JPH0717268Y2 - Brushless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a brushless motor.

[Conventional technology and its problems]

Conventionally, in a brushless motor that rotationally drives a magnetic disk, leakage flux of a rotor magnet or the like (which adversely affects the magnetic disk) has been prevented by the yoke of the rotor magnet. Therefore, the size and shape of the magnetic disk in the magnetic disk drive are standard according to the standard,
Due to the structure of the motor, the thickness of the yoke is limited, and the level of the leakage magnetic flux could not be lowered so much. For this reason, the magnetic flux leaking from the inside of the motor may affect the magnetic disk, causing a trouble in reading / writing information.

The present invention solves the above-mentioned problems of the related art, and makes it possible to extremely reduce the leakage magnetic flux of the rotor magnet and the like.
An object of the present invention is to provide a brushless motor that does not cause a read / write failure in a magnetic disk.

[Means for solving problems]

A brushless motor according to the present invention comprises a cylindrical magnetic disk mounting member having an upper wall and a peripheral side wall, a rotary shaft having one end fixed to the upper wall, a housing having a housing flange and a cylindrical portion, and the housing flange. A bearing interposed between the cylindrical portion and the rotating shaft, a yoke formed of a magnetic material and disposed on an inner peripheral surface of the peripheral side wall of the magnetic disk mounting member, and an inner portion of the yoke. A rotor magnet mounted on the peripheral surface, a stator mounted on the outer peripheral surface of the cylindrical portion facing the rotor magnet, and a magnetic liquid seal arranged between the cylindrical portion and the rotating shaft. The rotor magnet, the stator, and the magnetic liquid seal are housed in a space defined by the magnetic disk mounting member and the housing. In the brushless motor according to the present invention, a first shield member made of a magnetic material is disposed on a lower surface of the upper wall of the magnetic disk mounting member, and an inner peripheral edge portion of the first shield member is A second member formed of a magnetic material is extended to above the magnetic liquid seal, and is provided at a portion of the housing flange corresponding to the magnetic disk mounting member.
Is provided, and the leakage magnetic flux from the stator, the rotor magnet, and the magnetic liquid seal is substantially shielded by the actions of the yoke, the first shield member, and the second shield. It is a thing.

[Operation] In the brushless motor according to the present invention, a rotor magnet, a stator, and a magnetic liquid seal as magnetic element parts are provided in a space defined by the magnetic disk mounting member and the housing. These or by energization generate a predetermined magnetic flux. Along with this, the leakage magnetic flux deviating from the originally formed magnetic circuit tends to diverge to the outside of the motor. However, the first shield member made of a magnetic material is provided on the lower surface of the upper wall of the magnetic disk mounting member, and the inner peripheral edge portion of the first shield member extends to above the magnetic liquid seal. It is extended. Thereby, the leakage magnetic flux mainly from the stator and the magnetic liquid seal is shielded. That is, the magnetic flux leaking upward in the axial direction of the magnetic disk mounting member is shielded. Further, a yoke made of a magnetic material is provided between the inner peripheral surface of the magnetic disk mounting member and the rotor magnet. This mainly shields the leakage magnetic flux from the rotor magnet, particularly the magnetic flux leaking outward in the radial direction with respect to the axis. Further, a second shield member made of a magnetic material is provided at a portion of the housing flange corresponding to the magnetic disk mounting member. As a result, the magnetic flux hub mainly leaking from the stator and the rotor magnet is shielded in the axially downward direction. Therefore, according to the brushless motor of this configuration, the rotor magnet, the stator, and the magnetic liquid seal that generate magnetic flux are housed in the space defined by the magnetic disk mounting member and the housing. The inside of this space is magnetically shielded by the first and second shield members and the yoke. At that time, the magnetic flux is magnetically shielded in substantially all directions of the motor, and the magnetic flux inside the motor generated by the rotor magnet, the stator and the magnetic liquid seal does not leak to the outside of the motor.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to the drawings illustrating an embodiment.

FIG. 1 shows a brushless motor according to the present invention, which comprises a housing 2 having a cylindrical portion 1,
A rotating shaft 4 which is rotatably supported by a cylindrical portion 1 of the housing 2 via two bearings 3a and 3b; a stator 6 to which the cylindrical portion 1 is fixed and a coil 5 is wound; A magnetic disk mounting member 8 to which a disk (not shown) is mounted and a rotor magnet 7 is additionally provided. In this case, the magnetic disk mounting member 8 also serves as a rotor holder rotatably mounted on the housing 2 via the rotary shaft 4. The housing 2 is made of a non-magnetic material such as aluminum, and is fixed to the other member A via a housing flange 9 protruding from the outer peripheral surface of the cylindrical portion 1 in an outer brim shape.

Thus, the magnetic disk mounting member 8 has the upper wall 10 and the peripheral side wall.
And a rotor magnet 7 magnetized in multiple poles is attached to the inner peripheral surface thereof, and one end of the rotary shaft 4 is fixed to a substantially central portion of the upper wall 10. .
Specifically, the rotor magnet 7 is attached to the magnetic disk attachment member 8 via a cylindrical yoke 12 made of a magnetic material and fixed to the inner peripheral surface of the magnetic disk attachment member 8. A shield member 13 made of a magnetic material similar to that of the yoke 12 is provided on the upper wall 10 of the magnetic disk mounting member 8.
Is provided. That is, the shield member 13 has a shaft center hole 14
The bottom surface of the upper wall 10 made of a thin plate-shaped disc body provided with
Installed on 11. The outer diameter of the shield member 13 is set to be substantially the same as the inner diameter of the magnetic disk mounting portion. As shown in FIG. 1, the inner peripheral edge portion 33 of the shield member 13 is provided so as to extend above a magnetic liquid seal 19 described later. The stator 6 is formed by superposing a plurality of thin plate-shaped stator laminations 15 having a plurality of teeth facing each other inside the rotor magnet 7 by superposition, and the axial center hole of the stator lamination 15 is formed in the cylindrical portion 1 of the housing 2. Is fitted to. A rotor position detector including a Hall element, Hall IC, etc. attached to the housing flange 9
At 16, the rotational position of the rotor magnet 7 is detected, and based on the detection signal from the detector 16, the stator 6 is rotated.
The energization of the coil 5 is controlled to be switched, and the brushless motor rotates. Reference numeral 17 denotes a substrate on which the detector 16 is mounted, which is mounted on the housing flange 9. On the back side of the housing flange 9, as shown in the figure,
In some cases, a ring-shaped shield member 18 made of a magnetic material similar to the shield portion 13 and the yoke 12 is additionally provided to further improve the shield effect. The outer diameter of the shield member 18 is set to be substantially the same as the outer diameter of the yoke 12.

Reference numeral 19 denotes a magnetic liquid seal attached to the inner peripheral surface of the upper end of the cylindrical portion 1 of the housing 2, and when the rotating shaft 4 rotates, the bearing 3
This prevents grease and the like of a and 3b from invading the magnetic disk mounting side in a mist state, and prevents fine dust and dirt in the air from entering the magnetic disk mounting side. Reference numeral 20 is a positioning snap ring attached to the rotary shaft 4, and 21 is a resilient biasing force of a disc spring or the like interposed between the outer ring of the bearing 3b and the stepped portion provided on the inner peripheral surface of the cylindrical portion 1. It is a member, and the outer ring of the bearing 3b is always elastically biased in the direction of the arrow X to prevent vibration, and the rotary shaft 4 always rotates smoothly without noise. The bearing 3a
Of the bearing 3a is fixed to the inner peripheral surface of the cylindrical portion 1, the inner ring of the bearing 3b is fixed to the rotating shaft 4, and the outer ring of the bearing 3b is fixed to the cylindrical portion 1. It is possible to swing on the inner peripheral surface of.

Therefore, according to the above-mentioned brushless motor, the rotor magnet 7, the stator 6, and the magnetic liquid seal 19, which generate magnetic flux, are housed in the space defined by the magnetic disk mounting member 8 and the housing 2. And, in this space, the shield member 13, the shield member 18,
And the yoke 12 magnetically shields. In doing so, it is magnetically shielded in substantially all directions of the motor. That is, the shield member 13 shields the magnetic flux leaking upward in the axial direction of the motor (upward in the drawing). In this case, since the inner peripheral edge portion 33 of the shield member 13 is provided so as to extend above the magnetic liquid seal 19, the magnetic flux from the magnetic liquid seal 19 is effectively shielded in addition to the stator 6 and the rotor magnet 7. be able to.

Then, the yoke 12 shields the magnetic flux leaking outward in the radial direction (horizontal direction in the drawing) with respect to the axis of the motor. In this case, the magnetic flux mainly from the rotor magnet 7 is shielded.

Further, the shield member 18 shields the magnetic flux leaking downward in the axial direction of the motor (downward in the figure). In this case, the magnetic flux mainly from the stator 6 and the rotor magnet 7 is shielded.

Next, FIG. 2 shows another embodiment in which the rotor holder 22 and the magnetic disk mounting member 8 are formed as separate members. Specifically, in this case, the housing flange 9 of the housing 2 is provided so as to protrude from the substantially middle portion of the cylindrical portion 1 in an outer brim shape, and the upper portion of the cylindrical portion 1 is internally fitted to the magnetic disk mounting member 8. Then, the lower portion of the cylindrical portion 1 and the stator 6 are fitted into the rotor holder 22. That is, one end of the rotating shaft 4 is fixed to the substantially central portion of the wall surface portion 10 of the magnetic disk mounting member 8, and the rotor holder 22 is made of a disc body having a rising portion 23 on the outer periphery, and the substantially central portion thereof is Rotating shaft 4
The other end is fixed and rotatable. Reference numeral 24 is an elastic body such as an O-ring interposed between the outer ring of the bearing 3b and the inner peripheral surface of the cylindrical portion 1.

In this case also, the upper wall of the magnetic disk mounting member 8
Shield member 13 is provided on 10 and magnetic liquid sealing material 19
It prevents the magnetic flux from leaking upward from. The shield member 13 in this case is fitted in the upper wall 10. Further, the same reference numerals as those shown in FIG. 1 denote the same members as those shown in FIG.

[Effect of device]

The brushless motor of the present invention has the above-mentioned configuration, and the rotor magnet 7, the stator 6, and the magnetic liquid seal 19 that generate magnetic flux are provided in the space defined by the magnetic disk mounting member 8 and the housing 2. , Contained and housed. The inside of this space is magnetically shielded from the outside of the motor by the shield member 13, the shield member 18, and the yoke 12. Therefore, the magnetic flux inside the motor is prevented from leaking to the outside of the motor in substantially all directions.

Therefore, since the magnetic disk mounted on this brushless motor is not affected by the magnetic flux, it does not cause a read / write failure of information on the magnetic disk.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment according to the present invention, and FIG. 2 is a sectional view showing another embodiment. DESCRIPTION OF SYMBOLS 1 ... Cylindrical part, 2 ... Housing, 4 ... Rotating shaft, 8 ... Magnetic disk mounting member, 10 ... Upper wall, 13 ... Shield material part.

Claims (1)

[Scope of utility model registration request] 1. A cylindrical magnetic disk mounting member 8 having an upper wall 10 and a peripheral side wall 30, a rotary shaft 4 having one end fixed to the upper wall 10, a housing having a housing flange 9 and a cylindrical portion 1. 2, bearings 3a, 3b interposed between the cylindrical portion 1 of the housing flange 9 and the rotating shaft 4, and inside the peripheral side wall 30 of the magnetic disk mounting member 8 formed of a magnetic material. A yoke 12 disposed on the peripheral surface, a rotor magnet 7 attached to the inner peripheral surface of the yoke 12, a stator 6 facing the rotor magnet 7 and mounted on the outer peripheral surface of the cylindrical portion 1, A magnetic liquid seal 19 disposed between the cylindrical portion 1 and the rotary shaft 4, and the rotor magnet 7, the stator 6, and the magnetic liquid seal 19 are the magnetic disk mounting member 8 and the magnetic liquid seal 19. housing In the brushless motor accommodated in the space defined by the lower surface of the top wall 10 of the magnetic disk mounting member 8,
A first shield member 13 made of a magnetic material is provided, an inner peripheral edge portion of the first shield member 13 extends above the magnetic liquid seal 19, and A second shield member 18 made of a magnetic material is provided at a corresponding portion of the magnetic disk mounting member 8. The magnetic flux leaks from the stator 6, the rotor magnet 7, and the magnetic liquid seal 19. Is substantially shielded by the action of the yoke 12, the first shield member 13, and the second shield 18.