JPH0629385U - Brushless motor - Google Patents

Abstract

(57) [Abstract] [Purpose] In a flat-opposed brushless motor used in various electric devices, a magnetic disk (back yoke) due to the magnetic attraction of a drive magnet as the motor becomes thinner.
SUMMARY OF THE INVENTION It is an object of the present invention to solve the adverse effects of the deformation of the flat surface portion on the motor structure and characteristics, and to provide a thin, flat-faced brushless motor having excellent characteristics. [Structure] The back yoke 11a is preliminarily processed into an umbrella shape in a direction opposite to the direction in which the magnetic attraction force of the drive magnet acts so that the back yoke 11a maintains a flat surface in the state of being attracted by the magnetic force of the drive magnet 3. Also, the motor can be made thinner without adversely affecting the characteristics.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a tape drive source such as a cassette tape recorder or a video tape recorder, and a brushless motor used as a drive source for various other devices.

[0002]

[Prior art]

 In recent years, as devices such as cassette tape recorders and video tape recorders have become smaller and thinner, the motors used in these devices are also required to be smaller and thinner.

A conventional brushless motor will be described below. FIG. 3 is a sectional view of a conventional brushless motor. In FIG. 3, 1 is a shaft, 2 is a rotor boss for fixing the shaft 1, 3 is a drive magnet in which N and S poles are alternately magnetized in the circumferential direction, and 4 is a rotor yoke made of a magnetic material for fixing the drive magnet 3. Reference numeral 11 denotes a magnetic disk (hereinafter referred to as back yoke) that faces the drive magnet 3 with a gap in the axial direction, and is fixed to the rotor boss 2 and rotates integrally with the drive magnet 3. Reference numeral 5 is a position detecting element for detecting the positions of the N pole and S pole of the drive magnet 3 and a plurality of windings arranged in a disk shape facing each other with a gap between the drive magnet 3 and the back yoke 11 at equal pitches. It is a stator winding having a (Hall element). A fixed yoke 6 made of a magnetic material fixes the holding device 7 of the stator winding 5. A bearing housing 8 fixes the bearing 9 and the thrust receiver 10.

[0004]

[Problems to be solved by the device]

 However, in the conventional configuration shown in FIG. 3, when the gap between the drive magnet 3 and the back yoke 11 is very narrow due to the thinner motor, or when the magnetic force of the drive magnet 3 is very strong, or the back yoke 11 is used. If the material thickness is extremely thin or if the above conditions are combined, the magnetic attraction of the drive magnet 3 deforms the flat portion of the back yoke 11 toward the drive magnet 3 side, so that the gap becomes narrower and the stator winding 5 may be touched or the motor characteristics may be affected.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a brushless motor that can be made thinner without adversely affecting the motor structure and characteristics due to the magnetic attraction force of the drive magnet. And

[0006]

[Means for Solving the Problems]

 In order to achieve this object, the brushless motor of the present invention has a back yoke that is opposite to the direction in which the magnetic attraction force of the drive magnet acts so that the back yoke keeps a flat surface in the state where the back yoke is attracted by the magnetic force of the drive magnet. It has a shape that has been processed in the direction of an umbrella.

[0007]

[Action]

 With this configuration, the back yoke maintains a flat surface in the state where the magnetic attraction force of the drive magnet is exerted, so that it is possible to make the motor thinner without adversely affecting the motor structure and characteristics.

[0008]

【Example】

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

In FIG. 1, reference numeral 1 is a shaft, 2 is a rotor boss for fixing the shaft 1, and the rotor boss 2 has a drive magnet 3 in which N and S poles are alternately magnetized in the circumferential direction and a gap in the axial direction. The rotor yoke 4 and the umbrella-shaped back yoke 11a made of a magnetic material and facing each other and fixing the drive magnet 3 are fixed. That is, the umbrella-shaped back yoke 11a is preliminarily processed into an umbrella shape in a direction opposite to the direction in which the magnetic attraction force of the drive magnet acts, as shown in FIG. Has been applied. A fixed member 5 has a plurality of windings arranged in the space between the drive magnet 3 and the umbrella-shaped back yoke 11a and a position detection element (Hall element) for detecting the positions of the N and S poles of the drive magnet 3. It is a child winding. This stator winding 5 is fixed to a fixed yoke 6 made of a magnetic material via a holding device 7. A bearing housing 8 fixes the bearing 9 and the thrust receiver 10.

As described above, according to the present embodiment, the umbrella-shaped back yoke 11a maintains a flat surface in the state where the magnetic attraction force of the drive magnet 3 is exerted, which adversely affects the motor structure and characteristics. Without making the motor thinner.

[0011]

[Effect of device]

 As described above, according to the present invention, the back yoke is preliminarily processed into an umbrella shape in the direction opposite to the direction in which the magnetic attraction force of the drive magnet acts so that the back yoke maintains a flat surface in the state of being attracted by the magnetic force of the drive magnet. When the space between the drive magnet and the back yoke is very narrow, or when the magnetic force of the drive magnet is very strong, or when the material of the back yoke is very thin, or when the above conditions are combined, the drive magnet The flat surface of the back yoke is deformed to the drive magnet side by the magnetic attraction force of the back yoke, and the air gap becomes narrower, and it is possible to make the brushless motor thinner without contacting the stator winding or affecting the motor characteristics. Can be realized.

[Brief description of drawings]

FIG. 1 is a sectional structural view of a brushless motor according to an embodiment of the present invention.

FIG. 2 is a sectional view of a back yoke according to an embodiment of the present invention.

FIG. 3 is a sectional structural view of a conventional brushless motor.

[Explanation of symbols]

 1 axis 2 rotor boss 3 drive magnet 4 rotor yoke 5 stator winding 6 fixed yoke 7 holding device 8 bearing housing 9 bearing 10 thrust receiver 11 magnetic disk (back yoke) 11a magnetic disk processed as an umbrella (back yoke)

Claims (1)

[Scope of utility model registration request] 1. A rotor provided with a magnetic disk fixed to a rotary shaft, opposed to an annular drive magnet with a gap in the axial direction, and rotating integrally with the drive magnet, and the drive magnet and the magnetic disk. And a stator winding having a plurality of windings arranged with a certain gap between and having a rotating shaft passing through the center thereof, and the magnetic disk is previously arranged in a direction opposite to the attraction direction of the drive magnet. A brushless motor characterized by being processed into an umbrella shape.