KR19980030901A - Thrust bearing device with variable clearance - Google Patents

Abstract

The present invention relates to a thrust bearing device having a variable gap, and the configuration according to the present invention includes a center of rotation shaft, a sleeve to which the shaft is fitted, a bearing bracket for fixing the sleeve, and a sleeve to the sleeve. A thrust bearing having a first dynamic pressure generating groove formed therein so as to float the shaft, and formed in an inner diameter of the sleeve or an outer diameter of the shaft fitted to the sleeve to contactlessly rotate the sleeve and the shaft; In the thrust bearing device including a second dynamic pressure generating groove for the, the thrust bearing is characterized in that the center of the thrust bearing is more convex than the circumference of the thrust bearing, the effect of the present invention is the shaft and the drum If the shaft requires stable rotation in a short time by varying the gap of the bearing If you stop to soften the drive shaft can be achieved particularly useful results.

Description

Thrust bearing device with variable clearance

The present invention relates to a thrust bearing device having a variable gap, and more particularly, by varying the gap between the thrust bearing and the rotating shaft in which a dynamic pressure generating groove for supporting the thrust load of the rotating shaft is formed. The present invention relates to a thrust bearing device having a variable clearance which prevents overload and abrasion occurring in a rotating shaft and a thrust bearing, thereby increasing the life of the hydrodynamic bearing.

Recently, as information technology such as computer, audio system, video equipment, etc. and media industry have increased, the size of various devices mentioned above is miniaturized, and according to the miniaturization, there is a demand for components of devices with finer and more precise performance. In particular, a spindle motor drive of a hard disk (HDD), which is one of the storage devices for a computer, and a polygon mirror drive of a laser printer, a laser disk and a compact disc drive for an audio system, a VCR head and a camcorder for an imaging device. In general, the driving device of the motor rotates the rotating shaft and the rotating body which are coupled to the driving device at high speed, thereby storing and retrieving desired data and reproducing data. The rotating shaft rotates at a very high speed. Shaking, Shaking, Shaking of Shaft are the characteristics of the product during high speed rotation. All of these devices use bearings, one of the mechanical elements, to protect the problems caused by high-speed rotation. Drust bearings, among other types of bearings, have a minimum frictional force on the rotating shaft. The device is widely used.

Among the driving apparatuses having such a conventional thrust bearing device, a polygon mirror driving apparatus for irradiating a laser beam to a photosensitive drum of a laser printer 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 a fixing screw 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 first dynamic pressure generating groove 50a is disposed on the upper surface of the thrust bearing 50. The first dynamic pressure generating groove 50a is formed with a predetermined area and a predetermined depth starting from the circumferential surface of the upper surface of the thrust bearing 50 to the center of the upper surface, and the first dynamic pressure generating groove 50 is formed by etching or the like. It is precisely processed to a depth of several micrometers.

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 fastened by the sleeve 20 and the screw. In the middle portion of the shaft 30, the hub 70 is press-fitted and fixed to the shaft 30, and the hub 70 is joined to the hub 60 by only a portion thereof, and the shaft 30 is connected to the motor ( Rotate with 60, 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 2 and 3 attached to the operation of the polygon mirror driving device of the laser printer having a conventional thrust bearing device configured as described above are as follows.

First, when power is applied to the motor 60 shown only in part, the motor 60 gradually increases the 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) It will also rotate at the same angular speed as the motor.

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

[Equation 1]

P =

P: Fluid pressure to float the shaft

F: shaft weight and shaft load (kg _f )

A: clearance area between thrust bearing and shaft

Referring to Equation 1 in FIG. 2, the fluid flows into a portion A, which is the start of the first dynamic pressure generating groove 50a of the thrust bearing 50 by the rotation of the shaft 30, and then the first dynamic pressure generating groove. The fluid pressure (P) is formed in the central portion of the first dynamic pressure generating groove to rise to the center portion of the first dynamic pressure generating groove, the gap area (A) between the thrust bearing 50 and the lower end portion (30b) of the shaft As the overweight and axial weight (F) remain unchanged, the fluid pressure increases in proportion to the angular velocity of the shaft (30), while the shaft (30) reaches a predetermined revolutions per minute and the shaft's own weight and axial load (F) When the fluid pressure P becomes larger, the shaft 30 forms a constant gap from the first dynamic pressure generating groove and rises to the upper portion of the first dynamic pressure generating groove, thereby achieving an equilibrium state.

At this time, the time taken for the shaft 30 to rise is determined by the rotational speed of the shaft 30 and the gap area formed by the first dynamic pressure generating groove and the shaft lower end 30b as mentioned above.

However, in order for the shaft to rotate and float from the first dynamic pressure generating groove, it takes a predetermined time, that is, a certain time until the shaft rotates more than a predetermined number of revolutions per minute, so that the shaft does not float from the first dynamic pressure generating groove. The first dynamic pressure generating groove continues to be in friction with the shaft, and even when the shaft stops rotating, the rotational speed per minute of the shaft decreases so that the shaft starts to come into contact with the first dynamic pressure generating groove so that the shaft is completely stopped. As a result, the shaft and the first dynamic pressure generating groove continue to rub for a predetermined time. When the shaft is driven and the shaft stops rotating, abrasion caused by the friction between the shaft and the first dynamic pressure generating groove is severely generated. Problems such as malfunction, deterioration of performance and shortening of life due to gap change caused by wear of grooves and rotational stability during initial shaft drive and shaft stop There.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to reduce the floating time of the shaft and the first dynamic pressure generating groove during initial driving and stop of the shaft, and to reduce the shaft and the first dynamic pressure generating groove. The present invention provides a hydrodynamic fluid bearing having a variable gap for reducing the contact time of the shaft and preventing wear of the shaft and the first dynamic pressure generating groove and increasing rotational stability.

1 is a cross-sectional view showing a conventional thrust bearing device.

2 is a view showing a pressure distribution curve generated on a rotating shaft by a thrust bearing in a conventional thrust bearing device.

3 is a cross-sectional view and a graph showing a portion of the thrust bearing device and the pressure distribution curve according to the present invention.

Explanation of symbols for the main parts of the drawings

10: bearing bracket 20: sleeve

30: rotating shaft 50: thrust bearing

50a: first dynamic pressure generating groove

The thrust bearing device having a variable clearance for achieving the object of the present invention is fixed to the center of rotation axis, the sleeve in which the shaft is fitted, the bearing bracket for fixing the sleeve, and the sleeve A thrust bearing having a first dynamic pressure generating groove formed thereon to float the shaft, and a second dynamic pressure generating groove formed on a side surface of the shaft fitted to the sleeve for contactlessly rotating the sleeve and the shaft; In a thrust bearing device, the thrust bearing is characterized in that the center of the thrust bearing is more convex than the circumference of the thrust bearing.

Drust bearing device having a variable gap of the present invention will be described with reference to the accompanying drawings as follows, the same reference numerals and the same names will be used for the same parts as the conventional configuration.

3 is a cross-sectional view showing a part of the polygon mirror driving device of the laser printer in which a thrust bearing device having a variable gap according to the present invention is used, and a part not shown in the drawings is the same as a conventional configuration, and thus the description thereof is omitted. Let's do it.

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 and fixed to the bearing bracket 10 by a fixing screw. The shaft 30 is rotatably inserted into 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.

On the contact surface with the lower surface 30b of the shaft 30, a thrust bearing 50 for supporting the shaft weight and the axial load and floating the shaft 30 is installed, and the thrust bearing 50 is again sleeved. 20 and screws are fixed.

On the other hand, the lower end surface 30b of the shaft 30 and the thrust bearing 50 have the following relationship in the state in which the shaft 30 is stopped.

When the shaft 30 is not rotating, the gap formed between the lower surface 30b of the shaft and the circumferential surfaces A 'and C' of the thrust bearing 50 is CL ₁ , CL ₂ , and the lower surface 30b of the shaft 30. The gap between B ', which is the center of the first dynamic pressure generating groove of the thrust bearing 50, is defined as CL ₃ , and the lower end portion 30b of the thrust bearing 50 and the shaft 30 may be defined by the magnetic weight and the axial load of the shaft. ) Is in contact with the gap CL ₃ = 0 in the B 'portion, CL ₁ , CL _{2 which} is the gap between the A' and C 'portion of the thrust bearing 50 and the lower end surface 30b of the shaft, 0 CL ₁ , CL ₂ ≤ several μm, so the clearance CL ₁ , CL ₂ , CL ₃ is CL ₃ CL ₁ , CL ₂ ≤ few μm, so the first dynamic pressure generating groove in the thrust bearing is formed. The cross-sectional shape of the surface is a shape of an arc passing through three points A ', B', and C ', and the curvature of the arc is determined by CL ₃ based on CL ₁ and CL ₂ .

Referring to the operation of the thrust bearing device having a variable gap according to the present invention 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 this case, the lower end portion of the shaft corresponding to the rotation speed of the shaft 30 ( 30b), and a vortex is formed and the vortex formed along the first dynamic pressure generating groove B through the A 'and C' portions of the first dynamic pressure generating groove of the upper surface of the thrust bearing 50 facing the lower end portion 30b of the shaft. The 'B' portion is introduced while turning, and in the 'B' portion, the fluids introduced through the first dynamic pressure generating grooves are collected to generate a predetermined pressure (P).

At this time, the fluid pressure P is the force (kg _f , F) for pressing the shaft 30 in the direction of gravity by the shaft weight and the axial load, and the first dynamic pressure of the lower end portion 30b of the shaft and the thrust bearing 50 is generated. It is determined by the large and small of the clearance gap area A which is the space | interval space between grooves.

On the other hand, the fluid pressure (P) is determined by the gap area (A) and the rotational speed of the shaft (30) because the shaft weight and the shaft load are already determined. A ', C', which is the circumferential surface portion of the first dynamic pressure generating groove, and the lower end portion 30b of the shaft have the largest gap area, and the generated fluid pressure P is very small, but A 'to B' and C ' As the fluid flows into B ', the gap area decreases rapidly, so the fluid pressure P increases rapidly in response to the decrease in the gap area A, so that the minimum fluid pressure P _min for floating the shaft 30 is When the shaft 30 is driven at the initial rotational speed per minute and the shaft 30 is stopped, the rotation time between the shaft 30 and the first dynamic pressure generating groove is very short. When the screw shaft 30 is stopped, the load, the shaft, and the first dynamic pressure generating groove that are caught on the shaft are prevented.

As described in detail above, by varying the gap between the shaft and the thrust bearing, a particularly useful result can be obtained when the shaft requires stable rotation in a fast time or when the driving of the shaft needs to be smoothly stopped.

Claims (2)

A center of rotation shaft, a sleeve in which the shaft is fitted, a bearing bracket for fixing the sleeve, a thrust bearing having a first dynamic pressure generating groove formed in the sleeve to lift the shaft, A thrust bearing device formed in an outer diameter portion of the shaft fitted into the sleeve and the sleeve, and including a second dynamic pressure generating groove for contactlessly rotating the sleeve and the shaft. The thrust bearing is a thrust bearing device having a variable gap, characterized in that the center of the thrust bearing is convex than the circumference of the thrust bearing. The thrust bearing device according to claim 1, wherein the center of the thrust bearing and the shaft are in contact with each other.