JPH11190342A - Dynamic pressure type bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the deformation resistance and wear resistance of a thrust bearing, and prolong the life thereof by contact-supporting the protruding spherical thrust support surface of a rotating shaft supported in no contact by a dynamic pressure type bearing by a thrust bearing of ceramic material. SOLUTION: When a rotating shaft 2 is rotated by the electromagnetic force generated between stator coil 13 and a rotor 7, the oil impregnated in a radial bearing 4 is leaked to the radial bearing clearance to form a dynamic pressure film, and the outer circumferential surface of the rotating shaft 2 is supported in no contact in the radial direction to the radial bearing surface by this dynamic pressure film. The protruding spherical thrust support surface 2a of the rotating shaft 2 is also brought into contact with a thrust bearing 16 consisting of ceramic material and supported in the thrust direction. Since the ceramic is highly hard and excellent in wear resistance, deformation or wear of the thrust support part of the thrust bearing 16 is eliminated, and the life can be prolonged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic disk drive (HDD, FDD) and an optical disk drive (CD-ROM,
DVD-ROM, DVD-RAM, etc.), magneto-optical disk drive (MO), digital audio tape recorder (DAT), laser beam printer (LBP), digital FAX, digital PPC, etc. The present invention relates to a dynamic pressure type bearing device rotatably supported.

[0002]

2. Description of the Related Art FIG. 4 shows a laser beam printer (LB).
P) illustrates a scanner motor (1). The rotating shaft (2) is inserted into the housing (3), and is rotatably supported in the radial direction and the thrust direction by the radial bearing (4) and the thrust bearing (5).

The rotating shaft (2) has a convex spherical thrust support surface (2a) at the lower end, and a hub (6) is mounted at the upper end. Flange (6a) protruding from the lower part of hub (6)
A rotor (7) is fixed to the lower surface of the hub, and a polygonal mirror (polygon mirror) is provided on a step (6b) formed above the hub (6).
(8) is housed therein, and the pressurized spring (9) and the washer (1)
0) and fixed with bolts (11).

[0004] The housing (3) is a cylindrical body having a flange (3a) protruding at a lower portion. The stator coil (13) is fixed on the flange (3a) via a support plate (12). (7) is opposed via an axial gap (g).

The radial bearing (4) is a porous oil-impregnated bearing in which a porous body made of a sintered metal or the like is impregnated with lubricating oil or lubricating grease, and is fixed to the inner peripheral surface of the housing (3) by press fitting or the like. As shown in FIG. 5, the radial bearing (4)
Of the rotating shaft (2) is opposed to the outer circumferential surface of the rotating shaft (2) via a small radial bearing gap, and the inclined dynamic pressure groove (4)
A bearing surface (4a) having b) is formed.

The thrust bearing (5) has a washer (5b) made of resin (for example, polyamide resin) on the upper surface of the back metal (5a).
And is fixedly mounted on the lower opening end of the housing (3), and has a washer (5b) and a thrust support surface (2).
By contact with a), the rotating shaft (2) is supported in the thrust direction.

In the above configuration, the stator coil (1
3) The rotating shaft (2) is rotated by the electromagnetic force generated between the rotor (7) and the polygon mirror (8). At that time, with the rotation of the rotating shaft (2), the radial bearing (4)
(A lubricating oil or a base oil of a lubricating grease) permeates into the radial bearing gap, and further forms a dynamic pressure oil film in the radial bearing gap by the dynamic pressure action of the dynamic pressure groove (4b). The outer peripheral surface of the rotating shaft (2) is supported in a radially non-contact manner by the dynamic pressure oil film. Further, when the thrust support surface (2a) comes into contact with the washer (5b) of the thrust bearing (5), the rotating shaft (5) is supported in the thrust direction.

[0008]

The pivot support structure of the convex spherical thrust support surface (2a) and the flat plate-shaped resin washer (5b) has a modest frictional force reducing effect and low cost. Although it has been widely used as a thrust support structure, recently, the driving conditions of the rotating shaft (2) have become severe (high-speed rotation, improved rotation performance), and the frictional force has become insufficient and the wear resistance has become insufficient. It is getting. For example, in LBP, there is a demand of 20,000 rpm or more even for a low cost motor,
In this case, the amount of heat generated by the thrust support portion increases, and the surface of the resin washer is dented by softening, so that the contact area of the rotating shaft with the thrust support surface increases. Therefore, while the frictional force of the thrust support portion increases, the wear of the washer also increases, and the required life may not be satisfied.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the frictional force of the above-described thrust support portion, improve the life, and achieve high rotational accuracy,
An object of the present invention is to provide a dynamic pressure bearing device that realizes high-speed stability and low cost.

[0010]

According to the present invention, a rotating shaft having a convex spherical thrust support surface and a porous body made of a sintered metal are opposed to an outer peripheral surface of the rotating shaft via a radial bearing gap, In addition to forming a radial bearing surface having inclined dynamic pressure grooves, impregnated with lubricating oil or lubricating grease, the outer peripheral surface of the rotating shaft is not radially contacted by a dynamic pressure oil film of oil interposed in the radial bearing gap. A radial bearing for supporting, and a thrust bearing made of a ceramic material, and a thrust bearing for contacting and supporting the thrust support surface of the rotating shaft with the thrust support portion. The porous body made of the sintered metal is obtained by, for example, forming a metal powder containing copper or iron or both of them as a main component into a predetermined shape, followed by firing and sizing.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the dynamic pressure bearing device according to the present invention is applied to an LBP scanner motor shown in FIG. 4 will be described below with reference to FIGS. The same parts as those shown in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted. The difference is the thrust bearing (16).

In the embodiment shown in FIG. 1, the thrust bearing (16) is formed of a ceramic washer and is fixedly mounted on the lower end of the housing (3). As the material of the ceramic, silicon nitride, zirconia, alumina, or a composite thereof can be used.

The rotating shaft (2) is inserted through a radial bearing surface (4a) of the radial bearing (4). Stator coil (1
When the rotating shaft (2) rotates by the electromagnetic force generated between 3) and the rotor (7), the oil impregnated in the radial bearing (4) oozes into the radial bearing gap to form a dynamic pressure oil film,
The outer peripheral surface of the rotating shaft (2) is supported in a radially non-contact manner with respect to the radial bearing surface (4a) by the dynamic pressure oil film.

At the same time, the convex spherical thrust support surface (2a) of the rotating shaft (2) contacts the thrust bearing (16) and is supported in the thrust direction. Thrust bearings (16) because ceramic has high hardness and excellent wear resistance
There is no deformation and wear of the thrust support portion, and the life is prolonged.

According to the measurement using the actual LBP motor, the conventional polyamide resin becomes unusable due to thermal deformation in 1000 hours under the measurement conditions of 20,000 rpm and the atmosphere of 50 ° C., while the silicon nitride of the present invention has a temperature of 30 ° C.
It was confirmed that there was no thermal deformation at 00 hours and continuous use was possible.

In another embodiment shown in FIG. 3, the thrust bearing (17) is constituted by partially embedding a ceramic washer (17b) in a thrust support portion of a back metal (17a).

[0017]

According to the present invention, the outer peripheral surface of the rotating shaft is supported in a non-contact manner by the dynamic pressure type porous oil-impregnated radial bearing, and the convex spherical thrust supporting surface of the rotating shaft has a thrust supporting portion made of a ceramic material. Since it is configured to be supported by contact with the thrust bearing, deformation resistance and wear resistance of the thrust bearing are improved, and a long life is achieved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a dynamic pressure bearing device according to the present invention.

FIG. 2 is a longitudinal sectional view showing a bearing unit of the bearing device of FIG.

FIG. 3 is a longitudinal sectional view showing another embodiment of the dynamic pressure bearing device according to the present invention.

FIG. 4 is a longitudinal sectional view showing a conventional example of a dynamic pressure type bearing device.

FIG. 5 is a longitudinal sectional view showing a bearing unit of the bearing device of FIG. 4;

[Explanation of symbols]

 2 Rotary shaft 2a Thrust support surface 4 Radial bearing 16 Thrust bearing

Claims (1)

[Claims] An inclined dynamic pressure groove which opposes a rotary shaft having a convex spherical thrust support surface and a porous body made of a sintered metal with an outer peripheral surface of the rotary shaft interposed between radial bearings. A radial bearing that forms a radial bearing surface having: a lubricating oil or a lubricating grease; and a non-contact radially non-contact support of the outer peripheral surface of the rotating shaft by a hydrodynamic oil film of oil interposed in the radial bearing gap; and a ceramic material. A thrust bearing comprising: a thrust bearing comprising: a thrust bearing configured to contact a thrust support surface of the rotary shaft with the thrust support;