Air conditioner

Abstract

It is an object of the present invention to provide an air conditioner for inhibiting noise increase and heating performance degradation due to frost attachment onto an outdoor heat exchanger. In an air conditioner ( 1 ), a determining part ( 43 ) of a control unit ( 4 ) determines that the amount of frost attaching onto an outdoor heat exchanger ( 13 ) is increased when a difference between an outdoor temperature To and an outdoor heat exchanger temperature Te is increased, and executes a frost attaching condition operation control for reducing the rotation speed of an outdoor fan ( 23 ). The operating frequency of the compressor ( 11 ) is herein increased in accordance with the reduction amount of the temperature of an indoor heat exchanger ( 15 ). The control unit ( 4 ) includes change amounts preliminarily set for changing the operating frequency of the compressor ( 11 ) in stages. The change amounts correspond to the stages on a one-to-one basis. The control unit ( 4 ) increases the operating frequency of the compressor ( 11 ) by corresponding one of the change amounts required for upgrading a present stage of the operating frequency of the compressor ( 11 ) to a stage immediately higher than the present stage every time the temperature of the outdoor heat exchanger ( 15 ) is reduced by a predetermined amount, and reduces the rotation speed of the outdoor fan ( 23 ) in accordance with the change amount.

1 . An air conditioner using a vapor compression refrigeration cycle in which a refrigerant is sequentially circulated through a compressor, an indoor heat exchanger, a decompressor and an outdoor heat exchanger during execution of a heating operation, the air conditioner comprising:
 an outdoor fan configured to blow the outdoor heat exchanger; and   a control unit including a determining part configured to determine whether or not an amount of frost attaching onto the outdoor heat exchanger is increased during execution of the heating operation, the control unit configured to control an operating frequency of the compressor and a rotation speed of the outdoor fan,   the control unit being further configured to
 reduce the rotation speed of the outdoor fan when the determining part determines that the amount of frost attaching onto the outdoor heat exchanger is increased, and 
 execute a frost attaching condition operation control in order to increase the operating frequency of the compressor either simultaneously with reducing the rotation speed of the outdoor fan or when a predetermined performance degradation is substantially caused after reducing the rotation speed of the outdoor fan. 
   
     
     
         2 . The air conditioner recited in  claim 1 , wherein
 the control unit is further configured to reduce the rotation speed of the outdoor fan in accordance with an increase amount of the operating frequency of the compressor during execution of the frost attaching condition operation control.   
     
     
         3 . The air conditioner recited in  claim 1  further comprising:
 a first temperature sensor configured to detect an outdoor temperature; and 
 a second temperature sensor configured to detect a temperature of the outdoor heat exchanger, 
 the control unit being further configured to
 monitor a difference between a value detected by the first temperature sensor and a value detected by the second temperature sensor, and 
 determine that the amount of frost attaching onto the outdoor heat exchanger is increased when the difference is increased. 
 
 
     
     
         4 . The air conditioner recited in  claim 3 , further comprising:
 a third temperature sensor configured to detect a temperature of the indoor heat exchanger,   the control unit being further configured to
 monitor the temperature of the indoor heat exchanger with the third temperature sensor, and 
 increase the operating frequency of the compressor in accordance with a reduction amount of the temperature of the indoor heat exchanger during execution of the frost attaching condition operation control. 
   
     
     
         5 . The air conditioner recited in  claim 4 , wherein
 the control unit has change amounts preliminarily set in order to change the operating frequency of the compressor in stages, the change amounts corresponding to the stages on a one-to-one basis, and   the control unit is further configured to control the operating frequency of the compressor to be increased by corresponding one of the change amounts required to upgrade a present stage of the operating frequency of the compressor to a stage immediately higher than the present stage every time the temperature of the indoor heat exchanger is reduced by a predetermined amount.   
     
     
         6 . The air conditioner recited in  claim 3 , further comprising:
 a pressure sensor disposed on a discharge side of the compressor, the pressure sensor being configured to detect a higher side pressure,   the control unit being further configured to
 monitor the higher side pressure with the pressure sensor, and 
 increase the operating frequency of the compressor in accordance with a reduction amount of the higher side pressure during execution of the frost attaching condition operation control. 
   
     
     
         7 . The air conditioner recited in  claim 6 , wherein
 the control unit has change amounts preliminarily set in order to change the operating frequency of the compressor in stages, the change amounts corresponding to the stages on a one-to-one basis, and   the control unit is further configured to control the operating frequency of the compressor to be increased by corresponding one of the change amounts required to upgrade a present stage of the operating frequency of the compressor to a stage immediately higher than the present stage every time the higher side pressure is reduced by a predetermined amount.   
     
     
         8 . The air conditioner recited in  claim 1 , wherein
 the control unit is further configured to
 count an elapsed time after activation of the compressor, and 
 execute a defrosting operation control in order to resolve frost attachment onto the outdoor heat exchanger when the elapsed time reaches a predetermined period of time during execution of the frost attaching condition operation control while an evaporation temperature of the refrigerant reaches a predetermined temperature. 
   
     
     
         9 . The air conditioner recited in  claim 2 , further comprising:
 a first temperature sensor configured to detect an outdoor temperature; and   a second temperature sensor configured to detect a temperature of the outdoor heat exchanger,   the control unit being further configured to
 monitor a difference between a value detected by the first temperature sensor and a value detected by the second temperature sensor, and 
 determine that the amount of frost attaching onto the outdoor heat exchanger is increased when the difference is increased. 
   
     
     
         10 . The air conditioner recited in  claim 9 , further comprising:
 a third temperature sensor configured to detect a temperature of the indoor heat exchanger,   the control unit being further configured to
 monitor the temperature of the indoor heat exchanger with the third temperature sensor, and 
 increase the operating frequency of the compressor in accordance with a reduction amount of the temperature of the indoor heat exchanger during execution of the frost attaching condition operation control. 
   
     
     
         11 . The air conditioner recited in  claim 10 , wherein
 the control unit has change amounts preliminarily set in order to change the operating frequency of the compressor in stages, the change amounts corresponding to the stages on a one-to-one basis, and   the control unit is further configured to control the operating frequency of the compressor to be increased by corresponding one of the change amounts required to upgrade a present stage of the operating frequency of the compressor to a stage immediately higher than the present stage every time the temperature of the indoor heat exchanger is reduced by a predetermined amount.   
     
     
         12 . The air conditioner recited in  claim 9 , further comprising:
 a pressure sensor disposed on a discharge side of the compressor, the pressure sensor being configured to detect a higher side pressure,   the control unit being further configured to
 monitor the higher side pressure with the pressure sensor, and 
 increase the operating frequency of the compressor in accordance with a reduction amount of the higher side pressure during execution of the frost attaching condition operation control. 
   
     
     
         13 . The air conditioner recited in  claim 12 , wherein
 the control unit has change amounts preliminarily set in order to change the operating frequency of the compressor in stages, the change amounts corresponding to the stages on a one-to-one basis, and   the control unit is further configured to control the operating frequency of the compressor to be increased by corresponding one of the change amounts required to upgrade a present stage of the operating frequency of the compressor to a stage immediately higher than the present stage every time the higher side pressure is reduced by a predetermined amount.   
     
     
         14 . The air conditioner recited in  claim 2 , wherein
 the control unit is further configured to
 count an elapsed time after activation of the compressor, and 
 execute a defrosting operation control in order to resolve frost attachment onto the outdoor heat exchanger when the elapsed time reaches a predetermined period of time during execution of the frost attaching condition operation control while an evaporation temperature of the refrigerant reaches a predetermined temperature. 
   
     
     
         15 . The air conditioner recited in  claim 3 , wherein
 the control unit is further configured to
 count an elapsed time after activation of the compressor, and 
 execute a defrosting operation control in order to resolve frost attachment onto the outdoor heat exchanger when the elapsed time reaches a predetermined period of time during execution of the frost attaching condition operation control while an evaporation temperature of the refrigerant reaches a predetermined temperature.