JPS6428464A - Air-conditioning machine - Google Patents

Abstract

PURPOSE: To defrost without residual frost by a comfortable heating by supplying a part of a refrigerant to an outdoor heat exchanger via a defrosting bypass passage while maintaining a heating cycle in a set range of a heat exchange temperature of the exchanger, and switching a four-way valve to a cooling cycle at a set range or lower. CONSTITUTION: In the case of heat exchange temperature TE>-10 deg.C, a frost amount is judged to be relatively small. A controller 9 opens a two-way valve 6. A high temperature refrigerant gas discharged from a compressor 1 is partly passed from a branch point A through a defrosting bypass passage 7 via the valve 6, guided directly to an outdoor heat exchanger 3 to be defrosted. At this time, in the case of TE<-10 deg.C of maintaining a heating cycle, a frosted amount is judged to be large, the valve 6 is opened, part of high temperature refrigerant gas discharged from the compressor 1 is guided to the exchanger 3 via the passage 7 to defrost an inlet side of the exchanger 3 at the time of heating. After a predetermined time, the valve 6 is closed, and a four-way valve 2 is closed to be switched to a cooling cycle, and the refrigerant is circulated. Thus, the exchanger 3 is defrosted from its outlet side at the time of heating.