Vehicle Control Device Torque Limiting During Coordinated Shifts
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Solution Overview
Problem
In continuously variable transmissions with sub-transmissions, rapid changes in input torque during coordinated shifts lead to engagement or disengagement delays of friction elements, causing engine rotation fluctuations and discomfort for the driver due to the inability of actual hydraulic pressure to catch up with target pressure.
Innovation Solution
A vehicle control device and method that limit or prohibit specific control actions during coordinated shifts to prevent rapid torque changes, ensuring the hydraulic pressure supplied to friction elements aligns with target pressures, thereby stabilizing engine rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If coordinated shift is performed by changing CVT speed ratio in opposite direction to sub-transmission speed ratio change, then shift shock is suppressed, but hydraulic pressure cannot catch up with target pressure during rapid torque changes causing engagement delay
Solution Approach 1:
The system performs preliminary detection of rapid torque change instructions before they fully manifest during coordinated shift. The control device detects when rapid torque change is instructed and proactively limits the torque change amount, preventing the hydraulic pressure catch-up problem before it occurs.
Solution Approach 2:
The control device dynamically changes the torque parameter by limiting the torque change amount during coordinated shift when rapid torque change is detected. This parameter modification ensures hydraulic pressure can track target pressure accurately while maintaining shift smoothness.
2Productivity
If specific control causing torque fluctuation is executed during coordinated shift, then engine performance control is achieved, but hydraulic pressure fluctuation causes engagement/disengagement delay
Solution Approach 1:
The control device applies partial action by selectively limiting torque change only during coordinated shift when rapid torque change is detected, rather than continuously. This allows engine performance control to function normally outside of coordinated shift while preventing response delays during the critical shift period.
Solution Approach 2:
The system applies preliminary anti-action by detecting the instruction for specific control and preemptively limiting torque change before it can cause harmful hydraulic pressure fluctuations. This prevents engagement/disengagement delay while allowing engine performance control to resume after shift completion.
3Measurement precision
If hydraulic pressure is controlled based on rapidly changing input torque, then torque tracking is improved, but actual pressure cannot reach target pressure causing engine rotation fluctuation
Solution Approach 1:
The control device modifies the torque parameter by limiting the torque change amount during coordinated shift when rapid change is detected. This parameter change ensures that target hydraulic pressure changes remain within achievable limits, allowing actual pressure to track target pressure accurately and maintain engine rotation stability.
Data Source
AI summary
A vehicle control device has a controller configured to control a hydraulic pressure required for shifting of a sub-transmission based on an input torque to the sub-transmission during the coordinated shift, and to execute limitation processing in which, when an instruction to execute specific control causing fluctuation in the input torque to the sub-transmission during the coordinated shift is issued, execution of the specific control is prohibited or the specific control is executed by limiting a control amount.