High Pressure Fuel Pump Lubrication Control
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Solution Overview
Problem
High pressure fuel pumps in direct injection fuel systems experience degradation due to reduced lubrication and cooling when not in operation, leading to potential durability issues, and existing solutions require additional components for flow diversion and maintenance.
Innovation Solution
A method where a lower pressure fuel pump maintains fuel rail pressure and adjusts the operation of a higher pressure positive-displacement pump to maintain an elevated pressure in its pumping chamber below the fuel rail pressure, ensuring lubrication without additional components, by intermittently pulsing the stroke amount to monitor and confirm sufficient lubrication levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the high pressure fuel pump is turned off when no direct injection is requested, then fuel system simplicity is maintained, but pump durability deteriorates due to reduced lubrication and cooling
Solution Approach 1:
The system performs preliminary action by maintaining the high pressure pump in a pre-lubricated state through controlled operation at low stroke amounts before actual direct injection is needed. The pump is operated intermittently to maintain sufficient lubrication and cooling in the pump chamber, ensuring readiness for immediate high-pressure operation when direct injection is requested, thereby preventing degradation from complete shutdown.
Solution Approach 2:
The system applies dynamics by dynamically adjusting the stroke amount of the high pressure pump based on operating conditions. When direct injection is not requested, the stroke amount is reduced to a level that maintains sufficient lubrication without delivering fuel to the fuel rail. This dynamic adjustment allows the pump to adapt its operation to maintain reliability while avoiding unnecessary fuel delivery.
2Reliability
If a constant fuel lubrication flow is branched off from the delivery flow of a low pressure pump, then pump lubrication is improved, but device complexity increases due to additional components for flow diversion and maintenance
Solution Approach 1:
The system applies universality by making the high pressure pump serve multiple functions: it delivers fuel for direct injection when needed, and simultaneously serves as its own lubrication source through controlled operation at reduced stroke amounts. The pump chamber itself is used for both fuel storage and lubrication, eliminating the need for separate lubrication flow diversion components from the low pressure pump system.
Solution Approach 2:
The high pressure pump performs self-service by using its own operational output to provide lubrication for its internal components. By maintaining controlled operation at low stroke amounts, the pump generates sufficient pressure in the pump chamber to drive lubricating fuel through the piston bore interface, thereby lubricating itself without requiring external lubrication systems or flow diversion components.
3Device complexity
If the stroke amount of the high pressure pump is reduced to maintain pressure below fuel rail pressure, then lubrication is achieved without additional components, but control precision requirements increase
Solution Approach 1:
The system implements feedback control by continuously monitoring fuel rail pressure and adjusting the high pressure pump stroke amount accordingly. When fuel rail pressure rises above a threshold, the controller reduces the stroke amount to maintain pump chamber pressure below the fuel rail pressure, ensuring lubrication without fuel leakage. This feedback mechanism enables precise control of the stroke amount to balance lubrication requirements with pressure constraints.
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 pump degradation by maintaining lubrication and cooling of the high pressure pump without additional hardware, ensuring pump reliability and extending its operational life.
Implementation Method 1
operating the first pump to maintain a fuel rail pressure in the fuel rail
Implementation Method 2
adjusting operation of the second pump to maintain an elevated pressure in a pump chamber of the second pump below the fuel rail pressure
Implementation Method 3
lubrication and cooling of the higher pressure pump may be achieved using the available pump components
Implementation Method 4
an outlet of the pumping chamber may be coupled to a fuel rail via an outlet check valve
Implementation Method 5
An inlet of the pumping chamber may be coupled to the lower pressure pump via an inlet check valve
Implementation Method 6
a second higher pressure, positive-displacement pump configured to receive fuel from the first pump, and supply fuel to the engine cylinder via a direct injector
Data Source
AI summary
Methods and systems are provided for operating an engine fuel system including a low pressure pump and a high pressure pump. During conditions when direct injection is not requested, a fuel rail pressure is maintained by the low pressure pump and fuel is port injected. Further, a stroke amount of the high pressure pump is adjusted to maintain an outlet pressure of the high pressure pump just below the fuel rail pressure. By maintaining fuel flow within the high pressure pump when high pressure pump operation is not required, and without flowing fuel from the high pressure pump outlet into the fuel rail, the high pressure pump may be cooled and lubricated without affecting the fuel rail pressure.