High Pressure Fuel Pump Piston Radial Expansion
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Solution Overview
Problem
High pressure fuel pumps experience significant fuel leaks due to increased clearance between the piston and bore when fuel is under high pressure, leading to inefficiencies in fuel injection systems for internal combustion engines.
Innovation Solution
A cylindrical piston with a dilation mechanism, such as a recess or circular groove, that expands radially when pressurized, reducing the functional clearance by allowing pressurized fuel to flow into a low-pressure circuit through a groove ring and fuel path, thereby minimizing leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the piston is made cylindrical with fixed diameter, then the manufacturing is simple, but the clearance between piston and bore increases under high pressure causing fuel leakage
Solution Approach 1:
The piston structure is made dynamic by incorporating a dilation mechanism that allows the piston diameter to change based on fuel pressure. The peripheral wall includes a dilation zone that can radially expand when exposed to pressurized fuel, automatically adjusting the clearance between piston and bore to prevent leakage while maintaining manufacturing simplicity.
Solution Approach 2:
The piston diameter parameter is made variable through the dilation mechanism. Under low pressure, the piston maintains its base diameter for simple manufacturing compatibility. Under high pressure, the dilation mechanism activates to increase the piston diameter, reducing clearance and preventing fuel leakage through the functional gap.
2Loss of substance
If the piston expands radially under pressure, then the clearance is reduced preventing fuel leak, but the piston structure becomes more complex
Solution Approach 1:
The piston peripheral wall is segmented into different functional zones: a dilation zone with controlled thickness that can expand radially, and other structural zones that maintain the piston's overall integrity. This segmentation allows the dilation function to be isolated to specific areas, reducing the overall complexity while enabling effective clearance control.
Solution Approach 2:
The dilation mechanism acts as an intermediary between the pressurized fuel and the piston-bore interface. It mediates the pressure effects by converting axial fuel pressure into radial expansion, automatically adjusting the clearance without requiring external control systems or complex actuation mechanisms.
3Stability of the object's composition
If the peripheral wall is made thinner to allow expansion, then the radial dilation is enabled, but the structural strength is reduced
Solution Approach 1:
The peripheral wall is designed with local quality variations, having different thicknesses in different zones. The dilation zone has reduced thickness to enable radial expansion, while other structural zones maintain sufficient thickness for strength and stability. This localized thinning allows flexibility where needed without compromising overall structural integrity.
Solution Approach 2:
The piston is designed as a composite structure combining materials or zones with different mechanical properties. The dilation zone may use materials or geometries optimized for flexibility and radial expansion, while other zones use materials optimized for strength and structural support, creating a composite piston that balances both requirements.
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
The radial expansion of the piston's peripheral wall effectively compensates for the dilation of the bore, reducing fuel leaks and maintaining efficient fuel pressurization and expulsion in high-pressure conditions.
Implementation Method 1
piston provided with a dilation mechanism, such as a recess or circular groove, that expands radially when pressurized
Implementation Method 2
The fuel path extends from the groove ring towards the low pressure circuit
Data Source
Figure 1~2
Figure 3~4
AI summary
A fuel pump (10) is disclosed. It has a housing (12) provided with an axial bore (14) defining a compression chamber (16). The pump (10) is further provided with a cylindrical piston (18) slidably arranged in the bore (14), the piston (18) extending from a top extremity that is inside the bore (14), defining a high pressure extremity, to a lower extremity, defining a low pressure extremity. The piston (18) is able to reciprocally slide between a lower position where fuel at low pressure enters the compression chamber (16) via an inlet and, an top position where fuel present in the compression chamber (16) is pressurized before being expelled via an outlet. The piston (18) is also provided with a dilation mean (20, 22) arranged on its high pressure extremity, said mean (20, 22) enabling the piston (18) to expand radially when fuel in the compression chamber (16) is pressurized.