JP4668021B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner that appropriately maintains a refrigerant distribution indoors and outdoors in an air conditioner having a condenser both indoors and outdoors and solves problems due to a lack of refrigerant.

  Conventionally, a compressor, an outdoor heat exchanger (condenser), a gas-liquid separator, a first expansion valve, a first indoor heat exchanger (evaporator), and an accumulator are sequentially connected by piping. On the opposite side of the separator from the first expansion valve, a two-way valve, a second indoor heat exchanger, and a second expansion valve are sequentially connected to each other by piping so that a refrigeration cycle that joins the first expansion valve is provided. There exists an air conditioner (for example, refer patent document 1).

  In the conventional air conditioner described above, a condenser is provided indoors and outdoors, the indoor and outdoor temperatures change depending on the season and indoor objects to be cooled, and the refrigerant in the circuit stays in one condenser. The phenomenon occurs. When the stagnation phenomenon occurs in this way, the other condenser side becomes insufficient in refrigerant, resulting in problems such as insufficient operating capacity due to low pressure drop and shortened compressor life due to increased discharge temperature from the compressor, There were inconveniences such as the protector operating and stopping.

  In order to avoid these disadvantages, there is a method to prevent a shortage of refrigerant in the operation circuit even if a small amount of refrigerant stagnates in one condenser by enclosing a large amount of refrigerant in the circuit, In this method, there is a possibility that liquid back to the compressor may occur, and there is a problem that damage to the compressor is increased. In addition, encapsulating a large amount of refrigerant causes an increase in the cost of the refrigerant, and there is also a problem that there is a concern about the environmental impact in the event of atmospheric release.

  Some conventional air conditioners are provided with a liquid reservoir for accumulating surplus refrigerant generated by switching the operation mode (see, for example, Patent Document 2).

JP-A-5-240486 (page 4, FIG. 1) Japanese Unexamined Patent Publication No. 2003-262429 (page 5, FIG. 1)

  In the technology in which a large amount of refrigerant is sealed in order to eliminate the shortage of refrigerant due to the conventional stagnation phenomenon, there is an excessive amount of refrigerant in the operation circuit, resulting in performance degradation due to an increase in high pressure. There were various problems such as the possibility that the high-pressure protection was activated and the operation could be stopped abnormally.

  Moreover, in the technique which provided the liquid reservoir of patent document 2, the cost increase for a liquid reservoir and its connection piping will be caused. Further, it is necessary to further increase the amount of refrigerant filled by the amount of the liquid reservoir installed, resulting in an increase in the cost of the refrigerant and a cost-up spiral phenomenon. Moreover, the damage to the compressor at the time of liquid back also became large, and there were various problems such as concern about the environmental impact at the time of air release.

  The present invention has been made to solve the above-described problems, and eliminates the shortage of refrigerant in the refrigeration cycle caused by the stagnation phenomenon without increasing the amount of refrigerant or installing a liquid reservoir, and a compressor based on liquid back An object is to obtain an air conditioner that can reduce damage, avoid an abnormal stop such as performance degradation due to an increase in high pressure or a high-pressure protection in the worst case, and have cost merit.

In the air conditioner according to the present invention, a compressor, an outdoor solenoid valve, an outdoor condenser, a throttling device, and a cooler are sequentially connected by a refrigerant pipe, and further, the compressor and the outdoor solenoid valve The compressor is prepared for operation by controlling the refrigeration cycle that branches off from the interior, sequentially connects the indoor solenoid valve and the indoor condenser with refrigerant piping, and joins the expansion device, and the outdoor solenoid valve and the indoor solenoid valve. and a control unit for performing, the control unit, the solenoid valve for the outdoor opening, after the solenoid valve chamber were outdoor refrigerant recovery operation for driving the compressor is closed, the solenoid valve for the outdoor open, solenoid valve chamber The refrigerant recovery in the refrigeration cycle is eliminated by performing the preparatory operation without providing a liquid reservoir on the high-pressure side of the refrigeration cycle. .

  According to the present invention, the shortage of refrigerant in the refrigeration cycle can be solved by performing the preparatory operation of the compressor without increasing the amount of refrigerant or installing a liquid reservoir on the high pressure side of the refrigeration cycle. Therefore, it is possible to obtain an air conditioner that can solve various problems caused by a shortage of refrigerant in the refrigeration cycle.

Embodiment 1 FIG.
1 is a refrigerant circuit diagram of an air conditioner according to Embodiment 1 of the present invention.
The air conditioner includes a compressor 1, an outdoor solenoid valve 2, an outdoor condenser 3, an outdoor condenser check valve 4 that prevents the refrigerant from flowing into the outdoor condenser 3, a throttle device 5, and a cooler (evaporation) 6) are sequentially connected by refrigerant pipes 10 to 14, and further branched from between the compressor 1 and the outdoor electromagnetic valve 2, and are connected to the indoor electromagnetic valve 7, the indoor condenser 8, and the indoor condenser 8 The indoor condenser check valve 9 for preventing accumulation due to the refrigerant reverse flow is connected to the refrigerant pipes 15 and 16 in order, and is provided with a refrigeration cycle that joins the expansion device 5. An outdoor fan 20 that promotes refrigerant condensation in the outdoor condenser 3 and a common indoor fan 21 that promotes refrigerant evaporation in the cooler 6 and refrigerant condensation in the indoor condenser 8 are provided. The indoor fan 21 allows the room air to pass through the cooler 6 and then through the indoor condenser 8 to be blown out from the air conditioner. Of each component constituting the air conditioner, the outdoor fan 20 and the outdoor condenser 3 are installed outdoors, and the others are installed indoors. In the following description, the refrigerant pipes 10 to 16 are referred to according to the function of the refrigerant pipe, the refrigerant pipes 10, 11, and 15 are discharge pipes, the refrigerant pipes 12, 13, and 16 are liquid pipes, and the refrigerant pipe 14 is used. This is called the suction pipe 14.

FIG. 2 is a block diagram showing an electrical configuration of the air conditioner of FIG.
The air conditioner includes an operation unit 100 for inputting various settings such as a target temperature, an outdoor temperature sensor 101, a storage unit 102, and a control unit 103 configured by a microcomputer. The control unit 103 includes a CPU, a RAM that stores various data, and a ROM (none of which is shown) that stores a program for performing operation control in each operation mode described below. According to the program, the outdoor solenoid valve 2, the indoor solenoid valve 7, the expansion device 5, the indoor fan 21 and the outdoor fan 20 are appropriately controlled to perform various operation controls of a preparation operation, a cooling operation, a dehumidifying operation and an intermediate operation which will be described later.

  This air conditioner controls the heat radiation amount in the outdoor condenser 3 by opening and closing the outdoor electromagnetic valve 2 and the indoor electromagnetic valve 7, and adjusts the temperature while dehumidifying the room. Are cooling operation (operation to dehumidify while cooling the room), dehumidification operation (operation to dehumidify while heating the room), intermediate operation (weak heating and cooling the room by controlling the amount of heat radiation inside and outside the room) Or the operation | movement which dehumidifies, maintaining indoor temperature). Hereinafter, each operation will be described sequentially.

<Cooling operation>
First, during the cooling operation, the outdoor electromagnetic valve 2 is in an open state and the indoor electromagnetic valve 7 is in a closed state. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 flows into the outdoor condenser 3 through the discharge pipes 10 and 11, and dissipates heat by exchanging heat with outdoor air blown by the outdoor fan 20. Thereby, the gas refrigerant is condensed and liquefied. Then, the pressure is reduced by the expansion device 5 through the liquid pipe 12 to become a gas-liquid two-phase refrigerant and enters the cooler 6. The gas-liquid two-phase refrigerant that has entered the cooler 6 exchanges heat with the indoor air blown from the indoor fan 21 and absorbs heat, thereby performing a cooling operation. Then, the refrigerant in the gas state returns to the compressor 1 through the suction pipe 14. This cycle is repeated to cool the room.

<Dehumidifying operation>
First, during the dehumidifying operation, the outdoor electromagnetic valve 2 is in a closed state and the indoor electromagnetic valve 7 is in an open state. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 flows into the indoor condenser 8 through the discharge pipe 15. Here, the refrigerant radiates heat by exchanging heat with indoor air circulated by the indoor fan 21. Thereby, the gas refrigerant is condensed and liquefied. Then, it enters the expansion device 5 via the liquid pipe 16 and the indoor condenser check valve 9, where it is decompressed and becomes a gas-liquid two-phase refrigerant and enters the cooler 6. The gas-liquid two-phase refrigerant that has entered the cooler 6 exchanges heat with the indoor air blown from the indoor fan 21 and absorbs heat to return to the compressor 1 as a low-temperature low-pressure gas refrigerant. Here, the indoor air circulated by the indoor fan 21 is cooled by the low-temperature low-pressure gas-liquid two-phase refrigerant in the cooler 6, and moisture in the indoor air is condensed on the surface of the cooler 6 to be dehumidified. Thereafter, the indoor condenser 8 is heated by the high-temperature high-pressure gas refrigerant to increase the temperature, and the relative humidity decreases. In this way, the outdoor solenoid valve 2 is closed, the outdoor fan 20 is turned off, and all heat radiation in the refrigeration cycle is performed indoors, so that the air cooled by the cooler 6 is heated by the indoor condenser 8. Theoretically, an operation is performed in which the room is heated by the input of the compressor 1 and the condensation latent heat of water vapor.

<Intermediate operation>
First, during this intermediate operation, both the outdoor solenoid valve 2 and the indoor solenoid valve 7 are in an open state. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 flows into the indoor condenser 8 through the discharge pipe 15 when the indoor electromagnetic valve 7 and the outdoor electromagnetic valve 2 are opened, and condenses outside through the discharge pipe 11. Flows into the vessel 3. Then, heat is radiated and liquefied in each of the indoor condenser 8 and the outdoor condenser 3, and merges in the liquid pipe 13 through the liquid pipes 16 and 12. Then, the pressure is reduced by the expansion device 5 through the liquid pipe 12 to become a gas-liquid two-phase refrigerant and enters the cooler 6. Then, the heat is absorbed and gasified to obtain the suction pipe 14 and return to the compressor 1. In such an intermediate operation, the control unit 103 performs ON / OFF control of the outdoor fan 20 according to the outdoor temperature detected by the outdoor fan 20 (that is, OFF when the outdoor temperature is lower than a preset temperature, and ON when the outdoor temperature is higher). And control to always turn on the indoor fan 21. Note that the ON / OFF control of the outdoor fan 20 may be controlled according to the pressure on the high pressure side.

  Hereafter, the characteristic part of this invention is demonstrated. The air conditioner of this example eliminates the refrigerant non-uniformity in the refrigeration cycle by performing a preparatory operation at a predetermined timing without increasing the amount of refrigerant or installing a liquid reservoir that has been provided in the past. It is intended to solve the various problems described above.

  Here, prior to explaining the details of the preparatory operation, the situation in which refrigerant shortage occurs will be organized. For example, when the air conditioner is stopped for a long period of time, refrigerant stagnation occurs in the outdoor or indoor condenser due to a temperature difference between the indoor and outdoor environments. That is, the refrigerant moves due to a pressure difference from the high temperature side (high pressure side) to the low temperature side (low pressure side) and increases in viscosity at low temperatures, so that the refrigerant stagnation phenomenon occurs on the low temperature side condenser. appear. Thus, when the temperature balance between the indoor and outdoor is poor and the operation is restarted in a state where the refrigerant is trapped in the condenser on the low temperature side due to the long-term stop of the air conditioner, a shortage of refrigerant may occur.

  Specifically, for example, when the outdoor temperature is as low as about 0 ° C. in winter and the room is as high as about 30 ° C. for drying applications, a large amount of refrigerant stagnates on the low-temperature outdoor condenser 3 side. The refrigerant in the condenser 8 may become insufficient. When a command for dehumidifying operation is issued in such a state, the circuit of the outdoor condenser 3 where the refrigerant has stagnation is closed, and the refrigerant that has fallen into the outdoor condenser 3 must be operated without being recovered, and the dehumidifying operation is performed. The amount of refrigerant circulating in the operating circuit is insufficient.

  Further, for example, in the case of resuming operation from a long-term stop when the outdoor temperature is high at about 35 ° C. in summer and the indoor temperature is low at about 10 ° C., such as for seed storage, the refrigerant falls into the indoor condenser 8 and the refrigerant of the outdoor condenser 3. May become deficient. When a cooling operation command is issued in such a state, the circuit of the indoor condenser 8 where the refrigerant is stagnating is closed, and the refrigerant that has fallen into the indoor condenser 8 has to be operated without being recovered. The amount of refrigerant circulating in the operating circuit is insufficient.

  Moreover, the air conditioner of this invention has three types of operation modes as above-mentioned, and an operation mode changes with indoor temperature and humidity. For example, when the dehumidifying operation is performed in a state where the outdoor temperature is high and the indoor temperature is low, the refrigerant is unlikely to be short because the circuit of the indoor condenser 8 that is likely to stagnate the refrigerant due to low temperature is operated. . From this state, for example, when the indoor temperature rises due to, for example, opening / closing of the indoor door, a cooling command may be issued. In such a case, since the circuit of the indoor condenser 8 where the refrigerant stagnates is closed, a refrigerant shortage occurs in the cooling operation circuit.

  In addition, for example, when the cooling operation is performed under a condition where the outdoor temperature is low and the indoor temperature is high, the refrigerant is insufficient because the circuit of the outdoor condenser 3 that is likely to cause refrigerant stagnation due to low temperature is operated in an open state. It's hard to fall. From this state, for example, when the indoor temperature drops due to opening / closing of an indoor door, a dehumidification command may be issued subsequently. In such a case, since the circuit of the outdoor condenser 3 where the refrigerant stagnation is closed, the refrigerant is insufficient in the dehumidifying operation circuit.

  Furthermore, even when the same operation mode is continued for a long time, the refrigerant may stagnate in the indoor condenser 8 or the outdoor condenser 3 due to the slight leakage of the solenoid valves 2 and 7 continuing. Even if the dehumidifying operation is performed in a state where the indoor temperature is high and the outdoor temperature is low, the refrigerant does not become insufficient unless the refrigerant is insufficient at the start of operation or when the operation mode is switched. However, if the outdoor solenoid valve 2 leaks little by little due to valve leakage or the like while the dehumidifying operation is continued for hours without the refrigerant shortage, the low-temperature outdoor condenser 3 is The refrigerant may fall asleep. In this case, as a result, the operation circuit is in a refrigerant shortage state.

  For example, conversely, even if the cooling operation is performed in a state where the indoor temperature is low and the outdoor temperature is high, the refrigerant does not become insufficient unless the refrigerant is insufficient at the start of the operation or when the operation mode is switched. However, if the refrigerant leaks little by little, for example, because the indoor electromagnetic valve 7 leaks while the cooling operation is continued for hours without the lack of refrigerant, the indoor condenser 8 having a low temperature is used. The refrigerant may fall asleep. In this case, as a result, the operation circuit is in a refrigerant shortage state.

  As described above, since the refrigerant becomes insufficient when the compressor is started, when the operation mode is switched, and when the same operation mode is continued, the refrigerant is collected at these timings. As the refrigerant recovery operation, there are two patterns of an operation of recovering the refrigerant sleeping in the outdoor condenser 3 and a recovery of the refrigerant sleeping in the indoor condenser 8. In this example, the refrigerant recovery of the indoor condenser 8 as well as the refrigerant recovery of the outdoor condenser 3 is performed together without determining which of the refrigerant stagnation is likely to occur. This is called preparatory operation. Hereinafter, the preparation operation will be described.

  The preparatory operation is automatically performed when the compressor is started, when the operation mode is switched, and when the same operation mode is continued. After the first predetermined time (for example, 2 minutes), the cooling operation as the outdoor refrigerant recovery operation is performed. Then, the intermediate operation as the indoor refrigerant recovery operation is performed for a second predetermined time (here, 2 minutes, which is the same as the first predetermined time). Here, normally, the temperature outside the room is lower than the room, and the refrigerant stagnation into the outdoor condenser 3 tends to occur. In view of this, in the preparatory operation, first, a cooling operation for recovering the refrigerant stagnation in the outdoor condenser 3 is performed. For example, in an operation command from a long-term stop when the outdoor temperature is low, the refrigerant stagnates in the outdoor condenser 3 so much that the refrigerant can be recovered even during intermediate operation as well as dehumidification operation. May result in repeated low pressure drops. Therefore, it is effective to perform the cooling operation first.

  By the way, in the description of the situation where the above-described refrigerant shortage occurs, in the case of resuming operation from a long-term stop in the summer when the outdoor temperature is high at about 35 ° C. and the indoor temperature is low at about 10 ° C., the refrigerant falls into the indoor condenser 8 side. This is a shortage on the refrigerant side of the outdoor condenser 3. For this reason, when the cooling operation is first performed in the preparation operation, the operation is performed while the refrigerant is insufficient during the cooling operation. However, the cooling operation in this preparation operation is a short-time operation unlike the case of the cooling command, and thus does not cause various problems due to the lack of refrigerant.

  Next, an intermediate operation is performed. By performing the intermediate operation, the refrigerant that has accumulated in the indoor condenser 8 can be recovered. Here, in the intermediate operation when there is a lot of outdoor stagnation, the refrigerant in the outdoor condenser 3 hardly moves and the refrigerant in the outdoor condenser 3 cannot be recovered. This is because there is an extension pipe on the outdoor side and the pressure loss is high and it is difficult for the refrigerant to flow from the room. The indoor temperature range is about 5 ° C to 40 ° C, whereas the outdoor temperature range is -5 ° C. This is because it is as wide as about ~ 43 ° C. On the other hand, in the intermediate operation when there is a large amount of indoor stagnation, the refrigerant in the indoor condenser 8 can be efficiently recovered with little influence of the pressure loss of the extension pipe. The reason why the intermediate operation is performed after the cooling operation is that the intermediate operation has an effect of equalizing the refrigerant amounts of the indoor condenser 8 and the outdoor condenser 3 when the temperature is moderately high both indoors and outdoors. This is to prevent an increase in the high pressure due to the excessive amount of water and to deal with other than the shortage of the refrigerant due to the refrigerant stagnation.

As described above, according to the first embodiment, the preparatory operation is performed when necessary, such as when the compressor is started, when the operation mode is switched, and when the same operation mode is continued, so that the liquid can be stored without enclosing a large amount of refrigerant. The refrigerant distribution can be improved without providing it. As a result, the following effects can be obtained.
(1) A liquid air back can be prevented and a highly reliable air conditioner can be obtained.
(2) It is possible to avoid an abnormal stop such as a performance degradation due to an increase in high pressure or a high-pressure protection in the worst case.
(3) Since there is no need to enclose a large amount of refrigerant or to store a liquid, cost merit is high.

  In the above description, the preparatory operation is performed when the compressor is started, when the operation mode is switched, and when the same operation mode is continued. However, the preparatory operation may be performed when a refrigerant shortage is detected. That is, when the refrigerant is insufficient, a low pressure drop, a discharge temperature rise, etc. occur, so a low pressure detection means for detecting the pressure on the suction side of the compressor 1 and / or a discharge temperature detection means for detecting the discharge temperature of the compressor 1 are provided. You may make it implement at the time of a low-pressure pressure fall or / and discharge temperature rise. As specific control, normal data without a shortage of refrigerant at the time of a development test or the like is stored in the control unit 103 as a normal operation range, and control is performed so as to perform a preparatory operation when the range deviates. do it.

  The preparatory operation may be performed at all timings when the compressor is started, when the operation mode is switched, when the same operation mode is continued, and when the refrigerant shortage is detected, or at any one or more timings. It may be.

  In addition, in the above, the operation time of the cooling operation and the intermediate operation in the preparation operation is set to a predetermined time (both 2 minutes in this example) regardless of the indoor and outdoor temperature conditions. A temperature sensor may be provided and changed according to the temperature relationship between the room and the outside. That is, for example, under conditions where the indoor temperature is high and the outdoor temperature is low, the refrigerant stagnates outside, so the cooling operation time is lengthened. Conversely, when the indoor temperature is low and the outdoor temperature is high, Since there is much refrigerant stagnation, the intermediate operation may be lengthened. By controlling in this way, it is possible to efficiently and effectively recover the refrigerant according to the actual installation environment. As a result, it can be expected that the same effect as described above can be obtained more reliably.

  Alternatively, a temperature sensor may be provided only in the room or outdoors, and the operation time of each of the cooling operation and the intermediate operation in the preparation operation may be controlled according to the detection result of the temperature sensor. For example, when a temperature sensor is provided only in the room, it is determined that there is much refrigerant stagnation in the room when the room temperature is, for example, 15 ° C. or less, and the intermediate operation time is lengthened. The cooling operation time may be lengthened by judging that the refrigerant stagnation is large. On the other hand, when the temperature sensor is provided only outside, if the outdoor temperature is, for example, 15 ° C. or less, it is determined that there is much refrigerant stagnation outside the room, and the cooling operation time is extended. It may be determined that there is a lot of refrigerant stagnation, and the intermediate operation time may be lengthened.

  Further, when a variable frequency compressor (hereinafter referred to as an inverter compressor) capable of varying the operating frequency is mounted as the compressor 1, the efficiency of refrigerant recovery is improved by operating the operating frequency of the inverter compressor 1. be able to. That is, by increasing the operating frequency of the inverter compressor 1 and increasing the flow rate of the refrigerant, the refrigerant can be recovered more quickly. Since the preparation operation is an operation performed before the operation instructed from the original operation unit 100, the shorter the preparation operation, the better. For this reason, when the inverter compressor 1 is installed and the refrigerant recovery is accelerated and the refrigerant can be recovered efficiently, the temperature and humidity in the room can be brought close to the target value quickly, which is effective. In the first embodiment, the operation circuit is switched by an electromagnetic valve as an example. However, switching by a four-way valve or the like brings about the same effect.

Embodiment 2. FIG.
FIG. 3 is a refrigerant circuit diagram of an air conditioner according to Embodiment 2 of the present invention. The air conditioner according to the second embodiment further includes a bypass circuit that bypasses the liquid pipe 12 to the suction pipe 14 on the suction side of the compressor 1 in addition to the air conditioner according to the first embodiment shown in FIG. A pipe 31, a bypass solenoid valve 32 that controls the opening and closing of the bypass pipe 31, and a bypass circuit check valve 33 that prevents the refrigerant from flowing backward from the suction pipe 14 to the liquid pipe 12. Is the same as that of the first embodiment shown in FIG.

Since the second embodiment is basically the same as the first embodiment, here, the second embodiment will be described with a focus on the differences from the first embodiment, and a duplicate description will be omitted.
When the outdoor condenser 3 is started from a state in which the refrigerant stagnates, for example, if an irregular situation such as a small amount of refrigerant leakage occurs, the refrigerant may not be sufficiently recovered in the preparation operation. The second embodiment is designed to cope with such a case. By providing a bypass circuit for bypassing the refrigerant from the liquid pipe 12 to the suction pipe 14 to bypass the refrigerant, the refrigerant in the outdoor condenser 3 is placed indoors. It is designed to facilitate recovery.

  As a specific operation, the control unit 103 opens the bypass solenoid valve 32 during the cooling operation of the preparation operation. As a result, a bypass circuit can be formed in parallel with the circuit that reaches the suction pipe 14 via the expansion device 5 and the cooler 6, so that compared with the case of only the circuit that reaches the suction pipe 14 via the expansion device 5 and the cooler 6. The refrigerant can be recovered into the room faster.

  By the way, during the intermediate operation of the preparatory operation, the outdoor solenoid valve 2 is in an open state, and when the outdoor temperature is low and the indoor temperature is high, the refrigerant flows into the outdoor condenser 3 even when the outdoor fan 20 is OFF. A small amount accumulates. Further, during the intermediate operation, most of the refrigerant flows into the indoor condenser 8 as described above, and the refrigerant hardly moves in the outdoor condenser 3. In a state where the refrigerant is normally in the operation circuit, even if the refrigerant accumulated in the outdoor condenser 3 increases for some reason, there is no shortage of refrigerant in the operation circuit, but some irregularity (for example, a small amount of refrigerant leakage, etc.) ), The amount of refrigerant passing through the indoor condenser 8 due to accumulation in the outdoor condenser 3 may be insufficient.

  As a countermeasure, in the second embodiment, the refrigerant accumulated in the outdoor condenser 3 can be recovered indoors by opening the bypass solenoid valve 32 even during the intermediate operation of the preparation operation. Normally, in the intermediate operation in a state where the outdoor temperature is low, the outdoor fan 20 is turned off as described above. However, if this state continues for a long time, the refrigerant pressure in the outdoor condenser 3 and the liquid pipe 12 is saturated to the outside air temperature. To do. For example, if the outside air is −5 ° C., it is saturated to a pressure corresponding to −5 ° C. On the other hand, the refrigerant in the suction pipe 14 has an evaporation temperature saturation pressure, for example, equivalent to 0 ° C. In that case, the suction pipe 14 has a higher pressure than the outdoor condenser 3 and the liquid pipe 12, and the refrigerant accumulated in the outdoor condenser 3 cannot be moved from the liquid pipe 12 to the suction pipe 14. However, the intermediate operation of the preparatory operation is performed following the cooling operation of the preparatory operation, and the refrigerant during the cooling operation always flows through the outdoor condenser 3, so that the outdoor condenser 3 and the liquid pipe 12 are used during the intermediate operation of the preparatory operation. The internal refrigerant pressure does not saturate corresponding to the outside air temperature, and maintains a high pressure, so that the refrigerant temperature is maintained above the evaporation temperature saturation pressure, and a small amount of accumulated refrigerant can be reliably recovered through the bypass pipe 31. .

  As described above, according to the second embodiment, the same operation and effect as in the first embodiment can be obtained, and the bypass operation for bypassing the refrigerant in the liquid pipe 12 to the suction side of the compressor 1 in combination with the preparation operation. Therefore, even when it is difficult to recover the refrigerant that has fallen into the outdoor condenser 3 due to some irregular situation (for example, a small amount of refrigerant leakage), the refrigerant can be reliably recovered.

Embodiment 3 FIG.
FIG. 4 is a refrigerant circuit diagram of the air conditioner according to Embodiment 3 of the present invention. The air conditioner of the third embodiment uses an electronic expansion valve 41 as the throttle device 5 of the air conditioner of the first embodiment shown in FIG. 1, and other configurations are the same as those shown in FIG. This is the same as the first embodiment. Here, the electronic expansion valve is an electric signal whose opening is determined by an electrical signal. Compared with a temperature expansion valve that controls the opening only by superheat in the suction pipe 14, for example, a signal for starting the compressor 1 is used. There is an advantage that it can be controlled to any opening degree by any signal such as a signal for starting a preparatory operation.

  The operation of the third embodiment equipped with the electronic expansion valve 41 having such characteristics will be described. Note that the third embodiment is basically the same as the first embodiment, and therefore, here, the third embodiment will be described with a focus on the differences from the first embodiment, and a duplicate description will be omitted. Under conditions where the indoor temperature is low and the outdoor temperature is high, there is a high possibility that the refrigerant will stagnate in the indoor condenser 8. In the third embodiment, the opening degree of the electronic expansion valve 41 is set in advance at the start of the preparatory operation or at the start of the intermediate operation of the preparatory operation in order to efficiently collect the refrigerant stagnated in the indoor condenser 8 in this manner. The predetermined opening is controlled, or the opening is controlled by a predetermined amount set in advance. Here, the predetermined opening is an opening that is appropriate when the temperature of the environment to be cooled is as high as 25 ° C. and the humidity is as high as 80%, for example, and is compared with an appropriate opening in a normal operation state. Large opening. Therefore, at the start of the preparatory operation or the intermediate operation of the preparatory operation, the opening degree of the electronic expansion valve 41 is adjusted to an opening degree that is more open than in the normal state. Thus, by opening the opening of the electronic expansion valve 41, it is possible to recover mainly the refrigerant that has fallen into the indoor condenser 8.

  That is, by opening the opening of the electronic expansion valve 41, it is possible to recover the refrigerant blocked by the electronic expansion valve 41. Here, the outdoor condenser 3 also has a pressure loss in the extension pipe, and only a small amount can be recovered only by adjusting the opening of the electronic expansion valve 41. On the other hand, the indoor condenser 8 has no extension piping and no pressure loss. Therefore, it is possible to easily collect the refrigerant that has fallen into the indoor condenser 8 only by adjusting the opening degree of the electronic expansion valve 41.

  Note that whether the opening of the electronic expansion valve 41 is opened or not at the start of the preparatory operation or the intermediate operation of the preparatory operation is different depending on the model characteristics of the air conditioner. In other words, in the case of a model in which the refrigerant tends to accumulate in the outdoor condenser 3, the intermediate operation is started.

  As described above, according to the third embodiment, the same effect as that of the first embodiment can be obtained, and the opening degree of the electronic expansion valve 41 is opened at the start of the preparatory operation or at the start of the intermediate operation of the preparatory operation. Since it is made to feel light, it becomes possible to enhance the recovery capability of the refrigerant that has fallen into the indoor condenser 8.

Embodiment 4 FIG.
FIG. 5 is a refrigerant circuit diagram of an air conditioner according to Embodiment 4 of the present invention. The air conditioner of the fourth embodiment is the same as the air conditioner of the first embodiment shown in FIG. 1 except that the accumulator 51 that prevents the liquid refrigerant from returning to the suction side of the compressor 1 is provided on the low pressure side of the refrigeration cycle. Specifically, it is provided between the cooler 6 and the compressor 1, and the accumulator 51 and the compressor 1 are connected by a suction pipe 42, and the other configuration is the same as that of the first embodiment shown in FIG. is there.

Since the fourth embodiment is basically the same as the first embodiment, here, the fourth embodiment will be described with a focus on the differences from the first embodiment, and a duplicate description will be omitted.
In the preparatory operation, the refrigerant recovered from the outdoor condenser 3 and / or the indoor condenser 8 flows into the accumulator 51 through the suction pipe 14. Normally, since a large amount of refrigerant is collected in the preparatory operation as the refrigerant recovery operation, all the refrigerant cannot be temporarily evaporated by the cooler 6 and flows into the accumulator 51 with some liquid refrigerant. The refrigerant flowing into the accumulator 51 is separated into gas and liquid, and only the gas refrigerant is sucked into the compressor 1. That is, even when there is a liquid back operation during the preparation operation, the compressor damage can be reduced. Moreover, since the refrigerant can be held by the accumulator 51 without being accumulated in the heat exchanger, it is possible to cope with the shortage of the refrigerant. That is, it also functions as a liquid reservoir.

  As described above, according to the fourth embodiment, the same effects as those of the first embodiment can be obtained, and the accumulator 51 is provided on the low pressure side. Can be reduced. In addition, since it also serves as a liquid storage function for storing refrigerant, it is possible to provide an air conditioner that is unlikely to cause shortage of refrigerant even when the operating state changes. Further, providing a container that functions as a liquid reservoir as an accumulator rather than as a liquid reservoir also brings a cost merit. In other words, the liquid reservoir is a high-pressure part and the design pressure is as high as 4.15 MPa for HFC: R410A, and the liquid reservoir needs to be thicker than the accumulator, whereas the accumulator is a low-pressure part and the design pressure is HFC: R410A is about 2.21 MPa, and the wall thickness can be reduced compared with the liquid reservoir. Such a reduction in wall thickness reduces the cost of the member and brings about cost merit.

Embodiment 5 FIG.
Various refrigerants such as HCFC: R22, HFC: R407c, and HFC: R404A can be used as the refrigerant in the first to fourth embodiments, and the above-described effects are brought about in each case. On the other hand, in recent years, a high-pressure HFC refrigerant such as R410A has become the main stream of refrigerant gas, and Embodiment 5 uses HFC: R410A as the refrigerant.

  Here, when HFC: R410A is used as the refrigerant, shortage of the refrigerant in the operation circuit is likely to occur. Therefore, the above-described preparation operation is particularly effective as a measure for avoiding the shortage of refrigerant. Hereinafter, the reason why a refrigerant shortage is likely to occur when R410A is used as a refrigerant will be described.

  In general, the extension pipe is appropriately determined in consideration of pressure loss and oil return. This is because if the pipe is too thick, the refrigerant flow rate decreases and the amount of oil adhering to the inner surface of the pipe increases, or in the worst case, the refrigerant flow rate rises below the minimum speed (oil return limit speed) at which oil can rise and rise in the pipe. Thus, the oil discharged from the compressor 1 does not return to the compressor 1 and may cause a problem of oil exhaustion. Moreover, if the piping is too thin, the pressure loss increases and the capacity is lowered. In the worst case, the discharge pressure and the discharge temperature are increased, and the protection may be stopped. Further, the pressure loss is affected by the refrigerant circulation amount and the refrigerant viscosity if the pipe length and the pipe diameter are the same, but the influence of the refrigerant circulation amount is more dominant.

  Here, R410A is characterized by the physical properties of the refrigerant. Compared with other refrigerants R22, R404A and R407c, R410A has a large latent heat when the refrigerant evaporates, and the amount of refrigerant circulation required to provide the same cooling capacity can be reduced. . Therefore, the pressure loss is reduced as a result. Here, in general, as the extension pipe, a pipe that is not too thin, not too thick, contains a small amount of refrigerant, and is as thin as possible without incurring piping costs. For this reason, in an air conditioner using R410A, it is common to reduce the pipe diameter compared to models of similar capacity using other refrigerants (R22, R407c, R404A, etc.). Therefore, when the refrigerant stagnates, it is difficult to move the refrigerant and it becomes difficult to recover the refrigerant. In other words, when R410A is used as a refrigerant, it is more difficult to collect the stagnation refrigerant than when other refrigerants (R22, R407c, R404A, etc.) are used. Therefore, performing the preparatory operation is particularly effective in an air conditioner using R410A as a refrigerant.

  Furthermore, the device using R410A as a refrigerant has a higher design pressure than other refrigerants (R22, R407c, R404A, etc.). This is because the saturation pressure for the same temperature is high due to the difference in the physical properties of the refrigerant. The design pressure of R410A is about 4.15 MPa while the design pressure of other refrigerants (R22, R407c, R404A, etc.) is about 3 MPa. Because. Therefore, when a liquid reservoir is provided on the high-pressure side as in the past, it is necessary to increase the wall thickness for reasons of pressure resistance, which increases the cost of components and, in some cases, creates a new mold for container production. There is a concern about the cost increase. For this reason as well, the conventional high pressure side liquid reservoir abolition by preparatory operation when R410A is used as a refrigerant has a large cost merit compared to other refrigerants (R22, R407c, R404A, etc.).

  As described above, the configurations described in the first to fourth embodiments are particularly effective in an air conditioner that uses R410A as a refrigerant.

  By the way, in Embodiment 1-4 mentioned above, it demonstrated as another embodiment, respectively, but it is good also as an air conditioner which combined each embodiment suitably, and all of Embodiment 1-4 can be implemented. It is good also as an air conditioner. For example, by combining the first to third embodiments, it can be expected that the recovery speed of both the outdoor condenser 3 and the indoor condenser 8 is increased and an effective refrigerant recovery effect is obtained.

  Further, for example, the first to fourth embodiments may be combined so that a bypass circuit is provided at the upstream portion of the accumulator of the suction pipe 14 as shown in FIG. 6, and the electronic expansion valve 41 is used as a throttle device. Good. Here, in the bypass operation in the second embodiment, the refrigerant accumulated in the outdoor condenser 3 is bypassed to the suction pipe 14, and the refrigerant flowing into the suction pipe 14 is liquid refrigerant or gas-liquid two-phase refrigerant. In many cases, this results in a liquid back operation. Therefore, with the configuration shown in FIG. 6, the liquid-backed refrigerant can be gas-liquid separated by the accumulator 51, and the liquid back protection effect for the compressor 1 is great. Further, the third embodiment is a control that opens the electronic expansion valve 41. However, the amount of refrigerant that temporarily flows into the cooler 6 is increased by such control, and there is a high possibility that a liquid back operation will be caused. Become. Therefore, by providing the accumulator 51, the effect of liquid back protection for the compressor 1 is great.

It is a refrigerant circuit figure of the air conditioner in Embodiment 1 of this invention. It is a block diagram which shows the electrical constitution of the air conditioner of Embodiment 1 of this invention. It is a refrigerant circuit figure of the air conditioner in Embodiment 2 of this invention. It is a refrigerant circuit figure of the air conditioner in Embodiment 3 of this invention. It is a refrigerant circuit figure of the air conditioner in Embodiment 4 of this invention. It is a refrigerant circuit figure of the air conditioner at the time of combining Embodiments 1-4 of this invention.

Explanation of symbols

1 compressor, 2 outdoor solenoid valve, 3 outdoor condenser, 4 outdoor condenser check valve, 5 throttle device, 6 cooler, 7 indoor solenoid valve, 8 indoor condenser, 9 indoor condenser check valve, 10, 11 Discharge pipe, 12, 13 Liquid pipe, 14 Suction pipe, 15 Discharge pipe, 16 Liquid pipe, 20 Outdoor fan, 21 Indoor fan, 31 Bypass pipe, 32 Bypass solenoid valve, 33 Bypass circuit check valve, 41 Electronic expansion valve, 51 accumulator, 52 suction pipe, 101 outdoor temperature sensor, 103 control unit.

Claims (12)

A compressor, an outdoor solenoid valve, an outdoor condenser, a throttling device, and a cooler are sequentially connected by a refrigerant pipe, and further branched from between the compressor and the outdoor solenoid valve. And a refrigerating cycle in which indoor condensers are sequentially connected by refrigerant piping and merged with the expansion device,
A controller for controlling the outdoor solenoid valve and the indoor solenoid valve to perform a preparatory operation of the compressor;
The controller opens the outdoor solenoid valve, closes the indoor solenoid valve, performs an outdoor refrigerant recovery operation for operating the compressor, then opens the outdoor solenoid valve, and opens the indoor solenoid valve. The indoor refrigerant recovery operation for operating the compressor as open is performed as the preparatory operation,
An air conditioner characterized by eliminating the refrigerant shortage in the refrigeration cycle by performing the preparatory operation without providing a liquid reservoir on the high pressure side of the refrigeration cycle. The air conditioner according to claim 1, wherein the controller performs the preparatory operation when the compressor is started . The air conditioner according to claim 1 or 2, wherein the controller performs the preparatory operation when the operation mode is switched . The air conditioner according to any one of claims 1 to 3, wherein the controller performs the preparation operation when the same operation mode is continued for a predetermined time . 2. The compressor according to claim 1, wherein the compressor is a variable frequency compressor, and the control unit increases a refrigerant recovery rate by increasing an operating frequency of the variable frequency compressor during the preparatory operation. The air conditioner in any one of Claims 4 thru | or 4. The indoor temperature detector or / and the outdoor temperature detector are provided, and the control unit controls the time of the indoor / outdoor refrigerant recovery operation in the preparatory operation according to the detection result of the detector. The air conditioner according to any one of claims 5 to 5. Low pressure detection means for detecting the pressure on the suction side of the compressor and / or discharge temperature detection means for detecting the discharge temperature of the compressor are provided, and the control unit performs the preparatory operation when the low pressure is lowered or / and the discharge temperature. The air conditioner according to any one of claims 1 to 6, wherein control is performed when the vehicle is lifted . A bypass circuit that bypasses a pipe between the outdoor condenser and the throttle device to a pipe on the suction side of the compressor; and an electromagnetic valve that opens and closes the bypass circuit, and the control unit performs the preparatory operation. The air conditioner according to any one of claims 1 to 7, wherein the electromagnetic valve of the bypass circuit is controlled to open . The air conditioner according to any one of claims 1 to 8, wherein an electronic expansion valve is used as the throttle device . The air conditioner according to claim 9 , wherein the control unit adjusts an opening degree of the electronic expansion valve during the preparatory operation . The air conditioner according to any one of claims 1 to 10, further comprising an accumulator that prevents liquid refrigerant from returning to the suction side of the compressor on a low-pressure side of the refrigeration cycle .   The air conditioner according to any one of claims 1 to 11, wherein R410A is used as a refrigerant sealed in the refrigeration cycle.

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