JPH09210515A - Refrigerating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent residual frost by a method wherein, during defrost operation, a high-pressure refrigerant pressure is prevented from increasing more than-necessary. SOLUTION: A hot gas bypass passage 36 is connected to the middle of a high pressure gas piping 3a, which links together a compressor 31 and a condenser 32, through a four-passage switch valve 34. A differential pressure passage 35 for operation is connected between a low pressure gas piping 3b on the suction side of the compressor and the four-passage switch valve 34. A capillary tube CP-1 is arranged in the differential pressure passage 35 and when cooling operation is switched to defrost operation, a refrigerant is stored at the condenser 32, an amount of a refrigerant returning from the condenser 32 is reduced and a circulation amount of a refrigerant during defrost operation is held at a given amount.

Description

Detailed Description of the Invention

[0001]

[0001] The present invention relates to a refrigeration apparatus,
In particular, the present invention relates to a refrigeration system that performs a hot gas defrost operation.

[0002]

2. Description of the Related Art Conventionally, as a refrigerating device, there is a dual refrigerating device in which a high temperature side refrigerating cycle and a low temperature side refrigerating cycle individually perform a refrigerating operation. This dual refrigeration system
It is used to obtain a low temperature of minus several tens of degrees, and can be used in a highly efficient region from a high compression ratio to a low compression ratio, which is advantageous in terms of energy saving.

The high temperature side refrigeration cycle of the above-mentioned dual refrigeration system comprises a compressor, a condenser, an expansion valve and an evaporator of a cascade heat exchanger, which are connected in sequence, and the low temperature side refrigeration cycle is connected to a compressor. The cascade heat exchanger includes a condenser, an expansion valve, and an evaporator, which are sequentially connected. In the cascade heat exchanger, the heat of condensation of the low temperature side refrigeration cycle and the heat of evaporation of the high temperature side refrigeration cycle are exchanged.

[0004]

In the above-described binary refrigeration system, since frost is formed on the evaporator of the low temperature side refrigeration cycle, the gas refrigerant discharged from the compressor (hereinafter referred to as hot gas) is vaporized every predetermined time. It is supplied to the vessel to perform defrost operation.

At this time, one end of the hot gas bypass passage is connected to the high pressure gas pipe on the discharge side of the compressor via a switching valve, and the other end of the hot gas bypass passage is connected to the refrigerant inflow side of the evaporator. The hot gas is supplied to the evaporator.

However, if a four-way switching valve is applied to the above switching valve, the return port of the four-way switching valve will be connected to the low pressure gas pipe on the suction side of the compressor via a differential pressure circuit, and during defrost operation. However, there is a problem that the high-pressure refrigerant pressure rises due to the increase in the refrigerant circulation amount.

That is, in the case of a four-way switching valve, it is necessary to connect the differential pressure passage to the four-way switching valve so that the switching operation can be performed. When the four-way switching valve is switched from the cooling operation to the defrost operation, the condenser and the suction side of the compressor communicate with each other via the differential pressure passage. On the other hand, since the refrigerant circulation amount during the cooling operation is larger than the refrigerant circulation amount during the defrost operation, when switching from the cooling operation to the defrost operation, the refrigerant in the condenser returns to the compressor, and the defrost operation is performed. The refrigerant circulation amount increases.

As a result, the pressure of the high-pressure refrigerant increases during the defrost operation. In particular, when a scroll-type compressor is used as the compressor, the high-pressure refrigerant pressure is likely to rise because the compression efficiency is good, and the high-pressure refrigerant pressure rises due to the pipe resistance.

Further, the above-mentioned defrosting operation is terminated and returned to the cooling operation when the high-pressure refrigerant pressure reaches a predetermined value when the outside air temperature of the evaporator is high and the outside air temperature is high. Therefore, when the high-pressure refrigerant pressure rises faster than the rise of the refrigerant temperature on the outlet side of the evaporator for reasons such as the refrigerant circulation amount, despite defrosting not ending,
There was a problem that the defrost operation was terminated and residual frost was generated.

The present invention has been made in view of the above problems, and an object thereof is to prevent the generation of residual frost by preventing the high pressure refrigerant pressure from rising faster than necessary during defrost operation.

[0011]

[Means for Solving the Problems]

-Outline of the Invention-The present invention provides a hot gas bypass passage (36) through a four-way switching valve (34) in the middle of a high-pressure gas pipe (3a) connecting a compressor (31) and a condenser (32). In addition to the connection, a differential pressure passage (35) for operation is connected between the suction side low pressure gas pipe (3b) of the compressor and the four-way switching valve (34), and a flow rate adjusting mechanism (35) is connected to the differential pressure passage (35). CP-1) is installed to collect refrigerant in the condenser (32) when switching from cooling operation to defrost operation, and reduce the amount of refrigerant returned from the condenser (32) to circulate refrigerant during defrost operation. Try to keep the amount at a predetermined amount.

-Specific Items of the Invention-Specifically, as shown in FIG. 1, the means taken by the invention according to claim 1 is as follows. First, a compressor (31), a condenser (32), an expansion mechanism (EV). -2) and an evaporator (33) are connected in order, and a refrigerating apparatus (30) in which a refrigerant circulates is configured is assumed.

The compressor (31) and the condenser (32)
A four-way switching valve (34) having four ports is connected in the middle of a high-pressure gas pipe (3a) that connects with the pressure source side by a first port on the pressure source side and a third port on the inflow / outflow side. The four-way switching valve (34) communicates the first port and the third port during the cooling operation and also communicates the second port on the return side with the fourth port on the inflow and outflow side, and at the time of the defrost operation. While connecting the first port and the fourth port,
The second port and the third port are configured to communicate with each other.

Further, one end of a hot gas bypass passage (36) is connected to the fourth port of the four-way switching valve (34), and the other end of the hot gas bypass passage (36) is hot during defrost operation. Liquid pipe (3) between the expansion mechanism (EV-2) and the evaporator (33) so as to supply gas to the evaporator (33).
c) is connected to.

In addition, the second port of the four way switching valve (34) is connected to the low pressure gas pipe (3b) on the suction side of the compressor (31) via the differential pressure passage (35) for operation. The differential pressure passage (3
5) has a flow rate control mechanism (CP-1) that limits the flow rate of the refrigerant.
Is provided.

The means taken by the invention according to claim 2 is the differential pressure passageway (35) according to the invention described in claim 1.
A check valve (CV-1) that allows only the refrigerant to flow from the four-way switching valve (34) to the low-pressure gas pipe (3b) is provided in the.

The means taken by the invention according to claim 3 is the condenser (32) according to the invention described in claim 1.
Consists of the condenser (32) of the cascade heat exchanger (1H), while the evaporator (23) of the cascade heat exchanger (1H)
The refrigerant pipe of the high temperature side refrigeration cycle (20) is connected to the.

-Operation- Due to the above-mentioned matters specifying the invention, in the invention according to claim 1,
During the cooling operation, the first port and the third port of the four-way switching valve (34) are in communication with each other. In this state, the refrigerant discharged from the compressor (31) is condensed in the condenser (32) to become a liquid refrigerant. For example, in the invention according to claim 3, heat exchange with the refrigerant of the high temperature side refrigeration cycle (20) is performed. Then, it is condensed in the cascade heat exchanger (1H), and this liquid refrigerant expands (EV-
After the pressure is reduced in 2), it is evaporated in the evaporator (33) to become a gas refrigerant and returns to the compressor (31), and this circulation is repeated. Then, the evaporator (33) produces cooling air.

When a defrost operation period of a predetermined time such as 4 hours is reached, the first port and the fourth port of the four-way switching valve (34) are connected to each other.
The refrigerant discharged from the compressor (31) is supplied to the hot gas bypass passage (36) in communication with the port, the second port and the third port are communicated with each other, and the condenser is provided via the differential pressure passage (35). The (32) communicates with the suction side of the compressor (31). that time,
Since the flow rate adjustment mechanism (CP-1) is provided in the differential pressure passage (35), the amount of the refrigerant accumulated in the condenser (32) returned to the compressor (31) is reduced. It is suppressed, and the refrigerant circulation amount during the defrost operation is maintained at a predetermined amount.

In this state, the hot gas (gas refrigerant) discharged from the compressor (31) flows into the four-way switching valve (3
From 4), it flows through the hot gas bypass passage (36), is supplied to the evaporator (33), and returns to the compressor (31), whereby defrosting is performed.

[0021]

Therefore, according to the present invention, the differential pressure passage (3) that connects the four-way switching valve (34) and the suction side of the compressor (31).
Since the flow rate control mechanism (CP-1) is provided in 5), the amount of refrigerant returned from the condenser (32) to the compressor (31) during defrost operation can be suppressed, so during defrost operation The refrigerant circulation amount can be maintained at a predetermined amount.

As a result, an abnormal increase in the high-pressure refrigerant pressure in the refrigeration cycle (31) during the defrost operation can be suppressed, so that the end of the defrost operation can be determined by the refrigerant temperature of the evaporator (33) or the like. Therefore, residual frost can be surely prevented.

Particularly, according to the second aspect of the present invention, the check valve (CV-1) is provided in the differential pressure passage (35) to connect the suction side of the compressor (31) to the hot gas bypass passage (36). Since the circulation of the refrigerant is blocked, it is possible to reliably prevent the refrigerant from accumulating in the drain pan heater or the like.

[0024]

Embodiment 1 of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 2, the dual refrigeration system (10)
Is for cooling a refrigerator or a freezer, and includes a high temperature side unit (1A) and a low temperature side unit (1B), and a high temperature side unit (1A) and a part of the low temperature side unit (1B) While the side refrigeration cycle (20) is configured, the low temperature side refrigeration cycle (3
0) is configured.

The high temperature side refrigeration cycle (20) includes a compressor (21) and a high pressure gas pipe (2) on the discharge side of the compressor (21).
and a condenser (22) connected via a) and the condenser (2)
2) is provided with an evaporator (23) of a cascade heat exchanger (1H) connected to a liquid pipe (2b), and the evaporator (23) is connected to a compressor (2) via a low pressure gas pipe (2c). It is connected to the suction side of 21).

The condenser fan (22-) includes a condenser fan (22-
F) is provided, while an expansion valve (EV-1) is provided in the middle of the liquid pipe (2b). The compressor (21) side (base end side) is configured as the high temperature side unit (1A) from the middle of the liquid pipe (2b) and the low pressure gas pipe (2c) in the high temperature side refrigeration cycle (20). . Specifically, the high temperature unit (1A) consists of a compressor (21) and high pressure gas piping (2a).
And condenser (22) and condenser fan (22-F) and liquid piping (2
b) and part of the low-pressure gas pipe (2c).

As shown in FIG. 3, the expansion valve (EV-1) is composed of an external pressure equalizing type temperature sensitive expansion valve, and the temperature sensing cylinder (T-1).
1) is an evaporator (33) in a cascade heat exchanger (1H)
Attached to the refrigerant outlet side, that is, to the low-pressure gas pipe (2c). Further, an external pressure equalizing pipe (E1) is connected to the high temperature side expansion valve (EV-1), and the external pressure equalizing pipe (E1) includes a three-way switching valve (SV-1) and a low pressure gas pipe (2c). It is connected to the mounting part of the temperature sensitive tube (T1) in.

One port of the three-way switching valve (SV-1) is connected to the low pressure gas pipe (2c), and the three-way switching valve (SV-1) is connected.
The liquid refrigerant pressure acts on the expansion valve (EV-1) to close the expansion valve (EV-1) while the three-way switching valve (SV-1) is turned on.
Of the expansion valve (EV-) so that the pressure of the gas refrigerant acts on the expansion valve (EV-1) at the time of turning off the gas refrigerant so that the gas refrigerant has a predetermined superheat degree.
1) opens to a specified opening.

On the other hand, the low temperature side refrigeration cycle (30) is
As shown in FIG. 3, a compressor (31), a condenser (32) of a cascade heat exchanger (1H), and an expansion valve (EV-2) which is an expansion mechanism.
And an evaporator (33) are sequentially connected, and the evaporator (33) is provided with an evaporator fan (33-F). Then, from the middle of the liquid pipe (2b) and the low pressure gas pipe (2c) in the high temperature side refrigeration cycle (20) to the cascade heat exchanger (1H) side (tip side) and the low temperature side refrigeration cycle (3
0) and are configured in the low temperature side unit (1B). Specifically, the low temperature side unit (1B) includes the low temperature side refrigeration cycle (30), the condenser (32) of the cascade heat exchanger (1H), the liquid pipe (2b) and a part of the low pressure gas pipe (2c). It is formed by the high temperature side expansion valve (EV-1) and the temperature sensing tube (T1).

The low temperature side expansion valve (EV-2) is composed of an external pressure equalizing type temperature sensitive expansion valve, and the temperature sensing tube (T2) is located at the refrigerant outlet side of the low temperature side evaporator (33), that is, low pressure. It is attached to the gas pipe (3b) and is connected to the external pressure equalizing pipe (E2). The external pressure equalizing pipe (E2) is connected to the mounting portion of the temperature sensing cylinder (T2) in the low pressure gas pipe (3b), and the low temperature side expansion valve (EV-2) is arranged so that the gas refrigerant has a predetermined superheat degree. Open to a predetermined opening.

A four-way switching valve (34) is provided in the high-pressure gas pipe (3a) on the discharge side of the low temperature side compressor (31), and the four-way switching valve (34) is the first on the pressure source side. The port P and the third port A on the inflow / outflow side are connected to the high-pressure gas pipe (3a), while the differential port for operation (35) is provided on the second port R on the return side.
However, the hot gas bypass passages (36) are connected to the fourth port B on the inflow / outflow side, respectively.

The four-way switching valve (34) is turned off during the cooling operation, and the first port P and the third port A communicate with each other as shown by the solid line in FIG. The discharge refrigerant of 31) is supplied to the condenser (32) and the second port R and the fourth port B are communicated with each other.

Further, the four-way switching valve (34) is turned on during the defrost operation, as shown by the broken line in FIG.
The first port P and the fourth port B communicate with each other to allow the refrigerant discharged from the low temperature side compressor (31) to pass through the hot gas bypass passage (36).
And the second port R and the third port A are communicated with each other.

The hot gas bypass passage (36) is connected to the suction side of the low temperature side evaporator (33), that is, the liquid pipe (3c) between the expansion valve (EV-2) and the evaporator (33). The hot gas is supplied to the low temperature side evaporator (33) every predetermined time, for example, every 4 hours to remove frost formation on the evaporator (33). Further, a drain pan heater (H1), a drain receiving heater (H2) and a fan guard heater (H3) are connected in parallel with each other in the middle of the hot gas bypass passage (36), and a compressor (31) A check valve (CV-2) is provided so as to allow only the refrigerant to flow from the discharge side to the low temperature side evaporator (33).

The drain pan heater (H1) is for removing frost from the drain pan provided below the low temperature side evaporator (33), and the drain receiver heater (H2) is for removing the drain receiver formed on the drain pan. The fan guard heater (H3) removes frost formation, and removes frost formation around the evaporator fan (33-F).

The differential pressure passage (35) is a feature of the present invention, and is connected to the low pressure gas pipe (3b) on the suction side of the compressor (31) and the four-way switching valve (34). ), A check valve (CV-1) is provided so as to allow only the refrigerant to flow from the suction side of the compressor (31).

Particularly, the differential pressure passage (35) is a passage for switching operation of the four-way switching valve (34) and is provided with a capillary tube (CP-1). The capillary tube (CP-1) constitutes a flow rate adjusting mechanism for limiting the amount of refrigerant flow, that is, the condenser (32) during defrost operation.
The low pressure gas pipe (3b) on the suction side of the compressor (31) communicates with each other via the differential pressure passage (35), but is configured to suppress the refrigerant flow rate.

Further, each low temperature side refrigeration cycle (30) is provided with a capacity control bypass passage (37).
One end of the capacity control bypass passage (37) is connected to the compressor (3
1) and the four-way switching valve (34) are connected to the high pressure gas pipe (3a), and the other end is connected to the liquid pipe (3c) between the expansion valve (EV-2) and the evaporator (33). It is connected. The capacity control bypass passage (37) is provided with a solenoid valve (SV-3) and a capillary tube (CP-3), and the hot gas discharged from the compressor (31) is evaporated (33). To adjust the cooling capacity.

In the high pressure gas pipe (3a) of the low temperature side refrigeration cycle (30), a high pressure switch (HPS1) that outputs an abnormal signal when the high pressure refrigerant pressure rises abnormally, and the high pressure refrigerant pressure has a predetermined high pressure value. A high pressure sensor (HPS2) that outputs a high pressure signal is provided, and a defrost end signal is output to the hot gas bypass passage (36) when the high pressure refrigerant pressure that is the hot gas pressure reaches a predetermined high pressure value. A defrost pressure sensor (HPS3) is provided.

In the low pressure gas piping (3b) of the low temperature side refrigeration cycle (30), a low pressure switch (LPS1) which outputs an abnormal signal when the low pressure refrigerant pressure abnormally drops, and a low temperature side evaporator (33). ) Is provided with a defrost temperature sensor (Th-1) that outputs a defrost end signal when the refrigerant temperature on the refrigerant outflow side of (1) reaches a predetermined high temperature.

-Operation and Effect of Binary Refrigerator (10)-Next, the operation of the binary refrigerator (10) described above will be described.

First, when performing a cooling operation (thermo-on), both the high temperature side compressor (21) and the low temperature side compressor (31) are driven, and the high temperature side condenser fan (22-F) and the low temperature side evaporator are also driven. The fan (33-F) drives together. Then, the three-way switching valve (SV-1) is turned off and the high temperature side expansion valve (EV
-1) External equalizing pipe (E1) is in communication.

In this state, in the high temperature side refrigeration cycle (20), the refrigerant discharged from the compressor (21) is condensed in the condenser (22) to become a liquid refrigerant, and the low temperature side unit (1)
B). And the liquid refrigerant is an expansion valve (EV-1)
After depressurizing in the evaporator of the cascade heat exchanger (1H) (2
In 3), the refrigerant evaporates to become a gas refrigerant and returns to the compressor (21), and this circulation is repeated.

On the other hand, in the low temperature side refrigeration cycle (30), the four-way switching valve (34) is switched to the solid line in FIG.
The refrigerant discharged from the refrigerant passes through the high-pressure gas pipe (3a) and is condensed in the condenser (32) of the cascade heat exchanger (1H) to become liquid refrigerant. This liquid refrigerant is decompressed by the expansion valve (EV-2). After doing
It is evaporated in the evaporator (33) to become a gas refrigerant, and the compressor (31)
I will return to and repeat this cycle. Then, cooling air is generated by the low-temperature side evaporator (33) to cool the inside of the refrigerator.

When the internal temperature reaches a predetermined temperature, the thermostat is turned on, the cooling operation is stopped, the high temperature side compressor (21) and the low temperature side compressor (31) are stopped, and the low temperature side evaporator fan (33- F) drive only.

On the other hand, as a feature of the present invention, since the defrosting operation (defrosting operation) is performed every predetermined time such as 4 hours, the operation of this defrosting operation will be described with reference to FIG.

First, during the cooling operation described above, in step ST1, it is determined whether or not the preset operation cycle of the defrost operation has been reached, and the process waits in step ST1 until the defrost operation cycle is reached.

After that, when the defrost operation cycle comes, the determination in step ST1 becomes YES and the process moves to step ST2 to execute the defrost operation. Specifically, the operation of the high temperature side refrigeration cycle (20) is stopped, and the high temperature side compressor (21)
While stopping the high temperature side condenser fan (22-F), the low temperature side compressor (31) is used in the low temperature side refrigeration cycle (30).
And drive the low temperature side evaporator fan (33-F).

Then, the four-way switching valve (34) in the low temperature side refrigeration cycle (30) is switched to the broken line in FIG. 3 so that the first port P and the fourth port B communicate with each other and the low temperature side compressor (31) is closed. The discharged refrigerant is supplied to the hot gas bypass passage (36), the second port R and the third port A are communicated with each other, and the condenser (32) of the cascade heat exchanger (1H) is provided via the differential pressure passage (35). ) Is connected to the suction side of the low temperature side compressor (31). At that time, since the capillary tube (CP-1) is provided in the differential pressure passage (35), of the refrigerant accumulated in the condenser (32), the refrigerant flows to the low temperature side compressor (31). Therefore, the return amount of is suppressed, and the refrigerant circulation amount during the defrost operation is maintained at a predetermined amount.

In this state, the hot gas (gas refrigerant) discharged from the low temperature side compressor (31) flows into the four-way switching valve (3
It flows from 4) through the hot gas bypass passage (36) and is supplied to the low temperature side evaporator (33) in addition to the drain pan heater (H1) and returned to the compressor (31), which defrosts it. It will be.

On the other hand, after starting the above defrost operation,
From step ST2 to step ST3, it is determined whether or not the defrost end signal is output, and the process returns to step ST2 and the defrost operation is continued until the end signal is output.

After that, the refrigerant temperature on the refrigerant outlet side of the low temperature side evaporator (33) reaches a predetermined high temperature, and the defrost temperature sensor (Th-1) outputs an end signal or the compressor (31).
When the high-pressure refrigerant pressure on the discharge side becomes a predetermined pressure and the defrost pressure sensor (HPS3) outputs an end signal, or when a predetermined time has elapsed and an end signal is output, the determination in step ST3 is made. Is YES, the process moves to step ST1, and the cooling operation described above is restarted.

Therefore, according to the first embodiment, the capillary tube (CP-1) is provided in the differential pressure passage (35) connecting the four-way switching valve (34) and the suction side of the compressor (31). Therefore, the refrigerant return amount from the condenser (32) to the low temperature side compressor (31) during the defrost operation can be suppressed, so that the refrigerant circulation amount during the defrost operation can be maintained at a predetermined amount.

As a result, it is possible to suppress an abnormal increase in the high-pressure refrigerant pressure in the low temperature side refrigeration cycle (31) during the defrost operation, so that the end of the defrost operation is determined by the refrigerant temperature in the low temperature side evaporator (33). Therefore, residual frost can be surely prevented.

Further, a check valve (CV-
Since 1) is provided to prevent the refrigerant from flowing from the suction side of the compressor (31) to the hot gas bypass passage (36), it is possible to reliably prevent refrigerant accumulation in the drain pan heater (H1) and the like. it can.

[0057]

Embodiment 2 As shown in FIG. 5, this Embodiment 2 is configured by one refrigeration cycle instead of the description of the binary refrigeration system (10) in Embodiment 1 above. is there. That is, it is configured by only the low temperature side refrigeration cycle (30) in the first embodiment, and the condenser (32) is configured by an air-cooled condenser equipped with a condenser fan (32-F). Then, in addition to the four-way switching valve (34), a differential pressure passage (3 having a capillary tube (CP-1) and a check valve (CV-1) is provided.
5) is the same as in the first embodiment.

Specifically, as shown in Table 1, during the cooling operation (when the thermostat is on), the compressor (31), the condenser fan (32-F) and the evaporator fan (33-F) are driven. On the other hand, the four-way switching valve (34) is turned off to bring it to the state shown by the solid line in FIG.
When the cooling operation is stopped (when the thermostat is off), the compressor (31)
And stop the condenser fan (32-F) and drive only.

During defrost operation, the compressor (31)
Drive the fan and stop the condenser fan (32-F) and the evaporator fan (33-F) while turning on the four-way switching valve (34) to bring the hot gas into the hot gas state. It flows into the bypass passage (36) and is supplied to the evaporator (33).

[0060]

[Table 1]

The other operations and effects are similar to those of the first embodiment.

[0062]

Another Embodiment of the Invention In the second embodiment,
Although the air-cooled condenser (32) is applied, the present invention may be applied to the water-cooled condenser (32) for heat exchange between water and the refrigerant.

The hot gas bypass passage (36) is
Of course, the drain pan heater (H1) may not be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a refrigerant circuit diagram showing an outline of a binary refrigeration system.

FIG. 3 is a refrigerant circuit diagram showing a low temperature side refrigeration cycle.

FIG. 4 is a control flow chart showing a defrost operation.

FIG. 5 is a refrigerant circuit diagram showing a refrigeration cycle according to a second embodiment.

[Explanation of symbols]

 10 Dual refrigeration system 1A High temperature unit 1B Low temperature unit 1H Cascade heat exchanger 20 High temperature side refrigeration cycle 21 Compressor 22 Condenser 23 Evaporator EV-1 Expansion valve T1 Temperature sensing tube 30 Low temperature side refrigeration cycle 31 Compressor 32 Condenser 33 Evaporator 34 Four-way switching valve 35 Differential pressure passage 36 Hot gas bypass passage EV-2 Expansion valve (expansion mechanism) CP-1 Capillary tube (flow control mechanism) CV-1 Check valve

Claims (3)

[Claims] 1. A refrigeration cycle (30) in which a compressor (31), a condenser (32), an expansion mechanism (EV-2) and an evaporator (33) are sequentially connected to circulate a refrigerant. In the refrigeration system, a four-way switching valve (34) having four ports is provided in the middle of the high pressure gas pipe (3a) connecting the compressor (31) and the condenser (32) to the first port on the pressure source side. And a third port on the inflow / outflow side, the four-way switching valve (34) communicates the first port and the third port during the cooling operation, and the second port on the return side and the inflow / outflow side. The fourth port of the four-way selector valve is configured to communicate with the first port and the fourth port and to communicate with the second port and the third port during the defrost operation. One end of the hot gas bypass passage (36) is connected to the fourth port of The other end of the gas bypass passage (36) has a liquid pipe (3c) between the expansion mechanism (EV-2) and the evaporator (33) so that hot gas is supplied to the evaporator (33) during defrost operation. On the other hand, the second port of the four-way switching valve (34) is connected to the low pressure gas pipe (3b) on the suction side of the compressor (31) via the differential pressure passage (35) for operation. The differential pressure passage (35) is provided with a flow rate adjusting mechanism (CP-1) for limiting the amount of refrigerant flowing therein. 2. The refrigeration apparatus according to claim 1, wherein the differential pressure passage (35) has a check valve (CV) which allows only refrigerant to flow from the four-way switching valve (34) to the low-pressure gas pipe (3b). -1) is provided. 3. The refrigerating apparatus according to claim 1, wherein the condenser (32) is composed of a condenser (32) of the cascade heat exchanger (1H), and evaporation of the cascade heat exchanger (1H). The refrigerating device, wherein the refrigerant pipe of the high temperature side refrigeration cycle (20) is connected to the container (23).