Hybrid Vehicle Stall-Start Torque Management
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Solution Overview
Problem
Hybrid vehicles face limitations in maintaining the stall phase due to the lower thermal and torque capacity of clutches compared to torque converters, resulting in reduced engine torque buildup and transfer, which affects acceleration performance.
Innovation Solution
A stall-start method and apparatus for hybrid vehicles that utilizes a stall-start controller to configure the electric machine and clutches, allowing the electric machine to operate as a generator during the stall phase and as a motor during the start phase, with the first clutch in a non-engaged slip condition and the second clutch in an engaged configuration to manage thermal capacity, enabling increased torque buildup and transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a clutch is used instead of a torque converter in hybrid vehicles, then packaging limitations are addressed, but thermal and torque capacity are reduced
Solution Approach 1:
The electric machine acts as an intermediary between the engine and wheels, enabling torque management that protects the clutch from excessive thermal loads while maintaining the compact hybrid vehicle architecture. The electric machine absorbs and transfers torque dynamically, preventing the clutch from experiencing the full thermal stress that would occur in a direct engine-to-wheel connection.
Solution Approach 2:
The system dynamically changes operational parameters by controlling the electric machine's torque contribution and the clutch's engagement state. During acceleration, the electric machine provides additional torque to reduce the burden on the clutch, and the control system adjusts clutch slip ratio and engagement timing to optimize thermal management while maintaining acceleration performance.
2Speed
If the stall phase is extended to build up more engine torque, then acceleration performance is improved, but clutch overheating occurs
Solution Approach 1:
The system uses periodic modulation of the clutch engagement and electric machine torque contribution during the stall-start sequence. The clutch is engaged in controlled cycles with brief slip phases followed by engagement, allowing heat dissipation between cycles while still building up the necessary torque for acceleration. This periodic action prevents continuous thermal accumulation.
Solution Approach 2:
The electric machine serves as a thermal buffer by providing supplemental torque during the stall phase, reducing the torque burden on the clutch. This intermediary action allows the engine to build up torque without requiring the clutch to sustain high slip conditions for extended periods, thereby preventing overheating while maintaining acceleration capability.
3Power
If the clutch is kept in slip condition during stall phase, then torque buildup is enabled, but thermal capacity is exceeded
Solution Approach 1:
The system merges the torque output of the engine with the torque contribution of the electric machine during the stall phase. This combined torque delivery allows the engine to operate in a favorable torque range while the electric machine compensates for the clutch's limited thermal capacity, enabling torque buildup without excessive thermal energy loss in the clutch.
Solution Approach 2:
The control system dynamically changes the slip ratio parameter of the clutch during the stall phase, transitioning from sustained high-slip operation to controlled intermittent slip. This parameter modulation allows the clutch to operate within its thermal capacity while still enabling sufficient torque buildup for acceleration, by adjusting the duration and intensity of slip events.
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 allows for the build-up of higher torque levels during the stall phase and efficient transfer during the start phase, enhancing acceleration performance while preventing clutch overheating, thereby improving 0-60mph or 0-100kph times.
Implementation Method 1
configure the electric machine to operate as a generator during the stall phase and as a motor during the start phase
Data Source
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AI summary
The application relates to a method for stall-starting a hybrid vehicle comprising a combustion engine (12), an electric machine (14), a transmission (16) and two clutches (20, 22). In a first stall phase torque output of the combustion engine (12) is increased and compensated by the electric machine (14) operating as a generator. In the second start phase the method comprises configuring the electric machine (14) not to operate as a generator, in particular to operate as a motor. A further independent claim is directed to a stall-start apparatus. This avoids overhating the clutches (20, 22) and battery depletion, while at the same time providing high acceleration.