U.S. patent application number 09/985888 was filed with the patent office on 2002-05-16 for method for contolling linear expansion valve in air conditioner with two compressor.
Invention is credited to Kim, Cheol Min.
Application Number | 20020056280 09/985888 |
Document ID | / |
Family ID | 19698346 |
Filed Date | 2002-05-16 |
United States Patent
Application |
20020056280 |
Kind Code |
A1 |
Kim, Cheol Min |
May 16, 2002 |
Method for contolling linear expansion valve in air conditioner
with two compressor
Abstract
Method for controlling a linear expansion valve in an air
conditioner with two compressors, which can prevent breakage of the
compressor, and starting failure caused by liquidus refrigerant
introduced into the compressor at an initial starting, and
preventing drop of cooling performance caused by reduced
refrigerant flow coming from a low suction pressure of the
compressor at an initial unsteady state.
Inventors: |
Kim, Cheol Min; (Kyonggi-do,
KR) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
19698346 |
Appl. No.: |
09/985888 |
Filed: |
November 6, 2001 |
Current U.S.
Class: |
62/222 ;
62/175 |
Current CPC
Class: |
Y02B 30/70 20130101;
F25B 2600/2513 20130101; F25B 2500/26 20130101; F25B 13/00
20130101; F25B 2400/0751 20130101; F25B 41/347 20210101 |
Class at
Publication: |
62/222 ;
62/175 |
International
Class: |
F25B 007/00; F25B
041/04 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 10, 2000 |
KR |
2000-66778 |
Claims
What is claimed is:
1. A method for controlling a linear expansion valve in an air
conditioning system with two compressors of a large compressor and
a small compressor, comprising the steps of: (a) changing an LEV
pulse value from an initial value to P1, when a compressor
operation time period reaches to Ts-a after the compressors are put
into operation; (b) changing the LEV pulse value from P1 to P2,
when the compressor operation time period reaches to Tm-b; (c)
changing the LEV pulse value from P2 to a target value, when the
compressor operation time period reaches to T1-c; and, (d) starting
a superheat control, after the operation time period of the
compressors reaches to T2, where P1 denotes an initial pulse
value+a capacity ratio (%) of the small compressor.times.the target
value/100, P2 denotes an initial pulse value+a capacity ratio (%)
of the large compressor.times.the target value/100, T1 denotes a
time period to reach to the target value, T2 denotes a time
starting to control superheat, Ts denotes a capacity ratio (%) of
the small compressor.times.T1/100, Tm denotes a capacity ratio (%)
of the large compressor.times.T1/100, `a` denotes a time period the
LEV pulse is changed from the initial value to P1, `b` denotes a
time period the LEV pulse is changed from P1 to P2, and `c` denotes
a time period the LEV pulse is changed from P2 to the target
value.
2. A method as claimed in claim 1, wherein, when the LEV pulse
value is changed from the initial value to P1, the capacity ratio
of the large compressor is used.
3. A method as claimed in claim 1, wherein, when the LEV pulse
value is changed from P1 to P2, the capacity ratio of the small
compressor is used.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method for controlling a
linear expansion valve in an air conditioner with two compressors,
and more particularly, to a method for controlling a linear
expansion valve in an air conditioner with two compressors, in
which two compressors with different compression capacities are
provided for varying compression of refrigerant according to
cooling/heating load.
[0003] 2. Background of the Related Art
[0004] In general, the air conditioner cools/heats a room by using
refrigerant compressed to a high temperature, and a high pressure
at the compressor. The air conditioner with two compressors each
operative selectively according to a cooling/heating load is
provided for reducing a power required for driving the compressors,
has the following system.
[0005] Referring to FIG. 1, a related art air conditioner with two
compressors is provided with a large capacity compressor 2, and a
small capacity compressor 4 selectively operative during cooling a
room for varying compression of refrigerant, an outdoor heat
exchanger 6 for heat exchange of the refrigerant compressed at the
compressors 2, and 4, a linear expansion valve 8 for expanding the
refrigerant condensed at the outdoor heat exchanger 6, an indoor
heat exchanger 10 for heat exchange of the refrigerant expanded at
the linear expansion valve 8 with room air, and an oil separator
12.
[0006] The small compressor 2, and the large compressor 4 may be
made to make independent, or interlocked operation depending on a
room cooling load condition. Under a condition the two compressors
are required to operate simultaneously, the high temperature, and
high pressure refrigerant from the small compressor 2, and the
large compressor 4 passes through the oil separator 12 for
separating oil in the refrigerant. The refrigerant separated from
the oil is provided to the outdoor heat exchanger 6, condensed into
a high pressure liquid refrigerant, and converted into low
temperature, and low pressure refrigerant. Then, the low
temperature, and low pressure refrigerant is evaporated into
gaseous refrigerant as the low temperature, and low pressure
refrigerant passes through the indoor heat exchanger 10, passed
through two capillary tubes 14, and 16, and drawn to the
compressors 2, and 4 again via a first accumulator 18, and a second
accumulator 20, respectively.
[0007] If the small compressor 2, and the large compressor 4 are
used as heat pumps for room heating, the refrigerant is provided to
the indoor heat exchanger 10 via the oil separator 12, and a four
way valve (not shown), to condense the refrigerant, passed through
the linear expansion valve 8 to convert the refrigerant into low
temperature, and low pressure refrigerant, passed through the
outdoor heat exchanger 6, to evaporate the refrigerant, and drawn
into the compressors 10, and 20 again via the accumulators 18, and
20 again.
[0008] The oil discharged from the two compressors 2, and 4, and
separated from the refrigerant at the oil separator 12 is involved
in pressure drop as the oil passes through the first capillary tube
14, and the second capillary tube 16, and drawn into the
compressors, thereby being recovered by the compressors 2, and
4.
[0009] As explained, since respective capacities of the compressors
2, and 4 in the air conditioner with two compressors 2, and 4 can
be varied with a room load condition, as an expansion valve for
regulating a flow of the refrigerant in the air conditioner, the
linear expansion valve (LEV) 8 is used. The control of the LEV 8 is
divided into a starting control at starting of the compressor, and
a control after the starting control of the compressor is finished,
wherein, as shown in the drawing, the control after finish of
starting employs a control method in which a temperature difference
between a temperature sensor 22 at a compressor inlet, and a
temperature sensor 24 at a room pipeline is kept constant. The LEV
is controlled at the compressor starting, for preventing breakage
of the compressor caused by liquidus refrigerant introduced into
the compressor at an initial starting, and starting failure, and
preventing drop of cooling performance caused by reduced
refrigerant flow coming from a low suction pressure of the
compressor at an initial unsteady state.
[0010] FIG. 2 illustrates a graph of a related art LEV control
method.
[0011] Referring to FIG. 2, a pulse value to the LEV is set to a
value which minimizes the liquidus refrigerant introduction into
the compressor at starting of the compressor, and gradually
increased to a target value as an operation time period is
increased. A time period `t1` for reaching to the target value is
divided by `n` equally, and the pulse value is increased at fixed
time intervals, wherein an increment of the pulse value is obtained
by dividing a difference of the initial pulse value, and a target
pulse value by `n`, equally. Once the pulse value reaches to the
target value at a time the target value is expected to reach, the
pulse value to the LEV is regulated for controlling a degree of
superheat from a time for controlling the degree of superheat.
[0012] As shown in a dashed line on a graph shown in FIG. 3, the
related art LEV control has a problem of a poor initial cooling
performance at starting of the compressor caused by drop of a
compressor suction pressure, and a long unsteady state time period
until a proper suction pressure is reached.
SUMMARY OF THE INVENTION
[0013] Accordingly, the present invention is directed to a method
for controlling a linear expansion valve in an air conditioner with
two compressors that substantially obviates one or more of the
problems due to limitations and disadvantages of the related
art.
[0014] An object of the present invention is to provide a method
for controlling a linear expansion valve in an air conditioner with
two compressors, which can prevent breakage of the compressor, and
starting failure caused by liquidus refrigerant introduced into the
compressor at an initial starting, and preventing drop of cooling
performance caused by reduced refrigerant flow coming from a low
suction pressure of the compressor at an initial unsteady
state.
[0015] Additional features and advantages of the invention will be
set forth in the description which follows, and in part will be
apparent from the description, or may be learned by practice of the
invention. The objectives and other advantages of the invention
will be realized and attained by the structure particularly pointed
out in the written description and claims hereof as well as the
appended drawings.
[0016] To achieve these and other advantages and in accordance with
the purpose of the present invention, as embodied and broadly
described, the method for controlling a linear expansion valve in
an air conditioning system with two compressors of a large
compressor and a small compressor, includes the steps of (a)
changing an LEV pulse value from an initial value to P1, when a
compressor operation time period reaches to Ts-a after the
compressors are put into operation, (b) changing the LEV pulse
value from P1 to P2, when the compressor operation time period
reaches to Tm-b, (c) changing the LEV pulse value from P2 to a
target value, when the compressor operation time period reaches to
T1-c, and (d) starting a superheat control, after the operation
time period of the compressors reaches to T2,
[0017] where P1 denotes an initial pulse value+a capacity ratio (%)
of the small compressor.times.the target value/100,
[0018] P2 denotes an initial pulse value+a capacity ratio (%) of
the large compressor.times.the target value/100,
[0019] T1 denotes a time period to reach to the target value,
[0020] T2 denotes a time starting to control superheat,
[0021] Ts denotes a capacity ratio (%) of the small
compressor.times.T1,/100,
[0022] Tm denotes a capacity ratio (%) of the large
compressor.times.T/100,
[0023] `a` denotes a time period the LEV pulse is changed from the
initial value to P1,
[0024] `b` denotes a time period the LEV pulse is changed from P1
to P2, and
[0025] `c` denotes a time period the LEV pulse is changed from P2
to the target value.
[0026] When the LEV pulse value is changed from the initial value
to P1, the capacity ratio of the large compressor is used, and when
the LEV pulse value is changed from P1 to P2, the capacity ratio of
the small compressor is used.
[0027] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are intended to provide further explanation of
the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and together with the description serve to explain
the principles of the invention:
[0029] In the drawings:
[0030] FIG. 1 illustrates a system of a related art air conditioner
with two compressors, schematically;
[0031] FIG. 2 illustrates a graph showing an LEV opening pulse
value vs. compressor starting time period of a related art LEV
controlling method for an air conditioner with two compressors;
[0032] FIG. 3 illustrates a graph for comparing suction pressure
vs. operation time period of a related art LEV controlling method,
and an LEV controlling method of the present invention; and,
[0033] FIG. 4 illustrates a graph showing an LEV opening pulse
value vs. compressor starting time period in an LEV controlling
method for an air conditioner with two compressors in accordance
with a preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0034] Reference will now be made in detail to the preferred
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings. FIG. 4 illustrates a
graph showing an LEV 8 opening pulse value vs. compressor starting
time period in an LEV 8 controlling method for an air conditioner
with two compressors 2, and 4 in t accordance with a preferred
embodiment of the present invention. In a case of an air
conditioner system with two compressors 2, and 4, the initial pulse
value of the LEV 8 in an initial starting of the compressors 2, and
4 is selected such that the introduction of liquid refrigerant into
the compressors 2, and 4 is minimized, and a target value of the
LEV pulse to be reached at completion of the initial starting
control of the system, and a time period required for reaching to
the target value are fixed according to designed.
[0035] Referring to FIG. 4, in a first step 100 when a compressor
operation time period reaches to Ts-a after the compressors are put
into operation, the pulse value of the LEV is changed from the
initial value to P1, where Ts denotes a value obtained by
multiplying a capacity ratio of the small compressor to a total
capacity to a time period T1 required for reaching to the target
value, and `a` denotes a time period the pulse of the LEV is
changed from the initial value to the P1. P1 is a value obtained by
multiplying the capacity ratio of the small compressor to a total
capacity to the target value of the LEV, and adding the initial
value thereto.
[0036] In a second step 200 when the compressor operation time
period reaches to Tm-b, the pulse value of the LEV is changed from
P1 to P2, where Tm denotes a value obtained by multiplying a
capacity ratio of the large compressor to a total capacity to a
time period T1 required for reaching to the target value, and `b`
denotes a time period the pulse of the LEV is changed from the P1
to P2. P2 is a value obtained by multiplying the capacity ratio of
the large compressor to a total capacity to the target value of the
LEV, and adding the initial value thereto.
[0037] In a third step 300 when the compressor operation time
period reaches to T1-c, the pulse value of the LEV is changed from
P2 to the target value, where `c` denotes a time period the pulse
of the LEV is changed from P2 to the target value.
[0038] In a fourth step 400, when a preset time period is passed
after the pulse value of the LEV reaches to the target value, the
starting control is ended, and a superheat control is started, to
control the pulse of the LEV.
[0039] As has been explained, the method for controlling a linear
expansion valve in an air conditioner with two compressors of the
present invention requires only two steps of pulse changes during
the pulse reaches from the initial value to the target value by
controlling the LEV by using compressor capacity ratios. Variation
of compressor suction pressure vs. time in an air conditioner
system controlled according to the method of the present invention
is illustrated in a solid line in FIG. 3. It can be known from FIG.
3 that the method of the present invention shows a smaller initial
suction pressure drop than the related art, to permit the suction
pressure to reach to a proper suction pressure faster than the
related art after the compressors are started.
[0040] Thus, the method for controlling a linear expansion valve in
an air conditioner with two compressors of the present invention
can prevent drop of the suction pressure, and reduction of cooling
performance during starting because opening of an LEV is varied
from an initial value to a target value according to an operation
time period of the compressors with reference to capacity ratios of
the small compressor, and the large compressor.
[0041] Moreover, as the system can reach to a stable state within a
short period after the starting, a system efficiency can be
enhanced.
[0042] It will be apparent to those skilled in the art that various
modifications and variations can be made in the method for
controlling a linear expansion valve in an air conditioner with two
compressors of the present invention without departing from the
spirit or scope of the invention. Thus, it is intended that the
present invention cover the modifications and variations of this
invention provided they come within the scope of the appended
claims and their equivalents.
* * * * *