Air conditioner for vehicle

Abstract

To provide an air conditioner for a vehicle capable of solving a problem caused by shortage of a circulation amount of a refrigerant.SOLUTION: The refrigerant circuit 10 includes the bypass path that bypasses the high-temperature side heat exchanger 12 and joins the path on the downstream side of the path through which the refrigerant flows to the first low-temperature side heat exchanger 14 and the path through which the refrigerant flows to the second low-temperature side heat exchanger 16. A hot gas operation in which a part of the refrigerant discharged from the compressor 11 flows through the bypass path and the remaining refrigerant that does not flow through the bypass path flows through one of the first evaporator and the second evaporator, and a switching mode in which the refrigerant also flows through the other of the first low-temperature heat exchanger 14 and the second low-temperature heat exchanger 16 during the hot gas operation can be performed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an air conditioning system for a vehicle. [Background technology]

[0002] A vehicle air conditioner includes a refrigerant circuit, and various techniques have been proposed for the configuration of the refrigerant circuit. For example, Patent Document 1 discloses a refrigerant circuit including a first evaporator and a second evaporator. Patent Document 2 discloses a refrigerant circuit including a bypass path. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2023 / 0173887 [Patent Document 2] Japanese Patent Application Laid-Open No. 2024-062465 Summary of the Invention [Problem to be solved by the invention]

[0004] SUMMARY OF THE INVENTION An object of the present invention is to provide a vehicle air conditioner that can eliminate problems caused by an insufficient amount of refrigerant circulating. [Means for solving the problem]

[0005] According to one aspect of the present invention, a vehicle air conditioning system is provided with a refrigerant circuit having a compressor, a condenser that heats a heat medium, a first evaporator that cools the heat medium, and a second evaporator that is arranged in parallel with the first evaporator and cools the heat medium, and the refrigerant circuit has a bypass path that bypasses the condenser and joins a path downstream of the path through which refrigerant flows to the first evaporator and the path through which refrigerant flows to the second evaporator, and is capable of performing a hot gas operation in which a portion of the refrigerant discharged from the compressor flows to the bypass path and the remaining refrigerant that does not flow to the bypass path flows to either the first evaporator or the second evaporator, and a switching mode in which refrigerant also flows to the other of the first evaporator or the second evaporator while the hot gas operation is being performed. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a vehicle air conditioner that can eliminate problems caused by an insufficient amount of refrigerant circulating. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a circuit diagram showing an example of the configuration of a refrigerant circuit provided in a vehicle air conditioner. [Figure 2] FIG. 2 is an explanatory diagram showing a change in pressure of the refrigerant drawn into the compressor when the switching mode is executed. [Figure 3] FIG. 3 is an explanatory diagram showing a change in pressure of the refrigerant drawn into the compressor when the switching mode is executed. [Figure 4] FIG. 4 is an explanatory diagram showing a change in pressure of the refrigerant drawn into the compressor when the switching mode is executed. DETAILED DESCRIPTION OF THE INVENTION

[0008] [System Configuration] System Overview FIG. 1 is an explanatory diagram showing an outline of an example of the configuration of a vehicle air conditioner 1 according to this embodiment. The vehicle air conditioner 1 is mounted on a vehicle. The vehicle is preferably a vehicle equipped with a battery for driving. The vehicle may be, for example, an electric vehicle (BEV: Battery Electric Vehicle), a hybrid vehicle (HEV: Hybrid Electric Vehicle), a plug-in hybrid vehicle (PHEV: Plug-in Hybrid Electric Vehicle), or a fuel cell electric vehicle (FCEV: Fuel Cell Electric Vehicle).

[0009] The vehicle air conditioner 1 includes a refrigerant circuit 10 configured to circulate a refrigerant. The refrigerant may be, but is not limited to, a hydrofluoroolefin. The vehicle air conditioner 1 also includes a heat medium circuit (not shown) through which a heat medium fluid such as a coolant circulates, and a control device 200 that controls the operation of the refrigerant circuit 10 and the heat medium circuit.

[0010] <Refrigerant circuit> The refrigerant circuit 10 is configured to function as a heat pump that circulates a refrigerant and repeats compression, condensation, expansion, and evaporation.

[0011] The refrigerant circuit 10 includes a compressor 11, a high-temperature side heat exchanger 12 which is a condenser, pressure reducing devices 13a, 13b, and 13c, a first low-temperature side heat exchanger 14 which is a first evaporator, and a second low-temperature side heat exchanger 16 which is a second evaporator.

[0012] The compressor 11 compresses the gaseous refrigerant to a high temperature and pressure, and then discharges it.

[0013] The high-temperature side heat exchanger 12 includes a refrigerant passage 12a through which the refrigerant circulating in the refrigerant circuit 10 passes, and a heat medium passage 12b through which the heat medium pushed out by, for example, a circulation pump P20 installed in the heat medium circuit and passing through a heater core of the heat medium circuit passes. The high-temperature side heat exchanger 12 condenses the gaseous refrigerant compressed by the compressor 11 and releases heat, thereby heating the heat medium passing through the heater core. This allows the vehicle interior to be heated.

[0014] The pressure reducing devices 13a, 13b, and 13c are, for example, expansion valves, and expand the liquid refrigerant to reduce its pressure.

[0015] The first low-temperature side heat exchanger 14 includes a refrigerant passage 14a through which the refrigerant circulating in the refrigerant circuit 10 passes, and a heat medium passage 14b through which, for example, a heat medium passing through a cooler core passes. The first low-temperature side heat exchanger 14 evaporates the low-temperature, low-pressure liquid refrigerant to absorb heat, thereby cooling the heat medium passing through the cooler core. This allows the interior of the vehicle to be cooled.

[0016] The second low-temperature side heat exchanger 16 is disposed in parallel with the first low-temperature side heat exchanger 14. The second low-temperature side heat exchanger 16 includes a refrigerant passage 16a through which the refrigerant circulating in the refrigerant circuit 10 passes, and a heat medium passage 16b through which, for example, a heat medium passing through a battery temperature adjustment unit that adjusts the temperature of a battery passes. The second low-temperature side heat exchanger 16 cools the heat medium passing through the battery temperature adjustment unit by evaporating the low-temperature, low-pressure liquid refrigerant and absorbing heat. This allows the temperature of the battery to be adjusted.

[0017] The elements of the refrigerant circuit 10 are connected by refrigerant flow paths 10a, 10b, 10c, 10d, 10e, 10f, 10g, and 10h.

[0018] That is, the discharge side 11a of the compressor 11 is connected to the suction side 11b of the compressor 11 via a refrigerant flow path 10a connected thereto, a branch point a1, a refrigerant flow path 10b, a junction point b1, and a downstream refrigerant flow path 10c. A pressure reducing device 13a is installed on the path of the refrigerant flow path 10b. An accumulator 15 is installed on the path of the refrigerant flow path 10c.

[0019] The discharge side 11a of the compressor 11 is connected to the inlet of the refrigerant passage 12a of the high-temperature side heat exchanger 12 via a refrigerant passage 10d connected thereto. The outlet of the refrigerant passage 12a of the high-temperature side heat exchanger 12 is connected to the inlet of the refrigerant passage 14a of the first low-temperature side heat exchanger 14 via a refrigerant passage 10e connected thereto, a branch point a2, and a downstream refrigerant passage 10f. A pressure reducing device 13b is installed on the refrigerant passage 10f. That is, the pressure reducing device 13b is installed upstream of the first low-temperature side heat exchanger 14. The outlet of the refrigerant passage 14a of the first low-temperature side heat exchanger 14 is connected to the suction side 11b of the compressor 11 via a refrigerant passage 10i connected thereto, a junction b1, and a downstream refrigerant passage 10c.

[0020] The outlet of the refrigerant passage 12a of the high-temperature side heat exchanger 12 is connected to the inlet of the refrigerant passage 16a of the second low-temperature side heat exchanger 16 via the refrigerant passage 10e connected thereto, the branch point a2, and the downstream refrigerant passage 10h. A pressure reducing device 13c is installed on the refrigerant passage 10h. That is, the pressure reducing device 13c is installed upstream of the second low-temperature side heat exchanger 16. The outlet of the refrigerant passage 16a of the second low-temperature side heat exchanger 16 is connected to the suction side 11b of the compressor 11 via the refrigerant passage 10i connected thereto, the junction point b1, and the downstream refrigerant passage 10c. A check valve 18 is installed on the refrigerant passage 10i to prevent the refrigerant from flowing into the second low-temperature side heat exchanger 16. That is, the check valve 18 is installed upstream of the second low-temperature side heat exchanger 16.

[0021] By configuring the refrigerant flow path as described above, the refrigerant flow path 10b bypasses the high-temperature side heat exchanger 12 and functions as a bypass route that merges with the first low-temperature side heat exchanger 14 on the downstream side.

[0022] Furthermore, upstream of the suction side 11b of the compressor 11, there are provided a suction refrigerant pressure sensor 20a that detects the pressure of the refrigerant sucked by the compressor 11, and a suction refrigerant temperature sensor 20b that detects the temperature of the refrigerant sucked by the compressor 11. Furthermore, downstream of the discharge side 11a of the compressor 11, there are provided a discharge refrigerant pressure sensor 21a that detects the pressure of the refrigerant discharged from the compressor 11, and a discharge refrigerant temperature sensor 21b that detects the temperature of the refrigerant discharged from the compressor 11.

[0023] The control device 200 detects, for example, refrigerant stagnation in the first low-temperature side heat exchanger 14 or the second low-temperature side heat exchanger 16 based on detection information from various sensors. The control device 200 also detects the state of the refrigerant sucked into the compressor 11. In addition, the control device 200 controls the operation of the refrigerant circuit 10, such as by opening and closing the pressure reducing devices 13a, 13b, and 13c, by performing hot gas operation, or by performing a switching mode.

[0024] [System Operation] Next, a specific operation of the refrigerant circuit 10 included in the vehicle air conditioner 1 of this embodiment will be described.

[0025] <Hot gas heating operation> FIG. 1 shows the state of the refrigerant circuit 10 when hot gas heating is performed when the outside air temperature is extremely low (for example, −20° C. to −30° C.).

[0026] When hot gas heating operation is performed, pressure reduction device 13a is opened, and either pressure reduction device 13b or pressure reduction device 13c is opened while the other is fully closed. That is, when hot gas operation is performed, part of the refrigerant discharged from compressor 11 is made to flow through the bypass path, and the remaining refrigerant that does not flow through the bypass path is made to flow through either first low-temperature side heat exchanger 14 or second low-temperature side heat exchanger 16.

[0027] Specifically, the refrigerant discharged from the compressor 11 flows into the refrigerant flow paths 10a and 10d and passes through the refrigerant passage 12a of the high-temperature side heat exchanger 12. On the other hand, the heat medium that passes through the heater core in the heat medium circuit passes through the heat medium passage 12b. Then, the heat medium that absorbs heat in the high-temperature side heat exchanger 12 flows into the heater core, thereby heating the vehicle interior.

[0028] When pressure reducing device 13b is open and pressure reducing device 13c is fully closed, the refrigerant that has passed through refrigerant passage 12a of high-temperature side heat exchanger 12 flows into refrigerant flow paths 10e and 10f. As a result, the refrigerant that has been reduced to a low temperature and low pressure by pressure reducing device 13b passes through refrigerant passage 14a of first low-temperature side heat exchanger 14, passes through refrigerant flow paths 10g and 10c, and flows into suction side 11b of compressor 11. Thus, when pressure reducing device 13b is open and pressure reducing device 13c is fully closed, in hot gas heating operation, refrigerant flow paths 10a, 10d, 10e, 10f, 10g, and 10c form a circulation path in which the refrigerant discharged from compressor 11 passes through high-temperature side heat exchanger 12.

[0029] When pressure reducing device 13c is open and pressure reducing device 13b is fully closed, the refrigerant that has passed through refrigerant passage 12a of high-temperature side heat exchanger 12 flows into refrigerant flow paths 10e and 10h. As a result, the refrigerant that has been reduced to a low temperature and low pressure by pressure reducing device 13c passes through refrigerant passage 16a of second low-temperature side heat exchanger 16 and flows into suction side 11b of compressor 11 via refrigerant flow paths 10i and 10c. In this way, when pressure reducing device 13c is open and pressure reducing device 13b is fully closed, in hot gas heating operation, a circulation path is formed by refrigerant flow paths 10a, 10d, 10e, 10h, 10i, and 10c, in which the refrigerant discharged from compressor 11 passes through high-temperature side heat exchanger 12.

[0030] Furthermore, the refrigerant discharged from compressor 11 flows into refrigerant flow paths 10a, 10b, and 10c. As a result, the refrigerant that has been reduced to a low temperature and low pressure by pressure reducing device 13a flows into suction side 11b of compressor 11 without dissipating heat in high-temperature side heat exchanger 12. In this way, during hot gas heating operation, refrigerant flow paths 10a, 10b, and 10c form a circulation path in which the refrigerant discharged from compressor 11 bypasses high-temperature side heat exchanger 12.

[0031] The refrigerant flowing through the bypass path has a higher pressure when it returns to the suction side 11b of the compressor 11 than the refrigerant that passes through the high-temperature side heat exchanger 12. In hot gas heating operation, increasing the pressure of the refrigerant sucked into the compressor 11 makes it possible to increase the temperature of the refrigerant discharged from the compressor 11, thereby improving the heating capacity.

[0032] <Refrigerant accumulation during hot gas operation> As described above, in this embodiment, when hot gas operation is performed in a circuit in which the first low-temperature side heat exchanger 14 and the second low-temperature side heat exchanger 16 are connected in parallel, either one of the pressure reducing devices 13b and 13c is opened and the other is fully closed, so that refrigerant flows through either the first low-temperature side heat exchanger 14 or the second low-temperature side heat exchanger 16, but not through the other.

[0033] However, because high-pressure refrigerant circulates during hot gas operation, even if the pressure reducing device located upstream of the low-temperature heat exchanger, which does not allow refrigerant to flow, is fully closed, the pressure of the circulating refrigerant causes refrigerant to leak downstream of the pressure reducing device. Therefore, when hot gas operation is performed, refrigerant accumulates in the low-temperature heat exchanger, which does not allow refrigerant to flow, reducing the amount of refrigerant circulating in the refrigerant circuit 10. In particular, the longer hot gas operation is continued, the more significant the shortage of refrigerant circulating in the refrigerant circuit 10 becomes.

[0034] For example, in the refrigerant circuit 10, if the second low-temperature side heat exchanger 16 is not used as a flow path during hot gas operation, the difference in pressure between the upstream and downstream sides of the pressure reducing device 13c becomes large, causing refrigerant to leak downstream of the pressure reducing device 13c. Also, because the pressure downstream of the check valve 18 is higher than the pressure upstream of it, the refrigerant that has accumulated in the second low-temperature side heat exchanger 16 does not flow downstream of the check valve 18. As a result, refrigerant accumulates in the second low-temperature side heat exchanger 16.

[0035] Therefore, in order to prevent the refrigerant from accumulating, it is conceivable to provide a flow control valve instead of check valve 18, and when the refrigerant accumulates, open the flow control valve to connect the flow path of second low-temperature side heat exchanger 16. However, the pressure of the refrigerant in the flow path of second low-temperature side heat exchanger 16 is a pressure equivalent to the outside air temperature, and is therefore lower than the pressure of the refrigerant flowing through first low-temperature side heat exchanger 14. As a result, when the flow control valve is opened, the refrigerant may flow back to the second low-temperature side heat exchanger 16 side, causing further accumulation of refrigerant in second low-temperature side heat exchanger 16.

[0036] If the amount of refrigerant circulating through the refrigerant circuit 10 is insufficient, the temperature of the refrigerant discharged from the compressor 11 may rise too high, causing frequent malfunctions such as breakdown of the compressor 11 or deterioration of the durability of the system that constitutes the refrigerant circuit 10.

[0037] Therefore, in this embodiment, when the refrigerant that does not flow through the bypass path during hot gas operation is made to flow through either the first low-temperature side heat exchanger 14 or the second low-temperature side heat exchanger 16, a switching mode is executed in which the refrigerant is also made to flow through the other of the first low-temperature side heat exchanger 14 and the second low-temperature side heat exchanger 16 through which the refrigerant is not flowing. By making the refrigerant flow through the low-temperature side heat exchanger through which the refrigerant is not flowing, it is possible to recover the refrigerant that has accumulated in the low-temperature side heat exchanger through which the refrigerant is not flowing, and problems due to insufficient refrigerant circulation can be resolved.

[0038] Furthermore, in this embodiment, it is possible to execute switching mode 1 in which the refrigerant flows through both the first low-temperature side heat exchanger 14 and the second low-temperature side heat exchanger 16, and switching mode 2 in which the refrigerant flows through only one of the first low-temperature side heat exchanger 14 and the second low-temperature side heat exchanger 16 by switching between them. That is, in switching mode 1, the refrigerant flows through the first low-temperature side heat exchanger 14 and the second low-temperature side heat exchanger 16 at the same time. In addition, in switching mode 2, the timing at which the refrigerant flows through the first low-temperature side heat exchanger 14 and the second low-temperature side heat exchanger 16 is switched. The two types of switching modes 1 and 2 will be described below with reference to FIGS. 2 to 4.

[0039] <Switching mode 1> In switching mode 1, the pressure reduction device 13b or the pressure reduction device 13c, which is provided upstream of the first low-temperature side heat exchanger 14 or the second low-temperature side heat exchanger 16, through which the refrigerant is not flowing, is gradually opened, thereby causing the refrigerant to flow through both the first low-temperature side heat exchanger 14 and the second low-temperature side heat exchanger 16. As a result, the stagnant refrigerant gradually flows to the compressor 11, which makes it possible to suppress the impact on the temperature of the refrigerant discharged from the compressor 11, and hot gas operation can be continued. In this embodiment, as an example of gradually opening the pressure reduction device 13b or the pressure reduction device 13c, the opening degree of the pressure reduction device 13b or the pressure reduction device 13c is increased in stages.

[0040] Furthermore, in switching mode 1, based on a predetermined termination condition, pressure reducing device 13b or pressure reducing device 13c provided upstream of either first low-temperature side heat exchanger 14 or second low-temperature side heat exchanger 16 is fully closed. Therefore, by using either first low-temperature side heat exchanger 14 or second low-temperature side heat exchanger 16, the state of the refrigerant drawn into compressor 11 is stabilized, and temperature unevenness in the blown-out temperature due to hot gas operation can be suppressed.

[0041] The predetermined termination condition is a condition based on the amount of change in pressure of the refrigerant drawn by the compressor 11. Therefore, by detecting the state of the refrigerant drawn by the compressor 11, the recovery state of the accumulating refrigerant can be easily determined.

[0042] Furthermore, switching mode 1 is executed when refrigerant accumulation is detected in either the first low-temperature side heat exchanger 14 or the second low-temperature side heat exchanger 16, whichever is not flowing refrigerant. Therefore, by detecting refrigerant accumulation, problems caused by insufficient refrigerant circulation can be resolved.

[0043] Switching mode 1 is executed when the pressure of the refrigerant sucked into compressor 11 exceeds a predetermined threshold during hot gas operation. Therefore, by executing switching mode when the pressure of the refrigerant sucked into compressor 11 or the temperature of the refrigerant discharged from compressor 11 indicates an abnormality, deterioration of the durability of the system can be prevented.

[0044] Hereinafter, switching mode 1 will be described with reference to FIGS. 2 and 3, but the opening degrees of the pressure reducing devices 13b and 13c and the timing of changing the opening degrees are merely examples and are not limited to this embodiment.

[0045] (Example of not replacing the low-temperature side heat exchanger) FIG. 2 shows an example in which switching mode 1 is executed without switching between the first low-temperature side heat exchanger 14 and the second low-temperature side heat exchanger 16 through which the refrigerant flows.

[0046] In the example shown in FIG. 2, assume that hot gas operation is started at timing (1) with the opening degree of pressure reduction device 13b (indicated by the dashed-dotted line in the figure) set to 50 and the opening degree of pressure reduction device 13c (indicated by the dashed-dotted line in the figure) set to 0. That is, assume that hot gas operation is started with pressure reduction device 13b open and pressure reduction device 13c fully closed. In this case, as described above, a refrigerant circulation path is formed by refrigerant flow paths 10a, 10d, 10e, 10f, 10g, and 10c. On the other hand, a refrigerant circulation path is not formed by refrigerant flow paths 10a, 10d, 10e, 10h, 10i, and 10c. As a result, the refrigerant flows through first low-temperature side heat exchanger 14 but not through second low-temperature side heat exchanger 16.

[0047] In this state, if the pressure Ps of the refrigerant sucked into the compressor 11 drops and exceeds the lower limit value, which is a threshold value, during the period from (1) to (2), the refrigerant stagnation in the second low-temperature side heat exchanger 16, where no refrigerant is flowing, is detected and switching mode 1 is executed.

[0048] In this case, at the timing (2) when the pressure Ps of the refrigerant sucked into the compressor 11 has fallen to the lower limit value, the opening of the pressure reducing device 13c is set to 10 so that the pressure reducing device 13c is gradually opened. As a result, the refrigerant begins to flow not only to the first low-temperature side heat exchanger 14 but also to the second low-temperature side heat exchanger 16. On the other hand, if the opening of the pressure reducing device 13b is reduced too much at once, the pressure of the high-pressure side refrigerant may decrease, reducing the heating efficiency by hot gas operation. Therefore, the opening of the pressure reducing device 13b is set to 40 so that the pressure reducing device 13b is gradually closed.

[0049] Assume that pressure reduction device 13c is opened at timing (2), but the pressure Ps of the refrigerant sucked into compressor 11 further decreases during the period from (2) to (3). In this case, it is detected that refrigerant is increasingly stagnating in second low-temperature side heat exchanger 16. If pressure Ps reaches the lower limit protection value, there is a risk of compressor 11 failing. Therefore, at timing (3), the opening of pressure reduction device 13c is set to 20 so that pressure reduction device 13c is gradually opened. On the other hand, if the opening of pressure reduction device 13b is reduced too much at once, the pressure of the high-pressure side refrigerant may decrease, reducing the heating efficiency by hot gas operation. Therefore, the opening of pressure reduction device 13b is set to 30 so that pressure reduction device 13b is gradually closed.

[0050] As a result, during the period from (3) to (4), the pressure Ps of the refrigerant drawn into compressor 11 begins to rise. In this case, it is detected that the refrigerant accumulation in second low-temperature side heat exchanger 16 has begun to disappear and the amount of refrigerant drawn into compressor 11 has begun to recover. Therefore, at the timing of (4), the opening of pressure reducing device 13c is set to 10 so that pressure reducing device 13c is gradually closed. On the other hand, if the opening of pressure reducing device 13b is increased too much at once, the pressure of the refrigerant on the high-pressure side may increase and cause unstable hot gas operation, so the opening of pressure reducing device 13c is set to 40 so that pressure reducing device 13b is gradually opened.

[0051] As a result, during the period from (4) to (5), the pressure Ps of the refrigerant drawn into the compressor 11 rises sufficiently, eliminating the refrigerant stagnation in the second low-temperature side heat exchanger 16, and it is detected that the amount of refrigerant drawn into the compressor 11 has sufficiently recovered. In other words, it is detected that the stagnant refrigerant has been recovered and the amount of refrigerant circulating through the refrigerant circuit 10 has sufficiently recovered. Therefore, at the timing of (5), the aperture of the pressure reducing device 13c is set to 0. Also, the aperture of the pressure reducing device 13b is set to 50. As a result, the pressure reducing device 13b is opened, and the pressure reducing device 13c is fully closed.

[0052] That is, as a predetermined termination condition, when the amount of change in the pressure of the refrigerant sucked by the compressor 11 reaches an amount that sufficiently restores the amount of refrigerant circulating through the refrigerant circuit 10, the pressure reducing device 13c provided upstream of the second low-temperature side heat exchanger 16 is fully closed to terminate switching mode 1. In this case, refrigerant flows to the first low-temperature side heat exchanger 14 but not to the second low-temperature side heat exchanger 16. Therefore, the low-temperature side heat exchangers through which refrigerant flows are not switched between the first low-temperature side heat exchanger 14 and the second low-temperature side heat exchanger 16.

[0053] As described above, in the example shown in FIG. 2, when hot gas operation is performed, switching mode 1 is executed in the periods (2) to (5).

[0054] (Example of replacing the low-temperature heat exchanger) FIG. 3 shows an example in which the first low-temperature side heat exchanger 14 and the second low-temperature side heat exchanger 16 through which the refrigerant flows are switched by executing switching mode 1.

[0055] In the example shown in FIG. 3, assume that hot gas operation is started at timing (1) with the opening degree of pressure reduction device 13b (indicated by the dashed-dotted line in the figure) set to 50 and the opening degree of pressure reduction device 13c (indicated by the dashed-dotted line in the figure) set to 0. That is, assume that hot gas operation is started with pressure reduction device 13b open and pressure reduction device 13c fully closed. In this case, as described above, a refrigerant circulation path is formed by refrigerant flow paths 10a, 10d, 10e, 10f, 10g, and 10c. On the other hand, a refrigerant circulation path is not formed by refrigerant flow paths 10a, 10d, 10e, 10h, 10i, and 10c. As a result, the refrigerant flows through first low-temperature side heat exchanger 14 but not through second low-temperature side heat exchanger 16.

[0056] In this state, if the pressure Ps of the refrigerant sucked into the compressor 11 drops and exceeds the lower limit value, which is a threshold value, during the period from (1) to (2), the refrigerant stagnation in the second low-temperature side heat exchanger 16, where no refrigerant is flowing, is detected and switching mode 1 is executed.

[0057] In this case, at the timing (2) when the pressure Ps of the refrigerant sucked into the compressor 11 has fallen to the lower limit value, the opening of the pressure reducing device 13c is set to 10 so that the pressure reducing device 13c is gradually opened. As a result, the refrigerant begins to flow not only to the first low-temperature side heat exchanger 14 but also to the second low-temperature side heat exchanger 16. On the other hand, if the opening of the pressure reducing device 13b is reduced too much at once, the pressure of the high-pressure side refrigerant may decrease, reducing the heating efficiency by hot gas operation. Therefore, the opening of the pressure reducing device 13b is set to 40 so that the pressure reducing device 13b is gradually closed.

[0058] Assume that pressure reduction device 13c is opened at timing (2), but the pressure Ps of the refrigerant sucked into compressor 11 further decreases during the period from (2) to (3). In this case, it is detected that refrigerant is increasingly stagnating in second low-temperature side heat exchanger 16. Then, because there is a risk of compressor 11 failing if pressure Ps reaches the lower limit protection value, the opening degree of pressure reduction device 13b is set to 20 at timing (3) so that pressure reduction device 13c is gradually opened. On the other hand, if the opening degree of pressure reduction device 13b is reduced too much at once, the pressure of the high-pressure side refrigerant may decrease, resulting in a decrease in heating efficiency due to hot gas operation. Therefore, the opening degree of pressure reduction device 13c is set to 30 so that pressure reduction device 13b is gradually closed.

[0059] As a result, during the period from (3) to (4), the pressure Ps of the refrigerant drawn into compressor 11 begins to rise. In this case, it is detected that the refrigerant accumulation in second low-temperature side heat exchanger 16 has begun to disappear and the amount of refrigerant drawn into compressor 11 has begun to recover. Therefore, at the timing of (4), the opening degree of pressure reduction device 13c is set to 30 so that pressure reduction device 13c is gradually opened. On the other hand, if the opening degree of pressure reduction device 13b is reduced too much at once, the pressure of the high-pressure side refrigerant may increase and hot gas operation may become unstable. Therefore, the opening degree of pressure reduction device 13b is set to 20 so that pressure reduction device 13b is gradually closed.

[0060] As a result, the pressure Ps of the refrigerant drawn into compressor 11 continues to increase during the period from (4) to (5). In this case, it is detected that the refrigerant accumulation in second low-temperature side heat exchanger 16 has been eliminated and the amount of refrigerant drawn into compressor 11 has recovered. Therefore, at the timing of (5), the opening of pressure reducing device 13c is set to 40 so that pressure reducing device 13c is gradually opened. On the other hand, if the opening of pressure reducing device 13b is reduced too much at once, the pressure of the high-pressure side refrigerant may increase and hot gas operation may become unstable. Therefore, the opening of pressure reducing device 13b is set to 10 so that pressure reducing device 13b is gradually closed.

[0061] As a result, during the period from (5) to (6), the pressure Ps of the refrigerant drawn into the compressor 11 rises sufficiently, eliminating the refrigerant stagnation in the second low-temperature side heat exchanger 16, and it is detected that the amount of refrigerant drawn into the compressor 11 has sufficiently recovered. In other words, it is detected that the stagnation refrigerant has been recovered and the amount of refrigerant circulating through the refrigerant circuit 10 has sufficiently recovered. Therefore, at the timing of (5), the aperture of the pressure reducing device 13c is set to 50. Also, the aperture of the pressure reducing device 13b is set to 0. As a result, the pressure reducing device 13b is fully closed and the pressure reducing device 13c is opened.

[0062] That is, as a predetermined termination condition, when the amount of change in the pressure of the refrigerant sucked by the compressor 11 reaches an amount that sufficiently restores the amount of refrigerant circulating through the refrigerant circuit 10, the pressure reducing device 13b provided upstream of the first low-temperature side heat exchanger 14 is fully closed to terminate switching mode 1. In this case, the refrigerant does not flow through the first low-temperature side heat exchanger 14, but flows through the second low-temperature side heat exchanger 16. Therefore, the first low-temperature side heat exchanger 14 and the second low-temperature side heat exchanger 16 switch places as the low-temperature side heat exchangers through which the refrigerant flows.

[0063] As described above, in the example shown in FIG. 3, when hot gas operation is performed, switching mode 1 is executed in the periods (2) to (6).

[0064] In this embodiment, an example has been given in which the operation of the compressor 11 is not stopped in switching mode 1, but the operation of the compressor 11 may also be stopped when the opening degrees of the first low-temperature side heat exchanger 14 and the second low-temperature side heat exchanger 16 are changed.

[0065] <Executing switching mode 2> In switching mode 2, the operation of compressor 11 is stopped, and pressure reduction device 13b or pressure reduction device 13c provided upstream of either first low-temperature side heat exchanger 14 or second low-temperature side heat exchanger 16, whichever is flowing the refrigerant, is fully closed, while pressure reduction device 13b or pressure reduction device 13c provided upstream of whichever is not flowing the refrigerant, is opened. Therefore, by stopping compressor 11, it is possible to prevent system malfunctions due to sudden changes in refrigerant pressure, and hot gas operation can be performed stably.

[0066] Switching mode 2 is executed when refrigerant accumulation is detected in either the first low-temperature side heat exchanger 14 or the second low-temperature side heat exchanger 16, whichever is not flowing refrigerant. Therefore, by detecting refrigerant accumulation, problems caused by insufficient refrigerant circulation can be resolved.

[0067] Switching mode 2 is executed when the pressure of the refrigerant sucked into compressor 11 exceeds a predetermined threshold during hot gas operation. Therefore, by executing switching mode when the pressure of the refrigerant sucked into compressor 11 or the temperature of the refrigerant discharged from compressor 11 indicates an abnormality, deterioration of the durability of the system can be prevented.

[0068] Hereinafter, switching mode 2 will be described with reference to FIG. 4, but the opening degrees of the pressure reducing devices 13b and 13c, the timing of changing the opening degrees, and the timing of stopping the compressor 11 are merely examples and are not limited to this embodiment.

[0069] In the example shown in FIG. 4, assume that hot gas operation is started at timing (1) with the opening degree of pressure reduction device 13b (indicated by the dashed-dotted line in the figure) set to 50 and the opening degree of pressure reduction device 13c (indicated by the dashed-dotted line in the figure) set to 0. That is, assume that hot gas operation is started with pressure reduction device 13b opened and pressure reduction device 13c fully closed. In this case, as described above, a refrigerant circulation path is formed by refrigerant flow paths 10a, 10d, 10e, 10f, 10g, and 10c. As a result, the refrigerant flows through first low-temperature side heat exchanger 14. On the other hand, a refrigerant circulation path is not formed by refrigerant flow paths 10a, 10d, 10e, 10h, 10i, and 10c. As a result, the refrigerant flows through first low-temperature side heat exchanger 14 but not through second low-temperature side heat exchanger 16.

[0070] In this state, if the pressure Ps of the refrigerant sucked into the compressor 11 drops and exceeds the lower limit value, which is a threshold value, during the period from (1) to (2), the refrigerant stagnation in the second low-temperature side heat exchanger 16, where no refrigerant is flowing, is detected and switching mode 2 is executed.

[0071] In this case, it is predicted that the pressure Ps of the refrigerant sucked into the compressor 11 will drop to the lower limit before timing (2) is reached, and the operation of the compressor 11 is stopped around timing (2). Then, at timing (2) when the pressure Ps of the refrigerant sucked into the compressor 11 drops to the lower limit, the aperture of the pressure reducing device 13c is set to 50. On the other hand, the aperture of the pressure reducing device 13b is set to 0. As a result, the first low-temperature side heat exchanger 14 and the second low-temperature side heat exchanger 16 are switched, and the refrigerant does not flow through the first low-temperature side heat exchanger 14 but flows through the second low-temperature side heat exchanger 16.

[0072] As a result, during the period from (2) to (3), the pressure Ps of the refrigerant drawn into the compressor 11 begins to rise. In this case, it is detected that the refrigerant accumulation in the second low-temperature side heat exchanger 16 has disappeared and the amount of refrigerant drawn into the compressor 11 has recovered.

[0073] In this state, if the pressure Ps of the refrigerant sucked into the compressor 11 drops and exceeds the lower limit value, which is a threshold value, during the period from (3) to (4), the refrigerant stagnation in the first low-temperature side heat exchanger 14, where no refrigerant is flowing, is detected and switching mode 2 is executed.

[0074] In this case, it is predicted that the pressure Ps of the refrigerant sucked into the compressor 11 will drop to the lower limit before timing (4) is reached, and the operation of the compressor 11 is stopped around timing (4). Then, at timing (4) when the pressure Ps of the refrigerant sucked into the compressor 11 drops to the lower limit, the aperture of the pressure reducing device 13c is set to 0. On the other hand, the aperture of the pressure reducing device 13b is set to 50. As a result, the first low-temperature side heat exchanger 14 and the second low-temperature side heat exchanger 16 are switched, and the refrigerant does not flow through the second low-temperature side heat exchanger 16 but flows through the first low-temperature side heat exchanger 14.

[0075] As a result, during the period from (4) to (5), the pressure Ps of the refrigerant drawn into the compressor 11 begins to rise. In this case, it is detected that the refrigerant accumulation in the first low-temperature side heat exchanger 14 has disappeared and the amount of refrigerant drawn into the compressor 11 has recovered. Thereafter, the same control is repeated.

[0076] As described above, in the example shown in FIG. 4, when hot gas operation is performed, switching mode 2 is executed at the timings (2) and (4).

[0077] Although an example has been given in which the operation of compressor 11 is stopped in switching mode 2, it is not necessary to stop the operation of compressor 11, for example, by reducing the rotation speed of compressor 11 when switching the circulation path.

[0078] In this embodiment, an example has been described in which the first low-temperature side heat exchanger 14 exchanges heat with a heat medium passing through a cooler core, and the second low-temperature side heat exchanger 16 exchanges heat with a heat medium passing through a battery temperature control unit, but the temperature control target of the heat medium exchanged by the first low-temperature side heat exchanger 14 and the second low-temperature side heat exchanger 16 does not have to be limited to this embodiment.

[0079] In this embodiment, an example in which the check valve 18 is provided has been described, but a flow rate adjustment valve may be provided, or the check valve 18 may not be provided.

[0080] In this embodiment, an example has been described in which the predetermined termination condition is a condition based on the amount of change in the pressure of the refrigerant sucked into the compressor 11. However, the predetermined termination condition may also be a condition based on the amount of change between the temperature of the refrigerant sucked into the compressor 11 and the temperature of the refrigerant discharged from the compressor 11.

[0081] In this embodiment, an example has been given in which refrigerant stagnation is detected when the amount of change in pressure of the refrigerant sucked into compressor 11 exceeds a threshold lower limit value. However, refrigerant stagnation may also be detected by other methods, such as when the refrigerant becomes superheated, when the execution time of hot gas operation reaches a predetermined time, or when the temperature of the refrigerant on the discharge side of compressor 11 exceeds a predetermined temperature.

[0082] In this embodiment, an example has been given in which the switching mode is executed when the pressure of the refrigerant sucked into the compressor 11 during hot gas operation exceeds a lower limit value, which is a threshold value. However, the switching mode may also be executed when the temperature of the refrigerant discharged from the compressor 11 during hot gas operation exceeds an upper limit value, which is a threshold value, or when both exceed their respective threshold values.

[0083] [Effects of this embodiment] (1) A vehicle air conditioning system including a refrigerant circuit 10 having a compressor 11, a high-temperature side heat exchanger 12 as a condenser that heats a heat medium, a first low-temperature side heat exchanger 14 as a first evaporator that cools the heat medium, and a second low-temperature side heat exchanger 16 arranged in parallel with the first evaporator and as a second evaporator that cools the heat medium, The refrigerant circuit 10 includes a bypass path that bypasses the high-temperature side heat exchanger 12 and joins a path downstream of a path through which the refrigerant flows to the first low-temperature side heat exchanger 14 and a path through which the refrigerant flows to the second low-temperature side heat exchanger 16, a hot gas operation in which a part of the refrigerant discharged from the compressor 11 is caused to flow through a bypass path, and the remaining refrigerant that does not flow through the bypass path is caused to flow through either the first evaporator or the second evaporator; A switching mode in which refrigerant also flows through the other of the first low-temperature side heat exchanger 14 and the second low-temperature side heat exchanger 16 when the hot gas operation is being performed can be executed. When hot gas operation is performed in a circuit in which the first low-temperature side heat exchanger 14 and the second low-temperature side heat exchanger 16 are connected in parallel, refrigerant tends to accumulate in the first low-temperature side heat exchanger 14 or the second low-temperature side heat exchanger 16 through which refrigerant is not flowing, reducing the amount of refrigerant circulating. Therefore, in order to recover the refrigerant that has accumulated in the low-temperature side heat exchanger through which refrigerant is not flowing, the problem of insufficient refrigerant circulation can be resolved by flowing refrigerant through the low-temperature side heat exchanger through which refrigerant is not flowing.

[0084] (2) In the switching mode, the pressure reducing device 13b or the pressure reducing device 13c, which is located upstream of the first low-temperature side heat exchanger 14 or the second low-temperature side heat exchanger 16 through which the refrigerant is not flowing, is gradually opened (Figures 2 and 3). Therefore, the stagnant refrigerant gradually flows into the compressor 11, making it possible to suppress the effect on the temperature of the refrigerant discharged from the compressor 11, and hot gas operation can be continued.

[0085] (3) In the switching mode, based on a predetermined termination condition, the pressure reducing device 13b or 13c of either the first low-temperature side heat exchanger 14 or the second low-temperature side heat exchanger 16 is fully closed (Figures 2 and 3). Therefore, by using either the first low-temperature side heat exchanger 14 or the second low-temperature side heat exchanger 16, the state of the refrigerant drawn into the compressor 11 is stabilized, and the occurrence of temperature unevenness in the blowing temperature due to hot gas operation can be suppressed.

[0086] (4) The specified termination condition is that the amount of change in the pressure of the refrigerant sucked into the compressor 11 or the amount of change between the temperature of the refrigerant sucked into the compressor 11 and the temperature of the refrigerant discharged from the compressor 11 reaches a threshold value (Figures 2 and 3). Therefore, by detecting the state of the refrigerant sucked into the compressor 11, the recovery state of the stagnant refrigerant can be easily determined.

[0087] (5) The switching mode is executed when refrigerant stagnation is detected in either the first low-temperature side heat exchanger 14 or the second low-temperature side heat exchanger 16, whichever is not flowing refrigerant (Figures 2, 3, and 4). Therefore, by detecting refrigerant stagnation, problems caused by insufficient circulating refrigerant can be resolved.

[0088] It is preferable that the switching mode be executed by detecting refrigerant stagnation when at least one of the pressure of the refrigerant sucked into the compressor 11 or the temperature of the refrigerant discharged from the compressor 11 exceeds a predetermined threshold value during hot gas operation (Figures 2, 3, and 4). Therefore, by executing the switching mode when the pressure of the refrigerant sucked by the compressor 11 or the temperature of the refrigerant discharged from the compressor 11 indicates an abnormality, it is possible to prevent deterioration of the durability of the system.

[0089] (6) In the switching mode, the operation of the compressor 11 is stopped, and the pressure reducing device 13b or the pressure reducing device 13c provided upstream of the first low-temperature side heat exchanger 14 or the second low-temperature side heat exchanger 16 through which the refrigerant is flowing is fully closed, and the pressure reducing device 13b or the pressure reducing device 13c provided upstream of the one through which the refrigerant is not flowing is opened (Figure 4). Therefore, by stopping the compressor 11, it is possible to prevent malfunctions in the system due to sudden changes in the pressure of the refrigerant, and it is possible to stably perform hot gas operation.

[0090] The present invention has been described above by showing preferred embodiments, but it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention. [Explanation of symbols]

[0091] 1: Vehicle air conditioning system 10: Refrigerant circuit 13a, 13b, 13c: Pressure reducing device 18: Check valve a1, a2: Branching section b1,b2: Merging part 200: Control device

Claims

1. A vehicle air conditioning system including a refrigerant circuit having a compressor, a condenser that heats a heat medium, a first evaporator that cools the heat medium, and a second evaporator that is arranged in parallel with the first evaporator and cools the heat medium, the refrigerant circuit includes a bypass path that bypasses the condenser and joins a path downstream of a path through which the refrigerant flows to the first evaporator and a path through which the refrigerant flows to the second evaporator, a hot gas operation in which a portion of the refrigerant discharged from the compressor is caused to flow through the bypass path, and the remaining refrigerant that does not flow through the bypass path is caused to flow through either the first evaporator or the second evaporator; a switching mode in which refrigerant also flows through the other of the first evaporator and the second evaporator when the hot gas operation is being performed; 1. A vehicle air conditioning system comprising:

2. In the switching mode, the pressure reducing device provided upstream of the first evaporator or the second evaporator through which the refrigerant is not flowing is gradually opened.

2. The air conditioning system for a vehicle according to claim 1.

3. In the switching mode, a pressure reducing device provided upstream of either the first evaporator or the second evaporator is fully closed based on a predetermined termination condition.

2. The air conditioning system for a vehicle according to claim 1.

4. The predetermined termination condition is a condition based on a change in pressure of the refrigerant drawn into the compressor or a change in temperature between the refrigerant drawn into the compressor and the refrigerant discharged from the compressor.

4. The air conditioning system for a vehicle according to claim 3.

5. The switching mode is executed when refrigerant stagnation is detected in the first evaporator or the second evaporator, whichever is not flowing refrigerant.

2. The air conditioning system for a vehicle according to claim 1.

6. In the switching mode, the operation of the compressor is stopped, and the pressure reducing device provided on the upstream side of the first evaporator or the second evaporator through which the refrigerant flows is fully closed, and the pressure reducing device provided on the upstream side of the evaporator through which the refrigerant does not flow is opened.

2. The air conditioning system for a vehicle according to claim 1.

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