CVT Sub-Transmission Control for Power-On Downshift Delay
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Solution Overview
Problem
In coordinated shifts of a continuously variable transmission, power-on downshifts caused by accelerator pedal depression lead to shift delays due to insufficient correction of the frictional engagement element capacity, especially in high vehicle speed regions where input torque is low, resulting in slower input rotation speed increases.
Innovation Solution
A control method that determines if a shift is a power-on downshift and, if so, adds a rotation speed change rate feedback correction to the rotation speed feedback correction to adjust the capacity of the frictional engagement elements, promoting the shift and reducing delay by enhancing the input rotation speed change rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rotation speed feedback control is used to correct frictional engagement element capacity, then shift shock is reduced, but input rotation speed increases slowly causing shift delay in power-on downshift
Solution Approach 1:
The control method dynamically adjusts the frictional engagement element capacity correction amount based on the actual input rotation speed increase rate. When the increase rate is lower than the target rate, the correction amount is increased to accelerate the shift process, making the control system adaptive to different shift conditions and resolving the contradiction between smooth shifting and fast response.
Solution Approach 2:
The invention implements a dual-feedback control mechanism that monitors both the input rotation speed and its increase rate. The feedback loop continuously compares actual values with target values and adjusts the frictional engagement element capacity accordingly, enabling the system to automatically compensate for slow speed increase and reduce shift delay while maintaining shock reduction.
2Measurement precision
If frictional engagement element capacity is corrected based on rotation speed deviation, then speed control precision is improved, but correction amount becomes too small in high vehicle speed regions
Solution Approach 1:
The invention changes the control parameter from static rotation speed deviation to dynamic rotation speed increase rate. By monitoring how fast the input rotation speed is increasing rather than just the absolute deviation, the system can detect when the shift is progressing too slowly and apply appropriate correction, effectively addressing the insufficient correction amount in high vehicle speed regions.
Solution Approach 2:
The control method transitions from static speed deviation-based correction to dynamic increase rate-based correction. This dynamic approach allows the system to respond to the actual pace of speed change and adjust the frictional engagement element capacity accordingly, ensuring adequate correction power across different vehicle speed regions.
3Reliability
If coordinated shift is performed with variator speed ratio change, then overall speed ratio change is reduced, but shift delay occurs when sub-transmission mechanism needs faster response
Solution Approach 1:
The invention dynamically adjusts the frictional engagement element capacity based on the actual input rotation speed increase rate during coordinated shift. When the increase rate falls below the target rate, the system applies additional correction to accelerate the sub-transmission mechanism response, enabling the coordinated shift to maintain both smoothness and responsiveness under different operating conditions.
Solution Approach 2:
The dual-feedback mechanism monitoring input rotation speed and its increase rate enables real-time adjustment of the frictional engagement element capacity. This feedback control ensures that the coordinated shift progresses at the desired pace by continuously correcting capacity deviations, thereby resolving the conflict between shift smoothness and response speed.
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 reduces shift delays in the sub-transmission mechanism during power-on downshifts by quickly increasing the input rotation speed, ensuring timely gear position changes and minimizing shift shock.
Implementation Method 1
a capacity of a release-side frictional engagement element or engage-side frictional engagement element of the sub-transmission mechanism may be corrected
Data Source
AI summary
A transmission controller determines whether or not an input rotation speed of a sub-transmission mechanism is stagnant and executes a feedback control by adding a rotation speed change rate feedback correction amount caused by a difference between a target input rotation speed change rate and an actual input rotation speed change rate of the sub-transmission mechanism to a rotation speed feedback correction amount if the input rotation speed is determined to be stagnant.