Refrigeration apparatus

Abstract

A refrigeration apparatus ( 10 ) includes: a valve control means ( 33 ) configured to control the opening of an expansion valve ( 13 ); and opening degree detection means ( 32, 34 ) configured to perform, after a pump-down operation in which a compressor ( 11 ) is driven with the expansion valve ( 13 ) closed, an opening degree detection operation of detecting an opening degree that is an opening command value for use in changing the expansion valve ( 13 ) from a closed state to an open state, by determining whether the expansion valve ( 13 ) is open based on a change in state of low-pressure refrigerant between the expansion valve ( 13 ) and the suction side of the compressor ( 11 ), while gradually increasing the opening command value output to the expansion valve ( 13 ) with the compressor ( 11 ) deactivated. The valve control means ( 33 ) controls the expansion valve ( 13 ) using the opening degree detected in the opening degree detection operation.

1 . A refrigeration apparatus including 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 ), the refrigeration apparatus comprising:
 opening degree detection means ( 32 ,  34 ) configured to perform, after a pump-down operation in which the compressor ( 11 ) is driven with the expansion valve ( 13 ) closed, an opening degree detection operation of detecting an opening degree that is an opening command value for use in changing the expansion valve ( 13 ) from a closed state to an open state, by determining whether the expansion valve ( 13 ) is open based on a change in state of low-pressure refrigerant between the expansion valve ( 13 ) and the suction side of the compressor ( 11 ), while gradually increasing the opening command value output to the expansion valve ( 13 ) with the compressor ( 11 ) deactivated,   wherein the valve control means ( 33 ) is configured to control the expansion valve ( 13 ) using the opening degree detected in the opening degree detection operation.   
   
   
       2 . The refrigeration apparatus of  claim 1 , wherein the opening degree detection means ( 32 ,  34 ) is configured to adjust, in the pump-down operation, the high-side pressure of the refrigeration cycle within a fixed range. 
   
   
       3 . The refrigeration apparatus of  claim 1 , wherein the refrigeration apparatus is configured to perform, prior to the pump-down operation, a warming-up operation in which the opening degree detection means ( 32 ,  34 ) adjusts the high-side pressure of the refrigeration cycle within a fixed range while the compressor ( 11 ) is driven with the expansion valve ( 13 ) open. 
   
   
       4 . The refrigeration apparatus of  claim 1 , wherein the opening degree detection means ( 32 ,  34 ) is configured to detect as the opening degree an opening command value determined when the pressure of the low-pressure refrigerant exceeds a predetermined low-side pressure threshold value. 
   
   
       5 . The refrigeration apparatus of  claim 4 , wherein when the opening command value reaches a predetermined upper limit, the opening degree detection means ( 32 ,  34 ) detects the upper limit as the opening degree even if the pressure of the low-pressure refrigerant is the low-side pressure threshold value or below. 
   
   
       6 . The refrigeration apparatus of  claim 1 , wherein the opening degree detection means ( 32 ,  34 ) is configured to detect, in the opening degree detection operation, the opening degree by repeating a first operation of increasing the opening command value by a preset value and a second operation of determining whether the expansion valve ( 13 ) is open based on a change in state of the low-pressure refrigerant in this order until it is detected in the second operation that the expansion valve ( 13 ) is open. 
   
   
       7 . The refrigeration apparatus of  claim 1 , wherein
 the valve control means ( 33 ) is configured to determine the opening command value within a range not less than a lower limit command value previously set in the valve control means ( 33 ), and   the opening degree detection means ( 32 ,  34 ) is configured to correct the lower limit command value using the opening degree.   
   
   
       8 . The refrigeration apparatus of  claim 7 , wherein the opening degree detection means ( 32 ,  34 ) is configured to set an assumed value of the opening degree, calculate as a correction value a value obtained by subtracting the assumed value from the opening degree, and calculate a corrected lower limit command value by adding the correction value to the lower limit command value previously set in the valve control means ( 33 ). 
   
   
       9 . The refrigeration apparatus of  claim 7 , wherein the opening degree detection means ( 32 ,  34 ) is configured to correct again the lower limit command value, which has been corrected using the opening degree, if a predetermined criterion relating to the amount of refrigerant flow through the expansion valve ( 13 ) is satisfied in a lower-limit-controlled state in which, during a normal operation in which a space to be controlled is controlled in temperature, the opening command value is equal to the lower limit command value. 
   
   
       10 . The refrigeration apparatus of  claim 9 , wherein the opening degree detection means ( 32 ,  34 ) is configured to correct again the lower limit command value, which has been corrected using the opening degree, to a larger value, if a first condition in which the refrigerant flow through the expansion valve ( 13 ) is in a predetermined excessively small amount state is satisfied as the criterion in the lower-limit-controlled state. 
   
   
       11 . The refrigeration apparatus of  claim 9 , wherein the opening degree detection means ( 32 ,  34 ) is configured to correct again the lower limit command value, which has been corrected using the opening degree, to a smaller value, if a second condition in which the refrigerant flow through the expansion valve ( 13 ) is in a predetermined excessively large amount state is satisfied as the criterion in the lower-limit-controlled state. 
   
   
       12 . The refrigeration apparatus of  claim 1 , wherein the opening degree detection means ( 32 ,  34 ) is configured to perform the opening degree detection operation at startup of the refrigeration apparatus ( 10 ) only if a predetermined condition is satisfied. 
   
   
       13 . The refrigeration apparatus of  claim 9 , wherein
 the opening degree detection means ( 32 ,  34 ) is configured to perform the opening degree detection operation at startup of the refrigeration apparatus ( 10 ) only if a predetermined condition is satisfied, and   the opening degree detection means ( 32 ,  34 ) comprises a memory part ( 35 ) for storing as a correction value the difference between the lower limit command value previously set in the valve control means ( 33 ) and the corrected lower limit command value and is configured to correct the lower limit command value using the correction value stored in the memory part ( 35 ) if not performing the opening degree detection operation at startup of the refrigeration apparatus ( 10 ).