AU2019232055B2

AU2019232055B2 - Refrigerator and controlling method thereof

Info

Publication number: AU2019232055B2
Application number: AU2019232055A
Authority: AU
Inventors: Sangbok Choi; Sung Jhee; Sungwook Kim; Kyongbae Park
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2018-03-08
Filing date: 2019-01-31
Publication date: 2022-08-25
Anticipated expiration: 2039-01-31
Also published as: CN114704994A; KR102614564B1; WO2019172532A1; EP3764033A1; US20210055034A1; CN114704994B; CN111801539A; EP3764033A4; AU2019232055A1; CN111801539B; KR20190106242A

Abstract

A control method of a refrigerator, according to an embodiment of the present invention, comprises the steps in which: a heating element of a sensor which is responsive to a change in the flow rate of air is turned off after being turned on for a predetermined time; a first sensing temperature (Ht1) of the heating element is sensed in a state in which the heating element is on, and a second sensing temperature (Ht2) of the heating element is sensed in a state in which the heating element is off; and the amount of frost on an evaporator is sensed on the basis of the temperature difference value between the first sensing temperature (Ht1) and the second sensing temperature (Ht2).

Description

REFRIGERATOR AND CONTROLLING METHOD THE SAME

[Field]

[1] The present disclosure relates to a refrigerator and a control method

thereof.

[Background]

[2] Refrigerators are household appliances that are capable of storing

objects such as foods at a low temperature in a storage chamber 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.

[3] 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.

[4] 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.

[5] 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.

[6] 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.

[7] Thus, the refrigerator further includes a defroster for removing the frost

on the evaporator.

[8] A defrosting cycle variable method is disclosed in Korean Patent

Publication No. 2000-0004806 that is a prior art document.

[9] In the prior art document, the defrosting cycle is adjusted using a

cumulative operation time of the compressor and an external temperature.

[10] 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.

[11] 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 may be a disadvantage in that the defrosting cycle is

determined without reflecting the various environments.

[12] Moreover, in the case of the prior literature, there may be a

disadvantage that it is difficult to identify an exact defrost time point since the

amount of local frost of the evaporator can be detected but the amount of frost

on the entire evaporator cannot be detected.

[13] Accordingly, there may be 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.

[14] It is desired to address or ameliorate one or more disadvantages or

limitations associated with the prior art, provide a refrigerator and/or a method

for controlling the same, or to at least provide the public with a useful

alternative.

[Summary]

[15] According to the present invention, there is provided a method for

controlling a refrigerator, the method comprising:

turning on a heat generating element of a sensor unit in response to a

sensed change in a flow rate of air turning off the heat generating element after

a predetermined period of time;

sensing a first temperature (Htl) of the heat generating element in a

turned on state and a second temperature (Ht2) of the heat generating element

in a turned off state;

sensing an amount of frost on an evaporator based on a temperature

difference between the first temperature (Htl) and the second temperature

(Ht2); and

performing a defrost operation of removing frost generated on a surface

of the evaporator when it is determined that the temperature difference value

between the first detection temperature (Htl) and the second detection

temperature (Ht2) is less than a first reference difference value.

[16] The present invention also provides a method for controlling a

refrigerator comprising: operating for a predetermined period of time a heat generating element of a sensor unit in response to a change in a flow rate of air; sensing a plurality of temperatures of the heat generating element when the heat generating element is turned on; sensing an amount of frost on an evaporator based on a temperature difference between a first temperature (Ht) that is a lowest value and a second temperature (Ht2) that is a highest value among the sensed plurality of temperatures of the heat generating element; and performing a defrost operation of removing frost generated on a surface of the evaporator when it is determined that the temperature difference value between the first detection temperature (Htl) and the second detection temperature (Ht2) is less than a first reference difference value.

[17] The present invention further provides a refrigerator, comprising:

an inner case defining a storage space;

a cooling duct configured to guide flow of air to the storage space;

a heat exchange space defined between the inner case and the cooling

duct;

an evaporator disposed in the heat exchange space;

a bypass passage disposed to be recessed in the cool air duct and

configured to allow air flow to bypass the evaporator;

a sensor unit disposed in the bypass passage and including a heat

generating element disposed and a sensing element configured to sense a

plurality of temperatures of the heat generating element; and

a controller configured to sense an amount of frost on an evaporator

based on a temperature difference between a first temperature (Htl) of the heat generating element sensed in a turned on state and a second temperature

(Ht2) of the heat generating element sensed in a turned off state.

[18] Embodiments of the present disclosure may provide a refrigerator and

a control method thereof, which determines a time point for a defrosting

operation using parameters that vary depending on the amount of frost on an

evaporator.

[19] Embodiments of the present disclosure may also provide a refrigerator

and a control method thereof, which accurately determine a time point at which

defrosting is necessary according to the amount of frost on an evaporator using

a sensor having an output value that varies depending on the flow rate of air.

[20] Embodiments of the present disclosure may also provide a refrigerator

and a control method thereof, which accurately determine a defrosting time

point even when the precision of a sensor used to determine the defrosting

time point is low.

[21] Embodiments of the present disclosure may also provide a refrigerator

and a control method thereof, in which a detection logic for detecting an

amount of frost on an evaporator may be executed at an appropriate time point.

[22] Embodiments of the present disclosure may also provide a refrigerator

and a control method thereof, which improve reliability in consideration of

changes in an external environment in a process of detecting an amount of

frost on an evaporation.

[23] A control method of a refrigerator may include detecting an amount of

frost on an evaporator based on a temperature difference between the first

detection temperature (Htl) of the heat generating element detected in a state

in which the heat generating element is turned on and a second detection temperature (Ht2) of the heat generating element detected in a state in which the heat generating element is turned off, the sensor reacting to a change in a flow rate of air.

[24] As an example, the first detection temperature (Ht) may be a

temperature detected by a sensing element of the sensor immediately after

the heat generating element is turned on, and the second detection

temperature (Ht2) may be a temperature detected by a sensing element of the

sensor immediately after the heat generating element is turned off.

[25] As another example, the first detection temperature (Htl) may be a

lowest temperature value during a period of time when the heat generating

element is turned on and the second detection temperature (Ht2) is a highest

temperature value after the heat generating element is turned off.

[26] Further, the heat generating element may be in a turned-on state while

a storage compartment of the refrigerator is being cooled. As an example, the

heat generating element may be in a turned-on state while a flowing fan for

cooling the storage compartment is being driven.

[27] The control method of embodiments of the present disclosure may

further include determining whether a temperature difference value between

the first detection temperature (Htl) and the second detection temperature

(Ht2) is less than a first reference difference value, and performing a defrost

operation of removing frost generated on a surface of the evaporator when it

is determined that a temperature difference value between the first detection

temperature (Htl) and the second detection temperature (Ht2) is less than a

first reference difference value.

[28] The control method of embodiments of the present disclosure may

further include determining whether a temperature difference between the first

detection temperature (Htl) and the second detection temperature (Ht2) is less

than a second reference difference value when the heat generating element is

turned on for the predetermined period of time and then turned off, and the

heat generating element may be turned on according to whether a temperature

difference between the first detection temperature (Htl) and the second

detection temperature (Ht2) is less than a second reference difference value.

[29] The heat generating element may be turned on based on an

accumulated cooling operation time of the storage compartment when the

temperature difference between the first detection temperature (Htl) and the

second detection temperature (Ht2) is less than the second reference

difference value.

[30] A control method of a refrigerator may include detecting an amount of

frost on an evaporator based on a temperature difference between the first

detection temperature (Ht) that is a lowest value and the second detection

temperature (Ht2) that is a highest value among detection temperatures of the

heat generating element.

[31] In addition, the heat generating element may be in a turned-on state

while a storage compartment of the refrigerator is being cooled. As an example,

the heat generating element may be in a turned-on state while a flowing fan

for cooling the storage compartment is being driven.

[32] The control method of a refrigerator may further include determining

whether a temperature difference between the first detection temperature (Htl)

and the second detection temperature (Ht2) is less than a first reference difference value, and performing a defrost operation of removing frost generated on a surface of the evaporator when it is determined that a temperature difference between the first detection temperature (Htl) and the second detection temperature (Ht2) is less than a first reference difference value.

[33] A refrigerator may include a heat generating element, a sensor

including a sensing element that detects a temperature of the heat generating

element, and a controller that detects an amount of frost on an evaporator

based on a temperature difference between the first detection temperature

(Htl) of the heat generating element detected in a state in which the heat

generating element is turned on and a second detection temperature (Ht2) of

the heat generating element detected in a state in which the heat generating

element is turned off.

[34] According to embodiments of 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.

[35] In addition, even when the precision of a sensor used to determine a

defrost time point is low, it is possible to accurately determine the defrost time

point, thus significantly reducing the cost of the sensor.

[36] In addition, since a detection logic for detecting the amount of frost on

the evaporator may be performed at an appropriate time point, reducing power

consumption and improving convenience.

[37] In addition, since changes in external environments (e.g., internal

refrigerator load) are considered in a process of detecting the amount of frost

of the evaporator, product reliability is improved.

[38] The term "comprising" as used in the specification and claims means

"consisting at least in part of." When interpreting each statement in this

specification that includes the term "comprising," features other than that or

those prefaced by the term may also be present. Related terms "comprise" and

"comprises" are to be interpreted in the same manner.

[39] The reference in this specification to any prior publication (or

information derived from it), or to any matter which is known, is not, and should

not be taken as, an acknowledgement or admission or any form of suggestion

that that prior publication (or information derived from it) or known matter forms

part of the common general knowledge in the field of endeavour to which this

specification relates.

[Brief Description of the Drawings]

[40] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:

[41] FIG. 1 is a schematic longitudinal cross-sectional view of a refrigerator

according to an embodiment of the present disclosure.

[42] FIG. 2 is a perspective view of a cool air duct according to an

embodiment of the present disclosure.

[43] 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.

[44] 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.

[45] FIG. 5 is a schematic view illustrating a state in which a sensor is

disposed in the bypass passage.

[46] FIG. 6 is a view of the sensor according to an embodiment of the

present disclosure.

[47] FIG. 7 is a view illustrating a thermal flow around the sensor depending

on a flow of air flowing through the bypass passage.

[48] FIG. 8 is a control block diagram of a refrigerator according to an

embodiment of the present disclosure.

[49] FIG. 9 is a flow chart showing a control method for detecting an amount

of frost on an evaporator according to an embodiment of the present disclosure.

[50] FIG. 10 is a flowchart showing a method of performing a defrost

operation by determining a time point when a refrigerator needs to be defrosted

according to an embodiment of the present disclosure.

[51] FIG. 11 is a view showing changes in a temperature of a heat

generating element according to the turning on/off of the heat generating

element before and after frost on the evaporator according to an embodiment

of the present disclosure.

[52] FIG. 12 is a flow chart showing a control method for determining an

operating time point of a heat generating element according to an embodiment

of the present disclosure.

[Detailed Description]

[53] 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.

[54] 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.

[55] Fig. 1 is a schematic longitudinal cross-sectional view of a refrigerator

according to an embodiment of the present disclosure, Fig. 2 is a perspective

view of a cool air duct according to an embodiment of the present disclosure,

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.

[56] Referring to Figs. 1 to 3, a refrigerator 1 according to an embodiment of

the present disclosure may include an inner case 12 defining a storage space

11.

[57] The storage space may include one or more of a refrigerating storage

space and a freezing storage space.

[58] 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 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.

[59] 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.

[60] 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.

[61] 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.

[62] 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.

[63] 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.

[64] 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 cool air discharge hole

211.

[65] 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.

[66] 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.

[67] 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 to deteriorate heat exchange efficiency.

[68] In this embodiment, a time point at which defrosting for the evaporator

30 is required may be determined using a parameter that is changed according

to the amount of frost generated on the evaporator 30.

[69] 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.

[70] 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.

[71] 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.

[72] 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.

[73] The bypass passage 230 may extend from the cool air duct 20 in a

vertical direction.

[74] 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.

[75] 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.

[76] 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.

[77] 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.

[78] Fig. 4 is a view illustrating a flow of air in the heat exchange space and

the bypass passage before and after frost is generated.

[79] (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.

[80] 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).

[81] 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).

[82] 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.

[83] 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.

[84] Hereinafter, a structure and principle of the sensor 270 will be described.

[85] 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 disclosure, and Fig. 7 is a view illustrating a thermal flow around the sensor depending on a flow of air flowing through the bypass passage.

[86] 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 in response to a change in a flow rate of air.

[87] 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. For example, the

sensor 270 may be positioned a central portion of the bypass passage 230.

[88] 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.

[89] The sensor 270 may be, for example, a generated heat temperature

sensor. Particularly, the sensor 270 may include a sensor PCB 271, a heat

generating element 273 installed on the sensor PCB 271, and a sensing

element 274 installed on the sensor PCB 271 to sense a temperature of the

heat generating element 273.

[90] The heat generating element 273 may be a resistor that generates heat

when current is applied.

[91] The sensing element 274 may sense a temperature of the heat

generating element 273.

[92] 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.

[93] 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.

[94] The sensor PCB 271 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.

[95] 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 reference difference value.

[96] 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.

[97] 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.

[98] 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.

[99] 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.

[100] 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.

[101] The sensor 270 maybe further provided with a sensor housing 272 such

that air flowing through the bypass passage 230 is prevented from directly

contacting the sensor PCB 271, the heat generating element 273, and the

temperature sensor 274. In a state in which the sensor housing 272 is opened

at one side, an electric wire connected to the sensor PCB 271 may be drawn

out and then the opened portion may be covered by a cover portion.

[102] The sensor housing 271 may surround the sensor PCB 271, the heat

generating element 273, and the temperature sensor 274.

[103] FIG. 8 is a control block diagram of a refrigerator according to an

embodiment of the present disclosure.

[104] Referring to FIG. 8, the refrigerator 1 according to an embodiment of

the present disclosure may include the sensor 270 described above, a

defrosting device 50 operating for defrosting the evaporator 30, a compressor

60 for compressing refrigerant, a blowing fan 70 for generating air flow, and a controller 40 for controlling the sensor 270, the defrosting device 50, the compressor 60 and the blowing fan 70.

[105] The defrosting device 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 frost generated on the surface of the evaporator 30. The

heater may be connected to one side of the evaporator 30, or may be disposed

spaced apart from a position adjacent to the evaporator 30.

[106] The compressor 60 is a device for compressing low-temperature low

pressure refrigerant into a high-temperature high-pressure supersaturated

gaseous refrigerant. Specifically, the high-temperature high-pressure

supersaturated gaseous refrigerant compressed in the compressor 60 flows

into a condenser (not shown). The refrigerant is condensed into a high

temperature high-pressure saturated liquid refrigerant, and the condensed

high-temperature high-pressure saturated liquid refrigerant is introduced to an

expander (not shown) and is expanded to a low-temperature low-pressure two

phase refrigerant.

[107] Further, the low-temperature low-pressure two-phase refrigerant is

evaporated as the low-temperature low-pressure gaseous refrigerant while

passing through the evaporator 30. In this process, the refrigerant flowing

through the evaporator 30 may exchange heat with outside air, that is, air

flowing through the heat exchange space 222, thereby archiving air cooling.

[108] The blowing fan 70 is provided in the cold air passage 212 to generate

air flow. Specifically, when the blowing fan 70 is rotated, air passing through

the evaporator 30 flows into the cold air passage 212 through the cool air inflow hole 221 and is then discharged to the storage compartment 11 through the cool air discharge hole 211.

[109] The controller 40 may control the heat generating element 273 of the

sensor 270 to be turned on at regular cycles.

[110] In order to determine when defrosting is necessary, the heat generating

element 273 may maintain a turned-on state for a predetermined period of time,

and the temperature of the heat generating element 273 may be detected by

the sensing element 274.

[111] After the heat generating element 273 is turned on for the

predetermined period of time, the heat generating element 274 is turned off,

and the sensing element 274 may detect the temperature of the heat

generating element 273 which is turned off. In addition, the sensor PCB 263

may determine whether the maximum value of the temperature difference

between the turned-on/off state of the heat generating element 273 is equal to

or less than a reference difference value.

[112] In addition, it is determined that defrosting is necessary when the

maximum value of the temperature difference between the turned-on/off states

of the heat generating element 273 is equal to or less than the reference

difference value, and the defrosting device 50 may be turned on by the

controller 40.

[113] Although it has been described above that the sensor PCB 263

determines whether the temperature difference between the turned-on/off

states of the heat generating element 273 is equal to or less than the reference

difference value, alternatively, the controller 40 may determine whether the

temperature difference between the turned-on/off states of the heat generating element 273 is equal to or less than the reference difference value, and control the defrosting device 50 according to a result of the determination. That is, the sensor PCB 263 and the controller 40 may be electrically connected to each other.

[114] Hereinafter, a method for detecting the amount of frost on the

evaporator 30 using the heat generating element 273 will be described in detail

with reference to the drawings.

[115] FIG. 9 is a flowchart showing a control method for detecting an amount

of frost on an evaporator according to an embodiment of the present disclosure.

In the present embodiment, a method for detecting the amount of frost on the

evaporator 30 in a state in which the storage compartment 11, for example, a

freezing compartment is subjected to a cooling operation.

[116] Referring to FIG. 9, in step S11, the heat generating element 27 is

turned on.

[117] Specifically, the heat generating element 27 may be turned on in a state

in which the cooling operation of the storage compartment 11 (e.g., freezing

compartment) is performed.

[118] Here, the state in which the cooling operation of the freezing

compartment is performed may mean a state in which the compressor 60 and

the blowing fan 70 are being driven.

[119] As described above, when a change in the flow rate of the air increases

as the amount of frost on the evaporator 30 is large or small, the detection

accuracy of the sensor 260 may be improved. That is, when the change in the

flow rate of the air is large as the amount of frost on the evaporator 30 is large

or small, the amount of change in the temperature detected by the sensor 270 becomes large, so that the time point at the defrosting is necessary may be accurately determined.

[120] Therefore, it is possible to increase the accuracy of the sensor only

when frost on the evaporator 30 is detected in a state in which air flow occurs,

that is, the blowing fan 70 is being driven.

[121] Next, in step S13, the temperature of the heat generating element 273

is detected when the heat generating element 273 is turned on.

[122] Specifically, the heat generating element 273 may be turned on for a

predetermined period of time, and the temperature (Htl) of the heat generating

element 273 may be detected by the sensing element at a certain time point

in the state in which the heat generating element 273 is turned on.

[123] As the period of time during which the heat generating element 273 is

turned on increases, the temperature of the heat generating element 273 may

gradually increase. Further, the temperature of the heat generating element

273 may increase gradually and converge to the highest temperature point.

[124] On the other hand, when the amount of frost on the evaporator 30 is

large, the flow rate of the air flowing into the bypass passage 230 increases,

and thus the amount of cooling for the heat generating element 273 by air

flowing through the bypass passage 230 may increase. Then, the highest

temperature point of the heat generating element 273 may be set to be low by

the air flowing through the bypass passage 230.

[125] On the other hand, when the amount of frost on the evaporator 30 is

small, the flow rate of the air flowing into the bypass passage 230 decreases,

and thus the amount of cooling for the heat generating element 273 by air

flowing through the bypass passage 230 decreases. Then, the highest temperature point of the heat generating element 273 may be set to be high by the air flowing through the bypass passage 230.

[126] In the present embodiment, the temperature of the heat generating

element 273 may be detected at a time point at which the heat generating

element 273 is turned on. That is, in the present disclosure, it can be

understood that the lowest temperature value of the heat generating element

273 is detected after the heat generating element 273 is turned on.

[127] Next, in step S15, after the predetermined period of time has elapsed,

the heat generating element 273 is turned off.

[128] As an example, the heat generating element 273 may maintain in a

turned-on state for three minutes and then turned off.

[129] When the heat generating element 273 is turned off, the temperature of

the heat generating element 273 may decrease rapidly due to the air flowing

through the bypass passage 230.

[130] As the period of time during which the heat generating element 273 is

turned off increases, the temperature of the heat generating element 273 may

rapidly decrease. In addition, the temperature of the heat generating element

273 may rapidly decrease, and then gradually decrease from a specific time

point.

[131] Next, in step S17, the temperature of the heat generating element 273

is detected in a state in which the heat generating element 273 is turned off.

[132] Specifically, the temperature of the heat generating element 273 may

be detected at a certain time point in a state the heat generating element 273

is turned off.

[133] In the present embodiment, the temperature of the heat generating

element 273 may be detected at a time point at which the heat generating

element 273 is turned off. That is, in the present disclosure, it can be

understood that the highest temperature value of the heat generating element

273 is detected after the heat generating element 273 is turned off.

[134] Next, in step S19, the amount of frost on the evaporator 30 may be

determined based on the temperature difference between the temperature

detected in the state in which the heat generating element 273 is turned on

and the temperature in the state in which the heat generating element 273 is

turned off.

[135] As described above, when the amount of frost on the evaporator 30 is

large, the flow rate of the air flowing into the bypass passage 230 increases,

and thus the amount of cooling for the heat generating element 273 by air

flowing through the bypass passage 230 increases. Then, the detected highest

temperature value of the heat generating element 273 become small, and as

a result, the temperature difference between the lowest temperature value and

the highest temperature value of the heat generating element 273 may

become large.

[136] Conversely, when the amount of frost on the evaporator 30 is small, the

flow rate of the air flowing into the bypass passage 230 decreases, and thus

the amount of cooling for the heat generating element 273 by air flowing

through the bypass passage 230 decreases. Then, the detected highest

temperature value of the heat generating element 273 become large, and as

a result, the temperature difference between the lowest temperature value and the highest temperature value of the heat generating element 273 may become small.

[137] As described above, by detecting the lowest temperature value and the

highest temperature value when the heat generating element 273 is turned

on/off, the amount of cooling for the heat generating element 273 may be

accurately determined by air flowing through the bypass passage 230.

[138] In summary, when the temperature difference between the lowest

temperature value and the highest temperature value of the heat generating

element 273 is equal to or less than a reference value, it may be determined

that the amount of frost on the evaporator 30 is large. In addition, when it is

determined that the amount of frost on the evaporator 30 is large, a defrosting

operation may be performed.

[139] Hereinafter, a detailed method for detecting the amount of frost on the

evaporator 30 described above will be described in detail with reference to the

drawings.

[140] FIG. 10 is a flowchart showing a method of performing a defrost

operation by determining a time point when a refrigerator needs to be defrosted

according to an embodiment of the present disclosure, and FIG. 11 is a view

showing changes in a temperature of a heat generating element according to

the turning on/off of the heat generating element before and after frost on the

evaporator according to an embodiment of the present disclosure.

[141] FIG. 11(a) shows a change in temperature of the freezing compartment

and a change in temperature of the heat generating element before occurrence

of frost on the evaporator 30, and FIG. 11(b) shows a change in temperature

of the freezing compartment and a change in temperature of the heat generating element after occurrence of frost on the evaporator 30. In the present embodiment, it is assumed that a state before occurrence of frost is a state after a defrosting operation is completed.

[142] Referring to FIGS. 10 and 11, in step S21, the heat generating element

27 is turned on.

[143] Specifically, the heat generating element 27 maybe turned on in a state

in which the cooling operation is being performed on the storage compartment

11 (e.g., freezing compartment).

[144] As an example, as shown in FIG. 11, the heat generating element 273

may be turned on at a certain time point S1 while the blowing fan 70 is being

driven.

[145] The blower fan 70 maybe driven for a predetermined period of time to

cool the freezing compartment. In this case, the compressor 60 may be driven

at the same time. Therefore, when the blowing fan 70 is driven, the

temperature Ft of the freezing compartment may decrease.

[146] On the other hand, when the heat generating element 273 is turned on,

the temperature detected by the sensing element 274, that is, the temperature

Ht of the heat generating element 273 may increase rapidly.

[147] Next, in step S22, it may be determined whether the blowing fan 70 is

turned on.

[148] As described above, the sensor 270 may detect a change in

temperature of the heat generating element 273, which is changed due to air

of which the flow rate is changed according to the amount of frost on the

evaporator 30. Therefore, when no air flow occurs, it is difficult for the sensor

270 to accurately detect the amount of front on the evaporator 30.

[149] When the blowing fan 70 is being driven, in step S23, the temperature

Htl of the heat generating element may be detected.

[150] Specifically, the heat generating element 273 may be turned on for a

predetermined period of time, and the temperature (Htl) of the heat generating

element 273 may be detected by the sensing element at a certain time point

in the state in which the heat generating element 273 is turned on.

[151] In the present embodiment, the temperature Htl of the heat generating

element 273 may be detected at a time point at which the heat generating

element 273 is turned on. That is, in the present disclosure, the temperature

immediately after the heat generating element 273 is turned on may be

detected. Therefore, the detection temperature Htl of the heat generating

element may be defined as the lowest temperature in the state in which the

heat generating element 273 is turned on.

[152] Here, the temperature of the heat generating element 273 detected for

the first time may be referred to as a "first detection temperature (Ht)".

[153] Next, in step S24, it is determined whether a first reference time T1 has

elapsed while the heat generating element 273 is turned on.

[154] When the heat generating element 273 is maintained in the turned-on

state, the temperature detected by the sensing element 274, that is, the

temperature Htl of the heat generating element 273 may continuously

increase. However, when the heat generating element 273 is maintained in the

turned-on state, the temperature of the heat generating element 273 may

increase gradually and converge to the highest temperature point.

[155] Here, the first reference time T1 for which the heat generating element

273 is maintained in the turned-on state may be 3 minutes, but is not limited

thereto.

[156] When a predetermined period of time has elapsed while the heat

generating element 273 is turned on, in step S25, the heat generating element

273 is turned off.

[157] As in FIG. 11, the heat generating element 273 may be turned on for

the first reference time T1 and then turned off. When the heat generating

element 273 is turned off, the heat generating element 273 may be rapidly

cooled by air flowing through the bypass passage 230. Therefore, the

temperature Ht of the heat generating element 273 may rapidly decrease.

[158] However, when the turned-off state of the heat generating element 273

is maintained, the temperature Ht of the heat generating element may

gradually decrease, and the decrease rate thereof is significantly reduced.

[159] Next, in step S26, the temperature Ht2 of the heat generating element

may be detected.

[160] That is, the temperature Ht2 of the heat generating element is detected

by the sensing element 273 at a certain time point S2 in a state in which the

heat generating element 273 is turned off.

[161] In the present embodiment, the temperature Ht2 of the heat generating

element may be detected at a time point at which the heat generating element

273 is turned off. That is, in the present disclosure, the temperature

immediately after the heat generating element 273 is turned off may be

detected. Therefore, the detection temperature Ht2 of the heat generating element may be defined as the lowest temperature in the state in which the heat generating element 273 is turned off.

[162] Here, the temperature of the heat generating element 273 detected for

the second time may be referred to as a "second detection temperature (Ht2)".

[163] In summary, the temperature Ht of the heat generating element maybe

first detected at a time point S1 when the heat generating element 273 is

turned on, and may be additionally detected at a time point S2 at which the

heat generating element 273 is turned off. In this case, the first detection

temperature Htl that is detected for the first time may be the lowest

temperature in the state in which the heat generating element 273 is turned on,

and the second detection temperature Ht2 that is additionally detected may be

the highest temperature in the state in which the heat generating element 273

is turned off.

[164] Next, in step S27, it is determined whether a temperature stabilization

state has been achieved.

[165] Here, the temperature stabilization state may mean a state in which

internal refrigerator load does not occur, that is, a state in which the cooling of

the storage compartment is normally performed. In other words, the fact that

the temperature stabilization state is made may mean that the opening/closing

of a refrigerator door is not performed or there are no defects in components

(e.g., a compressor and an evaporator) for cooling the storage compartment

or the sensor 270.

[166] That is, the sensor 270 may accurately detect the amount of frost on

the evaporator 30 by determining whether or not temperature stabilization has

been achieved.

[167] In the present embodiment, in order to determine the temperature

stabilization state is achieved, it is possible to determine the amount of change

in the temperature of the freezing compartment for a predetermined period of

time. Alternatively, in order to determine the temperature stabilization state is

achieved, it is possible to determine the amount of change in the temperature

of the evaporator 30 for a predetermined period of time.

[168] For example, a state in which the amount of change in temperature of

the freezing compartment or in temperature of the evaporator 30 during the

predetermined period of time does not exceed 1.5 degrees may be defined as

the temperature stabilization state.

[169] As described above, the temperature Htof the heat generating element

may rapidly decrease immediately after the heat generating element 273 is

turned off, and then the temperature Ht of the heat generating element may

gradually decrease. Here, it is possible to determine whether temperature

stabilization has been achieved by determining whether the temperature Ht of

the heat generating element decreases normally after decreasing rapidly.

[170] When the temperature stabilization state is achieved, in step S28, the

temperature difference AHt between the temperature Htl detected when the

heat generating element 273 is turned on and the temperature Ht2 detected

when the heat generating element 273 is turned off may be calculated.

[171] In step S29, it is determined whether the temperature difference AHt is

less than a first reference temperature value.

[172] Specifically, when the amount of frost on the evaporator 30 is large, the

flow rate of the air flowing into the bypass passage 230 increases, and thus

the amount of cooling for the heat generating element 273 by air flowing through the bypass passage 230 may increase. When the amount of cooling increases, the temperature Ht2 of the heat generating element detected immediately after the heat generating element 273 is turned off may be relatively low compared to a case where the amount of frost on the evaporator

30 is small.

[173] As a result, when the amount of frost on the evaporator 30 is large, the

temperature difference AHt may be small. Accordingly, it is possible to

determine the amount of frost on the evaporator 30 through the temperature

difference AHt. Here, the first reference temperature value may be 32 degrees,

for example.

[174] Next, when the temperature difference AHtis less than the first

reference temperature value, in step S30, a defrosting operation is performed.

[175] When the defrosting operation is performed, the defrosting device 50 is

driven and heat generated by the heater is transferred to the evaporator 30 so

that the frost generated on the surface of the evaporator 30 is melted.

[176] On the other hand, instep S27, when the temperature stabilization state

is not achieved or, in step S29, when the temperature difference AHt is greater

than or equal to the first reference temperature value, the algorithm ends

without performing the defrosting operation.

[177] In the present embodiment, the temperature difference AHt may be

defined as a "logic temperature" for detection of frosting. The logic temperature

may be used as a temperature for determining a time point for a defrosting

operation of the refrigerator, and may be used as a temperature for

determining a time point at which the heat generating element 273 is turned

on, which is to be described later.

[178] FIG. 12 is a flow chart showing a control method for determining an

operating time point of a heat generating element according to an embodiment

of the present disclosure. The present embodiment may be understood as a

control method for determining a time point (step S21) at which the heat

generating element 373 is turned on in FIG. 10.

[179] Referring to FIGS. 11 and 12 together, in step S31, the heat generating

element 27 may be turned off. Here, step S31 may mean step S25 of FIG. 10

described above. That is, the present embodiment may be understood as a

control method after step S25.

[180] When the heat generating element 27 is turned off, in step S32, it is

determined whether the logic temperature AHt is less than a second reference

temperature value.

[181] The reason why it is determined whether the logic temperature AHt is

less than the second reference temperature value may be to detect the amount

of frost on the evaporator 30.

[182] For example, the second reference temperature value may be 35

degrees.

[183] Specifically, in FIG. 10, it has been described that the first reference

temperature value for performing the defrosting operation is 32 degrees. In this

case, the second reference temperature value may be set to be greater than

the first reference temperature value. That is, even when the defrosting

operation is completed, the amount of frost on the evaporator 30 may be large,

and therefore, the amount of frost on the evaporator 30 may be detected again.

[184] When the logic temperature AHt is less than the second reference

temperature value, in step S33, it is determined whether the accumulated operation time of the freezing compartment has reached the second reference time. Here, the second reference time may be 1 hour, for example.

[185] Next, when the logic temperature AHt is less than the second reference

temperature value, it may be determined whether the blowing fan 70 is being

driven in step S34.

[186] When the blowing fan 70 is driven, it is determined whether the

temperature stabilization state is achieved in step S35, and when temperature

stabilization state is achieved, the heat generating element 273 is turned on in

step S36.

[187] Here, the temperature stabilization state may mean a state in which

internal refrigerator load does not occur or a state in which the cooling of the

storage compartment is normally performed. In other words, the fact that the

temperature stabilization state is made may mean that the opening/closing of

a refrigerator door is not performed or there are no defects in components (e.g.,

a compressor and an evaporator) for cooling the storage compartment or the

sensor270.

[188] In the present embodiment, in order to determine the temperature

stabilization state, the heat generating element 273 may be turned on/off at a

predetermined time interval. For example, in the process of determining the

temperature stabilization state, the heat generating element 273 may be

turned on/off at the predetermined time interval. In this case, a time point when

the heat generating element 273 is turned on/off to determine the temperature

stabilization state may be a time point when the blowing fan 70 is turned on

(SO).

[189] That is, the heat generating element 273 may be turned on/off at the

predetermined time interval immediately after the blowing fan 70 is turned on.

For example, when the blowing fan 70 is driven, the heat generating element

273 may be repeatedly turned on/off every 10 seconds.

[190] In addition, it is determined whether the detected amount of

temperature change in the temperature change amount of the temperature (Ft)

of the freezing compartment and the temperature (Ht) of the heat generating

element is less than a third reference temperature value by detecting the

amount of temperature change in the temperature (Ft) of the freezing

compartment or in the temperature (Ht) of the heat generating element during

a predetermined period. For example, the third reference temperature value is

not limited thereto, but may be 0.5 degrees.

[191] As shown in FIG. 11, since the blowing fan 70 is being driven, the

temperature Ft of the freezing compartment may gradually decrease. In

addition, the temperature Ht of the heat generating element may increase by

a certain amount by turning on/off the heat generating element 273.

[192] In the present embodiment, a case in which the detected amount of

change in the temperature (Ft) of the freezing compartment and the detected

amount of change in the temperature (Ht) of the heat generating element are

less than the third reference temperature value may be determined to be the

temperature stabilization state.

[193] On the other hand, in step S32, when the logic temperature is equal to

or higher than the second reference temperature value, or in step S33, when

the accumulated operation time does not reach the second reference time, the

process returns to step S31.

[194] Further, in step S34, when the blowing fan is not driven, or in step 35,

when the temperature stabilization state is not achieved, the process returns

to step S31.

[195] Meanwhile, in the present embodiment, it is described that the amount

of frost on the evaporator 30 is detected based on a temperature difference

between the first detection temperature Htl detected in the state in which the

heat generating element 273 is turned on and the second detection

temperature Ht2 detected in the state in which the heat generating element

273 is turned off.

[196] However, alternatively, the temperature of the heat generating element

may be detected in the state in which the heat generating element 273 is

turned on. The amount of frost on the evaporator 30 may be detected based

on the temperature difference between the first detection temperature (Htl)

which is the lowest value of the detection temperatures of the heat generating

element and the second detection temperature (Ht2) which is the highest value

of the detection temperatures of the heat generating element.

[197] That is, it is possible to detect the amount of frost on the evaporator 30

through the detection temperatures Htl and Ht2 in the state in which the heat

generating element 273 is turned on, without detecting the temperature of the

heat generating element in the state in which the heat generating element 273

is turned off.

[198] According to the method of controlling a refrigerator, the time point at

which defrosting is necessary may be accurately determined using a sensor

having an output value which varies depending on the amount of frost on the

evaporator in the bypass passage. Accordingly, when the amount of frost is large, a rapid defrosting operation is possible, and when the amount of frost is small, a phenomenon in which defrosting starts is prevented.

[199] Although embodiments have been described with reference to a

number of illustrative embodiments thereof, it will be understood by those

skilled in the art that various changes in form and details may be made therein

without departing from the spirit and scope of the invention as defined by the

appended claims. Therefore, the preferred embodiments should be considered

in a descriptive sense only and not for purposes of limitation, and also the

technical scope of the invention is not limited to the embodiments. Furthermore,

the present invention is defined not by the detailed description of the invention

but by the appended claims, and all differences within the scope will be

construed as being comprised in the present disclosure.

[200] Many modifications will be apparent to those skilled in the art without

departing from the scope of the present invention as herein described with

reference to the accompanying drawings.

Claims

1. A method for controlling a refrigerator, the method comprising:

turning on a heat generating element of a sensor unit in response to a sensed

change in a flow rate of air turning off the heat generating element after a

predetermined period of time;

sensing a first temperature (Htl) of the heat generating element in a turned on

state and a second temperature (Ht2) of the heat generating element in a turned off

state;

sensing an amount of frost on an evaporator based on a temperature difference

between the first temperature (Htl) and the second temperature (Ht2); and

performing a defrost operation of removing frost generated on a surface of the

evaporator when it is determined that the temperature difference value between the

first detection temperature (Htl) and the second detection temperature (Ht2) is less

than a first reference difference value.

2. The method of claim 1, wherein the first temperature (Htl) is a temperature

sensed by a sensing element of the sensor unit immediately after the heat generating

element is turned on, or the second temperature (Ht2) is a temperature sensed by a

sensing element of the sensor unit immediately after the heat generating element is

turned off.

3. The method of claim 1, wherein the refrigerator comprises: a cool air duct

configured to define a heat-exchange space to receive an evaporator, and a bypass

passage configured to allow air flow to bypass the evaporator, and wherein the bypass passage is disposed to be recessed in the cool air duct.

4. The method of claim 3, wherein the refrigerator further comprises a passage

cover configured to partition the bypass passage from the heat exchange space.

5. The method of claim 1, wherein the first temperature (Htl) is a lowest

temperature value during a period of time when the heat generating element is turned

on, or

the second temperature (Ht2) is a highest temperature value after the heat

generating element is turned off.

6. The method of claim 4, wherein the sensor is spaced apart from the passage

cover .

7. The method of claim 1, wherein the heat generating element is turned on

while a storage compartment of the refrigerator is being cooled.

8. The method of claim 1, wherein the heat generating element is turned on

while a blowing fan for cooling a storage compartment of the refrigerator is being driven.

9. The method of claim 1, further comprising:

determining whether a temperature difference between the first temperature

(Htl) and the second temperature (Ht2) is less than a second reference difference

value when the heat generating element is turned on for the predetermined period of

time and then turned off, wherein the heat generating element is turned on according to whether a temperature difference between the first temperature (Htl) and the second temperature (Ht2) is less than a second reference difference value.

10. The method of claim 9, wherein the heat generating element is turned on

based on an accumulated cooling operation time of the storage compartment when

the temperature difference between the first temperature (Htl) and the second

temperature (Ht2) is less than the second reference difference value.

11. The method of claim 1, further comprising:

turning on the heat generating element based on an accumulated cooling

operation time of a storage compartment of the refrigerator when the heat generating

element is turned on for the predetermined period of time and then turned off.

12. A method for controlling a refrigerator comprising:

operating for a predetermined period of time a heat generating element of a

sensor unit in response to a change in a flow rate of air;

sensing a plurality of temperatures of the heat generating element when the

heat generating element is turned on;

sensing an amount of frost on an evaporator based on a temperature difference

between a first temperature (Htl) that is a lowest value and a second temperature

(Ht2) that is a highest value among the sensed plurality of temperatures of the heat

generating element; and

performing a defrost operation of removing frost generated on a surface of the

evaporator when it is determined that the temperature difference value between the first detection temperature (Htl) and the second detection temperature (Ht2) is less than a first reference difference value.

13. The method of claim 12, wherein refrigerator further comprises a cool air

duct configured to define a heat-exchange space to receive an evaporator, a bypass

passage configured to allow air flow to bypass the evaporator and in which the sensor

is received, and a bypass cover configured to partition the bypass passage from the

heat exchange space.

14. The method of claim 12, wherein the heat generating element is turned on

while a storage compartment of the refrigerator is being cooled.

15. The method of claim 12, wherein the heat generating element is turned on

16. A refrigerator, comprising:

an inner case defining a storage space;

a cooling duct configured to guide flow of air to the storage space;

a heat exchange space defined between the inner case and the cooling duct;

an evaporator disposed in the heat exchange space;

a bypass passage disposed to be recessed in the cool air duct and configured

to allow air flow to bypass the evaporator;

a sensor unit disposed in the bypass passage and including a heat generating

element disposed and a sensing element configured to sense a plurality of

temperatures of the heat generating element; and a controller configured to sense an amount of frost on an evaporator based on a temperature difference between a first temperature (Htl) of the heat generating element sensed in a turned on state and a second temperature (Ht2) of the heat generating element sensed in a turned off state.

17. The refrigerator of claim 16, wherein the first temperature (Ht) is a

temperature sensed by the sensing element immediately after the heat generating

element is turned on, or

the second temperature (Ht2) is a temperature sensed by the sensing element

immediately after the heat generating element is turned off.

18. The refrigerator of claim 16, wherein the sensor unit including a sensor

housing to receive the heat generating element and the sensing element such that air

flowing through the bypass passage is prevented from directly contacting the heat

generating element and the sensing element.

19. The refrigerator of claim 16, wherein the refrigerator further comprises a

passage cover configured to partition the bypass passage from the heat exchange

space.

20. The method of claim 16, wherein the first temperature (Htl) is a lowest

on, or

the second temperature (Ht2) is a highest temperature value after the heat

generating element is turned off.