U.S. patent application number 10/584205 was filed with the patent office on 2007-06-28 for refrigerator.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. Invention is credited to Hidetake Hayashi, Minoru Temmyo, Takahiro Yoshioka.
Application Number | 20070144190 10/584205 |
Document ID | / |
Family ID | 34708912 |
Filed Date | 2007-06-28 |
United States Patent
Application |
20070144190 |
Kind Code |
A1 |
Temmyo; Minoru ; et
al. |
June 28, 2007 |
Refrigerator
Abstract
A refrigerator in which a two-stage-compression mode
power-variable refrigerant circuit having a freezer cooler and
fresh-food cooler is controlled in accordance with information on
temperature in the fresh-food compartment. Thus, each of the
freezer and fresh-food compartment is properly controlled at a
temperature for storing. The refrigerant circuit includes an
inverter-driven power-variable compressor having a low-pressure
compression element and a high-pressure compression element, a
switching valve disposed downstream of a condenser receiving gas
refrigerant discharged from the compressor and selecting and
controlling channel and flow rate of the refrigerant, and a freezer
cooler and a fresh-food cooler, each connected with the switching
valve through a pressure reducer. A frequency of the compressor is
decided by a temperature in the freezer compartment and its target
temperature.
Inventors: |
Temmyo; Minoru; (Osaka,
JP) ; Yoshioka; Takahiro; (Osaka, JP) ;
Hayashi; Hidetake; (Osaka, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
KABUSHIKI KAISHA TOSHIBA
1-1, Shibaura 1-chome, Minato-ku
Tokyo
JP
105-8001
Toshiba Consumer Marketing Corporation
1-8, Sotokanda 1-chome, Chiyoda-ku
Tokyo
JP
101-0021
TOSHIBA HA PRODUCTS CO., LTD.
1-6, Ohta Toshiba-cho
Ibaraki-shi
JP
567-0013
|
Family ID: |
34708912 |
Appl. No.: |
10/584205 |
Filed: |
November 30, 2004 |
PCT Filed: |
November 30, 2004 |
PCT NO: |
PCT/JP04/17761 |
371 Date: |
June 23, 2006 |
Current U.S.
Class: |
62/180 ; 62/186;
62/228.4 |
Current CPC
Class: |
F25B 5/02 20130101; F25B
1/10 20130101; F25D 2700/122 20130101; F25B 2700/173 20130101; F25D
2317/0682 20130101; F25B 2600/2511 20130101; F25B 5/04 20130101;
F25B 2400/23 20130101; F25D 11/022 20130101; F25D 17/065 20130101;
F25B 2600/0253 20130101; F25B 2600/112 20130101; F25B 2600/021
20130101; Y02B 30/70 20130101; F25B 2400/13 20130101; F25D 2400/04
20130101; Y02B 40/00 20130101; F25D 29/00 20130101 |
Class at
Publication: |
062/180 ;
062/228.4; 062/186 |
International
Class: |
F25D 17/00 20060101
F25D017/00; F25D 17/04 20060101 F25D017/04; F25B 49/00 20060101
F25B049/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 24, 2003 |
JP |
2003-427845 |
Claims
1. A refrigerator having a refrigerant circuit comprising: an
inverter-driven power-variable compressor having a low-pressure
compression, element and a high-pressure compression element; a
switching valve that is disposed on downstream of a condenser
receiving gas refrigerant discharged from the compressor and
selects and controls flow channel and flow rate of refrigerant; and
coolers, for freezer and fresh-food compartments, each connected
with the switching valve through a pressure reducer; and wherein
frequency of the compressor is decided by temperature in the
freezer compartment and its target temperature.
2. A refrigerator having a refrigerant circuit comprising: an
inverter-driven power-variable compressor having a low-pressure
compression element and a high-pressure compression element; a
switching valve that is disposed on downstream of a condenser
receiving gas refrigerant discharged from the compressor and
selects and controls channel and rate of flowing of the
refrigerant; and coolers, for freezer and fresh-food compartments,
each connected with the switching valve through a pressure reducer;
and wherein frequency of the compressor is decided by temperature
in the fresh-food compartment and its target temperature and
wherein on deciding of the frequency, feedback rate of temperature
information from the freezer compartment is set larger than that
from the fresh-food compartment.
3. A refrigerator according to claim 2, wherein, only when
temperature of the fresh-food compartment is higher than its target
temperature, information on. such temperature is adopted in
deciding the frequency of the compressor.
4. A refrigerator according to claim 1, wherein, when temperature
of the fresh-food compartment is higher than its target
temperature, frequency of a fresh-food cooling fan is
increased.
5. A refrigerator according to claim 1, wherein, when temperature
of the fresh-food compartment is higher than its target
temperature, frequency of a freezer cooling fan is increased.
6. A refrigerator according to claim 2, wherein, when temperature
of the fresh-food compartment is higher than its target
temperature, frequency of a fresh-food cooling fan is
increased.
7. A refrigerator according to claim 3, wherein, when temperature
of the fresh-food compartment is higher than its target
temperature, frequency of a fresh-food cooling fan is
increased.
8. A refrigerator according to claim 2, wherein, when temperature
of the fresh-food compartment is higher than its target
temperature, frequency of a freezer cooling fan is increased.
9. A refrigerator according to claim 3, wherein, when temperature
of the fresh-food compartment is higher than its target
temperature, frequency of a freezer cooling fan is increased.
10. A refrigerator according to claim 4, wherein, when temperature
of the fresh-food compartment is higher than its target
temperature, frequency of a freezer cooling fan is increased.
11. A refrigerator according to claim 6, wherein, when temperature
of the fresh-food compartment is higher than its target
temperature, frequency of a freezer cooling fan is increased.
12. A refrigerator according to claim 7, wherein, when temperature
of the fresh-food compartment is higher than its target
temperature, frequency of a freezer cooling fan is increased.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a refrigerator having a
power-variable compressor of two-stage compression mode; and
particularly relates to such refrigerator in which frequency of the
compressor is decided in response to a temperature in a fresh-food
compartment.
BACKGROUND OF THE INVENTION
[0002] Refrigerators equipped with compressors that are variable in
power by inverter control have become widespread in recent years.
Refrigeration capacity of such refrigerator is variable, so that
cooling ability matching with refrigeration load is achieved; and
thereby electric power consumption is reduced.
[0003] A refrigerators being widespread in household use is usually
comprised of a freezer compartment cooled to about -18.sup.oC to
-20.sup.oC and a fresh-food compartment maintained at about
+1.sup.oC to 5.sup.oC. When only one compressor is used to cool
both of the freezer and fresh-food compartments, distribution of
cooled air flowing into the compartments is controlled by dampers
or the like. In accordance with overall load on the refrigerator,
driving and stopping of the compressor is made. When the compressor
is on inverter control, frequency of the compressor is controlled
in addition to the above. In this way, each of the storage
compartments is maintained at a predetermined temperature.
[0004] When the refrigerator is equipped with two compressors
respectively for the freezer and fresh-food compartments, flow
channels for refrigerant are switched with each other as to
distribute and control the refrigerant flow; and the compressors
are controlled in response to overall workload for the storage
compartments as a whole such as temperatures or temperature
difference.
[0005] Meanwhile, the compressors in refrigerators now on sale in
the market are of so-called single stage compression mode, that is,
have a single compression unit in each of compressor casing.
Nevertheless, idea of two-stage compression mode for a refrigerator
apparatus as shown in FIG. 13 is disclosed in recent years. Please
see JP2001-074325A (Japan's patent application publication
2001-74325) for example. It is constructed as follows as shown in
the figure. Two-stage compressor 39 that has a low-pressure or
lower-stage compression element 39a and a high-pressure or
higher-stage compression element 39b, as well as an electric motor,
are constructed in a sealed casing. Intermediate-pressure expansion
equipment 43 is connected with outlet of a condenser 40 that is
connected with outlet pipe 46 of the high-pressure compression
element 39b. Intermediate-pressure suction pipe 47 and inlet of the
high-pressure compression element 39b as well as outlet of the
low-pressure compression element 39a are communicated with each
other. An intermediate-pressure evaporator 35 is connected between
the intermediate-pressure suction pipe 47 and the
intermediate-pressure expansion equipment 43. Further, low-pressure
evaporator 34 is connected between inlet 45 of the low-pressure
compression unit 39a of the two-stage compressor 39 and
low-pressure expansion equipment 42 that is connected with outlet
of the condenser 40. By such construction, outlet of the
low-pressure compression element 39a and inlet of the high-pressure
compression element 39b are communicated with each other, within
the sealed casing of the compressor 39, so as to increase accuracy
of temperature control in the compartments and to achieve uniform
distribution of temperature in the compartments as well as high
efficiency and low power consumption.
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0006] In the refrigerant circuit shown in JP2001-74325A, its
efficiency improves when evaporation temperature in the
intermediate-pressure evaporator 35, which is a cooler for the
fresh-food compartment or fresh-food cooler, is higher than that of
the low-pressure evaporator 34, which is a cooler for the freezer
compartment or freezer cooler. Nevertheless, suction pipe of the
freezer cooler 34 is directly connected to the low-pressure
compression element 39a of the compressor and suction pipe 47 of
the fresh-food cooler 35 is connected with intermediate-pressure
room in the compressor 39; thus, refrigeration capacity for the
freezer compartment is difficult to be influenced by refrigerant
flowing through the fresh-food cooler 35. Thus, such conventional
method in which frequency of the compressor is controlled in
accordance with respective loads on freezer and fresh-food
compartments as well as total load may cause a problem such as
follows. When, for example, the freezer compartment is fully cooled
and the fresh-food compartment is excessively cooled, frequency of
the compressor will be lowered as to resultantly cause insufficient
cooling of the freezer compartment.
[0007] The invention is made in view of the above problem, is aimed
to provide a refrigerator in which each of the freezer and
fresh-food compartments is maintained as properly controlled at a
temperature for storage; by controlling the power-variable
refrigerant circuit of two-stage compression mode having the
freezer and fresh-food evaporators in accordance with temperature
information for the freezer compartment.
MEANS TO SOLVE THE PROBLEMS
[0008] The invention-wise refrigerator, for solving the above
problem, has a refrigerant circuit comprising: an inverter-driven
power-variable compressor having a low-pressure compression element
and a high-pressure compression element; a switching valve that
selects and controls flow channel and flow rate of refrigerant and
is disposed on downstream of a condenser, which receives gas
refrigerant discharged from the compressor; and coolers or
evaporators that are respectively for a freezer compartment and a
fresh-food compartment and are connected to the switching valve
through respective pressure reducers; and wherein frequency of the
compressor is decided in response to temperature in the freezer
compartment and its target temperature.
[0009] Meanwhile, according to claim 2, the invention-wise
refrigerator has a refrigerant circuit comprising: an
inverter-driven power-variable compressor having a low-pressure
compression element and a high-pressure compression element; a
switching valve that selects and controls flow channel and flow
rate of refrigerant and is disposed on downstream of a condenser,
which receives gas refrigerant discharged from the compressor; and
coolers or evaporators that are respectively for a freezer
compartment and a fresh-food compartment and are connected to the
switching valve through respective pressure reducers; and wherein
frequency of the compressor is decided in response to temperature
in the freezer compartment and its target temperature; and feedback
rate or weighting of temperature information from the freezer
compartment is made larger than that from the fresh-food
compartment at a time of deciding the frequency of the
compressor.
ADVANTAGEOUS EFFECT OF THE INVENTION
[0010] By such construction, evaporation temperatures in two
coolers for the freezer and fresh-food compartments are set in
accordance with extent of cooling of the compartments; thus, not
only improvement of efficiency in the refrigerant cycle as well as
switching between flow channels for the coolers and controlling
flow rate of refrigerant are achieved; but also temperature
fluctuations in the freezer and fresh-food compartments are
suppressed as a result of simultaneous cooling of the compartments,
so as to properly control the temperatures in the compartments.
BEST MODE FOR CARRYING OUT THE INVENTION
[0011] In following, first embodiment of the invention will be
explained in dependence upon the drawings. FIG. 2 shows a vertical
sectional view of a casing main body 1 of the refrigerator; and the
casing main body 1 forms a storage space at inside of an insulator
box and is partitioned to a plurality of storage chambers such as a
freezer chamber and an ice-forming chamber in a freezer compartment
2 as well as a fresh-food chamber and a vegetable chamber in a
fresh-food compartment 3.
[0012] Each of the storage chambers is cooled as maintained at a
predetermined temperature by a freezer cooler 4 or a fresh-food
cooler 5 and by a fan 6 or 7 for cooled air circulation. The
freezer and fresh-food coolers 4 and 5 are cooled by refrigerant
supplied from a compressor 9 that is arranged in a machine room 8
on rear-bottom part of the casing main body 1.
[0013] FIG. 1 shows a refrigerant circuit of the invention-wise
refrigerator, in which the compressor 9, a condenser 10 and a
switching valve 11 are connected and the freezer and fresh-food
coolers 4 and 5 are further connected in a parallel arrangement, as
to form a loop. The condenser 10 is in a flat shape and arranged on
outer bottom face of the casing main body 1, at front of the
machine room 8. Refrigerant that has been condensed at the
condenser 10 is supplied through the switching valve 11 to a
capillary 12 or 13 as a pressure reducer and then to the freezer
cooler 4 or the fresh-food cooler 5. Evaporation of the refrigerant
cools the cooler 4 or 5; and by air circulation by the cool-air fan
6 or 7, inside of the storage chambers are cooled to a
predetermined air temperature. Then, such vaporized refrigerant is
returned to the compressor, through an accumulator 14.
[0014] As to be notified and shown in detail on the FIG. 3, the
compressor 9 is a two-stage reciprocating compressor, in which
press pump part is comprised of a low-pressure compression element
9a and a high-pressure compression element 9b. Turning of a
rotation shaft 9e of an electric motor mechanism 9d that is kept in
a sealed casing 9c causes turning of an eccentric shaft 9f as to
thereby cause reciprocating motion of connecting rods 9g.
[0015] On end of the each connecting rod 9g, a piston 9i is secured
by fitting engagement. Reciprocating motion of the pistons 9i
within the cylinder 9j causes suction, compression and discharge of
refrigerant, alternately by the low-pressure compression element 9a
and the high-pressure compression element 9b. Ball joints 9h are
adopted to the compression elements; and thereby improving
volume-wise efficiency and curbing enlargement of contour size of
the two-stage compressor 9 that requires two compression elements
9a and 9b.
[0016] Suction inlet 9k of the low-pressure compression element 9a
is connected with an end of a suction pipe 15 that is connected to
a freezer cooler 4 through an accumulator 14. The low-pressure
compression element 9a has a discharge outlet 9m that is opened to
inside of the sealed casing 9c and is to discharge compressed gas
refrigerant. The high-pressure compression element 9b has a
discharge outlet 9n that is connected to an outlet pipe 16 of the
condenser 10.
[0017] The accumulator 14 serves to separate liquid refrigerant
from gas refrigerant and to store the liquid refrigerant that has
been left after passing the cooler 4, and thereby serves to send
out only the gas refrigerant. Thus the accumulator 14 serves to
curb a trouble that would otherwise occur when the liquid
refrigerant were flowed into the cylinder 9j of the compressor 9.
In this example, the accumulator is arranged only on downstream of
the freezer cooler 4.
[0018] A suction pipe 17 from the fresh-food cooler 5 is connected
to a room inside of the sealed casing 9c, in which pressure level
is intermediate, so as to lead refrigerant into the room.
Therefore, refrigerant sucked from the fresh-food cooler 5 does not
directly flow into a cylinder of the compressor; and hence an
accumulator is not necessarily required on downstream side of the
fresh-food cooler 5. Even when installing an accumulator there,
only a small one is enough. Gas refrigerant sucked through the
suction pipe 17 is then sucked through a suction inlet 9p of the
high-pressure compression element 9b and then compressed in the
element, along with gas refrigerant discharged from the discharge
outlet 9m of the low-pressure compression element 9a.
[0019] The compressor 9 is power variable by inverter control and
is operated by a control device formed by a microcomputer or the
like in a manner that; frequency is decided, within a range from 30
through 70 Hz for example, in accordance with temperatures detected
in the freezer and fresh-food compartments, with their deviations
from target temperatures, or with temperature variation rate or the
like.
[0020] The switching valve 11 is arranged on downstream of the
condenser 10 that receives gas refrigerant discharged from the
compressor 9 and serves to switch between two refrigerant flow
channels to the coolers 4 and 5 and to control flow rate of the
refrigerant. As shown in FIG. 4, the switching valve 11 is a
three-way valve, in which a valve seat 19 that is formed to have an
"A" or first valve port 19a leading to the freezer cooler 4 and a
"B" or second valve port 19b leading to the fresh-food cooler 5 is
formed within a valve casing 18 and in which a closure element 20
is placed on the valve seat 19.
[0021] The closure element 20 has an "A" or first groove 20a and a
"B" or second groove 20b, on bottom face of a thickly terraced part
20d having a predetermined contour. These two grooves 20a and 20b
have V-shaped cross section and run for predetermined distances
along arches differing in radius from center of the rotation shaft
20c in a manner to respectively cover the "A" valve port 19a and
the "B" valve port 19b when tracing by a rotation. The closure
element 20 is tightly overlaid on the valve seat 19 and is
turn-wise driven by a not-illustrated stepping motor arranged above
the valve at pulse steps in a range of 0-85.
[0022] As for the switching valve 11, the closure element 20 is
turned by pulse signal controlling the refrigerant circuit. When
the "A" valve port 19a and the "A" groove 20a on distal side from
rotational axis are overlapped with each other at predetermined
pulse positions, they are communicated with each other. Then,
refrigerant that is flowed into inside of the valve casing 18 by
way of an inlet valve port 21 flows through an opening, of the "A"
groove 20a, on contour of the thickly terraced part 20d, and to
inside the "A" groove 20a having V-shaped section. Subsequently,
refrigerant is led through the "A" valve port 19a in to a freezer
capillary 12, or a capillary for the freezer cooler, and is
vaporized in the freezer cooler 4.
[0023] When the "B" valve port 19b and the "B" groove 20b on
proximal side from rotational axis are overlapped with each other
as to be communicated with each other; refrigerant flowed into the
"B" groove 20b flows through the "B" valve port 19b and into a
fresh-food capillary 13, or a capillary for the fresh-food cooler,
and is evaporated in the fresh-food cooler 5.
[0024] The "B" groove 20b for the fresh-food cooler is constructed
in a manner that area of its V-shaped cross section becomes
progressively larger by approaching to the opening on the contour
of the thickly terraced part 20d and leaving from a turn-wise or
arch-wise distal end. Thus, by turning of the closure element 20,
size of area for communication with the "B" valve port 19b is
varied from minimum to maximum. In this way, switching between
refrigerant channels and adjustment of the flow rate are subtly
controllable; and the flow rate of refrigerant is efficiently and
linearly varied by turn-wise control with pulses.
[0025] For control of openness of the three-way valve 20, selection
may be made among following: full opening of valve ports 19a and
19b for the freezer and fresh-food coolers 4 and 5; full closure of
the two valve ports; narrowing down of the valve port for the
freezer cooler while fully opening the valve port for the
fresh-food cooler; narrowing down of the valve port for the
fresh-food cooler while fully opening the valve port for the
freezer cooler; and the like. In the example, while the freezer
cooler 4 and the fresh-food cooler 5 are connected in a parallel
arrangement, cooling control is made by selecting between two
occasions, namely, an occasion of simultaneous cooling of the
freezer and fresh-food compartments and an occasion of cooling only
the freezer compartment.
[0026] Refrigerant flowed out from the valve port 19a for the
freezer cooler passes through the freezer capillary 12 as to be
depressurized and then evaporates in the freezer cooler 4 at about
-25.sup.oC. The capillary 12 is constructed to achieve such
evaporation temperature corresponding to a cooling temperature that
should be achieved in the freezer compartment 2. In same manner as
above, refrigerant flowed out from the valve port 19b for the
fresh-food cooler flows to and evaporates in the fresh-food cooler
5 after passing through the capillary 13; which is constructed to
achieve evaporation temperature at about -5.sup.oC that is close to
a cooling temperature being should achieved in the fresh-food
compartment 3.
[0027] The capillary 12 and 13 for the freezer and fresh-food
coolers in the refrigerant circuit are constructed as follows. In
order to differentiate the evaporation temperatures in the freezer
and fresh-food coolers 4 and 5, throttling is more intensive in the
capillary 12 for the freezer cooler than in the other. This
construction entails that refrigerant is apt to flow more through
the capillary 13 having smaller resistance, for the fresh-food
cooler 5; and refrigerant flow through the capillary for the
freezer cooler becomes difficult, and might be even stopped at some
extreme occasion.
[0028] To improve the above, controlling of the switching valve 11
is made to slightly narrow down a flow passage to the fresh-food
cooler, to which refrigerant more apt to flow, for curbing
so-called one-sided refrigerant flow, in addition to controlling of
the flow of refrigerant for cooling freezer and fresh-food
compartments 2 and 3.
[0029] Resultantly, when the groove 20a and valve port 19a for the
freezer cooler are communicated to fully open the valve port, the
freezer cooler 4 exhibits an almost constant cooling capacity,
almost irrespective to refrigerant flow rate through the fresh-food
cooler. Thus, cooling capacity in the freezer compartment is subtly
controllable by an extent of openness or closure of the valve port
19b or communication between the groove 20b and the valve port 19b,
and by variation of frequency of the compressor 9.
[0030] By such control of refrigerant flow, evaporation temperature
in the fresh-food cooler 5 is set to be significantly higher than
that in the freezer cooler so as to achieve cooling at +1.sup.oC to
2.sup.oC in a fresh-food chamber. When heat-transmitting surface
area on the fresh-food cooler 5 is increased as to increase heat
exchange capacity for cooling the fresh-food compartment, then the
evaporation temperature in the cooler maybe further enhanced. In
such occasion, difference between the cooling temperature in the
fresh-food compartment 3 and temperature of the cooler 5 is
decreased as to decrease an amount of frost stuck on the fresh-food
cooler 5 and to achieve curbing of drying in the compartment and
keep humidity in the compartment as high.
[0031] In a general household refrigerator, cooling capacities
required for the freezer and fresh-food compartments are almost
equal. Thus, efficient cooling is achieved when heat-transmitting
surface area on the fresh-food cooler 5 is set to be same level
with or higher than that of the freezer cooler 4.
[0032] In following, operation of the refrigerant circuit is
explained. On turning on of the power, the compressor 9 is driven,
and gas refrigerant at high temperature and at high pressure is
discharged from outlet pipe 16 into the condenser 10 and arrives in
the switching valve 11. Whereas the switching valve 11 may be set
with various pattern of control as explained in the above, the
valve ports 19a and 19b are fully opened when the power is just
turned on because then the freezer and fresh-food compartments 2
and 3 are yet to be cooled. Thus, refrigerant flows into and
depressurized in the capillaries 12 and 13 for the freezer and
fresh-food coolers and evaporates in the freezer and fresh-food
coolers 4 and 5 at respective evaporation temperatures as to cool
the coolers to predetermined temperatures.
[0033] Refrigerant flowed out from the freezer cooler 4 flows into
the accumulator 14. If some liquid refrigerant is left after
passing through the cooler, the liquid refrigerant yet to be
vaporized is stored in the accumulator 14 and only gas refrigerant
passes through the suction pipe 15 and is sucked into the
low-pressure element 9a in the compressor 9. Meanwhile, gas
refrigerant having vaporized in the fresh-food cooler 5 passes
through the suction pipe 17 and is introduced into inside of the
sealed casing 9c of the compressor 9c, which is at an intermediate
pressure.
[0034] Gas refrigerant that has been sucked into the low-pressure
compression element 9a from the freezer cooler 4 and compressed and
discharged through the outlet 9m into inside of the sealed casing
9c merges with gas refrigerant that has been flowed from the
fresh-food cooler 5 into inside of the sealed casing 9c. Then, such
merged stream of gas refrigerant is sucked through an inlet 9p into
the high-pressure compression element 9b and is discharged through
an outlet 9n into the outlet pipe 16 to be led into the condenser
10. In this way, the refrigerant circuit is formed.
[0035] In the above refrigerant circuit, the freezer and fresh-food
coolers 4 and 5 are respectively provided with the capillaries 12
and 13 in a manner that; evaporation temperatures at the coolers
are suited for predetermined temperatures in the freezer and
fresh-food compartments 2 and 3, respectively. Gas refrigerant
vaporized in the fresh-food cooler 5 is then directly sucked into
the intermediate-pressure room in the sealed casing 9c while being
kept at an intermediate pressure that is higher than a pressure in
the freezer cooler. In this way, the evaporation temperature in the
fresh-food cooler 5 may be set higher than that in the freezer
cooler 4, in accordance with cooling temperature in the
compartments. Moreover, input power for the compressor is reduced,
and thereby, efficiency of the refrigerant circuit is increased and
power consumption is reduced.
[0036] Further, amount of the frost stuck on the cooler 5 is
decreased by raising evaporation temperature in the fresh-food
cooler 5 as to decrease temperature difference between the cooler
and inside of the fresh-food compartment. Thus, drying in the
fresh-food compartment is curbed and humidity is kept high so that
freshness of food is kept for a long period. Moreover, because
refrigerant may flow simultaneously through the freezer and
fresh-food coolers 4 and 5, temperature fluctuation is smaller than
a conventional way of alternately cooling the coolers.
[0037] The refrigerant circuit may in otherwise be constructed as
shown in FIG. 5, in which reference marks same with FIG. 1 are
attached. While the compressor 9, the condenser 10 and the
switching valve 11 are same as above, the freezer cooler 4 and the
fresh-food cooler 5 are connected in a serial arrangement.
Moreover, a bypass pipe 22 for bypassing the fresh-food capillary
13 and the fresh-food cooler 5 runs from the switching valve 11 and
connected with a gas-liquid separator 23, which is connected with
the freezer capillary 12 and there through to the freezer cooler 4.
A suction pipe 24 connects between upper portion of the gas-liquid
separator 23 and the intermediate-pressure room within the sealed
casing 9c of the compressor 9.
[0038] Resultantly, refrigerant flows through both of or either of
the freezer cooler 4 and the fresh-food cooler 5 by the switching
valve that is controlled as in the above. Refrigerant flowed from
the bypass pipe 22 or the fresh-food evaporator 5 flows into the
gas-liquid separator 23 and is subjected to separation between gas
refrigerant and liquid refrigerant. From the separator 23, the gas
refrigerant flows through fresh-food suction pipe 24 and goes back
to the intermediate-pressure room in the compressor 9; and the
liquid refrigerant evaporates at low temperature in the freezer
cooler 4 and then goes back to low-pressure compression element of
the compressor 9. As in the previous example, cooling of the
compartments at predetermined temperatures is made with
satisfactory efficiency in respect of the refrigerant circuit.
[0039] FIG. 6 shows-refrigeration capacity of the freezer cooler 4
and the fresh-food cooler where temperatures of the coolers and
temperature of the condenser are taken as constant and the
compressor 9 is operated at a constant frequency. In the figure,
the ordinate represents refrigeration capacity of the fresh-food
cooler 5; and the abscissa represents refrigeration capacity of the
freezer cooler 4. As appeared in the figure, point "a" represents
an occasion in which refrigerant flows only through the fresh-food
cooler 5 as a result of switching of the switching valve; point "b"
represents an occasion in which refrigerant flows only through the
freezer cooler 4; and "c" represents an occasion in which
refrigerant flows through both of the freezer and fresh-food
coolers 4 and 5 while the valve ports 19a and 19b are fully
opened.
[0040] In this graph, mass or volume of refrigerant that is
directly sucked into the low-pressure compression element 9a from
the freezer cooler 4 is determined by an excluded volume of the
cylinder in the low-pressure compression element 9a. Refrigeration
capacity corresponding such sucking is 69W when refrigerant flows
only through the freezer cooler, and is 64W when refrigerant flows
through both of the freezer and fresh-food coolers. Thus,
refrigeration capacity for the freezer is nearly constant and is
not greatly affected by return-wise flowing of refrigerant from the
fresh-food cooler 5 into the intermediate-pressure room in the
compressor 9.
[0041] On contrary, the refrigeration capacity of the fresh-food
cooler, which corresponds sucking of refrigerant from the
fresh-food cooler 5 into the compressor 9, is 155 W when flowing
only through the fresh-food cooler 5, and is 75 W as greatly
decreased when flowing through both of the freezer and fresh-food
coolers. In this way, the refrigeration capacity of the fresh-food
cooler is greatly varied by situations whether the refrigerant is
sucked from the freezer cooler or not; namely whether refrigerant
is sucked into the compressor only from the fresh-food cooler 5 or
from both of the freezer and fresh-food coolers 4 and 5 as merged
with each other.
[0042] Generally, temperature at inside of the fresh-food
compartment is +3.sup.oC to 5.sup.oC while temperature at inside of
the freezer compartment is -18.sup.oC to -20.sup.o C. Thus, for the
freezer compartment, temperature difference from that of the air is
great, and hence, refrigeration capacity larger than that for the
fresh-food compartment is usually required. If refrigeration
capacity for the freezer, namely refrigeration load for the
freezer, is recognized to be larger than that for the fresh food,
refrigeration operation is made as indicated by hatched area in the
FIG. 7 that schematically depicts the FIG. 6. In the hatched area,
refrigeration capacity for the freezer is superior.
[0043] As mentioned above, refrigeration capacity for the freezer
is not remarkably affected by flowing back of refrigerant from the
fresh-food cooler 5. Thus, refrigeration control for the freezer
compartment may be made by control of frequency of the compressor
9. When cooling is not enough, the frequency of the compressor 9 is
increased as to increase the refrigeration capacity. When cooling
is excessive, the frequency of the compressor 9 is decreased or the
compressor 9 is stopped so as to keep proper cooling temperature.
Meanwhile, as for the cooling of the fresh-food compartment,
openness or closure of the valve port in the switching valve 11 is
controlled instead of the frequency of the compressor, so as to
control flow rate of refrigerant and thereby control cooling
temperature in the fresh-food compartment.
[0044] By use of FIG. 8, which is a control block diagram, it is
explained a first example of invention-wise controlling of
frequency of the compressor. A temperature "Fa" at inside of the
freezer compartment 2 which is detected by a freezer temperature
sensor, in a freezer chamber for example, is compared with a
predetermined target temperature "Fr"; and difference between them
is inputted to PID controller 25 that is for deciding frequency of
the compressor.
[0045] If the temperature "Fa" in the freezer compartment 2 is
higher than the target temperature "Fr", PID calculated value
becomes high. Then, an operational control is made such that
cooling of the freezer compartment 2 is induced to reach the target
temperature by increasing frequency of the compressor in a
predetermined extent. If the temperature "Fa" in the freezer
compartment 2 is lower than the target temperature "Fr", the
frequency of the compressor is decreased or the compressor is
stopped so as to suppress refrigeration capacity.
[0046] In following, another example of invention-wise controlling
of frequency of the compressor is explained. In the previous
example, the frequency of the compressor is controlled on basis of
temperature information for inside of the freezer compartment; and
it is conceivable that refrigeration capacity of the fresh-food
compartment may become insufficient under some operational
conditions.
[0047] In view of the above, temperature information for the
freezer compartment 2 is also inputted along with that for the
fresh-food compartment 3 in a manner to make an operation of the
compressor 9 within the hatched area on the FIG. 7. Then, frequency
of the compressor 9 is increased and thus the refrigeration
capacity is increased not only for the freezer compartment 2 but
also for the fresh-food compartment 3.
[0048] Nevertheless, if the freezer compartment 2 is cooled to a
temperature not more than the target temperature, frequency
increase of the compressor 9 causes unnecessary cooling of the
freezer compartment 2 and wasteful consumption of the electric
power. In view of this, in a block diagram shown in FIG. 9,
frequency of the compressor 9 is determined as below, while the PID
controller 25 is inputted with not only the temperature "Fa" of the
freezer compartment and its target temperature "Fr" but also the
temperature "Ra" of the fresh-food compartment and its target
temperature "Rr". Feedback rate of information on temperature of
the freezer compartment 2 is made higher than that of the
fresh-food compartment 3. For example, data value on difference
between the temperature "Fa" of the freezer compartment and its
target temperature "Fr" is multiplied by two, so that such
multiplied data value is added as inputted.
[0049] In this way, frequency of the compressor 9 is determined by
laying emphasis on the freezer compartment by use of an
overestimated difference value as feedback temperature information
on freezer compartment 2. When the freezer compartment 2 has been
fully cooled, refrigeration capacity of the fresh-food cooler is
enhanced or suppressed by controlling rate of refrigerant flow
through the fresh-food cooler 5 by use of the switching valve 11,
not by enhancing frequency of the compressor. By such way of
controlling, excessive cooling of the freezer cooler is curbed and
the fresh-food compartment is kept in a proper temperature
range.
[0050] In the above example, explanation is made for an occasion in
which frequency of the compressor 9 is determined by taking into
account temperature information for the fresh-food compartment 3.
If temperature of the air at outside were decreased and temperature
in the fresh-food compartment 3 became lower than the target
temperature "Rr", there would arise a problem that frequency of the
compressor 9 becomes lower and resultantly refrigeration capacity
for the freezer compartment 2 becomes low.
[0051] FIG. 10 is a block diagram for coping with such an occasion.
When and only when temperature in the fresh-food compartment 3 is
higher than its target temperature "Rr", a function "Fx" for
feeding back temperature information for the fresh-food compartment
is introduced. When the temperature "Ra" in the fresh-food
compartment and its target temperature value "Rr" make small
difference, such target temperature value is inputted to the PID
controller 25. When deviation from the target temperature is minus
value, signal of zero value is inputted to the PID controller
25.
[0052] As a result of such manner of controlling, even when load
for the fresh-food compartment 3 is small and thereby actual
temperature "Ra" in the compartment is smaller than its target
temperature "Rr", temperature in the freezer compartment 2 is by
use of its temperature information, maintained at the target
temperature "Fr". Thus, it is curbed that temperature in the
freezer compartment 2 becomes higher than the target temperature
"Fr".
[0053] A still another example is explained. FIG. 11 shows
variation of refrigeration capacity "QF1" for the freezer cooler
and of refrigeration capacity "QR1" for the fresh-food cooler
where; the compressor 9 is driven at a constant frequency,
condenser temperature is constant and temperature of the fresh-food
cooler 5 is varied.
[0054] As for the fresh-food cooler 5, the refrigeration capacity
"QR1" is decreased by decreasing surface temperature of the cooler
and is increased by increasing the surface temperature of the
cooler. As for the freezer cooler, surface temperature is constant,
and is -23.5.sup.oC for example; and the refrigeration capacity
"QF1" of the freezer cooler is not greatly affected by variation of
the refrigeration capacity of the fresh-food cooler.
[0055] In respect of the fresh-food cooler 5, when frequency of a
fan 7 for the fresh-food cooler 5, or fresh-food fan 7, is
decreased, heat exchange rate on the cooler 5 is decreased as to
decrease surface temperature of the cooler 5 and resultantly, the
refrigeration capacity "QR1" of the fresh-food cooler is decreased.
Inversely, when the frequency of the fresh-food fan 7 is decreased,
heat exchange rate on the cooler 5 is increased as to increase
surface temperature of the cooler 5 and resultantly, the
refrigeration capacity "QR1" of the fresh-food cooler is
increased.
[0056] Hence, as for refrigeration control for the fresh-food
compartment 3, temperature in the compartment may be controlled by
increasing and decreasing of the frequency of the fresh-food fan 7.
When the temperature "Ra" in the fresh-food compartment is higher
than its target temperature "Rr", cooling may be made by increasing
the frequency of the fresh-food fan 7. When the compartment is
excessively cooled below the target temperature "Rr", the frequency
of the fan is decreased as to weaken the refrigeration ability. In
this way, controlling for keeping at proper temperature is
made.
[0057] FIG. 12 shows variation of refrigeration capacity "QF2" for
the freezer cooler and of refrigeration capacity "QR2" for the
fresh-food cooler where; the temperature of the freezer cooler 4 is
varied. By decreasing the temperature of the freezer cooler 4, flow
rate of refrigerant passing through the freezer cooler 4 as to be
sucked into the low-pressure compressor element is decreased so
that the refrigeration capacity "QF2" of the freezer cooler is
decreased. Moreover, flow rate of refrigerant passing into the
high-pressure compression element from the low-pressure compression
element is also decreased. Thus, in view of excluded volume of the
high-pressure compression element, flow rate of refrigerant passing
from the fresh-food cooler 5 to the intermediate-pressure room and
then sucked to the high-pressure compression element is increased
so that the refrigeration capacity "QR2" of the fresh-food cooler
is increased.
[0058] In view of the above, when temperature in the fresh-food
compartment 3 is higher than the target temperature "Rr" and
cooling is insufficient, or when the refrigeration capacity for the
freezer compartment 2 is excessive; frequency of a fan 6 for the
freezer compartment, or the freezer fan 6, is decreased so as to
decrease heat exchange rate on the freezer cooler 4, or in
otherwise, the refrigeration capacity "QR2" of the fresh-food
cooler is decreased. In this way, controlling for keeping the
freezer and fresh-food compartments at proper temperatures is
made.
[0059] The refrigeration circuit explained hereto enables
simultaneous flowing of refrigerant through both of the freezer and
fresh-food coolers 4 and 5. Thus, compared to a conventional one in
which refrigerant is alternately flows into the freezer and
fresh-food coolers, flowing of refrigerant would not become
one-sided to either of the coolers; and an amount of refrigerant
required to the refrigerant circuit does not become unnecessarily
large. Hence, amount of refrigerant is kept small even when
adopting a flammable refrigerant such as hydrocarbon compounds, as
to improve safety.
[0060] In respect of the two-stage compressor 9 in the above
examples, while it is explained that inside of the compressor
casing 9c is kept at an intermediate pressure, it may be also
constructed as follows though not illustrated. A suction pipe from
the freezer cooler may be communicated with a room inside of the
compressor casing, as a low-pressure casing; and then a suction
pipe from the fresh-food cooler is connected to a junction at which
outlet of the low-pressure compression element is joined with the
inlet of the high-pressure compression element. In otherwise, a
suction pipe from the freezer cooler may be communicated with a
room inside of the compressor casing, as a high-pressure casing;
then, a suction pipe from the fresh-food cooler is connected to the
junction at which outlet of the low-pressure compression element is
joined with the inlet of the high-pressure compression element; and
gas refrigerant discharged from the high-pressure compression
element is sent out through inside of the casing at high pressure,
to an outlet pipe to the condenser.
INDUSTRIAL APPLICABILITY
[0061] The invention is applicable to a refrigerator that has an
improved efficiency of a refrigerant circuit by a construction of a
two-stage compressor.
BRIEF DESCRIPTION OF THE DRAWING
[0062] FIG. 1 is a diagram of a refrigerant circuit of a
refrigerator according to first embodiment of the invention;
[0063] FIG. 2 is a schematic vertical sectional view of a
refrigerator having the refrigerant circuit of FIG. 1;
[0064] FIG. 3 is a vertical sectional view showing a detail of a
two-stage compressor shown in FIG. 1;
[0065] FIG. 4 is a plan view showing an essential part of the
three-way valve shown in the FIG. 1;
[0066] FIG. 5 is a construction diagram showing another embodiment
of the refrigerant circuit;
[0067] FIG. 6 is a graph of a relationship between refrigeration
capacities of the freezer and fresh-food coolers as well as flow
rate;
[0068] FIG. 7 is a schematic expression of the FIG. 6;
[0069] FIG. 8 is a block diagram on controlling of frequency of the
compressor;
[0070] FIG. 9 is a block diagram on controlling of frequency of the
compressor, where information on temperature in the fresh-food
compartment is added to the block diagram on FIG. 8;
[0071] FIG. 10 is a block diagram on the controlling, which is
further improved from that of FIG. 9;
[0072] FIG. 11 is an explanatory view showing variation of
refrigeration capacities of the freezer cooler and the fresh-food
cooler when temperature of the fresh-food cooler is varied;
[0073] FIG. 12 is an explanatory view showing variation of
refrigeration capacities of the freezer cooler and the fresh-food
cooler when temperature of the freezer cooler is varied; and
[0074] FIG. 13 is a diagram of a refrigerant circuit of a
conventional refrigerator.
REFERENCE NUMERALS OR MARKS
[0075] 1 casing main body; 2 freezer compartment; 3 fresh-food
compartment; 4 freezer cooler; 5 fresh-food cooler, or cooler for
fresh-food compartment; 6 and 7 cooling fans; 8 machine room;
two-stage compressor; 9a low-pressure compression element; 9b
high-pressure compression element; 9c casing; 10 condenser; 11
switching valve; 12 capillary for freezer cooler; 13 capillary for
fresh-food cooler; 14 accumulator; 15 suction pipe from the freezer
cooler; 16 outlet pipe; 17 and 24 suction pipes from the fresh-food
cooler; 18 valve casing; 19 valve seat; 19a valve port "A" for the
freezer cooler; 19b valve port "B" for the freezer cooler; 20
closure body of the valve; 20a groove "A" for freezer cooler; 20b
groove "B" for fresh-food cooler; 20c rotation shaft; 20d thickly
terraced part; 21 inlet valve port; 22 bypass pipe; 23 liquid-gas
separator; 25 PID controller
* * * * *