CVT Subtransmission Control for Power-Off Upshift Drivability
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Solution Overview
Problem
Conventional control devices for vehicle continuously variable transmissions experience hydraulic response delays during upshifts with negative torque input, leading to reduced drivability due to the subtransmission mechanism's disengagement side frictional engagement element's delayed response.
Innovation Solution
A control method and device that adjusts the engagement capacity of frictional engagement elements in the subtransmission mechanism to complete inertia phase processing before reaching the target rotation speed, and initiates torque phase processing earlier, while modifying the continuously variable transmission's speed ratio from low to high after the inertia phase starts, to minimize the substantial change in the overall speed ratio during gear position changes from the first to the second gear position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the gear position of the subtransmission mechanism is upshifted while torque input is negative torque, then the gear position changes from first to second gear position, but hydraulic response delay occurs in the disengagement side frictional engagement element
Solution Approach 1:
The control device completes the inertia phase processing instruction before the input rotation speed actually reaches the target rotation speed of the second gear position. This preliminary action anticipates the hydraulic response delay, ensuring that the disengagement side frictional engagement element has sufficient time to respond and disengage properly, thereby preventing shift shock and improving drivability during power-off upshifts with negative torque input
2Object-affected harmful factors
If the inertia phase processing is completed before the target rotation speed is reached, then the shift shock is reduced, but the control complexity increases
Solution Approach 1:
The control device uses feedback control during the inertia phase to adjust the engagement capacity of the frictional engagement elements based on the actual input rotation speed and its rate of change. By monitoring the rotation speed and comparing it with the target trajectory, the system dynamically adjusts hydraulic pressure to achieve the desired shift characteristics while accounting for hydraulic response delays, thereby reducing shift shock through closed-loop control
3Stability of the object's composition
If the speed ratio of the continuously variable transmission mechanism is modified from small to large after torque phase processing starts, then the substantial change in overall speed ratio is decreased, but the control coordination complexity increases
Solution Approach 1:
The control device merges the speed ratio modification of the continuously variable transmission mechanism with the gear position change of the subtransmission mechanism. By coordinating these two mechanisms, the overall speed ratio change is minimized during the shift transition, reducing the perceptible impact on the driver while managing the complexity through integrated control logic
Data Source
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AI summary
A control device for a vehicle continuously variable transmission 4 comprises: inertia phase processing completing means for completing an instruction relating to inertia phase processing before an input rotation speed of the subtransmission mechanism 30 actually reaches an input rotation speed of the second gear position ; and torque phase processing starting means for starting an instruction relating to torque phase processing, in which reception of an input torque of the subtransmission mechanism 30 is shifted from a disengagement side frictional engagement element to an engagement side frictional engagement element before the input rotation speed of the subtransmission mechanism 30 actually reaches the input rotation speed of the second gear position, after completing the instruction relating to the inertia phase processing.