US 4,867,291 A · Vehicle transmission hill holder with releasable one way clutch

Abstract

A hill holder device for a vehicle manual transmission includes a releasable one-way clutch which is coupled to the countershaft of the transmission. In particular, the one-way clutch includes a sprag clutch having an inner race secured to the countershaft, and an outer race secured to the vehicle transmission case by means of a releasable locking mechanism. When the locking mechanism is in its locked position, the sprag clutch enables rotation of the countershaft in only one direction. Thus, if the transmission is in a forward gear and comes to a stop on an ascending grade, the hill holder will lock the vehicle drive train and prevent the vehicle from rolling back down the grade, without requiring the driver to apply the brakes. Similarly, if the vehicle is in a reverse gear and is stopped on a descending grade, the hill holder will prevent the vehicle from rolling in a forward direction down the grade. If necessary, the locking mechanism can be unlocked to release the hill holder in order to facilitate shifting in the event torque lock of the vehicle drive train locks the gear shifting components after the hill holder has become engaged on an inclined surface.

Claims20

Dependent claims

A hill holder mechanism for a vehicle transmission having an input shaft coupled to the vehicle engine and an output shaft coupled to the vehicle drive wheels, the transmission including a countershaft spaced from and coupled to said input and output shafts by a gear train, the transmission further including shifting means for shifting the transmission between a forward gear position, a neutral position, and a reverse gear position, said hill holder mechanism comprising:

releasable one-way clutch means coupled to said output shaft of said transmission for permitting rotation of said output shaft in only one direction whenever said transmission is in said forward gear position and in only an opposite direction whenever said transmission is in said reverse gear position;
control means for selectively releasing said clutch means to enable rotation of said output shaft in either direction;
said clutch means including a one-way sprag clutch wherein said sprag clutch includes an inner race and an outer race, one of said inner and outer races coupled to a releasable locking means and the other one of said inner and outer races secured to said countershaft for rotation therewith;
and
said locking means moveable between a locked position wherein rotation of said other race is resisted relative to a rotational axis of said countershaft and an unlocked position wherein said other race can freely rotate in either direction relative to said countershaft axis, said locking means including a shiftable piston which is normally spring biased to said locked position, and is hydraulically shiftable to said unlocked position, said piston coupled to at least one locking element which resists rotation of said other race about said countershaft axis when said piston is in said locked position.

2 more elements

A vehicle transmission having a hill holder mechanism, said transmission including a main housing for rotatably supporting an input shaft coupled to the vehicle engine, an output shaft coupled to the vehicle drive wheels, a countershaft spaced from said output shaft, and a gear train interconnecting said input, output, and countershafts, said countershaft having a front end extending through a front wall of said main housing, said transmission being shiftable between a forward gear position, a neutral position, and a reverse gear position, said hill holder mechanism comprising:

a hill holder housing secured relative to said front wall of said main housing;
a releasable one-way sprag clutch having an inner and outer race, one of said inner and outer races secured to the front end of said countershaft for rotation therewith, and the other one of said inner and outer races coupled to said hill holder housing by locking means;
said locking means moveable between a locked position wherein said other race is prevented from rotating relative to said hill holder housing whereby said sprag clutch permits rotation of said countershaft in only one direction, and an unlocked position wherein said other race can rotate in either direction with said countershaft, said locking means including a shiftable piston which is normally spring biased to said locked position, and is hydraulically shiftable to said unlocked position, said piston coupled to at least one locking element which resists rotation of said other race relative to said hill holder housing when said piston is in said locked position;
and
control means for selectively moving said locking means between said locked and unlocked position.

2 more elements

Dependencies are inferred from the claim text.

Vehicle transmission hill holder with releasable one way clutch

Life of this patent

Vehicle transmission hill holder with releasable one way clutch

Life of this patent

Abstract

Claims20