Driveline Gear Shifting Torque Disturbance Control
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Solution Overview
Problem
Existing methods for shifting gear ranges in four-wheel drive electric vehicles often result in driveline torque disturbances due to gear lash, which can be noticeable as clunking sounds and speed changes, especially when transitioning from low to high gear ranges while the vehicle is moving.
Innovation Solution
The method involves ramping down the torque of an electric machine to a threshold positive torque, then adjusting it to a negative torque to control the slip speed of the high gear range clutch, engaging the synchronizer when slip is near zero, and closing the clutch to smoothly transition from low to high gear ranges without stopping the vehicle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the vehicle stops to shift from low gear range to high gear range, then gear teeth impact is reduced, but vehicle productivity and driver convenience deteriorate
Solution Approach 1:
The system performs preliminary actions by ramping down torque to threshold positive torque before the actual gear engagement, and adjusting to negative torque to control slip speed before clutch closing. This preparatory torque management prevents gear teeth impact while enabling seamless shifting without vehicle stoppage.
Solution Approach 2:
The system changes torque parameters dynamically during the shifting process - first ramping down to threshold positive torque, then adjusting to negative torque for slip control, and finally increasing after clutch closing. These parameter changes enable smooth gear transition without impact or vehicle stoppage.
2Object-affected harmful factors
If torque is ramped down to threshold positive torque before shifting, then gear teeth impact is reduced, but shifting time increases
Solution Approach 1:
The system maintains continuous useful action by keeping the vehicle moving throughout the shifting process. The torque ramping down to threshold positive torque and subsequent negative torque adjustment are performed continuously without interrupting vehicle motion, eliminating idle stopping time while preventing gear impact.
Solution Approach 2:
The preliminary torque reduction to threshold positive torque is performed rapidly and continuously, preparing the gear system for smooth engagement without creating idle time. This preliminary action sets the stage for immediate subsequent negative torque adjustment and clutch engagement.
3Reliability
If negative torque is applied to control clutch slip speed, then clutch wear is reduced, but torque transfer complexity increases
Solution Approach 1:
The system uses feedback control by monitoring clutch slip speed and adjusting negative torque accordingly. The negative torque is applied specifically to control slip speed during the transition, and this feedback mechanism reduces clutch wear while managing the complexity through automated control.
Solution Approach 2:
The system replaces purely mechanical clutch engagement with electrically controlled torque management. The electric machine's torque can be precisely adjusted to negative values for slip control, substituting mechanical wear-prone engagement with controllable electrical torque management.
Data Source
AI summary
Methods and system are described for changing a driveline gear range from a lower gear range to a higher gear range. The driveline may include two electric machines and four clutches in a four wheel drive configuration. The methods and systems permit a driveline to change from a lower gear range to a higher gear range in a way that may reduce torque disturbances that may result from gear lash.