CVT Control Device for Sailing-Stop Engagement Shock Reduction
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Solution Overview
Problem
The existing sailing-stop control technology faces challenges in efficiently engaging the engagement element in the power transmission mechanism during cancellation, leading to potential engagement shocks and delayed engine rotation speed control, which affects fuel efficiency and response time.
Innovation Solution
A control device and method that includes a control unit to set a target engine rotation speed based on vehicle speed and variator speed ratio, and downshifts the variator before engaging the engagement element if the target speed is below a predetermined value, thereby shortening the engagement time and reducing engagement shocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the engagement element is engaged immediately after engine start, then the response time is improved, but the engagement shock becomes large due to large input/output rotation speed difference
Solution Approach 1:
The control device performs preliminary downshifting of the variator before engaging the engagement element. By reducing the variator speed ratio in advance, the system prepares the transmission system to accept the engagement with minimal speed difference, thereby reducing engagement shock while maintaining quick response capability.
Solution Approach 2:
The system dynamically adjusts the variator speed ratio based on real-time engine rotation speed and vehicle conditions. The control unit continuously monitors engine speed and modulates the variator to optimize the speed match between input and output shafts, enabling smooth engagement at any engine speed condition.
2Object-affected harmful factors
If the engagement element is engaged after engine rotation speed is controlled, then the engagement shock is reduced, but the time until engagement is extended
Solution Approach 1:
The control device performs preliminary downshifting of the variator before engagement is required. This advance preparation reduces the variator speed ratio so that when engagement occurs, the speed difference between input and output shafts is already minimized, enabling quick engagement without excessive shock.
Solution Approach 2:
The system changes the variator speed ratio parameter dynamically based on engine rotation speed. By adjusting this parameter in real-time, the system can achieve optimal engagement conditions rapidly, balancing the trade-off between engagement speed and shock reduction.
3Loss of time
If the variator is downshifted before engagement, then the target engine rotation speed is raised and engagement time is shortened, but the fuel efficiency during sailing-stop control is reduced
Solution Approach 1:
The variator is downshifted only when necessary, specifically when the target engine rotation speed would be below a predetermined threshold. This conditional preliminary action ensures that the system maintains fuel efficiency during normal sailing-stop control while still enabling rapid engagement when needed.
Solution Approach 2:
The control unit dynamically adjusts the variator speed ratio based on real-time engine rotation speed and vehicle conditions. By changing this parameter only when beneficial, the system optimizes the balance between engagement speed and fuel efficiency, avoiding unnecessary energy consumption.
Data Source
AI summary
A transmission controller gives an engagement instruction to a forward clutch so that the forward clutch is engaged when a rotation speed of the engine becomes a target engine rotation speed set on the basis at least of a vehicle speed and a speed ratio of a continuously variable transmission after the engine is started, if a cancellation request for a sailing-stop control is made during execution of the sailing-stop control, and the continuously variable transmission is downshifted before the forward clutch is engaged, if the target engine rotation speed when the cancellation request for the sailing-stop control is made is less than a first predetermined value.