Vehicle heat pump system and control method therefor

A vehicle heat pump system, which includes:

• a compressor compressing and discharging refrigerant;
• an indoor heat exchanger installed within an air conditioning case and exchanging heat between indoor air and the refrigerant discharged from the compressor to radiate heat;
• a first expansion valve selectively expanding the refrigerant that has passed through the indoor heat exchanger;
• an outdoor heat exchanger exchanging heat between outdoor air and the refrigerant that has passed through the first expansion valve;
• and an evaporator installed within the air conditioning case and evaporating the refrigerant that has passed through the outdoor heat exchanger by exchanging heat with the outdoor air, the system comprising:
• a bypass line which branches between the first expansion valve and the outdoor heat exchanger, and bypasses the outdoor heat exchanger and the evaporator;
• a first refrigerant flow control valve which adjusts an opening degree between the bypass line and a refrigerant line directing the outdoor heat exchanger;
• a dehumidification line which branches between the first expansion valve and the first refrigerant flow control valve and supplies the refrigerant to the evaporator;
• and
• a control unit which controls a refrigerant amount supplied to the dehumidification line depending on a temperature of the outdoor air or a compressor RPM,
• wherein as the outdoor air temperature rises, the control unit decreases the opening degree of the first refrigerant flow control valve toward the bypass line to increase the refrigerant amount introduced into the dehumidification line.

A vehicle heat pump system, which includes:

• a compressor compressing and discharging refrigerant;
• an indoor heat exchanger installed within an air conditioning case and exchanging heat between indoor air and the refrigerant discharged from the compressor to radiate heat;
• a first expansion valve selectively expanding the refrigerant that has passed through the indoor heat exchanger;
• an outdoor heat exchanger exchanging heat between outdoor air and the refrigerant that has passed through the first expansion valve;
• and an evaporator installed within the air conditioning case and evaporating the refrigerant that has passed through the outdoor heat exchanger by exchanging heat with the outdoor air, the system comprising:
• a bypass line which branches between the first expansion valve and the outdoor heat exchanger, and bypasses the outdoor heat exchanger and the evaporator;
• a first refrigerant flow control valve which adjusts an opening degree between the bypass line and a refrigerant line directing the outdoor heat exchanger;
• a dehumidification line which branches between the first expansion valve and the first refrigerant flow control valve and supplies the refrigerant to the evaporator;
• a control unit which controls a refrigerant amount supplied to the dehumidification line depending on a temperature of the outdoor air or a compressor RPM;
• and
• a temperature sensor which detects the temperature of the evaporator,
• wherein if the temperature detected by the temperature sensor is higher than a target discharge temperature, the control unit controls the first refrigerant flow control valve in the direction of closing the bypass line, and
• wherein if the temperature detected by the temperature sensor remains higher than the target discharge temperature even when the first refrigerant flow control valve is fully closed, the control unit increases the compressor RPM.

A vehicle heat pump system, which includes:

• a compressor compressing and discharging refrigerant;
• an indoor heat exchanger installed within an air conditioning case and exchanging heat between indoor air and the refrigerant discharged from the compressor to radiate heat;
• a first expansion valve selectively expanding the refrigerant that has passed through the indoor heat exchanger;
• an outdoor heat exchanger exchanging heat between outdoor air and the refrigerant that has passed through the first expansion valve;
• and an evaporator installed within the air conditioning case and evaporating the refrigerant that has passed through the outdoor heat exchanger by exchanging heat with the outdoor air, the system comprising:
• a bypass line which branches between the first expansion valve and the outdoor heat exchanger, and bypasses the outdoor heat exchanger and the evaporator;
• a first refrigerant flow control valve which adjusts an opening degree between the bypass line and a refrigerant line directing the outdoor heat exchanger;
• a dehumidification line which branches between the first expansion valve and the first refrigerant flow control valve and supplies the refrigerant to the evaporator;
• and
• a control unit which controls a refrigerant amount supplied to the dehumidification line depending on a temperature of the outdoor air or a compressor RPM;
• and
• a second refrigerant flow control valve provided in the dehumidification line to control the flow rate of the refrigerant flowing to the evaporator,
• wherein the control unit fully opens the second refrigerant flow control valve and controls the refrigerant amount flowing into the dehumidification line using the opening degree of the first refrigerant flow control valve.

A control method for a vehicle heat pump system, which includes:

• a compressor compressing and discharging refrigerant;
• an indoor heat exchanger installed within an air conditioning case and exchanging heat between indoor air and the refrigerant discharged from the compressor to radiate heat;
• a first expansion valve selectively expanding the refrigerant that has passed through the indoor heat exchanger;
• an outdoor heat exchanger exchanging heat between outdoor air and the refrigerant that has passed through the first expansion valve;
• an evaporator installed within the air conditioning case and evaporating the refrigerant that has passed through the outdoor heat exchanger by exchanging heat with the outdoor air;
• a bypass line which branches between the first expansion valve and the outdoor heat exchanger, and bypasses the outdoor heat exchanger and the evaporator;
• a first refrigerant flow control valve which adjusts an opening degree between the bypass line and a refrigerant line directing the outdoor heat exchanger;
• and a dehumidification line which branches between the first expansion valve and the first refrigerant flow control valve and supplies the refrigerant to the evaporator, the control method comprising:
• a step of controlling a refrigerant amount supplied to the dehumidification line depending on a temperature of the outdoor air or a compressor RPM,
• wherein in a heat pump and dehumidification mode, the pressure of a refrigerant passage expanded through the first expansion valve is increased to increase the refrigerant amount toward the evaporator through the dehumidification line.