Heating systems – Automatic control – Heat source is a reverse cycle refrigerating system or heat...
Reexamination Certificate
2003-03-05
2003-12-30
Boles, Derek (Department: 3744)
Heating systems
Automatic control
Heat source is a reverse cycle refrigerating system or heat...
C062S159000
Reexamination Certificate
active
06669102
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an air conditioner, and more particularly to a method for operating an air conditioner to rapidly and efficiently eliminate a warming load.
2. Description of the Related Art
Generally, an air conditioner is an appliance for cooling or warming a room using a cooling cycle of a refrigerant compressed into a high-temperature and high-pressure state by a compressor.
The compressor includes a compressing unit having a compressing chamber for compressing the refrigerant, and a motor unit for varying the volume of the compressing chamber. In the case of an air conditioner equipped with a plurality of indoor units or a large-capacity air conditioner, a plurality of compressors are used. In association with such an air conditioner, it is possible to reduce the consumption of electric power required to drive compressors by varying the capacity of the compressors in accordance with the load to be eliminated.
FIG. 1
is a schematic diagram illustrating a cooling cycle established in a conventional air conditioner.
FIG. 2
is a schematic diagram illustrating a warming cycle established in the conventional air conditioner.
As shown in
FIGS. 1 and 2
, the conventional air conditioner includes an indoor heat exchanger
2
for heat-exchanging air in a room with a refrigerant, thereby cooling or warming the room, an outdoor heat exchanger
4
serving as a condenser for condensing the refrigerant when the indoor heat exchanger
2
functions as a cooler, while serving as an evaporator for evaporating the refrigerant when the indoor heat exchanger
2
functions as a heater, and first and second compressors
6
and
16
for compressing the refrigerant from a low-temperature and low-pressure gaseous state into a high-temperature and high-pressure gaseous state in order to supply the high-temperature and high-pressure gaseous refrigerant to the indoor heat exchanger
2
or outdoor heat exchanger
4
. The air conditioner also includes an expansion device
8
arranged between the indoor heat exchanger
2
and the outdoor heat exchanger
4
, and adapted to expand the refrigerant into a low-temperature and a low-pressure state, and a control unit (not shown) for controlling operations of the first and second compressors
6
and
16
in response to an operation of the user and in accordance with the load to be eliminated. The indoor heat exchanger
2
, outdoor heat exchanger
4
, first and second compressors
6
and
16
, and expansion device
8
are connected by a refrigerant pipe
9
.
In
FIGS. 1 and 2
, the reference numeral
24
denotes a common accumulator to which respective suction lines
6
a
and
16
a
of the first and second compressors
6
and
16
are connected. This common accumulator
24
serves to store a liquid refrigerant not evaporated by the indoor heat exchanger
2
or outdoor heat exchanger
4
, in order to prevent the liquid refrigerant from being introduced into the first and second compressors
6
and
16
. Introduction of such a liquid refrigerant into the compressors
6
and
16
may cause failure of those compressors.
Also, the reference numeral
26
denotes a direction change valve, for example, a 4-way valve, adapted to change the flowing direction of the refrigerant in accordance with a control signal from the control unit so that the air conditioning system is used for a cooling or warming purpose. This 4-way valve
26
communicates with the common accumulator
24
and respective discharge lines
6
b
and
16
b
of the first and second compressors
6
and
16
. The 4-way valve
26
guides the high-temperature and high-pressure gaseous refrigerant compressed by the first compressor
6
or second compressor
16
to the outdoor heat exchanger
4
in a cooling mode, while it guides the same gaseous refrigerant to the indoor heat exchanger
2
in a warming mode.
The reference numerals
32
and
34
are check valves respectively installed in the discharge lines
6
b
and
16
b
of the first and second compressors
6
and
16
, and adapted to prevent the refrigerant discharged from the currently-operating compressor, for example, the first compressor
6
, from being introduced into the currently-stopped compressor, for example, the second compressor
16
.
Meanwhile, the first compressor
6
has a capacity of X%, for example, 60%, whereas the second compressor
16
has a capacity of Y%, for example, 40%. Compressor operation is carried out with a capacity of 100%. or X% by operating both the first and second compressors
6
and
16
or operating only the first compressor
6
in accordance with a control signal from the control unit.
Now, the conventional air conditioner having the above described configuration will be described.
When the air conditioner is set to operate in a warming mode under the condition in which a target temperature T
0
is set, the control unit first switches the operating position of the 4-way valve
26
to correspond to the warming mode, as shown in
FIG. 2
, and operates the first and second compressors
6
and
16
.
The first and second compressors
6
and
16
discharge a high-temperature and high-pressure gaseous refrigerant which, in turn, passes through the indoor heat exchanger
2
. The refrigerant is condensed while discharging heat therefrom around the indoor heat exchanger
2
. In this case, the indoor heat exchanger
2
serves as a heater.
The refrigerant condensed into a high-temperature high-pressure liquid state while passing through the indoor heat exchanger
2
then passes through the expansion device
8
which, in turn, expands the refrigerant into a low-temperature and a low-pressure state so as to change the refrigerant into an easily evaporable state. The expanded refrigerant is then sent to the outdoor heat exchanger
4
. The refrigerant absorbs heat around the outdoor heat exchanger
4
while passing through the outdoor heat exchanger
4
, so that it is evaporated. The resultant refrigerant is introduced into the first and second compressors
6
and
16
. Thus, a warming cycle is established.
Once the warming load is substantially eliminated in accordance with the above described operations of the first and second compressors
6
and
16
, only the first compressor
6
is repeatedly operated and stopped in order to cope with a subsequent warming load under the condition that the second compressor
16
is maintained in a stopped state.
FIG. 3
is a graph depicting a variation in compression capacity depending on a variation in room temperature in the warming mode of the conventional air conditioner.
When the indoor heat exchanger
4
performs a warming operation in accordance with operations of the first and second compressors
6
and
16
, the room temperature T is increased, as shown in FIG.
3
. When the room temperature T exceeds an upper temperature limit of T
0
+&Dgr;T higher than the target temperature T
0
by an allowable temperature deviation &Dgr;T of, for example, 0.5° C., the control unit stops the first and second compressors
6
and
16
.
Subsequently, the room temperature T decreases gradually because the first and second compressors
6
and
16
are maintained in a stopped state. When the room temperature T is lowered below a lower temperature limit of T
0
−&Dgr;T lower than the target temperature T
0
by an allowable temperature deviation &Dgr;T of, for example, 0.5° C., the control unit again operates the first and second compressors
6
and
16
.
On the other hand, when the room temperature T again exceeds the upper temperature limit of T
0
+&Dgr;T in accordance with the re-operations of the first and second compressors
6
and
16
, the control unit again stops the first and second compressors
6
and
16
.
After operating the first and second compressors
6
and
16
two times in the above manner, the control unit determines that the warming load is substantially eliminated. Based on this determination, the control unit operates only the first compressor
6
when the room temperature T is again lowered below the
Boles Derek
Greenblum & Bernstein P.L.C.
LG Electronics Inc.
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