192 clutches and power-stop control – Elements – Lubricating – insulating – or cooling
Reexamination Certificate
1999-03-11
2001-02-20
Marmor, Charles A (Department: 3681)
192 clutches and power-stop control
Elements
Lubricating, insulating, or cooling
Reexamination Certificate
active
06189671
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns the field of freewheel devices used in automatic transmissions for motor vehicles, for example.
Freewheel devices generally comprise an outer ring with a cylindrical inner sliding path for cams of the freewheel, an inner ring or a shaft having a cylindrical outer sliding path for said cams of the freewheel, a freewheel between the sliding path of the outer ring and the sliding path of the inner ring or the shaft, and one or more bearing members for holding the inner and outer rings concentric and transmitting radial forces between said rings.
A bearing is a generally annular component having a radial part in the form of a substantially plane washer delimited by two circular edges to each of which an axial portion is joined. The axial portions bear on corresponding bearing surfaces of the rings, so centering the two rings relative to each other in the manner of smooth bearings. Said corresponding bearing surfaces of the rings can be an axial extension of the corresponding sliding paths.
The freewheel comprises a single cage or a double cage comprising two concentric cages with windows containing cams which, by becoming wedged between or sliding between the two sliding paths, assure unidirectional coupling between the inner and outer rings. The freewheel is able to transmit torque in one direction between the inner and outer rings and allows free rotation in the other direction.
To encourage tilting of the cams in the wedging direction a spring can be provided in the form of a strip applying to each cam a return torque urging it at all times into contact with the sliding paths.
The various components of the freewheel device can move relative to each other, rings relative to cams, cages relative to bearings, rings relative to bearings, or relative to adjoining components such as friction discs, retaining flanges, etc.
It is therefore necessary to lubricate these components to encourage sliding and to evacuate heat generated by friction.
Prior art documents, and in particular documents U.S. Pat. No. 4,875,564 and JP-A-326 866, describe lateral smooth bearings in freewheels and having in the middle of their disc-shape radial part lubricating holes through which the lubricant can be evacuated, which lubricant is generally injected under pressure into the assembly by means of a passage opening onto the path of the inner ring or the shaft.
This arrangement has certain drawbacks, however. Because the parts rotate, the lubricant tends to be centrifuged towards the outside of the sliding path on the outer ring. There is a volume radially between the lubricating holes of the bearings and the path of the outer ring in which the lubricant tends to stagnate with the result that it is not renewed or is not renewed properly. The lubricant circulates badly, heat is evacuated imperfectly and localized heating occurs in this area, which can further aggravate the phenomenon if the bearings are made of copper alloy.
The coefficient of thermal expansion of a copper alloy is higher than that of the steel constituting the other parts and in particular the rings. The bearings tend to bind on the outer ring and the small radial clearance between the bearing and the outer ring becomes insufficient to allow circulation of the lubricant. The phenomenon of stagnation of the lubricant is therefore aggravated and there is an increased risk of binding between the outside cylindrical bearing surfaces of the bearings and the corresponding bearing surface of the outer ring.
SUMMARY OF THE INVENTION
An aim of the invention is to improve the lubrication of the various components in contact in a freewheel device.
Another aim of the present invention is to propose a freewheel device in which the occurrence of localized heating is prevented.
The freewheel device in accordance with the invention is of the type comprising an outer ring having an inner sliding path, an inner ring or a shaft having an outer sliding path, a freewheel disposed between the sliding path of the outer ring and the sliding path of the inner ring and comprising a plurality of cams disposed in windows in a cylindrical part of at least one cage and assuring unidirectional coupling between the outer and inner rings, and at least one bearing member disposed radially between the outer and inner rings for maintaining said outer and inner rings concentric. The bearing member has a radial part provided with at least two holes for circulation of lubricant. At least one hole is near the outer ring. This encourages circulation of the lubricant.
In one embodiment of the invention the holes are distributed around two circles concentric with the rotation axis of the bearing. There can be at least one other hole near the inner ring.
The holes can be regularly distributed in the circumferential direction.
In one embodiment of the invention the holes near the outer ring alternate with the other holes in the circumferential direction. They can equally be offset relative to the other holes in the circumferential direction.
At least one hole can open onto the outside of the cylindrical part of the cage and at least one hole can open onto the inside of the cylindrical part of the cage, respectively to encourage circulation of the lubricant between the cage and the outer ring and between the cage and inner ring.
Accordingly, the lubricant can circulate freely in the freewheel assembly with no pockets of stagnant lubricant. This reduces the temperature inside the assembly. Lubrication between the flanks of the cage and the inner radial walls of the bearings is improved. Lubrication between the outer radial walls of the bearings and adjoining parts such as friction discs or retaining flanges is improved by the increased number and improved distribution of lubricant exit points. The risk of binding between parts in rubbing contact and the noise level in operation are reduced.
The present invention will be better understood after reading the detailed description of one particular embodiment given by way of non-limiting example and shown in the accompanying drawings, in which:
REFERENCES:
patent: 2834445 (1958-05-01), Gorsky
patent: 4875564 (1989-10-01), Leitz et al.
patent: 4913271 (1990-04-01), Kinoshita et al.
patent: 5320204 (1994-06-01), Riggle et al.
patent: 5671836 (1997-09-01), Shirataki et al.
patent: 0240847 A2 (1987-10-01), None
patent: 0370119 A1 (1990-05-01), None
patent: 59-166729 (1984-09-01), None
patent: 8-93889 (1996-04-01), None
Calve Marc Le
Houdayer Christophe
Marmor Charles A
Parekh Ankur
SKF France
Smith , Gambrell & Russell, LLP
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