JPH0736466Y2 - Rotation detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a rotation detecting device for detecting a rotation phase of a rotor of a motor for driving a disc in a compact disc player, a floppy disc player or the like.

[Conventional technology]

FIG. 6 is a sectional view showing the entire structure of a motor used as a drive source for a compact disc player or the like, and FIGS. 7 to 9 are enlarged plan views of a conventional motor rotation detection device.
FIGS. 10 to 12 are waveform diagrams of the super power detected by the detection device of FIGS. 7 to 9, respectively.

In FIG. 6, reference numeral 1 denotes a shaft, which is rotatably supported by a thrust bearing 2 and a radial bearing 3. A rotor yoke 4 is fixedly mounted on the shaft 1, and a magnet 8 that forms a pulse for detecting the rotational position of the motor is provided on the outer periphery of the rotor yoke 4.
A rotor magnet 5 having N and S poles alternately magnetized in the rotation direction is fixed to the lower surface of the rotor yoke 4.
Reference numeral 6 indicates a stator base formed of a magnetic material, and the rotor magnet 5 is provided on the stator base 6.
A plurality of stator coils 7 facing each other are fixed.
Further, the stator base 6 is provided with a magnetic detection member A at a position facing the magnet 8.

A Hall element, an MR element, or the like is used as the magnetic detection member A, but the Hall element is shown in each drawing. In the motor, when the rotor yoke 4 rotates and the magnet 8 passes the facing portion of the magnetic detection member A,
A voltage is generated in the Hall element by the magnetic field of the magnet 8.
In an actual device, the output waveform of this power is square wave shaped,
The rising edge of the shaped pulse is used as a detection time point for controlling the rotation phase of the motor.

[Problems to be solved by the device]

In the conventional example shown in FIG. 7, the facing surface 8a of the magnet 8 facing the magnetic detection member A is magnetized to the N pole on the entire surface. Therefore, the surface on the opposite side is the S pole. When the rotor yoke 4 is rotated in the α direction and the magnet 8 passes through the magnetic detection member A, of the magnetic flux generated from the N pole of the magnet 8, a magnetic flux perpendicular to the rotational direction α of the rotor yoke 4 (hereinafter A vertical magnetic flux) M ₁ acts to generate a voltage in the Hall element and a pulse P as shown in FIG. 10 is formed. However, in this case, at both ends of the N pole, as shown in the figure, N
The magnetic flux M ₂ from the pole to the S pole extends in a direction substantially perpendicular to the rotation direction α. Therefore, the magnet 8 is the magnetic detection member A.
When passing through the opposite portion of the Hall element, a reverse voltage is generated in the Hall element due to the magnetic flux M ₂ . Therefore, as shown in FIG. 10, the rising P ₁ and the falling P ₂ of the pulse P of the voltage generated when the magnet 8 passes through the magnetic detection member A have a sloping shape. As a result, it becomes impossible to accurately detect the rising or falling time of the pulse P.

On the other hand, there is a conventional example shown in FIGS. 8 and 9 as one for suppressing the sagging of the output waveform and making one of the rising and the falling steep to maintain the detection timing with high accuracy. In the conventional example shown in FIG. 8, the facing surface of the magnet 8 with respect to the magnetic detection member A is magnetized to N and S poles having the same surface area. However, in the rotation detecting device of FIG. 7, the pulse P ₃ having the opposite polarity to the pulse P is generated at a relatively high level (see FIG. 11). In this conventional example, it is possible to accurately generate the rising edge S of the pulse by performing the square wave shaping, but since the backward pulse P ₃ is generated, the processing means such as the waveform shaping circuit becomes complicated.

On the other hand, in the rotational position detector shown in FIG. 9, the magnetized area of the S pole on the surface of the magnet 8 is made smaller than that of the N pole, and the pulse P _{3 of the} opposite polarity is made smaller as shown in FIG. . However, in this case, it becomes very difficult to control the height of the pulse having the opposite polarity. Further, in the conventional example shown in FIG. 8 and FIG. 9, it is very difficult to magnetize the boundary position between the N pole and the S pole so that the boundary position between the N pole and the S pole is accurately set, and variations in the boundary position between the two poles easily occur. ing.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a rotation detection device for a motor, which can detect rotation of the motor with high accuracy.

[Means for Solving the Problems]

According to the present invention, in a rotation detecting device in which a magnet is provided on a rotating body, and a magnetism detecting member is arranged at a position where the magnet passes by rotation of the rotor, the magnet is opposed to the magnetism detecting member. It has an opposed surface and an inclined surface extending in an opposite direction to the magnetic detection member in the circumferential direction of the rotating body from the edge of the opposed surface, and different magnetic poles are provided on the opposed surface and the inclined surface. It is characterized by being magnetized.

[Action]

According to the above means, the N and S poles are magnetized to each other in the moving direction with respect to the magnet serving as the magnetism detection member of the motor rotation detection device, and one of the N and S poles is arranged around the rotor. Since the magnetic field is inclined in the direction opposite to the direction of the magnetic detection member, the magnetic flux toward the pole of the inclined surface is forcibly displaced from the direction perpendicular to the rotation direction of the rotating body. Further, since the magnetic flux toward the pole of the inclined surface is converged toward the inclined surface, the magnetic flux is dispersed. Therefore, the voltage of the pulse of the opposite polarity can be made very small, and the rising or falling of the waveform of the voltage generated when the boundary between the two poles passes through the magnetic detection member can be made sharp. Furthermore, since the boundary between the facing surface and the inclined surface is edge-shaped, N
The boundary between the pole and the S pole becomes clear. Therefore, the detection accuracy of the rising position of the pulse can be increased.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

1 is a plan view for explaining a rotation detecting device according to the present invention, FIG. 2 is an enlarged plan view showing the magnet and the magnet magnetic detecting member of FIG. 1, and FIG. 3 is a plan view of FIG. It is a wave form diagram of the voltage detected by the rotation position detection device.

In FIG. 1, reference numeral 4 indicates a rotor yoke (rotating body) which constitutes the motor shown in FIG. 6, and is fixed to a shaft 1 rotatably supported by a thrust bearing 2 and a radial bearing 3. In addition, the code | symbol A has shown the magnetic detection member, and the Hall element is shown in this Example. On the outer circumference of the rotor yoke 4, a pair of magnets 20 and 21 are fixedly provided, which serve as members to be magnetized when the rotational phase of the motor is detected. 180 for magnets 20 and 21
When the rotor yoke is rotated once from the state shown in FIG. 1, two pulses P _A and P _B are generated (see FIG. 3). Note that pulse P _A
Indicates a pulse formed by passage of the magnet 20, and a pulse P _B indicates a pulse formed by passage of the magnet 21.

The magnets 20 and 21 are formed with a facing plane E facing the magnetic detecting member A and an inclined surface F extending from the edge of the facing plane E in the direction opposite to the magnetic detecting member A in the circumferential direction of the rotating body. In the magnet 20 on one side, the opposing plane E
Is magnetized to the N pole, and the inclined plane F is magnetized to the S pole. As shown in FIG. 1, the other magnet 21 is magnetized with an S pole on the opposing plane and an N pole on the inclined surface F.

The inclined surface F may be a curved surface F ₁ as shown in FIG.

Next, the detection operation will be described.

The rotor yoke 4 is rotated in the α direction, the magnet 20 reaches the position facing the magnetism detecting member A, and a voltage change occurs in the Hall element due to a change in magnetic flux that occurs when the boundary between the S pole and the N pole passes. Then, a positive level pulse P _A as shown in FIG. 3 is generated. In this case, the S pole first faces the magnetic detection member A, but since the surface F oblique to the magnetic detection member A is formed, as shown by the magnetic flux M ₃ in FIG. The magnetic flux entering the poles is dispersed and, as shown by β, becomes a magnetic flux in an oblique direction with respect to the rotation direction of the rotor yoke 4, so that the vertical component that causes a voltage becomes extremely small. On the other hand, in the N pole, a magnetic flux M ₄ perpendicular to the Hall element and having a high magnetic flux density extends. Therefore, the formation of the minus level pulse P _A ′ that is formed prior to the plus level pulse P _A can be sufficiently suppressed. Further, at the boundary between the N pole and the S pole, since the high-density magnetic flux M ₄ extends perpendicularly to the Hall element from the N pole, a pulse having a steep rising S is formed. Then, the pulse P _A is square-wave shaped in synchronization with the rising S, and the rising of the pulse after shaping can be made clear. Further, in the magnet shape shown in FIG. 2, since the boundary between the N pole and the S pole is an edge, the magnetized boundary between both poles is also clear. Therefore, the accuracy of the rising position of the pulse also becomes high.

When the other magnet 21 reaches the position facing the magnetic detection member A, a negative level pulse P _B is formed as shown in FIG. Also in this case, similarly, it becomes possible to sufficiently suppress the formation of the positive level pulse P _B. In the N pole, the above same reason, such as the magnetic flux is distributed, so that the pulse P _B is formed to have a steep falling S 'from the magnetic detecting member A.

The present invention is not limited to the above embodiment.
That is, in the above-described embodiment, the case where the rotor is rotated in one direction has been described, but as shown in FIG. 5, different surfaces having the surfaces diagonally opposed to the magnetic detection member A are provided at both ends of the N pole or the S pole. It is also possible to magnetize the poles and rotate the rotor yoke 4 in both directions.

[Effect of device]

As described above, according to the present invention, the pulse having the polarity opposite to that of the detection magnetic pole can be made extremely small, and the rising edge of the pulse between the poles can be made clear. Furthermore, since the magnetized boundaries of the magnetic poles are edge-shaped, the magnetized boundaries can be made clear and the detection position accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a plan view for explaining a motor rotation detecting device according to the present invention, FIG. 2 is an enlarged plan view showing the magnet and the magnetic detecting member of FIG. 1, and FIG. 3 is a plan view of FIG. FIG. 4 is a plan view for explaining another embodiment of the present invention, and FIG. 6 is a drive source for a compact disc player or the like. Sectional views showing the entire structure of the motor used, FIGS. 7 to 9 are enlarged plan views of a conventional motor rotation detection device, and FIGS. 10 to 12 are detection devices of FIGS. 7 to 9, respectively. It is a wave form diagram of the voltage detected by. 1 ... Shaft, 4 ... Rotor yoke, 20,21 ... Magnet, A ... Magnetic detection member, E ... Opposing surface, F ... Inclined surface.

Claims (1)

[Scope of utility model registration request] 1. A rotation detecting device in which a magnet is provided on a rotating body, and a magnetism detecting member is arranged at a position where the magnet passes by rotation of the rotor, the magnet being opposed to the magnetism detecting member. And an inclined surface that extends from the edge of the opposed surface toward the circumferential direction of the rotating body in a direction opposite to the direction of the magnetic detection member. The opposed surface and the inclined surface are different from each other. Rotation detecting device characterized in that magnetic poles are magnetized