Method for controlling opening of expansion valve

Abstract

The invention discloses a method for controlling opening of an expansion valve. The method includes the steps of firstly, setting targeted superheat degree, superheat degree difference reduced value, quick action quantity, stable action quantity, quick waiting time and stable waiting time, wherein the quick waiting time is less than the stable waiting time; secondly calculating current superheat degree difference; and thirdly, judging whether absolute value of the current superheat degree difference is larger than the superheat degree difference reduced value or not, according to the judged result, controlling the expansion valve to act according to the quick action quantity or stable action quantity, and returning to the step 2 after corresponding quick waiting time or stable waiting time. The method is used for arranging corresponding regulation areas according to the superheat degree difference, and time interval of action of the expansion valve is short when the superheat degree difference is far from the targeted superheat degree, so that the superheat degree difference is conveniently close to the targeted superheat degree quickly; and time interval of action of the expansion valve is long when the superheat degree difference is close to the targeted superheat degree, the interval is regulated when the current superheat degree changes to be adaptable to the current opening, and accordingly lagged influence and vibration of a system are eliminated and opening of the expansion valve is approximately optimal.

Description

technical field [0001] The invention relates to the technical field of regulating valves, in particular to a method for controlling the opening of an expansion valve. Background technique [0002] In the existing fixed-speed domestic air-conditioning system, capillary tube or thermal expansion valve is generally used for throttling. However, when the capillary is throttling, the flow rate of the refrigerant cannot be adjusted with the change of the working conditions, resulting in the inability to optimize the cooling and heating capacity, poor room temperature reachability, and a series of system problems such as excessive pressure under high temperature conditions; The expansion valve can automatically adjust the refrigerant flow rate according to the degree of superheat, but due to the transfer process from temperature to pressure, there are problems of adjustment lag and large fluctuations, which lead to a decrease in system performance and cannot operate in an optimal s...

AI Technical Summary

Problems solved by technology

[0006] First, the degree of superheat is obtained by detecting the temperature of the outlet and inlet of the evaporator and calculating the difference, or detecting the temperature of the compressor suction inlet and the middle temperature of the evaporator and calculating the difference, and with the adjustment of the expansion valve opening, There is a stable process in the adjustment of the system temperature, and the detected temperature values ​​are often not the stable temperature corresponding to the current opening of the expansion valve. The formation of the stable temperature lags behind the adjustment of the expansion valve opening. Therefore, even if the current opening of the expansion valve The superheat requirement has been met. Due to hysteresis, the control system will continue to adjust the opening according to the detected temperature, which will cause relatively large oscillations in the expansion valve during the adjustment process, and it has not been able to stabilize at the required target value. superior

[0007] Second, when the optimal opening of the expansion valve is controlled by the method of calculating the optimal opening value range by the binary value range search method, the optimal opening determined by the binary value range search method must be above the optimal opening value range Between the lower limit, the minimum amount of expansion valve opening adjustment will be limited by the optimal opening value range, and it is impossible to achieve the minimum precision opening amount control

In addition, the binary value range search method may lead to continuous positive and negative adjustments when the expansion valve opening is adjusted, further increasing the oscillation of the system

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