AIR CONDITIONER AND METHOD OF CONTROLLING THE SAME

Abstract

A method of controlling an air conditioner including activating a refrigeration cycle by driving an compressor; detecting a high pressure and a low pressure when the refrigeration cycle is activated; adjusting an operating frequency of the compressor based on the detected high pressure or low pressure of the refrigeration cycle; determining a current load of an inside space through a load detecting unit; determining a load level of the inside space by comparing the current load with a reference load; and determining the operating frequency of the compressor based on the determined load level.

Claims

1. A method of controlling an air conditioner, comprising: activating, by a controller, a refrigeration cycle by driving a compressor; detecting, by a pressure sensor, a high pressure and a low pressure of the refrigeration cycle when the refrigeration cycle is activated; adjusting, by the controller, an operating frequency of the compressor based on the detected high pressure or the detected low pressure of the refrigeration cycle; determining, by a load detecting unit, a current load of an inside space, a load level of the inside space being determined by comparing the current load with a reference load; and determining, by the load detecting unit, the operating frequency of the compressor based on the determined load level, wherein the load detecting unit comprises: a frequency detector to detect the operating frequency of the compressor, and a power detector to detect current consumption and power consumption occurring upon the activation of the refrigeration cycle.

2. The method of claim 1, wherein the load level comprises: a high load in which the current load is greater than or equal to the reference load; and a low load in which the current load is less than the reference load.

3. The method of claim 2, wherein the reference load is a load corresponding to when an increase rate of the operating frequency of the compressor is a first set increase rate, or a load corresponding to when an increase rate of the power consumption or current consumption is a second set increase rate.

4. The method of claim 2, wherein the high pressure and the low pressure of the refrigeration cycle are detected when the refrigeration cycle is activated.

5. The method of claim 3, wherein, when it is determined that the increase rate of the operating frequency of the compressor is greater than the first set increase rate or when the increase rate of the power consumption or current consumption is greater than the second set increase rate, the current load is determined as the high load.

6. The method of claim 5, wherein, when the current load is determined as the high load, the operating frequency of the compressor is set to a first operating frequency based on information mapped to the operating frequency of the compressor.

7. The method of claim 6, wherein the first operating frequency includes the maximum operating frequency of the compressor.

8. The method of claim 5, further comprising determining, by the controller, an opening degree of a main expansion device based on the determined load level, wherein, when the current load is determined as the high load, the opening degree of the main expansion device is set to a full opening degree.

9. The method of claim 5, further comprising determining a number of rotations of an outside fan based on the determined load level, wherein, when the current load is determined as the high load, the number of rotations of the outside fan is set to the maximum number of rotations.

10. The method of claim 1, further comprising performing a temperature maintenance operation, by the controller, for maintaining the temperature of the inside space when the temperature of the inside space reaches a set temperature.

11. The method of claim 10, wherein, when the temperature maintenance operation is performed, the compressor is driven at an operating frequency that is lower than the determined operating frequency of the compressor.

12. The method of claim 1, wherein the reference load comprises a first reference load and a second reference load; and wherein the load level comprises: a high load in which the current load is greater than or equal to a first reference load, a low load in which the current load is less than the second reference load, and an intermediate load in which the current load is greater than or equal to the second reference load, and is less than the first reference load.

13. The method of claim 12, wherein the operating frequency of the compressor is differently controlled according to whether the current load is the high load, the low load, or the intermediate load.

14. An air conditioner comprising: a compressor with an adjustable operating frequency; an outside heat exchanger that condenses refrigerant compressed by the compressor in an air cooling operation; a main expansion device that decompresses the refrigerant condensed by the outside heat exchanger; an inside heat exchanger that evaporates the refrigerant decompressed by the main expansion device and discharges air into an inside space; a load detecting unit that detects a load of the inside space; and a memory unit that stores information about the operating frequency of the compressor, the stored information being mapped with the load detected by the load detecting unit.

15. The air conditioner of claim 14, wherein the load detecting unit comprises: a frequency detecting unit that detects a rate of change in the operating frequency of the compressor; and a power detecting unit that detects current consumption and power consumption occurring upon an operation of the air conditioner.

16. The air conditioner of claim 15, wherein the operating frequency of the compressor is set by a controller to a first operating frequency when the load detected by the load detecting unit is greater than or equal to a reference load, and the operating frequency of the compressor is set by the controller to a second operating frequency that is lower than the first operating frequency when the load detected by the load detecting unit is less than the reference load.

17. A method of controlling an air conditioner, comprising: activating, by a controller, a refrigeration cycle by driving a compressor; detecting, by a pressure sensor, a high pressure and a low pressure of the refrigeration cycle when the refrigeration cycle is activated; adjusting, by the controller, an operating frequency of the compressor based on the detected high pressure or the detected low pressure; determining, by a load detecting unit, a current load of an inside space, a load level of the inside space being determined by comparing the current load with a reference load; determining, by the load detecting unit, the operating frequency of the compressor based on the determined load level, wherein the reference load is a load corresponding to when an increase rate of the operating frequency of the compressor is a first set increase rate, and when the increase rate of the operating frequency of the compressor is greater than the first set increase rate, the current load is determined as a high load, and when the increase rate of the operating frequency of the compressor is less than the first set increase rate or the operating frequency of the compressor remains the same or decreases, the current load is determined as a low load.

18. The method of claim 17, further comprising setting, by the controller, the operating frequency of the compressor to the maximum operating frequency when the current load is determined as the high load.

19. The method of claim 16, further comprising setting, by the controller, an opening degree of the main expansion device to a full opening degree when the current load is determined as the high load.

20. The method of claim 17, further comprising setting, by the controller, a number of rotations of the outside fan to the maximum number of rotations when the current load is determined as the high load.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and together with the description serve to explain the principle of the invention. In the drawings:

[0034] FIG. 1 is a circuit diagram showing a refrigeration cycle of an air conditioner according to a first embodiment.

[0035] FIG. 2 is a block diagram of a configuration of an air conditioner according to the first embodiment.

[0036] FIG. 3 is a flowchart of a method of controlling an air conditioner according to the first embodiment.

[0037] FIG. 4 is a flowchart of a method of controlling an air conditioner according to a second embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] Embodiments of the present disclosure are described in detail with reference to the accompanying drawings. It should be noted that similar components are designated by similar reference numerals throughout the specification although they are illustrated in different drawings. For the purposes of clarity and simplicity, a detailed description of known functions and configurations incorporated herein may be omitted as it may obscure the subject matter of the present disclosure.

[0039] FIG. 1 is a circuit diagram showing a refrigeration cycle of an air conditioner according to a first embodiment, and FIG. 2 is a block diagram of a configuration of an air conditioner according to the first embodiment.

[0040] Referring to FIG. 1, the air conditioner 10 includes a compressor 100 configured to compress refrigerant. The compressor 100 includes an inverter compressor capable of adjusting an operating frequency.

[0041] The air conditioner 10 includes a discharge pipe 101 provided in an outlet of the compressor 100 to guide a liquid of the refrigerant compressed by the compressor 100. The discharge pipe 101 may include a first temperature sensor 161 configured to detect a temperature of the refrigerant compressed by the compressor 100. The first temperature sensor 161 may be referred to as a “discharge temperature sensor.” For example, a temperature value detected by the first temperature sensor 161 may be used to control an opening degree of a main expansion device 130.

[0042] The air conditioner 10 may further include a high pressure sensor 175 disposed in the discharge pipe 101 to detect a pressure of the refrigerant compressed by the compressor 100, that is, a high pressure of the refrigeration cycle. The pressure value detected by the high pressure sensor 175 may be used to perform control according to a target high pressure in an air heating operation.

[0043] The air conditioner 10 may further include a liquid changing valve 110 disposed in the discharge pipe 101 to change a liquid direction of the compressed refrigerant. For example, the liquid changing valve 110 may include a four-way valve.

[0044] The air conditioner 10 may include an outside heat exchanger 120 (outdoor and outside may be used synonymously herein) disposed in an outside unit and an inside heat exchanger 140 (indoor and inside may be used synonymously herein) disposed in an inside unit. The outside unit may be located outside and the inside unit may be located in an inside space.

[0045] When the air conditioner 10 operates in an air cooling operation mode, the refrigerant compressed by the compressor 100 is introduced into the outside heat exchanger 120 through the liquid changing valve 110. The refrigerant condensed by the outside heat exchanger 120 is decompressed by an inside expansion device (not illustrated) provided in the inside unit and is introduced into the inside heat exchanger 140. The refrigerant evaporated by the inside heat exchanger 140 is introduced into a gas liquid separator 150 through the liquid changing valve 110. Gas refrigerant separated by the gas liquid separator 150 is again sucked into the compressor 100.

[0046] On the other hand, when the air conditioner 10 operates in an air heating operation mode, the refrigerant compressed by the compressor 100 flows into the inside heat exchanger 140 through the liquid changing valve 110. The refrigerant condensed by the inside heat exchanger 140 is decompressed by the main expansion device 130 and is introduced into the outside heat exchanger 120. The refrigerant evaporated by the outside heat exchanger 120 is introduced into the gas liquid separator 150 through the liquid changing valve 110. Gas refrigerant separated by the gas liquid separator 150 is again sucked into the compressor 100.

[0047] The main expansion device 130 may be disposed in a pipe connecting the outside heat exchanger 120 and the inside heat exchanger 140. For example, the main expansion device 130 may include an electronic expansion valve capable of adjusting an opening degree.

[0048] The gas liquid separator 150 may be disposed on the side of a suction inlet of the compressor 100 to separate gas refrigerant from the evaporated refrigerant and provide the gas refrigerant to the compressor 100.

[0049] The air conditioner 10 may further include an outside fan 125 disposed on one side of the outside heat exchanger 120 to provide air flow so as to allow external air to flow toward the outside heat exchanger 120.

[0050] The air conditioner 10 may further include an inside fan 145 disposed on one side of the inside heat exchanger 140 to allow air in the inside space to flow toward the inside heat exchanger 140.

[0051] The air conditioner 10 may further include a second temperature sensor 165 that detects a temperature of the inside space. For example, a temperature value detected by the second temperature sensor 165 may be used to determine whether the temperature of the inside space reaches a set temperature during the air cooling operation or the air heating operation of the air conditioner 10 to determine whether an inside load is resolved.

[0052] The air conditioner 10 may further include a low pressure sensor 170 that detects a low pressure of the refrigeration cycle. The low pressure sensor 170 may be disposed in a path through which the evaporated refrigerant is sucked into the compressor 100. For example, the low pressure sensor 170 may be disposed in a “low pressure pipe” extending from the gas liquid separator 150 to the compressor 100 to guide the gas refrigerant separated by the gas liquid separator 150 to the compressor 100.

[0053] The air conditioner 10 may further include a load detecting unit 180 that detects a load of the inside space. The load of the inside space may be determined based on information about the size of the inside space or the thermal insulation of a building.

[0054] For example, the load detecting unit 180 may include a frequency detecting unit for detecting an operating frequency of the compressor 100. In order to allow a required cycle pressure, that is, a high pressure or a low pressure to be formed in a stable pressure range, during the air cooling operation or air heating operation of the air conditioner 10, the operating frequency of the compressor 100 may be increased or decreased. The frequency detecting unit may detect the rate of change in the operating frequency of the compressor 100. The operating frequency of the compressor 100 may be controlled to be increased to more quickly achieve the required cycle pressure.

[0055] For example, when the temperature of the inside space is not decreased during the air cooling operation of the air conditioner 10 at a sufficiently rapid rate, the low pressure of the refrigeration cycle may increase. Therefore, a control may be performed to increase the increase rate of the operating frequency of the compressor 100 in order to decrease the low pressure of the refrigeration cycle. When the control is performed, an inside load is determined as being large.

[0056] On the other hand, when the temperature of the inside space is rapidly decreased during the air cooling operation of the air conditioner 10, the low pressure of the refrigeration cycle typically decreases and therefore, controls may be performed to decrease the operating frequency of the compressor 100 or decrease the increase rate thereof to maintain the low pressure or decrease the low pressure of the refrigeration cycle. When the control is performed, the inside load is determined as being small.

[0057] As another example, the load detecting unit may include a power detecting unit that detects current consumption or power consumption in the air conditioner 10.

[0058] During the air cooling operation or air heating operation of the air conditioner 10, an inside load may be detected by using the current or power value detected through the current detecting unit or the power detecting unit. When an increase rate of the current or power value is large, it may be recognized that the inside load is large. On the other hand, when the increase rate of the current or power value is small, it may be recognized that the inside load is small.

[0059] The air conditioner 10 further includes a control unit 200 configured to control an operation of the compressor 100, the main expansion device 130, and/or the outside fan 125 based on information detected by the load detecting unit 180, the first temperature sensor 161, the second temperature sensor 165, the low pressure sensor 170, and/or the high pressure sensor 175.

[0060] The control unit 200 may be electrically connected to the load detecting unit 180, the temperature sensors 161 and 165, the low pressure sensor 170, the high pressure sensor 175, the load detecting unit 180, the compressor 100, the main expansion device 130, and/or the outside fan 125.

[0061] The air conditioner 10 may further include a memory unit 210 configured to store information about the operating frequency of the compressor 100 with respect to the operation modes of the air conditioner 10 in a mapping scheme. The memory unit 210 may store information about the opening degree of the main expansion device or information about the number of rotations of the outside fan 125, with respect to the operation modes of the air conditioner 10 in a mapping scheme.

[0062] FIG. 3 is a flowchart of a method of controlling an air conditioner, according to the first embodiment.

[0063] When the air conditioner 10 is turned on, the compressor 100 is driven, and an air cooling operation or an air heating operation is initiated.

[0064] For example, when the air conditioner 10 operates in the air heating operation mode, the compressor 100 may be controlled under what may be referred to as a “target high pressure control”. In the air heating operation, since the high pressure of the refrigeration cycle has a major impact on heating performance, the operating frequency of the compressor 100 may be determined such that the high pressure is formed in a set pressure range.

[0065] When the operating frequency of the compressor 100 increases, the high pressure may increase, and when the operating frequency of the compressor 100 decreases, the high pressure may decrease. When the compressor is driven at a predetermined operating frequency in the initial driving of the compressor 100, an increase rate of the high pressure is less than a predetermined increase rate, and the operating frequency of the compressor 100 may increase.

[0066] When the increase rate of the high pressure is less than a predetermined increase rate in a case where the operating frequency of the compressor 100 increases, the increase rate of the operating frequency of the compressor 100 may increase over time. In this case, an increase rate of the power consumption or current consumption of the air conditioner 10 may be relatively high.

[0067] On the contrary, when the compressor is driven at a predetermined operating frequency in the initial driving of the compressor 100, an increase rate of the high pressure is greater than a predetermined increase rate, and the operating frequency of the compressor 100 may be maintained or decrease. In this case, the increase rate of the power consumption or current consumption of the air conditioner 10 may be relatively low.

[0068] On the other hand, when the air conditioner 10 operates in the air cooling operation mode, the compressor 100 may be controlled under what may be referred to as a “target low pressure control”. In the air cooling operation, since the low pressure of the refrigeration cycle impacts cooling performance, the operating frequency of the compressor 100 may be determined such that the low pressure is formed in a set pressure range.

[0069] When the operating frequency of the compressor 100 increases, the low pressure may decrease, and when the operating frequency of the compressor 100 decreases, the low pressure may increase. When the compressor is driven at a predetermined operating frequency in the initial driving of the compressor 100, a decrease rate of the low pressure is less than a predetermined decrease rate, and the operating frequency of the compressor 100 may increase.

[0070] When the decrease rate of the low pressure is less than the predetermined decrease rate in a case where the operating frequency of the compressor 100 increases, the increase rate of the operating frequency of the compressor 100 may increase over time. In this case, the increase rate of the power consumption or current consumption of the air conditioner 10 may be relatively high.

[0071] On the contrary, when the compressor is driven at a predetermined operating frequency in the initial driving of the compressor 100, the decrease rate of the low pressure is greater than the predetermined decrease rate, and the operating frequency of the compressor 100 may remain the same or decrease. In this case, the increase rate of the power consumption or current consumption of the air conditioner 10 may be relatively low (S11 and S12).

[0072] The current load of the inside space may be determined through the load detecting unit 180. For example, the current load of the inside space may be determined based on a rate of change in the operating frequency of the compressor 100 or an increase rate of the power consumption or current consumption of the air conditioner 10. The determined current load is compared with a reference load to determine a level of the current load.

[0073] The reference load may correspond to a case where the increase rate of the operating frequency of the compressor 100 is a first set increase rate or a case where the increase rate of the power consumption or current consumption is a second set increase rate (S13 and S14).

[0074] When the determined current load is greater than or equal to the reference load, that is, when the increase rate of the operating frequency of the compressor 100 is greater than the first set increase rate, or when the increase rate of the power consumption or current consumption is greater than the second set increase rate, the determined current load may be referred to as a “high load”.

[0075] On the contrary, when the determined current load is greater than or equal to the reference load, that is, when the increase rate of the operating frequency of the compressor 100 is less than the first set increase rate or the operating frequency of the compressor 100 is maintained or decreases, or when the increase rate of the power consumption or current consumption is less than the second set increase rate, the determined current load may be referred to as a “low load”.

[0076] The air conditioner 10 may be controlled in different manners or control modes depending on whether the current load is determined as the “high load” or the “low load”.

[0077] For example, as shown in Table 1 below, when the current load is determined as the “high load”, the air conditioner 10 may be controlled to operate in a “high load operation mode”.

TABLE-US-00001 TABLE 1 Main expansion Mode Compressor device Outside fan High load First First set First set operation mode operating opening degree number of frequency rotations

[0078] In the “high load operation mode”, the operating frequency of the compressor 100 may be set to the first operating frequency. The first operating frequency may be set to an operating frequency that is close to the maximum operating frequency of the compressor 100. For example, the first operating frequency may be determined to be in a range from an operating frequency, which is 70% of the maximum operating frequency, to the maximum operating frequency.

[0079] In the “high load operation mode”, the opening degree of the main expansion device 130 may be set to a first set opening degree. The first set opening degree may be a relatively large opening degree as compared to when the air conditioner 10 is controlled to operate in the low load operation mode. For example, the first set opening degree may be set to a full opening degree. Since the first set opening degree is set to the relatively large opening degree, the amount of the refrigerant circulating through the refrigeration cycle increases, thus improving air conditioning performance.

[0080] When In the high load operation mode, the number of rotations of the outside fan 125 may be set to a first set number of rotations. The first set number of rotations may be a relatively large number of rotations as compared to when the air conditioner 10 is controlled to operate in the low load operation mode. For, the first set number of rotations may be set to the maximum number of rotations. Since the first set number of rotations is set to the relatively large number of rotations, the amount of heat exchanged in the outside heat exchanger increases, thus improving condensing performance or evaporation performance (S15, S16, and S17).

[0081] On the other hand, for example, as shown in Table 2 below, when the current load is determined as the “low load”, the air conditioner 10 may be controlled to operate in a “low load operation mode”.

TABLE-US-00002 TABLE 2 Main expansion Mode Compressor device Outside fan Low load Second Second set Second set operation mode operating opening degree number of frequency rotations

[0082] In the “low load operation mode”, the operating frequency of the compressor 100 may be set to the second operating frequency. The second operating frequency is understood as being a frequency value less than the first operating frequency. For example, the second operating frequency may be set to a value less than an operating frequency which is 70% of the maximum operating frequency.

[0083] In the low load operation mode, the opening degree of the main expansion device 130 may be set to the second set opening degree. The second set opening degree may be an opening degree less than the first set opening degree. For example, the second set opening degree may be set to an opening degree that is in a range of 50 to 80% of the full opening degree. Since the second set opening degree is set to the relatively small opening degree as compared to when the air conditioner 10 is controlled to operate in the high load operation mode, the amount of the refrigerant circulating through the refrigeration cycle slightly decreases, thus achieving the operation optimized to the low load.

[0084] When the air conditioner 10 may be controlled to operate in the low load operation mode, the number of rotations of the outside fan 125 may be set to the second set number of rotations. The second set number of rotations may be less than the first set number of rotations. For, the second set number of rotations may be set to the number of rotations that is in a range of 50 to 70% of the maximum number of rotations. Since the second set number of rotations is set to the relatively small number of rotations, the outside heat exchanger may achieve heat exchange performance optimized to the low load (S18 and S19).

[0085] When the air conditioner 10 operates in the high load operation mode or the low load operation mode, it may be determined whether the temperature of the inside space reaches a set temperature. The temperature of the inside space may be detected by the second temperature sensor 165 (S20).

[0086] When the temperature of the inside space reaches the set temperature, it is determined that the inside load is resolved, and an operation mode for maintaining the temperature of the inside space may be performed. This operation mode may be referred to herein as a “temperature maintenance operation mode”.

[0087] When the air conditioner 10 operates in the temperature maintenance operation mode, control may be performed to decrease a frequency of the compressor in a case where the air conditioner 10 operates in the high load operation mode or the low load operation mode. For example, in a case where the air conditioner 10 operates in the high load operation mode, when the temperature of the inside space reaches the set temperature, the operating frequency of the compressor 100 may be set to a frequency that is ½ of the first operating frequency. On the other hand, in a case where the air conditioner 10 operates in the low load operation mode, when the temperature of the inside space reaches the set temperature, the operating frequency of the compressor 100 may be set to a frequency that is ½ of the second operating frequency. Furthermore, the opening degree of the main expansion device 130 and the number of rotations of the outside fan 125 may be maintained (S21 and S22).

[0088] According to the above-described control method, it is possible to improve air cooling and air heating performance and prevent frequent thermo on/off by determining a load of the inside space through the load detecting unit and performing the high load operation mode and the low load operation mode based on the determined load of the inside space. When the temperature of the inside space reaches the set temperature, it is possible to perform an operation of maintaining the temperature of the inside space by decreasing the frequency of the compressor 100, thus allowing a user to continuously feel comfortable.

[0089] FIG. 4 is a flowchart of a method of controlling an air conditioner, according to a second embodiment. Since the second embodiment is different from the first embodiment in a partial configuration, a description will be given focusing on the difference and the same elements as the first embodiment quote the description and reference numerals of the first embodiment.

[0090] According to the second embodiment, when the air conditioner 10 is turned on, the compressor 100 is driven and an air cooling operation or an air heating operation is initiated. When the air conditioner 10 operates in an air heating operation mode, the compressor 100 is controlled under what is referred to as a “target high pressure control”. When the air conditioner 10 operates in an air cooling operation mode, the compressor 100 is controlled under what is referred to as a “target low pressure control”.

[0091] The current load of the inside space is determined through the load detecting unit 180. That is, the current load of the inside space may be determined based on a rate of change in the operating frequency of the compressor 100 or an increase rate of the power consumption or current consumption of the air conditioner 10. The determined current load may be compared with first and second reference loads.

[0092] The first reference load may correspond to a case where the increase rate of the operating frequency of the compressor 100 is a first set increase rate or a case where the increase rate of the power consumption or current consumption is a second set increase rate. In addition, the second reference load may correspond to a case where the increase rate of the operating frequency of the compressor 100 is a third set increase rate or a case where the increase rate of the power consumption or current consumption is a fourth set increase rate.

[0093] The third set increase rate may be lower than the first set increase rate, and the fourth set increase rate may be lower than the third set increase rate (S33 and S34).

[0094] When the determined current load is equal to or greater than the first reference load, that is, when the increase rate of the operating frequency of the compressor 100 is greater than the first set increase rate or when the increase rate of the power consumption or current consumption is greater than the second set increase rate, the determined current load may be referred to as a “high load”.

[0095] On the contrary, when the determined current load is less than the second reference load, that is, when the increase rate of the operating frequency of the compressor 100 is less than the third set increase rate or the operating frequency of the compressor 100 remains the same or decreases or when the increase rate of the power consumption or current consumption is less than the fourth set increase rate, the determined current load may be referred to as a “low load”.

[0096] In addition, when the determined current load is equal to or greater than the second reference load and is less than the first reference load, that is, when the increase rate of the operating frequency of the compressor 100 is equal to or greater than the third set increase rate and is less than the first set increase rate or when the increase rate of the power consumption or current consumption is equal to or greater than the fourth set increase rate and is less than the second set increase rate, the determined current load may be referred to as an “intermediate load”.

[0097] The air conditioner 10 may be controlled in different manners or control modes depending on whether the current load is determined as the “high load”, the “low load”, or the “intermediate load”.

[0098] Specifically, when the current load is determined as the “high load”, the air conditioner 10 may be controlled to operate in a “high load operation mode”, such as described above in Table 1. When the first operating frequency of the compressor 100 is set to be equal to or higher than a value that is 70% of the maximum operating frequency, the opening degree of the main expansion device 130 is set to a full opening degree, and the number of rotations of the outside fan 125 may be set to the maximum number of rotations.

[0099] When the current load is determined as the “low load”, the air conditioner 10 may be controlled to operate in the “low load operation mode”, such as described above in Table 2. When the second operating frequency of the compressor 100 is set to be equal to or less than a value that is 40% of the maximum operating frequency, the opening degree of the main expansion device 130 is set to be equal to or less than an opening degree that is 60% of the full opening degree, and the number of rotations of the outside fan 125 may be set to be equal to or less than a value that is 60% of the maximum number of rotations.

[0100] When the current load is determined as the “intermediate load”, the air conditioner 10 may be controlled to operate in a “general operation mode”. In this mode, the compressor 100 may be controlled to be driven at a third operating frequency, and the third operating frequency may be determined in a range of 40 to 70% of the maximum operating frequency. The opening degree of the main expansion device 130 may be determined in a range of 60 to 100% of the full opening degree and the number of rotations of the outside fan 125 may be determined in a range of 60 to 100% of the maximum number of rotations (S35 to S41).

[0101] When the air conditioner 10 operates in the high load operation mode, the low load operation mode, or the general operation mode, it is determined whether the temperature of the inside space reaches a set temperature. The temperature of the inside space may be detected by the second temperature sensor 165 (S42).

[0102] When the temperature of the inside space reaches the set temperature, it is determined that the inside load is resolved, and an operation mode for maintaining the temperature of the inside space may be performed. This operation mode may be referred to as a “temperature maintenance operation mode”.

[0103] When the air conditioner 10 operates in the temperature maintenance operation mode, control may be performed to decrease a frequency of the compressor in a case where the air conditioner 10 operates in the high load operation mode, the low load operation mode, or the general operation mode. For example, control may be performed to decrease the operating frequency of the compressor 100, which has been determined in each operation mode, by ½. Furthermore, the opening degree of the main expansion device 130 and the number of rotations of the outside fan 125 may be maintained (S43 and S44).

[0104] According to the above-described control method, it is possible to improve air cooling or heating performance and prevent frequent thermo on/off by determining a load of the inside space through the load detecting unit and performing the high load operation mode, the low load operation mode, or the general operation mode based on the determined load of the inside space. When the temperature of the inside space reaches the set temperature, an operation of maintaining the temperature of the inside space by decreasing the frequency of the compressor 100 may be performed, thus allowing a user to continuously feel comfortable.