U.S. patent application number 11/884444 was filed with the patent office on 2008-07-03 for refrigerator.
Invention is credited to Wei Chen, Mizuho Fukaya, Junji Miyakami, Satoshi Miyamoto, Hiroshi Tatsumi.
Application Number | 20080155994 11/884444 |
Document ID | / |
Family ID | 36916254 |
Filed Date | 2008-07-03 |
United States Patent
Application |
20080155994 |
Kind Code |
A1 |
Miyamoto; Satoshi ; et
al. |
July 3, 2008 |
Refrigerator
Abstract
A refrigerator for cooling a space inside thereof with a
Stirling refrigerating engine includes state detection means for
detecting an excessive cooling critical state of the Stirling
refrigerating engine and excessive cooling prevention means for
preventing excessive cooling of the Stirling refrigerating engine
based on detection of the excessive cooling critical state by the
state detection means. Excessive cooling of the Stirling
refrigerating engine can thus be prevented.
Inventors: |
Miyamoto; Satoshi; (Osaka,
JP) ; Tatsumi; Hiroshi; (Nara, JP) ; Chen;
Wei; (Aichi, JP) ; Fukaya; Mizuho; (Osaka,
JP) ; Miyakami; Junji; (Osaka, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
36916254 |
Appl. No.: |
11/884444 |
Filed: |
September 14, 2005 |
PCT Filed: |
September 14, 2005 |
PCT NO: |
PCT/JP05/16912 |
371 Date: |
August 16, 2007 |
Current U.S.
Class: |
62/6 |
Current CPC
Class: |
F25D 17/02 20130101;
F25D 11/02 20130101; F25D 17/045 20130101; F25D 2700/10 20130101;
F25D 2317/0682 20130101; F25B 9/14 20130101; F25D 17/065 20130101;
F25D 2323/00265 20130101; F25D 2700/02 20130101 |
Class at
Publication: |
62/6 |
International
Class: |
F25B 9/14 20060101
F25B009/14 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 17, 2005 |
JP |
2005-040640 |
Claims
1. A refrigerator (1) for cooling a space inside the refrigerator
with a Stirling refrigerating engine (30), comprising: state
detection means (81, S01, S1, S21, S31, S37, S39, S45, S74, S75,
S82, S84) for detecting an excessive cooling critical state of said
Stirling refrigerating engine; and excessive cooling prevention
means (S02) for preventing excessive cooling of said Stirling
refrigerating engine based on detection of said excessive cooling
critical state by said state detection means.
2. The refrigerator according to claim 1, further comprising: door
state detection means (82, 83) for detecting an open/close state of
a door (14, 15) of a cooling chamber (11, 12) of said refrigerator;
a cooling fan (22) supplying cold air cooled by said Stirling
refrigerating engine into the space inside; and cooling fan control
means (S22) for stopping said cooling fan while a door open state
is detected by said door state detection means; and said state
detection means detecting that a prescribed time period has elapsed
since detection of the door open state by said door state detection
means (S23).
3. The refrigerator according to claim 2, further comprising: a
first cooling chamber (12) and a second cooling chamber (11)
partitioned by a heat insulator and each having the door; said
first cooling chamber being supplied with cold air cooled by said
Stirling refrigerating engine by said cooling fan; an air passage
(20, 21, 21A) for guiding the cold air cooled by said Stirling
refrigerating engine to said second cooling chamber; shut-off means
(61) provided in said air passage, for shutting off the cold air
cooled by said Stirling refrigerating engine; and a blowing fan
(62) sending the cold air cooled by said Stirling refrigerating
engine to said air passage; wherein when said door state detection
means detects a closed state of the door of said first cooling
chamber and an open state of the door of said second cooling
chamber (S31), said excessive cooling prevention means causes said
shut-off means to shut off said air passage (S35) and cancels
stopped state of said cooling fan and drives said cooling fan
(S36), and when said door state detection means detects an open
state of the door of said first cooling chamber and a closed state
of the door of said second cooling chamber (S39), said excessive
cooling prevention means causes said shut-off means to cancel
shut-off of said air passage (S43) and drives said blowing fan
(S44).
4. The refrigerator according to claim 1, further comprising a
low-temperature side evaporator (42) receiving cold heat from a
low-temperature portion formed in said Stirling refrigerating
engine through a secondary coolant; wherein said state detection
means includes temperature detection means (81) for detecting a
temperature of said low-temperature portion, said low-temperature
side evaporator, or a low-temperature side condenser (41) paired
with said low-temperature side evaporator, and detects that the
temperature detected by said temperature detection means is lower
than a prescribed temperature (S01, S11, S74, S82, S84).
5. The refrigerator according to claim 4, wherein said excessive
cooling prevention means carries out, prior to stop control (S24,
S86) for controlling and stopping said Stirling refrigerating
engine, excessive cooling prevention control (S22, S78, S81)
different from said stop control, for preventing excessive cooling
of said Stirling refrigerating engine.
6. The refrigerator according to claim 5, wherein said prescribed
temperature includes a first temperature (T.sub.1) higher than a
temperature at which said Stirling refrigerating engine is
excessively cooled and a second temperature (T.sub.2) higher than
the temperature at which said Stirling refrigerating engine is
excessively cooled and lower than said first temperature, and when
said state detection means detects that the temperature detected by
said temperature detection means is lower than said first
temperature, said excessive cooling prevention means carries out
said excessive cooling prevention control, and when said coolant
state detection means detects that the temperature detected by said
temperature detection means is lower than said second temperature,
said excessive cooling prevention means carries out said stop
control.
7. The refrigerator according to claim 4, further comprising:
abnormality in temperature detection sensing means (81) for sensing
abnormality in detection of a temperature by said temperature
detection means, when said temperature detection means detects a
temperature.
8. The refrigerator according to claim 4, further comprising: a
cooling fan (22) supplying cold air cooled by said low-temperature
side evaporator into the space inside; wherein said excessive
cooling prevention means drives said cooling fan (S13, S36) or
increases a fan level of said cooling fan (S14, S78).
9. The refrigerator according to claim 8, wherein when said state
detection means detects that the temperature detected by said
temperature detection means is lower than said first temperature
(S74), said excessive cooling prevention means drives said cooling
fan or increases a fan level of said cooling fan (S78), and when
said state detection means detects that the temperature detected by
said temperature detection means is lower than said first
temperature (S82) after a prescribed time period has elapsed since
drive of said cooling fan or increase in the fan level of said
cooling fan (S79), said excessive cooling prevention means controls
said Stirling refrigerating engine to lower cooling capability
(S81).
10. The refrigerator according to claim 8, wherein said excessive
cooling prevention means includes revolution number control means
(90) for controlling number of revolutions of said cooling fan, and
when said state detection means detects that the temperature
detected by said temperature detection means is lower than said
first temperature, said excessive cooling prevention means drives
said cooling fan with the number of revolutions of said cooling fan
being set to maximum revolution capability (S78), and when said
state detection means detects that the temperature detected by said
temperature detection means is lower than said first temperature
(S82) after a prescribed time period has elapsed since drive of
said cooling fan at the maximum number of revolutions (S79), said
excessive cooling prevention means controls said Stirling
refrigerating engine to lower cooling capability (S81).
Description
TECHNICAL FIELD
[0001] The present invention relates to a refrigerator, and more
particularly to a refrigerator for cooling a space inside thereof
with a Stirling refrigerating engine.
BACKGROUND ART
[0002] Detrimental effects of CFCs on global environment have
recently been pointed out, and a refrigerator including a Stirling
refrigerating engine has been attracting attention as a
refrigerator free from CFCs. In the refrigerator, cold heat of a
cold head of the Stirling refrigerating engine is transmitted to a
low-temperature side evaporator through a secondary coolant and
cold air generated by the low-temperature side evaporator is
supplied to a space inside the refrigerator (see, for example,
Japanese Patent Laying-Open No. 2002-221384 (Patent Document 1)).
Patent Document 1: Japanese Patent Laying-Open No. 2002-221384
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0003] In conventional refrigerating equipment, however, if cooling
capability of the Stirling refrigerating engine is great, the
secondary coolant is frozen and the cold heat of the cold head of
the Stirling refrigerating engine is no longer transmitted to the
low-temperature side evaporator, namely, the space inside the
refrigerator is not cooled.
[0004] In addition, the Stirling refrigerating engine has such a
characteristic that it cannot increase output when a temperature of
the cold head is high. Accordingly, quick cooling of the space
inside is desired, even when the temperature of the cold head is
high, such as at the time of power-on of the refrigerator or
switching to a quick-freeze operation mode.
[0005] The present invention was made to solve the above-described
problems, and one object of the present invention is to provide a
refrigerator capable of preventing excessive cooling of a Stirling
refrigerating engine before the Stirling refrigerating engine is
excessively cooled.
[0006] Another object of the present invention is to provide a
refrigerator achieving improved efficiency in cooling a space
inside thereof.
Means for Solving the Problems
[0007] In order to achieve the above-described object, according to
one aspect of the present invention, a refrigerator for cooling a
space inside the refrigerator with a Stirling refrigerating engine
includes: a state detection portion detecting an excessive cooling
critical state of the Stirling refrigerating engine; and an
excessive cooling prevention portion preventing excessive cooling
of the Stirling refrigerating engine based on detection of the
excessive cooling critical state by the state detection
portion.
[0008] According to the present invention, a refrigerator capable
of avoiding excessive cooling of a Stirling refrigerating engine
before the Stirling refrigerating engine is excessively cooled can
be provided.
[0009] Preferably, the refrigerator further includes: a door state
detection portion detecting an open/close state of a door of a
cooling chamber of the refrigerator; a cooling fan supplying cold
air cooled by the Stirling refrigerating engine into the space
inside; and a cooling fan control portion stopping the cooling fan
while a door open state is detected by the door state detection
portion, and the state detection portion detects that a prescribed
time period has elapsed since detection of the door open state by
the door state detection portion.
[0010] According to the present invention, lapse of the prescribed
time period since the door was opened is detected. As the cooling
fan is stopped while the door is open, air around a low-temperature
side cooler is stagnant during that time period. Accordingly, if
the Stirling refrigerating engine continues to operate, the
temperature of the secondary coolant is lowered. Thus, a state
before the secondary coolant is frozen can be detected based on a
time period during which the cooling fan remains stopped.
[0011] Preferably, the refrigerator further includes: a first
cooling chamber and a second cooling chamber partitioned by a heat
insulator and each having the door; the first cooling chamber being
supplied with cold air cooled by the Stirling refrigerating engine
by the cooling fan; an air passage for guiding the cold air cooled
by the Stirling refrigerating engine to the second cooling chamber;
a shut-off portion provided in the air passage, for shutting off
the cold air cooled by the Stirling refrigerating engine; and a
blowing fan sending the cold air cooled by the Stirling
refrigerating engine to the air passage, and when the door state
detection portion detects a closed state of the door of the first
cooling chamber and an open state of the door of the second cooling
chamber, the excessive cooling prevention portion causes the
shut-off portion to shut off the air passage and cancels stopped
state of the cooling fan and drives the cooling fan, and when the
door state detection portion detects an open state of the door of
the first cooling chamber and a closed state of the door of the
second cooling chamber, the excessive cooling prevention portion
causes the shut-off portion to cancel shut-off of the air passage
and drives the blowing fan.
[0012] According to the present invention, when the closed state of
the door of the first cooling chamber and the open state of the
door of the second cooling chamber are detected, the air passage is
shut off and the cooling fan is driven. When the open state of the
door of the first cooling chamber and the closed state of the door
of the second cooling chamber are detected, shut-off of the air
passage is canceled and the blowing fan is driven. Accordingly, if
the door of the second cooling chamber is opened while the door of
the first cooling chamber is closed, the air cooled by the Stirling
refrigerating engine is supplied to the first cooling chamber, and
if the door of the first cooling chamber is opened while the door
of the second cooling chamber is closed, the air cooled by the
Stirling refrigerating engine is supplied to the second cooling
chamber. Whichever door of the first door and the second door may
be opened, convection of the air cooled by the Stirling
refrigerating engine is achieved, and therefore, excessive cooling
of the Stirling refrigerating engine can be prevented. In addition,
as the cold air sent to the cooling chamber of which door is open
can be decreased, leakage to the outside of the cold air in the
space inside can be prevented.
[0013] Preferably, the refrigerator further includes a
low-temperature side evaporator receiving cold heat from a
low-temperature portion formed on the Stirling refrigerating engine
through a secondary coolant. The state detection portion includes a
temperature detection portion detecting a temperature of the
low-temperature portion, the low-temperature side evaporator, or a
low-temperature side condenser paired with the low-temperature side
evaporator (a secondary coolant circulation circuit circulating the
secondary coolant between the low-temperature side evaporator and
the low-temperature side condenser), and detects that the
temperature detected by the temperature detection portion is lower
than a prescribed temperature.
[0014] According to the present invention, it is detected that the
temperature of the low-temperature portion or the secondary coolant
circulation circuit (represented by the low-temperature side
evaporator or the low-temperature side condenser) is lower than the
prescribed temperature. Accordingly, excessive cooling of the
Stirling refrigerating engine can be detected.
[0015] Preferably, a freezing prevention portion carries out, prior
to stop control for stopping the Stirling refrigerating engine,
excessive cooling prevention control different from the stop
control, for preventing excessive cooling of the Stirling
refrigerating engine.
[0016] According to the present invention, in order to prevent
excessive cooling of the Stirling refrigerating engine, excessive
cooling prevention control different from stop control for stopping
the Stirling refrigerating engine is carried out before the stop
control, so that excessive cooling of the Stirling refrigerating
engine is prevented. Accordingly, if excessive cooling of the
Stirling refrigerating engine can successfully be prevented by
excessive cooling prevention control, the stop control of the
Stirling refrigerating engine is not necessary. Consequently, stop
of the Stirling refrigerating engine can be avoided as much as
possible. Reliability of the refrigerator can thus be improved.
[0017] Preferably, the prescribed temperature includes a first
temperature higher than a temperature at which the Stirling
refrigerating engine is excessively cooled and a second temperature
higher than the temperature at which the Stirling refrigerating
engine is excessively cooled and lower than the first temperature,
and when the state detection portion detects that the temperature
detected by the temperature detection portion is lower than the
first temperature, the excessive cooling prevention portion carries
out the excessive cooling prevention control, and when the state
detection portion detects that the temperature detected by the
temperature detection portion is lower than the second temperature,
the excessive cooling prevention portion carries out the stop
control.
[0018] According to the present invention, initially, when the
temperature detected by the temperature detection portion is lower
than the first temperature that is higher than the temperature at
which the Stirling refrigerating engine is excessively cooled,
excessive cooling prevention control is carried out, and if the
temperature detected by the temperature detection portion is lower
than the second temperature that is higher than the temperature at
which the Stirling refrigerating engine is excessively cooled and
lower than the first temperature, stop control is carried out.
Accordingly, if excessive cooling prevention control prevents the
temperature detected by the temperature detection portion from
becoming lower than the second temperature and excessive cooling of
the Stirling refrigerating engine can successfully be prevented,
stop control of the Stirling refrigerating engine is not necessary.
Consequently, stop of the Stirling refrigerating engine can be
avoided as much as possible.
[0019] Preferably, the refrigerator further includes an abnormality
in temperature detection sensing portion sensing abnormality in
detection of a temperature by the temperature detection portion
when the temperature detection portion detects a temperature.
[0020] According to the present invention, as the abnormality in
detection of a temperature is sensed at the time of detection of a
temperature, erroneous detection of a temperature can be prevented.
Therefore, stop of the Stirling refrigerating engine based on
erroneous detection that the temperature detected by the
temperature detection portion is lower than the first temperature
can be avoided.
[0021] Preferably, the refrigerator further includes a cooling fan
supplying cold air cooled by the low-temperature side evaporator
into the space inside, and the excessive cooling prevention portion
drives the cooling fan or increases a fan level of the cooling
fan.
[0022] According to the present invention, as the cooling fan is
driven or the fan level of the cooling fan is increased, convection
of the air around the low-temperature side evaporator is achieved.
Accordingly, as the air newly sent to the low-temperature side
evaporator provides heat to the secondary coolant, the temperature
of the secondary coolant is raised. Consequently, excessive cooling
of the Stirling refrigerating engine can be prevented. In addition,
as convection of the air in the space inside is achieved by means
of the cooling fan, the air in the space inside can efficiently be
cooled by the Stirling refrigerating engine. Consequently, COP
(Coefficient of Performance) of the Stirling refrigerating engine
can be improved.
[0023] Preferably, when the state detection portion detects that
the temperature detected by the temperature detection portion is
lower than the first temperature, the excessive cooling prevention
portion drives the cooling fan or increases a fan level of the
cooling fan, and when the state detection portion detects that the
temperature detected by the temperature detection portion is lower
than the first temperature after a prescribed time period has
elapsed since drive of the cooling fan or increase in the fan level
of the cooling fan, the excessive cooling prevention portion
controls the Stirling refrigerating engine so as to lower cooling
capability.
[0024] According to the present invention, if the temperature of
the secondary coolant is not raised and the temperature detected by
the temperature detection portion is lower than the first
temperature in spite of heat provided to the secondary coolant, the
excessive cooling prevention portion controls the Stirling
refrigerating engine so as to lower its cooling capability. As
cooling of the secondary coolant is thus suppressed, the
temperature of the secondary coolant is raised. Consequently,
excessive cooling of the Stirling refrigerating engine can be
prevented.
[0025] Preferably, the excessive cooling prevention portion
includes a revolution number control portion controlling the number
of revolutions of the cooling fan, and when the state detection
portion detects that the temperature detected by the temperature
detection portion is lower than the first temperature, the
excessive cooling prevention portion drives the cooling fan with
the number of revolutions of the cooling fan being set to maximum
revolution capability, and when the state detection portion detects
that the temperature detected by the temperature detection portion
is lower than the first temperature after a prescribed time period
has elapsed since drive of the cooling fan with the number of
revolutions of the cooling fan being set to maximum revolution
capability of the cooling fan, the excessive cooling prevention
portion controls the Stirling refrigerating engine so as to lower
cooling capability.
[0026] According to the present invention, as the cooling fan is
driven with the number of revolutions thereof being set to maximum
revolution capability, excessive cooling of the Stirling
refrigerating engine can further be prevented, as compared with a
case where the number of revolutions is not set to the maximum. In
addition, by setting the number of revolutions to the maximum,
further convection of the air in the space inside is achieved by
means of the cooling fan, and therefore, COP of the Stirling
refrigerating engine can further be improved.
[0027] If the temperature of the secondary coolant is not raised
and the temperature detected by the temperature detection portion
is lower than the first temperature in spite of heat provided to
the secondary coolant, control for lowering the cooling capability
of the Stirling refrigerating engine is carried out. As cooling of
the secondary coolant is thus suppressed, the temperature of the
secondary coolant is raised. Consequently, excessive cooling of the
Stirling refrigerating engine can be prevented. Such freezing
prevention control is preferably carried out while the door is
closed. This is because, if the cooling fan is driven or the fan
level of the cooling fan is increased while the door is open, the
air in the space inside leaks to the outside, and when the door is
subsequently closed, the cooling capability of the Stirling
refrigerating engine should be increased in order to cool the air
in the space inside again.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a schematic cross-sectional view of one embodiment
of a refrigerator according to the present invention.
[0029] FIG. 2 schematically shows a flow of cold air in the
refrigerator in the present embodiment.
[0030] FIG. 3 is a functional block diagram showing a freezing
prevention function of a refrigerator in a first embodiment.
[0031] FIG. 4 is a flowchart showing a flow of freezing prevention
processing performed in the refrigerator in the first
embodiment.
[0032] FIG. 5 is a flowchart showing a flow of modified freezing
prevention processing performed in the refrigerator in the first
embodiment.
[0033] FIG. 6 is a functional block diagram showing a freezing
prevention function of a refrigerator in a second embodiment.
[0034] FIG. 7 is a flowchart showing a flow of freezing prevention
processing performed in the refrigerator in the second
embodiment.
[0035] FIG. 8 is a flowchart showing a flow of modified freezing
prevention processing performed in the refrigerator in the second
embodiment.
[0036] FIG. 9 is a functional block diagram showing a freezing
prevention function of a refrigerator in a third embodiment.
[0037] FIG. 10 is a flowchart showing a flow of freezing prevention
processing performed in the refrigerator in the third
embodiment.
DESCRIPTION OF THE REFERENCE CHARACTER SIGNS
[0038] 1 refrigerator; 2 cooling fan; 10 housing; 11 second cooling
chamber; 12 first cooling chamber; 14 upper door; 15 lower door; 17
packing; 18 shelf; 19 machine room; 20, 21 duct; 20A, 20B cold air
outlet; 22 cooling fan; 30 Stirling refrigerating engine; 40
low-temperature side circulation circuit; 41 low-temperature side
condenser; 42 low-temperature side evaporator; 50 high-temperature
side natural circulation circuit; 51 high-temperature side
evaporator; 52 high-temperature side condenser; 61 damper; 62
blowing fan; 81 temperature sensor; 82 upper door opening/closing
detection switch; 83 lower door opening/closing detection switch;
84 door opening/closing detection switch; 90 control portion; and
91 display portion.
Best Modes for Carrying out the Invention
[0039] An embodiment of the present invention will be described
hereinafter with reference to the drawings. In the description
below, the same elements have the same reference characters
allotted. Their label and function are also identical. Therefore,
detailed description thereof will not be repeated.
FIRST EMBODIMENT
[0040] FIG. 1 is a schematic cross-sectional view of one embodiment
of a refrigerator according to the present invention. FIG. 2
schematically shows a flow of cold air in the refrigerator in the
present embodiment. Referring to FIGS. 1 and 2, a refrigerator 1
for storing food includes a housing 10 of a heat-insulating
structure. Housing 10 is vertically partitioned into two cooling
chambers 11 and 12. Each of cooling chambers 11 and 12 has an
opening on the front side of housing 10 (on the left side in FIG.
1), and the opening is shut by an upper door 14 and a lower door 15
that are freely opened/closed. Upper door 14 and lower door 15
include a heat insulator, and a packing 17 surrounding the opening
of cooling chamber 11, 12 is attached to the back surface of the
door. Shelves 18 adapted to types of stored food are provided in
cooling chambers 11 and 12 as appropriate.
[0041] A cooling system and a heat dissipation system mainly
constituted of a Stirling refrigerating engine 30 are arranged from
an upper surface through a rear surface to a lower surface of
housing 10. A machine room 19 is provided in a part of the upper
rear surface of housing 10, and Stirling refrigerating engine 30 is
located in machine room 19.
[0042] A part of Stirling refrigerating engine 30 turns into a
low-temperature portion (hereinafter, referred to as a cold head)
when it is driven. A low-temperature side condenser 41 is attached
to the cold head. In addition, a low-temperature side evaporator 42
is located in the rear of cooling chamber 12. Low-temperature side
condenser 41 and low-temperature side evaporator 42 are connected
to each other through a coolant pipe, to together form a
low-temperature side circulation circuit (secondary coolant
circulation circuit) 40. A natural coolant such as CO.sub.2 is
sealed in low-temperature side circulation circuit 40, and heat is
supplied/received between low-temperature side evaporator 42 and
low-temperature side condenser 41.
[0043] Ducts 20 and 21 for distributing cold air obtained in
low-temperature side evaporator 42 to cooling chambers 11 and 12
are provided in housing 10. Duct 20 has a cold air outlet 20A
communicating to cooling chamber (first cooling chamber) 12 at an
appropriate position. In duct 20, a cooling fan 22 is located at an
appropriate position. Cooling fan 22 forcibly sends the cold air in
duct 20 into cooling chamber 12. In addition, when cooling fan 22
is driven, convection of the air around low-temperature side
evaporator 42 is achieved. Thus, different air at a relatively high
temperature is supplied to low-temperature side evaporator 42.
[0044] Duct 21 has a cold air outlet 21A communicating to cooling
chamber (second cooling chamber) 11 at an appropriate position. In
duct 21, a blowing fan 62 is located at an appropriate position.
Blowing fan 62 sends air to duct 21, and forcibly sends the cold
air in duct 21 into cooling chamber 11. In addition, a damper 61
that is freely opened and closed is located at one end of duct 21
on the side of low-temperature side evaporator 42. When damper 61
is closed, duct 21 and duct 20 are disconnected from each other.
Accordingly, the cold air in duct 20 is shut off by damper 61, and
it is prevented from moving into duct 21. When damper 61 is open,
duct 21 and duct 20 communicate with each other. Therefore, when
blowing fan 62 is driven while damper 61 is open, the cold air in
duct 20 flows into duct 21 and the cold air is forcibly sent into
cooling chamber 11.
[0045] Meanwhile, while damper 61 is open, blowing fan 62 may be
driven without driving cooling fan 22. In this state as well, the
cold air in duct 20 flows into duct 21, and the cold air is
forcibly sent into cooling chamber 11. In addition, when blowing
fan 62 is driven, convection of the air around low-temperature side
evaporator 42 is achieved. Thus, different air at a relatively high
temperature is supplied to low-temperature side evaporator 42.
[0046] In addition, while damper 61 is open, cooling fan 22 and
blowing fan 62 may be driven. In this state, some cold air in duct
20 is sent into cooling chamber 12 by means of cooling fan 22 and
some cold air in duct 20 is sent into cooling chamber 11 via duct
21 by means of blowing fan 62. In this case as well, convection of
the air around low-temperature side evaporator 42 is achieved and
different air at a relatively high temperature is supplied to
low-temperature side evaporator 42.
[0047] Though not shown, a duct recovering air from cooling
chambers 11 and 12 is also provided in housing 10. The duct has an
outlet below low-temperature side evaporator 42, and supplies the
air to be cooled to low-temperature side evaporator 42 as shown
with a dashed arrow in FIG. 1.
[0048] Another part of Stirling refrigerating engine 30 turns into
a warm head (high-temperature portion) when it is driven. A
high-temperature side evaporator 51 is attached to the warm head.
In addition, a high-temperature side condenser 52 dissipating heat
to an environment outside the refrigerator and a blowing fan 53 are
provided on the upper surface of housing 10. High-temperature side
evaporator 51 and high-temperature side condenser 52 are connected
to each other through a coolant pipe, to together form a
high-temperature side natural circulation circuit 50. Water
(including an aqueous solution) or a hydrocarbon-based natural
coolant is sealed in high-temperature side natural circulation
circuit 50, and the coolant naturally circulates through
high-temperature side natural circulation circuit 50.
[0049] An operation of refrigerator 1 structured as above will now
be described. When Stirling refrigerating engine 30 is driven in
refrigerator 1 structured as above, the temperature of the cold
head is lowered. Therefore, low-temperature side condenser 41 is
cooled, and the secondary coolant (hereinafter, abbreviated as the
coolant) inside is condensed.
[0050] The coolant condensed in low-temperature side condenser 41
flows into low-temperature side evaporator 42 through
low-temperature side circulation circuit 40. The coolant that
flowed into low-temperature side evaporator 42 is evaporated by
heat of air current that passes outside low-temperature side
evaporator 42, thereby lowering a surface temperature of
low-temperature side evaporator 42. Therefore, the air that passes
through low-temperature side evaporator 42 becomes cold, and the
cold air is blown into cooling chamber 11 through cold air outlet
20A of duct 20 and through cold air outlet 21A of duct 21. The
temperature of cooling chambers 11 and 12 is thus lowered.
Thereafter, the air in cooling chambers 11 and 12 returns to
low-temperature side evaporator 42 through a not-shown duct.
[0051] The coolant evaporated in low-temperature side evaporator 42
returns to low-temperature side condenser 41 through
low-temperature side circulation circuit 40, where heat is removed
and the coolant again condenses. Then, the heat exchange operation
as above is repeated.
[0052] Meanwhile, heat generated by drive of Stirling refrigerating
engine 30 or heat recovered from the space inside by the cold head
is dissipated from the warm head as exhaust heat. Therefore,
high-temperature side evaporator 51 is heated and the coolant
inside evaporates.
[0053] The coolant turned to vapor phase due to heat generated in
high-temperature side evaporator 51 flows into high-temperature
side condenser 52 provided in the upper portion, through
high-temperature side natural circulation circuit 50. Heat of the
coolant that has flowed into high-temperature side condenser 52 is
removed by the air current introduced into high-temperature side
condenser 52 from the outside by means of blowing fan 53 and the
coolant condenses. The coolant that has condensed in
high-temperature side condenser 52 returns to high-temperature side
evaporator 51 through high-temperature side natural circulation
circuit 50, where the coolant receives heat and again evaporates.
Then, the heat exchange operation as above is repeated.
[0054] FIG. 3 is a functional block diagram showing a freezing
prevention function of the refrigerator in a first embodiment.
Referring to FIG. 3, refrigerator 1 includes a control portion 90
for overall control of the refrigerator and a temperature sensor 81
connected thereto. Control portion 90 is connected to Stirling
refrigerating engine 30, cooling fan 22, damper 61, and blowing fan
62.
[0055] Temperature sensor 81 detects a temperature of
low-temperature side evaporator 42 or the low-temperature side
circulation circuit (represented by low-temperature side condenser
41 or the cold head of Stirling refrigerating engine 30). In the
present embodiment, the temperature of the coolant within
low-temperature side circulation circuit 40 should only be detected
directly, however, the temperature of low-temperature side
evaporator 42, low-temperature side condenser 41 or the cold head
of Stirling refrigerating engine 30 is detected, instead of direct
detection. Therefore, temperature sensor 81 may detect a
temperature of any of low-temperature side evaporator 42,
low-temperature side condenser 41, and the cold head of Stirling
refrigerating engine 30, however, preferably, temperature sensor 81
detects the temperature of low-temperature side condenser 41 and
further preferably it detects the temperature of the cold head.
[0056] Control portion 90 controls drive of Stirling refrigerating
engine 30. The Stirling refrigerating engine can be driven with
varied load. The Stirling refrigerating engine attains high cooling
capability in drive with greater load, and attains low cooling
capability in drive with lower load. Control portion 90 controls
the fan level of cooling fan 22 and blowing fan 62. In addition,
control portion 90 may control switching between drive and stop of
cooling fan 22 and blowing fan 62. Moreover, control portion 90
controls switching between an open state and a closed state of
damper 61.
[0057] FIG. 4 is a flowchart showing a flow of freezing prevention
processing performed in the refrigerator in the first embodiment.
Referring to FIG. 4, control portion 90 of refrigerator 1 receives
input of the temperature of the cold head of Stirling refrigerating
engine 30 from temperature sensor 81. Control portion 90 determines
whether the temperature of the cold head is lower than a prescribed
temperature T (step S01). If YES, the process proceeds to step S02,
and if NO, the process ends. Prescribed value T is predetermined
based on a freezing point of the coolant within low-temperature
side circulation circuit 40, and set to a temperature higher than
the freezing temperature of the coolant by approximately 3.degree.
C. The temperature of the coolant does not necessarily match with
the temperature of the cold head, however, it is never lower than
the temperature of the cold head. If a temperature difference D
between the temperature of the coolant and the temperature of the
cold head is known, the prescribed temperature should be set to at
least a value obtained by subtracting temperature difference D from
the freezing point of the coolant.
[0058] When temperature sensor 81 detects the temperature of
low-temperature side evaporator 42 or low-temperature side
condenser 41, the temperature of low-temperature side evaporator 42
or low-temperature side condenser 41 does not necessarily match
with the temperature of the coolant, however, the temperature of
the coolant is never higher than the temperature of low-temperature
side evaporator 42 or low-temperature side condenser 41. If a
temperature difference D1 between the temperature of the coolant
and the temperature of low-temperature side evaporator 42 or
low-temperature side condenser 41 is known, the prescribed
temperature should be set to at least a value obtained by adding
temperature difference D1 to the freezing point of the coolant.
[0059] In step S02, the Stirling refrigerating engine is stopped.
Thus, the coolant is no longer cooled and it does not freeze.
[0060] In step S02, the Stirling refrigerating engine is stopped,
however, the Stirling refrigerating engine may be driven with lower
load. In this case, though the coolant is cooled, the coolant can
be prevented from freezing if the Stirling refrigerating engine is
driven under such a load as maintaining the temperature of the
coolant at the current level.
[0061] <Variation of Freezing Prevention Processing>
[0062] FIG. 5 is a flowchart showing a flow of modified freezing
prevention processing performed in the refrigerator in the first
embodiment. Referring to FIG. 5, control portion 90 of refrigerator
1 receives input of the temperature of the cold head of Stirling
refrigerating engine 30 from temperature sensor 81. Control portion
90 determines whether the temperature of the cold head is lower
than prescribed temperature T (step S11). If YES, the process
proceeds to step S12, and if NO, the process proceeds to step
S20.
[0063] In step S12, whether cooling fan 22 has been stopped or not
is determined. If cooling fan 22 has been stopped, the process
proceeds to step S13. If cooling fan has not been stopped, the
process proceeds to step S14. In step S13, cooling fan 22 is
driven. When cooling fan 22 is driven, convection of the air around
low-temperature side evaporator 42 is achieved and the air at a
relatively high temperature is supplied to low-temperature side
evaporator 22. Thus, lowering in the temperature of the coolant is
prevented. Meanwhile, if the process proceeds to step S14, cooling
fan 22 is driven, and it is driven with its fan level being
increased. Thus, further active convection of the air around
low-temperature side evaporator 42 is achieved and lowering in the
temperature of the coolant is prevented.
[0064] In step S15, whether a prescribed time period has elapsed or
not is determined. If YES, the process proceeds to step S16, and if
NO, the process returns to step S11. In step S16, whether blowing
fan 62 has been stopped or not is determined. If blowing fan 62 has
been stopped, the process proceeds to step S17. If blowing fan 62
has not been stopped, the process proceeds to step S19. In step
S17, the damper is opened, and in next step S18, blowing fan 62 is
driven. When blowing fan 62 is driven, convection of the air around
low-temperature side evaporator 42 is achieved and the air at a
relatively high temperature is supplied to low-temperature side
evaporator 42. Thus, lowering in the temperature of the coolant is
further prevented. Meanwhile, if the process proceeds to step S19,
blowing fan 62 is driven and it is driven with its fan level being
increased. Thus, further active convection of the air around
low-temperature side evaporator 42 is achieved and lowering in the
temperature of the coolant is prevented.
[0065] After step S18 or step S19, the process returns to step S11.
In step S11, whether or not the temperature of the cold head is
lower than prescribed temperature T is again determined. If the
temperature of the cold head is not lower than prescribed
temperature T, the process proceeds to step S20. On the other hand,
if the temperature of the cold head is lower than prescribed
temperature T, the process proceeds to step S12. Namely, the
processing in step S12 to step S19 described above is performed
until the temperature of the cold head is equal to or higher than
prescribed temperature T. In step S20, cooling fan 22, damper 61
and blowing fan 62 are driven in a normal operation mode.
[0066] Thus, according to the variation of the first embodiment,
the cooling fan or both of the cooling fan and the blowing fan
is/are driven. Accordingly, convection of the air around
low-temperature side evaporator 42 is achieved and lowering in the
temperature of the coolant can be prevented. The coolant can thus
be prevented from freezing.
[0067] It is noted that control for stopping Stirling refrigerating
engine 30 described above or for driving Stirling refrigerating
engine 30 with its cooling capability being lowered and control for
driving the cooling fan or both of the cooling fan and the blowing
fan may be carried out together. Thus, freezing of the coolant can
further be prevented.
[0068] As described above, when the temperature of low-temperature
side evaporator 42, low-temperature side condenser 41 or the cold
head of Stirling refrigerating engine 30 is lower than prescribed
temperature T, refrigerator 1 in the first embodiment lowers the
cooling capability of the Stirling refrigerating engine or stops
the Stirling refrigerating engine. Accordingly, cooling of the
coolant is suppressed and the coolant can be prevented from
freezing.
[0069] In addition, if the temperature of low-temperature side
evaporator 42, low-temperature side condenser 41 or the cold head
of Stirling refrigerating engine 30 is lower than prescribed
temperature T, cooling fan 22 is driven or the fan level thereof is
increased. Therefore, convection of the air around low-temperature
side evaporator 42 is achieved and the coolant can be prevented
from freezing.
[0070] In the first embodiment, for example, prescribed temperature
T is set to a temperature higher than the freezing point of the
coolant by approximately 3.degree. C. Prescribed temperature T,
however, may naturally be set to other temperatures, so long as it
is higher than the freezing point of the coolant.
[0071] Here, a lowest temperature in a coolant temperature range
that is possible during operation in a rated state of Stirling
refrigerating engine 30 is adopted as prescribed temperature T, so
that the temperature of the coolant can be prevented from attaining
a temperature lower than the coolant temperature range that is
possible during the rated operation of Stirling refrigerating
engine 30.
[0072] Thus, as excessive cooling of the coolant resulting from
operation of Stirling refrigerating engine 30 is avoided and
excessive cooling of the cold head can be prevented, Stirling
refrigerating engine 30 can be prevented from entering an overload
state beyond the rated state. Consequently, deterioration of
Stirling refrigerating engine 30 can be prevented.
SECOND EMBODIMENT
[0073] A refrigerator in a second embodiment will now be described.
The refrigerator in the second embodiment is the same as the
refrigerator in the first embodiment in the structure except for
the freezing prevention function. In the following, the freezing
prevention function in the second embodiment will be described.
[0074] FIG. 6 is a functional block diagram showing the freezing
prevention function of the refrigerator in the second embodiment.
Referring to FIG. 6, refrigerator 1 includes control portion 90 for
overall control of the refrigerator and an upper door
opening/closing detection switch 82 and a lower door
opening/closing detection switch 83 connected thereto. Control
portion 90 is connected to Stirling refrigerating engine 30,
cooling fan 22, damper 61, and blowing fan 62.
[0075] Upper door opening/closing detection switch 82 detects
whether upper door 14 is open or closed. Lower door opening/closing
detection switch 83 detects whether lower door 15 is open or
closed.
[0076] FIG. 7 is a flowchart showing a flow of freezing prevention
processing performed in the refrigerator in the second embodiment.
Referring to FIG. 7, control portion 90 of refrigerator 1 receives
input of an open/close state of upper door 14 and lower door 15
from upper door opening/closing detection switch 82 or lower door
opening/closing detection switch 83. Control portion 90 determines
whether any of upper door 14 and lower door 15 is open (step S21).
If any of upper door 14 and lower door 15 is open, the process
proceeds to step S22, and otherwise, the process ends.
[0077] In step S22, cooling fan 22 is stopped. Thus, forced
flow-out of the cold air in cooling chambers 11, 12, of which door
is open, to the outside can be prevented. In next step S23, whether
a prescribed time period has elapsed or not is determined. The
elapsed time here may refer to any of a time counted from the time
point of detection of the open state of any of upper door 14 or
lower door 15 in step S21 or a time counted from the time point of
stop of the cooling fan. If the prescribed time period has elapsed,
the process proceeds to step S24, and if the prescribed time period
has not elapsed, the process returns to step S21. By stopping the
cooling fan, convection of the air around low-temperature side
evaporator 42 is stopped. Thus, the temperature of the coolant is
lowered. The prescribed time period is shorter than a time period
from the time point when lowering in the temperature of the coolant
started to the time point when the temperature of the coolant
reaches the freezing point. The prescribed time period may be a
single predetermined time period or may be a time period
predetermined for each load of the Stirling refrigerating engine.
Alternatively, the prescribed time period may be a time period
predetermined for each temperature in the space inside and each
load of the Stirling refrigerating engine.
[0078] In next step S24, the Stirling refrigerating engine is
stopped. Thus, the coolant is no longer cooled and can be prevented
from freezing.
[0079] In step S24, the Stirling refrigerating engine is stopped,
however, the Stirling refrigerating engine may be driven with lower
load. In this case, though the coolant is cooled, the coolant can
be prevented from freezing if the Stirling refrigerating engine is
driven under such a load as maintaining the temperature of the
coolant at the current level.
[0080] <First Variation of Freezing Prevention
Processing>
[0081] FIG. 8 is a flowchart showing a flow of modified freezing
prevention processing performed in the refrigerator in the second
embodiment. Referring to FIG. 8, control portion 90 determines
whether upper door 14 is open or not (step S31). If upper door 14
is open, the process proceeds to step S32, and otherwise, the
process proceeds to step S38.
[0082] In step S32, blowing fan 62 is stopped and in step S33,
cooling fan 22 is stopped. Thus, forced flow-out of the cold air in
cooling chamber 11 to the outside can be prevented even if upper
door 14 is open. Then, whether a prescribed time period has elapsed
or not is determined (step S34). If the prescribed time period has
elapsed, the process proceeds to step S35, and otherwise, the
process returns to step S31. In other words, if the prescribed time
period has elapsed with upper door 14 remaining open, the process
proceeds to step S35, however, if upper door 14 is closed before
the prescribed time period elapses, the process proceeds to step
S38. By stopping cooling fan 22 in step S33, convection of the air
around low-temperature side evaporator 42 is stopped. Thus, the
temperature of the coolant is lowered. If cooling fan 22 is left
stopped, the temperature of the coolant is lowered and reaches the
freezing point. Therefore, the prescribed time period should be
shorter than a time period required until the temperature of the
coolant reaches the freezing point. The prescribed time period may
be a single predetermined time period or may be a time period
predetermined for each load of the Stirling refrigerating engine.
Alternatively, the prescribed time period may be a time period
predetermined for each temperature in the space inside and each
load of the Stirling refrigerating engine.
[0083] In step S35, damper 61 is closed, and in step S36, cooling
fan 22 is driven. Thus, the cold air around low-temperature side
evaporator 42 is sent into cooling chamber 12 but not into cooling
chamber 11, because damper 61 is closed. Therefore, convection of
the air around low-temperature side evaporator 42 is achieved and
the air at a relatively high temperature is supplied to
low-temperature side evaporator 42. Thus, the temperature of the
coolant is prevented from lowering. Consequently, the coolant is
prevented from freezing. In addition, as the cold air around
low-temperature side evaporator 42 is not sent into cooling chamber
11, forced flow-out of the cold air in cooling chamber 11 from the
opened upper door can be prevented.
[0084] In step S37, whether upper door 14 is closed or not is
determined. If upper door 14 is closed, the process proceeds to
step S38, and otherwise, the process returns to step S35. The cold
air around low-temperature side evaporator 42 is sent into cooling
chamber 12 until upper door 14 is closed, and thus the coolant is
prevented from freezing.
[0085] In step S38, cooling fan 22, damper 61 and blowing fan 62
are driven in a normal operation mode.
[0086] In next step S39, control portion 90 determines whether
lower door 15 is open or not. If lower door 15 is open, the process
proceeds to step S40, and otherwise, the process ends.
[0087] In step S40, blowing fan 62 is stopped and in step S41,
cooling fan 22 is stopped. Thus, forced flow-out of the cold air in
cooling chamber 12 to the outside can be prevented even if lower
door 15 is open. In addition, convection of the air around
low-temperature side evaporator 42 is stopped. Then, whether a
prescribed time period has elapsed or not is determined (step S42).
If the prescribed time period has elapsed, the process proceeds to
step S43, and otherwise, the process returns to step S39. In other
words, if the prescribed time period has elapsed with lower door 15
remaining open, the process proceeds to step S43, however, if lower
door 15 is closed before the prescribed time period elapses, the
process ends. The prescribed time period here is the same as in
step S34.
[0088] In step S43, damper 61 is opened, and in step S44, blowing
fan 62 is driven. Thus, the cold air around low-temperature side
evaporator 42 is sent into cooling chamber 11 but not into cooling
chamber 12. Therefore, convection of the air around low-temperature
side evaporator 42 is achieved and the air at a relatively high
temperature is supplied to low-temperature side evaporator 42.
Thus, the temperature of the coolant is prevented from lowering,
and consequently, the coolant is prevented from freezing. In
addition, as an amount of cold air around low-temperature side
evaporator 42 that is sent into cooling chamber 12 is small, forced
flow-out of the cold air in cooling chamber 12 from the opened
lower door can be suppressed.
[0089] In step S45, whether lower door 15 is closed or not is
determined. If lower door 15 is closed, the process proceeds to
step S46, and otherwise, the process returns to step S43. Then, the
cold air around low-temperature side evaporator 42 is sent into
cooling chamber 11 until lower door 15 is closed, and thus the
coolant is prevented from freezing.
[0090] In step S46, cooling fan 22, damper 61 and blowing fan 62
are driven in a normal operation mode.
[0091] When the open state of any of upper door 14 and lower door
15 continues for a prescribed time period, refrigerator 1 in the
second embodiment lowers the cooling capability of the Stirling
refrigerating engine or stops the Stirling refrigerating engine.
Accordingly, cooling of the coolant is suppressed and the coolant
can be prevented from freezing.
[0092] In addition, if the open state of any of upper door 14 or
lower door 15 continues for a prescribed time period, cooling fan
22 is driven or the fan level thereof is increased. Therefore,
convection of the air around low-temperature side evaporator 42 is
achieved and the coolant can be prevented from freezing.
[0093] Moreover, if the open state of lower door 15 continues for a
prescribed time period, damper 61 is closed and cooling fan 22 is
driven. If the open state of the upper door continues for a
prescribed time period, damper 61 is opened and blowing fan 62 is
driven. Accordingly, whichever of upper door 14 and lower door 15
may be opened, the coolant can be prevented from freezing and
leakage to the outside of the cold air in the space inside can be
prevented.
[0094] The invention of the subject application is applicable to
quick-freeze operation for quickly passing a largest ice crystal
generation zone (-3.degree. C. to -7.degree. C.) in freezing food,
in which cooling fan 22 is once stopped to set the cold air around
low-temperature side evaporator 42 to an extremely low temperature
and thereafter cooling fan 22 is driven.
[0095] In the second embodiment, in order to prevent flow-out of
the cold air when upper door 14 or lower door 15 is open, cooling
fan 22 is stopped, and after a prescribed time period has elapsed,
Stirling refrigerating engine 30 is stopped.
[0096] The present invention, however, is not limited as such, and
cooling fan 22 and Stirling refrigerating engine 30 may be stopped
when upper door 14 or lower door 15 is opened. If the temperature
of the cold head of Stirling refrigerating engine 30 is controlled
to rapidly lower in order to prevent temperature increase in the
space inside refrigerator 1, accidental freezing of the coolant may
occur due to delay in control for stopping Stirling refrigerating
engine 30.
[0097] In order to avoid this, even when the door of refrigerator 1
is open, Stirling refrigerating engine 30 is stopped without
carrying out control for lowering the temperature of the cold head
of Stirling refrigerating engine 30 for preventing temperature
increase in refrigerator 1, and thus the coolant can be prevented
from freezing.
[0098] In addition, in the second embodiment, cooling fan 22 is
stopped when upper door 14 or lower door 15 is opened, and after a
prescribed time period has elapsed, Stirling refrigerating engine
30 is stopped.
[0099] The present invention, however, is not limited as such.
Cooling fan 22 may be stopped when upper door 14 or lower door 15
is opened, and Stirling refrigerating engine 30 may be stopped when
the temperature of the cold head of Stirling refrigerating engine
30 attains to a prescribed temperature.
[0100] Freezing of the coolant due to lowering in the temperature
of the cold head of Stirling refrigerating engine 30 can thus be
prevented. Alternatively, electric power input to Stirling
refrigerating engine 30 may be decreased in a stepped manner from
the time point when the door is opened to the time point when
Stirling refrigerating engine 30 is stopped. Thus, even when the
door is open, increase in the temperature in the space inside
refrigerator 1 due to flow-out of the cold air can be suppressed,
and at the same time, the coolant can be prevented from
freezing.
[0101] In addition, preferably, if Stirling refrigerating engine 30
is once stopped when upper door 14 or lower door 15 is opened and
thereafter upper door 14 and lower door 15 are closed, Stirling
refrigerating engine 30 is operated immediately or after a
prescribed time period (for example, after 5 seconds). Thus, the
temperature in the space inside refrigerator 1 that has increased
due to flow-out of the cold air can quickly be lowered.
[0102] Moreover, preferably, if Stirling refrigerating engine 30 is
once stopped when upper door 14 or lower door 15 is opened and
thereafter the temperature of the cold head of Stirling
refrigerating engine 30 increases to a prescribed temperature,
Stirling refrigerating engine 30 is operated. Thus, excessive
increase in the temperature in the space inside refrigerator 1 can
be prevented.
[0103] In the second embodiment, cooling fan 22 is stopped when
upper door 14 or lower door 15 is opened. The present invention,
however, is not limited as such, and cooling fan 22 may operate at
lower number of revolutions. Thus, as heat is supplied to the
coolant from air in refrigerator 1, of which temperature is higher
than that of the coolant, the temperature of the coolant gradually
increases and the coolant can be prevented from freezing.
[0104] In the second embodiment, Stirling refrigerating engine 30
is stopped when upper door 14 or lower door 15 is opened. The
present invention, however, is not limited as such, and electric
power input to Stirling refrigerating engine 30 may be decreased.
Thus, as quantity of heat removed from the coolant is decreased,
the temperature of the coolant increases and the coolant can be
prevented from freezing.
[0105] In the second embodiment, the prescribed time period is set
to a time period shorter than a time period from the time point
when cooling fan 22 is stopped to the time point when the
temperature of the coolant reaches the freezing point. The present
invention, however, is not limited as such, and the prescribed time
period may be set to a time period from the time point when cooling
fan 22 is stopped to the time point when the temperature of the
coolant reaches a prescribed temperature. The prescribed
temperature may be higher than the freezing point of the
coolant.
[0106] Thus, the temperature of the coolant can be prevented from
reaching the prescribed temperature. Here, a lowest temperature in
a coolant temperature range that is possible during rated operation
of Stirling refrigerating engine 30 is adopted as the prescribed
temperature, so that the temperature of the coolant can be
prevented from attaining a temperature lower than the coolant
temperature range that is possible during rated operation of
Stirling refrigerating engine 30.
[0107] Thus, excessive cooling of the coolant resulting from
operation of Stirling refrigerating engine 30 is avoided and
excessive cooling of the cold head can be prevented, and therefore,
Stirling refrigerating engine 30 can be prevented from entering an
overload state beyond the rated state. Consequently, deterioration
of Stirling refrigerating engine 30 can be prevented.
THIRD EMBODIMENT
[0108] A refrigerator in a third embodiment will now be described.
The refrigerator in the third embodiment is the same as the
refrigerator in the first embodiment in the structure except for
the freezing prevention function. In the following, the freezing
prevention function in the third embodiment will be described.
[0109] FIG. 9 is a functional block diagram showing the freezing
prevention function of the refrigerator in the third embodiment.
Referring to FIG. 9, refrigerator 1 includes control portion 90 for
overall control of refrigerator 1, temperature sensor 81, upper
door opening/closing detection switch 82, and lower door
opening/closing detection switch 83 connected thereto. Control
portion 90 is connected to Stirling refrigerating engine 30,
cooling fan 22, damper 61, blowing fan 62, and a display portion
91.
[0110] Display portion 91 displays information on an operation
status of the refrigerator. For example, display portion 91
displays indication that Stirling refrigerating engine 30 is
abnormal, indication that temperature sensor 81 is abnormal,
indication that upper door 14 or lower door 15 is open, or
indication that the normal operation is performed. In addition,
abnormality may be notified with voice and sound in accordance with
display on display portion 91.
[0111] FIG. 10 is a flowchart showing a flow of freezing prevention
processing performed in the refrigerator in the third embodiment.
Referring to FIG. 10, control portion 90 of refrigerator 1 detects
whether temperature sensor 81 is abnormal or not. Control portion
90 determines whether a thermistor of temperature sensor 81 is
abnormal or not (step S71). If the thermistor is abnormal, the
process proceeds to step S72, and if the thermistor is not
abnormal, the process proceeds to step S74. In step S72, display
portion 91 displays indication that the thermistor is abnormal.
Then, Stirling refrigerating engine 30 is stopped (step S73).
Thereafter, the process ends.
[0112] As described above, if the thermistor is abnormal, Stirling
refrigerating engine 30 is stopped regardless of the temperature of
the coolant. Thus, the coolant is no longer cooled by Stirling
refrigerating engine 30, and the coolant can be prevented from
freezing. In addition, detection of a temperature lower than an
actual temperature due to malfunction of the thermistor in S83
which will be described later and resultant inadvertent stop of
Stirling refrigerating engine 30 in S86 can be prevented. Moreover,
detection of a temperature higher than an actual temperature in S83
which will be described later due to malfunction of the thermistor,
and resultant failure in stopping Stirling refrigerating engine 30
in spite of freezing of the coolant because the coolant has reached
the freezing temperature, can be prevented.
[0113] Further, control portion 90 of refrigerator 1 receives input
of the temperature of the cold head of Stirling refrigerating
engine 30 from temperature sensor 81. Control portion 90 determines
whether the temperature of the cold head is lower than a
temperature T.sub.1 (step S74). If the temperature of the cold head
is lower than temperature T.sub.1, the process proceeds to step
S75. If the temperature of the cold head is not lower than
temperature T.sub.1, the process returns to step S71. For example,
temperature T.sub.1 is higher than the freezing temperature of the
coolant by approximately 3.degree. C.
[0114] Control portion 90 of refrigerator 1 receives input of an
open/close state of upper door 14 and lower door 15 from upper door
opening/closing detection switch 82 or lower door opening/closing
detection switch 83. Control portion 90 determines whether any of
upper door 14 and lower door 15 is open (step S75). If any of upper
door 14 and lower door 15 is open, the process proceeds to step
S76, and otherwise, the process proceeds to step S77.
[0115] In step S76, control portion 90 gives notification of
warning that upper door 14 or lower door 15 is open on display
portion 91. Thereafter, the process returns to S71.
[0116] In step S77, whether or not the number of revolutions of
cooling fan 22 has been set to the maximum tolerable number of
revolutions of cooling fan 22 is determined. If the maximum
tolerable number of revolutions has not been set, the process
proceeds to step S78, and if the maximum tolerable number of
revolutions has been set, the process proceeds to step S81.
[0117] In step S78, the number of revolutions of cooling fan 22 is
set to the maximum tolerable number of revolutions of cooling fan
22. Thus, as compared with the case where the number of revolutions
of cooling fan 22 is smaller than the maximum tolerable number of
revolutions, further active convection of the air around
low-temperature side evaporator 42 is achieved and lowering in the
temperature of the coolant can be suppressed. Then, whether a
prescribed time period has elapsed since the number of revolutions
of cooling fan 22 was set to the maximum tolerable number of
revolutions is determined (step S79). If the prescribed time period
has not elapsed, S79 is repeated. If the prescribed time period has
elapsed, the process proceeds to step S82.
[0118] Preferably, the prescribed time period is not shorter than a
time period required for the temperature of the coolant to increase
at least by such temperature variation that temperature sensor 81
is capable of detecting temperature increase when the number of
revolutions of cooling fan 22 is set to the maximum tolerable
number of revolutions during normal operation. For example, if
temperature detection error of temperature sensor 81 is
.+-.0.5.degree. C., a time period not shorter than a time period
required for the temperature of the coolant to increase by at least
1.degree. C. should be set as the prescribed time period.
[0119] In addition, preferably, the prescribed time period is
shorter than a time period until the temperature of the cold head
lowers from temperature T.sub.1 to a temperature T.sub.2 which will
be described later when the number of revolutions of cooling fan 22
is set to the maximum tolerable number of revolutions during
abnormal operation.
[0120] In step S81, electric power input to Stirling refrigerating
engine 30 is decreased by a prescribed amount. The cooling
capability of Stirling refrigerating engine 30 is thus lowered.
Therefore, a quantity of heat removed from the coolant can be
decreased and temperature lowering of the coolant can be
suppressed.
[0121] In step S82, control portion 90 again determines whether the
temperature of the cold head is lower than temperature T.sub.1. If
the temperature of the cold head is not lower than temperature
T.sub.1, the process proceeds to step S83. If the temperature of
the cold head is lower than temperature T.sub.1, the process
proceeds to step S84.
[0122] Namely, if the process proceeds to step S83, by setting the
number of revolutions of cooling fan 22 to the maximum tolerable
number of revolutions in step S78 or decreasing electric power
input to Stirling refrigerating engine 30 in step S81, the
temperature of the cold head returns from an abnormal value lower
than temperature T.sub.1 to a normal value not lower than
temperature T.sub.1. If the process proceeds to step S84, the
temperature of the cold head remains at abnormal value.
[0123] In step S83, the operation mode of Stirling refrigerating
engine 30, cooling fan 22, damper 61, and blowing fan 62 is
switched to the normal operation mode. Thereafter, the process
returns to step S71.
[0124] In step S84, control portion 90 determines whether the
temperature of the cold head is lower than temperature T.sub.2. If
the temperature of the cold head is not lower than temperature
T.sub.2, the process returns to step S81. If the temperature of the
cold head is lower than temperature T.sub.2, the process proceeds
to step S85. For example, temperature T.sub.2 is higher than the
freezing temperature of the coolant by approximately 1.degree.
C.
[0125] In step S85, control portion 90 displays indication that
Stirling refrigerating engine 30 is abnormal on display portion 91.
Then, in step S86, control portion 90 stops Stirling refrigerating
engine 30. Thereafter, the process ends.
[0126] In the present embodiment, the number of revolutions of
cooling fan 22 is set to the maximum tolerable number of
revolutions in step S78, however, the number of revolutions of
cooling fan 22 may be increased in a stepped manner. Then, if the
temperature of the cold head is not lower than temperature T.sub.1
after a prescribed time period elapsed, the operation returns to
the normal operation.
[0127] Thus, if the temperature of the cold head is not lower than
temperature T.sub.1 before the number of revolutions of cooling fan
22 reaches the maximum tolerable number of revolutions, it is not
necessary to increase the number of revolutions of cooling fan 22
more than necessary and power consumption can be suppressed. In
addition, as the temperature variation of the coolant is gradual,
the temperature of the coolant can be controlled more accurately
than when the temperature variation of the coolant is sudden.
[0128] In a mechanism for cooling the space inside refrigerator 1
using the coolant, the coolant may freeze. If the operation of
Stirling refrigerating engine 30 is continued with the coolant
remaining frozen, the temperature of the cold head suddenly lowers
and Stirling refrigerating engine 30 may fail.
[0129] Therefore, if the temperature of low-temperature side
circulation circuit 40 reaches a temperature around the freezing
temperature of the coolant as a result of detection of the
temperature of low-temperature side circulation circuit 40 of
Stirling refrigerating engine 30, Stirling refrigerating engine 30
should be stopped. If Stirling refrigerating engine 30 is suddenly
stopped, however, reliability of refrigerator 1 as a product is
remarkably harmed, which is not preferred.
[0130] As described above, refrigerator 1 in the third embodiment
carries out, prior to stop control for stopping Stirling
refrigerating engine 30 for preventing the coolant from freezing,
freezing prevention control for preventing freezing of the coolant
that is different from stop control, such as control for setting
the number of revolutions of cooling fan 22 to the maximum
tolerable number of revolutions or control for decreasing electric
power input to Stirling refrigerating engine 30, to thereby prevent
the coolant from freezing.
[0131] Therefore, if the coolant can be prevented from freezing as
a result of freezing prevention control, stop control of Stirling
refrigerating engine 30 is not necessary. Consequently, stop of the
Stirling refrigerating engine can be avoided as much as possible.
Reliability of the refrigerator as the product can thus be
improved.
[0132] In addition, in detecting a temperature by means of
temperature sensor 81, for example, abnormality in detection of the
temperature, such as abnormality of the thermistor of temperature
sensor 81, is sensed. Therefore, erroneous detection of the
temperature by temperature sensor 81 can be prevented. Thus, stop
of Stirling refrigerating engine 30 in step S86 based on erroneous
detection in step S84 that the temperature of the cold head is
lower than temperature T.sub.2 can be avoided.
[0133] In addition, if the temperature of the cold head is lower
than temperature T.sub.1 which is higher than the freezing
temperature of the coolant, freezing prevention control is carried
out. Meanwhile, if the temperature of the cold head is lower than
temperature T.sub.2 which is higher than the freezing temperature
of the coolant and lower than T.sub.1, stop control of Stirling
refrigerating engine 30 is carried out. Accordingly, if freezing
prevention control is able to prevent the temperature of the cold
head from becoming lower than temperature T.sub.2 and to prevent
the coolant from freezing, stop control of Stirling refrigerating
engine 30 is not necessary. Consequently, stop of Stirling
refrigerating engine 30 can be avoided as much as possible.
[0134] In addition, as the fan level of cooling fan 22 is
increased, convection of the air around low-temperature side
evaporator 42 is achieved. Accordingly, as the air newly sent to
low-temperature side evaporator 42 provides heat to the coolant,
the temperature of the coolant is raised. Consequently, the coolant
can be prevented from freezing.
[0135] Moreover, as convection of the air in the space inside is
achieved by means of cooling fan 22, the air in the space inside
can efficiently be cooled by low-temperature side evaporator 42.
Consequently, COP (Coefficient of Performance) of Stirling
refrigerating engine 30 can be improved.
[0136] Here, COP represents heating or cooling capability of a
heating apparatus or a cooling apparatus per power consumption, and
it is calculated as a ratio between a quantity of heat provided to
a non-heated object or a quantity of heat removed from a non-cooled
object and a value obtained by converting an amount of energy
consumed for heating or cooling to a heat quantity. In the present
embodiment, the cooling apparatus is refrigerator 1, and the
non-cooled object is the air in refrigerator 1 cooled by the
coolant cooled by the cold head of Stirling refrigerating engine
30. Here, COP can be found in the expression
COP=Q.sub.OUT/Q.sub.IN, where Q.sub.OUT represents a quantity of
heat removed from the non-cooled object and Q.sub.IN represents a
value obtained by converting the amount of consumed energy to heat
quantity.
[0137] Namely, as the heat quantity is efficiently removed from the
air convected by means of cooling fan 22 by the coolant cooled by
Stirling refrigerating engine 30, heat quantity Q.sub.OUT removed
from the air increases relative to value Q.sub.IN obtained by
converting the consumed electric power to heat quantity, and COP
thus improves.
[0138] If the temperature of the coolant is not raised and the
temperature of the cold head is lower than temperature T.sub.1 in
spite of the fact that the heat quantity is provided to the coolant
as a result of removal of heat quantity from the air, the cooling
capability of Stirling refrigerating engine 30 is lowered, that is,
control for decreasing electric power input to Stirling
refrigerating engine 30 is carried out.
[0139] Accordingly, as cooling of the coolant by Stirling
refrigerating engine 30 is suppressed, the temperature of the
coolant is raised. Consequently, the coolant is prevented from
freezing.
[0140] In addition, as cooling fan 22 is driven with the number of
revolutions of cooling fan 22 being set to the maximum tolerable
number of revolutions, freezing of the coolant can further be
prevented as compared with the case where the number of revolutions
is not set to the maximum tolerable number of revolutions.
Moreover, by setting the number of revolutions to the maximum
tolerable number of revolutions, further convection of the air in
the space inside is achieved by means of cooling fan 22, and
therefore, COP of Stirling refrigerating engine 30 can further be
improved.
[0141] If the temperature of the coolant is not raised and the
temperature of the cold head is lower than temperature T.sub.1 in
spite of the fact that the fan level of cooling fan 22 is increased
and the heat quantity is provided to the coolant, control for
decreasing electric power input to Stirling refrigerating engine 30
is carried out. As cooling of the coolant can thus be suppressed,
the temperature of the coolant is increased. Consequently, the
coolant can be prevented from freezing.
[0142] In addition, as warning about freezing of the coolant due to
abnormality of Stirling refrigerating engine 30 is notified before
the coolant freezes, one can be urged to take emergency measures
for addressing freezing of the coolant, for example, by opening and
closing the door.
[0143] In the third embodiment, for example, temperature T.sub.1 is
higher than the freezing point of the coolant by approximately
3.degree. C. and temperature T.sub.2 is higher than the freezing
point of the coolant by approximately 1.degree. C. It goes without
saying, however, that any other temperature may be set as
temperatures T.sub.1 and T.sub.2, so long as it is higher than the
freezing point of the coolant and relation of T.sub.1>T.sub.2 is
satisfied.
[0144] Here, a lowest temperature in a coolant temperature range
that is possible during operation in a rated state of Stirling
refrigerating engine 30 is adopted as temperature T.sub.2, and a
temperature lower than a highest temperature in the aforementioned
temperature range and higher than temperature T.sub.2 by several
degrees is adopted as temperature T.sub.1, so that the temperature
of the coolant can be prevented from attaining a temperature lower
than the coolant temperature range that is possible during rated
operation of Stirling refrigerating engine 30.
[0145] Thus, excessive cooling of the coolant resulting from
operation of Stirling refrigerating engine 30 is avoided and
excessive cooling of the cold head can be prevented. Therefore,
Stirling refrigerating engine 30 can be prevented from entering an
overload state beyond the rated state. Consequently, deterioration
of Stirling refrigerating engine 30 can be prevented.
[0146] In the first to third embodiments, refrigerator 1 has been
described, however, the invention may be understood as a method of
controlling refrigerator 1 or Stirling refrigerating engine 30
performing the processing shown in FIGS. 4, 5, 7, 8, and 10, a
program for controlling refrigerator 1 or Stirling refrigerating
engine 30 performing the processing shown in FIGS. 4, 5, 7, 8, and
10, and Stirling refrigerating engine 30 provided in refrigerator
1.
[0147] Although the present invention has been described and
illustrated in detail, it is clearly understood that the same is by
way of illustration and example only and is not to be taken by way
of limitation, the spirit and scope of the present invention being
limited only by the terms of the appended claims.
* * * * *