Hybrid Engine Stop Control via Motor Generator Angle
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Solution Overview
Problem
In conventional hybrid electric vehicles with a one-motor, two-clutch configuration, the engine stop control system cannot predictably control the engine's crank angle at stop, leading to unstable engine restart performance and reduced energy recovery efficiency due to disconnection of the motor/generator from the driving wheels during engine stop.
Innovation Solution
The engine stop control system maintains the motor/generator connected to the driving wheels by keeping the first clutch engaged and the second clutch in a slip state, allowing for controlled engine stop and regenerative braking, ensuring a predetermined crank angle for stable engine restart and improved energy recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the first clutch is released and the second clutch is engaged during engine stop control, then the engine friction loss is reduced and EV mileage is extended, but the engine stop crank angle cannot be controlled and restart performance becomes unstable
Solution Approach 1:
The system performs preliminary control of the engine stop crank angle by controlling the motor/generator rotation angle before the engine actually stops. The controller determines a target motor/generator rotation angle that corresponds to a desirable engine crank angle for restart, and controls the motor/generator to reach this target angle before engine stop, ensuring stable restart performance while maintaining EV mode benefits
Solution Approach 2:
The motor/generator acts as an intermediary between the engine and the external environment during engine stop control. By controlling the motor/generator's rotation angle, the system can indirectly control the engine's stop crank angle even when the first clutch is released. The motor/generator's inertia and controlled deceleration serve as a mediator to achieve predictable engine stop position without mechanical connection
2Reliability
If the second clutch is released during engine stop control to control engine stop crank angle, then the engine restart performance is improved, but the regenerative braking control cannot be conducted and energy recovery efficiency deteriorates
Solution Approach 1:
The system performs preliminary control of the engine stop crank angle through the motor/generator before engine stop, eliminating the need to release the second clutch. By determining a target motor/generator rotation angle in advance and controlling the motor/generator to reach this angle, the system achieves reliable engine restart performance while maintaining the second clutch engaged for continuous regenerative braking capability
Solution Approach 2:
The system dynamically controls the motor/generator's rotation angle and deceleration rate during engine stop control. By adjusting the motor/generator's dynamic behavior (rotation speed, acceleration, and angle control), the system achieves both engine stop crank angle control and maintains connection to driving wheels for regenerative braking, resolving the static contradiction between these two functions
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 a stable engine restart performance and enhances energy recovery efficiency by allowing regenerative braking during engine stop, preventing the deterioration of energy recovery efficiency and ensuring a controlled engine stop position.
Implementation Method 1
the motor/generator may recover additional energy corresponding to the engine friction with improved energy efficiency
Implementation Method 2
a first clutch, a motor/generator, a second clutch
Data Source
AI summary
An engine stop control system for a hybrid electric vehicle including a powertrain having an engine, an electric motor/generator, and driving wheels, including a first clutch coupling the engine to the motor/generator, a second clutch coupling the motor/generator to the driving wheels, a controller configured to select between two driving modes of the vehicle by controlling engagement and disengagement of the first clutch and the second clutch so that the vehicle may be driven either solely by the motor/generator or a combination of the engine and the motor/generator, and to control the stop position of the engine to be a desired stop position by controlling the rotation speed of the motor/generator while the first clutch in complete engagement and the second clutch in a slip state.