claw pole type motor characterized in that the distribution of the magnetic flux density in the gap in the circumferential direction is made sinusoidal. In claim 1,
A multi-phase claw pole type motor characterized by cogging torque converted into a sine wave. A stator in which a ring-shaped coil is sandwiched between an upper claw magnetic pole and a lower claw magnetic pole to constitute one phase, and at least two phases having the same shape are arranged in the axial direction;
In a multiphase claw pole type motor having a rotor with a magnet,
A multiphase claw pole type motor characterized in that the magnets are on the top and a gap is provided between each magnet. On the magnetic pole surface of the stator, a single phase is formed by sandwiching a ring-shaped coil between the upper and lower claw magnetic poles, and at least two phases having the same shape are arranged in the axial direction. In the rotor of a multi-phase claw pole type motor with a magnet through a gap,
The magnet is formed such that the gap between the stator and the rotor is narrow at the center and wide on both sides in the circumferential direction, and a gap is provided between the magnets. Rotor.

Images