JP6207982B2 - Cooling / heating free multi-type air conditioner refrigerant piping cleaning method - Google Patents

Description

  The present invention relates to a refrigerant pipe cleaning method for a cooling / heating free multi-type air conditioner that is renewed by reusing an existing refrigerant pipe and connecting a new outdoor unit or indoor unit thereto.

  When the air conditioner is updated to a new unit, a method may be employed in which the existing refrigerant piping system is reused and only the outdoor unit and the indoor unit are replaced with the new unit. In particular, in a multi-type air conditioner in which a plurality of indoor units are connected, the refrigerant piping system may be complicated and embedded in a building, and it is difficult to replace the refrigerant piping system. Is used as it is. This is because the outdoor unit and a plurality of indoor units are connected via three pipes, a high-pressure gas pipe, a low-pressure gas pipe and a high-pressure liquid pipe, so that the plurality of indoor units can be operated simultaneously with cooling and heating. The same applies to a free multi type air conditioner.

  In this way, when a new unit is connected and installed by reusing the existing refrigerant piping system, there is a possibility that oil corresponding to the old refrigerant or deteriorated oil may remain in the refrigerant piping system. Must be reused after washing to remove residual oil. In Patent Document 1, an oil recovery device (refresh kit) using hot gas refrigerant as a heating means is detachably connected to a low-pressure gas pipe through a plurality of operation valves. (1) High and low pressures are stable There are provided a method of performing pipe cleaning by operating in the order of preparation operation for ensuring the cooling operation state, (2) pipe cleaning operation by liquid back, and (3) refrigerant discharge operation in the tank.

JP 2012-225614 A

  What was provided by patent document 1 is related with the general multi-type air conditioner which can be switched to air_conditionaing | cooling operation and heating operation, and an outdoor unit and a plurality of indoor units are made into high pressure gas piping, such a technique, When applied to a cooling / heating free multi-type air conditioner that can be operated simultaneously with cooling and heating, connected via three pipes, a low-pressure gas pipe and a high-pressure liquid pipe, it compresses to recover residual oil in the high-pressure gas pipe. It is necessary to flow the superheated gas discharged from the machine into the high-pressure gas pipe and push the oil together with the refrigerant to the oil recovery device side by the flow velocity.

  However, if the refrigerant has stagnated on the high-pressure gas pipe side, a large amount of liquid refrigerant may be stagnant, especially in low ambient temperature conditions where the refrigerant is likely to condense. In this case, the high-pressure gas pipe is overheated by the superheated gas. Until then, the accumulated liquid refrigerant flows directly into the oil recovery tank of the oil recovery device via the low-pressure gas pipe. Therefore, the oil recovery tank overflows due to the liquid refrigerant, and the recovered oil flows out again. There was a problem such as end.

  The present invention has been made in view of such circumstances. When a cooling / heating free multi-type air conditioner is renewed by reusing an existing refrigerant piping system, a large amount of liquid refrigerant is trapped in the high-pressure gas piping. It is an object of the present invention to provide a refrigerant pipe cleaning method capable of recovering residual oil in the refrigerant pipe system stably by a cleaning operation even in the case of being discharged.

In order to solve the above-described problems, the refrigerant pipe cleaning method for a cooling / heating free multi-type air conditioner of the present invention employs the following means.
That is, the refrigerant pipe cleaning method for a cooling / heating free multi-type air conditioner according to the present invention includes three refrigerant pipe systems of a high-pressure gas pipe, a low-pressure gas pipe, and a high-pressure liquid pipe led out from an outdoor unit, A plurality of branch flow controllers having a switching valve are connected between a gas pipe and the low pressure gas pipe, and a plurality of indoor units are connected in parallel between the switching valve of the branch flow controller and the high pressure liquid pipe. The three high-pressure gas pipes, low-pressure gas pipes and high-pressure liquid pipes of the existing cooling / heating free multi-type air conditioner are reused by reusing the existing refrigerant piping system, and new outdoor units and indoor units are connected to it and updated. In the cooling / heating free multi-type air conditioner refrigerant pipe cleaning method for cleaning the refrigerant pipe system, the low-pressure gas pipe connected to the outdoor unit is connected to the three refrigerant pipe systems. An oil recovery device comprising an oil recovery tank for recovering the oil retained together with the refrigerant, and heating means for heating and evaporating the refrigerant recovered in the oil recovery tank and sucking the refrigerant into the compressor. In this state, the cooling / heating free multi-type air conditioner is operated by a cooling cycle, and the superheated gas discharged from the compressor is first flowed into the high-pressure gas pipe, so that the high-pressure at the flow rate. The oil remaining in the gas pipe is recovered together with the liquid refrigerant, etc., and during that time, the heating means of the oil recovery device is operated to perform a preparatory operation to evaporate the refrigerant, and then the electronic expansion valve of the indoor unit is opened. The liquid back operation state is performed in a slight manner, and the three high-pressure gas pipes, the low-pressure gas pipes, and the high-pressure liquid pipes are washed.

  According to the present invention, the existing high-pressure gas pipe, low-pressure gas pipe, and high-pressure liquid pipe are reused, and a new outdoor unit and indoor unit are connected to the cooling / heating-free multi-type air conditioner. When the oil corresponding to the old refrigerant remaining in the high-pressure gas pipe, low-pressure gas pipe, and high-pressure liquid pipe is washed with flowing refrigerant, if three pipes are washed at the same time, a large amount of liquid is contained in the high-pressure gas pipe. If the refrigerant is sunk, the liquid refrigerant flows into the oil recovery device via the low-pressure gas pipe until the high-pressure gas pipe is overheated by the superheated gas from the compressor, and the oil recovery tank overflows. Because there is a risk, first by flowing the superheated gas from the compressor to the high-pressure gas pipe in the preparatory operation, the oil remaining in the high-pressure gas pipe is recovered in the oil recovery tank together with the liquid refrigerant at that flow rate, in the meantime, The heating means of the recovery device to function to prevent the overflow of the oil recovery tank by evaporating the refrigerant. After that, when the liquid refrigerant in the high-pressure gas pipe is expelled, the operation mode is switched to the washing operation, and the electronic expansion valve on the indoor unit side is opened to enter the liquid back operation state, whereby three high-pressure gas pipes, low-pressure gas The oil corresponding to the old refrigerant remaining in the pipe and the high-pressure liquid pipe can be washed with the liquid-backed refrigerant and the high-pressure superheated refrigerant and recovered in the oil recovery tank of the oil recovery device. Therefore, liquid refrigerant accumulates in the oil recovery tank of the oil recovery device, avoids the risk of overflow, recovers residual oil, and cleans the refrigerant piping to be reused, thereby renewing the cooling / heating free multi Stable operation of the air conditioner can be ensured. In particular, even under a low outside temperature at which the refrigerant is likely to condense, the residual oil can be recovered steadily by a stable operation.

  Further, the cooling / heating free multi-type air conditioner refrigerant pipe cleaning method of the present invention is the above cooling / heating free multi-type air conditioner refrigerant pipe cleaning method, wherein the preparatory operation is accumulated in the main pipe of the high-pressure gas pipe. It is operated for a preset time based on the maximum amount of refrigerant that may be possible and the refrigerant flow rate that is returned to the low-pressure gas pipe through the shunt controller during the preliminary operation, and then switched to the cleaning operation. Features.

  According to the present invention, preparation is made for a preset time based on the maximum amount of refrigerant that may be accumulated in the main pipe of the high-pressure gas pipe and the refrigerant flow rate that is returned to the low-pressure gas pipe through the shunt controller during the preliminary operation. Since it is operated and then switched to the cleaning operation, it is possible to avoid an excessive increase in the pipe cleaning operation time due to the preparation operation. In other words, the maximum amount of refrigerant that can accumulate in the main pipe of the high-pressure gas pipe can be calculated from the length and diameter of the pipe, while the refrigerant returned to the low-pressure gas pipe through the shunt controller during the preparatory operation Since the flow rate can be calculated by obtaining the flow rate of a fixed throttle (capillary tube) etc. provided in the path, the time required for completely expelling the liquid refrigerant accumulated in the main pipe of the high-pressure gas pipe can be obtained. It can be predicted in advance. Therefore, by setting the time as the preparatory operation time and switching to the cleaning operation, it is possible to stably perform the pipe cleaning operation while avoiding an excessive increase in the cleaning operation time.

  Furthermore, the refrigerant pipe cleaning method for a cooling / heating free multi-type air conditioner according to the present invention is the refrigerant piping cleaning method for any one of the above-described cooling / heating free multi-type air conditioners, wherein the shunt controller includes the high-pressure gas piping. A parallel circuit of a first solenoid valve and a fixed throttle is connected to the inlet side of the switching valve, and a second solenoid valve that bypasses the switching valve and the parallel circuit between the high-pressure gas pipe and the low-pressure gas pipe. And an oil return operation bypass circuit having a fixed throttle is connected, and the first solenoid valve and the second solenoid valve of each circuit are closed during the preparatory operation and opened during the cleaning operation. Features.

  According to the present invention, in the shunt controller, the parallel circuit of the first electromagnetic valve and the fixed throttle is connected to the inlet side of the switching valve of the high pressure gas pipe, and the switching valve is provided between the high pressure gas pipe and the low pressure gas pipe. And a second solenoid valve for bypassing the parallel circuit and an oil return operation bypass circuit having a fixed throttle are connected. The first solenoid valve and the second solenoid valve of each circuit are closed during the preparation operation and opened during the cleaning operation. Therefore, during the preparatory operation for collecting a large amount of liquid refrigerant that may be trapped in the high-pressure gas pipe together with the residual oil, the liquid refrigerant is adjusted by a fixed throttle connected in parallel with the first solenoid valve. By returning to the low-pressure gas pipe little by little, it is possible to prevent an oil recovery tank from overflowing due to a large amount of liquid refrigerant being returned at once. That is, in the shunt controller, in order to prevent switching noise caused by switching of the switching valve under high differential pressure, a parallel circuit of the first solenoid valve and the fixed throttle is provided on the inlet side, and oil return during heating operation is further provided. An oil return operation bypass circuit having a second solenoid valve and a fixed throttle is provided between the high-pressure gas pipe and the low-pressure gas pipe in order to efficiently operate and prevent refrigerant flow noise at that time. And by opening and closing the first and second solenoid valves during the preparatory operation and the cleaning operation when the refrigerant pipe is cleaned, using the first solenoid valve and the second solenoid valve provided in each circuit. The return amount of the refrigerant from the high-pressure gas pipe can be controlled appropriately. Therefore, it is possible to prevent overflow of the oil recovery tank due to a large amount of liquid refrigerant stored in the high-pressure gas pipe flowing into the oil recovery device at a time, and to stabilize the pipe cleaning operation including the preparation operation.

  Furthermore, the refrigerant pipe cleaning method for a cooling / heating free multi-type air conditioner according to the present invention is the refrigerant pipe cleaning method for any one of the above-described cooling / heating free multi-type air conditioners, wherein the heating means of the oil recovery device is the compressor. From which the hot gas refrigerant can be circulated through an electromagnetic valve, and at least during the preparatory operation, the electromagnetic valve is opened and the hot gas refrigerant is introduced to be recovered together with oil in the oil recovery tank. The refrigerant is capable of being heated.

  According to the present invention, the heating means of the oil recovery device is configured such that hot gas refrigerant from the compressor can be circulated through the electromagnetic valve, and at least during the preparatory operation, the electromagnetic valve is opened, and the hot gas refrigerant is Since the refrigerant recovered together with the oil in the oil recovery tank can be heated by being introduced, in the oil recovery apparatus, a part of the hot gas refrigerant discharged from the compressor is supplied to the heating means via the electromagnetic valve. By introducing it, the refrigerant can be heated and evaporated by using it as a heat source. Accordingly, it is possible to prevent the oil recovery tank from overflowing due to the liquid refrigerant during the preparation operation.

  According to the present invention, at the time of pipe cleaning, first, the superheated gas from the compressor is caused to flow through the high-pressure gas pipe in a preparatory operation, so that the oil remaining in the high-pressure gas pipe is recovered in the oil recovery tank together with the refrigerant at that flow rate. In the meantime, the oil recovery tank is prevented from overflowing by causing the heating means of the oil recovery device to function and evaporating the refrigerant. After that, when the liquid refrigerant in the high-pressure gas pipe is expelled, the operation mode is switched to the washing operation, and the electronic expansion valve on the indoor unit side is opened to enter the liquid back operation state, whereby three high-pressure gas pipes, low-pressure gas The oil corresponding to the old refrigerant remaining in the piping and high-pressure liquid piping can be washed with the back-backed refrigerant and superheated refrigerant gas and recovered in the oil recovery tank of the oil recovery device. Stabilizes the renewed cooling / heating free multi-type air conditioner by recovering residual oil by avoiding the risk of liquid refrigerant accumulating in the oil recovery tank and overflowing, and by reliably cleaning the refrigerant piping to be reused Driving can be ensured. In particular, even under a low outside temperature at which the refrigerant is likely to condense, the residual oil can be recovered steadily by a stable operation.

It is a block diagram of the cooling / heating free multi type air conditioner used for the refrigerant | coolant piping washing | cleaning method of the cooling / heating free multi type air conditioner which concerns on one Embodiment of this invention. It is operation | movement explanatory drawing of the solenoid valve provided in the shunt controller and oil collection | recovery apparatus of the said cooling / heating free multi-type air conditioner.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2.
FIG. 1 shows a configuration diagram of a cooling / heating free multi-type air conditioner used in a refrigerant pipe cleaning method for a cooling / heating free multi-type air conditioner according to an embodiment of the present invention.
The cooling / heating free multi-type air conditioner 1 includes a single outdoor unit (outdoor unit) 2 and a plurality of indoor units (indoor units) 3 connected in parallel to the outdoor unit 2. Here, two indoor units (indoor units) 3 are shown and are indicated as indoor units 3A and 3B, respectively, but it is needless to say that more indoor units 3 can be connected.

  The outdoor unit (outdoor unit) 2 includes a compressor, an oil separator, a four-way switching valve for switching between heating and cooling, an outdoor heat exchanger, an electronic expansion valve, a receiver, a supercooling heat exchanger, an accumulator, and other outdoor unit side devices. One outdoor unit or a plurality of units as necessary are connected to each other through a refrigerant pipe to form an outdoor refrigerant circuit. Such an indoor unit 2 itself is known.

  From the outdoor unit 2, a high-pressure gas pipe 4 for deriving high-temperature and high-pressure superheated refrigerant gas compressed by the compressor through an operation valve from a discharge pipe branched upstream of the four-way switching valve, a four-way switching valve, The low-pressure gas pipe 5 led out from the suction pipe connected to the compressor through the accumulator through the operation valve and the high-pressure liquid refrigerant condensed by the outdoor heat exchanger and passed through the receiver, the supercooling heat exchanger, etc. Three refrigerant pipes of the high-pressure liquid pipe 6 led out through the operation valve are led out.

  A plurality of shunt controllers 7 are connected between the high-pressure gas pipe 4 and the low-pressure gas pipe 5 to the three high-pressure gas pipes 4, the low-pressure gas pipe 5 and the high-pressure liquid pipe 6 led out from the outdoor unit 2. In addition, a plurality of indoor units 3 are connected in parallel between the plurality of shunt controllers 7 and the high-pressure liquid pipe 6. The shunt controller 7 and the indoor unit 3 are connected in parallel to a branch pipe in which three high-pressure gas pipes 4, a low-pressure gas pipe 5, and a high-pressure liquid pipe 6 are branched through branch pipes. Yes. Hereinafter, the high-pressure gas pipe 4, the low-pressure gas pipe 5, and the high-pressure liquid pipe 6 before branching may be referred to as a main pipe, and the high-pressure gas pipe 4, the low-pressure gas pipe 5, and the high-pressure liquid pipe 6 after branching may be referred to as branch pipes.

  The shunt controller 7 includes an indoor side four-way switching valve (switching valve) 8 for arbitrarily switching each indoor unit 3 to the cooling operation state or the heating operation state. The indoor-side four-way switching valve 8 switches the communication state between the gas pipe connected to the indoor heat exchanger 16 of each indoor unit 3 and the branch pipe of the high-pressure gas pipe 4 or the branch pipe of the low-pressure gas pipe 5. The high-temperature and high-pressure refrigerant gas from the pipe 4 is led to each indoor unit 3 for heating, or the low-pressure refrigerant gas evaporated and vaporized by the indoor heat exchanger 16 of each indoor unit 3 during cooling is sent to the low-pressure gas pipe 5 side. It is for guiding. In addition, a part of the high-pressure refrigerant gas led to the high-pressure gas pipe 4 side during cooling is decompressed by a fixed throttle 9 such as a capillary tube and led to the low-pressure gas pipe 5 side.

  Further, in the branch flow controller 7, a parallel circuit 12 including a first electromagnetic valve (SVH) 10 on the inlet side of the indoor four-way switching valve 8 in the branch pipe of the high-pressure gas pipe 4 and a fixed throttle 11 made of a capillary tube or the like. Is connected. This parallel circuit 12 generates a switching sound when the indoor side four-way switching valve 8 is switched under a high differential pressure. Therefore, when switching the indoor side four-way switching valve 8, the first electromagnetic valve (SVH) 10 is closed and fixed. This is to suppress the generation of switching noise by reducing the pressure on the branch pipe side of the high-pressure gas pipe 4 with the throttle 11.

  Further, in the branch flow controller 7, the high-pressure gas pipe 4 is branched between the branch pipe of the high-pressure gas pipe 4 and the branch pipe of the low-pressure gas pipe 5 by bypassing the parallel circuit 12 and the indoor side four-way switching valve 8. An oil return operation bypass circuit 15 having a second solenoid valve (SVG) 13 and a fixed throttle 14 made of a capillary tube or the like that can flow a refrigerant from the piping side to the branch piping side of the low-pressure gas piping 5 is connected. ing. This oil return operation bypass circuit 15 is used when the oil return operation is performed so that the oil discharged together with the refrigerant gas from the compressor during the heating operation stays in the high-pressure gas pipe 4 and the compressor does not run out of oil. This circuit is used, and has a configuration in which a fixed throttle 14 is provided in order to reduce flow path pressure loss with respect to the parallel circuit 12 and the indoor-side four-way switching valve 8 and to prevent generation of refrigerant flow noise. .

The configuration of the diversion controller 7 described above is known from Japanese Patent Application No. 2004-316343 (Japanese Patent Laid-Open No. 2006-125762) filed with the present applicant.
The indoor unit 3 includes an indoor heat exchanger 16, a blower fan 17 that circulates indoor air through the indoor heat exchanger 16, and a liquid from a branch pipe of the high-pressure liquid pipe 6 connected to the indoor heat exchanger 16. And an electronic expansion valve 18 provided in the piping. During cooling, the indoor heat exchanger 16 cools the indoor air and supplies it to the cooling system. During heating, the indoor heat exchanger 16 heats the indoor air. It is used for heating. Each of the indoor units 3A and 3B can be individually cooled or heated.

  When the above-described cooling / heating free multi-type air conditioner 1 is reused by reusing the existing high-pressure gas pipe 4, low-pressure gas pipe 5, and high-pressure liquid pipe 6 to connect and update the new outdoor unit 2, indoor unit 3, etc. In order to wash the high-pressure gas pipe 4, the low-pressure gas pipe 5, and the high-pressure liquid pipe 6, which are the refrigerant piping system, an oil recovery device (refresh kit) 19 is detachably connected to the low-pressure gas pipe 5. ing.

  The oil recovery device (refresh kit) 19 is provided in an oil recovery tank 20 having a predetermined capacity, an oil and refrigerant inlet pipe 21 and an outlet pipe 22 connected to the oil recovery tank 20, and the oil recovery tank 20. The heating means 23 and a drain pipe 24 with a drain valve for draining oil from the oil recovery tank 20 are provided. Hot gas refrigerant discharged from the compressor in the outdoor unit 2 can be circulated in the heating means 23 through the pipe 25 and the electromagnetic valve (SV12) 26.

  The oil recovery device (refresh kit) 19 can be connected to the low-pressure gas pipe 5 via an operation valve kit 27. The operation valve kit 27 includes an operation valve 28 connected to the low-pressure gas pipe 5 and operation valves 29 and 30 to which the inlet pipe 21 and the outlet pipe 22 from the oil recovery apparatus 19 are connected. When connecting the device 19 to the low-pressure gas pipe 5, first, the operation valve kit 27 is connected to the low-pressure gas pipe 5, and the inlet pipe 21 and the outlet pipe 22 are connected to the operation valves 29 and 30 of the operation valve kit 27. The oil recovery device 19 is connectable.

  In the configuration described above, when the cooling / heating free multi-type air conditioner 1 is renewed by reusing the existing refrigerant piping system such as the high-pressure gas piping 4, the low-pressure gas piping 5, and the high-pressure liquid piping 6, those refrigerant pipings are used. It is necessary to clean the system and remove the oil corresponding to the old refrigerant and the deteriorated oil remaining in the refrigerant piping system to be reused. When cleaning the refrigerant pipe, as shown in FIG. 1, an oil recovery device (refresh kit) 19 is connected to the low-pressure gas pipe 5 via an operation valve kit 27, and the heating means 23 of the oil recovery device 19 is connected to the heating means 23. On the other hand, a hot gas refrigerant pipe 25 for circulating the hot gas refrigerant from the compressor is connected.

In this state, the pipe cleaning operation is performed. In this embodiment, the pipe cleaning operation is performed in two stages. The specific method will be described in detail below.
In the pipe cleaning operation, the cooling / heating free multi-type air conditioner 1 is usually operated by switching to the cooling cycle, and the compressor temperature and the discharge gas temperature are managed, while the electronic expansion valve 18 of each indoor unit 3 is opened. Therefore, it is common to intentionally create a liquid back operation state and wash away the oil remaining in the refrigerant pipe with the refrigerant.

  However, in this case, in addition to the refrigerant flowing out from the high pressure liquid piping 6 system through the indoor units 3 to the low pressure gas piping 5, the liquid refrigerant that has fallen into the high pressure gas piping 4 system is driven out by the superheated gas from the compressor. Then, it flows into the low-pressure gas pipe 5 and a large amount of liquid refrigerant together with oil flows into the oil recovery tank 20 of the oil recovery device 19 at the same time. As a result, the oil recovery tank 20 overflows, and there is a risk that the recovered oil will flow out again. That is, even if the liquid refrigerant stored in the high pressure gas pipe 4 system is heated by the superheated gas from the compressor, not all the liquid refrigerant is immediately evaporated, and the high pressure gas pipe 4 is in an overheated state. Until it becomes, it will flow into the low pressure gas piping 5 with a liquid refrigerant | coolant, and will flow in in the oil collection | recovery tank 20 of the oil collection | recovery apparatus 19. FIG.

In order to avoid such a situation, in this embodiment, the pipe cleaning operation is performed in two stages.
First, at the start of the cleaning operation, the electronic expansion valve 18 of the indoor unit 3 is superheated by the cooling cycle as in the normal cooling operation, and the refrigerant is evaporated by the indoor heat exchanger 16 so that the outlet superheat degree is constant. Control to be. At this time, as shown in FIG. 2, the first electromagnetic valve (SVH) 10 and the second electromagnetic valve (SVG) 13 provided in the flow dividing controller 7 are closed, and the hot connected to the heating means 23 of the oil recovery device 19. The electromagnetic valve (SV12) 26 provided in the gas refrigerant pipe 25 is opened, and the preparatory operation before the cleaning operation is started.

  Thus, the amount of refrigerant flowing out from the indoor unit 3 side to the low-pressure gas pipe 5 through the branch controller 7 is limited. On the other hand, a part of the superheated refrigerant gas discharged from the compressor flows into the high-pressure gas pipe 4. The liquid refrigerant stagnated in the high-pressure gas pipe 4 is expelled by the flow rate of the superheated gas, and the low-pressure gas pipe 5 passes through the fixed throttle 11 in the shunt controller 7, the indoor side four-way switching valve 8, and the fixed throttle 9 as liquid refrigerant. The oil remaining in the high-pressure gas pipe 4 is recovered in the oil recovery tank 20 of the oil recovery device 19 through the low-pressure gas pipe 5. The amount of the liquid refrigerant is reduced by the two fixed throttles 11 and 9, and is heated and evaporated by the heating means 23 in the oil recovery tank 20, so that the risk of overflow is eliminated.

The preparatory operation is an operation for expelling the liquid refrigerant that has fallen into the high-pressure gas pipe 4 and is continued for a preset time. This time can be set as follows.
In the case where the high-pressure gas pipe 4 is long, some of the high-pressure gas pipes exceed 100 m. For example, the amount of liquid refrigerant that accumulates in the high-pressure gas pipe 4 is calculated by calculating the main pipe volume from the length and diameter of the main pipe and the outside air temperature (= refrigerant temperature). From the refrigerant density, it is possible to calculate the maximum refrigerant amount that may be accumulated in the high-pressure gas pipe 4. In addition, it is natural that the stagnation amount of the liquid refrigerant increases at a low outside temperature where the refrigerant is easily condensed.

  On the other hand, the refrigerant outflow amount per time flowing out from the shunt controller 7 per unit to the low-pressure gas pipe 5 is the diameter and length of the fixed throttles 11 and 9 made of capillary tubes or the like and the outside air temperature (= refrigerant). Temperature), and the refrigerant outflow amount per hour can be calculated from the number of indoor units 3 connected thereto. Predicting the time required to expel all the liquid refrigerant that has accumulated in the high-pressure gas pipe 4 from the relationship between the refrigerant outflow amount and the maximum amount of refrigerant that may be accumulated in the high-pressure gas pipe 4 described above. You can do it. However, since all the refrigerant cannot be condensed and accumulated in the high-pressure gas pipe 4, the preparatory operation time may be set in consideration of this point.

  The preparatory operation for expelling the refrigerant that has fallen from the high-pressure gas pipe 4 is performed for a preset time as described above, and after that time elapses, the electronic expansion valve 18 of each indoor unit 3 is opened. Creates a liquid back operation state and shifts to a pipe cleaning operation. In this pipe washing operation, in order to improve the recovery efficiency of the residual oil while managing the compressor temperature and the discharge gas temperature, the liquid expansion operation is performed with the electronic expansion valve 18 open.

  At this time, as shown in FIG. 2, the electromagnetic valve (SV12) 26 in the hot gas refrigerant pipe 25 connected to the heating means 23 of the oil recovery device 19 is closed, and the first electromagnetic valve provided in the flow dividing controller 7 By opening (SVH) 10 and the second solenoid valve (SVG) 13 and reducing the refrigerant flow path pressure loss in the flow dividing controller 7, the oil remaining in the high-pressure gas pipe 4 is easily pushed away by the superheated gas. doing.

  In this way, by continuing the cleaning operation for a preset time, the oil remaining in the three high-pressure gas pipes 4, the low-pressure gas pipes 5 and the high-pressure liquid pipes 6 together with the refrigerant is recovered by the oil recovery device 19 It can be recovered in the tank 20. The oil remaining in the oil recovery tank 20 can be recovered by opening the on-off valve from the drain pipe 24.

Thus, according to the present embodiment, the following effects can be expected.
When the oil corresponding to the old refrigerant and the deteriorated oil remaining in the three high-pressure gas pipes 4, the low-pressure gas pipes 5, and the high-pressure liquid pipes 6 led out from the outdoor unit 2 are washed with flowing refrigerant, If a large amount of liquid refrigerant stagnates in the high-pressure gas pipe 4 when the pipes are cleaned at the same time, the liquid refrigerant is heated until the high-pressure gas pipe 4 is overheated by the superheated gas from the compressor. There is a risk that the oil recovery tank 20 flows into the oil recovery device (refresh kit) 19 via the low-pressure gas pipe 5 and overflows due to the liquid refrigerant.

  Therefore, first, a preparatory operation is performed for a set time, and the superheated gas from the compressor is caused to flow through the high-pressure gas pipe 4, whereby the oil remaining in the high-pressure gas pipe 4 at the flow velocity is combined with the refrigerant in the oil recovery tank 20. In the meantime, the oil recovery tank 20 is prevented from overflowing by allowing the heating means 23 of the oil recovery device 19 to function and evaporating the refrigerant. Thereafter, when the liquid refrigerant in the high-pressure gas pipe 4 is expelled, the operation is switched to the washing operation, and the compressor temperature and the discharge gas temperature are managed, while the electronic expansion valve 18 on the indoor unit 3 side is opened and the liquid back operation is performed. By setting the state, the oil corresponding to the old refrigerant remaining in the high pressure gas pipe 4, the low pressure gas pipe 5 and the high pressure liquid pipe 6 is washed with the liquid backed refrigerant and the high pressure superheated refrigerant. The oil can be recovered in the oil recovery tank 20.

  As a result, liquid refrigerant accumulates in the oil recovery tank 20 of the oil recovery device 19, avoids the risk of overflow, recovers the oil remaining in the refrigerant pipe, and reuses the high-pressure gas pipe 4 to be reused. Stable operation of the renewed cooling / heating free multi-type air conditioner 1 can be ensured by reliably cleaning the gas pipe 5 and the high-pressure liquid pipe 6. In particular, even under a low outside temperature at which the refrigerant is likely to condense, the residual oil in the refrigerant pipe can be steadily recovered through stable operation.

  In addition, the above preparatory operation is performed in advance based on the maximum amount of refrigerant that can be accumulated in the main pipe of the high-pressure gas pipe 4 and the refrigerant flow rate that is returned to the low-pressure gas pipe 5 through the shunt controller 7 during the preliminary operation. Since the operation is performed for the set time and then switched to the cleaning operation, it is possible to avoid an excessive increase in the cleaning operation time due to the preparation operation.

  In other words, the maximum amount of refrigerant that may accumulate in the main pipe of the high-pressure gas pipe 4 can be calculated from the length and diameter of the pipe, and is returned to the low-pressure gas pipe through the shunt controller 7 during the preparatory operation. The refrigerant flow rate can be calculated by obtaining the flow rates of the fixed throttles (capillary tubes) 11 and 9 provided in the path, so that the liquid refrigerant accumulated in the main pipe of the high-pressure gas pipe 4 is completely expelled. Can be predicted in advance. For this reason, set the time as the preparatory operation time, and switch to the cleaning operation after the preparatory operation time has elapsed, so that the pipe cleaning operation can be stably performed while avoiding an excessive increase in the cleaning operation time. Can do.

  Further, a parallel circuit 12 of a first electromagnetic valve (SVH) 10 and a fixed throttle 11 is connected to the branch flow controller 7 on the inlet side of the switching valve (indoor four-way switching valve) 8 of the high-pressure gas pipe 4, Between the gas pipe 4 and the low-pressure gas pipe 5, a bypass valve for oil return operation provided with a switching valve (indoor side four-way switching valve) 8, a second electromagnetic valve (SVG) 13 that bypasses the parallel circuit 12, and a fixed throttle 14. The circuit 15 is connected, and the first solenoid valve (SVH) 10 and the second solenoid valve (SVG) 13 provided in the circuits 13 and 15 are closed during the preparation operation and opened during the cleaning operation. Yes. Therefore, the fixed throttle in which the liquid refrigerant is connected in parallel with the first solenoid valve (SVH) 10 during the preparatory operation for recovering a large amount of liquid refrigerant that may be trapped in the high-pressure gas pipe 4 together with the residual oil. By adjusting to 11 and returning to the low pressure gas pipe 5 little by little, it is possible to prevent overflow of the oil recovery tank 20 due to the return of a large amount of liquid refrigerant at a time.

  In order to prevent switching noise caused by switching of the switching valve (indoor four-way switching valve) 8 under a high differential pressure, the first solenoid valve (SVH) 10 and the fixed throttle 11 are provided on the inlet side. The second solenoid valve is provided between the high-pressure gas pipe 4 and the low-pressure gas pipe 5 in order to efficiently perform the oil return operation during the heating operation and to prevent refrigerant flow noise at that time. An oil return operation bypass circuit 15 having an (SVG) 13 and a fixed throttle 14 is provided. The first solenoid valve (SVH) 10 and the second solenoid valve (SVG) 13 provided in these circuits 12 and 15 are used to perform the first operation during the preparatory operation and the cleaning operation when cleaning the refrigerant piping. By opening and closing the second electromagnetic valves 10 and 13, the return amount of the refrigerant from the high-pressure gas pipe 4 can be appropriately controlled.

  This prevents an overflow of the oil recovery tank 20 due to a large amount of liquid refrigerant that has accumulated in the high-pressure gas pipe 4 flowing into the oil recovery device 19 at once, and stabilizes the pipe cleaning operation including the preparation operation. it can.

  In the present embodiment, the heating means 23 of the oil recovery device 19 is configured such that hot gas refrigerant from the compressor can circulate through the electromagnetic valve (SV12) 26, and at least during the preparatory operation, the electromagnetic valve (SV12). ) 26 is opened, and the refrigerant recovered together with the oil in the oil recovery tank 20 can be heated by introducing the hot gas refrigerant. For this reason, in the oil recovery apparatus 19, by introducing a part of the hot gas refrigerant discharged from the compressor into the heating means 23 via the electromagnetic valve (SV12) 26, the refrigerant is heated and evaporated by using it as a heat source. be able to. Therefore, it is possible to prevent the oil recovery tank 20 from overflowing due to the liquid refrigerant during the preparation operation.

  In addition, this invention is not limited to the invention concerning the said embodiment, In the range which does not deviate from the summary, it can change suitably. For example, in the above embodiment, in the pipe cleaning operation after the preparatory operation, the compressor temperature and the discharge gas temperature are managed, while the electronic expansion valve 18 of all the indoor units 3 is opened and the cleaning operation is performed in the liquid back operation state. As described above, the cleaning operation is performed in the liquid-back operation of all indoor units 3 as described in Japanese Patent Application Laid-Open No. 2012-225614 (Japanese Patent Application No. 2011-95238) of Patent Document 1 described above. You may make it drive | work by dividing into a group and the stable operation ensuring group.

DESCRIPTION OF SYMBOLS 1 Cooling / heating free multi-type air conditioner 2 Outdoor unit 3 Indoor unit 4 High pressure gas piping 5 Low pressure gas piping 6 High pressure liquid piping 7 Split flow controller 8 Indoor four-way switching valve (switching valve)
10 First solenoid valve (SVH)
11 Fixed throttle 12 Parallel circuit 13 Second solenoid valve (SVG)
14 Fixed throttle 15 Oil return operation bypass circuit 18 Electronic expansion valve 19 Oil recovery device 20 Oil recovery tank 23 Heating means 25 Hot gas refrigerant pipe 26 Electromagnetic valve (SV12)
28, 29, 30 Operation valve

Claims (4)

Plural shunt controllers having three refrigerant piping systems of high-pressure gas piping, low-pressure gas piping, and high-pressure liquid piping led out from the outdoor unit and having a switching valve between the high-pressure gas piping and the low-pressure gas piping The three high-pressure gas pipes of the cooling / heating free multi-type air conditioner, in which a plurality of indoor units are connected in parallel between the switching valve of the shunt controller and the high-pressure liquid pipe, Refrigerant piping of a cooling / heating free multi-type air conditioner that cleans the refrigerant piping system when reusing the existing refrigerant piping system for the gas piping and the high-pressure liquid piping and connecting a new outdoor unit or indoor unit to it. In the cleaning method,
An oil recovery tank that recovers oil remaining in the three refrigerant piping systems together with the refrigerant to the low-pressure gas pipe connected to the outdoor unit, and heats the refrigerant recovered in the oil recovery tank An oil recovery device comprising a heating means that evaporates and sucks into the compressor is detachably connected via an operation valve,
In this state, the cooling / heating-free multi-type air conditioner is operated by a cooling cycle, and first, the superheated gas discharged from the compressor is caused to flow through the high-pressure gas pipe, so that the flow rate remains in the high-pressure gas pipe. Oil is recovered together with liquid refrigerant, etc., and during that time, the heating means of the oil recovery device is operated to perform a preparatory operation for evaporating the refrigerant,
Thereafter, the electronic expansion valve of the indoor unit is opened to make a liquid back operation state, and the three high-pressure gas pipes, the low-pressure gas pipes, and the high-pressure liquid pipes are washed. A refrigerant piping cleaning method for a multi-type air conditioner.   The preparatory operation is set in advance based on the maximum amount of refrigerant that may accumulate in the main pipe of the high-pressure gas pipe and the refrigerant flow rate that is returned to the low-pressure gas pipe through the shunt controller during the preliminary operation. 2. The refrigerant pipe cleaning method for a cooling / heating free multi-type air conditioner according to claim 1, wherein the cooling pipe is operated for a period of time and then switched to the cleaning operation.   A parallel circuit of a first solenoid valve and a fixed throttle is connected to the branch flow controller on the inlet side of the switching valve of the high-pressure gas pipe, and the switching is performed between the high-pressure gas pipe and the low-pressure gas pipe. A valve and a second solenoid valve that bypasses the parallel circuit and an oil return operation bypass circuit having a fixed throttle are connected, and the first solenoid valve and the second solenoid valve of each circuit are in the preparatory operation. The method for cleaning a refrigerant pipe of a cooling / heating free multi-type air conditioner according to claim 1, wherein the cooling pipe is closed and opened during the cleaning operation. The heating means of the oil recovery device is configured such that hot gas refrigerant from the compressor can be circulated through an electromagnetic valve, and at least during the preparatory operation, the electromagnetic valve is opened and hot gas refrigerant is introduced. The refrigerant pipe cleaning method for a cooling / heating free multi-type air conditioner according to any one of claims 1 to 3, wherein the refrigerant recovered together with the oil in the oil recovery tank can be heated.

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