JP3094998B2 - 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 having a plurality of low-stage secondary refrigerant circuits, and more particularly to a measure for preventing an excessive temperature rise of refrigerant discharged in a high-stage primary refrigerant circuit. Things.

[0002]

2. Description of the Related Art Conventionally, a binary refrigeration system is disclosed in
As disclosed in Japanese Patent No. 210515, a primary refrigerant circuit and a secondary refrigerant circuit that individually perform refrigeration operation are provided. This binary refrigeration apparatus is used to obtain a low temperature of minus several tens of degrees, and can be used in a high efficiency from a high compression ratio to a low compression ratio, which is advantageous in energy saving. And this binary refrigeration apparatus is mainly used for cooling the inside of a large freezer, a freezer warehouse, or a refrigerated warehouse.

[0003] The primary side refrigerant circuit of the above-mentioned two-way refrigeration system is configured by connecting a compressor, a condenser, an expansion valve, and an evaporator of a refrigerant heat exchanger in this order. Also, the secondary refrigerant circuit is
The compressor, the condensing part of the refrigerant heat exchanger, the expansion valve, and the evaporator are sequentially connected. In the refrigerant heat exchanger, heat is exchanged between the primary refrigerant in the primary refrigerant circuit and the secondary refrigerant in the secondary refrigerant circuit.

[0004] Some binary refrigeration systems include one primary refrigerant circuit and a plurality of secondary refrigerant circuits.
In this type of binary refrigeration apparatus, a plurality of refrigerant heat exchangers are provided corresponding to the secondary refrigerant circuit. The evaporating sections of each refrigerant heat exchanger are connected in parallel to each other and provided in the primary refrigerant circuit, while the condensing sections of each refrigerant heat exchanger are provided in separate secondary refrigerant circuits. Further, the primary refrigerant circuit is provided with one expansion valve corresponding to each refrigerant heat exchanger.

[0005]

In the two-way refrigeration system described above, the number of operating secondary refrigerant circuits may be changed to adjust the cooling capacity. If the number of operating units is changed, the operation of the primary-side refrigerant circuit may become unstable.

That is, the specifications of various components of the primary refrigerant circuit are determined so that stable operation can be performed when all the secondary refrigerant circuits are operated. Therefore, when only a part of the secondary refrigerant circuit is operated, it is necessary to balance the capacity of the secondary refrigerant circuit and the capacity of the primary refrigerant circuit. For this reason, control is performed such that the opening degree of the expansion valve of the primary-side refrigerant circuit is reduced to reduce the amount of refrigerant circulating in the primary-side refrigerant circuit. However, in the primary-side refrigerant circuit, when the expansion valve is throttled, the low pressure of the primary-side refrigerant circuit decreases, the compression ratio in the compressor increases, and there is a possibility that the refrigerant discharged from the compressor may overheat.

On the other hand, conventionally, an injection passage is provided in the primary-side refrigerant circuit to supply the liquid refrigerant to the suction side of the compressor. Specifically, the injection passage is provided so that the refrigerant flows by bypassing the expansion valve and the evaporating section of the refrigerant heat exchanger, and the injection passage is also provided with an expansion valve. Then, a part of the refrigerant condensed in the condenser is reduced in pressure and supplied to the suction side of the compressor through the injection passage.

[0008] However, depending on the operation state, there is a case in which the supply of the liquid refrigerant only through the injection passage cannot prevent the temperature of the refrigerant discharged from the compressor from excessively rising in the primary refrigerant circuit. Conventionally, in such a case, the expansion valve of the primary-side refrigerant circuit is opened more than the optimum opening degree, and the amount of circulation of the refrigerant in the primary-side refrigerant circuit is increased to prevent an excessive temperature rise of the discharged refrigerant. For this reason, there is a problem that the refrigerant evaporation pressure of the primary refrigerant circuit cannot be set to the optimum value, and the refrigerant condensation pressure of the secondary refrigerant circuit cannot be set to the optimum value. Then, there is a problem that the secondary refrigerant circuit cannot be operated under the optimum conditions for the cooling operation, and the energy consumption efficiency (EER) is reduced.

The present invention has been made in view of the above point, and an object of the present invention is to change the operation state of the secondary refrigerant circuit even when only a part of the secondary refrigerant circuit is operated. An object of the present invention is to prevent the temperature of the refrigerant discharged from the primary refrigerant circuit from excessively rising while maintaining the optimum conditions.

[0010]

According to the present invention, the opening of the expansion valve of the primary refrigerant circuit is adjusted even when the operation of the corresponding secondary refrigerant circuit is suspended.

Specifically, a first solution taken by the present invention is to connect a primary side compressor (21), a condenser (22), and a plurality of branch passages (5A, 5B) in parallel with each other. And the evaporating circuit (5) is connected in order to form a closed circuit in which the primary refrigerant circulates, while the branch passages (5A, 5B) have primary expansion valves (EV12a, EV12b) and Refrigerant heat exchanger (11a, 1
1b) a primary refrigerant circuit (20) provided in order with an evaporator, a secondary compressor (31), a condenser of each of the refrigerant heat exchangers (11a, 11b), and a secondary Expansion mechanism (EV21),
And a plurality of secondary sides in which the secondary refrigerant circulates and heat exchanges between the primary refrigerant and the secondary refrigerant in each of the refrigerant heat exchangers (11a, 11b) are performed. It is premised on a binary refrigeration apparatus having a refrigerant circuit (3A, 3B).

Each of the secondary refrigerant circuits (3A, 3B)
Control of the operation of the secondary refrigerant circuits (3A, 3B) by controlling the operation and stop of the
1) and a refrigerant heat exchanger (11b) connected to the secondary refrigerant circuit (3B) stopped by the capacity control means (71).
Primary expansion valve (EV12b) on the stopped side in the branched passage (5B) (hereinafter referred to as the stopped secondary refrigerant circuit (3B).
A corresponding stop-side primary expansion valve ) is provided with stop-side expansion valve control means (72) for adjusting the opening degree so that the temperature of the refrigerant discharged from the primary compressor (21) is maintained within a predetermined range. Things.

[0013] The second solution taken by the present invention is:
In the first solving means, the pressure detecting means (SPH1) for detecting the pressure of the refrigerant discharged from the primary compressor (21), and the temperature detecting means for detecting the temperature of the refrigerant discharged from the primary compressor (21) (TDH) and the stop-side expansion valve control means (7
2) derives the degree of superheat of the refrigerant discharged from the primary compressor (21) from the detected value of the pressure detecting means (SPH1) and the detected value of the temperature detecting means (TDH), The degree of opening of the stop-side primary expansion valve (EV12b) is adjusted based on the degree.

In the first solution, the primary refrigerant discharged from the primary compressor (21) of the primary refrigerant circuit (20) is supplied to the condenser (2).
Condensed in 2) and becomes liquid refrigerant. The liquid refrigerant flows into each branch passage (5A, 5B) of the evaporating circuit (5), and flows through the primary expansion valve (EV).
After the pressure is reduced by 12a, EV12b), it reaches the refrigerant heat exchanger (11a, 11b). Thereafter, the primary refrigerant is supplied to each of the refrigerant heat exchangers (11a, 11a).
After evaporating in the evaporating section of b) to become a gas refrigerant, they merge and return to the primary compressor (21) to repeat this circulation. Further, in each of the secondary-side refrigerant circuits (3A, 3B), the secondary refrigerant discharged from the secondary-side compressor (31) is condensed in the condensing section of the refrigerant heat exchanger (11a, 11b). It becomes a liquid refrigerant. The liquid refrigerant is decompressed by the secondary expansion mechanism (EV21), and then evaporates in the evaporating heat transfer tubes (5a, 5b) to become gas refrigerant and returns to the secondary compressor (31). repeat. In each of the refrigerant heat exchangers (11a, 11b), the primary refrigerant in the primary refrigerant circuit (20) exchanges heat with the secondary refrigerant in each of the secondary refrigerant circuits (3A, 3B). The heat is released from the refrigerant to the primary refrigerant, and the evaporator (50) evaporates the secondary refrigerant to generate cooling air, thereby cooling the inside of the refrigerator.

On the other hand, the capacity control means (71) controls the operation and stop of each of the secondary refrigerant circuits (3A, 3B) and changes the number of operating secondary refrigerant circuits (3A, 3B). Increase or decrease the cooling capacity. Furthermore, the stop-side expansion valve control means (7
2) The stop-side primary expansion valve (EV) corresponding to the secondary-side refrigerant circuit (3B) stopped by the capacity control means (71).
12b) Adjust the opening. Thereby, a part of the liquid refrigerant flows through the stop-side branch passage (5B) corresponding to the stopped secondary-side refrigerant circuit (3B). Then, an appropriate amount of the liquid refrigerant is bypassed through the operating-side branch passage (5A) corresponding to the secondary-side refrigerant circuit (3A) that continues to operate, and the primary-side compressor (21)
To the suction side of

In the second solution, the pressure detecting means (SPH1) detects the pressure of the refrigerant discharged from the primary compressor (21), and the temperature detecting means (TDH) controls the primary compressor (21). The temperature of the discharged refrigerant is detected. This pressure detection means (SPH1)
And the detection value of the temperature detection means (TDH) are input to the stop-side expansion valve control means (72).

On the other hand, the stop-side expansion valve control means (72) derives the degree of superheat of the refrigerant discharged from the primary compressor (21) from the detection values of the two detection means (SPH1, TDH). Specifically, the saturation temperature of the refrigerant at the pressure detected by the pressure detection means (SPH1) is obtained, and the difference between the detection temperature of the temperature detection means (TDH) and the obtained saturation temperature of the refrigerant is calculated to determine the degree of superheat of the discharged refrigerant. Derive. Then, the stop-side expansion valve control means (72) adjusts the opening of the stop-side primary expansion valve (EV12b) based on the temperature and the degree of superheat of the discharged refrigerant. Specifically, if the temperature of the refrigerant discharged from the primary compressor (21) is too high, the stop-side primary expansion valve (EV12b) is opened, and if the degree of superheat of the discharged refrigerant is lower than a predetermined value. The stop-side primary expansion valve (EV12b) is controlled to close.

[0018]

According to the first solution, the opening degree of the stop-side primary expansion valve (EV12b), which is conventionally fully closed, is adjusted. Therefore, a part of the liquid refrigerant can be supplied to the suction side of the primary-side compressor (21) through the stop-side branch passage (5B). Further, the amount of liquid refrigerant supplied to the suction side of the primary compressor (21) can be adjusted by adjusting the opening of the stop-side primary expansion valve (EV12b). As a result, the branch passage on the operation side (5A)
By bypassing this, an appropriate amount of liquid refrigerant can be supplied to the suction side of the primary-side compressor (21), and an excessive rise in the temperature of the refrigerant discharged from the primary-side compressor (21) can be reliably prevented.

According to the present invention, a sufficient amount of liquid refrigerant is supplied to the primary compressor (21) through the stop-side branch passage (5B).
Can be supplied to the suction side. Therefore, the primary-side expansion valve driving side (EV12a) may be opening adjustment by considering only the operation state of the secondary side refrigerant circuit (3A) in said continuous operation. That is, as in the conventional case, the primary expansion valve (EV12) on the operating side is taken into consideration in consideration of the temperature of refrigerant discharged from the primary compressor (21).
It is not necessary to make the opening of a) larger than the optimum opening. Therefore, the operation state of the secondary-side refrigerant circuit (3A) that continues the operation can be set to the optimal condition, and the energy consumption efficiency (EER) can be maintained high.

In some cases, a so-called injection passage which bypasses the evaporation circuit (5) and is connected to the outlet side of the condenser (22) and the suction side of the primary compressor (21) may be omitted. Can also. That is, if a sufficient amount of liquid refrigerant can be supplied only through the stop-side branch passage (5B) to prevent the refrigerant discharged from the primary compressor (21) from excessively rising in temperature, the injection passage is not required. It is possible to suppress the excessive rise in the temperature of the discharged refrigerant. Therefore,
In such a case, the primary refrigerant circuit (20) can be simplified, and the cost can be reduced.

In the second solution, the opening degree of the stop-side primary expansion valve (EV12b) is adjusted based on the temperature of the refrigerant discharged from the primary compressor (21). ing. Therefore, the condenser (22) passes through the stop-side branch passage (5B).
Thus, the optimum amount of refrigerant can be supplied to the discharge side of the primary-side compressor (21), and an excessive temperature rise of the refrigerant discharged from the primary-side compressor (21) can be reliably prevented. In addition, the opening of the primary expansion valve (EV12b) is adjusted in consideration of the degree of superheat of the refrigerant discharged from the primary compressor (21). For this reason, it is possible to prevent the refrigerant sucked into the primary compressor (21) from becoming excessively wet, and it is possible to reliably prevent troubles of the primary compressor (21) due to liquid back. Therefore, the primary compressor (2) can be used without causing trouble in the primary refrigerant circuit (20).
Excessive temperature rise of the refrigerant discharged in 1) can be reliably prevented, and the primary refrigerant circuit (20) can be operated stably.

[0022]

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

As shown in FIGS. 1 and 2, the binary refrigeration system (10) cools a refrigerator or a freezer.
An outdoor unit (1A), a cascade unit (1B), and a cooling unit (1C) are provided. Although not shown, each of the units (1A, 1B, 1C) is formed by housing a component device in a predetermined casing. The outdoor unit (1A) and a part of the cascade unit (1B) constitute a primary refrigerant circuit (20). In addition, the two secondary refrigerant circuits (3A, 3B) extend over the cascade unit (1B) and the cooling unit (1C).
Is configured. In addition, the cooling unit (1
In C), a not-shown inside temperature sensor for detecting the inside temperature is provided.

-Configuration of Refrigerant Circuit- The primary-side refrigerant circuit (20) is configured to be capable of reversible operation by switching the refrigerant circulation direction between a forward cycle and a reverse cycle. The primary refrigerant circuit (20) includes a primary compressor (21), a condenser (22), and an evaporation circuit (5). Although not shown, the outdoor unit (1A) is provided with an outdoor fan driven by a fan motor, and the outdoor fan sends air to the condenser (22).

The primary side compressor (21) has a first compressor on the discharge side.
The gas pipe (40) is connected, and the second gas pipe (4
1) is connected. The first gas pipe (40) is connected from the primary compressor (21) to the oil separator (23) and the four-way switching valve (24).
Are sequentially connected, and are connected to one end of the condenser (22). One end of a liquid pipe (42) is connected to the other end of the condenser (22), and the other end of the liquid pipe (42) is connected to the evaporation circuit (5).

The evaporating circuit (5) is configured by connecting a first branch passage (5A) and a second branch passage (5B), which are branch passages, in parallel with each other. In each of the passages (5A, 5B), in order from one end where the liquid pipe (42) is connected to the other end, the primary electric expansion valves (EV12a, EV12b) and the refrigerant heat exchangers (11a, 11b) are connected. An evaporator is provided. Specifically, the first branch passage (5A) is provided with a first primary-side electric expansion valve (EV12a) and an evaporator of the first refrigerant heat exchanger (11a), respectively, and is provided in the second branch passage (5B). Is provided with a second primary-side electric expansion valve (EV12b) and an evaporator of the second refrigerant heat exchanger (11b).

The second gas pipe (41) connects the accumulator (26) and the four-way switching valve (24) in order from the primary compressor (21), and is connected to the evaporation circuit (5). ing. Specifically, the second gas pipe (41) is connected to the first gas pipe (41).
And the refrigerant heat exchangers (11a, 11b) in the second branch passages (5A, 5B)
Connected to the side. That is, the evaporator of the first and second refrigerant heat exchangers (11a, 11b) is connected to the primary refrigerant circuit (20).
Are connected in parallel with each other. The evaporating circuit (5) is provided in the cascade unit (1B).

The first gas pipe (40) and the receiver (25)
A gas passage (43) is connected between the two. One end of the gas passage (43) is connected between the four-way switching valve (24) and the condenser (22) in the first gas pipe (40), and the other end is connected to the upper part of the receiver (25). Have been. And
The gas passage (43) is provided with an on-off valve (SV), and is configured to perform high-pressure control during a cooling operation and venting during a defrost operation.

The oil separator (23) and the primary compressor (21)
An oil return passage (44) having a capillary tube (CP) is connected between the oil return side and the suction side. Between the discharge side and the suction side of the primary compressor (21), a primary compressor (2) having a capillary tube (CP) and an on-off valve (SV) is provided.
The unload passage (45) of 1) is connected, and the middle of the unload passage (45) is connected to the primary compressor (21).

The first gas pipe (40) on the discharge side of the primary compressor (21) has a high-pressure pressure sensor (SPH1) for detecting the high-pressure refrigerant pressure, and a predetermined pressure when the high-pressure refrigerant pressure rises excessively. And a high pressure switch (HPS1) that outputs an off signal when the high pressure value is reached. This high pressure sensor (SP
H1) is configured as pressure detecting means for detecting the pressure of the refrigerant discharged from the primary compressor (21). Further, a low pressure sensor (SPL1) for detecting low pressure refrigerant pressure is provided in the second gas pipe (41) on the suction side of the primary compressor (21).

Further, a discharge pipe temperature sensor (TDH) is attached to the first gas pipe (40) near the connection to the primary compressor (21). In the vicinity of the connection of the first gas pipe (40) to the primary compressor (21), the gas refrigerant immediately after being discharged from the primary compressor (21) flows through the first gas pipe (40). ing. Therefore, the temperature of the first gas pipe (40) at the connection is substantially equal to the temperature of the refrigerant discharged from the primary compressor (21), and the discharge pipe temperature sensor (TDH) detects the temperature of the discharged refrigerant. Means.

On the other hand, the first circuit (3A) is configured to be capable of reversible operation by switching the refrigerant circulation direction between a forward cycle and a reverse cycle. The first circuit (3A) includes a secondary compressor (31), a condensing section of the first refrigerant heat exchanger (11a), and a heat transfer tube for evaporation (5a).

The discharge side of the secondary compressor (31) is
A gas pipe (60) is connected to one end of a condenser in the first refrigerant heat exchanger (11a) via an oil separator (32) and a four-way switching valve (33). In addition, the secondary compressor (3
In the first gas pipe (60) between 1) and the oil separator (32),
Although not shown, a discharge pipe temperature sensor is attached. The other end of the condensing section is connected to the heat transfer pipe for evaporation (CV), a receiver (34), and a secondary expansion valve (EV21) as a secondary expansion mechanism by a liquid pipe (61). 5a). The other end of the evaporation heat transfer tube (5a) is
Check valve (CV) and four-way selector valve (3
(3) and the secondary compressor (3) through the accumulator (35)
1) Connected to the suction side.

The first refrigerant heat exchanger (11a) is a cascade condenser having an evaporator of the primary refrigerant circuit (20) and a condenser of the first circuit (3A). It is configured. In the first refrigerant heat exchanger (11a), the refrigerant in the first circuit (3A) exchanges heat with the refrigerant in the primary refrigerant circuit (20), and the first circuit (3A)
Refrigerant dissipates heat and condenses, while the primary refrigerant circuit (20)
Refrigerant absorbs heat and evaporates.

The secondary expansion valve (EV21) is a temperature-sensitive expansion valve, and the temperature-sensitive cylinder (TS) is connected to the second gas pipe (62) on the outlet side of the evaporation heat transfer tube (5a). It is provided in.

Since the first circuit (3A) is configured to perform a reverse cycle defrost operation, a drain pan passage (63), a gas bypass passage (64), and a pressure reduction passage (6) are provided.
5). The drain pan passage (63) is
Connected to both ends of the check valve (CV) in the gas pipe (62), a drain pan heater (6a) and a check valve (CV) are provided, and the refrigerant (hot gas) discharged from the secondary compressor (31) ) Is configured to flow.

The gas bypass passage (64) is connected to both ends of the secondary expansion valve (EV21) in the liquid pipe (61), has a check valve (CV), and allows the liquid refrigerant to flow through the secondary side during defrost operation. It is configured to bypass the expansion valve (EV21).

The pressure reducing passage (65) is connected to both ends of the check valve (CV) in the liquid pipe (61), and includes an on-off valve (SV) and an expansion valve for defrost (EV22). It is configured to depressurize the refrigerant. The expansion valve for defrost (EV22) is a temperature-sensitive expansion valve,
A temperature sensing cylinder is provided in the second gas pipe (62) upstream of the accumulator (35).

An upper end of the receiver (34) is connected to one end of a gas vent passage (66). The gas vent passage (66) is provided with an on-off valve (SV) and a capillary tube (C
P), and the other end is connected to the second gas pipe (62) on the upstream side of the accumulator (35).

The oil separator (32) and the secondary compressor (31)
An oil return passage (67) having a capillary tube (CP) is connected between the oil return side and the suction side.

In the first gas pipe (60) on the discharge side of the secondary compressor (31), a high-pressure pressure sensor (SPH2) for detecting high-pressure refrigerant pressure and a high-pressure refrigerant pressure A high pressure switch (HPS2) that outputs an off signal when a predetermined high pressure value is reached is provided. Further, a low-pressure pressure sensor (SPL2) for detecting a low-pressure refrigerant pressure is provided in the second gas pipe (62) on the suction side of the secondary compressor (31).

The second circuit (3B) has substantially the same configuration as the first circuit (3A), but is configured to perform only the cooling operation without performing the defrost operation. The second circuit (3B)
Does not include the four-way switching valve (24) in the first circuit (3A), and further does not provide the drain pan passage (63), the gas bypass passage (64), and the pressure reducing passage (65). That is, the second circuit (3B) is connected to the secondary compressor (31) and the second circuit (3B).
The condenser section of the refrigerant heat exchanger (11b), the receiver (34), the secondary expansion valve (EV21), the evaporative heat transfer tube (5b), and the accumulator (35) are composed of a first gas pipe (60) and a liquid pipe ( 61) and the second
They are sequentially connected by a gas pipe (62). The condenser of the second refrigerant heat exchanger (11b) constitutes a condenser of the second circuit (3B). The second circuit (3
Similarly to the first circuit (3A), the discharge pipe temperature sensor, the high pressure sensor (SPH1), and the low pressure sensor (SPL)
1) and a high pressure switch (HPS1) are provided at predetermined positions.

The secondary expansion valve (EV21) is a temperature-sensitive expansion valve, and a temperature-sensitive cylinder is provided in the second gas pipe (62) on the outlet side of the heat transfer tube (5b) for evaporation. . The second refrigerant heat exchanger (11b) is a cascade condenser having an evaporator of the primary refrigerant circuit (20) and a condenser of the second circuit (3B), and is constituted by a plate-type heat exchanger. Have been. The second refrigerant heat exchanger (11b)
The refrigerant in the circuit (3B) exchanges heat with the refrigerant in the primary refrigerant circuit (20), and the refrigerant in the second circuit (3B) releases heat and condenses, while the refrigerant in the primary refrigerant circuit (20) absorbs heat. And evaporate.

The evaporating heat transfer tubes (5a, 5b) in the two secondary-side refrigerant circuits (3A, 3B) are constituted by one evaporator (50). The refrigerant in the side refrigerant circuit (3A, 3B) exchanges heat with the air in the refrigerator or the freezer. The evaporator (50), the secondary expansion valve (EV21) and the drain pan passage (63) are provided in the cooling unit (1C), while the other secondary compressor (3
1) and the like are provided in the cascade unit (1B). Although not shown, the cooling unit (1C) is provided with an in-compartment fan driven by a fan motor, and the in-compartment fan sends the in-compartment air to the evaporator (50).

-Configuration of Controller- As shown in FIG. 1, the binary refrigeration apparatus (10) of the present embodiment includes a controller (70) which is a feature of the present invention. The controller (70) includes a capacity control unit (71) and a stop-side expansion valve control unit (72).

The internal temperature detected by the internal temperature sensor and a set internal temperature are input to the capacity control means (71). Then, the capacity control means (71) changes the number of operating secondary-side refrigerant circuits (3A, 3B) based on the measured value and the set value of the internal temperature, and The refrigeration capacity is adjusted. That is, when operating at low capacity, the second circuit (3B) of the secondary-side refrigerant circuits (3A, 3B) is stopped and only the first circuit (3A) is operated. . Further, if the refrigerating capacity is still excessive, the first circuit (3A) is also stopped, and the cooling operation is stopped.

The stop-side expansion valve control means (72) receives the detection values of the high-pressure pressure sensor (SPH1) and the discharge pipe temperature sensor (TDH) provided in the primary-side refrigerant circuit (20), respectively. ing. The stop-side expansion valve control means (72) derives the degree of superheat of the refrigerant discharged from the primary-side compressor (21) from the detection values of the two sensors (SPH1, TDH), while determining the temperature and superheat of the discharged refrigerant. When the second circuit (3B) is stopped by the capacity control means (71) based on the degree, the second primary expansion valve (that is, the capacity ) corresponding to the second circuit (3B)
Connects to the second circuit (3B) stopped by the force control means (71).
The branch passage (5) provided with the connected refrigerant heat exchanger (11b)
It is configured to adjust the opening of the stop-side primary expansion valve (EV) in (B).

Specifically, the stop-side expansion valve control means (72)
First, the saturation temperature of the refrigerant at the detection pressure of the high-pressure pressure sensor (SPH1) is determined, and the discharge pipe temperature sensor (TD
The superheat degree of the discharged refrigerant is derived by taking the difference between the detected temperature of H) and the obtained saturation temperature of the refrigerant. When the temperature of the refrigerant discharged from the primary compressor (21) is too high, the stop-side expansion valve control means (72) controls the second primary expansion valve (EV12b) to open, and controls the discharged refrigerant. If the degree of superheat is lower than a predetermined value, control is performed to close the second primary expansion valve (EV12b).

-Operation of Binary Refrigeration Unit- Next, the operation of the binary refrigeration unit (10) will be described.

First, when performing the cooling operation, both the primary compressor (21) of the primary refrigerant circuit (20) and the compressors (31, 31) of the respective secondary refrigerant circuits (3A, 3B) are driven. . In this state, in the primary-side refrigerant circuit (20), the four-way switching valve (24) is switched to the solid line in FIG. 1, the electric expansion valve for defrost (EV11) is fully opened, and the first and second primary-side electric circuits are switched. Controls the opening of the expansion valves (EV12a, EV12b).

The primary refrigerant discharged from the primary compressor (21) of the primary refrigerant circuit (20) is condensed in the condenser (22) to become a liquid refrigerant and flows to the cascade unit (1B).
The liquid refrigerant is divided into a first branch passage (5A) and a second branch passage (5B), and the primary-side electric expansion valves (EV12a, EV12
After the pressure is reduced in 12b), the refrigerant evaporates in the evaporating section of each heat exchanger (11a, 11b). Thereafter, the gas refrigerant merges, flows through the second gas pipe (41), returns to the primary compressor (21),
This cycle is repeated.

On the other hand, in the first circuit (3A), the four-way switching valve (33) is switched to the solid line in FIG. 2, the defrost expansion valve (EV22) is fully closed, and the secondary expansion valve (EV21) is closed. Control the degree of superheat. In the second circuit (3B), the degree of superheat of the secondary expansion valve (EV21) is controlled.

In the two secondary-side refrigerant circuits (3A, 3B), the secondary refrigerant discharged from the compressors (31, 31) is condensed in the condensing sections of the two refrigerant heat exchangers (11a, 11b). After becoming a refrigerant, the liquid refrigerant is decompressed by the secondary expansion valve (EV21), and then evaporates in the evaporating heat transfer tubes (5a, 5b). Then, this gas refrigerant is transferred from the heat transfer tubes for evaporation (5a, 5b) to the compressor (31, 31).
And repeat this cycle.

The refrigerant heat exchangers (11a, 11b)
In, the primary refrigerant and the secondary refrigerant exchange heat, and the secondary refrigerant in the secondary refrigerant circuit (3A, 3B) is cooled and condensed.
On the other hand, in the evaporator (50), the secondary refrigerant evaporates to generate cooling air, thereby cooling the inside of the refrigerator.

The binary refrigeration system (10) performs a defrost operation. This defrost operation is performed every 6 hours during the refrigeration operation and every 12 hours during the freezing operation. The defrosting operation is performed by stopping the operation of the second circuit (3B) and reversing the circulation direction of the refrigerant between the first circuit (3A) and the primary refrigerant circuit (20).

More specifically, in the first circuit (3A), the four-way switching valve (33) is switched to the dashed line in FIG. 2, while the defrost expansion valve (EV22) is superheated and the secondary expansion valve (EV) is controlled. EV21)
Is fully closed.

The secondary refrigerant discharged from the secondary-side compressor (31) passes through a four-way switching valve (33) to a drain pan passage (63).
And the drain pan is heated by the drain pan heater (6a). Subsequently, the secondary refrigerant flows through the evaporator heat transfer tube (5a) to heat the evaporator (50), thereby melting the frost on the evaporator (50). Thereafter, the secondary refrigerant flowing through the evaporating heat transfer tube (5a) flows through the gas bypass passage (64), and flows into the receiver (3).
After passing through 4), it flows through the pressure reducing passage (65), and the pressure is reduced by the defrost expansion valve (EV22). Subsequently, the secondary refrigerant evaporates in the condensing section of the first refrigerant heat exchanger (11a), and the four-way switching valve (3
3) and the secondary compressor (3
Return to 1) and repeat this cycle.

On the other hand, in the primary refrigerant circuit (20), the four-way switching valve (24) is switched to the dashed line in FIG. 1, while the opening of the electric defrosting expansion valve (EV11) is controlled, and the first and second valves are switched.
Fully open the primary electric expansion valves (EV12a, EV12b).

The primary refrigerant discharged from the primary compressor (21) passes through the four-way switching valve (24) to the first refrigerant heat exchanger (11).
It flows into the evaporating section of a) and heats and condenses the secondary refrigerant in the first circuit (3A). Then, the first refrigerant heat exchanger (11a)
The primary refrigerant that has flowed through the evaporating section is reduced in pressure by the electric expansion valve for defrost (EV11) via the receiver (25). Subsequently, the primary refrigerant evaporates in the condenser (22), returns to the primary compressor (21) via the four-way switching valve (24) and the accumulator (26), and repeats this circulation.

In the above defrost operation, the liquid temperature sensor (Th21) detects the refrigerant temperature of, for example, 10 ° C., or the evaporator temperature sensor (Th22) detects the evaporator temperature of, for example, 20 ° C. Alternatively, when the high-pressure pressure sensor (SPH2) of the first circuit (3A) detects a high-pressure refrigerant pressure of, for example, 18 kgf / cm ² , the process ends. Note that the above defrost operation ends even with a one-hour guard timer.

In the cooling operation in addition to the defrost operation, the on-off valve (SV) of the gas vent passage (66) in each of the secondary refrigerant circuits (3A, 3B) is opened, and the liquid stored in the receiver (34) is opened. The refrigerant is returned to the low-temperature secondary compressor (31).

Further, when the pressure of the high-pressure refrigerant detected by the high-pressure pressure sensor (SPH1) decreases during the cooling operation, the gas passageway (43) in the primary-side refrigerant circuit (20) becomes, for example, 6 kgf / cm ^2. When the pressure drops, the on-off valve (SV) is opened, high-pressure refrigerant is supplied to the receiver (25), and the high-pressure refrigerant pressure is increased. When the pressure of the high-pressure refrigerant increases, for example, to 15 kgf / cm ² , the opening of the on-off valve (SV)
finish.

During the defrost operation, the on-off valve (SV) of the gas passage (43) is opened and the receiver (25) is opened.
Is returned to the primary side compressor (21) so that the liquid refrigerant accumulates in the receiver (25). That is, during the defrost operation, the liquid refrigerant is stored in the receiver (25) even when the outside air temperature is high.

Next, the control operation of the binary refrigeration system (10) by the controller (70) will be described.

The capacity control means (71) changes the number of operating secondary side refrigerant circuits (3A, 3B) in order to adjust the refrigeration capacity. Specifically, the first circuit (3A) and the second circuit (3B)
Description will be made from a state in which both are operated. In this state, when the internal temperature decreases and approaches the set value, the capacity control means (71) stops the second circuit (3B), and the first circuit (3A) and the primary refrigerant circuit (20) Continue driving. Then, thereafter, when the temperature in the refrigerator further decreases and reaches the set value, the first circuit (3A) and the primary refrigerant circuit (20) are also stopped. on the other hand,
The two secondary refrigerant circuits (3A, 3B) and the primary refrigerant circuit (2
When the internal temperature rises in a state where 0) is stopped, first, the first circuit (3A) and the primary-side refrigerant circuit (20) are activated. After that, when the internal temperature rises further, the second circuit (3B)
Also start.

When the second circuit (3B) is stopped by the capacity control means (71) and the first circuit (3A) and the primary refrigerant circuit (20) are operated, the capacity of the first circuit (3A) is It is necessary to balance with the capacity of the primary refrigerant circuit (20). For this reason, the opening degree of the first primary expansion valve (EV12a) is made relatively small by the controller (70), the amount of refrigerant circulating in the primary refrigerant circuit (20) is reduced, and the first circuit (3A) The refrigerant condensing pressure is maintained in a predetermined range.

However, simply reducing the amount of circulating refrigerant in the primary refrigerant circuit (20) reduces the low pressure in the primary refrigerant circuit, increases the compression ratio in the compressor, and increases the temperature of the refrigerant discharged from the compressor. Is too high. On the other hand, in the present embodiment, the stop-side expansion valve control means (72) adjusts the opening of the second primary-side expansion valve (EV12b). By controlling the opening, a part of the liquid refrigerant is removed from the evaporating circuit (5).
To the second branch passage (5B), bypasses the first branch passage (5A), and adjusts the amount of liquid refrigerant supplied to the suction side of the primary compressor (21). The temperature of the discharged refrigerant is maintained within a predetermined range.

The control operation of the stop-side expansion valve control means (72) will be described with reference to the flowchart of FIG. In step ST1, it is determined whether or not the second circuit (3B) is stopped, and if the second circuit (3B) is operating, this state is maintained. On the other hand, if the second circuit (3B) has stopped, the process proceeds to step ST2.

In step ST2, the discharge pipe temperature sensor (TD
The first parameter ΔEV1 is determined based on the detected value of H), that is, the temperature Tdh of the refrigerant discharged from the primary compressor (21).
Specifically, if the discharge refrigerant temperature Tdh is less than 100 ° C., Δ
EV1 = 0. If the discharged refrigerant temperature Tdh is equal to or higher than 100 ° C. and lower than 110 ° C., ΔEV1 = 1. If the discharge refrigerant temperature Tdh is 110 ° C. or more and less than 120 ° C., ΔEV
Let 1 = 2. If the discharge refrigerant temperature Tdh is 120 ° C. or higher, ΔEV1 = 3.

Here, the larger the value of the first parameter ΔEV1, the larger the operation amount for opening the second primary expansion valve (EV12b). Therefore, the discharge refrigerant temperature Tdh
The higher the value, the larger the degree of opening of the second primary expansion valve (EV12b) to increase the amount of refrigerant flowing through the second branch passage (5B) of the evaporation circuit (5).

Next, in step ST3, the detected value of the high-pressure pressure sensor (SPH1), that is, the equivalent saturation temperature Tch of the refrigerant at the pressure of the refrigerant discharged from the primary compressor (21) is obtained. The superheat degree Tdh-Tch of the discharged refrigerant is derived by taking the difference between the temperature Tdh of the discharged refrigerant detected by TDH) and the calculated equivalent saturation temperature Tch. If the derived superheat degree Tdh-Tch is less than 30 ° C., the second parameter ΔEV2 is set to −1, and if the superheat degree Tdh−Tch is 30 ° C. or more, the second parameter ΔEV2 is set to zero.

Here, it is shown that if the value of the second parameter ΔEV2 is negative, the second primary expansion valve (EV12b) is controlled to be closed. Therefore, if the degree of superheat Tdh−Tch is less than 30 ° C., the opening degree of the second primary expansion valve (EV12b) is reduced to reduce the refrigerant flow rate in the second branch passage (5B), or Expansion valve (EV12b)
The degree of opening of the second branch passage (5B) is reduced so as to reduce the increase width of the refrigerant flow rate in the second branch passage (5B).

Subsequently, in step ST4, a control parameter ΔEV is calculated based on the first parameter ΔEV1 and the second parameter ΔEV2. Specifically, the first parameter ΔEV1 multiplied by a correction coefficient α and the second parameter ΔE1
The control parameter Δ is the sum of V2 multiplied by the correction coefficient β.
EV. The correction coefficients α and β are determined experimentally for each model.

Then, in step ST5, the control parameter ΔE obtained in step ST4 is added to the current value of the opening degree parameter EV.
V to update the value of the opening parameter EV, and based on the updated value of the opening parameter EV, the second primary expansion valve (E
Change the opening of V12b). Specifically, for the second primary expansion valve (EV12b), the opening is increased if the value of the control parameter ΔEV is positive, and the opening is decreased if the value of the control parameter ΔEV is negative. Further, the larger the absolute value of the control parameter ΔEV is, the larger the operation amount of the opening degree of the second primary expansion valve (EV12b) is. Furthermore, if the opening parameter EV is zero, the opening of the second primary expansion valve (EV12b) is held as it is.

-Effects of the Embodiment- In the present embodiment, the second ability control means (71)
Even when the circuit (3B) is stopped and the first circuit (3A) and the primary refrigerant circuit (20) are operating, the opening of the second primary expansion valve (EV12b) is adjusted. Therefore, by using the second branch passage (5B), a part of the liquid refrigerant can be supplied to the suction side of the primary compressor (21) by bypassing the first branch passage (5A). As a result, an appropriate amount of liquid refrigerant can be supplied to the suction side of the primary-side compressor (21), and an excessive temperature rise of the refrigerant discharged from the primary-side compressor (21) can be reliably prevented.

Further, since a sufficient amount of liquid refrigerant can be supplied to the suction side of the primary compressor (21) through the second branch passage (5B), the first refrigerant corresponding to the operating first circuit (3A) can be supplied. For the primary expansion valve (EV12a), the secondary refrigerant circuit (3
The opening can be adjusted in consideration of only the operation state A). That is, unlike the conventional case, the first primary expansion valve (EV) is used in order to suppress the excessive temperature rise of the refrigerant discharged from the primary compressor (21).
It is not necessary to make the opening of 12a) larger than the optimum opening.
Therefore, the operation state of the first circuit (3A) can be set to the optimum condition, and the energy consumption efficiency (EER) can be maintained high.

In this embodiment, a so-called injection passage which bypasses the evaporating circuit (5) and is connected to the outlet side of the condenser (22) and the suction side of the primary compressor (21) is omitted. Have . This simplifies the primary refrigerant circuit (20) and reduces costs.

Further, based on the temperature of the refrigerant discharged from the primary compressor (21), the stop-side second primary expansion valve (EV12b)
The degree of opening is adjusted. For this reason, an optimal amount of liquid refrigerant can be supplied to the discharge side of the primary-side compressor (21) through the second branch passage (5B), and excessive temperature rise of the refrigerant discharged from the primary-side compressor (21) can be prevented. It can be reliably prevented. Also,
The opening degree of the primary expansion valve (EV12b) is adjusted in consideration of the degree of superheat of the refrigerant discharged from the primary compressor (21). For this reason, it is possible to prevent the refrigerant sucked into the primary compressor (21) from becoming excessively wet, and it is possible to reliably prevent troubles of the primary compressor (21) due to liquid back. Accordingly, it is possible to reliably prevent the temperature of the refrigerant discharged from the primary compressor (21) from excessively rising without causing trouble in the primary refrigerant circuit (20), and to stably operate the primary refrigerant circuit (20). It becomes possible.

[0079]

In the above embodiment, the injection passage is omitted in the above embodiment. However, this injection passage is provided with the primary refrigerant circuit (20), and the injection is performed while the second circuit (3B) is stopped. Liquid refrigerant may be supplied to the discharge side of the primary compressor (21) through both the passage and the second branch passage (5B). The injection passage is provided with an expansion valve and an on-off valve. Then, the pressure of the liquid refrigerant is reduced by the expansion valve, and then the primary side compressor (21)
When the supply of the liquid refrigerant is not necessary, the on-off valve is closed. Also in this case, the first primary expansion valve (EV12a) can be controlled to the optimum opening, and the first circuit (3A) during operation is operated under optimum conditions to maintain high energy consumption efficiency (EER). be able to.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram illustrating a main part of a primary-side refrigerant circuit according to an embodiment.

FIG. 2 is a refrigerant circuit diagram showing a secondary refrigerant circuit according to the embodiment.

FIG. 3 is a flowchart illustrating an operation of a stop-side expansion valve control unit of the controller according to the embodiment.

[Explanation of symbols]

 (3A) First circuit (secondary refrigerant circuit) (3B) Second circuit (secondary refrigerant circuit) (5) Evaporation circuit (5A) First branch passage (5B) Second branch passage (11a) 1 refrigerant heat exchanger (11b) 2nd refrigerant heat exchanger (20) Primary refrigerant circuit (21) Primary compressor (22) Condenser (31) Secondary compressor (50) Evaporator (71) Capacity Control means (72) Stop-side expansion valve control means (EV12a) First primary-side electric expansion valve (EV12b) Second primary-side electric expansion valve (SPH1) High-pressure pressure sensor (pressure detection means) (TDH) Discharge pipe temperature sensor ( Temperature detection means)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-9-269155 (JP, A) JP-A-3-191265 (JP, A) Full-fledged 1986-58469 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) F25B 7/00 F25B 5/02

Claims (2)

(57) [Claims] 1. A primary compressor (21) and a condenser (22).
And a plurality of branch passages (5A, 5B) connected in parallel to each other, and an evaporating circuit (5), which is connected in order to form a closed circuit in which the primary refrigerant circulates. (5A, 5B) includes a primary refrigerant circuit (20) in which a primary expansion valve (EV12a, EV12b) and an evaporator of a refrigerant heat exchanger (11a, 11b) are provided in order, and a secondary compressor. (31) and each of the refrigerant heat exchangers (11a, 11
b) Condensing section, secondary expansion mechanism (EV21), and evaporator (5
0) are connected in order, the secondary refrigerant circulates, and a plurality of secondary-side refrigerant circuits (11a, 11b) that exchange heat between the primary refrigerant and the secondary refrigerant in the respective refrigerant heat exchangers (11a, 11b). 3A, 3B), and controls the operation and stop of each of the secondary-side refrigerant circuits (3A, 3B) to adjust the number of operating secondary-side refrigerant circuits (3A, 3B). A capacity control means (71) for controlling the capacity and a refrigerant heat exchanger (11b) connected to the secondary refrigerant circuit (3B) stopped by the capacity control means (71 ) are provided.
Stop-side primary expansion valve (EV12 ) in the branch passage (5B)
b) a stop-side expansion valve control means (72) for adjusting the opening degree so that the temperature of the refrigerant discharged from the primary compressor (21) is maintained within a predetermined range. Refrigeration equipment. 2. The two-way refrigeration system according to claim 1, wherein a pressure detecting means (SPH1) for detecting a pressure of a refrigerant discharged from the primary compressor (21), and a refrigerant discharged from the primary compressor (21). The stop-side expansion valve control means (72) is provided with a pressure detection means (SPH1).
The superheat degree of the refrigerant discharged from the primary compressor (21) is derived from the detected value of the temperature and the detection value of the temperature detection means (TDH), and the primary expansion of the stop side based on the temperature and the superheat degree of the discharged refrigerant. A binary refrigeration apparatus characterized by being configured to adjust the opening of a valve (EV12b).