Patent ID: 6101440
Filing Date: 2000-08-08
Classification: B60W,F15B,F16H

Abstract:
In a control device for an automatic motor vehicle transmission having electrohydraulically actuated gearshift elements actuated by hydraulic pressure varied in multiple phases and then regulated by closed-loop control for increasing smoothness of shifting during a shifting operation, the improvement comprising:(a) means for rapidly bringing the hydraulic pressure to a desired variable by an open-loop control signal with a long duty cycle, in a first phase of the shifting operation in which idle travels of the gearshift elements are overcome;(b) means for building up the hydraulic pressure with a high duty cycle in a second phase of the shifting operation in which a transmission input moment changes over from the gearshift element of an old gear to the gearshift element of a new gear; and(c) means for:(ca) first rapidly open-loop controlling the hydraulic pressure to approach a desired variable, and(cb) thereafter closed-loop controlling the hydraulic pressure,through a change in the duty cycle in a third phase of the shifting operation in which a drop in engine rpm required to perform the gear change takes place.