Bearings – Rotary bearing – Plain bearing
Reexamination Certificate
1999-06-08
2001-08-21
Estremsky, Sherry (Department: 3681)
Bearings
Rotary bearing
Plain bearing
C384S368000, C384S123000
Reexamination Certificate
active
06276834
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns a semicircular or circular, axial bearing element, especially a thrust washer or flanged bearing shell, or flanged bearing bushing, with recesses valleys on the side facing the sliding partner to form radial oil outlet openings.
BACKGROUND OF THE INVENTION
Machines and transmissions are equipped with pumps which maintain a continuous flow of lubricant to the bearings. For bearings, of concern usually are sleeves, bushings or shells whose inner diameter is slightly larger than the diameter of the shaft for which the bearing serves. Pressurized lubricant, usually lubricating oil, is pressed into the gap between the shaft and its bearing element. The shaft is “lifted” by this and floats on the film of lubricant (hydrodynamic lubrication). In this way, less friction, lower temperatures and greater rotational velocity of the shaft are achieved than is the case using ball-bearings filled with lubricant.
The shaft can thus move in the axial direction, that is in the direction toward its ends. Limits are placed on this movement by axial bearing elements of the type being discussed here. If the shaft moves from its specified position, this axial movement is stopped by the axial bearing elements.
One always tries to keep motor components, and, as a part of such group, axial bearing elements, as small as possible, in order to maintain motor and transmission costs low. Axial bearing elements with high load carrying capacity and small size are, consequently, a desired goal.
Laboratory experiments have shown that many of the known constructions of axial bearing elements and their lubrication are ineffective for motor applications. They scarcely increase the load carrying capacity of the bearing.
In the case of a known axial bearing element (thrust bearing) for limiting axial movement of the crank shafts of combustion engines, valleys are provided on the face turned toward the sliding partner. These valleys are very deep, with depths of 0.3 to 0.65 mm. Over a range of 180 degrees, three of these valleys are provided, through which the lubricant can run radially out of the axial bearing location.
Because of the great depth of the valleys, the axial bearing elements must be made very thick. This increases the manufacturing costs, not, however, the load carrying capacity.
SUMMARY OF THE INVENTION
In view of this, it is an object of the present invention to increase the load carrying capacity of axial bearing elements of the above described type, without, however, increasing the space occupied by the structure. Also, manufacturing costs, as compared to costs for known axial bearing elements, should be decreased, or at least remain the same.
The above-mentioned object is achieved, according to the present invention, for an axial bearing element of the described type, by providing five to eight valleys in the circumferential direction over an angle of 180 degrees and by rounding the peaks between each two valleys, and further by providing the profile between the maxima of the peaks and the minima of the valleys with a depth of 0.05 to 0.2 mm.
In further development of the inventive concept, it has proven advantageous when the above-stated depth lies between 0.05 and 0.15 mm.
Additionally it has proven advantageous when five to seven recesses, preferably 6 recesses, are provided over the stated angle of 180 degrees.
It is, furthermore, considered to be especially advantageous when the peaks and valleys, which are preferably both rounded, run continuously into one another.
When, above, reference is made to a rounding of the peaks provided between two valleys, it is meant that, in contrast to the previous state of technology, there is no flat or planar surface shape. Thus, previously, this region between two valleys had an essentially planar shape. It has been found to be especially advantageous when the peaks between two valleys are rounded, hill-shaped, or, when considered in cross-section, of curved surface contour, since, in such case, the lubricant provided in the valleys, which lubricant exits radially outwards, at the same time is taken along in the circumferential direction into the region between the peaks and the sliding partner.
It was ascertained that, by increasing the number of valleys and because of their inventive shape (rounded shape of the peaks, relatively small depth), 50% increase of the load carrying capacity of the axial bearing element of could be achieved. Thus, according to the present invention, more peaks and valleys are provided and these are rounded and exhibit a reduced depth.
It was, however, not only possible to increase the load carrying capacity of the axial bearing element; it was also possible to achieve a higher natural frequency (less fatigue). It is considered especially advantageous that the bearing of the present invention can be used for both directions of rotation.
Also, it was possible to reduce the tendency for the sliding contact layer to separate from the carrier layer during operation. When the valleys are stamped, as is preferred according to the present invention, a smaller pressing force is used, as compared to manufacture of the deeper valleys of the previous practice.
Further details and advantages of the present invention will be understood from the appended claims as well as from the drawings and the following description of a preferred embodiment in the form of a thrust washer.
REFERENCES:
patent: 4795220 (1989-01-01), Mori
patent: 5611628 (1997-03-01), Brouwer
patent: 569740 (1957-04-01), None
Estremsky Sherry
Jones, Tullar & Cooper
KS Gleitlager GmbH
Lewis Tisha D.
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