JPH0638479A - Motor - Google Patents

Abstract

PURPOSE:To obtain a motor which can be effectively controlled to be rotated by providing a magnetic shield for increasing a distance between a magnetic pilot and a stator core, and a magnetic sensor provided adjacent to the pilot. CONSTITUTION:A magnetic shield 20 is formed of a peripheral groove formed so as to increase a distance of edges between a magnetic pilot 17 and a stator 10. A motor is so operated that, when a winding 9 of the stator 10 is conducted, a magnetic flux is generated at a stationary core 8 to attract or repel a permanent magnet 16 of a rotor 14 to rotate it. Since the rotation of the rotor 14 is decided according to a positional relationship of poles between the stator 10 and the magnet 16, the position of the pole of the magnet 16 is detected by a magnetic sensor 19 to calculate a signal under control, the winding 9 of the stator 10 is conducted to continuously rotate the rotor 14. As a result, since the leakage magnetic flux from the stator 10 is remarkably reduced by a large reluctance of the shield 20, its rotation control can be effectively executed substantially without magnetic influence from the stator 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for controlling rotation of an electric motor using a permanent magnet for a rotor.

[0002].

2. Description of the Related Art An electric motor that controls the rotation by using a permanent magnet for a rotor detects a position of the rotor in a rotation direction and rotates the rotor so that the rotor rotates. Is energized.

Since the rotor of the electric motor having such a structure is composed of permanent magnets, if a sensor for detecting magnetism such as a Hall element is provided near the rotor, the position of the rotor pole can be detected. can do. For this reason, in the past, there were many cases where the Hall element was adjacent to the rotor, but in this case, the magnetic signal of the disturbance other than the rotor enters the Hall element because it is affected by the magnetism of the stator. However, there was a problem that it could not be controlled accurately.

In order to solve such a problem, a permanent magnet for detecting a different rotational position is provided on a shaft supporting the rotor at a position distant from the rotor so as to avoid the influence of disturbance due to the magnetism of the stator. However, in order to configure in this way, in addition to the rotor, a permanent magnet for detecting the rotational position must be attached to the shaft, which makes the manufacturing cumbersome. Therefore, as shown in the longitudinal sectional view of the main part of the electric motor shown in FIG. 3, the axial length of the permanent magnet 2 constituting the rotor 1 is made longer than the length of the stator 3, so that the permanent magnet is moved from the acting portion of the stator 3 to the permanent magnet. There has been a structure in which a part of 2 is extended in the axial direction and a sensor such as a Hall element 5 is provided in this extended portion 4. According to such a configuration, it is not necessary to provide the shaft 6 with a permanent magnet for detecting the rotational position, which is convenient in terms of manufacturing.

However, since the magnetic center of the rotor 2 slightly moves in the axial direction with respect to the physical magnetic center of the stator 3, the magnetic center acts so as to match the magnetic center of the rotor 2. Then, thrust force acts in the axial direction as indicated by arrow 7 in the figure. The axial thrust generated in the rotor 2 causes noise due to the axial gap of the shaft and frictional resistance of the bearing. Furthermore, since thrust in the axial direction acts on the shaft at all times during operation, this type of electric motor using a radial bearing has a problem of shortening the bearing life.

The present invention has been made in view of the above circumstances, and is provided with a magnetic pilot for detecting the rotational position of the rotor without generating thrust in the axial direction, and rotation control can be performed reliably. The purpose is to provide an electric motor that can be easily manufactured.

[0007].

SUMMARY OF THE INVENTION According to the present invention, a stator iron core having windings wound on laminated iron cores, a rotor comprising a permanent magnet rotating on the inner diameter side of the iron core, and a shaft of the rotor. A magnetic pilot obtained by forming the directional length longer than the axial length of the stator core, and a magnetic shield for increasing the distance between the magnetic pilot and the stator core formed between the permanent magnet. The problem is solved by providing the unit and a magnetic sensor provided adjacent to the magnetic pilot.

[0008]

[Function] Since a part of the permanent magnet that constitutes the rotor extends in the axial direction from the working part of the stator, a magnetic sensor such as a Hall element can be provided in this extending part. Is not affected by the magnetism of the stator, because the magnetic shield of the permanent magnet is interposed. Therefore, an accurate signal of the permanent magnet of the rotor can be obtained without affecting the rotational position of the rotor by the magnetism of the stator, and accurate rotation control can be performed. Further, since the magnetic blocking portion formed between the permanent magnet and the magnetic pilot blocks the influence of the magnetism of the stator, axial thrust is not generated in the rotor,
Even if a radial bearing is used, the service life will not be shortened.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to an embodiment shown in the drawings. FIG. 1 is a vertical cross-sectional view showing an essential part of an electric motor according to an embodiment of the present invention. FIG. 2 is a vertical cross-sectional view of a main part of an electric motor according to another embodiment.

In FIG. 1, in the electric motor, steel plates are punched and laminated by a press to form an iron core 8, and a winding 9 is formed on the iron core 8.
And the stator 10 is formed. And the stator 1
In No. 0, a frame 11 is formed by a premix in which the iron core 8 and the winding wire 9 are integrally formed.
Brackets 12a and 12b are attached to both sides in the axial direction, respectively, and support the shaft 15 of the rotor 14 via bearings 13a and 13b. Furthermore, the rotor 14 is
A permanent magnet 16 is provided on the outer peripheral side so as to face the inner diameter side of the stator 10 with a slight gap therebetween.

Further, the permanent magnet 16 is provided with a magnetic pilot 17 which is formed to be longer than the axial length of the stator 10 in one direction and which is an extended portion. The magnetic pilot 17 is provided with a magnetic sensor 19 composed of a Hall element attached to a printed circuit board 18 embedded in the frame 11 so as to be adjacent thereto. Then, between the magnetic pilot 17 of the permanent magnet 16 and the stator 10, the magnetic blocking unit 2
0 is formed, and the magnetic interrupting portion 20 is formed by a circumferential groove formed so that the edge distance between the magnetic pilot 17 and the stator 10 becomes long.

In FIG. 2, the same parts as those in FIG. 1 are designated by the same reference numerals, and the description will be made with reference to FIG.
And are integrally formed in a circumferential step portion, and the magnetic sensor 19 composed of a Hall element is provided adjacent to the magnetic pilot 23 which is a step portion.

In such a structure, when the winding 9 of the stator 10 is energized, a magnetic flux is generated in the stator core 8 to attract or repel the permanent magnet 16 of the rotor 14 to rotate the motor. To work. Since the rotation of the rotor 14 is determined by the positional relationship of the magnetic poles of the stator 10 and the permanent magnet 16, the magnetic sensor 19 detects the magnetic pole position of the permanent magnet 16, and the signal of the magnetic sensor 19 is not shown. The rotor 14 is continuously rotated by calculating a current in the control circuit and energizing the winding 9 of the stator 10.
Then, the magnetic sensor 19 moves from the stator 10 to the rotor 1
Although it is affected by a part of leakage flux of the magnetic flux flowing in 4, the permanent magnet 16 is provided with the magnetic blocking portion 20 formed of a circumferential groove, and thus the magnetic blocking portion 20 has a large magnetic field. Due to the resistance, the leakage magnetic flux from the stator 10 is drastically reduced. Therefore, the rotation of the rotor 14 can be controlled by the signal of the magnetic sensor 19 with almost no magnetic influence from the stator 10.

In the electric motor according to another embodiment shown in FIG. 2, as in the electric motor shown in FIG. 1, a magnetic breaker 22 is provided between the stator 10 and the magnetic pilot 23.
When the magnetic flux of the stator 10 flows to the magnetic sensor 19, a large magnetic resistance is exhibited and the influence can be blocked.

Since the permanent magnets 16 and 21 forming the rotor 14 are molded products, the magnetic shields 20 and 22 are formed of circumferential grooves or steps.
Can be easily configured. In particular, as shown in FIG. 2, when the magnetic blocking portion 22 and the magnetic sensor 23 are integrally molded and manufactured at the stepped portion, the ease of removal from the molding die is improved and the manufacturing is facilitated.

On the other hand, the magnetic shields 20 and 22 shield the rotor 14 from magnetic influences between the magnetic pilots 17 and 23 of the permanent magnets 16 and 21 and the stator 10. The axial thrust generated is extremely small, and the shaft 15 hardly pushes the bearings 13a and 13b in the axial direction. Therefore, even if radial bearings are used for the bearings 13a and 13b, the service life is not adversely affected.

Further, since the permanent magnets 16 and 21 are molded integrally with the magnetic pilots 17 and 23, respectively, the assembly accuracy is excellent and the permanent magnets are magnetized integrally, so that the rotor in the rotational direction is rotated. The positional relationship between the position of 14 and the magnetic pilots 17 and 23 can be obtained extremely accurately, and accurate control can be performed.

[0018]

According to the present invention, it is possible to accurately detect the rotational position of the rotor without being influenced by the stator, to reliably control the rotation, and to prevent an axial thrust from being generated. Since it can be obtained, the life of the bearing can be extended, and it can be easily manufactured, and its effect is extremely large.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a main part of an electric motor according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of a main part of an electric motor according to another embodiment.

FIG. 3 is a vertical cross-sectional view of a main part of a conventional electric motor.

[Explanation of symbols]

 10 ... Stator core 14 ... Rotor 15 ... Shafts 16 and 21 ... Permanent magnets 17 and 23 ... Magnetic pilot 19 ... Magnetic sensors 20 and 22 ... Magnetic breaker

Claims (1)

[Claims] Claim: What is claimed is: 1. A stator core comprising a laminated core and windings, a rotor comprising a permanent magnet rotating on the inner diameter side of the core, and the axial length of the rotor being the axial length of the stator core. A magnetic pilot obtained by being formed longer than the axial length, a magnetic cutoff portion for increasing an edge surface distance between the magnetic pilot and the stator core formed between the permanent magnet, and the magnetic pilot. And a magnetic sensor provided adjacent to the electric motor.