Torque Control for Shift Shock in Variable-Speed Transmissions
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Solution Overview
Problem
Shift shocks occur in working machines like dumpers when operating with a torque-controlled internal combustion engine, particularly during gear changes, as the engine struggles to maintain constant torque, leading to immediate downshifts and unstable driving behavior.
Innovation Solution
The method involves controlling the internal combustion engine to adjust torque by the factor of the gear ratio change during shifts, ensuring consistent drive output torque, and incorporating torque converter management, along with limiting rotational speed and utilizing a retarder to regulate braking, all responsive to the accelerator pedal position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the internal combustion engine is operated in torque-controlled manner to maintain constant torque at fixed accelerator position, then the engine operates efficiently, but shift shock occurs during gear changes and the transmission becomes unstable with immediate downshifts
Solution Approach 1:
The control system anticipates the gear shift event and pre-adjusts the torque control strategy. Before the shift occurs, the system prepares to modify torque delivery characteristics, ensuring a smooth transition through the gear change without shock or instability. This preliminary adjustment prevents the immediate downshift problem by proactively managing torque during the transition period.
Solution Approach 2:
The system dynamically switches between torque-controlled and rotational-speed-controlled operation modes depending on the gear shift state. During normal operation, torque control maintains efficiency, but during gear shifts, the system transitions to rotational-speed control to prevent shift shock. This dynamic adaptation resolves the contradiction by allowing both efficient operation and stable shifting at different times.
2Use of energy by moving object
If the internal combustion engine is controlled to maintain constant torque during operation, then fuel efficiency improves, but during gear shifts the torque must be increased by the gear ratio change factor causing shift shock
Solution Approach 1:
The control system applies torque control periodically during stable gear operation to maintain fuel efficiency, but suspends or modifies this control during gear shift events. The system rhythmically switches between torque-controlled mode (for efficiency) and rotational-speed-controlled mode (to prevent shift shock), creating a periodic pattern of control strategy application that balances both requirements.
Solution Approach 2:
The system changes the control parameter from torque to rotational speed during gear shift events. By switching the controlled variable, the system can maintain fuel efficiency during normal operation while preventing shift shock during transitions. This parameter change allows the system to adapt to different operational requirements without compromising overall performance.
3Productivity
If the transmission shifts frequently to maintain optimal engine operation, then productivity increases, but driving comfort decreases due to shift shocks and unstable behavior
Solution Approach 1:
The control system continuously monitors gear shift events and engine operating conditions, using this feedback to adjust torque control strategies. When shift shock is detected or anticipated, the system modifies its behavior to prevent discomfort. This feedback mechanism allows frequent shifting for productivity while maintaining driving comfort by actively compensating for shift-related disturbances.
Solution Approach 2:
The control system acts as an intermediary between the torque-controlled engine and the transmission system. During gear shifts, it mediates the torque delivery to smooth out the transition and prevent shift shock. This intermediary control function allows frequent shifting to maintain productivity while protecting the driver from discomfort through active torque management during transition periods.
Data Source
AI summary
With a torque-controlled internal combustion engine and a variable-speed transmission having fixed shift gear ratios, during a shift, the internal combustion engine is controlled in such manner that the drive output torque of the transmission remains the same before and after the shift.