Thrust Lubrication Strategy for Roller Lifters in Common Rail Fuel Pumps
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Solution Overview
Problem
High-pressure common rail fuel systems face lubrication challenges, leading to premature wear and potential failure of roller lifters due to inadequate lubrication between thrust surfaces and tappet faces, especially at extreme pressures exceeding 200 MPa.
Innovation Solution
A common rail fuel pump design featuring a cam shaft with tappet assemblies that include an axle pin with a lubrication passage and a roller with non-contiguous thrust surfaces separated by lubrication grooves, ensuring lubrication fluid movement between thrust surfaces and faces, facilitating effective lubrication through a lubrication supply passage and grooves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high injection pressures are used to meet industry demands, then fuel system performance is improved, but lubrication adequacy deteriorates leading to premature wear
Solution Approach 1:
The roller thrust surface is segmented into multiple non-contiguous planar surfaces separated by lubrication grooves. This segmentation allows lubrication fluid to be channeled directly to the thrust contact positions, ensuring adequate lubrication even under high injection pressures that would otherwise cause premature wear.
Solution Approach 2:
Lubrication grooves are strategically positioned at specific locations on the roller thrust surfaces to deliver lubrication fluid precisely where needed - at the thrust contact positions. This local quality approach ensures that lubrication is concentrated at the critical contact zones between the roller and tappet thrust faces, maintaining reliability under high pressure conditions.
2Duration of action of stationary object
If continuous lubrication is maintained for the roller, then component life is extended, but lubrication fluid distribution becomes inadequate at high pressures
Solution Approach 1:
Lubrication grooves are pre-formed on the roller thrust surfaces to anticipate and prepare for the arrival of lubrication fluid. These grooves are positioned to receive and channel the lubrication fluid directly to the thrust contact positions before the roller makes contact with the tappet thrust faces, ensuring continuous lubrication is maintained even under high pressure conditions that would otherwise disrupt fluid distribution.
3Ease of manufacture
If simple roller design is used, then manufacturing cost is reduced, but lubrication effectiveness deteriorates under high pressure
Solution Approach 1:
The roller thrust surface is divided into multiple planar surfaces separated by lubrication grooves. This segmentation can be achieved through conventional manufacturing processes such as machining or forming, adding minimal complexity to manufacturing while dramatically improving lubrication effectiveness under high pressure conditions.
Solution Approach 2:
The lubrication grooves are positioned at specific locations on the roller to deliver lubrication fluid precisely where needed. This localized approach to lubrication can be integrated into standard roller manufacturing processes, maintaining ease of manufacture while significantly enhancing thrust surface lubrication reliability under high injection pressures.
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 design effectively lubricates the roller interaction and thrust surfaces, reducing premature wear and potential failure by ensuring an adequate lubrication supply, even at high pressures, thereby enhancing the operational life of the fuel pump.
Implementation Method 1
The roller interaction between the roller and the axle pin is lubricated from a lubrication passage that opens through a roller bearing surface of the axle pin. A thrust interaction between the roller and thrust faces of the tappet of the tappet assembly is lubricated by moving lubrication fluid from lubrication grooves separating planar thrust surfaces of the roller to between the thrust surfaces and thrust faces of the tappet.
Data Source
AI summary
A common rail fuel pump includes a cam shaft with at least one cam rotatably supported in a pump housing. A plurality of tappet assemblies are each reciprocatingly movable in the pump housing, and include an axle pin mounted in a tappet, and a roller mounted in contact for rotation about the axle pin. Each end of the roller includes a plurality of non-contiguous planar thrust surfaces separated by lubrication grooves. A lubrication pathway for the roller includes in sequence a lubrication passage that opens to a roller bearing surface, movement along the roller bearing surface into the lubrication grooves, and then between the planar thrust surface of the roller and a counterpart thrust face of the tappet responsive to rotation of the roller on the cam shaft.