Patent Description:
An example of a known storage that stores loads is a container including a refrigeration apparatus for refrigerating and cooling the inside of the storage (for example, refer to <CIT>).

Further examples of a previously known refrigeration system are derivable from <CIT> which discloses a refrigerating system according to the preamble of claim <NUM> as well as <CIT>.

Multiple containers including refrigeration apparatuses may be joined together to configure a storage. In this case, the refrigeration apparatuses of the containers are separately controlled so that each container separately performs a refrigerating-cooling operation. Since no consideration is made to a synchronous operation between the containers, there is room for improvement in this point.

It is an object of the present invention to provide a refrigeration system that synchronously operates refrigeration apparatuses of multiple containers.

To achieve the object, a refrigeration system according to claim <NUM> is provided. Distinct embodiments of the present invention are derivable from the dependent claims.

With this configuration, the refrigeration apparatuses of the containers are synchronously controlled through the communication units. This allows the refrigeration apparatuses of the containers to operate in synchronization with each other.

As an embodiment of a refrigeration system, a refrigeration system used as a stationary storage configured by joining multiple containers will now be described with reference to the drawings.

As shown in <FIG>, a refrigeration system <NUM> is used as a stationary storage in which a first container 1A, a second container 1B, and a third container 1C are joined together. The first container 1A includes an elongated-box-shaped casing 10A. The second container 1B and the third container 1C include a casing 10B and a casing 10C in the same manner as the first container 1A. In the description hereafter, the longitudinal direction of the containers 1A to 1C is defined as "the first direction X," and a direction orthogonal to the first direction X is defined as "the second direction Y.

In the second direction Y, the first container 1A is located at one side of the second container 1B, and the third container 1C is located at the other side of the second container 1B. The first container 1A includes an opening 11A formed by removing a wall of the first container 1A from a portion opposed to the second container 1B. The third container 1C includes an opening 11C formed by removing a wall of the third container 1C from a portion opposed to the second container 1B. The second container 1B includes openings 11B formed by removing walls of the second container 1B from portions opposed to the first container 1A and the third container 1C.

As shown in <FIG>, the first container 1A is joined to the second container 1B, and the third container 1C is joined to the second container 1B so that the second container 1B is sandwiched between the first container 1A and the third container 1C. This defines a single accommodation space S that connects the first container 1A, the second container 1B, and the third container 1C in the refrigeration system <NUM>. The accommodation space S accommodates, for example, loads CG (refer to <FIG>).

Each of the containers 1A to 1C includes a refrigeration apparatus <NUM>. That is, the refrigeration system <NUM> including the containers 1A to 1C includes multiple (in the present embodiment, three) refrigeration apparatuses <NUM>. The refrigeration apparatuses <NUM> refrigerate and cool the accommodation space S, which is the inside of the storage. The refrigeration apparatuses <NUM> are installed on respective walls <NUM> of the casings 10A to 10C.

Each of the containers 1A to 1C includes observation windows <NUM> and a ventilator <NUM> in an upper portion of the front side of the wall <NUM> in the first direction X. Each observation window <NUM> includes a door configured to open and close during maintenance. The ventilator <NUM> ventilates the storage. Two observation windows <NUM> are arranged next to each other in the second direction Y on the upper portion of the wall <NUM>. The walls <NUM> of the containers 1A to 1C have the same structure. <FIG> shows the structure of the wall <NUM> of the first container 1A as an example.

As shown in <FIG>, a lower portion of the wall <NUM> is bulged toward the interior of the first container 1A to form a concave portion <NUM>. As a result, an exterior accommodation space S1 is defined at an exterior side of the lower portion of the wall <NUM>, and an interior accommodation space S2 is defined at an interior side of the upper portion of the wall <NUM>. The wall <NUM> includes a metal exterior casing 12a, a metal interior casing 12b, and a thermal insulation layer 12c sandwiched between the metal exterior casing 12a and the metal interior casing 12b. An example of the material of the exterior casing 12a and the interior casing 12b is aluminum. The thermal insulation layer 12c is formed of a foamed material.

A partition plate <NUM> is disposed in an interior side of the casing 10A to separate the accommodation space S and the interior accommodation space S2 of the casing 10A. The partition plate <NUM> is spaced apart from the wall <NUM> in the first direction X.

The exterior accommodation space S1 and the interior accommodation space S2 accommodate the refrigeration apparatus <NUM> including a refrigerant circuit <NUM>. More specifically, the refrigeration apparatuses <NUM> includes, for example, a compressor <NUM>, a condenser <NUM>, an exterior fan <NUM>, an interior fan <NUM>, an evaporator <NUM>, and an electric component <NUM> (refer to <FIG>). The exterior accommodation space S1 accommodates the compressor <NUM>, the condenser <NUM>, the exterior fan <NUM>, and the electric component <NUM>. The interior accommodation space S2 accommodates the interior fan <NUM> and the evaporator <NUM>. The refrigeration apparatus <NUM> including a refrigerant circuit <NUM> of the second container 1B and the refrigeration apparatus <NUM> including a refrigerant circuit <NUM> of the third container 1C have the same structure as the refrigeration apparatus <NUM> including the refrigerant circuit <NUM> of the first container 1A. In the description hereafter, the refrigeration apparatus <NUM> of the first container 1A will be described. The refrigeration apparatus <NUM> of the second container 1B and the refrigeration apparatus <NUM> of the third container 1C will not be described in detail.

As shown in <FIG>, the refrigeration apparatus <NUM> includes the refrigerant circuit <NUM> in which, for example, the compressor <NUM>, the condenser <NUM>, and the evaporator <NUM> are connected by a refrigerant pipe. The refrigerant circuit <NUM> includes a main circuit <NUM>, a hot gas bypass circuit <NUM>, and a liquid refrigerant bypass circuit <NUM>.

The main circuit <NUM> is configured by sequentially connecting the compressor <NUM> that is driven by a motor, the condenser <NUM>, a first expansion valve 27A, and the evaporator <NUM> in series with the refrigerant pipe.

As shown in <FIG>, the exterior accommodation space accommodates, for example, the compressor <NUM>, the condenser <NUM>, the first expansion valve 27A, and the exterior fan <NUM>, which circulates the air outside the storage to the condenser <NUM>. The interior accommodation space accommodates, for example, the evaporator <NUM> and the interior fan <NUM>, which circulates the air in the storage to the evaporator <NUM>.

The compressor <NUM> may be, for example, a rotary compressor or a scroll compressor. The compressor <NUM> is configured so that the operating capacity is variable when an inverter controls the operating frequency to control the rotational speed.

The condenser <NUM> and the evaporator <NUM> may be a fin-and-tube heat exchanger. The condenser <NUM> exchanges heat between the air outside the storage supplied by the exterior fan <NUM> and the refrigerant circulating in the condenser <NUM>. The evaporator <NUM> exchanges heat between the air in the storage supplied by the interior fan <NUM> and the refrigerant circulating in the evaporator <NUM>. An example of the exterior fan <NUM> and the interior fan <NUM> is a propeller fan. A drain pan <NUM> is disposed below the evaporator <NUM>. The drain pan <NUM> collects, for example, frost and ice blocks falling from the evaporator <NUM> and water condensed from the air.

The first expansion valve 27A may be, for example, an electric expansion valve configured so that the opening degree is variable using a pulse motor.

The compressor <NUM> and the condenser <NUM> are connected by a high pressure gas pipe <NUM> that includes a first opening-closing valve 28A and a check valve <NUM> sequentially arranged in a direction in which the refrigerant flows. The first opening-closing valve 28A may be, for example, an electric expansion valve configured so that the opening degree is variable using a pulse motor. The check valve <NUM> allows the refrigerant to flow in directions of arrows shown in <FIG>.

The condenser <NUM> and the first expansion valve 27A are connected by a high pressure liquid pipe <NUM> that includes a receiver <NUM>, a second opening-closing valve 29B, a dryer <NUM>, and a supercooling heat exchanger <NUM> sequentially arranged in the direction in which the refrigerant flows. The second opening-closing valve 29B may be, for example, an electromagnetic valve configured to open and close.

The supercooling heat exchanger <NUM> includes a primary passage 33a and a secondary passage 33b configured to exchange heat with each other. The primary passage 33a is disposed in the main circuit <NUM> between the dryer <NUM> and the first expansion valve 27A. The secondary passage 33b is disposed in the liquid refrigerant bypass circuit <NUM>. The liquid refrigerant bypass circuit <NUM> is a bypass circuit that connects the high pressure liquid pipe <NUM> and an intermediate pressure portion (not shown) of a compression mechanism of the compressor <NUM>. A third opening-closing valve 29C and a second expansion valve 27B are sequentially connected, in the direction in which the high pressure liquid refrigerant flows, to the liquid refrigerant bypass circuit <NUM> between the high pressure liquid pipe <NUM> and the secondary passage 33b. In this configuration, when the liquid refrigerant flows into the liquid refrigerant bypass circuit <NUM> from the high pressure liquid pipe <NUM>, the second expansion valve 27B expands the liquid refrigerant to an intermediate pressure, so that the liquid refrigerant has a lower temperature than the liquid refrigerant flowing through the high pressure liquid pipe <NUM> and flows to the secondary passage 33b. Thus, the high pressure liquid refrigerant flowing through the primary passage 33a is supercooled by the refrigerant flowing through the secondary passage 33b. The third opening-closing valve 29C may be, for example, an electromagnetic valve configured to open and close. The second expansion valve 27B may be, for example, an electric expansion valve configured so that the opening degree is variable using a pulse motor.

The hot gas bypass circuit <NUM> connects a high pressure gas pipe <NUM> and the inlet side of the evaporator <NUM> to send the high-pressure high-temperature gas refrigerant discharged from the compressor <NUM> to the inlet side of the evaporator <NUM>. The hot gas bypass circuit <NUM> includes a main passage <NUM>, and a first branch passage <NUM> and a second branch passage <NUM> divided from the main passage <NUM>. The first branch passage <NUM> and the second branch passage <NUM> configure a parallel circuit in which one end of each of the first branch passage <NUM> and the second branch passage <NUM> is connected to the main passage <NUM> and the other end is connected to the inlet side of the evaporator <NUM>, that is, a low pressure connection pipe <NUM> that extends between the first expansion valve 27A and the evaporator <NUM>. The main passage <NUM> includes a fourth opening-closing valve 29D. The fourth opening-closing valve 29D may be, for example, an electromagnetic valve configured to open and close. The first branch passage <NUM> includes only a pipe. The second branch passage <NUM> includes a drain pan heater <NUM>. The drain pan heater <NUM> is disposed at the bottom of the drain pan <NUM> to heat the drain pan <NUM> with the refrigerant having a high temperature.

The refrigeration apparatus <NUM> including the refrigerant circuit <NUM> is provided with various sensors. In an example, the refrigeration apparatus <NUM> includes an intake air temperature detector <NUM> and a blow-out air temperature detector <NUM>. The intake air temperature detector <NUM> is disposed at the intake side of the evaporator <NUM> to detect the temperature of the air in the storage immediately before passing through the evaporator <NUM>. The blow-out air temperature detector <NUM> is disposed at the blow-out side of the evaporator <NUM> to detect the temperature of the air in the storage immediately after passing through the evaporator <NUM>.

As shown in <FIG>, the first container 1A of the refrigeration system <NUM> includes a first controller <NUM>, the second container 1B includes a second controller <NUM>, and the third container 1C includes a third controller <NUM>. The first controller <NUM> receives a signal (hereafter, referred to as "intake air temperature Tv1") corresponding to the temperature of the air in the storage immediately before passing through the evaporator <NUM>. The signal is a detection result of the intake air temperature detector <NUM> of the refrigeration apparatus <NUM> of the first container 1A. The first controller <NUM> also receives a signal (hereafter, referred to as "blow-out air temperature Tb1") corresponding to the temperature of the air in the storage immediately after passing through the evaporator <NUM>. The signal is a detection result of the blow-out air temperature detector <NUM> of the refrigeration apparatus <NUM> of the first container 1A. The second controller <NUM> receives a signal (hereafter, referred to as "intake air temperature Tv2") corresponding to the temperature of the air in the storage immediately before passing through the evaporator <NUM>. The signal is a detection result of the intake air temperature detector <NUM> of the refrigeration apparatus <NUM> of the second container 1B. The second controller <NUM> also receives a signal (hereafter, referred to as "blow-out air temperature Tb2") corresponding to the temperature of the air in the storage immediately after passing through the evaporator <NUM>. The signal is a detection result of the blow-out air temperature detector <NUM> of the refrigeration apparatus <NUM> of the second container 1B. The third controller <NUM> receives a signal (hereafter, referred to as "intake air temperature Tv3") corresponding to the temperature of the air in the storage immediately before passing through the evaporator <NUM>. The signal is a detection result of the intake air temperature detector <NUM> of the refrigeration apparatus <NUM> of the third container 1C. The third controller <NUM> also receives a signal (hereafter, referred to as "blow-out air temperature Tb3") corresponding to the temperature of the air in the storage immediately after passing through the evaporator <NUM>. The signal is a detection result of the blow-out air temperature detector <NUM> of the refrigeration apparatus <NUM> of the third container 1C. The first controller <NUM>, the second controller <NUM>, and the third controller <NUM> have the same configuration.

The first controller <NUM> includes a first control unit <NUM>, which is an example of a control unit, a first communication unit <NUM>, which is an example of a communication unit, a first operating unit <NUM>, which is an example of an operating unit, and a clock <NUM>. The first control unit <NUM> includes, for example, an arithmetic processing unit that executes a predetermined control program and a storage unit. The arithmetic processing unit includes, for example, a central processing unit (CPU) or a micro processing unit (MPU). The storage unit stores various control programs and information used for various control processes. The storage unit includes, for example, a nonvolatile memory and a volatile memory. The first communication unit <NUM> includes a transmitter 52a and a receiver 52b. The first communication unit <NUM> is electrically connected to the first control unit <NUM>, the first operating unit <NUM>, and the clock <NUM>. The first communication unit <NUM> communicates with the second controller <NUM> and the third controller <NUM>. The first operating unit <NUM> includes a touch screen or the like. When operated by an operator, the first operating unit <NUM> sends operating information such as a change in various settings to the first control unit <NUM>. The clock <NUM> may be, for example, an analog quartz clock.

In the same manner as the first controller <NUM>, the second controller <NUM> includes a second control unit <NUM>, which is an example of a control unit, a second communication unit <NUM>, which is an example of a communication unit, a second operating unit <NUM>, which is an example of an operating unit, and a clock <NUM>. The second communication unit <NUM> includes a transmitter 62a and a receiver 62b.

In the same manner as the first controller <NUM>, the third controller <NUM> includes a third control unit <NUM>, which is an example of a control unit, a third communication unit <NUM>, which is an example of a communication unit, a third operating unit <NUM>, which is an example of an operating unit, and a clock <NUM>. The third communication unit <NUM> includes a transmitter 72a and a receiver 72b.

The first communication unit <NUM>, the second communication unit <NUM>, and the third communication unit <NUM> are configured so that the refrigeration apparatuses <NUM> of the containers 1A to 1C connect and communicate with each other. More specifically, the first communication unit <NUM>, the second communication unit <NUM>, and the third communication unit <NUM> are connected so as to perform communication with each other. In the present embodiment, the first communication unit <NUM>, the second communication unit <NUM>, and the third communication unit <NUM> are connected by a communication line <NUM>. More specifically, the communication line <NUM> is connected to a communication port <NUM> of the first controller <NUM>, a communication port <NUM> of the second controller <NUM>, and a communication port <NUM> of the third controller <NUM>. The communication port <NUM> of the first controller <NUM> is electrically connected to the first communication unit <NUM>. The communication port <NUM> of the second controller <NUM> is electrically connected to the second communication unit <NUM>. The communication port <NUM> of the third controller <NUM> is electrically connected to the third communication unit <NUM>.

The control units <NUM>, <NUM>, and <NUM> control operations of the containers 1A to 1C such as a refrigerating-cooling operation and a defrosting operation. The refrigerating-cooling operation and the defrosting operation will now be described with reference to <FIG>.

In the refrigerating-cooling operation, the first opening-closing valve 28A, a second opening-closing valve 28B, and a third opening-closing valve 28C are open, and a fourth opening-closing valve 28D is closed. The opening degrees of the first expansion valve 27A and the second expansion valve 27B are appropriately adjusted. Also, the compressor <NUM>, the exterior fan <NUM>, and the interior fan <NUM> are operated.

In the refrigerating-cooling operation, the refrigerant circulates as indicated by the solid arrows. More specifically, the gas refrigerant is compressed in the compressor <NUM> and is condensed in the condenser <NUM> to become the liquid refrigerant. Subsequently, the liquid refrigerant is stored in the receiver <NUM>. The liquid refrigerant flows from the receiver <NUM> through the second opening-closing valve 28B and the dryer <NUM>. The liquid refrigerant is supercooled in the primary passage 33a of the supercooling heat exchanger <NUM> and flows to the first expansion valve 27A. As indicated by the wave arrows, a portion of the liquid refrigerant discharged from the receiver <NUM> flows as a supercooling source through the third opening-closing valve 28C and the second expansion valve 27B to become a low-pressure low-temperature refrigerant. The low-pressure low-temperature refrigerant flows to the secondary passage 33b of the supercooling heat exchanger <NUM> to supercool the liquid refrigerant in the primary passage 33a. The liquid refrigerant supercooled in the supercooling heat exchanger <NUM> is depressurized in the first expansion valve 27A and then flows through the evaporator <NUM>. In the evaporator <NUM>, the refrigerant absorbs heat from the air in the storage and evaporates. As a result, the air in the storage is cooled. The refrigerant evaporated in the evaporator <NUM> is drawn and compressed again in the compressor <NUM>.

When the refrigerating-cooling operation is continuously performed, frost collects on surfaces of, for example, a fin and a heat transfer tube of the evaporator <NUM>. The frost gradually develops and enlarges. The controllers <NUM>, <NUM>, and <NUM> perform the defrosting operation, that is, an operation for removing frost from the evaporators <NUM>.

As indicated by the broken arrows, the defrosting operation directly supplies a high-temperature high-pressure gas refrigerant, which is compressed in the compressor <NUM>, to the evaporator <NUM> bypassing the condenser <NUM>, the receiver <NUM>, the supercooling heat exchanger <NUM>, and the first expansion valve 27A. In the defrosting operation, the fourth opening-closing valve 28D is open, and the first opening-closing valve 28A, the second opening-closing valve 28B, the third opening-closing valve 28C, and the second expansion valve 27B are fully closed. The compressor <NUM> starts to operate, and the exterior fan <NUM> and the interior fan <NUM> are stopped.

The high-pressure gas refrigerant compressed in the compressor <NUM> flows through the main passage <NUM> and the fourth opening-closing valve 28D and then divides into the first branch passage <NUM> and the second branch passage <NUM>. The refrigerant divided into the second branch passage <NUM> flows through the drain pan heater <NUM>. The refrigerant discharged from the drain pan heater <NUM> joins the refrigerant that has passed through the first branch passage <NUM> and flows through the evaporator <NUM>. In the evaporator <NUM>, a high-pressure gas refrigerant (so-called hot gas) flows in the heat transfer tube. In the evaporator <NUM>, the frost collected on the fin and the heat transfer tube is gradually heated from an inner side by the refrigerant. As a result, the drain pan <NUM> gradually receives the frost from the evaporator <NUM>. The refrigerant used to defrost the evaporator <NUM> is drawn and compressed again in the compressor <NUM>. For example, an ice block falls from the surface of the evaporator <NUM> and is received in the drain pan <NUM>. The ice block is heated and melted by the refrigerant flowing in the drain pan heater <NUM>. The melted water is discharged out of the storage through a predetermined flow passage.

In the refrigeration system <NUM>, the containers 1A to 1C define the accommodation space S, and the refrigerating-cooling operation and the defrosting operation are performed in the accommodation space S. When the refrigerating-cooling operation is performed, after a predetermined time has elapsed from the start of the refrigerating-cooling operation, the controllers <NUM>, <NUM>, and <NUM> of the containers 1A to 1C start the defrosting operation. Since the times of the clocks <NUM>, <NUM>, and <NUM> of the controllers <NUM>, <NUM>, and <NUM> are set by an operator, the operator may set the clocks <NUM>, <NUM>, and <NUM> to different times. When analog quartz clocks are used as the clocks <NUM>, <NUM>, and <NUM>, the times of the clocks <NUM>, <NUM>, and <NUM> may differ from each other as time elapses. As a result, while one or more of the containers 1A to 1C start the defrosting operation, the rest of the containers 1A to 1C do not start the defrosting operation, that is, continue the refrigerating-cooling operation. This refrigerating-cooling operation may hinder completion of defrosting of the one or more of the containers 1A to 1C and termination of the defrosting operation. In addition, when the rest of the containers 1A to 1C perform the defrosting operation, the temperature of the accommodation space S will increase. This causes the one or more of the containers 1A to 1C performing the refrigerating-cooling operation to use power more than necessary for performing the refrigerating-cooling operation to reduce the temperature of the accommodation space S. As a result, the accommodation space S may be locally overcooled.

In this regard, the refrigeration system <NUM> of the present embodiment executes synchronized control that synchronously operates the refrigeration apparatuses <NUM> of the containers 1A to 1C. In an example of synchronized control, the refrigeration system <NUM> synchronizes timing at which the refrigeration apparatuses <NUM> of the containers 1A to 1C start the defrosting operation. Preferably, in synchronized control, the refrigeration system <NUM> synchronizes timing at which the refrigeration apparatuses <NUM> of the containers 1A to 1C end the defrosting operation. More preferably, in synchronized control, after the refrigeration apparatuses <NUM> of the containers 1A to 1C end the defrosting operation, the refrigeration system <NUM> synchronizes the start timing of the refrigerating-cooling operation.

When executing the synchronized control, the controllers <NUM>, <NUM>, and <NUM> of the containers 1A to 1C set one of the controllers <NUM>, <NUM>, and <NUM> to a master device and set the remaining two controllers to slave devices. For example, the first control unit <NUM> of the first controller <NUM> is set to a main control unit, and the second control unit <NUM> of the second controller <NUM> and the third control unit <NUM> of the third controller <NUM> are set to slave control units. The first communication unit <NUM> transmits time information of the clock <NUM> of the first controller <NUM> to the second communication unit <NUM> and the third communication unit <NUM>. In the synchronized control of the present embodiment, the containers 1A to 1C synchronously start each of the defrosting operation and the refrigerating-cooling operation based on the time of the clock of the master device.

The first control unit <NUM> executes the synchronized control. The procedures of the synchronized control will now be described with reference to the flowchart shown in <FIG>. The first control unit <NUM> executes the synchronized control in a period from when the refrigeration apparatuses <NUM> of the containers 1A to 1C start to operate to when the refrigeration apparatuses <NUM> of the containers 1A to 1C stops operating.

In step S11, the first control unit <NUM> obtains the time of the clock <NUM> of the master device (first controller <NUM>). In step S12, the first control unit <NUM> determines whether the time of the clock <NUM> of the master device is a scheduled start time of the defrosting operation. The scheduled start time of the defrosting operation is set to, for example, a time after a predetermined time elapses from when the containers 1A to 1C start the refrigerating-cooling operation. The scheduled start time of the defrosting operation may be set to multiple times. In this case, an interval from a scheduled start time of the defrosting operation to the next scheduled start time of the defrosting operation is set to be greater than a period in which the defrosting operation is executed.

When determining that the time of the clock <NUM> of the master device is not the scheduled start time of the defrosting operation (step S12: NO), the first control unit <NUM> proceeds to step S11. When determining that the time of the clock <NUM> of the master device is the scheduled start time of the defrosting operation (step S12: YES), the first control unit <NUM> proceeds to step S13 and synchronizes all of the containers 1A to 1C to start the defrosting operation. More specifically, the first control unit <NUM> transmits a defrosting start synchronization signal to the second control unit <NUM> and the third control unit <NUM> through the first communication unit <NUM> and starts the defrosting operation of the first container 1A. The defrosting start synchronization signal is an instruction signal for synchronously starting the defrosting operations of all of the containers 1A to 1C. When receiving the defrosting start synchronization signal from the first control unit <NUM> through the second communication unit <NUM>, the second control unit <NUM> starts the defrosting operation of the second container 1B. When receiving the defrosting start synchronization signal from the first control unit <NUM> through the third communication unit <NUM>, the third control unit <NUM> starts the defrosting operation of the third container 1C.

In step S14, the first control unit <NUM> determines whether the time of the clock <NUM> of the master device is a scheduled end time of the defrosting operation. The scheduled end time of the defrosting operation is set to a time after a predetermined time elapses from the scheduled start time of the defrosting operation. When multiple scheduled start times of the defrosting operation are set, multiple scheduled end times of the defrosting operation are set in correspondence with the scheduled start times.

When determining that the time of the clock <NUM> of the master device is not the scheduled end time of the defrosting operation (step S14: NO), the first control unit <NUM> returns to the determination of step S14. That is, when all of the containers 1A to 1C start the defrosting operations, the defrosting operations of all of the containers 1A to 1C continue until the scheduled end time of the defrosting operation.

When determining that the time of the clock <NUM> of the master device is the scheduled end time of the defrosting operation (step S14: YES), the first control unit <NUM> proceeds to step S15 to synchronously end the defrosting operations of all of the containers 1A to 1C. More specifically, the first control unit <NUM> transmits a defrosting end synchronization signal to the second control unit <NUM> and the third control unit <NUM> through the first communication unit <NUM> and ends the defrosting operation of the first container 1A. The defrosting end synchronization signal is an instruction signal for synchronously ending the defrosting operations of all of the containers 1A to 1C. When receiving the defrosting end synchronization signal from the first control unit <NUM> through the second communication unit <NUM>, the second control unit <NUM> ends the defrosting operation of the second container 1B. When receiving the defrosting end synchronization signal from the first control unit <NUM> through the third communication unit <NUM>, the third control unit <NUM> ends the defrosting operation of the third container 1C.

In step S16, the first control unit <NUM> synchronously starts the refrigerating-cooling operations of all of the containers 1A to 1C. More specifically, the first control unit <NUM> transmits a refrigerating-cooling start synchronization signal to the second control unit <NUM> and the third control unit <NUM> through the first communication unit <NUM> and starts the refrigerating-cooling operation of the first container 1A. The refrigerating-cooling start synchronization signal is an instruction signal for synchronously resuming the refrigerating-cooling operations of all of the containers 1A to 1C. When receiving the refrigerating-cooling start synchronization signal from the first control unit <NUM> through the second communication unit <NUM>, the second control unit <NUM> starts the refrigerating-cooling operation of the second container 1B. When receiving the refrigerating-cooling start synchronization signal from the first control unit <NUM> through the third communication unit <NUM>, the third control unit <NUM> starts the refrigerating-cooling operation of the third container 1C. Then, the process returns to step S11.

As described above, the master device (first controller <NUM>) and the slave devices (second controller <NUM> and third controller <NUM>) are set so that the synchronized control is executed. However, when the master device malfunctions as the master device, the master device may not be able to instruct the slave devices to start the defrosting operation or synchronize the refrigerating-cooling operations. This may result in a failure of execution of the synchronized control. In an example, as shown in the upper part of <FIG>, when the transmitter 52a of the first communication unit <NUM> is faulty, that is, when the first communication unit <NUM> cannot transmit the defrosting start synchronization signal, a defrosting end synchronization instruction, and the refrigerating-cooling start synchronization signal to the second communication unit <NUM> and the third communication unit <NUM>, the synchronized control cannot be executed.

In this regard, when the master device (first controller <NUM>) malfunctions as the master device, the refrigeration system <NUM> of the present embodiment executes setting change control that sets one of the slave devices (second controller <NUM> and third controller <NUM>) to a new master device and sets the master device (the first controller <NUM>) to a slave device. In the setting change control, for example, as shown in the lower part of <FIG>, when the second controller <NUM> is set to the master device, the second control unit <NUM> transmits the defrosting start synchronization signal, the defrosting end synchronization instruction, and the refrigerating-cooling start synchronization signal to the first control unit <NUM> and the third control unit <NUM>.

The procedures of the setting change control will now be described with reference to <FIG>. In the present embodiment, a case in which the second control unit <NUM> is changed from the slave control unit to the main control unit will be described.

In step S21, the second control unit <NUM> transmits a response check signal to the first control unit <NUM>. In step S22, the second control unit <NUM> determines whether a response signal is received from the first control unit <NUM>. When determining that the response signal is not received from the first control unit <NUM> (step S22: NO), the second control unit <NUM> proceeds to step S23 and determines whether a predetermined time has elapsed from when the response check signal is transmitted. The predetermined time is used to determine occurrence of an abnormality in transmission of a signal from the first control unit <NUM> and is set in advance through tests or the like.

When determining that the predetermined time has elapsed from when the response check signal is transmitted (step S23: YES), the second control unit <NUM> proceeds to step S24 and sets the second controller <NUM> to the master device and sets the first controller <NUM> to a slave device. In other words, the second control unit <NUM> is set to the main control unit, and the first control unit <NUM> is set to a slave control unit. In step S25, instead of the first control unit <NUM>, the second control unit <NUM> executes synchronized control. In this case, the second control unit <NUM> operates the first controller <NUM> based on information (operating information) related to the operation of the first container 1A obtained before the first controller <NUM> malfunctions as the master device. More specifically, the second control unit <NUM> transmits operating information of the first container 1A obtained before the first controller <NUM> malfunctions as the master device, that is, the operating information of the first container 1A lastly received from the first controller <NUM>, to the first controller <NUM>. The first control unit <NUM> operates the refrigeration apparatus <NUM> of the first container 1A based on the operating information of the first container 1A received from the second control unit <NUM>.

When determined that the predetermined time has not elapsed from when the response check signal is transmitted (step S23: NO), the second control unit <NUM> proceeds to step S22. When determining that the response signal is received from the first control unit <NUM> (step S22: YES), the second control unit <NUM> proceeds to step S21.

When executing the synchronized control, if at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of one or more of the containers 1A to 1C is faulty, the one or more of the containers 1A to 1C may fail to perform various operations. This may result in a failure of execution of the synchronized control. In an example, as shown in the upper part of <FIG>, when the blow-out air temperature detector <NUM> of the second container 1B is faulty, the second control unit <NUM> cannot obtain the blow-out air temperature Tb2 and thus may fail to start or end various operations of the second container 1B.

In this regard, in the refrigeration system <NUM> of the present embodiment, the containers 1A to 1C transmit operating information or the like to each other through the communication units <NUM>, <NUM>, and <NUM>. More specifically, the first control unit <NUM> receives information related to the operation performed by the second control unit <NUM> and information related to the operation performed by the third control unit <NUM>. The second control unit <NUM> receives information related to the operation performed by the first control unit <NUM> and information related to the operation performed by the third control unit <NUM>. The third control unit <NUM> receives information related to the operation performed by the first control unit <NUM> and information related to the operation performed by the second control unit <NUM>. Thus, the storage units of the control units <NUM>, <NUM>, and <NUM> store the information related to the operation performed by the first control unit <NUM>, the information related to the operation performed by the second control unit <NUM>, and the information related to the operation performed by the third control unit <NUM>. Information related to operations performed by the control units <NUM>, <NUM>, and <NUM> includes the intake air temperatures Tv1 to Tv3, the blow-out air temperatures Tb1 to Tb3, the kind of operation performed by the control units <NUM>, <NUM>, and <NUM> (refrigerating-cooling operation and defrosting operation), operating frequencies of the compressors <NUM>, rotational speeds of the exterior fans <NUM>, rotational speeds of the interior fans <NUM>, opening degrees of the expansion valves 27A and 27B, and opening degrees of the opening-closing valves 28A to 28D.

In the refrigeration system <NUM> of the present embodiment, when at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of one or more of the containers 1A to 1C is faulty, the operation of the one or more of the containers 1A to 1C is controlled based on detection results of the intake air temperature detector <NUM> and the blow-out air temperature detector <NUM> of a remaining one of the containers 1A to 1C. For example, as shown in the lower part of <FIG>, when the blow-out air temperature detector <NUM> of the second container 1B is faulty, substituted control is executed so that the second control unit <NUM> executes various operations based on the intake air temperature Tv1, which is the detection result of the intake air temperature detector <NUM> of the first container 1A, and the blow-out air temperature Tb1, which is the detection result of the blow-out air temperature detector <NUM> of the first container 1A. It is preferred that detection results of the intake air temperature detector <NUM> and the blow-out air temperature detector <NUM> of a container located adjacent to the faulty container be used in the substituted control.

The procedures of the substituted control will now be described with reference to <FIG> and <FIG>.

As shown in <FIG>, in step S31, the first control unit <NUM> determines whether at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of the first container 1A is faulty. More specifically, the first control unit <NUM> determines whether the intake air temperature detector <NUM> and the blow-out air temperature detector <NUM> of the first container 1A have each transmitted a detection signal to the first controller <NUM> in a predetermined period. When the detection signal has not been received from at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> in the predetermined period, the first control unit <NUM> determines that at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> is faulty.

When determining that neither the intake air temperature detector <NUM> nor the blow-out air temperature detector <NUM> of the first container 1A is faulty (step S31: NO), the first control unit <NUM> proceeds to step S32 and determines whether at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of the second container 1B is faulty. More specifically, the second control unit <NUM> determines whether the intake air temperature detector <NUM> and the blow-out air temperature detector <NUM> of the second container 1B have each transmitted a detection signal to the second controller <NUM> in a predetermined period. This determination process is executed in the same manner as step S31. The second control unit <NUM> transmits the determination result to the first control unit <NUM>.

When determining that neither the intake air temperature detector <NUM> nor the blow-out air temperature detector <NUM> of the second container 1B is faulty (step S32: NO), the first control unit <NUM> proceeds to step S33 and determines whether at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of the third container 1C is faulty. More specifically, the third control unit <NUM> determines whether the intake air temperature detector <NUM> and the blow-out air temperature detector <NUM> of the third container 1C have each transmitted a detection signal to the third controller <NUM> in a predetermined period. This determination process is executed in the same manner as step S31. The third control unit <NUM> transmits the determination result to the first control unit <NUM>.

When determining that neither the intake air temperature detector <NUM> nor the blow-out air temperature detector <NUM> of the third container 1C is faulty (step S33: NO), that is, when none of the intake air temperature detectors <NUM> and the blow-out air temperature detectors <NUM> of the containers 1A to 1C is faulty, the first control unit <NUM> temporarily ends the process.

When determining that at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of the second container 1B is faulty (step S32: YES), the first control unit <NUM> proceeds to step S34 and determines whether at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of the third container 1C is faulty. When determining that at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of the third container 1C is faulty (step S34: YES), the first control unit <NUM> proceeds to step S41. More specifically, when an affirmative determination is made in step S34, the intake air temperature detector <NUM> and the blow-out air temperature detector <NUM> of the first container 1A are not faulty, and at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of each of the second and third containers 1B and 1C is faulty. Therefore, in step S41, the first control unit <NUM> performs various operations of the second container 1B and the third container 1C based on the detection results of the intake air temperature detector <NUM> and the blow-out air temperature detector <NUM> of the first container 1A. When determining that neither the intake air temperature detector <NUM> nor the blow-out air temperature detector <NUM> of the third container 1C is faulty (step S34: NO), the first control unit <NUM> proceeds to step S42. More specifically, when a negative determination is made in step S34, neither the intake air temperature detectors <NUM> nor the blow-out air temperature detectors <NUM> of the first container 1A and the third container 1C are faulty, at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of the second container 1B is faulty. Therefore, in step S42, the first control unit <NUM> performs various operations of the second container 1B based on the detection results of the intake air temperature detector <NUM> and the blow-out air temperature detector <NUM> of the first container 1A. In step S42, the first control unit <NUM> may perform various operations of the second container 1B based on the detection results of the intake air temperature detector <NUM> and the blow-out air temperature detector <NUM> of the third container 1C.

When determining in step S33 that at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of the third container 1C is faulty (step S33: YES), the first control unit <NUM> proceeds to step S43. More specifically, when a negative determination is made in step S33, neither the intake air temperature detectors <NUM> nor the blow-out air temperature detectors <NUM> of the first container 1A and the second container 1B are faulty, and at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of the third container 1C is faulty. Therefore, in step S43, the first control unit <NUM> controls various operations of the third container 1C based on the detection results of the intake air temperature detector <NUM> and the blow-out air temperature detector <NUM> of the second container 1B.

As shown in <FIG> and <FIG>, when an affirmative determination is made in step S31, the first control unit <NUM> proceeds to step S35 and determines whether at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of the second container 1B is faulty. When determining that at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of the second container 1B is faulty (step S35: YES), the first control unit <NUM> proceeds to step S36 and determines whether at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of the third container 1C is faulty. When determining that at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of the third container 1C is faulty (step S35: YES), the first control unit <NUM> proceeds to step S44. More specifically, when an affirmative determination is made in step S35, at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of each of the containers 1A to 1C is faulty. In step S44, the first control unit <NUM> stops the operations of the containers 1A to 1C. In this case, the first control unit <NUM> may transmit a message indicating that the operations of the containers 1A to 1C are abnormal and have been stopped to, for example, a service center (control center) through the first communication unit <NUM>.

When determining that neither the intake air temperature detector <NUM> nor the blow-out air temperature detector <NUM> of the third container 1C is faulty (step S36: NO), the first control unit <NUM> proceeds to step S45. More specifically, when a negative determination is made in step S36, at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of each of the first and second containers 1A and 1B is faulty, and neither the intake air temperature detector <NUM> nor the blow-out air temperature detector <NUM> of the third container 1C is faulty. Therefore, in step S45, the first control unit <NUM> controls various operations of the first and second containers 1A and 1B based on the detection results of the intake air temperature detector <NUM> and the blow-out air temperature detector <NUM> of the third container 1C.

When determining in step S45 that neither the intake air temperature detector <NUM> nor the blow-out air temperature detector <NUM> of the second container 1B is faulty (step S35: NO), the first control unit <NUM> proceeds to step S37 and determines whether at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of the third container 1C is faulty. When determining that at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of the third container 1C is faulty (step S37: YES), the first control unit <NUM> proceeds to step S46. More specifically, when an affirmative determination is made in step S37, at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of each of the first and third containers 1A and 1C is faulty, and neither the intake air temperature detector <NUM> nor the blow-out air temperature detector <NUM> of the second container 1B is faulty. Therefore, in step S46, the first control unit <NUM> controls various operations of the first and third containers 1A and 1C based on the detection results of the intake air temperature detector <NUM> and the blow-out air temperature detector <NUM> of the second container 1B.

When determining that neither the intake air temperature detector <NUM> nor the blow-out air temperature detector <NUM> of the third container 1C is faulty (step S37: NO), the first control unit <NUM> proceeds to step S47. More specifically, when a negative determination is made in step S37, at least one of the intake air temperature detector <NUM> or the blow-out air temperature detector <NUM> of the first container 1A is faulty, and neither the intake air temperature detector <NUM> nor the blow-out air temperature detector <NUM> of the second and third containers 1B and 1C is faulty. Therefore, in step S47, the first control unit <NUM> controls various operations of the first container 1A based on the detection results of the intake air temperature detector <NUM> and the blow-out air temperature detector <NUM> of the second container 1B.

The refrigeration apparatuses <NUM> of the containers 1A to 1C perform synchronized operation at a point in time of starting the refrigerating-cooling operation and change from the synchronized operation to separated operation after starting the refrigerating-cooling operation. In the separated operation, the refrigeration apparatuses <NUM> of the containers 1A to 1C separately perform the refrigerating-cooling operation on at separate storage set temperatures. More specifically, in the separated operation, the refrigeration apparatuses <NUM> of the containers 1A to 1C separately control, for example, the compressor <NUM>, the interior fan <NUM>, and the exterior fan <NUM> in accordance with the difference between the storage set temperature and the storage temperature of the corresponding container. The refrigeration apparatus <NUM> of the first container 1A calculates the storage temperature based on, for example, the intake air temperature Tv1. The refrigeration apparatus <NUM> of the second container 1B calculates the storage temperature based on, for example, the intake air temperature Tv2. The refrigeration apparatus <NUM> of the third container 1C calculates the storage temperature based on, for example, the intake air temperature Tv3.

When the refrigeration apparatuses <NUM> of the containers 1A to 1C change from the synchronized operation to the separated operation, for example, if the first control unit <NUM> is the main control unit and the second control unit <NUM> and the third control unit <NUM> are the slave control units in the synchronized operation, the first control unit <NUM> transmits an instruction signal for starting the separated operation to the second control unit <NUM> and the third control unit <NUM> through the first communication unit <NUM>. When the instruction signal is received from the first control unit <NUM>, the second control unit <NUM> starts the separated operation of the second container 1B. When the instruction signal is received from the first control unit <NUM>, the third control unit <NUM> starts the separated operation of the third container 1C.

Depending on the needs of the operator, the separated control, which separately operates the refrigeration apparatuses <NUM> of the containers 1A to 1C, may be executed without execution of the synchronized control. In the separated control, when the clock <NUM> of the first controller <NUM> reaches the scheduled start time of the defrosting operation, the first control unit <NUM> performs the defrosting operation of the first container 1A. When the clock <NUM> of the second controller <NUM> reaches the scheduled start time of the defrosting operation, the second control unit <NUM> performs the defrosting operation of the second container 1B. When the clock <NUM> of the third controller <NUM> reaches the scheduled start time of the defrosting operation, the third control unit <NUM> performs the defrosting operation of the third container 1C. That is, in the separated control, the control units <NUM>, <NUM>, and <NUM> separately control the containers 1A to 1C. In the separated control, when one or more of the containers 1A to 1C start the defrosting operation, the rest of the containers 1A to 1C do not start the defrosting operation based on the start of the defrosting operation of the one or more of the containers 1A to 1C.

The operator may select the separated control and the synchronized control by operating the operating units <NUM>, <NUM>, and <NUM>. In addition, a first setting and a second setting may be selected. In the first setting, an operation performed on one of the operating units <NUM>, <NUM>, and <NUM> reflects operations of the remaining two operating units. In the second setting, an operation performed on one of the operating units <NUM>, <NUM>, and <NUM> does not reflect operations of the remaining two operating units. When the operating units <NUM>, <NUM>, and <NUM> are in the first setting and the operator selects the synchronized control using, for example, the first operating unit <NUM>, the first communication unit <NUM> transmits information indicating that synchronized control is selected to the second controller <NUM> and the third controller <NUM>. When the information is received from the first communication unit <NUM>, the second controller <NUM> sets the second container 1B so that the second container 1B is controlled synchronously with the first container 1A and the third container 1C. When the information is received from the first communication unit <NUM>, the third controller <NUM> sets the third container 1C so that the third container 1C is controlled synchronously with the first container 1A and the second container 1B. When the operating units <NUM>, <NUM>, and <NUM> are in the second setting, the operator operates each of the operating units <NUM>, <NUM>, and <NUM> to select, for example, the synchronized control. Accordingly, the controllers <NUM>, <NUM>, and <NUM> execute the synchronized control.

In addition, the operator may set the containers 1A to 1C to a container that is subject to the synchronized control. The operator may select a container that undergoes the synchronized control and a container that undergoes the separated control, for example, in accordance with the kind of load in the containers 1A to 1C. For example, when the first container 1A and the second container 1B store the same kind of loads and the third container 1C stores loads that differ in the kind from the loads of the first container 1A and the second container 1B, the synchronized control may be executed on the first container 1A and the second container 1B, and the separated control may be executed on the third container 1C.

In addition, the operator may set one of the controllers <NUM>, <NUM>, and <NUM> to the master device by operating the operating units <NUM>, <NUM>, and <NUM>. In this case, among the controllers <NUM>, <NUM>, and <NUM>, controllers other than the controller that is set to the master device are automatically set to the slave devices. More specifically, for example, when the operator operates the first operating unit <NUM> to set the first controller <NUM> to the master device, the first communication unit <NUM> transmits information indicating that the first controller <NUM> is the master device to the second controller <NUM> and the third controller <NUM>. When the information is received from the first communication unit <NUM>, the second controller <NUM> sets the second controller <NUM> to a slave device. When the information is received from the first communication unit <NUM>, the third controller <NUM> sets the third controller <NUM> to a slave device.

The operation of the present embodiment will now be described.

The controllers <NUM>, <NUM>, and <NUM> send time information of the clock <NUM> of the master device and information related to operations of the containers 1A to 1C to each other. For example, when the clock <NUM> has reached a preset time (scheduled start time of defrosting operation) and the clocks <NUM> and <NUM> have not reached the scheduled start time, the first control unit <NUM> sends information indicating that the clock <NUM> has reached the scheduled start time to the second control unit <NUM> and the third control unit <NUM> through the first communication unit <NUM>. The first control unit <NUM> transmits the defrosting start synchronization signal to the second control unit <NUM> and the third control unit <NUM> based on the information indicating that the clock <NUM> has reached the scheduled start time. As a result, the defrosting operations of the containers 1A to 1C synchronously start, thereby limiting separation between starts of the defrosting operations that would be caused by differences in the set time between the clocks <NUM>, <NUM>, and <NUM>. This reduces situations in which the defrosting operations of the containers 1A to 1C separately start, causing some of the containers 1A to 1C to execute the refrigerating-cooling operation.

The present embodiment has the following advantages.

A second embodiment of a refrigeration system <NUM> will now be described with reference to <FIG>. The refrigeration system <NUM> of the present embodiment differs from the refrigeration system <NUM> of the first embodiment in synchronized control. In the following description, the same reference numerals are given to those elements that are the same as the corresponding elements of the refrigeration system <NUM> of the first embodiment. Such elements will not be described in detail.

The containers 1A to 1C of the present embodiment perform the defrosting operation based on the amount of frost collected on the evaporator <NUM> and the difference (Tv1-Tb1, Tv2-Tb2, Tv3-Tb3) between the intake air temperature and the blow-out air temperature of the respective containers 1A to 1C. If the containers 1A to 1C are separately controlled, the amount of frost collected on the evaporator <NUM> varies between the containers 1A to 1C. This may produce a state in which one or more of the containers 1A to 1C perform the defrosting operation and the rest of the containers 1A to 1C perform the refrigerating-cooling operation. In such a case, termination of the defrosting operation of the one or more of the containers 1A to 1C is hindered. In addition, the refrigerating-cooling operation of the remaining containers 1A to 1C may overcool in the same manner as the first embodiment.

In addition, when the containers 1A to 1C are performing the defrosting operation, if one or more of the containers 1A to 1C end the defrosting operation and resume the refrigerating-cooling operation, the one or more of the containers 1A to 1C perform the refrigerating-cooling operation while the rest of the containers 1A to 1C perform the defrosting operation. This also may hinder termination of the defrosting operation and locally overcool a space where the refrigerating-cooling operation is performed.

In the same manner as the refrigeration system <NUM> of the first embodiment, the refrigeration system <NUM> of the present embodiment executes the synchronized control, in which information related to the operations performed by the control units <NUM>, <NUM>, and <NUM> is obtained, when one of the containers 1A to 1C has started the defrosting operation, the remaining containers start the defrosting operation, and when one of the containers 1A to 1C has started the refrigerating-cooling operation, the remaining containers start the refrigerating-cooling operation. Also, in the present embodiment, the first controller <NUM> is set to the master device, and the second controller <NUM> and the third controller <NUM> are set to the slave devices.

The first control unit <NUM> used as the main control unit executes the synchronized control. The procedures of the synchronized control will now be described with reference to the flowchart shown in <FIG>. The first control unit <NUM> executes the synchronized control during a period from when the containers 1A to 1C start to operate to when the containers 1A to 1C stops operating.

In step S51, the first control unit <NUM> obtains the kind of operation of each of the containers 1A to 1C. In step S52, the first control unit <NUM> determines whether any of the containers 1A to 1C has started the defrosting operation. More specifically, the first control unit <NUM>, the second control unit <NUM>, and the third control unit <NUM> send information indicating that the control units <NUM>, <NUM>, and <NUM> of the containers 1A to 1C have started the defrosting operation through the communication units <NUM>, <NUM>, and <NUM>. More specifically, when the first container 1A has started the defrosting operation, the first control unit <NUM> transmits a defrosting operation start signal to the second control unit <NUM> and the third control unit <NUM>. When the second container 1B has started the defrosting operation, the second control unit <NUM> transmits a defrosting operation start signal to the first control unit <NUM> and the third control unit <NUM>. When the third container 1C has started the defrosting operation, the third control unit <NUM> transmits a defrosting operation start signal to the first control unit <NUM> and the second control unit <NUM>. When the first control unit <NUM> transmits the defrosting operation start signal, the first control unit <NUM> determines that the first container 1A has started the defrosting operation. When the defrosting operation start signal is received from the second control unit <NUM>, the first control unit <NUM> determines that the second container 1B has started the defrosting operation. When the defrosting operation start signal is received from the third control unit <NUM>, the first control unit <NUM> determines that the third container 1C has started the defrosting operation.

When the first control unit <NUM> determines that any of the containers 1A to 1C has not started the defrosting operation (step S52: NO), the first control unit <NUM> proceeds to step S11. When the first control unit <NUM> determines that one of the containers 1A to 1C has started the defrosting operation (step S52: YES), the first control unit <NUM> proceeds to step S53 and synchronizes all of the containers 1A to 1C to start the defrosting operation. More specifically, when the first container 1A has started the defrosting operation, the second control unit <NUM> starts the defrosting operation of the second container 1B when receiving the defrosting operation start signal from the first control unit <NUM>, and the third control unit <NUM> starts the defrosting operation of the third container 1C when receiving the defrosting operation start signal from the first control unit <NUM>. When the second container 1B has started the defrosting operation, the first control unit <NUM> starts the defrosting operation of the first container 1A when receiving the defrosting operation start signal from the second control unit <NUM>, and the third control unit <NUM> starts the defrosting operation of the third container 1C when receiving the defrosting operation start signal from the second control unit <NUM>. When the third container 1C has started the defrosting operation, the first control unit <NUM> starts the defrosting operation of the first container 1A when receiving the defrosting operation start signal from the third control unit <NUM>, and the second control unit <NUM> starts the defrosting operation of the second container 1B when receiving the defrosting operation start signal from the third control unit <NUM>.

In step S54, the first control unit <NUM> determines whether all of the containers 1A to 1C have ended the defrosting operations. More specifically, the first control unit <NUM>, the second control unit <NUM>, and the third control unit <NUM> send information indicating that the control units <NUM>, <NUM>, and <NUM> of the containers 1A to 1C have ended the defrosting operations through the communication units <NUM>, <NUM>, and <NUM>. More specifically, when the first container 1A has end the defrosting operation, the first control unit <NUM> transmits a defrosting operation end signal to the second control unit <NUM> and the third control unit <NUM>. When the second container 1B has ended the defrosting operation, the second control unit <NUM> transmits a defrosting operation end signal to the first control unit <NUM> and the third control unit <NUM>. When the third container 1C has ended the defrosting operation, the third control unit <NUM> transmits a defrosting operation end signal to the first control unit <NUM> and the second control unit <NUM>. When the first control unit <NUM> transmits the defrosting operation end signal, the first control unit <NUM> determines that the first container 1A has ended the defrosting operation. Also, the first control unit <NUM> determines that the second container 1B has ended the defrosting operation when receiving the defrosting operation end signal from the second control unit <NUM>, and determines that the third container 1C has ended the defrosting operation when receiving the defrosting operation end signal from the third control unit <NUM>.

When determining that all of the containers 1A to 1C have not ended the defrosting operation (step S54: NO), the first control unit <NUM> again proceeds to the determination of step S54. In an example, when the first container 1A has ended the defrosting operation and the second container 1B and the third container 1C have not ended the defrosting operation, the operation of the first container 1A is stopped, and the second container 1B and the third container 1C continue the defrosting operation. Then, when the second container 1B has ended the defrosting operation and the third container 1C has not ended the defrosting operation, the operation of the first container 1A continues to be stopped, the operation of the second container 1B is stopped, and the third container 1C continues the defrosting operation.

When determining that all of the containers 1A to 1C have ended the defrosting operations (step S54: YES), the first control unit <NUM> proceeds to step S55 and synchronizes all of the containers 1A to 1C to start the refrigerating-cooling operation. More specifically, the first control unit <NUM> transmits the refrigerating-cooling start synchronization signal to the second control unit <NUM> and the third control unit <NUM> through the first communication unit <NUM>. Thus, the start of the refrigerating-cooling operation is synchronized between the containers 1A to 1C. More specifically, after transmitting the refrigerating-cooling start synchronization signal to the second control unit <NUM> and the third control unit <NUM>, the first control unit <NUM> performs the refrigerating-cooling operation of the first container 1A. When receiving the refrigerating-cooling start synchronization signal, the second control unit <NUM> performs the refrigerating-cooling operation of the second container 1B. When receiving the refrigerating-cooling start synchronization signal, the third control unit <NUM> performs the refrigerating-cooling operation of the third container 1C. Then, the process returns to step S51.

For example, when the first container 1A has started the defrosting operation, the first control unit <NUM> transmits the defrosting operation start signal to the second control unit <NUM> and the third control unit <NUM>. The second control unit <NUM> and the third control unit <NUM> start the defrosting operations of the second container 1B and the third container 1C based on the defrosting operation start signal. As described above, the second and third containers 1B and 1C start the defrosting operations in cooperation with the start of the defrosting operation of the first container 1A. Also, in this case, the containers 1A to 1C synchronously start the defrosting operation. This reduces situations in which the defrosting operations of the containers 1A to 1C separately start, causing some of the containers 1A to 1C to execute the refrigerating-cooling operation. The present embodiment has the same advantages as the first embodiment.

A third embodiment of a refrigeration system <NUM>, which does not form part of the present invention, will now be described with reference to <FIG>. The refrigeration system <NUM> of the present embodiment differs from the refrigeration system <NUM> of the first embodiment in the communication mode of the controllers <NUM>, <NUM>, and <NUM>. In the following description, the same reference numerals are given to those elements that are the same as the corresponding elements of the refrigeration system <NUM> of the first embodiment. Such elements will not be described in detail.

The first communication unit <NUM> of the first controller <NUM>, the second communication unit <NUM> of the second controller <NUM>, and the third communication unit <NUM> of the third controller <NUM> are configured to perform wireless communication with an external server <NUM>. An example of the server <NUM> is a cloud server. The server <NUM> includes a main control unit <NUM>. The main control unit <NUM> includes, for example, an arithmetic processing unit that executes a predetermined control program and a storage unit.

The communication units <NUM>, <NUM>, and <NUM> transmit the times of the clocks <NUM>, <NUM>, and <NUM> and information related to operations performed by the control units <NUM>, <NUM>, and <NUM> to the main control unit <NUM>. The main control unit <NUM> stores the times of the clocks <NUM>, <NUM>, and <NUM> and the information related to operations performed by the control units <NUM>, <NUM>, and <NUM>. Information related to operations performed by the control units <NUM>, <NUM>, and <NUM> includes the intake air temperatures Tv1 to Tv3, the blow-out air temperatures Tb1 to Tb3, the kind of operation performed by the control units <NUM>, <NUM>, and <NUM> (refrigerating-cooling operation and defrosting operation), operating frequencies of the compressors <NUM>, rotational speeds of the exterior fans <NUM>, rotational speeds of the interior fans <NUM>, opening degrees of the expansion valves 27A and 27B, and opening degrees of the opening-closing valves 28A to 28D.

The main control unit <NUM> transmits control signals related to operations of the containers 1A to 1C to the communication units <NUM>, <NUM>, and <NUM> based on the times of the clocks <NUM>, <NUM>, and <NUM> and the information related to operations performed by the control units <NUM>, <NUM>, and <NUM>. The control units <NUM>, <NUM>, and <NUM> control operations of the respective containers 1A to 1C based on the control signals of the main control unit <NUM>. That is, the control units <NUM>, <NUM>, and <NUM> are slave control units of the main control unit <NUM>.

More specifically, the main control unit <NUM> executes various controls such as the synchronized control and the substituted control on the containers 1A to 1C. In the synchronized control, the main control unit <NUM> transmits the defrosting start synchronization signal, the defrosting end synchronization signal, and the refrigerating-cooling start synchronization signal to the communication units <NUM>, <NUM>, and <NUM> in the same manner as in the synchronized control of the first embodiment. The communication units <NUM>, <NUM>, and <NUM> transmit the defrosting start synchronization signal, the defrosting end synchronization signal, and the refrigerating-cooling start synchronization signal to the control units <NUM>, <NUM>, and <NUM>. In the substituted control, the communication units <NUM>, <NUM>, and <NUM> transmit determination results indicating whether at least one of the intake air temperature detectors <NUM> or the blow-out air temperature detectors <NUM> of the containers 1A to 1C is faulty to the main control unit <NUM>. The main control unit <NUM> controls the operations of the containers 1A to 1C based on the determination results received from the communication units <NUM>, <NUM>, and <NUM> in the same manner as in the substituted control of the first embodiment.

The present embodiment, which does not form part of the invention, has the following advantages. (<NUM>-<NUM>) The communication units <NUM>, <NUM>, and <NUM> of the refrigeration apparatuses <NUM> of the containers 1A to 1C are configured to be connected to the server <NUM>. With this configuration, synchronization of the start of the refrigerating-cooling operation and synchronization of the start of the defrosting operation between the refrigeration apparatuses <NUM> are controlled through the main control unit <NUM> of the server <NUM>, which may be a cloud-based server. Thus, variations in the operation of the refrigeration apparatuses <NUM> are limited.

A fourth embodiment of a refrigeration system <NUM> will now be described with reference to <FIG>. The refrigeration system <NUM> of the present embodiment differs in the configurations of the controllers <NUM>, <NUM>, and <NUM>. In the following description, the same reference numerals are given to those elements that are the same as the corresponding elements of the refrigeration system <NUM> of the first embodiment. Such elements will not be described in detail.

The controllers <NUM>, <NUM>, and <NUM> of the present embodiment include atomic clocks <NUM>, <NUM>, and <NUM> instead of the clocks <NUM>, <NUM>, and <NUM>. The time of the atomic clock <NUM> is transmitted to the first control unit <NUM>. The time of the atomic clock <NUM> is transmitted to the second control unit <NUM>. The time of the atomic clock <NUM> is transmitted to the third control unit <NUM>.

The control units <NUM>, <NUM>, and <NUM> of the present embodiment start the defrosting operation at a preset first start time (scheduled start time of defrosting operation) and end the defrosting operation at a preset first end time (scheduled end time of defrosting operation). More specifically, when determining that the atomic clock <NUM> has reached the scheduled start time of the defrosting operation, the first control unit <NUM> starts the defrosting operation. When determining that the atomic clock <NUM> has reached the scheduled end time of the defrosting operation, the first control unit <NUM> ends the defrosting operation. When determining that the atomic clock <NUM> has reached the scheduled start time of the defrosting operation, the second control unit <NUM> starts the defrosting operation. When determining that the atomic clock <NUM> has reached the scheduled end time of the defrosting operation, the second control unit <NUM> ends the defrosting operation. When determining that the atomic clock <NUM> has reached the scheduled start time of the defrosting operation, the third control unit <NUM> starts the defrosting operation. When determining that the atomic clock <NUM> has reached the scheduled end time of the defrosting operation, the third control unit <NUM> ends the defrosting operation. As described above, the control units <NUM>, <NUM>, and <NUM> of the present embodiment separately control the starting and ending of the defrosting operation.

In addition, the control units <NUM>, <NUM>, and <NUM> start the refrigerating-cooling operation at a preset second start time (scheduled start time of refrigerating-cooling operation) and end the refrigerating-cooling operation at a preset second end time (scheduled end time of refrigerating-cooling operation). More specifically, when determining that the atomic clock <NUM> has reached the scheduled start time of the refrigerating-cooling operation, the first control unit <NUM> performs the refrigerating-cooling operation. When determining that the atomic clock <NUM> has reached the scheduled end time of the refrigerating-cooling operation, the first control unit <NUM> ends the refrigerating-cooling operation. When determining that the atomic clock <NUM> has reached the scheduled start time of the refrigerating-cooling operation, the second control unit <NUM> performs the refrigerating-cooling operation. When determining that the atomic clock <NUM> has reached the scheduled end time of the refrigerating-cooling operation, the second control unit <NUM> ends the refrigerating-cooling operation. When determining that the atomic clock <NUM> has reached the scheduled start time of the refrigerating-cooling operation, the third control unit <NUM> performs the refrigerating-cooling operation. When determining that the atomic clock <NUM> has reached the scheduled end time of the refrigerating-cooling operation, the third control unit <NUM> ends the refrigerating-cooling operation. In the present embodiment, a defrosting period (period from the scheduled start time of the defrosting operation to the scheduled end time of the defrosting operation) and a refrigerating-cooling period (period from the scheduled start time of the refrigerating-cooling operation to the scheduled end time of the refrigerating-cooling operation) are set so that the defrosting period does not overlap with the refrigerating-cooling period.

Each of the control units <NUM>, <NUM>, and <NUM> of the present embodiment may set the first start time to a time after a first predetermined time elapses from the second start time, which is the scheduled start time of the refrigerating-cooling operation. In addition, each of the control units <NUM>, <NUM>, and <NUM> may set the first end time, which is the scheduled end time of the defrosting operation, to a time after a second predetermined time elapses from the first start time, and may set a third start time, that is, a resuming time of the refrigerating-cooling operation, to a time after a third predetermined time elapses from the first end time. As described above, the control units <NUM>, <NUM>, and <NUM> may use the atomic clocks <NUM>, <NUM>, and <NUM> to interrupt the refrigerating-cooling operation and perform the defrosting operation. In addition, multiple first start times and multiple first end times may be set so that the refrigerating-cooling operation is interrupted with the defrosting operation a number of times. The first predetermined time, the second predetermined time, and the third predetermined time may be set in any manner. In an example, the second predetermined time is shorter than the first predetermined time, and the third predetermined time is shorter than the second predetermined time. In an example, the third predetermined time may be set to zero seconds so that the refrigerating-cooling operation is resumed immediately after the defrosting operation ends.

The present embodiment has the following advantages. (<NUM>-<NUM>) The control units <NUM>, <NUM>, and <NUM> start the defrosting operation or the refrigerating-cooling operation based on the times of the atomic clocks <NUM>, <NUM>, and <NUM> mounted on the refrigeration apparatuses <NUM> of the containers 1A to 1C. With this configuration, information of the atomic clocks <NUM>, <NUM>, and <NUM> mounted on the refrigeration apparatuses <NUM> of the containers 1A to 1C is used to control start of the refrigerating-cooling operation and start of the defrosting operation of the refrigeration apparatuses <NUM>. As a result, the refrigeration apparatuses <NUM> synchronously start the refrigerating-cooling operation, and the refrigeration apparatuses <NUM> synchronously start the defrosting operation. Thus, variations in the operation of the refrigeration apparatuses <NUM> are limited.

The above embodiments exemplify, without any intention to limit, applicable forms of a refrigeration system according to the present invention. In addition to the embodiments described above, the refrigeration system is applicable to, for example, modified examples of the above embodiments that are described below and combinations of at least two of the modified examples that do not contradict each other. In the following modified examples, the same reference numerals are given to those elements that are the same as the corresponding elements of the above embodiments. Such elements will not be described in detail.

In the first embodiment, as shown in <FIG>, the first communication unit <NUM> of the first controller <NUM>, the second communication unit <NUM> of the second controller <NUM>, and the third communication unit <NUM> of the third controller <NUM> may be configured to perform wireless communication with each other. In this configuration, the communication line <NUM> is omitted. The communication units <NUM>, <NUM>, and <NUM> that are configured to perform wireless communication with each other are, for example, a universal serial bus (USB) adapter configured to perform wireless communication such as a Wi-Fi (wireless LAN) slave device. The USB adapter is connected to each of the communication ports <NUM>, <NUM>, and <NUM>.

In the synchronized control of the second embodiment, when the first container 1A starts the defrosting operation, the first control unit <NUM> may transmit the defrosting start synchronization signal to the second control unit <NUM> and the third control unit <NUM> through the first communication unit <NUM>. Alternatively, when the defrosting operation start signal is received from the second control unit <NUM> or the third control unit <NUM>, the first control unit <NUM> may transmit the defrosting start synchronization signal to the second control unit <NUM> and the third control unit <NUM> through the first communication unit <NUM>. As described above, the first control unit <NUM> transmits the defrosting start synchronization signal, instead of the defrosting operation start signal, to the second control unit <NUM> and the third control unit <NUM> to synchronously start the defrosting operation of the containers 1A to 1C.

In the third embodiment not forming part of the present invention, when the main control unit <NUM> executes the synchronized control, the defrosting operation or the refrigerating-cooling operation may be started based on a clock (e.g., clock in the cloud) of the server <NUM>. With this configuration, information of the clock of the server <NUM> is used to control start of the refrigerating-cooling operation and start of the defrosting operation of the refrigeration apparatuses <NUM>. As a result, the refrigeration apparatuses <NUM> synchronously start the refrigerating-cooling operation, and the refrigeration apparatuses <NUM> synchronously start the defrosting operation. Thus, variations in the operation of the refrigeration apparatuses <NUM> are limited.

In the fourth embodiment, the first communication unit <NUM> may be added to the first controller <NUM>, the second communication unit <NUM> may be added to the second controller <NUM>, and the third communication unit <NUM> may be added to the third controller <NUM>. In this case, the controllers <NUM>, <NUM>, and <NUM> may send information related to operations performed by the containers 1A to 1C to each other.

In the first and third embodiments, the refrigeration system <NUM> may control the refrigeration apparatuses <NUM> of the containers 1A to 1C so that in the refrigeration apparatuses <NUM> of the containers 1A to 1C, a refrigeration apparatus <NUM> performing the defrosting operation coincides with a refrigeration apparatus <NUM> performing an operation other than the defrosting operation. More specifically, in the separated operation of the refrigeration system <NUM>, one of the refrigeration apparatuses <NUM> performing the defrosting operation may coincide with one of the refrigeration apparatuses <NUM> performing an operation other than the defrosting operation (e.g., refrigerating-cooling operation). In this case, the refrigeration system <NUM> determines whether to perform the defrosting operation based on, for example, the amount of frost collected on the evaporators <NUM> and the differences (Tv1-Tb1, Tv2-Tb2, Tv3-Tb3) between the intake air temperature and the blow-out air temperature of the containers 1A to 1C.

In each embodiment, in the separated operation of the containers 1A to 1C, the refrigeration system <NUM> may decrease cooling power of the refrigeration apparatus <NUM> corresponding to a location where the storage temperature is relatively low and increase cooling power of the refrigeration apparatus <NUM> corresponding to a location where the storage temperature is relatively high. The refrigeration system <NUM> controls the refrigerating-cooling operation of the refrigeration apparatuses <NUM> of the containers 1A to 1C so that the storage temperatures of the containers 1A to 1C reach the medium one of the storage temperatures of the containers 1A to 1C. In an example, when the storage temperature of the first container 1A is the lowest, the storage temperature of the third container 1C is the highest, and the storage temperature of the second container 1B is higher than the storage temperature of the first container 1A and lower than the storage temperature of the third container 1C, the refrigeration system <NUM> sets the storage set temperature to the storage temperature of the second container 1B. Thus, the refrigeration system <NUM> decreases cooling power of the refrigeration apparatus <NUM> of the first container 1A having the low storage temperature and increases cooling power of the refrigeration apparatus <NUM> of the third container 1C having the high storage temperature.

When the master device malfunctions as the master device, the setting change control of each embodiment may synchronize the master device with the slave devices and control the master device having the mulfunction based on operating information of the slave devices. More specifically, when the first controller <NUM> used as the master device malfunctions as the master device, the second control unit <NUM> synchronizes with the first controller <NUM> and operates the first controller <NUM> based on information (operating information) related to the operation of the second container 1B. Instead of the second control unit <NUM>, the third control unit <NUM> may synchronize with the first controller <NUM> and operate the first controller <NUM> based on information (operating information) related to the operation of the second container 1B.

In the setting change control of each embodiment, a case in which the master device malfunctions as the master device includes a case in which the clock <NUM> of the master device (first controller <NUM>) is faulty. In this case, one of the slave devices having a non-faulty clock is changed to the master device, and the master device (first controller <NUM>) is changed to a slave device. The new master device executes synchronized control based on the non-faulty clock. The specific procedures are shown in the flowchart of the setting change control in <FIG>. In step S61, the second control unit <NUM> determines whether the clock <NUM> of the master device is faulty. When determining that the clock <NUM> of the master device is not faulty (step S61: NO), the second control unit <NUM> temporarily ends the process. When determining that the clock <NUM> of the master device is faulty (step S61: YES), the second control unit <NUM> proceeds to step S62 and sets the second controller <NUM> to the master device and sets the first controller <NUM> to a slave device. In step S63, instead of the first control unit <NUM>, the second control unit <NUM> executes the synchronized control. Synchronized control executed by the second control unit <NUM> is executed based on the clock <NUM> of the second controller <NUM>. The setting change control of this modified example may be combined and executed with the setting change control of each embodiment.

In the setting change control of the embodiments and the modified example, when the master device malfunctions as the master device, the container having the malfunctioning master device may be operated based on information of the operation of a container located adjacent to the container having the new master device.

In the setting change control of the embodiments and the modified example, when the master device malfunctions as the master device, if the intake air temperature detector <NUM> and the blow-out air temperature detector <NUM> are not faulty, the container having the malfunctioning master device may control the operation based on the operating information of the container. In this case, the control unit of the container that is newly set to the master device transmits the defrosting start synchronization signal, the defrosting end synchronization signal, and the refrigerating-cooling start synchronization signal to the control unit of the container having the malfunctioning master device so that the containers 1A to 1C synchronize with each other.

In each embodiment, the operating units <NUM>, <NUM>, and <NUM> of the controllers <NUM>, <NUM>, and <NUM> may be configured to perform only one of the setting of the master device and the slave devices and the setting of the synchronized control, which synchronously operates the refrigeration apparatuses <NUM>, and the separated control, which separately operates the refrigeration apparatuses <NUM>.

In each embodiment, the operator may change the setting related to the containers 1A to 1C with a remote operation using an external device. In an example, as shown in <FIG>, the operator operates a tablet <NUM>, which is an example of the external device, to change the setting related to the containers 1A to 1C. The tablet <NUM> is configured to communicate with the controllers <NUM>, <NUM>, and <NUM>. The setting related to the containers 1A to 1C includes, for example, the selecting of the synchronized control and the separated control and the setting of the master device and the slave devices. A smartphone may be used instead of the tablet <NUM>. More specifically, the operator may use an external device configured to communicate with the containers 1A to 1C to change the setting related to the containers 1A to 1C. With this configuration, the operator may operate an external device to manually perform the setting of the master device and the slave devices and the setting of control (synchronized control) that synchronously operates the refrigeration apparatuses <NUM> and control (separated control) that separately operates the refrigeration apparatuses <NUM>.

In each embodiment, at least one of the containers 1A to 1C may be joined in the first direction X. In this case, the wall opposite to the wall <NUM>, on which the refrigeration apparatus <NUM> is disposed, in the first direction X may be removed to form an opening in each container. The openings may be opposed to each other to join the containers.

In each embodiment, multiple containers including the refrigeration apparatuses <NUM> may be joined to a container that does not include the refrigeration apparatus <NUM> to form a stationary storage.

In each embodiment, the refrigeration system <NUM> has a configuration in which the first container 1A, the second container 1B, and the third container 1C are joined. The number of containers in the refrigeration system <NUM> is not limited to this and may be changed to any number that is greater than or equal to two. For example, a refrigeration system may have a configuration in which four or more containers are joined.

Claim 1:
A refrigeration system comprising:
multiple containers (1A, 1B, 1C) joined together to form a storage, the multiple containers (1A, 1B, 1C) each including a refrigeration apparatus (<NUM>), wherein
the refrigeration apparatuses (<NUM>) of the containers (1A, 1B, 1C) each include a control unit (<NUM>, <NUM>, <NUM>) and a communication unit (<NUM>, <NUM>, <NUM>),
the communication units (<NUM>, <NUM>, <NUM>) of the refrigeration apparatuses (<NUM>) of the containers (1A, 1B, 1C) are configured so that the refrigeration apparatuses (<NUM>) of the containers (1A, 1B, 1C) connect and communicate with each other,
the control unit (<NUM>) of one of the refrigeration apparatuses (<NUM>) of the containers (1A, 1B, 1C) is set to a main control unit,
the control unit (<NUM>, <NUM>) of a remaining one of the refrigeration apparatuses is set to a slave control unit,
the communication units (<NUM>, <NUM>, <NUM>) in the refrigeration apparatuses (<NUM>) of the containers (1A, 1B, 1C) allow the main control unit (<NUM>) and the slave control unit (<NUM>, <NUM>) to communicate with each other,
characterized in that the containers (1A,1B,1C) when joined together define a single accommodation space S, and in that
when a defrosting operation is performed, the main control unit (<NUM>) sends time information of a clock (<NUM>) to the slave control unit (<NUM>, <NUM>) and causes the refrigeration apparatuses (<NUM>) of the containers (1A, 1B, 1C) to operate in synchronization with each other based on the time information of the clock (<NUM>).