U.S. patent application number 12/921026 was filed with the patent office on 2010-12-30 for refrigeration system.
Invention is credited to Satoru Sakae, Masaaki Takegami.
Application Number | 20100326125 12/921026 |
Document ID | / |
Family ID | 41064953 |
Filed Date | 2010-12-30 |
United States Patent
Application |
20100326125 |
Kind Code |
A1 |
Sakae; Satoru ; et
al. |
December 30, 2010 |
REFRIGERATION SYSTEM
Abstract
In a refrigeration system in which a compressor mechanism
including a plurality of compressors, oil separators (37a, 37b) are
provided at a discharge pipe (56a) of a first compressor (14a) and
a discharge pipe (56b) of a second compressor (14b), respectively.
An oil return passageway (32) for returning refrigerating machine
oil from the oil separators (37a, 37b) to a compressor mechanism
(40) is configured to combine streams of refrigerating machine oil
separated in the oil separators (37a, 37b) and distribute the
combined refrigerating machine oil to the first compressor (14a)
and the second compressor (14b).
Inventors: |
Sakae; Satoru; (Osaka,
JP) ; Takegami; Masaaki; (Osaka, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
41064953 |
Appl. No.: |
12/921026 |
Filed: |
March 5, 2009 |
PCT Filed: |
March 5, 2009 |
PCT NO: |
PCT/JP2009/000999 |
371 Date: |
September 3, 2010 |
Current U.S.
Class: |
62/470 ;
62/510 |
Current CPC
Class: |
F25B 2313/023 20130101;
F25B 2400/075 20130101; F25B 31/004 20130101; F25B 2313/006
20130101; F25B 2313/02741 20130101; F25B 13/00 20130101; F25B
2600/0251 20130101; F25B 2313/02743 20130101; F25B 43/02 20130101;
F25B 2313/007 20130101 |
Class at
Publication: |
62/470 ;
62/510 |
International
Class: |
F25B 43/02 20060101
F25B043/02; F25B 1/10 20060101 F25B001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 12, 2008 |
JP |
2008-062925 |
Claims
1. A refrigeration system including a refrigerant circuit (4) which
is configured to perform a refrigeration cycle and provided with a
compressor mechanism (40) including a first compressor (14a) and a
second compressor (14b) whose discharge sides are connected to each
other, the refrigeration system comprising: oil separators (37a,
37b) provided at a discharge pipe (56a) of the first compressor
(14a) and a discharge pipe (56b) of the second compressor (14b),
respectively; and an oil return passageway (32) configured to
combine streams of refrigerating machine oil separated in the oil
separators (37a, 37b) and distribute the combined refrigerating
machine oil to the first compressor (14a) and the second compressor
(14b).
2. The refrigeration system of claim 1, further comprising an
injection passageway (30) configured to inject a refrigerant into
the first compressor (14a) and the second compressor (14b), wherein
the oil return passageway (32) includes a junction passageway (48)
in which refrigerating machine oil from the oil separators (37a,
37b) flows, and the junction passageway (48) is connected to a
portion of the injection passageway (30) located upstream of a
branch point to the first compressor (14a) and the second
compressor (14b).
3. The refrigeration system of claim 2, wherein the compressor
mechanism (40) is configured to always operate the first compressor
(14a) and adjust an operation capacity of the compressor mechanism
(40) by switching the second compressor (14b) between operation and
nonoperation, the injection passageway (30) includes a first branch
injection passageway (42a) branching to the first compressor (14a)
and a second branch injection passageway (42b) branching to the
second compressor (14b), and only the second branch injection
passageway (42b) has an oil non-return valve (SV1) which is freely
opened and closed and prevents refrigerating machine oil from
returning to the compressor (14b) to which the branch injection
passageway (42b) is connected while the compressor (14b) stops.
4. The refrigeration system of claim 1 or 2, wherein the compressor
mechanism (40) is configured to always operate the first compressor
(14a) and adjust an operation capacity of the compressor mechanism
(40) by switching the second compressor (14b) between operation and
nonoperation, the oil return passageway (32) includes a first
pre-junction passageway (47a) connected to the oil separator (37a)
at the discharge pipe (56a) of the first compressor (14a) and a
second pre-junction passageway (47b) connected to the oil separator
(37b) at the discharge pipe (56b) of the second compressor (14b),
and only the second pre-junction passageway (47b) has a check valve
(CV4) for preventing refrigerating machine oil from returning to
the oil separator (37b).
5. The refrigeration system of claim 1, wherein in the second
compressor (14b), a discharge space (100) filled with a refrigerant
compressed in a fluid machine (82) configured to compress a fluid
in a compression chamber (73a, 73b) is formed in a casing (70)
housing the fluid machine (82), a refrigerant-inflow stop valve
(CV2) is provided at a portion of the discharge pipe (56b) of the
second compressor (14b) located downstream of the oil separator
(37b), and stops a flow of a refrigerant into the second compressor
(14b) in a nonoperation state, and when the second compressor (14b)
stops while the first compressor (14a) operates, the first
compressor (14a) sucks a refrigerant in the discharge space (100)
in the second compressor (14b) through the oil return passageway
(32).
6. The refrigeration system of claim 1, wherein an outlet side of
the oil return passageway (32) communicates with compression
chambers (73) with intermediate pressures of the respective
compressors (14a, 14b).
7. The refrigeration system of claim 1, wherein at least one of the
first compressor (14a) and the second compressor (14b) is a
compressor having a variable operation capacity.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a refrigeration system in
which a compressor mechanism including a plurality of compressors
is provided in a refrigerant circuit.
BACKGROUND ART
[0002] Conventional refrigeration systems in each of which a
compressor mechanism including a plurality of compressors is
provided in a refrigerant circuit are known. This type of
refrigeration systems are widely used in, for example, cooling
machines such as refrigerators or freezers for storing food and
other materials and air conditioners for cooling and heating the
air in rooms.
[0003] Patent Document 1 shows a refrigeration system in which an
oil separator is provided for a compressor mechanism. The oil
separator is located at a discharge junction pipe at which
discharge pipes from compressors are combined together. The outlet
of an oil return passageway extending from the oil separator
branches off into parts which are connected to the compressors and
communicate with compression chambers with intermediate pressures
of the compressors.
Citation List
Patent Document
[0004] PATENT DOCUMENT 1: Japanese Patent Publication No.
2007-178052
SUMMARY OF THE INVENTION
Technical Problem
[0005] In a conventional refrigeration system, one oil separator is
shared by a plurality of compressors. In a possible configuration
of this refrigeration system, an oil separator is provided on a
discharge pipe of each of the compressors. In this case, the
configuration can be simplified by connecting each oil separator to
an associated one of the compressors through an oil return pipe.
Refrigerating machine oil separated by the oil separator at the
discharge pipe of each of the compressors returns to the compressor
from which the oil was discharged.
[0006] However, in this configuration, even when an oil imbalance
occurs, i.e., refrigerating machine oil flows mainly into a
specific one of the compressors, all the refrigerating machine oil
separated by the oil separator at the discharge pipe of the
specific compressor returns to this specific compressor. Most part
of the refrigerating machine oil discharged from the specific
compressor circulates between the specific compressor and the oil
separator at the discharge pipe of the specific compressor.
Accordingly, despite a shortage of refrigerating machine oil in the
other compressors due to the oil imbalance, refrigerating machine
oil is hardly distributed to these compressors, and poor
lubrication might occurs in the compressors which are in short of
refrigerating machine oil.
[0007] It is therefore an object of the present invention to
provide a refrigeration system in which a compressor mechanism
including a plurality of compressors is provided, and in which an
oil imbalance, i.e., a phenomenon in which refrigerating machine
oil flows mainly into one or more of the compressors, is reduced to
reduce poor lubrication in the other compressors which are in short
of refrigerating machine oil.
Solution to the Problem
[0008] A first aspect of the present invention is directed to a
refrigeration system including a refrigerant circuit (4) which is
configured to perform a refrigeration cycle and provided with a
compressor mechanism (40) including a first compressor (14a) and a
second compressor (14b) whose discharge sides are connected to each
other. The refrigeration system includes: oil separators (37a, 37b)
provided at a discharge pipe (56a) of the first compressor (14a)
and a discharge pipe (56b) of the second compressor (14b),
respectively; and an oil return passageway (32) configured to
combine streams of refrigerating machine oil separated in the oil
separators (37a, 37b) and distribute the combined refrigerating
machine oil to the first compressor (14a) and the second compressor
(14b).
[0009] In a second aspect of the present invention, the
refrigeration system of the first aspect further includes an
injection passageway (30) configured to inject a refrigerant into
the first compressor (14a) and the second compressor (14b), wherein
the oil return passageway (32) includes a junction passageway (48)
in which refrigerating machine oil from the oil separators (37a,
37b) flows, and the junction passageway (48) is connected to a
portion of the injection passageway (30) located upstream of a
branch point to the first compressor (14a) and the second
compressor (14b).
[0010] In a third aspect of the present invention, in the
refrigeration system of the second aspect, the compressor mechanism
(40) is configured to always operate the first compressor (14a) and
adjust an operation capacity of the compressor mechanism (40) by
switching the second compressor (14b) between operation and
nonoperation, the injection passageway (30) includes a first branch
injection passageway (42a) branching to the first compressor (14a)
and a second branch injection passageway (42b) branching to the
second compressor (14b), and only the second branch injection
passageway (42b) has an oil non-return valve (SV1) which is freely
opened and closed and prevents refrigerating machine oil from
returning to the compressor (14b) to which the branch injection
passageway (42b) is connected while the compressor (14b) stops.
[0011] In a fourth aspect of the present invention, in the
refrigeration system of the first or second aspect, the compressor
mechanism (40) is configured to always operate the first compressor
(14a) and adjust an operation capacity of the compressor mechanism
(40) by switching the second compressor (14b) between operation and
nonoperation, the oil return passageway (32) includes a first
pre-junction passageway (47a) connected to the oil separator (37a)
at the discharge pipe (56a) of the first compressor (14a) and a
second pre-junction passageway (47b) connected to the oil separator
(37b) at the discharge pipe (56b) of the second compressor (14b),
and only the second pre-junction passageway (47b) has a check valve
(CV4) for preventing refrigerating machine oil from returning to
the oil separator (37b).
[0012] In a fifth aspect of the present invention, in the
refrigeration system of one of the first through fourth aspects, in
the second compressor (14b), a discharge space (100) filled with a
refrigerant compressed in a fluid machine (82) configured to
compress a fluid in a compression chamber (73a, 73b) is formed in a
casing (70) housing the fluid machine (82), a refrigerant-inflow
stop valve (CV2) is provided at a portion of the discharge pipe
(56b) of the second compressor (14b) located downstream of the oil
separator (37b), and stops a flow of a refrigerant into the second
compressor (14b) in a nonoperation state, when the second
compressor (14b) stops while the first compressor (14a) operates,
the first compressor (14a) sucks a refrigerant in the discharge
space (100) in the second compressor (14b) through the oil return
passageway (32).
[0013] In a sixth aspect of the present invention, in the
refrigeration system of one of the first through fifth aspects, an
outlet side of the oil return passageway (32) communicates with
compression chambers (73) with intermediate pressures of the
respective compressors (14a, 14b).
[0014] In a seventh aspect of the present invention, in the
refrigeration system of the first aspect, at least one of the first
compressor (14a) and the second compressor (14b) is a compressor
having a variable operation capacity.
--Advantages--
[0015] In the first aspect, refrigerating machine oil separated by
the oil separator (37a) at the discharge pipe (56a) of the first
compressor (14a) and refrigerating machine oil separated by the oil
separator (37b) at the discharge pipe (56b) of the second
compressor (14b) are combined in the oil return passageway (32),
and then the combined refrigerating machine oil is distributed to
the first compressor (14a) and the second compressor (14b). In each
of the compressors (14), as the oil surface in the oil sump becomes
higher, the oil mixture rate increases, i.e., the amount of
refrigerating machine oil contained in a discharged refrigerant per
a unit flow rate increases. Accordingly, supposing that the
operation capacities of the first compressor (14a) and the second
compressor (14b) are constant, when refrigerating machine oil
begins to flow mainly into the first compressor (14a) out of the
first compressor (14a) and the second compressor (14b), the flow
rate of refrigerating machine oil discharged from the first
compressor (14a) with an increasing oil surface level increases,
whereas the flow rate of refrigerating machine oil discharged from
the second compressor (14b) with a decreasing oil surface level
decreases. On the other hand, the flow rate of refrigerating
machine oil returning to the first compressor (14a) and the second
compressor (14b) varies depending on the total flow rate of
refrigerating machine oil discharged from the first compressor
(14a) and refrigerating machine oil discharged from the second
compressor (14b). Thus, even when the flow rate of refrigerating
machine oil discharged from the first compressor (14a) increases,
the flow rate of refrigerating machine oil returning to the first
compressor (14a) does not increase accordingly. Likewise, even when
the flow rate of refrigerating machine oil discharged from the
second compressor (14b) decreases, the flow rate of refrigerating
machine oil returning to the second compressor (14b) does not
decrease accordingly. Thus, when refrigerating machine oil begins
to flow mainly into the first compressor (14a), the amount of
refrigerating machine oil in the first compressor (14a) decreases,
whereas the amount of refrigerating machine oil in the second
compressor (14b) increases. In this manner, in the first aspect,
when an oil imbalance occurs, i.e., refrigerating machine oil
begins to flow mainly into a specific compressor (14) out of the
first compressor (14a) and the second compressor (14b), progress of
this oil imbalance is automatically reduced.
[0016] In the second aspect, the junction passageway (48) of the
oil return passageway (32) is connected to a portion of the
injection passageway (30) located upstream of the branch point to
the first compressor (14a) and the second compressor (14b). The oil
return passageway (32) is configured to distribute combined
refrigerating machine oil streams from the oil separators (37a,
37b) to the first compressor (14a) and the second compressor (14b)
by connecting the junction passageway (48) to the upstream portion
of the injection passageway (30). Refrigerating machine oil flowing
in the junction passageway (48) is combined with a refrigerant in
the injection passageway (30), and is distributed to the first
compressor (14a) and the second compressor (14b) at the branch
point of the injection passageway (30). In the second aspect,
refrigerating machine oil combined in the oil return passageway
(32) is distributed to the compressors (14) at the branch point of
the injection passageway (30).
[0017] In the third aspect, the second compressor (14b) stops while
the first compressor (14a) operates in some cases. In such a case,
the oil non-return valve (SV1) of the second branch injection
passageway (42b) is closed. Accordingly, refrigerating machine oil
flowing in the junction passageway (48) returns only to the first
compressor (14a) out of the first compressor (14a) and the second
compressor (14b).
[0018] In the fourth aspect, the second compressor (14b) stops
while the first compressor (14a) operates in some cases. In such a
case, if the check valve (CV4) were not provided in the second
pre-junction passageway (47b), when the pressure in the second
compressor (14b) decreases after the stop, a back-flow of
refrigerating machine oil in the oil return passageway (32) toward
the second compressor (14b) might occur, and thus, refrigerating
machine oil might accumulate in the second compressor (14b). In
contrast, in the fourth aspect, the check valve (CV4) is provided
in the second pre-junction passageway (47b) so as to prevent
refrigerating machine oil from flowing from the discharge side into
the nonoperating second compressor (14b).
[0019] In the fifth aspect, the refrigerant-inflow stop valve (CV2)
for stopping a flow of a refrigerant in the second compressor (14b)
in a nonoperation state is provided at a portion of the discharge
pipe (56b) of the second compressor (14b) located downstream of the
oil separator (37b). Accordingly, when the second compressor (14b)
stops while the first compressor (14a) operates, it is possible to
prevent a high-pressure refrigerant discharged from the first
compressor (14a) from flowing from the discharge side into the
second compressor (14b). In addition, the discharge side of the
second compressor (14b) communicates with the first compressor
(14a) through the oil return passageway (32). Accordingly, a
refrigerant in the discharge space (100) in the second compressor
(14b) is sucked into the operating first compressor (14a)
immediately after the stop of the second compressor (14b), thereby
gradually reducing the pressure of the discharge space (100) in the
second compressor (14b).
[0020] In the sixth aspect, the outlet side of the oil return
passageway (32) communicates with compression chambers (73) with
intermediate pressures of the respective compressors (14a, 14b).
Thus, refrigerating machine oil separated in each of the oil
separators (37a, 37b) returns to the compression chambers (73) with
the intermediate pressures of the respective compressors (14a,
14b).
[0021] In the seventh aspect, as the operation capacity of the
compressor (14) with a variable operation capacity increases, a
larger amount of refrigerating machine oil is discharged from this
compressor (14). Since the oil return passageway (32) is configured
to combine streams of refrigerating machine oil separated in the
oil separators (37a, 37b) and then distribute the combined
refrigerating machine oil to the first compressor (14a) and the
second compressor (14b), a larger amount of refrigerating machine
oil is distributed to one of the first compressor (14a) and the
second compressor (14b) having a larger operation capacity. The
flow rate ratio of refrigerating machine oil distributed to the
first compressor (14a) to refrigerating machine oil distributed to
the second compressor (14b) varies depending on the operation
capacity ratio of the first compressor (14a) to the second
compressor (14b). Accordingly, when the operation capacity of the
compressor (14) with a variable operation capacity increases, the
flow rate of refrigerating machine oil distributed to this
compressor (14) with the variable operation capacity increases as
long as the operation capacity of the other compressor (14) is
constant. In the seventh aspect, as the amount of refrigerating
machine oil discharged from a compressor (14) with a variable
operation capacity increases, a larger amount of refrigerating
machine oil returns to this compressor (14) with the variable
operation capacity.
Advantages of the Invention
[0022] According to the present invention, the oil return
passageway (32) is configured to combine streams of refrigerating
machine oil separated in the oil separators (37a, 37b) and
distribute the combined refrigerating machine oil to the first
compressor (14a) and the second compressor (14b). Accordingly, even
when an oil imbalance occurs, i.e., refrigerating machine oil
begins to flow mainly into a specific compressor (14) out of the
first compressor (14a) and the second compressor (14b), progress of
this oil imbalance is automatically reduced. Thus, a significant
imbalance of refrigerating machine oil in the specific compressor
(14) hardly occurs, and each of the compressors (14) is hardly in
short of refrigerating machine oil. As a result, lubrication
failures due to a shortage of refrigerating machine oil in the
compressors (14) can be reduced.
[0023] In the second aspect, refrigerating machine oil combined in
the oil return passageway (32) is distributed to the compressors
(14) at the branch point of the injection passageway (30). That is,
no branch point is provided on the oil return passageway (32), but
the branch point of the injection passageway (30) is used to
distribute the combined refrigerating machine oil to the
compressors (14). Accordingly, a configuration in which streams of
refrigerating machine oil separated in the oil separators (37a,
37b) are combined together and the resultant refrigerating machine
oil is distributed to the compressors (14), can be simplified.
[0024] In the third aspect, during operation of the first
compressor (14a) and nonoperation of the second compressor (14b),
refrigerating machine oil flowing in the junction passageway (48)
returns only to the first compressor (14a) out of the first
compressor (14a) and the second compressor (14b). This
configuration can prevent accumulation of refrigerating machine oil
in the nonoperating second compressor (14b). Accordingly, as
compared to a configuration in which no oil non-return valve (SV1)
is provided, a large amount of refrigerating machine oil can return
to the operating first compressor (14a) which needs refrigerating
machine oil. As a result, a shortage of refrigerating machine oil
in the first compressor (14a) can be reduced.
[0025] In the fourth aspect, the check valve (CV4) is provided in
the second pre-junction passageway (47b) to prevent refrigerating
machine oil from flowing from the discharge side into the second
compressor (14b) in a nonoperating state. Accordingly, as compared
to a configuration in which the check valve (CV4) is not provided
in the second pre-junction passageway (47b), a large amount of
refrigerating machine oil can return to the first compressor (14a)
in an operating state which needs refrigerating machine oil. As a
result, a shortage of refrigerating machine oil in the first
compressor (14a) can be reduced.
[0026] In the fifth aspect, when the second compressor (14b) stops
while the first compressor (14a) operates, the refrigerant-inflow
stop valve (CV2) prevents a flow of a high-pressure refrigerant
into the second compressor (14b), and a refrigerant in the
discharge space (100) in this second compressor (14b) is sucked
into the first compressor (14a). With this configuration, the
pressure of the discharge space (100) in the second compressor
(14b) is forcedly reduced. In a compressor such as a high-pressure
domed compressor in which the discharge space (100) filled with a
refrigerant compressed by the fluid machine (82) is formed in the
casing (70), when operation is stopped, a refrigerant flows from
the discharge space (100) into the fluid machine (82), and the
pressure in the fluid machine (82) becomes substantially equal to
that of the discharge space (100). Thus, if the pressure of the
discharge space (100) in the nonoperating second compressor (14b)
cannot be forcedly reduced, the fluid machine (82) compresses a
high-pressure refrigerant at a restart of the second compressor
(14b), and the pressure at the discharge side of the fluid machine
(82) might excessively increase to damage the fluid machine (82).
In contrast, in the fifth aspect, the pressure in the discharge
space (100) in the second compressor (14b) is forcedly reduced, and
the pressure in the fluid machine (82) of the second compressor
(14b) is reduced according to the decrease in the pressure of the
discharge space (100). Accordingly, it is possible to prevent the
fluid machine (82) of the second compressor (14b) from compressing
a high-pressure refrigerant at the restart, thereby preventing
damage on the second compressor (14b) at the restart.
[0027] In the sixth aspect, refrigerating machine oil separated in
each of the oil separators (37a, 37b) returns to the compression
chambers (73) with intermediate pressures of the respective
compressors (14a, 14b). If refrigerating machine oil separated in
the oil separators (37) returned to the suction side of each of the
compressors (14), the flow rate of a low-pressure refrigerant
sucked by the compressors (14) decreases according to the amount of
returned refrigerating machine oil. Accordingly, the amount of a
refrigerant circulating in the refrigerant circuit (4) decreases,
thereby reducing the operating capability of the refrigeration
system. In contrast, in the sixth aspect, the flow rate of a
low-pressure refrigerant to be sucked by the compressors (14) does
not change depending on returned refrigerating machine oil.
Accordingly, refrigerating machine oil can return to the
compressors (14) without degradation of operating capability of the
refrigeration system.
[0028] In the seventh aspect, as the amount of refrigerating
machine oil discharged from a compressor (14) with a variable
operation capacity increases, a larger amount of refrigerating
machine oil returns to this compressor (14) with the variable
operation capacity. That is, even when the operation capacity of
the compressor (14) with the variable operation capacity varies to
change the flow rate of discharged refrigerating machine oil, the
amount of refrigerating machine oil in the compressor (14) with the
variable operation capacity does not greatly change. Accordingly,
even in the case of using a compressor (14) with a variable
operation capacity in which the flow rate of refrigerating machine
oil changes depending on the operation capacity thereof, an oil
imbalance in the compressor mechanism (40) can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a refrigerant circuit diagram of a refrigeration
system according to a first embodiment of the present
invention.
[0030] FIG. 2 is a longitudinal cross-sectional view illustrating a
compressor according to the first embodiment.
[0031] FIG. 3 is a transverse cross-sectional view illustrating a
fixed scroll of the compressor of the first embodiment.
[0032] FIG. 4 is a refrigerant circuit diagram of a refrigeration
system according to a second embodiment of the present
invention.
DESCRIPTION OF REFERENCE CHARACTERS
[0033] 1 refrigeration system [0034] 4 refrigerant circuit [0035]
14a first compressor [0036] 14b second compressor [0037] 30
injection passageway [0038] 32 oil return passageway [0039] 37 oil
separator [0040] 40 compressor mechanism [0041] 42 branch injection
pipe (branch injection passageway) [0042] 47 pre-junction pipe
(pre-junction passageway) [0043] 48 junction pipe (junction
passageway) [0044] 56 discharge pipe
DESCRIPTION OF EMBODIMENTS
[0045] Embodiments of the present invention will be described
hereinafter with reference to the drawings.
First Embodiment
[0046] A first embodiment of the present invention will be
described. The first embodiment is directed to a refrigeration
system (1) according to the present invention. The refrigeration
system (1) is a so-called separate-type refrigeration system (1) in
which two internal units (60) are connected to one external unit
(10), and is configured to cool the inside of a refrigerator.
[0047] The external unit (10) includes an external circuit (11).
Each of the internal units (60) includes an internal circuit (61).
In the refrigeration system (1), the internal circuits (61) are
connected in parallel to the external circuit (11) through a liquid
connection pipe (2) and a gas connection pipe (3), thereby forming
a refrigerant circuit (4) which performs a vapor compression
refrigeration cycle.
[0048] A first shut-off valve (12) and a second shut-off valve (13)
are provided at respective ends of the external circuit (11). The
first shut-off valve (12) is connected to one end of the liquid
connection pipe (2). The other end of the liquid connection pipe
(2) is divided into two parts respectively connected to liquid ends
of the internal circuits (61). The second shut-off valve (13) is
connected to one end of the gas connection pipe (3). The other end
of the gas connection pipe (3) is divided into two parts
respectively connected to gas ends of the internal circuits
(61).
<<External Unit>>
[0049] The external circuit (11) of the external unit (10) includes
a compressor mechanism (40), an external heat exchanger (15), a
receiver (16), a cooling heat exchanger (17), a first external
expansion valve (18), a second external expansion valve (19), and a
four-way selector valve (20).
[0050] The compressor mechanism (40) includes a first compressor
(14a) having a variable operation capacity, a second compressor
(14b) having a fixed operation capacity, and a third compressor
(14c) having a fixed operation capacity. These compressors (14a,
14b, 14c) are connected in parallel.
[0051] Each of the first compressor (14a), the second compressor
(14b), and the third compressor (14c) is a high-pressure domed
hermetic scroll compressor. Power is supplied to the first
compressor (14a) through an inverter. The operation capacity of the
first compressor (14a) can be adjusted stepwise by changing the
output frequency of the inverter. On the other hand, each of the
second compressor (14b) and the third compressor (14c) is operated
by driving an electric motor at a constant rotation speed, and the
operation capacities of the second compressor (14b) and the third
compressor (14c) cannot be changed. The configuration of the
compressors (14) will be specifically described later.
[0052] In the compressor mechanism (40), only the first compressor
(14a) is started at a startup (i.e., at a start of operation) of
the compressor mechanism (40). In the compressor mechanism (40)
after the startup, as the necessary operation capacity increases,
the second compressor (14b) and the third compressor (14c) are
started in this order. On the other hand, as the necessary
operation capacity decreases, the third compressor (14c) and the
second compressor (14b) are stopped in this order. In the
compressor mechanism (40), the first compressor (14a) is
continuously operated from the startup to the stop of the
compressor mechanism (40). During this period, the second
compressor (14b) and the third compressor (14c) are turned on/off
according to the necessary operation capacity.
[0053] A first discharge pipe (56a) of the first compressor (14a),
a second discharge pipe (56b) of the second compressor (14b), and a
third discharge pipe (56c) of the third compressor (14c) are
connected to one discharge junction pipe (21). On each of the
discharge pipes (56), an oil separator (37), a high-pressure
pressure switch (39), a check valve (CV1, CV2, CV3) are provided in
this order from the side close to the compressor (14).
[0054] Each of the check valves (CV1, CV2, CV3) is configured to
stop a flow of a refrigerant toward the compressor (14). The
high-pressure pressure switch (39) is configured to urgently stop
the compressor (14). The oil separator (37) is in the shape of a
hermetic container, and is configured to separate refrigerating
machine oil from a refrigerant discharged from the compressor (14).
The oil separator (37) constitutes an oil separation mechanism (38)
configured to separate refrigerating machine oil from a refrigerant
discharged from the compressor mechanism (40). In the first
embodiment, the oil separator (37) is provided on each discharge
pipe (56). In this configuration, the size of the oil separator
(37) can be reduced, as compared to a configuration in which one
oil separator is provided on the discharge junction pipe (21).
[0055] In the first embodiment, an oil return passageway (32) is
provided in order to return refrigerating machine oil separated by
the oil separators (37) to the compressors (14). The oil return
passageway (32) is connected to the bottoms (specifically, the
bottom surfaces) of the oil separators (37). The oil return
passageway (32) temporally combines streams of refrigerating
machine oil separated by the oil separators (37), and then
distributes the resultant refrigerating machine oil to the
compressors (14). Specifically, the oil return passageway (32)
includes three pre-junction pipes (47) and one junction pipe (48).
The three pre-junction pipes (47) are made of a first pre-junction
pipe (47a), a second pre-junction pipe (47b), and a third
pre-junction pipe (47c). Each of the pre-junction pipes (47)
constitutes a pre-junction passageway (47). The junction pipe (48)
constitutes a junction passageway (48).
[0056] An end of the first pre-junction pipe (47a) is connected to
a first oil separator (37a) on the first discharge pipe (56a). An
end of the second pre-junction pipe (47b) is connected to a second
oil separator (37b) on the second discharge pipe (56b). An end of
the third pre-junction pipe (47c) is connected to a third oil
separator (37c) on the third discharge pipe (56c). The other end of
the first pre-junction pipe (47a) and the other end of the second
pre-junction pipe (47b) are joined together at an end of the
junction pipe (48). The other end of the third pre-junction pipe
(47c) is connected to the second pre-junction pipe (47b).
[0057] The other end of the junction pipe (48) is connected to a
connection injection tube (33) of an injection passageway (30),
which will be described later. The oil return passageway (32) of
this embodiment is configured to allow combined refrigerating
machine oil from the oil separators (37) to be distributed to the
compressors (14) by connecting the junction passageway (48) to a
portion of the injection passageway (30) located upstream of a
branch point of the injection passageway (30) to the compressors
(14). The junction pipe (48) communicates with compression chambers
(73) having intermediate pressures of the compressors (14) through
the injection passageway (30).
[0058] The first pre-junction pipe (47a) includes a capillary tube
(41a) for reducing the pressure of a high-pressure refrigerant to
the intermediate pressure. On the second pre-junction pipe (47b)
and the third pre-junction pipe (47c), check valves (CV4, CV5) for
stopping flows of refrigerants to the oil separators (37b, 37c) and
capillary tubes (41b, 41c) for reducing the pressures of
high-pressure refrigerants to the intermediate pressures are
provided in this order from the side close to the oil separators
(37).
[0059] In this embodiment, the check valves (CV4, CV5) are provided
only on the pre-junction pipes (47b, 47c) connected to the second
compressor (14b) and the third compressor (14c) which are turned
on/off during a period from the startup to the stop of the
compressor mechanism (40). The check valve (CV4) prevents
refrigerating machine oil from flowing from the discharge side into
the second compressor (14b) through the second oil separator (37b)
when the internal pressure of the second compressor (14b) decreases
while the first compressor (14a) operates and the second compressor
(14b) does not operate. The check valve (CV5) prevents
refrigerating machine oil from flowing from the discharge side into
the third compressor (14c) through the third oil separator (37c)
when the internal pressure of the third compressor (14c) decreases
while the first compressor (14a) operates and the third compressor
(14c) does not operate.
[0060] A first suction pipe (57a) is connected to the suction side
of the first compressor (14a). A second suction pipe (57b) is
connected to the suction side of the second compressor (14b). A
third suction pipe (57c) is connected to the suction side of the
third compressor (14c). The inlet ends of these suction pipes (57a,
57b, 57c) are connected to the four-way selector valve (20) through
a suction junction pipe (22).
[0061] The external heat exchanger (15) is a cross-fin type
fin-and-tube heat exchanger. An external fan (23) for sending
external air to the external heat exchanger (15) is provided near
the external heat exchanger (15). The external heat exchanger (15)
performs heat exchange between a refrigerant and external air.
[0062] A gas side of the external heat exchanger (15) is connected
to the four-way selector valve (20). A liquid side of the external
heat exchanger (15) is connected to the top of the receiver (16)
through the first liquid pipe (24). The first liquid pipe (24)
includes a check valve (CV8) for stopping a flow of a refrigerant
toward the external heat exchanger (15). On the first liquid pipe
(24), a capillary tube (51) is provided in parallel with the check
valve (CV8).
[0063] The cooling heat exchanger (17) includes a high-pressure
side channel (17a) and a low-pressure side channel (17b), and
performs heat exchange between refrigerants respectively flowing in
the channels (17a, 17b). The cooling heat exchanger (17) is a plate
heat exchanger, for example. The cooling heat exchanger (17) may be
other types of heat exchangers such as a dual-tube heat
exchanger.
[0064] An inflow end of the high-pressure side channel (17a) is
connected to the bottom of the receiver (16) through a refrigerant
pipe. An outflow end of the high-pressure side channel (17a) is
connected to the first shut-off valve (12) through a second liquid
pipe (25). The second liquid pipe (25) has a check valve (CV9) for
stopping a flow of a refrigerant toward the high-pressure side
channel (17a).
[0065] On the other hand, an inflow end of the low-pressure side
channel (17b) is connected to a first branch pipe (26) branching
off from a portion of the second liquid pipe (25) between the
cooling heat exchanger (17) and the check valve (CV9). The first
branch pipe (26) has the second external expansion valve (19). The
second external expansion valve (19) is an electronic expansion
valve having an adjustable opening degree. An outflow end of the
low-pressure side channel (17b) is connected to an end of the
connection injection tube (33).
[0066] The other end of the connection injection tube (33) is
divided into a first branch injection pipe (42a) constituting a
first branch injection passageway (42a), a second branch injection
pipe (42b) constituting a second branch injection passageway (42b),
and a third branch injection pipe (42c) constituting a third branch
injection passageway (42c). The first branch injection pipe (42a)
is connected to the compression chamber (73) having an intermediate
pressure of the first compressor (14a). The second branch injection
pipe (42b) is connected to the compression chamber (73) having an
intermediate pressure of the second compressor (14b). The third
branch injection pipe (42c) is connected to the compression chamber
(73) having an intermediate pressure of the third compressor (14c).
The connection injection tube (33) is connected to an outlet end of
the junction pipe (48). The connection injection tube (33), the
first branch injection pipe (42a), the second branch injection pipe
(42b), and the third branch injection pipe (42c) constitute the
injection passageway (30) for injecting a refrigerant into the
compression chambers (73) having intermediate pressures of the
compressors (14).
[0067] On the second branch injection pipe (42b) and the third
branch injection pipe (42c), solenoid valves (SV1, SV2) which are
freely opened and closed and check valves (CV6, CV7) for stopping
flows of refrigerants toward the cooling heat exchanger (17) are
provided in this order from the side close to the connection
injection tube (33). In this embodiment, the solenoid valves (SV1,
SV2) and the check valves (CV6, CV7) are provided only on the
branch injection pipes (42b, 42c) connected to the second
compressor (14b) and the third compressor (14c) which are turned
on/off from the startup to the stop of the compressor mechanism
(40).
[0068] The solenoid valve (SV1) is open during operation of the
second compressor (14b), and is closed during nonoperation of the
second compressor (14b). In the same manner, the solenoid valve
(SV2) is open during operation of the third compressor (14c), and
is closed during nonoperation of the third compressor (14c).
Accordingly, refrigerating machine oil in the oil return passageway
(32) does not return to the nonoperating compressor (14), but
returns to only the operating compressor (14). Each of the solenoid
valves (SV1, SV2) constitutes an oil non-return valve.
[0069] The solenoid valves (SV1, SV2) are pilot-operated solenoid
valves. Accordingly, even in the closed state of the solenoid
valves (SV1, SV2), leakage of refrigerants from the compressors
(14b, 14c) occurs. In the first embodiment, in order to prevent
such refrigerant leakage, the check valves (CV6, CV7) are provided
in addition to the solenoid valves (SV1, SV2).
[0070] The receiver (16) is located between the external heat
exchanger (15) and the cooling heat exchanger (17), and can
temporarily store a high-pressure refrigerant condensed in the
external heat exchanger (15). The gas vent pipe (44) connected to
the connection injection tube (33) is connected to the top of the
receiver (16). The gas vent pipe (44) has a solenoid valve (SV3)
which is freely opened and closed.
[0071] A second branch pipe (28) branches off from a portion of the
second liquid pipe (25) between the check valve (CV9) and the first
shut-off valve (12). An end of the second branch pipe (28) opposite
an end thereof connected to the second liquid pipe (25) is
connected to a portion of the first liquid pipe (24) between the
check valve (CV8) and the receiver (16). The second branch pipe
(28) has a check valve (CV10) for stopping a flow of a refrigerant
from the receiver (16).
[0072] A third branch pipe (29) branches off from a portion of the
second liquid pipe (25) between the cooling heat exchanger (17) and
the check valve (CV9). An end of the third branch pipe (29)
opposite an end thereof connected to the second liquid pipe (25) is
connected to a portion of the first liquid pipe (24) between the
external heat exchanger (15) and the check valve (CV8). A
refrigerant flowing in the third branch pipe (29) bypasses the
receiver (16) and the cooling heat exchanger (17). The third branch
pipe (29) has a first external expansion valve (18) made of an
electronic expansion valve having an adjustable opening degree.
[0073] The four-way selector valve (20) has a first port (P1)
connected to the discharge junction pipe (21), a second port (P2)
connected to the suction junction pipe (22), a third port (P3)
connected to the external heat exchanger (15), and a fourth port
(P4) connected to the second shut-off valve (13). This four-way
selector valve (20) can be switched between a first state
(indicated by solid lines in FIG. 1) in which the first port (P1)
communicates with the third port (P3) and the second port (P2)
communicates with the fourth port (P4) and a second state
(indicated by broken lines in FIG. 1) in which the first port (P1)
communicates with the fourth port (P4) and the second port (P2)
communicates with the third port (P3).
[0074] The external unit (10) includes various types of sensors.
Specifically, the discharge junction pipe (21) includes a discharge
pressure sensor (43). The discharge pipes (56) are provided with
discharge temperature sensors (34a, 34b, 34c). The first suction
pipe (57a) includes a suction pressure sensor (36). The suction
junction pipe (22) includes a suction temperature sensor (58). The
second liquid pipe (25) includes a liquid temperature sensor (45).
An external temperature sensor (46) is provided near the external
fan (23).
<<Internal Unit>>
[0075] The two internal units (60) have the same configuration. In
each of the internal circuits (61) of the internal units (60), a
drain-pan heating pipe (62), an internal expansion valve (63), and
an internal heat exchanger (64) are provided in this order from the
liquid end to the gas end of the internal circuit (61).
[0076] The internal expansion valve (63) is made of an electronic
expansion valve having an adjustable opening degree. The internal
heat exchanger (64) is made of a cross-fin type fin-and-tube heat
exchanger. An internal fan (65) for sending internal air to the
internal heat exchanger (64) is provided near the internal heat
exchanger (64). The internal heat exchanger (64) performs heat
exchange between internal air and a refrigerant.
[0077] A drain pan (66) including a drain-pan heating pipe (62) is
provided below the internal heat exchanger (64). The drain pan (66)
is used for collecting frost or dew condensation water dropping
from the surface of the internal heat exchanger (64). In the drain
pan (66), ice blocks generated by freezing of the collected frost
or dew condensation water are melted by utilizing heat of a
refrigerant flowing in the drain-pan heating pipe (62).
[0078] Each of the internal units (60) has three temperature
sensors. Specifically, an evaporation temperature sensor (67) is
provided on the heat exchanger tube of the internal heat exchanger
(64). A gas temperature sensor (68) is provided near the gas end of
the internal circuit (61). An internal temperature sensor (69) is
provided near the internal fan (65).
<Configuration of Compressor>
[0079] Configurations of the compressors (14a, 14b, 14c) will be
described hereinafter with reference to FIGS. 2 and 3. The
compressors (14a, 14b, 14c) have the same configuration, and thus,
only the configuration of the first compressor (14a) will be
described below.
[0080] The first compressor (14a) includes a casing (70) in the
shape of a vertically oriented hermetic container. In the casing
(70), an electric motor (85) and a fluid machine (82) are disposed
such that the electric motor (85) is located below the fluid
machine (82). The electric motor (85) includes a stator (83) fixed
to the body of the casing (70), and a rotor (84) located inside the
stator (83). A crank shaft (90) is coupled to the rotor (84).
[0081] The fluid machine (82) includes a movable scroll (76) and a
fixed scroll (75). The movable scroll (76) includes a substantially
disc-shaped movable-side head (76b) and a spiral movable-side lap
(76a). A cylindrical projection (76c) into which an eccentric
portion of the crank shaft (90) is inserted, is formed so as to
stand on the back surface (i.e., the lower surface) of the
movable-side head (76b). The movable scroll (76) is supported by a
housing (77) located below the movable scroll (76) with an Oldham
ring (79) sandwiched therebetween. On the other hand, the fixed
scroll (75) includes a substantially disc-shaped fixed-side head
(75b) and a spiral fixed-side lap (75a). In the fluid machine (82),
the fixed-side lap (75a) engages with the movable-side lap (76a),
thereby forming a plurality of compression chambers (73) between
these laps (75a, 76a).
[0082] Each of the compressors (14) of the first embodiment employs
a so-called asymmetric spiral structure, and the number of turns
(i.e., the length of the spiral) of the fixed-side lap (75a)
differs from that of the movable-side lap (76a). The compression
chambers (73) include: a first compression chamber (73a) located
between the inner peripheral surface of the fixed-side lap (75a)
and the outer peripheral surface of the movable-side lap (76a); and
a second compression chamber (73b) located between the outer
peripheral surface of the fixed-side lap (75a) and the inner
peripheral surface of the movable-side lap (76a).
[0083] The fluid machine (82) has a suction port (98) formed in an
outer edge portion of the fixed scroll (75). The suction port (98)
is connected to the first suction pipe (57a). The suction port (98)
intermittently communicates with one of the first compression
chamber (73a) and the second compression chamber (73b), according
to revolution of the movable scroll (76). The suction port (98) has
a suction check valve (not shown) for stopping a flow of a
refrigerant returning to the first suction pipe (57a) from the
compression chambers (73).
[0084] The fluid machine (82) also has a discharge port (93) formed
in a center portion of the fixed-side head (75b). The discharge
port (93) intermittently communicates with one of the first
compression chamber (73a) and the second compression chamber (73b),
according to revolution of the movable scroll (76). The discharge
port (93) is open to a muffler space (96) located above the fixed
scroll (75).
[0085] In the fixed-side head (75b) of the fluid machine (82), an
intermediate-pressure port (99) connected to the first branch
injection pipe (42a) is formed. The intermediate-pressure port (99)
is formed to extend across the fixed-side lap (75a) near a portion
between the center of the fixed-side head (75b) and the external
periphery. The intermediate-pressure port (99) communicates with
both of the first compression chamber (73a) with an intermediate
pressure and the second compression chamber (73b) with an
intermediate pressure.
[0086] The casing (70) is divided by the disc-shaped housing (77)
into an upper suction space (101) and a lower discharge space
(100). The suction space (101) communicates with the suction port
(98) through a communication port, which is not shown. The
discharge space (100) communicates with the muffler space (96)
through a communication passageway (103). During operation, a
refrigerant discharged from the discharge port (93) flows into the
discharge space (100) through the muffler space (96), and thus, the
discharge space (100) becomes a high-pressure space which is filled
with a refrigerant compressed in the fluid machine (82). The first
discharge pipe (56a) is open to the discharge space (100).
[0087] An oil sump for storing refrigerating machine oil is formed
at the bottom of the casing (70). A first oil supply passageway
(104) which is open to the oil sump is formed in the crank shaft
(90). The movable-side head (76b) has a second oil supply
passageway (105) connected to the first oil supply passageway
(104). In this compressor (14), refrigerating machine oil from the
oil sump is supplied to the low-pressure side compression chambers
(73) through the first oil supply passageway (104) and the second
oil supply passageway (105).
--Operational Behavior--
[0088] Operational behavior of the refrigeration system (1) of the
first embodiment will be described below. In cooling operation of
the refrigeration system (1), a least the first compressor (14a) of
the three compressors (14a, 14b, 14c) is operated so that the
interior (i.e., the inside of, for example, a refrigerator) is
cooled by the internal units (60).
<Cooling Operation>
[0089] In cooling operation, the four-way selector valve (20) is
set in the first state, and the first external expansion valve (18)
is fully closed. When the compressor mechanism (40) is operated in
this state, a vapor compression refrigeration cycle in which the
external heat exchanger (15) serves as a condenser and each of the
internal heat exchangers (64) serves as a evaporator, is performed
in the refrigerant circuit (4). In this refrigerant circuit (4), a
refrigerant flows in the direction indicated by arrows of solid
lines in FIG. 1.
[0090] During the cooling operation, superheat degree control of
controlling the opening degree of each of the internal expansion
valves (63) is performed such that the difference between the value
detected by each of the gas temperature sensors (68) and the value
detected by each of the evaporation temperature sensors (67) is
constant. The opening degree of the second external expansion valve
(19) is controlled such that the value detected by the liquid
temperature sensor (45) is constant.
[0091] Specifically, when operation of the compressor mechanism
(40) is started, refrigerating machine oil is separated in the oil
separators (37) from a refrigerant discharged from the compressor
mechanism (40), and the resultant refrigerant flows into the
external heat exchanger (15). In the external heat exchanger (15),
the refrigerant exchanges heat with external air to be condensed.
The refrigerant condensed in the external heat exchanger (15)
passes through the receiver (16), and then through the
high-pressure side channel (17a) of the cooling heat exchanger
(17), and flows into the second liquid pipe (25). In the second
liquid pipe (25), part of the refrigerant flows into the first
branch pipe (26). The other part of the refrigerant flows into the
liquid connection pipe (2).
[0092] The refrigerant which has flown into the first branch pipe
(26) is subjected to pressure reduction in the second external
expansion valve (19), and then flows through the low-pressure side
channel (17b) of the cooling heat exchanger (17). In the cooling
heat exchanger (17), an intermediate-pressure refrigerant in the
low-pressure side channel (17b) is heated by a high-pressure
refrigerant in the high-pressure side channel (17a). On the other
hand, the refrigerant in the high-pressure side channel (17a) is
cooled by the intermediate-pressure refrigerant in the low-pressure
side channel (17b) to be in a subcooling state. The refrigerant
heated in the low-pressure side channel (17b) is combined with the
refrigerating machine oil in the oil return passageway (32), and is
distributed to the branch injection pipes (42) to be injected into
the compression chambers (73) with the intermediate pressures of
the compressors (14). In the first embodiment, mixture of the
refrigerant flowing into the compression chambers (73) under the
intermediate pressures of the compressors (14) with an oil drop can
reduce noise caused by the flow of the refrigerant.
[0093] On the other hand, the refrigerant which has flown into the
liquid connection pipe (2) is distributed to the internal circuits
(61), is subjected to pressure reduction in the internal expansion
valves (63), and then flows into the internal heat exchangers (64).
In each of the internal heat exchangers (64), the refrigerant
exchanges heat with internal air, and evaporates. The internal air
is cooled by the refrigerant. The refrigerants which have
evaporated in the internal heat exchangers (64) are combined
together in the gas connection pipe (3), and then are sucked into
the suction sides of the compressors (14).
<Defrosting Operation>
[0094] In this refrigeration system (1), when the amount of frost
attached to the internal heat exchangers (64) during cooling
operation increases, defrosting operation is performed in order to
remove the frost. In the defrosting operation, defrosting processes
of the respective internal heat exchangers (64) are performed at
the same time.
[0095] In the defrosting operation, the four-way selector valve
(20) is set in the second state, and each of the internal expansion
valves (63) is fully opened. When the compressor mechanism (40) is
operated in this state, a vapor compression refrigeration cycle in
which the external heat exchanger (15) serves as an evaporator and
each of the internal heat exchangers (64) serves as a condenser, is
performed in the refrigerant circuit (4). In this refrigerant
circuit (4), a refrigerant flows in the direction indicated by
arrows of broken lines in FIG. 1. In the defrosting operation, the
opening degrees of the first external expansion valve (18) and the
second external expansion valve (19) are adjusted as necessary.
[0096] Specifically, when operation of the compressor mechanism
(40) is started, refrigerating machine oil is separated in the oil
separators (37) from a refrigerant discharged from the compressor
mechanism (40), and then the resultant refrigerant is distributed
to the internal heat exchangers (64). In each of the internal heat
exchangers (64), frost attached to the internal heat exchanger (64)
is melted by a high-pressure refrigerant, and the refrigerant is
cooled by the frost to be condensed. The refrigerants condensed in
the respective internal heat exchangers (64) are combined together
in the liquid connection pipe (2), and the resultant refrigerant
passes through the receiver (16), and then flows into the third
branch pipe (29) through the high-pressure side channel (17a) of
the cooling heat exchanger (17). The refrigerant which has flown
into the third branch pipe (29) is subjected to pressure reduction
in the first external expansion valve (18), and then flows into the
external heat exchanger (15). In the external heat exchanger (15),
the refrigerant exchanges heat with external air, and evaporates.
The refrigerant which has evaporated in the external heat exchanger
(15) is sucked into the suction sides of the compressors (14).
[0097] In the first embodiment, in the cooling operation and the
defrosting operation, refrigerating machine oil discharged together
with refrigerants from the compressors (14), flows into the oil
separators (37), and is separated from the refrigerants in the oil
separators (37). The refrigerating machine oil separated in one of
the oil separators (37) flows into the junction pipe (48) through
the pre-junction pipes (47), and is combined together with
refrigerating machine oil separated in the other oil separators
(37). The refrigerating machine oil streams combined in the
junction pipe (48) are combined with a refrigerant in the injection
passageway (30), and the resultant refrigerating machine oil is
distributed to the compressors (14) at a branch point of the
injection passageway (30). The refrigerating machine oil
distributed to the compressors (14) flows into the compression
chambers (73) with intermediate pressures of the respective
compressors (14).
[0098] In the first embodiment, refrigerating machine oil streams
separated in the oil separators (37) are combined together in the
oil return passageway (32), and then the resultant refrigerating
machine oil is distributed to the compressors (14). In each of the
compressors (14), as the oil surface in the oil sump becomes
higher, the oil mixture rate increases, i.e., the amount of
refrigerating machine oil contained in a discharged refrigerant per
a unit flow rate increases. Accordingly, when refrigerating machine
oil begins to flow mainly into, for example, the first compressor
(14a), the flow rate of refrigerating machine oil discharged from
the first compressor (14a) increases, and the flow rate of
refrigerating machine oil discharged from the second and third
compressors (14b, 14c) decreases. On the other hand, the flow rate
of refrigerating machine oil returning to the compressors (14)
changes according to the total flow rate of refrigerating machine
oil discharged from the compressors (14). Thus, even when the flow
rate of refrigerating machine oil discharged from the first
compressor (14a) increases, the flow rate of the refrigerating
machine oil returning to the first compressor (14a) does not
increase accordingly. Likewise, even when the flow rate of
refrigerating machine oil discharged from the second and third
compressors (14b, 14c) decreases, the flow rate of refrigerating
machine oil returning to the second and third compressors (14b,
14c) does not decrease accordingly. Therefore, when refrigerating
machine oil begins to flow mainly into the first compressor (14a),
the amount of refrigerating machine oil in the first compressor
(14a) decreases, and the amount of refrigerating machine oil in the
second and third compressors (14b, 14c) increases. In this manner,
in this embodiment, when an oil imbalance begins to occur in the
compressor mechanism (40), progress of this oil imbalance is
automatically reduced.
[0099] In the first embodiment, as the operation capacity of the
first compressor (14a) increases, a larger amount of refrigerating
machine oil is discharged from the first compressor (14a). On the
other hand, as the operation capacity of the first compressor (14a)
increases, the flow rate of refrigerating machine oil to be
distributed to the first compressor (14a) increases. Accordingly,
in the first compressor (14a), even when the operation capacity
changes to change the flow rate of discharged refrigerating machine
oil, the amount of refrigerating machine oil in the oil sump does
not greatly change. Thus, in the second and third compressors (14b,
14c), the amount of refrigerating machine oil in the oil sump does
not greatly change, either.
[0100] In the first embodiment, the second compressor (14b) is
switched from an operating state to a nonoperation state while the
first compressor (14a) operates in some cases. In such cases, when
the second compressor (14b) is stopped, the movable scroll (76)
pushed against the fixed scroll (75) during operation falls in the
second compressor (14b), and a refrigerant in the discharge space
(100) flows into the suction check valve, so that the pressure in
the fluid machine (82) becomes high. If the second compressor (14b)
is started again with the pressure in the fluid machine (82) being
high, the fluid machine (82) compresses the high-pressure
refrigerant, resulting in that the discharge pressure of the fluid
machine (82) excessively increases to damage the fluid machine (82)
in some cases. In the first embodiment, to prevent the second
compressor (14b) from being damaged at the restart of the second
compressor (14b), the check valve (CV2) constituting a
refrigerant-inflow stop valve is provided and the discharge side of
the second compressor (14b) communicates with the compression
chamber (73) with the intermediate pressure of the first compressor
(14a) through the second pre-junction pipe (47b), the junction pipe
(48), and the first branch injection pipe (42a). With this
configuration, a flow of the refrigerant discharged from the first
compressor (14a) into the nonoperating second compressor (14b) is
stopped, and in addition, a refrigerant in the discharge space
(100) in the second compressor (14b) is sucked by the first
compressor (14a). Accordingly, the pressure of the discharge space
(100) in the second compressor (14b) and the pressure in the fluid
machine (82) gradually decrease immediately after the second
compressor (14b) is stopped. In the same manner, in the case where
the third compressor (14c) is stopped, the pressure of the
discharge space (100) in the third compressor (14c) and the
pressure in the fluid machine (82) gradually decrease.
Advantages of First Embodiment
[0101] In the first embodiment, the oil return passageway (32) is
configured so as to combine refrigerating machine oil streams
respectively separated in the oil separators (37), and then
distribute the resultant refrigerating machine oil to the
compressors (14). With this configuration, even when an oil
imbalance in which refrigerating machine oil flows mainly into a
specific one of the compressors (14) occurs in the compressor
mechanism (40), progress of the oil imbalance is automatically
reduced. Accordingly, a significant imbalance of refrigerating
machine oil in a specific compressor (14) hardly occurs, and each
of the compressors (14) is hardly in short of refrigerating machine
oil. As a result, lubrication failures due to a shortage of
refrigerating machine oil in one of the compressors (14) can be
reduced.
[0102] In the first embodiment, refrigerating machine oil combined
in the oil return passageway (32) is distributed to the compressors
(14) at a branch point of the injection passageway (30). That is,
no branch point is provided on the oil return passageway (32), but
the branch point of the injection passageway (30) is used to
distribute the combined refrigerating machine oil to the
compressors (14). Accordingly, a configuration in which
refrigerating machine oil streams separated in the oil separators
(37) are combined together and the resultant refrigerating machine
oil is distributed to the compressors (14), can be simplified.
[0103] In the first embodiment, refrigerating machine oil in the
oil return passageway (32) does not return to nonoperating ones of
the compressors (14) and returns only to an operating one of the
compressors (14). This configuration can reduce accumulation of the
refrigerating machine oil in the nonoperating compressors (14).
Accordingly, as compared to a configuration in which the oil
non-return valve (SV1) is not provided, a large amount of
refrigerating machine oil can return to an operating one of the
compressors (14) which needs refrigerating machine oil. As a
result, a shortage of refrigerating machine oil in the operating
compressor (14) can be reduced.
[0104] In the first embodiment, the check valve (CV4) is provided
in the second pre-junction pipe (47b) such that a flow of
refrigerating machine oil from the discharge side into the
nonoperating second compressor (14b) is stopped. Accordingly, as
compared to a configuration in which the check valve (CV4) is not
provided in the second pre-junction pipe (47b), a large amount of
refrigerating machine oil can return to the operating first
compressor (14a) which needs refrigerating machine oil. As a
result, a shortage of refrigerating machine oil in the first
compressor (14a) can be reduced. The same advantages can also be
obtained by providing the check valve (CV5) on the third
pre-junction pipe (47c).
[0105] In the first embodiment, in the case where the second
compressor (14b) is stopped while the first compressor (14a)
operates, the check valve (CV2) stops a flow of a high-pressure
refrigerant into the second compressor (14b), and a refrigerant in
the discharge space (100) in the second compressor (14b) is sucked
by the first compressor (14a). With this configuration, the
pressure of the discharge space (100) in the second compressor
(14b) is forcedly reduced. This decrease in the pressure of the
discharge space (100) causes the pressure in the fluid machine (82)
of the second compressor (14b) to also decrease. Consequently, it
is possible to prevent the fluid machine (82) of the second
compressor (14b) from compressing a high-pressure refrigerant at a
restart of the second compressor (14b), thereby reducing damage on
the second compressor (14b) at the restart. The same advantages can
also be obtained by providing the check valve (CV3) in the third
discharge pipe (56c).
[0106] In the first embodiment, refrigerating machine oil separated
in the oil separators (37) is returned to the compression chambers
(73) with the intermediate pressures of the compressors (14). Thus,
the flow rates of low-pressure refrigerants to be sucked by the
compressors (14) do not change depending on the returned
refrigerating machine oil. Accordingly, refrigerating machine oil
can return to the compressors (14) without degradation of operating
capability of the refrigeration system.
[0107] In the first embodiment, as the amount of refrigerating
machine oil discharged from the first compressor (14a) with a
variable operation capacity increases, a larger amount of
refrigerating machine oil returns to the first compressor (14a).
That is, even when the operation capacity of the first compressor
(14a) varies to change the flow rate of discharged refrigerating
machine oil, the amount of refrigerating machine oil in the first
compressor (14a) does not greatly change. Accordingly, in the case
of using a compressor (14) with a variable operation capacity in
which the flow rate of refrigerating machine oil changes depending
on the operation capacity, an oil imbalance in the compressor
mechanism (40) can be reduced.
Second Embodiment
[0108] A second embodiment of the present invention will be
described. In the following description, aspects different from
those in the first embodiment are described.
[0109] As illustrated in FIG. 4, a refrigeration system (1)
according to the second embodiment includes an air conditioning
unit (50) configured to perform air conditioning of interior space,
and an internal units (60) including a cold storage unit (60a) and
a refrigeration unit (60b). A refrigerant circuit (4) includes an
air conditioning section (71) provided with the air conditioning
unit (50) and a cooling section (72) provided with the cold storage
unit (60a) and the refrigeration unit (60b). The air conditioning
section (71) and the cooling section (72) share a liquid connection
pipe (2). In the cooling section (72), a booster unit (80) is
serially connected to the refrigeration unit (60b).
<<External Unit>>
[0110] A discharge side of a compressor mechanism (40) is provided
with a second four-way selector valve (111). The second four-way
selector valve (111) has a first port (P1) connected to a discharge
branch pipe (97) branching off from a discharge junction pipe (21),
a second port (P2) connected to a third suction pipe (57c), and a
fourth port (P4) connected to a second port (P2) of a first
four-way selector valve (20). A third port (P3) of the second
four-way selector valve (111) is configured as a shut-off port
which is closed.
[0111] On the other hand, a suction side of the compressor
mechanism (40) is provided with a third four-way selector valve
(112). The third four-way selector valve (112) has a first port
(P1) connected to a second high-pressure pipe (121), which will be
described later, a second port (P2) connected to a second suction
pipe (57b), a third port (P3) connected to a second suction branch
pipe (31b) branching off from a third suction pipe (57c), and a
fourth port (P4) connected to a first suction branch pipe (31a)
branching off from a first suction pipe (57a). The first suction
branch pipe (31a) and the second suction branch pipe (31b)
respectively have check valves (CV11, CV12) which allow only flows
of refrigerants toward the third four-way selector valve (112). The
first suction pipe (57a) is connected to a third shut-off valve
(113).
[0112] Each of the first through third four-way selector valves
(20, 111, 112) can be switched between a first state (indicated by
solid lines in FIG. 1) in which the first port (P1) communicates
with the third port (P3) and the second port (P2) communicates with
the fourth port (P4) and a second state (indicated by broken lines
in FIG. 1) in which the first port (P1) communicates with the
fourth port (P4) and the second port (P2) communicates with the
third port (P3).
[0113] A check valve (CV13) for stopping a flow of a refrigerant
toward a first oil separator (37a) is provided at a position of a
first pre-junction pipe (47a) upstream of a capillary tube (41a).
On a first branch injection pipe (42a), a solenoid valve (SV4)
which is freely opened and closed and a check valve (CV14) for
stopping a flow of a refrigerant toward a connection injection tube
(33) are provided in this order from the side close to the
connection injection tube (33).
[0114] As the solenoid valves (SV1, SV2) are, the solenoid valve
(SV4) is open during operation of a first compressor (14a), and is
closed during nonoperation of the first compressor (14a). The
solenoid valve (SV4) is a pilot-operated solenoid valve. Even in
the closed state of the solenoid valve (SV4), a refrigerant leaks
from a portion near the first compressor (14a). Accordingly, the
check valve (CV14) is provided in order to prevent a back-flow of a
refrigerant in the first branch injection pipe (42a).
[0115] A second branch pipe (28) branches off from a first branch
pipe (26). The second branch pipe (28) has a third external
expansion valve (110) made of an electronic expansion valve having
an adjustable opening degree. On the second branch pipe (28), a
solenoid valve (SV5) which is freely opened and closed is provided
in parallel with the third external expansion valve (110). A first
high-pressure pipe (120) connected to the discharge junction pipe
(21) branches off from the second branch pipe (28). The first
high-pressure pipe (120) has a check valve (CV15) allowing only a
flow of a refrigerant toward the discharge junction pipe (21). A
second high-pressure pipe (121) connected to the third four-way
selector valve (112) branches off from the first high-pressure pipe
(120). A third high-pressure tube (122) connected to a first liquid
pipe (24) branches off from the second high-pressure pipe (121).
The third high-pressure tube (122) has a solenoid valve (SV6) which
is freely opened and closed.
<<Air Conditioning Unit>>
[0116] The air conditioning unit (50) houses an air conditioning
circuit (52) constituting part of the air conditioning section
(71). A gas side of the air conditioning circuit (52) is connected
to a third gas connection pipe (3c). A liquid side of the air
conditioning circuit (52) is connected to a third liquid connection
pipe (2c) branching off from the liquid connection pipe (2).
[0117] In the air conditioning circuit (52), an indoor expansion
valve (53) made of an electronic expansion valve having an
adjustable opening degree and an indoor heat exchanger (54) made of
a cross-fin type fin-and-tube heat exchanger are provided in this
order from the liquid end to the gas end. An indoor fan (55) for
sending indoor air to the indoor heat exchanger (54) is provided
near the indoor heat exchanger (54).
<<Cold Storage Unit, Refrigeration Unit>>
[0118] The cold storage unit (60a) and the refrigeration unit (60b)
respectively house internal circuits (61a, 61b) constituting part
of the cooling section (72). A gas side of the first internal
circuit (61a) of the cold storage unit (60a) is connected to a
first gas connection pipe (3a). A liquid side of the first internal
circuit (61a) is connected to a first liquid connection pipe (2a)
branching off from the liquid connection pipe (2). On the other
hand, a gas side of the second internal circuit (61b) of the
refrigeration unit (60b) is connected to a second gas connection
pipe (3b). A liquid side of the second internal circuit (61b) is
connected to a second liquid connection pipe (2b) branching off
from the liquid connection pipe (2).
[0119] In the internal circuits (61a, 61b), internal expansion
valves (63a, 63b) made of electronic expansion valves having
adjustable opening degrees and internal heat exchangers (64a, 64b)
made of cross-fin type fin-and-tube heat exchangers are provided in
this order from the liquid end to the gas end. Internal fans (65a,
65b) for sending internal air to the internal heat exchangers (64a,
64b) are provided near the internal heat exchangers (64a, 64b).
<<Booster Unit>>
[0120] The booster unit (80) houses a booster circuit (81)
constituting part of the cooling section (72). The booster circuit
(81) includes a booster compressor (86). On a discharge pipe (78)
of the booster compressor (86), an oil separator (87), a
high-pressure pressure switch (88), and a check valve (CV16) are
provided in this order from the side close to the booster
compressor (86). The oil separator (87) is connected to an oil
return pipe (92) including a capillary tube (91). The booster
circuit (81) includes a bypass pipe (95) for allowing a refrigerant
to bypass the booster compressor (86). The bypass pipe (95) has a
check valve (CV17).
--Operational Behavior--
[0121] Operational behavior of the refrigeration system (1) will be
described hereinafter for each operation. The refrigeration system
(1) is configured to select from among eight operation modes.
Specifically, the eight operation modes are: <i> air cooling
operation of performing only air cooling by the air conditioning
unit (50); <ii> air heating operation of performing only air
heating by the air conditioning unit (50); <iii> cooling
operation of performing only cooling of the interior (i.e., the
inside of, for example, a refrigerator) by the cold storage unit
(60a) and the refrigeration unit (60b); <iv> first air
cooling/cooling operation of performing cooling of the interior by
the cold storage unit (60a) and the refrigeration unit (60b) and
air cooling by the air conditioning unit (50); <v> second air
cooling/cooling operation performed when the air conditioning unit
(50) has an insufficient air-cooling capability in the first air
cooling/cooling operation; <vi> first air heating/cooling
operation of performing cooling of the interior by the cold storage
unit (60a) and the refrigeration unit (60b) and air heating by the
air conditioning unit (50) without using the external heat
exchanger (15); <vii> second air heating/cooling operation
performed when the air conditioning unit (50) has a redundant air
heating capability in the first air heating/cooling operation; and
<viii> third air heating/cooling operation performed when the
air conditioning unit (50) has an insufficient air heating
capability in the first air heating/cooling operation. In this
refrigeration system (1), the opening degree of the second external
expansion valve (19) is adjusted as necessary, thereby adjusting
the flow rate of a refrigerant to be injected into compression
chambers (73) with intermediate pressures of compressors (14).
<Air Cooling Operation>
[0122] In air cooling operation, the third compressor (14c) is
operated with the first four-way selector valve (20) and the second
four-way selector valve (111) set in the first state. The opening
degree of the indoor expansion valve (53) is adjusted as necessary.
The first external expansion valve (18) and the internal expansion
valves (63) are closed. In the air cooling operation, when the air
cooling capability is insufficient, the second compressor (14b) is
also operated. In this case, the third four-way selector valve
(112) is set in the second state. The first compressor (14a) is
always stopped. In the air cooling operation, a vapor compression
refrigeration cycle in which the external heat exchanger (15)
serves as a condenser and the indoor heat exchanger (54) serves as
an evaporator, is performed.
<Air Heating Operation>
[0123] In air heating operation, the third compressor (14c) is
operated with the first four-way selector valve (20) set in the
second state and the second four-way selector valve (111) set in
the first state. The opening degrees of the indoor expansion valve
(53) and the first external expansion valve (18) are adjusted as
necessary. The internal expansion valves (63) are closed. In the
air heating operation, when the air heating capability is
insufficient, the second compressor (14b) is also performed. In
this case, the third four-way selector valve (112) is set in the
second state. The first compressor (14a) is always stopped. In the
air heating operation, a vapor compression refrigeration cycle in
which the indoor heat exchanger (54) serves as a condenser and the
external heat exchanger (15) serves as an evaporator, is
performed.
<Cooling Operation>
[0124] In cooling operation, the first compressor (14a) is operated
with the first four-way selector valve (20) set in the first state.
The opening degrees of the internal expansion valves (63) are
adjusted as necessary. The first external expansion valve (18) and
the indoor expansion valve (53) are closed. In the cooling
operation, when the cooling capability for the interior is
insufficient, the second compressor (14b) is also performed. In
this case, the third four-way selector valve (112) is set in the
first state. The third compressor (14c) is always stopped. In the
cooling operation, a vapor compression refrigeration cycle in which
the external heat exchanger (15) serves as a condenser and each of
the internal heat exchangers (64) serves as an evaporator, is
performed.
<First Air Cooling/Cooling Operation>
[0125] In first air cooling/cooling operation, the first compressor
(14a) and the third compressor (14c) are operated with the first
four-way selector valve (20) and the second four-way selector valve
(111) set in the first state. The opening degrees of the internal
expansion valves (63) and the indoor expansion valve (53) are
adjusted as necessary. The first external expansion valve (18) is
closed. In the first air cooling/cooling operation, when the
cooling capability for the interior is insufficient, the second
compressor (14b) is also operated. In this case, the third four-way
selector valve (112) is set in the first state. In the first air
cooling/cooling operation, a vapor compression refrigeration cycle
in which the external heat exchanger (15) serves as a condenser and
each of the indoor heat exchanger (54) and the internal heat
exchangers (64) serves as an evaporator, is performed.
<Second Air Cooling/Cooling Operation>
[0126] Second air cooling/cooling operation is performed by
switching the third four-way selector valve (112) to the second
state when the air cooling capability is insufficient in the first
air cooling/cooling operation. In the second air cooling/cooling
operation, the second compressor (14b) is switched to the air
conditioning section (71). The settings in the second air
cooling/cooling operation are basically the same as those in the
first air cooling/cooling operation, except for the third four-way
selector valve (112).
<First Air Heating/Cooling Operation>
[0127] First air heating/cooling operation is 100% heat recovery
operation in which the external heat exchanger (15) is not used and
cooling of the interior by the cold storage unit (60a) and the
refrigeration unit (60b) and air heating by the air conditioning
unit (50) are performed. In the first air heating/cooling
operation, the first compressor (14a) is operated with the first
four-way selector valve (20) set in the second state and the second
four-way selector valve (111) set in the first state. The opening
degrees of the internal expansion valves (63) and the indoor
expansion valve (53) are adjusted as necessary. The first external
expansion valve (18), the second external expansion valve (19), and
the third external expansion valve (110) are closed. In the first
air heating/cooling operation, when the cooling capability for the
interior is insufficient, the second compressor (14b) is also
operated. In this case, the third four-way selector valve (112) is
set in the first state. In the first air heating/cooling operation,
a vapor compression refrigeration cycle in which the indoor heat
exchanger (54) serves as a condenser and each of the internal heat
exchangers (64) serves as an evaporator, is performed.
<Second Air Heating/Cooling Operation>
[0128] Second air heating/cooling operation is performed by
switching the second four-way selector valve (111) to the second
state when the air heating capability is redundant in the first air
heating/cooling operation. In the second air heating/cooling
operation, the external heat exchanger (15) serves as a condenser.
The settings in the second air heating/cooling operation are
basically the same as those in the first air heating/cooling
operation, except for the second four-way selector valve (111).
<Third Air Heating/Cooling Operation>
[0129] Third air heating/cooling operation is performed by
operating the third compressor (14c) with the second four-way
selector valve (111) set in the first state and the first external
expansion valve (18) opened, when the air heating capability is
insufficient in the first air heating/cooling operation. In the
third air heating/cooling operation, a vapor compression
refrigeration cycle in which the indoor heat exchanger (54) serves
as a condenser and each of the internal heat exchangers (64) and
the external heat exchanger (15) serves as an evaporator, is
performed.
Other Embodiments
[0130] The foregoing embodiments may have the following
configurations.
[0131] In the foregoing embodiments, the oil return passageway (32)
may be configured to allow refrigerating machine oil to return to
the suction pipes (57).
[0132] In the foregoing embodiments, the compressors (14) may be
compressors with symmetric spiral structures, or compressors except
scroll compressors.
[0133] In the foregoing embodiments, the second compressor (14b)
and the third compressor (14c) may be compressors having variable
operation capacities.
[0134] In the foregoing embodiments, the refrigeration system (1)
may be configured to perform a supercritical cycle in which the
high pressure of a refrigeration cycle is higher than a critical
pressure of a refrigerant. In this case, a heat exchanger serving
as a condenser in a normal refrigeration cycle in which the high
pressure of a refrigeration cycle is lower than a critical pressure
of a refrigerant, serves as a gas cooler.
[0135] The foregoing embodiments are merely preferred examples in
nature, and are not intended to limit the scope, applications, and
use of the invention.
INDUSTRIAL APPLICABILITY
[0136] As described above, the present invention is useful for a
refrigeration system in which a compressor mechanism including a
plurality of compressors is provided in a refrigerant circuit.
* * * * *