Common Rail Pressure Control for Fast Engine Restart
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Solution Overview
Problem
In internal combustion engines with start/stop systems, the restart of the engine is delayed due to rapid rail pressure reduction caused by injector leaks, leading to increased hydraulic component stress and loss of time when restarting.
Innovation Solution
Increasing the rail pressure to a higher target level before engine shutdown and maintaining it in a controlled mode, with the high-pressure pump set to full delivery and the pressure control valve closed, to ensure sufficient pressure for immediate restart and reduce leakage effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the rail pressure is reduced when the engine is switched off, then the engine shutdown is efficient, but the restart is delayed and hydraulic components are heavily loaded
Solution Approach 1:
The patent applies preliminary action by increasing the rail pressure to a first target pressure (e.g., 1000-1500 bar) shortly before the engine stops. This pre-pressure buildup ensures that when the engine restarts, the rail pressure is already sufficient for immediate injection, eliminating the need for pressure buildup time during restart.
Solution Approach 2:
The patent implements dynamic pressure control by adjusting the rail pressure to different target pressures based on the engine operating state. During shutdown, pressure is increased to a high first target pressure, then reduced to a lower second target pressure after shutdown, optimizing both restart performance and energy efficiency.
2Loss of time
If the rail pressure is maintained at target idling pressure after shutdown, then restart is accelerated, but the pressure drops rapidly due to injector leaks
Solution Approach 1:
The patent applies preliminary action by building up excess pressure (first target pressure significantly higher than second target pressure) before shutdown. This creates a pressure buffer that compensates for injector leaks during the standstill period, ensuring pressure remains above injection release pressure (e.g., 120 bar) long enough for immediate restart.
Solution Approach 2:
The patent implements beforehand cushioning by intentionally over-pressurizing the rail before shutdown. The excess pressure acts as a cushion against pressure loss from injector leaks, ensuring that even with leakage, the pressure remains sufficient for restart within the required time window.
3Loss of time
If the rail pressure is increased to a higher target level before shutdown, then the pressure remains sufficient for restart longer, but the pressure control system operates differently
Solution Approach 1:
The patent implements dynamic pressure control by adjusting the rail pressure to different target pressures based on the engine operating state. During shutdown, pressure is increased to a high first target pressure, then reduced to a lower second target pressure after shutdown, optimizing both restart performance and energy efficiency.
Solution Approach 2:
The patent uses feedback control through the rail pressure control circuit to maintain pressure at the desired first or second target pressure. The control system continuously monitors rail pressure and adjusts the high-pressure pump and pressure control valve to maintain the setpoint, ensuring precise pressure management despite the dynamic changes.
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 method extends the time the rail pressure remains above the injection release pressure, reducing the need for pressure buildup during restart and minimizing hydraulic component stress, allowing quicker engine restart and maintaining engine functionality.
Implementation Method 1
the amount of fuel delivered by the pump into the rail causes an additional pressure build-up in the rail
Implementation Method 2
in the case of a metering unit mounted upstream of the high-pressure pump on the suction side, this is brought into its fully open state and, if there is a pressure-regulating valve on the high-pressure side, this is brought into its fully closed state
Implementation Method 3
the injectors used can have more or less large leaks, which lead to an undesirably rapid pressure reduction when the system is at a standstill
Data Source
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AI summary
The present invention relates to a method for providing a rail pressure sufficient for restarting a common rail internal combustion engine, wherein the internal combustion engine is operated in a start/stop mode in which the internal combustion engine is shut down in response to a stop request (t0) and is restarted in response to a successive start requested, wherein the rail pressure (p) is increased beyond a control pressure value (pR) after a stop request (t0) and before standstill (t1) of the internal combustion engine.