JPS62281741A - Motor - Google Patents

Abstract

PURPOSE:To decrease an in balance between the pressurizing forces upper and lower bearings by offsetting a magnetic force acting between a shielding plate and a rotor magnet with a magnetic force acting between a sealing device annular magnet and a drive shaft. CONSTITUTION:An annular sealing magnet 13 magnetized axially of a drive shaft 7 is bonded to an outer ring of an upper bearing 4, a collar-like portion composed of a magnetic material and formed integrally with the drive shaft 7 is opposed to the top face of said magnet 13 with a fixed gap therebetween and a magnetic fluid 15 is inserted into said gap portion. The vertically magnetized sealing magnet 13 forms a magnetic loop together with the magnetic fluid 15, collar-like portion, drive shaft 7 and upper bearing 5 and intercepts dust and so on coming from the inner part of the upper bearing 5 by the magnetic fluid 15 for the sealing purpose. Also, the sealing magnet 13 draws the shaft 7 downward to enable an improvement of unbalance of pressurized force generated in the upper bearing 5 and the lower one 6.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to a motor, and is particularly characterized by a sealing device between a drive shaft of a motor and a bracket.

2. Description of the Related Art Conventionally, in motors for recording and reproducing devices, etc., a sealing device has been used to seal between a drive shaft and a bracket in order to prevent dust from coming out from the bearing portion.

A conventional sealing device will be described below with reference to the drawings.

FIG. 4 is a sectional view of a motor equipped with a conventional sealing device. The core 2 around which the armature coil 1 is wound is fixed to a bracket 4, and the bracket 4 has an upper bearing 6,
The outer ring of the lower bearing 6 is shrink-fitted, and the drive shaft 7 is fixed to the inner ring to rotatably support the drive shaft 7. Further, a rotor 9 having an annular rotor magnet 8 fixed thereto is press-fitted into the lower part of the drive shaft 7 at a position facing the core 2 in the circumferential direction, and an upper and lower bearing 6.
The preload spring 10 for suppressing the vibration of 6 is connected to the upper spacer 11.
It has a structure in which it is sandwiched between lower spacers 12. Further, an annular sealing magnet 13 magnetized in the radial direction of the drive shaft is attached to the upper part of the outer ring of the upper bearing 6, and its outer circumference is attached to the bracket 4.
A magnetic washer 14 with a certain gap between the shaft 7 and the sealing magnet 13 is adhered to the upper part of the washer 14 so that no air gap is created between the shaft 7 and the washer 14. It has a configuration in which a fluid 16 is inserted,
As shown in FIG. 6, from the sealing magnet 13 to the washer 14
．． Magnetic fluid 16. By rotating the magnetic loop to the shaft A and the upper bearing 6, the magnetic fluid 15 prevents dust from the upper bearing 5 and the like from coming out to the upper part of the motor. In addition, 3
is a magnetic shield plate provided on the bracket 4 so as to face the core 2 and the rotor magnet 8 closer to each other in the axial direction of the drive shaft 7.

Problems to be Solved by the Invention However, in the above configuration, as shown in FIGS. 6 and 7, in addition to the repulsive force F of the preload spring 10, the magnet 8 is attracted to the magnetic shield plate 3 by the force FB. , preload force is lower bearing 6
This causes a problem in that the preload force of the upper bearing 6 becomes small and the upper and lower preload forces become unbalanced.

The present invention solves the above-mentioned conventional problems, and aims to provide a motor with less imbalance in the preload forces of the upper and lower bearings.

Means for Solving the Problem In order to solve this problem, the motor of the present invention has a drive shaft fixed to the inner ring of a bearing whose outer ring is fixed to a bracket, and a core around which an armature coil is wound around the bracket. of,
A rotor magnet is attached to the drive shaft so that it faces the core from the circumferential direction.
・A magnetic plate is provided on the plug and rotor so as to face the core and rotor magnet in the axial direction of the drive shaft, and an annular magnet is magnetized in the axial direction, and its outer periphery is on the plug.・A collar-shaped body made of a magnetic material that is in close contact with the front side and is arranged so that there is a gap between the inner circumference and the drive shaft, and whose inner circumference is closely attached to the drive shaft is used as an annular magnet. ), and a magnetic fluid is interposed between the annular magnet and the flange-shaped body.

Effects According to the above configuration, the force that moves the drive shaft due to the magnetic attraction between the magnetic plate and the rotor magnet is offset by the magnetic attraction between the annular magnet and the flange-like body that constitute the sealing device, and the upper and lower bearings It is possible to reduce the unbalance of the preload force.

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

FIG. 1 shows a sectional view of a motor in one embodiment of the present invention. 1 is the armature coil, 2 is the core, 3 is the shield plate, 4 is the plug, 6 is the upper bearing, 6 is the lower bearing, 7 is the drive shaft, 8 is the rotor magnet, 9
1 is a rotor, 1Q is a preload spring, 11 is an upper spacer, and 12 is a lower spacer, which are the same as those in the conventional example, so their explanation will be omitted. A drive shaft 7 is attached to the outer ring of the upper bearing 4.
A next-layer sealing magnet magnetized in the axial direction of v) 13
A flange-shaped portion T, which is integrally formed with the drive shaft 7 made of a magnetic material, faces the top surface of the magnetic material T with a certain gap, and a magnetic material is attached to the gap portion. It has a structure in which a fluid 16 is inserted.

The operation of the sealing device of this embodiment configured as described above will be explained below. As shown in FIG. 2, a sealed magnet 13 magnetized in the vertical direction is connected to a magnetic fluid 16. Flange-shaped part 7
&, drive shaft 7. A magnetic loop is formed with the upper bearing 6, and the magnetic fluid 16 blocks out dust and the like from inside the upper bearing 6 and seals it.

Further, since the shaft 7 is pulled downward by the force of Fo as shown in FIG. 3 by the sealing magnet 13, the unbalance of the preload force generated between the upper bearing 5 and the lower bearing 6 can be improved. Furthermore, if the collar-like body is formed integrally with the drive shaft as in this embodiment, the magnetic washer 14 in the conventional configuration is replaced by the shaft 7, which eliminates the need for the washer 14 and increases the number of assembly steps. I can do it.

Effects of the Invention As described above, according to the present invention, the magnetic force FC acting between the annular magnet of the sealing device and the drive shaft acts to cancel out the magnetic force FB acting between the shield plate and the rotor magnet (drive shaft). , it is possible to improve the unbalance of the preload force between the upper and lower bearings.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a motor according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of the flow of magnetic flux in the sealed magnet of the same embodiment, and FIG. 3 is a cross-sectional view showing the preload force of the same embodiment. Figure 4 is a sectional view of a conventional motor, Figure 5 is an explanatory diagram of the flow of magnetic flux in a conventional sealed magnet, Figure 6 is a sectional view of a conventional motor with only a preload spring, and Figure 7 is a diagram of a conventional shield plate. FIG. 3 is a cross-sectional view of the considered motor. 4...Bracket, 5...Upper bearing, 6...Lower bearing, 7...
Drive shaft, 7a...Brim portion, 1o...
Preload spring, 13...Sealing magnet, 14...
...Shaft sealing part, 15...Magnetic fluid. Name of agent: Patent attorney Toshio Nakao and 1 other person/-
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Claims (1)

[Claims] A drive shaft is fixed to an inner ring of a bearing whose outer ring is fixed to a bracket, a core around which an armature coil is wound is provided to the bracket, and a rotor magnet is provided to the drive shaft so as to face the core from the circumferential direction. At the same time, a magnetic plate is provided on the bracket so as to face the core and the rotor magnet in the axial direction of the drive shaft, and the outer periphery of the annular magnet magnetized in the axial direction is in close contact with the bracket, A flange-shaped body made of a magnetic material is arranged so that its inner circumference has a gap with the drive shaft, and its inner circumference is in close contact with the drive shaft. 1. A motor characterized in that a magnetic fluid is interposed between the annular magnet and the collar-shaped body.