U.S. patent application number 12/923951 was filed with the patent office on 2011-05-12 for frost detecting apparatus, and cooling system and refrigerator having the same.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Nak Hyun Kim, Tae Gyu Kim, Young Chul Ko, Hyun Suk Kwak.
Application Number | 20110107779 12/923951 |
Document ID | / |
Family ID | 43770590 |
Filed Date | 2011-05-12 |
United States Patent
Application |
20110107779 |
Kind Code |
A1 |
Kwak; Hyun Suk ; et
al. |
May 12, 2011 |
Frost detecting apparatus, and cooling system and refrigerator
having the same
Abstract
A frost detecting apparatus including a first electrode to
generate an electric field in a frost detection region, a second
electrode to prevent the electric field from leaking into a frost
non-detection region, an insulator arranged between the first
electrode and the second electrode, to insulate the first
electrode, and a shield arranged around an exposed portion of the
insulator, to prevent the electric field from leaking into the
frost non-detection region through the exposed portion of the
insulator. As the same potential is established at the first and
second electrodes, it is possible to prevent electric field from
leaking into a frost non-detection region through side surfaces of
the first electrode. Accordingly, the electric field is varied only
by frost formed in a frost detection region, so that it is possible
to more accurately detect formation of frost and the amount of the
formed frost.
Inventors: |
Kwak; Hyun Suk; (Gwangju-si,
KR) ; Ko; Young Chul; (Suwon-si, KR) ; Kim;
Tae Gyu; (Busan, KR) ; Kim; Nak Hyun;
(Suwon-si, KR) |
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Suwon-si
KR
|
Family ID: |
43770590 |
Appl. No.: |
12/923951 |
Filed: |
October 15, 2010 |
Current U.S.
Class: |
62/140 ;
62/515 |
Current CPC
Class: |
F25D 21/02 20130101 |
Class at
Publication: |
62/140 ;
62/515 |
International
Class: |
F25D 21/02 20060101
F25D021/02; F25B 39/02 20060101 F25B039/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 12, 2009 |
KR |
10-2009-109312 |
Claims
1. A frost detecting apparatus comprising: a first electrode to
generate an electric field in a frost detection region; a second
electrode to prevent the electric field from leaking into a frost
non-detection region; an insulator arranged between the first
electrode and the second electrode, to insulate the first
electrode; and a shield arranged around an exposed portion of the
insulator, to prevent the electric field from leaking into the
frost non-detection region through the exposed portion of the
insulator.
2. The frost detecting apparatus according to claim 1, wherein the
shield is electrically connected to the second electrode.
3. The frost detecting apparatus according to claim 2, wherein the
shield surrounds side surfaces of the insulator.
4. The frost detecting apparatus according to claim 3, wherein the
shield extends around side surfaces of the first electrode.
5. The frost detecting apparatus according to claim 2, wherein the
shield is spaced apart from the first electrode such that an
insulating gap is defined between the shield and the first
electrode, to insulate the first electrode.
6. The frost detecting apparatus according to claim 2, wherein the
shield is formed integrally with the second electrode.
7. The frost detecting apparatus according to claim 6, wherein the
second electrode is bent toward the insulator such that at least
one outer portion of the second electrode surrounds the
insulator.
8. The frost detecting apparatus according to claim 1, wherein the
same potential is established at the first and second
electrodes.
9. The frost detecting apparatus according to claim 1, wherein the
same potential is established at the shield and the first
electrode.
10. The frost detecting apparatus according to claim 1, further
comprising: a second insulator formed on an outer surface of the
second electrode.
11. The frost detecting apparatus according to claim 10, wherein an
object, for which detection of frost formation will be performed,
is in contact with an outer surface of the second insulator.
12. The frost detecting apparatus according to claim 1, wherein the
shield prevents the electric field generated in the frost detection
region from varying in spite of a variation in dielectric constant
caused by a variation in ambient temperature around the
insulator.
13. A frost detecting apparatus comprising: a first electrode to
generate an electric field in a frost detection region; a shield
laterally arranged around the first electrode such that the shield
surrounds the first electrode while being insulated from the first
electrode, to prevent the electric field from leaking into a frost
non-detection region through a side surface of the first electrode;
an insulator arranged in contact with a back surface of the first
electrode and a back surface of the shield; and a second electrode
arranged in contact with a back surface of the insulator, to
prevent the electric field from leaking into the frost
non-detection region through the back surface of the first
insulator.
14. The frost detecting apparatus according to claim 13, further
comprising: a conductor to electrically connect the shield and the
second electrode.
15. The frost detecting apparatus according to claim 14, wherein
the conductor extends from the second electrode around the
insulator, to laterally surround the insulator.
16. The frost detecting apparatus according to claim 13, further
comprising: at least one hole extending through the insulator, and
a conductor formed in the hole, wherein the conductor prevents the
electric field from leaking into the frost non-detection region
through at least one of the side surface of the first electrode and
a side surface of the insulator.
17. The frost detecting apparatus according to claim 16, wherein
the at least one hole comprises at least four holes formed along
the side surface of the insulator, and connected to the second
electrode.
18. The frost detecting apparatus according to claim 13, wherein
the same potential is established at the second electrode, the
first electrode, and the shield.
19. The frost detecting apparatus according to claim 13, wherein:
the shield is spaced apart from the first electrode, to define an
insulating gap between the shield and the first electrode; the
first electrode is connected to a sensor terminal; and the second
electrode and the shield are connected to a shield terminal.
20. The frost detecting apparatus according to claim 13, further
comprising: a second insulator formed on a back surface of the
second electrode; and the second insulator insulates the first
electrode, to prevent the first electrode from being eroded by
moisture.
21. The frost detecting apparatus according to claim 14, wherein
the conductor extends from the second electrode such that the
conductor laterally surrounds the insulator.
22. The frost detecting apparatus according to claim 13, wherein
the frost non-detection region is a region where an electric field
generated by the first electrode in an opposite direction to an
electric field generated in the frost detecting region by the first
electrode is established.
23. A frost detecting apparatus comprising: a plate-shaped first
electrode to generate an electric field in a frost detection
region; a plate-shaped first insulator arranged in contact with a
back surface of the first electrode; a plate-shaped second
electrode arranged in contact with the first insulator, to prevent
the electric field from leaking through the back surface of the
first electrode; a plate-shaped second insulator arranged in
contact with a back surface of the second electrode; and a shield
to prevent the electric field from leaking through a side surface
of the first insulator, wherein the shield is formed to laterally
surround the first insulator.
24. The frost detecting apparatus according to claim 23, wherein
the shield extends along side surfaces of the first electrode.
25. The frost detecting apparatus according to claim 23, wherein:
the shield is electrically connected to the second electrode; and
the shield has a plate structure bent to surround the first
insulator and the first electrode.
26. The frost detecting apparatus according to claim 23, wherein
the same potential is established at the shield and the first
electrode.
27. A cooling system comprising an evaporator mounted with a first
cooling fin and a second cooling fin, further comprising: a frost
detecting apparatus comprising a first electrode arranged to face
the first cooling fin, the first electrode generating an electric
field in a region between the first electrode and the first cooling
fin, to detect formation of frost, a first insulator arranged at a
back surface of the first electrode, a second electrode arranged at
a back surface of the first insulator, to prevent the electric
field from leaking toward the second cooling fin, a second
insulator arranged in contact with the second cooling fin, to
insulate the second cooling fin from the second electrode, and a
shield arranged around an exposed portion of the first insulator,
to prevent the electric field from leaking toward the second
cooling fin through the exposed portion of the first insulator.
28. The cooling system according to claim 27, wherein: the shield
extends along side surfaces of the first insulator; and the shield
extends to a lower level than upper ends of the side surfaces of
the first insulator.
29. The cooling system according to claim 27, further comprising: a
detector to detect a voltage corresponding to a variation in the
electric field generated between the first electrode of the frost
detecting apparatus and the first cooling fin; and a controller to
control a defrosting operation, based on the voltage detected by
the detector.
30. The cooling system according to claim 27, wherein the shield
extends to a region surrounding the first electrode above the
exposed portion of the first insulator.
31. The cooling system according to claim 27, further comprising: a
voltage supplier to supply the same voltage to the first and second
electrodes, thereby establishing the same potential at the first
and second electrodes, wherein the first electrode is connected to
a sensor terminal, and the second electrode is connected to a
shield terminal.
32. The cooling system according to claim 27, wherein the frost
detecting apparatus has a U-shaped structure having bent portions,
so as to be attached to the second cooling fin facing the first
cooling fin.
33. The cooling system according to claim 27, wherein the frost
detecting apparatus has a double structure comprising two frost
detecting units each having the same structure as the frost
detecting apparatus, the second insulators of the frost detecting
units being in contact with each other.
34. The cooling system according to claim 33, further comprising: a
detector to detect a voltage corresponding to a variation in the
electric field generated between the first electrode of the frost
detecting apparatus and the first cooling fin; and a controller to
control a defrosting operation, based on the voltage detected by
the detector, wherein the controller receives, from the detector,
voltages respectively corresponding to capacitances generated in
the frost detecting units, sums the voltages, and controls the
defrosting operation, based on the summed voltage.
35. The cooling system according to claim 27, wherein the shield is
electrically connected to the second electrode.
36. The cooling system according to claim 35, wherein the shield
comprises a plurality of holes extending through the first
insulator, and a conductor formed in each of the holes, so as to
electrically connect the shield to the second electrode via the
conductor.
37. The cooling system according to claim 36, wherein the shield
extends to a level equal to a level of upper ends of side surfaces
of the first electrode, and is spaced apart from the first
electrode such that a gap is defined between the shield and the
first electrode, to electrically insulate the shield from the first
electrode.
38. The cooling system according to claim 27, wherein the shield
has at least one outer portion bent toward the first cooling fin to
surround at least one side surface of the first insulator.
39. The cooling system according to claim 38, wherein: the shield
extends to a level equal to a level of upper ends of side surfaces
of the first electrode; the first insulator insulates the shield
from the first electrode.
40. A refrigerator comprising an evaporator mounted with a first
cooling fin and a second cooling fin, further comprising: a frost
detecting apparatus comprising a first electrode arranged to face
the first cooling fin, the first electrode generating an electric
field, a first insulator arranged at a back surface of the first
electrode, a second electrode arranged at a back surface of the
first insulator, to prevent the electric field from leaking toward
the second cooling fin, a second insulator to insulate the second
cooling fin from the second electrode, a shield arranged around an
outer peripheral surface of the first insulator, to prevent the
electric field from leaking toward the second cooling fin through
the outer peripheral surface of the first insulator, and an
insulating gap to insulate the shield and the first electrode from
each other.
41. The refrigerator according to claim 40, wherein the shield is
formed integrally with the second electrode.
42. The refrigerator according to claim 40, wherein: the shield is
laterally spaced apart from the first electrode; the shield
comprises a plurality of holes extending through the first
insulator; and each of the holes electrically connects the shield
and the second electrode.
43. The refrigerator according to claim 40, wherein the shield
further comprises a conductor formed along side surfaces of the
first insulator, to electrically connect the shield to the second
electrode.
44. The refrigerator according to any one of claims 41, wherein the
shield extends to a level equal to a level of upper ends of side
surfaces of the first electrode.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Patent
Application No. 2009-109312 filed on Nov. 12, 2009 in the Korean
Intellectual Property Office, the disclosures of which are
incorporated herein by reference in its entirety.
BACKGROUND
[0002] 1. Field
[0003] Embodiments relate to a frost detecting apparatus, and a
cooling system and a refrigerator, which have the frost detecting
apparatus, and, more particularly, to a frost detecting apparatus
to detect frost formed on an evaporator due to heat exchange, and a
cooling system and a refrigerator, which have the frost detecting
apparatus.
[0004] 2. Description of the Related Art
[0005] A cooling system is adapted to cool a confined space by
circulating a refrigerant through a refrigeration cycle. As such a
cooling system, there are a refrigerator, a Kimchi refrigerator, an
air conditioner, etc.
[0006] Here, the refrigeration cycle includes four stages to change
the phase of the refrigerant, namely, compression, condensation,
expansion, and vaporization stages. To this end, the cooling system
should include a compressor, a condenser, an expansion valve, and
an evaporator. When a gaseous refrigerant is supplied to the
condenser after being compressed in accordance with operation of a
compressor, the refrigerant, which is in a compressed state, is
cooled as it exchanges heat with air around the condenser. As a
result, the refrigerant is condensed into a liquid phase. The
liquid refrigerant is then injected into the evaporator while being
adjusted in flow rate by the expansion valve. As a result, the
refrigerant is abruptly expanded, so that it is vaporized. As the
refrigerant is vaporized, it absorbs heat from air around the
evaporator, thereby generating cold air. The cold air is supplied
to a confined space such as a storage chamber or a room, thereby
cooling the confined space. The refrigerant, which has been changed
into the gaseous phase in the evaporator, is again introduced into
the compressor, and is then compressed into the liquid phase. Thus,
the above stages of the refrigeration cycle are repeated for the
refrigerant.
[0007] The surface temperature of the evaporator, which functions
to cool a confined space by absorbing heat from the confined space
through the refrigeration cycle, is relatively lower than the
temperature of air present in the confined space. As a result,
moisture condensed from the air in the confined space, which is in
a moisture-rich state, is attached to the surface of the
evaporator, so that frost is formed on the surface of the
evaporator. The frost formed on the surface of the evaporator is
accumulated with passage of time, so that the thickness of the
front is increased. As a result, the heat exchange efficiency of
the cold air flowing around the evaporator is degraded, thereby
causing degradation in cooling efficiency and excessive power
consumption.
[0008] In order to solve such problems, in conventional cases, an
operating time of the compressor is accumulated, and a defrosting
operation is carried out when the accumulated operating time
exceeds a predetermined time. In the defrosting operation, a heater
arranged around the evaporator operates to remove the frost formed
on the evaporator. However, this method is inefficient to remove
the frost formed on the evaporator because the defrosting operation
is carried out based on the operating time of the compressor,
irrespective of the actual amount of the frost formed on the
evaporator.
[0009] To this end, in order to efficiently control operation of a
defrosting heater, there is a conventional frost detecting
apparatus to directly detect the amount of frost formed on an
evaporator. An example of such a conventional frost detecting
apparatus, in particular, a conventional frost detecting apparatus
using an electric field, is disclosed in U.S. Pat. No. 7,466,146.
The configuration of the disclosed frost detecting apparatus is
shown in FIG. 1.
[0010] As shown in FIG. 1, the frost detecting apparatus, which
uses an electric field, includes a first electrode 11 to detect
frost formed between the first electrode 11 and a first cooling fin
21 of an evaporator 20, a first insulator 12 arranged adjacent to
the first electrode 11, a second electrode 13 arranged adjacent to
the first insulator 12, a second cooling fin 22 arranged opposite
the first cooling fin 21, and a second insulator 14 arranged
between the second cooling fin 22 and the second electrode 13, to
insulate the second cooling fin 22 and second electrode 13 from
each other. The first electrode 11 is connected to a sensor
terminal A, whereas the second electrode 13 is connected to a
shield terminal B.
[0011] In the frost detecting apparatus, an electric field is
generated between the first electrode 11 and the first cooling fin
21. When frost is formed between the first cooling fin 21 and the
first electrode 11, the electric field is varied due to the formed
frost. As a result, the dielectric constants of the first cooling
fin 21 and first electrode 11 are varied, so that a variation in
capacitance occurs. The varied capacitance is output in the form of
a voltage through the sensor terminal A. In this case, whether or
not frost has been formed and the amount of the formed frost are
detected based on the voltage output through the sensor terminal
A.
[0012] Upon detecting formation of frost, the same voltage is
supplied to the first electrode 11 and second electrode 13 of the
frost detecting apparatus 10, in order to prevent an electric field
from being generated in a region beneath the first electrode 11
(namely, a frost non-detection region).
[0013] However, an electric field is inevitably formed between the
first electrode 11 and the second electrode 13. This electric field
is partially applied to the second cooling fin 22 via corners of
the first electrode 11. That is, the distance between the first
electrode 11 and the second cooling fin 22 is shorter than the
distance between the first electrode 11 and the first cooling fin
21 because the thickness of the frost detecting apparatus 10 is
small, so that a great portion of the electric field is applied
from the corners of the first electrode 11 to the second cooling
fin 22. Since the region arranged toward the second cooling fin 22
with respect to the first electrode 11 is not the frost detection
region, the electric field established at the side of the second
cooling fin 22 functions as a signal other than a frost detection
signal, namely, noise.
[0014] The temperature of the evaporator may be abruptly varied in
accordance with the operating time of the compressor. In this case,
the dielectric constant of the first insulator 12 may be varied, so
that the electric field, which is applied from the first electrode
11 to the second cooling fin 22 via the first insulator 12, may be
varied. As a result, the electric field, which is applied from the
first electrode 11 to the second cooling fin 22, may be also
varied. To this end, it is necessary to take into consideration a
variation in the electric field of the first electrode 11 depending
on the temperature variation of the first insulator 12, upon
detecting formation of frost using the frost detecting apparatus.
This will be described with reference to FIGS. 2 and 3.
[0015] FIG. 2 is a graph depicting a variation in dielectric
constant according to a variation in the temperature of the first
insulator 12 in association with various composition ratios
(content ratios of epoxy (a) and silicon (b)) of the first
insulator 12. Referring to FIG. 2, it may be seen that, in
association with silicon (b), a dielectric constant variation of
0.5 or more is exhibited when the ambient temperature of the frost
detecting apparatus ranges between 70 to -30.degree. C.
[0016] FIG. 3A is a graph depicting a variation in noise value
exhibited according to a decrease in temperature from room
temperature to -23.degree. C. under the condition that there is no
artificial humidification after installation of the frost detecting
apparatus at a cooling fin of an evaporator in a refrigerator. In
detail, FIG. 3A is a graph depicting temperature variations of the
evaporator and frost detecting apparatus depending on the driving
time of a compressor. FIG. 3B is a graph depicting a variation in
output voltage according to a variation in the dielectric constant
of the first insulator 12 depending on the driving time of the
compressor.
[0017] As shown in FIG. 3A, the output voltage of the frost
detecting apparatus 10, which initially has a value of 2.491V, is
increased to 2.499V due to an abrupt temperature variation for
about 60 seconds. Referring to FIG. 3A, it may be seen that, due to
the temperature variation for about 60 seconds, the output voltage
is varied by 0.008V (Namely, the output voltage becomes noise.). As
the temperature is stabilized, the output voltage becomes
constant.
[0018] That is, when it is assumed that the output voltage
variation caused by formation of frost is 0.025V, there may be an
error of about 30% unless the noise value of 0.008V generated due
to the temperature variation is compensated for.
[0019] To this end, it may be necessary to attach a separate
temperature sensor to the evaporator, in order to achieve
temperature compensation according to variation in ambient
temperature of the frost detecting apparatus.
[0020] As frost is formed on the evaporator, the capacitance
established between the frost detecting apparatus and the cooling
fin is increase. In this case, the output voltage must be
decreased. However, an increase in output voltage occurs due to
output noise caused by a decrease in temperature. In order to
accurately compensate for this error, it may be necessary to
accurately detect the dielectric constant of the insulator varied
in accordance with a variation in temperature. It may also be
necessary to take into consideration a deviation occurring during
manufacture of the frost detecting apparatus.
SUMMARY
[0021] In accordance with one aspect, a frost detecting apparatus
includes a first electrode to generate an electric field in a frost
detection region, a second electrode to prevent the electric field
from leaking into a frost non-detection region, an insulator
arranged between the first electrode and the second electrode, to
insulate the first electrode, and a shield arranged around an
exposed portion of the insulator, to prevent the electric field
from leaking into the frost non-detection region through the
exposed portion of the insulator.
[0022] The shield may be electrically connected to the second
electrode.
[0023] The shield may surround side surfaces of the insulator.
[0024] The shield may extend around side surfaces of the first
electrode.
[0025] The shield may be spaced apart from the first electrode such
that an insulating gap is defined between the shield and the first
electrode, to insulate the first electrode.
[0026] The shield may be formed integrally with the second
electrode.
[0027] The second electrode may be bent toward the insulator such
that at least one outer portion of the second electrode surrounds
the insulator.
[0028] The same potential may be established at the first and
second electrodes.
[0029] The same potential may be established at the shield and the
first electrode.
[0030] The frost detecting apparatus may further include a second
insulator formed on an outer surface of the second electrode.
[0031] An object, for which detection of frost formation will be
performed, may be in contact with an outer surface of the second
insulator.
[0032] The shield may prevent the electric field generated in the
frost detection region from varying in spite of a variation in
dielectric constant caused by a variation in ambient temperature
around the insulator.
[0033] In accordance with another aspect, a frost detecting
apparatus includes a first electrode to generate an electric field
in a frost detection region, a shield laterally arranged around the
first electrode such that the shield surrounds the first electrode
while being insulated from the first electrode, to prevent the
electric field from leaking into a frost non-detection region
through a side surface of the first electrode, an insulator
arranged in contact with a back surface of the first electrode and
a back surface of the shield, and a second electrode arranged in
contact with a back surface of the insulator, to prevent the
electric field from leaking into the frost non-detection region
through the back surface of the first insulator.
[0034] The frost detecting apparatus may further include a
conductor to electrically connect the shield and the second
electrode.
[0035] The conductor may extend from the second electrode around
the insulator, to laterally surround the insulator.
[0036] The frost detecting apparatus may further include at least
one hole extending through the insulator, and a conductor formed in
the hole. The conductor may prevent the electric field from leaking
into the frost non-detection region through at least one of the
side surface of the first electrode and a side surface of the
insulator.
[0037] The at least one hole may include at least four holes formed
along the side surface of the insulator, and connected to the
second electrode.
[0038] The same potential may be established at the second
electrode, the first electrode, and the shield.
[0039] The shield may be spaced apart from the first electrode, to
define an insulating gap between the shield and the first
electrode. The first electrode may be connected to a sensor
terminal. The second electrode and the shield may be connected to a
shield terminal.
[0040] The frost detecting apparatus may further include a second
insulator formed on a back surface of the second electrode, and the
second insulator insulates the first electrode, to prevent the
first electrode from being eroded by moisture.
[0041] The conductor may extend from the second electrode such that
the conductor laterally surrounds the insulator.
[0042] The frost non-detection region may be a region where an
electric field generated by the first electrode in an opposite
direction to an electric field generated in the frost detecting
region by the first electrode is established.
[0043] In accordance with another aspect, a frost detecting
apparatus includes a plate-shaped first electrode to generate an
electric field in a frost detection region, a plate-shaped first
insulator arranged in contact with a back surface of the first
electrode, a plate-shaped second electrode arranged in contact with
the first insulator, to prevent the electric field from leaking
through the back surface of the first electrode, a plate-shaped
second insulator arranged in contact with a back surface of the
second electrode, and a shield to prevent the electric field from
leaking through a side surface of the first insulator, wherein the
shield is formed to laterally surround the first insulator.
[0044] The shield may extend along side surfaces of the first
electrode.
[0045] The shield may be electrically connected to the second
electrode. The shield may have a plate structure bent to surround
the first insulator and the first electrode.
[0046] The same potential may be established at the shield and the
first electrode.
[0047] In accordance with another aspect, a cooling system, which
includes an evaporator mounted with a first cooling fin and a
second cooling fin, further includes a frost detecting apparatus
including a first electrode arranged to face the first cooling fin,
the first electrode generating an electric field in a region
between the first electrode and the first cooling fin, to detect
formation of frost, a first insulator arranged at a back surface of
the first electrode, a second electrode arranged at a back surface
of the first insulator, to prevent the electric field from leaking
toward the second cooling fin, a second insulator arranged in
contact with the second cooling fin, to insulate the second cooling
fin from the second electrode, and a shield arranged around an
exposed portion of the first insulator, to prevent the electric
field from leaking toward the second cooling fin through the
exposed portion of the first insulator.
[0048] The shield may extend along side surfaces of the first
insulator. The shield may extend to a lower level than upper ends
of the side surfaces of the first insulator.
[0049] The cooling system may further include a detector to detect
a voltage corresponding to a variation in the electric field
generated between the first electrode of the frost detecting
apparatus and the first cooling fin, and a controller to control a
defrosting operation, based on the voltage detected by the
detector.
[0050] The shield may extend to a region surrounding the first
electrode above the exposed portion of the first insulator.
[0051] The cooling system may further include a voltage supplier to
supply the same voltage to the first and second electrodes, thereby
establishing the same potential at the first and second electrodes.
The first electrode may be connected to a sensor terminal, and the
second electrode is connected to a shield terminal.
[0052] The frost detecting apparatus may have a U-shaped structure
having bent portions, so as to be attached to the second cooling
fin facing the first cooling fin.
[0053] The frost detecting apparatus may have a double structure
including two frost detecting units each having the same structure
as the frost detecting apparatus. The second insulators of the
frost detecting units may be in contact with each other.
[0054] The cooling system may further include a detector to detect
a voltage corresponding to a variation in the electric field
generated between the first electrode of the frost detecting
apparatus and the first cooling fin, and a controller to control a
defrosting operation, based on the voltage detected by the
detector. The controller may receives, from the detector, voltages
respectively corresponding to capacitances generated in the frost
detecting units, may sum the voltages, and may control the
defrosting operation, based on the summed voltage.
[0055] The shield may be electrically connected to the second
electrode.
[0056] The shield may include a plurality of holes extending
through the first insulator, and a conductor formed in each of the
holes, so as to electrically connect the shield to the second
electrode via the conductor.
[0057] The shield may extend to a level equal to a level of upper
ends of side surfaces of the first electrode, and may be spaced
apart from the first electrode such that a gap is defined between
the shield and the first electrode, to electrically insulate the
shield from the first electrode.
[0058] The shield may have at least one outer portion bent toward
the first cooling fin to surround at least one side surface of the
first insulator.
[0059] The shield may extend to a level equal to a level of upper
ends of side surfaces of the first electrode. The first insulator
may insulate the shield from the first electrode.
[0060] In accordance with another aspect, a refrigerator, which
includes an evaporator mounted with a first cooling fin and a
second cooling fin, further includes a frost detecting apparatus
including a first electrode arranged to face the first cooling fin,
the first electrode generating an electric field, a first insulator
arranged at a back surface of the first electrode, a second
electrode arranged at a back surface of the first insulator, to
prevent the electric field from leaking toward the second cooling
fin, a second insulator to insulate the second cooling fin from the
second electrode, a shield arranged around an outer peripheral
surface of the first insulator, to prevent the electric field from
leaking toward the second cooling fin through the outer peripheral
surface of the first insulator, and an insulating gap to insulate
the shield and the first electrode from each other.
[0061] The shield may be formed integrally with the second
electrode.
[0062] The shield may be laterally spaced apart from the first
electrode. The shield may include a plurality of holes extending
through the first insulator. Each of the holes may electrically
connect the shield and the second electrode.
[0063] The shield may further include a conductor formed along side
surfaces of the first insulator, to electrically connect the shield
to the second electrode.
[0064] The shield may extend to a level equal to a level of upper
ends of side surfaces of the first electrode.
[0065] In accordance with one aspect, an electrode is arranged
around an electrode functioning to detect formation of frost, and
the same potential is established at the electrodes, in order to
prevent electric field from leaking into a frost non-detection
region through side surfaces of the frost-detecting electrode.
Accordingly, the electric field generated by the frost-detecting
electrode may be varied only by frost formed in a frost detection
region. As a result, it may be possible to more accurately detect
formation of frost on the refrigerant tube and cooling fins of the
evaporator, and the amount of the formed frost. It may also be
possible to accurately determine a defrosting operation start point
and a defrosting operation end point. Thus, an enhancement in
defrosting performance may be achieved.
[0066] In accordance with another aspect, an electrode is arranged
around an electrode functioning to detect formation of frost such
that an insulator is interposed between the electrodes, and the
same potential is established at the electrodes, in order to
prevent electric field from leaking into a frost non-detection
region through side surface edges of the frost-detecting
electrode.
[0067] It may also be possible to prevent the electric field
leaking into the frost non-detection region from varying in spite
of a variation in dielectric constant of an insulator caused by a
variation in ambient temperature around the evaporator. That is, it
may be possible to prevent the electric field established in the
frost detection region from leaking into other regions.
Accordingly, it may be possible to more accurately detect formation
of frost on the refrigerant tube and cooling fins of the
evaporator, and the amount of the formed frost, without temperature
compensation required due to a variation in ambient temperature
around the frost detecting apparatus. Thus, an enhancement in
defrosting performance may be achieved.
[0068] In this regard, it may be possible to simplify the
configuration of the frost detecting apparatus because it may be
unnecessary to mount a temperature sensor to the evaporator. It may
also be possible to easily control the defrosting operation without
errors caused by temperature compensation because it may be
unnecessary to perform temperature compensation based on a
temperature sensed by the temperature sensor during the defrosting
operation control. Thus, it may be possible to more accurately
detect formation of frost and the amount of the formed frost.
[0069] In this regard, it may be possible to start or stop driving
of a heater for a defrosting operation at an appropriate point of
time in accordance with the accurately-detected frost amount and
the accurately-determined defrosting operation ending time, and
thus to optimize the defrosting operation. Accordingly, an
enhancement in heat exchange performance of the evaporator may be
achieved. Also, an enhancement in energy efficiency may be achieved
through a reduction in consumption of energy caused by the
defrosting operation.
[0070] Where the cooling system is a refrigerator, it may be
possible to control the defrosting operation at an appropriate
point of time, based on the accurately-detected frost amount and
the accurately-determined defrosting operation ending time.
Accordingly, it is possible to prevent degradation in the cooling
efficiency of the evaporator caused by degradation in heat exchange
and air flow occurring due to formation of frost. It is also
possible to efficiently drive a heater used to remove frost. In
this case, accordingly, it may be possible to minimize temperature
variation occurring in the interior of the refrigerator, and to
store food in the refrigerator in a fresh state for a prolonged
period of time.
BRIEF DESCRIPTION OF THE DRAWINGS
[0071] These and/or other aspects will become apparent and more
readily appreciated from the following description of the
embodiments, taken in conjunction with the accompanying drawings of
which:
[0072] FIG. 1 is a schematic view illustrating a configuration of a
conventional frost detecting apparatus provided at a cooling
system;
[0073] FIG. 2 is a graph depicting a variation in the dielectric
constant of an insulator in the conventional frost detecting
apparatus in accordance with variation in ambient temperature of
the frost detecting apparatus
[0074] FIG. 3A s a graph depicting temperature variations of an
evaporator included in the cooling system and the conventional
frost detecting apparatus depending on the driving time of a
compressor included in the cooling system;
[0075] FIG. 3B is a graph depicting a variation in the output
voltage of the conventional frost detecting apparatus depending on
the driving time of the compressor;
[0076] FIG. 4 is a view illustrating an internal configuration of a
refrigerator according to an exemplary embodiment;
[0077] FIG. 5 is a view illustrating installation of a frost
detecting apparatus provided at the refrigerator according to the
illustrated exemplary embodiment;
[0078] FIG. 6 is a block diagram illustrating a defrosting control
configuration of the refrigerator according to the illustrated
exemplary embodiment.
[0079] FIG. 7A is a perspective view of a frost detecting apparatus
configured in accordance with an exemplary embodiment;
[0080] FIG. 7B is a sectional view of the frost detecting apparatus
according to the exemplary embodiment illustrated in FIG. 7A;
[0081] FIGS. 8A and 8B are distribution diagrams of electric fields
respectively generated in a conventional frost detecting apparatus
and the frost detecting apparatus according to the illustrated
exemplary embodiment;
[0082] FIG. 9 depicts graphs of surface charge densities at
respective first electrodes in the conventional frost detecting
apparatus and the frost detecting apparatus according to the
illustrated exemplary embodiment;
[0083] FIGS. 10A and 10B are graphs depicting variation in output
voltage from the frost detecting apparatus depending on variation
in ambient temperature of the frost detecting apparatus in
accordance with an exemplary embodiment;
[0084] FIG. 11A is a perspective view illustrating a frost
detecting apparatus according to an exemplary embodiment;
[0085] FIGS. 11B to 11D are sectional views respectively
illustrating different structures of a second insulator included in
the frost detecting apparatus shown in FIG. 11A;
[0086] FIG. 12 is a view illustrating an installed state of a frost
detecting apparatus according to an exemplary embodiment;
[0087] FIG. 13 is a graph depicting a voltage corresponding to an
amount of frost detected by the frost detecting apparatus in
accordance with an exemplary embodiment;
[0088] FIG. 14A is a perspective view of a frost detecting
apparatus according to another exemplary embodiment;
[0089] FIG. 14B is a sectional view of the frost detecting
apparatus shown in FIG. 14A;
[0090] FIG. 14C is a sectional view of the frost detecting
apparatus shown in FIG. 14B, which additionally includes a second
insulator;
[0091] FIG. 15 is a sectional view of a frost detecting apparatus
according to another exemplary embodiment;
[0092] FIG. 16A is a sectional view of a frost detecting apparatus
according to another exemplary embodiment;
[0093] FIG. 16B is a sectional view illustrating the frost
detecting apparatus shown in FIG. 16A;
[0094] FIG. 17 is a sectional view of a frost detecting apparatus
according to another exemplary embodiment;
[0095] FIG. 18 is a perspective view of a frost detecting apparatus
according to another exemplary embodiment;
[0096] FIG. 19 is a perspective view illustrating an installed
state of the frost detecting apparatus shown in FIG. 18;
[0097] FIG. 20A is a perspective view of a frost detecting
apparatus according to another exemplary embodiment;
[0098] FIG. 20B is a cross-sectional view taken along the line X-X
in FIG. 20A, illustrating the frost detecting apparatus shown in
FIG. 20A; and
[0099] FIG. 21 is a perspective view illustrating an installed
state of the frost detecting apparatus shown in FIGS. 20A and
20B.
DETAILED DESCRIPTION
[0100] Hereinafter, exemplary embodiments will be described by
referring to the figures.
[0101] Each exemplary embodiment is adapted to enhance the
defrosting efficiency of a cooling system, and thus to reduce power
consumption by accurately detecting whether or not frost has been
formed on an evaporator of the cooling system and the amount of the
formed frost, and controlling driving of a heater based on the
results of the detection, thereby controlling a defrosting
operation. The exemplary embodiments are described in conjunction
with an example in which the cooling system is applied to a
refrigerator.
[0102] FIG. 4 is a view illustrating an internal configuration of a
refrigerator according to an exemplary embodiment. FIG. 5 is a view
illustrating installation of a frost detecting apparatus provided
at the refrigerator according to the illustrated exemplary
embodiment. FIG. 6 is a block diagram illustrating a defrosting
control configuration of the refrigerator according to the
illustrated embodiment.
[0103] A refrigerator is adapted to store food in a fresh state for
a prolonged period of time by maintaining a storage chamber in a
low-temperature state through repetition of a refrigeration cycle
to sequentially compress, condense, expand, and vaporize a
refrigerant.
[0104] As shown in FIG. 4, such a refrigerator, which is designated
by reference numeral 100, includes a body 110 having an open front
side, and a storage chamber 120 defined in the body 110, to store
food. The storage chamber 120 is laterally divided into a freezing
compartment and a refrigerating compartment by an intermediate
barrier wall. Each of the freezing and refrigerating compartments
is open at a front side thereof. A door 130 is provided at the open
front side of each compartment, to shield the compartment from an
outside of the compartment. A duct D, through which air flows, is
formed between the body 110 and one wall of the storage chamber
120. A plurality of holes are formed through the wall of the
storage chamber 120. Through the holes, air flows between the
storage chamber 120 and the duct D.
[0105] Installed in the duct D are an evaporator 140 to cool
ambient air present around the evaporator 140 in accordance with a
cooling operation of absorbing latent heat from the ambient air
while evaporating a refrigerant supplied from a condenser (not
shown), a fan 150 to suck air from the storage chamber 120 while
supplying air passing around the evaporator 140 to the storage
chamber 120, and a heater 160 to remove frost formed on the
evaporator 140. In a machinery chamber defined in a lower portion
of the body 110, a compressor 170 to supply the refrigerant after
compressing the refrigerant is installed. The condenser (not shown)
is also installed in the machinery chamber, to discharge heat from
the refrigerant, which has been compressed into a high-temperature
and high-pressure state, thereby condensing the refrigerant.
[0106] The evaporator 140 includes a refrigerant tube 141, through
which the refrigerant flows, and a plurality of cooling fins 142
(142a and 142b) mounted to the refrigerant tube 141, to achieve an
enhancement in heat exchange efficiency. The evaporator 140
functions to heat-exchange the refrigerant, which is maintained in
a low-temperature and low-pressure state, with air present in the
storage chamber at a higher temperature than the refrigerant, and
thus to evaporate the refrigerant, thereby lowering the internal
temperature of the storage chamber. Due to a temperature difference
between the refrigerant and the air in the storage chamber, frost
is continuously formed on the refrigerant tube 141 and cooling fins
142.
[0107] In order to remove the frost formed on the evaporator 140, a
defrosting operation is carried out. To control the defrosting
operation, driving of the heater 160 is controlled under control of
the controller 180. In order to control the defrosting operation,
it is necessary to know whether or not frost has been formed on the
evaporator 140 and the amount of the formed frost.
[0108] As shown in FIGS. 5 and 6, the refrigerator, which is an
example of the cooling system, further includes a frost detecting
apparatus 200 installed at at least one of the refrigerant tube 141
and plural cooling fins 142 (142a and 142b) of the evaporator 140,
to detect whether or not frost has been formed on the evaporator
140 and the amount of the formed frost.
[0109] The cooling system, namely, the refrigerator, further
includes a detector 190 electrically connected with the frost
detecting apparatus 200, to receive frost data from the frost
detecting apparatus, and to transmit the data to the controller
180. The refrigerator further includes a power supply P to supply
voltages having the same phase and magnitude to a sensor terminal A
and a shield terminal B, which are included in the frost detecting
apparatus 200, so as to establish the same potential at first and
second electrodes 210 and 230 of the frost detecting apparatus
200.
[0110] The frost data generated from the frost detecting apparatus
200 represents a capacitance C detected between the frost detecting
apparatus 200 and the cooling fin 142 where the frost detecting
apparatus 200 is installed. As the amount of frost formed between
the frost detecting apparatus 200 and the cooling fin 142
increases, an increase in dielectric constant occurs, thereby
causing the capacitance C to increase. In accordance with the
capacitance increase, a decrease in voltage occurs. That is, the
voltage generated between the frost detecting apparatus 200 and the
cooling fin 142 is proportional to the impedance Z established
between the frost detecting apparatus 200 and the cooling fin 142.
On the other hand, the impedance Z is inversely proportional to the
capacitance C (Z=1/jwC). As a result, the voltage between the frost
detecting apparatus 200 and the cooling fin 142 is inversely
proportional to the capacitance C between the frost detecting
apparatus 200 and the cooling fin 142.
[0111] The detector 190 is connected to the sensor terminal A of
the frost detecting apparatus 200, to detect a voltage generated in
accordance with the capacitance between the frost detecting
apparatus 200 and the cooling fin 142. The detector 190 transmits
the detected voltage to the controller 180.
[0112] The controller 180 compares the voltage received from the
detector 190 with a first reference voltage, to determine a point
of time when a defrosting operation is to be begun. That is, when
the voltage received from the detector 190 is lower than the first
reference voltage, the controller 180 determines that it is time to
perform a defrosting operation. In this case, the controller 180
controls the fan 150 and compressor 170 to stop. The controller 180
also controls the heater 160 to be driven. In accordance with these
control operations, a defrosting operation is carried out.
[0113] During the defrosting operation, the controller 180 compares
the voltage received from the detector 190 with a second reference
voltage, to determine a point of time when the defrosting operation
is to be ended. That is, when the voltage received from the
detector 190 is higher than the second reference voltage, the
controller 180 determines that it is time to end the defrosting
operation in that defrosting operation is no longer required
because there is no frost. In this case, the controller 180
controls the heater 160 to stop. The controller 180 also controls
the fan 150 and compressor 170 to be driven. In accordance with
these operations, a cooling operation is carried out. At this time,
the controller 180 controls the compressor 170 and fan 150 to be
drive in accordance with an operation mode set by the user, in
order to maintain the storage chamber at a predetermined
temperature.
[0114] Frost amount data, which is represented by a corresponding
voltage, is experimentally acquired. Based on the acquired frost
amount data, the first reference voltage associated with the point
of time when the defrosting operation is to be begun, and the
second reference voltage associated with the point of time when the
defrosting operation is to be ended are determined. The determined
first and second reference voltages are stored in a memory (not
shown) or the like so that they may be subsequently used.
[0115] Alternatively, the frost detecting apparatus 200 may be
installed at the cooling fin 142 of the evaporator 140, to
experimentally acquire an initial voltage generated between the
frost detecting apparatus 200 and the cooling fin 142, and to
experimentally acquire a saturated voltage generated in a frost
saturation state. In this case, the first reference voltage may be
set to a voltage obtained through comparison between the initial
voltage and the saturated voltage. Also, the second reference
voltage is set to "0". The set first and second voltages may then
be stored in the memory (not shown), so as to be subsequently
used.
[0116] The reason why the second reference voltage is set to "0" is
that the initial voltage is output when the defrosting operation
for the evaporator 140 is ended, because frost is no longer present
between the frost detecting apparatus 200 and the cooling fin
142.
[0117] Then, the controller 180 compares the current voltage
between the frost detecting apparatus 200 and the cooling fin 142
with the initial voltage, and subsequently compares the resulting
comparison voltage with the first reference voltage. When the
comparison voltage is higher than the first reference voltage, the
controller 180 performs a control operation to begin a defrosting
operation. During the defrosting operation, the controller 180
compares the current voltage between the frost detecting apparatus
200 and the cooling fin 142 with the initial voltage, and then
compares the resulting comparison voltage with the second reference
voltage. When the comparison voltage is lower than the second
reference voltage, the controller 180 performs a control operation
to end the defrosting operation.
[0118] Upon setting the first and second reference voltages, the
distance between the cooling fins 142 should be taken into
consideration.
[0119] That is, the distance between one of the cooling fins 142
and the frost detecting apparatus 200 is varied in accordance with
the distance between the frost detecting apparatus 200 and the
other cooling fin 142 where the frost detecting apparatus 200 is
installed. For this reason, the capacitance between the one cooling
fin 142 and the frost detecting apparatus 200
(C=k.epsilon..sub.0A/d (A: the area of the first electrode, d: the
distance between the cooling fins, k: the dielectric constant
between the electrodes, and .epsilon..sub.0: the dielectric
constant of free space)) is varied, thereby varying the voltage
between the frost detecting apparatus 200 and the cooling fin
142.
[0120] It may also be possible to experimentally acquire amounts of
frost respectively corresponding to given different voltages and
times respectively taken to remove the amounts of frost
corresponding to the given different voltages, and to store the
acquired data in the memory (not shown). In this case, the
controller 180 may control the defrosting operation by controlling
the heater 160 to be driven for the stored time corresponding to a
detected voltage.
[0121] Thus, it may be possible to optimize the defrosting
operation by starting the defrosting operation at an appropriate
point of time, and ending the defrosting operation at an
appropriate point of time. Accordingly, power consumption may be
minimized.
[0122] Hereinafter, the frost detecting apparatus 200 will be
described with reference to FIG. 7.
[0123] FIG. 7A is a perspective view of the frost detecting
apparatus 200, which is configured in accordance with an exemplary
embodiment. FIG. 7B is a sectional view of the frost detecting
apparatus 200 according to the illustrated exemplary
embodiment.
[0124] The frost detecting apparatus 200 includes a first electrode
210 to detect formation of frost, a first insulator 220 arranged in
contact with the first electrode 210, and a second electrode 230
arranged in contact with the first insulator 220.
[0125] In detail, the second electrode 230 is arranged in contact
with the back surface of the first insulator 220. The second
electrode 230 extends around an exposed portion of the first
insulator 220, so as to surround the exposed portion of the first
insulator 220. Thus, the second electrode 230 extends along the
surfaces of the first electrode 210, except for the front surface
of the first electrode 210, (namely, the side surfaces of the first
electrode 210), so as to surround the first electrode 210. In this
case, the first electrode 210 is arranged to face the first cooling
fin, to detect formation of frost.
[0126] In accordance with this arrangement, the second electrode
230 functions as a shield to cut off an electric field leaking at
side surface edges of the first insulator 220 and first electrode
210.
[0127] The second electrode 230 may extend to a higher level than
the side surfaces of the first electrode 210. In this case, the
second electrode 230 guides an electric field generated from the
first electrode 210 such that the electric field of the first
electrode 210 defines a frost detection region.
[0128] Of course, the second electrode 230 may extend to a lower
level than the side surfaces of the first electrode 210.
[0129] An insulation gap g is formed between the second electrode
230 and the first electrode 210, to insulate the second electrode
230 from the first electrode 210. Of course, an insulator may be
inserted between the second electrode 230 and the first electrode
210.
[0130] The first electrode 210 of the frost detecting apparatus 200
is connected to a sensor terminal A, whereas the second electrode
230 is connected to a shield terminal B. Voltages having the same
phase and magnitude are applied to the first electrode 210 and
second electrode 230, respectively. As a result, the same potential
is established at both the electrodes 210 and 230. Thus, the
electric field generated from the second electrode 230 prevents the
electric field generated from the first electrode 210 from being
transmitted to the second cooling fin.
[0131] In the frost detecting apparatus 200, the same potential is
established at both the first electrode 210 and the second
electrode 230. In particular, the same potential is established at
both the side surfaces of the first electrode 210 and the portions
of the second electrode 230 arranged around the side surfaces of
the first electrode 210. Accordingly, it may be possible to prevent
the electric field generated from the first electrode 210 from
leaking at the side surface edges of the first electrode 210. It
may also be possible to prevent the electric field of the first
electrode 210 from leaking through the side surface edges of the
first insulator 220. Thus, it may be possible to prevent the
electric field of the first electrode 210, which defines the frost
detection region, from being varied. That is, the electric field of
the first electrode 210 is guided only to the first cooling fin
without leaking, by the second electrode 230. Thus, the electric
field of the first electrode 210 in the frost detecting apparatus
200 is varied only by frost formed between the first electrode 210
and the first cooling fin.
[0132] Meanwhile, the first insulator 220 of the frost detecting
apparatus 200 exhibits a variation in dielectric constant in
accordance with a variation in ambient temperature around the first
insulator 220. In this case, the surface charge density of the
first electrode 210 may be varied, thereby causing a variation in
the electric field leaking through the first insulator 220.
However, the second electrode 230 may prevent the electric field
from leaking at the side surface edges of the first insulator 220
even when the dielectric constant of the first insulator 220
varies, and thus prevent the electric field from being varied. That
is, it may be possible to prevent the electric field generated
between the first electrode 210 and the second cooling fin from
leaking and varying in spite of a variation in the dielectric
constant of the first insulator 220. Thus, the electric field
generated between the first electrode 210 and the first cooling fin
may be varied only by frost formed between the first electrode 210
and the first cooling fin. This will be described with reference to
FIGS. 8 and 9.
[0133] FIGS. 8A and 8B depict distribution diagrams of electric
fields respectively generated in a conventional frost detecting
apparatus and the frost detecting apparatus according to the
illustrated exemplary embodiment. FIG. 9 depicts graphs of surface
charge densities at respective first electrodes in the conventional
frost detecting apparatus and the frost detecting apparatus
according to the illustrated exemplary embodiment.
[0134] FIG. 8A is a distribution diagram of an electric field
generated from a first electrode 11 where a second electrode 13 in
a conventional frost detecting apparatus 10 is formed only beneath
a first insulator 12, as in the conventional case shown in FIG. 1.
FIG. 8B is a distribution diagram of an electric field generated
from the first electrode 210 where the second electrode 230 of the
frost detecting apparatus 200 is formed to surround the first
insulator 220 and first electrode 210. Referring to FIGS. 8A and
8B, it may be seen that, in the frost detecting apparatus 200, in
which the second electrode 230 surrounds the first insulator 220
and first electrode 210, the electric field distribution of the
first electrode 210 is denser in the frost detection region.
[0135] FIG. 9 is a graph depicting a variation in the surface
charge density of the first electrode 11 or 210 exhibited when the
dielectric constant of the first insulator 12 or 220 interposed
between the two electrodes 11 and 13 in the conventional frost
detecting apparatus or between the two electrodes 210 and 230 in
the frost detecting apparatus according to the illustrated
embodiment varies between 1 and 5. Where the second electrode 13 is
formed only beneath the first insulator 12, as in the conventional
case, it may be seen that a relatively-considerable variation in
surface charge density occurs in accordance with a variation in the
dielectric constant of the first insulator 12. On the other hand,
where the second electrode 230 surrounds the first insulator 220,
as in the illustrated embodiment, it may be seen that there is no
variation in surface charge density in spite of a variation in the
dielectric constant of the first insulator 220.
[0136] In the conventional case, the dielectric constant of the
first insulator 12 is varied in accordance with variation in
ambient temperature of the defrost detecting apparatus 10, so that
the surface charge density between the first insulator 12 and the
first electrode 11 is varied, thereby causing a variation in the
electric field leaking from the first electrode 11 into the frost
non-detection region. As a result, the electric field between the
first electrode 11 and the first cooling fin 21 is varied, so that
the frost detection signal generated due to formation of frost is
varied. In the illustrated embodiment, however, it may be seen that
the surface charge density is constant in spite of a variation in
the dielectric constant of the first insulator 220 according to
temperature variation, because the second electrode 230 is formed
to surround the first electrode 210 and first insulator 220, and
the same potential is established at both the first and second
electrodes 210 and 230.
[0137] Thus, the second electrode 230, which has the same potential
as the first electrode 210, may prevent the electric field of the
first electrode 210, which will be established in the frost
detection region, from leaking into a non-detection region, and
thus prevent the electric field between the first electrode 210 and
the first cooling fin from being varied due to a variation in
temperature. This will be described with reference to FIG. 10A and
FIG. 10B
[0138] FIG. 10A is a graph depicting variation in output voltage
from the frost detecting apparatus 200 depending on variation in
ambient temperature of the frost detecting apparatus 200 in
accordance with an exemplary embodiment.
[0139] As the compressor 170 operates for a cooling operation, the
ambient temperature of the evaporator 140 is decreased. As a
result, the ambient temperature of the frost detecting apparatus
200 is lowered from about 15.degree. C. to about -25.degree. C., as
shown in FIG. 10B. In this case, however, the electric field
between the first electrode 210 and the cooling fin is constant in
spite of a variation in the dielectric constant of the first
insulator 220 caused by the ambient temperature variation of the
frost detecting apparatus 200, as shown in FIG. 10A That is, there
is no variation in capacitance. Thus, it may be seen that the
voltage output from the sensor terminal A connected to the first
electrode 210 of the frost detecting apparatus 200 is constant.
[0140] That is, the frost detection signal from the first electrode
210 is not influenced by the ambient temperature variation of the
frost detecting apparatus 200. In other words, the electric field
established between the first electrode 210 and the cooling fin is
influenced only by formation of frost.
[0141] As a result, it may be unnecessary to perform a temperature
compensation procedure upon detecting formation of frost.
Accordingly, it may be unnecessary to mount a separate temperature
sensor in the vicinity of the frost detecting apparatus 200. Also,
it may be possible to use a simple and easy control algorithm in
that no temperature compensation algorithm is needed upon detecting
formation of frost.
[0142] The first and second electrodes 210 and 230 of the frost
detecting apparatus 200 are made of a conductive material such as
aluminum or copper. Where the frost detecting apparatus 200 is
installed at the cooling fin 142, which is made of metal, a second
insulator 240 is formed on the second electrode 230, which comes
into contact with the second cooling fin, in order to insulate the
second cooling fin from the second electrode 230. This will be
described with reference to FIG. 11.
[0143] FIG. 11A to 11D are a perspective view and sectional views
illustrating frost detecting apparatuses according to exemplary
embodiments. In each embodiment, the frost detecting apparatus 200
thereof includes a first electrode 210, a first insulator 220, a
second electrode 230, and a second insulator 240.
[0144] FIG. 11A is a perspective view of the frost detecting
apparatus, and FIG. 11B is a sectional view of the frost detecting
apparatus. The second insulator 240 of the frost detecting
apparatus 200 is formed on an outer surface of the second electrode
230, to shield the second electrode 230, and thus to prevent the
second electrode 230 from being electrically connected to a cooling
fin. The second insulator 240 of the frost detecting apparatus 200
is in contact with a cooling fin 142 of an evaporator 140.
[0145] In the case of FIG. 11C, the second insulator 240 of the
frost detecting apparatus 200 shields a region around the second
electrode 230, in order to prevent the second electrode 230 from
being electrically connected with a cooling fin. The second
insulator 240 is formed on an outer surface of the first electrode
210, which is made of metal, to prevent the first electrode 210
from being eroded by frost. Thus, the second insulator 240 shields
the first electrode 210. The second insulator 240 is also filled in
an insulating gap g, so that it shields the insulating gap g from
the outside of the frost detecting apparatus 200.
[0146] In the case of FIG. 11D, the second insulator 240 of the
frost detecting apparatus 200 is formed on an outer surface of the
second electrode 230, in order to prevent the second electrode 230
from being electrically connected with a cooling fin. Thus, the
second insulator 240 shields the second electrode 230. The second
insulator 240 is also formed on surfaces of the first electrode 210
and surfaces defining an insulating gap g, in order to prevent the
first electrode 210, which is made of metal, from being eroded by
frost. Thus, the second insulator 240 shields the first electrode
210 and insulating gap g.
[0147] FIG. 12 is a view illustrating an installed state of a frost
detecting apparatus 200 according to an exemplary embodiment.
[0148] The frost detecting apparatus 200 is installed at an
evaporator 140, which includes a refrigerant tube 141, through
which a refrigerant flows, and a plurality of cooling fins 142, for
example, a first cooling fin 142a and a second cooling fin 142b. In
detail, the frost detecting apparatus 200 is mounted to at least
one of the plural cooling fins.
[0149] In more detail, the frost detecting apparatus 200 includes a
first electrode 210 arranged to face the first cooling fin 142a
while being connected to a sensor terminal A, a first insulator 220
arranged in contact with the first electrode 210, a second
electrode 230 arranged in contact with a back surface of the first
insulator 220 and connected to a shield terminal B while
surrounding the first insulator 220 and first electrode 210, and a
second insulator 240 arranged in contact with the second electrode
230 and formed on an outer surface of the second electrode 230 to
surround the second electrode 230 while being in contact with the
second cooling fin 142b. An insulating gap g is formed between the
second electrode 230 and the first electrode 210, in order to
prevent the second electrode 230 from being electrically connected
with the first electrode 210.
[0150] In the above-described frost detecting apparatus 200, the
second insulator 240 is in contact with the second cooling fin
142b. In this case, the first electrode 210 faces the first cooling
fin 142a of the evaporator 140.
[0151] A frost detection region S1 is formed between a front
surface of the first electrode 210 and the first cooling fin 142a.
A frost non-detection region S2 is formed between a front surface
of the first electrode 210 and the second cooling fin 142b. That
is, the frost detecting apparatus 200 detects formation of frost in
the frost detection region S1 between the first electrode 210 and
the first cooling fin 142a.
[0152] The frost non-detection region S2 is a region where an
electric field generated by the first electrode 210 in an opposite
direction to an electric field generated in the frost detecting
region S1 by the first electrode 210 is established.
[0153] In the frost detecting apparatus 200, voltages having the
same phase and magnitude are supplied to the first electrode 210
and second electrode 230 via the sensor terminal A and shield
terminal B, respectively. As a result, the same potential is
established at both the first electrode 210 and second electrode
230.
[0154] Accordingly, it may be possible to prevent the electric
field from leaking at the side surface edges of the first electrode
210 and first insulating layer 220. Also, there is no variation in
electric field corresponding to a variation in the dielectric
constant of the first insulator 220, which may occur when the
ambient temperature of the frost detecting apparatus 200
varies.
[0155] That is, the electric field of the first electrode 210 is
guided, by the second electrode 230, to the frost detection region
S1 without leakage and variation in spite of a variation in the
dielectric constant of the first insulator 220 caused by a
variation in temperature. Thus, the electric field is varied only
by frost formed in the frost detection region S1 between the first
electrode 210 and the first cooling fin 142a.
[0156] Accordingly, it may be possible to achieve an enhancement in
frost detection performance. As a result, it may be possible to
accurately determine a defrosting operation start point and a
defrosting operation end point, and thus to appropriately control
the defrosting operation. Thus, it may be possible to prevent
degradation in the cooling efficiency of the evaporator caused by
degradation in heat exchange and air flow occurring due to
formation of frost. It is also possible to efficiently drive a
heater used to remove frost where the cooling system is a
refrigerator. In this case, accordingly, it may be possible to
minimize temperature variation occurring in the interior of the
refrigerator, and to store food in the refrigerator in a fresh
state for a prolonged period of time.
[0157] When a voltage is applied to the first electrode 210 in the
frost detecting apparatus 200, charges are distributed to both the
first electrode 210 and the first cooling fin 142a. As a result, an
electric field is generated in a region between the first electrode
210 and the first cooling fin 142a.
[0158] This electric field is reduced in accordance with an
increase in dielectric constant caused by formation of frost
between the first electrode 210 and the first cooling fin 142a.
Such a dielectric constant variation also causes a variation in
capacitance, which is, in turn, output in the form of a voltage
from the sensor terminal A. That is, a voltage corresponding to the
varied capacitance is output from the sensor terminal A connected
to the first electrode 210. The output voltage is detected by the
detector 190.
[0159] The output voltage of the frost detecting apparatus 200
according to formation of frost on the evaporator 140 will be
described with reference to FIG. 13.
[0160] FIG. 13 is a graph depicting a voltage corresponding to an
amount of frost detected by the frost detecting apparatus 200 in
accordance with an exemplary embodiment.
[0161] When the compressor 170 operates for a cooling operation,
heat exchange is carried out at the evaporator 140, so that frost
is formed in the frost detection region S1 between the first
electrode 210 and the first cooling fin 142a. As the amount of the
frost formed in the frost detection region S1 increases, the
electric field between the first electrode 210 and the first
cooling fin 142a is varied. The electric field variation causes a
variation in capacitance. Thus, it may be seen that, as the amount
of frost formed in the frost detection region S1, the voltage
output from the sensor terminal A is lowered.
[0162] Referring to FIG. 13, it may be seen that the output voltage
generated in a state, in which the formation of frost in the frost
detection region S1 is saturated, is lower than the output voltage
generated in a state, in which no frost is formed, by about 30
mV.
[0163] Of course, the output voltage difference of 30 mV may be
varied in accordance with the distance between the first cooling
fin and the frost detecting apparatus, the applied voltage,
etc.
[0164] In this case, it may be possible to set the result of the
comparison between the output voltage from the frost detecting
apparatus 200 in a frost saturation state and the output voltage
from the frost detecting apparatus 200 in a frost non-formation
state, namely, a voltage difference (about 30 mV), to a reference
voltage at a defrosting operation start point, namely, a first
reference voltage. In this case, a reference voltage at a
defrosting operation end point, namely, a second reference voltage,
may also be set to 0 because, in the defrosting operation end
point, the frost detecting apparatus 200 outputs a voltage equal to
the output voltage in the frost non-formation state, in accordance
with complete removal of frost from the frost detection region
S1.
[0165] Meanwhile, the distance between the frost detecting
apparatus 200 and the first cooling fin 142a is varied in
accordance with the distance between the two cooling fins 142a and
142b. In accordance with the distance between the frost detecting
apparatus 200 and the first cooling fin 142a, the capacitance of
the frost detection region S1 between the frost detecting apparatus
200 and the first cooling fin 142a is varied, thereby causing the
output voltage from the frost detecting apparatus 200 to be varied.
To this end, it may be necessary to take into consideration the
distance between the cooling fins 142a and 142b upon setting the
first and second reference voltages.
[0166] FIG. 14A is a perspective view of a frost detecting
apparatus 200 according to another exemplary embodiment. FIG. 14B
is a sectional view of the frost detecting apparatus 200 shown in
FIG. 14A.
[0167] The frost detecting apparatus 200 includes a first electrode
210, a first insulator 220 arranged in contact with the first
electrode 210, a second electrode 230 arranged in contact with the
first insulator 220, and a shield 250 arranged around the first
electrode 210 while being spaced apart from the first electrode
210, to define an insulation gap g for insulation from the first
electrode 210. The shield 250 is arranged in contact with the first
insulator 220.
[0168] The frost detecting apparatus 200 also includes one or more
holes h extending through the shield 250, first insulator 220, and
second electrode 230. A wire as a conductor 260 may be inserted
into each hole h, in order to electrically connect the second
electrode 230 and shield 250. Alternatively, the conductor 260 may
be formed by plating a conductive material in the hole h.
[0169] In the frost detecting apparatus 200, voltages having the
same phase and magnitude are supplied to the first electrode 210
and second electrode 230 via the sensor terminal A and shield
terminal B, respectively. As a result, the same potential is
established at both the first electrode 210 and second electrode
230.
[0170] When a voltage is applied to the first electrode 210 in the
frost detecting apparatus 200, charges are distributed to both the
first electrode 210 and the cooling fin. As a result, an electric
field is generated in a region between the first electrode 210 and
the cooling fin.
[0171] In the frost detecting apparatus 200, the dielectric field,
electric field, and capacitance between the first electrode 210 and
the cooling fin are varied due to frost formed between the first
electrode 210 and the cooling fin. The varied capacitance is output
in the form of a voltage from the sensor terminal A. That is, a
voltage corresponding to the varied capacitance is output from the
sensor terminal A connected to the first electrode 210. The output
voltage is detected by the detector 190.
[0172] In the frost detecting apparatus 200, the same potential is
established at both the first electrode 210 and the second
electrode 230, and the same potential is established at both the
shield 250 electrically connected to the second electrode 230 via
the holes h and the first electrode 210. Accordingly, it may be
possible to prevent the electric field from leaking into the frost
non-detection region at the side surface edges of the first
electrode 210. Also, the conductors 260 are formed by inserting
wires into respective holes h, which extend through the shield 250,
first insulator 220, and second electrode 230 while being arranged
around the first electrode 210 or plating a conductive material in
the holes h. By the conductors 260, the same potential is
established at both the first electrode 210 and the portion of the
first insulator 220 arranged around the first electrode 210.
Accordingly, it may be possible to prevent the electric field from
leaking into the frost non-detection region through the first
insulator 220. Since the same potential is established at both the
first electrode 210 and the portion of the first insulator 220
arranged around the first electrode 210, there may be no electric
field variation corresponding to a variation in the dielectric
constant of the first insulator 220 possibly caused by variation in
ambient temperature of the frost detecting apparatus 200. That is,
the electric field is varied only by frost formed in the frost
detection region between the first electrode 210 and the cooling
fin.
[0173] FIG. 14C is a sectional view of the frost detecting
apparatus 200 shown in FIGS. 14A and 14B. As shown in FIG. 14C, the
frost detecting apparatus 200 further includes a second insulator
240.
[0174] The first electrode 210 and second electrode 230 are made of
a conductive material such as aluminum or copper. Where the frost
detecting apparatus 200 is installed at the cooling fin 142, which
is made of metal, the second insulator 240 may be formed over the
entire outer surface of the frost detecting apparatus 200, in order
to prevent the second electrode 230 and cooling fin 142 from being
electrically connected to each other, and to prevent the first
electrode 210 from being eroded by moisture.
[0175] The second insulator 240 may be formed on the second
electrode 230, which comes into contact with the cooling fin 142,
in order to insulate the second electrode 230 from the cooling fin
142. The second insulator 240 may also be formed on the first
electrode 210, in order to prevent the first electrode 210 from
being eroded by moisture.
[0176] FIG. 15 is a sectional view of a frost detecting apparatus
200 according to another exemplary embodiment.
[0177] As shown in FIG. 15, the frost detecting apparatus 200
includes a first electrode 210, a first insulator 220 arranged in
contact with the first electrode 210, a second electrode 230
arranged in contact with the first insulator 220, a shield 250
arranged around the first electrode 210 while being spaced apart
from the first electrode 210, to define an insulation gap g for
insulation from the first electrode 210, and a conductor 270
arranged in contact with side surfaces of the second electrode 230,
first insulator 220, and shield 250. The conductor 270 is a plating
layer formed on the side surfaces of the second electrode 230,
first insulator 220, and shield 250. The conductor 270 functions to
electrically connect the second electrode 230 and shield 250.
[0178] In this frost detecting apparatus 200, voltages having the
same phase and magnitude are applied to the first electrode 210 and
second electrode 230 via a sensor terminal A and a shield terminal
B, respectively. As a result, the same potential is established
among the first electrode 210, second electrode 230, shield 250,
and conductor 270.
[0179] When a voltage is applied to the first electrode 210 in the
frost detecting apparatus 200, an electric field is generated in a
region between the first electrode 210 and the cooling fin. This
electric field is varied due to a variation in dielectric constant
caused by frost formed between the first electrode 210 and the
cooling fin. Due to the varied dielectric constant and electric
field, a variation in capacitance occurs. The varied capacitance is
output in the form of a voltage from the sensor terminal A. That
is, a voltage corresponding to the varied capacitance is output
from the sensor terminal A connected to the first electrode 210.
The output voltage is detected by the detector 190.
[0180] In the frost detecting apparatus 200, the same potential is
established at the first electrode 210, second electrode 230,
shield 250, and conductor 270. Accordingly, it may be possible to
prevent the electric field from leaking at the side surface edges
of the first electrode 210 and the first insulator 220. Also, the
potential in a region around the first insulator 220 is equal to
the potential at the first electrode 210. Accordingly, there is no
electric field variation corresponding to the dielectric constant
variation of the first insulator 220, which may occur due to
variation in ambient temperature of the frost detecting apparatus
220. Thus, the electric field variation occurs only due to frost
formed between the first electrode 210 and the first cooling
fin.
[0181] The first and second electrodes 210 and 230 of the frost
detecting apparatus 200 are made of a conductive material such as
aluminum or copper. Accordingly, a second insulator 240 may be
formed on the first electrode 210, second electrode 230, and
conductor 270, in order to prevent the second electrode 230 and
cooling fin 142 from being electrically connected, and to prevent
the first electrode 210, conductor 270, etc. from being eroded by
moisture. Alternatively, the second insulator 240 may be formed on
the entire outer surface of the frost detecting apparatus 200.
[0182] FIG. 16A is a sectional view of a frost detecting apparatus
200 according to another exemplary embodiment.
[0183] As shown in FIG. 16A, the frost detecting apparatus 200
includes a first electrode 210, a first insulator 220 arranged in
contact with the first electrode 210, and a second electrode 230
arranged in contact with the first insulator 220. The second
electrode 230 extends around an exposed portion 211 of the first
insulator 220, to surround the first insulator 220.
[0184] In this case, the second electrode 230 may extend to a
higher level than the exposed portion 211 of the first insulator
220, or may extend to a lower level than the exposed portion 211 of
the first insulator 220.
[0185] When a voltage is applied to the first electrode 210 in the
frost detecting apparatus 200, an electric field is generated in a
region between the first electrode 210 and the cooling fin. This
electric field is varied due to frost formed between the first
electrode 210 and the cooling fin. Due to the varied electric
field, a variation in capacitance occurs. The varied capacitance is
output in the form of a voltage from the sensor terminal A. That
is, a voltage corresponding to the varied capacitance is output
from the sensor terminal A connected to the first electrode 210.
The output voltage is detected by the detector 190.
[0186] In the frost detecting apparatus 200, a voltage equal to the
voltage supplied to the first electrode 210 is supplied to the
second electrode 230, so that the potential established at the
second electrode 230 is equal to the potential at the first
electrode 210. As a result, it is possible to prevent the electric
field from leaking through the first insulator 220. Also, there is
no variation in electric field corresponding to a variation in the
dielectric constant of the first insulator 220, which may occur
when the ambient temperature of the frost detecting apparatus 200
varies. That is, the electric field is varied only by frost formed
in the frost detection region between the first electrode 210 and
the cooling fin, irrespective of the dielectric constant variation
of the first insulator 220.
[0187] Thus, the second electrode 230 functions as a shield to
shield the electric field of the first electrode 210, which may
leak into the exposed portion 211 of the first insulator 220.
[0188] FIG. 16B is a sectional view illustrating the frost
detecting apparatus 200 shown in FIG. 16A. Referring to FIG. 16B,
the frost detecting apparatus 200 further includes a second
insulator 240.
[0189] The first and second electrodes 210 and 230 of the frost
detecting apparatus 200 are made of a conductive material such as
aluminum or copper. Where the frost detecting apparatus 200 is
installed at the cooling fin, which is made of metal, the second
insulator 240 may be formed on the entire outer surface of the
frost detecting apparatus 200, in order to prevent the second
electrode 230 and cooling fin from being electrically connected,
and to prevent the first electrode 210 from being eroded by
moisture.
[0190] The second insulator 240 may be formed on the second
electrode 230, which comes into contact with the cooling fin 142,
in order to insulate the second electrode 230 from the cooling fin
142. The second insulator 240 may also be formed on the first
electrode 210, in order to prevent the first electrode 210 from
being eroded by moisture.
[0191] FIG. 17 is a sectional view of a frost detecting apparatus
200 according to another exemplary embodiment.
[0192] As shown in FIG. 17, the frost detecting apparatus 200
includes a first electrode 210, a first insulator 220 arranged in
contact with the first electrode 210, a second electrode 230
arranged adjacent to the first insulator 220, and a shield 250
arranged around the first electrode 210 while being spaced apart
from the first electrode 210, to define an insulation gap g for
insulation from the first electrode 210.
[0193] When a voltage is applied to the first electrode 210 in the
frost detecting apparatus 200, an electric field is generated in a
region between the first electrode 210 and the cooling fin. This
electric field is varied by frost formed between the first
electrode 210 and the cooling fin. Due to the varied electric
field, a variation in capacitance occurs. The varied capacitance is
output in the form of a voltage from the sensor terminal A. That
is, a voltage corresponding to the varied capacitance is output
from the sensor terminal A connected to the first electrode 210.
The output voltage is detected by the detector 190.
[0194] In the frost detecting apparatus 200, a voltage equal to the
voltage supplied to the first electrode 210 is supplied to the
second electrode 230 and shield 250 via the shield terminal B, so
that the potential established at the second electrode 230 and
shield 250 is equal to the potential at the first electrode 210. As
a result, it is possible to prevent the electric field from leaking
into the frost non-detection region through the side surface edges
of the first electrode 210.
[0195] Also, the first insulator 220 of the frost detecting
apparatus 200 has a thickness allowing the first insulator 220 to
prevent leakage of the electric field and to minimize a variation
in dielectric constant in spite of temperature variation.
Accordingly, it may be possible to minimize the amount of electric
field leaking through the first insulator 220.
[0196] Thus, the electric field variation of the first electrode
210 occurs only by frost formed in the frost detection region
between the first electrode 210 and the cooling fin.
[0197] FIG. 18 is a perspective view of a frost detecting apparatus
200 according to another exemplary embodiment. FIG. 19 is a
perspective view illustrating an installed state of the frost
detecting apparatus 200 shown in FIG. 18.
[0198] The frost detecting apparatus 200 is installed at an
evaporator. The evaporator includes a refrigerant tube 141, through
which the refrigerant flows, and a plurality of cooling fins 142
(142a and 142b) mounted to the refrigerant tube 141. The frost
detecting apparatus 200 is mounted to at least one of the plural
cooling fins.
[0199] The frost detecting apparatus 200 has a U-shaped structure
having two bent portions, taking into consideration the structure
of the evaporator in which the refrigerant tube 141 extends through
the cooling fins 142. As the frost detecting apparatus 200 has the
U-shaped structure, the area of a first electrode 210, which is
included in the frost detecting apparatus 200, is maximized.
Accordingly, the capacitance formed between the first electrode 210
and the cooling fin is increased. Thus, it may be possible to
easily detect a voltage output through the sensor terminal A in
accordance with the amount of frost formed on the evaporator.
[0200] In detail, the frost detecting apparatus 200 includes a
first electrode 210 arranged to correspond to the second cooling
fin 142b, a first insulator 220 arranged in contact with the first
electrode 210, a second electrode 230 arranged in contact with the
first insulator 220 while being in contact with side surfaces of
the first insulator 220 and first electrode 210 to surround the
first insulator 220 and first electrode 210, and a second insulator
240 arranged in contact with the first insulator 220 while
extending around the second electrode 230 to surround the second
electrode 230. The second insulator 240 is arranged in contact with
the second cooling fin 142b. An insulating gap g is formed between
the second electrode 230 and the first electrode 210, in order to
prevent the second electrode 230 from being electrically connected
with the first electrode 210.
[0201] As shown in FIG. 19, the frost detecting apparatus 200 is
installed such that the second insulator 240 is in contact with the
second cooling fin 142b, and the refrigerant tube 141 extends
through an opening O (FIG. 18). In this case, the first electrode
210 is arranged to face the first cooling fin 142a of the
evaporator 210. Thus, the frost detecting apparatus 200 detects
formation of frost between the first electrode 210 and the first
cooling fin 142a.
[0202] When a voltage is applied to the first electrode 210 in the
frost detecting apparatus 200, charges are distributed to both the
first electrode 210 and the first cooling fin 142a. As a result, an
electric field is generated in a region between the first electrode
210 and the first cooling fin 142a.
[0203] The electric field between the first electrode 210 and the
first cooling fin 142a is varied due to frost formed between the
first electrode 210 and the first cooling fin 142a. The electric
field variation causes a variation in capacitance, which is, in
turn, output in the formation of a voltage from the sensor terminal
A. That is, a voltage corresponding to the varied capacitance is
output from the sensor terminal A connected to the first electrode
210. The output voltage is detected by the detector 190.
[0204] In the frost detecting apparatus 200, voltages having the
same phase and magnitude are supplied to the first electrode 210
and second electrode 230 via the sensor terminal A and shield
terminal B, respectively. As a result, the same potential is
established at both the first electrode 210 and second electrode
230. Accordingly, it may be possible to prevent an electric field
from leaking at the side surface edges of the first electrode 210.
It may also be possible to prevent the electric field of the first
electrode 210 from leaking through the side surface edges of the
first insulator 220. Thus, it may be possible to prevent electric
field of the first electrode 210, which defines the frost detection
region, from being varied.
[0205] Also, there is no variation in electric field corresponding
to a variation in the dielectric constant of the first insulator
220, which may occur when the ambient temperature of the frost
detecting apparatus 200 varies. That is, the electric field is
varied only by frost formed in the frost detection region S1
between the first electrode 210 and the first cooling fin 142a.
[0206] FIG. 20A is a perspective view of a frost detecting
apparatus according to another exemplary embodiment. FIG. 20B is a
cross-sectional view taken along the line X-X in FIG. 20A,
illustrating the frost detecting apparatus shown in FIG. 20A.
[0207] The frost detection apparatus has a double structure
including two frost detecting units 200 and 200' each having a
U-shaped structure with two bent portions, taking into
consideration the structure of the evaporator in which a
refrigerant tube extends through a plurality of cooling fins. In
the double structure, second insulators 240 and 240' of the frost
detecting units 200 and 200' are in contact with each other. In
this case, first electrodes 210 and 210' of the frost detecting
units 200 and 200' are connected to a sensor terminal A, whereas
second electrodes 230 and 230' of the frost detecting units 200 and
200' are connected to a shield terminal B.
[0208] In this frost detecting apparatus, the areas of the first
electrodes 210 and 210' are maximized. Accordingly, the capacitance
formed between each of the first electrodes 210 and 210' and the
cooling fin is increased. Thus, it may be possible to easily detect
a voltage output through the sensor terminal A in accordance with
the amount of frost formed on the evaporator.
[0209] In more detail, the frost detecting apparatus includes the
first electrode 210, a first insulator 220 arranged in contact with
the first electrode 210, the second electrode 230, which is
arranged in contact with the first insulator 220 while extending
around the first insulator 220 and first electrode 210, to surround
the first electrode 210, the second insulator 240, which is
arranged in contact with the second electrode 230 while extending
around the second electrode 230, to surround the second electrode
230, the second insulator 240' arranged in contact with the second
insulator 240, the second electrode 230' surrounded by the second
insulator 240', a first insulator 220' surrounded by the second
electrode 230', and the first electrode 210' arranged in contact
with the first insulator 220' while being laterally adjacent to the
second electrode 230', to define an insulating gap g between the
first electrode 210' and the second electrode 230'.
[0210] FIG. 21 is a perspective view illustrating an installed
state of the frost detecting apparatus shown in FIGS. 20A and
20B.
[0211] The frost detecting apparatus is installed at an evaporator.
The evaporator includes a refrigerant tube 141, through which the
refrigerant flows, and a plurality of cooling fins 142 (142a,
142a', and 142b) mounted to the refrigerant tube 141. The frost
detecting apparatus is mounted to at least one of the plural
cooling fins, for example, the second cooling fin 142b. In this
case, the U-shaped frost detecting units 200 and 200' are installed
on opposite surfaces of the second cooling fin 142b,
respectively.
[0212] Alternatively, the frost detecting apparatus may be
installed between opposite ends of the cooling fin, using a
separate mounting device.
[0213] The frost detecting unit 200 is installed such that the
second insulator 240 is in contact with one surface of the second
cooling fin 142b, and the refrigerant tube 141 of the evaporator
140 extends through an opening formed at the frost detecting unit
200. In this case, the first electrode 210 faces the first cooling
fins 142a and 142a'.
[0214] On the other hand, the frost detecting unit 200' is
installed such that the second insulator 240' is in contact with
the other surface of the second cooling fin 142b, and the
refrigerant tube 141 of the evaporator 140 extends through an
opening formed at the frost detecting unit 200'. In this case, the
first electrode 210' faces the first cooling fin 142a' of the
evaporator 140.
[0215] Accordingly, the frost detecting units 200 and 200' detect
formation of frost between the first electrode 210 and the first
cooling fin 142a and formation of frost between the first electrode
210' and the first cooling fin 142a', respectively.
[0216] When a voltage is applied to the first electrodes 210 and
210' in the frost detecting units 200 and 200', charges are
distributed to both the first electrode 210 and the first cooling
fin 142a while being distributed to both the first electrode 210'
and the first cooling fin 142a'. As a result, an electric field is
generated in a region between the first electrode 210 and the first
cooling fin 142a, and an electric field is generated in a region
between the first electrode 210' and the first cooling fin
142a'.
[0217] The electric field between the first electrode 210 and the
first cooling fin 142a is varied due to frost formed between the
first electrode 210 and the first cooling fin 142a. Also, the
electric field between the first electrode 210' and the first
cooling fin 142a' is varied due to frost formed between the first
electrode 210' and the first cooling fin 142a'. The electric field
variation causes a variation in capacitance, which is, in turn,
output in the form of a voltage from the sensor terminal A. That
is, a voltage corresponding to the varied capacitance is output
from the sensor terminal A connected to a corresponding one of the
first electrodes 210 and 210'. The output voltage is detected by
the detector 190.
[0218] The controller 180 sums voltages, namely, data as to frost
formed between the frost detecting unit 200 and the first cooling
fin 142a and data as to frost formed between the frost detecting
unit 200' and the first cooling fin 142a', and controls a
defrosting operation based on the summed voltage. First and second
reference voltages used to control the defrosting operation are
experimentally acquired based on the summed voltage, and stored in
the memory so that they may be subsequently used.
[0219] In the frost detecting unit 200, voltages having the same
phase and magnitude are supplied to the first electrode 210 and
second electrode 230 via the sensor terminal A and shield terminal
B, respectively. As a result, the same potential is established at
both the first electrode 210 and second electrode 230. Also, in the
frost detecting unit 200', voltages having the same phase and
magnitude are supplied to the first electrode 210' and second
electrode 230' via the sensor terminal A and shield terminal B,
respectively. As a result, the same potential is established at
both the first electrode 210' and second electrode 230'.
[0220] Accordingly, it may be possible to prevent an electric field
from leaking through the side surface edges of the first electrodes
210 and 210' and the first insulators 220 and 220'. Also, there is
no variation in electric field corresponding to a variation in the
dielectric constant of the first insulator 220 or 220', which may
occur when the ambient temperature of the frost detecting unit 200
or 200' varies. That is, the electric field is varied only by frost
formed in the frost detection region between the first electrode
210 and the first cooling fin 142a or by frost formed in the frost
detection region between the first electrode 210' and the first
cooling fin 142a'.
[0221] Accordingly, it may be possible to more accurately detect
whether or not frost has been formed on the refrigerant tube and
cooling fins of the evaporator and the amount of the formed frost.
As a result, it may be possible to accurately determine a
defrosting operation start point and a defrosting operation end
point.
[0222] As the amount of frost formed on the evaporator and the
defrosting operation completion time may be accurately determined,
it may be possible to drive or stop the heater used for the
defrosting operation at an appropriate point of time. Accordingly,
the defrosting operation may be optimized, so that the heat
exchange performance of the evaporator may be enhanced. Also,
energy consumption caused by the defrosting operation may be
reduced, so that an enhancement in energy efficiency may be
achieved.
[0223] Although a few embodiments have been shown and described, it
would be appreciated by those skilled in the art that changes may
be made in these embodiments without departing from the principles
and spirit of the invention, the scope of which is defined in the
claims and their equivalents.
* * * * *