JPS63310358A - Rotary position detecting method for rotor - Google Patents

Abstract

PURPOSE:To facilitate index without detection without requiring special machining, by making a hole through the side wall of a rotor yoke and detecting flux of a magnet for rotating a motor. CONSTITUTION:A hole 11b is made through the outer wall 11a of a rotor yoke 11. The hole 11b is aligned with a magnet 12. When a magnetic sensor 18 is arranged close to the hole 11b, flux of the magnet 12 leaked through the hole 11b can be detected sufficiently. The rotor yoke 11 absorbs the flux of the magnet 12 and decreases magnetic resistance of magnetic circuit, and when the hole 11b is made, flux of the permanent magnet 12 arranged at the position of the hole 11b is not completely absorbed by the rotor yoke 11 but leaks partially to the outside of the yoke 11. A magnetic focusing member 18A may be provided for the magnetic sensor 18 in order to improve detection sensitivity.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for detecting the rotational position (hereinafter referred to as index) of a rotor of a magnet-rotating motor.

[Conventional technology]

Detection of the rotor position is performed in various motors such as floppy disk drives. Conventionally, as an index detection method for a magnet rotary motor in which a magnet is attached to a rotor yoke, a rare earth magnet 3 is attached to the outer periphery of a rotor yoke 2 to which a magnet 1 is attached, as shown in Fig. 2, and the magnetic flux generated by the magnet is detected. A method is known in which index detection is performed by detecting the index using a magnetic sensor 4 such as a Hall element, Hall IC, or magnetoresistive element. This method requires the installation of the index detection magnet 3, which increases the cost.Also, since the detection magnet is provided on the outer periphery of the rotor yoke, extra space is required for the installation of the magnetic sensor 4, which reduces the overall motor efficiency. It has the disadvantage of being large. FIG. 3 is a diagram showing another example of the conventional index detection method, in which (A) is a partial sectional view of a rotor yoke and a magnet, and (B) is a perspective view thereof. In this conventional example, the rotor yoke 2 is provided with a notch 2^, and a portion l^ of the magnet 1 protrudes from the notch 2A to the outside of the rotor yoke. Then, index detection is performed by detecting the magnetic flux due to the protruding portion IA of the magnet using a coil, a magnetic sensor, or the like. This method requires machining of the magnet 1, and since a part of the magnet 1 is made to protrude outside the rotor yoke 2, it has the drawback of increasing the size of the motor, similar to the conventional example shown in FIG. [Problems to be Solved by the Invention] The present invention eliminates the disadvantages of the conventional method described above, such as increased cost and increased size of the motor, and provides a method that is low cost and does not require extra space for index detection. The purpose is to provide an index detection method that does not require

[Means to solve the problem]

To achieve this purpose, a hole whose central axis coincides with one of the permanent magnets is provided in the rotor yoke to which a plurality of permanent magnets are attached, and magnetic flux leaking from the hole is detected. It is characterized by detecting the rotational position of the rotor. [Function J] According to the present invention, the index is detected by making a hole in the side wall of the rotor yoke and detecting the magnetic flux of the magnet for rotating the motor, so there is no need for a special magnet for index detection. No special machining is required, and the space for index detection can be reduced, making it possible to downsize the motor. [Embodiments] The present invention will be described in detail below with reference to the drawings. Fig. 1 is a cross-sectional view schematically showing a motor to which the index detection method of the present invention is applied. A plurality of permanent magnets 12, for example eight, are attached to the side wall 11^ of the rotor yoke 11 with the direction of magnetization oriented in the radial direction of the yoke. A shaft 13 is fixed to the center of the rotor yoke 11. A bearing 15 is provided on the stator 14 and supports the shaft 13 in a freely rotatable manner. The stator 14 has a magnet 1
For example, six coils 16 are fixed opposite to the rotor yoke 2, and the rotor yoke, and therefore the shaft 13, is rotated by controlling the current flowing through the coils 16. 17 is a steel ball that supports the shaft 13; 18
is a magnetic sensor, 18^ is a magnetic material for magnetic convergence, and 18B is a Hall element. This is a sensor such as a magnetoresistive element. The feature of the embodiment shown in FIG. 1 is that the outer wall of the rotor yoke
The point is that holes 11B are provided at 11 locations. Hole 1
It is preferable that the center of 1B coincides with the magnet 12.If the magnetic sensor 18 is installed close to the hole 11B,
The magnetic flux of the magnet 12 leaking from 1B can be sufficiently detected. The rotor yoke 11 absorbs the magnetic flux of each magnet 12 and reduces the magnetic resistance of the magnetic circuit, but if the hole 11B is provided, the magnetic flux of the permanent magnet installed at the position of this hole is completely absorbed by the rotor yoke. Some of the magnetic flux leaks out of the yoke.The amount of magnetic flux leaking is from the side wall of the yoke! 1
For example, if the thickness of the yoke side wall is 1 ms and the diameter of the hole 11B is about 41 mm, a normal magnetic sensor can be placed 1 to 2 mm away from the rotor yoke side wall. If it is provided at a distance of , the leakage magnetic flux can be sufficiently detected and the position of the rotor can be detected. In the above embodiments, a circumferentially opposed type motor was explained as an example, but it goes without saying that the present invention can be applied to a surfacely opposed type motor in which magnets are provided on the rotor side, as shown in FIG. As shown in FIG.
A can be provided to improve detection sensitivity. [Effects of the Invention] As explained above, according to the present invention, since index detection is performed by making a hole in the side wall of the rotor yoke and detecting the magnetic flux of the magnet for rotating the motor, a special magnet for index detection is required. , no special processing is required for the magnet, and the space for index detection can be reduced, making it possible to downsize the motor.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a motor showing an embodiment of the present invention, Fig. 2 is a sectional view of a rotor to explain a conventional method, and Fig. 3 (A) is a partial sectional view to explain another conventional method. figure,
Figure (B) is a perspective view thereof. DESCRIPTION OF SYMBOLS 1... Magnet, l8... Projection part, 2... Rotor yoke, 3... Index detection magnet, 4... Magnetic sensor, 11... Rotor yoke, 11A... Side wall, 11B. ... Hole, 12... Magnet, 13... Shaft, 14... Stator, 15... Bearing, 16... Coil, 17... Steel ball, 18... Magnetic sensor. 13 ◆ Figure 1 Figure 2 20- Tayoke (A) Figure 3

Claims (1)

[Claims] A hole whose central axis coincides with one of the plurality of permanent magnets is provided in the rotor yoke to which a plurality of permanent magnets are attached, and the rotational position of the rotor is detected by detecting the magnetic flux leaking from the hole. A rotational position detection method characterized by: