WO2021192074A1

WO2021192074A1 - Air conditioner

Info

Publication number: WO2021192074A1
Application number: PCT/JP2020/013216
Authority: WO
Inventors: 亮祐大畑; 有騎新井
Original assignee: 日立ジョンソンコントロールズ空調株式会社
Priority date: 2020-03-25
Filing date: 2020-03-25
Publication date: 2021-09-30
Also published as: TW202136691A

Abstract

Provided is a highly reliable air conditioner that produces a sanitary state in an indoor heat exchanger. An air conditioner (100) is equipped with a refrigerant circuit (Q), and is equipped with a bypass pipe (W) for guiding a portion of the refrigerant condensed in an outdoor heat exchanger (2) to the suction side of a compressor (1), a bypass expansion valve (7) provided in the bypass pipe (W), and a control unit. When an indoor heat exchanger (10) is in the process of freezing or condensing, the control unit controls an indoor expansion valve (12) on the basis of the temperature of the indoor heat exchanger (10), and controls the bypass expansion valve (7) on the basis of the discharge temperature of the compressor (1).

Description

Air conditioner

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 describes that the heat exchanger to be cleaned is defrosted and then defrosted. Further, Patent Document 1 describes that when the high / low pressure difference of the air conditioner reaches a preset condition, the four-way valve is controlled to switch to defrosting the indoor heat exchanger.

Japanese Patent No. 6598393

For example, in a multi-type air conditioner equipped with a plurality of indoor units, the length of the piping connecting the outdoor unit and each indoor unit is often relatively long. With such a configuration, if the indoor heat exchanger is frozen when the outdoor temperature is high, the temperature of the refrigerant guided from the indoor heat exchanger to the compressor rises due to the endothermic heat from the outside air. While the indoor heat exchanger is frozen, the refrigerant circulates in the cooling cycle, but the temperature of the pipe through which the gas refrigerant flows is lower than that during the normal cooling operation. As a result, the gas refrigerant flowing through the pipe is likely to absorb heat from the outside air, and in some cases, the discharge temperature of the compressor may exceed a predetermined allowable range. Patent Document 1 does not describe such a technique focusing on a problem peculiar to freezing of an indoor heat exchanger.

Therefore, an object of the present invention is to provide a highly reliable air conditioner that keeps the indoor heat exchanger in a clean state.

In order to solve the above-mentioned problems, the air conditioner according to the present invention includes an outdoor unit having a compressor and an outdoor heat exchanger, and at least one indoor unit having a first expansion valve and an indoor heat exchanger. A bypass pipe for guiding a part of the refrigerant condensed by the outdoor heat exchanger to the suction side of the compressor and a second expansion valve provided in the bypass pipe are provided. The compressor, the first expansion valve, and a control unit that controls the second expansion valve are provided, and the control unit heats the room during the process of freezing or condensing the room heat exchanger. It was decided to control the first expansion valve based on the temperature of the exchanger and control the second expansion valve based on the discharge temperature of the compressor.

According to the present invention, it is possible to provide a highly reliable air conditioner that keeps the indoor heat exchanger in a clean state.

It is a block diagram which includes the refrigerant circuit of the air conditioner which concerns on 1st Embodiment. It is explanatory drawing which shows the connection relation of each device of the air conditioner which concerns on 1st Embodiment. It is a functional block diagram of the air conditioner which concerns on 1st Embodiment. It is a flowchart of the process executed by the control part of the air conditioner which concerns on 1st Embodiment. It is a block diagram which includes the refrigerant circuit of the air conditioner which concerns on 2nd Embodiment. It is a block diagram which includes the refrigerant circuit of the air conditioner which concerns on 3rd Embodiment.

<< First Embodiment >>
<Composition of air conditioner>
FIG. 1 is a configuration diagram including a refrigerant circuit Q of the air conditioner 100 according to the first embodiment.
In FIG. 1, the flow of the refrigerant in the cooling cycle (refrigeration cycle during the cooling operation) is indicated by a solid line arrow, while the flow of the refrigerant in the heating cycle (refrigeration cycle during the heating operation) is indicated by a broken line arrow. Further, in FIG. 1, the air flow in the vicinity of the outdoor heat exchanger 2 and the four indoor heat exchangers 10 is indicated by white arrows.

The air conditioner 100 is a device that performs air conditioning such as cooling operation and heating operation. In FIG. 1, as an example, one system of a multi-type air conditioner 100 in which one outdoor unit Uo and four indoor units U1, U2, U3, U4 are predeterminedly connected via a pipe is used. Shown.

The air conditioner 100 includes a compressor 1, an outdoor heat exchanger 2, an outdoor fan 3, an outdoor expansion valve 4, a four-way valve 5, and an accumulator 6 as devices provided in the outdoor unit Uo. There is. Further, in addition to the above-described configuration, the air conditioner 100 includes a bypass pipe W, a bypass expansion valve 7 (second expansion valve), an outdoor temperature sensor 8, and a discharge temperature as equipment provided in the outdoor unit Uo. It includes a sensor 9 and blocking valves Va and Vb.

The compressor 1 is a device that compresses a low-temperature low-pressure gas refrigerant and discharges it as a high-temperature high-pressure gas refrigerant, and includes a compressor motor 1a (see FIG. 3) as a drive source. As such a compressor 1, for example, a scroll type compressor or a rotary type compressor is used.

The outdoor heat exchanger 2 is a heat exchanger in which heat exchange is performed between the refrigerant passing through the heat transfer tube (not shown) and the outside air sent from the outdoor fan 3. One end g1 of the outdoor heat exchanger 2 is connected to the suction side or the discharge side of the compressor 1 by switching the four-way valve 5, and the other end g2 is connected to the liquid side pipe J1.

The outdoor fan 3 is a fan that sends outside air to the outdoor heat exchanger 2. The outdoor fan 3 includes an outdoor fan motor 3a as a drive source, and is installed in the vicinity of the outdoor heat exchanger 2.
The outdoor expansion valve 4 is an electronic expansion valve that adjusts the flow rate of the refrigerant flowing through the outdoor heat exchanger 2 and reduces the pressure of the refrigerant when the outdoor heat exchanger 2 functions as an evaporator. It is provided in J1.

The four-way valve 5 is a valve that switches the flow path of the refrigerant to a predetermined value according to the operation mode during air conditioning.
The accumulator 6 is a shell-shaped member that gas-liquid separates the refrigerant flowing through the four-way valve 5. After gas-liquid separation by the accumulator 6, a gaseous refrigerant is guided to the suction side of the compressor 1.

The bypass pipe W is a pipe that guides a part of the refrigerant condensed by the condenser (outdoor heat exchanger 2 or indoor heat exchanger 10) to the suction side of the compressor 1. In the example of FIG. 1, one end i1 of the bypass pipe W is connected between the outdoor expansion valve 4 and the blocking valve Vb in the pipe J1. Further, the other end i2 of the bypass pipe W is connected to the pipe J15 connecting the four-way valve 5 and the accumulator 6. As described above, the configuration in which the bypass pipe W is connected to the pipe J15 on the upstream side of the accumulator 6 is also included in the matter of "leading the refrigerant to the suction side of the compressor 1 via the bypass pipe W".

The bypass expansion valve 7 (second expansion valve) has a function of adjusting the flow rate of the refrigerant flowing through the bypass pipe W and reducing the pressure of the refrigerant flowing through the bypass pipe W, and the bypass pipe W has a function. It is provided.

The outdoor temperature sensor 8 is a sensor that detects the outdoor temperature (the temperature of the outside air), and is installed at a predetermined position of the outdoor unit Uo (in the example of FIG. 1, the air suction side of the outdoor heat exchanger 2).
The discharge temperature sensor 9 is a sensor that detects the temperature of the refrigerant discharged from the compressor 1. In the example of FIG. 1, the discharge temperature sensor 9 is provided in the pipe J16 on the discharge side of the compressor 1. In the housing of the compressor 1 (not shown), the discharge temperature sensor 9 may be installed near the connection point with the pipe J16.
In addition, although not shown in FIG. 1, each sensor for detecting one or more of the suction pressure, the suction temperature, and the discharge pressure of the compressor 1 may be appropriately provided.

The blocking valves Va and Vb are valves for spreading the refrigerant sealed in the outdoor unit Uo throughout the refrigerant circuit Q by opening the valves after the air conditioner 100 is installed. One blocking valve Va is provided in the gas side pipe J10, and the other blocking valve Vb is provided in the liquid side pipe J1.

Further, the air conditioner 100 includes an indoor heat exchanger 10, an indoor fan 11, an indoor expansion valve 12 (first expansion valve), an indoor temperature sensor 13, and an indoor heat exchange as equipment provided in the indoor unit U1. It includes a vessel temperature sensor 14.
The indoor heat exchanger 10 is a heat exchanger in which heat is exchanged between the refrigerant passing through the heat transfer tube (not shown) and the indoor air (air in the air conditioning room) sent from the indoor fan 11. be. One end h1 of the indoor heat exchanger 10 is connected to the gas side pipe J3, and the other end h2 is connected to the liquid side pipe J2.

The indoor fan 11 is a fan that sends indoor air to the indoor heat exchanger 10. The indoor fan 11 has an indoor fan motor 11a as a drive source, and is installed in the vicinity of the indoor heat exchanger 10.
The indoor expansion valve 12 is an electronic expansion valve that adjusts the flow rate of the refrigerant flowing through the indoor heat exchanger 10 and reduces the pressure of the refrigerant when the indoor heat exchanger 10 functions as an evaporator, and is a pipe on the liquid side. It is provided in J2.
The indoor temperature sensor 13 is a sensor that detects the temperature of the indoor air. In the example of FIG. 1, the indoor temperature sensor 13 is installed on the air suction side of the indoor heat exchanger 10.

The indoor heat exchanger temperature sensor 14 is a sensor that detects the temperature of the indoor heat exchanger 10. In the example of FIG. 1, the indoor heat exchanger temperature sensor 14 is installed near the other end h2 of the indoor heat exchanger 10 in the pipe J2.
The position of the indoor heat exchanger temperature sensor 14 is not limited to the example of FIG. For example, in the pipe J3, the indoor heat exchanger temperature sensor 14 may be installed near one end h1 of the indoor heat exchanger 10. Further, the indoor heat exchanger temperature sensor 14 may be installed directly on the indoor heat exchanger 10.
The remaining three indoor units U2, U3, and U4 have the same configuration as the indoor unit U1 described above, and thus the description thereof will be omitted.

The liquid side connection portions K1, K2, and K3 split the refrigerant during the cooling cycle and merge the refrigerant during the heating cycle. For example, during the cooling cycle, the refrigerant flowing through the liquid-side pipe J1 is sequentially distributed to the four indoor heat exchangers 10 via the liquid-side connection portions K1, K2, and K3. One end of the liquid side pipe J1 is connected to the other end g2 of the outdoor heat exchanger 2, and the other end is the liquid side connection portion K1 (the first diversion when the outdoor heat exchanger 2 functions as a condenser). It is connected to the place).

The gas side connection portions K4, K5, and K6 combine the refrigerant during the cooling cycle and divide the refrigerant during the heating cycle. For example, during the cooling cycle, the refrigerants merge from the four indoor heat exchangers 10 through the gas side connection portions K4, K5, and K6 in sequence.

Then, the refrigerant circulates in a well-known refrigeration cycle (cooling cycle or heating cycle shown in FIG. 1) in the refrigerant circuit Q according to the operation mode at the time of air conditioning. For example, in the cooling cycle, the refrigerant circulates in sequence through the compressor 1, the outdoor heat exchanger 2 (condenser), the outdoor expansion valve 4, the indoor expansion valve 12, and the indoor heat exchanger 10 (evaporator). .. On the other hand, in the heating cycle, the refrigerant circulates in sequence through the compressor 1, the indoor heat exchanger 10 (condenser), the indoor expansion valve 12, the outdoor expansion valve 4, and the outdoor heat exchanger 2 (evaporator). ..

FIG. 2 is an explanatory diagram showing a connection relationship of each device of the air conditioner 100.
As shown in FIG. 2, the air conditioner 100 includes a remote controller 15 and a centralized management device 16 in addition to the above-described configuration. Further, the outdoor unit Uo includes an outdoor control circuit 17, while the indoor units U1, U2, U3, and U4 each include an indoor control circuit 18.

Although not shown, the outdoor control circuit 17 and the indoor control circuit 18 are configured to include 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. 2, the outdoor control circuit 17 is connected to the outdoor temperature sensor 8 via the wiring m11, and is also connected to the discharge temperature sensor 9 via the wiring m12. Then, in addition to the detected values of the outdoor temperature sensor 8 and the discharge temperature sensor 9, the outdoor control circuit 17 calculates the control command value of each device based on the signal from the remote controller 15 and the like.

Further, the outdoor control circuit 17 is connected to the indoor control circuit 18 via the communication line m3. The indoor control circuit 18 is connected to the indoor temperature sensor 13 via the wiring m21, and is also connected to the indoor heat exchanger temperature sensor 14 via the wiring m22. Each of these detected values is transmitted from the indoor control circuit 18 to the outdoor control circuit 17 via the communication line m3. The indoor control circuit 18 controls the indoor fan motor 11a (see FIG. 1) and the indoor expansion valve 12 (see FIG. 1) based on the control command value calculated by the outdoor control circuit 17.

In the example of FIG. 2, the four remote controllers 15 are connected via the wiring m4 so as to have a one-to-one correspondence with the indoor control circuits 18 of the four indoor units U1, U2, U3, and U4. A plurality of indoor units may be connected to one remote controller 15.
The remote controller 15 connected to the indoor unit U1 has a function of giving a predetermined control command to the indoor unit U1 by a user operation. Examples of the control command described above include operation / stop of the air conditioner 100, switching of the operation mode, change of the set temperature, air volume, and wind direction, and start of the cleaning process described later. The same applies to the other indoor units U2, U3, and U4.

The centralized management device 16 is a device that controls the display and settings of the four remote controllers 15, and is connected to the outdoor control circuit 17 via the communication line m5. By the user (administrator) operating the centralized management device 16 in a predetermined manner, it is possible to change not only the air conditioning setting but also the display method on the four remote controllers 15.

FIG. 3 is a functional block diagram of the air conditioner 100.
In FIG. 3, one of the four indoor units U1, U2, U3, and U4 is illustrated, and the remaining three indoor units U2, U3, and U4 are not shown.
As shown in FIG. 3, the outdoor control circuit 17 includes a storage unit 17a and an outdoor control unit 17b. In the storage unit 17a, in addition to a predetermined program and detection values of each sensor, data input from the centralized management device 16 and the like are stored. The outdoor control unit 17b controls the compressor motor 1a, the four-way valve 5, the outdoor expansion valve 4, the outdoor fan motor 3a, the bypass expansion valve 7, and the like based on the data stored in the storage unit 17a.

On the other hand, the indoor control circuit 18 includes a storage unit 18a and an indoor control unit 18b.
In the storage unit 18a, in addition to a predetermined program and detection values of each sensor, data input via the remote controller 15 and the like are stored. The indoor control unit 18b predeterminedly controls the indoor expansion valve 12, the indoor fan motor 11a, the wind direction plate motor 19, and the like based on the data stored in the storage unit 18a. Hereinafter, the outdoor control circuit 17 and the indoor control circuit 18 are collectively referred to as “control unit 20”.
The wind direction plate motor 19 shown in FIG. 3 is a motor that adjusts the wind direction of the air blown into the room by adjusting the angle of the wind direction plate (not shown) of the indoor unit U1.

Next, a series of processes for cleaning the indoor heat exchanger 10 (see FIG. 1) will be described.
A filter (not shown) for collecting dust and dirt is often provided on the air suction side of the indoor heat exchanger 10. However, fine dust and dirt may pass through the filter and adhere to the indoor heat exchanger 10. Therefore, it is desirable to clean the indoor heat exchanger 10 on a regular basis. Therefore, in the first embodiment, after the indoor heat exchanger 10 is frozen (frosted), the indoor heat exchanger 10 is washed by melting the ice and frost of the indoor heat exchanger 10. Such a series of processes is referred to as "cleaning process" of the indoor heat exchanger 10.

FIG. 4 is a flowchart of processing executed by the control unit of the air conditioner (see FIGS. 1 and 3 as appropriate).
Note that in FIG. 4, processes other than the cleaning process (normal air conditioning operation, etc.) are omitted. Further, at the time of "START" in FIG. 4, it is assumed that the indoor units U1, U2, U3 and U4 are stopped in addition to the outdoor unit Uo.

In step S101, the control unit 20 determines whether or not the condition for starting the cleaning process of the indoor heat exchanger 10 is satisfied. For example, the control unit 20 integrates the air-conditioning operation time from the end of the previous cleaning process in the predetermined indoor unit set by the centralized management device 16 among the four indoor units U1, U2, U3, U4. It is determined whether or not the value (or the integrated value of the driving time of the indoor fan 11) has reached a predetermined value. Of the four indoor units U1, U2, U3, and U4, the indoor units whose integrated values such as the air-conditioning operation time have reached a predetermined value may be individually cleaned.

In step S101, when the start condition of the cleaning process of the indoor heat exchanger 10 is not satisfied (S101: No), the process of the control unit 20 returns to "START" (RETURN). On the other hand, in step S101, when the start condition of the cleaning process of the indoor heat exchanger 10 is satisfied (S101: Yes), the process of the control unit 20 proceeds to step S102.

In step S102, the control unit 20 freezes the indoor heat exchanger 10. That is, the control unit 20 causes the indoor heat exchanger 10 to function as an evaporator, and frosts (freezes) the indoor heat exchanger 10. More specifically, the control unit 20 sets the valve body (not shown) of the four-way valve 5 at the position of the cooling cycle, drives the compressor 1 at a predetermined rotation speed, and further expands the indoor expansion valve 12 and the bypass. The valve 7 is controlled as follows.

That is, during the process of freezing the indoor heat exchanger 10, the control unit 20 bases the indoor expansion valve 12 (first expansion valve) based on the detected value (temperature of the indoor heat exchanger 10) of the indoor heat exchanger temperature sensor 14. ) Is controlled. For example, when the detected value of the indoor heat exchanger temperature sensor 14 is higher than a predetermined target temperature (value below freezing point), the control unit 20 makes the opening degree of the indoor expansion valve 12 smaller than the current state. On the other hand, when the detected value of the indoor heat exchanger temperature sensor 14 is lower than the predetermined target temperature, the control unit 20 makes the opening degree of the indoor expansion valve 12 larger than the current state. As a result, the temperature of the indoor heat exchanger 10 approaches a predetermined target temperature, and frost formation of the indoor heat exchanger 10 proceeds.

Further, the control unit 20 controls the bypass expansion valve 7 (second expansion valve) based on the discharge temperature of the compressor 1 during the process of freezing the indoor heat exchanger 10. For example, the control unit 20 increases the opening degree of the bypass expansion valve 7 as the discharge temperature of the compressor 1 increases while the indoor heat exchanger 10 is frozen. The larger the opening degree of the bypass expansion valve 7, the larger the amount of refrigerant guided to the suction side of the compressor 1 via the bypass pipe W. As a result, the relatively low temperature refrigerant that is not endothermic in the indoor heat exchanger 10 is guided to the suction side of the compressor 1, so that the discharge temperature of the compressor 1 can be suppressed to a predetermined allowable temperature or lower.

For example, in an environment where the gas side pipes J3, J5, J7, J9, and J10 are relatively long and the outside air temperature is high, the following situations are likely to occur during freezing of the indoor heat exchanger 10. .. That is, during the freezing of the indoor heat exchanger 10, the refrigerant evaporated in the indoor heat exchanger 10 absorbs heat from the outside air in the process of passing through the gas side pipes J3, J5, J7, J9, J10, and the temperature of the refrigerant rises. As a result, the discharge temperature of the compressor 1 tends to rise. On the other hand, in the first embodiment, the control unit 20 controls the bypass expansion valve 7 in a predetermined manner so as to guide the relatively low temperature refrigerant to the suction side of the compressor 1 via the bypass pipe W. I have to. This makes it possible to prevent the discharge temperature of the compressor 1 from becoming too high. Further, as described above, since the opening degree of the indoor expansion valve 12 is adjusted based on the temperature of the indoor heat exchanger 10, the indoor heat exchanger 10 is frozen while suppressing the increase in the discharge temperature of the compressor 1. Can be promoted.

The control of the bypass expansion valve 7 is not limited to the above example. For example, during freezing of the indoor heat exchanger 10, the control unit 20 may increase the opening degree of the bypass expansion valve 7 as the degree of discharge superheat based on the discharge temperature of the compressor 1 increases. Even with such control, an increase in the discharge temperature of the compressor 1 can be suppressed.

The above-mentioned "discharge superheat degree" is the superheat degree of the refrigerant on the discharge side of the compressor 1. The "superheat degree" of the refrigerant is a value obtained by subtracting the saturation temperature (also referred to as evaporation temperature) of the gas refrigerant from the actual temperature of the gas refrigerant (detected value of the discharge temperature sensor 9). Further, the saturation temperature of the refrigerant is calculated based on, for example, the detected value of the discharge pressure of the compressor 1. The control unit 20 may calculate the saturation temperature of the refrigerant based on the temperature of the refrigerant near the outlet of the condenser (for example, the outdoor heat exchanger 2 during the cooling cycle).

The control unit 20 drives the outdoor fan 3 at a predetermined rotation speed while each indoor heat exchanger 10 is frozen, while stopping each indoor fan 11. As a result, outside air is sent to the outdoor heat exchanger 2 that functions as a condenser. On the other hand, air flows by natural convection through the gaps between the fins (not shown) of the indoor heat exchanger 10. As a result, it is possible to prevent the air conditioning room from being excessively cooled. During freezing of each indoor heat exchanger 10, the control unit 20 may drive the indoor fan 11 at a low speed. The outdoor expansion valve 4 may be in a predetermined open state (for example, a fully open state) while the indoor heat exchanger 10 is frozen.

Further, the control unit 20 is in the process of freezing the indoor heat exchanger 10 when the discharge temperature of the compressor 1 is equal to or lower than a predetermined value, or when the discharge superheat degree based on the discharge temperature of the compressor 1 is equal to or lower than a predetermined value. In some cases, it is preferable to close the bypass expansion valve 7 (second expansion valve). The above-mentioned "predetermined value" is a threshold value that serves as a criterion for determining whether or not to close the bypass expansion valve 7, and is set in advance. This makes it possible to prevent the discharge temperature of the compressor 1 from becoming too low.

Next, in step S103, the control unit 20 defrosts the indoor heat exchanger 10. That is, the control unit 20 freezes the indoor heat exchanger 10 and then causes the indoor heat exchanger 10 to function as a condenser to thaw the indoor heat exchanger 10. Specifically, the control unit 20 switches the four-way valve 5 from the cooling cycle to the heating cycle, sets the outdoor expansion valve 4 and the indoor expansion valve 12 (first expansion valve) to a predetermined opening degree, and drives the compressor 1. Let me. As a result, the indoor heat exchanger 10 functions as a condenser, and the frost of the indoor heat exchanger 10 melts. Then, the dust and dirt of the indoor heat exchanger 10 are washed away by the water accompanying the thawing of the frost.

Further, the control unit 20 maintains the bypass expansion valve 7 (second expansion valve) in the closed state while the indoor heat exchanger 10 is thawed. As a result, the flow of the refrigerant through the bypass pipe W is blocked, so that a sufficient flow rate of the refrigerant flowing through the indoor heat exchanger 10 (condenser) can be secured. During the thawing of the indoor heat exchanger 10, the temperature of the refrigerant rises due to endothermic heat from the outside air in the process of guiding the refrigerant to the outdoor heat exchanger 2 via the pipes J2, J4, J6, J8 and pipe J1. However, there is no particular problem. This is because the refrigerant only evaporates on the upstream side of the outdoor expansion valve 4.

In addition to the temperature of the air conditioner room, the control unit 20 may be a part of the indoor units U1, U2, U3, U4 (for example, the indoor units U1, U2, U3) depending on the model and setting conditions of each indoor unit. While the indoor heat exchanger 10 is frozen, the remaining indoor heat exchanger 10 (for example, the indoor unit U4) may not be frozen. Even in such a case, during the thawing of the indoor heat exchanger 10, the control unit 20 keeps the indoor expansion valves 12 of all the indoor units U1, U2, U3, and U4 open (for example, fully open). As a result, it is possible to prevent the liquid refrigerant from accumulating in the indoor heat exchanger 10 of the indoor unit (for example, the indoor unit U4) that is not subject to freezing.

Further, during the thawing of the indoor heat exchanger 10, the control unit 20 drives the outdoor fan 3 at a predetermined rotation speed, while maintaining each indoor fan 11 in a stopped state. As a result, it is possible to prevent the cold air accompanying the thawing of the indoor heat exchanger 10 from flowing into the air conditioning chamber from the indoor units U1, U2, U3, U4. During thawing of the indoor heat exchanger 10, the control unit 20 may drive the indoor fan 11 at a low speed.

Next, in step S104, the control unit 20 dries the indoor heat exchanger 10. For example, the control unit 20 puts each device including the compressor 1 in a stopped state, and prohibits the air conditioning operation for a predetermined period from the end of defrosting. As a result, the indoor heat exchanger 10 is dried by the natural convection of air. Further, it is possible to suppress the cold air accompanying the drying of the indoor heat exchanger 10 from flowing into the air conditioning room from the indoor units U1, U2, U3, U4. The control unit 20 may drive the indoor fan 11 at a low speed while the indoor heat exchanger 10 is drying. After performing the process of step S104, the process of the control unit 20 returns to "START" (RETURN).

<Effect>
According to the first embodiment, during the process of freezing the indoor heat exchanger 10, the control unit 20 controls the indoor expansion valve 12 based on the temperature of the indoor heat exchanger 10 and the discharge temperature of the compressor 1. The bypass expansion valve 7 is controlled based on the above. As a result, a sufficient amount of frost can be attached to the indoor heat exchanger 10, and further, it is possible to prevent the discharge temperature of the compressor 1 from becoming too high.

If the bypass pipe W and the bypass expansion valve 7 are not provided, the control unit 20 uses the indoor expansion valve 12 to suppress an increase in the discharge temperature of the compressor 1 while the indoor heat exchanger 10 is frozen. If the opening degree of is increased, the following problems may occur. That is, since the refrigerant is not sufficiently depressurized by the indoor expansion valve 12, the amount of frost formed in the indoor heat exchanger 10 is reduced. Further, since the refrigerant is less likely to evaporate in the indoor heat exchanger 10, the liquid refrigerant tends to flow into the suction side of the compressor 1, and there is a high possibility that so-called liquid compression occurs.

On the other hand, in the first embodiment, since the above-mentioned control is performed on the indoor expansion valve 12 and the bypass expansion valve 7, the indoor heat exchanger 10 can be appropriately frozen, and further, the compressor 1 can be frozen. The rise in discharge temperature can be suppressed. Further, there is almost no possibility that liquid compression will occur in the compressor 1 while the indoor heat exchanger 10 is frozen. As described above, according to the first embodiment, it is possible to provide a highly reliable air conditioner 100 that keeps the indoor heat exchanger 10 in a clean state.

<< Second Embodiment >>
In the second embodiment, the air conditioner 100A (see FIG. 5) is provided with a supercooler E (see FIG. 5), and the bypass expansion valve 7 (see FIG. 5) of the supercooler E is predeterminedly controlled. The point is different from the first embodiment. Others are the same as those in the first embodiment (see FIGS. 2 to 4). Therefore, a part different from the first embodiment will be described, and a description of the overlapping part will be omitted.

FIG. 5 is a configuration diagram including a refrigerant circuit QA of the air conditioner 100A according to the second embodiment.
As shown in FIG. 5, the air conditioner 100A includes a supercooler E. The supercooler E has a function of cooling the refrigerant condensed by the condenser (outdoor heat exchanger 2 or indoor heat exchanger 10).

The supercooler E shown in FIG. 5 includes a first heat exchange unit Ea, a second heat exchange unit Eb, and a bypass expansion valve 7 (second expansion valve).
The first heat exchange unit Ea is a predetermined heat transfer tube, and is included in the liquid side pipe J1. The liquid-side pipe J1 is a pipe through which the refrigerant condensed by the outdoor heat exchanger 2 flows when the refrigerant is circulated in the cooling cycle in the refrigerant circuit QA. When the refrigerant is circulated in the heating cycle in the refrigerant circuit QA, the refrigerant condensed by the indoor heat exchanger 10 passes through the liquid side pipe J1.

The second heat exchange section Eb is a predetermined heat transfer tube and is included in the bypass pipe WA. In the example of FIG. 5, one end i1 of the bypass pipe WA is connected between the outdoor expansion valve 4 and the first heat exchange portion Ea in the pipe J1. Further, the other end i2 of the bypass pipe WA is connected to the pipe J15 that connects the four-way valve 5 and the accumulator 6.
The bypass expansion valve 7 has a function of adjusting the flow rate of the refrigerant flowing through the bypass pipe WA and reducing the pressure of the refrigerant flowing through the bypass pipe WA, and is provided in the bypass pipe WA.

The bypass pipe WA has a second heat exchange portion Eb on the downstream side of the bypass expansion valve 7 (second expansion valve) in this bypass pipe WA. Then, heat exchange is performed between the refrigerant flowing through the first heat exchange unit Ea and the refrigerant flowing through the second heat exchange unit Eb. Examples of the structure of the first heat exchange section Ea and the second heat exchange section Eb include, but are not limited to, a well-known double tube structure.

The control unit 20 (see FIG. 3) supercools the bypass expansion valve 7, the first heat exchange unit Ea, and the second heat exchange unit Eb during normal air conditioning operation (during cooling operation or heating operation). To function as. Here, "functioning as a supercooler" means that the refrigerant flowing through the first heat exchange section Ea of the supercooler E is cooled by the refrigerant flowing through the second heat exchange section Eb. ing.

As a result, the specific enthalpy of the refrigerant on the inlet side of the evaporator (indoor heat exchanger 10 or outdoor heat exchanger 2) becomes smaller, so that the difference in the specific enthalpy of the refrigerant on the inlet side and the outlet side of the evaporator is sufficiently secured. NS. Therefore, the air conditioning capacity in normal air conditioning operation can be increased.

During normal air conditioning operation, the control unit 20 controls the bypass expansion valve 7 based on, for example, the degree of supercooling of the refrigerant cooled by the first heat exchange unit Ea of the supercooler E. The "supercooling degree" is calculated by subtracting the temperature of the refrigerant on the downstream side of the first heat exchange unit Ea from the saturation temperature (condensation temperature) of the refrigerant.

Further, the control unit 20 (see FIG. 3) functions as a supercooler by using the bypass expansion valve 7, the first heat exchange unit Ea, and the second heat exchange unit Eb even during the freezing process of the indoor heat exchanger 10. Let me. As a result, the specific enthalpy of the refrigerant on the inlet side of the evaporator (indoor heat exchanger 10) becomes small, so that the indoor heat exchanger 10 is easily frosted.

The cleaning treatment of the indoor heat exchanger 10 (S101 to S104 in FIG. 4) is the same as that in the first embodiment. Further, the control of the bypass expansion valve 7 during freezing of the indoor heat exchanger 10 is the same as that of the first embodiment. That is, the control unit 20 controls the indoor expansion valve 12 (first expansion valve) based on the temperature of the indoor heat exchanger 10 during the process of freezing the indoor heat exchanger 10, and the discharge temperature of the compressor 1. The bypass expansion valve 7 (second expansion valve) is controlled based on the above. Further, the control unit 20 increases the opening degree of the bypass expansion valve 7 as the discharge temperature (or discharge superheat degree) of the compressor 1 increases during the freezing process of the indoor heat exchanger 10. As a result, a sufficient amount of frost can be attached to the indoor heat exchanger 10, and it is possible to prevent the discharge temperature of the compressor 1 from becoming too high.

<Effect>
According to the second embodiment, during freezing of the indoor heat exchanger 10, the control unit 20 controls the bypass expansion valve 7 of the supercooler E based on the discharge temperature of the compressor 1. This makes it possible to prevent the discharge temperature of the compressor 1 from becoming too high during freezing of the indoor heat exchanger 10. Further, the supercooler E used for improving the air conditioning capacity can also be used (also used) for freezing the indoor heat exchanger 10.

<< Third Embodiment >>
In the third embodiment, instead of the bypass expansion valve 7 (see FIG. 1) of the first embodiment, the bypass pipe WB (see FIG. 6) has a capillary tube 31 (see FIG. 6) and a two-way valve 32 (see FIG. 6). (See) is provided, which is different from the first embodiment. Others are the same as those in the first embodiment (see FIGS. 2 to 4). Therefore, a part different from the first embodiment will be described, and a description of the overlapping part will be omitted.

FIG. 6 is a configuration diagram including a refrigerant circuit QB of the air conditioner 100B according to the third embodiment.
As shown in FIG. 6, the air conditioner 100B includes a capillary tube 31 and a two-way valve 32. The capillary tube 31 is a pipe for reducing the pressure of the refrigerant flowing through the bypass pipe WB, and is provided in the bypass pipe WB. The two-way valve 32 is a solenoid valve that switches the flow / shutoff of the refrigerant in the bypass pipe WB. That is, when the two-way valve 32 is in the valve open state, the refrigerant flows through the bypass pipe WB, while when the two-way valve 32 is in the valve closed state, the refrigerant flows in the bypass pipe WB. Is blocked.

In the example of FIG. 6, a two-way valve 32 is provided on the downstream side of the capillary tube 31 in the bypass pipe WB. Since the connection points of one end i1 and the other end i2 of the bypass pipe WB are the same as those of the bypass pipe W (see FIG. 1) of the first embodiment, the description thereof will be omitted.

The control unit 20 (see FIG. 3) controls the indoor expansion valve 12 based on the temperature of the indoor heat exchanger 10 while the indoor heat exchanger 10 is frozen, and the unit is based on the discharge temperature of the compressor 1. The valve opening time of the two-way valve 32 per hour is adjusted. For example, the control unit 20 lengthens the valve opening time of the two-way valve 32 per unit time as the discharge temperature (or discharge superheat degree) of the compressor 1 increases. As a result, the flow rate per unit time in the bypass pipe WB is increased, so that an increase in the discharge temperature of the compressor 1 can be suppressed.
When the two-way valve 32 is opened and closed a plurality of times per unit time, the sum of the times during which the two-way valve 32 is in the open state is "the two-way valve 32 per unit time". Valve opening time ". Further, the control unit 20 may perform the following processing regarding the adjustment of the valve opening time of the two-way valve 32. For example, when the two-way valve 32 is opened and closed a predetermined number of times per unit time, the higher the discharge temperature (or the degree of discharge superheat) of the compressor 1, the more the control unit 20 causes the two-way valve 32 to open and close. The valve opening time per valve opening may be lengthened. As a result, it is possible to suppress an increase in the discharge temperature of the compressor 1.

Further, the control unit 20 (see FIG. 3) maintains the two-way valve 32 in the closed state during the thawing of the indoor heat exchanger 10. As a result, a sufficient flow rate of the refrigerant flowing through the indoor heat exchanger 10 can be secured. Regarding the cleaning process of the indoor heat exchanger 10, the control of each device other than the two-way valve 32 is the same as that of the first embodiment, and thus the description thereof will be omitted.

<Effect>
According to the third embodiment, while the indoor heat exchanger 10 is frozen, the capillary tube 31 and the two-way valve 32 are used to suppress an increase in the discharge temperature of the compressor 1 and enhance the reliability of the air conditioner 100B. be able to.

≪Modification example≫
Although the air conditioner 100 according to the present invention has been described above in each embodiment, the present invention is not limited to these descriptions, and various modifications can be made.
For example, in the first embodiment, the process of freezing the indoor heat exchanger 10 has been described, but the present invention is not limited to this. That is, instead of freezing the indoor heat exchanger 10, dew condensation may occur on the indoor heat exchanger 10. When dew condensation occurs on the indoor heat exchanger 10 in this way, the control unit 20 determines that the temperature of the indoor heat exchanger 10 is equal to or lower than the dew point of the outside air and is higher than the predetermined freezing temperature. The opening degree of 12 and the like are adjusted, and the state is continued for a predetermined time. The above-mentioned "freezing temperature" is a temperature at which the moisture contained in the air begins to freeze in the indoor heat exchanger 10 when the temperature of the indoor heat exchanger 10 is gradually lowered. The control content is the same as in the case of "freezing" except that the opening degree of the indoor expansion valve 12 is larger in "condensation" than in the case of "freezing" the indoor heat exchanger 10. The same can be said for the second embodiment.
Then, the control unit 20 controls the indoor expansion valve 12 (first expansion valve) based on the temperature of the indoor heat exchanger 10 during the process of dew condensation on the indoor heat exchanger 10, and also discharges the compressor 1. The bypass expansion valve 7 (second expansion valve) is controlled based on the above.

Further, in each embodiment, after the indoor heat exchanger 10 is frozen, the control unit 20 has described the process of causing the indoor heat exchanger 10 to function as a condenser and thawing the indoor heat exchanger 10, but the present invention is not limited to this. .. For example, after the indoor heat exchanger 10 is frozen, the control unit 20 may set the opening degree of the indoor expansion valve 12 to be larger than that at the time of freezing (for example, fully open). As a result, the high-temperature refrigerant flows from the outdoor heat exchanger 2 through the indoor expansion valve 12 into the indoor heat exchanger 10, so that the indoor heat exchanger 10 is thawed.

Further, in each embodiment, the case where freezing, thawing, and drying are sequentially performed as the cleaning treatment of the indoor heat exchanger 10 has been described (see FIG. 4), but the present invention is not limited to this. For example, one or both of thawing and drying of the indoor heat exchanger 10 may be omitted as appropriate. This is because the natural convection of air in the indoor unit promotes thawing and drying of the indoor heat exchanger 10.

Further, in the second embodiment (see FIG. 5), a configuration in which one end i1 of the bypass pipe WA is connected between the first heat exchange portion Ea and the outdoor expansion valve 4 in the liquid side pipe J1 has been described. , Not limited to this. For example, one end i1 of the bypass pipe WA may be connected between the first heat exchange portion Ea and the blocking valve Vb in the liquid side pipe J1.

Further, in the third embodiment (see FIG. 6), the configuration in which the two-way valve 32 is provided on the downstream side of the capillary tube 31 in the bypass pipe WB has been described, but the present invention is not limited to this. That is, the two-way valve 32 may be provided on the upstream side of the capillary tube 31 in the bypass pipe WB.

Further, in the third embodiment (see FIG. 6), when the two-way valve 32 is opened and closed a predetermined number of times per unit time, the higher the discharge temperature (or the degree of discharge superheat) of the compressor 1, the higher the discharge temperature (or the degree of superheat). , The process of lengthening the valve opening time of the two-way valve 32 at one time has been described, but the present invention is not limited to this. For example, when the valve opening time of the two-way valve 32 is set as a fixed value, the control unit 20 may adjust the number of valve opening times of the two-way valve 32 per unit time. .. Specifically, the control unit 20 increases the number of times the two-way valve 32 is opened per unit time as the discharge temperature (or discharge superheat degree) of the compressor 1 increases. As a result, the flow rate per unit time in the bypass pipe WB is increased, so that an increase in the discharge temperature of the compressor 1 can be suppressed.
Both the number of valve opening times per unit time of the two-way valve 32 and the valve opening time per one time of the two-way valve 32 may be adjusted. Such processing is also included in the matter that the control unit 20 adjusts the valve opening time of the two-way valve per unit time.

In addition, each embodiment can be combined as appropriate. For example, the second embodiment (see FIG. 5) and the third embodiment (see FIG. 6) may be combined and configured as follows. That is, instead of the bypass expansion valve 7 of the supercooler E (second embodiment), the capillary tube 31 and the two-way valve 32 (third embodiment) may be provided in the bypass pipe WA. Since the control of the bypass expansion valve 7 during freezing of the indoor heat exchanger 10 is the same as that of the third embodiment, the description thereof will be omitted.

The types of indoor units U1 to U4 are not particularly limited. For example, any one of a plurality of types such as a four-way cassette type, a ceiling-embedded type, a floor-standing type, and a wall-mounted type may be used, or a plurality of types of indoor units may be mixed.

Further, in each embodiment, the configuration in which the outdoor unit Uo (see FIG. 1) includes the outdoor expansion valve 4 and the four-way valve 5 has been described, but the present invention is not limited to this. For example, in an air conditioner dedicated to cooling, the outdoor expansion valve 4 and the four-way valve 5 may be omitted.
Further, in each embodiment, the configuration in which four indoor units U1, U2, U3, U4 (see FIG. 1) are provided has been described, but the number of indoor units connected to the outdoor unit Uo is one. It may be two or three, or five or more. That is, at least one indoor unit needs to be connected to the outdoor unit Uo.

Further, in each embodiment, the configuration in which the air conditioner 100 (see FIG. 1) includes one outdoor unit Uo has been described, but a configuration in which a plurality of outdoor units are connected in parallel in one system may be used. ..
Further, each embodiment can be applied to various types of air conditioners such as a multi air conditioner for buildings (VRF: Variable Refrigerant Flow), a packaged air conditioner (PAC: Packaged Air Conditioner), and a room air conditioner.

Further, it is possible to provide a program for causing the computer to execute the processing of the control unit 20 (see FIG. 4) via a communication line, and write a predetermined program to a recording medium such as a CD-ROM. It is also possible to distribute.

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 other configurations with respect to a part of the configurations of each embodiment.
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.

1 Compressor 2 Outdoor heat exchanger 3 Outdoor fan 4 Outdoor expansion valve 5 Four-way valve 6 Accumulator 7 Bypass expansion valve (second expansion valve)
8 Outdoor temperature sensor
9 Discharge temperature sensor 10 Indoor heat exchanger 11 Indoor fan 12 Indoor expansion valve (1st expansion valve)
13 Indoor temperature sensor 14 Indoor heat exchanger Temperature sensor 15 Remote control 16 Centralized control equipment 20 Control unit 31 Capillary tube 32 Two-

way valve

100, 100A, 100B Air conditioner E Supercooler Ea 1st heat exchange unit Eb 2nd heat exchange Part Q, QA, QB Refrigerant circuit Uo, UAo, UBo Outdoor unit U1, U2, U3, U4 Indoor unit W, WA, WB Bypass piping

Claims

It is provided with a refrigerant circuit in which an outdoor unit having a compressor and an outdoor heat exchanger and at least one indoor unit having a first expansion valve and an indoor heat exchanger are connected via piping.
A bypass pipe that guides a part of the refrigerant condensed by the outdoor heat exchanger to the suction side of the compressor, and
The second expansion valve provided in the bypass pipe and
It includes at least the compressor, the first expansion valve, and a control unit that controls the second expansion valve.
The control unit controls the first expansion valve based on the temperature of the indoor heat exchanger and the discharge temperature of the compressor during the process of freezing or dew condensation on the indoor heat exchanger. An air conditioner that controls the second expansion valve.
The air conditioner according to claim 1, wherein the control unit increases the opening degree of the second expansion valve as the discharge temperature of the compressor increases during the processing.
The air conditioner according to claim 1, wherein the control unit increases the opening degree of the second expansion valve as the discharge superheat degree of the compressor increases during the processing.
The pipe through which the refrigerant condensed by the outdoor heat exchanger flows has a first heat exchange section.
The bypass pipe has a second heat exchange portion on the downstream side of the second expansion valve in the bypass pipe.
The air conditioner according to claim 1, wherein heat exchange is performed between the refrigerant flowing through the first heat exchange section and the refrigerant flowing through the second heat exchange section.
The control unit
During normal air conditioning operation, the second expansion valve, the first heat exchange section, and the second heat exchange section are made to function as supercoolers.
The air conditioner according to claim 4, wherein the second expansion valve, the first heat exchange section, and the second heat exchange section function as supercoolers even during the process.
The control unit
During normal air conditioning operation, the second expansion valve is controlled based on the degree of supercooling of the refrigerant cooled in the first heat exchange section.
The air conditioner according to claim 5, wherein the second expansion valve is controlled based on the discharge temperature of the compressor during the processing.
The bypass pipe is provided with a capillary tube and a two-way valve in place of the second expansion valve.
The air conditioner according to claim 1, wherein the control unit adjusts the valve opening time of the two-way valve per unit time based on the discharge temperature of the compressor.
After freezing the indoor heat exchanger as the process, the control unit causes the indoor heat exchanger to function as a condenser, defrosts the indoor heat exchanger, and during thawing of the indoor heat exchanger, The air conditioner according to claim 1, wherein the first expansion valve is set to a predetermined opening degree while the second expansion valve is maintained in a closed state.
During the process, the control unit closes the second expansion valve when the discharge temperature of the compressor is equal to or lower than a predetermined value or when the discharge superheat degree of the compressor is equal to or lower than a predetermined value. The air conditioner according to claim 1.