Expansion valve device

Abstract

An expansion valve device includes an electric driver having a stepping motor so as to control an opening degree of a refrigerant passage by displacing a valve member in accordance with a rotation angle of the stepping motor. A controller drives the stepping motor in a micro step when a flow rate of refrigerant flowing through the refrigerant passage is equal to or less than a predetermined value, and drives the stepping motor in a full step when the flow rate of the refrigerant is larger than the predetermined value.

1 . An expansion valve device arranged in a refrigerating cycle, the expansion valve device decompressing and expanding refrigerant circulating in the refrigerating cycle, the expansion valve device comprising:
 a housing defining a refrigerant passage through which the refrigerant circulates;   a valve member arranged in the housing so as to change an opening degree of the refrigerant passage;   an electric driver having 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; and   a controller that drives and controls the stepping motor, wherein   the controller drives the stepping motor in a micro step when the opening degree is changed within a first flow rate region where a flow rate of the refrigerant flowing through the refrigerant passage is equal to or less than a predetermined value, and   the controller drives the stepping motor in a full step when the opening degree is changed within a second flow rate region where the flow rate of the refrigerant flowing through the refrigerant passage is larger than the predetermined value.   
     
     
         2 . The expansion valve device according to  claim 1 , wherein
 the controller selectively switches an operation mode of the refrigerating cycle between a decompression mode and a full-open mode,   in the decompression mode, the refrigerant is decompressed and expanded within the first flow rate region when it is necessary to decompress the refrigerant passing through the refrigerant passage,   in the full-open mode, the valve member causes the opening degree of the refrigerant passage to become the maximum in a manner that the flow rate of the refrigerant flowing through the refrigerant passage becomes the maximum within the second flow rate region when it is unnecessary to decompress the refrigerant passing through the refrigerant passage, and   the controller drives the stepping motor in the full step when the controller switches one of the decompression mode and the full open mode into the other.   
     
     
         3 . The expansion valve device according to  claim 1 , wherein
 the controller drives the stepping motor in the micro step by supplying a constant current when the opening degree is changed in the first flow rate region.   
     
     
         4 . The expansion valve device according to  claim 3 , wherein
 the controller increases the constant current in accordance with an increase in a pressure difference between a pressure of the refrigerant upstream of the valve member and a pressure of the refrigerant downstream of the valve member, or the controller increases the constant current in accordance with an increase in a pressure of the refrigerant upstream of the valve member.