CVT Shift Response via Adaptive Subtransmission Speed Control
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Solution Overview
Problem
The existing continuously variable transmission systems face challenges in responding to different shift response requirements due to the limited freedom in setting the time for coordinated shifts, primarily because the shift speed of the variator is lower than that of the subtransmission mechanism, making it difficult to maintain a constant through speed ratio during varying operating conditions.
Innovation Solution
A continuously variable transmission system that includes a belt type variator and a subtransmission mechanism with a shift control unit, a coordinated shifting unit, and a shift response improvement unit, which allows for adjusting the shift speed of the subtransmission mechanism and varying the speed ratio of the variator to improve shift response by increasing the shift speed when required, thereby reducing the time needed for coordinated shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the variator is shifted to maintain constant through speed ratio during coordinated shift, then the through speed ratio stability is improved, but the shift response time is increased due to the lower shift speed of the variator
Solution Approach 1:
The patent applies dynamics by making the shift control strategy adaptive to operating conditions. The control unit dynamically adjusts whether to prioritize through speed ratio stability or shift response time based on real-time vehicle operating conditions, transforming a static control approach into a dynamic one that can optimize for different scenarios.
Solution Approach 2:
The patent changes the control parameter from a fixed priority (always maintaining constant through speed ratio) to a variable priority that depends on operating conditions. By monitoring parameters such as vehicle speed, acceleration requests, and load conditions, the system adjusts the through speed ratio target accordingly, allowing faster shifts when conditions permit and smoother transitions when conditions require stability.
2Speed
If the shift speed of the subtransmission mechanism is increased to improve shift response, then the shift responsiveness is improved, but the heat generation and wear of frictional engagement elements increases
Solution Approach 1:
The patent implements dynamic adjustment of shift speed based on operating conditions. The control unit monitors vehicle state and dynamically determines the appropriate shift speed profile, allowing high-speed shifts when conditions are favorable (reducing overall heat generation through fewer shifts) and low-speed shifts when conditions require gentler operation.
Solution Approach 2:
The patent employs periodic monitoring of operating conditions to determine when high-speed shifting is appropriate. By continuously evaluating vehicle state parameters and adjusting shift strategy periodically, the system optimizes the balance between shift response and friction element wear over time.
Data Source
AI summary
The transmission controller changes the gear position of the subtransmission mechanism and varies the speed ratio of the variator in an opposite direction to a speed ratio variation direction of the subtransmission mechanism when the actual through speed ratio passes a predetermined mode switch line. When the improvement in the shift response of the continuously variable transmission is determined to be required and the actual through speed ratio passes the mode switch line from a Low side to the High side, the transmission controller increases a shift speed of the subtransmission mechanism compared with a normal coordinated shift.