Refrigerating cycle for two chamber type refrigerated vehicle

Abstract

To suppress component cost and simplify control in a refrigerating cycle used for a two chamber type refrigerating vehicle.SOLUTION: A control unit 50 that switches between a first cooling mode in which the on-off valve 28 is opened, the first blower 122 is operated, and the second blower 132 is stopped and a second cooling mode in which the on-off valve 28 is closed, the first blower 122 is stopped, and the second blower 132 is operated, the controller 50 executes the first cooling mode when the first intake air temperature Ts1 is equal to or higher than the first switching temperature α 1, switches to the second cooling mode when the first intake air temperature Ts1 becomes lower than the first switching temperature α 1, maintains the second cooling mode when the first intake air temperature Ts1 is lower than the second switching temperature α 2 higher than the first switching temperature α 1 in the second cooling mode, and switches to the first cooling mode when the first intake air temperature Ts1 becomes equal to or higher than the second switching temperature α 2 in the second cooling mode.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a refrigeration cycle used in a two-compartment refrigerated vehicle. [Background technology]

[0002] A conventional vehicle refrigeration system mounted on a refrigerated vehicle having two refrigerator compartments is described in Patent Document 1. A first evaporator that cools the air in one refrigerator compartment and a second evaporator that cools the air in the other refrigerator compartment are arranged in parallel with each other in the refrigerant flow, and the introduction and interruption of refrigerant to the first and second evaporators are alternately performed, thereby cooling (freezing or refrigerating) the two refrigerator compartments to different temperatures.

[0003] Specifically, the system includes a first on-off valve that switches on and off the introduction of refrigerant to the first evaporator, a second on-off valve that switches on and off the introduction of refrigerant to the second evaporator, and a control unit that controls the first and second on-off valves, and the control unit alternately opens and closes the first and second on-off valves to alternately introduce and interrupt the introduction of refrigerant to the first and second evaporators (so-called FIR control). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-132635 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned conventional technology, two on-off valves are used to switch between introducing and stopping the refrigerant into the first and second evaporators, which leads to an increase in parts costs and complicated control.

[0006] In view of the above, an object of the present invention is to reduce component costs and simplify control in a refrigeration cycle used in a two-compartment refrigerated vehicle. [Means for solving the problem]

[0007] In order to achieve the above object, the refrigeration cycle for a two-compartment refrigerated vehicle according to claim 1 comprises: A refrigeration cycle used in a two-compartment refrigerator vehicle having a first refrigerated compartment (111) that is kept cold and a second refrigerated compartment (112) that is kept cold at a temperature higher than that of the first refrigerated compartment (111), a compressor (20) that sucks and compresses a refrigerant; a radiator (21) for radiating heat from the refrigerant compressed by the compressor (20); a first pressure reducing section (25) and a second pressure reducing section (29) that are arranged in parallel with each other in the refrigerant flow and reduce the pressure of the refrigerant whose heat has been radiated in the radiator (21); a first evaporator (26) that evaporates the refrigerant decompressed in the first decompression part (25) to cool the air in the first refrigerated compartment (111); a second evaporator (30) that evaporates the refrigerant decompressed in the second decompression section (29) to cool the air in the second refrigerated compartment (112); an on-off valve (28) capable of interrupting the flow of the refrigerant to the first pressure reducing section (25) and the first evaporator (26); a check valve (27) for preventing the refrigerant flowing out of the second evaporator (30) from flowing back into the first evaporator (26); a first fan (122) for blowing air to the first evaporator (26); a second blower (132) that blows air to the second evaporator (30); an intake air temperature detection section (71) for detecting a first intake air temperature (Ts1), which is the temperature of air sucked into the first evaporator (26); a control unit (50) that switches between a first cooling mode in which the on-off valve (28) is opened, the first fan (122) is operated, and the second fan (132) is stopped, and a second cooling mode in which the on-off valve (28) is closed, the first fan (122) is stopped, and the second fan (132) is operated, the first pressure reducing section (25) is a thermal expansion valve having a mechanical mechanism that changes its throttle opening by deforming in accordance with the temperature and pressure of the refrigerant at the outlet side of the first evaporator (26); The control unit (50) When the first intake air temperature (Ts1) is equal to or higher than a first switching temperature (α1), the first cooling mode is performed; When the first intake air temperature (Ts1) becomes lower than the first switching temperature (α1), the cooling mode is switched to the second cooling mode, When the first intake air temperature (Ts1) is lower than a second switching temperature (α2) that is higher than the first switching temperature (α1) in the second cooling mode, the second cooling mode is maintained; When the first intake air temperature (Ts1) becomes equal to or higher than a second switching temperature (α2) in the second cooling mode, the mode is switched to the first cooling mode.

[0008] According to this, in the first cooling mode, the air in the first refrigerated compartment (111) is cooled by the first evaporator (26) and the temperature is reduced, while the air in the second refrigerated compartment (112) is hardly cooled by the second evaporator (30). Immediately after switching to the first cooling mode, refrigerant flows through the second pressure reduction section (29) and the second evaporator (30). However, since the second blower (132) is stopped and the temperature of the second evaporator (30) is reduced, the second pressure reduction section (29) is throttled, and the refrigerant does not easily flow through the second pressure reduction section (29) and the second evaporator (30).

[0009] When the air temperature in the first refrigerated compartment (111) decreases in the first cooling mode and the first intake air temperature (Ts1) becomes lower than the first switchover temperature (α1), the mode is switched to the second cooling mode. In the second cooling mode, the air in the second refrigerated compartment (112) is cooled by the second evaporator (30) and its temperature decreases, while the air temperature in the first refrigerated compartment (111) gradually increases. This is because the on-off valve (28) is closed, preventing refrigerant from flowing through the first pressure reduction section (25) and the first evaporator (26).

[0010] In the second cooling mode, the air temperature in the first refrigerated compartment (111) gradually increases, and when the first intake air temperature (Ts1) becomes equal to or higher than the second switching temperature (α2), the mode switches back to the first cooling mode. As a result, the air in the first refrigerated compartment (111) is cooled by the first evaporator (26) and its temperature decreases, while the air in the second refrigerated compartment (112) is hardly cooled by the second evaporator (30).

[0011] By repeating such switching between the first cooling mode and the second cooling mode, the first refrigerated compartment (111) can be kept cool, and the second refrigerated compartment (112) can be kept cool at a temperature higher than that of the first refrigerated compartment (111).

[0012] Therefore, compared to the above-described conventional technology in which two on-off valves are controlled to keep two refrigerators at different temperatures, component costs can be reduced and control can be simplified.

[0013] In order to achieve the above object, the refrigeration cycle for a two-compartment refrigerated vehicle according to claim 2 comprises: A refrigeration cycle used in a two-compartment refrigerator vehicle having a first refrigerated compartment (111) that is kept cold and a second refrigerated compartment (112) that is kept cold at a temperature higher than that of the first refrigerated compartment (111), a compressor (20) that sucks and compresses a refrigerant; a radiator (21) for radiating heat from the refrigerant compressed by the compressor (20); a first pressure reducing section (25) and a second pressure reducing section (29) that are arranged in parallel with each other in the refrigerant flow and reduce the pressure of the refrigerant whose heat has been radiated in the radiator (21); a first evaporator (26) that evaporates the refrigerant decompressed in the first decompression part (25) to cool the air in the first refrigerated compartment (111); a second evaporator (30) that evaporates the refrigerant decompressed in the second decompression section (29) to cool the air in the second refrigerated compartment (112); an on-off valve (28) capable of interrupting the flow of the refrigerant to the second pressure reducing section (29) and the second evaporator (30); a check valve (27) for preventing the refrigerant flowing out of the second evaporator (30) from flowing back into the first evaporator (26); a first fan (122) for blowing air to the first evaporator (26); a second blower (132) that blows air to the second evaporator (30); an intake air temperature detection section (71) for detecting a first intake air temperature (Ts1), which is the temperature of air sucked into the first evaporator (26); a control unit (50) that switches between a first cooling mode in which the on-off valve (28) is closed, the first fan (122) is operated, and the second fan (132) is stopped, and a second cooling mode in which the on-off valve (28) is opened, the first fan (122) is stopped, and the second fan (132) is operated, the first pressure reducing section (25) is a thermal expansion valve having a mechanical mechanism that changes its throttle opening by deforming in accordance with the temperature of the refrigerant at the outlet side of the first evaporator (26), The control unit (50) When the first intake air temperature (Ts1) is equal to or higher than a first switching temperature (α1), the first cooling mode is performed; When the first intake air temperature (Ts1) becomes lower than the first switching temperature (α1), the cooling mode is switched to the second cooling mode, When the first intake air temperature (Ts1) is lower than a second switching temperature (α2) that is higher than the first switching temperature (α1) in the second cooling mode, the second cooling mode is maintained; When the first intake air temperature (Ts1) becomes equal to or higher than a second switching temperature (α2) in the second cooling mode, the mode is switched to the first cooling mode.

[0014] According to this, in the first cooling mode, the air in the first refrigerated compartment (111) is cooled by the first evaporator (26) to decrease in temperature, while the air in the second refrigerated compartment (112) is not cooled by the second evaporator (30). This is because the on-off valve (28) is closed, preventing refrigerant from flowing to the second pressure reducing section (29) and the second evaporator (30).

[0015] When the air temperature in the first refrigerated compartment (111) decreases in the first cooling mode and the first intake air temperature (Ts1) becomes less than the first switching temperature (α1), the mode is switched to the second cooling mode. In the second cooling mode, the air in the second refrigerated compartment (112) is cooled by the second evaporator (30) and its temperature decreases, while the air temperature in the first refrigerated compartment (111) gradually increases. Immediately after switching to the second cooling mode, refrigerant flows through the first pressure reduction section (25) and the first evaporator (26). However, since the first blower (122) is stopped and the temperature of the first evaporator (26) decreases, the first pressure reduction section (25) is throttled, and it becomes difficult for refrigerant to flow through the first pressure reduction section (25) and the first evaporator (26).

[0016] In the second cooling mode, the air temperature in the first refrigerated compartment (111) gradually increases, and when the first intake air temperature (Ts1) becomes equal to or higher than the second switching temperature (α2), the mode switches back to the first cooling mode. As a result, the air in the first refrigerated compartment (111) is cooled by the first evaporator (26) and its temperature decreases, while the air in the second refrigerated compartment (112) is no longer cooled by the second evaporator (30).

[0017] By repeating such switching between the first cooling mode and the second cooling mode, the first refrigerated compartment (111) can be kept cool, and the second refrigerated compartment (112) can be kept cool at a temperature higher than that of the first refrigerated compartment (111).

[0018] Therefore, compared to the above-described conventional technology in which two on-off valves are controlled to keep two refrigerators at different temperatures, component costs can be reduced and control can be simplified.

[0019] The refrigeration cycle for a two-compartment freezer vehicle according to claim 3 is the refrigeration cycle for a two-compartment freezer vehicle according to claim 1 or 2, wherein the second switching temperature (α2) is set to a temperature lower than the refrigeration temperature of the second refrigerated compartment (112). Thus, the first refrigerated compartment (111), which is required to be kept at a lower temperature than the second refrigerated compartment (112), can be kept at an appropriate temperature by repeatedly switching between the first cooling mode and the second cooling mode.

[0020] The symbols in parentheses for each means described in this section and in the claims indicate the correspondence with the specific means described in the embodiments to be described later. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic diagram showing a two-compartment refrigerated vehicle in a first embodiment. FIG. [Figure 2] 1 is an overall configuration diagram of a refrigeration cycle used in a two-compartment refrigerated vehicle according to a first embodiment. [Figure 3] 3 is a flowchart showing a part of a control process executed by a control device for a refrigeration cycle in the first embodiment. [Figure 4] 4 is a time chart showing an example of operation of a refrigeration cycle in the first embodiment. [Figure 5] FIG. 10 is an overall configuration diagram of a refrigeration cycle used in a two-compartment refrigerated vehicle according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] (First embodiment) A first embodiment of the present invention will now be described. Fig. 1 is a cross-sectional view schematically showing a dual-compartment refrigerated vehicle of this embodiment. In Fig. 1, the up, down, front, and rear arrows indicate the up, down, front, and rear directions of the dual-compartment refrigerated vehicle. A dual-compartment refrigerated vehicle is a vehicle that stores and transports items to be kept refrigerated, such as food, at a temperature lower than room temperature. A dual-compartment refrigerated vehicle is a refrigerated vehicle that has two refrigerated compartments for storing items to be kept refrigerated.

[0023] The two-compartment refrigerated vehicle of this embodiment has a refrigerator compartment 11 for storing items to be kept refrigerated, located behind a driver's cab 10 located at the front of the vehicle. This refrigerator compartment 11 is formed in a box shape using a heat insulating material or the like. Within the refrigerator compartment 11, a first refrigerator compartment 111 and a second refrigerator compartment 112 are formed as compartments.

[0024] First refrigerated compartment 111 is a low-temperature compartment (freezer compartment) in which the refrigeration temperature is set to a low temperature, for example, about −18° C., and second refrigerated compartment 112 is a medium-temperature compartment (refrigerator compartment) in which the refrigeration temperature is set to a higher temperature, for example, about +5° C., than first refrigerated compartment 111. The volume of first refrigerated compartment 111 is smaller than the volume of second refrigerated compartment 112.

[0025] Although not shown in the figure, the side surfaces of the first refrigerated compartment 111 and the second refrigerated compartment 112 are provided with openings for carrying in and out items to be refrigerated, and opening / closing doors for opening and closing these openings.

[0026] A first cooling unit 12 is arranged in the first cold storage compartment 111, and a second cooling unit 13 is arranged in the second cold storage compartment 112.

[0027] 1, first cooling unit 12 draws in and cools air from first refrigerated compartment 111 and blows it out into first refrigerated compartment 111. First refrigerated compartment 111 is cooled by the cool air blown out from first cooling unit 12.

[0028] 1, second cooling unit 13 draws in air from second refrigerated compartment 112, cools it, and blows it out into second refrigerated compartment 112. Second refrigerated compartment 112 is cooled by the cool air blown out from second cooling unit 13.

[0029] First cooling unit 12 accommodates first blower 122, first evaporator 26 of the refrigeration cycle, and the like within first unit case 121. When first blower 122 is activated, air from first refrigerated compartment 111 is drawn into first unit case 121 and cooled as it passes through first evaporator 26, and the cooled air that has passed through first evaporator 26 is blown out from first unit case 121 into first refrigerated compartment 111.

[0030] Similarly, second cooling unit 13 accommodates second blower 132, second evaporator 30 of the refrigeration cycle, and the like in second unit case 131. When second blower 132 is activated, air from second refrigerated compartment 112 is drawn into second unit case 131 and cooled as it passes through second evaporator 30, and the cooled air that has passed through second evaporator 30 is blown out from second unit case 131 into second refrigerated compartment 112.

[0031] Figure 2 is an overall configuration diagram of a refrigeration cycle (a refrigeration cycle for a two-compartment refrigeration vehicle) installed in the two-compartment refrigeration vehicle of Figure 1. Compressor 20, which sucks and compresses the refrigerant of the refrigeration cycle, has an electromagnetic clutch (not shown) and is rotationally driven by a vehicle engine (not shown) via this electromagnetic clutch.

[0032] Compressor 20 is disposed, for example, in the engine compartment of the vehicle. A radiator 21 is connected to the discharge side of compressor 20. The radiator 21 exchanges heat between the high-pressure refrigerant discharged from compressor 20 and outside air (air outside the vehicle cabin) blown by blower 15, thereby cooling the high-pressure refrigerant.

[0033] In this embodiment, a refrigerant whose high pressure does not exceed the critical pressure, such as a fluorocarbon-based or HC-based refrigerant, is used as the refrigeration cycle, which constitutes a vapor compression subcritical cycle. Therefore, the radiator 21 functions as a condenser that condenses the refrigerant.

[0034] The high-pressure gas refrigerant discharged from the compressor 20 radiates heat to the outside air and condenses in the radiator 21. A liquid receiver 22 is connected to the outlet side of the radiator 21, and the refrigerant (condensed refrigerant) at the outlet of the radiator 21 is separated into gas and liquid in the liquid receiver 22. Excess liquid refrigerant is stored inside the liquid receiver 22, and the liquid refrigerant is discharged downstream of the liquid receiver 22.

[0035] The high-pressure refrigerant pipe downstream of the receiver 22 branches into two parallel passages. That is, a branch section Z1 that branches into a first refrigerant passage 23 and a second refrigerant passage 24 is provided downstream of the receiver 22. Therefore, refrigerant flows in parallel through the first refrigerant passage 23 and the second refrigerant passage 24.

[0036] In the first refrigerant passage 23, an on-off valve 28 which is an electrically controlled valve, a first expansion valve 25 which constitutes a first pressure reducing section, a first evaporator 26, and a check valve 27 are provided in series from the upstream side to the downstream side. The on-off valve 28, the first expansion valve 25, the first evaporator 26, and the check valve 27 are housed in a first unit case 121 together with a first blower 122 to constitute the first cooling unit 12.

[0037] The on-off valve 28 is a solenoid valve that can interrupt the flow of refrigerant to the fourth expansion valve 25 and the first evaporator 26, and is controlled to open and close by the control device 50. The on-off valve 28 is opened when the first evaporator 26 is to exert a cooling effect, and is closed when the first evaporator 26 is not to exert a cooling effect.

[0038] The first expansion valve 25 is configured so that the valve element opening (cross-sectional area of ​​the flow path) is adjustable. In this example, the first expansion valve 25 is a thermostatic expansion valve having a mechanical mechanism that changes the throttle opening by deforming in accordance with the temperature and pressure of the refrigerant on the outlet side of the first evaporator 26, thereby adjusting the refrigerant flow rate to the first evaporator 26 and maintaining the temperature of the refrigerant on the outlet side of the first evaporator 26 at a predetermined value. Specifically, the first expansion valve 25 is a thermostatic expansion valve that has a temperature-sensing part that has a deformable member (so-called diaphragm) that deforms in accordance with the temperature and pressure of the refrigerant on the outlet side of the first evaporator 26, and a valve element part that displaces in accordance with the deformation of the deformable member to change the throttle opening.

[0039] The first expansion valve 25 increases its throttle opening as the temperature of the refrigerant on the outlet side of the first evaporator 26 increases, and decreases its throttle opening as the temperature of the refrigerant on the outlet side of the first evaporator 26 decreases. As a result, when the temperature of the refrigerant on the outlet side of the first evaporator 26 increases, the refrigerant flow rate to the first evaporator 26 increases, and the temperature of the refrigerant on the outlet side of the first evaporator 26 decreases, and the refrigerant flow rate to the first evaporator 26 increases, and the temperature of the refrigerant on the outlet side of the first evaporator 26 increases. In this example, the first expansion valve 25 reaches its minimum throttle opening and is nearly closed when the temperature of the refrigerant on the outlet side of the first evaporator 26 is about -20°C.

[0040] A low-pressure refrigerant decompressed by first expansion valve 25 flows into first evaporator 26, and this low-pressure refrigerant absorbs heat from air blown by first blower 122 and evaporates, thereby cooling the air. The air (cold air) cooled by first evaporator 26 is blown into first refrigerated compartment 111 shown in FIG. 1.

[0041] The check valve 27 is a check valve that allows the refrigerant to flow from the first evaporator 26 side toward the compressor 20 side and blocks the refrigerant from flowing from the compressor 20 side toward the first evaporator 26 side.

[0042] A second expansion valve 29 constituting a second pressure reducing section and a second evaporator 30 are provided in series from the upstream side to the downstream side of the second refrigerant passage 24. The second expansion valve 29 and the second evaporator 30 are housed in a second unit case 131 together with a second blower 132 to form the second cooling unit 13.

[0043] The second expansion valve 29 is configured so that the valve element opening (cross-sectional area of ​​the flow path) is adjustable. In this example, the second expansion valve 29 is a thermostatic expansion valve having a mechanical mechanism that changes the throttle opening by deforming in accordance with the temperature and pressure of the refrigerant on the outlet side of the second evaporator 30, thereby adjusting the refrigerant flow rate to the second evaporator 30 and maintaining the temperature of the refrigerant on the outlet side of the second evaporator 30 at a predetermined value. Specifically, the second expansion valve 29 is a thermostatic expansion valve that has a temperature-sensing part that has a deformable member (so-called diaphragm) that deforms in accordance with the temperature and pressure of the refrigerant on the outlet side of the second evaporator 30, and a valve element part that changes the throttle opening by displacing in accordance with the deformation of the deformable member.

[0044] The second expansion valve 29 increases the throttle opening degree as the temperature of the refrigerant on the outlet side of the second evaporator 30 increases, and decreases the throttle opening degree as the temperature of the refrigerant on the outlet side of the second evaporator 30 decreases. As a result, when the temperature of the refrigerant on the outlet side of the second evaporator 30 increases, the refrigerant flow rate to the second evaporator 30 increases and the temperature of the refrigerant on the outlet side of the second evaporator 30 decreases, and when the temperature of the refrigerant on the outlet side of the second evaporator 30 decreases, the refrigerant flow rate to the second evaporator 30 decreases and the temperature of the refrigerant on the outlet side of the second evaporator 30 increases.

[0045] A low-pressure refrigerant decompressed by the second expansion valve 29 flows into the second evaporator 30, and this low-pressure refrigerant absorbs heat from the air blown by the second blower 132 and evaporates, thereby cooling the air. The blown air (cold air) cooled by the second evaporator 30 is blown into the second refrigerated compartment 112 shown in FIG. 1.

[0046] A junction Z2 where the first refrigerant passage 23 and the second refrigerant passage 24 join is provided downstream of the first evaporator 26 and the second evaporator 30. The gas-phase refrigerant that joins at the junction Z2 is drawn into the compressor 20.

[0047] The control device 50 has a well-known microcomputer including a CPU, ROM, RAM, etc., and its peripheral circuits. The control device 50 performs various calculations and processes based on a control program stored in the ROM. The control device 50 is a control unit that controls the operation of various control target devices connected to the output side based on the calculation and processing results.

[0048] The first fan 122, the second fan 132, the on-off valve 28, etc. are connected to the output side of the control device 50. The control device 50 controls the on / off switching (in other words, operation / stop) of the first fan 122 and the second fan 132. The control device 50 controls the opening and closing of the on-off valve 28.

[0049] A group of control sensors is connected to the input side of the control device 50. The group of control sensors includes a first intake air temperature sensor 71, a second intake air temperature sensor 72, etc. The first intake air temperature sensor 71 is an intake air temperature detection unit (first intake air temperature detection unit) that detects the temperature of air taken into the first evaporator 26 (hereinafter referred to as the first intake air temperature Ts1). The second intake air temperature sensor 72 is an intake air temperature detection unit (second intake air temperature detection unit) that detects the temperature of air taken into the second evaporator 30 (hereinafter referred to as the second intake air temperature Ts2).

[0050] The control device 50 does not necessarily have to be a single control device, but may be made up of multiple control devices (for example, a main control device and a sub-control device), with the control processing being shared among the multiple control devices.

[0051] 3 is a flowchart showing a control process related to switching of the cooling mode of the refrigeration cycle among the control processes executed by the control device 50. First, in step S100, it is determined whether the first intake air temperature Ts1 is equal to or higher than a first switching temperature α1. The first switching temperature α1 is, for example, −18° C.

[0052] If it is determined in step S100 that the first intake air temperature Ts1 is equal to or higher than the first switching temperature α1, the process proceeds to step S110, where the cooling mode of the refrigeration cycle is switched to the first cooling mode. In the first cooling mode, the first fan 122 is turned on, the second fan 132 is turned off, and the on-off valve 28 is opened.

[0053] Therefore, in the first cooling mode, refrigerant flows through the first expansion valve 25 and the first evaporator 26 of the first refrigerant passage 23, and the air in the first refrigerated compartment 111 is cooled by the first evaporator 26, but the air in the second refrigerated compartment 112 is not blown to the second evaporator 30, and therefore the air in the second refrigerated compartment 112 is hardly cooled by the second evaporator 30. Immediately after switching to the first cooling mode, refrigerant flows through the second expansion valve 29 and the second evaporator 30 of the second refrigerant passage 24, but because the second blower 132 is turned off, the temperature of the second evaporator 30 (in other words, the temperature and pressure of the refrigerant on the outlet side of the second evaporator 30) drops, and the second expansion valve 29 is throttled to an opening that is almost closed, and almost no refrigerant flows through the second expansion valve 29 and the second evaporator 30.

[0054] If it is determined in step S100 that the first intake air temperature Ts1 is lower than the first switching temperature α1, the process proceeds to step S120, where the cooling mode of the refrigeration cycle is switched to the second cooling mode. In the second cooling mode, the first fan 122 is turned off, the second fan 132 is turned on, and the on-off valve 28 is closed.

[0055] Therefore, in the second cooling mode, refrigerant flows through the second expansion valve 29 and the second evaporator 30 of the second refrigerant passage 24, and the air in the second cold storage compartment 112 is cooled by the second evaporator 30, whereas refrigerant does not flow through the first expansion valve 25 and the first evaporator 26 of the first refrigerant passage 23, and therefore the air in the first cold storage compartment 111 is not cooled by the first evaporator 26. At this time, the check valve 27 prevents the refrigerant that has flowed out of the second evaporator 30 in the second refrigerant passage 24 from flowing back into the first evaporator 26 via the junction Z2.

[0056] In the next step S130, it is determined whether the first intake air temperature Ts1 is equal to or higher than the second switch temperature α2. The second switch temperature α2 is a temperature higher than the first switch temperature α1, and is, for example, -16°C.

[0057] If it is determined in step S130 that the first intake air temperature Ts1 is lower than the second switching temperature α2, step S130 is repeated, thereby maintaining the second cooling mode.

[0058] If it is determined in step S130 that the first intake air temperature Ts1 is equal to or higher than the second switching temperature α2, the process proceeds to step S110, where the mode is switched to the first cooling mode.

[0059] An example of operation in the above configuration will be described using the time chart in Figure 4. The refrigeration cycle is started when the compressor 20 is driven to rotate by the vehicle engine via the electromagnetic clutch. Immediately after the refrigeration cycle is started, the first intake air temperature Ts1 is approximately the same as the outside air temperature and is therefore equal to or higher than the first switch temperature α1, so the cooling mode of the refrigeration cycle becomes the first cooling mode. That is, the first blower 122 is turned on, the second blower 132 is turned off, and the on-off valve 28 is opened.

[0060] As a result, refrigerant flows through first expansion valve 25 and first evaporator 26, and first evaporator 26 cools the air in first refrigerated compartment 111, lowering its temperature. However, because air from second refrigerated compartment 112 is not blown to second evaporator 30, second evaporator 30 hardly cools the air in second refrigerated compartment 112. Refrigerant decompressed by second expansion valve 29 flows through second evaporator 30, but as the temperature of second evaporator 30 (in other words, the temperature Te2 and pressure of the refrigerant on the outlet side of second evaporator 30) decreases over time, second expansion valve 29 is throttled to an opening that nearly closes it, and almost no refrigerant flows through second expansion valve 29 and second evaporator 30. In the first cooling mode, almost no air is cooled by second evaporator 30, so the refrigeration capacity of the refrigeration cycle is concentrated in first evaporator 26, and the temperature of the air in first refrigerated compartment 111 drops quickly.

[0061] When the air temperature in first refrigerated compartment 111 drops in the first cooling mode and first intake air temperature Ts1 becomes lower than first switching temperature α1 (−18° C. in this example), the cooling mode of the refrigeration cycle is switched to the second cooling mode. That is, first blower 122 is turned off, second blower 132 is turned on, and opening / closing valve 28 is closed.

[0062] As a result, air from second refrigerated compartment 112 is blown to second evaporator 30, causing the temperature of second evaporator 30 (in other words, the temperature Te2 and pressure of the refrigerant on the outlet side of second evaporator 30) to rise, and the throttle opening of second expansion valve 29 to increase. As a result, refrigerant decompressed by second expansion valve 29 flows to second evaporator 30, and the air in second refrigerated compartment 112 is cooled by second evaporator 30, causing the temperature to drop. Meanwhile, no refrigerant flows through first expansion valve 25 or first evaporator 26, so the air in first refrigerated compartment 111 is no longer cooled by first evaporator 26, and the temperature gradually rises. In second cooling mode, refrigerant does not flow through first evaporator 26 but flows primarily through second evaporator 30, causing the temperature of the air in second refrigerated compartment 112 to drop quickly.

[0063] In the second cooling mode, when the air temperature in first refrigerated compartment 111 gradually rises and first suction air temperature Ts1 becomes equal to or higher than second switching temperature α2 (−16° C. in this example), the cooling mode of the refrigeration cycle switches back to the first cooling mode. As a result, the air in first refrigerated compartment 111 is cooled by first evaporator 26 and its temperature drops, while the air in second refrigerated compartment 112 is hardly cooled by second evaporator 30.

[0064] The first switching temperature α1 and the second switching temperature α2 are set so that the temperature of the second refrigerated compartment 112 when switching from the second cooling mode to the first cooling mode is approximately the required refrigeration temperature (in this example, +5°C).

[0065] By repeating this switching between the first cooling mode and the second cooling mode, the temperature of first refrigerated compartment 111 is maintained at about -18°C, and the temperature of second refrigerated compartment 112 is maintained at about 5°C.

[0066] The refrigeration capacity of the entire refrigeration cycle is sufficient to cool first refrigerated compartment 111 to about -20°C, so even if the second cooling mode is performed for a short period of time, it is fully possible to maintain the temperature of second refrigerated compartment 112 at about 5°C. Therefore, by repeatedly switching between the first cooling mode and the second cooling mode, it is possible to maintain the temperature of first refrigerated compartment 111 at about -17°C while maintaining the temperature of second refrigerated compartment 112 at about 5°C.

[0067] Because the refrigeration capacity of the entire refrigeration cycle is first concentrated and used in first cold storage compartment 111, first cold storage compartment 111 can be cooled more quickly than when the refrigeration capacity of the entire refrigeration cycle is used simultaneously in both first cold storage compartment 111 and second cold storage compartment 112. Then, once first cold storage compartment 111 has cooled down, the refrigeration capacity of the entire refrigeration cycle is concentrated and used in second cold storage compartment 112, so second cold storage compartment 112 can be cooled more quickly. As a result, both first cold storage compartment 111 and second cold storage compartment 112 can be cooled more quickly than when the refrigeration capacity of the entire refrigeration cycle is used simultaneously in both first cold storage compartment 111 and second cold storage compartment 112.

[0068] (Second embodiment) In the above embodiment, the on-off valve 28 is disposed in the first refrigerant passage 23 in the refrigeration cycle, but in this embodiment, the on-off valve 28 is disposed in the second refrigerant passage 24 as shown in FIG.

[0069] In this embodiment, in the first cooling mode, the first fan 122 is turned on, the second fan 132 is turned off, and the on-off valve 28 is closed. Therefore, in the first cooling mode, refrigerant flows through the first expansion valve 25 and the first evaporator 26 of the first refrigerant passage 23, and the air in the first cold storage compartment 111 is cooled by the first evaporator 26, but refrigerant does not flow through the second expansion valve 29 and the second evaporator 30 of the second refrigerant passage 24, and therefore the air in the second cold storage compartment 112 is not cooled by the second evaporator 30.

[0070] In the present embodiment, in the second cooling mode, the first blower 122 is turned off, the second blower 132 is turned on, and the on-off valve 28 is opened. Therefore, in the second cooling mode, the refrigerant flows through the second expansion valve 29 and the second evaporator 30 of the second refrigerant passage 24, and the air in the second cold storage compartment 112 is cooled by the second evaporator 30. Immediately after switching to the second cooling mode, the refrigerant flows through the first expansion valve 25 and the first evaporator 26 of the first refrigerant passage 23, but because the first blower 122 is turned off, the temperature of the first evaporator 26 (in other words, the temperature and pressure of the refrigerant on the outlet side of the first evaporator 26) drops, and the first expansion valve 25 is throttled to an opening degree that nearly closes, and almost no refrigerant flows through the first expansion valve 25 and the first evaporator 26. At this time, the check valve 27 prevents the refrigerant that has flowed out of the second evaporator 30 in the second refrigerant passage 24 from flowing back into the first evaporator 26 via the junction Z2.

[0071] The control process for switching between the first and second cooling modes is the same as that of the first embodiment (FIG. 3). That is, the control device 50 implements the first cooling mode when the first intake air temperature Ts1 is equal to or higher than the first switching temperature α1, switches to the second cooling mode when the first intake air temperature Ts1 becomes lower than the first switching temperature α1, maintains the second cooling mode when the first intake air temperature Ts1 is lower than a second switching temperature α2 that is higher than the first switching temperature α1 in the second cooling mode, and switches to the first cooling mode when the first intake air temperature Ts1 becomes equal to or higher than the second switching temperature α2 in the second cooling mode.

[0072] In this manner, in this embodiment, as in the first embodiment, the temperature of first refrigerated compartment 111 is maintained at approximately −18° C. and the temperature of second refrigerated compartment 112 is maintained at approximately 5° C. by repeatedly switching between the first cooling mode and the second cooling mode. Therefore, this embodiment can also achieve the same effects as the first embodiment.

[0073] (Other embodiments) The present invention is not limited to the above-described embodiment, but can be modified in various ways as follows.

[0074] (1) In the above-described embodiment, a vapor compression subcritical cycle is described in which a refrigerant such as a fluorocarbon or hydrocarbon refrigerant whose high-pressure pressure does not exceed its critical pressure is used as the refrigerant. However, a refrigerant whose high-pressure pressure exceeds its critical pressure, such as carbon dioxide, may also be used as the refrigerant.

[0075] (2) In the above embodiment, the compressor 20 is rotationally driven by the vehicle engine. However, the compressor 20 may be driven by an electric motor. [Explanation of symbols]

[0076] 20 Compressor 21 Heatsink 25 First expansion valve (first pressure reducing section) 26 First evaporator 28 On-off valve 29 Second expansion valve (second pressure reducing section) 30 Second evaporator 50 Control device (control unit) 71 First intake air temperature sensor (intake air temperature detection unit) 111 First cold storage room 112 Second cold storage room 122 1st blower 132 2nd blower Ts1 No. 1 intake air temperature α1 First switching temperature α2 Second switching temperature

Claims

1. A refrigeration cycle used in a two-compartment refrigerator car having a first refrigerated compartment (111) that is kept cold and a second refrigerated compartment (112) that is kept cold at a temperature higher than that of the first refrigerated compartment (111), a compressor (20) for sucking and compressing a refrigerant; a radiator (21) for radiating heat from the refrigerant compressed by the compressor (20); a first pressure reducing section (25) and a second pressure reducing section (29) that are arranged in parallel with each other in the refrigerant flow and reduce the pressure of the refrigerant whose heat has been radiated in the radiator (21); a first evaporator (26) that evaporates the refrigerant decompressed in the first decompression section (25) and cools the air in the first cold storage compartment (111); a second evaporator (30) that evaporates the refrigerant decompressed in the second decompression section (29) and cools the air in the second cold storage compartment (112); an on-off valve (28) capable of interrupting the flow of the refrigerant to the first pressure reducing section (25) and the first evaporator (26); a check valve (27) for preventing the refrigerant flowing out of the second evaporator (30) from flowing back into the first evaporator (26); a first blower (122) for blowing air to the first evaporator (26); a second blower (132) for blowing air to the second evaporator (30); an intake air temperature detection unit (71) for detecting a first intake air temperature (Ts1) which is the temperature of air sucked into the first evaporator (26); a control unit (50) for switching between a first cooling mode in which the on-off valve (28) is opened, the first blower (122) is operated, and the second blower (132) is stopped, and a second cooling mode in which the on-off valve (28) is closed, the first blower (122) is stopped, and the second blower (132) is operated, the first pressure reducing section (25) is a temperature type expansion valve having a mechanical mechanism that changes its throttle opening by deforming in accordance with the temperature of the refrigerant at the outlet side of the first evaporator (26), The control unit (50) When the first intake air temperature (Ts1) is equal to or higher than a first switching temperature (α1), the first cooling mode is performed; When the first intake air temperature (Ts1) becomes lower than the first switching temperature (α1), the cooling mode is switched to the second cooling mode. When the first intake air temperature (Ts1) is lower than a second switching temperature (α2) that is higher than the first switching temperature (α1) in the second cooling mode, the second cooling mode is maintained; The refrigeration cycle for a dual-compartment refrigerated vehicle switches to the first cooling mode when the first intake air temperature (Ts1) becomes equal to or higher than a second switching temperature (α2) in the second cooling mode.

2. A refrigeration cycle used in a two-compartment refrigerator car having a first refrigerated compartment (111) that is kept cold and a second refrigerated compartment (112) that is kept cold at a temperature higher than that of the first refrigerated compartment (111), a compressor (20) for sucking and compressing a refrigerant; a radiator (21) for radiating heat from the refrigerant compressed by the compressor (20); a first pressure reducing section (25) and a second pressure reducing section (29) that are arranged in parallel with each other in the refrigerant flow and reduce the pressure of the refrigerant whose heat has been radiated in the radiator (21); a first evaporator (26) that evaporates the refrigerant decompressed in the first decompression section (25) and cools the air in the first cold storage compartment (111); a second evaporator (30) that evaporates the refrigerant decompressed in the second decompression section (29) and cools the air in the second cold storage compartment (112); an on-off valve (28) capable of interrupting the flow of the refrigerant to the second pressure reducing section (29) and the second evaporator (30); a check valve (27) for preventing the refrigerant flowing out of the second evaporator (30) from flowing back into the first evaporator (26); a first blower (122) for blowing air to the first evaporator (26); a second blower (132) for blowing air to the second evaporator (30); an intake air temperature detection unit (71) for detecting a first intake air temperature (Ts1) which is the temperature of air sucked into the first evaporator (26); a control unit (50) for switching between a first cooling mode in which the on-off valve (28) is closed, the first blower (122) is operated, and the second blower (132) is stopped, and a second cooling mode in which the on-off valve (28) is opened, the first blower (122) is stopped, and the second blower (132) is operated, the first pressure reducing section (25) is a temperature type expansion valve having a mechanical mechanism that changes its throttle opening by deforming in accordance with the temperature of the refrigerant at the outlet side of the first evaporator (26), The control unit (50) When the first intake air temperature (Ts1) is equal to or higher than a first switching temperature (α1), the first cooling mode is performed; When the first intake air temperature (Ts1) becomes lower than the first switching temperature (α1), the cooling mode is switched to the second cooling mode. When the first intake air temperature (Ts1) is lower than a second switching temperature (α2) that is higher than the first switching temperature (α1) in the second cooling mode, the second cooling mode is maintained; The refrigeration cycle for a dual-compartment refrigerated vehicle switches to the first cooling mode when the first intake air temperature (Ts1) becomes equal to or higher than a second switching temperature (α2) in the second cooling mode.

3. 3. The refrigeration cycle for a dual-chamber refrigerated vehicle according to claim 1, wherein the second switching temperature (α2) is set to a temperature lower than the refrigeration temperature of the second refrigerated compartment (112).

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