Bearings – Rotary bearing – Plain bearing
Reexamination Certificate
1998-06-15
2001-04-03
Hannon, Thomas R. (Department: 3682)
Bearings
Rotary bearing
Plain bearing
C384S321000
Reexamination Certificate
active
06210042
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to journal bearings under fluid lubrication, solid and powder lubrication, or dry contact.
The invention can improve the thermal efficiency, performance and service life of bearings, and can find applications in various industries, such as the bearing, automotive and heavy-duty machinery industries.
BACKGROUND OF THE INVENTION
Frictional heat is generated at the interface of two elements in a relative motion as a product of surface rubbing. Some of the heat generated is dissipated through the non-contacting surface area into a convective medium, such as air or a lubricant. However, a considerably large amount of heat is conducted into the solid media of the contacting elements, resulting in a temperature increase in the solid. The temperature of the contact interface can be much higher than that of the surrounding material. Today, the demands for compact design may require bearing surfaces to work under severe conditions, such as high loads. It is anticipated that the accumulation of frictional heat will become a major problem in these situations.
Bearings with less lubricant supply are attractive due to the economic and environmental considerations. Lubrication by solid powder represents a new direction in bearing development (ASME 95-Trib-42, by Heshmat and Brewe, 1995, pages 1 to 2). However, heat is a serious barrier that controls the load capacity of the bearing and limits the reduction in the use of fluid lubricants. Solid lubricants can replace the lubrication function of the conventional fluid lubricants. It is anticipated that if the cooling function is provided by appropriate means, bearings with solid lubricants can compete with the fluid-lubricated journal bearings.
Due to the continuous release of the frictional heat, the contact interface constantly works under a high temperature, facing scuffing and seizure failures (Wang et al.,
Tribology Transactions,
pp. 587-593, 1994; Ni and Cheng,
Tribology Transactions,
pp. 121-129, 1995). Temperature uniformity is critical for conformal contact elements, such as journal bearings, whose performance is strongly controlled by clearance. Due to the bearing structural distortion caused by frictional heating, the bearing may lose its designed clearance, resulting in multi-contacts and seizure failure (Hazlett and Khonsari,
Tribology International,
pp. 177-182, 1992; and Wang et al., ASME 95-Trib-33, 1995). It is clear that temperature reduction at the contact interface and prompt dissipation of frictional heat from the contact region are crucial to protecting tribological interfaces and retaining the anti-failure capability of bearing surfaces. They are also critical to the development of bearings for future machinery with high load capacity and less lubricant consumption.
Generation of frictional heat at the contact interface creates heat sources. If a heat sink could be created at appropriate locations, it would be possible to transfer the frictional heat directly away through the sink. Heat pipes are ideal heat sinks for this consideration. The isothermal journal bearings that incorporate heat pipes can be ideal structures for bearings with low tendency of failure. These bearings may find wide applications in heavy-duty machinery. They can also be used for the bearings lubricated by a solid lubricant, such as lubricious powders, or as bearings without lubrication.
SUMMARY OF THE INVENTION
The objective of this invention is to develop isothermal journal bearings with excellent thermal-mechanical performance. The key to these new journal bearings is the incorporation of heat pipes into the bodies, rings, or bushings of the bearings for effective heat conduction and dissipation. Heat pipes are heat transfer devices that have a superior effective thermal conductance as high as hundreds of times that of copper. Detailed descriptions on heat pipes, including two-phase closed thermosyphons, can be found in a publication entitled
Heat Pipes,
by Dunn and Ready, Pergamon, N.Y., 1982, where a general description on heat pipes is contained on pages 1 to 20.
The heat pipes used for isothermal journal bearings are gravity-assisted heat pipes. The new journal bearing thus developed sandwiches a group of circumferential heat pipes between two rings, namely the inner and outer rings. The fabrication process of the isothermal journal bearings involves machining the heat pipe grooves on the bearing rings and assembling those rings to form the bearing structure. Evacuation, fluid filling, and welding of the heat pipe then follow after the assembly of the rings. Final machining of the bearing working surfaces may be conducted then to correct potential geometry distortion caused by welding. The isothermal journal bearing thus produced will have a configuration similar to that of the conventional bearings, but are much more effective in conducting and dissipating the frictional heat. The aforementioned new isothermal journal bearing has the following technological advantages:
1. The groove heat pipes have small cross-sectional areas and extend to the entire circumference of the bearing. The evaporation and condensation process in the heat pipes result in a rapid heat transfer in the circumferential direction and an enhanced convective cooling through the entire bearing surface. If an external cooling is provided, the bearing can be maintained at a low and constant temperature.
2. Due to the extremely high thermal conductance and quick response of the heat pipe, frictional heat can be promptly dissipated by the heat pipe from the location where it is generated. Therefore, the surface temperature in the bearing contact area can be greatly decreased, and the tendency of contact failure could be significantly reduced.
3. Uniform temperature is one of the critical factors to preventing contact failures induced by structural distortion. As a result of the heat pipe function, the bearing temperature in the circumferential direction will be relatively uniform. The structural distortion could be controlled within a small scale and the working clearance of the journal bearing can be well maintained. Thus, failures induced by thermal distortion may be prevented.
4. Heat pipe cooling is completely passive. Since no additional energy sources are needed to support the cooling process, the isothermal journal bearing can function well on an energy-saving basis.
5. The new bearing has a simple structure with low manufacturing costs. Therefore, the isothermal journal bearing presented herein provides a unique cooling technique without any technical barriers.
REFERENCES:
patent: 1723928 (1929-08-01), Fisher
patent: 2744796 (1956-05-01), Walters
patent: 2774566 (1956-12-01), Richardson
patent: 2826463 (1958-03-01), Newman
patent: 3267997 (1966-08-01), Matarese et al.
patent: 994402 (1976-08-01), None
patent: 264105 (1927-01-01), None
patent: 781085 (1957-08-01), None
patent: 193930 (1983-11-01), None
Cao Yiding
Wang Qian
Hannon Thomas R.
Wang Qian
LandOfFree
Isothermal journal bearing does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Isothermal journal bearing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Isothermal journal bearing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2536870