EP4726290A1

EP4726290A1 - Refrigeration device, refrigerant leakage determination method, and program

Info

Publication number: EP4726290A1
Application number: EP25828075.9A
Authority: EP
Inventors: Kazuhiro Suzuki; Makoto Ikemiya
Original assignee: Daikin Industries Ltd
Current assignee: Daikin Industries Ltd
Priority date: 2024-07-02
Filing date: 2025-05-27
Publication date: 2026-04-15
Also published as: JP2026007135A; WO2026009604A1; JP7824539B2

Abstract

A controller (100) selectively conducts a first operation to determine leakage of a carbon dioxide refrigerant based on a detected value of a sensor (63) and a second operation to determine leakage of a carbon dioxide refrigerant based on an operating state of a refrigerant circuit (R).

Description

TECHNICAL FIELD

The present disclosure relates to a refrigeration apparatus, a method of determining leakage of a refrigerant, and a program.

BACKGROUND ART

Patent Document 1 discloses a refrigeration apparatus that performs a refrigeration cycle using carbon dioxide as a refrigerant. The refrigeration apparatus includes a sensor that senses the carbon dioxide concentration in a container. If a refrigerant has leaked from a refrigerant circuit of the refrigeration apparatus and the detected value of the sensor becomes greater than a predetermined value, a display device informs the operator of the situation.

CITATION LIST

PATENT DOCUMENT

PATENT DOCUMENT 1: Japanese Translation of PCT International Application, No. 2011-510294

SUMMARY OF THE INVENTION

TECHNICAL PROBLEM

The internal space of the refrigeration apparatus may store items which consume oxygen and do respiration, such as fruits, vegetables, flowers, or plants. When these items do respiration, the carbon dioxide concentration of the internal space increases. Thus, while a refrigerant does not leak from the refrigerant circuit, it may be erroneously determined based on the detected value of the sensor that a refrigerant has leaked.
An object of the present disclosure is to reduce erroneously determining leakage of a refrigerant due to respiration of fruits, vegetables, flowers, or plants.

SOLUTION TO THE PROBLEM

A first aspect is directed to a refrigeration apparatus. The refrigeration apparatus includes: a refrigerant circuit (R) including a compressor (25), a radiator (26), an expansion mechanism (31), and an evaporator (29), and configured to perform a refrigeration cycle using carbon dioxide as a refrigerant; and a sensor (63) configured to detect a carbon dioxide concentration of an internal space (3) cooled by the evaporator (29); and a controller (100). The controller (100) selectively conducts a first operation to determine leakage of the refrigerant based on a detected value of the sensor (63), and a second operation to determine leakage of the refrigerant based on an operating state of the refrigerant circuit (R).
In the first aspect, the controller (100) selectively conducts the first operation and the second operation. In the second operation, the controller (100) determines leakage of a refrigerant based on the operating state of the refrigerant circuit (R), which is not affected by the respiration of fruits, vegetables, flowers, or plants. By conducting the second operation based on a predetermined condition, it is possible to determine leakage of a refrigerant while not affected by the respiration of fruits, vegetables, flowers, or plants.
A second aspect is an embodiment of the first aspect. In the second aspect, the controller (100) determines whether a first condition that a fruit, a vegetable, a flower, or a plant is present in the internal space (3) is satisfied. The controller (100) performs the second operation if the first condition is satisfied, and performs the first operation if the first condition is not satisfied.
In the second aspect, the controller (100) performs the second operation if the first condition that fruits, vegetables, flowers, or plants are present in the internal space (3) is satisfied. Accordingly, it is possible to determine leakage of a refrigerant while not affected by the respiration of fruits, vegetables, flowers, or plants.
The controller (100) performs the first operation if the first condition is not satisfied, that is, if fruits, vegetables, flowers, and plants are not present in the internal space (3). In this case, in the internal space (3), the carbon dioxide concentration does not increase due to the respiration of fruits, vegetables, flowers, or plants, and thus it is possible for the sensor (63) to immediately determine leakage of a refrigerant.
A third aspect is an embodiment of the second aspect. In the third aspect, the refrigeration apparatus further includes an adjusting device (50) configured to perform an adjusting operation to adjust a composition of air in the internal space (3).
In the third aspect, it is possible for the adjusting device (50) to adjust the composition of the air in the internal space (3).
A fourth aspect is an embodiment of the third aspect. In the fourth aspect, the controller (100) determines that the refrigerant has leaked if a second condition that the detected value of the sensor (63) is greater than a control range of the carbon dioxide concentration of the internal space (3) in the adjusting operation is satisfied.
In the fourth aspect, the controller (100) determines that the refrigerant has leaked if the detected value of the sensor (63) is greater than a control range of the carbon dioxide concentration in the adjusting operation. This is because when the carbon dioxide concentration of the internal space (3) exceeds the control range of the adjusting operation, it is highly probable that the refrigerant has leaked.
A fifth aspect is an embodiment of the third or fourth aspect. In the fifth aspect, the first condition includes a condition that the adjusting device (50) is performing the adjusting operation.
In the fifth aspect, the condition that the adjusting device (50) is performing the adjusting operation is used as the first condition that fruits, vegetables, flowers, or plants are present in the internal space (3). This is because when the adjusting device (50) is performing the adjusting operation, it is highly probable that fruits, vegetables, flowers, or plants are present in the internal space (3).
A sixth aspect is an embodiment of any one of the second to fifth aspects. In the sixth aspect, the first condition includes a condition that a set temperature of air in the internal space (3) is greater than a predetermined temperature that is lower than 0°C.
In the sixth aspect, the condition that the set temperature of the air in the internal space (3) is greater than the predetermined temperature that is lower than 0°C is used as the first condition that fruits, vegetables, flowers, or plants are present in the internal space (3). This is because when fruits, vegetables, flowers, or plants are stored in the internal space (3), it is highly probable that the set temperature is set relatively high in order to maintain the quality of these items.
A seventh aspect is an embodiment of any one of the second to sixth aspects. In the seventh aspect, the first condition includes a condition that a rate of decrease in the oxygen concentration of the internal space (3) is greater than a predetermined value.
In the seventh aspect, the condition that the rate of decrease in the oxygen concentration of the internal space (3) is greater than the predetermined value is used as the first condition that fruits, vegetables, flowers, or plants are present in the internal space (3). This is because when fruits, vegetables, flowers, or plants are present in the internal space (3), they consume oxygen in the internal space (3), and the rate of decrease in the oxygen concentration increases.
An eighth aspect is an embodiment of any one of the second to seventh aspects. In the eighth aspect, the first condition includes a condition that information showing that a stored item in the internal space (3) is a fruit, a vegetable, a flower, or a plant is input to the controller (100), or a condition that an ethylene concentration of the internal space (3) is greater than or equal to a predetermined value, or a condition that an amount of moisture generated in the internal space (3) is greater than or equal to a predetermined value, or a condition that a cooling load in the internal space (3) has increased.
In the eighth aspect, the first condition includes the condition that the information showing that the stored items in the internal space (3) are fruits, vegetables, flowers, or plants is input to the controller (100). This is because when this information is input, fruits, vegetables, flowers, or plants are stored in the internal space (3).
The first condition includes the condition that the ethylene concentration of the internal space (3) is greater than or equal to a predetermined value. This is because when fruits, vegetables, flowers, or plants are present in the internal space (3), the ethylene concentration of the internal space (3) increases.
The first condition includes the condition that the amount of moisture generated in the internal space (3) is greater than or equal to a predetermined value. This is because when fruits, vegetables, flowers, or plants in the internal space (3) do respiration, moisture is generated in the internal space (3).
The first condition includes the condition that the cooling load in the internal space (3) has increased. This is because when fruits, vegetables, flowers, or plants in the internal space (3) do respiration, respiratory heat is generated in the internal space (3), and the cooling load in the internal space (3) increases.
A ninth aspect is an embodiment of any one of the third to fifth aspects. In the ninth aspect, the controller (100) determines that the refrigerant has leaked if a rate of increase in the detected value of the sensor (63) is greater than a predetermined value while the adjusting device (50) is not performing the adjusting operation.
In the ninth aspect, the controller (100) determines that a refrigerant has leaked if the adjusting operation is not performed and the rate of increase in the carbon dioxide concentration detected by the sensor (63) is greater than a predetermined value. This is because when the refrigerant has leaked while the adjusting operation is not performed, the carbon dioxide concentration significantly increases.
A tenth aspect is an embodiment of any one of the first to ninth aspects. In the tenth aspect, the refrigeration apparatus further includes an internal fan (30) configured to transport air in the internal space (3). When the refrigeration apparatus (10) turns from an OFF state to an ON state, the controller (100) instructs the internal fan (30) to operate and determines leakage of the refrigerant based on the detected value of the sensor (63).
In the tenth aspect, when the refrigeration apparatus (10) turns from the OFF state to the ON state, the internal fan (30) is operated to stir the internal air in the internal space (3). Under this situation, the controller (100) determines leakage of the refrigerant based on the detected value of the sensor (63). Accordingly, if the refrigerant in the refrigerant circuit (R) has leaked while the container refrigeration apparatus (10) is in the OFF state, this situation can be determined immediately.
An eleventh aspect is an embodiment of any one of the first to tenth aspects. In the eleventh aspect, in the second operation, the controller (100) determines leakage of the refrigerant based on a pressure of the refrigerant in the refrigerant circuit (R), a temperature of the refrigerant in the refrigerant circuit (R), or an opening degree of an expansion valve (31) as an expansion mechanism.
In the eleventh aspect, based on this index of the operating state of the refrigerant circuit (R), it is possible to determine leakage of a refrigerant while not affected by the respiration of fruits, vegetables, flowers, or plants.
A twelfth aspect is an embodiment of any one of the first to eleventh aspects. In the twelfth aspect, the refrigeration apparatus further includes a ventilating unit (40, 50) configured to perform a ventilating operation to ventilate the internal space (3). The controller (100) instructs the ventilating unit (40, 50) to perform the ventilating operation if it is determined that the refrigerant has leaked.
In the twelfth aspect, the ventilating unit (40, 50) performs the ventilating operation if it is determined that the refrigerant has leaked, and thus the carbon dioxide concentration of the internal space (3) can be reduced immediately.
A thirteenth aspect is directed to a method of determining leakage of a refrigerant in a refrigeration apparatus including: a refrigerant circuit (R) including a compressor (25), a radiator (26), an expansion mechanism (31), and an evaporator (29), and configured to perform a refrigeration cycle using carbon dioxide as a refrigerant; and a sensor (63) configured to detect a carbon dioxide concentration of an internal space (3) cooled by the evaporator (29). The method includes selectively conducting a first operation to determine leakage of the refrigerant based on a detected value of the sensor (63), and a second operation to determine leakage of the refrigerant based on an operating state of the refrigerant circuit (R).
A fourteenth aspect is directed to a program to instruct a computer to execute the method of the thirteenth aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] FIG. 1 is a perspective view of a container refrigeration apparatus of an embodiment as viewed from front.
[FIG. 2] FIG. 2 is a vertical sectional view of the container refrigeration apparatus.
[FIG. 3] FIG. 3 is a block diagram of main components of the container refrigeration apparatus.
[FIG. 4] FIG. 4 is a piping system diagram of the container refrigeration apparatus.
[FIG. 5] FIG. 5 is a flowchart of basic control of a method of determining leakage of a refrigerant.
[FIG. 6] FIG. 6 is a flowchart of a method of determining a first condition.
[FIG. 7] FIG. 7 is a flowchart of the method of determining leakage of a refrigerant where the container refrigeration apparatus turns into an ON state.
[FIG. 8] FIG. 8 is a flowchart of basic control of a method of determining leakage of a refrigerant according to a second variation.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present disclosure will be described in detail below with reference to the drawings. The present disclosure is not limited to the embodiment shown below, and various changes can be made within the scope without departing from the technical concept of the present disclosure. Since each of the drawings is intended to illustrate the present disclosure conceptually, dimensions, ratios, or numbers may be exaggerated or simplified as necessary for ease of understanding.

(1) Overall Configuration of Container Refrigeration Apparatus

A container refrigeration apparatus (10) will be described. As shown in FIGS. 1 and 2, the container refrigeration apparatus (10) is provided in a container (1). The container (1) is used for marine transportation. The container (1) is a refrigeration container that cools the inside air. The container (1) includes a container body (2) and the container refrigeration apparatus (10). The container body (2) stores items. The items include fruits, vegetables, flowers, and plants. The container refrigeration apparatus (10) of this embodiment has a function of adjusting the composition of the air in the container (1).
As shown in FIG. 2, the container body (2) includes a front surface on which a front opening (4) is formed. The container refrigeration apparatus (10) is attached to the container body (2) so as to close the front opening (4). The container refrigeration apparatus (10) includes a cooling unit (U), a ventilating device (40), and an adjusting device (50). The cooling unit (U) cools the air in the internal space (3) of the container body (2). The ventilating device (40) ventilates the internal space (3). The adjusting device (50) adjusts the composition of the air in the internal space (3).

(2) Cooling Unit

The cooling unit (U) includes a casing (11), an internal fan (30), an external fan (27), and a refrigerant circuit (R). The refrigerant circuit (R) includes, as main components, a compressor (25), an external heat exchanger (26), an expansion valve (31) as an expansion mechanism, and an internal heat exchanger (29). The refrigerant circuit (R) performs a refrigeration cycle using carbon dioxide as a refrigerant.

(2-1) Casing

The casing (11) forms the lid of the front opening (4) of the container body (2). The casing (11) includes a casing body (12) and a partition plate (13). The casing body (12) separates the external space (5) and the internal space (3). The partition plate (13) is located on the back side (the rear side) of the casing (11).
As shown in FIG. 2, the casing body (12) includes a flat plate portion (12a) and a recessed portion (12b). The flat plate portion (12a) is an upper part of the casing body (12) that is substantially flush with the front opening (4) of the casing (11). As shown in FIG. 1, the flat plate portion (12a) is provided with an inspection window (22). The inspection window (22) is disposed in a right part of the flat plate portion (12a). The inspection window (22) is a transparent window that allows inspection of the inside of the casing body (12).
The recessed portion (12b) is formed in a lower part of the casing (11). The recessed portion (12b) is recessed backward from the lower end of the flat plate portion (12a). An external storage space (14) is formed on the front side of the recessed portion (12b). An internal storage space (15) is formed above the recessed portion (12b) and between the flat plate portion (12a) and the partition plate (13). The lower end of the recessed portion (12b) forms a bottom plate (12c). The bottom plate (12c) extends between the right end and the left end of the casing body (12).

(2-2) Partition Plate and Air Passage

As shown in FIG. 2, the partition plate (13) is a plate member located behind the recessed portion (12b). The partition plate (13) extends in the top-bottom direction while being located at a predetermined distance away from the back surface of the recessed portion (12b). An internal passage (16) through which the internal air flows is formed between the casing body (12) and the partition plate (13). An inflow port (20) is formed between the upper end of the partition plate (13) and the upper wall (2a) of the container body (2). The inflow port (20) allows the internal space (3) and the inflow end of the internal passage (16) to communicate with each other. An outflow port (21) is formed between the lower end of the partition plate (13) and the lower wall (2b) of the container body (2). The outflow port (21) allows the internal space (3) and the outflow end of the internal passage (16) to communicate with each other.

(2-3) External Components

The compressor (25) is installed on the bottom plate (12c) of the casing (11). The compressor (25) is located in a lower part of the external storage space (14). The compressor (25) is located in a right part of the external storage space (14).
The external fan (27) is located in an upper part of the external storage space (14). The external fan (27) is a propeller fan. As shown in FIG. 2, an external passage (28) through which the external air flows is formed behind the external fan (27).
The external heat exchanger (26) is disposed above the compressor (25) in the external storage space (14). The external heat exchanger (26) is located in the external passage (28). The external heat exchanger (26) is a fin-and-tube heat exchanger.

(2-4) Internal Components

The internal heat exchanger (29) and the internal fan (30) are provided in the internal storage space (15). The internal heat exchanger (29) is supported by the casing (11) so as to extend between the casing body (12) and the partition plate (13). The internal heat exchanger (29) is a fin-and-tube heat exchanger.

(2-5) Refrigerant Circuit

As shown in FIG. 4, the cooling unit (U) includes a refrigerant circuit (R). The compressor (25) compresses a sucked refrigerant. The compressor (25) discharges a compressed refrigerant. The discharge portion of the compressor (25) is connected with a discharge pipe (32). The suction portion of the compressor (25) is connected with a suction pipe (33). The suction pipe (33) is provided with an accumulator (34). The accumulator (34) is a container that stores a liquid refrigerant.
The external heat exchanger (26) exchanges heat between the refrigerant flowing therein and the external air. The gas end of the external heat exchanger (26) communicates with the discharge pipe (32). The liquid end of the external heat exchanger (26) is connected with the liquid end of the internal heat exchanger (29) via a liquid pipe (35). The external heat exchanger (26) functions as a radiator (a condenser) through which the refrigerant dissipates heat to the air.
The expansion valve (31) is provided in the liquid pipe (35). The expansion valve (31) is an expansion mechanism that decompresses a high-pressure refrigerant to a low-pressure refrigerant. The expansion valve (31) is an electronic expansion valve of which the opening degree is adjustable. The expansion mechanism may be a capillary tube or an expansion device. A receiver (36) is provided in part of the liquid pipe (35) that is between the external heat exchanger (26) and the expansion valve (31). The receiver (36) is a container that stores an excessive refrigerant of the refrigerant circuit (R).
The internal heat exchanger (29) exchanges heat between the refrigerant flowing therein and the internal air. The gas end of the internal heat exchanger (29) communicates with the suction pipe (33). The internal heat exchanger (29) functions as an evaporator through which the refrigerant absorbs heat from the air, and cools the internal air in the internal space (3).

(3) Ventilating Device

The ventilating device (40) performs a ventilating operation to ventilate the internal space (3) of the container body (2). The ventilating device (40) of this embodiment has a supply function of supplying the external air to the internal space (3) and an exhaust function of discharging the internal air to the external space (5).
As shown in FIG. 1, the ventilating device (40) is disposed in a left part of the flat plate portion (12a) of the casing body (12). As shown in FIG. 2, the ventilating device (40) is provided in a ventilation mounting opening (6) formed in the front surface of the casing body (12). The ventilation mounting opening (6) runs through the casing body (12) in the front-back direction.
A supply passage (41) and an exhaust passage (42) are formed in the ventilating device (40). The supply passage (41) and the exhaust passage (42) allow the internal space (3) and the external space (5) to communicate with each other. Specifically, the inflow end of the supply passage (41) communicates with the external space (5). The outflow end of the supply passage (41) communicates with the primary side (the upstream side) of the internal fan (30) in the internal passage (16). The inflow end of the exhaust passage (42) communicates with the secondary side (the downstream side) of the internal fan (30) in the internal passage (16). The outflow end of the exhaust passage (42) communicates with the external space (5).
The ventilating device (40) has a ventilating fan. The ventilating fan is formed by the internal fan (30) described above. The internal fan (30) of this embodiment is shared by the ventilating device (40) and the cooling unit (U). When the internal fan (30) is driven, the external air in the external space (5) is supplied to the internal space (3) through the supply passage (41). At the same time, the air in the internal space (3) is discharged to the external space (5) through the exhaust passage (42).
A supply communication port (41a) is formed at the end portion of the supply passage (41) that is close to the external space (5). An exhaust communication port (42a) is formed at the end portion of the exhaust passage (42) that is close to the external space (5).
As shown in FIG. 2, the ventilating device (40) includes a motor (43), a drive shaft (44) driven and rotated by the motor (43), and an opening/closing cover (45) coupled to the drive shaft (44). The motor (43) is a stepping motor. The drive shaft (44) is directly coupled to the motor (43).
The opening/closing cover (45) is provided on the front side of the drive shaft (44). The opening/closing cover (45) is rotatable about the axis of the drive shaft (44). The opening/closing cover (45) opens and closes the supply passage (41) and the exhaust passage (42) in accordance with the rotational angle. The rotational angle of the opening/closing cover (45) is adjusted between the closed position and the fully open position, whereby the opening degrees of the supply passage (41) and the exhaust passage (42) are adjusted, and also the amount of ventilation by the ventilating device (40) is adjusted.

(4) Adjusting Device

The adjusting device (50) adjusts the composition of the air in the internal space (3). Specifically, the adjusting device (50) performs an adjusting operation to adjust oxygen concentration, carbon dioxide concentration, and nitrogen concentration of the air in the internal space (3). As schematically shown in FIG. 2, the adjusting device (50) is disposed in the external storage space (14) of the casing (11). The adjusting device (50) includes a supply path (51), an exhaust path (52), an air pump (53), and a PSA device (54).
The supply path (51) is a flow path for introducing the external air into the internal space (3). The inflow end of the supply path (51) is open to the external space (5). The outflow end of the supply path (51) communicates with the internal space (3). The exhaust path (52) is a flow path for discharging the air from the PSA device (54) to the external space (5).
The supply path (51) is provided with the air pump (53) and the PSA device (54). The air pump (53) is a transporting portion to transport air. The air pump (53) serves as a compressing portion to compress air and a decompressing portion to decompress air.
The PSA device (54) is the main adjusting portion for adjusting the composition of the air. The PSA device (54) has two adsorbing portions. The adsorbing portion is an adsorbing tower filled with an adsorbent that adsorbs nitrogen in the air. The adsorbent is zeolite, for example. The main adjusting portion may be a gas separation membrane device, for example.
The air pump (53) compresses one of the two adsorbing portions and decompresses the other. In the compressed adsorbing portion, the adsorbent adsorbs nitrogen in the air, whereby oxygen-enriched air with a lower nitrogen concentration and a higher oxygen concentration than the external air is produced. In the decompressed adsorbing portion, the adsorbent releases nitrogen, whereby nitrogen-enriched air with a higher nitrogen concentration and a lower oxygen concentration than the external air is produced. The oxygen-enriched air is discharged to the external space (5) through the exhaust path (52). The nitrogen-enriched air is supplied to the internal space (3) through the supply path (51). Accordingly, the oxygen concentration of the internal space (3) is adjusted.

(5) Other Configurations

(5-1) Sensors

The container refrigeration apparatus (10) includes a plurality of sensors. As shown in FIGS. 2 and 3, the plurality of sensors include an internal temperature sensor (61), an external temperature sensor (62), a carbon dioxide sensor (63), and an oxygen sensor (64).
The internal temperature sensor (61) detects the temperature of the internal air in the container (1). The internal temperature sensor (61) is disposed upstream of the internal fan (30) in the air flow in the internal passage (16). The internal temperature sensor (61) is disposed near the inflow port (20) of the internal passage (16).
The external temperature sensor (62) detects the temperature of the external air outside the container (1). The external temperature sensor (62) is disposed upstream of the external heat exchanger (26) in the air flow in the external passage (28). The external temperature sensor (62) is disposed near the inflow port of the external passage (28).
The carbon dioxide sensor (63) detects the carbon dioxide concentration of the internal space (3). The carbon dioxide sensor (63) is disposed in the internal passage (16). The carbon dioxide sensor (63) is disposed upstream of the internal fan (30) in the air flow in the internal passage (16). The carbon dioxide sensor (63) is disposed in an upper part of the internal passage (16). The carbon dioxide sensor (63) may be disposed downstream of the internal fan (30) in the air flow in the internal passage (16). The carbon dioxide sensor (63) may be disposed in a lower part of the internal passage (16). The carbon dioxide sensor (63) is a non-dispersive infrared (NDIR) sensor, for example.
The oxygen sensor (64) detects the oxygen concentration of the internal space (3). The oxygen sensor (64) is disposed in the internal passage (16). The oxygen sensor (64) is disposed upstream of the internal fan (30) in the air flow in the internal passage (16), for example. The oxygen sensor (64) may be disposed downstream of the internal fan (30) in the air flow in the internal passage (16). The oxygen sensor (64) is a zirconia sensor, for example.

(5-2) Controller

As shown in FIG. 3, the container refrigeration apparatus (10) includes a controller (100). The controller (100) controls the cooling unit (U), the ventilating device (40), and the adjusting device (50). The controller (100) includes a microprocessor, an electric circuit, and an electronic circuit. The microprocessor includes a central processing unit (CPU), a memory, a communication interface, an analog input/output, and a contact input/output interface. The memory stores various programs executed by the CPU and the data employed by the programs.
The controller (100) controls each component of the cooling unit (U). Specifically, the controller (100) controls the number of rotations of the compressor (25), the number of rotations of the internal fan (30), the number of rotations of the external fan (27), the opening degree of the expansion valve (31), and others. The controller (100) controls the motor (43) of the ventilating device (40). The controller (100) adjusts the opening degrees of the supply passage (41) and the exhaust passage (42) of the ventilating device (40), and also adjusts the amount of ventilation of the ventilating device (40). The controller (100) controls the air pump (53) and the PSA device (54) of the adjusting device (50).

(5-3) Operating Unit

As shown in FIG. 3, the container refrigeration apparatus (10) includes an operating unit (110). The operating unit (110) includes, for example, a touch panel, a remote controller, a switch, or the like provided in the container refrigeration apparatus (10). The operating unit (110) may be a communication terminal connected to the container refrigeration apparatus (10) via a network. By operating the operating unit (110), the user can switch the operation mode of the container refrigeration apparatus (10) and change the set value of each operation mode. The set value includes the target value of a temperature of the internal air, the target value of oxygen concentration of the internal air, and the target value of carbon dioxide concentration of the internal air.

(5-4) Alerting Unit

As shown in FIG. 3, the container refrigeration apparatus (10) includes an alerting unit (120). The alerting unit (120) provides the user with predetermined information. The predetermined information includes first information showing that the refrigerant in the refrigerant circuit (R) has leaked. The alerting unit (120) includes a display, a speaker, or a communication device that sends the first information to another terminal. If the controller (100) determines that a refrigerant has leaked, the alerting unit (120) releases the first information.

(6) Operation

(6-1) Cooling Operation

The container refrigeration apparatus (10) performs a cooling operation. The cooling operation is conducted by a user or the like operating the operating unit (110).
In the cooling operation, the refrigeration cycle is created in which the refrigerant compressed in the compressor (25) is condensed in the external heat exchanger (26), then decompressed in the expansion valve (31), and then evaporated in the internal heat exchanger (29). The air having flowed out from the internal space (3) to the internal passage (16) is cooled by the internal heat exchanger (29) that functions as an evaporator. The cooled air is sent to the internal space (3).
In the cooling operation, the controller (100) controls the compressor (25) so that the temperature of the internal air reaches a target temperature. If the temperature of the internal air reaches the target temperature (the thermostat-OFF temperature; for example, -18°C), the controller (100) stops the compressor (25). As a result, the internal heat exchanger (29) substantially turns into the stop state (the thermostat-OFF state). Then, if the temperature of the internal air reaches a predetermined temperature (the thermostat-ON temperature; for example, -16°C) higher than the target temperature, the controller (100) instructs the compressor (25) to operate so that the internal heat exchanger (29) functions as an evaporator. The controller (100) controls the number of rotations of the compressor (25) so as to adjust the evaporation temperature of the internal heat exchanger (29). As a result, the temperature of the internal air is held within a predetermined target range.

(6-2) Adjusting Operation

The adjusting device (50) performs an adjusting operation to adjust the composition of the internal air in the internal space (3). The adjusting device (50) of this embodiment adjusts oxygen concentration and carbon dioxide concentration of the internal air. The adjusting operation is conducted in parallel with the cooling operation described above. The adjusting operation includes a first adjusting operation and a second adjusting operation. The first adjusting operation is an operation to concentrate nitrogen in the external air and then supply nitrogen-enriched air to the internal space (3). The second adjusting operation is an operation to supply the external air to the internal space (3) without concentration. In the following, the adjusting operation will be described, where the control range of oxygen concentration of the internal air is 4% to 6% and the control range of carbon dioxide concentration of the internal air is 1% to 30%. The control values of those control ranges are set values which the user sets by operating the operating unit (110).
At the time when the operation to load items such as fruits, vegetables, flowers, and plants into the container (1) has been completed, the composition of the internal air is substantially the same as the composition of the atmosphere (nitrogen concentration: 78%, oxygen concentration: 21%, and carbon dioxide concentration: 0.04%). Then, at the time, the controller (100) instructs execution of the first adjusting operation in order to reduce the oxygen concentration of the internal air. In the first adjusting operation, nitrogen-enriched air is supplied to the internal space. As a result, the oxygen concentration of the internal air decreases.
If the oxygen concentration of the internal air reaches the upper limit value (6%) of the control range, the controller (100) instructs the adjusting device (50) to stop the first adjusting operation. As a result, fruits, vegetables, flowers, and plants in the internal space (3) do respiration, whereby the oxygen concentration of the internal air gradually decreases. At the same time, the carbon dioxide concentration of the internal air gradually increases.
If the carbon dioxide concentration of the internal air reaches the upper limit value (30%) of the control range when the adjusting device (50) is stopped, the controller (100) instructs the adjusting device (50) to conduct the first adjusting operation. As a result, nitrogen-enriched air is supplied to the internal space (3), and the carbon dioxide concentration of the internal air decreases.
If the carbon dioxide concentration of the internal air reaches the lower limit (1%) of the control range when the adjusting device (50) is performing the first adjusting operation, the controller (100) instructs the adjusting device (50) to stop the first adjusting operation. If the oxygen concentration of the internal air reaches the lower limit (4%) of the control range when the adjusting device (50) is performing the first adjusting operation, the controller (100) instructs the adjusting device (50) to conduct the second adjusting operation. Then, if the oxygen concentration of the internal air reaches the upper limit value (6%) of the control range, the adjusting device (50) stops the second adjusting operation.

(7) Control to Detect Leakage of Refrigerant

If the carbon dioxide in the refrigerant circuit (R) leaks into the internal space (3), the body of the user or the like and the items in the internal space (3) are badly affected. In addition, leakage of the refrigerant lowers the cooling performance of the cooling unit (U), which impairs the temperature management of the items. In this embodiment, the following control is conducted in order to solve those problems.

(7-1) Basic Control

The basic control of leakage of a refrigerant will be described with reference to FIG. 5. In the following description, the carbon dioxide concentration (C) refers to the detected value of the carbon dioxide concentration of the internal air detected by the carbon dioxide sensor (63). The method of determining leakage of a refrigerant includes a first operation and a second operation. The first operation is the operation to determine leakage of a refrigerant based on the detected value of the carbon dioxide sensor (63). The second operation is the operation to determine leakage of a refrigerant based on the operating state of the refrigerant circuit (R). In the internal space (3), fruits, vegetables, flowers, and plants do respiration, and thus the carbon dioxide concentration of the internal air increases. By selectively conducting the first operation and the second operation, it is possible to reduce erroneously determining leakage of a refrigerant due to that respiration. The following method of determining leakage of a refrigerant is conducted when the cooling unit (U) is being operated.
In step ST11, the controller (100) determines whether the carbon dioxide concentration (C) is greater than a first value (Cs1). The first value (Cs1) is the upper limit value (for example, 30%) of the control range of the carbon dioxide concentration of the adjusting device (50). If the carbon dioxide concentration (C) is greater than the first value (Cs1), or in other words, if the carbon dioxide concentration (C) exceeds the control range of the adjusting device (50), it is highly probable that a refrigerant is leaking from the refrigerant circuit (R). In this case, in step ST18, the controller (100) instructs the alerting unit (120) to release the first information. As a result, the user or the like can immediately notice that a refrigerant has leaked from the refrigerant circuit (R), and thus can make a predetermined response.
Next, in step ST19, the controller (100) instructs the ventilating device (40) to conduct the ventilating operation. Specifically, the controller (100) controls the opening/closing cover (45) of the ventilating device (40) in order to turn the supply passage (41) and the exhaust passage (42) into the open state. The controller (100) turns the internal fan (30) into the operating state. As a result, the external air is supplied to the internal space (3) through the supply passage (41). At the same time, the external air is discharged to the outside through the exhaust passage (42). As a result, the carbon dioxide concentration of the internal space (3) can be reduced immediately. In the ventilating operation of step ST19, the supply passage (41) and the exhaust passage (42) of the ventilating device (40) are open at the maximum opening degree in one preferred embodiment. In addition, the internal fan (30) operates at the maximum volume of air in one preferred embodiment. Accordingly, the carbon dioxide concentration of the internal air can be reduced more immediately.
In step ST11, if the carbon dioxide concentration (C) is lower than or equal to the first value (Cs1), the process goes to step ST12. In step ST12, the controller (100) determines whether the first condition that fruits, vegetables, flowers, or plants are present in the internal space (3) is satisfied. This is because fruits, vegetables, flowers, and plants emit carbon dioxide as they do respiration, and whether these items are present or not affects determining leakage of a refrigerant. The first condition will be described in detail later.
If it is determined that fruits, vegetables, flowers, and plants are not present (NO in step ST12), the process goes to step ST17. In step ST17, the first operation is performed. Specifically, in step ST17, the controller (100) determines whether the carbon dioxide concentration (C) is greater than a second value (Cs2). The second value (Cs2) is a predetermined value that is smaller than the first value (Cs1) and greater than the carbon dioxide concentration of the atmosphere (for example, 0.04%). The second value (Cs2) is set to 0.1%, for example. If the carbon dioxide concentration (C) is relatively large while fruits, vegetables, flowers, and plants are not present in the internal space (3), it is highly probable that a refrigerant is leaking from the refrigerant circuit (R). Then, if the condition of step ST17 is satisfied, the process goes to steps ST18 and ST19, where the operation for the response to leakage of a refrigerant is conducted.
In step ST12, if it is determined that fruits, vegetables, flowers, or plants are present, the process goes to step ST13. In step ST13, the controller (100) determines whether the adjusting device (50) is operating. Specifically, for example, the controller (100) determines whether the adjusting device (50) is conducting the first adjusting operation or the second adjusting operation. If the condition of step ST13 is satisfied, the process goes to step ST14.
In step ST14, the second operation is performed. In step ST14, the controller (100) determines leakage of a refrigerant based on the operating state of the refrigerant circuit (R). Specifically, for example, the controller (100) determines leakage of a refrigerant based on the pressure of the refrigerant in the refrigerant circuit (R), the temperature of the refrigerant in the refrigerant circuit (R), or the opening degree of the expansion valve (31).
The pressure of the refrigerant includes a pressure on the high-pressure side and a pressure on the low-pressure side of the refrigerant circuit (R). The pressure of the refrigerant is detected by a pressure sensor. If the refrigerant leaks from the refrigerant circuit (R), these pressures decrease. Thus, it is possible to determine leakage of a refrigerant based on the pressure of the refrigerant or a change in the pressure of the refrigerant.
The temperature of the refrigerant includes the condensation temperature (the heat dissipation temperature) and the evaporation temperature of the refrigerant circuit (R). The temperature of the refrigerant is detected by a temperature sensor. If the refrigerant leaks from the refrigerant circuit (R), the temperature of the refrigerant changes significantly. Thus, it is possible to determine leakage of a refrigerant based on the temperature of the refrigerant or a change in the temperature of the refrigerant.
The controller (100) controls the opening degree of the expansion valve (31) based on the degree of suction superheat. If the refrigerant leaks from the refrigerant circuit (R), the degree of suction superheat is likely to increase, and the opening degree of the expansion valve (31) is likely to increase. Thus, it is possible to determine leakage of a refrigerant based on the opening degree of the expansion valve (31) or a change in the opening degree of the expansion valve (31).
In the second operation, the controller (100) may determine leakage of a refrigerant based on other operating states of the refrigerant circuit (R), such as the degree of subcooling, the degree of suction superheat, and the degree of discharge superheat of the refrigerant circuit (R); and the number of rotations of the compressor (25).
In step ST14, if it is determined that a refrigerant has leaked, the process goes to steps ST18 and ST19, where the operation for the response to leakage of a refrigerant is conducted.
If the condition of step ST13 is not satisfied, or in other words, if it is determined that the adjusting device (50) is stopped, the process goes to step ST15. In step ST15, similarly to step ST14, the second operation is conducted. In step ST15, if it is determined based on the operating state of the refrigerant circuit (R) that a refrigerant has leaked, the process goes to steps ST18 and ST19, where the operation for the response to leakage of a refrigerant is conducted.
If the condition of step ST15 is not satisfied, the process goes to step ST16, where the controller (100) determines whether the rate of increase in the carbon dioxide concentration (C) is greater than a predetermined value α. If the refrigerant significantly leaks from the refrigerant circuit (R), it may be impossible to immediately determine leakage of the refrigerant only based on the operating state of the refrigerant circuit (R). This is because the index on the operating state of the refrigerant circuit (R) is the index indirectly showing leakage of a refrigerant and is less responsive to detect leakage of a refrigerant than the carbon dioxide sensor (63). Thus, in step ST16, the controller (100) determines leakage of a refrigerant based on the condition that the rate of increase in the carbon dioxide concentration (C) is greater than the predetermined value α. If the condition of step ST16 is satisfied, the process goes to steps ST18 and ST19, where the operation for the response to leakage of a refrigerant is conducted. Accordingly, if the refrigerant has significantly leaked from the refrigerant circuit (R), it is possible to immediately detect this situation and make a predetermined response.

(7-2) Determine Presence or Absence of Fruits, Vegetables, Flowers, and Plants

In step ST12 described above, the controller (100) determines whether the first condition that fruits, vegetables, flowers, or plants are present in the internal space (3) is satisfied. The details of determining the first condition will be described with reference to FIG. 6.
In step ST31, the controller (100) determines whether the adjusting device (50) is operating. If the adjusting device (50) is performing the adjusting operation, the process goes to step ST35, where the controller (100) determines that fruits, vegetables, flowers, or plants are present in the internal space (3), that is, the first condition is satisfied. This is because the adjusting device (50) performs an operation to keep the freshness of fruits, vegetables, flowers, and plants stored in the internal space (3), and in general does not perform an operation while fruits, vegetables, flowers, and plants are not stored.
If the condition of step ST31 is not satisfied, the process goes to step ST32, where the controller (100) checks the input information. The user controls the operating unit (110), whereby the input information is input to the controller (100). The input information includes information on the type of items (stored items) in the internal space (3). The controller (100) refers to the input information to determine whether the type of the stored items is fruit, vegetable, flower, or plant. In other words, the controller (100) determines whether the input information is the information showing that the stored items in the internal space (3) are fruits, vegetables, flowers, or plants. If the type of the stored items shown by the input information is fruit, vegetable, flower, or plant, or in other words, the condition of step ST32 is satisfied, the process goes to step ST35, where the controller (100) determines that fruits, vegetables, flowers, or plants are present in the internal space (3).
If the condition of step ST32 is not satisfied, the process goes to step ST33, where the controller (100) determines whether the set temperature (Ts) of the internal air is greater than a first temperature (T1). The set temperature (Ts) of the internal air is a temperature set by the user or the like operating the operating unit (110), and corresponds to the target temperature of the internal air. The first temperature (T1) is a predetermined temperature that is lower than 0°C, or for example, -10°C. The first temperature (T1) can be regarded as the lowest temperature for maintaining the quality of fruits, vegetables, flowers, and plants. In order to store fruits, vegetables, flowers, or plants in the internal space (3), the user generally does not set the target temperature of the internal air to the first temperature (-10°C) or below. This is because the quality of fruits, vegetables, flowers, and plants is reduced if the internal temperature is -10°C or below. Thus, in step ST33, if the set temperature (Ts) of the internal air is lower than or equal to the first temperature (T1) (NO in step ST33), the process goes to step ST36, where the controller (100) determines that fruits, vegetables, flowers, and plants are not present in the internal space (3).
In step ST33, if the set temperature (Ts) of the internal air is greater than the first temperature (T1), the process goes to step ST34, where the controller (100) determines whether the rate of decrease in the oxygen concentration of the internal space (3) is greater than a predetermined value β. The oxygen concentration is detected by the oxygen sensor (64). If fruits, vegetables, flowers, or plants are present in the internal space (3), these fruits, vegetables, flowers, or plants consume oxygen in the internal space (3), and the oxygen concentration decreases. Compared with the carbon dioxide concentration, the oxygen concentration of the internal space (3) is not significantly affected by leakage of a refrigerant. Thus, if the condition of step ST34 is satisfied, the process goes to step ST35, where the controller (100) determines that fruits, vegetables, flowers, or plants are present in the internal space (3). If the condition of step ST34 is not satisfied, the process goes to step ST36, where the controller (100) determines that fruits, vegetables, flowers, and plants are not present in the internal space (3).

(7-3) Control in Turning Container Refrigeration Apparatus into ON State

The control in turning the container refrigeration apparatus (10) from the OFF state to the ON state will be described. The "OFF state" referred to herein means the state in which no electric power is supplied to the container refrigeration apparatus (10). For example, when the container (1) is placed in a repair facility and the container (1) does not store items, the container refrigeration apparatus (10) is in the OFF state. The "ON state" referred to herein means the state in which electric power is supplied to the container refrigeration apparatus (10). For example, when the container (1) is placed on a container ship and electric power is supplied from a power source in the container ship to the container refrigeration apparatus (10), the container refrigeration apparatus (10) is in the ON state.
As shown in FIG. 7, in step ST51, if the container refrigeration apparatus (10) turns from the OFF state to the ON state, the process goes to step ST52, where the controller (100) operates the internal fan (30). Accordingly, the internal air in the internal space (3) circulates. The volume of air of the internal fan (30) is the maximum volume of air in one preferred embodiment.
Next, in step ST53, the controller (100) determines whether the carbon dioxide concentration (C) is greater than a third value (Cs3). At this time, the internal fan (30) is in the operating state, and thus if the refrigerant is leaking from the refrigerant circuit (R), the carbon dioxide concentration can be detected immediately. More specifically, the carbon dioxide has a greater density than the air and tends to accumulate in the lower portion of the internal space (3). Thus, the detection of leakage of the refrigerant by the carbon dioxide sensor (63) may be delayed. In contrast, by instructing the internal fan (30) to operate, it is possible to stir the carbon dioxide in the lower portion of the internal space (3), and thus the carbon dioxide can be immediately sent to around the carbon dioxide sensor (63). Accordingly, leakage of a refrigerant can be detected immediately.
If the condition of step ST53 is satisfied, the process goes to step ST54, where the controller (100) instructs the alerting unit (120) to release the first information. Next, in step ST55, the controller (100) instructs the ventilating device (40) to conduct the ventilating operation.
As described above, in this embodiment, when the container refrigeration apparatus (10) turns from the OFF state to the ON state, the controller (100) instructs the internal fan (30) to operate and determines leakage of a refrigerant based on the detected value of the carbon dioxide sensor (63). Accordingly, if a refrigerant is leaking while the container refrigeration apparatus (10) is in the OFF state, this situation can be detected as soon as possible.

(8) Features

The internal space (3) of the container refrigeration apparatus (10) may store items which consume oxygen and do respiration, such as fruits, vegetables, flowers, or plants. When these items do respiration, the carbon dioxide concentration increases. Thus, while a refrigerant does not leak, it may be erroneously determined based on the detected value of the sensor that a refrigerant has leaked.
In order to avoid this erroneous determination, it is conceivable to determine leakage of a refrigerant based on the operating state of the refrigerant circuit (R). However, the method based on the operating state of the refrigerant circuit (R) is not a method of directly determining leakage of a carbon dioxide refrigerant, and thus it may be impossible to immediately determine leakage of a refrigerant. Accordingly, if there is a delay in determining leakage of a refrigerant, the user may be affected by the carbon dioxide in the internal space (3), or the cooling performance of the refrigerant circuit (R) may be lowered so that the quality of the items is reduced. This embodiment solves this problem.

(8-1)
The controller (100) selectively conducts the first operation to determine leakage of a refrigerant based on the detected value of the sensor (63) and the second operation to determine leakage of a refrigerant based on the operating state of the refrigerant circuit (R). In the second operation, the controller (100) determines leakage of a refrigerant based on the operating state of the refrigerant circuit (R), which is not affected by the respiration of fruits, vegetables, flowers, or plants. By conducting the second operation, it is possible to determine leakage of a refrigerant while not affected by the respiration of fruits, vegetables, flowers, or plants. In the first operation, leakage of a refrigerant is detected directly, and thus it is possible to immediately determine leakage of a refrigerant. By selectively conducting these two operations, it is possible to immediately determine leakage of a refrigerant while reducing erroneously determining leakage of a refrigerant. As a result, it is possible to reduce the user being affected by the carbon dioxide in the internal space (3), or the cooling performance of the refrigerant circuit (R) being lowered.
(8-2)
In step ST12, the controller (100) determines whether the first condition that fruits, vegetables, flowers, or plants are present in the internal space (3) is satisfied. If the first condition is satisfied, the controller (100) performs the second operation in step ST14 or ST15. If the first condition is not satisfied, the controller (100) performs the first operation in step ST17. Accordingly, if fruits, vegetables, flowers, or plants are present in the internal space (3), it is possible according to the second operation to determine leakage of a refrigerant while not affected by the respiration. If fruits, vegetables, flowers, and plants are not present in the internal space (3), it is possible to immediately determine leakage of a refrigerant based on the detected value of the carbon dioxide sensor (63).
(8-3)
The container refrigeration apparatus (10) includes the adjusting device (50) that performs the adjusting operation to adjust the composition of the air in the internal space (3). The controller (100) determines that a refrigerant has leaked if the second condition that the detected value of the sensor (63) is greater than the control range of the carbon dioxide concentration of the internal space (3) in the adjusting operation is satisfied.

Accordingly, when the carbon dioxide concentration of the internal space (3) is clearly high, it is possible to immediately determine leakage of a refrigerant.
(8-4)
The first condition includes the condition that the adjusting device (50) is performing the adjusting operation (step ST31). This is because when the adjusting device (50) is performing the adjusting operation, it is highly probable that fruits, vegetables, flowers, or plants are present in the internal space (3).
The first condition includes the condition that the set temperature of the air in the internal space (3) is greater than a predetermined temperature that is lower than 0°C (step ST33). This is because when fruits, vegetables, flowers, or plants are stored in the internal space (3), it is highly probable that the set temperature is set relatively high in order to maintain the quality of these items.
The first condition includes the condition that the rate of decrease in the oxygen concentration of the internal space (3) is greater than the predetermined value β (step ST34). This is because when fruits, vegetables, flowers, or plants are present in the internal space (3), they consume oxygen in the internal space (3), and the rate of decrease in the oxygen concentration increases.
The first condition includes the condition that the information showing that the stored items in the internal space (3) are fruits, vegetables, flowers, or plants is input to the controller (100) (step ST32). This is because when this information is input, fruits, vegetables, flowers, or plants are generally stored in the internal space (3).
In this embodiment, by using this first condition, it is possible to accurately determine with a simple configuration that vegetables, flowers, or plants are present in the internal space (3).

(8-5)
The controller (100) determines that a refrigerant has leaked if the rate of increase in the detected value of the sensor (63) is greater than a predetermined value while the adjusting device (50) is not performing the adjusting operation (YES in step ST16). Accordingly, if carbon dioxide is significantly leaking from the refrigerant circuit (R), this situation can be determined immediately.
(8-6)
When the container refrigeration apparatus (10) turns from the OFF state to the ON state, the controller (100) instructs the internal fan (30) to operate and determines leakage of a refrigerant based on the detected value of the sensor (63). Accordingly, if a refrigerant has leaked while the container refrigeration apparatus (10) is in the OFF state, this situation can be determined immediately.
(8-7)
In the second operation, the controller (100) determines leakage of a refrigerant based on the pressure of the refrigerant in the refrigerant circuit (R), the temperature of the refrigerant in the refrigerant circuit (R), or the opening degree of the expansion valve (31) as an expansion mechanism. By referring to these factors, it is possible to determine leakage of a refrigerant while not affected by the respiration.
(8-8)
The controller (100) operates the ventilating device (40) if it is determined that a refrigerant has leaked. Accordingly, if a refrigerant has leaked, the carbon dioxide concentration of the internal space (3) can be reduced immediately. As a result, it is possible to reduce the user being affected by the carbon dioxide in the internal space (3).

(9) Variations

The above embodiment may be modified as the following variations. Differences from the above embodiment will be described below.

(9-1) First Variation

In a first variation, the first condition that fruits, vegetables, flowers, or plants are present in the internal space (3) includes at least one of the following conditions A to C.
The condition A is the condition that the ethylene concentration is greater than or equal to a predetermined value. The ethylene concentration is detected by an ethylene sensor disposed in the internal space (3). When fruits, vegetables, flowers, or plants are present in the internal space, they generate ethylene, and the ethylene concentration increases. Thus, if the ethylene concentration is greater than or equal to the predetermined value, the controller (100) determines that fruits, vegetables, flowers, or plants are present in the internal space (3).
The condition B is the condition that the amount of moisture generated in the internal space (3) is greater than or equal to a predetermined value. When fruits, vegetables, flowers, or plants are present in the internal space (3), moisture is generated as they do respiration. By defining the first condition including the condition that the amount of this moisture is greater than or equal to the predetermined value, it is possible to determine that fruits, vegetables, flowers, or plants are present. The controller (100) estimates the amount of moisture generated in the internal space (3) based on the amount of water discharged from a drain pan that receives water generated in the internal space (3). The controller (100) may estimate the amount of moisture based on the humidity of the internal air in the internal space (3).
The condition C is the condition that the cooling load in the internal space (3) has increased. When fruits, vegetables, flowers, or plants are present in the internal space (3), the cooling load increases as they produce respiratory heat. By defining the first condition including the condition that the cooling load increases, it is possible to determine that fruits, vegetables, flowers, or plants are present. The increase in the cooling load is obtained, for example, based on the data including the current output of the cooling unit (U) and the predetermined output of the cooling unit (U). The output referred to herein is the number of rotations of the compressor (25) or the power consumption of the cooling unit (U). For example, the data includes an output that corresponds to each of the external air temperature, the internal temperature, and the set temperature. The controller (100) determines an output for comparison based on the current outdoor air temperature, internal temperature, and set temperature. For example, from the difference between the current output of the cooling unit (U) and the output for comparison, the controller (100) determines an increase in the cooling load based on the respiratory heat.

(9-2) Second Variation

The container refrigeration apparatus (10) of a second variation does not include the adjusting device (50) of the first embodiment. In other words, the container refrigeration apparatus (10) does not have the function of adjusting the composition of the air in the internal space (3).
The controller (100) of the second variation conducts the method of determining leakage of a refrigerant shown in FIG. 8. In the second variation, in step ST61, if the first condition is not satisfied, the process goes to step ST66, where the first operation based on the detected value of the carbon dioxide is performed. In step ST61, if the first condition is satisfied, the process goes to step ST62, where the second operation based on the operating state of the refrigerant circuit (R) is performed. In step ST62, if it is determined that a refrigerant has leaked, the process goes to steps ST63 and ST64, where the operation for the response is conducted. In step ST62, if it is determined that a refrigerant does not leak, the process goes to step ST65, where the same operation as in step ST16 of the embodiment is conducted. The first condition of the second variation does not include the condition of step ST31 of the embodiment. The effects of these controls of the second variation are the same as those of the embodiment.

(9-3) Third Variation

The container refrigeration apparatus (10) of a third variation controls not the ventilating device (40) but the adjusting device (50) in the ventilating operation in step ST19 of FIG. 5 or step ST55 of FIG. 7. Specifically, in this process, the controller (100) controls the adjusting device (50) so as to introduce the outdoor air into the internal space (3). At this time, the controller (100) controls the adjusting device (50) so as to discharge the internal air to the outdoor in one preferred embodiment. As described above, in the third variation, the adjusting device (50) is an example of the ventilating unit.

(10) Other Embodiments

The above embodiment and variations may be configured as follows.
The refrigeration apparatus may be not a container refrigeration apparatus but a stationary refrigeration apparatus that cools the inside of a warehouse or the like. The container (1) may be not for marine transportation but for land transportation where the container is transported by a vehicle such as a trailer or by rail.
The controller (100) may be physically separated from the container refrigeration apparatus (10). In this case, for example, the controller (100) forms a server device connected with the cooling unit (U) via a network. In this case, the refrigeration apparatus forms a refrigeration system including the cooling unit (U) and the controller (100). The controller (100) may be provided in the adjusting device (50) or may be provided in the operating unit (110).
The ventilating unit may only have the function of supplying the external air in the external space (5) to the internal space (3) and may not have the function of exhausting the air. The fan of the ventilating device (40) may be a ventilation-dedicated fan different from the internal fan.
The expansion mechanism may be not an expansion valve but a capillary tube or an expansion device.

(11) Other Descriptions

The method of determining leakage of a refrigerant according to the embodiment, the variations, and the other embodiments described above include any of the steps described above. The controller (100) according to the embodiment, the variations, and the other embodiments described above includes a program to instruct a computer to execute these steps, and a storage device or a storage medium that stores this program.
While the embodiment and variations thereof have been described above, it will be understood that various changes in form and details may be made without departing from the spirit and scope of the claims. The embodiment, the variation thereof, and the other embodiments may be combined and replaced with each other without deteriorating intended functions of the present disclosure.
The expressions of "first," "second," "third," . . . described above are used to distinguish the words to which these expressions are given, and the number and order of the words are not limited.

INDUSTRIAL APPLICABILITY

As described above, the present disclosure is useful for a container refrigeration apparatus.

DESCRIPTION OF REFERENCE CHARACTERS

3: Internal Space
10: Container Refrigeration Apparatus (Refrigeration Apparatus)
25: Compressor
26: External Heat Exchanger (Radiator)
29: Internal Heat Exchanger (Evaporator)
30: Internal Fan
31: Expansion Valve (Expansion Mechanism)
40: Ventilating Device (Ventilating Unit)
50: Adjusting Device (Ventilating Unit)
63: Carbon Dioxide Sensor (Sensor)
100: Controller

Claims

A refrigeration apparatus comprising:
a refrigerant circuit (R) including a compressor (25), a radiator (26), an expansion mechanism (31), and an evaporator (29), and configured to perform a refrigeration cycle using carbon dioxide as a refrigerant;

a sensor (63) configured to detect a carbon dioxide concentration of an internal space (3) cooled by the evaporator (29); and

a controller (100),

wherein

the controller (100) selectively conducts
a first operation to determine leakage of the refrigerant based on a detected value of the sensor (63), and

a second operation to determine leakage of the refrigerant based on an operating state of the refrigerant circuit (R).
The refrigeration apparatus of claim 1, wherein
the controller (100)
determines whether a first condition that a fruit, a vegetable, a flower, or a plant is present in the internal space (3) is satisfied,

performs the second operation if the first condition is satisfied, and

performs the first operation if the first condition is not satisfied.
The refrigeration apparatus of claim 2, further comprising:
an adjusting device (50) configured to perform an adjusting operation to adjust a composition of air in the internal space (3).
The refrigeration apparatus of claim 3, wherein
the controller (100) determines that the refrigerant has leaked if a second condition that the detected value of the sensor (63) is greater than a control range of the carbon dioxide concentration of the internal space (3) in the adjusting operation is satisfied.
The refrigeration apparatus of claim 3 or 4, wherein
the first condition includes a condition that the adjusting device (50) is performing the adjusting operation.
The refrigeration apparatus of any one of claims 2 to 5, wherein
the first condition includes a condition that a set temperature of air in the internal space (3) is greater than a predetermined temperature that is lower than 0°C.
The refrigeration apparatus of any one of claims 2 to 6, wherein
the first condition includes a condition that a rate of decrease in the oxygen concentration of the internal space (3) is greater than a predetermined value.
The refrigeration apparatus of any one of claims 2 to 7, wherein
the first condition includes
a condition that information showing that a stored item in the internal space (3) is a fruit, a vegetable, a flower, or a plant is input to the controller (100), or

a condition that an ethylene concentration of the internal space (3) is greater than or equal to a predetermined value, or

a condition that an amount of moisture generated in the internal space (3) is greater than or equal to a predetermined value, or

a condition that a cooling load in the internal space (3) has increased.
The refrigeration apparatus of any one of claims 3 to 5, wherein
the controller (100)
determines that the refrigerant has leaked if a rate of increase in the detected value of the sensor (63) is greater than a predetermined value while the adjusting device (50) is not performing the adjusting operation.
The refrigeration apparatus of any one of claims 1 to 9, further comprising:
an internal fan (30) configured to transport air in the internal space (3),

wherein

when the refrigeration apparatus (10) turns from an OFF state to an ON state, the controller (100) instructs the internal fan (30) to operate and determines leakage of the refrigerant based on the detected value of the sensor (63).
The refrigeration apparatus of any one of claims 1 to 10, wherein
in the second operation, the controller (100) determines leakage of the refrigerant based on a pressure of the refrigerant in the refrigerant circuit (R), a temperature of the refrigerant in the refrigerant circuit (R), or an opening degree of an expansion valve (31) as an expansion mechanism.
The refrigeration apparatus of any one of claims 1 to 11, further comprising:
a ventilating unit (40, 50) configured to ventilate the internal space (3),

wherein

the controller (100) operates the ventilating unit (40, 50) if it is determined that the refrigerant has leaked.
A method of determining leakage of a refrigerant in a refrigeration apparatus including:
a refrigerant circuit (R) including a compressor (25), a radiator (26), an expansion mechanism (31), and an evaporator (29), and configured to perform a refrigeration cycle using carbon dioxide as a refrigerant; and

a sensor (63) configured to detect a carbon dioxide concentration of an internal space (3) cooled by the evaporator (29),

the method comprising: selectively conducting
a first operation to determine leakage of the refrigerant based on a detected value of the sensor (63), and

a second operation to determine leakage of the refrigerant based on an operating state of the refrigerant circuit (R).
A program to instruct a computer to execute the method of claim 13.