JP3202147B2 - Fluid bearing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrodynamic bearing device for rotatably supporting a rotary shaft such as a main shaft of a machine tool through a pressurized fluid.

[0002]

2. Description of the Related Art FIG. 6 shows a hydrodynamic bearing device according to the prior art. A fluid bearing device 10 that supports a rotating shaft by the pressure of a fluid includes a bearing 12 formed in a cylindrical shape, and a rotating shaft 14 that has been ground and inserted into the bearing 12.
Rectangular static pressure pockets 16a-1 on the inner wall of the bearing 12
6d are defined, and lands 18a to 18d are formed between the respective static pressure pockets 16a to 16d (see FIG. 7). The static pressure pockets 16a to 16d and the land 18
An edge portion forming a boundary with a to 18d is formed parallel to the axial direction of the rotating shaft 14 (see FIG. 8). Fluid supply passages 20a to 20d through which a pressure fluid is introduced are defined at substantially the center of the static pressure pockets 16a to 16d, and the fluid supply passages 20a to 20d communicate with a pressure fluid supply source (not shown).

In the above-described configuration, when a pressure fluid supply source (not shown) is energized, the pressure fluid flows from the fluid supply passages 20a to 20d to the static pressure pockets 16a to 16d at a constant pressure.
16d, the fluid pressure is applied to the outer periphery of the rotating shaft 14, and the rotating shaft 14 is levitated and supported by the fluid pressure.

[0004]

However, according to the above-mentioned conventional hydrodynamic bearing device, the ground shaft 1 is ground.
No. 4 is affected by the accuracy of the machine tool or the accuracy of the roundness of the grinding wheel during the grinding, and a small degree of roundness distortion is likely to occur along its axial direction. When the rotating shaft 14 having such distortion is used, for example, the rotating shaft 1
In the case where the minute protrusion 22 extends along the axial direction of the protrusion 4 when the protrusion 22 faces one of the static pressure pockets 16a to 16d, the protrusion 22 has The fluid pressure introduced into the static pressure pockets 16a to 16d is applied, and the rotating shaft 14 is displaced in the direction opposite to the convex portion 22 by the fluid pressure (see FIG. 7). However, rotating shaft 1
When the projection 4 rotates and the projection 22 moves to a position facing one of the lands 18a to 18d, no fluid pressure is applied to the projection 22, so that the rotating shaft 14 is displaced toward the center of the axis. I do. For this reason, when the rotating shaft 14 rotates, the convex portion 22 is moved to the static pressure pockets 16a to 16d and the land portions 18a to
18d, the rotating shaft 14 is displaced every time it moves, and the rotation accuracy is deteriorated.

[0005] Further, the convex portion 22 is connected to one of the land portions 18a to 1 from one of the static pressure pockets 16a to 16d.
When moving to a position facing 8d, the fluid pressure applied to the convex portion 22 decreases instantaneously, and the rotating shaft 14 is rapidly displaced. Furthermore, the convex portion 22 is connected to any of the land portions 18.
any of static pressure pockets 16a-16d from a-18d
, The fluid pressure is momentarily applied to the convex portion 22, and the rotating shaft 14 is rapidly displaced. Thus, the convex portion 22
Are static pressure pockets 16a to 16d and lands 18a to 18
Every time the boundary with d is exceeded, the rotating shaft 14 is suddenly displaced, and center runout occurs. Therefore, a high-precision rotation operation cannot be obtained, and when this type of fluid bearing device is used for a machine tool, there are various disadvantages such as poor machining accuracy and poor durability of the bearing device itself.

SUMMARY OF THE INVENTION The present invention has been made to overcome the above-mentioned various inconveniences. In the case where there are distortions and irregularities along the axis of the rotating shaft, the displacement of the rotating shaft is reduced to improve the rotational accuracy. It is an object of the present invention to provide a hydrodynamic bearing device which improves the machining accuracy and the like by preventing the rotation shaft from oscillating.

[0007]

To achieve the above object, the present invention comprises a plurality of static pressure pockets defined on an inner wall of a bearing, and a rotating shaft inserted through the bearing, wherein the fluid bearing device for rotatably supporting the rotary shaft by the pressure of the fluid supplied to the hydrostatic pocket, at least one edge facing the direction of rotation with one of said hydrostatic pockets (e.g. , The first edge) is one of the edges
One end (first corner, chevron end of FIG. 4 or FIG. 5)
One end of the waveform, etc.) and at least one portion (second corner, angled bend in FIG. 4 ) that is relatively displaced in the circumferential direction
Or the other end of the waveform of FIG. 5) . Also, for one of the static pressure pockets,
The one end of the one edge and the one edge
The relative distance in the circumferential direction to the portion is a first distance (for example,
Length A) , adjacent to said one end and said one edge
The other edge of the other abutting static pressure pocket (eg,
Circumferential phase with one end (third corner) of the second edge)
The pair distance was set to a second distance (for example, length A-length B).
When the first distance is larger than the second distance
You may.

[0008]

According to the present invention, the rotating shaft is evenly levitated and supported by the fluid pressure introduced into the static pressure pocket. When the rotating shaft has irregularities or roundness distortion along the axial direction thereof, when the rotating shaft rotates to move the distortion or the like from the static pressure pocket to a position facing the land portion, the distortion or the like occurs. Moves relatively gradually from one end of the static pressure pocket to the other end of the static pressure pocket. Therefore, the area of the static pressure pocket facing the distortion or the like gradually decreases, and the fluid pressure applied to the distortion or the like gradually decreases. Similarly, when the strain or the like moves from the land to a position facing the static pressure pocket, the fluid pressure applied to the strain or the like gradually increases. For this reason, the fluid pressure applied to the distortion or the like does not suddenly change, and it is possible to suppress the center runout of the rotating shaft. Ma
Further, according to the present invention, when the rotating shaft rotates, the distortion
Immediately before reaching the end of the static pressure pocket,
Because it is applied to the end of the static pressure pocket,
Fluid pressure is applied from one of the static pressure pockets
Therefore, the amount of deviation of the rotating shaft is suppressed, and the rotation accuracy is improved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A hydrodynamic bearing device according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a partially sectional perspective view of a hydrodynamic bearing device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the hydrodynamic bearing device shown in FIG. 1, and FIG. 3 is a hydrodynamic bearing device shown in FIG. FIG.

In FIG. 1, reference numeral 30 denotes a hydrodynamic bearing device according to the present embodiment. This hydrodynamic bearing device 30 includes a bearing 32 formed in a cylindrical shape, and a rotating shaft 34 rotatably inserted inside the bearing 32. On the inner wall of the bearing 32, static pressure pockets 36a to 36d
And each of the static pressure pockets 36a
One of the first edges 38a to 38d and the other second edges 40a to 40d in the circumferential direction are formed on the first to the second edges 36a to 36d (see FIG. 2). One first corner 4 of one of first edges 38a to 38d
2a to 42d are circumferentially offset by a length A in the circumferential direction with respect to the other second corners 44a to 44d, and similarly, the second edge 40a
One of the third corners 46a to 46d is deviated by a length A in the circumferential direction with respect to the other fourth corners 48a to 48d.
6a to 36d are defined in a shape twisted along the circumferential direction (see FIG. 3).

The first corner 4 of the static pressure pocket 36a
2a and a static pressure pocket 3 adjacent to said first corner 42a.
The circumferential distance between the third corner portion 46b and the third corner portion 46b is smaller than the length A, and similarly, the first corner portion 42b of the static pressure pocket 36b and the third corner portion of the static pressure pocket 36c. 46
c, a first corner 42c of the static pressure pocket 36c, a third corner 46d of the static pressure pocket 36d, a first corner 42d of the static pressure pocket 36d, and a third corner 4 of the static pressure pocket 36a.
The interval of 6a is formed smaller than the length A. For this reason, the first corners 42a to 42 of the first edges 38a to 38d.
The vicinity of d is the fourth corner 48b of the second edges 40b to 40a.
４８48a and the length B in the axial direction of the rotating shaft 34.

In the above-described configuration, fluid supply passages 50a to 50d through which a pressure fluid is introduced are defined substantially at the center of the static pressure pockets 36a to 36d, and the fluid supply passages 50a to 50d have a pressure (not shown). Communicate with fluid supply.

The hydrodynamic bearing device 30 according to the present embodiment is basically configured as described above, and the operation thereof will be described next.

When a pressure fluid supply source (not shown) is energized, a fluid such as oil is introduced into the static pressure pockets 36a to 36d from the fluid supply passages 50a to 50d at a constant pressure. Is applied, and the rotating shaft 3
4 is floated and supported by this fluid pressure. For this reason, the rotating shaft 34 can rotate the inside of the bearing 32 with extremely small friction.

If the rotary shaft 34 has irregularities or roundness distortion along the axial direction, for example, the small convex portions 52
2 (see the broken line in FIG. 2) extends in the axial direction of the rotating shaft 34, and when the convex portion 52 faces the static pressure pocket 36a, the fluid pressure applied to the convex portion 52 causes the rotating shaft 3 to move.
4 deviates in the direction opposite to the convex portion 52 (see FIG. 2).

When the rotating shaft 34 rotates, the convex portion 52 is engaged with the second corner portion 44a of the static pressure pocket 36a (see FIG. 3), and when the rotary shaft 34 is further rotated, the convex portion 52 becomes the first edge portion 38a.
Are relatively moved, and the area of the convex portion 52 facing the static pressure pocket 36a is gradually reduced. For this reason, the fluid pressure applied to the convex portion 52 gradually decreases, and the rotating shaft 34 is displaced toward the center of the axis.

Immediately before the convex portion 52 reaches the first corner portion 42a, the convex portion 52 extends over the fourth corner portion 48b of the adjacent second edge portion 40b. The fluid pressure is applied from both the static pressure pocket 36a and the static pressure pocket 36b.

When the rotating shaft 34 further rotates, the area of the convex portion 52 facing the static pressure pocket 36b increases, and the fluid pressure applied to the convex portion 52 gradually increases. And deviates in the opposite direction. Then, the convex portion 52 reaches a position facing the static pressure pocket 36b via the third corner portion 46b.

As described above, the pressure applied to the projection 52 is the first
Since the angle gradually changes at the edges 38a to 38d and the second edges 40a to 40d, the rotation of the rotary shaft 34 from the axis does not occur abruptly, and the rotary shaft 34 rotates without causing runout. Also,
The convex portion 52 is always provided with one of the static pressure pockets 36a to 36d.
, The amount of deflection of the rotating shaft 34 is suppressed, and the rotation accuracy is improved.

In this embodiment, the static pressure pockets 36a to 36a-3
6d first edges 38a-38d, second edges 40a-40
Although d is formed spirally, that is, twisted along the inner wall of the bearing 32, it is formed in a shape bent in the circumferential direction as shown in FIG. 4 or in a curved shape as shown in FIG. You may. The number of the static pressure pockets 36a to 36d is not limited to four, but may be three or less, or five or more.

[0022]

According to the hydrodynamic bearing device of the present invention, the following effects can be obtained.

The edges of the static pressure pocket are circumferentially relative to each other.
When there is unevenness or distortion along the axis of the rotating shaft, the fluid pressure applied to the distortion or the like gradually changes, so that it is possible to prevent the occurrence of center runout.
it can. In addition, the static pressure pocket has a
Fluid pressure from any of the static pressure pockets
As a result, the amount of deflection of the rotating shaft is reduced, and a hydrodynamic bearing device capable of improving rotation accuracy can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a sectional view of the hydrodynamic bearing device shown in FIG.

FIG. 3 is a development view of a bearing of the hydrodynamic bearing device shown in FIG.

FIG. 4 is a development view of a bearing of a fluid dynamic bearing device according to another embodiment of the present invention.

FIG. 5 is a development view of a bearing of a hydrodynamic bearing device according to another embodiment of the present invention.

FIG. 6 is a partially sectional perspective view of a hydrodynamic bearing device according to a conventional technique.

7 is a cross-sectional view of the hydrodynamic bearing device shown in FIG.

8 is a development view of a bearing of the hydrodynamic bearing device shown in FIG.

9 is a cross-sectional view showing an operation state of the hydrodynamic bearing device shown in FIG.

[Explanation of symbols]

Reference Signs List 30 hydrodynamic bearing device 32 bearing 34 rotating shaft 36a to 36d static pressure pockets 38a to 38d, 40a to 40d edge 52 projection

Claims (2)

(57) [Claims] 1. A static pressure pocket defined on an inner wall of a bearing, and a rotating shaft inserted into the bearing, wherein the rotating shaft is rotated by a pressure of a fluid supplied to the static pressure pocket. In a freely bearing hydrodynamic bearing device, for one of the static pressure pockets, at least one edge facing the rotation direction is offset relative to one end of the edge in the circumferential direction. A hydrodynamic bearing device comprising at least one part. 2. The hydrodynamic bearing device according to claim 1, wherein, for one of the static pressure pockets, a circumference of the one end of the one edge and the portion of the one edge. Direction relative distance is a first distance, and the circumferential relative distance between the one end and one end of the other edge of the other static pressure pocket adjacent to the one edge is the first distance. 2. The hydrodynamic bearing device according to claim 1, wherein when the distance is 2, the first distance is larger than the second distance.