Refrigerant cycle device with ejector

Abstract

A refrigerant cycle device having an ejector includes a first evaporator for evaporating refrigerant flowing out of the ejector, a first passage portion for guiding refrigerant to a refrigerant suction port of the ejector, a throttle unit located in the first passage portion, a second evaporator located in the first passage portion downstream of the throttle unit, a bypass passage portion for guiding hot gas refrigerant from a compressor into the second evaporator, a bypass opening and closing unit provided in the bypass passage portion. Furthermore, a second passage portion is branched from the bypass passage portion downstream of the bypass opening and closing unit, and a flow control unit is provided in the second passage portion to prevent a flow of refrigerant from the first evaporator to the second evaporator through the second passage portion. Therefore, defrosting of both the first and second evaporators can be suitably performed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Additional objects and advantages of the present invention will be more readily apparent from the following detailed description of preferred embodiments when taken together with the accompanying drawings. In which:

FIG. 1 is a schematic diagram showing a refrigerant cycle device in a cooling mode according to a first embodiment of the present invention;

FIG. 2 is a schematic diagram showing the refrigerant cycle device in a defrosting mode according to the first embodiment;

FIG. 3 is a graph showing a relationship between a refrigerant pressure, a refrigerant temperature and an enthalpy in a refrigerant cycle operation, according to the first embodiment;

FIG. 4 is a graph showing a relationship between a refrigerant pressure and an enthalpy in a refrigerant cycle, according to the first embodiment;

FIG. 5 is a graph showing a time required for a defrosting operation and a time required for a cool-down of a refrigerating operation, in the first embodiment and in a comparative example;

FIG. 6 is a schematic diagram showing a refrigerant cycle device in a cooling mode according to a second embodiment of the present invention;

FIG. 7 is a schematic diagram showing the refrigerant cycle device in a defrosting mode according to the second embodiment;

FIG. 8 is a schematic diagram showing a refrigerant cycle device in a cooling mode according to a third embodiment of the present invention;

FIG. 9 is a schematic diagram showing the refrigerant cycle device in a defrosting mode according to the third embodiment;

FIG. 10 is a graph showing a relationship between an open degree of a flow adjusting valve and a refrigerant temperature, according to the third embodiment;

FIG. 11 is a schematic diagram showing a refrigerant cycle device in a cooling mode according to a fourth embodiment of the present invention;

FIG. 12 is a schematic diagram showing the refrigerant cycle device in a defrosting mode according to the fourth embodiment;

FIG. 13 is a schematic diagram showing a refrigerant cycle device in a cooling mode according to a fifth embodiment of the present invention;

FIG. 14 is a schematic diagram showing the refrigerant cycle device in a defrosting mode according to the fifth embodiment;

FIG. 15 is a schematic diagram showing a refrigerant cycle device according to a sixth embodiment of the present invention;

FIG. 16A is a schematic front view showing a first evaporator, and FIG. 16B is a schematic front view showing a second evaporator, according to the sixth embodiment;

FIG. 17 is a graph showing a relationship between a refrigerant pressure and an enthalpy during a defrosting mode in a refrigerant cycle, according to the sixth embodiment;

FIG. 18A and FIG. 18B are graphs showing a defrosting time ratio obtained when an outside air temperature (TAM) is 35° C. and when the outside air temperature (TAM) is 0° C. in a case where the flow resistant of refrigerant is identical, according to the sixth embodiment;

FIG. 19A is a schematic front view showing a first evaporator, and FIG. 19B is a schematic front view showing a second evaporator, according to a seventh embodiment of the present invention;

FIG. 20A is a schematic front view showing a first evaporator, and FIG. 20B is a schematic front view showing a second evaporator, according to an eighth embodiment of the present invention; and

FIG. 21 is a schematic diagram showing a refrigerant cycle device according to a ninth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

A first embodiment of the present invention will be now described with reference to FIGS. 1 to 5.

FIG. 1 illustrates an example in which a vapor-compression refrigerant cycle device 10 of the first embodiment is typically used for a refrigeration cycle of an air conditioner for vehicles. The refrigerant cycle device 10 is provided with a refrigerant circulation passage 11, and a compressor 12 that sucks in and compresses refrigerant is located in the refrigerant circulation passage 11.

The compressor 12 is rotationally driven by a vehicle running engine, not shown, through a belt or the like. For the compressor 12, a variable displacement compressor whose refrigerant discharging capacity can be adjusted by change in a discharge capacity may be used. A discharge capacity of refrigerant discharged from the compressor 12 is equivalent to a refrigerant discharge quantity per rotation. The discharge capacity can be changed by changing a capacity for sucking in refrigerant.

A swash plate compressor can be used as the variable displacement compressor 12. For example, the swash plate compressor can be so constructed that the capacity for sucking in refrigerant is changed by changing the angle of a swash plate to change a piston stroke. The angle of the swash plate is externally electrically controlled by varying the pressure (control pressure) in a swash plate chamber. This control can be carried out through an electromagnetic pressure control device (not shown) that constructs a displacement control mechanism.

A radiator 13 is located downstream of the compressor 12 with respect to the flow of refrigerant. The radiator 13 exchanges heat between high-pressure refrigerant discharged from the compressor 12 and outside air (i.e., air outside the vehicle compartment) sent by a cooling fan. Thus, the radiator 13 cools the high-pressure refrigerant discharged from the compressor 12.

An ejector 14 is located downstream of the radiator 13 with respect to the flow of refrigerant. This ejector 14 has a nozzle section 14a as decompressing means for reducing the pressure of refrigerant. At the same time, the ejector 14 is used as a kinetic vacuum pump that conveys fluid by suction due to a high-speed flow of refrigerant jetted from the nozzle section 14a.

The ejector 14 includes the nozzle section 14a and a suction port (refrigerant suction port) 14c. The nozzle section 14a reduces the area of the passage of high-pressure refrigerant flowing from the radiator 13 so as to isentropically decompress and expand the high-pressure refrigerant. The refrigerant suction port 14c is so provided that it communicates with the refrigerant jet hole of the nozzle section 14a and sucks in refrigerant from a second evaporator 19 described later.

Further, at a downstream side of the nozzle section 14a and the refrigerant suction port 14c with respect to the flow of refrigerant, there is provided a diffuser section 14b that forms a pressurizing section in the ejector 14. This diffuser section 14b is formed in such a shape that the area of the refrigerant passage is gradually increased. Therefore, the diffuser section 14b functions to decelerate the flow of refrigerant so as to increase the refrigerant pressure, that is, to convert the velocity energy of refrigerant into pressure energy.

Refrigerant that flowed out of the diffuser section 14b of the ejector 14 flows into a first evaporator 15. The first evaporator 15 is located in, for example, an air duct of a vehicle air conditioning unit (not shown), and functions to cool the interior of a vehicle compartment.

More specific description will be given. Air to be blown into the vehicle compartment is sent to the first evaporator 15 by the electric blower, and is cooled in the first evaporator 15 by evaporating refrigerant depressurized at the nozzle section 14a of the ejector 14. That is, low-pressure refrigerant from the ejector 14 absorbs heat from the air to be blown into the vehicle compartment, and is evaporated in the first evaporator 15. Thus, the air to be blown into the vehicle compartment is cooled, and cooling capacity can be obtained by the evaporator 15. The vapor-phase refrigerant evaporated at the first evaporator 15 is sucked into the compressor 12, and circulates through the refrigerant circulation passage 11 again.

In the vapor-compression refrigerant cycle device 10 using the ejector 14 of this embodiment, there is formed a first branch passage 17. The first branch passage 17 branches at an area in the refrigerant circulation passage 11 between the radiator 13 and the nozzle section 14a of the ejector 14. Then, the first branch passage 17 is joined to the refrigerant circulation passage 11 at the refrigerant suction port 140 of the ejector 14. This branch passage 17 is also referred to as a passage for guiding refrigerant into the refrigerant suction port 14c of the ejector 14. In the high-pressure passage of the refrigeration cycle, the branch passage 17 branches from the pipe located downstream of the radiator 13 where a relatively large quantity of liquid refrigerant exists. In this embodiment, the branch portion 16 located downstream of the radiator 13 forms a liquid refrigerant supply section. In this branch passage 17, there is located a throttling mechanism 18 for depressurizing refrigerant with a predetermined throttling open degree. The throttling mechanism 18 provides throttling means in the branch passage 17.

A second evaporator 19 is located downstream of this throttling mechanism 18 with respect to the flow of refrigerant. This second evaporator 19 is located in, for example, a refrigerator (not shown) mounted in the vehicle, and cools the air in the refrigerator, sent by an electric blower.

A temperature sensor 22 is located at a position in proximity to the second evaporator 19. The temperature of air in proximity to the second evaporator 19 is detected with this temperature sensor 22, and a temperature signal obtained by this detection of the temperature sensor 22 is inputted to an electrical control unit 21 (ECU).

A bypass passage 23 is provided between the refrigerant circulation passage 11 and the branch passage 17. The bypass passage 23 is a passage for letting high-temperature refrigerant, discharged from the compressor 12, flow directly into the second evaporator 19. Specifically, the bypass passage 23 is formed as a passage connected to the passage area between the compressor 12 and the radiator 13 and the passage area between the throttling mechanism 18 and the second evaporator 19, as shown in FIGS. 1 and 2.

An opening and closing device 24 (switching device) is located at a position in the bypass passage 23. The opening and closing device 24 switches the bypass passage 23 between substantial refrigerant circulated state and refrigerant blocked state, and is also referred to as switching means. The opening and closing device 24 may include a valve mechanism in which the opening/closing is controlled by the electrical control unit 21. It is normally controlled into a closed state and the circulation of refrigerant in the bypass passage 23 is blocked. The opening and closing device 24 is so constructed that when it is opened, it depressurizes high-pressure and high-temperature refrigerant from the compressor 12 and lets the refrigerant through with a predetermined throttling opening.

A second branch passage 25 is formed to be branched from the bypass passage 23 at a position downstream of the opening and closing device 24, and is connected to an inlet side of the first evaporator 15. The second branch passage 25 is a passage through which the bypass passage 23 can directly communicate with the first evaporator 15. In this branch passage 25, there is provided a check valve 26a (flow control unit, backward flow preventing means). The check valve 26a permits the flow of refrigerant from the opening and closing device 24 side to the first evaporator 15 side. At the same time, it prevents the backward flow of refrigerant from the first evaporator 15 side to the opening and closing device 24 (second evaporator 19) side. In this embodiment, the second branch passage 25 branched from the bypass passage 23 at a downstream side of the opening and closing device 24 is joined to the refrigerant circulation passage 11 at a position between the refrigerant outlet of the ejector 14 and the refrigerant inlet of the first evaporator 15.

Downstream of the radiator 13 and upstream of the branch portion 16 of the branch passage 17, there is located an opening and closing device 31 in which the opening/closing is controlled by the electrical control unit 21. The opening and closing device 31 is also referred to as opening and closing means for opening and closing the refrigerant flow from the radiator 13. When the opening and closing device 31 is closed, the opening and closing device 31 substantially blocks the flow of refrigerant in the major path of the radiator 13 in the refrigeration cycle.

Description will be given to the operation of the vapor-compression refrigerant cycle device 10 based on the above construction.

1. Cooling Mode (FIG. 1)

FIG. 1 illustrates the flow of refrigerant (solid line arrows) in the cooling mode. In the cooling mode, the opening and closing device 24 is closed and the opening and closing device 31 is opened by the electrical control unit 21. When the compressor 12 is driven by the vehicle engine, the refrigerant compressed by the compressor 12 and brought into high temperature and high pressure state flows into the radiator 13. The high temperature and high pressure refrigerant is cooled in the radiator 13 by the outside air and is condensed therein. After flowing out of the radiator 13, the high-pressure liquid refrigerant flows through the opening and closing device 31, and then is divided into a refrigerant stream that goes from the branch portion 16 to the refrigerant circulation passage 11 and a refrigerant stream that goes through the branch passage 17 from the branch portion 16.

The refrigerant that flows through the branch passage 17 is depressurized at the throttling mechanism 18 and brought into low pressure state. This low-pressure refrigerant absorbs heat from the air in the refrigerator, sent by the electric blower, and is evaporated in the second evaporator 19. Thus, the second evaporator 19 functions to cool the interior of the refrigerator.

The refrigerant that flows through the refrigerant circulation passage 11 flows into the nozzle section 14a of the ejector 14, and is depressurized and expanded at the nozzle section 14a. Therefore, the pressure energy of the refrigerant is converted into velocity energy at the nozzle section 14a. The refrigerant is jetted out of the nozzle jet port, thereby a pressure around the nozzle jet port is reduced. At this time, the vapor-phase refrigerant evaporated at the second evaporator 19 is sucked in through the refrigerant suction port 14c by reduction in the pressure in proximity to the nozzle jet port.

The refrigerant jetted out of the nozzle section 14a and the refrigerant sucked from the refrigerant suction port 140 are mixed together downstream of the nozzle section 14a, and flow into the diffuser section 14b. At the diffuser section 14b, the velocity (expansion) energy of the refrigerant is converted into pressure energy due to increase in the area of the passage. This increases the pressure of the refrigerant in the diffuser section 14b. The refrigerant flowing out of the diffuser section 14b of the ejector 14 flows into the first evaporator 15.

At the first evaporator 15, the refrigerant absorbs heat from the conditioning air to be blown into the vehicle compartment by the electric blower, and is evaporated. Thus, the first evaporator 15 functions to cool the interior of the vehicle compartment. The evaporated vapor-phase refrigerant is sucked into the compressor 12 and compressed therein, and circulates through the refrigerant circulation passage 11 again. At this time, an electromagnetic pressure control unit may control the displacement of the compressor 12, so as to control the refrigerant discharging capacity of the compressor 12.

Therefore, the cooling capacity for cooling a space to be cooled, for example, the cooling capacity for cooling the interior of the vehicle compartment can be obtained by the first evaporator 15. The flow amount of refrigerant to the first evaporator 15 is adjusted and further the number of revolutions (blast quantity) of the electric blower is controlled, so that the cooling capacity can be controlled.

The refrigerant evaporating pressure of the first evaporator 15 is a pressure obtained by pressurizing the refrigerant at the diffuser section 14b of the ejector 14. The outlet of the second evaporator 19 is connected to the refrigerant suction port 14c of the ejector 14. Therefore, it is possible to apply the lowest pressure obtained immediately after depressurization at the nozzle section 14a, to the second evaporator 19.

Therefore, the refrigerant evaporating pressure (refrigerant evaporating temperature) of the second evaporator 19 can be made lower than the refrigerant evaporating pressure (refrigerant evaporating temperature) of the first evaporator 15. As a result, the first evaporator 15 can be caused to obtain cooling action in a relatively high-temperature range suitable for cooling the interior of the vehicle compartment. At the same time, the second evaporator 19 can be caused to obtain cooling action in an even lower-temperature range suitable for cooling the interior of the refrigerator.

In the cooling mode, the pressure at the first evaporator 15 is made higher than that at the second evaporator 19 due to the pressurizing action of the ejector 14. In this vapor-compression refrigerant cycle device 10, the flow of refrigerant from the first evaporator 15 to the second evaporator 19 can be blocked by the check valve 26a installed in the branch passage 25. Therefore, the cooling mode can be carried out in the refrigerant cycle device 10, thereby performing cooling operation using the first evaporator 15 and the second evaporator 19.

2. Defrosting Mode (FIG. 2)

FIG. 2 illustrates the flow of refrigerant (broken line arrows) in the defrosting mode. In the above-mentioned cooling mode, the evaporators 15, 19 may be operated under the condition that the refrigerant evaporating temperature is lower than 0° C. Therefore, degradation in cooling capacity is caused due to frost (formation of frost) on each evaporator 15, 19.

In this embodiment, each evaporator 15, 19 can be automatically defrosted by the control operation of the electrical control unit 21. For example, the electrical control unit 21 determines presence or absence of frosting in the second evaporator 19 based on the temperature detected by the temperature sensor 22 provided in proximity to the second evaporator 19. Then, the electrical control unit 21 performs the defrosting mode for the evaporators 15, 19 when the electrical control unit 21 determines the frosting in the second evaporator 19

When the temperature of air immediately after passing through the second evaporator 19, detected by the temperature sensor 22, lowers to a value lower than a preset frost determination temperature Ta, the electrical control unit 21 determines that the second evaporator 19 is frosted, and the opening and closing device 24 is opened and the opening and closing device 31 is closed.

Then, the high-temperature refrigerant discharged from the compressor 12 flows into the bypass passage 23 while bypassing the radiator 13. At the same time, the flow of refrigerant from the downstream side of the radiator 13 to the nozzle section 14a of the ejector 14 and to the throttling mechanism 18 is blocked.

The high-temperature refrigerant that has flowed into the bypass passage 23 is depressurized by the opening and closing device 24 having a throttle function. Further, the depressurized refrigerant from the opening and closing device 24 flows into the second evaporator 19 through the bypass passage 23, and flows into the first evaporator 15 through the branch passage 25. At this time, each evaporator 15, 19 functions as a refrigerant radiator that radiates heat from the high-temperature refrigerant, and thus removes frost. The refrigerant flowing out of the second evaporator 19 flows through the refrigerant suction port 14c of the ejector 14, and meets the high-temperature refrigerant from the branch passage 25 and flows into the first evaporator 15.

In a comparative example where a hot gas refrigerant cycle is constructed without the above branch passage 25 and the check valve 26, as illustrated in FIG. 3 and FIG. 4, the high-temperature refrigerant discharged from the compressor 12 flows by the following route: from the second evaporator inlet “a”, to the second evaporator outlet “b”, to the ejector 14, to the first evaporator inlet “c”, and to the first evaporator outlet “d”. Thus, in the hot gas refrigerant cycle of the comparative example, the flow of refrigerant is in series with the first and second evaporators 15, 19. Thus, in the comparative example, because the ejector 14 resists to the flow of refrigerant, the refrigerant pressure P1a is accordingly raised at the second evaporator inlet “a,”. Therefore, the second evaporator inlet temperature T1 becomes accordingly higher relative to the first evaporator inlet temperature T2, and the temperature difference is prone to be increased.

In contrast, this embodiment adopts the cycle construction described in relation to FIG. 1 and FIG. 2. The high-temperature refrigerant discharged from the compressor 12 in the defrosting mode can be thereby divided and caused to flow into the second evaporator 19 and the first evaporator 15. More specific description will be given. In the related art (comparative example), all the flow amount G of refrigerant from the compressor 12 flows to the first and second evaporators 15, 19 in series. In this embodiment, the flow amount G2 of refrigerant from the second evaporator 19 to the ejector 14 is equivalent to a flow amount that is obtained by subtracting the flow amount G1 of refrigerant flowing to the branch passage 25 from the flow amount G of refrigerant from the compressor (G2=G−G1). Thus, the flow amount of refrigerant passing through the second evaporator 19 and the ejector 14 can be reduced relative to the total flow amount G of refrigerant discharged from the compressor 12, in the defrosting mode. Therefore, the flow resistance caused in the ejector 14 can be reduced, and the refrigerant pressure at the second evaporator 19 can be reduced from P1a in the comparative example to P1e, as shown in FIG. 4. In this embodiment, the second evaporator inlet is plotted in the position marked with “e” (refrigerant temperature line T3), and the plotting position of the second evaporator outlet is shifted to that marked with “f.”

The flow of refrigerant with the flow amount of G1, guided from the bypass passage 23 to the branch passage 25 and to the inlet of the first evaporator 15, is mixed with the flow of refrigerant with the flow amount of G2 that flowed from the second evaporator outlet “f” and passed through the ejector 14. Then, it is brought into the state of enthalpy at the first evaporator inlet “g” where the enthalpy is higher than at the first evaporator inlet “c” in the comparative example. For this reason, the inlet temperature of the first evaporator 15 of this embodiment becomes higher than the first evaporator temperature T2 in the comparative example and comes close to the inlet temperature T2 of the second evaporator. Thus, in the first embodiment, the temperature difference between the first and second evaporators 15, 19 can be reduced as the whole as compared with the comparative example. As a result, degradation in refrigeration capacity after the defrosting mode and degradation in cool-down speed can be suppressed. The time required for cool-down (i.e., cooling in FIG. 5) after a restart of the cooling mode can be reduced by reducing the temperature difference between the first and second evaporator 15, 19. In the first embodiment, time reduction of approximately four minutes can be obtained as compared with the comparative example without the branch passage 25, as illustrated in FIG. 5.

In this embodiment, the opening and closing device 31 is provided downstream of the radiator 13, such that the opening and closing device 31 is closed in the defrosting mode. Therefore, the amount of flow of high-temperature refrigerant caused to flow from the compressor 12 directly into the second evaporator 19 and the first evaporator 15 can be increased. As a result, the defrosting mode can be effectively carried out.

Second Embodiment

FIG. 6 and FIG. 7 illustrate a second embodiment of the invention. The second embodiment is implemented by replacing the check valve 26a in the first embodiment with an on-off switching valve 26b (flow control unit, backward flow preventing means).

The on-off switching valve 26b is a valve installed in the branch passage 25, the opening/closing of which is controlled by the electrical control unit 21. For example, the on-off switching valve 26b is so constructed that: it is closed when the opening and closing device 24 in the bypass passage 23 is closed in the cooling mode; and it is opened when the opening and closing device 24 is opened in the defrosting mode.

In the second embodiment, the other parts of the refrigerant cycle device 10 can be made similar to those of the above described first embodiment.

Thus, the flow of refrigerant (solid line arrows) illustrated in FIG. 6 can be formed in the cooling mode; and the flow of refrigerant (broken line arrows) illustrated in FIG. 7 is formed in the defrosting mode, similarly to the above-described first embodiment. Accordingly, the same operation as in the first embodiment and its action and effect can be obtained.

Third Embodiment

FIG. 8 to FIG. 10 illustrate a third embodiment of the invention. In the third embodiment, a flow adjusting valve 26c (flow control unit, backward flow preventing means) is used instead of the check valve 26a of the first embodiment; a temperature detector 27 for directly or indirectly detecting the refrigerant temperature on the refrigerant inlet side of the first evaporator 15 is provided; and a temperature detector 28 for directly or indirectly detecting the refrigerant temperature on the outlet side of the second evaporator 19 is provided. The flow adjusting valve 26c is located to adjust a flow amount of refrigerant flowing through the branch passage 25. An open degree of the flow adjusting valve 26c is set zero in the cooling mode. The temperature detector 27 is located to detect the refrigerant temperature flowing into the first evaporator 15. The temperature detector 28 is located to detect the refrigerant temperature flowing out of the second evaporator 19.

The flow adjusting valve 26c has its valve opening controlled by the electrical control unit 21. The flow adjusting valve 26c has a valve closing function with which it closes the branch passage 25 completely. The flow adjusting valve 26c has a flow regulating function with which its valve open degree is adjusted when it is opened and adjusts the flow amount of refrigerant flowing through the branch passage 25.

The temperature detectors 27, 28 are temperature sensors that respectively directly detect the inlet-side refrigerant temperature of the first evaporator 15 and the outlet-side refrigerant temperature of the second evaporator 19. Temperature signals obtained as the result of detection by the temperature detectors 27, 28 are inputted to the electrical control unit 21.

In the third embodiment, in the cooling mode, the electrical control unit 21 closes the opening and closing device 24, brings the flow adjusting valve 26c into the closed state, and opens the opening and closing device 31. Thus, the flow of refrigerant (solid line arrows) illustrated FIG. 8 is formed.

In the defrosting mode, the electrical control unit 21 opens the opening and closing device 24, brings the flow adjusting valve 26c into an open state, and closes the opening and closing device 31. Thus, the flow of refrigerant (broken line arrows) illustrated in FIG. 9 is formed.

The electrical control unit 21 adjusts the valve open degree of the flow adjusting valve 26c according to temperature signals obtained from the temperature detectors 27, 28. More specific description will be given. In the graph of FIG. 10, the inlet-side refrigerant temperature of the first evaporator 15 is referred to as T4, and the outlet-side refrigerant temperature of the second evaporator 19 is referred to as T5. The electrical control unit 21 compares these refrigerant temperatures T4, T5 with each other, and operates as follows: the more the refrigerant temperature T4 is lower than the refrigerant temperature T5, that is, the more the value of (T5−T4) is increased, the electrical control unit 21 adjusts and brings the valve open degree of the flow adjusting valve 26c closer to the full open position; conversely, the more the refrigerant temperature T4 is higher than the refrigerant temperature T5, that is, the more the absolute value of (T5−T4) is increased, the electrical control unit 21 adjusts and brings the valve open degree of the flow adjusting valve 26c closer to the full closed position.

Thus, in the defrosting mode, more high-temperature refrigerant can be let to flow into the evaporator (either 15 or 19) at which the refrigerant temperature is lower of the first evaporator 15 and the second evaporator 19. Therefore, the defrosting mode can be effectively carried out, and further a defrosting time can be shortened.

In this example of FIGS. 9 and 10, the temperature detectors 27, 28 for directly detecting respective refrigerant temperatures, that is, temperature sensors are used as inlet-side temperature detecting means for detecting the refrigerant temperature at the refrigerant inlet side of the first evaporator 15, and outlet-side temperature detecting means for detecting the refrigerant temperature at the refrigerant outlet side of the second evaporator 19. Instead of that, the pressure of refrigerant can be detected using pressure sensors at the refrigerant inlet side of the first evaporator 15 and at the refrigerant outlet side of the second evaporator 19, and a refrigerant temperature corresponding to the pressure can be computed and determined based on a preset map having the relationship between the refrigerant pressure and the refrigerant temperature. Furthermore, a temperature sensor may be used for one of the temperature detectors 27, 28, and a pressure sensor may be used for the other one.

Fourth Embodiment

FIG. 11 and FIG. 12 illustrate a fourth embodiment of the invention. The fourth embodiment is constructed by adding a branch passage (i.e., third branch passage) 29 and a check valve 30a (flow control unit, backward flow preventing means), to the refrigerant cycle device 10 of the first embodiment. The check valve 30a is located to only allow a refrigerant flow from the refrigerant outlet side of the second evaporator 19 to the refrigerant inlet side of the first evaporator 15.

The branch passage 29 is branched from a refrigerant downstream side of the second evaporator 19, that is, from a branch portion between the second evaporator 19 and the refrigerant suction port 14c of the ejector 14. At the same time, the branch passage 29 is connected to a refrigerant upstream side of the first evaporator 15 at a join portion between the refrigerant outlet of the ejector 14 and the refrigerant inlet of the first evaporator 15. The check valve 30a is provided in this branch passage 29, and permits the flow of refrigerant from the second evaporator 19 side to the first evaporator 15 side. At the same time, the check valve 30a prevents the backward flow of refrigerant from the first evaporator 15 side to the second evaporator 19 side.

In the cooling mode in the refrigerant cycle device of the fourth embodiment, the opening and closing device 24 is closed and the opening and closing device 31 is opened by the electrical control unit 21. Thus, the flow of refrigerant (solid line arrows) illustrated in FIG. 11 is formed. In the cooling mode, the refrigerant pressure on the first evaporator 15 side is higher than the refrigerant pressure on the second evaporator 19 side. Therefore, the refrigerant flowing out of the second evaporator 19 does not go through the branch passage 29 and flows through the ejector 14 through the refrigerant suction port 14c.

In the defrosting mode of the refrigerant cycle device 10 of the fourth embodiment, the opening and closing device 24 is opened and the opening and closing device 31 is closed by the electrical control unit 21. Thus, the flow of refrigerant (broken line arrows) illustrated in FIG. 12 is formed. In the defrosting mode, the level of the refrigerant pressure on the second evaporator 19 side is slightly higher than that on the first evaporator 15 side. As a result, the refrigerant flowing out of the second evaporator 19 bypasses the ejector 14, and goes through the branch passage 29 and the check valve 30a and flows into the first evaporator 15.

This makes it possible to prevent the high-temperature refrigerant that flows from the bypass passage 23 into the second evaporator 19 from encountering resistance from the ejector 14. Therefore, the refrigerant pressure at the second evaporator 19 can be further reduced, and the refrigerant temperature can be made more even between the first and second evaporators 15, 19 in the defrosting mode.

An on-off switching valve (second on-off switching valve) may be used instead of the check valve 30a, in the fourth embodiment. In this case, the opening/closing of the on-off switching valve provided in the branch passage 29 is controlled by the electrical control unit 21. For example, the on-off switching valve provided in the branch passage 29 is opened when the opening and closing device 24 is opened, and closed when the opening and closing device 24 is closed. Also, in this case, the same effect as mentioned above can be obtained.

Alternatively, a flow adjusting valve may be used instead of the check valve 30a, in the fourth embodiment. In this case, the flow adjusting valve can be closed and makes it possible to regulate the flow amount of refrigerant through adjustment of the valve opening.

In addition, the check valve 26a may be replaced with the on-off switching valve 26b or the flow adjusting valve 26c as in the second or third embodiment.

Fifth Embodiment

FIG. 13 and FIG. 14 illustrate a fifth embodiment of the invention. In the fifth embodiment, a vapor-compression refrigerant cycle device 10 includes: a gas-liquid separator 35 that is provided downstream of the first evaporator 15 in a refrigerant flow; and a branch passage 36 that is provided as a refrigerant passage between the gas-liquid separator 35 and the refrigerant suction port 14c of the ejector 14.

The gas-liquid separator 35 is a container body, for example. The gas-liquid separator 35 separates the refrigerant flowing out of the first evaporator 15 into vapor and liquid, and guides the vapor-phase refrigerant to the refrigerant suction side of the compressor 12 and collects the liquid-phase refrigerant therein.

The branch passage 36 is provided so that it is connected from a liquid-phase refrigerant outlet side of the gas-liquid separator 35 to the refrigerant suction port 14c of the ejector 14. In this embodiment, the liquid storing section of the gas-liquid separator 35 is used as a liquid refrigerant supply section for supplying liquid refrigerant into the branch passage 36. The throttling mechanism 18 and the second evaporator 19 are located in the branch passage 36, in this order from the gas-liquid separator 35 side of the branch passage 36. Further, an opening and closing device 32 is provided on the inlet side of the throttling mechanism 18, that is, between the gas-liquid separator 35 and the throttling mechanism 18. The opening and closing device 32 opens and closes the branch passage 36 under the control of the electrical control unit 21. The opening and closing device 32 may be provided downstream of the throttling mechanism 18 (between the throttling mechanism 18 and the second evaporator 19). Alternatively, the opening and closing device 32 may be combined with the throttling mechanism 18 to form an integrated structure.

In the vapor-compression refrigerant cycle device 10 of the fifth embodiment, during the cooling mode, the opening and closing device 24 is closed and the opening and closing devices 31, 32 are opened, by the electrical control unit 21. Thus, the flow of refrigerant (solid line arrows) illustrated in FIG. 13 is formed. More specific description will be given. The refrigerant flowing in the refrigerant circulation passage 11, goes through the nozzle section 14a of the ejector 14 from the radiator 13, flows out of the first evaporator 15, and is separated into vapor and liquid at the gas-liquid separator 35. Then, the vapor-phase refrigerant is sucked into the compressor 12 from the gas-liquid separator 35. The liquid-phase refrigerant in the gas-liquid separator 35 flows into the branch passage 36 and goes through the throttling mechanism 18 and the second evaporator 19. Then, the refrigerant after passing through the second evaporator 19 is sucked into the refrigerant suction port 14c of the ejector 14. Therefore, the first evaporator 15 is caused to perform a cooling operation in a relatively high-temperature range suitable for cooling the interior of the vehicle compartment as in the first embodiment. At the same time, the second evaporator 19 is caused to perform a cooling operation in an even lower-temperature range suitable for cooling the interior of the refrigerator as in the first embodiment.

In the defrosting mode of the refrigerant cycle device 10, the opening and closing device 24 is opened and the opening and closing devices 31, 32 are closed by the electrical control unit 21. Thus, the flow of refrigerant (broken line arrows) illustrated in FIG. 14 is formed. That is, the high-temperature refrigerant discharged from the compressor 12 flows into the bypass passage 23. At the same time, the flow of refrigerant from the downstream side of the radiator 13 to the nozzle section 14a of the ejector 14 is shut.

After flowing into the bypass passage 23 from the compressor 12, the high-temperature refrigerant is depressurized by the opening and closing device 24 with a predetermined throttle degree. The decompressed refrigerant from the opening and closing device 24 further flows from the bypass passage 23 into the second evaporator 19, and at the same time, flows from the branch passage 25 into the first evaporator 15. The refrigerant flowing out of the ejector 14 is mixed with the high-temperature refrigerant flowing from the branch passage 25, and the mixed refrigerant flows into the first evaporator 15.

Thus, in the refrigerant cycle device 10 of the fifth embodiment, the same flow of refrigerant as in the first embodiment can be formed. Therefore, the difference in refrigerant temperature between the evaporators 15, 19 can be reduced in the defrosting mode. As a result, degradation in refrigeration capacity after the defrosting mode and degradation in cool-down speed after restart of the cooling mode can be suppressed.

Modifications of Embodiments

In the above-described first to fifth embodiments, the opening and closing device 31 is provided on the refrigerant outlet side of the radiator 13. Instead, the opening and closing device 21 may be provided on the refrigerant inlet side of the radiator 13. Further, the radiator 13 may be so constructed that its heat radiating capacity is adjusted by the air quantity of the cooling fan, and the opening and closing device 31 may be omitted. In this case, in the defrosting mode, the air quantity blown by the cooling fan is zeroed so that the heat radiating capacity of the radiator 13 is adjusted to be approximately zeroed.

Furthermore, the branch point of the bypass passage 23 may be provided downstream of the radiator 13.

In the above-described first to fourth embodiments, a gas-liquid separator may be provided downstream of the first evaporator 15. In this case, the compressor 12 can suck in only vapor-phase refrigerant without fail, and the occurrence of liquid compression in the compressor 12 can be prevented.

Furthermore, in the above-described first to fifth embodiments, a temperature sensor may be provided in proximity to the first evaporator 15, and a control unit may be provided which controls the opening and closing device 24 to carry out frost prevention control based on the temperature detected by this temperature sensor. In this case, the control unit determines the state of frost formation in the first evaporator 15 and the amount of formed frost based on the temperature detected by the temperature sensor. When the control unit determines that the first evaporator is in frost formation state, that is, frosted, it opens the opening and closing device 24 and closes the opening and closing device 31 to perform the defrosting mode. Alternatively, the individual evaporators 15, 19 may be provided with a temperature sensor as means for detecting frost formation, and defrosting control may be independently carried out on an evaporator-by-evaporator basis. Further, instead of frost formation detection by a temperature sensor, the defrosting mode may be performed such that the opening and closing device 24 is opened and the opening and closing device 31 is closed at predetermined equal time intervals.

Sixth Embodiment

Hereafter, description will be given to a refrigerant cycle device in a sixth embodiment with reference to FIG. 15 to FIG. 18B.

In the sixth embodiment, the branch passage 25 and the check valve 26a described in the above first embodiment are not provided, as compared with the first embodiment. Therefore, during the defrosting mode, all refrigerant discharged from the compressor 12 flows into the second evaporator 19 through the bypass passage 23, and flows into the first evaporator 15 through the ejector 14.

In the sixth embodiment, the first evaporator 15 is located in, for example, a vehicle compartment to cool air to be blown into the vehicle compartment by a first blower 20A, and the second evaporator 19 is located in, for example, a refrigerator (not shown) mounted in a vehicle and functions to cool the interior of the refrigerator. This embodiment is so constructed that the air in the refrigerator is sent to the second evaporator 19 by a second blower 20B.

Furthermore, in the sixth embodiment, a variable displacement compressor 12 is used, arid a discharge capacity of refrigerant discharged from the variable displacement compressor 12 is controlled by an electromagnetic pressure control portion 12a in accordance with a control signal from the electrical control unit 21.

The bypass passage 23 that directly connects the refrigerant passage on the discharge side of the compressor 12 and the inlet portion of the second evaporator 19 is formed. A shutting mechanism 24 (opening and closing device) is provided in this bypass passage 23. Specifically, the shutting mechanism 24 can be constructed of a normally closed electromagnetic valve that is opened only when it is energized, for example.

This bypass passage 23 is a hot gas passage through which hot-gas refrigerant discharged from the compressor 12 can be directly introduced into the second evaporator 19. When the surface of the second evaporator 19 is frosted, the shutting mechanism 24 is opened to have a predetermined throttle so that the hot gas refrigerant discharged from the compressor 12 flows directly to the second evaporator 19 while bypassing the radiator 13 and the throttling mechanism 18.

In normal time (cooling mode) at which the second evaporator 19 need not be defrosted, the shutting mechanism 24 is kept in shut state according to a control signal from the electrical control unit 21 described later. For this reason, in the cooling mode, refrigerant is not passed through the bypass passage 23; therefore, a refrigeration cycle is carried out by the operation of the compressor 12. Thus, the cooling operation of cooling the interior of the vehicle compartment can be performed by the first evaporator 15, and at the same time the cooling operation of cooling the interior of the refrigerator can be performed by the second evaporator 19.

The temperature sensor 22 is located at a position in proximity to the second evaporator 19. The temperature of air immediately after passing through the second evaporator 19 is detected by this temperature sensor 22. Detection signals of the temperature sensor 22 are inputted to the electrical control unit 21 described later.

In the defrosting mode, at least the second evaporator 19 is defrosted based on the temperature of air in proximity to the second evaporator 19 detected by the temperature sensor 22. In the defrosting mode, the shutting mechanism 24 is opened according to a control signal from the electrical control unit 21. For this reason, the high-temperature, high-pressure vapor-phase refrigerant on the discharge side of the compressor 12 passes through the bypass passage 23 and flows into the second evaporator 19. Thus, the front formed on the surface of the second evaporator 19 can be melted and removed.

This embodiment is so constructed that the following are electrically controlled according to control signals from the electrical control unit 21: the electromagnetic pressure control portion 12a of the variable displacement compressor 12, the first and second blowers 20A, 20B, the throttling mechanism 18, and the like.

The first evaporator 15 is an evaporator that exchanges heat between the refrigerant depressurized at the nozzle section 14a of the ejector 14 and the air in the vehicle compartment sent by the first blower 20A; and it thereby causes the refrigerant to absorb heat from the air in the vehicle compartment.

FIG. 16A shows the first evaporator 15. As illustrated in FIG. 16A, the first evaporator 15 in this embodiment is a fin-and-tube-type heat exchanger having a core section 110, 120 constructed of tubes 110 and fins 120.

The first evaporator 15 is constructed of plural members such as the core section 110, 120 and left and right header tanks 130. Each member that constructs these components of the evaporator 15 is formed of aluminum or aluminum alloy. The evaporator 15 is constructed by: assembling together these members by fitting, caulking, fixing using jig, or the like; and joining the assembled member with the brazing filler material provided beforehand on the surface of each member by integral brazing.

In the core section 110, 120, there are disposed predetermined total numbers of multiple tubes 110 in which refrigerant flows and multiple fins 120 formed in plate shape. The fins 120 are disposed in the direction of the length of the tubes 110 with predetermined fin pitch according to the cooling load in the vehicle compartment.

Each of the multiple tubes 110 is a pipe Φd in inside diameter formed in substantially cylindrical shape, for example. The tubes 110 are arranged in two rows on the upwind side and on the downwind side in a staggered pattern along the direction of the flow of air. A predetermined number N1 of the tubes 110 are arranged with a predetermined pitch.

The paired header tanks 130 extended in the direction of the lamination of the tubes 110 are provided at the longitudinal ends of the multiple tubes 110. Each of the header tanks 130 is integrally formed of a tank section, a core plate, and an end plate that are not shown in the drawing.

The tank section (not shown) is a box-like casing body that has substantially U-shaped section and has an opening on the core plate side. The core plate (not shown) has a swaging portion, not shown, at both its ends in the direction of its short sides and is formed in substantially U shape. The core plate has multiple tube insertion holes (not shown) formed at positions corresponding to the ends of the tubes 110.

The ends of the tubes 110 are joined with these tube insertion holes, and the tank spaces and the interior of the tubes 110 are thereby caused to communicate with each other. The end plate of the header tank 130 is a member for closing both the ends of the tank space formed by the tank sections and the core plates.

At one end of the right header tank 130, there is formed a refrigerant inlet 140 through which refrigerant flows into the header tank 130. At one end of the left header tank 130, there is formed a refrigerant outlet 150 through which refrigerant that underwent heat exchange flows out of the header tank 130.

FIG. 16B shows the second evaporator 19. The second evaporator 19 exchanges heat between refrigerant depressurized at the throttling mechanism 18 and the air in the refrigerator sent by the second blower 20B. The second evaporator 19 thereby causes the refrigerant to absorb heat from the air in the refrigerator.

As illustrated in FIG. 16B, the second evaporator 19 in this embodiment is a fin-and-tube-type heat exchanger having a core section constructed of tubes 110 and fins 120, similarly to those of the first evaporator 15.

However, the second evaporator 19 uses the following as the multiple tubes 110 disposed between the paired header tanks 130: pipe-like tubes 110 in inside diameter Φd formed in substantially cylindrical shape that are identical in the passage sectional area on the refrigerant side with those used in the first evaporator 15. In this example, the second evaporator 19 is so constructed that the number N2 of the tubes 110 is smaller than the number N1 of the tubes 110 in the first evaporator 15.

In other words, the second evaporator 19 is so formed that the flow resistance on the refrigerant side is greater than the flow resistance on the refrigerant side of the first evaporator 15. That is, the first and second evaporators 15, 19 are so constructed that the pressure loss of the refrigerant in the second evaporator 19 is larger than the pressure loss of the refrigerant in the first evaporator 15.

A predetermined total number of the fins 120 for the second evaporator 19 are arranged with predetermined fin pitch according to the cooling load in the refrigerator. Therefore, the total number of the fins 120 of the second evaporator 19 is different from that of the first evaporator 15.

In this embodiment, the first evaporator 15 and the second evaporator 19 are so constructed that the paired header tanks 130 are located at both ends of the tubes 110. The construction of the first evaporator 15 and the second evaporator 19 is not limited to this. For example, the first evaporator 15 and the second evaporator 19 may be so constructed that the following is implemented: the openings at both ends of the tubes 110 are connected using connecting pipes (not shown) in substantially U shape without use of the header tanks 130. In this case, the refrigerant that flows into the refrigerant inlet 140 flows leftward, rightward, and then leftward to repeat U-turns in the tubes 110, and flows out through the refrigerant outlet 150.

Description will be given to the operation of the refrigerant cycle device 10 of this embodiment constructed as mentioned above. First, the cooling mode of the refrigerant cycle device 10 will be now described. When the compressor 12 is operated, refrigerant is compressed at the compressor 12 and brought into high-temperature, high-pressure state. This refrigerant discharged from the compressor 12 flows into the radiator 13, and is cooled by the outside air and may be condensed. After flowing out of the radiator 13, the high-pressure refrigerant is divided into a flow going through the refrigerant circulation passage 11 and a flow going through the branch passage 17.

In the cooling mode at which the second evaporator 19 need not be defrosted (normal time), the throttling mechanism 18 in the branch passage 17 functions as a fixed throttle according to a control signal from the electrical control unit 21. Therefore, the refrigerant flowing through the branch passage 17 is depressurized at the throttling mechanism 18 and brought into low-pressure state. This low-pressure refrigerant absorbs heat from the air in the refrigerator, sent by the second blower 20B, in the second evaporator 19, and is evaporated. Thus, the second evaporator 19 performs the operation of cooling the interior of the refrigerator.

This embodiment is so constructed that the throttling mechanism 18 is controlled as a fixed throttle. The construction of the embodiment is not limited to this. The throttling mechanism 18 may be controlled as a variable throttle so that its opening is adjusted. Thus, it is possible to regulate the flow amount of refrigerant that passes through the first branch passage 17 and flows into the second evaporator 19. Therefore, the cooling capacity for cooling a space to be cooled (specifically, the space in the refrigerator) by using the second evaporator 19 can be controlled by controlling the number of revolutions (quantity of blown air) of the second blower 20B at the electrical control unit 21.

The vapor-phase refrigerant flowing out of the second evaporator 19 is sucked into the refrigerant suction port 14c of the ejector 14. Meanwhile, the flow of refrigerant going through the refrigerant circulation passage 11 flows into the nozzle section 14a of the ejector 14, so that the refrigerant is depressurized and expanded at the nozzle section 14a. Therefore, the pressure energy of refrigerant is converted into velocity energy at the nozzle section 14a, and the refrigerant is accelerated and jetted out of the nozzle jet port. At this time, the pressure drops in proximity to the nozzle jet port, and the vapor-phase refrigerant evaporated at the second evaporator 19 is sucked in through the refrigerant suction port 14c by this pressure drop.

The refrigerant jetted from the nozzle section 14a and the refrigerant sucked in through the refrigerant suction port 14c are mixed together downstream of the nozzle section 14a, and flow into the diffuser section 14b. At the diffuser section 14b, the velocity (expansion) energy of the refrigerant is converted into pressure energy by increase in the area of the passage. This raises the pressure of the refrigerant. The refrigerant flowing out of the diffuser section 14b of the ejector 14 flows into the first evaporator 15.

At the first evaporator 15, the refrigerant absorbs heat from the conditioning air to be blown out into the vehicle compartment and is evaporated. The evaporated vapor-phase refrigerant is sucked into the compressor 12 and compressed therein, and circulates through the refrigerant circulation passage 11 again. The electrical control unit 21 can control the displacement of the compressor 12, and thereby control the refrigerant discharging capacity of the compressor 12.

Thus, the cooling capacity of the first evaporator 15 to cool a space to be cooled, specifically, the cooling capacity of the first evaporator 15 to cool the interior of the vehicle compartment can be controlled by the electrical control unit 21. In this embodiment, the flow amount of refrigerant flowing to the first evaporator 15 is adjusted and further the number of revolutions (quantity of blown air) of the first blower 20A is controlled, so as to control the cooling capacity of the first evaporator 15.

The refrigerant evaporating pressure of the first evaporator 15 is a pressure obtained by pressurizing the refrigerant at the diffuser section 14b. The refrigerant outlet of the second evaporator 19 is connected to the refrigerant suction port 14c of the ejector 14. Therefore, it is possible to exert the low pressure on the second evaporator 19, as compared with the first evaporator 15.

Thus, the refrigerant evaporating pressure (refrigerant evaporating temperature) of the second evaporator 19 can be made lower than the refrigerant evaporating pressure (refrigerant evaporating temperature) of the first evaporator 15. As a result, the first evaporator 15 can be caused to perform cooling action in a relatively high-temperature range suitable for cooling the interior of the vehicle compartment. At the same time, the second evaporator 19 can be caused to perform cooling action in an even lower-temperature range suitable for cooling the interior of the refrigerator.

The second evaporator 19 may be operated under the condition that the refrigerant evaporating temperature is lower than 0° C. Therefore, degradation in cooling capacity caused by frost (formation of frost) on the second evaporator 19 becomes a problem. In this embodiment, to cope with this, the second evaporator 19 is automatically defrosted by taking the following measure: the temperature sensor 22 is located in proximity to the second evaporator 19; and the presence or absence of frosting in the second evaporator 19 is determined by the electrical control unit 21 based on the temperature detected by this temperature sensor 22.

More specific description will be given. When the temperature of air in proximity to the second evaporator 19, detected by the temperature sensor 22, lowers to a value lower than a preset frost determination temperature Ta, the electrical control unit 21 determines that the second evaporator 19 is frosted and opens the shutting mechanism 24 (opening and closing device).

As a result, the high-temperature, high-pressure vapor-phase refrigerant on the discharge side of the compressor 12 passes through the bypass passage 23 and flows into the second evaporator 19. Therefore, the frost formed on the surface of the second evaporator 19 can be melted and removed, and the operation of defrosting the second evaporator 19 can be performed through a very simple construction.

By performing this defrosting mode, the temperature of air in proximity to the second evaporator 19 is raised to a defrosting termination temperature Tb, which is higher than the frost determination temperature Ta by a predetermined temperature α(Tb=Ta+α). Then, the electrical control unit 21 determines that the defrosting mode should be terminated and returns the shutting mechanism 24 to the shut state. Thus, the throttling mechanism 18 functions as a fixed throttle again, and the second evaporator 19 is also returned to the normal state in which it performs the cooling action.

In this defrosting mode, the electrical control unit 21 carries out control so that the first blower 20A and the second blower 20B are brought into stopped state. As a result, when frost is formed on the surface of the second evaporator 19 and the temperature of air in proximity thereto drops to the frost determination temperature Ta or below, the cooling action of the first evaporator 15 is stopped until the temperature of air in proximity to the second evaporator 19 rises to the defrosting termination temperature Tb or higher.

To shorten this defrosting time, this embodiment is so constructed that the flow resistance on the refrigerant side of the second evaporator 19 is greater than the flow resistance on the refrigerant side of the first evaporator 15. More specific description will be given. Consideration made by the inventors of this application revealed the following: when the flow resistance of the second evaporator 19 is made greater than the flow resistance of the first evaporator 15, the temperature of refrigerant flowing into the second evaporator 19 rises; and this raises the average temperature of refrigerant flowing through the tubes 110 of the second evaporator 19.

Description will be given to the foregoing with reference to the Mollier chart in FIG. 17 indicating the cycle behavior in the defrosting mode of this embodiment. In the drawing of FIG. 17, the solid line indicates the cycle behavior in the sixth embodiment which is constructed such that the second evaporator 19 is greater than the first evaporator 15 in the flow resistance on the refrigerant side; and the broken line indicates the cycle behavior observed when the cycle is so constructed that the second evaporator 19 and the first evaporator 15 are equal with each other in flow resistance.

Point A of FIG. 17 indicates the state of the pressure of discharged refrigerant compressed at the compressor 12 and an enthalpy. Furthermore, in FIG. 17, point B indicates the state of refrigerant flowing into the second evaporator 19; point C indicates the state of refrigerant flowing out of the second evaporator 19; point D indicates the state of refrigerant flowing into the first evaporator 15; and point E indicates the state of refrigerant flowing out of the first evaporator 15.

Point B₀ shown in the drawing of FIG. 17 indicates the state of refrigerant flowing into the second evaporator 19 when the second evaporator 19 and the first evaporator 15 are so formed that they are identical with each other in flow resistance. Drop in pressure from point C to point D represents pressure loss that occurs the refrigerant let out of the second evaporator 19 flows into the ejector 14. Drop in pressure from point A to point B represents pressure loss that occurs when the refrigerant discharged from the compressor 12 flows through the bypass passage 23 and the shutting mechanism 24.

Drop in pressure from point B to point C represents pressure loss that occurs when the refrigerant flows through the second evaporator 19. Drop in pressure from point D to point E represents pressure loss that occurs when the refrigerant flows through the first evaporator 15.

Drop in pressure from point B₀ to point C represents pressure loss that occurs when the refrigerant flows through the second evaporator 19 so formed that it is identical with the first evaporator in flow resistance. It is indicated with substantially the same gradient as the oblique line connecting point D and point E.

Thus, the oblique line connecting point B and point C is steeper than the oblique line connecting point B₀ and point C. That is, it was found that when the gradient of the oblique line connecting point B and point C is increased, the refrigerant temperature is more raised at point B than at point B₀ in the Mollier diagram. In the Mollier diagram of FIG. 7, more specifically, the temperature at point B₀ is T1 and the temperature at point B is T2. That is, the temperature T2 at point B is higher than the temperature T1 at point B₀ in terms of isothermal lines (IL(T2), IL(T1)).

Accordingly, when the second evaporator 19 and the first evaporator 15 are so formed that the former is greater than the latter in flow resistance as in this embodiment, the following advantage is brought: in the defrosting mode, the temperature of refrigerant flowing into the second evaporator 19 becomes higher; and the average temperature of refrigerant flowing through the tubes 110 of the second evaporator 19 can be raised, as compared with the following cases where the second evaporator 19 and the first evaporator 15 are so formed that they are identical with each other in flow resistance.

Thus, in this embodiment, a defrosting time can be shortened as compared with cases where the second evaporator 19 and the first evaporator 15 are so formed that they are identical with each other in flow resistance. When the second evaporator 19 and the first evaporator 15 are so formed that the former is lower than the latter in flow resistance, the temperature of refrigerant flowing into the second evaporator 19 cannot be raised because the gradient of the oblique line connecting point B and point C is gentler than the gradient of the oblique line connecting point B₀ and point C.

FIG. 18A and FIG. 18B are diagrams illustrating the relationship between the defrosting time ratio according to this embodiment and the defrosting time ratio obtained when the second evaporator 19 and the first evaporator 15 are so formed that they are identical in flow resistance (equal flow resistance), when outside air temperature (TAM) is taken as a parameter. FIG. 18A illustrates the defrosting time ratio obtained when the outside air temperature (TAM) is 35° C., and FIG. 18B illustrates that obtained when the outside air temperature (TAM) is 0° C. Defrosting time ratio refers to a ratio of a defrosting time to a normal operating time.

When the outside air temperature (TAM) is 35° C., as illustrated in FIG. 18A, the defrosting time ratio can be reduced by approximately 30% in this embodiment, as compared with the defrosting time ratio obtained in the cases where the second evaporator 19 and first evaporator 15 are so formed that they are identical with each other in flow resistance.

When the outside air temperature (TAM) is 0° C., as illustrated in FIG. 18B, the defrosting time ratio can be reduced by approximately 60% in this embodiment, as compared with the defrosting time ratio obtained in the cases where the second evaporator 19 and the first evaporator 15 are so formed that they are identical with each other in flow resistance. That is, as the outside air temperature drops, the defrosting time ratio can be significantly reduced in this embodiment.

In the ejector refrigeration cycle of the sixth embodiment, the first evaporator 15 and the second evaporator 19 are formed using the tubes 110 identical in the passage sectional area on the refrigerant side. They are so formed that the number of tubes 110 in the second evaporator 19 is smaller than the number of tubes 110 in the first evaporator 15. Thus, the refrigerant flow resistance of the second evaporator 19 can be made greater than the refrigerant flow resistance of the first evaporator 15.

In the defrosting mode, the high-pressure refrigerant discharged from the compressor 12 flows to the second evaporator 19, the ejector 14 and the first evaporator 15, in this order. At this time, the flow resistance on the refrigerant side of the second evaporator 19 is greater than the flow resistance on the refrigerant side of the first evaporator 15. This increases the pressure loss at the second evaporator 19, and the inlet refrigerant temperature of the second evaporator 19 rises. This rise in the inlet refrigerant temperature of the second evaporator 19 raises the average temperature of refrigerant flowing through the second evaporator 19, and consequently the defrosting time can be shortened.

In this embodiment, in normal refrigeration cycle operation in which the shutting mechanism 24 is closed, a diverged part of refrigerant flows to the second evaporator 19; and all of refrigerant flowing through the cycle flows to the first evaporator 15. Further, since the second evaporator 15 is positioned on the upstream side, refrigerant containing a relatively large quantity of liquid content flows to the second evaporator 19.

For this reason, even when the second evaporator 19 has a relatively great flow resistance, an excessive pressure loss is prevented from being produced in the second evaporator 19 in normal operation. Since the first evaporator 15 has a relatively low flow resistance, even when all the amount of flow of the refrigeration cycle flows through the first evaporator 15 in the normal operation, an excessive pressure loss is prevented from being produced in the first evaporator 15.

Seventh Embodiment

In the above-mentioned sixth embodiment, the second evaporator 19 and the first evaporator 15 are constructed so that the former is greater than the latter in flow resistance. That is, in the seventh embodiment, the first evaporator 15 and the second evaporator 19 are formed using the tubes 110 identical in the passage sectional area on the refrigerant side, while the number of tubes 110 of the second evaporator 19 is made smaller than the number of tubes 110 of the first evaporator 15. However, the second evaporator 19 and the first evaporator 15 may be so formed that the former is smaller than the latter in the passage sectional area of the tubes 110.

As illustrated in FIG. 19A and FIG. 19B, each of the tubes 110 of the first evaporator 15 is formed to have an inside diameter φd1, and each of the tubes 110 of the second evaporator 19 is formed to have an inside diameter φd2 smaller than φd1. The numbers N of the arranged tubes 110 are identical with each other in both the first evaporator 15 and the second evaporator 19.

With this construction, it is possible to make the flow resistance on the refrigerant side of the second evaporator 19 greater than the flow resistance on the refrigerant side of the first evaporator 15. Therefore, when the pressure loss on the inlet side of the second evaporator 19 is increased, the inlet temperature of the second evaporator 19 is raised. This rise in inlet temperature raises the average temperature of the refrigerant flowing through the second evaporator 19, and thus a defrosting time can be shortened.

In the refrigerant cycle device of the seventh embodiment, the other parts can be made similar to those of the above-described sixth embodiment, thereby obtaining the same advantages as those of the above-described sixth embodiment.

Eighth Embodiment

In this embodiment, as illustrated in FIG. 20A and FIG. 20B, the tubes 110 of the first evaporator 15 are formed to have a length of L1; and the tubes 110 of the second evaporator 19 are formed to have a length of L2 that is longer than L1. The numbers N of the arranged tubes 110 are identical with each other in both the first evaporator 15 and the second evaporator 19. The first evaporator 15 and the second evaporator 19 use the tubes 110 having the identical refrigerant passage sectional area.

With this construction, it is possible to make the flow resistance on the refrigerant side of the second evaporator 19 greater than the flow resistance on the refrigerant side of the first evaporator 15.

In the refrigerant cycle device 10 of the eighth embodiment, the other parts can be made similar to those of the above-described sixth embodiment, thereby obtaining the same advantages as those of the above-described sixth embodiment.

Ninth Embodiment

In a refrigerant cycle device 10 of a ninth embodiment, as illustrated in FIG. 21, a refrigeration unit 37 is constructed of the first evaporator 15 and the second evaporator 19. The refrigeration unit 37 cools a common space to be cooled (specifically, the space in a refrigerator mounted in a vehicle) to a low temperature as 0° C. or below.

More specific description will be given. The first evaporator 15 is located upstream of the first blower 20A with respect to the flow of air, and the second evaporator 19 is located downstream of the first evaporator 15 with respect to the flow of air. Cool air that has passed through the second evaporator 19 is blown into the space to be cooled (space in the refrigerator). The first evaporator 15 and the second evaporator 19 may be integrally formed by such means as brazing.

In this embodiment, the common space to be cooled (space in the refrigerator) is cooled to so low a temperature of 0° C. or below with the first evaporator 15 and the second evaporator 19. Therefore, it is required to perform defrosting operation for both the first evaporator 15 and the second evaporator 19.

Description will be given to the operation of the ejector refrigerant cycle device 10 having the refrigeration unit 37. In a normal operation (cooling mode), the compressor 12, a cooling fan, not shown, for the radiator 13, and the blower 20A (first blower) of the refrigeration unit 37 are brought into operation. The throttling mechanism 18 is controlled into a predetermined throttling state. The shutting mechanism 24 is kept in shut state.

Thus, in the refrigerant cycle device 10 of the ninth embodiment, the air sent by the blower 20A is cooled by heat absorbing action due to the evaporation of refrigerant at the first evaporator 15 and the second evaporator 19. The space to be cooled in the refrigeration unit 37 can be thereby cooled. That is, normal cooling operation can be performed by using the first and second evaporators 15, 19 in the refrigerant cycle device 10.

When the temperature detected by the temperature sensor 22 falls below the frost determination temperature, the electrical control unit 21 determines that the first and second evaporators 15, 19 are frosted, and changes the operation mode in the refrigerant cycle device 10 to the defrosting mode.

More specific description will be given. When the defrosting mode is set, the electrical control unit 21 opens the shutting mechanism 24 and, at the same time, brings the blower 20A into a stopped state. The cooling fan for the radiator 13 may be in a stopped state or in an operating state in the defrosting mode.

As the result of the shutting mechanism 24 being opened, the high-temperature refrigerant (hot gas) discharged from the compressor 12 flows directly into the second evaporator 19 so that heat is radiated and the temperature of the refrigerant is lowered by a predetermined amount at the second evaporator 19; and the thus obtained intermediate-temperature refrigerant passes through the refrigerant suction port 14c of the ejector 14 and flows into the first evaporator 15. As mentioned above, the high-temperature refrigerant discharged from the compressor 12 flows to both the second evaporator 19 and the first evaporator 15 in this order, and the second evaporator 19 and the first evaporator 15 are thereby simultaneously defrosted.

In this embodiment, the second evaporator 19 and the first evaporator 15 are so formed that the flow resistance on the refrigerant side of the second evaporator 19 is greater than the flow resistance on the refrigerant side of the first evaporator 15. As a result, the pressure loss on the inlet side of the second evaporator 19 is increased, and thus the inlet temperature of the second evaporator 19 rises. This rise in inlet temperature raises the average temperature of refrigerant flowing through the second evaporator 19. Further, the intermediate-temperature refrigerant obtained by radiating heat and lowering its temperature by a predetermined amount at the second evaporator 19 can be caused to flow into the first evaporator 15.

Therefore, it is possible to defrost the first and second evaporators 15, 19 and further shorten the defrosting time for the second evaporator 19 and the first evaporator 15.

Other Embodiments

Although the present invention has been fully described in connection with the preferred embodiments and modifications thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art.

For example, in the refrigerant cycle device 10 of each of the above-described first to fifth embodiments, the structures of the first evaporator 15 and the second evaporator 19 of any one of the above-described sixth to eighth embodiments can be used.

In the sixth to ninth embodiments, the first and second evaporators 15, 19 are constructed of fin-and-tube-type heat exchangers having the core section 110, 120 constructed of tubes 110 and fins 120. The sixth to ninth embodiments are not limited to this construction. Instead, the evaporators 15, 19 may be constructed of heat exchangers of such that tubes 110 are laminated flat tubes and corrugated fins 120 are located between the flat tubes 110.

In the sixth to ninth embodiments, the interior of the tubes 110 is formed of a smooth passage. The sixth to ninth embodiments are not limited to this construction. Instead, the interior of the tubes 110 may be formed of a grooved passage. Alternatively, the tubes 110 of the second evaporator 19 may be formed of grooved passages and the tubes 110 of the first evaporator 15 may be formed of smooth passages.

In the above-described embodiments, the defrosting mode is automatically performed by detecting the temperature of air in proximity to the second evaporator 19 with the temperature sensor 22. This is just an example. Automatic control of the defrosting mode can be variously modified. For example, the automatic control of the defrosting mode may be carried out by detecting the temperature of the surface of the second evaporator 19, not the temperature of air in proximity to the evaporator 19, with the temperature sensor 22.

Alternatively, the following construction may be adopted: a refrigerant temperature sensor for detecting the temperature of refrigerant is provided in the refrigerant passage in proximity to the second evaporator 19; and the automatic control of the defrosting mode is carried out based on the temperature of refrigerant in proximity to the second evaporator 19. There is a correlation between the temperature of refrigerant and the pressure of refrigerant in proximity to the second evaporator 19. Therefore, the following construction may be adopted: a refrigerant pressure sensor for detecting the pressure of refrigerant in proximity to the second evaporator 19 is provided; and the automatic control of the defrosting mode can be carried out based on the pressure of refrigerant in proximity to the second evaporator 19.

Such a temperature sensor 22 and a refrigerant pressure sensor as mentioned above may be disused. Instead, after the cycle is started, the defrosting mode may be automatically performed only by predetermined times at predetermined time intervals using the timer function of the electrical control unit 21.

The above description of the first to ninth embodiments takes as examples cases where the refrigerant cycle device is used for an air conditioner and refrigerators for vehicles. Instead, the first evaporator 15 at which the refrigerant evaporating temperature is higher and the second evaporator 19 at which the refrigerant evaporating temperature is lower may be both used to cool a single space to be cooled, e.g., the interior of the refrigerator. For example, the following construction may be adopted: the cold room of the refrigerator is cooled with the first evaporator 15 at which the refrigerant evaporating temperature is higher; and the freezing compartment of the refrigerator is cooled with the second evaporator 19 at which the refrigerant evaporating temperature is lower.

In the example of the ninth embodiment (FIG. 21), the one refrigeration unit 37 is constructed of the first evaporator 15 and the second evaporator 19. Then, the interior of one refrigerator is cooled with this refrigeration unit 37. Instead, the following construction may be adopted: the first evaporator 15 and the second evaporator 19 are located in different refrigerators; and the different refrigerators are respectively cooled with the first evaporator 15 and the second evaporator 19.

In the description of the above embodiments, the type of refrigerant is not specified. Any type of refrigerant, including chlorofluorocarbons, HC alternatives for chlorofluorocarbons, and carbon dioxide (CO₂), may be adopted as long as it is applicable to vapor compression refrigerant cycles.

Chlorofluorocarbon cited here is a generic name for organic compounds composed of carbon, fluorine, chlorine, and hydrogen, and is widely used as refrigerant. Fluorocarbon refrigerant includes HCFC (hydrochlorofluorocarbon) refrigerant, HFC (hydrofluorocarbon) refrigerant, and the like, for example. These refrigerants are designated as alternatives for chlorofluorocarbon because they do not destroy the ozone layer.

HC (hydrocarbon) refrigerant is refrigerant substances that contain hydrogen and carbon and occur in nature. The HC refrigerant includes R600a (isobutane), R290 (propane), and the like, for example.

In the above-described sixth to ninth embodiments, the displacement of the variable displacement compressor 12 is controlled with the electrical control unit 21 to control the refrigerant discharging capacity of the compressor 12. Instead, a fixed displacement compressor may be used for the compressor 12. In this case, the operation of the fixed displacement compressor 12 is on/off-controlled with an electromagnetic clutch. Thus, the ratio of the turn-on/off operation of the compressor 12 is controlled, and the refrigerant discharging capacity of the compressor 12 is thereby controlled. When an electric compressor is used for the compressor 12, its refrigerant discharging capacity can be controlled by controlling the number of revolutions of the electric compressor 12.

In the above embodiments, a variable flow ejector may be used for the ejector 14. This ejector detects the degree of overheating of refrigerant at the outlet of the first evaporator 15, and adjusts the area of the refrigerant channel in the nozzle section 14a of the ejector 14, so as to regulate a flow rate of refrigerant in the ejector. In this case, the pressure of refrigerant jetted from the nozzle section 14a can be controlled so that the flow rate of vapor-phase refrigerant sucked in the ejector 14 can be controlled.

In the above embodiments, each evaporator 15, 19 is constructed as an indoor heat exchanger as a user-side heat exchanger. However, the construction of the above embodiments can also be applied to cycles in which an outdoor heat exchanger designated as the non-user-side heat exchanger or the heat source-side heat exchanger is used for each evaporator 15, 19 mentioned above.

For example, the above-mentioned embodiments can also be used for cycles designated as heat pumps. Such cycles include refrigerant cycles for heating in which each evaporator is constructed as an outdoor heat exchanger and a condenser is constructed as an indoor heat exchanger; and refrigerant cycles for supplying hot water in which water is heated by the radiator 13.

Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims.

Claims

1. A refrigerant cycle device comprising: a compressor that sucks in and compresses refrigerant;a radiator located to cool high-pressure hot gas refrigerant discharged from the compressor;an ejector that has a nozzle section for decompressing and expanding refrigerant downstream of the radiator, a refrigerant suction port for sucking in refrigerant by a high-speed flow of refrigerant jetted from the nozzle section, and a pressurizing section for mixing and pressurizing the refrigerant jetted at high speed and the refrigerant sucked through the refrigerant suction port;a first evaporator for evaporating refrigerant flowing out of the ejector;a first passage portion for guiding refrigerant to the refrigerant suction port;a throttle unit that is located in the first passage portion and decompresses the refrigerant flowing in the first passage portion;a second evaporator that is located in the first passage portion downstream of the throttle unit in a refrigerant flow to evaporate refrigerant;a bypass passage portion for guiding the hot gas refrigerant discharged from the compressor into the second evaporator;a bypass opening and closing unit that is provided in the bypass passage portion to open and close the bypass passage portion, the bypass opening and closing unit having a throttling open degree when being opened;a second passage portion that is branched from the bypass passage portion downstream of the bypass opening and closing unit in a refrigerant flow, wherein the hot gas refrigerant in the bypass passage portion flows to the first evaporator through the second passage portion; anda first flow control unit that is provided in the second passage portion to prevent a flow of refrigerant from a side of the first evaporator to a side of the second evaporator through the second passage portion.

2. The refrigerant cycle device according to claim 1, wherein the first passage portion is a branch passage branched from an upstream side of the nozzle section of the ejector in a refrigerant flow from the radiator, to guide the refrigerant from the radiator to the refrigerant suction port of the ejector.

3. The refrigerant cycle device according to claim 1, further comprising a gas-liquid separator that separates refrigerant flowing out of the first evaporator into vapor refrigerant and liquid refrigerant, collects the liquid refrigerant therein, and guides the vapor refrigerant out to a refrigerant suction side of the compressor,wherein the first passage portion is a connection passage that connects a liquid refrigerant outlet portion of the gas-liquid separator to the refrigerant suction port.

4. The refrigerant cycle device according to claim 1, wherein the first flow control unit is a check valve, which is located to only permit a flow of refrigerant from the bypass passage portion to the first evaporator through the second passage portion.

5. The refrigerant cycle device according to claim 1, wherein the first flow control unit is a switching valve that located to open and close the second passage portion.

6. The refrigerant cycle device according to claim 5, wherein the switching valve is opened when the bypass opening and closing unit is opened, and is closed when the bypass opening and closing unit is closed.

7. The refrigerant cycle device according to claim 1, wherein the first flow control unit is a flow adjusting valve that is located to be brought into a closed state and to regulate a flow amount of refrigerant in accordance with its valve open degree that is adjustable.

8. The refrigerant cycle device according to claim 7, further comprising: an inlet-side temperature detector that is located to directly or indirectly detect a refrigerant temperature at a refrigerant inlet side of the first evaporator; andan outlet-side temperature detector that is located to directly or indirectly detect a refrigerant temperature at a refrigerant outlet side of the second evaporator, whereinthe flow adjusting valve is brought into the closed state when the bypass opening and closing unit is closed, andwhen the bypass opening and closing unit is opened, the flow adjusting valve increases its valve open degree more as the refrigerant temperature detected by the inlet-side temperature detector is lower than the refrigerant temperature detected by the outlet-side temperature detector, and the flow adjusting valve decreases its valve open degree more as the refrigerant temperature detected by the inlet-side temperature detector is higher than the refrigerant temperature detected by the outlet-side temperature detector.

9. The refrigerant cycle device according to claim 1, further comprising: a third passage portion that is branched from the first passage portion at a position downstream of the second evaporator in a flow of refrigerant from the second evaporator, to guide the flow of the refrigerant from the second evaporator to the first evaporator; anda second flow control unit that is located in the third passage portion to prevent a flow of refrigerant from the first evaporator to the second evaporator through the third passage portion.

10. The refrigerant cycle device according to claim 9, wherein the second flow control unit is a check valve, which is located to only permit a flow of refrigerant from the second evaporator to the first evaporator through the third passage portion.

11. The refrigerant cycle device according to claim 9, wherein the second flow control unit is a switching valve that is located to open and close the third passage portion.

12. The refrigerant cycle device according to claim 11, wherein the switching valve is opened when the bypass opening and closing unit is opened, and is closed when the bypass opening and closing unit is closed.

13. The refrigerant cycle device according to claim 9, wherein the second flow control unit is a flow adjusting valve that is located to be brought into a closed state and to regulate a flow amount of refrigerant in accordance with its valve open degree that is adjustable

14. The refrigerant cycle device according to claim 1, further comprising a passage opening and closing unit located to open and close a refrigerant passage connected to a refrigerant inlet or a refrigerant outlet of the radiator,wherein the passage opening and closing unit is closed when the bypass opening and closing unit is opened.

15. The refrigerant cycle device according to claim 3, further comprising: a throttle opening and closing unit located in the connection passage to open and close a refrigerant passage connected to a refrigerant inlet or a refrigerant outlet of the throttle unit,wherein the throttle opening and closing unit is closed when the bypass opening and closing unit is opened.

16. The refrigerant cycle device according to claim 1, wherein the first evaporator and the second evaporator are constituted such that a flow resistance of refrigerant flowing in the second evaporator is greater than that of refrigerant flowing in the first evaporator.

17. A refrigerant cycle device comprising: a compressor that sucks in and compresses refrigerant;a radiator located to cool high-pressure hot gas refrigerant discharged from the compressor;an ejector that has a nozzle section for decompressing and expanding refrigerant downstream of the radiator, and a refrigerant suction port for sucking in refrigerant by a high-speed flow of refrigerant jetted from the nozzle section;a first evaporator for evaporating refrigerant flowing out of the ejector;a branch passage portion branched from an upstream side of the nozzle section and joined to the refrigerant suction port of the ejector;a throttle unit that is located in the branch passage portion and decompresses the refrigerant flowing in the branch passage portion;a second evaporator that is located in the branch passage portion downstream of the throttle unit in a refrigerant flow;a bypass passage portion for guiding the hot gas refrigerant discharged from the compressor into the second evaporator; anda bypass opening and closing unit that is located in the bypass passage portion to open and close the bypass passage portion,wherein the first evaporator and the second evaporator are constituted such that a flow resistance of refrigerant flowing in the second evaporator is greater than that of refrigerant flowing in the first evaporator.

18. The refrigerant cycle device according to claim 17, wherein: the first evaporator includes a plurality of first tubes in which refrigerant flows;the second evaporator includes a plurality of second tubes in which refrigerant flows;each first tube and each second tube are identical in a passage sectional area therein; andthe second tubes of the second evaporator have a tube number that is smaller than that of the first tubes of the first evaporator.

19. The refrigerant cycle device according to claim 17, wherein: the first evaporator includes a plurality of first tubes in which refrigerant flows;the second evaporator includes a plurality of second tubes in which refrigerant flows;the first tubes of the first evaporator and the second tubes of the second evaporator are identical in a tube length; andeach of the second tubes of the second evaporator has therein a passage sectional area that is smaller than that of each first tube of the first evaporator.

20. The refrigerant cycle device according to claim 17, wherein: the first evaporator includes a plurality of first tubes in which refrigerant flows;the second evaporator includes a plurality of second tubes in which refrigerant flows;each first tube of the first evaporator and each second tube of the second evaporator are identical in a passage sectional area therein; andeach of the second tubes of the second evaporator has a tube length that is larger than that of the first tubes of the first evaporator.

21. The refrigerant cycle device according to claim 17, wherein: the first evaporator includes a plurality of first tubes in which refrigerant flows;the second evaporator includes a plurality of second tubes in which refrigerant flows;each first tube of the first evaporator and each second tube of the second evaporator are identical in a passage sectional area therein; andwherein the second tubes of the second evaporator have therein grooved passages, and the second tubes of the first evaporator have therein flat passages.

22. The refrigerant cycle device according to claim 17, wherein the bypass opening and closing unit opens the bypass passage portion in a defrosting mode where a defrosting operation of at least the second evaporator is performed.