Expansion Valve Dynamic Current Control for Fast Flow Mode Switching
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Solution Overview
Problem
Existing expansion valve devices take a long time to reach the target valve opening degree when switching between small and large flow rate control regions, affecting control accuracy and efficiency.
Innovation Solution
The expansion valve device incorporates a drive control device with a stepping motor and a deceleration mechanism, using a constant current drive that increases in value during mode changes between small and large flow rate regions, and restricts current increases when temperature thresholds are exceeded to prevent functional errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a stepping motor with reduction gear is used to control valve opening, then high flow rate control accuracy is achieved, but it takes long time to move the valve member when switching between small and large flow rate control regions
Solution Approach 1:
The patent applies dynamics by making the driving force variable rather than constant. The drive control device dynamically adjusts the current value based on the operation mode: using a first current value for small flow rate control and a second, larger current value for large flow rate control. This dynamic adjustment allows the system to optimize between precision and speed by selecting appropriate current levels according to the required valve opening range.
Solution Approach 2:
The patent changes the electrical parameter (current value) to resolve the contradiction. By switching between different current values (first current value for precision control in small flow region, second current value for rapid movement in large flow region), the system achieves both high control accuracy when needed and fast response when transitioning between regions.
2Reliability
If constant current drive is used for the stepping motor, then stable motor operation is achieved, but the valve member moves slowly when transitioning between flow rate control modes
Solution Approach 1:
The system transitions from static constant current to dynamic variable current. The drive control device determines the operation mode and selects appropriate current values dynamically. This allows the motor to operate stably at lower current during precision control while enabling rapid movement at higher current during mode transitions, resolving the contradiction between stability and speed.
Solution Approach 2:
The patent implements periodic action by alternating between different current levels based on operational requirements. The system periodically switches between first and second current values depending on whether small or large flow rate control is needed, enabling both stable operation and rapid response at appropriate intervals.
3Speed
If high current is continuously applied to the stepping motor, then fast valve opening changes are achieved, but temperature increase causes functional errors
Solution Approach 1:
The patent applies partial action by using high current (second current value) only when necessary for rapid valve opening changes during large flow rate control, rather than continuously. During small flow rate control, the system uses lower current (first current value). This selective application of high current achieves fast response when needed while minimizing temperature accumulation and functional errors.
Solution Approach 2:
The system uses periodic action by alternating between low and high current states based on operational mode. High current is applied periodically only during transitions to large flow rate control, allowing the motor to cool down during low current periods and preventing excessive temperature rise that would cause functional errors.
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
This solution allows for quicker valve opening degree changes and maintains high flow control accuracy, while preventing temperature-related functional errors, thus improving operational efficiency and reducing transition times between flow rate control modes.
Implementation Method 1
The electric driver has a stepping motor so as to control the opening degree of the refrigerant passage by displacing the valve member in accordance with a rotation angle of the stepping motor
Data Source
AI summary
A drive control device performs a mode change with a constant current between a first mode in which an opening degree of a refrigerant passage is changed in a first flow region where a flow rate of refrigerant flowing through the refrigerant passage is lower than or equal to a predetermined value and a second mode in which the opening degree of the refrigerant passage is changed in a second flow region where the flow rate of refrigerant flowing through the refrigerant passage is higher than the predetermined value. The drive control device increases a value of the constant current at the mode change to be larger than a value of a constant current when the opening degree of the refrigerant passage is changed in the first mode.