JP2012233632A - Air conditioner and control method of air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner and a control method of the air conditioner which are capable of shortening a rise time until a predetermined cooling capacity or heating capacity is exercised, by enhancing the evaporation of a liquid refrigerant accumulated in a compressor.SOLUTION: The air conditioner includes a refrigerant circuit having a compressor 3 which compresses the refrigerant by being driven by a motor, an outdoor heat exchanger 5 which condenses the compressed refrigerant, an expansion valve 14 for cooling which expands the condensed refrigerant, and an indoor heat exchanger 7 which evaporates the expanded refrigerant, a determination portion which determines whether the liquid refrigerant is contained or not in the refrigerant supplied from the indoor heat exchanger 7 to the compressor 3, and a control portion which changes the efficiency of the motor driving the compressor 3 according to the determination whether the liquid refrigerant is contained or not.

Description

  The present invention relates to an air conditioner having a compressor driven by an electric motor, in which a refrigerant circulates in a refrigerant circuit, and a control method for the air conditioner.

  In the air conditioner, a liquid refrigerant (hereinafter referred to as “liquid refrigerant”) may accumulate in the compressor case after the stop state continues for a long time or depending on indoor and outdoor temperature conditions during operation. At this time, the refrigerant dissolves in the lubricating oil of the compressor, and the lubricating oil becomes highly diluted, causing poor lubrication of the compressor and the like.

  Patent Document 1 discloses a technique for removing a liquid-phase refrigerant accumulated in a compressor. Patent Document 2 discloses a technique for preventing the dilution of the lubricating oil of the compressor from being increased by the liquefied refrigerant during low-performance / low-frequency operation.

JP 2006-170575 A Japanese Patent No. 3480766

  By the way, when the compressor is operated at a high frequency while the liquid refrigerant is accumulated, the lubricating oil flows out of the compressor together with the refrigerant. As a result, the compressor malfunctions due to poor lubrication, or the lubricating oil adheres to the refrigerant piping and the wall surface of the condenser, and the refrigerant circulation rate decreases and the heat exchange rate deteriorates. Therefore, in a state where liquid refrigerant is accumulated in the compressor, protection control is provided so that the frequency of the compressor does not increase so that the lubricating oil does not flow out of the compressor.

  During this time, the electronic expansion valve (EEV) is adjusted so that the refrigerant supplied from the evaporator to the compressor does not contain liquid refrigerant, that is, while suppressing liquid back, The liquid refrigerant is evaporated using a case heater or an electric motor as a heat source. However, with the recent increase in efficiency of electric motors, power consumption during operation is suppressed, and the amount of heat generated by the electric motor tends to decrease, so that it takes a long time to heat the refrigerant.

  In addition, when the air conditioner starts operating, liquid refrigerant accumulates in the compressor, and if the liquid back continues for a long time from the gas pipe connecting the indoor unit and outdoor unit after the operation starts, it takes time to evaporate the refrigerant. The state where the liquid refrigerant is accumulated in the compressor continues. Even in this case, since the calorific value of the electric motor tends to decrease, it takes a long time to heat the refrigerant. And since it takes a long time from the start of the operation of the air conditioner to the transition to the high frequency operation, a delay occurs in the start-up until the desired cooling capacity or heating capacity is exhibited. In addition, it may cause a compressor failure.

  The present invention has been made in view of such circumstances, and promotes the evaporation of the liquid refrigerant accumulated in the compressor and shortens the rise time until the desired cooling capacity or heating capacity is exhibited. It is an object of the present invention to provide an air conditioner capable of performing the above-mentioned and a method for controlling the air conditioner.

In order to solve the above problems, the air conditioner and the control method for the air conditioner of the present invention employ the following means.
That is, an air conditioner according to the present invention includes a compressor that is driven by an electric motor to compress refrigerant, a condenser that condenses the compressed refrigerant, an expansion valve that expands the condensed refrigerant, and an expanded refrigerant. A refrigerant circuit having an evaporator to evaporate, a determination unit that determines whether or not liquid refrigerant is included in the refrigerant supplied from the evaporator to the compressor, and determination whether or not liquid refrigerant is included And a controller that changes the efficiency of the electric motor that drives the compressor.

  According to the present invention, in the refrigerant circuit, the refrigerant is compressed by the compressor, the compressed refrigerant is condensed by the condenser, the condensed refrigerant is expanded by the expansion valve, and the expanded refrigerant is evaporated by the evaporator. Is done. At this time, it is desirable that all the refrigerant evaporates in the evaporator, but all the refrigerant does not evaporate and liquid refrigerant may be supplied to the compressor. In the present invention, it is determined whether or not the refrigerant supplied from the evaporator to the compressor includes liquid refrigerant, and the electric motor that drives the compressor is determined according to whether or not liquid refrigerant is included. Efficiency changes. Hereinafter, the fact that the refrigerant supplied from the evaporator to the compressor includes liquid refrigerant is also referred to as “liquid back”.

  When the efficiency of the motor is low during operation, for example, when the power factor of the motor is low, the amount of heat generated by the motor is higher than when the power factor is high. Therefore, for example, when it is determined that a liquid back has occurred, the heat generation amount of the motor is increased by reducing the efficiency of the motor, and the temperature of the refrigerant is increased in the compressor by the heat generation of the motor, and the refrigerant is evaporated. be able to. As a result, when the liquid refrigerant is dissolved in the lubricating oil used in the compressor, the lubricating oil can be left in the compressor by evaporating the refrigerant.

  The determination as to whether or not the liquid back has occurred is made based on the temperature near the compressor or the compressor such as the degree of superheat under the dome, the degree of discharge superheat (TdSH), or the temperature under the dome or at the discharge port. . For example, when the liquid back is generated, the temperature of the compressor is lowered. Therefore, it can be determined whether the liquid back is generated based on the temperature of the compressor or the vicinity of the compressor.

  In the above invention, the determination unit may determine whether or not a liquid refrigerant is included in the refrigerant supplied from the evaporator to the compressor during operation of the compressor.

  According to the present invention, it is determined whether or not liquid refrigerant is included in the refrigerant supplied from the evaporator to the compressor during operation of the compressor. Therefore, during operation of the compressor (for example, during normal operation) When a liquid back occurs in the motor, the efficiency of the electric motor that drives the compressor changes. For example, when it is determined that a liquid back is generated during the operation of the compressor, the heat generation amount of the motor is increased by reducing the efficiency of the motor, and the temperature of the refrigerant is increased in the compressor by the heat generation of the motor, The refrigerant can be evaporated.

  In the above invention, the determination unit may determine whether or not liquid refrigerant is included in the refrigerant supplied from the evaporator to the compressor immediately after the start of operation of the compressor.

  According to the present invention, since it is determined whether or not liquid refrigerant is included in the refrigerant supplied from the evaporator to the compressor immediately after the operation of the compressor is started, the liquid back is immediately after the operation of the compressor is started. When it occurs, the efficiency of the motor driving the compressor changes. Immediately after the compressor starts operating, when the liquid refrigerant is accumulated in the compressor, the refrigerant is dissolved in the lubricating oil, so that the lubricating oil does not flow out to the condenser side of the refrigerant circuit together with the refrigerant. The time to move to is delayed. In the present invention, when it is determined that a liquid back has occurred immediately after the start of the operation of the compressor, for example, by reducing the efficiency of the electric motor, the amount of heat generated by the electric motor is increased, and the heat generated by the electric motor increases within the compressor. The temperature of the refrigerant is raised and the refrigerant is evaporated. As a result, the time when the compressor can shift to high frequency operation can be advanced.

  In the above invention, the control unit may change the efficiency of the motor by changing a current flowing through the motor.

  According to the present invention, the efficiency of the electric motor changes according to the current flowing through the electric motor. For example, by changing the ratio of the current component orthogonal to the magnetic pole and the current component parallel to the magnetic pole, a large amount of current can be passed without changing the torque. In this case, the copper loss of the electric motor is increased, and operation with reduced efficiency is possible.

  Further, the control method of the air conditioner according to the present invention includes a compressor that is driven by an electric motor to compress the refrigerant, a condenser that condenses the compressed refrigerant, an expansion valve that expands the condensed refrigerant, and an expansion. A method of controlling an air conditioner including a refrigerant circuit having an evaporator for evaporating the refrigerant, and determining whether or not liquid refrigerant is included in the refrigerant supplied from the evaporator to the compressor; And changing the efficiency of the electric motor that drives the compressor in accordance with whether or not the liquid refrigerant is included.

  According to this invention, it is determined whether or not liquid refrigerant is included in the refrigerant supplied from the evaporator to the compressor, and the compressor is driven depending on whether or not liquid refrigerant is included. The efficiency of the motor changes. When the efficiency of the motor is low during operation, for example, when the power factor of the motor is low, the amount of heat generated by the motor is higher than when the power factor is high. Therefore, for example, when it is determined that a liquid back has occurred, the heat generation amount of the motor is increased by reducing the efficiency of the motor, and the temperature of the refrigerant is increased in the compressor by the heat generation of the motor, and the refrigerant is evaporated. be able to. As a result, when the liquid refrigerant is dissolved in the lubricating oil used in the compressor, the lubricating oil can be left in the compressor by evaporating the refrigerant.

  According to the present invention, it is possible to accelerate the evaporation of the liquid refrigerant accumulated in the compressor and shorten the rise time until the desired cooling capacity or heating capacity is exhibited.

It is a lineblock diagram showing the air harmony device concerning one embodiment of the present invention. It is a lineblock diagram showing the compressor of the air harmony device concerning one embodiment of the present invention. It is a flowchart which shows the liquid refrigerant removal operation | movement at the time of normal driving | operation operation | movement of the air conditioning apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the other example of the liquid refrigerant removal operation | movement at the time of normal driving | operation operation | movement of the air conditioning apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the liquid refrigerant removal operation | movement at the time of starting of the air conditioning apparatus which concerns on one Embodiment of this invention.

Hereinafter, an air conditioner according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram illustrating an air conditioner according to an embodiment of the present invention.
The air conditioner includes an outdoor unit 1 and an indoor unit 2 and includes a refrigerant circuit including a refrigerant pipe.
The outdoor unit 1 mainly includes a compressor 3, a four-way valve 4, an outdoor heat exchanger 5, an accumulator 6, a heating expansion valve 13, and an outdoor controller (not shown) for controlling each part of the outdoor unit 1. It is provided as a component. The indoor unit 2 includes an indoor heat exchanger 7, a cooling expansion valve 14, and an indoor controller (not shown). The outdoor heat exchanger 5 in the outdoor unit 1 and the indoor heat exchanger 7 in the indoor unit 2 are connected by a gas pipe 8 and a liquid pipe 9.

  In the outdoor unit 1, the discharge side of the compressor 3 is connected to the four-way valve 4 inserted in the middle of the gas pipe 8, and the suction side of the compressor 3 is connected to the four-way valve 4 via the accumulator 6. Has been. Here, the compressor 3 is an inverter-driven variable capacity compressor.

  When the four-way valve 4 is off, the compressor 3, the outdoor heat exchanger 5, the indoor heat exchanger 7, and the accumulator 6 are sequentially connected. Further, when the four-way valve 4 is on, the compressor 3, the indoor heat exchanger 7, the outdoor heat exchanger 5, and the accumulator 6 are sequentially connected.

  During the cooling operation of the air conditioner, the high-temperature and high-pressure gas refrigerant discharged from the compressor 3 of the outdoor unit 1 passes through a check valve (not shown) and the four-way valve 4 as indicated by solid arrows. It is sent to the outdoor heat exchanger 5 where it is condensed and liquefied by exchanging heat with the outside air. The liquid refrigerant flows into the indoor unit 2 through the strainer 10 and the liquid side operation valve 11 in order. The liquid refrigerant undergoes adiabatic expansion in the process of passing through the cooling expansion valve 14 and is then sent to the indoor heat exchanger 7 where it evaporates and evaporates by cooling the indoor air. The refrigerant which has absorbed heat in the indoor heat exchanger 7 flows into the gas pipe 8, passes through the gas side operation valve 12, flows into the outdoor unit 1, passes through the four-way switching valve 4 and the accumulator 6, and then enters the compressor. Sent to 3.

  Here, during the cooling operation, the outdoor heat exchanger 5 is an example of a condenser, and the indoor heat exchanger 7 is an example of an evaporator. The compressor 3, the outdoor heat exchanger 5, the cooling expansion valve 14, and the indoor heat exchanger 7 constitute a refrigerant circuit.

  Further, during the heating operation, the four-way valve 4 is switched in a direction different from that during the cooling operation. The refrigerant discharged from the compressor 3 of the outdoor unit 1 passes through the check valve (not shown), the four-way valve 4, the gas side operation valve 12, and the gas pipe 8, as indicated by the broken line arrow, and the indoor unit 2 Into the indoor heat exchanger 7 where it is condensed and liquefied by dissipating heat to the indoor air. The liquid refrigerant flows into the outdoor unit 1 through the liquid pipe 9 and the liquid side operation valve 11. Then, the liquid refrigerant undergoes adiabatic expansion in the process of passing through the strainer 10 and passes through the heating expansion valve 13, and then is sent to the outdoor heat exchanger 5, where it evaporates by absorbing heat from the outside air. Next, this gas refrigerant is sent to the compressor 3 through the four-way valve 4 and the accumulator 6.

  Here, during the heating operation, the indoor heat exchanger 7 is an example of a condenser, and the outdoor heat exchanger 5 is an example of an evaporator. The compressor 3, the indoor heat exchanger 7, the heating expansion valve 13, and the outdoor heat exchanger 5 constitute a refrigerant circuit.

  A low pressure sensor 24 is provided on the pipe connected to the inlet of the accumulator 6. The low pressure sensor 24 measures the pressure of the low pressure gas refrigerant sucked into the compressor 3. A dome lower temperature sensor 17 is provided on the outer surface of the bottom side of the compressor 3. The under-dome temperature sensor 17 measures the external temperature on the bottom side of the main body of the compressor 3 (the dome below the compressor 3).

  The pipe connected to the discharge port of the compressor 3 is provided with a discharge pipe temperature sensor 18 and a high pressure sensor 25. The discharge pipe temperature sensor 18 measures the temperature of the pipe connected to the discharge port of the compressor 3. The high pressure sensor 25 measures the pressure of the high pressure gas refrigerant discharged from the compressor 3.

  An outdoor air temperature sensor 19 is provided on the outdoor air intake side of the outdoor heat exchanger 5. The outside air temperature sensor 19 measures the temperature of outside air taken into the outdoor unit 5.

Next, the compressor 3 will be described with reference to FIG.
The compressor 3 is, for example, a scroll compressor having a turning scroll 22 combined with a fixed scroll (not shown). The orbiting scroll 22 uses the electric motor 22 as a drive source and rotates via the rotary shaft 21. As the orbiting scroll 22 rotates, the sucked refrigerant is compressed, and the compressed refrigerant is discharged from the discharge port.

  The electric motor 20 is adjusted in torque and rotational speed in accordance with a command from the determination / control unit 23 provided in the inverter.

  The determination / control unit 23 is an example of a determination unit, and at the time of the operation of the compressor 3 or immediately after the start of the operation of the compressor 3, the indoor heat exchanger 7 as an evaporator during the cooling operation, or the heating operation It is determined whether or not liquid refrigerant is included in the refrigerant supplied to the compressor 3 from the outdoor heat exchanger 5 serving as an evaporator. That is, the determination / control unit 23 determines whether or not liquid back has occurred.

  Whether the liquid back has occurred is determined based on the temperature near the compressor 3 or the compressor 3 such as the degree of superheat under the dome, the degree of superheat (TdSH), or the temperature under the dome or at the outlet. Is done. For example, when the liquid back is generated, the temperature of the compressor 3 is lowered. Therefore, it can be determined whether the liquid back is generated based on the temperature of the compressor 3 or the vicinity of the compressor 3.

  The determination / control unit 23 is an example of a control unit, and changes the efficiency of the electric motor 20 that drives the compressor 3 depending on whether or not liquid refrigerant is included. For example, for example, when it is determined that a liquid back has occurred, the efficiency of the electric motor 20 is reduced to increase the amount of heat generated by the electric motor 20 and the heat generated by the electric motor 20 increases the temperature of the refrigerant in the compressor 3. The refrigerant can be evaporated. As a result, when the liquid refrigerant is dissolved in the lubricating oil used in the compressor 3 in the compressor 3, the lubricating oil can be left in the compressor 3 by evaporating the refrigerant.

  Next, the liquid refrigerant removing operation of the air conditioner according to the present embodiment will be described. The liquid refrigerant removing operation is an operation for evaporating the liquid refrigerant accumulated in the compressor 3.

First, the liquid refrigerant removing operation when the air conditioner is operating normally will be described.
The liquid refrigerant removing operation in the present embodiment is performed during the compressor operation. Therefore, first, it is determined whether or not the compressor 3 of the air conditioner is in operation (step S1). When the compressor 3 is not operating but is stopped, the stopped state is maintained as it is. On the other hand, when the compressor 3 is in operation, it is determined whether the degree of superheat (SH) under the dome is 7 deg or less (step S2).

  Here, the degree of superheat under the dome is obtained by subtracting the saturation temperature of the refrigerant sucked into the compressor 3 measured by the low pressure sensor 24 from the temperature under the dome measured by the temperature under the dome sensor 17. In step S2, it may be determined whether the under-dome temperature is 0 ° C. or less, not the under-dome superheat degree. In addition, it may be determined whether one of the condition of the degree of superheat under the dome and the condition of the temperature under the dome is satisfied.

  If the condition is not satisfied in step S2, the temperature in the compressor 3 has not decreased, that is, there is no liquid refrigerant in the compressor 3 or there is little liquid refrigerant. 20 performs a normal operation. At this time, the electric motor 20 is driven by a normal inverter operation, and the current flowing through the electric motor 20 is controlled so as to be as efficient as possible when obtaining a desired torque and rotational speed.

  On the other hand, if the condition is satisfied in step S2, the temperature in the compressor 3 has decreased, so it is estimated that liquid refrigerant has accumulated in the compressor 3 or liquid back has occurred. Is done. At this time, a liquid refrigerant removing process is performed. That is, the electric motor 20 performs the power factor deterioration operation so that the efficiency of the electric motor 20, that is, the power factor of the electric motor 20 is deteriorated as compared with the normal operation (step S3).

  When the efficiency of the electric motor 20 is low due to the power factor deterioration operation, for example, when the electric power factor of the electric motor 20 is low, the amount of heat generated by the electric motor 20 is higher than when the electric power factor is high. Therefore, when it is determined that liquid back has occurred, the efficiency of the electric motor 20 is reduced. As a result, the amount of heat generated by the electric motor 20 can be increased, and the temperature of the refrigerant can be raised in the compressor 3 by the heat generated by the electric motor 20 to evaporate the liquid refrigerant 3. As a result, when the liquid refrigerant is dissolved in the lubricating oil used in the compressor 3 in the compressor 3, the lubricating oil can be left in the compressor 3 by evaporating the refrigerant.

  As the power factor deterioration operation continues, the temperature of the compressor 3 increases. Therefore, after shifting to the power factor deterioration operation, it is determined whether or not the degree of superheat under the dome exceeds 10 deg (step S4). In step S4, in addition to the degree of superheat under the dome, it may be determined based on whether or not the temperature under the dome exceeds 5 ° C.

  In step S4, when the condition is not satisfied, the temperature in the compressor 3 is still low, so it is estimated that liquid refrigerant has accumulated in the compressor 3. Therefore, the power factor deterioration operation is continued (step S3), and the liquid refrigerant is evaporated.

  On the other hand, if the condition is satisfied in step S <b> 4, it is estimated that the temperature of the compressor 3 has risen and no liquid refrigerant has accumulated in the compressor 3. Therefore, the electric motor 20 cancels the power factor deterioration operation and performs normal operation (step S5).

  According to the above operation, the liquid refrigerant in the compressor 3 is evaporated when the liquid refrigerant is accumulated in the compressor 3 or when a liquid back is generated during the operation of the compressor. In addition, the setting of the power factor in the power factor deterioration operation in step S3 may be uniquely determined, or may be changed in multiple steps or continuously according to the degree of superheat under the dome or the temperature under the dome. .

  In the above operation, whether to shift to the power factor deterioration operation is determined based on the degree of superheat under the dome or the temperature under the dome, or may be determined based on another degree of superheat or temperature.

  In the example shown in the flowchart of FIG. 4, it is determined whether to shift to the power factor deterioration operation based on the discharge superheat degree (TdSH). When the liquid refrigerant is discharged from the compressor 3, the temperature of the discharge pipe decreases, so that it is estimated that the liquid refrigerant is accumulated in the compressor 3 or a liquid back is generated. At this time, a liquid refrigerant removing process is performed. That is, the electric motor 20 performs the power factor deterioration operation so that the efficiency of the electric motor 20, that is, the power factor of the electric motor 20 is deteriorated as compared with the normal operation.

  In step S12, when the compressor 3 is operating, it is determined whether or not the state where the discharge superheat degree is less than 7 deg continues for 30 seconds. Since steps S11 to S15 in the example shown in FIG. 4 are the same as steps S1 to S5 in the example shown in FIG. 3, the detailed description is omitted.

  The discharge superheat degree is obtained by subtracting the saturation temperature of the refrigerant discharged from the compressor 3 measured by the high pressure sensor 25 from the temperature of the discharge pipe measured by the discharge pipe temperature sensor 18.

  According to the example shown in FIG. 4, for example, even in the case of an air conditioner in which a temperature sensor is not provided under the dome, liquid refrigerant has accumulated in the compressor 3 or liquid back has occurred. It can be detected that the electric motor 20 is shifted to the power factor deterioration operation.

  Next, with reference to FIG. 5, the liquid refrigerant removing operation immediately after the air conditioner starts operation will be described.

  First, after turning on the power of the air conditioner, whether or not the external temperature at the start of the cooling operation is 10 ° C. or lower, or the external temperature at the start of the heating operation is 0 ° C. It is determined whether or not the following is true (step S21). If the condition is not satisfied in step S21, the motor 20 performs a normal operation because there is no liquid refrigerant in the compressor 3 or there is little. In addition, since the distance from the indoor heat exchanger 7 which is an evaporator during cooling operation to the compressor 3 is longer than the distance from the outdoor heat exchanger 5 which is an evaporator during heating operation to the compressor 3, The amount of liquid refrigerant at the start of operation is larger than that at the start of heating operation. For this reason, the judgment condition for the external temperature is set higher when the cooling operation is started.

  On the other hand, if the condition is satisfied in step S21, it is further determined whether the under-dome superheat degree (SH) is 15 deg or less (step S22). If the condition is not satisfied in step S22, the electric motor 20 performs a normal operation because there is no liquid refrigerant in the compressor 3 or there is little. On the other hand, when the condition is satisfied, it is presumed that the liquid refrigerant is accumulated in the compressor 3 or the liquid back is generated. At this time, a liquid refrigerant removing process is performed. That is, the electric motor 20 performs the power factor deterioration operation so that the efficiency of the electric motor 20, that is, the power factor of the electric motor 20 is deteriorated as compared with the normal operation (step S23).

  As the power factor deterioration operation continues, the temperature of the compressor 3 increases. Therefore, after shifting to the power factor deterioration operation, it is determined whether or not the degree of superheat below the dome exceeds 15 deg (step S24). In step S24, when the condition is not satisfied, it is estimated that the liquid refrigerant is accumulated in the compressor 3 because the temperature in the compressor 3 is low. Therefore, the power factor deterioration operation is continued (step S23), and the liquid refrigerant is evaporated. On the other hand, if the condition is satisfied in step S <b> 24, it is estimated that the temperature of the compressor 3 has risen and no liquid refrigerant has accumulated in the compressor 3. Therefore, the electric motor 20 cancels the power factor deterioration operation and performs normal operation (step S25).

  By implementing the example shown in FIG. 5 alone without combining with the example shown in FIGS. 3 and 4, the liquid refrigerant removal process is limited to the first activation after the power is turned on. As a result, the liquid refrigerant removal process is performed during normal operation, or when the first activation of the compressor 3 is already completed after the power is turned on and the second and subsequent activations are performed. Absent. The liquid refrigerant removal process of the present embodiment lowers the power factor and raises the temperature of the compressor 3. For the liquid refrigerant removal process, if the power factor is frequently lowered, the power consumption increases. End up. Therefore, by implementing the example shown in FIG. 5 alone without combining with the example shown in FIGS. 3 and 4, an increase in power consumption in the liquid refrigerant removal process can be suppressed as much as possible.

  In FIG. 5, as a reliable example that liquid refrigerant has accumulated in the compressor 3, the case where the necessity of the liquid refrigerant removal process is determined at the first activation after power-on has been described. The timing for determining whether or not the refrigerant removal process is necessary may be, for example, the first activation after the defrosting (defrosting) operation ends. Thereby, the refrigerant | coolant collected in the compressor 3 can be evaporated at the time of the 1st starting after the completion | finish of a defrost (defrost) driving | operation.

  Note that the values of the degree of superheat under the dome, the temperature under the dome, and the outside temperature in the examples shown in FIGS. 3 to 5 are merely examples, and the present invention is not limited to this example.

Next, an example of the power factor deterioration operation will be described.
The torque and rotation speed of the electric motor 20 are controlled by calculating the rotor speed and the magnetic pole position based on the detected current / voltage, and a current component parallel to the magnetic pole and a current component orthogonal to the magnetic pole. It is done by controlling.

  The torque of the motor 20 is dominated by the magnet torque proportional to the current in the direction orthogonal to the magnetic pole, but the reluctance torque is also used by setting the current component in the direction parallel to the magnetic pole to be negative. it can. Therefore, the efficiency of operation can be increased by adjusting the reluctance torque.

  Thus, in this embodiment, switching between normal high-efficiency operation and low-efficiency operation at low frequency (low speed) is performed by changing the command value related to the current parallel to the magnetic pole. Do by.

  When normal high-efficiency operation is intended, a parallel-direction current command value and an orthogonal-direction current command value that are high in efficiency are calculated in advance for each operation speed and each torque command, and are tabulated. And the high efficiency driving | operation is aimed at by controlling the torque and rotation speed of the electric motor 20 using this table.

  On the other hand, when trying to operate with reduced efficiency at low frequency (low speed), the current command value in the parallel direction is controlled to be positive with respect to the normal high-efficiency operation. increase. As a result, even if the torque of the electric motor 20 is equal, a large amount of current can be passed, and the copper loss of the electric motor 20 is increased, and operation with reduced efficiency is possible.

  As described above, according to an embodiment of the present invention, for example, when the air conditioner is not started, that is, in a state where the main power is OFF, energization or the like by the crankcase is not performed and liquid refrigerant is accumulated in the compressor 3. In addition, when the liquid back is generated depending on the temperature condition during the normal operation and the liquid refrigerant is accumulated in the compressor 3, the evaporation of the liquid refrigerant can be promoted. As a result, the transition time from the low frequency operation to the high frequency operation can be shortened, and the rise time until the desired cooling capacity or heating capacity is exhibited can be improved. In addition, it is possible to reduce the cause of the failure of the compressor 3. In particular, in the present embodiment, the refrigerant in the compressor 3 can be heated by the heat generated by the electric motor 20 regardless of the suppression of power consumption during operation accompanying the recent increase in efficiency of the electric motor 20, and the evaporation of the refrigerant can be promoted.

DESCRIPTION OF SYMBOLS 1 Outdoor unit 2 Indoor unit 3 Compressor 4 Four-way valve 5 Outdoor heat exchanger 6 Accumulator 7 Indoor heat exchanger 8 Gas pipe 9 Liquid pipe 10 Strainer 11 Liquid side operation valve 12 Gas side operation valve 13 Heating expansion valve 14 For cooling Expansion valve 17 Dome temperature sensor 18 Discharge pipe temperature sensor 19 Outside air temperature sensor 20 Electric motor 21 Rotating shaft 22 Rotating scroll 23 Judgment / control unit 24 Low pressure sensor 25 High pressure sensor

Claims (5)

A refrigerant circuit having a compressor driven by an electric motor to compress the refrigerant, a condenser for condensing the compressed refrigerant, an expansion valve for expanding the condensed refrigerant, and an evaporator for evaporating the expanded refrigerant;
A determination unit for determining whether or not liquid refrigerant is included in the refrigerant supplied from the evaporator to the compressor;
A control unit that changes the efficiency of the electric motor that drives the compressor according to whether or not the liquid refrigerant is included;
An air conditioner comprising:   The air conditioning apparatus according to claim 1, wherein the determination unit determines whether or not a liquid refrigerant is included in the refrigerant supplied from the evaporator to the compressor during operation of the compressor.   The air conditioner according to claim 1, wherein the determination unit determines whether or not liquid refrigerant is included in the refrigerant supplied from the evaporator to the compressor immediately after the operation of the compressor is started.   The air conditioning apparatus according to claim 1, wherein the control unit changes the efficiency of the electric motor by changing a current flowing through the electric motor. A refrigerant circuit having a compressor driven by an electric motor to compress refrigerant, a condenser for condensing the compressed refrigerant, an expansion valve for expanding the condensed refrigerant, and an evaporator for evaporating the expanded refrigerant. A control method for an air conditioner, comprising:
Determining whether the refrigerant supplied from the evaporator to the compressor includes liquid refrigerant;
Changing the efficiency of the electric motor driving the compressor in response to determining whether or not a liquid refrigerant is included;
A control method for an air conditioner comprising:

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