KR100395920B1 - Control system for starting of air conditioner and control method thereof - Google Patents

Abstract

The air conditioner of the present invention is a compressor controlled by a pulse width modulation method according to a duty control signal, an 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, electric expansion Low pressure pipe that connects the outlet side of the valve and the suction side of the compressor, one end is connected to the high pressure pipe, the other end is installed in the middle of the bypass pipe, bypass pipe to control the flow of fluid flowing through the bypass pipe It includes a flow control valve. The controller controls the compressor to close the electric expansion valve and open the flow regulating valve at the start of the compressor, and generates a duty control signal with a shorter period than in normal operation to control the compressor. The bypass pipe includes a vent bypass pipe connecting the receiver and the low pressure pipe upstream and 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 installed in the vent bypass pipe. Includes vent valves and hot gas valves installed in hot gas bypass lines.

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 become larger, there is an increasing demand for multi-air conditioners in which a plurality of indoor units are connected to one outdoor unit. 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. If the power of the indoor unit is cut off abruptly without using the remote control, the power supply is cut off because the electric expansion valve that constitutes the indoor unit does not close. Therefore, the high pressure liquid in the refrigerant pipe between the condenser and the electric expansion valve is not closed. The refrigerant is introduced into the compressor or the accumulator upstream of the compressor without being evaporated through the electric expansion valve and the 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 at the start of the compressor. Cause damage.

On the other hand, in the case of multi-air conditioners, not only large cooling demands are required, but also the cooling demands are changed because the indoor unit to be driven and the indoor unit not to drive are changed 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 rotational variable compressor has a problem in that it is difficult to control the rotational speed of the motor with 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.

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 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 any control system or control method for applying a pulse width modulation compressor to a multi-air conditioner, in particular, a control system or control method for quickly and safely starting.

SUMMARY OF THE INVENTION The present invention has been made under the above-described background, and an object of the present invention is to provide a starter control system and a control method of an air conditioner that can perform a starter of a compressor quickly and safely while employing a compressor controlled by a pulse width modulation method. It is done.

Another object of the present invention is to provide a system for controlling the start of an air conditioner and a method of controlling the same, which can prevent the inflow of liquid refrigerant at the time of starting in an air conditioner employing a pulse width modulation compressor.

1 is a configuration of a refrigeration cycle of the air conditioner start 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 an air conditioner starting control system according to 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 4: electric expansion valve

5: evaporator 8: outdoor unit

9: Indoor unit 13: Vent valve

16: hot gas valve 17: liquid valve

26: PWM valve 27: outdoor control unit

The air conditioner start control system of the present invention for achieving the above object, the compressor controlled by the pulse width modulation method, an electric expansion valve for expanding the refrigerant compressed by the compressor, the discharge side of the compressor and the inlet side of the expander A high pressure pipe for connecting, a low pressure pipe for connecting the outlet side of the expander and the suction side of the compressor, one end of which is connected to the high pressure pipe and the other end of which is installed in the middle of the bypass pipe and the bypass pipe. A flow control valve for controlling the flow rate of the fluid flowing in the bypass pipe, controlling the driving of the electric expansion valve and the flow control valve to close the electric expansion valve and open the flow control valve when the compressor is started; It includes a compressor control unit for generating a duty control signal of a shorter period than in normal operation to control the compressor.

In addition, the start control system of the air conditioner according to the present invention includes a compressor controlled by a pulse width modulation method, an electric expansion valve for expanding the refrigerant compressed by the compressor, a high pressure connecting the discharge side of the compressor and the inlet side of the expander Low pressure pipe connecting the outlet side of the expander and the suction side of the compressor, one end is connected to the high pressure pipe and the other end is connected to the low pressure pipe, the bypass pipe is installed in the middle of the bypass pipe and the bypass And a control unit for controlling the flow rate control valve, the electric expansion valve, and the compressor to prevent the liquid refrigerant from flowing into the compressor when the compressor is started.

In addition, the air conditioner start control method of the present invention, the step of determining whether the start signal is input to the compressor controlled by the pulse width modulation method, if the start signal is received at the step, closes the electric expansion valve and the discharge side and suction of the compressor A start operation step of operating the compressor with the flow control valve of the bypass pipe connecting the side open; determining whether a predetermined time has elapsed during the start operation; It includes a step.

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 pipe 12 is provided above the receiver 11 to allow only the gaseous refrigerant to flow therein, and a vent valve 13 is provided as a flow control valve 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 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. In the middle of the hot gas bypass pipe 14, a hot gas valve 16, which is one of the flow control valves, is installed to adjust the flow rate of the bypassed hot gas, and the liquid valve 17 in the middle of the liquid bypass pipe 15. ) To adjust the flow rate of the liquid refrigerant bypassed. 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 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. . 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 operates according to the cooling request ability transmitted from the indoor unit when the power is supplied to the compressor and the startup is completed. The start operation refers to the operation performed for starting when the start signal is input to the compressor. .

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.

With reference to FIG. 5, the press-balancing process and starting operation before entering into a starting operation are demonstrated. First, it is determined whether the compressor 2 is stopped under the control of the outdoor control unit 27 (S101), and when the compressor 2 is in the stopped state, the electric expansion valve 4 and the vent valve 13 are completely opened. (S102) (S103). In this state, it is determined whether 30 seconds have elapsed (S104), and when 30 seconds has elapsed, the hot gas valve 16 is opened. Next, it is determined whether 2 minutes and 30 seconds (3 minutes after opening the electric expansion valve 4 and the vent valve 13) have elapsed after the hot gas valve is opened (S105). When 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. The start operation is also performed under the control of the outdoor control unit 27. First, it is determined whether the start signal of the compressor 2 is input (S108), and if the start signal is received, the compressor 2 is operated to operate the motor expansion valve 4 ) Is closed, and the hot gas valve 16 and the vent valve 13 are opened (S109). 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 severe, and the possibility of inflow of liquid refrigerant from the accumulator 10 to the compressor 2 is possible. This makes it possible to perform the maneuver quickly and safely by loading frequently and with relatively short loading times. In this embodiment, the start operation cycle is 20 to 80% of the normal operation cycle, and 50% is most preferable. The lower limit of the start cycle is 20% because the loading time and unloading time are usually in seconds, and there is a limit to reducing the minimum possible period. The upper limit is 80%. This is because the cycle shortening has little effect. Therefore, when the cycle of the normal operation is 20 seconds, the cycle of the start operation is 4 seconds to 16 seconds, the most preferable period is 10 seconds.

In addition, during start-up operation, the compressor operates with 20 to 50% modulation, where 20% modulation refers to the compressor running at 2 seconds loading time and 8 seconds unloading time. Driving with a loading time of seconds and an unloading time of 5 seconds. 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.

The reason for closing all the electric expansion valves 4 during the start-up operation is that the liquid refrigerant in the receiver 11 and the evaporator 5, which have passed through the condenser 3 at the beginning of the start-up, flows into the accumulator 10 at a time and enters the compressor 2. This is to prevent inhalation. In addition, the quick start can be realized by closing the electric expansion valve 4 to quickly bring the inside of the refrigerant pipe between the evaporator 5 and the compressor 2 and the suction part of the compressor 2 into a low pressure state.

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 flows into the accumulator 10, thereby preventing the refrigerant pressure of the accumulator 10 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.

For reference, the liquid valve 17 is opened when it is necessary to replenish the liquid component because the degree of superheat of the refrigerant sucked into the compressor 2 is high.

On the other hand, step 108 is performed for about 1 to 5 minutes, preferably 1 minute. That is, it is determined whether 1 minute has elapsed while performing step 108 (S109). If 1 minute has elapsed, the start operation is terminated. Otherwise, step 108 is continued. Such start operation time is set to a time suitable for starting the cooling operation as soon as possible while achieving the intended purpose of the start operation. If only safety start is considered, it is better to perform the start operation for a sufficient time, but in this case, the start time of normal operation or cooling operation is delayed, so this time is set to 1 minute in this example. If you focus on, it can be up to 5 minutes.

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.

Claims (13)

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, At the start of the compressor, the electric expansion valve is closed and the drive of the electric expansion valve and the flow control valve is controlled to open the flow control valve, and the duty control signal is generated in a shorter period than in normal operation to operate the compressor. Air conditioner starting control system including a control unit for controlling. According to claim 1, wherein the accumulator is installed in the middle of the low pressure pipe, the bypass pipe is a hot gas bypass pipe connecting the accumulator and the high pressure pipe between the compressor and the condenser, the flow control valve is the hot Air conditioner starting control system, characterized in that the hot gas valve installed in the gas bypass pipe. The method of claim 1, wherein the accumulator is installed in the middle of the low pressure pipe, the high pressure pipe downstream of the condenser is installed, the bypass pipe is a vent bypass pipe connecting the upstream side of the receiver and the accumulator, And the flow control valve is a vent valve installed in the vent bypass pipe. The air conditioner starting control system according to claim 1, wherein the duty control signal period during the start operation of the compressor is 20 to 80% of the duty control signal period during the normal operation of the compressor. The air conditioner starting control system according to claim 1, wherein the ratio of the loading time and the unloading time during the compressor starting operation is 2: 8 to 5: 5. The air conditioner starting control system according to claim 1, wherein the starting operation of the compressor is performed for 1 to 5 minutes. 2. The air conditioner starting control system according to claim 1, wherein the period of the duty control signal during the start-up operation of the compressor is 4 to 16 seconds. delete Determining whether a start signal is input to the compressor controlled by the pulse width modulation method according to the duty control signal; And a start operation step of operating the compressor for a predetermined time with the flow control valve of the bypass pipe connecting the discharge side and the suction side of the compressor open when the start signal is received in the step. Starting control method of the machine. 10. The method of claim 9, wherein the start operation step operates the compressor with a duty control signal having a shorter period than a normal operation. The method of claim 9, wherein the duty cycle of the duty control signal of the compressor in the start operation step is 20 to 80% of the duty control signal cycle of the normal operation. The method of claim 9, wherein the ratio of the loading time and the unloading time of the compressor in the start operation step is 2: 8 to 5: 5. The start control method of the air conditioner of claim 9, wherein the start operation is performed for 1 to 5 minutes.