Clutch Torque Trajectory Correction for Automatic Transmission Upshifts
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Solution Overview
Problem
Conventional automatic transmissions experience unpleasant shift shocks due to the 'torque hole' effect during upshifts, where output torque momentarily drops and then rises, causing discomfort for vehicle occupants, due to simultaneous engagement and release of friction elements leading to transient torque disturbances.
Innovation Solution
A control strategy using powertrain sensors to provide real-time torque feedback, allowing for accurate calculation and modulation of friction element torques, ensuring seamless transitions by coordinating actuators to minimize torque disturbances and eliminate the torque hole effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If simultaneous engagement of oncoming clutch and release of off-going clutch is used during upshift, then gear ratio changing speed is improved, but output torque stability deteriorates causing torque hole effect
Solution Approach 1:
The system performs preliminary actions by pre-stroking the oncoming clutch actuator during the preparatory phase and pre-reducing off-going clutch torque capacity before the actual torque transfer begins. This ensures both clutches are ready for simultaneous engagement/release, enabling fast gear ratio change while maintaining torque stability through coordinated preliminary preparation of both friction elements.
Solution Approach 2:
The control system uses feedback from torque sensors and clutch position sensors to continuously monitor actual torque transfer and actuator positions during the upshift event. This feedback enables real-time adjustment of clutch actuation pressures to maintain stable output torque despite the simultaneous engagement and release of friction elements, preventing the torque hole effect.
2Speed
If off-going clutch torque capacity is reduced during preparatory phase, then upshift speed is improved, but torque control precision deteriorates causing transient torque disturbances
Solution Approach 1:
The system employs feedback control using torque sensors to monitor actual torque transfer during the preparatory phase when off-going clutch torque capacity is being reduced. This feedback enables precise adjustment of the torque reduction rate, ensuring fast upshift execution while maintaining accurate torque control and preventing transient torque disturbances that would otherwise occur during clutch capacity transitions.
Solution Approach 2:
The control system dynamically adjusts the off-going clutch torque capacity reduction profile based on real-time operating conditions. Rather than using a fixed reduction schedule, the system modulates the rate of torque capacity reduction to match actual torque transfer needs, enabling both fast upshift execution and precise torque control during the transitional preparatory phase.
3Reliability
If oncoming clutch torque is raised during torque phase, then gear ratio transition completeness is improved, but output torque stability worsens causing torque hole
Solution Approach 1:
The system merges the control of oncoming and off-going clutches into a coordinated unified control strategy. By simultaneously managing both clutch torque profiles with coupled control algorithms, the system ensures complete gear ratio transition through the oncoming clutch while the off-going clutch releases in a synchronized manner, preventing the torque hole effect that would result from independent clutch control.
Solution Approach 2:
During the torque phase, feedback from torque sensors enables real-time monitoring of the torque transfer as oncoming clutch torque is raised. This feedback allows the control system to adjust the torque raise profile to ensure complete gear ratio transition while maintaining stable output torque, preventing the torque hole effect through continuous correction based on actual torque measurements.
Data Source
AI summary
A control system and method for controlling a multiple gear ratio automatic transmission in a powertrain for an automatic transmission having pressure activated fiction torque elements to effect gear ratio upshifts. The friction torque elements are synchronously engaged and released during a torque phase of an upshift event as torque from a torque source is increased while allowing the off-going friction elements to slip, followed by an inertia phase during which torque from a torque source is modulated. A perceptible transmission output torque reduction during an upshift is avoided. Measured torque values are used during a torque phase of the upshift to correct an estimated oncoming friction element target torque so that transient torque disturbances at an oncoming clutch are avoided and torque transients at the output shaft are reduced.