Parking pawl assembly

Details Parking pawl assembly Parking pawl assembly

2000-02-17

2001-08-28

Bonck, Rodney H. (Department: 3681)

192 clutches and power-stop control

Transmission and brake

Motor vehicle

C188S031000

Reexamination Certificate

active

06279713

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a parking pawl assembly and more particularly, to a selectively movable parking pawl assembly which provides a relatively quiet and smooth release of torque when the vehicle is shifted out of the “parked” position.
BACKGROUND OF THE INVENTION
Parking pawl assemblies are used in automotive vehicles to operatively engage the vehicle's park gear, thereby maintaining the vehicle in a “parked” position or state. Parking pawl assemblies typically include a rotatable member or a “parking pawl,” which is selectively engaged by the park rod of the vehicle when the transmission of the vehicle is shifted into the “parked” position. When the park rod engages the parking pawl, the parking pawl pivots or rotates into a position where it is disposed between a pair of teeth on the park gear, thereby substantially preventing the park gear and the output shaft from further rotating. A return spring is typically connected to the parking pawl and causes the parking pawl to disengage from the park gear when the park rod is retracted (i.e., when the vehicle is shifted out of the “parked” position).
While these prior parking pawl assemblies are effective to prevent further rotation of the park gear and the output shaft when a vehicle is in the “parked” position, they suffer from some drawbacks. For example and without limitation, when residual torque remains within the output shaft (e.g., when the vehicle is parked on an inclined or declined surface), the park gear imparts a torsional force or load on the parking pawl. The parking pawl holds the park gear in a fixed angular position until the parking pawl is completely disengaged from the park gear (e.g., when the vehicle is shifted out of the “parked” position). Once the parking pawl is completely disengaged from the park gear, the residual torque remaining within the output shaft is rapidly released and is effective to cause the park gear to relatively rapidly rotate or move. This relative rapid release of torque and the relative rapid movement of the park gear generates an undesirable and relatively loud and unaesthetic noise or sound, which is audible within the passenger compartment of the vehicle and can be heard by the occupants of the vehicle. Additionally, this rapid release of torque often results in undesirable vibrations which can be “felt” or experienced at the vehicle's shifter.
There is therefore a need for a new and improved parking pawl assembly for use in a vehicle which overcomes many, if not all, of the previously delineated drawbacks of such prior parking pawl assemblies.
SUMMARY OF THE INVENTION
It is a first object of the invention to provide a parking pawl assembly which overcomes at least some of the previously delineated drawbacks of prior parking pawl assemblies.
It is a second object of the invention to provide a parking pawl assembly which substantially reduces the amount of residual torque which is stored within the park gear before the parking pawl is completely disengaged from the park gear.
It is a third object of the invention to provide a parking pawl assembly which allows the parking gear to move angularly before the parking pawl is completely disengaged from the park gear.
It is a fourth object of the invention to provide a parking pawl assembly for use in a vehicle which substantially reduces the amount of noise and vibration generated when a vehicle is shifted out of the “parked” position.
According to a first aspect of the invention, a parking pawl assembly for use in combination with a gear and a torque producing output shaft is provided. The parking pawl assembly includes a member which is movable between a first gear engagement position and a second position. The member has a portion which controllably releases the torque produced by the output shaft as the member is moved from the first gear engagement position to the second position.
According to a second aspect of the invention, a method for use in combination with a parking pawl of the type adapted to selectively engage and disengage a gear which is connected to a torque producing output shaft is provided. The method is effective to release the torque and includes the steps of selectively allowing the parking pawl to move in response to the torque, thereby smoothly releasing the torque.
These and other features, aspects, and advantages of the invention will become apparent by reading the following specification and by reference to the following drawings.


REFERENCES:
patent: 4157745 (1979-06-01), Nelson
patent: 4267748 (1981-05-01), Grunewald et al.
patent: 6105459 (2000-08-01), Troiano
patent: 58-207572 (1983-12-01), None

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