Refrigeration apparatus

Abstract

A refrigeration apparatus ( 10 ) includes: a refrigerant circuit ( 20 ) provided with a variable-opening expansion valve ( 13 ); and a valve control means ( 33 ) for controlling the opening of the expansion valve ( 13 ) by outputting to the expansion valve ( 13 ) an opening command value equal to or larger than a lower limit command value. During operation of a refrigeration cycle and in a lower-limit-controlled state in which the opening command value is equal to the lower limit command value, the valve control means ( 33 ) performs a first determination operation of determining whether the refrigerant flow through the expansion valve ( 13 ) is in an excessively large amount state or not based on a condition of refrigerant between the expansion valve ( 13 ) and the suction side of a compressor ( 11 ), and corrects the lower limit command value to a smaller value if the determination result in the first determination operation is that the refrigerant flow through the expansion valve ( 13 ) is in an excessively large amount state.

1 . A refrigeration apparatus comprising:
 a refrigerant circuit ( 20 ) provided with a compressor ( 11 ) and an expansion valve ( 13 ) variable in opening, the refrigerant circuit ( 20 ) being operable in a refrigeration cycle; and   a valve control means ( 33 ) configured to control the opening of the expansion valve ( 13 ) by outputting to the expansion valve ( 13 ) an opening command value equal to or larger than a lower limit command value, wherein   the valve control means ( 33 ) is configured to perform, during operation of the refrigeration cycle and in a lower-limit-controlled state in which the opening command value is equal to the lower limit command value, a first determination operation of determining whether the refrigerant flow through the expansion valve ( 13 ) is in an excessively large amount state or not based on a condition of low-pressure refrigerant between the expansion valve ( 13 ) and the suction side of the compressor ( 11 ), and correct the lower limit command value to a smaller value if the determination result in the first determination operation is that the refrigerant flow through the expansion valve ( 13 ) is in an excessively large amount state.   
     
     
         2 . The refrigeration apparatus of  claim 1 , wherein the valve control means ( 33 ) is configured to perform, during operation of the refrigeration cycle and in the lower-limit-controlled state, a second determination operation of determining whether the refrigerant flow through the expansion valve ( 13 ) is in an excessively small amount state or not based on a condition of the low-pressure refrigerant, and correct the lower limit command value to a larger value if the determination result in the second determination operation is that the refrigerant flow through the expansion valve ( 13 ) is in an excessively small amount state. 
     
     
         3 . The refrigeration apparatus of  claim 2 , wherein the valve control means ( 33 ) is configured to perform the second determination operation after start of the lower-limit-controlled state and then perform the first determination operation. 
     
     
         4 . The refrigeration apparatus of  claim 2 , wherein the valve control means ( 33 ) calculates a corrected lower limit command value by subtracting a predetermined first correction coefficient from the current lower limit command value if the determination result in the first determination operation is that the refrigerant flow through the expansion valve ( 13 ) is in an excessively large amount state, and the valve control means ( 33 ) calculates a corrected lower limit command value by adding a predetermined second correction coefficient larger than the first correction coefficient to the current lower limit command value if the determination result in the second determination operation is that the refrigerant flow through the expansion valve ( 13 ) is in an excessively small amount state. 
     
     
         5 . The refrigeration apparatus of  claim 2 , wherein the valve control means ( 33 ) performs the first determination operation when the duration of the lower-limit-controlled state reaches a predetermined reference time value. 
     
     
         6 . The refrigeration apparatus of  claim 2 , wherein the valve control means ( 33 ) performs, during operation of the refrigeration cycle, a superheat control by controlling the opening of the expansion valve ( 13 ) to bring the degree of superheat of refrigerant sucked in the compressor ( 11 ) to a predetermined desired degree of superheat, but stops the superheat control throughout the second determination operation. 
     
     
         7 . The refrigeration apparatus of  claim 1 , wherein if in the first determination operation the degree of superheat of the low-pressure refrigerant is below a predetermined wet-side reference value, the valve control means ( 33 ) determines that the refrigerant flow through the expansion valve ( 13 ) is in an excessively large amount state. 
     
     
         8 . The refrigeration apparatus of  claim 2 , wherein if in the second determination operation at least one of a condition in which the pressure of the low-pressure refrigerant is below a predetermined pressure reference value, and a condition in which the degree of superheat of the low-pressure refrigerant is above a predetermined dry-side reference value is satisfied, the valve control means ( 33 ) determines that the refrigerant flow through the expansion valve ( 13 ) is in an excessively small amount state.