Line pressure control for automatic transmission.

摘要

An automatic transmission is disclosed wherein an accumulator back-up pressure (PB) is variable in response to engine load and also to the progress of a shift taking place. A line pressure solenoid (24) is provided which controls a signal pressure supplied to an accumulator control valve (70) which generates the accumulator back-up valve supplied to an accumulator (64) that is arranged to soften an increase in servo activating hydraulic fluid pressure supplied to a frictional device during the shift.