U.S. patent application number 11/839925 was filed with the patent office on 2008-09-04 for air conditioner and control method thereof.
This patent application is currently assigned to LG Electronics Inc.. Invention is credited to Jae Heuk Choi, Sung Oh Choi, Baik Young Chung, Sai Kee Oh, Pil Hyun Yoon.
Application Number | 20080209924 11/839925 |
Document ID | / |
Family ID | 39732141 |
Filed Date | 2008-09-04 |
United States Patent
Application |
20080209924 |
Kind Code |
A1 |
Yoon; Pil Hyun ; et
al. |
September 4, 2008 |
AIR CONDITIONER AND CONTROL METHOD THEREOF
Abstract
An air conditioner including a plurality of compressors uses at
least one oil separator for separating oil from an oil-mixed
refrigerant discharged from the compressors. The air conditioner
performs an oil balancing operation, during which some compressors
operate and some do not. At least a portion of the oil separated by
the oil separator is distributed to the compressors that are not
operating during the oil balancing operation.
Inventors: |
Yoon; Pil Hyun; (Seoul,
KR) ; Choi; Sung Oh; (Seoul, KR) ; Choi; Jae
Heuk; (Seoul, KR) ; Chung; Baik Young; (Seoul,
KR) ; Oh; Sai Kee; (Seoul, KR) |
Correspondence
Address: |
KED & ASSOCIATES, LLP
P.O. Box 221200
Chantilly
VA
20153-1200
US
|
Assignee: |
LG Electronics Inc.
|
Family ID: |
39732141 |
Appl. No.: |
11/839925 |
Filed: |
August 16, 2007 |
Current U.S.
Class: |
62/84 ;
184/6.16 |
Current CPC
Class: |
F25B 31/004 20130101;
F25B 2400/075 20130101; F25B 2700/03 20130101; F25B 2600/0251
20130101 |
Class at
Publication: |
62/84 ;
184/6.16 |
International
Class: |
F25B 43/02 20060101
F25B043/02; F01M 1/10 20060101 F01M001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 2, 2007 |
KR |
10-2007-0021118 |
Claims
1. An air conditioner, comprising: a plurality of compressors; at
least one oil separator for separating oil from a mixture of oil
and refrigerant discharged from the compressors; and an oil
balancer that operates, during an oil balancing operation, to send
oil from the at least one oil separator to a compressor that is not
operating during the oil balancing operation.
2. The air conditioner of claim 1, further comprising a plurality
of recovery lines, wherein each recovery line connects the at least
one oil separator to an intake of one of the compressors.
3. The air conditioner of claim 2, further comprising a plurality
of recovery valves, wherein each recovery valve is arranged on one
of the recovery lines to control a flow of oil passing through the
recovery line to the intake of the associated compressor.
4. The air conditioner of claim 3, further comprising a controller
that controls the recovery valves.
5. The air conditioner of claim 4, wherein during the oil recovery
operation, one of the compressors operates and one of the
compressors does not operate, and wherein the controller controls
the plurality of recovery valves so that at least a portion of the
oil separated by the at least one oil separator is directed to the
non-operating compressor.
6. The air conditioner of claim 2, wherein the at least one oil
separator comprises a plurality of oil separators, wherein one oil
separator is provided for each compressor, and wherein each
recovery line couples one of the oil separators to its
corresponding compressor.
7. The air conditioner of claim 6, wherein the oil balancer
includes a bypass line that allows oil to flow between the
plurality of recovery lines.
8. The air conditioner of claim 7, wherein the oil balancer further
includes at least one bypass valve arranged in the bypass line, to
control a flow of oil through the bypass line.
9. The air conditioner of claim 8, further comprising a controller
that controls the at least one bypass valve, wherein during the oil
recovery operation, one of the compressors operates and one of the
compressors does not operate, and wherein the controller controls
the at least one bypass valve so that at least a portion of the oil
separated by the oil separator of the operating compressor is
directed to the non-operating compressor.
10. The air conditioner of claim 7, further comprising a plurality
of recovery valves, wherein each recovery valve is arranged on one
of the recovery lines to control a flow of oil passing through the
recovery line to the intake of the associated compressor.
11. The air conditioner of claim 10, further comprising a
controller that controls the plurality of recovery valves, wherein
during the oil recovery operation, one of the compressors operates
and one of the compressors does not operate, and wherein the
controller controls the plurality of recovery valves so that at
least a portion of the oil separated by the oil separator of the
operating compressor is directed to the non-operating
compressor.
12. The air conditioner of claim 11, wherein the oil balancer
further includes at least one bypass valve arranged in the bypass
line, to control a flow of oil through the bypass line, and wherein
the controller also controls the at least one bypass valve.
13. The air conditioner of claim 2, further comprising a plurality
of expansion devices, wherein each expansion device operates to
reduce a pressure of oil flowing through one of the recovery
lines.
14. The air conditioner of claim 1, wherein the compressors operate
sequentially during the oil balancing operation.
15. The air conditioner of claim 1, further comprising a plurality
of sensors, wherein each sensor detects an amount of oil contained
in one of the compressors.
16. The air conditioner of claim 15, further comprising a
controller that controls the oil balancer to supply oil to a
compressor which contains an insufficient amount of oil, based on
sensing data from the sensors.
17. An air conditioner comprising: a plurality of compressors; at
least one oil separator for separating oil from a mixture of oil
and refrigerant discharged from the compressors; and an oil
balancer that operates, during an oil balancing operation, to
distribute balanced amounts of oil to the compressors, wherein the
compressors operate sequentially during the oil balancing
operation.
18. The air conditioner of claim 17, wherein during the oil
balancing operation, at least one of the compressors operates, and
at least one of the compressors does not operate, and wherein the
oil balancer supplies oil to all of the compressors except for the
compressor that is operating.
19. The air conditioner of claim 17, wherein during the oil
balancing operation, at least one of the compressors operates, and
at least one of the compressors does not operate, and wherein the
oil balancer supplies oil to one of the non-operating
compressors.
20. The air conditioner of claim 17, wherein the at least one oil
separator comprises a plurality of oil separators, wherein each oil
separator corresponds to one of the compressors, and wherein during
normal operations, the oil separated in each of the oil separators
is returned to an inlet of its corresponding compressor.
21. A method for controlling an air conditioner that includes a
plurality of compressors and at least one oil separator that
separates oil from a mixture of oil and refrigerant discharged from
the compressors, comprising: conducting a normal operation step,
during which, oil separated by the at least one oil separator is
returned to the operating ones of the plurality of compressors; and
conducting an oil balancing operation, during which, the oil
separated by the at least one oil separator is returned to less
than all of the compressors.
22. The method of claim 21, wherein during the oil balancing
operation, oil is not returned to one of the compressors that is
operating during the oil balancing operation.
23. The method of claim 21, wherein during the oil balancing
operation, one of the compressors operates and one of the
compressors does not operate, and wherein oil is returned to the
compressor that is not operating.
24. The method of claim 23, wherein during the oil balancing
operation, oil is returned to both the non-operating compressor,
and at least one of the operating compressors.
25. The method of claim 21, wherein during the oil balancing
operation, the compressors are operated sequentially, and wherein
during each sequential operation, oil is not returned to the
compressor that is operating.
26. The method of claim 21, wherein during the oil balancing
operation, the compressors are operated sequentially, and wherein
during each sequential operation, only a portion of the oil being
discharged by the operating compressor is returned to the operating
compressor.
27. The method of claim 21, wherein the air conditioner comprises a
plurality of oil separators, wherein each oil separator corresponds
to one of the compressors, wherein recovery lines connect each oil
separator to its corresponding compressor, wherein a bypass line
allows oil to flow between the recovery lines, and wherein during
the oil balancing operation, oil from the oil separator of an
operating compressor is sent through the bypass line to at least
one of the non-operating compressors.
28. A method for controlling an air conditioner that includes a
plurality of compressors and at least one oil separator that
separates oil from a mixture of oil and refrigerant discharged from
the compressors, comprising: conducting a normal operation step,
during which, oil separated by the at least one oil separator is
returned to each of the plurality of compressors that are
operating; and conducting an oil balancing operation, during which,
at least one of the compressors is not operating, wherein the oil
separated by the at least one oil separator is returned to the
non-operating compressor.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of Korean Patent
Application No. 10-2007-0021118, filed on Mar. 2, 2007, which is
hereby incorporated by reference as if fully set forth herein.
BACKGROUND
[0002] 1. Field
[0003] The present application discloses an air conditioner
including a plurality of compressors which is configured to supply
balanced amounts of oil to the compressors, and a control method
thereof.
[0004] 2. Background
[0005] Generally, an air conditioner performs air conditioning
using heat absorbed by or discharged from a refrigerant. The
refrigerant is subjected to a refrigeration cycle of compression,
condensation, expansion, and evaporation. One essential element of
such an air conditioner is a compressor functioning to compress the
refrigerant. The compressor is subjected to a high pressure, high
temperatures, and the moving parts of the compressor may experience
a high degree of friction. As a result, if the compressor is not
properly lubricated, it can be easily damaged.
[0006] In order to ensure reliability of such a compressor, it is
important to lubricate and cool the compressor. The lubrication and
cooling is achieved by oil. The compressor should always contain a
certain amount of oil.
[0007] However when the refrigerant is discharged from the
compressor, after being compressed, a portion of the oil in the
compressor may be mixed in with the refrigerant. As a result, the
oil is discharged together with the refrigerant. As the compressor
continues to operate, the amount of oil contained in the compressor
decreases gradually. In conventional compressors, an oil separator
is arranged in a discharge line connected to an outlet of the
compressor. The separator separates the oil from the refrigerant
and returns the separated oil to the compressor.
[0008] Where a plurality of compressors are used together in a
single air conditioning system, typically connected in parallel,
and where the amounts of refrigerant discharged from the respective
compressors is different due to different capacities of the
compressors, the amounts of oil contained in the respective
compressors may not be balanced. As a result, the compressor or
compressors containing an insufficient amount of oil may be
damaged. In this case, there are considerable adverse affects on
the performance of the overall system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The embodiments will be described in detail with reference
to the following drawings, in which like reference numerals refer
to like elements, and wherein:
[0010] FIG. 1 is a diagram schematically illustrating a first
embodiment of an air conditioner with multiple compressors;
[0011] FIG. 2 is an enlarged diagram of a portion of the air
conditioning system shown in FIG. 1 which includes an accumulator,
compressors and oil separators;
[0012] FIG. 3 is an enlarged diagram of an alternate embodiment of
the same portion of the air conditioner as shown in FIG. 2;
[0013] FIG. 4 is an enlarged diagram of another alternate
embodiment of the same portion of the air conditioner as shown in
FIG. 2;
[0014] FIG. 5 is an enlarged diagram of another alternate
embodiment of the same portion of the air conditioner as shown in
FIG. 2; and
[0015] FIG. 6 is an enlarged diagram of still another alternate
embodiment of the same portion of the air conditioner as shown in
FIG. 2.
DETAILED DESCRIPTION
[0016] Reference will now be made in detail to the preferred
embodiments, examples of which are illustrated in the accompanying
drawings. Wherever possible, the same reference numbers will be
used throughout the drawings to refer to the same or like
parts.
[0017] The air conditioner shown in FIG. 1 includes an outdoor unit
1, a distribution unit 2, and an indoor unit 3. The air conditioner
may perform only a cooling operation, only a heating operation, or
the air conditioner may simultaneously perform both a cooling
operation and a heating operation. The indoor unit 3 may comprise
one indoor unit, or may comprise a plurality of indoor units.
Accordingly, the distribution unit 2 may be dispensed with or may
be required, in accordance with the configuration of the indoor
unit(s) 3.
[0018] The outdoor unit 1 includes a compression unit 10, a heat
exchanging unit 30, and an expansion device 40. Although not shown,
the indoor unit 3 includes an indoor heat exchanger and an
expansion valve. The distribution unit 2 can include a refrigerant
line connecting the outdoor unit 1 and indoor unit 3, and various
valves, to control a refrigerant flow between the outdoor unit 1
and the indoor unit 3.
[0019] Where the air conditioner is adapted to perform both a
cooling operation and a heating operation (including both a
simultaneous type or a switching type), a switching valve 20 is
installed in the outdoor unit 1. The switching valve 20 switches
the flow direction of a refrigerant discharged from the compression
unit 10.
[0020] The air conditioner includes oil separation units 100
respectively connected to a plurality of compressors constituting
the compression unit 10. Each oil separation unit 100 separates oil
mixed with a refrigerant discharged from the associated compressor,
and returns the separated oil to the associated compressor.
[0021] In FIG. 1, reference numeral "50" designates an accumulator.
The accumulator temporarily stores the refrigerant to be returned
to each compressor, to control the refrigerant amount in each
compressor.
[0022] As shown in FIG. 2, the compression unit 10 includes three
compressors 10a, 10b, 10c. The number of oil separation units
corresponds to the number of compressors. The oil separation units
101, 102, 103 may be connected to the compressors by a plurality of
recovery lines, respectively. In order to balance the amounts of
oil in the compressors, an oil balancer is provided. The oil
balancer may include a bypass line communicating with the recovery
lines and one or more bypass valves arranged in the bypass
line.
[0023] In detail, the compression unit 10 includes a first
compressor 10a, a second compressor 10b, and a third compressor
10c. Of course, any number of compressors could be used, as long as
the number of compressors is plural. Also, the plural compressors
may comprise constant speed compressors or variable speed
compressors. Alternatively, the plural compressors may comprise a
combination of variable speed compressors and constant speed
compressors.
[0024] Discharge lines 11a, 11b, and 11c are connected to
respective outlets of the compressors 10a, 10b, and 10c. Compressed
refrigerant flow through the discharge lines 11a, 11b, and 11c
after it is discharged from the compressors 10a, 10b, and 10c.
[0025] The oil separation unit includes a first oil separator 101,
a second oil separator 102, and a third oil separator 103. The
first oil separator 101 is connected to the first discharge line
11a, to communicate with the first compressor 10a. The second oil
separator 102 is connected to the second discharge line 11b, to
communicate with the second compressor 10b. The third oil separator
103 is connected to the third discharge line 11c, to communicate
with the third compressor 10c.
[0026] The supply lines, through which refrigerant flows from the
accumulator 50 to the respective compressors includes a first
supply line 12a connected to the first compressor 10a, a second
supply line 12b connected to the second compressor 10b, and a third
supply line 12c connected to the third compressor 10c.
[0027] The oil separators 101, 102, and 103 separate oil mixed with
the refrigerant discharged from the compressors 10a, 10b, and 10c.
The separated oil is then returned to the compressors via the
supply lines 12a, 12b, and 12c, so as to return the separated oil
to the compressors 10a, 10b, and 10c, respectively. The air
conditioner includes recovery lines 111, 112, and 113, through
which oil flows from the oil separators 101, 102, and 103 to the
compressors 10a, 10b, and 10c. The recovery lines 111, 112, and 113
comprise a first recovery line 111 connected between the first oil
separator 101 and the first supply line 12a, a second recovery line
112 connected between the second oil separator 102 and the second
supply line 12b, and a third recovery line 113 connected between
the third oil separator 103 and the third supply line 12c.
[0028] Opening/closing valves 151, 152, and 153 are arranged in the
recovery lines 111, 112, and 113, to open or close the recovery
lines 111, 112, and 113, and thus, to control recovery of oil to
the compressors 10a, 10b, and 10c, respectively. The
opening/closing valves 151, 152, and 153 comprise a first
opening/closing valve 151 for controlling recovery of oil through
the first recovery line 111, a second opening/closing valve 152 for
controlling recovery of oil through the second recovery line 112,
and a third opening/closing valve 153 for controlling recovery of
oil through the third recovery line 113.
[0029] Preferably, expansion devices 141, 142, and 143 are arranged
in the recovery lines 111, 112, and 113. The expansion devices act
to expand (lower the pressure) oil which is being returned to the
compressors 10a, 10b, and 10c. The expansion devices 141, 142, and
143 comprise a first expansion device 141 for expanding oil
recovered through the first recovery line 111, a second expansion
device 142 for expanding oil recovered through the second recovery
line 112, and a third expansion device 143 for expanding oil
recovered through the third recovery line 113.
[0030] The reason why the expansion devices 141, 142, and 143 are
installed is that there is a pressure difference between the
refrigerant supplied from the accumulator 50 to each of the
compressors 10a, 10b, and 10c and the oil recovered from the
associated oil separators 101, 102, or 103. The refrigerant from
the accumulator 50 has a low pressure, whereas the oil separated
from the compressed refrigerant has a high pressure.
[0031] The expansion devices reduce the pressure of oil flowing
through the recovery lines 111, 112, and 113, and thus, reducing
the pressure difference between each recovery line 111, 112, or 113
and the associated return line 12a, 12b, or 12c. The pressure
reduction function is also desirable because a reduction in
temperature is also achieved during the expansion of the oil, and
this helps to reduce an oil evaporation phenomenon to a certain
degree.
[0032] The recovery lines 111, 112, and 113 are connected to a
bypass line 120 such that the recovery lines 111, 112, and 113
communicate. In detail, the recovery lines 111, 112, and 113
comprise a first recovery line 111, a second recovery line 112, and
a third recovery line 113 which all communicate with the bypass
line 120. Accordingly, oil from the first oil separator 101 flowing
through the first recovery line 111 may be sent through the bypass
line 120 such that it is introduced into the second and third
recovery lines 112 and 113, to thereby be recovered to the second
and third compressors 10b and 10c. Thus, the oil recovered from any
of the oil separators 101, 102, and 103 can be supplied, via the
bypass line 120, to a compressor which contains an insufficient
amount of oil.
[0033] Preferably, control valves 131 and 132 are arranged in the
bypass line 120, to control oil flows among the recovery lines 111,
112, and 113. The control valves 131 and 132 comprise a first
control valve 131 arranged in a portion of the bypass line 120
connecting the first and second recovery lines 111 and 112, and a
second control valve 132 arranged in a portion of the bypass line
120 connecting the second and third recovery lines 112 and 113. The
first control valve 131 controls an oil flow between the first
recovery line 111 and the second recovery line 112. The second
control valve 132 controls an oil flow between the second recovery
line 112 and the third recovery line 113. For the control valves,
solenoid valves may be used. Also, valves, which can adjust an
opening degree thereof, may be used.
[0034] Now, a control method for the embodiment shown in FIG. 2
will be described. The control method for the first embodiment may
include a normal operation step where oil separated by the
plurality of oil separators 101, 102, and 103 is returned to their
corresponding compressors 10a, 10b, and 10c. The method would also
include an oil balancing operation step for sequentially
introducing the oil separated by the oil separators 101, 102, and
103 into the compressors 10a, 10b, and 10c. A controller, which is
included in the air conditioner may execute the normal operation
step and the oil balancing operation step at intervals of a
predetermined time. Alternatively, the controller may execute the
normal operation step and the oil balancing operation step, based
on data obtained in accordance with a measurement by a sensor for
sensing the amount of oil of each compressor.
[0035] During normal operations, the controller closes the first
and second control valves 131 and 132, and opens the first, second,
and third opening/closing valves 151, 152, and 153, to enable the
normal operation to be executed. In this state, oil separated by
the first oil separator 101 is introduced into the first compressor
10a. Oil separated by the second oil separator 102 is introduced
into the second compressor 10b, and oil separated by the third oil
separator 103 is introduced into the third compressor 10c. As the
normal operation is repeatedly executed, the amount of oil
contained in each compressor may vary.
[0036] Where a plurality of compressors having different capacities
are used, an oil shortage may occur in one of the compressors. Even
in the case in which the compressors have similar capacities, an
oil unbalance phenomenon may occur because the driving times of the
compressors may be different. When an unbalance occurs, an oil
balancing operation is executed in the air conditioner. In detail,
the controller of the air conditioner controls the oil balancer
included in the air conditioner to supply balanced amounts of oil
to the compressors.
[0037] The oil balancing operation step may include step A of
operating at least one compressor while stopping the remaining
compressors, and a step B of controlling the oil balancer to allow
oil to be supplied to the non-operating compressors. The oil
balancing operation step may further include a step C of operating
at least one compressor including the compressor supplied with oil,
and introducing oil into the compressors, except for the operating
compressor. The oil balancing operation step may include repeating
steps A, B, and C for all the plural compressors.
[0038] In the following description, it is assumed that during the
normal operation step, all of the first, second, and third
compressors were operated, and that an oil unbalance occurred among
the compressors. Of course, the oil balancing operation can be
executed for a compressor which did not operate during the normal
operation step.
[0039] During the balancing operation, the controller of the air
conditioner operates one of the plural compressors, while stopping
the remaining compressors. The controller then controls the oil
balancer such that oil separated by the oil separator associated
with the operating compressor is supplied to one or both of the
stopped compressors. In detail, the controller operates the first
compressor 10a, while stopping the second and third compressors 10b
and 10c. The controller then opens the first control valve 131 and
second opening/closing valve 152, while closing the second control
valve 132, first opening/closing valve 151, and third
opening/closing valve 153. Accordingly, oil separated by the first
oil separator 101 is introduced into the stopped second compressor
10b via the bypass line 120 and second recovery line 112. In this
case, the controller operates the first compressor 10a for a first
predetermined time.
[0040] After the operation of the first compressor 10a is
completed, the controller maintains the first and third compressors
10a and 10c in a stopped state. Simultaneously, the controller
operates the second compressor 10b, which has been supplied with
oil in the above procedure. Thereafter, the controller opens the
second control valve 132 and third opening/closing valve 153, while
closing the first control valve 131, first opening/closing valve
151, and second opening/closing valve 152. Accordingly, oil
separated by the second oil separator 102 is introduced into the
stopped third compressor 10c via the bypass line 120 and third
recovery line 113. In this case, the controller operates the second
compressor 10b for a second predetermined time.
[0041] The controller sequentially executes the above-described
procedures for all compressors. Here, sequential operations of the
compressors mean that all compressors operate sequentially in a
given order. In detail, in the embodiment shown in FIG. 2, after
the operation of the second compressor 10b is completed, the
controller maintains the second compressor 10b and first compressor
10a in a stopped state. Simultaneously, the controller operates the
third compressor 10c. Thereafter, the controller opens the first
control valve 131, the second control valve 132 and first
opening/closing valve 151, while closing the second opening/closing
valve 152, and third opening/closing valve 153. Accordingly, oil
separated by the third oil separator 103 is introduced into the
first compressor 10a via the bypass line 120 and first recovery
line 111. In this case, the controller operates the third
compressor 10c for a third predetermined time.
[0042] The controller may execute the above-described procedures
once for all compressors. If necessary, the controller may repeat
the above-described procedures several times. After completion of
the above-described procedures, the amounts of oil supplied to the
compressors are balanced due to the following reasons.
[0043] Since different amounts of oil are contained in the
compressors before the oil balancing operation, the ratio of oil
mixed with a refrigerant in one compressor during operation of the
compressor is different from those in the remaining compressors.
For example, in a compressor containing a large amount of oil, a
large amount of oil is mixed with a refrigerant. As a result, when
that compressor is operated, a large amount of oil is discharged
from the compressor, and this relatively large amount of oil is
introduced into another one of the compressors. On the other hand,
in a compressor containing a small amount of oil, a small amount of
oil is mixed with a refrigerant. As a result, when that compressor
operates, only a small amount of oil will be transferred over to
another compressor. When all compressors operate sequentially, as
explained above, the amounts of oil contained in the compressors
tends to balanced out.
[0044] If sensors are installed in the respective compressors, to
sense the amounts of oil contained in the respective compressors,
the air conditioner according to the first embodiment can operate
in the following manner. First, the controller determines which one
of the compressors 10a, 10b, and 10c, contains an insufficient
amount of oil, based on sensing data from the sensors. If it is
determined that the second compressor 10b has an insufficient
amount of oil, the controller then operates the first compressor
10a, while stopping the second and third compressors 10b and 10c.
Thereafter, the controller opens the first control valve 131 and
second opening/closing valve 152, while closing the second control
valve 132, first opening/closing valve 151, and third
opening/closing valve 153. Accordingly, oil separated by the first
oil separator 101 is introduced into the second compressor 10b via
the bypass line 120 and second recovery line 112. Thus, the second
compressor 10b is replenished with the oil.
[0045] If it is determined that the third compressor 10c has an
insufficient amount of oil, the controller will then execute a
control operation to introduce oil separated by the first oil
separator 101 into the third compressor 10c, and thus, to replenish
the third compressor 10c with the oil. Similarly, if it is
determined that the first compressor 10a has an insufficient amount
of oil, the controller will then execute a control operation to
supply oil only to the first compressor 10a.
[0046] Hereinafter, a procedure, in which an oil balancing
operation is carried out in a second embodiment of the air
conditioner, will be described with reference to FIG. 3.
[0047] In the air conditioner according to the second embodiment,
the first and second control valves 131 and 132 are eliminated.
That is, the first, second, and third recovery lines 111, 112, and
113 are always in communication by the bypass line 120. Of course,
the control method according to this embodiment is also applicable
to the case in which the first and second control valves 131 and
132 are used, as long as the first and second control valves 131
and 132 are maintained in an opened state. In the following
description, it is assumed that, during the normal operation step,
all the first, second, and third compressors were operated, and an
oil unbalance occurred among the compressors.
[0048] For the oil balancing operation in the air conditioner
according to the second embodiment, the controller first operates
the first and second compressors 10a and 10b, while stopping the
third compressor 10c. The controller then closes the first and
second opening/closing valves 151 and 152, while opening the third
opening/closing valve 153. Accordingly, oil separated by each of
the first and second oil separators 101 and 102 passes through the
bypass line 120, and is then introduced into the third compressor
10c via the third recovery line 113. In this case, the controller
operates the first and second compressors 10a and 10b for a first
predetermined time.
[0049] After the operations of the first and second compressors 10a
and 10b are completed, the controller operates the second and third
compressors 10b and 10c, while maintaining the first compressor 10a
in a stopped state. The controller closes the second and third
opening/closing valves 152 and 153, while opening the first
opening/closing valve 151. Accordingly, oil separated by each of
the second and third oil separators 102 and 103 passes through the
bypass line 120, and is then introduced into the first compressor
10a via the first recovery line 111. In this case, the controller
operates the second and third compressors 10b and 10c for a second
predetermined time.
[0050] After the operations of the second and third compressors 10b
and 10c are completed, the controller operates the third and first
compressors 10c and 10a, while maintaining the second compressor
10b in a stopped state. The controller closes the third and first
opening/closing valves 153 and 151, while opening the second
opening/closing valve 152. Accordingly, oil separated by each of
the third and first oil separators 103 and 101 passes through to
the bypass line 120, and is then introduced into the second
compressor 10b via the second recovery line 112. In this case, the
controller operates the third and first compressors 10c and 10a for
a third predetermined time.
[0051] The controller may execute the above-described procedures
once. If necessary, the controller may repeat the above-described
procedures several times. After completion of the above-described
oil balancing operation, the controller opens the first, second,
and third opening/closing valves 151, 152, and 153, to enable a
normal operation to be executed. In the normal operation, oil
emerging from the first oil separator 101, oil emerging from the
second oil separator 102, and oil emerging from the third oil
separator 103 will be mixed in the bypass line 120.
[0052] Of course, where the control valves 131 and 132 are used,
they are opened in the oil balancing operation, but are closed in
the normal operation.
[0053] If sensors are installed in the respective compressors, to
sense the amounts of oil contained in the respective compressors,
the controller will not operate a compressor which contains an
insufficient amount of oil. Instead, the controller will operate at
least one of the remaining compressors and control the
opening/closing valves to supply oil to the compressor containing
an insufficient amount of oil.
[0054] For example, when the first compressor 10a contains an
insufficient amount of oil, the controller does not operate the
first compressor 10a, but operates the second compressor 10b, which
contains a sufficient amount of oil. Thereafter, the controller
closes the second and third opening/closing valves 152 and 153,
while opening the first opening/closing valve 151.
[0055] Accordingly, oil separated by the oil separator 102
associated with the operating second compressor 10b is introduced
into the first compressor 10a via the first recovery line 111. In
this case, the sensor of the first compressor 10a senses the amount
of oil in the first compressor 10a, to determine the operating time
of the second compressor 10b.
[0056] Hereinafter, an oil balancing operation carried out in a
third embodiment will be described with reference to FIG. 4. The
air conditioner according to this embodiment eliminates the
opening/closing valves, but additionally includes a second bypass
line 121 for connecting the third recovery line 113 and first
recovery line 111. A third control valve 133 is arranged in the
second bypass line 121, to control a flow of oil passing through
the second bypass line 121. In the following description, an oil
balancing operation is executed when it is assumed that, during the
normal operation step, all of the first, second, and third
compressors were operated, and an oil unbalance occurred among the
compressors.
[0057] The controller first operates the first compressor 10a,
while stopping the second and third compressors 10b and 10c. The
controller then closes the second and third control valves 132 and
133, while opening the first control valve 131. Accordingly, oil
separated by the first oil separator 101 is partially introduced
into the first compressor 10a via the first recovery line 111. The
remaining portion of the separated oil is introduced into the
second compressor 10b via the bypass line 120. In this case, the
controller operates the first compressor 10a for a first
predetermined time.
[0058] After the operation of the first compressor 10a is
completed, the controller operates the second compressor 10b, while
maintaining the third and first compressors 10c and 10a in a
stopped state. The controller closes the third and first control
valves 133 and 131, while opening the second control valve 132.
Accordingly, oil separated by the second oil separator 102 is
partially introduced into the second compressor 10b via the second
recovery line 112. The remaining portion of the separated oil is
introduced into the third compressor 10c via the bypass line 120.
In this case, the controller operates the second compressor 10b for
a second predetermined time.
[0059] After the operation of the second compressor 10b is
completed, the controller operates the third compressor 10c, while
maintaining the first and second compressors 10a and 10c in a
stopped state. The controller closes the first and second control
valves 131 and 132, while opening the third control valve 133.
Accordingly, oil separated by the third oil separator 103 is
partially introduced into the third compressor 10c via the third
recovery line 113. The remaining portion of the separated oil is
introduced into the first compressor 10a via the second bypass line
121. In this case, the controller operates the third compressor 10c
for a third predetermined time.
[0060] The controller may execute the above-described procedures
once. If necessary, the controller may repeat the above-described
procedures several times. After completion of the above-described
oil balancing operation, the controller executes a control
operation for a normal operation of the air conditioner. That is,
the controller closes the first, second, and third control valves
131, 132, and 133, and operates at least one of the first, second,
and third compressors 10a, 10b, and 10c, which is required for the
normal operation. During normal operations, oil emerging from the
first oil separator 101 is introduced into the first compressor
10a. Oil emerging from the second oil separator 102 is introduced
into the second compressor 10b, and oil emerging from the third oil
separator 103 is introduced into the third compressor 10c.
[0061] If sensors are installed in the respective compressors, to
sense the amounts of oil contained in the respective compressors,
the controller will not operate the compressor which contains an
insufficient amount of oil, but will operate at least one of the
remaining compressors and control the control valves to supply oil
to the compressor containing an insufficient amount of oil.
[0062] For example, when the first compressor 10a contains an
insufficient amount of oil, the controller does not operate the
first compressor 10a, but operates the second compressor 10b, which
contains a sufficient amount of oil. The controller closes the
second and third control valves 132 and 133, while opening the
first control valve 131.
[0063] Accordingly, oil separated by the second oil separator 102
is partially introduced into the first compressor 10a via the
bypass line 120 and first recovery line 111. The remaining portion
of the separated oil is introduced into the second compressor 10b.
In this case, the sensor of the first compressor 10a senses the
amount of oil in the first compressor 10a during the operation of
the second compressor 10b, to determine the operating time of the
second compressor 10b.
[0064] Hereinafter, a fourth embodiment of the air conditioner will
be described with reference to FIG. 5. The air conditioner
according to the fourth embodiment of the present invention
includes two compressors. A control procedure for the air
conditioner according to the fourth embodiment will now be
described in detail. In the following description, an oil balancing
operation is executed when it is assumed that, during the normal
operation step, both the first and second compressors were
operated, and an oil unbalance occurred between the
compressors.
[0065] The controller first operates one of the two compressors.
For example, as shown in FIG. 5, the controller operates the first
compressor 10a, while stopping the second compressor 10b.
Thereafter, the controller closes the first opening/closing valve
151, while opening the second opening/closing valve 152 and control
valve 131. As the first compressor 10a operates, oil separated by
the first oil separator 101 is introduced into the second
compressor 10b via the bypass line 120 and second recovery line
112. In this case, the controller operates the first compressor 10a
for a first predetermined time.
[0066] After the operation of the first compressor 10a is
completed, the controller maintains the first compressor 10a in a
stopped state, while operating the second compressor 10b.
Thereafter, the controller closes the second opening/closing valve
152, while opening the first opening/closing valve 151 and control
valve 131. Accordingly, oil separated by the second oil separator
102 is introduced into the first compressor 10a via the bypass line
120 and first recovery line 111. In this case, the controller
operates the second compressor 10a for a second predetermined
time.
[0067] When the oil balancing operation is completed, the
controller closes the control valve 131, while opening the first
and second opening/closing valves 151 and 152, to enable a normal
operation to be executed.
[0068] If sensors are installed in respective compressors, to sense
the amounts of oil contained in respective compressors, the air
conditioner according to the fourth embodiment can operate in the
following manner. First, if it is determined that the first
compressor 10a contains an insufficient amount of oil, based on
sensing data from the sensors, the controller stops the first
compressor 10a, and operates the second compressor 10b. The
controller opens the first opening/closing valve 151, closes the
second opening/closing valve 152, and opens the control valve 131.
As the second compressor 10b operates, oil separated by the second
oil separator 102 is introduced into the first compressor 10a via
the bypass line 120 and first recovery line 111. Thus, the second
compressor 10b is replenished with oil.
[0069] On the other hand, if it is determined that the second
compressor 10b contains an insufficient amount of oil, the
controller stops the second compressor 10b, and operates the first
compressor 10a. The controller opens the second opening/closing
valve 152 and control valve 131, and closes the first
opening/closing valve 151. As the first compressor 10a operates,
oil separated by the first oil separator 101 is introduced into the
second compressor 10b via the bypass line 120 and second recovery
line 112. Thus, the second compressor 10b is replenished with
oil.
[0070] When the oil balancing operation is completed, the
controller closes the control valve 131, while opening the first
and second opening/closing valves 151 and 152, to enable a normal
operation to be executed.
[0071] Hereinafter, a fifth embodiment of the air conditioner will
be described with reference to FIG. 6. The air conditioner
according to this embodiment includes a single oil separator 200.
An oil balancing operation in the air conditioner according to the
fifth embodiment will now be described. In the following
description, an oil balancing operation is executed when it is
assumed that during the normal operation step, all the first,
second, and third compressors were operated, and an oil unbalance
occurred among the compressors.
[0072] The controller first operates the first compressor 10a,
while stopping the second and third compressors 10b and 10c. The
controller then closes the first and third opening/closing valves
151 and 153, while opening the second opening/closing valve 152.
Accordingly, oil separated by the oil separator 200 is introduced
into the second compressor 10b via the second recovery line 112. In
this case, the controller operates the first compressor 10a for a
first predetermined time.
[0073] After the operation of the first compressor 10a is
completed, the controller operates the second compressor 10b, while
maintaining the third and first compressors 10c and 11a in a
stopped state. Thereafter, the controller closes the second and
first opening/closing valves 152 and 151, while opening the third
opening/closing valve 153. Accordingly, oil separated by the oil
separator 200 is introduced into the third compressor 10c via the
third recovery line 113. In this case, the controller operates the
second compressor 10b for a second predetermined time.
[0074] After the operation of the second compressor 10b is
completed, the controller operates the third compressor 10c, while
maintaining the first and second compressors 10a and 10b in a
stopped state. Thereafter, the controller closes the third and
second opening/closing valves 153 and 152, while opening the first
opening/closing valve 151. Accordingly, oil separated by the oil
separator 200 is introduced into the first compressor 10a via the
first recovery line 111. In this case, the controller operates the
third compressor 10c for a third predetermined time.
[0075] The controller may execute the above-described procedures
once. If necessary, the controller may repeat the above-described
procedures several times. After completion of the above-described
oil balancing operation, the controller opens the first, second,
and third opening/closing valves 151, 152, and 153, to enable a
normal operation to be executed. In the normal operation, oil
emerging from the oil separator 200 is introduced into the
compressors via the first, second and third recovery lines,
respectively.
[0076] Of course, if there are sensors for sensing amounts of oil
contained in respective compressors, the controller will not
operate the compressor which contains an insufficient amount of
oil, but will operate at least one of the remaining compressors and
control the opening/closing valves to supply oil to the compressor
containing an insufficient amount of oil.
[0077] For example, when the first compressor 10a contains an
insufficient amount of oil, the controller does not operate the
first compressor 10a, but operates the second compressor 10b, which
contains a sufficient amount of oil. The controller closes the
second and third opening/closing valves 152 and 153, while opening
the first opening/closing valve 151. Accordingly, oil separated by
the oil separator 200 is introduced into the first compressor 10a
via the first recovery line 111. In this case, the sensor of the
first compressor 10a senses the amount of oil in the first
compressor 10a, to determine the operating time of the second
compressor 10b.
[0078] As apparent from the above description, the air conditioners
and control methods thereof can effectively perform oil balancing
for a plurality of compressors, to achieve an enhancement in the
operation reliability of the compressors. In particular, during the
oil balancing operations, all the compressors, which were operated
in a normal operation, are sequentially operated. Thus, oil
balancing can be effectively achieved.
[0079] In the oil balancing operations, at least a portion of the
oil separated from an oil-refrigerant mixture discharged from the
compressor which operates during the oil balancing operation is
supplied to at least one of the stopped compressors. Accordingly,
oil balancing can be effectively achieved.
[0080] An air conditioning system as described above can include
both high-pressure type and low-pressure type compressors,
connected in series, and are independently controlled. Accordingly,
there is an advantage in that it is possible to easily adjust the
compression ratio of the compression system. Also, the
high-pressure type and low-pressure type compressors are connected
using an oil connecting line. Accordingly, it is possible to
equally distribute oil to the high-pressure type and low-pressure
type compressors, through a simple method using the hydrostatic
pressure of oil.
[0081] Any reference in this specification to "one embodiment," "an
embodiment," "example embodiment," etc., means that a particular
feature, structure, or characteristic described in connection with
the embodiment is included in at least one embodiment of the
invention. The appearances of such phrases in various places in the
specification are not necessarily all referring to the same
embodiment. Further, when a particular feature, structure, or
characteristic is described in connection with any embodiment, it
is submitted that it is within the purview of one skilled in the
art to effect such feature, structure, or characteristic in
connection with other ones of the embodiments.
[0082] Although a number of illustrative embodiments have been
described, it should be understood that numerous other
modifications and embodiments can be devised by those skilled in
the art that will fall within the spirit and scope of the
principles of this disclosure. More particularly, variations and
modifications are possible in the component parts and/or
arrangements of the subject combinations which would fall within
the scope of the disclosure, the drawings and the appended claims.
In addition to variations and modifications in the component parts
and/or arrangements, alternative uses will also be apparent to
those skilled in the art.
* * * * *