Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Clutch control
Reexamination Certificate
1999-08-04
2001-06-26
Louis-Jacques, Jacques H. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Clutch control
C701S068000, C192S003300, C192S003310, C477S070000, C477S083000, C477S171000
Reexamination Certificate
active
06253140
ABSTRACT:
BACKGROUND OF THE INVENTION
Automatic transmissions used in automotive vehicles may include a hydraulic pressure control system for controlling the application of friction clutches and brakes to accomplish gear ratio changes and to effect startup from a standing start in either forward drive or reverse drive. A clutch is used during vehicle startup to establish a torque flow path between an engine-driven turbine of a hydrokinetic torque converter and the torque input gear element of the transmission. The clutch, however, does not include a mechanism for compensating for normal wear of the clutch nor for changes in driveline variables such as temperature changes and engine calibration tolerances. The transmission, furthermore, is not typically calibrated to satisfy the requirements of different drivers with varying driver habits. A smooth clutch engagement for one driver might not occur with a second driver with different driving habits.
Variations, over time, in quality of the clutch engagement may occur also due to normal wear of the valve elements and changes in the characteristics of springs that are used to control valve movements.
Examples of known automatic transmissions that employ startup clutches for multiple-ratio gearing may be seen by referring to U.S. Pat. Nos. 4,527,678, 5,150,297 and 5,157,608, which are assigned to the assignee of this invention. The disclosures of these patents are incorporated in the present disclosure by reference.
BRIEF DESCRIPTION OF THE INVENTION
The invention comprises an adaptive control system for providing consistent, smooth engagement of a forward or reverse clutch in a multiple-ratio transmission during vehicle startup. It includes a closed-loop and adaptive strategy that provides for fast engagement of the clutch while maintaining consistent engagement quality. The closed-loop and adaptive strategy takes into account changes in the system dynamics of the transmission throughout the life of the transmission and also eliminates variations in the dynamic characteristics when the same transmission is used with any of a variety of engines in an automotive vehicle driveline.
Engagement quality is maintained at a consistent level by adapting the initial clutch pressure commanded at the beginning of the torque phase of the engagement cycle. This is based on a linearly extrapolated slip change time and the time from the start of engagement to the start of the slip change mode.
Adaptive pressure values are stored in a microprocessor keep-alive memory (KAM) for each engagement. The engagement parameters are adjusted based on the results of previous engagements. In this way, system variations caused, for example, by changes in coefficient of friction, spring loads, clutch wear, etc., are accommodated. Engagement strategy will provide for a reduced stroke and a reduced torque transfer time while maintaining actual slip rate changes to values approximately equal to the desired slip rate change.
During an engagement, two control elements are required (i.e., the control elements could be a friction clutch and a friction brake or a friction clutch and an overrunning brake). One control element, which may be a clutch or a brake, is applied in advance of the engagement cycle. The other control element, which is the oncoming friction element, responds to pressure controlled in a closed-loop fashion to achieve a controlled slip rate. A torque feed-forward technique is used to improve the response to changes in transmission input torque. When the engagement of the clutch is near completion, a shaping function is used to reduce the desired slip rate to effect a smooth termination of the slip change mode.
The system includes a digital microprocessor that receives and stores input signals from sensors and executes the transmission control logic output of the microprocessor during successive control loops. The logic uses sensor input developed in real time for conditioning control valve solenoid actuators that enable engagement of the friction elements. Sensors monitor the engine torque, the turbine speed, the output shaft speed, the throttle position and the transmission range selection, among other variables. The solenoid signals, during each control loop, calculated by the microprocessor for the oncoming clutch, are based upon the clutch control logic and the parameters calculated during preceding control loops.
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Jain Pramod Kumar
Kuhn Howard Cecil
Vodicka Ronald James
Ford Global Technologies Inc.
Louis-Jacques Jacques H.
McKenzie Frank G.
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