KR102500807B1 - Air conditioner and a method for controlling the same - Google Patents

Abstract

According to the control method of the air conditioner according to the present embodiment, the step of driving the refrigeration cycle to perform a heating operation; starting a defrosting operation by changing a control state of a flow switching valve when it is determined that a defrosting operation start point has arrived during the heating operation; and adjusting the operating frequency of the compressor and the opening degree of the main expansion device when the defrosting operation is performed. In the step of adjusting the operating frequency of the compressor and the opening degree of the main expansion device, the operating frequency of the compressor is Controlling the low pressure of the refrigerating cycle to be equal to or higher than the minimum target low pressure; and controlling the opening degree of the main expansion device so that the discharge temperature of the compressor is equal to or greater than a target discharge temperature.

Description

Air conditioner and its control method {Air conditioner and a method for controlling the same}

The present invention relates to an air conditioner and a control method thereof.

In general, an air conditioner refers to a device that controls room temperature to create a comfortable indoor air environment.

Such an air conditioner includes an indoor unit installed indoors and an outdoor unit supplying refrigerant to the indoor unit. In addition, one or more indoor units may be connected to the outdoor unit.

The air conditioner may be operated in a cooling or heating operation by supplying refrigerant to the indoor unit. Here, a cooling operation or a heating operation, which is an operating method of the air conditioner, is determined according to the flow of the circulating refrigerant. That is, the air conditioner may operate in either a cooling operation or a heating operation according to the flow of the refrigerant.

First, the flow of refrigerant when the air conditioner operates in a cooling mode will be described. The refrigerant compressed by the compressor of the outdoor unit passes through an outdoor heat exchanger functioning as a condenser to become medium-temperature and high-pressure liquid refrigerant. When the liquid refrigerant is supplied to the indoor unit, vaporization may occur as the refrigerant expands in an indoor heat exchanger functioning as an evaporator. The temperature of the ambient air around the indoor heat exchanger is lowered by the evaporation phenomenon. Further, when the fan of the indoor unit rotates, the ambient air of the heat exchanger of the indoor unit, the temperature of which is lowered, is discharged into the room.

Next, when the air conditioner operates in a heating operation, the flow of refrigerant is as follows. When the high-temperature, high-pressure gaseous refrigerant is supplied to the indoor unit from the compressor of the outdoor unit, the high-temperature and high-pressure gaseous refrigerant may be liquefied in an indoor heat exchanger functioning as a condenser. The energy released by the liquefaction phenomenon increases the temperature of the ambient air of the indoor heat exchanger. Further, when the fan of the indoor unit rotates, ambient air of the indoor heat exchanger, the temperature of which has risen, may be discharged into the room. After the liquefied refrigerant is expanded in the main expansion device, it may be introduced into an outdoor heat exchanger functioning as an evaporator and vaporized.

Meanwhile, when the air conditioner performs a heating operation, if the temperature of the outdoor air is too low or the humidity is high, ice may form on the surface of the outdoor heat exchanger. The implanted ice may degrade the heat exchange performance of the outdoor heat exchanger.

To prevent this phenomenon, the air conditioner may perform a defrosting operation.

The present applicant has filed and registered the following patent application (hereinafter referred to as prior literature) with respect to an air conditioner in which a defrosting operation is performed.

1. Registration number (registration date): 10-0194105 (February 8, 1999)

2. Title of Invention: Automatic defrost heat pump cycle of air conditioner for both heating and cooling

According to the prior literature, an expansion valve and a solenoid valve are connected in parallel between the outlet end of the compressor and the condenser, and a temperature sensor is configured in the condenser pipe to operate the expansion valve and the solenoid valve when the temperature of the outdoor heat exchanger decreases. An idea of continuously performing a heating operation by preventing frost from occurring in an outdoor heat exchanger is disclosed.

According to these prior documents, since the refrigerant gas discharged during the heating operation is bypassed to the outdoor heat exchanger, the heating performance is lowered during the bypass, and the low pressure of the cycle decreases when the bypass continues, thereby reducing the reliability of the compressor. problems may arise.

Meanwhile, in order to solve this problem, a defrosting operation may be performed to remove frost by operating a reverse cycle corresponding to the cooling operation so that the outdoor heat exchanger functions as a condenser.

However, according to the conventional defrosting operation, the operating frequency of the compressor and the opening degree of the main expansion device are controlled to predetermined values or step-controlled, so that it is difficult to actively cope with the changing physical properties of the cycle during the defrosting operation. There was a problem.

In order to solve the above problems, an object of the present embodiment is to provide an air conditioner capable of improving operation efficiency during defrosting operation and a control method thereof.

According to the control method of the air conditioner according to the present embodiment, the step of driving the refrigeration cycle to perform a heating operation; starting a defrosting operation by changing a control state of a flow switching valve when it is determined that a defrosting operation start point has arrived during the heating operation; and adjusting the operating frequency of the compressor and the opening degree of the main expansion device when the defrosting operation is performed. In the step of adjusting the operating frequency of the compressor and the opening degree of the main expansion device, the operating frequency of the compressor is Controlling the low pressure of the refrigerating cycle to be equal to or higher than the minimum target low pressure; and controlling the opening degree of the main expansion device so that the discharge temperature of the compressor is equal to or greater than a target discharge temperature.

The step of determining an end point of the defrosting operation is further included, and the step of determining the end point of the defrosting operation includes determining whether the temperature of the outdoor heat exchanger is equal to or greater than a second set value. .

The method may further include determining whether or not the temperature of the outdoor heat exchanger is greater than or equal to a first set value lower than the second set value.

In addition, when it is recognized that the temperature of the outdoor heat exchanger is equal to or greater than the first set value, an outdoor fan installed on one side of the outdoor heat exchanger is reversely rotated to supply air inside the outdoor unit case to the outdoor heat exchanger. More steps are included.

In addition, when the temperature of the outdoor heat exchanger is equal to or higher than the second set value during the reverse rotation of the outdoor fan, the outdoor fan is rotated forward for the heating operation to supply outside air to the outdoor heat exchanger. It is characterized in that it is supplied to the side.

In addition, the step of adjusting the operating frequency of the compressor and the opening degree of the main expansion device includes increasing the opening degree of the main expansion device when the discharge temperature of the compressor is equal to or less than the target discharge temperature.

In addition, the step of adjusting the operating frequency of the compressor and the opening of the main expansion device includes reducing the operating frequency of the compressor when the low pressure of the refrigerating cycle is less than the minimum target low pressure.

In addition, in the step of performing the heating operation, adjusting the operating frequency of the compressor so that the high pressure of the refrigeration cycle can be formed within a set pressure range; and adjusting the opening degree of the main expansion device so that the discharge temperature of the compressor can be formed within a set discharge temperature range.

In addition, when the defrosting operation starts, the operating frequency of the compressor is lowered to a first operating frequency lower than the operating frequency during the heating operation and maintained for a first set time, and when the first set time elapses, the refrigeration It is characterized in that the low pressure of the cycle is controlled to be more than the minimum target low pressure.

In addition, when the defrosting operation starts, the opening degree of the main expansion device is maintained at the set opening degree P1 for a second set time, and when the second set time elapses, the discharge temperature of the compressor is set to a target discharge temperature or higher. As much as possible, it is characterized in that the opening degree of the main expansion device is adjusted.

In addition, it is determined that the defrosting operation start time has arrived based on the fact that a set time has elapsed after the heating operation has been performed or based on the temperature value of the outdoor heat exchanger or the temperature value of the outside air.

According to the air conditioner according to another aspect, based on the value detected by the low pressure sensor or the first temperature sensor, a control unit for controlling the operating frequency of the compressor or the opening degree of the main expansion device during defrosting operation is included.

In addition, during the defrosting operation, the control unit adjusts the operating frequency of the compressor so that the pressure value sensed by the low pressure sensor is equal to or greater than a minimum target low pressure, and the temperature value sensed by the first temperature sensor is set to a target discharge temperature It is characterized in that the opening degree of the main expansion device is adjusted so that it is ideal.

Also, during the defrosting operation, when the temperature value sensed by the second temperature sensor is equal to or greater than the first set value, the control unit may control the outdoor fan to rotate in reverse.

Also, during the heating operation, the control unit may control the outdoor fan to rotate normally.

According to the present embodiment, when the defrosting operation starts, the low pressure of the cycle is detected and the operating frequency of the compressor is adjusted so that the detected low pressure does not fall below the set low pressure, so that the discharge temperature (or discharge superheat) of the compressor is too high. There is an effect that the reliability of the compressor can be secured according to the control so as not to increase.

In addition, since the discharge temperature of the compressor can be detected and the opening degree of the main expansion device can be controlled so that the detected temperature does not exceed the set temperature, the reliability of the compressor can be secured and the operating efficiency of the air conditioner can be improved. It works.

In addition, during the defrosting operation, the temperature of the outdoor heat exchanger is detected, and when the detected temperature is equal to or higher than a first set temperature, the outdoor fan is reversely rotated to supply warm air inside the outdoor unit case to the outdoor heat exchanger. Since the defrosting operation can be terminated when the temperature exceeds the second set temperature, there is an advantage in that the defrosting time can be shortened.

1 is a diagram showing a refrigeration cycle of an air conditioner according to an embodiment of the present invention.
2 is a block diagram showing the configuration of an air conditioner according to an embodiment of the present invention.
3 and 4 are flow charts showing a method for controlling an air conditioner according to an embodiment of the present invention.
5 is a graph showing a control state of parts constituting an air conditioner according to an embodiment of the present invention.
6 is an experimental graph showing how the defrosting time is shortened by the control method of the air conditioner according to the embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail through exemplary drawings. In adding reference numerals to components of each drawing, it should be noted that the same components have the same numerals as much as possible even if they are displayed on different drawings. In addition, in describing an embodiment of the present invention, if it is determined that a detailed description of a related known configuration or function hinders understanding of the embodiment of the present invention, the detailed description will be omitted.

Also, terms such as first, second, A, B, (a), and (b) may be used to describe components of an embodiment of the present invention. These terms are only used to distinguish the component from other components, and the nature, order, or order of the corresponding component is not limited by the term. When an element is described as being “connected,” “coupled to,” or “connected” to another element, that element may be directly connected or connected to the other element, but there may be another element between the elements. It should be understood that may be "connected", "coupled" or "connected".

1 is a diagram showing a refrigeration cycle of an air conditioner according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of an air conditioner according to an embodiment of the present invention.

Referring to FIG. 1 , an air conditioner 10 according to an embodiment of the present invention includes a compressor 100 for compressing a refrigerant. The compressor 100 includes an inverter compressor capable of controlling an operating frequency.

The air conditioner 10 includes a discharge pipe 101 provided at an outlet side of the compressor 100 and guiding the flow of the refrigerant compressed in the compressor 100 . A first temperature sensor 161 for sensing the temperature of the refrigerant compressed in the compressor 100 is included in the discharge pipe 101 . The first temperature sensor 161 may be referred to as a "discharge temperature sensor".

For example, the temperature value detected by the first temperature sensor 161 may be used to control the opening degree of the main expansion device 130 .

The air conditioner 10 further includes a flow switching valve 110 installed in the discharge pipe 101 and changing a flow direction of the compressed refrigerant. For example, the flow conversion valve 110 may include a four-way valve.

The air conditioner 10 includes an outdoor heat exchanger 121 installed in an outdoor unit and an indoor heat exchanger 140 installed in an indoor unit.

When the air conditioner 10 is in a cooling operation, the refrigerant compressed in the compressor 100 flows into the outdoor heat exchanger 121 via the flow conversion valve 110, and the outdoor heat exchanger 121 The refrigerant condensed in ) is depressurized in an indoor expansion device (not shown) provided inside the indoor unit and introduced into the indoor heat exchanger 140 . The refrigerant evaporated in the indoor heat exchanger 140 flows into the gas-liquid separator 150 via the flow conversion valve 110 . Then, the gaseous refrigerant separated in the gas-liquid separator 150 is sucked back into the compressor 100 .

On the other hand, when the air conditioner 10 is in a heating operation, the refrigerant compressed in the compressor 100 flows toward the indoor heat exchanger 140 via the flow conversion valve 110, and the indoor heat exchange The refrigerant condensed in the group 140 is depressurized in the main expansion device 130 and introduced into the outdoor heat exchanger 121. The refrigerant evaporated in the outdoor heat exchanger 121 flows into the gas-liquid separator 150 via the flow conversion valve 110 . Then, the gaseous refrigerant separated in the gas-liquid separator 150 is sucked back into the compressor 100 .

The main expansion device 130 may be installed in a pipe connecting the outdoor heat exchanger 121 and the indoor heat exchanger 140 . For example, the main expansion device 130 may include an electronic expansion valve capable of adjusting an opening.

Also, the gas-liquid separator 150 is installed on the suction side of the compressor 100 and separates the gaseous refrigerant from the evaporated refrigerant and supplies it to the compressor 100 .

The air conditioner 10 further includes an outdoor fan 125 installed on one side of the outdoor heat exchanger 121 to provide blowing force so that outside air flows toward the outdoor heat exchanger 121 . The air conditioner 10 is coupled with a fan motor 125a that is controlled to allow forward or reverse rotation of the outdoor fan 125 .

The outdoor heat exchanger 121 , the outdoor fan 125 , and the fan motor 125a may be installed inside the outdoor unit case 120 . For convenience of explanation, FIG. 1 shows that only the outdoor heat exchanger 121, the outdoor fan 125, and the fan motor 125a are installed inside the outdoor unit case 120, but the compressor 100 ), a gas-liquid separator 150, a flow conversion valve 110, and a main expansion device 130 may also be installed inside the outdoor unit case 120.

When the outdoor fan 125 rotates forward, outside air flows into the outdoor unit case 120 and exchanges heat with the outdoor heat exchanger 121, and the heat-exchanged outdoor air is discharged to the outside of the outdoor unit case 120. It can be.

On the other hand, when the outdoor fan 125 reversely rotates, the internal air of the outdoor unit case 120 flows toward the outdoor heat exchanger 121 and exchanges heat, and the heat-exchanged internal air of the outdoor unit case 120 can be discharged to the outside.

The air conditioner 10 further includes an indoor fan 145 installed on one side of the indoor heat exchanger 140 to flow air in the indoor space toward the indoor heat exchanger 140 .

The air conditioner 10 further includes a second temperature sensor 163 that senses the pipe temperature of the outdoor heat exchanger 121 . For example, the second temperature sensor 163 may be installed at an approximate midpoint of the refrigerant pipes provided in the outdoor heat exchanger 121 to detect the surface temperature between the refrigerant pipes. The temperature value sensed by the second temperature sensor 163 may be used to control the outdoor fan 125 or determine a defrosting end point of the air conditioner 10 .

The air conditioner 10 further includes a third temperature sensor 165 for sensing the temperature of the outside air. For example, the temperature value sensed by the third temperature sensor 165 may be used to determine the defrosting start time of the air conditioner 10 .

The air conditioner 10 further includes a low pressure sensor 170 for detecting a low pressure in the refrigeration cycle. The low pressure sensor 170 may be installed in a path through which evaporated refrigerant is sucked into the compressor 100 . For example, the low pressure sensor 170 extends from the gas-liquid separator 150 to the compressor 100, and guides the gas-phase refrigerant separated from the gas-liquid separator 150 to the compressor 100. can be installed on

In the air conditioner 10, based on information detected by the first temperature sensor 161, the second temperature sensor 163, the third temperature sensor 165, or the low pressure sensor 170, the compressor ( 100), a control unit 200 for controlling the operation of the main expansion device 130 or the outdoor fan 125 is further included.

The controller 200, the temperature sensors 161, 163, and 165, the low pressure sensor 170, the compressor 100, the main expansion device 130, and the outdoor fan 125 may be electrically connected.

3 and 4 are flow charts showing a method for controlling an air conditioner according to an embodiment of the present invention. A control method of the air conditioner 10 according to an embodiment of the present invention will be described with reference to FIGS. 3 and 4 .

The air conditioner 10 is turned on, the compressor 100 starts, and the heating operation starts. During the heating operation, the compressor 100 performs "target high pressure control". In the case of the heating operation, since the high pressure of the refrigeration cycle has a significant effect on the heating performance, the operating frequency of the compressor 100 may be determined so that the high pressure may be formed within a set pressure range. For example, when the operating frequency of the compressor 100 increases, the high pressure may increase, and when the operating frequency decreases, the high pressure may decrease. The high pressure of the refrigeration cycle may be detected by a high pressure sensor (not shown) installed in the discharge pipe 101.

And, the opening degree of the main expansion device 130 is such that the discharge temperature of the refrigerant discharged from the compressor 100 corresponds to the "target discharge temperature", that is, the discharge temperature of the refrigerant is within the target discharge temperature range. It can be determined so that it can be formed. For example, when the opening of the main expansion device 130 increases, the amount of refrigerant circulating in the refrigerating cycle increases, so the discharge temperature of the refrigerant decreases. When the opening decreases, the amount of refrigerant circulating in the refrigerating cycle decreases. The discharge temperature of may increase.

The outdoor fan 125 may be controlled to rotate forward at a set number of rotations. For example, the number of rotations of the outdoor fan 125 may be determined as the maximum number of rotations.

The flow conversion valve 110 is controlled to be in an “on” state and guides the refrigerant discharged from the compressor 100 to the indoor heat exchanger 140 . In addition, the indoor fan 145 can be driven at a rotational speed corresponding to the set air volume. For example, the air volume may be set by the user (S11).

In the process of performing the heating operation, it is recognized whether or not the time to perform the defrosting operation (hereinafter referred to as defrosting time) has arrived. For example, the defrosting time point may be determined to have arrived when a set time elapses after the heating operation is performed. That is, the defrosting operation may be performed according to a set cycle.

As another example, the defrosting time may be determined based on a temperature value sensed by the second temperature sensor 163 or a temperature value sensed by the third temperature sensor 165 . In detail, when the temperature value detected by the third temperature sensor 165 is less than or equal to the set temperature value, or when the difference between the temperature values detected by the second and third temperature sensors 163 and 165 is greater than or equal to the set value, the defrosting time point It may be determined that it has arrived (S12).

When the defrosting time arrives and the defrosting operation of the air conditioner 10 starts, the reverse cycle of the heating operation, that is, the cooling operation cycle is performed. That is, the flow conversion valve 110 is controlled to be in an “OFF” state, and guides the refrigerant discharged from the compressor 100 to the outdoor heat exchanger 120 . In addition, the indoor fan 145 may be turned off immediately after starting the defrosting operation or after a preset time has elapsed (see FIG. 5 ).

Also, the operating frequency of the compressor 100 is controlled to be lower than the operating frequency during the heating operation. Since the purpose of the defrosting operation is not to cool the indoor space but to supply high-temperature refrigerant to the outdoor heat exchanger 121, a relatively large amount of compression work is not required. Accordingly, the operating frequency of the compressor 100 may be lowered and maintained at the first operating frequency f1 (see FIG. 5). And, the state of the first operating frequency can be maintained for a set time (S13, S14).

After the set time elapses, “minimum target low pressure control” of the compressor 100 may be performed. In detail, the compressor 100 may be designed to operate at a set minimum low pressure or higher. If the refrigerant suction pressure of the compressor 100, that is, the low pressure is formed lower than the set minimum low pressure, the reliability of the compressor 100 is lowered, so the operating frequency can be controlled so that the low pressure of the compressor is equal to or greater than the minimum low pressure. can The low pressure may be detected by the low pressure sensor 170 (S15).

Meanwhile, when the defrosting time arrives, the opening of the main expansion device 130 may be controlled to the set opening (P1, see FIG. 5).

The set opening degree may be greater than the opening degree of the main expansion device 130 during the heating operation. By controlling the opening of the main expansion device 130, a sufficient amount of refrigerant for defrosting the outdoor heat exchanger 121 can be secured. In addition, control of the set opening degree of the main expansion device 130 may be maintained for a set time, and when the set time elapses, "target discharge temperature control" may be performed.

The value of the "target discharge temperature" during the defrosting operation may have a different value from the value of the "target discharge temperature" during the heating operation. The "target discharge temperature" during the heating operation may be referred to as a "first discharge temperature", and the "target discharge temperature" during the defrosting operation may be referred to as a "second discharge temperature". For example, the second discharge temperature may have a higher value than the first discharge temperature.

In order to defrost the outdoor heat exchanger 121, the temperature of the refrigerant to be supplied to the outdoor heat exchanger 121 needs to be maintained above a set temperature, that is, a “target discharge temperature”. As described above, the discharge temperature of the compressor may be determined based on the amount of refrigerant circulating in the refrigeration cycle.

In detail, when the discharge temperature of the compressor 100 is equal to or higher than the target discharge temperature, the amount of refrigerant is increased by increasing the opening of the main expansion device 130, and when the discharge temperature of the compressor 100 is less than the target discharge temperature. In this case, the amount of refrigerant may be reduced by reducing the opening of the main expansion device 130 .

Meanwhile, when the amount of refrigerant changes according to the adjustment of the opening of the main expansion device 130, the low pressure of the refrigerating cycle may change accordingly. For example, when the amount of the refrigerant increases, the low pressure of the refrigeration cycle increases, and when the amount of the refrigerant decreases, the low pressure of the refrigeration cycle decreases.

That is, the adjustment of the opening degree of the main expansion device 130 can affect the “minimum target low pressure control” of the compressor 100 . In detail, when the low pressure of the refrigerating cycle decreases due to the decrease in the amount of refrigerant, the operating frequency of the compressor 100 may be reduced to control the low pressure of the refrigerating cycle to be greater than or equal to the “minimum target low pressure”.

In summary, the opening degree of the main expansion device 130 can be controlled based on the target discharge temperature of the compressor, and the operating frequency of the compressor 100 can be controlled based on the minimum target low pressure. During this process, the control of the opening of the main expansion device 130 may affect the low pressure of the refrigerating cycle, and the control of the operating frequency of the compressor 100 may affect the discharge temperature of the compressor.

For example, when the operating frequency of the compressor 100 is lowered and the opening of the main expansion device 130 is increased, the low pressure of the refrigeration cycle may increase and the discharge temperature of the compressor 100 may decrease. However, if the discharge temperature is excessively reduced, defrosting performance may deteriorate.

Therefore, the operating frequency of the compressor 100 can be controlled to increase. However, when the operating frequency of the compressor 100 increases, the low pressure of the refrigerating cycle may also decrease. Also, if the low pressure decreases too much to be below the minimum target low pressure, the reliability of the compressor may deteriorate. In consideration of this phenomenon, the compressor 100 controls the minimum target low pressure, the main expansion device ( 130) may perform target discharge temperature control.

As a result, the main expansion device 130 and the compressor 100 can be controlled based on different cycle factors, and in this process, the optimal cycle temperature and pressure during defrosting operation can be maintained. It is possible to secure reliability and improve the operation efficiency of the refrigerating cycle (S16).

Meanwhile, as described above, when the time of defrosting operation arrives, the indoor fan 145 may be turned off immediately after the start of the defrosting operation or after a preset time has elapsed. During the defrosting operation, since there is no need to condition the indoor space, the number of revolutions of the indoor fan 145 can be reduced and turned off (S17).

In the process of performing the defrosting operation, it may be recognized whether or not an end point of the defrosting operation has arrived. Whether or not the end point of the defrosting operation has arrived may be determined based on a value detected by the second temperature sensor 163 (S18).

In detail, it can be recognized whether the temperature value sensed by the second temperature sensor 163 (hereinafter referred to as the detected value) is greater than or equal to the first set value T1 (refer to FIG. 6). The first set value may be determined as a value lower than the second set value (T2, see FIG. 6) for determining the end point of the defrosting operation.

That is, when the detected value of the second temperature sensor 163 reaches the second set value, it is determined that the defrosting operation is to be terminated, but before the detected value reaches the second set value, that is, the 1 When the set value is reached, it can be used as the control reference value.

When the detected value is greater than or equal to the first set value, the outdoor fan 125 reversely rotates. For example, the outdoor fan 125 may be reversely rotated with "weak wind". It may be understood that the weak wind is an air volume lower than the discharge air volume during the heating operation. When the outdoor fan 125 reversely rotates, as described above, the internal air of the outdoor unit case 120 flows toward the outdoor heat exchanger 121 and exchanges heat, and the heat-exchanged internal air is exchanged with the outdoor unit case 120. ) can be discharged to the outside.

As a result, the hot air existing inside the outdoor unit case 120 acts on the outdoor heat exchanger 121 to increase the defrosting performance of the outdoor heat exchanger 121 and shorten the defrosting time (S19 and S20).

While the reverse rotation of the outdoor fan 125 is performed, it is recognized whether the detected value of the second temperature sensor 163 is greater than or equal to the second set value. If the detected value is equal to or greater than the second set value, it is determined that the end point of the defrosting operation has arrived (S21 and S22).

When the defrosting operation ends, the air conditioner 10 switches to heating operation. In detail, the flow switching valve 110 may be turned on and the indoor fan 145 may be operated at a rotational speed to discharge a set amount of air. In addition, the outdoor fan 125 rotates forward to allow the outside air to flow toward the outdoor heat exchanger 121 to help evaporate the refrigerant.

And, the main expansion device 130 is controlled to the set opening degree P1 and maintained for a set time. And, based on the target discharge temperature of the refrigerating cycle during the heating operation, the opening degree of the main expansion device 130 is adjusted.

The compressor 100 is controlled at the first operating frequency f1 for a set period of time, and then performs "target high pressure control" which has a significant effect on heating performance. That is, the operating frequency of the compressor 100 may be determined so that the high pressure of the refrigeration cycle may be formed within a set pressure range.

5 is a graph showing a control state of parts constituting an air conditioner according to an embodiment of the present invention, and FIG. 6 shows a state in which a defrost time is shortened by a control method of an air conditioner according to an embodiment of the present invention. This is an experimental graph.

Referring to FIG. 5 , the compressor 100 performs the “target high pressure control” during the heating operation, and when the defrosting operation starts, the operation frequency is controlled to be lowered to the first operation frequency f1. Then, when the set time (t1-t0) elapses, "minimum target low pressure control" is performed. When the defrosting operation is finished, the first operation frequency f1 is maintained for a set time, and then "target high pressure control" is performed during the heating operation. The set time (t1-t0) is called a "first set time".

In the case of the main expansion device 130, during the heating operation, the "target discharge temperature control" of the compressor 100 is performed, and when the defrosting operation starts, the opening degree may be controlled to the set opening degree P1. Then, when the set time (t2-t0) elapses, "target discharge temperature control" is performed. When the defrosting operation is finished, the set opening degree (P1) is maintained for a set time, and then, during the heating operation, "target discharge temperature control" is performed. The set time period (t2-t0) is called a "second set time".

In the case of the outdoor fan 125, it rotates forward at a set number of revolutions during the heating operation, and is turned off when the defrosting operation starts. Then, at a time t3 before the defrosting operation end point t4, the outdoor fan 125 reversely rotates. And, when the defrosting operation is completed, the outdoor fan 125 is switched to normal rotation and helps the refrigerant evaporation in the outdoor heat exchanger 121 .

Referring to FIG. 6, since the outdoor fan 125 reversely rotates before the end time of the defrosting operation to help the defrosting operation, compared to the defrosting operation end point t4' according to the prior art, Δt It can be seen that the defrosting operation end point t4 arrives early.

In the case of the prior art, in determining the end point of the defrosting operation, the temperature of the outdoor heat exchanger 121 is not used and only whether the set defrosting time has elapsed is used, so the temperature of the outdoor heat exchanger 121 is too high. There was a problem in that the defrost operation was maintained until the temperature increased. Also, if the temperature of the outdoor heat exchanger 121 is too high, it takes a lot of time for the temperature of the outdoor heat exchanger 121 to reach the evaporation temperature when switching back to heating operation.

In the case of the flow conversion valve 110, it can be controlled to be turned on during heating operation, turned off during defrosting operation, and turned on again when the defrosting operation is finished.

In the case of the indoor fan 145, it is operated at a rotational speed corresponding to the set air volume during heating operation, when the defrosting operation starts, the rotational speed decreases and is turned off, and when the defrosting operation ends, the rotational speed corresponding to the set air volume will rotate

In summary, the reliability of the compressor can be secured by controlling the low pressure of the refrigerating cycle to be equal to or higher than the minimum target low pressure during the defrosting operation by the control method according to the present embodiment. In addition, since the discharge temperature of the compressor can be equal to or higher than the target discharge temperature through the adjustment of the opening of the main expansion device 130, defrosting operation efficiency can be improved.

In addition, since the outdoor fan 125 reversely rotates before the end of the defrosting operation, hot heat inside the outdoor unit case 120 can be supplied to the outdoor heat exchanger 121, so the defrosting operation time can be shortened. There is an effect that can prevent the deterioration of heating performance.

100: compressor 101: discharge piping
110: fluid conversion valve 120: outdoor unit case
121: outdoor heat exchanger 125: outdoor fan
130: main expansion device 140: indoor heat exchanger
145: indoor fan 150: gas-liquid separator
161: first temperature sensor 163: second temperature sensor
165: third temperature sensor 170: low pressure sensor

Claims (15)

A step in which a refrigeration cycle is driven and a heating operation is performed;
starting a defrosting operation by changing a control state of a flow switching valve when it is determined that a defrosting operation start point has arrived during the heating operation; and
When the defrosting operation is performed, the operation frequency of the compressor and the opening degree of the main expansion device are adjusted.
In the step of adjusting the operating frequency of the compressor and the opening degree of the main expansion device,
Controlling the operating frequency of the compressor so that the low pressure of the refrigerating cycle is equal to or greater than the minimum target low pressure; and
The opening degree of the main expansion device includes the step of controlling the discharge temperature of the compressor to be equal to or higher than the target discharge temperature,
When the defrosting operation starts,
The opening degree of the main expansion device is controlled to a set opening degree (P1), and the set opening degree (P1) is greater than the opening degree of the main expansion device during the heating operation. According to claim 1,
After the step of controlling the discharge temperature of the compressor to be equal to or higher than the target discharge temperature, the step of determining an end point of the defrosting operation is further included,
In the step of determining the end point of the defrosting operation,
An air conditioner control method comprising determining whether a temperature of an outdoor heat exchanger is equal to or greater than a second set value. According to claim 2,
In the step of determining the end point of the defrosting operation,
Prior to the step of determining whether the temperature of the outdoor heat exchanger is equal to or greater than the second set value,
The temperature of the outdoor heat exchanger,
The method of controlling an air conditioner further comprising determining whether or not the first set value is equal to or greater than the second set value. According to claim 3,
When it is recognized that the temperature of the outdoor heat exchanger is equal to or greater than the first set value,
By reversely rotating the outdoor fan installed on one side of the outdoor heat exchanger,
The air conditioner control method further includes supplying air inside the outdoor unit case to the outdoor heat exchanger. According to claim 4,
In the process of reverse rotation of the outdoor fan,
When the temperature of the outdoor heat exchanger is equal to or higher than the second set value,
For the heating operation, the outdoor fan is rotated forward to supply outside air to the outdoor heat exchanger. According to claim 1,
In the step of adjusting the operating frequency of the compressor and the opening degree of the main expansion device,
and increasing an opening degree of the main expansion device when the discharge temperature of the compressor is equal to or less than the target discharge temperature. According to claim 1,
In the step of adjusting the operating frequency of the compressor and the opening degree of the main expansion device,
and reducing an operating frequency of the compressor when the low pressure of the refrigerating cycle is equal to or less than the minimum target low pressure. According to claim 1,
In the step of performing the heating operation,
Adjusting the operating frequency of the compressor so that the high pressure of the refrigerating cycle can be formed within a set pressure range; and
and adjusting an opening degree of the main expansion device so that the discharge temperature of the compressor is within a set discharge temperature range. According to claim 1,
When the defrosting operation starts,
The operating frequency of the compressor is lowered to a first operating frequency lower than the operating frequency during the heating operation and maintained for a first set time,
The method of controlling an air conditioner, characterized in that, when the first set time elapses, the low pressure of the refrigeration cycle is controlled to be equal to or higher than a minimum target low pressure. According to claim 1,
When the defrosting operation starts,
The opening degree of the main expansion device is maintained at the set opening degree P1 for a second set time, and when the second set time elapses,
The air conditioner control method according to claim 1 , wherein the opening of the main expansion device is adjusted so that the discharge temperature of the compressor is equal to or higher than a target discharge temperature. According to claim 1,
It is recognized that the set time has elapsed after the heating operation is performed,
Based on the temperature value of the outdoor heat exchanger or the temperature value of the outside air,
A control method of an air conditioner, characterized in that it is determined that the defrosting operation start point has arrived. A compressor capable of adjusting the operating frequency;
A flow conversion valve installed on the outlet side of the compressor;
an indoor heat exchanger connected to the outlet side of the flow switching valve and condensing the refrigerant compressed in the compressor during heating operation;
a main expansion device for depressurizing the refrigerant condensed in the indoor heat exchanger;
an outdoor heat exchanger for evaporating the refrigerant depressurized by the main expansion device;
a low pressure sensor for sensing a low pressure of the refrigerant sucked into the compressor;
a first temperature sensor for sensing the temperature of the refrigerant discharged from the compressor; and
A control unit for controlling an operating frequency of the compressor or an opening degree of the main expansion device during a defrosting operation based on a value detected by the low pressure sensor or the first temperature sensor;
The control unit controls the opening degree of the main expansion device during the defrosting operation to a set opening degree (P1), and the set opening degree (P1) is greater than the opening degree of the main expansion device during the heating operation. . According to claim 12,
During the defrosting operation, the control unit,
Adjusting the operating frequency of the compressor so that the pressure value detected by the low pressure sensor is equal to or greater than the minimum target low pressure;
The air conditioner according to claim 1 , wherein an opening degree of the main expansion device is adjusted so that the temperature value sensed by the first temperature sensor is equal to or higher than a target discharge temperature. According to claim 12,
a second temperature sensor for sensing the temperature of the outdoor heat exchanger; and
An outdoor fan installed on one side of the outdoor heat exchanger is further included,
During the defrosting operation, when the temperature value sensed by the second temperature sensor is greater than or equal to the first set value,
The air conditioner according to claim 1 , wherein the control unit controls the outdoor fan to rotate in reverse. 15. The method of claim 14,
During the heating operation, the control unit,
An air conditioner characterized in that the outdoor fan is controlled to rotate forward.

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