KR20060078324A - A device for controlling the capacity and controlling method thereof - Google Patents

Abstract

The present invention relates to a capacity control device of an air conditioner and a control method thereof. The present invention relates to a refrigerant flow path of an air conditioner having two first and second compressors and a plurality of indoor units. Equipped with a four-way switching member and a solenoid valve, such as 100%, 60%, and 40% for the first and second compressors, it improves the compression capacity through continuous three-stage capacity control, making it easier to operate the variable energy. In addition to reducing the pressure, the load capacity of the plurality of indoor units is immediately responded, and the pressure imbalance of the compressor is quickly healed, thereby preventing the wear of the first and second compressors.

Multi-Air Conditioner, Capacity Control, Four-way Valve, Equal Pressure, Pressure Balance, Solenoid Valve

Description

Capacity control device of air conditioner and control method {A Device For Controlling The Capacity And Controlling Method Thereof}             

1 is a block diagram of a conventional air conditioner incorporating first and second compressors and first and second chambers,

2 is a view showing a capacity control method of a general first and second compressors,

3 is a configuration diagram of an air conditioner incorporating first and second compressors and first and second chambers according to the present invention;

4 is a flowchart illustrating a state in which both the first and second compressors according to the present invention are operated.

5 is a view of a state in which only the first compressor operating in accordance with the present invention,

6 is a view of a state in which only the second compressor according to the invention operates,

7 is a block diagram of a capacity control device for an air conditioner according to the present invention;

8 is an operation flowchart of the start operation control according to the present invention,

9 is an operational flow chart according to the 100% start-up operation control according to the present invention,

10 is an operational flow chart according to the 60% starting operation control according to the present invention,

11 is an operation flowchart of the 40% start-up operation control according to the present invention,

12 is an operation flowchart of a normal operation control process according to the present invention,

13 is a flow chart of operation of the 40% to 60% capacity control according to the present invention,

14 is a flowchart of operation by 60% to 100% capacity control according to the present invention,

15 is a flow chart of operation of the 40% to 100% capacity control according to the present invention,

16 is an operational flow chart according to the 100% to 60% capacity control according to the present invention,

17 is a flowchart of operation by 60% to 40% capacity control according to the present invention,

18 is a flow chart of operation of the 100% to 40% capacity control according to the present invention,

19 is an operational flow diagram according to the stop operation control according to the present invention,

20 is a graph showing a change in capability and power consumption according to various operating conditions according to the present invention.

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

A: Indoor device B: Outdoor device

102: evaporator 104: first suction tube

106: second suction pipe 112: first compressor

114: second compressor 116: low pressure connector

116a: branch pipe 118: first discharge pipe

120: second discharge pipe 122: four-way switching member

124: solenoid valve 126: check valve

128: condenser 140: control unit

142: signal input unit 150: safety device

PAC: Room 1 RAC: Room 2

The present invention relates to an air conditioner employing a plurality of indoor units and a plurality of compressors. In particular, the present invention relates to a pressure balance of a compressor input / output stage in a refrigerant passage of an air conditioner having two first and second compressors and a plurality of indoor units. Equipped with a four-way switching member and a solenoid valve to switch in all directions, such as 100%, 60%, and 40% for the first and second compressors, it is possible to improve the compression capacity through continuous three-stage capacity control to facilitate variable operation. Capacity control device of air conditioner and control method which prevents wear of first and second compressors as it not only saves energy but also responds immediately to load capacity of multiple indoor units and quickly heals pressure imbalance of compressor. It is about.

In general, an air conditioner compresses a refrigerant to a high pressure with an outdoor heat exchanger driven by a motor, and liquefies the refrigerant condensed at a high pressure by evaporating the refrigerant in an indoor heat exchanger while moving it to a tube having a small diameter. Cold air is generated by lowering the temperature, and cooling is performed since the generated cold air is discharged into the room.

In addition, the refrigerant vaporized while absorbing heat in the indoor heat exchanger moves from the compressor to the outdoor heat exchanger to condense and liquefy to release heat to the outside to continuously cool through the above process.

1 is a configuration diagram of a conventional air conditioner incorporating first and second compressors and first and second chambers, and FIG. 2 is a view illustrating a capacity control method of a general first and second compressors.

The conventional air conditioner including the first and second compressors and the first and second chambers is an outdoor device (B) that is installed outdoors. The first and second compressors compress the refrigerant at high temperature and high pressure. Two compressors 12 and 14; First and second discharge pipes (16) (18) for transferring the compressed refrigerant of the first and second compressors (12) and (14); First and second check valves (20) and (22) installed in the first and second discharge pipes (16) and (18) to prevent the refrigerant flowing back; A condenser 24 for condensing the refrigerant transferred through the first and second check valves 20 and 22 to a low temperature and high pressure state, and selectively storing the refrigerant condensed in the condenser 24 in a first chamber (PAC). And a second selection valve for selectively transferring the refrigerant condensed in the condenser 24 to the second chamber RAC.

In addition, as the indoor device A installed indoors, an expansion valve for rapidly expanding the refrigerant conveyed through the condenser 24 in each of the first indoor chamber (PAC) and the second indoor chamber (RAC) to a low temperature and low pressure state ( 26); An evaporator (2) having a high temperature and low pressure so as to absorb the heat of the room from the expansion refrigerant by the expansion valve (26) to discharge cold air; It consists of first and second suction pipes (4) (6) for branching the refrigerant evaporated in the evaporator (2).

At this time, the expansion valve 26 of the second chamber RAC may be installed before the second selection valve of the outdoor device (A).

When the total capacity of the refrigerant is 100%, the first compressor 12 has a compression capacity capable of compressing 40% of the total refrigerant capacity, and the second compressor 14 compresses 60% of the total refrigerant capacity. It is installed to have the compression capacity that it can.

Looking at the state using the conventional air conditioner, first, when the user performs a drive that requires 100%, the first and second compressors 12, 14 are driven simultaneously to the first, second The refrigerant sucked into the suction pipes 4 and 6 is discharged to the first and second discharge pipes 16 and 18 to move.

Then, the first and second check valves 20 and 22 condense in the condenser 24 in a state of preventing backflow, and supply the cold air indoors through the expansion valve 26 and the evaporator 2.

On the other hand, when the air conditioner operates a mode for power saving, only one of the first and second compressors 12 and 14 is selectively operated to weakly supply cold air.

As shown in FIG. 2, when operating in the automatic operation mode, driving control of the first and second compressors is performed according to the load capacities of the first chamber and the second chamber.

That is, the load capacity DT in the first room = room temperature (RT)-defined as the air conditioner set temperature (ST), and similarly the load capacity DT in the second room (DT) = room temperature (RT)-air conditioner set temperature ( ST) and is set by the sum of the load capacities DT of the first room and the second room.

If the load capacity DT rises above the set value 1 (DTS1), it is judged to be 100% operation and drives both the first and second compressors 12 and 14, and the load capacity DT is When it is between the set value 1 (DTS1) and the set value 2 (DTS2), only the second compressor 14 is driven, and the load capacity DT is set between the set value 2 (DTS2) and the set value 3 (DTS3). If it is in, only the first compressor 12 will be driven.

Through this control process, the load capacity DT is minimized to properly maintain the room temperature RT.

However, the conventional multi-stage multi air conditioner uses excessive current at the start of the first and second compressors 12 and 14 so that the energy consumption efficiency is remarkably lowered as the compressor starts and stops continuously. Has the problem.

A high pressure is applied between the first and second compressor pipes 16 and 18 between the first and second compressors 12 and 14 and the shank valves 20 and 22. Since the low pressure acts on the first and second suction pipes 4 and 6 at the rear end of the two compressors 12 and 14, the first and second compressors 12 and 14 stopped when the pressure balance is not maintained. In operation, significant difficulties arise in the activation of the first and second compressors 12 and 14. Therefore, there is a problem in that the compressor cannot be operated immediately because the time required for the equalization for operating the stationary compressor is required.

In addition, the air conditioning system using the plurality of compressors frequently increases and decreases the energy efficiency by repeatedly operating / stopping the compressor. Since the liquid back phenomenon occurs due to the pressure difference during the operation of the compressor, the compressor is frequently used. Due to the operation / stop of the cause of wear of the compressor has a problem of reducing the reliability of the compressor.

The present invention has been made in view of this point, and an object of the present invention is to switch in all directions for the pressure balance of the compressor input / output stage to a refrigerant flow path of an air conditioner having two first and second compressors and a plurality of indoor units. Equipped with a four-way switching member and a solenoid valve, the first and second compressors, such as 100%, 60%, and 40%, improve the compression capacity through continuous three-stage capacity control to facilitate variable operation by dramatically improving energy. In addition to reducing the load capacity of a plurality of indoor units and to immediately heal the pressure imbalance of the compressor to provide a capacity control device and an control method of the air conditioner to prevent wear of the first and second compressors have.

The capacity control apparatus of the air conditioner according to the present invention for realizing the above object is provided with a first and a second compressor and a plurality of indoor units in the air conditioner having a continuous variable capacity, the first, second First and second suction pipes for branching the refrigerant transferred through the transfer pipe from the evaporator to suck the refrigerant into the two compressors; First and second discharge pipes for supplying a refrigerant compressed by the first and second compressors to a condenser; A check valve for preventing a refrigerant from flowing back from the second discharge pipe to the first discharge pipe; A bypass circuit connected between the first and second discharge pipes and the transfer pipe to maintain a uniform pressure by communicating a high pressure applied to a front end of the first and second compressors to a low pressure formed at a rear end thereof. It is done.

The bypass circuit may include a low pressure connection pipe connected between the first discharge pipe and the transfer pipe to equalize the high pressure of the front end of the first compressor to a low pressure; A solenoid valve installed in the low pressure connection pipe to control the transfer of refrigerant; A branch pipe connected to the low pressure connecting pipe from the second discharge pipe; It is provided in the second discharge pipe and the branch pipe is made of a four-way switching member for opening and closing the transfer of the refrigerant to equalize the high pressure of the front end of the second compressor to low pressure.

The controller may be configured to control the first and second compressors, the four-way switching member, and the solenoid valve, respectively, and include a signal input unit for inputting a control signal to the controller.

The four-way switching member is preferably a three-way valve or a four-way valve that opens and closes the second discharge pipe and the branch pipe, respectively.

In addition, the capacity control method of the air conditioner according to the present invention is a pressure control method of the air conditioner having a first variable, a second compressor and a plurality of indoor units having a continuous variable capability, desired operation in the signal input unit Inputting the control unit to select an operation mode; Selectively starting the first and second compressors after the step and performing any one of the starting operation during the highest capacity, the middle capacity and the lowest capacity operation; After the step, the control unit determines whether the safety device is in operation, if there is an error, enters the stop operation mode; otherwise, terminates the start operation and enters the normal operation mode; After the step, the control unit determines the load of the first and second compressors for the load capacity of the plurality of indoor units, and then selects one of the normal operation modes among the load increase operation, the load reduction operation, the load maintenance operation, and the stop operation. Driving; Determining whether the safety device is operated after the step, and if there is an error, entering the stop operation mode; otherwise, continuing the normal operation mode; After the step, the input signal to the stop signal is input to the control unit or the safety device is detected when the abnormality is detected when entering the stop operation mode comprising the step of stopping the first and second compressors It is done.

In addition, the 100% start-up operation step, which is the highest capacity for starting both the first and second compressors during the start-up operation step, opens the solenoid valve, connects the first discharge pipe and the low pressure connection pipe, and equalizes the pressure to low pressure. Turning on the switching member to connect the second discharge pipe to the branch pipe to equalize it at low pressure; Operating said first compressor after said step; Closing the solenoid valve after the step; After the step, the second compressor is operated, and the four-way switching member is turned off.

And, 60% start-up operation step of the intermediate capacity for starting only the second compressor during the start-up operation step, the ON and the four-way switching member to connect the second discharge pipe to the branch pipe to equalize to low pressure; Connecting the second discharge pipe to the condenser by turning off the four-way switching member after the step; After the step consists of operating only the second compressor.

The 40% start-up operation step, which is the lowest capacity for starting only the first compressor during the start-up operation step, opens the solenoid valve, connects the first discharge pipe and the low pressure connecting pipe to equalize the pressure at low pressure, and turns on the four-way switching member. Connecting the second discharge pipe to the branch pipe to equalize it at low pressure; Operating said first compressor after said step; After the step consists of shutting off the solenoid valve.

The operation of increasing the load from the 40% capacity of the lowest capacity to the 60% capacity of the intermediate capacity among the load increase operation steps of increasing the load in the normal operation step operates the second compressor while the first compressor is in operation. Making a step; Connecting the first discharge pipe to a condenser by turning off the four-way switching member after the step; Stopping the first compressor; After the step, the solenoid valve is operated to connect the first discharge pipe to the low pressure connection pipe to equalize to low pressure, and after a certain time, the solenoid valve is shut off.

In addition, the operation of increasing the load from the intermediate capacity of 60% to the highest capacity of 100% in the load increasing operation step of increasing the load in the normal operation step operates the solenoid valve while the second compressor is in operation. Connecting the first discharge pipe to the low pressure connecting pipe to equalize the low pressure; Operating the first compressor; After the step consists of shutting off the solenoid valve.

The operation of increasing the load from the 40% capacity of the lowest capacity to the 100% capacity of the highest capacity among the load increasing operation steps of increasing the load in the normal operation step operates the second compressor while the first compressor is in operation. Making a step; After the step, the four-way switching member is turned off to connect the second discharge pipe to the condenser.

In the normal operation step, the operation of reducing the load from the 100% capacity of the highest capacity to the 60% capacity of the medium capacity of the load reduction operation step reduces the first compressor in a state in which both the first and second compressors are in operation. Stopping; Opening the solenoid valve after the step and connecting the first discharge pipe and the low pressure connection pipe to equalize to low pressure; After the step consists of shutting off the solenoid valve.

In the normal operation step, the operation of reducing the load from the intermediate capacity of 60% to the lowest capacity of 40% capacity is performed by opening the solenoid valve while the second compressor is in operation. Connecting the first discharge pipe and the low pressure connecting pipe to a low pressure; Operating said first compressor after said step; Shutting off the solenoid valve after the step; After the step, the four-way switching member is turned on to connect the second discharge pipe and the branch pipe to the low pressure, and then the step of stopping the second compressor.

In addition, the operation of reducing the load from the 100% capacity of the highest capacity to the 40% capacity of the lowest capacity among the load reduction operation steps of reducing the load in the normal operation step may be performed on all four sides in a state in which both the first and second compressors are in operation. Turning on the member to connect the second discharge pipe and the branch pipe to equalize the pressure at low pressure; After the step consists of stopping the second compressor.

In the step of stopping the first and second compressors after the 40% operation, which is the lowest capacity, the four-way switching member is first turned off to connect the second discharge pipe to the condenser, and then the first compressor is stopped. It is preferable.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In addition, this embodiment is presented by way of example only, not limitation of the scope of the invention.

3 is a configuration diagram of an air conditioner incorporating the first and second compressors and the first and second chambers according to the present invention, and FIG. 4 is a diagram illustrating the operation of both the first and second compressors according to the present invention. 5 is a view of a state in which only the first compressor according to the present invention operates, FIG. 6 is a view of a state in which only the second compressor according to the present invention operates, and FIG. 7 is a view of an air conditioner according to the present invention. 8 is a configuration diagram of a capacity control device, and FIG. 8 is a flowchart of operation by starting operation control according to the present invention.

The configuration of the capacity control device of the air conditioner of the present invention, the first, second compressor 112, 114 and the first, the second room (PAC) (RAC) is provided to exhibit a continuous variable capacity In the air conditioner, the first and second suction pipes 104 which branch the refrigerant transferred from the evaporator 102 through the transfer pipe 103 to suck the refrigerant into the first and second compressors 112 and 114. 106; First and second discharge pipes (118) (120) for supplying the refrigerant compressed by the first and second compressors (112, 114) to the condenser (128); A check valve (126) for preventing a refrigerant from flowing back from the second discharge pipe (120) to the first discharge pipe (118); Low pressure is connected between the first and second discharge pipes 118 and 120 and the transfer pipe 103 to be applied to the front end of the first and second compressors 112 and 114 at a lower end thereof. It consists of a bypass circuit (C) to communicate with each other to maintain a uniform pressure.

At this time, the first compressor 112 has a compression capacity capable of compressing 40% of the total refrigerant capacity when the total capacity of the refrigerant is 100%, the second compressor 114 is 60 of the total refrigerant capacity Installed to have a compression capability to compress%.

The capacity of such compressors can be distributed at different rates as they are distributed as needed.

In addition, the bypass circuit (C) is connected between the first discharge pipe (118) and the transfer pipe 103, the low-pressure connection pipe 116 for equalizing the high pressure of the front end of the first compressor 112 to low pressure )and; A solenoid valve 124 installed in the low pressure connecting pipe 116 to control the transfer of the refrigerant; A branch pipe 116a connected to the low pressure connecting pipe 116 from the second discharge pipe 120; It is installed in the second discharge pipe 120 and the branch pipe (116a) is made of a four-way switching member 122 for opening and closing the transfer of the refrigerant to equalize the high pressure of the front end of the second compressor 114 to low pressure.

In addition, the controller 140 is configured to control the first and second compressors 112 and 114, the four-way switching member 122, and the solenoid valve 124, respectively, and provides a control signal to the controller 140. It comprises a signal input unit 142 for input.

The four-way switching member 122 uses a three-way valve or a four-way valve that opens and closes the second discharge pipe 120 and the branch pipe 116a, respectively.

Or less, on the basis of the accompanying drawings to look at the capacity control method of the air conditioner according to the present invention.

As shown in FIGS. 7 and 8, after inputting a desired operation to the signal input unit 142, the controller 142 determines the load capacity in the first and second indoor (PAC) RAC according to the corresponding operation. The controller 142 selects an operation mode. (S10)

After the above step, the first and second compressors 112 and 114 are selectively started to perform any one of the starting operation during the highest capacity, the middle capacity, and the lowest capacity operation.

At this time, as shown in Figure 9, during the start operation step (S20), the 100% start operation step (S110) of the highest capacity for starting both the first and second compressors 112, 114, the solenoid Open the valve 124 to connect the first discharge pipe 118 and the low pressure connection pipe 116 to equalize to low pressure. (S111)

Then, the four-way switching member 122 is turned on to connect the second discharge pipe 120 to the branch pipe 116a so as to equalize to a low pressure.

After the step, the first compressor 112 is operated to shut off the solenoid valve 124. (S113) (S114)

Then, after the step, the second compressor 114 is operated to turn off the four-way switching member 122. (S115) (S116)

In addition, as shown in FIG. 10, for example, the 60% starting operation step S120, which is an intermediate capacity for starting only the second compressor 114 during the starting operation step S20, the four-way switching member 122. ON to connect the second discharge pipe 120 to the branch pipe (116a) to equalize to low pressure. (S121)

After the step, the four-way switching member 122 is turned off to connect the second discharge pipe 120 to the condenser 128, and to operate only the second compressor 123. (S122) (S123)

And, as shown in FIG. 11, for example, the lowest capacity for starting only the first compressor 112 during the start operation step (S20), for example, 40% start operation step (S130), the solenoid valve 124 Open and connect the first discharge pipe 118 and the low pressure connection pipe 116 to equalize the low pressure, turn on the four-way switching member 122 to connect the second discharge pipe 120 to the branch pipe (116a) low pressure To equalize. (S131) (S132)

Then, the first compressor 112 is operated, and after the step, the solenoid valve 124 is blocked. (S133) (S134)

And, as shown in Figure 8, after the step, the control unit 140 determines whether the safety device 150 is operating, if there is an error, enters the stop operation mode (S40), otherwise, start operation End to enter the normal operation mode. (S30) (S40)

On the other hand, as shown in Figure 12, after the step after determining the load of the first, second compressors 112, 114 for the load capacity by a plurality of indoor units after the step, the load increase operation, load Select one of the normal operation modes during the reduction operation, the load maintenance operation, and the stop operation. (S60) (S70)

At this time, the operation of increasing the load from the 40% capacity of the lowest capacity to the 60% capacity of the medium capacity in the load increase operation step (S140) of increasing the load in the normal operation step (S70), the first compressor 112 In operation, the second compressor 114 is operated. (S141)

Then, the four-way switching member 122 is turned off to connect the first discharge pipe 120 to the condenser 128, and to stop the first compressor 112. (S142) (S143)

Then, after the step, the solenoid valve 124 is operated to connect the first discharge pipe 118 to the low pressure connection pipe 116 to equalize to low pressure and to shut off the solenoid valve 124 after a predetermined time. S144) (S145)

As shown in FIG. 14, the operation of increasing the load from the 60% capacity of the medium capacity to the 100% capacity of the maximum capacity during the load increase operation step S140 of increasing the load in the normal operation step S70 is performed by the second operation. The solenoid valve 124 is operated while the compressor 114 is in operation to connect the first discharge pipe 118 to the low pressure connecting pipe 116 to equalize to a low pressure.

Then, the first compressor 112 is operated to shut off the solenoid valve 124. (S147) (S148)

As shown in FIG. 15, the operation of increasing the load from the 40% capacity of the lowest capacity to the 100% capacity of the highest capacity in the load increasing operation step (S140) of increasing the load in the normal operation step (S70) is performed by the first operation. The second compressor 114 is operated while the compressor 112 is in operation, and the four-way switching member 122 is turned off to connect the second discharge pipe 120 to the condenser 128 (S149). (S150)

As shown in FIG. 16, the operation of reducing the load from the 100% capacity of the highest capacity to the 60% capacity of the medium capacity in the load reduction operation step S160 of reducing the load in the normal operation step S70 includes: The first compressor 112 is stopped while both the compressors 112 and 114 are in operation (S161).

Then, the solenoid valve 124 is opened to connect the first discharge pipe 118 and the low pressure connecting pipe 116 to equalize to low pressure, and shut off the solenoid valve 124. (S162) (S163)

As shown in FIG. 17, the operation of reducing the load from the 60% capacity of the medium capacity to the 40% capacity of the lowest capacity in the load reduction operation step S160 of reducing the load in the normal operation step S70 is performed in the second operation. The solenoid valve 124 is opened while the compressor 114 is in operation to connect the first discharge pipe 118 and the low pressure connecting pipe 116 to equalize to low pressure.

Then, the first compressor 112 is operated to block the solenoid valve 124.

Then, the four-way switching member 122 is turned on to connect the second discharge pipe 120 and the branch pipe 116a to be equalized to low pressure, and then the second compressor 114 is stopped. (S167) (S168) )

As shown in FIG. 18, the operation of reducing the load from the 100% capacity of the highest capacity to the 40% capacity of the lowest capacity in the load reduction operation step S160 of reducing the load in the normal operation step S70 may include: In the state in which both of the second compressors 114 are in operation, the four-way switching member 122 is turned on to connect the second discharge pipe 120 and the branch pipe 116a to equalize to a low pressure, and the second compressor 114 (S169) (S170).

And, as shown in Figure 12, after the step is determined whether the operation of the safety device 150, if there is an error, enters the stop operation mode (S40), otherwise, continue the normal operation mode to continue. (S80)

Meanwhile, as shown in FIG. 9, when the signal input unit 142 receives a stop signal and is received by the control unit 140, or when an abnormality is detected in the safety device 150, the vehicle enters the stop operation mode S40. One case is determined by the controller 140 to stop the first and second compressors 112 and 114. (S40) (S90) (S92) (S94)

At this time, in the step (S90) of stopping the first and second compressors 112 and 114, when stopping after the 40% of the lowest capacity, the four-way switching member 122 is first turned off to the second discharge. After the pipe 120 is connected to the condenser 128, the first compressor 112 is stopped.

20 is a graph showing a change in power and power consumption according to various operating conditions according to the present invention. FIG. 20 shows the power and power consumption of 100%, 60% and 40% of power input. Indicates power and capacity.

As described above, the present invention includes a four-way switching member and a solenoid valve that are switched in all directions for pressure equalization of the compressor input and output terminals in a refrigerant passage of an air conditioner having two first and second compressors and a plurality of indoor units. As the first and second compressors, such as 100%, 60%, 40%, etc., continuous three-stage capacity control improves the compression capacity to make variable operation easier, which not only saves energy dramatically, but also loads a plurality of indoor units. It immediately responds to the capacity and quickly heals pressure imbalances in the compressor, which has the advantage of preventing wear of the first and second compressors.

In addition, there is an advantage to significantly reduce the liquid back phenomenon occurring at the start of the compressor under any operating conditions to improve the reliability and efficiency of the compressor.

Claims (15)

In the air conditioner equipped with the first and second compressors and a plurality of indoor units exhibiting continuous variable capacity, First and second suction pipes which branch the refrigerant transferred through the transfer pipe from the evaporator to suck the refrigerant into the first and second compressors; First and second discharge pipes for supplying a refrigerant compressed by the first and second compressors to a condenser; A check valve for preventing a refrigerant from flowing back from the second discharge pipe to the first discharge pipe; A bypass circuit connected between the first and second discharge pipes and the transfer pipe to communicate a high pressure applied to a front end of the first and second compressors with a low pressure formed at a rear end to maintain a uniform pressure; Capacity control device of the air conditioner, characterized in that consisting of. The method of claim 1, wherein the bypass circuit, A low pressure connection pipe connected between the first discharge pipe and the transfer pipe to equalize the high pressure of the front end of the first compressor to a low pressure; A solenoid valve installed in the low pressure connection pipe to control the transfer of refrigerant; A branch pipe connected to the low pressure connecting pipe from the second discharge pipe; A four-way switching member installed in the second discharge pipe and the branch pipe to open and close the transfer of the refrigerant to equalize the high pressure in front of the second compressor to low pressure; Capacity control device of the air conditioner, characterized in that consisting of. The control unit according to claim 1 or 2, further comprising a control unit for controlling the first and second compressors, the four-way switching member, and the solenoid valve, and a signal input unit for inputting a control signal to the control unit. Capacity controller of an air conditioner. The capacity control apparatus of claim 2, wherein the four-way switching member is a three-way valve or a four-way valve that opens and closes the second discharge pipe and the branch pipe, respectively. In the control method of the air conditioner equipped with the first and second compressors and a plurality of indoor units exhibiting a continuous variable capacity, Inputting a desired operation to a signal input unit so that the control unit selects an operation mode; Selectively starting the first and second compressors after the step and performing any one of the starting operation during the highest capacity, the middle capacity and the lowest capacity operation; After the step, the control unit determines whether the safety device is in operation, if there is an error, enters the stop operation mode; otherwise, terminates the start operation and enters the normal operation mode; After the step, the control unit determines the load of the first and second compressors for the load capacity of the plurality of indoor units, and then selects one of the normal operation modes among the load increase operation, the load reduction operation, the load maintenance operation, and the stop operation. Driving; Determining whether the safety device is operated after the step, and if there is an error, entering the stop operation mode; otherwise, continuing the normal operation mode; Stopping the first and second compressors by determining a case in which a stop signal is input to the control unit by the signal input unit after the step or a case where an abnormality is detected in the safety device and the vehicle enters the stop operation mode; Capacity control method of the air conditioner, characterized in that consisting of. The 100% start operation step according to claim 5, wherein the 100% start operation step, which is the highest capacity for starting both the first and second compressors during the start operation step, Opening the solenoid valve to connect the first discharge pipe and the low pressure connecting pipe to equalize the low pressure, and turn on the four-way switching member to connect the second discharge pipe to the branch pipe to equalize the low pressure; Operating said first compressor after said step; Closing the solenoid valve after the step; Operating the second compressor after the step and turning off the four-way switching member; Capacity control method of the air conditioner, characterized in that consisting of. The 60% start operation step according to claim 5, wherein the 60% start operation step, which is an intermediate capacity for starting only the second compressor during the start operation step, Turning on the four-way switching member to connect the second discharge pipe to the branch pipe and to equalize it at low pressure; Connecting the second discharge pipe to the condenser by turning off the four-way switching member after the step; Starting only the second compressor after the step; Capacity control method of the air conditioner, characterized in that consisting of. The 40% start operation step according to claim 5, wherein the 40% start operation step, which is the lowest capacity for starting only the first compressor during the start operation step, Opening the solenoid valve to connect the first discharge pipe and the low pressure connecting pipe to equalize the low pressure, turn on the four-way switching member, and connect the second discharge pipe to the branch pipe to equalize to low pressure; Operating said first compressor after said step; Shutting off the solenoid valve after the step Capacity control method of the air conditioner, characterized in that consisting of. The method of claim 5, wherein the operation of increasing the load from the 40% capacity of the lowest capacity to the 60% capacity of the medium capacity among the load increase operation steps of increasing the load in the normal operation step, Operating the second compressor while the first compressor is in operation; Connecting the first discharge pipe to a condenser by turning off the four-way switching member after the step; Stopping the first compressor; Operating the solenoid valve after the step to connect the first discharge pipe to the low pressure connecting pipe to equalize to low pressure and to shut off the solenoid valve after a certain time; Capacity control method of the air conditioner, characterized in that consisting of. The method of claim 5, wherein the operation of increasing the load from the intermediate capacity of 60% capacity to the highest capacity 100% capacity among the load increase operation steps of increasing the load in the normal operation step, Operating the solenoid valve in the state where the second compressor is in operation to connect the first discharge pipe to the low pressure connecting pipe to equalize to low pressure; Operating the first compressor; Shutting off the solenoid valve after the step; Capacity control method of the air conditioner, characterized in that consisting of. The method of claim 5, wherein the operation of increasing the load from the 40% capacity of the lowest capacity to the 100% capacity of the highest capacity among the load increase operation steps of increasing the load in the normal operation step, Operating the second compressor while the first compressor is in operation; Connecting the second discharge pipe to a condenser by turning off the four-way switching member after the step; Capacity control method of the air conditioner, characterized in that consisting of. The method of claim 5, wherein the operation of reducing the load from the 100% capacity of the highest capacity to the 60% capacity of the medium capacity among the load reduction operation steps of reducing the load in the normal operation step, Stopping the first compressor while both the first and second compressors are in operation; Opening the solenoid valve after the step and connecting the first discharge pipe and the low pressure connection pipe to equalize to low pressure; Shutting off the solenoid valve after the step; Capacity control method of the air conditioner, characterized in that consisting of. The method of claim 5, wherein in the normal operation step, the operation for reducing the load from the medium capacity of 60% capacity to the lowest capacity 40% capacity is performed. Opening the solenoid valve in a state where the second compressor is in operation to connect the first discharge pipe and the low pressure connecting pipe to equalize to low pressure; Operating said first compressor after said step; Shutting off the solenoid valve after the step; After the step, the four-way switching member is turned on and the second discharge pipe and the branch pipe are connected to equal pressure at low pressure, Stopping the second compressor; Capacity control method of the air conditioner, characterized in that consisting of. The method of claim 5, wherein the operation for reducing the load from the 100% capacity of the highest capacity to the 40% capacity of the lowest capacity among the load reduction operation steps of reducing the load in the normal operation step, Turning on the four-way switching member in a state in which both the first and second compressors are in operation to connect the second discharge pipe and the branch pipe to equalize the pressure at low pressure; Stopping the second compressor after the step Capacity control method of the air conditioner, characterized in that consisting of. The method of claim 5, wherein when stopping after the 40% operation, which is the lowest capacity among the steps of stopping the first and second compressors, the four-way switching member is first turned off to connect the second discharge pipe to the condenser. A capacity control method of an air conditioner, characterized in that the first compressor is stopped.

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