Fluid Control Valve Orifice Design for Cv Stability
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Solution Overview
Problem
Conventional fluid control valves for high-temperature gases in semiconductor manufacturing exhibit unstable Cv values, leading to increased costs due to the need for additional control units and inability to achieve the required accuracy of ±5% variation rate for precise gas supply.
Innovation Solution
A fluid control valve design featuring a metal diaphragm with an orifice diameter set to 50% or less of the second flow passage diameter, reducing Cv value variation to ±10% or less, and further optimized to ±5% or less by setting the orifice diameter to 40% or less, eliminating the need for separate control units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a metal diaphragm is used for high-temperature gas resistance, then temperature resistance is improved, but Cv value stability deteriorates
Solution Approach 1:
The invention changes the geometric parameter of the flow passage by introducing an orifice with a specific diameter ratio (50% or less of the second flow passage diameter). This parameter change stabilizes the Cv value by controlling the flow characteristics through the orifice, compensating for the unstable behavior of the metal diaphragm while maintaining high-temperature resistance.
2Reliability
If a control unit is added to adjust diaphragm stroke, then Cv value stability is improved, but device complexity increases
Solution Approach 1:
The invention makes the flow passage structure itself perform the control function by incorporating an orifice with a specifically designed diameter ratio. The orifice automatically stabilizes the Cv value through its geometric constraints on flow, eliminating the need for external control units or active adjustment mechanisms while maintaining stability.
3Reliability
If orifice diameter is reduced to 50% or less of flow passage diameter, then Cv value variation is reduced, but flow capacity decreases
Solution Approach 1:
The invention optimizes the orifice diameter parameter to be 50% or less of the second flow passage diameter, achieving a balance where Cv value variation is reduced to acceptable levels while maintaining sufficient flow capacity for the application requirements.
Solution Approach 2:
The invention applies a localized constriction (orifice) at a specific position in the flow passage rather than uniformly reducing the entire passage diameter. This localized quality change stabilizes flow characteristics where needed while preserving overall flow capacity through the larger second flow passage.
Data Source
AI summary
A fluid control valve for controlling high-temperature fluid includes: a valve body including a valve chamber communicating with first and second flow passages, and a valve seat provided in the valve chamber; a metal diaphragm that contacts with and separates from the valve seat; a stem that moves the metal diaphragm up and down; and an actuator that drives the stem. The first flow passage includes a first orifice having a diameter set to 50% or less of a diameter of the second flow passage. Alternatively, the second flow passage includes a second orifice having a diameter set to 50% or less of the diameter of the second flow passage. The diameter of the second flow passage is calculated by converting a cylindrical flow passage area defined between the valve seat and the metal diaphragm when separated from the valve seat into a diameter of a circular flow passage.