Motor

• US 20060125334A1
• Filed: 12/12/2005
• Published: 06/15/2006
• Est. Priority Date: 12/13/2004
• Status: Active Grant

• Current Assignee: Nidec Corporation
• Original Assignee: Nidec Corporation
• Inventors: Nakanishi, Keita, Kataoka, Nakaba
• Granted Patent: US 7,518,273 B2
• Time in Patent Office: Days
• US Class Current: 310/68.B
• CPC Class Codes: H02K 29/08 using magnetic effect devices, e.g. Hall-plates, magneto-resistors H02K29/12 takes precedence

Abstract

In a motor, an sensor magnet is attached to a shaft and three hole sensors for detecting the position of the sensor magnet are mounted on a circuit board. By using neodymium-iron-boron base rare earth magnet having radial anisotropy as a sensor magnet, the detection accuracy for the position of a field magnet via the sensor magnet by the hole sensor can be improved.

Claims

1. An electric motor comprising:

a static part includes a stator;

a field magnet having a cylindrical shape;

a rotor part having the field magnet for generating a torque around a central axis with respect to the stator;

a bearing part for supporting the rotor part rotatably with respect to the static portion around the central axis;

a sensor magnet that is a substantially ring-like rare earth anisotropic magnet and magnetized in multiple poles, the sensor magnet secured on the rotor part and arranged with the field magnet coaxially; and

a sensor disposed so as to oppose the sensor magnet, for detecting the position of the sensor magnet.

2. The motor according to claim 1, wherein the sensor magnet has radial anisotropy.

3. The motor according to claim 2, wherein the sensor is disposed so as to oppose the outer peripheral face of the sensor magnet.

4. The motor according to claim 3, wherein the diameter of the sensor magnet is approximately equal to the diameter of the field magnet.

5. The motor according to claim 1, wherein the sensor is disposed so as to oppose a main face perpendicular to the central axis of the sensor magnet.

6. The motor according to claim 1, wherein the sensor magnet is made of magnet material molded by hot extrusion so as to be supplied with anisotropy, the magnet material being magnetized.

7. The motor according to claim 1, wherein the sensor magnet is made of magnetic material molded in magnetic field so as to be supplied with anisotropy and sintered, the magnet material being magnetized.

8. The motor according to claim 1, wherein the sensor magnet is based on neodymium-iron-boron.

9. The motor according to claim 1, wherein the sensor is a hole sensor.

10. The motor according to claim 1, the motor being used in system for assisting an operation of a vehicle.

11. The motor according to claim 1, the motor directly assisting the steering operation of the vehicle.

12. The motor according to claim 1, the sensor magnet and the field magnet are formed with a single material.

13. The motor according to claim 1, the sensor magnet is formed a material different from a material of the field magnet.

14. The motor according to claim 1, the field magnet is a rare earth isotropy magnet.