US20110192177A1

US20110192177A1 - Air conditioner and control method thereof

Info

Publication number: US20110192177A1
Application number: US13/019,664
Authority: US
Inventors: Dong Seok Bae; Kyoung Rock Kim; Jae Gil Lee; Chang Seon Lee; Hyung Jin Kwon
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2010-02-08
Filing date: 2011-02-02
Publication date: 2011-08-11
Also published as: CN102147141A; KR20110092147A; CN102147141B

Abstract

Disclosed herein are an air conditioner which controls a pressure of a refrigerant of an outdoor unit by adjusting an opening degree of an outdoor expansion valve or an indoor expansion valve, and a control method thereof. The air conditioner measures a pressure of the refrigerant discharged from a compressor during a cooling operation, and raises the pressure of the refrigerant to be higher than a designated pressure by controlling an opening degree of at least one of the outdoor expansion valve and the indoor expansion valve, if the pressure of the refrigerant is lower than the designated pressure. Further, the air conditioner measures the pressure of the refrigerant inhaled into the compressor during a heating operation, and adjusts the pressure of the refrigerant to be lower than a designated pressure by controlling the opening degree of the outdoor expansion valve, if the pressure of the refrigerant is higher than the designated pressure.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of Korean Patent Application No. 10-2010-0011651, filed on Feb. 8, 2010 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND

1. Field
Embodiments relate to an air conditioner to condition indoor air and a control method thereof.
2. Description of the Related Art
In general, air conditioners are cooling/heating apparatuses which cool or heat air of an indoor space, such as an office or a house, and form a series of cycles consisting of compression, condensation, expansion, and evaporation. Such air conditioners discharge condensation heat or evaporation heat to an outdoor space mainly using air of the indoor space.
Air conditioners are divided into an air cooling type air conditioner using air as a heat source, a water cooling type air conditioner using water as a heat source, and a geothermal heat type air conditioner using an underground heat source (a lake or a river), according to kinds of heat sources.
Further, as is well known, air conditioners are divided into an integrated type air conditioner in which an indoor unit conditioning air of an indoor space and an outdoor unit exchanging heat with a refrigerant circulated from the indoor unit are integrally formed, and a split type air conditioner in which an indoor unit and an outdoor unit are separated from each other such that the indoor unit is installed in an indoor space and the outdoor unit is installed in an outdoor space.

SUMMARY

Therefore, it is an aspect to provide an air conditioner which controls an opening degree of an electric expansion valve to maintain pressure of a refrigerant of an outdoor unit in a high pressure range or a low pressure range, and a control method thereof.
Additional aspects of the embodiments will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the embodiments.
In accordance with one aspect, a control method of an air conditioner, which has an outdoor unit including a compressor and an outdoor expansion valve, and an indoor unit including an indoor expansion valve, includes measuring a pressure of a refrigerant discharged from the compressor during a cooling operation, and raising the pressure of the refrigerant to be higher than a designated pressure by controlling an opening degree of at least one of the outdoor expansion valve and the indoor expansion valve, if the pressure of the refrigerant is lower than the designated pressure.
The opening degree of the indoor expansion valve may be controlled by adjusting a target superheat degree of the indoor unit, if the pressure of the refrigerant is lower than the designated pressure.
The opening degree of the indoor expansion valve may be decreased by raising the target superheat degree of the indoor unit, if the pressure of the refrigerant is lower than the designated pressure.
The pressure of the refrigerant may be raised to be higher than the designated pressure by decreasing the opening degree of the at least one of the outdoor expansion valve and the indoor expansion valve, if the pressure of the refrigerant is lower than the designated pressure.
The outdoor unit may further include a receiver, and the pressure of the refrigerant transmitted to the indoor unit may be raised by transmitting high-pressure gas discharged from the compressor to the receiver, if the pressure of the refrigerant is lower than the designated pressure.
A superheat degree of the refrigerant transmitted to an inlet side of the compressor may be detected, and the superheat degree of the refrigerant transmitted to the inlet side of the compressor may be raised by decreasing the opening degree of the indoor expansion valve, if the superheat degree is lower than a designated reference.
In accordance with another aspect, a control method of an air conditioner, which has an outdoor unit including a compressor and an outdoor expansion valve, and an indoor unit including an indoor expansion valve, includes measuring a pressure of a refrigerant inhaled into the compressor during a heating operation, and lowering the pressure of the refrigerant to be lower than a designated pressure by controlling an opening degree of the outdoor expansion valve, if the pressure of the refrigerant is higher than the designated pressure.
An amount of the refrigerant flowing in a direction of inhaling the refrigerant into the compressor may be decreased by decreasing the opening degree of the outdoor expansion valve, if the pressure of the refrigerant is higher than the designated pressure.
The opening degree of the outdoor expansion valve may be controlled by adjusting a superheat degree of the indoor unit.
In accordance with a further aspect, an air conditioner includes a pressure sensor installed at a refrigerant outlet side of a compressor to measure a pressure of a refrigerant, and a control unit of an outdoor unit to raise the pressure of the refrigerant to be higher than a designated pressure by controlling an opening degree of an outdoor expansion valve, if the pressure of the refrigerant is lower than the designated pressure during a cooling operation.
The control unit of the outdoor unit may raise the pressure of the refrigerant to be higher than the designated pressure by decreasing the opening degree of the outdoor expansion valve, if the pressure of the refrigerant is lower than the designated pressure.
The air conditioner may further include a control unit of an indoor unit to raise the pressure of the refrigerant to be higher than a designated pressure by controlling an opening degree of the indoor expansion valve, if the pressure of the refrigerant is lower than the designated pressure.
The control unit of the indoor unit may raise the pressure of the refrigerant to be higher than the designated pressure by decreasing the opening degree of the indoor expansion valve, if the pressure of the refrigerant is lower than the designated pressure.
The control unit of the indoor unit may decrease the opening degree of the indoor expansion valve by adjusting a target superheat degree of the indoor unit.
The control unit of the indoor unit may decrease the opening degree of the indoor expansion valve by raising the target superheat degree of the indoor unit.
The air conditioner may further include a pressure sensor installed at a refrigerant inlet side of the compressor to measure the pressure of the refrigerant, and a control unit of an indoor unit to receive data regarding the pressure of the refrigerant from the pressure sensor, installed at the refrigerant inlet side of the compressor, during a heating operation, and to adjust the pressure of the refrigerant to be lower than a designated pressure by controlling a target superheat degree of the refrigerant inhaled into the compressor, if the pressure of the refrigerant is higher than the designated pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects of the embodiments will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic view illustrating an installation state of a water cooling type air conditioner in accordance with one embodiment;

FIG. 2 is a block diagram illustrating a configuration of the air conditioner in accordance with the embodiment;

FIG. 3 is a control block diagram of the air conditioner in accordance with the embodiment;

FIG. 4 is a flow chart illustrating a method of maintaining high pressure of a refrigerant by controlling an opening degree of an outdoor expansion valve during a cooling operation of an air conditioner in accordance with one embodiment;

FIG. 5 is a flow chart illustrating a method of maintaining low pressure of a refrigerant by controlling an opening degree of an outdoor expansion valve during a heating operation of an air conditioner in accordance with another embodiment;

FIG. 6 is a flow chart illustrating a method of maintaining high pressure of a refrigerant by controlling an opening degree of an indoor expansion valve during a cooling operation of an air conditioner in accordance with another embodiment; and

FIG. 7 is a flow chart illustrating a method of adjusting a superheat degree of an inhaled refrigerant of a compressor by controlling a superheat degree of an indoor unit during a cooling operation of an air conditioner in accordance with another embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.
FIG. 1 is a schematic view illustrating an installation state of a water cooling type air conditioner in accordance with one embodiment, and FIG. 2 is a block diagram illustrating a configuration of the air conditioner in accordance with the embodiment.
With reference to FIGS. 1 and 2, the water cooling type air conditioner is installed to condition air of indoor spaces within a large-scale building or a high-rise building provided with the plural indoor spaces. Therefore, a building in which the water cooling type air conditioner is installed is provided with plural indoor spaces, and the water cooling type air conditioner serves to condition air of the plural indoor spaces.
In the air conditioner in accordance with this embodiment, indoor units 100 are respectively installed in plural indoor spaces provided in a building, and an air conditioning room A, in which an outdoor unit 200 connected with the plural indoor spaces 100 by pipes is installed, is provided at the side of the indoor spaces in which the indoor units 100 are respectively installed.
In each indoor space, the indoor unit 100 in a type suited to each indoor space is installed, thus conditioning air in each indoor space. That is, indoor units 100 of various models, i.e., a stand type, a ceiling-mounted type, and a wall-mounted type, may be used according to user selection. These indoor units 100 are connected with the outdoor unit 200 by refrigerant pipes 300, and the refrigerant pipes 300 guide flow of a refrigerant between the indoor units 100 and the outdoor unit 200.
The refrigerant pipes 300 are installed so as to connect the indoor units 100 and the outdoor unit 200, and are formed in the shape of a circular pipe having a designated diameter such that the refrigerant serving as an operating fluid flows along the inner spaces of the refrigerant pipes 300. Therefore, the refrigerant pipes 300 are branched off from the refrigerant pipe 300 connected to the outdoor unit 200, and are connected to the respective indoor units 100.
A cooling tower 400 to cool water to generate cooling water is installed on the top of the building in which the water cooling type air conditioner is installed. The cooling tower 400 causes water to directly contact air, thereby cooling water to generate cooling water.
The cooling water generated in the inner space of the cooling tower 400 is guided to the inner space of the outdoor unit 200 by a cooling water supply pipe 420. The cooling water exchanges heat with the refrigerant in the outdoor unit 200, is guided to the upper end of the cooling tower 400 by a cooling water recovery pipe 440, is again cooled in the cooling tower 400, and then flows to the inner space of the outdoor unit 200. This process is repeated.
A cooling water pump 460 is mounted on the cooling water supply pipe 420, and supplies the cooling water generated from the cooling tower 400 to the inner space of the outdoor unit 200 at a regular pressure.
An indoor heat exchanger 120 to inhale or pull air in the indoor space and to perform heat exchange of the inhaled air with the refrigerant to condition the air in the indoor space is mounted in the indoor unit 100. The indoor heat exchanger 120 is formed by bending a circular pipe having a designated diameter several times, and the refrigerant serving as the operating fluid flows within the indoor heat exchanger 120.
An indoor expansion valve 140 to adjust an amount of the refrigerant introduced into the indoor heat exchanger 120 or the refrigerant discharged from the indoor heat exchanger 120 is provided in the indoor unit 100. The indoor expansion valve 140 expands the refrigerant passing therethrough, thereby reducing the pressure of the refrigerant.
The refrigerant pipes 300 are connected between the indoor units 100 and the outdoor unit 200 such that the refrigerant is circulated through the refrigerant pipes 300. The refrigerant pipes 300 include high pressure pipes through which the refrigerant of a high pressure flows, and low pressure pipes through which the refrigerant of a low pressure flows. The refrigerant pipes 300 are branched off from the refrigerant pipe 300 connected to the outdoor unit 200, and are connected to the respective indoor units 100, thereby guiding the refrigerant to the insides of the indoor heat exchangers 120.
Therefore, the refrigerant flowing along the refrigerant pipe 300 is introduced into the outdoor unit 200 and exchanges heat with the cooling water guided by the cooling water supply pipe 420, and the refrigerant having exchanged heat moves to the insides of the indoor heat exchangers 120 along the refrigerant pipes 300, exchanges heat with air of the indoor spaces, in which the indoor units 100 are respectively installed, and thus conditions the air in the indoor spaces.
Further, the cooling water having exchanged heat with the refrigerant within the outdoor unit 200 flows to the inner space of the cooling tower 400 along the cooling water recovery pipe 440, thus forming one cycle.
With reference to FIG. 2, an inner configuration of the outdoor unit 200 will be described in more detail. An oil separator 265 and a refrigerant high pressure sensor 241 are provided at an output side of a compressor 260. The oil separator 265 separates oil contained in the refrigerant, which is compressed into a high temperature and high pressure state in the compressor 260 and is discharged to the outside of the compressor 260 together with the refrigerant, from the refrigerant. The refrigerant high pressure sensor 241 is installed in a high pressure pipe and measures high pressure of the refrigerant discharged from the compressor 260.
The oil separator 265 is formed in the shape of a cylinder having designated diameter and height. The oil separator 265 causes the oil to flow into the compressor 260 so as to cool frictional heat generated due to driving of the compressor 260, and the oil having flown into the compressor 260, is contained in the refrigerant compressed into the high temperature and high pressure state in the compressor 260 and is discharged to the outside of the compressor 260. The oil contained in the refrigerant and discharged to the outside of the compressor 260 is separated from the refrigerant by the oil separator 265, and is returned to the compressor 260 via an oil recovery pipe 271.
The oil separator 265 is connected to a refrigerant control valve 270 by a pipe. The refrigerant control valve 270 employs a four-way valve, and serves to convert a flow direction of the refrigerant according to operation modes of the water cooling type air conditioner. Among ports of the refrigerant control valve 270, one port is connected to the oil separator 265, and the remaining ports are connected to the indoor heat exchangers 120, an outdoor heat exchanger 230, and an accumulator 264 by pipes.
One end of the pipe connecting one port among the ports of the refrigerant control valve 280 to the outdoor heat exchanger 230 is connected to a refrigerant inlet side 233 through which the refrigerant is introduced to the inner space of the outdoor heat exchanger 230, and a refrigerant outlet side 234 through which the refrigerant having been introduced into the outdoor heat exchanger 230 through the refrigerant inlet side 233 and exchanged heat with cooling water in the outdoor heat exchanger 230 is discharged from the outdoor heat exchanger 230 is connected to the indoor heat exchangers 120 by an pipe.
An outdoor expansion valve 280 is mounted on the pipe connecting the refrigerant output 234 and the indoor heat exchangers 120.
A supercooler 282 to supercool the refrigerant is provided between the outdoor expansion valve 280 and the indoor heat exchangers 120. The supercooler 282 is a device to supercool the refrigerant having exchanged heat in the indoor heat exchangers 120 and the outdoor heat exchanger 230.
The accumulator 264 to temporarily store the refrigerant is provided on the pipe between the indoor heat exchangers 120 and the compressor 260. The accumulator 264 separates a refrigerant in a gaseous state from the refrigerant introduced into the compressor 260 such that only the refrigerant in the gaseous state flows into the compressor 260. The accumulator 264 temporarily stores the refrigerant introduced to an inlet side of the compressor 260 from the outdoor heat exchanger 230 or the indoor heat exchangers 120. The accumulator 264 divides the introduced refrigerant into the refrigerant in the gaseous state and a refrigerant in a liquid state. The refrigerant in the gaseous state separated by the accumulator 264 is inhaled to the low pressure inlet side of the compressor 260.
A refrigerant low pressure sensor 242 and a temperature sensor 243 are provided between the accumulator 264 and the compressor 260. The refrigerant low pressure sensor 242 measures a low pressure of the refrigerant introduced into the inlet side of the compressor 260, and the temperature sensor 243 measures a temperature of the refrigerant introduced into the inlet side of the compressor 260.
Although FIGS. 1 and 2 illustrate the water cooling type air conditioner using water as a heat exchange source with the refrigerant flowing in the outdoor heat exchanger 230, the embodiments may be applied to a geothermal heat type air conditioner using geothermal heat as a heat exchange source. The geothermal heat type air conditioner is buried underground or under surface water, such as a lake or a river, so as to exchange heat with heat source water, and has the same configuration as that of the water cooling type air conditioner except that the geothermal heat type air conditioner uses geothermal heat as the heat exchange.
FIG. 3 is a control block diagram of the air conditioner in accordance with the embodiment.
The outdoor unit 200 and the indoor unit 100 include sensor units 101 and 201, control units 102 and 202, storage units 103 and 203, communication units 105 and 205, and driving units 104 and 204, respectively.
The sensor unit 201 of the outdoor unit 200 includes the refrigerant high pressure sensor 241, the refrigerant low pressure sensor 242, and the temperature sensor 243. The refrigerant high pressure sensor 241 is installed at the outlet side of the compressor 260, and measures a high pressure of the refrigerant discharged from the compressor 260. The refrigerant low pressure sensor 242 is installed at the inlet side of the compressor 260, and measures a low pressure of the refrigerant inhaled into the compressor 260. The temperature sensor 243 is installed at the inlet side of the compressor 260, and measures a temperature of the refrigerant.
The control unit 202 of the outdoor unit 200 controls the pressure of the refrigerant of the outdoor unit 200 in a designated high pressure range during a cooling operation. The control unit 202 of the outdoor unit 200 controls an opening degree of the outdoor expansion valve 280 according to data regarding the high pressure of the refrigerant transmitted from the refrigerant high pressure sensor 241 during the cooling operation, thus maintaining the high pressure of the refrigerant at a designated level. The control unit 202 of the outdoor unit 200 detects the high pressure of the refrigerant discharged from the compressor 260 through the refrigerant high pressure sensor 241, and decreases the opening degree of the outdoor expansion valve 280, if the high pressure of the refrigerant is lower than a reference pressure, thus raising the high pressure of the refrigerant. If the opening degree of the outdoor expansion valve 280 is decreased, an amount of the refrigerant discharged from the outdoor heat exchanger 230 to a receiver 290 is decreased, and thus an amount of the refrigerant between the compressor 260 and the outdoor heat exchanger 230 is increased and the pressure of the refrigerant at the outlet side of the compressor 260 is raised.
The control unit 202 of the outdoor unit 200 detects the high pressure of the refrigerant discharged from the compressor 260 through the refrigerant high pressure sensor 241, and transmits a high pressure gas of the compressor 260 to the receiver 290, if the high pressure of the refrigerant is lower than the reference pressure. When the high pressure gas is supplied to the receiver 290, the pressure of the refrigerant is output from the receiver 290 to the indoor units 100 is raised, thus preventing lowering of the performance of the indoor units 100.
The control unit 202 of the outdoor unit 200 controls the pressure of the refrigerant of the outdoor unit 200 in a designated low pressure range during a heating operation. The control unit 202 of the outdoor unit 200 controls the opening degree of the outdoor expansion valve 280 according to data regarding the low pressure of the refrigerant transmitted from the refrigerant low pressure sensor 242 during the heating operation, thus maintaining the low pressure of the refrigerant at a designated level. The control unit 202 of the outdoor unit 200 detects the low pressure of the refrigerant discharged from the compressor 260 using the refrigerant low pressure sensor 242, and decreases the opening degree of the outdoor expansion valve 280, if the low pressure of the refrigerant is higher than a reference pressure, and thus lowers the low pressure of the refrigerant. If the opening degree of the outdoor expansion valve 280 is decreased, an amount of the refrigerant flowing from the receiver 290 to the outdoor heat exchanger 230 is decreased, and thus an amount of the refrigerant flowing through the indoor heat exchangers 230 to the accumulator 264 is decreased and the pressure of the refrigerant at the inlet side of the compressor 260 is lowered.
The control unit 202 of the outdoor unit 200 adjusts a superheat degree of the inhaled refrigerant of the compressor 260 according to the data regarding the low pressure of the refrigerant transmitted from the refrigerant low pressure sensor 242 during the heating operation, thus controlling the opening degree of the outdoor expansion valve 280. The superheat degree of the inhaled refrigerant of the compressor 260 is obtained by Expression 1 below.
Superheat Degree of Inhaled Refrigerant=Temperature of Inhaled Refrigerant−Saturation Temperature of Inhaled Refrigerant Expression 1
In Expression 1, the temperature of the inhaled refrigerant is measured by the temperature sensor 243 installed at the inlet side of the compressor 260, and the saturation temperature of the inhaled refrigerant is determined by the pressure of the refrigerant measured by the refrigerant low pressure sensor 242 installed at the inlet side of the compressor 260. Saturation temperatures according to pressures of the refrigerant are stored in advance in the storage unit 203. For example, when the pressure of the refrigerant measured by the refrigerant low pressure sensor 242 is 7 kg/cm², the saturation temperature corresponding to this pressure which is stored in advance in the storage unit 203 is about 0° C. Hereinafter, a method of controlling the opening degree of the outdoor expansion valve 280 by adjusting the superheat degree of the inhaled refrigerant will be described.
The control unit 202 of the outdoor unit 200 detects the low pressure of the refrigerant inhaled into the compressor 260 using the refrigerant low pressure sensor 242, and increases the superheat degree of the inhaled refrigerant, if the low pressure of the refrigerant is higher than the reference pressure. In order to increase the superheat degree of the inhaled refrigerant of the compressor 260, the opening degree of the outdoor expansion valve 280 is decreased. If the opening degree of the outdoor expansion valve 280 is decreased, the amount of the refrigerant flowing from the receiver 290 to the outdoor heat exchanger 230 is decreased, the refrigerant greatly exchanges heat in the outdoor heat exchanger 230 and thus the temperature of the refrigerant is raised, and the refrigerant having the raised temperature flows to the compressor 260 via the accumulator 264. During this process, the temperature of the inhaled refrigerant of the compressor 260 is raised, and thus the superheat degree of the inhaled refrigerant of the compressor 260 is increased with reference to Expression 1. Further, if the opening degree of the outdoor expansion valve 280 is decreased, the pressure of the inhaled refrigerant of the compressor 260 is lowered through the above-described process, and thus the pressure of the refrigerant measured by the refrigerant low pressure sensor 242 installed at the inlet side of the compressor 260 may be lowered.
The storage unit 203 of the outdoor unit 200 stores saturation temperatures according to pressures of the refrigerant.
The communication unit 205 of the outdoor unit 200 receives data transmitted from the indoor units 100, or transmits data to the indoor units 100.
The driving unit 204 of the outdoor unit 200 drives the compressor 260 and the outdoor expansion valve 280 under the control of the control unit 202.
The sensor unit 101 of the indoor unit 100 includes temperature sensors 161 and 162. The temperature sensors 161 and 162 of the sensor unit 101 are installed at inlet side and outlets of the indoor heat exchanger 120, and measure the temperature of the refrigerant.
The control unit 102 of the indoor unit 100 controls an opening degree of the indoor expansion valve 140 according to data regarding the high pressure of the refrigerant transmitted from the communication unit 205 of the outdoor unit 200 during the cooling operation, thus maintaining the high pressure of the refrigerant of the outdoor unit 200 at a designated level. The communication unit 105 of the indoor unit 100 receives data transmitted from the outdoor unit 200 through the communication unit 205, and the control unit 102 of the indoor unit 100 controls the opening degree of the indoor expansion valve 140 according to the data transmitted from the outdoor unit 200. If the opening degree of the indoor expansion valve 140 is decreased, an amount of the refrigerant input to the indoor unit 100 is decreased, and if the amount of the refrigerant input to the indoor unit 100 is decreased, an amount of the refrigerant staying in the outdoor unit 200 is increased and thus the pressure of the refrigerant of the outdoor unit 200 is raised.
The control unit 102 of the indoor unit 100 adjusts a superheat degree of the indoor unit 100 according to the superheat degree of the inhaled refrigerant of the compressor 260, transmitted from the communication unit 205 of the outdoor unit 200, thus maintaining the pressure of the refrigerant of the outdoor unit 200 at a designated high pressure. The superheat degree of the inhaled refrigerant of the compressor 260 is obtained by Expression 1, which is described above, and the superheat degree of the indoor unit 100 is obtained by Expression 2, below.
Superheat Degree of Indoor Unit=Temperature of Outlet of Indoor Heat Exchanger−Temperature of Inlet of Indoor Heat Exchanger Expression 2
In Expression 2, the outlet of the indoor heat exchanger 120 means a side surface of the indoor heat exchanger 120 through which the refrigerant is discharged to the outside of the indoor heat exchanger 120 during the cooling operation, and the inlet of the indoor heat exchanger 120 means a side surface of the indoor heat exchanger through which the refrigerant is introduced into the indoor heat exchanger 120 during the cooling operation. Hereinafter, a method of adjusting the pressure of the refrigerant of the outdoor unit 200 to a designated high pressure by adjusting the superheat degree of the indoor unit 100 according to the superheat degree of inhaled refrigerant of the compressor 260 will be described in detail.
If the superheat degree of the inhaled refrigerant of the compressor 260 during the cooling operation is lowered, the control unit 202 of the outdoor unit 200 transmits designated data to the control unit 102 of the indoor unit 100, thus increasing the superheat degree of the indoor unit 100. In order to increase the superheat degree of the indoor unit 100, the opening degree of the indoor expansion valve 140 needs to be decreased. If the opening degree of the indoor expansion valve 140 is decreased, the amount of the refrigerant introduced into the indoor heat exchanger 120 is decreased, and if the amount of the refrigerant introduced into the indoor heat exchanger 120 is decreased, the refrigerant greatly exchanges heat in the indoor heat exchanger 120 and thus is discharged through the outlet of the indoor heat exchanger 120 under the condition that the temperature of the refrigerant is more increased than that of the refrigerant if the amount of the refrigerant is increased. (During the cooling operation, the temperature of the outlet side of the indoor heat exchanger is higher than the temperature of the inlet side of the indoor heat exchanger). With reference to Expression 2, it is understood that the temperature of the outlet of the indoor heat exchanger 120 is more raised and thus the superheat degree of the indoor unit 100 is increased. Further, since the temperature of the refrigerant transmitted from the indoor unit 100 to the outdoor unit 200 is raised, the temperature of the refrigerant flowing to the inlet side of the compressor 260 is raised, and thereby the superheat degree of the inhaled refrigerant of Expression 1 is increased.
On the other hand, with reference to Expression 1, it is understood that the reason why the superheat degree of the inhaled refrigerant is lowered is that the temperature of the inhaled refrigerant is lowered or the saturation temperature of the inhaled refrigerant is raised. Hereinafter, the saturation temperature of the inhaled refrigerant has a much smaller variation than that of the temperature of the inhaled refrigerant, and thus a case that the temperature of the inhaled refrigerant is lowered will be exemplarily described.
The temperature of the inhaled refrigerant is lowered, if the amount of the refrigerant transmitted from the indoor heat exchanger 120 to the outdoor unit 200 is large (the large amount of the refrigerant causing poor evaporation), or if the refrigerant having poorly exchanged heat due to load abnormality of the indoor heat exchanger 120 is transmitted to the outdoor unit 200. In case of the former, the refrigerant of the outdoor unit 200 may be in a high pressure state already (or may be in a low pressure state), and in case of the latter, the pressure of the refrigerant of the outdoor unit 200 may be in a high pressure state or a low pressure state. Thereby, the control unit 102 of the indoor unit 100 may adjust the superheat degree of the indoor unit 100 to a high level, if the pressure of the refrigerant of the outdoor unit 200 is low and the superheat degree of the inhaled refrigerant of the compressor 260 is low. If the superheat degree of the indoor unit 100 is adjusted to the high level, as described above, the opening degree of the indoor expansion valve 140 is decreased, and if the opening degree of the indoor expansion valve 140 is decreased, an amount of the refrigerant staying in the outdoor unit 200 is increased and thus the pressure of the refrigerant of the outdoor unit 200 is raised. On the other hand, if the pressure of the refrigerant of the outdoor unit 200 is high, the superheat degree of the inhaled refrigerant of the compressor 260 may be increased by increasing the superheat degree of the indoor unit 100. Here, the pressure of the refrigerant of the outdoor unit 200 may be further raised by decreasing the opening degree of the indoor expansion valve 140, but is generally adjusted by a separate control method.
The communication unit 105 of the indoor unit 100 receives data transmitted from the outdoor unit 200, or transmits data to the communication unit 205 of the outdoor unit 200.
The storage unit 103 of the indoor unit 100 stores various data used to operate the indoor unit 100. The storage unit 103 of the indoor unit 100 stores the superheat degree to be adjusted according to the superheat degree of the inhaled refrigerant of the compressor 260. The driving unit 104 of the indoor unit 100 drives the indoor expansion valve 140 and so on.
FIG. 4 is a flow chart illustrating a method of maintaining high pressure of a refrigerant by controlling an opening degree of an outdoor expansion valve during the cooling operation of an air conditioner in accordance with one embodiment.
When the cooling operation is started, the control unit 202 of the outdoor unit 200 adjusts the opening degree of the outdoor expansion valve 280 to S₁(operation 500).
Thereafter, the control unit 202 of the outdoor unit 200 receives data regarding the high pressure of the refrigerant transmitted from the refrigerant high pressure sensor 241 installed at the refrigerant outlet side of the compressor 260 (operation 501).
Thereafter, the control unit 202 of the outdoor unit 200 compares the high pressure P_hof the refrigerant measured during operation 501 with a first reference pressure P₁(operation 502), and adjusts the opening degree of the outdoor expansion valve 280 to S₂, if the high pressure P_hof the refrigerant is lower than the first reference pressure P₁(operation 503). That is, the control unit 202 of the outdoor unit 200 decreases the opening degree of the outdoor expansion valve 280, thereby raising the pressure of the refrigerant of the outdoor unit 200.
On the other hand, the control unit 202 of the outdoor unit 200 compares the high pressure P_hof the refrigerant with a second reference pressure P₂, if the high pressure P_hof the refrigerant is higher than the first reference pressure P₁(operation 504), and adjusts the opening degree of the outdoor expansion valve 280 to S₃, if the high pressure P_hof the refrigerant is higher than the second reference pressure P₂(operation 505). That is, the control unit 202 of the outdoor unit 200 increases the opening degree of the outdoor expansion valve 280, thereby lowering the pressure of the refrigerant of the outdoor unit 200.
Further, the control unit 202 of the outdoor unit 200 maintains the opening degree of the outdoor expansion valve 280 to S₁, if the high pressure P_hof the refrigerant is lower than the second reference pressure P₂(operation 506), and then the process is fed back to operation 500.
Here, S₁, S₂, and S₃represent opening degrees of the outdoor expansion valve 280, and for example, satisfy an equation of S₂<S₁<S₃. Further, the control unit 202 of the outdoor unit 200 judges that air conditioner reaches a normal state, when an equation of P₁<P_h<P₂is satisfied.
FIG. 5 is a flow chart illustrating a method of maintaining low pressure of a refrigerant by controlling an opening degree of an outdoor expansion valve during a heating operation of an air conditioner in accordance with another embodiment.
When the heating operation is started, the control unit 202 of the outdoor unit 200 adjusts the opening degree of the outdoor expansion valve 280 to SH₁. The adjustment of the opening degree of the outdoor expansion valve 280 to SH₁means adjustment of the opening of the outdoor expansion valve 280 according to the superheat degree of the inhaled refrigerant of the compressor 260. That is, the control unit 202 of the outdoor unit 200 adjusts the opening degree of the outdoor expansion valve 280 according to the superheat degree of the inhaled refrigerant of the compressor 260 (operation 510).
Thereafter, the control unit 202 of the outdoor unit 200 receives data regarding the low pressure of the refrigerant transmitted from the refrigerant low pressure sensor 242 installed at the refrigerant inlet side of the compressor 260. The refrigerant low pressure sensor 242 is a pressure sensor mounted at the inlet side of the compressor 260 (operation 511).
Thereafter, the control unit 202 of the outdoor unit 200 compares the low pressure P_Lof the refrigerant measured during operation 511 with a third reference pressure P₃(operation 512), and maintains or adjusts the opening degree of the outdoor expansion valve 280 to SH₁, if the low pressure P_Lof the refrigerant is lower than the third reference pressure P₃(operation 514).
On the other hand, the control unit 202 of the outdoor unit 200 compares the low pressure P_Lof the refrigerant measured during operation 511 with a fourth reference pressure P₄, if the low pressure P_Lof the refrigerant is higher than the third reference pressure P₃(operation 513), and adjusts the opening degree of the outdoor expansion valve 280 to SH₂(for example, adjusts the opening degree of the outdoor expansion valve 280 according to superheat of 10° C.), if the low pressure P_Lof the refrigerant is lower than the fourth reference pressure P₄(operation 515). That is, the control unit 202 of the outdoor unit 200 decreases the opening degree of the outdoor expansion valve 280, thereby lowering the pressure of the refrigerant of the outdoor unit 200.
Further, the control unit 202 of the outdoor unit 200 adjusts the opening degree of the outdoor expansion valve 280 to SH₃(for example, adjusts the opening degree of the outdoor expansion valve 280 according to superheat of 15° C.), if the low pressure P_Lof the refrigerant measured during operation 511 is lower than the fourth reference pressure P₄(operation 513 and operation 516).
Here, SH₁, SH₂, and SH₃mean target superheat degrees to adjust the opening degree of the outdoor expansion valve 280, and for example, satisfy an equation of SH₁<SH₂<SH₃.
FIG. 6 is a flow chart illustrating a method of maintaining high pressure of a refrigerant by controlling an opening degree of an indoor expansion valve during a cooling operation of an air conditioner in accordance with another embodiment.
When the cooling operation is started, the control unit 102 of the indoor unit 100 adjusts the opening degree of the indoor expansion valve 140 to ID_SH₁. ID_SH₁(Indoor_Super Heat1) means a target superheat to control the opening degree of the indoor expansion valve 140. For example, the adjustment of the opening degree of the indoor expansion valve 140 to ID_SH₁is achieved by adjusting the opening degree of the indoor expansion valve 140 to control superheat of 2° C. of the indoor unit 100 (operation 520).
Thereafter, the control unit 102 of the indoor unit 100 receives data regarding the high pressure of the refrigerant at the outlet side of the compressor 260, transmitted from the communication unit 205 of the outdoor unit 200 (operation 521).
Thereafter, the control unit 102 of the indoor unit 100 compares the high pressure P_hof the refrigerant with a fifth reference pressure P₅(operation 522), and adjusts the opening degree of the indoor expansion valve 140 to ID_SH₂, if the high pressure P_hof the refrigerant is lower than the fifth reference pressure P₅(operation 523). That is, the control unit 102 of the indoor unit 100 decreases the opening degree of the indoor expansion valve 140, thereby raising the pressure of the refrigerant of the outdoor unit 200.
On the other hand, the control unit 102 of the indoor unit 100 maintains or adjusts the opening degree of the indoor expansion valve 140 to ID_SH₁, if the high pressure P_hof the refrigerant transmitted from operation 521 is higher than the fifth reference pressure P₅, and the process is fed back to operation 521 (operation 522 and operation 524).
Here, ID_SH₁and ID_SH₂mean target superheat degrees to control the opening degree of the indoor expansion valve 140, and for example, satisfy an equation of ID_SH₁<ID_SH₂.
FIG. 7 is a flow chart illustrating a method of adjusting a superheat degree of an inhaled refrigerant of a compressor by controlling a superheat degree of an indoor unit during a cooling operation of an air conditioner in accordance with another embodiment.
When the cooling operation is started, the control unit 102 of the indoor unit 100 adjusts the opening degree of the indoor expansion valve 140 to ID_SH₃. ID_SH₃(Indoor_Super Heat3) represents the opening degree of the indoor expansion valve 140 according to the superheat degree of the indoor unit 100. For example, ID_SH₃represents the opening degree of the indoor expansion valve 140 according to superheat of 4° C. of the indoor unit 100 (operation 530).
Thereafter, the communication unit 105 of the indoor unit 100 receives data regarding the superheat degree of the inhaled refrigerant of the compressor 260, transmitted from the communication unit 205 of the outdoor unit 200 (operation 531).
Therefore, the control unit 102 of the indoor unit 100 compares the superheat degree of the inhaled refrigerant of the compressor 260 with a first reference value (operation 532), and maintains or adjusts the opening degree of the indoor expansion valve 140 to ID_SH₃, if the superheat degree of the inhaled refrigerant is lower than the first reference pressure value (operation 534). When the superheat degree of the inhaled refrigerant of the compressor 260 is low, the opening degree of the indoor expansion valve 140 is maintained or adjusted to a low value and thus an amount of the refrigerant transmitted to the outdoor unit 200 is decreased. When the amount of the refrigerant transmitted to the outdoor unit 200 is decreased, the refrigerant greatly exchanges heat in the indoor heat exchanger 120, as described above, and when the refrigerant greatly exchanges heat in the indoor heat exchanger 120, the temperature of the refrigerant transmitted to the inlet side of the compressor 260 is raised, and thus the superheat degree of the inhaled refrigerant of the compressor 260 is raised
On the other hand, the control unit 102 of the indoor unit 100 compares the superheat degree of the inhaled refrigerant of the compressor 260 with a second reference value, if the superheat degree of the inhaled refrigerant of the compressor 260 is higher than the second reference pressure value (operation 533). The control unit 102 of the indoor unit 100 maintains or adjusts the opening degree of the indoor expansion valve 140 to ID_SH₄, if the superheat degree of the inhaled refrigerant of the compressor 260 is lower than the second reference pressure value (operation 535). ID_SH₄represents a state in which the opening degree of the indoor expansion valve 140 according to the control of the superheat degree is lower than that of than ID_SH₃.
Further, the control unit 102 of the indoor unit 100 maintains or adjusts the opening degree of the indoor expansion valve 140 to ID_SH₅, if the superheat degree of the inhaled refrigerant of the compressor 260 is higher than the second reference pressure value (operation 536). ID_SH₅represents a state in which the opening degree of the indoor expansion valve 140 according to the control of the superheat degree is lower than that of ID_SH₄.
The embodiment of FIG. 7, which illustrates control of the superheat degree of the refrigerant inhaled into the compressor 260 by adjusting the superheat degree of the indoor unit 100, may be carried out together with the embodiments of FIGS. 4 to 6.
Although the above embodiments separately illustrate control of the opening degree of the indoor expansion valve 140 and control of the opening degree of the outdoor expansion valve 280, control of the opening degree of the indoor expansion valve 140 and control of the opening degree of the outdoor expansion valve 280 may be simultaneously performed by the control unit 202 of the outdoor unit 200 and the control unit 102 of the indoor unit 100.
As is apparent from the above description, in an air conditioner and a control method thereof in accordance with one embodiment, the pressure of a refrigerant of an outdoor unit is maintained at a regular level during a heating operation or a cooling operation, thereby obtaining reliability in operation of the air conditioner.
Although a few embodiments have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the embodiments, the scope of which is defined in the claims and their equivalents.

Claims

1. A control method of an air conditioner, which has an outdoor unit including a compressor and an outdoor expansion valve, and an indoor unit including an indoor expansion valve, comprising:

measuring a pressure of a refrigerant discharged from the compressor during a cooling operation; and

raising the pressure of the refrigerant to be higher than a designated pressure by controlling an opening degree of at least one of the outdoor expansion valve and the indoor expansion valve, if the pressure of the refrigerant is lower than the designated pressure.

2. The control method according to claim 1, wherein the opening degree of the indoor expansion valve is controlled by adjusting a target superheat degree of the indoor unit, if the pressure of the refrigerant is lower than the designated pressure.

3. The control method according to claim 2, wherein the opening degree of the indoor expansion valve is decreased by raising the target superheat degree of the indoor unit, if the pressure of the refrigerant is lower than the designated pressure.

4. The control method according to claim 1, wherein the pressure of the refrigerant is raised to be higher than the designated pressure by decreasing the opening degree of the at least one of the outdoor expansion valve and the indoor expansion valve, if the pressure of the refrigerant is lower than the designated pressure.

5. The control method according to claim 1, wherein:

the outdoor unit further includes a receiver; and

the pressure of the refrigerant transmitted to the indoor unit is raised by transmitting high-pressure gas discharged from the compressor to the receiver, if the pressure of the refrigerant is lower than the designated pressure.

6. The control method according to claim 1, wherein:

a superheat degree of the refrigerant transmitted to an inlet side of the compressor is detected; and

the superheat degree of the refrigerant transmitted to the inlet side of the compressor is raised by decreasing the opening degree of the indoor expansion valve, if the superheat degree is lower than a designated reference.

7. A control method of an air conditioner, which has an outdoor unit including a compressor and an outdoor expansion valve, and an indoor unit including an indoor expansion valve, comprising:

measuring a pressure of a refrigerant inhaled into the compressor during a heating operation; and

lowering the pressure of the refrigerant to be lower than a designated pressure by controlling an opening degree of the outdoor expansion valve, if the pressure of the refrigerant is higher than the designated pressure.

8. The control method according to claim 7, wherein an amount of the refrigerant flowing in a direction of inhaling the refrigerant into the compressor is decreased by decreasing the opening degree of the outdoor expansion valve, if the pressure of the refrigerant is higher than the designated pressure.

9. The control method according to claim 7, wherein the opening degree of the outdoor expansion valve is controlled by adjusting a superheat degree of the indoor unit.

10. An air conditioner comprising:

a pressure sensor installed at a refrigerant outlet side of a compressor to measure a pressure of a refrigerant; and

a control unit of an outdoor unit to raise the pressure of the refrigerant to be higher than a designated pressure by controlling an opening degree of an outdoor expansion valve, if the pressure of the refrigerant is lower than the designated pressure during a cooling operation.

11. The air conditioner according to claim 10, wherein the control unit of the outdoor unit raises the pressure of the refrigerant to be higher than the designated pressure by decreasing the opening degree of the outdoor expansion valve, if the pressure of the refrigerant is lower than the designated pressure.

12. The air conditioner according to claim 10, further comprising a control unit of an indoor unit to raise the pressure of the refrigerant to be higher than a designated pressure by controlling an opening degree of the indoor expansion valve, if the pressure of the refrigerant is lower than the designated pressure.

13. The air conditioner according to claim 12, wherein the control unit of the indoor unit raises the pressure of the refrigerant to be higher than the designated pressure by decreasing the opening degree of the indoor expansion valve, if the pressure of the refrigerant is lower than the designated pressure.

14. The air conditioner according to claim 13, wherein the control unit of the indoor unit decreases the opening degree of the indoor expansion valve by adjusting a target superheat degree of the indoor unit.

15. The air conditioner according to claim 14, wherein the control unit of the indoor unit decreases the opening degree of the indoor expansion valve by raising the target superheat degree of the indoor unit.

16. The air conditioner according to claim 10, further comprising:

a pressure sensor installed at a refrigerant inlet side of the compressor to measure the pressure of the refrigerant; and

a control unit of an indoor unit to receive data regarding the pressure of the refrigerant from the pressure sensor, installed at the refrigerant inlet side of the compressor, during a heating operation, and to adjust the pressure of the refrigerant to be lower than a designated pressure by controlling a target superheat degree of the refrigerant inhaled into the compressor, if the pressure of the refrigerant is higher than the designated pressure.