JP2000074513A - Supercritical refrigerating cycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the coefficient of performance of a CO2 cycle from becoming worse when a compressor is started and, at the same time, to prevent the occurrence of faults in the CO2 cycle. SOLUTION: In a supercritical refrigerating cycle, a by-pass passage 600 which leads a refrigerant flowing out of a radiator 200 to an evaporator 400 by taking a long way around a pressure control valve 300 and, at the same time, has a prescribed passage resistance is used. Since the refrigerant can be supplied to the evaporator 400 even when the valve 300 is completely closed when a compressor 100 is started, the coefficient of performance of a CO2 cycle can be prevented from becoming worse when the compressor 100 is started and, at the same time, the CO2 cycle can be prevented from being broken.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supercritical refrigeration cycle in which the pressure on the discharge side (high pressure side) of a compressor exceeds a critical pressure of a refrigerant, and is effective for use in a vehicle air conditioner.

[0002]

2. Description of the Related Art A supercritical refrigeration cycle using carbon dioxide (CO ₂ ) as a refrigerant (hereinafter, this supercritical refrigeration cycle is called CO 2
Called _two cycles. In (3), when increasing the refrigerating capacity, it is necessary to increase the CO ₂ pressure on the radiator outlet side (high pressure side) as described in JP-T-3-503206.

However, if the pressure on the high pressure side is simply increased to increase the refrigeration capacity, the amount of increase in the compression work of the compressor is larger than the increase in the refrigeration capacity.
There is a problem that the coefficient of performance of _two cycles is deteriorated. Therefore, the applicant has already filed an application for a pressure control valve that controls the CO ₂ pressure at the radiator outlet side based on the CO ₂ temperature at the radiator outlet side so that the coefficient of performance is maximized (Japanese Patent Application No. Hei 10-26138). 9-231249). That is, in the pressure control valve according to this application, as described later, the opening degree of the pressure control valve is reduced in accordance with the rise in the refrigerant temperature on the radiator outlet side to increase the refrigerant pressure on the radiator outlet side. .

[0004]

By the way, the present inventors have conducted various tests and studies in order to put the CO ₂ cycle into practical use, and found the following problem.
That is, not only in the supercritical refrigeration cycle but also in a refrigeration cycle using chlorofluorocarbon as a refrigerant, a temperature sensor is used to prevent the water vapor in the air cooled by the evaporator from condensing (frosting). Detects the temperature of the air cooled by the compressor. If the temperature detected by the temperature sensor is equal to or lower than a predetermined temperature, the compressor is stopped, and if the temperature is higher than the predetermined temperature, the compressor is operated. Is operating.

However, as described above, since the opening of the pressure control valve is adjusted based on the refrigerant temperature at the radiator outlet side, for example, when the compressor is stopped, the refrigerant temperature at the radiator outlet side is increased. While the pressure hardly decreases, the pressure at the radiator outlet side decreases, so that the degree of opening decreases, and finally the state becomes the fully closed state. Therefore, the refrigerant (CO ₂ ) is no longer supplied to the evaporator, so that the refrigerant in the evaporator evaporates and the pressure in the evaporator increases.

When the compressor starts again, the discharge pressure (pressure at the radiator outlet) rises relatively quickly because the pressure (suction pressure) inside the evaporator increases, but the discharge pressure at the radiator outlet side increases. Since the refrigerant temperature of the compressor hardly changes, the pressure control valve maintains the fully closed state in order to make the refrigerant pressure at the radiator outlet side a pressure corresponding to the refrigerant temperature at that time, so the refrigerant sucked by the compressor decreases. , The discharge refrigerant amount decreases, and the rate of increase of the discharge pressure becomes slow.

[0007] Therefore, despite the operation of the compressor, the state in which the pressure control valve is fully closed continues, and the amount of refrigerant evaporated (refrigeration capacity) in the evaporator decreases. On the other hand, since the compressor is operating, there is a problem that the driving force of the compressor with respect to the refrigerating capacity increases and the coefficient of performance deteriorates. As is apparent from the above description, this problem does not occur only at the time of the frost prevention control, but occurs with the stop and operation of the compressor.

If the compressor is stopped and the pressure control valve is closed for a long time in a high temperature condition such as in summer, the pressure in the evaporator rises excessively. May rise excessively, causing a failure in the supercritical refrigeration cycle. Also, when the compressor is restarted from a state in which almost no refrigerant exists on the high pressure side of the supercritical refrigeration cycle (the range from the compressor to the pressure control valve), the low pressure side of the supercritical refrigeration cycle (compressed from the pressure control valve ), The refrigerant on the high pressure side does not rise to a predetermined pressure or more. For this reason, since the refrigerant cannot circulate in the supercritical refrigeration cycle, there is a high possibility that the supercritical refrigeration cycle will break down.

In view of the above, it is an object of the present invention to prevent a coefficient of performance from deteriorating when a compressor is started in a supercritical refrigeration cycle and to cause a failure in the supercritical refrigeration cycle. I do.

[0010]

The present invention uses the following technical means to achieve the above object. According to the first aspect of the present invention, the refrigerant flowing out of the radiator (200) is guided to the evaporator (400) by bypassing the pressure control valve (300), and the bypass passage (600) having a predetermined passage resistance is formed. It is characterized by having.

Thus, even if the pressure control valve (300) is fully closed when the compressor (100) is started, the refrigerant can be supplied to the evaporator (400). When 100) is activated, it is possible to prevent the coefficient of performance from deteriorating. In addition, the bypass passage (60
0) supplies the refrigerant to the evaporator (400),
Even when the compressor (100) is stopped and the pressure control valve (300) is closed for a long time in a high temperature condition such as summer, the pressure in the evaporator (400) is excessively increased. Can be prevented. Therefore, it is possible to prevent the supercritical cycle from being damaged.

Further, since the refrigerant can be supplied to the low pressure side from the bypass passage (600), the supercritical refrigeration cycle will be broken even if the refrigerant exists in any part of the supercritical refrigeration cycle. Can be prevented. As described above, according to the present invention, when the compressor (100) is restarted, it is possible to prevent the coefficient of performance from deteriorating and to prevent damage and breakdown of the supercritical cycle.

According to the second aspect of the present invention, the valve means (900, 950) for opening and closing the bypass passage (600) is connected to the bypass passage (600) until a predetermined time elapses after the start of the compressor (100). 600) is opened.
As a result, similarly to the first aspect, when the compressor (100) is restarted, it is possible to prevent the coefficient of performance from deteriorating and to prevent damage and breakdown of the supercritical cycle.

According to the third aspect of the present invention, the compressor (10
After the start-up of 0), the radiator (200) side and the evaporator (400) side are communicated at least until a predetermined time elapses. As a result, similarly to the first aspect, when the compressor (100) is restarted, it is possible to prevent the coefficient of performance from deteriorating and to prevent damage and breakdown of the supercritical cycle.

According to the present invention, the refrigerant flowing out of the radiator (200) is introduced into the pressure control valve (300) to the evaporator (400) while bypassing the pressure control section (303). Bypass passage having a passage resistance of (6)
00) is provided. As a result, similarly to the first aspect, when the compressor (100) is restarted, it is possible to prevent the coefficient of performance from deteriorating and to prevent damage and breakdown of the supercritical cycle.

Incidentally, the reference numerals in parentheses of the above means are examples showing the correspondence with specific means described in the embodiments described later.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment)
The supercritical refrigeration cycle according to the present invention is applied to a CO ₂ cycle for a vehicle, and FIG. 1 is a schematic diagram of the CO ₂ cycle. In FIG. 1, reference numeral 100 denotes a compressor that sucks and compresses a refrigerant (CO ₂ ). The compressor 100 operates by receiving a driving force from a vehicle running engine (not shown) via an electromagnetic clutch 110. Reference numeral 200 denotes a radiator that exchanges heat with the atmosphere and cools the refrigerant discharged from the compressor 100, and also has a radiator whose internal pressure exceeds the critical pressure of the refrigerant. The pressure control valve controls the pressure at the outlet of the radiator 200 based on the refrigerant pressure at the outlet of the device 200. The details of the pressure control valve 300 will be described later.

An evaporator 400 evaporates the refrigerant depressurized by the pressure control valve 300 to cool the air.
Is an accumulator (gas-liquid separation unit) that stores excess refrigerant in the CO ₂ cycle, separates refrigerant flowing out of the evaporator 400 into gas-phase refrigerant and liquid-phase refrigerant, and discharges the gas-phase refrigerant to the compressor 100 side. It is. Reference numeral 600 denotes a bypass passage which is set so as to guide the refrigerant flowing out of the radiator 200 to the evaporator 400 by bypassing the pressure control valve 300 and to have a predetermined passage resistance (pressure loss).

Reference numeral 700 denotes a temperature sensor (temperature detecting means) for detecting the temperature of the air cooled by the evaporator 400.
The electronic control unit (ECU) 800 turns on the electromagnetic clutch 110 based on the temperature detected by the temperature sensor 700.
-OFF is controlled. Specifically, the detected temperature is 3 ° C
When the temperature becomes below, the electromagnetic clutch 110 is turned off to stop the compressor 100, and when the detected temperature becomes 4 ° C. or more, the electromagnetic clutch 110 is turned on to operate the compressor 100.

Next, the pressure control valve 300 will be described.
FIG. 2 is a cross-sectional view of the pressure control valve 300;
Reference numeral 2 denotes a control valve body (pressure control unit) that constitutes a refrigerant passage and reduces the pressure of the refrigerant flowing out of the radiator 200 and controls the pressure at the outlet of the radiator 200 based on the refrigerant pressure at the outlet of the radiator 200. This is a casing for storing the 303. In the control valve body 303, reference numeral 304 denotes a temperature sensing part that senses the temperature of the refrigerant, and the temperature sensing part 304 forms a closed space 306 together with a thin-film diaphragm (pressure-responsive member) 305 and the diaphragm 305. It is composed of a housing 307.

In the closed space 306, the refrigerant (C
The density of O ₂ ) ranges from the saturated liquid density at 0 ° C. to the saturated liquid density at the critical point of the refrigerant (in the present embodiment, about 62%).
5 kg / m ³ ). Reference numeral 307 denotes an encapsulation tube for enclosing the refrigerant in the temperature sensing part 304 (sealed space 306).
It is made of a metal having a high thermal conductivity such as copper so that the temperature of the refrigerant in the closed space 306 can follow the temperature of the refrigerant in the internal space without a time difference.

309 is a pressure control valve 300 (control valve body 3
03) is a needle valve body (hereinafter abbreviated as a valve body) for adjusting the opening of the valve port 310, and the valve body 309 is joined to the diaphragm 305. Therefore, when the temperature of the temperature sensing portion 304 (inside of the closed space 306) rises (internal pressure rises), the valve body 309 is displaced in a direction to reduce the opening of the valve port 310.

Reference numeral 311 denotes a spring (elastic body) for adjusting the valve closing pressure of the pressure control valve 300. The initial load of the spring 311 is adjusted by turning the adjustment nut 312. The initial load (elastic force in a state in which the valve port 310 is closed) is such that, in the condensation region where the refrigerant is below the critical pressure,
It is set to have a predetermined degree of subcooling (about 10 ° C. in the present embodiment), and specifically, is about 1 [MPa] in terms of the pressure in the closed space 306 at the initially set load.

Therefore, in the supercritical region, the pressure control valve 300 moves along the isopycnic line of 625 kg / m ³ ,
Based on the refrigerant temperature at the outlet side of the radiator 200, the radiator 20
The refrigerant pressure at the outlet 0 side is controlled, and in the condensation area, the refrigerant pressure is controlled so as to have a predetermined degree of supercooling (see the thick line η _{max in} FIG. 3). Next, features of the present embodiment will be described.

According to the present embodiment, the refrigerant flowing out of the radiator 200 is bypassed by the pressure control valve 300,
Since the bypass passage 600 leading to zero is formed, even if the pressure control valve 300 is in the fully closed state when the compressor 100 is stopped and then the compressor 100 is restarted,
A refrigerant can be supplied to the evaporator 400. Therefore, when the compressor 100 is started, also possible to prevent the coefficient of performance is deteriorated, because the bypass passage 600 can be supplied to the refrigerant in the low-pressure side (evaporator 400 side), the refrigerant is CO ₂ cycle in Irrespective of which part, the CO ₂ cycle can be prevented from breaking down.

By the way, since the bypass passage 600 always connects the radiator 200 and the evaporator 400, even if the opening of the pressure control valve 300 is reduced, the refrigerant flows into the bypass passage 600, and There is a possibility that the refrigerant pressure on the outlet side of the vessel 200 cannot be controlled. Therefore, in the present embodiment, a predetermined passage resistance is provided in the bypass passage 600 so that the refrigerant flowing out of the radiator 200 does not excessively flow into the bypass passage 600.

Further, the evaporator 4 is provided by the bypass passage 600.
Since the refrigerant is supplied to the evaporator 400, even if the compressor 100 is stopped and the pressure control valve 300 is closed for a long time in a high temperature condition such as summer, the pressure in the evaporator 400 is excessively high. It can be prevented from rising. Therefore, CO
_Two cycles can be prevented from being damaged or broken.

As described above, the C according to this embodiment is
In the O ₂ cycle, when the compressor 100 restarts,
It is possible to prevent the CO ₂ cycle from being damaged or broken while preventing the coefficient of performance from deteriorating. In the present embodiment, as shown in FIG.
It may be formed within 0.

(Second Embodiment) In this embodiment, an electromagnetic valve (valve means) 900 for opening and closing the bypass passage 600 is provided in the bypass passage 600. Then, the electronic control unit 800 opens the solenoid valve 900 until a predetermined time (about 5 seconds in this embodiment) elapses after the compressor 100 is started, and sends the refrigerant flowing out of the radiator 200 to the pressure control valve 300. It is supplied to the evaporator 400 by bypassing.

When the compressor 100 is stopped,
After a predetermined period of time has elapsed after the start of the compressor 100, the solenoid valve 900 is closed, and the radiator 200 is opened by the pressure control valve 300.
Controls the refrigerant pressure on the outlet side. Here, the predetermined time is
This is the time required for the pressure control valve 300 to open and start the refrigerant pressure control on the outlet side of the radiator 200 by the pressure control valve 300, and is selected based on the discharge capacity of the compressor 100 and the like.

Thus, even if the pressure control valve 300 is fully closed when the compressor 100 is restarted, the refrigerant can be supplied to the evaporator 400.
When 00 is activated, it is possible to prevent the coefficient of performance from deteriorating and prevent the discharge pressure from excessively increasing, thereby preventing the CO ₂ cycle from being damaged. In addition, since the refrigerant can be supplied to the low pressure side by opening the pressure control valve 300, the failure of the CO ₂ cycle can be prevented.

FIG. 6A shows the bypass passage 6.
FIG. 6 is a graph showing the state of the CO ₂ cycle according to the related art not having the solenoid valve 900 and the solenoid valve 900, and FIG. 6B is a graph showing the state of the CO ₂ cycle according to the present embodiment. FIG. 7 is a bar graph showing the power consumption of the compressor 100. 6 and 7, in the CO ₂ cycle according to the present embodiment, the operating time and the consumption driving force of the compressor 100 are reduced to the CO ₂ cycle and the refrigeration cycle using Freon as a refrigerant according to the related art. It can be seen that it has been shortened in comparison.

FIG. 8 is a graph showing a change in the discharge pressure of the compressor 100 when the compressor 100 is started after the compressor 100 is stopped for a long time in a high temperature state. As is apparent, the CO 2 according to the present embodiment is
It can be seen that in the _two cycles (solid line), the discharge pressure is prevented from excessively increasing as compared with the conventional CO ₂ cycle (dashed line).

(Third Embodiment) In the present embodiment, the CO ₂ cycle according to the second embodiment is electronically controlled including the pressure control valve 300. That is, as shown in FIG. 9, the bypass passage 600 is eliminated, and the pressure control valve 300 is changed to an electric type. By the way,
The structure of the electric pressure control valve 300 is similar to the structure of the electric expansion valve of a refrigeration cycle using chlorofluorocarbon as a refrigerant.

The electronic control unit 800 includes a radiator 2
The detection signals of a pressure sensor (pressure detection means) 810 for detecting the refrigerant pressure at the outlet side of 00 and a temperature sensor (temperature detection means) 820 for detecting the refrigerant temperature at the outlet side of the radiator 200 are input. Then, the electronic control unit 800 performs a predetermined time (about 5 seconds in the present embodiment) after the compressor 100 is started.
Until elapses, the pressure control valve 300 is opened and the refrigerant flowing out of the radiator 200 is supplied to the evaporator 400 regardless of the temperature detected by the temperature sensor 820.

After a predetermined time has elapsed, the electronic control unit 800 determines the refrigerant temperature at the outlet of the radiator 200 (the temperature detected by the temperature sensor 820) and the refrigerant pressure at the outlet of the radiator 200 (the pressure detected by the pressure sensor 810). ) Is adjusted based on the temperature detected by the temperature sensor 820 so that the solid line ηmax in FIG. (Fourth Embodiment) The present embodiment relates to the C according to the second embodiment.
In the O ₂ cycle, the solenoid valve 900 is replaced with a mechanical valve means 950 (see FIG. 10).

FIG. 11 is a cross-sectional view of the mechanical valve means 950. The valve means 950 is adapted to change the pressure in the temperature-sensitive chamber 951 depending on the refrigerant temperature at the outlet of the evaporator 400 and the pressure at the outlet of the accumulator 500. The bypass passage 600 is opened and closed using a pressure difference from the refrigerant pressure. That is, the temperature sensing chamber 951 communicates with the diaphragm 952 movable according to the pressure change in the temperature sensing chamber 951 and the space in the temperature sensing chamber 951 to detect the temperature of the refrigerant at the outlet side of the evaporator 400. 10).
On the other hand, the refrigerant pressure on the outlet side of the accumulator 500 is guided to a space 954 opposite to the temperature sensing chamber 951 with the diaphragm 952 interposed therebetween.

Reference numeral 955 denotes an inlet of the bypass passage 600 connected to the radiator 200, and reference numeral 956 denotes an outlet of the bypass passage 600 connected to the evaporator 400. Reference numeral 957 denotes a valve port that connects the inflow port 955 and the outflow port 956, and 958 denotes a valve body that opens and closes the valve port 957. Reference numeral 959 denotes a coil spring (elastic member) for applying an elastic force in a direction to close the valve port 957 to the valve element 958. Reference numeral 960 denotes a push rod which contacts the valve element 958 and is joined to the diaphragm 952. is there. When the refrigerant temperature on the outlet side of the evaporator 400 rises and the pressure in the temperature-sensitive chamber 951 becomes higher than the refrigerant pressure on the outlet side of the accumulator 500, the push rod 960 generates a force for opening the valve port 957. Valve 85
8

Therefore, when the compressor 100 is stopped and the pressure control valve 300 is closed to increase the temperature and pressure in the evaporator 400, the push rod 960 overcomes the elastic force of the coil spring 959 and pushes down the valve body 958. Therefore, the valve port 957 (bypass passage 60) opens. And
After the compressor 100 is started, the discharge pressure rises and the pressure control valve 3
When 00 starts to open, the refrigerant is supplied to the evaporator 400, so that the temperature and the pressure in the evaporator 400 decrease and the pressure in the temperature sensing chamber 951 decreases, and the valve port 957 (bypass passage 60) closes.

(Fifth Embodiment) In the first embodiment, the bypass passage 600 is provided independently of the pressure control valve 300. However, in the present embodiment, as shown in FIG. The control valve body 303
A bleed port (bypass passage 600) that bypasses the bleed port is provided.

In the above embodiment, CO ₂ is used as the refrigerant. However, the refrigerant in the supercritical refrigeration cycle according to the present invention is not limited to this. For example, ethylene, ethane, nitrogen oxide, etc. may be used. . Further, in the second and third embodiments, it was determined whether or not the compressor 100 was started based on the ON-OFF signal of the electromagnetic clutch 110. However, the compressor 100 was started due to, for example, a pressure change on the outlet side of the radiator 200. It may be determined whether or not.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a CO ₂ cycle (supercritical refrigeration cycle) according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the pressure control valve according to the first embodiment of the present invention.

FIG. 3 is a Mollier diagram of CO ₂ of the present invention.

FIG. 4 is a sectional view showing a modified example of the pressure control valve according to the first embodiment of the present invention.

FIG. 5 is a schematic diagram of a CO ₂ cycle according to a second embodiment of the present invention.

6 (a) is a graph showing the state of the CO ₂ cycle according to the prior art which does not have the bypass passage and the solenoid valve, (b) is a CO ₂ cycle in accordance with the second embodiment It is a graph which shows a state.

FIG. 7 is a bar graph showing power consumption of the compressor.

FIG. 8 is a graph showing a change in the discharge pressure of the compressor when the compressor is started after the compressor has been stopped for a long time in a high temperature state.

FIG. 9 is a schematic diagram of a CO ₂ cycle according to a third embodiment of the present invention.

FIG. 10 is a schematic diagram of a CO ₂ cycle according to a fourth embodiment of the present invention.

FIG. 11 is a sectional view of a valve means according to a fourth embodiment of the present invention.

FIG. 12 is a sectional view of valve means according to a fifth embodiment of the present invention.

[Explanation of symbols]

100: compressor, 200: radiator, 300: pressure control valve, 400: evaporator, 500: accumulator, 60
0: bypass passage.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasutaka Kuroda 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Koji Yamanaka 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Denso Corporation Inside

Claims (4)

[Claims] A compressor (100) for compressing a refrigerant, a radiator (2) for cooling the refrigerant discharged from the compressor (100) and having an internal pressure exceeding a critical pressure of the refrigerant.
00) and a pressure control valve for reducing the pressure of the refrigerant flowing out of the radiator (200) and controlling the refrigerant pressure at the outlet of the radiator (200) based on the temperature of the refrigerant at the outlet of the radiator (200). (300), an evaporator (400) for evaporating the refrigerant depressurized by the pressure control valve (300), and a refrigerant flowing out of the radiator (200) bypassing the pressure control valve (300). The bypass passage (60) which leads to the evaporator (400) and has a predetermined passage resistance.
0). 2. A compressor (100) for compressing a refrigerant, and a radiator (2) for cooling the refrigerant discharged from the compressor (100) and having an internal pressure exceeding a critical pressure of the refrigerant.
00) and a pressure control valve for reducing the pressure of the refrigerant flowing out of the radiator (200) and controlling the refrigerant pressure at the outlet of the radiator (200) based on the temperature of the refrigerant at the outlet of the radiator (200). (300), an evaporator (400) for evaporating the refrigerant depressurized by the pressure control valve (300), and a refrigerant flowing out of the radiator (200) bypassing the pressure control valve (300). A bypass passage (600) leading to the evaporator (400); and valve means (900, 950) provided in the bypass passage (600) for opening and closing the bypass passage (600). , 950) is the compressor (10).
A supercritical refrigeration cycle characterized in that the bypass passage (600) is opened until a predetermined time elapses after the start of 0). 3. A compressor (100) for compressing a refrigerant, and a radiator (2) for cooling the refrigerant discharged from the compressor (100) and having an internal pressure exceeding a critical pressure of the refrigerant.
00) and a pressure control valve for reducing the pressure of the refrigerant flowing out of the radiator (200) and controlling the refrigerant pressure at the outlet of the radiator (200) based on the temperature of the refrigerant at the outlet of the radiator (200). (300), and an evaporator (400) for evaporating the refrigerant depressurized by the pressure control valve (300). After the compressor (100) is started, at least until a predetermined time elapses. A supercritical refrigeration cycle, wherein the side of the radiator (200) communicates with the side of the evaporator (400). 4. A compressor (100) for compressing a refrigerant, and a radiator (2) for cooling the refrigerant discharged from the compressor (100) and having an internal pressure exceeding a critical pressure of the refrigerant.
00) and a pressure controller that reduces the pressure of the refrigerant flowing out of the radiator (200) and controls the refrigerant pressure at the outlet of the radiator (200) based on the refrigerant temperature at the outlet of the radiator (200). A pressure control valve (300) having a pressure control valve (303); and an evaporator (400) for evaporating the refrigerant depressurized by the pressure control valve (300). Heatsink (20
0) bypassing the pressure control section (303) to guide the refrigerant flowing out of the pressure control section (303) to the evaporator (400), and provided with a bypass passage (600) having a predetermined passage resistance. Critical refrigeration cycle.