Gear Shift Control for Continuously Variable Transmission
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Solution Overview
Problem
In vehicular transmissions with a variator and sub transmission, the 2-1 speed gear-shift during deceleration can result in insufficient driving force when starting from a stopped state, due to the avoidance of gear-shift shocks and variator up-shifting, leading to incomplete gear ratio changes during short stop durations.
Innovation Solution
A gear-shift control apparatus and method that initiates a down-shift from the 2nd speed gear stage to a higher gear stage while maintaining the variator at the lowest gear ratio during deceleration, ensuring the sub transmission is in a lower gear stage by the time the vehicle stops, thereby improving driving force response upon starting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the sub transmission performs 2-1 speed gear-shift during deceleration to avoid gear-shift shocks, then the shock is avoided, but the driving force becomes insufficient when starting from stopped state
Solution Approach 1:
The control device initiates the down-shift operation of the sub transmission before the vehicle comes to a complete stop. By predicting the stop timing based on current deceleration state, the system performs the gear-shift in advance so that the sub transmission is already in the lower gear stage (1st speed) when the vehicle stops, ensuring driving force availability without causing shock during the stop itself
2Stability of the object's composition
If the gear-shift is delayed until the vehicle is determined to be stopped, then the variator can be maintained at lowest gear ratio, but the sub transmission remains in 2nd speed causing insufficient driving force
Solution Approach 1:
Instead of waiting for the vehicle to be determined as stopped before initiating gear-shift, the control device performs preliminary action by starting the down-shift based on current deceleration detection. This ensures the sub transmission gear-shift is completed or substantially completed before the vehicle stops, while the variator is already maintained at lowest gear ratio, thus resolving both requirements
3Power
If the sub transmission is forced to perform 2-1 speed gear-shift on vehicle start request, then driving force is improved, but the gear-shift causes shock and delays driving force availability
Solution Approach 1:
The control device performs the down-shift operation in advance during deceleration, so that when the vehicle stop is detected or start is requested, the sub transmission is already in the 1st speed gear stage. This preliminary action eliminates the need for forced gear-shift at start request, providing immediate driving force without shock or delay
Data Source
AI summary
In gear-shift control apparatus and method for a vehicular transmission, a variator which is interposed between an engine and driving wheels and which is capable of modifying a gear (speed) ratio continuously; a sub transmission which is installed in series with the variator and which is capable of switching a plurality of gear-shift stages through a replacement of engagement elements; and a transmission controller which performs a gear ratio control for the variator and a gear-shift stage control for the sub transmission are installed. During a deceleration through a second speed stage of the sub transmission, when the variator is a state in which the variator is at a lowest gear (speed) ratio, a down-shift in which the sub transmission is forced to perform the gear-shift from a second speed stage to a first speed stage, with the variator maintained at the lowest gear (speed) ratio.