CVT Sub-Transmission Downshift Control via Torque Rate
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Solution Overview
Problem
Existing continuously variable transmission systems experience shift shocks and reduced durability due to premature downshifting of the sub-transmission mechanism, particularly when the accelerator pedal is depressed at high speeds with low torque change rates, leading to a phenomenon known as draw-shock.
Innovation Solution
A transmission controller that determines whether to downshift the sub-transmission mechanism based on the accelerator pedal opening, its speed, and the torque change rate of the power source, preventing downshifts when the torque change rate is small to avoid draw-shock, thereby suppressing the occurrence of shift shocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the downshift of the sub-transmission mechanism is started when the accelerator pedal opening is larger than a predetermined opening, then the shift frequency decreases and durability is improved, but a draw-shock occurs when the torque change rate is small
Solution Approach 1:
The patent introduces a new control parameter (torque change rate) in addition to the existing accelerator pedal opening threshold. By monitoring both the accelerator pedal opening and the torque change rate, the system dynamically adjusts the downshift timing to avoid conditions that cause draw-shock while still preventing excessive shifting for durability.
Solution Approach 2:
The system continuously monitors the torque change rate as feedback from the power source and uses this information to determine whether to permit downshift. This feedback mechanism allows the control device to adapt to real-time engine conditions and prevent draw-shock by blocking downshifts when the torque change rate is insufficient.
2Speed
If the accelerator pedal is depressed at high speed after being depressed at low speed, then the opening speed increases, but shift shock occurs due to premature downshift when torque change rate is small
Solution Approach 1:
The patent adds torque change rate monitoring to the existing accelerator pedal opening control logic. This additional parameter allows the system to distinguish between legitimate high-speed pedal depression requiring downshift and cases where the engine cannot respond quickly enough, thereby preventing shift shock while maintaining responsive acceleration.
Data Source
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AI summary
A transmission controller determines whether or not to downshift a sub-transmission mechanism based on an opening and an opening speed of an accelerator pedal and a torque change rate of an engine, and downshifts the sub-transmission mechanism when a determination is made to downshift the sub-transmission mechanism.