Cam Actuated Fuel Pump Segmented Shaft Stress Reduction
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Solution Overview
Problem
Fuel pumps in internal combustion engine fuel injection systems face increased mechanical stresses due to efforts to enhance fuel pressure and reduce pump size, leading to durability issues.
Innovation Solution
The design integrates a camshaft with a cam arrangement that includes a central core and an outer sleeve, where the cam is either integral to the shaft or an independent member, and features annular members surrounding the bearings to distribute forces and reduce mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If fuel pressure is increased toward 3000 bar and above, then fuel efficiency and combustion are improved, but mechanical stresses internal to the pump increase
Solution Approach 1:
The camshaft is divided into a central core and an outer sleeve that can rotate relative to each other. This segmentation allows the cam mechanism to be isolated from the pump housing, reducing stress transmission to the housing and improving overall pump durability while maintaining high fuel pressure capability.
Solution Approach 2:
The outer sleeve acts as an intermediary element between the cam and the pump housing. It absorbs and isolates mechanical stresses generated by high-pressure fuel delivery, preventing these stresses from being transmitted to the housing and thereby protecting the pump structure while enabling high operating pressures.
2Volume of moving object
If pump size is decreased for easier packaging, then packaging efficiency is improved, but mechanical stresses internal to the pump increase
Solution Approach 1:
By segmenting the camshaft into a central core and an outer sleeve, the design achieves a more compact overall structure that reduces pump size for easier packaging. The relative rotation capability allows the mechanism to maintain its stress-distribution function in a smaller package, preventing increased mechanical stresses despite the reduced size.
Solution Approach 2:
The cam mechanism utilizes relative rotation between the central core and outer sleeve, introducing an additional rotational degree of freedom. This dimensional change allows the pump to achieve compact sizing while maintaining durability through enhanced stress distribution across multiple moving components rather than relying solely on a rigid single-piece structure.
3Volume of moving object
If the cam mechanism is made more compact, then pump size is reduced, but stress concentration in the cam or housing increases
Solution Approach 1:
The camshaft is segmented into a central core and an outer sleeve that can rotate relative to each other within the cambox. This segmentation distributes mechanical stresses across two separate rotating components rather than concentrating them in a single rigid cam structure, reducing stress concentration in the cambox housing while maintaining a compact overall size.
Solution Approach 2:
The cam mechanism employs dynamic relative rotation between the central core and outer sleeve, transforming a static rigid cam structure into a dynamic multi-component system. This dynamic configuration allows the cambox to be more compact while the relative motion between components distributes and reduces stress concentration in the housing.
Data Source
Figure 1~2
Figure 3~4
AI summary
A fuel pump (12) of a fuel injection equipment (10) comprises a camshaft (18) rotating about a main axis (X) in a cambox (14) and cooperating with a piston. The camshaft (18) comprises a shaft member (38) and a cam member (16) that comprises a core (44) fixed on a shaft (38) and an outer sleeve (48) arranged over the core (44), the piston cooperating with the outer face (32) of said sleeve, the core (44) being narrower than the sleeve (48) so that an annular recess (50, 52) is defined on at least one side of the cam.