CVT Control Device for Driving Force Gap Reduction
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Solution Overview
Problem
In continuously variable transmissions (CVTs) with auxiliary transmissions, a driving force gap or acceleration gap (G-drop) occurs during up-shifting, leading to a sluggish feeling for the driver, particularly when accelerating from low speeds, due to the interstage ratio between the first and second speed stages of the auxiliary transmission mechanism, making it difficult to eliminate or minimize this gap without significant hardware or control logic changes.
Innovation Solution
A control device for CVTs that implements a coordinated speed change mechanism and torque regulating control, where the speed change of the auxiliary transmission mechanism is synchronized with the continuously variable transmission, and torque control is applied to advance the start and delay the end of the drive force gap, thereby smoothing the drive force transition between speed stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coordinated speed change is carried out in the auxiliary transmission mechanism, then shift shock is reduced, but a driving force gap (G-drop) is produced during up-shifting
Solution Approach 1:
The control device initiates torque regulation before the driving force gap fully develops. By detecting the phase transition from torque phase to inertia phase, the system applies preliminary torque adjustment to prevent the gap from becoming pronounced, thereby maintaining drive force continuity while preserving the shift shock reduction benefits of coordinated speed change
Solution Approach 2:
The control device continuously monitors the operating phase of the auxiliary transmission mechanism and adjusts engine torque based on feedback from phase detection. When transitioning from torque phase to inertia phase, the system increases torque to compensate for the emerging driving force gap, creating a closed-loop control that eliminates G-drop while maintaining coordinated speed change operation
2Loss of energy
If the speed change stage is shifted from 1st speed to 2nd speed in the torque phase, then the auxiliary transmission mechanism operates at higher efficiency, but the vehicle driving force is lowered
Solution Approach 1:
The control device dynamically adjusts the engine torque parameter in response to auxiliary transmission phase changes. When the system transitions to the inertia phase after up-shifting, torque is increased to compensate for the driving force reduction, allowing the transmission to operate at higher efficiency ratios while maintaining adequate vehicle propulsion force through parameter modulation
3Force
If the speed change ratio of the variator is shifted from High-side to Low-side in the inertia phase, then the vehicle driving force is restored, but the driving force gap becomes more pronounced
Solution Approach 1:
The control device applies preliminary anti-action by increasing torque before the variator speed change ratio shift completes. This preemptive torque increase counteracts the emerging driving force gap that would result from the High-side to Low-side variator transition, allowing driving force restoration while preventing G-drop through advance compensation
Data Source
AI summary
Disclosed is a control device for a continuously variable transmission (4) that has, as forward speed change stages, a first speed change stage (32) and a second speed change stage (33). The control device comprises a coordinated speed change means (12a) that carries out a coordinated speed changing in such a manner that when the speed change stage of an auxiliary transmission mechanism (30) is about to be changed, a speed change speed of the auxiliary transmission mechanism (30) is coordinated with a variator (20) and the variator (20) is controlled to carry out a speed change in a direction opposite to that of the auxiliary transmission mechanism (30) while carrying out the speed change operation of the auxiliary transmission mechanism (30), and a torque control means (12b) that carries out a torque regulating control during the coordinated speed changing under up-shifting by the coordinated speed change means, the torque regulating control being a control for effecting a torque-up operation to a driving source (1) after effecting a torque-down operation to the driving source and including a timing through which a starting time point of a drive force gap caused by the coordinated speed changing is advanced and a timing through which an ending time point of the drive force gap is delayed.