U.S. patent application number 10/012353 was filed with the patent office on 2002-06-13 for two-evaporator refrigerator having a bypass and channel-switching means for refrigerant.
Invention is credited to Doi, Takashi, Kashima, Koji, Noguchi, Akihiro, Sakuma, Tsutomu.
Application Number | 20020069654 10/012353 |
Document ID | / |
Family ID | 18846557 |
Filed Date | 2002-06-13 |
United States Patent
Application |
20020069654 |
Kind Code |
A1 |
Doi, Takashi ; et
al. |
June 13, 2002 |
Two-evaporator refrigerator having a bypass and channel-switching
means for refrigerant
Abstract
A refrigerator has a two-stage compressor and means for
switching refrigerant flow between a primary channel and a
bypassing channel at downstream of a condenser that is connected
with an outlet of the two-stage compressor. The primary channel
extends from a first exit of the means for switching, through a
first capillary tube and a first evaporator, to a gas-liquid
separator, a gas-exit of which is connected with a second
evaporator through a second capillary tube. The bypassing channel
extends from a second exit of the means for switching, through a
bypass capillary, to the gas-liquid separator. When flow of
refrigerant in the second evaporator is substantially interrupted
and so detected, refrigerant flow is switched to the bypassing
channel, by means for controlling.
Inventors: |
Doi, Takashi; (Tokyo,
JP) ; Sakuma, Tsutomu; (Tokyo, JP) ; Kashima,
Koji; (Tokyo, JP) ; Noguchi, Akihiro; (Tokyo,
JP) |
Correspondence
Address: |
PILLSBURY WINTHROP, LLP
P.O. BOX 10500
MCLEAN
VA
22102
US
|
Family ID: |
18846557 |
Appl. No.: |
10/012353 |
Filed: |
December 12, 2001 |
Current U.S.
Class: |
62/199 ;
62/228.5 |
Current CPC
Class: |
F25D 2317/0682 20130101;
F25B 41/39 20210101; F25B 2700/2109 20130101; F25D 17/065 20130101;
F25B 2400/04 20130101; F25B 1/10 20130101; F25B 5/04 20130101; F25D
2400/04 20130101; F25B 2400/23 20130101; F25B 2341/062 20130101;
F25B 2400/13 20130101 |
Class at
Publication: |
62/199 ;
62/228.5 |
International
Class: |
F25B 005/00; F25B
001/00; F25B 049/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 12, 2000 |
JP |
2000-377897 |
Claims
What is claimed is
1. A refrigerator comprising: a two-stage compressor having an
outlet and first and second inlets, pressure of said fist inlet
being intermediate between pressures of the outlet at higher
pressure and the second inlet at lower pressure; means for
switching of refrigerant flow channels at downstream of a condenser
connected with said outlet; means for separating gaseous and liquid
phase parts of refrigerant from each other at downstream of a first
evaporator for fresh food compartment, said first evaporator being
connected from first exit of said means for switching through a
first capillary tube; a first suction pipe connecting from a
gaseous part exit of said means for separating to said first inlet
of the two-stage compressor; a second capillary tube connecting
from a liquid part exit of said means for separating to a second
evaporator for freezer compartment; a bypass capillary tube
connecting to the second evaporator from second exit of said means
for switching; a second suction pipe connecting from the second
evaporator to said second inlet of the two-stage compressor; and
means for controlling a refrigeration cycle in a manner of
bypassing the first evaporator when temperatures of said first
suction pipe becomes lower than a predetermined value, by closing
said first exit of the means for switching and by opening said
second exit thereof.
2. A refrigerator comprising: a two-stage compressor having an
outlet and first and second inlets, pressure of said fist inlet
being intermediate between pressures of the outlet at higher
pressure and the second inlet at lower pressure; means for
switching of refrigerant flow channels at downstream of a condenser
connected with said outlet; means for separating gaseous and liquid
phase parts of refrigerant from each other at downstream of a first
evaporator for fresh food compartment, said first evaporator being
connected from first exit of said means for switching through a
first capillary tube; a first suction pipe connecting from a
gaseous part exit of said means for separating to said first inlet
of the two-stage compressor; a second capillary tube connecting
from a liquid part exit of said means for separating to a second
evaporator for freezer compartment; a bypass capillary tube
connecting to the second evaporator from second exit of said means
for switching; a second suction pipe connecting from the second
evaporator to said second inlet of the two-stage compressor; and
means for controlling a refrigeration cycle in a manner of
bypassing the first evaporator when the temperatures of said second
suction pipe becomes higher than a predetermined value, by closing
said first exit of the means for switching and by opening said
second exit thereof.
3. A refrigerator comprising: a two-stage compressor having an
outlet and first and second inlets, pressure of said fist inlet
being intermediate between pressures of the outlet at higher
pressure and the second inlet at lower pressure; means for
switching of refrigerant flow channels at downstream of a condenser
connected with said outlet; means for separating gaseous and liquid
phase parts of refrigerant from each other at downstream of a first
evaporator for fresh food compartment, said first evaporator being
connected from first exit of said means for switching through a
first capillary tube; a first suction pipe connecting from a
gaseous part exit of said means for separating to said first inlet
of the two-stage compressor; a second capillary tube connecting
from a liquid part exit of said means for separating to a second
evaporator for freezer compartment; a bypass capillary tube
connecting to the second evaporator from second exit of said means
for switching; a second suction pipe connecting from the second
evaporator to said second inlet of the two-stage compressor; and
means for controlling a refrigeration cycle in a manner of
bypassing the first evaporator when temperature of the means for
separating becomes lower than a predetermined value, by closing
said first exit of the means for switching and by opening said
second exit thereof.
4. A refrigerator comprising: a two-stage compressor having an
outlet and first and second inlets, pressure of said fist inlet
being intermediate between pressures of the outlet at higher
pressure and the second inlet at lower pressure; means for
switching of refrigerant flow channels at downstream of a condenser
connected with said outlet; means for separating gaseous and liquid
phase parts of refrigerant from each other at downstream of a first
evaporator for fresh food compartment, said first evaporator being
connected from first exit of said means for switching through a
first capillary tube; a first suction pipe connecting from a
gaseous part exit of said means for separating to said first inlet
of the two-stage compressor; a second capillary tube connecting
from a liquid part exit of said means for separating to a second
evaporator for freezer compartment; a bypass capillary tube
connecting to the second evaporator from second exit of said means
for switching; a second suction pipe connecting from the second
evaporator to said second inlet of the two-stage compressor; and
means for controlling a refrigeration cycle in a manner of
bypassing the first evaporator when temperatures of the means for
separating and the second evaporator being become substantially
same, by closing said first exit of the means for switching and by
opening said second exit thereof.
5. A refrigerator comprising: a two-stage compressor having an
outlet and first and second inlets, pressure of said fist inlet
being intermediate between pressures of the outlet at higher
pressure and the second inlet at lower pressure; means for
switching of refrigerant flow channels at downstream of a condenser
connected with said outlet; means for separating gaseous and liquid
phase parts of refrigerant from each other at downstream of a first
evaporator for fresh food compartment, said first evaporator being
connected from first exit of said means for switching through a
first capillary tube; a first suction pipe connecting from a
gaseous part exit of said means for separating to said first inlet
of the two-stage compressor; a second capillary tube connecting
from a liquid part exit of said means for separating to a second
evaporator for freezer compartment; a bypass capillary tube
connecting to the second evaporator from second exit of said means
for switching; a second suction pipe connecting from the second
evaporator to said second inlet of the two-stage compressor; and
means for controlling a refrigeration cycle in a manner of
bypassing the first evaporator when drive frequency of a motor for
operating said two-stage compressor increases to a predetermined
magnification, by closing said first exit of the means for
switching and by opening said second exit thereof.
6. A refrigerator according to anyone of claims 1-6, wherein a fan
for leading air around said first evaporator into the fresh food
compartment is driven at a time of said bypassing by said means for
controlling.
7. A refrigerator comprising: a two-stage compressor having an
outlet and first and second inlets, pressure of said fist inlet
being intermediate between pressures of the outlet at higher
pressure and the second inlet at lower pressure; means for
switching of refrigerant flow channels at downstream of a condenser
connected with said outlet; means for separating gaseous and liquid
phase parts of refrigerant from each other at downstream of a first
evaporator for fresh food compartment, said first evaporator being
connected from first exit of said means for switching through a
first capillary tube; a first suction pipe connecting from a
gaseous part exit of said means for separating to said first inlet
of the two-stage compressor; a second capillary tube connecting
from a liquid part exit of said means for separating to a second
evaporator for freezer compartment; a bypass capillary tube
connecting to the second evaporator from second exit of said means
for switching; a second suction pipe connecting from the second
evaporator to said second inlet of the two-stage compressor; and
means for controlling a refrigeration cycle in a manner to detect
refrigerant flow being substantially interrupted in a passage
connecting from said means for separating to said second inlet
through the second capillary tube, the second evaporator and the
second suction pipe, and to bypass the first evaporator during such
substantial interruption being detected, by closing said first exit
of the means for switching and by opening said second exit
thereof.
8. A refrigerator according to claim 7, wherein a fan for leading
air around said first evaporator into the fresh food compartment is
driven at a time of said bypassing by said means for
controlling.
9. A refrigerator according to claim 7, said bypassing being made
during substantially whole period of said substantial
interruption.
10. A refrigerator comprising: a two-stage compressor having an
outlet and first and second inlets, pressure of said fist inlet
being intermediate between pressures of the outlet at higher
pressure and the second inlet at lower pressure; means for
switching of refrigerant flow channels at downstream of a condenser
connected with said outlet; means for separating gaseous and liquid
phase parts of refrigerant from each other at downstream of a first
evaporator for fresh food compartment, said first evaporator being
connected from first exit of said means for switching through a
first capillary tube; a first suction pipe connecting from a
gaseous part exit of said means for separating to said first inlet
of the two-stage compressor; a second capillary tube connecting
from a liquid part exit of said means for separating to a second
evaporator for freezer compartment; a bypass capillary tube
connecting to the second evaporator from second exit of said means
for switching; a second suction pipe connecting from the second
evaporator to said second inlet of the two-stage compressor; and
means for controlling a refrigeration cycle in a manner to detect
refrigerant flow being substantially interrupted or smaller than a
predetermined level in a passage connecting from said means for
separating to said second inlet through the second capillary tube,
the second evaporator and the second suction pipe, and to bypass
the first evaporator during such substantial interruption or
insufficient flow being detected, by closing said first exit of the
means for switching and by opening said second exit thereof.
11. A refrigerator having a refrigeration cycle comprised of a
normal operation and a bypassing operation, and a controller for
switching the refrigeration cycle between the normal and bypassing
operations, said normal operation comprises: partly condensing
gaseous refrigerant flowed out from an outlet of two-stage
compressor by heat exchange to form first two-phase refrigerant
composed of gas and liquid phases; reducing pressure of the first
two-phase refrigerant; making a heat exchange by passing the first
two-phase refrigerant through a first evaporator; separating
gas-phase and liquid-phase parts, of the first two-phase
refrigerant flowed out from the first evaporator, from each other
in a separator; returning gaseous refrigerant flowed out from the
separator to a first inlet of the two-stage compressor, while
reducing pressure of liquid refrigerant flowed out from the
separator to form second two-phase refrigerant having pressure
lower than that of the first two-phase refrigerant in the first
evaporator and subsequently making a heat-exchange by passing the
second two-phase refrigerant through a second evaporator; and
returning gaseous refrigerant flowed out from the second evaporator
to second inlet of the two-stage compressor; said bypassing
operation being in same manner with said normal operation except
that the first two-phase refrigerant formed by said partly
condensing is led to the second evaporator in manner of bypassing
the first evaporator and the separator; said controller switching
the refrigerant cycle to said bypassing operation when refrigerant
flow in a passage connecting the separator to said second inlet
through the second evaporator is substantially interrupted.
12. A refrigerator according to claim 7 or claim 11, wherein a fan
for leading air around said first evaporator into the fresh food
compartment is driven at a time of said bypassing by said means for
controlling.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a refrigerator equipped with a
two-stage compressor and two evaporators for performing a
refrigeration cycle.
[0002] Such a refrigerator has been proposed and described in U.S.
Pat. No. 4,918,942.
[0003] The refrigeration cycle of the prior art document comprises
following steps; each of the steps will be explained by referring
FIG. 8, which shows a refrigerant circuit 100.
[0004] (1) Gaseous refrigerant streams out at high pressure from an
outlet of the two-stage compressor. Then, the gaseous refrigerant
is condensed at interior of a condenser 14 to become a two-phase
refrigerant composed of gas and liquid phases at high pressure.
[0005] (2) The two-phase refrigerant at high pressure is subjected
to pressure reduction in a capillary tube 16'. Then, the two-phase
refrigerant at intermediate pressure flows into an evaporator 18
for fresh food compartments or non-freezing refrigerator
compartment (hereinafter referred as "fresh food evaporator").
[0006] (3) Liquid-phase part of the two-phase refrigerant partly
evaporates at inside of the fresh food evaporator 18. Then, the
two-phase refrigerant enters into a separator 20', through which
gas-phase and liquid-phase parts are separated from each other.
[0007] (4) Gaseous refrigerant that is separated from liquid
refrigerant by the separator 20' flows through a suction pipe 22 at
intermediate pressure; and then returns to the two-stage compressor
12 through its intermediate-pressure side inlet.
[0008] (5) Liquid refrigerant that is separated from the gaseous
refrigerant by the separator 20' is subjected to pressure reduction
at a throttle valve 114, to form a two-phase refrigerant at low
pressure. Then, the two-phase refrigerant at low pressure flows
into an evaporator 26 for freezer compartment (hereinafter referred
as "freezer evaporator").
[0009] (6) Liquid part of the two-phase refrigerant evaporates in
the freezer evaporator 26. Thus formed gaseous refrigerant flows
through a suction pipe 28 at low pressure; and then returns to the
two-stage compressor 12 through its low-pressure side inlet.
[0010] The prior art refrigeration cycle has a problem of
occasional occurrence of so-called "one-sided flow" and resulting
interruption of cooling of the freezer compartment. The "one-sided
flow" means undesirable interruption of refrigerant flow in the
freezer evaporator 26 while refrigerant continues to flow through
the other passage in the refrigerant circuit. In other words, whole
of refrigerant taken into the separator 20' flows out to the
suction pipe 22 at intermediate pressure, and then into the
intermediate-pressure side inlet of the compressor 12. The
"one-sided flow" occurs when a pressure balance between the fresh
food evaporator 18 and the freezer evaporator 26 is lost. The
"one-sided flow" does occur especially when heat-exchange
temperature of the freezer evaporator 26 rises too high at occasion
of excessive rise of temperature in the freezer compartment.
[0011] Meanwhile, at occasion of dropped room temperature in winter
season or the like, no cooling at the fresh food evaporator 18 is
needed while need of cooling at the freezer evaporator 26 still
remains. The prior art refrigeration cycle also has a problem in
such occasion. Because the fresh food evaporator 18 and the freezer
evaporator 16 are connected in serial, refrigerant also have to
flow through the fresh food evaporator 18.
[0012] The "one-sided flow" also occurs when an excessive cooling
or heat exchange is made by the fresh food evaporator 18, because
such excessive heat exchange makes liquid-phase refrigerant
entirely evaporates in the fresh food evaporator 18 and thus
exhausting the liquid-phase refrigerant that is in otherwise to be
sent to the freezer evaporator 26.
BRIEF SUMMARY OF THE INVENTION
[0013] First aspect of invention-wise refrigerator comprising: a
two-stage compressor having an outlet and first and second inlets,
pressure of said fist inlet being intermediate between pressures of
the outlet at higher pressure and the second inlet at lower
pressure; means for switching of refrigerant flow channels at
downstream of a condenser connected with said outlet; means for
separating gaseous and liquid phase parts of refrigerant from each
other at downstream of a first evaporator for fresh food
compartment, said first evaporator being connected from first exit
of said means for switching through a first capillary tube; a first
suction pipe connecting from a gaseous part exit of said means for
separating to said first inlet of the two-stage compressor; a
second capillary tube connecting from a liquid part exit of said
means for separating to a second evaporator for freezer
compartment; a bypass capillary tube connecting to the second
evaporator from second exit of said means for switching; a second
suction pipe connecting from the second evaporator to said second
inlet of the two-stage compressor; and means for controlling a
refrigeration cycle in a manner of bypassing or skipping the first
evaporator when temperatures of said first suction pipe becomes
lower than a predetermined value, by closing said first exit of the
means for switching and by opening said second exit of the means
for switching.
[0014] According to second aspect of the invention, said bypassing
is made when temperature of the second suction pipe becomes higher
than a predetermined value, alternative to that of the first aspect
of the invention--bypassing is made when the temperatures of said
second suction pipe becomes lower than a predetermined value.
[0015] According to third aspect of the invention, said bypassing
is made when temperature of the means for separating becomes lower
than a predetermined value, alternative to those of former aspects
of the invention.
[0016] According to fourth aspect of the invention, said bypassing
is made when temperatures of the means for separating and the
second evaporator being become substantially same, alternative to
those of former aspects of the invention.
[0017] According to fifth aspect of the invention, said bypassing
is made when drive frequency of a motor for operating said
two-stage compressor increases to a predetermined magnification,
alternative to those of former aspects of the invention.
[0018] According to sixth aspect of the invention, a fan for
leading air around said first evaporator into the fresh food
compartment is driven at a time of said bypassing by said means for
controlling.
[0019] A normal mode of refrigeration cycle of the refrigerator is
explained in below.
[0020] (1) Gaseous refrigerant streams out at high pressure from an
outlet of a two-stage compressor, and is condensed in a condenser
to form a two-phase refrigerant composed of gaseous and liquid
phases.
[0021] (2) The two-phase refrigerant of high pressure is subjected
to pressure reduction within a first capillary tube to become a
two-phase refrigerant of intermediate pressure; and then flows into
a first evaporator for cooling a fresh food compartment.
[0022] (3) Liquid part of the two-phase refrigerant partly
evaporates in the first evaporator. Then, the two-phase refrigerant
flows into means for separating gaseous and liquid parts of
refrigerant from each other.
[0023] (4) Gaseous refrigerant that is separated from liquid
refrigerant by the means for separating returns directly through a
first suction pipe into the two-stage compressor from its first
inlet. The first inlet is at an intermediate pressure between
pressures at outlet and second inlet of the two-stage
compressor.
[0024] (5) Liquid refrigerant that is separated from the gaseous
refrigerant by the separator flows through a second capillary tube
as being reduced in pressure to become a two-phase refrigerant;
then the two-phase refrigerant at lower pressure flows into a
second evaporator for cooling a freezer compartment.
[0025] (6) Liquid part of the two-phase refrigerant evaporates in
the freezer compartment. Thus formed gaseous refrigerant returns,
through a second suction pipe at pressure lower than that of the
first suction pipe, into the two-stage compressor 12 from its
second inlet.
[0026] The invention-wise refrigerator operates not only in normal
mode but also in "bypassing" mode of refrigeration cycle as in
below.
[0027] According to the first aspect of the invention, occurring of
"one-sided flow" is assumed when temperature of the first suction
pipe exceeds a predetermined temperature. In such occasion, the
first exit of the switching means is closed while the second exit
of the switching means is opened, thereby bypassing refrigerant
directly to the second evaporator for the freezer compartment while
skipping the first evaporator for the fresh food compartment. In
this way, the "one-sided flow" is prevented or quenched by directly
providing refrigerant to the second evaporator, and thus cooling of
the freezer compartment being effected.
[0028] According to the second aspect of the invention, the
"one-sided flow" is detected by temperature of the second suction
pipe, pressure in which is lower than that of the first suction
pipe. Meanwhile, the "one-sided flow" is detected by: temperature
of the separating means in the third aspect of the invention; by
temperature difference between the separating means and the first
evaporator in the fourth aspect of the invention; by drive
frequency of a motor for operating the two-stage compressor in the
fifth aspect of the invention.
BRIEF DESCRIPTION OF THE DRAWING
[0029] FIG. 1 shows construction of a refrigerant circuit of first
embodiment;
[0030] FIG. 2 shows a vertical sectional view of a
refrigerator;
[0031] FIG. 3A is a graph showing a temperature variation of a
first suction pipe at intermediate pressure, upon occasion of the
one-sided flow;
[0032] FIG. 3B is a graph showing a temperature variation of the
first suction pipe at intermediate pressure at a time of no
occurrence of the one-sided flow;
[0033] FIG. 4 shows construction of a refrigerant circuit of second
embodiment;
[0034] FIG. 5A is a graph showing a temperature variation of a
low-pressure suction pipe at an occasion of the one-sided flow;
[0035] FIG. 5B is a graph showing a temperature variation of a
low-pressure suction pipe at a time of no occurrence of the
one-sided flow;
[0036] FIG. 6 shows construction of a refrigerant circuit of third
embodiment;
[0037] FIG. 7A is an explanatory illustration of a gas-liquid
separator in a normal state at a time of no occurrence of the
one-sided flow;
[0038] FIG. 7B is an explanatory illustration of a gas-liquid
separator at an occasion of the one-sided flow;
[0039] FIG. 8 shows construction of a refrigerant circuit in the
prior art.
DETAILED DESCRIPTION OF THE INVENTION
FIRST EMBODIMENT
[0040] The first embodiment of the present invention will be
described with reference to FIGS. 1 through 3. FIG. 1 shows
construction of a refrigerant circuit of first embodiment; and FIG.
2 shows a vertical sectional view of a refrigerator.
[0041] 1. Structure of a refrigerator
[0042] On first hand, a structure of a refrigerator is explained
with reference to the FIG. 1. At inside of a refrigerator 1, there
are arranged a fresh food compartment 2, a vegetable compartment 3,
an ice-forming compartment 4 and a freezer compartment 5, in serial
in this order from upside to down. At backside of the refrigerator
1, a machinery compartment 6 is arranged with a two-stage
compressor 12 (herein after merely referred as "compressor").
[0043] At backside of the ice-forming compartment 4, a freezer
evaporator 26, or an evaporator for freezing, is disposed for
cooling the ice-forming compartment 4 and the freezer compartment
5. Further, at backside of the vegetable compartment 3, a fresh
food evaporator 18, or an evaporator for non-freezing
refrigeration, is disposed for cooling the fresh food compartment 2
and the vegetable compartment 3.
[0044] At upside of the freezer evaporator 26, first fan 27 is
disposed for sending out an air cooled by the freezer evaporator 26
into the ice-forming compartment 4 and the freezer compartment 5.
Further, at upside of the fresh food evaporator 18, second fan 19
is disposed for sending out an air cooled by the fresh food
evaporator 18 into the fresh food compartment 2 and the vegetable
compartment 3.
[0045] A controller section 7 formed of a microcomputer is arranged
at backside of top-plate part in the refrigerator 1.
[0046] 2. Construction of the refrigerant circuit 10
[0047] Construction of the refrigerant circuit 10 in a refrigerator
1 is explained with reference to the FIG. 1.
[0048] A compressor 12 has an exit at higher-pressure side of the
circuit that is connected to a condenser 14. The condenser 14 is
then connected to a three-way valve 15 having a first exit, which
is connected with a first capillary 16 at higher-pressure side and
which is further connected there through with the fresh food
evaporator 18.
[0049] An exit of the fresh food evaporator 18 is connected to a
refrigerant inlet of a gas-liquid separator 20. A gas-exit pipe of
the gas-liquid separator 20 is connected with a first suction pipe
22 and further connected there through with an
intermediate-pressure-side inlet of the compressor 12. Meanwhile, a
liquid-exit pipe of the gas-liquid separator 20 is connected to an
end of second capillary tube 24, pressure in which is lower than
the first capillary tube 16. Moreover, the second exit of the
above-mentioned three-way valve 15 is connected with an end of a
bypass capillary 25 while the other end of the bypass capillary 25
and the other end of the second capillary 24 are connected to an
end of the freezer evaporator 26. The other end of the freezer
evaporator 26 is connected to lower-pressure-side inlet of the
compressor 12, through a second suction pipe 28.
[0050] The first suction pipe 22 is equipped with a temperature
sensor 30 for detecting a temperature of the pipe. The temperature
sensor 30 is electrically connected to the controller section 7
that operates opening and closing of the first and second exit of
the three-way valve 15.
[0051] 3. Operation of the refrigerant circuit 10--refrigeration
cycle
[0052] Normal mode of operation of the above-explained refrigerant
circuit 10 is explained in following. In the normal mode, the
controller section 7 makes the first exit of the three-way valve 15
as opened and the second exit of the valve as closed.
[0053] (1) Gaseous refrigerant is compressed in the compressor 12
and outputted from an outlet of the compressor 12 at high
pressure.
[0054] (2) The gaseous refrigerant at high pressure is condensed at
interior of a condenser 14 to be outputted as a two-phase
refrigerant composed of gas and liquid phases at high pressure, and
then flows into the three-way valve 15.
[0055] (3) The two-phase refrigerant at high pressure is subjected
to pressure reduction in the first capillary tube 16. Then, the
two-phase refrigerant of intermediate pressure flows into the fresh
food evaporator 18.
[0056] (4) Liquid-phase part of the two-phase refrigerant partly
evaporates at inside of the fresh food evaporator 18. Then, the
two-phase refrigerant enters into the gas-liquid separator 20,
through which gas-phase and liquid-phase parts are separated from
each other.
[0057] (5) Gaseous refrigerant that is separated from liquid
refrigerant at the interior of the separator 20 flows through a
suction pipe 22 at intermediate pressure; and such
intermediate-pressure gaseous refrigerant flows to the two-stage
compressor 12 through its intermediate-pressure side inlet to be
mixed with refrigerant at lower pressure.
[0058] (6) Liquid refrigerant that is separated from the gaseous
refrigerant by the separator 20 is subjected to pressure reduction
at the second capillary tube 24, to form a two-phase refrigerant at
low pressure. Then, the two-phase refrigerant at low pressure flows
into the freezer evaporator 26.
[0059] (7) Liquid part of the two-phase refrigerant evaporates in
the freezer evaporator 26 to form a gaseous refrigerant.
[0060] (8) The gaseous refrigerant flowing out from the freezer
evaporator 26 flows through a suction pipe 28 at low pressure; and
such low-pressure gaseous refrigerant returns to the two-stage
compressor 12 through its low-pressure side inlet.
[0061] (9) In the compressor 12, the low-pressure gaseous
refrigerant is compressed at a lower-pressure side compartment of
the compressor 12 to an intermediate pressure; then added and mixed
with the intermediate-pressure gaseous refrigerant that is taken in
from the intermediate-pressure side inlet; and further compressed
in a higher-pressure side compartment of the compressor 12 to be
outputted at high pressure from the exit.
[0062] 4. Prevention of the one-sided flow
[0063] The one-sided flow may occur during the above operation of
the refrigeration cycle. Operation for preventing or quenching of
the one-sided flow is explained as follows.
[0064] As mentioned in the Background of the Invention, the
one-sided flow means a state where refrigerant flows not through
the freezer evaporator 26 and only through a channel connecting the
fresh food evaporator 18, the gas-liquid separator 20, the first
suction pipe 22 and the compressor 12 in serial in this order.
[0065] On the occasion of occurring of the one-sided flow,
temperature of the first suction pipe 22 is found to become lower
than usual, as illustrated in FIG. 3A, by our investigation.
[0066] In this embodiment, if a temperature detected by the
temperature sensor 30 attached onto the first suction pipe 22
become 25.degree. C. or lower, the controller section 7 operates as
to close the first exit of the three-way valve 15 and open the
second exit of the three-way valve 15. As a result, the refrigerant
flows not into the fresh food evaporator 18 and flows through the
bypass capillary tube 25 and directly into the freezer evaporator
26. Such an operation of the refrigerant circuit is to be referred
as bypassing operation. By the bypassing operation, a cooling at
the freezer evaporator 26 takes place in a such a manner to prevent
temperature rise at the freezer evaporator 26 that is the case in
the prior art at occasion of the one-sided flows.
[0067] FIG. 3B shows a graph illustrating a temperature variation
curve of the first suction pipe 22 observed when the bypassing
operation is performed. As shown in the figure, temperature of the
first suction pipe 22 is kept higher than the value of 25.degree.
C. as to prevent the one-sided flow.
[0068] The bypassing operation is adopted not only when to prevent
or quench the one-sided flows, but also when cooling is needed only
at the freezer evaporator 26 and not at the fresh food evaporator
28 because of dropped room temperature in winter season or the
like. If the refrigerant channel is switched to the bypass
capillary 25 that is directly connected to the freezer evaporator
26 in such bypassing operation, cooling is made only at the freezer
evaporator 26.
[0069] Moreover, the bypassing operation will be also adopted to
conduct cooling at the freezer evaporator 26 in following occasion;
when excessive cooling load is applied on the fresh food evaporator
18, evaporation of the liquid part of the refrigerant is completed
in the fresh food evaporator 18 as to disrupt flowing of
refrigerant to the freezer evaporator 26.
SECOND EMBODIMENT
[0070] The second embodiment of the present invention will be
described with reference to FIGS. 4, 5A and 5B.
[0071] This embodiment differs from the first embodiment in manner
of detecting occurrence of the one-sided flow as follows:
temperature variation of the second suction pipe 28, which is at
pressure lower than that of the first suction pipe 22, is monitored
to determine whether the one-sided flow is in a state or not; it is
noted that in the above first embodiment, on contrary, the
temperature variation of the second suction pipe 22 is
monitored.
[0072] It is found that the one-sided flow is in a state of
operation of the refrigeration cycle if and only if the temperature
of the second suction pipe 28 exceeds 2720 C. Thus, temperature
sensor 32 is attached on the second suction pipe 28; when the
detected temperature becomes 28.degree. C. or more, occurrence of
the one-sided flow is assumed; and based on such assumption, the
bypassing operation is conducted (FIG. 5B).
THIRD EBODIMENT
[0073] The third embodiment of the present invention will be
described with reference to FIGS. 6, 7A and 7B.
[0074] This embodiment differs from the first embodiment in manner
of detecting occurrence of the one-sided flow as follows:
temperature variation of the gas-liquid separator 20 is monitored
to detect the one-sided flow.
[0075] As shown in the FIG. 7A, interior of the separator 20 is
almost filled with gaseous refrigerant in normal state, thereby
keeping the temperature of the separator 20 as stable, for example,
at about -2.degree. C. If the one-sided flow occurs, the interior
of the separator 20 becomes to be filled with liquid refrigerant as
shown in FIG. 7B, and in same time, the temperature of the
separator 20 drops, for example, to -3.degree. C.
[0076] In view of this, a temperature sensor 34 is attached on the
gas-liquid separator 20; when the detected temperature becomes
-3.degree. C., occurrence of the one-sided flow is assumed; and
based on such assumption, the bypassing operation is conducted.
FOURTH EMBODIMENT
[0077] The fourth embodiment of the present invention will be
described.
[0078] This embodiment differs from the first embodiment also in
manner of detecting occurrence of the one-sided flow as follows:
temperature difference between the fresh food evaporator 18 and the
gas-liquid separator 20 is monitored to detect the one-sided flow.
Specifically, temperature sensors are disposed to detect
evaporation temperature of the fresh food evaporator 18 and surface
of the gas-liquid separator 20.
[0079] In normal state, interior of the separator 20 is kept at
pressure same with interior of the fresh food evaporator 18 while
no evaporation proceeds in the separator 20. For this reason,
temperature of the interior of the separator 20 is easily affected
by outside and is kept higher than that of the fresh food
evaporator by about 1.degree. C. For example, temperature of the
fresh food evaporator 18 is kept at -3.degree. C. while temperature
of the gas-liquid evaporator 20 is kept at -2.degree. C.
[0080] At occurrence of the one-sided flow, the interior of the
separator 20 becomes filled with liquid refrigerant, and the
temperature of the separator 20 becomes equal to the temperature of
the fresh food evaporator 18, for example, to -3.degree. C. Thus,
when the detected temperatures become equal, occurrence of the
one-sided flow is assumed; and based on such assumption, the
bypassing operation is conducted.
FIFTH EMBODIMENT
[0081] The fifth embodiment of the present invention will be
described, which also differs from the first embodiment in manner
of detecting occurrence of the one-sided flow.
[0082] Because the one-sided flow is derived from imbalance of
load, due to opening and closing of door of the refrigerant for
example, such imbalance causes increase of drive frequency of the
compressor 12 in a motion to compensate such imbalance of load.
Thus, when the increasing of the drive frequency is detected, the
bypassing operation is conducted. For example, if the compressor 12
has been operated at frequency of 30 Hz and starts to be operated
at frequency of 45 Hz, or 1.5 times of the 30 Hz, the occurrence of
the one-sided flow is assumed; and based on such assumption, the
bypassing operation is conducted.
OTHER MODIFICATIONS
[0083] In each of the here to-mentioned embodiments, the bypassing
operation is conducted at every occurrence of the one-sided flow,
as to effect enough cooling at the freezer evaporator 26. However,
the bypassing operation is not needed if the cooling capacity of
the freezer evaporator 26 is sufficiently large and cooling is
needed only at the fresh food evaporator 18. In such a
circumstance, the one-sided flow is not always troublesome. Thus,
at sometimes, the bypassing operation may be skipped. For example,
the bypassing operation will be skipped, even at occurrence of the
one-sided flow, when temperature of the fresh food evaporator 18 is
higher than normal and temperature of the freezer evaporator 26 is
lower than normal.
[0084] In otherwise, frost removing may be made as follows.
[0085] Because refrigerant continuously flows through the fresh
food evaporator 18 and the freezer evaporator 26 in the refrigerant
circuit 10, frost may be deposited onto the fresh food evaporator
18. Meanwhile, at the bypassing operation, refrigerant does not
flow through the fresh food evaporator 18.
[0086] In view of the above, the bypassing operation is conducted
while operating the first fan 27 for sending air around the fresh
food evaporator 18. By such airflow, the frost on the fresh food
evaporator 18 is removed.
[0087] Additionally, by such a way, the refrigerant filled in the
fresh food evaporator 18 is sent to the freezer evaporator 26, to
enhance cooling ability of the freezer evaporator 26.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0088] This application is based upon and claims the benefits of
priority from the prior Japanese Patent Applications No.
2000-377897 filed on Dec. 12, 2000; the contents of which are
incorporated herein by reference.
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