refrigerator

Abstract

To provide a refrigerator capable of surely performing defrosting and reducing cost of manufacture while suppressing energy consumption.SOLUTION: A refrigerator comprises: a cooling circuit 20 in which a coolant flows successively through a compressor 21, a condenser 22 and an evaporator 24; and a hot gas bypass pipe 30 directly connecting a discharge side of the compressor 21 or the condenser 22 with an inflow side of the evaporator 24. The refrigerator also comprises: a switching valve 31 for switching a normal operation state and a state where hot gas defrosting processing in which the coolant discharged from the compressor 21 flows through the hot gas bypass pipe 30 to the evaporator 24 is performed; a control unit for controlling the compressor 21 and the switching valve 31; and an outside air temperature sensor which detects an outside air temperature and transmits detection data to the control unit. A rotation speed of the compressor 21 is variable and when performing the hot gas defrosting processing, the control unit operates the compressor 21 at a rotation speed corresponding to an outside air temperature detected by the outside air temperature sensor. When the outside air temperature has a relation of T1<T2, a rotation speed of the compressor 21 at T1 is higher than a rotation speed of the compressor 21 at T2.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 a hot gaseous refrigerant. [Background technology]

[0002] An evaporator, which constitutes part of a refrigerator's cooling circuit, may become frosted as the surrounding water vapor is cooled, resulting in a risk of a decline in cooling performance.To address this issue, a hot gas defrosting process is known in which a hot gas bypass pipe is provided downstream of a compressor, which constitutes part of the cooling circuit, connecting 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 perform defrosting (see, for example, Patent Document 1).In Patent Document 1, the evaporator is heated and defrosted by directly supplying hot gaseous refrigerant discharged from the compressor to the inlet of a heat exchange pipe of the evaporator. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-54287 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the hot gas defrosting process described in Patent Document 1, due to changes in the outside air temperature and the operating conditions of the compressor, the amount of heat added to the evaporator by the hot gas refrigerant changes, resulting in a problem that the defrosting time varies. In the refrigerator described in Patent Document 1, although a heating heater is provided to melt the frost that has fallen from the evaporator to the frost receiving tray, if the capacity of the heating heater is increased in accordance with a longer defrosting time, there is a risk of excessive energy consumption. On the other hand, if the capacity of the heating heater is decreased in accordance with a shorter defrosting time, there is a risk of insufficient ability to melt the frost. Also, although it is conceivable to provide a temperature sensor on the frost receiving tray and control the heating heater by the temperature sensor, in that case, there is a problem that the manufacturing cost increases.

[0005] Therefore, an object of the present invention is to provide a refrigerator that can surely perform hot gas defrosting while suppressing energy consumption at a low manufacturing cost.

Means for Solving the Problems

[0006] The refrigerator of the present invention has a cooling circuit in which a refrigerant flows in the order of a compressor, a condenser, and an evaporator and returns to the compressor again to perform a cooling cycle, a hot gas bypass pipe that directly connects the discharge side of the compressor or the condenser to the inflow side of the evaporator, a switching valve that switches between a state of performing the cooling cycle and a state of performing hot gas defrosting in which the refrigerant discharged from the compressor flows through the hot gas bypass pipe to the evaporator, a control unit that controls the compressor and the switching valve, an outside air temperature sensor that detects the outside air temperature and transmits the detection data to the control unit, and is provided with the rotational speed of the compressor is variable, <000004​​

[0007] The heat sources for the refrigerant in hot gas defrosting are mainly the outside air and heat generated by the motor. Therefore, when the outside air temperature is low, the refrigerant temperature is low, so the compressor operates at a higher rotation speed to increase the amount of refrigerant flowing in. On the other hand, when the outside air temperature is high, the compressor operates at a lower rotation speed to prevent excessive heat from flowing into the evaporator. This makes it possible to reduce variations in defrosting time even when the outside air temperature varies.

[0008] In the hot gas defrosting process, by controlling the compressor rotation speed in accordance with the outside air temperature, defrosting can be performed efficiently without adding any special device, and variations in defrosting time can be reduced. As a result, a refrigerator capable of reliably performing hot gas defrosting while reducing energy consumption can be provided at low manufacturing cost.

[0009] In addition, in the refrigerator of the present invention, The control unit is characterized in that it performs control to increase the rotation speed of the compressor as time passes from the start of the hot gas defrosting process.

[0010] According to the present invention, the control unit controls the compressor to increase its rotation speed as time passes from the start of the hot gas defrosting process, so that even if the amount of frost adhering to the evaporator varies, variation in defrosting time can be suppressed and efficient defrosting can be achieved.

[0011] In addition, in the refrigerator of the present invention, a condensing fan that cools the compressor and the condenser, Before the hot gas defrosting process is performed, the control unit controls to stop the condensing fan.

[0012] According to the present invention, the control unit controls to stop the condensing fan before performing hot gas defrosting, thereby making it possible to increase the temperature of the refrigerant discharged from the compressor in advance. As a result, in the hot gas defrosting process, refrigerant whose temperature has been increased in advance is supplied to the evaporator, making it possible to perform defrosting more efficiently.

[0013] In addition, in the refrigerator of the present invention, In the cooling circuit, a capillary tube is disposed between the condenser and the evaporator, and an on-off valve is disposed between the condenser and the capillary tube, When the hot gas defrosting process is performed, the control unit controls the on-off valve to close, thereby preventing the refrigerant coming out of the condenser from flowing into the capillary tube.

[0014] During hot gas defrosting, if the on-off valve is open, the refrigerant from the condenser flows into the capillary tube, causing a drop in the refrigerant temperature. This may result in a drop in the temperature of the refrigerant flowing into the evaporator, reducing the efficiency of defrosting. Therefore, in the present invention, when hot gas defrosting is performed, the control unit closes the on-off valve to prevent the refrigerant from flowing into the capillary tube, thereby suppressing a drop in the refrigerant temperature and achieving efficient defrosting.

[0015] In addition, in the refrigerator of the present invention, Further provided is a defrost sensor that detects the temperature of the evaporator and transmits the detected data to the control unit, When performing the hot gas defrosting process, the control unit changes the rotation speed of the compressor based on the temperature of the evaporator detected by the defrost sensor, and when the temperature of the evaporator exceeds a predetermined value, controls to terminate the hot gas defrosting process.

[0016] In the present invention, when hot gas defrosting is performed, the control unit operates the compressor at a rotation speed corresponding to the outside air temperature, and further changes the rotation speed based on the evaporator temperature, thereby achieving more efficient defrosting feedback control corresponding to the actual evaporator temperature. Furthermore, when the temperature of the evaporator exceeds a predetermined value, that is, when it reaches a temperature at which it is estimated that defrosting of the evaporator has been completed, control is performed to terminate the hot gas defrosting process, thereby achieving efficient defrosting process with reduced energy consumption. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a refrigerator capable of reliably performing hot gas defrosting while reducing energy consumption, at low manufacturing cost. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a side cross-sectional view schematically showing a refrigerator according to one embodiment of the present invention. [Figure 2] 1 is a diagram showing the configuration of a cooling circuit of a refrigerator according to one embodiment of the present invention. [Figure 3] 1 is a diagram illustrating a control system related to defrosting of a refrigerator according to one embodiment of the present invention. FIG. [Figure 4] 4 is a time chart showing an example of control for performing hot gas defrosting processing. [Figure 5] 10 is a flowchart showing an example of control for performing hot gas defrosting processing. [Figure 6A] 6 is a graph showing detected data such as the temperature of the refrigerant discharged from the compressor when the condensing fan is operating normally. [Figure 6B] 10 is a graph showing detected data such as the temperature of the refrigerant discharged from the compressor when the condensing fan is stopped. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The refrigerator described below is intended to embody the technical concept of the present invention, and unless otherwise specified, the present invention is not limited to the following. In each drawing, components having the same function may be assigned the same reference numerals. The size and positional relationship of components shown in each drawing may be exaggerated for clarity of explanation.

[0020] 1 is a side cross-sectional view that schematically shows a refrigerator 1 according to one embodiment of the present invention. First, an overview of the refrigerator 1 according to one embodiment of the present invention will be described with reference to FIG.

[0021] The refrigerator 1 has a housing 2, and when placed on a horizontal floor, has an upper door 3 and a lower door 4 rotatably attached to the front part of the housing 2. Inside the housing 2 (hereinafter referred to as the "interior"), a freezer compartment 6 and a refrigerator compartment 7 are arranged. Heat insulating material is arranged between the inner surface of the housing 2 and the outer surfaces of the freezer compartment 6 and the refrigerator compartment 7.

[0022] <Cooling channel> As shown in FIG. 1, a cooling flow path 10 is provided behind the freezer compartment 6 and the refrigerator compartment 7, and is composed of a lower cooling flow path 10A and an upper cooling flow path 10B separated by partition plates 11A and 11B, respectively. An evaporator 24 is disposed in the cooling flow path 10 (more specifically, the lower cooling flow path 10A). As will be described later, the evaporator 24 constitutes part of the cooling circuit 20 of the refrigerator 1. A fan 12 is disposed above the evaporator 24 within the cooling flow path 10. The fan 12 causes the gas inside the compartment to circulate, and the gas that has passed through the evaporator 24 and been cooled can be supplied from the cooling flow path 10 to the freezer compartment 6 and the refrigerator compartment 7.

[0023] A freezer compartment damper 13 is disposed in the upper opening of the lower partition plate 11A. When the freezer compartment damper 13 is open, the gas that has passed through the evaporator 24 flows from the cooling flow path 10 (lower cooling flow path 10A) to the freezer compartment 6. On the other hand, when the freezer compartment damper 13 is closed, the gas that has passed through the evaporator 24 does not flow from the cooling flow path 10 (lower cooling flow path 10A) to the freezer compartment 6. Figure 1 shows the freezer compartment damper 13 in the closed state.

[0024] When the fan 12 is operating and the freezer compartment damper 13 is open, the gas that has flowed into the freezer compartment 6 from the cooling flow path 10 (lower cooling flow path 10A) circulates within the freezer compartment 6 and returns to the cooling flow path 10 (lower cooling flow path 10A) from the lower opening of the lower partition plate 11A. As a result, the gas passes through the evaporator 24 again and is cooled, repeating a similar flow cycle. In this way, the stored items in the freezer compartment 6 can be cooled.

[0025] However, the method of switching whether or not to allow gas to flow into freezer compartment 6 is not limited to using freezer compartment damper 13. For example, a movable fan cover that covers the outside of fan 12 can also be used. When the fan cover is open, gas discharged from fan 12 flows into freezer compartment 6, and when the fan cover is closed, gas discharged from fan 12 is prevented from flowing into freezer compartment 6.

[0026] Furthermore, a refrigerator compartment damper 14 is disposed between the lower cooling flow path 10A and the upper cooling flow path 10B. When the refrigerator compartment damper 14 is open, gas that has passed through the evaporator 24 flows from the lower cooling flow path 10A to the upper cooling flow path 10B. Furthermore, the gas that has flowed into the upper cooling flow path 10B flows from the cooling flow path 10 (upper cooling flow path 10B) into the refrigerator compartment 7 through openings provided at multiple height positions. On the other hand, when the refrigerator compartment damper 14 is closed, gas that has passed through the evaporator 24 does not flow from the lower cooling flow path 10A to the upper cooling flow path 10B. FIG. 1 shows the refrigerator compartment damper 14 in an open state, and the gas flow at this time is schematically indicated by dotted arrows.

[0027] When fan 12 is operating and refrigerator compartment damper 14 is open, the gas that has flowed into refrigerator compartment 7 from cooling flow path 10 (upper cooling flow path 10B) circulates within refrigerator compartment 7 and flows into inlet 15A of return flow path 15 that opens at the bottom of refrigerator compartment 7. While the gas that has passed through evaporator 24 circulates within refrigerator compartment 7, it can cool the items stored in freezer compartment 6.

[0028] <Return flow path> The return flow path 15 is a flow path that allows the gas that has circulated in the refrigerator compartment 7 to flow into the lower side of the cooling flow path 10 (lower cooling flow path 10A) without flowing into the freezer compartment 6. The return flow path 15 is arranged separated from the cooling flow path 10. The gas that flows into the refrigerator compartment 7 from the cooling flow path 10 (upper cooling flow path 10B) and circulates inside the refrigerator compartment 7 flows into the return flow path 15 from the inlet 15A. The gas then flows through the return flow path 15 and flows into the lower side of the cooling flow path 10 (lower cooling flow path 10A) from the lower outlet 15B. In other words, the gas flows into the lower side of the evaporator 24 arranged in the cooling flow path 10 (lower cooling flow path 10A). As a result, the gas passes through the evaporator 24 again and is cooled, repeating a similar flow cycle. Therefore, the stored items in the refrigerator compartment 7 can be cooled.

[0029] A machine room 40 is arranged at the rear and bottom of the housing 2, and contains a compressor 21, a condenser 22, and an evaporation tray 42. Furthermore, a condensing fan 41 that cools the compressor 21 and the condenser 22 is arranged in the machine room 40.

[0030] <Other configurations> Furthermore, a frost tray 33 is provided to receive and drop frost adhering to the evaporator 24 when defrosting is performed. A heater 34 is also provided near the frost tray 33. The heater 34 melts the frost in the frost tray 33 and allows it to be discharged to an evaporator tray 42 in the machine compartment 40 via a drain pipe 35. An outside air temperature sensor 50 that detects the outside air temperature is also attached to the top of the upper door 3. Furthermore, a defrost sensor 51 that detects the temperature of the evaporator 24 is attached to the evaporator 24.

[0031] <Cooling circuit> 2 is a diagram showing the configuration of a cooling circuit 20 of a refrigerator 1 according to one embodiment of the present invention. Next, an overview of the cooling circuit 20 will be described with reference to FIG.

[0032] 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 by piping in the above order, forming a first refrigerant flow path through which the refrigerant circulates within the cooling circuit 20. A normal cooling cycle is performed through the first refrigerant flow path.

[0033] The compressor 21 compresses the gaseous refrigerant to a high-temperature, high-pressure state. The compressed refrigerant is sent to the condenser 22 through piping. The compressor 21 is equipped with an inverter, which makes its rotation speed variable, allowing the cooling capacity of the cooling circuit 20 to be controlled. 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 piping.

[0034] The capillary tube 23 reduces the pressure of the refrigerant condensed in the condenser 22, causing it to expand and lower its temperature. The expanded refrigerant is sent through piping to the heat exchange pipe of the evaporator 24. In the heat exchange pipe, where heat exchange is promoted by fins, the refrigerant decompressed by the capillary tube 23 evaporates and absorbs heat. The evaporated refrigerant, now in a gaseous state, is sent through the suction pipe 28 to the compressor 21 and compressed again. This is how the refrigeration circuit 20 operates.

[0035] The suction pipe 28, which carries the refrigerant from the evaporator 24 to the compressor 21, is arranged at least partially in close proximity to the capillary tube 23 so as to enable heat exchange between the suction pipe 28 and the capillary tube 23. In Fig. 2, an area 29 surrounded by a dotted line shows an outline of the heat exchange section.

[0036] In a normal cooling cycle using a first refrigerant flow path in which refrigerant circulates through the compressor 21, condenser 22, capillary tube 23, and evaporator 24, the cooling capacity is increased by increasing the rotation speed of the compressor 21. Therefore, basically, when the outside air temperature is high, the rotation speed of the compressor 21 is increased to increase the cooling capacity, and when the outside air temperature is low, the rotation speed of the compressor 21 is decreased to suppress the cooling capacity.

[0037] When evaporator 24 exchanges heat with the gas flowing inside refrigerator 1, water vapor contained in the gas may frost, so it is necessary to defrost evaporator 24. In refrigerator 1 according to this embodiment, as will be described later, defrosting is performed by directly supplying hot gas refrigerant compressed by compressor 21 to evaporator 24. This is called hot gas defrosting. To perform hot gas defrosting, cooling circuit 20 includes hot gas bypass pipe 30 that directly connects the outlet side of compressor 21 and the inlet side of condenser 22.

[0038] A switching valve (three-way valve) 31 is disposed on the outlet side of the compressor 21. The switching valve (three-way valve) 31 can switch between a state in which the refrigerant discharged from the compressor 21 flows to the condenser 22 side and a state in which the refrigerant discharged from the compressor 21 flows to the hot gas bypass pipe 30 side.

[0039] The hot gas bypass pipe 30 constitutes a second refrigerant flow path in which the refrigerant flows through the compressor 21, the hot gas bypass pipe 30, and the evaporator 24, which is different from the first refrigerant flow path in which the refrigerant flows through the compressor 21, the condenser 22, the capillary tube 23, and the evaporator 24 in the above-mentioned cooling circuit.

[0040] The control unit 100 (see FIG. 3) controls the opening and closing of the switching valve (three-way valve) 31. The control unit 100 controls the switching valve (three-way valve) 31 to open the condenser 22 side, thereby performing a normal cooling cycle in which the refrigerant flows through the first refrigerant flow path. On the other hand, the control unit 100 controls the switching valve (three-way valve) 31 to open the hot gas bypass pipe 30 side, thereby performing a hot gas defrosting process in which the refrigerant flows through the second refrigerant flow path.

[0041] When the refrigerant flows through the second refrigerant flow path, the hot gaseous refrigerant that leaves the compressor 21 can be supplied directly to the heat exchange pipes of the evaporator 24 via the hot gas bypass pipe 30. As the hot gaseous refrigerant flows through the heat exchange pipes, the heat exchange pipes are heated, and the fins are also heated by thermal conduction. This allows for a hot gas defrosting process that melts frost on the evaporator 24. The frost melts in the areas in contact with the fins and falls off.

[0042] The dropped liquid is collected in a frost tray 33 arranged below the evaporator 24. If only the frost tray 33 were present, there is a risk that the partially melted frost would refreeze, but in this embodiment, a heater 34 is arranged near the frost tray 33. The frost is melted by the heater 34, and the resulting liquid flows into an evaporation tray 42 in the machine chamber 40 via a drain pipe 35. The liquid that flows into the evaporation tray 42 evaporates into the atmosphere.

[0043] In addition, an on-off valve 32 is disposed between the condenser 23 and the capillary tube 23. When the on-off valve 32 is open, the refrigerant flows from the condenser 23 to the capillary tube 23, and when the on-off valve 32 is closed, the refrigerant does not flow from the condenser 23 to the capillary tube 23. When a normal cooling cycle is performed, the on-off valve 32 is open. When a hot gas defrosting process is performed, as will be described later, the on-off valve 32 is closed.

[0044] <Modification> The following is a possible modification of this embodiment. Because the refrigerant leaving the condenser 22 is also at a sufficiently high temperature, a hot gas bypass pipe 30 may be provided that directly connects the outlet side of the condenser 22 with the inlet side of the evaporator 24. In this case, a changeover valve (three-way valve) 31 is disposed on the outlet side of the condenser 22. As a result, the hot gas bypass pipe 30 forms a second refrigerant flow path in which the refrigerant flows through the compressor 21-condenser 22-hot gas bypass pipe 30-evaporator 24. In this case, the changeover valve (three-way valve) 31 fulfills the function of the on-off valve 32 described above.

[0045] (Control system for hot gas defrosting process) 3 is a diagram showing a control system related to defrosting of the refrigerator 1 according to one embodiment of the present invention. Next, a control system for performing hot gas defrosting processing will be described with reference to FIG.

[0046] The control system for the hot gas defrosting process constitutes part of the control system of the refrigerator 1. The control unit 100 is electrically connected to an outside air temperature sensor 50 attached to the top of the upper door 3, and is adapted to receive detected data (signals) of the outside air temperature. The control unit 100 is also electrically connected to a defrost sensor 51 attached to the evaporator 24, and is adapted to receive detected data (signals) of the temperature of the evaporator 24.

[0047] The control unit 100 can transmit control signals to control the operation of the compressor 21 and the condensing fan 41. The control unit 100 can also transmit control signals to the switching valve (three-way valve) 31 and the on-off valve 32 to control their opening and closing. The control unit 100 can also transmit control signals to control the operation of the heater 34.

[0048] (Hot gas defrosting) 2 , the refrigerator 1 according to this embodiment includes the cooling circuit 20 that performs a cooling cycle in which the refrigerant flows through the compressor 21, the condenser 22, and the evaporator 24 in this order and returns to the compressor 21, the hot gas bypass pipe 30 that directly connects the outlet side of the compressor 21 and the inlet side of the evaporator 24, and the switching valve 31 that switches between a state in which the cooling cycle is performed and a state in which the refrigerant discharged from the compressor 21 flows into the evaporator 24 through the hot gas bypass pipe 30. However, there may also be a case in which the hot gas bypass pipe 30 directly connects the outlet side of the condenser 22 and the inlet side of the evaporator 24.

[0049] 3, the control system further includes a control unit 100 that controls the compressor 21 and the switching valve (three-way valve) 31, and an outside air temperature sensor 50 that detects the outside air temperature and transmits the detected data to the control unit 100. At this time, the rotation speed of the compressor 21 is variable, and the rotation speed of the compressor 21 can be changed by the control unit 100.

[0050] With this configuration, the control unit 100 controls the switching valve (three-way valve) 31 so that the hot gas bypass pipe 30 side is open, thereby performing hot gas defrosting processing in which the refrigerant discharged from the compressor 21 flows into the evaporator 24 via the hot gas bypass pipe 30. At this time, the control unit 100 operates the compressor 21 at a rotation speed corresponding to the outside air temperature detected by the outside air temperature sensor 50.

[0051] In a normal refrigeration cycle in which refrigerant discharged from the compressor 21 flows to the evaporator 24 via the condenser 22 and the capillary tube 23, increasing the rotation speed of the compressor 21 increases the flow rate of refrigerant flowing through the refrigeration circuit 20, thereby increasing the cooling capacity. On the other hand, decreasing the rotation speed of the compressor 21 decreases the flow rate of refrigerant flowing through the refrigeration circuit 20, thereby decreasing the cooling capacity. In other words, generally, when the external temperature is high, the rotation speed of the compressor 21 is increased to increase the cooling capacity, and when the external temperature is low, the rotation speed of the compressor 21 is decreased to decrease the cooling capacity.

[0052] When the rotation speed of the compressor 21 is increased, not only does the flow rate of the refrigerant increase, but the temperature of the discharged refrigerant also rises. However, in a normal refrigeration cycle, the refrigerant discharged from the compressor 21 is condensed in the condenser 22, and its temperature is lowered in the capillary tube 23 before it flows into the evaporator 24. On the other hand, in the hot gas defrosting process, the high-temperature refrigerant discharged from the compressor 21 flows directly into the evaporator 24 via the hot gas bypass pipe 30.

[0053] In the hot gas defrosting process, when the outside air temperature is low, since the temperature of the refrigerant is low, the compressor 21 is operated at a higher rotational speed to increase the inflow rate of the refrigerant. On the other hand, when the outside air temperature is high, the compressor 21 is operated at a lower rotational speed to suppress excessive heat inflow into the evaporator 24. Thereby, even when the outside air temperature is different, the variation in the defrosting time can be suppressed.

[0054] That is, when the outside air temperature detected by the outside air temperature sensor 50 has a relationship of T1 < T2, it is preferable to control such that the rotational speed of the compressor 21 at T1 is higher than the rotational speed of the compressor 21 at T2. At this time, during the hot gas defrosting process, the compressor 21 may be operated at a constant rotational speed corresponding to the outside air temperature, or as will be described later, the rotational speed may be changed according to the passage of time.

[0055] As described above, in the hot gas defrosting process, by the control unit 100 controlling the rotational speed of the compressor 21 corresponding to the outside air temperature as described above, the variation in the defrosting time can be suppressed without adding a special device. Thereby, it is not necessary to give the heating heater 34, which melts the frost that has melted and fallen onto the drip tray 33, an excessive capacity, and even when the outside air temperature changes, the heating heater 34 can be operated with a load within a certain range. Thereby, the manufacturing cost can be reduced and the energy consumption can be reduced. Therefore, a refrigerator that can surely perform the hot gas defrosting process while suppressing energy consumption can be provided at a low manufacturing cost.

[0056] <Control Corresponding to the Temperature of the Evaporator> As described above, when the compressor 21 is operated at a rotation speed corresponding to the outside air temperature, the rotation speed of the compressor 21 can also be changed based on the temperature of the evaporator 24 detected by the defrost sensor 51. For example, when the compressor 21 is operated at a relatively high rotation speed corresponding to a relatively low outside air temperature, if the detected temperature of the evaporator 24 tends to be higher than a predetermined temperature, it is possible to control the compressor 21 to decrease the rotation speed. Conversely, when the compressor 21 is operated at a relatively low rotation speed corresponding to a relatively high outside air temperature, if the detected temperature of the evaporator 24 tends to be lower than a predetermined temperature, it is possible to control the compressor 21 to increase the rotation speed.

[0057] As described above, when hot gas defrosting is performed, more efficient feedback control of defrosting corresponding to the actual temperature of the evaporator 24 can be realized based on the control of operating the compressor 21 at a rotation speed corresponding to the outside air temperature.

[0058] Furthermore, the control unit 100 can also perform control to terminate the hot gas defrosting process when the temperature of the evaporator 24 detected by the defrost sensor 51 exceeds a predetermined value. It is preferable to set the predetermined value to a temperature at which it is assumed that no frost has adhered to the evaporator 24. Even if the hot gas defrosting process is continued for only a predetermined period of time, an efficient defrosting process can be achieved with reduced energy consumption by terminating the hot gas defrosting process when the temperature of the evaporator 24 exceeds the predetermined value.

[0059] <Condensing fan stop> Furthermore, before performing the hot gas defrosting process, the control unit 100 may perform control to stop the condensing fan 41 that cools the compressor 21. For example, the control may be such that the condensing fan 41 is stopped when a flag for performing the defrosting process is established.

[0060] Here, Fig. 6A is a graph showing detected data such as the temperature of the refrigerant discharged from the compressor 21 when the condensing fan 41 is operating normally. Fig. 6B is a graph showing detected data such as the temperature of the refrigerant discharged from the compressor 21 when the condensing fan 41 is stopped. The horizontal axis of the graph represents time, and the vertical axis represents temperature. In Figs. 6A and 6B, the upper graph shows the temperature of the refrigerant discharged from the compressor 21, and the lower graph shows the temperature of the evaporator 24 detected by the defrost sensor 51.

[0061] 6A and 6B, when compressor 21 starts operating from a stopped state, if condensing fan 41 is stopped, the temperature gradient, which is the degree of temporal increase in the temperature of the refrigerant discharged from compressor 21, is larger than when condensing fan 41 is operating normally. As a result, the temperature of the refrigerant at the start of hot gas defrosting processing is higher than when condensing fan 41 is operating normally. Accordingly, when compressor 21 is operated with condensing fan 41 stopped, the temperature gradient of the temperature of evaporator 24 is larger than when condensing fan 41 is operating normally. As a result, the time required for hot gas defrosting processing is reduced by approximately 40 minutes.

[0062] In this way, the control unit 100 controls the condensing fan 41 to stop before the hot gas defrosting process, thereby making it possible to further increase the temperature of the refrigerant discharged from the compressor 21. As a result, in the hot gas defrosting process, refrigerant whose temperature has been increased in advance is supplied to the evaporator 24, making it possible to perform defrosting more efficiently.

[0063] <On-off valve control> As described above, in the cooling circuit 20, the capillary tube 23 is arranged between the condenser 22 and the evaporator 24, and the on-off valve 32 is arranged between the condenser 22 and the capillary tube 23. In this embodiment, when hot gas defrosting processing is performed, it is preferable that the control unit 100 performs control to close the on-off valve 32. This control prevents the refrigerant coming out of the condenser 22 from flowing into the capillary tube 23.

[0064] When the on-off valve 32 is open, the refrigerant coming out of the condenser 22 flows into the capillary tube 23, which may cause a drop in the temperature of the refrigerant. In other words, when the on-off valve 32 is open during hot gas defrosting, the temperature of the refrigerant flowing into the evaporator 24 may drop, which may cause a drop in defrosting efficiency. For this reason, in this embodiment, when hot gas defrosting is performed, the control unit 100 controls the on-off valve 32 to close. This control prevents the refrigerant coming out of the condenser 22 from flowing into the capillary tube 23, thereby suppressing a drop in the temperature of the refrigerant and achieving efficient defrosting.

[0065] However, since the defrosting time can be extended by opening the on-off valve 32, it is also possible to adjust the defrosting time by opening and closing the on-off valve 32.

[0066] (An example of control when hot gas defrosting is performed) <Time chart> Fig. 4 is a time chart showing an example of control for performing hot gas defrosting. Next, an example of control for performing hot gas defrosting will be described with reference to the time chart of Fig. 4. This time chart shows that when a normal cooling cycle is being performed, the defrost flag is set, and after the cooling period in which compressor 21 operates ends, a pre-defrost cycle is performed, then hot gas defrosting is performed, and after the hot gas defrosting is completed, the normal cooling cycle is started again.

[0067] During the cooling period of the normal cooling cycle on the left side of the time chart, the compressor 21 operates, and the condensing fan 41 also operates. In addition, the switching valve (three-way valve) 31 is open on the condenser 22 side and closed on the hot gas bypass pipe 30 side. The on-off valve 32 between the condenser 22 and the capillary tube 23 is open. As a result, the refrigerant flows through the first refrigerant flow path consisting of the compressor 21, condenser 22, capillary tube 23, and evaporator 24.

[0068] If the defrost flag is set during this cooling period, the pre-defrost cycle starts after the cooling period ends. The defrost flag can be set when a predetermined time has elapsed since the previous defrosting process, or based on the temperature detected by the defrost sensor 51. It can also be set at any other timing.

[0069] The first half of the pre-defrost cycle is the same as the cooling pause period of a normal cooling cycle, and the compressor 21 and the condensing fan 41 are stopped. The switching valve (three-way valve) 31 maintains the condenser 22 side open, and the open on-off valve 32 is closed. The second half corresponds to the cooling period of a normal cooling cycle, but the compressor 21 operates with the condensing fan 41 stopped, allowing the temperature and discharge temperature of the compressor 21 to increase. However, if the ambient temperature of the machine room 40 is high, the condensing fan 41 may be operated. At this time, the refrigerant flows through a first refrigerant flow path consisting of the compressor 21, the condenser 22, the capillary tube 23, and the evaporator 24.

[0070] After cooling is completed under predetermined conditions, hot gas dehumidification processing is started. To this end, the switching valve (three-way valve) 31 is switched so that the hot gas bypass pipe 30 side is open and the condenser 22 side is closed, and the on-off valve 32 is changed from open to closed. As a result, the refrigerant flows through the second refrigerant flow path consisting of the compressor 21, hot gas bypass pipe 30, and evaporator 24. At this time, the compressor 21 is operated at low rotation speed during defrosting for a certain period of time to prevent the refrigerant from returning to liquid form. The low rotation speed during defrosting is basically the minimum rotation speed.

[0071] After operating the compressor 21 at a low rotation speed during defrosting for a certain period of time, the compressor 21 is operated at a rotation speed determined in accordance with the outdoor air temperature detected by the outdoor air temperature sensor 50. In the example shown in FIG. 4, the compressor 21 is not operated at a constant rotation speed during hot gas defrosting, but rather is controlled to increase the rotation speed in steps in accordance with the elapsed time. FIG. 4 shows control that increases the rotation speed in three steps over time. In this case, the control may proceed to the next step after the same amount of time has elapsed in each step, or may proceed to the next step after different amounts of time have elapsed in each step. The rotation speed of the compressor 21 may also be increased in any other number of steps.

[0072] By increasing the rotation speed of the compressor 21 in a stepwise manner, it is possible to reduce variations in the defrosting time regardless of the amount of frost adhering to the evaporator 24. If it is possible to infer whether defrosting has been completed based on the temperature of the evaporator 24 detected by the defrost sensor 51, then if the amount of frost adhering to the evaporator 24 is small, the defrosting process can be completed in a step with a low rotation speed. On the other hand, if the amount of frost adhering to the evaporator 24 is large, steps with a high rotation speed are used to supply more refrigerant to the evaporator 24, and the defrosting process can be reliably completed within a predetermined time.

[0073] After performing a hot gas defrosting process in which the rotation speed of the compressor 21 is increased in steps, the cooling cycle after defrosting is started. Specifically, the rotation speed of the compressor 21 is changed to a speed lower than the rotation speed of the last step. In addition, the switching valve (three-way valve) 31 is switched so that the condenser 22 side is opened and the hot gas bypass pipe 30 side is closed, and the on-off valve 32 is opened. As a result, the refrigerant flows through the first refrigerant flow path consisting of the compressor 21, condenser 22, capillary tube 23, and evaporator 24. In addition, in order to raise the temperature of the compressor 21 in preparation for the normal cooling cycle, the condensing fan 41 starts operating with a delay after a predetermined time has elapsed.

[0074] In addition to the control of increasing the rotation speed in a stepwise manner in response to the elapsed time as described above, it is also possible to control the rotation speed of the compressor 21 in a stepwise manner based on the temperature of the evaporator 24 detected by the defrost sensor 51. For example, it is possible to control the rotation speed in a stepwise manner in response to a temperature gradient that captures the temperature change of the evaporator 24 over time. It is also possible to control the rotation speed of the compressor 21 in a stepwise manner, triggered by the temperature of the evaporator 24 reaching a predetermined value. In either case, the compressor 21 is operated at a rotation speed determined in response to the outside air temperature detected by the outside air temperature sensor 50, and the rotation speed is controlled to increase based on the temperature of the evaporator 24 detected by the defrost sensor 51.

[0075] In the example shown in Fig. 4, the rotation speed of the compressor 21 is controlled to be increased in a stepwise manner, but this is not limiting. For example, the rotation speed of the compressor 21 can also be controlled to be increased continuously as time passes. In this case, control to increase the rotation speed of the compressor 21 in proportion to time is conceivable. Furthermore, control to increase the rotation speed of the compressor 21 continuously using any other arbitrary function with time as a variable is also conceivable. In any of the above cases, it can be said that the control unit 100 controls the rotation speed of the compressor 21 to be increased as time passes from the start of the hot gas defrosting process.

[0076] As described above, the control unit 100 controls the rotation speed of the compressor 21 to increase as time passes from the start of the hot gas defrosting process, thereby suppressing variations in the defrosting time and achieving efficient defrosting even when the amount of frost adhering to the evaporator 24 varies.

[0077] <Flowchart> Fig. 5 is a flowchart showing an example of control for performing hot gas defrosting processing. Next, with reference to Fig. 5, a detailed control flow of the control shown in the time chart of Fig. 4 will be described.

[0078] First, it is determined whether or not a cooling cycle is being performed (step S2). If it is determined that a cooling cycle is not being performed (NO), the control process is terminated. If it is determined that a cooling cycle is being performed (YES) in step S2, it is then determined whether or not a defrost flag is set (step S4). If it is determined that the defrost flag is not set (NO), the process enters a standby state in which this determination process is repeated. If it is determined that the defrost flag is set (YES) in step S4, it is then determined whether or not the cooling period has ended (step S6).

[0079] If it is determined in this determination that the cooling period has not ended (NO), the system enters a standby state in which this determination process is repeated. If it is determined in step S6 that the cooling period has ended (YES), the condensing fan 41 is stopped and a pre-defrost cycle is performed (step S8). A detailed description of the pre-defrost cycle is omitted as it is the same as above. After the pre-defrost cycle is performed, the hot gas defrosting process is then started (step S10). Then, as described above, the switching valve (three-way valve) 31 is switched so that the hot gas bypass pipe 30 side is opened and the condenser 22 side is closed, and the on-off valve 32 is closed (step S12). The condensing fan 41 remains stopped.

[0080] Then, 1 is input to the value of counter j (step S14), and compressor 21 is operated at rotation speed r(j) (step S16). The rotation speed r(1) for j=1 is the low rotation speed during defrosting. As the value of j increases, the value of rotation speed r(j) increases.

[0081] Next, it is determined whether the temperature of the evaporator 24 detected by the defrost sensor 51 exceeds a predetermined value (step S18). If it is determined that the temperature of the evaporator 24 exceeds the predetermined value (YES), it is assumed that defrosting of the evaporator 24 is completed, and this control process is terminated.

[0082] If it is determined in step S18 that the temperature of the evaporator 24 is equal to or lower than the predetermined value (NO), it is then determined whether a predetermined time T(j) has elapsed (step S20). Here, the time T(j) may be a fixed time or may vary depending on the value of j.

[0083] If it is determined in step 20 that the predetermined time T(j) has not elapsed (NO), the process goes into a standby state in which this determination process is repeated. During this time, compressor 21 continues to operate at rotation speed r(j). If it is determined in step 20 that the predetermined time T(j) has elapsed (YES), a control process is performed in which 1 is added to the value of counter j (step S22), and it is determined whether the counted-up value of j has reached the value N (step S24). N is a parameter that determines the number of steps, and in the example shown in FIG. 4, N=3.

[0084] If it is determined in step S24 that the value of j has not reached the value of N (NO), the process returns to step S16, and the control process from step S16 to step S24 is repeated. This allows the rotation speed r(j) to be increased stepwise over time to operate the compressor 21.

[0085] If it is determined in step S24 that the value of j has reached the value of N (YES), the hot gas defrosting process is terminated (step S26), and as described above, the rotation speed of compressor 21 is changed, switching valve (three-way valve) 31 is switched so that the condenser 22 side is opened and the hot gas bypass pipe 30 side is closed, and on-off valve 32 is opened. Then, after a predetermined time has elapsed, condensing fan 41 is operated (step S28). This completes the control process shown in the time chart of FIG. 4.

[0086] Although the embodiments and modes of implementation of the present invention have been described, the disclosed contents may vary in the details of the configuration, and changes in the combination and order of elements in the embodiments and modes of implementation may be realized without departing from the scope and spirit of the claimed invention. [Explanation of symbols]

[0087] 1 refrigerator 2. Case 3 Upper door 4 Lower door 6 Freezer 7 Refrigerator 10 Cooling Channel 10A lower cooling channel 10B Upper cooling channel 11A Lower partition plate 11B Upper partition plate 12 Fans 13 Freezer damper 14 Refrigerator damper 15 Return flow path 15A Entrance 15B Exit 20 Cooling circuit 21 Compressor 22 Condenser 23 Capillary tube 24 Evaporator 28 Suction pipe 30 Hot gas bypass pipe 31 Switching valve (three-way valve) 32 On-off valve 33 Frost tray 34 Heater 35 Drain pipe 40 Machine room 41 Condensing Fan 42 Evaporating dish 50 Outside air temperature sensor 51 Defrost sensor 100 control section

Claims

1. a cooling circuit in which a cooling cycle is implemented in which a refrigerant flows through a compressor, a condenser, an evaporator, and then returns to the compressor; a hot gas bypass pipe that directly connects the discharge side of the compressor or the condenser to the inlet side of the evaporator; a switching valve for switching between a state in which the refrigeration cycle is performed and a state in which a hot gas defrosting process is performed in which the refrigerant discharged from the compressor flows into the evaporator through the hot gas bypass pipe; a control unit that controls the compressor and the switching valve; an outside air temperature sensor that detects an outside air temperature and transmits the detected data to the control unit; a defrost sensor that detects the temperature of the evaporator and transmits the detected data to the control unit; Equipped with The rotation speed of the compressor is variable, When performing the hot gas defrosting process, the control unit operates the compressor at a rotation speed corresponding to an outside air temperature, and then controls to change the rotation speed of the compressor based on the temperature of the evaporator detected by the defrost sensor, When the compressor is operated at a rotation speed corresponding to the outside air temperature detected by the outside air temperature sensor, and the outside air temperature has a relationship of T1<T2, the rotation speed of the compressor at T1 is set to N1 and the rotation speed of the compressor at T2 is set to N2, and the relationship N1>N2 is satisfied; The control unit After operating the compressor at a rotation speed N1, when the temperature of the evaporator is higher than an expected temperature, control is performed to reduce the rotation speed of the compressor; The refrigerator is characterized in that, after the compressor is operated at a rotation speed N2, when the temperature of the evaporator is lower than the assumed temperature, the rotation speed of the compressor is controlled to be increased.

2. a condensing fan that cools the compressor and the condenser, The refrigerator according to claim 1, wherein the control unit controls the condensing fan to stop before the hot gas defrosting process is performed.

3. In the cooling circuit, a capillary tube is disposed between the condenser and the evaporator, and an on-off valve is disposed between the condenser and the capillary tube, 3. The refrigerator according to claim 1, wherein, when the hot gas defrosting process is performed, the control unit controls the on-off valve to close so that the refrigerant coming out of the condenser does not flow into the capillary tube.

4. A refrigerator as described in any one of claims 1 to 3, characterized in that when performing the hot gas defrosting process, the control unit controls to terminate the hot gas defrosting process when the temperature of the evaporator detected by the defrost sensor exceeds a predetermined value.

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