JP3303689B2 - Binary refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binary refrigeration system, and more particularly to a measure for avoiding a situation in which refrigeration capacity is significantly reduced.

[0002]

2. Description of the Related Art Conventionally, as one type of refrigerating apparatus used for a freezer or the like, a binary refrigerating apparatus in which a high-temperature-side refrigerant circuit and a low-temperature-side refrigerant circuit individually perform a freezing operation has been known. . This type of binary refrigeration system is for obtaining a low temperature of minus several tens of degrees, and can be operated at high efficiency from a high compression ratio to a low compression ratio, which is advantageous in terms of energy saving.

[0003] The specific configuration of this binary refrigeration apparatus will be described. First, the high-temperature side refrigerant circuit is configured by connecting a compressor, a condenser, an expansion mechanism, and an evaporator of a cascade heat exchanger in this order. On the other hand, the low-temperature side refrigerant circuit is configured by connecting a compressor, a condenser of a cascade heat exchanger, an expansion mechanism, and an evaporator in this order. Then, in the cascade heat exchanger, the heat of evaporation of the high-temperature side refrigerant circuit and the heat of condensation of the low-temperature side refrigerant circuit exchange heat.

The low-temperature side refrigerant circuit is provided with a hot gas bypass pipe for controlling the capacity connecting the discharge side of the compressor and the upstream side of the evaporator. The refrigeration capacity is controlled by adjusting the bypass amount. Specifically, an electromagnetic valve is provided in the hot gas bypass pipe, and the discharged refrigerant is bypassed to the evaporator by opening the electromagnetic valve. When the internal temperature becomes higher than a predetermined value, the solenoid valve is opened to evaporate the discharged refrigerant in order to prevent the necessary refrigerating capacity from being increased and the load on the high-temperature side refrigerant circuit from being excessively increased. Bypass to vessel. That is,
By reducing the load, a stable operation state can be obtained while using a small-sized unit of the high-temperature side refrigerant circuit.

FIG. 6 is a diagram showing a change in the refrigerating capacity of the refrigerating apparatus with respect to the temperature in the refrigerator. As described above, when the temperature in the refrigerator is equal to or lower than the point A (for example, −10 ° C.), the higher the temperature in the refrigerator, the higher the refrigerating capacity is to perform the refrigeration operation (FIG. 6).
Curve I). On the other hand, when the internal temperature is equal to or higher than the point A, the refrigerating capacity is slightly reduced by the hot gas bypass operation. In this state, the higher the internal temperature, the higher the refrigerating capacity is set to perform the refrigerating operation. (Curve I in FIG. 6
I). Then, in a state where the hot gas bypass operation is being performed, if the internal temperature drops to the point B (for example, −12 ° C.), the hot gas bypass is stopped.

On the other hand, a hot gas bypass pipe is also provided in the high temperature side refrigerant circuit. The hot gas bypass pipe connects the discharge side and the suction side of the compressor, and adjusts the low pressure refrigerant pressure of the high temperature side refrigerant circuit by adjusting the hot gas bypass state. Specifically, an electromagnetic valve is provided in the hot gas bypass pipe, and when the low-pressure refrigerant pressure becomes equal to or lower than a predetermined value, the electromagnetic valve is opened and a part of the discharged refrigerant is bypassed to the suction side of the compressor. It is kept at or above a predetermined value.

[0007]

By the way, in the conventional binary refrigeration system described above, the bypass operation of each hot gas in the high-pressure side refrigerant circuit and the low-pressure side refrigerant circuit is performed individually. . Therefore, depending on the operation state, a situation may occur in which each refrigerant circuit performs a hot gas bypass operation together. Particularly, in a situation where the capacity adjustment operation by the hot gas bypass operation is performed in the low-temperature side refrigerant circuit, when the outside air temperature is relatively low, the low-pressure refrigerant pressure in the high-temperature side refrigerant circuit decreases, thereby The hot gas bypass operation is also performed in the refrigerant circuit.

[0008] FIG. 6 shows a change state of the refrigerating capacity of the refrigerating apparatus with respect to the internal temperature in such a situation by a dashed line. In this way, in a situation where both the low-temperature side refrigerant circuit and the high-temperature side refrigerant circuit are performing the hot gas bypass operation, the performance of the entire refrigeration apparatus will be significantly reduced,
Problems such as taking a long time to obtain an appropriate internal temperature will be caused.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and an object of the present invention is to avoid a significant decrease in refrigeration capacity due to a hot gas bypass operation performed by both a high-pressure refrigerant circuit and a low-pressure refrigerant circuit. And

[0010]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention avoids the occurrence of a situation where both the low-temperature side refrigerant circuit and the high-temperature side refrigerant circuit perform a hot gas bypass operation. is there.

Specifically, the invention according to claim 1 is a compressor
(21), a condenser (22), an expansion mechanism (EV-1), and an evaporator (23) of a cascade type heat exchanger (1H) are connected in order and a high-temperature side refrigerant circuit ( 20), while the compressor (31)
The condenser (32) of the cascade type heat exchanger (1H), the expansion mechanism (EV-2), and the low temperature side refrigerant circuit (30) in which the refrigerant circulates by connecting the evaporator (33) in this order. Make up each refrigerant circuit (20,30)
Then, a part of the refrigerant discharged from the compressors (21, 31) is
Bypass means capable of bypassing to the low pressure side in (20,30)
It assumes a binary refrigeration system equipped with (27, EV-3) and (37, SV-3). The bypass means (27, EV-3) and (37, SV-3) of each refrigerant circuit (20, 30) are provided with a bypass means (51) for avoiding simultaneous refrigerant bypass operation. .

According to this specific matter, each refrigerant circuit (20, 30)
In the cascade heat exchanger (1H), heat is exchanged between these refrigerant circuits (20, 30), and the refrigerant is circulated in the evaporator (33) of the low-temperature side refrigerant circuit (30), for example. A low temperature of minus several tens degrees is obtained. In such an operation state, the bypass means (27, EV-3) and (37, SV-3) of each refrigerant circuit (20, 30) are discharged from the compressor (21, 31) according to the operation state. A part of the refrigerant is bypassed to the low pressure side in each of the circuits (20, 30), for example, to perform capacity control. Then, each refrigerant circuit (2
In the situation where the bypass means (27, EV-3) and (37, SV-3) of (0, 30) simultaneously perform the refrigerant bypass operation, that is, in the situation in which the refrigeration capacity is significantly reduced, the avoidance means (51, ) Operate to prevent the two from simultaneously performing a bypass operation. As a result, a large decrease in the refrigeration capacity is prevented.

According to a second aspect of the present invention, in the binary refrigerating apparatus of the first aspect, the bypass means of the high-temperature side refrigerant circuit (20) is connected between the discharge side and the suction side of the compressor (21). A hot gas bypass pipe (27) and an on-off valve (EV-3) provided in the hot gas bypass pipe (27) are provided.
Then, the low pressure refrigerant pressure of the high temperature side refrigerant circuit (20) is adjusted by the opening / closing operation of the opening / closing valve (EV-3). On the other hand, a bypass means of the low-temperature side refrigerant circuit (30) is provided with a hot gas bypass pipe (37) connecting the discharge side of the compressor (31) and the refrigerant introduction side of the evaporator (33), and the hot gas bypass pipe. (37) and an on-off valve (SV-3) provided in (37). The refrigerating capacity is adjusted by opening and closing the on-off valve (SV-3).

In this particular matter, in particular, the high temperature side refrigerant circuit
(20) bypass means (27, EV-3) and low-temperature side refrigerant circuit (30)
The operation of the bypass means (37, SV-3) is independent of each other, and it is easy for these to perform a bypass operation at the same time. Bypass operation will be avoided.

According to a third aspect of the present invention, in the binary refrigeration apparatus according to the first or second aspect, the high-temperature side refrigerant circuit (20) is provided.
The bypass means (27, EV-3) is provided with a judgment means (52) for judging that the condition for performing the bypass operation is satisfied, the avoidance means (51) receives the output of the judgment means (52), While the bypass means (37, SV-3) of the low-temperature refrigerant circuit (30) is performing the bypass operation, the bypass means of the high-temperature refrigerant circuit (20) is
(27, EV-3) when the condition for bypass operation is satisfied,
The bypass operation of the low-temperature side refrigerant circuit (30) by the bypass means (37, SV-3) is stopped.

According to a fourth aspect of the present invention, in the binary refrigeration apparatus of the first or second aspect, the low-temperature side refrigerant circuit (30) is provided.
Of the evaporator (33) is provided with a fan (33-F) capable of adjusting the air volume, and the same determination means (52) as described above.
Then, the avoiding means (51) receives the output of the determining means (52), and in a state where the bypass means (37, SV-3) of the low-temperature side refrigerant circuit (30) is performing the bypass operation, the high-temperature side refrigerant is When the condition for performing the bypass operation of the bypass means (27, EV-3) of the circuit (20) is satisfied, the air volume of the fan (33-F) is increased.

According to a fifth aspect of the present invention, there is provided the binary refrigeration apparatus of the first or second aspect, wherein the high-temperature side refrigerant circuit (20) is provided.
Of the condenser (22) is provided with a fan (22-F) capable of adjusting the air volume, and the same determination means (52) as described above.
Then, the avoiding means (51) receives the output of the determining means (52), and in a state where the bypass means (37, SV-3) of the low-temperature side refrigerant circuit (30) is performing the bypass operation, the high-temperature side refrigerant is When the condition for performing the bypass operation of the bypass means (27, EV-3) of the circuit (20) is satisfied, the air volume of the fan (22-F) is reduced.

According to these specific items, each refrigerant circuit (20, 3
The operation of the avoiding means (51) for preventing the bypass means (27, EV-3) and (37, SV-3) of (0) from simultaneously performing the refrigerant bypass operation is embodied.

The invention according to claim 6 is the invention according to claims 3 and 4.
Or the high-temperature side refrigerant circuit
(20) is provided with a low-pressure detecting means (LPS2) for detecting the low-pressure refrigerant pressure, and the judging means (52) receives the output of the low-pressure detecting means (LPS2), and the low-pressure side of the high-temperature side refrigerant circuit (20) is a predetermined pressure. When the value falls below the value, the bypass means (27, EV-3) determines that the condition for performing the bypass operation is satisfied.

The invention according to claim 7 is the invention according to claims 3 and 4.
Or the high-temperature side refrigerant circuit
A gas temperature detecting means (Th-e) for detecting the gas side temperature of the evaporator (23) of (20) is provided, and the judging means (52) receives the output of the gas temperature detecting means (Th-e). When the gas side temperature of the evaporator (23) of the high-temperature side refrigerant circuit (20) drops below a predetermined value, it is determined that the condition for performing the bypass operation by the bypass means (27, EV-3) is satisfied. ing.

The invention according to claim 8 is the invention according to claims 3 and 4.
Or the high-temperature side refrigerant circuit
(20) outside air temperature detecting means (Th-a) for detecting the temperature of the outside air that performs heat exchange with the refrigerant flowing through the condenser (22),
The judging means (52) receives the output of the outside air temperature detecting means (Th-a), and determines whether the bypass means (2
7) determines that the condition for performing the bypass operation is satisfied.

According to these specific items, the high-temperature side refrigerant circuit (2
The judgment operation of the judgment means (52) for judging that the condition for performing the bypass operation by the bypass means (27, EV-3) of (0) is specifically obtained.

[0023]

Next, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) First, a first embodiment of the present invention will be described. As shown in FIG. 1, the binary refrigeration apparatus (10) according to the present embodiment cools a refrigerator or a freezer, and includes a high-temperature unit (1A) and a low-temperature unit (1B). ing. The high-temperature side unit (1A) and a part of the low-temperature side unit (1B) constitute a high-temperature side refrigeration cycle (20) as a high-temperature side refrigerant circuit. A low temperature side refrigeration cycle (30) is configured as a side refrigerant circuit.

As shown in FIG. 2, the high temperature side refrigeration cycle (20) is connected to a compressor (21) via a high pressure gas pipe (2a) to the discharge side of the compressor (21). Condenser (2
2), and the condenser (22) has a condenser fan (22-
F) is provided. Further, one end of a main liquid pipe (2b) is connected to the condenser (22), and one end of a main gas pipe (2c) is connected to a suction side of the compressor (21). The main gas pipe (2c) is provided with an accumulator (24).

In the middle of the main liquid pipe (2b), the receiver (2
5) and an expansion valve (EV-1) (see FIG. 3), and the other end of the main liquid pipe (2b) is connected to the cascade heat exchanger (1).
H) is connected to the evaporator (23). The other end of the main gas pipe (2c) is also connected to the evaporator (23) of the cascade heat exchanger (1H). The main liquid pipe (2b) and the main gas pipe (2
From the middle of c), the compressor (21) side is
A) is configured. Specifically, the high-temperature side unit (1
A) consists of a compressor (21), high-pressure gas piping (2a) and a condenser (2
2) and the condenser fan (22-F) and a part of the main liquid pipe (2b) and the main gas pipe (2c).

The high temperature side refrigeration cycle (20) is provided with a hot gas bypass passage (27).
One end of the hot gas bypass passage (27) is connected to the high-pressure gas pipe (2a), and the other end is connected to the upstream side of the accumulator (24). The hot gas bypass passage (27) is provided with an on-off valve (EV-3). This on-off valve
(EV-3), the pressure on the upstream side of the accumulator (24) is introduced by the pressure introduction pipe (E3), and the accumulator (2
When the pressure on the upstream side of 4) drops below a predetermined value, the on-off valve (EV-
3) is opened, and a part of the hot gas discharged from the compressor (21) is supplied to the low pressure side to prevent the low pressure from lowering. This constitutes hot gas bypass means in the high temperature side refrigeration cycle (20).

An unloader circuit (28) in FIG. 2 includes an electromagnetic valve (SV-4) and a capillary tube (CP-4), and adjusts the opening of the electromagnetic valve (SV-4). By doing so, the capacity is controlled. Further, (29) is a liquid injection circuit, which includes a solenoid valve (SV-5) and a capillary tube (CP-5), and opens and closes the solenoid valve (SV-5) to open the main gas pipe (2c). The degree of superheat of the flowing refrigerant is adjusted.

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-sensitive cylinder (T1) is connected to the cascade heat exchanger (1H). It is attached to the refrigerant outlet side of the evaporator (23), that is, the main gas pipe (2c). Further, an external pressure equalizing pipe (E1) is connected to the high temperature side expansion valve (EV-1). The external pressure equalizing pipe (E1) includes a three-way switching valve (SV-1) and has a main gas pipe (2c). Is connected to the mounting part of the temperature-sensitive tube (T1).

One port of the three-way switching valve (SV-1) is connected to the main gas pipe (2c), and when the three-way switching valve (SV-1) is turned on, the liquid refrigerant pressure is increased by the expansion valve (EV-1). ), The expansion valve (EV-1) is closed, and when the three-way switching valve (SV-1) is turned off, the gas refrigerant pressure acts on the expansion valve (EV-1) to cause the gas refrigerant to reach a predetermined level. The expansion valve (EV-1) is opened to a predetermined degree so as to reach a degree of superheat.

The high-pressure gas pipe (2a) of the high-temperature side refrigeration cycle (20) is provided with a high-pressure pressure sensor (HPS4) that outputs a high-pressure signal when the high-pressure refrigerant pressure reaches a predetermined high pressure value. The low-pressure gas pipe (2c) of the high-temperature side refrigeration cycle (20) is provided with a low-pressure pressure sensor (LPS2) that outputs a low-pressure signal when the low-pressure refrigerant pressure reaches a predetermined low pressure value. Further, an upstream temperature sensor (Th-a) for detecting the temperature of the outside air introduced into the air passage is provided at an upstream portion of the air passage of the condenser (22). In addition, evaporator (23)
A gas temperature sensor (Th-e) for detecting the temperature of the gas refrigerant derived from the evaporator (23) is provided on the refrigerant outlet side of the evaporator (23).

On the other hand, the low-temperature side refrigeration cycle (30) is shown in FIG.
As shown in the figure, the compressor (31) and the cascade heat exchanger (1
H), a condenser (32), an expansion valve (EV-2) as an expansion mechanism, and an evaporator (33) are connected in order, and the evaporator (33) has an evaporator fan (33-F ) Is provided. Then, the cascade heat exchanger (1H) side and the low-temperature side refrigeration cycle (30) from the middle of the main liquid pipe (2b) and the main gas pipe (2c) in the high-temperature side refrigeration cycle (20). 1B) is configured. Specifically, the low-temperature side unit (1B) consists of the low-temperature side refrigeration cycle (30), the evaporator (23) of the cascade heat exchanger (1H) and the main liquid pipe (2).
b) and a part of the main gas pipe (2c) and the high temperature side expansion valve (EV-
1) and a temperature sensing tube (T1).

The low temperature side expansion valve (EV-2) is constituted by an external pressure equalizing type temperature sensitive expansion valve, and the temperature sensitive cylinder (T2) is connected to the refrigerant outlet side of the low temperature side evaporator (33), Attached to the gas pipe (3b) and connected to an external pressure equalizing pipe (E2). The external pressure equalizing pipe (E2) is connected to a portion of the low-pressure gas pipe (3b) to which the temperature-sensitive cylinder (T2) is attached, and the low-temperature side expansion valve (EV-2) is set so that the gas refrigerant has a predetermined degree of superheat. Open to a predetermined opening.

The high-pressure gas pipe (3a) on the discharge side of the low-temperature side compressor (31) is provided with a four-way switching valve (34), and the four-way switching valve (34) is connected to the first port on the pressure side. And the third on the outflow and entry side
The port is connected to the high-pressure gas pipe (3a), the operating differential pressure passage (35) is connected to the second port on the return side, and the defrost passage (36) is connected to the fourth port on the outflow / inflow side. I have.

The differential pressure passage (35) is connected to the low-pressure gas pipe (3b) on the suction side of the compressor (31) and from the four-way switching valve (34) to the suction side of the compressor (31). Check valve (CV-1) and capillary tube (CP
-1) is provided.

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

The drain pan heater (H1) removes frost from a drain pan (not shown) provided below the low-temperature side evaporator (33). The drain receiving heater (H2) serves as a lower end of the evaporator (33). A heater for heating a drain receiving member that is provided in the section and receives frost that is about to fall from the evaporator (33) to the outside of the drain pan, the fan guard heater (H3) includes:
It removes frost around the evaporator fan (33-F).

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

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

The low-pressure gas pipe (3b) of the low-temperature side refrigeration cycle (30) has a low-pressure pressure switch (LPS1) that outputs an abnormal signal when the low-pressure refrigerant pressure abnormally drops, and a low-temperature side evaporator (33). A) a defrost temperature sensor (Th-1) for outputting a defrost end signal when the refrigerant temperature on the refrigerant outflow side reaches a predetermined high temperature.

Each device of each unit (1A, 1B) is controlled by a controller (50). That is, the control of each solenoid valve and the electric valve and the control of the air volume of each fan are performed by the controller (50).

The controller (50) includes a judging means (52) and an avoiding means (51). Judging means (52)
Is the hot gas bypass passage of the high temperature side refrigeration cycle (20)
It is determined that the condition for performing the bypass operation according to (27) has been satisfied, and specifically, the low-pressure pressure sensor
When the output from the (LPS2) is received and the low-pressure refrigerant pressure of the high-temperature side refrigeration cycle (20) decreases to a predetermined value or less, the bypass means (27) determines that the condition for performing the bypass operation has been satisfied, and outputs a determination signal. Output. Note that the set value of the low-pressure refrigerant pressure for judging that this condition is satisfied is determined by the on-off valve (E
V-3) is set to be equal to or slightly higher than the pressure at which the opening operation is performed.

On the other hand, the avoiding means (51) is provided with the determining means (52).
When the determination signal is received from the low-temperature refrigeration cycle (30), if the bypass operation by the hot gas bypass passage (37) is being performed, the low-temperature refrigeration cycle (30) To stop. That is, the solenoid valve (SV-3) of this hot gas bypass passage (37)
Is forcibly closed to avoid simultaneous refrigerant bypass operation in each of the refrigeration cycles (20, 30).

Next, the operation of the binary refrigeration system (10) will be described. During this operation, the high temperature side compressor (21) and the low temperature side compressor (31) are both driven,
The high-temperature condenser fan (22-F) and the low-temperature evaporator fan (33-F) are both driven. And three-way switching valve (SV-1)
Is turned off, and the external pressure equalizing pipe (E1) of the high temperature side expansion valve (EV-1) communicates.

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 refrigerant discharged from the compressor (31) is condensed in the condenser (32) of the cascade heat exchanger (1H) to become a liquid refrigerant. After the pressure is reduced by the expansion valve (EV-2), the refrigerant evaporates in the evaporator (33) and returns to the compressor (31) as a gas refrigerant, and this circulation is repeated. Then, cooling air is generated by the low-temperature side evaporator (33) to cool the inside of the refrigerator.

A defrosting operation (defrosting operation) is performed every predetermined time such as 4 hours. In this case, the operation of the high-temperature side refrigeration cycle (20) is stopped.
1) and the high-temperature condenser fan (22-F) is stopped, and the three-way switching valve (SV-1) is turned on to fully close the high-temperature expansion valve (EV-1). Then, in the low-temperature refrigeration cycle (30), the four-way switching valve (34) is switched to the broken line in FIG. 2 to drive the compressor (31). In this state, the hot gas (high-temperature gas refrigerant) discharged from the low-temperature side compressor (31) flows through the hot gas bypass passage (36) from the four-way switching valve (34) and passes through each heater (H1, H2, H3). ), Is supplied to the low-temperature side evaporator (33) and returns to the compressor (31), whereby defrosting is performed.

Next, the operation of the hot gas bypass operation in each of the refrigeration cycles (20, 30) during the above-described refrigeration operation will be described. First, the high temperature side refrigeration cycle (2
In (0), when the pressure on the upstream side of the accumulator (24) drops below a predetermined value, this pressure acts on the on-off valve (EV-3) by the pressure introducing pipe (E3), and the on-off valve (EV-3) Opens. Thus, a part of the hot gas discharged from the compressor (21) is supplied to the low pressure side to prevent the low pressure from lowering.

On the other hand, in the low-temperature side refrigeration cycle (30), when the temperature in the refrigerator becomes higher than a predetermined temperature (for example, -10.degree. C.), the required refrigeration capacity increases and the high-pressure side refrigeration cycle (20) In order to prevent the load of the refrigerant from rising excessively, the solenoid valve (SV-3) of the hot gas bypass passage (37) is opened to partially bypass the discharged refrigerant to the evaporator (33).

A specific example of the hot gas bypass operation in the low temperature side refrigeration cycle (30) will be described with reference to the flowchart of FIG. 4. First, in step ST1, the internal temperature detected by the internal temperature sensor (not shown) is-. 10 ℃
It is determined whether or not this is the case. If YES is determined here, the process proceeds to step ST2 to open the solenoid valve (SV-3) and to bypass a part of the discharged refrigerant to the evaporator (33). This suppresses the load on the high-pressure side refrigeration cycle (30). Then, in step ST3, it is determined whether or not the temperature in the refrigerator has become -12 ° C or less.
Moving to 4, the solenoid valve (SV-3) is closed, the bypass of the discharged refrigerant is released, the operation is returned to the normal operation, and the process returns to step ST1.
By repeating such an operation, the load is appropriately maintained.

Such a hot gas bypass operation is performed by each refrigeration cycle (20, 30).

The feature of the present embodiment is that the hot gas bypass operation performed by each of the refrigeration cycles (20, 30) is not performed simultaneously. Hereinafter, the operation which is a feature of this embodiment will be described with reference to the flowchart of FIG.

First, in step ST11, it is determined whether or not the low-pressure refrigerant pressure detected by the low-pressure pressure sensor (LPS2) of the high-temperature side refrigeration cycle (20) is 1.5 kg / cm ² or less. This determination is for determining whether or not the start condition of the hot gas bypass operation is satisfied in the high temperature side refrigeration cycle (20). If the determination is YES, the process proceeds to step ST12 to determine whether the solenoid valve (SV-3) is open.
That is, it is determined whether or not the hot gas bypass operation is being performed in the low temperature side refrigeration cycle (30). This judgment is YES
In the case of, it moves to step ST13,
Forcibly close the solenoid valve (SV-3) of (30). This allows
The hot gas bypass operation in the low temperature side refrigeration cycle (30) is regulated. At the same time, the hot gas refrigeration cycle (20) performs a hot gas bypass operation.

In this state, the process proceeds to step ST14, where the low pressure detected by the low pressure sensor (LPS2) is 3.5 kg / cm.
^It is determined whether or not it becomes ² or more. This determination is for determining whether or not the stop condition of the hot gas bypass operation is satisfied in the high temperature side refrigeration cycle (20). If this determination is YES, the process moves to step ST15 to release the forced closed state of the solenoid valve (SV-3), and at the same time, returns the high-temperature side refrigeration cycle (20) to normal operation. In other words, this solenoid valve
The opening / closing operation of (SV-3) is returned to the normal state, the opening / closing operation of the solenoid valve (SV-3) is performed based on the above-described flowchart of FIG. 4, and the process returns to step ST11.

On the other hand, if NO is determined in step ST12, the process proceeds to step ST16, where the hot gas bypass operation of the high temperature side refrigeration cycle (20) is performed. Thereafter, in step ST17, it is determined whether or not the low pressure detected by the low pressure sensor (LPS2) is 3.5 kg / cm ² or more.
(EV-3) is closed and the operation returns to the normal operation, while if NO, the operation returns to step ST12. With such an operation, the determining means (52) is configured in step ST11, and the avoiding means (51) is configured in step ST13.

By repeating such an operation, when the conditions for starting the hot gas bypass operation in the high-temperature side refrigeration cycle (20) are satisfied, the low-temperature side refrigeration cycle
If (30) is performing hot gas bypass operation,
The bypass operation on the low temperature side is forcibly stopped, and the hot gas bypass operation is performed only in the high temperature side refrigeration cycle (20). On the other hand, when the start condition of the hot gas bypass operation in the high temperature side refrigeration cycle (20) is satisfied, if the low temperature side refrigeration cycle (30) is not performing the hot gas bypass operation, The hot gas bypass operation is performed in the refrigeration cycle (20).
When the stop condition of the hot gas bypass operation is not satisfied in the high temperature refrigeration cycle (20), the hot gas bypass operation is performed only in the low temperature refrigeration cycle (30) according to the operation described in the flowchart of FIG. The operation is performed.

That is, the hot gas bypass operation is performed in only one of the high-temperature side refrigeration cycle (20) and the low-temperature side refrigeration cycle (30). For this reason, it is possible to avoid a situation in which the hot gas bypass operation is performed in both refrigeration cycles (20, 30) and the refrigeration capacity is greatly reduced as in the related art. Further, according to the operation of the present embodiment, the high-temperature side refrigeration cycle
When the start condition of the hot gas bypass operation is satisfied in (20), the hot gas bypass operation of the low temperature side refrigeration cycle (30) is forcibly stopped, so that the cascade heat exchanger (1H) , The amount of heat exchange of the high-temperature refrigeration cycle (20) can be increased. For this reason, the time of the hot gas bypass operation in the high-temperature side refrigeration cycle (20) can be shortened, and the occurrence of dew condensation in the main gas pipe (2c) of the high-temperature side refrigeration cycle (20) can be avoided.

(Other Embodiment) Next, another embodiment will be described. The following forms are avoidance means (51) and determination means
This is a modified example of (52), and other configurations and control operations are the same as those of the above-described first embodiment. Therefore, here, only the avoiding means (51) and the determining means (52) will be described.

-Second Embodiment-In this embodiment, the determination means (52) is replaced with the detection of the low-pressure refrigerant pressure of the high-temperature refrigeration cycle (20) described above, and the evaporator ( 23) By detecting the refrigerant temperature at the outlet side, it is determined whether or not the condition for performing the bypass operation of the high-temperature side refrigeration cycle (20) is satisfied. That is, the evaporator detected by the gas temperature sensor (Th-e)
(23) When the refrigerant temperature on the outlet side drops to a predetermined value, the hot gas bypass operation in the low temperature side refrigeration cycle (30) is regulated. In other words, the high temperature side refrigeration cycle (2
The detection of the refrigerant pressure at the outlet side of the evaporator (23) in step (0) is substituted for the detection of the low-pressure refrigerant pressure.

This operation also enables the high-temperature side refrigeration cycle
The hot gas bypass operation is performed in only one of (20) and the low temperature side refrigeration cycle (30). For this reason, it is possible to avoid a situation in which the hot gas bypass operation is performed in both refrigeration cycles and the refrigeration capacity is greatly reduced as in the related art.

The operation of releasing the restriction on the hot gas bypass operation in the low-temperature side refrigeration cycle (30) is performed by controlling the refrigerant temperature at the outlet side of the evaporator (23) detected by the gas temperature sensor (Th-e). When it becomes slightly higher than the above-mentioned predetermined value,
Release the restriction of the bypass operation.

-Third Embodiment- In the present embodiment, the avoiding means (51) is replaced by restricting the hot gas bypass operation in the low temperature side refrigeration cycle (30) as in the first embodiment described above. The air volume of the evaporator fan (33-F) of the low temperature side refrigeration cycle (30) is increased.

That is, when the determination means (52) determines that the condition for performing the bypass operation of the high-temperature side refrigeration cycle (20) is satisfied, the air volume of the evaporator fan (33-F) is increased. As a result, the evaporation capacity of the low-temperature refrigeration cycle (30) is increased to increase the low-pressure refrigerant pressure and high-pressure refrigerant pressure of the low-temperature refrigeration cycle (30), and accordingly, the low-pressure refrigerant of the high-temperature refrigeration cycle (20) is increased. Increase pressure. Therefore, in the high temperature side refrigeration cycle (20), an operation is performed in which the condition for performing the bypass operation is not satisfied.

The operation of returning the air volume of the evaporator fan (33-F) is performed when the low-pressure refrigerant pressure of the high-temperature side refrigeration cycle (20) becomes slightly higher than the predetermined value. Let it.

Fourth Embodiment In this embodiment, the determination means (52) detects the outside air temperature instead of detecting the low-pressure refrigerant pressure of the high-temperature side refrigeration cycle (20), thereby detecting the high-temperature side refrigeration cycle. (20) determines whether or not the condition for performing the bypass operation is satisfied. That is, when the outside air temperature detected by the outside air temperature sensor (Th-a) is equal to or lower than a predetermined value, the hot gas bypass operation in the low temperature refrigeration cycle (30) is restricted.

This is especially true when the outside air temperature is low.
This control is based on the consideration that the condensation capacity in the high-temperature side refrigeration cycle (20) is not sufficiently exhibited, and the low-pressure refrigerant pressure is likely to decrease.

This operation also enables both refrigeration cycles
At (20, 30), the occurrence of a situation in which the hot gas bypass operation is performed and the refrigeration capacity is greatly reduced is avoided.

-Fifth Embodiment- This embodiment determines whether or not the condition for performing the bypass operation of the high-temperature side refrigeration cycle (20) is established by detecting the outside air temperature as in the above-described fourth embodiment. When the outside air temperature detected by the outside air temperature sensor (Th-a) is equal to or less than a predetermined value, the air volume of the condenser fan (22-F) is significantly reduced. I have. That is, the pressure of the low-pressure refrigerant in the high-temperature side refrigeration cycle (20) is increased by reducing the condensation function of the high-temperature side refrigeration cycle (20).

Specifically, a conventional condenser fan (22-F)
In the case where the air flow is switched in two stages, the air flow is further reduced.

This operation also allows both refrigeration cycles
At (20, 30), the occurrence of a situation in which the hot gas bypass operation is performed and the refrigeration capacity is greatly reduced is avoided.

In each of the embodiments described above, a case has been described in which the present invention is applied to a two-way refrigeration apparatus for cooling a refrigerator or a freezer. However, the present invention is not limited to this, and may be applied to other two-way refrigeration apparatuses. It is also applicable.

[0072]

As described above, according to the present invention, the following effects can be obtained. According to the first aspect of the present invention, with respect to the dual refrigeration system including the bypass means for bypassing the refrigerant discharged from the compressor to the low pressure side on each of the high temperature side and the low temperature side, the bypass means of each refrigerant circuit is simultaneously operated. The refrigerant bypass operation is avoided.
Therefore, it is possible to prevent the simultaneous bypass operation from causing a significant decrease in the refrigeration capacity, and it is possible to perform an efficient refrigeration operation.

According to the second aspect of the present invention, the bypass means of the high-temperature side refrigerant circuit is for adjusting the low-pressure refrigerant pressure, and the bypass means of the low-temperature side refrigerant circuit is for adjusting the refrigeration capacity. In such a case, since the high-temperature side and the low-temperature side bypass means operate independently of each other, a situation in which they perform the bypass operation at the same time easily occurs. Even if there is, simultaneous refrigeration operation can be avoided, and efficient refrigeration operation can be performed.

According to the third to fifth aspects of the present invention, the operation of the avoiding means for avoiding the simultaneous bypass operation can be embodied, and the practicality of the binary refrigeration apparatus according to the present invention can be improved.

According to the inventions of claims 6 to 8, the judgment operation of the judgment means for judging that the condition for performing the bypass operation in the high-temperature side refrigerant circuit is specifically obtained, which also provides the present invention. The practicality of such a binary refrigeration system can be improved.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram illustrating a binary refrigeration apparatus according to an embodiment.

FIG. 2 is a refrigerant circuit diagram showing a high-temperature side unit.

FIG. 3 is a refrigerant circuit diagram showing a low-temperature side unit.

FIG. 4 is a flowchart illustrating a hot gas bypass operation of the low-temperature side refrigeration cycle.

FIG. 5 is a flowchart illustrating a control state of a hot gas bypass operation in each refrigeration cycle.

FIG. 6 is a diagram showing a relationship between the internal temperature of the binary refrigeration apparatus and the refrigeration capacity.

[Explanation of symbols]

 (20) High temperature refrigeration cycle (30) Low temperature refrigeration cycle (21,31) Compressor (22,32) Condenser (22-F) Condenser fan (23,33) Evaporator (33-F) Evaporator Fan (27,37) Hot gas bypass passage (51) Avoidance means (52) Judgment means (EV-1, EV-2) Expansion valve (EV-3) Open / close valve (Th-e) Gas temperature sensor (gas temperature detection Means) (Th-a) Outside air temperature sensor (outside air temperature detecting means) (LPS2) Low pressure sensor (low pressure detecting means)

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F25B 7/00

Claims (8)

(57) [Claims] 1. A compressor (21), a condenser (22), and an expansion mechanism
(EV-1) and the evaporator (23) of the cascade type heat exchanger (1H) are connected in order to form a high-temperature side refrigerant circuit (20) in which refrigerant circulates, while the compressor (31) and , Cascade type heat exchanger (1H) condenser (32)
The expansion mechanism (EV-2) and the evaporator (33) are sequentially connected to form a low-temperature side refrigerant circuit (30) in which the refrigerant circulates, and each of the refrigerant circuits (20, 30) is compressed. Means (27, EV-3) and (37, SV-3) capable of bypassing a part of the refrigerant discharged from the machines (21, 31) to the low pressure side in each circuit (20, 30). In the binary refrigeration system, bypass means (27, EV-3), (37, SV-
3) A binary refrigeration system characterized by being provided with an avoiding means (51) for avoiding simultaneous refrigerant bypass operation. 2. The two-way refrigeration system according to claim 1, wherein the bypass means of the high-temperature side refrigerant circuit (20) is a hot gas bypass pipe (27) connecting the discharge side and the suction side of the compressor (21).
And an on-off valve provided in the hot gas bypass pipe (27).
(EV-3), and adjusts the low-pressure refrigerant pressure of the high-temperature side refrigerant circuit (20) by opening and closing the on-off valve (EV-3), while the low-temperature side refrigerant circuit (30) The hot air bypass pipe (37) connecting the discharge side of the compressor (31) and the refrigerant introduction side of the evaporator (33), and an on-off valve provided in the hot gas bypass pipe (37) (SV-3) and an on-off valve (SV-3)
A refrigeration capacity is adjusted by opening and closing operations of the two-stage refrigeration apparatus. 3. The two-way refrigeration system according to claim 1, wherein the bypass means (27, EV-3) of the high-temperature side refrigerant circuit (20) determines that a condition for performing a bypass operation is satisfied. (Five
2), the avoidance means (51) receives the output of the determination means (52), and the bypass means (37, SV-3) of the low-temperature side refrigerant circuit (30) performs a bypass operation, When the bypass means (27, EV-3) of the high-temperature side refrigerant circuit (20) performs the bypass operation, the bypass operation by the bypass means (37, SV-3) of the low-temperature side refrigerant circuit (30) is stopped. A binary refrigeration system characterized by: 4. The binary refrigeration apparatus according to claim 1, wherein the evaporator (33) of the low-temperature side refrigerant circuit (30) is provided with a fan (33-F) capable of adjusting an air volume, Judging means (5) for judging that the condition for performing the bypass operation of the bypass means (27, EV-3) of the high-temperature side refrigerant circuit (20) is satisfied.
2), the avoidance means (51) receives the output of the determination means (52), and the bypass means (37, SV-3) of the low-temperature side refrigerant circuit (30) performs a bypass operation, A binary refrigeration system characterized by increasing the air volume of the fan (33-F) when a condition for bypass operation of a bypass means (27, EV-3) of a high-temperature side refrigerant circuit (20) is satisfied. 5. The two-way refrigeration system according to claim 1, wherein the condenser (22) of the high-temperature side refrigerant circuit (20) is provided with a fan (22-F) capable of adjusting an air volume. The judging means (5) for judging that the condition for performing the bypass operation by the bypass means (27, EV-3) of the side refrigerant circuit (20) is satisfied.
2), the avoidance means (51) receives the output of the determination means (52), and the bypass means (37, SV-3) of the low-temperature side refrigerant circuit (30) performs a bypass operation, A binary refrigeration apparatus characterized in that when a condition for bypass operation of a bypass means (27, EV-3) of a high-temperature side refrigerant circuit (20) is satisfied, the air volume of the fan (22-F) is reduced. 6. The binary refrigeration apparatus according to claim 3, further comprising a low-pressure detection means (LPS2) for detecting a low-pressure refrigerant pressure of the high-temperature side refrigerant circuit (20), wherein the determination means (52) comprises: Upon receiving the output of the low-pressure detection means (LPS2), when the low-pressure side of the high-temperature side refrigerant circuit (20) drops below a predetermined value, it is determined that the condition for performing the bypass operation of the bypass means (27, EV-3) is satisfied. A binary refrigeration system characterized by: 7. The binary refrigeration system according to claim 3, wherein the gas temperature detecting means (Th-e) for detecting the gas side temperature of the evaporator (23) of the high temperature side refrigerant circuit (20) is provided. The determining means (52) receives the output of the gas temperature detecting means (Th-e), and when the gas side temperature of the evaporator (23) of the high-temperature side refrigerant circuit (20) decreases to a predetermined value or less. Bypass means (27, EV-3)
Wherein the condition for performing the bypass operation is satisfied. 8. The two-way refrigeration apparatus according to claim 3, wherein the temperature of the outside air that exchanges heat with the refrigerant flowing through the condenser (22) of the high-temperature side refrigerant circuit (20) is detected. Outside temperature detection means (Th-
a), the judgment means (52) receives the output of the outside air temperature detection means (Th-a), and when the outside air temperature is equal to or lower than a predetermined value, the bypass means (2)
The binary refrigeration apparatus characterized in that 7) determines that the condition for performing the bypass operation is satisfied.