Intake Pressure Control for Restart-Enabled Idle Stop
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Solution Overview
Problem
Existing engine shutdown and restart methods during temporary stops can result in undesired noise and vibration due to air charge in cylinders, leading to delays in engine restart and increased wear, as closed throttle operation during shutdown can degrade restart attempts and the engine may spin down too far for the starter to effectively engage.
Innovation Solution
The method involves controlling the engine's intake manifold pressure during shutdown to maintain a specific pressure trajectory, adjusting the throttle to keep air charge below a threshold that causes noise and vibration, and restarting the engine before it reaches zero speed, allowing for faster return to idle without complete engine stop and potentially without a starter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the throttle is closed during engine shutdown to reduce air charge, then noise and vibration are reduced, but the engine restart is degraded due to insufficient air in the cylinder
Solution Approach 1:
The throttle is made dynamically controllable with multiple positions (closed, intermediate, open) rather than being fixed. The system transitions the throttle from closed to open position based on real-time engine speed and restart requirements, allowing optimization of both noise reduction during shutdown and air availability for restart.
Solution Approach 2:
The system changes the throttle position parameter from closed to open based on engine operating conditions. When engine speed drops below a threshold during shutdown, the throttle opens to increase manifold pressure and air charge, ensuring sufficient air is available for successful restart while maintaining noise reduction benefits during the shutdown phase.
2Reliability
If the throttle is opened at restart request to increase air charge, then restart capability is improved, but there is a substantial delay between restart request and vehicle launch
Solution Approach 1:
The throttle opens before the restart request is made, during the spin-down phase when engine speed drops below a threshold. This preliminary action ensures air charge is already available when restart is requested, eliminating the delay that would occur if the throttle opened after the restart request.
Solution Approach 2:
The system continuously monitors engine speed and provides feedback to control the throttle position. When engine speed drops below a predetermined threshold during shutdown, this feedback triggers the throttle to open, automatically preparing the air charge for upcoming restart without requiring a restart request first.
3Reliability
If the engine is allowed to spin down completely to rest, then restart from rest is achieved, but the starter may not be able to properly engage and the delay is substantial
Solution Approach 1:
The system performs preliminary preparation by opening the throttle and building air charge during the spin-down phase before the engine reaches zero speed. This allows restart to occur while the engine is still rotating at low speed, avoiding the need for complete stop and starter engagement, thereby reducing launch delay.
Solution Approach 2:
The system skips the complete stop phase by initiating restart before the engine reaches zero speed. By monitoring engine speed and triggering restart at a predetermined threshold above zero, the system rushes through the critical transition phase, preventing the engine from fully stopping and eliminating the associated delays.
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 reduces engine noise and vibration, enables quicker restarts, and maintains engine performance by controlling air charge levels, allowing for faster vehicle launch without the need for a complete stop or starter engagement.
Implementation Method 1
Air in one or more cylinders, known as 'air charge ', may compress and expand in the cylinder during shutdown, acting as a spring or an air cushion
Implementation Method 2
adjusting the throttle to maintain manifold pressure at a first value during the automatically initiated engine shut down
Implementation Method 3
the vehicle may shutdown the engine by discontinuing fuel supply and/or ignition so that the engine spins down to rest
Data Source
AI summary
Methods and systems are provided for controlling an engine of a vehicle. In one example, a throttle is adjusted improve engine restarting during an automatic engine stop where an operator requests an engine restart. The methods and systems may improve vehicle drivability.