Vehicle air conditioning system or device

Abstract

Vehicle air conditioning device (1) comprising the following: a compressor (11) that draws in, compresses and discharges a refrigerant containing a refrigerant oil; a radiator (12) which heats air by exchanging heat between the refrigerant supplied by the compressor (11) and the air supplied to a passenger compartment; an external heat exchanger (20) that exchanges heat between the refrigerant flowing out of the radiator (12) and outside air; an evaporator (23) which evaporates the refrigerant by exchanging heat between the refrigerant flowing out of the external heat exchanger (20) and the air flowing into the radiator (12); a first decompressor (13a) that decompresses the refrigerant flowing out of the radiator (12); a second decompressor (22a) that decompresses the refrigerant flowing out of the outer heat exchanger (20); a switching section (25a, 28a) that switches between the following: a series dehumidification heating mode in which the external heat exchanger (20) and the evaporator (23) are connected in series with respect to a flow of refrigerant, and a parallel dehumidification heating mode in which the external heat exchanger (20) and the evaporator (23) are connected in parallel to each other with respect to the flow of the refrigerant, and a control unit (40) designed to control the switching section (25a, 28a) to switch from the parallel dehumidification heating mode to the series dehumidification heating mode when the control unit (40) determines that the amount of refrigerant oil flowing from the external heat exchanger (20) to the compressor (11) is insufficient.

Description

Cross-reference to related registration

[0001] This application is based on the Japanese patent application JP 2018 - 083 581 A filed on November 25, 2016, the disclosure of which is incorporated herein by reference. Technical field

[0002] The present disclosure relates to a vehicle air conditioning system that performs a dehumidification heating mode. State of the art

[0003] Patent literature 1 discloses a refrigeration circuit device comprising a compressor, an inner condenser, a first expansion valve, an outer heat exchanger, a second expansion valve and an inner evaporator.

[0004] In patent literature 1, a first dehumidification heating mode and a second dehumidification heating mode are suitably switched based on an operating condition in a vehicle air conditioning system.

[0005] In the first dehumidification-heating mode, the outer heat exchanger and the inner evaporator are connected in series with respect to the refrigerant flow. Specifically, in this mode, a high-pressure refrigerant, delivered by the compressor, flows into the inner condenser. This refrigerant releases heat by exchanging it with air blown into the passenger compartment. Consequently, the air supplied to the vehicle interior is heated.

[0006] The refrigerant exiting the inner condenser is decompressed and expanded by the first expansion valve to become a low-pressure refrigerant. This low-pressure refrigerant then enters the outer heat exchanger and exchanges heat with the outside air, absorbing it. The refrigerant exiting the outer heat exchanger then enters the inner evaporator and exchanges heat with the air being blown into the passenger compartment, absorbing heat as well. This process dehumidifies the air entering the vehicle interior. The dehumidified air then flows into the inner condenser to be heated, thus dehumidifying and heating the passenger compartment. Finally, the refrigerant exiting the inner evaporator is drawn into the compressor and compressed again.

[0007] In contrast, in the second dehumidification heating mode, a high-pressure refrigerant, delivered by the compressor, flows into the inner condenser. This refrigerant releases heat by exchanging it with air blown into the passenger compartment. Consequently, the air supplied to the vehicle interior is heated.

[0008] The refrigerant exiting the inner condenser is split into two streams: one entering the first expansion valve and the other entering the second. The refrigerant entering the first expansion valve is decompressed and expanded until it becomes a low-pressure refrigerant. This low-pressure refrigerant then enters the outer heat exchanger and exchanges heat with the outside air to absorb heat.

[0009] The refrigerant flowing into the second expansion valve is decompressed and expanded until it becomes a low-pressure refrigerant. This decompressed and expanded refrigerant then flows into the inner evaporator, exchanging heat with the air circulating in the passenger compartment. Consequently, the refrigerant absorbs heat, thus dehumidifying the air supplied to the vehicle interior. The dehumidified air then flows into the inner condenser to be heated, further dehumidifying and heating the passenger compartment. Finally, the refrigerant exiting the outer heat exchanger and the refrigerant exiting the inner evaporator are drawn into the compressor and compressed again.

[0010] In the second dehumidification heating mode, unlike the first, the outer heat exchanger and the inner evaporator are connected in parallel with respect to the refrigerant flow, and the saturation temperature (i.e., evaporation temperature) of the refrigerant in the outer heat exchanger is lower than the saturation temperature (i.e., evaporation temperature) of the refrigerant in the inner evaporator. Consequently, the heating capacity of the air can be higher in the second dehumidification heating mode than in the first.

[0011] The refrigerant is mixed with refrigerant oil, which serves as a lubricating oil for a compressor, and the refrigerant oil partially circulates in the cycle or circuit together with the refrigerant. State of the art document (patent literature)

[0012] Patent literature 1: JP 2012 - 225 637 A Summary of the invention

[0013] In the patent literature 1, in the second dehumidification heating mode, the outer heat exchanger and the inner evaporator are connected in parallel with respect to the refrigerant flow. In the second dehumidification heating mode, the opening degree of the first expansion valve is occasionally throttled as much as possible in order to reduce the temperature of the inner evaporator to a setpoint temperature.

[0014] According to studies by the inventors of the present disclosure, in the second dehumidification heating mode the flow rate of the refrigerant flowing through the external heat exchanger decreases. Consequently, refrigerant oil may remain in the external heat exchanger without flowing out of it, and the lubrication or lubricating capacity in the compressor may be impaired.

[0015] One purpose of the present disclosure is to limit the amount of refrigerant oil remaining in an external heat exchanger in a vehicle air conditioning system in which the external heat exchanger and the evaporator are connected or linked in parallel to each other in a coolant flow.

[0016] A vehicle air conditioning system or vehicle air conditioning device according to one aspect of the present disclosure comprises a compressor, a radiator, an external heat exchanger, an evaporator, a first decompressor, a second decompressor, a switching section, and a control unit or controller. The compressor draws in, compresses, and discharges a refrigerant containing a refrigerant oil. The radiator heats air by exchanging heat between the refrigerant discharged by the compressor and the air supplied to a passenger compartment or passenger space. The external heat exchanger is designed to exchange heat between the outside air and the refrigerant flowing from the radiator. The evaporator evaporates the refrigerant by exchanging heat between the refrigerant flowing from the external heat exchanger and the air flowing through the radiator.The first decompressor decompresses the refrigerant flowing out of the radiator. The second decompressor decompresses the refrigerant flowing out of the external heat exchanger. The switching section toggles between a series dehumidification heating mode, in which the external heat exchanger and the evaporator are connected in series with respect to refrigerant flow, and a parallel dehumidification heating mode, in which the external heat exchanger and the evaporator are connected in parallel with respect to refrigerant flow. The control unit is designed to control the switching section to switch from the parallel dehumidification heating mode to the series dehumidification heating mode when the amount of refrigerant flowing from the external heat exchanger to the compressor is insufficient in the parallel dehumidification heating mode.

[0017] Switching from parallel dehumidification heating mode to series dehumidification heating mode increases the amount of refrigerant flowing through the external heat exchanger, and consequently, it is likely that the refrigerant oil in the external heat exchanger will return to the compressor. Therefore, the amount of refrigerant oil remaining in the external heat exchanger can be limited.

[0018] A vehicle air conditioning system or vehicle air conditioning device according to another aspect of the present disclosure comprises a compressor, a radiator, an external heat exchanger, an evaporator, a first decompressor, a second decompressor, and a control unit or controller. The compressor draws in, compresses, and discharges a refrigerant containing a refrigerant oil. The radiator heats air by exchanging heat between the refrigerant discharged by the compressor and the air supplied to a passenger compartment. The external heat exchanger is designed to exchange heat between the outside air and the refrigerant flowing out of the radiator. The evaporator evaporates the refrigerant by exchanging heat between the refrigerant flowing out of the external heat exchanger and the air flowing through the radiator. The first decompressor or controllerThe pressure reducer decompresses the refrigerant flowing from the radiator. The second decompressor decompresses the refrigerant flowing from the external heat exchanger. The control unit is designed to regulate the opening degree of the first decompressor. The external heat exchanger and the evaporator are connected in parallel with respect to the refrigerant flow. The control unit increases the opening degree of the first decompressor if the amount of refrigerant flowing from the external heat exchanger to the compressor is insufficient.

[0019] Accordingly, since increasing the flow rate of the refrigerant passing through the external heat exchanger by increasing the opening degree of the first decompressor, the refrigerant oil can likely return from the external heat exchanger to the compressor. Therefore, the refrigerant oil can be confined to remaining in the external heat exchanger. Brief description of the drawings Fig. Figure 1 is a diagram showing a refrigeration circuit or refrigerant circuit in a cooling mode and a series dehumidification heating mode of a heat pump circuit according to an embodiment of the present disclosure. Fig. Figure 2 is a diagram that shows a refrigeration cycle or a refrigerant circuit in a parallel dehumidification heating mode of the heat pump circuit according to the embodiment. Fig. Figure 3 is a diagram that represents a refrigerant circuit or refrigeration circuit in a heating mode of the heat pump circuit according to the embodiment. Fig. Figure 4 is a Mollier diagram representing a state of a refrigerant in the series dehumidification heating mode of the heat pump circuit according to the embodiment. Fig. Figure 5 is a Mollier diagram representing a state of a refrigerant in the parallel dehumidification heating mode of the heat pump circuit according to the embodiment. Fig. Figure 6 is a flowchart that illustrates a control process of the heat pump circuit according to the embodiment. Fig. Figure 7 is a control property diagram used in the control process of the heat pump circuit according to the embodiment. Description of embodiments

[0020] Embodiments are described below with reference to the drawings. In the present embodiment, a heat pump circuit or cycle 10 is used in a vehicle air conditioning system or vehicle climate control device 1 of a hybrid vehicle, which obtains motive power for driving from a machine (i.e., an internal combustion engine) and an electric drive motor. The heat pump circuit 10 is a vapor compression refrigeration circuit.

[0021] The heat pump circuit 10 performs a function of cooling or heating air supplied to a passenger compartment in the vehicle air conditioning system 1. Accordingly, an air conditioning target space of the present embodiment is a space containing the passenger compartment, and a target heat exchange fluid of the present embodiment is the air supplied to the passenger compartment.

[0022] The heat pump cycle 10 is designed to switch between a cooling circuit and a cooling mode that is in Fig. Figure 1 shows a cooling circuit of a series dehumidification heating mode, which is in Fig. Figure 1 shows a cooling circuit of a parallel dehumidification heating mode, which is in Fig. 2 is shown, and a cooling circuit is switchable between a heating mode, which is in Fig. 3 is shown. Fig. Figures 1 to 3 show the flow of refrigerant in each of the operating modes with solid or filled arrows.

[0023] Cooling mode is an operating mode used to cool the air supplied to the passenger compartment. Series dehumidification heating mode and parallel dehumidification heating mode are operating modes used to heat the air supplied to the passenger compartment after it has been dehumidified, thus dehumidifying and heating the compartment. Heating mode is an operating mode used to heat the air supplied to the passenger compartment.

[0024] The heat pump cycle 10 uses an HFC refrigerant (specifically R134a) as the refrigerant and forms a subcritical vapor compression refrigerant circuit in which the high-pressure-side refrigerant pressure does not exceed the refrigerant's critical pressure. Needless to say, an HFO-based refrigerant (for example, R1234yf) or the like can also be used as the refrigerant. The refrigerant is mixed with refrigerant oil, which acts as a lubricant for a compressor 11, and the refrigerant oil partially circulates in the cycle along with the refrigerant.

[0025] Compressor 11 of the heat pump circuit 10 draws in the refrigerant, compresses it, and releases it. Compressor 11 is located in the vehicle's engine compartment. Compressor 11 is an electric compressor that houses a compression mechanism and an electric motor within a casing that defines its outer body.

[0026] The housing of the compressor 11 has an inlet port 11a, through which the low-pressure refrigerant is drawn into the compression mechanism from an outside of the housing, and a discharge port 11c, through which the high-pressure refrigerant is discharged from the compression mechanism to the outside of the housing. A screw compression mechanism, a vane compression mechanism, or a rotary piston compression mechanism can be used as the compression mechanism, for example.

[0027] The speed of the electric motor of compressor 11 is controlled by control signals output by a control unit 40. Any AC or DC motor can be used as the electric motor. By controlling the speed of the electric motor, the refrigerant discharge capacity of compressor 11 is varied. Accordingly, the electric motor is a discharge capacity-changing section of compressor 11.

[0028] A refrigerant inlet side of the inner condenser 12 is connected to the discharge port 11c of the compressor 11. The inner condenser 12 is located in an air conditioning housing 31 of an inner air conditioning unit 30 of the vehicle air conditioning system 1 and functions as a radiator (i.e., high-pressure-side heat exchanger) that distributes or dissipates heat from the temperature- and high-pressure refrigerant delivered by the high-pressure-side compression mechanism of the compressor 11. The inner condenser 12 is an air-heating heat exchanger that warms the air passing through the inner evaporator 23.

[0029] A high-pressure refrigerant passage 13 is connected to an outlet side of the inner condenser. The high-pressure refrigerant passage 13 is a refrigerant passage that carries the refrigerant flowing out of the inner condenser 12 to the outer heat exchanger 20. A high-pressure expansion valve 13a is located in the high-pressure refrigerant passage 13. The high-pressure expansion valve 13a is a high-pressure decompressor that decompresses the high-pressure refrigerant flowing out of the inner condenser 12 until the high-pressure refrigerant becomes an intermediate-pressure refrigerant. The high-pressure expansion valve 13a is a first decompressor.

[0030] The high-stage expansion valve 13a is an electrically variable throttle mechanism comprising a valve body whose throttle opening is changeable and an electrical actuator formed from a stepper motor which changes the throttle opening degree of the valve body.

[0031] The high-stage expansion valve 13a can be fully opened to disable refrigerant decompression. Operation of the high-stage expansion valve 13a is controlled by a control signal output from a control unit or control unit 40.

[0032] An outlet side of the high-stage expansion valve 13a is connected to a refrigerant inlet side of the external heat exchanger 20. The external heat exchanger 20 is located inside the hood or engine compartment of the vehicle and exchanges heat between the refrigerant flowing within it and the outside air blown out by a blower fan 21. The external heat exchanger 20 functions as an evaporator, designed to exert a heat-absorbing effect by evaporating the low-pressure refrigerant, at least during heating mode, and as a radiator, designed to radiate heat from the high-pressure refrigerant, for example, during cooling mode.

[0033] A refrigerant passage 22 is connected to the refrigerant outlet side of the outer heat exchanger 20. The refrigerant passage 22 is a refrigerant passage that carries the refrigerant flowing out of the outer heat exchanger 20 to a suction side of the compressor 11 through an accumulator or pressure reservoir 24.

[0034] A refrigeration expansion valve 22a is located in the refrigeration refrigerant passage 22. The refrigeration expansion valve 22a decompresses the refrigerant flowing out of the outer heat exchanger 20 and into the inner evaporator 23, for example, during cooling operation. The configuration of the refrigeration expansion valve 22a is essentially the same as that of the high-stage expansion valve 13a, and the operation of the refrigeration expansion valve 22a is controlled by control signals output by the control unit 40. The refrigeration expansion valve 22a is a secondary decompressor.

[0035] An outlet side of the cooling expansion valve 22a is connected to a refrigerant inlet side of the inner evaporator 23. The inner evaporator 23 is located upstream of the inner condenser 12 with respect to the airflow in the air conditioning housing 31 of the inner air conditioning unit 30. The inner evaporator 23 is a heat exchanger that functions as an evaporator (i.e., an air-cooling heat exchanger) that cools the air supplied to the passenger compartment by evaporating the refrigerant flowing through it, thus performing a heat absorption function during the cooling and dehumidifying heating operating modes.

[0036] The inlet side of the accumulator or pressure accumulator 24 is connected to an outlet side of the internal evaporator 23. The accumulator 24 is a low-pressure gas-liquid separator that separates the gas and liquid components in the refrigerant, which flows into the accumulator 24 to accumulate or store excess refrigerant under pressure. The gaseous refrigerant outlet of the accumulator 24 is connected to the inlet port 11a of the compressor 11. Similarly, the internal evaporator 23 is connected to the suction port 11a of the compressor 11 to supply or deliver the refrigerant.

[0037] A low-pressure bypass passage 25 is connected to the refrigerant outlet side of the outer heat exchanger 20. The low-pressure bypass passage 25 is a refrigerant passage through which the refrigerant flowing out of the outer heat exchanger 20 bypasses the cooling expansion valve 22a and the inner evaporator 23 and is directed to the inlet side of the accumulator 24. A low-pressure on / off valve 25a is located in the low-pressure bypass passage 25.

[0038] The low-pressure on / off valve 25a is an electromagnetic valve that opens and closes the low-pressure bypass passage 25, and the opening and closing of the low-pressure on / off valve 25a is controlled by control voltages output by the control unit 40.

[0039] The pressure drop that occurs when the refrigerant passes through the low-pressure-side on / off valve 25a is extremely small compared to the pressure drop that occurs when the refrigerant passes through the cooling expansion valve 22a. Therefore, when the low-pressure-side on / off valve 25a is open, the refrigerant that has flowed out of the outer heat exchanger 20 flows into the accumulator 24 through the low-pressure-side bypass 25. At this point, the cooling expansion valve 22a may be completely closed.

[0040] The refrigerant flowing out of the outer heat exchanger 20 flows into the inner evaporator 23 through the cooling expansion valve 22a when the low-pressure-side on / off valve 25a is closed. Accordingly, the low-pressure-side on / off valve 25a is designed to switch the refrigerant flow of the heat pump cycle 10. The low-pressure-side on / off valve 25a is therefore a refrigerant flow switching section that reverses the flow of the refrigerant circulating in the cycle. The refrigerant flow switching section can be a switching or changeover section.

[0041] A constant pressure valve 27 is located between the outlet side of the inner evaporator 23 and the inlet side of the accumulator 24. The constant pressure valve 27 is a constant pressure regulator or constant pressure regulating device that maintains the pressure of the refrigerant on an outlet side of the inner evaporator 23 to a predetermined pressure.

[0042] The high-pressure bypass passage 28 is a refrigerant passage through which the refrigerant flowing out of the inner condenser 12 bypasses the outer heat exchanger 20 and is directed to the inlet side of the cooling expansion valve 22a.

[0043] A high-pressure on / off valve 28a is located in the high-pressure bypass passage 28. The high-pressure on / off valve 28a is an electromagnetic valve that opens and closes the high-pressure bypass passage 28. Operation of the high-pressure on / off valve 28a is controlled by a control signal output by a control unit 40.

[0044] The high-pressure-side on / off valve 28a opens and closes the high-pressure-side bypass passage 28 to switch a cycle configuration (i.e., a refrigerant flow). Accordingly, the high-pressure-side on / off valve 28a is a refrigerant flow switching section that reverses the refrigerant flow of the refrigerant circulating in the circuit. The refrigerant flow switching section can be a switching or changeover section.

[0045] A shut-off valve 29 is located on the outlet side of the outer heat exchanger 20. The shut-off valve 29 is a non-return valve section that allows the refrigerant to flow from the outlet side of the outer heat exchanger 20 to the inlet side of the cooling expansion valve 22a, and prevents the refrigerant from flowing from the inlet side of the cooling expansion valve 22a to the outlet side of the outer heat exchanger 20. The shut-off valve 29 prevents the refrigerant flowing through the high-pressure-side bypass 28 from flowing back to the outer heat exchanger 20.

[0046] Next, the internal air conditioning unit 30 is described. The internal air conditioning unit is located on the inside of an instrument panel positioned furthest forward in the passenger compartment. The internal air conditioning unit 30 includes the air conditioning housing 31. The air conditioning housing 31 defines an outer body of the air conditioning unit 30. An air passage for the air supplied to the passenger compartment is defined in the air conditioning housing 31. The air passage in the air conditioning housing 31 contains a blower 32, the internal condenser 12, the internal evaporator 23, and the like.

[0047] An indoor-outdoor air switching device 33, which switches the introduced air between indoor and outdoor air, is located at the most upstream part of the air conditioning housing 31. The indoor-outdoor air switching device 33 has an indoor air inlet connection through which the indoor air flows into the air conditioning housing 31, and an outdoor air inlet connection through which the outdoor air flows into the air conditioning housing 31. The indoor-outdoor air switching device 33 is an indoor-outdoor air ratio regulator or an indoor-outdoor air ratio regulating device that continuously adjusts an opening area or opening range of the indoor air inlet connection and an opening range or opening area of ​​the outdoor air inlet connection through the indoor-outdoor air switching door and continuously changes the air volume ratio of an indoor air volume to an outdoor air volume.

[0048] The blower 32, which supplies air drawn in via the indoor / outdoor air switching device 33 to the vehicle interior, is located on the downstream side of the indoor / outdoor air switching device 33. The blower 32 is an electric blower that drives a multi-blade centrifugal fan using an electric motor. The speed (i.e., air supply rate) of the blower 32 is controlled by a control voltage output by the control unit 40.

[0049] The inner evaporator 23 and the inner condenser 12 are arranged on the downstream side of the blower 32 in the order of the inner evaporator 23 and the inner condenser 12 along the airflow supplied to the passenger compartment. In other words, the inner evaporator 23 is arranged on the upstream side of the inner condenser 12 along the airflow.

[0050] A heating core, not shown, is located between the inner evaporator 23 and the inner condenser 12. The heating core is a heating auxiliary heat exchanger that additionally heats the air by exchanging heat between the machine cooling water and the air that has passed through the inner evaporator 23.

[0051] A bypass passage 35, through which air that has passed through the inner evaporator 23 bypasses the heating core and the inner condenser 12, is located in the air conditioning housing 31 and an air mixing door 34 is located downstream of the inner evaporator 23 and upstream of the heating core and the inner condenser 12.

[0052] The air mixing door 34 is a flow rate regulator or flow rate regulating device that adjusts the flow rate (i.e., volume of air) of the air entering the inner condenser 12 by adjusting the ratio of the air flowing through the heating core and the inner condenser 12 to the air flowing through the bypass passage 35. The air mixing door 34 adjusts the heat exchange capacity of the inner condenser 12.

[0053] A merging chamber 36, in which the air heated by heat exchange with the refrigerant in the inner condenser 12 and the air not heated by passing through the bypass passage 35 are combined, is provided on the downstream side of the inner condenser 12 and the bypass passage 35.

[0054] Openings for blowing the air, which is combined in the junction chamber 36, into the passenger compartment as the cooling target chamber are provided in the furthest downstream section of the air conditioning housing 31. In particular, the openings comprise a defroster opening 37a for blowing an air conditioning breeze towards an inner surface of a vehicle windscreen, a face opening 37b for blowing the air-conditioned air towards the upper half of an occupant in the vehicle compartment, and a foot opening 37c for blowing the air-conditioned air towards the feet of the occupant.

[0055] The air mixing door 34 adjusts the air volume ratio between the air volume allowed to pass through the inner condenser 12 and the air volume allowed to pass through the bypass passage 35, thereby setting a temperature of the air in the mixing chamber 36. The air mixing door 34 is driven by a servo motor (not shown), the operation of which is controlled by a control signal output by the control unit 40.

[0056] A defrost door 38a, which sets the opening area or opening surface of the defrost opening 35a, a face door 38b, which sets the opening area of ​​the defrost opening 37a, a foot door 38c, which sets the opening area of ​​the foot opening 37c, is located upstream of the defrost opening 35a, the face opening 37b or the foot opening 37c.

[0057] The defroster door 38a, front door 38b, and foot door 38c each open the openings 37a to 37c and form an air outlet mode switching device for changing the air outlet mode. Operation of the outlet mode switching device is driven by a servo motor (not shown), the operation of which is controlled by a control signal output by the control unit 40 via a linkage mechanism or the like.

[0058] The downstream sides of the defroster opening 37a, the face opening 37b and the foot opening 37c are connected to a face outlet, a foot outlet and a defroster outlet provided in the vehicle compartment, by channels which each form air passages.

[0059] The exhaust port mode features a face mode in which the face opening 37b is fully open to blow air through the face opening to the occupant's upper body, a two-stage mode in which the face opening 37b and the foot opening 37c are open to blow air to the occupant's upper body and feet, and a foot mode in which the foot opening 37c is fully open and the defroster opening 37a is slightly open to blow air mainly through, for example, the foot opening.

[0060] An electrical control unit of the present embodiment is described below. The control unit 40 comprises a known microcomputer including a CPU, ROM, RAM, and the like, and peripheral circuits. The control unit performs various calculations and processes based on an air conditioning control program stored in the ROM. The control unit 40 controls the operation of various air conditioning control devices, such as the compressor 11, the high-pressure side expansion valve 13a, the air blower 21, the cooling expansion valve 22a, the low-pressure side on / off valve 25a, the high-pressure side on / off valve 28a, and the blower 32.

[0061] Sensors 41 for the air conditioning system are connected to an input side of the control unit 40. The sensors 41 include, for example, an indoor air sensor, an outdoor air sensor, a solar radiation sensor, an evaporation temperature sensor, a discharge pressure sensor, a condenser temperature sensor, and a suction pressure sensor.

[0062] The interior air sensor measures the vehicle interior temperature. The exterior air sensor measures the outside air temperature. The insulation sensor measures the degree of insulation in the passenger compartment or vehicle interior. The evaporator temperature sensor measures the temperature of the air blown out of the interior evaporator 23 (i.e., evaporator temperature). The discharge pressure sensor measures the pressure of the high-pressure refrigerant discharged by the compressor 11. The condenser temperature sensor measures the temperature of the refrigerant flowing out of the inner condenser 12. The suction pressure sensor measures the pressure of the refrigerant being drawn into the compressor 11.

[0063] The control unit 40 has an input end connected to an operating panel (not shown) that receives operating signals from various climate control operating switches provided with the operating panel. The operating panel is located near the instrument panel in the front part of the passenger compartment. The various climate control operating switches on the operating panel include an operating switch for the vehicle climate control device 1, a passenger compartment temperature setting switch for adjusting the passenger compartment temperature, and a mode setting switch for selecting between cooling, dehumidifying / heating, and heating modes.

[0064] The control unit 40 is integrated with control units for controlling the operation of the various climate control devices, which are connected to the output side of the control unit 40. Within the control unit 40, configurations (in particular hardware and software) that control the operation of each of the control target devices form a control unit that controls the operation of each of the control target devices.

[0065] For example, a part (especially hardware and software) of the control unit 40 that controls the operation of the electric motor of the compressor 11 forms a delivery capacity controller or delivery capacity control unit. For example, a part (especially hardware and software) of the control unit 40 that controls the operation of the low-pressure-side on / off valve 25a and the high-pressure-side on / off valve 28a forms a refrigerant circuit control unit. It goes without saying that the delivery capacity control unit and the refrigerant circuit control unit can be designed as separate control devices for the control unit 40.

[0066] Next, the operation of the vehicle air conditioning system 1 according to the following embodiment in the preceding configuration is described. The vehicle air conditioning system 1 of the present embodiment is designed to switch between the cooling mode for cooling the passenger compartment, the in-line dehumidification heating mode and the parallel dehumidification heating mode for dehumidifying and heating the passenger compartment, and the heating mode for heating the passenger compartment.

[0067] Switching between these operating modes is performed by executing the climate control program. The climate control program is executed when the automatic switch on the control panel is turned on.

[0068] In the main routine of the climate control program, the detection signal from the sensor group for the climate control and the operating signal from various climate control operating switches are read. Then, based on the value of the detection signal and the value of the operating signal, a target outlet temperature (TAO), which is the target temperature of the air blown into the vehicle interior, is calculated based on formula F1. TAO=Kset×Tset−Kr×Tr−Kam×Tam−Ks×As+C

[0069] Tset is the set temperature in the passenger compartment, set using the temperature control switch; Tr is the passenger compartment temperature (i.e., interior air temperature) as measured by the interior air sensor; Tam is the exterior air temperature as measured by the exterior air sensor; and As is the amount of solar radiation as measured by the solar radiation sensor. The formula also includes Kset, Kr, Kam, and Ks, which represent control gains, and C, which specifies a correction constant.

[0070] When the control panel's cooling switch is turned on and the set outlet temperature TAO is lower than a predetermined cooling reference temperature α, the cooling mode is activated. The series dehumidification heating mode is activated when the following conditions are met: the control panel's cooling switch is turned on; the set outlet temperature TAO is at or above the cooling reference temperature α; and the outside air temperature Tam is higher than a predetermined dehumidification heating reference temperature β.

[0071] The parallel dehumidification heating mode is activated when the following conditions are met: the cooling switch on the control panel is turned on; the set outlet temperature TAO is at or above the cooling reference temperature α; and the outside air temperature Tam is at or below the dehumidification heating reference temperature β. If the cooling switch is not turned on, the heating mode is activated.

[0072] According to this climate control program, cooling mode is used when the outside air temperature is relatively high, primarily in summer. Series dehumidification heating mode is used primarily in spring and autumn. Parallel dehumidification heating mode is used primarily in early spring and late autumn when a higher heating capacity than required in series dehumidification heating mode is needed to heat the air. Heating mode is used primarily in winter when the outside air temperature is low. (a) Cooling mode

[0073] In the cooling mode or cooling operating mode, the control unit 40 controls: the high-pressure side expansion valve 13a to be fully open; the cooling expansion valve 22a to be in a throttling state in which the cooling expansion valve 22a performs a decompression function; the low-pressure side on / off valve 25a to be closed; and the high-pressure side on / off valve 28a to be closed.

[0074] Accordingly, in the cooling mode, the vapor compression refrigeration cycle is carried out, in which the refrigerant flows through the compressor 11, the external heat exchanger 20, the refrigeration expansion valve 22a, the internal evaporator 23, the constant pressure valve 27, the accumulator 24 and the compressor 11 in that order, as shown in Fig. 1 is shown.

[0075] The control unit 40 regulates the operation of the compressor 11 such that the temperature of the air blown out of the inner evaporator 23 is at the setpoint evaporator temperature TEO. The setpoint evaporator temperature TEO is determined to minimize the reduction in the setpoint outlet temperature TAO. The setpoint evaporator temperature TEO is determined within a range that limits frost formation on the inner evaporator 23.

[0076] The control unit 40 controls the operation of the refrigeration expansion valve 22a such that the COP of the cycle reaches its local maximum value based on the pressure of the refrigerant flowing into the refrigeration expansion valve 22a. The control unit 40 moves the air mixing door 34 to completely close the air passage on the side of the inner condenser 12.

[0077] In the refrigeration circuit, in cooling mode, the outer heat exchanger 20 functions as a radiator and the inner evaporator 23 functions as an evaporator. The heat absorbed by the refrigerant when it evaporates in the inner evaporator 23 is transferred to the outside air in the outer heat exchanger 20. This allows the air to be cooled.

[0078] Accordingly, in cooling mode, the passenger compartment can be cooled by blowing air cooled by the internal evaporator 23 into the passenger compartment. (b) Series dehumidification heating mode

[0079] In the series dehumidification heating mode, the control unit 40 controls: the high-stage expansion valve 13a to be in a throttled state, in which the high-stage expansion valve 22a performs a decompression function; the cooling expansion valve 22a to be in a throttled state, in which the cooling expansion valve 22a performs a decompression function; the low-pressure on / off valve 25a to be closed; and the high-pressure on / off valve 28a to be closed.

[0080] Accordingly, in the series dehumidification heating mode, the vapor compression refrigeration circuit is formed in which the refrigerant flows through, in the sequence from the compressor 11, the inner condenser 12, the high-stage expansion valve 13a, the outer heat exchanger 20, the cooling expansion valve 22a, the inner evaporator 23, the constant pressure valve 27, the accumulator 24 and the compressor 11, as shown in Fig. Figure 1 shows that the refrigeration circuit is formed in which the outer heat exchanger 20 and the inner evaporator 23 are connected in series with respect to the refrigerant flow.

[0081] In this cycle, the control unit 40 controls the operation of the compressor as in cooling mode. The control unit 40 controls the operation of the high-stage expansion valve 13a and the cooling expansion valve 22a such that the temperature of the air blown out of the inner condenser 12 is at a setpoint condenser temperature TAVO. The setpoint condenser temperature TAVO is designed to increase with the rise in the setpoint outlet temperature TAO.

[0082] At this point, the control unit 40 reduces the throttling degree of the high-stage expansion valve 13a and increases the throttling degree of the cooling expansion valve 22a as the target condenser temperature TAVO rises. The control unit 40 moves the air mixing door 34 to fully open the air passage on the side of the inner condenser 12.

[0083] Accordingly, in the series dehumidification heating mode, the state of the refrigerant circulating in the cycle changes, as shown in the Mollier diagram. Fig. 4 is shown.

[0084] That is, the high-pressure refrigerant that is discharged by compressor 11 (point a1 of Fig. 4), flows into the inner condenser 12 to release heat by exchanging heat with the air, which is cooled and dehumidified by the inner evaporator 23 (point a1 to point a2 of Fig. 4) Accordingly, the air supplied to the passenger compartment or vehicle interior is heated.

[0085] The refrigerant flowing out of the inner condenser 12 flows into the high-stage expansion valve 13a and is decompressed, i.e., its pressure is reduced, to become the intermediate-pressure refrigerant (points a2 to a3 of Fig. 4) The intermediate pressure refrigerant, which is decompressed by the upstage expansion valve 13a, flows into the outer heat exchanger 20 and releases heat to the outside air (point a3 to point a4 of Fig. 4).

[0086] The refrigerant flowing out of the outer heat exchanger 20 flows into the cooling expansion valve 22a and is decompressed and expands through the cooling expansion valve 22a to become the low-pressure refrigerant (points a4 to a5 of Fig. 4) The low-pressure refrigerant, decompressed through the cooling expansion valve 22a, flows into the inner evaporator 23 and evaporates by absorbing heat from the air (point a5 to point a6 of Fig. 4) Accordingly, the air supplied to the vehicle interior or passenger compartment is cooled. The refrigerant flowing out of the inner evaporator 23 passes through, in the following sequence, the constant pressure valve 27, the accumulator 24, and the suction side of the compressor 11, and then flows into the compressor 11 to be compressed again (point a6 to point a1 via point a7 of Fig. 4).

[0087] In series dehumidification heating mode, the inner condenser 12 functions as a radiator and the inner evaporator 23 functions as an evaporator. If the saturation temperature of the refrigerant in the outer heat exchanger 20 is higher than the outside air temperature, the outer heat exchanger 20 functions as a radiator. If the saturation temperature of the refrigerant in the outer heat exchanger 20 is lower than the outside air temperature, the outer heat exchanger 20 functions as an evaporator.

[0088] Accordingly, if the saturation temperature of the refrigerant in the outer heat exchanger 20 is higher than the saturation temperature of the outside air, the amount of heat radiated by the refrigerant in the outer heat exchanger 20 can be reduced by lowering the saturation temperature of the refrigerant in the outer heat exchanger 20 by increasing the target condenser temperature TAVO. Conversely, the amount of heat radiated by the refrigerant in the inner condenser 12 is increased to increase its heat capacity.

[0089] Accordingly, if the saturation temperature of the refrigerant in the outer heat exchanger 20 is lower than the ambient air temperature, the amount of heat absorption of the refrigerant in the outer heat exchanger 20 can be increased by lowering the saturation temperature of the refrigerant in the outer heat exchanger 20 by increasing the target condenser temperature TAVO. Similarly, the amount of heat radiated by the refrigerant in the inner condenser 12 is increased to enhance its heat capacity.

[0090] Accordingly, in the series dehumidification-heating mode, dehumidification and heating can be carried out by blowing the air, which has been cooled and dehumidified by the inner evaporator 23, before reheating the air by the inner condenser 12. Furthermore, the air heating capacity of the inner condenser 12 can be adjusted by setting the throttling degree of the high-stage expansion valve 13a and the cooling expansion valve 22a. (c) Parallel dehumidification heating mode

[0091] In the parallel dehumidification heating mode, the control unit 40 controls: the high-pressure side expansion valve 13a to be in a throttling state in which the high-pressure side expansion valve 13a performs a decompression function; the cooling expansion valve 22a to be in a throttling state in which the cooling expansion valve 22a performs a decompression function; the low-pressure side on / off valve 25a to be fully open; and the high-pressure side on / off valve 28a to be fully open.

[0092] Accordingly, in the parallel dehumidification heating mode, the vapor compression refrigeration cycle is formed, in which the refrigerant flows through the compressor 11, the inner condenser 12, the high-stage expansion valve 13a, the outer heat exchanger 20, the accumulator or pressure accumulator 24, and the compressor 11 in the following sequence. Furthermore, in the refrigeration cycle or refrigerant circuit, the refrigerant flows through the compressor 11, the inner condenser 12, the refrigeration expansion valve 22a, the inner evaporator 23, the constant pressure valve 27, the accumulator 24, and the compressor 11, as shown in Fig. 2 is shown. That is, the refrigerant circuit is formed in which the outer heat exchanger 20 and the inner evaporator 23 are connected parallel to each other with respect to the refrigerant flow.

[0093] The control unit 40 controls the operation of the compressor 11 such that the temperature of the air blown out of the inner condenser 12 is the setpoint condenser temperature TAVO. The control unit 40 controls the operation of the refrigeration expansion valve 22a and the high-stage expansion valve 13a such that the COP (coefficient of performance) of the cycle approaches its local maximum value range, based on the pressure of the refrigerant flowing into the high-stage expansion valve 13a. At this point, the control unit 40 decreases the throttling degree of the high-stage expansion valve 13a and increases the throttling degree of the refrigeration expansion valve 22a as the setpoint condenser temperature TAVO increases. The control unit 40 moves the air mixing door 34 to fully open the air passage on the side of the inner condenser 12.

[0094] Accordingly, in the parallel dehumidification heating mode, the state of the refrigerant circulating in the cycle changes, as shown in the Mollier diagram. Fig. 5 is shown.

[0095] That is, the high-pressure refrigerant that is discharged by compressor 11 (point b1 of Fig. 5), flows into the inner condenser 12 to release heat by exchanging heat with the air that has been cooled and dehumidified by the inner evaporator 23 (point b1 to point b2 of Fig. 5).

[0096] Accordingly, the air supplied to the vehicle interior is heated. The flow of refrigerant exiting the inner condenser 12 is split or diverted into the flow entering the high-stage expansion valve 13a and the flow entering the cooling expansion valve 22a.

[0097] The refrigerant flowing into the high-stage expansion valve 13a is decompressed to become the low-pressure refrigerant and then flows into the outer heat exchanger 20 (point b2 to point b3 of Fig. 5) The refrigerant flowing into the outer heat exchanger 20 absorbs heat from the outside air blown by the blower fan (points b3 to b4 of Fig. 5).

[0098] In contrast, the refrigerant flowing into the cooling expansion valve 22a is decompressed to become the low-pressure refrigerant and then flows into the inner evaporator 23 (points b2 to b5 of Fig. 5) The refrigerant flowing into the inner evaporator 23 absorbs heat from the air and evaporates (point b5 to point b6 of Fig. 5) Accordingly, the air supplied to the passenger compartment is cooled.

[0099] The refrigerant flowing into the inner evaporator 23 flows into the constant pressure valve 27. Accordingly, the pressure of the refrigerant in the inner evaporator 23 is adjusted to the predetermined pressure by the constant pressure valve 27 (point b6 to point b7 of Fig. 5) The refrigerant flowing out of the external heat exchanger 20 and the refrigerant flowing out of the constant pressure valve 27 combine on the inlet side of the accumulator or pressure storage tank 24 (points b4 to b8, b7 to b8 of Fig. 5), and the refrigerant flows from the accumulator 24 to the suction side of the compressor 11 and is compressed again by the compressor 11.

[0100] In parallel dehumidification heating mode, the inner condenser 12 functions as a radiator, and the outer heat exchanger 20 and the inner evaporator 23 function as evaporators. Accordingly, the heat absorption capacity of the refrigerant in the outer heat exchanger 20 can be increased by lowering the refrigerant saturation temperature in the outer heat exchanger 20 as the target condenser temperature TAVO increases. Conversely, the heat dissipation capacity of the refrigerant in the inner condenser 12 is increased to enhance its heat capacity.

[0101] Accordingly, in the parallel dehumidification-heating mode, dehumidification and heating can be carried out by blowing air that has been cooled and dehumidified by the inner evaporator 23, after reheating it by the inner condenser 12. Since the saturation temperature (i.e., evaporation temperature) of the refrigerant in the outer heat exchanger 20 can be reduced to be lower than the saturation temperature (i.e., evaporation temperature) of the refrigerant in the inner evaporator 23, the heat capacity of the air can be higher than that in the series dehumidification-heating mode. (d) Heating mode

[0102] In heating mode, the control unit 40 controls: the high-pressure side expansion valve 13a to be in a throttling state in which the high-pressure side expansion valve 13a performs a decompression function; the cooling expansion valve 22a to be fully closed; the low-pressure side on / off valve 25a to be fully open; and the high-pressure side on / off valve 28a to be closed.

[0103] Accordingly, in heating mode, the vapor compression refrigeration cycle is carried out, in which the refrigerant flows through the discharge port 11c of the compressor 11, the internal condenser 12, the high-stage expansion valve 13a, the external heat exchanger 20 and the suction port 11a of the compressor 11 in this order, as shown in Fig. 3 is shown.

[0104] The control unit 40 controls the operation of the compressor 11 such that the temperature of the refrigerant flowing into the inner condenser 12 is the setpoint condenser temperature TAVO. The control unit 40 controls the operation of the high-stage expansion valve 13a such that the COP of the cycle reaches its local maximum value based on the pressure of the refrigerant flowing into the high-stage expansion valve 13a. The control unit 40 moves the air mixing door 34 to fully open the air passage on the side of the inner condenser 12.

[0105] In the refrigeration circuit device in heating mode, the inner condenser 12 functions as a radiator and the outer heat exchanger 20 functions as an evaporator. The heat absorbed by the refrigerant when it evaporates in the outer heat exchanger 20 is transferred to the air in the inner condenser 12. This allows the air to be heated.

[0106] Accordingly, in heating mode, the passenger compartment can be warmed or heated by blowing the air, which is heated by the inner condenser 12, into the passenger compartment.

[0107] In the vehicle air conditioning device 1 of the present embodiment, different cycles are formed by switching the refrigerant flow of the heat pump cycle 10, as described above, and accordingly cooling, heating and dehumidifying heating of the passenger compartment are appropriately carried out.

[0108] In the vehicle air conditioning device 1 used in the hybrid vehicle, as in the present embodiment, the engine exhaust heat may occasionally be insufficient as a heat source for heating. Accordingly, it may be effective to achieve a high COP in the heating operating mode, regardless of the heating load, as in the heat pump cycle 10 of the present embodiment.

[0109] In the parallel dehumidification heating mode, since the opening degree of the high-stage expansion valve 13a is throttled as small as possible to sufficiently reduce the temperature of the outer heat exchanger 20, the flow rate of the refrigerant flowing through the outer heat exchanger 20 decreases. Consequently, the refrigerant oil may remain in the outer heat exchanger 20 without flowing out of it, and the lubrication of the compressor 11 may be impaired.

[0110] In the parallel dehumidification heating mode, the control unit 40 limits the refrigerant oil to remaining in the outer heat exchanger 20 by performing the control process shown in the flowchart of Fig. 6 is shown.

[0111] The control process, which is shown in the flowchart of Fig. The function shown in Figure 6 is executed as a superroutine for the main routine of the air conditioning control program.

[0112] In step S100, the value of a counter is reset to 0. In the subsequent step S110, a predetermined number is added to the counter value. An example of the predetermined number is shown in the control map of Fig. Figure 7 is shown. If the outside air temperature is at or below 5°C, 0.23 counts are added per second. If the outside air temperature is between 5°C and 25°C, the count increases with the rise in the outside air temperature within a range of 0.23 to 1 count per second. For example, if the outside air temperature is 10°C, 0.45 counts are added per second. If the outside air temperature is at or above 25°C, 1 count is added per second.

[0113] In the following step S120, it is determined whether the counter value has reached 840. For example, according to Fig. 7. When the outside air temperature is 5°C, the counter reaches 840 counts 60.8 minutes after the parallel dehumidification heating mode is activated. When the outside air temperature is 10°C, the counter reaches 840 counts 31.1 minutes after the parallel dehumidification heating mode is activated. When the outside air temperature is 25°C, the counter reaches 840 counts 14 minutes after the parallel dehumidification heating mode is activated. This means that when the outside air temperature is low, the time it takes to reach 840 counts is longer.

[0114] If it is determined that the counter value has not reached 840 in step S120, it is determined that "oil retention" does not occur, and the process returns to step S100. Oil retention refers to a situation in which the refrigerant oil remains in the outer heat exchanger 20 and insufficient refrigerant oil returns from the outer heat exchanger 20 to the compressor 11. Oil retention can also refer to a situation in which the refrigerant oil remains in the outer heat exchanger 20 and the amount of refrigerant oil flowing from the outer heat exchanger 20 to the compressor 11 is insufficient.

[0115] In contrast, if it is determined that the counter value has reached 840 in step S120, it is determined that the oil residue occurs, and the process continues with step S130.

[0116] For example, if the predetermined counter is based on Fig.7 is determined, the time to reach 840 counts, i.e., the time when the oil stay is determined, is determined as follows.

[0117] When the outside air temperature is 5°C, it is determined that 840 counters have been reached and the oil stay occurs 60.8 minutes after switching to the parallel dehumidification heating mode. When the outside air temperature is 10°C, it is determined that 840 counters have been reached and the oil stay occurs 31.1 minutes after switching to the parallel dehumidification heating mode. When the outside air temperature is 25°C, it is determined that 840 counters have been reached and the oil stay occurs 14 minutes after switching to the parallel dehumidification heating mode.

[0118] This means that when the outside air temperature is low, the time between switching to the parallel dehumidification heating mode and determining the oil level is long. The reasons for this are described below.

[0119] In parallel dehumidification heating mode, the external heat exchanger 20 functions as an evaporator. The vapor quality of the refrigerant at the outlet of the external heat exchanger 20 decreases when the outside air temperature is lower. When the vapor quality of the refrigerant is low, the amount of refrigerant oil dissolved in the refrigerant and returning to the compressor increases, and consequently, the time until the oil remains in the system is longer.

[0120] In light of this point, the time required to determine the oil remaining after switching to the parallel dehumidification heating mode is extended by decreasing the counter that is added every second when the outside air temperature is low.

[0121] In a subsequent step S130, it is determined whether the outside air temperature is less than 10°C. If it is determined that the outside air temperature is not less than 10°C, the process continues with step S140, and refrigerant oil return is performed by switching to the series dehumidification heating mode. Refrigerant oil return means that the refrigerant oil remaining in the outer heat exchanger 20 is returned to the compressor 11. Since the flow rate of the refrigerant flowing through the outer heat exchanger 20 increases when switching to the series dehumidification heating mode, the refrigerant oil remaining in the outer heat exchanger 20 can be returned to the compressor 11.

[0122] In the subsequent step S150, 4 counters per second are subtracted from the counter value. In the subsequent step S160, it is determined whether the counter value has reached 0. In the present embodiment, since 4 counters per second are subtracted, the counter value reaches 0 counters 210 seconds after switching to the series dehumidification heating mode in step S140.

[0123] If step S160 determines that the counter value has not reached 0, it is determined that the refrigerant oil return has not been completed, and the process returns to step S150.

[0124] In contrast, if step S160 determines that the counter value has reached 0, it is determined that the refrigerant oil return has been completed, and the process continues with step S170. Furthermore, after switching to the parallel dehumidification heating mode, the air conditioning control program returns to the main routine. That is, it is determined that the refrigerant oil return has ended 210 seconds after switching to the series dehumidification heating mode, and then the operating mode is switched to the parallel dehumidification heating mode.

[0125] In contrast, if step S130 determines that the outside air temperature is less than 10°C, the process continues with step S180, the parallel dehumidification heating mode is continued, and the opening of the high-stage expansion valve 13a is increased. For example, refrigerant oil return is performed by increasing the opening of the high-stage expansion valve 13a by 5% above its normal opening for 10 seconds, and then the opening returns to its normal opening for 60 seconds. That is, in step S180, the opening of the high-stage expansion valve 13a is periodically increased. The normal opening can refer to the opening of the high-stage expansion valve 13a before it is increased.

[0126] Since the flow rate of the refrigerant flowing through the outer heat exchanger 20 increases due to an increase in the opening degree of the high-stage expansion valve 13a, the refrigerant oil remaining in the outer heat exchanger 20 can be returned to the compressor 11. Cycle destabilization due to an increase in the temperature of the inner evaporator 23 can be suppressed by periodically returning the opening degree of the high-stage expansion valve 13a to its normal opening degree.

[0127] Since the heating capacity in the series dehumidification heating mode is lower than in the parallel dehumidification heating mode, it may be difficult to maintain a blow temperature TAV at the target blow temperature TAO if refrigerant oil recirculation is carried out in the series dehumidification heating mode when the outside air temperature is less than 10°C.

[0128] Accordingly, if it is determined in step S180 that the outside air temperature is less than 10°C, the opening degree of the high-stage expansion valve 13a is increased with a continuation of the parallel dehumidification heating mode, which has a higher heating capacity than the series dehumidification heating mode, and accordingly the refrigerant oil return can be carried out with a maintenance of the blow temperature TAV at the set outlet temperature TAO.

[0129] In the subsequent step S190, 210 counters are subtracted from the counter value. In the subsequent step S200, it is determined whether the counter value has reached 0. In the present embodiment, the counter value is set to 0 by increasing the opening degree of the high-stage expansion valve 13a four times in step S180.

[0130] If it is determined that the counter value has not reached 0 in step S200, it is determined that the refrigerant oil return has not ended or been completed, and the process returns to step S180.

[0131] In contrast, when it is determined that the counter value has reached 0 in step S200, it is determined that the refrigerant oil return is complete, and the process continues with step S210. Furthermore, after the opening degree of the high-stage expansion valve 13a returns to its normal opening degree, the air conditioning control program returns to the main routine.

[0132] In the present embodiment, as described in steps S140 and S170, the control unit 40 controls the low-pressure side on / off valve 25a and the high-pressure side on / off valve 28a to switch to the series dehumidification heating mode when it is determined that the refrigerant oil does not return sufficiently from the external heat exchanger 20 to the compressor 11 in the parallel dehumidification heating mode.

[0133] By switching from the parallel dehumidification heating mode to the series dehumidification heating mode, the amount of refrigerant flowing through the outer heat exchanger 20 increases, and consequently, the refrigerant oil in the outer heat exchanger 20 likely returns to the compressor 11. Therefore, the amount of refrigerant oil remaining in the outer heat exchanger 20 can be limited.

[0134] In the present embodiment, as described in steps S120 and S180, the control unit 40 increases the opening degree of the high-stage expansion valve 13a when it is determined that the refrigerant oil is not returning sufficiently from the external heat exchanger 20 to the compressor 11.

[0135] Accordingly, since the flow rate of the refrigerant flowing through the external heat exchanger 20 is increased by increasing the opening degree of the high-stage expansion valve 13a, the refrigerant oil can likely return from the external heat exchanger 20 to the compressor 11. Therefore, the amount of refrigerant oil remaining in the external heat exchanger 20 can be limited.

[0136] In the present embodiment, as described in steps S120 to S140 and S120 to S180, when it is determined that the refrigerant oil does not return sufficiently from the external heat exchanger 20 to the compressor 11 in the parallel dehumidification heating mode, the control unit 40 (i) controls the low-pressure-side on / off valve 25a and the high-pressure-side expansion valve 13a to switch to the series dehumidification heating mode when the external heat exchanger temperature is higher than the predetermined temperature, and (ii) increases the opening degree of the high-pressure-side expansion valve 13a when the outside air temperature is lower than the predetermined temperature while maintaining the parallel dehumidification heating mode.

[0137] Accordingly, since the operating mode or operating mode is switched to the series dehumidification heating mode when the outside air temperature is high, it can certainly be prevented that the refrigerant oil remains in the outer heat exchanger 20.

[0138] In contrast, since the opening degree of the high-stage expansion valve 13a is increased while maintaining the parallel dehumidification heating mode when the outside air temperature is low, a deficit or shortfall in the air heating capacity of the radiator 12 can be suppressed by suppressing the retention of refrigerant oil in the outer heat exchanger 20.

[0139] In the present embodiment, as described in steps S110 and S120, the control unit 40 determines that the refrigerant oil does not return sufficiently from the external heat exchanger 20 to the compressor 11 when the predetermined time elapses after the parallel dehumidification heating mode begins.

[0140] Accordingly, since the refrigerant oil can be returned from the outer heat exchanger 20 to the compressor 11 in a timely manner, the refrigerant oil can be suitably prevented from remaining in the outer heat exchanger 20.

[0141] As described above, the vapor quality of the refrigerant at the outlet of the external heat exchanger 20 decreases with a decrease in the outside air temperature. When the vapor quality of the refrigerant is low, the amount of refrigerant oil dissolved in the refrigerant and returning to the compressor increases, and consequently, the oil stay time is longer.

[0142] In view of this point, in the present embodiment the control unit 40 increases the predetermined time when the outside air temperature is lower, as described in steps S110 and S120.

[0143] Accordingly, since the refrigerant oil can be returned from the external heat exchanger 20 to the compressor 11 in a timely manner, the refrigerant oil can be suitably prevented from remaining in the external heat exchanger 20.

[0144] In the present embodiment, as described in step S180, when the control unit 40 increases the opening degree of the high-stage expansion valve 13a and determines that the refrigerant oil returns sufficiently from the external heat exchanger 20 to the compressor 11, the control unit 40 periodically returns the opening degree of the high-stage expansion valve 13a to the normal opening degree.

[0145] Accordingly, the shortfall or deficit in the air heating capacity of the radiator 12 can be suppressed even if the opening degree of the high-stage expansion valve 13a is increased to allow the refrigerant oil to return from the external heat exchanger 20 to the compressor 11.

[0146] The embodiments described above can be modified in various ways as follows.

[0147] In steps S140 to S170 of the embodiment described above, when the refrigerant oil return by the series dehumidification heating mode is terminated or completed, the refrigerant oil return is terminated by a return of the operating mode to the parallel dehumidification heating mode. However, after the refrigerant oil return by the series dehumidification heating mode is completed, the series dehumidification heating mode can be continued if the discharge temperature TAV can be maintained to be the target discharge temperature TAO, using the series dehumidification heating mode instead of a return to the parallel dehumidification heating mode, and the operating mode or...The operating mode can be reduced to the parallel dehumidification heating mode to maintain the blowing temperature TAV in order to be the target blowing temperature TAO, if the blowing temperature TAV cannot be maintained in order to be the target blowing temperature TAO, using the series dehumidification heating mode.

[0148] The embodiment described above provides an example in which the heat pump cycle 10 is used in the vehicle air conditioning unit 1 of the hybrid vehicle. However, the heat pump cycle 10 of the present disclosure can be used in a vehicle air conditioning unit of an electric vehicle that obtains driving power for an electric motor. The heat pump cycle 10 can be used, for example, in a stationary air conditioning system.

[0149] The embodiment described above illustrates an example in which the operating mode is switched by executing the air conditioning control program. However, switching the operating mode is not limited to this specific example. For instance, the operating mode can be switched with reference to a control map that is pre-stored in the control unit, based on the target outlet temperature TAO and the outside air temperature Tam.

[0150] The cooling mode, the series dehumidification heating mode, the parallel dehumidification heating mode and the heating mode can be switched based on operating signals from an operating mode switch provided on the control panel.

[0151] Although the present revelation has been described in accordance with the examples, it is understood that the present revelation is not limited to the preceding examples or structures. On the contrary, the present revelation is intended to encompass various modifications and equivalent arrangements. Furthermore, while the various elements are shown in different combinations and configurations, which are exemplary, other combinations and configurations that include more, less, or only a single element are also within the spirit and scope of protection of the present revelation.

Claims

[1] Vehicle air conditioning device (1) comprising the following: a compressor (11) that draws in, compresses and discharges a refrigerant containing a refrigerant oil; a radiator (12) which heats air by exchanging heat between the refrigerant supplied by the compressor (11) and the air supplied to a passenger compartment; an external heat exchanger (20) that exchanges heat between the refrigerant flowing out of the radiator (12) and outside air; an evaporator (23) which evaporates the refrigerant by exchanging heat between the refrigerant flowing out of the external heat exchanger (20) and the air flowing into the radiator (12); a first decompressor (13a) that decompresses the refrigerant flowing out of the radiator (12); a second decompressor (22a) that decompresses the refrigerant flowing out of the outer heat exchanger (20); a switching section (25a, 28a) that switches between the following: a series dehumidification heating mode in which the external heat exchanger (20) and the evaporator (23) are connected in series with respect to a flow of refrigerant, and a parallel dehumidification heating mode in which the external heat exchanger (20) and the evaporator (23) are connected in parallel to each other with respect to the flow of the refrigerant, and a control unit (40) designed to control the switching section (25a, 28a) to switch from the parallel dehumidification heating mode to the series dehumidification heating mode when the control unit (40) determines that the amount of refrigerant oil flowing from the external heat exchanger (20) to the compressor (11) is insufficient. [2] Vehicle air conditioning device (1) according to claim 1, wherein the control unit (40) is designed to control an opening degree of the first decompressor (13a), and the control unit (40) controls the switching section (25a, 28a) to switch from the parallel dehumidification heating mode to the series dehumidification heating mode when The control unit (40) determines that the amount of refrigerant oil flowing from the external heat exchanger (20) to the compressor (11) during the parallel dehumidification heating mode is insufficient, and a temperature of the outside air is higher than a predetermined temperature, and the control unit (40) maintains the parallel dehumidification heating mode and increases the opening degree of the first decompressor (13a) when The control unit (40) determines that the amount of refrigerant oil flowing from the external heat exchanger (20) to the compressor (11) during the parallel dehumidification heating mode is insufficient, and the temperature of the outside air is lower than the predetermined temperature. [3] Vehicle air conditioning device (1) according to one of claims 1 and 2, wherein the control unit (40) determines that the amount of refrigerant oil flowing from the external heat exchanger (20) to the compressor (11) is insufficient when a predetermined time has elapsed since the parallel dehumidification heating mode was started. [4] Vehicle air conditioning device (1) according to claim 3, wherein the control unit (40) extends the predetermined time if the outside air temperature is lower.

Images