JP4253537B2 - Refrigeration air conditioner - Google Patents

Description

なお、この目標蒸発温度ＥＴｍのシフトは所定時間間隔、例えば１分間隔で実施される。
【００２２】
ステップ１３では、設定された目標蒸発温度ＥＴｍに応じて、圧縮機３の回転数を制御する。吸入圧力Ｐｓを飽和温度換算した蒸発温度ＥＴと目標蒸発温度ＥＴｍを比較し、ＥＴｍ＞ＥＴならば圧縮機３の回転数を減少させ、逆にＥＴｍ＜ＥＴならば圧縮機３の回転数を増大させる。圧縮機３の回転数制御はＰＩＤ制御を用いて行うが、ファジー制御などその他の制御方式を用いてもよい。
また、ステップ１３における圧縮機３の回転数制御の時間間隔は、ステップ１２の目標蒸発温度ＥＴｍをシフトする時間間隔と同じにする必要はなく、冷却能力の応答性や安定性などを考慮して適宜実施される。
【００２３】
ステップ１２、１３によって、例えば１分程度の短い周期で目標蒸発温度ＥＴｍに基づきシフト量変更して圧縮機３の容量を制御する。さらに長い時間周期、例えば３０分運転する毎に、ステップ１４で目標蒸発温度の基準値ＥＴｍ０の設定が適切であったかどうか判定する。そのために運転しているショーケース２に対して、まず各ショーケース２内温度Ｔａと目標冷却温度Ｔｍとの偏差ΔＴａの平均値ΔＴａｓを下式（３）で求める。

この計算式では温度偏差ΔＴａに各ショーケース２の所定容量の重み付けをしてΔＴａの平均値ΔＴａｓを求めている。そしてΔＴａｓ＜０℃である場合、ショーケース２内温度Ｔａが目標冷却温度Ｔｍより低くなっているので、冷却負荷に対して装置の冷却能力が過大と判定し目標蒸発温度の基準値ＥＴｍ０を高く再設定し、例えば０．５℃程度高く設定する。また０℃≦ΔＴａｓ≦２℃の場合、ショーケース２内温度Ｔａが目標冷却温度Ｔｍとほぼ同じになっているので、冷却負荷に装置の冷却能力が釣り合っていると判定し、目標蒸発温度の基準値ＥＴｍ０はそのままの値に設定する。またΔＴａｓ＞２℃の場合、ショーケース２内温度Ｔａが目標冷却温度Ｔｍより高くなっているので、冷却負荷に対し装置の冷却能力が不足と判定し、目標蒸発温度の基準値ＥＴｍ０を低く再設定し、例えば０．５℃程度低く設定する。目標蒸発温度ＥＴｍを高くすると圧縮機３の回転数は低く運転され装置の冷却能力は減少し、目標蒸発温度ＥＴｍを低くすると圧縮機３回転数は高く運転され装置の冷却能力は増加するようになり、冷却負荷に釣り合った運転が可能となる。
この後、Ａ５に戻って、冷凍空調装置の運転を続行する。
【００２４】
以上のようにこの実施の形態によれば、圧縮機容量制御手段２１によって、運転されている蒸発器９の個別の目標冷却温度に基づいて運転されている蒸発器９を含む冷凍サイクルの目標とする状態、ここでは目標蒸発温度を定めるので、運転中にその状態に適した冷凍サイクルの目標状態を設定できる。さらに冷凍サイクルの目標状態を最適に設定することで、装置全体の運転効率を高めると共に、ショーケース２に保存してある食品などの鮮度悪化を回避でき、信頼性の高い運転を実現することができる。冷凍サイクルの状態とは、冷凍サイクルの冷媒の状態を表し、ここで用いた冷媒の蒸発温度の他、例えば高圧や低圧などの圧力値、冷媒の流量や流速や液量など、冷凍サイクル内を循環している冷媒の状態を意味している。
【００２５】
特にステップ１２では、複数のショーケース２が運転される場合に、運転されているショーケース２の中の高い方の目標冷却温度Ｔｍに基づいて蒸発温度ＥＴを高く設定して運転する。目標冷却温度Ｔｍが高いショーケース２は次々に目標冷却温度Ｔｍが満足されて運転停止することになり、実際には蒸発温度ＥＴは徐々に低く設定して運転される。このように、ショーケース２の目標冷却温度Ｔｍに見合った蒸発温度ＥＴで運転することが可能となり、過度に低い蒸発温度ＥＴで運転するのを回避でき、装置全体の運転効率を高く運転することができる。これと共に、ショーケース２の吹出空気温度が設定温度よりも大きく低下することによる鮮度悪化を回避し信頼性の高い運転を実現することができる。
さらに、冷却対象の目標冷却温度Ｔｍが複数のショーケース２間で大きく異なる場合に、ショーケース２の目標冷却温度Ｔｍに適した蒸発温度ＥＴで運転することができるので、上記効果をより発揮できる。
【００２６】
【表１】

【００２７】
表１はこの運転制御に基づいて目標蒸発温度ＥＴｍをシフトさせて装置の運転を実施した場合（下側）、および従来例のように目標蒸発温度ＥＴｍを固定して運転を実施した場合（上側）の運転状況を示す。表１にあるように、装置入力の多くなる場合、即ちショーケース２ａ、２ｂ、２ｃを全て運転する場合の入力低減効果が大きく、時間平均で４％程度運転効率の高い運転を実現できる。
【００２８】
なお、ステップ１２における目標蒸発温度ＥＴｍのシフト量△Ｔｍの演算方法については一例であり、上記以外にも他の方法をとってもよく、上記と同様の効果を奏する。
例えば、運転状態のショーケース２の目標冷却温度Ｔｍの平均値と装置に接続される全ショーケース２の目標冷却温度Ｔｍの平均値の差に基づいて、目標蒸発温度ＥＴｍをシフトしてもよい。
また、この平均値計算に際して、各ショーケース２の所定容量で重み付けをして平均値を算出してもよい。即ち、運転している前記蒸発器の目標冷却温度を各々の冷却対象の容量で重み付けした平均値と全ての前記蒸発器の目標冷却温度を各々の冷却対象の容量で重み付けした平均値との差に基づいて、目標蒸発温度ＥＴｍをシフトしてもよい。
【００２９】
また、全ショーケース２を目標冷却温度Ｔｍで２以上の温度域に分類し、運転しているショーケース２の目標冷却温度が属する温度域に応じてシフト量を定めてもよい。
例えば、高温のショーケースと低温のショーケースに２分し、図１の構成の場合には青果用ショーケース２ａ（Ｔｍ＝８℃）と日配品用ショーケース２ｂ（Ｔｍ＝５℃）を高温のショーケース、生鮮品用ショーケース２ｃ（Ｔｍ＝０℃）を低温のショーケースに分類する。そして、目標冷却温度Ｔｍの高いショーケース２が所定の台数以上運転状態のときは予め定められた温度差分高く、例えば５℃程度高く目標蒸発温度ＥＴｍをシフトさせ、そうでない場合は目標蒸発温度ＥＴｍのシフト量△Ｔｍを０とするようにしてもよい。ここで、目標冷却温度を複数の温度域に分類する場合、一例として所定値ここでは５℃よりも小さい温度差のものを同じ温度域とし、５℃以上差がある温度差のものを異なる温度域になるというように分類する。ただし、これに限るものではなく、ショーケース２の目標冷却温度の幅などを考慮して設定すればよい。
この場合においても、目標冷却温度Ｔｍが高いショーケース２が運転状態の場合に、過度に低い蒸発温度ＥＴで運転されることを回避して信頼性を向上できると共に、装置全体の運転効率を高くすることができる。
【００３０】
また、目標蒸発温度ＥＴｍのシフト量△Ｔｍをショーケース２の目標冷却温度Ｔｍだけでなく、各ショーケース２内温度Ｔａと目標冷却温度Ｔｍとの偏差ΔＴａを勘案してシフト量を決定してもよい。ショーケース２では一般にデフロストはヒータで実施され、デフロスト終了後のショーケース２内温度Ｔａは目標冷却温度Ｔｍより相当高くなっている場合がある。このような場合にはショーケース２内商品の品質低下を防止するためショーケース２内温度Ｔａを急速に低下させ、素早く目標冷却温度Ｔｍに近づけることが望ましい。従って、ショーケース２の中で目標冷却温度Ｔｍとその時のショーケース２内温度Ｔａとの差が所定値以上高い、例えば５℃以上高いショーケース２が存在する場合には、目標冷却温度Ｔｍの高いショーケース２が運転されていても目標蒸発温度ＥＴｍのシフト量△Ｔｍを０とする、あるいは低温側に、例えば２℃低くシフトさせる。
このように運転することでデフロスト終了後や運転開始時など、ショーケース２内温度Ｔａが目標冷却温度Ｔｍより大幅に高くなっている場合でも、ショーケース２内温度Ｔａの低下を促進し、ショーケース２内商品の信頼を確保する信頼性の高い運転を実現できる。
ここでデフロスト運転については、ショーケース２の計測制御装置１７から実施・終了情報を受け取り、終了後一定時間は目標冷却温度Ｔｍが高いショーケース２が運転されていても目標蒸発温度ＥＴｍのシフト量△Ｔｍを０とする、あるいは目標蒸発温度ＥＴｍを低温側にシフトするように運転してもよい。
【００３１】
また、ある一定期間の運転実績から目標蒸発温度ＥＴｍのシフト量△Ｔｍを決定してもよい。図６はある一定期間の目標冷却温度Ｔｍの高いショーケース２内の温度と目標冷却温度Ｔｍの低いショーケース２内の温度変化を表すもので、図４に示す圧縮機３の容量制御方法を実施した場合の時間に対するショーケースの運転／停止状態、目標蒸発温度ＥＴｍ、ショーケース内温度Ｔａを示すグラフである。ショーケース内温度Ｔａの上側は、目標冷却温度Ｔｍの高いショーケースを示し、下側は目標冷却温度Ｔｍの低いショーケースを示す。
図にあるように、目標冷却温度Ｔｍの高いショーケース２が運転される場合、目標蒸発温度ＥＴｍは高くシフトされ、目標冷却温度Ｔｍの高いショーケース２が重点的に冷却されショーケース２内温度が低下する一方で、目標冷却温度Ｔｍの低いショーケース２の温度は次第に上昇する。目標冷却温度Ｔｍの高いショーケース２内の温度が目標値まで冷却し、停止状態になると目標蒸発温度ＥＴｍのシフト量は小さく設定され、目標冷却温度Ｔｍの低いショーケース２が冷却されてショーケース２内温度は次第に低下する。このときの目標冷却温度Ｔｍの低いショーケース２の温度変化によって目標蒸発温度ＥＴｍのシフト量を変更する。例えば、ある一定期間中の目標冷却温度Ｔｍの低いショーケース２の温度が最も高くなった時点でのショーケース２内温度Ｔａと目標冷却温度Ｔｍとの偏差ΔＴａが所定値、例えば１℃以下の場合は、目標蒸発温度ＥＴｍをシフトさせている運転中であっても目標冷却温度Ｔｍの低いショーケース２も十分に冷却されているので、さらに目標冷却温度Ｔｍの高いショーケース２を重点的に冷却することが可能となる。従ってこの場合には上述された各方法で算出したシフト量よりもさらにシフト量を大きくし、例えば１℃高く目標蒸発温度ＥＴｍをシフトさせる。逆に、ΔＴａが所定値以上、例えば３℃以上の場合は、目標蒸発温度ＥＴｍをシフトしている運転中の目標冷却温度Ｔｍの低いショーケース２の冷却が十分でないので、目標冷却温度Ｔｍの低いショーケース２の冷却量が増加するように上述された各方法で算出したシフト量よりもシフト量を小さくし、例えば１℃低く目標蒸発温度ＥＴｍをシフトさせる。
【００３２】
即ち、一定期間の間の目標冷却温度Ｔｍの低いショーケース２の目標冷却温度Ｔｍとショーケース２内温度Ｔａとの偏差ΔＴａの動作に着目し、目標冷却温度Ｔｍの低いショーケース２が十分に冷却されている場合は、目標蒸発温度ＥＴｍのシフト量を大きくし、高い蒸発温度で運転することで高効率の運転を実現する。一方、目標冷却温度Ｔｍの低いショーケース２の冷却が十分でない場合は、目標蒸発温度ＥＴｍのシフト量を小さくし、低い蒸発温度で運転し目標冷却温度Ｔｍの低いショーケース２の冷却量を確保する。このように、ある一定期間の運転実績から目標蒸発温度ＥＴｍのシフト量△Ｔｍを決定することで、冷却不足によるショーケース２内温度の過剰な上昇を抑制し、さらに信頼性の高い冷凍空調装置が得られる。
【００３３】
なお、図５におけるシフト量の算出では、運転開始後にステップ１１で基準値ＥＴｍ０を全ショーケース２の目標冷却温度の最低値に基づいて設定する場合について記載している。ここで、基準値ＥＴｍ０を全ショーケース２の目標冷却温度の最高値に基づいて設定してもよい。この場合には式（２）で設定されるシフト量の算出も下式のようになる。

また、ステップ１１で基準値ＥＴｍ０には全ショーケース２の目標冷却温度の中間の温度を設定してもよい。ただし、この設定に伴って式（２）の算出方法は異なってくる。
いずれの場合においても、目標冷却温度Ｔｍが高いショーケース２が運転状態の場合に、運転効率を高くできると共に、過度に低い蒸発温度ＥＴで運転されることを回避して装置全体の信頼性を向上することができる。
【００３４】
また、図５のステップ１４において、目標蒸発温度の基準値ＥＴｍ０を長い時間周期で変更する際に、上記の設定方法に限るものではない。例えば所定期間の各ショーケース２の運転、停止状態を記憶し、その期間中に一度も停止状態とならなかったショーケース２が所定数以上あった場合、例えば全ショーケース数の２０％以上あった場合には、装置の冷却能力が冷却負荷に対して不足と判断し、目標蒸発温度の基準値ＥＴｍ０を所定値、例えば１℃低い値に変更する。一方、その期間中に一度も停止状態とならなかったショーケース２が所定数以下であった場合、例えば全ショーケース数の５％以下であった場合には装置の冷却能力が冷却負荷に対して過剰と判断し、目標蒸発温度の基準値ＥＴｍ０を所定値、例えば１℃高い値に変更する。
【００３５】
また、所定期間の各ショーケース２内温度Ｔａと目標冷却温度Ｔｍとの偏差ΔＴａを記憶し、期間中のΔＴａの最大値が所定値、例えば３℃より高い値となるショーケース２の数が所定数以上あった場合、例えば全ショーケース数の２０％以上あった場合には、装置の冷却能力が冷却負荷に対して不足と判断し、目標蒸発温度の基準値ＥＴｍ０を所定値、例えば１℃低い値に変更する。一方、その期間中のΔＴａの最大値が３℃より高い値となるショーケース２の数が所定数以下であった場合、例えば全ショーケース数の５％以下であった場合には装置の冷却能力が冷却負荷に対して過剰と判断し、目標蒸発温度の基準値ＥＴｍ０を所定値、例えば１℃高い値に変更する。
【００３６】
いずれの方法で目標蒸発温度の基準値ＥＴｍ０を設定しても、冷却負荷と釣り合った冷却能力で装置を運転することができる。即ち、適正な冷却能力で冷やし過ぎを回避し効率のよい運転を実現すると共に、冷却不足によるショーケース２内温度の上昇を回避しショーケース２内商品の品質を確保して信頼性の高い運転を実現できる。
【００３７】
以上のように、この実施の形態では、目標蒸発温度ＥＴｍを長い時間周期で変更する基準値ＥＴｍ０と短い時間周期で変更するシフト量△Ｔｍの和で計算し、これに基づいて制御するので、主に冷却能力の確保に関連する基準値ＥＴｍ０と、主に運転効率の向上に関連するシフト量△Ｔｍをそれぞれ最適に設定できる。
ここで、基準値ＥＴｍ０とシフト量△Ｔｍを変更する時間周期については、この実施の形態に限定されるものではなく、冷凍空調装置を適用場所の状況に応じて設定すればよい。
【００３８】
また、目標蒸発温度ＥＴｍのシフト量△Ｔｍや目標蒸発温度の基準値ＥＴｍ０の変更に際しては、その変更量を運転中のショーケース２の目標冷却温度Ｔｍの平均値やショーケース２内温度Ｔａと目標冷却温度Ｔｍとの偏差ΔＴａなどの情報をもとにしたＰＩＤ制御やファジー制御によるフィードバック制御を用いる。
【００３９】
また、圧縮機３の運転容量はインバータにより回転数制御を行うことで実施するとしたが、圧縮機３を複数台搭載し、その運転台数を増減させることで運転容量を制御してもよい。また、アンロード機能を備えた圧縮機を搭載し、アンロード運転の実施有無により容量制御を実施してもよい。また、インバータ駆動の圧縮機と一定速圧縮機を複数台組み合わせ、圧縮機の回転数と運転台数を共に制御し運転容量を制御してもよい。
【００４０】
また、ショーケース２内温度Ｔａは、吸込・吹出空気温度の平均値としたが、吹出温度、吸込温度いずれか一方の値を用いてもよい。また、ショーケース２内の空間に別途空気温度センサを設けて、その測定値を用いてもよいし、ショーケース２内の商品温度を直接測定する温度センサを設け、その測定値を用いてもよい。
【００４１】
また、ショーケース２の冷却温度域は上記の形態に限るものではなく、例えば冷凍食品、アイスクリーム用など冷却温度が−２０℃前後のいわゆる冷凍域のショーケースに適用してもよい。また、上記では冷却対象を一般的なショーケース２内の商品として温度の判断に用いる所定値を設定したが、商品の種類に応じての適当な所定値を設定すればよい。また、冷却対象はショーケース２内の商品に限るものではなく冷蔵倉庫などに適用してもよいし、水やブラインなどを介して間接的に冷却するシステムであってもよい。
また、この実施の形態の運転制御は一般の空調域にも用いることもできる。例えば機械設備と人が存在する空間を一つの装置で冷却する場合で機械設備の目標冷却温度が３５℃、人が存在する空間の目標冷却温度が２７℃であるような場合にも適用可能である。
いずれの場合も運転中の蒸発器９の冷却対象の目標冷却温度に応じて圧縮機３の運転容量を制御することで、高効率の装置運転を実現することができる。
【００４２】
また、この実施の形態では、目標蒸発温度ＥＴｍを定め、吸入圧力を飽和温度換算した蒸発温度ＥＴがＥＴｍになるように圧縮機３の運転容量を決定して容量制御を実施したが、目標蒸発温度ＥＴｍから目標吸入圧力を換算し、吸入圧力が目標吸入圧力になるように圧縮機３の容量制御を実施しても同様の効果が得られる。
また、蒸発温度を直接求め、例えば各ショーケース２の蒸発器９の入口冷媒温度を温度センサ１３ｄなど測定した温度を蒸発温度ＥＴとし、その情報をショーケース２の計測制御装置１７からコンデンシングユニット１の計測制御装置１６に伝送し、その蒸発温度ＥＴが目標値ＥＴｍになるように圧縮機３の容量を制御してもよい。
【００４３】
また、蒸発温度の目標値の代わりに吸入圧力Ｐｓの目標値Ｐｓｍを直接定め、圧力センサ１５ａで測定される吸入圧力ＰｓがＰｓｍになるように圧縮機３の容量制御を実施してもよい。この場合には、例えば式（２）における右辺を圧力に換算して目標吸入圧力の基準値及びシフト量を設定すればよい。
【００４４】
また、ショーケース２の計測制御装置１７は各ショーケース２のそれぞれに設けられているが、１台の計測制御装置１７に複数台制御する機能を持たせてもよい。また、複数の計測制御装置１７を統合するマスターコントローラを設けてもよい。各ショーケース２の目標冷却温度Ｔｍなどショーケース２の運転に際して外部入力が必要な情報をマスターコントローラに一括して入力し、その情報を各ショーケース２の計測制御装置１７に伝送する構成とすることで、外部入力を簡便に行うことができる。また、各ショーケース２の運転状況を一括管理できるようにすることで、運転状況のモニタや不具合発生時の確認を容易に実施でき、信頼性の高い冷凍空調装置が得られる。
【００４５】
また、冷凍空調装置の制御方法として、複数の蒸発器を圧縮機に並列に接続して成る冷凍サイクルを運転する際、複数の蒸発器毎に個別に目標冷却温度を設定する目標温度設定ステップ（図４、ステップ１）と、複数の蒸発器のうちでそれぞれの冷却対象の温度がその目標冷却温度に到達した蒸発器の運転を停止する蒸発器運転停止ステップ（図４、ステップ４〜ステップ７）と、複数の蒸発器が運転されているときに前記蒸発器の個別の目標冷却温度の最低値よりも高い冷却温度が得られるように前記冷凍サイクルの目標蒸発温度または目標吸入圧力を設定する目標状態設定ステップ（図５、ステップ１２）と、前記目標蒸発温度または目標吸入圧力を実現しうる容量で圧縮機を運転制御する圧縮機容量制御運転ステップ（図５、ステップ１３）と、を備えたことにより、冷却温度が異なる複数の冷却対象を持つ冷凍空調装置を運転効率よく制御することができる。
【００４６】
実施の形態２．
以下、この発明の実施の形態２による冷凍空調装置について説明する。この実施の形態における装置の構成及び圧縮機３の容量制御方法については、図１及び図５に示す実施の形態１と同様であり、その説明を省略する。ここでは各ショーケース２の減圧装置である電子膨張弁８の制御方法について主に説明する。実施の形態１では、計測制御装置１７によって電子膨張弁８の流動抵抗を制御する際に、蒸発器９出口の過熱度ＳＨが予め設定された目標値ＳＨｍになるように電子膨張弁８の開度を設定して流動抵抗を制御するとした。これに対し、実施の形態２では装置の運転状態に応じて蒸発器９の出口過熱度の目標値ＳＨｍを変更する。ここで、蒸発器９の下流側の冷媒状態の目標値として、蒸発器９の出口過熱度の目標値を設定するが、これに限るものではない。例えば、圧縮機３の吸入過熱度や圧縮機３の吐出過熱度を用いて制御することもできる。
【００４７】
図７は蒸発器９の出口過熱度ＳＨに対する冷凍空調装置の運転効率の変動状況を模式的に表したグラフであり、横軸に過熱度ＳＨ、縦軸に運転効率を示す。過熱度ＳＨが変化すると装置の運転状況に次のような影響を及ぼす。まず過熱度ＳＨが大きくなると蒸発器９出口温度は高くなり、冷媒エンタルピも増大する。従って蒸発器９出入口でのエンタルピ差も増大し、蒸発器９に同流量の冷媒が流れるとしても、より多くの熱を周囲から奪うことができる。従って冷却能力が増大し装置の運転効率は点線アに示すように上昇する傾向となる。一方過熱度ＳＨが大きくなると、蒸発器９内部での気液二相部の領域が減少し、ガス部領域が増大する。一般に冷媒の熱伝達率は気液二相部が大きく、ガス部が小さくなるのでガス部領域が増大すると蒸発器９全体では伝熱の効率が低下する。従って冷却能力が減少し、装置の運転効率は点線イに示すように低下する傾向となる。これらから図７の実線に示すように、エンタルピ差増大の影響と伝熱効率の低下の影響が相まって、装置の運転効率としてはある過熱度ＳＨで効率最大となるピークを持つ。一般にこの効率最大となる過熱度ＳＨの値は５℃前後になる。そこで実施の形態１では全ての蒸発器９の過熱度ＳＨを５℃程度に設定している。
【００４８】
しかし、この効率最大となる過熱度ＳＨは、運転中の冷凍サイクルの冷媒状態によって変化する。図８は低圧が変化したときの冷媒状態（冷凍サイクル）を、図９は過熱度ＳＨが変化したときの冷媒状態を示すＰＨ線図である。冷媒の飽和ガスエンタルピは圧力が低下すればするほど低下し、それに伴い同一の過熱度をとる場合であっても、低圧が低下すると蒸発器９出入口でのエンタルピ差（図８、ΔＨ１）も減少する。一方過熱度が大きくなった場合のエンタルピの増加量（図９、ΔＨ２）は圧力によらずほぼ一定であるので、過熱度が大きくなることによるエンタルピ差の増大率（ΔＨ２／ΔＨ１）は低圧の低い運転状態の方が大きくなり、装置の運転効率を増大させる影響も高くなる。従って、図１０に示されるように低圧が低い運転状態（実線）の方が、低圧が高い運転状態（点線）よりも、運転効率が最大となる過熱度ＳＨは大きくなる。
【００４９】
図１１はこの実施の形態に係る計測制御装置１７の構成を示すブロック図である。図において、３５は目標値変更手段、３６は目標値記憶手段である。過熱度ＳＨと装置の運転効率については図１０に示したような相関があるので、運転状態の変化に応じて目標値変更手段３５によって過熱度の目標値ＳＨｍを運転効率が最大になるように変更する。圧縮機３の容量は、例えば実施の形態１にあるように目標蒸発温度ＥＴｍを定めて、吸入圧力Ｐｓを換算した蒸発温度ＥＴが目標蒸発温度ＥＴｍになるように運転制御される。目標値記憶手段３６には、図１２に示すように予め目標蒸発温度ＥＴｍに対する過熱度目標値ＳＨｍの関係をテーブルなどで記憶しておく。
【００５０】
この時、目標蒸発温度ＥＴｍが−１５℃程度に低い場合は過熱度目標値ＳＨｍを例えば１０℃〜１５℃になるように大きく、目標蒸発温度ＥＴｍが−５℃程度に高い場合は過熱度目標値ＳＨｍを例えば２〜５℃になるように小さく定める。その間は、目標蒸発温度ＥＴｍが低くなるに連れて直線的に過熱度目標値ＳＨｍを増加させてもよいし、数段階の階段状に変化させてもよい。そして各ショーケース２の計測制御装置１７では、圧縮機３の容量制御運転中に決定された目標蒸発温度ＥＴｍの情報をコンデンシングユニット１の計測制御装置１６から受け取る。そして、目標値変更手段３５によって目標蒸発温度ＥＴｍに応じて目標値記憶手段３６を参照して運転効率の最大が得られる過熱度目標値ＳＨｍを決定する。その後、流動抵抗制御手段３４によって過熱度ＳＨが過熱度目標値ＳＨｍになるように電子膨張弁８の開度、即ち流動抵抗を制御する。
【００５１】
このように例えば蒸発器９出口の過熱度のような蒸発器９の下流側の冷媒状態が、予め設定された目標値になるように電子膨張弁９の開度を制御している冷凍空調装置において、蒸発器９出口の過熱度の目標値を運転中の冷凍サイクルの冷媒状態での運転効率が最適になるように変更している。運転中には蒸発器９のいずれかが停止したり逆に運転状態になったりして、刻々と冷凍サイクルの冷媒の状態は変化するが、これに応じて目標値を変更するので、常に運転効率を良好に保つことができる。ここでは例えば目標蒸発温度のような冷凍サイクル全体の運転状態を表わす状態量に応じて、その目標値を変更しており、運転している各蒸発器９で同一の目標値が設定される。
【００５２】
なお、この実施の形態では、図１２にあるように過熱度目標値ＳＨｍに上下限を設けている。上限については、過熱度ＳＨが大きくなると同時に圧縮機３の吐出温度も上昇するので、吐出温度が圧縮機３の信頼性に影響を及ぼすまでに上昇しないように、過熱度目標値ＳＨｍの上限を設ける。また下限については、過熱度ＳＨが余りに小さい場合、例えば２℃以下の場合には運転の変動の影響を受けやすく過熱度ＳＨが安定しにくいので、安定運転が実現できるように過熱度目標値ＳＨｍの下限を設けている。
【００５３】
構成としては図１１に示したように、ショーケース２のそれぞれに設けられた計測制御装置１７に、蒸発器９各々の下流側の冷媒状態が予め設定された目標値になるように電子膨張弁８各々の流動抵抗を制御する流動抵抗制御手段３４と、冷凍サイクルの運転状態の変化または運転されている蒸発器９の個別の目標冷却温度または運転されている蒸発器９各々の冷却対象の温度に基づいて目標値を変更する目標値変更手段３５と、を備えることで、運転条件、即ち運転中の蒸発器９が冷却対象としているショーケース２の状態が変化し、それに基づき冷凍サイクルの蒸発温度が変化するような場合であっても、運転効率の高い状態で運転できる冷凍空調装置が得られる。
【００５４】
なお、圧縮機３の容量制御が実施の形態１のようになされない場合であっても、現在運転中の蒸発温度ＥＴを各ショーケース２の蒸発器９入口の温度センサ１４などで測定し、その測定結果に基づいて過熱度目標値ＳＨｍを定めてもよい。またコンデンシングユニット１の圧力センサ１５ａで計測される吸入圧力Ｐｓの情報を計測制御装置１６より受け取り、その情報に基づいて過熱度目標値ＳＨｍを定めてもよい。なお現在運転中の状況に応じて制御の目標値を変える場合、目標値が頻繁に変わると安定した運転が難しいので、所定の時間間隔をとって目標値を設定する、あるいは蒸発温度情報などを取得する際に一定時間の平均を取るなどして制御する際の目標値が頻繁に変わらないようにすることが望ましい。
【００５５】
また、目標蒸発温度ＥＴｍに限らずショーケース２の運転状態・停止状態とその目標冷却温度Ｔｍやショーケース２内温度Ｔａに応じて過熱度の目標値ＳＨｍを変化させてもよい。
運転状態であるショーケース２の目標冷却温度Ｔｍの平均値が高い場合、あるいは運転状態であるショーケース２の中に目標冷却温度Ｔｍの高いものが含まれる場合には、装置の運転として蒸発温度ＥＴおよび吸入圧力Ｐｓが高い状態で運転されやすい。逆に運転状態であるショーケース２の目標冷却温度Ｔｍの平均値が低い場合、あるいは運転状態であるショーケース２の中に目標冷却温度Ｔｍの高いものが含まれない場合には、装置の運転として蒸発温度ＥＴおよび吸入圧力Ｐｓが低い状態で運転されやすい。そこで現在運転状態であるショーケース２の目標冷却温度Ｔｍを取得しその平均値を演算し、図１３に示すような相関で目標冷却温度Ｔｍの平均値が高い場合には過熱度の目標値ＳＨｍを小さく、目標冷却温度Ｔｍの平均値が低い場合には過熱度の目標値ＳＨｍを大きく設定しても、上記と同様の効果を奏する。
【００５６】
同様に、現在のショーケース２内温度Ｔａが高い場合には蒸発温度ＥＴおよび吸入圧力Ｐｓが高く、ショーケース２内温度Ｔａが低い場合には蒸発温度ＥＴおよび吸入圧力Ｐｓが低く運転されやすくなる。このことから、前述の目標冷却温度Ｔｍに変えて現在のショーケース２内温度Ｔａを用いてもよい。この場合は、ショーケース２内温度Ｔａの平均値が高い場合は過熱度の目標値ＳＨｍを小さく設定し、ショーケース２内温度Ｔａの平均値が低い場合は過熱度の目標値ＳＨｍを大きく設定する。
【００５７】
また、運転時の高圧や高圧に影響を与える外気温度に応じて過熱度の目標値ＳＨｍを変化させてもよい。
図１４は高圧が変化したときの冷媒状態（冷凍サイクル）を表わすＰＨ線図である。この装置では凝縮器４出口に液レシーバ５が設けられているので、凝縮器４出口ではちょうど冷媒は飽和液となる。図１４にあるように、高圧が高い場合には、飽和液エンタルピは大きくなり、凝縮器４出口エンタルピおよび蒸発器９入口エンタルピも大きくなる。一方高圧が低い場合には、飽和液エンタルピは小さくなり、凝縮器４出口エンタルピおよび蒸発器９入口エンタルピも小さくなる。従って高圧が高い場合には蒸発器９出入口のエンタルピ差（図１４、ΔＨ１）は小さく、高圧が低い場合には蒸発器９出入口のエンタルピ差は大きくなる。前述したように蒸発器９出入口のエンタルピ差が小さい場合には過熱度の目標値ＳＨｍを大きく、蒸発器９出入口のエンタルピ差が大きい場合には過熱度の目標値ＳＨｍを小さくする方が運転効率が良くなる。このため、現在運転中の高圧値、あるいは所定時間の高圧の平均値を圧力センサ１５ｂで測定し、その値が高いと過熱度の目標値ＳＨｍを大きく設定し、その値が低いと過熱度の目標値ＳＨｍを小さく設定してもよい。
また、高圧は外気温度によって影響を受け、外気温度が高いほど高圧が高くなるので、温度センサ１４ｃで測定される外気温度が高いと過熱度の目標値ＳＨｍを大きく設定し、外気温度が低いと過熱度の目標値ＳＨｍを小さく設定してもよい。
【００５８】
図１５は、以上に説明した蒸発器９の出口過熱度の目標値を変更して運転する際の処理の一例を示すフローチャートである。ステップ２１、２２、２３のそれぞれによって、冷凍サイクル２０の運転状態が変化したかどうかを判断している。ここでは、冷凍サイクル２０の運転状態の変化として、例えば冷凍サイクルの低圧値または高圧値の変化（ステップ２１）、運転されている蒸発器の目標冷却温度の平均値が変化（ステップ２２）、運転されている蒸発器の冷却対象温度の平均値の変化（ステップ２３）を検知している。それぞれの運転状態が変化した場合には、ステップ２４、２５、２６に示すように目標値変更手段３５によって目標値記憶手段３６を参照して出口過熱度の目標値を設定する。そして、流動抵抗制御手段３４によってこの出口過熱度の目標値になるように電子膨張弁８の開度を制御する（ステップ２７）。
ここで、ステップ２１、２２、２３の３つの判断によって蒸発器の出口過熱度の目標値を変更するように構成したが、少なくともいずれか１つの判断を行い、その判断結果に応じて目標値を変更してもよい。
【００５９】
なお、過熱度の目標値ＳＨｍは各ショーケース２で基本的に同じに設定するが、各ショーケース２の特性に合わせて個別に調整をしてもよい。すなわちショーケース２内の蒸発器９の大きさや蒸発器９のパスパターンや送風量などによって、蒸発器９出口で過熱度が大きくなりやすいショーケース２、なりにくいショーケース２が存在する。そこでショーケース２の特性を予め把握しておき、その特性に基づいて上述した方法で求められた過熱度の目標値ＳＨｍを補正してもよい。例えば過熱度ＳＨの大きくなりやすいショーケース２は、一般に伝熱の効率がよいため図７に示す過熱度ＳＨが大きくなったときの伝熱効率低下の運転効率に及ぼす影響、即ち点線イにおいて、過熱度ＳＨが大きくなったときの運転効率の低下量が少なくなる。従って過熱度ＳＨが大きいところで効率最大となる傾向があるので、このようなショーケース２の場合には過熱度の目標値ＳＨｍを大きく補正する。逆に過熱度の大きくなりにくいショーケース２では、過熱度ＳＨが大きくなったときの運転効率の低下量が大きく、過熱度ＳＨが低いところで効率最大となる傾向となるため、過熱度の目標値ＳＨｍを小さく補正する。
【００６０】
また、各ショーケース２の蒸発器９出入口の冷媒温度差で過熱度ＳＨを求めているが、この方法では蒸発器９での冷媒の圧力損失による蒸発温度の低下分だけ過熱度ＳＨを小さく演算することになる。従って各ショーケース２の圧力損失による影響を予め補正しておき、過熱度演算の際に補正するようにしてもよい。なお、蒸発器９出口の過熱度を演算するときに圧力センサ１５ａによる吸入圧力Ｐｓの測定値をコンデンシングユニット１の計測制御装置１６から情報として受け取り、吸入圧力Ｐｓと蒸発器９出口温度にて過熱度ＳＨを求めてもよい。この場合には、蒸発器９出口から圧縮機３吸入までの圧力損失の補正が場合によって必要となるが、各ショーケース２内での圧力損失の影響は無くなる。
【００６１】
また、蒸発器９出口の過熱度ＳＨの制御を電子膨張弁８の開度で流動抵抗を制御して行っているが、他の減圧装置を用いて流動抵抗を制御してもよい。例えば短い時間間隔で開閉を繰り返し、開である時間の比率で流量や減圧量を制御する弁を用いてもよいし、複数の固定開度の弁を並列に配置し、開閉する弁の数を制御することで流量や減圧量を制御してもよい。またキャピラリーチューブなどの減圧装置を並列あるいは直列に設置して、減圧幅の調整を実施するなどの構造をとってもよい。
【００６２】
また、図１の構成では電磁弁７の下流側に電子膨張弁８を配置する構成としているが、電子膨張弁８の下流側に電磁弁７を配置する構成としてもよい。このような構成とすることで、電磁弁７を開いたときの液ハンマーにより電子膨張弁８が損傷することを防止し、信頼性の高い装置を得ることができる。
【００６３】
また、電子膨張弁８の制御目標として蒸発器９出口の過熱度ＳＨを用いているが、過熱度ＳＨと相関のある他の状態を計測して制御してもよい。例えば圧縮機３の吸入側での過熱度ＳＨｓを温度センサ１３ａ、圧力センサ１５ａを用いて求め、この過熱度ＳＨｓが設定された目標値となるように制御してもよい。圧縮機３の吸入過熱度ＳＨｓは各ショーケース２の蒸発器９の出口過熱度ＳＨを各ショーケース２を流れる流量で重み付けをして平均した値となるので、蒸発器９の出口過熱度ＳＨと同様の値となる。従ってこの場合の目標値の設定も蒸発器９の出口過熱度の目標値ＳＨｍの設定方法と同様の方法を取ることができる。
圧縮機３の吸入過熱度を制御する場合には、圧縮機３の吸入状態を見て直接制御することになるので、液バック発生時など圧縮機３運転の信頼性に影響がある運転となったときに素早く対応することができ、より信頼性の高い運転制御を実施することができる。
【００６４】
また、電子膨張弁８の制御目標として温度センサ１３ｂで測定される圧縮機３の吐出温度Ｔｄや温度センサ１３ｂと圧力センサ１５ｂの測定値から演算される圧縮機３の吐出過熱度ＳＨｄを用いてもよい。これらの値は圧縮機３の吸入過熱度ＳＨｓと正の相関があるので、予め運転効率最大となるこれらの値や蒸発温度ＥＴによる目標値の変化量などを求めておいて、上述した方法などにより運転状態によって目標値を定め、電子膨張弁８の開度制御を実施してもよい。
この場合も吐出温度の過上昇や、高圧シェル圧縮機であった場合の吐出温度Ｔｄあるいは吐出過熱度ＳＨｄ低下による冷凍機油への冷媒寝込みに起因する冷凍機油の濃度低下など、圧縮機３運転の信頼性に影響がある運転となったときに素早く対応することができ、より信頼性の高い運転制御を実施することができる。
【００６５】
なお、ショーケース２を複数有する場合で、特に圧縮機３の吸入過熱度ＳＨｓなど１つの制御目標で制御する場合には、以下のようにして各ショーケース２の電子膨張弁８の制御を実施する。まず現在運転中の電子膨張弁８の開度の合計値を求める。そしてこの合計値を圧縮機３の吸入過熱度ＳＨｓなどの制御目標が目標値となるように増減する。そして増減された電子膨張弁８の開度の合計値を各ショーケース２の電子膨張弁８の開度に割り振る。このとき膨張弁開度の割り振りは基本的には所定のショーケース２の容量に応じた比率で分配するが、ショーケース２の過熱度ＳＨのつきやすさなどによって調整してもよい。
【００６６】
また、現在のショーケース２内温度Ｔａとショーケース２の目標冷却温度Ｔｍとの偏差ΔＴａによって調整し、偏差ΔＴａが小さいショーケース２については、現状で多くの冷却能力を必要としないので、蒸発器９の出口過熱度ＳＨが大きくなるように電子膨張弁８の開度を小さく調整するなどの制御を実施してもよい。
このような電子膨張弁８の制御を実施する場合には、各ショーケース２の計測制御装置１７を統合するマスターコントローラがあると簡易に制御システムを構築することができる。
【００６７】
また、油回収運転などの特殊な運転モード時には、一部もしくは全ての電子膨張弁８で過熱度制御などのフィードバック制御を実施せず予め定められた方法で制御するフィードフォワード制御を実施してもよい。
圧縮機３が低容量で長時間連続運転した場合、ガス管１２を流れる冷凍機油の流速が低下し、ガス管１２内の油滞留量が増加する運転となる。このとき、ガス管１２内の油滞留量が多くなり過ぎると、圧縮機３に保持される油量が減少し圧縮機３の運転信頼性が低下する可能性がある。そこで、図１６に示すように計測制御装置１６に圧縮機３の保持油量を検知する油量検知手段２３を備え、油回収運転モードを行う冷凍空調装置について説明する。
【００６８】
図１７は油回収運転モードの処理を示すフローチャートである。即ち、油量検知手段２３によって圧縮機３の保持油量を検知し、その保持油量が減少したかどうかを判断する（ステップ３１）。例えば油量検知手段２３は圧縮機３の運転容量と運転時間によって、圧縮機３の保持油量を経験的に把握している。即ち、圧縮機３が所定容量、例えば４０％以下の容量で所定時間、例えば１時間以上連続運転した場合には、ガス管１２の油滞留量が増加し、圧縮機３の保持油量が低下すると予測される。そこで、このような場合にはガス管１２の油を回収するため、ステップ３２〜ステップ３４の油回収運転モードを実施する。ステップ３２で、圧縮機３で運転容量を増加させてガス管１２を流れる冷凍機油の流速を増加させ、ガス管１２内の油滞留量を減少させるように運転する。これと同時に、運転している蒸発器９の中で、冷却負荷の大きな蒸発器を選択する（ステップ３３）。ここでは、運転中の蒸発器９のうちの冷却負荷の大きな蒸発器９に対して、その出口の冷媒状態を気液二相状態にすることで、油回収を行う。
【００６９】
さらにコンデンシングユニット１の計測制御装置１６から各ショーケース２の計測制御装置１７へ油回収運転モードに入ったことを通信する。各ショーケース２の計測制御装置１７でこの通信を受けると、ステップ３３で選択された蒸発器９の上流側の電子膨張弁８に対して、流動抵抗制御手段３４によって開度を予め定められた開度に大きく制御、例えば全開に制御し、蒸発器９出口が気液二相状態になるようにする（ステップ３４）。このように制御するとガス管１２に気液二相の冷媒が流れる。このとき液冷媒と油が溶解することにより油の粘度が低下し、流れやすくなり、この結果、ガス管１２の油滞留量を減少させ、圧縮機３の保持油量を増加させることができる。そこでステップ３５で圧縮機３の保持油量が回復したことを確認して油回収運転モードを終了する。例えば予め油回収し得る所定時間を実際の運転で確認しておき、この所定時間油回収運転を行なう。油回収運転モードの終了は油量検知手段２３で判定する。このように運転することで、圧縮機３の運転信頼性を確保し、信頼性の高い冷凍空調装置を得ることができる。
【００７０】
なお、油回収運転モード実施時に、ステップ３３で電子膨張弁８の開度を大きく制御する蒸発器９を選択する際、そのショーケース２の台数については、ショーケース２の全台数の一定割合以下にし、残りのショーケース２については通常運転どおり、蒸発器９出口の過熱度が目標値になるように制御することが望ましい。仮に全ショーケース２において、電子膨張弁８の開度を大きくした場合、多くの液冷媒が蒸発器９で蒸発されず、ガス管１２を経て圧縮機３に吸入されることになる。余りに多くの液が圧縮機３に吸入されると、液圧縮などにより圧縮機３の運転信頼性を低下させる可能性がある。そこで、電子膨張弁８の開度を大きく制御するショーケース２の台数を一定量以下にし、残りのショーケース２では通常運転として蒸発器９出口の過熱度による制御を実施し、圧縮機３に吸入される液冷媒量を一定値以下にする。この量としては、例えば圧縮機３での吸入冷媒の乾き度がおよそ０．７以上になるようにする。乾き度０．７以上にすると吸入された液冷媒がほぼすべて、圧縮機３内で冷媒になされる仕事やモータ発熱などで熱をもらい蒸発することができるので、液圧縮による信頼性低下を回避できる。
【００７１】
電子膨張弁８の開度を大きく制御するショーケース２では、最も液戻り量が多くなる場合を想定すると、液戻り量は蒸発器９入口での冷媒乾き度で決定され、その乾き度は通常の冷凍サイクルの場合、０．２〜０．３程度の値となる。一方、蒸発器９出口で過熱度がつくように運転制御される場合、蒸発器９出口の冷媒乾き度はほぼ１．０になる。そこで、電子膨張弁８の開度を大きく制御するショーケース２の台数は、各ショーケース２の容量がほぼ一定である場合には、全台数の４０％以下になるように規定する。このとき、圧縮機３の吸入冷媒乾き度は、少なくても０．２×０．４＋１．０×０．６＝０．６８以上となり、圧縮機３の吸入冷媒乾き度をほぼ０．７以上にすることができる。なお、各ショーケース２の容量が一定でなく、流れる冷媒流量が異なる場合には、冷媒流量による重み付けを行って、電子膨張弁８の開度を大きく制御するショーケース２の台数を決定する。
【００７２】
なお、電子膨張弁８の開度を大きく制御するショーケース２の決定に際しては、予めショーケース２の計測制御装置１７に油回収運転モードとなったときの対応（運転モードに対応して電子膨張弁８を開くか、通常運転どおりの制御を継続するか）を規定しておき、その規定によって決定する。またその他の方法として、計測制御装置１７を統合するマスターコントローラを設け、このマスターコントローラにより各ショーケース２の運転状態を把握し、ショーケース２の運転状態に応じて油回収運転モードとなったときの対応を決定してもよい。電子膨張弁８の開度を大きく制御する方がショーケース２に流入する冷媒流量が多くなり、冷媒の熱伝達率が大きくなることから、一般に蒸発器９での熱交換量が大きくなる。従って、運転しているショーケース２の中で、負荷が大きく多くの熱交換量を要する目標冷却温度Ｔｍの低いショーケース２を、油回収運転モードとなったときに電子膨張弁８の開度を開くショーケースに設定してもよい。この場合、油回収機能だけでなく、ショーケース２の冷却能力を負荷に追随するように運転でき、ショーケース内の商品の品質を確保し信頼性の高い装置とすることができる。
【００７３】
また、ショーケース２の運転状態として、現在のショーケース２内温度Ｔａと目標冷却温度Ｔｍとの偏差ΔＴａの大きいショーケース２を油回収運転モードとなったときに電子膨張弁８の開度を開くショーケース２に設定してもよい。この場合も同様に、負荷に追随した運転を実現でき、信頼性の高い装置を得ることができる。
【００７４】
上記では圧縮機３の保持油量の低下を、圧縮機３の容量と連続運転時間によって予測したが、これに限るものではなく、圧縮機３のシェル内の油量低下をフロートスイッチなどで直接検出してもよいし、冷凍サイクルの他の部分に油を保持し圧縮機３に油を供給する、オイルセパレータやアキュムレータなどの油貯留部の油量低下をフロートスイッチなどで検出してもよい。また、油回収運転モードは予め油が回収されるであろう所定時間を設定して、その時間運転してもよいし、油の液面を検出できる場合にはその液面が所定値になるまで運転するようにしてもよい。
【００７５】
また、ここでは図１〜図６に示した構成及び制御を行なう冷凍空調装置について記載したが、これに限るものではない。空気調和機などの冷凍空調装置において、従来は蒸発器の下流側の冷媒状態、例えば蒸発器出口過熱度を５℃程度の固定の目標値を設定してこれになるように電子膨張弁の開度を制御しているが、この目標値を冷凍サイクルの運転状態に応じて変更すれば、運転効率の向上を図ることができる。例えば、１台の蒸発器を有する場合にも、外気温度や冷却負荷などによって冷凍サイクルの高圧値や低圧値が変化することがあるので、蒸発器の下流側の冷媒状態の目標値を高い運転効率が得られるように変更し、この目標値となるように蒸発器の上流側に設けられている電子膨張弁を制御すれば、運転効率を向上できる。
【００７６】
また、冷凍空調装置の制御方法として、減圧装置と蒸発器を接続した組合わせを複数個並列に圧縮機に接続して成る冷凍サイクルを運転する際、複数の前記蒸発器毎に個別に目標冷却温度を設定する目標温度設定ステップと、前記蒸発器それぞれの下流側の冷媒状態が予め設定された目標値になるように前記減圧装置それぞれの流動抵抗を制御する流動抵抗制御ステップ（図１５、ステップ２７）と、前記冷凍サイクルの運転状態の変化に応じて前記目標値を変更する目標値変更ステップ（図１５、ステップ２４、２５、２６）と、を備えたことにより、冷却温度が異なる複数の冷却対象を持つ冷凍空調装置を運転効率よく制御することができる。
【００７７】
また、冷凍空調装置の制御方法として、減圧装置と蒸発器を接続した組合わせを複数個並列に圧縮機に接続して成る冷凍サイクルにおける前記圧縮機の保持油量の低下を検知する油量検知ステップ（図１７、ステップ３１）と、前記油量検知ステップで前記圧縮機の保持油量が減少していると検知したときに、運転している複数の前記蒸発器のうちで冷却負荷の大きな蒸発器を選択する蒸発器選択ステップ（図１７、ステップ３３）と、前記蒸発器選択ステップで選択した蒸発器の出口での冷媒が気液ニ相状態になるようにその蒸発器の上流側に接続する前記減圧装置の流動抵抗を制御する流動抵抗制御ステップ（図１７、ステップ３４）と、を備えたことにより、圧縮機３の油量を必要量に保持できると共に、蒸発器９の冷却能力を負荷に追随するように運転して、冷却対象の温度を目標冷却温度に維持でき信頼性の高い運転制御を行なうことができる。
【００７８】
実施の形態３．
以下、この発明の実施の形態３による冷凍空調装置について説明する。この実施の形態では、冷凍空調装置の構成及び圧縮機３の容量制御方法については、図１及び図５に示す実施の形態１と同様であり、その説明を省略する。ここでは各ショーケース２の電子膨張弁８の制御方法について説明する。実施の形態２では各ショーケース２の電子膨張弁８の制御に際し、蒸発器９の下流側の冷媒状態の制御目標値である蒸発器９出口の過熱度の目標値ＳＨｍは、基本的に各ショーケース２で同一としたが、この実施の形態では各ショーケース２の目標冷却温度Ｔｍまたはショーケース２内温度Ｔａに応じて過熱度の目標値ＳＨｍを変更するなど、ショーケース２毎に電子膨張弁８の制御方法を変更する。ここでも、蒸発器９の下流側の冷媒状態の目標値として、蒸発器９の出口過熱度の目標値を設定するが、これに限るものではない。例えば、圧縮機３の吸入過熱度や圧縮機３の吐出過熱度を用いて制御することもできる。
【００７９】
実施の形態１記載の圧縮機３の容量制御方法を実施した場合のショーケース２内の温度変化は図６に示したように、まず目標冷却温度Ｔｍの高いショーケース２が冷却され、そのショーケース２が停止状態となった後で目標冷却温度Ｔｍの低いショーケース２が冷却されるという過程をとる。なお、このようなショーケース２の運転状況は、目標冷却温度Ｔｍの高いショーケース２の方が冷却負荷が少ない傾向にあるので、従来例のような他の圧縮機３の容量制御方法を実施しても発生する。
【００８０】
この過程で目標冷却温度Ｔｍの高いショーケース２が停止状態になると、目標冷却温度Ｔｍの低いショーケース２のみが運転される。即ち、装置全体で見ると冷媒の流通する蒸発器９の数が少なくなっており、蒸発器９の伝熱面積の減少に伴い装置の運転効率が低下する運転となる。そこで、ここでは電子膨張弁８により目標冷却温度Ｔｍの高いショーケース２が停止状態となるのを回避し、装置全体の蒸発器９の伝熱面積を確保することで、運転効率の低下を防止する。
【００８１】
図１８はこの実施の形態に係る計測制御装置１７の構成を示すブロック図である。図において、３７は目標冷却温度分類手段であり、複数の蒸発器９の個別の目標冷却温度を少なくとも２つ以上の温度域に分類する。例えば、各ショーケース２の目標冷却温度Ｔｍが、ショーケース２ａでＴｍａ＝８℃、ショーケース２ｂでＴｍｂ＝５℃、ショーケース２ｃでＴｍｃ＝０℃に設定されており、２つの温度域に分類する場合、ショーケース２ａ、２ｂを高温側、ショーケース２ｃを低温側とする。この分類で蒸発器９がどちらの分類に属するかで、目標値変更手段３５によって蒸発器に対する蒸発器下流側の冷媒状態の目標値の変更方法を変える。
【００８２】
以下、計測制御装置１７で行なう電子膨張弁８の制御方法について、図１９に基づいて説明する。この蒸発器下流側の冷媒状態の目標値の変更は、運転している蒸発器９各々に対して個別に行われるが、ここでは１つの蒸発器９に対する制御について説明する。目標冷却温度分類手段３７で、複数の蒸発器９の中で今制御対象としている蒸発器９が目標冷却温度Ｔｍの高いショーケース２か目標冷却温度Ｔｍの低いショーケース２かを把握しておく。そして、蒸発器９が目標冷却温度Ｔｍの高いショーケース２に該当するかどうかを判断する（ステップ４１）。そして目標冷却温度の低いショーケース２であった場合には、ステップ４２に進み、実施の形態２に記載されているように運転効率がよくなるような過熱度の目標値ＳＨｍを設定し、蒸発器９出口の過熱度ＳＨが目標値ＳＨｍとなるように、流動抵抗制御手段３４によって電子式膨張弁８の開度を制御する。一方、ステップ４１の温度域判断ステップの判断で、制御する蒸発器９が目標冷却温度Ｔｍの高い蒸発器であると判断した場合には、ステップ４３に進み、現在のショーケース２内温度Ｔａと目標冷却温度Ｔｍとの偏差ΔＴａがどの程度あるか判断する。ΔＴａが予め定められた値、例えば３℃以上である場合は、そのショーケース２は温度が高くなっていて十分に冷却されることが必要となるので、ステップ４４で蒸発器９出口の過熱度の目標値ＳＨｍを低い値、例えば２℃に設定して過熱度ＳＨがこの値になるように電子膨張弁８の開度を制御する。
【００８３】
このような制御を実施すると、蒸発器９では気液二相部が多くガス部が少なくなる状態で運転するので、蒸発器９での冷却量が増大しショーケース２において十分な冷却を実現できる。一方ステップ４３でΔＴａが３℃以下であった場合には、ショーケース２の冷却がある程度なされており、多くの冷却能力は必要としないので、ステップ４５で蒸発器９出口の過熱度の目標値ＳＨｍを大きい値に設定する。過熱度ＳＨが大きいと、蒸発器９では気液二相部が少なく、ガス部が多くなるので冷却量が減少する。即ちステップ４５は、制御するショーケース２が目標冷却温度Ｔｍの高いショーケース２であり、現在のショーケース２内温度Ｔａと目標冷却温度Ｔｍとの偏差ΔＴａが所定値以下の場合に、蒸発器９出口の過熱度の目標値ＳＨｍを大きい値に設定して冷却能力が小さくなるように制御する流動抵抗制御ステップを行なう。ΔＴａが小さいほど多くの冷却能力を要しないことになるので、例えば図２０に示す相関に基づいて、ΔＴａが小さいほど過熱度の目標値ＳＨｍを大きく設定すればよい。
【００８４】
このように目標値変更手段３５によって、運転している蒸発器９毎にその蒸発器９の冷却状態に応じて個別に電子膨張弁８の開度を制御することにより、冷凍空調装置の運転中に状況に適して運転制御でき、運転効率を向上できる。
特に目標冷却温度Ｔｍの低いショーケース２では、装置の運転効率がよくなるような蒸発器９の出口過熱度ＳＨで運転する。また、目標冷却温度Ｔｍの高いショーケース２では、ショーケース２内温度Ｔａと目標冷却温度Ｔｍとの偏差ΔＴａが大きい場合には十分な冷却を実現することでショーケース２内温度Ｔａが高温状態であることを回避できる。また、蒸発器の冷却対象温度が目標冷却温度に近づいたとき、即ちΔＴａが小さい場合には、ショーケース２が停止状態にならないように冷却能力を下げることで、装置全体の蒸発器９の面積が減少しないような運転を実現できる。従ってこの制御により運転効率を高くできると共にショーケース２の温度上昇を回避できる信頼性の高い冷凍空調装置を得ることができる。
【００８５】
なお、ステップ４２における過熱度目標値ＳＨｍの設定では、実施の形態１と同様、５℃程度の所定値に設定してもよく、またここで述べたように実施の形態２同様、運転している冷凍サイクルの冷媒状態に応じて運転効率を考慮して過熱度ＳＨを変更してもよい。
【００８６】
表２にこの実施の形態における運転制御に基づいて実際に行った運転状況を示す。この表は、目標冷却温度Ｔｍの低い生鮮用のショーケース２ｃの過熱度目標値を２℃に設定すると共に、目標冷却温度Ｔｍが高く、多くの冷却能力を必要としない青果用のショーケース２ａ、日配用のショーケース２ｂの過熱度目標値ＳＨｍを、ショーケース２ａ、２ｂが停止状態にならないようにΔＴａに基づいて高く設定して運転した場合（表の下側）と、運転している各ショーケース２の全てにおいて同一過熱度目標値ＳＨｍで運転を実施した場合（表の上側）の運転状況を示す。表２にあるように、全てのショーケース２が停止状態にならないように過熱度目標値ＳＨｍを設定することで、時間平均で４．５％程度運転効率の高い運転を実現できた。
【００８７】
【表２】

【００８８】
また、図１９のステップ４５では、蒸発器出口過熱度目標値ＳＨｍをショーケース２内温度Ｔａと目標冷却温度Ｔｍとの偏差ΔＴａに基づいて設定して電子膨張弁８の制御を実施したが、ΔＴａに基づき電子膨張弁８の開度をフィードバック制御し、ΔＴａが予め設定された値、例えば０．５℃になるように制御を行ってもよい。この場合でもΔＴａが小さい場合にショーケース２が停止状態にならないように運転を実施でき、運転効率のよい冷凍空調装置を得ることができる。
【００８９】
【発明の効果】
この発明は以上説明したように、目標冷却温度に応じた冷媒状態になるように冷凍サイクルを運転して、効率のよい冷凍空調装置が得られると共に、冷却対象の過剰な温度低下を回避して、信頼性の高い冷凍空調装置が得られる。
【００９０】
ここで、計測制御装置１７によって目標冷却温度分類手段３７の動作を行なうとしたが、熱源側の計測制御装置１６にこの動作を行なう手段を設けてもよい。そして、計測制御装置１７では分類した結果その蒸発器９が属する温度域を認識していればよい。
【００９１】
また、冷凍空調装置の制御方法として、図１９のステップ４２、４３、４４に示すように、蒸発器それぞれの下流側の冷媒状態が予め設定された目標値になるように前記減圧装置それぞれの流動抵抗を制御する流動抵抗制御ステップと、前記冷凍サイクルの運転状態の変化に応じて個別に前記目標値を変更する目標値変更ステップと、を備えたことにより、冷却温度が異なる複数の冷却対象を持つ冷凍空調装置を運転効率よく制御することができる。
【００９２】
また、冷凍空調装置の制御方法として、減圧装置と蒸発器を接続した組合わせを複数個並列に圧縮機に接続して成る冷凍サイクルを運転する際、複数の前記蒸発器毎に個別に目標冷却温度を設定する目標温度設定ステップと、複数の前記蒸発器のうちで目標冷却温度が高い温度域の蒸発器であることを判断する温度域判断ステップ（ステップ４１）と、前記高い温度域と判断された蒸発器のうちで冷却対象の温度とその目標冷却温度との差が前記所定値以下の蒸発器に対し、その上流側に接続する減圧装置の流動抵抗を制御して冷却能力が小さくなるように制御する流動抵抗制御ステップ（ステップ４５）と、を備えたことにより、冷却温度が異なる複数の冷却対象を持つ冷凍空調装置を運転効率よく制御することができる。
【００９３】
実施の形態１〜実施の形態３において、計測制御装置１６、１７はそれぞれ例えばマイクロコンピューターで構成し、これに含まれる各手段の動作は、ソフトウエアプログラムによって行なっている。
また、実施の形態１〜実施の形態３において、主に負荷側がショーケースの場合について説明したが、空気調和機など、他の冷凍空調装置にも適用できる。ただし、圧縮機に並列に複数の蒸発器が接続され、蒸発器の各々で冷却する冷却対象の目標冷却温度が異なる冷凍空調装置に有効である。
【００９４】
実施の形態１〜実施の形態３において、冷凍空調装置に用いる冷媒は特に限定されるものではなく、Ｒ−２２などのＨＣＦＣ冷媒や、Ｒ−１３４ａやＲ−４０４ＡなどのＨＦＣ系の冷媒や混合冷媒、またアンモニア、ＣＯ２、炭化水素などの自然冷媒やこれらの混合冷媒など各冷媒に適用可能である。また冷凍機油についても鉱油、エステル油、ＨＡＢ油など各種の油を用いた場合に適用可能である。
なお上記では、冷媒として例えばＲ―２２を用いた場合の蒸発温度や蒸発器９の出口過熱度の温度を説明したが、他の冷媒を用いる場合には、その冷媒で構成される冷凍サイクルのＰＨ線図に応じて、各所定値を設定すればよい。
【００９５】
【発明の効果】
この発明は以上説明したように、複数の蒸発器を圧縮機に並列に接続して成る冷凍サイクルと、前記蒸発器毎に冷却対象の目標冷却温度を個別に設定する目標温度設定手段と、前記冷却対象の温度と前記目標冷却温度に応じて前記蒸発器毎に運転停止を決定する蒸発器運転決定手段と、運転されている蒸発器の個別の目標冷却温度に基づいて前記運転されている蒸発器を含む冷凍サイクルの目標とする状態を定めこれを実現するように前記圧縮機の運転容量を決定して運転する圧縮機容量制御手段と、を備えたことにより、目標冷却温度に応じた冷媒状態になるように冷凍サイクルを運転して、効率のよい冷凍空調装置が得られると共に、冷却対象の過剰な温度低下を回避して、信頼性の高い冷凍空調装置が得られる。
【図面の簡単な説明】
【図１】 この発明の実施の形態１による冷凍空調装置を示す冷媒回路図である。
【図２】 実施の形態１に係る計測制御装置１６の構成を示すブロック図である。
【図３】 実施の形態１に係る計測制御装置１７の構成を示すブロック図である。
【図４】 実施の形態１によるショーケースの運転制御方法を示すフローチャートである。
【図５】 実施の形態１による圧縮機の運転制御方法を示すフローチャートである。
【図６】 実施の形態１による運転制御を実施した場合の冷凍空調装置の運転状態を表す説明図である。
【図７】 本発明の実施の形態２に係る過熱度と運転効率の相関を示すグラフである。
【図８】 実施の形態２に係る低圧が変化したときの冷凍サイクルの状態を示すＰＨ線図である。
【図９】 実施の形態２に係る過熱度が変化したときの冷凍サイクルの状態を示すＰＨ線図である。
【図１０】 実施の形態２に係る低圧が変化したときの過熱度と運転効率の相関を示すグラフである。
【図１１】 実施の形態２に係る計測制御装置１７の構成を示すブロック図である。
【図１２】 実施の形態２に係り、目標蒸発温度に対し過熱度目標値を設定する設定方法を示すグラフである。
【図１３】 実施の形態２に係り、目標冷却温度の平均値に対し過熱度目標値を設定する設定方法を示すグラフである。
【図１４】 実施の形態２に係る高圧が変化したときの冷凍サイクルの状態を示すＰＨ線図である。
【図１５】 実施の形態２による電子膨張弁の運転制御方法を示すフローチャートである。
【図１６】 実施の形態２に係る計測制御装置１６の構成を示すブロック図である。
【図１７】 実施の形態２による油回収運転モードの運転制御方法を示すフローチャートである。
【図１８】 この発明の実施の形態３に係る計測制御装置１７の構成を示すブロック図である。
【図１９】 実施の形態３による電子膨張弁の運転制御方法を示すフローチャートである。
【図２０】 実施の形態３に係り、ショーケース内温度と目標冷却温度との偏差に対し、過熱度目標値を設定する設定方法を示すグラフである。
【符号の説明】
１ コンデンシングユニット、２ ショーケース、３ 圧縮機、４ 凝縮器、５ レシーバ、６ アキュムレータ、７ 電磁弁、８ 電子膨張弁、９ 蒸発器、１０、１８ ファン、１１ 液管、１２ ガス管、１３ 冷媒温度センサ、１４ 空気温度センサ、１５ 圧力センサ、１６、１７ 計測制御装置、２０ 冷凍サイクル、２１ 圧縮機容量制御手段、２３油量検知手段、３１ 目標温度設定手段、３２ 蒸発器運転決定手段、３４ 流動抵抗制御手段、３５ 目標値変更手段、３６ 目標値記憶手段、３７ 目標冷却温度分類手段。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a refrigeration air conditioner, and more particularly to a refrigeration air conditioner having a plurality of cooling objects with different cooling temperatures and a control method for the refrigeration air conditioner.
[0002]
[Prior art]
Conventionally, a refrigeration air conditioner having a plurality of evaporators has a condensing unit having an inverter-driven compressor on the heat source side and evaporators installed in a plurality of showcases on the load side. The rotation speed of the compressor is controlled so that the suction pressure becomes a set target value. In each showcase, the target value of the blown air temperature is determined, the blown air temperature of the showcase is measured, and if the blown air temperature> the target value, the solenoid valve provided on the upstream side of the evaporator is opened. If the case is in an operating state and the blown air temperature is less than the target value, the solenoid valve is closed and the showcase is stopped. Then, the operating rate of the solenoid valve within a certain period of time, that is, the ratio of the open time is measured, and the compressor suction pressure target value is set so that this operating rate is 40 to 90% in all showcases. The number of rotations of the compressor is controlled so that the suction pressure becomes this target value for the next fixed time (see, for example, Patent Document 1). By carrying out such an operation, the compressor capacity was controlled in accordance with the cooling load of the showcase.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-217974 (6th and 7th pages, FIG. 5)
[0004]
[Problems to be solved by the invention]
The conventional refrigeration and air-conditioning apparatus has the following problems. Generally, the cooling temperature is set according to the object to be cooled in a plurality of showcases. For example, when cooling fruits and vegetables, 5-10 ° C, when cooling daily items such as bento, 5 ° C, fresh products such as meat fish When the camera is cooled, the inside of the showcase is cooled to a temperature of about 0 ° C. In recent years, with the increase in capacity of refrigerators, a large number of showcases are connected to one refrigerator, and showcases that cool fruits and vegetables, daily products, and fresh products are connected simultaneously as the temperature zone of the refrigerated area. There is also a case. In this case, the target value of the blowout temperature is set higher in the order of fruits and vegetables> daily products> fresh products, and the cooling load is also lighter for fruits and vegetables and daily products. If done, the run time of the showcase will be shorter for fruits and vegetables, daily products and longer for fresh products. Therefore, the operation pattern of the showcase is roughly divided into a case where the showcases of fruits, vegetables, daily products and fresh products are simultaneously operated (pattern 1) and a case where only fresh products are operated (pattern 2). In the case of the operation control of the conventional example, both the pattern 1 and the pattern 2 are operated at the same suction pressure of the compressor, and the evaporation temperature of each showcase is also operated at the same temperature. At this time, it is operated at an evaporating temperature that can provide sufficient cooling capacity even in a fresh product showcase with a low set temperature. It will be cooled. In the case of cooling the object to be cooled in the refrigeration cycle, the efficiency deteriorates as it is cooled by a lower temperature heat source. In the case of the conventional example, the efficiency is lowered in the cooling of fruits and vegetables with high set temperatures and daily showcases. As a result, there is a problem that the operation efficiency of the entire apparatus is lowered. In addition, because fruits and vegetables are cooled at an excessively low evaporating temperature in daily goods showcases, the air temperature of the blowout will be greatly reduced below the set temperature, and some fruits and vegetables will deteriorate in freshness due to low temperature failures. There was a problem.
[0005]
The present invention has been made to solve the above-described problems. When a target having different cooling temperatures is cooled by a plurality of evaporators, the compressor is operated at a capacity suitable for the temperature of the target. An object of the present invention is to obtain a refrigeration air conditioner and a method for controlling the refrigeration air conditioner that can improve the operation efficiency.
[0006]
[Means for Solving the Problems]
In the refrigeration air conditioner according to the present invention, a refrigeration cycle comprising a plurality of evaporators connected in parallel to a compressor, and target temperature setting means for individually setting a target cooling temperature to be cooled for each evaporator. , An evaporator operation determining means for determining an operation stop for each evaporator according to the temperature of the cooling target and the target cooling temperature, and an individual target cooling temperature of the operated evaporator The target suction pressure or target evaporation temperature of the refrigeration cycle is determined from the above, and the operating capacity of the compressor is determined so that the suction pressure or evaporation temperature of the refrigeration cycle becomes the target suction pressure or target evaporation temperature. Compressor capacity control means The target suction pressure or the target evaporation temperature is higher than a preset reference value of the target value, and the maximum value of the target cooling temperature of the operating evaporator among the plurality of evaporators and the plurality of evaporators The reference value is shifted based on the difference between all the target cooling temperatures and the minimum value, and set as a new target suction pressure or target evaporation temperature. Based on the new target suction pressure or target evaporation temperature, the compressor The capacity was controlled And features.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
1 is a refrigerant circuit diagram showing a refrigerating and air-conditioning apparatus according to Embodiment 1 of the present invention. In FIG. 1, 1 is a heat source side, for example, a condensing unit, 2a, 2b, 2c are load side showcases, and this portion is shown in a cross-sectional configuration. For example, there are three showcases 2. The showcase 2a is for fruits and vegetables, the showcase 2b is for daily delivery, and the showcase 2c is for fresh food. The white arrow in the showcase 2 indicates the flow of air in the showcase 2. 3 is a compressor whose rotational speed is variable by an inverter, for example, 4 is a condenser, 5 is a liquid receiver, and 6 is an accumulator, which are built in the condensing unit 1. 7a, 7b and 7c are electromagnetic valves, 8a, 8b and 8c are electronic expansion valves which are pressure reducing devices, 9a, 9b and 9c are evaporators, 10a, 10b and 10c are for cooling the inside of the showcases 2a, 2b and 2c. It is a fan that blows air to the object to be cooled in the showcase 2 through the evaporators 9a, 9b, 9c, and the electromagnetic valve 7, the electronic expansion valve 8, the evaporator 9, and the fan 10 are built in the showcase 2. The liquid pipe 11 and the gas pipe 12 are refrigerant pipes connecting the condensing unit 1 and the showcases 2a, 2b, and 2c. The compressor 3, the condenser 4, the electromagnetic valve 7, the electronic expansion valve 8, and the evaporator 9 are connected by refrigerant pipes 11 and 12 to constitute a refrigeration cycle 20. In particular, in this air-conditioning refrigeration apparatus, a plurality of cooling loads are connected in parallel to one heat source, and the respective target cooling temperatures can be set individually to cool each cooling target to a different target cooling temperature.
[0008]
Further, 13 is a refrigerant temperature sensor, 13a is the suction temperature of the compressor 3, 13b is the discharge temperature of the compressor 3, 13c is the outlet temperature of the condenser 4, 13d is the inlet temperature of the evaporator 9a, and 13e is the evaporator. The outlet temperature of 9a, 13f is the inlet temperature of the evaporator 9b, 13g is the outlet temperature of the evaporator 9b, 13h is the inlet temperature of the evaporator 9c, and 13i is the outlet temperature of the evaporator 9c. 14 is an air temperature sensor, 14a is the outside air temperature around the condenser 4, 14b is the intake air temperature of the evaporator 9a, 14c is the blown air temperature of the evaporator 9a, 14d is the intake air temperature of the evaporator 9b, and 14e is The blown air temperature of the evaporator 9b, 14f measures the intake air temperature of the evaporator 9c, and 14g measures the blown air temperature of the evaporator 9c. 15 is a refrigerant pressure sensor, 15a measures the suction pressure of the compressor 3 which is the low pressure of the refrigeration cycle, and 15b measures the discharge pressure of the compressor 3 which is the high pressure of the refrigeration cycle.
[0009]
Reference numeral 16 denotes a measurement control device of the condensing unit 1, and FIG. 2 is a block diagram showing a main configuration of the measurement control device 16. Based on the measured values of the refrigerant temperature sensors 13a, 13b, 13c, the air temperature sensor 14a, and the refrigerant pressure sensors 15a, 15b, the number of rotations of the compressor 3 and the air volume of the fan 18 blown to the condenser 4 are controlled. . That is, the measurement control device 16 includes a compressor capacity control means 21 and a fan air volume control means 22. Reference numerals 17 a, 17 b, and 17 c denote measurement control devices of each showcase 2, and FIG. 3 is a block diagram illustrating a main configuration of the measurement control device 17. Based on the measured values of the refrigerant temperature at the inlet / outlet of the evaporator 9 and the air temperature of the blowout / suction by the refrigerant temperature sensor 13 and the air temperature sensor 14, the opening / closing of the electromagnetic valve 7, the opening of the electronic expansion valve 8, the fan 10 airflow is controlled. Further, the target cooling temperature to be cooled of the evaporator 9 input by the input means is also stored. That is, the measurement control means 17 includes target temperature setting means 31, evaporator operation determining means 32, fan air volume control means 33, and flow resistance control means 34 for controlling the flow resistance by controlling the opening of the electronic expansion valve 8. It is a waste. In addition, the measurement control device 16 of the condensing unit 1 and the measurement control device 17 of the showcase 2 can communicate with each other, and each measurement value and information communication of the controlled device can be performed. In FIG. 1 to FIG. 3, the state of information delivery is illustrated by dotted lines.
[0010]
Next, the flow of the refrigerant in this embodiment will be described. The high-temperature and high-pressure gas refrigerant discharged from the compressor 3 exchanges heat with the outside air in the condenser 4 and is condensed and liquefied. Thereafter, the liquid flows into the showcases 2a, 2b, and 2c through the liquid receiver 5 and the liquid pipe 11. The refrigerant that has passed through the electromagnetic valves 7a, 7b, and 7c is decompressed by the electronic expansion valves 8a, 8b, and 8c to become a low-pressure two-phase refrigerant, and is then evaporated and gasified by the evaporators 9a, 9b, and 9c. Cold heat is supplied to the air blown by 10b and 10c. Thereafter, the refrigerant passes through the gas pipe 12 and the accumulator 6 and is sucked into the compressor 3.
[0011]
Next, the operation control method in this embodiment will be described. First, a method for controlling the showcases 2a, 2b, and 2c performed by the measurement control devices 17a, 17b, and 17c will be described. As described above, the showcase 2a is for fruits and vegetables, the showcase 2b is for daily goods, and the showcase 2c is for fresh goods. The target cooling temperature Tm of each showcase 2 is different, and Tma = 8 in the showcase 2a. C, Tmb = 5 ° C. in the showcase 2b, and Tmc = 0 ° C. in the showcase 2c. The target cooling temperature Tm is individually input to the target temperature setting unit 31 from, for example, an input unit provided in the showcase 2 or the measurement control device 17 and is stored and held in the measurement control device 17 of each showcase 2. . Since the following control method is the same in each showcase 2, the operation control method of the showcase 2a will be described based on FIG. 4 as a representative.
[0012]
In step 1, 8 ° C. is inputted to the target cooling temperature Tma of the showcase 2a by the target temperature setting means 31 by external input and stored. Then, the initial state of the showcase 2a is set to the operating state, the electromagnetic valve 7a is opened via the evaporator operation determining means 32 and the flow resistance control means 34, and the opening of the electronic expansion valve 8a is set to the initial operating opening. To do.
[0013]
Next, in step 2, the air temperature sensors 14b and 14c measure the intake and blown air temperatures of the showcase 2a at regular intervals, for example, about every 2 seconds, and the average temperature of both is obtained. And That is, the temperature in the showcase Ta = (suction air temperature + blow air temperature) / 2 is calculated.
[0014]
Next, in step 3 to step 7, the evaporator operation determining means 32 determines operation stop of the evaporator 9 according to the showcase internal temperature Ta and the target cooling temperature Tm, and opens and closes the electromagnetic valve 7 according to this determination. Then, the flow resistance control means 34 sets the opening degree of the electronic expansion valve 8. First, in step 3, the temperature Ta in the showcase 2 and the target cooling temperature Tm are compared. If the showcase 2a is currently in operation and Ta <Tm, the showcase 2a is sufficiently cooled and satisfies the target cooling temperature, so step 4 is performed. That is, in step 4, the showcase 2a is changed to a stop state, the electromagnetic valve 7a is changed to a closed state, and the opening degree of the electronic expansion valve 8a is set to a predetermined opening degree. By closing the electromagnetic valve 7a, the amount of refrigerant flowing into the evaporator 9a is made almost zero, and the cooling capacity of the showcase 2a is made almost zero.
[0015]
On the other hand, when the showcase 2a is currently in operation and Ta ≧ Tm in the comparison of step 3, the showcase 2a is not sufficiently cooled, and the process proceeds to step 5. In step 5, the operation state is continued and the solenoid valve 7a is kept open. At this time, the electronic expansion valve 8a is controlled such that the refrigerant superheat degree SHa at the outlet of the showcase 2a becomes a preset target value SHam. The degree of superheat SHa is obtained as the temperature difference between the refrigerant temperatures at the inlet and outlet of the evaporator 9a measured by the refrigerant temperature sensors 13d and 13e, and is obtained by the following equation (1).
SHa = evaporator 9a outlet refrigerant temperature−evaporator 9a inlet refrigerant temperature (1)
Next, the degree of superheat SHa and the target value SHam are compared, and if SHa> SHam, the opening degree of the electronic expansion valve 8a is increased, and if SHa <SHam, the opening degree of the electronic expansion valve 8a is controlled to be small. The superheat degree target value SHam is set to a preset value, for example, SHam = 5 ° C. so as to improve the operation efficiency of the entire apparatus. Moreover, the opening degree control method of the electronic expansion valve 8a is implemented by PID control. As the opening degree control method, other control methods such as fuzzy control may be used.
[0016]
Further, in the comparison of Step 3, when the showcase 2a is currently stopped and Ta <Tm + ΔTdiff, the showcase 2a is still sufficiently cooled and the process proceeds to Step 6. In Step 6, the stop state of the showcase 2a is continued, the electromagnetic valve 7a is closed, and the opening degree of the electronic expansion valve 8a is set to a predetermined opening degree during the stop. Here, ΔTdiff is a temperature differential, and is set to prevent frequent switching of the operation / stop state of the showcase 2, for example, ΔTdiff = 2 ° C. This value is held in the measurement control device 17a as a preset value or an externally input value.
[0017]
Next, in the comparison of step 3, if the showcase 2a is currently stopped and Ta ≧ Tm + ΔTdiff, it is determined that the showcase 2a has warmed up and the process proceeds to step 7. In step 7, the showcase 2a is switched to the operating state, the electromagnetic valve 7a is opened, and the opening of the electronic expansion valve 8a is set to the initial operation opening. As described above, the operation control of the showcase 2a is performed by the measurement control device 17, thereby controlling the temperature Ta in the showcase 2 to the target cooling temperature Tm.
In step 3 to step 7, the operation stop of the evaporator 9 is determined, the electromagnetic valve 7 is opened and closed in accordance with this determination, and the opening degree of the electronic expansion valve 8 is set. Continue driving.
In FIG. 4, the flowchart is such that both the operation stop control of the evaporator 9 and the opening degree control of the electronic expansion valve 8 by the opening / closing control of the electromagnetic valve 7 are performed every 2 seconds. Absent. If the electronic expansion valve 8 is controlled in an extremely short time, the operation state tends to become unstable.
[0018]
As for the control of the fan 10a, in order to prevent heat from entering the showcase 2a, the fan 10a is blown regardless of the operation / stopped state, and the heat shielding effect by the air curtain is exhibited. When the electronic expansion valve 8a has a closing function, the solenoid valve 7a is eliminated, and the opening control of the electronic expansion valve 8a is performed, that is, the control is performed such that the electronic expansion valve 8a is closed in the stopped state and opened to the predetermined opening in the operating state. By doing so, you may substitute the function of the solenoid valve 7a.
[0019]
Next, a method for controlling the condensing unit 1 performed by the measurement control device 16 will be described. Regarding the air volume control of the fan 18 that blows air to the condenser 4, the refrigerant temperature at the outlet of the condenser 4 is measured by the temperature sensor 13 c and is controlled by the fan air volume control means 22 so that the measured value becomes a predetermined target value.
[0020]
Hereinafter, a control method of the compressor 3 performed by the measurement control device 16 will be described with reference to FIG. The compressor capacity control means 21 controls the capacity of the compressor 3 by controlling the rotational speed by an inverter. For example, the rotational speed control of the compressor 3 is controlled so that the evaporation temperature ET obtained by setting the target evaporation temperature ETm and converting the suction pressure Ps measured by the refrigerant pressure sensor 15a to saturation becomes the target evaporation temperature ETm. carry out. In step 11, first, the reference value ETm0 is set as the initial value of the target evaporation temperature ETm. The value of the reference value ETm0 is corrected by feedback control according to the driving situation of the showcase 2 as will be described later. However, when there is no driving information for performing the feedback control at the initial startup or the like, for example, the showcase 2 is set based on the lowest value of the target cooling temperature Tm. Therefore, in order to ensure cooling even in the showcase 2c having the lowest target cooling temperature Tm, for example, the target evaporation temperature is set so that the evaporation temperature of the evaporator 2c is about 10 ° C. lower than the target cooling temperature 0 ° C. Set the reference value ETm0 = −10 ° C.
[0021]
Next, at step 12, the target evaporating temperature ETm is shifted according to the target cooling temperature Tm of the showcase 2 that is currently operated at a short time period, for example, every fixed time of about 1 minute. For example, when all of the showcases 2a, 2b, and 2c are in operation, if the target evaporation temperature ETm is set to −10 ° C., the showcase 2a for fruits and vegetables having a high target cooling temperature Tm, the showcase for daily delivery In 2b, it is cooled at an excessively low temperature, and the operating efficiency of the apparatus is lowered. In such a case, the target evaporation temperature ETm is shifted in accordance with the fruit and vegetable showcase 2a having a high target cooling temperature Tm. Since the target cooling temperature Tm of the showcase 2a is 8 ° C. higher than the showcase 2c, the target evaporation temperature ETm is shifted 8 ° C. higher than the reference value ETm0 and set to ETm = −2 ° C. Further, when the showcase 2a that is set to a high target cooling temperature Tm and is easily cooled quickly is stopped and the showcases 2b and 2c are in an operating state, the showcase 2b is shifted in accordance with the showcase 2b having a high target cooling temperature Tm. Since the target cooling temperature Tm of the showcase 2b is 5 ° C. higher than that of the showcase 2c, the target evaporation temperature ETm is shifted 5 ° C. higher than the reference value ETm0 to set ETm = −5 ° C. When both the showcases 2a and 2b are stopped and only the showcase 2c is in an operating state, the target evaporation temperature ETm is not shifted and remains ETm = ETm0 = −10 ° C. That is, the target evaporation temperature ETm is shifted from the reference value ETm0 by ΔTm calculated by the following equation (2).

Note that the shift of the target evaporation temperature ETm is performed at a predetermined time interval, for example, at an interval of 1 minute.
[0022]
In step 13, the rotational speed of the compressor 3 is controlled according to the set target evaporation temperature ETm. The evaporation temperature ET obtained by converting the suction pressure Ps into the saturation temperature is compared with the target evaporation temperature ETm. If ETm> ET, the rotation speed of the compressor 3 is decreased. Conversely, if ETm <ET, the rotation speed of the compressor 3 is increased. Let Although the rotation speed control of the compressor 3 is performed using PID control, other control methods such as fuzzy control may be used.
Further, the time interval for controlling the rotation speed of the compressor 3 in step 13 does not have to be the same as the time interval for shifting the target evaporation temperature ETm in step 12, taking into account the responsiveness and stability of the cooling capacity. Implemented as appropriate.
[0023]
In steps 12 and 13, the capacity of the compressor 3 is controlled by changing the shift amount based on the target evaporation temperature ETm in a short cycle of about 1 minute, for example. It is determined in step 14 whether the setting of the reference value ETm0 of the target evaporation temperature is appropriate every time a longer time period, for example, 30 minutes of operation. For this purpose, first, an average value ΔTas of deviation ΔTa between each showcase 2 internal temperature Ta and the target cooling temperature Tm is obtained by the following equation (3).

In this calculation formula, the temperature deviation ΔTa is weighted by a predetermined capacity of each showcase 2 to obtain an average value ΔTas of ΔTa. If ΔTas <0 ° C., the temperature Ta in the showcase 2 is lower than the target cooling temperature Tm, so it is determined that the cooling capacity of the device is excessive with respect to the cooling load, and the reference value ETm0 of the target evaporation temperature is increased. Reset, for example, set higher by about 0.5 ° C. When 0 ° C. ≦ ΔTas ≦ 2 ° C., the temperature Ta in the showcase 2 is substantially the same as the target cooling temperature Tm. Therefore, it is determined that the cooling capacity of the apparatus is balanced with the cooling load, and the target evaporation temperature The reference value ETm0 is set as it is. Further, when ΔTas> 2 ° C., the temperature Ta in the showcase 2 is higher than the target cooling temperature Tm. Therefore, it is determined that the cooling capacity of the apparatus is insufficient with respect to the cooling load, and the reference value ETm0 of the target evaporation temperature is reduced again. Set, for example, lower by about 0.5 ° C. When the target evaporation temperature ETm is increased, the rotation speed of the compressor 3 is operated low and the cooling capacity of the apparatus is decreased. When the target evaporation temperature ETm is decreased, the rotation speed of the compressor 3 is increased and the cooling capacity of the apparatus is increased. Thus, operation in proportion to the cooling load becomes possible.
Thereafter, the process returns to A5 and the operation of the refrigeration air conditioner is continued.
[0024]
As described above, according to this embodiment, the compressor capacity control means 21 includes the target of the refrigeration cycle including the evaporator 9 operated based on the individual target cooling temperature of the operated evaporator 9 and Since the target evaporation temperature is determined here, the target state of the refrigeration cycle suitable for that state can be set during operation. Furthermore, by setting the target state of the refrigeration cycle optimally, the operation efficiency of the entire apparatus can be improved, and deterioration of freshness of food stored in the showcase 2 can be avoided, thereby realizing highly reliable operation. it can. The state of the refrigeration cycle represents the state of the refrigerant in the refrigeration cycle. In addition to the evaporation temperature of the refrigerant used here, for example, the pressure value such as high pressure or low pressure, the flow rate of the refrigerant, the flow rate, the amount of liquid, etc. It means the state of the circulating refrigerant.
[0025]
In particular, in step 12, when a plurality of showcases 2 are operated, the operation is performed with the evaporating temperature ET set high based on the higher target cooling temperature Tm in the operated showcase 2. The showcase 2 having a high target cooling temperature Tm is successively operated with the target cooling temperature Tm being satisfied, and is actually operated with the evaporation temperature ET set gradually lower. In this way, it is possible to operate at the evaporation temperature ET commensurate with the target cooling temperature Tm of the showcase 2, and it is possible to avoid operation at an excessively low evaporation temperature ET, and to operate with high operating efficiency of the entire apparatus. Can do. At the same time, it is possible to avoid the deterioration of freshness caused by the temperature of the air blown from the showcase 2 being significantly lower than the set temperature, and to realize a highly reliable operation.
Further, when the target cooling temperature Tm to be cooled is greatly different between the plurality of showcases 2, the operation can be performed at the evaporation temperature ET suitable for the target cooling temperature Tm of the showcase 2, so that the above effect can be further exhibited. .
[0026]
[Table 1]

[0027]
Table 1 shows a case where the apparatus is operated by shifting the target evaporation temperature ETm based on this operation control (lower side), and a case where the operation is performed with the target evaporation temperature ETm fixed as in the conventional example (upper side). ) Shows the driving situation. As shown in Table 1, when the apparatus input increases, that is, when the showcases 2a, 2b, and 2c are all operated, the input reduction effect is large, and an operation with a high operation efficiency of about 4% can be realized on a time average.
[0028]
Note that the method of calculating the shift amount ΔTm of the target evaporation temperature ETm in step 12 is an example, and other methods may be used besides the above, and the same effects as described above are obtained.
For example, the target evaporation temperature ETm may be shifted based on the difference between the average value of the target cooling temperature Tm of the showcase 2 in the operating state and the average value of the target cooling temperature Tm of all the showcases 2 connected to the apparatus. .
In calculating the average value, the average value may be calculated by weighting with a predetermined capacity of each showcase 2. That is, the difference between the average value obtained by weighting the target cooling temperature of the operating evaporator with the capacity of each cooling target and the average value obtained by weighting the target cooling temperature of all the evaporators with the capacity of each cooling target. Based on the above, the target evaporation temperature ETm may be shifted.
[0029]
Alternatively, all the showcases 2 may be classified into two or more temperature ranges with the target cooling temperature Tm, and the shift amount may be determined according to the temperature range to which the target cooling temperature of the operating showcase 2 belongs.
For example, a high-temperature showcase and a low-temperature showcase are divided into two, and in the case of the configuration shown in FIG. 1, a fruit and vegetable showcase 2a (Tm = 8 ° C.) and a daily goods showcase 2b (Tm = 5 ° C.) are used. A high-temperature showcase and a fresh product showcase 2c (Tm = 0 ° C.) are classified as a low-temperature showcase. When the number of showcases 2 with a high target cooling temperature Tm is in an operating state of a predetermined number or more, the target evaporation temperature ETm is shifted higher by a predetermined temperature difference, for example, about 5 ° C., otherwise the target evaporation temperature ETm. The shift amount ΔTm may be set to zero. Here, when classifying the target cooling temperature into a plurality of temperature ranges, as an example, a predetermined value, here a temperature difference smaller than 5 ° C. is the same temperature range, and a temperature difference having a difference of 5 ° C. or more is a different temperature. It is classified as becoming an area. However, the present invention is not limited to this, and may be set in consideration of the range of the target cooling temperature of the showcase 2 or the like.
Even in this case, when the showcase 2 with a high target cooling temperature Tm is in an operating state, it is possible to improve the reliability by avoiding operation at an excessively low evaporation temperature ET and to increase the operation efficiency of the entire apparatus. can do.
[0030]
Further, the shift amount ΔTm of the target evaporation temperature ETm is determined in consideration of not only the target cooling temperature Tm of the showcase 2 but also the deviation ΔTa between each showcase 2 internal temperature Ta and the target cooling temperature Tm. Also good. In the showcase 2, defrosting is generally performed by a heater, and the temperature Ta within the showcase 2 after the defrosting may be considerably higher than the target cooling temperature Tm. In such a case, it is desirable to rapidly lower the temperature Ta within the showcase 2 and quickly bring it closer to the target cooling temperature Tm in order to prevent the quality of the products in the showcase 2 from deteriorating. Therefore, when there is a showcase 2 in which the difference between the target cooling temperature Tm and the temperature Ta in the showcase 2 at that time is higher than a predetermined value in the showcase 2, for example, 5 ° C or higher, the target cooling temperature Tm Even if the high showcase 2 is operated, the shift amount ΔTm of the target evaporation temperature ETm is set to 0, or is shifted to a low temperature side, for example, 2 ° C. lower.
By operating in this way, even if the temperature Ta within the showcase 2 is significantly higher than the target cooling temperature Tm after defrosting or at the start of the operation, the decrease in the temperature Ta within the showcase 2 is promoted. A highly reliable operation that ensures the reliability of the product in Case 2 can be realized.
Here, regarding the defrost operation, the execution / end information is received from the measurement control device 17 of the showcase 2, and even if the showcase 2 having the high target cooling temperature Tm is operated for a certain period of time after the end, the shift amount of the target evaporation temperature ETm. You may drive | operate so that (DELTA) Tm may be set to 0 or the target evaporation temperature ETm is shifted to a low temperature side.
[0031]
Further, the shift amount ΔTm of the target evaporation temperature ETm may be determined from the operation results for a certain period. FIG. 6 shows the temperature change in the showcase 2 where the target cooling temperature Tm is high for a certain period and the temperature change in the showcase 2 where the target cooling temperature Tm is low. The capacity control method of the compressor 3 shown in FIG. It is a graph which shows the operation / stop state of the showcase with respect to time at the time of implementation, the target evaporation temperature ETm, and the showcase internal temperature Ta. The upper side of the showcase internal temperature Ta indicates a showcase with a high target cooling temperature Tm, and the lower side indicates a showcase with a low target cooling temperature Tm.
As shown in the figure, when the showcase 2 having a high target cooling temperature Tm is operated, the target evaporation temperature ETm is shifted to a high level, and the showcase 2 having a high target cooling temperature Tm is intensively cooled and the temperature inside the showcase 2 is increased. While the temperature decreases, the temperature of the showcase 2 with the low target cooling temperature Tm gradually increases. When the temperature in the showcase 2 with the high target cooling temperature Tm is cooled to the target value and the stop state is reached, the shift amount of the target evaporation temperature ETm is set small, and the showcase 2 with the low target cooling temperature Tm is cooled to showcase. The temperature in 2 gradually decreases. At this time, the shift amount of the target evaporation temperature ETm is changed according to the temperature change of the showcase 2 having a low target cooling temperature Tm. For example, the deviation ΔTa between the temperature Ta within the showcase 2 and the target cooling temperature Tm at the time when the temperature of the showcase 2 having a low target cooling temperature Tm during a certain period becomes the highest is a predetermined value, for example, 1 ° C. or less. In this case, since the showcase 2 with the low target cooling temperature Tm is sufficiently cooled even during the operation in which the target evaporation temperature ETm is shifted, the showcase 2 with the higher target cooling temperature Tm is focused on. It becomes possible to cool. Therefore, in this case, the shift amount is made larger than the shift amounts calculated by the above-described methods, and the target evaporation temperature ETm is shifted, for example, by 1 ° C. On the other hand, when ΔTa is equal to or greater than a predetermined value, for example, 3 ° C. or higher, the cooling of the showcase 2 having a low target cooling temperature Tm during operation that is shifting the target evaporation temperature ETm is not sufficient, so the target cooling temperature Tm The shift amount is made smaller than the shift amount calculated by the above-described methods so that the cooling amount of the low showcase 2 is increased, and the target evaporation temperature ETm is shifted by 1 ° C., for example.
[0032]
That is, paying attention to the operation of the deviation ΔTa between the target cooling temperature Tm of the showcase 2 having a low target cooling temperature Tm and the internal temperature Ta of the showcase 2 during a certain period, the showcase 2 having a low target cooling temperature Tm is sufficiently In the case of being cooled, the shift amount of the target evaporation temperature ETm is increased, and high-efficiency operation is realized by operating at a high evaporation temperature. On the other hand, when the cooling of the showcase 2 with the low target cooling temperature Tm is not sufficient, the shift amount of the target evaporation temperature ETm is reduced, and the cooling of the showcase 2 with the low target cooling temperature Tm is secured by operating at the low evaporation temperature. To do. In this way, by determining the shift amount ΔTm of the target evaporation temperature ETm from the operation results for a certain period, an excessive increase in the temperature in the showcase 2 due to insufficient cooling is suppressed, and a more reliable refrigeration air conditioner Is obtained.
[0033]
In the calculation of the shift amount in FIG. 5, the case where the reference value ETm0 is set based on the minimum value of the target cooling temperature of all the showcases 2 in step 11 after the operation is started is described. Here, the reference value ETm0 may be set based on the maximum value of the target cooling temperature of all the showcases 2. In this case, the shift amount set by equation (2) is also calculated by the following equation.

In step 11, an intermediate temperature between the target cooling temperatures of all the showcases 2 may be set as the reference value ETm0. However, the calculation method of Formula (2) differs with this setting.
In any case, when the showcase 2 having a high target cooling temperature Tm is in an operating state, the operation efficiency can be increased, and the reliability of the entire apparatus can be improved by avoiding operation at an excessively low evaporation temperature ET. Can be improved.
[0034]
Further, in step 14 of FIG. 5, when the reference value ETm0 of the target evaporation temperature is changed at a long time period, the setting method is not limited to the above. For example, the operation and stop state of each showcase 2 during a predetermined period is stored, and when there are a predetermined number or more of showcases 2 that have never been stopped during that period, for example, 20% or more of the total number of showcases. In such a case, it is determined that the cooling capacity of the apparatus is insufficient with respect to the cooling load, and the reference value ETm0 of the target evaporation temperature is changed to a predetermined value, for example, a value lower by 1 ° C. On the other hand, if the number of showcases 2 that have never been stopped during that period is less than a predetermined number, for example, less than 5% of the total number of showcases, the cooling capacity of the apparatus is less than the cooling load. Therefore, the target evaporation temperature reference value ETm0 is changed to a predetermined value, for example, a value higher by 1 ° C.
[0035]
Further, the deviation ΔTa between each showcase 2 internal temperature Ta and the target cooling temperature Tm in a predetermined period is stored, and the number of showcases 2 in which the maximum value of ΔTa during the period is higher than a predetermined value, for example, 3 ° C. If there is a predetermined number or more, for example, if it is 20% or more of the total number of showcases, it is determined that the cooling capacity of the apparatus is insufficient for the cooling load, and the target evaporation temperature reference value ETm0 is set to a predetermined value, for example, 1 Change to a lower value. On the other hand, if the number of showcases 2 in which the maximum value of ΔTa during that period is higher than 3 ° C. is a predetermined number or less, for example, 5% or less of the total number of showcases, the apparatus is cooled. It is determined that the capacity is excessive with respect to the cooling load, and the reference value ETm0 of the target evaporation temperature is changed to a predetermined value, for example, a value higher by 1 ° C.
[0036]
Regardless of which method is used to set the reference value ETm0 of the target evaporation temperature, the apparatus can be operated with a cooling capacity balanced with the cooling load. In other words, it is possible to avoid over-cooling with an appropriate cooling capacity and to realize an efficient operation, and to avoid an increase in the temperature in the showcase 2 due to insufficient cooling to ensure the quality of the products in the showcase 2 and to operate with high reliability. Can be realized.
[0037]
As described above, in this embodiment, the target evaporation temperature ETm is calculated by the sum of the reference value ETm0 that is changed in a long time period and the shift amount ΔTm that is changed in a short time period, and is controlled based on this. It is possible to optimally set the reference value ETm0 mainly related to securing the cooling capacity and the shift amount ΔTm mainly related to improving the operation efficiency.
Here, the time period for changing the reference value ETm0 and the shift amount ΔTm is not limited to this embodiment, and the refrigeration air conditioner may be set according to the situation of the application place.
[0038]
Further, when changing the shift amount ΔTm of the target evaporation temperature ETm or the reference value ETm0 of the target evaporation temperature, the change amount is calculated based on the average value of the target cooling temperature Tm of the operating showcase 2 and the temperature Ta within the showcase 2. Feedback control using PID control or fuzzy control based on information such as deviation ΔTa from the target cooling temperature Tm is used.
[0039]
In addition, although the operation capacity of the compressor 3 is implemented by controlling the rotation speed with an inverter, the operation capacity may be controlled by mounting a plurality of the compressors 3 and increasing or decreasing the number of the operation. In addition, a compressor having an unload function may be installed, and capacity control may be performed depending on whether or not the unload operation is performed. Alternatively, a plurality of inverter-driven compressors and constant speed compressors may be combined, and the operating capacity may be controlled by controlling both the number of rotations and the number of operating compressors.
[0040]
Moreover, although the temperature Ta in the showcase 2 is an average value of the suction / blow-out air temperature, either the blow-out temperature or the suction temperature may be used. Further, an air temperature sensor may be separately provided in the space in the showcase 2 and the measured value may be used, or a temperature sensor that directly measures the product temperature in the showcase 2 may be provided and the measured value may be used. Good.
[0041]
In addition, the cooling temperature range of the showcase 2 is not limited to the above-described form, and may be applied to a so-called freezing range showcase having a cooling temperature of around −20 ° C., for example, for frozen foods and ice creams. In the above description, a predetermined value used for determining the temperature is set as a product in the general showcase 2 as a cooling target. However, an appropriate predetermined value may be set according to the type of the product. Further, the object to be cooled is not limited to the products in the showcase 2 but may be applied to a refrigerated warehouse or the like, or a system that indirectly cools through water, brine, or the like.
The operation control of this embodiment can also be used for a general air-conditioning area. For example, it can be applied to the case where the space where a machine and a person are present is cooled by a single device, the target cooling temperature of the machine is 35 ° C, and the target cooling temperature of a space where a person exists is 27 ° C. is there.
In any case, highly efficient device operation can be realized by controlling the operation capacity of the compressor 3 in accordance with the target cooling temperature to be cooled by the evaporator 9 during operation.
[0042]
Further, in this embodiment, the target evaporation temperature ETm is determined, and the operation capacity of the compressor 3 is determined so that the evaporation temperature ET obtained by converting the suction pressure to the saturation temperature becomes ETm. The same effect can be obtained by converting the target suction pressure from the temperature ETm and controlling the capacity of the compressor 3 so that the suction pressure becomes the target suction pressure.
Further, the evaporating temperature is directly obtained, for example, the temperature measured at the inlet 9 of the evaporator 9 of each showcase 2 is measured by the temperature sensor 13d or the like as the evaporating temperature ET, and the information is sent from the measurement control device 17 of the showcase 2 to the condensing unit. 1 may be transmitted to the measurement control device 16 to control the capacity of the compressor 3 so that the evaporation temperature ET becomes the target value ETm.
[0043]
Alternatively, the target value Psm of the suction pressure Ps may be directly determined instead of the target value of the evaporation temperature, and the capacity control of the compressor 3 may be performed so that the suction pressure Ps measured by the pressure sensor 15a becomes Psm. In this case, for example, the reference value and the shift amount of the target suction pressure may be set by converting the right side in Expression (2) into pressure.
[0044]
Further, the measurement control device 17 of the showcase 2 is provided in each showcase 2, but one measurement control device 17 may have a function of controlling a plurality of the measurement control devices 17. Further, a master controller that integrates a plurality of measurement control devices 17 may be provided. Information that requires external input during operation of the showcase 2 such as the target cooling temperature Tm of each showcase 2 is collectively input to the master controller, and the information is transmitted to the measurement control device 17 of each showcase 2. Thus, external input can be performed easily. In addition, by making it possible to collectively manage the operation status of each showcase 2, it is possible to easily monitor the operation status and check when a problem occurs, and to obtain a highly reliable refrigeration air conditioner.
[0045]
Further, as a control method of the refrigeration air conditioner, when operating a refrigeration cycle in which a plurality of evaporators are connected in parallel to a compressor, a target temperature setting step (in which a target cooling temperature is individually set for each of the plurality of evaporators) FIG. 4, Step 1) and an evaporator operation stop step (FIG. 4, Step 4 to Step 7) for stopping the operation of the evaporator in which the temperature of each cooling target has reached the target cooling temperature among the plurality of evaporators. And the target evaporating temperature or the target suction pressure of the refrigeration cycle is set so that a cooling temperature higher than the minimum value of the individual target cooling temperature of the evaporator is obtained when a plurality of evaporators are operated. A target state setting step (FIG. 5, step 12) and a compressor capacity control operation step (FIG. 5, step) for controlling the operation of the compressor with a capacity capable of realizing the target evaporation temperature or the target suction pressure. 3) and, by providing the can cooling temperature is controlled with operation efficiency of the refrigeration air conditioning system having a plurality of different objects to be cooled.
[0046]
Embodiment 2. FIG.
Hereinafter, a refrigerating and air-conditioning apparatus according to Embodiment 2 of the present invention will be described. The configuration of the apparatus and the capacity control method of the compressor 3 in this embodiment are the same as those in the first embodiment shown in FIGS. 1 and 5 and will not be described. Here, the control method of the electronic expansion valve 8 which is a pressure reducing device of each showcase 2 will be mainly described. In the first embodiment, when the flow resistance of the electronic expansion valve 8 is controlled by the measurement control device 17, the electronic expansion valve 8 is opened so that the superheat degree SH at the outlet of the evaporator 9 becomes a preset target value SHm. The flow resistance is controlled by setting the degree. On the other hand, in Embodiment 2, the target value SHm of the outlet superheat degree of the evaporator 9 is changed according to the operating state of the apparatus. Here, the target value of the outlet superheat degree of the evaporator 9 is set as the target value of the refrigerant state downstream of the evaporator 9, but the present invention is not limited to this. For example, the control can be performed using the suction superheat degree of the compressor 3 and the discharge superheat degree of the compressor 3.
[0047]
FIG. 7 is a graph schematically showing a fluctuation state of the operating efficiency of the refrigeration air conditioner with respect to the outlet superheat degree SH of the evaporator 9, and the horizontal axis shows the superheat degree SH and the vertical axis shows the operation efficiency. When the degree of superheat SH changes, the operation status of the apparatus is affected as follows. First, when the degree of superheat SH increases, the outlet temperature of the evaporator 9 increases and the refrigerant enthalpy also increases. Therefore, the enthalpy difference at the entrance and exit of the evaporator 9 also increases, and even if the same flow rate of refrigerant flows through the evaporator 9, more heat can be taken from the surroundings. Accordingly, the cooling capacity increases and the operating efficiency of the apparatus tends to increase as shown by the dotted line a. On the other hand, when the degree of superheat SH increases, the gas-liquid two-phase region in the evaporator 9 decreases and the gas region increases. In general, the heat transfer coefficient of the refrigerant is large in the gas-liquid two-phase part and the gas part is small. Therefore, if the gas part region is increased, the efficiency of heat transfer is reduced in the entire evaporator 9. Therefore, the cooling capacity decreases, and the operating efficiency of the apparatus tends to decrease as shown by the dotted line a. From these, as shown by the solid line in FIG. 7, the effect of increasing the enthalpy difference and the effect of decreasing the heat transfer efficiency are combined, and the operating efficiency of the apparatus has a peak at which the efficiency becomes maximum at a certain degree of superheat SH. In general, the value of the superheat degree SH at which the efficiency becomes maximum is around 5 ° C. Therefore, in the first embodiment, the superheat degree SH of all the evaporators 9 is set to about 5 ° C.
[0048]
However, the superheat degree SH that maximizes the efficiency varies depending on the refrigerant state of the refrigeration cycle during operation. FIG. 8 is a PH diagram showing the refrigerant state (refrigeration cycle) when the low pressure changes, and FIG. 9 is a PH diagram showing the refrigerant state when the superheat degree SH changes. The saturated gas enthalpy of the refrigerant decreases as the pressure decreases, and the enthalpy difference at the inlet / outlet of the evaporator 9 (FIG. 8, ΔH1) decreases as the low pressure decreases even when the same superheat is taken. To do. On the other hand, since the amount of increase in enthalpy when the degree of superheat increases (FIG. 9, ΔH2) is almost constant regardless of the pressure, the rate of increase in enthalpy difference due to the increase in superheat (ΔH2 / ΔH1) is low. The lower operation state becomes larger, and the influence of increasing the operation efficiency of the device is also increased. Therefore, as shown in FIG. 10, the superheat degree SH at which the operating efficiency is maximized is greater in the operation state where the low pressure is lower (solid line) than in the operation state where the low pressure is higher (dotted line).
[0049]
FIG. 11 is a block diagram showing the configuration of the measurement control device 17 according to this embodiment. In the figure, 35 is a target value changing means, and 36 is a target value storage means. Since there is a correlation as shown in FIG. 10 between the superheat degree SH and the operating efficiency of the apparatus, the target value SHm is set to the maximum superheat degree target value SHm by the target value changing means 35 according to the change in the operating state. change. The capacity of the compressor 3 is controlled so that, for example, the target evaporation temperature ETm is determined as in the first embodiment, and the evaporation temperature ET converted from the suction pressure Ps becomes the target evaporation temperature ETm. In the target value storage means 36, as shown in FIG. 12, the relationship of the superheat degree target value SHm with respect to the target evaporation temperature ETm is previously stored in a table or the like.
[0050]
At this time, when the target evaporation temperature ETm is as low as about −15 ° C., the superheat degree target value SHm is increased to be, for example, 10 ° C. to 15 ° C., and when the target evaporation temperature ETm is as high as about −5 ° C. The value SHm is determined to be small, for example, 2 to 5 ° C. In the meantime, the superheat degree target value SHm may be increased linearly as the target evaporation temperature ETm becomes lower, or may be changed in several steps. The measurement control device 17 of each showcase 2 receives information on the target evaporation temperature ETm determined during the capacity control operation of the compressor 3 from the measurement control device 16 of the condensing unit 1. Then, the target value changing unit 35 refers to the target value storage unit 36 according to the target evaporation temperature ETm, and determines the superheat degree target value SHm at which the maximum operating efficiency is obtained. Thereafter, the opening degree of the electronic expansion valve 8, that is, the flow resistance is controlled by the flow resistance control means 34 so that the superheat degree SH becomes the superheat degree target value SHm.
[0051]
Thus, for example, the refrigerating and air-conditioning apparatus that controls the opening degree of the electronic expansion valve 9 so that the refrigerant state on the downstream side of the evaporator 9 such as the degree of superheat at the outlet of the evaporator 9 becomes a preset target value. The target value of the superheat degree at the outlet of the evaporator 9 is changed so that the operation efficiency in the refrigerant state of the refrigeration cycle during operation is optimized. During operation, one of the evaporators 9 stops or reversely enters the operation state, and the refrigerant state of the refrigeration cycle changes every moment, but the target value is changed accordingly, so the operation is always performed. The efficiency can be kept good. Here, for example, the target value is changed according to the state quantity representing the operation state of the entire refrigeration cycle such as the target evaporation temperature, and the same target value is set in each operating evaporator 9.
[0052]
In this embodiment, as shown in FIG. 12, upper and lower limits are provided for the superheat degree target value SHm. As for the upper limit, since the superheat degree SH increases and the discharge temperature of the compressor 3 also increases, the upper limit of the superheat degree target value SHm is set so that the discharge temperature does not increase until it affects the reliability of the compressor 3. Provide. As for the lower limit, when the superheat degree SH is too small, for example, 2 ° C. or less, the superheat degree SH is not easily stabilized because it is easily affected by fluctuations in the operation. The lower limit is set.
[0053]
As shown in FIG. 11, an electronic expansion valve is provided in the measurement control device 17 provided in each showcase 2 so that the refrigerant state downstream of each evaporator 9 becomes a preset target value. 8 Flow resistance control means 34 for controlling the flow resistance of each, and the change in the operating state of the refrigeration cycle, the individual target cooling temperature of the operated evaporator 9 or the temperature of the cooling target of each operated evaporator 9 The target value changing means 35 for changing the target value based on the operating condition, that is, the operating condition, that is, the state of the showcase 2 to be cooled by the evaporator 9 in operation is changed, and the evaporation of the refrigeration cycle is based on the change. Even if the temperature changes, a refrigeration air conditioner that can be operated with high operating efficiency is obtained.
[0054]
Even when the capacity control of the compressor 3 is not performed as in the first embodiment, the evaporation temperature ET currently in operation is measured by the temperature sensor 14 at the inlet of the evaporator 9 of each showcase 2, and the like. The superheat degree target value SHm may be determined based on the measurement result. Further, information on the suction pressure Ps measured by the pressure sensor 15a of the condensing unit 1 may be received from the measurement control device 16, and the superheat degree target value SHm may be determined based on the information. When changing the target value for control according to the current driving situation, stable operation is difficult if the target value changes frequently, so set the target value at a predetermined time interval or evaporate temperature information, etc. It is desirable that the target value for the control is not changed frequently by taking an average for a certain time when acquiring.
[0055]
Further, the superheat degree target value SHm may be changed not only according to the target evaporation temperature ETm but also depending on the operating state / stopped state of the showcase 2 and the target cooling temperature Tm or the showcase 2 internal temperature Ta.
When the average value of the target cooling temperature Tm of the showcase 2 in the operating state is high, or when the showcase 2 in the operating state includes a high target cooling temperature Tm, the evaporation temperature is used as the operation of the apparatus. It is easy to operate with high ET and suction pressure Ps. Conversely, when the average value of the target cooling temperature Tm of the showcase 2 in the operating state is low, or when the showcase 2 in the operating state does not include a target cooling temperature Tm that is high, the operation of the apparatus is performed. It is easy to operate in a state where the evaporation temperature ET and the suction pressure Ps are low. Accordingly, the target cooling temperature Tm of the showcase 2 that is currently in operation is acquired and the average value is calculated. If the average value of the target cooling temperature Tm is high as shown in FIG. 13, the superheat target value SHm is calculated. If the average value of the target cooling temperature Tm is low, the same effect as described above can be obtained even if the superheat degree target value SHm is set large.
[0056]
Similarly, when the current internal temperature Ta of the showcase 2 is high, the evaporation temperature ET and the suction pressure Ps are high, and when the internal temperature Ta of the showcase 2 is low, the evaporation temperature ET and the intake pressure Ps are low. . For this reason, the current internal temperature Ta of the showcase 2 may be used instead of the target cooling temperature Tm. In this case, when the average value of the temperature Ta in the showcase 2 is high, the target value SHm of the superheat degree is set small, and when the average value of the temperature Ta in the showcase 2 is low, the target value SHm of the superheat degree is set large. To do.
[0057]
Further, the target value SHm of the superheat degree may be changed according to the high pressure during operation and the outside air temperature that affects the high pressure.
FIG. 14 is a PH diagram showing the refrigerant state (refrigeration cycle) when the high pressure changes. In this apparatus, since the liquid receiver 5 is provided at the outlet of the condenser 4, the refrigerant just becomes a saturated liquid at the outlet of the condenser 4. As shown in FIG. 14, when the high pressure is high, the saturated liquid enthalpy increases and the condenser 4 outlet enthalpy and the evaporator 9 inlet enthalpy also increase. On the other hand, when the high pressure is low, the saturated liquid enthalpy is small, and the condenser 4 outlet enthalpy and the evaporator 9 inlet enthalpy are also small. Therefore, when the high pressure is high, the enthalpy difference at the entrance and exit of the evaporator 9 (FIG. 14, ΔH1) is small, and when the high pressure is low, the enthalpy difference at the entrance and exit of the evaporator 9 is large. As described above, when the difference in enthalpy at the inlet / outlet of the evaporator 9 is small, the target value SHm of the superheat degree is increased, and when the difference of enthalpy at the inlet / outlet of the evaporator 9 is large, the target value SHm of the superheat degree is decreased. Will be better. For this reason, the high pressure value during the current operation or the average value of the high pressure for a predetermined time is measured by the pressure sensor 15b. If the value is high, the target value SHm of the superheat degree is set large, and if the value is low, the superheat degree is low. The target value SHm may be set small.
Further, the high pressure is affected by the outside air temperature, and the higher the outside temperature, the higher the high pressure. Therefore, if the outside air temperature measured by the temperature sensor 14c is high, the target value SHm of the superheat degree is set large, and the outside air temperature is low. The target value SHm of the superheat degree may be set small.
[0058]
FIG. 15 is a flowchart showing an example of processing when the operation is performed while changing the target value of the outlet superheat degree of the evaporator 9 described above. Whether or not the operating state of the refrigeration cycle 20 has changed is determined by each of Steps 21, 22, and 23. Here, as a change in the operating state of the refrigeration cycle 20, for example, a change in the low pressure value or the high pressure value of the refrigeration cycle (step 21), the average value of the target cooling temperature of the operated evaporator changes (step 22), and the operation A change (step 23) in the average value of the cooling target temperature of the evaporator is detected. When each operation state changes, as shown in steps 24, 25 and 26, the target value changing means 35 refers to the target value storage means 36 to set the target value of the outlet superheat degree. Then, the opening degree of the electronic expansion valve 8 is controlled by the flow resistance control means 34 so as to reach the target value of the outlet superheat degree (step 27).
Here, the target value of the outlet superheat degree of the evaporator is changed by the three determinations of steps 21, 22, and 23. However, at least one of the determinations is performed, and the target value is set according to the determination result. It may be changed.
[0059]
Although the target value SHm of the superheat degree is basically set to be the same for each showcase 2, it may be individually adjusted according to the characteristics of each showcase 2. That is, depending on the size of the evaporator 9 in the showcase 2, the pass pattern of the evaporator 9, the air flow rate, and the like, there are a showcase 2 in which the degree of superheat tends to increase at the outlet of the evaporator 9 and a showcase 2 that is unlikely to become. Therefore, the characteristics of the showcase 2 may be grasped in advance, and the superheat target value SHm obtained by the method described above may be corrected based on the characteristics. For example, in the showcase 2 in which the degree of superheat SH tends to increase, the heat transfer efficiency is generally good. Therefore, the influence of the decrease in heat transfer efficiency on the operation efficiency when the degree of superheat SH shown in FIG. The amount of decrease in operating efficiency when the degree SH increases is reduced. Accordingly, since the efficiency tends to become maximum when the superheat degree SH is large, the target value SHm of the superheat degree is corrected to be large in the case of such a showcase 2. On the other hand, in the showcase 2 in which the degree of superheat is difficult to increase, the amount of decrease in operating efficiency when the degree of superheat SH increases is large, and the efficiency tends to become maximum when the degree of superheat SH is low. SHm is corrected to be small.
[0060]
In addition, the superheat degree SH is obtained from the refrigerant temperature difference between the inlet and outlet of the evaporator 9 of each showcase 2. In this method, the superheat degree SH is calculated to be smaller by the amount of decrease in the evaporation temperature due to the refrigerant pressure loss in the evaporator 9. Will do. Therefore, the influence of the pressure loss of each showcase 2 may be corrected in advance and corrected when the superheat degree is calculated. When the superheat degree at the outlet of the evaporator 9 is calculated, the measured value of the suction pressure Ps by the pressure sensor 15a is received as information from the measurement control device 16 of the condensing unit 1, and the suction pressure Ps and the evaporator 9 outlet temperature are obtained. The degree of superheat SH may be obtained. In this case, correction of the pressure loss from the outlet of the evaporator 9 to the suction of the compressor 3 is necessary in some cases, but the influence of the pressure loss in each showcase 2 is eliminated.
[0061]
Further, although the superheat degree SH at the outlet of the evaporator 9 is controlled by controlling the flow resistance by the opening degree of the electronic expansion valve 8, the flow resistance may be controlled using another decompression device. For example, a valve that repeatedly opens and closes at a short time interval and controls the flow rate and the amount of pressure reduction at a ratio of the open time may be used, or a plurality of fixed opening valves are arranged in parallel, and the number of valves to be opened and closed You may control a flow volume and the pressure reduction amount by controlling. Further, a structure may be adopted in which a decompression device such as a capillary tube is installed in parallel or in series to adjust the decompression width.
[0062]
In the configuration of FIG. 1, the electronic expansion valve 8 is arranged on the downstream side of the electromagnetic valve 7, but the electromagnetic valve 7 may be arranged on the downstream side of the electronic expansion valve 8. With such a configuration, the electronic expansion valve 8 can be prevented from being damaged by the liquid hammer when the electromagnetic valve 7 is opened, and a highly reliable device can be obtained.
[0063]
Further, although the superheat degree SH at the outlet of the evaporator 9 is used as a control target of the electronic expansion valve 8, another state having a correlation with the superheat degree SH may be measured and controlled. For example, the superheat degree SHs on the suction side of the compressor 3 may be obtained by using the temperature sensor 13a and the pressure sensor 15a, and the superheat degree SHs may be controlled to be a set target value. The suction superheat degree SHs of the compressor 3 is an average value obtained by weighting the outlet superheat degree SH of the evaporator 9 of each showcase 2 with the flow rate flowing through each showcase 2, and therefore the outlet superheat degree SH of the evaporator 9. It becomes the same value as. Accordingly, in this case, the target value can be set in the same manner as the method for setting the target value SHm of the outlet superheat degree of the evaporator 9.
When the suction superheat degree of the compressor 3 is controlled, it is directly controlled by looking at the suction state of the compressor 3, so that the operation affecting the reliability of the compressor 3 operation such as when a liquid back is generated. Can be handled quickly, and more reliable operation control can be performed.
[0064]
Further, as the control target of the electronic expansion valve 8, the discharge temperature Td of the compressor 3 measured by the temperature sensor 13b and the discharge superheat degree SHd of the compressor 3 calculated from the measured values of the temperature sensor 13b and the pressure sensor 15b are used. Also good. Since these values have a positive correlation with the suction superheat degree SHs of the compressor 3, these values that maximize the operating efficiency, the amount of change in the target value due to the evaporation temperature ET, and the like are obtained in advance, and the method described above, etc. Thus, the target value may be determined according to the operating state, and the opening degree control of the electronic expansion valve 8 may be performed.
Also in this case, the operation of the compressor 3 may be performed such as an excessive increase in the discharge temperature or a decrease in the concentration of the refrigerating machine oil due to the refrigerant stagnation in the refrigerating machine oil due to a decrease in the discharge temperature Td or the discharge superheat degree SHd in the case of the high pressure shell compressor When the operation has an influence on the reliability, it is possible to quickly cope with the operation, and it is possible to perform the operation control with higher reliability.
[0065]
When there are a plurality of showcases 2 and control is performed with one control target such as the suction superheat degree SHs of the compressor 3, the electronic expansion valve 8 of each showcase 2 is controlled as follows. To do. First, the total opening degree of the electronic expansion valve 8 currently in operation is obtained. The total value is increased or decreased so that the control target such as the suction superheat degree SHs of the compressor 3 becomes the target value. And the total value of the opening degree of the electronic expansion valve 8 increased or decreased is allocated to the opening degree of the electronic expansion valve 8 of each showcase 2. At this time, the allocation of the opening degree of the expansion valve is basically distributed at a ratio corresponding to the predetermined capacity of the showcase 2, but may be adjusted depending on the degree of superheat SH of the showcase 2 or the like.
[0066]
Further, the adjustment is made according to the deviation ΔTa between the current temperature Ta in the showcase 2 and the target cooling temperature Tm of the showcase 2, and the showcase 2 having a small deviation ΔTa does not require a large amount of cooling capacity at present. Control such as adjusting the opening degree of the electronic expansion valve 8 to be small so that the outlet superheat degree SH of the container 9 becomes large may be performed.
When such control of the electronic expansion valve 8 is carried out, if there is a master controller that integrates the measurement control device 17 of each showcase 2, a control system can be easily constructed.
[0067]
In addition, in a special operation mode such as oil recovery operation, feed forward control in which control is performed by a predetermined method without performing feedback control such as superheat control on some or all of the electronic expansion valves 8 may be performed. Good.
When the compressor 3 is continuously operated at a low capacity for a long time, the flow rate of the refrigerating machine oil flowing through the gas pipe 12 is decreased, and the oil retention amount in the gas pipe 12 is increased. At this time, if the oil retention amount in the gas pipe 12 becomes too large, the amount of oil retained in the compressor 3 may be reduced, and the operation reliability of the compressor 3 may be reduced. Therefore, a refrigerating and air-conditioning apparatus that includes an oil amount detection means 23 that detects the amount of oil retained in the compressor 3 and that performs the oil recovery operation mode as shown in FIG. 16 will be described.
[0068]
FIG. 17 is a flowchart showing processing in the oil recovery operation mode. That is, the oil amount detecting means 23 detects the amount of oil retained in the compressor 3 and determines whether or not the amount of retained oil has decreased (step 31). For example, the oil amount detection means 23 empirically grasps the retained oil amount of the compressor 3 based on the operation capacity and operation time of the compressor 3. That is, when the compressor 3 is continuously operated at a predetermined capacity, for example, 40% or less, for a predetermined time, for example, 1 hour or more, the oil retention amount of the gas pipe 12 increases and the retained oil amount of the compressor 3 decreases. That is expected. Therefore, in such a case, in order to recover the oil in the gas pipe 12, the oil recovery operation mode of step 32 to step 34 is performed. In step 32, the compressor 3 is operated so as to increase the operating capacity to increase the flow rate of the refrigerating machine oil flowing through the gas pipe 12 and to reduce the oil retention amount in the gas pipe 12. At the same time, an evaporator having a large cooling load is selected from the operating evaporators 9 (step 33). Here, oil recovery is performed by setting the refrigerant state of the outlet of the evaporator 9 having a large cooling load among the evaporators 9 in operation to a gas-liquid two-phase state.
[0069]
Further, it communicates from the measurement control device 16 of the condensing unit 1 to the measurement control device 17 of each showcase 2 that the oil recovery operation mode has been entered. When the measurement control device 17 of each showcase 2 receives this communication, the opening degree of the electronic expansion valve 8 on the upstream side of the evaporator 9 selected in step 33 is predetermined by the flow resistance control means 34. The opening is largely controlled, for example, fully opened, so that the outlet of the evaporator 9 is in a gas-liquid two-phase state (step 34). When controlled in this way, a gas-liquid two-phase refrigerant flows through the gas pipe 12. At this time, since the liquid refrigerant and the oil are dissolved, the viscosity of the oil is lowered and the oil flows easily. As a result, the oil retention amount in the gas pipe 12 can be decreased and the retained oil amount in the compressor 3 can be increased. Accordingly, in step 35, it is confirmed that the amount of oil retained in the compressor 3 has been recovered, and the oil recovery operation mode is terminated. For example, a predetermined time during which oil can be recovered is confirmed in advance by actual operation, and the oil recovery operation is performed for this predetermined time. The end of the oil recovery operation mode is determined by the oil amount detection means 23. By operating in this way, the operation reliability of the compressor 3 can be ensured and a highly reliable refrigeration air conditioner can be obtained.
[0070]
When the evaporator 9 that largely controls the opening degree of the electronic expansion valve 8 is selected in step 33 when the oil recovery operation mode is performed, the number of the showcases 2 is less than a certain percentage of the total number of the showcases 2. The remaining showcase 2 is preferably controlled so that the degree of superheat at the outlet of the evaporator 9 becomes a target value as in normal operation. If the opening degree of the electronic expansion valve 8 is increased in all the showcases 2, a large amount of liquid refrigerant is not evaporated by the evaporator 9 but is sucked into the compressor 3 through the gas pipe 12. If too much liquid is sucked into the compressor 3, there is a possibility that the operation reliability of the compressor 3 is lowered due to liquid compression or the like. Therefore, the number of showcases 2 that largely control the opening degree of the electronic expansion valve 8 is set to a predetermined amount or less, and the remaining showcases 2 are controlled by the degree of superheat at the outlet of the evaporator 9 as a normal operation. Reduce the amount of liquid refrigerant to be sucked below a certain value. As this amount, for example, the dryness of the suction refrigerant in the compressor 3 is set to about 0.7 or more. When the degree of dryness is 0.7 or more, almost all of the sucked liquid refrigerant can be evaporated by heat generated by work or motor heat generated by the refrigerant in the compressor 3, thereby avoiding a decrease in reliability due to liquid compression. it can.
[0071]
In the showcase 2 in which the opening degree of the electronic expansion valve 8 is largely controlled, assuming that the liquid return amount is maximized, the liquid return amount is determined by the refrigerant dryness at the inlet of the evaporator 9, and the dryness is usually In the case of the refrigeration cycle, the value is about 0.2 to 0.3. On the other hand, when the operation is controlled so that the degree of superheat is generated at the outlet of the evaporator 9, the refrigerant dryness at the outlet of the evaporator 9 is approximately 1.0. Therefore, the number of showcases 2 for largely controlling the opening degree of the electronic expansion valve 8 is defined to be 40% or less of the total number when the capacity of each showcase 2 is substantially constant. At this time, the suction refrigerant dryness of the compressor 3 is at least 0.2 × 0.4 + 1.0 × 0.6 = 0.68 or more, and the suction refrigerant dryness of the compressor 3 is approximately 0.7 or more. Can be. In addition, when the capacity | capacitance of each showcase 2 is not constant and the refrigerant | coolant flow rates which flow differ, weighting by a refrigerant | coolant flow rate is performed and the number of the showcases 2 which control the opening degree of the electronic expansion valve 8 largely is determined.
[0072]
When the showcase 2 that largely controls the opening degree of the electronic expansion valve 8 is determined, the measurement control device 17 of the showcase 2 is preliminarily responded to the oil recovery operation mode (electronic expansion corresponding to the operation mode). Whether to open the valve 8 or continue control as in normal operation) is determined, and is determined according to the rule. As another method, when a master controller that integrates the measurement control device 17 is provided, the operation state of each showcase 2 is grasped by this master controller, and the oil recovery operation mode is set according to the operation state of the showcase 2 May be determined. When the opening degree of the electronic expansion valve 8 is controlled to be larger, the flow rate of the refrigerant flowing into the showcase 2 is increased and the heat transfer coefficient of the refrigerant is increased, so that the amount of heat exchange in the evaporator 9 is generally increased. Accordingly, the opening degree of the electronic expansion valve 8 when the showcase 2 having a low target cooling temperature Tm, which has a large load and requires a large amount of heat exchange, is in the oil recovery operation mode. It may be set to a showcase that opens. In this case, not only the oil recovery function but also the cooling capacity of the showcase 2 can be operated to follow the load, so that the quality of the product in the showcase can be ensured and the apparatus can be made highly reliable.
[0073]
Further, as the operation state of the showcase 2, when the showcase 2 having a large deviation ΔTa between the current temperature Ta in the showcase 2 and the target cooling temperature Tm is set in the oil recovery operation mode, the opening degree of the electronic expansion valve 8 is set. You may set to the showcase 2 to open. In this case as well, an operation that follows the load can be realized, and a highly reliable device can be obtained.
[0074]
In the above, the decrease in the amount of oil retained in the compressor 3 is predicted by the capacity of the compressor 3 and the continuous operation time. However, the present invention is not limited to this, and the decrease in the amount of oil in the shell of the compressor 3 is directly controlled by a float switch or the like. It may be detected, or a decrease in the amount of oil in an oil storage unit such as an oil separator or an accumulator that holds oil in other parts of the refrigeration cycle and supplies oil to the compressor 3 may be detected by a float switch or the like. . The oil recovery operation mode may be set in advance for a predetermined time during which oil will be recovered, and may be operated for that time. If the oil level can be detected, the liquid level becomes a predetermined value. You may make it drive to.
[0075]
Moreover, although the refrigeration air conditioner which performs the structure and control shown in FIGS. 1-6 was described here, it is not restricted to this. In refrigeration and air-conditioning systems such as air conditioners, conventionally, the state of the refrigerant on the downstream side of the evaporator, for example, the degree of superheat of the evaporator outlet, is set to a fixed target value of about 5 ° C., and the electronic expansion valve is opened so as to become this. However, if this target value is changed according to the operating state of the refrigeration cycle, the operating efficiency can be improved. For example, even in the case of having one evaporator, the high pressure value and low pressure value of the refrigeration cycle may change depending on the outside air temperature, the cooling load, etc. If it changes so that efficiency may be obtained and the electronic expansion valve provided in the upstream of an evaporator is controlled so that it may become this target value, operation efficiency can be improved.
[0076]
Further, as a control method for the refrigeration air conditioner, when operating a refrigeration cycle in which a plurality of combinations of pressure reducing devices and evaporators connected in parallel are connected to a compressor, target cooling is individually performed for each of the plurality of evaporators. A target temperature setting step for setting the temperature, and a flow resistance control step for controlling the flow resistance of each of the decompression devices so that the downstream refrigerant state of each of the evaporators becomes a preset target value (FIG. 15, step) 27) and a target value changing step (FIG. 15, Steps 24, 25, and 26) for changing the target value in accordance with a change in the operating state of the refrigeration cycle. It is possible to control a refrigeration air conditioner having a cooling target with high operation efficiency.
[0077]
In addition, as a control method of the refrigeration air conditioner, an oil amount detection for detecting a decrease in the amount of oil retained in the compressor in a refrigeration cycle in which a plurality of combinations in which a decompression device and an evaporator are connected are connected in parallel to the compressor. When it is detected in step (FIG. 17, step 31) and the amount of retained oil in the compressor is decreased in the oil amount detection step, the cooling load is large among the plurality of operating evaporators. An evaporator selection step (FIG. 17, Step 33) for selecting an evaporator, and an upstream side of the evaporator so that the refrigerant at the outlet of the evaporator selected in the evaporator selection step is in a gas-liquid two-phase state. The flow resistance control step (FIG. 17, step 34) for controlling the flow resistance of the pressure reducing device to be connected is provided, so that the oil amount of the compressor 3 can be held at a required amount and the cooling capacity of the evaporator 9 To load Driving to Sui, it is possible to perform temperature can be maintained at the target cooling temperature reliable operation control of the cooling object.
[0078]
Embodiment 3 FIG.
Hereinafter, a refrigerating and air-conditioning apparatus according to Embodiment 3 of the present invention will be described. In this embodiment, the configuration of the refrigeration air conditioner and the capacity control method of the compressor 3 are the same as those in the first embodiment shown in FIGS. 1 and 5, and the description thereof is omitted. Here, the control method of the electronic expansion valve 8 of each showcase 2 is demonstrated. In the second embodiment, when the electronic expansion valve 8 of each showcase 2 is controlled, the target value SHm of the superheat degree at the outlet of the evaporator 9 which is the control target value of the refrigerant state downstream of the evaporator 9 is basically Although it is the same for each showcase 2, in this embodiment, an electronic value is set for each showcase 2 such as changing the target value SHm of the superheat degree according to the target cooling temperature Tm of each showcase 2 or the temperature Ta within the showcase 2. The control method of the expansion valve 8 is changed. Here, the target value of the outlet superheat degree of the evaporator 9 is set as the target value of the refrigerant state downstream of the evaporator 9, but the present invention is not limited to this. For example, the control can be performed using the suction superheat degree of the compressor 3 and the discharge superheat degree of the compressor 3.
[0079]
As shown in FIG. 6, the temperature change in the showcase 2 when the capacity control method for the compressor 3 described in the first embodiment is performed is as follows. First, the showcase 2 having a high target cooling temperature Tm is cooled. After the case 2 is stopped, the showcase 2 having a low target cooling temperature Tm is cooled. It should be noted that since the operating condition of such a showcase 2 tends to have a lower cooling load in the showcase 2 having a higher target cooling temperature Tm, the capacity control method of another compressor 3 as in the conventional example is performed. Even if it occurs.
[0080]
In this process, when the showcase 2 having a high target cooling temperature Tm is stopped, only the showcase 2 having a low target cooling temperature Tm is operated. That is, the number of the evaporators 9 through which the refrigerant flows is reduced when viewed from the whole apparatus, and the operation efficiency of the apparatus is lowered as the heat transfer area of the evaporator 9 is reduced. Therefore, here, the electronic expansion valve 8 prevents the showcase 2 having a high target cooling temperature Tm from being stopped and secures the heat transfer area of the evaporator 9 in the entire apparatus, thereby preventing a reduction in operating efficiency. To do.
[0081]
FIG. 18 is a block diagram showing the configuration of the measurement control device 17 according to this embodiment. In the figure, reference numeral 37 denotes target cooling temperature classification means for classifying the individual target cooling temperatures of the plurality of evaporators 9 into at least two temperature ranges. For example, the target cooling temperature Tm of each showcase 2 is set to Tma = 8 ° C. in the showcase 2a, Tmb = 5 ° C. in the showcase 2b, and Tmc = 0 ° C. in the showcase 2c. When classifying, the showcases 2a and 2b are on the high temperature side, and the showcase 2c is on the low temperature side. Depending on which class the evaporator 9 belongs to in this classification, the target value changing means 35 changes the method for changing the target value of the refrigerant state downstream of the evaporator with respect to the evaporator.
[0082]
Hereinafter, a method of controlling the electronic expansion valve 8 performed by the measurement control device 17 will be described with reference to FIG. The change of the target value of the refrigerant state on the downstream side of the evaporator is performed individually for each of the operating evaporators 9. Here, control for one evaporator 9 will be described. The target cooling temperature classification means 37 grasps whether the evaporator 9 that is currently controlled among the plurality of evaporators 9 is the showcase 2 with the high target cooling temperature Tm or the showcase 2 with the low target cooling temperature Tm. . And it is judged whether the evaporator 9 corresponds to the showcase 2 with the high target cooling temperature Tm (step 41). If the showcase 2 has a low target cooling temperature, the routine proceeds to step 42, where a target value SHm of superheat degree that improves the operating efficiency is set as described in the second embodiment, and the evaporator The opening degree of the electronic expansion valve 8 is controlled by the flow resistance control means 34 so that the superheat degree SH at the 9 outlet becomes the target value SHm. On the other hand, if it is determined in step 41 that the evaporator 9 to be controlled is an evaporator having a high target cooling temperature Tm, the process proceeds to step 43, where the current temperature Ta in the showcase 2 is It is determined how much the deviation ΔTa from the target cooling temperature Tm is. When ΔTa is a predetermined value, for example, 3 ° C. or more, the showcase 2 is high in temperature and needs to be sufficiently cooled. The target value SHm is set to a low value, for example, 2 ° C., and the opening degree of the electronic expansion valve 8 is controlled so that the degree of superheat SH becomes this value.
[0083]
When such control is carried out, the evaporator 9 is operated in a state where there are many gas-liquid two-phase parts and less gas parts, so the amount of cooling in the evaporator 9 increases and sufficient cooling in the showcase 2 can be realized. . On the other hand, if ΔTa is 3 ° C. or less in step 43, the showcase 2 has been cooled to some extent and a large amount of cooling capacity is not required, so in step 45 the target value of the superheat degree at the outlet of the evaporator 9 is obtained. Set SHm to a large value. If the degree of superheat SH is large, the evaporator 9 has a small number of gas-liquid two-phase portions and a large amount of gas portions, so that the cooling amount decreases. That is, in step 45, when the showcase 2 to be controlled is a showcase 2 with a high target cooling temperature Tm, and the deviation ΔTa between the current temperature Ta in the showcase 2 and the target cooling temperature Tm is a predetermined value or less, the evaporator A flow resistance control step is performed in which the target value SHm of the degree of superheat at the 9 outlet is set to a large value and the cooling capacity is controlled to be small. As ΔTa is smaller, more cooling capacity is not required. Therefore, based on the correlation shown in FIG. 20, for example, as ΔTa is smaller, the target value SHm of the superheat degree may be set larger.
[0084]
In this way, the target value changing means 35 controls the opening degree of the electronic expansion valve 8 individually for each operating evaporator 9 according to the cooling state of the evaporator 9, thereby operating the refrigeration air conditioner. Therefore, it is possible to control the operation according to the situation and improve the operation efficiency.
In particular, in the showcase 2 where the target cooling temperature Tm is low, the operation is performed at the outlet superheat degree SH of the evaporator 9 so that the operation efficiency of the apparatus is improved. Further, in the showcase 2 having a high target cooling temperature Tm, if the deviation ΔTa between the temperature Ta in the showcase 2 and the target cooling temperature Tm is large, sufficient cooling is realized so that the temperature Ta in the showcase 2 is high. Can be avoided. Further, when the cooling target temperature of the evaporator approaches the target cooling temperature, that is, when ΔTa is small, the cooling capacity is lowered so that the showcase 2 does not stop, so that the area of the evaporator 9 of the entire apparatus is reduced. Operation that does not decrease can be realized. Therefore, this control makes it possible to obtain a highly reliable refrigeration air conditioner that can increase the operating efficiency and avoid the temperature increase of the showcase 2.
[0085]
In the setting of the superheat degree target value SHm in step 42, it may be set to a predetermined value of about 5 ° C. as in the first embodiment, and as described here, the operation is performed as in the second embodiment. The superheat degree SH may be changed in consideration of the operation efficiency according to the refrigerant state of the refrigeration cycle.
[0086]
Table 2 shows the actual driving situation based on the driving control in this embodiment. This table shows that the superheat degree target value of a fresh showcase 2c for fresh food having a low target cooling temperature Tm is set to 2 ° C., and the showcase 2a for fruits and vegetables that has a high target cooling temperature Tm and does not require much cooling capacity. When the operation is carried out when the superheat degree target value SHm of the daily showcase 2b is set high based on ΔTa so that the showcases 2a and 2b are not stopped (lower side of the table) The operation state when the operation is carried out with the same superheat degree target value SHm in all the showcases 2 (upper side of the table) is shown. As shown in Table 2, by setting the superheat degree target value SHm so that all the showcases 2 are not stopped, it is possible to realize an operation with a high operation efficiency of about 4.5% in terms of time average.
[0087]
[Table 2]

[0088]
In step 45 of FIG. 19, the evaporator outlet superheat target value SHm is set based on the deviation ΔTa between the showcase 2 internal temperature Ta and the target cooling temperature Tm, and the electronic expansion valve 8 is controlled. The opening degree of the electronic expansion valve 8 may be feedback controlled based on ΔTa, and control may be performed so that ΔTa becomes a preset value, for example, 0.5 ° C. Even in this case, when ΔTa is small, the operation can be performed so that the showcase 2 is not stopped, and a refrigerating and air-conditioning apparatus with high operation efficiency can be obtained.
[0089]
【The invention's effect】
As described above, the present invention ,Eye By operating the refrigeration cycle so as to obtain a refrigerant state corresponding to the target cooling temperature, an efficient refrigeration air conditioner can be obtained, and an excessive temperature drop of the cooling target can be avoided, and a highly reliable refrigeration air conditioner can be obtained. can get.
[0090]
Here, although the operation of the target cooling temperature classification means 37 is performed by the measurement control device 17, the measurement control device 16 on the heat source side may be provided with means for performing this operation. The measurement control device 17 only needs to recognize the temperature range to which the evaporator 9 belongs as a result of the classification.
[0091]
Further, as a control method of the refrigerating and air-conditioning apparatus, as shown in steps 42, 43, and 44 of FIG. 19, the flow of each decompression apparatus is adjusted so that the refrigerant state downstream of each evaporator becomes a preset target value. By providing a flow resistance control step for controlling resistance and a target value changing step for individually changing the target value in accordance with a change in the operating state of the refrigeration cycle, a plurality of cooling objects having different cooling temperatures are provided. It is possible to control the refrigeration and air-conditioning apparatus with high operational efficiency.
[0092]
Further, as a control method for the refrigeration air conditioner, when operating a refrigeration cycle in which a plurality of combinations of pressure reducing devices and evaporators connected in parallel are connected to a compressor, target cooling is individually performed for each of the plurality of evaporators. A target temperature setting step for setting a temperature; a temperature range determination step (step 41) for determining that the target cooling temperature is an evaporator in a high temperature range among the plurality of evaporators; Among the evaporators, the difference between the temperature to be cooled and the target cooling temperature is less than the predetermined value, and the cooling capacity is reduced by controlling the flow resistance of the decompression device connected to the upstream side. By providing the flow resistance control step (step 45) to be controlled as described above, a refrigeration air conditioner having a plurality of cooling objects with different cooling temperatures can be controlled with high operating efficiency.
[0093]
In the first to third embodiments, the measurement control devices 16 and 17 are each configured by a microcomputer, for example, and the operation of each means included therein is performed by a software program.
In the first to third embodiments, the case where the load side is mainly a showcase has been described. However, the present invention can also be applied to other refrigeration air conditioners such as an air conditioner. However, this is effective for a refrigerating and air-conditioning apparatus in which a plurality of evaporators are connected in parallel to the compressor, and the target cooling temperatures to be cooled differ by each of the evaporators.
[0094]
In the first to third embodiments, the refrigerant used in the refrigeration air conditioner is not particularly limited, and is an HCFC refrigerant such as R-22, or an HFC refrigerant or mixture such as R-134a or R-404A. The present invention can be applied to refrigerants, natural refrigerants such as ammonia, CO2, and hydrocarbons, and mixed refrigerants thereof. The refrigerator oil can also be applied when various oils such as mineral oil, ester oil, and HAB oil are used.
In the above description, the evaporating temperature when, for example, R-22 is used as the refrigerant and the temperature of the outlet superheat degree of the evaporator 9 have been described. However, when using other refrigerants, Each predetermined value may be set according to the PH diagram.
[0095]
【The invention's effect】
As described above, the present invention provides a refrigeration cycle in which a plurality of evaporators are connected in parallel to a compressor, target temperature setting means for individually setting a target cooling temperature to be cooled for each evaporator, Evaporator operation determining means for determining operation stop for each evaporator according to the temperature to be cooled and the target cooling temperature, and the operation of evaporation based on the individual target cooling temperature of the operated evaporator And a compressor capacity control means for determining and operating the compressor so that the target state of the refrigeration cycle including the compressor is determined and realized, so that the refrigerant according to the target cooling temperature is provided. By operating the refrigeration cycle so as to be in a state, an efficient refrigeration air conditioner can be obtained, and an excessive temperature decrease of the cooling target can be avoided to obtain a highly reliable refrigeration air conditioner.
[Brief description of the drawings]
FIG. 1 is a refrigerant circuit diagram showing a refrigerating and air-conditioning apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a block diagram showing a configuration of a measurement control device 16 according to the first embodiment.
FIG. 3 is a block diagram showing a configuration of a measurement control device 17 according to the first embodiment.
FIG. 4 is a flowchart showing a showcase operation control method according to Embodiment 1;
FIG. 5 is a flowchart illustrating a compressor operation control method according to the first embodiment.
FIG. 6 is an explanatory diagram showing an operating state of the refrigeration air conditioner when the operation control according to the first embodiment is performed.
FIG. 7 is a graph showing the correlation between the degree of superheat and the operation efficiency according to Embodiment 2 of the present invention.
FIG. 8 is a PH diagram showing the state of the refrigeration cycle when the low pressure changes according to the second embodiment.
FIG. 9 is a PH diagram showing the state of the refrigeration cycle when the degree of superheat according to Embodiment 2 changes.
FIG. 10 is a graph showing the correlation between the degree of superheat and operating efficiency when the low pressure changes according to the second embodiment.
FIG. 11 is a block diagram showing a configuration of a measurement control device 17 according to the second embodiment.
FIG. 12 is a graph showing a setting method according to the second embodiment for setting a superheat degree target value with respect to a target evaporation temperature.
FIG. 13 is a graph illustrating a setting method according to the second embodiment in which a superheat degree target value is set with respect to an average value of target cooling temperatures.
FIG. 14 is a PH diagram showing a state of the refrigeration cycle when the high pressure according to the second embodiment changes.
FIG. 15 is a flowchart illustrating an operation control method for an electronic expansion valve according to a second embodiment.
FIG. 16 is a block diagram showing a configuration of a measurement control device 16 according to the second embodiment.
FIG. 17 is a flowchart showing an operation control method in an oil recovery operation mode according to the second embodiment.
FIG. 18 is a block diagram showing a configuration of a measurement control device 17 according to Embodiment 3 of the present invention.
FIG. 19 is a flowchart showing an operation control method for an electronic expansion valve according to a third embodiment.
FIG. 20 is a graph illustrating a setting method for setting a superheat degree target value with respect to a deviation between the showcase internal temperature and the target cooling temperature according to the third embodiment.
[Explanation of symbols]
1 Condensing unit, 2 Showcase, 3 Compressor, 4 Condenser, 5 Receiver, 6 Accumulator, 7 Solenoid valve, 8 Electronic expansion valve, 9 Evaporator, 10, 18 Fan, 11 Liquid pipe, 12 Gas pipe, 13 Refrigerant temperature sensor, 14 Air temperature sensor, 15 Pressure sensor, 16, 17 Measurement control device, 20 Refrigeration cycle, 21 Compressor capacity control means, 23 Oil amount detection means, 31 Target temperature setting means, 32 Evaporator operation determination means, 34 flow resistance control means, 35 target value changing means, 36 target value storage means, 37 target cooling temperature classification means.

Claims (5)

A refrigeration cycle comprising a plurality of evaporators connected in parallel to a compressor, target temperature setting means for individually setting a target cooling temperature to be cooled for each of the evaporators, the temperature to be cooled and the target cooling temperature An evaporator operation determining means for determining operation stop for each of the evaporators, and determining a target suction pressure or a target evaporation temperature of the refrigeration cycle from an individual target cooling temperature of the operated evaporator, Compressor capacity control means for determining an operating capacity of the compressor so that the suction pressure or evaporation temperature of the cycle becomes the target suction pressure or the target evaporation temperature, and the target suction pressure or the target evaporation temperature is , With respect to a preset reference value of the target value, the maximum value of the target cooling temperature of the operating evaporator among the plurality of evaporators and the minimum value of the target cooling temperature of all the plurality of evaporators, By shifting the reference value based on the difference is set as a new target suction pressure or the target evaporation temperature, characterized in that so as to control the capacity of said compressor based on said new target suction pressure or the target evaporation temperature Refrigeration air conditioner. A refrigeration cycle comprising a plurality of evaporators connected in parallel to a compressor, target temperature setting means for individually setting a target cooling temperature to be cooled for each of the evaporators, the temperature to be cooled and the target cooling temperature And an evaporator operation determining means for determining the operation stop for each evaporator, and determining a target suction pressure or a target evaporation temperature of the refrigeration cycle from an individual target cooling temperature of the operating evaporator, Compressor capacity control means for determining an operating capacity of the compressor so that the suction pressure or evaporation temperature of the cycle becomes the target suction pressure or the target evaporation temperature, and the target suction pressure or the target evaporation temperature is , With respect to a preset reference value of the target value, an average value of the target cooling temperatures of the evaporators operating among the plurality of evaporators and an average value of the target cooling temperatures of all the plurality of evaporators Or the average value obtained by weighting the target cooling temperature of the operating evaporator among the plurality of evaporators by the capacity of each cooling target and the target cooling temperature of all the plurality of evaporators The reference value is shifted based on the difference from the average value weighted by the capacity of the compressor and set as a new target suction pressure or target evaporation temperature, and the capacity of the compressor is set based on the new target suction pressure or target evaporation temperature. A refrigerating and air-conditioning apparatus characterized by controlling the above .   The reference value is set based on an operation / stop state of the plurality of evaporators during a predetermined period, or a deviation between a temperature to be cooled by the plurality of evaporators during a predetermined period and a target cooling temperature. The refrigeration air conditioner according to claim 1 or 2. The refrigerating and air-conditioning apparatus according to claim 3, wherein the reference value is reset in a time period longer than a time period in which the reference value is shifted to set a new target suction pressure or target evaporation temperature. . The target evaporating temperature is not shifted or shifted to a low temperature side even if an evaporator having a high target cooling temperature is operated for a certain time after the defrosting is completed. The refrigeration air conditioning apparatus in any one.

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