Linear compressor and methods of setpoint control

Abstract

A linear compressor and methods of operation, for example, to control a setpoint and vary cooling capacity of the linear compressor, are provided herein. An appliance may include a linear compressor having a reciprocating piston movable in a negative axial direction toward a chamber and positive axial direction away from the chamber. The appliance may further include a motor operatively coupled to the reciprocating piston, the motor having a resting setpoint, an inverter configured to supply a variable frequency waveform to the motor, and a controller configured to control the variable frequency waveform. The controller may be configured to direct a positive DC voltage to the motor to shift the resting setpoint to increase a cooling capacity of the linear compressor.

What is claimed is: 
     
         1 . An appliance, comprising:
 a linear compressor, the linear compressor having a reciprocating piston movable in a negative axial direction toward a chamber and positive axial direction away from the chamber a motor operatively coupled to the reciprocating piston, the motor having a resting setpoint;   an inverter configured to supply a variable frequency waveform to the motor; and   a controller configured to control the variable frequency waveform, the controller being further configured to direct a positive DC voltage to the motor to shift the resting setpoint to increase a cooling capacity of the linear compressor.   
     
     
         2 . The appliance of  claim 1 , wherein the positive DC voltage is a constant voltage applied across a plurality of sinusoidal cycles of the variable frequency waveform. 
     
     
         3 . The appliance of  claim 1 , wherein the controller is further configured to apply an amplitude skew increasing half-cycle amplitude in the positive axial direction for a plurality of sinusoidal cycles of the linear compressor. 
     
     
         4 . The appliance of  claim 1 , wherein the controller is further configured to apply a phase skew increasing half-cycle wavelength in the positive axial direction for a plurality of sinusoidal cycles of the linear compressor. 
     
     
         5 . The appliance of  claim 1 , wherein the controller is further configured to:
 determine that additional cooling capacity is required at the refrigerator; and   increase the positive DC voltage in response to determining that additional cooling capacity is required.   
     
     
         6 . The appliance of  claim 5 , wherein increasing the positive DC voltage comprises increasing the positive DC voltage by a predetermined voltage value. 
     
     
         7 . The appliance of  claim 6 , wherein the predetermined voltage value is chosen from a predetermined range of voltage values associated with increased cooling capacities. 
     
     
         8 . The appliance of  claim 1 , further comprising a temperature sensor configured to signal that a pull-down event is required at the refrigerator. 
     
     
         9 . The appliance of  claim 1 , further comprising a temperature selection control configured to select additional cooling capacity from the linear compressor. 
     
     
         10 . The appliance of  claim 1 , wherein the controller is further configured to decrease the positive DC voltage to zero volts to reset the resting setpoint to return to a nominal cooling capacity of the linear compressor 
     
     
         11 . A method for operating a linear compressor of a refrigerator, the linear compressor comprising a motor and a reciprocating piston movable in a negative axial direction toward a chamber and positive axial direction away from the chamber, the method comprising:
 supplying a variable frequency waveform to the motor of the linear compressor to produce a reciprocal motion in the piston at a first cooling capacity;   determining that an increase in cooling capacity is required; and   directing a positive direct current (DC) voltage to the motor to induce an extension force at the motor in the positive axial direction during at least a portion of the supplying step in response to the determining step.   
     
     
         12 . The method of  claim 11 , wherein the positive DC voltage is a constant voltage applied across a plurality of sinusoidal cycles of the linear compressor. 
     
     
         13 . The method of  claim 11 , further comprising applying an amplitude skew increasing half-cycle amplitude in the positive axial direction for a plurality of sinusoidal cycles of the linear compressor. 
     
     
         14 . The method of  claim 11 , further comprising applying a phase skew increasing half-cycle wavelength in the positive axial direction for a plurality of sinusoidal cycles of the linear compressor. 
     
     
         15 . The method of  claim 11 , wherein the determining that the increase in cooling capacity is required comprises determining that a pull-down event is occurring in the refrigerator. 
     
     
         16 . The method of  claim 11 , wherein the determining that the increase in cooling capacity is required comprises receiving a selection to pull-down a temperature of a storage area of the refrigerator. 
     
     
         17 . The method of  claim 11 , further comprising:
 determining whether additional cooling capacity is required after applying the extension force; and   increasing the positive DC voltage in response to determining that additional cooling capacity is required.   
     
     
         18 . The method of  claim 17 , wherein increasing the positive DC voltage comprises increasing the positive DC voltage by a predetermined voltage value. 
     
     
         19 . The method of  claim 18 , wherein the predetermined voltage value is chosen from a predetermined range of voltage values associated with increased cooling capacities. 
     
     
         20 . The method of  claim 11 , wherein the extension force is sufficient to shift a resting setpoint of the linear compressor.