Heat pump

According to an embodiment of the present invention, provided is a heat pump. The heat pump comprises: a compressor connected to a compressor absorbing passage and a compressor discharging passage; a cooling and heating transfer valve connected to the compressor absorbing passage and the compressor discharge passage; an outdoor heat exchanger having a main passage connected to the cooling and heating transfer valve through an outdoor heat exchanger connecting line and a sub passage; an indoor heat exchanger connected to the cooling and heating transfer valve through an indoor heat exchanger connecting line; an outdoor expansion device connected to the main passage through a first expansion device connecting line; an indoor expansion device connected to the indoor heat exchanger through a second expansion device connecting line and connected to the outdoor expansion device through a third expansion device connecting line; a first bypass line connecting the compressor discharging passage to the sub passage; a second bypass line connecting the sub passage to one of the first expansion device connecting line and the third expansion device connecting line; and a capillary tube installed on the second bypass line. Accordingly, frost in the lower portion of the outdoor heat exchanger can be minimized with a simple structure. 본 실시예는 압축기 흡입유로 및 압축기 토출유로가 연결된 압축기와; 압축기 흡입유로 및 압축기 토출유로가 연결된 냉난방절환밸브와; 냉난방절환밸브와 실외열교환기 연결라인으로 연결된 메인유로와, 서브유로를 갖는 실외열교환기와; 냉난방절환밸브와 실내열교환기 연결라인으로 연결된 실내열교환기와; 메인유로와 제1팽창기구 연결라인으로 연결된 실외팽창기구와; 실내열교환기와 제2팽창기구 연결라인으로 연결되고 실외팽창기구와 제3팽창기구 연결라인으로 연결된 실내팽창기구와; 압축기 토출유로와 상기 서브유로를 연결하는 제1바이패스 라인과; 제1팽창기구 연결라인과 제3팽창기구 연결라인 중 어느 하나와 서브유로을 연결하는 제2바이패스 라인과; 제2바이패스 라인에 설치된 캐필러리 튜브를 포함하여, 간단한 구조로 실외열교환기 하부의 착상을 최소화할 수 있다.