Motor vehicles – Having four wheels driven – Including separate mechanical assemblies for transmitting...
Reexamination Certificate
1999-08-30
2001-02-27
Hurley, Kevin (Department: 3619)
Motor vehicles
Having four wheels driven
Including separate mechanical assemblies for transmitting...
C180S298000
Reexamination Certificate
active
06193006
ABSTRACT:
TECHNICAL FIELD
This invention relates to all wheel drive powertrains and more particularly to such drives having a control element to disconnect the all wheel drive from one pair of driving wheels.
BACKGROUND OF THE INVENTION
Many modern vehicles employ four wheel drive systems. These systems have been marketed in two forms. Systems generally termed four wheel drive (4WD) have a transfer case which is controlled by the operator to select two wheel or four wheel drive. If the operator selects the four wheel drive condition, the vehicle drives all four wheel continuously. Some of these systems have employed overrunning clutches at two of the wheel to alleviate some of the disadvantages of 4WD which result from tire pressure differential and cornering to name a few.
All wheel drive (AWD) systems also provide the benefits of a four wheel drive vehicle and do not require the operator to intentionally select this condition. These systems often employ a viscous clutch in the center differential to transfer torque to the drive wheels that are not sensed as slipping. In tight cornering situations and during towing, these AWD systems present a disadvantage. The vehicle must be placed on a flat-bed type towing vehicle to prevent overheating of the powertrain during towing. In cornering situations, noise and vibration can result from the AWD system being engaged. While this is not detrimental to the powertrain during short durations, it can be disconcerting to the operator.
One solution to this problem is can be found in U.S. Ser. No. 09/247,116 filed Feb. 9, 1999 and assigned to the assignee of this application. This previous application provides two positive displacement pumps each of which selectively pressurizes a respective clutch to establish a positive drive connection to each normally non-driven axle.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved all wheel drive powertrain having a single control pump and a single clutch.
In one aspect of the present invention, a powertrain has a pair of normally driven wheels and a pair of normally non-driven wheels and a selectively engageable clutch for connecting a differential of the normally non-driven wheels with the prime mover. In another aspect of the present invention, a drive shaft is positioned to transmit power from a multi-speed transmission through a selectively engageable clutch with the differential of the normally non-driven wheels.
In another aspect of the present invention, a positive displacement pump is disposed between the drive shaft and the input to the differential to supply fluid to the clutch when a speed differential is present between the drive shaft and the input to the differential. In yet another aspect of the present invention, a valve selectively operable valve member is in fluid communication between a fluid reservoir and the inlet to the pump to limit pump operation. In a further aspect of the present invention, the selectively operable valve member permits fluid communication between a reservoir and the pump inlet only when a traction loss is identified at the normally driven wheels.
In one embodiment of the present invention, a powertrain has a multi-speed transmission that is connected to drive the front wheels of a vehicle. A transfer gear set is positioned to supply power to a drive shaft that is connected, through a selectively engageable clutch and a differential gearing, with the rear wheels of the vehicle. A positive displacement pump is located between the drive shaft and the input to the differential gearing. One member of the pump is driven by the drive shaft and the other member is driven by the differential gearing input. When a speed differential is present between the pump members and fluid is supplied to the pump inlet, the outlet fluid of the pump will enforce engagement of a friction clutch which is selectively connectable between the drive shaft and the differential gearing input. The pump inlet is supplied with fluid only when a speed differential representing a loss of traction is sensed at the normally driven front wheels. When the clutch is engaged, the rear wheels will receive power from the engine of the vehicle through the transmission to establish an all wheel drive powertrain.
REFERENCES:
patent: 4676336 (1987-06-01), Hiramatsu et al.
patent: 5005662 (1991-04-01), Kodama
patent: 5056640 (1991-10-01), Yamamoto
patent: 5080187 (1992-01-01), Asano et al.
patent: 5219038 (1993-06-01), Hamada et al.
patent: 5927426 (1999-07-01), Hall et al.
patent: 6009968 (2000-01-01), Kouno
patent: 6045476 (2000-04-01), Haka
Deutschel Brian William
Straitiff Donald Graham
Fischer Andrew J.
General Motors Corporation
Hurley Kevin
Leahy Charles E.
LandOfFree
Dynamic all wheel drive control does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Dynamic all wheel drive control, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dynamic all wheel drive control will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2609231