JPH0412A - Bearing system - Google Patents

Abstract

PURPOSE:To stabilize rotational movement in a bearing system of a spidle motor adopted for a disc device or the like by providing a magnet which generate magnetic force on a part of a bearing surface of bearing members for journalling a magnetic shaft member. CONSTITUTION:A magnetic circuit C is formed by providing a magnet 3 between sintered alloy bearing members 2a and 2b which support a shaft member 1 made of magnetic material. Attraction force is generated on the shaft member 1 in a G direction to always cause linear contact. Mechanical oscillations and unbalanceness are eliminated, so that inexpensive and stable rotation is obtained.

Description

Detailed Description of the Invention Technical Field The present invention relates to a bearing mechanism, and more particularly to a bearing mechanism for a spindle motor that uses a sintered bearing and is widely used in direct drive floppy disk devices, hard disk devices, optical disk devices, etc. .

Prior Art Conventionally, in this type of bearing mechanism, the shaft member 1 is supported by two or one annular sintered oil-impregnated bearing, as shown in FIG.

The shaft member 1 is rotatable after being inserted into the bearing members 2a and 2b.

Further, the bearing members 2a and 2b were press-fitted and fixed in a housing 5 made of a non-magnetic material, and the rotational power due to the repulsive force of the stator 7 and the drive magnet 8 was transmitted to the jig member 1 via the rotor yoke 9.

Note that 6 is a mounting plate for fixing the housing 5, and 10 is a mounting plate for fixing the housing 5.
is a screw for fixing the rotor yoke 9 to the shaft 1.

The conventional bearing mechanism described above obtains rotational force as a motor by changes in the magnetomotive force of the stator 7 and attraction/repulsion with the permanent magnet 8, and applies rotational force to the shaft member 1 via the rotor yoke 9 and screws 10. was communicating.

However, due to the axial force F other than the rotational force generated when the stator 7 and the permanent magnets 8 attract and repel, a so-called slicing motion occurs, which is transmitted to the shaft member 1 via the rotor yoke 9 and the screw 10. The shaft member 1 has bearing members 2a, 2
Since it moves in the direction of the arrow within the range of clearance 4 with respect to b, there was a drawback that the axial vibration accuracy could not be improved.

In addition, in order to improve the axial vibration accuracy, the shaft member] and the bearing member 2a are
, 2b may be reduced. This makes it possible to improve accuracy to some extent. However, by reducing the clearance 4, there is a drawback that friction loss increases and the input/output efficiency of the motor deteriorates. Furthermore, in addition to improving the precision of the shaft member 1 and bearing members 2'a and 2b as parts, it is also possible to reduce the clearance 4 when considering dimensional control, oil film formation, fat expansion and contraction due to temperature changes, etc. There are limitations, and the disadvantage is that shaft runout cannot be effectively suppressed.

OBJECTS OF THE INVENTION The present invention has been made to solve the above-mentioned conventional drawbacks, and its purpose is to provide a bearing mechanism that provides stable rotational motion.

Structure of the Invention A bearing mechanism according to the present invention includes a shaft member formed of a magnetic material, a bearing member that rotatably supports the shaft member, and a magnet that applies magnetic force to a part of the bearing surface of the bearing member. It is characterized by having the following.

Example Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a longitudinal sectional view of an embodiment of a bearing mechanism according to the present invention, and parts equivalent to those in FIG. 4 are designated by the same reference numerals. In the figure, a shaft member 1 is made of a magnetic material and is rotatable together with a rotor yoke 9.

The bearing members 2a and 2b are circular rings having substantially the same shape. These bearing members 2a and 2b are made of a sintered alloy and are oil-impregnated bearings as in the conventional case.

Further, an annular magnet 3 is provided between these bearing members 2a and 2b. This magnet 3 is shown in Figure 2 (a).
The shape is as shown in , and a part of it is subjected to magnetization treatment. In this example, the range in which the magnetization process is performed is a range of 180 degrees around the ring, as shown by the shaded area H in the figure. That is,
When viewed from the top, only half is magnetized. Therefore, the same figure (b) which is a sectional view of the A-A section of the same figure (a)
Referring to , the magnet 3 is polarized so that an N pole and an S pole appear on the top and bottom surfaces, respectively.

Therefore, if this is provided between the bearing members 2a and 2b, a magnetic circuit C is formed as shown by the broken line in FIG. As a result, an attractive force acts on the shaft member 1 in the direction of arrow G, and the shaft member 1 is drawn toward the magnetized portion of the magnet 3. Therefore, the shaft member 1 rotates while being in line contact with the inner surfaces of the bearing members 2a and 2b, that is, one side of the bearing surface.

In this way, the shaft member 1 is in contact with the bearing members 2a and 2b.
By rotating the sintered alloy, the oil film formation on the sintered alloy is in the original state according to the theory, and the magnetic imbalance and mechanical runout from the motor drive system are resolved, resulting in highly accurate rotation characteristics.

Note that the magnetized portion of the magnet 3 has a maximum range of 180 degrees in order to draw the shaft member 1 to one side. Therefore, a narrower range, such as a 90 degree range, may be used.

Alternatively, a semicircular magnet 3a shown in FIG. 3(a) may be used. In this case as well, as shown in Figure (b), which is a cross-sectional view of section B-B in Figure (a), the polarization is such that N and S poles appear on the top and bottom surfaces, respectively. It is clear that the same effect as in the case of using the magnet shown in FIG. 2 can be obtained by using the magnet shown in FIG. Furthermore, 1
A /4 annular magnet may also be used.

Further, since the shaft member 1 needs to be made of a magnetic material, it is sufficient to use a stainless steel alloy or to mix magnetic particles during the sintering process. In addition, it is possible to use various materials for the bearing member and shaft member in consideration of mechanical strength.

DETAILED DESCRIPTION OF THE INVENTION As described above, the present invention uses a shaft member and two bearing members made of a magnetic material, further inserts a macnet between the two bearing members, and connects the shaft member to the bearing member. By being in constant line contact with a part of the bearing, an oil film is formed that is inherent to sintered metal, and the shaft member is moved to one side of the inner surface of the bearing member, and the magnetic attraction from the motor drive unit and the repulsive force of the rotor yoke are prevented. The movement is suppressed, the mechanical vibration and unbalance of the rotor yoke can be resolved, and the axial vibration accuracy is improved.
There is no need to manage the clearance between the shaft member and bearing member.
This has the advantage of being able to supply a bearing mechanism that is inexpensive and stable in terms of quality.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a bearing mechanism according to an embodiment of the present invention, FIGS. 2 and 3 are external views showing the magnetization mode of the magnet, and FIG. 4 is a longitudinal sectional view of a conventional bearing mechanism. . Explanation of symbols of main parts 1...Shaft members 2a, 2b...Bearing members 3.3a...Magnet

Claims (1)

[Claims] (1) A shaft member made of a magnetic material, a bearing member that rotatably supports the shaft member, and a magnet that applies magnetic force to a part of the bearing surface of the bearing member. Bearing mechanism.