Toroidal CVT Control for Safe Reverse Shifting
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Solution Overview
Problem
Conventional automatic transmissions face challenges in safely and quickly decelerating and stopping a vehicle when the select lever is operated in a reverse direction to the vehicle's running direction, leading to potential sudden speed reductions, tire locking, engine stalling, and transmission damage.
Innovation Solution
A transmission control device for continuously variable transmissions, comprising a toroidal continuously variable transmission, a differential mechanism, and a clutch, which adjusts the speed ratio based on the vehicle's running state and throttle position, allowing the output shaft to switch between forward and reverse rotation while maintaining clutch engagement, thereby preventing sudden changes and allowing safe deceleration and stopping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the transmission ratio is adjusted to correspond to the select lever position when the select lever is operated in the reverse direction to the vehicle running direction, then the vehicle can run according to the select lever position, but sudden speed reduction, tire locking, engine stalling, and transmission damage occur
Solution Approach 1:
The control unit detects the vehicle running direction and select lever position in advance, and when a reverse operation is detected, it preliminarily adjusts the transmission ratio to a predetermined value (corresponding to neutral or high gear) before the clutch is fully engaged. This preliminary action prevents sudden speed reduction and transmission damage by preparing the transmission system for the direction change ahead of time.
Solution Approach 2:
The transmission ratio is dynamically adjusted based on the vehicle running state and select lever position. When the select lever is operated in the reverse direction, the transmission ratio is continuously changed from the current value to the predetermined value, rather than being abruptly switched. This dynamic adjustment smooths the transition and prevents sudden vehicle behavior changes.
2Reliability
If the select lever operation is restricted to prevent reverse direction operation, then transmission damage is prevented, but the vehicle cannot respond to intentional reverse operation needs
Solution Approach 1:
The control unit continuously monitors the vehicle running direction and select lever position, providing real-time feedback to detect when the select lever is operated in the reverse direction to the vehicle running direction. Based on this feedback, the control unit automatically adjusts the transmission ratio to the predetermined value, allowing the vehicle to respond to intentional reverse operation needs while protecting the transmission from damage.
3Speed
If the transmission ratio is quickly adjusted to the target value, then the vehicle responds quickly to select lever operation, but sudden vehicle behavior change and transmission damage occur
Solution Approach 1:
The transmission ratio is dynamically adjusted from the current value to the predetermined value corresponding to neutral or high gear when reverse direction operation is detected. This continuous adjustment process maintains vehicle stability while preventing sudden behavior changes, resolving the contradiction between quick response and transmission safety.
Data Source
AI summary
In a continuously variable transmission apparatus, by adjusting the transmission ratio of a toroidal continuously variable transmission, an output shaft can be stopped while an input shaft is left rotating in one direction by a drive source. And, when, while the vehicle is running, a select lever is operated to a select position in the reverse direction to the vehicle running direction, in a state where a clutch device is connected, the speed ratio of the continuously variable transmission apparatus is changed from a value corresponding to the vehicle running state to a value 0 capable of realizing the above-mentioned stopping state along a preset condition.