Diesel Fuel Pump Inlet Positioning for Pressure Wave Attenuation
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Solution Overview
Problem
Current high pressure diesel fuel pumps experience detrimental pressure waves due to the return flow of fluid through the tappet vent, which can cause damage to upstream components, especially in systems with limited pipe/connector lengths, leading to minimal attenuation of these waves.
Innovation Solution
The low pressure inlet is repositioned to feed into the spring chamber, located within 90° rotation of the vent around the pumping axis, allowing fluid to flow through the spring chamber and minimizing reverse flow, thereby attenuating pressure pulsations before they affect other components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the low pressure inlet feeds directly into the cambox or lower portion of the vent, then cooling flow is provided to driveshaft components, but pressure waves are carried back through the inlet causing detrimental effects on upstream components
Solution Approach 1:
The spring chamber serves as an intermediary location between the inlet and the cambox/vent system. By positioning the inlet to feed into the spring chamber rather than directly into the cambox, the system creates a buffer zone that allows pressure waves to attenuate before reaching the inlet, while still maintaining cooling flow to driveshaft components through the vent pathway
Solution Approach 2:
The solution introduces a spatial dimension by positioning the inlet at a specific angular location (within 90° rotation) relative to the vent around the pumping axis. This spatial arrangement creates a flow path that is geometrically separated from the pressure wave generation source, allowing pressure attenuation while maintaining cooling functionality
2Object-affected harmful factors
If long pipe/connector lengths are used to increase attenuation, then pressure wave effects are reduced, but engine packaging restrictions prevent sufficient length
Solution Approach 1:
The invention changes the critical parameter from pipe length to inlet positioning geometry. By modifying where the inlet feeds into the system (into the spring chamber rather than directly into the cambox) and its angular position relative to the vent, the system achieves pressure wave attenuation without requiring increased connector length, thus respecting engine packaging constraints
3Temperature
If the inlet is positioned close to the cambox, then cooling flow is effective, but pressure waves have minimal attenuation and cause reverse flow
Solution Approach 1:
The system performs preliminary attenuation of pressure waves by allowing them to travel through the spring chamber and vent pathway before reaching the inlet. This preliminary action of pressure reduction occurs upstream of the inlet, preventing reverse flow while maintaining cooling effectiveness through the same vent pathway
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 arrangement reduces the impact of pressure waves on upstream components, improving lubrication and durability by establishing a defined fluid flow path and minimizing flow fluctuations and cavities caused by reverse flow.
Implementation Method 1
the pressure pulsations have time to attenuate to a level that has minimal effect on the rest of the system
Implementation Method 2
The inlet 50a/ 50b provides cooling flow of fluid to the driveshaft components
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The invention relates to a high pressure diesel fuel pump comprising a drivetrain assembly within a drivetrain housing and a pumping assembly. The drivetrain assembly comprises a cam mounted in a cambox, a tappet member arranged for reciprocal movement with the cam within a tappet chamber, and a spring mounted in a spring chamber acting on an upper surface of the tappet member. The pumping assembly comprises a pump housing and a plunger mounted within a bore formed in the pump housing for reciprocal movement along a pumping axis under the influence of the tappet member. The housing comprises a vent arranged to connect said spring chamber and/or said tappet chamber with the cambox and a low pressure inlet for delivery of fluid to the drivetrain assembly, characterised in that the low pressure inlet is arranged to feed into the spring chamber. The invention also covers a drivetrain housing.