US 5,289,741 AGranted

Adaptive transmission pressure control with run-through detection

AssigneeGeneral Motors Corporation

InventorsWilliam E. Debs, Robert L. Moses

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Abstract

An improved adaptive line pressure control which detects the occurrence of run-through and overrides the normal adaptive pressure control in response to a detected run-through condition so that the line pressure during subsequent shifting is increased instead of decreased. A run-through condition is detected by periodically sampling the transmission speed ratio in the course of the inertia phase of an upshift from a lower speed ratio to an upper speed ratio, and determining the average ratio for the upshift. If the average ratio is within a reference amount of the normal value (ratio midpoint), the adaptive control is allowed to update the adaptive pressure value in relation to the difference between the measured shift time and a desired shift time. If the average ratio exceeds the normal value (midpoint) by more than the reference amount, a run-through is detected, and the adaptive pressure amount is increased regardless of the measured shift time.

Claims6

Dependent claims

In a motor vehicle multiple speed ratio automatic transmission including a fluid operated torque transmitting device to be engaged for shifting the transmission from a current speed ratio to a target speed ratio, a source of fluid pressure, regulator means for regulating said fluid pressure in accordance with a predetermined pressure command to form a regulated line pressure, a shift valve operative when activated to direct said line pressure to said torque transmitting device for engaging such device, and fluid accumulator means for absorbing a portion of the fluid directed to said torque transmitting device by said shift valve during a stroke interval of said shift, control apparatus comprising:

means effective during a sampling period defined by a progression of said speed ratio from said current speed ratio to said target speed ratio for periodically sampling said speed ratio;
means effective upon conclusion of said sampling period to determine an average ratio signal corresponding to the average of said periodically sampled speed ratios;
detection means for comparing the determined average ratio signal to a desired average ratio to detect an abnormal shift condition in which the change in speed ratio is completed after said stroke interval;
and
means for adjusting said predetermined pressure command in a direction to increase said regulated line pressure in subsequent shifting to said target speed ratio in response to a detection of said abnormal shift condition, thereby to prevent a recurrence of said abnormal shift condition.

2 more elements

means effective during said shift to said target speed ratio for measuring a shift time corresponding to the duration of a detected change in speed ratio;
shift quality control means for adjusting said predetermined pressure command based on a detected deviation between said measured shift time and a predetermined shift time which is characteristic of high shift quality under normal conditions;
means for comparing a measure of the average speed ratio during said detected change in speed ratio with a desired average speed ratio to detect an abnormal shift condition in which the change in speed ratio is completed after said stroke interval;
and
override means for overriding the adjustment of said shift quality control means in response to a detection of said abnormal shift condition, and instead, adjusting said predetermined pressure command in a direction to increase said regulated line pressure in subsequent shifting to said target speed ratio, thereby to prevent a recurrence of said abnormal shift condition.

2 more elements

Dependencies are inferred from the claim text.