Refrigerator

Abstract

To provide a refrigerator capable of executing defrosting of an evaporator efficiently with a small amount of energy consumption.SOLUTION: A refrigerator includes: an evaporator 20 which has a cooling tube 24 where a refrigerant flows inside and a cooling fin 26 mounted on the cooling tube 24; a heater 34 arranged below the evaporator 20, and for melting frost attached to the cooling fin 26 and the cooling tube 24; a light source 30 for irradiating the cooling fin 26 and the cooling tube 24 with light having wavelength in the ultraviolet light range or in the visible light range; and a control part for controlling the light source 30. At least a part of the surface of the cooling fin 26 is coated with photocatalyst which is activated by the light emitted from the light source 30. When performing a defrosting operation for the first time after the power is turned on, or when the evaporator 20 is in a state of capable of defrosting and the activation of the photocatalyst is not continuing, the control part turns on the light source 30, and when the activation completion time of the photocatalyst has elapsed, it turns off the light source 30.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a refrigerator equipped with an evaporator, and more particularly to defrosting of the evaporator. [Background technology]

[0002] In refrigerators, defrosting to remove frost that has adhered to the surfaces of the evaporator's cooling fins is important to maintain the cooling performance of the evaporator. To perform defrosting efficiently, refrigerators have been proposed in which a visible light-reactive photocatalytic coating is applied to the surfaces of the evaporator's cooling fins (see, for example, Patent Document 1). In the refrigerator described in Patent Document 1, during humidification operation with the compressor stopped, the photocatalyst is exposed to light to activate it and make it superhydrophilic. Because the photocatalytic coating applied to the cooling fins is superhydrophilic, frost formation and granulation of ice are suppressed, and melting is also leveled, allowing the defrosting action to proceed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-261669 Summary of the Invention [Problem to be solved by the invention]

[0004] However, during humidification operation, the compressor is stopped but the heater is not used, so the evaporator temperature remains low and the defrosting effect due to the photocatalyst becoming superhydrophilic is limited. Furthermore, in the refrigerator described in Cited Document 1, the light source is operated not only during the humidification operation, which is performed for about 40 minutes, but also continuously until the initial stage of the subsequent cooling operation. However, it is generally considered that photocatalyst activation is completed within a relatively short light irradiation time, and from the viewpoint of energy conservation, it cannot be said that the light source is operated efficiently.

[0005] Therefore, an object of the present invention is to solve the above problems and to provide a refrigerator that can efficiently defrost an evaporator with little energy consumption. [Means for solving the problem]

[0006] In order to achieve the above object, the first aspect of the present invention is an evaporator having cooling tubes through which a refrigerant flows and cooling fins attached to the cooling tubes; a heater disposed below the evaporator and configured to melt frost adhering to the cooling fins and the cooling tubes; a light source that irradiates the cooling fins and the cooling tubes with light having a wavelength in the ultraviolet region or the visible region; a control unit that controls the light source; Equipped with At least a part of the surface of the cooling fin is coated with a photocatalyst that is activated by light emitted from the light source, The control unit When defrosting is performed for the first time after power is turned on, or When the evaporator is in a state where defrosting is possible and activation of the photocatalyst is not sustained, Turn on the light source, When the activation completion time of the photocatalyst has elapsed, the light source is turned off. This is a refrigerator that uses light irradiation processing.

[0007] When the defrosting operation is performed for the first time after power-on, the photocatalyst is not activated, so it is preferable to turn on the light source when the defrosting operation starts. Furthermore, for example, when the evaporator temperature is higher than 0°C and defrosting is possible, if the photocatalyst has superhydrophilic properties, it will easily melt the frost, and the evaporator will be defrosted effectively. In this embodiment, the light source is turned on to activate the photocatalyst only when the photocatalyst is not activated. When the photocatalyst remains activated, the light source is not turned on, allowing for efficient use of the light source.

[0008] Furthermore, once the activation completion time has elapsed after the start of irradiating the photocatalyst with light, further irradiation with light will not further activate the photocatalyst. In this embodiment, the light source is turned on and then turned off when the activation completion time has elapsed, thereby reducing the power consumption of the light source while reliably making the photocatalyst superhydrophilic and achieving effective defrosting. Therefore, in this embodiment, the evaporator can be defrosted efficiently with little energy consumption.

[0009] In addition, a second aspect of the present invention is the first aspect, When the first defrosting operation is started after power-on, the control unit starts the light irradiation process.

[0010] The initial defrosting operation after power-on corresponds to the first defrosting operation of the refrigerator or the first defrosting operation after a long period of shutdown. In such cases, there is uncertainty about the activation state of the photocatalyst immediately after light irradiation, so it is preferable to turn on the light source at the start of the defrosting operation to be on the safe side. According to this aspect, light irradiation begins when the heater starts heating, so that the photocatalyst can be reliably made superhydrophilic when the evaporator temperature rises above 0°C and the frost begins to melt.

[0011] In addition, a third aspect of the present invention is the first or second aspect, a temperature sensor for measuring the temperature of the evaporator; In the second or subsequent defrosting operation after power-on, after the previous light irradiation process is completed, the activation duration of the photocatalyst has elapsed, the control unit turns on the heater to start the defrosting operation, and when the measurement value of the temperature sensor becomes higher than 0°C, the control unit starts the light irradiation process.

[0012] When performing defrosting operation, if the cooling fins are superhydrophilic, defrosting of the cooling fins is promoted. If the photocatalyst activation duration has elapsed, the photocatalyst should be made superhydrophilic by irradiating it with light. However, since the photocatalyst quickly becomes superhydrophilic after light irradiation, there is no need to turn on the light source when starting defrosting operation. By turning on the heater to heat the evaporator, and starting light irradiation when the evaporator temperature rises above 0°C, the photocatalyst can be quickly activated and made superhydrophilic. This allows for effective defrosting operation while reducing the power consumption of the light source.

[0013] Further, a fourth aspect of the present invention is any one of the first to third aspects, a temperature sensor for measuring the temperature of the evaporator; In this refrigerator, after the previous light irradiation process is completed, the activation duration of the photocatalyst has elapsed and the measured value of the temperature sensor has become higher than 0°C, and then the control unit starts the light irradiation process.

[0014] When the temperature sensor measuring the evaporator temperature rises above 0°C, defrosting of the cooling fins is promoted if the surface of the cooling fins is superhydrophilic. Even if the photocatalyst activation duration has elapsed, irradiating the surface with light from the light source immediately activates the photocatalyst, making it superhydrophilic, and immediately promoting defrosting of the cooling fins. This allows for effective defrosting while reducing the power consumption of the light source.

[0015] Further, a fifth aspect of the present invention is a method for producing a composition comprising the steps of: A refrigerator wherein the activation duration is determined based on measurements from the temperature sensor.

[0016] The activation duration of a photocatalyst varies depending on the temperature. In this embodiment, the activation duration is determined based on the temperature of the evaporator coated with the photocatalyst, so it is possible to more accurately determine whether the activation of the photocatalyst is maintained.

[0017] Further, a sixth aspect of the present invention is any one of the first to fifth aspects, The light source is disposed above the evaporator in the refrigerator.

[0018] When defrosting is performed by heating with a heater placed below the evaporator, defrosting progresses more quickly on the lower side of the evaporator than on the upper side. Therefore, defrosting can be promoted by irradiating the photocatalyst-coated surface on the upper side of the evaporator, where defrosting is slower, with stronger light. In addition, since there is no heater or heater cover on the upper side, it is easier to irradiate the light from the light source onto the catalyst-coated surface.

[0019] In addition, a seventh aspect of the present invention is the sixth aspect, The refrigerator has a reflector disposed on a side surface of the evaporator in a direction perpendicular to the surface of the cooling fin.

[0020] In this embodiment, a reflector is arranged on the side of the evaporator that is perpendicular to the surface of the cooling fin, so that light from the light source can be more effectively directed onto the photocatalyst coated on the cooling fin.

[0021] An eighth aspect of the present invention is any one of the first to seventh aspects, The refrigerator is one in which the photocatalyst is coated from above the evaporator to a predetermined area.

[0022] During defrosting operation, the heater located below the evaporator heats the evaporator to defrost it, so the lower side of the evaporator defrosts more quickly than the upper side. Therefore, sufficient defrosting can be expected even without a photocatalytic coating on the lower side of the evaporator. This reduces the amount of photocatalyst needed for coating, contributing to lower evaporator manufacturing costs. [Effects of the Invention]

[0023] As described above, in this aspect, it is possible to provide a refrigerator that can efficiently defrost the evaporator with little energy consumption. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a perspective view schematically illustrating an example of the external shape of a refrigerator according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing a cross section AA in FIG. 1, and is a side cross-sectional view that schematically shows the internal structure of a refrigerator. [Figure 3] 3 is a side view of the evaporator shown in FIG. 2 in a direction perpendicular to the surface of the cooling fins. [Figure 4] FIG. 2 is a block diagram illustrating an example of a control unit according to an embodiment of the present invention. [Figure 5] 10 is a flowchart showing an example of a control process when a heater is turned on to perform a defrosting operation. [Figure 6] 10 is a flowchart illustrating an example of a control process when it is determined that the evaporator is in a state where defrosting is possible based on the temperature of the evaporator. [Figure 7] 10 is a flowchart showing an example of a control process for setting a photocatalyst activation duration. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In each drawing, corresponding components having the same function are assigned the same reference numerals. For convenience, the embodiments may be shown separately in consideration of ease of explanation or understanding of the main points, but partial substitution or combination of configurations shown in different embodiments is possible. In the embodiments described below, descriptions of matters common to the above-mentioned embodiments will be omitted, and only differences will be described. In particular, similar effects due to similar configurations will not be mentioned sequentially in each embodiment. The size and positional relationship of components 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 surface, the side with the door is the front side, the opposite side is the rear side, and left and right are indicated when facing the door.

[0026] (Refrigerator according to an embodiment of the present invention) First, an overview of a refrigerator according to an embodiment of the present invention will be described with reference to Fig. 1 to Fig. 3. Fig. 1 is a perspective view schematically showing an example of the external shape of a refrigerator according to an embodiment of the present invention. Fig. 2 is a view showing section AA of Fig. 1, and is a side cross-sectional view schematically showing the internal structure of the refrigerator. Fig. 3 is a side view in a direction perpendicular to the surface of the cooling fin of the evaporator shown in Fig. 2.

[0027] A refrigerator 2 according to an embodiment of the present invention includes a freezer compartment 6A below a housing 4A and a refrigerator compartment 6B above the housing 4A. An openable lower door 8A is provided at the front opening of the freezer compartment 6A. An openable upper door 8B is provided at the front opening of the refrigerator compartment 6B.

[0028] A cooling flow path 4B separated by a partition plate is disposed at the rear of the interior of the refrigerator 2. An evaporator 20 and a cooling fan 40 that circulates the gas cooled by the evaporator 20 inside the interior of the refrigerator are disposed in the cooling flow path 4B. Furthermore, dampers 42A and 42B are disposed to switch between allowing or preventing the gas cooled by the evaporator 20 from flowing into the freezer compartment 6A and the refrigerator compartment 6B.

[0029] The compressor 10 and the condenser 12 that constitute the refrigeration circuit 50 are disposed in a machine room 4C located at the lower rear of the refrigerator 2. Furthermore, a fan for cooling the compressor 10, the condenser 12, etc. is also disposed in the machine room 4C. The condenser 12 and the evaporator 20 are connected by a capillary tube 14, and the evaporator 20 and the compressor 10 are connected by a suction pipe 16. As described above, the refrigeration circuit 50 of the refrigerator 2 according to this embodiment is mainly composed of the compressor 10, the condenser 12, the capillary tube 14, the evaporator 20, the suction pipe 16, and other pipes that connect these components.

[0030] As shown in FIG. 3 , the evaporator 20 is configured such that cooling tubes 24 are attached to left and right frames 22 so as to extend vertically and snake laterally. A plurality of thin cooling fins 26 are attached to the cooling tubes 24. The cooling tubes 24 and the cooling fins 26 are formed of a metal material with high thermal conductivity. A cooling circuit 50 causes a refrigerant to flow through the cooling tubes 24. The refrigerant flows from top to bottom while snaked laterally through the cooling tubes 24, makes a U-turn at the lowest position, and flows from bottom to top while snaked laterally through the cooling tubes 24 before flowing out of the evaporator 20. In FIG. 3 , the cooling tubes 24 through which the refrigerant flows from top to bottom and the cooling tubes 24 through which the refrigerant flows from bottom to top are shown overlapping.

[0031] When the gas inside the cabinet caused by the cooling fan 40 passes between the multiple cooling fins 26, it exchanges heat with the cooling fins 26 and the cooling tubes 24 and is cooled. A temperature sensor 62 that measures the temperature of the evaporator 20 is attached to an upper position of the cooling tubes 24. The temperature sensor 62 can be attached to the cooling tube 24 on the side where the refrigerant flows into the evaporator 20, or can be attached to the cooling tube 24 on the side where the refrigerant flows out of the evaporator 20. Because the cooling tubes 24 and cooling fins 26 have high thermal conductivity, it can be said that the measurement value of the temperature sensor 62 almost coincides with the temperature of the cooling tubes 24 and cooling fins 26.

[0032] <Cooling cycle> The cooling cycle in which refrigerant circulates through the cooling circuit 50 to cool the evaporator 20 is as follows: High-temperature, high-pressure gaseous refrigerant discharged from the compressor 10 flows through the condenser 12. The refrigerant's temperature drops due to heat dissipation in the condenser 12, becoming a liquid or a gas-liquid mixture. This liquid or gas-liquid mixture flows through the capillary tube 14 and is reduced in pressure, resulting in the low-temperature, low-pressure liquid refrigerant entering the evaporator 20. This refrigerant absorbs heat from the gas flowing around the cooling tubes 24 between the cooling fins 26 of the evaporator 20 and vaporizes. The cooled air, cooled as it flows between the cooling fins 26, flows into the freezer compartment 6A and the refrigerator compartment 6B, cooling the storage areas. The vaporized refrigerant in the evaporator 20 returns to the suction side of the compressor 10 through the suction pipe 16, and this cooling cycle is repeated.

[0033] <Heater> When the gas inside the refrigerator flows between the cooling fins 26 of the evaporator 20, the moisture contained in the gas freezes and turns into frost, which adheres to the surfaces of the cooling fins 26 and the cooling tubes 24. If a lot of frost accumulates on the evaporator 20 in this way, the gas cooling efficiency decreases, so the evaporator 20 needs to be defrosted periodically.

[0034] For this reason, in this embodiment, as shown in Figures 2 and 3, a heater 34 that melts frost adhering to the cooling fins 26 and the cooling tubes 24 is disposed below the evaporator 20. Furthermore, a liquid-receiving surface 44 that receives defrosted water (liquid) generated by melting frost adhering to the cooling fins 26 and the cooling tubes 24 of the evaporator 20 is disposed below the heater 34. A drain pipe 46 is attached to an opening provided in this liquid-receiving surface 44, and the lower end of the drain pipe 46 opens above an evaporation tray disposed in the machine chamber 4C. As a result, the defrosted water (liquid) that has been melted by the heater 34 and dropped from the cooling fins 26 and the cooling tubes 24 of the evaporator 20 flows into an evaporation tray 48 via the drain pipe 46. The defrosted water (liquid) that has flowed into the evaporation tray 48 evaporates into the atmosphere.

[0035] <Photocatalyst> To more effectively defrost the evaporator 20, in this embodiment, the surfaces of the cooling fins 26 and the cooling tubes 24 are coated with a photocatalyst that is activated by light with a wavelength in the ultraviolet or visible light range. In this embodiment, a photocatalyst that is activated by light with any wavelength in the ultraviolet or visible light range can be used. For example, titanium oxide is a photocatalyst that is activated by ultraviolet light. By doping this titanium oxide with nitrogen or by ion-implanting a different metal, a photocatalyst that is activated by visible light with a wavelength of 400-600 nm can be obtained.

[0036] In the illustrated example, the entire surfaces of the cooling fins 26 and the cooling tubes 24 are coated with the photocatalyst, but this is not limited to this. For example, only the cooling fins 26 may be coated, or partial areas of the cooling fins 26 and the cooling tubes 24 may be coated, or only partial areas of the cooling fins 26 may be coated. In this embodiment, at least a portion of the surface of the cooling fins 26 is coated with the photocatalyst to promote defrosting of the evaporator 20.

[0037] <Light source> In this embodiment, a light source 30 is provided that irradiates the photocatalyst coated on the cooling fins 26 and the cooling tubes 24 with light of a wavelength in the ultraviolet or visible light range. In the illustrated example, the light source 30 is provided above the evaporator 20. The light source 30 has a light-emitting section that extends in the width direction of the evaporator 20, and multiple LEDs are provided in the light-emitting section. Furthermore, a structure in which the LEDs are covered with a translucent resin member that contains fluorescent particles or scattering particles can also be employed. The emission wavelength of the LEDs or fluorescent particles can be appropriately selected to match the wavelength range in which the photocatalyst is activated.

[0038] Furthermore, a reflector 32 is disposed on the side of the evaporator 20 in a direction perpendicular to the surface of the cooling fins 26 (see FIG. 2). The reflector 32 can be formed from a metal plate such as aluminum. In FIG. 2, the reflector 32 is disposed on both the front and rear sides of the evaporator 20. In FIG. 2, the light from the light source 30 reflected by the reflector 32 is schematically indicated by dotted arrows.

[0039] However, this is not a limitation, and the reflector 32 may be disposed either on the front side or the rear side of the evaporator 20. In the illustrated example, the reflector 32 is disposed over the entire top and bottom areas of the evaporator 20, but this is not a limitation. For example, the reflector 32 may be disposed only in the upper area of the evaporator 20.

[0040] By turning on the light source 30, light is irradiated onto the photocatalyst coated on the surfaces of the cooling fins 26 and cooling tubes 24, activating the photocatalyst. When irradiated with light of a predetermined wavelength, the photocatalyst is quickly activated and becomes superhydrophilic. After the start of light irradiation, a relatively short time, about 5 to 15 minutes, has elapsed, and the activation of the photocatalyst is completed. This time is called the "activation completion time." Irradiating light for a period longer than the "activation completion time" does not further advance the activation of the photocatalyst.

[0041] On the other hand, the time during which the superhydrophilicity of the photocatalyst is maintained is referred to as the "activation duration" of the photocatalyst. The "activation duration" is relatively long, ranging from several hours to several days, depending on the components of the photocatalyst. However, since this activation duration varies with temperature, it is preferable to determine the "activation duration" based on the temperature of the evaporator 20 measured by the temperature sensor 62, as described below.

[0042] In this way, when the surfaces of the cooling fins 26 and cooling tubes 24 of the evaporator 20, or at least a part of the cooling fins 26, are coated with a photocatalyst and activated by irradiation with light, the surface becomes superhydrophilic, making it difficult for frost to adhere, and when the temperature of the evaporator 20 is higher than 0°C and in a defrostable state, the frost melts easily, enabling effective defrosting of the evaporator 20.

[0043] <Control unit> Next, an example of a control unit according to an embodiment of the present invention will be described with reference to FIG. 5. FIG. 5 is a block diagram showing an example of a control unit according to an embodiment of the present invention. As shown in FIG. 5, the control unit 60 is electrically connected to the compressor 10, the light source 30, the heater 34, the cooling fan 40, and the dampers 42A and 42B for the freezer and refrigerator, and can control these devices. The control unit 60 is also electrically connected to a temperature sensor 62 that measures the temperature of the evaporator 20, and receives measurement data from the temperature sensor 62. In the drawing, the direction in which a signal travels is schematically indicated by an arrow.

[0044] (control processing) Next, the control process by the control unit 60, particularly the control process related to defrosting of frost that has adhered to the evaporator 20, will be described in detail below. <Defrosting operation> First, the control process when performing the defrosting operation will be described with reference to Fig. 5. Fig. 5 is a flowchart showing an example of the control process when performing the defrosting operation with the heater turned on.

[0045] In order to remove frost adhering to the evaporator 20, a defrosting operation is performed at regular intervals. For example, a defrosting operation may be performed once every 24 hours for about 30 minutes. In the flowchart shown in FIG. 5, first, it is determined whether or not a dehumidifying operation is to be performed (step S2). If it is determined in this determination that a dehumidifying operation is not to be performed (NO), the refrigerator enters a standby state. If it is determined in step S2 that a dehumidifying operation is to be performed (YES), it is then determined whether or not this is the first defrosting operation since the refrigerator 2 was powered on (step S4). If it is determined in this determination that this is the first defrosting operation since the refrigerator 2 was powered on (YES), the heater 34 is turned on to start the defrosting operation (step S6), and the light source 30 is turned on (step S8) to start the light irradiation process, and the process proceeds to step S18.

[0046] The initial defrosting operation after power-on corresponds to the first defrosting operation of the refrigerator 2 or the start of defrosting operation after a long period of shutdown. In such cases, there is uncertainty about the activation state of the photocatalyst immediately after light irradiation, so it is preferable to turn on the light source at the start of the defrosting operation to be on the safe side.

[0047] In this embodiment, when the first defrosting operation (YES in step S4) is started (step S6) after power-on, the control unit 60 starts the light irradiation process (step S8). This ensures that the photocatalyst becomes superhydrophilic when the temperature of the evaporator 20 reaches a defrostable state above 0°C due to heating by the heater 34.

[0048] If it is determined in step S4 that this is not the first defrosting operation since power-on (NO), the heater 34 is then turned on to start the defrosting operation (step S10). Then, based on the measurement value of the temperature sensor 62, it is determined whether the temperature of the evaporator 20 is 0°C or higher (step S12). If it is determined in this determination that the temperature of the evaporator 20 is below 0°C (NO), the system enters a standby state. If it is determined in step S12 that the temperature of the evaporator 20 is 0°C or higher (YES), it is next determined whether the activation duration of the photocatalyst coated on the evaporator 20 has elapsed since the previous light irradiation process ended (step S14).

[0049] <Temperature activation duration> As described above, the activation duration of the photocatalyst varies depending on the temperature. Here, a control process for determining the activation duration based on the temperature will be described with reference to Fig. 7. Fig. 7 is a flowchart showing an example of the control process for setting the activation duration of the photocatalyst.

[0050] In the flowchart shown in Fig. 7, first, the average value of the measurements of the temperature sensor 62 after the light source 30 was turned on to irradiate the photocatalyst with light and then turned off to end the light irradiation is calculated (step S40). That is, the average value of the temperature of the evaporator 20 after the light irradiation is ended is calculated. Next, a correspondence table between temperature and activation duration is read out, and the activation duration corresponding to the calculated average temperature is selected (step S42). The selected activation duration is used to perform the judgment process of step S14 in Fig. 5.

[0051] The method for determining the activation duration corresponding to the temperature is not limited to the above. For example, a function that calculates the activation duration using the temperature as a variable can be used. Also, if the average temperature of the evaporator 20 in the determination process of step S14 does not change significantly each time, a certain constant activation duration can be used.

[0052] As described above, the activation duration of the photocatalyst varies depending on the temperature, but as described above, the activation duration is determined based on the measurement value of the temperature sensor 62, so it is possible to more accurately determine whether the activation of the photocatalyst is being maintained.

[0053] 5, if it is determined in step S14 that the activation duration has not elapsed (NO), that is, if it is determined that the superhydrophilicity of the photocatalyst coated on the evaporator 20 is maintained, the light source 30 is not turned on and the process proceeds to step S22. If it is determined in step S14 that the activation duration has elapsed (YES), the light source 30 is turned on (step S16).

[0054] After turning on the light source 30 in step S8 or step S16, it is next determined whether the activation completion time has elapsed (step S18). If it is determined that the activation completion time has not yet elapsed (NO), the system enters a standby state and light irradiation by the light source 30 continues. If it is determined in step S18 that the activation completion time has elapsed (YES), the light source 30 is turned off (step S20).

[0055] Next, it is determined whether the defrost termination condition is satisfied (step S22). If it is determined that the defrost termination condition is not satisfied (NO), the system enters a standby state and heating by the heater 34 continues. If it is determined in step S22 that the defrost termination condition is satisfied (YES), the heater 34 is turned off (step S24), and this subroutine is terminated. Note that the photocatalyst is activated in a relatively short time after being irradiated with light, so activation is completed before the heater 34 is turned off.

[0056] As described above, the refrigerator 2 according to this embodiment includes the temperature sensor 62 that measures the temperature of the evaporator 20, and in the second or subsequent defrosting operation after power-on, after the previous light irradiation process is completed, the activation duration of the photocatalyst has elapsed (YES in step S14), the control unit 60 turns on the heater to start the defrosting operation (step S10), and when the measurement value of the temperature sensor 62 becomes higher than 0°C (YES in step S12), the control unit 60 starts the light irradiation process (step S16).

[0057] Because the cooling fins 26 and the cooling tubes 24 are made of metal with high thermal conductivity, even if the temperature sensor 62 measures the region above the cooling tubes 24, the temperature will be approximately the same as the temperature of the cooling fins 26 on which frost has adhered, i.e., the temperature of the adhered frost. When the compressor 10 is turned off and the heater 34 is turned on to start defrosting operation, and the frost on the cooling fins 26 leaves the latent heat region and becomes higher than 0°C, i.e., when the measurement value of the temperature sensor 62 becomes higher than 0°C, the frost on the cooling fins 26 begins to melt. At this time, if the photocatalyst coated on the surface of the cooling fins 26 is superhydrophilic, defrosting is promoted.

[0058] If the photocatalyst activation duration has elapsed, the photocatalyst should be irradiated with light to make it superhydrophilic. However, since the photocatalyst quickly becomes superhydrophilic after being irradiated with light, there is no need to turn on the light source 30 when starting the defrosting operation for the second or subsequent defrosting operations after power-on. By turning on the heater 30 to heat the evaporator and starting light irradiation when the evaporator temperature rises above 0°C, the photocatalyst can be quickly activated and made superhydrophilic.

[0059] In this way, in this embodiment, the light source 30 is turned on to activate the photocatalyst when the frost has left the latent heat region, rather than when the heater 34 is turned on and defrosting operation begins, so that defrosting can be performed effectively while reducing the power consumption of the light source 30.

[0060] <Evaporator is ready for defrosting> Next, the control process when the evaporator is in a state where defrosting is possible will be described with reference to Fig. 6. Fig. 6 is a flowchart showing an example of the control process when it is determined that the evaporator is in a state where defrosting is possible based on the temperature of the evaporator. This flowchart shows a control process that is not limited to defrosting operation, but makes the photocatalyst coated on the evaporator 20 superhydrophilic when the frost on the evaporator is in a state where it can be melted.

[0061] In the flowchart shown in Fig. 6, first, it is determined whether the temperature of the evaporator 20 is equal to or higher than 0°C based on the measurement value of the temperature sensor 62 (step S30). If it is determined in this determination that the temperature of the evaporator 20 is lower than 0°C (NO), the system enters a standby state. If it is determined in step S30 that the temperature of the evaporator 20 is equal to or higher than 0°C (YES), it is next determined whether the activation duration of the photocatalyst coated on the evaporator 20 has elapsed (step S32). In this determination, as described above, the activation duration determined corresponding to the temperature of the evaporator 20 determined in the control process shown in Fig. 6 is used.

[0062] If it is determined in step S32 that the activation duration has not elapsed (NO), that is, if the superhydrophilicity of the photocatalyst coated on the evaporator 20 is maintained, the light source 30 is not turned on and this subrun is terminated. If it is determined in step S32 that the activation duration has elapsed (YES), the light source 30 is turned on (step S34).

[0063] Next, it is determined whether the activation completion time has elapsed (step S34). If it is determined that the activation completion time has not yet elapsed (NO), the system enters a standby state and continues irradiating light from light source 30. If it is determined in step S34 that the activation completion time has elapsed (YES), light source 30 is turned off (step S38), and this subroutine is terminated.

[0064] As described above, the refrigerator 2 according to this embodiment is provided with the temperature sensor 62 that measures the temperature of the evaporator 20, and after the previous light irradiation process is completed, when the activation duration of the photocatalyst has elapsed (YES in step S32) and the measurement value of the temperature sensor 62 becomes higher than 0°C (YES in step S30), the control unit 60 starts the light irradiation process.

[0065] The control processing by this subroutine may be applied when a special operation such as humidification operation is being performed while the compressor 10 is not running, or when the activation duration time has not elapsed when the defrosting operation is started but has elapsed while the defrosting operation is continuing.

[0066] When the measurement value of the temperature sensor 62 that measures the temperature of the evaporator 20 becomes higher than 0°C, if the surfaces of the cooling fins 26 are superhydrophilic, defrosting of the cooling fins 26 is promoted. Even if the activation duration of the photocatalyst has elapsed, when light is irradiated from the light source 30, the photocatalyst is immediately activated and becomes superhydrophilic, so defrosting of the cooling fins 26 is immediately promoted. This allows effective defrosting to be performed while reducing the power consumption of the light source 30.

[0067] As described above, the refrigerator 2 according to the above embodiment includes the evaporator 20 having the cooling tubes 24 through which a refrigerant flows and the cooling fins 26 attached to the cooling tubes 24, the heater 34 disposed below the evaporator 20 and configured to melt frost adhering to the cooling fins 26 and the cooling tubes 24, the light source 30 configured to irradiate the cooling fins 26 and the cooling tubes 24 with light having a wavelength in the ultraviolet or visible light range, and the control unit 60 configured to control the light source 30, wherein at least a portion of the surface of the cooling fins 26 is coated with a photocatalyst that is activated by the light emitted from the light source 30, and the control unit 60 performs a light irradiation process in which the light source 30 is turned on when a defrosting operation is performed for the first time after the power is turned on, or when the evaporator 20 is in a state where defrosting is possible and activation of the photocatalyst has not been sustained, and the light source 30 is turned off when the activation completion time of the photocatalyst has elapsed.

[0068] When the defrosting operation is performed for the first time after power-on, the photocatalyst is not activated, so it is preferable to turn on the light source when the defrosting operation starts. Furthermore, for example, when the temperature of the evaporator 20 is higher than 0°C and defrosting is possible, if the photocatalyst has superhydrophilic properties, it will easily melt the frost, and defrosting of the evaporator 20 will be performed effectively. In the above embodiment, the light source 30 is turned on to activate the photocatalyst only when the photocatalyst is not activated. When the photocatalyst remains activated, the light source 30 is not turned on, allowing for efficient use of the light source.

[0069] Furthermore, once the activation completion time has elapsed after the start of irradiating the photocatalyst with light, further irradiation with light will not further activate the photocatalyst. In the above embodiment, the light source 30 is turned on and then turned off when the activation completion time has elapsed. This reduces the power consumption of the light source 30 while reliably making the photocatalyst superhydrophilic, thereby achieving effective defrosting. Therefore, the evaporator 20 can be defrosted efficiently with little energy consumption.

[0070] (Structural features) In the refrigerator according to this embodiment, the heater 34 is disposed below the evaporator, and the light source 30 is disposed above the evaporator 20, as shown in FIGS.

[0071] When defrosting is performed by heating with the heater 34 arranged below the evaporator 20, defrosting proceeds more efficiently on the lower side of the evaporator 20 than on the upper side. Therefore, defrosting can be promoted by irradiating the photocatalyst-coated surface on the upper side of the evaporator 20, where defrosting is slower, with stronger light. In addition, since there is no heater 34 or heater cover on the upper side, it becomes easier to irradiate the light from the light source 30 onto the catalyst-coated surface.

[0072] Furthermore, in this embodiment, as shown in Figure 2, a reflector 32 is arranged on the side of the evaporator 20 in a direction perpendicular to the surface of the cooling fin 26, so that light from the light source 30 can be more effectively directed onto the photocatalyst coated on the cooling fin 26.

[0073] Furthermore, as described above, it is not necessary to coat the entire cooling fins 26 and cooling tubes 24 of the evaporator 20 with photocatalyst. For example, the photocatalyst may be coated from the top of the evaporator 20 to a predetermined area. During defrosting operation, defrosting is performed by heating with the heater 34 arranged below the evaporator 20, so defrosting proceeds more efficiently on the lower side of the evaporator 20 than on the upper side. Therefore, sufficient defrosting can be expected even if the lower side of the evaporator 20 is not coated with photocatalyst. This reduces the amount of photocatalyst to be coated, contributing to a reduction in the manufacturing cost of the evaporator 20.

[0074] 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]

[0075] 2. Refrigerator 4A housing 4B Cooling channel 4C Machine room 6A Freezer 6B Refrigerator Doors 8A and 8B 10 Compressor 12 Condenser 14 Capillary tube 16 Suction pipe 20 Evaporator 22 frames 24 cooling tubes 26 Cooling fins 30 light source 32 Reflector 34 Heater 40 Cooling fan 42A, 42B damper 44 Liquid receiving surface 46 Drain pipe 48 Evaporating dish 50 Cooling circuit 60 Control Unit 62 Temperature Sensor

Claims

1. an evaporator having cooling tubes through which a refrigerant flows and cooling fins attached to the cooling tubes; a heater disposed below the evaporator and configured to melt frost adhering to the cooling fins and the cooling tubes; a light source that irradiates the cooling fins and the cooling tubes with light having a wavelength in the ultraviolet region or the visible region; a control unit that controls the light source; Equipped with At least a part of the surface of the cooling fin is coated with a photocatalyst that is activated by light emitted from the light source, The control unit When defrosting is performed for the first time after power is turned on, or When the evaporator is in a state where defrosting is possible and activation of the photocatalyst is not sustained, Turn on the light source, When the activation completion time of the photocatalyst has elapsed, the light source is turned off. A refrigerator characterized by performing light irradiation treatment.

2. The refrigerator according to claim 1, wherein the control unit starts the light irradiation process when a first defrosting operation is started after power-on.

3. a temperature sensor for measuring the temperature of the evaporator; 2. The refrigerator according to claim 1, wherein, in a second or subsequent defrosting operation after power-on, after the previous light irradiation process is completed, an activation duration time of the photocatalyst has elapsed, the control unit turns on the heater to start the defrosting operation, and when the measured value of the temperature sensor becomes higher than 0°C, the control unit starts the light irradiation process.

4. a temperature sensor for measuring the temperature of the evaporator; 2. The refrigerator according to claim 1, wherein the control unit starts the light irradiation process when the activation duration of the photocatalyst has elapsed after the previous light irradiation process has ended and the measured value of the temperature sensor has become higher than 0°C.

5. 5. The refrigerator according to claim 3, wherein the activation duration is determined based on the measurement value of the temperature sensor.

6. 5. The refrigerator according to claim 1, wherein the light source is disposed above the evaporator.

7. 7. The refrigerator according to claim 6, wherein a reflector is disposed on a side surface of the evaporator in a direction perpendicular to the surface of the cooling fins.

8. 5. The refrigerator according to claim 1, wherein the photocatalyst is coated on the evaporator up to a predetermined area.

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