Transmission Control for Smooth Upshifts
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Solution Overview
Problem
Existing continuously variable transmissions experience discomfort to drivers during stepped shifting due to incomplete upshifts and rapid changes in speed ratio, especially when the variator reaches its highest speed ratio, leading to an unsatisfactory acceleration feel.
Innovation Solution
A transmission system with a variator and a stepped transmission mechanism, where the gear position of the auxiliary transmission mechanism is switched from the n-th to the n+1 position before the through speed ratio reaches the highest speed ratio of the variator, allowing for smoother upshifts and maintaining a high speed ratio on the high side, thereby preventing discomfort to the driver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the gear position of the auxiliary transmission mechanism is fixed at the n-th gear position, then the structure is simple, but the variator cannot perform upshifting when the speed ratio reaches the Highest, resulting in insufficient upshift amount and driver discomfort
Solution Approach 1:
The patent applies dynamics by making the gear position of the auxiliary transmission mechanism changeable rather than fixed. The control unit switches the gear position from the n-th gear position to the n+1 gear position based on the speed ratio of the variator, enabling the system to adapt dynamically to different operating conditions and achieve sufficient upshift amount throughout the entire speed ratio range.
2Productivity
If the gear position is switched from the n-th gear position to the n+1 gear position when the speed ratio reaches the Highest, then the upshift amount is sufficient, but the upshift and gear switching occur simultaneously causing rapid change rate of through speed ratio and driver discomfort
Solution Approach 1:
The patent applies preliminary action by switching the gear position of the auxiliary transmission mechanism before the speed ratio of the variator reaches the Highest, rather than at the moment it reaches the Highest. This advance switching ensures that the upshift amount is sufficient while avoiding simultaneous occurrence of upshift and gear switching, thereby preventing rapid changes in through speed ratio and maintaining driver comfort.
3Ease of operation
If the start timing of the inertia phase is delayed, then the gear position switching occurs after the upshift to the Highest, but the upshift is made in two stages in a short period causing driver discomfort
Solution Approach 1:
The patent applies feedback by having the control unit continuously monitor the speed ratio of the variator and switch the gear position of the auxiliary transmission mechanism based on this feedback. The control unit switches the gear position when the speed ratio is determined to be less than the Highest, ensuring optimal timing that avoids two-stage upshifts and maintains smooth acceleration while preventing driver discomfort.
Data Source
AI summary
A transmission including a variator capable of continuously changing a speed ratio, a stepped transmission mechanism arranged in series with the variator and in which a gear position is switched and a shilling control unit executing stepped shifting repeatedly performing a shifting suppression phase and an upshift phase when a stepped upshift shifting condition is satisfied is provided, and the shifting control unit completes a change from an n-th gear position of the stepped transmission mechanism to an n+1 gear position if the stepped transmission mechanism is at the n-th gear position before the through speed ratio reaches a Highest speed ratio of the variator when the stepped shifting is performed.