ELECTRONIC/HYDRAULIC CONTROL SYSTEM FOR AN AUTOMATIC TRANSMISSION

摘要

An electro/hydraulic control system for automatically shifting gear stages of a multiple stage transmission gear mechanism by selectively controlling the operable effectiveness of various hydraulically operated friction units in accordance with vehicle operating conditions is provided. The control system includes a series of hydraulic shift valves arranged in combination with at least two pressure regulator valves (110, 112) for controlling the supply of hydraulic actuating fluid to the friction units in response to ratio selection signals derived in an electronic control. The control system further includes at least one variable pressure solenoid (372) whose variable pressure output is multiplexed to each pressure regulator valve (110, 112) in the system to provide for quality shifts between gear ratios. The desired end is effected by programmably profiling the output of the variable pressure solenoid (372). The regulator valves (110, 112) allow the profiled output of the variable pressure solenoid (372) to pass to the effected friction unit to effect a smooth transition between gear ratios and then delivers full actuating fluid pressure to the respective friction unit to complete the shift. The full actuating fluid pressure which is delivered to the respective friction unit is derived by either maximizing the pressure output of the variable pressure solenoid (372) after the shift or gear change is effected or by allowing full actuating fluid pressure to pass through the regulator valve (110, 112) from the shift valve to the respective friction unit. In either manner, the friction unit is assuredly operated and the gear shift is effected.