CVT Shift Control Device Hysteresis Kick-Down
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Solution Overview
Problem
Conventional continuously variable transmissions (CVTs) experience delayed torque response during gear shifting, leading to uncomfortable driving sensations due to torque being absorbed by pulley inertia, and may fail to initiate kick-down control if the accelerator pedal is depressed slowly.
Innovation Solution
A shift control device for CVTs that includes a detector for accelerator operation, a converter to convert continuous operation into a stepped operation, and a controller to manage gear ratios based on the stepped operation, implementing hysteresis and specific threshold-based control strategies for kick-down and upshift operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the accelerator pedal is depressed slowly, then the driver's intended acceleration is gradual, but kick-down control is not initiated even when the accelerator position and depression amount are sufficient
Solution Approach 1:
The system pre-calculates and stores multiple threshold values (first threshold, second threshold, third threshold) corresponding to different accelerator operation rates. When kick-down control is requested, the system proactively selects the appropriate threshold based on the detected operation rate, ensuring that kick-down control can be initiated reliably regardless of whether the accelerator is depressed quickly or slowly.
2Adaptability or versatility
If the gear ratio is controlled continuously based on accelerator position, then the transmission can adapt to driver intent, but torque is absorbed by pulley inertia during gear shifting causing delayed response
Solution Approach 1:
The control system segments the gear ratio control into discrete steps rather than continuous adjustment. By dividing the gear ratio changes into multiple predetermined steps, the system reduces the inertia burden on pulleys during each transition while maintaining overall adaptability to driver intent through multi-stage adjustment.
Solution Approach 2:
The system implements periodic gear ratio adjustments through multiple steps rather than a single continuous change. Each step allows the system to pause and stabilize before the next adjustment, reducing torque absorption by inertia and improving response speed while maintaining adaptability through the multi-step process.
Data Source
AI summary
A transmission control device includes a converter that converts continuous accelerator positions detected by an accelerator pedal sensor into a stepped step position, and a controller that controls the gear ratio of a continuously variable transmission based on the converted step position. The converter creates a hysteresis regarding the converted step position, when the accelerator depression amount increases, and when the accelerator depression amount decreases. In the case where the step position reaches a predetermined position or greater, the controller executes kick-down control where the gear ratio is controlled to a low side.