JPH0487543A - Motor - Google Patents

Abstract

PURPOSE:To increase starting torque and rotational speed easily by an arrangement wherein magnetic line of force passing through a permanent magnet passes through a part of a ring composed of soft magnetic material, a toroidal winding is applied on the ring and power supply to the toroidal winding is controlled. CONSTITUTION:In a motor 100, a permanent magnet 1 magnetized in eight poles and a rotor 3 comprising a rotor yoke 2 are supported rotatably by a shaft 4 and a bearing 5, and six air-core windings 6 are fixed opposite to a stator yoke 7 composed of soft magnetic material. A toroidal winding 8 is applied on the stator yoke 7. In the motor 100, a Hall sensor detects the rotor position and power supply to the windings 6 is switched according to thus detected rotor position. Accordingly, a miniature motor having high starting torque and high maximum rotational speed can be obtained at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a permanent magnet field type motor whose characteristics can be controlled from the outside, and particularly to a motor that has a high starting torque (and can rotate at high speed).

[Prior art J] A permanent magnet field type motor is well known as an rDC motor that rotates an armature with a fixed field, or an rDC brushless motor that rotates a field with a fixed armature, and is widely applied. has been done.

[Problem to be solved by the invention]

This type of motor generally has a property that the torque is proportional to the current, and in order to obtain a large torque, it is desirable that this proportionality coefficient be large. -On the other hand, this motor has a configuration similar to a DC generator, and generates an electromotive force (called a back electromotive force) that is proportional to the number of rotations. A power supply voltage higher than electric power is required. In order to increase the rotational speed of the motor, this proportionality coefficient is required to be small, but this proportionality coefficient is equal to the proportionality coefficient between the torque and current, and it is necessary to increase the rotational speed of the motor with a large torque. difficult to obtain.

SUMMARY OF THE INVENTION An object of the present invention is to provide a motor that has a large starting torque and can easily obtain a high rotational speed by controlling the lines of magnetic force passing through permanent magnets.

[Means for Solving the Problems] A motor according to the present invention is a permanent magnet field type motor designed such that lines of magnetic force passing through the permanent magnet pass through a part of a ring made of a soft magnetic material. This ring is provided with a toroidal winding, and current supply to the toroidal winding is controlled by current control means.

[In the invention of Effect 1-, the proportionality coefficient (called motor constant) by which torque is proportional to current is determined by the strength of the field, the number of turns of the winding,
Determined by mechanical shape (number of poles, radius, length, etc.). These are generally parameters given at the time of design, but the present invention controls the motor constant by adjusting the field strength by applying electricity to the toroidal winding.

The strength of the magnetic field is determined by the strength of the permanent magnet and the magnetic resistance within the magnetic circuit. In order to obtain a high magnetic field, a typical motor is made of a material with high magnetic permeability, such as a silicon steel plate, except for the air gap portion (including the coil portion in the case of a coreless structure). It includes a cylindrical section so that the magnetic path can always be closed against rotation of the rotor. In other words, a radial gap type motor has a cylindrical magnetic body,
An axial gap type motor has a disc-shaped magnetic body. The latter can be made into a ring by making a hole in the center.

The gist of the invention is to provide such a ring with a toroidal winding. A ring made of such a magnetic material has an extremely low magnetic resistance, so that by passing a small amount of current through the toroidal winding, a large magnetic flux is generated and the ring can be easily saturated. When the ring portion becomes saturated, the magnetic resistance increases and the field strength decreases. Normally, it is sufficient to reduce the motor constant by energizing the toroidal winding at a certain rotation speed or higher.

[Embodiment 1] FIG. 1 shows an embodiment of a motor 100 of the present invention, and shows an example in which the motor 100 is applied to an axial gap type coreless morph. Such a motor 100 is widely used for the purpose of rotating an information recording medium at a constant speed or rotating a polyhedral mirror at high speed for scanning a laser beam. In such applications, a motor with high torque at startup is required in order to shorten the startup time of the device, and at the same time, it is also required to be able to reach the required rotational speed.

In the motor 100 shown in FIG. 1, a rotor 3 consisting of a permanent magnet 1 magnetized into eight poles and a rotor yoke 2 is rotatably supported by a shaft 4 and a bearing 5, and six air-core windings 6 are attached. It faces a stator yoke 7 made of a soft magnetic material. A toroidal winding 8 is provided on the stator yoke 7. This motor 1oO detects the rotor position using a Hall sensor, and the winding 6
Continuous rotation is obtained by switching the energization to.

Note that the sensor and the energization switching circuit are not shown.

FIG. 2 shows the torque rotational speed characteristics of the motor 100 of the present invention. In this figure, straight line A shows the torque rotational speed characteristics when the toroidal winding 8 is not energized, and straight line B shows the torque rotation speed characteristics when the toroidal winding 8 is energized. straight line A
It can be seen that better characteristics can be obtained by energizing the toroidal winding 8 on the right side of the intersection C of the straight line B, that is, when the rotational speed is high.

FIG. 3 is a circuit showing an example of a current control means for performing the above-mentioned control, in which a speed signal obtained inside the motor driver 9 that performs low-speed control is compared with a reference value S by a comparator 1o, Only when it is detected that the speed is higher than a certain speed, the transistor 11 is turned on, and the toroidal winding 8 in the motor 100 is energized.

Note that the present invention can be applied to a radial gap type motor in exactly the same manner.

〔Effect of the invention〕

As explained in detail above, according to the present invention, there is provided a ring made of a soft magnetic material through which a part of magnetic lines of force passing through a permanent magnet passes, a toroidal winding applied to this ring, and a toroidal winding. Since it is equipped with a current control means for controlling the current in the line, it is possible to switch the motor characteristics with a simple device, and it is possible to construct a small and inexpensive motor with high starting torque and a large maximum rotation speed. There are advantages that can be achieved.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of essential parts showing an embodiment of the present invention;
Figure 2 shows the torque for explaining the operating principle of this invention.
The rotational speed characteristic diagram, FIG. 3, is a schematic diagram of a circuit showing an example of the current control means of the present invention. In the figure, 1 is a permanent magnet, 2 is a rotor yoke, 3 is a rotor,
4 is a shaft, 5 is a bearing, 6 is a winding, 7 is a stator yoke, 8 is a toroidal winding, 9 is a motor driver, 1o
1 is a comparator, 11 is a transistor, and 100 is a motor. Machi Kago;

Claims (1)

[Claims] A plurality of magnetic poles formed by a permanent magnet and a plurality of magnetic poles formed by a winding are arranged facing each other so that their relative positional relationship can be changed, and energization to the winding is controlled according to the positional relationship. This motor is a permanent magnet field type motor that is powered by a permanent magnet, and includes a ring made of a soft magnetic material through which part of the magnetic field lines passing through the permanent magnet passes, a toroidal winding attached to this ring, and 1. A motor comprising: current control means for controlling current in a toroidal winding.