Hybrid Engine Stop Control via Clutch Timing
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Solution Overview
Problem
Hybrid vehicles with direct injection engines face challenges in promptly adjusting the crankshaft angle for efficient ignition start due to differential rotation and friction issues when the clutch is constantly engaged or disconnected, leading to insufficient rotation energy and high assist torque requirements.
Innovation Solution
An engine stop control device that temporarily reconnects the clutch during engine stop to align the crankshaft with a low pumping energy region, ensuring proper ignition start by managing the connection torque and timing to overcome friction and achieve a suitable crankshaft position for ignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the clutch is constantly engaged to rotate the crankshaft during engine stop, then the crankshaft can be rotated to adjust crank angle, but the rotation energy is insufficient and high assist torque is required from the rotating machine
Solution Approach 1:
The clutch is temporarily connected before engine start to rotate the crankshaft and position it in the expansion stroke range. This preliminary action prepares the engine for ignition start by ensuring the crankshaft is at an appropriate angle, reducing the assist torque needed at the actual start moment.
Solution Approach 2:
The clutch is temporarily connected for a specific duration during engine stop, then disconnected. This periodic engagement provides sufficient rotation energy to the crankshaft without requiring continuous high assist torque, optimizing the balance between crankshaft positioning and power consumption.
2Use of energy by moving object
If the clutch is constantly disconnected during engine stop, then the rotating machine power consumption is reduced, but the crankshaft cannot be rotated promptly to achieve ignition start
Solution Approach 1:
The clutch is temporarily connected before engine start to rotate the crankshaft and position it in the expansion stroke range. This preliminary action prepares the engine for ignition start by ensuring the crankshaft is at an appropriate angle, reducing the assist torque needed at the actual start moment.
Solution Approach 2:
The clutch is temporarily connected for a specific duration during engine stop, then disconnected. This periodic engagement provides sufficient rotation energy to the crankshaft without requiring continuous high assist torque, optimizing the balance between crankshaft positioning and power consumption.
3Loss of energy
If the clutch is temporarily connected to rotate the crankshaft, then the crankshaft can be positioned in low pumping energy region, but the control complexity increases
Solution Approach 1:
The system utilizes the engine's own pumping action and compression energy to rotate the crankshaft and position it in the expansion stroke range. By temporarily connecting the clutch, the engine's internal forces are harnessed to achieve crankshaft positioning, reducing the need for external assist torque and simplifying the control requirements.
Solution Approach 2:
The clutch connection duration and timing are optimized to allow the crankshaft to naturally settle into the expansion stroke range through the engine's pumping action. By controlling the clutch engagement time parameter, the system achieves energy-efficient crankshaft positioning without complex control algorithms.
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
Enables efficient ignition start with reduced assist torque by aligning the crankshaft with low pumping energy, ensuring reliable engine restart and minimizing energy loss and fuel consumption.
Implementation Method 1
a clutch connecting/disconnecting the direct injection engine to/from a power transmission path
Implementation Method 2
a pumping action due to compression of air in the cylinders is acquired
Data Source
Figure 1
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Figure 3
AI summary
When a K0 clutch 34 is interrupted to stop a direct injection engine 12 during vehicle running, if a stop position of a crankshaft 114 is out of a range of a target stop range ϕtarget, the once interrupted K0 clutch 34 is temporarily frictionally engaged to slightly rotate the crankshaft 114. As a result, the crankshaft 114 stopped near compression TDC (top dead center) is rotated to and stopped in a minimum region of pumping energy in combination with a pumping action. Since the minimum region of the pumping energy overlaps with the target stop range ϕtarget suitable for ignition start associated with a small assist torque at the time of engine start, the ignition start can properly be performed at the next engine start and the assist torque at the time of engine start can be reduced.