Pump Assembly Driveshaft Cooling Circuit
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Solution Overview
Problem
Existing high pressure pump assemblies in internal combustion engines face limitations in bearing durability due to inability to handle higher temperature fuel and debris, which leads to reduced bearing life and potential blockages, especially as delivery pressure increases and fuel injector backleak flow introduces hotter fuel.
Innovation Solution
The pump assembly includes axial and radial drillings in the driveshaft to create a fluid communication network between bearings and the cambox, with throttled channels and annular galleries to ensure clean, low-temperature fuel is force-fed to bearings, while an unrestricted backleak path prevents debris accumulation and pressure spikes, maintaining bearing material integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If fuel injector backleak flow is fed into the pump inlet, then the pump can handle higher delivery pressures, but the bearing temperature increases and bearing life decreases
Solution Approach 1:
The pump assembly segments the fuel flow paths into distinct circuits: a first circuit force-feeds cool fuel to bearings for lubrication and cooling, while a second circuit handles hot plunger leakage and backleak flow separately through the chamber and exit pathway, preventing thermal mixing and protecting bearings from high temperatures
Solution Approach 2:
The chamber acts as an intermediary component that receives hot fuel from plunger leakage and backleak paths, then directs it through the exit pathway to the backleak circuit, serving as a buffer that prevents direct thermal contact between hot fuel and bearings while maintaining pressure balance
2Stress or pressure
If orifice size is reduced to control cambox pressure, then pressure control improves, but debris accumulation increases and blockage risk increases
Solution Approach 1:
The exit pathway is segmented into multiple independent pathways (first exit pathway section from cambox volume, second exit pathway section from annular gallery) with different functions, allowing the cambox orifice to be optimized for pressure control while the larger annular gallery provides a debris-resistant alternative route
Solution Approach 2:
The system changes the flow path geometry parameters dynamically - using the restricted orifice for precise pressure control when clean fuel is available, while the unrestricted annular gallery provides a backup path with larger cross-sectional area that resists debris accumulation and blockages
3Use of energy by moving object
If bearing clearances are reduced to improve lubrication efficiency, then lubrication efficiency improves, but heat transfer to bearings increases and bearing material integrity deteriorates
Solution Approach 1:
The invention extracts the hot fuel source (plunger leakage) from the bearing lubrication circuit by directing it through the chamber and exit pathway to the backleak circuit, separating the high-temperature flow path from the bearing cooling function, thereby allowing tight clearances for efficient lubrication without compromising bearing temperature control
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 design enhances bearing durability by maintaining low temperatures and preventing debris accumulation, reducing the risk of blockages and extending the life of PEEK or PTFE bearings, while minimizing CO2 emissions and reducing pump packaging volume.
Implementation Method 1
lubrication and cooling of the bearings is achieved by a forced flow of fuel from the cambox 8
Implementation Method 2
the chamber is also in fluid communication, via drillings provided in the driveshaft, with a front bearing and a front journal surface
Implementation Method 3
The cambox is pressurised, to allow leakage past the bearing clearances. The leakage is evacuated to a backleak path
Data Source
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AI summary
A high pressure pump, comprising a lubrication and cooling circuit for driveshaft bearings (140-142), wherein low temperature, filtered fuel from the fuel tank (150) is supplied to a chamber (158) at the rear of the driveshaft (106), wherein the chamber (158) communicates directly with the rear bearing clearances, and with the front bearing clearances and cambox (108) via axial (134) and radial (136,138) driveshaft drillings, wherein the system is sealed at backleak pressure, and optionally a channel (160,172) is provided directly from the chamber to the cambox volume thereby to cool a tappet/cam rider interface.