KR100373075B1 - Control system for starting of air conditioner and control method thereof - Google Patents

Abstract

The air conditioner of the present invention includes a compressor controlled by a pulse width modulation method according to a duty control signal, and an electric expansion valve for expanding a refrigerant compressed in the compressor. The discharge side of the compressor and the inlet side of the electric expansion valve are connected by a high pressure pipe, and the outlet side of the electric expansion valve and the suction side of the compressor are connected by a low pressure pipe. One end of the bypass pipe is connected to the high pressure pipe, the other end is connected to the low pressure pipe, and a flow control valve is installed in the middle of the bypass pipe. The control unit performs the start operation of the compressor in two stages, so that in the first start-up operation, the flow control valve is opened and the electric expansion valve is closed. In the second start-up operation, the flow control valve is closed and the motor-expansion valve is opened at approximately 17%. Control, and the compressor is controlled by a duty control signal with a shorter period than normal operation. The ratio of the loading time and the unloading time during the second start operation of the compressor is approximately 5: 5.

Description

Control system for starting of air conditioner and control method

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

As buildings are enlarged, consumer demand for multi-air conditioners in which a plurality of indoor units are connected to one outdoor unit is increasing. Since the multi-air conditioner is installed relatively far away from the outdoor unit and the indoor unit, the length of the refrigerant pipe connecting the outdoor unit and the indoor unit is increased, thereby increasing the amount of refrigerant filling and increasing the possibility of inflow of liquid refrigerant into the compressor at startup.

In particular, if the power supply of any indoor unit is suddenly cut off during operation of the multi air conditioner, the possibility of inflow of liquid refrigerant is increased. In other words, if the power of the indoor unit is cut off abruptly, the power supply is interrupted to the electric expansion valve constituting the indoor unit. Therefore, the electric expansion valve remains open and the high-pressure liquid refrigerant in the refrigerant pipe between the condenser and the evaporator It enters the compressor or accumulator through expansion valve and evaporator.

This phenomenon continues until the pressure balance between the high pressure side and the low pressure side is achieved. The liquid refrigerant introduced into the compressor is mixed with the oil in the compressor to lower the concentration of oil, thereby inhibiting the lubrication of the friction part when the compressor starts. Causes damage.

On the other hand, in the case of a multi-air conditioner, not only a large cooling demand is required, but also a cooling demand ability is changed because the indoor unit that operates and the indoor unit that does not drive changes from time to time. In response to these demands, a large-capacity, variable-speed compressor is used in a multi-air conditioner. 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 good response and accuracy because it has to control the motor that is rotating 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 commercial AC input power is converted from a converter device to a DC power source and then converted into 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.

In addition, the variable-speed compressor is difficult to control the large capacity, it is difficult to meet the requirements of the large-capacity compressor with a 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 is usually used together with a variable speed compressor. 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 preceding material contains a control system or control method for applying a pulse width modulated compressor to a multi-air conditioner, in particular, to quickly and safely perform startup, to prevent the introduction of liquid refrigerant during startup, or to smoothly connect startup and normal operation. No control system or control method is disclosed.

SUMMARY OF THE INVENTION The present invention has been made under the above-mentioned background, and an object thereof is to provide a start control system and a method of controlling the same, which can quickly and safely start a compressor in an air conditioner employing a compressor controlled by a pulse width modulation method. .

Another object of the present invention is to provide an air conditioner starting control system and a method of controlling the same, which can prevent the liquid refrigerant from flowing into the compressor as much as possible in an air conditioner employing a pulse width modulation compressor. .

It is still another object of the present invention to provide a start control system and a control method for smoothly connecting start and normal operation by performing start operation in two stages in an air conditioner employing a pulse width modulation compressor.

1 is a cycle configuration diagram of an air conditioner starting 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 start control system of the present invention.

5 is a flowchart illustrating a process of controlling an air conditioner starting 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

33: compressor temperature sensor 34: condenser temperature sensor

The air conditioner start control system of the present invention for achieving the above object is a compressor controlled by a pulse width modulation method according to the duty control signal, an electric expansion valve for expanding the refrigerant compressed by the compressor, the discharge side of the compressor and the A high pressure pipe connecting the inflow side of the electric expansion valve, a low pressure pipe connecting the outlet side of the electric expansion valve and the suction side of the compressor, one end connected to the high pressure pipe and the other end connected to the low pressure pipe, A flow control valve installed in the middle of the bypass pipe to regulate the flow rate of the fluid flowing through the bypass pipe, and the start operation of the compressor is performed in two stages. Close the valve, and in the second start-up operation, the flow control valve is closed and the electric expansion valve is opened in a predetermined opening degree. And controlling driving of the flow control valve, and a control unit for controlling the compressor with the duty control signal of a period shorter than the normal operation.

The present invention also provides a control method for an air conditioner including a compressor controlled by a pulse width modulation method according to a duty control signal and an electric expansion valve for expanding a refrigerant compressed by the compressor. In the judging step, if the start signal is received in the step, the duty cycle of the compressor is operated in the normal operation state by closing the electric expansion valve and opening the flow control valve of the bypass pipe connecting the discharge side and the suction side of the compressor. A first start operation step of operating the compressor for a predetermined time by shortening the cycle, and following the first start operation, the motor expansion valve is opened at a predetermined opening degree and the cycle of the duty cycle of the compressor is opened with the flow control valve open; And a second start operation step of operating the compressor by shortening the period in the normal operation. 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. The double-dotted arrow indicates the flow direction of the gas refrigerant flowing through the vent-by-packet tube 12.

The high pressure tube exiting 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 an accumulator downstream of the hot gas bypass pipe 14 and the receiver 11 connecting the high pressure pipe 6 from the compressor 2 to the condenser 3 and the accumulator 10. And a liquid bypass pipe 15 connecting the upstream of 10). 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.

On the other hand, a compressor temperature sensor 33 for measuring the temperature of the refrigerant gas discharged is provided on the discharge side of the compressor 2, and in the middle of the condenser 3, the temperature of the condenser 3, preferably the condenser 3 Condenser temperature sensor 34 for measuring the central temperature of the is installed. The compressor temperature sensor 33 and the condenser temperature sensor 34 are connected to the outdoor control unit 27 as described later.

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 a suction port (18) and a discharge port (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 control unit 27 is connected to the outdoor communication circuit unit 28 to transmit and receive data, and is connected to the vent valve 13, the hot gas valve 16, and the liquid valve 17 to drive control these valves as necessary. . In addition, the above-mentioned compressor temperature sensor 33 and the condenser temperature sensor 34 is connected to the outdoor control unit 27.

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. 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.

In the present invention, the operation of the compressor 2 is divided into normal operation and start operation. Normal operation means that the compressor is operated according to the cooling request ability transmitted from the indoor unit when the power is already supplied to the compressor, that is, the startup is completed. The start operation is performed for starting when the start signal is input to the compressor. Say driving.

In the normal operation mode, the indoor control unit 29 receives signals from the temperature detection 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 its own cooling capability information, and when calculating the cooling demand capability, it is also possible to calculate the cooling demand capability based on the difference between the room temperature and the set temperature and their own cooling capability. 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 capacity is calculated and the compressor is operated with the loading time and the unloading time of the compressor 2 predetermined according to the total cooling demand capacity.

Referring to FIG. 5, the pressure balance process and the start operation before entering the start operation will be described. When it is determined whether the operation of the compressor in operation is stopped (S101), when the operation of the compressor is stopped, the electric expansion valve 4 and the vent will be described. The valve 13 is completely opened (S102). In this state, it is determined whether 30 seconds have elapsed (S103). If 30 seconds have not elapsed, step 102 is continued. If 30 seconds has elapsed, the hot gas valve 16 is opened (S104). Next, it is determined whether 3 minutes (2 minutes and 30 seconds after opening the hot gas valve) have elapsed after opening the electric expansion valve 4 and the vent valve 13 (S105). If 3 minutes have not elapsed in step 105, the steps 102 and 104 are continued to open the electric expansion valve 4, the vent valve 13 and the hot gas valve 16, and if 3 minutes have elapsed, the electric expansion valve ( 4), the vent valve 13 and the hot gas valve 16 are closed (S106). The reason why the pressure balance process is performed for 3 minutes is to reduce the starting load at the initial stage of operation of the compressor by forming a balance between high pressure and low pressure in the cycle. 3 minutes is the time required to balance the high and low pressures in the cycle, so it can vary from system to system.

Next, the start operation will be described. In this embodiment, the start operation consists of two stages. First, when the first stage start operation is described, it is determined whether the start signal of the compressor 2 has been input (S107). If the start signal has been received, the compressor 2 is operated, and the electric expansion valve 4 is closed. The hot gas valve 16 and the vent valve 13 are opened (S108). At this time, the period of the duty control signal for controlling the compressor 2 is shorter than the period of the duty control signal in the normal operation. The reason why the start operation cycle is shorter than that of the normal operation is that the pressure fluctuations are severe when starting with the normal operation cycle, which affects the reliability of the compressor and makes it difficult to realize safe starting. In addition, if the unloading time during normal operation is long, there is a problem that it takes a relatively long time to start, and if the loading time is long, the pressure drop is increased, as well as the possibility of inflow of liquid refrigerant from the accumulator 10 to the compressor 2. Because of this, maneuvering can be performed quickly and safely by loading frequently with relatively short loading times. In this embodiment, the duty cycle of the duty control signal of the compressor in the first stage start operation is 20 to 80% of the normal operation cycle, and 50% is most preferable. In the first stage start operation, the lower limit of the cycle is 20% because the loading time and the unloading time are usually in seconds, and there is a limit to reducing the minimum period. The upper limit is 80% or more. This is because the cycle shortening has little effect. Therefore, when the cycle of normal operation is 20 seconds, the cycle of the first stage start operation is 4 seconds to 16 seconds, and the most preferable period is 10 seconds.

In the first stage start-up operation, the compressor operates with 20 to 50% modulation. 20% modulation refers to the compressor operating at 2 seconds loading time and 8 seconds unloading time. Compressor runs with 5 seconds loading time and 5 seconds unloading time. The most desirable is 30% modulation, in which case the ratio of loading time to unloading time is 3: 7. The reason that the start operation is 50% or less of modulation is because the start operation is not a normal operation, and thus there is a limit to increase the modulation. If the modulation is increased at low temperature, the pressure drop is too high, which may affect the reliability of the compressor. Because.

This first stage start-up operation is carried out for 1 to 5 minutes, preferably 1 minute. Therefore, after performing the first step start operation, it is determined whether one minute has elapsed (S109), and when one minute has elapsed, it is switched to the second step start operation.

The reason for closing all the electric expansion valves 4 during the first stage start operation is that the liquid refrigerant in the receiver 11 and the evaporator 5, which have passed through the condenser 3 at the initial stage of start-up, flows into the accumulator 10 temporarily and the compressor 2 To prevent inhalation. In addition, by closing the motor expansion valve 4, the low-pressure refrigerant between the evaporator 5 and the compressor 2 is rapidly moved into the compressor 2 to be compressed and discharged, so that a quick start can be realized.

On the other hand, when all the motor expansion valves 4 are closed and the compressor 2 is operated, the refrigerant pressure drop between the motor expansion valve 4 and the compressor 2 occurs severely and the normal refrigerant is not circulated. May cause overheating. Therefore, the hot gas valve 16 is opened to connect the discharge side of the compressor 2 and the low pressure pipe upstream of the accumulator 10. Then, a part of the hot gas from the compressor 2 is introduced into the accumulator 10, thereby preventing the refrigerant pressure of the accumulator 10 portion from being severely lowered and the compressor 2 operates normally.

In addition, since the circulation of the refrigerant is not normally performed in the state in which all the electric expansion valves 4 are closed, the refrigerant condensed in the condenser 3 does not flow into the receiver 11 quickly. Therefore, by opening the vent valve 13 and drawing the gas refrigerant in the receiver 11 toward the low pressure side, the liquid refrigerant flows into the receiver 11 quickly, thereby realizing smooth starting.

In the second stage start-up operation, start-up and some cooling are performed simultaneously. To explain this, first, it is determined whether the difference between the discharge temperature of the compressor 2 and the central temperature of the condenser 3 is 10 to 30 ° C. or more (preferably 20 ° C. or more) (S110). The discharge temperature of the compressor (2) is detected by a compressor temperature sensor (33) installed on the discharge side of the compressor (2), and the central temperature of the condenser (3) is supplied to the condenser temperature sensor (34) provided at the center of the condenser (3). Is detected, and these detected temperatures are transmitted to the outdoor control unit 27. The outdoor controller 27 calculates the difference between the compressor discharge temperature and the condenser center temperature based on the transmitted temperature, and determines whether the difference is 10 to 30 ° C. or more (preferably 20 ° C. or more) (S110). If it is 30 ° C. or more (preferably 20 ° C.), the operation is switched to the normal operation (S114). Otherwise, the soft start (soft start) operation is performed (S111). When the difference between the compressor discharge temperature and the condenser center temperature is 10 to 30 ° C or more, the reason for switching to normal operation is that there is almost no inflow of liquid refrigerant into the compressor in that state. Therefore, this temperature range can vary from system to system.

In the soft start operation S111, the duty control signal cycle of the compressor 2 is set to 20 to 80% of the normal operation cycle in the same manner as the cycle in the above-described first stage start-up operation. In addition, the ratio of the loading time and the unloading time of the compressor in the soft start operation S111 is set to 4: 6 to 7: 3. In soft start operation, in addition to the start function, a small amount of coolant must be supplied to the indoor unit to perform a little cooling. Therefore, the ratio of loading time and unloading time is slightly higher than the ratio of loading time and unloading time in the first stage start operation. . Again, the preferred ratio of loading time to unloading time is 5: 5.

In the soft start operation S111, the electric expansion valve 4 is opened by about 5 to 33% (the most preferable opening degree is 17%) of the full opening, and the hot gas valve 16 and the vent valve 13 are opened. The operation of the second stage start operation with the modulation higher than that of the first stage start operation and opening at approximately 17% of the opening of the electric expansion valve 4 prevents the liquid refrigerant from entering the compressor 2 as much as possible. This is to realize a start and at the same time perform some cooling operation to smoothly switch to normal operation.

On the other hand, while performing step 111, it is determined whether the difference between the compressor discharge temperature and the condenser center temperature is 10 to 30 ° C or more (preferably 20 ° C) (S112), and 10 to 30 ° C or more (preferably 20 ° C). If the above), the operation is switched to the normal operation (S114), otherwise, the soft start operation of step 111 is performed only for a predetermined time and the operation is switched to the normal operation (S114). That is, even if the difference between the compressor discharge temperature and the condenser center temperature during the step 111 does not exceed 10 to 30 ° C (preferably 20 ° C or more), 3 to 8 minutes (preferably 5 minutes) have elapsed. If it is determined (S113) that 3 to 8 minutes (preferably 5 minutes) have elapsed, the process returns to the normal operation (S114). The reason is that if 3 to 8 minutes (preferably 5 minutes) has elapsed, the operation of the compressor enters a safe phase and therefore it is judged that there is almost no inflow of liquid refrigerant. Here, the time (3 to 8 minutes) is determined in consideration of both because the longer the better when the safety start is considered first, and the shorter the better when the cooling operation is to be started quickly.

As described in detail above, according to the start control system and control method of the air conditioner according to the present invention, a compressor that is controlled by a pulse width modulation method is adopted, and an electric expansion valve and a hot gas valve that is a flow regulating valve, a vent valve. By appropriately controlling the opening and closing of the compressor, it is possible to quickly and safely start the compressor. In addition, it is possible to prevent the introduction of the liquid refrigerant to the maximum when the compressor is started.

In addition, according to the start operation of the present invention and the control method thereof, the start operation of the compressor of the pulse width modulation method can be performed in two stages to smoothly connect the start operation and the normal operation.

Claims (15)

Compressor controlled by pulse width modulation method according to duty control signal, Electric expansion valve for expanding the refrigerant compressed by the compressor, A high pressure pipe connecting the discharge side of the compressor and the inlet side of the electric expansion valve, Low pressure pipe connecting the outlet side of the electric expansion valve and the suction side of the compressor, One end is connected to the high pressure pipe and the other end is a bypass pipe connected to the low pressure pipe, Is installed in the middle of the bypass pipe flow rate control valve for adjusting the flow rate of the fluid flowing through the bypass pipe, In the first start-up operation, the flow control valve is opened and the electric expansion valve is closed in the first start-up operation. In the second start-up operation, the flow control valve is closed and the motor-expansion valve is opened in a predetermined opening degree. And a control unit for controlling driving of the electric expansion valve and the flow regulating valve and controlling the compressor with a duty control signal having a shorter period than normal operation. In claim 1, And an accumulator installed in the middle of the low pressure pipe. In claim 2, The bypass pipe is a hot gas bypass pipe connecting the high pressure pipe between the compressor and the condenser and the accumulator, and the flow control valve is a hot gas valve installed in the hot gas bypass pipe. Starting control system. In claim 2, A receiver is installed in the high pressure pipe between the condenser and the expander, and the bypass pipe is a vent bypass pipe connecting the receiver and the upstream side of the accumulator, and the flow control valve is a vent installed in the vent bypass pipe. Air conditioner starting control system, characterized in that the valve. In claim 1, The duty cycle of the duty cycle during the startup operation of the compressor is 20 to 80% of the duty cycle period during the normal operation of the compressor. In claim 1, And a ratio of the loading time and the unloading time during the second startup operation of the compressor is 4: 6 to 7: 3. In claim 1, And a condenser temperature sensor for detecting a discharge temperature of the compressor and a condenser temperature sensor for detecting a central temperature of the condenser, wherein the second starting step has a difference of 10 to 30 ° C. between the compressor discharge temperature and the condenser central temperature. Air conditioner starting control system, characterized in that performed until. In claim 1, And the second start operation is performed for 3 to 8 minutes. In a control method of an air conditioner including a compressor controlled by a pulse width modulation method according to the duty control signal and an electric expansion valve for expanding the refrigerant compressed by the compressor, Determining whether the compressor start signal is input; If the start signal is received in this step, the cycle of the duty cycle of the compressor is shorter than that of the normal operation with the electric expansion valve closed and the flow control valve of the bypass pipe connecting the discharge side and the suction side of the compressor open. A first start operation step of operating the compressor for a predetermined time; A second startup operation step of operating the compressor by shortening the cycle of the duty cycle of the compressor to a period smaller than that in the normal operation with the electric expansion valve open to the predetermined opening following the first startup operation; Start control method of the air conditioner comprising a. In claim 9, The duty cycle period of the compressor in the second start operation step is 20 to 80% of the duty cycle period of the normal operation, the start control method of the air conditioner. In claim 9, The ratio of the loading time and the unloading time of the compressor in the second start operation step is 4: 6 to 7: 3, the start control method of the air conditioner. In claim 9, And the second starting operation step is performed until the difference between the compressor discharge temperature and the condenser central temperature is 10 to 30 ° C. In claim 9, And the second starting operation step is performed until it is determined that liquid refrigerant is not substantially introduced into the compressor. In claim 9, The second start operation step is the start control method of the air conditioner, characterized in that performed for 3 to 8. In claim 9, And the opening degree of the electric expansion valve in the second start operation step is approximately 5 to 33%.