Hybrid Transmission Clutch Support to Prevent Uphill Rollback
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Solution Overview
Problem
In hybrid electric vehicles, the disengagement of the ILE clutch during brake pedal application and subsequent release can lead to vehicle rollback on uphill grades, due to the delay in re-engaging the clutch and providing idle creep torque.
Innovation Solution
Implementing a transmission clutch support mode that includes an extended brake hold and simultaneous engagement of the ILE clutch, ensuring concurrent blend-out of brake torque and blend-in of motor torque, thereby preventing vehicle rollback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the ILE clutch is disengaged during brake pedal application and re-engaged after release, then the hybrid powertrain can operate independently from the driveline, but vehicle rollback occurs on uphill grades due to delay in re-engaging the clutch
Solution Approach 1:
The clutch is re-engaged before the brake pedal is fully released, performing the engagement action in advance to ensure the powertrain is connected to the driveline before brake torque is removed. This preliminary engagement prevents the gap that causes rollback on uphill grades.
Solution Approach 2:
The system applies counter-action by maintaining brake hold momentarily after clutch engagement begins, preventing the vehicle from rolling back during the transition period. The brake torque is held constant or increased slightly to counteract gravity on uphill grades until the clutch is fully engaged and motor torque can support the vehicle.
2Speed
If the clutch is re-engaged quickly after brake release, then the vehicle can resume motion faster, but torque transition becomes abrupt causing vehicle behavior issues
Solution Approach 1:
The clutch engagement process is made dynamic and adaptive rather than fixed. The engagement speed and torque transfer are adjusted in real-time based on vehicle conditions, particularly uphill grade detection. The system transitions from disengaged to engaged state with variable rates, ensuring smooth torque transfer that prevents abrupt vehicle behavior while maintaining adequate engagement speed.
Data Source
AI summary
A vehicle system for a hybrid electric vehicle that implements a transmission clutch support mode during a stop of the vehicle includes a hybrid powertrain, a brake system, a clutch and a controller. The hybrid powertrain includes an internal combustion engine and an electric motor that provides motor torque to a driveline for propelling the vehicle. The brake system selectively provides brake torque to drive wheels based on application of a brake pedal. The clutch opens and closes to engage the powertrain with the driveline. The controller initiates clutch support mode and determines whether a brake pedal release has been detected; commands a brake hold that maintains brake pressure of the brake system subsequent to detection of the brake pedal release; and commands the clutch to move to an engaged position while cancelling the brake hold resulting in concurrent blend-out of the brake torque and blend-in of the motor torque.