JPS6165905A - Dynamic pressure bearing system - Google Patents

Abstract

PURPOSE:To increase thrust rigidity and floating power, and reduce a torque loss by using gases as a lubricant for a radial bearing and oils of high viscosity as a lubricant for a thrust bearing. CONSTITUTION:A thrust pad 3 is fixed to the end of a hollow cylindrical housing 2 and a rotary shaft 1 is so provided in a cylindrical hole formed by the housing 2 and the thrust pad 3 that it can rotate. Spiral grooves 4a are formed on a carrier 4 as related to the rotary shaft 1 of the thrust pad 3. Herring ball grooves 5 are formed on the rotary shaft 1. And space between the rotary shaft 1 and the housing 2 is filled with air as a radial dynamic pressure fluid 6 and space between the thrust pad 3 and the rotary shaft 1 is filled with grease as a thrust dynamic pressure fluid 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Scope of Industrial Application] The present invention relates to a dynamic pressure bearing device, for example, a high speed dynamic pressure bearing device used in a motor for a polygon scanner.

[Conventional technology]

Conventionally, as shown in FIG. 5, when using only air as the radial dynamic pressure working fluid 6 and the thrust dynamic pressure working fluid 6', this type of dynamic pressure bearing suffers from insufficient thrust rigidity or a high flying height. There are disadvantages such as the need to reduce the weight of the rotating body due to the small size and the tendency for the thrust bearing to seize. In addition, when only liquid such as oil is used as a lubricant, torque loss tends to increase, so measures such as increasing the motor output have to be taken. The overall configuration of the motor is shown in Figure 6.

In the figure, 20 is a polygon mirror, 21 is a coil, 2
2 is a magnet, and 23 is a case.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and an object of the present invention is to provide a hydrodynamic bearing device that can increase thrust rigidity, obtain a sufficient flying height, and reduce torque loss. do.

[Means for solving problems]

The object of the present invention is achieved by using gas as the 111 lubricant for the radial bearing, and by using high viscosity oil or grease as the lubricant for the thrust bearing.

〔Example〕

Embodiments of the present invention will be specifically described below based on the drawings.

FIG. 1 shows an embodiment of the present invention. As shown in FIG. 6, which is a cross-sectional view of a hydrodynamic bearing device, a thrust receiver 3 is fixed to the end of a hollow cylindrical housing 2. A rotary shaft 1 is rotatably inserted into a cylindrical hole formed by. A spiral groove 4a is provided on the surface 4 of the thrust receiver 3 facing the rotating shaft 1, and the spiral groove 4a has a spiral shape as shown in FIG. 1(b). The rotating shaft 1 is provided with a Hering ball groove 5, which generates radial pressure when the rotating shaft 1 rotates, and acts as a radial bearing.
The space between the rotating shaft 1 and the housing 2 is filled with air or other gas as a radial dynamic pressure working fluid 6. A space between the thrust receiver 3 and the rotating shaft 1 is filled with oil or grease as a thrust dynamic pressure working fluid 7.

Next, the effect will be explained. For example, the diameter of rotating shaft 1 is 12
mm, and when rotating at a rotational speed of 23.50 rpm, it is radial as in the conventional example (Fig. 5).

When air is used as the dynamic pressure working fluid for both thrust bearings, the thrust rigidity is 0.3 Kg/la, the flying height is 4p,
The radial rigidity can be obtained at 4 kg/deflection, but as in the present invention, low viscosity oil (for example, 6 kg) is used in the thrust dynamic pressure working fluid 7.
cp), the thrust rigidity is 2 Kg/
It becomes possible to obtain a flying height of 10- or more, and it also becomes possible to reduce the flying height to about 10-. In addition, since oil is used only in the thrust section, the loss torque only increases slightly.
The loss of 4rJ is much smaller than when oil is used for both radial and thrust. In other words, since low-viscosity oil is used as the dynamic pressure working fluid in the thrust bearing, it has a higher viscosity than gas, so it is possible to obtain a large dynamic pressure effect and increase the flying height and thrust rigidity. . Further, since the portion using low viscosity oil is limited to the thrust bearing portion, the area where low viscosity oil, which increases loss torque, is used is small, so it is possible to keep loss torque relatively low.

FIG. 2 shows another embodiment in which a magnetic fluid is used as the thrust dynamic pressure working fluid 7, and a permanent magnet 8 is arranged at the boundary between the radial bearing and the thrust bearing. This makes it possible to prevent the thrust dynamic pressure working fluid 7 from flowing into the radial working fluid 6. In other words, even if a force acts that causes the magnetic fluid, which is the thrust dynamic pressure working fluid 7, to flow toward the radial bearing, the permanent magnet 8 is arranged, so the magnetic fluid is restrained by the permanent magnet 8, and the magnetic fluid becomes completely sealed. Therefore, it is possible to prevent the thrust dynamic pressure working fluid 7 from flowing into the radial working fluid 6.

Furthermore, by arranging the permanent magnet 9 in the center of the thrust bearing as shown in Figure 3, the magnetic fluid is concentrated in the center, and the thrust receiver 3 and the rotating shaft are in a non-contact state during startup and stop, resulting in wear and tear. This makes it possible to prevent damage caused by this and reduce starting torque.

In addition, in the case where there is no seal as mentioned above (Fig. 2), if grease is used for the thrust dynamic pressure working fluid 7,
Furthermore, even when oil is used, it is possible to implement the method if the positional relationship of the bearings is fixed. In other words, when using grease, the grease acts like a solid during non-rotation, so the grease, which is the thrust dynamic pressure working fluid 7, does not flow into the radial working fluid 6. It is obvious that the same thing can be said if the thrust bearing part is located below the radial bearing part and their positional relationship is fixed in the case of use.

In the above explanation, we have talked about axis rotation.
Exactly the same effect can be obtained even when the shaft is fixed and the cylindrical member is rotated.

In addition, in FIGS. 2 and 3, the permanent magnet 8, which is placed at the boundary between the radial bearing g8 and the thrust bearing, is placed in the thrust receiver 3, but if it is at the boundary, the rotation axis l Alternatively, the same effect can be obtained even if it is arranged in the cylindrical member 2.

In addition, although the permanent magnet 9 located at the center of the thrust portion in FIG. 3 is arranged on the thrust receiver 3, the same applies if it is arranged on the rotating shaft.

Furthermore, although a helinkon type dynamic pressure bearing has been described as a radial bearing, the same effect can be obtained with a multi-start thread type radial/thrust type axial pressure bearing as shown in FIG. In the figure, 5' is a multi-threaded shallow groove.

〔Effect of the invention〕

As explained above, by using air as the lubricant for the radial bearing part and oil or grease as the lubricant for the thrust bearing part, dynamic pressure with less increase in torque loss and large thrust rigidity and flying height can be achieved. A bearing device can be obtained.

In addition, by using magnetic fluid as the lubricant for the thrust bearing and placing a permanent magnet at the boundary between the radial and thrust bearings, the lubricant in the thrust bearing can be prevented from mixing with the lubricant in the radial bearing. It can be prevented.

Furthermore, by arranging a permanent magnet in the center of the thrust bearing, it is possible to prevent damage during starting and stopping and to reduce starting torque.

[Brief explanation of drawings]

FIG. 1(a) is a sectional view of an embodiment of a hydrodynamic bearing device according to the present invention, FIG. 1(b) is a plan view of a thrust receiver, FIG. 2(a), FIG. 3(a), FIG. 4(a) is a sectional view of another embodiment, FIG. 2(b), FIG. 3(b), and FIG.
5 is a sectional view of a conventional example, and FIG. 6 is a sectional view showing the overall configuration of a motor for a polygon scanner. 61 is a rotating shaft, 2 is a housing, and 3 is a sectional view of a conventional example. In the thrust receiver, 6 is a radial dynamic pressure working fluid, 7 is a thrust dynamic pressure working fluid, and 8 and 9 are permanent magnets.

Claims (3)

[Claims] (1) In a hydrodynamic bearing device that has a shallow groove for a radial bearing and a shallow groove for a thrust bearing on either a rotating member or a stationary member that have opposing surfaces, gas is used as a lubricant for the radial bearing part, A hydrodynamic bearing device characterized by using high viscosity oil or grease as a lubricant for the thrust bearing. (2) The dynamic pressure bearing device according to claim 1, characterized in that a magnetic fluid is used to lubricate the thrust bearing member, and a permanent magnet is arranged at the boundary between the thrust bearing part and the radial bearing part. (3) The hydrodynamic bearing device according to claim 2, characterized in that a permanent magnet is disposed at the center of the thrust bearing portion.