Heat Pump with Pulse Width Modulation Control

Abstract

A heat pump is provided with a component that has a pulse width modulation control to adjust system capacity. Thus, by utilizing a pulse width modulation technique to control this component, the present invention is able to closely tailor the delivered capacity of the heat pump to that which is demanded, without cycling the unit. In one embodiment, the component has a suction pulse width modulation valve. In another embodiment, the component which is modulated is the compressor pump unit, and, in particular, a pair of scroll members that are allowed to move into and out of contact with each other. The pulse width modulation control device can also be utilized in combination with a heat pump having an economizer function and/or an un-loader function.

1 . A heat pump comprising:
 a compressor for delivering a compressed refrigerant to a discharge line;   a routing flow control device for selectively routing refrigerant from said discharge line to either an outdoor heat exchanger when in a cooling mode of operation, and to an indoor heat exchanger when in a heating mode of operation; and   at least one component provided with a pulse width modulation control to control the amount of refrigerant passing through this component.   
   
   
       2 . The heat pump as set forth in  claim 1 , wherein said at least one component is a suction pulse width modulation valve provided on a suction line delivering refrigerant to said compressor. 
   
   
       3 . The heat pump as set forth in  claim 1 , wherein pulse width modulation cycle is between 3 and 30 seconds. 
   
   
       4 . The heat pump as set forth in  claim 1 , wherein said at least one component is a compressor pump unit. 
   
   
       5 . The heat pump as set forth in  claim 4 , wherein said compressor pump unit is modulated by said pulse width modulation control to allow scroll members to move into and out of contact with each other. 
   
   
       6 . The heat pump as set forth in  claim 1 , wherein said heat pump is further provided with an economizer function. 
   
   
       7 . The heat pump as set forth in  claim 6 , wherein said economizer function is provided with an economizer heat exchanger. 
   
   
       8 . The heat pump as set forth in  claim 6 , wherein said economizer function is provided with a flash tank. 
   
   
       9 . The heat pump as set forth in  claim 1 , wherein an unloader function selectively unloads at least a portion of refrigerant at least partially compressed by said compressor back to a suction line. 
   
   
       10 . A method of operating a heat pump comprising the steps of:
 (1) providing a compressor, said compressor being provided with a discharge line, said discharge line communicating with a flow control device for selectively routing refrigerant from said discharge line to either an indoor heat exchanger in a heating mode of operation, or to an outdoor heat exchanger in a cooling mode of operation;   (2) operating said flow control device to selectively route refrigerant from said discharge line to one of said indoor and outdoor heat exchangers, and to route refrigerant from the other of said indoor and outdoor exchangers back to said compressor; and   (3) selectively operating at least one component in the heat pump with a pulse width modulation control to improve the match between the delivered capacity of the heat pump and a desired capacity.   
   
   
       11 . The method as set forth in  claim 10 , wherein said at least one component is a suction pulse width modulation valve provided on a suction line delivering refrigerant to said compressor. 
   
   
       12 . The method as set forth in  claim 10 , wherein pulse width modulation cycle is between 3 and 30 seconds. 
   
   
       13 . The method as set forth in  claim 10 , wherein said at least one component is a compressor pump unit. 
   
   
       14 . The method as set forth in  claim 13 , wherein said compressor pump unit is modulated by said pulse width modulation control to allow scroll members to move into and out of contact with each other. 
   
   
       15 . The method as set forth in  claim 10 , wherein said heat pump is further provided with an economizer function. 
   
   
       16 . The method as set forth in  claim 15 , wherein said economizer function is provided with an economizer heat exchanger. 
   
   
       17 . The method as set forth in  claim 15 , wherein said economizer function is provided with a flash tank. 
   
   
       18 . The method as set forth in  claim 10 , wherein an unloader function selectively unloads at least a portion of refrigerant at least partially compressed by said compressor back to a suction line.