EP2006615A2

EP2006615A2 - Multi air-conditioner for simultaneously cooling/heating room air and method for controlling the same

Info

Publication number: EP2006615A2
Application number: EP20080150592
Authority: EP
Inventors: Sung Goo Kim
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2007-06-22
Filing date: 2008-01-24
Publication date: 2008-12-24
Also published as: KR20080112670A; CN101329093B; EP2006615A3; KR101176635B1; CN101329093A

Abstract

A multi air-conditioner (100) for simultaneously cooling/heating room air and a method for controlling the same are disclosed. The multi air-conditioner for simultaneously cooling/heating room air includes: a high-pressure gas pipe (410), a low-pressure gas pipe (430), and a liquid line (420), which are connected between at least one outdoor unit (200) and a plurality of cooling/heating switching sets (300); a flow-regulating valve (260) mounted to a bypass pipe (250) connected between the high-pressure gas pipe (410) and the liquid pipe (420); and a controller (500) for increasing an opening degree of the flow-regulating valve, if a heating rate is not below a reference rate during a heating-biased operation and is equal to or less than a required cooling capacity of an indoor cooling unit during the heating-biased operation.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 2007-0061375, filed on June 22, 2007 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multi air-conditioner for simultaneously cooling/heating room air and a method for controlling the same, and more particularly to a multi air-conditioner for simultaneously cooling/heating room air and a method for controlling the same, which prevents a compressor from being excessively operated during the heating-biased operation in which heating capacity is greater than cooling capacity, prevents a refrigerant from being stagnated in an outdoor heat-exchanger, and prevents the refrigerant from being frozen in an indoor heat-exchanger.

2. Description of the Related Art

Generally, the air-conditioner has been widely used to cool or heat the room air via the cooling cycle. Recently, a multi air-conditioner composed of not only a single outdoor unit for effectively cooling/heating the air of several rooms but also several indoor units installed at individual rooms has been developed and come into the market.
However, although some rooms require the cooling operation and the remaining rooms require the heating operation, the above-mentioned multi air-conditioner has been designed to perform only one of the heating and cooling operations, so that the individual rooms cannot be properly heated or cooled.
In order to solve the above-mentioned problems, an improved multi air-conditioner capable of simultaneously cooling/heating the room air has been recently developed, which controls the indoor units installed in some rooms to perform the heating operation and controls the other indoor units installed in the other rooms to perform the cooling operation.
During a heating-biased operation in which heating-capacity rate is higher than the cooling-capacity rate, the multi air-conditioner for simultaneously cooling/heating the room air controls the high-pressure gas refrigerant compressed by the compressor to be applied to the cooling/heating conversion unit via the high-pressure gas pipe. The high-pressure gas refrigerant applied to the cooling/heating conversion unit is applied to the heat-exchanger of the heating indoor unit in which the heating valve is open. The high-pressure gas refrigerant applied to the heat-exchanger of the heating indoor unit is heat-exchanged with the room air, so that it is changed to the liquid refrigerant and the liquid refrigerant is discharged to the outside. Some parts of the liquid refrigerant discharged from the heating indoor unit flow in the outdoor unit along the liquid pipe, and the remaining parts flow in the indoor cooling unit performing the cooling operation.
However, the liquid refrigerant may be excessively applied to the outdoor unit during the heating-biased operation, and the liquid refrigerant applied to the indoor cooling unit may be insufficient, so that the cooling capacity of the indoor cooling unit is deteriorated.
A representative example for solving the above-mentioned problems has been disclosed in Korean Patent Laid-open Publication N0. 2005-0005089 , which is hereby incorporated by reference.
According to the above-mentioned Korean Patent Laid-open Publication No. 2005-0005989 , if the conventional multi air-conditioner performs the heating-biased operation, some parts of the high-pressure gas refrigerant flowing in the high-pressure gas pipe are applied to the liquid pipe via the bypass pipe, restrain the refrigerant flowing in the outdoor heat-exchanger, and increase the amount of the refrigerant flowing in the indoor cooling unit, so that the cooling capacity of the indoor cooling unit increases.
However, the above-mentioned conventional multi air-conditioner allows some parts of the refrigerant flowing in the high-pressure gas pipe to be applied to the liquid pipe, so that the inner pressure of the high-pressure gas pipe is reduced. In order to compensate for the lowered inner pressure of the high-pressure gas pipe, the compressor is driven with a large compression capacity, so that the power consumption of the conventional multi air-conditioner increases and the effectiveness of the conventional multi air-conditioner is deteriorated.
According to the conventional multi air-conditioner, the outdoor heat-exchanger is used as an evaporator although the air temperature of the outside at which the outdoor unit is installed is low, so that the inner pressure of the outdoor heat-exchanger is lowered. Also, the inner pressure of the low-pressure gas pipe connected to the outdoor heat-exchanger and the inner pressure of the indoor heat-exchanger connected to the low-pressure gas pipe are lowered, and the refrigerant temperature of the indoor heat-exchanger is lowered, so that the dew on the indoor heat-exchanger is unavoidably frozen due to the lowered temperature of the refrigerant.

SUMMARY OF THE INVENTION

Therefore, it is an aspect of the invention to provide a multi air-conditioner for simultaneously cooling/heating the room air, which prevents the high-pressure refrigerant from being bypassed during the heating-biased operation, so that it prevents the compressor from being excessively driven, resulting in reduction of power consumption.
It is another aspect of the invention to provide a multi air-conditioner for simultaneously cooling/heating the room air, in which, if the heating-capacity rate is less than the reference rate and the air temperature detected at the outside including the outdoor unit is low, the multi air-conditioner prevents the outdoor heat-exchanger from being used as an evaporator, and prevents the saturation pressure of the outdoor heat-exchanger from being less than the inner pressure of the low-pressure gas pipe. As a result, the multi air-conditioner prevents the refrigerant from being liquefied/stagnated in the outdoor heat-exchanger, and prevents the inner pressure of the outdoor heat-exchanger from being excessively lowered, so that it prevents the refrigerant from being frozen in the inner heat-exchanger.
Additional aspects and/or advantages of the invention 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 invention.
In accordance with the invention, the above and/or other aspects can be achieved by the provision of a multi air-conditioner for simultaneously cooling/heating room air comprising: a high-pressure gas pipe, a low-pressure gas pipe, and a liquid line, which are connected between at least one outdoor unit and a plurality of cooling/heating switching sets; a flow-regulating valve mounted to a bypass pipe connected between the high-pressure gas pipe and the liquid pipe; and a controller for increasing an opening degree of the flow-regulating valve, if a heating rate is not below a reference rate during a heating-biased operation and is equal to or less than a required cooling capacity of a indoor cooling unit during the heating-biased operation.
Preferably, the multi air-conditioner further comprises: an outdoor expansion valve and an outdoor ventilation fan, and the controller for performing a superheat control using the outdoor expansion valve, performing a low-pressure control using the outdoor ventilation fan, and performing the opening degree of the flow-regulating valve according to an average opening-degree of the indoor cooling unit.
In accordance with another aspect of the present invention, there is provided a multi air-conditioner for simultaneously cooling/heating room air comprising: an outdoor temperature sensor for detecting an outdoor temperature; a low-pressure sensor for detecting an internal pressure of the low-pressure gas pipe; and a controller for calculating a saturation pressure of an outdoor heat-exchanger on the basis of an outdoor temperature detected by the outdoor temperature sensor, calculating a refrigerant stagnation pressure using pressure detected by the low-pressure sensor, comparing the saturation pressure with the refrigerant stagnation pressure, and performing a first operation for improving a cooling/heating capacity or a second operation for preventing a refrigerant from being stagnated.
Preferably, the multi air-conditioner further comprises: a flow-regulating valve mounted to a bypass pipe connected between a high-pressure gas pipe and a liquid pipe, a cutoff valve for blocking a refrigerant moving to an outdoor heat-exchanger, and an outdoor ventilation fan, wherein, during the first operation for improving the cooling/heating capacity, the controller for blocking the flow-regulating valve and the cutoff valve during the first operation for improving the cooling/heating capacity, and at the same time stopping the outdoor ventilation fan.
Preferably, the multi air-conditioner further comprises: a flow-regulating valve mounted to a bypass pipe connected between a high-pressure gas pipe and a liquid pipe, a cutoff valve for blocking a refrigerant moving to an outdoor heat-exchanger, and an outdoor ventilation fan, wherein, during the second operation for preventing the refrigerant from being stagnated, the controller for opening the flow-regulating valve and the cutoff valve and stopping the outdoor ventilation fan, detecting a low pressure, increasing an opening degree of an outdoor electric expansion valve if the detected low pressure is not higher than a cooling-capacity optimization pressure, and reducing the opening degree of the outdoor electric expansion valve if the detected low pressure is higher than the cooling-capacity optimization pressure.
In accordance with yet another aspect of the present invention, there is provided a method for controlling a multi air-conditioner capable of simultaneously cooling/heating room air comprising: determining whether a heating-capacity rate is equal to or higher than a reference rate during a heating-biased operation; and if the heating-capacity rate is equal to or higher than the reference rate during the heating-biased operation, and regulating a flow of a high-pressure gas which flows from a high-pressure gas pipe to a liquid pipe.
Preferably, the regulating of the flow includes: performing a superheat control by regulating an opening degree of an outdoor electric expansion valve, performing a low-pressure control by regulating an air-volume of an outdoor ventilation fan, and at the same time opening a cutoff valve.
Preferably, the regulating of the flow includes: calculating an average opening-degree of an indoor electric expansion valve of a indoor cooling unit; and reducing the flow if the calculated average opening-degree is not higher than a reference opening-degree, and increasing the flow if the calculated average opening-degree is higher than the reference opening-degree.
In accordance with yet another aspect of the present invention, there is provided a method for controlling a multi air-conditioner capable of simultaneously cooling/heating room air comprising: determining whether a heating-capacity rate is equal to or higher than a reference rate during a heating-biased operation; and if the heating-capacity rate is less than the reference rate, performing an operation for preventing a refrigerant from being stagnated when a saturation pressure of an outdoor heat-exchanger is less than a refrigerant stagnation pressure of a low-pressure gas pipe, and performing an operation for guaranteeing a cooling/heating-capacity when the saturation pressure of the outdoor heat-exchanger is not less than the refrigerant stagnation pressure of the low-pressure gas pipe.
Preferably, the operation for guaranteeing the cooling/heating-capacity includes: closing a flow-regulating valve and a cutoff valve, and stopping an outdoor ventilation fan; and calculating an average outlet temperature of a heating indoor unit, increasing an opening degree of the flow-regulating valve when an average outlet temperature of the heating indoor unit is less than an optimum temperature, and reducing the opening degree of the flow-regulating valve when the average outlet temperature of the heating indoor unit is not less than the optimum temperature.
Preferably, the operation for preventing the refrigerant from being stagnated includes: closing a flow-regulating valve and a cutoff valve, and stopping an outdoor ventilation fan; and reducing an opening degree of an outdoor electric expansion valve when a low pressure of the low-pressure gas pipe is higher than a cooling-capacity optimization pressure, and increasing the opening degree of the outdoor electric expansion valve when the low pressure of the low-pressure gas pipe is not higher than the cooling-capacity optimization pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention 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 shows passages of a multi air-conditioner for simultaneously cooling/heating room air according to the present invention;
FIG. 2 is a block diagram illustrating a system for controlling a multi air-conditioner for simultaneously cooling/heating room air according to the present invention;
FIGS. 3A to 3C are flow charts illustrating a method for controlling a multi air-conditioner for simultaneously cooling/heating room air according to the present invention; and
FIG. 4 shows the status of passages of a multi air-conditioner for simultaneously cooling/heating room air according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below to explain the present invention by referring to the figures.
Referring to FIGS. 1 and 2, the multi air-conditioner 100 for simultaneously cooling/heating room air according to the present invention includes an outdoor unit 200 installed outdoors, a plurality of indoor units 300 installed indoors, a cooling/heating switching unit 400 for allowing the indoor units 300 to perform a cooling or heating operation, and a controller 500 for controlling overall operations of the multi air-conditioner 100.
The outdoor unit 200 includes a compressor 210 for compressing a refrigerant; an outdoor heat-exchanger 220 for performing a heat-exchanging operation between the refrigerant and the outdoor air; a 4-way valve 230 for establishing a heating or cooling cycle according to an operation mode of the multi air-conditioner 100 for simultaneously cooling/heating room air; an accumulator 201 mounted to a suction port of the compressor 210; a low-pressure gas pipe 430 for providing the accumulator 201 with a passage via which the accumulator 201 receives a low-pressure gas refrigerant; an outdoor electric expansion valve 280 connected to one side of the outdoor heat-exchanger 220; a first connector 213 for connecting the other side of the outdoor heat-exchanger 220 to the 4-way valve 230; a second connector 214 for connecting the 4-way valve 230 to the accumulator 201; a third connector 215 for connecting the outdoor heat-exchanger 220 to the outdoor electric expansion valve 280; a receiver tank 202 connected between the outdoor electric expansion valve 280 and the liquid pipe 420; a high-pressure gas pipe 410 connected to the 4-way valve 230 so that the high-pressure gas refrigerant received via the 4-way valve 230 moves to the refrigerant conversion unit 400; a high-pressure branch pipe 204; and a bypass pipe 250 for allowing some high-pressure gas of the high-pressure gas pipe 410 to be bypassed to the liquid pipe 420.
The compressor 210 includes a constant-speed compressor 211 and a variable-speed compressor 212.
The compressor 210 sucks up the low-pressure gas refrigerant from some or all parts of the low-pressure gas pipe 430 and the outdoor heat-exchanger 220 according to operation modes of the multi air-conditioner 100 for simultaneously cooling/heating room air, compresses the sucked refrigerant at a high pressure, and transmits the high-pressure gas refrigerant to some or all parts of the high-pressure gas pipe 410 and the outdoor heat-exchanger 220. The constant-speed compressor 210 is driven by predetermined or fixed compression capacity, and the variable-speed compressor 212 is driven by variable compression capacity according to a control signal of the controller 500.
The accumulator 201 is connected to the suction port of the compressor 210, so that it allows the gas refrigerant to flow in the compressor 210, resulting in guaranteed reliability of the compressor 210.
In other words, the accumulator 201 temporarily stores a liquid refrigerant from among the refrigerant which moves to the compressor 220 via the low-pressure gas pipe 430, and temporarily stores a liquid refrigerant from among the refrigerant received via the second connector 214. Then, if the liquid refrigerant is converted into the gas refrigerant, the accumulator 201 allows the gas refrigerant to be received in the compressor 210. Therefore, the compressor 210 receives only the gas refrigerant, so that it can be reliably and stably operated.
The low-pressure sensor 270 for detecting an inner pressure of the low-pressure gas pipe 430 is connected to a suction port of the compressor 210. The low-pressure sensor 270 detects the inner pressure of the low-pressure gas pipe 430, and transmits the low pressure indicating the inner pressure value of the low-pressure gas pipe 430 to the controller 500.
The outdoor heat-exchanger 220 includes a plurality of heat-exchanger pins and a refrigerant pipe 221. One end of the refrigerant pipe 221 is connected to the first connector 213, and the other end of the refrigerant pipe 221 is connected to the outdoor electric expansion valve 280.
The outdoor ventilation fan 290 is adjacent to the outdoor heat-exchanger 220, so that the outdoor air is compulsorily blown to the outdoor heat-exchanger 220. The outdoor ventilation fan 290 is switched on or off by the controller 500, and its ventilation quantity is also controlled by the controller 500.
The first connector 213 is connected to the second port 230B of the 4-way valve 230. The high-pressure branch pipe 204 branched from the first connector 213 is connected to the high-pressure gas pipe 410, and the high-pressure branch valve 205 is located on the high-pressure branch pipe 204. The high-pressure gas pipe 410 of the high-pressure branch valve 205 is connected to the check valve 206, so that the moving direction of the fluid flowing in the high-pressure branch pipe 204 is unidirectional. The high-pressure branch pipe valve 205 is open when the multi air-conditioner 100 is in the heating-biased operation, so that the high-pressure gas discharged from the compressor 210 is partially applied to the high-pressure gas pipe 410.
The valve 207 connected in parallel to the outdoor electric expansion valve 280 controls the refrigerant discharged from the outdoor heat-exchanger 220 to be selectively floated.
The receiver tank 202 is connected to a connection part between the outdoor electric expansion valve 280 and the liquid pipe 420, so that the quantity of the refrigerant received in the outdoor heat-exchanger 220 becomes constant. As a result, the reliability of the multi air-conditioner 100 for simultaneously cooling/heating the room air is guaranteed.
A cutoff valve 270 is mounted to a part adjacent to the receiver tank 202 in the connection part between the outdoor electric expansion valve 280 and the liquid pipe 420.
The bypass pipe 250 is connected to the liquid pipe 420 located opposite to the receiver tank 202 on the basis of the cutoff valve 270. A flow-regulating valve 260 for regulating a flow rate (i.e., flow) of the refrigerant flowing in the bypass pipe 250 is mounted to the bypass pipe 250. If the flow-regulating valve 260 is open during the heating-biased operation of the multi air-conditioner 100, the refrigerant discharged from the indoor unit 300 conducting the heating operation flows in the indoor unit 300 conducting the cooling operation, so that the cooling capacity of the indoor unit 300 increases.
The 4-way valve 230 includes a first port 230A, a second port 230B, a third port 230C, and a fourth port 230D. The 4-way valve 230 is controlled by the controller 500, so that the compressor 210, the indoor heat-exchangers 302, and the outdoor heat-exchangers 220 form the cooling cycle. In other words, in order to form the cooling-refrigerant cycle, the 4-way valve 230 is controlled by the controller 500 so that the first port 230A is connected to the second port 230B. Therefore, the refrigerant is sequentially applied in the order of the compressor 210 → the outdoor heat-exchanger 220 → the indoor electric expansion valve 304 → the indoor heat-exchanger 302 → the compressor 210.
In order to form the heating-refrigerant cycle, the 4-way valve 230 is controlled by the controller 500, so that the first port 230A is connected to the fourth port 230D. Therefore, the refrigerant is sequentially applied in the order of the compressor 210 → the indoor heat-exchanger 302 → the outdoor electric expansion valve 280 → the outdoor heat-exchanger 220 → the compressor 210.
The outdoor temperature sensor 520 for detecting the temperature of the outdoor air is contained in the outdoor unit 200. The outdoor temperature sensor 520 detects the temperature of the outdoor air, and transmits the value indicating the outdoor-air temperature to the controller 500.
The cooling/heating conversion unit 400 includes a plurality of cooling/heating conversion sets 440 composed of heating valves 441 and cooling valves 442; a first high-pressure gas branch pipe 412 branched from the high-pressure gas pipe 410; a first low-pressure gas branch pipe 432 branched from the low-pressure gas pipe 430; and a first liquid-branch pipe 422 branched from the liquid pipe 420.
In addition, the cooling/heating conversion unit 400 further includes the second high-pressure gas branch pipe 413 branched from the first high-pressure gas pipe 412, the second liquid-branch pipe 423 branched from the first liquid-branch pipe 422, and the second low-pressure gas branch pipe 433 branched from the first low-pressure gas branch pipe 432.
The heating valve 441 of the cooling/heating conversion set 440 is connected to the second high-pressure gas branch pipe 413, and the cooling valve 442 of the cooling/heating conversion set 440 is connected to the second low-pressure gas branch pipe 433. The heating valve 441 and the cooling valve 442 are connected to the indoor connector 305. The indoor connector 305 is connected to one end of the indoor heat-exchanger 302. The second liquid-branch pipe 423 is connected to the indoor electric expansion valve 304 of the indoor unit 300.
The cooling/heating conversion unit 400 controls each indoor unit 300 to perform the heating or cooling operation. In other words, if any one of the indoor unit 300 performs the heating operation, the heating valve 441 is open, and the cooling valve 442 is closed. The refrigerant flowing in the second high-pressure gas branch pipe 413 is applied to the indoor heat-exchanger 302, and is condensed, so that the condensed refrigerant moves along the second liquid-branch pipe 423. If any one of the indoor unit 300 performs the cooling operation, the heating valve 441 is closed, the cooling valve 442 is open, and the liquid refrigerant flowing in the second liquid branch pipe 423 is received in the indoor heat-exchanger 302, is evaporated, and then moves along the second low-pressure gas pipe 433.
The indoor unit 300 includes the indoor heat-exchanger 302 for performing a heat-exchanging operation between the room air and the refrigerant; the indoor electric expansion valve 304 mounted to a connection part between the indoor heat-exchanger 302 and the second liquid-branch pipe 423; and a temperature sensor 302 mounted to a connection part between the indoor heat-exchanger 302 and the indoor electric expansion valve 304 so that it detects a temperature of the air discharged from an outlet of the heating indoor unit.
In this case, the heating indoor unit is selected from among the indoor units 300, so that the selected heating indoor unit can perform the heating operation from among the indoor units 300.
There are a plurality of indoor units 300, the individual indoor units 300 are mounted to the individual rooms or compartments, respectively, so that the individual rooms or compartment are cooled or heated.
The controller 500 controls overall operations of the multi air-conditioner 100 for simultaneously cooling/heating the room air. The outdoor temperature sensor 520, the low-pressure sensor 530, the temperature sensor 301 for the outlet of the heating indoor unit, and the input unit 510 for allowing the user to enter a control command are connected to the input terminals of the controller 500. The compressor driver 540 for driving the compressor 210, the 4-way valve driver 550 for driving the 4-way valve 230, the flow-regulating valve driver 560 for driving the flow-regulating valve 260, the cutoff-valve driver 570 for driving the cutoff valve 270, the cooling/heating driver 580 for driving the cooling/heating conversion set 440, the outdoor electric expansion valve driver 590 for driving the outdoor electric expansion valve 280, and the indoor expansion valve driver 595 for driving the indoor expansion valve 304.
A method for controlling the multi air-conditioner for simultaneously cooling/heating the room air according to the present invention will hereinafter be described with reference to the annexed drawings.
Referring to FIGS. 3A, 3B, 3C, and 4, if the multi air-conditioner 100 is powered on at operation 801, the controller 500 determines whether an operation start command is entered by the user at operation 802.
If the user does not enter the operation start command, the controller 500 determines whether the operation start command is continuously entered by the user. If the operation start command is entered by the user, the controller 500 calculates the heating-capacity rate at operation 803. In this case, the heating-capacity rate indicates the ratio (or percentage) of the operation capacity of overall indoor units to the operation capacity of the heating indoor unit performing the heating operation.
Then, the controller 500 determines whether the heating-capacity rate is the heating-capacity ratio corresponding to the heating-biased operation at operation 804. In this case, the heating-capacity rate corresponding to the heating-biased operation is about 50% ~ 99%.
In this case, if the heating-capacity rate does not correspond to the heating-capacity rate corresponding to the heating-biased operation, the controller 500 controls the multi air-conditioner 100 to perform the operation of the remaining heating-capacity rates at operation 805. In other words, if the heating capacity is 100%, the controller 500 controls the multi air-conditioner 100 to perform the heating operation. If the heating capacity is about 1%~49%, the controller 500 controls the multi air-conditioner 100 to perform the cooling-biased operation. If the heating capacity is 0%, the controller 500 controls the multi air-conditioner 100 to perform the cooling operation.
The controller 500 determines whether a current operation condition is the completion condition of the operation corresponding to the remaining heating-capacity rates at operation 806. In this case, if the current operation condition is not equal to the completion condition of the operation corresponding to the remaining heating-capacity rates, the controller 500 controls the multi air-conditioner 100 to continuously perform the operation corresponding to the remaining heating-capacity rates. If the current operation condition is equal to the completion condition of the operation corresponding to the remaining heating-capacity rates, the controller 500 determines whether the operation completion condition is established or not at operation 807.
In this case, the controller 500 determines whether the operation completion condition is established. If the operation completion condition is not established, the controller 500 returns to operation 803 for calculating the heating-capacity rate. If the operation completion condition is established, the controller 500 controls the multi air-conditioner to be powered off at operation 808.
If the heating-capacity rate is equal to a heating-capacity rate corresponding to the heating-biased operation at operation 804, the controller 500 closes the flow-regulating valve 260, and controls the multi air-conditioner 100 to perform the heating-biased operation at operation 809. The heating valve 441 of the cooling/heating conversion set 440 corresponding to the heating indoor unit 300 performing the heating operation is open, and the cooling valve 442 is closed. The heating valve 441 of the cooling/heating conversion set 440 corresponding to the indoor cooling unit 300 performing the cooling operation is closed, and the cooling valve 442 is open. The first port 230A of the 4-way valve 230 of the outdoor unit 200 is connected to the fourth port 230D, and the second port 230B of the 4-way valve 230 is connected to the third port 230C. Therefore, the high-pressure refrigerant compressed by the compressor 210 passes through the high-pressure gas pipe 410 and the heating valve 441 of the cooling/heating conversion set 440, so that it passes through the indoor heat-exchanger 302 of the heating indoor unit 300. In this case, the high-pressure refrigerant is heat-exchanged with the room air, so that it is condensed. The refrigerant condensed by the indoor heat-exchanger 302 of the heating indoor unit 300 is sequentially applied to the second liquid-branch pipe 423 the first liquid-branch pipe 422, and the second liquid-branch pipe 423, so that it passes through the indoor heat-exchanger 302 of the indoor cooling unit 300 performing the cooling operation. In this case, the refrigerant flowing in the indoor heat-exchanger 302 of the indoor cooling unit 300 is heat-exchanged with the room air, so that it is evaporated. The refrigerant evaporated via the indoor heat-exchanger 302 is applied to the cooling valve 442 of the cooling/heating conversion set 440, and the second and first low- pressure branch pipes 433 and 432, and is then applied to the compressor 210 via the low-pressure gas pipe 430.
In this way, the controller 500 determines whether the cooling-capacity rate is equal to or less than a reference rate at operation 810.
If the heating-capacity rate is not equal to or less than the reference rate, the controller 500 controls the cutoff valve 270 to be open. The controller 500 controls the opening degree of the outdoor electric expansion valve 280 to prevent a target object from being overheated, and controls a low-pressure control operation using the outdoor ventilation fan 290 at operation 811.
The controller 500 measures the opening degree of the indoor electric expansion valve 304 of the indoor cooling unit 300 performing the cooling operation, so that it calculates the average opening degree at operation 812.
The controller 500 determines whether the calculated average opening degree is equal to or higher than a reference opening degree at operation 813. In this case, if the calculated average opening degree is not equal to or higher than the reference opening degree, the controller 500 reduces the opening degree of the flow-regulating valve 260, so that the flow rate of the high-pressure gas refrigerant bypassed via the flow-regulating valve 260 is reduced at operation 814. If the calculated average opening degree is higher than the reference opening degree, the controller 500 increases the opening degree of the flow-regulating valve 260, so that the flow rate of the high-pressure gas refrigerant is bypassed via the flow-regulating valve 260 at operation 815. Therefore, the refrigerant flowing in the indoor cooling unit 300 becomes the refrigerant required by the indoor cooling unit 300, so that the cooling capacity of the indoor cooling unit 300 increases.
The controller 500 determines whether the completion condition of the heating-biased operation is established at operation 816. In this case, if the completion condition of the heating-biased operation is not established, the controller 500 performs the heating-biased operation. If the completion condition of the heating-biased operation is established, the controller 500 determines whether the operation completion condition is established at operation 807, and goes to the next operations.
If the heating-capacity rate is equal to or less than the reference rate at operation 810, the controller 500 receives the outdoor temperature value from the outdoor temperature sensor 520, and calculates a saturation pressure at which the refrigerant of the outdoor heat-exchanger 220 is saturated. And, the controller 500 receives the inner pressure value of the low-pressure gas pipe 430 from the low-pressure sensor 530.
Then, the controller 500 determines whether the saturation pressure is less than the refrigerant stagnation pressure at operation 818. In this case, the refrigerant stagnation pressure indicates a specific pressure value acquired when the reliability value is added to the low pressure detected by the low-pressure sensor 270.
In this case, if the saturation pressure is not less than the refrigerant stagnation pressure, the controller 500 closes the cutoff valve 270, and stops operation of the outdoor ventilation fan 290 at operation 819. The controller 500 receives the temperature value of the air discharged from the outlet of the heating indoor unit from the temperature sensor 301 at operation 820, and calculates the average temperature of the air discharged from the heating indoor unit 300 at operation 821.
The controller 500 determines whether the air temperature of the outlet of the heating indoor unit 300 is less than an optimum temperature at operation 822.
In this case, if the average temperature of the air discharged from the outlet of the heating indoor unit 300 is not less than the optimum temperature for the heating capacity, the controller 500 reduces the opening degree of the flow-regulating valve 260, so that the heating capacity of the heating indoor unit 300 performing the heating operation is guaranteed at operation 825. If the average temperature of the air discharged from the outlet of the heating indoor unit 300 is less than the optimum temperature for the heating capacity, the controller 500 increases the opening degree of the flow-regulating valve 260, so that the heating capacity of the indoor cooling unit 300 performing the cooling operation is guaranteed at operation 824. The controller 500 determines whether the heating-capacity rate is changed to another at operation 830. In this case, if the heating-capacity rate is not changed, the heating-biased operation is performed. If the heating-capacity rate is changed to another, the controller 500 determines whether the completion condition of the heating-biased operation is established or not at operation 816, and goes to the next operations.
If the saturation pressure is less than the refrigerant stagnation pressure at operation 818, the controller 500 opens the flow-regulating valve 260 and the cutoff valve 270, and opens the outdoor electric expansion valve 280 by a predetermined opening degree, so that it stops operation of the outdoor ventilation fan 290. Therefore, the inner saturation pressure of the outdoor heat-exchanger 220 increases.
The controller 500 receives again the low-pressure value from the low-pressure gas sensor 270 at operation 826.
Then, the controller 500 determines whether the low-pressure value is higher than the cooling-capacity optimum pressure at operation 827.
If the low-pressure value is higher than the cooling-capacity optimum value, the controller 500 reduces the opening degree of the outdoor electric expansion valve 280 and reduces the pressure of the low-pressure gas pipe 430 at operation 828, so that the cooling capacity is guaranteed and the performance is improved. Therefore, the cooling capacity and the performance of the indoor cooling unit 300 increase. Otherwise, if the low-pressure value is equal to or less than the cooling-capacity optimum value, the controller 500 increases the opening degree of the outdoor electric expansion valve 280 at operation 829, so that the cooling capacity and the performance are improved. Then, the controller 500 determines whether the heating-capacity rate is changed to another at operation 830. In this case, if the heating-capacity rate is not changed to another, the controller 500 performs the heating-biased operation. If the heating-capacity rate is changed to another, the controller 500 determines whether the heating-biased operation completion condition is established at operation 816, and goes to the next operations.
If there is no receiver tank 202 in the multi air-conditioner 100, the controller 500 can fully close the outdoor electric expansion valve 280 in the same manner as in the cutoff valve 270, so that the receiver tank 202 and the cutoff valve 270 may be removed from the multi air-conditioner as necessary.
As is apparent from the above description, the multi air-conditioner for simultaneously cooling/heating the room air prevents the high-pressure refrigerant from being bypassed during the heating-biased operation, so that it prevents the compressor from being excessively driven, resulting in the reduction of power consumption.
If the heating-capacity rate is less than the reference rate and the air temperature detected at the outside including the outdoor unit is low, the multi air-conditioner prevents the outdoor heat-exchanger from being used as an evaporator, and prevents the saturation pressure of the outdoor heat-exchanger from being less than the inner pressure of the low-pressure gas pipe. As a result, the multi air-conditioner prevents the refrigerant from being liquefied/stagnated in the outdoor heat-exchanger, and prevents the inner pressure of the outdoor heat-exchanger from being excessively lowered, so that it prevents the refrigerant from being frozen in the inner heat-exchanger.
Although a few embodiments of the present invention 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 invention, the scope of which is defined in the claims and their equivalents.

Claims

A multi air-conditioner for simultaneously cooling/heating room air comprising:
a high-pressure gas pipe, a low-pressure gas pipe, and a liquid line, which are connected between at least one outdoor unit and a plurality of cooling/heating switching sets;

a flow-regulating valve mounted to a bypass pipe connected between the high-pressure gas pipe and the liquid pipe; and

a controller for increasing an opening degree of the flow-regulating valve, if a heating rate is not below a reference rate during a heating-biased operation and is equal to or less than a required cooling capacity of a indoor cooling unit during the heating-biased operation.
The multi air-conditioner according to claim 1, further comprising:
an outdoor expansion valve and an outdoor ventilation fan, and

the controller for performing a superheat control using the outdoor expansion valve, performing a low-pressure control using the outdoor ventilation fan, and performing the opening degree of the flow-regulating valve according to an average opening-degree of the indoor cooling unit.
A multi air-conditioner for simultaneously cooling/heating room air comprising:
an outdoor temperature sensor for detecting an outdoor temperature;

a low-pressure sensor for detecting an internal pressure of the low-pressure gas pipe; and

a controller for calculating a saturation pressure of an outdoor heat-exchanger on the basis of an outdoor temperature detected by the outdoor temperature sensor, calculating a refrigerant stagnation pressure using pressure detected by the low-pressure sensor, comparing the saturation pressure with the refrigerant stagnation pressure, and performing a first operation for improving a cooling/heating capacity or a second operation for preventing a refrigerant from being stagnated.
The multi air-conditioner according to claim 3, further comprising:
a flow-regulating valve mounted to a bypass pipe connected between a high-pressure gas pipe and a liquid pipe, a cutoff valve for blocking a refrigerant moving to an outdoor heat-exchanger, and an outdoor ventilation fan,
wherein, during the first operation for improving the cooling/heating capacity, the controller for blocking the flow-regulating valve and the cutoff valve during the first operation for improving the cooling/heating capacity, and at the same time stopping the outdoor ventilation fan.
The multi air-conditioner according to claim 3, further comprising:
a flow-regulating valve mounted to a bypass pipe connected between a high-pressure gas pipe and a liquid pipe, a cutoff valve for blocking a refrigerant moving to an outdoor heat-exchanger, and an outdoor ventilation fan,
wherein, during the second operation for preventing the refrigerant from being stagnated, the controller for opening the flow-regulating valve and the cutoff valve and stopping the outdoor ventilation fan, detecting a low pressure, increasing an opening degree of an outdoor electric expansion valve if the detected low pressure is not higher than a cooling-capacity optimization pressure, and reducing the opening degree of the outdoor electric expansion valve if the detected low pressure is higher than the cooling-capacity optimization pressure.
A method for controlling a multi air-conditioner capable of simultaneously cooling/heating room air comprising:
determining whether a heating-capacity rate is equal to or higher than a reference rate during a heating-biased operation; and

if the heating-capacity rate is equal to or higher than the reference rate during the heating-biased operation, and regulating a flow of a high-pressure gas which flows from a high-pressure gas pipe to a liquid pipe.
The method according to claim 6, wherein the regulating of the flow includes:
performing a superheat control by regulating an opening degree of an outdoor electric expansion valve, performing a low-pressure control by regulating an air-volume of an outdoor ventilation fan, and at the same time opening a cutoff valve.
The method according to claim 6, wherein the regulating of the flow includes:
calculating an average opening-degree of an indoor electric expansion valve of a indoor cooling unit; and

reducing the flow if the calculated average opening-degree is not higher than a reference opening-degree, and increasing the flow if the calculated average opening-degree is higher than the reference opening-degree.
A method for controlling a multi air-conditioner capable of simultaneously cooling/heating room air comprising:
determining whether a heating-capacity rate is equal to or higher than a reference rate during a heating-biased operation; and

if the heating-capacity rate is less than the reference rate, performing an operation for preventing a refrigerant from being stagnated when a saturation pressure of an outdoor heat-exchanger is less than a refrigerant stagnation pressure of a low-pressure gas pipe, and performing an operation for guaranteeing a cooling/heating-capacity when the saturation pressure of the outdoor heat-exchanger is not less than the refrigerant stagnation pressure of the low-pressure gas pipe.
The method according to claim 9, wherein the operation for guaranteeing the cooling/heating-capacity includes:
closing a flow-regulating valve and a cutoff valve, and stopping an outdoor ventilation fan; and

calculating an average outlet temperature of a heating indoor unit, increasing an opening degree of the flow-regulating valve when an average outlet temperature of the heating indoor unit is less than an optimum temperature, and reducing the opening degree of the flow-regulating valve when the average outlet temperature of the heating indoor unit is not less than the optimum temperature.
The method according to claim 9, wherein the operation for preventing the refrigerant from being stagnated includes:
closing a flow-regulating valve and a cutoff valve, and stopping an outdoor ventilation fan; and

reducing an opening degree of an outdoor electric expansion valve when a low pressure of the low-pressure gas pipe is higher than a cooling-capacity optimization pressure, and increasing the opening degree of the outdoor electric expansion valve when the low pressure of the low-pressure gas pipe is not higher than the cooling-capacity optimization pressure.