JPS58170347A - Rotor magnet - Google Patents

Abstract

PURPOSE:To make the surface magnetic flux density distribution of a rotor magnet in the circumferential direction to form sine wave by a method wherein sector shaped permanent magnets consisting of a plane plate face on the surface side and a curved plate face on the back side are arranged in the hollow disk type as to have different polarity alternately in the circumferential direction. CONSTITUTION:Sector shaped permanent magnet segments 4 consisting of the plane plate face on the surface side (lower side) and the curved plate face on the back side (upper side), and consisting of a plastic magnet (for example) saturatedly magnetized in the perpendicular direction to the plate face on the surface side, and the sector shaped permanent magnet segments 5 having the same shape and the same quality with the sector shaped permanent magnet segments 4 thereof and saturatedly magnetized in the opposite direction are put in order alternately in the circumferential direction placing the plate faces on the surface side on the same plane to constitute the hollow disk type. At this time, the curved surface of the plate face on the back side is decided as to make thicknesses of the respective fan type permanent magnet segments 4, 5 to be in a fixed function in the circumferential direction. Accordingly, surface magnetic flux density distribution of the plate face on the surface side is apt to form the sine wave, and moreover magnetization can be attained in a simply saturated magnetic field.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in p-ta magnets used, for example, in brushless, coreless, 7-rat motors.

Conventionally, this type of rotor magnet consists of a hollow disk-shaped permanent magnet plate that is magnetized with multiple poles such as 8 or 10 poles, and the magnetization direction is perpendicular to the plate surface and alternately in opposite directions in the circumferential direction. The surface magnetic flux density on the stator side of the 0-rotor magnet, which is magnetized and driven by the rotating magnetic field formed by the armature coil (stator) placed opposite to it, reduces speed fluctuations. Therefore, it is considered ideal to have a sinusoidal distribution in the circumferential direction.

As shown in Figure 1, conventional rotor magnets are formed by using hollow circular permanent magnet plates of equal thickness and magnetizing them by sandwiching them between magnetizers. It is extremely difficult to design the yoke shape of the magnetizer and control the excitation coil current in order to obtain a wave curve, and in reality, the only way to obtain a distribution curve is one that deviates considerably from a sine wave, as shown in Figure 2. There wasn't.

Figure 2 is a circumferential cross-sectional view of a conventional rotor magnet (
) and the distribution curve (b) of the surface magnetic flux density at the corresponding position, where 1 is the rotor magnet, 2 is the ideal sine wave curve, 3 is the actual distribution curve, and φ is the rotation angle. , B is the surface magnetic flux density.

An object of the present invention is to provide a rotor magnet that eliminates the above-mentioned drawbacks.

In order to achieve the above object, the p-ta magnet of the present invention has the following features:
A fan-shaped permanent magnet plate whose front plate surface is flat and whose back plate surface is curved and is saturated magnetized in the direction perpendicular to the front plate surface; fan-shaped permanent magnet plates are arranged alternately in the circumferential direction with the front plate surfaces aligned on one plane to form a hollow disk shape, and the surface magnetic flux density distribution of the front plate surfaces is arranged circumferentially. It is designed to form a sinusoidal curve in the direction.

Next, examples of the present invention will be described.

FIG. 3 is a perspective view showing an embodiment of the rotor magnet of the present invention, and 4 is a sector-shaped permanent magnet plate made of, for example, a plastic magnet, the lower plate surface of which is flat and the upper plate surface of which is curved. It is saturated magnetized in the direction perpendicular to the lower plate surface. Reference numeral 5 indicates a magnet plate piece having the same shape and the same quality as the magnet plate piece 4, but which is saturated magnetized in the opposite direction. It is located in the shape of a hollow disk.

Since the lower plate surface is the surface facing the stator in the motor, it can be functionally called the front plate surface.

The shape of the curved surface of the upper plate surface is determined by determining the plate thickness as follows.

The surface magnetic flux density II'b(1) when the thickness of a permanent magnet plate of the same material, which is saturation magnetized perpendicular to the plate surface, is 1 is shown by a curve as shown in Fig. 4. Thickness of the piece? The curved surface of the upper plate surface is determined so that 1(φ) becomes 'E1(φ)=Aeinφ/yb(1) (A + constant).

By doing so, the distribution state of the surface magnetic flux density in the circumferential direction on the lower (front) plate surface of the hollow disc-shaped rotor magnet becomes as shown in FIG. Figure 5 (,) is a circumferential cross-sectional view of the rotor magnet B of the present invention, and (b) is a distribution curve of the surface magnetic flux density of the lower (front) plate surface at the corresponding position, which is an ideal sine wave. It shows. Since the boundary where the magnetization direction is reversed is the thinnest part of the plate, it is easy to form it accurately, and this is a condition that makes it easy to obtain a sinusoidal distribution.

The magnetizer used in the rotor magnet of the present invention does not need to create a special magnetic field to obtain a sinusoidal magnetic flux density distribution as in the past, and can be prepared very easily because it only needs to create a simple saturation magnetic field. .

Further, the rotor magnet of the present invention may be formed by forming each magnet plate piece separately and then integrating them into a hollow disk shape, or may be formed by integrally molding them into a hollow disk shape from the beginning. When each magnet plate piece is formed separately using a plastic magnet material, etc., it is saturated magnetized by molding in a magnetic field, and the use of a separate magnetizer can be omitted, and the integration of each magnet plate piece is extremely easy. They can be joined without deformation by sonic welding or high-frequency welding.

The rotor magnet of the present invention may be provided with a non-magnetized inner ring 7 and outer ring 8, as shown in FIG. 6, for the purpose of reducing air resistance during rotation and for reinforcement purposes.
A back yoke or a non-magnetic cover plate may be placed around the curved upper plate surface.

As is clear from the above description, according to the present invention, a rotor magnet that is magnetized in the direction perpendicular to the plate surface and has a sinusoidal surface magnetic flux density distribution in the circumferential direction can be obtained reliably and easily. Industrial Use (5) The effects of use are extremely high.

[Brief explanation of the drawing]

Figures 1 and 2 are explanatory diagrams of conventional four-ta magnets,
FIG. 3, FIG. 5, and FIG. 6 are explanatory diagrams of the p-ta magnet of the present invention, and FIG. 4 is a diagram showing the relationship between plate thickness and surface magnetic flux density. 1. Conventional rotor magnet, 2. Axis sinusoidal distribution curve, 3. Actual distribution curve, 4.5. Axial layered permanent magnet plate piece.
611: Rotor magnet of the present invention, 7: Inner circumferential ring of fist shaft, 8: Outer circumferential ring. Agent: Patent attorney Takezo Nagata (6)

Claims (1)

[Claims] A fan-shaped permanent magnet plate whose front plate surface is flat and whose back plate surface is curved and is saturated magnetized in a direction perpendicular to the front plate surface; A rotor magnet characterized in that the fan-shaped permanent magnet plate pieces are arranged alternately in the circumferential direction with the front plate surfaces aligned on one plane and configured in the shape of a hollow disk.