US 4,838,126 AGranted

Electro/hydraulic control system for an automatic transmission

AssigneeBTR Engineering (Australia) Limited

InventorsErich L. Wilfinger, Ronald J. Polomski, Darren L. Firth

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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. To assure performance and commercial reliability, the control system includes a unique redundancy feature or characteristic. That is, 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 after the shift or gear change is effected or by allowing full actuating fluid pressure to pass through the regulator valve from the shift valve to the respective friction unit. In either manner, the friction unit is assuredly operated and the gear shift is effected.

Claims48

Dependent claims

An automatic transmission for a vehicle having an engine capable of producing torque, said transmission including gear elements capable of developing at least two different gear ratios between an input member and an output member, a first fluidically actuatable friction unit operable in combination with said gear elements for establishing a first gear ratio, a second fluidically actuatable friction unit operable in combination with said gear elements for establishing a second gear ratio, and an electrohydraulic control system for said automatic transmission comprising:

means for generating an actuating fluid pressure deliverable through separate fluidic circuits to said first and second friction units;
first shift valve means disposed in a fluidic circuit leading to said first fluidicially actuatable friction unit;
second shift valve means disposed in a fluidic circuit leading to said second fluidically actuatable friction unit;
first regulator means shiftable between two operable states in response to electrical signals being delivered thereto and arranged in combination with said first shift valve means for controlling fluid flow to said first fluidically actuatable friction unit as a function of the operable state of said regulator means;
second regulator means shiftable between two operable states in response to electrical signals being delivered thereto and arranged in combination with said second shift valve means for controlling fluid flow to said second fluidically actuatable friction unit as a function of the operable state of said regulator means;
at least one variable pressure solenoid whose variable pressure output is multiplexed to said first and second regulator means in a manner influencing the operable state of said first and second regulator means;
and
electronic control means for converting input signals thereto relating to operating conditions of said transmission into output signals in accordance with a predetermined set of criteria and for providing shift quality between gear ratios by selectively operating said regulator valves such that a programmably profiled fluid output from said variable pressure solenoid is delivered to an on-coming friction unit to effect a smooth transition between gear ratios and then full actuating fluid pressure is delivered to the on-coming friction unit by either maximizing the pressure output of the variable pressure solenoid or changing the present state of the respective regulator valve to allow full actuating fluid pressure to pass to the respective friction unit.

5 more elements

a source of operating fluid;
first fluid passage means for supplying operating fluid to said clutch means for engaging said clutch means;
second fluid passage means for supplying operating fluid to said brake means for engaging said brake means;
first shiftable valve means disposed in said first fluid passage means for controlling fluid flow to said clutch means in a manner effecting transmission output;
second shiftable valve means disposed in said second fluid passage for controlling fluid flow to said brake means in a manner effecting transmission output;
a two state clutch regulator valve means disposed in combination with said first shiftable valve means for controlling fluid flow to said clutch means;
a two state band regulator valve means disposed in combination with said second shiftable valve means for controlling fluid flow to said brake means;
at least one variable pressure solenoid whose variable pressure fluid output is multiplexed to both regulator valve means and is a profiled function of a program;
and
electronic control means for converting input signals thereto relating to operating conditions of said transmission into output signals in a preprogrammed manner, said output signals controlling said profile program, the operational states of said regulator valve means, and the position of said shift valves in a manner effecting a smooth transition between gear ratios and causing a redundancy in operation of said regulator valve means to prevent damage to either the clutch means or brake means.

7 more elements

A control system for an automatic transmission for a vehicle having an engine capable of producing torque, said transmission having an input shaft and an output shaft with multiple ratio gearing including a plurality of rotary elements connected to and between said input shaft to said engine, a first clutch means for controlling the relative motion of some of the elements of said gearing to establish a first gear ratio, band means for controlling the relative motion of some other elements of said gearing and which combines with said first clutch means to establish and disestablish ratio changes between the first gear ratio and a second gear ratio, and a second clutch means arranged in combination with said band means for controlling the relative rotation of still other gearing elements to establish and disestablish gear ratio changes between second and third gear ratios, said control system comprising:

a source of operating fluid;
conduit structure individually connecting said source of operating fluid to each of said clutch and band means;
12 shift valve means for selectively controlling the distribution of operating fluid through said conduit structure as a function of its linear disposition;
2-3 shift valve means for selectively controlling the distribution of operating fluid through said conduit structure as a function of its linear disposition;
two state band regulator valve means arranged in combination with the 12 shift valve means for controlling the distribution of operating fluid through said conduit structure;
two state clutch regulator valve means arranged in combination with the 2-3 shift valve means for controlling the distribution of operating fluid through said conduit structure;
at least one variable pressure solenoid whose variable pressure fluid output is delivered to both regulator valve means, the variable pressure output of said solenoid being controlled by a program which profiles the output of said solenoid between a maximum output level and a lower output level;
and
electronic control means for converting input signals thereto relating to operating conditions of said transmission into output signals by software means, said electronic control means output signals controlling the state of both of said regulator valve means such that said band and clutch means operate under the programmable profiled output of said variable pressure solenoid during a shift change and then allows full line pressure or the maximum output level of the variable pressure solenoid to be delivered to the respective means for controlling the relative motion of the elements of said gearing after a gear change has been effected.

6 more elements

Dependencies are inferred from the claim text.