JPH01255462A - motor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention reduces cogging torque in a core-type motor having salient poles, and reduces torque fluctuations and mechanical vibrations accompanying rotation of the motor. It is something.

[Conventional technology]

Motors used in audio equipment, VTRs, etc. are required to rotate extremely smoothly. This requires that the rotational torque be constant at all rotational positions of the rotor. However, in reality, such a motor does not exist, and the torque ripple caused by the rotational position is smoothed out by increasing the inertia of the rotor.

Incidentally, one of the causes of torque ripple is reluctance torque (cogging) that occurs due to changes in static magnetic energy depending on the rotational position of the rotor even in a non-energized state. In the past, coreless motors were often used because core-type motors could not solve cogging problems. Recently, it has become possible to reduce cogging to an almost negligible level even in core-type motors (for example, see Japanese Patent Application Laid-Open No. 61-254054), and core-type motors are more efficient than coreless motors. It has come to be widely used in VTRs, etc.

Furthermore, a method of reducing cogging torque by continuously changing the gap length between the magnet and the salient pole and sinusoidally changing the radial magnetic flux density in the gap, as shown in Japanese Patent Application Laid-Open No. 61-121757. There is also.

[Problem to be solved by the invention]

The method disclosed in Japanese Unexamined Patent Publication No. 61-254054 is a method of controlling the magnetization pattern of the magnet, and it is necessary to accurately control the accuracy of the magnetizer and the magnetization voltage, and it is difficult to use the magnet without being magnetized. This left room for cost reduction, as there was a magnet part that was exposed.

Furthermore, the method disclosed in Japanese Patent Application Laid-Open No. 61-121757 has a problem in that the operating point of the magnet is lowered in areas where the gap length is large, resulting in low utilization efficiency.

This invention was made to solve the above-mentioned problems. It is only necessary to uniformly magnetize the magnets, and even if a simple magnetizer is used, the cogging torque can be small, and the amount of magnets used can be minimized. The purpose is to provide a motor with high torque.

[Means to solve the problem]

The motor according to the present invention includes a stator comprising magnetic poles consisting of N and S poles of a permanent magnet and a magnetic yoke on the outer periphery thereof, and a rotor comprising a core having a salient pole arranged inside the magnetic poles. The magnetic yoke is set such that the curvature of the contact surface of the magnetic yoke with the magnetic pole is small at the boundary between the north and south poles and becomes large at the center of the north and south poles.

[Effect]

In this invention, since the radial magnetic flux density distribution created by each magnetic pole in the core gap becomes sinusoidal, the cogging torque becomes extremely small.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing one embodiment of the present invention, where 1 is a magnetic pole, which consists of an N pole and an S pole made of a permanent magnet, and a magnetic yoke 2 is closely provided on the outside of the magnetic pole, which constitutes a stator 3. are doing. Reference numeral 4 denotes salient poles, and three salient poles are provided on the rotating shaft 5 at equal intervals, and each salient pole 4 is provided with a winding 6 to form a rotor 7. Note that bearings and other parts are omitted. The configuration of the embodiment shown in FIG. 1 is an example of the simplest motor with two magnetic poles and three salient poles.

The gap length g between the magnetic pole 1 and the salient pole 4 is constant, and the curvature of the contact surface of the magnetic yoke 2 with the magnetic pole 1 is small at the boundary between the north and south poles and large at the center between the north and south poles. It is changing continuously. In this embodiment, it has an elliptical shape. 1ii18i1 is magnetized uniformly and sufficiently large in the radial direction.

In this case, the magnetic flux density distribution on the surface of the magnetic pole 1 has a shape close to a sine wave as shown in FIG. If the curvature of the boundary between Ni and S poles is further reduced so that the thickness of the magnet at the boundary between N and S poles becomes zero, it becomes a nearly perfect sine wave.

Also, when a C-type permanent magnet is used as magnetic pole 1, there may be a gap between the N and S poles, but even in this case, as long as the angle of this gap is 10% or less of 1 magnetic pole. The deviation of the magnetic flux density distribution from the sine wave is small, and there is no problem in implementing the present invention.

FIG. 4 is a schematic cross-sectional view of a conventional motor shown for comparison with the present invention, and differs from the present invention in that the magnetic pole 1 and the magnetic yoke 2 are circular.

The magnetic flux distribution on the magnetic pole surface in this case is shown in FIG.

In FIG. 3, the cogging torque when sufficient magnetization is performed is shown by curve A in the case of the present invention and curve B in the case of the conventional example. As can be seen in Fig. 3, the cogging torque of the motor according to the present invention is approximately 1/10 of that of a conventional fully magnetized motor, and
As can be seen from the comparison between the figure and FIG. 4, the amount of permanent magnets used can be reduced and the motor can be made smaller.

Since the magnet used in this invention has a more complicated shape than conventional magnets, it is most desirable to use a plastic magnet formed by injection or pressing.

(Effects of the Invention) As explained above, the present invention reduces the curvature of the contact surface of the magnetic yoke with the magnetic pole at the boundary between the N pole and the S pole, and
By continuously changing the flux so that it increases at the poles and the center, the radial magnetic flux distribution in the gap between the magnetic pole and the salient pole becomes sinusoidal, the coking torque becomes extremely small, and the permanent magnet The amount used can be reduced and the overall size can be made smaller, which is of great industrial significance.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing one embodiment of the present invention, FIG. 2 is a diagram showing the magnetic flux density distribution on the magnetic pole surface in the embodiment of FIG. 1, and FIG. 3 is a diagram showing the embodiment of FIG. 1 and the conventional motor. FIG. 4 is a schematic cross-sectional view showing an example of a conventional motor, and FIG. 5 is a diagram showing the magnetic flux density distribution on the magnetic pole surface in the conventional example of FIG. In the figure, 1 is a magnetic pole, 2 is a magnetic yoke, 3 is a stator, 4 is a salient pole, 5 is a rotating shaft, 6 is a winding, and 7 is a rotor. 1st factor'/, rotor 2nd figure 3rd figure 4th figure 5th figure

Claims (1)

[Claims] A motor comprising a stator including a magnetic pole consisting of an N pole and an S pole of a permanent magnet and a magnetic yoke on the outer periphery of the stator, and a rotor including a core having a salient pole arranged inside the magnetic pole. A motor characterized in that the curvature of the contact surface with the magnetic pole is continuously changed so that it is small at the boundary between the north and south poles and becomes large at the center of the north and south poles.