Dual Spring Piston Pump Separating Tappet and Piston Return Loads
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Solution Overview
Problem
In conventional radial piston fuel supply pumps for common rail fuel injection systems, the increased reciprocating mass in V-6 or V-8 engines due to longer, heavier tappets leads to excessive side loads on the pumping piston, causing piston seizures, particularly when using larger return springs to manage the added mass.
Innovation Solution
The tappet return function is separated from the piston return function, with a stronger outer spring handling the tappet load and a weaker inner spring managing the piston load, minimizing side loads on the piston by distributing the total load into two separate springs with distinct biasing means.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a larger, more powerful single return spring is used to handle the increased reciprocating mass of longer tappets in V-6 or V-8 engines, then the tappet can be returned effectively, but excessive side loads are imparted to the pumping piston causing piston seizures
Solution Approach 1:
The invention divides the single return spring into two separate springs: an outer tappet return spring that handles the tappet mass and an inner piston return spring that handles the piston mass. This segmentation eliminates the harmful side loads on the piston while maintaining effective return force for both components, directly resolving the contradiction between sufficient return force and harmful side loads.
2Length of moving object
If a longer, heavier tappet is used to reach the centrally located cam shaft in push-rod type engines, then the desired pump position can be achieved, but the reciprocating mass increases requiring more than two times the typical return spring load
Solution Approach 1:
The invention segments the return spring function into two independent springs, allowing each spring to be optimized for its specific mass. The outer spring handles only the tappet mass while the inner spring handles only the piston mass, eliminating the need for a single oversized spring and reducing harmful side loads on the piston.
3Reliability
If a more powerful return spring is used to handle increased mass, then the reciprocating components can be returned, but the spring induces significant unwanted side loads that can produce piston seizures
Solution Approach 1:
By segmenting the return spring into two separate springs with distinct functions, the invention eliminates the side loads on the piston that cause seizures while maintaining reliable return function for both the tappet and piston. The outer spring contacts only the tappet and the inner spring contacts only the piston, ensuring clean force application.
4Device complexity
If a single return spring is used to handle both tappet and piston return functions, then the device complexity is minimized, but the spring must be larger and more powerful causing harmful side loads
Solution Approach 1:
The invention accepts the increased device complexity of using two separate springs as necessary to eliminate harmful side loads on the piston. The segmented configuration allows each spring to be smaller and more appropriately sized for its specific function, resolving the contradiction between simplicity and harmful effects.
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 configuration reduces spring-induced piston side loads, preventing piston seizures by ensuring the outer spring does not impart any load to the piston, thus maintaining efficient operation and reducing assembly complexity.
Implementation Method 1
each of which is an elongated coil spring
Data Source
Figure 1~2
AI summary
Pump piston seizures caused by excessive side loads produced by the uneven loading of a large piston return spring are prevented by separating the tappet return function from the piston return function, thereby minimizing the spring force acting on the piston. Separate and distinct biasing means perform the respective functions. Preferably! a stronger, heavier load outer spring is mounted between the pump body and the tappet, such that it imparts no load and therefore no side loads to the pumping piston. A weaker, lighter load inner spring imparts less side load to the pumping piston than a conventional piston return spring, because the inner spring need not carry any tappet load. During both the pumping and charging strokes of the piston, the piston return spring can assist the tappet return spring, but the tappet return spring does not assist the piston return spring.