Stepped Piston Pressure Valve for Common Rail Systems
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Solution Overview
Problem
Pressure relief valves in common rail systems of internal combustion engines are prone to damage and failure due to sudden movements during the injection cycle, leading to reliability issues and potential total failure.
Innovation Solution
The valve body is designed as a stepped piston with two axial stages, featuring circumferential throttle gaps that provide hydraulic damping to slow down the valve piston's closing movement, preventing sudden closures and movements, and allowing for multi-stage control behavior through adjustable hydraulic resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a spherical valve body is used, then the valve can be simple in structure, but it is prone to sudden movements and damage during the injection cycle
Solution Approach 1:
The valve body is segmented into a stepped piston structure with multiple stages (first stage and second stage), each having different diameters and pressure surfaces. This segmentation allows the valve to control pressure in a multi-stage manner, reducing sudden movements and improving reliability while maintaining reasonable structural complexity.
Solution Approach 2:
The valve body is designed as an axially movable stepped piston that can dynamically adjust its position and the effective pressure area during operation. This dynamic adjustment allows the valve to modulate the closing force progressively, preventing sudden closures and movements that lead to damage.
2Speed
If the valve piston closes quickly, then the response time is short, but it causes sudden movements and potential damage
Solution Approach 1:
The closing spring is designed to provide a progressive closing force that increases as the valve piston moves toward the closed position. This beforehand cushioning effect prevents sudden impacts and damage by ensuring the closing action is controlled and gradual, rather than abrupt.
Solution Approach 2:
The valve utilizes hydraulic pressure from the fuel medium to assist in controlling the valve piston movement. The pressure differential across the stepped piston creates a controlled closing force that prevents sudden movements, combining hydraulic principles with mechanical spring force for reliable operation.
3Force
If the pressure area is large, then the closing force is strong, but the valve becomes more sensitive to pressure fluctuations
Solution Approach 1:
The total pressure area is segmented into multiple stages with different diameters. The first stage has a smaller pressure area and the second stage has a larger pressure area, allowing the valve to respond differently to pressure fluctuations at different operating conditions. This segmentation reduces overall sensitivity while maintaining strong closing force when needed.
Solution Approach 2:
The effective pressure area parameter changes dynamically as the valve piston moves between stages. At different positions, different pressure areas are exposed to the fuel pressure, allowing the valve to adapt its sensitivity and closing force based on operating conditions rather than having a fixed large pressure area.
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 enhances the robustness against pressure pulsations and contamination, reduces susceptibility to damage, and allows for adaptable control behavior by optimizing the ratio of hydraulic partial resistances, ensuring reliable operation and extended valve life.
Implementation Method 1
the two throttle gaps cause hydraulic damping of the movement of the valve piston in the valve-closing direction
Implementation Method 2
the spring-loaded valve piston in particular is braked during its closing movement by the hydraulic resistance, which is made up of a hydraulic partial resistance of the first throttle gap and a hydraulic partial resistance of the second throttle gap
Implementation Method 3
an axially movable valve piston being arranged between the valve body and a closing spring, which generates a closing force against a pressure acting on the inlet opening
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The invention relates to a pressure-limiting valve (1), in particular for arrangement in a return line of a common rail system of an internal combustion engine, comprising a valve housing (2), which has a housing head (3) and a hollow cylindrical housing jacket (4), in which an axial inlet opening (6) and at least one outlet opening (7) axially spaced from the inlet opening (6) are located in a valve base (5) of the valve housing (2), wherein an inner valve seat (8) for a valve body (9) is connected to the inlet opening (6) in the valve base (5), and wherein an axially movable valve piston (11) is arranged between the valve body (9) and a closing spring (10), which produces a closing force against a pressure (p) acting at the inlet opening (6). In order to improve the functional characteristics of the valve (1), the valve body (9) is designed as a stepped piston, which in the first step (9a) of the stepped piston has a first area (A1) to which the pressure (p) can be applied in the axial direction on the side of the stepped piston facing the inlet opening (6) and a first axial length (L1), over which the stepped piston forms a first circumferentially extending throttling gap (14) with an inner surface (8b) of the valve seat (8) by means of the outer surface (9d) of the stepped piston in a closed position, and which in the second step (9b) of the stepped piston has a second area (A2) to which the pressure (p) can be applied in the axial direction (X-X), which second area forms an overall pressure area (AG) together with the first area (A1), wherein in the second step (9b) a second circumferentially extending throttling gap (15) having a second gap width (Sw) is formed between the outer surface (9e) of the stepped piston (9) and an inner surface (2a) of the housing jacket (4) over a second axial length (L2).