KR100395918B1 - Air conditioner control system and control method thereof - Google Patents

Abstract

The air conditioner of the present invention includes an outdoor unit and a plurality of indoor units. The outdoor unit includes a compressor and a condenser controlled by a pulse width modulation method, an accumulator installed in a low pressure pipe upstream of the compressor, and a receiver installed in a high pressure pipe downstream of the condenser. The outdoor unit includes an outdoor controller connected to the compressor and the PWM valve to transmit a signal. The outdoor controller is connected to the outdoor communication circuit to transmit and receive data. Each indoor unit includes an indoor control unit, and a temperature detecting unit and a temperature setting unit are connected to an input port of the indoor control unit. Each indoor unit includes an indoor communication circuit unit that is capable of transmitting and receiving data with the indoor control unit. The indoor control unit receives a signal from the temperature detecting unit and the temperature setting unit and calculates the cooling demand of the indoor unit based on the cooling capacity and the difference between the indoor temperature and the set temperature. The calculated cooling demands of each indoor unit are transmitted to the outdoor control unit through the communication circuit unit, and the outdoor control unit calculates the total cooling demands of the indoor units together to generate the duty control signal and controls the compressor and PWM valve. do.

Description

Control system of air conditioner and control method thereof

The present invention relates to an air conditioner, and more particularly, to a control system of an air conditioner employing a pulse width modulation type compressor and a control method thereof.

An air conditioner uses a refrigeration cycle to realize air conditioning by regulating conditions such as room temperature and humidity in residential buildings or office buildings. However, the requirements for air conditioning vary from time to time because each person living or working in a building has different hopes and different outdoor environments. In particular, in a multi-air conditioner in which a plurality of indoor units are connected to one outdoor unit, the cooling requirements are different for each indoor unit, and in general, each indoor unit is operated independently, so the total cooling requirement is the sum of the cooling requirements of all indoor units. Will also change.

BACKGROUND ART A variable speed compressor is known as a compressor capable of varying a capacity (capacity) according to a variable cooling demand. The variable speed compressor can adjust the capacity of the compressor according to the change in cooling demand by controlling the number of revolutions of the motor by changing the frequency of the current applied to the motor through inverter control. However, the conventional variable speed compressor has a problem in that it is difficult to control the rotational speed of the motor with a good response and accuracy because it needs to directly control the rotating motor in accordance with the cooling requirements. In addition, since the rotational speed of the motor changes from time to time, vibration and noise are generated, resulting in shortening the service life of the motor and the compressor, and reducing the overall mechanical reliability.

In addition, in order to convert the frequency of the current applied to the motor is not only expensive and complicated circuit arrangements, but also has a disadvantage of less efficient than the general compressor because the power consumption is large. In particular, in the variable speed compressor, the first commercially available AC input power is changed from a converter device to a DC power source and then to an AC power source of the frequency required by the converter device. The circuit configuration becomes very complicated and a lot of electronic noise occurs.

On the other hand, as the size of the building increases, the number of indoor units connected to one outdoor unit increases, and thus, the total cooling demand capability also increases. However, the variable-speed compressor is difficult to control the large capacity, it is difficult to meet the requirements of the large-capacity compressor with one variable speed compressor because of the problems such as difficult to control, low efficiency, large overall size, expensive. Therefore, two or more compressors are used under a large capacity requirement. In this case, a standard compressor in which a motor rotates at a constant speed together with a variable speed compressor is usually used. In the case of using a plurality of compressors, the overall size of the outdoor unit becomes very large, and thus handling is difficult.

Another type of variable capacity compressor is a pulse width modulated compressor disclosed in US Pat. No. 6,047,557 and Japanese Patent Laid-Open No. 8-334094. However, such a compressor is used in a refrigeration system having a plurality of refrigerating chambers or freezing chambers, and it is assumed that the compressor is used for short pipes having a short length of the refrigerant pipe between the compressor and the evaporator. Therefore, it is inevitably a long pipe and the control environment cannot be applied to an air conditioning system of a building different from a refrigeration system. In addition, the above prior material does not disclose a control system or a control method for applying a pulse width modulation compressor to an air conditioner, especially a multi-air conditioner.

The present invention has been made under the above-described background, and the control of an air conditioner employing a compressor controlled by a pulse width modulation method so that the indoor unit and the outdoor unit are relatively far apart and suitable for a building air conditioner in which a plurality of indoor units are connected to one outdoor unit. It is an object to provide a system and a control method thereof.

Another object of the present invention is to calculate the cooling demand capacity of each indoor unit in each indoor unit to transmit to the outdoor unit and calculate the total cooling demand capacity in the outdoor unit effectively calculate the cooling demand capacity, pulse width modulation method according to the calculated cooling demand capacity It is to provide a control system of the air conditioner that can effectively vary the compressor of the compressor and its control method.

It is still another object of the present invention to provide a control system of an air conditioner, in which a refrigeration cycle including a plurality of evaporators together with a pulse width modulation compressor is effectively configured to be suitable for air conditioning of a building.

1 is a configuration of a refrigeration cycle of the air conditioner control system according to the present invention.

Figure 2a shows a loading state of the pulse width modulation type compressor used in the air conditioner of the present invention, Figure 2b shows an unloading state.

FIG. 3 illustrates a relationship between loading and unloading and a refrigerant discharge amount during operation of the compressor of FIG. 2.

4 is an overall block diagram of the air conditioner control system of the present invention.

5 is a view for explaining the relationship between the difference between the room temperature and the set temperature and the correction coefficient used in the air conditioner control system and control method of the present invention.

6A is a flowchart illustrating a control process performed in the indoor control unit of the air conditioner according to the present invention.

6B is a flowchart illustrating a control process performed in the outdoor controller of the air conditioner according to the present invention.

* Description of symbols on the main parts of the drawings *

2: compressor 5: evaporator

8: outdoor unit 9: indoor unit

26: PWM valve 27: outdoor control unit

28: outdoor communication circuit unit 29: indoor control unit

30: temperature detection unit 32: indoor communication circuit unit

In the air conditioner control system of the present invention for achieving the above object, the loading time during which the refrigerant is discharged and the unloading time during which the refrigerant is not discharged are repeated during operation, and the loading time and the unloading time are pulsed. A compressor controlled by a width modulation method, a condenser coupled to fluid flow with the compressor, a plurality of indoor units provided with the compressor and an evaporator coupled to fluid flow with the compressor, and an indoor controller configured to calculate a cooling demand of the indoor unit; And an outdoor control unit for generating a duty control signal for controlling the loading time and the unloading time of the compressor according to the cooling request capability transmitted from the indoor control unit, and adjusting the capacity of the compressor according to the duty control signal. It is done.

In addition, the air conditioning control system of the present invention is a compressor in which the loading time during which the refrigerant is discharged and the unloading time during which the refrigerant is not discharged are repeated, and the loading time and the unloading time are controlled by a pulse width modulation method. And a condenser connected to the fluid flow, the compressor and the evaporator connected to the fluid flow, the temperature sensor for sensing the indoor temperature of the air conditioning target space, the room temperature and the air conditioning target space sensed by the temperature sensor Calculating a cooling demand capability based on a difference from the set temperature set to a desired temperature of the controller, and generating a duty control signal for controlling the loading time and the unloading time of the compressor according to the calculated cooling demand capability. It characterized in that it comprises a control unit for adjusting the capacity of the compressor according to.

In addition, the air conditioner control system of the present invention includes a compressor in which the loading time during which the refrigerant is discharged and the unloading time during which the refrigerant is not discharged are repeated, and the loading time and the unloading time are controlled by a pulse width modulation method; A control unit for controlling the compressor, wherein the control unit generates a duty control signal which is a function of a cooling requirement transmitted from an indoor unit, adjusts the capacity of the compressor according to the duty control signal, and the duty control signal in the compressor And the loading time for discharging the coolant and the unloading time for discharging the coolant.

The present invention also provides a control method of an air conditioner including an outdoor unit having a compressor controlled by a pulse width modulation method and a plurality of indoor units having an evaporator, the method comprising: calculating a cooling demand capability of the indoor unit under the control of each indoor unit; Transmitting the cooling request capability calculated in the step to the outdoor unit, summing the cooling request capability of each indoor unit transmitted in the step under the control of the outdoor unit, the duty control being a function of the total cooling request capability in the step; Generating a signal and adjusting a capacity of the compressor according to the duty control signal, wherein the duty control signal is generated to determine a loading time for discharging the refrigerant from the compressor and an unloading time for discharging the refrigerant; It is characterized by.

The present invention also provides a control method of an air conditioner including a compressor controlled by a pulse width modulation method and an evaporator installed in a harmonic target space, detecting an indoor temperature of an air conditioning target space, and detecting the indoor temperature in the step. Calculating a difference between the preset temperature and the desired temperature of the air conditioning target space; calculating a cooling demand capacity based on the difference value obtained in the step; and a duty control signal as a function of the cooling demand capacity calculated in the step. And adjusting the capacity of the compressor according to the duty control signal, wherein the duty control signal is generated to determine a loading time for discharging the refrigerant from the compressor and an unloading time for discharging the refrigerant. It features.

Hereinafter, with reference to the accompanying drawings will be described embodiments of the present invention; 1 is a cycle configuration diagram of an air conditioner according to the present invention. The air conditioner (1) of the present invention includes a compressor (2), a condenser (3), an electric expansion valve (4), and an evaporator (5) sequentially connected by a refrigerant pipe to form a closed circuit. Among the refrigerant pipes, the refrigerant pipe connecting the discharge side of the compressor 2 and the inflow side of the electric expansion valve 4 is a high pressure tube 6 for guiding the flow of the high pressure refrigerant discharged from the compressor 2, and the electric expansion valve ( The refrigerant pipe connecting the outlet side of 4) and the suction side of the compressor 2 is a low pressure tube 7 for guiding the flow of the low pressure refrigerant expanded by the electric expansion valve 4. The condenser 3 is installed in the middle of the high pressure tube 6, and the evaporator 5 is installed in the middle of the low pressure tube 7. When the compressor 2 operates, the refrigerant flows in the direction of the solid arrow.

Meanwhile, the air conditioner 1 of the present invention includes an outdoor unit 8 and an indoor unit 9. The outdoor unit 8 includes the compressor 2 and the condenser 3 described above, and the accumulator 10 installed in the low pressure tube 7 upstream of the compressor 2 and the high pressure tube 6 downstream of the condenser 3. It includes a receiver 11 installed in. The accumulator 10 collects and vaporizes the liquid refrigerant which failed to evaporate in the evaporator 5 so as to flow into the compressor 2. That is, when the evaporator 5 does not completely evaporate, the refrigerant entering the accumulator 10 is a mixture of liquid and gaseous state, and the accumulator 10 vaporizes the liquid refrigerant, so that only the gaseous refrigerant (gas refrigerant) is compressed. Inhalation should be done. To this end, the refrigerant pipe inlet end and the refrigerant pipe outlet end of the accumulator 10 are preferably located above the accumulator 10.

Similarly, when complete condensation is not achieved in the condenser 3, the refrigerant entering the receiver 11 is a mixture of a liquid phase and a gaseous phase. The receiver 11 is configured to separate the liquid refrigerant and the gaseous refrigerant so that only the liquid refrigerant flows out. For this purpose, the refrigerant pipe inlet and outlet ends of the receiver 11 extend to the lower side of the receiver 11.

In order to bypass the gaseous refrigerant inside the receiver 11, a vent bypass pipe 12 is provided which connects the receiver 11 and the low pressure pipe 7 upstream of the accumulator 10. The inlet end of the vent bypass tube 12 is provided above the receiver 11 to allow only the gaseous refrigerant to flow therein, and a vent valve 13 is provided to adjust the flow rate of the bypassed gas refrigerant. 1 indicates the flow direction of the gas refrigerant flowing through the vent bypass pipe 12.

The high pressure tube from the receiver 11 is configured to pass through the accumulator 10. This is for vaporizing a low temperature liquid refrigerant in the accumulator 10 by using a refrigerant of a relatively high temperature passing through the high pressure tube. In order to effectively perform vaporization in the accumulator 10, the low pressure refrigerant tube inside the accumulator 10 is formed in a U shape, and the high pressure refrigerant tube passing through the accumulator 10 is arranged to pass through the inside of the U type low pressure refrigerant tube. do.

In addition, the outdoor unit 8 includes a hot gas bypass pipe 14 and a receiver 11 which connect the high pressure pipe between the compressor 2 and the condenser 3 and the accumulator 10 and the accumulator 10. And a liquid bypass pipe 15 connecting upstream. A hot gas valve 16 is installed in the midway of the hot gas bypass pipe 14 to adjust the flow rate of the hot gas bypassed, and a liquid valve 17 is installed in the midway of the liquid bypass pipe 15 to bypass. Adjust the flow rate of the liquid refrigerant. Therefore, when the hot gas valve 16 is opened, a part of the hot gas from the compressor 2 flows along the hot gas bypass pipe 14 in the direction of the dashed arrow, and when the liquid valve 17 is opened, the receiver 11 A part of the liquid refrigerant which flows out flows along the liquid bypass pipe 15 in the direction of a dashed-dotted arrow.

Several indoor units 9 are arranged in parallel, and each indoor unit 9 includes an electric expansion valve 4 and an evaporator 5. Therefore, a plurality of indoor units 9 are connected to one outdoor unit 8. The capacity and shape of each indoor unit 9 may be the same or different.

As shown in Figs. 2A and 2B, a variable capacity compressor 2 controlled by a pulse width modulation method is used as the compressor. The compressor (2) has a casing (20) provided with an inlet (18) and an outlet (19), a motor (21) provided inside the casing (20), and a rotating scroll (22) rotating under the rotational force of the motor (21). ) And a fixed scroll (24) for forming a compression chamber (23) between the orbiting scroll (22). The casing 20 is provided with a bypass tube 25 connecting the upper side of the fixed scroll 24 and the inlet 18, and the bypass tube 25 has a PWM valve in the form of a solenoid valve; 26) is installed. Fig. 2A shows a state where the PWM valve 26 is turned off to block the bypass pipe 25. In this state, the compressor 2 discharges the compressed refrigerant. This state is called loading, and the compressor 2 operates at a capacity of 100%. 2B illustrates a state in which the PWM valve 26 is turned on to open the bypass pipe 25, in which the refrigerant is not discharged from the compressor 2. This state is called unloading and the compressor 2 is operated at a capacity of 0%. The compressor 2 is supplied with power, whether loaded or unloaded, and the motor 21 rotates at a constant speed. When the power supply to the compressor 2 is cut off, the motor 21 does not rotate and the operation of the compressor 2 is stopped.

As shown in Fig. 3, the compressor 2 repeats loading and unloading at regular intervals during operation. In each cycle, the loading time and the unloading time vary depending on the cooling demand. At the loading time, the compressor 2 discharges the refrigerant, so that the temperature of the evaporator 5 decreases. Since it does not discharge, the temperature of the evaporator 5 rises. In FIG. 3, the area of the hatched portion represents the amount of refrigerant discharged. The signal controlling the loading time and the unloading time is called a duty control signal. In the embodiment of the present invention, the period is set to, for example, 20 seconds and takes a manner of varying the capacity of the compressor 2 by varying the loading time and the unloading time according to the total cooling demand of the indoor unit 9. .

4 is a block diagram of an air conditioner control system according to the present invention. As shown in FIG. 4, the outdoor unit 8 includes an outdoor controller 27 connected to the compressor 2 and the PWM valve 26 to enable signal transmission. The outdoor controller 27 is connected to the outdoor communication circuit 28 to transmit and receive data. Each indoor unit 9 includes an indoor control unit 29. A temperature detecting unit 30 and a temperature setting unit 31 are connected to an input port of the indoor control unit 29, and an electric expansion valve 4 is connected to the output port. Is connected. The temperature detector 30 is a temperature sensor that senses the temperature of the room, which is the harmonic space, and the cooling demand is calculated based on the temperature sensed by the temperature detector 30. Instead of a temperature sensor, a pressure sensor for sensing the pressure of the refrigerant may be used. The temperature sensor and the pressure sensor are load sensors for calculating a cooling demand of the indoor unit, that is, a load. Each indoor unit 9 includes an indoor communication circuit 32 that is capable of transmitting and receiving data with the indoor control unit 29. The outdoor communication circuit unit 28 and the indoor communication circuit unit 32 are provided to enable data transmission and reception by wire or wirelessly.

The indoor control unit 29 receives signals from the temperature detecting unit 30 and the temperature setting unit 31 and calculates the cooling demand capability of the indoor unit 9 based on the difference between the indoor temperature and the set temperature. In addition, the indoor control unit 29 has information on its cooling capacity, and when calculating the cooling demand capability, the indoor control unit 29 may calculate the cooling demand capability based on the difference between the room temperature and the set temperature and its own cooling capacity. Cooling capacity can be calculated based on the cooling capacity of.

When the indoor control unit 29 calculates the cooling demand based on only its cooling capacity, its cooling capacity becomes the cooling demand. In this case, the cooling capacity is converted into a capacity code value as shown in Table 1 and applied.

TABLE 1

Indoor unit 1 Indoor unit 2 Indoor unit 3 Indoor unit 4 Indoor unit 5 Indoor unit 6 Whole room Cooling capacity (kcal / hr) 6200 3550 2800 2800 1800 1800 18900 Ability code 62 35 28 28 18 18 189

In the example shown in Table 1, when six indoor units are connected to a 7.5 hp compressor, the capacity code is set to be a multiple of each indoor unit cooling capacity.

When calculating the cooling demand capacity of the indoor unit considering both the difference between the room temperature and the set temperature and its own cooling capacity, multiply the correction factor determined based on the difference between the room temperature and the set temperature and the capacity code obtained in Table 1. The value is cooling demand. The correction coefficient DELTA Q / 3 is determined by FIG.

As shown in Fig. 5,? Q is determined based on the difference between the room temperature and the set temperature, and even when the temperature difference is the same, the correction coefficient is different when the room temperature is going down and when the room temperature is going up. For example, △ Q is 3 when the room temperature is lower than the set temperature when the room temperature is lowered, △ Q is 2 when the room temperature is lower than 1 ℃ below the set temperature, and △ Q is 0 when it is lower than 1 ℃. . When ΔQ is 0, the motor expansion valve 5 is closed. When the electric expansion valve 5 is closed, the refrigerant does not flow to the indoor unit (9). If the room temperature rises and there is no difference between the room temperature and the set temperature, open the electric expansion valve (5). If the room temperature rises further and the room temperature is 1 ° C or lower than the set temperature, △ Q is 2 and △ Q is higher than 1 ° C. Is 3.

The cooling request capacity of each indoor unit thus calculated is transmitted to the outdoor control unit 27 through the communication circuits 28 and 32, and the outdoor control unit 27 sums the total cooling request of the indoor unit 9 by adding the cooling request capabilities. The capability is calculated to control the compressor 2 and the PWM valve 26. Table 2 shows the loading and unloading times set according to the total cooling requirements in the 20 second period.

TABLE 2

Loading time (sec) Unloading time (seconds) Total cooling requirement Loading time (sec) Unloading time (seconds) Total cooling requirement 20 0 157.5 ↑ 10 10 84.5-94.4 18 2 148.5-157.4 9 11 74.5-84.4 17 3 138.5-148.4 8 12 63.5-74.4 16 4 132.5-138.4 7 13 51.5-63.4 15 5 126.5-132.4 6 14 40.5-51.4 14 6 120.5-126.4 5 15 28.5-40.4 13 7 114.5-120.4 4 16 19.5-28.4 12 8 104.5-114.4 3 17 10.5-19.4 11 9 94.5-104.4 2 18 10.4 ↓

Next, a control method of an air conditioner according to the present invention will be described with reference to FIGS. 6A and 6B.

Referring to FIG. 6A, the control process of the indoor unit 9 will be described. The indoor control unit 27 determines whether the indoor unit 9 is on (S101). When the indoor unit 9 is in the on state, the indoor temperature is detected through the temperature detector 30 (S102), and the set temperature is detected through the temperature setting unit 31 (S103) to obtain a difference between the indoor temperature and the set temperature. (S104).

Next, the cooling request ability of the indoor unit 9 is calculated based on the cooling ability of the indoor unit 9 and the difference between the room temperature and the set temperature obtained above (105). In this step, the cooling capacity of the indoor unit 9 is converted into a capacity code value as shown in Table 1 above. The cooling demand of the indoor unit 9 is a value obtained by multiplying the above capacity code value by a correction factor determined by the difference between the room temperature and the set temperature. The correction coefficient DELTA Q / 3 is determined by FIG. 5, as described above. The cooling request capability of each indoor unit thus calculated is transmitted to the outdoor control unit 27 through the communication circuits 28 and 32 (S106). If the indoor unit 9 is in the off state in step 101, the indoor unit cooling request ability becomes 0 (S107), and this value is transmitted to the outdoor unit.

Referring to FIG. 6B, a control process of the outdoor unit 8 will be described. First, a total cooling request capability is calculated by summing cooling request capabilities transmitted from each indoor unit 9 (S201). Subsequently, if the total cooling demand is 0, the compressor 2 is stopped (S206), and if not 0, the compressor 2 is operated. When the compressor 2 is operated, a duty control signal is generated according to the total cooling demand capability obtained above (S204), and then the on / off control of the PWM valve is performed according to the generated duty control signal. The duty control signal refers to a signal for determining the loading time and the unloading time. The loading time and the unloading time are determined according to the total cooling requirements as shown in Table 2. When the duty control signal, that is, the loading time and the unloading time is determined, the outdoor controller 29 controls the PWM valve according to the duty control signal (S205).

As described in detail above, according to the control system and the control method of the air conditioner according to the present invention, a plurality of indoor units are connected to one outdoor unit by controlling the capability of the air conditioner using a pulse width modulation compressor It is also possible to efficiently control a large cooling load capacity such as an air conditioner.

In addition, by providing a communication circuit unit in the outdoor unit and the indoor unit to calculate the cooling requirements in each indoor unit to take the method to be transmitted to the outdoor unit can be effectively used for air conditioning of large buildings relatively far apart.

In addition, by calculating the cooling requirements of each indoor unit in each indoor unit and transmitting them to the outdoor unit, and calculating the total cooling requirements in the outdoor unit, the cooling requirements are effectively calculated. By generating the duty control signal of the pulse width modulation type compressor can effectively vary the capacity.

In addition, the air conditioner control system of the present invention using a pulse width modulated compressor, unlike the variable speed compressor that controls the rotating motor, the motor rotates at a constant speed even if the operating capacity of the compressor changes It is responsive and does not generate vibration and noise due to the change of rotational speed of the motor, which extends the life of the motor and compressor and improves the overall mechanical reliability. In addition, there is no need to convert the frequency of the current applied to the motor has the advantage of a simple structure of the control circuit and low power consumption.

Claims (32)

A compressor installed in an outdoor unit, the loading time of discharging the refrigerant and the unloading time of discharging the refrigerant during operation are repeated, and the loading time and the unloading time are controlled by a pulse width modulation method; A condenser in fluid communication with the compressor, A plurality of indoor units each provided with an evaporator connected to the compressor and the condenser to enable fluid flow; An indoor control unit calculating a cooling demand of the indoor unit; Air conditioning including an outdoor control unit for generating a duty control signal for controlling the loading time and the unloading time of the compressor according to the cooling request capability transmitted from the indoor control unit to adjust the capacity of the compressor according to the duty control signal Control system. In claim 1, Each indoor unit includes an indoor communication circuit unit for transmitting the cooling request capability calculated by the indoor control unit, and the outdoor unit includes an outdoor communication circuit unit for receiving data transmitted from the indoor communication circuit unit and transmitting the received data to the outdoor control unit. Air conditioning control system. In claim 1, And the indoor control unit is provided for each indoor unit, and the outdoor control unit changes the capability of the compressor according to the total cooling request capability summed up by the cooling request capability transmitted from each indoor control unit. In claim 1, The indoor unit includes a temperature sensor for sensing the indoor temperature, the indoor control unit is an air conditioner control system for calculating the cooling demand capacity based on the difference between the sensed indoor temperature and the preset set temperature. In claim 1, The indoor unit includes a temperature sensor for sensing an indoor temperature, wherein the indoor control unit is an air conditioner control system for calculating a cooling demand capacity based on the difference between the sensed room temperature and a predetermined set temperature and its own cooling capacity. In claim 5, The air conditioner control system is the cooling request ability is a value multiplied by a correction factor determined by the difference between the sensed room temperature and the set temperature and a capacity code that is a multiple of the cooling capacity. In paragraph 6 The correction factor is an air conditioner control system having a higher value when the room temperature is lower than when the room temperature is higher. In claim 1, The air conditioner control system having a capacity of 100% and 0% of the compressor. In claim 1, The air conditioner control system, characterized in that the plurality of indoor units are arranged in parallel. In claim 1, The outdoor unit further includes an accumulator installed in the low pressure pipe upstream of the compressor and a receiver installed in the high pressure pipe downstream of the condenser. In claim 10, And the outdoor unit further comprises a vent bypass pipe connecting the receiver and the low pressure refrigerant pipe upstream of the accumulator and a vent valve provided in the middle of the vent bypass pipe. In claim 11, The low pressure refrigerant pipe inside the accumulator is formed in a U shape, the high pressure refrigerant pipe passing through the accumulator from the receiver is arranged to pass through the interior of the U-type low pressure refrigerant pipe. In claim 10, The outdoor unit further comprises a hot gas bypass pipe branched between the compressor and the condenser to connect the accumulator and a hot gas valve installed in the middle of the hot gas bypass pipe. . In paragraph 10 The outdoor unit further includes a liquid bypass pipe connecting a downstream of the receiver and an upstream of the accumulator, and a liquid valve installed in the middle of the liquid bypass pipe. A compressor in which a loading time for discharging the refrigerant and an unloading time for discharging the refrigerant are repeated during operation, wherein the loading time and the unloading time are controlled by a pulse width modulation method; A condenser in fluid communication with the compressor, An evaporator in fluid communication with the compressor and the condenser, Temperature sensor for sensing the indoor temperature of the air conditioning target space, The cooling demand capacity is calculated based on the difference between the room temperature sensed by the temperature sensor and the set temperature set to the desired temperature of the air conditioning target space, and the loading time and the unloading time of the compressor according to the calculated cooling demand capacity. And a controller configured to generate a duty control signal for controlling the controller and adjust the capacity of the compressor according to the duty control signal. The method of claim 15, The air conditioner control system of the two states of the compressor is 100% and 0%, respectively. The method of claim 15, The control unit is an air conditioner control system for calculating a cooling demand capacity in consideration of the cooling capacity of the evaporator. The method of claim 15, The evaporator is a control system of the air conditioner is connected in plurality. delete A loading time during which the refrigerant is discharged and an unloading time during which the refrigerant is not discharged are repeated, and the loading time and the unloading time are controlled by a pulse width modulation method, and a control unit for controlling the compressor, The control unit generates a duty control signal which is a function of the cooling requirement transmitted from the indoor unit, and adjusts the capacity of the compressor according to the duty control signal, And the duty control signal is generated to determine the loading time for discharging the refrigerant from the compressor and the unloading time for discharging the refrigerant. The method of claim 20, The compressor capacity is 100% at the loading time and the compressor capacity is 0% at the unloading time. A control method of an air conditioner including an outdoor unit having a compressor controlled by a pulse width modulation method and a plurality of indoor units having an evaporator, Calculating a cooling demand capability of the indoor unit under the control of each indoor unit, Transmitting the cooling request ability calculated in the step to the outdoor unit, Summing up the cooling demands of each indoor unit transmitted in the step under the control of the outdoor unit; Generating a duty control signal which is a function of the total cooling demand capability in the step, and adjusting the capacity of the compressor according to the duty control signal, The duty control signal is generated to determine the loading time for discharging the refrigerant from the compressor and the unloading time for discharging the refrigerant. The method of claim 22, The control method of the air conditioner, characterized in that the cooling request ability of the indoor unit in the step of calculating the cooling demand capacity of the indoor unit is calculated based on its cooling capacity. At the twenty-second In the step of calculating the cooling demand capacity of the indoor unit, the cooling demand capacity of the indoor unit is calculated on the basis of its cooling capacity and the difference between the room temperature and the set temperature. The method of claim 24, The air conditioner control method of the indoor unit is characterized by multiplying the capacity code value, which is a multiple of its own cooling capacity, with a correction factor determined by the difference between the room temperature and the set temperature. The method of claim 25, The correction coefficient is an air conditioner control method having a higher value when the room temperature is lower than when the room temperature is increased. The method of claim 22, The cooling request capability transmitting step is a control method of the air conditioner, characterized in that transmitted from the communication circuit unit of the indoor unit to the communication circuit unit of the outdoor unit. delete The method of claim 22, The compressor capacity is 100% at the loading time, and the compressor capacity is 0% at the unloading time. A control method of an air conditioner including a compressor controlled by a pulse width modulation method and an evaporator installed in a space to be harmonized, Detecting an indoor temperature of an air conditioning target space, Obtaining a difference between the preset temperature set by the desired temperature of the air conditioning target space and the detected indoor temperature; Calculating a cooling requirement based on the difference value obtained in the above step, Generating a duty control signal which is a function of the cooling demand capability calculated in the step to adjust the capacity of the compressor according to the duty control signal, The duty control signal is generated to determine the loading time for discharging the refrigerant from the compressor and the unloading time for discharging the refrigerant. The method of claim 30, Wherein the step of calculating the cooling requirement, the control method of the air conditioner, characterized in that to obtain a correction coefficient determined by the difference between the room temperature and the set temperature multiplied by the capacity code value determined as a multiple of the cooling capacity of the evaporator. The method of claim 31, And the correction coefficient is higher when the room temperature is lower than when the room temperature is high.