JP2011232008A - Refrigerating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigerating device capable of improving stability of an inner temperature by optimizing a cooling operation time in accordance with defrosting state by a predetermined defrost operation.SOLUTION: A refrigerating device (1) includes an operation switching section (81) that switches between cooling operation and defrost operation and executes them. The operation switching section (81) includes: a defrost termination section (82) that terminates defrost operation to switch to cooling operation when either termination condition is met of a first termination condition in which the inner temperature in a heat exchanger (53) increases up to a predetermined temperature after the start of defrost operation and a second termination condition in which a predetermined time elapses until the temperature increases up to the predetermined temperature; and a cooling termination section (83) that terminates cooling operation to switch to defrost operation when a predetermined cooling operation time has elapsed after the start of cooling operation, and on the other hand, changes the cooling operation time from the previous cooling operation time in accordance with termination conditions of the defrost operation by the defrost termination section (82).

Description

    The present invention relates to a refrigeration apparatus that performs a defrost operation, and particularly relates to improving the stability of the internal temperature.

    Conventionally, a refrigeration apparatus that cools the inside of a freezer or the like using a refrigeration cycle is known. For example, Patent Document 1 discloses a refrigeration apparatus of this type. This refrigeration apparatus includes a refrigerant circuit that performs a vapor compression refrigeration cycle, and a compressor, a heat source side heat exchanger, an expansion valve, and a use side heat exchanger are sequentially connected to the refrigerant circuit. The refrigerant discharged from the compressor condenses in the heat source side heat exchanger to become liquid refrigerant, is depressurized by the expansion valve, evaporates in the use side heat exchanger, and returns to the compressor. This refrigerant circulation is repeated, and the refrigerant absorbs heat from the internal air in the use side heat exchanger, whereby a cooling operation for cooling the internal space is performed.

    Moreover, in the refrigerating apparatus of the said patent document 1, the defrost (defrost) driving | operation which heats a utilization side heat exchanger and defrosts this utilization side heat exchanger is performed. This refrigeration apparatus is controlled to switch to the defrost operation every time the cooling operation is performed for a predetermined time.

JP 2006-162240 A

    Incidentally, switching from the defrost operation to the cooling operation is generally performed as follows.

    In the defrost operation, when the temperature of the use side heat exchanger rises and reaches a predetermined value (first end condition), it is considered that the frost in the use side heat exchanger has almost melted, and the defrost operation is ended and switched to the cooling operation. . In addition, when a predetermined time limit elapses without the temperature of the use side heat exchanger reaching a predetermined value (second end condition), the defrost operation is forcibly ended from the viewpoint of preventing an excessive increase in the internal temperature. Then it can be switched to cooling operation.

    However, if the cooling operation is always performed for a fixed time as in the refrigeration apparatus of Patent Document 1 regardless of the above-described defrost operation termination conditions, there are the following problems.

    That is, in a state where the defrost operation is forcibly terminated due to the second termination condition, there is a high possibility that frost remains in the use side heat exchanger. If the cooling operation is performed for a predetermined time in this state, frosting further proceeds and the frost enlarges, and there is a possibility that the defrosting cannot be completed in the next defrost operation. If it does so, it will be in the state where frost always remained in the utilization side heat exchanger, and there was a problem that the proper cooling capacity was not exhibited in the cooling operation, and the stability of the internal temperature was impaired.

    In addition, in the state where the defrost operation is terminated due to the first termination condition, since frost hardly remains in the use side heat exchanger, the frosting does not proceed so much even if the cooling operation is performed for a predetermined time in this state. The possibility of enlargement is low. On the other hand, from the viewpoint of maintaining the stability of the internal temperature, it is preferable that the operation time of the cooling operation is long. However, in the above-described refrigeration apparatus, the cooling operation is performed only for a preset time even in a state where the possibility of frost enlargement is low, so that the stability of the internal temperature is sufficiently ensured. I could not say it.

    Therefore, the present invention has been made in view of such a point, and the object thereof is to improve the stability of the internal temperature by optimizing the cooling operation time according to the defrosting state by a predetermined defrost operation. There is to make it.

    In the first invention, the compressor (21), the heat source side heat exchanger (25), and the use side heat exchanger (53) for cooling the interior are connected, and the refrigerant circulates to perform the refrigeration cycle. Switching between the refrigerant circuit (10), the cooling operation for cooling the interior with the use side heat exchanger (53), and the defrost operation for heating and defrosting the use side heat exchanger (53) It is premised on a refrigeration apparatus including an operation switching unit (81). In the present invention, the operation switching unit (81) includes a first end condition in which the temperature of the use side heat exchanger (53) rises to a predetermined temperature after the start of the defrost operation, and the use side heat exchange. A defrost end section that ends the defrost operation and switches to the cooling operation when one end condition is satisfied among the second end conditions in which a predetermined time elapses until the temperature of the vessel (53) rises to the predetermined temperature. (82) and when a predetermined cooling operation time has elapsed after the start of the cooling operation, the cooling operation is terminated and switched to the defrost operation, while depending on the defrost operation end condition by the defrost end unit (82). And a cooling end section (83) for changing the cooling operation time from the previous cooling operation time.

    The refrigeration apparatus of the above invention is repeatedly executed by switching between the cooling operation and the defrost operation. In the cooling operation, the refrigerant compressed by the compressor (21) condenses in the heat source side heat exchanger (25), then evaporates in the use side heat exchanger (53) and absorbs heat from the air in the box, Cooling is performed. In the defrost operation, the use side heat exchanger (53) is heated to defrost the use side heat exchanger (53).

    In the present invention, the cooling operation time until the switching to the defrost operation after the start of the cooling operation is not constant and is changed from the previous cooling operation time. The change of the cooling operation time is performed in accordance with the end condition of the defrost operation performed before. The defrost operation end condition includes a first end condition and a second end condition. The first termination condition is that the temperature of the use side heat exchanger (53) rises during the defrost operation and reaches a temperature at which defrosting can be regarded as almost completed. On the other hand, the second end condition is that a predetermined time limit elapses without the temperature of the use-side heat exchanger (53) reaching a temperature at which defrosting can be considered to be almost completed. In the refrigeration apparatus, the cooling operation time is changed in a direction to stabilize the internal temperature, regardless of which condition is satisfied and the defrost operation ends. Then, the next cooling operation is performed with the changed cooling operation time.

    In a second aspect based on the first aspect, the cooling end section (83) makes the cooling operation time longer than the previous cooling operation time when the first end condition is satisfied and the defrost operation ends. On the other hand, when the second end condition is satisfied and the defrost operation ends, the cooling operation time is made shorter than the previous cooling operation time.

    In the present invention, when the first ending condition is satisfied and the defrost operation is ended, the defrosting of the use side heat exchanger (53) is generally ended. The cooling operation time is set longer than the previous cooling operation time, and the cooling operation is performed. In this way, even if the cooling operation is performed with a longer cooling operation time than the previous time with almost no frost remaining, frosting on the use side heat exchanger (53) does not progress so much. That is, since the cooling operation is performed for a longer time in a state where appropriate cooling capacity is exhibited as the use side heat exchanger (53), the internal temperature can be stably maintained.

    On the other hand, when the second ending condition is satisfied and the defrost operation is ended, there is a high possibility that the frost in the use side heat exchanger (53) remains. The cooling operation time is set shorter than the previous time, and the cooling operation is performed. Thus, even if frost remains, by performing the cooling operation shorter than the previous time, the enlargement of the frost is suppressed, and the possibility that the defrosting is completed in the next defrost operation is increased. When the defrosting is completed, an appropriate cooling capacity is exhibited in the use side heat exchanger (53) during the subsequent cooling operation, and the internal temperature can be stably maintained.

    According to a third aspect of the present invention, in the first or second aspect of the invention, the defrosting operation is performed by supplying a refrigerant so that the use side heat exchanger (53) functions as a condenser in the refrigerant circuit (10). It is an operation to circulate.

    In the present invention, in the defrost operation, the refrigerant is circulated in the direction opposite to the circulation direction during the cooling operation. Therefore, the high-temperature refrigerant compressed by the compressor (21) is discharged toward the usage-side heat exchanger (53) and condensed in the usage-side heat exchanger (53), so that the usage-side heat exchanger (53) Is defrosted by heating.

    According to the refrigeration apparatus of the present invention, the cooling operation time is changed in accordance with the defrost operation end condition. Therefore, the refrigeration apparatus can adjust the cooling operation time in a direction to stabilize the internal temperature in accordance with the defrosting state at the end of the defrost operation.

In addition, the refrigeration apparatus adjusts the cooling operation time each time switching from the defrost operation to the cooling operation is performed. As a result, the adjustment of the cooling operation time is repeated,
The cooling operation time gradually approaches an optimum value at which the inside temperature is stable. Eventually, the cooling operation time reaches the optimum value, and the internal temperature is maintained in a more stable state. Thus, the said refrigeration apparatus can implement | achieve the state which the interior temperature becomes more stable by adjusting cooling operation time repeatedly, and can improve the reliability of a refrigeration apparatus.

    Moreover, in the said refrigeration apparatus, even if in-chamber environment changes, such as a penetration | invasion of a water | moisture content and the change of set internal temperature, cooling operation time is changed according to the defrosting state at that time. That is, when the internal environment changes, first, the cooling operation time is adjusted according to the defrosting state by the defrost operation after the change. Then, by repeatedly adjusting, the cooling operation time reaches an optimal value, and the internal temperature becomes more stable. Thus, in the said refrigeration apparatus, even if the internal environment changes, the internal temperature can be stabilized quickly.

    Further, according to the refrigeration apparatus according to the second aspect of the present invention, when the defrost operation is completed by satisfying the first end condition among the defrost operation end conditions, the cooling operation time is set longer than the previous cooling operation time. did. When the first ending condition is satisfied and the defrost operation is ended, the defrosting of the use side heat exchanger (53) is almost ended. In this way, even if the cooling operation is performed with a longer cooling operation time than the previous time with almost no frost remaining, frosting on the use side heat exchanger (53) does not progress so much. That is, since the cooling operation is performed for a longer time in a state where appropriate cooling capacity is exhibited as the use side heat exchanger (53), the internal temperature can be stably maintained.

    Further, according to the refrigeration apparatus according to the second aspect of the present invention, when the defrost operation is completed by satisfying the second end condition among the defrost operation end conditions, the cooling operation time is set to be shorter than the previous cooling operation time. did. When the second end condition is satisfied and the defrost operation is ended, there is a high possibility that frost remains in the use side heat exchanger (53). However, when the cooling operation is performed with a shorter cooling operation time than the previous time, the enlargement of frost is suppressed, and the possibility that the defrosting is completed in the next defrost operation increases. When the defrosting is completed, an appropriate cooling capacity is exhibited in the subsequent cooling operation, so that the internal temperature can be stably maintained.

    In the refrigeration apparatus, the cooling operation time is optimized by repeatedly adjusting the cooling operation time according to the first and second end conditions of the defrost operation. That is, in the refrigeration apparatus, if the defrosting is finished within a predetermined time limit, the cooling operation time is lengthened, and if the defrosting is not finished, the cooling operation time is shortened repeatedly. Then, the cooling operation time reaches the longest optimum value in a range where the defrosting is always finished by a predetermined time limit. When the refrigeration apparatus performs the cooling operation at the optimum value of the cooling operation time, the cooling operation time in which the cooling capacity is appropriately exhibited in the internal heat exchanger (53) is the longest, and the internal temperature is the highest. It can be kept stable.

    Moreover, according to the refrigeration apparatus according to the third aspect of the present invention, in the defrost operation, the refrigerant is circulated in the direction opposite to the circulation direction during the cooling operation. The high-temperature refrigerant discharged from the compressor (21) toward the use side heat exchanger (53) heats the use side heat exchanger (53) to perform defrosting. Therefore, a new mechanism is not added for the defrost operation, and the refrigeration apparatus that performs the defrost operation can be downsized. Further, since the high-temperature refrigerant heats the use side heat exchanger (53) from the inside of the pipe, the defrosting operation can be performed without greatly affecting the internal temperature.

FIG. 1 is a piping diagram illustrating the configuration of the refrigeration apparatus according to the embodiment. FIG. 2 is a piping system diagram showing the refrigerant flow during the cooling operation in the embodiment. FIG. 3 is a piping diagram illustrating the refrigerant flow during the defrost operation in the embodiment. FIG. 4 is a control flow diagram of the defrost end unit in the embodiment. FIG. 5 is a control flow diagram of the cooling end unit in the embodiment.

    Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

    As shown in FIG. 1, the refrigeration apparatus (1) of this embodiment cools the inside of a freezer. This refrigeration system (1) includes an external unit (2), an internal unit (3), and a controller (80), and the external unit (2) and internal unit (3) are connected to the liquid side communication pipe ( 14) and gas side connecting pipe (15).

    The external unit (2) is provided with an external circuit (20), and the internal unit (3) is provided with an internal circuit (50). In this refrigeration system (1), a refrigerant circuit capable of a vapor compression refrigeration cycle by connecting the internal circuit (50) to the external circuit (20) by the connecting pipe (14, 15) described above. (10) is configured. The refrigerant circuit (10) is configured so that the refrigerant circulation direction is switched between a forward cycle cooling operation and a reverse cycle defrosting operation. The refrigerant circuit (10) is filled with, for example, R410A as a refrigerant.

<Outside unit>
The external circuit (20) of the external unit (2) includes a compressor (21), a four-way selector valve (24), an external heat exchanger (25), a receiver (27), a supercooling heat exchanger. (28) are sequentially connected by refrigerant piping.

    A discharge pipe (22) is connected to the discharge side of the compressor (21), and the discharge pipe (22) is provided with an oil separator (38) and a check valve (CV). The check valve (CV) is a valve that allows only the flow of refrigerant from the compressor (21) toward the four-way switching valve (24). A suction pipe (23) is connected to the suction side of the compressor (21).

    The oil separator (38) is connected to the compressor (21) via an oil return pipe (39) and communicates with a compression chamber of intermediate pressure.

    The first port of the four-way selector valve (24) is connected to a discharge pipe (22) on the discharge side of the compressor (21), and the second port is a suction pipe (23 on the suction side of the compressor (21)). ), The third port is connected to one end on the gas side of the external heat exchanger (25), and the fourth port is connected to the gas side communication pipe (15) via the shut-off valve (12). ing. When the cooling operation is performed, the four-way switching valve (24) is in a first state (shown by a solid line in FIG. 1) in which the first port and the third port communicate with each other and the second port and the fourth port communicate with each other. When the defrosting operation is performed, the first port and the fourth port communicate with each other and the second port and the third port communicate with each other (state indicated by a broken line in FIG. 1). It is comprised so that it may switch.

    The external heat exchanger (25) is a cross fin type fin-and-tube heat exchanger, and constitutes a heat source side heat exchanger. An external fan (26) is provided in the vicinity of the external heat exchanger (25). The external heat exchanger (25) is configured such that the refrigerant exchanges heat with the air sent by the external fan (26). As described above, one end on the gas side of the external heat exchanger (25) is connected to the third port of the four-way switching valve (31), and the other end on the liquid side is connected to the first liquid pipe (32). Connected to the receiver (27). The first liquid pipe (32) is provided with a check valve (CV) that allows only the flow of refrigerant toward the receiver (27).

    The receiver (27) can temporarily store the liquid refrigerant condensed in the external heat exchanger (25).

    The supercooling heat exchanger (28) constitutes a supercooler that supercools the liquid refrigerant condensed in the external heat exchanger (25), and includes a high pressure side channel (28a) and a low pressure side channel (28b). For example, it is comprised with the plate-type heat exchanger. The inflow end of the high pressure side flow path (28a) is connected to the bottom of the receiver (27), and the outflow end of the high pressure side flow path (28a) is connected to the closing valve (11) via the second liquid pipe (33). It is connected. The second liquid pipe (33) is provided with a check valve (CV) that allows only the flow of refrigerant toward the closing valve (11). On the other hand, the inflow end of the low-pressure channel (28b) is connected to the second liquid pipe (33) via the first branch pipe (34). The first branch pipe (34) branches from the upstream side of the check valve (CV) in the second liquid pipe (33). The first branch pipe (34) is provided with a supercooling expansion valve (29). The supercooling expansion valve (29) is an electronic expansion valve having a variable opening. One end of an injection pipe (37) is connected to the outflow end of the low-pressure channel (28b). The supercooling heat exchanger (28) superheats the refrigerant in the high-pressure channel (28a) by exchanging heat between the refrigerant in the high-pressure channel (28a) and the refrigerant in the low-pressure channel (28b). Is configured to do.

    The other end (outflow end) of the injection pipe (37) is connected to the oil return pipe (39) and communicates with the compression chamber of the intermediate pressure of the compressor (21).

    One end of the second branch pipe (35) is connected between the check valve (CV) and the closing valve (11) in the second liquid pipe (33). The other end of the second branch pipe (35) is connected to the downstream side of the check valve (CV) in the first liquid pipe (32). The second branch pipe (35) is provided with a check valve (CV) that allows only the flow of refrigerant toward the first liquid pipe (32). A third branch pipe (36) that bypasses the receiver (27) and the supercooling heat exchanger (28) is connected between the first liquid pipe (32) and the second liquid pipe (33). Yes. That is, one end of the third branch pipe (36) is connected to the upstream side of the check valve (CV) in the first liquid pipe (32), and the other end is the first branch pipe (34 in the second liquid pipe (33). ) Is connected to the upstream side of the connection part. The third branch pipe (36) is provided with an external expansion valve (31). The external expansion valve (31) is an electronic expansion valve whose opening degree can be adjusted.

    The external circuit (20) is provided with various sensors and pressure switches. Specifically, the discharge pipe (22) is provided with a discharge pipe temperature sensor (61) and a high pressure switch (62). The discharge pipe temperature sensor (61) detects the temperature of the discharge pipe (22), and the high pressure switch (62) detects the discharge pressure and urgently stops the refrigeration system (1) at abnormally high pressure. . The suction pipe (23) is provided with a suction pipe temperature sensor (63) for detecting the temperature of the suction pipe (23). An outside air temperature sensor (67) for detecting the outside air temperature is provided in the vicinity of the outside-compartment fan (26). The second liquid pipe (33) is provided with a liquid temperature sensor (68) for detecting the temperature of the liquid refrigerant.

<Inside unit>
The internal circuit (50) of the internal unit (3) includes a heating pipe (51), an internal expansion valve (52), and an internal heat exchanger (in order from the liquid side end to the gas side end). 53).

    The heating pipe (51) is a pipe connected to the liquid side communication pipe (14), and is disposed below the internal heat exchanger (53), and further around the heating pipe (51). The drain pan (55) is provided. The drain pan (55) collects frost and condensed water falling from the surface of the internal heat exchanger (53). That is, the heating pipe (51) is for heating and melting the ice block (residual frost) generated by freezing the frost and condensed water collected in the drain pan (55) with the refrigerant.

    The internal expansion valve (52) is an electronic expansion valve whose opening degree can be adjusted, and constitutes a use side expansion valve.

    The internal heat exchanger (53) is a cross-fin type fin-and-tube heat exchanger and constitutes a use side heat exchanger. An internal fan (54) is provided in the vicinity of the internal heat exchanger (53). The internal heat exchanger (53) is configured such that the refrigerant exchanges heat with the internal air sent by the internal fan (54).

    The internal circuit (50) is provided with four temperature sensors. Specifically, the heat transfer tube of the internal heat exchanger (53) is provided with an evaporation temperature sensor (72) for detecting the evaporation temperature of the refrigerant. A refrigerant temperature sensor (73) for detecting the temperature of the gas refrigerant is provided in the vicinity of the gas side end of the internal circuit (50). In the vicinity of the internal fan (54), an internal temperature sensor (74) for detecting the internal temperature is provided. Further, a pipe temperature sensor (75) for detecting the temperature of the heating pipe (51) is provided in the vicinity of the heating pipe (51).

<controller>
The controller (80) controls the drive of the compressor (21) and the fan (26, 54), switches the various valves (24, 29, 31, 52), and adjusts the opening degree. It controls operation and defrost operation. The controller (80) is provided with an operation switching unit (81).

    The operation switching unit (81) is configured to switch between the cooling operation and the defrost operation. The operation switching part (81) has a defrost end part (82) and a cooling / cooling end part (83).

    The defrost end section (82) is configured to end the defrost operation and switch to the cooling operation when the defrost operation end condition is satisfied after the start of the defrost operation. The end condition of the defrost operation includes a first end condition in which the temperature of the internal heat exchanger (53) rises to a predetermined temperature, and a predetermined time until the temperature of the internal heat exchanger (53) rises to the predetermined temperature. There is a second end condition in which elapses. The predetermined temperature is a temperature at which defrosting of the internal heat exchanger (53) can be regarded as almost completed. As the temperature of the internal heat exchanger (53), for example, the temperature of the evaporation temperature sensor (72) in the internal heat exchanger (53) is used. The position for detecting the temperature is not limited to the inside of the internal heat exchanger (53) and may be anywhere near the internal heat exchanger (53). The predetermined time is a time limit for defrost operation. As described above, in the refrigeration apparatus (1), by providing the time limit for the defrost operation in advance, it is possible to prevent the defrost operation from being excessively prolonged and to suppress a significant increase in the internal temperature.

The cooling end section (83) is configured to perform control to end the cooling operation and switch to the defrost operation when a predetermined cooling operation time has elapsed. The cooling end section (83) is configured to change the cooling operation time from the previous cooling operation time according to the defrost operation end condition.
Specific control operations of the defrost end section (82) and the cooling end section (83) will be described later.

-Driving action-
Next, the operation of the refrigeration apparatus (1) will be described with reference to FIGS. In the refrigeration apparatus (1), a cooling operation for cooling the inside of the freezer and a defrosting operation for heating and defrosting the internal heat exchanger (53) are performed.

<Cooling operation>
First, the operation of the cooling operation will be described. As shown in FIG. 2, in this cooling operation, the four-way selector valve (24) is set to the first state. Further, superheat control is performed to adjust the opening of the internal expansion valve (52) so that the difference between the detected value of the evaporation temperature sensor (72) and the detected value of the refrigerant temperature sensor (73) becomes a predetermined value. . The opening degree of the supercooling expansion valve (29) is controlled so that the detection value of the liquid temperature sensor (68) becomes a predetermined value. The outside expansion valve (31) is set to a fully closed state.

    In this cooling operation, in the refrigerant circuit (10), a vapor compression refrigeration cycle is performed in which the external heat exchanger (25) functions as a condenser and the internal heat exchanger (53) functions as an evaporator. That is, when the compressor (21) is driven, the refrigerant flows in the direction of the arrow shown in FIG. 2 in the refrigerant circuit (10).

    Specifically, the high-temperature and high-pressure gas refrigerant compressed by the compressor (21) is discharged to the discharge pipe (22). At that time, in the oil separator (38), the refrigerating machine oil is separated and stored from the discharged refrigerant that has flowed. The stored refrigeration oil flows into the compressor (21) through the oil return pipe (39).

    The refrigerant discharged to the discharge pipe (22) flows into the external heat exchanger (25) through the four-way switching valve (24). In the outside heat exchanger (25), the refrigerant exchanges heat with outside air and condenses (heatsinks). The condensed refrigerant passes through the first liquid pipe (32), the receiver (27), and the high pressure side flow path (28a) of the supercooling heat exchanger (28) in order, and flows into the second liquid pipe (33). A part of the refrigerant flowing into the second liquid pipe (33) flows to the first branch pipe (34), and the rest flows to the liquid side connecting pipe (14).

The refrigerant (branch refrigerant) flowing to the first branch pipe (34) is depressurized by the supercooling expansion valve (29) and then flows into the low pressure side flow path (28b) of the supercooling heat exchanger (28). . In the supercooling heat exchanger (28), heat is exchanged between the refrigerant in the high-pressure channel (28a) and the refrigerant (branch refrigerant) in the low-pressure channel (28b). As a result, the refrigerant in the high-pressure channel (28a) is supercooled, and the refrigerant in the low-pressure channel (28b) evaporates. The gas refrigerant evaporated in the low pressure side flow path (28b) flows to the injection pipe (37). Therefore, the liquid refrigerant supercooled by the supercooling heat exchanger (28) flows into the liquid side communication pipe (14).

    On the other hand, the gas refrigerant flowing into the injection pipe (37) merges with the refrigeration oil flowing in from the oil return pipe (39), and flows into the intermediate pressure compression chamber in the compression mechanism of the compressor (21). Here, the refrigeration apparatus (1) is configured such that the pressure of the refrigerant to be injected is higher than the pressure of the refrigerant in the compression chamber of the intermediate pressure. Otherwise, it is difficult for the refrigerant to flow from the injection pipe (37) into the compression chamber of intermediate pressure. In the intermediate pressure compression chamber, the refrigerant in the compression chamber and the injected refrigerant are mixed. That is, the refrigerant in the compression chamber having the intermediate pressure is compressed while being cooled. This prevents an abnormal increase in the refrigerant temperature discharged from the compressor (21).

    The refrigerant that has flowed into the liquid side connection pipe (14) flows into the internal circuit (50), and first flows through the heating pipe (51). Then, the residual frost collected in the drain pan (55) is heated and melted by the refrigerant flowing through the heating pipe (51). Thereby, the refrigerant flowing through the heating pipe (51) is further cooled. The melted frost (water) is discharged to the outside of the drain pan (55) through the predetermined drainage path, and thus to the outside of the warehouse.

    The refrigerant flowing out of the heating pipe (51) is decompressed by the internal expansion valve (52) and then flows into the internal heat exchanger (53). In the internal heat exchanger (53), the refrigerant evaporates by exchanging heat with the internal air. Thereby, the air in a warehouse is cooled. The refrigerant evaporated in the internal heat exchanger (53) flows again into the external circuit (20) through the gas side communication pipe (15). The refrigerant flowing into the external circuit (20) is sucked into the compressor (21) from the suction pipe (23) through the four-way switching valve (24). The refrigerant sucked into the compressor (21) is compressed and then discharged again, and this refrigerant circulation is repeated.

<Defrost operation>
As shown in FIG. 3, in the defrost operation, the four-way selector valve (24) is set to the second state. The internal expansion valve (52) is set to a fully open state, while the supercooling expansion valve (29) is set to a fully closed state. When the compressor (21) is operated in this state, the external heat exchanger (25) functions as an evaporator and the internal heat exchanger (53) functions as a condenser in the refrigerant circuit (10). A vapor compression refrigeration cycle is performed. In the refrigerant circuit (10), the refrigerant flows in the direction of the arrow shown in FIG. During the defrosting operation, the opening degree of the external expansion valve (31) is adjusted as appropriate.

    Specifically, the refrigerant discharged from the compressor (21) flows into the internal heat exchanger (53) through the four-way switching valve (24) after the refrigerating machine oil is separated by the oil separator (38). . In the internal heat exchanger (53), the attached frost is heated and melted by the high-temperature refrigerant, while the refrigerant is cooled by the frost and condensed (heat radiation). The refrigerant condensed in the internal heat exchanger (53) flows through the heating pipe (51) and is used for melting residual frost in the drain pan (55). The refrigerant which has passed through the heating pipe (51) passes through the receiver (27) via the liquid side connecting pipe (14) and the second branch pipe (35), and passes through the supercooling heat exchanger (28). It flows into the 3 branch pipe (36). The refrigerant flowing into the third branch pipe (36) is decompressed by the external expansion valve (31) and then flows into the external heat exchanger (25). In the external heat exchanger (25), the refrigerant exchanges heat with external air and evaporates. The refrigerant evaporated in the external heat exchanger (25) is sucked into the compressor (21) from the suction pipe (23) through the four-way switching valve (24). The refrigerant sucked into the compressor (21) is compressed and then discharged again, and this refrigerant circulation is repeated.

<Operation of controller>
Next, the control operation of the cooling operation and the defrost operation performed in the operation switching unit (81) of the controller (80) will be described.

    The refrigeration apparatus (1) of the present embodiment is repeatedly executed by switching between the cooling operation and the defrost operation by the operation switching unit (81). Specifically, switching from the defrost operation to the cooling operation is performed by the defrost end section (82) of the operation switching section (81). On the other hand, switching from the cooling operation to the defrost operation is performed by the cooling end unit (83) of the operation switching unit (81).

    As shown in FIG. 4, in the defrost operation, first, in step ST1, it is determined whether or not the first end condition is satisfied. When the first end condition is satisfied, it is considered that the defrosting of the internal heat exchanger (53) is almost completed, and the defrost operation is terminated by the defrost end section (82). On the other hand, if the first end condition is not satisfied, the process proceeds to step ST2.

    In step ST2, it is determined whether or not the second end condition is satisfied. When the second end condition is satisfied, the defrost operation is ended by the defrost end section (82). On the other hand, if the second end condition is not satisfied, the process returns to step ST1 again. In this way, step ST1 and step ST2 are repeated until either the first end condition or the second end condition is satisfied, and when either end condition is satisfied, the defrost operation is terminated by the defrost end unit (82). To do. When the defrost operation ends, the defrost end section (82) switches to the cooling operation.

    Next, as shown in FIG. 5, in the cooling operation, first, in step ST11, the number of cooling operations is determined. If the cooling operation is the first time, the process proceeds to step ST12. On the other hand, if the cooling operation is the second or later, the process proceeds to step ST13.

    In step ST12, the cooling operation is started using the preset time as the cooling operation time. The preset cooling operation time may be longer than at least the cooling operation time at which the internal set temperature can be generally maintained. When the cooling operation is started, the process proceeds to step ST16. When the preset cooling operation time has elapsed, the cooling operation ends. When the cooling operation ends, the cooling end section (83) switches to the defrost operation.

    In step ST13, it is determined whether or not the defrost operation is ended under the first end condition. If the defrosting operation is terminated with the first termination condition, the process proceeds to step ST14. If the defrosting operation is terminated with the second termination condition without being terminated with the first termination condition, the process proceeds to step ST15.

    In step ST14, the cooling operation time is changed by the cooling end section (83) to be longer than the previous cooling operation time by a fixed time, and the cooling operation is started. When the cooling operation is started, the process proceeds to step ST16. Then, when the changed cooling operation time elapses, the cooling operation ends. When the cooling operation ends, the cooling end section (83) switches to the defrost operation.

    The process proceeds to step ST14 when the previous defrost operation is completed after satisfying the first termination condition, and the defrosting of the internal heat exchanger (53) is almost completed. In such a case, even if the cooling operation time is set longer than the previous cooling operation time, frost formation on the internal heat exchanger (53) does not proceed so much. That is, since the cooling operation is performed for a longer time in a state where the cooling capacity is appropriately exhibited as the internal heat exchanger (53), the internal temperature can be stably maintained.

    In step ST15, the cooling operation time is changed by the cooling end section (83) to be shorter than the previous cooling operation time by a fixed time, and the cooling operation is started. When the cooling operation is started, the process proceeds to step ST16. Then, when the changed cooling operation time elapses, the cooling operation ends. When the cooling operation ends, the cooling end section (83) switches to the defrost operation.

    The process proceeds to step ST15 when the previous defrost operation is completed after satisfying the second end condition, and there is a high possibility that frost in the internal heat exchanger (53) remains. In such a case, even if frost remains, by performing the cooling operation shorter than the previous time, the frost enlargement is suppressed, and the possibility that the defrosting is completed in the next defrost operation is increased. If the defrosting is completed, an appropriate cooling capacity is exhibited in the cooling operation performed thereafter, and the internal temperature can be stably maintained.

    In both step ST14 and step ST15, the cooling operation time is changed by a certain time from the previous time. For example, the change time is set in units of 1 to several hours. In addition, the change time may be changed during the cooling operation and the defrost operation.

    Further, when the cooling operation time is changed in step ST14, it is possible to set an upper limit value for the cooling operation time in accordance with the internal set temperature. For example, when the set temperature in the refrigerator is lower than −5 ° C., the moisture in the refrigerator floats in a solid (crystallized) state, so it is difficult for the internal heat exchanger (53) to form frost, Hard to occur. Therefore, the upper limit value of the cooling operation time is set as high as 10 hours, for example. On the other hand, when the internal temperature is −5 ° C. or higher, moisture floats in a state where the internal temperature is not solidified, so that the internal heat exchanger (53) is easily frosted and frost is likely to be enlarged. For this reason, the refrigeration apparatus (1) sets the upper limit value of the cooling operation time as low as 3 hours, for example, and prevents frost enlargement due to long-time cooling. That is, in the refrigeration apparatus (1), the cooling operation time can be changed within a range in which the cooling capacity is not significantly reduced due to frost enlargement.

-Effect of the embodiment-
According to the embodiment, every time switching from the defrost operation to the cooling operation is performed, the cooling operation time is changed from the previous cooling operation time in accordance with the termination condition of the defrost operation.

    Specifically, when the temperature of the internal heat exchanger (53) reaches a predetermined temperature within a predetermined defrost time limit (first end condition), the cooling operation time is set to be less than the previous time by the defrost end section (82). Changed to be longer. When the first ending condition is satisfied and the defrost operation is ended, the defrosting of the internal heat exchanger (53) is generally ended. Thus, even if the cooling operation is performed with a cooling operation time longer than the previous time with almost no frost remaining, the frosting on the internal heat exchanger (53) does not progress so much. That is, since the cooling operation is performed for a longer time in a state where the proper cooling capacity is exhibited as the internal heat exchanger (53), the internal temperature can be stably maintained.

    On the other hand, when the predetermined time elapses without the temperature of the internal heat exchanger (53) reaching the predetermined temperature (second end condition), the cooling operation time is made shorter than the previous time by the defrost end section (82). changed. When the second ending condition is satisfied and the defrost operation is ended, there is a high possibility that frost remains in the internal heat exchanger (53). However, when the cooling operation is performed with a shorter cooling operation time than the previous time, the enlargement of frost is suppressed, and the possibility that the defrosting is completed in the next defrost operation increases. When the defrosting is completed, an appropriate cooling capacity is exhibited in the internal heat exchanger (53) during the subsequent cooling operation, so that the internal temperature can be stably maintained.

    In the refrigeration system (1), the cooling operation time is optimized by repeatedly changing the cooling operation time according to the first and second end conditions of the defrost operation every time the defrost operation is switched to the cooling operation. Is done. That is, in the refrigeration apparatus (1), the cooling operation time is lengthened if the defrosting is completed within a predetermined time limit, and the cooling operation time is shortened if the defrosting is not completed. Then, the cooling operation time reaches the longest optimum value in a range where the defrosting is always finished by a predetermined time limit. When the refrigeration apparatus (1) performs the cooling operation at the optimum value of the cooling operation time, the cooling operation time in which the cooling capacity is appropriately exhibited becomes the longest, and the internal temperature can be most stably maintained.

    Further, in the refrigeration apparatus (1), the cooling operation time is changed according to the defrosting state by the defrost operation even if the internal environment changes, such as moisture intrusion or change in the internal set temperature. That is, when the internal environment changes, the cooling operation time is adjusted according to the defrost state after the change. Then, by repeatedly adjusting, the cooling operation time reaches an optimal value, and the internal temperature becomes more stable. Thus, in the refrigeration apparatus (1), the internal temperature can be stabilized quickly even if the internal environment changes.

    Note that the cooling end section (83) of the present embodiment performs both the cooling operation time lengthening (step ST14 in FIG. 5) and the cooling operation time shortening (step ST15 in FIG. 5). However, the present invention may perform only one of them. Even in this case, the cooling operation time can be optimized as compared with the prior art.

1 Refrigeration equipment
10 Refrigerant circuit
21 Compressor
25 External heat exchanger (heat source side heat exchanger)
53 Internal heat exchanger (use side heat exchanger)
81 Operation switching section
82 Defrost end
83 Cooling end

Claims (3)

A refrigerant circuit (10) in which a compressor (21), a heat source side heat exchanger (25), and a use side heat exchanger (53) for cooling the inside of the refrigerator are connected and the refrigerant circulates to perform a refrigeration cycle; ,
An operation switching unit (81) for switching between a cooling operation for cooling the interior with the use side heat exchanger (53) and a defrost operation for performing defrosting by heating the use side heat exchanger (53). A refrigeration apparatus comprising:
The operation switching part (81)
After the start of the defrost operation, the first end condition in which the temperature of the use side heat exchanger (53) rises to a predetermined temperature and the temperature of the use side heat exchanger (53) rises to the predetermined temperature. A defrost end section (82) that ends the defrost operation and switches to the cooling operation when one end condition is satisfied among the second end conditions for which the predetermined time elapses;
When a predetermined cooling operation time elapses after the start of the cooling operation, the cooling operation is terminated and switched to the defrost operation, while the cooling operation time is changed according to the defrost operation end condition by the defrost end unit (82). And a cooling end unit (83) that changes the previous cooling operation time from the previous cooling operation time. In claim 1,
The cooling end section (83), when the first end condition is satisfied and the defrost operation ends, makes the cooling operation time longer than the previous cooling operation time, while the second end condition is satisfied and the defrost operation is performed. When finished, the cooling operation time is made shorter than the previous cooling operation time. In any one of Claim 1 or 2,
The refrigeration apparatus is characterized in that the defrost operation is an operation of circulating the refrigerant so that the use side heat exchanger (53) functions as a condenser in the refrigerant circuit (10).

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