JP7243313B2

JP7243313B2 - air conditioner

Info

Publication number: JP7243313B2
Application number: JP2019044348A
Authority: JP
Inventors: 幹夫木嶋
Original assignee: Fujitsu General Ltd
Current assignee: Fujitsu General Ltd
Priority date: 2019-03-12
Filing date: 2019-03-12
Publication date: 2023-03-22
Anticipated expiration: 2039-03-12
Also published as: JP2020148361A

Description

本発明は、室外機に複数台の室内機が冷媒配管で接続された空気調和装置に関する。 TECHNICAL FIELD The present invention relates to an air conditioner in which a plurality of indoor units are connected to an outdoor unit by refrigerant pipes.

従来、空気調和装置としては、１台の室外機に複数台の室内機が液管およびガス管で接続され、複数台の室内機で同時に冷房運転あるいは暖房運転を行うことが可能であるものが知られている。このような空気調和装置の室外機には、室内機の台数と同数の膨張弁が設けられているものがあり、各室内機に対応する膨張弁の開度を調整することによって、各室内機における冷媒流量を調整できるようになっている。 Conventionally, as an air conditioner, a plurality of indoor units are connected to one outdoor unit by liquid pipes and gas pipes, and the plurality of indoor units can simultaneously perform cooling operation or heating operation. Are known. Some outdoor units of such air conditioners are provided with the same number of expansion valves as the number of indoor units. The refrigerant flow rate in can be adjusted.

上記のような空気調和装置で冷房運転を行っているとき、室外機で凝縮・減圧された低圧の冷媒が液管を流れて室内機に流入し、蒸発器として機能する室内熱交換器で蒸発してガス状態、あるいは、気液二相状態の低圧の冷媒がガス管を流れる。つまり、冷房運転時のガス管には、低圧であることに起因して密度・温度ともに低い状態の冷媒が流れている。 When the above air conditioner is in cooling operation, the low-pressure refrigerant condensed and decompressed in the outdoor unit flows through the liquid pipe into the indoor unit, where it evaporates in the indoor heat exchanger that functions as an evaporator. Then, a low-pressure refrigerant in a gas state or a gas-liquid two-phase state flows through the gas pipe. In other words, the refrigerant with low density and low temperature flows through the gas pipe during the cooling operation due to the low pressure.

空調運転時に圧縮機が駆動すれば、圧縮機内部に滞留している冷凍機油が冷媒とともに圧縮機から冷媒回路へと吐出される。冷媒回路に吐出された冷凍機油は冷媒とともに冷媒回路を循環するが、上述した冷房運転時のガス管では、冷媒の温度が低くなっていることによって冷凍機油の温度も低下して冷凍機油の粘度が大きくなる。また、冷房運転時のガス管には、密度の低い冷媒が流れている。これら冷凍機油の粘度が大きくなることと密度の低い冷媒が流れていることにより、ガス管内では、冷媒とともに冷凍機油が流れにくくなるので冷房運転時のガス管には冷凍機油が滞留しやすい。 When the compressor is driven during air conditioning operation, the refrigerating machine oil remaining inside the compressor is discharged from the compressor into the refrigerant circuit together with the refrigerant. The refrigerating machine oil discharged into the refrigerant circuit circulates in the refrigerant circuit together with the refrigerant, but in the gas pipe during the cooling operation described above, the temperature of the refrigerating machine oil drops due to the lower temperature of the refrigerant, and the viscosity of the refrigerating machine oil decreases. becomes larger. In addition, a low-density refrigerant flows through the gas pipe during cooling operation. Due to the increased viscosity of the refrigerating machine oil and the flow of refrigerant with low density, it becomes difficult for the refrigerating machine oil to flow together with the refrigerant in the gas pipe, so the refrigerating machine oil tends to stay in the gas pipe during cooling operation.

上述した冷房運転時のガス管での冷凍機油の滞留量は、冷房運転時の圧縮機の運転時間が長くなるほど多くなる。そして、ガス管での冷凍機油の滞留量が多くなれば、圧縮機で冷凍機油が不足して潤滑不良を起こす恐れがある。そこで、圧縮機の運転時間が所定時間（例えば、３時間）となったとき、圧縮機の回転数（例えば、７０ｒｐｓ）を所定の回転数で駆動するとともに、各室内機に対応する膨張弁の開度をそれぞれ所定開度（例えば、全開）として、ガス管を流れる冷媒の密度を高くするとともに、ガス管を流れる冷媒量を増加させることで、ガス管に滞留する冷凍機油を圧縮機に戻す油回収運転を行う空気調和装置が提案されている（例えば、特許文献１）。 The amount of refrigerating machine oil that remains in the gas pipe during the cooling operation described above increases as the operation time of the compressor during the cooling operation increases. If the amount of refrigerating machine oil remaining in the gas pipe increases, the compressor may run out of refrigerating machine oil, resulting in poor lubrication. Therefore, when the operating time of the compressor reaches a predetermined time (for example, 3 hours), the rotation speed (for example, 70 rps) of the compressor is driven at a predetermined rotation speed, and the expansion valve corresponding to each indoor unit is opened. Each opening is set to a predetermined opening (for example, fully open) to increase the density of the refrigerant flowing through the gas pipes and increase the amount of refrigerant flowing through the gas pipes, thereby returning the refrigerating machine oil remaining in the gas pipes to the compressor. An air conditioner that performs an oil recovery operation has been proposed (for example, Patent Document 1).

特開２００８－９６０１９号公報JP 2008-96019 A

冷房運転時のガス管での冷凍機油の滞留量は、上述した圧縮機の運転時間以外の要因でも変化する。例えば、運転時間が所定時間となるまでの間、膨張弁の開度が他の室内機と比べて小さくされている時間が長い室内機では、上記他の室内機と比べてガス管を流れる冷媒の密度が低くなるため、及び、ガス管を流れる冷媒量が減少するため、ガス管に滞留する冷凍機油量が多くなる。このような、膨張弁開度が小さいことによるガス管での冷凍機油の滞留量の増加は、室内温度が設定温度に近い温度となり、わずかな冷房能力しか必要としないために冷媒の流量が少ない状態で運転が継続する場合に発生する。 The amount of refrigerating machine oil that remains in the gas pipe during cooling operation also changes due to factors other than the operating time of the compressor described above. For example, until the operating time reaches a predetermined time, in an indoor unit in which the degree of opening of the expansion valve is smaller than in other indoor units, the amount of refrigerant flowing through the gas pipe is greater than that in the other indoor units. and the amount of refrigerant flowing through the gas pipe decreases, the amount of refrigerating machine oil remaining in the gas pipe increases. Such an increase in the amount of refrigerating machine oil that remains in the gas pipe due to a small opening of the expansion valve causes the room temperature to become close to the set temperature, requiring only a small amount of cooling capacity, resulting in a low refrigerant flow rate. Occurs when driving continues in a state.

一方、運転時間が所定時間となるまでの間、膨張弁の開度が他の室内機と比べて大きくされている時間が長い室内機では膨張弁で冷媒がさほど減圧されないので、上記他の室内機と比べてガス管を流れる冷媒の密度が高くなるため、及び、ガス管を流れる冷媒量が増加するため、ガス管に滞留する冷凍機油量が少なくなる。なお、このような膨張弁開度が大きいことによるガス管での冷凍機油の滞留量の減少は、室内温度と設定温度との温度差が大きくなり、大きな冷房能力が必要となって冷媒の流量が増加した場合に発生する。 On the other hand, until the operating time reaches the predetermined time, in the indoor unit whose opening degree of the expansion valve is large compared to the other indoor units, the refrigerant is not decompressed so much by the expansion valve. Since the density of the refrigerant flowing through the gas pipe is higher than that of the refrigerator and the amount of refrigerant flowing through the gas pipe is increased, the amount of refrigerating machine oil remaining in the gas pipe is reduced. A decrease in the amount of refrigerating machine oil retained in the gas pipe due to such a large degree of opening of the expansion valve increases the temperature difference between the room temperature and the set temperature, requiring a large cooling capacity, resulting in a large refrigerant flow rate. Occurs when increases.

つまり、冷房運転中にガス管に滞留する冷凍機油量は、圧縮機の運転時間が所定時間となるまでの間の、膨張弁の開度によって変化するガス管を流れる冷媒の密度及び流量によって変化し、同じ所定時間であってもガス管に滞留する冷凍機油量が多い場合や少ない場合がある。特許文献１に記載の空気調和装置では、単純に圧縮機の運転時間が所定時間となれば油回収運転を行っているため、ガス管に滞留する冷凍機油量が多く、運転時間が所定時間となる前に圧縮機で冷凍機油が不足する事態が起こったとしても対処できない。また、ガス管に滞留する冷凍機油量が少なく、運転時間が所定時間となっても圧縮機に十分な量の冷凍機油があるにも関わらず油回収運転が行われてしまう場合がある。 In other words, the amount of refrigerating machine oil that remains in the gas pipe during cooling operation varies depending on the degree of opening of the expansion valve and the density and flow rate of the refrigerant flowing through the gas pipe until the operating time of the compressor reaches a predetermined time. However, even if the predetermined time is the same, the amount of refrigerating machine oil remaining in the gas pipe may be large or small. In the air conditioner described in Patent Document 1, the oil recovery operation is performed simply when the operating time of the compressor reaches a predetermined time. Even if there is a shortage of refrigerating machine oil in the compressor before it becomes, it cannot be dealt with. In addition, the amount of refrigerating machine oil remaining in the gas pipe is small, and the oil recovery operation may be performed even though the compressor has a sufficient amount of refrigerating machine oil even after the operating time reaches the predetermined time.

本発明は、以上に説明した問題点を解決するものであり、適切なタイミングで油回収運転を実行できる空気調和装置を提供することを目的とする。 SUMMARY OF THE INVENTION It is an object of the present invention to solve the problems described above and to provide an air conditioner that can perform an oil recovery operation at an appropriate timing.

室外機と、複数台の室内機と、前記室外機と複数台の前記室内機が複数台の前記室内機と同数のガス管及び液管で接続されて形成される冷媒回路と、前記各液管に組み込まれ前記室内機の台数と同じ数だけ設けられる膨張弁と、制御手段とを有する空気調和装置であって、前記室外機は、圧縮機と、四方弁と、室外熱交換器とを有し、複数台の前記室内機は、前記室内熱交換器と、室内温度を検出する室内温度検出手段と、室内熱交換器の温度を検出する室内熱交換器温度検出手段とを有し、前記制御手段は、冷房運転を行っているとき、各前記室内機における前記室内温度検出手段で検出した室内温度と前記室内熱交換器温度検出手段で検出した室内熱交換器温度とを取り込み、室内温度と室内熱交換器温度との温度差が予め定められた所定温度差より小さい状態が所定時間継続している油滞留室内機が存在するときに、少なくとも前記油滞留室内機に対応する前記膨張弁の開度を全開として前記圧縮機に前記ガス管に滞留する冷凍機油を戻す油回収運転を行う。 an outdoor unit, a plurality of indoor units, a refrigerant circuit formed by connecting the outdoor unit and the plurality of indoor units with the same number of gas pipes and liquid pipes as the plurality of indoor units, and each liquid An air conditioner comprising: expansion valves incorporated in pipes and provided in the same number as the indoor units; and control means, wherein the outdoor unit comprises a compressor, a four-way valve, and an outdoor heat exchanger. wherein the plurality of indoor units includes the indoor heat exchanger, indoor temperature detection means for detecting the indoor temperature, and indoor heat exchanger temperature detection means for detecting the temperature of the indoor heat exchanger, The control means acquires the indoor temperature detected by the indoor temperature detecting means and the indoor heat exchanger temperature detected by the indoor heat exchanger temperature detecting means in each of the indoor units during cooling operation, and When there is an oil-retaining indoor unit in which the temperature difference between the temperature and the indoor heat exchanger temperature is smaller than a predetermined temperature difference for a predetermined time, the expansion corresponding to at least the oil-retaining indoor unit An oil recovery operation is performed in which the valve is fully opened and the refrigerating machine oil remaining in the gas pipe is returned to the compressor.

上記のように構成した本発明の空気調和装置は、適切なタイミングで油回収運転を実行できる。 The air conditioner of the present invention configured as described above can perform the oil recovery operation at an appropriate timing.

本発明の実施形態である空気調和装置の説明図であり、（Ａ）が冷媒回路図、（Ｂ）が室外機制御手段のブロック図である。BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of the air conditioner which is embodiment of this invention, (A) is a refrigerant circuit diagram, (B) is a block diagram of an outdoor unit control means. 本発明の実施例１における、室外機制御手段での処理を説明するフローチャートである。4 is a flow chart illustrating processing by an outdoor unit control means in Embodiment 1 of the present invention. 本発明の実施例２における、室外機制御手段での処理を説明するフローチャートである。It is a flow chart explaining processing by outdoor unit control means in Example 2 of the present invention. 本発明の実施例３における、室外機制御手段での処理を説明するフローチャートである。It is a flow chart explaining processing by outdoor unit control means in Example 3 of the present invention.

以下、本発明の実施の形態を、添付図面に基づいて詳細に説明する。実施形態としては、１台の室外機に１０台の室内機が冷媒配管で並列に接続され、全ての室内機で同時に冷房運転が行える空気調和装置を例に挙げて説明する。尚、本発明は以下の実施形態に限定されることはなく、本発明の主旨を逸脱しない範囲で種々変形することが可能である。 BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. As an embodiment, an air conditioner in which 10 indoor units are connected in parallel to one outdoor unit through refrigerant pipes and all of the indoor units can perform cooling operation at the same time will be described as an example. The present invention is not limited to the following embodiments, and various modifications can be made without departing from the gist of the present invention.

図１（Ａ）に示すように、本実施形態における空気調和装置１は、１台の室外機２に１０台の室内機５が、室内機５の台数と同じ１０本の液管８および１０本のガス管９で並列に接続されている。具体的には、室外機２に設けられる１０個の液側閉鎖弁２７と１０台の室内機５の液管接続部５３がそれぞれ１０本の液管８で接続されている。また、室外機２に設けられる１０個のガス側閉鎖弁２８と１０台の室内機５のガス管接続部５４がそれぞれ１０本のガス管９で接続されている。このように、室外機２と１０台の室内機５が１０本の液管８および１０本のガス管９で接続されて、空気調和装置１の冷媒回路１０を形成している。尚、図１（Ａ）では、１０台の室内機５のうちの３台のみ、１０本の液管８および１０本のガス管９のうちのそれぞれを３本のみ、１０個の液側閉鎖弁２７をおよび１０個のガス側閉鎖弁２８を３個について、それぞれ描画している。 As shown in FIG. 1(A), the air conditioner 1 according to the present embodiment includes one outdoor unit 2 and ten indoor units 5, and ten liquid pipes 8 and 10, which are the same as the number of indoor units 5. They are connected in parallel with one gas pipe 9 . Specifically, the ten liquid side shutoff valves 27 provided in the outdoor unit 2 and the liquid pipe connection portions 53 of the ten indoor units 5 are connected by ten liquid pipes 8, respectively. Ten gas side shutoff valves 28 provided in the outdoor unit 2 and gas pipe connection portions 54 of the ten indoor units 5 are connected by ten gas pipes 9, respectively. Thus, the outdoor unit 2 and ten indoor units 5 are connected by ten liquid pipes 8 and ten gas pipes 9 to form the refrigerant circuit 10 of the air conditioner 1 . In addition, in FIG. 1(A), only three out of the ten indoor units 5, only three out of the ten liquid pipes 8 and ten gas pipes 9, and ten liquid side closed The valves 27 and 3 of the 10 gas-side closing valves 28 are drawn respectively.

＜室外機の構成＞
まずは、室外機２について説明する。室外機２は、圧縮機２１と、四方弁２２と、室外熱交換器２３と、１０個の膨張弁２４と、アキュムレータ２５と、室外ファン２６と、上述した１０個の液側閉鎖弁２７および１０個のガス側閉鎖弁２８と、室外機制御手段２００を備えている。そして、室外ファン２６および室外機制御手段２００を除くこれら各装置が、以下で詳述する各冷媒配管で相互に接続されて、冷媒回路１０の一部をなす室外機冷媒回路２０を形成している。尚、図１（Ａ）では、１０個の膨張弁２４のうち３個のみを描画している。 <Configuration of outdoor unit>
First, the outdoor unit 2 will be explained. The outdoor unit 2 includes a compressor 21, a four-way valve 22, an outdoor heat exchanger 23, ten expansion valves 24, an accumulator 25, an outdoor fan 26, the above ten liquid side shutoff valves 27 and It has ten gas side shutoff valves 28 and outdoor unit control means 200 . These devices other than the outdoor fan 26 and the outdoor unit control means 200 are connected to each other by refrigerant pipes described in detail below to form the outdoor unit refrigerant circuit 20 forming a part of the refrigerant circuit 10. there is Only three of the ten expansion valves 24 are shown in FIG. 1(A).

圧縮機２１は、インバータにより回転数が制御される図示しないモータによって駆動されることで運転容量を可変できる能力可変型圧縮機である。圧縮機２１の冷媒吐出口と四方弁２２のポートａが吐出管４１で接続されており、また、圧縮機２１の冷媒吸入側とアキュムレータ２５の冷媒流出側が吸入管４２で接続されている。 The compressor 21 is a variable capacity compressor that can vary its operating capacity by being driven by a motor (not shown) whose rotational speed is controlled by an inverter. A refrigerant discharge port of the compressor 21 and the port a of the four-way valve 22 are connected by a discharge pipe 41 , and a refrigerant suction side of the compressor 21 and a refrigerant outflow side of the accumulator 25 are connected by a suction pipe 42 .

四方弁２２は、冷媒の流れる方向を切り換えるための弁であり、ａ、ｂ、ｃ、ｄの４つのポートを備えている。上述したように、ポートａと圧縮機２１の冷媒吐出口が吐出管４１で接続されている。ポートｂと室外熱交換器２３の一方の冷媒出入口が冷媒配管４３で接続されている。ポートｃとアキュムレータ２５の冷媒流入側が冷媒配管４６で接続されている。そして、ポートｄには室外機ガス管４５の一端が接続されている。室外機ガス管４５の他端には、１０本の室外機ガス分管４５ａ（図１（Ａ）では、これらのうち３本を描画）の各々の一端が接続されており、１０本の室外機ガス分管４５ａの各々の他端は、１０個のガス側閉鎖弁２８に接続されている。 The four-way valve 22 is a valve for switching the direction of refrigerant flow, and has four ports a, b, c, and d. As described above, the port a and the refrigerant discharge port of the compressor 21 are connected by the discharge pipe 41 . The port b and one refrigerant inlet/outlet of the outdoor heat exchanger 23 are connected by a refrigerant pipe 43 . A refrigerant pipe 46 connects the port c and the refrigerant inflow side of the accumulator 25 . One end of the outdoor unit gas pipe 45 is connected to the port d. One end of each of 10 outdoor unit gas branch pipes 45a (three of them are drawn in FIG. 1A) is connected to the other end of the outdoor unit gas pipe 45. The other end of each of the gas branch pipes 45a is connected to ten gas side shutoff valves 28. As shown in FIG.

室外熱交換器２３は、室外ファン２６の回転により図示しない吸込口から室外機２の内部に取り込まれた外気と冷媒を熱交換させる。上述したように、室外熱交換器２３の一方の冷媒出入口と四方弁２２のポートｂが冷媒配管４３で接続されている。また、室外熱交換器２３の他方の冷媒出入口には室外機液管４４の一端が接続されている。室外熱交換器２３は、冷媒回路１０が冷房サイクルとなる場合は凝縮器として機能し、冷媒回路１０が暖房サイクルとなる場合は蒸発器として機能する。 The outdoor heat exchanger 23 heat-exchanges the refrigerant with the outside air taken into the outdoor unit 2 through a suction port (not shown) by the rotation of the outdoor fan 26 . As described above, one refrigerant inlet/outlet of the outdoor heat exchanger 23 and the port b of the four-way valve 22 are connected by the refrigerant pipe 43 . One end of an outdoor unit liquid pipe 44 is connected to the other refrigerant inlet/outlet of the outdoor heat exchanger 23 . The outdoor heat exchanger 23 functions as a condenser when the refrigerant circuit 10 is in the cooling cycle, and functions as an evaporator when the refrigerant circuit 10 is in the heating cycle.

室外機液管４４の他端には、１０本の室外機液分管４４ａ（図１（Ａ）では、これらのうち３本を描画）の各々の一端が接続され、１０本の室外機液分管４４ａの各々の他端は、１０個の液側閉鎖弁２７に接続されている。そして、各室外機液分管４４ａには、それぞれに膨張弁２４が組み込まれている。つまり、各膨張弁２４は、室外熱交換器２３と、各室内熱交換器５１の間に配置される。これら１０個の膨張弁２４は、全て室外機制御手段２００によりその開度が調整される。各膨張弁２４の開度を調整することによって、各膨張弁２４に接続される１０台の室内機５に流れる冷媒量が調整される。１０個の膨張弁２４は、図示しないパルスモータにより駆動される電子膨張弁であり、パルスモータに与えられるパルス数によって開度が調整される。 One end of each of ten outdoor unit liquid branch pipes 44a (three of them are drawn in FIG. 1A) is connected to the other end of the outdoor unit liquid branch pipe 44, and the ten outdoor unit liquid branch pipes 44a are connected. The other end of each of 44a is connected to ten liquid side shut-off valves 27. As shown in FIG. An expansion valve 24 is incorporated in each of the outdoor unit liquid branch pipes 44a. That is, each expansion valve 24 is arranged between the outdoor heat exchanger 23 and each indoor heat exchanger 51 . The opening degrees of all the ten expansion valves 24 are adjusted by the outdoor unit control means 200 . By adjusting the degree of opening of each expansion valve 24, the amount of refrigerant flowing through the ten indoor units 5 connected to each expansion valve 24 is adjusted. The ten expansion valves 24 are electronic expansion valves driven by pulse motors (not shown), and their openings are adjusted by the number of pulses given to the pulse motors.

アキュムレータ２５は、上述したように、冷媒流入側と四方弁２２のポートｃが冷媒配管４６で接続され、冷媒流出側と圧縮機２１の冷媒吸入口が吸入管４２で接続されている。アキュムレータ２５は、流入した冷媒をガス冷媒と液冷媒とに分離し、ガス冷媒のみを吸入管４２を介して圧縮機２１に吸入させる。 As described above, the accumulator 25 has the refrigerant inflow side and the port c of the four-way valve 22 connected by the refrigerant pipe 46 , and the refrigerant outflow side and the refrigerant suction port of the compressor 21 are connected by the suction pipe 42 . The accumulator 25 separates the flowing refrigerant into gas refrigerant and liquid refrigerant, and allows the compressor 21 to suck only the gas refrigerant through the suction pipe 42 .

室外ファン２６は、樹脂材で形成されたプロペラファンであり、室外熱交換器２３の近傍に配置されている。室外ファン２６は、図示しないファンモータによって回転することで、室外機２に設けられた図示しない吸込口から室外機２の内部に外気を取り込み、室外熱交換器２３を流れる冷媒と熱交換した外気を室外機２に設けられた図示しない吹出口から室外機２の外部へ放出する。 The outdoor fan 26 is a propeller fan made of a resin material and arranged near the outdoor heat exchanger 23 . The outdoor fan 26 is rotated by a fan motor (not shown) to take in outside air into the inside of the outdoor unit 2 from a suction port (not shown) provided in the outdoor unit 2 and exchange heat with the refrigerant flowing through the outdoor heat exchanger 23. is discharged to the outside of the outdoor unit 2 from an air outlet (not shown) provided in the outdoor unit 2 .

以上説明した装置や部材、及び、各冷媒配管の他に、室外機２には各種のセンサが設けられている。図１（Ａ）に示すように、吐出管４１には、圧縮機２１から吐出される冷媒の圧力を検出する高圧センサ３１と、圧縮機２１から吐出される冷媒の温度を検出する吐出温度センサ３３が設けられている。冷媒配管４６におけるアキュムレータ２５の冷媒流入側近傍には、圧縮機２１に吸入される冷媒の圧力を検出する低圧センサ３２と、圧縮機２１に吸入される冷媒の温度を検出する吸入温度センサ３４が設けられている。 In addition to the devices, members, and refrigerant pipes described above, the outdoor unit 2 is provided with various sensors. As shown in FIG. 1A, the discharge pipe 41 includes a high-pressure sensor 31 that detects the pressure of the refrigerant discharged from the compressor 21 and a discharge temperature sensor that detects the temperature of the refrigerant discharged from the compressor 21. 33 are provided. A low-pressure sensor 32 for detecting the pressure of the refrigerant sucked into the compressor 21 and a suction temperature sensor 34 for detecting the temperature of the refrigerant sucked into the compressor 21 are provided near the refrigerant inflow side of the accumulator 25 in the refrigerant pipe 46 . is provided.

室外熱交換器２３の図示しない伝熱管の中間部には、室外熱交換器２３の温度を検出する室外熱交換器温度センサ３５が設けられている。また、室外機２の図示しない吸込口付近には、室外機２の内部に流入する外気の温度、すなわち外気温度を検出する外気温度センサ３６が備えられている。 An outdoor heat exchanger temperature sensor 35 for detecting the temperature of the outdoor heat exchanger 23 is provided at an intermediate portion of the heat transfer tube (not shown) of the outdoor heat exchanger 23 . An outside air temperature sensor 36 for detecting the temperature of the outside air flowing into the inside of the outdoor unit 2, that is, the outside air temperature, is provided near the suction port (not shown) of the outdoor unit 2 .

各室外機液分管４４ａにおける膨張弁２４と液側閉鎖弁２７の間には、各室外機液分管４４ａを流れる冷媒の温度を検出する液側温度センサ３７がそれぞれ設けられている。 A liquid-side temperature sensor 37 for detecting the temperature of the refrigerant flowing through each outdoor unit liquid branch pipe 44a is provided between the expansion valve 24 and the liquid side closing valve 27 in each outdoor unit liquid branch pipe 44a.

また、室外機２には、室外機制御手段２００が備えられている。室外機制御手段２００は、室外機２の図示しない電装品箱に格納された制御基板に搭載されており、図１（Ｂ）に示すように、ＣＰＵ２１０と、記憶部２２０と、通信部２３０と、センサ入力部２４０とを備えている。 Further, the outdoor unit 2 is provided with an outdoor unit control means 200 . The outdoor unit control means 200 is mounted on a control board housed in an electrical component box (not shown) of the outdoor unit 2, and as shown in FIG. , and a sensor input unit 240 .

記憶部２２０は、例えばフラッシュメモリであり、室外機２の制御プログラムや各種センサからの検出信号に対応した検出値、圧縮機２１や室外ファン２６の駆動状態、１０台の室内機５の各々から送信される運転情報（運転／停止情報や設定温度情報等を含む）等を記憶する。通信部２３０は、１０台の室内機５の各々との通信を行うインターフェイスである。センサ入力部２４０は、室外機２の各種センサでの検出結果を取り込んでＣＰＵ２１０に出力する。ＣＰＵ２１０は、センサ入力部２４０を介して各種センサでの検出値を定期的（例えば、１分毎）に取り込むとともに、１０台の室内機５の各々から送信される運転情報を含んだ信号が通信部２３０を介して入力される。ＣＰＵ２１０は、これら入力された各種情報に基づいて、膨張弁２４の開度調整、圧縮機２１や室外ファン２６の駆動制御を行う。また、図示は省略するが、ＣＰＵ２１０は、タイマー計測機能を有している。 The storage unit 220 is, for example, a flash memory, and stores a control program for the outdoor unit 2, detection values corresponding to detection signals from various sensors, driving states of the compressor 21 and the outdoor fan 26, and data from each of the ten indoor units 5. Stores the transmitted operation information (including operation/stop information, set temperature information, etc.) and the like. The communication unit 230 is an interface that communicates with each of the ten indoor units 5 . The sensor input unit 240 takes in detection results from various sensors of the outdoor unit 2 and outputs them to the CPU 210 . The CPU 210 periodically (for example, every 1 minute) takes in detected values from various sensors via the sensor input unit 240, and transmits signals including operation information transmitted from each of the ten indoor units 5. Input via the unit 230 . The CPU 210 adjusts the degree of opening of the expansion valve 24 and controls the driving of the compressor 21 and the outdoor fan 26 based on the input various information. Although not shown, the CPU 210 has a timer measurement function.

＜各室内機の構成＞
次に、室内機５について説明する。１０台の室内機５はそれぞれ、室内熱交換器５１と、液管接続部５３と、ガス管接続部５４と、室内ファン５５を備えている。そして、室内ファン５５を除くこれら各装置が以下で詳述する各冷媒配管で相互に接続されて、冷媒回路１０の一部をなす室内機冷媒回路５０を形成している。 <Configuration of each indoor unit>
Next, the indoor unit 5 will be explained. Each of the ten indoor units 5 includes an indoor heat exchanger 51 , a liquid pipe connection portion 53 , a gas pipe connection portion 54 and an indoor fan 55 . These devices excluding the indoor fan 55 are connected to each other by refrigerant pipes, which will be described in detail below, to form an indoor unit refrigerant circuit 50 forming a part of the refrigerant circuit 10 .

室内熱交換器５１は、冷媒と、室内ファン５５の回転により室内機５に備えられた図示しない吸込口から室内機５の内部に取り込まれた室内空気を熱交換させるものである。室内熱交換器５１の一方の冷媒出入口と液管接続部５３が室内機液管７１で接続されている。室内熱交換器５１の他方の冷媒出入口とガス管接続部５４が室内機ガス管７２で接続されている。尚、液管接続部５３やガス管接続部５４には、各冷媒配管が溶接やフレアナット等によって接続されている。
室内熱交換器５１は、室内機５が冷房運転を行う場合は蒸発器として機能し、室内機５が暖房運転を行う場合は凝縮器として機能する。 The indoor heat exchanger 51 exchanges heat between the refrigerant and the indoor air taken into the indoor unit 5 from a suction port (not shown) provided in the indoor unit 5 by the rotation of the indoor fan 55 . One refrigerant inlet/outlet of the indoor heat exchanger 51 and the liquid pipe connection portion 53 are connected by an indoor unit liquid pipe 71 . The other refrigerant inlet/outlet of the indoor heat exchanger 51 and the gas pipe connection portion 54 are connected by an indoor unit gas pipe 72 . Refrigerant pipes are connected to the liquid pipe connection portion 53 and the gas pipe connection portion 54 by welding, flare nuts, or the like.
The indoor heat exchanger 51 functions as an evaporator when the indoor unit 5 performs cooling operation, and functions as a condenser when the indoor unit 5 performs heating operation.

室内ファン５５は、樹脂材で形成されたクロスフローファンであり、室内熱交換器５１の近傍に配置されている。室内ファン５５は、図示しないファンモータによって回転することで、図示しない吸込口から室内機５の内部に室内空気を取り込み、室内熱交換器５１において冷媒と熱交換した室内空気を室内機５に備えられた図示しない吹出口から室内へ供給する。 The indoor fan 55 is a cross-flow fan made of a resin material and arranged near the indoor heat exchanger 51 . The indoor fan 55 is rotated by a fan motor (not shown) to take indoor air into the indoor unit 5 from a suction port (not shown), and provide the indoor unit 5 with the indoor air heat-exchanged with the refrigerant in the indoor heat exchanger 51. The air is supplied into the room from an air outlet (not shown).

以上説明した装置や部材、及び、各冷媒配管の他に、室内機５には各種のセンサが設けられている。室内熱交換器５１の図示しない伝熱管の中間部には、室内熱交換器５１の温度（以降、室内熱交温度と記載する場合がある）を検出する室内熱交換器温度検出手段である室内熱交換器温度センサ６１が設けられている。また、室内機５の図示しない吸込口付近には、室内機５の内部に流入する室内空気の温度、すなわち室内温度を検出する室内温度検出手段である室内温度センサ６２が備えられている。なお、以上説明した室外機液管４４、各室外機液分管４４ａ、３本の液管８、及び、室内機液管７１が、本発明の「液管」に相当する。また、以上説明した室外機ガス管４５、各室外機ガス分管４５ａ、３本のガス管９、及び、室内機ガス管７２が、本発明の「ガス管」に相当する。 In addition to the above-described devices, members, and refrigerant pipes, the indoor unit 5 is provided with various sensors. In the intermediate part of the heat transfer tube (not shown) of the indoor heat exchanger 51, an indoor A heat exchanger temperature sensor 61 is provided. Further, an indoor temperature sensor 62, which is an indoor temperature detecting means for detecting the temperature of the indoor air flowing into the indoor unit 5, that is, the indoor temperature, is provided near the suction port (not shown) of the indoor unit 5. The outdoor unit liquid pipe 44, the outdoor unit liquid branch pipes 44a, the three liquid pipes 8, and the indoor unit liquid pipe 71 described above correspond to the "liquid pipe" of the present invention. Further, the outdoor unit gas pipe 45, the outdoor unit gas branch pipes 45a, the three gas pipes 9, and the indoor unit gas pipe 72 described above correspond to the "gas pipe" of the present invention.

＜冷媒回路の動作＞
次に、本実施形態の空気調和装置１が冷房運転を行うときの冷媒回路１０における冷媒の流れや各部の動作を、図１（Ａ）を用いて説明する。以下の説明では、１０台の室内機５が全て冷房運転を行っている場合について説明する。図１（Ａ）において、矢印は、冷媒回路１０における冷房運転時の冷媒の流れを示しており、また、四方弁２２については、冷房運転時の各ポート間の連通状態を実線で示している。 <Operation of refrigerant circuit>
Next, the flow of the refrigerant and the operation of each part in the refrigerant circuit 10 when the air conditioner 1 of the present embodiment performs cooling operation will be described with reference to FIG. 1(A). In the following description, a case will be described in which all of the ten indoor units 5 are performing the cooling operation. In FIG. 1A, the arrows indicate the flow of refrigerant in the refrigerant circuit 10 during cooling operation, and the solid line indicates the state of communication between the ports of the four-way valve 22 during cooling operation. .

尚、空気調和装置１が暖房運転を行うときの冷媒回路１０における冷媒の流れや各部の動作については詳細な説明を省略するが、暖房運転時は四方弁２２の各ポート間の連通状態は、図１（Ａ）に破線で示す状態となり、室外熱交換器２３が蒸発器として機能し、各室内熱交換器５１が凝縮器として機能する。 A detailed description of the flow of the refrigerant and the operation of each part in the refrigerant circuit 10 when the air conditioner 1 performs heating operation will be omitted. The state shown by the broken line in FIG. 1(A) is reached, the outdoor heat exchanger 23 functions as an evaporator, and each indoor heat exchanger 51 functions as a condenser.

室内機５が冷房運転を行う場合は、四方弁２２が図１（Ａ）に実線で示す状態、すなわち、四方弁２２のポートａとポートｂが連通するように、また、ポートｃとポートｄが連通するように切り換えられる。これにより、冷媒回路１０が図１（Ａ）に矢印で示す方向に冷媒が流れる状態となり、室外熱交換器２３が凝縮器として機能するとともに、各室内熱交換器５１が蒸発器として機能する。 When the indoor unit 5 performs cooling operation, the four-way valve 22 is in the state indicated by the solid line in FIG. are switched so that the As a result, the refrigerant circuit 10 is in a state where the refrigerant flows in the direction indicated by the arrow in FIG. 1A, the outdoor heat exchanger 23 functions as a condenser, and each indoor heat exchanger 51 functions as an evaporator.

上記のような冷媒回路１０の状態で圧縮機２１が駆動しているとき、圧縮機２１から吐出された高温・高圧の冷媒は吐出管４１から四方弁２２に流入し、四方弁２２から冷媒配管４３を流れて室外熱交換器２３に流入する。室外熱交換器２３に流入した冷媒は、室外ファン２６の回転によって室外機２の内部に取り込まれた外気と熱交換を行って凝縮し、室外熱交換器２３から室外機液管４４に流出する。室外機液管４４に流入した冷媒は、各室外機液分管４４ａに分流し全開とされている各膨張弁２４を通過して、各液側閉鎖弁２７を介して各液管８に流入する。 When the compressor 21 is driven in the state of the refrigerant circuit 10 as described above, the high-temperature/high-pressure refrigerant discharged from the compressor 21 flows from the discharge pipe 41 into the four-way valve 22, and flows from the four-way valve 22 into the refrigerant pipe. 43 into the outdoor heat exchanger 23 . The refrigerant that has flowed into the outdoor heat exchanger 23 exchanges heat with the outside air taken into the outdoor unit 2 by the rotation of the outdoor fan 26, is condensed, and flows out from the outdoor heat exchanger 23 to the outdoor unit liquid pipe 44. . The refrigerant that has flowed into the outdoor unit liquid pipe 44 is divided into the outdoor unit liquid branch pipes 44a, passes through the fully opened expansion valves 24, and flows into the liquid pipes 8 via the liquid side closing valves 27. .

各液管８から各液管接続部５３を介して各室内機５に流入した冷媒は、各室内機液管７１を流れて各室内熱交換器５１に流入し、各室内ファン５５の回転によって室内機２の内部に取り込まれた室内空気と熱交換を行って蒸発する。各室内熱交換器５１から各室内機ガス管７２に流出した冷媒は、各ガス管接続部５４を介して各ガス管９に流入し、各ガス管９を流れて各ガス側閉鎖弁２８を介して室外機２に流入する。室外機２に流入した冷媒は、各室外機ガス分管４５ａから室外機ガス管４５、四方弁２２、冷媒配管４６へと流れてアキュムレータ２５に流入し、アキュムレータ２５でガス冷媒と液冷媒とに分離される。アキュムレータ２５から吸入管４２へと流出したガス冷媒は、吸入管４２を流れて圧縮機２１に吸入され、再び圧縮される。 The refrigerant that has flowed from each liquid pipe 8 into each indoor unit 5 via each liquid pipe connection part 53 flows through each indoor unit liquid pipe 71 and flows into each indoor heat exchanger 51, and is It evaporates by exchanging heat with indoor air taken into the interior of the indoor unit 2 . The refrigerant flowing out from each indoor heat exchanger 51 to each indoor unit gas pipe 72 flows into each gas pipe 9 via each gas pipe connection portion 54, flows through each gas pipe 9, and passes through each gas side closing valve 28. It flows into the outdoor unit 2 through the air. The refrigerant that has flowed into the outdoor unit 2 flows from each outdoor unit gas branch pipe 45a to the outdoor unit gas pipe 45, the four-way valve 22, and the refrigerant pipe 46, flows into the accumulator 25, and is separated into gas refrigerant and liquid refrigerant in the accumulator 25. be done. The gas refrigerant that has flowed out from the accumulator 25 into the suction pipe 42 flows through the suction pipe 42, is sucked into the compressor 21, and is compressed again.

＜油回収運転について＞
次に、油回収運転について説明する。圧縮機２１から吐出された冷凍機油は冷媒とともに冷媒回路１０を循環する。冷房運転時のガス管９には、温度が低い冷媒が流れているため、冷媒とともにガス管９を流れる冷凍機油の温度も低下して冷凍機油の粘度が大きくなる。また、冷房運転時のガス管９には、密度が低い冷媒が流れているため、ガス管９を密度が高い冷媒が流れる場合と比べて、冷凍機油が冷媒とともに流れにくい。以上の理由により、冷房運転時のガス管９には冷凍機油が滞留しやすい。そして、冷房運転時のガス管９での冷凍機油の滞留量は、冷房運転時の圧縮機２１の運転時間が長くなるほど多くなる。 <Oil recovery operation>
Next, the oil recovery operation will be explained. Refrigerating machine oil discharged from the compressor 21 circulates through the refrigerant circuit 10 together with the refrigerant. Since the refrigerant with a low temperature flows through the gas pipe 9 during the cooling operation, the temperature of the refrigerating machine oil flowing through the gas pipe 9 together with the refrigerant also decreases and the viscosity of the refrigerating machine oil increases. In addition, since a refrigerant with a low density flows through the gas pipe 9 during cooling operation, the refrigerating machine oil is less likely to flow together with the refrigerant than when a refrigerant with a high density flows through the gas pipe 9 . For the above reasons, refrigerating machine oil tends to stay in the gas pipe 9 during cooling operation. The amount of refrigerating machine oil that remains in the gas pipe 9 during the cooling operation increases as the operation time of the compressor 21 during the cooling operation increases.

また、冷房運転時のガス管９での冷凍機油の滞留量は、圧縮機２１の運転時間以外の要因でも変化する。例えば、運転時間が所定時間となるまでの間、膨張弁２４の開度が他の室内機５と比べて小さくされている時間が長い室内機５では、上記他の室内機５と比べてガス管９を流れる冷媒の密度が低くなるため、及び、ガス管９を流れる冷媒量が減少するため、ガス管９に滞留する冷凍機油量が多くなる。このような、膨張弁２４の開度が小さいことによるガス管９での冷凍機油の滞留量の増加は、室内温度が設定温度に近い温度となり、わずかな冷房能力しか必要としないため、冷媒の流量が少ない状態で運転が継続する場合、例えば、所定時間中に室内機５がサーモオフ／サーモオンを繰り返しているとき、つまり、室内温度が設定温度に近い温度となっており、サーモオンとなってもわずかな冷房能力しか必要としない場合に発生する。ここで、サーモオフとは冷房運転時に室内機５で検出する室内温度が、この室内温度の目標値となる設定温度より所定温度だけ下回った場合、室内機５に搭載される室内ファン５５を停止させるとともに、室内機５に対応する膨張弁２４の開度を全閉とする状態である。また、サーモオンとはサーモオフ時に室内温度が設定温度より上昇した場合、室内機５に搭載される室内ファン５５を再起動させるとともに、室内機５に対応する膨張弁２４の開度を、圧縮機２１の吐出温度に応じた開度とする状態である。 In addition, the amount of refrigerating machine oil that remains in the gas pipe 9 during cooling operation also changes due to factors other than the operating time of the compressor 21 . For example, in the indoor unit 5 in which the opening degree of the expansion valve 24 is kept small compared to the other indoor units 5 for a long time until the operation time reaches the predetermined time, the amount of gas is reduced compared to the other indoor units 5. Since the density of the refrigerant flowing through the pipe 9 decreases and the amount of refrigerant flowing through the gas pipe 9 decreases, the amount of refrigerating machine oil remaining in the gas pipe 9 increases. Such an increase in the amount of refrigerating machine oil retained in the gas pipe 9 due to the small opening of the expansion valve 24 causes the room temperature to approach the set temperature, requiring only a small amount of cooling capacity. When the operation continues with a small flow rate, for example, when the indoor unit 5 repeats thermo-off/thermo-on for a predetermined time, that is, the indoor temperature is close to the set temperature, even if the thermo-on is turned on. Occurs when only a small amount of cooling capacity is required. Here, thermo-off means that the indoor fan 55 mounted in the indoor unit 5 is stopped when the indoor temperature detected by the indoor unit 5 during cooling operation is lower than the set temperature, which is the target value of the indoor temperature, by a predetermined temperature. At the same time, the expansion valve 24 corresponding to the indoor unit 5 is fully closed. When the indoor temperature rises above the set temperature when the thermostat is off, the indoor fan 55 mounted on the indoor unit 5 is restarted, and the opening of the expansion valve 24 corresponding to the indoor unit 5 is adjusted to the compressor 21 This is a state in which the degree of opening is set according to the discharge temperature.

一方、運転時間が所定時間となるまでの間、膨張弁２４の開度が他の室内機５と比べて大きくされている時間が長い室内機５では膨張弁２４で冷媒がさほど減圧されないので、上記他の室内機５と比べてガス管９を流れる冷媒の密度が高くなるため、及び、ガス管９を流れる冷媒量が増加するため、ガス管９に滞留する冷凍機油量が少なくなる。なお、このような膨張弁２４の開度が大きいことによるガス管９での冷凍機油の滞留量の減少は、室内温度と設定温度との温度差が大きくなり、大きな冷房能力が必要となって、冷媒の流量が増加する場合、例えば、空気調和装置の使用者が冷房運転中に設定温度を変更して現在より大きい冷房能力が要求されることが頻繁に発生する場合や、室内機５が設置された部屋の空調負荷が大きくてサーモオン時に大きな冷房能力が必要とされる場合に発生する。 On the other hand, until the operating time reaches the predetermined time, the expansion valve 24 does not decompress the refrigerant so much in the indoor unit 5 in which the degree of opening of the expansion valve 24 is larger than in the other indoor units 5. Since the density of the refrigerant flowing through the gas pipe 9 is higher than in the other indoor units 5 and the amount of refrigerant flowing through the gas pipe 9 is increased, the amount of refrigerating machine oil remaining in the gas pipe 9 is reduced. The reduction in the amount of refrigerating machine oil retained in the gas pipe 9 due to the large opening of the expansion valve 24 increases the temperature difference between the room temperature and the set temperature, requiring a large cooling capacity. , when the flow rate of the refrigerant increases, for example, when the user of the air conditioner frequently changes the set temperature during cooling operation and requests a larger cooling capacity than the current one, or when the indoor unit 5 This occurs when the installed room has a large air conditioning load and a large cooling capacity is required when the thermostat is turned on.

つまり、冷房運転中にガス管９に滞留する冷凍機油量は、圧縮機２１の運転時間が所定時間となるまでの間の、膨張弁２４の開度によって変化するガス管９を流れる冷媒の状態によって変化し、同じ所定時間であってもガス管９に滞留する冷凍機油量が多い場合や少ない場合がある。このような、所定時間中の膨張弁２４の開度による冷凍機油の滞留量の違いを考慮せず、単純に圧縮機２１の運転時間が所定時間となれば油回収運転を行っていると、ガス管９に滞留する冷凍機油量が多く、運転時間が所定時間となる前に圧縮機２１で冷凍機油が不足する事態が起こったとしても対処できない。また、ガス管９に滞留する冷凍機油量が少なく、運転時間が所定時間となっても圧縮機２１に十分な量の冷凍機油があるにも関わらず油回収運転が行われてしまう場合がある。 In other words, the amount of refrigerating machine oil remaining in the gas pipe 9 during cooling operation changes depending on the opening of the expansion valve 24 until the operating time of the compressor 21 reaches a predetermined time. The amount of refrigerating machine oil remaining in the gas pipe 9 may be large or small even for the same predetermined time. If the oil recovery operation is simply performed when the operation time of the compressor 21 reaches the predetermined time without considering such a difference in the amount of refrigerating machine oil that remains due to the opening degree of the expansion valve 24 during the predetermined time, Even if the amount of refrigerating machine oil remaining in the gas pipe 9 is large and the compressor 21 runs out of refrigerating machine oil before the operating time reaches the predetermined time, it cannot be dealt with. In addition, the amount of refrigerating machine oil remaining in the gas pipe 9 is small, and the oil recovery operation may be performed even though the compressor 21 has a sufficient amount of refrigerating machine oil even after the operating time reaches the predetermined time. .

そこで、本実施形態の空気調和装置１では、冷房運転時に各室内機５において検出した室内温度と室内熱交温度との温度差を用いて、油回収運転の要否を判断する。具体的には、室内温度の方が室内熱交温度よりも高い温度であり、かつ、その温度差が所定温度差（例えば、８℃）より小さい状態が、連続して所定時間（例えば、２時間）継続した室内機５（以降、油滞留室内機と記載する場合がある）が１台でも存在する場合は、油回収運転を実行する。 Therefore, in the air conditioner 1 of the present embodiment, the temperature difference between the indoor temperature detected in each indoor unit 5 and the indoor heat exchanger temperature during the cooling operation is used to determine the necessity of the oil recovery operation. Specifically, the state in which the indoor temperature is higher than the indoor heat exchanger temperature and the temperature difference is smaller than a predetermined temperature difference (e.g., 8 ° C.) continues for a predetermined time (e.g., 2 Time) If there is even one indoor unit 5 (which may be referred to as an oil retention indoor unit hereinafter) that continues, the oil recovery operation is performed.

次に、油回収運転における、冷房運転中にガス管９に滞留する冷凍機油量の判断について以下に詳述する。前述した、室内機５がサーモオフ／サーモオンを繰り返しているときのような、室内温度が設定温度に近い温度となってわずかな冷房能力しか必要としない場合は、この室内機５に対応する膨張弁２４の開度は小さくされている。膨張弁２４の開度が小さくされていると、室内熱交換器５１に流入する冷媒量も少なくなり、流入する冷媒量が多い場合と比べて当該室内熱交換器５１の室内熱交温度が高くなって、室内温度から室内熱交温度を減じて求めた温度差は小さくなる。 Next, the determination of the amount of refrigerating machine oil remaining in the gas pipe 9 during the cooling operation in the oil recovery operation will be described in detail below. When the indoor temperature is close to the set temperature and only a small amount of cooling capacity is required, such as when the indoor unit 5 repeats thermo-off/thermo-on as described above, the expansion valve corresponding to this indoor unit 5 24 is made smaller. When the degree of opening of the expansion valve 24 is small, the amount of refrigerant flowing into the indoor heat exchanger 51 is also small, and the indoor heat exchange temperature of the indoor heat exchanger 51 is higher than when the amount of refrigerant flowing is large. As a result, the temperature difference obtained by subtracting the indoor heat exchanger temperature from the indoor temperature becomes smaller.

一方で、冷房運転中に設定温度を変更して現在より大きい冷房能力が要求されることが頻繁に発生する場合や、設置された部屋の空調負荷が大きくてサーモオン時に大きな冷房能力が必要とされる場合のような、室内温度と設定温度との温度差が大きくなって大きな冷房能力が必要となることで、冷媒の流量を増加させる室内機５では、この室内機５に対応する膨張弁２４の開度は大きくされている。膨張弁２４の開度が大きくされていると、室内熱交換器５１に流入する冷媒量も多くなり、流入する冷媒量が少ない場合と比べて当該室内熱交換器５１の室内熱交温度が低くなって、室内温度から室内熱交温度を減じて求めた温度差は大きくなる。 On the other hand, if the set temperature is changed during cooling operation and a larger cooling capacity is required frequently, or if the air conditioning load in the installed room is large, a large cooling capacity is required when the thermostat is on. The expansion valve 24 corresponding to the indoor unit 5, which increases the refrigerant flow rate due to the need for a large cooling capacity due to the large temperature difference between the indoor temperature and the set temperature. is enlarged. When the degree of opening of the expansion valve 24 is increased, the amount of refrigerant flowing into the indoor heat exchanger 51 also increases, and the indoor heat exchange temperature of the indoor heat exchanger 51 is lower than when the amount of refrigerant flowing is small. As a result, the temperature difference obtained by subtracting the indoor heat exchanger temperature from the indoor temperature increases.

つまり、室内温度から室内熱交温度を減じて求めた温度差を見ることで、各室内機５に接続されるガス管９における冷凍機油の滞留のしやすさを推定することができ、同じ時間内であれば温度差が大きいほどガス管９を流れる冷媒の密度が高く、かつ、流量が多いことによりガス管９に冷凍機油が滞留しにくく、温度差が小さいほどガス管９を流れる冷媒の密度が低く、かつ、流量が少ないことによりガス管９に冷凍機油が滞留しやすいと推定できる。そして、このような温度差が所定時間継続しているか否かを見ることで、ガス管９に滞留する冷凍機油量が、圧縮機２１の潤滑に支障をきたす量であるか否かを推定できる。 In other words, by looking at the temperature difference obtained by subtracting the indoor heat exchanger temperature from the indoor temperature, it is possible to estimate how easily the refrigerating machine oil stays in the gas pipe 9 connected to each indoor unit 5. If the temperature difference is large, the density of the refrigerant flowing through the gas pipe 9 is high, and since the flow rate is large, the refrigerating machine oil is less likely to stay in the gas pipe 9, and the smaller the temperature difference is, the refrigerant flowing through the gas pipe 9 It can be estimated that the refrigerating machine oil tends to stay in the gas pipe 9 due to its low density and low flow rate. By checking whether such a temperature difference continues for a predetermined period of time, it is possible to estimate whether or not the amount of refrigerating machine oil remaining in the gas pipe 9 is an amount that interferes with the lubrication of the compressor 21. .

ここで、上述した所定温度差の値および所定時間は、予め試験などを行って求められて室外機制御手段２００の記憶部２２０に記憶されている値である。空気調和装置１では、発揮できる空調能力に基づいて圧縮機２１の能力が定められ、この圧縮機２１には必要となる固有の量の冷凍機油が封入されている。上記所定温度差の値および所定時間は、室外機２に搭載される圧縮機２１に封入されている冷凍機油量やガス管９の内容積などに応じた値であり、圧縮機２１が潤滑不良となる前に圧縮機２１に十分な量の冷凍機油が戻せるように定められる。 Here, the value of the predetermined temperature difference and the predetermined time described above are values that are obtained by conducting tests in advance and stored in the storage unit 220 of the outdoor unit control means 200 . In the air conditioner 1, the capacity of the compressor 21 is determined based on the air conditioning capacity that can be exhibited, and the compressor 21 is filled with a required specific amount of refrigerating machine oil. The value of the predetermined temperature difference and the predetermined time are values according to the amount of refrigerating machine oil enclosed in the compressor 21 mounted on the outdoor unit 2, the internal volume of the gas pipe 9, etc. It is determined so that a sufficient amount of refrigerating machine oil can be returned to the compressor 21 before .

そして、本実施形態の空気調和装置１は、室内温度から室内熱交温度を減じて求めた温度差が所定温度差より小さくなっている状態が所定時間継続する室内機５が現れた場合に、圧縮機２１の回転数を所定の回転数（例えば、７０ｒｐｓ）で駆動するとともに、冷媒回路１０に滞留する冷凍機油を圧縮機２１に戻す油回収運転を実行する。油回収運転では、全ての膨張弁２４の開度を全開とする。これにより、ガス管９に流れる冷媒量を増加させるとともに各室内機５の室内熱交換器５１で冷媒が蒸発しきらずにガス管９を液冷媒の混ざった気液二相冷媒、つまり、密度の高い冷媒を流して、ガス管９に滞留する冷凍機油を圧縮機２１に戻す。ここで、上記所定の回転数は、予め試験などを行って定められたものであり、油回収運転時に、この回転数で圧縮機２１を駆動すれば、ガス管９に滞留する冷凍機油を圧縮機２１に戻せることが判明している値である。 Then, in the air conditioner 1 of the present embodiment, when there is an indoor unit 5 in which the temperature difference obtained by subtracting the indoor heat exchanger temperature from the indoor temperature is smaller than the predetermined temperature difference for a predetermined time, The compressor 21 is driven at a predetermined rotational speed (for example, 70 rps), and an oil recovery operation is performed to return the refrigerating machine oil remaining in the refrigerant circuit 10 to the compressor 21 . In the oil recovery operation, all the expansion valves 24 are fully opened. As a result, the amount of refrigerant flowing through the gas pipes 9 is increased, and the refrigerant is not completely evaporated in the indoor heat exchangers 51 of the indoor units 5, and the gas pipes 9 are filled with gas-liquid two-phase refrigerant mixed with the liquid refrigerant, that is, the density is reduced. Refrigerant oil remaining in the gas pipe 9 is returned to the compressor 21 by flowing high refrigerant. Here, the above-described predetermined number of revolutions is determined by conducting tests in advance. If the compressor 21 is driven at this number of revolutions during the oil recovery operation, the refrigerating machine oil remaining in the gas pipe 9 can be compressed. This value is known to be returned to the machine 21 .

＜油回収運転に関わる制御の流れ＞
以下、図２に示すフローチャートを用いて、本発明の空気調和装置１で冷房運転中に油回収運転を行うときに、ＣＰＵ２１０が実行する処理について説明する。図２に示すフローチャートでは、ＳＴは処理のステップを表し、これに続く数字はステップ番号を表している。尚、図２では、本発明に関わる処理を中心に説明しており、これ以外の処理、例えば、空調運転時に使用者が指示した設定温度や風量等の運転条件に応じた制御といった、空気調和装置１に関わる一般的な処理については説明を省略する。 <Flow of control related to oil recovery operation>
Processing executed by the CPU 210 when the air conditioner 1 of the present invention performs the oil recovery operation during the cooling operation will be described below with reference to the flowchart shown in FIG. In the flowchart shown in FIG. 2, ST represents a processing step, and the numbers following ST represent step numbers. In addition, FIG. 2 mainly describes the processing related to the present invention. A description of general processing related to the device 1 is omitted.

使用者が各室内機５の図示しないリモコン等を操作して冷房運転開始を指示すると、室外機２の室外機制御手段２００であるＣＰＵ２１０は、タイマー計測を開始する（ＳＴ１）。ここで、ＳＴ１のタイマー計測開始時点は、少なくとも１台の室内機５が冷房運転を開始した時点とする。次に、ＣＰＵ２１０は、ＳＴ１で冷房運転を開始した全ての室内機５の室内温度センサ６２で検出した室内温度と、ＳＴ１で冷房運転を開始した全ての室内機の室内熱交換器温度センサ６１で検出した室内熱交温度を室外機制御手段２００である通信部２３０を介してそれぞれ取り込む（ＳＴ２）。次に、ＣＰＵ２１０は、ＳＴ２でそれぞれ取り込んだ室内温度と室内熱交温度との温度差を算出する（ＳＴ３）。具体的には、室内温度から室内熱交温度を減じて温度差を算出する。 When a user operates a remote controller (not shown) of each indoor unit 5 to instruct the start of cooling operation, the CPU 210, which is the outdoor unit control means 200 of the outdoor unit 2, starts timer measurement (ST1). Here, the timer measurement start time point in ST1 is the time point when at least one indoor unit 5 starts the cooling operation. Next, the CPU 210 detects the indoor temperatures detected by the indoor temperature sensors 62 of all the indoor units 5 that started cooling operation in ST1, and the indoor heat exchanger temperature sensors 61 of all the indoor units that started cooling operation in ST1. The detected indoor heat exchanger temperatures are fetched through the communication unit 230, which is the outdoor unit control means 200 (ST2). Next, the CPU 210 calculates the temperature difference between the indoor temperature and the indoor heat exchanger temperature taken in at ST2 (ST3). Specifically, the temperature difference is calculated by subtracting the indoor heat exchanger temperature from the room temperature.

次に、ＣＰＵ２１０は、ＳＴ３で算出した各温度差のうち所定温度差（例えば、８℃）以下となっている室内機５が存在するか否かを判断する（ＳＴ４）。温度差が所定温度差以下となっている室内機５が存在しなければ（ＳＴ４－Ｎｏ）、ＣＰＵ２１０はＳＴ８に処理を進める。温度差が所定温度差以下となっている室内機５が少なくとも１台存在すれば（ＳＴ４－Ｙｅｓ）、ＣＰＵ２１０はＳＴ５に処理を進める。 Next, the CPU 210 determines whether or not there is an indoor unit 5 having a predetermined temperature difference (for example, 8° C.) or less among the temperature differences calculated in ST3 (ST4). If there is no indoor unit 5 whose temperature difference is equal to or less than the predetermined temperature difference (ST4-No), the CPU 210 proceeds to ST8. If there is at least one indoor unit 5 whose temperature difference is equal to or less than the predetermined temperature difference (ST4-Yes), the CPU 210 advances the process to ST5.

ＳＴ５において、ＣＰＵ２１０は、ＳＴ１でタイマー計測を開始してから、所定時間（例えば、１時間）が経過したか否かを判断する。所定時間が経過していなければ（ＳＴ５－Ｎｏ）、ＣＰＵ２１０は、ＳＴ２に処理を戻す。所定時間が経過していれば（ＳＴ５－Ｙｅｓ）、ＣＰＵ２１０は、ＳＴ６に処理を進める。 In ST5, the CPU 210 determines whether or not a predetermined period of time (for example, one hour) has elapsed since timer measurement was started in ST1. If the predetermined time has not passed (ST5-No), the CPU 210 returns the process to ST2. If the predetermined time has passed (ST5-Yes), the CPU 210 advances the process to ST6.

ＳＴ６において、ＣＰＵ２１０は、全ての油滞留室内機の膨張弁２４を全開にして、油回収運転を開始する。次に、油回収運転を実行しているとき、ＣＰＵ２１０は、油回収運転の終了条件が成立しているか否かを判断する（ＳＴ７）。ここで油回収運転の終了条件とは、膨張弁２４を全開にしてから油回収時間（例えば、１０分間）が経過しているか否かであり、具体的には、ＣＰＵ２１０は、膨張弁２４を全開とした時点から時間の計測を開始して、油回収時間が経過しているか否かを判断する。ここで、油回収時間は、実験等を行って予め定められた時間であり、ガス管９に滞留した冷凍機油が少なくとも圧縮機２１の潤滑不良を起こさない程度に圧縮機２１に戻るとみなされる時間である。 In ST6, the CPU 210 fully opens the expansion valves 24 of all the oil retention indoor units to start the oil recovery operation. Next, when the oil recovery operation is being executed, the CPU 210 determines whether or not conditions for terminating the oil recovery operation are satisfied (ST7). Here, the end condition of the oil recovery operation is whether or not the oil recovery time (for example, 10 minutes) has elapsed since the expansion valve 24 was fully opened. Time measurement is started from the time when the valve is fully opened, and it is determined whether or not the oil recovery time has elapsed. Here, the oil recovery time is a time determined in advance by conducting an experiment or the like, and it is assumed that the refrigerating machine oil remaining in the gas pipe 9 returns to the compressor 21 at least to the extent that it does not cause poor lubrication of the compressor 21. It's time.

ＳＴ７において、油回収運転の終了条件が成立していなければ（ＳＴ７－Ｎｏ）、ＣＰＵ２１０は、ＳＴ６に処理を戻し、油回収運転を継続する。油回収運転の終了条件が成立していれば（ＳＴ７－Ｙｅｓ）、ＣＰＵ２１０は、油回収運転を終了してタイマーをリセットして（ＳＴ８）、ＳＴ１に処理を戻す。 In ST7, if the condition for terminating the oil recovery operation is not satisfied (ST7-No), the CPU 210 returns to ST6 to continue the oil recovery operation. If the conditions for terminating the oil recovery operation are satisfied (ST7-Yes), the CPU 210 terminates the oil recovery operation, resets the timer (ST8), and returns the process to ST1.

以上説明したように、本実施形態の空気調和装置１は、冷房運転を行っているときに、室内温度と室内熱交温度との温度差が所定温度差より小さい状態が所定時間継続している室内機５、つまり、油滞留室内機が発生した場合に、油回収運転を行う。これにより、圧縮機２１の潤滑に支障をきたすほどの量の冷凍機油が冷媒回路１０に滞留してしまう前に油回収運転を行えるので、圧縮機２１の信頼性が向上する。また、圧縮機２１の潤滑に支障をきたすほどではない少量の冷凍機油が冷媒回路１０に滞留している場合は油回収運転を行わないため、不要に膨張弁２４の開度が全開とされることで、各室内機５で発揮される冷房能力が変動することを防止でき、使用者の快適性も損なわれない。 As described above, in the air conditioner 1 of the present embodiment, the temperature difference between the indoor temperature and the indoor heat exchanger temperature is smaller than the predetermined temperature difference for a predetermined period of time during cooling operation. When the indoor unit 5, that is, the oil retention indoor unit occurs, the oil recovery operation is performed. As a result, the oil recovery operation can be performed before the amount of refrigerating machine oil that interferes with the lubrication of the compressor 21 accumulates in the refrigerant circuit 10, so the reliability of the compressor 21 is improved. Further, when a small amount of refrigerating machine oil that does not hinder the lubrication of the compressor 21 remains in the refrigerant circuit 10, the oil recovery operation is not performed, so the opening of the expansion valve 24 is unnecessarily fully opened. As a result, it is possible to prevent the cooling capacity exhibited by each indoor unit 5 from fluctuating, and the user's comfort is not impaired.

次に、本発明の第２の実施形態について説明する。第１の実施形態では、冷房運転を行っているときに、各室内機５の室内温度と室内熱交温度との温度差が所定温度差より小さくなっている状態が所定時間継続しているか否かで、油滞留室内機があるか否かを判断した。本実施形態では、これら第１実施形態の条件に加えて、所定時間内に室内機５がサーモオフとなっている時間の合計値であるサーモオフ積算時間を用いて、油滞留室内機があるか否かを判断する。 Next, a second embodiment of the invention will be described. In the first embodiment, whether or not the temperature difference between the indoor temperature of each indoor unit 5 and the indoor heat exchanger temperature is smaller than a predetermined temperature difference continues for a predetermined time during cooling operation. It was determined whether or not there was an oil-retaining indoor unit. In this embodiment, in addition to the conditions of the first embodiment, whether or not there is an oil-retaining indoor unit is determined using a thermo-off integrated time, which is the total value of the times during which the indoor unit 5 is thermo-off within a predetermined time. to judge whether

冷房運転時にサーモオフとなる室内機５では、対応する膨張弁２４の開度が全閉とされる。これにより、サーモオフとなる室内機５には、サーモオフ中は冷媒および冷凍機油が流入しない。従って、サーモオフ中は当該室内機５に接続されるガス管９の内部に滞留する冷凍機油が増加することはなく、また、室内温度と室内熱交温度との温度差も室内熱交温度が上昇することによって小さくなる。 In the indoor unit 5 in which the thermostat is turned off during the cooling operation, the opening degree of the corresponding expansion valve 24 is fully closed. As a result, the refrigerant and refrigerating machine oil do not flow into the indoor unit 5 when the thermostat is off. Therefore, when the thermostat is off, the refrigerating machine oil remaining in the gas pipe 9 connected to the indoor unit 5 does not increase, and the temperature difference between the indoor temperature and the indoor heat exchanger temperature increases. become smaller by doing

従って、第１の実施形態で説明した、室内温度と室内熱交温度との温度差が所定温度差より小さくなっている状態が所定時間継続している室内機５であっても、所定時間内でサーモオフ積算時間が長い場合は、サーモオフ積算時間が短い場合と比べてガス管９に滞留する冷凍機油量が少なくなる。本実施形態では、このようなサーモオフ積算時間とガス管９に滞留する冷凍機油量との関係を用いて、より正確に油滞留室内機の発生を推定する。 Therefore, even in the indoor unit 5 in which the temperature difference between the indoor temperature and the indoor heat exchanger temperature is smaller than the predetermined temperature difference, as described in the first embodiment, continues for a predetermined time, When the accumulated thermo-off time is long, the amount of refrigerating machine oil remaining in the gas pipe 9 is smaller than when the accumulated thermo-off time is short. In the present embodiment, the relationship between the accumulated thermo-off time and the amount of refrigerating machine oil remaining in the gas pipe 9 is used to more accurately estimate the occurrence of the oil retention indoor unit.

そして、本実施形態では、一例として、サーモオフ積算時間が所定時間の１／４の時間（以降、閾時間と記載する場合がある）より長い場合は、第１の実施形態で説明した条件が成立しても、つまり、室内温度と室内熱交温度との温度差が所定温度差より小さくなっている状態が所定時間継続しても、油回収運転は行わず、サーモオフ積算時間が閾時間より短い場合は、油回収運転を行う。ここで、閾時間は、予め試験などを行って求められて室外機制御手段２００の記憶部２２０に記憶されている値である。空気調和装置１では、必要とされる空調能力に基づいて圧縮機２１の能力が定められ、この圧縮機２１に必要となる固有の冷凍機油量が定められる。閾時間は、室外機２に搭載される圧縮機２１に封入されている冷凍機油量やガス管９の内容積などに応じた値となる。 In the present embodiment, as an example, when the thermostat off accumulated time is longer than 1/4 of the predetermined time (hereinafter sometimes referred to as threshold time), the condition described in the first embodiment is established. In other words, even if the temperature difference between the indoor temperature and the indoor heat exchanger temperature is smaller than the predetermined temperature difference continues for a predetermined time, the oil recovery operation is not performed, and the thermo-off accumulated time is shorter than the threshold time. If so, perform oil recovery operation. Here, the threshold time is a value that is obtained by conducting tests in advance and stored in the storage unit 220 of the outdoor unit control means 200 . In the air conditioner 1, the capacity of the compressor 21 is determined based on the required air conditioning capacity, and the specific amount of refrigerating machine oil required for this compressor 21 is determined. The threshold time is a value corresponding to the amount of refrigerating machine oil enclosed in the compressor 21 mounted on the outdoor unit 2, the internal volume of the gas pipe 9, and the like.

以下、図３に示すフローチャートを用いて、本発明の空気調和装置１が油回収運転を行うときに、ＣＰＵ２１０が実行する処理について説明する。ＳＴ２１～ＳＴ２５までは、第１の実施形態のＳＴ１～ＳＴ５と同じ処理のため、説明を省略する。 Processing executed by the CPU 210 when the air conditioner 1 of the present invention performs the oil recovery operation will be described below with reference to the flowchart shown in FIG. Since ST21 to ST25 are the same as ST1 to ST5 of the first embodiment, description thereof is omitted.

ＳＴ２５において、室外機２の室外機制御手段２００であるＣＰＵ２１０は、ＳＴ２１でタイマー計測を開始してから、所定時間（例えば、１時間）が経過していれば（ＳＴ２５－Ｙｅｓ）、サーモオフ積算時間が閾時間以下となっている室内機５が存在するか否かを判断する（ＳＴ２６）。サーモオフ積算時間が閾時間（例えば、１５分）以下となっている室内機５が少なくとも１台以上存在すれば（ＳＴ２６－Ｙｅｓ）、ＣＰＵ２１０は、油滞留室内機の膨張弁２４を全開にして、油回収運転を開始する（ＳＴ２７）。サーモオフ積算時間が閾時間以下となっている室内機５が存在しなければ（ＳＴ２６－Ｎｏ）、ＣＰＵ２１０は、ＳＴ２９に処理を進める。ここでサーモオフ積算時間とは、室内機５がサーモオフとなっている時間の合計値であり、具体的には、ＣＰＵ２１０は、サーモオフ積算時間を算出して閾時間以下であるか否かを判断する。 In ST25, the CPU 210, which is the outdoor unit control means 200 of the outdoor unit 2, starts the timer measurement in ST21. is equal to or less than the threshold time exists (ST26). If there is at least one indoor unit 5 for which the thermostat-off integrated time is equal to or less than the threshold time (for example, 15 minutes) (ST26-Yes), the CPU 210 fully opens the expansion valve 24 of the oil retention indoor unit, The oil recovery operation is started (ST27). If there is no indoor unit 5 for which the thermostat-off integrated time is equal to or less than the threshold time (ST26-No), the CPU 210 advances the process to ST29. Here, the accumulated thermo-off time is the total amount of time during which the indoor unit 5 is thermo-off. Specifically, the CPU 210 calculates the thermo-off accumulated time and determines whether it is equal to or less than the threshold time. .

ＳＴ２７において、油回収運転を実行しているとき、ＣＰＵ２１０は、油回収運転の終了条件が成立しているか否かを判断する（ＳＴ２８）。油回収運転の終了条件が成立していなければ（ＳＴ２８－Ｎｏ）、ＣＰＵ２１０は、ＳＴ２７に処理を戻し、油回収運転を継続する。油回収運転の終了条件が成立していれば（ＳＴ２８－Ｙｅｓ）、ＣＰＵ２１０は、油回収運転を終了してタイマーをリセットして（ＳＴ２９）、ＳＴ２１に処理を戻す。 When the oil recovery operation is being executed in ST27, the CPU 210 determines whether or not conditions for terminating the oil recovery operation are satisfied (ST28). If the conditions for terminating the oil recovery operation are not satisfied (ST28-No), the CPU 210 returns to ST27 and continues the oil recovery operation. If the condition for terminating the oil recovery operation is satisfied (ST28-Yes), the CPU 210 terminates the oil recovery operation, resets the timer (ST29), and returns the process to ST21.

以上説明したように、本実施形態の空気調和装置１は、冷房運転を行っているときに、室内温度と室内熱交温度との温度差が所定温度差より小さい状態が所定時間継続している室内機５が存在し、かつ、当該室内機におけるサーモオフ積算時間が閾時間（本実施形態では、所定時間の１／４の時間）に満たない場合に、油回収運転を行う。これにより、第１の実施形態と比べてより正確に油滞留運転の有無を判断でき、より適切に油回収運転の要否を判断できる。 As described above, in the air conditioner 1 of the present embodiment, the temperature difference between the indoor temperature and the indoor heat exchanger temperature is smaller than the predetermined temperature difference for a predetermined period of time during cooling operation. When the indoor unit 5 is present and the accumulated thermo-off time in the indoor unit is less than the threshold time (1/4 of the predetermined time in this embodiment), the oil recovery operation is performed. As a result, it is possible to determine whether or not the oil retention operation is to be performed more accurately than in the first embodiment, and to more appropriately determine whether or not the oil recovery operation is required.

次に、本発明の第３の実施形態について説明する。第１の実施形態や第２の実施形態では、冷房運転を行っているときに、各室内機５の室内温度と室内熱交温度との温度差が所定温度差より小さくなっている状態が所定時間継続しているか否か、かつ、これらにサーモオフ積算時間が閾時間より長いか否かという判断を加えて、油滞留室内機があるか否かを判断した。本実施形態では、第１の実施形態や第２の実施形態で説明した方法によって判定した油滞留室内機の台数が全ての室内機５の台数に対して所定台数（以降、境界台数と記載する場合がある）存在するか否かに応じて、油滞留室内機に対応する膨張弁２４の開度のみを全開とする第１油回収運転と、全ての膨張弁２４の開度を全開とする第２油回収運転を選択して行う。 Next, a third embodiment of the invention will be described. In the first embodiment and the second embodiment, the temperature difference between the indoor temperature of each indoor unit 5 and the indoor heat exchanger temperature is smaller than the predetermined temperature difference during cooling operation. It was determined whether or not there was an oil-stagnation indoor unit by determining whether or not it continued for a certain period of time, and whether or not the thermostat-off integrated time was longer than the threshold time. In the present embodiment, the number of oil-retaining indoor units determined by the method described in the first and second embodiments is a predetermined number (hereinafter referred to as the boundary number of indoor units 5) with respect to the total number of indoor units 5. depending on whether or not there exists a first oil recovery operation in which only the opening degree of the expansion valve 24 corresponding to the oil retention indoor unit is fully opened, and the opening degree of all the expansion valves 24 is fully opened. A second oil recovery operation is selected and performed.

ここで、境界台数は、予め試験などを行って求められており、室外機制御手段２００の記憶部２２０に記憶されている値である。空気調和装置１では、必要とされ空調能力に基づいて圧縮機２１の能力が定められ、圧縮機２１には必要となる固有の量の冷凍機油が封入されている。ここで上記境界台数は、室外機２に搭載される圧縮機２１に封入されている冷凍機油量やガス管９の内容積などに応じた値となる。 Here, the boundary number of units is obtained by conducting tests in advance and is a value stored in the storage unit 220 of the outdoor unit control means 200 . In the air conditioner 1, the capacity of the compressor 21 is determined based on the required air conditioning capacity, and the compressor 21 is filled with a required specific amount of refrigerating machine oil. Here, the boundary number is a value corresponding to the amount of refrigerating machine oil enclosed in the compressor 21 mounted on the outdoor unit 2, the internal volume of the gas pipe 9, and the like.

より具体的には、境界台数は、冷房運転中に発生する油滞留室内機がこの境界台数（例えば、３台）より少ない場合は、当該油滞留室内機に対応する膨張弁２４のみ、その開度を全開として当該油滞留室内機に接続されるガス管９に滞留する冷凍機油のみを圧縮機２１に戻せば、圧縮機２１の潤滑には支障がないことが判明している値である。言い換えれば、冷房運転中に発生する油滞留室内機がこの境界台数より多い場合は、全ての室内機５に対応する膨張弁２４の開度を全開として全てのガス管９に滞留する冷凍機油を圧縮機２１に戻す必要がある。 More specifically, when the number of oil-retaining indoor units that occur during cooling operation is less than the boundary number (for example, three units), only the expansion valve 24 corresponding to the oil-retaining indoor unit is opened. It has been found that if only the refrigerating machine oil retained in the gas pipe 9 connected to the oil retaining indoor unit is returned to the compressor 21 with the oil retention degree fully open, the lubrication of the compressor 21 is not hindered. In other words, when the number of indoor units with accumulated oil generated during the cooling operation exceeds this limit, the expansion valves 24 corresponding to all the indoor units 5 are fully opened to remove the refrigerating machine oil accumulated in all the gas pipes 9. It must be returned to the compressor 21.

以下、図４に示すフローチャートを用いて、本発明の空気調和装置１が油回収運転を行うときに、ＣＰＵ２１０が実行する処理について説明する。ＳＴ４１～ＳＴ４５までは、第１の実施形態のＳＴ１～ＳＴ５と同じ処理のため、説明を省略する。 Processing executed by the CPU 210 when the air conditioner 1 of the present invention performs the oil recovery operation will be described below with reference to the flowchart shown in FIG. Since ST41 to ST45 are the same as ST1 to ST5 of the first embodiment, description thereof is omitted.

ＳＴ４５において、ＣＰＵ２１０は、ＳＴ４１でタイマー計測を開始してから、所定時間（例えば、１時間）が経過していれば（ＳＴ４５－Ｙｅｓ）、第１の実施形態や第２の実施形態で説明した方法によって判定した油滞留室内機が境界台数以下か否かを判断する（ＳＴ４６）。油滞留室内機が境界台数以下であれば（ＳＴ４６－Ｙｅｓ）、ＣＰＵ２１０は、油滞留室内機に対応する膨張弁２４を全開にして、第１油回収運転を開始する（ＳＴ４７）。油滞留室内機が境界台数より多ければ（ＳＴ４６－Ｎｏ）、ＣＰＵ２１０は、全ての膨張弁２４を全開として、第２油回収運転を開始する（ＳＴ５０）。 In ST45, the CPU 210 determines that a predetermined time (for example, 1 hour) has elapsed since the timer measurement was started in ST41 (ST45-Yes), as described in the first and second embodiments. It is determined whether or not the number of oil-retaining indoor units determined by the method is equal to or less than the boundary number (ST46). If the number of oil-retaining indoor units is equal to or less than the boundary number (ST46-Yes), the CPU 210 fully opens the expansion valve 24 corresponding to the oil-retaining indoor unit and starts the first oil recovery operation (ST47). If the number of oil retention indoor units is greater than the boundary number (ST46-No), the CPU 210 fully opens all the expansion valves 24 and starts the second oil recovery operation (ST50).

ＣＰＵ２１０は、第１油回収運転を実行しているとき、第１油回収運転の終了条件が成立しているか否かを判断する（ＳＴ４８）。ここで第１油回収運転の終了条件とは、膨張弁２４を全開にしてから第１油回収時間（例えば、１０分間）が経過しているか否かである。ここで、第１油回収時間は、実験等を行って予め定められた時間であり、ガス管９に滞留した冷凍機油が少なくとも圧縮機２１の潤滑不良を起こさない程度に圧縮機２１に戻るとみなされる時間である。 When executing the first oil recovery operation, the CPU 210 determines whether or not conditions for ending the first oil recovery operation are satisfied (ST48). Here, the termination condition of the first oil recovery operation is whether or not the first oil recovery time (for example, 10 minutes) has elapsed since the expansion valve 24 was fully opened. Here, the first oil recovery time is a time predetermined by conducting an experiment or the like. It is time to be considered.

ＳＴ４８において、第１油回収運転の終了条件が成立していなければ（ＳＴ４８－Ｎｏ）、ＣＰＵ２１０は、ＳＴ４７に処理を戻し、第１油回収運転を継続する。第１油回収運転の終了条件が成立していれば（ＳＴ４８－Ｙｅｓ）、ＣＰＵ２１０は、第１油回収運転を終了してタイマーをリセットして（ＳＴ４９）、ＳＴ４１に処理を戻す。 In ST48, if the conditions for terminating the first oil recovery operation are not satisfied (ST48-No), the CPU 210 returns to ST47 and continues the first oil recovery operation. If the conditions for ending the first oil recovery operation are satisfied (ST48-Yes), the CPU 210 ends the first oil recovery operation, resets the timer (ST49), and returns the process to ST41.

一方、ＳＴ５０において、ＣＰＵ２１０は、第２油回収運転を実行しているとき、第２油回収運転の終了条件が成立しているか否かを判断する（ＳＴ５１）。ここで第２油回収運転の終了条件とは、膨張弁２４を全開にしてから第２油回収時間（例えば、１０分間）が経過しているか否かである。ここで、第２油回収時間は、実験等を行って予め定められた時間であり、ガス管９に滞留した冷凍機油が少なくとも圧縮機２１の潤滑不良を起こさない程度に圧縮機２１に戻るとみなされる時間である。 On the other hand, in ST50, when the second oil recovery operation is being executed, the CPU 210 determines whether or not conditions for ending the second oil recovery operation are satisfied (ST51). Here, the condition for ending the second oil recovery operation is whether or not the second oil recovery time (for example, 10 minutes) has elapsed since the expansion valve 24 was fully opened. Here, the second oil recovery time is a time determined in advance by conducting an experiment or the like, and when the refrigerating machine oil remaining in the gas pipe 9 returns to the compressor 21 at least to such an extent that it does not cause poor lubrication of the compressor 21. It is time to be considered.

ＳＴ５１において、第２油回収運転の終了条件が成立していなければ（ＳＴ５１－Ｎｏ）、ＣＰＵ２１０は、ＳＴ５０に処理を戻し、第２油回収運転を継続する。第２油回収運転の終了条件が成立していれば（ＳＴ５１－Ｙｅｓ）、ＣＰＵ２１０は、第２油回収運転を終了してタイマーをリセットして（ＳＴ４９）、ＳＴ４１に処理を戻す。 In ST51, if the conditions for terminating the second oil recovery operation are not satisfied (ST51-No), the CPU 210 returns the process to ST50 and continues the second oil recovery operation. If the conditions for ending the second oil recovery operation are satisfied (ST51-Yes), the CPU 210 ends the second oil recovery operation, resets the timer (ST49), and returns the process to ST41.

以上説明したように、本実施形態の空気調和装置１は、冷房運転を行っているときに、油滞留室内機が発生した場合に、油滞留室内機の台数に応じて行う油回収運転を異ならせる。第１油回収運転を行うことで、冷凍機油が滞留しているガス管９に対応する室内機５の膨張弁２４の開度が全開とされるので、他の室内機５の冷房運転への影響はなく、かつ、圧縮機２１が少なくとも圧縮機２１の潤滑不良を起こさない程度に油滞留室内機から冷凍機油を戻すことができる。また、第２油回収運転を行うことで、全ての室内機５に接続されているガス管９の各々から圧縮機２１に冷凍機油が回収でき、圧縮機２１が潤滑不良となることを防止できる。 As described above, in the air conditioner 1 of the present embodiment, when oil retention indoor units occur during cooling operation, the oil recovery operation is performed differently depending on the number of oil retention indoor units. Let By performing the first oil recovery operation, the degree of opening of the expansion valve 24 of the indoor unit 5 corresponding to the gas pipe 9 in which the refrigerating machine oil is stagnant is fully opened. There is no effect, and the refrigerating machine oil can be returned from the oil-retaining indoor unit to the extent that at least the compressor 21 does not suffer from poor lubrication. In addition, by performing the second oil recovery operation, the refrigerating machine oil can be recovered from each of the gas pipes 9 connected to all the indoor units 5 to the compressor 21, and it is possible to prevent the compressor 21 from becoming poorly lubricated. .

１空気調和装置
２室外機
５室内機
１０冷媒回路
２１圧縮機
２２四方弁
２３室外熱交換器
２４膨張弁
５１室内熱交換器
６１室内熱交換器温度センサ
６２室内温度センサ
２００室外機制御部
２１０ＣＰＵ
２２０記憶部
２３０通信部
２４０センサ入力部 1 air conditioner 2 outdoor unit 5 indoor unit 10 refrigerant circuit 21 compressor 22 four-way valve 23 outdoor heat exchanger 24 expansion valve 51 indoor heat exchanger 61 indoor heat exchanger temperature sensor 62 indoor temperature sensor 200 outdoor unit control section 210 CPU
220 storage unit 230 communication unit 240 sensor input unit

Claims

an outdoor unit, a plurality of indoor units, a refrigerant circuit formed by connecting the outdoor unit and the plurality of indoor units with the same number of gas pipes and liquid pipes as the plurality of indoor units, and each liquid An air conditioner having expansion valves incorporated in a pipe and provided in the same number as the number of indoor units, and control means,
The outdoor unit has a compressor, a four-way valve, and an outdoor heat exchanger. and an indoor heat exchanger temperature detection means for detecting the temperature of the device,
When the control means is performing cooling operation,
The indoor temperature detected by the indoor temperature detecting means and the indoor heat exchanger temperature detected by the indoor heat exchanger temperature detecting means in each of the indoor units are taken in, and the temperature difference between the indoor temperature and the indoor heat exchanger temperature is determined in advance. When there is an oil-retaining indoor unit in which a state of less than a predetermined temperature difference continues for a predetermined time, at least the opening of the expansion valve corresponding to the oil-retaining indoor unit is fully opened, and the gas is supplied to the compressor. Perform oil recovery operation to return refrigerating machine oil that remains in the pipe,
An air conditioner characterized by:

The control means is
When the oil retention indoor unit is thermo-off within the predetermined time, calculating the total thermo-off time, which is the total time during which the oil retention indoor unit is thermo-off,
when the accumulated thermo-off time of the oil retention indoor unit is shorter than a predetermined time, the oil recovery operation is performed;
The air conditioner according to claim 1, characterized by:

The control means is
executing a first oil recovery operation and a second oil recovery operation as the oil recovery operation,
In the first oil recovery operation, the expansion valve corresponding to the oil retention indoor unit is fully opened,
In the second oil recovery operation, all the expansion valves are fully opened,
3. The method according to claim 1, wherein either the first oil recovery operation or the second oil recovery operation is selected and executed according to the number of the oil retention indoor units. air conditioner.

The control means is
when the number of the oil-retaining indoor units is less than a predetermined boundary number, executing the first oil recovery operation;
When the number of the oil-retaining indoor units is greater than the boundary number, the second oil recovery operation is executed.
The air conditioner according to claim 3, characterized in that: