Disconnect Clutch Power Allocation for EV Dual Drive Units
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Solution Overview
Problem
Four-wheel drive electric vehicles experience reduced efficiency and range anxiety due to the need for simultaneous power delivery to all wheels, which can deplete the battery quickly, especially when engaging the driveline disconnect clutch.
Innovation Solution
A method for adjusting the power delivery to a main drive unit (MDU) and a secondary drive unit (SDU) in response to a request to close a disconnect clutch and the available power from a traction battery, ensuring timely disconnect clutch closing and managing electric power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If four-wheel drive system operates continuously, then vehicle traction and stability are improved, but energy consumption increases and range is reduced
Solution Approach 1:
The system performs preliminary speed synchronization of the uncoupled electric machine before closing the disconnect clutch. By pre-synchronizing the rotational speed of the uncoupled electric machine to match the driveline speed, the system ensures that when the clutch closes, there is minimal speed difference and thus minimal torque disturbance. This preliminary action allows the four-wheel drive system to be engaged smoothly and efficiently, maintaining traction and stability while avoiding energy-wasting torque fluctuations during clutch engagement.
2Loss of time
If disconnect clutch is closed quickly, then four-wheel drive engagement time is reduced, but torque disturbance during engagement increases
Solution Approach 1:
The control system performs preliminary speed synchronization of the uncoupled electric machine before closing the disconnect clutch. By adjusting the uncoupled electric machine's rotational speed to match the driveline speed in advance, the system ensures that when the clutch closes, there is minimal speed difference between the coupled and uncoupled sides. This preliminary action enables the clutch to close quickly without generating significant torque disturbances, thus reducing engagement time while maintaining driveline torque stability.
3Power
If power is delivered to both main drive unit and secondary drive unit simultaneously, then vehicle propulsion capability is improved, but battery power depletion occurs
Solution Approach 1:
The system segments the power delivery function into two distinct drive units: a main drive unit that is always coupled to the driveline and a secondary drive unit that can be uncoupled via the disconnect clutch. By segmenting the four-wheel drive system this way, the vehicle can operate with only the main drive unit engaged during normal conditions, conserving battery power. When four-wheel drive capability is needed, the secondary drive unit is engaged through the disconnect clutch. This segmentation allows the vehicle to maintain propulsion capability while managing battery power consumption effectively.
Data Source
AI summary
Methods and system are described for allocating power to two electric machines when closing of a disconnect clutch is requested. In one example, the allocation of power may be based on a level of urgency for closing the disconnect clutch. Priority for supplying power to a secondary drive unit may be increased in response to a high urgency level.