Electronic shift controller for a multiple ratio automotive transmission
First Claim
1. An electronic control system for a multiple ratio automatic transmission for use in an automotive vehicle driveline having a throttle controlled internal combustion engine, said transmission having gearing elements defining a first speed ratio and a second speed ratio;
- fluid pressure actuated clutch and brake means for controlling the relative speeds of said gearing elements to effect speed ratio changes between said first and second speed ratios;
said clutch and brake means including a friction brake adapted to anchor a reaction element of said gearing that is common to both of said speed ratios and a friction clutch adapted to connect two of said gearing elements together to effect said second speed ratio, said friction clutch being released and said friction brake being applied to effect a speed ratio downshift;
a fluid pressure operated brake servo means for applying and releasing said brake and a fluid pressure operated actuator for applying and releasing said clutch, said brake servo having a pressure actuated piston defining in part a brake apply pressure chamber and a brake release pressure chamber; and
means for regulating the rate of exhaust of pressure from said clutch actuator and from said brake release pressure chamber in response to changes in vehicle driveline operating variables thereby achieving smooth speed ratio changes.
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Accused Products
Abstract
An automatic transmission mechanism having multiple ratio gearing and clutch and brake elements operated by fluid pressure operated servos for changing speed ratio in the transmission and a controller for actuating and releasing the clutches and brakes in response to operating demands determined by sensed variables such as vehicle speed, engine torque, manual valve position, transmission turbine speed, and engine temperature, and means for achieving improved control of a synchronous downshift event by electronically regulating the exhaust pressure from an off-going friction element of the clutch and brake structure, thus controlling the torque-carrying capacity of that off-going element during the downshift interval.
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Citations
12 Claims
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1. An electronic control system for a multiple ratio automatic transmission for use in an automotive vehicle driveline having a throttle controlled internal combustion engine, said transmission having gearing elements defining a first speed ratio and a second speed ratio;
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fluid pressure actuated clutch and brake means for controlling the relative speeds of said gearing elements to effect speed ratio changes between said first and second speed ratios; said clutch and brake means including a friction brake adapted to anchor a reaction element of said gearing that is common to both of said speed ratios and a friction clutch adapted to connect two of said gearing elements together to effect said second speed ratio, said friction clutch being released and said friction brake being applied to effect a speed ratio downshift; a fluid pressure operated brake servo means for applying and releasing said brake and a fluid pressure operated actuator for applying and releasing said clutch, said brake servo having a pressure actuated piston defining in part a brake apply pressure chamber and a brake release pressure chamber; and means for regulating the rate of exhaust of pressure from said clutch actuator and from said brake release pressure chamber in response to changes in vehicle driveline operating variables thereby achieving smooth speed ratio changes. - View Dependent Claims (2, 3)
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4. An automatic power transmission mechanism comprising multiple ratio gearing elements adapted to establish plural torque flow paths between a throttle controlled engine and a driven shaft, said gearing elements being adapted to establish a first speed ratio and a second speed ratio, said second speed ratio being higher than said second speed ratio;
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fluid pressure actuated clutch means and brake means for controlling the relative speeds of said gearing elements to effect upshifts and downshifts between said first and second speed ratios; a hydraulic control system including a source of control pressure, a fluid pressure operated clutch actuator and a fluid pressure operated brake servo, said brake servo having a brake piston defining in part a servo apply pressure chamber and a servo release pressure chamber and a valve circuit connecting said pressure source to said clutch actuator and said brake servo; said valve circuit comprising shift valve means for connecting said source to said servo and said actuator, an electronic processor means responsive to operating variables of said transmission for shifting said shift valve means; a downshift timing valve means communicating with said clutch and said servo release pressure chamber, a solenoid operated control pressure valve means having a control signal output port communicating with said timing valve means for actuating the latter thereby controlling the rate of release of fluid pressure from said clutch actuator and said servo release pressure chamber during a downshift from said second speed ratio to said first speed ratio; said electronic processor including means for developing a control pressure signal adapted to act on said timing valve means, said processor being adapted to respond to control variables for said transmission for developing said control pressure signal whereby smoothness in a downshift is achieved for each set of operating conditions. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11)
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12. A method for controlling multiple ratio gearing elements in an automatic power transmission mechanism, said gearing elements being controlled by fluid pressure actuated clutch means and brake means to establish plural torque flow paths between a throttle controlled engine and a driven shaft, said torque flow paths defining a first speed ratio and a second speed ratio;
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controlling the relative speeds of said gearing elements to effect upshifts and downshifts between said first and second speed ratios; controlling the rate of release of fluid pressure from said clutch means and the application of said brake means upon a downshift from said second speed ratio to said first speed ratio in response to changes in operating variables of said transmission including engine throttle position changes and changes in the speed of said driven shaft; ramping down pressure of said clutch means following initiation of said downshift, the ratio of said ramping down being determined by percent of shift completion, terminating said ramping down of clutch pressure during the downshift interval and maintaining a lower steady clutch pressure thereafter during said downshift interval until completion of said downshift.
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Specification