JP4981411B2 - Air conditioner - Google Patents

Description

  The present invention relates to a multi-type air conditioner in which a plurality of indoor units are connected to one outdoor unit.

  A multi-type air conditioner in which a plurality of indoor units are connected in parallel to one outdoor unit tends to have a relatively long refrigerant pipe length, and the plurality of indoor units are individually turned on and off. Therefore, in general, each indoor unit is provided with an expansion valve, and the refrigerant circulation amount is individually controlled. For this reason, the refrigerant conveyance of the liquid piping connecting the outdoor unit and the indoor unit is performed by the liquid phase refrigerant. On the other hand, in a so-called pair type air conditioner in which one indoor unit is connected to one outdoor unit, the refrigerant pipe length may be relatively short, and the expansion valve causes the refrigerant to flow in a gas-liquid two-phase flow. In many cases, an expansion valve is provided in the outdoor unit in order to eliminate the propagation of the refrigerant flow sound generated in the room to the room. Therefore, normally, an indoor unit of a pair type air conditioner cannot be used as it is connected to an outdoor unit of a multi type air conditioner.

This means that indoor units for multi-type air conditioners and indoor units for pair-type air conditioners must be produced separately, even though they are indoor units of the same capacity, and production management is complicated. It was one of the factors that reduced production efficiency.
In addition, a multi-type air conditioner that takes advantage of the excellent quietness of the indoor unit for the pair machine by connecting the indoor unit for the pair machine to the outdoor unit of the multi-type air conditioner. It was a bottleneck in providing it.

Therefore, in a multi-type air conditioner, a branch box (branch unit) is connected between the gas pipe and the liquid pipe led out from the outdoor unit, and the pair machine is separated from the multi-unit indoor unit via this branch box. A multi-type air conditioner in which a plurality of indoor units can be connected has been proposed (see, for example, Patent Document 1).
This branch box includes a plurality of sets of branch gas pipes and branch liquid pipes branched from gas pipes and liquid pipes led out from the outdoor unit, and expansion valves for paired indoor units provided in each branch liquid pipe It is set as the structure provided with these.

Japanese Patent Laid-Open No. 2002-13763

However, in the configuration of Patent Document 1, an expansion valve is provided in the branch box, and the liquid piping between the branch box and the indoor unit serves as refrigerant conveyance by a gas-liquid two-phase refrigerant, so depending on the installation position of the branch box. Therefore, the required refrigerant amount in the system greatly fluctuates at the time of capacity change such as thermo-off. In particular, in a multi-type air conditioner, the refrigerant piping length with respect to the indoor unit tends to be long, so that the fluctuation of the necessary refrigerant amount appears remarkably. In order to absorb this change in the required amount of refrigerant, it is conceivable to increase the receiver capacity provided in the outdoor unit, but there will be problems in installation space and costs due to the increase in size of the receiver, It was not preferable. In addition, since the refrigerant naturally condenses in the indoor unit that is thermo-off during heating, this may cause overheating.
Moreover, in the indoor unit that is thermo-off during the heating operation, there is a possibility that the refrigerant may condense when the refrigerant naturally condenses or by the air blowing operation. In order to establish the heating operation, it is necessary to collect these condensed refrigerants as a system, so that the refrigerant flows through the heating indoor unit, which may cause overheating.

  The present invention has been made in view of such circumstances, and can be diversified by mixing indoor units that are not equipped with an expansion valve and have excellent quietness. An object of the present invention is to provide a multi-type air conditioner that can absorb air and can prevent overheating and the like and perform comfortable air conditioning.

In order to solve the above problems, the air conditioner of the present invention employs the following means.
That is, the air conditioner according to the present invention is a multi-type air conditioner in which a plurality of first indoor units including a first indoor heat exchanger and a first expansion valve are connected to one outdoor unit. At least one branch box is connected between the gas pipe and the liquid pipe led out from the outdoor unit, and a plurality of second indoor units including a second indoor heat exchanger can be connected to the branch box. In the air conditioner, the branch box is provided for a plurality of sets of branch gas pipes and branch liquid pipes branched from the gas pipe and the liquid pipe, and the second indoor unit provided in each branch liquid pipe. A second expansion valve and a first on-off valve provided in each branch gas pipe, and the second indoor unit is connected between the branch gas pipe and the branch liquid pipe via the branch box. And before Between the plurality of sets of the branch gas pipe and the branch liquid pipe said gas pipe and the liquid pipe before branching in the branch box, a flow rate adjusting means, the only refrigerant flow from the gas piping side to said liquid pipe side A bypass circuit having a check valve to allow is provided.

Since the multi-type air conditioner is an air conditioner that presupposes that a plurality of indoor units are individually operated, an expansion valve is generally provided in each indoor unit. For this reason, the refrigerant | coolant conveyance of the liquid piping which connects between an outdoor unit and an indoor unit is performed with the liquid phase refrigerant | coolant. On the other hand, in so-called pair type air conditioners, in order to eliminate the radiation of refrigerant flow sound into the room, an expansion valve is often provided in the outdoor unit. It cannot be connected to an outdoor unit of type air conditioner. Therefore, a branch box is connected between the gas pipe and the liquid pipe led out from the outdoor unit of the multi-type air conditioner, and a plurality of so-called pair type air conditioner indoor units can be connected to the branch box. .
In the present invention, the branch box includes a plurality of sets of branch gas pipes and branch liquid pipes branched from the gas pipe and the liquid pipe, and a second expansion valve for the second indoor unit provided in each branch liquid pipe, A first on-off valve provided in each branch gas pipe, and the second indoor unit is connected between the branch gas pipe and the branch liquid pipe of the branch box. The indoor unit can be connected to the outdoor unit of the multi-type air conditioner while being mixed with the first indoor unit. Therefore, it becomes possible to mix and connect the second indoor unit of the so-called pair type air conditioner to the outdoor unit of the multi-type air conditioner, share the second indoor unit, and improve the productivity. it can. In addition, since the second indoor unit does not include an expansion valve, there is no generation of refrigerant flow noise due to the expansion valve, and various multi-type air conditioners that combine the second indoor unit with excellent quietness are provided. be able to. In addition, since the second expansion valve for the second indoor unit is provided in the branch box, the liquid pipe between the branch box and the second indoor unit serves as refrigerant conveyance by the gas-liquid two-phase refrigerant, Depending on the installation position, the required amount of refrigerant in the system varies greatly. However, by appropriately controlling the first on-off valve and the second expansion valve provided in each branch gas pipe and branch liquid pipe, the second indoor unit that is thermo-off and its refrigerant pipe should be used as a liquid reservoir. Can do. Thereby, the fluctuation | variation of a required refrigerant | coolant amount can be absorbed easily and it can be made to drive | operate appropriately, without increasing the receiver capacity | capacitance provided in an outdoor unit. Moreover, since the refrigerant | coolant inflow to a thermo-off indoor unit can be interrupted by closing the 1st on-off valve provided in the branch gas piping of a thermo-off indoor unit at the time of heating, overheating is prevented and comfortable air conditioning is implement | achieved. Can do. Furthermore, a plurality of sets of branch gas pipes and branch liquid pipes in the branch box are connected between the gas pipe and the liquid pipe before branching, and a non-return that allows only the refrigerant flow from the gas pipe side to the liquid pipe side. A bypass circuit including a valve is provided, and the refrigerant can be bypassed from the gas piping side to the liquid piping side via the bypass circuit even when the first on-off valve is closed by heating thermo-off. For this reason, it can prevent that the refrigerant | coolant and lubricating oil which condensed in the gas piping remain.

  Furthermore, the air conditioner of the present invention controls the opening of the second expansion valve in each of the branch gas pipe and the branch liquid pipe to which the second indoor unit is connected in the air conditioner described above. A temperature sensor is provided.

  Since the second indoor unit does not incorporate an expansion valve, it generally does not have a function of controlling the opening degree of the expansion valve. According to the present invention, the temperature sensor for controlling the opening degree of the second expansion valve is provided in each of the branch gas pipe and the branch liquid pipe to which the second indoor unit is connected. Based on the value, the second indoor unit can be individually operated by controlling the degree of superheat at the outlet of the second indoor heat exchanger during cooling and controlling the degree of supercooling at the outlet of the second indoor heat exchanger during heating. .

  Furthermore, the air conditioner according to the present invention is the air conditioner according to any one of the above-described air conditioners, wherein the second indoor unit determines whether or not the refrigerant is stored when the cooling thermo-off is performed, closes the first on-off valve, and the second expansion valve. By opening the, excess refrigerant can be stored.

  According to the present invention, since the second indoor unit determines whether or not the refrigerant is stored when the cooling thermostat is off, and closes the first on-off valve and opens the second expansion valve, the excess refrigerant can be stored. When the liquid refrigerant is stored in the second indoor unit when the thermo is turned off during operation, the excess liquid refrigerant can be stored after determining the quality of the refrigerant by determining the dew point temperature etc. it can. Therefore, it is possible to prevent the occurrence of condensation due to the accumulation of the liquid refrigerant and to prevent the condensation water from dripping into the room.

  Furthermore, in the air conditioner of the present invention, in any of the above-described air conditioners, the branch gas pipe is provided with a parallel circuit including a flow rate adjusting unit in parallel with the first on-off valve. It is characterized by.

  According to the present invention, the branch gas pipe is provided with the parallel circuit including the flow rate adjusting means in parallel with the first on-off valve. Therefore, when the second indoor unit and its refrigerant pipe are used as a liquid reservoir. In addition, an appropriate amount of refrigerant can be passed through the flow rate adjusting means. Therefore, it is possible to prevent the lubricating oil from staying in the liquid refrigerant stored in the second indoor unit and its refrigerant pipe.

  Furthermore, the air conditioner of the present invention is characterized in that, in the above air conditioner, the parallel circuit is provided with a second on-off valve in series with the flow rate adjusting means.

  According to the present invention, the second on-off valve is provided in series with the flow rate adjusting means. Since this circuit is provided between the second indoor heat exchanger (evaporator) and the compressor inlet side, it has a function of restricting the flow of refrigerant so that the evaporation pressure does not decrease below a certain pressure. . Therefore, for any second indoor unit, the first on-off valve is closed and the second on-off valve is opened to control the refrigerant evaporation pressure in the second indoor heat exchanger (Evaporative Pressure Regulator (hereinafter referred to as “EPR”). ).), The second indoor unit can be continuously operated by preventing the second indoor heat exchanger from freezing while avoiding frequent thermo-off even at a low outside air temperature. Therefore, it can be used in places where cooling is necessary throughout the year, such as a computer room, and the application can be expanded.

  Furthermore, the air conditioner of the present invention is any one of the above-described air conditioners, characterized in that a receiver is provided in the liquid pipe in the branch box.

  According to the present invention, since the receiver is provided in the liquid pipe in the branch box, the necessity in the system is obtained by using the receiver together with the liquid reservoir using the second indoor unit or by the liquid reservoir function of the receiver alone. Even if the amount of refrigerant fluctuates greatly, it can be reliably absorbed and stable operation can be performed.

According to the present invention, the second indoor unit that does not include the expansion valve can be connected to the outdoor unit of the multi-type air conditioner while being mixed with the first indoor unit. On the other hand, it becomes possible to connect so-called pair type air conditioner second indoor units. Therefore, it is possible to share the second indoor unit and improve its productivity. In addition, since the second indoor unit does not include an expansion valve, there is no generation of refrigerant flow noise due to the expansion valve, and various multi-type air conditioners that combine the second indoor unit with excellent quietness are provided. be able to. Further, by appropriately controlling the first on-off valve and the second expansion valve provided in each branch gas pipe and branch liquid pipe, the second indoor unit that is thermo-off and its refrigerant pipe are used as a liquid reservoir. Can do. Thereby, since the fluctuation | variation of a required refrigerant | coolant amount can be absorbed easily, it can be made to drive | operate appropriately, without increasing the receiver capacity | capacitance provided in an outdoor unit. In addition, by closing the first on-off valve of the thermo-off indoor unit during heating and shutting off refrigerant inflow, overheating can be prevented and comfortable air conditioning can be performed. Furthermore, even if the first on-off valve is closed due to the heating thermo-off, the refrigerant can be bypassed from the gas pipe side to the liquid pipe side via the bypass circuit. It is possible to prevent oil from staying.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows a refrigerant circuit diagram of a multi-type air conditioner 1 according to an embodiment of the present invention, and FIG. 2 shows an enlarged configuration diagram of the branch box.
The air conditioner 1 according to the present embodiment is connected to one outdoor unit 2, a plurality of indoor units 3A and 3B connected in parallel to the outdoor unit 2, and the indoor units 3A and 3B in parallel. And a plurality of indoor units 6A and 6B connected to the branch box 4 in parallel with each other.

  The outdoor unit 2 includes an inverter-driven compressor 21 that compresses the refrigerant, a four-way switching valve 22 that switches the circulation direction of the refrigerant, an outdoor heat exchanger 23 that exchanges heat between the refrigerant and the outside air, and an outdoor electronic expansion valve 24. And at least a receiver 25 for storing liquid refrigerant, which are connected by a refrigerant pipe 26 as is well known to constitute a refrigerant circuit 27 on the outdoor unit 2 side. From the outdoor unit 2, a gas pipe 7 and a liquid pipe 8 to which the indoor units 3A and 3B and the branch box 4 are connected are led out.

  Each of the indoor units 3A and 3B includes an indoor heat exchanger 31 that exchanges heat with room air and an indoor electronic expansion valve 32, and is disposed in each air-conditioning zone or each room. The indoor units 3A and 3B are configured as indoor units of multi-type air conditioners (hereinafter referred to as “multi-unit indoor units”), and have an indoor electronic expansion valve 32 for individually controlling the amount of refrigerant circulation. Built-in. The multi-unit indoor units 3A and 3B are connected in parallel to the gas pipe 7 and the liquid pipe 8 led out from the outdoor unit 2 through the indoor side gas pipe 33 and the indoor side liquid pipe 34.

  The branch box 4 includes a plurality of sets of branch gas pipes 41A and 41B and branch liquid pipes 42A and 42B branched from the gas pipe 7 and the liquid pipe 8, and first solenoid valves (SV1) provided in the branch gas pipes 41A and 41B. ) (First on-off valve) 43A, 43B, electronic expansion valves 44A, 44B for indoor units 6A, 6B provided in the branch liquid pipes 42A, 42B, flow rate adjusting capillary tubes 45A, 45B connected in series, The second solenoid valve (SV2) (second on-off valve) 46A, 46B is provided, and parallel circuits 47A, 47B connected in parallel to the first solenoid valve (SV1) 43A, 43B, and a thick pipe provided in the liquid pipe 7. A receiver 48 constituted by a pipe is connected between the gas pipe 6 and the liquid pipe 7, and the liquid distribution is performed from the flow rate adjusting capillary tube 49 and the gas pipe 6 side. Temperature sensors 52A, 52B and 53A, 53B provided in the bypass circuit 51 having a check valve 50 that allows only the refrigerant flow to the 7 side, the branch gas pipes 41A, 41B, and the branch liquid pipes 42A, 42B, respectively. And is connected to the gas pipe 7 and the liquid pipe 8 in parallel with the indoor units 3A and 3B.

Each of the indoor units 6A and 6B includes an indoor heat exchanger 61 that exchanges heat with room air, and is disposed in each air conditioning zone or each room. The indoor units 6A and 6B are configured as a pair type air conditioner indoor unit (hereinafter referred to as "pair unit indoor unit") and do not include an expansion valve. The paired indoor units 6A and 6B are connected in parallel to each other between the branch gas pipes 41A and 41B and the branch liquid pipes 42A and 42B of the branch box 4 through the indoor side gas pipe 62 and the indoor side liquid pipe 63. .
The branch box 4 is disposed at an appropriate position away from the outdoor unit 2 and at an appropriate position convenient for piping for the plurality of paired indoor units 6A and 6B connected to the branch box 4. Established.

Next, the operation state of the air conditioner 1 described above will be described with reference to the refrigerant flowcharts shown in FIGS. 3 to 6 and the flowcharts shown in FIGS. 7 to 11. Here, the operating states of the branch box 4 and the paired indoor units 6A and 6B will be mainly described.
[When starting]
As shown in FIG. 7, in the stopped state, the compressor 21 is stopped, the electronic expansion valves 44A and 44B are opened (the degree of opening is undecided), the first electromagnetic valves (SV1) 43A and 43B are closed, and the second The electromagnetic valves (SV2) 46A and 46B are opened. When the remote control switch or the like is turned on in this state and the operation is started (S1), it is determined whether the operation mode is cooling or heating (S2). In the cooling mode, since it is unclear whether the excess refrigerant was stored in the receiver 25 or the paired indoor units 6A and 6B in the previous operation, all the indoor units were installed for the purpose of preventing liquid back at startup. The liquid back prevention suppression control is performed on the target. In this liquid back prevention suppression control, after the compressor 21 is started, the first electromagnetic valve (SV1) 43A, 43B is closed, the second electromagnetic valve (SV2) 46A, 46B is opened for a certain time (for example, 2 minutes), The indoor electronic expansion valve 32 and the electronic expansion valves 44A and 44B are executed with a fixed opening (set opening). After a predetermined time (2 minutes) has elapsed, the first solenoid valves (SV1) 43A and 43B are opened, and the second solenoid valves (SV2) 46A and 46B are closed (may be opened). The expansion valves 44A and 44B are each shifted to normal control, and normal cooling operation is performed (S3).

  In the normal control described above, the indoor electronic expansion valve 32 is controlled so that the outlet superheat degree of the indoor heat exchanger 31 becomes a set value by an indoor controller (not shown) built in the multi-machine indoor units 3A and 3B. Be controlled. On the other hand, the refrigerant circulation amount to the paired indoor units 6A and 6B having no expansion valve is such that the electronic expansion valves 44A and 44B provided in the branch box 4 are branched gas pipes 41A and 41B and branch liquid pipes 42A, Based on the detection values of temperature sensors 52A, 52B and 53A, 53B provided in 42B, the control is performed by PI control so that the outlet superheat degree of the indoor heat exchanger 61 becomes a set value.

Further, in the heating mode, since the high-pressure refrigerant gas is pushed from the gas pipe 7 side, there is no fear of liquid back, and the reliability of the system is ensured. Therefore, after the compressor 21 is started (for example, 2 minutes), the first solenoid valves (SV1) 43A and 43B are opened, and the second solenoid valves (SV2) 46A and 46B are closed (may be opened). The electronic expansion valve 32 and the electronic expansion valves 44A and 44B are shifted to normal control, respectively, and normal heating operation is performed (S4).
In this case, the normal control is controlled by PI control of the degree of outlet supercooling of the indoor heat exchangers 31 and 61 as in the case of cooling.
[Cooling cycle operation]
FIG. 3 shows the refrigerant flow during the cooling cycle operation. The refrigerant compressed by the compressor 21 is led to the outdoor heat exchanger 23 by the four-way switching valve 22 as shown by solid arrows, and is heat-exchanged with the outside air to be condensed and liquefied. The liquid refrigerant is once stored in the receiver 25, then led out from the outdoor unit 2 through the liquid pipe 8, and is divided into the multi-unit indoor units 3 </ b> A and 3 </ b> B and the branch box 4. The refrigerant introduced into the indoor units 3A and 3B for the multi-machine through the indoor side liquid pipe 34 is adiabatically expanded by the indoor electronic expansion valve 32, and then flows into the indoor heat exchanger 31 to exchange heat with indoor air. The indoor air is cooled to evaporate gas, and reaches the gas pipe 7 through the indoor side gas pipe 33.

  The refrigerant branched into the branch box 4 is further branched into a plurality of sets of branch liquid pipes 42A and 42B in the branch box 4, and then reaches the electronic expansion valves 44A and 44B, where it is adiabatically expanded and gas-liquid The two-phase refrigerant is transported through the indoor side liquid pipe 63 to the paired indoor units 6A and 6B. The refrigerant introduced into the paired indoor units 6A and 6B flows into the indoor heat exchanger 61, exchanges heat with the indoor air, and is converted into evaporative gas by cooling the indoor air, and branches through the indoor side gas pipe 62. It reaches the branch gas pipes 41A and 41B of the box 4, and further passes through the first electromagnetic valves (SV1) 43A and 43B to the gas pipe 7. The refrigerant is combined with the refrigerant from the multi-unit indoor units 3A and 3B through the gas pipe 7 and returned to the outdoor unit 2, and is sucked into the compressor 21 through the four-way switching valve 22 and then compressed again, thereby cooling operation. Is done.

[Cooling thermo ON / OFF operation]
During the cooling operation, the multi-unit indoor units 3A and 3B and the paired indoor units 6A and 6B are in either the thermo-ON state or the thermo-OFF state as shown in FIG. In the indoor unit 3A for multi-units in the thermo-ON state, the indoor electronic expansion valve 32 is PI-controlled as described above, and the adiabatically expanded refrigerant is supplied to the indoor heat exchanger 31 and is subjected to a cooling operation. On the other hand, in the indoor unit 3B for multi-units in the thermo OFF state, the indoor electronic expansion valve 32 is fully closed, and the supply of refrigerant to the indoor heat exchanger 31 is stopped.

Further, in the paired indoor units 6A and 6B, the first solenoid valves (SV1) 43A and 43B, the second solenoid valves (SV2) 46A and 46B, and the electronic expansion valves 44A and 44A in the branch box 4 are turned on and off by the thermo. 44B is in the following state as shown in FIG.
(1) Thermo-ON indoor unit (refer to paired indoor unit 6A in FIG. 3)
The first solenoid valve (SV1) 43A is opened, the second solenoid valve (SV2) 46A is closed, and the electronic expansion valve 44A is PI-controlled. Thereby, the refrigerant adiabatically expanded by the electronic expansion valve 44A is supplied to the indoor heat exchanger 61, and is supplied to the cooling operation.
(2) Thermo OFF indoor unit (no refrigerant accumulation)
The first solenoid valve (SV1) 43A is opened, the second solenoid valve (SV2) 46A is closed, and the electronic expansion valve 44A is fully closed. Thereby, the refrigerant supply to the indoor heat exchanger 61 is stopped, and the thermo is turned off.
(3) Thermo OFF indoor unit (with refrigerant storage) (see indoor unit 6B for pair machine in FIG. 3)
The first solenoid valve (SV1) 43A is closed, the second solenoid valve (SV2) 46A is opened (may be closed), and the electronic expansion valve 44A is fully opened. As a result, surplus liquid refrigerant is supplied to and stored in the indoor heat exchanger 61, the indoor side gas pipe 62, and the indoor side liquid pipe 63, and the thermo is turned off.

Here, the operation when the paired indoor unit 6B that has been thermo-off is thermo-ON will be described with reference to FIG.
When the thermo-ON command is issued (S11), it is determined whether or not liquid refrigerant is stored in the paired indoor unit 6B (S12). In this case, the system can determine whether or not the liquid refrigerant is stored in the indoor heat exchanger 61. When the liquid refrigerant is stored, the liquid back prevention suppression control is performed on the paired indoor unit 6B. In this liquid back prevention suppression control, the first solenoid valve (SV1) 43B is closed, the second solenoid valve (SV2) 46B is opened, and the electronic expansion valve 44B is fixed after a thermo-ON command for a certain time (for example, 2 minutes). It is executed as an opening (set opening). After a predetermined time (2 minutes), the first solenoid valve (SV1) 43B is opened, the second solenoid valve (SV2) 46B is closed (may be opened), and the electronic expansion valve 44B is normally controlled (indoor heat exchanger). 61, and the normal cooling operation is performed (S13).
On the other hand, when the liquid refrigerant is not stored, the first solenoid valve (SV1) 43B is opened, the second solenoid valve (SV2) 46B is closed (may be opened), and the electronic expansion valve 44B is normally controlled ( It is set as the outlet superheat degree PI control of the indoor heat exchanger 61), and the normal cooling operation is performed as it is (S14).

[Refrigerant accumulation judgment during cooling]
The operation of storing the excess liquid refrigerant in the above-described thermo-OFF indoor unit (see the paired indoor unit 6B in FIG. 3) will be described with reference to FIG.
The refrigerant needs to be stored when the capacity changes during operation, that is, when the number of indoor units operated changes (S21). For example, the stop machine is started, the thermo-ON indoor unit is thermo-OFF, or the thermo-ON room is in operation. The remote control of the machine is off. In this case, first, it is determined whether or not excess refrigerant is generated (S22). In the case of cooling, for example, when the degree of outlet supercooling of the outdoor heat exchanger (here, condenser) 23 is 10 Degg or more and the high pressure is 3.5 MPaG or more, the capacity of the receiver 25 is exceeded. Therefore, it is determined that there is excess refrigerant. Otherwise, it is determined that there is no surplus refrigerant.

  If it is determined that there is surplus refrigerant, the indoor unit storage quality is subsequently determined (determination of condensation risk) (S23). In the case of cooling, this indoor unit storage quality is normally determined by determining the indoor dew point temperature from the detected values of the humidity sensor and the suction temperature sensor provided in the indoor unit, and checking the liquid refrigerant temperature from the operating state, When both are compared, if the liquid refrigerant temperature <dew point temperature, it is determined that condensation has occurred, and if the liquid refrigerant temperature> dew point temperature, it is determined that no condensation has occurred. If it is determined that condensation has occurred, the surplus refrigerant cannot be stored in the indoor unit, the liquid refrigerant is held in the branch liquid pipe 42A and the receiver 48 (S24), and the process returns to the determination of whether surplus refrigerant has been generated (S22). .

If it is determined that no condensation has occurred, accumulation of surplus refrigerant in the paired indoor unit 6B that is thermo-off is started (S25). As shown in FIG. 3, the surplus refrigerant is stored in the indoor unit by closing the first solenoid valve (SV1) 43B, opening the second solenoid valve (SV2) 46B, and opening the electronic expansion valve 44B of the pair unit indoor unit 6B. It is executed as fully open. When this process is executed, normal control is continued (S26). In the above description, the normal control is continued even when it is determined that there is no surplus refrigerant (S26).
As described above, the presence / absence of surplus refrigerant is determined, and whether or not the indoor unit is stored is determined to prevent condensation from occurring when excess refrigerant is stored in the paired indoor units 6A and 6B and functions as a receiver. In order to prevent the condensed water from dripping into the room.

[Evaporation pressure control judgment during cooling at low outside air temperature]
If the cooling operation is continued at a low outside air temperature, the evaporation temperature of the indoor heat exchanger (evaporator) may be lowered and frosted. In such a case, the frost prevention sensor generally operates and the thermo is turned off. In this embodiment, as shown in FIG. 10, by performing the evaporation pressure control determination, the cooling operation can be continued even at a low outside air temperature. This evaporation pressure control determination is performed for each indoor unit during the cooling operation (S31).
First, it is determined whether the continuous operation time of each paired indoor unit 6A, 6B is, for example, 20 minutes or longer (S32). Here, if the continuous operation time is 20 minutes or more, the operation is continued as it is (S33), and if the continuous operation time is less than 20 minutes, the ON / OFF count is next determined (S34). For example, if the number of ON / OFF times per hour is less than 4, it is determined as normal thermo ON / OFF, and the operation is continued as it is (S33). On the other hand, when the number of ON / OFF times is 4 or more, the evaporation pressure control is executed (S35).

The evaporation pressure control (EPR function) is performed by closing the first electromagnetic valves (SV1) 43A and 43B provided in the branch box 4 and opening the second electromagnetic valves (SV2) 46A and 46B. FIG. 4 shows a refrigerant flow diagram during the low outside air temperature cooling cycle operation in which the evaporation pressure control is performed. Here, the evaporation pressure control is executed with the paired indoor unit 6B in the thermo-ON state, the first solenoid valve (SV1) 43B is closed, the second solenoid valve (SV2) 46B is opened, and the electronic expansion is performed. The valve 44B is PI controlled. Thus, the refrigerant evaporated in the indoor heat exchanger 61 of the paired indoor unit 6B flows through the flow rate adjusting capillary tube 45B, increasing the evaporation pressure and increasing the evaporation temperature. For this reason, the frost of the indoor heat exchanger 61 is prevented, and the operation of the paired indoor unit 6B is continued.
The paired indoor unit 6A is thermo-off, the first solenoid valve (SV1) 43A is opened, the second solenoid valve (SV2) 46A is closed (may be opened), and the electronic expansion valve 44A is fully closed. A state in which no liquid refrigerant is accumulated is shown.

[Heating cycle operation]
FIG. 5 shows the refrigerant flow during the heating cycle operation. The refrigerant compressed by the compressor 21 is guided to the gas pipe 7 side by the four-way switching valve 22 as shown by a solid line arrow, and is divided into the multi-machine indoor units 3A and 3B and the branch box 4 through the gas pipe 7. Is done. The refrigerant introduced into the indoor units 3A and 3B for the multi-machine through the indoor side gas pipe 33 dissipates heat in the indoor heat exchanger 31 to heat indoor air and is used for heating. The degree of supercooling of the refrigerant liquefied by releasing heat in the indoor heat exchanger 31 is controlled by the indoor electronic expansion valve 32 that is PI-controlled, and reaches the liquid pipe 8 through the indoor side liquid pipe 34. On the other hand, the refrigerant branched to the branch box 4 side is branched into a plurality of sets of branch gas pipes 41A and 41B in the branch box 4, and then passes through the first electromagnetic valves (SV1) 43A and 43B to form a pair machine room. It is introduced into the indoor heat exchanger 61 of the machines 6A and 6B. The refrigerant introduced into the indoor heat exchanger 61 radiates heat here to heat indoor air and is used for heating. The degree of supercooling of the refrigerant condensed and liquefied in the indoor heat exchanger 61 is controlled by the PI-controlled electronic expansion valves 44A and 44B, and reaches the liquid pipe 8 via the branch liquid pipes 42A and 42B.

The refrigerant merged in the liquid pipe 8 as described above returns to the outdoor unit 2 through the liquid pipe 8 and reaches the outdoor expansion valve 24 through the receiver 25. The refrigerant adiabatically expanded by the outdoor expansion valve 24 is introduced into the outdoor heat exchanger 23 and is evaporated and gasified by absorbing heat from the outside air. This low-pressure gas refrigerant is sucked into the compressor 21 through the four-way switching valve 22 and is repeatedly compressed, whereby the heating operation is performed.
When the paired indoor units 6A and 6B are thermo-off during the heating cycle operation, the refrigerant and lubricating oil condensed therein are collected in the gas pipe 7 leading to the branch box 4 so as not to be retained. Bypass to the liquid piping 8 side through a bypass circuit 51 having a capillary tube 49 and a check valve 50.

[Heating thermo ON / OFF operation]
During the heating operation, the multi-unit indoor units 3A and 3B and the paired indoor units 6A and 6B are in either the thermo-ON state or the thermo-OFF state, as shown in FIGS. In the indoor unit 3A for multi-units in the thermo-ON state, high-temperature and high-pressure refrigerant gas is supplied to the indoor heat exchanger 31, and heating operation is performed by the heat radiation. The indoor electronic expansion valve 32 is PI-controlled as described above to control the degree of supercooling of the refrigerant to be condensed and liquefied. On the other hand, in the indoor unit 3B for multi-units in the thermo OFF state, the indoor electronic expansion valve 32 is slightly opened so that the naturally condensed refrigerant does not accumulate in the indoor heat exchanger 31.

Further, in the paired indoor units 6A and 6B, the first solenoid valves (SV1) 43A and 43B, the second solenoid valves (SV2) 46A and 46B, and the electronic expansion valves 44A and 44A in the branch box 4 are turned on and off by the thermo. As shown in FIG. 11, 44B is in the following state.
(1) Thermo-ON indoor unit (refer to paired indoor unit 6A in FIGS. 5 and 6)
The first solenoid valve (SV1) 43A is opened, the second solenoid valve (SV2) 46A is closed, and the electronic expansion valve 44A is PI-controlled. As a result, the high-temperature and high-pressure refrigerant gas is supplied to the indoor heat exchanger 61 and is used for heating.
(2) Thermo OFF indoor unit (with refrigerant storage) (see indoor unit 6B for pair machine in FIG. 5)
The first solenoid valve (SV1) 43B is closed, the second solenoid valve (SV2) 46B is opened, and the electronic expansion valve 44B is slightly opened. As a result, excess liquid refrigerant is stored in the indoor heat exchanger 61 and the indoor side gas pipe 62, and the thermo is turned off. In this case, the electronic expansion valve 44B is slightly opened to flow a small amount of refrigerant so that the lubricating oil is not retained.
(3) Thermo-OFF indoor unit (no refrigerant accumulation) (refer to pair unit indoor unit 6B in FIG. 6)
The first solenoid valve (SV1) 43B is closed, the second solenoid valve (SV2) 46B is closed, and the electronic expansion valve 44B is slightly opened. As a result, the supply of refrigerant to the indoor heat exchanger 61 is completely shut off, and the thermo is turned off.

Here, an operation when the paired indoor unit 6B that has been thermo-off is thermo-ON will be described with reference to FIG.
In the heating cycle operation, as described above, since the high-pressure refrigerant gas is pushed from the gas pipe 7, there is no fear of liquid back, and the reliability of the system is ensured. Therefore, when the thermo-ON command is issued (S41), the first solenoid valves (SV1) and 43B are immediately opened and the second solenoid valve (SV2) 46B is closed (may be opened). Further, the electronic expansion valve 44B is shifted to the normal PI control, and the normal heating operation is performed as it is (S42).

Thus, according to the present embodiment, the following effects can be obtained.
For a plurality of sets of branch gas pipes 41A and 41B and branch liquid pipes 42A and 42B branched from the gas pipe 7 and the liquid pipe 8, respectively, and for pair machine indoor units 6A and 6B provided in the respective branch liquid pipes 42A and 42B The branch box 4 having the electronic expansion valves 44A and 44B and the first electromagnetic valves 43A and 43B provided in the branch gas pipes 41A and 41B is led out from the outdoor unit 2 of the multi-type air conditioner 1. It connects between the gas piping 7 and the liquid piping 8, and the indoor unit 6A, 6B for pair machines is connected to this branch box 4. This makes it possible to connect the paired indoor units 6A and 6B that do not incorporate the expansion valve to the outdoor unit 2 of the multi-type air conditioner 1 in a mixed manner with the multi-unit indoor units 3A and 3B. Therefore, the paired indoor units 6A and 6B can be mixedly connected to the outdoor unit 2 of the multi-type air conditioner 1, and the productivity can be improved by sharing the paired indoor units 6A and 6B. it can.

Further, since the paired indoor units 6A and 6B do not include an expansion valve, the paired indoor units 6A and 6B have a feature that refrigerant flow noise is not generated when the refrigerant is gas-liquid two-phase flow by the expansion valve. Therefore, it is possible to provide various multi-type air conditioners that combine the paired indoor units 6A and 6B having the quietness utilizing this feature.
In addition, the liquid pipe 63 between the branch box 4 and the paired indoor units 6A and 6B is a refrigerant transport using a gas-liquid two-phase refrigerant during cooling, and depending on the installation position of the branch box 4, it may be necessary in the system when the capacity changes. The amount of refrigerant fluctuates greatly. However, the presence or absence of excess refrigerant is determined, and the first electromagnetic valves 43A and 43B and the electronic expansion valves 44A and 44B are appropriately controlled to use the indoor units 6A and 6B for thermostat-off as a liquid reservoir. Can do. For this reason, the fluctuation | variation of a required refrigerant | coolant amount can be absorbed easily and it can be made to drive | operate appropriately, without increasing the capacity | capacitance of the receiver 25 provided in the outdoor unit 2. FIG.

Further, since the first electromagnetic valves 43A and 43B are provided in the branch gas pipes 41A and 41B, the refrigerant flows into the indoor heat exchanger 61 by closing the first electromagnetic valves 43A and 43B when the heating thermo-off is performed. Can be blocked. Therefore, comfortable air conditioning without overheating can be realized.
Furthermore, temperature sensors 52A, 52B for controlling the opening degree of the electronic expansion valves 44A, 44B are respectively connected to the branch gas pipes 41A, 41B and the branch liquid pipes 42A, 42B to which the paired indoor units 6A, 6B are connected. Since 53A and 53B are provided, based on the detected value, the outlet superheat control of the indoor heat exchanger 61 can be performed during cooling, and the outlet supercooling control of the indoor heat exchanger 61 can be performed during heating. Therefore, the paired indoor units 6A and 6B can be operated individually.
Furthermore, when the indoor heat exchanger 61 of the paired indoor units 6A and 6B is used as a liquid reservoir, the quality of the reservoir is determined and whether or not condensation has occurred is determined. It is possible to surely prevent dew condensation and prevent the condensation water from dripping into the room.
Further, since the branch gas pipe 62 is provided with parallel circuits 47A and 47B having flow rate adjusting capillary tubes 45A and 45B in parallel with the first electromagnetic valves 43A and 43B, the pair machine indoor units 6A and 6B are liquidated. Even when the reservoir is used, an appropriate amount of refrigerant can be flowed through the flow rate adjusting capillary tubes 45A and 45B. Therefore, it is possible to prevent the lubricating oil from being dissolved and staying in the refrigerant stored in the paired indoor units 6A and 6B.

  Furthermore, since the second electromagnetic valves 46A and 46B are provided in series with the flow rate adjusting capillary tubes 45A and 45B in the parallel circuits 47A and 47B, the first electromagnetic valve 43A, By closing 43B and opening the second electromagnetic valves 46A and 46B, the evaporation pressure in the indoor heat exchanger 61 can be controlled (EPR function). For this reason, at the time of low outside air temperature, the evaporation temperature is increased, the frost of the indoor heat exchanger 61 is prevented, the frequent thermo-off is avoided, and the paired indoor units 6A and 6B are continuously operated. Can do. Therefore, it can be used for cooling a computer room or the like, and the range of use can be expanded.

Further, since the receiver 48 is provided in the liquid pipe 8 in the branch box 4, the system can be used in combination with the liquid reservoir using the pair machine indoor units 6A and 6B or by the liquid reservoir function of the receiver 48 alone. Even if the required amount of refrigerant fluctuates greatly, it can be reliably absorbed and stable operation can be performed.
Further, a bypass circuit including a flow rate adjusting capillary tube 49 and a check valve 50 that allows only a refrigerant flow from the gas pipe 7 side to the liquid pipe 8 side between the gas pipe 7 and the liquid pipe 8 in the branch box 4. 51 is provided, even if the first electromagnetic valves 43A and 43B and the second electromagnetic valves 46A and 46B are closed by the heating thermo-off, the refrigerant is supplied from the gas pipe 7 side to the liquid pipe 8 side through the bypass circuit 51. Can be bypassed. Therefore, it is possible to prevent the refrigerant and lubricating oil condensed therein from staying in the gas pipe 7.

  In the above embodiment, the air conditioner 1 is illustrated in which two indoor units 3A and 3B for multi-machines, one branch box 4 and two indoor units 6A and 6B for pair machines are connected. However, the number of connected indoor units 3A and 3B and the paired indoor units 6A and 6B may be three or more, and two or more branch boxes 4 may be connected. Of course.

It is a refrigerant circuit diagram of the air conditioner concerning one embodiment of the present invention. It is an enlarged block diagram of the branch box of the air conditioner shown in FIG. It is refrigerant | coolant flow explanatory drawing at the time of the air_conditioning | cooling cycle driving | running (with refrigerant | coolant accumulation) of the air conditioner shown in FIG. It is refrigerant | coolant flow explanatory drawing at the time of the low external temperature air_conditioning | cooling cycle driving | operation of the air conditioner shown in FIG. It is refrigerant | coolant flow explanatory drawing at the time of the heating cycle operation | movement (with refrigerant | coolant accumulation) of the air conditioner shown in FIG. It is a refrigerant | coolant flow explanatory drawing at the time of the heating cycle driving | operation of the air conditioner shown in FIG. 1 (no refrigerant | coolant accumulation). It is a control flowchart figure at the time of starting of the air conditioner shown in FIG. It is a control flowchart figure at the time of cooling thermo ON / OFF of the air conditioner shown in FIG. It is a control flowchart figure at the time of the cooling refrigerant | coolant accumulation determination of the air conditioner shown in FIG. It is a control flowchart figure at the time of the cooling evaporation pressure control of the air conditioner shown in FIG. It is a control flowchart figure at the time of heating thermo ON / OFF of the air conditioner shown in FIG.

1 Air conditioner 2 Outdoor unit 3A, 3B Multi-unit indoor unit (first indoor unit)
4 Branch box 6A, 6B Pair machine indoor unit (second indoor unit)
7 Gas piping 8 Liquid piping 31 Indoor heat exchanger (first indoor heat exchanger)
32 Indoor electronic expansion valve (first expansion valve)
41A, 41B Branch gas piping 42A, 42B Branch liquid piping 43A, 43B First solenoid valve (first on-off valve)
44A, 44B Electronic expansion valve (second expansion valve)
45A, 45B Flow rate adjustment capillary tube (flow rate adjustment means)
46A, 46B Second solenoid valve (second on-off valve)
47A, 47B Parallel circuit 48 Receiver 49 Flow rate adjusting capillary tube (flow rate adjusting means)
50 check valve 51 bypass circuit 52A, 52B, 53A, 53B temperature sensor 61 indoor heat exchanger (second indoor heat exchanger)

Claims (6)

Gas piping and liquid derived from the outdoor unit of a multi-type air conditioner in which a plurality of first indoor units including a first indoor heat exchanger and a first expansion valve are connected to one outdoor unit In the air conditioner in which at least one branch box is connected between the pipes, and a plurality of second indoor units including the second indoor heat exchanger can be connected to the branch box.
The branch box includes a plurality of sets of branch gas pipes and branch liquid pipes branched from the gas pipe and the liquid pipe,
A second expansion valve for the second indoor unit provided in each branch liquid pipe;
A first on-off valve provided in each branch gas pipe,
The second indoor unit is connected between the branch gas pipe and the branch liquid pipe via the branch box,
Between the gas pipe and the liquid pipe before branching the plurality of sets of branch gas pipes and branch liquid pipes in the branch box, only the flow rate adjusting means and the refrigerant flow from the gas pipe side to the liquid pipe side. An air conditioner characterized in that a bypass circuit including a check valve that permits air is provided.   The temperature sensor for controlling the opening degree of the said 2nd expansion valve is provided in the said branch gas piping and the said branch liquid piping to which a said 2nd indoor unit is connected, respectively. Air conditioner.   The second indoor unit is configured to allow surplus refrigerant to be stored by determining whether or not the refrigerant is stored when the cooling thermostat is off, closing the first on-off valve, and opening the second expansion valve. The air conditioner according to claim 1 or 2.   The air conditioner according to any one of claims 1 to 3, wherein the branch gas pipe is provided with a parallel circuit including a flow rate adjusting unit in parallel with the first on-off valve.   The air conditioner according to claim 4, wherein the parallel circuit is provided with a second on-off valve in series with the flow rate adjusting means.   The air conditioner according to any one of claims 1 to 5, wherein a receiver is provided in the liquid pipe in the branch box.

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