Disconnect Clutch Pressure Control for Engine Cranking
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Solution Overview
Problem
In hybrid electric vehicles, existing modular hybrid transmission systems face challenges in consistently and quickly starting the engine due to varying accelerations caused by a one-size-fits-all disconnect clutch pressure profile, leading to issues like fuel/air cranking calibrations and potential no-starts, and difficulty in controlling engine speed.
Innovation Solution
The method involves actuating a clutch with desired pressure related to the known crank angle during restart and using different open-loop pressure profiles for disconnect clutch pressure control based on the engine's stopping position to reduce the torque required for engine cranking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a one-size-fits-all disconnect clutch pressure profile is used, then the system is simple to control, but engine starting consistency and acceleration vary
Solution Approach 1:
The clutch pressure profile is made dynamic by selecting different pressure profiles based on the engine's stopping crank angle position. The system transitions from a static one-size-fits-all approach to a dynamic adaptive approach where the pressure profile changes according to the detected stopping position, improving starting consistency without requiring complex real-time adjustments during cranking
Solution Approach 2:
The system performs preliminary action by determining the engine's stopping crank angle position before initiating the start command. Based on this pre-known position, the appropriate pressure profile is selected in advance, allowing optimal clutch pressure application from the moment cranking begins, rather than attempting to adjust during the cranking process
2Productivity
If clutch pressure is varied based on engine speed or acceleration, then engine starting performance may improve, but control difficulty increases due to coordination between VSC and disconnect clutch pressure controller
Solution Approach 1:
The system determines the engine's stopping crank angle position before the start command is initiated. This preliminary knowledge allows the disconnect clutch pressure controller to select the appropriate pressure profile in advance, eliminating the need for complex real-time coordination with the VSC during cranking. The pressure profile is predetermined based on the stopping position, simplifying the control architecture
Solution Approach 2:
The clutch pressure control is segmented into multiple discrete pressure profiles, each optimized for a specific range of stopping crank angle positions. Instead of using a continuous complex control algorithm that coordinates with engine speed and acceleration, the system divides the control space into segments, selecting the appropriate segment (pressure profile) based on the detected stopping position, thereby simplifying the overall control task
3Reliability
If higher starting torque is applied to ensure consistent engine starts, then starting reliability improves, but more reserve starting torque is required from the starting motor
Solution Approach 1:
The system applies local quality by tailoring the clutch pressure profile to the specific stopping crank angle position. Each pressure profile is locally optimized for its corresponding stopping position range, applying the right amount of torque at the right time. This eliminates the need to apply uniformly high torque across all stopping positions, reducing overall energy consumption while maintaining starting reliability
Solution Approach 2:
The system changes the clutch pressure parameter based on the stopping crank angle position. By adjusting the pressure profile parameter according to the detected stopping position, the system optimizes the torque transmission characteristics for each specific condition, achieving reliable starts with minimized energy requirements rather than using a fixed high-torque approach
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 a reduction in the torque needed to crank the engine, enabling consistent and efficient engine restarts with reduced energy waste and improved engine speed control.
Implementation Method 1
actuating a clutch located in a torque path between a starting motor and the engine with desired pressure related to the known crank angle
Implementation Method 2
disconnect clutch pressure profile established how much electric machine torque will be directed to cranking the engine
Implementation Method 3
using the starting motor to drive the engine during the restart
Implementation Method 4
modular hybrid transmission (MHT) is an arrangement of powertrain components that includes an internal combustion engine, torsion damper
Data Source
AI summary
A method for restarting a vehicle engine that is stopped at a known crank angle includes actuating a clutch located in a torque path between a starting motor and the engine with desired pressure related to the known crank angle during the restart, and using the starting motor to drive the engine during the restart.