Servo-Controlled Fluid Valve Closure Under Thermal Seat Expansion
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Solution Overview
Problem
Existing fluid control valves using linear servomotors face issues with valve seat expansion due to high temperatures, leading to motor overload and potential breakage, as well as sealing failures from misalignment of valve elements, which are exacerbated by thermal expansion and abrasion of the valve seat.
Innovation Solution
A fluid control valve design incorporating an elastic member to apply a closing force, utilizing position and thrust control modes with a predetermined switch to ensure the valve element reaches the close position solely through the elastic force, avoiding motor overload and ensuring contact with the valve seat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a linear servomotor is used to precisely control the valve element position, then the valve open degree can be accurately controlled, but the motor is subjected to high load when the valve seat expands due to thermal heating, causing potential motor breakage
Solution Approach 1:
The origin position of the servomotor is set in advance at a position where the valve element and valve seat are separated by a predetermined distance, rather than at the contact position. This preliminary positioning prevents the motor from applying high load when thermal expansion occurs during operation
Solution Approach 2:
The control system changes the reference origin position parameter based on thermal conditions. By setting the origin position considering thermal expansion of the valve seat, the system adapts to temperature changes and prevents motor overload while maintaining control precision
2Reliability
If the origin position is set at the contact position between valve element and valve seat, then the valve can be fully closed, but thermal expansion of the valve seat causes the valve element to contact the valve seat before the motor reaches the origin position, creating high load on the motor
Solution Approach 1:
The origin position is predetermined to be separated from the contact position by a specific distance. This preliminary separation ensures that when the motor returns to the origin position, the valve element does not contact the thermally expanded valve seat, preventing high load conditions
3Reliability
If the valve seat is made of resin material like PFA for sealing performance, then the sealing ability is improved, but the valve seat expands significantly when heated by the control fluid, causing misalignment and potential sealing failure
Solution Approach 1:
The control system compensates for thermal expansion by changing the origin position parameter. The origin position is set considering the expected thermal expansion of the resin valve seat, allowing the system to maintain proper valve closure and sealing performance under elevated temperature 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
Prevents motor burnout and sealing failures by using an elastic member to ensure valve closure, maintaining the closed state without motor load and ensuring reliable valve operation under thermal expansion and abrasion conditions.
Implementation Method 1
provided with an elastic member to apply an urging force to the valve element in a closing direction
Implementation Method 2
the valve seat is heated by the control fluid and expanded. By this expansion, a dimension of the valve seat in an opening/closing direction (a thickness dimension) of a valve element could be larger than a dimension under the normal temperature
Data Source
AI summary
The present invention has: a valve body; a servo motor having a drive shaft for operating the valve body; a position control mode for controlling the drive shaft to move the drive shaft to a target position, and a thrust control mode for controlling the drive shaft to cause the drive shaft to obtain a target thrust; and a control program that, when operating the valve body from a valve open position to a valve close position, controls the servo motor in the position control mode from the valve open position until the valve body reaches a predetermined position before reaching the valve close position, and, from the predetermined position, switches the control of the servo motor from the position control mode to the thrust control mode with a target thrust of zero, and causes the valve body to reach the valve close position only by the biasing force.