JP2966738B2 - Dynamic pressure thrust 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 dynamic thrust bearing device for supporting a rotating member and a fixed member so as to be relatively rotatable by dynamic pressure of a bearing fluid.

[0002]

2. Description of the Related Art In recent years, hydrodynamic bearing devices have been widely used in various devices requiring high precision and high speed rotation, such as motors. This dynamic pressure bearing device rotatably supports a rotating member by using the dynamic pressure of a predetermined bearing fluid, and is usually provided with a dynamic pressure radial sliding bearing and a dynamic pressure thrust bearing.

In the dynamic pressure thrust bearing, as shown in FIG. 5, for example, a plurality of grooves 2 for generating dynamic pressure are formed on a sliding surface 1 where a rotating member and a fixed member face each other. . Each of the grooves 2 for generating dynamic pressure is formed so as to extend spirally in a substantially radial direction, and a plurality of these grooves are arranged in parallel in the circumferential direction.

Each of the grooves 2 for generating dynamic pressure is usually formed at a uniform depth along the extending direction of the groove, and has a substantially rectangular cross section along the groove. That is, the groove 2 for generating dynamic pressure has a substantially uniform groove depth over the entire area of the sliding surface so as to obtain a necessary dynamic pressure during steady rotation.

[0005]

However, such a general dynamic pressure thrust bearing has a problem that a sufficient dynamic pressure cannot be obtained at the time of starting. That is, as shown by A in FIG. 3, from the time when the flying height (horizontal axis) is "0" to the time when the flying height is small, the dynamic pressure generation defined by the flying height per unit loss torque is started. The efficiency (vertical axis) is extremely small. For this reason, the contact time between the shaft and the bearing tends to be longer at the time of starting, and there is a problem that the sliding surface is liable to be worn and the starting torque is increased.

Accordingly, an object of the present invention is to provide a dynamic pressure thrust bearing device capable of obtaining a good dynamic pressure even at the time of starting without impairing the dynamic pressure at the time of steady rotation.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a sliding member in which a rotating member and a fixed member face each other.
A groove for generating a dynamic pressure extending spirally in a substantially radial direction for supporting the rotating member and the fixed member so as to be relatively rotatable; In the dynamic pressure thrust bearing device formed so that a plurality of dynamic pressure generating grooves are arranged in parallel in the circumferential direction, some of the plurality of dynamic pressure generating grooves In addition to the means for forming the shape having the generation efficiency, the other grooves for generating the dynamic pressure are formed in the shape having the maximum dynamic pressure generation efficiency at the time of starting.

[0008]

In such a means, a concave groove formed in a shape having a maximum dynamic pressure generation efficiency during steady rotation is provided;
With the concave groove formed in the shape having the maximum dynamic pressure generation efficiency at the time of startup, it is possible to obtain a good dynamic pressure both at the time of steady rotation and at the time of startup.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an HDD spindle motor will be described below in detail with reference to the drawings.

First, an example of an HDD spindle motor having a dynamic pressure thrust bearing will be described with reference to FIG. The HDD spindle motor shown in FIG. 2 includes a stator set 20 as a fixed member mounted on the frame 10 side, and a rotor as a rotating member mounted on the stator set 20 in a stacked manner from the upper side in the figure. And a set 30. The stator core 21 constituting the stator set 20 is fitted around the outer periphery of a substantially cylindrical bearing holder 22 erected at a substantially central position of the frame 1, and the salient pole portion of the stator core 21 is provided. Is wound.

A pair of integrally formed radial slide bearings 24, 24 are provided at an inner peripheral portion of the bearing holder 22 at predetermined intervals in the axial direction. The pair of radial slide bearings 24, 24 are provided by the pair of radial slide bearings 24, 24. , A rotating shaft 31 is rotatably supported. That is, the inner peripheral surfaces of the two radial sliding bearings 24, 24 are
The sliding surface is slidably slidable via a predetermined bearing fluid, and the inner peripheral surface of each of the radial sliding bearings 24 and the rotating shaft 31.
A radial dynamic pressure sliding surface is constituted by the outer peripheral surface of the shaft.

Further, the tip (the lower part in the figure) of the rotating shaft 31 is supported by a dynamic thrust bearing. This dynamic pressure thrust bearing has a thrust receiving plate 25 that covers an opening at the lower end side of the bearing holder 22 in the drawing, and the sliding surface of the thrust receiving plate 25 is a tip end of the rotating shaft 31 (lower side in the drawing). Part). This thrust receiving plate 25
A spiral-shaped groove for generating a dynamic pressure as described later is formed on the sliding surface of. The tip surface of the rotating shaft 31 and the receiving surface of the thrust receiving plate 25 constitute a thrust-direction dynamic pressure sliding surface so that the bearing fluid is interposed therebetween.

A base (upper end in the figure) of the rotary shaft 31
The hub 33 constituting the rotor set 30 is fixed so as to rotate integrally. The hub 33 has a substantially cylindrical body portion 33a for mounting a plurality of magnetic disks 34 on the outer peripheral portion, and has a mounting portion 33b at a lower end edge of the body portion 33a in the figure. Mounting part 33b
Further, a driving magnet 36 is annularly mounted via a back yoke 35. The drive magnet 36 is disposed in proximity to the outer peripheral end surface of the stator core 21 so as to annularly face the outer peripheral end surface.

Further, a magnetic fluid seal 26 for preventing the above-mentioned outflow of the bearing fluid is disposed at an opening on the upper end side of the bearing holder 22 in the figure. The magnetic fluid seal 26 includes a pair of thin ring-shaped pole pieces 2.
6a and 26a.
Magnetic fluids 26b are held between the inner peripheral edges of the shafts a and 26a and the outer peripheral surface of the rotating shaft 31, respectively. These magnetic fluids 26b provide the sealing function of the bearing fluid described above. Is configured.

Next, a description will be given of the groove for generating dynamic pressure provided on the thrust receiving plate 25 constituting the dynamic pressure thrust bearing. As shown in FIG. 1, on a sliding surface of the thrust receiving plate 25, a dynamic pressure generating groove 251 extending spirally in a substantially radial direction is formed so as to be arranged in parallel in a circumferential direction. . A total of eight grooves 251 for generating dynamic pressure are provided. Of these, four members denoted by reference numeral 251a are formed in a shape having the maximum dynamic pressure generation efficiency at the time of steady rotation, and the remaining grooves are formed. The four members denoted by reference numeral 251b are formed in shapes having the maximum dynamic pressure generation efficiency at the time of startup.

More specifically, the concave groove 251a for dynamic pressure generation formed in a shape having the maximum dynamic pressure generation efficiency at the time of steady rotation is such that the bottom gradually becomes shallower from the outer peripheral side toward the rotation center O. The cross-section along the groove extending direction is formed in a wedge shape. On the other hand, the dynamic pressure generating concave groove 251b formed in a shape having the maximum dynamic pressure generation efficiency at the time of startup is formed with a uniform groove depth from the outer peripheral side toward the rotation center O, and has an inner peripheral end. The part has a wall that rises sharply. That is, the groove 251b for generating dynamic pressure has a stepped cross section along the groove extending direction. Each of these grooves 251 for generating dynamic pressure
a and 251b are alternately arranged in the circumferential direction.

In the dynamic thrust bearing according to the first embodiment, the groove 251 for generating dynamic pressure is formed in a stepped shape having the maximum dynamic pressure generating efficiency during steady rotation.
b and the wedge-shaped concave groove 251a formed in a wedge shape having the maximum dynamic pressure generation efficiency at the time of start-up, so that good dynamic pressure can be obtained both at the time of steady rotation and at the time of start-up. .

For example, as shown by reference numeral C in FIG. 3, from the time when the flying height (horizontal axis) is “0” to the time when the flying height is small, the bearing fluid is moved in a wedge-shaped motion. The dynamic pressure generation efficiency defined by the flying height per unit loss torque (FIG. 3) is obtained because the fluid quickly enters the center sliding surface from the outer peripheral side along the inclined bottom surface of the pressure generating groove 251a.
The vertical axis) has a considerably higher value at startup than the above-described conventional dynamic pressure thrust bearing (see A).
The dynamic pressure generation efficiency during steady rotation is slightly lower than that of the conventional type, but maintains a good value.

On the other hand, in the dynamic pressure thrust bearing 252 of the second embodiment shown in FIG. 4, the dynamic pressure generation bearing formed in a uniform groove-shaped stepped shape having the maximum dynamic pressure generation efficiency during steady rotation. Six concave grooves 252b are provided in the circumferential direction, and a wedge-shaped concave groove 252a formed in a wedge shape having a maximum dynamic pressure generation efficiency at the time of starting is formed by the dynamic groove 252b. Two bodies are provided between them.

In the dynamic thrust bearing according to the second embodiment, as indicated by reference numeral D in FIG. 3, the dynamic pressure generation efficiency at startup (vertical axis) is lower than that of the conventional dynamic thrust bearing. The value is made higher than that of the pressure thrust bearing (see A), and the dynamic pressure generation efficiency at the time of steady rotation is improved as compared with the first embodiment described above.

Reference numeral E in FIG. 3 denotes seven dynamic pressure generating grooves formed in a stepped shape of a uniform groove having a maximum dynamic pressure generating efficiency during steady rotation, and a maximum dynamic pressure during startup. This is a case where a single wedge-shaped groove for generating dynamic pressure having a generation efficiency is formed. In the dynamic pressure thrust bearing according to the third embodiment, the dynamic pressure generation efficiency at startup (vertical axis) is slightly improved as compared with the conventional dynamic pressure thrust bearing (see A), and the dynamic pressure at the time of steady rotation is improved. The pressure generation efficiency is further stabilized as compared with the embodiments described above.

Reference numeral B in FIG. 3 indicates a case where all of the eight grooves for generating dynamic pressure are formed in a wedge shape having a maximum dynamic pressure generating efficiency at the time of startup. The dynamic pressure generation efficiency (vertical axis) at the time is extremely increased,
It is considered that actual application is impossible because the dynamic pressure generation efficiency at the time of steady rotation is reduced.

Although the invention made by the inventor has been specifically described based on the embodiments, the present invention is not limited to the above-described embodiments, and can be variously modified without departing from the gist thereof. Needless to say. For example, the total number of grooves for generating dynamic pressure is not limited to eight as in the above embodiments. Further, the present invention can be similarly applied to all types of devices using dynamic pressure bearings other than motors.

[0027]

As described above, the dynamic thrust bearing device according to the present invention has a dynamic pressure generating groove formed in a shape having the maximum dynamic pressure generation efficiency during steady rotation, and a maximum dynamic pressure generation groove at startup. By providing a dynamic pressure generating groove formed in a shape having a pressure generation efficiency, a good dynamic pressure can be obtained both at the time of steady rotation and at the time of starting, so that the steady rotation state is spoiled. It is possible to reduce the occurrence of wear and the starting torque at the time of starting without increasing the reliability of the dynamic pressure thrust bearing device.

[Brief description of the drawings]

FIG. 1 is an external perspective explanatory view showing a dynamic pressure thrust bearing device according to a first embodiment of the present invention.

FIG. 2 is a half cross-sectional explanatory view showing an example of an HDD motor using the dynamic pressure thrust bearing device according to the present invention.

FIG. 3 is a diagram showing a comparison of dynamic pressure generation efficiencies.

FIG. 4 is an external perspective explanatory view showing a dynamic thrust bearing device according to a second embodiment of the present invention.

FIG. 5 is an external perspective explanatory view showing a general configuration of a dynamic pressure thrust bearing.

[Explanation of symbols]

 251, 252 Groove for generating dynamic pressure 251a, 252a Groove for generating wedge-shaped dynamic pressure 251b, 252b Groove for generating step-shaped dynamic pressure

Claims (3)

(57) [Claims] 1. A dynamic pressure generating groove extending spirally in a substantially radial direction is provided on a sliding surface of a rotating member and a fixed member opposed to each other, so that the rotating member and the fixed member are relatively fixed to each other. A dynamic pressure thrust bearing device which is rotatably supported and is formed so that a plurality of the dynamic pressure generating grooves are arranged in parallel in the circumferential direction. Some of the grooves for generating dynamic pressure are formed to have the maximum dynamic pressure generation efficiency at the time of steady rotation, and the other grooves for generating dynamic pressure are formed to have the maximum dynamic pressure generation efficiency at the time of startup. A hydrodynamic thrust bearing device characterized by being formed. 2. The dynamic pressure thrust bearing device according to claim 1, wherein the dynamic pressure generating groove formed in a shape having the maximum dynamic pressure generating efficiency at the time of starting has a substantially wedge-shaped cross section along the groove extending direction. The groove for dynamic pressure generation formed in a shape having the maximum dynamic pressure generation efficiency during steady rotation is formed in a stepped cross-sectional shape along the groove extending direction. Dynamic pressure thrust bearing device. 3. The dynamic pressure thrust bearing device according to claim 1, wherein the dynamic pressure generating groove formed into a shape having the maximum dynamic pressure generation efficiency at the time of startup has the maximum dynamic pressure generation efficiency at the time of steady rotation. A dynamic pressure thrust bearing device, wherein the number is equal to or less than the number of grooves for generating dynamic pressure formed in a shape having the same.