CVT Shift Control for Accelerator Release and Steering Response
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Solution Overview
Problem
Existing shift control methods in continuously variable transmissions fail to accurately manage engine rotation speed when the accelerator is released, leading to potential mismatch between driver intention and vehicle performance, resulting in either excessive or insufficient power delivery during steering.
Innovation Solution
Implementing a multi-process shift control strategy that adjusts the speed ratio based on the accelerator opening speed and turbine rotation speed, including upshifts and fixing speed ratios to maintain optimal engine rotation speeds, thereby preventing engine rotation speed from becoming too high or too low for the driver's intention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the speed ratio is upshifted to a fixed speed ratio smaller than the immediately preceding speed ratio when deceleration intention is determined, then the engine rotation speed is decreased and deceleration G is controlled, but the engine rotation speed may become excessively low for subsequent steering by the driver
Solution Approach 1:
The patent applies dynamics by making the speed ratio change strategy adaptive rather than fixed. The control device dynamically selects between different upshift patterns (first pattern for steady traveling, second pattern for deceleration) based on real-time detection of driver intention through accelerator operation characteristics. This allows the engine rotation speed to be dynamically adjusted to match the driver's actual needs, preventing it from becoming excessively low when subsequent steering is required.
Solution Approach 2:
The patent changes the parameter of speed ratio adjustment strategy based on detected driver intention. When steady traveling intention is detected, a first upshift pattern is applied; when deceleration intention is detected, a second upshift pattern is applied. This parameter change in control strategy ensures that the engine rotation speed is maintained at an appropriate level for subsequent steering operations while still achieving deceleration control when needed.
2Speed
If the speed ratio is maintained at the immediately preceding speed ratio when accelerator is released, then the engine rotation speed is maintained, but deceleration G equal to or more than driver intention occurs due to insufficient engine brake reduction
Solution Approach 1:
The patent changes the speed ratio parameter based on detected driver intention. When deceleration intention is detected through accelerator release characteristics, the control device applies a second upshift pattern that upshifts to a fixed speed ratio smaller than the immediately preceding speed ratio. This parameter change in speed ratio enables the engine rotation speed to decrease appropriately, providing sufficient engine brake reduction to prevent excessive deceleration G while still responding to driver intent.
3Device complexity
If only two shift patterns are provided for accelerator release operations, then the control logic is simple, but the shift control may not match the driver's intention in all situations
Solution Approach 1:
The patent introduces a parameter-based differentiation in control strategy by detecting the rate of accelerator opening change. When the change rate exceeds a threshold, steady traveling intention is detected and the first upshift pattern is applied. When the change rate is below the threshold, deceleration intention is detected and the second upshift pattern is applied. This parameter-based approach enables the system to adapt to different driver intentions while maintaining relatively simple control logic based on a single detectable parameter.
Data Source
AI summary
A transmission used for executing, a process of performing, when a speed at which an accelerator opening is decreased is higher than a predetermined speed, an upshift until a predetermined opening is reached, and fixing a speed ratio, a process of performing, when the speed is equal to or lower than the predetermined speed and a turbine rotation speed is higher than a predetermined rotation speed, the upshift until the predetermined opening is reached, and performing, when the accelerator opening is smaller than the predetermined opening, the upshift so as to fix the speed ratio, and a process of performing, when the speed is equal to or lower than the predetermined speed and the turbine rotation speed is equal to or lower than the predetermined rotation speed, the upshift until the predetermined opening is reached, and performing, when the accelerator opening is smaller than the predetermined opening, the upshift.