KR19980046992A - Dynamic Hydraulic Bearings - Google Patents

Abstract

The present invention relates to a hydrodynamic fluid bearing device, and more particularly, to a fluid bearing in which a spiral groove for generating fluid pressure is formed in at least two circumferential arrays to distribute and smooth the fluid pressure to improve rotational stability of the shaft. Relates to a device. The present invention for this purpose, a predetermined center of rotation shaft, the sleeve in which the shaft is fitted, the bearing bracket for fixing the sleeve, the spiral groove fixed to the sleeve to make the shaft A fluid bearing device comprising: a thrust bearing having a dynamic pressure generating groove formed therein; and a second dynamic pressure generating groove formed at an outer diameter portion of the shaft fitted to the sleeve and for contactlessly rotating the sleeve and the shaft. The first dynamic pressure generating groove formed in the thrust bearing is characterized in that the multi-stage columnar arrangement of at least double.

Description

Dynamic Hydraulic Bearings

The present invention relates to a hydrodynamic fluid bearing device, and more particularly, to a fluid bearing in which a spiral groove for generating fluid pressure is formed in at least two circumferential arrays to distribute and smooth the fluid pressure to improve rotational stability of the shaft. Relates to a device.

In recent years, as information technology such as computers, audio systems, video devices, and the like increase in the technology of the media industry, the size of the various devices is downsized, and according to the miniaturization, there is a demand for parts of devices having finer and more precise performance. , Spindle motor drive of hard disk (HDD) which is one of the storage devices for computer and polygon mirror drive of laser printer, laser disk and compact disc drive for audio system, VCR head and camcorder for video equipment The device and the like rotate and rotate the rotating shaft and the rotating body, which are commonly connected to the driving device, to store and search for desired data and to play data. At this time, the rotating shaft rotates at a very high speed. And shaft vibration, shaft vibration, etc. As a result, all of these devices use bearings, which are one of the mechanical elements, to secure the problems caused by high-speed rotation. In particular, fluid bearings, among other types of bearings, have a minimum frictional force on the rotating shaft. The device is widely used.

A polygon mirror driving apparatus for irradiating a laser beam to a photosensitive drum of a laser printer among driving apparatuses having such a conventional fluid bearing device will be described as an example.

1 is a view illustrating a polygon mirror driving apparatus of a laser printer, in which a through hole having a predetermined diameter is formed in a bearing bracket 10, and a sleeve 20 as shown in the through hole is fitted into the through hole. The bearing bracket 10 is fastened and fixed by the fixing screw 22 or the like, and the shaft 30 is rotatably inserted into the sleeve 20.

The lower end portion 30b of the shaft 30 is interviewed with the thrust bearing 50 receiving the vertical thrust load of the shaft 30, and the upper surface of the thrust bearing 50 has a predetermined shape, for example, spiral groove. The first dynamic pressure generating groove 50a is formed in the shape of a groove or herringbone groove, and the first dynamic pressure generating groove 50a starts from the circumferential surface of the upper surface of the thrust bearing 50 and extends to a central portion of the upper surface. The first dynamic pressure generating groove 50a is precisely processed to a depth of several mu m by etching or the like.

As such, the thrust bearing 50 having the first dynamic pressure generating groove 50a is supported by the thrust pedestal 40 again, and the thrust pedestal 40 is the sleeve 20 and the screw 42. And the like, and the hub 70 is press-fitted to the middle portion of the shaft 30 and fixed to the shaft 30, and the motor 60, which is only partially shown, is joined to the hub 70, and the shaft 30 is joined to the shaft 30. Rotates with the motor 60, and the polygon mirror 80 is attached to the hub 70.

In addition, the sleeve 20 has a vent hole 20a formed at the portion where the thrust bearing 50 and the shaft 30 are interviewed, and the shaft 30 is inserted into the hole of the sleeve 20. A second dynamic pressure generating groove 30a having a herringbone shape is formed in the shaft 30 or the sleeve 20 of the surface in which the inner diameter of the sleeve 20 faces, and thus, the second dynamic pressure generating groove 30a is formed. The groove angle is generally about 30 degrees, and the depth of the second dynamic pressure generating groove 30a is about several micrometers.

Referring to Figures 1 and 2 attached to the operation of the polygon mirror driving device of the laser printer equipped with a conventional fluid bearing device configured as described above are as follows.

First, when power is applied to the motor 60, which is only partially shown, the motor 60 gradually increases its angular velocity in a state where the angular velocity is 0, and reaches a maximum angular velocity after a predetermined time, whereby the angular velocity becomes constant. 30) rotates at the same angular speed as the motor.

Equation 1 shows the relationship between the fluid pressure, the magnetic weight of the shaft and the load of the shaft, the gap area and the axial angular velocity.

[Equation 1]

P: Fluid pressure to float the shaft

V: axis angular velocity

F: shaft weight and shaft load (kg _f )

S: clearance area between thrust bearing and shaft

Applying Equation 1 to FIG. 2, the fluid flows into the A (or C) portion of the thrust bearing 50, which is the start of the first dynamic pressure generating groove 50a by the rotation of the shaft 30. A fluid pressure P is formed to flow into the portion B, which is the center of the first dynamic pressure generating groove 50a, and to float the shaft 30 in the central portion B of the first dynamic pressure generating groove 50a. ) And the area S of the lower end portion 30b of the shaft, and the middle and axial loads F of the shaft are unchanged, so that the fluid pressure increases in proportion to the angular velocity V of the shaft 30, When the predetermined pressure is reached and the fluid pressure P becomes larger than the self-weight of the shaft and the axial load F, the shaft 30 forms a constant gap from the first dynamic pressure generating groove 50a and the first dynamic pressure generating groove ( After injury to the top of 50a), equilibrium is achieved.

By the way, in the fluid bearing device which acts as above to float the rotating shaft, the first dynamic pressure generating groove of the spiral groove type is formed in a single shape spiral as shown in detail in FIG. There was a problem of generating fluid pressure. That is, the fluid pressure generated in the first dynamic pressure generating groove 50a of the fluid bearing device starts to be generated on the outer circumferential surface A of the first dynamic pressure generating groove 50a in the form of a spiral groove, and then increases, and then the center portion C thereof. Since the axis of rotation causes the shaft to float and rotate due to the fluid pressure, shaft shaking, shaft shaking, and shaft vibration are generated, which lowers the rotational stability, causing problems such as product malfunction, performance degradation, and shortened life. .

The present invention has been made to solve the above problems, by improving the spiral groove-shaped first dynamic pressure generating groove formed in the fluid bearing device from the conventional single spiral form to the dynamic pressure generating groove shape of at least double arrangement It is an object of the present invention to provide a hydrostatic fluid bearing device capable of improving the rotational stability of the shaft.

1 is a cross-sectional view showing a polygon mirror drive device using a conventional fluid bearing device,

Figure 2 is a configuration diagram showing a conventional fluid bearing device and the type of fluid pressure generated in the bearing device in association with,

Figure 3 is a plan view showing in detail the shape of a spiral groove formed in a conventional fluid bearing device,

4 is a configuration diagram showing the dynamic pressure type fluid bearing device according to the present invention and the type of fluid pressure generated in the bearing device.

5A to 5C are plan views showing various forms of a double circumferential array spiral groove applied to the hydrodynamic fluid bearing device of the present invention.

Explanation of symbols for main parts of the drawings

10: bearing bracket 20: sleeve

30: rotating shaft 100: thrust bearing

110: first dynamic pressure generating groove 110a: outer spiral groove

110b: inner spiral groove

In order to achieve the above object, a hydrostatic fluid bearing device according to the present invention is provided.

A predetermined center of rotation shaft, a sleeve into which the shaft is fitted, a bearing bracket for fixing the sleeve, and a first dynamic pressure generating groove in the form of a spiral groove to be fixed to the sleeve to float the shaft; A fluid bearing device comprising a thrust bearing, and a second dynamic pressure generating groove formed in an outer diameter portion of the shaft fitted to the sleeve, for contactlessly rotating the sleeve and the shaft.

The first dynamic pressure generating groove formed in the thrust bearing is characterized in that at least two or more multistage columnar arrays are formed.

In a preferred embodiment of the present invention, the shape size of the spiral grooves of the first dynamic pressure generating groove, which is a multi-stage circumferential array of two or more, may be different or the same according to the number of arrangement stages.

In a preferred embodiment of the present invention, the number of spiral grooves constituting the first dynamic pressure generating groove may be different or the same for each array stage.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the fluid bearing device according to the present invention. For convenience of description, the same reference numerals and the same names will be used for the same member as the conventional member.

Figure 4 is a cross-sectional view showing a part of the polygon mirror driving apparatus of the laser printer using the fluid bearing device according to the present invention, the parts not shown in the drawings are the same as the conventional configuration will be omitted.

A through hole having a predetermined diameter is formed in the lower bearing bracket 10, and a sleeve 20 as shown in the through hole is fitted therein, and then is fastened to the bearing bracket 10 by a fixing screw 22 or the like. It is fixed and the shaft 30 is rotatably inserted in the sleeve 20.

In addition, a second dynamic pressure generating groove 30a having a herringbone shape is formed at a side surface of the shaft 30 inserted into the sleeve 20 so that the sleeve 20 and the shaft 30 can be rotated without contact. have. On the other hand, the gap between the sleeve 20 and the shaft 30 is very finely processed to several micrometers.

The contact surface with the lower surface 30b of the shaft 30 is provided with a thrust bearing 100 that supports the shaft self-weight and the axial load and floats the shaft 30, and the thrust bearing 100 is sleeved again. It is fixed by the 20 and the screw 24 etc.

Spiral grooves 110a and 110b having a double columnar array are formed on the upper surface of the thrust bearing 100, and the spiral grooves 110a and 110b of the double columnar array are formed in the present invention. The first characteristic is the first dynamic pressure generating groove 110. Here, the spiral groove indicated by 110a is arranged outside the upper surface of the thrust bearing 100 to form the first dynamic pressure generating groove 110, and the spiral groove indicated by 110b is the thrust bearing 100. It is arranged inside the upper surface of the) to form the first dynamic pressure generating groove (110). Although the shape of the spiral grooves 110a and 110b forming the first dynamic pressure generating groove 110 may be preferably in the form of the conventional spiral groove 50a shown in FIG. 3, the thrust bearing 100 The size and number of spiral grooves 110a (hereinafter referred to as an outer spiral groove bra) formed at the upper end of the upper surface and the spiral grooves 110b (hereinafter referred to as inner spiral groove bra) formed at the inner end thereof are Each array can be the same or different from each other.

FIG. 5A illustrates an example of the same size and number of inner and outer spiral grooves 110a and 110b forming the first dynamic pressure generating groove 110. FIG. 5B illustrates an outer spiral groove 110a and an inner spiral. The shape sizes of the 110b are different, but the number is an exemplary view, and FIG. 5C is an exemplary view when the size and the number of the inner and outer spiral grooves 110a and 110b are different. Here, the size and shape of the spiral grooves formed in the same arrangement stage are the same.

Referring to Figures 4 and 5 the action of the fluid bearing device according to the present invention configured as described above are as follows.

First, when power is applied to a motor (not shown) and the motor starts to rotate, the shaft 30 coupled to the motor also rotates at the same angular speed as the motor, in which case the lower end of the shaft corresponds to the rotational speed of the shaft 30. A vortex is formed in the 30b, and the vortex is pivoted inward through the outer thrust grooves 110a of the first dynamic pressure generating groove 110 of the upper surface of the thrust bearing 100 facing the lower end portion 30b of the shaft. While flowing in and at the end, the introduced fluids gather to generate a first pressure p1 of a predetermined size.

The first fluid pressure p1 and the vortex generated as described above are introduced again while turning inward through the inner thrust grooves 110b, and at the end thereof, a second fluid pressure that is somewhat larger than the first fluid pressure p1. (p2) is generated.

Thus, the first fluid pressure p1 and the second fluid pressure p2 are combined to form the total fluid pressure generated in the thrust bearing 100, which is in the form of a graph as shown in FIG. 4. Looking at the shape of the fluid pressure generated by the fluid bearing device of the present invention, as shown in Figure 4 has a smooth structure in which the pressure distribution is dispersed, which is the first dynamic pressure generating groove 110 is a dual multi-stage columnar arrangement This is caused by the spiral grooves 110a and 110b. The smoothness of the fluid pressure generated by the present invention is proportional to the number of multi-stage columnar arrays of spiral grooves forming the first dynamic pressure generating groove 110.

As described above, the fluid pressure in which the pressure distribution is dispersed stabilizes the rotation state of the shaft 30 because the lower end portion of the fluid pressure is uniformly supported throughout the rotation of the shaft 30.

Until now, the circumferential arrangement of the spiral groove forming the first dynamic pressure generating groove 110 according to the present invention has been described and limited to a two-stage circumferential arrangement. It will be apparent to those skilled in the art that this may be extremely easy in form.

As described in detail above, according to the present invention, the shaft stability, the shaft shaking and the shaft vibration is not generated when the shaft 30 floats and rotates due to the dispersed fluid pressure, the effect of improving the rotational stability of the shaft There is. Thus, the present invention provides the advantage of improving the performance, life and reliability of the product.

Claims (6)

A predetermined center of rotation shaft, a sleeve into which the shaft is fitted, a bearing bracket for fixing the sleeve, and a first dynamic pressure generating groove in the form of a spiral groove to be fixed to the sleeve to float the shaft; A fluid bearing device comprising a thrust bearing, and a second dynamic pressure generating groove formed in an outer diameter portion of the shaft fitted to the sleeve, for contactlessly rotating the sleeve and the shaft. And the first dynamic pressure generating groove formed in the thrust bearing comprises at least two or more multistage columnar arrays. 2. The fluid bearing device according to claim 1, wherein the shape sizes of the spiral grooves of the first dynamic pressure generating groove, each of which is formed of two or more multistage circumferential arrays, are the same regardless of the number of arrangement stages. 2. The fluid bearing apparatus according to claim 1, wherein the number of spiral grooves of the first dynamic pressure generating groove formed in the two or more multistage columnar arrays is the same regardless of the number of arrangement stages. 2. The fluid bearing device according to claim 1, wherein the shape size of the spiral grooves of the first dynamic pressure generating groove having the multi-stage circumferential array of two or more is different depending on the number of stages. 2. The fluid bearing apparatus according to claim 1, wherein the number of spiral grooves of the first dynamic pressure generating groove formed in the two or more multistage columnar arrays is different depending on the number of arrangement stages. 6. The fluid bearing device according to claim 4 or 5, wherein the spiral grooves of the first dynamic pressure generating groove, each of which is formed of two or more multistage columnar arrays, are identical in the same arrangement stage.