EP1703235B1

EP1703235B1 - Method for controlling air conditioner having several compressors

Info

Publication number: EP1703235B1
Application number: EP05004500A
Authority: EP
Inventors: Won-Hee Lee
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2005-03-02
Filing date: 2005-03-02
Publication date: 2011-11-16
Anticipated expiration: 2025-03-02
Also published as: EP1703235A1

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an air conditioner, and particularly, to a method for controlling an air conditioner having a multi-compressor.

2. Description of the Prior Art

In general, an air conditioner cools warm air or heats cool air in a room. Hereinafter, a construction of an air conditioner having two compressors in accordance with a conventional art will now be described with reference to Figure 1. Herein, the two compressors are selectively operated according to a cooling load of a room.
Figure 1 a schematic view showing a construction of an air conditioner having two compressors in accordance with the conventional art.
As shown therein, the air conditioner having two compressors includes a first compressor 18A and a second compressor 18B selectively operated according to a cooling load of a room to vary a compressing capacity; a condenser 1 for radiating heat of a refrigerant compressed by the first and second compressors 18A, 18B; an expansion valve 2 for expanding the refrigerant discharged from the condenser 1; and an evaporator 3 receiving the refrigerant expanded by the expansion valve 2 and generating cool air. Hereinafter, on the assumption that the first compressor 18A is a compressor of a small compressing capacity and the second compressor 18B is a compressor of a high compressing capacity, a construction of an air conditioner having the two compressors will now be described.
First, suction pipes 9, 13 respectively connected to the first compressor 18A and the second compressor 18B are connected by hoses 5, 7 diverged from a suction hose 4 connected to the evaporator 3. In addition, discharge pipes 11, 14 respectively connected to the first compressor 18A and the second compressor 18B are connected by hoses 10, 16 diverged from a discharge hose 17 connected to the condenser 1.
To the diverged hose 5, 7, 10, 16 are respectively connected suction valves 6, 8 and discharge valves 12, 15 which are selectively opened/closed by hand or a control means such as a microcomputer or the like.
Accordingly, the air conditioner having two compressors controls a cooling cycle by operating the first compressor 18A or/and the second compressor 18B according to a cooling load. That is, compressing capacity of the compressors are changed in such a manner that the air conditioner operates only the first compressor 18A when a cooling load of a room is small, operates only the second compressor 18B when the cooling load of a room is large, and operates both first and second compressors 18A, 18B when the cooling load of the room is maximum.
Recently, an air conditioner having four compressors has been used. General operations of the air conditioner having four compressors are the same as those of the air conditioner of Figure 1. But, the four compressors may be designed to have the same compressing capacity or may be designed to have different compressing capacities.
In a control method of an air conditioner having the four compressors, an internal temperature is controlled by increasing or decreasing a compressing capacity of the compressors level (10%) by level depending on the cooling load. For example, in case the air conditioner is in a cooling mode, if an internal temperature reaches a temperature lower than a desired temperature preset by a user by 0.5 degree, the compressors are operated for the certain time with a compressing capacity lower than a previous compressing capacity by one level. After the certain time elapses, the desired temperature and an internal temperature are compared again. If the internal temperature is not the same as the desired temperature (lower or higher than the desired temperature), the compressors are operated with a compressing capacity higher or lower than a previous compressing capacity by one level.
However, the method for controlling the air conditioner in accordance with the conventional art has following problems.
In the method for controlling the air conditioner in accordance with the present invention, a compressing capacity of the compressor is increased or decreased level by level depending on an internal cooling load or a heating load. Accordingly, the air conditioner slowly copes with the cooling load or the heating load, and energy loss of the air conditioner is increased. For example, on the assumption that total compressing capacity is 100%, when the air conditioner intends to lower the compressing capacity of the compressor from 70% to 50%, the compressing capacity of 70% is lowered to 60% and then the compressing capacity of 60% is lowered to 50%. For this reason, the air conditioner slowly copes with the cooling load or the heating load, and the energy loss of the air conditioner is increased.
An air conditioner having a multi-compressor in accordance with the conventional art is disclosed in detail on U.S Patent No. 6,519,957 issued in Feb. 18, 2003, and in US 2004/098997 and US 2004/118135 .

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a method for controlling an air conditioner having a multi-compressors capable of improving capability of coping with a cooling load or a heating load and reducing energy loss by pre-storing a compressing capacity according to a temperature difference between a previous room temperature and a desired temperature set by a user; and changing the pre-stored compressing capacity based on a temperature difference between a current room temperature and the desired-temperature.
Another object of the present invention is to provide a method for controlling an air conditioner having a multi-compressors capable of improving pleasantness by pre-storing a compressing capacity according to a temperature difference between a previous room temperature and a previous desired temperature and body adaptation time, changing the desired temperature according to the body adaptation time and changing the pre-stored compressing capacity based on a temperature difference between a current room temperature and the changed desired-temperature.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a method for controlling an air conditioner having a multi-compressor including: a step in which compressing capacity of compressors according to a temperature difference between a previous room temperature and a desired temperature set by a user is pre-stored; and a step in which the pre-stored compressing capacity is changed based on a current room temperature and the desired temperature.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a method for controlling an air conditioner having a multi-compressor including: a step in which compressing capacity of compressors is pre-stored according to a temperature difference between a previous room temperature and a desired temperature preset by a user; a step in which when the air conditioner is in a cooling mode and a current room temperature reaches a lower limit temperature less than the desired temperature, the pre-stored compressing capacity is changed to compressing capacity for maintaining the lower limit temperature, and the compressors are operated with the changed compressing capacity; and a step in which after the compressors have been operated with the changed compressing capacity for the preset time, a temperature difference between a current room temperature and the desired temperature is detected, the changed compressing capacity is changed again to preset compressing capacity according to the detected temperature difference, and the compressors are operated with the re-changed compressing capacity.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a method for controlling an air conditioner having a multi-compressor including: a step in which compressing capacity of compressors according to a temperature difference between a previous room temperature and a desired temperature set by a user is pre-stored; a step in which when the air conditioner is in a cooling mode and the current room temperature reaches a lower limit temperature lower than the desired temperature, the pre-stored compressing capacity is changed to compressing capacity for maintaining the lower limit temperature, and the compressors are operated with the changed compressing capacity; a step in which after the compressors have been operated with the changed compressing capacity for the preset time, a temperature difference between the current room temperature and the desired temperature is detected, the changed compressing capacity is changed again to preset compressing capacity according to the detected temperature difference, and the compressors are operated with the re-changed compressing capacity; a step in which if compressing capacity corresponding to a current operation mode for operating the compressors with the changed compressing capacity is the same as that corresponding to a maximum operation mode, the compressors are operated in the maximum operation mode; a step in which if the compressing capacity corresponding to the current operation mode is smaller than that corresponding to the maximum operation mode, the compressing capacity corresponding to the current operation mode and compressing capacity corresponding to a previous operation mode are compared, and if the compressing capacity corresponding to the current operation mode is smaller than that corresponding to the previous operation mode, the compressors are operated in the previous operation mode; and a step in which if the compressing capacity corresponding to the current operation mode is larger than that corresponding to the previous operation mode, the compressor are operated in the current operation mode, wherein the maximum operation mode is for operating the compressors with total compressing capacity of the multi-compressor, and the previous operation mode is for operating the compressors with pre-stored compressing capacity.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a method for controlling an air conditioner having a multi-compressor including: a step in which compressing capacity according to a previous room temperature and a desired temperature and body adaptation time are pre-stored; a step in which the pre-stored compressing capacity is changed based on a temperature difference between a current room temperature and the desired temperature, and when the body adaptation time elapses while compressors are operated with the changed compressing capacity, the desired temperature is changed; and a step in which the changed compressing capacity is changed again based on a temperature difference between a current room temperature and the changed desired temperature.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a unit of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.
In the drawings:

Figure 1 is a schematic view showing a construction of an air conditioner having two compressors in accordance with the conventional art;
Figure 2 is a graph showing a method for increasing or decreasing a compressing capacity of a compressor level by level according to a temperature difference between an internal temperature and a desired temperature in controlling the air conditioner having a plurality of compressors in accordance with the conventional art; and
Figure 3 is a flow chart showing a method for controlling an air conditioner having a multi-compressor in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, there will be described in detail with reference to Figure 3 a preferred embodiment of a method for controlling an air conditioner having a multi-compressor capable of improving capability for coping with a cooling load or a heat load, reducing energy loss and improving pleasantness in a room, by pre-storing a compressing capacity according to a temperature difference between a previous room temperature and a desired temperature and body adaptation time, changing the desired temperature when the body adaptation time elapses while compressors are operated after the pre-stored compressing capacity has been changed based on a current room temperature and the desired temperature, and changing the changed compressing capacity again based on a temperature difference between the current room temperature and the changed desired temperature.
Figure 3 is a flow chart of a method for controlling an air conditioner having a multi-compressor in accordance with an embodiment of the present invention.
As shown in Figure 3, a method for controlling an air conditioner having a multi-compressor in accordance with an embodiment of the present invention includes: a step in which when an internal temperature is controlled at a previous stage, compressing capacity of compressors according to a temperature difference between a previous room temperature and a desired temperature set by a user, and body adaptation time (time taken to adapt a human body to a temperature) are pre-stored; a step in which when a user selects a cooling mode and a current room temperature reaches a lower limit temperature less than a desired temperature set by a user, the pre-stored compressing capacity is changed to preset compressing capacity in order to maintain the lower limit temperature, and the compressors are operated with the changed compressing capacity; a step in which after the compressors has been operated for the preset time with the changed compressing capacity, a temperature difference between the current room temperature and the desired temperature is detected in order to operate the compressors with optical compressing capacity, the changed compressing capacity is changed again to preset compressing capacity according to the detected temperature difference, and the compressors are operated with the re-changed compressing capacity.
For example, on the assumption that the multi-compressor consists of four compressors, and total compressing capacity of the four compressors is 100%, two compressors each having a compressing capacity of 20% and two compressors each having a compressing capacity of 30% are respectively installed in the air condition, a user selects a cooling mode, and two compressors having a compressing capacity of 20% and one compressor having a compressing capacity of 30% are operated (operating the compressors with the pre-stored compressing capacity). In this case, when a current room temperature reaches a temperature (lower limit temperature) less than a desired temperature by 0.5 degree during the operation, operation of one compressor having compressing capacity of 20% is stopped, and one compressor having compressing capacity of 20% and one compressor having compressing capacity of 30% are operated for the preset time (e.g., for three minutes). Thereafter, a temperature difference between the current room temperature and a desired temperature is detected, and the changed compressing capacity is changed to preset compressing capacity again according to the detected temperature difference. That is, when there are four compressors, and total compressing capacity of the four compressors is 100%, the compressing capacity of the multi-compressor is changed by selectively operating two compressors having compressing capacity of 20% and two compressors having compressing capacity of 30%.
In addition, the method for controlling the air conditioner having a multi-compressor may further include: a step in which the changed compressing capacity is changed again, and when the compressors are operated with the re-changed compressing capacity, if compressing capacity corresponding to a current operation mode for operating the compressors with the re-changed compressing capacity is the same as compressing capacity corresponding to a maximum operation mode, the compressors are operated in the maximum operation mode; a step in which if the compressing capacity corresponding to the current operation mode is smaller than that corresponding to the maximum operation mode, the compressing capacity corresponding to the current operation mode and that corresponding to a previous operation mode are compared, and if the compressing capacity corresponding to the current operation mode is smaller than that corresponding to the previous operation mode, the compressors are operated in the previous operation mode; and a step in which if the compressing capacity corresponding to the current operation mode is larger than that corresponding to the previous operation mode, the compressors are operated in the current operation mode. Herein, the operation mode is for operating the compressors with the changed compressing capacity, the maximum operation mode is for operating the compressors with total compressing capacity (100%) of the multi-compressor, and the previous operation mode is for operating the compressors with a pre-stored compressing capacity (e.g., 70%).
A method for controlling an air conditioner having a multi-compressor in accordance with an embodiment of the present invention may further include: a step in which the changed compressing capacity is changed again to preset compressing capacity according to the detected temperature difference, a new desired temperature is set by changing the desired temperature when the body adaptation time elapses while the compressors are operated with the re-changed compressing capacity, a temperature difference between the new desired temperature and a current room temperature is detected, the current compressing capacity is changed to preset compressing capacity according to the detected temperature difference and the compressors are operated with the changed compressing capacity.
Hereinafter, a method for controlling an air conditioner having a multi-compressor in accordance with an embodiment of the present invention will now be described in detail.
First, when a room temperature is controlled at a previous stage, compressing capacity of a multi-compressor for reducing a temperature difference between a previous room temperature and a desired temperature set by a user, and body adaptation time are pre-stored (S1).
The compressing capacity of the compressors are changed to preset compressing capacity according to a temperature difference between a room temperature and a desired temperature. But, in order to explain a preferred embodiment in accordance with the present invention, it is assumed that four compressors are applied to the air conditioner, total compressing capacity of the four compressors is 100%, and the preset compressing capacity is 70%. In addition, the body adaptation time means time taken to adapt a human body to a specific temperature and is slightly different depending on a person. But in general, when exposed to a specific temperature (e.g., 20 degrees) for 20 ~ 40 minutes, a human body adapts to the specific temperature. Accordingly, in order to provide a user with pleasantness, preferably, the desired temperature is changed every thirty minutes.
Thereafter, when a user selects a cooling mode (S2), the compressors are operated with the pre-stored compressing capacity (e.g., 70%) (S3).
While the compressor are operated with the pre-stored compressing capacity, when a current room temperature reaches a lower limit temperature less than a current desired temperature set by a user (S4), the pre-stored compressing capacity is changed to preset compressing capacity (e.g., 50%) in order to maintain the lower limit temperature (S5). Herein, the lower limit temperature is near the desired temperature set by a user and is lower than 1 degree (e.g., 0.5 degree). For example, on the assumption that a desired temperature is 20 degrees and the lower limit temperature is 0.5 degree, when the room temperature is 19.5 degrees, the compressors are operated with a preset compressing capacity (e.g. 50% of total compressing capacity) in order to maintain 19.5 degrees.
After the compressors have been operated with the changed compressing capacity (e.g., 50%) for the preset time (e.g., three minutes) (S6), a temperature difference between a current room temperature and a desired temperature is detected (S7).
Thereafter, the temperature difference between the current room temperature and the desired temperature is compared with a reference value (S8), the changed compressing capacity (e.g., 50%) is changed to preset compressing capacity based on the comparison result, and the compressors are operated with the re-changed compressing capacity. That is, if the temperature difference between the current room temperature and the desired temperature is larger than a first reference value (e.g., 2 degrees), the changed compressing capacity (e.g., 50%) is increased by two level (e.g., 20%), and thus the compressors are operated with the increased compressing capacity.
If a temperature difference between the current room temperature and a desired temperature is smaller than the first reference value and larger than a second reference value (e.g., 1 degree), the changed compressing capacity (e.g., 50%) is increased by one level (e.g., 10%), and the compressors are operated with the increased compressing capacity.
In addition, if a temperature difference between the current room temperature and the desired temperature is smaller than the second reference value (e.g., 1 degree) and larger than a third reference value (e.g., 0 degree), the changed compressing capacity (e.g., 50%) is maintained and the compressors are operated therewith. When a temperature difference between the current room temperature and the desired temperature is smaller than the third reference value (0 degree), the changed compressing capacity (e.g., 50%) is decreased by one level (e.g., 10%), and the compressors are operated with the decreased compressing capacity (S9).
For example, when a user selects a cooling mode, and a room temperature reaches a temperature less than a desired temperature by 0.5 degree while the compressors are operated with pre-stored compressing capacity of 70%, the compressing capacity of 70% is changed to compressing capacity of 50%, and the compressors are operated with the changed compressing capacity of 50% for the preset time (e.g., three minutes). Thereafter, when a temperature difference between the current room temperature and the desired temperature is larger than 2 degrees, the compressing capacity of 50% is increased by 20%, and the compressors are operated with the increased compressing capacity. When the temperature difference between the current room temperature and the desired temperature is 1~2 degrees, the compressing capacity of 50% is increased by 10%, and the compressors are operated with the increased compressing capacity. When the temperature difference between the current room temperature and the desired temperature is 0~1 degree, the compressing capacity of 50% is maintained. When the current room temperature is lower than the desired temperature, the compressors are stopped, or the compressing capacity of 50% is decreased and the compressors are operated with the decreased compressing capacity. Herein the compressing capacity changed according to the temperature difference between the room temperature and the desired temperature is preset according to the number of compressors mounted in an air conditioner and a compressing capacity ratio of the compressors.
Thereafter, when a compressing capacity corresponding to a current operation mode for operating the compressors with the changed compressing capacity is the same as compressing capacity corresponding to a maximum operation mode (maximum compressing capacity (100%) of a multi-compressor), the compressors are operated in the maximum operation mode. In addition, when the compressing capacity corresponding to the current operation mode is smaller than that corresponding to the maximum operation mode, the compressing capacity corresponding to the current operation mode and a compressing capacity corresponding to a previous operation mode are compared. If the compressing capacity corresponding to the current operation mode is smaller than that corresponding to the previous operation mode, the compressors are operated in the previous operation mode. In addition, when the compressing capacity corresponding to the current operation mode is larger than that corresponding to the previous operation mode, the compressors are operated in the current operation mode.
Accordingly, in the present invention, the compressing capacity of a multi-compressor is quickly changed and the compressors are operated with the changed compressing capacity, by pre-storing a compressing capacity according to a temperature difference between a previous room temperature and a previous desired temperature when a room temperature is controlled at a previous stage, and then changing the pre-stored compressing capacity based on a temperature difference between a current room temperature and a current desired temperature. For example, when compressing capacity is lowered from 70% to 50%, the compressing capacity of 70% is directly lowered to a compressing capacity of 50%. For this reason, an air conditioner in accordance with the present invention quickly copes with a cooling load and a heating load, and its energy loss can be reduced.
Thereafter, the changed compressing capacity is changed again to preset compressing capacity according to the detected temperature difference, and the compressors are operated with the re-changed compressing capacity (S9). Thereafter, when body adaptation time elapses (S10), the desired temperature is changed by adding or subtracting a preset value (e.g., 1 degree) to/from the desired temperature (S11). A temperature difference between the changed desired temperature and a current room temperature is detected, the current compressing capacity is changed to preset compressing capacity according to the detected temperature difference, and the compressors are operated with the changed compressing capacity.
For example, the changed compressing capacity is re-changed to preset compressing capacity according to the detected temperature difference, and the compressors are operated with the re-changed compressing capacity (S9). Thereafter, when body adaptation time, thirty-minute, is elapses, a new desired temperature is set by adding 1 degree to a desired temperature set by a user. A temperature different between the new desired temperature and a current room temperature is detected, the current compressing capacity is changed to preset compressing capacity according to the detected temperature difference, and the compressors are operated with the changed compressing capacity.
In addition, when the body adaptation time, 30-minuite is elapses again while the compressors are operated after the current compressing capacity has been changed, the new desired temperature is changed by adding or subtracting 1 degree to/from the new desired temperature, and a temperature difference between the changed new desired temperature and a current room temperature is detected. Then, the current compressing capacity is changed to preset compressing capacity according to the detected temperature difference, and the compressors are operated with the changed compressing capacity. Theses processes (S7~S9) are repeatedly performed. That is, whenever the body adaptation time elapses, a desired temperature set by a user is changed, thereby increasing pleasantness.
A compressing capacity of compressors according to a temperature difference between a room temperature and a desired temperature is pre-stored when a room temperature is controlled at a previous stage (S1). Thereafter, when a user selects a heating mode, and a current room temperature reaches an upper limit temperature more than a desired temperature set by a user (S13) while the compressors are operated with the pre-stored compressing capacity (e.g., 70%) (S12), the pre-stored compressing capacity is changed to preset compressing capacity in order to maintain the upper limit temperature (S14), and the compressors are operated with the changed compressing capacity. That is, after the compressors are operated with the changed compressing capacity, the processes (S6~S11) are performed (S15).
As so far described, a method for controlling an air conditioner having a multi-compressor in accordance with the convention art can improve capability of coping with a cooling load and a heating load by pre-storing compressing capacity according to a temperature difference between a previous room temperature and a previous desired temperature and then changing the pre-stored compressing capacity based on a temperature difference between a current room temperature and a desired temperature.
In addition, a method for controlling an air conditioner having a multi-compressor in accordance with the present invention can reduce the energy loss of an air conditioner by pre-storing compressing capacity according to a temperature difference between a previous room temperature and a previous desired temperature and then changing the pre-stored compressing capacity based on a temperature difference between a current room temperature and a desired temperature.
In addition, a method for controlling an air conditioner having a multi-compressor in accordance with the present invention can improve pleasantness by pre-storing compressing capacity according to a temperature difference between a previous room temperature and a previous desired temperature and body adaptation time, then changing the desired temperature according to the body adaptation time, and changing the pre-stored compressing capacity based on a temperature difference between a current room temperature and the changed desired-temperature.

Claims

A method for controlling an air conditioner having a multi-compressor comprising:
a step (S3, S12) in which compressors are operated with a certain pre-stored capacity according to a temperature difference between an initial room temperature and a desired temperature set by a user; and

a step (S5, S14) in which the pre-stored compressing capacity is changed based on a current room temperature and the desired temperature,

characterized in that the method further comprises a step (S7-S11, S15) in which the pre-stored compressing capacity is changed based on a temperature difference between the current room temperature and the desired temperature, a new desired temperature is set by changing the desired temperature when a body adaptation time elapses while the compressors are operated with the changed compressing capacity, and the changed compressing capacity is changed again based on a temperature difference between the new desired temperature and a current room temperature.
The method of claim 1, wherein the desired temperature is increased or decreased by a preset value whenever the body adaptation time elapses.
The method of claim 2, wherein the preset value is 1 degree.
The method of claim 2, wherein the body adaptation time means time taken to adapt a human body to a temperature, and is 20-40 minutes.
The method of claim 1, wherein the pre-stored compressing capacity is changed by selectively operating compressors having the same compressing capacity and compressors having difference compressing capacities, based on a temperature difference between the current room temperature and the desired temperature.
The method of claim 1, wherein the step (S5, S14) in which the pre-stored compressing capacity is changed is a step (S5, S14) in which the pre-stored compressing capacity is changed based on a temperature difference between the current room temperature and the desired temperature in order to increase a speed corresponding to a cooling load and a heating load.
The method of claim 1, wherein the step (S5, S14) in which the pre-stored compressing capacity is changed comprises:
a step (S5) in which when the air conditioner is in a cooling mode and the current room temperature reaches a lower limit temperature lower than the desired temperature, the pre-stored compressing capacity is changed to compressing capacity for maintaining the lower limit temperature, and the compressors are operated with the changed compressing capacity; and

a step (S7-S9) in which after the compressors have been operated with the changed compressing capacity for a preset

time, a temperature difference between the current room temperature and the desired temperature is detected, the changed compressing capacity is changed again to preset compressing capacity according to the detected temperature difference, and the compressors are operated with the re-changed compressing capacity.
The method of claim 1, wherein the step (S5, S14) in which the pre-stored compressing capacity is changed comprises:
a step (S14) in which when the air conditioner is in a heating mode, and the current room temperature reaches an upper limit temperature more than the desired temperature, the pre-stored compressing capacity is changed to compressing capacity for maintaining the upper limit temperature, and the compressors are operated with the changed compressing capacity; and

a step (S15) in which after the compressors have been operated with the changed compressing capacity for the preset time, a temperature difference between the current room temperature and the desired temperature is detected, the changed compressing capacity is changed again to preset compressing capacity according to the detected temperature difference, and the compressors are operated with the re-changed compressing capacity.
The method of claim 1, further comprising:
a step in which if compressing capacity corresponding to a current operation mode for operating the compressors with the changed compressing capacity is the same as that corresponding to a maximum operation mode, the compressors are operated in the maximum operation mode;

a step in which if the compressing capacity corresponding to the current operation mode is smaller than that corresponding to the maximum operation mode, the compressing capacity corresponding to the current operation mode and compressing capacity corresponding to a previous operation mode are compared, and if the compressing capacity corresponding to the current operation mode is smaller than that corresponding to the previous operation mode, the compressors are operated in the previous operation mode; and

a step in which if the compressing capacity corresponding to the current operation mode is larger than that corresponding to the previous operation mode, the compressor are operated in the current operation mode,
wherein the maximum operation mode is for operating the compressors with total compressing capacity of the multi-compressor, and the previous operation mode is for operating the compressors with pre-stored compressing capacity.
A method for controlling an air conditioner having a multi-compressor comprising:
a step (S3, S12) in which compressors are operated with a certain pre-stored capacity according to a temperature difference between an initial room temperature and a desired temperature set by a user; and

a step (S5, S14) in which the pre-stored compressing capacity is changed based on a current room temperature and the desired temperature,

characterized in that wherein the step (S5, S14) in which the pre-stored compressing capacity is changed comprises:
a step (S5) in which when the air conditioner is in a cooling mode and the current room temperature reaches a lower limit temperature lower than the desired temperature, the pre-stored compressing capacity is changed to compressing capacity for maintaining the lower limit temperature, and the compressors are operated with the changed compressing capacity; and

a step (S7-S9) in which after the compressors have been operated with the changed compressing capacity for a preset time, a temperature difference between the current room temperature and the desired temperature is detected, the changed compressing capacity is changed again to preset compressing capacity according to the detected temperature difference, and the compressors are operated with the re-changed compressing capacity.
A method for controlling an air conditioner having a multi-compressor comprising:
a step (S3, S12) in which compressors are operated with a certain pre-stored capacity according to a temperature difference between an initial room temperature and a desired temperature set by a user; and

a step (S5, S14) in which the pre-stored compressing capacity is changed based on a current room temperature and the desired temperature,

characterized in that the step (S5, S14) in which the pre-stored compressing capacity is changed comprises:
a step (S14) in which when the air conditioner is in a heating mode, and the current room temperature reaches an upper limit temperature more than the desired temperature, the pre-stored compressing capacity is changed to compressing capacity for maintaining the upper limit temperature, and the compressors are operated with the changed compressing capacity; and

a step (S15) in which after the compressors have been operated with the changed compressing capacity or the preset time, a temperature difference between the current room temperature and the desired temperature is detected, the changed compressing capacity is changed again to preset compressing capacity according to the detected temperature difference, and the compressors are operated with the re-changed compressing capacity.