High-Pressure Pump Cam Wear Reduction via Offset Rollers
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Solution Overview
Problem
High-pressure pumps in fuel injection systems experience reduced service life due to increased cam wear caused by rollers running one after the other on the outer peripheral surface, leading to excessive friction and wear, which is costly and space-intensive to mitigate.
Innovation Solution
The design features rollers that are axially offset and run side by side on the cam's outer peripheral surface, reducing friction and wear by avoiding overlapping running surfaces, and utilizing a double cam with 180° projections to enhance pump piston movement and delivery capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If rollers are arranged to run one behind the other on the cam's outer peripheral surface, then the pump structure is compact and simple, but the cam wear increases significantly reducing service life
Solution Approach 1:
The patent transitions from a single-plane roller arrangement to a multi-dimensional arrangement where rollers are distributed across different axial positions and angular positions on the cam. This spatial redistribution in multiple dimensions allows the pump to maintain compact structure while significantly reducing cam wear by avoiding concentrated loading on one area.
2Reliability
If multiple separate eccentrics or cams are arranged side by side, then cam wear is reduced, but manufacturing effort and installation space increase significantly
Solution Approach 1:
The patent segments the loading function across multiple rollers that operate simultaneously on different portions of a single cam's outer peripheral surface. Instead of using multiple separate cams, the cam is divided into multiple active zones where different rollers apply force at different axial and angular positions, achieving wear distribution without requiring multiple cam components.
Solution Approach 2:
The single cam design serves multiple functions by supporting multiple pump elements through different rollers positioned at various axial and angular locations. This multi-functional cam replaces what would traditionally require multiple separate cams, reducing manufacturing complexity while maintaining the wear-reduction benefits of distributed loading.
3Reliability
If multiple separate eccentrics or cams are arranged side by side, then cam wear is reduced, but installation space requirements increase
Solution Approach 1:
The patent arranges rollers and pump elements in a nested configuration where multiple pump elements are positioned at different radial distances from the cam axis and at different axial positions. This nesting allows multiple pumping functions to be accommodated within a compact cylindrical space, eliminating the need for the extended axial space that would be required for multiple separate cams.
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 significantly extends the service life of the high-pressure pump, potentially doubling it, while reducing production costs and installation space requirements, making it suitable for various vehicle applications.
Implementation Method 1
Each pump element has a pump piston (4, 4') which is supported on a cam (6) via a tappet assembly (5, 5'), so that the pump piston (4, 4') can be driven into a stroke by a rotation of the drive shaft (2)
Implementation Method 2
The tappet assemblies (5, 5') comprise rollers (7, 7') which bear against an outer circumferential surface (8) of the cam (6), axially offset from one another with respect to a longitudinal axis (A) of the drive shaft (2) and with respect to their angular positions. Due to the axial offset of the rollers (7, 7'), they do not run one behind the other, but axially offset side by side, on the outer circumferential surface (8) of the cam (6). The frictional stress on the cam's outer circumferential surface, and the associated wear, can be significantly reduced in this way.
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a high-pressure pump for a fuel injection system, particularly a common rail injection system, comprising a pump housing (1) in which at least two pump elements (3, 3') are received and arranged radially about a drive shaft (2), each pump element (3, 3') comprising a pump piston (4, 4') that is supported indirectly, by means of a plunger assembly (5, 5'), on a cam (6) of the drive shaft (2) such that said pump piston (4, 4') can be driven, by a rotation of the drive shaft (2), to implement a reciprocating motion. According to the invention, the plunger assemblies (5, 5') comprise rollers (7, 7') which lie axially relative to a longitudinal axis (A) of the drive shaft (2) and offset to one another with regard to their angle positions, on an outer circumferential surface (8) of the cam (6).