Preloaded Piezo Actuator Housing for Stable Gas Valve Control
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Solution Overview
Problem
Existing piezoelectric actuators lack protection from environmental factors such as high temperatures and moisture, and do not provide adequate preloading, which is essential for accurate control of gas flow in applications like semiconductor manufacturing.
Innovation Solution
A piezoelectric actuator arrangement that encloses the piezoelectric element in a housing made of materials with minimal thermal expansion, such as Invar or Kovar, and uses preloading elements like Belleville washers to maintain constant preloading, while also sealing the element from the environment using bellows or a hermetic seal for the electrical leads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the piezoelectric element is exposed to the environment for actuation, then the actuator can control gas flow, but the piezoelectric element is damaged by ambient moisture and high temperatures
Solution Approach 1:
A bellows structure is used to seal the piezoelectric element from the ambient environment while allowing for the expansion and contraction movements of the piezoelectric element during actuation. The bellows provides both protection from moisture and thermal isolation, enabling the element to operate safely in harsh environments.
Solution Approach 2:
The piezoelectric element is housed within a sealed housing that creates a protected internal environment. This housing isolates the element from harmful external factors including moisture and high temperatures, allowing the element to maintain its operational integrity while still performing its actuation function.
2Device complexity
If standard housing materials are used, then the actuator structure is simple, but thermal expansion causes inconsistent preloading at elevated temperatures
Solution Approach 1:
The housing is specifically designed with materials and structural features that account for and compensate for thermal expansion effects. This ensures that the preloading force remains consistent even when the actuator operates at elevated temperatures, preventing degradation of actuation performance.
Solution Approach 2:
The actuator employs a composite structure combining the piezoelectric element with preloading elements and a specially designed housing. This composite arrangement allows the housing to provide both mechanical support and thermal compensation, maintaining stable preloading conditions across a range of operating temperatures.
3Measurement precision
If the piezoelectric element is preloaded properly, then accurate control of minute gas flow is achieved, but the element requires protection from environmental damage
Solution Approach 1:
The bellows provides a flexible seal that protects the piezoelectric element while accommodating its dimensional changes during operation. This allows the element to maintain proper preloading for accurate gas flow control without being exposed to environmental damage.
Solution Approach 2:
The sealed housing creates a protected environment that isolates the piezoelectric element from harmful external conditions, ensuring both the reliability of the element and the precision of gas flow control by maintaining consistent preloading conditions.
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 solution provides reliable preloading and protection of the piezoelectric element, enabling accurate control of gas flow even at elevated temperatures and in high-moisture environments, preventing damage from ambient conditions and maintaining consistent performance.
Implementation Method 1
Actuators employing the expansion of piezoelectric elements upon application of voltage potential are known in the art
Implementation Method 2
the housing is made of a material that minimizes thermal expansion in order to maintain constant preloading
Implementation Method 3
The spring washers are stacked and compressed between the housing and the piezoelectric element so as to preload the piezoelectric element
Data Source
AI summary
A valve arrangement for controlling gas flow. A gas block includes a gas inlet, a gas outlet, and a gas cavity fluidly connecting the gas inlet to the gas outlet. A diaphragm is configured for controlling gas flow between the gas inlet and the gas outlet. An actuator is configured to vary the position of the diaphragm so as to control the gas flow. The actuator comprises a tubular housing; a plunger positioned inside the housing and having an actuating extension extending outside of the housing and coupled to the diaphragm, the plunger configured to be slidable inside the housing; a piezoelectric body positioned inside the plunger; and a pre-loader applying force to the plunger so as to press the plunger against the piezoelectric body.