U.S. patent application number 09/899414 was filed with the patent office on 2002-02-28 for freezing apparatus.
Invention is credited to Aida, Kenji, Kiyokawa, Yasunori, Noboru, Yoshinori, Sato, Takashi, Sugimoto, Kazuyoshi, Suzuki, Jyunichi.
Application Number | 20020023459 09/899414 |
Document ID | / |
Family ID | 26595629 |
Filed Date | 2002-02-28 |
United States Patent
Application |
20020023459 |
Kind Code |
A1 |
Kiyokawa, Yasunori ; et
al. |
February 28, 2002 |
Freezing apparatus
Abstract
It is an object of the invention to avoid lack of lubricant oil
in any of a plurality of compressors disposed in parallel in a
single refrigerant circuit. A freezer unit, wherein a first kind
oil return pipe 18 leading to a refrigerant suction pipe 4 of a
first compressor 1 from an oil separator installed in a discharged
refrigerant junction pipe 8 is installed, and a second kind oil
return pipe 12 leading to a refrigerant suction pipe 5 of a second
compressor 2 from the regular oil level height of the first
compressor 1.
Inventors: |
Kiyokawa, Yasunori;
(Osaka-fu, JP) ; Noboru, Yoshinori; (Osaka-fu,
JP) ; Sugimoto, Kazuyoshi; (Osaka-fu, JP) ;
Sato, Takashi; (Osaka-fu, JP) ; Suzuki, Jyunichi;
(Osaka-fu, JP) ; Aida, Kenji; (Osaka-fu,
JP) |
Correspondence
Address: |
WEINGARTEN, SCHURGIN, GAGNEBIN & LEBOVICI LLP
TEN POST OFFICE SQUARE
BOSTON
MA
02109
US
|
Family ID: |
26595629 |
Appl. No.: |
09/899414 |
Filed: |
July 5, 2001 |
Current U.S.
Class: |
62/469 ;
62/510 |
Current CPC
Class: |
F04C 29/028 20130101;
F04C 18/0215 20130101; F25B 31/002 20130101; F04C 29/02 20130101;
F25B 2400/075 20130101; F04C 29/026 20130101; F04C 23/001 20130101;
F04C 23/008 20130101 |
Class at
Publication: |
62/469 ;
62/510 |
International
Class: |
F25B 043/02; F25B
001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 7, 2000 |
JP |
2000-207158 |
Jul 7, 2000 |
JP |
2000-207164 |
Claims
What is claimed is:
1. A freezer unit comprising a refrigerant circuit where a
plurality of internal high pressure type compressors is installed
in parallel, wherein: an oil separator is installed in a discharged
refrigerant junction pipe where meet and flow refrigerants
discharged from respective compressors, a first kind oil return
pipe leading to a refrigerant suction pipe of a first compressor
from the oil separator is installed, and a second kind oil return
pipe leading to a refrigerant suction pipe of a second compressor
from the regular oil level height of the first compressor is
installed.
2. A freezer unit comprising a refrigerant circuit where a
plurality of internal high pressure type compressors is installed
in parallel, wherein: an oil separator is installed in a discharged
refrigerant junction pipe where meet and flow refrigerant
discharged from respective compressors, a first kind oil return
pipe provided with an on-off valve in the pipe leading to a
refrigerant suction pipe of each compressor from this oil separator
is installed, and a second kind oil return pipe leading to a
refrigerant suction pipe of a second compressor from the regular
oil level height of the first compressor is installed.
3. The freezer unit of claim 1 or 2, wherein: the first compressor
is a variable compression capacity type compressor.
4. A freezer unit comprising a refrigerant circuit where a
plurality of compressors of a vessel structure having a low
pressure portion and a high pressure portion divided through a
discharge port of a compression pump are installed in parallel,
wherein: an oil balance pipe provided with a pressure reduction
means leading from the high pressure portion of a compressor to a
refrigerant suction pipe of another compressor is installed.
5. A freezer unit comprising a refrigerant circuit where a first
compressor of a vessel structure having a low pressure portion and
a high pressure portion divided through a discharge port of a
compression pump and a second compressor of a high pressure vessel
structure are installed in parallel, wherein: an oil balance pipe
provided with a pressure reduction means leading to a refrigerant
suction pipe of the second compressor from the high pressure
portion of the first compressor, and an oil balance pipe provided
with a pressure reduction means leading to a refrigerant suction
pipe of the first compressor from the vicinity of the regular oil
level surface of the second compressor are installed.
6. The freezer unit of claim 4 or 5, wherein: one end of the oil
balance pipe is connected to the ascending slope portion of a
refrigerant suction pipe branched.
7. The freezer unit of one of claims 4 to 6, wherein: the
refrigerant discharge pipe is connected horizontally to the
compressor, and one end of the oil balance pipe is connected to a
position where a central angle .theta. on an arc between the
refrigerant discharge pipe and the oil balance pipe becomes equal
or inferior to 45 degrees, at the underside of this refrigerant
discharge pipe connection part.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention concerns a freezer unit (including air
conditioner) composed by providing a plurality of compressors for
compressing refrigerant in parallel.
[0003] 2. Detailed Description of the Prior Art
[0004] In general, the lubricant oil (called simply oil,
hereinafter) that the compressor holds is discharged from the
compressor with compressed refrigerant, lowering the oil level in
the compressor and the lubrication becomes insufficient; therefore,
an oil separator is installed in the refrigerant discharge pipe, in
a way to return oil separated from refrigerant by this oil
separator.
[0005] On the other hand, in a freezer unit connecting in parallel
a plurality of compressors provided with a oil reservoir section in
the low pressure portion, oil quantity balance is maintained by
communication respective oil reservoir sections through an oil
balance pipe.
[0006] However, in case of freezer unit wherein oil quantity
balance is maintained by communication respective oil reservoir
sections through an oil balance pipe, when at least one of
compressors is a capacity controllable compressor, or when a
plurality of compressors of different compression capacity are
connected in parallel for enlarging the scale, oil increases in the
high output compressor, oil lacks in the low output compressor,
abrasion progresses at the sliding parts of oil lacking
compressors, and the apparatus life reduces or other problems
occur, because the pressure difference is generated in the
compression vessel, oil is sucked by the high output compressor, or
for other reasons.
[0007] It is necessary to connect an oil balance pipe having a
large diameter to a compressor of high output, in order to solve
the imbalance of oil quantity; however, the oil balance pipe
becomes complicated, and increases the cost, because an effort is
applied to the oil balance pipe when the compressor is started.
[0008] Also, in a freezer unit comprising a plurality of
compressors of a vessel structure having a low pressure portion and
a high pressure portion divided through a discharge port of a
compression pump and internal high pressure compressors are
installed in parallel, an oil sensor for detecting the oil level
surface is installed in respective compressors, and the oil
quantity balance of respective compressors is maintained by
controlling the oil return quantity from the oil separator based on
the state of the oil level surface.
[0009] However, the oil sensor is complicated in structure and
expensive. In, addition, the oil return control circuit also become
complicated and expensive.
[0010] [Means for Solving the Problems]
[0011] Therefore, it is necessary to avoid lack of oil in some
compressors by a simple composition without cost increase, even if
refrigerant compression capacity differs or the passage resistance
of the refrigerant discharge pipe differs from one compressor to
the other, and it has been the problem to be resolved.
SUMMARY OF THE INVENTION
[0012] The present invention intends to solve the problems of the
prior art mentioned above, by providing:
[0013] a freezer unit of a first composition comprising a single
refrigerant circuit where a plurality of internal high pressure
type compressors are installed in parallel, wherein an oil
separator is installed in a discharged refrigerant junction pipe
where meet and flow refrigerant discharged from respective
compressors, a first kind oil return pipe leading to a refrigerant
suction pipe of a first compressor from this oil separator is
installed, and a second kind oil return pipe leading to a
refrigerant suction pipe of a second compressor from the regular
oil level height of the first compressor,
[0014] a freezer unit of a second composition comprising a
refrigerant circuit where a plurality of internal high pressure
type compressors is installed in parallel, wherein an oil separator
is installed in a discharged refrigerant junction pipe where meet
and flow refrigerant discharged from respective compressors, a
first kind oil return pipe provided with an on-off valve in the
pipe leading to a refrigerant suction pipe of each compressors from
this oil separator is installed, and a second kind oil return pipe
leading to a refrigerant suction pipe of a second compressor from
the regular oil level height of the first compressor is
installed,
[0015] a freezer unit of a third composition, wherein the first
compressor is a variable compression capacity type compressor in
the freezer unit of said first or second composition,
[0016] a freezer unit of a fourth composition comprising a
refrigerant circuit where a plurality of compressors of a vessel
structure having a low pressure portion and a high pressure portion
divided through a discharge port of a compression pump are
installed in parallel, wherein an oil balance pipe provided with a
pressure reduction means leading from the high pressure portion of
a compressor to a refrigerant suction pipe of another compressor is
installed,
[0017] a freezer unit of a fifth composition comprising a
refrigerant circuit where a first compressor of a vessel structure
having a low pressure portion and a high pressure portion divided
through a discharge port of a compression pump and a second
compressor of a high pressure vessel structure are installed in
parallel, wherein an oil balance pipe provided with a pressure
reduction means leading to a refrigerant suction pipe of the second
compressor from the high pressure portion of the second compressor,
and an oil balance pipe provided with a pressure reduction means
leading to a refrigerant suction pipe of the first compressor from
the vicinity of the regular oil level surface of the second
compressor is installed,
[0018] a freezer unit of a sixth composition, wherein one end of
the oil balance pipe is connected to the ascending slope portion of
a branched refrigerant suction pipe in the freezer unit of said
fourth or fifth composition, and
[0019] a freezer unit of a seventh composition 6, wherein the
refrigerant suction pipe is connected horizontally to the
compressor, and one end of the oil balance pipe is connected to a
position where a central angle .theta. on an arc between the
refrigerant suction pipe and the oil balance pipe becomes equal or
inferior to 45 degrees, at the underside of this refrigerant
suction pipe connection part in the freezer unit of one of claim 4
to 6, as concrete means to solve problems of the aforementioned
prior art.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is an illustration showing a first embodiment of the
invention;
[0021] FIG. 2 is an illustration showing a second embodiment of the
invention;
[0022] FIG. 3 is an illustration showing a third embodiment of the
invention;
[0023] FIG. 4 is an illustration showing essential parts of the
third embodiment;
[0024] FIG. 5 is an illustration showing a fourth embodiment of the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0025] First Embodiment
[0026] Now, a first embodiment of the present invention will be
described in detail, based on FIG. 1.
[0027] In the drawing, 1 and 2 indicate internal high pressure type
compressors composing a freezer unit with not shown condenser,
evaporator or others, and installed in parallel in a single
refrigerant circuit.
[0028] In short, one compressor 1 is connected to one refrigerant
suction pipe 4 branching from a refrigerant suction pipe 3, and the
other compressor 2 is connected to the other refrigerant suction
pipe 5 branching from a refrigerant suction pipe 3. In addition, a
refrigerant discharge pipe 6, 7 and a discharged refrigerant
junction pipe 8 are installed so that refrigerant compressed by the
one compressor 1 is discharged into one refrigerant discharge pipe
6 while refrigerant compressed by the other compressor 2 is
discharged into the other refrigerant discharge pipe 7, meet each
other, and supply not shown condenser, evaporator or others by
circulation.
[0029] Then, an oil separator 9 provided with conventionally
well-known functions per se is installed in the discharged
refrigerant junction pipe 8, a fist kind oil return pipe 10 from
this oil separator 9 to the refrigerant suction pipe 4 to which one
of compressors 1, 2, for example, compressor 1 provided with a
variable refrigerant compressing capability is installed, and a
capillary tube 11 as pressure reducing means is installed in the
middle of this fist kind oil return pipe 10.
[0030] In addition, one end of a second kind oil return pipe 12 is
connected to the level of the regular oil surface of the compressor
1, the other end thereof is connected to the refrigerant suction
pipe 5 connected to the compressor 2 of non variable refrigerant
compression capability, and a capillary tube 13 as pressure
reducing means is installed in the middle of this second kind oil
return pipe 12.
[0031] For a full power operation of the freezer unit of the
aforementioned composition, both compressors 1, 2 are operated, and
for a save operation, with low air-conditioning load, only
compressor 1 provided with variable refrigerant compressing
capability is operated.
[0032] In the freezer unit of the invention, oil discharged to the
refrigerant discharge pipe 6, 7 with refrigerant from the
compressor 1, 2 is separated from the refrigerant by the oil
separator 9. There, oil stored in the oil separator 9 returns first
to the compressor 1 through the downstream portion of the first oil
return pipe 10 and the refrigerant suction pipe 4 and, further, oil
in the compressor 1 positioned higher than the connection portion
with the second kind oil return pipe 12 returns to the compressor 2
through the downstream portion of the second oil return pipe 12 and
the refrigerant suction pipe 5.
[0033] Moreover, as the compressor 1 side connection area of the
second kind oil return pipe 12 is connected to the oil regular
height, oil does not return to the compressor 2 so much as
provoking lack of oil in the compressor 1, and oil is not stored
excessively in the compressor 1 provoking lack of oil in the
compressor 2.
[0034] Second Embodiment
[0035] Now, a second embodiment of the invention will be described
in detail based on FIG. 2.
[0036] In the freezer unit shown in FIG. 2, parts having the same
function as the freezer unit shown in said FIG. 1 are indicated by
the same symbols so as to facilitate the comprehension.
[0037] In the freezer unit shown in this FIG. 2, still another fist
kind oil return pipe 10A is installed so as to allow to communicate
between the oil separator 9, and the upstream side of the capillary
tube 13 of the second kind oil return pipe 12, and to return oil
stored in the oil separator 9 without passing through the
compressor 1. In addition, the fist kind oil return pipe 10 is
provided with an on-off valve 14 and the fist kind oil return pipe
l0A with an on-off valve 15.
[0038] For a full power operation of the freezer unit of the
aforementioned composition, the on-off valve 14 is opened and the
on-off valve 15 is closed to operate both compressors 1, 2, and for
the save operation with low air-conditioning load, only one side of
the compressor 1 or compressor 2 is operated. At this moment, the
on-off valve 14 is opened and the on-off valve 15 is closed for
operating only the compressor 1, while the on-off valve 15 is
opened and the on-off valve 14 is closed when only the compressor 2
is operated.
[0039] Third Embodiment
[0040] Now, a third embodiment of the invention will be described
in detail based on FIG. 3 and FIG. 4.
[0041] In these illustrations showing the third embodiment also,
parts having the same function as the freezer unit shown in said
drawings are indicated by the same symbols so as to facilitate the
comprehension.
[0042] The compressor 1, 2 in this embodiment is a low pressure
scroll type compressor having a vessel structure, dividing the low
pressure portion L and the high pressure portion H through a
discharge section P1 of a compression pump P. Further, oil 25 is
stored at the bottom of the low pressure portion L for
lubrication.
[0043] One refrigerant suction pipe 4 branching from a refrigerant
suction pipe 3 is connected to the low pressure portion L of the
compressor 1, and the other refrigerant suction pipe 5 branching
from a refrigerant suction pipe 3 is connected to the low pressure
portion L of the compressor 2.
[0044] In addition, a refrigerant discharge pipe 6 is connected to
the high pressure portion H of the compressor 1, and a refrigerant
discharge pipe 7 is connected to the high pressure portion H of the
compressor 2, and a discharged refrigerant junction pipe 8 is
installed so that high pressure refrigerant discharged into the
refrigerant discharge pipe 6, 7 meet each other, and supply not
shown condenser, evaporator or others by circulation. Moreover, an
accumulator 17 is installed in the refrigerant suction pipe 3, and
respective refrigerant discharge pipe 6, 7 is provided with a check
valve.
[0045] Further, an oil balance pipe 18 is installed from the high
pressure portion H of the compressor 1 to the refrigerant suction
pipe 5, and a capillary tube 19 as pressure reducing means is
installed in the middle of this oil balance pipe 18. In addition,
an oil balance pipe 20 is installed from the high pressure portion
H of the compressor 2 to the refrigerant suction pipe 4, and a
capillary tube 21 as pressure reducing means is installed in the
middle of this oil balance pipe 20.
[0046] Here, the refrigerant discharge pipe 6, 7 is connected
horizontally to the compressor 1, 2, as shown in FIG. 4, and one
end of the oil balance pipe 18, 20 is connected thereunder. At this
moment, the refrigerant discharge pipe 6 and the oil balance pipe
18, or the refrigerant discharge pipe 7 and the oil balance pipe 20
are both connected at a position where the central angle .theta.
becomes equal or inferior to 45 degrees.
[0047] The other end of the oil balance pipe 18, 20 is connected to
the ascending slope portion of the refrigerant suction pipe 4, 5
branched from the refrigerant suction pipe 3.
[0048] In the freezer unit of the aforementioned composition, in
both of compressors 1, 2, oil 25 that has lubricated the sliding
parts of the compression pump P is discharged into the high
pressure portion H with compressed refrigerant, and if there is
some space in this high pressure portion H, oil 25 is separated
from the refrigerant therein, and accumulates at the bottom of the
high pressure portion H.
[0049] High pressure refrigerant compressed by the compression pump
P and supplied to the high pressure portion H from the discharge
section P1 is discharged into the refrigerant discharge pipe 6, 7,
therefore, it flows much from the discharge portion P1 to the
connection part of the refrigerant discharge pipe 6, 7, and oil 25
separated from the refrigerant accumulates more at the bottom of
this passage.
[0050] Then, and one end of the oil balance pipe 18, 20 is
connected to this portion, oil 25 accumulated in the high pressure
portion H of the compressor 1 is sucked in the low pressure portion
L of the compressor 2 with refrigerant gas through the oil balance
pipe 18 and the refrigerant suction pipe 5, oil 25 accumulated in
the high pressure portion H of the compressor 2 is sucked in the
low pressure portion L of the compressor 1 with refrigerant gas
through the oil balance pipe 20 and the refrigerant suction pipe 4,
5, and added to oil 25 accumulated at the respective bottom.
[0051] At this moment, only oil 25 that has lubricated the sliding
parts of respective compression pump P and is discharged in the
high pressure portion H thereof is supplied from the compressor 1
to the compressor 2, and from the compressor 2 to the compressor 1,
and oil 25 accumulated in the low pressure portion L is not taken
out; therefore, even when the refrigerant compression capability is
different for the compressors 1, 2, oil 25 is prevented from being
accumulated excessively in any one of compressors 1, 2, and from
being insufficient in the other compressor.
[0052] When one compressor, for instance the compressor 1 is in
operation, and the other compressor 2 is stopped, as refrigerant
gas does not flow to the compressor 2 through the refrigerant
suction pipe 5, oil 25 that has lubricated the sliding parts of the
compression pump P and is discharged in the high pressure portion H
of the compressor 1, and accumulated in the bottom thereof is
sucked into the compressor 1 with refrigerant gas through the oil
balance pipe 18, a part of the refrigerant suction pipe 5 and the
refrigerant suction pipe 4. Therefore, the compressor 1 is
prevented from being short of oil.
[0053] Moreover, as the refrigerant suction pipe 6 and the oil
balance pipe, and the refrigerant suction pipe 7 and the oil
balance pipe 20 are mounted on the compressor 1, 2 in a close state
so that the central angle .theta. becomes equal or inferior to 45
degrees respectively, oil 25 separated in the high pressure portion
H of the compressor 1 is supplied effectively to the low pressure
portion L of the compressor 2 and oil 25 separated in the high
pressure portion H of the compressor 2 is supplied effectively to
the low pressure portion L of the compressor 1, respectively.
[0054] Fourth Embodiment
[0055] Now, a fourth embodiment of the invention will be described
in detail based on FIG. 5.
[0056] In these illustrations showing the fourth embodiment also,
parts having the same function as the freezer unit shown in said
drawings are indicated by the same symbols so as to facilitate the
comprehension.
[0057] The freezer unit shown in this FIG. 5 is a freezer unit
where a compressor 1 of low pressure scroll type of the same
structure as the compressor 1, 2 shown in said FIG. 3, and a
compressor 2 of internal high pressure type of the same structure
as the compressor 1, 2 shown in said FIG. 1, FIG. 2 are arranged in
parallel to the refrigerant pipe.
[0058] And, in this freezer unit, the high pressure portion H of
the compressor 1 and the refrigerant suction pipe 5 are connected
by an oil balance pipe 18 provided with a capillary tube 19, and
the vicinity of the regular oil level surface of the compressor 2
and the refrigerant suction pipe 4 are connected by an oil balance
pipe 22 provided with a capillary tube 23.
[0059] In the freezer unit of the aforementioned composition also,
oil 25 that has lubricated the sliding parts of the compression
pump P is discharged into the high pressure portion H with
compressed refrigerant, and accumulated at the bottom of this high
pressure portion H. Then, oil 25 accumulated in the high pressure
portion H of the compressor 1 is sucked in the low pressure portion
L of the compressor 2 with refrigerant gas through the oil balance
pipe 18 and the refrigerant suction pipe 5, and a part of oil 25
mixed into the compression gas is discharged into the refrigerant
discharge pipe 7 with refrigerant gas, but oil 25 separated in the
high pressure portion H accumulates at the bottom thereof, and is
supplied to respective sliding parts.
[0060] On the other hand, oil 25 accumulated in the high pressure
portion H of the compressor 2 is sucked in the low pressure portion
L of the compressor 1 with refrigerant gas through the oil balance
pipe 20 and the refrigerant suction pipe 4 and oil 25 accumulated
at the bottom is supplied to respective sliding parts.
[0061] In the freezer unit of the structure shown in FIG. 5, as the
high pressure portion H of the compressor 1 of low pressure scroll
type is connected through the oil balance pipe 18, only oil 25
separated from the refrigerant is supplied from the compressor 2 to
the compressor 1, and a quantity of oil 25 accumulated in the low
pressure portion L is not sucked even if the capacity of the
compressor 2 is large, and therefore, the compressors 1 is
prevented from being short of oil 25.
[0062] Similarly, for the oil 25 accumulated in the high pressure
portion H of the compressor 2, oil 25 at the position lower than
the regular oil level surface is not sucked by the compressor 1
through the oil balance pipe 22, because the oil balance pipe 22 is
connected to the vicinity of the regular oil level surface;
therefore, the compressors 2 is also prevented from being short of
oil 25.
[0063] The invention is not limited to the embodiments shown and
described herein; accordingly, various modifications may be made
without departing from the spirit or scope as defined by the
appended claims.
[0064] For instance, in any of freezer unit of the first embodiment
shown in FIG. 1, freezer unit of the second embodiment shown in
FIG. 2 and freezer unit of the third embodiment shown in FIG. 3,
the freezer unit can be composed by installing three or more
compressors in parallel.
[0065] In short, in the freezer unit of the first embodiment shown
in FIG. 1, when n (n>=3) compressors in total are installed, a
second kind oil return pipe is installed further up to the second
kind oil return pipe 12 leading to the n th compressor from the n-1
th compressor.
[0066] Also, when n (n>=3) compressors in total are installed in
the freezer unit of the second embodiment shown in FIG. 2, a fist
kind oil return pipe providing with an on-off valve leading to the
refrigerant suction pipe of all compressors from the oil separator
and, at the same time, a second kind oil return pipe is installed
up to the second kind oil return pipe leading to the n th
compressor from the n-1 th compressor.
[0067] In addition, an on-off valve 16 may be disposed in the
second kind oil return pipe 12 and the on-off valve 14 is opened
and the on-off valve 15, 16 are closed for operating only the
compressor 1, the on-off valve 15 is opened and the on-off valve
14, 16 are closed when only the compressor 2 is operated and the
on-off valve 14, 16 are opened and the on-off valve 15 is closed to
operate both compressors.
[0068] Moreover, when n (n.gtoreq.3) compressors in total are
installed in the freezer unit of the third embodiment shown in FIG.
3, an oil balance pipe provided with a pressure reducing means in
the pipe leading to the refrigerant suction pipe of the second
compressor from the high pressure portion of the first compressor
is installed, an oil balance pipe provided with a pressure reducing
means in the pipe leading to the refrigerant suction pipe of the
third compressor from the high pressure portion of the second
compressor is installed, an oil balance pipe provided with a
pressure reducing means in the pipe leading to the refrigerant
suction pipe of the n th compressor from the high pressure portion
of the n-1 th compressor is installed similarly and sequentially,
and further, an oil balance pipe provided with a pressure reducing
means in the pipe leading to the refrigerant suction pipe of the
first compressor from the high pressure portion of the n th
compressor is installed.
[0069] In addition, in the compressors 1, 2 shown in FIG. 3 and the
compressor shown in FIG. 5, an oil separation plate may be disposed
in the high pressure portion, H and the refrigerant suction pipe
and the oil balance pipe may be disposed at a position where the
central angle .theta. becomes equal or inferior to 45 degrees.
[0070] It is also possible to combine the piping composition shown
in FIG. 3, and the piping composition shown in FIG. 5.
[0071] As abovedescribed, since any of a plurality of compressors
installed in series according to the present invention do not cause
lack of oil, there are not cases where particular compressor falls
into lack of lubricant and a sliding part wears to make the
lifetime of an unit short.
[0072] Especially, according to the third invention, the compressor
operation time can be balanced, because the compressor to be
operated for a partial load can be selected freely.
[0073] In addition, according to the sixth invention, oil can be
received or delivered between compressors in operation
independently of the stopped compressor, because one end of the oil
balance pipe is connected to the upstream section installed on the
ascending slope portion of the refrigerant suction pipe.
[0074] Further, according to the seventh invention, oil accumulated
near the refrigerant discharge pipe connection part is supplied
effectively to the other compressor through the oil balance pipe,
as the refrigerant suction pipe and the oil balance pipe approach
so that the central angle .theta. becomes equal or inferior to 45
degrees, and, the oil balance pipe is connected to the underside of
the refrigerant discharge pipe.
* * * * *