초록 ▼

A hydraulic control system comprises a plurality of shift valves and a fluid circuit which directs a line pressure instead of a governor pressure to set the shift valves in a state wherein a predetermined speed ratio except the highest speed ratio and the lowest speed ratio is established when an id

A hydraulic control system comprises a plurality of shift valves and a fluid circuit which directs a line pressure instead of a governor pressure to set the shift valves in a state wherein a predetermined speed ratio except the highest speed ratio and the lowest speed ratio is established when an idle solenoid is turned on in response to closure of an idle switch.

대표청구항 ▼

A hydraulic control system for an automatic transmission including an input member operatively connected to an engine of a motor vehicle having an accelerator pedal, an output member, and fluid operated devices which are to be selectively engaged and disengaged for establishing a plurality of forwar

A hydraulic control system for an automatic transmission including an input member operatively connected to an engine of a motor vehicle having an accelerator pedal, an output member, and fluid operated devices which are to be selectively engaged and disengaged for establishing a plurality of forward speed ratios including an overdrive speed ratio and a next adjacent lower speed ratio, said hydraulic control system comprising; means for generating a servo actuating line fluid pressure; means for regulating said servo actuating line fluid pressure and generating a fluid pressure signal which is always lower than said line fluid pressure; a plurality of shift valve means for controlling supply of said line fluid pressure to and discharge of said line fluid pressure from said fluid operated devices, said plurality of shift valve means being divided into a first group which effects shifts between the overdrive speed ratio and the next adjacent lower speed ratio and a second group which effects shifts between the forward speed ratios except the overdrive speed ratio and the next adjacent lower speed ratio; means for detecting load on the engine and generating a no-load state indicative signal when the load on the engine is less than a predetermined level; means for allowing application of said fluid pressure signal to said plurality of shift valve means in response to absence of said no-load state indicative signal, but prohibiting said application of said fluid pressure signal to said second group of said plurality of shift valve means and allowing in lieu thereof application of said line fluid pressure to said second group of said plurality of shift valve means in response to presence of said no-load state indicative signal so as to prohibit said plurality of shift valve means from establishing any one of the forward speed ratios except the overdrive speed ratio and the next adjacent lower speed ratio; and means for forcing said first group of said plurality of shift valve means to establish the next adjacent lower speed ratio in response to presence of said no-load state indicative signal.