refrigerator

Abstract

To provide a refrigerator enabling a degradation in the defrosting capability thereof to be suppressed by reducing the amount of refrigerant flowing in a hot gas bypass pipe.SOLUTION: The refrigerator comprises: a cooling circuit having a first flow path in which refrigerant is circulated and a compressor compressing the refrigerant, a condenser condensing the refrigerant, a capillary tube expanding the refrigerant, and an evaporator evaporating the refrigerant are connected in this order, the cooling circuit comprises: a hot gas bypass pipe provided for configuring a second flow path in which the refrigerant compressed by the compressor flows from the compressor to the evaporator; a three-way valve provided in the first flow path between the compressor and the condenser and connected to the hot gas bypass pipe; and a two-way valve provided in the first flow path between the condenser and the capillary tube. The three-way valve allows the refrigerant delivered from the compressor to flow into the condenser or the hot gas bypass pipe, and the two-way valve can be closed to shut off the flow of the refrigerant discharged from the condenser.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a refrigerator, and more particularly to a refrigerator that removes frost adhering to an evaporator by using hot gas. [Background technology]

[0002] The evaporator, which is one of the cooling circuits of a refrigerator, may become frosted due to the cooling of the surrounding water vapor, resulting in a decrease in cooling performance. To solve this problem, a hot gas defrosting method is known in which a hot gas bypass pipe is provided downstream of a compressor, which is one of the cooling circuits, and connected to the upstream side of the evaporator, and high-temperature gas is temporarily passed through the hot gas bypass pipe to heat the evaporator and defrost it. In the hot gas defrosting method, if the amount of liquid return of the refrigerant passed through the hot gas bypass pipe to the compressor increases, the reliability of the compressor decreases. For example, Patent Document 1 discloses an invention that reduces the amount of liquid return to the compressor and improves the reliability of the refrigeration cycle device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Application No. 2017-554766 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the invention disclosed in Patent Document 1 requires a complex system for adjusting the flow rate flowing through the hot gas bypass pipe, such as a flow regulator connected to the hot gas bypass piping for adjusting the flow rate of the refrigerant flowing through the hot gas bypass piping, a refrigerant state detection means for detecting the discharge superheat of the refrigerant discharged from the compressor and the suction pressure of the compressor, and a defrost control means for closing the flow regulator during normal cooling operation and increasing or decreasing the flow rate of the refrigerant flowing through the hot gas bypass piping using the flow regulator in accordance with the discharge superheat and suction pressure detected by the refrigerant state detection means during defrost operation.

[0005] Therefore, an object of the present invention is to provide a refrigerator that can easily reduce the flow rate of refrigerant flowing through a hot gas bypass pipe and suppress a decrease in defrosting capacity without being equipped with a complex system. [Means for solving the problem]

[0006] A refrigerator according to the present invention includes a cooling circuit having a first flow path for circulating a refrigerant, the first flow path being connected in this order: a compressor that compresses a refrigerant sent from an evaporator; a condenser that condenses the refrigerant sent from the compressor; a capillary tube that expands the refrigerant sent from the condenser; and the evaporator that evaporates the refrigerant sent from the capillary tube. The cooling circuit includes a hot gas bypass pipe provided to form a second flow path for flowing the refrigerant compressed by the compressor from the evaporator to the evaporator; a three-way valve provided in the first flow path between the compressor and the condenser and connected to the hot gas bypass pipe; and a two-way valve provided in the first flow path between the condenser and the capillary tube. The three-way valve can cause the refrigerant discharged from the compressor to flow into the condenser or the hot gas bypass pipe. The two-way valve can be closed to block the flow of the refrigerant discharged from the condenser.

[0007] According to the present invention, in a refrigerator that defrosts an evaporator by a hot gas defrosting method, a three-way valve is provided downstream of a compressor and upstream of a condenser, and a two-way valve is provided downstream of the condenser and upstream of a capillary tube. A hot gas defrosting pipe is provided to bypass a refrigerant in a hot gas state from the downstream of the compressor to the upstream of the evaporator via the three-way valve. By configuring the cooling circuit in this way, the flow path of the refrigerant can be changed. Also, the flow of the refrigerant can be blocked. Therefore, it is expected that the flow rate of the refrigerant flowing through the hot gas bypass pipe can be easily reduced without a complicated system, and a decrease in defrosting capacity can be suppressed.

[0008] Furthermore, the present invention is characterized in that the refrigerator includes a control device which switches the cooling circuit between a normal operation for cooling the evaporator and a defrosting operation for defrosting the evaporator, and the control device can control whether the three-way valve causes a fluid to flow to the condenser or the hot gas bypass pipe and can further control opening and closing of the two-way valve, and when the control device switches from the normal operation to the defrosting operation, the three-way valve causes the refrigerant to flow to the condenser and the two-way valve is closed to discharge the refrigerant to the condenser by the compressor, and thereafter, the three-way valve causes the refrigerant to flow to the hot gas bypass pipe.

[0009] According to the present invention, before the defrosting operation, the two-way valve is closed to store the refrigerant in the condenser, and then the three-way valve is switched to flow the refrigerant into the hot gas bypass pipe, thereby executing the defrosting operation. By reducing the amount of refrigerant flowing in the cooling circuit during the defrosting operation, the possibility of the refrigerant in a hot gas state condensing is reduced, thereby suppressing a decrease in the defrosting capacity.

[0010] The present invention is also characterized in that the evaporator is provided with a temperature sensor, and the control device controls the three-way valve and the two-way valve in accordance with the temperature measured by the temperature sensor during the defrosting operation, thereby adjusting the amount of the refrigerant.

[0011] According to the present invention, the control device can grasp whether the defrosting capacity is decreasing or not according to the temperature measured by the temperature sensor. As a result, when it is detected that the amount of refrigerant currently circulating in the cooling circuit is too much or too little, the control device can adjust the amount of refrigerant circulating in the cooling circuit by switching the three-way valve and the two-way valve to switch the flow path of the refrigerant.

[0012] In the present invention, an inner diameter of the hot gas bypass pipe is equal to or larger than an inner diameter of a discharge pipe through which the refrigerant is discharged from the compressor.

[0013] According to the present invention, in a refrigerator that defrosts an evaporator by a hot gas defrost system, it is possible to reduce the pressure loss when the refrigerant flows through the hot gas bypass pipe, and to suppress condensation of the refrigerant.

[0014] In the present invention, an inner diameter of the three-way valve is equal to or larger than the inner diameter of the discharge pipe of the compressor.

[0015] According to the present invention, in a refrigerator that defrosts an evaporator by a hot gas defrosting system, it is possible to reduce the pressure loss when the refrigerant flows through a three-way valve, and to suppress condensation of the refrigerant. Effect of the Invention

[0016] According to the present invention, it is possible to provide a refrigerator that can easily reduce the flow rate of the refrigerant flowing through a hot gas bypass pipe and suppress a decrease in defrosting capacity without including a complicated system. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a side cross-sectional view of a refrigerator according to this embodiment. [Diagram 2] FIG. 2 is a circuit diagram showing a cooling circuit of the refrigerator according to this embodiment. [Diagram 3] FIG. 3 is a block diagram showing a control system for the refrigerator according to this embodiment. [Figure 4] FIG. 4 is a circuit diagram showing an example of a conventional cooling circuit. [Diagram 5] FIG. 5 is a timing chart of the control system for the refrigerator according to this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] With reference to FIG. 1, an overview of a refrigerator 1 according to an embodiment of the present invention will be described. FIG. 1 is a schematic side cross-sectional view of a refrigerator according to this embodiment. The refrigerator 1 has a refrigerator body 2, a door body 3 rotatably provided at the front part of the refrigerator body 2 when placed on a horizontal surface, and a drawer 4 movable in the front-rear direction. The door body 3 is connected to the refrigerator body 2 at its upper and lower parts by a hinge provided at least on either the left or right side, and rotates around the hinge axis. The refrigerator 1 according to this embodiment has two opening and closing parts, the door body 3 and the drawer 4, as described above, but is not limited thereto. For example, the refrigerator 1 may have an additional drawer, or all opening and closing parts may be composed of the door body.

[0019] The refrigerator 1 also has an outer box 5 that constitutes the exterior of the refrigerator body 2, and an upper inner box 6 and a lower inner box 7 that constitute the internal storage chamber. In the refrigerator 1 according to this embodiment, the upper inner box 6 constitutes the refrigeration chamber, and the lower inner box 7 constitutes the freezer chamber. When the door body 3 is opened, the interior of the upper inner box 6 can be accessed, and when the drawer 4 is opened, the interior of the lower inner box 7 can be accessed. A storage box (not shown) that moves together with the drawer 4 is attached to the drawer 4. The storage box has an opening at the top, and when the user stores the item in the lower inner box 7, the item is placed in the storage box through the opening and stored in the storage box. A foam insulation material 8 is filled between the outer box 5 and each of the inner boxes 6, 7, and insulates each of the inner boxes 6, 7 from the outside of the refrigerator body 2. A foam insulation material 8 is also filled between the upper inner box 6 and the lower inner box 7.

[0020] As shown in Fig. 1, a cooling chamber 9 is provided at the rear of the lower inner box 7, and an evaporator 24, which is a cooling device, is disposed in the cooling chamber 9. As described later, the evaporator 24 constitutes a part of a cooling circuit 20 of the refrigerator. A fan 10 is provided in the cooling chamber 9, and the fan 10 blows the cool air generated by the evaporator 24 to each of the inner boxes 6 and 7 through a duct 11.

[0021] The duct 11 is provided at the rear of each of the inner boxes 6 and 7, and guides the cold air generated in the cooling chamber 9 to the front of each of the inner boxes 6 and 7 through a vent provided at the front of the duct 11. A damper 12 is provided in the duct 11, and the damper 12 is configured to be controlled to open and close by a control device 41 described later. The control device 41 detects the temperature inside the chamber by a refrigerator chamber temperature sensor 14 (not shown) provided in the upper inner box 6, and controls the above-mentioned opening and closing based on the temperature. This adjusts the flow rate of cold air flowing into the upper inner box 6, which is the refrigerator chamber, and the temperature inside the upper inner box 6 can be kept constant in a temperature range different from the temperature inside the lower inner box 7, which is the freezer chamber.

[0022] A machine room 13 is provided at the rear and bottom of the refrigerator main body 2, in which are arranged the compressor 21, a condensing fan 13 (not shown) that cools the compressor 21 and the condenser 22, and an evaporation tray (not shown) that collects and evaporates drain water generated by defrosting the evaporator 24.

[0023] FIG. 2 shows the cooling circuit 20 of the refrigerator 1 according to this embodiment. The cooling circuit 20 includes a compressor 21, a condenser 22, a capillary tube 23, and an evaporator 24. The components of the cooling circuit 20 are fluidly connected in the above order by piping as described later, forming a first flow path through which the refrigerant circulates in the cooling circuit 20. The arrows in FIG. 2 indicate the direction of the refrigerant flow. That is, in the cooling circuit 20, for example, in the relationship between the compressor 21 and the evaporator 24 described later, the refrigerant flows from the evaporator 24 on the upstream side of the flow path to the compressor 21 on the downstream side of the flow path via a suction pipe 28.

[0024] The compressor 21 compresses the refrigerant in a gaseous state to a high temperature and high pressure state. The compressed refrigerant is sent to the condenser 22 through the pipe 25. The pipe 25 is provided with a three-way valve 31 as described later, and is divided into a pipe 25a and a pipe 25b. The compressor 21 is provided with an inverter, and by changing the rotation speed, the amount of refrigerant discharged by the compressor per unit time can be adjusted, and the cooling capacity of the cooling circuit 20 can be controlled. The compressor 21 is electrically connected to a control device 41 as described later, and the rotation speed is controlled by a signal transmitted from the control device 41. The condenser 22 releases heat from the refrigerant compressed by the compressor 21, and condenses the refrigerant. The condensed refrigerant is sent to the capillary tube 23 through the pipe 26. The pipe 26 is provided with a two-way valve 32 as described later, and is divided into a pipe 26a and a pipe 26b.

[0025] The capillary tube 23 reduces the pressure of the refrigerant condensed in the condenser 22, causing it to expand, and therefore reducing its temperature. The expanded refrigerant is sent to the evaporator 24 through the pipe 27. The evaporator 24 evaporates the refrigerant decompressed in the capillary tube 23 and absorbs heat. The evaporated refrigerant in a gaseous state is sent to the compressor 21 through the suction pipe 28 and compressed again. In this manner, the cooling circuit 20 operates. In this embodiment, the capillary tube 23 is connected to the condenser 22 and the evaporator 24 through the pipe 26b and the pipe 27, but the capillary tube 23 may include the pipes 26b and 27.

[0026] The suction pipe 28, which carries the refrigerant from the evaporator 24 to the compressor 21, is disposed at least partially in close proximity to the capillary tube 23 so as to exchange heat with the capillary tube 23. In Fig. 2, an area 29 surrounded by a dotted line shows an outline of the heat exchange section.

[0027] When the evaporator 24 operates to cool the inside of the refrigerator 1, there is a possibility that water vapor around the evaporator 24 may frost. In order to defrost the evaporator 24, the refrigerator 1 according to the present embodiment employs a hot gas defrosting method and uses hot gas, which is a refrigerant compressed by the compressor 21. For this reason, the cooling circuit 20 includes a hot gas bypass pipe 30 connected to a pipe 25 that connects the downstream of the compressor 21 and the upstream of the condenser 22. A three-way valve 31 is provided at the connection portion, and the three-way valve 31 can change the refrigerant sent from the compressor 21 through the pipe 25a to flow to either the condenser 22 (i.e., the pipe 25b) or the hot gas bypass pipe 30. This makes it possible to control whether the refrigerant flows to the condenser 22 to cool the evaporator 24, or flows to the hot gas bypass pipe 30 to defrost the evaporator 24. The hot gas bypass pipe 30 is connected to a pipe that connects the downstream of the capillary tube 23 and the upstream of the evaporator 24.

[0028] The hot gas bypass pipe 30 constitutes a second flow path in which the refrigerant flows through the compressor 21-piping 25-hot gas bypass pipe 30-piping 27-evaporator 24, which is different from the flow path in which the refrigerant flows through the compressor 21-piping 25-condenser 23-piping 26-capillary tube 23-piping 27-evaporator 24 in the above-mentioned first flow path.

[0029] The three-way valve 31 is connected to a control device 41, which will be described later, and the switching of the path through which the refrigerant flows is controlled by the control device 41 based on predetermined conditions. The control device 41 controls the three-way valve 31 so that the refrigerant discharged from the compressor 21 via the pipe 25a flows to the condenser 22 (i.e., the pipe 25b) during normal operation, which will be described later, and to the hot gas bypass pipe 30 during defrosting operation, which will be described later.

[0030] In this specification, a state in which the refrigerator 1 is operating normally (i.e., a state in which the refrigerator is operating to cool the inside of the refrigerator or to maintain the inside temperature) is appropriately referred to as a "normal operation." Also, a state in which the refrigerator 1 is operating to defrost the evaporator 24 (i.e., a state in which the refrigerator is operating by opening the three-way valve 31 so that the refrigerant flows from the three-way valve 31 to the hot gas bypass pipe 30 and hot gas flows to the evaporator 24) is appropriately referred to as a "defrosting operation."

[0031] The cooling circuit 20 of the refrigerator 1 according to this embodiment includes a two-way valve 32 in a pipe 26 that fluidly connects the condenser 22 and the capillary tube 23. The two-way valve 32 is connected to a control device 41. The control device 41 controls the opening and closing of the two-way valve 32 based on a predetermined condition for the refrigerant discharged from the condenser 22. By closing the two-way valve 32, the flow of the refrigerant to the pipe 26b can be blocked.

[0032] Fig. 3 is a block diagram showing the configuration of a control system 40 of the refrigerator 1 according to this embodiment. The control system 40 of the refrigerator 1 according to this embodiment includes a control device 41, which controls various devices. The control device 41 may be made up of multiple control devices. The control device 41 is made up of, for example, a control unit and a storage unit, not shown.

[0033] The control unit includes a general-purpose processor such as a CPU or MPU that executes a program to realize a predetermined function. The control unit calls and executes an arithmetic program stored in the storage unit, for example, to realize various processes in the control device 41 and transmission of signals to each component. The control unit is not limited to a unit that realizes a predetermined function by cooperation between hardware and software, and may be a hardware circuit designed specifically to realize a predetermined function. In other words, the control unit can be realized by various processors such as a GPU, FPGA, DSP, ASIC, etc., in addition to a CPU or MPU. Such a control unit can be composed of, for example, a signal processing circuit that is a semiconductor integrated circuit.

[0034] The storage unit is a recording medium capable of recording various information. The storage unit is realized, for example, by a memory such as a DRAM, an SRAM, or a flash memory, an HDD, an SSD, or other storage devices, or by an appropriate combination of them. The storage unit can store, for example, the temperature acquired by the refrigerator compartment temperature sensor 14 and the evaporator temperature sensor 15, the pressure value acquired by the pressure sensor described above, and the like. In addition, the storage unit can store a program for controlling each component such as the compressor 21, the three-way valve 31, the two-way valve 32, the fan 10, the damper 12, and the like based on the temperature, pressure, and the like. It may also store a control program related to the normal operation and the defrosting operation described later. Each component may directly transmit and receive information between each component through the control unit without going through the storage unit.

[0035] As described above, the control device 41 is electrically connected to the compressor 21, the three-way valve 31, and the two-way valve 32. The control device 41 is also electrically connected to the fan 10, the damper 12, the condensing fan 13, the refrigerator compartment temperature sensor 14, the evaporator temperature sensor 15, and the like. Another temperature sensor, such as a freezer compartment temperature sensor, may be attached to the lower inner box 7 constituting the freezer compartment, and the temperature sensor may be electrically connected to the control device 41. The control device 41 controls the temperatures of the refrigerator compartment, the freezer compartment, and the like to be kept at predetermined temperatures based on signals from the refrigerator compartment temperature sensor 14, etc.

[0036] The control device 41 can start the defrosting operation under any condition. For example, the refrigerator 1 can be provided with a defrosting switch (not shown), and when the control device 41 detects that the user has turned on the switch, the defrosting operation can be started. A timer can be provided instead of or in addition to the defrosting switch, and the defrosting operation can be started when a period set by the user on the timer has elapsed. The control device 41 can also be provided with an elapsed time detection function, and can be configured to start the defrosting operation when the elapsed time from the previous defrosting operation exceeds a predetermined period. A sensor can be provided that can detect the opening and closing of at least one of the door body 3 and the drawer 4, detects the number of openings and closings, and starts the defrosting operation when the number of openings and closings exceeds a predetermined threshold.

[0037] As in the cooling circuit 20 of the refrigerator 1 according to the present embodiment, by providing the three-way valve 31 and the two-way valve 32, it is possible to suppress a decrease in the defrosting capacity of the defrosting operation when the refrigerant is caused to flow into the hot gas bypass pipe 30. An operation example of the cooling circuit 20 will be described below.

[0038] In the refrigerator 1, during normal operation, the three-way valve 31 is open so as to allow the refrigerant to flow to the condenser 22. This state of the three-way valve 31 is hereinafter referred to as a "first state" as appropriate. Also, the state in which the three-way valve 31 is open so as to allow the refrigerant to flow to the hot gas bypass pipe 30 is hereinafter referred to as a "second state" as appropriate. The two-way valve 32 is configured to be controlled to open and close by the control device 41 in accordance with the operation of the compressor 21. Therefore, during normal operation, when the compressor 21 compresses and discharges the refrigerant, the two-way valve 32 is in an open state. Also, in the present embodiment, when the compressor 21 is stopped, the two-way valve 32 is in a closed state. However, this is not limited thereto, and the two-way valve may be maintained in an open state during normal operation and when the compressor 21 is stopped.

[0039] When the operation of the cooling circuit 20 is shifted from a normal operation state to a defrosting operation, the control device 41 first changes the two-way valve 32 to a closed state while maintaining the three-way valve 31 in the first state. As a result, the refrigerant does not flow downstream of the pipe 26b. In this state, the control device 41 operates the compressor 21 to discharge the refrigerant to the condenser 22. As a result, the refrigerant can be stored in the condenser 22 and the pipes 25b and 26a (hereinafter, for the sake of simplicity, it is referred to as storing the refrigerant in the condenser 22). The rotation speed of the compressor 21 may be changed to increase or decrease the discharge amount. For example, by increasing the discharge amount from the compressor 21, the refrigerant can be stored in the condenser 22 more quickly, and more refrigerant can be stored.

[0040] After storing the refrigerant in the condenser 22, the control device 41 changes the three-way valve 31 to the second state and performs a defrosting operation. Therefore, the refrigerant (hot gas) is discharged from the compressor 21 to the hot gas bypass pipe 30. At this time, the two-way valve 32 maintains a closed state. The control device 41 may perform the above-mentioned switching of the three-way valve 31 by detecting, for example, that the refrigerant has been stored in the condenser 22 for a predetermined time. In addition, the control device 41 may detect the load of the compressor 21 by measuring the rotation speed and current value of the motor provided in the compressor 21 and perform the switching. A pressure sensor may be provided in the flow path from the compressor 21 to the condenser 22 or in the condenser 22, etc., so as to detect the pressure of the refrigerant at that part, and the switching may be performed when the pressure sensor detects that the pressure at that part has reached a predetermined threshold value or higher.

[0041] In this way, by controlling the three-way valve 31 and the two-way valve 32, the amount of refrigerant in the cooling circuit 20 during the defrosting operation can be reduced. As described above as the first flow path, the cooling circuit 20 during normal operation is a flow path in which the refrigerant flows into the evaporator 24 after being discharged from the compressor 21 through the condenser 22 and the capillary tube 23. On the other hand, as described above as the second flow path, the cooling circuit 20 during the defrosting operation is a flow path in which the refrigerant flows into the evaporator 24 after being discharged from the compressor 21 through the hot gas bypass pipe 30. In this way, the second flow path has a smaller number of components through which the refrigerant passes than the first flow path. In addition, the condenser 22 generally has a long flow path in order to release the heat of the refrigerant compressed by the compressor 21. Therefore, the second flow path has a shorter overall flow path length than the first flow path. Therefore, the amount of refrigerant may be excessive for the length of the flow path.

[0042] If the amount of refrigerant during the defrosting operation becomes too large, the refrigerant that has become a hot gas is likely to condense into a liquid state (i.e., hot gas is likely to return to liquid state). If the refrigerant becomes liquid and flows into the compressor 21, there is a risk that the reliability of the compressor 21 will decrease, such as a decrease in performance. In addition, the temperature of the suction pipe 28 will decrease, and condensation may occur.

[0043] In addition, when the amount of refrigerant in the pipe increases and liquid refrigerant is generated in the pipe, the space through which hot gas refrigerant can pass through the pipe becomes narrower, resulting in an increase in the flow rate of the refrigerant and an increase in pressure loss, which in turn makes it easier for the hot gas refrigerant to condense into a liquid state.

[0044] However, as in the cooling circuit 20 of the refrigerator 1 according to the present embodiment, the amount of refrigerant flowing in the cooling circuit during the defrosting operation is reduced before the defrosting operation is performed, which reduces the possibility that the refrigerant in a hot gas state will condense. This makes it possible to suppress a decrease in the defrosting capacity.

[0045] Moreover, in the cooling circuit 20 of the refrigerator 1 according to this embodiment, the evaporator temperature sensor 15 is provided in the evaporator 24. The evaporator temperature sensor 15 is attached, for example, to a portion where the refrigerant is discharged from the evaporator 24. The evaporator temperature sensor 15 detects the temperature of the evaporator 24 and transmits it to the control device 41. This allows the control device 41 to detect whether a predetermined defrosting capacity is being exerted in the defrosting operation.

[0046] During the defrosting operation, if the temperature detected by the evaporator temperature sensor 15 is lower than a predetermined value, the evaporator 24 may not be sufficiently defrosted. In such a case, one of the causes is considered to be the above-mentioned reduction in defrosting capacity due to condensation of the refrigerant caused by an excess of the refrigerant. Therefore, it is preferable to reduce the amount of the refrigerant flowing through the second flow path during the defrosting operation.

[0047] Therefore, during the defrosting operation, when the control device 41 detects that the temperature of the evaporator temperature sensor 15 is lower than a predetermined value even though the refrigerant in a hot gas state is flowing through the evaporator 24, the control device 41 controls to adjust the flow rate of the refrigerant flowing through the second flow path. Specifically, for example, the flow rate of the refrigerant can be adjusted by switching the above-mentioned three-way valve 31.

[0048] During the defrosting operation, as described above, the three-way valve 31 is in the second state, and the two-way valve 32 is in the closed state. By switching the three-way valve 31 to the first state and operating the compressor, the refrigerant discharged from the compressor 21 flows to the condenser 22. Because the two-way valve 32 is in the closed state, the refrigerant cannot flow downstream of the pipe 26a and accumulates in the condenser 22. Thereafter, by switching the three-way valve 31 to the second state, the flow rate of the refrigerant flowing through the second flow path can be reduced. This makes it possible to suppress condensation of the refrigerant in a hot gas state in the pipe, and to suppress a decrease in the defrosting capacity.

[0049] The cooling circuit 20a shown in FIG. 4 shows an example of a simple cooling circuit of a conventional refrigerator employing a hot gas defrost system. The same components as those of the cooling circuit 20 are given the same reference numerals. As is clear from a comparison between FIG. 2 and FIG. 4, the cooling circuit 20a of the conventional refrigerator is different from the cooling circuit 20 in that the cooling circuit 20 does not include the two-way valve 32. As described above, the cooling circuit 20 of the refrigerator 1 according to the present embodiment can reduce the flow rate of the refrigerant flowing through the second flow path by simply adding the two-way valve 32 to the cooling circuit 20a of the conventional refrigerator and adding control of the two-way valve 32. Therefore, it is possible to easily suppress the condensation of the refrigerant in a hot gas state in the piping during the defrosting operation, and to suppress a decrease in the defrosting capacity.

[0050] Also, the decrease in defrosting capacity may be due to factors other than an excess amount of refrigerant. For example, it is assumed that the inner diameter 30a of the hot gas bypass pipe 30 is smaller than the inner diameter 21a of the discharge pipe that discharges the refrigerant from the compressor 21. In such a case, the flow rate of the refrigerant flowing through the pipe increases, the pressure loss increases, and the refrigerant in a hot gas state is likely to condense. Therefore, by making the inner diameter 30a of the hot gas bypass pipe 30 larger than or equal to the inner diameter 21a of the discharge pipe of the compressor 21, the pressure loss when the refrigerant flows can be reduced and the condensation of the refrigerant can be suppressed. Also, by making the inner diameter 30a of the hot gas bypass pipe 30 larger, the circuit volume of the cooling circuit 20 used during the defrosting operation, including the second flow path, can be increased.

[0051] In addition, the size of the opening diameter 31a (hereinafter, appropriately referred to as the inner diameter 31a of the three-way valve 31), which is the inner diameter of the smallest part in the space inside the three-way valve 31 through which the refrigerant flows, is also considered to affect the decrease in the defrosting capacity. If the inner diameter 31a of the three-way valve 31 is small compared to the inner diameter 21a of the discharge pipe that discharges the refrigerant from the compressor 21, the flow rate of the refrigerant flowing through the three-way valve 31 increases, the pressure loss increases, and the refrigerant in a hot gas state becomes more likely to condense. Therefore, by making the inner diameter 31a of the three-way valve 31 larger than the inner diameter 21a of the discharge pipe of the compressor 21, the pressure loss when the refrigerant flows can be reduced and the condensation of the refrigerant can be suppressed.

[0052] Table 1 shows an example of a change in temperature T of the evaporator 24 due to the defrosting operation when the inner diameter 30a of the hot gas bypass pipe 30 and the inner diameter 31a of the three-way valve 31 are changed relative to the inner diameter 21a of the discharge pipe of the compressor 21. The temperature T represents a temperature measured by a temperature sensor (not shown) attached for measurement to a lower portion of the evaporator 24, which is a portion of the evaporator 24 where the temperature is difficult to increase.

[0053] [Table 1]

[0054] In the above example, the discharge pipe of the compressor 21 has an inner diameter 21a of φ4.76 (i.e., 4.76 mm), and the experiment was performed at an ambient temperature of 16° C. In this example, the hot gas bypass pipes 30 have inner diameters 30a of φ4 and φ6. Also, the three-way valves 31 have inner diameters 31a of φ2, φ4, and φ6.

[0055] As shown in Table 1, when the inner diameter 30a of the hot gas bypass pipe 30 is φ4, changing the inner diameter 31a of the three-way valve 31 to φ2, φ4, or φ6 results in the temperature T at the end of defrosting measured by the temperature sensor attached to the evaporator 24 being −0.4° C., 5.4° C., and 5.8° C., respectively. Thus, it can be seen from Table 1 that by making the inner diameter 31a of the three-way valve 31 larger than the inner diameter 21a of the discharge pipe of the compressor 21, the pressure loss when the refrigerant flows can be reduced, and a decrease in the defrosting capacity can be suppressed.

[0056] Furthermore, when the inner diameter 31a of the three-way valve 31 is φ6, changing the inner diameter 30a of the hot gas bypass pipe 30 to φ4 and φ6 resulted in the temperatures at the end of defrosting measured by the temperature sensor attached to the evaporator 24 being 5.8° C. and 7.2° C., respectively. As seen from Table 1, by making the inner diameter 30a of the hot gas bypass pipe 30 larger than the inner diameter 21a of the discharge pipe of the compressor 21, it is possible to reduce the pressure loss when the refrigerant flows and suppress a decrease in the defrosting capacity.

[0057] Fig. 5 is a timing chart of the operation of the cooling circuit 20 and other cooling devices according to this embodiment. In Fig. 5, (a) illustrates the operation timing of the compressor 21, (b) the two-way valve 32, (c) the three-way valve 31, (d) the fan 10, (e) the damper 12, and (f) the condensing fan. The control device 41 may control each device by transmitting a control signal as described below to each device.

[0058] 5(a) shows the rotation speed of the compressor 21. "OFF" means that the compressor 21 is stopped. "LOW" means that the rotation speed of the motor of the compressor 21 is low. "HIGH" means that the rotation speed of the motor of the compressor 21 is high.

[0059] 5(b), "ON" means that the two-way valve 32 is open, and "OFF" means that it is closed.

[0060] 5(c), "ON" means that the three-way valve 31 is in the second state, and "OFF" means that it is in the first state.

[0061] In Figures 5(d) and (f), "ON" means that each fan is operating, and "OFF" means that each fan is stopped.

[0062] In Fig. 5(e), "ON" means that the damper 12 is open so that cool air from the cooling chamber 9 can be blown upward in the duct 11. Also, "OFF" means that the damper 12 is closed.

[0063] Period A in Fig. 5 indicates a period during which normal operation is performed. During normal operation, the compressor 21 and the two-way valve 32 operate in conjunction with each other. When the compressor 21 is operating, the two-way valve 32 is in an open state. When the compressor 21 is stopped, the two-way valve 32 is in a closed state. In contrast, the three-way valve 31 is in the first state in either case.

[0064] Period B is a preparation stage before the defrosting operation, during which the refrigerant is stored in the condenser 32 (i.e., a so-called pump-down is temporarily performed). During period B, the compressor 21 continues to operate, but the two-way valve 32 is switched to the closed state. The three-way valve 31 is in the first state, as in normal operation. In the timing chart shown in FIG. 5, the compressor 21 operates at the same rotation speed as in normal operation, but the rotation speed may be increased or decreased as described above.

[0065] Period C indicates a period during which a defrosting operation is performed. The compressor 21 operates in the same manner as in periods A and B. The two-way valve 32 is in a closed state. The three-way valve 31 is switched to the second state and configured to allow the refrigerant to flow to the hot gas bypass pipe 30. In the timing chart shown in FIG. 5, the rotation speed of the compressor 21 is increased compared to normal operation, but it may be the same as the rotation speed during normal operation or may be decreased compared to normal operation.

[0066] Period D indicates a certain period after the defrosting operation is completed. After the defrosting operation is completed, the compressor 21 is stopped and the three-way valve 31 is switched to the first state. After the certain period has elapsed, the compressor 21 is operated again to perform normal operation, and the two-way valve 32 is switched to the open state. At this time, since high-temperature refrigerant is flowing through the evaporator 24 during the defrosting operation, the temperature of the evaporator 24 is higher than normal. Therefore, in order to lower the temperature of the evaporator 24, the fan 10 and the like are operated after the certain period has elapsed, and normal operation is started.

[0067] Basically, the fan 10 is controlled in conjunction with the operation of the compressor 21 during normal operation. When the compressor 21 is operating during normal operation, the fan 10 also operates. The fan 10 stops operating during defrosting operation and during pump-down to transition to defrosting operation. In addition, when transitioning from defrosting operation to normal operation, the evaporator 24, which has been heated during the defrosting operation, needs to be cooled after the compressor 21 starts operating, so the fan 10 starts operating a certain period after the compressor 21.

[0068] Basically, the opening and closing of the damper 12 is controlled in conjunction with the operation of the fan 10. Although not shown, the damper 12 may be closed even when the fan 10 is operating in order to keep the temperature inside the upper inner box 6 constant according to the temperature detected by a refrigerator compartment temperature sensor attached inside the upper inner box 6, which serves as the refrigerator compartment.

[0069] The condensing fan operates in conjunction with the compressor 21.

[0070] In this manner, the control device 41 controls the compressor 21, the two-way valve 32, and the three-way valve 31, so that the cooling circuit of the refrigerator 1 according to this embodiment can suppress a decrease in the defrosting capacity.

[0071] The present invention is not limited to the illustrated embodiment, and various improvements and design modifications are possible without departing from the gist of the present invention. [Industrial Applicability]

[0072] As described above, according to the present invention, it is possible to provide refrigerator 1 that can easily reduce the flow rate of the refrigerant flowing through hot gas bypass pipe 30 and suppress a decrease in defrosting capacity without including a complicated system, and therefore the refrigerator can be suitably used in the industrial field of this type of refrigerator. [Explanation of symbols]

[0073] 1. Refrigerator 20 Cooling circuit 21 Compressor 22 Condenser 23 Capillary tube 24 Evaporator 25, 26, 27 Piping 28 Suction pipe 30 Hot gas bypass pipe 30a Inner diameter of hot gas bypass pipe 31 Three-way valve 31a Three-way valve inner diameter 32 Two-way valve 41 Control circuit

Claims

1. a compressor for compressing a refrigerant sent from an evaporator, a condenser for condensing the refrigerant sent from the compressor, a capillary tube for expanding the refrigerant sent from the condenser, and the evaporator for evaporating the refrigerant sent from the capillary tube, the first flow path being connected in this order to circulate the refrigerant; The cooling circuit includes: a hot gas bypass pipe provided to form a second flow path through which the refrigerant compressed by the compressor flows from the compressor to the evaporator; a first valve provided in the first flow passage between the compressor and the condenser and connected to the hot gas bypass pipe; a second valve provided in the first flow path between the condenser and the capillary tube; The first valve is capable of allowing the refrigerant discharged from the compressor to flow into the condenser or the hot gas bypass pipe, the second valve is configured to be able to close to block the flow of the refrigerant discharged from the condenser; Further, a control device is provided for switching the cooling circuit between a normal operation for cooling the evaporator and a defrosting operation for defrosting the evaporator, the control device can control whether the first valve allows a fluid to flow through the condenser or the hot gas bypass pipe, and can further control opening and closing of the second valve; When switching from the normal operation to the defrosting operation, the control device controls the first valve to flow the refrigerant to the condenser and the second valve to close, thereby discharging the refrigerant to the condenser by the compressor, and then controls the first valve to flow the refrigerant to the hot gas bypass pipe to start the defrosting operation; the evaporator is provided with a temperature sensor, and the control device performs control to reduce a flow rate of the refrigerant flowing through the second flow path when a temperature measured by the temperature sensor is lower than a predetermined value after starting the defrosting operation.

2. 2. The refrigerator according to claim 1, wherein, as a control to reduce a flow rate of the refrigerant flowing through the second flow path, the control device controls the second valve to maintain a closed state and the first valve to flow the refrigerant to the condenser.

3. 3. The refrigerator according to claim 1, wherein an inner diameter of the hot gas bypass pipe is equal to or larger than an inner diameter of a discharge pipe through which the refrigerant is discharged from the compressor.

4. The refrigerator according to any one of claims 1 to 3, wherein an inner diameter of the first valve is equal to or larger than an inner diameter of a discharge pipe through which the refrigerant is discharged from the compressor.

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