Fuel Injection Rail Pressure Control for Hybrid Engine Restart
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Solution Overview
Problem
The pressure in the fuel injection rail of a heat engine decreases below the minimum restart pressure during shutdown, leading to degraded restart time performance in hybrid vehicles, as existing methods fail to maintain the pressure above the required level for an extended period.
Innovation Solution
A method to control the initial pressure setpoint in the fuel injection rail based on the temperature difference between the rail and the heat engine, using a forced increase to maintain the pressure above the minimum injection authorization pressure, thereby optimizing restart time by determining the pressure increase through temperature conversion and correction factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the engine shutdown duration is extended in hybrid vehicles, then fuel economy is improved, but the pressure in the injection rail drops below the minimum restart pressure
Solution Approach 1:
The system performs preliminary action by heating the injection rail to a target temperature before engine shutdown to pre-establish the thermal conditions necessary for maintaining pressure during the shutdown period. This advance preparation ensures that when shutdown occurs, the thermal gradient is already optimized to prevent pressure drop.
Solution Approach 2:
The system changes physical parameters by controlling the injection rail temperature to a specific target range (80-120°C) before shutdown. By adjusting the thermal state of the injection rail, the system modifies the pressure decay characteristics, allowing extended shutdown durations while maintaining minimum restart pressure requirements.
2Duration of action of moving object
If the injection rail is heated by the engine during shutdown, then pressure is maintained longer, but this only works when temperature difference is significant
Solution Approach 1:
The system applies preliminary heating to the injection rail before shutdown to ensure the rail reaches an optimal temperature range. This advance thermal preparation ensures that regardless of the engine's shutdown state, the injection rail maintains sufficient thermal energy to prevent pressure drop for the required duration.
Solution Approach 2:
The system utilizes the engine's own thermal energy during shutdown to heat the injection rail, converting what would otherwise be wasted heat into a useful function. The engine coolant system serves dual purposes: cooling the engine while simultaneously heating the injection rail through thermal coupling.
3Reliability
If a high-pressure pump is used to maintain injection rail pressure, then restart reliability is improved, but system complexity and cost increase
Solution Approach 1:
The system extracts and utilizes the thermal energy from the engine coolant that would otherwise be wasted during shutdown. By removing the need for active heating or pressurization systems, the solution eliminates complex components while relying on the naturally available thermal resource already present in the engine system.
Solution Approach 2:
The engine's cooling system serves a dual function: cooling the engine blocks and heating the injection rail simultaneously. This self-service approach uses the engine's own operational thermal field to maintain injection pressure, eliminating the need for separate heating elements, pumps, or pressure maintenance systems.
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 effectively keeps the pressure in the injection rail above the minimum injection pressure for a longer duration, improving restart performance and reducing the need for a high-pressure pump, thus enhancing restart efficiency and reducing economic costs.
Implementation Method 1
the engine, being hotter than the fuel rail, will heat the fuel rail while it gradually cools down during the engine's shutdown period
Implementation Method 2
Once the temperature and pressure in the fuel rail have stabilized, the pressure in the fuel rail will gradually drop due to natural leaks from the high-pressure pump and the decrease in fuel rail temperature
Implementation Method 3
the pressure in the fuel rail will gradually drop due to natural leaks from the high-pressure pump and the decrease in fuel rail temperature, which closely follows that of the engine
Data Source
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AI summary
The invention relates to a method for optimising a motor vehicle heat engine restart time, the heat engine being associated with a pressurised fuel injection rail, the pressure in the injection rail necessarily being above a threshold that can be calibrated in order to authorise injection during the restart phase of the heat engine after a stoppage period of the heat engine during which the pressure in the injection rail drops from a so-called initial pressure setpoint (Cons Prail ini) at the start of the stoppage of the heat engine. The initial pressure setpoint (Cons Prail ini) is determined as a function of a difference (∆T) between the temperatures of the injection rail (Trail) and the heat engine (Tmot), and the pressure in the injection rail when the engine is stopped is forcibly increased until reaching the initial pressure setpoint (Cons Prail ini).