Refrigerant system with pulse width modulation control in combination with expansion device control

Abstract

A refrigerant system is provided with pulse width modulation control to adjust the amount of refrigerant compressed by a compressor. In one embodiment, a pulse width modulation control controls a suction modulation valve cycled between open and closed positions. In a second embodiment, the compressor itself is cycled between a position at which it compresses refrigerant and a position at which the compression elements are disengaged. In either embodiment, the control also cycles the expansion device in concert with cycling the pulse width modulation valve or the compressor. In this manner, pressure fluctuations in the refrigerant system do not exceed desirable levels. Typical cycle time for pulse width modulation control is between 5 and 30 seconds, and typical offset (delay) time for an expansion device may be between 0 and 3 seconds.

1 . A refrigerant system comprising:
 a compressor for compressing a refrigerant and delivering the refrigerant to a first heat exchanger, refrigerant passing from said first heat exchanger through an expansion device, into a second heat exchanger, refrigerant passing from said second heat exchanger back to said compressor; and   a pulse width modulation control for rapidly modulating the flow of refrigerant from the compressor between high and low flow positions, said control also using pulse width modulation for moving said expansion device predominantly toward a closed position when the compressor is in said low flow position and moving said expansion device predominantly toward an open position when the compressor is in said high flow position.   
   
   
       2 . The refrigerant system as set forth in  claim 1 , wherein said expansion device is an electronically controlled expansion device. 
   
   
       3 . The refrigerant system as set forth in  claim 1 , wherein a suction modulation valve is positioned between said second heat exchanger and said compressor, and said suction modulation valve being controlled to rapidly open and close to adjust the flow of refrigerant to said compressor between the high and low flow positions. 
   
   
       4 . The refrigerant system as set forth in  claim 1 , wherein said compressor being a scroll compressor, and having a back pressure chamber, which is rapidly cycled between high and low pressure conditions to move said compressor between the high and low flow positions. 
   
   
       5 . The refrigerant system as set forth in  claim 1 , wherein said expansion device is moved to a fully closed position when the compressor is in said low flow position. 
   
   
       6 . The refrigerant system as set forth in  claim 1 , wherein a pulse width modulation cycle time is between 2 and 30 seconds. 
   
   
       7 . The refrigerant system as set forth in  claim 1 , wherein an expansion device time in said closed position is different from a compressor time in said low flow position. 
   
   
       8 . The refrigerant system as set forth in  claim 7 , wherein said time difference is between 1 and 3 seconds. 
   
   
       9 . The refrigerant system as set forth in  claim 1 , wherein the expansion device cycle is delayed with respect to the compressor cycle. 
   
   
       10 . The refrigerant system as set forth in  claim 9 , wherein said delay is between 1 and 3 seconds. 
   
   
       11 . The refrigerant system as set forth in  claim 1 , wherein vibration on at least one component in the refrigerant system is monitored, and the monitored vibration being utilized to adjust at least one operational parameter of at least one of the pulse width modulated expansion device and the pulse width modulated refrigerant flow from the compressor. 
   
   
       12 . The refrigerant system as set forth in  claim 1 , wherein pressure fluctuation control is provided to tightly maintain at least one of temperature and humidity in an environment to be conditioned. 
   
   
       13 . The refrigerant system as set forth in  claim 1 , wherein the pulse width modulation of the expansion device and the pulse width modulation of the refrigerant flow from the compressor are provided to control and limit pressure fluctuations within said first heat exchanger, within said second heat exchanger or within both said first and said second heat exchangers. 
   
   
       14 .- 25 . (canceled) 
   
   
       26 . A refrigerant system comprising:
 a compressor for compressing a refrigerant and delivering the refrigerant to a first heat exchanger, refrigerant passing from said first heat exchanger through an expansion device, into a second heat exchanger, refrigerant passing from said second heat exchanger back to said compressor; and   a pulse width modulation control for a suction modulation valve positioned between said second heat exchanger and said compressor, and said suction modulation valve being rapidly modulated between open and close positions to adjust the flow of refrigerant to the compressor and said control also using pulse width modulation to move said expansion device predominantly toward a closed position when the suction modulation valve is moved toward a closed position and to move said expansion device predominantly toward an open position when the suction modulation valve is moved toward an open position.   
   
   
       27 . A refrigerant system comprising:
 a compressor for compressing a refrigerant and delivering the refrigerant to a first heat exchanger, refrigerant passing from said first heat exchanger through an expansion device, into a second heat exchanger, refrigerant passing from said second heat exchanger back to said compressor, and   said compressor being a scroll compressor, and having a back pressure chamber, which is rapidly cycled by a control using pulse width modulation, to move between high and low pressure conditions to move said compressor between high and low flow positions and said expansion device also being controlled by pulse width modulation and being moved predominantly toward a closed position when said compressor is in said low flow position and being moved predominantly toward an open position when said compressor is in said high flow position.