JP2014119232A - Container refrigeration device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the stability of an internal temperature during defrosting operation.SOLUTION: A container refrigeration device (1) includes an internal heat exchanger (31) including a first heat exchange unit (31a) and a second heat exchange unit (31b) in a refrigeration circuit (10). This container refrigeration device (1) performs a defrosting operation for alternately executing a first defrosting operation for circulating refrigerant discharged from a compressor (21) through the first heat exchange unit (31a) and the second heat exchange unit (31b) in this order, defrosting the refrigerant in the first heat exchange unit (31a), evaporating the refrigerant in the second heat exchange unit (31b), and thereby cooling internal air, and a second defrosting operation for circulating the refrigerant discharged from the compressor (21) through the second heat exchange unit (31b) and the first heat exchange unit (31a) in this order, defrosting the refrigerant in the second heat exchange unit (31b), evaporating the refrigerant in the first heat exchange unit (31a), and thereby cooling the internal air.

Description

  The present invention relates to a container refrigeration apparatus, and particularly relates to an improvement in the stability of the internal temperature during a defrosting operation.

  Conventionally, a container refrigeration apparatus for cooling the inside of a container is known. For example, the container refrigeration apparatus disclosed in Patent Document 1 includes a refrigerant circuit in which a compressor, a condenser outside the warehouse, an expansion valve, and an evaporator inside the warehouse are connected in order. In this refrigerant circuit, the refrigerant circulates to perform a vapor compression refrigeration cycle, and the refrigerant absorbs heat from the air in the warehouse and evaporates in the evaporator, thereby cooling the inside air.

  In this refrigeration apparatus, when the cooling operation for cooling the internal air is continued, frost adheres to the evaporator, and the heat exchange efficiency of the evaporator gradually decreases. Therefore, every time a predetermined time has elapsed since the start of the cooling operation, the operation is switched to the defrosting operation. In the defrosting operation, a high-temperature refrigerant is supplied from the compressor to the evaporator. Thereby, the frost adhering to the evaporator is heated and melted by the high-temperature refrigerant.

JP 2008-215645 A

  However, in the refrigeration apparatus of Patent Document 1, when a high-temperature refrigerant is supplied to the evaporator during the defrosting operation, not only frost but also the internal air is heated by the high-temperature refrigerant. For this reason, the internal temperature rises and it is difficult to maintain the internal temperature at a predetermined temperature.

  This invention is made | formed in view of this point, and it aims at providing the container refrigeration apparatus maintained stably, without raising the internal temperature during a defrost operation.

  A first invention includes a refrigerant circuit (10) to which a compressor (21), a heat source side heat exchanger (22), and a use side heat exchanger (31) are connected and the refrigerant circulates to perform a refrigeration cycle. Targeted container refrigeration equipment. And the said use side heat exchanger (31) has a 1st heat exchange part (31a) and a 2nd heat exchange part (31b), and the said refrigerant circuit (10) is the said compressor (21). The discharged refrigerant is divided into the two heat exchanging parts (31a, 31b) through the heat source side heat exchanger (22), and the refrigerant is evaporated by the two heat exchanging parts (31a, 31b). Cooling operation for cooling the refrigerant, and the refrigerant discharged from the compressor (21) is passed through the first heat exchanging part (31a) and the second heat exchanging part (31b) in this order in the first heat exchanging part (31a). A first defrosting operation for defrosting and evaporating the refrigerant in the second heat exchange part (31b) to cool the air in the cabinet, and discharging refrigerant from the compressor (21) into the second heat exchange part (31b) The second heat exchanger (31a) is flowed in this order, defrosted by the second heat exchanger (31b), and the refrigerant is evaporated by the first heat exchanger (31a) to cool the internal air. The defrosting operation is performed alternately. As the defrosting operation is performed, and a switching mechanism for switching the flow state of the refrigerant (40).

  In the first aspect of the invention, the cooling operation and the defrosting operation can be performed by the switching mechanism (40). In the defrosting operation, the first defrosting operation and the second defrosting operation are performed alternately.

  In the first defrosting operation, the refrigerant flows in the order of the first heat exchange unit (31a) and the second heat exchange unit (31b). In the first heat exchange section (31a), the relatively high-temperature refrigerant discharged from the compressor (21) flows in and the frost is heated and melted by the refrigerant, while the refrigerant is cooled by the frost. In the second heat exchange section (31b), the refrigerant cooled in the first heat exchange section (31a) and the internal air exchange heat, and the internal air is cooled by evaporating the refrigerant.

  On the other hand, in the second defrosting operation, the refrigerant flows in the order of the second heat exchange unit (31b) and the first heat exchange unit (31a). In the second heat exchange section (31b), the relatively high-temperature refrigerant discharged from the compressor (21) flows in and the frost is heated and melted by the refrigerant, while the refrigerant is cooled by the frost. In the first heat exchange section (31a), the refrigerant cooled in the second heat exchange section (31b) and the internal air exchange heat, and the internal air is cooled by evaporating the refrigerant.

  As described above, in the first aspect of the invention, during the defrosting operation, the defrosting is performed at the upstream heat exchange section (31a, 31b), and the internal air is cooled by the downstream heat exchange section (31a, 31b). Are alternately performed between the two heat exchange sections (31a, 31b) of the use side heat exchanger (31). Therefore, the entire use side heat exchanger (31) is defrosted and the temperature rise in the warehouse is suppressed.

  In a second aspect based on the first aspect, in the first defrosting operation, the switching mechanism (40) passes the refrigerant discharged from the compressor (21) via the heat source side heat exchanger (22). In the second defrosting operation, the refrigerant discharged from the compressor (21) is passed through the second heat exchange unit (22) without passing through the heat source side heat exchanger (22). The refrigerant circulation state is switched so that the first defrosting mode flowing to 31b) is executed.

  In the second aspect of the invention, when the first defrost mode is executed, the refrigerant discharged from the compressor (21) does not go through the heat source side heat exchanger (22), and the upstream side heat exchange section (31a, 31b) Flows directly into. Therefore, in the upstream heat exchange section (31a, 31b), a high heating capacity (defrosting capacity) is obtained by the high-temperature discharged refrigerant, and the defrosting time is shortened.

  In a third aspect based on the second aspect, in the first defrosting operation, the switching mechanism (40) passes the refrigerant discharged from the compressor (21) via the heat source side heat exchanger (22). In the second defrosting operation, the refrigerant discharged from the compressor (21) is passed through the heat source side heat exchanger (22) to the second heat exchange unit (31b). The flow state of the refrigerant is switched so that the second defrosting mode to flow into is executed.

  In the third aspect, in addition to the first defrost mode, the second defrost mode can be executed. When the second defrosting mode is executed, the refrigerant discharged from the compressor (21) flows into the heat source side heat exchanger (22), condenses, and then flows into the upstream heat exchange section (31a, 31b). In the heat exchange section (31a, 31b) on the upstream side, defrosting is performed by the condensed refrigerant, and the condensed refrigerant is supercooled by the frost. In the heat exchange section (31a, 31b) on the downstream side, the enthalpy is increased by the amount that the refrigerant is supercooled, so that the cooling capacity for cooling the internal air is increased. Therefore, during the defrosting operation, a situation in which the cooling capacity is insufficient and the internal temperature rises is reliably avoided, and the internal temperature is further stabilized.

  According to the present invention, the use side heat exchanger (31) is provided with the two heat exchange portions (31a, 31b). During the defrosting operation, the first heat exchange unit (31a) defrosts and the second heat exchange unit (31b) cools the internal air, and the second heat exchange unit (31b) The second defrosting operation of defrosting and cooling the internal air in the first heat exchange section (31a) was alternately performed. Thereby, the temperature rise in a store | warehouse | chamber can be suppressed and the interior temperature can be maintained stably, defrosting the utilization side heat exchanger (31) whole.

  According to the second aspect, during each defrosting operation, the refrigerant discharged from the compressor (21) is caused to flow directly to the upstream heat exchange section (31a, 31b) without passing through the heat source side heat exchanger (22). Thus, the first defrosting mode for defrosting the upstream heat exchange section (31a, 31b) is made executable. By carrying out like this, the defrost capability of an upstream heat exchange part (31a, 31b) can be improved, and the time which defrosts a utilization side heat exchanger (31) can be shortened.

  According to the third invention, in addition to the first defrosting mode, the refrigerant discharged from the compressor (21) is transferred to the upstream heat exchange section (31a, 31b) via the heat source side heat exchanger (22). The second defrosting mode for defrosting the upstream heat exchange section (31a, 31b) was made possible by flowing. Thereby, if a user sets and performs the 1st defrost mode, the defrost capability of the upstream heat exchange part (31a, 31b) will be raised, and the defrost operation which gave priority to shortening of defrost time will be performed. On the other hand, when the user sets and executes the second defrosting mode, the cooling capacity of the downstream heat exchange section (31a, 31b) is increased, and the defrosting operation is focused on stabilizing the internal temperature. It can be performed.

FIG. 1 is a refrigerant circuit diagram of the container refrigeration apparatus according to the first embodiment. FIG. 2 is a refrigerant circuit diagram illustrating a refrigerant flow during a cooling operation in the container refrigeration apparatus according to the first embodiment. FIG. 3 is a refrigerant circuit diagram illustrating a refrigerant flow during the first defrosting operation in the container refrigeration apparatus according to the first embodiment. FIG. 4 is a refrigerant circuit diagram illustrating a refrigerant flow during the second defrosting operation in the container refrigeration apparatus according to the first embodiment. FIG. 5 is a refrigerant circuit diagram illustrating a refrigerant flow when the on-off valve is opened during the first defrosting operation in the container refrigeration apparatus according to the first embodiment. FIG. 6 is a refrigerant circuit diagram illustrating a refrigerant flow when the on-off valve is opened during the second defrosting operation in the container refrigeration apparatus according to the first embodiment. FIG. 7 is a refrigerant circuit diagram illustrating a refrigerant flow during a cooling operation of the container refrigeration apparatus according to the modification of the first embodiment. FIG. 8 is a refrigerant circuit diagram illustrating a refrigerant flow during a first defrosting operation of the container refrigeration apparatus according to the modification of the first embodiment. FIG. 9 is a refrigerant circuit diagram illustrating a refrigerant flow during a second defrosting operation of the container refrigeration apparatus according to the modification of the first embodiment. FIG. 10 is a refrigerant circuit diagram of the container refrigeration apparatus according to the second embodiment. FIG. 11 is a refrigerant circuit diagram illustrating a refrigerant flow during a cooling operation in the container refrigeration apparatus according to the second embodiment. FIG. 12 is a refrigerant circuit diagram illustrating a refrigerant flow during the first defrosting operation in the first defrosting mode in the container refrigeration apparatus according to the second embodiment. FIG. 13 is a refrigerant circuit diagram illustrating a refrigerant flow during a second defrosting operation in the first defrosting mode in the container refrigeration apparatus according to the second embodiment. FIG. 14 is a refrigerant circuit diagram illustrating a refrigerant flow during the first defrosting operation in the second defrosting mode in the container refrigeration apparatus according to the second embodiment. FIG. 15 is a refrigerant circuit diagram illustrating a refrigerant flow during the second defrosting operation in the second defrosting mode in the container refrigeration apparatus according to the second embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are essentially preferable examples, and are not intended to limit the scope of the present invention, its application, or its use.

Embodiment 1
<overall structure>
The container refrigeration apparatus (1) of this embodiment cools the inside of a container (not shown) used for marine transportation or the like. As shown in FIG. 1, the container refrigeration apparatus (1) includes an outside unit (2) provided outside the warehouse and an inside unit (3) provided inside the warehouse. And the refrigerant | coolant circuit (10) which circulates a refrigerant | coolant and performs a refrigerating cycle is formed by connecting the external unit (2) and the internal unit (3) with piping.

  The refrigerant circuit (10) includes a compressor (21), an external heat exchanger (22), a receiver (24), and an internal heat exchanger (31), and further includes a refrigerant in the refrigerant circuit (10). The switching mechanism (40) for switching the flow state of the first four-way switching valve (40a), the second four-way switching valve (40b), the on-off valve (40c), the first expansion valve (40d), and the second expansion valve ( 40e) is provided. The compressor (21), the first four-way switching valve (40a), the second four-way switching valve (40b), the on-off valve (40c), the external heat exchanger (22), and the receiver (24) are connected to the external unit ( 2) is housed. On the other hand, the first expansion valve (40d), the second expansion valve (40e), and the internal heat exchanger (31) are accommodated in the internal unit (3).

  The compressor (21) is composed of, for example, a variable capacity scroll compressor in which the rotation speed of the compressor motor is variable. A discharge pipe (51) is connected to the discharge side of the compressor (21), and a suction pipe (52) is connected to the suction side of the compressor (21).

  The discharge pipe (51) is branched into a first discharge path (51a) and a second discharge path (51b) on the way. The first discharge path (51a) is connected to the first port of the first four-way switching valve (40a), and the second discharge path (51b) is connected to the first port of the second four-way switching valve (40b). Yes.

  The suction pipe (52) branches into the first suction path (52a) and the second suction path (52b) on the way. The first suction path (52a) is connected to the second port of the first four-way switching valve (40a), and the second suction path (52b) is connected to the second port of the second four-way switching valve (40b). Yes.

  The first four-way switching valve (40a) and the second four-way switching valve (40b) each have four ports, the first port and the third port communicate with each other, and the second port and the fourth port communicate with each other. A first state (state indicated by a solid line in FIG. 1) that communicates, and a second state (state indicated by a broken line in FIG. 1) in which the first port and the fourth port communicate with each other and the second port and the third port communicate with each other. ) And can be switched to.

  A first gas pipe (53) is connected to the third port of the first four-way switching valve (40a). The first gas pipe (53) is connected to the inflow end (gas side end) of the external heat exchanger (22), and in the middle of the check valve (CV1) in order from the first four-way switching valve (40a) side. An on-off valve (40c) is provided. The check valve (CV1) allows only the flow of refrigerant from the first four-way switching valve (40a) toward the external heat exchanger (22). The on-off valve (40c) is a so-called electromagnetic valve, and its open / close state is switched by an external signal.

  A second gas pipe (54) is connected to the third port of the second four-way switching valve (40b). The second gas pipe (54) is connected between the check valve (CV1) and the on-off valve (40c) of the first gas pipe (53), and a check valve (CV2) is provided in the middle. . The check valve (CV2) allows only the flow of refrigerant from the second four-way switching valve (40b) toward the first gas pipe (53).

  The external heat exchanger (22) condenses the refrigerant and constitutes the heat source side heat exchanger of the present invention. This external heat exchanger (22) is a so-called cross fin type fin-and-tube heat exchanger. An external fan (23) is provided in the vicinity of the external heat exchanger (22). In the outside heat exchanger (22), the outside air sent by the outside fan (23) and the refrigerant exchange heat.

  The outflow end (liquid side end) of the external heat exchanger (22) is connected to one end of the liquid pipe (55), and the other end of the liquid pipe (55) is connected to the liquid side first inlet / outlet pipe (56a). It is connected to the liquid side second inlet / outlet pipe (56b). The liquid pipe (55) is provided with a check valve (CV3) and a receiver (24) in order from the external heat exchanger (22) side. The check valve (CV3) allows only the refrigerant flow from the external heat exchanger (22) to the receiver (24). The receiver (24) temporarily stores the liquid refrigerant condensed in the external heat exchanger (22).

  The liquid side first inlet / outlet pipe (56a) is connected to one end (liquid side end) of a first heat exchanging portion (31a) (described later) of the internal heat exchanger (31), and the first expansion valve (40d) ) Is provided. On the other hand, the liquid side second inlet / outlet pipe (56b) is connected to one end (liquid side end) of the second heat exchanging portion (31b) (described later) of the internal heat exchanger (31), and the second expansion valve in the middle. (40e) is provided.

  The first expansion valve (40d) and the second expansion valve (40e) are so-called electronic expansion valves, and are configured such that the opening degree can be changed by an electric signal from the outside.

  The internal heat exchanger (31) cools the internal air by evaporating the refrigerant, and constitutes the use side heat exchanger of the present invention. This internal heat exchanger (31) has a 1st heat exchange part (31a) and a 2nd heat exchange part (31b). These two heat exchange parts (31a, 31b) are cross-fin type fin-and-tube heat exchangers, respectively. An in-compartment fan (32a, 32b) is provided in the vicinity of each heat exchange section (31a, 31b). In each heat exchange part (31a, 31b), the internal air and the refrigerant sent by the internal fans (32a, 32b) exchange heat.

  The gas side first inlet / outlet pipe (57a) is connected to the other end (gas side end) of the first heat exchange section (31a). The gas side first inlet / outlet pipe (57a) is connected to the fourth port of the first four-way switching valve (40a), and a drain pan heater (58a) is provided in the middle. The drain pan heater (58a) heats the drain pan disposed at the lower portion of the first heat exchange section (31a).

  A gas side second inlet / outlet pipe (57b) is connected to the other end (gas side end) of the second heat exchange section (31b). The gas side second inlet / outlet pipe (57b) is connected to the fourth port of the second four-way switching valve (40b), and a drain pan heater (58b) is provided in the middle. This drain pan heater (58b) heats the drain pan arranged at the lower part of the second heat exchange section (31b).

  The refrigerant circuit (10) is provided with a first communication pipe (61) and a second communication pipe (62). One end of the first communication pipe (61) is connected between the first expansion valve (40d) and the first heat exchange section (31a) in the liquid first inlet / outlet pipe (56a), and the other end is connected to the liquid pipe ( 55) is connected between the check valve (CV3) and the receiver (24). The first communication pipe (61) is provided with a check valve (CV4) that allows only the flow of refrigerant from the liquid-side first inlet / outlet pipe (56a) toward the liquid pipe (55).

  The second communication pipe (62) has one end connected between the second expansion valve (40e) and the second heat exchange part (31b) in the liquid side second inlet / outlet pipe (56b), and the other end connected to the first communication pipe. The pipe (61) is connected to the liquid pipe (55) side of the check valve (CV4). The second communication pipe (62) is provided with a check valve (CV5) that allows only a refrigerant flow from the liquid-side second inlet / outlet pipe (56b) to the first communication pipe (61).

-Driving action-
Next, the operation of the container refrigeration apparatus (1) will be described. In this container refrigeration system (1), a cooling operation for cooling the interior of the container and a removal operation for melting frost adhering to the two heat exchange sections (31a, 31b) of the interior heat exchanger (31). Frost operation is performed.

<Cooling operation>
The operation during the cooling operation will be described with reference to FIG.

  In the cooling operation, both the first four-way switching valve (40a) and the second four-way switching valve (40b) are set to the first state and the on-off valve (40c) is set to the open state as the switching mechanism (40). . Furthermore, the opening degree of the first expansion valve (40d) is adjusted so that the degree of superheat of the refrigerant flowing out from the first heat exchange unit (31a) becomes a predetermined target value, and the second heat exchange unit (31b) The opening degree of the second expansion valve (40e) is adjusted so that the degree of superheat of the refrigerant flowing out becomes a predetermined target value.

  Also, the outside fan (23) is operated, the outside air is supplied to the outside heat exchanger (22), the two inside fans (32a, 32b) are operated, and the inside air is heated by each heat. It is supplied to the exchange part (31a, 31b).

  In the cooling operation, when the refrigerant compressed by the compressor (21) is discharged to the discharge pipe (51), the discharged refrigerant is separated from the first four-way switching valve (40a) side and the second four-way switching valve (40b) side. Then, the gas is merged by the first gas pipe (53) and flows into the external heat exchanger (22). In the outside heat exchanger (22), the refrigerant and the outside air exchange heat, and the refrigerant dissipates heat to the outside air and condenses. The refrigerant condensed in the external heat exchanger (22) passes through the receiver (24), and then is divided into the liquid side first inlet / outlet pipe (56a) side and the liquid side second inlet / outlet pipe (56b) side. .

  The refrigerant flowing into the liquid side first inlet / outlet pipe (56a) is depressurized by the first expansion valve (40d), and then flows into the first heat exchange section (31a) of the internal heat exchanger (31). In the first heat exchange section (31a), the refrigerant and the internal air exchange heat, and the refrigerant absorbs heat from the internal air and evaporates, whereby the internal air is cooled.

  On the other hand, the refrigerant flowing into the liquid side second inlet / outlet pipe (56b) is depressurized by the second expansion valve (40e) and then flows into the second heat exchange section (31b) of the internal heat exchanger (31). . In the second heat exchange section (31b), the refrigerant and the internal air exchange heat, and the refrigerant absorbs heat from the internal air and evaporates, whereby the internal air is cooled.

  The refrigerant evaporated in the first heat exchange section (31a) flows out to the gas side first inlet / outlet pipe (57a), passes through the first four-way switching valve (40a), and then the first suction path of the suction pipe (52). (52a) On the other hand, the refrigerant evaporated in the second heat exchange section (31b) flows out into the gas side second inlet / outlet pipe (57b), passes through the second four-way switching valve (40b), and then passes through the second of the suction pipe (52). It flows into the suction passage (52b). Thereafter, the refrigerant on the first suction path (52a) side and the refrigerant on the second suction path (52b) side merge in the suction pipe (52) and are sucked into the compressor (21). In the compressor (21), the refrigerant is compressed again and discharged to the discharge pipe (51).

  Thus, in the cooling operation, the internal air is cooled by both the first heat exchange part (31a) and the second heat exchange part (31b) of the internal heat exchanger (31).

<Defrosting operation>
If the cooling operation is continued, frost adheres to the surface of the heat exchanger tubes (31a, 31b) of the internal heat exchanger (31), and the frost gradually grows and enlarges. To go. Therefore, the container refrigeration apparatus (1) is switched to the defrosting operation every time a predetermined time elapses after the cooling operation is performed. In the defrosting operation, the first defrosting operation and the second defrosting operation are alternately performed at predetermined time intervals.

<First defrosting operation>
First, the first defrosting operation will be described with reference to FIG.

  The first defrosting operation is an operation in which defrosting is performed by the first heat exchange unit (31a) and the internal air is cooled by the second heat exchange unit (31b).

  In the first defrosting operation, as the switching mechanism (40), the first four-way switching valve (40a) is set to the second state, the second four-way switching valve (40b) is set to the first state, and the on-off valve (40c ) Is set to the closed state. Further, the first expansion valve (40d) is set to a fully closed state, and the opening degree of the second expansion valve (40e) is determined so that the degree of superheat of the refrigerant flowing out of the second heat exchange unit (31b) is a predetermined target value. Adjusted to be.

  Further, the outside fan (23) is stopped. Only the second internal fan (36b) is operated as the internal fans (32a, 32b), and the internal air is supplied to the second heat exchange section (31b).

  In the first defrosting operation, when the refrigerant compressed by the compressor (21) is discharged to the discharge pipe (51), the discharged refrigerant is discharged from the first four-way switching valve (40a) to the gas side first inlet / outlet pipe ( After passing through 57a), it flows into the first heat exchange section (31a) of the internal heat exchanger (31). In the first heat exchange section (31a), the frost and the refrigerant adhering during the cooling operation exchange heat, the frost is heated and melted, and the refrigerant condenses.

  The refrigerant condensed in the first heat exchange section (31a) flows out from the first heat exchange section (31a) to the liquid side first inlet / outlet pipe (56a), and then passes through the first communication pipe (61) to the receiver ( After passing through 24), it flows into the liquid side second inlet / outlet pipe (56b).

  The refrigerant flowing into the liquid side second inlet / outlet pipe (56b) is depressurized by the second expansion valve (40e) and then sent to the second heat exchange section (31b) of the internal heat exchanger (31). In the second heat exchange section (31b), the refrigerant and the internal air exchange heat, and the refrigerant absorbs heat from the internal air and evaporates, whereby the internal air is cooled.

  The refrigerant evaporated in the second heat exchange part (31b) flows out from the second heat exchange part (31b) to the gas side second inlet / outlet pipe (57b). Thereafter, the refrigerant passes through the second four-way switching valve (40b) and the suction pipe (52) and is sucked into the compressor (21). In the compressor (21), the refrigerant is compressed again and discharged to the discharge pipe (51).

  When the first defrosting operation is continuously performed, the first heat exchange unit (31a) is defrosted to reduce the amount of frost formation, while the second heat exchange unit (31b) increases the frost amount. Heat exchange efficiency will fall. Therefore, the first defrosting operation is switched to the second defrosting operation when the defrosting is performed to some extent in the first heat exchange unit (31a) (when a predetermined operation time has elapsed).

<Second defrosting operation>
Next, the second defrosting operation will be described with reference to FIG.

  The second defrosting operation is an operation in which the defrosting is performed by the second heat exchange unit (31b) and the internal air is cooled by the first heat exchange unit (31a).

  In the second defrosting operation, as the switching mechanism (40), the first four-way switching valve (40a) is set to the first state, the second four-way switching valve (40b) is set to the second state, and the on-off valve (40c ) Is set to the closed state. Furthermore, the second expansion valve (40e) is set to a fully closed state, and the opening degree of the first expansion valve (40d) is determined so that the degree of superheat of the refrigerant flowing out of the first heat exchange section (31a) is a predetermined target value. Adjusted to be.

  Further, the outside fan (23) is stopped. As for the internal fans (32a, 32b), only the first internal fan (36a) is operated, and the internal air is supplied to the first heat exchange section (31a).

  In the second defrosting operation, when the refrigerant compressed by the compressor (21) is discharged to the discharge pipe (51), the discharged refrigerant flows from the second four-way switching valve (40b) to the gas side second inlet / outlet pipe ( After passing through 57b), it flows into the second heat exchange section (31b) of the internal heat exchanger (31). In the second heat exchange section (31b), the frost and the refrigerant adhering during the cooling operation exchange heat, the frost is heated and melted, and the refrigerant condenses.

  The refrigerant condensed in the second heat exchange section (31b) flows out from the second heat exchange section (31b) to the liquid side second inlet / outlet pipe (56b), and then the second communication pipe (62) and the first communication pipe. After passing through the receiver (24) through (61), it flows into the liquid side first inlet / outlet pipe (56a).

  The refrigerant flowing into the liquid side first inlet / outlet pipe (56a) is depressurized by the first expansion valve (40d), and then sent to the first heat exchange section (31a) of the internal heat exchanger (31). In the first heat exchange section (31a), the refrigerant and the internal air exchange heat, and the refrigerant absorbs heat from the internal air and evaporates, whereby the internal air is cooled.

  The refrigerant evaporated in the first heat exchange section (31a) flows out from the first heat exchange section (31a) to the gas side first inlet / outlet pipe (57a). Thereafter, the refrigerant passes through the first four-way switching valve (40a) and the suction pipe (52) and is sucked into the compressor (21). In the compressor (21), the refrigerant is compressed again and discharged to the discharge pipe (51).

  When the second defrosting operation is continuously performed, the second heat exchange unit (31b) is defrosted to reduce the amount of frost formation, while the first heat exchange unit (31a) increases the frost formation amount. Heat exchange efficiency will fall. Therefore, the second defrosting operation is switched to the first defrosting operation when the defrosting is performed to some extent in the second heat exchange unit (31b) (when a predetermined operation time has elapsed).

  Thus, in the container refrigeration apparatus (1) of the present embodiment, the first defrosting operation and the second defrosting operation are alternately performed during the defrosting operation. Therefore, the two heat exchange parts (31a, 31b) of the internal heat exchanger (31) are defrosted, the internal air is cooled, and the internal temperature is maintained at a predetermined temperature.

-Effect of Embodiment 1-
According to the present embodiment, the internal heat exchanger (31) is provided with the two heat exchange portions (31a, 31b). During the defrosting operation, the first heat exchange unit (31a) defrosts and the second heat exchange unit (31b) cools the internal air, and the second heat exchange unit (31b) The second defrosting operation of defrosting and cooling the internal air in the first heat exchange section (31a) was alternately performed. Thereby, during the defrosting operation, the temperature inside the warehouse can be suppressed and the inside temperature can be stably maintained while defrosting the entire inside heat exchanger (31).

  Further, according to the present embodiment, during each defrosting operation of the defrosting operation, the refrigerant discharged from the compressor (21) is not passed through the external heat exchanger (22), and the upstream heat exchange section (31a, 31b ) To defrost the heat exchange section (31a, 31b) on the upstream side. By carrying out like this, the heating capability (defrosting capability) which defrosts an upstream heat exchange part (31a, 31b) can be raised, and the use side heat exchanger (31) whole can be defrosted in a short time. Can do.

  In this embodiment, during each defrosting operation in the defrosting operation, when the defrosting progresses and the amount of frost formation on the upstream heat exchange section (31a, 31b) decreases, the amount of heat exchange between the frost and the refrigerant Since (the amount of heat released from the refrigerant) decreases, the refrigerant temperature gradually increases, and as a result, the refrigerant discharged from the compressor (21) may rise abnormally. However, in the present embodiment, as shown in FIG. 5, when the temperature of the refrigerant discharged from the compressor (21) exceeds a predetermined temperature during the first defrosting operation, the on-off valve (40c) opens and the refrigerant discharged A part flows through the second four-way selector valve (40b) and the second gas pipe (54) to the external heat exchanger (22) side. As shown in FIG. 6, when the temperature of the refrigerant discharged from the compressor (21) becomes equal to or higher than a predetermined temperature during the second defrosting operation, the on-off valve (40c) is opened and a part of the refrigerant discharged is the first. It flows to the external heat exchanger (22) side through the four-way switching valve (40a) and the first gas pipe (53). In other words, during each defrosting operation, part of the discharged refrigerant can be released to the external heat exchanger (22) side to suppress the pressure abnormality of the discharged refrigerant, and a stable defrosting operation can be performed for a long time. it can.

<Modification of Embodiment 1>
As shown in FIGS. 7 to 9, the container refrigeration apparatus (1) of the present modification supercools the condensed refrigerant in the refrigerant circuit (10) of the container refrigeration apparatus (1) of the first embodiment. A supercooling heat exchanger (25) is added.

  The subcooling heat exchanger (25) has a primary side passage (25a) and a secondary side passage (25b), and flows through the refrigerant flowing through the primary side passage (25a) and the secondary side passage (25b). The refrigerant is configured to exchange heat. The primary side passage (25a) is connected to the downstream side of the receiver (24) of the liquid pipe (55), and the secondary side passage (25b) is connected to the supercooling branch pipe (55a).

  The subcooling branch pipe (55a) has an inflow end connected between the receiver (24) and the supercooling heat exchanger (25) in the liquid pipe (55), and an outflow end of the subcooling branch pipe (55a) compressed by the compressor (21). It is connected to a compression chamber (intermediate compression chamber) in the middle (intermediate pressure state). The supercooling branch pipe (55a) is provided with an expansion valve (26) for reducing the pressure of the refrigerant flowing through the supercooling branch pipe (55a).

<Cooling operation>
As shown in FIG. 7, when the refrigerant condenses in the external heat exchanger (22) during the cooling operation, the condensed refrigerant passes through the receiver (24), and then the liquid pipe (55) side and the supercooled branch pipe (55a) Divide to the side. The refrigerant on the liquid pipe (55) side flows into the primary side passage (25a) of the supercooling heat exchanger (25), and the refrigerant on the supercooling branch pipe (55a) side passes through the expansion valve (26). After being depressurized, it flows into the secondary passage (25b) of the supercooling heat exchanger (25).

  In the supercooling heat exchanger (25), the refrigerant flowing into the primary passage (25a) and the refrigerant flowing into the secondary passage (25b) exchange heat. The refrigerant flowing into the primary side passage (25a) is supercooled, and the refrigerant flowing into the secondary side passage (25b) evaporates.

  Thereafter, the refrigerant supercooled in the primary passage (25a) is sent to the two heat exchange parts (31a, 31b) of the internal heat exchanger (31), and the two heat exchange parts (31a, 31b). ), The refrigerant evaporates to cool the internal air. On the other hand, the refrigerant evaporated in the secondary passage (25b) is returned to the intermediate compression chamber of the compressor (21).

<Defrosting operation>
<First defrosting operation>
As shown in FIG. 8, when the refrigerant condenses in the first heat exchange section (31a) during the first defrosting operation in the defrosting operation, the condensed refrigerant passes through the receiver (24) and then passes through the liquid pipe (55 ) Side and subcooled branch pipe (55a) side. The refrigerant on the liquid pipe (55) side flows into the primary side passage (25a) of the supercooling heat exchanger (25), and the refrigerant on the supercooling branch pipe (55a) side passes through the expansion valve (26). After being depressurized, it flows into the secondary passage (25b) of the supercooling heat exchanger (25).

  In the supercooling heat exchanger (25), the refrigerant flowing into the primary passage (25a) and the refrigerant flowing into the secondary passage (25b) exchange heat. The refrigerant flowing into the primary side passage (25a) is supercooled, and the refrigerant flowing into the secondary side passage (25b) evaporates.

  Thereafter, the refrigerant supercooled in the primary passage (25a) is sent to the second heat exchange section (31b), and the refrigerant in the second heat exchange section (31b) evaporates to cool the internal air. The On the other hand, the refrigerant evaporated in the secondary passage (25b) is returned to the intermediate compression chamber of the compressor (21).

<Second defrosting operation>
As shown in FIG. 9, when the refrigerant condenses in the second heat exchange section (31b) during the second defrosting operation in the defrosting operation, the condensed refrigerant passes through the receiver (24), and then the liquid pipe (55 ) Side and subcooled branch pipe (55a) side. The refrigerant on the liquid pipe (55) side flows into the primary side passage (25a) of the supercooling heat exchanger (25), and the refrigerant on the supercooling branch pipe (55a) side passes through the expansion valve (26). After being depressurized, it flows into the secondary passage (25b) of the supercooling heat exchanger (25).

  In the supercooling heat exchanger (25), the refrigerant flowing into the primary passage (25a) and the refrigerant flowing into the secondary passage (25b) exchange heat. The refrigerant flowing into the primary side passage (25a) is supercooled, and the refrigerant flowing into the secondary side passage (25b) evaporates.

  Thereafter, the refrigerant supercooled in the primary passage (25a) is sent to the first heat exchange section (31a), and the refrigerant evaporates in the first heat exchange section (31a) to cool the internal air. . On the other hand, the refrigerant evaporated in the secondary passage (25b) is returned to the intermediate compression chamber of the compressor (21).

  Thus, in this modification, the refrigerant condensed in the upstream heat exchange section (31a, 31b) during the defrosting operation is supercooled and then sent to the downstream heat exchange section (31a, 31b). Try to evaporate. Therefore, the enthalpy of the refrigerant is increased by the amount of supercooling, and the cooling capacity of the downstream heat exchange section (31a, 31b) can be increased, and the downstream heat exchange section (31a, 31b, The situation where the cooling capacity of 31b) is insufficient and the internal temperature rises can be avoided more reliably.

<< Embodiment 2 of the Invention >>
The container refrigeration apparatus (1) according to the second embodiment is obtained by adding an operation mode of the defrosting operation in the first embodiment. That is, in the first embodiment, the refrigerant discharged from the compressor (21) is directly flowed to any one of the heat exchangers (31a, 31b) of the internal heat exchanger (31), and the heat exchanger (31a, 31b) The defrost mode (hereinafter referred to as the first defrost mode) for defrosting can be executed. However, in Embodiment 2 above, in addition to the first defrosting mode, the refrigerant discharged from the compressor (21) is passed through the heat source side heat exchanger (22) and then the heat exchanger (31) inside the chamber. This heat exchange part (31a, 31b) was flowed to enable the defrost mode (hereinafter referred to as the second defrost mode) to defrost the heat exchange part (31a, 31b).

  As shown in FIG. 10, in the second embodiment, the refrigerant circuit (10) of the first embodiment has six third open / close pipes (63) and four fourth connect pipes (64) and six opening / closing mechanisms (40). A valve (40f-40k) is added.

  One end of the third communication pipe (63) is connected between the first heat exchanging portion (31a) of the gas side first inlet / outlet pipe (57a) and the drain pan heater (58a), and the other end is the liquid side second. The inlet / outlet pipe (56b) is connected to the liquid pipe (55) side of the second expansion valve (40e).

  One end of the fourth communication pipe (64) is connected between the second heat exchange part (31b) and the drain pan heater (58b) of the gas side second inlet / outlet pipe (57b), and the other end is the liquid side first. The inlet / outlet pipe (56a) is connected to the liquid pipe (55) side of the first expansion valve (40d).

  The first on-off valve (40f) is provided in the liquid side first inlet / outlet pipe (56a) closer to the liquid pipe (55) than the fourth connecting pipe (64), and the second on-off valve (40g) The second inlet / outlet pipe (56b) is provided closer to the liquid pipe (55) than the third communication pipe (63). The third on-off valve (40h) is provided in the third connecting pipe (63), and the fourth on-off valve (40i) is provided in the fourth connecting pipe (64). The fifth on-off valve (40j) is provided between the third communication pipe (63) and the drain pan heater (58a) in the gas side first inlet / outlet pipe (57a), and the sixth on-off valve (40k) The side second inlet / outlet pipe (57b) is provided between the fourth connecting pipe (64) and the drain pan heater (58b).

<Cooling operation>
The operation during the cooling operation will be described with reference to FIG.

  In the cooling operation, both the first four-way switching valve (40a) and the second four-way switching valve (40b) are set to the first state and the on-off valve (40c) is set to the open state as the switching mechanism (40). . Further, the first on-off valve (40f), the second on-off valve (40g), the fifth on-off valve (40j), and the sixth on-off valve (40k) are set to the open state, and the third on-off valve (40h) and the second on-off valve (40h) The 4 on-off valve (40i) is set to the closed state. Furthermore, the opening degree of the first expansion valve (40d) is adjusted so that the degree of superheat of the refrigerant flowing out from the first heat exchange unit (31a) becomes a predetermined target value, and the second heat exchange unit (31b) The opening degree of the second expansion valve (40e) is adjusted so that the degree of superheat of the refrigerant flowing out becomes a predetermined target value.

  In the cooling operation, when the refrigerant compressed by the compressor (21) is discharged to the discharge pipe (51), the discharged refrigerant is separated from the first four-way switching valve (40a) side and the second four-way switching valve (40b) side. Then, the gas is merged by the first gas pipe (53) and flows into the external heat exchanger (22). In the outside heat exchanger (22), the refrigerant and the outside air exchange heat, and the refrigerant dissipates heat to the outside air and condenses. The refrigerant condensed in the external heat exchanger (22) passes through the receiver (24), and then from the liquid pipe (55) to the liquid side first inlet / outlet pipe (56a) side and the liquid side second inlet / outlet pipe (56b). ) Divide to the side.

  The refrigerant flowing into the liquid side first inlet / outlet pipe (56a) is depressurized by the first expansion valve (40d), and then flows into the first heat exchange section (31a) of the internal heat exchanger (31). In the first heat exchange section (31a), the refrigerant and the internal air exchange heat, and the refrigerant absorbs heat from the internal air and evaporates, whereby the internal air is cooled.

  On the other hand, the refrigerant flowing into the liquid side second inlet / outlet pipe (56b) is depressurized by the second expansion valve (40e) and then flows into the second heat exchange section (31b) of the internal heat exchanger (31). . In the second heat exchange section (31b), the refrigerant and the internal air exchange heat, and the refrigerant absorbs heat from the internal air and evaporates, whereby the internal air is cooled.

  Thereafter, the refrigerant evaporated in the first heat exchange section (31a) flows out to the gas side first inlet / outlet pipe (57a), passes through the first four-way switching valve (40a), and then passes through the first inlet pipe (52). It flows into the suction passage (52a). On the other hand, the refrigerant evaporated in the second heat exchange section (31b) flows out into the gas side second inlet / outlet pipe (57b), passes through the second four-way switching valve (40b), and then passes through the second of the suction pipe (52). It flows into the suction passage (52b). Thereafter, the refrigerant on the first suction path (52a) side and the refrigerant on the second suction path (52b) side merge in the suction pipe (52) and are sucked into the compressor (21). In the compressor (21), the refrigerant is compressed again and discharged to the discharge pipe (51).

  Thus, in the cooling operation, the internal air is cooled by both the first heat exchange part (31a) and the second heat exchange part (31b) of the internal heat exchanger (31).

<Defrosting operation>
Next, the operation | movement operation | movement at the time of a defrost operation is demonstrated, referring FIGS. In the second embodiment, before the defrosting operation, one of the first defrosting mode and the second defrosting mode is set by the user.

<First defrosting mode>
When the first defrost mode is set by the user, the container refrigeration apparatus (1) is switched to the defrost operation in the first defrost mode every time a predetermined time elapses after the cooling operation is performed. The first defrosting operation and the second defrosting operation in the first defrosting mode are alternately executed at predetermined time intervals.

<First Defrosting Operation in First Defrosting Mode>
The first defrosting operation in the first defrosting mode will be described with reference to FIG.

  In the first defrosting operation, as the switching mechanism (40), the first four-way switching valve (40a) is set to the second state, the second four-way switching valve (40b) is set to the first state, and the on-off valve (40c ) Is set to the closed state. Furthermore, the second on-off valve (40g), the fifth on-off valve (40j), and the sixth on-off valve (40k) are set to the open state, the first on-off valve (40f), the third on-off valve (40h), and The fourth on-off valve (40i) is set to the closed state. Further, the first expansion valve (40d) is set to a fully closed state, and the second expansion valve (40e) is set so that the degree of superheat of the refrigerant flowing out from the second heat exchange section (31b) becomes a predetermined target value. The opening is adjusted.

  In the first defrosting operation, when the refrigerant compressed by the compressor (21) is discharged to the discharge pipe (51), the discharged refrigerant is discharged from the first four-way switching valve (40a) to the gas side first inlet / outlet pipe ( After passing through 57a), it flows into the first heat exchange section (31a) of the internal heat exchanger (31). In the first heat exchange section (31a), the frost and the refrigerant adhering during the cooling operation exchange heat, the frost is heated and melted, and the refrigerant condenses.

  The refrigerant condensed in the first heat exchange section (31a) flows out from the first heat exchange section (31a) to the liquid side first inlet / outlet pipe (56a), and then passes through the first communication pipe (61) to the receiver ( After passing through 24), it flows into the liquid side second inlet / outlet pipe (56b).

  The refrigerant flowing into the liquid side second inlet / outlet pipe (56b) is depressurized by the second expansion valve (40e) and then sent to the second heat exchange section (31b) of the internal heat exchanger (31). In the second heat exchange section (31b), the refrigerant and the internal air exchange heat, and the refrigerant absorbs heat from the internal air and evaporates, whereby the internal air is cooled.

  Thereafter, the refrigerant evaporated in the second heat exchange section (31b) flows out from the second heat exchange section (31b) to the gas side second inlet / outlet pipe (57b). Thereafter, the refrigerant passes through the second four-way switching valve (40b) and the suction pipe (52) and is sucked into the compressor (21). In the compressor (21), the refrigerant is compressed again and discharged to the discharge pipe (51).

  When the first defrosting operation is continuously performed, the first heat exchange unit (31a) is defrosted to reduce the amount of frost formation, while the second heat exchange unit (31b) increases the frost amount. Heat exchange efficiency will fall. Therefore, the first defrosting operation is switched to the second defrosting operation when the defrosting is performed to some extent in the first heat exchange unit (31a) (when a predetermined operation time has elapsed).

<Second Defrosting Operation in First Defrosting Mode>
Next, the second defrosting operation in the first defrosting mode will be described with reference to FIG.

  In the second defrosting operation, as the switching mechanism (40), the first four-way switching valve (40a) is set to the first state, the second four-way switching valve (40b) is set to the second state, and the on-off valve (40c ) Is set to the closed state. Further, the first on-off valve (40f), the fifth on-off valve (40j), and the sixth on-off valve (40k) are set to the open state, the second on-off valve (40g), the third on-off valve (40h), and The fourth on-off valve (40i) is set to the closed state. Further, the second expansion valve (40e) is set to a fully closed state, and the first expansion valve (40d) is set so that the degree of superheat of the refrigerant flowing out from the first heat exchange section (31a) becomes a predetermined target value. The opening is adjusted.

  In the second defrosting operation, when the refrigerant compressed by the compressor (21) is discharged to the discharge pipe (51), the discharged refrigerant flows from the second four-way switching valve (40b) to the gas side second inlet / outlet pipe ( After passing through 57b), it flows into the second heat exchange section (31b) of the internal heat exchanger (31). In the second heat exchange section (31b), the frost and the refrigerant adhering during the cooling operation exchange heat, the frost is heated and melted, and the refrigerant condenses.

  The refrigerant condensed in the second heat exchange section (31b) flows out from the second heat exchange section (31b) to the liquid side second inlet / outlet pipe (56b), and then the second communication pipe (62) and the first communication pipe. After passing through the receiver (24) through (61), it flows into the liquid side first inlet / outlet pipe (56a).

  The refrigerant flowing into the liquid side first inlet / outlet pipe (56a) is depressurized by the first expansion valve (40d), and then sent to the first heat exchange section (31a) of the internal heat exchanger (31). In the first heat exchange section (31a), the refrigerant and the internal air exchange heat, and the refrigerant absorbs heat from the internal air and evaporates, whereby the internal air is cooled.

  Thereafter, the refrigerant evaporated in the first heat exchange section (31a) flows out from the first heat exchange section (31a) to the gas side first inlet / outlet pipe (57a). Thereafter, the refrigerant passes through the first four-way switching valve (40a) and the suction pipe (52) and is sucked into the compressor (21). In the compressor (21), the refrigerant is compressed again and discharged to the discharge pipe (51).

  When the second defrosting operation is continuously performed, the second heat exchange unit (31b) is defrosted to reduce the amount of frost formation, while the first heat exchange unit (31a) increases the frost formation amount. Heat exchange efficiency will fall. Therefore, the second defrosting operation is switched to the first defrosting operation when the defrosting is performed to some extent in the second heat exchange unit (31b) (when a predetermined operation time has elapsed).

  As described above, in the container refrigeration apparatus (1) of the present embodiment, when the first defrost mode is set, the first defrost operation and the second defrost operation in the first defrost mode are performed during the defrost operation. The frost operation is performed alternately. The upstream heat exchange section (31a, 31b) performs defrosting, and the downstream heat exchange section (31a, 31b) cools the interior air and maintains the interior at a predetermined temperature.

  In the first defrosting mode, the refrigerant discharged from the compressor (21) flows directly into the upstream heat exchange section (31a, 31b) without going through the external heat exchanger (22). Therefore, in the upstream heat exchange section (31a, 31b), a high heating capability (defrosting capability) is obtained by this high-temperature discharged refrigerant, and the defrosting time is shortened.

<Second defrosting mode>
When the second defrost mode is set by the user, the container refrigeration apparatus (1) is switched to the defrost operation in the second defrost mode every time a predetermined time elapses after the cooling operation is performed. The first defrosting operation and the second defrosting operation in the second defrosting mode are alternately executed at predetermined time intervals.

<First Defrosting Operation in Second Defrosting Mode>
The first defrosting operation in the second defrosting mode will be described with reference to FIG.

  In the first defrosting operation, both the first four-way switching valve (40a) and the second four-way switching valve (40b) are set to the first state as the switching mechanism (40), and the on-off valve (40c) is opened. Is set. Further, the first on-off valve (40f), the third on-off valve (40h), and the sixth on-off valve (40k) are set to the open state, the second on-off valve (40g), the fourth on-off valve (40i), and The fifth on-off valve (40j) is set to the closed state. Further, the first expansion valve (40d) is set to a fully open state, and the second expansion valve (40e) is set so that the degree of superheat of the refrigerant flowing out of the second heat exchange section (31b) becomes a predetermined target value. The opening is adjusted.

  In the first defrosting operation, when the refrigerant compressed by the compressor (21) is discharged to the discharge pipe (51), the discharged refrigerant is divided into the first four-way switching valve (40a) side and the second four-way switching valve (40b). ), And then merges at the first gas pipe (53) and flows into the external heat exchanger (22). In the outside heat exchanger (22), the refrigerant and the outside air exchange heat, and the refrigerant dissipates heat to the outside air and condenses. And the refrigerant | coolant condensed with the external heat exchanger (22) flows into a liquid side 1st inlet / outlet pipe | tube (56a), after passing through a receiver (24), and is 1st of a heat exchanger (31) in a warehouse. It flows into the heat exchange part (31a). In the first heat exchange section (31a), the frost and the refrigerant adhering during the cooling operation exchange heat, the frost is heated and melted, and the refrigerant is supercooled.

  The refrigerant supercooled in the first heat exchange section (31a) passes through the gas side first inlet / outlet pipe (57a) and the third communication pipe (63) in this order from the first heat exchange section (31a) to the liquid side second. After flowing into the inlet / outlet pipe (56b) and being depressurized by the second expansion valve (40e), it flows into the second heat exchange section (31b) of the internal heat exchanger (31). In the second heat exchange section (31b), the refrigerant and the internal air exchange heat, and the refrigerant absorbs heat from the internal air and evaporates, whereby the internal air is cooled.

  Thereafter, the refrigerant evaporated in the second heat exchange section (31b) flows out from the second heat exchange section (31b) to the gas side second inlet / outlet pipe (57b). Thereafter, the refrigerant passes through the second four-way switching valve (40b) and the suction pipe (52) and is sucked into the compressor (21). In the compressor (21), the refrigerant is compressed again and discharged to the discharge pipe (51).

  When the first defrosting operation is continuously performed, the first heat exchange unit (31a) is defrosted to reduce the amount of frost formation, while the second heat exchange unit (31b) increases the frost amount. Heat exchange efficiency will fall. Therefore, the first defrosting operation is switched to the second defrosting operation when the defrosting is performed to some extent in the first heat exchange unit (31a) (when a predetermined operation time has elapsed).

<Second Defrosting Operation in Second Defrosting Mode>
The second defrosting operation in the second defrosting mode will be described with reference to FIG.

  In the second defrosting operation, both the first four-way switching valve (40a) and the second four-way switching valve (40b) are set to the first state as the switching mechanism (40), and the on-off valve (40c) is opened. Is set. Further, the second on-off valve (40g), the fourth on-off valve (40i), and the fifth on-off valve (40j) are set to the open state, the first on-off valve (40f), the third on-off valve (40h), and The sixth on-off valve (40k) is set to the closed state. Further, the opening degree of the first expansion valve (40d) is adjusted so that the degree of superheat of the refrigerant flowing out from the first heat exchange part (31a) becomes a predetermined target value, and the opening degree of the second expansion valve (40e) is adjusted. Is set to the fully open state.

  In the second defrosting operation, when the refrigerant compressed by the compressor (21) is discharged to the discharge pipe (51), the discharged refrigerant is divided into the first four-way switching valve (40a) side and the second four-way switching valve (40b). ), And then merges at the first gas pipe (53) and flows into the external heat exchanger (22). In the outside heat exchanger (22), the refrigerant and the outside air exchange heat, and the refrigerant dissipates heat to the outside air and condenses. And the refrigerant | coolant condensed with the external heat exchanger (22) flows into a liquid side 2nd inlet / outlet pipe (56b), after passing a receiver (24), and is 2nd of the internal heat exchanger (31). It flows into the heat exchange part (31b). In the second heat exchange section (31b), the frost and the refrigerant adhering during the cooling operation exchange heat, and the frost is heated and melted, and the refrigerant is supercooled.

  The refrigerant supercooled in the second heat exchange section (31b) passes through the gas side second inlet / outlet pipe (57b) and the fourth communication pipe (64) in this order from the second heat exchange section (31b) to the liquid side first. It flows into the inlet / outlet pipe (56a), is decompressed by the first expansion valve (40d), and then flows into the first heat exchange section (31a) of the internal heat exchanger (31). In the first heat exchange section (31a), the refrigerant and the internal air exchange heat, and the refrigerant absorbs heat from the internal air and evaporates, whereby the internal air is cooled.

  Thereafter, the refrigerant evaporated in the first heat exchange section (31a) flows out from the first heat exchange section (31a) to the gas side first inlet / outlet pipe (57a). Thereafter, the refrigerant passes through the first four-way switching valve (40a) and the suction pipe (52) and is sucked into the compressor (21). In the compressor (21), the refrigerant is compressed again and discharged to the discharge pipe (51).

  When the second defrosting operation is continuously performed, the second heat exchange unit (31b) is defrosted to reduce the amount of frost formation, while the first heat exchange unit (31a) increases the frost formation amount. Heat exchange efficiency will fall. Therefore, the second defrosting operation is switched to the first defrosting operation when the defrosting is performed to some extent in the second heat exchange unit (31b) (when a predetermined operation time has elapsed).

  As described above, in the container refrigeration apparatus (1) of the present embodiment, when the second defrosting mode is set, the first defrosting operation and the second defrosting in the second defrosting mode are performed during the defrosting operation. The frost operation is performed alternately. The upstream heat exchange section (31a, 31b) performs defrosting, and the downstream heat exchange section (31a, 31b) cools the interior air and maintains the interior at a predetermined temperature.

  In the second defrosting mode, after the refrigerant discharged from the compressor (21) is condensed in the external heat exchanger (22), the upstream heat exchange section (31a, 31b) and the downstream heat exchange section (31a , 31b). Therefore, defrosting is performed by the condensed refrigerant in the upstream heat exchange section (31a, 31b), and this condensed refrigerant is supercooled by the frost. In the downstream heat exchange section (31a, 31b), the enthalpy is increased by the amount of the supercooled condensed refrigerant in the upstream heat exchange section (31a, 31b). Becomes higher. Therefore, during the defrosting operation, a situation in which the ability to cool the internal air is insufficient and the internal temperature rises is reliably avoided, and the internal temperature is further stabilized.

-Effect of Embodiment 2-
In the present embodiment, the first defrosting mode and the second defrosting mode can be executed, and the user sets and executes one of the defrosting modes. Thereby, when a user performs 1st defrost mode, the defrost capability of the upstream heat exchange part (31a, 31b) is improved, and the defrost operation which gave priority to shortening of defrost time is performed. On the other hand, the user can execute the second defrosting mode to increase the cooling capacity of the downstream heat exchange section (31a, 31b) and perform the defrosting operation with an emphasis on stabilization of the internal temperature. it can.

<< Other Embodiments >>
About the said embodiment, it is good also as the following structures.

  In the above embodiment, the time required for defrosting the heat exchange section (31a, 31b) on the upstream side to some extent is set as the operation time of each defrost operation, and every time the operation time elapses, the defrost operation is performed. Has been switched. However, the switching control of the defrosting operation is not limited to this. For example, the defrosting state of the upstream heat exchange unit (31a, 31b) is detected, and the defrosting operation is switched according to the detected defrosting state. You may make it change. By carrying out like this, the defrosting operation | movement which defrosts in an upstream heat exchange part (31a, 31b), and cools the inside of a store | warehouse | chamber in a downstream heat exchange part (31a, 31b) can be performed more reliably.

  As described above, the present invention is useful for a container refrigeration apparatus that cools the inside of a container.

1 Container refrigeration equipment
10 Refrigerant circuit
21 Compressor
22 External heat exchanger (heat source side heat exchanger)
31 Internal heat exchanger (use side heat exchanger)
31a First heat exchanger
31b Second heat exchange section
40 Switching mechanism

Claims (3)

A container refrigeration apparatus comprising a refrigerant circuit (10) connected to a compressor (21), a heat source side heat exchanger (22), and a use side heat exchanger (31), wherein the refrigerant circulates to perform a refrigeration cycle. There,
The use side heat exchanger (31) has a first heat exchange part (31a) and a second heat exchange part (31b),
The refrigerant circuit (10) diverts the refrigerant discharged from the compressor (21) to the two heat exchange units (31a, 31b) via the heat source side heat exchanger (22), and exchanges the two heats. Cooling operation for evaporating the refrigerant in the parts (31a, 31b) to cool the internal air, and the refrigerant discharged from the compressor (21) is used as the first heat exchange part (31a), the second heat exchange part (31b ) In the order of defrosting at the first heat exchanging portion (31a) and evaporating the refrigerant at the second heat exchanging portion (31b) to cool the internal air, and the compressor ( The discharged refrigerant of 21) is flowed in the order of the second heat exchanging part (31b) and the first heat exchanging part (31a) to defrost the second heat exchanging part (31b), and the first heat exchanging part (31a And a switching mechanism (40) for switching the refrigerant flow state so that the defrosting operation in which the second defrosting operation for evaporating the refrigerant to cool the air in the cabinet is performed alternately is performed. Iko Refrigerating apparatus for container according to claim. In claim 1,
In the first defrosting operation, the switching mechanism (40) causes the refrigerant discharged from the compressor (21) to flow to the first heat exchange unit (31a) without passing through the heat source side heat exchanger (22), In the second defrosting operation, a first defrosting mode is performed in which the refrigerant discharged from the compressor (21) flows to the second heat exchange unit (31b) without passing through the heat source side heat exchanger (22). Thus, the container refrigeration apparatus characterized by switching the flow state of the refrigerant. In claim 2,
In the first defrosting operation, the switching mechanism (40) causes the refrigerant discharged from the compressor (21) to flow to the first heat exchange unit (31a) via the heat source side heat exchanger (22), and In the second defrosting operation, a second defrosting mode is executed in which the refrigerant discharged from the compressor (21) flows to the second heat exchange unit (31b) via the heat source side heat exchanger (22). A container refrigeration apparatus characterized by switching a refrigerant distribution state.

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