【０００１】
【発明の属する技術分野】
本発明は空気調和機の除霜制御技術に係わり、詳しくは、外気温が低い条件の暖房運転時でも「空除霜」を防止し、最適の着霜状態で除霜をさせることができ、低温暖房能力の向上および快適性が向上することができる空気調和機の除霜制御方法に関する。
【０００２】
【従来の技術】
空気調和機の冷凍サイクルは例えば図１に示すように、圧縮機１と、四方弁２と、室内熱交換器３と、減圧装置４と、室外熱交換器５とを環状に連結してなり、暖房運転時に圧縮機１より吐出した冷媒は四方弁２を経て室内熱交換器３、減圧装置４、室外熱交換器５の順に流れ、再度、四方弁２を経て圧縮機１に循環するようになっており、室内熱交換器３にはその配管温度を検出する温度センサ６が設けられている。
【０００３】
ところで、暖房運転においては、室外熱交換器５に凝縮水が付着し、これが結氷することにより熱交換に悪影響を及ぼすことになる。そこで、従来の空気調和機では暖房運転時に室内熱交換器３の温度が除霜運転開始温度まで降下すると除霜タイマーがセットされ、この除霜タイマーがタイムアップするまで除霜制御が行われるようになっていた。
しかしながら、以上説明したような従来の除霜運転制御方法では、既に除霜が終了しているような場合であっても除霜タイマーがタイムアップするまで除霜制御動作が続くことになり、元の暖房運転に戻るのが遅れ、快適性が損なわれる恐れがあった。
【０００４】
そこで、（１’）一定時間毎に温度センサ６ が検出した室内熱交換器３の温度の低下量が所定値以上である場合、除霜を開始し、除霜運転開始後、所定時間毎に室内熱交換器の温度を検出し、前後２回の検出温度の温度差が所定値以下のとき、除霜運転を終了させるようにした構成としたものがある。また、前記温度差が所定値以上のとき、除霜運転時間が所定時間を経過した場合には除霜運転を終了させるようにしたものがある（例えば、特許文献１参照。）。
または、（２’）温度センサ６ が検出した室内熱交換器３の温度と、室温度センサが検出した室温との温度差が所定値以下である場合、除霜運転を行う。
または、（３’）暖房運転時間が所定時間経過した場合、除霜運転を行う。
【０００５】
しかし、（１’）では室内熱交換器温度の低下量の測定中に運転を停止され再び運転開始した場合（設定温度に到達して圧縮機が停止した場合も同様）、再び低下量を再検出しなくてはならない。そして、これを繰返すと除霜が動作せずに霜が着霜し続けてしまう。ある程度霜が付着した状態で運転を開始された場合、室外機での熱交換が行われないため室内熱交換器温度は最初から低く、室内熱交換器温度の低下量を検出することができずに除霜が動作しなくなってしまう。そのため（１’）だけではなくて（２’）、（３’）の条件が成立した場合でも除霜を動作させる制御方法を行っている。
但し、暖房運転時間が所定時間経過する前に運転を停止され、再び運転開始した場合も同様のことが起きてしまうため、除霜動作までのマスクタイムは短めに設定されている。
【０００６】
しかしながら、（２’）では除霜動作条件に室内熱交換器温度と室内温度の差を使用しているが、室内熱交換器温度は外気温度によって大きく変化してしまうため、外気温が低い状態で運転された場合、霜が付着してないにも関わらず室内熱交換器温度が低く室温との温度差も小さくなってしまい、マスクタイムが経過した時点で除霜が動作してしまう（空除霜）。従って、通常以上に暖房能力が必要とされる外気温が低い時に、短めに設定されたマスクタイムで暖房運転が中段され除霜が動作してしまう問題がある。
【０００７】
【特許文献１】
特開２０００−３９２３８号公報（第２〜４頁、第１〜４図）
【０００８】
【発明が解決しようとする課題】
本発明においては、上記問題点に鑑み、外気温が低い条件の暖房運転時でも「空除霜」を防止し、最適の着霜状態で除霜をさせることができるため、暖房運転時間を従来よりも長くすることが可能となり、低温暖房能力の向上および快適性が向上することができる空気調和機の除霜制御方法を提供することを目的としている。
【０００９】
【課題を解決するための手段】
本発明は上記の課題を解決するためになされたもので、少なくとも暖房運転時に冷凍サイクルを構成する室内熱交換器の所定時間毎の温度変化、または前記室内熱交換器の温度と室内温度との温度差および、または暖房運転開始からの一定のマスクタイム経過時間により、室外熱交換器の除霜運転を所定時間行うようにしてなる空気調和機において、
前記室内熱交換器の温度の低下が所定値以下で、前記マスクタイムによる除霜が複数回連続して行われた場合、外気温が目標温度より低いと判断し、前記室内熱交換器の温度と室内温度との温度差を当初の設定値より所定値小さくする、低外気温動作条件に切換えて除霜運転を行うようにしてなる構成となっている。
【００１０】
また、少なくとも暖房運転時に冷凍サイクルを構成する室内熱交換器の所定時間毎の温度変化、または前記室内熱交換器の温度と室内温度との温度差および、または暖房運転開始からの一定のマスクタイム経過時間により、室外熱交換器の除霜運転を所定時間行うようにしてなる空気調和機において、
前記室内熱交換器の温度の低下が所定値以下で、前記マスクタイムによる除霜が複数回連続して行われた場合、外気温が目標温度より低いと判断し、前記マスクタイムを当初の設定値より所定値長くする、低外気温動作条件に切換えて除霜運転を行うようにしてなる構成となっている。
【００１１】
また、少なくとも暖房運転時に冷凍サイクルを構成する室内熱交換器の所定時間毎の温度変化、または前記室内熱交換器の温度と室内温度との温度差および、または暖房運転開始からの一定のマスクタイム経過時間により、室外熱交換器の除霜運転を所定時間行うようにしてなる空気調和機において、
前記室内熱交換器の温度の低下が所定値以下で、前記マスクタイムによる除霜が複数回連続して行われた場合、外気温が目標温度より低いと判断し、前記室内熱交換器の所定時間毎の温度が所定値に低下するまで除霜を行わないようにする、低外気温動作条件に切換えて除霜運転を行うようにしてなる構成となっている。
【００１２】
また、前記低外気温動作条件でのマスクタイムによる除霜が複数回連続して行われた場合、外気温が更に低い極低外気温と判断し、前記室内熱交換器の温度と室内温度との温度差を低外気温動作条件の設定値より所定値小さくする、極低外気温動作条件に切換えて除霜運転を行うようにしてなる構成となっている。
【００１３】
また、前記低外気温動作条件でのマスクタイムによる除霜が複数回連続して行われた場合、外気温が更に低い極低外気温と判断し、前記マスクタイムを低外気温動作条件の設定値より所定値長くする、極低外気温動作条件に切換えて除霜運転を行うようにしてなる構成となっている。
【００１４】
また、前記低外気温動作条件でのマスクタイムによる除霜が複数回連続して行われた場合、外気温が更に低い極低外気温と判断し、前記室内熱交換器の所定時間毎の温度が所定値低下するまで除霜を行わないようにする、極低外気温動作条件に切換えて除霜運転を行うようにしてなる構成となっている。
【００１５】
【発明の実施の形態】
以下、本発明の実施の形態を図１〜図４に基づいて説明する。
図１は本発明の除霜制御方法を実行する冷凍サイクルで、圧縮機１、四方弁２、室内熱交換器３、減圧装置４、室外熱交換器５を環状に連結してなり、暖房運転時の冷媒は実線細矢印の方向に循環し、除霜（冷房）運転時の冷媒は実線太矢印の方向に循環するようになっている。なお、室内熱交換器３にはその配管温度を検出する温度センサ６が設けられている。
【００１６】
図２は当該空気調和機の制御系のブロック図である。室内機Ａ側には室内熱交換器３で熱交換された空気を室内へ送出する室内送風機７および室内への風向を調節する風向調節装置８等を制御する室内機制御部９の他、運転状態等を報知する報知部１０、室温検出用の温度センサ１１、および前記温度センサ６が設けられ、一方の室外機Ｂ側には室内機制御部９からの指令に基づき、圧縮機１、四方弁２、室外送風機１２等を制御する室外機制御部１３が設けられている。
【００１７】
暖房運転において、室外熱交換器５に凝縮水が付着し、これが結氷すると除霜運転が行われる。まず、暖房運転を開始してから除霜開始を抑制しておく時間（マスクタイム）を３０分としておく。そして、以下の除霜動作条件を設定する。
（１）一定時間毎に温度センサ６が検出した室内熱交換器３の温度Ｔｎの低下量が所定値Ｔ１以上である場合。
（２）温度センサ６が検出した室内熱交換器３の温度Ｔｎと、温度センサ１１が検出した室温Ｔｓとの温度差が所定値Ｔ２以下である場合。
（３）暖房運転時間が所定時間経過した場合。
上記（１）〜（３）のいずれかの条件に達した場合、通常の除霜運転を所定時間行い、除霜タイマーがタイムアップしたら除霜を終了し、暖房運転に復帰する。
【００１８】
しかし、前記室内熱交換器３の温度の低下が所定値以下で、前記マスクタイムによる除霜が複数回（例えば、４回）連続して行われた場合（空除霜）、外気温が設計目標温度より低いと判断し、除霜動作条件を以下の低外気温動作条件にする。
（４）前記室内熱交換器３の温度Ｔｎと、室内温度Ｔｓとの温度差を当初の設定値Ｔ２より３℃小さくする。
（５）前記マスクタイムを当初の設定値３０分より、更に３０分延長し、６０分とする。
（６）前記室内熱交換器３の所定時間毎の温度が所定値に低下するまで除霜を行わないようにする。（室内熱交換器３の温度と室内温度との温度差では除霜を動作させない）。
上記（４）〜（６）のいずれかの低外気温動作条件に切換えて除霜運転を所定時間行い、除霜タイマーがタイムアップしたら除霜を終了し、暖房運転に復帰する。
【００１９】
また、前記各低外気温動作条件での除霜運転の繰返し回数をカウントし、この回数が所定回数（例えば、４回）以上に達した場合、外気温が更に低い極低外気温と判断し、除霜動作条件を以下の極低外気温動作条件にする。
（７）前記室内熱交換器３の温度Ｔｎと、室内温度Ｔｓとの温度差を当初の設定値Ｔ２より５℃小さくする。
（８）前記マスクタイムを当初の設定値３０分より、更に６０分延長し、９０分とする。
（９）前記室内熱交換器３の所定時間毎の温度が所定値に低下するまで除霜を行わないようにする。（室内熱交換器３の温度と室内温度との温度差では除霜を動作させない）。
上記（７）〜（９）のいずれかの極低外気温動作条件に切換えて除霜運転を所定時間行い、除霜タイマーがタイムアップしたら除霜を終了し、暖房運転に復帰する。
【００２０】
以下、本発明の除霜制御方法を図３のフローチャートにより説明する。
まず、暖房運転が開始されると、ステップＳＴ１で除霜開始を抑制しておく時間（マスクタイム）が３０分経過したかどうか判断される。もし３０分経過していれば、ステップＳＴ２で上述の（１）〜（３）の除霜動作条件に達したかどうか判定され、もし、条件に達していなければ、ステップＳＴ３に進め５分間の時間待ちをし、ステップＳＴ４で再度除霜動作条件に達したかどうか判定され、もし、条件に達していればステップＳＴ５で除霜運転を行う。この時室内送風機７、圧縮機１、室外送風機１２の運転を停止させ、報知部１０に除霜表示を行い、四方弁２を暖房運転時の状態から除霜（冷房）運転時の状態に切り替える。そして除霜タイマーがタイムアップしたら除霜を終了し、ステップＳＴ６で暖房運転に復帰する。
【００２１】
前記ステップＳＴ２で除霜動作条件に達していれば、ステップＳＴ７で除霜動作条件が上述の（１）の室内熱交換器３の温度Ｔｎの低下量が所定値Ｔ１以上であるかどうか確認され、もし、所定値Ｔ１以上であれば、ステップＳＴ８で、上記同様に、通常の除霜運転が行われ、ステップＳＴ９で暖房運転に復帰する。
【００２２】
次に、ステップＳＴ２で除霜動作条件に達していなければ、即ち、温度Ｔｎの低下量が所定値Ｔ１以下であれば、マスクタイムによる除霜回数をカウントし（ステップＳＴ１０）、除霜回数が４回以上かどうか判断され（ステップＳＴ１１）、もし、４回以上であれば外気温が設計目標温度より低く、「空除霜」であると判断し、ステップＳＴ１２で低外気温除霜制御へ移行する。もし、４回以下であれば、ステップＳＴ８で上記と同様に、通常の除霜を行う。
【００２３】
そして、ステップＳＴ１３で低外気温での除霜回数をカウントし、除霜回数が４回以上かどうか判断され、もし、４回以下であれば、ステップＳＴ１４で低外気温除霜へ切換えて、上述の（４）〜（６）のいずれかの低外気温動作条件であれば除霜運転を行い暖房運転に復帰する（ステップＳＴ１５〜１７）。
【００２４】
もし、ステップＳＴ１３でカウンタが４回であれば、ステップＳＴ１８で極低外気温除霜制御へ移行する。そして、上述の（７）〜（９）のいずれかの極低外気温動作条件であれば除霜運転を行い暖房運転に復帰する（ステップＳＴ１９〜２１）。
【００２５】
以上説明したように、前記室内熱交換器３の温度の低下が所定値以下で、マスクタイムによる除霜が複数回連続して行われた場合、外気温が目標温度より低いと判断し、除霜動作条件を、前記室内熱交換器３の温度と室内温度との温度差を当初の設定値より所定値小さくする、または前記マスクタイムを当初の設定値より所定値長くする、または前記室内熱交換器３の所定時間毎の温度が所定値に低下するまで除霜を行わないようにし、これらのいずれかの低外気温動作条件に切換えて除霜運転を行うようにした構成とすることにより、外気温が低い条件の暖房運転時でも「空除霜」を防止し、最適の着霜状態で除霜をさせることができるため、暖房運転時間を従来よりも長くすることが可能となり、低温暖房能力の向上および快適性が向上することができる空気調和機の除霜制御方法となる。
【００２６】
【発明の効果】
以上説明したような除霜制御機能を備えた空気調和機であれば、外気温が低い条件の暖房運転時でも「空除霜」を防止し、最適の着霜状態で除霜をさせることができるため、暖房運転時間を従来よりも長くすることが可能となり、低温暖房能力の向上および快適性が向上することができる空気調和機の除霜制御方法となる。
【図面の簡単な説明】
【図１】本発明および従来例に係わる空気調和機の冷凍サイクルである。
【図２】本発明に係わる空気調和機の制御系のブロック図である。
【図３】本発明の除霜制御動作の概略を示すフローチャートである。
【符号の説明】
Ａ 室内機
Ｂ 室外機
１ 圧縮機
２ 四方弁
３ 室内熱交換器
４ 減圧装置
５ 室外熱交換器
６ 温度センサ（室内熱交換器用）
７ 室内送風機
９ 室内機制御部
１０ 報知部
１１ 室温センサ
１２ 室外送風機
１３ 室外機制御部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to the defrost control technology of the air conditioner, in particular, to prevent "empty defrost" even during the heating operation under conditions where the outside air temperature is low, it is possible to perform defrost in an optimal frost state, The present invention relates to a method for controlling defrosting of an air conditioner that can improve low-temperature heating capacity and comfort.
[0002]
[Prior art]
As shown in FIG. 1, for example, the refrigeration cycle of the air conditioner is formed by connecting a compressor 1, a four-way valve 2, an indoor heat exchanger 3, a pressure reducing device 4, and an outdoor heat exchanger 5 in a ring shape. During the heating operation, the refrigerant discharged from the compressor 1 flows through the four-way valve 2, flows through the indoor heat exchanger 3, the pressure reducing device 4, and the outdoor heat exchanger 5 in this order, and circulates again through the four-way valve 2 to the compressor 1. The indoor heat exchanger 3 is provided with a temperature sensor 6 for detecting the pipe temperature.
[0003]
By the way, in the heating operation, condensed water adheres to the outdoor heat exchanger 5 and freezes, which adversely affects heat exchange. Therefore, in the conventional air conditioner, when the temperature of the indoor heat exchanger 3 drops to the defrost operation start temperature during the heating operation, a defrost timer is set, and the defrost control is performed until the defrost timer times out. Had become.
However, in the conventional defrosting operation control method as described above, even if the defrosting has already been completed, the defrosting control operation continues until the defrosting timer expires. It was delayed to return to the heating operation, and the comfort could be impaired.
[0004]
Therefore, (1 ′) when the amount of decrease in the temperature of the indoor heat exchanger 3 detected by the temperature sensor 6 at regular intervals is equal to or greater than a predetermined value, defrosting is started, and after the start of the defrosting operation, at regular intervals. There is a configuration in which the temperature of the indoor heat exchanger is detected, and the defrosting operation is terminated when the temperature difference between the two detected temperatures before and after is less than or equal to a predetermined value. Further, when the temperature difference is equal to or larger than a predetermined value, the defrosting operation is terminated when the defrosting operation time exceeds a predetermined time (for example, see Patent Document 1).
Alternatively, (2 ′) the defrosting operation is performed when the temperature difference between the temperature of the indoor heat exchanger 3 detected by the temperature sensor 6 and the room temperature detected by the room temperature sensor is equal to or less than a predetermined value.
Alternatively, (3 ′) when the heating operation time has passed a predetermined time, the defrosting operation is performed.
[0005]
However, in (1 ′), when the operation is stopped and the operation is started again during the measurement of the decrease in the temperature of the indoor heat exchanger (the same is true when the set temperature is reached and the compressor is stopped), the decrease is again measured. Must be detected. When this is repeated, defrost does not operate and frost continues to form. If the operation is started in a state where some frost has adhered, the indoor heat exchanger temperature is low from the beginning because no heat is exchanged in the outdoor unit, and the amount of decrease in the indoor heat exchanger temperature cannot be detected. The defrost stops working. Therefore, a control method for operating the defrosting is performed even when the conditions (2 ′) and (3 ′) are satisfied in addition to the condition (1 ′).
However, when the operation is stopped before the heating operation time elapses the predetermined time and the operation is started again, the same thing occurs. Therefore, the mask time until the defrosting operation is set short.
[0006]
However, in (2 ′), the difference between the indoor heat exchanger temperature and the indoor temperature is used as the defrosting operation condition. However, since the indoor heat exchanger temperature greatly changes depending on the outdoor air temperature, the external air temperature is low. If the operation is performed in a room, the temperature of the indoor heat exchanger is low and the temperature difference from the room temperature is small even though no frost is attached, and defrosting is performed when the mask time elapses (empty). Defrost). Accordingly, there is a problem that when the outside air temperature that requires more heating capacity than usual is low, the heating operation is performed in the middle stage with a short mask time and defrosting is performed.
[0007]
[Patent Document 1]
JP-A-2000-39238 (pages 2 to 4, FIGS. 1 to 4)
[0008]
[Problems to be solved by the invention]
In the present invention, in view of the above problems, even during the heating operation under conditions where the outside air temperature is low, it is possible to prevent "empty defrost" and perform defrosting in an optimal frosted state, so that the heating operation time can be reduced by the conventional method. It is an object of the present invention to provide a method for controlling defrosting of an air conditioner, which can increase the low-temperature heating capacity and the comfort.
[0009]
[Means for Solving the Problems]
The present invention has been made in order to solve the above-described problems, and at least a temperature change of an indoor heat exchanger constituting a refrigeration cycle at least every predetermined time during a heating operation, or a temperature change of the indoor heat exchanger and an indoor temperature. In the air conditioner configured to perform the defrosting operation of the outdoor heat exchanger for a predetermined time by the temperature difference and or a certain mask time elapsed from the start of the heating operation,
When the decrease in the temperature of the indoor heat exchanger is equal to or less than a predetermined value and the defrosting by the mask time is performed a plurality of times in succession, it is determined that the outside air temperature is lower than the target temperature, and the temperature of the indoor heat exchanger is The defrosting operation is performed by switching to a low outside air temperature operating condition in which the temperature difference between the room temperature and the room temperature is reduced by a predetermined value from an initial set value.
[0010]
Further, at least a temperature change of the indoor heat exchanger constituting the refrigeration cycle at every predetermined time during the heating operation, or a temperature difference between the temperature of the indoor heat exchanger and the indoor temperature, and / or a certain mask time from the start of the heating operation. In the air conditioner configured to perform the defrosting operation of the outdoor heat exchanger for a predetermined time by the elapsed time,
When the temperature of the indoor heat exchanger is equal to or lower than a predetermined value and the defrosting by the mask time is performed a plurality of times in succession, it is determined that the outside air temperature is lower than the target temperature, and the mask time is initially set. The defrosting operation is performed by switching to a low outside air temperature operation condition that is longer than a predetermined value by a predetermined value.
[0011]
Further, at least a temperature change of the indoor heat exchanger constituting the refrigeration cycle at every predetermined time during the heating operation, or a temperature difference between the temperature of the indoor heat exchanger and the indoor temperature, and / or a certain mask time from the start of the heating operation. In the air conditioner configured to perform the defrosting operation of the outdoor heat exchanger for a predetermined time by the elapsed time,
If the decrease in the temperature of the indoor heat exchanger is equal to or less than a predetermined value and the defrosting by the mask time is performed a plurality of times in succession, it is determined that the outside air temperature is lower than the target temperature, and the predetermined temperature of the indoor heat exchanger is determined. The defrosting operation is performed by switching to a low outside air temperature operation condition so that defrosting is not performed until the temperature at each time drops to a predetermined value.
[0012]
Further, when the defrosting by the mask time under the low outside air temperature operation condition is continuously performed a plurality of times, it is determined that the outside air temperature is lower than the extremely low outside air temperature, and the temperature of the indoor heat exchanger and the indoor temperature are compared. The defrosting operation is performed by switching to the extremely low outside air temperature operation condition, in which the temperature difference is smaller than the set value of the low outside air temperature operation condition by a predetermined value.
[0013]
Further, when defrosting by the mask time under the low outside temperature operation condition is continuously performed a plurality of times, it is determined that the outside air temperature is lower than the extremely low outside temperature, and the mask time is set to the low outside temperature operation condition. The defrosting operation is performed by switching to an extremely low outside air temperature operation condition that is longer than a predetermined value.
[0014]
Further, when the defrosting by the mask time under the low outside air temperature operation condition is continuously performed a plurality of times, it is determined that the outside air temperature is lower than the extremely low outside air temperature, and the temperature of the indoor heat exchanger at a predetermined time interval is determined. The defrosting operation is performed by switching to the extremely low outside air temperature operation condition so that the defrosting is not performed until the temperature decreases by a predetermined value.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows a refrigeration cycle for executing a defrosting control method of the present invention, in which a compressor 1, a four-way valve 2, an indoor heat exchanger 3, a decompression device 4, and an outdoor heat exchanger 5 are connected in a ring shape to perform a heating operation. The refrigerant at the time circulates in the direction of the solid thin arrow, and the refrigerant during the defrost (cooling) operation circulates in the direction of the solid thick arrow. The indoor heat exchanger 3 is provided with a temperature sensor 6 for detecting the temperature of the pipe.
[0016]
FIG. 2 is a block diagram of a control system of the air conditioner. On the indoor unit A side, in addition to the indoor unit control unit 9 for controlling an indoor blower 7 for sending out the air heat exchanged by the indoor heat exchanger 3 to the room and a wind direction adjusting device 8 for adjusting the wind direction to the room, etc. A notifying unit 10 for notifying a state and the like, a temperature sensor 11 for detecting room temperature, and the temperature sensor 6 are provided. On the one side of the outdoor unit B, the compressor 1, the four-way An outdoor unit control unit 13 that controls the valve 2, the outdoor blower 12, and the like is provided.
[0017]
In the heating operation, when condensed water adheres to the outdoor heat exchanger 5 and freezes, defrosting operation is performed. First, the time (mask time) for suppressing the start of defrosting after starting the heating operation is set to 30 minutes. Then, the following defrosting operation conditions are set.
(1) A case where the amount of decrease in the temperature Tn of the indoor heat exchanger 3 detected by the temperature sensor 6 at regular intervals is equal to or more than a predetermined value T1.
(2) When the temperature difference between the temperature Tn of the indoor heat exchanger 3 detected by the temperature sensor 6 and the room temperature Ts detected by the temperature sensor 11 is equal to or less than a predetermined value T2.
(3) When the heating operation time has passed a predetermined time.
When any of the above conditions (1) to (3) is reached, normal defrosting operation is performed for a predetermined time, and when the defrost timer expires, defrosting is terminated and the operation returns to the heating operation.
[0018]
However, when the temperature of the indoor heat exchanger 3 is lower than a predetermined value and the defrosting by the mask time is performed a plurality of times (for example, four times) continuously (empty defrosting), the outside air temperature is designed. It is determined that the temperature is lower than the target temperature, and the defrosting operation condition is set to the following low outside air temperature operation condition.
(4) The temperature difference between the temperature Tn of the indoor heat exchanger 3 and the indoor temperature Ts is reduced by 3 ° C. from the initial set value T2.
(5) The mask time is further extended by 30 minutes from the initially set value of 30 minutes to 60 minutes.
(6) Defrosting is not performed until the temperature of the indoor heat exchanger 3 at a predetermined time decreases to a predetermined value. (Defrosting is not operated at a temperature difference between the temperature of the indoor heat exchanger 3 and the indoor temperature).
The defrosting operation is performed for a predetermined time by switching to any of the low outside air temperature operation conditions of (4) to (6) above. When the defrost timer expires, the defrost is terminated and the operation returns to the heating operation.
[0019]
Further, the number of repetitions of the defrosting operation under each of the low outside air temperature operation conditions is counted, and when this number reaches a predetermined number (for example, 4 times) or more, it is determined that the outside air temperature is a very low outside air temperature. The defrosting operation conditions are set to the following extremely low outside air temperature operation conditions.
(7) The temperature difference between the temperature Tn of the indoor heat exchanger 3 and the indoor temperature Ts is reduced by 5 ° C. from the initial set value T2.
(8) The mask time is further extended by 60 minutes from the initially set value of 30 minutes to 90 minutes.
(9) Defrosting is not performed until the temperature of the indoor heat exchanger 3 every predetermined time decreases to a predetermined value. (Defrosting is not operated at a temperature difference between the temperature of the indoor heat exchanger 3 and the indoor temperature).
The defrosting operation is performed for a predetermined time by switching to any of the extremely low outside air temperature operation conditions (7) to (9), and when the defrost timer expires, the defrost is terminated and the operation returns to the heating operation.
[0020]
Hereinafter, the defrost control method of the present invention will be described with reference to the flowchart of FIG.
First, when the heating operation is started, it is determined whether or not the time (mask time) for suppressing the start of defrosting in step ST1 has elapsed 30 minutes. If 30 minutes have elapsed, it is determined in step ST2 whether or not the above-described defrosting operation conditions (1) to (3) have been reached. If the conditions have not been reached, the process proceeds to step ST3 for 5 minutes. After waiting for time, it is determined whether or not the defrosting operation condition has been reached again in step ST4. If the condition has been reached, the defrosting operation is performed in step ST5. At this time, the operation of the indoor blower 7, the compressor 1, and the outdoor blower 12 is stopped, a defrost display is displayed on the notification unit 10, and the four-way valve 2 is switched from the state of the heating operation to the state of the defrost (cooling) operation. . When the defrost timer times out, the defrost ends, and the process returns to the heating operation in step ST6.
[0021]
If the defrosting operation condition has been reached in step ST2, it is checked in step ST7 whether the defrosting operation condition is the above-mentioned (1) in which the amount of decrease in the temperature Tn of the indoor heat exchanger 3 is equal to or more than a predetermined value T1. If it is equal to or more than the predetermined value T1, the normal defrosting operation is performed in the same manner as described above in step ST8, and the operation returns to the heating operation in step ST9.
[0022]
Next, if the defrosting operation condition has not been reached in step ST2, that is, if the amount of decrease in the temperature Tn is equal to or less than the predetermined value T1, the number of times of defrosting by the mask time is counted (step ST10). It is determined whether it is four or more times (step ST11). If it is four or more times, it is determined that the outside air temperature is lower than the design target temperature and that it is "empty defrost", and the process proceeds to low outside air temperature defrost control in step ST12. Transition. If not more than four times, normal defrosting is performed in step ST8 in the same manner as described above.
[0023]
Then, in step ST13, the number of times of defrosting at low outside air temperature is counted, and it is determined whether or not the number of times of defrosting is 4 times or more. If the low outside air temperature operation condition is one of the above (4) to (6), the defrosting operation is performed and the operation returns to the heating operation (steps ST15 to ST17).
[0024]
If the counter is four times in step ST13, the process proceeds to extremely low outside temperature defrost control in step ST18. Then, if any of the above-mentioned (7) to (9) extremely low outside air temperature operation conditions, the defrost operation is performed and the operation returns to the heating operation (steps ST19 to ST21).
[0025]
As described above, when the temperature of the indoor heat exchanger 3 is lower than the predetermined value and the defrosting by the mask time is performed plural times continuously, it is determined that the outside air temperature is lower than the target temperature, The frost operation condition is such that the temperature difference between the temperature of the indoor heat exchanger 3 and the indoor temperature is made smaller by a predetermined value than an initial set value, or the mask time is made longer by a predetermined value than an initial set value, or The defrosting operation is not performed until the temperature of the exchanger 3 every predetermined time decreases to a predetermined value, and the defrosting operation is performed by switching to one of these low outside air temperature operation conditions. Even during a heating operation under conditions where the outside air temperature is low, it is possible to prevent "empty defrost" and perform defrosting in an optimal frosted state, so that the heating operation time can be longer than before, and low temperature Improved heating capacity and comfort A defrosting control method of an air conditioner that can Rukoto.
[0026]
【The invention's effect】
With an air conditioner having a defrost control function as described above, it is possible to prevent "empty defrost" even during a heating operation under a low outside temperature condition, and to perform defrost in an optimal frost state. Therefore, the heating operation time can be made longer than before, and the method for controlling defrosting of the air conditioner can improve the low-temperature heating capacity and the comfort.
[Brief description of the drawings]
FIG. 1 is a refrigeration cycle of an air conditioner according to the present invention and a conventional example.
FIG. 2 is a block diagram of a control system of the air conditioner according to the present invention.
FIG. 3 is a flowchart showing an outline of a defrost control operation of the present invention.
[Explanation of symbols]
A indoor unit B outdoor unit 1 compressor 2 four-way valve 3 indoor heat exchanger 4 decompression device 5 outdoor heat exchanger 6 temperature sensor (for indoor heat exchanger)
7 indoor blower 9 indoor unit control unit 10 notification unit 11 room temperature sensor 12 outdoor blower 13 outdoor unit control unit
