JP2004116978A

JP2004116978A - Controller for multi-room air conditioner

Info

Publication number: JP2004116978A
Application number: JP2002285170A
Authority: JP
Inventors: Shuntaro Ito; 伊藤　俊太郎; Nobuhiro Kusumoto; 楠本　伸廣; Hin Sai; 蔡　品; Takao Aichi; 愛知　隆夫; Tetsuya Ito; 伊藤　哲也; Chuya Aun; アウン　チュヤ; Takahiro Matsunaga; 松永　隆廣
Original assignee: Fujitsu General Ltd
Current assignee: Fujitsu General Ltd
Priority date: 2002-09-30
Filing date: 2002-09-30
Publication date: 2004-04-15

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly efficient controller for a multi-room air conditioner capable of suppressing an intake gas refrigerant of a compressor in a saturated gas condition by computing a target discharge refrigerant temperature according to a temperature/pressure of each part detected only on the outdoor unit side and a constant of the compressor and controlling an opening of an expansion valve on the basis of the target temperature. <P>SOLUTION: This controller is provided with an intake temperature/pressure sensor 9/9' detecting a temperature/pressure on the intake side of the compressor, a discharge temperature/pressure sensor 10/10' detecting a temperature/pressure on the discharge side of the compressor, an outdoor heat exchange temperature sensor 11 detecting a temperature of an outdoor heat exchanger, a constant setting part 13e storing the constant decided according to characteristics of the compressor found experimentally in advance, a comparison computing part 13f comparing and computing the detected present temperature/pressure on the intake side, the temperature/pressure on the discharge side, the temperature of the outdoor heat exchanger, and the constant for finding the target discharge refrigerant temperature, and a control part 13 controlling an opening of the expansion valve 6 on the basis of the target discharge refrigerant temperature in heating operation. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、室外ユニットと複数台の室内ユニットからなる多室形空気調和機の制御装置に係わり、より詳しくは、圧縮機の吐出ガス温度が目標値になるよう室外側膨脹弁の開度を制御することにより、吸入冷媒を乾き飽和ガス状態にする制御装置に関する。
【０００２】
【従来の技術】
従来より空気調和機の冷凍サイクルにおける圧縮機の吸入冷媒は、乾き飽和ガスの状態にすることが、能力、圧縮機の効率の面で良い。これは、室外ユニットの膨脹弁の開度を調整することで可能である。
一般には、室外および室内ユニットの熱交換器の温度センサ又は圧力センサの検出した温度又は圧力によって膨脹弁の開度が制御されているが、実際には乾き飽和ガスでの制御ではなく、過熱度をある程度の範囲に抑える制御である（例えば、特許文献１参照。）。
【０００３】
しかしながら、上記従来例の場合、過熱度が大きくなると効率が低下してしまう。また、室外および室内ユニットの熱交換器の温度又は圧力を検出して膨脹弁の開度の制御を行う場合、この制御方法を多室形空気調和機の制御に用いると、室内ユニットが多い場合、室外と室内ユニット間の通信が込み合い応答性が悪くなり、また各室内ユニットの熱交換器の温度又は圧力が一定とならない。
更に、室外と室内ユニット間の接続配管が長い場合には、配管の圧力損力があるため、実際の吸入ガスの過熱度制御が難しく、室外ユニットの検出信号のみにより制御することが望まれる。
【０００４】
【特許文献１】
特開２００１−２５５０２４号公報（第６−９頁、第１−２図）。
【０００５】
【発明が解決しようとする課題】
本発明においては、上記の問題点に鑑み、暖房運転時に、室外ユニット側のみで検出した各部の温度又は圧力と、圧縮機のポリトロープ指数により、目標吐出冷媒温度を算出し、この目標吐出冷媒温度に基づいて膨脹弁の開度を制御することにより、圧縮機の吸入ガス冷媒が飽和ガス状態に制御でき、高効率な冷凍サイクルによる多室形空気調和機の制御装置を提供することを目的とする。
【０００６】
【課題を解決するための手段】
本発明は上記課題を解決するため、少なくとも１台の圧縮機と、四方弁と、室外熱交換器と、膨脹弁からなる室外ユニットと、室内熱交換器と絞り機構を備えた複数の室内ユニットとを接続して冷媒回路を構成してなる多室形空気調和機であって、
前記圧縮機の吸入側の温度または圧力を検出する吸入温度センサまたは吸入圧力センサと、前記圧縮機の吐出側の温度または圧力を検出する吐出温度センサまたは吐出圧力センサと、前記室外熱交換器の温度を検出する室外熱交温度センサと、予め実験的に求めた前記圧縮機の特性により決まる定数を記憶する定数設定部と、現在の検出した前記吸入側の温度または圧力、吐出側の温度または圧力および前記室外熱交換器の温度と前記定数とを比較演算し目標吐出冷媒温度を算出する比較演算部と、暖房運転時に前記目標吐出冷媒温度に基づいて前記膨脹弁の開度を制御する制御部とを備えてなる構成となっている。
【０００７】
また、前記圧縮機が、１台のインバータ圧縮機、又は並列に接続された複数のインバータ圧縮機と複数の一定速型圧縮機、又は並列に接続された複数の一定速型圧縮機からなる構成となっている。
【０００８】
また、前記複数の一定速型圧縮機は、夫々能力が異なる構成となっている。
【０００９】
また、前記定数がポリトロープ指数である構成となっている。
【００１０】
また、前記定数を外気温別に実験的に求めてなる構成となっている。
【００１１】
【発明の実施の形態】
以下、本発明の実施の形態を、添付図面に基づいた実施例として説明する。
図１は本発明による多室形空気調和機の冷媒回路の構成図である。図において、１は室外に設置された室外ユニット、２ａ，２ｂ，２ｃは夫々並列に接続された３台の室内ユニットである。
【００１２】
前記室外ユニット１は、少なくとも１台の圧縮機３と、四方弁４と、室外熱交換器５と、膨張弁６とをそれぞれ接続して構成され、また前記室内ユニット２ａ，２ｂ，２ｃは、夫々電子膨張弁からなる絞り機構７ａ，７ｂ，７ｃと、室内熱交換器８ａ，８ｂ，８ｃとを夫々接続して構成されている。
【００１３】
これら前記室外ユニット１と前記室内ユニット２ａ，２ｂ，２ｃとが第一接続部Ａ１と第二接続部Ａ２を介して冷媒配管により接続され冷媒回路が構成されている。
【００１４】
前記圧縮機３の吸入側には吸入冷媒の温度を検出する吸入温度センサ９、又は吸入冷媒の圧力（低圧）を検出する吸入圧力センサ９’が設けられている。また、前記圧縮機３の吐出側には吐出冷媒の温度を検出する吐出温度センサ１０及び又は吐出冷媒の圧力を検出する吐出圧力センサ１０’　が設けられ、前記室外熱交換器５には室外熱交換器５の中間の温度を検出する室外熱交温度センサ１１が設けられている。
【００１５】
上記において、冷房運転時には、図１中実線矢印で示すように、圧縮機３で高温高圧となったガス冷媒が、室外熱交換器５に送られ、室外空気との間の熱交換によりガス冷媒が冷却され凝縮し、高温高圧の液冷媒となる。この高温高圧の液冷媒は、膨張弁６において減圧されて低温低圧の液冷媒となる。この低温低圧の液冷媒は、室内熱交換ユニット２ａ，２ｂ，２ｃに送られ、室内空気との間の熱交換により室内空気を冷却するとともに、自身は加温され蒸発して低温低圧のガス冷媒となる。この際、室内熱交換器８ａ，８ｂ，８ｃは液冷媒を蒸発させる蒸発器として機能する。この低温低圧のガス冷媒は、四方弁４を経て圧縮機３に戻されて高温高圧のガス冷媒となり、以後この過程が繰り返される。
【００１６】
また暖房運転時においては、破線矢印で示すように、圧縮機３を経た冷媒が室内熱交換ユニット２ａ，２ｂ，２ｃに流れるように四方弁４を設定する。暖房運転時には、圧縮機３で高温高圧となったガス冷媒が、室内熱交換ユニット２ａ，２ｂ，２ｃに送られ、室内空気との間の熱交換により室内空気を加温するとともに、自身は冷却され凝縮して高温高圧の液冷媒となる。この際、室内熱交換器８ａ，８ｂ，８ｃはガス冷媒を凝縮させる凝縮器として機能する。この高温高圧の液冷媒は、膨張弁６において減圧されて低温低圧の液冷媒となる。この低温低圧の液冷媒は室外熱交換器５に送られ、室外空気との間の熱交換により加温され蒸発し、低温低圧のガス冷媒となる。この際、室外熱交換器５は液冷媒を蒸発させる蒸発器として機能する。この低温低圧のガス冷媒は、四方弁４を経て圧縮機３に戻されて高温高圧のガス冷媒となり、以後この過程が繰り返される。
【００１７】
図２は空気調和機の運転過程における冷媒の熱力学的変化を示すモリエル線図である。以下、この図について説明する。
（１）圧縮機３において、ガス冷媒が圧縮される過程では、圧力もエンタルピも増加するため冷媒の状態は図中右上がりに変化する（ａ点からｂ点）。以下、この過程を圧縮過程という。
（２）室内熱交換ユニット２ａ，２ｂ，２ｃまたは室外熱交換ユニット１において、ガス冷媒が冷却され液冷媒となる過程では、圧力（Ｐ２）が変化せずにエンタルピが減少するため、冷媒の状態は図中左方向に変化し、飽和蒸気線Ｇに達した時点で凝縮が始まり、飽和液線Ｌに達した時点で冷媒は完全に液化し、更に若干の過冷却度をもつように冷却される（ｂ点からｃ点）。以下、この過程を凝縮過程という。
（３）膨張弁６において液冷媒が低温低圧となる過程では、熱の出入りがないためエンタルピが変化せずに圧力が低下することから、冷媒の状態は図中下方に変化する（ｃ点からｄ点）。以下、この過程を減圧過程という。
（４）室内熱交換ユニット２ａ，２ｂ，２ｃまたは室外熱交換ユニット１において、液冷媒が加温されガス冷媒となる過程では、圧力（Ｐ１）が変化せずにエンタルピが増加するため、冷媒の状態は図中右方向に変化し、飽和蒸気線Ｇに達した時点（ａ点）で完全に蒸発する。以下、この過程を蒸発過程という。
【００１８】
図２において、Ｔ１は前記吸入温度センサ９で検出された吸入冷媒温度で、Ｔ５は前記室外熱交温度センサ１１で検出された室外熱交換器５の中間温度であり、Ｔ１、Ｔ５は飽和温度なので予め設定されている冷媒物性の関係より、低圧の吸入圧力Ｐ１及び高圧の吐出圧力Ｐ２を求めることができる。また、Ｔ２は前記吐出温度センサ１０で直接検出する。
尚、前記圧力Ｐ１，Ｐ２　は前記吸入圧力センサ９’及び吐出圧力センサ１０’　で直接検出し、前記吸入冷媒温度Ｔ１は、前記圧力Ｐ１から冷媒物性の関係より求めてもよい。
【００１９】
上記冷凍サイクルにおいて、前記圧縮機３の圧縮効率は、圧縮機に固有定数（ポリトロープ指数ｎ）によって表わされる。ポリトロープ指数ｎは、圧縮機３の吸入側と吐出側の冷媒の状態から求められる値で、冷媒が圧縮されるときの圧力と比体積の関係を示す。このポリトロープ指数ｎは、冷凍サイクルを構成している圧縮機に固有の値であり、この値によって圧縮過程のカーブ（図では近似的に直線としている）が決定される。
図２をポリトロープ指数ｎを用いて表わすと、次の（１）式の関係となる。
【数１】

【００２０】
本発明においては、このポリトロープ指数ｎを外気温Ｔ０別に実験的に求めることで、低圧の吸入圧力Ｐ１及び高圧の吐出圧力Ｐ２から、目標とする吐出冷媒温度Ｔ２を算出する。
例えば、次のようにｎを予め設定する。
外気温Ｔ０が、Ｔ０＜−１０℃の場合、ｎ＝１．３
外気温Ｔ０が、２℃≦Ｔ０≦１０℃の場合、ｎ＝１．２
外気温Ｔ０が、２０℃＜Ｔ０の場合、ｎ＝１．１
【００２１】
図３は運転条件が変わった場合のモリエル線図を示したものである。前記ポリトロープ指数ｎは運転条件によって異なり、ｎが異なると図３に示すように圧縮過程がａ’点からｂ’点、或いはｅ’点からｆ’点へと傾斜が異なってくる。
現在の吐出圧力Ｐ２’　、吸入圧力Ｐ１’　又はＰ３’　を検出し、吸入冷媒温度Ｔ１’　又はＴ３’　を冷媒物性の関係より求めることにより、目標吐出冷媒温度Ｔ２’　又はＴ４’　は前記（１）式の関係から夫々次の式で算出（演算）することができる。
【数２】

【数３】

【００２２】
次に上記構成において、本発明の制御動作について、図４の制御ブロック図及び図５のフローチャート図に基づいて説明する。
制御部１３は、前記圧縮機３の吸入側の吸入温度センサ９、又は吸入圧力センサ９’が検出した温度又は圧力を検知する吸入温度・吸入圧力検出部１３ａ　と、吐出側の吐出温度センサ１０及び又は吐出圧力センサ１０’　が検出した温度又は圧力を検知する吸入温度・吸入圧力検出部１３ｂ　と、室外熱交温度センサ１１が検出した温度を検知する室外熱交温度検出部１３ｃ　と、外気温センサ１２が検出した温度を検知する外気温検出部１３ｄ　と、外気温別に予め実験的に求めた前記圧縮機３の特性により決まる定数（ポリトロープ指数ｎ）を記憶する定数設定部１３ｅ　と、現在の検出した吸入側の温度または圧力、吐出側の温度または圧力、および前記室外熱交換器５の温度と前記定数とを比較演算し目標吐出ガス温度を算出する比較演算部１３ｆ　と、暖房運転時に前記目標吐出ガス温度に基づいた制御信号により前記膨脹弁６の開度を制御す弁開度制御部１３ｇ　とから構成することにより、室外ユニットの検出信号のみで制御することができ、従来例のように、室外と室内ユニット間の通信が込み合いによる応答性の悪化や、接続配管の長さによる圧力損力にも関係しない制御ができる。
【００２３】
図５のフローチャート図において、多室形空気調和機の運転がスタートすると、まず、ステップＳＴ１で暖房運転かどうか判定される。もし暖房運転であれば、ステップＳＴ２で図３の実施例にしたがって、吸入圧力Ｐ１’，Ｐ３’　及び吸入温度Ｔ１’，Ｔ３’　を検出、又は冷媒物性の関係より算出すると同時に、吐出圧力Ｐ２’　を検出する。
【００２４】
次に、ステップＳＴ３で外気温センサ１２が検出した外気温Ｔ０が、−１０℃以下かどうか判断され、以下であればステップＳＴ４でポリトロープ指数ｎを１．３　に設定し、ステップＳＴ９で目標吐出冷媒温度Ｔ２’，Ｔ４’　等が演算され、ステップＳＴ１０で膨脹弁６が目標吐出冷媒温度に合った目標弁開度に制御され終了する（ＳＴ１１）。
もし、ステップＳＴ３で外気温Ｔ０が、−１０℃以下でなければ、ステップＳＴ５で外気温Ｔ０が、２℃≦Ｔ０≦１０℃の範囲内かどうか判定される。もし、範囲内であれば、上記と同様ステップＳＴ９〜ＳＴ１０の作業が行われステップＳＴ１１で終了する。
もし、ステップＳＴ５で外気温Ｔ０が範囲内でなければ、ステップＳＴ７で外気温Ｔ０が２０℃以上かどうか判定される。もし、以上であれば、上記と同様ステップＳＴ９〜ＳＴ１０の作業が行われステップＳＴ１１で終了する。
【００２５】
以上に説明したように、現在の検出した吸入側の温度または圧力、吐出側の温度または圧力および前記室外熱交換器５の温度と、予め実験的に求めた前記圧縮機３の特性により決まる定数（ポリトロープ指数ｎ）とを比較演算し、目標吐出冷媒温度を算出し、暖房運転時に目標吐出冷媒温度に基づいて前記膨脹弁６の開度を制御することにより、室外ユニットの検出信号のみで制御ができ、圧縮機３の吸入ガス冷媒が飽和ガス状態に制御できるため、従来例のように、室外と室内ユニット間の通信が込み合い応答性が悪くなることがなく、また室外と室内ユニット間の接続配管が長い場合でも、配管の圧力損力に関係しない、高効率な冷凍サイクルによる多室形空気調和機の制御装置となる。
【００２６】
【発明の効果】
以上説明したように本発明によれば、暖房運転時に、室外ユニット側のみで検出した各部の温度又は圧力と、圧縮機のポリトロープ指数により、目標吐出冷媒温度を算出し、この目標吐出冷媒温度に基づいて膨脹弁の開度を制御することにより、圧縮機の吸入ガス冷媒が飽和ガス状態に制御でき、高効率な冷凍サイクルによる多室形空気調和機の制御装置となる。
【図面の簡単な説明】
【図１】本発明における多室形空気調和機の実施例を示す冷媒回路図である。
【図２】本発明における圧縮機の定数を求める説明のためのモリエル線図である。
【図３】本発明における一実施例を説明のためのモリエル線図である。
【図４】本発明における制御ブロック図である。
【図５】本発明におけるフローチャート図である。
【符号の説明】
１　室外ユニット
２ａ，２ｂ，２ｃ　室内ユニット
３圧縮機
４　四方弁
５　室外熱交換器
６　膨張弁
７ａ，７ｂ，７ｃ　絞り機構（電子膨張弁）
８ａ，８ｂ，８ｃ　室内熱交換器
９　吸入温度センサ
９’　吸入圧力センサ
１０　吐出温度センサ
１０’　吐出圧力センサ
１１　室外熱交温度センサ
１２　外気温センサ
１３　制御部
１３ａ　吸入温度・吸入圧力検出部
１３ｂ　吐出温度・吐出圧力検出部
１３ｃ　室外熱交温度検出部
１３ｄ　外気温検出部
１３ｅ　定数設定部
１３ｆ　比較演算部
１３ｇ　弁開度制御部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device for a multi-room air conditioner comprising an outdoor unit and a plurality of indoor units, and more particularly, to an opening degree of an outdoor expansion valve so that a discharge gas temperature of a compressor becomes a target value. The present invention relates to a control device for controlling a suction refrigerant to be in a dry saturated gas state by controlling the same.
[0002]
[Prior art]
Conventionally, the intake refrigerant of a compressor in a refrigeration cycle of an air conditioner is preferably in a state of a dry saturated gas in terms of capacity and efficiency of the compressor. This can be achieved by adjusting the opening of the expansion valve of the outdoor unit.
In general, the opening degree of the expansion valve is controlled by the temperature or pressure detected by the temperature sensor or pressure sensor of the heat exchanger of the outdoor and indoor units. Is controlled to be within a certain range (for example, see Patent Document 1).
[0003]
However, in the case of the above-mentioned conventional example, the efficiency decreases as the degree of superheat increases. Further, when controlling the degree of opening of the expansion valve by detecting the temperature or pressure of the heat exchangers of the outdoor and indoor units, if this control method is used to control a multi-room air conditioner, there are many indoor units. In addition, communication between the outdoor unit and the indoor unit becomes crowded, the response is deteriorated, and the temperature or pressure of the heat exchanger of each indoor unit is not constant.
Further, when the connection pipe between the outdoor unit and the indoor unit is long, there is a pressure loss in the pipe, so that it is difficult to actually control the degree of superheat of the suction gas, and it is desired that the control be performed only by the detection signal of the outdoor unit.
[0004]
[Patent Document 1]
JP-A-2001-255024 (page 6-9, FIG. 1-2).
[0005]
[Problems to be solved by the invention]
In the present invention, in view of the above problems, during the heating operation, the target discharge refrigerant temperature is calculated by the temperature or pressure of each part detected only on the outdoor unit side and the polytropic index of the compressor, and the target discharge refrigerant temperature is calculated. By controlling the opening degree of the expansion valve on the basis of the above, the suction gas refrigerant of the compressor can be controlled to a saturated gas state, and an object of the present invention is to provide a control device of a multi-room air conditioner with a high efficiency refrigeration cycle. I do.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides an outdoor unit including at least one compressor, a four-way valve, an outdoor heat exchanger, an expansion valve, and a plurality of indoor units including an indoor heat exchanger and a throttle mechanism. And a multi-chamber air conditioner configured as a refrigerant circuit by connecting
A suction temperature sensor or a suction pressure sensor for detecting a temperature or a pressure on a suction side of the compressor; a discharge temperature sensor or a discharge pressure sensor for detecting a temperature or pressure on a discharge side of the compressor; and an outdoor heat exchanger. An outdoor heat exchange temperature sensor for detecting a temperature, a constant setting unit for storing a constant determined by the characteristics of the compressor obtained experimentally in advance, and a current detected temperature or pressure on the suction side, a temperature on the discharge side or A comparison operation unit for comparing a pressure and the temperature of the outdoor heat exchanger with the constant to calculate a target discharge refrigerant temperature, and a control for controlling an opening degree of the expansion valve based on the target discharge refrigerant temperature during a heating operation. And a unit.
[0007]
Further, the compressor is constituted by one inverter compressor, or a plurality of inverter compressors and a plurality of constant speed compressors connected in parallel, or a plurality of constant speed compressors connected in parallel. It has become.
[0008]
Further, the plurality of constant speed compressors are configured to have different capacities.
[0009]
Further, the constant is a polytropic index.
[0010]
Further, the constant is experimentally obtained for each outside temperature.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described as examples based on the accompanying drawings.
FIG. 1 is a configuration diagram of a refrigerant circuit of a multi-room air conditioner according to the present invention. In the figure, 1 is an outdoor unit installed outdoors, and 2a, 2b, and 2c are three indoor units connected in parallel, respectively.
[0012]
The outdoor unit 1 is configured by connecting at least one compressor 3, a four-way valve 4, an outdoor heat exchanger 5, and an expansion valve 6, respectively, and the

indoor units

2a, 2b, 2c The

throttle mechanisms

7a, 7b, 7c each comprising an electronic expansion valve are connected to the

indoor heat exchangers

8a, 8b, 8c, respectively.
[0013]
The outdoor unit 1 and the

indoor units

2a, 2b, 2c are connected by a refrigerant pipe via a first connection part A1 and a second connection part A2 to form a refrigerant circuit.
[0014]
On the suction side of the compressor 3, a suction temperature sensor 9 for detecting the temperature of the suction refrigerant or a suction pressure sensor 9 'for detecting the pressure (low pressure) of the suction refrigerant is provided. A discharge temperature sensor 10 for detecting the temperature of the discharged refrigerant and / or a discharge pressure sensor 10 'for detecting the pressure of the discharged refrigerant are provided on the discharge side of the compressor 3, and the outdoor heat exchanger 5 has an outdoor heat exchanger. An outdoor heat exchange temperature sensor 11 for detecting an intermediate temperature of the exchanger 5 is provided.
[0015]
In the above, at the time of the cooling operation, as shown by a solid line arrow in FIG. 1, the gas refrigerant which has become high temperature and high pressure in the compressor 3 is sent to the outdoor heat exchanger 5, and the gas refrigerant is exchanged with outdoor air by heat exchange. Is cooled and condensed to become a high-temperature and high-pressure liquid refrigerant. The high-temperature and high-pressure liquid refrigerant is reduced in pressure in the expansion valve 6 to become a low-temperature and low-pressure liquid refrigerant. The low-temperature and low-pressure liquid refrigerant is sent to the indoor

heat exchange units

2a, 2b and 2c, and cools the indoor air by exchanging heat with the indoor air. It becomes. At this time, the

indoor heat exchangers

8a, 8b, 8c function as evaporators for evaporating the liquid refrigerant. The low-temperature and low-pressure gas refrigerant is returned to the compressor 3 via the four-way valve 4 to become a high-temperature and high-pressure gas refrigerant, and this process is repeated thereafter.
[0016]
During the heating operation, the four-way valve 4 is set so that the refrigerant that has passed through the compressor 3 flows to the indoor

heat exchange units

2a, 2b, and 2c, as indicated by the dashed arrows. During the heating operation, the gas refrigerant, which has become high temperature and high pressure in the compressor 3, is sent to the indoor

heat exchange units

2a, 2b, 2c to heat the indoor air by heat exchange with the indoor air and to cool itself. Is condensed and becomes a high-temperature and high-pressure liquid refrigerant. At this time, the

indoor heat exchangers

8a, 8b, 8c function as condensers for condensing the gas refrigerant. The high-temperature and high-pressure liquid refrigerant is reduced in pressure in the expansion valve 6 to become a low-temperature and low-pressure liquid refrigerant. The low-temperature and low-pressure liquid refrigerant is sent to the outdoor heat exchanger 5, where the liquid refrigerant is heated and evaporated by heat exchange with outdoor air to be a low-temperature and low-pressure gas refrigerant. At this time, the outdoor heat exchanger 5 functions as an evaporator for evaporating the liquid refrigerant. The low-temperature and low-pressure gas refrigerant is returned to the compressor 3 via the four-way valve 4 to become a high-temperature and high-pressure gas refrigerant, and this process is repeated thereafter.
[0017]
FIG. 2 is a Mollier diagram showing the thermodynamic change of the refrigerant in the operation process of the air conditioner. Hereinafter, this figure will be described.
(1) In the process of compressing the gas refrigerant in the compressor 3, the pressure and the enthalpy both increase, so that the state of the refrigerant changes to the upper right in the figure (from point a to point b). Hereinafter, this process is called a compression process.
(2) In the indoor

heat exchange units

2a, 2b, 2c or the outdoor heat exchange unit 1, in the process in which the gas refrigerant is cooled and turned into the liquid refrigerant, the pressure (P2) does not change and the enthalpy decreases, so the state of the refrigerant Changes to the left in the figure, when the saturated vapor line G is reached, condensation starts, and when the saturated liquid line L is reached, the refrigerant completely liquefies and is further cooled to have a slight degree of supercooling. (Point b to point c). Hereinafter, this process is referred to as a condensation process.
(3) In the process in which the liquid refrigerant becomes low-temperature and low-pressure in the expansion valve 6, since the heat does not flow in and out, the enthalpy does not change and the pressure drops, so that the state of the refrigerant changes downward in the figure (from point c). d point). Hereinafter, this process is referred to as a decompression process.
(4) In the indoor

heat exchange units

2a, 2b, 2c or the outdoor heat exchange unit 1, in the process in which the liquid refrigerant is heated and turned into a gas refrigerant, the pressure (P1) does not change and the enthalpy increases. The state changes to the right in the figure, and when the saturated vapor line G is reached (point a), the vaporization is completed. Hereinafter, this process is called an evaporation process.
[0018]
In FIG. 2, T1 is the suction refrigerant temperature detected by the suction temperature sensor 9, T5 is the intermediate temperature of the outdoor heat exchanger 5 detected by the outdoor heat exchange temperature sensor 11, and T1 and T5 are the saturation temperatures. Therefore, the low-pressure suction pressure P1 and the high-pressure discharge pressure P2 can be obtained from the relationship between the predetermined refrigerant properties. Further, T2 is directly detected by the discharge temperature sensor 10.
The pressures P1 and P2 may be directly detected by the suction pressure sensor 9 'and the discharge pressure sensor 10', and the suction refrigerant temperature T1 may be obtained from the pressure P1 based on the relationship between refrigerant physical properties.
[0019]
In the refrigeration cycle, the compression efficiency of the compressor 3 is represented by a constant (polytropic index n) unique to the compressor. The polytropic index n is a value obtained from the state of the refrigerant on the suction side and the discharge side of the compressor 3, and indicates the relationship between the pressure and the specific volume when the refrigerant is compressed. The polytropic index n is a value specific to the compressor constituting the refrigeration cycle, and the curve of the compression process (approximately a straight line in the figure) is determined by this value.
When FIG. 2 is represented by using the polytropic index n, the following equation (1) is obtained.
(Equation 1)

[0020]
In the present invention, a target discharge refrigerant temperature T2 is calculated from the low-pressure suction pressure P1 and the high-pressure discharge pressure P2 by experimentally obtaining the polytropic index n for each outside temperature T0.
For example, n is set in advance as follows.
When the outside air temperature T0 is T0 <−10 ° C., n = 1.3.
When the outside temperature T0 is 2 ° C. ≦ T0 ≦ 10 ° C., n = 1.2
When the outside temperature T0 is 20 ° C. <T0, n = 1.1
[0021]
FIG. 3 shows a Mollier diagram when the operating conditions are changed. The polytropic index n differs depending on the operating conditions. If n is different, the slope of the compression process changes from point a 'to point b' or from point e 'to point f' as shown in FIG.
By detecting the current discharge pressure P2 ', suction pressure P1' or P3 'and obtaining the suction refrigerant temperature T1' or T3 'from the relationship of the refrigerant physical properties, the target discharge refrigerant temperature T2' or T4 'can be calculated by the above (1). From the relations of the equations, they can be calculated (calculated) by the following equations.
(Equation 2)

[Equation 3]

[0022]
Next, in the above configuration, the control operation of the present invention will be described based on the control block diagram of FIG. 4 and the flowchart of FIG.
The control unit 13 includes a suction temperature / suction pressure detection unit 13a for detecting the temperature or pressure detected by the suction temperature sensor 9 or the suction pressure sensor 9 'on the suction side of the compressor 3, and a discharge temperature sensor 10 on the discharge side. A suction temperature / suction pressure detection unit 13b for detecting a temperature or pressure detected by the discharge pressure sensor 10 '; an outdoor heat exchange temperature detection unit 13c for detecting a temperature detected by the outdoor heat exchange temperature sensor 11; An outside air temperature detecting unit 13d for detecting the temperature detected by the sensor 12, a constant setting unit 13e for storing a constant (polytropic index n) determined by the characteristics of the compressor 3 experimentally obtained in advance for each outside air temperature, A comparison operation unit for comparing the detected suction-side temperature or pressure, the discharge-side temperature or pressure, and the temperature of the outdoor heat exchanger 5 with the constant, and calculating a target discharge gas temperature. 3f and a valve opening controller 13g for controlling the opening of the expansion valve 6 by a control signal based on the target discharge gas temperature during the heating operation, so that the control is performed only by the detection signal of the outdoor unit. As in the conventional example, it is possible to perform control irrespective of deterioration of responsiveness due to crowded communication between the outdoor unit and the indoor unit and pressure loss due to the length of the connection pipe.
[0023]
In the flowchart of FIG. 5, when the operation of the multi-room air conditioner starts, first, in step ST1, it is determined whether or not the heating operation is performed. If the heating operation is performed, the suction pressures P1 'and P3' and the suction temperatures T1 'and T3' are detected or calculated from the relationship between the refrigerant physical properties and the discharge pressure P2 'in step ST2 according to the embodiment of FIG. Is detected.
[0024]
Next, in step ST3, it is determined whether or not the outside air temperature T0 detected by the outside air temperature sensor 12 is equal to or lower than -10 ° C. If not, the polytropic index n is set to 1.3 in step ST4, and the target discharge is performed in step ST9. Refrigerant temperatures T2 ', T4', etc. are calculated, and the expansion valve 6 is controlled to the target valve opening degree corresponding to the target discharge refrigerant temperature in step ST10, and the process ends (ST11).
If the outside air temperature T0 is not lower than −10 ° C. in step ST3, it is determined in step ST5 whether the outside air temperature T0 is within the range of 2 ° C. ≦ T0 ≦ 10 ° C. If it is within the range, the operations of steps ST9 to ST10 are performed as described above, and the process ends in step ST11.
If the outside temperature T0 is not within the range in step ST5, it is determined in step ST7 whether the outside temperature T0 is equal to or higher than 20 ° C. If so, the operations of steps ST9 to ST10 are performed in the same manner as described above, and the process ends in step ST11.
[0025]
As described above, the currently detected temperature or pressure on the suction side, the temperature or pressure on the discharge side, the temperature of the outdoor heat exchanger 5, and the constant determined by the characteristics of the compressor 3 experimentally obtained in advance. (Polytropic index n) to calculate the target discharge refrigerant temperature, and control the opening of the expansion valve 6 based on the target discharge refrigerant temperature during the heating operation, thereby controlling only the detection signal of the outdoor unit. Since the suction gas refrigerant of the compressor 3 can be controlled to a saturated gas state, communication between the outdoor unit and the indoor unit is not crowded as in the conventional example, and the responsiveness is not deteriorated. Even if the connecting pipe is long, the control device of the multi-room air conditioner with a high-efficiency refrigeration cycle is not related to the pressure loss of the pipe.
[0026]
【The invention's effect】
As described above, according to the present invention, during the heating operation, the target discharge refrigerant temperature is calculated by the temperature or pressure of each unit detected only on the outdoor unit side and the polytropic index of the compressor, and the target discharge refrigerant temperature By controlling the degree of opening of the expansion valve based on this, the suction gas refrigerant of the compressor can be controlled to be in a saturated gas state, and a multi-room air conditioner control device with a highly efficient refrigeration cycle can be obtained.
[Brief description of the drawings]
FIG. 1 is a refrigerant circuit diagram illustrating an embodiment of a multi-room air conditioner according to the present invention.
FIG. 2 is a Mollier diagram for explaining a constant of a compressor in the present invention.
FIG. 3 is a Mollier diagram for explaining one embodiment of the present invention.
FIG. 4 is a control block diagram according to the present invention.
FIG. 5 is a flowchart in the present invention.
[Explanation of symbols]
Reference Signs List 1

outdoor units

2a, 2b, 2c indoor unit 3 compressor 4 four-way valve 5 outdoor heat exchanger 6

expansion valves

7a, 7b, 7c throttle mechanism (electronic expansion valve)
8a, 8b, 8c Indoor heat exchanger 9 Suction temperature sensor 9 'Suction pressure sensor 10 Discharge temperature sensor 10' Discharge pressure sensor 11 Outdoor heat exchange temperature sensor 12 Outside air temperature sensor 13 Control unit 13a Suction temperature / suction pressure detection unit 13b Discharge Temperature / discharge pressure detection unit 13c Outdoor heat exchange temperature detection unit 13d Outside air temperature detection unit 13e Constant setting unit 13f Comparison calculation unit 13g Valve opening control unit

Claims

A refrigerant circuit is formed by connecting at least one compressor, a four-way valve, an outdoor heat exchanger, an outdoor unit including an expansion valve, and an indoor heat exchanger and a plurality of indoor units including a throttle mechanism. A multi-room air conditioner,
A suction temperature sensor or a suction pressure sensor for detecting a temperature or a pressure on a suction side of the compressor; a discharge temperature sensor or a discharge pressure sensor for detecting a temperature or pressure on a discharge side of the compressor; and an outdoor heat exchanger. An outdoor heat exchange temperature sensor for detecting a temperature, a constant setting unit for storing a constant determined by the characteristics of the compressor obtained experimentally in advance, and a current detected temperature or pressure on the suction side, a temperature on the discharge side or A comparison operation unit for comparing a pressure and the temperature of the outdoor heat exchanger with the constant to calculate a target discharge refrigerant temperature, and a control for controlling an opening degree of the expansion valve based on the target discharge refrigerant temperature during a heating operation. A control device for a multi-room air conditioner, comprising:

The compressor comprises one inverter compressor, or a plurality of inverter compressors and a plurality of constant speed compressors connected in parallel, or a plurality of constant speed compressors connected in parallel. The control device for a multi-room air conditioner according to claim 1, wherein

The control device for a multi-room air conditioner according to claim 1, wherein the plurality of constant speed compressors have different capacities.

The control device for a multi-room air conditioner according to claim 1, wherein the constant is a polytropic index.

The control device for a multi-room air conditioner according to claim 1, wherein the constant is obtained experimentally for each outside temperature.