Method for reaching a neutral position of a gearshift fork in a shift transmission
AssigneeGetrag Ford Transmissions GmbH
InventorsMartin Leibbrandt, Stefan Huepkes, Helmuth Bosch
Life of this patent
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Abstract
A method for reaching a neutral position N located between two end positions of a gearshift fork in a shift transmission in a motor vehicle from a starting position of the gearshift fork. The method allows finding the neutral position of the gearshift fork without a sensor determining the position of the gearshift fork or in the alternative in case such the sensor is defect.
Claims9
In a motor vehicle, a method for failsafe disengaging of a gear and reaching a neutral position located between a first end position and a second end position of a gearshift fork in a shift transmission from a starting position of the gearshift fork where a first gear is engaged, said transmission being adapted to move the gearshift fork between the first end position where a first gear is engaged and a second end position where a second gear is engaged in a first direction and in a second direction;
- and synchronize a rotational speed of an input shaft of the shift transmission with a rotational speed of an output shaft of the shift transmission at a respective first synchronization point that is related to the first gear and a second synchronization point that is related to the second gear;
- said method comprising the steps of:
- applying a latching force to the gearshift fork that pushes the gearshift fork in a direction of the neutral position when located in a first position, and away from the neutral position when the gearshift fork is located in a second position that is more remote from the neutral position than the first position, wherein the latching force preferably reaches a maximum in the neutral position;
- determining a first time period Δt1 that is high enough so that the gearshift fork is pressed from the engaged gear into a section where the latching force starts urging the gearshift fork into the neutral position;
- applying in a step S1 from a starting position of the gearshift fork where the first gear is engaged over the first time period Δt1 a first actuating force to the gearshift fork that is higher than the maximum latching force, said first actuating force acting in one of the first and second directions and pushing the gear shift fork from the starting position where the first gear is engaged within the first time period Δt1 into a section where the latching force starts urging the gearshift fork into the neutral position;
- and
- terminating in a step S2 the first actuating force after the first time period Δt1 has expired to allow the latching force to urge the gearshift fork into the neutral position.
Dependencies are inferred from the claim text.