CVT Control for Rapid Deceleration Startup
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Solution Overview
Problem
In continuously variable transmissions with a subtransmission mechanism, rapid deceleration can prevent the variator's speed ratio from returning to the Lowest speed ratio before the vehicle stops, leading to inadequate startup performance due to increased time required for speed ratio variation during coordinated shifts.
Innovation Solution
A control method and system that includes a rapid deceleration determining unit to halt coordinated shifts during rapid deceleration, allowing the variator to directly shift toward the Lowest speed ratio at maximum speed, ensuring the speed ratio is as close to the Lowest speed ratio as possible before the vehicle stops, thereby improving startup performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If coordinated shift is performed to maintain constant through speed ratio, then shift shock is suppressed, but the time required for variator speed ratio variation increases during rapid deceleration
Solution Approach 1:
The patent applies dynamics by making the shift control strategy adaptive based on vehicle operating conditions. The control unit dynamically switches between coordinated shift control (for normal conditions) and non-coordinated shift control (for rapid deceleration conditions), allowing the system to optimize performance based on real-time requirements rather than using a fixed control approach
Solution Approach 2:
The patent changes the control parameters by adjusting the relationship between subtransmission gear position changes and variator speed ratio changes. During rapid deceleration, the control unit modifies these parameters by reducing the variator's speed ratio variation amount compared to coordinated shift, enabling faster response to achieve Lowest speed ratio before vehicle stop
2Stability of the object's composition
If coordinated shift is performed during rapid deceleration, then through speed ratio remains constant, but the variator cannot reach Lowest speed ratio before vehicle stops
Solution Approach 1:
The control system dynamically adjusts its behavior based on deceleration detection. When rapid deceleration is detected, the system transitions from maintaining constant through speed ratio to prioritizing speed ratio variation speed, allowing the variator to reach Lowest speed ratio quickly despite the subtransmission downshift
Solution Approach 2:
During rapid deceleration, the patent applies the skipping principle by allowing the variator to rush through the speed ratio variation process more quickly. The control unit reduces the speed ratio variation amount of the variator during non-coordinated shift, enabling it to reach the Lowest speed ratio in less time than coordinated shift would allow
3Reliability
If variator speed ratio does not return to Lowest before vehicle stops, then startup driving force is insufficient, but achieving Lowest speed ratio during rapid deceleration conflicts with coordinated shift requirements
Solution Approach 1:
The patent applies skipping by implementing a simplified control mode during rapid deceleration. Instead of performing the complex coordinated shift sequence, the system rushes through the deceleration process with reduced variator speed ratio variation, ensuring the Lowest speed ratio is achieved quickly for reliable subsequent startup
Solution Approach 2:
The control unit changes operational parameters by detecting rapid deceleration conditions and switching from coordinated shift parameters to non-coordinated shift parameters. This parameter change simplifies the control logic during critical deceleration phases while maintaining reliability for startup performance
Data Source
AI summary
A continuously variable transmission includes a variator capable of varying a speed ratio continuously, and a subtransmission mechanism provided in series with the variator. When an actual through speed ratio passes a predetermined mode switch speed ratio, a transmission controller performs a coordinated shift in which a gear position of the subtransmission mechanism is changed and a speed ratio of the variator is varied in an opposite direction to a speed ratio variation direction of the subtransmission mechanism. When the rapid deceleration is determined to be underway, the transmission controller decreases a speed ratio variation amount of the variator in the direction of a High side accompanied by a downshift of the subtransmission mechanism compared with the coordinated shift.