192 clutches and power-stop control – Transmission and brake – Motor vehicle
Reexamination Certificate
2000-01-20
2001-09-18
Bonck, Rodney H. (Department: 3681)
192 clutches and power-stop control
Transmission and brake
Motor vehicle
C188S031000
Reexamination Certificate
active
06290047
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a parking pawl assembly and more particularly, to a parking pawl assembly having a selectively rotatable cam assembly which ensures that consistent loads are provided to the vehicle's shifter each time the vehicle is shifted into “park”.
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 “park” 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.
The park rod typically includes a spring which is compressed during certain “shifts” into park. Particularly, when the park rod engages the parking pawl and causes it to pivot into the park gear, the parking pawl is sometimes pivoted into and engages a “tooth” of the park gear. During these types of shifts, the pivotal movement of the parking pawl is temporarily limited or stopped by the gear tooth, and is effective to prevent further movement of the park rod until the park gear is rotated, thereby causing the spring within the park rod to be compressed. When the park gear rotates, the parking pawl slides along the gear tooth with which it is engaged until it “drops into” or is forced into a space between the teeth of the park gear.
During other shifts into the park position, the parking pawl is engaged by the park rod and is rotated or pivoted directly into a space between gear teeth. During these types of shifts, the parking pawl does not “block” or prevent the movement of the park rod and the spring within the park rod is not compressed.
The resulting inconsistency in the compression of the park rod causes the force required to shift the vehicle into park to vary from shift to shift. Hence, in these prior systems a driver or an operator of the shifter undesirably “feels” or experiences different forces when shifting the vehicle into park (e.g., the operator is required to exert different amounts or levels of force at the shifter to shift the vehicle into park during different shifts).
Additionally, the speed at which the pawl “drops into” or engages space between gear teeth varies from shift to shift in these prior systems. For example and without limitation, when the parking pawl first engages a tooth of the park gear and subsequently “drops into” or is forced into a space between gear teeth, the speed at which the parking pawl engages the gear teeth depends, at least in part, upon the speed at which the park gear rotates. This speed varies based upon the incline of the vehicle, the speed of the vehicle, and the residual torque remaining within the output shaft of the vehicle when the vehicle is shifted into park. These variables cause the parking pawl to “drop into” position or to engage the teeth of the park gear undesirably fast during certain shifts, thereby producing unaesthetic “clicking” or “clicking” sounds.
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 causes the park rod to be compressed each time the vehicle is shifted into park.
It is a third object of the invention to provide a parking pawl assembly which provides for a consistent load at the vehicle's shifter assembly each time the vehicle is shifted into park.
It is a fourth object of the invention to provide a parking pawl assembly which engages the park gear at a relatively consistent speed each time the vehicle is shifted into park.
According to a first aspect of the present invention, a parking pawl assembly is provided for use in combination with a vehicle of the type having a park gear, a shifter assembly which is movable to a park position, and a park rod having a selectively compressible spring. The park rod is coupled to the shifter and is actuatable in response to the movement of the shifter to the park position. The parking pawl assembly includes a pawl member which abuts the park rod. The pawl member is selectively movable between a first position in which the pawl member is remote from the park gear, and a second position, in which the pawl member engages the park gear. The pawl member is movable from the first to the second position in response to the actuation of the park rod. The parking pawl assembly further includes a generally cylindrical member which is coupled to the park gear, and a cam assembly which is coupled to the pawl member. The cam assembly includes a movable cam member which abuttingly engages the generally cylindrical member, and is effective to hold the pawl member in the first position until the spring is compressed, thereby causing the spring to be compressed substantially every time the shifter moves to the park position.
According to a second aspect of the present invention, a method for providing a consistent force at a shifter within a vehicle each time the shifter is moved into a park position is provided. The shifter includes a park gear, a parking pawl which selectively engages the park gear, and a park rod having a selectively compressible spring and being movable in response to the shifting of the shifter. The method includes the steps of: providing a hub member; coupling the hub member to the park gear; providing a cam assembly which is movable between a first position and a second position; coupling the cam assembly to the parking pawl so that the cam assembly abuts the hub member and is effective to prevent the parking pawl from engaging the park gear while the cam assembly is in the first position, and to allow the parking pawl to engage the park gear while the cam assembly is in the second position; and moving the cam assembly from the first position to the second position only after the shifter is moved to the park position and the spring has been compressed.
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: 4585103 (1986-04-01), Kuwayama et al.
patent: 4606242 (1986-08-01), Hasegawa et al.
patent: 4610337 (1986-09-01), Kuwayama et al.
patent: 4614256 (1986-09-01), Kuwayama et al.
patent: 5964335 (1999-10-01), Taniguchi et al.
patent: 58-191630 (1983-11-01), None
patent: WO 9725231 (1997-07-01), None
Adamczyk David William
Borders John D.
Hildebrand Daniel Hugh
Shedd Ernest Russell
Bonck Rodney H.
Ford Global Tech. Inc.
Ford Global Tech., Inc.
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