JP7633546B2 - Container refrigeration equipment - Google Patents

Description

This disclosure relates to a container refrigeration system.

Container refrigeration systems that cool the inside of a container are known. Food and other objects are stored in the container. Container refrigeration systems cool the air inside the container using an evaporator. As a result, the temperature around the object is maintained below a predetermined temperature.

Patent No. 5625582

When the air inside a container is rapidly cooled by a container refrigeration system, the pressure inside the container drops. As a result, the pressure inside the container becomes negative, lower than atmospheric pressure, and there is a risk that the container may be damaged.

The present disclosure aims to prevent damage to a container caused by a drop in pressure inside the container.

The first aspect is directed to a container refrigeration system, and includes a pressure detection unit (P) that detects the pressure inside a container (1), a pressure equalization mechanism (40, 80) that equalizes the pressure inside and outside the container (1), and a control unit (100) that controls the pressure equalization mechanism (40, 80) to perform a pressure equalization operation to equalize the pressure inside and outside the container (1) when the pressure detected by the pressure detection unit (P) is lower than a predetermined first pressure that is lower than atmospheric pressure during a cooling operation for cooling the inside of the container (1). Here, the "pressure detection unit" includes not only a means for directly detecting pressure using a sensor, but also a means for indirectly detecting pressure using an index for estimating pressure.

In the first aspect, in a cooling operation for cooling the inside of the container (1), when the pressure inside the container (1) is lower than a predetermined first pressure, the control unit (100) causes the pressure equalization mechanism (40, 80) to execute a pressure equalization operation. In the pressure equalization operation, the pressure equalization mechanism (40, 80) equalizes the pressure inside and outside the container (1), thereby preventing the internal pressure of the container (1) from becoming negative. As a result, damage to the container (1) can be prevented.

In the second aspect, in the first aspect, the pressure equalization mechanism (40, 80) is a ventilation device (40) that ventilates the container (1), and the ventilation device (40) introduces air outside the container (1) into the interior of the container (1) during the pressure equalization operation.

In the second mode of pressure equalization, the ventilation device (40) as a pressure equalization mechanism introduces air from outside the container (1) into the container (1). As a result, the internal pressure of the container (1) can be prevented from becoming negative, and damage to the container (1) can be prevented.

In the third aspect, in the first aspect, the pressure equalization mechanism (40, 80) is an adjustment device (80) that adjusts the composition of the air inside the container (1), and the adjustment device (80) introduces air outside the container (1) into the container (1) during the pressure equalization operation.

In the third embodiment of the pressure equalization operation, the adjustment device (80) as a pressure equalization mechanism introduces air from outside the container (1) into the container (1). As a result, the internal pressure of the container (1) can be prevented from becoming negative, and damage to the container (1) can be prevented.

In a fourth aspect, in any one of the first to third aspects, the control unit (100) terminates the pressure equalization operation when the pressure detected by the pressure detection unit (P) during the pressure equalization operation is higher than a predetermined second pressure that is lower than atmospheric pressure.

In the fourth aspect, during the pressure equalization operation, if the pressure inside the container (1) is higher than a predetermined first pressure, the control unit (100) terminates the pressure equalization operation. This makes it possible to quickly prevent the air temperature inside the container (1) from increasing due to the pressure equalization operation.

In the fifth aspect, in the fourth aspect, the control unit (100) terminates the pressure equalization operation when the pressure in the container (1) is higher than a predetermined first pressure and the temperature of the air in the container (1) is lower than a predetermined temperature.

In the fifth aspect, the pressure equalization operation is terminated when the pressure inside the container (1) is higher than a predetermined first pressure and the temperature of the air inside the container (1) is lower than a predetermined temperature. If the pressure equalization operation is terminated under conditions where the temperature of the air inside the container (1) is relatively high, the air temperature may further decrease as a result of the cooling operation, causing the negative pressure inside the container (1) to increase again. In contrast, in the present invention, the pressure equalization operation is terminated after the temperature of the air inside the container (1) becomes relatively low, so that the negative pressure inside the container (1) can be prevented from increasing again during the subsequent cooling operation. As a result, damage to the container (1) can be prevented.

In a sixth aspect, in any one of the first to fifth aspects, when the pressure detected by the pressure detection unit (P) during the first cooling operation after start-up of the container refrigeration system is lower than a predetermined first pressure that is lower than atmospheric pressure, the control unit (100) controls the pressure equalization mechanism (40, 80) to perform a first pressure equalization operation as the pressure equalization operation.

In the sixth aspect, during the first cooling operation after startup of the container refrigeration system, if the pressure detected by the pressure detection unit (P) is lower than a predetermined first pressure that is lower than atmospheric pressure, a first pressure equalization operation is performed. Therefore, even if the temperature of the air inside the container (1) is suddenly cooled by the first cooling operation, damage to the container (1) can be suppressed.

In a seventh aspect, in any one of the first to fifth aspects, the control unit (100) executes a second pressure equalization operation as the pressure equalization operation when the pressure detected by the pressure detection unit (P) is lower than a predetermined first pressure that is lower than atmospheric pressure after the door (D) of the container (1) is opened or closed during the cooling operation.

In the seventh aspect, after the door (D) is temporarily opened during the cooling operation, if the pressure detected by the pressure detection unit (P) is lower than a predetermined first pressure that is lower than atmospheric pressure, the second pressure equalization operation is executed. Therefore, even if relatively high-temperature air enters the container (1) when the door (D) is opened and this air is rapidly cooled, damage to the container (1) can be suppressed.

In the eighth aspect, in the seventh aspect, when the pressure detected by the pressure detection unit (P) during the first cooling operation after start-up of the container refrigeration system is lower than a predetermined first pressure lower than atmospheric pressure, the control unit (100) controls the pressure equalization mechanism (40, 80) to perform a first pressure equalization operation as the pressure equalization operation, and in the second pressure equalization operation, the pressure equalization mechanism (40, 80) introduces air outside the container (1) into the inside of the container (1) at a flow rate higher than that in the first pressure equalization operation.

In the eighth aspect, in the second pressure equalization operation, the pressure equalization mechanism (40, 80) introduces a larger flow rate of outside air into the container (1) than in the first pressure equalization operation. This is because, when relatively high-temperature air is cooled inside the container (1) after the door (D) is temporarily opened, the internal pressure of the container (1) is likely to decrease more quickly than during the initial cooling operation after startup of the container refrigeration system.

In the ninth aspect, in any one of the first to eighth aspects, the control unit (100) controls the pressure equalization mechanism (40, 80) in the cooling operation so that the flow rate of air introduced from the outside to the inside of the container (1) decreases as the temperature of the air inside the container (1) decreases.

In the ninth aspect, when the temperature of the air in the container (1) is high and the negative pressure in the container (1) is likely to increase, the amount of outside air introduced is large. When the temperature of the air in the container (1) is low and the cooling load due to the introduction of outside air is likely to increase, the amount of outside air introduced is small.

The tenth aspect is any one of the first to ninth aspects, in which the pressure detection unit (P) is a pressure sensor (53).

In the tenth aspect, the internal pressure of the container (1) is detected by a pressure sensor (53).

The eleventh aspect is any one of the first to ninth aspects, and includes a drain pipe (60) that discharges condensed water generated inside the container (1) to the outside of the container (1) and has a trap section (61) in which the condensed water accumulates, and the pressure detection section (P) detects the pressure inside the container (1) based on the water level in the trap section (61).

In the eleventh aspect, the pressure inside the container (1) is detected based on the water level in the trap portion (61) of the drain pipe (60). This is because when the pressure inside the container (1) changes, the water level in the trap portion (61) changes.

In a twelfth aspect, in any one of the first to ninth aspects, the pressure detection unit (P) detects the pressure inside the container (1) based on the temperature of the air inside the container (1) before or at the start of the cooling operation and the temperature of the air inside the container (1) during the cooling operation.

In the twelfth aspect, the pressure inside the container (1) is detected based on the temperature of the air inside the container (1) before and after the start of the cooling operation. This is because when the temperature of the air inside the container (1) decreases due to the cooling operation, the pressure inside the container (1) changes.

In a thirteenth aspect, in any one of the first to ninth aspects, a gas sensor (71, 72) is provided for detecting the concentration of a gas component in the air inside the container (1), and the pressure detection unit (P) detects the pressure inside the container (1) based on the detected concentration of the gas sensor (71, 72) before or at the start of the cooling operation and the detected concentration of the gas sensor (71, 72) during the cooling operation.

In the thirteenth aspect, the pressure inside the container (1) is detected based on the concentrations detected by the gas sensors (71, 72) before and after the start of the cooling operation. This is because there is a correlation between the concentrations detected by the gas sensors (71, 72) and the pressure inside the container (1).

FIG. 1 is a front perspective view of a container refrigeration unit according to an embodiment. FIG. 2 is a vertical cross-sectional view of a container refrigeration unit. FIG. 3 is a block diagram of the main components of the container refrigeration system. FIG. 4 is a piping diagram of a container refrigeration unit. Figure 5 is a schematic front view of the ventilator, with Figure 5(A) showing the lid in a closed position, Figure 5(B) showing the lid in an intermediate position, and Figure 5(C) showing the lid in a fully open position. FIG. 6 is a perspective view of the container as seen from the rear side (door side). FIG. 7 is a flowchart for explaining the control operation of the pressure equalization mechanism. FIG. 8 is a flowchart for explaining the control of the pressure equalizing mechanism in the first mode. FIG. 9 is a flowchart for illustrating the control of the pressure equalizing mechanism in the second mode. FIG. 10 is a schematic diagram showing the drain pipe and the pressure detection unit of the modified example 1A, and shows a state in which the pressure inside the container is equal to the pressure outside the container. FIG. 11 is a schematic diagram showing the drain pipe and the pressure detection unit of the modification 1A, illustrating a state in which the pressure inside the container is lower than the pressure outside the container. FIG. 12 is a diagram of modified example 1C corresponding to FIG. FIG. 13 is a diagram of the modified example 1D, which corresponds to FIG. FIG. 14 is a diagram of modified example 2A corresponding to FIG. FIG. 15 is a diagram of modified example 2B corresponding to FIG.

Embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below, and various modifications are possible without departing from the technical spirit of the present disclosure. Each drawing is intended to conceptually explain the present disclosure, and therefore dimensions, ratios, or numbers may be exaggerated or simplified as necessary for ease of understanding.

(1) Overall Configuration of the Container Refrigeration Unit The container refrigeration unit (10) will be described. In the following description, the terms "front,""rear,""upper,""lower,""right," and "left" are based on the directions indicated by the arrows in FIG. 1.

As shown in Figures 1 and 2, the container refrigeration unit (10) is provided in a container (1). The container (1) is used for marine transportation. The container (1) is a refrigerated container that cools the air inside the container (1). The container (1) has a container body (2) and a container refrigeration unit (10). The container body (2) stores objects such as food and plants. The container refrigeration unit (10) cools the air in the interior space (3) of the container body (2). As shown in Figure 2, a front opening (4) is formed in the front of the container body (2). The container refrigeration unit (10) is attached to the container body (2) so as to close the front opening (4) of the container body (2).

As shown in FIG. 3, the container refrigeration system (10) has a cooling unit (10A) for cooling the interior space (3) and a ventilation system (40) for ventilating the interior space (3).

(2) Cooling Unit As shown in Figures 1 and 2, the cooling unit (10A) has a casing (11). The casing (11) constitutes a lid for the front opening (4) of the container body (2). The casing (11) has a casing body (12) and a partition plate (13). The casing body (12) separates the container body (2) into an external space (5), which is an external space, and the internal space (3). The partition plate (13) is located on the back side (rear side) of the casing (11).

The cooling unit (10A) has a compressor (25), an external heat exchanger (26), and an external fan (27) as devices arranged outside the cabinet. The cooling unit (10A) has an internal heat exchanger (29) and an internal fan (30) as devices arranged inside the cabinet.

(2-1) Casing Body As shown in Fig. 2, the casing body (12) has a flat plate portion (12a) and a recessed portion (12b). The flat plate portion (12a) is formed on the upper part of the casing body (12) so as to be substantially flush with the front opening (4) of the casing (11). As shown in Fig. 1, an inspection window (22) is provided in the flat plate portion (12a). The inspection window (22) is located in the right-hand portion of the flat plate portion (12a). The inspection window (22) is a transparent window through which the inside of the casing body (12) can be seen.

The recess (12b) is formed in the lower part of the casing (11). The recess (12b) is recessed rearward from the lower end of the flat plate portion (12a). An external storage space (14) is formed in front of the recess (12b). An internal storage space (15) is formed above the recess (12b) and between the flat plate portion (12a) and the partition plate (13). The lower end of the recess (12b) constitutes the bottom plate (12c). The bottom plate (12c) extends across both the left and right ends of the casing body (12).

The casing body (12) is formed by stacking an external casing (16), an insulating layer (17), and an internal casing (18) in the thickness direction (front-rear direction). The external casing (16) faces the external space (5). The internal casing (18) faces the interior of the cabinet. The insulating layer (17) is provided between the external casing (16) and the internal casing (18). The external casing (16) is made of an aluminum material. The internal casing (18) is made of fiber-reinforced plastic (FRP). The insulating layer (17) is made of foamed resin.

(2-2) Partition Plate and Air Passage As shown in FIG. 2, the partition plate (13) is a plate-like member located on the rear side of the recessed portion (12b). The partition plate (13) extends in the vertical direction so as to be spaced a predetermined distance from the rear surface of the recessed portion (12b). An internal passage (19) through which the internal air flows is formed between the casing body (12) and the partition plate (13). An inlet (20) is formed between the upper end of the partition plate (13) and the upper wall (2a) of the container body (2). The inlet (20) connects the internal space (3) to the inlet end of the internal passage (19). An outlet (21) is formed between the lower end of the partition plate (13) and the lower wall (2b) of the container body (2). The outlet (21) connects the internal space (3) to the outlet end of the internal passage (19).

(2-3) Equipment in the Exterior Space A compressor (25), an exterior heat exchanger (26), and an exterior fan (27) are provided in the exterior storage space (14). The compressor (25) is installed on the bottom plate (12c) of the casing (11). The compressor (25) is disposed toward the lower part of the exterior storage space (14). The compressor (25) is disposed toward the right of the exterior storage space (14).

The external fan (27) is located toward the upper part of the external storage space (14). The external fan (27) is a propeller fan. As shown in FIG. 2, an external passage (28) through which the outside air flows is formed on the rear side of the external fan (27).

The external heat exchanger (26) is provided in the external storage space (14) at a height position between the external fan (27) and the compressor (25). The external heat exchanger (26) is located in the external passage (28). The external heat exchanger (26) is a fin-and-tube type heat exchanger.

(2-4) Equipment in the Internal Space An internal heat exchanger (29) and an internal fan (30) are provided in the internal storage space (15). The internal heat exchanger (29) is supported by the casing (11) so as to span the casing body (12) and the partition plate (13). The internal heat exchanger (29) is a fin-and-tube type heat exchanger.

(2-5) Refrigerant Circuit As shown in FIG. 4, the cooling unit (10A) has a refrigerant circuit (R). The refrigerant circuit (R) is filled with a refrigerant. The refrigerant circuit (R) performs a vapor compression refrigeration cycle by circulating the refrigerant. As the refrigerant in the refrigerant circuit (R), for example, propane or carbon dioxide, which is a natural refrigerant, is used.

The refrigerant circuit (R) mainly includes a compressor (25), an external heat exchanger (26), an expansion valve (31), and an internal heat exchanger (29).

The compressor (25) compresses the sucked refrigerant. The compressor (25) discharges the compressed refrigerant. A discharge pipe (32) is connected to the discharge section of the compressor (25). A suction pipe (33) is connected to the suction section of the compressor (25). An accumulator (34) is provided in the suction pipe (33). The accumulator (34) is a container that stores liquid refrigerant.

The external heat exchanger (26) exchanges heat between the refrigerant flowing therethrough and the air outside the cabinet. The gas end of the external heat exchanger (26) communicates with the discharge pipe (32). The liquid end of the external heat exchanger (26) is connected to the liquid end of the internal heat exchanger (29) via the liquid pipe (35). The external heat exchanger (26) functions as a radiator (condenser) that radiates heat from the refrigerant to the air.

The expansion valve (31) is provided in the liquid pipe (35). The expansion valve (31) is an expansion mechanism that reduces the pressure of high-pressure refrigerant to low-pressure refrigerant. The expansion valve (31) is an electronic expansion valve with an adjustable opening. The expansion mechanism may be a capillary tube or an expander. A receiver (36) is provided in the liquid pipe (35) between the external heat exchanger (26) and the expansion valve (31). The receiver (36) is a container that stores excess refrigerant in the refrigerant circuit (R).

The internal heat exchanger (29) exchanges heat between the refrigerant flowing therethrough and the internal air. The gas end of the internal heat exchanger (29) communicates with the suction pipe (33). The internal heat exchanger (29) functions as an evaporator in which the refrigerant absorbs heat from the air.

The refrigerant circuit (R) has a bypass pipe (37). The inlet end of the bypass pipe (37) communicates with the discharge pipe (32), and the outlet end of the bypass pipe (37) communicates with the liquid pipe (35). The bypass pipe (37) sends the refrigerant discharged from the compressor (25) to the internal heat exchanger (29), bypassing the external heat exchanger (26).

The refrigerant circuit (R) is provided with a first valve (38) and a second valve (39). The first valve (38) is provided between the discharge side of the compressor (25) and the gas end of the external heat exchanger (26), and downstream of the connection of the bypass pipe (37). The second valve (39) is provided in the bypass pipe (37). The first valve (38) and the second valve (39) are configured as solenoid on-off valves. The first valve (38) and the second valve (39) may be flow rate control valves whose opening degree is adjustable.

(3) Ventilation Device The configuration of the ventilation device (40) will be described with reference to Figs. 1, 2, and 5. The ventilation device (40) ventilates the internal space (3) of the container body (2). The ventilation device (40) of this embodiment has an air supply function of supplying outside air, which is outdoor air, to the internal space (3) and an exhaust function of discharging the internal air to the external space (5). In this embodiment, the ventilation device (40) also serves as a pressure equalization mechanism.

As shown in FIG. 1, the ventilation device (40) is disposed in the left-side portion of the flat plate portion (12a) of the casing body (12). As shown in FIG. 2, the ventilation device (40) is provided in a ventilation mounting opening (6) formed in the front surface of the casing body (12). The ventilation mounting opening (6) penetrates the casing body (12) from the front to the rear. The ventilation mounting opening (6) is formed across the exterior casing (16), the insulating layer (17), and the interior casing (18).

An air supply passage (41) and an exhaust passage (42) are formed inside the ventilation device (40). The air supply passage (41) and the exhaust passage (42) communicate between the internal space (3) and the external space (5). Specifically, the inflow end of the air supply passage (41) communicates with the external space (5). The outflow end of the air supply passage (41) communicates with the primary side (upstream side) of the internal fan (30) in the internal passage (19). The inflow end of the exhaust passage (42) communicates with the secondary side (downstream side) of the internal fan (30) in the internal passage (19). The outflow end of the exhaust passage (42) communicates with the external space (5).

The ventilation device (40) has a ventilation fan. The ventilation fan is constituted by the above-mentioned internal fan (30). In this embodiment, the internal fan (30) is used both as the ventilation device (40) and the cooling unit (10A). When the internal fan (30) is driven, outside air from the external space (5) is supplied to the internal space (3) through the air supply passage (41). At the same time, the internal air from the internal space (3) is exhausted to the external space (5) through the exhaust passage (42).

As shown in Figs. 2 and 5, an air supply communication port (41a) is formed at the end of the air supply passage (41) facing the external space (5). An exhaust communication port (42a) is formed at the end of the exhaust passage (42) facing the external space (5).

As shown in FIG. 2, the ventilation device (40) has a motor (43), a drive shaft (44) that is rotationally driven by the motor (43), and an open/close cover (45) that is connected to the drive shaft (44). The motor (43) and the drive shaft (44) are housed in a casing of the ventilation device (40). The motor (43) is a stepping motor. The drive shaft (44) is directly connected to the motor (43). The drive shaft (44) may be indirectly connected to the motor (43) via a pinion or gear.

The opening/closing lid (45) is provided in front of the drive shaft (44). The opening/closing lid (45) is configured to be rotatable around the axis of the drive shaft (44). The opening/closing lid (45) opens and closes the air supply passage (41) and the exhaust passage (42) depending on the angle of rotation. The opening/closing lid (45) constitutes an opening adjustment mechanism that adjusts the opening of the air supply passage (41) and the exhaust passage (42).

As shown in FIG. 5, the opening/closing cover (45) is formed with an air supply opening (46) and an exhaust opening (47). The air supply opening (46) is configured to be able to communicate with the air supply communication port (41a). The exhaust opening (47) is configured to be able to communicate with the exhaust communication port (42a).

Specifically, when the opening/closing lid (45) is at the first rotation angle (closed position) shown in FIG. 5(A), the entire air supply communication port (41a) is covered by the opening/closing lid (45), and the entire exhaust communication port (42a) is covered by the opening/closing lid (45). As a result, the air supply passage (41) and the exhaust passage (42) are in a fully closed state.

When the opening/closing cover (45) is at the second rotation angle (fully open position) shown in FIG. 5(C), the entire air supply communication port (41a) overlaps with the air supply opening (46), and the entire exhaust communication port (42a) overlaps with the exhaust opening (47). Therefore, the air supply passage (41) and the exhaust passage (42) are fully open.

When the opening/closing cover (45) is at the third rotation angle (intermediate position) shown in FIG. 5(B), a portion of the air supply communication port (41a) overlaps with the air supply opening (46) in the axial direction, and a portion of the exhaust communication port (42a) overlaps with the exhaust opening (47) in the axial direction. The intermediate position is a position between the closed position and the fully open position. Therefore, the opening degree of the air supply passage (41) and the exhaust passage (42) is smaller than the fully open state.

By adjusting the rotation angle of the opening/closing lid (45) between the closed position and the fully open position, the opening degree of the air supply passage (41) and the exhaust passage (42) is adjusted, and further the ventilation volume of the ventilation device (40) is adjusted.

(4) Sensors The container refrigeration system (10) has a plurality of sensors. As shown in Figures 2 and 3, the plurality of sensors include an inside compartment temperature sensor (51), an outside compartment temperature sensor (52), and a pressure sensor (53).

The internal temperature sensor (51) detects the temperature of the internal air in the container (1). The internal temperature sensor (51) is disposed upstream of the internal fan (30) in the air flow in the internal passage (19). The internal temperature sensor (51) is disposed near the inlet (20) of the internal passage (19).

The outside temperature sensor (52) detects the temperature of the outside air outside the container (1). The outside temperature sensor (52) is disposed upstream of the air flow in the external passage (28) from the external heat exchanger (26). The outside temperature sensor (52) is disposed near the inlet of the external passage (28).

The pressure sensor (53) is an example of a pressure detection unit (P). The pressure sensor (53) detects the pressure inside the container (1). The pressure sensor (53) is disposed in the internal passage (19). The pressure sensor (53) is disposed, for example, upstream of the air flow in the internal passage (19) from the internal fan (30), but may be disposed downstream of the air flow in the internal passage (19) from the internal fan (30).

(5) Control Unit and Operation Unit As shown in Figure 3, the container refrigeration system (10) has a control unit (100). The control unit (100) controls the cooling unit (10A) and the ventilation system (40). The control unit (100) includes a microprocessor, an electric circuit, and an electronic circuit. The microprocessor includes a CPU (Central Processing Unit), a memory, a communication interface, analog input/output, and a contact input/output interface. The memory stores various programs executed by the CPU and data used by the programs.

The control unit (100) controls each device of the cooling unit (10A). Specifically, the control unit (100) controls the rotation speed of the compressor (25), the rotation speed of the internal fan (30), the rotation speed of the external fan (27), the opening of the expansion valve (31), and the like. The control unit (100) controls the motor (43) of the ventilation device (40). The control unit (100) adjusts the opening of the supply passage (41) and the exhaust passage (42) of the ventilation device (40), and further adjusts the ventilation volume of the ventilation device (40).

As shown in FIG. 3, the container refrigeration unit (10) has an operation unit (110). The operation unit (110) is composed of, for example, a touch panel, a remote controller, a switch, etc., provided on the container refrigeration unit (10). The operation unit (110) may be a communication terminal connected to the container refrigeration unit (10) via a network. A user can operate the operation unit (110) to switch the operation mode of the container refrigeration unit (10) or change the set values of each operation mode. The set values include a target temperature for the interior space (3).

(6) Overview of Cooling Operation The container refrigeration system (10) performs a cooling operation. The cooling operation is an operation mode that is executed by a user or the like operating the operation unit (110).

During cooling operation, a refrigeration cycle is performed in which the refrigerant compressed by the compressor (25) condenses in the external heat exchanger (26), is decompressed by the expansion valve (31), and evaporates in the internal heat exchanger (29). Air flowing out from the internal space (3) to the internal passage (19) is cooled by the internal heat exchanger (29) functioning as an evaporator. The cooled air is sent to the internal space (3). During cooling operation, the control unit (100) controls the rotation speed of the compressor (25) based on the difference between the temperature of the internal air in the internal space (3) and the target temperature.

In the cooling operation, the control unit (100) controls the compressor (25) so that the temperature of the internal air reaches the target temperature. When the temperature of the internal air reaches the target temperature (thermo-off temperature, e.g., -18°C), the control unit (100) stops the compressor (25). As a result, the internal heat exchanger (29) is substantially in a stopped state (thermo-off state). Thereafter, when the temperature of the internal air reaches a predetermined temperature (thermo-on temperature, e.g., -16°C) higher than the target temperature, the control unit (100) operates the compressor (25) to make the internal heat exchanger (29) function as an evaporator. The control unit (100) controls the rotation speed of the compressor (25) so as to adjust the evaporation temperature of the internal heat exchanger (29). As a result, the temperature of the internal air is maintained within a predetermined target range. The thermo-off temperature corresponds to the set temperature input by the operation unit (110). The thermo-on temperature is the set temperature plus a specified temperature (e.g., 2°C).

(7) Measures against container destruction during cooling operation (7-1) Issues During the above-mentioned cooling operation, the air inside the container is cooled, thereby decreasing the temperature of the air inside the container. When the temperature of the air inside the container decreases during cooling operation, the volume of the air inside the container decreases, causing the pressure inside the container (1) to decrease, and this pressure may become a negative pressure lower than atmospheric pressure. As a result, the negative pressure inside the container (1) exceeds the withstand pressure of the container (1), causing a problem that the container (1) may be destroyed. Damage to the container (1) may occur, for example, when the container body (2) is deformed due to the negative pressure inside the container (1).

In particular, during cooling operation, the pressure in the container (1) drops rapidly during the following two periods:

The first period is a pull-down operation period. The pull-down operation is the first cooling operation after the container refrigeration system (10) is started. In other words, the pull-down operation is the first cooling operation after the container refrigeration system (10) is turned on. At the start of the pull-down operation, the temperature of the inside air is relatively high, close to the outside air temperature. In the pull-down operation, the relatively high temperature inside air is cooled to a temperature for refrigerating or freezing the object. For example, if the temperature of the inside air at the start of the pull-down operation is 30°C, this air may be cooled to a target temperature of -12°C. In this way, when the relatively high temperature inside air is cooled by a large temperature difference, the pressure inside the container (1) decreases and the negative pressure increases.

The second period is a period after the door (D) of the container (1) is temporarily opened during the cooling operation. As shown in FIG. 6, the container (1) has a door (D) for putting in and taking out an object. The door (D) is provided, for example, on the rear surface (7) of the rear side of the container (1). The door (D) opens and closes an opening formed on the rear surface and communicating with the interior space (3). In the cooling operation, the temperature of the interior air is maintained within a target range, that is, a range between the above-mentioned thermo-off temperature (−18°C) and thermo-on temperature (−16°C). When the interior heat exchanger (29) is in the thermo-off state, it is assumed that an operator temporarily opens the door (D) of the container (1) for some purpose and then closes it. When the door (D) is opened, air outside the container (1) enters the interior of the container (1). The air that enters from the outside of the container (1) to the interior is at a relatively high temperature (e.g., 30°C) compared to the temperature of the interior air (e.g., −18°C). As a result, the infiltrating air is rapidly cooled by the surrounding air inside the container. Furthermore, when the temperature of the air inside the container rises above the thermo-on temperature due to the infiltration of outside air, the compressor (25) is operated and the internal heat exchanger (29) is switched to the thermo-on state. As a result, the infiltrating air is rapidly cooled by the internal heat exchanger (29). For this reason, when the door (D) is opened or closed during cooling operation, the pressure inside the container (1) drops rapidly and the negative pressure increases. This problem is particularly noticeable when the door (D) is opened or closed when the internal heat exchanger (29) is in the thermo-off state.

Furthermore, the problem of damage to the container (1) is caused by the following. From the viewpoint of quality control of the object, the container (1) is required to have improved airtightness. The more airtight the container (1) is, the less air leaks through gaps in the container (1). As a result, the container refrigeration system (10) is more energy efficient. On the other hand, if the container (1) is more airtight, it becomes more difficult for air outside the container (1) to enter the container (1) through gaps when the inside of the container (1) becomes negative pressure during cooling operation. For this reason, the negative pressure inside the container (1) increases further as the cooling operation proceeds, and this negative pressure exceeds the withstand pressure of the container (1).

(7-2) Control of Pressure Equalization Mechanism In order to solve the above problems, the container refrigeration system (10) performs a pressure equalization operation. The pressure equalization operation is an operation of equalizing the pressure between the outside and the inside of the container (1) when the negative pressure inside the container (1) increases during the cooling operation. In other words, the pressure equalization operation is an operation of introducing the air outside the container (1) into the inside of the container (1) when the negative pressure inside the container (1) increases during the cooling operation. The pressure equalization operation of this embodiment is performed by the ventilation device (40) which is a pressure equalization mechanism. The pressure equalization operation includes a first pressure equalization operation and a second pressure equalization operation. The first pressure equalization operation is an operation of equalizing the pressure between the outside and the inside of the container (1) in the above-mentioned pull-down operation. The second pressure equalization operation is an operation of equalizing the pressure between the outside and the inside of the container (1) after the door (D) is opened and closed during the cooling operation. The first pressure equalization operation is performed in the first mode. The first mode is a control mode for controlling the pressure equalizing mechanism during pull-down operation. The second pressure equalizing operation is performed in the second mode. The second mode is a control mode for controlling the pressure equalizing mechanism after the door (D) is opened or closed.

The control of the pressure equalization mechanism will be explained in detail with reference to the flowcharts in Figures 7 to 9.

(7-2-1) Basic Control As shown in Fig. 7, when a command to start the cooling operation is received in step S11, the control unit (100) starts the cooling operation in step S12. The command to start the cooling operation is input to the control unit (100) by a user operating the operation unit (110). Note that, at the start of the cooling operation, the ventilation device (40) does not equalize the pressure between the inside and the outside of the container (1). Specifically, the opening/closing lid (45) of the ventilation device (40) is in the fully closed position.

The control unit (100) determines whether to perform a pressure equalization operation based on the pressure detected by the pressure sensor (53). The pressure detected by the pressure sensor (53) corresponds to the pressure inside the container (1). The control unit (100) determines whether to transition to the first mode or the second mode depending on the rate of change of the detected pressure until the detected pressure becomes equal to or lower than the first pressure. If the rate of change is slow, the control unit (100) transitions to the first mode, and if the rate of change is fast, the control unit (100) transitions to the second mode.

Specifically, in step S13, if the first condition is satisfied that the pressure detected by the pressure sensor (53) is equal to or lower than the first pressure, and the time Δt until the detected pressure reaches the first pressure is equal to or higher than the predetermined time t1, the control unit (100) performs the process of the first mode in step S17. The first pressure is a predetermined pressure lower than the atmospheric pressure. The detected pressure being equal to or lower than the first pressure means, in other words, that the negative pressure is equal to or higher than a predetermined value. The first pressure is, for example, a pressure equivalent to a negative pressure of 2 [KPa]. The negative pressure equivalent to the first pressure is set to a predetermined value lower than the withstand pressure of the container (1). The time Δt until the detected pressure reaches the first pressure is the time from the time ta when the detected pressure starts to decrease to the time tb when the detected pressure reaches the first pressure. The control unit (100) sets the time ta to, for example, the time when the detected pressure starts to decrease at a predetermined rate of change (gradient).

In this way, in step S13, if the time Δt until the detected pressure reaches the first pressure is relatively long, it can be determined that the pressure inside the container (1) is decreasing due to the pull-down operation. Therefore, the process proceeds to the first mode in step S17, and the control of the ventilation device (40) corresponding to the pull-down operation shown in FIG. 8 is executed.

If the condition of step S13 is not satisfied, the process proceeds to step S14. In step S14, if the first condition that the detected pressure is equal to or lower than the first pressure is satisfied and the time Δt until the detected pressure reaches the first pressure is shorter than the predetermined time t1, the control unit (100) performs the process of the second mode of step S18. When the air inside the container (1) is cooled due to the opening and closing of the door (D) during the cooling operation, the speed at which the pressure inside the container (1) decreases becomes faster compared to the pull-down operation. Therefore, if the time Δt until the detected pressure reaches the first pressure is relatively short, it can be determined that the pressure inside the container (1) is decreasing due to the opening and closing of the door (D). Therefore, the process proceeds to the second mode of step S18, and the control of the ventilation device (40) after the opening and closing of the door (D) shown in FIG. 9 is executed.

If the conditions of steps S13 and S14 are not satisfied, the process proceeds to step S15. If a command to end the cooling operation is issued in step S15, the control unit (100) ends the cooling operation in step S16. The command to end the cooling operation is input to the control unit (100) by the user operating the operation unit (110).

(7-2-2) First Mode The first mode is a control mode of the ventilation device (40) during pull-down operation. As shown in Fig. 8, when transitioning to the first mode, in step S21, the control unit (100) controls the ventilation device (40) to perform a pressure equalization operation for equalizing the pressure inside and outside the container (1). In other words, when the first condition in step S13 is satisfied during the first cooling operation (pull-down operation) after start-up of the container refrigeration system (10), the control unit (100) controls the ventilation device (40) to perform a first pressure equalization operation as a pressure equalization operation.

In step S21, the control unit (100) controls the ventilation device (40) so that a first flow rate of outside air is introduced into the container (1). Specifically, the control unit (100) adjusts the rotation angle of the open/close lid (45) of the ventilation device (40), i.e., the opening degree of the air supply passage (41) and the exhaust passage (42), so that the flow rate of air introduced into the container (1) becomes the first flow rate. By introducing outside air into the container (1), the pressure outside and inside the container (1) are equalized. As a result, the pressure inside the container (1) increases rapidly. In other words, the negative pressure inside the container (1) decreases.

Next, in step S22, if the detected pressure is higher than the second pressure and the inside temperature is equal to or lower than the first temperature, the process proceeds to step S23. In step S23, the control unit (100) controls the ventilation device (40) so that a second flow rate of outside air is introduced into the container (1). The second pressure is the same value as the first pressure and corresponds to a negative pressure of 2 [Kpa]. The second pressure may be higher than the first pressure or lower than the first pressure. The second flow rate is a predetermined flow rate smaller than the first flow rate. The first flow rate is, for example, 5 [m ³ /h], and the second flow rate is, for example, 3 [m ³ /h]. The first temperature is, for example, 10° C. The inside temperature is a value detected by the inside temperature sensor (51).

As described above, in this embodiment, when the temperature of the inside air falls below a predetermined temperature during pressure equalization, the control unit (100) reduces the amount of air introduced into the container (1). This is because when the temperature of the inside air falls, the pressure inside the container (1) does not drop significantly, and the risk of damage to the container (1) is reduced. By reducing the amount of outside air introduced, the inside air can be cooled quickly during pull-down operation. By reducing the amount of outside air introduced, the cooling load inside the container (1) can be reduced, and the pull-down operation can be completed quickly.

Next, in step S24, if the second condition that the detected pressure is higher than the second pressure is satisfied and the third condition that the internal temperature is equal to or lower than the second temperature is satisfied, the process proceeds to step S25. In step S25, the control unit (100) ends the pressure equalization control of the ventilation device (40). Specifically, the control unit (100) sets the opening/closing lid (45) of the ventilation device (40) to the fully closed position. The second temperature is a predetermined temperature lower than the first temperature. The second temperature is, for example, 0°C.

When the temperature of the air inside the container reaches the second temperature (e.g., 0°C), even if the temperature of the air inside the container is further reduced by the pull-down operation, the internal pressure of the container (1) does not decrease significantly, and the possibility of the inside of the container (1) becoming negative pressure is also reduced. Therefore, in step S24, when the second and third conditions are satisfied, the control unit (100) ends the pressure equalization operation of the ventilation device (40).

By the above control, even if the pressure inside the container (1) drops during the pulldown operation, the negative pressure inside the container (1) can be prevented from becoming greater than the withstand pressure of the container (1). As a result, damage to the container (1) due to the pulldown operation can be prevented.

(7-2-3) Second Mode The second mode is a control mode of the ventilation device (40) after the door (D) is temporarily opened or closed during cooling operation. As described above, the condition for transition to the second mode (step S14) is likely to be satisfied when the door (D) is temporarily opened or closed while the internal heat exchanger (29) is in the thermo-off state, in other words, while the internal temperature is within the target range.

As shown in FIG. 9, when the second mode is entered, in step S31, the control unit (100) controls the ventilation device (40) to perform a pressure equalization operation to equalize the pressure inside and outside the container (1). In other words, when the first condition in step S14 is satisfied after the door (D) is opened or closed during the cooling operation, the control unit (100) controls the ventilation device (40) to perform a second pressure equalization operation as a pressure equalization operation.

In step S31, the control unit (100) controls the ventilation device (40) so that the third flow rate of outside air is introduced into the container (1). Specifically, the control unit (100) adjusts the rotation angle of the open/close lid (45) of the ventilation device (40), i.e., the opening degree of the air supply passage (41) and the exhaust passage (42), so that the flow rate of air introduced into the container (1) becomes the third flow rate. By introducing the outside air into the container (1), the pressure outside and inside the container (1) are equalized. As a result, the pressure inside the container (1) increases rapidly. In other words, the negative pressure inside the container (1) decreases.

Here, the third flow rate is greater than the first flow rate and the second flow rate in the first mode. The third flow rate is, for example, 10 [m ³ /h]. That is, in the second pressure equalization operation, the ventilation device (40) introduces air outside the container (1) into the container (1) at a flow rate greater than that in the first pressure equalization operation. As described above, after the door (D) is opened and closed, the pressure inside the container (1) decreases faster than in the pull-down operation. In response to this, the ventilation device (40) introduces outside air at a relatively large flow rate, and therefore, the negative pressure inside the container (1) can be prevented from reaching the withstand pressure of the container (1).

Next, in step S32, if the second condition is met, that is, the detected pressure is higher than the second pressure, the process proceeds to step S33. In step S33, the control unit (100) ends the pressure equalization control of the ventilation device (40). Specifically, the control unit (100) sets the opening/closing lid (45) of the ventilation device (40) to the fully closed position.

By the above control, even if the pressure inside the container (1) decreases due to the opening and closing of the door (D), the negative pressure inside the container (1) can be prevented from exceeding the withstand pressure of the container (1). As a result, damage to the container (1) caused by the opening and closing of the door (D) can be prevented.

(8) Effects of the embodiment (8-1)
The control unit (100) of this embodiment controls the ventilation device (40) to perform a pressure equalization operation to equalize the pressure inside and outside the container (1) when a first condition is satisfied in which the pressure detected by the pressure detection unit (P) is lower than a predetermined first pressure that is lower than atmospheric pressure during a cooling operation for cooling the inside of the container (1).

Therefore, even if the pressure inside the container (1) decreases due to the air inside the container (1) being cooled, the pressure equalization operation can quickly increase the pressure inside the container (1). As a result, the negative pressure inside the container (1) can be prevented from increasing, and damage to the container (1) can be prevented.

In addition, by performing such control, even if a highly airtight container (1) is used, damage to the container (1) can be suppressed. As a result, it is possible to suppress a loss of energy efficiency of the container refrigeration system (10) due to the intrusion of outside air through gaps in the container (1).

(8-2)
In the embodiment, the pressure equalization mechanism is a ventilation device (40) that ventilates the container (1). Therefore, the ventilation device (40) can be used as a pressure equalization mechanism, and the number of parts can be reduced. The ventilation device (40) can introduce a relatively large flow rate of outside air into the container (1). Therefore, even if the pressure in the container (1) suddenly drops, outside air that can compensate for this can be quickly introduced into the container (1).

Furthermore, the ventilation device (40) can adjust the ventilation volume, i.e., the amount of outside air introduced. Therefore, outside air can be introduced into the container (1) in proportion to the pressure drop inside the container (1). As a result, it is possible to prevent the energy-saving properties of the container refrigeration unit (10) from being impaired by the introduction of excessive outside air.

(8-3)
The control section (100) terminates the pressure equalization operation when the pressure detected by the pressure detection section (P) during the pressure equalization operation is higher than a predetermined second pressure that is lower than atmospheric pressure.

This makes it possible to avoid the pressure equalization operation continuing even when the pressure inside the container (1) is high. As a result, it is possible to prevent the energy-saving performance of the container refrigeration system (10) from being impaired by the introduction of excessive outside air.

(8-4)
The control unit (100) terminates the pressure equalization operation when the pressure detected by the pressure detection unit (P) is higher than a predetermined second pressure lower than atmospheric pressure and the temperature of the air in the container (1) is lower than a predetermined temperature. In other words, even if the pressure detected by the pressure detection unit (P) is higher than the predetermined second pressure lower than atmospheric pressure, the control unit (100) does not terminate the pressure equalization operation when the temperature of the air in the container (1) is equal to or higher than a predetermined temperature.

If the temperature of the air inside the container (1) is low (e.g., 0°C), there is little risk that the negative pressure inside the container (1) will increase as a result of the air being further cooled. This prevents the negative pressure inside the container (1) from increasing again after the pressure equalization operation is completed, which could result in damage to the container (1).

(8-5)
The control unit (100) controls the ventilation device (40) to perform a first pressure equalization operation as a pressure equalization operation when the pressure detected by the pressure detection unit (P) is lower than a predetermined first pressure that is lower than atmospheric pressure during the first cooling operation (pull-down operation) after start-up of the container refrigeration unit (10).

During pull-down operation, the negative pressure inside the container (1) is likely to increase, increasing the risk of damage to the container (1). By performing the first pressure equalization operation at this time, damage to the container (1) can be avoided.

(8-6)
The control unit (100) controls the ventilation device (40) to perform a second pressure equalization operation as a pressure equalization operation when the pressure detected by the pressure detection unit (P) is lower than a predetermined first pressure that is lower than atmospheric pressure after the door (D) of the container (1) is opened or closed during the cooling operation.

When the door of the container (1) is temporarily opened and closed, the negative pressure inside the container (1) is likely to increase, increasing the risk of damage to the container (1). By performing the second pressure equalization operation at this time, damage to the container (1) can be avoided.

(8-7)
During the cooling operation (strictly speaking, the pull-down operation), the control unit (100) controls the pressure equalization mechanism (40, 80) so that the flow rate of air introduced from the outside to the inside of the container (1) decreases as the temperature of the air inside the container decreases.

When the temperature of the air inside the storage compartment is high, the negative pressure in the container (1) is likely to increase due to the cooling of the air inside the storage compartment. At this time, the amount of outside air introduced increases, which reliably prevents damage to the container (1).

When the temperature of the air inside the container is low, the negative pressure in the container (1) is unlikely to increase due to cooling of the air inside the container. At this time, the amount of outside air introduced is small, so the amount of outside air introduced does not become excessively large. As a result, it is possible to prevent the reliability of the container refrigeration unit (10) from being impaired due to the introduction of outside air. In particular, when the temperature of the air inside the container is low, the temperature difference between the outside air and the inside air is large, and the cooling load of the container (1) is likely to increase due to the introduction of outside air. At this time, by reducing the amount of outside air introduced, it is possible to avoid the energy saving performance of the container refrigeration unit (10) being impaired.

(8-8)
The pressure detection part (P) is a pressure sensor (53), so that the pressure inside the container (1) can be accurately detected.

(9) Modifications The above-described embodiment may be modified as follows. The following describes the differences from the above-described embodiment.

(9-1) Modification 1: Modifications of Pressure Detection Unit The pressure detection unit (P) of the above embodiment may have the following modified configuration.

(9-1-1) Modification 1A
As shown in FIG. 10, the container refrigeration system (10) of the modified example 1A includes a drain pipe (60). An inflow end (60a) of the drain pipe (60) communicates with the internal space (3) inside the container (1). An outflow end (60b) of the drain pipe (60) communicates with the external space (5) outside the container (1). The inflow end (60a) of the drain pipe (60) forms a flow path for discharging water received in a drain pan inside the container (1) to the outside of the container (1). The drain pan is disposed below the internal heat exchanger (29) and receives condensed water generated from air cooled by the internal heat exchanger (29). The drain pipe (60) may be a flexible resin hose or a hard metal pipe.

The drain pipe (60) has a trap section (61) that is curved downward. The trap section (61) has a first straight section (62) that is closer to the inside of the container (1), a second straight section (63) that is closer to the outside of the container (1), and a U-shaped U-section (64) that is continuous with the lower end of the first straight section (62) and the lower end of the second straight section (63). The first straight section (62) and the second straight section (63) extend in the vertical direction. The flow path cross-sectional area of the first straight section (62) is equal to the flow path cross-sectional area of the second straight section (63). Water accumulates in the trap section (61), and the water separates the inside of the container (1) from the outside of the container (1).

The pressure detection unit (P) of the modified example 1A includes a water level gauge that measures the water level in the trap section (61), and a control unit (100). The water level gauge includes a first water level sensor (65) and a second water level sensor (66). The first water level sensor (65) and the second water level sensor (66) are ultrasonic, radio wave, electrode, float, or other types. The first water level sensor (65) is disposed inside the first straight section (62). The first water level sensor (65) measures the water level in the first straight section (62). The second water level sensor (66) is disposed inside the second straight section (63). The second water level sensor (66) measures the water level in the second straight section (63).

The pressure detection unit (P) detects the pressure based on the water level difference between the first straight section (62) and the second straight section (63). When the pressure Pb inside the container (1) is equal to the pressure P0 (atmospheric pressure) outside the container (1), the water level h1 in the first straight section (62) is equal to the water level h2 in the second straight section (63), as shown in FIG. 10. In contrast, when the pressure Pb inside the container (1) decreases during the cooling operation, the pressure Pb becomes smaller than the pressure P0 outside the container (1). As a result, as shown in FIG. 11, the water level h1 in the first straight section (62) becomes higher than the water level h2 in the second straight section (63). In the state shown in FIG. 11, the following relational expression (1) is established.

Pb×A1+ρ×g×H×A1=P0×A2...(1)
Here, A1 is the flow path cross-sectional area of the first straight portion (62), and A2 is the flow path cross-sectional area of the second straight portion (63). In this example, A1 is equal to A2. ρ is the density of water, g is the acceleration of gravity, and H is the difference between the water level h1 and the water level h2 (H=h1-h2).

The control unit (100) calculates Pb inside the container (1) using the water levels measured by the first water level sensor (65) and the second water level sensor (66) and the relational expression (1). As described above, in the first modification, the pressure inside the container (1) can be detected.

(9-1-2) Modification 1B
The pressure detection unit (P) of the modification 1B detects the pressure inside the container (1) based on the temperature of the air inside the container (1) and the temperature of the air inside the container (1) during the cooling operation. The pressure detection unit (P) includes an internal temperature sensor (51) and a control unit (100).

The internal temperature sensor (51) measures the temperature T0 of the air inside the container (1) before or at the start of the cooling operation. Thereafter, the internal temperature sensor (51) measures the temperature Tb of the air inside the container (1) during the cooling operation. The control unit (100) calculates the pressure Pb inside the container (1) based on the following relational expression (2) based on Boyle's law.

P0×V/T0=Pb×V/Tb...(2)
Here, P0 is the pressure inside the container (1) before or at the start of the cooling operation, and corresponds to atmospheric pressure. V is the volume of the interior space (3) inside the container (1). As described above, in the second modification, the pressure inside the container (1) can be detected.

The pressure detection unit (P) may include an outside temperature sensor (52). The temperature detected by the outside temperature sensor (52) may be the temperature T0 of the air inside the container (1) before or at the start of the cooling operation.

(9-1-3) Modification 1C
As shown in FIG. 12 , the pressure detection unit (P) of the modification 1C includes a humidity sensor (71) which is a gas sensor, and a control unit (100). The humidity sensor (71) measures the concentration of water vapor in the air inside the container (1), i.e., the humidity of the air. The humidity sensor (71) is disposed inside the container (1). The humidity sensor (71) is disposed in the internal passage (19) upstream of the air flow from the internal fan (30). The humidity sensor (71) is of a capacitive or resistive type. The humidity sensor (71) has a characteristic that the detection value changes depending on the surrounding pressure.

The humidity sensor (71) measures the humidity R0 of the air in the container (1) before or at the start of the cooling operation. Thereafter, the humidity sensor (71) measures the humidity Rb of the air in the container (1) during the cooling operation. The humidity detected by the humidity sensor (71) varies depending on the pressure in the container (1). In other words, there is a correlation between the humidity detected by the humidity sensor (71) and the pressure in the container (1). The control unit (100) stores data correlating the humidity detected by the humidity sensor (71) and the pressure in the container (1). This data is a relational expression or a table. The control unit (100) calculates the pressure in the container (1) using this data, the humidity R0, and the humidity Rb. As described above, in modification 1C, the pressure inside the container (1) can be detected using the humidity sensor (71).

The humidity sensor (71) is also used to adjust the humidity of the air inside the container (1). The control unit (100) controls the refrigerant circuit (R) based on the detection value of the humidity sensor (71).

(9-1-4) Modification 1D
As shown in FIG. 13 , the pressure detection unit (P) of the modified example 1D includes a carbon dioxide sensor (72) which is a gas sensor, and a control unit (100). The carbon dioxide sensor (72) measures the concentration of carbon dioxide in the air inside the container (1). The carbon dioxide sensor (72) is disposed inside the container (1). The carbon dioxide sensor (72) is disposed in the internal passage (19) upstream of the air flow from the interior fan (30). The carbon dioxide sensor (72) is of a semiconductor type, an infrared type (NDIR type), or a thermal conductivity type. The carbon dioxide sensor (72) has a characteristic that the detection value changes depending on the surrounding pressure.

The carbon dioxide sensor (72) measures the carbon dioxide concentration C0 in the air in the container (1) before or at the start of the cooling operation. Thereafter, the carbon dioxide sensor (72) measures the carbon dioxide concentration Cb in the air in the container (1) during the cooling operation. The carbon dioxide concentration detected by the carbon dioxide sensor (72) varies depending on the pressure in the container (1). In other words, there is a correlation between the concentration detected by the carbon dioxide sensor (72) and the pressure in the container (1). The control unit (100) stores data correlating the concentration detected by the carbon dioxide sensor (72) and the pressure in the container (1). This data is a relational expression or a table. The control unit (100) calculates the pressure in the container (1) using this data, the concentration C0, and the concentration Cb. As described above, in the modified example 1D, the pressure inside the container (1) can be detected using the carbon dioxide sensor (72). The gas sensor may be an oxygen sensor that measures the oxygen concentration in the air in the container (1) instead of the carbon dioxide sensor (72).

The carbon dioxide sensor (72) and oxygen sensor are used to adjust the composition of the air in the container (1). The control unit (100) controls the adjustment device (80) based on the concentrations detected by the carbon dioxide sensor (72) and oxygen sensor. The adjustment device (80) adjusts the composition of the air in the interior space (3) using, for example, a PSA (Pressure Swing Adsorption) device or a gas separation membrane. The adjustment device (80) will be described in detail later.

The control unit (100) may adjust the ventilation volume of the ventilation device (40) based on the concentrations detected by the carbon dioxide sensor (72) and the oxygen sensor.

(9-2) Modification 2: Modification of Pressure Equalizing Mechanism The pressure equalizing mechanism (40, 80) of the above embodiment may have the following modified configuration.

(9-2-1) Modification 2A
As shown in Fig. 14, the pressure equalization mechanism of the modification 2A is a regulator (80) that regulates the composition of air inside the container (1). The regulator (80) is disposed in the external storage space (14) of the casing (11). The regulator (80) has a supply path (81), an exhaust path (82), an air pump (83), and a PSA device (84).

The supply path (81) is a flow path for introducing outside air into the internal space (3). The inflow end of the supply path (81) opens into the external space (5). The outflow end of the supply path (81) communicates with the internal space (3). The exhaust path (82) is a flow path for discharging air from the PSA device (84) into the external space (5).

The supply path (81) is provided with an air pump (83) and a PSA device (84). The air pump (83) is a transport section that transports air. The air pump (83) is a pressurizing section that pressurizes the air and a decompressing section that decompresses the air. The PSA device (84) has two adsorption sections. The adsorption sections are adsorption towers filled with an adsorbent that adsorbs nitrogen in the air. The adsorbent is, for example, zeolite.

The air pump (83) pressurizes one of the two adsorption sections and depressurizes the other. In the pressurized adsorption section, nitrogen in the air is adsorbed by the adsorbent, generating oxygen-enriched air with a lower nitrogen concentration and a higher oxygen concentration than the outside air. In the depressurized adsorption section, nitrogen is desorbed from the adsorbent, generating nitrogen-enriched air with a higher nitrogen concentration and a lower oxygen concentration than the outside air. The oxygen-enriched air is exhausted to the outside space (5) through the exhaust path (82). The nitrogen-enriched air is supplied to the interior space (3) through the supply path (81). This adjusts the oxygen concentration in the interior space (3).

In Modification 2A, when the pressure inside the container (1) falls below the first pressure during the cooling operation, the control unit (100) controls the adjustment device (80) to equalize the pressure inside and outside the container (1). Specifically, the control unit (100) operates the air pump (83) to perform a pressure equalization operation in which air outside the container (1) is introduced into the container (1) through the supply path (81). This makes it possible to prevent damage to the container (1) caused by negative pressure.

The adjustment device (80) preferably has a bypass flow path that allows the air in the supply path (81) to bypass the PSA device (84) and be supplied to the interior space (3) during pressure equalization. This allows the outside air to be introduced into the container (1) with its composition unchanged. In addition, the flow resistance of the air flowing through the supply path (81) can be reduced, and the power required for the air pump (83) can be reduced.

During the pressure equalization operation, the regulator (80) may introduce air pressurized to a pressure higher than atmospheric pressure by an air pump (83). This allows the pressure inside the container (1) to be increased quickly.

When the pressure inside the container (1) becomes higher than the second pressure as a result of the pressure equalization operation, the control unit (100) ends the pressure equalization operation of the adjustment device (80). Specifically, the control unit (100) stops the air pump (83).

In variant 2B, the adjustment device (80) not only adjusts the air composition but also functions as a pressure equalization mechanism, thereby reducing the number of parts.

(9-2-2) Modification 2B
Modification 2B is directed to a refrigeration container (C) including a container refrigeration unit (10) and a container (1). The pressure equalization mechanism of modification 2B is the door (D) of the container (1). As shown in Figure 15, the refrigeration container (1) has a drive mechanism (90) that automatically opens and closes the door (D). The drive mechanism (90) opens and closes the door (D) in response to a command from a control unit (100).

When the pressure inside the container (1) falls below the first pressure during the cooling operation, the control unit (100) controls the drive mechanism (90) to equalize the pressure inside and outside the container (1) and opens the door (D). This allows the pressure inside the container (1) to be increased quickly, and damage to the container (1) caused by negative pressure to be suppressed.

When the pressure inside the container (1) becomes higher than the second pressure as a result of the pressure equalization operation, the control unit (100) terminates the pressure equalization operation of the adjustment device (80). Specifically, the control unit (100) controls the drive mechanism (90) to close the door (D).

(9-3) Modification 3
When a first condition is satisfied, that is, the cooling operation is the pull-down operation and the detected pressure is equal to or lower than a first pressure, the control unit (100) may execute control in the first mode shown in Fig. 8. When a first command to start the cooling operation is received after the container refrigeration system (10) is turned on, the control unit (100) determines that the cooling operation is the pull-down operation.

(9-4) Modification 4
The container refrigeration system (10) may have a detection unit that detects opening and closing of the door (D). The control unit (100) may execute control in the second mode shown in Figure 9 when a fourth condition is satisfied, that is, the detection unit detects that the door (D) is opened or closed during the cooling operation, and then a first condition is satisfied, that is, the detected pressure is equal to or lower than the first pressure.

The control unit (100) may execute the second mode control when the first condition is satisfied after the fifth condition is satisfied, that is, when the temperature of the air inside the storage compartment rises from within the target range to above the range. The control unit (100) may execute the second mode control when the fourth condition, the fifth condition, and the first condition are satisfied in this order.

(9-5) Modification 5
The first pressure (see step S14), which is a judgment value for performing the second pressure equalization operation in the second mode, may be higher than the first pressure (see step S13), which is a judgment value for performing the first pressure equalization operation in the first mode. In this case, if the pressure inside the container (1) drops due to opening and closing of the door (D) during the cooling operation, the second pressure equalization operation in the second mode can be performed quickly. As described above, the pressure inside the container (1) drops suddenly after the door (D) is opened and closed, but damage to the container (1) can be suppressed by quickly responding to this pressure change.

(9-6) Modification 6
The control unit (100) may control the pressure equalizing mechanism (40, 80) during the cooling operation so that the flow rate of air introduced from the outside to the inside of the container (1) decreases as the time of the cooling operation elapses. In particular, during the pull-down operation, the control unit (100) preferably controls the pressure equalizing mechanism (40, 80) so that the flow rate of air introduced from the outside to the inside of the container (1) decreases as the time of the cooling operation elapses.

The temperature of the air inside the container decreases as the cooling operation progresses. When the temperature of the air inside the container is low, the negative pressure in the container (1) is less likely to increase due to the cooling of the air inside the container. At this time, the amount of outside air introduced is small, so that the amount of outside air introduced does not become excessively large. As a result, it is possible to prevent the reliability of the container refrigeration unit (10) from being impaired due to the introduction of outside air. When the temperature of the air inside the container is low, the cooling load of the container (1) is likely to increase due to the introduction of outside air. At this time, by reducing the amount of outside air introduced, it is possible to avoid the energy saving performance of the container refrigeration unit (10) being impaired.

(9-7) Variation 7
The control unit (100) of the seventh modification controls the refrigerant circuit (R) to perform a dehumidification operation for dehumidifying the air inside the container before the cooling operation. In the dehumidification operation, the compressor (25) is operated, and the internal heat exchanger (29) functions as an evaporator. The control unit (100) adjusts the rotation speed of the compressor (25) and, in turn, the evaporation temperature of the internal heat exchanger (29) so that the temperature of the air cooled by the internal heat exchanger (29) is equal to or lower than the dew point temperature. The evaporation temperature Te1 in the dehumidification operation is higher than the evaporation temperature Te2 in the cooling operation. Therefore, in the dehumidification operation, the air inside the container (1) can be dehumidified without significantly decreasing the temperature of the air.

When the cooling operation is performed after the dehumidification operation, the temperature of the air inside the container (1) drops as described above. Here, the humidity of the air inside the container has been reduced by the dehumidification operation. Therefore, even if the air inside the container (1) is cooled, a significant drop in the pressure inside the container (1) can be prevented. As a result, damage to the container (1) due to negative pressure can be prevented.

(10) Other Embodiments In the above embodiment and each of the modified examples, the following configurations may be adopted.

The container (1) does not have to be for sea transport, but may be for land transport, carried by vehicle such as a trailer or by rail.

The ventilation device (40) may only have an air supply function that supplies outside air from the exterior space (5) to the interior space (3), and may not have an exhaust function. In other words, the ventilation device (40) may only have an air supply passage (41), and exhaust may be naturally performed through an exhaust port provided in the container body (2).

The ventilation fan of the ventilation device (40) may be a fan dedicated to ventilation, separate from the interior fan.

The opening adjustment mechanism for adjusting the opening of the air supply passage (41) and the exhaust passage (42) does not necessarily have to be an opening/closing lid (45). The opening adjustment mechanism may be a damper or valve mechanism provided in the air supply passage (41) and the exhaust passage (42).

Although the embodiments and modifications have been described above, it will be understood that various modifications of form and details are possible without departing from the spirit and scope of the claims. Furthermore, the above embodiments, modifications, and other embodiments may be combined or substituted as appropriate as long as the functionality of the subject matter of this disclosure is not impaired.

The descriptions "first," "second," "third," etc. mentioned above are used to distinguish the words to which they are attached, and do not limit the number or order of those words.

As explained above, the present disclosure is useful for container refrigeration systems.

1 Container
10 Refrigeration equipment for containers
40 Ventilation system (pressure equalization mechanism)
53 Pressure Sensor
60 Drain piping
61 Trap section
71,72 Gas sensors
80 Adjustment device (pressure equalization mechanism)
100 Control section
D Door
P Pressure detection section

Claims (12)

a pressure detection unit (P) for detecting the pressure inside the container (1);
a pressure equalization mechanism (40, 80) for equalizing the pressure inside and outside the container (1);
a control unit (100) that controls the pressure equalizing mechanism (40, 80) so as to perform a pressure equalization operation for equalizing the pressure inside and outside the container (1) when the pressure detected by the pressure detection unit (P) is lower than a predetermined first pressure that is lower than atmospheric pressure during a cooling operation for cooling the inside of the container (1) ,
the pressure equalization mechanism (40, 80) is a ventilation device (40) that ventilates the container (1),
The ventilation device (40) has a ventilation fan (30) that introduces air outside the container (1) into the container (1) during the pressure equalization operation.
Container refrigeration equipment. a pressure detection unit (P) for detecting the pressure inside the container (1);
a pressure equalization mechanism (40, 80) for equalizing the pressure inside and outside the container (1);
a control unit (100) that controls the pressure equalizing mechanism (40, 80) so as to perform a pressure equalization operation for equalizing the pressure inside and outside the container (1) when the pressure detected by the pressure detection unit (P) is lower than a predetermined first pressure that is lower than atmospheric pressure during a cooling operation for cooling the inside of the container (1),
the pressure equalization mechanism (40, 80) is an adjusting device (80) that adjusts the composition of the air inside the container (1);
The adjusting device (80) has an air pump (83) that introduces air from outside the container (1) into the container (1) during the pressure equalization operation.
Container refrigeration equipment. 3. The container refrigeration system according to claim 1, wherein the control unit (100) terminates the pressure equalization operation when the pressure detected by the pressure detection unit ( P ) during the pressure equalization operation is higher than a predetermined second pressure that is lower than atmospheric pressure. 4. The container refrigeration system according to claim 3, wherein the control unit (100) terminates the pressure equalization operation when the pressure detected by the pressure detection unit (P ) is higher than a predetermined second pressure that is lower than atmospheric pressure and the temperature of the air in the container (1) is lower than a predetermined temperature. 3. The container refrigeration system according to claim 1, wherein, during an initial cooling operation after start-up of the container refrigeration system, the control unit (100) controls the pressure equalizing mechanism (40, 80) to perform a first pressure equalizing operation as the pressure equalizing operation, when the pressure detected by the pressure detection unit (P) is lower than a predetermined first pressure that is lower than atmospheric pressure. 3. The container refrigeration system according to claim 1, wherein, when the pressure detected by the pressure detection unit (P) is lower than a predetermined first pressure that is lower than atmospheric pressure, the control unit (100) controls the pressure equalization mechanism (40, 80) to perform a second pressure equalization operation as the pressure equalization operation after the door of the container (1) is opened or closed during a cooling operation. The container refrigeration system according to claim 1 or 2 , wherein the pressure detection part (P) is a pressure sensor (53). 3. The container refrigeration device according to claim 1 or 2, wherein the pressure detection unit (P) detects the pressure inside the container (1) based on the temperature of the air inside the container (1) before or at the start of the cooling operation and the temperature of the air inside the container (1) during the cooling operation. a pressure detection unit (P) for detecting the pressure inside the container (1);
a pressure equalization mechanism (40, 80) for equalizing the pressure inside and outside the container (1);
a control unit (100) that controls the pressure equalizing mechanism (40, 80) so as to perform a pressure equalization operation for equalizing the pressure inside and outside the container (1) when the pressure detected by the pressure detection unit (P) is lower than a predetermined first pressure that is lower than atmospheric pressure during a cooling operation for cooling the inside of the container (1),
the control unit (100) controls the pressure equalizing mechanism (40, 80) to perform a second pressure equalization operation as the pressure equalization operation when the pressure detected by the pressure detection unit (P) is lower than a predetermined first pressure that is lower than atmospheric pressure after the door of the container (1) is opened or closed during a cooling operation;
the control unit (100) controls the pressure equalizing mechanism (40, 80) to perform a first pressure equalization operation as the pressure equalization operation when the pressure detected by the pressure detection unit (P) is lower than a predetermined first pressure that is lower than atmospheric pressure, during an initial cooling operation after start-up of the container refrigeration unit;
The pressure equalizing mechanism (40, 80) in the second pressure equalizing operation introduces air outside the container (1) into the container (1) at a flow rate greater than that in the first pressure equalizing operation. a pressure detection unit (P) for detecting the pressure inside the container (1);
a pressure equalization mechanism (40, 80) for equalizing the pressure inside and outside the container (1);
a control unit (100) that controls the pressure equalizing mechanism (40, 80) so as to perform a pressure equalization operation for equalizing the pressure inside and outside the container (1) when the pressure detected by the pressure detection unit (P) is lower than a predetermined first pressure that is lower than atmospheric pressure during a cooling operation for cooling the inside of the container (1),
The control unit (100) controls the pressure equalization mechanism (40, 80) in a cooling operation so that the flow rate of air introduced from the outside to the inside of the container (1) decreases as the temperature of the air inside the container (1) decreases. a pressure detection unit (P) for detecting the pressure inside the container (1);
a pressure equalization mechanism (40, 80) for equalizing the pressure inside and outside the container (1);
a control unit (100) that controls the pressure equalizing mechanism (40, 80) so as to perform a pressure equalization operation for equalizing the pressure inside and outside the container (1) when the pressure detected by the pressure detection unit (P) is lower than a predetermined first pressure that is lower than atmospheric pressure during a cooling operation for cooling the inside of the container (1),
a drain pipe (60) for discharging condensed water generated inside the container (1) to the outside of the container (1) and having a trap portion (61) in which the condensed water accumulates;
The pressure detection unit (P) detects the internal pressure of the container (1) based on the water level in the trap unit (61). a pressure detection unit (P) for detecting the pressure inside the container (1);
a pressure equalization mechanism (40, 80) for equalizing the pressure inside and outside the container (1);
a control unit (100) that controls the pressure equalizing mechanism (40, 80) so as to perform a pressure equalization operation for equalizing the pressure inside and outside the container (1) when the pressure detected by the pressure detection unit (P) is lower than a predetermined first pressure that is lower than atmospheric pressure during a cooling operation for cooling the inside of the container (1),
a gas sensor (71, 72) for detecting a concentration of a gas component in the air inside the container (1);
The pressure detection unit (P) detects the pressure inside the container (1) based on the detected concentration of the gas by the gas sensor (71, 72) before or at the start of the cooling operation and the detected concentration of the gas by the gas sensor (71, 72) during the cooling operation.