JPWO2020148846A1 - Air conditioner - Google Patents

Abstract

The air conditioner includes a refrigerant circuit in which the refrigerant circulates in the refrigeration cycle through the compressor, the condenser, the outdoor expansion valve, and the evaporator in order, and at least a control unit that controls the compressor and the outdoor expansion valve. One of the condenser and the evaporator is an outdoor heat exchanger, the other is an indoor heat exchanger, and the control unit makes the indoor heat exchanger function as an evaporator and freezes the indoor heat exchanger. If the first condition is satisfied (step S21: Yes), the liquid compression prevention control is performed (step S24), and if the second condition is satisfied during the liquid compression prevention control (step S25: Yes), the liquid compression prevention control is performed. Is released (step S26).

Description

The present invention relates to an air conditioner.

As a technique for cleaning the indoor heat exchanger of an air conditioner, for example, Patent Document 1 states, "The control unit causes the indoor heat exchanger to function as an evaporator and freezes or condenses the indoor heat exchanger. After freezing the indoor heat exchanger, the control unit increases the opening degree of the expansion valve. ”The air conditioner is described.

International Publication No. 2018/1983390 Japanese Unexamined Patent Publication No. 8-313070

However, in the technique described in Patent Document 1, the inventors have found a phenomenon in which liquid is easily compressed by a compressor when the indoor heat exchanger is intentionally frozen for cleaning, and the indoor heat exchanger is used. Various issues for proper cleaning were examined.

Patent Document 2 proposes a refrigerating apparatus capable of improving the reliability of a compressor and expanding its guaranteed operation area. However, this Patent Document 2 does not describe the case where the freezing treatment is intentionally performed for cleaning the indoor heat exchanger, which is the object of the present invention. That is, Patent Document 2 has no motivation for solving the problem of the present invention.

The present invention is an invention for solving the above-mentioned problems, and an object of the present invention is to provide an air conditioner capable of appropriately cleaning an indoor heat exchanger.

In order to achieve the above object, the air conditioner of the present invention includes a refrigerant circuit in which the refrigerant circulates in the refrigeration cycle via the compressor, the condenser, the expansion valve, and the evaporator in order, and at least the compressor and the expansion valve. One of the condenser and the evaporator is an outdoor heat exchanger and the other is an indoor heat exchanger, and the control unit makes the indoor heat exchanger function as an evaporator and indoors. If a predetermined condition is satisfied during the freezing process of freezing the heat exchanger, the first control is to reduce the rotation speed of the compressor or to control the compressor to stop the compressor. Other aspects of the present invention will be described in embodiments described below.

According to the present invention, it is possible to provide an air conditioner capable of appropriately cleaning an indoor heat exchanger.

It is external block diagram which shows the air conditioner which concerns on 1st Embodiment. It is explanatory drawing which shows the vertical cross-sectional structure of the indoor unit of the air conditioner which concerns on 1st Embodiment. It is explanatory drawing which shows the refrigerant circuit of the air conditioner which concerns on 1st Embodiment. It is a block diagram which shows the control function of the air conditioner which concerns on 1st Embodiment. It is a flowchart which shows the cleaning process which the control part of the air conditioner which concerns on 1st Embodiment executes. It is a flowchart which shows the detail of the process for freezing the indoor heat exchanger which concerns on 1st Embodiment. It is a map showing the relationship between the relative humidity of indoor air and the freezing time. It is a map showing the relationship between the outdoor temperature and the rotation speed of the compressor. It is explanatory drawing which shows an example of the time change of the temperature of an indoor heat exchanger. It is explanatory drawing which shows the control object and control method of liquid compression prevention control. It is a flowchart which shows an example of interlocking control of liquid compression prevention control. It is a flowchart which shows another example of interlocking control of liquid compression prevention control. It is a flowchart which shows the detail of the process for thawing the indoor heat exchanger. It is a flowchart which shows the detail of the process for drying an indoor heat exchanger. It is explanatory drawing which shows the refrigerant circuit of the air conditioner which concerns on 2nd Embodiment. It is a flowchart which shows the process for freezing the 2nd chamber heat exchanger which concerns on 2nd Embodiment. It is explanatory drawing which shows the internal volume of accumulator with respect to the amount of refrigerant of various accumulators.

<< First Embodiment >>
<Composition of air conditioner>
FIG. 1 is an external configuration diagram showing an air conditioner 100 according to the first embodiment. FIG. 1 shows a front view of the indoor unit 10, the outdoor unit 30, and the remote controller 40 included in the air conditioner 100. The air conditioner 100 is a device that performs air conditioning by circulating a refrigerant in a refrigeration cycle (heat pump cycle). As shown in FIG. 1, the air conditioner 100 includes an indoor unit 10 installed indoors (air-conditioned space), an outdoor unit 30 installed outdoors, and a remote controller 40 operated by a user. There is.

The indoor unit 10 includes a remote control signal transmission / reception unit 11. The remote control signal transmission / reception unit 11 transmits / receives a predetermined signal to / from the remote control 40 by infrared communication or the like. For example, the remote control signal transmission / reception unit 11 receives signals such as an operation / stop command, a change in the set temperature, a change in the operation mode, and a timer setting from the remote controller 40. Further, the remote control signal transmission / reception unit 11 transmits the detected value of the room temperature and the like to the remote control 40. Although omitted in FIG. 1, the indoor unit 10 and the outdoor unit 30 are connected via a refrigerant pipe and also via a communication line.

FIG. 2 is an explanatory view showing a vertical cross-sectional configuration of the indoor unit 10 of the air conditioner 100 according to the first embodiment. In addition to the remote control signal transmitter / receiver 11 (see FIG. 1), the indoor unit 10 includes an indoor heat exchanger 12, a drain pan 13, an indoor fan 14, a housing base 15, filters 16, 16 and a front surface. A panel 17, a left-right wind direction plate 18, and a vertical wind direction plate 19 are provided.

The indoor heat exchanger 12 is a heat exchanger in which heat exchange is performed between the refrigerant passing through the heat transfer tube 12g and the indoor air. The drain pan 13 receives the water dripping from the indoor heat exchanger 12, and is arranged below the indoor heat exchanger 12. The water that has fallen into the drain pan 13 is discharged to the outside via a drain hose (not shown). The indoor fan 14 is, for example, a cylindrical cross-flow fan, which is driven by an indoor fan motor 14a (see FIG. 4). The housing base 15 is a housing in which devices such as the indoor heat exchanger 12 and the indoor fan 14 are installed.

The filters 16 and 16 remove dust from the air taken in through the air suction port h1 and the like, and are installed on the upper side and the front side of the indoor heat exchanger 12. The front panel 17 is a panel installed so as to cover the filter 16 on the front side, and is rotatable forward with the lower end as an axis. The front panel 17 may not rotate.

The left-right wind direction plate 18 is a plate-shaped member that adjusts the flow direction of the air blown out toward the room in the left-right direction. The left and right wind direction plates 18 are arranged on the downstream side of the indoor fan 14, and are rotated in the left and right directions by the left and right wind direction plate motors 21 (see FIG. 4).

The vertical wind direction plate 19 is a plate-shaped member that adjusts the flow direction of the air blown out toward the room in the vertical direction. The vertical wind direction plate 19 is arranged on the downstream side of the indoor fan 14, and is rotated in the vertical direction by the vertical wind direction plate motor 22 (see FIG. 4).

Then, the air sucked through the air suction port h1 exchanges heat with the refrigerant flowing through the heat transfer tube 12g, and the heat exchanged air is guided to the blowout air passage h2. The air flowing through the blowout air passage h2 is guided in a predetermined direction by the left and right wind direction plates 18 and the upper and lower wind direction plates 19, and is further blown into the room through the air outlet h3.

FIG. 3 is an explanatory diagram showing a refrigerant circuit Q of the air conditioner 100 according to the first embodiment. The solid line arrow in FIG. 3 indicates the flow of the refrigerant during the heating operation. Further, the broken line arrow in FIG. 3 indicates the flow of the refrigerant during the cooling operation. As shown in FIG. 3, the outdoor unit 30 includes a compressor 31, an outdoor heat exchanger 32, an outdoor fan 33, an outdoor expansion valve 34 (first expansion valve), a four-way valve 35, an accumulator 39, and the like. It has.

The compressor 31 is a device that compresses a low-temperature low-pressure gas refrigerant by driving the compressor motor 31a and discharges it as a high-temperature high-pressure gas refrigerant. The outdoor heat exchanger 32 is a heat exchanger in which heat is exchanged between the refrigerant passing through the heat transfer tube (not shown) and the outside air sent from the outdoor fan 33. The accumulator 39 is installed on the suction pipe side of the compressor 31, and has the purpose of preventing the compressor 31 from being damaged due to liquid compression when a large amount of liquid refrigerant is sucked into the compressor 31.

The outdoor fan 33 is a fan that sends outside air to the outdoor heat exchanger 32 by driving the outdoor fan motor 33a, and is installed in the vicinity of the outdoor heat exchanger 32. The outdoor expansion valve 34 has a function of reducing the pressure of the refrigerant condensed by the "condenser" (one of the outdoor heat exchanger 32 and the indoor heat exchanger 12). The refrigerant decompressed by the outdoor expansion valve 34 is guided to the "evaporator" (the other of the outdoor heat exchanger 32 and the indoor heat exchanger 12).

The four-way valve 35 is a valve that switches the flow path of the refrigerant according to the operation mode of the air conditioner 100. That is, during the cooling operation in which the refrigerant flows in the direction of the broken line arrow, the compressor 31, the outdoor heat exchanger 32 (condenser), the outdoor expansion valve 34, and the indoor heat exchanger 12 (evaporator) pass through the four-way valve 35. In the refrigerant circuit Q which is sequentially connected in an annular shape, the refrigerant circulates in the refrigeration cycle.

Further, during the heating operation in which the refrigerant flows in the direction of the solid line arrow, the compressor 31, the indoor heat exchanger 12 (condenser), the outdoor expansion valve 34, and the outdoor heat exchanger 32 (evaporator) pass through the four-way valve 35. In the refrigerant circuit Q which is sequentially connected in an annular shape, the refrigerant circulates in the refrigeration cycle.

That is, in the refrigerant circuit Q in which the refrigerant circulates in the refrigeration cycle through the compressor 31, the "condenser", the outdoor expansion valve 34, and the "evaporator" in that order, the "condenser" and the "evaporator" described above. One is the outdoor heat exchanger 32 and the other is the indoor heat exchanger 12.

FIG. 4 is a block diagram showing a control function of the air conditioner 100 according to the first embodiment. The indoor unit 10 shown in FIG. 4 includes an imaging unit 23, an indoor environment detection unit 24, and an indoor control circuit 25, in addition to the above-described configuration. The image pickup unit 23 takes an image of a room (air-conditioned space), and includes an image pickup element such as a CCD sensor (Charge Coupled Device) and a CMOS sensor (Complementary Metal Oxide Semiconductor). Based on the imaging result of the imaging unit 23, the indoor control circuit 25 detects a person (resident) in the room. The "person detection unit" that detects a person existing in the air-conditioned space includes an imaging unit 23 and an indoor control circuit 25.

The indoor environment detection unit 24 has a function of detecting the indoor state and the state of the equipment of the indoor unit 10, and includes an indoor temperature sensor 24a, a humidity sensor 24b, and an indoor heat exchanger temperature sensor 24c. .. The indoor temperature sensor 24a is a sensor that detects the temperature in the room (air-conditioned space). The indoor temperature sensor 24a is installed on the air suction side of the filters 16 and 16 (see FIG. 2). As a result, when the indoor heat exchanger 12 is frozen as described later, it is possible to suppress a detection error due to the influence of the heat radiation.

The humidity sensor 24b is a sensor that detects the humidity of the air in the room (air-conditioned space), and is installed at a predetermined position of the indoor unit 10. The indoor heat exchanger temperature sensor 24c is a sensor that detects the temperature of the indoor heat exchanger 12 (see FIG. 2), and is installed in the indoor heat exchanger 12. The detected values of the indoor temperature sensor 24a, the humidity sensor 24b, and the indoor heat exchanger temperature sensor 24c are output to the indoor control circuit 25.

Although not shown, the indoor control circuit 25 includes electronic circuits such as a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and various interfaces. Then, the program stored in the ROM is read out and expanded in the RAM, and the CPU executes various processes.

As shown in FIG. 4, the indoor control circuit 25 includes a storage unit 25a and an indoor control unit 25b. In addition to the predetermined program, the storage unit 25a stores the imaging result of the imaging unit 23, the detection result of the indoor environment detection unit 24, the data received via the remote control signal transmission / reception unit 11, and the like. The indoor control unit 25b executes a predetermined control based on the data stored in the storage unit 25a. The process executed by the indoor control unit 25b will be described later.

In addition to the above-described configuration, the outdoor unit 30 includes an outdoor environment detection unit 36 (outdoor temperature sensor 36a, outdoor heat exchanger temperature sensor 36c) and an outdoor control circuit 37. The outdoor temperature sensor 36a is a sensor that detects the outdoor temperature (outside air temperature), and is installed at a predetermined position of the outdoor unit 30. The outdoor heat exchanger temperature sensor 36c is a sensor that detects the temperature of the outdoor heat exchanger 32 (see FIG. 3), and is installed in the outdoor heat exchanger 32. Although omitted in FIG. 4, the outdoor unit 30 also includes a sensor for detecting the discharge temperature of the compressor 31 (see FIG. 3). In addition, sensors for detecting the suction temperature, discharge pressure, refrigerant flow rate, etc. of the compressor 31 (see FIG. 3) may be provided. The detected value of each sensor including the outdoor temperature sensor 36a is output to the outdoor control circuit 37.

Although not shown, the outdoor control circuit 37 includes electronic circuits such as a CPU, ROM, RAM, and various interfaces, and is connected to the indoor control circuit 25 via a communication line. Further, a temperature sensor 38 for detecting the temperature of an electric product is installed in the outdoor control circuit 37. The temperature sensor 38 may be omitted. As shown in FIG. 4, the outdoor control circuit 37 includes a storage unit 37a and an outdoor control unit 37b. In addition to the predetermined program, the storage unit 37a stores the detection values of each sensor including the outdoor temperature sensor 36a. The outdoor control unit 37b controls the compressor motor 31a (that is, the compressor 31), the outdoor fan motor 33a, the outdoor expansion valve 34, and the like based on the data stored in the storage unit 37a. Hereinafter, the indoor control circuit 25 and the outdoor control circuit 37 are referred to as “control unit K”.

Next, a process for cleaning the indoor heat exchanger 12 (see FIG. 2) will be described.
As described above, a filter 16 (see FIG. 2) for collecting dust and dirt is installed on the upper side and the front side (air suction side) of the indoor heat exchanger 12. However, since fine dust and dirt may pass through the filter 16 and adhere to the indoor heat exchanger 12, it is desirable to periodically clean the indoor heat exchanger 12. Therefore, in the present embodiment, the indoor heat exchanger 12 is washed by freezing the moisture contained in the air taken into the indoor unit 10 by the indoor heat exchanger 12 and then melting the ice of the indoor heat exchanger 12. I try to do it. Such a series of processes is referred to as "cleaning process" of the indoor heat exchanger 12.

FIG. 5 is a flowchart showing a cleaning process executed by the control unit K of the air conditioner 100 according to the first embodiment. This flowchart will be described with reference to FIGS. 3 and 4 as appropriate. It is assumed that the predetermined air conditioning operation (cooling operation, heating operation, etc.) has been performed until the time of "START" in FIG.

Further, it is assumed that the start condition of the cleaning process of the indoor heat exchanger 12 is satisfied at the time of "START". The "cleaning process start condition" is, for example, a condition that the value obtained by integrating the execution time of the air conditioning operation from the end of the previous cleaning process has reached a predetermined value (dirt on the surface of the indoor heat exchanger 12). When it should be cleaned after it adheres). The time zone for performing the cleaning process may be set by the operation of the remote controller 40 by the user.

In step S101, the control unit K stops the air conditioning operation for a predetermined time (for example, several minutes). The predetermined time described above is a time for stabilizing the refrigeration cycle and is set in advance. For example, when the heating operation that had been performed until "START" is interrupted and the indoor heat exchanger 12 is frozen (S102), the control unit K moves the refrigerant in the opposite direction to that during the heating operation. Controls the valve 35.

Here, if the direction in which the refrigerant flows is suddenly changed, the compressor 31 will be overloaded, and the sound or the like will cause the user to feel uncomfortable. Therefore, in the present embodiment, the air conditioning operation is stopped for a predetermined time prior to freezing (S102) of the indoor heat exchanger 12 (S101). In this case, the control unit K may freeze the indoor heat exchanger 12 after a predetermined time has elapsed from the time when the air conditioning operation is stopped.

When the cooling operation is interrupted to freeze the indoor heat exchanger 12, the process of step S101 may be omitted. This is because the direction in which the refrigerant flows during the cooling operation (START) and the direction in which the refrigerant flows during freezing (S102) of the indoor heat exchanger 12 are the same.

Next, in step S102, the control unit K freezes the indoor heat exchanger 12 (the control unit K executes the freezing process). That is, the control unit K causes the indoor heat exchanger 12 to function as an evaporator, and freezes the moisture contained in the air taken into the indoor unit 10 by frosting and icing on the surface of the indoor heat exchanger 12.

In step S103, the control unit K thawes the indoor heat exchanger 12 (ice adhering to the surface thereof). For example, the control unit K melts and thawes the ice on the surface of the indoor heat exchanger 12 by making the indoor heat exchanger 12 function as a condenser. As a result, the dust and dirt adhering to the indoor heat exchanger 12 are washed away. In addition, natural thawing may be performed, or thawing may be performed by turning the indoor fan 14 and blowing wind.

In step S104, the control unit K dries the indoor heat exchanger 12. For example, the control unit K dries the water on the surface of the indoor heat exchanger 12 by driving the indoor fan 14. As a result, the indoor heat exchanger 12 can be kept clean. After performing the process of step S104, the control unit K ends a series of processes (END).

Next, the details of each step of FIG. 5 will be described.
FIG. 6 is a flowchart showing details of a process for freezing the indoor heat exchanger 12 (S102 in FIG. 5, freezing process). Refer to FIGS. 3 and 4 as appropriate. In step S11, the control unit K makes initial settings. As initial setting items, freezing time (time from the start of freezing treatment to the end of freezing treatment), temperature which is a criterion for freezing (upper freezing temperature Tu, lower freezing temperature Td1 (first condition temperature), lower freezing temperature). There is Td2 (temperature of the second condition)) and the like.

FIG. 7 is a map showing the relationship between the relative humidity of indoor air and the freezing time. The horizontal axis of FIG. 7 is the relative humidity of the indoor air, which is detected by the humidity sensor 24b (see FIG. 4). The vertical axis of FIG. 7 is the freezing time set corresponding to the relative humidity of the indoor air.

As shown in FIG. 7, the control unit K shortens the freezing time for freezing the indoor heat exchanger 12 as the relative humidity of the indoor air increases. This is because the higher the relative humidity of the indoor air, the larger the amount of water contained in the predetermined volume of indoor air, and the more easily the water adheres to the indoor heat exchanger 12. By setting the freezing time in this way, an appropriate amount of water required for cleaning the indoor heat exchanger 12 can be attached to the indoor heat exchanger 12 and further frozen.

In addition, instead of the map (data table) shown in FIG. 7, a predetermined mathematical formula may be used. Further, the control unit K may set the freezing time based on the absolute humidity of the indoor air instead of the relative humidity of the indoor air. That is, the control unit K may shorten the freezing time as the absolute humidity of the indoor air increases.

Returning to FIG. 6, in step S12, the control unit K controls the four-way valve 35. That is, the control unit K controls the four-way valve 35 so that the outdoor heat exchanger 32 functions as a condenser and the indoor heat exchanger 12 functions as an evaporator. If the cooling operation is performed immediately before the "cleaning process" (a series of processes shown in FIG. 5), the control device maintains the state of the four-way valve 35 in step S12.

Next, in step S13, the control unit K sets the rotation speed of the compressor 31. That is, the control unit K sets the rotation speed of the compressor motor 31a based on the outdoor temperature which is the detected value of the outdoor temperature sensor 36a, and drives the compressor 31.

FIG. 8 is a map showing the relationship between the outdoor temperature and the rotation speed of the compressor 31. When freezing the indoor heat exchanger 12, the control unit K increases the rotation speed of the compressor motor 31a as the outdoor temperature increases, as shown in FIG. This is because in order for the indoor heat exchanger 12 to take heat from the indoor air, it is necessary that the outdoor heat exchanger 32 sufficiently dissipates heat accordingly. For example, when the outdoor temperature is relatively high, the control unit K increases the temperature and pressure of the refrigerant discharged from the compressor 31 by increasing the rotation speed of the compressor motor 31a. As a result, heat exchange in the outdoor heat exchanger 32 is appropriately performed, and by extension, freezing of the indoor heat exchanger 12 is also appropriately performed. In addition, instead of the map (data table) shown in FIG. 8, a predetermined mathematical formula may be used.

Incidentally, in normal air conditioning operation (cooling operation or heating operation), the rotation speed of the compressor 31 is often controlled based on the temperature of the refrigerant discharged from the compressor 31 or the like. On the other hand, when the indoor heat exchanger 12 is frozen, the temperature of the refrigerant discharged from the compressor 31 tends to be lower than that during normal air conditioning operation, so the outdoor temperature is used as another parameter. ..

Returning to FIG. 6, in step S14, the control unit K adjusts the opening degree of the outdoor expansion valve 34. In step S14, it is desirable that the opening degree of the outdoor expansion valve 34 is smaller than that during normal cooling operation. As a result, the refrigerant having a lower temperature and lower pressure than that during the normal cooling operation flows into the indoor heat exchanger 12 via the outdoor expansion valve 34. Therefore, the water adhering to the indoor heat exchanger 12 is likely to freeze, and the power consumption required for freezing the indoor heat exchanger 12 can be reduced.

In step S15, the indoor fan 14 is stopped. When the indoor heat exchanger 12 is frozen (that is, until a predetermined freezing time elapses), the control unit K may stop the indoor fan 14 or the indoor fan 14 may be stopped. May be driven at a predetermined rotation speed. In either case, the indoor heat exchanger 12 is frozen.

In step S16, the control unit K sets the rotation speed of the outdoor fan 33. That is, normally, the control unit K sets the rotation speed of the outdoor fan 33 based on the rotation speed of the compressor motor 31a.

Next, in step S20, the control unit K performs the end processing of the freezing process including the liquid compression prevention control. The end process of the freezing process is composed of steps S21 to S26.

In step S21, the control unit K determines whether or not the first condition (details will be described later) of the liquid compression prevention control is satisfied. If the first condition is not satisfied (S21: No), the control unit K proceeds to step S22, and if the first condition is satisfied (S21: Yes), enters the liquid compression prevention control (step S24, details will be described later). , Step S23.

In step S22, the control unit K determines whether or not the liquid compression prevention control is in progress (in S24). If the control unit K is not in the liquid compression prevention control (S22: No), the process proceeds to step S23, and if the liquid compression prevention control is in progress (S22: Yes), does the control unit K satisfy the second condition (details will be described later)? Whether or not it is determined (step S25). When the second condition is not satisfied (S25: No), the control unit K proceeds to step S24, and when the second condition is satisfied (S25: Yes), the liquid compression prevention control is released (step S26), and the process proceeds to step S23. move on.

Then, in step S23, it is determined whether or not the freezing end condition is satisfied, and if the freezing end condition is satisfied (S23: Yes), the process is completed and the freezing end condition is not satisfied (S23: No), step S21. Return to. Specifically, assuming that the freezing end condition is a predetermined time after the freezing process is started, it is determined whether or not the freezing process has reached the freezing time set in step S11. It may be terminated under other freezing termination conditions (for example, when the temperature of the indoor heat exchanger is below a predetermined temperature and continues for a predetermined time).

Next, the first condition in step S21, the second condition in step S25, and the liquid compression prevention control in step S24 will be described.
The first condition (predetermined condition) is
(1) When the temperature of the indoor heat exchanger 12 is equal to or lower than the predetermined temperature
(2) When the temperature difference between the temperature of the indoor temperature sensor 24a (room temperature sensor) and the temperature of the indoor heat exchanger 12 is equal to or greater than the predetermined temperature difference.
(3) When the dryness of the intake refrigerant of the compressor 31 is equal to or less than the predetermined dryness.
(4) When the dryness of the intake refrigerant of the compressor 31 is equal to or less than the predetermined dryness in a predetermined time.
Is. When at least one of the conditions (the first condition) is satisfied, the liquid compression prevention control (step S24) is started.

In the above (2), when the temperature difference is equal to or larger than the predetermined temperature difference, it means that the temperature difference is too large to evaporate in the evaporator. For example, if the room temperature is 20 ° C. and the temperature of the indoor heat exchanger 12 is −30 ° C., the amount of air passing through the indoor heat exchanger 12 is small, so that even if heat is exchanged, the amount of refrigerant evaporation is small. The liquid refrigerant remains.

As the second condition, if it is controlled by one point of the first condition, it is chattered or has a width to be affected by noise, and this width is set to the set width (hysteresis, adjustment sensitivity, operation gap, dead zone). ). That is, in the case of (1) above, the temperature of the indoor heat exchanger 12 is equal to or greater than the value obtained by adding the set width at the predetermined temperature. As a result, it is possible to prevent the repeated operation of the liquid compression prevention control from being prevented immediately after the liquid compression prevention control is released.

That is, as the second condition,
(5) When the temperature of the indoor heat exchanger 12 is equal to or higher than the value obtained by adding the predetermined set width to the predetermined temperature.
(6) When the temperature difference between the temperature of the indoor temperature sensor 24a (room temperature sensor) and the temperature of the indoor heat exchanger 12 is equal to or less than the predetermined temperature difference minus the predetermined set width.
(7) When the dryness of the intake refrigerant of the compressor 31 is equal to or greater than the value obtained by adding the predetermined set width to the predetermined dryness.
(8) When the dryness of the intake refrigerant of the compressor 31 is equal to or greater than the value obtained by adding the predetermined set width to the predetermined dryness at the predetermined time.
Is. When at least one of the conditions (the second condition) is satisfied, the liquid compression prevention control (step S24) is released (step S26).

As the liquid compression prevention control, at least one or more control targets of the compressor 31, the indoor fan 14, the outdoor fan 33, and the outdoor expansion valve 34 are controlled.
(A) Compressor 31: Decrease the rotation speed of the compressor 31 or stop the compressor 31. When the rotation speed of the compressor 31 is lowered to lower the flow rate of the refrigerant, the accumulator 39 is less likely to overflow, the amount of heat exchange of the indoor heat exchanger 12 per unit flow rate is increased, and the amount of evaporation is increased. When the compressor 31 is stopped, the refrigeration cycle is stopped, so that the compressor 31 by liquid compression can be protected.
(B) Indoor fan 14: Increase the rotation speed of the indoor fan. The rotation speed of the indoor fan 14 is increased (the air volume is increased) to increase the indoor heat exchange amount by the indoor heat exchanger 12.
(C) Outdoor fan 33: The rotation speed of the outdoor fan 33 is reduced, or the outdoor fan 33 is stopped. The rotation speed of the outdoor fan 33 is reduced to reduce the amount of liquid in the condenser, and as a result, the amount of liquid at the outlet of the evaporator is reduced.
(D) Outdoor expansion valve 34: The opening degree of the outdoor expansion valve 34 is reduced. When the outdoor expansion valve 34 is throttled, the amount of refrigerant circulating is reduced, and evaporation is relatively active.

The dryness of the intake refrigerant of the compressor 31 in (3) and (4) is the discharge temperature of the compressor 31, the condensation temperature of the condenser (the temperature of the outdoor heat exchange 32), and the evaporation temperature of the evaporator (the temperature of the outdoor heat exchange 32). The temperature of the indoor heat exchanger 12), the flow rate of the refrigerant, and the compressor power consumption of the compressor 31 are detected, and compression is performed based on the discharge temperature, condensation temperature, evaporation temperature, refrigerant flow rate, compressor power consumption, and the like. It is advisable to estimate the suction dryness of the machine 31. Further, for example, the discharge temperature of the compressor 31, the condensation temperature of the condenser, the evaporation temperature of the evaporator, the flow rate of the refrigerant, and the power consumption of the compressor 31 are detected, and the detected discharge temperature, condensation temperature, and the like. The compressor efficiency ηc is calculated based on the evaporation temperature, the refrigerant flow rate, and the power consumption of the compressor 31. Then, the control unit K may estimate the suction dryness Xs of the compressor 31 based on the calculated compressor efficiency ηc.

The process of step S20 described above will be specifically described with reference to FIG.
FIG. 9 is an explanatory diagram showing an example of a temporal change in the temperature of the indoor heat exchanger 12. FIG. 9 shows, as the first condition (predetermined condition), when the temperature TE of the indoor heat exchanger 12 (detected value of the indoor heat exchanger temperature sensor 24c: see FIG. 4) is equal to or lower than the predetermined temperature.

The horizontal axis of FIG. 9 is the elapsed time from the time of “START” in FIG. The vertical axis of FIG. 9 is the temperature TE of the indoor heat exchanger 12. When the temperature is less than 0 ° C., there are a freezing upper limit temperature Tu, which is a determination reference temperature for the upper limit of freezing, and freezing lower limit temperatures Td1 and Td2 (Td1 <Td2), which are determination reference temperatures for the lower limit of freezing. Here, the lower freezing temperature Td1 is used as the first condition for preventing the condensation temperature, and the lower freezing temperature Td2 is used as the second condition.

When the temperature TE of the indoor heat exchanger 12 starts the freezing process, the freezing proceeds smoothly (curve C1) or the freezing progresses rapidly based on the relative humidity of the indoor air (air-conditioned space) and the like (curve C1). There is a curve C2). In this case, as shown in curve C1, when the freezing proceeds smoothly, the temperature TE of the indoor heat exchanger 12 does not fall below the freezing lower limit temperature Td1. Therefore, when the freezing time (for example, 20 minutes) is reached, the freezing process is performed. Is completed, and the process proceeds to the next step.

On the other hand, when the temperature TE of the indoor heat exchanger 12 becomes equal to or less than the freezing lower limit temperature Td1 (when the first condition is satisfied) when freezing progresses rapidly as shown in the curve C2, the liquid compression prevention control is started (time t). ₂₁ ). When the evaporation function is advanced by the liquid compression prevention control, the temperature TE of the indoor heat exchanger 12 rises. Then, when the temperature TE of the indoor heat exchanger 12 becomes equal to or higher than the freezing lower limit temperature Td2 (when the second condition is satisfied), the liquid compression prevention control is released (returns to the control value before the liquid compression prevention control process), and the freezing process is performed. a (refer to time _{t 22).} After that, when the freezing time is reached, the freezing process is completed and the process proceeds to the next step.

FIG. 10 is an explanatory diagram showing a control target and a control method of the liquid compression prevention control. As the liquid compression prevention control, as described above, at least one or more of the compressor 31, the indoor fan 14, the outdoor fan 33, and the outdoor expansion valve 34 are controlled.
(A) Compressor 31: After starting the freezing process operation, when the first condition is satisfied, the liquid compression prevention control for lowering or stopping the rotation speed is entered, and when the second condition is satisfied, the freezing process is restarted.
(B) Indoor fan 14: After the freezing operation is started, when the first condition is satisfied, the liquid compression prevention control for increasing the rotation speed is entered, and when the second condition is satisfied, the freezing process is restarted.
(C) Outdoor fan 33: After starting the freezing operation, when the first condition is satisfied, the liquid compression prevention control for lowering or stopping the rotation speed is entered, and when the second condition is satisfied, the freezing process is restarted.
(D) Outdoor expansion valve 34: After the freezing operation is started, when the first condition is satisfied, the liquid compression prevention control for narrowing the opening is started, and when the second condition is satisfied, the freezing process is restarted.
Although the control content of each control target is shown in FIG. 10, a plurality of control targets may be interlocked and controlled.

FIG. 11 is a flowchart showing an example of interlocking control of the liquid compression prevention control. FIG. 11 shows an example of interlocking control of the compressor 31, the outdoor fan 33, and the indoor fan 14. When the liquid compression prevention control starts, the control unit K stops the compressor 31 (step S31) and stops the outdoor fan 33 (step S32). Then, the control unit K determines whether or not the liquid compression prevention control time, which is the cumulative time since the start of the liquid compression prevention control, has elapsed (step S33), and determines the liquid compression prevention control time. When the time has passed (S33: Yes), the rotation speed of the indoor fan 14 is increased, and when the liquid compression prevention control time has not passed the predetermined time (S33: No), the process proceeds to step S23 (see FIG. 6).

For Figure 11, by stopping the compressor 31 and the outdoor fan 33, for example, in FIG. 9, when at time t ₂₁ after not increase the temperature TE of the indoor heat exchanger 12, the liquid to increase the rotational speed of the indoor fan 14 Anti-compression control is added to enhance the effect of liquid anti-compression control.

FIG. 12 is a flowchart showing another example of interlocking control of the liquid compression prevention control. FIG. 12 shows an example of interlocking control of the compressor 31 and the outdoor expansion valve 34. When the liquid compression prevention control starts, the control unit K reduces the rotation speed of the compressor 31 (step S41). Then, the control unit K determines whether or not the liquid compression prevention control time, which is the cumulative time since the start of the liquid compression prevention control, has elapsed (step S42), and determines the liquid compression prevention control time. When the time has elapsed (S42: Yes), the outdoor expansion valve 34 is throttled, and when the liquid compression prevention control time does not elapse the predetermined time (S42: No), the process proceeds to step S23 (see FIG. 6).

For Figure 12, also lowers the rotational speed of the compressor 31, for example, in FIG. 9, when at time t ₂₁ after not increase the temperature TE of the indoor heat exchanger 12, liquid compression prevention control throttling the outdoor expansion valve 34 Is added to enhance the effect of liquid compression prevention control.

FIG. 13 is a flowchart showing the details of the process for thawing the indoor heat exchanger 12 (S103 in FIG. 5) (see FIGS. 3 and 4 as appropriate). The control unit K freezes the indoor heat exchanger 12 by the process of step S102 (see FIG. 6), and then executes a series of processes of step S103 shown in FIG.

In step S103a, the control unit K determines whether or not the room temperature (temperature of the air-conditioned space) is equal to or higher than a predetermined value. This predetermined value is a threshold value that serves as a criterion for determining whether or not the indoor heat exchanger 12 functions as a condenser, and is set in advance.

When the indoor temperature is equal to or higher than a predetermined value (for example, the temperature at which the ice in the indoor heat exchanger 12 can be thawed by natural thawing) in step S103a (S103a: Yes), the control unit K is for thawing the indoor heat exchanger 12. End the process (END). As will be described next, when the indoor heat exchanger 12 is thawed, the four-way valve 35 is controlled in the same manner as during the heating operation, but when the indoor temperature is above a predetermined value, the condensing side of the refrigeration cycle (here). This is because the heat load of the indoor heat exchanger 12) becomes too large and the balance with the evaporation side (here, the outdoor heat exchanger 32) cannot be achieved. Further, when the indoor temperature is relatively high, the ice in the indoor heat exchanger 12 melts naturally with the passage of time.

The processing after step S103b is a control method of the modification. In step S103b, the control unit K controls the four-way valve 35. That is, the control unit K controls the four-way valve 35 so that the indoor heat exchanger 12 functions as a condenser and the outdoor heat exchanger 32 functions as an evaporator. That is, the control unit K controls the four-way valve 35 as in the heating operation.

In step S103c, the control unit K closes the vertical wind direction plate 19 (see FIG. 2). As a result, even if the indoor fan 14 is driven next (S103d), it is possible to prevent water droplets from jumping out into the room together with the air.

In step S103d, the control unit K drives the indoor fan 14. As a result, air is taken in through the air suction port h1 (see FIG. 2), and the taken-in air leaks into the room through the gaps between the vertical wind direction plates 19 and the like. Therefore, it is possible to prevent the temperature of the indoor heat exchanger 12 (condenser) from becoming too high.

In step S103e, the control unit K sets the rotation speed of the compressor 31 to a predetermined value and drives the compressor 31. In step S103f, the control unit K adjusts the opening degree of the outdoor expansion valve 34. By appropriately controlling the compressor 31 and the outdoor expansion valve 34 in this way, the high-temperature refrigerant flows through the indoor heat exchanger 12 which is a condenser. As a result, the ice in the indoor heat exchanger 12 melts at once, so that the dust and dirt adhering to the indoor heat exchanger 12 are washed away. Then, dust and water containing dust fall into the drain pan 13 (see FIG. 2) and are discharged to the outside via a drain hose (not shown).

In step S103g, the control unit K determines whether or not a predetermined time has elapsed from the time of "START" in FIG. This predetermined time is the time required for thawing the indoor heat exchanger 12, and is set in advance. If a predetermined time has not elapsed since "START" in step S103g (S103g: No), the process of the control unit K returns to step S103f. On the other hand, when a predetermined time has elapsed from the time of "START" (S103g: Yes), the control unit K ends a series of processes for thawing the indoor heat exchanger 12 (END).

The compressor 31 and the indoor fan 14 may be maintained in a stopped state. This is because the ice in the indoor heat exchanger 12 melts naturally at room temperature even if the indoor heat exchanger 12 does not function as a condenser. As a result, the power consumption required for thawing the indoor heat exchanger 12 can be reduced. In addition, it is possible to prevent water droplets from adhering to the inside of the vertical wind direction plate 19 (see FIG. 2).

FIG. 14 is a flowchart showing the details of the process for drying the indoor heat exchanger 12 (S104 in FIG. 5). The control unit K thawes the indoor heat exchanger 12 by the processes of steps S103a to S103g described above (see FIG. 13), and then executes a series of processes shown in FIG.

In step S104a, the control unit K maintains the driving state of the four-way valve 35, the compressor 31, the indoor fan 14, and the like. That is, the control unit K controls the four-way valve 35 in the same manner as when the indoor heat exchanger 12 is thawed so that the indoor heat exchanger 12 becomes a condenser, and also drives the compressor 31, the indoor fan 14, and the like. Keep letting. By performing the same control as during the heating operation in this way, the high-temperature refrigerant flows through the indoor heat exchanger 12, and air is taken into the indoor unit 10. As a result, the water adhering to the indoor heat exchanger 12 evaporates.

Next, in step S104b, the control unit K determines whether or not a predetermined time (for example, a preset heating / drying time) has elapsed since the process of step S104a was started. If the predetermined time has not elapsed (S104b: No), the process of the control unit K returns to step S104a. On the other hand, when the predetermined time has elapsed (S104b: Yes), the process of the control unit K proceeds to step S104c.

In step S104c, the control unit K executes the ventilation operation. That is, the control unit K stops the compressor 31 and drives the indoor fan 14 at a predetermined rotation speed. As a result, the inside of the indoor unit 10 is dried, so that the effects of antibacterial and antifungal effects are exhibited.

During the processing of step S104a and step S104c, the vertical wind direction plate 19 (see FIG. 2) may be closed, or the vertical wind direction plate 19 may be opened.

Next, in step S104d, the control unit K determines whether or not a predetermined time (for example, a preset blast drying time) has elapsed since the process of step S104c was started. If the predetermined time has not elapsed (S104d: No), the process of the control unit K returns to step S104c. On the other hand, when the predetermined time has elapsed (S104d: Yes), the control unit K ends a series of processes for drying the indoor heat exchanger 12 (END).

<Effect>
According to the first embodiment, the control unit K performs liquid compression prevention control when a predetermined condition (for example, the first condition) is satisfied during the freezing process of freezing the indoor heat exchanger 12. As a result, it is possible to prevent the compressor 31 from compressing the liquid.

The first control of the liquid compression prevention control is to reduce the rotation speed of the compressor 31 or stop the compressor 31, increase the rotation speed of the indoor fan 14, decrease the rotation speed of the outdoor fan 33, or decrease the rotation speed of the outdoor fan 33. The opening degree of the outdoor expansion valve 34 (expansion valve) may be reduced.

Further, when freezing the indoor heat exchanger 12, the control unit K sets the freezing time based on, for example, the relative humidity of the indoor air (see S11 and FIG. 7 in FIG. 6). Thereby, an appropriate amount of water required for cleaning the indoor heat exchanger 12 can be frozen in the indoor heat exchanger 12.

Further, when the indoor heat exchanger 12 is frozen, the control unit K sets the rotation speed of the compressor motor 31a based on the outdoor temperature (see S11 and FIG. 8 in FIG. 6). As a result, heat can be appropriately dissipated in the outdoor heat exchanger 32 while the indoor heat exchanger 12 is frozen.

<< Second Embodiment >>
In the second embodiment, the indoor heat exchanger 12A (see FIG. 15) has a first indoor heat exchanger 12a and a second indoor heat exchanger 12b, and these first indoor heat exchanger 12a and the second indoor heat exchanger 12a. It differs from the first embodiment in that the exchanger 12b is connected via the indoor expansion valve V (see FIG. 15).

Further, the second embodiment is different from the first embodiment in that a part of the indoor heat exchanger 12A is frozen by performing a so-called reheat dehumidification operation. The other points (the configuration shown in FIGS. 1 and 4, the flowcharts of FIGS. 5 and 6 and the like) are the same as those in the first embodiment. Therefore, a part different from the first embodiment will be described, and a description of the overlapping part will be omitted.

FIG. 15 is an explanatory diagram showing the refrigerant circuit QA of the air conditioner 100A according to the second embodiment. As shown in FIG. 15, the indoor unit 10A includes an indoor heat exchanger 12A, an indoor expansion valve V (second expansion valve), an indoor fan 14, and the like. Further, the indoor heat exchanger 12A includes a first indoor heat exchanger 12a and a second indoor heat exchanger 12b. The indoor heat exchanger 12A is configured by connecting the first indoor heat exchanger 12a and the second indoor heat exchanger 12b to each other via the indoor expansion valve V. Further, in the example shown in FIG. 14, the second chamber heat exchanger 12b is located above the first chamber heat exchanger 12a.

When performing a normal air conditioning operation (cooling operation, heating operation, etc.), the indoor expansion valve V is controlled to be fully opened, and the opening degree of the outdoor expansion valve 34 is appropriately adjusted. On the other hand, when the so-called reheat dehumidification operation is performed, the outdoor expansion valve 34 is controlled to be fully opened, and the opening degree of the indoor expansion valve V is appropriately adjusted. The reheat dehumidification operation will be described later.

FIG. 16 is a flowchart showing a process for freezing the second chamber heat exchanger 12b (corresponding to S102 in FIG. 5). Refer to FIGS. 4 and 15 as appropriate. In step S102A of FIG. 16, after setting the four-way valve 35 in step S12, the process of the control unit K proceeds to step S17.

In step S17, the control unit K executes the reheat dehumidification operation. That is, the control unit K controls the four-way valve 35 so that the outdoor heat exchanger 32 and the first indoor heat exchanger 12a function as condensers and the second indoor heat exchanger 12b functions as an evaporator. In other words, the control unit K uses one of the first chamber heat exchanger 12a and the second chamber heat exchanger 12b located on the downstream side of the chamber expansion valve V (second chamber heat exchanger 12b) as an evaporator. Make it work.

Further, the control unit K opens the outdoor expansion valve 34 fully and sets the indoor expansion valve V to a predetermined opening degree. As a result, the low-temperature air heat-exchanged by the second chamber heat exchanger 12b, which is an evaporator, is appropriately heated and dehumidified by the other first chamber heat exchanger 12a, which is a condenser.

After performing the process of step S17, the control unit K sets the rotation speed of the compressor 31 in step S18, and drives the compressor 31 at the rotation speed. In step S19, the control unit K appropriately adjusts the opening degree of the indoor expansion valve V.

Next, the processes after step S20 are executed. In steps S21 and S25 during this process, for example, the temperature TE of the indoor heat exchanger 12 is changed as the temperature of the second indoor heat exchanger 12b for determination processing.

The process of thawing the second chamber heat exchanger 12b and further drying the first chamber heat exchanger 12a and the second chamber heat exchanger 12b is the same as that of the first embodiment (see FIGS. 13 and 14). Since it is the same, the description thereof will be omitted. By the way, at the time of thawing and drying, the control unit K opens the indoor expansion valve V fully and adjusts the opening degree of the outdoor expansion valve 34 as appropriate.

As described above, of the first chamber heat exchanger 12a and the second chamber heat exchanger 12b shown in FIG. 15, one (second chamber heat exchanger 12b) is the other (first chamber heat exchanger 12a). It is located on the upper side. According to such a configuration, when the frozen ice in the second chamber heat exchanger 12b melts, the water flows down to the first chamber heat exchanger 12a. As a result, both the first chamber heat exchanger 12a and the second chamber heat exchanger 12b can be cleaned.

<Effect>
According to the second embodiment, the control unit K performs liquid compression prevention control when a predetermined condition (for example, the first condition) is satisfied during the reheat dehumidification operation. As a result, it is possible to prevent the compressor 31 from compressing the liquid.

According to the second embodiment, the second chamber heat exchanger 12b can be frozen by performing the reheat dehumidification operation. Further, since the first chamber heat exchanger 12a is located below the second chamber heat exchanger 12b, when the second chamber heat exchanger 12b is thawed, the water causes the first chamber heat exchanger 12a. And the second chamber heat exchanger 12b can both be cleaned.

≪Modification example≫
Although the air conditioner 100 and the like according to the present invention have been described above in each embodiment, the present invention is not limited to these descriptions, and various modifications can be made.

The air conditioner 100 has a temperature sensor 38 that detects the temperature of an electric component provided in the outdoor unit 30, and controls when the temperature of the temperature sensor rises above a predetermined temperature during outdoor fan control as the first control. The unit K may control the rotation speed of the outdoor fan 33 or intermittently operate the outdoor fan 33. As a result, the electric product can be cooled and the reliability of the electric product can be improved.

When the temperature of the outdoor heat exchanger 32 or the temperature of the discharged refrigerant of the compressor 31 becomes equal to or higher than a predetermined value during the first control, the control unit K performs the second control to restore the control contents of the first control. (See Fig. 9). As a result, a significant increase in the discharge pressure of the compressor 31 can be suppressed, and the reliability of the compressor 31 can be improved.

When the temperature of the indoor heat exchanger 12 is equal to or higher than the predetermined temperature during the first control, the control unit K increases the rotation speed of the outdoor fan 33 or controls the second outdoor fan that operates the outdoor fan 33 intermittently. Good to do. As a result, it is possible to avoid a significant decrease in the amount of frost formation in the indoor heat exchanger 12 and to prevent liquid compression of the compressor 31 and to achieve both frost formation.

The control unit K may set a predetermined rotation speed of the compressor 31 (rotation speed of the compressor motor 31a) based on the rotation speed of the outdoor fan 33 during the outdoor fan control as the first control. For example, when the rotation speed of the outdoor fan 33 is 500 rpm and the rotation speed of the compressor 31 is 2000 rpm, the rotation speed of the compressor 31 becomes 1500 rpm and 1000 rpm as the rotation speed of the outdoor fan 33 decreases to 300 rpm and 100 rpm. You should lower it. When the rotation speed of the outdoor fan 33 decreases or stops during the first control, the noise from the compressor 31 may become remarkable. When the rotation speed of the outdoor fan 33 is reduced or stopped, the noise generated from the compressor 31 can be reduced by reducing the rotation speed of the compressor 31.

If the predetermined condition (first condition) cannot be resolved even after performing the first control other than the indoor fan 14, the control unit K may perform the second indoor fan control for increasing the rotation speed of the indoor fan 14 (FIG. FIG. 11). As a result, the effect of the liquid compression prevention control can be enhanced by adding the liquid compression prevention control that increases the rotation speed of the indoor fan 14.

When the temperature of the indoor heat exchanger 12 becomes higher than the predetermined temperature during the control of the expansion valve (for example, the outdoor expansion valve 34) as the first control, the control unit K relaxes the throttle of the expansion valve. Valve control should be performed. That is, when the degree of superheat (super heat) of the refrigerant flowing through the indoor heat exchanger 12 becomes higher than a predetermined value, the control unit K may relax the throttle of the expansion valve. As a result, it is possible to avoid a significant decrease in the circulation flow rate due to excessive throttle of the expansion valve, and to prevent liquid compression and to achieve both frost formation. A capillary tube (not shown) is provided in place of the expansion valve described above, and the control unit K appropriately controls the rotation speed of the compressor 31, the rotation speed of the indoor fan 14, the rotation speed of the outdoor fan 33, and the like. You may do so.

If the predetermined condition can be resolved during the first control, the control unit K may perform the second control to restore the control contents of the first control. As a result, it is possible to prevent the amount of frost formation from decreasing due to unnecessary liquid compression prevention control.

The predetermined condition is when the temperature of the indoor heat exchanger 12 is equal to or lower than the predetermined temperature, or when the temperature difference between the temperature of the indoor temperature sensor 24a (room temperature sensor) and the temperature of the indoor heat exchanger 12 is equal to or greater than the predetermined temperature difference. When the dryness of the suction refrigerant of the compressor 31 is equal to or less than the predetermined dryness, or when the dryness of the suction refrigerant of the compressor 31 is equal to or less than the predetermined dryness in a predetermined time.

During the freezing process, the control unit K may set the predetermined dryness of the intake refrigerant of the compressor 31 to be lower than the dryness (for example, 0.8) during normal air conditioning operation (for example, 0.6).

In normal air conditioning operation (cooling or the like), the rotation speed of the compressor 31 is relatively high, and the amount of refrigerant circulating in the refrigerant circuit Q (see FIG. 3) is large, so that control sensitive to dryness is required. When the heat exchange in the indoor heat exchanger 12 becomes poor, the amount of liquid refrigerant increases. Therefore, the dryness is set to, for example, 0.8 or more. On the other hand, in the freezing process of the freeze washing of the present embodiment, the rotation speed of the compressor 31 is set lower than that during the normal air conditioning operation. Therefore, since the circulation amount of the refrigerant in the refrigerant circuit Q is small, the dryness can be set low. That is, by setting the dryness low, the liquid refrigerant prevention control can be effectively functioned.

The control unit K may execute the first control at least at least in the latter half of the preset freezing time during the freezing process. Even if the freezing treatment is started, liquid refrigerant compression rarely occurs in the first half of the freezing time. Therefore, the determination of the liquid compression protection control is not performed in the first half of the freezing time, the processing time is shortened, and even if the determination is performed in the latter half of the freezing time, appropriate protection control of the liquid compression protection can be performed.

The liquid refrigerant protection control of the present embodiment can also be applied to an air conditioner in which the accumulator 39 is not installed on the suction side of the compressor 31 in the refrigerant circuit Q (see FIG. 3). As a result, the cost of the air conditioner can be reduced.

Further, in the refrigerant circuit Q (see FIG. 3), the accumulator 39 is installed on the suction side of the compressor 31, and the internal volume of the accumulator with respect to the amount of the refrigerant may be applied to an air conditioner of 700 mL / kg or less.

FIG. 17 is an explanatory diagram showing the internal volume of the accumulator with respect to the amount of the refrigerant of the various accumulators A to C. In the accumulators A to C, the internal volume indicates the effective internal volume when it is assumed that the accumulator is filled with the liquid refrigerant. The effective internal volume indicates the difference between the external dimensions of the accumulator and the volume of the internal pipe. The accumulator A is the case of R410A as the refrigerant, and the accumulators B and C are the case of R32 as the refrigerant. From the empirical experiments of the inventors, it was found that when the internal volume of the accumulator with respect to the amount of refrigerant is 700 mL / kg or less, the frequency of liquid refrigerant compression in the compressor 31 increases. Therefore, when the internal volume of the accumulator is small, the compressor 31 can be protected and the indoor heat exchanger can be appropriately cleaned by the liquid refrigerant protection control of the present embodiment.

According to the present embodiment (see FIGS. 3 and 6), the control unit K satisfies the first condition during the freezing process in which the indoor heat exchanger 12 functions as an evaporator and the indoor heat exchanger 12 is frozen. (Step S21: Yes), the liquid compression prevention control is performed (step S24), and when the second condition is satisfied during the liquid compression prevention control (step S25: Yes), the liquid compression prevention control is released (step S26). This makes it possible to prevent liquid compression of the compressor during freeze washing.

Further, in each embodiment, the configuration in which the indoor unit 10 (see FIG. 3) and the outdoor unit 30 (see FIG. 3) are provided one by one has been described, but the present invention is not limited to this. That is, a plurality of indoor units connected in parallel may be provided, or a plurality of outdoor units connected in parallel may be provided.

Further, each embodiment is described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one including all the configurations described. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration. In addition, the above-mentioned mechanism and configuration show what is considered necessary for explanation, and do not necessarily show all the mechanisms and configurations in the product.

100,100A Air conditioner 10,10A Indoor unit 12,12A Indoor heat exchanger (evaporator / condenser)
12a 1st indoor heat exchanger 12b 2nd indoor heat exchanger 14 Indoor fan 18 Left and right wind direction plate 19 Vertical wind direction plate 23 Imaging unit (human detection unit)
24 Indoor environment detector 30 Outdoor unit 31 Compressor 31a Compressor motor (compressor motor)
32 Outdoor heat exchanger (condenser / evaporator)
33 Outdoor fan 34 Outdoor expansion valve (first expansion valve, expansion valve)
35 Four-way valve 36 Outdoor environment detector 38 Temperature sensor 39 Accumulator 40 Remote control K control unit Q, QA Refrigerant circuit S20 Freezing process including liquid compression prevention control S24 Liquid compression prevention control S26 Liquid compression prevention control release Tu Freezing upper limit temperature Td1 Freezing lower limit Temperature (Temperature of the first condition)
Td2 lower freezing temperature (temperature of the second condition)
V Indoor expansion valve (second expansion valve)

In order to achieve the above object, the air conditioner of the present invention includes a compressor circuit in which the refrigerant circulates in the refrigeration cycle through the compressor, the condenser, the expansion valve, and the evaporator in order, and at least the compressor and the expansion valve. One of the condenser and the compressor is an outdoor heat exchanger and the other is an indoor heat exchanger, and the control unit makes the indoor heat exchanger function as an evaporator and indoors. during freezing process for freezing the heat exchanger, and a predetermined condition is satisfied, as the first control, reduce the rotational speed of the compressor, or have rows compressor control for stopping the compressor, the outdoor during the first control When the temperature of the heat exchanger exceeds a predetermined value, the control unit performs a second control for restoring the control contents of the first control . Other aspects of the present invention will be described in embodiments described below.

Claims (17)

A refrigerant circuit in which the refrigerant circulates in the refrigeration cycle through the compressor, condenser, expansion valve, and evaporator in order.
At least a control unit for controlling the compressor and the expansion valve is provided.
One of the condenser and the evaporator is an outdoor heat exchanger, and the other is an indoor heat exchanger.
When a predetermined condition is satisfied during the freezing process in which the indoor heat exchanger functions as the evaporator and the indoor heat exchanger is frozen, the control unit lowers the rotation speed of the compressor as the first control. Or, an air conditioner that controls the compressor to stop the compressor. A refrigerant circuit in which the refrigerant circulates in the refrigeration cycle through the compressor, condenser, expansion valve, and evaporator in order.
At least a control unit for controlling the compressor and the expansion valve is provided.
One of the condenser and the evaporator is an outdoor heat exchanger, and the other is an indoor heat exchanger.
When a predetermined condition is satisfied during the freezing process in which the indoor heat exchanger functions as the evaporator and the indoor heat exchanger is frozen, the control unit raises the rotation speed of the indoor fan as the first control. An air conditioner that controls the fan. A refrigerant circuit in which the refrigerant circulates in the refrigeration cycle through the compressor, condenser, expansion valve, and evaporator in order.
At least a control unit for controlling the compressor and the expansion valve is provided.
One of the condenser and the evaporator is an outdoor heat exchanger, and the other is an indoor heat exchanger.
If a predetermined condition is satisfied during the freezing process in which the indoor heat exchanger functions as the evaporator and the indoor heat exchanger is frozen, the control unit lowers the rotation speed of the outdoor fan as the first control. Or, an air conditioner that controls an outdoor fan to stop the outdoor fan. A refrigerant circuit in which the refrigerant circulates in the refrigeration cycle through the compressor, condenser, expansion valve, and evaporator in order.
At least a control unit for controlling the compressor and the expansion valve is provided.
One of the condenser and the evaporator is an outdoor heat exchanger, and the other is an indoor heat exchanger.
When a predetermined condition is satisfied during the freezing process in which the indoor heat exchanger functions as the evaporator and the indoor heat exchanger is frozen, the control unit narrows the opening degree of the expansion valve as the first control. An air conditioner that controls the expansion valve. In the air conditioner according to claim 3,
The air conditioner has a temperature sensor that detects the temperature of an electric component provided in the outdoor unit.
When the temperature of the temperature sensor rises above a predetermined temperature during the outdoor fan control as the first control,
The control unit is an air conditioner characterized by increasing the rotation speed of the outdoor fan or controlling the operation of the outdoor fan intermittently. In the air conditioner according to any one of claims 1 to 4.
When the temperature of the outdoor heat exchanger exceeds a predetermined value during the first control,
The control unit is an air conditioner characterized in that it performs a second control that restores the control content of the first control. In the air conditioner according to any one of claims 1 to 3.
When the temperature of the indoor heat exchanger is equal to or higher than the predetermined temperature during the first control,
The control unit is an air conditioner characterized in that the rotation speed of the outdoor fan is increased or the second outdoor fan that operates the outdoor fan intermittently is controlled. In the air conditioner according to claim 3,
The air conditioner is characterized in that the control unit sets a predetermined rotation speed of the compressor based on the rotation speed of the outdoor fan during the outdoor fan control as the first control. In the air conditioner according to any one of claims 1, 3, and 4.
If the predetermined condition cannot be resolved even after performing the first control,
The control unit is an air conditioner characterized in that it controls a second indoor fan that increases the rotation speed of the indoor fan. In the air conditioner according to claim 4,
When the temperature of the indoor heat exchanger becomes higher than the predetermined temperature during the expansion valve control as the first control,
The control unit is an air conditioner characterized in that it controls a second expansion valve that relaxes the throttle of the expansion valve. In the air conditioner according to any one of claims 1 to 4.
When the predetermined condition can be eliminated during the expansion valve control as the first control,
The control unit is an air conditioner characterized in that it performs a second expansion valve control that restores the control content of the first control. In the air conditioner according to any one of claims 1 to 4.
The predetermined condition is that the temperature of the indoor heat exchanger is equal to or lower than the predetermined temperature, or the temperature difference between the temperature of the room temperature sensor and the temperature of the indoor heat exchanger is equal to or greater than the predetermined temperature difference. Characterized air conditioner. In the air conditioner according to any one of claims 1 to 4.
The predetermined condition is that the dryness of the intake refrigerant of the compressor is equal to or less than the predetermined dryness, or the dryness of the intake refrigerant of the compressor is equal to or less than the predetermined dryness in a predetermined time. Characterized air conditioner. In the air conditioner according to claim 13,
The control unit is an air conditioner characterized in that, during the freezing process, the predetermined dryness of the dryness is set lower than the dryness during normal air conditioning operation. In the air conditioner according to any one of claims 1 to 4.
The air conditioner is characterized in that the control unit executes the first control at least at least in the latter half of a preset freezing time during the freezing process. In the air conditioner according to any one of claims 1 to 4.
An air conditioner characterized in that an accumulator is not installed on the suction side of the compressor in the refrigerant circuit. In the air conditioner according to any one of claims 1 to 4.
In the refrigerant circuit, an accumulator is installed on the suction side of the compressor.
An air conditioner characterized in that the internal volume of the accumulator with respect to the amount of refrigerant is 700 mL / kg or less.

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