Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
2002-09-09
2004-06-29
Jiang, Chen Wen (Department: 3744)
Refrigeration
Automatic control
Refrigeration producer
C062S231000, C417S044100, C417S001000
Reexamination Certificate
active
06755040
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Patent Application No. 2002-23991, filed May 1, 2002, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in general, to an air conditioner and, more particularly, to an air conditioner with a variable capacity compressor and a method of controlling such an air conditioner.
2. Description of the Related Art
As well known to those skilled in the art, an air conditioner controls an indoor temperature by transferring heat between a refrigerant and one of indoor air and outdoor air. The air conditioner typically includes an indoor heat exchanger, an outdoor heat exchanger, a compressor, etc. During a cooling mode operation of the air conditioner, the heat is transferred from the indoor air to the refrigerant in the indoor heat exchanger and is dissipated from the refrigerant to the outdoor air in the outdoor heat exchanger so as to cool the indoor air. During a heating mode operation of the air conditioner, the refrigerant absorbs the heat generated in the outdoor heat exchanger and dissipates the heat to the indoor air at the indoor heat exchanger, thus heating the indoor air.
FIG. 1A
is a block diagram showing a construction of an air conditioner having a conventional outdoor unit. As shown in
FIG. 1A
, the refrigerant flowing from an indoor unit
114
during a cooling mode operation of the air conditioner is introduced into a compressor
104
through a four-way valve
106
. The compressor
104
compresses the input refrigerant to make high pressure and high temperature refrigerant, and discharges the refrigerant. The discharged refrigerant from the compressor
104
passes through the four-way valve
106
and flows into an outdoor heat exchanger
110
. Thereafter, the refrigerant returns from the outdoor heat exchanger
110
to the indoor unit
114
, and the above-mentioned cycle of the refrigerant repeats during the cooling mode operation.
The compressor
104
also contains lubricating oil therein. Therefore, during an operation of the compressor
104
, a small quantity of lubricating oil is discharged from the compressor
104
together with the discharged refrigerant. In such a case, the lubricating oil discharged from the compressor
104
circulates through a refrigerant circulating line (refrigerant pipe) of the air conditioner and may reduce a heat exchanging efficiency of the outdoor and indoor units
102
and
114
. Particularly, an excessive amount of the lubricating oil may be discharged from the compressor
104
during the operation to severely degrade an operational reliability of the air conditioner. Therefore, an oil separator
108
, used for separating the lubricating oil from the refrigerant, is provided on the refrigerant circulating line at a position between the compressor
104
and the four-way valve
106
. In such a case, a pressure of the oil separator
106
connected to an outlet port of the compressor
104
is higher than that of an inlet port of the compressor
104
, and so the lubricating oil separated from the refrigerant in the oil separator
106
can be returned to the compressor
104
.
In a case of a multiunit-type air conditioner with a plurality of indoor units, several compressors may be provided in the outdoor unit to meet an entire load imposed on the multiunit-type air conditioner by the indoor units. Alternatively, the multiunit-type air conditioner may be provided with a compressor having a large capacity suitable for effectively driving the entire indoor units. However, during an operation of the multiunit-type air conditioner, it is occasionally desired to operate only a part of the several indoor units. The entire load imposed on the compressor of the multiunit-type air conditioner thus varies in accordance with the number of the indoor units to be operated. Therefore, it is possible to install a variable capacity compressor in the multiunit-type air conditioner and operate the multiunit-type air conditioner while controlling a variable capacity of the variable capacity compressor in accordance with a variable load determined by the number of the indoor units to be operated.
Examples of the conventional variable capacity compressors in an air conditioner are a rotary type compressor and a reciprocating type compressor. A capacity control of the rotary type compressor is accomplished by controlling a motor speed by using an inverter. In the reciprocating type compressor with two pistons connected to a single crankshaft, a crankshaft is rotated in a forward direction or a reverse direction such that the crankshaft drives one piston set in one cylinder or two pistons set in two cylinders, thus controlling the variable capacity of the variable capacity compressor.
FIG. 1B
is a view schematically showing a construction of the conventional variable capacity compressor of the reciprocating type typically used in the air conditioner. As shown in
FIG. 1B
, a first set of a cylinder
156
a
and a piston
158
a
forms a first compression stage of the compressor while a second set of a cylinder
156
b
and a piston
158
b
forms a second compression stage. The two pistons
158
a
and
158
b
are connected to a single crankshaft
152
and communicate with the four-way valve
106
. The crankshaft
152
rotates by a motor
154
, and a rotating motion of the motored crankshaft
152
is converted to a rectilinear reciprocating motion of the two pistons
158
a
and
158
b
. Of course, it should be understood that such rectilinear reciprocating motion of the two pistons
158
a
and
158
b
converted from the rotating motion may be accomplished by the use of an appropriate eccentric rotary body in place of the crankshaft
152
. Due to such rectilinear reciprocating motion of the two pistons
158
A and
158
B, refrigerant received in the two cylinders
156
a
and
156
b
is compressed to become high pressure and high temperature refrigerant prior to being discharged from the compressor
104
to the indoor unit
114
.
However, when the compressor
104
stops an operation for a lengthy period of time, liquid refrigerant remaining in the refrigerant circulating line gradually moves from the refrigerant circulating line to the compressor
104
so as to coexist with the lubricating oil in the compressor
104
. In such a case, a temperature of the stopped compressor
104
is lower than that of the operating compressor
104
, thus resulting in an oil separation of the lubricating oil from the refrigerant in the compressor
104
, in which the refrigerant moves downward to a lower portion of the compressor
104
while the lubricating oil moves upward to an upper portion of the compressor
104
. In a case of starting the operation of the compressor after the oil separation has occurred, liquid refrigerant in place of the lubricating oil may be fed to the parts of the compressor
104
during an initial stage of the operation of the compressor
104
. This means that a desired amount of lubricating oil cannot be fed to the parts of the compressor and that a smooth lubricating effect of the parts may not be accomplished.
In an effort to overcome such a problem caused by the oil separation from the refrigerant, two heaters
160
a
and
160
b
may be installed at lower ends of the two cylinders
156
a
and
156
b
, respectively. The two heaters
160
a
and
160
b
heat the liquid refrigerant in the compressor
104
during the stoppage of the operation of the compressor, thus vaporizing the refrigerant, discharging the vaporized refrigerant to an outside of the compressor
104
, and allowing only the lubricating oil to remain in the compressor
104
.
However, the use of such heaters
160
a
and
160
b
in the compressor
104
undesirably increases a production cost and a maintenance cost of the compressor
104
. Furthermore, the heaters
160
a
and
160
b
may be broken and badly affect the compressor
104
. However, since the conventional compressor doe
Jeong Jae-Hyo
Kim Jong-Moon
Kim Seung-Chul
Lee Jai-Kwon
Park Youn-Cheol
Jiang Chen Wen
Staas & Halsey , LLP
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