Air-conditioning apparatus for vehicle

1. A heat pump type air conditioning apparatus for a vehicle in which an operation mode is switched for an operation between a cooling operation in which a refrigerant discharged from a compressor is subject to heat exchange in an external condenser, and then is depressurized and supplied to an internal evaporator and a heating operation in which the refrigerant discharged from the compressor is subject to heat exchange in an internal condenser, and then is depressurized and supplied to an external evaporator, the apparatus comprising:

the external evaporator provided as a component different from the external condenser,

a refrigerant heater that is provided between the internal evaporator and a suction side of the compressor to be in parallel with the external evaporator, the refrigerant heater heats the refrigerant which is suctioned into the compressor; and

a control apparatus that determines whether the external evaporator is frosted,

wherein the heat pump type air conditioning apparatus is configured to perform a defrosting operation, when the control apparatus determines that the external evaporator is frosted during the heating operation, said defrosting operation including stopping a supply of the refrigerant subject to the heat exchange in the internal condenser to the external evaporator, supplying the refrigerant discharged from the compressor to the external condenser via the internal condenser, and then supplying the refrigerant to the refrigerant heater via the internal evaporator, heating the refrigerant and then, suctioning the heated refrigerant into the compressor.

2. The air conditioning apparatus for a vehicle according to claim 1 , further comprising:

a first thermostatic expansion valve that is provided between the internal condenser and the external evaporator; and

a second thermostatic expansion valve that is provided between the internal condenser and the refrigerant heater,

wherein opening angles of the first and the second thermostatic expansion valves are controlled in conjunction with an operation of the refrigerant heater and thus, a flow path of the refrigerant is specified.

3. The air conditioning apparatus for a vehicle according to claim 2 ,

wherein the second thermostatic expansion valve includes a first passage with a pressure reduction mechanism and a second passage without a pressure reduction mechanism, and

wherein the refrigerant flowing out of the refrigerant heater is suctioned into the compressor via the second passage.

4. The air conditioning apparatus for a vehicle according to claim 2 ,

wherein while the frost formation determination unit determines that the external evaporator is not frosted during the heating operation,

a heating operation is performed in which the refrigerant discharged from the compressor dissipates heat in the internal condenser, is depressurized, absorbs heat in the external evaporator, and then is suctioned into the compressor, and

wherein while the frost formation determination unit determines that the external evaporator is frosted during the heating operation,

a dehumidification and heating operation is performed in an inside air circulation mode in which the refrigerant discharged from the compressor dissipates heat in the internal condenser, is depressurized, absorbs heat in the internal evaporator, is heated in the refrigerant heater, and then is suctioned into the compressor, or

a heating operation is performed in an outside air introduction mode in which the refrigerant discharged from the compressor dissipates heat in the internal condenser, is heated in the refrigerant heater that is a heat source, and then is suctioned into the compressor.

5. The air conditioning apparatus for a vehicle according to claim 1 ,

wherein while the control apparatus determines that the external evaporator is not frosted during the heating operation,

a heating operation is performed in which the refrigerant discharged from the compressor dissipates heat in the internal condenser, is depressurized, absorbs heat in the external evaporator, and then is suctioned into the compressor, and

wherein while the control apparatus determines that the external evaporator is frosted during the heating operation,

a dehumidification and heating operation is performed in an inside air circulation mode in which the refrigerant discharged from the compressor dissipates heat in the internal condenser, is depressurized, absorbs heat in the internal evaporator, is heated in the refrigerant heater, and then is suctioned into the compressor, or

a heating operation is performed in an outside air introduction mode in which the refrigerant discharged from the compressor dissipates heat in the internal condenser, is heated in the refrigerant heater that is a heat source, and then is suctioned into the compressor.

6. The air conditioning apparatus for a vehicle according to claim 5 , wherein, in the heating operation in the outside air introduction mode, the refrigerant heated in the refrigerant heater is not supplied to either one of the external evaporator and the external condenser.

7. The air conditioning apparatus for a vehicle according to claim 1 , wherein the refrigerant heater includes an electric sheathed heater or an electric heater using a positive temperature coefficient element.

8. The air conditioning apparatus for a vehicle according to claim 1 , further comprising an internal heat exchanger that is provided between the suction side of the compressor and an outlet side of a receiver, wherein the internal heat exchanger exchanges heat between a refrigerant flowing through the outlet side of the receiver and the refrigerant flowing through the suction side of the compressor.

9. The air conditioning apparatus for a vehicle according to claim 1 , wherein the apparatus is configured such that the refrigerant does not flow into the internal evaporator and the internal condenser successively during the heating operation.

10. The air conditioning apparatus for a vehicle according to claim 1 ,

wherein when it is determined that the external evaporator is frosted,

the heat pump type air conditioning apparatus is configured to perform the defrosting operation of the external evaporator in a state where the vehicle stops, and an occupant is not in the vehicle, and while a battery of the vehicle is being charged or when the battery has a spare capacity.

11. The air conditioning apparatus for a vehicle according to claim 1 , the heat pump type air conditioning apparatus is configured to determine that the vehicle stops when the vehicle electric power is OFF.