KR100260918B1 - Air dynamic pressure bearing apparatus having increased radial stiffness - Google Patents

Abstract

PURPOSE: An air dynamic pressure bearing device having increased rigidity in a radial direction is provided to reduce a size and a manufacturing cost by removing a spacer and reducing the number of hemispheres and to secure stability in rotation by increasing the rigidity against tilting of a bushing. CONSTITUTION: An air dynamic pressure bearing device having increased rigidity in a radius direction includes a step bearing(150) fixed on an upper portion of a shaft(120), a hemisphere(130) fixed on a lower portion of the shaft and having a plurality of dynamic pressure generating holes(135), and a bushing(140) inserted into the shaft to rotate between the step bearing and the hemisphere and having a through hole(146) at the center. The step bearing has a first diameter plate member(152) fixed on an end of the shaft for covering an upper end of the bushing, a second diameter air pocket member(154) axially piled up on the plate member and a third diameter recess member(156) axially piled up on the air pocket member. The first diameter is larger than the second diameter and the second diameter is larger than the third diameter. The bushing has a hemispherical hole for receiving the hemisphere at a lower end surface and a receiving hole(141) for receiving the air pocket and the recess member at an upper end surface.

Description

Pneumatic hydrodynamic bearing device with increased radial stiffness

The present invention relates to a pneumatic hydrodynamic bearing device that increases the rigidity of the radial direction, in particular, by installing a step bearing formed with an air pocket in the upper air flow out to generate a thrust load and a radial load to achieve stability of rotation and bushing It relates to a pneumatic hydrodynamic bearing device which increases the radial stiffness which increases the stiffness with respect to the tilting of.

Recently, due to the rapid development of information and computer industry, drive motors required to drive various devices, such as polygon mirror drive of laser printer, spindle motor of hard disk and head drive motor of VCR, etc. In order to perform data retrieval, storage and retrieval in a short time, high precision and high speed rotation performance without shaft shaking or shaft vibration is required. Accordingly, research and development are being promoted for a bearing device that enables the motor rotation as well as the development of a drive motor that stably rotates at high speed while suppressing shaft shake and shaft vibration of the drive motor. Among such bearing devices, in particular, the research and development is being actively conducted for a dynamic pressure fluid bearing device which supports radial load and thrust load at the same time and is suitable for high speed rotation.

1 is a cross-sectional view showing a polygon mirror driving device of a laser printer to which a hemispherical bearing device, which is a type of hydrodynamic fluid bearing device, is applied.

As shown, the shaft 20 is fixed to the lower housing 70, and the upper and lower hemispheres 30 and 35 are fixed to face each other at a predetermined distance from the predetermined position of the shaft 20.

In addition, through holes and hemisphere grooves 30a and 30b are formed in the bushing 40 to accommodate the shaft 20 and the upper and lower hemispheres 30 and 35 so that the bushing 40 can rotate. The through hole is fitted with a spacer 40a for adjusting the clearance between the upper and lower hemispheres 30 and 35 and the hemisphere grooves 30a and 30b. Although not shown, a plurality of dynamic pressure generating grooves are formed in the axial direction on the hemispheres of each of the hemisphere grooves 30a and 30b. In addition, the hub 60 having the polygon mirror 10, the stator 50, and the rotor 55 mounted on the outer circumferential surface of the bushing 40 is press-fitted to rotate together with the bushing 40.

When power is applied to the stator 50, the rotor 55 is rotated by the electromagnetic action of the opposite rotor 55, thereby rotating the hub 60, the bushing 40. At the beginning of rotation, a force acts in the direction of gravity by the weight of the bushing 40 so that the bushing 40 contacts the lower hemisphere 30 and maintains a constant distance from the upper hemisphere 35.

Then, as the bushing 40 rotates, fluid flows through the gap between the upper and lower hemispheres 30 and 35 and the hemisphere grooves 30a and 30b to generate dynamic pressure, respectively. At this time, since the gap between the lower hemisphere 30 and the hemisphere groove 30a is smaller, a larger dynamic pressure is generated and thus the bushing 40 is floated.

The bushing 40 is then moved up and down between the upper and lower hemispheres 30 and 35 facing each other, and the equal pressure equalization gap between the two hemispheres 30 and 35 and the hemisphere grooves 30a and 30b is the same. Rotate in equilibrium at.

However, there is a problem that it is very difficult to manufacture a fluid bearing device that operates in this manner and the manufacturing cost is high.

First, since the spacer inserted into the through hole formed inside the bushing has to be processed to a very precise dimension due to its operation characteristics, it takes a lot of time and cost to manufacture the bearing, and the size of the bearing device is increased by the spacer.

In addition, the manufacturing cost is increased because two hemispheres having a hemispherical surface that is precisely processed through a lapping process and the like, in which a dynamic pressure generating groove is formed, should be used up and down.

In addition, there is a problem that is weak against the tilting (tilting) of the bushing by the disturbance.

In addition, because the gap between the upper and lower hemispheres and the bushing must be precisely adjusted, the assembly efficiency is low, and there is a problem that takes a lot of time.

Accordingly, an object of the present invention is to reduce the manufacturing cost and reduce the size by removing the spacers and reducing the number of hemispheres used.

Another object of the present invention is to increase the rigidity against tilting of the bushing by disturbance to ensure rotational stability.

Another object of the present invention is to simplify assembly.

1 is a cross-sectional view showing a cross section of a conventional hemisphere bearing device,

Figure 2 is a partial cut cross-sectional view showing an air dynamic bearing device with increased radial rigidity according to the present invention,

3 is an enlarged perspective view of the step bearing of FIG.

Figure 4 is an enlarged cross-sectional view for explaining the operation of the pneumatic hydrodynamic bearing device of the present invention,

5 is a detail view of the cross hatch pattern.

According to a preferred embodiment of the present invention, the step bearing is fixed to the upper part of the shaft, and the hemisphere having a plurality of dynamic pressure generating grooves is fixed to the lower part, and a through hole is formed at the center of the bushing to rotate between the step bearing and the hemisphere. It is fitted to the shaft in the through hole if possible. The step bearing is a plate member of a first diameter fixed at the end of the shaft to cover the top surface of the bushing, an air pocket member of a second diameter laminated on the plate member in the axial direction, and an air pocket member in the axial direction. Consisting of a recessed member of a third diameter, which is sized in the order of the first diameter-the second diameter-the third diameter. In addition, the lower surface of the bushing is formed with a hemisphere groove for receiving a hemisphere, the upper surface of the bushing is formed with a receiving groove for receiving the air pocket and the recess member.

Preferably, the step bearing may be integrally formed and manufactured by plastic injection molding.

Air pockets are also formed on the outer circumferential surface of the air pocket member, and the air pockets are cross hatched, preferably, the air pocket member is located within 45 degrees of the circumference at the center of the top surface of the shaft.

Hereinafter, a fluid bearing device according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings. In the present invention, the case of using air in the fluid will be described as an example.

Referring to FIG. 2, the step bearing 150 is fixed to the upper portion of the shaft 120. The step bearing 150 is formed by sequentially combining the plate member 152, the air pocket member 154, and the recess member 156 from the end of the shaft 120. Preferably, plate member 152, air pocket member 154 and recess member 156 are integrally fabricated. In addition, through-holes 158 are formed in the center of each of the plate member 152, the air pocket member 154, and the recess member 156 to form a ring shape. On the other hand, in the size of diameter, it becomes small in order of plate member 152-air pocket member 154-recess member 156.

As described later, the diameter of the plate member 152 is the same as the diameter of the bushing 140, and covers the entire end portion in appearance in opposition to the minute gap with the bushing 140.

On the outer circumferential surface of the air pocket member 154, an air pocket 154a is formed over the entire surface. Referring to FIG. 5, the air pocket 154a has a cross hatch shape and knurling an outer circumferential surface to generate a cross hatch. Optionally, when the step bearing 150 itself is manufactured by plastic injection molding, the air pocket 154a may be formed simultaneously with the injection without the need for knurling.

Further, a recess 156a having a predetermined diameter and depth is formed from the bottom of the recess member 156.

Meanwhile, the hemisphere 130 is inserted into the lower portion of the shaft 120 and the shaft 120 is inserted into and fixed to the center. Normal dynamic pressure generating grooves 135 are formed on the hemisphere of the hemisphere 130.

The bushing 140 has a cylindrical shape in which a through hole 146 is formed therein, and is rotatably fitted to the shaft 120 between the step bearing 150 and the hemisphere 130.

A ring-shaped receiving groove 141 is formed along the circumferential direction of the upper surface of the bushing 140 to accommodate the air pocket member 154 and the recess member 156 of the step bearing 150. In addition, a hemisphere groove 142 is formed on the bottom surface of the bushing 140 to accommodate the hemisphere 130.

Meanwhile, as shown in FIG. 1, the hub 60 is mounted on the outer circumferential surface of the bushing 140, and other components are the same as described above with reference to FIG. 1, and detailed description thereof will be omitted.

Hereinafter, the operation of the bearing device according to a preferred embodiment of the present invention will be described in detail.

When power is applied to the stator, the rotor is rotated by the electromagnetic action of the opposite rotor, thereby rotating the hub and bushing 140. Prior to starting the rotation, a force acts in the direction of gravity by the weight of the bushing 140 so that the hemisphere groove 142 formed on the bottom surface of the bushing 140 contacts the hemisphere surface of the hemisphere 130.

When the rotation of the bushing 140 starts, air is introduced through the gap between the hemisphere 130 and the hemisphere groove 142 of the bushing 140. The introduced air generates dynamic pressure between the hemisphere groove 142 and the hemisphere by the dynamic pressure generating groove 135 formed in the hemisphere 130 of the hemisphere 130, and the gap between the hemisphere groove 142 and the hemisphere is very large. Small to generate a large dynamic pressure to float the bushing 140 in a short time.

Air passing through the gap between the bushing 140 and the shaft 120 is then introduced into the recess 156a formed at the bottom of the recess member 156 and externally along the arrows A-B-C shown in FIG. In this process, thrust load and radial load are generated.

In detail, first, in the first step, the recess 156a has a large volume and a gap between the recess member 156 and the surface of the receiving groove 141 has a small volume, so that the introduced air is recessed. As it flows out of 156a through the gap between the recess member 156 and the receiving groove 141 surface, a load is generated by the enlarged-contracted flow of the space volume.

Subsequently, when air flows along the arrow B in the second step, an air pocket 154a in the form of a cross hatch is formed on the outer circumferential surface of the air pocket member 154 to generate dynamic pressure. That is, in the case of the Couette flow in which the relative motion exists, the relative speed is converted into pressure energy, and a pressure rise occurs.

Where L is the moving distance of air, υ is the moving speed, γ is the specific gravity of the medium, λ is the coefficient of friction, and C is the clearance. According to this equation, it can be seen that the smaller the gap, the larger the moving speed, and the larger the coefficient of friction, the greater the amount of pressure generated. Therefore, the pressure generation amount is increased because the coefficient of friction for the flow of air flowing along the arrow B is increased by the air pocket 154a formed on the outer circumferential surface of the air pocket member 154.

In addition, in the third step, the load is generated by the expansion-contraction flow of the space volume even when air flows out through the gap between the plate member 152 and the upper surface of the bushing 140 in the receiving groove 141. .

At this time, the generated load is related to the gap t1 between the recess member 156 and the receiving groove 141 surface and the gap t2 between the plate member 152 and the top surface of the bushing 140, respectively, and the gaps t1 and t2. Since the smaller the larger the load is generated, as the dynamic pressure generated by the dynamic pressure generating groove 135 of the hemisphere 130 floats the bushing 140, and the gap t1 and t2 becomes smaller, a larger load is generated.

Through such time series steps, thrust and radial loads are generated, respectively, of which thrust load acts on the step bearing 150 and the bushing 140 simultaneously, but the step bearing 150 is fixed to the shaft 120. As such, only bushing 140 is affected by the load, which results in pushing bushing 140 downward.

The radial load also acts as a force to restore the bushing 140 when it is tilted during rotation. In particular, as shown in FIG. 4, most of the air pocket members 154 having the air pockets 154a formed on the outer circumferential surface thereof are located within 45 degrees of the circumference at the center of the upper end of the shaft 120. The dynamic pressure generated by the increased frictional force acts as a radial load, thereby making the rotation more stable due to the rigidity against the tilting of the bushing 140.

As the bushing 140 is pushed downward, the gap between the hemisphere groove 132 and the hemisphere of the bushing 140 becomes small, and the dynamic pressure generated accordingly increases, thereby causing the bushing 140 to rise again. Thereafter, while the above-described process is repeated, the bushing 140 flows up and down between the step bearing 150 and the hemisphere 130, and then the flow is stopped while the thrust load generated at both ends of the bushing 140 is balanced. Keep stable rotation.

As described above, the bearing device according to the preferred embodiment of the present invention has various advantages.

First, the production cost can be reduced by using only one hemisphere, and the manufacturing process can be made simpler. In particular, the injection molding of the step bearing can reduce the manufacturing cost and improve productivity.

In addition, the plate member of the step bearing can prevent contamination of the upper end surface of the bushing.

In addition, the radial load is generated by the air flowing out, and the rigidity caused by the disturbance of the bushing due to the disturbance is increased by the radial load generated by the increased frictional force by the air pocket, thereby ensuring stable rotation.

As described above, according to the present invention, the plate member covering the bushing on the upper part of the shaft and the air pocket member having the air pocket formed on the outer circumferential surface and the recess member having the recess formed therein are fixed to the step bearing integrally formed in the axial direction. The hemisphere having the dynamic pressure generating groove is fixed to the lower part of the shaft, and the bushing is rotatably inserted about the shaft between the step bearing and the hemisphere. As a result, manufacturing cost can be reduced, manufacturing process can be made simpler, and step bearings can prevent contamination of the upper surface of the bushing. In addition, by increasing the rigidity against the tilting of the bushing can ensure a stable rotation.

On the other hand, the present invention has been described in the case that the bushing rotates, for example, it can be equally applied to the case of rotating the shaft.

In addition, although specific embodiments of the present invention have been described and illustrated, the present invention may be variously modified and practiced by those skilled in the art, and such modified embodiments should not be individually understood from the technical spirit or viewpoint of the present invention. Such modified embodiments should fall within the scope of the appended claims.

Claims (6)

Axles; A step bearing fixed to the upper portion of the shaft; A hemisphere fixed to a lower portion of the shaft and having a plurality of dynamic pressure generating grooves formed on a surface thereof; A through hole formed at a center thereof and including a bushing fitted to the shaft to be rotatable between the step bearing and the hemisphere; The step bearing A plate member of a first diameter fixed to an end of the shaft to cover the top surface of the bushing; An air pocket member of a second diameter laminated on said plate member in an axial direction; A recessed member of a third diameter laminated on the air pocket member in the axial direction, The first diameter is greater than the second diameter and the second diameter is greater than the third diameter, Hemispherical grooves for receiving the hemisphere is formed on the bottom surface of the bushing, The upper surface of the bushing is a pneumatic dynamic bearing device for increasing the radial rigidity, characterized in that the receiving groove for receiving the air pocket and the recess member is formed. The pneumatic hydrodynamic bearing apparatus according to claim 1, wherein the step bearing is integrally formed. The pneumatic hydrodynamic bearing apparatus according to claim 1, wherein air pockets are formed on an outer circumferential surface of the air pocket member. 4. The pneumatic hydrodynamic bearing device of claim 3, wherein the air pockets are cross hatched. 4. The pneumatic hydrodynamic bearing device of claim 3, wherein the air pocket member is located within 45 degrees of a circumference at the center of the top surface of the shaft. 2. The pneumatic hydrodynamic bearing apparatus according to claim 1, wherein the step bearing is made of plastic injection molding.

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