Hybrid Vehicle Clutch Slip Control via Input Speed
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Solution Overview
Problem
Hybrid electric vehicles face challenges in maintaining torque output under large loads or inclines, as the launch clutch slips due to insufficient line pressure, preventing effective propulsion.
Innovation Solution
A method and system where the current supplied to an electric machine is altered to increase torque output, and upon clutch slipping, the speed of the clutch input is increased to enhance line pressure, allowing controlled slipping and eventual lockup to meet torque demands, with the engine providing additional torque to overcome load and incline challenges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the current supplied to the electric machine is increased to increase torque output, then the torque transmission capability is improved, but the clutch slips due to insufficient line pressure
Solution Approach 1:
The system preemptively increases the speed of the clutch input shaft before clutch engagement to build sufficient line pressure in advance. This preliminary speed increase ensures that when the clutch is engaged under high torque demand, adequate line pressure is already available to prevent slipping, thus resolving the contradiction between high torque output and clutch engagement stability.
Solution Approach 2:
The control system acts as an intermediary by detecting clutch slip conditions and mediating between the electric machine's torque output and the clutch's pressure capacity. When slipping is detected, the controller increases input shaft speed to boost line pressure, thereby mediating the conflict between high torque demand and insufficient clutch pressure to maintain reliable engagement.
2Reliability
If the speed of the clutch input is increased to increase line pressure, then the clutch engagement reliability is improved, but the system complexity increases
Solution Approach 1:
The control system employs feedback by continuously monitoring clutch slip conditions and using this information to adjust the speed of the clutch input shaft. When clutch slip is detected, the feedback loop triggers an increase in input shaft speed to build line pressure, and when slipping stops, the speed increase is halted. This feedback mechanism improves clutch engagement reliability while keeping the control logic relatively simple and rule-based.
3Power
If the engine is started to provide additional torque, then the power output is improved, but the loss of time occurs during engine start
Solution Approach 1:
The system performs preliminary action by increasing the speed of the clutch input shaft and building line pressure before the engine is started. This head start on pressure buildup reduces the time penalty associated with engine starting, as the hydraulic system is already prepared to transmit torque effectively once the engine becomes operational, thereby minimizing the overall time loss.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures effective torque transmission to wheels even under heavy loads or inclines by dynamically managing clutch pressure and engine torque, enabling smooth acceleration and propulsion.
Implementation Method 1
A current supplied to an electric machine is altered. The electric machine is coupled to wheels via a locked clutch. The altered current alters a torque output of the electric machine.
Implementation Method 2
In response to a slipping of the clutch due to the altered torque output, a speed of an input of the clutch is increased in order to increase a line pressure available to the clutch.
Implementation Method 3
the line pressure is applied to control the slipping of the clutch
Data Source
AI summary
A vehicle includes an engine and is at least partially propelled by a fraction battery and a traction motor. A clutch is configured to be coupled to the traction motor. An electrical and/or mechanical pump provides pressure to control the clutch. At least one controller determines if the clutch is slipping. In response to the clutch slipping, the at least one controller commands an increase in speed of an input of the clutch such that the available line pressure to control the slipping of the clutch is increased. The line pressure is then applied to the clutch in order to control the slipping of the clutch.