JP6819112B2

JP6819112B2 - Air conditioner

Info

Publication number: JP6819112B2
Application number: JP2016143690A
Authority: JP
Inventors: 慎太郎真田; 賢一 ▲高▼野; 博俊竹内; 亮 ▲高▼岡
Original assignee: Fujitsu General Ltd
Current assignee: Fujitsu General Ltd
Priority date: 2016-07-21
Filing date: 2016-07-21
Publication date: 2021-01-27
Anticipated expiration: 2036-07-21
Also published as: JP2018013301A

Description

本発明は、室外機に複数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。 The present invention relates to an air conditioner in which a plurality of indoor units are connected to an outdoor unit by a refrigerant pipe.

空気調和装置が暖房運転を行っているとき、蒸発器として機能する室外熱交換器に着霜する場合がある。室外熱交換器に着霜すると、室外熱交換器での通風が霜によって阻害されて室外熱交換器における熱交換効率が低下する恐れがある。そこで、室外熱交換器に着霜したときに暖房運転を中断し、室外熱交換器が凝縮器として機能するように冷媒回路を切り替えて圧縮機から吐出された高温の冷媒を室外熱交換器に流すことで、室外熱交換器に付着している霜を融かす除霜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１参照）。 When the air conditioner is in heating operation, frost may form on the outdoor heat exchanger, which functions as an evaporator. When frost is formed on the outdoor heat exchanger, the ventilation in the outdoor heat exchanger is obstructed by the frost, and the heat exchange efficiency in the outdoor heat exchanger may decrease. Therefore, when the outdoor heat exchanger is frosted, the heating operation is interrupted, the refrigerant circuit is switched so that the outdoor heat exchanger functions as a condenser, and the high-temperature refrigerant discharged from the compressor is used as the outdoor heat exchanger. An air conditioner that performs a defrosting operation to melt the frost adhering to the outdoor heat exchanger by flowing it has been proposed (see, for example, Patent Document 1).

上記のような空気調和装置では、暖房運転中に室外熱交換器に着霜したか否かを、室外機に設けられた各種温度センサで検出した値や、暖房運転の継続時間を用いて判断している。例えば、暖房運転中に室外熱交換器から流出する冷媒温度である熱交出口温度が−１４℃より低い、外気温度と熱交出口温度の温度差が５℃より大きい、暖房運転の継続時間が３時間を超えている等という状態であれば、室外熱交換器での着霜量が暖房能力に支障をきたすレベルであると判断して除霜運転が実行される。 In the above air conditioner, whether or not the outdoor heat exchanger has frosted during the heating operation is determined by using the values detected by various temperature sensors provided in the outdoor unit and the duration of the heating operation. doing. For example, the heat exchange outlet temperature, which is the temperature of the refrigerant flowing out of the outdoor heat exchanger during the heating operation, is lower than -14 ° C, the temperature difference between the outside air temperature and the heat exchange outlet temperature is larger than 5 ° C, and the duration of the heating operation is longer. If it exceeds 3 hours or the like, it is determined that the amount of frost formed in the outdoor heat exchanger is at a level that hinders the heating capacity, and the defrosting operation is executed.

一方、暖房運転中の外気温度が低くかつ外気の湿度が高い場合は、室外熱交換器で急激に着霜が進む（短時間で多量の霜が室外熱交換器に付着する）ことがある。このような急激な着霜の進行は、上述した着霜発生の判断方法では検出できない。そこで、室外熱交換器の温度が急激に低下しているか否かを見て、室外熱交換器で急激に着霜が進行しているか否かを判断することが考えられる。例えば、室外熱交換器の出口温度を定期的（例えば、５分毎）に検出し、この室外熱交換器の出口温度が−６℃より低いときに、現在の室外熱交換器の出口温度を前回（５分前に）検出した室外熱交換器の出口温度から減じて求めた室外熱交換器の出口温度の低下率が２℃／５分より大きければ、室外熱交換器で急激に着霜が進行していると判断して、除霜運転が実行される。 On the other hand, when the outside air temperature is low and the humidity of the outside air is high during the heating operation, frost formation may proceed rapidly in the outdoor heat exchanger (a large amount of frost adheres to the outdoor heat exchanger in a short time). Such rapid progress of frost formation cannot be detected by the above-mentioned method for determining the occurrence of frost formation. Therefore, it is conceivable to determine whether or not frost formation is rapidly progressing in the outdoor heat exchanger by observing whether or not the temperature of the outdoor heat exchanger is rapidly decreasing. For example, the outlet temperature of the outdoor heat exchanger is detected periodically (for example, every 5 minutes), and when the outlet temperature of this outdoor heat exchanger is lower than -6 ° C, the current outlet temperature of the outdoor heat exchanger is determined. If the rate of decrease in the outlet temperature of the outdoor heat exchanger obtained by subtracting from the outlet temperature of the outdoor heat exchanger detected last time (5 minutes ago) is greater than 2 ° C / 5 minutes, the outdoor heat exchanger will rapidly frost. Is determined to be in progress, and the defrosting operation is executed.

１台の室外機に複数台の室内機が接続された空気調和装置では、暖房運転中に運転する室内機が増加する（それまで停止していた室内機が暖房運転を開始する）ことがある。運転する室内機が増加すれば、増加した室内機の台数に応じて圧縮機の回転数を上昇させるが、このときの回転数の上昇値は、運転する室内機が１台だけ増加した場合であっても通常の要求能力の変更時（例えば、室内機で設定温度が１℃上げられたとき）と比べて大きくなる。そして、圧縮機の回転数上昇値が大きいと圧縮機の吸入圧力が大きく低下し、これに応じて室外熱交換器の出口温度も大きく低下する。従って、暖房運転中に上述した室外熱交換器の出口温度の低下率を見て室外熱交換器で急激に着霜が進行しているか否かを判断しているときに室内機の運転台数が増加すれば、実際は室外熱交換器で急激に着霜が進行していないにも関わらず室外熱交換器の出口温度の低下率が大きくなるため、誤って急激に着霜が進行していると判断される恐れがあった。 In an air conditioner in which a plurality of indoor units are connected to one outdoor unit, the number of indoor units operated during the heating operation may increase (the indoor unit that has been stopped until then starts the heating operation). .. If the number of indoor units to be operated increases, the rotation speed of the compressor will be increased according to the increased number of indoor units, but the increase value of the rotation speed at this time is when only one indoor unit is to be operated. Even if there is, it will be larger than when the normal required capacity is changed (for example, when the set temperature is raised by 1 ° C in the indoor unit). If the increase in the number of revolutions of the compressor is large, the suction pressure of the compressor is greatly reduced, and the outlet temperature of the outdoor heat exchanger is also greatly reduced accordingly. Therefore, the number of indoor units in operation is increased when it is determined whether or not frost formation is rapidly progressing in the outdoor heat exchanger by observing the rate of decrease in the outlet temperature of the outdoor heat exchanger described above during the heating operation. If it increases, the rate of decrease in the outlet temperature of the outdoor heat exchanger will increase even though frosting has not actually progressed rapidly in the outdoor heat exchanger. There was a risk of being judged.

これに対して、本出願人は、先に、暖房運転時の室外熱交換器における室外熱交換器の出口温度およびこの室外熱交換器の出口温度の低下率に加えて、暖房運転を行っている室内機台数が増加したか否かを考慮して着霜の有無を判断する空気調和装置を提案した（特願２０１５−０４２５３３号）。これによれば、運転台数が増加したことに起因する着霜の誤判定を防止できる。 On the other hand, the applicant first performs the heating operation in addition to the rate of decrease of the outlet temperature of the outdoor heat exchanger and the outlet temperature of the outdoor heat exchanger in the outdoor heat exchanger during the heating operation. We have proposed an air conditioner that determines the presence or absence of frost in consideration of whether or not the number of indoor units in the room has increased (Japanese Patent Application No. 2015-042533). According to this, it is possible to prevent erroneous determination of frost formation due to an increase in the number of operating vehicles.

特開２００９−２２８９２８号公報JP-A-2009-228928

しかし、室内機の運転台数の増加が繰り返されると室外熱交換器の入口付近だけ部分的に着霜が進行する恐れがある。すなわち、室内機の運転台数が増えた直後は停止していた室内機およびそれに接続されている配管に分布する冷媒は流れずその場に滞留しており、冷媒がすぐには循環しないため、圧縮機の回転数が上がってから停止していた室内機に滞留していた冷媒が圧縮機に吸入されるまでに時間差が生じる。その結果、圧縮機吸入側の圧力（低圧圧力）が一時的に急降下する。この時、蒸発温度も低下する。室外熱交換器温度と外気温度との温度差が大きくなるため、冷媒は室外熱交換器の流路の中間あたりから過熱され、室外熱交換器の入口から中間あたりまでが部分的に温度が低下する。これが繰り返されると、室外熱交換器の入口付近だけ部分的に着霜が進行してしまう。上記した従来の空気調和装置（特願２０１５−０４２５３３号）だと、室内機の運転台数が増加した場合には着霜と判定されない。 However, if the number of indoor units in operation is repeatedly increased, frost formation may partially proceed only near the inlet of the outdoor heat exchanger. That is, the refrigerant distributed in the indoor unit and the piping connected to the indoor unit, which was stopped immediately after the number of indoor units in operation increased, does not flow and stays there, and the refrigerant does not circulate immediately, so that it is compressed. There is a time lag between the increase in the number of revolutions of the machine and the suction of the refrigerant staying in the indoor unit, which has been stopped, into the compressor. As a result, the pressure on the suction side of the compressor (low pressure) drops temporarily. At this time, the evaporation temperature also decreases. Since the temperature difference between the outdoor heat exchanger temperature and the outside air temperature becomes large, the refrigerant is overheated from the middle of the flow path of the outdoor heat exchanger, and the temperature partially drops from the inlet to the middle of the outdoor heat exchanger. To do. If this is repeated, frost formation will partially proceed only near the inlet of the outdoor heat exchanger. With the above-mentioned conventional air conditioner (Japanese Patent Application No. 2015-042533), it is not determined that frost has formed when the number of indoor units in operation increases.

本発明は以上述べた問題点を解決するものであって、室内機の運転台数が増加したことにより室外熱交換器で着霜が進行しているか否かを誤りなく判断できる空気調和装置を提供することを目的とする。 The present invention solves the above-mentioned problems, and provides an air conditioner capable of correctly determining whether or not frost formation is progressing in the outdoor heat exchanger due to an increase in the number of indoor units in operation. The purpose is to do.

上記の課題を解決するために、本発明の空気調和装置は、圧縮機と四方弁と室外熱交換器と室外熱交換器が蒸発器として機能するときに室外熱交換器から流出する冷媒の温度である熱交出口温度を検出する熱交出口温度検出手段と外気温度を検出する外気温度検出手段を有する室外機と、室内熱交換器を有する複数の室内機と、圧縮機と四方弁と室外熱交換器と複数の室内熱交換器が冷媒配管で接続された冷媒回路と、圧縮機や四方弁を制御する制御手段とを有するものである。制御手段は、冷媒回路を暖房サイクルとして複数の室内機で暖房運転を行っているとき、熱交出口温度検出手段で検出した熱交出口温度と外気温度検出手段で検出した外気温度と暖房運転を行っている室内機の運転台数を定期的に取り込んで時系列で記憶する。そして、制御手段は、室外熱交換器に着霜する条件である第１着霜条件あるいは第２着霜条件のうちいずれか一方が成立すれば、四方弁を切り替えて冷媒回路を冷房サイクルとし室外熱交換器を除霜する除霜運転を実行する。ここで、第１着霜条件は、熱交出口温度が第１閾値温度より低いか否か、あるいは、暖房運転の継続時間が所定継続時間より長いか否か、あるいは、外気温度と熱交出口温度の温度差が所定温度差より大きいか否か、のうち少なくとも１つを含む。また、第２着霜条件は、室内機の運転台数が増加した回数が所定回数以上となったかである。 In order to solve the above problems, in the air conditioner of the present invention, the temperature of the refrigerant flowing out from the outdoor heat exchanger when the compressor, the four-way valve, the outdoor heat exchanger and the outdoor heat exchanger function as evaporators. An outdoor unit having a heat exchange outlet temperature detecting means for detecting the heat exchange outlet temperature and an outside air temperature detecting means for detecting the outside air temperature, a plurality of indoor units having an indoor heat exchanger, a compressor, a four-way valve, and an outdoor unit. It has a refrigerant circuit in which a heat exchanger and a plurality of indoor heat exchangers are connected by a refrigerant pipe, and a control means for controlling a compressor and a four-way valve. The control means controls the heat exchange outlet temperature detected by the heat exchange outlet temperature detecting means and the outside air temperature and the heating operation detected by the outside air temperature detecting means when the heating operation is performed by a plurality of indoor units using the refrigerant circuit as a heating cycle. Periodically capture the number of indoor units in operation and store them in chronological order. Then, if either the first frost condition or the second frost condition, which is the condition for frosting on the outdoor heat exchanger, is satisfied, the control means switches the four-way valve to set the refrigerant circuit as a cooling cycle and outdoors. Perform a defrosting operation to defrost the heat exchanger. Here, the first frost condition is whether or not the heat exchange outlet temperature is lower than the first threshold temperature, whether or not the duration of the heating operation is longer than the predetermined duration, or whether or not the outside air temperature and the heat exchange outlet are met. Includes at least one of whether or not the temperature difference in temperature is greater than the predetermined temperature difference. The second frost formation condition is whether the number of times the number of indoor units in operation has increased exceeds a predetermined number of times.

上記のように構成した本発明の空気調和装置は、暖房運転時の暖房運転を行っている室内機台数が増加した回数をもって着霜しているか否かを判断するので、室内機の運転台数が増加したことにより室外熱交換器で着霜が進行しているか否かを誤りなく判断できる。 Since the air conditioner of the present invention configured as described above determines whether or not frost is formed by the number of times the number of indoor units performing the heating operation during the heating operation increases, the number of indoor units in operation is increased. Due to the increase, it can be determined without error whether or not frost formation is progressing in the outdoor heat exchanger.

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。It is explanatory drawing of the air conditioner which is an embodiment of this invention, (A) is a refrigerant circuit diagram, (B) is a block diagram of an outdoor unit control means. 本発明の実施形態における、暖房運転時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 flowchart explaining the process by the outdoor unit control means at the time of a heating operation in embodiment of this 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３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あるいは暖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。 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 three indoor units are connected in parallel to one outdoor unit by a refrigerant pipe and all the indoor units can be simultaneously cooled or heated 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と、室外機２に第１液管８ａ、第２液管８ｂ、第３液管８ｃ、およびガス管９で並列に接続された３台の室内機５ａ〜５ｃを備えている。 As shown in FIG. 1A, the air conditioner 1 in the present embodiment includes one outdoor unit 2 and the outdoor unit 2 with a first liquid pipe 8a, a second liquid pipe 8b, and a third liquid pipe 8c. It also includes three indoor units 5a to 5c connected in parallel by a gas pipe 9.

上記各構成要素は次のように接続されている。第１液管８ａの一端が室外機２の第１液側閉鎖弁２７ａに接続され、第１液管８ａの他端が室内機５ａの液管接続部５３ａに接続されている。第２液管８ｂの一端が室外機２の第２液側閉鎖弁２７ｂに接続され、第２液管８ｂの他端が室内機５ｂの液管接続部５３ｂに接続されている。第３液管８ｃの一端が室外機２の第３液側閉鎖弁２７ｃに接続され、第３液管８ｃの他端が室内機５ｃの液管接続部５３ｃに接続されている。ガス管９の一端は室外機２のガス側閉鎖弁２８に接続され、ガス管９の他端は分岐して室内機５ａ〜５ｃの各ガス管接続部５４ａ〜５４ｃにそれぞれ接続されている。このように、室外機２と室内機５ａ〜５ｃとが第１液管８ａ、第２液管８ｂ、第３液管８ｃ、およびガス管９で接続されて、空気調和装置１の冷媒回路１０が構成されている。 Each of the above components is connected as follows. One end of the first liquid pipe 8a is connected to the first liquid side closing valve 27a of the outdoor unit 2, and the other end of the first liquid pipe 8a is connected to the liquid pipe connecting portion 53a of the indoor unit 5a. One end of the second liquid pipe 8b is connected to the second liquid side closing valve 27b of the outdoor unit 2, and the other end of the second liquid pipe 8b is connected to the liquid pipe connecting portion 53b of the indoor unit 5b. One end of the third liquid pipe 8c is connected to the third liquid side closing valve 27c of the outdoor unit 2, and the other end of the third liquid pipe 8c is connected to the liquid pipe connecting portion 53c of the indoor unit 5c. One end of the gas pipe 9 is connected to the gas side closing valve 28 of the outdoor unit 2, and the other end of the gas pipe 9 is branched and connected to the gas pipe connecting portions 54a to 54c of the indoor units 5a to 5c, respectively. In this way, the outdoor unit 2 and the indoor units 5a to 5c are connected by the first liquid pipe 8a, the second liquid pipe 8b, the third liquid pipe 8c, and the gas pipe 9, and the refrigerant circuit 10 of the air conditioner 1 is connected. Is configured.

室外機２は、圧縮機２１と、四方弁２２と、室外熱交換器２３と、第１膨張弁２４ａと、第２膨張弁２４ｂと、第３膨張弁２４ｃと、アキュムレータ２５と、室外ファン２６と、上述した第１液側閉鎖弁２７ａ、第２液側閉鎖弁２７ｂ、第３液側閉鎖弁２７ｃ、およびガス側閉鎖弁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を構成している。 The outdoor unit 2 includes a compressor 21, a four-way valve 22, an outdoor heat exchanger 23, a first expansion valve 24a, a second expansion valve 24b, a third expansion valve 24c, an accumulator 25, and an outdoor fan 26. The above-mentioned first liquid side closing valve 27a, second liquid side closing valve 27b, third liquid side closing valve 27c, gas side closing valve 28, and outdoor unit control means 200 are provided. Then, each of these devices except the outdoor fan 26 and the outdoor unit control means 200 is connected to each other by the refrigerant pipes described in detail below to form the outdoor unit refrigerant circuit 20 forming a part of the refrigerant circuit 10. There is.

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 whose operating capacity can be changed by being driven by a motor (not shown) whose rotation speed is controlled by an inverter. The 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 the refrigerant suction side of the compressor 21 and the 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とガス側閉鎖弁２８が室外機ガス管４５で接続されている。 The four-way valve 22 is a valve for switching the flow direction of the refrigerant, 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 a discharge pipe 41. One of the refrigerant inlets and outlets of the port b and the outdoor heat exchanger 23 is connected by a refrigerant pipe 43. The port c and the refrigerant inflow side of the accumulator 25 are connected by a refrigerant pipe 46. Then, the port d and the gas side closing valve 28 are connected by an outdoor unit gas pipe 45.

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ものである。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と第１液分管４４ａ〜第３液分管４４ｃの各々の一端が室外機液管４４で接続されている。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 exchanges heat between the outside air taken into the outdoor unit 2 and the refrigerant from 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 a refrigerant pipe 43. Further, the other refrigerant inlet / outlet of the outdoor heat exchanger 23 and one end of each of the first liquid dividing pipe 44a to the third liquid dividing pipe 44c are connected by the outdoor unit liquid pipe 44. 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.

第１膨張弁２４ａは第１液分管４４ａに設けられている。第１液分管４４ａの一端は室外機液管４４に接続され、他端は第１液側閉鎖弁２７ａに接続されている。第２膨張弁２４ｂは第２液分管４４ｂに設けられている。第２液分管４４ｂの一端は室外機液管４４に接続され、他端は第２液側閉鎖弁２７ｂに接続されている。第３膨張弁２４ｃは第３液分管４４ｃに設けられている。第３液分管４４ｃの一端は室外機液管４４に接続され、他端は第３液側閉鎖弁２７ｃに接続されている。 The first expansion valve 24a is provided in the first liquid branch tube 44a. One end of the first liquid branch pipe 44a is connected to the outdoor unit liquid pipe 44, and the other end is connected to the first liquid side closing valve 27a. The second expansion valve 24b is provided in the second liquid branch pipe 44b. One end of the second liquid branch pipe 44b is connected to the outdoor unit liquid pipe 44, and the other end is connected to the second liquid side closing valve 27b. The third expansion valve 24c is provided in the third liquid branch tube 44c. One end of the third liquid branch pipe 44c is connected to the outdoor unit liquid pipe 44, and the other end is connected to the third liquid side closing valve 27c.

第１膨張弁２４ａ、第２膨張弁２４ｂ、および第３膨張弁２４ｃは、全て室外機制御手段２００によりその開度が制御される。第１膨張弁２４ａの開度を制御することによって、室内機５ａに流れる冷媒量が調整される。第２膨張弁２４ｂの開度を制御することによって、室内機５ｂに流れる冷媒量が調整される。第３膨張弁２４ｃの開度を制御することによって、室内機５ｃに流れる冷媒量が調整される。第１膨張弁２４ａ、第２膨張弁２４ｂ、および第３膨張弁２４ｃ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。 The opening degrees of the first expansion valve 24a, the second expansion valve 24b, and the third expansion valve 24c are all controlled by the outdoor unit control means 200. By controlling the opening degree of the first expansion valve 24a, the amount of refrigerant flowing through the indoor unit 5a is adjusted. By controlling the opening degree of the second expansion valve 24b, the amount of refrigerant flowing through the indoor unit 5b is adjusted. By controlling the opening degree of the third expansion valve 24c, the amount of refrigerant flowing through the indoor unit 5c is adjusted. The first expansion valve 24a, the second expansion valve 24b, and the third expansion valve 24c are electronic expansion valves driven by a pulse motor (not shown), and the opening degree is adjusted by the number of pulses given to the pulse motor.

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。 In the accumulator 25, as described above, the refrigerant inflow side and the port c of the four-way valve 22 are 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 inflowing refrigerant into a gas refrigerant and a liquid refrigerant, and causes the compressor 21 to suck only the gas refrigerant through the suction pipe 42.

室外ファン２６は、室外熱交換器２３の近傍に配置される樹脂材で形成されたプロペラファンであり、図示しないファンモータによって室外ファン２６が回転することで、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 arranged in the vicinity of the outdoor heat exchanger 23, and is provided in the outdoor unit 2 by rotating the outdoor fan 26 by a fan motor (not shown), which is not shown. The outside air is taken into the outdoor unit 2 from the suction port, and the outside air that has exchanged heat with the refrigerant flowing through the outdoor heat exchanger 23 is discharged to the outside of the outdoor unit 2 from an outlet (not shown) provided in the outdoor unit 2.

以上説明した構成の他に、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とが設けられている。 In addition to the configuration described above, the outdoor unit 2 is provided with various sensors. As shown in FIG. 1A, the discharge pipe 41 has 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 is provided. In the vicinity of the refrigerant inflow side of the accumulator 25 in the refrigerant pipe 46, a low pressure sensor 32 that detects the pressure of the refrigerant sucked into the compressor 21 and a suction temperature sensor 34 that detects the temperature of the refrigerant sucked into the compressor 21 Is provided.

冷媒配管４３における室外熱交換器２３の近傍には、室外熱交換器２３が蒸発器として機能する際に室外熱交換器２３から流出する冷媒の温度を検出する熱交出口温度検出手段である冷媒温度センサ３５が設けられている。室外機液管４４には、室外熱交換器２３が蒸発器として機能する際に室外熱交換器２３に流入する冷媒の温度を検出する冷媒温度センサ３６が設けられている。そして、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検出手段である外気温度センサ３７が備えられている。 In the vicinity of the outdoor heat exchanger 23 in the refrigerant pipe 43, a refrigerant which is a heat exchange outlet temperature detecting means for detecting the temperature of the refrigerant flowing out from the outdoor heat exchanger 23 when the outdoor heat exchanger 23 functions as an evaporator. A temperature sensor 35 is provided. The outdoor unit liquid pipe 44 is provided with a refrigerant temperature sensor 36 that detects the temperature of the refrigerant flowing into the outdoor heat exchanger 23 when the outdoor heat exchanger 23 functions as an evaporator. An outside air temperature sensor 37, which is an outside air temperature detecting means 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 in the vicinity of the suction port (not shown) of the outdoor unit 2.

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. 1B, the CPU 210, the storage unit 220, and the communication unit 230 , The sensor input unit 240 is provided.

記憶部２２０は、ＲＯＭやＲＡＭで構成されており、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、室内機５ａ〜５ｃから送信される室内機５ａ〜５ｃの運転情報（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、室内機５ａ〜５ｃ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、５分毎）に取り込むとともに、室内機５ａ〜５ｃから送信される運転開始／停止信号や運転情報（設定温度や室内温度等）を含んだ運転情報信号が通信部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、第１膨張弁２４ａ〜第３膨張弁２４ｃの開度制御、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 composed of a ROM and a RAM, and includes a detection value corresponding to a control program of the outdoor unit 2 and detection signals from various sensors, a driving state of the compressor 21 and the outdoor fan 26, and the indoor units 5a to 5c. The transmitted operation information (including operation / stop information, set temperature information, etc.) of the indoor units 5a to 5c is stored. The communication unit 230 is an interface for communicating with the indoor units 5a to 5c. The sensor input unit 240 captures the detection results of the various sensors of the outdoor unit 2 and outputs them to the CPU 210. The CPU 210 periodically (for example, every 5 minutes) captures the values detected by various sensors via the sensor input unit 240, and also performs operation start / stop signals and operation information (set temperature) transmitted from the indoor units 5a to 5c. The operation information signal including the room temperature, etc.) is input via the communication unit 230. The CPU 210 controls the opening degree of the first expansion valve 24a to the third expansion valve 24c, and controls the drive of the compressor 21 and the outdoor fan 26 based on the various input information. Further, although not shown, the CPU 210 has a timer measurement function.

次に、３台の室内機５ａ〜５ｃについて説明する。３台の室内機５ａ〜５ｃは、室内熱交換器５１ａ〜５１ｃと、液管接続部５３ａ〜５３ｃと、ガス管接続部５４ａ〜５４ｃと、室内ファン５５ａ〜５５ｃを備えている。そして、室内ファン５５ａ〜５５ｃ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５０ａ〜５０ｃを構成している。 Next, the three indoor units 5a to 5c will be described. The three indoor units 5a to 5c include indoor heat exchangers 51a to 51c, liquid pipe connecting portions 53a to 53c, gas pipe connecting portions 54a to 54c, and indoor fans 55a to 55c. Then, these devices except for the indoor fans 55a to 55c are connected to each other by the refrigerant pipes described in detail below to form the indoor unit refrigerant circuits 50a to 50c forming a part of the refrigerant circuit 10.

尚、室内機５ａ〜５ｃの構成は全て同じであるため、以下の説明では、室内機５ａの構成についてのみ説明を行い、その他の室内機５ｂ、５ｃについては説明を省略する。また、図１（Ａ）では、室内機５ａの構成に付与した番号の末尾をａからｂおよびｃにそれぞれ変更したものが、室外機５ａの構成と対応する室内機５ｂ、５ｃの構成となる。 Since the configurations of the indoor units 5a to 5c are all the same, in the following description, only the configuration of the indoor unit 5a will be described, and the description of the other indoor units 5b and 5c will be omitted. Further, in FIG. 1A, the numbers given to the configuration of the indoor unit 5a are changed from a to b and c, respectively, to form the indoor units 5b and 5c corresponding to the configuration of the outdoor unit 5a. ..

室内熱交換器５１ａは、冷媒と、室内ファン５５ａの回転により室内機５ａに備えられた図示しない吸込口から室内機５ａ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５１ａの一方の冷媒出入口と液管接続部５３ａが室内機液管７１ａで接続されている。室内熱交換器５１ａの他方の冷媒出入口とガス管接続部５４ａが室内機ガス管７２ａで接続されている。尚、液管接続部５３ａやガス管接続部５４ａ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５１ａは、室内機５ａが冷房運転を行う場合は蒸発器として機能し、室内機５ａ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 51a exchanges heat between the refrigerant and the indoor air taken into the indoor unit 5a from a suction port (not shown) provided in the indoor unit 5a by rotating the indoor fan 55a. One of the refrigerant inlets / outlets of the indoor heat exchanger 51a and the liquid pipe connecting portion 53a are connected by the indoor unit liquid pipe 71a. The other refrigerant inlet / outlet of the indoor heat exchanger 51a and the gas pipe connecting portion 54a are connected by the indoor unit gas pipe 72a. Each refrigerant pipe is connected to the liquid pipe connecting portion 53a and the gas pipe connecting portion 54a by welding, flare nut, or the like.
The indoor heat exchanger 51a functions as an evaporator when the indoor unit 5a performs a cooling operation, and functions as a condenser when the indoor unit 5a performs a heating operation.

室内ファン５５ａは、室内熱交換器５１ａの近傍に配置される樹脂材で形成されたクロスフローファンであり、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５ａの内部に室内空気を取り込み、室内熱交換器５１ａにおいて冷媒と熱交換した室内空気を室内機５ａ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 55a is a cross-flow fan made of a resin material arranged in the vicinity of the indoor heat exchanger 51a, and is rotated by a fan motor (not shown) to enter the interior of the indoor unit 5a from a suction port (not shown). The indoor air that takes in air and exchanges heat with the refrigerant in the indoor heat exchanger 51a is supplied into the room from an outlet (not shown) provided in the indoor unit 5a.

以上説明した構成の他に、室内機５ａには各種のセンサが設けられている。室内機液管７１ａには、室内熱交換器５１ａに流入あるいは室内熱交換器５１ａから流出する冷媒の温度を検出する液側温度センサ６１ａが設けられている。室内機ガス管７２ａには、室内熱交換器５１ａから流出あるいは室内熱交換器５１ａに流入する冷媒の温度を検出するガス側温度センサ６２ａが設けられている。そして、室内機５ａの図示しない吸込口付近には、室内機５ａ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センサ６３ａが備えられている。 In addition to the configuration described above, the indoor unit 5a is provided with various sensors. The indoor unit liquid pipe 71a is provided with a liquid side temperature sensor 61a that detects the temperature of the refrigerant flowing into the indoor heat exchanger 51a or flowing out of the indoor heat exchanger 51a. The indoor unit gas pipe 72a is provided with a gas side temperature sensor 62a that detects the temperature of the refrigerant flowing out of the indoor heat exchanger 51a or flowing into the indoor heat exchanger 51a. An indoor temperature sensor 63a for detecting the temperature of the indoor air flowing into the indoor unit 5a, that is, the indoor temperature is provided in the vicinity of the suction port (not shown) of the indoor unit 5a.

次に、本実施形態の空気調和装置１が暖房運転を行うとき、および、暖房運転中に後述する第１着霜条件あるいは第２着霜条件あるいは第３着霜条件のうちいずれか一つが成立して除霜運転を行うときの各々について、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、まず、暖房運転時の冷媒回路１０における冷媒の流れや各部の動作について説明し、次に第１着霜条件および第２着霜条件および第３着霜条件について詳細に説明した後、除霜運転時の冷媒回路１０における冷媒の流れや各部の動作について説明する。 Next, when the air conditioner 1 of the present embodiment performs the heating operation, and during the heating operation, any one of the first frost formation condition, the second frost formation condition, and the third frost formation condition, which will be described later, is satisfied. The flow of the refrigerant in the refrigerant circuit 10 and the operation of each part will be described with reference to FIG. 1A for each of the defrosting operations. In the following description, first, the flow of the refrigerant in the refrigerant circuit 10 and the operation of each part during the heating operation will be described, and then the first frost condition, the second frost condition, and the third frost condition will be described in detail. Later, the flow of the refrigerant in the refrigerant circuit 10 and the operation of each part during the defrosting operation will be described.

尚、図１（Ａ）において、実線矢印は暖房運転時の冷媒の流れを示し、破線矢印は除霜運転時の冷媒の流れを示している。但し、圧縮機２１から四方弁２２のポートａまでの冷媒の流れと、四方弁２２のポートｃから圧縮機２１までの冷媒の流れは、暖房運転時と除霜運転時で同じであるため実線矢印のみで示している。また、四方弁２２については、暖房運転時の各ポート間の連通状態を実線で示し、除霜運転時の各ポート間の連通状態を破線で示している。 In FIG. 1A, the solid line arrow indicates the flow of the refrigerant during the heating operation, and the broken line arrow indicates the flow of the refrigerant during the defrosting operation. However, the flow of the refrigerant from the compressor 21 to the port a of the four-way valve 22 and the flow of the refrigerant from the port c of the four-way valve 22 to the compressor 21 are the same during the heating operation and the defrosting operation, so the solid line It is shown only by the arrow. Further, regarding the four-way valve 22, the communication state between the ports during the heating operation is shown by a solid line, and the communication state between the ports during the defrosting operation is shown by a broken line.

＜暖房運転＞
室内機５ａ〜５ｃが暖房運転を行う場合、つまり、冷媒回路１０が暖房サイクルとなる場合は、室外機制御手段２００のＣＰＵ２１０は、図１（Ａ）に示すように四方弁２２を実線で示す状態、すなわち、四方弁２２のポートａとポートｄが連通するように、また、ポートｂとポートｃが連通するように切り換える。これにより、室外熱交換器２３が蒸発器として機能するとともに、室内熱交換器５１ａ〜５１ｃが凝縮器として機能する。そして、ＣＰＵ２１０は、圧縮機２１および室外ファン２６を起動する。 <Heating operation>
When the indoor units 5a to 5c perform the heating operation, that is, when the refrigerant circuit 10 is in the heating cycle, the CPU 210 of the outdoor unit control means 200 shows the four-way valve 22 with a solid line as shown in FIG. 1 (A). The state is switched so that the port a and the port d of the four-way valve 22 communicate with each other, and the port b and the port c communicate with each other. As a result, the outdoor heat exchanger 23 functions as an evaporator, and the indoor heat exchangers 51a to 51c function as a condenser. Then, the CPU 210 activates the compressor 21 and the outdoor fan 26.

圧縮機２１が起動すると、図１（Ａ）に示す実線矢印のように冷媒回路１０を冷媒が循環する。すなわち、圧縮機２１から吐出された高圧の冷媒は、吐出管４１から四方弁２２に流入し、四方弁２２から室外機ガス管４５を流れガス側閉鎖弁２８を介してガス管９に流入する。ガス管９に流入した冷媒は分流し、ガス管接続部５４ａ〜５４ｃを介して室内機５ａ〜５ｃに流入する。室内機５ａ〜５ｃに流入した冷媒は、室内機ガス管７２ａ〜７２ｃを流れて室内熱交換器５１ａ〜５１ｃに流入し、室内ファン５５ａ〜５５ｃの回転により室内機５ａ〜５ｃの内部に取り込まれた室内空気と熱交換を行って凝縮する。このように、室内熱交換器５１ａ〜５１ｃが凝縮器として機能し、室内熱交換器５１ａ〜５１ｃで冷媒と熱交換を行った室内空気が図示しない吹出口から室内に吹き出されることによって、室内機５ａ〜５ｃが設置された室内の暖房が行われる。 When the compressor 21 is started, the refrigerant circulates in the refrigerant circuit 10 as shown by the solid arrow shown in FIG. 1 (A). That is, the high-pressure refrigerant discharged from the compressor 21 flows from the discharge pipe 41 into the four-way valve 22, flows from the four-way valve 22 through the outdoor unit gas pipe 45, and flows into the gas pipe 9 via the gas side closing valve 28. .. The refrigerant that has flowed into the gas pipe 9 is split and flows into the indoor units 5a to 5c via the gas pipe connecting portions 54a to 54c. The refrigerant that has flowed into the indoor units 5a to 5c flows through the indoor unit gas pipes 72a to 72c, flows into the indoor heat exchangers 51a to 51c, and is taken into the indoor units 5a to 5c by the rotation of the indoor fans 55a to 55c. It condenses by exchanging heat with the indoor air. In this way, the indoor heat exchangers 51a to 51c function as condensers, and the indoor air that has exchanged heat with the refrigerant in the indoor heat exchangers 51a to 51c is blown into the room from an outlet (not shown), so that the room is indoors. The room in which the machines 5a to 5c are installed is heated.

室内熱交換器５１ａ〜５１ｃから流出した冷媒は室内機液管７１ａ〜７１ｃを流れ、液管接続部５３ａ〜５３ｃを介して第１液管８ａ〜第３液管８ｃに流入する。第１液管８ａ〜第３液管８ｃに流入した冷媒は、第１液側閉鎖弁２７ａ〜第３液側閉鎖弁２７ｃを介して室外機２に流入し、第１液分管４４ａ〜第３液分管４４ｃを流れる際に第１膨張弁２４ａ〜第３膨張弁２４ｃを通過して減圧される。 The refrigerant flowing out of the indoor heat exchangers 51a to 51c flows through the indoor unit liquid pipes 71a to 71c and flows into the first liquid pipes 8a to the third liquid pipe 8c via the liquid pipe connecting portions 53a to 53c. The refrigerant that has flowed into the first liquid pipes 8a to the third liquid pipe 8c flows into the outdoor unit 2 via the first liquid side closing valve 27a to the third liquid side closing valve 27c, and flows into the outdoor unit 2 and is flown into the first liquid branch pipes 44a to the third. When flowing through the liquid separation pipe 44c, the pressure is reduced by passing through the first expansion valve 24a to the third expansion valve 24c.

各膨張弁で減圧された冷媒は、第１液分管４４ａ〜第３液分管４４ｃから室外機液管４４に流入して合流した後、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の回転により室外機２の内部に取り込まれた外気と熱交換を行って蒸発する。室外熱交換器２３から冷媒配管４３に流出した冷媒は、四方弁２２を介して冷媒配管４６を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 decompressed by each expansion valve flows into the outdoor unit liquid pipe 44 from the first liquid dividing pipe 44a to the third liquid dividing pipe 44c, merges, and then flows into the outdoor heat exchanger 23. The refrigerant flowing 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 and evaporates. The refrigerant flowing out from the outdoor heat exchanger 23 to the refrigerant pipe 43 flows through the refrigerant pipe 46 via the four-way valve 22 and flows into the accumulator 25, and is separated into a gas refrigerant and a liquid refrigerant by the accumulator 25. The gas refrigerant flowing out of the accumulator 25 flows through the suction pipe 42, is sucked into the compressor 21, and is compressed again.

＜除霜運転＞
上記のように空気調和装置１が暖房運転を行っているときに、以下に説明する第１着霜条件あるいは第２着霜条件あるいは第３着霜条件のうちいずれか一方が成立していれば、ＣＰＵ２１０は暖房運転を中断して室外熱交換器２３を除霜する除霜運転を実行する。 <Defrosting operation>
If either the first frost condition, the second frost condition, or the third frost condition described below is satisfied when the air conditioner 1 is performing the heating operation as described above. , The CPU 210 interrupts the heating operation and executes a defrosting operation for defrosting the outdoor heat exchanger 23.

ここで、第１着霜条件とは、室外熱交換器２３での着霜量が暖房能力に支障をきたすレベルとなっている恐れがあることを示す条件である。具体的には、暖房運転中に冷媒温度センサ３５で検出する温度であり蒸発器として機能している室外熱交換器２３の温度を示す熱交出口温度が予め定められた第１閾温度（例えば、−１４℃）より低いか否か、あるいは、外気温度センサ３７で検出した外気温度と熱交出口温度の温度差が予め定められた所定温度差（例えば、５℃）より大きいか否か、あるいは、暖房運転の継続時間が予め定められた所定継続維持間（例えば、３時間）より長いか否か、のうち少なくとも１つを含む。尚、ＣＰＵ２１０は、冷媒温度センサ３５で検出した熱交出口温度や外気温度センサ３７で検出した外気温度を定期的（例えば、５分毎）にセンサ入力部２４０を介して取り込み、取り込んだ熱交出口温度や外気温度を時系列で記憶部２２０に記憶している。 Here, the first frost formation condition is a condition indicating that the amount of frost formation in the outdoor heat exchanger 23 may be at a level that hinders the heating capacity. Specifically, the heat exchange outlet temperature, which is the temperature detected by the refrigerant temperature sensor 35 during the heating operation and indicates the temperature of the outdoor heat exchanger 23 functioning as an evaporator, is a predetermined first threshold temperature (for example). , -14 ° C), or whether the temperature difference between the outside air temperature and the heat exchange outlet temperature detected by the outside air temperature sensor 37 is larger than a predetermined predetermined temperature difference (for example, 5 ° C). Alternatively, it includes at least one of whether or not the duration of the heating operation is longer than a predetermined predetermined continuation maintenance period (for example, 3 hours). The CPU 210 takes in the heat exchange outlet temperature detected by the refrigerant temperature sensor 35 and the outside air temperature detected by the outside air temperature sensor 37 periodically (for example, every 5 minutes) via the sensor input unit 240, and takes in the heat exchange. The outlet temperature and the outside air temperature are stored in the storage unit 220 in chronological order.

一方、第２着霜条件とは、第１着霜条件や後述する第３着霜条件には含まれないが、室外熱交換器２３で部分的に着霜が進行していることを示す条件である。具体的には、外気温度が所定温度（例えば、５℃）より低いか否か、および、空気調和装置１が暖房運転を開始してから、若しくは前回除霜運転が終了してから運転している室内機５ａ〜５ｃの台数が増加した回数が所定回数（例えば、３０回）以上となったかである。尚、ＣＰＵ２１０は、運転している室内機５ａ〜５ｃの台数が増加したら記憶部２２０に回数を記憶している。 On the other hand, the second frosting condition is not included in the first frosting condition or the third frosting condition described later, but is a condition indicating that frosting is partially progressing in the outdoor heat exchanger 23. Is. Specifically, whether or not the outside air temperature is lower than a predetermined temperature (for example, 5 ° C.), and after the air conditioner 1 starts the heating operation or after the previous defrosting operation is completed, the operation is performed. Whether the number of times the number of indoor units 5a to 5c has increased has reached a predetermined number of times (for example, 30 times) or more. The CPU 210 stores the number of times in the storage unit 220 when the number of the indoor units 5a to 5c being operated increases.

一方、第３着霜条件とは、室外熱交換器２３での着霜量が暖房能力に支障をきたすレベルまで急速に到達する恐れがあることを示す条件である。具体的には、暖房運転中に熱交出口温度が第１閾温度よりも高い温度であり予め定められた第２閾温度（例えば、−６℃）よりも低いか否か、および、現在の熱交出口温度を前回（５分前）に検出した熱交出口温度から減じて求めた熱交出口温度の低下率が所定低下率（例えば、２℃／５分）より大きいか否か、および、連続する２つの熱交出口温度を記憶する間に運転している室内機５ａ〜５ｃの台数が増加したか否かを含む。尚、室内機５ａ〜５ｃの運転台数は、前述した記憶部２２０に記憶されている室内機５ａ〜５ｃから送信される室内機５ａ〜５ｃの運転情報に含まれる運転／停止情報を、ＣＰＵ２１０が参照して把握する。この運転／停止情報は、室内機５ａ〜５ｃが運転を開始あるいは停止する度に送信され、これを受信する度にＣＰＵ２１０は記憶部２２０に記憶している運転／停止情報を更新している。 On the other hand, the third frost formation condition is a condition indicating that the amount of frost formation in the outdoor heat exchanger 23 may rapidly reach a level that hinders the heating capacity. Specifically, whether or not the heat exchange outlet temperature is higher than the first threshold temperature and lower than the predetermined second threshold temperature (for example, -6 ° C) during the heating operation, and the current temperature. Whether or not the decrease rate of the heat exchange outlet temperature obtained by subtracting the heat exchange outlet temperature from the previously detected heat exchange outlet temperature (for example, 2 ° C./5 minutes) is larger than the predetermined decrease rate (for example, 2 ° C./5 minutes), and Includes whether or not the number of indoor units 5a to 5c operating while storing two consecutive heat exchange outlet temperatures has increased. As for the number of indoor units 5a to 5c in operation, the CPU 210 uses the operation / stop information included in the operation information of the indoor units 5a to 5c transmitted from the indoor units 5a to 5c stored in the storage unit 220 described above. Refer to and grasp. This operation / stop information is transmitted every time the indoor units 5a to 5c start or stop the operation, and each time the operation / stop information is received, the CPU 210 updates the operation / stop information stored in the storage unit 220.

暖房運転中の外気温度が低くかつ湿度が高い場合は、室外熱交換器２３で急激に着霜が進む（短時間で多量の霜が室外熱交換器２３に付着する）ことがある。このような場合、上述した第１着霜条件による判断では、室外熱交換器２３の温度が急激に低下しているか否かを判断できないため、室外熱交換器２３での急激な着霜の進行を検出できない。そこで、定期的に検出した熱交出口温度を用いて熱交出口温度の低下率を算出し、熱交出口温度が第２閾温度よりも低いか否かおよび熱交出口温度の低下率が所定低下率より大きいか否かを見て室外熱交換器２３の温度が急激に低下しているか否かを判断すれば、室外熱交換器２３で急激に着霜が進行しているか否かを判断することができる。 When the outside air temperature is low and the humidity is high during the heating operation, frost formation may proceed rapidly on the outdoor heat exchanger 23 (a large amount of frost adheres to the outdoor heat exchanger 23 in a short time). In such a case, since it is not possible to determine whether or not the temperature of the outdoor heat exchanger 23 has dropped sharply by the judgment based on the first frosting condition described above, the rapid progress of frost formation in the outdoor heat exchanger 23 Cannot be detected. Therefore, the rate of decrease in the heat exchange outlet temperature is calculated using the heat exchange outlet temperature detected periodically, and whether or not the heat exchange outlet temperature is lower than the second threshold temperature and the rate of decrease in the heat exchange outlet temperature are predetermined. If it is determined whether or not the temperature of the outdoor heat exchanger 23 is rapidly decreasing by looking at whether or not it is larger than the rate of decrease, it is determined whether or not frost formation is rapidly progressing in the outdoor heat exchanger 23. can do.

また、空気調和装置１の暖房運転中に室内機の運転台数が増加すれば、これに応じて圧縮機２１の回転数が上昇する。このときの圧縮機の回転数の上昇値は、運転する室内機が１台だけ増加した場合であっても通常の要求能力の変更時（例えば、室内機５ａ〜５ｃで設定温度が１℃上げられたとき）と比べて大きくなる。圧縮機２１の回転数の上昇値が大きいと圧縮機２１の吸入圧力が大きく低下し、これに応じて室外熱交換器２３における熱交出口温度も大きく低下する。従って、熱交出口温度の低下率を用いて急激な着霜の進行を検出するときに上述した室内機の運転台数が増加した場合は、本来であれば室外熱交換器２３の温度が急激に低下していないにも関わらず熱交出口温度の低下率が大きくなるため、誤って急激に室外熱交換器２３で着霜が進行していると判断する恐れがある。 Further, if the number of indoor units in operation increases during the heating operation of the air conditioner 1, the rotation speed of the compressor 21 increases accordingly. The increase value of the rotation speed of the compressor at this time is that the set temperature is increased by 1 ° C. when the normal required capacity is changed (for example, in the indoor units 5a to 5c) even when only one indoor unit is operated. It will be larger than when it was done). If the increase value of the rotation speed of the compressor 21 is large, the suction pressure of the compressor 21 is greatly reduced, and the heat exchange outlet temperature in the outdoor heat exchanger 23 is also greatly reduced accordingly. Therefore, if the number of indoor units in operation increases when the rapid progress of frost formation is detected using the rate of decrease in the heat exchange outlet temperature, the temperature of the outdoor heat exchanger 23 would normally suddenly increase. Since the rate of decrease in the heat exchange outlet temperature increases even though the temperature has not decreased, it may be erroneously determined that frost formation is proceeding rapidly in the outdoor heat exchanger 23.

そのため、上述した第３着霜条件として、熱交出口温度が第２閾温度よりも低いか否かおよび熱交出口温度の低下率が所定低下率より大きいか否かに加えて、連続する２つの熱交出口温度を記憶する間に運転している室内機５ａ〜５ｃの台数が増加したか否かも見ている。これにより、たとえ熱交出口温度が急激に低下していても、室内機５ａ〜５ｃの運転台数が増加、例えば１台増加していれば、運転台数の増加によって圧縮機２１の回転数が上昇しこれに起因して熱交出口温度の低下率が所定低下率より大きくなっていても、誤って室外熱交換器２３で急激に着霜が進行していると判断して除霜運転を開始することを防いでいる。 Therefore, as the above-mentioned third frost condition, in addition to whether or not the heat exchange outlet temperature is lower than the second threshold temperature and whether or not the decrease rate of the heat exchange outlet temperature is larger than the predetermined decrease rate, continuous 2 It is also checked whether the number of indoor units 5a to 5c operating while storing the temperature of one heat exchange outlet has increased. As a result, even if the heat exchange outlet temperature drops sharply, the number of indoor units 5a to 5c in operation increases, for example, if one unit increases, the number of operating units increases and the number of revolutions of the compressor 21 increases. Even if the rate of decrease in the heat exchange outlet temperature is greater than the predetermined rate due to this, it is mistakenly determined that frost formation is progressing rapidly in the outdoor heat exchanger 23, and the defrosting operation is started. It prevents you from doing it.

ところで、室内機５ａ〜５ｃの運転台数の増加が繰り返された場合、室外熱交換器２３の入口付近だけ部分的に着霜が進行する恐れがある。すなわち、室内機５ａ〜５ｃの運転台数が増えた直後は停止していた室内機およびそれに接続されている配管に分布する冷媒は流れずその場に滞留しており、冷媒がすぐには循環しないため、圧縮機の回転数が上がってから停止していた室内機に滞留していた冷媒が圧縮機に吸入されるまでに時間差が生じる。その結果、圧縮機２１の吸入側の圧力（低圧圧力）が一時的に急降下する。この時、蒸発温度も低下する。室外熱交換器温度と外気温度との温度差が大きくなるため、冷媒は室外熱交換器２３の流路の中間あたりから過熱され、室外熱交換器２３の入口から中間あたりまでが部分的に温度が低下する。これが繰り返されると、室外熱交換器２３の入口付近だけ部分的に着霜が進行してしまう。このように着霜が進行する状況となっても、室内機５ａ〜５ｃの運転台数が増加しているので上述の第３着霜条件では除霜運転を開始できない。 By the way, when the number of indoor units 5a to 5c in operation is repeatedly increased, frost formation may partially proceed only in the vicinity of the inlet of the outdoor heat exchanger 23. That is, the refrigerant distributed in the indoor unit and the piping connected to the indoor unit, which was stopped immediately after the number of indoor units 5a to 5c in operation increased, does not flow and stays there, and the refrigerant does not circulate immediately. Therefore, there is a time lag between the increase in the number of revolutions of the compressor and the suction of the refrigerant staying in the indoor unit, which has been stopped, into the compressor. As a result, the pressure (low pressure) on the suction side of the compressor 21 temporarily drops sharply. At this time, the evaporation temperature also decreases. Since the temperature difference between the outdoor heat exchanger temperature and the outside air temperature becomes large, the refrigerant is overheated from the middle of the flow path of the outdoor heat exchanger 23, and the temperature is partially from the inlet to the middle of the outdoor heat exchanger 23. Decreases. If this is repeated, frost formation will partially proceed only in the vicinity of the inlet of the outdoor heat exchanger 23. Even if frost formation progresses in this way, the defrosting operation cannot be started under the above-mentioned third frost formation condition because the number of indoor units 5a to 5c in operation is increasing.

そこで本発明では、上述した第２着霜条件として、外気温度が所定温度より低いか否か、および、空気調和装置１が暖房運転を開始してから、若しくは前回除霜運転が終了してから運転している室内機５ａ〜５ｃの台数が増加した回数が所定回数以上となったかを見ている。これにより、室内機５ａ〜５ｃの運転台数が増加した回数が所定回数、例えば３０回以上となったら、室内機５ａ〜５ｃの運転台数の増加が繰り返されて部分的に着霜が進行していると判断して除霜運転を開始することができる。所定回数は、予め実験等により着霜の進行が確認された回数が設定されるが、外気温度センサ３７の検出値および外気湿度センサ３８の検出値に応じて変動させてもよい。この場合、室外熱交換器２３に着霜し易い条件である高外気温・高外気湿度（絶対湿度が高くなる条件）では回数を少なく、低外気温・低外気湿度では回数を多く設定する。 Therefore, in the present invention, as the second frost formation condition described above, whether or not the outside air temperature is lower than the predetermined temperature, and after the air conditioner 1 starts the heating operation or after the previous defrosting operation is completed. It is checked whether the number of times the number of indoor units 5a to 5c being operated has increased exceeds the predetermined number of times. As a result, when the number of operating units of the indoor units 5a to 5c increases a predetermined number of times, for example, 30 times or more, the number of operating units of the indoor units 5a to 5c is repeatedly increased and frost formation progresses partially. It can be determined that the defrosting operation is started. The predetermined number of times is set to the number of times that the progress of frost formation is confirmed in advance by an experiment or the like, but it may be changed according to the detection value of the outside air temperature sensor 37 and the detection value of the outside air humidity sensor 38. In this case, the number of times is set to be small under the conditions of high outside air temperature and high outside air humidity (conditions where the absolute humidity is high), which are conditions that easily cause frost on the outdoor heat exchanger 23, and the number of times is set to be large under the conditions of low outside air temperature and low outside air humidity.

第１着霜条件あるいは第２着霜条件あるいは第３着霜条件が成立すれば、ＣＰＵ２１０は暖房運転を中断して除霜運転を行う。ＣＰＵ２１０は、圧縮機２１および室外ファン２６を停止し、図１（Ａ）に示すように四方弁２２を破線で示す状態、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る。これにより、室外熱交換器２３が凝縮器として機能するとともに、室内熱交換器５１ａ〜５１ｃが蒸発器として機能する。そして、ＣＰＵ２１０は、室外ファン２６は停止したままとして圧縮機２１を再起動する。 If the first frost condition, the second frost condition, or the third frost condition is satisfied, the CPU 210 interrupts the heating operation and performs the defrost operation. The CPU 210 stops the compressor 21 and the outdoor fan 26, and as shown in FIG. 1 (A), the four-way valve 22 is shown by a broken line, that is, so that the port a and the port b of the four-way valve 22 communicate with each other. , Switch so that port c and port d communicate with each other. As a result, the outdoor heat exchanger 23 functions as a condenser, and the indoor heat exchangers 51a to 51c function as an evaporator. Then, the CPU 210 restarts the compressor 21 with the outdoor fan 26 stopped.

圧縮機２１が再起動すると、図１（Ａ）に示す破線矢印のように冷媒回路１０を冷媒が循環する。すなわち、圧縮機２１から吐出された高圧の冷媒は、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、室外熱交換器２３に付着した霜を融解し、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、第１液分管４４ａ〜第３液分管４４ｃに分流し全開とされている第１膨張弁２４ａ〜第３膨張弁２４ｃを通過し、第１液側閉鎖弁２７ａ〜第３液側閉鎖弁２７ｃを介して第１液管８ａ〜第３液管８ｃに流入する。 When the compressor 21 is restarted, the refrigerant circulates in the refrigerant circuit 10 as shown by the broken line arrow shown in FIG. 1 (A). That is, the high-pressure refrigerant discharged from the compressor 21 flows into the four-way valve 22 from the discharge pipe 41, flows through the refrigerant pipe 43 from the four-way valve 22, and flows into the outdoor heat exchanger 23. The refrigerant flowing into the outdoor heat exchanger 23 melts the frost adhering to the outdoor heat exchanger 23 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 passes through the first expansion valve 24a to the third expansion valve 24c, which is divided into the first liquid branch pipe 44a to the third liquid branch pipe 44c and is fully opened, and closes on the first liquid side. It flows into the first liquid pipe 8a to the third liquid pipe 8c through the valves 27a to the third liquid side closing valve 27c.

第１液管８ａ〜第３液管８ｃから液管接続部５３ａ〜５３ｃを介して室内機５ａ〜５ｃに流入した冷媒は、室内機液管７１ａ〜７１ｃを流れて室内熱交換器５１ａ〜５１ｃに流入し室内空気と熱交換を行って蒸発する。尚、除霜運転中は室内ファン５５ａ〜５５ｃは停止している。室内熱交換器５１ａ〜５１ｃから室内機ガス管７２ａ〜７２ｃに流出した冷媒は、ガス管接続部５４ａ〜５４ｃを介してガス管９に流入し、ガス管９を流れてガス側閉鎖弁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、室外機ガス管４５、四方弁２２、冷媒配管４６を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 the first liquid pipes 8a to the third liquid pipe 8c into the indoor units 5a to 5c via the liquid pipe connecting portions 53a to 53c flows through the indoor unit liquid pipes 71a to 71c and the indoor heat exchangers 51a to 51c. It flows into the air and exchanges heat with the indoor air to evaporate. During the defrosting operation, the indoor fans 55a to 55c are stopped. The refrigerant flowing out from the indoor heat exchangers 51a to 51c to the indoor unit gas pipes 72a to 72c flows into the gas pipe 9 via the gas pipe connecting portions 54a to 54c, flows through the gas pipe 9, and closes the gas side closing valve 28. It flows into the outdoor unit 2 through the outdoor unit 2. The refrigerant that has flowed into the outdoor unit 2 flows through 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 a gas refrigerant and a liquid refrigerant by the accumulator 25. The gas refrigerant flowing out of the accumulator 25 flows through the suction pipe 42, is sucked into the compressor 21, and is compressed again.

次に、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が暖房運転を行うときに、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、暖房運転時に使用者が指示した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。また、以下の説明では、外気温度センサ３７で検出する外気温度をＴｏ、冷媒温度センサ３５で検出する熱交出口温度をＴｅｏ、室内機５ａ〜５ｃのうち運転している室内機の台数である運転台数をＮｉとする。さらには、第１着霜条件として、冷媒温度センサ３５で検出した熱交出口温度が第１閾温度である−１４℃以下であるか否かを判断し、また、第３着霜条件の第２閾温度として−６℃、所定低下率として２℃／５分とする。 Next, the process executed by the CPU 210 when the air conditioner 1 of the present invention performs the heating operation will be described with reference to the flowchart shown in FIG. In the flowchart shown in FIG. 2, ST represents a step of processing, and the number following it represents a step number. Note that FIG. 2 mainly describes the processing related to the present invention, and other processing, for example, general processing related to the air conditioner 1 such as control according to the operating conditions instructed by the user during the heating operation. The description of such processing will be omitted. Further, in the following description, the outside air temperature detected by the outside air temperature sensor 37 is To, the heat exchange outlet temperature detected by the refrigerant temperature sensor 35 is Teo, and the number of indoor units operating among the indoor units 5a to 5c. Let Ni be the number of operating units. Further, as the first frosting condition, it is determined whether or not the heat exchange outlet temperature detected by the refrigerant temperature sensor 35 is -14 ° C. or lower, which is the first threshold temperature, and the third frosting condition is the third. The two-threshold temperature is -6 ° C, and the predetermined rate of decrease is 2 ° C / 5 minutes.

ＣＰＵ２１０は暖房運転を開始すると、タイマー計測を開始する（ＳＴ１）。次に、ＣＰＵ２１０は、ＳＴ１でタイマー計測を開始してから第１所定時間が経過したか否かを判断する（ＳＴ２）。ここで、第１所定時間とは、予め試験等を行って求められ記憶部２２０に記憶されているものであり、暖房運転を開始してから冷媒回路１０における冷媒の温度や圧力が安定するまでに必要な時間（例えば、１０分間）である。 When the CPU 210 starts the heating operation, the timer measurement is started (ST1). Next, the CPU 210 determines whether or not the first predetermined time has elapsed since the timer measurement was started in ST1 (ST2). Here, the first predetermined time is obtained by performing a test or the like in advance and is stored in the storage unit 220, from the start of the heating operation until the temperature and pressure of the refrigerant in the refrigerant circuit 10 stabilize. The time required for the operation (for example, 10 minutes).

第１所定時間が経過していなければ（ＳＴ２−Ｎｏ）、ＣＰＵ２１０は、ＳＴ２に処理を戻す。第１所定時間が経過していれば（ＳＴ２−Ｙｅｓ）、ＣＰＵ２１０は、タイマーをリセットし（ＳＴ３）、外気温度センサ３７で検出した外気温度Ｔｏと冷媒温度センサ３５で検出した熱交出口温度Ｔｅｏをセンサ入力部２４０を介して取り込むとともに、記憶部２２０から現在の室内機５ａ〜５ｃの運転台数Ｎｉを読み込む（ＳＴ４）。ＣＰＵ２１０は、ＳＴ４の処理を行ったときに、取り込んだ外気温度Ｔｏと熱交出口温度Ｔｅｏ、および室内機５ａ〜５ｃの運転台数Ｎｉを併せて記憶部２２０に記憶する。 If the first predetermined time has not elapsed (ST2-No), the CPU 210 returns the process to ST2. If the first predetermined time has elapsed (ST2-Yes), the CPU 210 resets the timer (ST3), and the outside air temperature To detected by the outside air temperature sensor 37 and the heat exchange outlet temperature Teo detected by the refrigerant temperature sensor 35. Is taken in via the sensor input unit 240, and the operating number Ni of the current indoor units 5a to 5c is read from the storage unit 220 (ST4). When the processing of ST4 is performed, the CPU 210 stores the captured outside air temperature To, the heat exchange outlet temperature Too, and the operating number Ni of the indoor units 5a to 5c in the storage unit 220 together.

次に、ＣＰＵ２１０は、第１着霜条件が成立しているか否かを判断する（ＳＴ５）。具体的には、ＣＰＵ２１０は、ＳＴ４で取り込んで記憶部２２０に記憶している熱交出口温度Ｔｅｏを読み出し、熱交出口温度Ｔｅｏが−１４℃以下であるか否かを判断する。 Next, the CPU 210 determines whether or not the first frost formation condition is satisfied (ST5). Specifically, the CPU 210 reads out the heat exchange outlet temperature Too taken in by ST4 and stored in the storage unit 220, and determines whether or not the heat exchange outlet temperature Too is −14 ° C. or lower.

第１着霜条件が成立していれば（ＳＴ５−Ｙｅｓ）、つまり、熱交出口温度Ｔｅｏが外気温度Ｔｏより５℃以上低ければ、ＣＰＵ２１０は、ＳＴ１２に処理を進める。第１着霜条件が成立していなければ（ＳＴ５−Ｎｏ）、つまり、熱交出口温度Ｔｅｏが−１４℃以下でなければ、ＣＰＵ２１０は、タイマー計測を開始し（ＳＴ６）、ＳＴ６でタイマー計測を開始してから第２所定時間が経過したか否かを判断する（ＳＴ７）。ここで、第２所定時間とは、外気温度センサ３７で検出した外気温度Ｔｏや冷媒温度センサ３５で検出した熱交出口温度Ｔｅｏを取り込む間隔時間であり、ここでは５分間である。 If the first frost formation condition is satisfied (ST5-Yes), that is, if the heat exchange outlet temperature Too is 5 ° C. or more lower than the outside air temperature To, the CPU 210 proceeds to ST12. If the first frost formation condition is not satisfied (ST5-No), that is, if the heat exchange outlet temperature Too is not -14 ° C or lower, the CPU 210 starts timer measurement (ST6) and performs timer measurement at ST6. It is determined whether or not the second predetermined time has elapsed since the start (ST7). Here, the second predetermined time is an interval time for taking in the outside air temperature To detected by the outside air temperature sensor 37 and the heat exchange outlet temperature Too detected by the refrigerant temperature sensor 35, and is 5 minutes here.

第２所定時間が経過していなければ（ＳＴ７−Ｎｏ）、ＣＰＵ２１０は、ＳＴ７に処理を戻す。第２所定時間が経過していれば（ＳＴ７−Ｙｅｓ）、ＣＰＵ２１０は、タイマーをリセットし（ＳＴ８）、外気温度センサ３７で検出した外気温度Ｔｏと冷媒温度センサ３５で検出した熱交出口温度Ｔｅｏをセンサ入力部２４０を介して取り込むとともに、記憶部２２０から現在の室内機５ａ〜５ｃの運転台数Ｎｉを読み込む（ＳＴ９）。ここでも、ＣＰＵ２１０は、取り込んだ外気温度Ｔｏと熱交出口温度Ｔｅｏ、および室内機５ａ〜５ｃの運転台数Ｎｉを併せて記憶部２２０に記憶する。 If the second predetermined time has not elapsed (ST7-No), the CPU 210 returns the process to ST7. If the second predetermined time has elapsed (ST7-Yes), the CPU 210 resets the timer (ST8), and the outside air temperature To detected by the outside air temperature sensor 37 and the heat exchange outlet temperature Teo detected by the refrigerant temperature sensor 35. Is taken in via the sensor input unit 240, and the operating number Ni of the current indoor units 5a to 5c is read from the storage unit 220 (ST9). Here, too, the CPU 210 stores the captured outside air temperature To, the heat exchange outlet temperature Too, and the operating number Ni of the indoor units 5a to 5c together in the storage unit 220.

次に、ＣＰＵ２１０は、第３着霜条件が成立しているか否かを判断する（ＳＴ１０）。具体的には、ＣＰＵ２１０は、ＳＴ４およびＳＴ９で記憶部２２０に記憶した熱交出口温度Ｔｅｏを読み出し、ＳＴ９で記憶した熱交出口温度Ｔｅｏが−６℃以下か否か、かつ、ＳＴ９で記憶した熱交出口温度ＴｅｏとＳＴ４で記憶した熱交出口温度Ｔｅｏを用いて算出した熱交出口温度の低下率が２℃／５分以上か否か、かつ、ＳＴ４およびＳＴ９で記憶部２２０に記憶した室内機５ａ〜５ｃの運転台数を比較して室内機５ａ〜５ｃの運転台数が増加したか否かを判断している。すなわち、連続する２つの熱交出口温度Ｔｅｏを記憶する間に室内機５ａ〜ｃの運転台数が増加したか否かを判断している。 Next, the CPU 210 determines whether or not the third frost formation condition is satisfied (ST10). Specifically, the CPU 210 reads out the heat exchange outlet temperature Too stored in the storage unit 220 in ST4 and ST9, and stores whether or not the heat exchange outlet temperature Too stored in ST9 is −6 ° C. or lower and is stored in ST9. Whether or not the rate of decrease in the heat exchange outlet temperature calculated using the heat exchange outlet temperature Too and the heat exchange outlet temperature Too stored in ST4 is 2 ° C./5 minutes or more, and stored in the storage unit 220 in ST4 and ST9. By comparing the operating numbers of the indoor units 5a to 5c, it is determined whether or not the operating number of the indoor units 5a to 5c has increased. That is, it is determined whether or not the number of indoor units 5a to 5c in operation has increased while storing two consecutive heat exchange outlet temperatures Too.

第３着霜条件が成立していなければ（ＳＴ１０−Ｎｏ）、つまり、熱交出口温度Ｔｅｏが−６℃より高いあるいは熱交出口温度の低下率が２℃／５分未満あるいは室内機５ａ〜５ｃの運転台数が増加していれば、ＣＰＵ２１０は、第２着霜条件が成立しているか否かを判断する（ＳＴ１１）。具体的には、ＣＰＵ２１０は、ＳＴ１１において、ＳＴ９で記憶部２２０に記憶した外気温度Ｔｏが所定値が５℃より低いか否か、かつ、ＳＴ４およびＳＴ９で記憶部２２０に記憶した室内機５ａ〜５ｃの運転台数を比較して室内機５ａ〜５ｃの運転台数が増加した回数が３０回以上となったか否かを判断している。尚、室内機５ａ〜５ｃの運転台数が増加した回数は、空気調和装置１が暖房運転を開始してから、若しくは前回除霜運転を終了したときを起点として積算され、記憶部２２０に記憶される。第２着霜条件が成立していなければ（ＳＴ１１−Ｎｏ）、つまり、室内機５ａ〜５ｃの運転台数が増加した回数が３０回以上となっていなければ、ＣＰＵ２１０は、ＳＴ５に処理を戻す。第３着霜条件が成立していれば（ＳＴ１０−Ｙｅｓ）、つまり、熱交出口温度Ｔｅｏが−６℃以下および熱交出口温度の低下率が２℃／５分以上および室内機５ａ〜５ｃの運転台数が増加していなければ、ＣＰＵ２１０は、除霜運転準備処理を実行する（ＳＴ１２）。同様に、第２着霜条件が成立していれば（ＳＴ１１−Ｙｅｓ）、つまり、室内機５ａ〜５ｃの運転台数が増加した回数が３０回以上であれば、室内機５ａ〜５ｃの運転台数の増加が繰り返されて部分的に着霜が進行していると判断し、ＣＰＵ２１０は、除霜運転準備処理を実行する（ＳＴ１２）。除霜運転準備処理とは、除霜運転を行うために冷媒回路１０を切り替えるときにＣＰＵ２１０が行う処理であり、前述したように、ＣＰＵ２１０は、圧縮機２１および室外ファン２６を停止し、図１（Ａ）に示すように四方弁２２を破線で示す状態、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、また、ポートｃとポートｄが連通するよう、切り換える。そして、ＳＴ１２の処理を終えたＣＰＵ２１０は、圧縮機２１を再起動して除霜運転を開始する（ＳＴ１３）。 If the third frost condition is not satisfied (ST10-No), that is, the heat exchange outlet temperature Too is higher than -6 ° C, the rate of decrease in the heat exchange outlet temperature is less than 2 ° C./5 minutes, or the indoor unit 5a ~ If the number of operating units of 5c is increasing, the CPU 210 determines whether or not the second frost formation condition is satisfied (ST11). Specifically, the CPU 210 determines whether the outside air temperature To stored in the storage unit 220 in ST9 is lower than 5 ° C. in ST11, and the indoor units 5a to 5a stored in the storage unit 220 in ST4 and ST9. By comparing the number of operating units of 5c, it is determined whether or not the number of times the number of operating units of the indoor units 5a to 5c has increased is 30 or more. The number of times the number of indoor units 5a to 5c in operation has increased is accumulated starting from the time when the air conditioner 1 starts the heating operation or when the previous defrosting operation is finished, and is stored in the storage unit 220. To. If the second frost formation condition is not satisfied (ST11-No), that is, if the number of times the number of operating indoor units 5a to 5c has increased is not 30 or more, the CPU 210 returns the process to ST5. If the third frost condition is satisfied (ST10-Yes), that is, the heat exchange outlet temperature Too is -6 ° C or less, the rate of decrease of the heat exchange outlet temperature is 2 ° C./5 minutes or more, and the indoor unit 5a to 5c. If the number of operating units is not increasing, the CPU 210 executes the defrosting operation preparatory process (ST12). Similarly, if the second frost formation condition is satisfied (ST11-Yes), that is, if the number of times the number of indoor units 5a to 5c has increased is 30 or more, the number of indoor units 5a to 5c operated It is determined that the frost formation is partially progressing due to the repeated increase of the frost formation, and the CPU 210 executes the defrosting operation preparation process (ST12). The defrosting operation preparatory process is a process performed by the CPU 210 when the refrigerant circuit 10 is switched to perform the defrosting operation. As described above, the CPU 210 stops the compressor 21 and the outdoor fan 26, and FIG. As shown in (A), the four-way valve 22 is switched so as to be shown by a broken line, that is, so that the port a and the port b of the four-way valve 22 communicate with each other, and the port c and the port d communicate with each other. Then, the CPU 210 that has completed the processing of ST12 restarts the compressor 21 and starts the defrosting operation (ST13).

次に、ＣＰＵ２１０は、除霜運転終了条件が成立したか否かを判断する（ＳＴ１４）。除霜運転終了条件とは、例えば、除霜運転中に取り込んだ熱交出口温度Ｔｅｏが１０℃以上となった場合や、ＳＴ１２で除霜運転を開始してから１０分以上が経過した場合のように、室外熱交換器２３に付着していた霜が全て融解したと考えられる条件である。 Next, the CPU 210 determines whether or not the defrosting operation end condition is satisfied (ST14). The defrosting operation end condition is, for example, when the heat exchange outlet temperature Too taken in during the defrosting operation becomes 10 ° C. or higher, or when 10 minutes or more have passed since the defrosting operation was started in ST12. As described above, it is a condition that all the frost adhering to the outdoor heat exchanger 23 is considered to have melted.

除霜運転終了条件が成立していなければ（ＳＴ１４−Ｎｏ）、ＣＰＵ２１０は、ＳＴ１３に処理を戻して除霜運転を継続する。除霜運転終了条件が成立していれば（ＳＴ１４−Ｙｅｓ）、ＣＰＵ２１０は、暖房運転再開処理を実行する（ＳＴ１５）。暖房運転再開処理とは、除霜運転から暖房運転に復帰するために冷媒回路１０を切り替えるときにＣＰＵ２１０が行う処理であり、ＣＰＵ２１０は、圧縮機２１を停止した後、図１（Ａ）に示すように四方弁２２を実線で示す状態、すなわち、四方弁２２のポートａとポートｄが連通するよう、また、ポートｂとポートｃが連通するよう、切り換える。そして、ＳＴ１４の処理を終えたＣＰＵ２１０は、圧縮機２１および室外ファン２６を再起動して暖房運転を再開し（ＳＴ１６）、ＳＴ１に処理を戻す。 If the defrosting operation end condition is not satisfied (ST14-No), the CPU 210 returns the process to ST13 and continues the defrosting operation. If the defrosting operation end condition is satisfied (ST14-Yes), the CPU 210 executes the heating operation restart process (ST15). The heating operation restart process is a process performed by the CPU 210 when the refrigerant circuit 10 is switched to return from the defrosting operation to the heating operation, and the CPU 210 is shown in FIG. 1 (A) after the compressor 21 is stopped. As described above, the four-way valve 22 is switched so as to be shown by a solid line, that is, so that the port a and the port d of the four-way valve 22 communicate with each other, and the port b and the port c communicate with each other. Then, the CPU 210 that has completed the processing of ST14 restarts the compressor 21 and the outdoor fan 26 to restart the heating operation (ST16), and returns the processing to ST1.

１空気調和装置
２室外機
５ａ〜５ｃ室内機
２１圧縮機
２２四方弁
２３室外熱交換器
３５冷媒温度センサ
３７外気温度センサ
２００室外機制御部
２１０ＣＰＵ
２２０記憶部
２４０センサ入力部 1 Air conditioner 2 Outdoor unit 5a to 5c Indoor unit 21 Compressor 22 Four-way valve 23 Outdoor heat exchanger 35 Refrigerant temperature sensor 37 Outdoor air temperature sensor 200 Outdoor unit control unit 210 CPU
220 Storage unit 240 Sensor input unit

Claims

A heat exchange outlet that detects the heat exchange outlet temperature, which is the temperature of the refrigerant flowing out of the outdoor heat exchanger when the compressor, the four-way valve, the outdoor heat exchanger, and the outdoor heat exchanger function as an evaporator. An outdoor unit having a temperature detecting means and an outside air temperature detecting means for detecting the outside air temperature,
Multiple indoor units with indoor heat exchangers and
A refrigerant circuit in which the compressor, the four-way valve, the outdoor heat exchanger, and a plurality of the indoor heat exchangers are connected by a refrigerant pipe.
Control means for controlling the compressor and the four-way valve,
It is an air conditioner with
When the control means uses the refrigerant circuit as a heating cycle to perform heating operation in the plurality of indoor units.
The heat exchange outlet temperature detected by the heat exchange outlet temperature detecting means, the outside air temperature detected by the outside air temperature detecting means, and the number of operating units of the indoor unit performing the heating operation are periodically taken in in a time series. Remember in
If either the first frost condition or the second frost condition, which is the condition for frost formation in the outdoor heat exchanger, is satisfied, the four-way valve is switched to use the refrigerant circuit as a cooling cycle, and the outdoor Perform a defrosting operation to defrost the heat exchanger,
The first frost condition is whether or not the heat exchange outlet temperature is lower than the first threshold temperature, or whether or not the duration of the heating operation is longer than the predetermined duration, or the outside air temperature and the above. Including at least one of whether or not the temperature difference of the heat exchange outlet temperature is larger than the predetermined temperature difference.
The second frosting condition is whether or not the outside air temperature is lower than the predetermined temperature, and the number of times the number of indoor units in operation has increased since the heating operation was started or the previous defrosting operation was completed. An air conditioner characterized in that the number of times has exceeded a predetermined number of times.

The air conditioner according to claim 1, wherein the predetermined number of times is set to a smaller value as the outside air temperature becomes higher.

If any one of the first frost condition and the second frost condition and the third frost condition, which is a condition for frost formation in the outdoor heat exchanger, is satisfied, the four-way valve is opened. The refrigerant circuit is switched to a cooling cycle, and a defrosting operation for defrosting the outdoor heat exchanger is executed.
The third frost condition is stored in time series as to whether or not the latest heat exchange outlet temperature among the heat exchange outlet temperatures stored in time series is lower than the second threshold temperature higher than the first threshold temperature. Whether or not the rate of decrease in the heat exchange outlet temperature calculated using the two consecutive heat exchange outlet temperatures out of the above-mentioned heat exchange outlet temperatures is greater than the predetermined decrease rate, and the two consecutive heat exchange outlet temperatures are determined. Including whether or not the number of operating units of the indoor unit increased during storage,
The air conditioner according to claim 1 or 2, wherein the air conditioner.