Servo Valve Nozzle Assembly Thermal Expansion Compensation
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Solution Overview
Problem
Current servo valve nozzle designs face challenges due to high manufacturing costs and calibration difficulties caused by tight interference fits between nozzles and housing, which are exacerbated by thermal expansion differences between materials, leading to stress on the housing and precision requirements.
Innovation Solution
A nozzle assembly comprising multiple parts with matched thermal expansion coefficients, where the first and third nozzle parts are made of the same material and the nozzle housing and second nozzle part are made of the same material, with specific interference fits that adjust retention force in response to temperature changes, allowing for easier calibration and reduced stress on the housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tight interference fit is used to secure the nozzle in the housing, then the nozzle remains in the correct position across temperature changes, but the manufacturing cost increases and calibration becomes difficult
Solution Approach 1:
The nozzle is divided into multiple parts (first nozzle part, second nozzle part, third nozzle part) with different material properties. The first and third nozzle parts are made of materials with a first coefficient of thermal expansion, while the second nozzle part is made of a material with a second coefficient of thermal expansion. This segmentation allows each part to expand or contract differently in response to temperature changes, maintaining the interference fit and nozzle position stability without requiring excessively tight fits that would increase manufacturing cost.
Solution Approach 2:
The invention changes the material parameters (coefficients of thermal expansion) of different nozzle parts to create a thermal compensation mechanism. By selecting materials with different thermal expansion characteristics, the system automatically adjusts the interference fit pressure in response to temperature changes, maintaining reliable nozzle positioning without requiring extremely tight initial fits that would drive up manufacturing costs.
2Reliability
If a tight interference fit is used to secure the nozzle in the housing, then the nozzle remains in the correct position across temperature changes, but the calibration difficulty increases
Solution Approach 1:
The multi-part nozzle construction with different material properties allows the nozzle to be assembled with a manageable interference fit that doesn't completely prevent axial movement. The thermal compensation effect ensures that the interference fit remains sufficient for position stability while still allowing enough play for calibration adjustments to be made.
Solution Approach 2:
By using materials with different thermal expansion coefficients, the interference fit pressure changes with temperature, creating a window of opportunity during calibration where the fit is loose enough to allow adjustment but tight enough to maintain position during operation.
3Reliability
If a tight interference fit is used to secure the nozzle in the housing, then the nozzle remains in the correct position, but the stress on the housing increases
Solution Approach 1:
The segmentation of the nozzle into parts with different thermal expansion properties creates a progressive interference fit system. The first portion of the first nozzle part is interference fitted within the second nozzle part, and the first portion of the third nozzle part is interference fitted with the first portion of the second nozzle part. This distributes the stress across multiple interfaces rather than concentrating it at a single housing-nozzle interface, reducing overall housing stress while maintaining position stability.
Solution Approach 2:
The thermal expansion parameter differences allow the interference fit to self-regulate with temperature changes. As temperature increases, the material with the higher coefficient of thermal expansion expands more, maintaining the interference pressure. As temperature decreases, the fit loosens slightly, reducing stress on the housing while preventing excessive movement.
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 reduces manufacturing costs and simplifies calibration by maintaining nozzle position across a range of temperatures, minimizing stress on the housing and allowing for easier axial movement, thus improving the operational efficiency and precision of servo valves.
Implementation Method 1
The first nozzle part and third nozzle part are made of materials having approximately the same first coefficient of thermal expansion
Implementation Method 2
The nozzle housing and the second nozzle part are made of materials having approximately the same second coefficient of thermal expansion
Implementation Method 3
The first portion of the first nozzle part is interference fitted within the second nozzle part. The first portion of the third nozzle part is interference fitted with the first portion of the second nozzle part. A second portion of the second nozzle part is received with an interference fit within the housing.
Data Source
AI summary
The present disclosure relates to a nozzle assembly for use in a servo valve. The nozzle assembly comprises three nozzle parts and a housing. The second part is coaxial with the first part and surrounds at least a first portion of the first part. The third part is coaxial with the first part, and a first portion of the third nozzle part surrounds a first portion of the second nozzle part, and a second portion of the third part is attached to a second portion of the first part. First and second nozzle parts are made of materials having approximately the same first coefficient of thermal expansion (TE1), and third part and housing are made of materials having approximately the same second coefficient of thermal expansion (TE2). TE1 is different from TE2. The interaction between the portions due to the differences in TE1 and TE2 allow the nozzle assembly to compensate for temperature fluctuations during and operation whilst remaining firmly held in position.