Erich L Wilfinger

US Patent:

48381268, Jun 13, 1989

Filed:

Nov 25, 1987

Appl. No.:

7/125121

Inventors:

Erich L. Wilfinger - Livonia MI
Ronald J. Polomski - Pinckney MI
Darren L. Firth - Baulkham Hills, AU

Assignee:

BTR Engineering (Australia) Limited - Melbourne

International Classification:

B60K 4110

US Classification:

74869

Abstract:

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. The control system includes a series of hydraulic shift valves arranged in combination with at least two pressure regulator valves 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 whose variable pressure output is multiplexed to each pressure regulator valve 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. The regulator valves allows the profiled output of the variable pressure solenoid to pass to the effected friction unit to effect a smooth transition between gear ratios and then to deliver full actuating fluid pressure to the respective friction unit to complete the shift.