CVT Coordinated Shift Torque Control for Dragging Feel
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Solution Overview
Problem
During downshifting in manual mode, the continuously variable transmission with a sub-transmission mechanism experiences a dragging feeling due to delayed deceleration G generation and rotation speed difference absorption by the sub-transmission mechanism's frictional engagement element, causing discomfort to the driver.
Innovation Solution
The system includes a variator capable of continuously changing speed ratios and a stepped sub-transmission mechanism, with target value setting and shift control means to maintain the through speed ratio during downshifting, and torque increasing means to enhance torque input from the power source during coordinated shifts, thereby suppressing unintended deceleration G generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sub-transmission mechanism is shifted successively in torque phase and inertia phase during coasting, then the rotation speed difference is absorbed by frictional engagement element, but the deceleration G generation is delayed causing dragging feeling
Solution Approach 1:
The control device performs preliminary action by advancing the torque phase of the sub-transmission mechanism shift before the inertia phase. Specifically, when a downshift instruction is detected during coasting, the control device controls the variator to maintain through speed ratio and immediately controls the sub-transmission mechanism to perform torque phase shift, thereby generating deceleration G in advance and suppressing the dragging feeling that would otherwise occur during the subsequent inertia phase shift.
2Speed
If the variator speed ratio is changed to high side while sub-transmission mechanism gear position is changed to low side, then the through speed ratio is maintained, but the secondary rotation speed of variator increases causing frictional engagement element to absorb rotation speed difference
Solution Approach 1:
The control device applies preliminary anti-action by detecting when the sub-transmission mechanism will absorb rotation speed difference and generate unwanted deceleration G. In response, the control device increases engine torque output in advance to counteract the harmful deceleration G that would be generated by the frictional engagement element during the coordinated shift, thereby eliminating the dragging feeling without compromising the through speed ratio stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively suppresses the generation of deceleration G and dragging feelings by increasing torque input during coordinated shifts, ensuring smoother transitions and improved driver comfort during downshifting in manual mode.
Implementation Method 1
an engaging-side frictional engagement element of the sub-transmission mechanism is gradually engaged while absorbing a rotation speed difference before and after the coordinated shift, whereby a torque is transferred before and after the shift
Data Source
AI summary
A continuously variable transmission includes a variator, a sub-transmission mechanism, target value setting means configured to set a speed ratio corresponding to a select gear position as a target value of a through speed ratio which is an overall speed ratio of the variator and the sub-transmission mechanism, shift control means configured to perform a variator shift of downshifting the variator so that the through speed ratio reaches the target value and a coordinated shift of upshifting the variator to maintain the through speed ratio while downshifting the sub-transmission mechanism immediately after the variator is downshifted, and torque increasing means configured to increase a torque input to the continuously variable transmission from the power source more than a torque before the determination of the downshift instruction during the coordinated shift.