Control Valve Stroke Stop Element for Hydraulic Sticking
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Solution Overview
Problem
Modern common rail injection systems face challenges with rapid needle closing due to hydraulic sticking, which causes undesired bouncing and delays in valve closure, especially when metal hits metal, leading to variable stroke/stroke spreads and poor robustness in injector design.
Innovation Solution
A relocatable stroke stop element that minimizes contact surface area with the valve needle, features sharp edges, and is pretensioned by a stop spring to prevent hydraulic sticking, allowing the valve needle to separate from the stop element during hydraulic sticking, ensuring rapid closure and reliable resetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a hard stroke stop is used to limit valve needle stroke, then stroke limitation is achieved, but hydraulic sticking and delayed needle closing occur
Solution Approach 1:
The stroke stop element is made relocatable rather than fixed, allowing it to move axially relative to the valve needle. This dynamic configuration enables the stroke stop to separate from the valve needle during operation, preventing hydraulic sticking while maintaining stroke limitation functionality through the squeezing gap mechanism.
Solution Approach 2:
A squeezing gap is introduced as an intermediary element between the stroke stop and the valve needle. This gap prevents direct metal-to-metal contact and the resulting hydraulic sticking, while still allowing the stroke stop to effectively limit the valve needle stroke through controlled hydraulic pressure in the gap.
2Stability of the object's composition
If contact surface between stroke stop and valve needle is increased, then stability is improved, but hydraulic sticking is promoted
Solution Approach 1:
The contact surface between the stroke stop and valve needle is minimized to a sharp edge rather than a broad surface. This localized contact point provides sufficient stability for stroke limitation while dramatically reducing the contact area that would otherwise promote hydraulic sticking and delayed needle closing.
Solution Approach 2:
The stroke stop element features a sharp edge geometry rather than a flat or curved surface. This sharp edge configuration concentrates the contact to a minimal point, providing stable stroke limitation while preventing the distributed contact that causes hydraulic sticking.
3Manufacturing precision
If metal hits metal against hard stroke stop, then stroke limitation is achieved, but bouncing and noise occur
Solution Approach 1:
The squeezing gap acts as an intermediary that prevents direct metal-to-metal contact between the stroke stop and valve needle. This gap eliminates bouncing and noise by allowing controlled hydraulic pressure buildup rather than impact, while still achieving effective stroke limitation.
Solution Approach 2:
The squeezing gap provides beforehand cushioning by creating a controlled compressible space before actual contact occurs. This pre-cushioning mechanism prevents impact bouncing and noise by allowing the hydraulic fluid in the gap to compress and absorb the stopping energy.
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 solution prevents undesired bouncing and hydraulic sticking, ensuring rapid and consistent valve closure, reducing stroke variations and enhancing the robustness of the injector design by allowing the valve needle to separate from the stop element during hydraulic sticking, thus preventing delayed closure.
Implementation Method 1
the stroke stop element is pretensioned by a stop spring
Implementation Method 2
hydraulic sticking occurs on the stroke stop element
Data Source
Figure 1
Figure 2~3
AI summary
The device has a valve needle (20) movably guided back and forth for implementing a valve needle stroke. A stroke stop element (40, 50) limits a squeezing gap (45, 55) and the valve needle stroke. The stroke stop element is movably limited relative to the valve needle, which is limited movably relative to the stroke stop element. A contact surface between the stroke stop element and the valve needle is minimized, where the stroke stop element is prestressed by a stop spring (44, 54). The stop element is guided on the valve needle.