Offgoing Clutch Pressure Control for Negative Torque Upshifts
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Solution Overview
Problem
In clutch-to-clutch transmissions, existing systems face challenges in efficiently managing gear shifts when engine torque is negative, particularly during regenerative braking, as they often prioritize engaging the oncoming clutch over disengaging the offgoing clutch, leading to suboptimal transmission input speed synchronization.
Innovation Solution
A clutch control system that includes a shift command module and an offgoing clutch control module, which commands an upshift by increasing the offgoing clutch pressure above a predetermined apply pressure when engine torque is negative, ensuring the offgoing clutch is fully engaged, and controls the disengagement of the offgoing clutch to achieve more desirable characteristics during negative torque conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the system prioritizes engaging the oncoming clutch during negative torque conditions, then the oncoming clutch engagement speed is improved, but the transmission input speed synchronization deteriorates
Solution Approach 1:
The patent inverts the conventional priority by prioritizing offgoing clutch disengagement over oncoming clutch engagement during negative torque conditions. Instead of engaging the oncoming clutch first as in traditional systems, the control module increases offgoing clutch pressure above apply pressure to ensure complete disengagement before initiating oncoming clutch engagement, thereby achieving better transmission input speed synchronization.
2Reliability
If the offgoing clutch pressure is increased above apply pressure during negative torque upshift, then the transmission input speed synchronization is improved, but the clutch control complexity increases
Solution Approach 1:
The patent changes the pressure parameter of the offgoing clutch from the standard apply pressure to a higher pressure level during negative torque conditions. By increasing offgoing clutch pressure above apply pressure, the system ensures complete disengagement and improves transmission input speed synchronization. This parameter change is implemented through conditional logic in the control module that detects negative torque conditions and adjusts pressure accordingly.
Data Source
AI summary
A clutch control system for a vehicle includes a shift command module and an offgoing clutch control module. The shift command module commands an upshift of a clutch-to-clutch transmission when an engine torque is less than a predetermined negative torque. The offgoing clutch control module increases an offgoing clutch pressure above a predetermined apply pressure in response to the command. An offgoing clutch is fully engaged when the offgoing clutch pressure is greater than the predetermined apply pressure.