JPH06341429A - Dynamic pressure gas bearing - Google Patents

Abstract

PURPOSE:To reduce frictional resistance between a rotary shaft and pads for a long term, in a dynamic pressure gas bearing. CONSTITUTION:In a gas bearing journaling a rotary shaft 4 by fitting pads of over three pieces to a bearing housing 1 in the circumferential direction through pivots 2, carbon sliding material 3 is fitted onto the surface on the rotationary shaft side of the pad 3, high strength super hard ceramic sliding material 4A such as tungusten carbide is fitted onto the surface on the pad side of the rotary shaft 4, and hence the frictional resistance is reduced and the sliding property between both is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure gas bearing applied to a turbomachine or the like.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional dynamic pressure gas bearing. As a countermeasure against contact wear between the rotary shaft 04 and the pad 03 when the rotary shaft 04 repeatedly starts and stops, TiN,
Surface treatments 04B and 03B such as TiC and Al ₂ O ₃ are applied.

[0003]

In the conventional dynamic pressure gas bearing, the rotary shaft 04 rotates while contacting the pad 03 until the gas film is sufficiently formed. Therefore, since the surfaces of the rotary shaft 04 and the pad 03 are worn at the time of starting and stopping, surface treatments 04B and 03B such as TiN, TiC, and Al ₂ O ₃ have been applied to both of them.

However, although these surface treatments are effective as a measure against wear, they have a large frictional resistance at the time of starting and require a large driving torque. Particularly, when a heavy and large horizontal rotor is supported by a dynamic pressure gas bearing, there is a drawback that the driving torque becomes excessive.

Japanese Patent Laid-Open No. 3-121306 proposes coating or applying a solid lubricant on the surface of the surface treatment 03B of the pad 03 in order to reduce frictional resistance at the time of starting. There was a problem that it deteriorates during repeated operation and loses its function due to short-time contact during high-speed rotation.

The present invention is intended to provide a dynamic pressure gas bearing which can solve the above problems.

[0007]

[Means for Solving the Problems]

(1) According to the present invention, in a dynamic pressure gas bearing in which three or more pads are circumferentially mounted on a bearing housing via a pivot to support a rotary shaft, a carbon sliding member is mounted on the rotary shaft side surface of the pad. Moreover, a ceramic sliding member is attached to the pad side surface of the rotary shaft.

(2) Further, in the present invention, in the dynamic pressure gas bearing of the above (1), the ceramic sliding material is tungsten carbide (WC), chromium carbide (Cr ₃ C ₂ ),
Silicon Carbide (SiC), Chromium Oxide (Cr ₂ O)
It is characterized by high strength and super hard ceramics such as ₃ ).

[0009]

According to the present invention, the ceramic sliding material on the pad side surface of the rotary shaft is combined with the carbon sliding material on the rotary shaft side surface of the pad, and the ceramic sliding material is made of tungsten carbide, chrome carbide or silicon. By using high-strength, ultra-hard ceramic such as carbide and chromium oxide, the hard ceramic sliding material and the carbon sliding material that has excellent sliding characteristics with it will come into surface contact.
The coefficient of friction is greatly reduced. Therefore, the frictional resistance at the time of start-up becomes small, and even when the rotation shaft and the pad come into contact with each other at the time of high-speed rotation, sliding is possible.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A dynamic pressure gas bearing according to an embodiment of the present invention will be described with reference to FIG. Turbomachine rotor (not shown)
The bearing housing 1 is provided so as to surround the rotary shaft 4 at both ends of the, and the pivots 2 are mounted at three locations in the circumferential direction. A pad 3 is held in each pivot 2 so as to be tilted freely, and three pads 3 are arranged so as to surround a rotary shaft 4 in the bearing housing 1 in the circumferential direction.

A carbon sliding material 3A is attached to the surface of the pad 3 on the rotary shaft 4 side with an adhesive, and tungsten, chromium carbide, silicon carbide, chromium oxide or the like is attached to the pad side surface of the rotary shaft 4. The high-strength, super-hard ceramic sliding material 4A is fitted around the entire circumference by the spring plate 4B. Further, the ceramic sliding member 4A may be directly formed on the rotary shaft 4 by thermal spraying.

The carbon sliding material 3A and the ceramic sliding material 4A are formed by directly surface-treating the pad 3 and the rotary shaft 4 by physical vapor deposition (PVD) or chemical vapor deposition (CVD). Good.

Since this embodiment is configured as described above, the sliding between the ceramic sliding member 4A having a high hardness on the pad side surface of the rotary shaft 4 and the ceramic sliding member 4A on the rotary shaft side surface of the pad 3 is performed. The carbon sliding material 3A, which has excellent dynamic characteristics, comes into contact with the surface, and the coefficient of friction is greatly reduced.

FIG. 3 shows a representative example of the coefficient of friction compared by the inventors under the same test conditions as in this embodiment. In FIG. 3, the case where the tungsten carbide, chrome carbide, and chromium oxide sliding materials and the carbon sliding material used in this example are used is compared with the case where the conventional TiN sliding material is used in combination. It shows that the coefficient of friction was greatly reduced. In FIG. 3, the sliding speed ratio means that the value 1 on the horizontal axis corresponds to the sliding speed of about 3 m / s in the experiment, while the friction coefficient ratio on the vertical axis means the conventional value (TiN / TiN: *). Is a friction coefficient when using the sliding material of tungsten carbide, chromium carbide, and chromium oxide and the carbon sliding material used in the present embodiment when the friction coefficient of the above is set to the illustrated value. From the experience so far, it can be said that the characteristics of silicon carbide are similar to those of tungsten carbide.

Therefore, the frictional resistance at the time of start-up can be reduced, and smooth sliding can be performed even when the rotary shaft 4 and the pad 3 come into contact with each other during high-speed rotation, and this state is maintained for a long period of time. Can be held over.

[0016]

According to the present invention, a tungsten carbide or other ceramic is provided on the pad side surface of the rotary shaft of the dynamic pressure gas bearing in which three or more pads are mounted in the bearing housing in the circumferential direction via the pivot to support the rotary shaft. Since the sliding material is attached and the carbon sliding material is attached to the surface of the pad on the rotating shaft side, the sliding characteristics are excellent due to the combination of these, so the friction coefficient can be greatly reduced compared to the conventional one. it can. Therefore, the frictional resistance at the time of start-up becomes small, and it is not necessary to use a drive machine having a large start-up torque as in the past or a drive machine having a capacity much larger than the drive force required at the time of steady operation. Further, since the sliding property is excellent, there is no deterioration due to repeated start and stop, and the function of the bearing is not lost even if it comes into contact during high speed rotation.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a dynamic pressure gas bearing according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a conventional dynamic pressure gas bearing.

FIG. 3 is a graph showing a representative example of comparison of friction coefficients when using a ceramic sliding material and a carbon sliding material used in the above-mentioned embodiment of the present invention and when using a conventional TiN sliding material in combination. is there.

[Explanation of symbols]

 1 Bearing Housing 2 Pivot 3 Pad 3A Carbon Sliding Material 4 Rotating Shaft 4A Ceramic Sliding Material

Claims (2)

[Claims] 1. A dynamic pressure gas bearing in which three or more pads are mounted in a bearing housing in the circumferential direction via pivots to support a rotary shaft, and a carbon sliding member is mounted on the rotary shaft side surface of the pad, and A dynamic pressure gas bearing characterized in that a ceramic sliding material is attached to the pad side surface of the rotating shaft. 2. The dynamic pressure gas bearing according to claim 1, wherein the ceramic sliding material is a high-strength / super-hard ceramic such as tungsten carbide, chromium carbide, silicon carbide, or chromium oxide.