Vacuum Valve Bellofram Damage Detection by Opening-Degree Feedback
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Solution Overview
Problem
The bellofram in the drive unit of the vacuum open-close valve is prone to damage due to rubbing, leading to inaccurate pressure control and potential semiconductor manufacturing defects.
Innovation Solution
A vacuum pressure control system with an abnormality detection program that calculates the difference between the opening-degree command value and the actual opening degree to detect bellofram damage, setting a threshold value to determine if the bellofram is torn or broken.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the bellofram is deeply folded back in the cylinder to enable piston movement, then the drive unit can achieve the required opening degree adjustment, but the bellofram becomes prone to rubbing and damage
Solution Approach 1:
The system performs preliminary detection of bellofram abnormalities by monitoring the relationship between command values and actual opening degrees before complete failure occurs. The controller calculates opening degree differences and compares them against thresholds to detect early signs of bellofram damage, enabling preventive maintenance before the bellofram completely fails
Solution Approach 2:
The system implements feedback control by continuously monitoring the actual opening degree of the valve element and comparing it with the commanded opening degree. The controller receives feedback through the opening degree detection unit and adjusts its detection algorithm to identify when the bellofram is no longer providing accurate positioning, indicating damage
2Reliability
If the bellofram is damaged due to rubbing, then the piston chamber loses airtightness allowing air leakage, but detecting this damage requires complex monitoring systems
Solution Approach 1:
The system uses self-service detection by leveraging existing sensors and control units already present in the vacuum pressure control system. The opening degree detection unit and controller work together to detect bellofram damage without requiring external monitoring equipment. The system detects damage by analyzing the relationship between commanded and actual opening degrees, which naturally deviates when the bellofram is damaged
Solution Approach 2:
The controller performs multiple functions: it controls the vacuum open-close valve operation and simultaneously detects bellofram abnormalities. The opening degree detection unit serves both to provide feedback for precise valve control and to monitor bellofram health. This multi-functionality eliminates the need for separate dedicated detection systems
3Reliability
If the opening degree difference threshold is set low for sensitive detection, then bellofram damage is detected earlier, but false alarms increase due to normal operational variations
Solution Approach 1:
The system applies partial detection by monitoring opening degree differences only during specific operational conditions where the valve is actively adjusting. Rather than continuously monitoring all operations, the detection focuses on periods when the valve element is moving between opening and closing states, which is when bellofram damage would manifest as abnormal positioning errors
Solution Approach 2:
The system dynamically adjusts the threshold value based on operational parameters. The threshold is not fixed but varies according to the operating conditions of the vacuum system, allowing the detection algorithm to distinguish between normal operational variations and actual bellofram damage. This adaptive thresholding reduces false alarms while maintaining sensitivity to real damage
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 system effectively detects bellofram damage, preventing inaccurate pressure control and ensuring reliable vacuum chamber pressure management.
Implementation Method 1
a compression coil spring that urges the piston in a valve closing direction
Implementation Method 2
When compressed air is supplied to the drive unit, the piston is moved in the valve opening direction
Data Source
AI summary
A vacuum open-close valve includes a drive unit for driving a valve element based on an opening-degree command value. The drive unit includes a drive shaft connected to the valve element, a piston connected to the drive shaft at an opposite end from the valve element, a cylinder provided with a piston chamber housing the piston, and a bellofram that is retained by the piston and partitions the piston chamber. A controller is provided with an abnormality detection program configured to calculate an opening-degree difference between an opening-degree command value outputted to the vacuum open-close valve and an actual opening degree of the valve element driven by the opening-degree command value, and determine that the bellofram is damaged when the opening-degree difference is a first predetermined threshold value or more.