U.S. patent application number 11/259348 was filed with the patent office on 2006-06-08 for defrost apparatus of refrigerator.
Invention is credited to Jung-Wook Bae, Sunghee Kang, Suwon Lee, Jongmin Shin, Deokhyun Youn.
Application Number | 20060117768 11/259348 |
Document ID | / |
Family ID | 36572659 |
Filed Date | 2006-06-08 |
United States Patent
Application |
20060117768 |
Kind Code |
A1 |
Lee; Suwon ; et al. |
June 8, 2006 |
Defrost apparatus of refrigerator
Abstract
The present invention discloses a defrost apparatus of a
refrigerator which can defrost an evaporator by a defrost heater,
when moisture of the ambient air of the evaporator is frozen on the
surface of the evaporator. The defrost apparatus of the
refrigerator includes a pair of evaporators and a pair of defrost
heaters to selectively defrost the pair of evaporators. A path
varying means for guiding air flow is installed near the pair of
evaporators. The air is not supplied to the defrosted evaporator,
for performing the defrosting operation. The air is supplied to the
non-defrosted evaporator, for performing the cooling operation. As
a result, the defrosting operation is efficiently performed, and
the temperature does not sharply increase in freezing and
refrigerating chambers, so that the food can be maintained fresh
for an extended period of time.
Inventors: |
Lee; Suwon; (Changwon-shi,
KR) ; Kang; Sunghee; (Changwon-shi, KR) ; Bae;
Jung-Wook; (Changwon-shi, KR) ; Shin; Jongmin;
(Busan, KR) ; Youn; Deokhyun; (Kimhae-shi,
KR) |
Correspondence
Address: |
FLESHNER & KIM, LLP
P.O. BOX 221200
CHANTILLY
VA
20153
US
|
Family ID: |
36572659 |
Appl. No.: |
11/259348 |
Filed: |
October 27, 2005 |
Current U.S.
Class: |
62/151 ; 62/154;
62/276 |
Current CPC
Class: |
F25D 21/08 20130101;
F25B 2347/021 20130101 |
Class at
Publication: |
062/151 ;
062/154; 062/276 |
International
Class: |
F25D 21/06 20060101
F25D021/06 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 2, 2004 |
KR |
10-2004-0088252 |
Claims
1. A defrost apparatus of a refrigerator, comprising: a
refrigerator main body in which a freezing chamber and a
refrigerating chamber are formed, cool air circulation holes being
formed on a partition wall for separating the freezing chamber from
the refrigerating chamber; a freezing cycle including first and
second evaporators installed on a cool air circulation path on the
inner wall of the freezing chamber, for cooling the air by the heat
exchange operation with refrigerants, and a compressor, a condenser
and expansion means built in one side of the refrigerator main body
to be connected to the first and second evaporators, for
circulating the refrigerants; a ventilation device installed at one
side of the first and second evaporators, for sending the cool air
from the first and second evaporators to the freezing chamber;
temperature sensors installed in the first and second evaporators,
for sensing temperature variations of the first and second
evaporators, respectively; first and second defrost heaters
installed in the first and second evaporators and controlled
according to the sensing values of the temperature sensors, for
defrosting the first and second evaporators, respectively; a
refrigerant distributing means for wholly or selectively
distributing the refrigerants to the first and second evaporators;
a path varying means installed between the first and second
evaporators, for controlling inflow of the cool air to the first
and second evaporators; and a control unit for controlling the
operations of the ventilation device, the first and second defrost
heaters, the refrigerant distributing means and the path varying
means according to the sensing values of the temperature
sensors.
2. The defrost apparatus of claim 1, wherein the expansion means
are first and second capillary tubes connected to the first and
second evaporators, respectively, for decompressing the
refrigerants, and the refrigerant distributing means is a 3-way
valve installed between the condenser and the first and second
capillary tubes.
3. The defrost apparatus of claim 2, wherein the path varying means
comprises a partition wall installed on the cool air circulation
path, for partitioning off the first and second evaporators, and
first and second dampers rotatably installed on the front and rear
ends of the partition wall, for selectively controlling inflow of
the cool air to the first and second evaporators.
4. The defrost apparatus of claim 3, wherein the control unit
operates one of the first and second defrost heaters or stops the
first and second defrost heaters according to the sensing values of
the temperature sensors, and continuously operates the ventilation
device.
5. The defrost apparatus of claim 4, wherein, when the first
defrost heater is operated, the control unit controls the 3-way
valve to supply the refrigerants to the second capillary tube and
the second evaporator, and also controls the first and second
dampers to supply the cool air to the second evaporator.
6. The defrost apparatus of claim 4, wherein, when the second
defrost heater is operated, the control unit controls the 3-way
valve to supply the refrigerants to the first capillary tube and
the first evaporator, and also controls the first and second
dampers to supply the cool air to the first evaporator.
7. The defrost apparatus of claim 4, wherein, when the first and
second defrost heaters are not operated, the control unit controls
the 3-way valve to supply the refrigerants to the first and second
capillary tubes and the first and second evaporators, and also
controls the first and second dampers to supply the cool air to the
first and second evaporators.
8. The defrost apparatus of claim 5, wherein, when the second
defrost heater is operated, the control unit controls the 3-way
valve to supply the refrigerants to the first capillary tube and
the first evaporator, and also controls the first and second
dampers to supply the cool air to the first evaporator.
9. The defrost apparatus of claim 5, wherein, when the first and
second defrost heaters are not operated, the control unit controls
the 3-way valve to supply the refrigerants to the first and second
capillary tubes and the first and second evaporators, and also
controls the first and second dampers to supply the cool air to the
first and second evaporators.
10. The defrost apparatus of claim 6, wherein, when the first and
second defrost heaters are not operated, the control unit controls
the 3-way valve to supply the refrigerants to the first and second
capillary tubes and the first and second evaporators, and also
controls the first and second dampers to supply the cool air to the
first and second evaporators.
Description
TECHNICAL FIELD
[0001] The present invention relates to a defrost apparatus of a
refrigerator which can perform a defrosting operation by using a
defrost heater and controlling inflow of the ambient air, when
moisture of the ambient air of an evaporator is frozen on the
surface of the evaporator.
BACKGROUND ART
[0002] In general, refrigerators are classified into a direct
cooling type refrigerator and an indirect cooling type refrigerator
according to a cooling method. In the direct cooling type
refrigerator, evaporators are installed on inner walls of a
freezing chamber and a refrigerating chamber. The cool air
generated around the evaporators is naturally convected to cool the
freezing chamber and the refrigerating chamber. In the indirect
cooling type refrigerator, an evaporator is installed in inner
walls of a freezing chamber, and a fan is installed on a cool air
circulation path. The cool air generated around the evaporator is
forcibly sent by the fan to cool the freezing chamber and the
refrigerating chamber.
[0003] In the indirect cooling type refrigerator, when the fan is
operated, the air of the freezing chamber and the refrigerating
chamber directly passes through the evaporator, and then is
circulated. Therefore, moisture of the air of the freezing chamber
and the refrigerating chamber is frozen on the surface of the
evaporator, thereby deteriorating the heat exchange performance. In
order to solve the above problem, an electric heater is installed
at the lower portion of the evaporator, for directly defrosting the
surface of the evaporator.
[0004] FIG. 1 is a side-sectional view illustrating a conventional
defrost apparatus of a refrigerator, and FIG. 2 is a graph showing
a temperature inside the refrigerator in the operation of the
conventional defrost apparatus of the refrigerator.
[0005] Referring to FIG. 1, in the conventional refrigerator, a
freezing chamber F and a refrigerating chamber R are installed at
upper and lower portions of a front surface of a refrigerator main
body 2a and 2b, a freezing chamber door 4a and a refrigerating
chamber door 4b are installed to be opened and closed on the front
surface of the refrigerator main body 2a and 2b, an evaporator 10
is installed on the space formed on the inner wall of the freezing
chamber F, a freezing cycle including the evaporator 10 is
installed at one side of the refrigerator main body 2a and 2b, and
a ventilation fan 12 and a motor 14 are installed at the upper
portion of the evaporator 10, for sending the cool air to the
freezing chamber F and the refrigerating chamber R.
[0006] Here, the refrigerator main body 2a and 2b includes an
insulation material (not shown) between an outer casing 2a and an
inner casing 2b. A compressor 6, a condenser 8 and a capillary tube
(not shown) connected to the evaporator 10 through refrigerant
tubes are built in a mechanical chamber formed at the lower portion
of the refrigerator main body 2a and 2b. The evaporator 10 is built
in the inner casing 2b of the freezing chamber F, and a drain tube
(not shown) for guiding condensed water formed on the surface of
the evaporator 10 and a drain fan (not shown) for collecting the
condensed water are installed at the lower portion of the condenser
8.
[0007] A cool air circulation path is formed inside the inner
casing 2b of the refrigerating chamber R and a plurality of cool
air distribution holes 2h are formed in the inner casing 2b of the
refrigerating chamber R, so that the cool air heat-exchanged in the
evaporator 10 can be circulated in the refrigerating chamber R as
well as the freezing chamber F.
[0008] A temperature sensor (not shown) and a defrost heater 20 are
installed at one side of the evaporator 10. Even if moisture of the
air passing through the evaporator 10 is frozen on the surface of
the evaporator 10, frost formation is sensed by the temperature
sensor and the evaporator 10 is defrosted by the defrost heater
20.
[0009] The components such as the compressor 6 and the motor 14 are
connected to and controlled by a control unit (not shown).
[0010] Accordingly, when the control unit operates the compressor 6
and the motor 14, the refrigerants are circulated through the
compressor 6, the condenser 8, the capillary tube and the
evaporator 10, and exchange heat with the ambient air of the
evaporator 10, thereby generating the cool air. When the
ventilation fan 12 is rotated, the cool air is sent to the freezing
chamber F and the refrigerating chamber R in order to perform the
freezing and refrigerating operations.
[0011] On the other hand, when the control unit senses frost
formation on the surface of the evaporator 10 by the temperature
sensor, the control unit stops the operations of the compressor 6
and the ventilation fan 12, and operates the defrost heater 20 to
defrost the evaporator 10. When the surface of the evaporator 10 is
defrosted, the control unit resumes the freezing and refrigerating
operations.
[0012] However, the conventional defrost apparatus of the
refrigerator includes the defrost heater 20 adjacently to the
evaporator 10 so as to defrost the surface of the evaporator 10. As
illustrated in FIG. 2, while the defrost heater 20 is operated, the
air heated along the opened cool air circulation path is circulated
to cause a heat shock sharply increasing the temperature of the
freezing chamber F. It is thus difficult to maintain the food
fresh.
[0013] To solve the foregoing problem, as disclosed under Japanese
Laid-Open Patent Application 9-33157, an evaporator is partitioned
off by a center partition plate, and thermostats and heaters
corresponding to each area of the evaporator are installed at the
upper and lower portions thereof. The heaters are individually
operated to partially defrost the evaporator.
[0014] However, in the conventional defrost apparatus, when the two
heaters are installed in each area of the evaporator, even if the
partition is installed to partition the two heaters and each area
of the evaporator, the air paths are linked at the top and bottom
ends of the evaporator. Accordingly, the air passing through the
defrosted portion of the evaporator and the air passing through the
non-defrosted portion of the evaporator are mixed and supplied to
the freezing chamber F, to increase the temperature of the freezing
chamber F.
[0015] In addition, in the conventional defrost apparatus, one
evaporator formed by installing a plurality of fins on one
refrigerant tube is partitioned off by the partition, and the
defrost heaters are installed in each area of the evaporator. Even
if heat is applied to one side evaporator of the partition, heat is
transmitted to the other side evaporator through the refrigerant
tube and the plurality of fins, thereby performing the defrosting
operation at a time. The heat transmitted to the whole evaporator
heats the ambient air and supplies the heated air to the freezing
chamber F, thereby increasing the temperature of the freezing
chamber F. As a result, the food cannot be maintained fresh for an
extended period of time.
DISCLOSURE OF THE INVENTION
[0016] The present invention is achieved to solve the above
problems. An object of the present invention is to provide a
defrost apparatus of a refrigerator which can prevent temperature
rise in a whole freezing chamber by locally defrosting two
evaporators individually installed on the inner wall of the
freezing chamber by heaters corresponding to the evaporators.
[0017] Another object of the present invention is to provide a
defrost apparatus of a refrigerator which can prevent temperature
rise in a freezing chamber by selectively forming air guiding
paths, even if two evaporators installed on the inner wall of the
freezing chamber are defrosted by heaters corresponding to the
evaporators.
[0018] In order to achieve the above-described objects of the
invention, there is provided a defrost apparatus of a refrigerator,
including: a refrigerator main body in which a freezing chamber and
a refrigerating chamber are formed, cool air circulation holes
being formed on a partition wall for separating the freezing
chamber from the refrigerating chamber; a freezing cycle including
first and second evaporators installed on a cool air circulation
path on the inner wall of the freezing chamber, for cooling the air
by the heat exchange operation with refrigerants, and a compressor,
a condenser and expansion means built in one side of the
refrigerator main body to be connected to the first and second
evaporators, for circulating the refrigerants; a ventilation device
installed at one side of the first and second evaporators, for
sending the cool air from the first and second evaporators to the
freezing chamber; temperature sensors installed in the first and
second evaporators, for sensing temperature variations of the first
and second evaporators, respectively; first and second defrost
heaters installed in the first and second evaporators and
controlled according to the sensing values of the temperature
sensors, for defrosting the first and second evaporators,
respectively; a refrigerant distributing means for wholly or
selectively distributing the refrigerants to the first and second
evaporators; a path varying means installed between the first and
second evaporators, for controlling inflow of the cool air to the
first and second evaporators; and a control unit for controlling
the operations of the ventilation device, the first and second
defrost heaters, the refrigerant distributing means and the path
varying means according to the sensing values of the temperature
sensors.
[0019] Preferably, the expansion means are first and second
capillary tubes connected to the first and second evaporators,
respectively, for decompressing the refrigerants, and the
refrigerant distributing means is a 3-way valve installed between
the condenser and the first and second capillary tubes.
[0020] Preferably, the path varying means includes a partition wall
installed on the cool air circulation path, for partitioning off
the first and second evaporators, and first and second dampers
rotatably installed on the front and rear ends of the partition
wall, for selectively controlling inflow of the cool air to the
first and second evaporators.
[0021] Preferably, the control unit operates one of the first and
second defrost heaters or stops the first and second defrost
heaters according to the sensing values of the temperature sensors,
and continuously operates the ventilation device.
[0022] More preferably, when the first defrost heater is operated,
the control unit controls the 3-way valve to supply the
refrigerants to the second capillary tube and the second
evaporator, and also controls the first and second dampers to
supply the cool air to the second evaporator. Conversely, when the
second defrost heater is operated, the control unit controls the
3-way valve to supply the refrigerants to the first capillary tube
and the first evaporator, and also controls the first and second
dampers to supply the cool air to the first evaporator.
[0023] Preferably, when the first and second defrost heaters are
not operated, the control unit controls the 3-way valve to supply
the refrigerants to the first and second capillary tubes and the
first and second evaporators, and also controls the first and
second dampers to supply the cool air to the first and second
evaporators.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The present invention will become better understood with
reference to the accompanying drawings which are given only by way
of illustration and thus are not limitative of the present
invention, wherein;
[0025] FIG. 1 is a side-sectional view illustrating a conventional
defrost apparatus of a refrigerator;
[0026] FIG. 2 is a graph showing a temperature inside the
refrigerator in the operation of the conventional defrost apparatus
of the refrigerator;
[0027] FIG. 3 is a partially-cut front view illustrating a
refrigerator main body to which a defrost apparatus is applied in
accordance with the present invention;
[0028] FIG. 4 is a structure view illustrating a freezing cycle of
the refrigerator using the defrost apparatus in accordance with the
present invention;
[0029] FIG. 5 is a block diagram illustrating control flow of the
defrost apparatus of the refrigerator in accordance with the
present invention; and
[0030] FIGS. 6a and 6b are structure views illustrating refrigerant
flow and air flow in the defrosting operation in the freezing cycle
of the refrigerator using the defrost apparatus in accordance with
the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0031] A defrost apparatus of a refrigerator in accordance with the
present invention will now be described in detail with reference to
the accompanying drawings.
[0032] Referring to FIGS. 3 and 5, in the refrigerator, a freezing
chamber F and a refrigerating chamber R are formed at both sides of
a refrigerator main body 52 having its front surface opened, a cool
air circulation path A is formed on the inner wall of the freezing
chamber F, first and second evaporators 68a and 68b and a
ventilation device are installed on the cool air circulation path A
of the freezing chamber F, and the freezing cycle except the first
and second evaporators 68a and 68b is installed in a space formed
at one side of the freezing chamber F and/or the refrigerating
chamber R. When the freezing cycle and the ventilation device are
driven, the cool air is supplied to the freezing chamber F and the
refrigerating chamber R. First and second temperature sensors 69a
and 69b and first and second defrost heaters 72a and 72b are
installed at the upper and lower portions of the first and second
evaporators 68a and 68b in order to rapidly sense and defrost the
frost-formed surfaces of the first and second evaporators 68a and
68b. A path varying means is further installed to guide flow of the
ambient air of the first and second evaporators 68a and 68b by the
operations of the first and second defrost heaters 72a and 72b. A
control unit 90 controls the operations of the components including
the path varying means.
[0033] A partition wall 54 is formed long in the up/down
longitudinal direction in the refrigerator main body 52 having its
front surface opened. The freezing chamber F and the refrigerating
chamber R are formed side by side at both sides of the partition
wall 54. The first and second evaporators 68a and 68b are installed
side by side on the cool air circulation path A on the inner wall
of the freezing chamber F, and cool air discharge holes 52h for
discharging the cool air generated around the first and second
evaporators 68a and 68b are formed thereon.
[0034] Here, an inflow path 54a for supplying the cool air of the
freezing chamber F to the refrigerating chamber R and a recovering
path 54b for recovering the cool air of the refrigerating chamber R
to the cool air circulation path A of the freezing chamber F are
formed on the partition wall 54. Preferably, the inflow path 54a
and the recovering path 54b are formed at the upper and lower
portions of the partition wall 54, respectively, so that the cool
air supplied to the refrigerating chamber R through the inflow path
54a can be circulated in the refrigerating chamber R and
recovered.
[0035] The freezing cycle includes a compressor 62, a condenser 64,
expansion means 66a and 66b and the first and second evaporators
68a and 68b connected to each other through refrigerant tubes, so
that the refrigerants can be compressed, condensed, evaporated and
expanded during the circulation to perform the cooling operation.
The expansion means 66a and 66b can be comprised of first and
second electronic expansion valves for controlling decompression of
refrigerants, but are comprised of generally-used first and second
capillary tubes 66a and 66b. The first and second capillary tubes
66a and 66b are connected to the first and second evaporators 68a
and 68b, respectively.
[0036] The decompression degree of the first and second capillary
tubes 66a and 66b is determined in proportion to the capacity of
the first and second evaporators 68a and 68b. The diameter and
length of the first and second capillary tubes 66a and 66b are
determined according to the decompression degree. Here, when the
decompression degree of the first and second capillary tubes 66a
and 66b increases, the diameter thereof is narrowed and the length
thereof is lengthened.
[0037] A refrigerant distributing means for wholly or selectively
distributing the refrigerants to the first and second evaporators
68a and 68b by controlling the inflow direction of the refrigerants
is installed between the condenser 64 and the first and second
capillary tubes 66a and 66b. Preferably, a 3-way valve 65 is used
as the refrigerant distributing means. The 3-way valve 65 is
installed at the branch point of the refrigerant tubes between the
condenser 64 and the first and second capillary tubes 66a and
66b.
[0038] The ventilation device is fixedly installed on the cool air
circulation path A to be positioned over the first and second
evaporators 68a and 68b. The ventilation device includes a
ventilation fan 70 and a motor to send the cool air. When the
ventilation fan 70 is operated, the cool air passing through the
first and second evaporators 68a and 68b is forcibly sent and
discharged through the cool air discharge holes 52h.
[0039] The ventilation device can be comprised of a pair of
ventilation fans and motors installed at the upper portions of the
first and second evaporators 68a and 68b, respectively.
[0040] The first and second temperature sensors 69a and 69b are
installed at the upper portions of the first and second evaporators
68a and 68b, for sensing the temperature of the surfaces of the
first and second evaporators 68a and 68b, respectively. The
temperature and the temperature variations are inputted to the
control unit 90. The control unit 90 controls the operations of
each component.
[0041] Here, the sensing values of the first and second temperature
sensors 69a and 69b are inputted to the control unit 90. The
control unit 90 decides whether frost has been formed on the first
and second evaporators 68a and 68b according to the sensing value
variations of the first and second temperature sensors 69a and 69b
and the refrigerant supply to the first and second evaporators 68a
and 68b. Even if the refrigerants are supplied to the first and
second evaporators 68a and 68b, if the sensing values of the first
and second temperature sensors 69a and 69b are over a predetermined
temperature, the control unit 90 decides that frost has been formed
on the first and second evaporators 68a and 68b.
[0042] The first and second defrost heaters 72a and 72b are
electric heaters installed at the lower portions of the first and
second evaporators 68a and 68b for defrosting the surfaces of the
first and second evaporators 68a and 68b, respectively. The
operations of the first and second defrost heaters 72a and 72b are
controlled by the control unit 90 according to the sensing values
from the first and second temperature sensors 69a and 69b.
[0043] The first and second defrost heaters 72a and 72b are not
operated at the same time but selectively operated. Preferably, the
capacity of the first and second defrost heaters 72a and 72b is
determined in proportion to the capacity of the first and second
evaporators 68a and 68b.
[0044] The path varying means includes a partition wall 82 for
partitioning off the first and second evaporators 68a and 68b side
by side on the cool air circulation path A, and first and second
dampers 84a and 84b rotatably installed at the front and rear ends
of the partition wall 82, for selectively controlling inflow of the
cool air to the first and second evaporators 68a and 68b. The
operations of the first and second dampers 84a and 84b are also
controlled by the control unit 90.
[0045] More components can be used to control the operations of the
first and second dampers 84a and 84b by the control unit 90, but
detailed explanations thereof are omitted.
[0046] In the freezing and refrigerating operations, the control
unit 90 senses the temperature of the freezing chamber F and the
temperature of the refrigerating chamber R, and controls the
operations of each component. However, in the defrosting operation,
the control unit 90 controls the operations of the first and second
defrost heaters 72a and 72b, the first and second dampers 84a and
84b and the 3-way valve 65 according to the temperature values of
the first and second temperature sensors 69a and 69b.
[0047] In the freezing and refrigerating operations, the control
unit 90 wholly opens the 3-way valve 65 and operates the compressor
62 and the ventilation fan 70, so that the refrigerants can pass
through the compressor 62, the condenser 64, the first and second
capillary tubes 66a and 66b and the first and second evaporators
68a and 68b, and that the cool air generated by the heat exchange
operation around the first and second evaporators 68a and 68b can
be supplied to the freezing chamber F and the refrigerating chamber
R.
[0048] Preferably, the first and second dampers 84a and 84b are
positioned in the neutral position, so that the air can flow
through the first and second evaporators 68a and 68b to maximize
the heat exchange area.
[0049] On the other hand, in the defrosting operation, the control
unit 90 decides whether the first and second evaporators 68a and
68b have been defrosted according to the measured temperature
values of the first and second temperature sensors 69a and 69b. In
a state where the ventilation fan 70 is continuously operated, the
first and second evaporators 68a and 68b are sequentially defrosted
one by one, which will now be explained in detail.
[0050] The operation of the defrost apparatus of the refrigerator
in accordance with the present invention will now be described in
detail.
[0051] When the control unit 90 senses frost formation on the
surface of the first evaporator 68a according to the measured
temperature values of the first and second temperature sensors 69a
and 69b, as shown in FIG. 6a, the control unit 90 operates the
first defrost heater 72a, controls the 3-way valve 65 to supply the
refrigerants to the second capillary tube 66b and the second
evaporator 68b, controls the first and second dampers 84a and 84b
to intercept air flow to the first evaporator 68a and open air flow
to the second evaporator 68b, and continuously operates the
ventilation fan 70.
[0052] Accordingly, when the first defrost heater 72a is operated,
the surface of the first evaporator 68a is defrosted. The
refrigerants are circulated through the compressor 62, the
condenser 64, the second capillary tube 66b and the second
evaporator 68b, thereby cooling the ambient air of the second
evaporator 68b. When the ventilation fan 70 is operated, the air is
supplied merely to the second evaporator 68b, and thus the cool air
around the second evaporator 68b is re-supplied to and circulated
in the freezing chamber F. Conversely, the warm air around the
first evaporator 68a is not directly supplied to the freezing
chamber F.
[0053] On the other hand, when the control unit 90 senses frost
formation on the surface of the second evaporator 68b according to
the measured temperature values of the first and second temperature
sensors 69a and 69b, as shown in FIG. 6b, the control unit 90
operates the second defrost heater 72b, controls the 3-way valve 65
to supply the refrigerants to the first capillary tube 66a and the
first evaporator 68a, controls the first and second dampers 84a and
84b to intercept air flow to the second evaporator 68b and open air
flow to the first evaporator 68a, and continuously operates the
ventilation fan 70.
[0054] Therefore, when the second defrost heater 72b is operated,
the surface of the second evaporator 68b is defrosted. The
refrigerants are circulated through the compressor 62, the
condenser 64, the first capillary tube 66a and the first evaporator
68a, thereby cooling the ambient air of the first evaporator 68a.
When the ventilation fan 70 is operated, the air is supplied merely
to the first evaporator 68a, and thus the cool air around the first
evaporator 68a is re-supplied to and circulated in the freezing
chamber F. Conversely, the warm air around the second evaporator
68b is not directly supplied to the freezing chamber F.
[0055] When the control unit 90 senses frost formation on the
surfaces of the first and second evaporators 68a and 68b at the
same time according to the measured temperature values of the first
and second temperature sensors 69a and 69b, the control unit 90
sequentially defrosts the first and second evaporators 68a and 68b
in the same manner.
[0056] Although the preferred embodiments of the present invention
have been described, it is understood that the present invention
should not be limited to these preferred embodiments but various
changes and modifications can be made by one skilled in the art
within the spirit and scope of the present invention as hereinafter
claimed.
* * * * *