Vehicle air conditioning system and vehicle air conditioning method

Abstract

To provide a vehicular air-conditioning system that comprises a refrigerant circuit and a heat medium circuit and includes a plurality of vehicle exterior-side heat exchangers which perform heat-exchange of outdoor air with a heat medium.SOLUTION: A vehicular air-conditioning system comprises: a refrigerant circuit; a heat medium circuit; a vehicle interior-side heat exchanger; vehicle exterior-side heat exchangers which are a first heat exchanger and a second heat exchanger arranged in series with respect to flow of air caused by an air blower; a switching part; a sensing part for sensing a degree of frost formation; and a control device. Operation modes include a defrosting mode in which a heat medium of a high-temperature medium circuit is supplied to the exchanger to be defrosted alternatively selected, of the first heat exchanger and the second heat exchanger connected in parallel in the heat medium circuit, by operating the switching part. The control device, when it is determined that both of the first heat exchanger and the second heat exchanger are required to be defrosted, selects the first heat exchanger positioned closer to a windward side preferentially over the second heat exchanger positioned at downwind side.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to an air conditioning system equipped in a vehicle, a system including a refrigerant circuit and a heat medium circuit, and an air conditioning method using the system.

Background Art

[0002] In vehicles such as electric vehicles that cannot utilize the exhaust heat of an engine, heat sources are often insufficient. In addition to the air conditioning functions required for vehicles such as heating, cooling, dehumidification, and ventilation, heat management of in-vehicle devices such as batteries and exhaust heat utilization are also required. Conventionally, in response to such requirements, in addition to electric heaters and heat pump systems, a plurality of systems such as a system including a chiller for cooling a battery and a system for transporting water heated by the exhaust heat of a radiator to a heat load by a pump have been used.

[0003] As a vehicle air conditioning system capable of integrating air conditioning and heat management, a system has been proposed that includes a primary loop in which a refrigerant circulates according to a refrigeration cycle and a secondary loop in which a heat medium (water) that exchanges heat with the refrigerant in the primary loop is transported to in-vehicle devices by a pump (for example, Patent Document 1). The vehicle air conditioning system described in Patent Document 1 includes a low-pressure refrigerant / water heat exchanger that exchanges heat between the low-pressure side refrigerant and water, a high-pressure refrigerant / water heat exchanger that exchanges heat between the high-pressure side refrigerant and water, an in-vehicle heat exchanger that exchanges heat between water and cabin air, an outside-vehicle heat exchanger that exchanges heat between water and outside air, and a plurality of valves for switching the direction of the water flow. Such a vehicle system further includes a heater used during defrosting operation in order to surely melt the frost adhering to the outside-vehicle heat exchanger during heating operation. Water heated by the heater is supplied to the outside-vehicle heat exchanger.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to enhance the heating capacity, the inventor of the present disclosure has been considering the practical application of a novel vehicle air - conditioning system including two or more outdoor heat exchangers that absorb heat from air as a heat source to a heat medium. An example of an air - conditioning system including a refrigerant circuit and a heat - medium circuit and having two or more outdoor heat exchangers is not known. By taking appropriate measures against frosting on these outdoor heat exchangers, it is desired to ensure the heating capacity during defrosting operation. Based on the above, the object of the present disclosure relates to the improvement of a vehicle air - conditioning system and a vehicle air - conditioning method including a refrigerant circuit and a heat - medium circuit and including a plurality of outdoor heat exchangers that exchange heat between outside air and the heat medium.

Means for Solving the Problems

[0006] The present disclosure is a vehicle air - conditioning system including a refrigerant circuit in which a refrigerant circulates according to a refrigeration cycle, a high - temperature medium circuit in which a heat medium that absorbs heat from the refrigerant in the refrigerant circuit circulates, and a heat - medium circuit including a low - temperature medium circuit in which a heat medium that radiates heat to the refrigerant in the refrigerant circuit circulates, an in - vehicle heat exchanger that exchanges heat between the heat medium and air, an outdoor heat exchanger that exchanges heat between the heat medium and air, the first heat exchanger and the second heat exchanger arranged in series with respect to the air flow by a blower, a switching unit configured to be able to switch the flow of the heat medium, a detection unit for detecting the degree of frosting of each of the first heat exchanger and the second heat exchanger, and a control device for controlling the operation of the switching unit according to the operation mode of the air - conditioning system. The operation mode includes a defrosting mode in which the heat medium of the high - temperature medium circuit is supplied to a defrosting target selectively selected from among the first heat exchanger and the second heat exchanger connected in parallel in the heat - medium circuit by the operation of the switching unit. When selecting a defrost target by the operation of the switching unit, based on the detection result of the frost accumulation degree by the detection unit, if only the first heat exchanger is determined to require defrosting, the first heat exchanger is selected as the defrost target. If only the second heat exchanger is determined to require defrosting, the second heat exchanger is selected as the defrost target. If both the first heat exchanger and the second heat exchanger are determined to require defrosting, the first heat exchanger located upstream of the second heat exchanger located downstream is preferentially selected as the defrost target.

[0007] Further, the present disclosure is an air conditioning method using an air conditioning system for a vehicle. The air conditioning system includes a refrigerant circuit in which a refrigerant circulates according to a refrigeration cycle, a high-temperature medium circuit in which a heat medium that absorbs heat from the refrigerant circulates, and a low-temperature medium circuit in which a heat medium that radiates heat to the refrigerant circulates. The heat medium circuit includes an in-vehicle heat exchanger that exchanges heat between the heat medium and air, and an out-of-vehicle heat exchanger that exchanges heat between the heat medium and air. The out-of-vehicle heat exchanger includes a first heat exchanger and a second heat exchanger that are arranged in series with respect to the air flow by a blower, and a switching unit configured to be able to switch the flow of the heat medium. In the air conditioning method of the present disclosure, when supplying the heat medium of the high-temperature medium circuit to an alternative defrost target selected from among the first heat exchanger and the second heat exchanger connected in parallel by the operation of the switching unit, based on the detection result of the frost accumulation degree of each of the first heat exchanger located upstream and the second heat exchanger located downstream, if only the first heat exchanger is determined to require defrosting, the first heat exchanger is selected as the defrost target. If only the second heat exchanger is determined to require defrosting, the second heat exchanger is selected as the defrost target. If both the first heat exchanger and the second heat exchanger are determined to require defrosting, the first heat exchanger is preferentially selected as the defrost target over the second heat exchanger.

Advantages of the Invention

[0008] In the vehicle air conditioning system and the vehicle air conditioning method according to the present disclosure, while determining whether each of the first heat exchanger and the second heat exchanger requires defrosting based on the frost accumulation degree, the first heat exchanger and the second heat exchanger are alternatively selected as the defrost target, and the first heat exchanger upstream is given priority over the second heat exchanger downstream. Then, when the flow rate of the air flowing through the second heat exchanger decreases due to an increase in air resistance caused by frosting on the first heat exchanger upwind, the high-temperature medium is supplied to the first heat exchanger prior to being supplied to the second heat exchanger downwind. Thus, the frost on the first heat exchanger can be melted to recover the heat exchange amount by the first heat exchanger, and the air passage of the first heat exchanger necessary for recovering the heat exchange amount of the second heat exchanger can be ensured.

[0009] According to the fact that the defrosting process of the first heat exchanger is performed prior to that of the second heat exchanger, the high-temperature medium distributed to the inside and outside of the vehicle is effectively used to recover the heat exchange amount by each of the first heat exchanger and the second heat exchanger. During the implementation of the defrosting mode, frosting on the first heat exchanger upwind is maintained to such an extent that the air volume is not excessively reduced. Therefore, according to the present disclosure, not only in the heating mode but also in the defrosting mode, at least a certain amount of heating capacity can be ensured by the first heat exchanger. Moreover, by supplying the high-temperature medium to the appropriate location in a timely manner, as a whole of the first heat exchanger and the second heat exchanger, the defrosting mode can be terminated early and the heating mode can be restored.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. (Overall Configuration) The vehicle air conditioning system 1 shown in FIG. 1 is installed in a vehicle (not shown), such as an electric vehicle. The vehicle air conditioning system 1 is responsible for air conditioning such as heating, cooling, dehumidifying, and ventilating the passenger compartment 2 where passengers board, as well as heat management and waste heat recovery of in-vehicle equipment (not shown) mounted on the vehicle. Note that the vehicle in which the vehicle air conditioning system 1 is installed is not limited to an electric vehicle, and may be a vehicle equipped with an engine.

[0012] The vehicle air conditioning system 1 mainly includes a refrigerant circuit 10 in which a refrigerant circulates according to a refrigeration cycle, a heat medium circuit 20 in which a heat medium that exchanges heat with the refrigerant circulates, an in-vehicle heat exchanger 30, a blower 33 for the in-vehicle heat exchanger 30, a plurality of outside-vehicle heat exchangers (41, 42), a blower 43 for the outside-vehicle heat exchangers (41, 42), a detection unit 5 for detecting the degree of frosting in the outside-vehicle heat exchangers (41, 42), a switching unit 6 configured to be able to switch the flow of the heat medium in the heat medium circuit 20, and a control device 7 that controls the operation of the switching unit 6 according to the operation mode of the vehicle air conditioning system 1.

[0013] In addition to the cooling mode shown in FIG. 1 and the heating mode shown in FIG. 2, the vehicle air conditioning system 1 has operation modes such as a defrost mode shown in FIGS. 3 and 4. As will be described later, the vehicle air conditioning system 1 of the present embodiment performs a defrost operation based on the degree of frosting of each of the plurality of outside-vehicle heat exchangers (41, 42).

[0014] The operation mode required for the vehicle air conditioning system 1 varies depending on the region where the vehicle is used. For example, the vehicle air conditioning system 1 may not have a cooling mode.

[0015] (Refrigerant circuit) The refrigerant circuit 10 includes a compressor 11 that compresses the refrigerant, a heat exchanger 12 for heat absorption, an expansion valve 13 as a decompression unit that reduces the pressure of the refrigerant passing through the compressor 11 and the heat exchanger 12 for heat absorption, and a heat exchanger 14 for heat dissipation. The refrigerant circuit 10 generates a heat source (heat exchanger 12 for heat absorption) for the heat medium and a cold heat source (heat exchanger 14 for heat dissipation) for the heat medium by a refrigeration cycle. The compressor 11, the heat exchanger 12 for heat absorption, the expansion valve 13, the heat exchanger 14 for heat dissipation, and the refrigerant pipes connecting these elements are installed outside the passenger compartment 2.

[0016] As the refrigerant, a known appropriate single refrigerant or mixed refrigerant can be used. For example, HFC (Hydro Fluoro Carbon) refrigerants such as R410A and R32, HFO (Hydro Fluoro Olefin) refrigerants such as R1234ze and R1234yf, hydrocarbon (HC) - based refrigerants such as propane and isobutane, or carbon dioxide can be used as the refrigerant.

[0017] The heat exchanger 12 for heat absorption causes the refrigerant gas discharged from the compressor 11 to exchange heat with the heat medium, thereby absorbing heat from the refrigerant to the heat medium. By the heat exchange between the refrigerant and the heat medium in the heat exchanger 12 for heat absorption, typically, the refrigerant changes to the liquid phase. In this case, the heat exchanger 12 for heat absorption corresponds to a condenser.

[0018] The heat exchanger 14 for heat dissipation causes the refrigerant passing through the expansion valve 13 to exchange heat with the heat medium, thereby dissipating heat from the heat medium to the refrigerant. The heat exchanger 14 for heat dissipation corresponds to an evaporator. The refrigerant that has changed to the gas phase in the heat exchanger 14 for heat dissipation is sucked into the compressor 11. The refrigerant circulates through the refrigerant circuit 10 due to the difference between the refrigerant pressure in the heat exchanger 12 for heat absorption and the refrigerant pressure in the heat exchanger 14 for heat dissipation.

[0019] (Heat medium circuit) The heat medium circuit 20 conveys a heat medium that exchanges heat with the heat source and cold heat source formed by the refrigerant circuit 10 to the in-vehicle heat exchanger 30 and the outside-vehicle heat exchangers (41, 42). The heat medium can be used not only for air conditioning in the passenger compartment 2 but also for heat management such as heating and cooling of in-vehicle devices and recovery of waste heat from in-vehicle devices. The in-vehicle devices include, for example, a drive source such as an electric motor, a drive circuit section, and a power supply device including a battery. The heat medium is a liquid such as water or brine that circulates in the heat medium circuit 20 while maintaining a liquid phase state. Examples of brine include a mixture of water and propylene glycol or a mixture of water and ethylene glycol.

[0020] In the heat medium circuit 20, a relatively high-temperature heat medium (high-temperature medium) and a relatively low-temperature heat medium (low-temperature medium) circulate respectively. In either the cooling mode or the heating mode, the high-temperature medium absorbs heat from the refrigerant in the heat absorption heat exchanger 12, and the low-temperature medium dissipates heat to the refrigerant in the heat dissipation heat exchanger 14.

[0021] In FIG. 1, the flow of the low-temperature medium is indicated by a solid-line arrow, and the flow of the high-temperature medium is indicated by a one-dot chain-line arrow. In the heat medium circuit 20, the path where the heat medium does not flow is indicated by a broken line. The same applies to FIG. 2 and below. The high-temperature medium circulates through a predetermined path on the heat medium circuit 20 according to the operation mode, as indicated by a one-dot chain-line arrow in FIG. 1 for example. The low-temperature medium circulates through a path on the heat medium circuit 20 according to the operation mode, as indicated by a solid-line arrow in FIG. 1 for example.

[0022] The heat medium circuit 20 is divided by a switching unit 6 that switches the flow of the heat medium into a low-temperature medium circuit 21 through which a low-temperature medium circulates and a high-temperature medium circuit 22 through which a high-temperature medium circulates. In FIG. 1, A to D on the heat medium circuit 20 are shown. Only the low-temperature medium flows from A to B. Only the high-temperature medium flows from C to D. In the remaining sections of the heat medium circuit 20, either the low-temperature medium or the high-temperature medium flows according to the operation mode. The high-temperature medium is pumped through the high-temperature medium circuit 22 by a pump 22P downstream of the heat exchanger 12 for heat absorption. The low-temperature medium is pumped through the low-temperature medium circuit 21 by a pump 21P downstream of the heat exchanger 14 for heat dissipation.

[0023] Even if the outside air temperature is so low that it is difficult to ensure the heating capacity with the refrigerant circuit 10 alone, the heat medium circuit 20 that stably conveys a heat medium that does not undergo a phase change in the operating temperature range by pumps 21P and 22P is used in combination with the refrigerant circuit 10, so that the heating capacity at low outside air temperatures can be ensured.

[0024] In the cooling mode (FIG. 1), the low-temperature medium circulates between the heat exchanger 14 for heat dissipation and the in-vehicle heat exchanger 30 through the pipes of the heat medium circuit 20 and is used for cooling the interior of the vehicle compartment 2. At this time, the high-temperature medium circulates between the heat exchanger 12 for heat absorption and the outside-vehicle heat exchangers (41, 42) through the pipes of the heat medium circuit 20. On the other hand, in the heating mode (FIG. 2), the high-temperature medium circulates between the heat exchanger 12 for heat absorption and the in-vehicle heat exchanger 30 and is used for heating the interior of the vehicle compartment 2. At this time, the low-temperature medium circulates between the heat exchanger 14 for heat dissipation and the outside-vehicle heat exchangers (41, 42).

[0025] In any operation mode, the heat medium circuit 20 supplies the high-temperature medium to at least one of the in-vehicle heat exchanger 30 and the outside-vehicle heat exchangers (41, 42), and supplies the low-temperature medium to at least one of the in-vehicle heat exchanger 30 and the outside-vehicle heat exchangers (41, 42).

[0026] (In-vehicle heat exchanger) The in-vehicle heat exchanger 30 is provided inside the console, walls, etc. of the passenger compartment 2, and exchanges heat between the supplied low-temperature medium or high-temperature medium and the air in the passenger compartment 2. Although detailed illustration of the in-vehicle heat exchanger 30 is omitted, it constitutes an HVAC (Heating, Ventilation, and Air Conditioning) unit 3 together with a blower 33, a duct through which the air sent by the blower 33 flows, a damper whose opening degree can be adjusted, and the like.

[0027] The in-vehicle heat exchanger 30 consists of a single heat exchanger or a plurality of heat exchangers arranged in series with respect to the air flow by the blower 33. When the in-vehicle heat exchanger 30 consists of a plurality of heat exchangers, for example, two heat exchangers, by opening and closing a valve provided between these heat exchangers, the two heat exchangers can be switched between series connection and parallel connection with respect to the flow of the heat medium. It is preferable that the flow of the heat medium flowing sequentially through the two series-connected heat exchangers and the flow of the air flowing sequentially through the two heat exchangers form a countercurrent. When two heat exchangers as the in-vehicle heat exchanger 30 are connected in parallel, a low-temperature medium can be supplied to one of the two heat exchangers and a high-temperature medium can be supplied to the other. Therefore, it is possible to implement a dehumidifying and heating mode in which the amount of water vapor in the air is reduced by taking heat from the air with a low-temperature medium and then the air is heated with a high-temperature medium to obtain conditioned air. In the dehumidifying and heating mode, a low-temperature medium is supplied to the heat exchanger on the upwind side, and a high-temperature medium is supplied to the heat exchanger on the downwind side.

[0028] The air in or outside the passenger compartment 2 sucked by the blower 33 is supplied to the in-vehicle heat exchanger 30 through a duct, and the air cooled by heat exchange with the low-temperature medium or heated by heat exchange with the high-temperature medium in the in-vehicle heat exchanger 30 is blown into the passenger compartment 2 from a blowout port (not shown).

[0029] (Out-vehicle heat exchanger) The first heat exchanger 41 and the second heat exchanger 42 exchange heat between the air (outside air) taken in from outside the passenger compartment 2 by the blower 43 (a blower) and a low-temperature medium or a high-temperature medium. In the cooling mode shown in FIG. 1, the high-temperature medium having a temperature higher than that of the outside air is radiated to the outside air by the first heat exchanger 41 and the second heat exchanger 42, and in the heating mode shown in FIG. 2, the low-temperature medium having a temperature lower than that of the outside air absorbs heat from the outside air. According to the heat absorption by the plurality of outside-vehicle heat exchangers (41, 42), in the air-conditioning system 1 mounted on a vehicle such as an electric vehicle that tends to lack a heat source, sufficient heating capacity can be ensured.

[0030] The first heat exchanger 41 and the second heat exchanger 42 are arranged in series with respect to the flow AF of the air given by the blower 43. The first heat exchanger 41 is arranged on the upstream side (windward side) of the air flow by the blower 43. The second heat exchanger 42 is arranged on the downstream side (leeward side) of the air flow by the blower 43. Therefore, the air flowing by the blower 43 sequentially flows through the first heat exchanger 41 and the second heat exchanger 42 in this order.

[0031] The first heat exchanger 41 and the second heat exchanger 42 are connected via an intermediate valve 60. The connection between the first heat exchanger 41 and the second heat exchanger 42 can be switched between series and parallel with respect to the flow of the heat medium in the heat medium circuit 20 by a switching unit 6 including the intermediate valve 60. The first heat exchanger 41 and the second heat exchanger 42 are connected in series in both the cooling mode in which the low-temperature medium is supplied as shown in FIG. 1 and the heating mode in which the high-temperature medium is supplied as shown in FIG. 2.

[0032] When connected in series, regardless of the operation mode such as cooling and heating, in the heat medium circuit 20, the second heat exchanger 42 is located upstream and the first heat exchanger 41 is located downstream. That is, the heat medium flows from the second heat exchanger 42 and the first heat exchanger 41 from the leeward side to the windward side. Here, the flow of the heat medium flowing sequentially through the second heat exchanger 42 and the first heat exchanger 41 and the flow of air flowing sequentially through the first heat exchanger 41 and the second heat exchanger 42 form a countercurrent flow. Therefore, efficient heat exchange can be performed while ensuring a sufficient temperature difference between the air and the heat medium throughout the entire heat exchange process by the first heat exchanger 41 and the second heat exchanger 42.

[0033] Incidentally, during the heating operation, frosting occurs when drain water or moisture in the air condenses on the surfaces of the first heat exchanger 41 and the second heat exchanger 42. As the frost grows, the resistance of the air passing through the gaps (air passages) of members such as fins and tubes provided in the heat exchangers 41 and 42 increases and the air volume decreases. Along with this, the amount of heat exchanged decreases, resulting in a decrease in heating performance. If the air passage is completely blocked due to further growth of the frost, heat exchange between the outside air and the heat medium cannot be performed. In order to avoid a decrease in the amount of heat exchanged due to a decrease in the air volume, in the present embodiment, frost is melted by supplying a high-temperature medium according to the necessity of defrosting based on the degree of frosting (degree of frosting) on the first heat exchanger 41 and the second heat exchanger 42.

[0034] The degree of frosting in the outside vehicle heat exchanger is an amount related to the amount of frost that affects the flow rate of the air flowing through the air passage. Specifically, it corresponds to the thickness of the deposited frost, the density of the frost, etc. The greater the amount of adhering frost, the greater the degree of blockage of the air passage by the frost. As the heat medium supplied to the heat exchanger progresses in the blockage of the air passage, it cannot absorb heat from the air and is cooled by the frost, resulting in a decrease in temperature. That is, there is a correlation between the degree of frosting and the temperature of the heat medium flowing through the heat exchanger. In the present embodiment, as will be described later, a temperature sensor is used to detect the degree of frosting.

[0035] While continuously heating the passenger compartment 2 to ensure passenger comfort, it is desired to defrost the heat exchanger that requires defrosting. Therefore, in the defrost mode, by distributing the high-temperature medium to the in-vehicle heat exchanger 30 and the out-vehicle heat exchangers (41, 42), while suppressing the heating in the passenger compartment 2 due to the supply of the high-temperature medium to the in-vehicle heat exchanger 30 to the necessary limit, the high-temperature medium is supplied to the defrost target selectively selected from the first heat exchanger 41 and the second heat exchanger 42.

[0036] In order to ensure a certain level of heating capacity even during operation in the defrost mode, the high-temperature medium is not supplied to the two heat exchangers 41, 42 simultaneously, but is supplied one by one according to the necessity of defrosting. Therefore, in the defrost mode, by the operation of the switching unit 6, the first heat exchanger 41 and the second heat exchanger 42 are connected in parallel, and the supply destination of the high-temperature medium is switched between the first heat exchanger 41 and the second heat exchanger 42. That is, when the high-temperature medium is supplied to one of the first heat exchanger 41 and the second heat exchanger 42, the low-temperature medium is supplied to the other.

[0037] The degree of frosting on the first heat exchanger 41 located upwind and the degree of frosting on the second heat exchanger 42 located downwind are not necessarily the same. When frost grows on the upwind first heat exchanger 41, the air resistance increases due to the frost and the air volume decreases. Therefore, even if the second heat exchanger 42 is not frosted, the heat exchange capacity of the second heat exchanger 42 also decreases as the air flow rate flowing through the air passage of the second heat exchanger 42 decreases.

[0038] When the air volume has decreased due to frosting on the first heat exchanger 41, even if the high-temperature medium is supplied to the frosted second heat exchanger 42 to melt the frost on the second heat exchanger 42, the heat exchange capacity of the second heat exchanger 42 will not recover. In order to ensure the heat exchange capacity of the second heat exchanger 42, it is necessary to ensure the air passage of the first heat exchanger 41 by performing the defrosting of the first heat exchanger 41 prior to the defrosting of the second heat exchanger 42.

[0039] Therefore, in the present embodiment, the necessity of defrosting is determined based on the degree of frosting of each of the first heat exchanger 41 and the second heat exchanger 42, and defrosting of the first heat exchanger 41 on the windward side is preferentially performed over defrosting of the second heat exchanger 42 on the leeward side. Regardless of whether defrosting of the second heat exchanger 42 is necessary, if it is determined from the degree of frosting of the first heat exchanger 41 that defrosting of the first heat exchanger 41 is necessary, defrosting of the first heat exchanger 41 is promptly performed. As will be described later, defrosting of the second heat exchanger 42 is performed only when it is determined that defrosting of the first heat exchanger 41 is unnecessary.

[0040] (Detection unit) The detection unit 5 includes a first temperature detection unit 51 capable of detecting temperature information indicating a temperature drop of the heat medium due to frosting on the first heat exchanger 41, and a second temperature detection unit 52 capable of detecting temperature information indicating a temperature drop of the heat medium due to frosting on the second heat exchanger 42. The first temperature detection unit 51 of the present embodiment corresponds to a temperature sensor that detects the temperature of the heat medium that has flowed through the entire or part of the path of the heat medium set in the first heat exchanger 41 from the inlet to the outlet. The first temperature detection unit 51 is preferably installed at or near the outlet of the heat medium of the first heat exchanger 41. The first temperature detection unit 51 is installed, for example, in the pipe at the outlet of the first heat exchanger 41 to indirectly contact the heat medium, or directly contact the heat medium flowing out of the outlet.

[0041] Similarly, the second temperature detection unit 52 corresponds to a temperature sensor that detects the temperature of the heat medium that has flowed through the entire or part of the path of the heat medium set in the second heat exchanger 42 from the inlet to the outlet by indirectly or directly contacting the heat medium. The second temperature detection unit 52 is preferably installed at or near the outlet of the heat medium of the second heat exchanger 42.

[0042] As described above, the temperature of the heat medium flowing through the outside vehicle heat exchangers (41, 42) changes according to the degree of blockage of the air passage related to the degree of frosting. Therefore, the first temperature detection unit 51 detects the degree of frost formation adhering to the first heat exchanger 41 by detecting the temperature of the heat medium flowing through the first heat exchanger 41. Similarly, the second temperature detection unit 52 also detects the degree of frost formation adhering to the second heat exchanger 42 by detecting the temperature of the heat medium flowing through the second heat exchanger 42.

[0043] Not limited to this embodiment, the first temperature detection unit 51 may include two or more temperature sensors. In that case, for example, the temperature difference between the temperature of the heat medium at the inlet and the temperature of the heat medium at the outlet is obtained from the detected temperatures of the temperature sensors provided one each at the inlet and the outlet of the first heat exchanger 41, and the degree of frost formation is detected based on the temperature difference. The same applies to the second temperature detection unit 52.

[0044] (Switching unit) The switching unit 6 includes the above-described intermediate valve 60 between the first heat exchanger 41 and the second heat exchanger 42, and upstream valves 611 to 613 and downstream valves 621 to 623 all provided in the heat medium circuit 20. The switching unit 6 switches the respective flows of the high-temperature medium and the low-temperature medium by these valves 60, 611 to 613, 621 to 623. The valves 60, 611 to 613, 621 to 623 are all solenoid valves, and are opened and closed by a control command issued from the control device 7.

[0045] The above-described intermediate valve 60, upstream valve 611, and upstream valve 612 are all three-way valves, and the upstream valve 613 is a four-way valve. The downstream valves 621 and 622 are both three-way valves, and the downstream valve 623 is a four-way valve. Depending on the operation mode, the ports of each valve are selectively opened and closed, and the heat medium flows through the heat medium circuit 20 according to the flow path set inside the valve.

[0046] The upstream valves 611 to 613 are located upstream in the heat medium circuit 20 with reference to the heat absorption heat exchanger 12 and the heat dissipation heat exchanger 14. The downstream valves 621 to 623 are located downstream in the heat medium circuit 20 with reference to the heat absorption heat exchanger 12 and the heat dissipation heat exchanger 14. Depending on the operation mode, by controlling the opening / closing states of the intermediate valve 60, the respective opening / closing states of the upstream valves 611 to 613, and the respective opening / closing states of the downstream valves 621 to 623, the supply destination of the heat medium is switched.

[0047] For example, in the cooling mode shown in FIG. 1, heat is dissipated to the refrigerant in the heat dissipation heat exchanger 14, and the low-temperature medium (shown by the solid line) flowing out from the heat dissipation heat exchanger 14 to the pipe 801 flows sequentially through the pipes 802 and 803 according to the opening / closing states of the respective ports of the downstream valves 621 and 623 and is supplied to the in-vehicle heat exchanger 30. The low-temperature medium flowing out from the in-vehicle heat exchanger 30 to the pipe 804 flows sequentially through the pipes 805 and 806 according to the opening / closing states of the upstream valves 613 and 611 and returns to the heat dissipation heat exchanger 14.

[0048] On the other hand, the high-temperature medium (shown by the dashed-dotted line) that absorbs heat from the refrigerant in the heat absorption heat exchanger 12 flows out from the heat absorption heat exchanger 12 to the pipe 821, sequentially flows through the downstream valve 622, the pipe 822, and the pipe 823, and is supplied to the second heat exchanger 42 and the first heat exchanger 41. By the heat exchange between the high-temperature medium and the outside air by the second heat exchanger 42 and the first heat exchanger 41, the exhaust heat of the vehicle air conditioning system 1 can be released to the outside air. The high-temperature medium flowing out from the first heat exchanger 41 to the pipe 824 flows sequentially through the pipes 825 and 826 according to the opening / closing states of the upstream valves 611 and 612 and returns to the heat absorption heat exchanger 12.

[0049] In the heating mode shown in FIG. 2, the heat absorption heat exchanger 12 absorbs heat from the refrigerant, and the high-temperature medium flowing out from the heat absorption heat exchanger 12 to the pipe 811 sequentially flows through the pipes 807 and 803 according to the opening and closing states of the ports of the downstream valve 622 and the downstream valve 623, and is supplied to the in-vehicle heat exchanger 30. The high-temperature medium flowing out from the in-vehicle heat exchanger 30 to the pipe 804 sequentially flows through the pipes 808 and 826 according to the opening and closing states of the upstream valves 613 and 612 and returns to the heat absorption heat exchanger 12.

[0050] On the other hand, the low-temperature medium that dissipates heat to the refrigerant in the heat dissipation heat exchanger 14 flows out from the heat dissipation heat exchanger 14 to the pipe 801, sequentially flows through the downstream valve 621 and the pipe 823, and is supplied to the second heat exchanger 42 and the first heat exchanger 41. By the heat exchange between the low-temperature medium and the outside air in the second heat exchanger 42 and the first heat exchanger 41, heat can be absorbed from the outside air into the heat medium. The high-temperature medium flowing out from the first heat exchanger 41 to the pipe 824 flows through the pipe 826 based on the opening and closing states of the upstream valves 611 and 612 and returns to the heat dissipation heat exchanger 14.

[0051] FIG. 3 shows the first defrosting process P1 in the defrosting mode. The defrosting target during the first defrosting process P1 is the first heat exchanger 41. FIG. 4 shows the second defrosting process P2 in the defrosting mode. The defrosting target during the second defrosting process P2 is the second heat exchanger 42. In the defrosting mode, the first heat exchanger 41 and the second heat exchanger 42 are connected in parallel with respect to the flow of the heat medium, and by switching the opening and closing states of the respective ports of the upstream valve 613 and the downstream valve 622, the high-temperature medium is supplied to the in-vehicle heat exchanger 30 and the heat exchangers 41 and 42 outside the vehicle. In addition, by switching the opening and closing states of the respective ports of the upstream valve 613 and the downstream valve 623, either one of the first heat exchanger 41 and the second heat exchanger 42 is selected as the defrosting target.

[0052] As shown in FIG. 3, during the first defrosting process P1, the high-temperature medium flowing out of the heat exchanger 12 for heat absorption is supplied to the first heat exchanger 41 to be defrosted through the downstream valve 622 and the downstream valve 623. At this time, the low-temperature medium flowing out of the heat exchanger 14 for heat dissipation is supplied to the second heat exchanger 42 through the downstream valve 621 and the downstream valve 623. During the first defrosting process P1, since the first heat exchanger 41 supplied with the high-temperature medium cannot absorb heat from the outside air, only the second heat exchanger 42 absorbs heat from the outside air into the low-temperature medium.

[0053] As shown in FIG. 4, during the second defrosting process P2, the high-temperature medium flowing out of the heat exchanger 12 for heat absorption is supplied to the second heat exchanger 42 through the downstream valve 622 and the downstream valve 623. At this time, the low-temperature medium flowing out of the heat exchanger 14 for heat dissipation is supplied to the first heat exchanger 41 through the downstream valve 621 and the downstream valve 623. During the second defrosting process P2, only the first heat exchanger 41 absorbs heat from the outside air into the low-temperature medium.

[0054] The number and arrangement of the valves forming the switching unit 6 in the present embodiment, and the setting of the respective paths of the low-temperature medium and the high-temperature medium in each operation mode accordingly are merely examples. In order to realize the respective flows of the low-temperature medium and the high-temperature medium in each operation mode provided in the vehicle air-conditioning system 1, a switching unit with an appropriate configuration can be adopted.

[0055] (Control device) The control device 7 controls at least the operation of the switching unit 6 in the air-conditioning system 1. FIG. 5(a) shows, as a part of the control modules provided in the control device 7, a mode selection unit 71 for selecting an operation mode, a switching operation control unit 72 for controlling the operation of the switching unit 6, a defrosting necessity determination unit 73 and a defrosting target selection unit 74 related to the defrosting operation. Each control module is included in a computer program executed by a computer or an embedded program executed by an electronic circuit.

[0056] The mode selection unit 71 selects one operation mode from a plurality of operation modes such as a cooling mode, a heating mode, and a defrosting mode, either by a user operation or by the control of the control device 7. The switching operation control unit 72 sends control commands to the valves 60, 611 to 613, 621 to 623 of the switching unit 6 according to the operation mode selected by the mode selection unit 71, thereby switching the flows of the high-temperature medium and the low-temperature medium in the heat medium circuit 20.

[0057] The defrost necessity determination unit 73 determines the necessity of defrosting the first heat exchanger 41 based on the detection result (temperature) by the first temperature detection unit 51. When starting the first defrosting process P1 for defrosting the first heat exchanger 41, for example, if the detected temperature by the first temperature detection unit 51 is lower than a predetermined first start threshold value T s1 it is determined that defrosting is required, and if the detected temperature is higher than the first start threshold value T s1 it is determined that defrosting is not required. The same applies to the second heat exchanger 42. When starting the second defrosting process P2 for defrosting the second heat exchanger 42, the defrost necessity determination unit 73 determines that defrosting is required if the detected temperature by the second temperature detection unit 52 is lower than a predetermined second start threshold value T s2 and determines that defrosting is not required if the detected temperature is higher than the second start threshold value T s2 For the second heat exchanger 42, the defrost necessity determination unit 73 determines that defrosting is required if the detected temperature by the second temperature detection unit 52 is lower than a predetermined second start threshold value T Considering the degree of blockage of the air passage of the first heat exchanger 41, an appropriate value can be set for the first start threshold value T s1 Similarly, considering the degree of blockage of the air passage of the second heat exchanger 42, an appropriate value can be set for the second start threshold value T s2 For the first start threshold value T s1 and the second start threshold value T s2 they may be the same or different.

[0058] Also, after starting the first defrosting process P1, the defrost necessity determination unit 73 determines that defrosting is required and continues the first defrosting process P1 if, for example, the detected temperature by the first temperature detection unit 51 is lower than a predetermined first end threshold value T s1 higher than the first start threshold value T. If the detected temperature by the first temperature detection unit 51 is lower than a predetermined first end threshold value T f1 For the first end threshold value T f1If the detected temperature is high for , it is determined that defrosting is not required, and the first defrosting process P1 is terminated. The same applies to the second heat exchanger 42. After the start of the second defrosting process P2, the defrosting necessity determination unit 73, for example, a predetermined second end threshold value T higher than the second start threshold value T s2 If the detected temperature by the second temperature detection unit 52 is lower than f2 it is determined that defrosting is required, and the second defrosting process P2 is continued. If the detected temperature is high for the second end threshold value T f2 it is determined that defrosting is not required, and the second defrosting process P2 is terminated.

[0059] The defrosting target selection unit 74 selects a defrosting target based on the necessity of defrosting by the defrosting necessity determination unit 73 while giving priority to the upstream first heat exchanger 41. FIG. 5(b) shows the logic used for selecting a defrosting target by the defrosting target selection unit 74. Based on the necessity of defrosting based on the detection result by the first temperature detection unit 51 and the detection result by the second temperature detection unit 52, there can be four cases A1 to A4 shown in FIG. 5(b).

[0060] Case A1: When only the first heat exchanger 41 is determined to require defrosting, the first heat exchanger 41 is selected as the defrosting target. Case A2: When only the second heat exchanger 42 is determined to require defrosting, the second heat exchanger 42 is selected as the defrosting target. Case A3: When both the first heat exchanger 41 and the second heat exchanger 42 are determined to require defrosting, the first heat exchanger 41 located upstream is preferentially selected as the defrosting target over the second heat exchanger 42 located downstream. Case A4: When both the first heat exchanger 41 and the second heat exchanger 42 are determined not to require defrosting, neither the first heat exchanger 41 nor the second heat exchanger 42 is selected as the defrosting target. (There is no applicable defrosting target)

[0061] (Processing in the defrosting mode) Referring to FIG. 6, as an example of the processing procedure, the flow of the processing in the defrosting mode M1 will be described. The processing in the defrosting mode M1 is shown surrounded by a dashed line. On the left side in FIG. 6, the processing related to the upstream heat exchanger 41 is shown surrounded by a one-dot chain line. On the right side in FIG. 6, the processing related to the downstream heat exchanger 42 is shown surrounded by a one-dot chain line. Note that the processing related to the second heat exchanger 42 includes the determination of whether defrosting of the first heat exchanger 41 is necessary (steps S22, S25).

[0062] During the endothermic operation (step S00) of causing at least one of the first heat exchanger 41 and the second heat exchanger 42 to perform an endothermic operation, the determination of whether defrosting of the first heat exchanger 41 is necessary (steps S11, S22) based on the detection result of the frost formation degree by the first temperature detection unit 51 and the determination of whether defrosting of the second heat exchanger 42 is necessary (step S21) based on the detection result of the frost formation degree by the second temperature detection unit 52 are performed in parallel. If it is determined that neither the first heat exchanger 41 nor the second heat exchanger 42 requires defrosting (No in step S11 and No in step S21), there is no defrosting target, and the endothermic operation (S00) is continued. This corresponds to case A4 in FIG. 5(b).

[0063] During the endothermic operation (step S00), if it is determined from the detection result of the frost formation degree that the first heat exchanger 41 requires defrosting (Yes in step S11), the defrosting mode M1 is implemented, and the first heat exchanger 41 is selected as the defrosting target (case A1) by switching the opening and closing states of valves 613, 623, etc., and the first defrosting process P1 is started (step S12). Note that even during the implementation of the first defrosting process P1, the heating in the passenger compartment 2 is continued by supplying a high-temperature medium to the in-vehicle heat exchanger 30. The same applies during the second defrosting process P2.

[0064] The first defrosting process P1 is continuously performed until it is determined from the detection result of the frost formation degree that the first heat exchanger 41 does not require defrosting (Yes in step S14).

[0065] When the first defrosting process P1 starts and the high-temperature medium flows into the first heat exchanger 41 according to the opening and closing states of the respective ports of the downstream valves 622, 623 and the upstream valves 613, 612, the frost adhering to the first heat exchanger 41 melts due to the heat of the high-temperature medium, and thus the defrosting proceeds (step S13). As a result, if it is determined that the first heat exchanger 41 does not require defrosting (Yes in step S14), the opening and closing states of the valves 613, 623, etc. are switched to end the first defrosting process P1 (step S15).

[0066] On the other hand, during the endothermic operation (step S00), if it is determined from the detection result of the frosting degree that the second heat exchanger 42 requires defrosting (Yes in step S21), only when it is determined from the frosting degree of the first heat exchanger 41 that the first heat exchanger 41 does not require defrosting (Yes in step S22), the defrosting mode M1 is entered, and the second heat exchanger 42 is selected as the defrosting target by switching the opening and closing states of the valves 613, 623, etc. (case A2), and the second defrosting process P2 is started (step S23). Even if it is determined that the second heat exchanger 42 requires defrosting, if it is determined that the first heat exchanger 41 requires defrosting (No in step S22), the defrosting process P2 of the second heat exchanger 42 is not performed. At this time, based on the fact that the first heat exchanger 41 requires defrosting (Yes in step S11), the first defrosting process P1 is started or has already been performed. That is, in case A3 where it is determined that both the first heat exchanger 41 and the second heat exchanger 42 require defrosting, the first heat exchanger 41 upwind is preferentially selected as the defrosting target (step S12).

[0067] The second defrosting process P2 continues until it is determined that the second heat exchanger 42 does not require defrosting as a result of the progress of the melting of the frost on the second heat exchanger 42, or until it is determined that the first heat exchanger 41 requires defrosting due to the progress of frosting on the first heat exchanger 41 during the implementation of the second defrosting process P2 (Yes in step S25). If it is determined in step S25 that the first heat exchanger 41 requires defrosting, since both the first heat exchanger 41 and the second heat exchanger 42 require defrosting (case A3), similar to step S22, the defrosting process P1 of the first heat exchanger 41 is prioritized.

[0068] During the implementation of the second defrosting process P2, heat is absorbed from the outside air to the low-temperature medium only by the upwind first heat exchanger 41. Therefore, since the heat exchange amount between the outside air and the low-temperature medium decreases compared to the case where heat is absorbed from the outside air to the low-temperature medium by the two heat exchangers 41 and 42, the temperature of the low-temperature medium flowing through the first heat exchanger 41 decreases and frosting of the first heat exchanger 41 tends to progress. If it comes to the determination that the first heat exchanger 41 requires defrosting, since the flow rate of the air flowing through the second heat exchanger 42 has decreased, sufficient heat exchange in the second heat exchanger 42 cannot be expected regardless of the degree of frosting of the second heat exchanger 42. Therefore, even if the defrosting of the second heat exchanger 42 has not yet ended (the second heat exchanger 42 requires defrosting), the opening / closing states of valves 613, 623, etc. are switched to end the second defrosting process P2 (step S26), and the process proceeds to the first defrosting process P1 (step S12).

[0069] When ending the defrosting of the first heat exchanger 41 (step S15), if it is determined that the second heat exchanger 42 requires defrosting (Yes in step S21), at that time, since the first heat exchanger 41 is determined not to require defrosting (Yes in step S22), the process shifts from the first defrosting process P1 to the second defrosting process P2. After that, if the second defrosting process P2 ends (Yes in step S26), it is possible to return from the defrosting mode M1 to the heating mode. In the heating mode, heat is absorbed from the outside air to the low-temperature medium flowing through the two serially connected heat exchangers 41 and 42, so heating operation at maximum capacity becomes possible.

[0070] (Main operational effects of this embodiment) According to the vehicle air conditioning system 1 of the present embodiment and the vehicle air conditioning method using the system, while determining whether defrosting is required for each of the first heat exchanger 41 and the second heat exchanger 42 based on the degree of frosting, the first heat exchanger 41 and the second heat exchanger 42 are alternately selected as the defrosting target, and the first heat exchanger 41 upwind is given priority over the second heat exchanger 42 downwind. Then, when the flow rate of the air flowing through the second heat exchanger 42 decreases due to an increase in air resistance caused by frosting on the first heat exchanger 41 upwind, the high-temperature medium is supplied to the first heat exchanger 41 prior to being supplied to the second heat exchanger 42 downwind. Thus, the frost on the first heat exchanger 41 is melted to recover the heat exchange amount by the first heat exchanger 41, and the air passage of the first heat exchanger 41 necessary for recovering the heat exchange amount of the second heat exchanger 42 can be ensured.

[0071] According to the fact that the defrosting process P1 of the first heat exchanger 41 is performed prior to the defrosting process P2 of the second heat exchanger 42, the high-temperature medium distributed between the inside and outside of the vehicle is effectively used to recover the heat exchange amount of each of the first heat exchanger 41 and the second heat exchanger 42. And by performing the first defrosting process P1 based on the determination of whether defrosting is required for the first heat exchanger 41 (steps S11, S22, S25), the degree of frosting on the first heat exchanger 41 upwind is maintained so that the air volume is not excessively reduced during the implementation of the defrosting mode M1. Therefore, according to the present embodiment, not only in the heating mode but also in the defrosting mode M1, at least a certain amount of heating capacity can be ensured by the first heat exchanger 41. Moreover, by timely supplying the high-temperature medium to the appropriate location, as a whole of the first heat exchanger 41 and the second heat exchanger 42, the defrosting mode M1 can be terminated early and the heating mode can be restored.

[0072] Further, according to the vehicle air conditioning system 1 of the present embodiment and the vehicle air conditioning method using the system, by switching the connection between the first heat exchanger 41 and the second heat exchanger 42 in series or in parallel by the switching unit 6 to set the paths of the high-temperature medium and the low-temperature medium respectively, various operation modes including the cooling / heating mode in which the first and second heat exchangers 41, 42 are connected in series and the defrosting mode in which the first and second heat exchangers 41, 42 are connected in parallel can be realized with a simple structure and control at low cost.

[0073] (Modification example) In addition to the above, it is possible to select and combine the configurations described in the above embodiment, or to appropriately modify them to other configurations.

[0074] By appropriately setting the paths of the high-temperature medium and the low-temperature medium according to the opening and closing states of the respective valves as the switching unit 6, various operation modes can be realized not limited to the above embodiment. The vehicle air conditioning system 1 may, for example, be provided with a freeze cleaning mode in which after frosting the inside vehicle heat exchanger 30 by supplying a low-temperature medium to the inside vehicle heat exchanger 30, the frost is melted by supplying a high-temperature medium to the inside vehicle heat exchanger 30 to clean the surface of the inside vehicle heat exchanger 30.

[0075] In the cooling mode or the heating mode, connecting the first heat exchanger 41 and the second heat exchanger 42 in parallel with respect to the flow of the heat medium, or operating by connecting only one of the first and second heat exchangers 41, 42 to the heat medium circuit is not excluded.

[0076] The vehicle air conditioning system of the present disclosure may include three or more outdoor heat exchangers. For example, in addition to the above-described first heat exchanger 41 and second heat exchanger 42, when a third heat exchanger arranged in series with respect to the air flow by the blower is provided together with these first heat exchanger 41 and second heat exchanger 42, the detection unit 5 detects the degree of frosting of each of the first to third heat exchangers and determines whether defrosting is required for each of the first to third heat exchangers. Then, in the same manner as in the above embodiment, while alternately selecting, as a defrosting target, those determined to require defrosting from the first to third heat exchangers connected in parallel with respect to the flow of the heat medium, when two or more of the first to third heat exchangers are determined to require defrosting, defrosting of the heat exchanger located relatively upstream in the wind direction among the heat exchangers determined to require defrosting is preferentially performed. Here, with respect to the third heat exchanger, when starting the defrosting process, in addition to determining whether defrosting is required for the third heat exchanger, it is also determined whether defrosting is required for the first heat exchanger 41 and whether defrosting is required for the second heat exchanger 42. Further, after the start of the defrosting process of the third heat exchanger, if the first heat exchanger 41 or the second heat exchanger 42 is determined to require defrosting, the defrosting process of the third heat exchanger is terminated.

[0077] As the detection unit 5 for detecting the degree of frosting of each of the first heat exchanger 41 and the second heat exchanger 42, in addition to the temperature detection units 51 and 52, for example, a camera that images the exteriors of the first heat exchanger 41 and the second heat exchanger 42 can also be used. For example, image data indicating the degree of frosting of each of the first heat exchanger 41 and the second heat exchanger 42 can be acquired by one camera. The defrosting necessity determination unit 73 can determine whether defrosting is required for each of the first heat exchanger 41 and the second heat exchanger 42 by image processing of the image data.

[0078] 〔Supplementary Note〕 The vehicle air conditioning system and the vehicle air conditioning method described above are understood as follows. 〔1〕The vehicle air conditioning system 1 includes a refrigerant circuit 10 in which a refrigerant circulates according to a refrigeration cycle, a high-temperature medium circuit 22 in which a heat medium that absorbs heat from the refrigerant in the refrigerant circuit 10 circulates, and a low-temperature medium circuit 21 in which a heat medium that dissipates heat to the refrigerant in the refrigerant circuit 10 circulates, a heat medium circuit 20, an in-vehicle heat exchanger 30 that exchanges heat between the heat medium and air, an outside-vehicle heat exchanger that exchanges heat between the heat medium and air, a first heat exchanger 41 and a second heat exchanger 42 that are arranged in series with respect to the air flow by a blower 43, a switching unit 6 configured to be able to switch the flow of the heat medium, a detection unit 5 for detecting the degree of frosting of each of the first heat exchanger 41 and the second heat exchanger 42, and a control device 7 that controls the operation of the switching unit 6 according to the operation mode of the air conditioning system 1. The operation mode includes a defrosting mode M1 in which the heat medium of the high-temperature medium circuit 22 is supplied to a defrosting target that is selectively selected from among the first heat exchanger 41 and the second heat exchanger 42 that are connected in parallel in the heat medium circuit 20 by the operation of the switching unit 6. When selecting a defrosting target by the operation of the switching unit 6, the control device 7 selects the first heat exchanger 41 as the defrosting target when it is determined that only the first heat exchanger 41 needs defrosting based on the detection result of the degree of frosting by the detection unit 5, selects the second heat exchanger 42 as the defrosting target when it is determined that only the second heat exchanger 42 needs defrosting, and when it is determined that both the first heat exchanger 41 and the second heat exchanger 42 need defrosting, preferentially selects the first heat exchanger 41 located upwind over the second heat exchanger 42 located downwind as the defrosting target. 〔2〕The control device 7 includes a defrost necessity determination unit 73 that determines the necessity of defrosting for each of the first heat exchanger 41 and the second heat exchanger 42 from the detection results, and a defrost target selection unit 74 that selects a defrost target based on the necessity of defrosting determined by the defrost necessity determination unit 73 while prioritizing the first heat exchanger 41 on the windward side. If the first heat exchanger 41 is determined to require defrosting, the defrost target selection unit 74 starts the first defrosting process P1 that supplies the heat medium of the high-temperature medium circuit 22 to the first heat exchanger 41 as the defrost target. After the start of the first defrosting process P1, as the first heat exchanger 41 is determined not to require defrosting, the first defrosting process P1 is terminated. If the second heat exchanger 42 is determined to require defrosting and the first heat exchanger 41 is determined not to require defrosting, the second defrosting process P2 that supplies the heat medium of the high-temperature medium circuit 22 to the second heat exchanger 42 as the defrost target is started. After the start of the second defrosting process P2, if the first heat exchanger 41 is determined to require defrosting, or if the second heat exchanger 42 is determined not to require defrosting, the second defrosting process P2 is terminated. 〔3〕The vehicle air conditioning system 1 includes, as the detection unit 5, a first temperature detection unit 51 capable of detecting temperature information indicating a temperature drop of the heat medium due to frosting on the first heat exchanger 41, and a second temperature detection unit 52 capable of detecting temperature information indicating a temperature drop of the heat medium due to frosting on the second heat exchanger 42. 〔4〕The operation mode includes a heating mode in which the heat medium of the low-temperature medium circuit 21 is supplied to the first heat exchanger 41 and the second heat exchanger 42 connected in series by the operation of the switching unit 6. In the heating mode, the heat medium flows from the leeward side to the windward side through the second heat exchanger 42 and the first heat exchanger 41. 〔5〕The switching unit 6 includes a three-way valve located between the first heat exchanger 41 and the second heat exchanger 42. 〔6〕In an air conditioning method using an air conditioning system 1 for a vehicle, the air conditioning system 1 includes a refrigerant circuit 10 in which a refrigerant circulates according to a refrigeration cycle, a high-temperature medium circuit 22 in which a heat medium that absorbs heat from the refrigerant circulates, and a low-temperature medium circuit 21 in which a heat medium that releases heat to the refrigerant circulates, a heat medium circuit 20, an in-vehicle heat exchanger 30 that exchanges heat between the heat medium and air, and an out-vehicle heat exchanger that exchanges heat between the heat medium and air, and includes a first heat exchanger 41 and a second heat exchanger 42 that are arranged in series with respect to the air flow by a blower 43, and a switching unit 6 configured to be able to switch the flow of the heat medium. In the air conditioning method of the present disclosure, when supplying the heat medium of the high-temperature medium circuit 22 to a defrosting target that is selectively selected from among the first heat exchanger 41 and the second heat exchanger 42 connected in parallel by the operation of the switching unit 6, based on the detection results of the frosting degrees of the first heat exchanger 41 located upwind and the second heat exchanger 42 located downwind, when it is determined that only the first heat exchanger 41 requires defrosting, the first heat exchanger 41 is selected as the defrosting target, when it is determined that only the second heat exchanger 42 requires defrosting, the second heat exchanger 42 is selected as the defrosting target, and when it is determined that both the first heat exchanger 41 and the second heat exchanger 42 require defrosting, the first heat exchanger 41 is preferentially selected as the defrosting target over the second heat exchanger 42. 〔7〕When performing defrosting of each of the first heat exchanger 41 and the second heat exchanger 42 while selecting a defrosting target based on whether defrosting is required determined from the detection results while giving priority to the first heat exchanger 41, if it is determined that the first heat exchanger 41 requires defrosting, a first defrosting process P1 for supplying the heat medium of the high-temperature medium circuit 22 to the first heat exchanger 41 as the defrosting target is started, and after the start of the first defrosting process P1, as it is determined that the first heat exchanger 41 does not require defrosting, the first defrosting process P1 is terminated, and if it is determined that the second heat exchanger 42 requires defrosting and the first heat exchanger 41 does not require defrosting, a second defrosting process P2 for supplying the heat medium of the high-temperature medium circuit 22 to the second heat exchanger 42 as the defrosting target is started, and after the start of the second defrosting process P2, if it is determined that the first heat exchanger 41 requires defrosting, or if it is determined that the second heat exchanger 42 does not require defrosting, the second defrosting process P2 is terminated.

Description of Signs

[0079] 1 Vehicle air conditioning system 2 Passenger compartment 3 HVAC unit 5 Detection unit 6 Switching unit 7 Control device 10 Refrigerant circuit 11 Compressor 12 Heat exchanger for heat absorption 13 Expansion valve 14 Heat exchanger for heat dissipation 20 Heat medium circuit 21 Low-temperature medium circuit 21P Pump 22 High-temperature medium circuit 22P Pump 30 Interior heat exchanger 33 Blower 41 First heat exchanger 42 Second heat exchanger 43 Blower (fan) 51 First temperature detection unit 52 Second temperature detection unit 60 Intermediate valve 71 Mode selection unit 72 Switching operation control unit 73 Defrost necessity determination unit 74 Defrost target selection unit 611~613 Upstream valve 621~623 Downstream valve 801~811 Pipe 821~826 Pipe M1 Defrost mode P1 First defrosting process P2 Second defrosting process S00,S11~S15,S21~S26 Steps T s1 First start threshold value T f1 First end threshold value T s2 Second start threshold value T f2 Second end threshold value

Claims

1. An air conditioning system for a vehicle, comprising: a refrigerant circuit in which a refrigerant circulates according to a refrigeration cycle; a heat medium circuit including a high-temperature heat medium circuit in which a heat medium that absorbs heat from the refrigerant in the refrigerant circuit circulates, and a low-temperature heat medium circuit in which a heat medium that dissipates heat to the refrigerant in the refrigerant circuit circulates; an in-vehicle heat exchanger that exchanges heat between the heat medium and air; an out-vehicle heat exchanger that exchanges heat between the heat medium and air, the out-vehicle heat exchanger including a first heat exchanger and a second heat exchanger arranged in series with respect to an air flow by a blower; a switching unit configured to be able to switch the flow of the heat medium; a detection unit for detecting the degree of frosting of each of the first heat exchanger and the second heat exchanger; a control device that controls the operation of the switching unit according to an operation mode of the air conditioning system, wherein the operation mode includes a defrosting mode in which the heat medium in the high-temperature heat medium circuit is supplied to a defrosting target selectively selected from the first heat exchanger and the second heat exchanger connected in parallel in the heat medium circuit by the operation of the switching unit; when selecting the defrosting target by the operation of the switching unit, the control device selects the first heat exchanger as the defrosting target when it is determined that only the first heat exchanger needs defrosting based on the detection result of the degree of frosting by the detection unit; selects the second heat exchanger as the defrosting target when it is determined that only the second heat exchanger needs defrosting; selects the first heat exchanger located upwind preferentially as the defrosting target rather than the second heat exchanger located downwind when it is determined that both the first heat exchanger and the second heat exchanger need defrosting. An air conditioning system for a vehicle.

2. The control device includes a defrosting necessity determination unit that determines the necessity of defrosting for each of the first heat exchanger and the second heat exchanger from the detection result; and a defrosting target selection unit that selects the defrosting target based on the necessity of defrosting determined by the defrosting necessity determination unit while giving priority to the first heat exchanger upwind. The defrosting target selection unit starts a first defrosting process of supplying the heat medium in the high-temperature heat medium circuit to the first heat exchanger as the defrosting target when it is determined that the first heat exchanger needs defrosting; ends the first defrosting process when it is determined that the first heat exchanger does not need defrosting after the start of the first defrosting process. ​ When it is determined that the second heat exchanger requires defrosting and the first heat exchanger is determined not to require defrosting, a second defrosting process is started to supply the heat medium of the high-temperature medium circuit to the second heat exchanger as the defrosting target. After the start of the second defrosting process, if it is determined that the first heat exchanger requires defrosting or the second heat exchanger is determined not to require defrosting, the second defrosting process is terminated. The vehicle air conditioning system according to claim 1.

3. As the detection unit, A first temperature detection unit capable of detecting temperature information indicating a temperature drop of the heat medium due to frosting on the first heat exchanger, A second temperature detection unit capable of detecting temperature information indicating a temperature drop of the heat medium due to frosting on the second heat exchanger, and comprising: The vehicle air conditioning system according to claim 1 or 2.

4. The operation mode includes a heating mode in which the heat medium of the low-temperature medium circuit is supplied to the first heat exchanger and the second heat exchanger connected in series by the operation of the switching unit. In the heating mode, the heat medium flows from the second heat exchanger and the first heat exchanger from downwind to upwind. The vehicle air conditioning system according to any one of claims 1 to 3.

5. The switching unit, Includes a three-way valve located between the first heat exchanger and the second heat exchanger. The vehicle air conditioning system according to any one of claims 1 to 4.

6. An air conditioning method using a vehicle air conditioning system, The air conditioning system, A refrigerant circuit in which a refrigerant circulates according to a refrigeration cycle, a high-temperature medium circuit in which a heat medium that absorbs heat from the refrigerant circulates, and a heat medium circuit including a low-temperature medium circuit in which a heat medium that radiates heat to the refrigerant circulates, an in-vehicle heat exchanger that exchanges heat between the heat medium and air, and an outside-vehicle heat exchanger that exchanges heat between the heat medium and air, the first heat exchanger and the second heat exchanger being arranged in series with respect to the flow of air by a blower, and a switching unit configured to be able to switch the flow of the heat medium. The air conditioning method, When supplying the heat medium of the high-temperature medium circuit to an alternately selected defrosting target among the first heat exchanger and the second heat exchanger connected in parallel by the operation of the switching unit, Based on the detection results of the degree of frosting of each of the first heat exchanger located upwind and the second heat exchanger located downwind, When it is determined that only the first heat exchanger requires defrosting, the first heat exchanger is selected as the defrosting target. When it is determined that only the second heat exchanger requires defrosting, the second heat exchanger is selected as the defrosting target, When it is determined that both the first heat exchanger and the second heat exchanger require defrosting, the first heat exchanger is preferentially selected as the defrosting target over the second heat exchanger. Vehicle air conditioning method.

7. When performing defrosting of each of the first heat exchanger and the second heat exchanger while selecting the defrosting target based on the necessity of defrosting determined from the detection result while giving priority to the first heat exchanger, If it is determined that the first heat exchanger requires defrosting, a first defrosting process for supplying the heat medium of the high-temperature medium circuit to the first heat exchanger as the defrosting target is started. After the start of the first defrosting process, as it is determined that the first heat exchanger does not require defrosting, the first defrosting process is terminated. If it is determined that the second heat exchanger requires defrosting and the first heat exchanger does not require defrosting, a second defrosting process for supplying the heat medium of the high-temperature medium circuit to the second heat exchanger as the defrosting target is started. After the start of the second defrosting process, if it is determined that the first heat exchanger requires defrosting or the second heat exchanger does not require defrosting, the second defrosting process is terminated. The vehicle air conditioning method according to claim 6.

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