Seal for a joint or juncture – Seal between relatively movable parts – Relatively rotatable radially extending sealing face member
C277S562000, C060S330000, C060S366000
This invention relates to lip seals, and more particularly, to torque converter lip seals having a sealing lip and a splash lip to prevent a stream of oil with high velocity energy from directly impinging the sealing lip.
BACKGROUND OF THE INVENTION
Power transmissions include a torque converter which is effective to transmit power from an engine to a multi-speed power transmission. The torque converter permits the transmission to operate at a neutral condition without disengaging the clutches and/or brakes in the transmission. The torque converter will also provide power to a power take-off gear (PTO). When significant PTO power or high engine power without vehicle travel is required, the transmission gearing is placed in neutral so that the engine can operate at elevated power levels.
In vehicles such as cement mixers, the throttle setting and therefore the engine speed and power requirement can be quite high during load mixing. Engine speeds in the range of 2000 to 3000 rpm are not uncommon during these operations. Since the hydraulic control pump is driven directly by the torque converter impeller, the pump speed, output volume and torque converter pressure are quite high. Under this condition, a significant amount of oil is circulated to the torque converter and the lubrication and cooling circuits causing an increase in the volume of oil sent to the lubrication and cooling circuit; and also to the bushing supporting the hub connecting the impeller with the control pump.
Under this condition, it has been found that an inordinate amount of oil can bypass a lip seal which sealingly abuts the control pump drive hub on the torque converter impeller. The area beyond the seal is open to atmosphere therefore, any leakage which occurs will be visible. It has been noted that this condition appears after many hours of operation and not in transmissions newly put into use.
One solution to the problem is found in U.S. patent application Ser. No. 09/149,126, filed Sep. 8, 1998, which is assigned to the assignee of this application.
SUMMARY OF THE INVENTION
Testing of prior art transmissions, after leakage is observed has resulted in the following conclusions. Transmission input speed, converter inlet pressure, and sump temperature have much influence on the leaks. It has also been noted that increasing the diametral clearance of a bushing axially adjacent the lip seal increases the leakage. Placing additional exhaust passages in the chamber between the bushing and seal does not alleviate the problem.
Therefore, it is an object of the present invention to provide an improved seal structure for reducing the oil velocity along a rotating shaft.
In one aspect of the present invention, a splash lip is disposed axially along the shaft between a support bushing and a sealing lip to reduce the energy in a high velocity stream of oil leaving the bushing.
In another aspect of the present invention, the splash lip is comprised of a flexible portion and a rigid portion.
In yet another aspect of the present invention, the splash lip and the seal lip are secured in axial relation by a casing which is secured in a housing.
In a further aspect of the present invention, the rigid portion of the splash lip has apertures for permitting lubrication oil to contact the sealing lip after the energy of the oil stream is reduced.
In a yet further aspect of the present invention, the flexible portion of the splash lip conforms to the diameter of the shaft and is orientated to increase contact therewith when impinged by the stream of oil.
After much testing, it was determined that the converter-in pressure at the transmission control pump side of the bushing had little effect on the amount of leakage. The pressure in the chamber between the bushing and the seal likewise did not significantly influence the leakage. The inventor then considered that the velocity of the oil leaving the bushing and impinging on the seal lip was a primary factor of this phenomenon. The aforementioned object and aspects provide a solution to the problem. The structure proposed, reduces the axial velocity of the oil leaving the bushing prior to reaching the lip of the oil seal.
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General Motors Corporation
Peavey Enoch E.
Wideman Laura C.
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