Hydrodynamic bearing rotary device and information apparatus

Abstract

A hydrodynamic bearing rotary device which can reduce rotation friction, and recording and reproducing apparatus including the same are provided. In the hydrodynamic bearing rotary device such as hard disc devices, a rotary shaft having a hub on one end is provided in a bearing of a sleeve so as to be rotatable. Thrust hydrodynamic grooves are provided on the other end surface of the rotary shaft, to form a thrust bearing with the thrust plate. A communication path is provided in the sleeve. The second gap between the hub and the sleeve end surface is used as a flow channel and is connected to the communication path. In this way, the rotation friction torque of the thrust bearing can be made sufficiently small, and internal pressure in bonded portions of the rotary shaft or the bottom plate can be suppressed. Thus, the oil can be prevented from oozing out from a small space of the bonded surfaces. Furthermore, the hydrodynamic bearing can be made thin. These effects can be combined to realize an optimal hydrodynamic bearing rotary device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a hydrodynamic bearing device according to an embodiment of the present invention.

FIG. 2 is a detailed plan view of the thrust hydrodynamic grooves.

FIG. 3 is a detailed cross-sectional view of the hydrodynamic bearing FIG. 4 is a diagram illustrating a proportion of friction torques of the hydrodynamic bearing device.

FIG. 5 is a detailed cross-sectional view of a fourth gap of the hydrodynamic bearing device.

FIG. 6 is a diagram illustrating oil sealing force of the hydrodynamic bearing device.

FIG. 7 is a perspective view of a sintered sleeve of the hydrodynamic bearing device.

FIG. 8 is a cross-sectional view of a conventional hydrodynamic bearing device.

FIG. 9 is a detailed plan view of thrust bearing hydrodynamic grooves of the hydrodynamic bearing device.

FIG. 10 is a diagram illustrating a friction torque of the hydrodynamic bearing device.

FIG. 11 is cross-sectional view of a recording and reproducing apparatus including a hydrodynamic bearing device.

FIG. 12 shows a detailed enlarged cross-sectional view of a hydrodynamic bearing rotary device according to another embodiment of the present invention.

FIG. 13 is an enlarged view of a hydrodynamic bearing rotary device according to yet another embodiment of the present invention.

Claims

1. A hydrodynamic bearing rotary device, comprising a sleeve formed into a tubular shape;a rotary shaft having a first surface in a direction orthogonal to an axial direction of the sleeve which is fitted to the sleeve and supported so as to be rotatable with respect to the sleeve;a thrust plate located at a position opposing the first surface; anda hub which is fitted to the rotary shaft at a position remote from the first surface and has an additional member receiving surface on which an additional member to a motor can be loaded, wherein,a first gap (S1) to which a lubricant is injected is formed between the first surface and the thrust plate,a second gap (S2) to which the lubricant is injected is formed between the hub and an end surface of the sleeve on the side of the hub along the axial direction, andwidths of the second gap (S2) and the first gap (S1) satisfy the following relational expression (1): S2>S1  (1).

2. The hydrodynamic bearing rotary device according to claim 1, wherein: a third gap (G1) to which the lubricant is injected is formed between an inner peripheral surface of the sleeve and the rotary shaft;a fourth gap (G2) to which the lubricant is injected is formed between an outer peripheral surface of the sleeve on the side near the hub and a inner peripheral surface of the hub which opposes the outer peripheral surface; andthe third gap (G1), the second gap (S2) and the fourth gap (G2) satisfy the following relational expression (2): G2>S2>G1  (2).

3. A hydrodynamic bearing rotary device, comprising: a sleeve having a bearing hole,a rotary shaft which is inserted into the bearing hole of the sleeve so as to be rotatable;a hub which is attached to one end of the rotary shaft and has a disc receiving surface on which a disc can be loaded;a thrust plate which is placed so as to oppose an end surface of the other end of the rotary shaft;a second gap provided between the hub and an end surface of the sleeve which has a minimum gap S2;a thrust bearing portion provided in a first gap which is a gap S1 with thrust hydrodynamic grooves formed on at least one of the thrust plate and the end surface of the other end of the rotary shaft;a radial bearing portion formed in a third gap which is a gap G1 with radial hydrodynamic grooves formed on at least one of an outer peripheral surface of the rotary shaft and an inner peripheral surface of the sleeve;a communication path provided to connect the first gap and the second gap;a fourth gap which has a maximum gap G2 and is provided between an outer peripheral surface of the sleeve on the side near the hub and an inner peripheral surface of the hub, which has a diameter slightly larger than that of the outer peripheral surface; anda lubricant injected into the communication path, the first gap, the second gap, the third gap, and the fourth gap,wherein widths of the gaps S1, S2, and G2 satisfy the relations, S2>S1 and G2>S2>G1.

4. The hydrodynamic bearing rotary device according to claim 1, wherein: the sleeve has a flange portion protruding in a direction orthogonal to an axial direction near the hub on a surface opposing the hub, andthe hub has a stopper ring to be hooked to the flange portion.

5. The hydrodynamic bearing rotary device according to claim 2, wherein, on the outer peripheral surface of the sleeve which defines the fourth gap, a surface is formed such that the gap becomes narrower toward the second gap.

6. The hydrodynamic bearing rotary device according to claim 1, further comprising a base plate for fixing the sleeve, wherein: the hub includes a rotor magnet; andthe rotor magnet generates a magnetic attraction force in a direction toward the base plate.

7. The hydrodynamic bearing rotary device according to claim 1, wherein the sleeve includes a sintered sleeve formed of metal sintered material, and a sleeve collar surrounding the outer circumference of the sintered sleeve, and the communication path which connects the first gap and the second gap is formed between the sintered sleeve and the sleeve collar.

8. The hydrodynamic bearing rotary device according to claim 7, wherein the sintered sleeve includes iron or copper as a main component at a sintered density of 90% or higher, and a surface thereof is provided with a triiron tetroxide film or treated with electroless nickel plating.

9. The hydrodynamic bearing rotary device according to claim 1, wherein the additional member is at least one of a magnetic disc, an optical disc, a polygon mirror, and a rotary head.

10. An information apparatus, comprising: the hydrodynamic bearing rotary device according to claim 1; anda head portion which inputs and outputs data to and from a disc for recording data which is to be fitted to the hub and formed into a disc-like shape.

11. A hydrodynamic bearing rotary device, comprising: a sleeve having a bearing hole,a flangeless rotary shaft which is inserted into the bearing hole of the sleeve so as to be relatively rotatable;a hub which is attached to one end of the rotary shaft and has an additional member receiving surface on which an additional member to a motor can be loaded;a thrust plate which is fixed so as to oppose the other end of the rotary shaft;a first gap (S1) between an end surface of the other end of the rotary shaft and the thrust plate, to which a lubricant is injected;a second gap (S2) between a surface of the hub and an one end surface of the sleeve on the side of the one end of the rotary shaft, which oppose one another;a third gap (G1) with radial hydrodynamic grooves formed on at least one of an outer peripheral surface of the rotary shaft and an inner peripheral surface of the sleeve; anda fourth gap which has a maximum gap (G2) and is provided between an outer peripheral surface of the sleeve on the side of the one end surface of the sleeve and an inner peripheral surface of the hub, which has a diameter slightly larger than that of the outer peripheral surface of the sleeve,wherein the maximum gap (G2) of the fourth gap has a width which satisfy the following relational expression (3): G2>S2>G1  (3).

12. The hydrodynamic bearing rotary device according to claim 11, wherein: the sleeve has a flange portion protruding in a direction orthogonal to an axial direction near the hub on a surface opposing the hub, andthe hub has a stopper ring to be hooked to the flange portion.

13. The hydrodynamic bearing rotary device according to claim 11, wherein, on the outer peripheral surface of the sleeve which defines the fourth gap, a surface is formed such that the gap becomes narrower toward the second gap.

14. The hydrodynamic bearing rotary device according to claim 11, further comprising a base plate for fixing the sleeve, wherein: the hub includes a rotor magnet; andthe rotor magnet generates a magnetic attraction force in a direction toward the base plate.

15. The hydrodynamic bearing rotary device according to claim 11, wherein the sleeve includes a sintered sleeve formed of metal sintered material, and a sleeve collar surrounding the outer circumference of the sintered sleeve, and the communication path which connects the first gap and the second gap is formed between the sintered sleeve and the sleeve collar.

16. The hydrodynamic bearing rotary device according to claim 15, wherein the sintered sleeve includes iron or copper as a main component at a sintered density of 90% or higher, and a surface thereof is provided with a triiron tetroxide film or treated with electroless nickel plating.

17. The hydrodynamic bearing rotary device according to claim 11, wherein the additional member is at least one of a magnetic disc, an optical disc, a polygon mirror, and a rotary head.

18. An information apparatus, comprising: The hydrodynamic bearing rotary device according to claim 11; anda head portion which inputs and outputs data to and from a disc for recording data which is to be fitted to the rotary shaft and formed into a disc-like shape.

19. The hydrodynamic bearing type rotary device according to claim 3, wherein a minimum gap G20 of the fourth gap is formed to have a width which satisfies the following relational expression (4): G20>S2  (4).

20. The hydrodynamic bearing type rotary device according to claim 5, wherein a minimum gap G20 of the fourth gap is formed to have a width which satisfies the following relational expression (5): G20>S2  (5).

21. The hydrodynamic bearing type rotary device according to claim 13, wherein a minimum gap G20 of the fourth gap is formed to have a width which satisfies the following relational expression (6): G20>S2  (6).