US 4,220,058 AGranted

Electronic control system for automatic transmission

AssigneeBorg-Warner Corporation

InventorWerner P. Petzold

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Abstract

An upshift gear ratio change is made in an automatic transmission by monitoring the driveline torque and operating a closed loop control system in response to that torque to in turn control the torque to obtain a desired shift. Shift quality is optimized, while torque transients are minimized, by initially closing the loop at the end of the static phase of the upshift when the driveline torque drops to its minimum turnaround point, the torque thereafter being controlled such that it increases from the turnaround point at a specified rate and in accordance with a predetermined first ramp command. As the increasing driveline torque then reaches a prescribed reset level, at an early stage in the dynamic phase, the closed loop control system is released and reset in order to control the torque in accordance with a second ramp command, the second ramp, that the torque is made to follow, thereby starting at a higher level than the first ramp. By initially closing the loop at the relatively low turnaround point undesired torque transients are precluded, and then by resetting the loop shortly thereafter, so that the torque ramp starts at a relatively high level, shift duration is maintained at a desired length and shift quality is enhanced. As a result, each time there is an upshift in the transmission there will be a smooth transition from the original engine speed to the new engine speed.

Claims9

Dependent claims

An electronic control system for regulating the change of gear ratio in an automatic transmission having a pair of friction elements and an output mechanical driving connection for supplying driveline torque to a load, where an upshift change of gear ratio has an initially occurring static phase, during which one of the friction elements is released and the driveline torque drops to a minimum turnaround level, and a subsequently occurring dynamic phase during which the other friction element is engaged and the driveline torque increases from the turnaround point until the shift is completed, comprising:

monitoring means for sensing the driveline torque at the transmission output driving connection and for producing an output torque signal which varies as a function of the driveline torque;
a closed loop control system having a loop which, when closed, controls the engagement of the on-coming friction element to regulate the driveline torque;
detecting means responsive to said output torque signal for closing the loop, when said driveline torque is generally at its turnaround point, and for causing the driveline torque to increase, from the turnaround point, under the control of a predetermined first ramp command;
and rest means responsive to said output torque signal for releasing and resetting said closed loop control system when the driveline torque increases to a predetermined reset level during the dynamic phase, the driveline torque thereafter increasing from the reset point, under the control of a predetermined second ramp command, until the shift is completed.

1 more element

Dependencies are inferred from the claim text.