AU2018409749A1

AU2018409749A1 - Refrigerator

Info

Publication number: AU2018409749A1
Application number: AU2018409749A
Authority: AU
Inventors: Sangbok Choi; Sung Jhee; Sungwook Kim; Kyongbae Park
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2018-02-23
Filing date: 2018-10-25
Publication date: 2020-09-10
Anticipated expiration: 2038-10-25
Also published as: EP3757487A4; US20200370815A1; EP3757487A1; AU2018409749B2; CN111771092A; CN111771092B; CN114674108A; CN114674108B; KR20190101669A; KR102627972B1; WO2019164084A1

Abstract

A refrigerator of the present invention comprises: an inner case for forming a storage chamber; a cold-air duct for guiding air flowing in the storage chamber and forming a heat exchange space, together with the inner case; an evaporator positioned in the heat exchange space between the inner case and the cold-air duct; a bypass flow channel disposed in a shape recessed from the cold-air duct and allowing air to flow while bypassing the evaporator; a sensor disposed in the bypass flow channel and having an output value which changes according to the flow rate of the air flowing through the bypass flow channel; a defrosting means for removing frost generated on a surface of the evaporator; and a control unit for controlling the defrosting means on the basis of the value output by the sensor.

Description

DESCRIPTION REFRIGERATOR

TECHNICAL FIELD This specification relates to a refrigerator.

BACKGROUNDART Refrigerators are household appliances that are capable of store objects such as foods at a low temperature in a storage space provided in a cabinet. Since the storage space is surrounded by heat insulation wall, the inside of the storage space may be maintained at a temperature less than an external temperature. The storage space may be classified into a refrigerating storage space or a freezing storage space according to a temperature range of the storage space. The refrigerator may further include an evaporator for supplying cool air to the storage space. Air in the storage space is cooled while flowing to a space, in which the evaporator is disposed, so as to be heat-exchanged with the evaporator, and the cooled air is supplied again to the storage space. Here, if the air heat-exchanged with the evaporator is contained in moisture, when the air is heat-exchanged with the evaporator, the moisture is frozen on a surface of the evaporator to generate frost on the surface of the evaporator. Since flow resistance of the air acts on the frost, the more an amount of frost frozen on the surface of the evaporator increases, the more the flow resistance increases. As a result, heat-exchange efficiency of the evaporator may be deteriorated, and thus, power consumption may increase. Thus, the refrigerator further include a defroster for removing the frost on the evaporator. A defrosting cycle variable method is disclosed in Korean Patent Publication No. 2000-0004806 that is a prior art document.

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In the prior art document, the defrosting cycle is adjusted using a cumulative operation time of the compressor and an external temperature. However, like the prior art document, when defrosting cycle is determined only using the cumulative operation time of the compressor and the external temperature, an amount of frost (hereinafter, referred to as a frost generation amount) on the evaporator is not reflected. Thus, it is difficult accurately determine the time point at which the defrosting is required. That is, the frost generation amount may increase or decrease according to various environments such as the user's refrigerator usage pattern and the degree to which air retains moisture. In the case of the prior art document, there is a disadvantage in that the defrosting cycle is determined without reflecting the various environments. Accordingly, there is a disadvantage in that the defrosting does not start despite a large amount of generated frost to deteriorate cooling performance, or the defrosting starts despite a low frost generation amount to increase in power consumption due to the unnecessary defrosting.

DISCLOSURE OF THE INVENTION TECHNICAL PROBLEM The present invention provides a refrigerator that is capable of determining whether a defrosting operation is performed by using a parameter that varies depending on an amount of frost generated on an evaporator. In addition, the present invention provides a refrigerator that is capable of accurately determining a time point at which defrosting is required according to an amount of frost generated on an evaporator by using a bypass passage for sensing the generated frost. In addition, the present invention provides a refrigerator that is capable of minimizing a length of a passage for sensing generated frost. In addition, the present invention provides a refrigerator that is capable of accurately determining a time point at which defrosting is required even though

89335628.1 accuracy of a sensor used for determining the time point at which the defrosting is required. In addition, the present invention provides a refrigerator that is capable of preventing frost from being generated around a sensor for sensing generated frost. In addition, the present invention provides a refrigerator that is capable of preventing a liquid from being introduced into a bypass passage for sensing generated frost.

TECHNICAL SOLUTION A refrigerator for achieving the above objects includes a cool air duct inside an inner case configured to define a storage space, and the cool air duct defines a heat-exchange space together with the inner case. An evaporator is disposed in the heat exchange space, a bypass passage is disposed to be recessed in the cool air duct, and a sensor is disposed in a bypass passage. In the present invention, the sensor may be a sensor having an output value varying according to a flow rate of the air flowing through the bypass passage, and a time point at which defrosting for the evaporator is required may be determined by using the output value of the sensor. The refrigerator according to this embodiment includes a defroster configured to remove frost generated on a surface of the evaporator and a controller configured to control the defroster based on the output value of the sensor. When it is determined that the defrosting is required, the controller may operate the defroster. In this embodiment, the sensor may include: a heat generating element; a sensing element configured to sense a temperature of the heat generating element; and a sensor PCB on which the heat generating element and the sensing element are installed. The sensor may further include a sensor housing configured to surround the heat generating element, the sensing element, and the sensor PCB.

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In this embodiment, when a difference value between a temperature sensed by the sensing element in a state in which the heat generating element is turned on and a temperature sensed by the sensing element in a state in which the heat generating element is turned off is equal to or less than a reference temperature value, it may be determined that the defrosting is required. In this embodiment, the refrigerator may further include a passage cover configured to cover the bypass passage so as to partition the bypass passage from the heat exchange space. In this embodiment, the cool air duct may further include a vertical extension surface that is a surface in which the bypass passage is defined, and the passage cover may include: a cover plate configured to cover the bypass passage; and a barrier extending from the cover plate, the barrier protruding downward from the vertical extension surface in a state in which the cover plate covers the bypass passage, and thus, a flow rate of the air flowing through the bypass passage before the frost is generated may be reduced. In this embodiment, the bypass passage may extend vertically from the vertical extension surface in a straight-line shape so that the bypass passage is minimized in length. The barrier protruding to the outside of the bypass passage may further include: a rear barrier continuously extending from the cover plate, the rear barrier being disposed adjacent to the evaporator; a plurality of side barriers extending from the rear barrier, the plurality of side barriers being spaced apart from each other in a left and right direction; and a front barrier connected to the plurality of side barriers, spaced apart from the rear barrier, and disposed at an opposite side of the evaporator with respect to the rear barrier. In this embodiment, the cool air duct may further include an inclined surface extending to be inclined from an end of the vertical extension surface and configured to guide the air toward the evaporator. In this embodiment, the cool air duct may further include a slot configured to define a passage for allowing the air flowing along the inclined surface to flow

89335628.1 toward the evaporator is provided in the rear barrier. The slot may provide an air path and be defined in the rear barrier. In this embodiment, the sensor may be disposed to be spaced apart from a bottom surface of the bypass passage and the passage cover to prevent the frost from being generated around the sensor within the bypass passage. The sensor may be disposed to be spaced apart from the inlet and the outlet of the bypass passage so as to improve sensing accuracy of the sensor and may be disposed at a point at which a distance between the bottom wall and the cover plate is bisected in the bypass passage. In this embodiment, the bypass pass may be disposed so as not to vertically overlap the cool air inflow hole, thereby preventing the air discharged from the outlet of the bypass passage from being affected by the flow rate of the air introduced into the cool air inflow hole. In addition, the outlet of the bypass passage may be disposed outside the limit region having a diameter greater than that of the blower fan with respect to a center of the blower fan provided in the cool air duct. In this embodiment, a blocking rib may be provided above the bypass passage in the cool air duct to prevent a liquid from being introduced into the bypass passage. For example, the blocking rib may have a left-right minimum length greater than a left-right minimum width of the bypass passage, and the entire bypass passage in the left and right direction may be disposed to overlap the blocking rib in the vertical direction.

ADVANTAGEOUS EFFECTS According to the proposed invention, since the time point at which the defrosting is required is determined using the sensor having the output value varying according to the amount of frost generated on the evaporator in the bypass passage, the time point at which the defrosting is required may be accurately determined.

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In addition, in the present invention, since the bypass passage vertically extend in the straight-line shape from the cool air duct, the length of the bypass passage may be minimized. In addition, in the present invention, since the sensor according to the embodiment is disposed at the point, at which the change in flow rate is less, in the bypass passage and disposed in the central region of the passage in the fully development flow region. In addition, in the present invention, in the embodiments the sensor may be disposed to be spaced apart from the bottom surface of the bypass passage and the passage cover to prevent the frost from being generated around the sensor. In addition, in the case of the present invention, in the embodiments, since the passage cover includes the barrier protruding to the outside of the bypass passage, the flow rate in the bypass passage before the generation of the frost, the flow rate of the bypass passage may be minimized to improve the accuracy in determining of the time point, at which the defrosting is required, through the sensor. In addition, according to the present invention, the blocking rib may be provided above the bypass passage to prevent the liquid from being introduced into the bypass passage.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic longitudinal cross-sectional view of a refrigerator according to an embodiment of the present invention. Fig. 2 is a perspective view of a cool air duct according to an embodiment of the present invention. Fig. 3 is an exploded perspective view illustrating a state in which a passage cover and a sensor are separated from each other in the cool air duct. Fig. 4 is a view illustrating a flow of air in a heat exchange space and a bypass passage before and after frost is generated.

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Fig. 5 is a schematic view illustrating a state in which a sensor is disposed in the bypass passage. Fig. 6 is a view of the sensor according to an embodiment of the present invention. Fig. 7 is a view illustrating a thermal flow around the sensor depending on a flow of air flowing through the bypass passage. Fig. 8 is a view illustrating a position of the sensor in the bypass passage. Fig. 9 is a view illustrating an air flow pattern in the bypass passage. Fig. 10 is a view illustrating a flow of air in the state in which the sensor is installed in the bypass passage. Fig. 11 is a view illustrating an arrangement of the bypass passage and the passage cover in the cool air duct according to an embodiment of the present invention. Fig. 12 is an enlarged view illustrating the bypass passage and a rib for preventing defrosting water from being introduced according to an embodiment of the present invention. Fig. 13 is a view illustrating a barrier of the passage cover according to an embodiment of the present invention. Fig. 14 is a view illustrating a variation in temperature sensed by the sensor depending on a protruding length of the barrier. Fig. 15 is a cross-sectional view of the barrier, taken along line A-A of Fig. 13. Fig. 16 is a view illustrating a change in flow of air depending on whether a slot is provided in the barrier. Fig. 17 is a view illustrating a variation in temperature sensed by the sensor depending on a length of the slot defined in the barrier. Fig. 18 is a view illustrating a flow of air introduced into a heat exchange space according to an embodiment of the present invention. Fig. 19 is a control block diagram of the refrigerator according to an embodiment of the present invention.

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MODE FOR CARRYING OUT THE INVENTION Hereinafter, some embodiments of the present invention will be described in detail with reference to the accompanying drawings. Exemplary embodiments of the present invention will be described below in more detail with reference to the accompanying drawings. It is noted that the same or similar components in the drawings are designated by the same reference numerals as far as possible even if they are shown in different drawings. Further, in description of embodiments of the present disclosure, when it is determined that detailed descriptions of well known configurations or functions disturb understanding of the embodiments of the present disclosure, the detailed descriptions will be omitted. Also, in the description of the embodiments of the present disclosure, the terms such as first, second, A, B, (a) and (b) may be used. Each of the terms is merely used to distinguish the corresponding component from other components, and does not delimit an essence, an order or a sequence of the corresponding component. It should be understood that when one component is "connected", "coupled" or "joined" to another component, the former may be directly connected or jointed to the latter or may be "connected", coupled" or "joined" to the latter with a third component interposed therebetween. Fig. 1 is a schematic longitudinal cross-sectional view of a refrigerator according to an embodiment of the present invention, Fig. 2 is a perspective view of a cool air duct according to an embodiment of the present invention, and Fig. 3 is an exploded perspective view illustrating a state in which a passage cover and a sensor are separated from each other in the cool air duct. Referring to Figs. 1 to 3, a refrigerator 1 according to an embodiment of the present invention may include an inner case 12 defining a storage space 11. The storage space may include one or more of a refrigerating storage space and a freezing storage space. A cool air duct 20 providing a passage, through which cool air supplied to the storage space 11 flows, in a rear space of the storage space 11. Also, an

89335628.1 evaporator 30 is disposed between the cool air duct 20 and a rear wall 13 of the inner case 12. That is, a heat exchange space 222 in which the evaporator 30 is disposed is defined between the cool air duct 20 and the rear wall 13. Thus, air of the storage space 11 may flow to the heat exchange space 222 between the cool air duct 20 and the rear wall 13 of the inner case 12 and then be heat-exchanged with the evaporator 30. Thereafter, the air may flow through the inside of the cool air duct 20 and then be supplied to the storage space 11. The cool air duct 20 may include, but is not limited thereto, a first duct 210 and a second duct 220 coupled to a rear surface of the first duct 210. A front surface of the first duct 210 is a surface facing the storage space 11, and a rear surface of the first duct 220 is a surface facing the rear wall 13 of the inner case 12. A cool air passage 212 may be provided between the first duct 210 and the second duct 220 in a state in which the first duct 210 and the second duct 220 are coupled to each other. Also, a cool air inflow hole 221 may be defined in the second duct 220, and a cool air discharge hole 211 may be defined in the first duct 210. A blower fan (not shown) may be provided in the cool air passage 212. Thus, when the blower fan rotates, air passing through the evaporator 13 is introduced into the cool air passage 212 through the cool air inflow hole 221 and is discharged to the storage space 11 through the discharge hole 211. The evaporator 30 is disposed between the cool air duct 20 and the rear wall 13. Here, the evaporator 30 may be disposed below the cool air inflow hole 221. Thus, the air in the storage space 11 ascends to be heat-exchanged with the evaporator 30 and then is introduced into the cool air inflow hole 221. According to this arrangement, when an amount of frost generated on the evaporator 30 increases, an amount of air passing through the evaporator 30 may be reduced. In this embodiment, a time point at which defrosting for the evaporator 30

89335628.1 is required may be determined using a parameter that is changed according to the amount of frost generated on the evaporator 30. For example, the cool air duct 20 may further include a frost generation sensing portion configured so that at least a portion of the air flowing through the heat exchange space 222 is bypassed and configured to determine a time point, at which the defrosting is required, by using the sensor having a different output according to a flow rate of the air. The frost generation sensing portion may include a bypass passage 230 bypassing at least a portion of the air flowing through the heat exchange space 222 and a sensor 270 disposed in the bypass passage 230. Although not limited, the bypass passage 230 may be provided in a recessed shape in the first duct 210. Alternatively, the bypass passage 230 may be provided in the second duct 220. The bypass passage 230 may be provided by recessing a portion of the first duct 210 or the second duct 220 in a direction away from the evaporator 30. The bypass passage 230 may extend from the cool air duct 20 in a vertical direction. The bypass passage 230 may be disposed to face the evaporator 30 within a left and right width range of the evaporator 30 so that the air in the heat exchange space 222 is bypassed to the bypass passage 230. The frost generation sensing portion may further include a passage cover 260 that allows the bypass passage 230 to be partitioned from the heat exchange space 222. The passage cover 260 may be coupled to the cool air duct 20 to cover at least a portion of the bypass passage 230 extending vertically. The passage cover 260 may include a cover plate 261, an upper extension portion 262 extending upward from the cover plate 261, and a barrier 263 provided below the cover plate 261. A specific shape of the passage cover 260 will be described later with reference to the drawings. Fig. 4 is a view illustrating a flow of air in the heat exchange space and the

89335628.1 bypass passage before and after frost is generated. (a) of Fig. 4 illustrates a flow of air before frost is generated, and (b) of Fig. 4 illustrates a flow of air after frost is generated. In this embodiment, as an example, it is assumed that a state after a defrosting operation is complicated is a state before frost is generated. First, referring to (a) of Fig. 4, in the case in which frost does not exist on the evaporator 30, or an amount of generated frost is remarkably small, most of the air passes through the evaporator 30 in the heat exchange space 222 (see arrow A). On the other hand, some of the air may flow through the bypass passage 230 (see arrow B). Referring to (b) of Fig. 4, when the amount of frost generated on the evaporator 30 is large (when the defrosting is required), since the frost of the evaporator 30 acts as flow resistance, an amount of air flowing through the heat exchange space 222 may decrease (see arrow C), and an amount of air flowing through the bypass passage 230 may increase (see arrow D). As described above, the amount (or flow rate) of air flowing through the bypass passage 230 varies according to an amount of frost generated on the evaporator 30. In this embodiment, the sensor 270 may have an output value that varies according to a change in flow rate of the air flowing through the bypass passage 230. Thus, whether the defrosting is required may be determined based on the change in output value. Hereinafter, a structure and principle of the sensor 270 will be described. Fig. 5 is a schematic view illustrating a state in which the sensor is disposed in the bypass passage, Fig. 6 is a view of the sensor according to an embodiment of the present invention, and Fig. 7 is a view illustrating a thermal flow around the sensor depending on a flow of air flowing through the bypass passage. Referring to Figs. 5 to 7, the sensor 270 may be disposed at one point in the bypass passage 230. Thus, the sensor 270 may contact the air flowing along the bypass passage 230, and an output value of the sensor 270 may be changed

89335628.1 in response to a change in a flow rate of air. The sensor 270 may be disposed at a position spaced from each of an inlet 231 and an outlet 232 of the bypass passage 230. A specific location of the sensor 270 in the bypass passage 230 will be described later with reference to the drawings. Since the sensor 270 is disposed on the bypass passage 230, the sensor 270 may face the evaporator 30 within the left and right width range of the evaporator 30. The sensor 270 may be, for example, a generated heat temperature sensor. Particularly, the sensor 270 may include a sensor PCB 272, a heat generating element 273 installed on the sensor PCB 272, and a sensing element 274 installed on the sensor PCB 272 to sense a temperature of the heat generating element 273. The heat generating element 273 may be a resistor that generates heat when current is applied. The sensing element 274 may sense a temperature of the heat generating element 273. When a flow rate of air flowing through the bypass passage 230 is low, since a cooled amount of the heat generating element 273 by the air is small, a temperature sensed by the sensing element 274 is high. On the other hand, if a flow rate of the air flowing through the bypass passage 230 is large, since the cooled amount of the heat generating element 273 by the air flowing through the bypass passage 230 increases, a temperature sensed by the sensing element 274 decreases. The sensor PCB 272 may determine a difference between a temperature sensed by the sensing element 274 in a state in which the heat generating element 273 is turned off and a temperature by the sensing element 274 in a state in which the heat generating element 273 is turned on. The sensor PCB 271 may determine whether the difference value between the states in which the heat generating element 273 is turned on/off is less than a

89335628.1 reference difference value. For example, referring to Figs. 4 and 7, when an amount of frost generated on the evaporator 30 is small, a flow rate of air flowing to the bypass passage 230 is small. In this case, a heat flow of the heat generating element 273 is little, and a cooled amount of the heat generating element 273 by the air is small. On the other hand, when the amount of frost generated on the evaporator 30 is large, a flow rate of air flowing to the bypass passage 230 is large. Then, the heat flow and cooled amount of the heat generating element 273 are large by the air flowing along the bypass passage 230. Thus, the temperature sensed by the sensing element 274 when the amount of frost generated on the evaporator 30 is large is less than that sensed by the sensing element 274 when the amount of frost generated on the evaporator 30 is small. Thus, in this embodiment, when the difference between the temperature sensed by the sensing element 274 in the state in which the heat generating element 273 is turned on and the temperature by the sensing element 274 in the state in which the heat generating element 273 is turned off is less than the reference temperature difference, it may be determined that the defrosting is required. According to this embodiment, the sensor 270 may sense a variation in temperature of the heat generating element 273, which varies by the air of which a flow rate varies according to the amount of generated frost to accurately determine a time point, at which the defrosting is required, according to the amount of frost generated on the evaporator 30. The sensor 270 may further include a sensor housing 271 to prevent the air flowing through the bypass passage 230 from directly contacting the sensor PCB 272, the heat generating element 273, and the temperature sensor 274. In the sensor housing 271, a wire connected to the sensor PCB 271 is withdrawn in a state in which one side of the sensor housing 271 is opened. Thereafter, the opened portion may be covered by the cover portion.

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The sensor housing 271 may surround the sensor PCB 272, the heat generating element 273, and the temperature sensor 274. Fig. 8 is a view illustrating a position of the sensor in the bypass passage, Fig. 9 is a view illustrating an air flow pattern in the bypass passage, and Fig. 10 is a view illustrating a flow of air in the state in which the sensor is installed in the bypass passage. Referring to Figs. 5 and 8 to 10, the passage cover 260 may cover a portion of the bypass passage 230 in the vertical direction. Thus, the air may flow along a region (that is partitioned from the heat exchange space) of the bypass passage 230, in which the passage cover 260 substantially exists. As described above, the sensor 270 may be disposed to be spaced apart from the inlet 231 and the outlet 232 of the bypass passage 230. The sensor 270 may be disposed at a position at which the sensor 270 is less affected by a change in flow of the air flowing through the bypass passage 230. For example, the sensor 270 may be disposed at a position (hereinafter, referred to as an "inlet reference position") that is spaced at least 6Dg (or 6

* diameter of the passage) from the inlet (actually, a lower end of the passage cover 260)ofthe bypass passage 230. Alternatively, the sensor 270 may be disposed at a position (hereinafter, referred to as an "outlet reference position") that is spaced at least 3Dg (or 3 *

diameter of the passage) from the outlet (actually, an upper end of the passage cover 260) of the bypass passage 230. A change in flow of air is severe while the air is introduced into the bypass passage 230 or discharged from the bypass passage 230. If the change in flow of air is large, it may be wrongly determined that the defrosting is required despite a small amount of generated frost. Thus, in this embodiment, when air flows along the bypass passage 230, the sensor 270 is installed at a position at which the change in flow is small to reduce detection

89335628.1 errors. For example, the sensor 270 may be disposed within a range between the inlet reference position and the outlet reference position. The sensor 270 may be disposed closer to the outlet reference position than the inlet reference position. Therefore, the sensor 270 may be disposed closer to the outlet 232 than the inlet 231 in the bypass passage 230. Since the flow is stabilized at least at the inlet reference position, and the flow is stabilized until the outlet reference position, if the sensor 270 is disposed close to the outlet reference position, the air having the stabilized flow may contact the sensor 270. Thus, since it is not affected other than the flow change due to the large and small amount of generated frost, the sensing accuracy of the sensor 270 may be improved. Also, referring to Fig. 9, the farther away from the inlet 231 in the bypass passage 230, the air becomes a fully developed flow form. Since the sensor 270 is very sensitive to the change in flow of air, when the sensor 270 is disposed at a center of the bypass passage 230 at the point at which the fully developed flow occurs, the sensor 270 may accurately sense the change in flow. Thus, as illustrated in Fig. 10, the sensor 270 may be installed in a central region within the bypass passage 230. Here, the central region of the bypass passage 230 is a region including a portion at which a distance between the bottom wall 236 of the recessed portion of the bypass passage 230 and the passage cover 260 is bisected. That is, a portion of the sensor 270 may be disposed at a point at which the distance between the bottom wall 236 of the recessed portion of the bypass passage 230 and the passage cover 260 is bisected. Referring to Fig. 10, the sensor 270 may be spaced apart from the bottom wall 236 of the bypass passage 230 and the passage cover 260. Thus, a portion of the air in the bypass passage 230 may flow through a space between the

89335628.1 bottom wall 236 and the sensor 270, and the other portion of the air may flow through a space between the sensor 270 and the passage cover 260. In summary, the sensor 270 has to be installed in the central region of the passage at the point at which the change in flow of air is minimized in the bypass passage 230 and at the point at which the fully developed flow flows so as to improve accuracy sensing. Due to this arrangement, the sensor 270 may sensitively react to the change in flow of air according to the large or small amount of generated frost. That is, a variation in temperature sensed by the sensor 270 may increase. As described above, when the variation in temperature sensed by the sensor 270 increases, it is possible to determine the time point at which the defrosting is required even if the temperature sensing accuracy of the sensor 270 itself is lowered. Since the temperature sensing accuracy of the sensor itself is related to prices, it is possible to determine the time point at which the defrosting is required even if the sensor 270 having a relatively low price due to low accuracy is used. Fig. 11 is a view illustrating an arrangement of the bypass passage and the passage cover in the cool air duct according to an embodiment of the present invention. Referring to Fig. 11, a lower end 260a of the passage cover 260 may be disposed at a height similar to that of a lower end of the evaporator 30 or a height less than that of the lower end of the evaporator 30. According to this arrangement, when the amount of frost generated on the evaporator 30 increases, the air may easily flow to the bypass passage 230. In this embodiment, since the blower fan is disposed in the cool air duct 20, when the blower fan rotates, a portion of the air inflow hole 221 of the cool air duct 20 may serve as a low pressure region. Also, since the air flows upward along the evaporator 30, a lower side of the evaporator 30 with respect to the evaporator 30 may serve as a high pressure region, and an upper side of the evaporator 30 with respect to the evaporator 30

89335628.1 may serve as a low pressure region. In this embodiment, the upper end 260b of the passage cover 260 may be disposed in the low pressure region. Thus, since the lower end 260a of the passage cover 260 is disposed in the high pressure region, and the upper end 260b is disposed in the low pressure region, the flow of the air to the bypass passage 230 is possible. In addition, in this embodiment, the upper end 260b of the passage cover 260 may be disposed higher than the evaporator 30. Thus, the phenomenon in which the air discharged from the bypass passage 230 is affected by the air passing through the evaporator may be reduced. The bypass passage 230 may be disposed so as not to vertically overlap the air flow hole 221. This is to prevent the air discharged from the outlet 232 of the bypass passage 230 from being affected by the air introduced into the air flow hole 221. Also, the outlet 232 of the bypass passage 230 may be disposed lower than a center C of the blower fan. Also, the outlet 232 of the bypass passage 230 may be disposed lower than the lowest point of the air flow hole 221. In this embodiment, the air flow hole 221 has a diameter D1, and the blower fan has a diameter D2. The diameter D2 of the blower fan may be greater than the diameter D1 of the air flow hole 221. A limit region having a diameter D3 greater than the diameter D2 of the blower fan may be set based on the center C of the blower fan, and the outlet 232 of the bypass passage 230 may be disposed in a region outside the limit region having the diameter D3. Also, to minimize a length of the bypass passage 230, the bypass passage 230 may extend vertically in a straight line shape in the region outside the limit region. Here, although not limited, the diameter D3 may be set to 1.5 times or more of the diameter of the blower fan. Since the air is introduced into the cool air duct 20 through the air flow hole

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221, a flow velocity in the air flow hole 221 is fast. Also, due to the fast flow rate of the air flow hole 221, the flow velocity of the air in the region having the diameter D3 is fast. If the outlet 232 of the bypass passage 230 is disposed in the limit region, there is a change in flow of air in the bypass passage 230 due to the effect of a fast flow velocity, and thus, the sensing accuracy of the sensor 270 is reduced. Thus, in this embodiment, the bypass passage 230 may extend in the straight line shape so as not to be affected by the air having a fast flow velocity around the air flow hole 221 while reducing the length of the bypass passage 230, and the outlet 232 may be disposed outside the limit region. Fig. 12 is an enlarged view illustrating the bypass passage and a rib for preventing defrosting water from being introduced according to an embodiment of the present invention. Referring to Figs. 10 and 12, since the air flowing through the bypass passage 230 contains moisture, frost may be generated in the passage due to a capillary phenomenon in a space between the sensor 270 and a wall defined by the bypass passage 230 in the bypass passage 230. Thus, in this embodiment, the sensor 270 may be spaced apart from the bottom wall 236 of the bypass passage 230 and the passage cover 260 to prevent the frost from being generated in the passage. Although not limited, the sensor 270 may be designed to be spaced at least 1.5 mm from each of the bottom wall 236 and the passage cover 260 (which may be referred to as a "minimum separation distance"). Thus, a depth D of the bypass passage 230 may be equal to or larger than a thickness of (2 * the minimum separation distance) and the sensor 270. The left and right width W of the bypass passage 230 may be greater than the depth D. If the left and right width W of the bypass passage 230 are larger than the depth D, when the air flows to the bypass passage 230, a contact area between the air and the sensor 270 increases, and thus, the variation in temperature

89335628.1 detected by the sensor 270 may increase. The cool air duct 20 may be provided with a blocking rib 240 for preventing a liquid such as defrosting water or moisture generated by being melted during the defrosting process from being introduced into the bypass passage 230. The blocking rib 240 may be disposed above the outlet 232 of the bypass passage 230. The blocking rib 240 may have a protrusion shape protruding from the cool air duct 20. The blocking rib 240 may allow the dropping liquid to be spread horizontally so as to prevent the liquid from being introduced into the bypass passage 230. The blocking rib 240 may be provided horizontally in a straight line shape or be provided in a rounded shape to be convex upward. The blocking rib 240 may be disposed to overlap with the entire left and right side of the bypass passage 230 in the vertical direction and may have a minimum left and right length greater than the right and left width of the bypass passage 230. When the blocking rib 240 is provided in the cool air duct 20, since the blocking rib 240 serves as flow resistance of air, the minimum left and right length of the blocking rib 240 may be set to two times or less of the right and left width W. As the blocking rib 240 is disposed closer to the bypass passage 230, the length of the blocking rib 240 may be shortened. On the other hand, the defrosting water may flow over the blocking rib 240 and then be introduced into the bypass passage 230. Thus, the blocking rib 240 may be spaced apart from the bypass passage 230 in the vertical direction, and the maximum separation distance may be set within a range of the right and left width W of the bypass passage 230. The cool air duct 20 may further include a sensor installation groove 235 recessed to install the sensor 270. The cool air duct 20 may include a bottom wall 236 and both sidewalls 233 and 234 for providing the bypass passage 230, and the sensor installation groove

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235 may be recessed in one or more of both the sidewall 233 and 234. In the state in which the sensor 270 is installed in the sensor installation groove 235, the sensor 270 may be spaced the minimum separation distance from the bottom wall 236 and the passage cover 260 as described above. Fig. 13 is a view illustrating a barrier of the passage cover according to an embodiment of the present invention, Fig. 14 is a view illustrating a variation in temperature sensed by the sensor depending on a protruding length of the barrier, and Fig. 15 is a cross-sectional view of the barrier, taken along line A-A of Fig. 13. Fig. 16 is a view illustrating a change in flow of air depending on whether a slot is provided in the barrier, and Fig. 17 is a view illustrating a variation in temperature sensed by the sensor depending on a length of the slot defined in the barrier. Fig. 18 is a view illustrating a flow of air introduced into the heat exchange space according to an embodiment of the present invention. Referring to Figs. 3, 8, and 12 to 18, the passage cover 260 may include a cover plate 261, an upper extension portion 262 and a barrier 263. The cover plate 261 may cover the bypass passage 230 and may be provided in a thin plate shape. For example, the cover plate 261 may cover the bypass passage 230 in a state of being spaced apart from the bottom wall 236. A seating groove 235a for seating the cover plate 261 may be defined vertically in the cool air duct 20. When the cover plate 261 is seated in the seating groove 235a, an outer surface of the cover plate 261 may provide a substantially continuous surface with respect to the cool air duct 20. The upper extension portion 262 may also cover a portion of the bypass passage 230 and extend to be inclined at a predetermined angle from the cover plate 261. The upper extension portion 262 is configured to extend to be inclined from the cover plate 261 corresponding to a portion (226: hereinafter, referred to as an "upper inclined portion") of the cool air duct 20. If the cool air duct 20 does not include an upper inclined portion, the upper

89335628.1 extension portion 262 may be omitted, and the cover plate 261 may be provided in the straight line shape. The upper extension portion 262 covers only a portion of the bypass passage 230. Thus, a portion of the bypass passage 230 is exposed to the outside to be the outlet 232. A portion of the barrier 263 is disposed outside the bypass passage 230 while the cover plate 261 covers the bypass passage 230. For example, the barrier 263 may protrude downward from upper and lower extension surfaces 227 of the cool air duct 20. Thus, one portion of the barrier 263 is disposed in the bypass passage 230, and the other portion protrudes downward from the bypass passage 230. Specifically, the barrier 263 includes a rear barrier 267 disposed close to the evaporator 30, a front barrier 264 spaced forward from the rear barrier 267, and a plurality of side barriers 265 and 266 connecting the front barrier 264 to the rear barrier 267. The plurality of side barriers 265 and 266 may be spaced apart from each other in the left-right direction. Although not limited, the plurality of side barriers 265 and 266 may be disposed in parallel to each other. The rear barrier 267 is a wall provided to be continuous with the cover plate 261. The plurality of side barriers 265 and 266 are walls extending forward from the rear barrier 267. The front barrier 264 is a wall connecting front ends of the plurality of side barriers 265 and 266 to each other. The front barrier 264 is disposed at an opposite side of the evaporator 30 with respect to the rear barrier 267. Then, a bottom surface of the barrier 263 is opened. Thus, a guide passage 268 for guiding air to the bypass passage 230 is provided by the front barrier 264, the plurality of side barriers 265 and 266, and the rear barrier 267. The guide passage 268 is a passage communicating with the bypass passage 230 at the outside of the bypass passage 230. The guide passage 268 also serves as the bypass passage. In the cool air duct 20, a vertical extension surface 227 in which the bypass

89335628.1 passage 230 is provided may be a substantially vertical surface. The bypass passage 230 may extend vertically in a straight line shape from the vertical extension surface 227. The cool air duct 20 may further include an inclined surface 228 extending from a lower end of the vertical extension surface 227. The inclined surface 228 may extend downward as a distance from the evaporator 30 increases. The inclined surface 228 is a surface that guides the air in the storage space11 to the heatexchange space 222. Thus, the air in the storage space 11 may flow to be inclined upward by the inclined surface 228 when viewed from a side surface of the heat exchange space 222. In this embodiment, the barrier 263 may serve to limit an introduction of the air flowing to the heat exchange space 222 into the bypass passage 230 when an amount of frost generated on the evaporator 30 is small. On the other hand, the barrier 230 may serve to effectively guide the air introduced into the heat exchange space 222 to the bypass passage 230 when an amount of frost generated on the evaporator 30 is large. As described above, when the change in flow rate of the air increases due to the large and small amount of frost generated on the evaporator 30, the sensing accuracy of the sensor 270 may be improved by the barrier 263. That is, if the change in flow rate of the air is large due to the large and small amount of frost generated on the evaporator 30, the variation in temperature sensed by the sensor 270 is large, and thus, the time point at which the defrosting is required may be accurately determined. In addition, as described above, when the variation in temperature sensed by the sensor 270 increases due to the large and small amount of frost generated on the evaporator 30, even when the sensor 270 having low sensor accuracy is used, the time point at which the defrosting is required may be determined. In this embodiment, a flow rate of air introduced into the bypass passage 230 may vary according to a length of the barrier 263 protruding from the lower

89335628.1 end (that is a boundary between the vertical extension surface 227 and the inclined surface 228) of the vertical extension surface 227. Referring to Fig. 14, a horizontal axis represents the protruding length of the barrier, and a vertical axis represents the variation in temperature before and after the frost generation. When the protruding length of the barrier 263 is short, the flow rate of the air flowing through the bypass passage 230 increases even before the frost generation. When the flow rate of the air flowing through the bypass passage 230 is large before the frost generation, the variation in temperature sensed by the sensor 270 (for example, a difference value between the highest temperature and the lowest temperature) is large. Thus, the flow rate of the air flowing through the bypass passage 230 is large even after the frost generation, and the variation in temperature sensed by the sensor 270 is large. As a result, the variation between the temperature sensed by the sensor 270 before the frost generation and the temperature sensed by the sensor 270 after the frost generation (for example, the difference between the lowest temperature before the frost generation and the lowest temperature after the frost generation) decreases. On the other hand, when the protruding length of the barrier 263 increases, the flow rate of the air flowing through the bypass passage 230 before the frost generation decreases. The variation in temperature sensed by the sensor 270 before the frost generation decreases. On the other hand, since the variation in temperature sensed by the sensor 270 is large after the frost generation, the variation between the temperature sensed by the sensor 270 before the frost generation and the temperature sensed by the sensor 270 after the frost generation increases. However, when the protruding length of the barrier 263 is too long, the flow rate of the air flowing into the bypass passage 230 decreases before and after the frost generation. As a result, the variation between the temperature sensed by

89335628.1 the sensor 270 before the frost generation and the temperature sensed by the sensor 270 after the frost generation decreases. Accordingly, the protrusion length of the barrier 230 may be set to a value ranging of about 10 mm to about 17 mm so that the variation in temperature sensed by the sensor 270 before and after the frost generation is greater than the reference variation. The lower end of the barrier 263 may be horizontally disposed. For example, the front barrier 264 and the plurality of side barriers 265 and 266 may be disposed on substantially the same horizontal plane. In this case, as illustrated in (a) of Fig. 16, since the air in the storage space 11 flows upward along the inclined surface 228, when the air, which passes through the front barrier 264, of the air that flows to be inclined collides with the rear barrier 267, the air flows to the bypass passage 230 without flowing to the evaporator 30. In this case, the flow rate of the air flowing into the bypass passage 230 increases regardless of the amount of generated frost. In the case of this embodiment, the accuracy of determining the time point at which the defrosting is required may be improved only when the flow rate of the air flowing through the bypass passage 230 is minimized before the frost generation. Thus, a slot 269 providing a flow path of air may be defined in the rear barrier 267 so that the air passing through the lower end of the front barrier 264 flows directly to the evaporator 30. When the slot 269 is defined in the rear barrier 267 as illustrated in (b) of Fig. 16, the air passing through the lower end of the front barrier 264 may not collide with the rear barrier 267 and thus may not directly flow to the evaporator 30. In this embodiment, the air colliding with the front barrier 264 flows along the plurality of side barriers 265 and 266 and then flows toward the rear barrier 267. When the slot 269 is not defined in the rear barrier 267, the air flowing

89335628.1 along the side barriers 265 and 266 does not flow to the bypass passage 230 but flows to the evaporator 30. On the other hand, when the slot 269 is defined in the rear barrier 267, the air flowing along the side barriers 265 and 266 flows to the bypass passage 230 by the slot 269. Thus, in this embodiment, the flow rate of the air flowing to the bypass passage 230 may be determined actually by the flow rate of the air directly introduced into the guide passage 268 of at least the barrier 263 and the flow rate of the air introduced into the barrier 263 along the slot 269 after flowing along a circumference of the barrier 263. In this embodiment, if a length of the slot 269 (a height from the lower end of the barrier 262) is small, the flow rate of the air flowing into the bypass passage 230 is large, and when the slot 269 increases in length, the flow rate of the air flowing into the bypass passage 230 is reduced. However, if the length of the slot 269 is too long, the flow rate of the air flowing through the slot 269 after flowing along the side barriers 265 and 266 increases, and even before the frost generation, the flow rate of the air flowing into the bypass passage 230 increases. Thus, in this embodiment, the length of the slot may be set to a value ranging of about 4 mm to about 9 mm so that the flow rate of the air flowing into the bypass passage 230 is minimized before the frost generation. Although not limited, the length of the slot 269 may be designed within a range of about 1/5 to about 1/2 of the protruding length of the barrier 263. Fig. 19 is a control block diagram of the refrigerator according to an embodiment of the present invention. Referring to Fig. 19, the refrigerator 1 according to an embodiment of the present invention may further include a defroster 50 operating to defrost the evaporator 30 and a controller 40 controlling the defroster 50. The defroster 50 may include, for example, a heater. When the heater is turned on, heat generated by the heater is transferred to the evaporator 30 to melt

89335628.1 frost generated on the surface of the evaporator 30. The controller 40 may control the heat generating element 273 of the sensor 270 so as to be turned on with a regular cycle. To determine the time point at which the defrosting is required, the heat generating element 273 may be maintained in the turn-on state for a certain time, and a temperature of the heat generating element 273 may be sensed by the sensing element 274. After the heat generating element 273 is turned on for the certain time, the heat generating element 274 may be turned off, and the sensing element 274 may sense the temperature of the off heat generating element 274. Also, the sensor PCB 272 may determine whether a maximum value of the temperature difference value in the turn on/off state of the heat generating element 273 is equal to or less than the reference difference value. Then, when the maximum value of the temperature difference value in the turn on/off state of the heat generating element 273 is equal to or less than the reference difference value, it is determined that defrosting is required. Thus, the defroster 50 may be turned on by the controller 40. In the above, it has been described as determining whether the temperature difference value of the turn on/off state of the heat generating element 273 in the sensor PCB 272 is equal to or less than the reference difference value. On the other hand, the controller 40 may determine whether the temperature difference value in the turn on/off state of the heat generating element 273 is equal to or less than the reference difference value and then control the defroster 50 according to the determination result.

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Claims

1. A refrigerator comprising: an inner case configured to define a storage space; a cool air duct configured to guide a flow of air within the storage space, the cool air duct being configured to define a heat-exchange space together with the inner case; an evaporator disposed in the heat exchange space between the inner case and the cool air duct; a bypass passage disposed to be recessed in the cool air duct, the bypass passage being configured so that the air flows to bypass the evaporator; a sensor disposed in the bypass passage, the sensor having an output value varying according to a flow rate of the air flowing through the bypass passage; a defroster configured to remove frost generated on a surface of the evaporator; and a controller configured to control the defroster based on the output value of the sensor.

2. The refrigerator of claim 1, wherein the sensor comprises: a heat generating element; a sensing element configured to sense a temperature of the heat generating element; and a sensor PCB on which the heat generating element and the sensing element are installed.

3. The refrigerator of claim 2, wherein, when a difference value between a temperature sensed by the sensing element in a state in which the heat generating element is turned on and a temperature sensed by the sensing element in a state in which the heat generating element is turned off is equal to or less than

89335628.1 a reference temperature value, the controller operates the defroster.

4. The refrigerator of claim 2, wherein the sensor further comprises a sensor housing configured to surround the heat generating element, the sensing element, and the sensor PCB.

5. The refrigerator of claim 1, further comprising a passage cover configured to cover the bypass passage so as to partition the bypass passage from the heat exchange space.

6. The refrigerator of claim 5, wherein the cool air duct comprises a vertical extension surface that is a surface in which the bypass passage is defined, and the passage cover comprises: a cover plate configured to cover the bypass passage; and a barrier extending from the cover plate, the barrier protruding downward from the vertical extension surface in a state in which the cover plate covers the bypass passage.

7. The refrigerator of claim 6, wherein the bypass passage extends vertically from the vertical extension surface in a straight-line shape.

8. The refrigerator of claim 6, wherein the barrier further comprises: a rear barrier continuously extending from the cover plate, the rear barrier being disposed adjacent to the evaporator; a plurality of side barriers extending from the rear barrier, the plurality of side barriers being spaced apart from each other in a left and right direction; and a front barrier connected to the plurality of side barriers, spaced apart from the rear barrier, and disposed at an opposite side of the evaporator with respect to the rear barrier.

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9. The refrigerator of claim 8, wherein the barrier has an opened bottom surface, and the rear barrier, the plurality of side barriers, and the rear barrier define a guide passage configured to guide air to the bypass passage.

10. The refrigerator of claim 8, wherein the cool air duct further comprises an inclined surface extending to be inclined from an end of the vertical extension surface and configured to guide the air toward the evaporator, and a slot configured to define a passage for allowing the air flowing along the inclined surface to flow toward the evaporator is provided in the rear barrier.

11. The refrigerator of claim 5, wherein the cool air duct comprises a bottom wall and both sidewalls, which define the bypass passage, the passage cover comprises a cover plate configured to cover the bypass passage in a state of being spaced apart from the bottom wall, and the sensor is disposed to be spaced apart from the bottom wall and the cover plate in the bypass passage.

12. The refrigerator of claim 11, wherein the sensor is disposed to be spaced apart from an inlet and an outlet of the bypass passage, and a portion of the sensor is disposed at a point at which a distance between the bottom wall and the cover plate is bisected in the bypass passage.

13. The refrigerator of claim 12, wherein the sensor is disposed closer to the outlet than the inlet of the bypass passage.

14. The refrigerator of claim 5, wherein at least a portion of the bypass passage and the passage cover is disposed to face the evaporator within a range of a left and right width of the evaporator.

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15. The refrigerator of claim 5, wherein a blower fan is disposed in the cool air duct, a cool air inflow hole into which the cool air is introduced is defined in the cool air duct, and the bypass passage does not overlap the cool air inflow hole in the vertical direction.

16. The refrigerator of claim 15, wherein an outlet of the bypass passage is disposed in a region outside a limit region having a diameter greater than that of the blower fan with respect to a center of the blower fan.

17. The refrigerator of claim 16, wherein the outlet of the bypass passage is disposed higher than an upper end of the evaporator.

18. The refrigerator of claim 16, wherein the limit region has a diameter greater 1.5 times or more than the diameter of the blower fan.

19. The refrigerator of claim 1, wherein a blocking rib configured to block an introduction of a liquid into the bypass passage is disposed above the bypass passage in the cool air duct.

20. The refrigerator of claim 19, wherein the blocking rib has a left-right minimum length greater than a left-right minimum width of the bypass passage, and the entire bypass passage in the left and right direction is disposed to overlap the blocking rib in the vertical direction.

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