Patent ID: 6077187
Filing Date: 2000-06-20
Classification: F16H,Y10S,Y10T

Abstract:
An electronic transmission control system having a fail-safe system for an automotive vehicle with a continuously variable automatic transmission whose speed-change ratio is changeable continuously depending on vehicle speed and engine load, comprising:a hydraulic modulator producing at least a regulated line pressure necessary to adjust the speed-change ratio hydraulically;a desired speed-change ratio arithmetic processing section for calculating a desired speed-change ratio based on the vehicle speed and the engine load;a desired line pressure arithmetic processing section for calculating a first duty cycle of a line-pressure solenoid valve that corresponds to a desired line pressure based on the desired speed-change ratio and the engine load; anda fail-safe section comprising:(a) a comparing portion for comparing the first duty cycle to a second duty cycle of the line-pressure solenoid valve that corresponds to a predetermined line pressure threshold; and(b) a speed-change ratio retaining portion for retaining the speed-change ratio of the continuously variable automatic transmission unchanged, when the first duty cycle exceeds the second duty cycle.