CVT Shift Control for Slope Driving Force and Restart
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Solution Overview
Problem
Conventional continuously variable transmissions with auxiliary mechanisms struggle to ensure driving force and restart performance when a vehicle is on a slope road, leading to deteriorated drivability due to insufficient transmission ratios and delayed shifts.
Innovation Solution
A continuously variable transmission system comprising a variator and a stepwise auxiliary transmission mechanism, with a shift controller that calculates a desired target rotational speed and sets a through transmission ratio, prohibiting upshifts on slopes and coordinating shifts between the variator and auxiliary transmission to maintain consistent transmission ratios, ensuring adequate driving force and restart performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the auxiliary transmission mechanism is fixed to the low side transmission ratio to ensure driving force on slope roads, then the driving force is improved, but the variator transmission ratio becomes high side which causes insufficient driving force at restart
Solution Approach 1:
The patent applies dynamics by making the transmission ratio configuration adaptive rather than fixed. The control section dynamically adjusts the transmission ratio based on vehicle state (running vs. stopped), switching between low-side fixed configuration during operation for adequate driving force, and high-side fixed configuration at stop for adequate restart performance. This dynamic reconfiguration resolves the contradiction between ensuring driving force during operation and ensuring restart performance.
2Loss of time
If the vehicle stops on slope road with variator transmission ratio on high side, then the stopping time is reduced, but the driving force at restart becomes deficient
Solution Approach 1:
The patent applies preliminary action by proactively controlling the variator transmission ratio before the vehicle stops on a slope road. The control section detects slope conditions and pre-adjusts the transmission ratio to the low side before stopping occurs, ensuring that when the vehicle stops, the variator is already in the optimal position for restart. This preliminary adjustment prevents the problem of insufficient driving force at restart while maintaining adequate stopping time.
3Force
If upshift is prohibited on slope roads to ensure driving force, then the driving force is maintained, but the transmission ratio cannot be optimized for different running states
Solution Approach 1:
The patent applies dynamics by implementing conditional upshift prohibition rather than absolute prohibition. The control section monitors vehicle state and slope conditions, prohibiting upshift only when necessary to maintain driving force on slope roads, while permitting upshift when conditions allow. This dynamic control strategy maintains driving force when needed while preserving transmission ratio adaptability for different running states, resolving the contradiction between force maintenance and adaptability.
Data Source
AI summary
Continuously variable transmission includes: a variator; a stepwise auxiliary transmission mechanism; and a shift controller configured to set a desired through transmission ratio based on the calculated desired target rotational speed, the shift control section including; a slope road upshift prohibiting section configured to prohibit upshift of the auxiliary transmission mechanism when the vehicle runs on a slope road, and a slope road upshift section configured to upshift the auxiliary transmission mechanism when the vehicle runs in a predetermined running state when the slope road upshift prohibiting section prohibits upshift of the auxiliary transmission mechanism, and to perform the shift of the auxiliary transmission mechanism while the transmission ratio of the variator is varied in accordance with the variation of the transmission ratio of the auxiliary transmission mechanism to prevent varying the through transmission ratio even when the vehicle runs on the slope road.