Air conditioner and control method thereof

Abstract

An air conditioner including a plurality of compressors uses at least one oil separator for separating oil from an oil-mixed refrigerant discharged from the compressors. The air conditioner performs an oil balancing operation, during which some compressors operate and some do not. At least a portion of the oil separated by the oil separator is distributed to the compressors that are not operating during the oil balancing operation.

1 . An air conditioner, comprising:
 a plurality of compressors;   at least one oil separator for separating oil from a mixture of oil and refrigerant discharged from the compressors; and   an oil balancer that operates, during an oil balancing operation, to send oil from the at least one oil separator to a compressor that is not operating during the oil balancing operation.   
   
   
       2 . The air conditioner of  claim 1 , further comprising a plurality of recovery lines, wherein each recovery line connects the at least one oil separator to an intake of one of the compressors. 
   
   
       3 . The air conditioner of  claim 2 , further comprising a plurality of recovery valves, wherein each recovery valve is arranged on one of the recovery lines to control a flow of oil passing through the recovery line to the intake of the associated compressor. 
   
   
       4 . The air conditioner of  claim 3 , further comprising a controller that controls the recovery valves. 
   
   
       5 . The air conditioner of  claim 4 , wherein during the oil recovery operation, one of the compressors operates and one of the compressors does not operate, and wherein the controller controls the plurality of recovery valves so that at least a portion of the oil separated by the at least one oil separator is directed to the non-operating compressor. 
   
   
       6 . The air conditioner of  claim 2 , wherein the at least one oil separator comprises a plurality of oil separators, wherein one oil separator is provided for each compressor, and wherein each recovery line couples one of the oil separators to its corresponding compressor. 
   
   
       7 . The air conditioner of  claim 6 , wherein the oil balancer includes a bypass line that allows oil to flow between the plurality of recovery lines. 
   
   
       8 . The air conditioner of  claim 7 , wherein the oil balancer further includes at least one bypass valve arranged in the bypass line, to control a flow of oil through the bypass line. 
   
   
       9 . The air conditioner of  claim 8 , further comprising a controller that controls the at least one bypass valve, wherein during the oil recovery operation, one of the compressors operates and one of the compressors does not operate, and wherein the controller controls the at least one bypass valve so that at least a portion of the oil separated by the oil separator of the operating compressor is directed to the non-operating compressor. 
   
   
       10 . The air conditioner of  claim 7 , further comprising a plurality of recovery valves, wherein each recovery valve is arranged on one of the recovery lines to control a flow of oil passing through the recovery line to the intake of the associated compressor. 
   
   
       11 . The air conditioner of  claim 10 , further comprising a controller that controls the plurality of recovery valves, wherein during the oil recovery operation, one of the compressors operates and one of the compressors does not operate, and wherein the controller controls the plurality of recovery valves so that at least a portion of the oil separated by the oil separator of the operating compressor is directed to the non-operating compressor. 
   
   
       12 . The air conditioner of  claim 11 , wherein the oil balancer further includes at least one bypass valve arranged in the bypass line, to control a flow of oil through the bypass line, and wherein the controller also controls the at least one bypass valve. 
   
   
       13 . The air conditioner of  claim 2 , further comprising a plurality of expansion devices, wherein each expansion device operates to reduce a pressure of oil flowing through one of the recovery lines. 
   
   
       14 . The air conditioner of  claim 1 , wherein the compressors operate sequentially during the oil balancing operation. 
   
   
       15 . The air conditioner of  claim 1 , further comprising a plurality of sensors, wherein each sensor detects an amount of oil contained in one of the compressors. 
   
   
       16 . The air conditioner of  claim 15 , further comprising a controller that controls the oil balancer to supply oil to a compressor which contains an insufficient amount of oil, based on sensing data from the sensors. 
   
   
       17 . An air conditioner comprising:
 a plurality of compressors;   at least one oil separator for separating oil from a mixture of oil and refrigerant discharged from the compressors; and   an oil balancer that operates, during an oil balancing operation, to distribute balanced amounts of oil to the compressors, wherein the compressors operate sequentially during the oil balancing operation.   
   
   
       18 . The air conditioner of  claim 17 , wherein during the oil balancing operation, at least one of the compressors operates, and at least one of the compressors does not operate, and wherein the oil balancer supplies oil to all of the compressors except for the compressor that is operating. 
   
   
       19 . The air conditioner of  claim 17 , wherein during the oil balancing operation, at least one of the compressors operates, and at least one of the compressors does not operate, and wherein the oil balancer supplies oil to one of the non-operating compressors. 
   
   
       20 . The air conditioner of  claim 17 , wherein the at least one oil separator comprises a plurality of oil separators, wherein each oil separator corresponds to one of the compressors, and wherein during normal operations, the oil separated in each of the oil separators is returned to an inlet of its corresponding compressor. 
   
   
       21 . A method for controlling an air conditioner that includes a plurality of compressors and at least one oil separator that separates oil from a mixture of oil and refrigerant discharged from the compressors, comprising:
 conducting a normal operation step, during which, oil separated by the at least one oil separator is returned to the operating ones of the plurality of compressors; and   conducting an oil balancing operation, during which, the oil separated by the at least one oil separator is returned to less than all of the compressors.   
   
   
       22 . The method of  claim 21 , wherein during the oil balancing operation, oil is not returned to one of the compressors that is operating during the oil balancing operation. 
   
   
       23 . The method of  claim 21 , wherein during the oil balancing operation, one of the compressors operates and one of the compressors does not operate, and wherein oil is returned to the compressor that is not operating. 
   
   
       24 . The method of  claim 23 , wherein during the oil balancing operation, oil is returned to both the non-operating compressor, and at least one of the operating compressors. 
   
   
       25 . The method of  claim 21 , wherein during the oil balancing operation, the compressors are operated sequentially, and wherein during each sequential operation, oil is not returned to the compressor that is operating. 
   
   
       26 . The method of  claim 21 , wherein during the oil balancing operation, the compressors are operated sequentially, and wherein during each sequential operation, only a portion of the oil being discharged by the operating compressor is returned to the operating compressor. 
   
   
       27 . The method of  claim 21 , wherein the air conditioner comprises a plurality of oil separators, wherein each oil separator corresponds to one of the compressors, wherein recovery lines connect each oil separator to its corresponding compressor, wherein a bypass line allows oil to flow between the recovery lines, and wherein during the oil balancing operation, oil from the oil separator of an operating compressor is sent through the bypass line to at least one of the non-operating compressors. 
   
   
       28 . A method for controlling an air conditioner that includes a plurality of compressors and at least one oil separator that separates oil from a mixture of oil and refrigerant discharged from the compressors, comprising:
 conducting a normal operation step, during which, oil separated by the at least one oil separator is returned to each of the plurality of compressors that are operating; and   conducting an oil balancing operation, during which, at least one of the compressors is not operating, wherein the oil separated by the at least one oil separator is returned to the non-operating compressor.