JPH05292729A - Brushless motor - Google Patents

Abstract

PURPOSE:To obtain a brushless motor which is reduced in size and weight and has excellent vibration resistance by providing a magnetic sensor for detecting rotary information detecting magnet on an inner periphery opposed to the magnet. CONSTITUTION:A rotor 4 is rotatably supported in a brushless motor body 7, and provided with a field magnet 13 on an inter periphery integrally at a lower end of a rotary shaft 2 with a rotor yoke 14. Further, the yoke 14 is formed with a hollow part 15 therein, and an annular sensor magnet 18 and a magnetic encoder magnet 19 are adhesively fixed to an inner periphery of the part 15 over upper and lower stages. A pole discriminator 21 for switching energization of an armature coil 9 and a magnetic encoder sensor 22 for detecting a magnetic encoder magnet pole are installed on a support 20 formed integrally with resin 10 opposed to the magnets 18 and 19 through radial gaps.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor in which a magnet for detecting rotation information of a brushless motor and a magnetic sensor for detecting the magnet are arranged inside the rotor.

[0002]

2. Description of the Related Art FIG. 2 is a partial vertical sectional view of a conventional and well-known general brushless motor 1-1, which will be described below. This brushless motor 1-1 has a rotary shaft 2-1.
The field magnet 3 is fixed to the rotor to form the rotor 4-1.
A stator armature 5-1 is arranged through the rotor 4-1 and a radial gap.

At the end of the brushless motor 1-1,
Committee for switching the energization of the stator armature 5-1.
A motion sensor and a speed detector 6 are provided.

[0004]

[Problems of the Prior Art] Brushless motors other than those mentioned above are devised so as not to be provided with a commissioning sensor and a speed detector so as to largely protrude from the motor body. If a design aiming at downsizing and weight reduction like the brushless motor 1-1 is made, the commissioning sensor and the speed detector 6 cannot be reasonably built in the main body of the brushless motor 1-1. As a brushless motor 1-1 shown in FIG. 2, a commutation sensor and a speed detector 6 must be provided at the end of the brushless motor 1-1 so as to project greatly.
It has a drawback that the brushless motor 1-1 cannot be made compact and lightweight.

In addition, since the tandem construction in which the motor portion, the commutation sensor and the speed detector 6 are superposed in the axial direction is adopted, it is difficult to reduce the size and weight and the vibration resistance is inferior. There is a defect that is not suitable for a brushless motor used as.

[0006]

SUMMARY OF THE INVENTION In order to reduce the size and weight of the brushless motor, a rotation information detecting magnet corresponding to the commissioning sensor and the speed detector 6 and a magnetic sensor for detecting the rotation information detecting magnet are limited. -The challenge was to obtain a brushless motor with excellent vibration resistance while allowing it to be built into the space inside the main body of the motor.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to make at least one end of a rotor, such as a rotating shaft of a brushless motor, in which a armature and a field magnet rotate relative to each other. This can be achieved by forming a magnet and providing a rotation information detecting magnet on the inner circumference of the hollow portion, and by providing a magnetic sensor for detecting the rotation information detecting magnet on the inner circumference facing the rotation information detecting magnet.

[0008]

The magnetic pole of the sensor magnet 18 is detected by the magnetic pole discriminating element 21 and the energization of the armature coil 9 of the stator armature 5 is switched to rotate the brushless motor 1 in an appropriate direction. When the rotor 4 is rotated, the magnetic pole of the magnetic encoder magnet 19 is moved to the magnetic encoder sensor 22.
Is detected, the encoder signal can be obtained, and the brushless motor 1 can be controlled based on this signal.

[0009]

FIG. 1 is a vertical sectional view of a brushless motor 1 according to the present invention.
An inner rotor having a stator 4 rotatably provided with a stator armature 5 as a stator on its outer circumference with a radial gap.
Type.

The brushless motor main body 7 is formed by molding a stator armature 5 formed by winding an armature coil 9 around a stator armature core 8 into an annular shape with resin 10. The upper end opening of the cup-shaped stator 11 is provided with a disc-shaped bracket 12.
It is formed by closing with.

Inside the brushless motor main body 7, a roller is installed.
The rotor 4 is rotatably supported, and the rotor 4 has a lower end portion of a rotating shaft 2 formed of a magnetic material having an upper end protruding from the upper end portion of the bracket 12 and having a diameter smaller than that of the rotating shaft 2. It is formed by integrating with a large rotor yoke 14 and providing a field magnet 13 on the outer periphery of the rotor yoke 14.

The rotor yoke 14 has a hollow portion 15 formed inside and a radial thickness of l.

The rotor 4 is rotatably supported by a bearing 16 provided at the center of the bracket 12 and a bearing 17 arranged at the inner periphery of the lower end of the rotor yoke 14.

The rotor yoke 14 is for strengthening the magnetic field produced by the field magnet 13.
The radial thickness l of the rotor yoke 14 is sufficient if the thickness l is large enough to allow the magnetic flux generated by the field magnet 13 to pass therethrough.

That is, even if the rotor yoke 14 is formed in the shape of a hollow ring having a thickness 1 in the radial direction, the rotor yoke 14 sufficiently fulfills its role.

Therefore, in this brushless motor 1, an annular sensor magnet 18 and a magnetic encoder magnet 19 are fixedly adhered to the inner circumference of the hollow portion 15 in two steps.

The sensor magnet 18 is a small brushless motor which cannot directly detect the magnetic pole of the field magnet 13.
Therefore, N poles and S poles are magnetized at the same position as the field magnet 13 with the same number of magnetic poles.

The magnetic encoder magnet 19 is magnetized in a fine pitch along the circumferential direction in order to form a rotary magnetic encoder in the brushless motor 1.

The sensor magnet 18, magnetic encoder
A magnetic pole discriminating element 21 for switching the energization of the armature coil 9 to a sensor support portion 20 integrally formed of the resin 10 facing the respective magnets 19 via a radial gap, and a magnetic encoder magnet magnetic pole are detected. A magnetic encoder sensor 22 is installed.

As the magnetic pole discriminating element 21 and the magnetic encoder sensor 22, it is sufficient to use an appropriate magnetoelectric conversion element such as a hall element, a hall IC, a magnetoresistive element or the like.

[0021]

According to the brushless motor of the present invention,
Since the rotation information detection mechanism of the motor including the encoder is built into the rotor without adopting a structure in which the motor and the motor are stacked in tandem, the motor can be shortened in the axial direction and is vibration resistant. Can be improved.

In addition, without changing the characteristics of the motor,
Since the inside of the motor is hollow, the rotor inertia can be reduced, the acceleration / deceleration characteristics of the motor can be improved, and it can contribute to the high-speed response of the system operation.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a brushless motor showing an embodiment of the present invention.

FIG. 2 is a partial vertical cross-sectional view of a conventional brushless motor.

[Explanation of symbols]

 1,1-1 Brushless motor 2,2-1 Rotation shaft 3 Field magnet 4,4-1 Rotor 5,5-1 Stator armature 6 Commissioning sensor and speed detector 7 Brushless motor -Main body 8 Stater armature iron core 9 Armature coil 10 Resin 11 Cup type stator 12 Bracket 13 Field magnet 14 Rotor yoke 15 Hollow part 16,17 Bearing 18 Sensor magnet 19 Magnetic encoder magnet 20 Sensor support portion 21 Magnetic pole discrimination element 22 Magnetic encoder sensor

Claims (1)

[Claims] 1. A hollow portion having at least one end of a rotor such as a rotating shaft of a brushless motor in which an armature and a field magnet are rotated relative to each other. A brushless motor comprising a detection magnet, and a magnetic sensor for detecting the rotation information detection magnet provided on an inner peripheral portion facing the rotation information detection magnet.