U.S. patent application number 10/509117 was filed with the patent office on 2005-07-14 for refrigerating equipment.
Invention is credited to Takegami, Masaaki, Tanimoto, Kenji.
Application Number | 20050150246 10/509117 |
Document ID | / |
Family ID | 28671780 |
Filed Date | 2005-07-14 |
United States Patent
Application |
20050150246 |
Kind Code |
A1 |
Takegami, Masaaki ; et
al. |
July 14, 2005 |
Refrigerating equipment
Abstract
In a refrigerating apparatus in which gas refrigerant is
injected into suction pipes (10a, 10b) of compressors (2A, 2B) from
an oil return passageway (21) and from a gas injection passageway,
a liquid injection passageway (15) through which liquid refrigerant
is injected into the suction side of compressors (2A, 2B) is
provided and, in addition, the oil return passageway (21) and the
gas injection passageway are connected to the liquid injection
passageway (15), thereby making it possible to prevent the
occurrence of abnormal noise due to the intermixing of gas
refrigerants in the suction pipes (10a, 10b).
Inventors: |
Takegami, Masaaki; (Osaka,
JP) ; Tanimoto, Kenji; (Osaka, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
28671780 |
Appl. No.: |
10/509117 |
Filed: |
September 28, 2004 |
PCT Filed: |
March 25, 2003 |
PCT NO: |
PCT/JP03/03658 |
Current U.S.
Class: |
62/470 ; 62/468;
62/498 |
Current CPC
Class: |
F25B 2600/021 20130101;
Y02B 30/741 20130101; F25B 2700/1931 20130101; F25B 2400/075
20130101; Y02B 30/70 20130101; F25B 2500/12 20130101; F25D 2700/12
20130101; F25B 2400/22 20130101; F25B 2700/1933 20130101; F25B
2700/21152 20130101; F25B 2700/21151 20130101; F25B 2400/0751
20130101; F25B 31/004 20130101; F25B 2400/16 20130101 |
Class at
Publication: |
062/470 ;
062/468; 062/498 |
International
Class: |
F25B 043/02; F25B
001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2002 |
JP |
2002094183 |
Claims
What is claimed is:
1. A refrigerating apparatus in which a refrigerant circuit (1E)
which performs a vapor compression refrigerating cycle is provided
with an oil return passageway (21) through which refrigerating
machine oil separated on the discharge side of compressors (2A, 2B)
is injected into the suction side of said compressors (2A, 2B),
comprising: a liquid injection passageway (15) through which liquid
refrigerant is injected into the suction side of said compressors
(2A, 2B), wherein said oil return passageway (21) is connected to
said liquid injection passageway (15).
2. A refrigerating apparatus in which a refrigerant circuit (1E)
which performs a vapor compression refrigerating cycle is provided
with a gas injection passageway (37) through which gas refrigerant
is injected into the suction side of compressors (2A, 2B),
comprising: a liquid injection passageway (15) through which liquid
refrigerant is injected into the suction side of said compressors
(2A, 2B), wherein said gas injection passageway (37) is connected
to said liquid injection passageway (15).
3. The refrigerating apparatus of either claim 1 or claim 2,
comprising: a heat source side unit (1A) and utilization side units
(1B, 1C, 1D), said units (1A, 1B, 1C, 1D) being connected with one
another, wherein the degree of superheat of suction refrigerant of
said compressors (2A, 2B) is controlled by adjusting the rate of
flow of refrigerant flowing through said liquid injection
passageway (15) without operating expansion mechanisms (42, 52)
provided in said utilization side units (1B, 1C, 1D).
4. The refrigerating apparatus of claim 3, wherein said compressors
(2A, 2B) are variable displacement compressors, wherein said liquid
injection passageway (15) is opened whenever the operating capacity
of said compressors (2A, 2B) exceeds a predetermined value.
Description
TECHNICAL FIELD
[0001] This invention relates to refrigerating apparatuses and more
particularly to noise reduction techniques for reducing noise
generated on the suction side of a compressor due to oil returning
and gas injection operations.
BACKGROUND ART
[0002] Refrigerating apparatuses which perform a vapor compression
refrigerating cycle have been known in the prior art. Such a type
of refrigerating apparatus is widely utilized as a cooling device
for use in air conditioners which perform cooling and heating of
the air in a room, refrigerators for cold storage of foods or the
like, freezers, et cetera. In this refrigerating apparatus,
refrigerant discharged out of a compressor flows through a
condenser, an expansion mechanism, and an evaporator in that order,
and a vapor compression refrigerating cycle is performed.
[0003] In such a refrigerant circuit, the refrigerant discharged
out of the compressor contains refrigerating machine oil for
lubrication of the inside of the compressor. In order to bring the
refrigerating machine oil back to the compressor, an oil separator
disposed on the discharge side of the compressor is connected,
through an oil return passageway, to a suction pipe of the
compressor (see for example Japanese Patent Application Kokai
Publication No. 2001-280719). The oil return passageway is
generally provided with a switching (opening/closing) valve. In
this configuration, by placing the switching valve in the open
position, refrigerating machine oil separated from the discharged
gas refrigerant in the oil separator is brought back to the
compressor through the oil return passageway and though the suction
pipe. This makes it possible to prevent the compressor from
suffering a lack of refrigerating machine oil.
[0004] Problems to be Solved
[0005] However, when the switching valve of the oil return
passageway is opened, not only refrigerating machine oil but also
gas refrigerant flows out of the oil separator. Consequently, the
gas refrigerant, together with the refrigerating machine oil,
passes through the oil return passageway and is injected into the
suction pipe, and the gas refrigerants are mixed with each other in
the inside of the suction pipe. And, when the gas refrigerant is
injected into the suction pipe of the compressor, the flow of
refrigerant is disturbed in the suction pipe, resulting in
generation of abnormal noise which is transmitted to the outside
from the suction pipe.
[0006] As just described above, in the conventional refrigerating
apparatus, gas refrigerant is injected into the suction pipe where
the gas refrigerants are mixed with each other. This arises a
problem that abnormal noise is generated. This is the problem which
arises not only when performing an oil returning operation but also
when performing a gas injection operation for a different purpose
because gas refrigerant is injected into the suction side of the
compressor.
[0007] Bearing in mind the above-described problems, the present
invention was made. Accordingly, an object of the present invention
is to prevent the occurrence of abnormal noise in a refrigerating
apparatus of the type in which gas refrigerants are injected into
the suction side of the compressor.
DISCLOSURE OF INVENTION
[0008] The present invention is an refrigerating apparatus in which
a liquid injection passageway (15) is provided and an oil return
passageway (21) and a gas injection passageway are connected to the
liquid injection passageway (15).
[0009] More specifically, an invention as set forth in Claim 1 is
directed to a refrigerating apparatus in which a refrigerant
circuit (1E) which performs a vapor compression refrigerating cycle
is provided with an oil return passageway (21) through which
refrigerating machine oil separated on the discharge side of
compressors (2A, 2B) is injected into the suction side of the
compressors (2A, 2B). And, the refrigerating apparatus is
characterized in that it is provided with a liquid injection
passageway (15) through which liquid refrigerant is injected into
the suction side of the compressors (2A, 2B) and is further
characterized in that the oil return passageway (21) is connected
to the liquid injection passageway (15). Connecting the liquid
injection passageway (15) to suction pipes of the compressors (2A,
2B) can first be considered as a means for "injecting liquid
refrigerant into the suction side of the compressors (2A, 2B)" in
the above-described arrangement; however, in some cases any other
techniques may be employed (for example, the outlet of the liquid
injection passageway (15) is connected directly to the domes of the
compressors (2A, 2B).
[0010] In the invention as set forth in Claim 1, refrigerating
machine oil and gas refrigerant flowing in the oil return
passageway (21) are injected, through the liquid injection
passageway (15), into the suction side of the compressors (2A, 2B).
Consequently, liquid droplets-containing refrigerant in the inside
of the liquid injection passageway (15) is mixed with the gas
refrigerant. Because of this, abnormal noise due to the
intermixture of gas refrigerants will no longer occur. Even when
there is such occurrence, the abnormal noise is absorbed in the
liquid and is diminished. From the above, the leakage of noise to
the outside on the suction side of the compressors is
suppressed.
[0011] The present invention is intended originally for abnormal
noise reduction by the intermixing of gas refrigerant and liquid
refrigerant without the mixing of gas refrigerants on the suction
side of the compressors (2A, 2B). Consequently, in an invention as
set forth in Claim 2, it is specified that in an apparatus which
performs a gas injection operation, gas refrigerant is injected not
into the suction pipes of the compressors (2A, 2B) but into the
liquid injection passageway (15).
[0012] More specifically, the invention as set forth in Claim 2 is
directed to a refrigerating apparatus in which a refrigerant
circuit (1E) which performs a vapor compression refrigerating cycle
is provided with a gas injection passageway (37) through which gas
refrigerant is injected into the suction side of compressors (2A,
2B). And, the refrigerating apparatus is characterized in that the
refrigerating apparatus is provided with a liquid injection
passageway (15) through which liquid refrigerant is injected into
the suction side of the compressors (2A, 2B) and is further
characterized in that the gas injection passageway (37) is
connected to the liquid injection passageway (15).
[0013] In the invention as set forth in Claim 2, gas refrigerant
flowing in the gas injection passageway (37) is injected, through
the liquid injection passageway (15), into the suction side of the
compressors (2A, 2B), in the same way as described above.
Therefore, also in this case, liquid-containing refrigerant in the
liquid injection passageway (15) is mixed with the gas refrigerant.
Because of this, abnormal noise due to the intermixture of gas
refrigerants will no longer occur. Even when there is such
occurrence, the abnormal noise is absorbed in the liquid and is
diminished. From the above, the leakage of noise to the outside on
the suction side of the compressors is suppressed.
[0014] In addition, a refrigerating apparatus of an invention as
set forth in Claim 3 according to either Claim 1 or Claim 2 is
characterized in that a heat source side unit (1A) and utilization
side units (1B, 1C, 1D) are provided which are connected with one
another and is further characterized in that the degree of
superheat of suction refrigerant of the compressors (2A, 2B) is
controlled by adjusting the rate of flow of refrigerant flowing
through the liquid injection passageway (15) without operating
expansion mechanisms (42, 52) provided in the utilization side
units (1B, 1C, 1D).
[0015] The refrigerating apparatus of the invention as set forth in
Claim 3 is provided with the liquid injection passageway (15) for
controlling the degree of superheat of suction refrigerant of the
compressors (2A, 2B). And, in this refrigerating apparatus, the
liquid injection passageway (15) is used when performing for
example an oil return operation, so that liquid refrigerant and gas
refrigerant are mixed with each other and the mixture is injected
into the compressors.
[0016] In addition, a refrigerating apparatus of an invention as
set forth in Claim 4 according to Claim 3 is characterized in that
the compressors (2A, 2B) are variable displacement compressors and
is further characterized in that the liquid injection passageway
(15) is opened whenever the operating capacity of the compressors
(2A, 2B) exceeds a predetermined value. It may be arranged such
that, when the operating capacity of the compressors (2A, 2B) falls
below the predetermined value, the liquid injection passageway (15)
is closed.
[0017] In the invention as set forth in Claim 4, the liquid
injection passageway (15) is placed in the open state whenever the
operating capacity of the compressors (2A, 2B) exceeds a
predetermined value, and the degree of superheat of the suction
refrigerant is controlled. And, although at this time gas
refrigerant is injected into the liquid injection passageway (15)
from the oil return passageway (21) or from the gas injection
passageway (37), the occurrence of abnormal noise is suppressed, as
described above. In addition, when the operating capacity of the
compressors (2A, 2B) falls blow the predetermined value, gas
refrigerant is injected (not through the liquid injection
passageway (15)) into the compressors (2A, 2B) from the oil return
passageway (21) or from the gas injection passageway (37) if the
liquid injection passageway (15) is closed. However, at this time
the flow velocity of refrigerant is slow, and abnormal noise will
hardly occur.
[0018] Effects
[0019] In accordance with the invention as set forth in Claim 1,
since the oil return passageway (21) is connected to the liquid
injection passageway (15), this makes it possible to cause
refrigerating machine oil and gas refrigerant flowing in the oil
return passageway (21) to be injected, through the liquid injection
passageway (15), into the suction side of the compressors (2A, 2B).
By virtue of such arrangement, the occurrence of abnormal noise due
to the intermixing of gas refrigerants is suppressed. Furthermore,
an increase in the degree of superheat due to the injection of gas
into the suction side of the compressors (2A, 2B) during the oil
return operation is prevented.
[0020] In addition, in accordance with the invention as set forth
in Claim 2, since the gas injection passageway (37) is connected to
the liquid injection passageway (15), this makes it possible to
cause gas refrigerant flowing in the gas injection passageway (37)
to be injected, through the liquid injection passageway (15), into
the suction side of the compressors (2A, 2B). By virtue of such
arrangement, the occurrence of abnormal noise due to the
intermixing of gas refrigerants is suppressed, as in the invention
as set forth in Claim 1, and it is possible to prevent the degree
of superheat of refrigerant of the compressors (2A, 2B) from
increasing excessively.
[0021] Furthermore, in accordance with the invention as set forth
in Claim 3, since the occurrence of abnormal noise is suppressed by
making utilization of the liquid injection passageway (15) in the
refrigerating apparatus which includes the liquid injection
passageway (15) as its original part, this prevents the apparatus
configuration from becoming complicated.
[0022] Finally, in accordance with the invention as set forth in
Claim 4, the occurrence of abnormal noise is avoided effectively
when there is the possibility that abnormal noise becomes a problem
because the operating capacity of the compressors (2A, 2B) exceeds
the predetermined value.
BRIEF DESCRIPTION OF DRAWINGS
[0023] FIG. 1 is a refrigerant circuit diagram of a refrigerating
apparatus according to an embodiment of the present invention;
and
[0024] FIG. 2 is a flowchart representing control steps of the
degree of valve opening of an expansion valve in a liquid injection
passageway.
BEST MODE FOR CARRYING OUT INVENTION
[0025] Hereinbelow, embodiments of the present invention will be
described in detail with reference to the drawings.
[0026] Referring to FIG. 1, there is shown a refrigerant circuit
diagram of a refrigerating apparatus (1) according to an embodiment
of the present invention. The refrigerating apparatus (1) is
intended for installation in a convenience store or the like and is
so constructed as to keep the inside of a plurality of showcases
cold. In the example illustrated in FIG. 1, there is shown a
refrigerating apparatus which is provided with two cold storage
showcases and a single freeze storage showcase. However, any
changes in the number of showcases may be made as required.
[0027] The refrigerating apparatus (1) has an outdoor unit (1A),
cold storage units (1B, 1C), and a freeze storage unit (1D). The
cold storage units (1B, 1C) installed in respective showcases for
cold storage are so constructed as to cool the air in the cold
storage showcases. On the other hand, the freeze storage unit (1D)
installed in a showcase for freeze storage is so constructed as to
cool the air in the freeze storage showcase. And, in the
refrigerating apparatus (1), the units (1A, 1B, 1C, 1D) are
connected to form a refrigerant circuit (1E) which performs a vapor
compression refrigerating cycle.
[0028] Outdoor Unit
[0029] The outdoor unit (1A) is provided with a compression
mechanism (2) in which two compressors (2A, 2B) are connected in
parallel. The outdoor unit (1A) further includes an outdoor heat
exchanger (3) which is a heat exchanger on the heat source side,
and a receiver (4).
[0030] The compressors (2A, 2B) are for example high pressure dome
scroll compressors of the hermetic sealed type. The compression
mechanism (2) is made up of the non inverter compressor (2A) which
is a first compressor and the inverter compressor (2B) which is a
second compressor. The non inverter compressor (2A) is a fixed
displacement compressor in which the motor rotates at a fixed
rotational speed. On the other hand, the inverter compressor (2B)
is a variable displacement compressor in which the motor is
inverter-controlled so that its capacity is varied in stages or in
succession.
[0031] A discharge pipe (4a) of the non inverter compressor (2A)
and a discharge pipe (4b) of the inverter compressor (2B) are
connected to a single high pressure gas pipe (discharge piping)
(5). In addition, the discharge pipe (4a) of the non inverter
compressor (2A) is provided with a check valve (6).
[0032] The outdoor heat exchanger (3) is for example a fin and tube
heat exchanger of the cross fin type, and an outdoor fan (3F) which
is a heat source fan is disposed in the vicinity of the outdoor
heat exchanger (3). And, the high pressure gas pipe (5) is
connected to a gas side end of the outdoor heat exchanger (3).
[0033] One end of an outdoor liquid pipe (7) is connected to a
liquid side end of the outdoor heat exchanger (3). The receiver (4)
is disposed midway in the outdoor liquid pipe (7), and the other
end of the outdoor liquid pipe (7) is connected, through a liquid
stop valve (8), to an interunit liquid pipe (31). In addition, the
outdoor liquid pipe (7) is provided, between the outdoor heat
exchanger (3) and the receiver (4), with a check valve (9) which
permits the refrigerant to flow in the direction of the receiver
(4) only.
[0034] Both a suction pipe (10a) of the non inverter compressor
(2A) and a suction pipe (10b) of the inverter compressor (2B) are
connected to one end of a low pressure gas pipe (11). The other end
of the low pressure gas pipe (11) is connected, through a gas stop
valve (12), to an interunit gas pipe (32).
[0035] In the above-described arrangement, the discharge pipes (4a,
4b) and the high pressure gas pipe (5) together make up a high
pressure gas line (1L). On the other hand, the interunit gas pipe
(32), the low pressure gas pipe (11), and the suction pipes (10a,
10b) of the compression mechanism (2) together make up a low
pressure gas line (1M).
[0036] One end of a liquid injection passageway (15) is connected
to a portion of the outdoor liquid pipe (7) situated between the
receiver (4) and the liquid stop valve (8). The other end of the
liquid injection passageway (15) is connected to the low pressure
gas pipe (11), being in communication with the suction pipes (10a,
10b) of the compressors (2A, 2B). The liquid injection passageway
(15) is provided with an electric expansion valve (16) for
controlling the rate of flow of refrigerant.
[0037] The high pressure gas pipe (5) is provided with an oil
separator (20). One end of an oil return passageway (21) is
connected to the oil separator (20). The oil return passageway (21)
is provided with a solenoid valve (22) as a switching valve, and
the other end of the oil return passageway (21) is connected to a
portion of the liquid injection passageway (15) situated between
the electric expansion valve (16) and the low pressure gas pipe
(11). In other words, the oil return passageway (21) is connected
to the suction pipes (10a, 10b) of the compressors (2A, 2B) not in
direct manner but in indirect manner through the liquid injection
passageway (15).
[0038] In addition, an oil level equalizing pipe (25) is connected
between the dome (oil sump) of the non inverter compressor (2A) and
the suction pipe (10b) of the inverter compressor (2B). The oil
level equalizing pipe (25) is provided with a solenoid valve
(26).
[0039] Cold Storage Unit
[0040] The cold storage units (1B, 1C) are each provided with a
respective cold storage heat exchanger (41) which is a utilization
side heat exchanger and a respective cold storage expansion valve
(42) which is an expansion mechanism. A liquid side of the cold
storage heat exchanger (41) is connected, through the cold storage
expansion valve (42) and a solenoid valve (43), to the interunit
liquid pipe (31). On the other hand, a gas side of the cold storage
heat exchanger (41) is connected to the interunit gas pipe (32),
being in communication with the suction side of the compression
mechanism (2).
[0041] In addition, the cold storage expansion valve (42) is a
temperature sensitive expansion valve whose temperature sensing
bulb is mounted on the gas side of the cold storage heat exchanger
(41). The cold storage heat exchanger (41) is implemented by for
example a fin and tube heat exchanger of the cross fin type, and a
cold storage fan (4F) which is a cooling fan is disposed in the
vicinity of the cold storage heat exchanger (41).
[0042] Freeze Storage Unit
[0043] The freeze storage unit (1D) has a freezing heat exchanger
(51) which is a utilization-side heat exchanger, a freezing
expansion valve (52) which is an expansion mechanism, and a booster
compressor (53) which is a freezing compressor. A branch liquid
pipe (33) branched off from the interunit liquid pipe (31) is
connected, via the solenoid valve (54) and the freezing expansion
valve (52), to a liquid side of the freezing heat exchanger
(51).
[0044] A gas side of the freezing heat exchanger (51) and a suction
side of the booster compressor (53) are connected together by a
connecting gas pipe (55). A branch gas pipe (34) branched off from
the interunit gas pipe (32) is connected to a discharge side of the
booster compressor (53). The branch gas pipe (34) is provided with
a check valve (56) and an oil separator (57). Connected between the
oil separator (57) and the connecting gas pipe (55) is an oil
return passageway (59) having a capillary tube (58).
[0045] The booster compressor (53) performs two-stage compression
of refrigerant together with the compression mechanism (2) of the
outdoor unit (1A) so that the refrigerant evaporating temperature
of the freezing heat exchanger (51) becomes lower than the
refrigerant evaporating temperature of the cold storage heat
exchanger (41). The refrigerant evaporating temperature of the cold
storage heat exchanger (41) is set to, for example, -10 degrees
Centigrade. On the other hand, the refrigerant evaporating
temperature of the freezing heat exchanger (51) is set to, for
example, -40 degrees Centigrade.
[0046] In addition, the freezing expansion valve (52) is a
temperature sensitive expansion valve whose temperature sensing
bulb is mounted on the gas side of the freezing heat exchanger
(51). The freezing heat exchanger (51) is implemented by for
example a fin and tube heat exchanger of the cross fin type, and a
freezing fan (5F) which is a cooling fan is disposed in the
vicinity of the freezing heat exchanger (51).
[0047] In addition, a bypass pipe (61) having a check valve (60) is
connected between the connecting gas pipe (55) which is the suction
side of the booster compressor (53) and the branch gas pipe (34)
which is the discharge side of the booster compressor (53). The
bypass pipe (61) is constructed such that, when the booster
compressor (53) is stopped by failure or the like, refrigerant
flows, bypassing the booster compressor (53).
[0048] Control System
[0049] Various sensors and switches are provided in the refrigerant
circuit (1E). The high pressure gas pipe (5) of the outdoor unit
(1A) is provided with a pressure sensor (71) for high-level
pressure which is a pressure detecting means for detecting the
pressure of high pressure refrigerant and a discharge temperature
sensor (72) which is a temperature detecting means for detecting
the temperature of high pressure refrigerant. In addition, the
discharge pipe (4b) of the inverter compressor (2B) is provided a
pressure switch (73) which is placed in the opened position when
the pressure of high pressure refrigerant becomes a predetermined
value.
[0050] The low pressure gas pipe (11) is provided with a pressure
sensor (74) for low-level pressure which is a pressure detecting
means for detecting the pressure of low pressure refrigerant and a
suction temperature sensor (75) which is a temperature detecting
means for detecting the temperature of low pressure refrigerant. In
addition, the outdoor unit (1A) is provided with an outside air
temperature sensor (76) which is a temperature detecting means for
detecting the temperature of outside air.
[0051] The cold storage units (1B, 1C) are each provided with a
cold storage temperature sensor (77) which is a temperature
detecting means for detecting the inside temperature of the
associated cold storage showcase. On the other hand, the freeze
storage unit (1D) is provided with a freezing temperature sensor
(78) which is a temperature detecting means for detecting the
inside temperature of the freeze storage showcase.
[0052] Output signals from the above-mentioned various sensors and
switches are fed to a controller (80). And, the controller (80)
controls the operating capacity of the compression mechanism (2)
according to the refrigerating capacities required for the cold
storage heat exchanger (41) and the freezing heat exchanger (51).
In addition, the controller (80) is so configured as to control the
degree of superheat of the suction refrigerant by adjusting the
valve opening of the electric expansion valve (16) of the liquid
injection passageway (15).
[0053] Running Operation
[0054] Hereinbelow, the running operation of the refrigerating
apparatus (1) will be described.
[0055] In the first place, the activation and shutdown of the non
inverter compressor (2A) and the activation, capacity control, and
shutdown of the inverter compressor (2B) in the compression
mechanism (2) are controlled by the operation of the controller
(80) so that refrigerating capacities required in the cold storage
heat exchanger (41) and the freezing heat exchanger (51) are
obtained. During the cooling operation by the freezing heat
exchanger (51), the booster compressor (53) is activated and its
capacity is also controlled. In addition, during the cold storage
operation of the cold storage units (1B, 1C) and the freeze storage
operation of the freeze storage unit (1D) (i.e., during the
thermo-on operation), the solenoid valves (43) of the cold storage
units (1B, 1C) and the solenoid valve (54) of the freeze storage
unit (1D) are opened. On the other hand, during the shutdown
operation which stops cooling operations (during the thermo-off
operation) the solenoid valves (43, 54) are closed.
[0056] Furthermore, the expansion valve of the liquid injection
passageway (15) is placed normally in the "open" state and its
valve opening is controlled. In other words, in the present
embodiment the degree of superheat of the suction refrigerant is
controlled by execution of a liquid injection operation because the
expansion valves (42, 52) of the temperature sensitive type are
employed in the cold and freeze storage units (1B, 1C, 1D).
[0057] In the above-described setting, refrigerant discharged out
of the non inverter compressor (2A) and refrigerant discharged out
of the inverter compressor (2B) flow together in the high pressure
gas pipe (5), flow into the outdoor heat exchanger (3), and
condense to a liquid refrigerant. The liquid refrigerant passes
through the outdoor liquid pipe (7) and through the receiver (4)
and then flows to the interunit liquid pipe (31).
[0058] The liquid refrigerant flowing through the interunit liquid
pipe (31) expands in the cold storage expansion valve (42) on the
side of the cold storage units (1B, 1C) and thereafter flows
through the cold storage heat exchanger (41) where it changes into
vapor. Meanwhile, a part of the liquid refrigerant flowing through
the interunit liquid pipe (31) branches off into the branch liquid
pipe (33), flows into the freeze storage unit (1D), expands in the
freezing expansion valve (52), and thereafter flows through the
freezing heat exchanger (51) where it changes into vapor. The gas
refrigerant evaporated in the freezing heat exchanger (51) is drawn
into the booster compressor (53) and is discharged into the branch
gas pipe (34).
[0059] The gas refrigerant evaporated in the cold storage heat
exchanger (41) and the gas refrigerant discharged out of the
booster compressor (53) join and flow together in the interunit gas
pipe (32), return to the outdoor unit (1A), flow through the low
pressure gas pipe (11), and are brought back to the non inverter
compressor (2A) and to the inverter compressor (2B).
[0060] As a result of the repetition of such refrigerant
circulation, the inside of the cold storage and freeze storage
showcases is cooled. When the inside of each showcase is kept
sufficiently cool, the solenoid valves (43) of the cold storage
units (1B, 1C) and the solenoid valve (54) of the freeze storage
unit (1D) are closed individually. Consequently, the refrigerating
apparatus enters the resting operation state (thermo-off operation
state) in which no refrigerant circulates in the heat exchangers
(41, 51) and only an operation of supplying air is carried out.
[0061] In the compression mechanism (2), it is constructed such
that only the inverter compressor (2B) is controlled in capacity
until a certain operating capacity, with the non inverter
compressor (2A) placed in the stopped state, and when operating
capacities more than it is required, both the compressors (2A, 2B)
are activated at the same time and the capacity of the inverter
compressor (2B) is controlled. In addition, in some cases the
inverter compressor (2B) is stopped and only the non inverter
compressor (2A) is activated.
[0062] In the refrigerating apparatus (1), the utilization side is
a cold storage/freeze storage side, and the level of low pressure
is lower in comparison with that of air conditioning apparatuses.
Because of this, there is a region that requires an increase in the
operating capacity of the compression mechanism (2) although the
flow velocity of suction refrigerant is slow. In such a case, the
degree of superheat of refrigerant of the compression mechanism (2)
tends to increase. Besides, both the expansion mechanism (42) of
each of the cold storage units (1B, 1C) and the expansion mechanism
(52) of the freeze storage unit (1D) are expansion valves of the
temperature sensitive type, as described above. Accordingly, the
valve opening of these expansion mechanisms cannot be adjusted from
the side of the outdoor unit (1A). To cope with this, in the
present embodiment, a liquid injection operation is carried out in
order to prevent the degree of superheat of refrigerant of the
compression mechanism (2) from excessively increasing.
[0063] The electric expansion valve (16) of the liquid injection
passageway (15) is placed constantly in the open state in normal
conditions although it may be closed exceptionally when the
compression mechanism (2) is operated in low capacity regions.
Control of the valve opening of the electric expansion valve (16)
during the normal operations is carried out according to steps of a
flowchart shown in FIG. 2.
[0064] In Step ST1 of the flowchart, the valve-opening control
amount of the electric expansion valve (16) is calculated based on
the degree of superheat of refrigerants on the suction side and on
the discharge side of the compression mechanism (2). In Step ST2,
it is determined whether the electric expansion valve (16) is fully
closed or not. The time when the electric expansion valve (16) is
placed in the fully closed state during the normal operations is
for example a time when the refrigerating apparatus is activated.
At this time, in Step ST3 an operation of forcing the electric
expansion valve (16) to open slightly is performed and the valve
opening is set to the initial value. In addition, if in Step ST2 it
is decided that the electric expansion valve (16) is already placed
in the open state, then the valve-opening control procedure
proceeds to Step ST4. In Step ST4, based on the valve-opening
control amount found in Step ST1 and on the current valve opening,
the electric expansion valve (16) is adjusted in valve opening. As
a result of such arrangement, while constantly injecting a small
amount of liquid refrigerant into the suction pipes (10a, 10b), its
flow rate adjustment is made, thereby controlling the degree of
superheat of refrigerant of the compression mechanism (2).
[0065] In the present embodiment the high pressure gas pipe (5) on
the discharge side of the compression mechanism (2) is provided
with the oil separator (20), as described above. And, the oil
return passageway (21) extending from the oil separator (20) is
connected to the liquid injection passageway (15). The solenoid
valve (22) of the oil return passageway (21) is controlled such
that it turns on and off intermittently at a predetermined timing
interval, and when placed in the ON state an operation of returning
oil to the compression mechanism (2) is carried out.
[0066] To sum up, refrigerating machine oil contained in
refrigerant discharged out of the compression mechanism (2) is
separated from the refrigerant in the oil separator (20). When the
solenoid valve (22) is placed in the open state, the refrigerating
machine oil passes through the oil return passageway (21), the
liquid injection passageway (15), the low pressure gas pipe (11),
and the suction pipes (10a, 10b), and is drawn into the compression
mechanism (2). At the time when both of the two compressors (2A,
2B) are being operated, generally the non inverter compressor (2A)
is greater in capacity than the inverter compressor (2B), and the
refrigerating machine oil is recovered mainly into the non inverter
compressor (2A). In addition, when refrigerating machine oil is
stored excessively in the non inverter compressor (2A), the
refrigerating machine oil is recovered into the inverter compressor
(2B) when the solenoid valve (26) of the oil level equalizing pipe
(25) is placed in the open state.
[0067] In the present embodiment, when the solenoid valve (22) of
the oil return passageway (21) is opened, gas refrigerant flows
through the oil return passageway (21), together with refrigerating
machine oil, and the same operation as gas injection is carried
out. At this time, the refrigerating machine oil and the gas
refrigerant flow first into the liquid injection passageway (15).
Consequently, in the liquid injection passageway (15), gas
refrigerant is mixed into refrigerant containing therein liquid
droplets. Therefore, abnormal noise due to the intermixing of gas
refrigerants is hardly generated. Even when generated, such
abnormal noise is absorbed into the liquid since the refrigerant
flowing through the liquid injection passageway (15) contains
therein liquid. As stated above, the leakage of abnormal noise to
the outside on the suction side of the compression mechanism (2) is
suppressed.
EFFECTS OF EMBODIMENT
[0068] As has been described above, in accordance with the present
embodiment, it is possible to suppress the occurrence of abnormal
noise on the suction side of the compression mechanism (2) during
the oil return operation.
[0069] In addition, it is contemplated that the degree of superheat
of the refrigerant increases in the compressors (2A, 2B) if gas
refrigerant on the discharge side is injected directly to the
suction side of the compressors (2A, 2B) by an oil return
operation; however, it is possible to prevent the degree of
superheat from increasing excessively if the oil return passageway
(21) is made to join the liquid injection passageway (15).
[0070] In addition, it is impossible to adjust the valve opening of
the expansion valves (42, 52) of the showcases from the side of the
outdoor unit (1A) because these valves are of the temperature
sensitive type, in view of which the refrigerating apparatus (1) is
provided, as its original part, with the liquid injection
passageway (15) for controlling the degree of suction superheat.
Accordingly, even when it is arranged such that the oil return
passageway (21) is connected to the liquid injection passageway
(15), this will not make the structure complicated.
[0071] Furthermore, even when the occurrence of abnormal noise due
to the oil return operation is likely to take place because the
operating capacity of the compression mechanism (2) exceeds a
predetermined value, such an occurrence is avoided effectively.
OTHER EMBODIMENTS
[0072] In the above-described embodiment, the description has been
made in terms of an example in which the oil return passageway (21)
is connected to the liquid injection passageway (15). However, the
present invention is, in essentials, to suppress the occurrence of
abnormal noise by injecting gas refrigerant to refrigerant in the
liquid injection passageway (15) without the intermixing of gas
refrigerants on the suction side of the compression mechanism
(2).
[0073] Because of this, the present invention is applicable not
only to refrigerating apparatuses provided with an oil return
passageway but also to refrigerating apparatuses provided with a
gas injection passageway for injecting gas refrigerant into a
compressor. For example, for the case of the circuit configuration
of the above-described embodiment, it may be arranged such that a
gas injection passageway (37), provided with a flow rate adjusting
valve (36) and extending from an upper end portion of the receiver
(4), is connected to the liquid injection passageway (15), as
indicated by broken line of FIG. 1. When the inside of the receiver
(4) is filled with gas refrigerant, the internal pressure of the
receiver (4) becomes high, therefore making it difficult for liquid
refrigerant to flow into the receiver (4) from the outdoor heat
exchanger (3). In such a case, the gas injection passageway (37)
can be used as a gas-vent passageway. As a result of such
arrangement, gas refrigerant withdrawn from the receiver (4) is
injected into the liquid injection passageway (15), thereby
suppressing the occurrence of abnormal noise at the injection
portion. In the conventional apparatus in which a gas injection
passageway is connected directly to a suction pipe of a compressor,
abnormal noise is produced because gas refrigerants are mixed with
each other in the inside of the suction pipe. On the other hand, it
is possible to prevent the occurrence of abnormal noise by the same
actions as the above-described embodiment, when the gas injection
passageway is connected to the liquid injection passageway.
[0074] Industrial Applicability
[0075] As has been described above, the present invention is useful
for refrigerating apparatuses.
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