JP2000009135A - Fluid bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the outflow of a lubricant by making the outer diameter of an upper shaft part and the diameter of an inner diameter part of a thrust plate smaller than the inner diameter of a sleeve bearing hole, providing a smaller diameter part than the bearing hole, on the base member side of a radial dynamic pressure groove, adjacently to the bearing hole, and providing an opposed fixed shaft with a small diameter shaft part. SOLUTION: A sleeve 10 and a thrust plate 7 are rotated by a motor rotor 13, and the sleeve 10 is rotated in a completely contactless state to a fixed shaft 2 by dynamic pressure grooves 3A, 3B, 5, 6. Since the outer diameter of an upper shaft 2A and the inner diameter of the thrust plate 7 are smaller than the inner diameter of a bearing surface 10F where the fixed shaft 2 abuts the sleeve 10, a lubricant 11 is moved form a small diameter part to a large diameter part by centrifugal force acting upon the lubricant 11 even during high speed rotation to prevent the lubricant 11 from flowing outside. Since the inner diameter of a small diameter part 2i of the fixed shaft 2 and the inner diameter of a small diameter part 10G of the sleeve 10 are smaller than the inner diameter of the bearing hole 10F, centrifugal force F1 acts upon a lubricant 11A even during high speed rotation, and its component force F2 prevents the lubricant 11A from flowing out from below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

2. Description of the Related Art In recent years, a recording apparatus using a disk or the like has an increased memory capacity and a higher data transfer speed. A high-speed, high-precision rotation is required, and a fluid bearing device having a structure in which both ends of a center shaft are supported as disclosed in US Pat. No. 5,504,637 is used for the rotating main shaft. The present invention relates to a dynamic pressure type fluid bearing device used for a disk recording device for recording and reproducing signals while rotating a magnetic disk, a rotating head device for a video tape recorder which rotates at a high speed, and the like.

[0002]

2. Description of the Related Art An example of the above-described conventional hydrodynamic bearing device will be described below with reference to FIG. In FIG. 6, a shaft 22 is fixed to the base member 21 at one end, and a sleeve 25A is rotatably fitted therein. A flange 23 has a male screw 2 on the other end surface of the shaft 22.
The thrust plate 26 faces the flange 23 and is fixed by being screwed down by a screw member 24A having 4B.
25A. At least one of the outer peripheral surface of the shaft 22 and the inner peripheral surface of the sleeve 25A is provided.
A pair of, usually two, fishbone-shaped dynamic pressure grooves 25B and 25C are provided, and at least one of the sleeve 25A, the flange 23 and the thrust plate 26 has a spiral dynamic pressure groove 23.
A, 23B are provided, and respective grooves, 25B, 25
C, 23A, 23B and an oil or air reservoir 22
A and 25E are filled with a lubricant 28 which is lubricated.
A rotor 25 is integrally formed with the sleeve 25A, and the rotor 25 has disks 30A, 30B, 30C, and 30D.
, Spacers 27A, 27B and 27C are fixed, a rotor magnet 32 is mounted on the rotor 25, a motor stator 31 is mounted on the base member 21, and an upper cover 29 is screwed on the upper part. 24.

The operation of the conventional hydrodynamic bearing device configured as described above will be described with reference to FIG.
In FIG. 6, when a motor stator 31 is energized and a rotating magnetic field is generated, a rotor magnet 32 is driven by a rotor 25, a sleeve 25A, a thrust plate 26, and disks 30A, 30.
B, 30C, 30D, spacers 27A, 27B, 27C
Start rotating with. At this time, the fishbone dynamic pressure grooves 25B, 2
5C scrapes the lubricant 28 to generate pressure by the pumping action, and the spiral dynamic pressure grooves 23A and 23B also scrape the lubricant 28, respectively, and the sleeve 25A is brought into a completely non-contact state with the shaft 22 by the generated pressure. Rotate.

[0004]

However, the above configuration has the following problems. As shown in FIG. 6, at high speed rotation, parts 28A and 28B of the lubricant 28 flow out of the gap between the shaft 22 and the thrust plate 26, and the lubricant 28C flows out of the lower part of the gap between the shaft 22 and the sleeve 25A. There was something to do.

[0005]

In order to solve the above-mentioned problems, a hydrodynamic bearing device according to the present invention has one end fixed to a base member, a flange member near the other end and an opposite side of the flange member to the base member. A fixed shaft having an upper shaft portion on the side thereof, a sleeve having a bearing hole provided rotatably with respect to the fixed shaft at a substantially central portion of the fixed shaft, and a sleeve on the upper shaft portion side of the flange member. A thrust plate having a flat portion abutting on a flat surface and an inner peripheral portion abutting on the outer peripheral surface of the upper shaft portion is fixed to the sleeve, and an outer peripheral surface of the fixed shaft and an inner peripheral surface of a bearing hole of the sleeve are fixed. A radial dynamic pressure groove on at least one of the mutual opposing surfaces, and an outer thrust dynamic pressure groove on at least one of the mutual opposing surfaces of the flange member and the thrust plate, and an inner diameter of a bearing hole of the sleeve. Than the upper shaft The outer diameter of the thrust plate and the diameter of the inner peripheral portion of the thrust plate are configured to be small, and a portion smaller than the bearing hole of the sleeve is provided on the base member side of the radial dynamic pressure groove adjacent to the bearing hole of the sleeve. The fixed shaft facing the small-diameter portion has a small-diameter shaft portion, and the radial dynamic pressure groove and the outer thrust dynamic pressure groove are filled with a lubricant.

According to the present invention, a fluid bearing having no lubricant outflow is obtained by the above-described structure.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A hydrodynamic bearing device according to an embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a sectional view of a hydrodynamic bearing device according to an embodiment of the present invention. In FIG. 1, one end of a fixed shaft 2 is fixed to a base member 1. The fixed shaft 2 has a flange member 4 near the other end and an upper shaft portion 2A extending from the flange member 4, A sleeve 10 having a bearing hole 10F is rotatably fitted around the outer periphery of the fixed shaft 2, and the flange member 4 is provided with a step 10A of the sleeve 10.
It is stored in. Further, a thrust plate 7 having a surface facing the outer peripheral surface of the flange member 4 and the upper shaft 2 </ b> A and having a substantially spiral thrust dynamic pressure groove 5 provided on the surface facing the flange member 4 is provided in the recess 10 </ b> B of the sleeve 10. Fixed. At least one set, usually two sets, for example, fishbone-shaped radial dynamic pressure grooves 3A and 3B are provided on one of the outer peripheral surface of the fixed shaft 2 and the bearing surface 10F of the sleeve 10. End face of portion 10A and stepped portion 10 of flange member 4
A helical inner thrust dynamic pressure groove 6 is provided on one of the contact surfaces with A, if necessary.
And an outer thrust dynamic pressure groove 5 is provided on one of the contact surfaces of the thrust plates 7 with each other.
B, outer thrust dynamic pressure groove 5, inner thrust dynamic pressure groove 6
Is lubricated with a lubricant 11. A motor rotor 13 is fixed to the hub 9 fixed to the sleeve 10, and a motor stator 12 is fixed to the base member 1. Between the flange member 4 and the radial dynamic pressure grooves 3A and 3B, there are ventilation holes 2E and 2F which open on the outer peripheral surface of the fixed shaft 2 and communicate with the outside air through the inside of the fixed shaft 2 as shown in FIG. As shown, the diameter of the inner diameter portion of the thrust plate 7 (D4 in the figure) is the diameter of the bearing surface 10F of the sleeve 10 abutting on the fixed shaft 2 (D3 in the figure).
As shown in FIGS. 4 and 5, a smaller diameter portion 2i is provided on the outer peripheral surface of the fixed shaft 2 on the side of the base member 1 outside the radial dynamic pressure grooves 3A and 3B. This small diameter part 2
i has a taper whose diameter becomes smaller as the distance from the flange member 4 increases as needed. 15A, 15B, 15C,
15D is a disk, and 16A, 16B and 16C are spacers. 2D is a concave portion provided as needed in the opening of the ventilation hole 2E, and the upper shaft portion 2A is provided with a tapered portion 2B and a screw portion 2H as necessary. The fixed shaft 2 has a concave portion 2C as necessary, and the sleeve 10 has a large-diameter portion 1C.
0C is provided, and a space formed by the concave portion 2C and the large-diameter portion 10C is a pool of air and the lubricant 11. If necessary, the flange member 4 has a concave portion 4A serving as an air reservoir.

The operation of the hydrodynamic bearing device according to an embodiment of the present invention configured as described above will be described with reference to FIGS. In FIG. 1, a motor stator 1 is shown.
2 is energized to generate a rotating magnetic field, the motor rotor 13 turns the hub 9, sleeve 10, thrust plate 7, disks 15A, 15B, 15C, 15D, spacers 16A,
Start rotation with 16B and 16C. At this time, the dynamic pressure groove 3
A and 3B scrape the lubricant 11 to generate pressure by the pumping action, and the outer thrust dynamic pressure groove 5 and the inner thrust dynamic pressure groove 6 also scrape the lubricant 11, respectively, so that the sleeve 10 is fixed to the fixed shaft 2 by the generated pressure. It turns into a completely non-contact state. A more detailed operation of the hydrodynamic bearing device according to the present embodiment will be described with reference to FIGS.
In FIG. 2, even during high-speed rotation, the inner diameter (D4 in the figure) of the thrust plate 7 is smaller than the inner diameter (D3 in the figure) of the bearing surface 10F in which the fixed shaft 2 abuts on the sleeve 10; Also, the lubricant 11 does not scatter above the thrust plate 7. In other words, the centrifugal force acting on the lubricant 11 causes the lubricant to move from the small-diameter portion to the large-diameter portion, and prevents the lubricant 11 from flowing out. Since the upper and lower surfaces of the flange member 4 are sealed by the step 10A of the sleeve 10, the lubricant 1
1 does not flow. Next, the fixed shaft 2 is provided with a concave portion 2 as necessary.
D is provided, that is, between the flange member 4 and the radial dynamic pressure grooves 3A and 3B, and the expanded air is discharged to the outside via the ventilation holes 2E and 2F.
The lubricant 11 is not extruded. In FIG. 3, the bubbles aggregate as indicated by 17B, 17C, 17D, and 17E, and when the temperature increases due to the rotation of the motor and the volume of the bubbles increases, the gas-liquid boundary surfaces 18A and 18B once slightly move. Eventually, however, the air bubbles are reduced to the step 1 as shown in FIG. 17D.
0A and through the gap between the lower surface of the flange member 4 and the ventilation hole 2
E, 2F are discharged to the outside via the gas and liquid interface 18
A and 18B eventually return to a stable state as shown in FIG. Also, in FIG.
Since the inside diameter of the small diameter portion 2i of the fixed shaft 2 and the small diameter portion 10G of the sleeve 10 is smaller than the inside diameter of the bearing hole 10F of the sleeve 10, the lubricant 1
1 does not scatter above the thrust plate 7. That is, the centrifugal force F1 acts on the lubricant 11A, and the component force F2 prevents the lubricant from flowing out. Next, a detailed operation will be described with reference to FIG. FIG. 5 shows a state after the hydrodynamic bearing device according to the present embodiment has been stably rotated for a sufficient time. The radial dynamic pressure grooves 3A and 3B each have L2 longer than L1 and L4 longer than L3.
The gas-liquid interface 18C is located at a position where L1 and L5 are substantially equal, and the gas-liquid interface 18D is located at a position where L3 and L6 are approximately equal. At this time, the large diameter portion 1 of the sleeve 10
The pressure of the aggregated bubbles 17G confined at 0C is almost the same as the atmospheric pressure. Next, when the bubble 17G expands due to a change in temperature or a change in pressure, the gas-liquid boundary surfaces 18C and 18D move up and down, and the aggregated bubble 17G is slightly compressed. If it does, the aggregated air bubbles 17G move to the radial dynamic pressure grooves 3A or 3B during rotation or stop, and 17B in the figure.
H, 17I, it is discharged upward or downward and returns to a stable state. The two radial dynamic pressure grooves 3A, 3
Since there is no ventilation hole communicating with the outside between B,
The lubricant stored in the large diameter portion 10C never flows out.

As described above, according to the present embodiment, the lubricant 11 has high reliability because the lubricant 11 does not flow out to the outside even during high-speed rotation, during stoppage, or when there is a change in pressure or temperature. The configuration of the hydrodynamic bearing device is obtained.

[0010]

As described above, the hydrodynamic bearing device of the present invention
The outer diameter of the upper shaft portion of the fixed shaft and the diameter of the inner diameter portion of the flange member are configured to be smaller than the diameter of the bearing hole in the sleeve. By making the fixed shaft facing the small diameter portion also small in diameter, the centrifugal force acts on the lubricant rotating at high speed, so that the lubricant can be completely prevented from flowing out.

[Brief description of the drawings]

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

FIG. 2 is a detailed view of a main part of the hydrodynamic bearing device shown in FIG.

FIG. 3 is a detailed view of a main part of the hydrodynamic bearing device shown in FIG. 1;

FIG. 4 is a detailed view of a main part of the hydrodynamic bearing device shown in FIG. 1;

FIG. 5 is a detailed view of a main part of the hydrodynamic bearing device shown in FIG. 1;

FIG. 6 is a sectional view of a conventional hydrodynamic bearing device.

[Explanation of symbols]

 Reference Signs List 1 base member 2 fixed shaft 2A upper shaft portion 3A, 3B radial dynamic pressure groove 4 flange member 5 outer thrust dynamic pressure groove 6 inner thrust dynamic pressure groove 7 thrust plate 9 hub 10 sleeve 11 lubricant 2E, 2F ventilation hole

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Riki Hamada 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 3J011 AA07 BA02 BA09 CA02 CA04 JA02 KA02 KA03 MA03 MA24

Claims (4)

[Claims] 1. A fixed shaft having one end fixed to a base member and having a flange member near the other end and an upper shaft portion on a side of the flange member opposite to the base member, and a substantially central portion of the fixed shaft. A sleeve having a bearing hole rotatably provided with respect to the fixed shaft, a flat portion contacting a plane on the upper shaft portion side of the flange member, and an inner periphery contacting an outer peripheral surface of the upper shaft portion. A thrust plate having a portion is fixed to the sleeve, and a radial dynamic pressure groove is provided on at least one of an outer peripheral surface of the fixed shaft and an inner peripheral surface of a bearing hole of the sleeve. At least one of the mutually opposing surfaces of the thrust plate and the thrust plate has an outer thrust dynamic pressure groove, and the outer diameter of the upper shaft portion and the diameter of the inner peripheral portion of the thrust plate are larger than the inner diameter of the bearing hole of the sleeve. Small and said three Adjacent to the bearing hole of the sleeve, the radial dynamic pressure groove has a portion having a smaller diameter than the bearing hole of the sleeve on the base member side, and the fixed shaft facing the small diameter portion has a small diameter shaft portion, A hydrodynamic bearing device in which the radial dynamic pressure groove and the outer thrust dynamic pressure groove are filled with lubricant. 2. The hydrodynamic bearing device according to claim 1, wherein the upper shaft portion has a tapered portion whose diameter decreases as the distance from the flange member increases. 3. The hydrodynamic bearing device according to claim 1, wherein the small-diameter shaft portion has a tapered portion whose diameter decreases as the distance from the flange member increases. 4. A fixing device according to claim 1, further comprising: a flange member; and a vent hole which is opened substantially at an intermediate portion of the radial dynamic pressure groove and on an outer peripheral surface of the fixed shaft and communicates with the outside air through the inside of the fixed shaft. 4. The hydrodynamic bearing device according to 3.