CVT Shift Control for Manual Mode Responsiveness
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Solution Overview
Problem
In continuously variable transmissions with both a variator and a sub-transmission mechanism, the difference in shift responsiveness between the variator and sub-transmission mechanism creates a sense of incongruity for the driver, particularly in manual mode where quicker shifts are intended.
Innovation Solution
A shift control system that sets a final through speed ratio as a target based on driving conditions, using a combination of variator and sub-transmission mechanism speed ratios to achieve this ratio in a specified response, prioritizing variator changes in manual mode to align with driver intentions and accelerate sub-transmission changes when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the sub-transmission mechanism is shifted to change speed ratio, then the speed ratio can be changed, but the hydraulic control preparation time causes slower shift responsiveness compared to the variator
Solution Approach 1:
The system performs preliminary actions by having the variator start changing the speed ratio immediately in response to a shift instruction, before the sub-transmission mechanism is ready. This preliminary speed ratio change by the variator ensures that the overall transmission speed ratio can still follow the target ratio quickly, compensating for the delayed sub-transmission response.
2Speed
If the variator speed ratio is changed quickly to achieve driver's intention, then shift responsiveness is improved, but the difference in shift responsiveness between variator and sub-transmission mechanism creates a sense of incongruity
Solution Approach 1:
The system merges the speed ratio changes of the variator and sub-transmission mechanism by coordinating their actions. The control unit calculates a target overall speed ratio and controls both components to work together, ensuring that their combined effect produces a consistent and congruent shifting sensation for the driver, even though they operate at different speeds.
Solution Approach 2:
The control unit acts as an intermediary that coordinates between the variator and sub-transmission mechanism. It calculates the target overall speed ratio and manages the timing and magnitude of speed ratio changes for each component, ensuring they work together harmoniously to eliminate the sense of incongruity.
3Use of energy by moving object
If the sub-transmission mechanism is used to enlarge the ratio range, then fuel economy is improved, but the difference in shift responsiveness creates a sense of incongruity in manual mode
Solution Approach 1:
The system dynamically adjusts the control strategy based on the operating mode. In manual mode, when the variator reaches its speed ratio limits, the control unit dynamically switches to using the sub-transmission mechanism for further speed ratio changes, ensuring that the overall transmission can still respond to driver intentions while maintaining fuel efficiency through the sub-transmission's gear ratios.
Data Source
AI summary
The shift control unit executes a control to cause the through speed ratio to follow the final through speed ratio by changing only the speed ratio of the variator if a shift instruction is given from the driver a plurality of times in a row when the manual mode is selected, and advances the start of a change in the speed ratio of the sub-transmission mechanism or accelerates the progression of the change of the speed ratio as compared with the case where the manual mode is not selected when the speed ratio of the variator is maximized or minimized and the through speed ratio cannot follow the final through speed ratio.