Lift Pump Control for Fuel Rail Pressure Stability
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Solution Overview
Problem
Existing fuel lift pump systems experience delays in pressure adjustments, leading to fuel rail pressure undershoots and overshoots, which can result in drivability and performance issues due to the time it takes for the lift pump to add pressure to the fuel rail after being powered on.
Innovation Solution
Implementing a predictive method to determine when the fuel rail pressure will decrease below a threshold, allowing the lift pump to be powered on before this occurs, and using a controlled voltage ramp-up to ensure timely pressure addition, thereby preventing undesired pressure drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the lift pump is powered on only when fuel rail pressure decreases to a minimum threshold, then energy efficiency is improved, but fuel rail pressure undershoots occur leading to fueling errors
Solution Approach 1:
The controller predicts future fuel rail pressure based on current injection rates and activates the lift pump before the pressure actually drops below the threshold. This preliminary action prevents pressure undershoots while allowing the pump to remain off during periods when pressure would have otherwise been stable, maintaining energy efficiency.
Solution Approach 2:
The system uses feedback from pressure sensors and injection rate data to continuously update predictions of fuel rail pressure. This feedback loop enables the controller to make informed decisions about when to activate the lift pump, balancing energy efficiency with pressure stability.
2Stability of the object's composition
If the lift pump is powered on when fuel rail pressure reaches a threshold, then pressure stability is improved, but there is a delay before pressure changes are reflected due to check valve dynamics
Solution Approach 1:
The controller anticipates pressure drops by predicting future pressure based on current injection rates and activates the lift pump in advance. This preliminary action compensates for the delay caused by check valve dynamics, ensuring pressure stability without excessive response time.
3Loss of energy
If the lift pump remains off during low engine loads, then energy consumption is reduced, but fuel rail pressure may drop below acceptable levels
Solution Approach 1:
The controller predicts when fuel rail pressure will drop below acceptable levels based on current injection rates and activates the lift pump before the actual drop occurs. This allows the pump to remain off during stable pressure periods (reducing energy consumption) while ensuring timely activation when needed (maintaining pressure reliability).
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 fuel rail pressure undershoots, maintains engine performance, and conserves fuel by scheduling lift pump activation to prevent pressure drops, ensuring consistent fuel delivery.
Implementation Method 1
Engine fuel may be pumped out of a fuel tank by a lift pump. The lift pump propels fuel towards a fuel rail before being injected by fuel injectors.
Implementation Method 2
A check valve may be included between the lift pump and the fuel rail to maintain fuel rail pressure and prevent fuel in the fuel rail from flowing back towards the lift pump.
Data Source
AI summary
Methods and systems are provided for operating a lift pump of an engine fuel system. In one example, a method may comprise predicting when a fuel rail pressure will decrease below a threshold assuming that a lift pump remains off. The method may further comprise powering on the lift pump before the fuel rail pressure decreases below to the threshold to prevent fuel rail pressure from decreasing below the threshold.