Method and apparatus for control of a variable speed compressor

Abstract

A vapor compression system includes a fluid circuit circulating a refrigerant in a closed loop. The fluid circuit has operably disposed therein, in serial order, a variable speed compressor, a first heat exchanger, an expansion device and a second heat exchanger. A first blower device is associated with the first heat exchanger. A speed of the first blower device is dependent upon a speed of the compressor. A second blower device is associated with the second heat exchanger. A speed of the second blower device is dependent upon the speed of the compressor.

1 . A vapor compression system comprising: 
 a fluid circuit circulating a refrigerant in a closed loop, said fluid circuit having operably disposed therein, in serial order, a variable speed compressor, a first heat exchanger, an expansion device and a second heat exchanger;    a first blower device associated with said first heat exchanger, a speed of said first blower device being dependent upon a speed of said compressor; and    a second blower device associated with said second heat exchanger, a speed of said second blower device being dependent upon the speed of said compressor.    
   
   
       2 . The system of  claim 1  wherein said first heat exchanger comprises a condenser, said second heat exchanger comprising an evaporator.  
   
   
       3 . The system of  claim 1  wherein the speed of said first blower device is approximately equal to the speed of said second blower device.  
   
   
       4 . The system of  claim 3  further comprising a blower motor operatively coupled to each of said first blower device and said second blower device.  
   
   
       5 . The system of  claim 4  wherein the blower motor has a plurality of discrete operating speeds each corresponding to a respective range of compressor speeds.  
   
   
       6 . A method of controlling a room temperature, said method comprising the steps of: 
 determining a first temperature differential between a first actual temperature and a desired temperature;    operating a compressor;    ascertaining a subsequent temperature differential between a subsequent actual temperature and the desired temperature after said operating step;    decreasing a speed of said compressor if the subsequent temperature differential is less than an immediately preceding temperature differential; and    repeating said operating, ascertaining, and decreasing steps so long as the speed of said compressor is greater than a threshold speed and the subsequent temperature differential is greater than a threshold temperature differential.    
   
   
       7 . The method of  claim 6  comprising the further step of selecting one of a first mode and a second mode of operating said compressor, said compressor being operated at a highest speed in the first mode if the first temperature differential exceeds a first value, said compressor being operated at the highest speed in the second mode if the first temperature differential exceeds a second value greater than the first value.  
   
   
       8 . The method of  claim 7  wherein said selecting step includes selecting one of the first mode, the second mode, and a third mode in which the speed of said compressor is substantially continuously varied based upon determined temperature differentials.  
   
   
       9 . The method of  claim 6  comprising the further step of increasing the speed of said compressor if the subsequent temperature differential is greater than an immediately preceding temperature differential.  
   
   
       10 . The method of  claim 6  wherein the threshold speed comprises a minimum speed.  
   
   
       11 . The method of  claim 6  wherein the threshold temperature differential is approximately zero.  
   
   
       12 . The method of  claim 6  comprising the further step of operating a fan motor at a speed dependent upon the speed of the compressor.  
   
   
       13 . The method of  claim 6  wherein a time period between said ascertaining steps is dependent upon the speed of the compressor.  
   
   
       14 . A vapor compression system comprising: 
 a variable speed compressor; and    a control device configured to: 
 repetitively determine a temperature differential between an actual room temperature and a desired room temperature; and  
 selectively operate said compressor in a first mode and a second mode, the first mode including decreasing a speed of said compressor after each said temperature differential determination so long as a most recently determined temperature differential is less than a second most recently determined temperature differential, the second mode including substantially continuously varying the speed of said compressor based upon the determined temperature differentials.  
   
   
   
       15 . The system of  claim 14  wherein the first mode includes increasing the speed of said compressor if the most recently determined temperature differential is greater than the second most recently determined temperature differential.  
   
   
       16 . The system of  claim 14  wherein the speed of said compressor is decreased after each said temperature differential determination so long as the speed of said compressor is greater than a threshold speed.  
   
   
       17 . The system of  claim 16  wherein the threshold speed comprises a minimum speed.  
   
   
       18 . The system of  claim 16  wherein said control device is configured to operate said compressor so long as the actual room temperature is greater than the desired room temperature.  
   
   
       19 . The system of  claim 16  further comprising a fan motor configured to blow air across a heat exchanger that is in fluid communication with said compressor, said control device being configured to operate said fan motor at a speed dependent upon the speed of the compressor.  
   
   
       20 . The system of  claim 16  wherein said control device is configured to repetitively determine the temperature differential at time intervals that are dependent upon the speed of the compressor.