U.S. patent application number 12/656630 was filed with the patent office on 2010-08-19 for air conditioner and method of controlling the same.
Invention is credited to Baik Young Chung, Ho Jong Jeong, Sai Kee Oh, Chi Woo Song.
Application Number | 20100206000 12/656630 |
Document ID | / |
Family ID | 42199001 |
Filed Date | 2010-08-19 |
United States Patent
Application |
20100206000 |
Kind Code |
A1 |
Jeong; Ho Jong ; et
al. |
August 19, 2010 |
Air conditioner and method of controlling the same
Abstract
An air conditioner includes a plurality of compressors, a common
intake pipe, and a plurality of oil equalizing pipes that connect
the compressors to the common intake pipe such that oil existing
above a reference oil level in the compressors can be transferred
to the common intake pipe. An oil equalizing valve provided on at
least two of the oil equalizing pipes controls oil flowing through
the oil equalizing pipes, where at least two of the oil equalizing
valves can be opened together during performance of oil equalizing
operation such that amounts of the oil in at least two compressors
can be equalized.
Inventors: |
Jeong; Ho Jong; (Seoul,
KR) ; Song; Chi Woo; (Seoul, KR) ; Chung; Baik
Young; (Seoul, KR) ; Oh; Sai Kee; (Seoul,
KR) |
Correspondence
Address: |
MCKENNA LONG & ALDRIDGE LLP
1900 K STREET, NW
WASHINGTON
DC
20006
US
|
Family ID: |
42199001 |
Appl. No.: |
12/656630 |
Filed: |
February 5, 2010 |
Current U.S.
Class: |
62/470 ;
62/510 |
Current CPC
Class: |
F25B 2313/02742
20130101; F25B 2400/075 20130101; F25B 2313/0253 20130101; F25B
2700/21152 20130101; F25B 2700/2105 20130101; F25B 31/004 20130101;
F25B 13/00 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 |
Feb 16, 2009 |
KR |
10-2009-0012519 |
Claims
1. An air conditioner comprising: a plurality of compressors; a
common intake pipe; a plurality of oil equalizing pipes that
connect the compressors to the common intake pipe such that oil
existing above a reference oil level in the compressors can be
transferred to the common intake pipe; and an oil equalizing valve
provided on at least two of the oil equalizing pipes to control oil
flowing through the oil equalizing pipes, wherein at least two of
the oil equalizing valves can be opened together during performance
of oil equalizing operation such that amounts of the oil in at
least two compressors can be equalized.
2. The air conditioner according to claim 1, further comprising an
oil separator that is provided on an output port side of each of
the compressors to return the oil contained in refrigerant
discharged from the compressors to the compressors.
3. The air conditioner according to claim 1, further comprising: a
first temperature sensor to measure a temperature of the
refrigerant at an output port side of the compressors; and a second
temperature sensor to measure a temperature of the refrigerant at
an oil equalizing pipe side of the compressors.
4. The air conditioner according to claim 3, wherein the oil
equalizing operation is performed when degrees of discharged heat
of all of the compressors are equal to or greater than a reference
value.
5. The air conditioner according to claim 4, wherein, when a
difference between a temperature measured by the first temperature
sensor and a temperature measured by the second temperature sensor
for at least two compressors is equal to or greater than a
predetermined value during the oil equalizing operation, the at
least two opened oil equalizing valves are closed to stop the oil
equalizing operation.
6. The air conditioner according to claim 4, wherein, when a
difference between a temperature measured by the first temperature
sensor and a temperature measured by the second temperature sensor
for at least two compressors is equal to or less than a
predetermined value during the oil equalizing operation, the at
least two opened oil equalizing valves are closed to stop the oil
equalizing operation.
7. The air conditioner according to claim 4, wherein, when the oil
equalizing operation starts and a predetermined time passes, the at
least two opened oil equalizing valves are closed to stop the oil
equalizing operation.
8. The air conditioner according to claim 1, further comprising a
plurality of capillary tubes provided on each of the oil equalizing
pipes.
9. The air conditioner according to claim 1, wherein each of the
compressors comprises a compressor shell having a first side that
is connected to the oil separator to collect the oil and/or
refrigerant and a second side that is connected to the
corresponding oil equalizing pipe so that the oil/refrigerant
existing above a reference oil level can be transferred to the
corresponding oil equalizing pipe.
10. An air conditioner comprising: a plurality of compressors; a
common intake pipe; a plurality of oil equalizing pipes that
connect the compressors to the common intake pipe such that oil
existing above a reference oil level in the compressors can be
transferred to the common intake pipe; and a control unit
configured to control flow of oil in at least two oil equalizing
pipes and to sense temperature at an output port side and an oil
equalizing pipe side of at least two compressors that are
operating.
11. The air conditioner according to claim 10, wherein the control
unit is configured to stop oil equalizing operation based on a
difference between the temperature measured at the output port side
and a temperature measured at a downstream side of a capillary tube
provided on the oil equalizing pipe in at least two of the
compressors that are operating.
12. The air conditioner according to claim 11, wherein the control
unit is configured to stop oil equalizing operation when the
difference is equal to or greater than a predetermined value.
13. The air conditioner according to claim 11, wherein the control
unit is configured to stop oil equalizing operation when the
difference is equal to or less than a predetermined value.
14. The air conditioner according to claim 11, wherein the control
unit is configured to stop oil equalizing operation when a
predetermined time passes after the oil equalizing operation
starts.
15. The air conditioner according to claim 10, wherein the control
unit is configured to perform oil equalizing operation when degrees
of discharged heat of at least two compressors that are operating
are equal to or greater than a reference value.
16. An air conditioner comprising: a plurality of compressors; a
common intake pipe; a plurality of oil equalizing pipes that
connect the compressors to the common intake pipe such that oil
existing above a reference oil level in the compressors can be
transferred to the common intake pipe; and a control unit
configured to open oil equalizing valves of at least two oil
equalizing pipes connected respectively to at least two compressors
that are operating for a predetermined time when degrees of
discharge heat of at least two of the compressors that are
operating are equal to or greater than a reference value.
17. The air conditioner according to claim 16, wherein the control
unit further configured to measure a temperature of an output port
side and a temperature of an oil equalizing pipe side in each of
the at least two compressors after a predetermined passes; and the
control unit configured to close all of the oil equalizing valves
depending on a difference between the measured temperatures.
18. The air conditioner according to claim 17, wherein, the control
unit is configured to close off the at least two opened when the
difference is equal to or greater than a predetermined value.
19. The air conditioner according to claim 17, wherein, the control
unit is configured to close off the at least two opened oil
equalizing valves when the difference is equal to or less than a
predetermined value.
20. The air conditioner according to claim 17, wherein, the control
unit is configured to close the at least two opened oil equalizing
valves when of the at least two the oil equalizing valves are
opened and a predetermined time passes.
Description
[0001] This application claims priority from Korean Patent
Application No. 10-2009-0012519 filed on Feb. 16, 2009, in the
Korean Intellectual Property Office, the disclosure of which is
incorporated herein by reference in its entirety.
BACKGROUND
[0002] 1. Field of the Disclosure
[0003] The present disclosure relates to an air conditioner, and
more particularly, to an air conditioner and method of controlling
the same, which is directed to solving oil imbalance between a
plurality of compressors.
[0004] 2. Description of the Related Art
[0005] Generally, an air conditioner is an appliance that cools or
heats an indoor space by performing heat-exchange between
refrigerant and indoor air using a refrigeration cycle in which the
refrigerant is compressed, condensed, expanded, and evaporated. Air
conditioners are classified into cooling air conditioners that
supply cool air to an indoor space by operating the refrigeration
cycle in only one direction and cooling-and-heating air
conditioners that supply cool or hot air indoors by selectively
operating the refrigeration cycle in one of two directions.
[0006] Air conditioners are further classified according to the
connection structure of their indoor and outdoor units into
standard air conditioners that have one indoor unit connected to
one outdoor unit, and multi-type air conditioners that have a
plurality of indoor units connected to at least one outdoor
unit.
[0007] A typical multi-type air conditioner is used for selectively
air-conditioning a plurality of separated spaces in a building by
selectively operating as many compressors as necessary depending on
the overall air conditioning load.
[0008] When multiple compressors operate, oil flows into the
respective compressors along with the refrigerant. At this point,
there is a difference in the amount of oil between the compressors
according to the operating state of each compressor. That is, there
may be compressors to which oil is excessively supplied and
compressors to which oil is insufficiently supplied. Specifically,
limitations such as reduced air conditioning efficiency may arise
when oil is insufficiently supplied to compressors, which may burn
out, generate excessive noise, and/or be deteriorated in
performance. Therefore, it is critical to supply oil equally to
multiple compressors.
SUMMARY
[0009] Accordingly, the present disclosure is directed to an air
conditioner and method of controlling the same that substantially
obviate one or more problems due to limitations and disadvantages
of the related art.
[0010] One object is to provide an air conditioner and method of
controlling the same, which can prevent oil from being excessively
or insufficiently supplied to each of a plurality of
compressors.
[0011] Another object is to provide an air conditioner and method
of controlling the same, which can equally supply oil to each of a
plurality of compressors.
[0012] Additional advantages, objects, and features will be set
forth in part in the description which follows and in part will
become apparent to those having ordinary skill in the art upon
examination of the following or may be learned from practice of the
invention. The objectives and other advantages may be realized and
attained by the structure particularly pointed out in the written
description and claims hereof as well as the appended drawings.
[0013] To achieve these objects and other advantages and in
accordance with the purpose of the invention, as embodied and
broadly described herein, there is provided an air conditioner
including a plurality of compressors, a common intake pipe, and a
plurality of oil equalizing pipes that connect the compressors to
the common intake pipe such that oil existing above a reference oil
level in the compressors can be transferred to the common intake
pipe. An oil equalizing valve provided on at least two of the oil
equalizing pipes controls oil flowing through the oil equalizing
pipes, where at least two of the oil equalizing valves can be
opened together during performance of oil equalizing operation such
that amounts of the oil in at least two compressors can be
equalized.
[0014] In another aspect, there is provided an air conditioner
including a plurality of compressors, a common intake pipe, and a
plurality of oil equalizing pipes that connect the compressors to
the common intake pipe such that oil existing above a reference oil
level in the compressors can be transferred to the common intake
pipe. A control unit is configured to control flow of oil in at
least two oil equalizing pipes and to sense temperature at an
output port side and an oil equalizing pipe side of at least two
compressors that are operating.
[0015] In a further another aspect, there is provided an air
conditioner including a plurality of compressors, a common intake
pipe, and a plurality of oil equalizing pipes that connect the
compressors to the common intake pipe such that oil existing above
a reference oil level in the compressors can be transferred to the
common intake pipe. A control unit is configured to open oil
equalizing valves of at least two oil equalizing pipes connected
respectively to at least two compressors that are operating for a
predetermined time when degrees of discharge heat of at least two
of the compressors that are operating are equal to or greater than
a reference value.
[0016] It is to be understood that both the foregoing general
description and the following detailed are exemplary and
explanatory and are intended to provide an explanation of the
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The accompanying drawings, which are included to provide a
further understanding of the disclosure and are incorporated in and
constitute a part of this application, illustrate embodiment(s) of
the invention and together with the description serve to explain
the principle of the invention. In the drawings:
[0018] FIG. 1 is a schematic diagram of an air conditioner
according to an embodiment of the present invention;
[0019] FIG. 2 is a detailed diagram of an outdoor unit depicted in
FIG. 1;
[0020] FIG. 3 is a schematic diagram illustrating devices that are
directed to equally supplying oil to a plurality of compressors
depicted in FIG. 2;
[0021] FIG. 4 is a block diagram of control system according to an
embodiment of the present invention;
[0022] FIG. 5 is an exemplary graph illustrating a relationship
between an amount of oil flowing into compressors and a value
(Td-Tpipe); and
[0023] FIG. 6 is a flowchart illustrating a method of controlling
an air conditioner according to an embodiment of the present
invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0024] Advantages and features, and implementation methods thereof
will be clarified through following embodiments described with
reference to the accompanying drawings. The present invention may,
however, be embodied in different forms and should not be construed
as limited to the embodiments set forth herein. Rather, these
embodiments are provided so that this disclosure will be thorough
and complete, and will fully convey the principle of the present
invention to those skilled in the art. like reference numerals
refer to like elements throughout.
[0025] FIG. 1 is a schematic diagram of an air conditioner
according to an embodiment of the present invention, and FIG. 2 is
a detailed diagram of an outdoor unit depicted in FIG. 1. Referring
to FIGS. 1 and 2, an air conditioner of an embodiment of the
present invention includes a plurality of outdoor units 100 and a
plurality of indoor units 200. It is sufficient to have at least
one indoor unit 100 and at least one outdoor unit 200, and thus the
number of the indoor and outdoor units 100 and 200 are not limited
to those shown in the figure. A high-low pressure common tube 117
may be installed between the outdoor units 100.
[0026] The outdoor unit 100 includes a plurality of compressors
120a, 120b, and 120c that are interconnected by a refrigerant pipe
110, an outdoor heat exchanger 176, an outdoor expansion valve 171,
and a super cooler 180. Pressure sensors 175 and 177 for measuring
pressure of refrigerant flowing along the refrigerant pipe 110 may
be installed on the refrigerant pipe 110. A solenoid valve 174 for
adjusting the flow of the refrigerant may be installed on the
refrigerant pipe 110.
[0027] The compressors 120a, 120b, and 120c compress low
temperature/low pressure refrigerant into high temperature/high
pressure refrigerant. The compressors 120a, 120b, and 120c may be
variously structured. For example, inverter type compressors or
constant speed compressors may be used as the compressors 120a,
120h, and 120c. The compressors 120a, 120b, and 120c are connected
to the refrigerant common intake pipe, 111 in parallel. That is,
the compressors 120a, 120b, and 120c are connected to the
refrigerant common pipe 110 in parallel by respective refrigerant
intake pipes 111a, 111b, and 111c. An accumulator 162 may be
provided to prevent the liquid-phase refrigerant from flowing into
the compressors 120a, 120b, and 120c.
[0028] The compressors 120a, 120b, and 120c compress the
refrigerant and discharge the compressed refrigerant to respective
refrigerant discharge pipes 112a, 112b, and 112c. Hereinafter,
compressor ports connected to the refrigerant discharge pipes 112a,
112b, and 112c will be referred to as output ports. Pressure
switches 132a, 132b, and 132c may be provided on the respective
refrigerant discharge pipes 112a, 112b, and 112c to adjust pressure
of the refrigerant that is being discharged.
[0029] Oil contained in the refrigerant discharged to each of the
refrigerant discharge pipes 112a, 112b, and 112c is separated from
the refrigerant by each of oil separators 140a, 140b, and 140c. The
separated oil is recovered to the compressors 120a, 120b, and 120c
through respective oil recovery pipes 113a, 113b, and 113c. That
is, the refrigerant compressed by the compressors 120a, 120b, and
120c contains the oil to smoothly operate the compressors 120a,
120b, and 120c. The oil separators 140a, 140b, and 140c separate
the oil from the refrigerant and return the separated oil to the
compressors 120a, 120b, and 120c through the oil recovery pipes
113a, 113b, and 113c so that the oil in the compressors 120a, 120b,
and 120c remains at a constant level. At this point, the oil
recovery pipes 113a, 113b, and 113c connect the oil separators
140a, 140b, and 140c to respective compressor shells that are
provided in the respective compressors 120a, 120b, and 120c so as
to collect the oil in the shells.
[0030] When an amount of the oil collected in the compressor shells
increases to or above a reference oil level from which the
compressors 120a, 120b, and 120c can normally operate, the oil
existing above the reference oil level is transferred toward the
refrigerant common intake pipe 111. To realize this, oil equalizing
pipes 114a, 114b, and 114c that connect the compressor shells of
the respective compressors 120a, 120b, and 120c to the refrigerant
common intake pipe 111 are provided. Capillary tubes 137a, 137b,
and 137c may be respectively provided on the oil equalizing pipes
114a, 114b, and 114c.
[0031] A four-way valve 172 that is a directional control valve
functions to guide the refrigerant compressed in the compressors
120a, 120b, and 120c to the outdoor heat exchanger 176 in a cooling
mode and to the indoor heat exchanger 220 in a heating mode. The
four-way valve 172 connects into state A in the cooling mode and
into state B in the heating mode.
[0032] The outdoor heat exchanger 176 is generally disposed at an
outdoor space. The refrigerant heat-exchanges with the outdoor air
while passing through the outdoor heat exchanger 176. The outdoor
heat exchanger 176 functions as a condenser in the cooling mode and
as a vaporizer in the heating mode. The outdoor expansion valve 171
expands the refrigerant directed from the indoor unit 200 in the
heating mode. A blower fan 178 may be provided to discharge heat
generated by the heat-exchange between the outdoor air and the
refrigerant flowing along the outdoor heat exchanger 178 to an
external side.
[0033] A first bypass pipe 179 is provided so that the refrigerant
passing through the outdoor heat exchanger 176 can bypass the
outdoor expansion valve 171 in the cooling mode. A check valve 173
for selectively checking the first bypass pipe 179 is provided. The
check valve 173 is opened in the cooling mode.
[0034] The super cooler 180 includes a super cooling heat exchanger
182, a second bypass pipe 181, and a super cooling expansion valve
184. In the cooling mode, the second bypass pipe 181 directs the
refrigerant flowing from the outdoor heat exchanger 176 toward the
indoor unit 200 along a liquid pipe 115 to the super cooling
expansion valve 184.
[0035] In the cooling mode, the super cooling expansion valve 184
expands the refrigerant passing through the second bypass pipe 181.
Although there is a variety of types of super cooling expansion
valves, a linear expansion valve may be used as the supper cooling
expansion valve 184 considering convenience in use and control. The
refrigerant that is condensed while passing through the outdoor
heat exchanger 176 is super-cooled by heat-exchanging with the
refrigerant that expands and is cooled down by the super cooling
expansion valve 184 in the super cooling heat exchanger 182 while
flowing toward the indoor units 200 along the liquid tube 115 and
is then directed to the indoor units 200. Meanwhile, the
refrigerant passing through the second bypass pipe 181
heat-exchanges in the super cooling heat exchanger 182 and is then
transferred to the accumulator 162.
[0036] In this embodiment, each of the indoor units 200 includes an
indoor expansion valve 210, an indoor heat exchanger 220, and an
indoor flow fan 230 directing heat-exchanged air to the indoor
space. The air conditioner may have one or more indoor units 200,
and has four indoor units 200 in this embodiment.
[0037] The indoor heat exchanger 220 is generally disposed at the
indoor space. The refrigerant passing through the indoor heat
exchanger 220 heat-exchanges with the indoor air. The indoor heat
exchanger 220 functions as a vaporizer in the cooling mode and as a
condenser in the heating mode.
[0038] The indoor expansion valve 210 is a device for expanding the
refrigerant that is supplied in the cooling mode. Although there is
a variety of types of indoor expansion valves, a linear expansion
valve may be used as the indoor expansion valve 210 considering
convenience in use and control. The opening of the indoor expansion
valve 210 may be adjusted depending on an air conditioning load of
the indoor space where the indoor unit 210 is installed, and an air
conditioning capacity of the indoor unit 200.
[0039] The following will describe the flow of the refrigerant in
the cooling mode of the above-described air conditioner.
[0040] The high temperature/high pressure gas-phase refrigerant
discharged from the compressors 120a, 120b, and 120c is directed
into the outdoor heat exchanger 176 via the four-way valve 172. The
refrigerant is condensed in the outdoor heat exchanger 176 by
heat-exchanging with the outdoor air. The refrigerant passing
through the outdoor heat exchanger 176 is super-cooled while
passing through the super cooler 180 and is then directed into the
indoor unit 200 through the liquid pipe 115. At this point, the
refrigerant in the second bypass pipe 181 of the super cooler 180
is directed to the accumulator 162.
[0041] Meanwhile, the refrigerant directed into each of the
respective indoor units 200 expands by the indoor expansion valve
210 that is opened by a predetermined degree of opening and is
vaporized in the indoor heat exchanger 220 by heat-exchanging with
the indoor air. The vaporized refrigerant is transferred to the
accumulator 162 through an air pipe 116 via the four-way valve 172.
Hence, the refrigerant collected through the second bypass pipe 181
of the super cooler 180 and the refrigerant transferred from the
indoor unit 200 are collected together in the accumulator 162. The
collected refrigerant is supplied to the respective compressors
120a, 120b, and 120c through the refrigerant common intake pipe
111, thereby continuously realizing a cooling cycle.
[0042] The following will describe the flow of the refrigerant in
the heating mode of the above-described air conditioner.
[0043] The high temperature/high pressure gas-phase refrigerant
discharged from the compressors 120a, 120b, and 120c is directed
into the indoor unit 200 through the air pipe 116 via the four-way
valve 172. The refrigerant directed into the indoor unit 200 is
condensed by heat-exchanging with the indoor air while passing
through the indoor heat exchanger 220 and is then directed into the
outdoor unit 100 through the liquid pipe 115, after which the
refrigerant expands while passing through the indoor expansion
valve 171 and is then vaporized by heat-exchanging with the outdoor
air while passing through the outdoor heat exchanger 176. The
vaporized refrigerant is directed to the respective compressors
120a, 120b, and 120c via the four-way valve 172, accumulator 162,
and refrigerant common intake pipe 111, thereby continuously
realizing a heating cycle.
[0044] The following will describe the flow of the oil in the
above-described air conditioner.
[0045] The refrigerant is compressed by the compressors 120a, 120b,
and 120c and discharged to the refrigerant discharge pipes 112a,
112b, and 112c through the respective output ports. The oil
separators 140a, 140b, and 140c separate the oil from the
refrigerant and return the oil to the compressors 120a, 120b, and
120c through the respective oil recovery pipes 113a, 113b, and
113c. At this point, since the oil recovery pipes 113a, 113b, and
113c are structured to respectively connect the oil separators
140a, 140b, and 140c to the compressors 120a, 120b, and 120c, the
redirection of the refrigerant into input ports of the compressors
120a, 120b, and 120c through the respective oil recovery pipes
113a, 113b, and 113c can be prevented by the compressors 120a,
120b, and 120c and thus there is an effect that the compression
efficiency and the coefficient of performance of the system can be
improved.
[0046] In the above-described structure, since the oil separated by
the oil separators 140a, 140b, and 140c is, however, redirected
into the corresponding compressors 120a, 120b, and 120c, a
compressor lacking oil continues suffering from a shortage of oil
and a compressor having excessive oil continues to have excessive
oil. In order to discharge the oil existing above the reference oil
level in the compressor shells, oil equalizing ports are processed
in the compressor shells and connected to the oil equalizing pipes
114a, 114b, and 114c.
[0047] The oil existing above the reference oil level in the
compressors 120a, 120b, and 120c is dispensed to the refrigerant
common intake pipe 111 through the oil equalizing pipes 114a, 114b,
and 114c. The oil dispensed to the refrigerant common intake pipe
111 together with the refrigerant is supplied again to the
respective compressors 120a, 120b, and 120c. The oil equalizing
process between the compressors 120a, 120b, and 120c will be
described in more detail later.
[0048] FIG. 3 shows major parts of FIGS. 1 and 2, illustrating
devices for equalizing oil between the compressors 120a, 120b, and
120c. FIG. 4 is a block diagram of a control system according to an
embodiment of the present invention. FIG. 5 is a graph illustrating
a relationship between an amount of oil flowing into compressors
and a value (Td-Tpipe).
[0049] The following will describe the oil equalizing process
between the compressors 120a and 120b on the assumption that the
compressors 120a and 120b are operating, the compressor 120c stops
operating, the compressor 120a is in an oil excessive state, and
the compressor 120b is in an oil shortage state.
[0050] When the oil equalizing operation starts, a control unit 150
opens the oil equalizing pipes 114a and 114b. The oil existing
above the reference oil level and collected in the compressor 120a
is directed to the common intake pipe 111 through the oil
equalizing pipe 114a. Meanwhile, since discharge pressure of the
compressor 120b is applied to the compressor shell of the
compressor 120b through the oil recovery pipe 113b, the refrigerant
is directed to the oil equalizing pipe 114b.
[0051] When the oil equalizing operation is continued, the
refrigerant containing the oil is dispensed to the compressors 120a
and 120b that are operating through the common intake pipe 111.
Accordingly, an amount of the oil of the compressor 120b that is in
the oil shortage state gradually increases and an amount in the
compressor 120a that is in the oil excessive state gradually
decreases, thereby equalizing the oil between the compressors 120a
and 120b.
[0052] In order to measure the temperature of the refrigerant
discharged from the compressors 120a, 120b, and 120c, first
temperature sensors 131a, 131b, and 131c are provided on the
discharge pipes 112a, 112b, and 112c and second temperature sensors
133a, 133b, and 133c are provided on the oil equalizing pipes 114a,
114b, and 114c.
[0053] The control unit 150 controls the first temperature sensors
131a, 131b, and 131c, second temperature sensors 133a, 133b, and
133c, and/or oil equalizing valves 135a, 135b, and 135c such that
the oil equalizing operation is ended when a specific condition is
satisfied.
[0054] Referring to FIG. 5, a difference between a value Td
obtained by measuring a temperature of the refrigerant discharged
through the output port of the compressor 120 by the first
temperature sensor 131 and a value Tpipe obtained by measuring a
temperature of the refrigerant discharged to the oil equalizing
pipe 114 by the second temperature sensor 133 is generally reduced
as the temperature of the outdoor air increases. At this point, the
second temperature sensor 133 is connected to a downstream side of
the capillary tube 137 provided on the oil equalizing pipe 114.
FIG. 5 shows a curve "a" illustrating a state where the oil is
exactly collected up to the reference oil level in the compressor
120, a curve "b" illustrating a state where the oil is collected
below the reference oil level in the compressor 120, and a curve
"c" illustrating a state where the oil is collected above the
reference oil level in the compressor 120.
[0055] It can be noted that the difference (Td-Tpipe) of the curve
"b" is generally higher than that of the curve "a." The difference
(Td-Tpipe) of the curve "c" is generally lower than that of the
curve "a." When the amount of the oil collected in the compressor
120 is equal to or less than the reference oil level, only the
refrigerant is directed into the oil equalizing pipe 114. The
refrigerant directed into the oil equalizing pipe 114 adiabatically
expands while passing through the capillary tube 137. Therefore,
the value Tpipe is relatively low and the value (Td-Tpipe) is
relatively high.
[0056] On the other hand, when the oil is collected above the
reference oil level in the compressor 120, the oil existing above
the reference oil level is directed into the oil equalizing pipe
114 and thus the Value Tpipe of the temperature measured by the
second temperature sensors 133a, 133b, and 133c is relatively high
and the difference (Td-Tpipe) is relatively low.
[0057] As described above, by utilizing a characteristic where the
value (Td-Tpipe) measured in the compressor 120a that is in the oil
excessive state is different from the value (Td-Tpipe) measured in
the compressor 120b that is in the oil shortage state, it can be
determined if the oil equalization between the compressors is
realized and if the oil equalizing operation stops. This will be
described in more detail with reference to FIG. 6.
[0058] FIG. 6 is a flowchart illustrating a method of controlling
an air conditioner according to an embodiment of the present
invention. Referring to FIG. 6, a normal operation step where the
air conditioner operates to cool or heat the indoor air is
performed (S10). In Step S10, at least one of the compressors 120a,
120b, and 120c operates.
[0059] When at least two of the compressors 120a, 120b, and 120c
operate (S20), the at least two of the compressors 120a, 120b, and
120c continuously operate for a predetermined time (S30). The
predetermined time is a time in which the degree of discharged heat
of each of the at least two compressors reaches a reference value.
The predetermined time may be 2 hours.
[0060] The following will be described on the assumption that the
compressors 120a and 120b are operating and the compressor 120c is
not operating in Step S10. In addition, it is assumed that the
predetermined time is 2 hours. However, the assumptions should not
be construed as limitations. The predetermined time can be
variously set depending on the air conditioning load or the
compressor efficiency.
[0061] It is determined if the degrees of discharged heat of the
compressors 120a and 120b that are operating are greater than a
reference value after the compressors 120a and 120b operate for 2
hours (S40). In this embodiment, the reference value is 10 degrees,
which should not be construed as a limitation.
[0062] When the degrees of discharged heat of the compressors 120a
and 120b are greater than the reference value, both the oil
equalizing valves 135a and 135b are opened and the oil equalizing
operation starts (S50). The oil equalizing valves 135a and 135b
maintain the opened state for a predetermined time and the oil
equalizing operation is continued. In this embodiment, the
predetermined time is set to be 90 seconds, which should not be
construed as a limitation. The predetermined time may be set
considering the number of the compressors that are operating,
compression capacity, and/or compression performance such that the
oil equalization between the compressors that are operating is
sufficiently realized.
[0063] When the oil equalizing valves 135a and 135b are opened, the
oil existing above the reference oil level in the compressor 120a
is directed to the refrigerant common intake pipe 111 through the
oil equalizing pipe 114a and is then dispensed to the compressors
120a and 120b that are operating, after which the oil together with
the refrigerant is introduced. In this process, the oil existing
above the reference oil level is dispensed to the compressor 120b
that is in the oil shortage state. This process is repeated for 90
seconds. In this process, when the oil is excessively supplied to
the compressor 120b above the reference oil level, the oil existing
above the reference oil level in the compressor 120b is dispensed
to the refrigerant common intake pipe 111 through the oil
equalizing pipe 114b. As this process is repeated, the oil
equalization where the oil is equally dispensed to the compressors
120a and 120b is finally realized.
[0064] After the above, it is determined if the value (Td-Tpipe)
measured in each of the compressors 120a and 120b is greater than a
predetermined value (S60). When the value (Td-Tpipe) measured in
each of the compressors 120a and 120b is greater than the
predetermined value, this is a case where both the compressors 120a
and 120b are in the oil shortage state, i.e., a case where the oil
cannot be sufficiently supplied up to the reference oil level in
the compressors 120a and 120b. Therefore, the opened oil equalizing
valves 135a and 135c are closed (S61) and the oil equalizing
operation is stopped (S70).
[0065] On the other hand, when the value (Td-Tpipe) measured in
each of the compressors 120a and 120b is less than the
predetermined value, this is a case where the oil is sufficiently
supplied to the compressors 120a and 120b. Therefore, there is no
need to perform the oil equalizing operation and thus the opened
oil equalizing valves 135a and 135c are closed (S61) and the oil
equalizing operation is stopped (S70).
[0066] Meanwhile, when the value (Td-Tpipe) measured in one of the
compressors 120a and 120b that are operating is greater than the
predetermined value and the value (Td-Tpipe) measured in the other
of the compressors 120a and 120b is less than the predetermined
value, this means that the oil equalization between the compressors
120a and 120b is not yet realized. Therefore, the oil equalizing
operation is further performed until a predetermined time passed.
At this point, the predetermined time may be set considering
durability of the compressor that is in the oil shortage state such
that the oil equalization between the compressors 120a and 120b is
sufficiently realized. In this embodiment, the predetermined time
is set to be 4 minutes, which should not be construed as a
limitation.
[0067] Meanwhile, the value Tpipe is a value that is measured at
the downstream side of the capillary tube 137 of the oil equalizing
pipe 114. However, when the capillary tube 137 is not provided, the
value Tpipe measured in a case where the oil flows along the oil
equalizing pipe 114 is different from that measured in a case where
the oil does not flow along the oil equalizing pipe 114 even if the
value Td is obtained in the oil equalizing pipe 114. Therefore, it
will be possible to determine the oil equalizing operation state
depending on the value (Td-Tpipe).
[0068] According to the air conditioner and method of controlling
the air conditioner of the present disclosure, the following
effects may be attained.
[0069] First, since the oil is supplied from the compressor that is
in the oil excessive state to the compressor that is in the oil
shortage state, no compressor that is in the oil shortage state may
exist.
[0070] Second, the damage of components of the compressor, which is
caused by the oil shortage, may be prevented.
[0071] Third, an oil imbalance phenomenon caused by differences in
RPM between the compressors may be prevented.
[0072] Fourth, since the oil recovery unit returns the separated
oil to the compressors without mixing the oil with the refrigerant,
the compression efficiency and coefficient of performance of the
compressors may be improved.
[0073] The effects as described in the disclosure are not limited
to those above, and it will be clear to those skilled in the art
that other effects not described can be realized when practicing
the following claims.
[0074] It will be apparent to those skilled in the art that various
modifications and variations can be made. Thus, it should be
understood that all embodiments described above are merely
exemplary and not restrictive. It is intended that all varied or
modified forms derived from the spirit and scope of the appended
claims, and equivalents thereof will covered by the scope of the
claims to follow.
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