Load Sensing Valve Priority Element for Saturation Flow Stability
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Solution Overview
Problem
In hydraulic systems, especially in machines like excavators, simultaneous movements often lead to saturation conditions where the pump cannot maintain a constant pressure differential, causing proportional flow-rate reductions across all elements, necessitating a solution to exclude certain functions from this reduction while maintaining constant flow rates.
Innovation Solution
A sectional directional control valve with a dedicated element that includes a bore for transmitting pressure signals to an intermediate chamber, using a local compensator and load sensing signal selector, allowing it to maintain constant flow rates irrespective of load variations without additional circuits, thus reducing costs and space requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate circuit is provided to operate a function independently under saturation conditions, then that function can maintain fixed flow-rate, but the device complexity and space requirements increase
Solution Approach 1:
The patent merges the independent function control into the existing directional control valve by integrating a priority mechanism within one of the elements. The bore transmitting pump pressure to the intermediate chamber, local compensator, and load sensing signal selector are all incorporated within the same element structure, eliminating the need for separate circuits while maintaining flow-rate stability under saturation conditions.
Solution Approach 2:
The element in the directional control valve is designed to perform multiple functions: it serves as a standard load-sensing element while simultaneously incorporating a priority mechanism that ensures fixed flow-rate for specific functions under saturation conditions. The local compensator and load sensing signal selector within the element enable it to adapt its behavior based on pressure conditions, providing both load-sensing capability and priority function control through a single multi-functional component.
2Reliability
If a separate circuit is provided to operate a function independently under saturation conditions, then that function can maintain fixed flow-rate, but the manufacturing costs increase
Solution Approach 1:
The patent combines the priority function mechanism within the existing element structure of the directional control valve. By integrating the bore, local compensator, and load sensing signal selector into a single element rather than adding separate circuits, the manufacturing process is simplified and material costs are reduced while achieving the same flow-rate stability function.
3Productivity
If proportional flow-rate reduction occurs across all elements under saturation conditions, then the pump cannot maintain constant pressure differential, but this causes loss of control precision for individual functions
Solution Approach 1:
The patent applies local quality by creating a differentiated pressure control mechanism within a specific element. The bore in the element transmits pump pressure directly to an intermediate chamber that acts on the load sensing signal selector, creating a local pressure control zone. This allows the element to maintain a fixed pressure differential (5 bar) independently of the global pressure reduction affecting other elements, thereby preserving precise flow-rate control for specific functions while allowing proportional reduction elsewhere.
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 solution ensures that at least one function can maintain a fixed flow rate independent of load variations under saturation conditions, reducing costs and space requirements while maintaining proper machine control, as demonstrated by maintaining a constant 5-bar pressure drop in the element prioritized for independent operation.
Implementation Method 1
a bore (16) in the element (E4) excluded from proportional flow-rate reduction, which is designed to transmit the pressure signal received from the pump to an intermediate chamber (19) between a suitable local compensator (9) and a suitable load sensing signal selector (8)
Data Source
AI summary
The invention relates to the field of load sensing, flow sharing directional control valves for controlling an operating machine, such as an excavator. The directional control valve of the present invention is particularly characterized by the addition of at least one element (E4) wherein the provision of a bore (16) and the replacement of components (30), (50), (M1) with a compensator (9), having a spring (14) operating on one side thereof (9a), and a piston/load sensing signal selector (8) impart to this single element (E4) the feature of non participating in flow-rate reduction under saturation conditions, while preserving the feature of maintaining a constant flow-rate to the user, irrespective of the variation of the load.