Transmission shuttle shift deceleration method
AssigneeDeere & Company
InventorKevin L. Vaughters
Life of this patent
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Abstract
A powershift transmission includes a plurality of clutches, including a final or directional set of clutches. The clutches are controlled by electro-hydraulic direct acting valves and two electro-hydraulic proportional or pressure modulating valves. The pressure modulating valves modulate the pressure supplied to the direct acting valves associated with the three directional clutches. Vehicle deceleration during a shuttle shift is achieved by releasing (unpressurizing) all clutches, then gradually pressurizing only two clutches in the final or directional set.
Claims3
A method of decelerating an output shaft of a vehicle powershift transmission during a shuttle shift whereby rotation of the output shaft is reversed from a first direction to a second direction, the transmission having a plurality of hydraulic pressure operated clutch elements for shifting the transmission, including a set of directional clutches, the method comprising the following steps:
- disengaging all the clutch elements, including all the directional clutches;
- applying pressurized fluid to only to both a first directional clutch and to a second directional clutch to lock up the transmission;
- when the output shaft speed is less than a threshold value, applying pressurized fluid to at least one selected clutch other than a directional clutch to engage a desired gear and to cause the output shaft to rotate in the second direction;
- and
- releasing pressure from at least the first directional clutch.
Dependencies are inferred from the claim text.