JP2000130895A - Chiller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform defrost surely in a cooler for refrigerator by melting dews completely while eliminating useless defrost operation. SOLUTION: A primary refrigerating circuit is provided with two refrigerant heat exchangers 11 through which the primary refrigerating circuit is coupled with secondary refrigerant circuits, i.e., first and second circuits 3A, 3B. Heat transfer tubes 5a, 5b for evaporation of both secondary refrigerant circuits 3A, 3B constitute an integral evaporator 50 and an evaporator temperature sensor Th 22 is provided at the lower end thereof. A liquid temperature sensor Th 21 is provided in front of a distributor 55 in the liquid pipe 61 of the first circuit 3A. The defrost end detecting section 71 of a controller 70 detects the end of defrost when both temperatures detected through the evaporator temperature sensor Th 22 and the liquid temperature sensor Th 21 exceeds reference levels, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling device for cooling air, and more particularly to a measure for detecting completion of defrost.

[0002]

2. Description of the Related Art Conventionally, a refrigerating apparatus is provided with a refrigerant circuit in which a compressor, a condenser, an expansion mechanism, and an evaporator are connected in order, so as to cool a refrigerator or a freezer. There are refrigeration equipment. In addition, as disclosed in Japanese Patent Application Laid-Open No. 9-210515,
There is also known a dual refrigeration cycle that includes a high-stage primary refrigerant circuit and a low-stage secondary refrigerant circuit that individually perform refrigeration operations.

In this type of refrigeration apparatus, frost adheres to an evaporator that exchanges heat between the air in the refrigerator and the refrigerant, so that it is necessary to perform a defrost operation. As a method of the defrost operation, a reverse cycle method in which the refrigerant circulation direction of the refrigerant circuit is reversed and the refrigerant is condensed by the evaporator is widely used. However, the inside of the refrigerator cannot be cooled during the defrost operation, not limited to the reverse cycle type. Therefore, if the defrost operation is performed for an unnecessarily long time, the internal temperature of the refrigerator increases.

[0004] On the other hand, conventionally, it has been detected by some means whether or not the defrost operation has been completed, so that the defrost operation time does not become too long. Specifically, when performing the reverse cycle type defrost operation, the refrigerant temperature at the evaporator outlet during the defrost operation is detected, and when the refrigerant temperature exceeds the reference value, the defrost operation is stopped, assuming that the defrost has ended. I was

[0005]

However, as described above, it is difficult to reliably detect the end of defrost only based on the refrigerant temperature at the evaporator outlet during the defrost operation. In other words, frost does not always adhere uniformly,
Rather, the evaporator usually has a portion where much frost adheres and a portion where little frost is present. For this reason, if the defrost operation is continued for a certain period of time, a state may occur in which the frost is melted in only a part of the evaporator while the frost is melted in most of the evaporator. In such a case, although the frost remains, frost is present only in a part of the evaporator, so that the refrigerant temperature at the evaporator outlet may exceed a predetermined reference value, and defrosting may occur. The end could not be reliably detected. Therefore, conventionally,
There is a problem that the defrost operation may be terminated even though frost remains.

To cope with this problem, it is conceivable to set the above-mentioned reference value to a high value and to perform the defrosting operation for a long time to surely melt the frost. However, in this measure, there is a possibility that the defrost operation is continued unnecessarily even though the frost is completely melted. Then, there is a disadvantage that the temperature inside the refrigerator increases due to unnecessary defrost operation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to reliably detect the end of defrost and completely eliminate frost while eliminating unnecessary defrost operation. To perform defrost reliably.

[0008]

SUMMARY OF THE INVENTION The present invention detects the end of defrost based on the temperature of a portion where frost hardly melts during a defrost operation such as a lower end portion of an evaporator.

[0009] Specifically, a first solution taken by the present invention is a refrigerant circuit comprising a compressor (31), a condenser (11), an expansion mechanism (EV21) and an evaporator (50) connected in this order. (3A, 3B)
And a refrigeration apparatus that is configured to cool the inside of the refrigerator with the evaporator (50) and perform defrost operation. Then, a device temperature detecting means (Th22) for detecting the temperature of the lower end of the evaporator (50), and a defrost end detecting means (71) for detecting the end of the defrost based on the detection value of the device temperature detecting means (Th22). ).

[0010] The second solution taken by the present invention is:
In the first solution, the device temperature detecting means (Th2
2) The evaporator (50) during the cooling operation in the forward cycle
Is configured to detect the temperature near the refrigerant inlet.

Further, a third solution taken by the present invention is:
A refrigerant circuit (3A, 3B) formed by connecting a compressor (31), a condenser (11), an expansion mechanism (EV21), and an evaporator (50) in order;
The present invention is directed to a refrigerating apparatus configured to be able to perform defrost operation while cooling the inside of the refrigerator by the evaporator (50). Then, a device temperature detecting means (Th22) for detecting a temperature of a portion of the constituent members of the refrigeration apparatus where frost is difficult to melt by the defrost operation, and a defrosting operation based on the detection value of the device temperature detecting means (Th22). And a defrost end detecting means (71) for detecting the end.

A fourth solution taken by the present invention is:
In any one of the first to third solving means, the refrigerant circuit (3A, 3B) is configured to perform the defrost operation by setting the refrigerant circulation direction to a reverse cycle, while the evaporator (50) during the defrost operation. A refrigerant temperature detecting means (Th21) for detecting a refrigerant temperature at an outlet of the air conditioner; a defrost end detecting means (71); a detecting value of the equipment temperature detecting means (Th22) being equal to or more than a predetermined value; When the detected value of (Th21) is equal to or more than a predetermined value, the end of the defrost is detected.

Further, a fifth solution taken by the present invention is:
In any one of the first to fourth solving means, the refrigerant circuit (3A, 3B) is configured as a secondary refrigeration circuit (3A, 3B), while the compressor (21) and the condenser (22). , The primary side refrigeration circuit (2
0), and the condenser (1) of the secondary refrigeration circuit (3A, 3B)
1) and the evaporator (11) of the primary side refrigeration circuit (20) constitute an integral refrigerant heat exchanger (11, 11) for exchanging heat between the primary refrigerant and the secondary refrigerant, and The refrigerant circuit (20) and the secondary refrigerant circuits (3A, 3B) constitute a binary refrigeration cycle.

-Operation- In the first solution, during the cooling operation, the refrigerant discharged from the compressor (31) of the refrigerant circuit (3A, 3B)
It is condensed in the condenser (11) and becomes a liquid refrigerant. The liquid refrigerant is decompressed by the expansion mechanism (EV21) and then flows to the evaporator (50) to evaporate, thereby cooling the inside of the refrigerator. Thereafter, the evaporated refrigerant returns to the compressor (21) and repeats this circulation. During the defrost operation, the cooling operation is stopped, and the attached frost is warmed and melted.

During the defrost operation, the device temperature detecting means (Th22) detects the temperature at the lower end of the evaporator (50).
The lower end of the evaporator (50) is a portion where frost is particularly likely to be formed and hardly melted in the evaporator (50). That is, during the cooling operation, the refrigerant flows into the lower end of the evaporator (50), so that the lower end has a lower temperature and a greater amount of frost than the other parts. In addition, during the defrost operation, the frost at the upper part of the evaporator (50) melts and becomes drain and flows to the lower end part. For this reason, the temperature at the lower end portion is not easily increased, and the frost at the lower end portion is not easily melted. Further, when performing the reverse cycle type defrost operation, the refrigerant flowing into the evaporator (50) flows out from the lower end of the evaporator (50). Therefore, the refrigerant whose temperature has decreased flows through the lower end of the evaporator (50), and the temperature of the lower end hardly rises and frost hardly melts.

As described above, at the time of the defrost operation, the lower end of the evaporator (50) is a place where the time is required to increase the temperature most. And the temperature of this lower end is 0 ° C
If the temperature is sufficiently higher than that, it can be assumed that the temperature of the entire evaporator (50) is higher than 0 ° C. and that no frost remains in the evaporator (50). Therefore, the defrost end detecting means (71)
Evaporator (50) detected by the device temperature detection means (Th22)
The end of the defrost is detected based on the temperature at the lower end of the.

[0017] In the second solution, the device temperature detecting means (Th22) comprises an evaporator (50) for cooling operation.
The temperature near the refrigerant inlet (hereinafter, referred to as cooling inlet) is detected. During the cooling operation, the vicinity of the inlet at the time of cooling is a place where the amount of frost is large because the temperature is particularly low even in the lower end portion of the evaporator (50). Further, when performing the reverse cycle type defrosting operation, the refrigerant flows out from the cooling-time inlet. Therefore, in this case, the vicinity of the inlet at the time of the cooling is a portion of the evaporator (50) that is the least likely to warm up during the defrost operation and is less likely to melt frost.

Further, in the third solution, the first solution
The cooling operation and the defrost operation are performed in the same manner as in the solution of (1). On the other hand, the device temperature detecting means (Th22) detects the temperature of a component of the refrigeration unit that is difficult to melt frost by the defrost operation, that is, a portion where the temperature does not easily increase during the defrost operation. If the temperature detected by the device temperature detecting means (Th22) is sufficiently higher than 0 ° C., it can be estimated that no frost remains at any point. Therefore, the defrost end detecting means (71) detects the end of defrost based on the temperature detected by the device temperature detecting means (Th22).

In the fourth means, the refrigerant circulation direction in the refrigerant circuit (20) is reversed to perform a reverse cycle type defrost operation. That is, the refrigerant discharged from the compressor (31) is condensed in the evaporator (50) and expands (EV21)
After the pressure is reduced in the condenser (11), the mixture is evaporated in the condenser (11), and then returns to the compressor (31). Then, the frost is heated and melted using the condensation heat radiated from the refrigerant when condensing in the evaporator (50).

The refrigerant temperature detecting means (Th21) detects the refrigerant temperature at the outlet of the evaporator (50) during the defrost operation (hereinafter referred to as the defrost outlet). The defrost end detecting means (71) detects the end of defrost when both the refrigerant temperature at the outlet at the time of defrost and the temperature detected by the device temperature detecting means (Th22) exceed respective reference values.

In the fifth solution, the refrigerant circuit (3A, 3B) is a secondary refrigeration circuit (3A, 3B), and the secondary refrigerant circuit (3A, 3B) and the primary refrigerant circuit (3A, 3B) 20) constitutes a binary refrigeration cycle. During the cooling operation, in the primary-side refrigerant circuit (20), the primary refrigerant discharged from the compressor (21) flows to the condenser (22) and condenses into a liquid refrigerant. The liquid refrigerant is depressurized by the expansion mechanism (EV12), flows into the refrigerant heat exchanger (11), exchanges heat with the secondary refrigerant, and evaporates. Thereafter, the evaporated refrigerant returns to the compressor (21) and repeats this circulation. On the other hand, in the secondary refrigeration circuit (3A, 3B), which is a refrigerant circuit, the secondary refrigerant exchanges heat with the primary refrigerant in the refrigerant heat exchanger (11), condenses, and evaporates in the evaporator (50). Cool inside.

[0022]

According to the first or second solution, the end of the defrost is detected based on the temperature of the lower end of the evaporator (50), which is a portion where frost is particularly likely to be formed and hardly melts. ing. Further, in the third solving means, the end of the defrost is detected based on the temperature of a portion of the component of the refrigerating device where the frost is not easily melted by the defrost operation. Therefore, the end of the defrost can be reliably detected. As a result, frost can be completely melted while unnecessary defrosting operation is eliminated, and reliable defrosting becomes possible.

According to the fourth solution, the end of the defrost is detected based on the detected temperatures of both the device temperature detecting means (Th22) and the refrigerant temperature detecting means (Th21). The end of the defrost can be reliably detected.

According to the fifth aspect of the present invention, since a binary refrigeration cycle is configured, a low temperature of minus several tens degrees can be obtained while maintaining the efficiency of the apparatus. Can be expanded.

[0025]

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.

The primary 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. And the primary side refrigerant circuit (20)
Has a compressor (21), a condenser (22), and an evaporator of two refrigerant heat exchangers (11, 11). The evaporator of the refrigerant heat exchanger (11, 11) forms an evaporator of the primary refrigerant circuit (20). 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).

A first gas pipe (40) is connected to the discharge side of the compressor (21), and a second gas pipe (41) is connected to the suction side. The first gas pipe (40) includes a compressor (21)
, An oil separator (23) and a four-way switching valve (24) are connected in order, and 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),
The liquid pipe (42) has a main pipe (4a) and two branch pipes (4
b, 4c). Each branch pipe (4b, 4c) is connected to each evaporator of the two refrigerant heat exchangers (11, 11).

The main pipe (4a) of the liquid pipe (42) connects the electric expansion valve for defrost (EV11) and the receiver (25) in order from the condenser (22). On the other hand, the above-mentioned branch pipes (4b, 4c) have an electric expansion valve for cooling (EV1
2) is provided.

The second gas pipe (41) is a main pipe (4d)
And two branch pipes (4e, 4f). The main pipe (4d) of the second gas pipe (41) connects the accumulator (26) and the four-way switching valve (24) in order from the compressor (21), while the branch pipes (4e, 4f) Is connected to the evaporator of each refrigerant heat exchanger (11, 11). That is, the evaporators of the two refrigerant heat exchangers (11, 11) are connected in parallel to each other in the primary refrigerant circuit (20).

The branch pipes (4b, 4c, 4e, 4f) of the liquid pipe (42) and the second gas pipe (41) are 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.

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

A first gas pipe (40) on the discharge side of the compressor (21) has a high-pressure pressure sensor (SPH1) for detecting a high-pressure refrigerant pressure, and a high-pressure refrigerant pressure excessively increases to a predetermined high pressure value. And a high-pressure switch (HPS1) for outputting an off signal. Also, compressor (21) and oil separator (23)
A discharge pipe temperature sensor (TDH) is attached to the first gas pipe (40) in the vicinity of the first gas pipe (40) near the connection to the compressor (21). Further, the second compressor on the suction side of the compressor (21)
The gas pipe (41) is provided with a low-pressure pressure sensor (SPL1) for detecting a low-pressure refrigerant pressure.

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 compressor (31), a condensing section of the first refrigerant heat exchanger (11), and a heat transfer tube for evaporation (5a). This refrigerant heat exchanger (1
The condenser section 1) constitutes the condenser of the first circuit (3A).

The discharge side of the compressor (31) is connected to a first refrigerant heat exchanger (11) via a first gas pipe (60) via an oil separator (32) and a four-way switching valve (33). Is connected to one end of the condenser section. The other end of the condenser is connected to a liquid pipe (6
1) is connected to one end of the heat transfer tube for evaporation (5a) via a check valve (CV), a receiver (34), and a cooling expansion valve (EV21) as an expansion mechanism. The heat transfer tube for evaporation (5a)
Is connected to the suction side of the compressor (31) via a check valve (CV), a four-way switching valve (33), and an accumulator (35) by a second gas pipe (62).

The first refrigerant heat exchanger (11) is a cascade condenser having an evaporator of the primary refrigerant circuit (20) and a condenser of the first circuit (3A), and is a plate-type heat exchanger. It is constituted by. In the first refrigerant heat exchanger (11), the refrigerant in the first circuit (3A) exchanges heat with the refrigerant in the primary refrigerant circuit (20), and the refrigerant in the first circuit (3A) radiates heat. The refrigerant in the primary refrigerant circuit (20) absorbs heat and evaporates.

The cooling 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). Is provided.

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
A drain pan heater (6a) and a check valve (CV) are provided, connected to both ends of the check valve (CV) in the gas passage (62), and refrigerant (hot gas) discharged from the compressor (31) flows. It is configured as follows.

The gas bypass passage (64) is connected to both ends of the cooling expansion valve (EV21) in the liquid pipe (61), and is provided with a check valve (CV). (EV21).

The pressure reducing passage (65) is connected to both ends of the check valve (CV) in the liquid pipe (61), and has 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).

Further, one end of a gas vent passage (66) is connected to an upper portion of the receiver (34). 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).

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

A first gas pipe (60) on the discharge side of the compressor (31) has a high-pressure pressure sensor (SPH2) for detecting a high-pressure refrigerant pressure, and a high-pressure refrigerant pressure which is excessively increased to a predetermined high pressure value. And a high-pressure switch (HPS2) for outputting an off signal. Also, compressor (31) and oil separator (32)
A discharge pipe temperature sensor (TDL) is attached to the first gas pipe (60) in the vicinity of the connection point to the compressor (31). Further, the second side of the suction side of the compressor (31)
The gas pipe (62) is provided with a low pressure sensor (SPL2) for detecting the low pressure refrigerant pressure.

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 furthermore, the drain pan passage (63), the gas bypass passage (64), and the pressure reducing passage (65) Not provided. That is, the second circuit (3B) includes a condenser (31), a condenser of the second refrigerant heat exchanger (11), a receiver (34), a cooling expansion valve (EV21), and an evaporating heat transfer tube (5b). ) And an accumulator (35) are sequentially connected by a first gas pipe (60), a liquid pipe (61), and a second gas pipe (62). The condenser of the second refrigerant heat exchanger (11) constitutes the condenser of the second circuit (3B). The second circuit (3
Similarly to the first circuit (3A), the discharge pipe temperature sensor (TDL), the high pressure sensor (SPH1), the low pressure sensor (SPL1), and the high pressure switch (HPS1) are located at predetermined positions. Is provided.

The cooling 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 evaporation heat transfer tube (5b). The second refrigerant heat exchanger (11) is a cascade condenser having an evaporator of the primary refrigerant circuit (20) and a condenser of the second circuit (3B). It is configured. The second refrigerant heat exchanger (11)
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 cooling expansion valve (EV21) and the drain pan passage (63) are provided in the cooling unit (1C), while another compressor (31) is provided in the cascade unit (1B). Have been. Although not shown, the cooling unit (1C) is provided with an internal fan driven by a fan motor,
The in-compartment fan sends the in-compartment air to the evaporator (50).

As shown in FIGS. 3 and 4, the evaporator (50) is composed of a plurality of plate-like fins (51) provided with the evaporating heat transfer tubes (5a, 5b) penetrating therethrough. (52)
And a pair of tube sheets (5) provided on both sides of the main body (52).
3), and is configured as a so-called plate-fin type heat exchanger. Further, the tube arrangement of the evaporator (50) is a so-called staggered arrangement in which adjacent rows in a plurality of rows and a plurality of rows are shifted from each other by half the step pitch.

Each of the evaporation heat transfer tubes (5a, 5b) has a last row (left end in FIG. 4) located downstream of the air flow.
At one end of the secondary refrigerant circuit (3) via a flow divider (55).
A, 3B) is connected to the liquid pipe (61), and one end of the liquid pipe (61) is configured as an inlet for cooling. Further, each of the evaporating heat transfer tubes (5a, 5b) is connected to the other end of the front row (right end in FIG. 4) located on the upstream side of the air flow via a header (not shown) through the secondary refrigerant circuit ( 3A, 3B) is connected to the second gas pipe (62). The evaporative heat transfer tube (5a) of the first circuit (3A) is arranged at the lowermost stage of the main body (52).

The main body portion (52) of the evaporator (50) is provided with an evaporator temperature sensor (Th22) located on the side surface on the last row side of the lower end, that is, on the back side of the lower end. . Specifically, the evaporator temperature sensor (Th22) is formed in a rod shape, and is attached and fixed to the main body (52) by a pair of clips (54). Then, the evaporator temperature sensor (Th2
2) is configured as device temperature detecting means for detecting the temperature near the inlet at the time of cooling at the lower end of the evaporator (50). Also,
The flow divider (5) of the liquid pipe (61) in the first circuit (3A)
A liquid temperature sensor (Th21) for detecting the temperature of the liquid refrigerant is provided near the connection to 5). This liquid temperature sensor (Th21) constitutes a refrigerant temperature detecting means.

A drain pan is provided below the evaporator (50) for receiving drain water flowing down from the evaporator (50) during the defrost operation and discharging the drain water out of the refrigerator. The drain pan is provided with the drain pan heater (6a).

The binary refrigeration system (10) of the present embodiment is shown in FIG.
As shown in (1), a controller (70) is provided. The controller (70) includes a defrost end detection unit (71).

The defrost end detecting section (71) includes the evaporator temperature sensor (Th22) and the liquid temperature sensor (Th21).
Are detected. The defrost end detection section (71) is configured as defrost end detection means for detecting the end of defrost when the detection values of the sensors (Th22, Th21) both exceed a predetermined reference value during the defrost operation. I have. The defrost end detection unit (71) is configured to determine whether the refrigerant condensing temperature in the evaporator (50) during the defrost operation has become equal to or higher than a reference value, when the defrost operation has continued for a predetermined time, or It is configured to detect the end of defrost even when a defrost flow signal is input.

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

First, when performing the cooling operation, the compressor (21) of the primary-side refrigerant circuit (20) and both the secondary-side refrigerant circuits (3A, 3A)
B) The two compressors (31, 31) are driven together. In this state, in the primary 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 electric expansion valve for cooling (EV1) is opened.
2) control the opening.

The compressor (21) of the primary refrigerant circuit (20)
The primary refrigerant discharged from the condenser is condensed in the condenser (22) to become a liquid refrigerant and flows to the cascade unit (1B). The liquid refrigerant is divided into two branch pipes (4b, 4c), and after being decompressed by the electric cooling expansion valve (EV12), evaporates in each evaporator of the two refrigerant heat exchangers (11, 11). . Thereafter, the gas refrigerant returns to the compressor (21) from each of the evaporating sections, and repeats this circulation.

On the other hand, in the first circuit (3A), the four-way switching valve (33) is switched to the solid line in FIG. 2, while the defrost expansion valve (EV22) is fully closed, and the cooling expansion valve (EV21) is overheated. Control the degree. In the second circuit (3B), the degree of superheat of the cooling 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 section of the refrigerant heat exchanger (11, 11) and becomes a liquid refrigerant. After the pressure of the liquid refrigerant is reduced by the cooling expansion valve (EV21), the liquid refrigerant is evaporated by the evaporating heat transfer tubes (5a, 5b). Then, the gas refrigerant returns from the heat transfer tubes for evaporation (5a, 5b) to the compressor (31, 31), and repeats this circulation.

In the refrigerant heat exchangers (11, 11), the primary refrigerant and the secondary refrigerant exchange heat, and the secondary refrigerant in the secondary refrigerant circuits (3A, 3B) is cooled and condensed. I do. 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 cooling expansion valve (EV21) is controlled. )
Is fully closed.

The secondary refrigerant discharged from the compressor (31) passes through the four-way switching valve (33), passes through the drain pan passage (63), and heats the drain pan 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 evaporation heat transfer tube (5a) flows through the gas bypass passage (64), flows through the receiver (34), flows through the pressure reduction passage (65), and then flows through the defrost expansion valve (EV2).
Reduce the pressure in 2). Subsequently, the secondary refrigerant evaporates in the condensing section of the refrigerant heat exchanger (11), returns to the compressor (31) via the four-way switching valve (33) and the accumulator (35), and repeats this circulation. .

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 defrost electric expansion valve (EV11) is controlled, and the cooling electric expansion valve is operated. (EV12) fully open.

The primary refrigerant discharged from the compressor (21) passes through the four-way switching valve (24) to the first refrigerant heat exchanger (11).
And heats the secondary refrigerant in the first circuit (3A). Thereafter, the primary refrigerant flowing through the evaporator of the refrigerant heat exchanger (11) passes through the receiver (25) and is depressurized by the electric defrost expansion valve (EV11). Subsequently, the primary refrigerant evaporates in the condenser (22), returns to the compressor (21) via the four-way switching valve (24) and the accumulator (26), and repeats this circulation.

-Operation of Controller- During the above-described defrost operation, the controller (70)
Performs a predetermined operation, and the defrost end detecting section (71) of the controller (70) detects the end of defrost. The operation of the controller (70) during the defrost operation will be described with reference to the flowchart of FIG.

When the defrost operation is started, the defrost end detecting section (71) performs the operations of steps ST1 and ST2. Specifically, in step ST1, it is determined whether or not any of the following conditions is satisfied. That is,
The state where the detection pressure of the high pressure sensor (SPH2) is 18 kgf / cm ² or more, that is, the refrigerant condensation temperature in the evaporator (50) is 48 ° C. or more, and the detection temperature of the liquid temperature sensor (Th21) is 35 ° C.
When the temperature detected by the evaporator temperature sensor (Th22) is 5
℃ or more, the defrost operation duration is 60
It is determined whether the state is equal to or longer than one minute or a state in which a compulsory defrost operation end signal is input.
Then, when any of the above-mentioned conditions is reached, step
Move to ST2 to detect the end of defrost.

When the end of the defrost is detected in step ST2, the process proceeds to step ST3, where a stop signal for the defrost operation is output, the defrost operation is stopped, and the cooling operation is restarted.

On the other hand, if none of the above conditions is satisfied in step ST1, the process proceeds to step ST4, waits for one minute, and then proceeds to step ST5. In step ST5, it is determined whether or not the detected temperature of the discharge pipe temperature sensor (TDL) of the first circuit (3A) is equal to or higher than a reference value. If the detected temperature is lower than 110 ° C., the process returns to step ST1 to perform the defrost operation. To continue. On the other hand, if the detected temperature is equal to or higher than 110 ° C., the process shifts to step ST3 to stop the defrost operation.

As described above, the evaporator temperature sensor (Th22)
Is provided at the lower end of the main body (52) of the evaporator (50),
The temperature near the inlet at the time of cooling at the lower end is detected. The location where the evaporator temperature sensor (Th22) is attached is a location in the evaporator (50) where frost is particularly easily formed and hardly melts. That is, during the cooling operation, the refrigerant flows into the evaporator (50) from the cooling inlet. Therefore, the location of the evaporator (50) has a lower temperature and a greater amount of frost than other portions. In addition, the evaporator (50)
Since the frost on the top melts and becomes drain and flows to the lower end,
The temperature at the lower end of the evaporator (50) does not easily rise, and the frost in this part is hard to melt.

Further, in this embodiment, since the reverse cycle type defrost operation is performed, during the defrost operation, the refrigerant circulation direction in the first circuit (3A) is a reverse cycle, and the cooling inlet is connected to the defrost operation. When it comes to the exit. That is, during the defrost operation, the refrigerant at the lowest temperature flows to the outlet at the time of defrost. For this reason, evaporator (50)
The mounting location of the evaporator temperature sensor (Th22) in
The temperature does not easily rise, and the frost at the location hardly melts.

Then, the defrost end detecting section (71)
Means that the temperature detected by the liquid temperature sensor (Th21) is 35 ° C or higher,
When the temperature detected by the evaporator temperature sensor (Th22) becomes 5 ° C. or more, the end of the defrost is detected. In other words, if the temperature detected by the evaporator temperature sensor (Th22) is 5 ° C. or higher, it is considered that the entire evaporator (50) is 5 ° C. or higher and all the attached frost is melted. I try to detect.

-Effects of the Embodiment- In the present embodiment, the evaporator temperature sensor (Th) is attached to a portion of the evaporator (50) where frost is particularly likely to adhere and hardly melts.
The end of defrost is detected based on the detected temperature of 22). Therefore, the end of the defrost can be reliably detected. Therefore, frost can be completely melted while unnecessary defrosting operation is eliminated, and reliable defrosting can be performed. Evaporator temperature sensor (Th22)
Since the end of the defrost is detected based on both the detected temperatures of the liquid temperature sensor (Th21) and the liquid temperature sensor (Th21), the end of the defrost can be more reliably detected.

[0073]

In the above embodiment, the liquid pipe (61) is connected to one end of the evaporating heat transfer tubes (5a, 5b) on the last row side.
The evaporator temperature sensor (Th22) is disposed on the back side of the lower end of the main body (52) of the evaporator (50) because the one end is used as a refrigerant inlet for cooling. On the other hand, when the liquid pipe (61) is connected to the other end on the front row of each evaporating heat transfer tube (5a, 5b) and the other end is used as a cooling-medium inlet, the evaporator (50) The evaporator temperature sensor (Th22) is arranged on the front side of the lower end of the evaporator.

In the above embodiment, the evaporator temperature sensor (Th22) is provided on the main body (52) of the evaporator (50). On the other hand, the tube plate (53) of the evaporator (50)
Of these, the evaporator temperature sensor (Th22) may be provided at the lower end of the tube sheet (53) located on the refrigerant inlet side during cooling.

In the above embodiment, the evaporator (50) is provided with the evaporator temperature sensor (Th22), and the evaporator temperature sensor (Th22) is used as a device temperature detecting means. On the other hand, a temperature sensor may be provided at a position of the drain pan farthest from the drain pan heater (6a), and the temperature sensor may be used as device temperature detecting means. That is, the location of the drain pan is also a location where the temperature does not easily rise during the defrost operation and frost does not easily melt. Therefore, a temperature sensor may be provided in such a location, and the end of defrost may be detected based on the temperature detected by the temperature sensor. still,
When the drain pan is not provided with a drain pan heater, a temperature sensor may be provided at any part of the drain pan.

In some cases, frost may form on the casing of the cooling unit (1C). Specifically, when the air passage is defined by the casing and the evaporator (50) is provided over the entire cross section of the air passage, the main body (52) and the tube plate (53) of the evaporator (50) are provided. ) And the casing come into contact with each other. Therefore, when the temperature of the evaporator (50) becomes low during the cooling operation, the temperature of the casing that comes into contact with the evaporator (50) also decreases, and frost may adhere. Since the evaporator (50) is directly heated by the defrost operation, the temperature of the casing in contact with the evaporator (50) does not easily rise, and the frost adhering to the location is hard to melt. In such a case, a temperature sensor may be provided in the casing in the vicinity of the contact point with the evaporator (50), and the temperature sensor may be used as device temperature detecting means. A temperature sensor may be provided at such a location, and the end of defrost may be detected based on the temperature detected by the temperature sensor.

[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 an enlarged view of a main part of the evaporator according to the embodiment as viewed from the back side.

FIG. 4 is an enlarged view of a main part viewed from a side of the evaporator according to the embodiment.

FIG. 5 is a flowchart illustrating an operation of the controller according to the embodiment during a defrost operation.

[Explanation of symbols]

(3A) First circuit (secondary refrigerant circuit) (3B) Second circuit (secondary refrigerant circuit) (11) Refrigerant heat exchanger (evaporator of primary refrigerant circuit, condenser of secondary refrigerant circuit) (20) Primary refrigerant circuit (21) Compressor (22) Condenser (31) Compressor (50) Evaporator (71) Defrost end detection unit (Defrost end detection means) (EV12) Electric expansion valve for cooling ( (Expansion mechanism) (EV21) Cooling expansion valve (Expansion mechanism) (Th21) Liquid temperature sensor (Refrigerant temperature detection means) (Th22) Evaporator temperature sensor (Equipment temperature detection means)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takeo Ueno 1304 Kanaokacho, Sakai City, Osaka Daikin Industries, Ltd. Sakai Plant Kanaoka Plant

Claims (5)

[Claims] 1. A refrigerant circuit (3A, 3B) comprising a compressor (31), a condenser (11), an expansion mechanism (EV21) and an evaporator (50) connected in this order, wherein the evaporator (50) is provided. A refrigerator that is configured to be able to perform defrost operation while cooling the inside of the refrigerator, wherein a device temperature detecting means (Th22) for detecting the temperature at the lower end of the evaporator (50); And a defrost end detecting means (71) for detecting the end of defrost based on the detected value of (1). 2. The refrigerating apparatus according to claim 1, wherein the device temperature detecting means (Th22) is configured to detect a temperature near a refrigerant inlet of the evaporator (50) during a cooling operation in a normal cycle. Refrigeration equipment. 3. A refrigerant circuit (3A, 3B) formed by sequentially connecting a compressor (31), a condenser (11), an expansion mechanism (EV21) and an evaporator (50); An apparatus temperature detecting means (Th22) for detecting the temperature of a part of the components of the refrigeration apparatus that is difficult to melt frost by the defrost operation, wherein the refrigeration apparatus is configured to be able to perform a defrost operation while cooling the inside of the refrigerator. A refrigerating apparatus comprising: defrost end detecting means (71) for detecting the end of defrost based on a detection value of the device temperature detecting means (Th22). 4. The refrigerating apparatus according to claim 1, wherein the refrigerant circuit (3A, 3B) is configured to perform a defrost operation in a reverse cycle of a refrigerant circulation direction. And a refrigerant temperature detecting means (Th21) for detecting a refrigerant temperature at an outlet of the evaporator (50), wherein the defrost end detecting means (71) detects a device temperature detecting means (Th22) of a predetermined value or more, A refrigeration apparatus configured to detect the end of defrost when the detected value of the refrigerant temperature detecting means (Th21) becomes equal to or more than a predetermined value. 5. The refrigeration apparatus according to claim 1, wherein the refrigerant circuit (3A, 3B) is configured as a secondary refrigeration circuit (3A, 3B), and the compressor (21). , A condenser (22), an expansion mechanism (EV12), and an evaporator (11) connected in this order to a primary refrigeration circuit (20), and a condenser (11) for the secondary refrigeration circuit (3A, 3B). ) And the evaporator (11) of the primary refrigeration circuit (20) are an integral refrigerant heat exchanger (11,11) for exchanging heat between the primary refrigerant and the secondary refrigerant.
The primary refrigerant circuit (20) and the secondary refrigerant circuit (3A, 3
B) is a refrigeration system that constitutes a binary refrigeration cycle.