Fluid Pressure Control Device Spool Stability
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Solution Overview
Problem
The existing hydraulic control devices face issues with unstable operation of hydraulic cylinders due to the interference between pilot pressure and relief back pressure, leading to unintended spool movement and reduced contraction speed when the relief valve is opened during operation.
Innovation Solution
The fluid pressure control device incorporates a load holding mechanism with a switching valve and relief valve configuration, where the relief pressure oil is discharged directly to the tank, preventing interference with the switching valve and maintaining stable operation by ensuring the spool is not moved to the closing direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the relief valve is opened to reduce load pressure, then the pressure in the bottom-side pressure chamber is lowered, but the relief back pressure causes unintended spool movement and reduces contraction speed
Solution Approach 1:
The invention separates the relief back pressure path from the pilot chamber by introducing a relief valve that bypasses the back pressure to the tank, preventing it from affecting the spool position while still achieving pressure reduction
Solution Approach 2:
The relief valve acts as an intermediary component that manages the relief back pressure independently, allowing the pilot pressure to maintain control of the spool without interference from the relief operation
2Reliability
If the relief back pressure acts on the spool, then the spool may move to the closing direction, but this prevents stable operation of the cylinder
Solution Approach 1:
The invention extracts the harmful relief back pressure from the pilot chamber system by providing a separate bypass path to the tank, eliminating its interfering effect on spool control while maintaining the necessary pressure control functions
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 ensures stable and intended contraction and extension speeds of the hydraulic cylinder, preventing unintended spool movement and maintaining operational stability even when the relief valve is opened, thus enhancing the reliability of hydraulic operations.
Implementation Method 1
the pilot pressure is led to the pilot chamber of the switching valve. The pilot pressure acts on the sub spool, and the sub spool applies a thrust to the spool, whereby the spool is opened
Implementation Method 2
a relief valve opening the valve when a load pressure in a bottom-side pressure chamber of the cylinder device increases
Implementation Method 3
the relief valve is opened, a relief back pressure is generated on an upstream side of an orifice provided on a downstream of the relief valve
Implementation Method 4
a control valve controlling an extension and contraction operation of the cylinder device
Data Source
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AI summary
A fluid pressure control device includes a switching valve (22) configured to switch an operation of an operate check valve (21), a relief valve (41) configured to open when a pressure in a load-side pressure chamber (2b) reaches a predetermined pressure, and a relief discharge passage (77) configured to lead a relief fluid discharged from the relief valve (41) to a tank (T). The switching valve (22) includes a piston (50) giving thrust to a spool (56) upon receipt of a pilot pressure on a back surface, a drain chamber (51) defined by the spool (56) and the piston (50), and a drain passage (76a, 76b) allowing the drain chamber (51) and a spring chamber (54) to communicate with the relief discharge passage (77). The relief fluid discharged from the relief valve (41) is discharged to the tank (T) through the relief discharge passage (77) and does not operate the switching valve (22).