JPH034823Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial field of application The invention relates to bearing devices for high-temperature rotating machinery.
It is also used as a bearing device for a rotating shaft in a high-temperature rotating machine such as a small, general-purpose gas turbine.

Conventional technology Conventionally, the mainstream bearings for superchargers, which are a type of high-temperature rotating machinery, have been floating bush-type plain bearings made of metal, but rolling bearings such as ball bearings and roller bearings have also been occasionally adopted. Both use lubricating oil as the lubricant.

Problems that the invention aims to solve As mentioned above, conventional turbocharger bearings are installed adjacent to the turbine that utilizes high-temperature exhaust gas, and lubricating oil is used for lubrication. ,
The high-temperature exhaust gas accelerates the deterioration of lubricating oil.
Not only does the frequency of oil changes increase, but oil leakage problems also occur, and in particular, when the lubricating oil is stopped, the residual lubricating oil around the bearings often reaches a high temperature of several hundred degrees (℃) due to the heat soak back phenomenon. There are other problems, such as problems such as carbonization (carbon bridging), and corrosion caused by additives such as sulfur in the high-temperature oil reacting with metal materials. The present invention attempts to solve these problems. That is, an object of the present invention is to provide a bearing device for a high-temperature rotating machine that can withstand high temperatures and is free from troubles associated with lubricating oil.

Means for Solving the Problems The bearing is an oil-free rolling bearing in which at least the rolling elements are made of ceramic, and the rolling bearing is supported by a water film damper. That is, the configuration of the present invention includes an oil-free rolling bearing that rotatably supports the rotating shaft of a high-temperature rotating machine and at least the rolling elements are made of ceramic, and is provided in a floating state within the bearing housing via a water film. a water film damper supporting the rolling bearing, and the bearing housing is provided with water for forming the water film between an inner circumferential surface of the bearing housing and an outer circumferential surface of the water film damper. It is characterized by having a conduit that supplies water.

Function Since the rolling elements, which are the main part of the rolling bearing, are made of ceramic, they are resistant to high temperatures, and since the rolling bearings are oil-free, there is no need to supply lubricating oil, and problems caused by lubricating oil are avoided. In addition, the water film damper acts to damp the vibration of the rolling bearing, and moreover, the bearing is indirectly cooled by water.

Embodiment The drawing shows an embodiment of the invention. That is, a supercharger is shown as an example of a high-temperature rotating machine. In the figure, 1 is a turbine casing, 2 is a bearing casing, 3 is a compressor casing, 4 is a turbine shaft,
5 is a turbine impeller, 6 is a compressor impeller,
7 is a turbine side ball bearing which will be described later; 8 is a compressor side ball bearing which will be described later; 9 is a bearing housing provided in the bearing chamber 2; and 10 is provided in a floating state within the bearing housing 9 via a water film. 11 is the water film, 12 is a bearing spacer, 13 is a coiled preload spring, 14 is a shaft end nut, 15 is a cooling water inlet, and 16 is a water film damper supporting both ball bearings 7 and 8. A cooling water outlet, 17 a cooling water chamber, 18 a first water conduit,
19 is a second water conduit, and 20 is a third water conduit.

To explain further, the turbine shaft 4 rotating at high speed
The turbine side ball bearing 7 and the compressor side ball bearing 8, which rotatably support the , are both made of ceramic in which only the balls, which are the rolling elements, are made of ceramic, and in the case of full ceramic, in which the inner and outer rings are also made of ceramic. However, in the case of a supercharger, since the inner ring receives tensile force due to thermal expansion of the turbine shaft 4, it is preferable to use a heat-resistant alloy and only the balls to be made of ceramic. Also, it is better to use a self-lubricating material for the ball retainer in terms of durability and other aspects. Generally, up to about 200℃, Teflon type,
If the temperature is higher than that, it is better to use a graphite cage. The principle behind this self-lubrication is that when the retainer comes into contact with the balls during rotation, a small amount of the retainer peels off and becomes powdered lubricant.

The water film damper 10 is used as a vibration damping mechanism for the turbine side ball bearing 7 and the compressor side ball bearing 8, but since water has a lower viscosity than lubricating oil, it is necessary to reduce the gap between the squeeze films, etc. The basic action can be obtained in the same way as oil by taking some dimensions into account. Now, let the viscosity be μ, the radius of the water film damper 10 be R, the length of the water film 11 be L, the thickness of the water film 11 be C, and the damping value be D, then D≒μπR(L/C) is given by ³ . Therefore, it is only necessary to reduce the thickness C of the water film 11 by the amount that the viscosity μ becomes smaller.

Also, compared to the oil film, the water film 11 has
In addition to the above, care must be taken to avoid leakage and evaporation. The problem of easy leakage is dealt with by reducing the gap between the axial end face of the water film damper 10 and the bearing housing 9, but leakage cannot be completely eliminated. However, the water that leaks does not cause much harm. If the water film 11 on the outer periphery of the water film damper 10 disappears due to evaporation or leakage, the vibration damping effect cannot be obtained, so it is necessary to maintain it at all times during operation.

Therefore, in the illustrated example, the cooling water is supplied to the cooling water inlet 15 of the bearing casing 2, and the cooling water is supplied to the first water conduit 18.
The water is supplied between the inner circumferential surface of the bearing housing 9 and the outer circumferential surface of the water film damper 10 through the second water conduit 19, where the water film 11 is formed. As a result, the squeeze effect is maintained, and the turbine side ball bearing 7 and the compressor side ball bearing 9 are indirectly cooled via the water film damper 10. In addition, the inner peripheral surface of the bearing housing 9 and the water film damper 1
The cooling water supplied between the outer peripheral surfaces of damper 1
After circulating around the cooling water 0, the water is discharged from the third water conduit 20 to the cooling water chamber 17 with some pressure, so the above-mentioned water leakage is extremely small. Therefore, the illustrated supercharger can be used not only horizontally, but also vertically, which improves engine mountability.

In this way, since at least the balls of the turbine side ball bearing 7 and the compressor side ball bearing 8 are made of ceramic, they can withstand high temperatures, and both bearings 7 and 8 can withstand high temperatures.
Since it is oil-free and indirectly water-cooled,
An appropriate cooling effect is obtained, there is no need to supply lubricating oil, and conventional troubles caused by lubricating oil are completely eliminated, and the water film damper 10 is provided in a floating state via the water film 11. Therefore, the vibrations of both bearings 7 and 8 are reliably suppressed, and stable rotation of the turbine shaft 4 is guaranteed.

In the above embodiment, a ball bearing is used as the bearing, but a roller bearing having at least the rollers made of ceramic may be used in the same manner. If you want to reverse the cooling water supply method from the above embodiment, you can provide a cooling water inlet a in the bearing housing 9 and supply the cooling water to the cooling water inlet a at an appropriate pressure. 11 is formed,
After circulating around the water film damper 10, the water passes through the first water conduit 18 and the second water conduit 19 in reverse, and is discharged from the cooling water inlet 15 as a cooling water outlet.
Further, in order to directly guide a portion of the water in the water film 11 to the bearings 7 and 8, the water film damper 10 may be provided with small holes facing the bearings 7 and 8.

Effects of the invention In this invention, the bearing is an oil-free rolling bearing, and the damper supporting the bearing is a water film damper, so friction loss is extremely small compared to conventional floating bush type plain bearings. Furthermore, since no lubricating oil is used, the lubricating oil eliminates stirring loss, dramatically improving mechanical efficiency, eliminating the need for oil piping for lubricating, and eliminating the conventional troubles associated with oil. In addition, it can be installed not only horizontally but also vertically, making installation more flexible. Moreover, since at least the rolling elements of the bearing are made of ceramic, the heat resistance is dramatically improved and the service life can be extended. It is also economical because it uses water instead of oil.

[Brief explanation of the drawing]

The figure is a partially cutaway sectional front view showing an embodiment of the present invention. 4... Turbine shaft, 7, 8... Ball bearing, 9...
Bearing housing, 10...Water film damper, 1
1... Water film, 18, 19... Headrace.

Claims (1)

[Scope of utility model registration request] An oil-free rolling bearing rotatably supports a rotating shaft of a high-temperature rotating machine and has at least rolling elements made of ceramic; a water film damper, and the bearing housing is provided with a conduit for supplying water to form the water film between the inner peripheral surface of the bearing housing and the outer peripheral surface of the water film damper. A bearing device for high-temperature rotating machinery, characterized by: