Refrigerator

Abstract

To provide a refrigerator capable of performing hot gas defrosting processing without damaging a compressor.SOLUTION: A refrigerator includes: a cooling circuit 50 in which a cooling cycle is executed where a refrigerant flows in a compressor 10, a condenser 12 and an evaporator 16 in this order and then returns to the compressor; a hot gas bypass pipe 20 for directly connecting the discharge side of the compressor or the condenser and the inflow side of the evaporator; a first switching valve 22 for switching between a state of performing the cooling cycle and a state of performing hot gas defrosting processing in which the refrigerant flows to the evaporator via the hot gas bypass pipe; and a second switching valve 30 for switching between a throttled state where the refrigerant which has gone out of the evaporator flows in a throttled flow passage and returns to the compressor, and a non-throttled state where it flows in a non-throttled flow passage and returns to the compressor. When a control part controls the compressor and the first switching valve so as to perform the cooling cycle, it controls the second switching valve so as to come into a non-throttled state, and when it controls the compressor and the first switching valve so as to perform the hot gas defrosting processing, it controls the second switching valve so as to come into a throttled state.SELECTED DRAWING: Figure 3B

Description

Technical Field

[0001] The present invention relates to a refrigerator, and more particularly to a refrigerator capable of performing a hot gas defrosting process.

Background Art

[0002] In order to remove frost adhering to an evaporator provided in a refrigerator, a hot gas defrosting process is known in which hot gas refrigerant discharged from a compressor or a condenser is directly supplied to the evaporator to perform defrosting. Regarding this hot gas defrosting process, in order to perform defrosting efficiently, a technique of changing the frequency of a drive motor of a compressor during the hot gas defrosting process has been proposed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the hot gas defrosting process, since the high-temperature refrigerant discharged from the compressor or the condenser flows into the evaporator without being decompressed by the capillary tube, a low compression ratio operation with a small difference between the discharge pressure and the suction pressure of the compressor occurs. In such a low compression ratio operation, it is known that there is a risk that the valve and the piston of the compressor come into contact with each other and are damaged.

[0005] Therefore, an object of the present invention is to solve the above problems and provide a refrigerator capable of performing a hot gas defrosting process without damaging the compressor and efficiently performing a cooling cycle.

Means for Solving the Problems

[0006] To achieve the above object, a first aspect of the present invention is A cooling circuit in which refrigerant flows in the order of a compressor, a condenser, and an evaporator and then returns to the compressor again is implemented, 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 first switching valve that switches between a state of performing the cooling cycle and a state of performing a hot gas defrosting process in which the refrigerant discharged from the compressor flows to the evaporator via the hot gas bypass pipe, a second switching valve that switches between a throttling state in which the refrigerant discharged from the evaporator flows through a throttled flow path and returns to the compressor and a non-throttling state in which the refrigerant discharged from the evaporator flows through an unthrottled flow path and returns to the compressor, a control unit that controls the compressor, the first switching valve, and the second switching valve, and is provided with wherein the control unit when controlling the compressor and the first switching valve to perform the cooling cycle, controls the second switching valve to be in the non-throttling state, and when controlling the compressor and the first switching valve to perform the hot gas defrosting process, controls the second switching valve to be in the throttling state. The refrigerator is

[0007] Even if the refrigerant discharged from the compressor is made to flow to the evaporator without passing through the capillary tube in order to perform the hot gas defrosting process, the refrigerant discharged from the evaporator flows through the throttled flow path and returns to the compressor, so that the pressure of the refrigerant returning to the compressor can be reduced. For this reason, even when operating with the discharge pressure of the compressor suppressed, it is possible to ensure the differential pressure between the suction side and the discharge side of the compressor such that the valve and the piston do not come into contact and get damaged. On the other hand, when performing a normal cooling cycle, the refrigerant discharged from the evaporator can be made to flow through an unthrottled flow path and return to the compressor. For this reason, the refrigerant circulates through a flow path with less flow resistance, and an efficient cooling cycle can be realized.

[0008] Thereby, the hot gas defrosting process can be performed without damaging the compressor, and the cooling cycle can be performed efficiently.

[0009] Further, in a second aspect of the present invention, in the first aspect, a second switching valve that can be changed between a throttled state and a non-throttled state is disposed in a flow path through which the refrigerant discharged from the evaporator returns to the compressor, and the control unit controls the second switching valve to determine whether to flow the refrigerant in a throttled state or in a non-throttled state. This is a refrigerator.

[0010] In this aspect, by simply providing one switching valve in the flow path through which the refrigerant discharged from the evaporator returns to the compressor, it is possible to surely perform the hot gas defrosting process without damaging the compressor and to efficiently perform the cooling cycle.

[0011] Further, in a third aspect of the present invention, in the first aspect, the flow path through which the refrigerant discharged from the evaporator returns to the compressor includes a flow path having a throttle that can be switched by the second switching valve and a flow path having no throttle, and the control unit controls the second switching valve to determine through which flow path the refrigerant flows. This is a refrigerator.

[0012] In this aspect, in the flow path through which the refrigerant discharged from the evaporator returns to the compressor, the second switching valve switches whether to flow the refrigerant through the flow path having a throttle or the flow path having no throttle. Therefore, it is possible to surely perform the hot gas defrosting process without damaging the compressor and to efficiently perform the cooling cycle.

Advantages of the Invention

[0013] As described above, in this aspect, it is possible to provide a refrigerator that can perform the hot gas defrosting process without damaging the compressor and can efficiently perform the cooling cycle.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4A

Figure 4B

Figure 5

Figure 6A

Figure 6B

Figure 7

Figure 8A

Figure 8B

[0015] Hereinafter, embodiments for implementing the present invention will be described with reference to the drawings. In each drawing, corresponding members having the same function are denoted by the same reference numerals. For the sake of easy explanation or understanding of the key points, the embodiments may be shown separately for convenience, but partial substitution or combination of the configurations shown in different embodiments is possible. In the embodiments described below, descriptions of matters common to the foregoing embodiments will be omitted, and only different points will be explained. In particular, the same operational effects due to the same configuration will not be sequentially mentioned for each embodiment. The sizes, positional relationships, etc. of the members shown in the drawings may be exaggerated for clarity of explanation. In the drawings and the following description, the refrigerator is placed on a horizontal plane, the side with the door is the front side, the opposite side is the rear side, and the left and right are indicated toward the door. Also, in the diagram showing the flow path, the flow of the refrigerant may be schematically indicated by an arrow.

[0016] (Refrigerator according to an embodiment of the present invention) First, with reference to FIGS. 1 and 2, an overview of the refrigerator according to an embodiment of the present invention will be described. FIG. 1 is a perspective view schematically showing an example of the outer shape of the refrigerator according to the present invention. FIG. 2 is a view showing the cross-section A-A of FIG. 1, and is a side cross-sectional view schematically showing the internal structure of the refrigerator. The refrigerators shown in FIGS. 1 and 2 correspond to any of the refrigerators according to the first and second embodiments described later.

[0017] The refrigerator 2 according to an embodiment of the present invention includes a freezer compartment 6A below the housing 4A and a refrigerator compartment 6B above the housing 4A. An openable lower door 8A is installed at the front opening of the freezer compartment 6A. An openable upper door 8B is installed at the front opening of the refrigerator compartment 6B.

[0018] At the rear of the interior of the refrigerator 2, a cooling flow path 4B partitioned by a partition plate is arranged. Inside the cooling flow path 4B, an evaporator 16 and a cooling fan 40 for circulating the gas cooled by the evaporator 16 in the interior are arranged. Further, dampers 42A and 42B for switching the gas cooled by the evaporator 16 to flow into or not flow into the freezer compartment 6A or the refrigerator compartment 6B are arranged.

[0019] In the machine room 4C located at the lower rear of the refrigerator 2, a compressor 10 and a condenser 12 that constitute the cooling circuit 50 are arranged. Further, in the machine room 4C, a fan for cooling the compressor 10, the condenser 12, etc. is also arranged. The condenser 12 and the evaporator 16 are connected by a capillary tube 14, and the evaporator 16 and the compressor 10 are connected by a suction tube 24. Thus, the cooling circuit 50 of the refrigerator 2 according to the present embodiment is mainly composed of a compressor 10, a condenser 12, a capillary tube 14, an evaporator 16, a suction tube 24, and other tubes connecting these members.

[0020] Also, in the machine room 4C, an evaporating dish 26 for storing defrosting water (liquid) generated by melting the frost adhering to the fins of the evaporator 16 is arranged. The defrosting water (liquid) melted from the evaporator 16 and falling flows into the evaporating dish 26 through the drain D.

[0021] <Cooling cycle> Next, an overview of the cooling cycle in which the refrigerant circulates through the cooling circuit 50 to cool the evaporator 16 will be described. In the cooling cycle, the high-temperature, high-pressure gaseous refrigerant discharged by the compressor 10 arranged in the machine room 4C becomes a liquid or gas-liquid mixed refrigerant by heat dissipation in the condenser 12, flows through the capillary tube 14 and is depressurized, and the low-temperature, low-pressure liquid refrigerant enters the evaporator 16. The solvent flowing through the heat exchange tubes of the evaporator 16 takes away the heat of the gas flowing between the fins and vaporizes, and returns to the suction side of the compressor 10 again through the suction tube 24. This cooling cycle is repeated.

[0022] <Hot gas defrosting process> When the evaporator 16 exchanges heat with the gas flowing inside the compartment, the water vapor contained in the gas may frost, so it is necessary to defrost the evaporator 16 regularly. In the refrigerator 2 according to the present embodiment, as will be described later, a hot gas defrosting process is performed in which the refrigerant in the form of a high-temperature gas (hot gas) compressed by the compressor 10 is directly supplied to the evaporator 16 for defrosting. The hot gas defrosting process in the refrigerator 2 according to the present embodiment will be described in detail later with reference to FIGS. 3A to 4B.

[0023] (Hot gas defrosting process in a conventional refrigerator) Before explaining the hot gas defrosting process according to the present embodiment, the hot gas defrosting process in a conventional refrigerator will be explained with reference to FIGS. 6A and 6B, and the problems that occur at that time will be explained. FIG. 6A is a diagram schematically showing the cooling circuit of a conventional refrigerator, and is a diagram showing the case of performing a cooling cycle. FIG. 6B is a diagram schematically showing the cooling circuit of a conventional refrigerator, and is a diagram showing the case of performing a hot gas defrosting process. In FIGS. 6A and 6B, the flow path through which the refrigerant flows is shown by a solid line, and the flow path through which the refrigerant does not flow is shown by a broken line.

[0024] The cooling circuit 150 of a conventional refrigerator is mainly composed of a compressor 110, a condenser 112, a capillary tube 114, an evaporator 116, a suction tube 124, and other tubes connecting these members. Further, in order to perform a hot gas defrosting process, the cooling circuit 150 includes a hot gas bypass tube 120 that directly connects the discharge side of the compressor 110 and the inflow side of the evaporator 116.

[0025] A switching valve 122 is disposed on the discharge side of the compressor 110. By the switching valve 122, it is possible to switch between a state in which the refrigerant discharged from the compressor 110 flows to the condenser 112 side as shown in FIG. 6A to perform a cooling cycle and a state in which the refrigerant discharged from the compressor 110 flows to the hot gas bypass tube 120 side as shown in FIG. 6B to perform a hot gas defrosting process.

[0026] By switching the switching valve 122 so that the condenser 112 side is opened, the refrigerant can flow through the path of the compressor 110 - condenser 112 - capillary tube 114 - evaporator 116 - suction pipe 124 and return to the compressor 110 to perform a normal cooling cycle.

[0027] On the other hand, by switching the switching valve 122 so that the hot gas bypass pipe 120 side is opened, the refrigerant can flow through the path of the compressor 110 - hot gas bypass pipe 120 - evaporator 116 - suction pipe 124 and return to the compressor 110 to perform a hot gas defrosting process. In the hot gas defrosting process, since the hot gas - state refrigerant discharged from the compressor 110 can be directly supplied to the evaporator 116 via the hot gas bypass pipe 120, the frost attached to the evaporator 116 can be efficiently melted.

[0028] <Problems occurring in the hot gas defrosting process> Next, with reference to FIGS. 7, 8A, and 8B, the problems occurring in the above - described hot gas defrosting process will be explained. FIG. 7 is a graph showing the pressures of the refrigerant on the suction side and the discharge side of the compressor when performing a cooling cycle and a hot gas defrosting process in the cooling circuit of a refrigerator. The vertical axis of the graph indicates pressure, and the horizontal axis indicates time. FIG. 8A is a side cross - sectional view schematically showing a part of the internal structure of the compressor. FIG. 8B is a side cross - sectional view schematically showing the case when low - compression - ratio operation is performed in the compressor shown in FIG. 8A.

[0029] In the cooling cycle, the high - temperature and high - pressure gaseous refrigerant discharged from the compressor 110 is cooled by heat dissipation in the condenser 12, and the temperature of the refrigerant drops to become a liquid or a gas - liquid mixture. This liquid or gas - liquid mixture refrigerant is depressurized while flowing through the capillary tube 114, flows into the evaporator 116, takes away the heat of the gas passing between the fins and vaporizes, and returns to the compressor 110 through the suction pipe 124. That is, in the cooling cycle, the refrigerant discharged from the compressor 110 is depressurized by the capillary tube 114, flows through the evaporator 12, and returns to the compressor 110. Therefore, inevitably, the differential pressure between the suction - side pressure and the discharge - side pressure of the compressor 110 becomes large.

[0030] Therefore, as shown in the graph during the cooling cycle in FIG. 7, the differential pressure between the suction side pressure of the refrigerant flowing into the compressor 110 through the suction pipe 124 and the discharge side pressure of the refrigerant discharged from the compressor 110 is greater than the proper operating differential pressure.

[0031] On the other hand, in the hot gas defrosting process, since the refrigerant discharged from the compressor 110 does not flow through the capillary tube 114, it is not significantly depressurized, and there is no large decompression element in the flow path through which the refrigerant circulates. That is, the refrigerant discharged from the compressor 110 returns to the suction side of the compressor 110 while maintaining a pressure close to the discharge pressure. Therefore, as shown in the graph during the hot gas defrosting process in FIG. 7, inevitably, the differential pressure ΔP' between the suction side pressure and the discharge side pressure of the refrigerant in the compressor 110 becomes small and is smaller than the proper operating differential pressure of the compressor 110.

[0032] As shown in FIG. 8A, in many cases, as the compressor 110, a reciprocating compressor in which the piston 130 reciprocates inside the cylinder 134 to discharge the compressed refrigerant is used. Due to the rotational driving force of the drive motor, the cylinder 134 reciprocates via the crank and the rod 136. When the cylinder 134 moves to the right side of the drawing, when the refrigerant pressure in the cylinder 134 becomes approximately the same as the inlet side of the suction side valve 132 during the process of re-expanding the compressed refrigerant remaining in the cylinder 134, the suction side valve 132 opens and the refrigerant flows into the cylinder 134. Thereafter, with the suction side valve 132 and the discharge side valve 138 closed, when the piston 130 moves to the left side of the drawing, the refrigerant is compressed, and the discharge side valve 138 is opened by the pressure of the compressed refrigerant, so that the refrigerant is discharged from the compressor 110.

[0033] In the low compression ratio operation of the hot gas defrosting process, when the refrigerant is compressed in the cylinder 134 due to the low pressure on the discharge side, the pressure of the refrigerant is in a relatively low state, that is, the suction valve 132 opens at a timing earlier than that at the proper operating differential pressure. At this time, as shown in Fig. 8B, there is a risk that the suction valve 132 contacts and is damaged by opening before the piston 130 escapes completely. In the refrigerator 2 according to the embodiment of the present invention shown below, this problem is solved, and the hot gas defrosting process can be surely performed without damaging the compressor.

[0034] (Refrigerator according to the first embodiment of the present invention) Next, with reference to Figs. 3A and 3B, the refrigerator according to the first embodiment of the present invention will be described. Fig. 3A is a diagram schematically showing the cooling circuit of the refrigerator according to the first embodiment of the present invention, and is a diagram showing the case of performing a cooling cycle. Fig. 3B is a diagram schematically showing the cooling circuit of the refrigerator according to the first embodiment of the present invention, and is a diagram showing the case of performing a hot gas defrosting process. In Figs. 3A and 3B, the flow path through which the refrigerant flows is shown by a solid line, and the flow path through which the refrigerant does not flow is shown by a broken line.

[0035] In the cooling circuit 50 in the present embodiment, compared with the above-described conventional cooling circuit 150, it is different in that it has a configuration for solving the above problems in the flow path through which the refrigerant returns from the evaporator 16 to the compressor 10. The cooling circuit 50 according to the present embodiment is mainly composed of a compressor 10, a condenser 12, a capillary tube 14, an evaporator 16, a suction pipe 24, and other pipes connecting these members. Further, in order to perform a hot gas defrosting process, the cooling circuit 50 includes a hot gas bypass pipe 20 that directly connects the discharge side of the compressor 10 and the inflow side of the evaporator 16.

[0036] Between the compressor 10 and the condenser 12, that is, on the discharge side of the compressor 10, a first switching valve 22 is arranged. By the first switching valve 22, it is possible to switch between a state of performing a cooling cycle in which the refrigerant discharged from the compressor 10 flows to the condenser 22 side as shown in Fig. 3A and a state of performing a hot gas defrosting process in which the refrigerant discharged from the compressor 10 flows to the hot gas bypass pipe 20 side as shown in Fig. 3B.

[0037] Furthermore, a second switching valve 30 is installed in the suction pipe 24 between the evaporator 16 and the compressor 10. The second switching valve 30 according to the present embodiment is a variable throttle valve capable of changing the throttle state of the valve by driving an actuator. Thereby, it is possible to switch between a throttle state in which the refrigerant flowing out from the evaporator 16 flows through a throttled flow path and returns to the compressor 10, and a non-throttled state in which the refrigerant flowing out from the evaporator 16 flows through an unthrottled flow path and returns to the compressor 10. When such a variable throttle valve is used, the opening degree for throttling the flow path can also be changed according to the situation.

[0038] However, as the second switching valve 30, not only a variable throttle valve driven by an actuator but also a solenoid valve that can be switched between a throttled state and a non-throttled state (fully open state) by solenoid switching can be adopted.

[0039] <Control unit> Next, an example of the control unit according to the embodiment of the present invention will be described with reference to FIG. 5. FIG. 5 is a block diagram showing an example of the control unit according to the embodiment of the present invention. As shown in FIG. 5, the control unit 60 is electrically connected to the compressor 10, the cooling fan 40, the dampers 42A and 42B for the freezer compartment and the refrigerator, the first switching valve 22, and the second switching valve 30, and can control these devices.

[0040] <Cooling cycle> When performing a normal cooling cycle, the control unit 60 controls the first switching valve 22 to switch it so that the condenser 12 side is open, and controls the second switching valve 30 to be in a non-throttling state. Then, the control unit 60 operates the compressor 10 during normal operation. As a result, as shown in FIG. 3A (solid line flow path), the refrigerant can flow through the path of the compressor 10 - condenser 12 - capillary tube 14 - evaporator 16 - suction pipe 24 and return to the compressor 10 to perform a normal cooling cycle. At this time, the control unit 60 can operate the cooling fan 40 to make the gas in the compartment flow, and pass the gas between the fins of the evaporator 16 for cooling. By the control unit 60 controlling the dampers 42A and 42B for the freezer compartment and the refrigerator compartment, the cold air that has passed through the evaporator 16 can be supplied to the freezer compartment 6A and the refrigerator compartment 6B.

[0041] Speaking of the cooling cycle in more detail, the high-temperature and high-pressure gaseous refrigerant discharged from the compressor 10 flows through the condenser 12. The temperature of the refrigerant drops due to heat dissipation in the condenser 12, and it becomes a liquid or gas-liquid mixed refrigerant. This liquid or gas-liquid mixed refrigerant flows through the capillary tube 14 and is depressurized, and the low-temperature and low-pressure liquid refrigerant enters the evaporator 16. While this refrigerant flows through the cooling tubes of the evaporator 16, it absorbs the heat of the gas flowing between the fins, that is, around the cooling tubes, and vaporizes. The cold air cooled when flowing between the fins flows into the freezer compartment 6A and the refrigerator compartment 6B to cool the storage area. The refrigerant vaporized in the evaporator 16 returns to the suction side of the compressor 10 through the suction pipe 24, and this cooling cycle is repeated.

[0042] Since the second switching valve 30 arranged in the suction pipe 24 is in a non-throttling state, the flow resistance when the refrigerant flows can be suppressed, and the cooling cycle can be efficiently performed.

[0043] In this embodiment, since the refrigerant flowing through the condenser 12 branches and flows into the two capillary tubes 14 by the branch valve 18, the decompression of the more efficiently liquefied solvent can be performed more efficiently. Further, an electromagnetic switching valve is adopted as the branch valve 18, and switching can be performed between a state in which the refrigerant flows through both capillary tubes 14, a state in which the refrigerant flows only through one capillary tube 14, and a state in which the refrigerant does not flow through either capillary tube 14.

[0044] The suction pipe 24 through which the refrigerant flows from the evaporator 16 to the compressor 10 is arranged at least partially close to the capillary tube 14 so as to be able to exchange heat with the capillary tube 14. The region surrounded by the dotted line in FIG. 3A represents the outline of the heat exchange portion.

[0045] <Hot gas defrosting process> On the other hand, when performing the hot gas defrosting process, the control unit 60 controls the first switching valve 22 to switch so that the hot gas bypass pipe 20 side is opened, and controls the second switching valve 30 to be in a throttled state. Then, the control unit 60 operates the compressor 10. As a result, as shown in FIG. 3B (solid line flow path), a hot gas defrosting process can be performed in which the refrigerant flows through the path of the compressor 10 - hot gas bypass pipe 20 - evaporator 16 - suction pipe 24 and returns to the compressor 10. At this time, the control unit 60 controls the cooling fan 40 to be in a stopped state. The refrigerant basically circulates through the path of the compressor 10 - hot gas bypass pipe 20 - evaporator 16 - suction pipe 24 in a vaporized state.

[0046] In the hot gas defrosting process, the hot gas refrigerant discharged from the compressor 10 can be directly supplied to the heat exchange pipes of the evaporator 16 through the hot gas bypass pipe 20. As the hot gas refrigerant flows through the heat exchange pipes, the heat exchange pipes are heated, and the fins are also heated by heat conduction. Thus, a hot gas defrosting process for melting the frost adhering to the evaporator 16 can be performed. The frost melted in the contact area with the fins drops. The dropped liquid flows into the evaporation tray 26 in the machine room 4C through the drain pipe D (see Fig. 2). The liquid flowing into the evaporation tray 26 evaporates into the atmosphere.

[0047] In the hot gas defrosting process, there is no pressure reduction of the refrigerant by the capillary tube 14. However, in this embodiment, since the second switching valve 30 disposed in the suction pipe 24 is in a throttled state, the pressure of the refrigerant returning to the compressor 10 decreases due to the flow resistance. Therefore, as shown in the graph of Fig. 7, the differential pressure ΔP from the discharge pressure of the compressor 10 can be made larger than the proper operation differential pressure. Thus, the hot gas defrosting process can be performed without damaging the compressor 10. As for the degree of throttling (opening degree) of the second switching valve 30, it is necessary to adjust so that the differential pressure ΔP between the suction side and the discharge side of the compressor 10 becomes larger than the proper operation differential pressure and the gaseous refrigerant circulates. However, it is considered that the adjustment is possible within a certain range.

[0048] In this embodiment, the refrigerant circulates through the path of the compressor 10 - hot gas bypass pipe 20 - evaporator 16 - suction pipe 24, but it is not limited thereto. The first switching valve 22 is disposed between the condenser 12 and the capillary tube 14. In the hot gas defrosting process, there may be a case where the refrigerant flows through the path of the compressor 10 - condenser 12 - hot gas bypass pipe 20 - evaporator 16 - suction pipe 24 and returns to the compressor 10. Even in that case, it is necessary to operate the compressor 10 in a low compression ratio operation when performing the hot gas defrosting process. Even in that case, by setting the second switching valve 30 disposed in the suction pipe 24 to a throttled state, the hot gas defrosting process can be performed without damaging the compressor 10.

[0049] In the above description, an electromagnetic switching valve is adopted as the branch valve 18 that branches into the two capillary tubes 14. However, when the first switching valve 22 is arranged between the condenser 12 and the capillary tube 14, this electromagnetic valve can also be used as the first switching valve 22.

[0050] As described above, in the present embodiment, a second switching valve 30 that can be changed between a throttled state and a non-throttled state is arranged in the flow path (suction pipe) 24 through which the refrigerant discharged from the evaporator 16 returns to the compressor 10, and the control unit 60 controls the second switching valve 30 to determine whether to flow the refrigerant in the throttled state or in the non-throttled state.

[0051] In this way, by providing only one switching valve 30 in the flow path (suction pipe) 24 connecting between the evaporator 16 and the compressor 10, it is possible to surely perform the hot gas defrosting process without damaging the compressor 10 and to efficiently perform the cooling cycle.

[0052] (Refrigerator according to the second embodiment of the present invention) Next, a refrigerator according to the second embodiment of the present invention will be described with reference to FIGS. 4A and 4B. FIG. 4A is a diagram schematically showing a cooling circuit of the refrigerator according to the second embodiment of the present invention, and is a diagram showing a case where a cooling cycle is performed. FIG. 4B is a diagram schematically showing a cooling circuit of the refrigerator according to the second embodiment of the present invention, and is a diagram showing a case where a hot gas defrosting process is performed. In FIGS. 4A and 4B, the flow path through which the refrigerant flows is shown by a solid line, and the flow path through which the refrigerant does not flow is shown by a broken line.

[0053] In the above-described first embodiment, the second switching valve 30 that can be changed between a throttled state and a non-throttled state is arranged in the suction pipe 24. However, in the present embodiment, the suction pipe 24 includes a flow path 24A having a throttle and a flow path 24B not having a throttle, and the second switching valve 34 can switch through which flow path the refrigerant flows.

[0054] More specifically, the second switching valve 34 is a solenoid valve that operates under the control of the control unit 60 to selectively flow the refrigerant from the evaporator 16 to either the flow path 24A or the flow path 24B. A throttle valve 32 is disposed in the flow path 24A, and a throttled flow path is formed. The throttle valve 32 can be manually adjusted to change the opening degree of the throttle. However, it is not limited thereto, and a throttle valve whose opening degree is changed by the operation of an actuator can also be employed, or a member with a fixed throttle opening degree such as an orifice can also be used. On the other hand, the flow path 24B is composed of a flow path in which no member for throttling the flow path is disposed.

[0055] <Cooling cycle> When performing normal cooling control, the control unit 60 controls the first switching valve 22 to switch it so that the condenser 12 side is open, and controls the second switching valve 34 so that the refrigerant flows through the flow path 24B without throttling. Then, the control unit 60 operates the compressor 10 during normal operation. As a result, as shown in FIG. 4A (solid line flow path), the refrigerant can perform a normal cooling cycle in which it flows through the compressor 10 - condenser 12 - capillary tube 14 - evaporator 16 - suction pipe 24 (flow path 24B without throttling) and returns to the compressor 110. At this time, the control unit 60 operates the cooling fan 40 to flow the air in the storage compartment, and the air is cooled when it passes between the fins of the evaporator 16. By the control unit 60 controlling the dampers 42A and 42B for the freezer compartment and the refrigerator compartment, the cold air that has passed through the evaporator 16 can be supplied to the freezer compartment 6A and the refrigerator compartment 6B.

[0056] <Hot gas defrosting process> On the other hand, when performing the hot gas defrosting process, the control unit 60 controls the first switching valve 22 to switch so that the hot gas bypass pipe 20 side is opened, and controls the second switching valve 34 to control the refrigerant to flow through the throttled flow path 24A. Then, the control unit 60 operates the compressor 10. As a result, as shown in FIG. 4B (solid line flow path), a hot gas defrosting process can be performed in which the refrigerant flows through the path of the compressor 10 - hot gas bypass pipe 20 - evaporator 16 - suction pipe 24 (throttled flow path 24A) and returns to the compressor 10. At this time, the control unit 60 controls the cooling fan 40 to be stopped. The refrigerant basically circulates through the path of the compressor 10 - hot gas bypass pipe 20 - evaporator 16 - suction pipe 24 in a vaporized state.

[0057] Since the refrigerant does not pass through the capillary tube, the pressure of the refrigerant after leaving the evaporator is close to the discharge pressure. However, due to the flow resistance of the refrigerant flowing through the throttled flow path 24A, the pressure of the refrigerant returning to the compressor 10 decreases. Therefore, as shown in the graph of FIG. 7, the differential pressure ΔP from the discharge pressure of the compressor 10 can be made larger than the appropriate operating differential pressure. As a result, the hot gas defrosting process can be performed without damaging the compressor 10.

[0058] As described above, in the present embodiment, the flow path (suction pipe) 24 through which the refrigerant discharged from the evaporator 16 returns to the compressor 10 includes a flow path 24A having a throttle that can be switched by the second switching valve 34 and a flow path 24B having no throttle, and the control unit 60 controls the second switching valve 34 to determine through which flow path the refrigerant flows.

[0059] In this way, in the flow path (suction pipe) 24 through which the refrigerant discharged from the evaporator 16 returns to the compressor 10, the second switching valve 34 can switch whether the refrigerant flows through the flow path 24A having a throttle or the flow path 24B having no throttle. Thus, it is possible to surely perform the hot gas defrosting process without damaging the compressor 10 and to efficiently perform the cooling cycle.

[0060] In any of the above-described first and second embodiments, in the refrigerator 2 according to the present embodiment, a cooling cycle in which the refrigerant flows in the order of the compressor 10, the condenser 12, and the evaporator 16 and returns to the compressor 10 again is implemented in a cooling circuit 50, a hot gas bypass pipe 20 that directly connects the discharge side of the compressor 10 or the condenser 12 and the inflow side of the evaporator 16, a state in which the cooling cycle is performed, and a state in which a hot gas defrosting process is performed in which the refrigerant discharged from the compressor 10 flows through the hot gas bypass pipe 20 to the evaporator 16. A first switching valve 22 for switching between the two, a throttle state in which the refrigerant discharged from the evaporator 16 flows through a throttled flow path and returns to the compressor 10, and a non-throttled state in which the refrigerant discharged from the evaporator 16 flows through an unthrottled flow path and returns to the compressor 10. Second switching valves 30 and 34 for switching between the two, and a control unit 60 for controlling the compressor 10, the first switching valve 22, and the second switching valves 30 and 34. When the control unit 60 controls the compressor 10 and the first switching valve 22 to perform the cooling cycle, the second switching valves 30 and 34 are controlled to be in the non-throttled state, and when the compressor 10 and the first switching valve 22 are controlled to perform the hot gas defrosting process, the second switching valves 30 and 34 are controlled to be in the throttled state.

[0061] Even if an operation is performed to suppress the discharge pressure of the compressor 10 in order to perform the hot gas defrosting process, since the refrigerant discharged from the evaporator 16 flows through a throttled flow path and returns to the compressor 10, the pressure of the refrigerant returning to the compressor 10 can be reduced. Therefore, even when an operation is performed to suppress the discharge pressure of the compressor 10, it is possible to ensure a differential pressure between the suction side and the discharge side of the compressor 10 such that the valve and the piston do not come into contact with each other and are not damaged. On the other hand, when performing a normal cooling cycle, the refrigerant discharged from the evaporator 16 can flow through an unthrottled flow path and return to the compressor 10. Therefore, the refrigerant circulates through a flow path with low flow resistance, and an efficient cooling cycle can be realized.

[0062] As a result, it is possible to provide a refrigerator 2 that can perform the hot gas defrosting process without damaging the compressor 10 and can perform the cooling cycle efficiently.

[0063] Although the embodiments and modes of implementation of the present invention have been described, the disclosed content may change in the details of the configuration, and changes in the combination and order of elements in the embodiments and modes of implementation can be realized without departing from the scope and spirit of the claimed invention.

Explanation of Reference Numerals

[0064] 2 Refrigerator 4A Housing 4B Cooling Flow Path 4C Machine Room 6A Freezer Compartment 6B Refrigerator Compartment 8A, 8B Door 10 Compressor 12 Condenser 14 Capillary Tube 16 Evaporator 18 Branch Valve 20 Hot Gas Bypass Pipe 22 First Switching Valve 24 Suction Pipe 24A, 24B Flow Path 30 Second Switching Valve 32 Throttle Valve 34 Second Switching Valve 40 Cooling Fan 42A, 42B Damper 50 Cooling Circuit 60 Control Unit 110 Compressor 112 Condenser 114 Capillary Tube 116 Evaporator 118 Branch Valve 120 Hot Gas Bypass Pipe 122 Switching Valve 124 Suction Pipe 130 Piston 132 Suction Side Valve 134 Cylinder 136 Rod 138 Discharge Side Valve 150 Cooling Circuit

Claims

1. A cooling circuit in which refrigerant flows in the order of a compressor, a condenser, and an evaporator and then returns to the compressor again, A hot gas bypass pipe directly connecting the discharge side of the compressor or the condenser to the inlet side of the evaporator, A first switching valve that switches between a state of performing the cooling cycle and a state of performing a hot gas defrosting process in which the refrigerant discharged from the compressor flows through the hot gas bypass pipe to the evaporator, A second switching valve that switches between a throttling state in which the refrigerant discharged from the evaporator flows through a throttled flow path and returns to the compressor and a non-throttling state in which the refrigerant discharged from the evaporator flows through an unthrottled flow path and returns to the compressor, A control unit that controls the compressor, the first switching valve, and the second switching valve, Comprising, The control unit, When controlling the compressor and the first switching valve to perform the cooling cycle, controls the second switching valve to be in the non-throttling state, When controlling the compressor and the first switching valve to perform the hot gas defrosting process, controls the second switching valve to be in the throttling state. A refrigerator characterized by this.

2. The second switching valve that can be changed between a throttling state and a non-throttling state is arranged in the flow path through which the refrigerant discharged from the evaporator returns to the compressor, and the control unit controls the second switching valve to determine whether to flow the refrigerant in the throttling state or in the non-throttling state. The refrigerator according to claim 1, characterized by this.

3. The flow path through which the refrigerant discharged from the evaporator returns to the compressor includes a flow path having a throttle that can be switched by the second switching valve and a flow path having no throttle, and the control unit controls the second switching valve to determine through which flow path to flow the refrigerant. The refrigerator according to claim 1, characterized by this.

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