JP5526267B2 - air compressor - Google Patents

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JP5526267B2
JP5526267B2 JP2013151259A JP2013151259A JP5526267B2 JP 5526267 B2 JP5526267 B2 JP 5526267B2 JP 2013151259 A JP2013151259 A JP 2013151259A JP 2013151259 A JP2013151259 A JP 2013151259A JP 5526267 B2 JP5526267 B2 JP 5526267B2
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pressure stage
air
low
stage compressor
compressor body
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JP2013241942A (en
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仁 西村
広志 太田
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Hitachi Industrial Equipment Systems Co Ltd
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本発明は空気圧縮機に係り、特に、低圧段圧縮機本体と高圧段圧縮機本体を有する回転速度可変形の空気圧縮機に好適なものである。   The present invention relates to an air compressor, and is particularly suitable for an air compressor of a variable rotational speed type having a low pressure stage compressor body and a high pressure stage compressor body.

従来の回転速度可変形スクリュー圧縮機は、例えば特許文献1に記載のように、低圧段スクリュー圧縮部と高圧段スクリュー圧縮部とを直列に連結し、この2つの圧縮部間にクーラを接続していた。そして、低圧段スクリュー圧縮部と高圧段スクリュー圧縮部にそれぞれモータを連結し、このモータをインバータで可変速駆動していた。このように構成した回転速度可変形スクリュー圧縮機では、低流量になると低圧段スクリュー圧縮部と高圧段スクリュー圧縮部とも低回転になり、内部漏れ量を無視できなくなるので、出口配管に放風弁を接続し、低圧段スクリュー圧縮部と高圧段スクリュー圧縮部を最低回転で運転しながら、放風制御していた。   In a conventional rotary speed variable screw compressor, for example, as described in Patent Document 1, a low-pressure stage screw compressor and a high-pressure stage screw compressor are connected in series, and a cooler is connected between the two compressors. It was. A motor is connected to each of the low-pressure stage screw compression section and the high-pressure stage screw compression section, and this motor is driven at a variable speed by an inverter. In the variable speed screw compressor constructed as described above, when the flow rate is low, both the low pressure stage screw compression part and the high pressure stage screw compression part become low rotation, and the amount of internal leakage cannot be ignored. The low pressure stage screw compression section and the high pressure stage screw compression section were operated at the minimum rotation to control the air discharge.

特開平10-82391号公報JP-A-10-82391

低圧段と高圧段の2段の圧縮機を有するオイルフリースクリュー圧縮機では、単段オイルフリースクリュー圧縮機よりも無負荷時の消費動力が全負荷時に比べて小さい。そのため、上記公報に記載の方法を無負荷運転時に適用しても、吸込み絞り弁を絞る従来の方法よりも消費動力がそれほど低下しない不具合があった。   In an oil-free screw compressor having a two-stage compressor of a low-pressure stage and a high-pressure stage, the power consumption at no load is smaller than that at full load as compared with a single-stage oil-free screw compressor. Therefore, even if the method described in the above publication is applied during no-load operation, there is a problem that the power consumption does not decrease much as compared with the conventional method in which the suction throttle valve is throttled.

本発明は上記従来の技術の不具合に鑑みなされたものであり、その目的は低圧段圧縮機と高圧段圧縮機とを有する空気圧縮機において、無負荷時と低負荷時の消費動力を軽減することにある。   The present invention has been made in view of the above-mentioned problems of the prior art, and an object thereof is to reduce power consumption during no load and low load in an air compressor having a low pressure stage compressor and a high pressure stage compressor. There is.

上記目的を達成する本発明の第1の特徴は、低圧段圧縮機本体と高圧段圧縮機本体の回転速度とを変化させて利用側の消費空気量に応じた運転を行う回転速度可変形の空気圧縮機において、前記低圧段圧縮機本体を回転駆動するための電動機と、前記電動機の回転速度を変化させるためのインバータと、前記高圧段圧縮機本体の吐出側に設けられた第1放気手段(高圧段パージ)と、前記インバータと前記第1放気手段を制御するための制御手段とを備え、前記制御手段が、消費空気量が最大空気量から予め定めた設定空気量の範囲では、前記低圧段圧縮機本体及び高圧段圧縮機本体の回転速度を変化させる負荷運転を行わせ、前記消費空気量がゼロの無負荷運転では低圧段圧縮機本体と高圧段圧縮機本体をそれぞれの圧縮機本体毎に予め定められた設定下限設定速度で運転させると共に前記第1放気手段(高圧段パージ)から吐出側の圧縮空気を放気させ、消費空気量が設定空気量以下では、前記負荷運転と前記無負荷運転とを繰り返すように制御する。   The first feature of the present invention that achieves the above object is a variable rotation speed type that performs operation in accordance with the amount of air consumed on the use side by changing the rotation speeds of the low pressure stage compressor body and the high pressure stage compressor body. In the air compressor, an electric motor for rotationally driving the low-pressure stage compressor main body, an inverter for changing a rotation speed of the electric motor, and a first air discharge provided on a discharge side of the high-pressure stage compressor main body Means (high pressure stage purge), control means for controlling the inverter and the first air discharge means, wherein the control means is configured so that the amount of consumed air is within a predetermined air amount range from a maximum air amount. The load operation for changing the rotation speed of the low-pressure stage compressor body and the high-pressure stage compressor body is performed, and in the no-load operation where the air consumption is zero, the low-pressure stage compressor body and the high-pressure stage compressor body are respectively connected. Predetermined for each compressor And at the set lower limit set speed, the compressed air on the discharge side is discharged from the first discharge means (high pressure purge), and when the amount of consumed air is less than the set amount of air, the load operation and the no-load operation are performed. And control to repeat.

また、前記低圧段圧縮機本体の吸い込み側には、吸い込み絞り込み弁が設けられ、前記制御手段が、
前記無負荷運転で、前記吸い込み絞り弁を絞る制御を更に行うことが望ましい。
Further, a suction throttle valve is provided on the suction side of the low-pressure stage compressor body, and the control means includes:
It is desirable to further control to throttle the suction throttle valve during the no-load operation.

また、上記圧縮機の前記低圧段圧縮機本体と、前記高圧段圧縮機本体とを接続する配管の途中に、圧縮空気を放気するための第2放気手段を更に備え、前記制御手段が、前記無負荷運転で、前記第2放気手段から圧縮空気を更に放気する制御を行うのが望ましい。   Further, the control means further comprises a second air release means for releasing compressed air in the middle of a pipe connecting the low pressure stage compressor body and the high pressure stage compressor body of the compressor. In the no-load operation, it is preferable to perform a control for further releasing the compressed air from the second air releasing means.

また、上記圧縮機の前記高圧段圧縮機本体の吐出し側に、圧縮空気を冷却するアフタークーラと、前記低圧段圧縮機本体の吐出し側と前記高圧段圧縮機本体の吸い込み側の間に、圧縮空気を冷却するインタークーラとを更に備えるのが望ましい。   Further, an after cooler for cooling the compressed air is disposed on the discharge side of the high-pressure stage compressor body of the compressor, and between the discharge side of the low-pressure stage compressor body and the suction side of the high-pressure stage compressor body. It is desirable to further include an intercooler for cooling the compressed air.

更に好ましくは、前記低圧段縮機本体及び前記高圧段圧縮機本体がスクリュー圧縮機であるのが望ましい。   More preferably, the low-pressure stage compressor main body and the high-pressure stage compressor main body are preferably screw compressors.

更に好ましくは、前記低圧段圧縮機本体及び前記高圧段圧縮機本体がオイルフリー圧縮機であることが望ましい。   More preferably, the low-pressure stage compressor body and the high-pressure stage compressor body are oil-free compressors.

そして、前記高圧段圧縮機の吐出側に、前記消費空気量を検出する圧力検出器を備え、前記制御手段が、前記圧力検出器の検出信号を受信するようにしてもよい。   In addition, a pressure detector that detects the amount of air consumed may be provided on the discharge side of the high-pressure compressor, and the control unit may receive a detection signal of the pressure detector.

以上詳述したように、本発明によれば、回転速度可変型の2段の圧縮機本体を備えた空気圧縮機において、無負荷運転時に圧縮空気を大気に放気可能としたので、無負荷時の空気圧縮機の消費動力を大幅に低減できる。さらに、無負荷運転と設定下限回転速度での負荷運転とを繰り返す低負荷運転時にも消費動力を低減できる。   As described above in detail, according to the present invention, in an air compressor provided with a two-stage compressor body of variable rotation speed, compressed air can be discharged to the atmosphere during no-load operation. The power consumption of the air compressor at the time can be greatly reduced. Furthermore, power consumption can be reduced even during low-load operation in which no-load operation and load operation at the set lower limit rotational speed are repeated.

本発明に係るインバータ駆動形オイルフリースクリュー圧縮機の一実施例の構成図である。It is a block diagram of one Example of the inverter drive type oil free screw compressor which concerns on this invention. 図1に示したオイルフリースクリュー圧縮機の運転方法を説明する図である。It is a figure explaining the operating method of the oil free screw compressor shown in FIG. 図1に示したオイルフリースクリュー圧縮機の消費動力特性を説明する図である。It is a figure explaining the power consumption characteristic of the oil free screw compressor shown in FIG. 本発明に係るインバータ駆動形オイルフリースクリュー圧縮機の他の実施例の構成図である。It is a block diagram of the other Example of the inverter drive type oil free screw compressor which concerns on this invention. 図4に示したオイルフリースクリュー圧縮機の無負荷運転時の圧力特性を説明する図である。It is a figure explaining the pressure characteristic at the time of a no-load driving | operation of the oil free screw compressor shown in FIG.

以下、本発明のいくつかの実施例を、図面を用いて説明する。   Several embodiments of the present invention will be described below with reference to the drawings.

図1は、オイルフリースクリュー圧縮機の構成図であり、図2および図3はこの図1に示されたオイルフリースクリュー圧縮機の運転方法を説明する図である。   FIG. 1 is a configuration diagram of an oil-free screw compressor, and FIGS. 2 and 3 are diagrams for explaining an operation method of the oil-free screw compressor shown in FIG.

オイルフリースクリュー圧縮機100は、低圧段圧縮機本体1と高圧段圧縮機本体2とを有している。低圧段圧縮機1は、雌雄一対のロータを、外周部に冷却ジャケットが形成されたケーシング内に保持している。そして、一対のロータは、各ロータの軸端部に取付けられたタイミングギヤが噛合うことにより同期回転している。一方のロータのタイミングギヤ取付け端とは反対側の回転軸1A端部には、ピニオンギヤ6が取付けられている。
同様に、高圧段圧縮機2は、雌雄一対のロータを、外周部に冷却ジャケットが形成されたケーシング内に保持している。そして、一対のロータは、各ロータの軸端部に取付けられたタイミングギヤが噛合うことにより同期回転している。一方のロータのタイミングギヤ取付け端とは反対側の回転軸2A端部には、ピニオンギヤ7が取付けられている。
The oil-free screw compressor 100 includes a low-pressure stage compressor body 1 and a high-pressure stage compressor body 2. The low-pressure stage compressor 1 holds a pair of male and female rotors in a casing having a cooling jacket formed on the outer periphery. The pair of rotors rotate synchronously when the timing gears attached to the shaft end portions of the rotors mesh with each other. A pinion gear 6 is attached to the end of the rotary shaft 1A opposite to the timing gear attachment end of one rotor.
Similarly, the high-pressure stage compressor 2 holds a pair of male and female rotors in a casing having a cooling jacket formed on the outer periphery. The pair of rotors rotate synchronously when the timing gears attached to the shaft end portions of the rotors mesh with each other. A pinion gear 7 is attached to the end of the rotary shaft 2A opposite to the timing gear attachment end of one rotor.

2個のピニオンギア6,7は、モータ4の回転軸4Aにカップリング接続されたブル軸に取付けたブルギヤ5と噛合っている。モータ4は、インバータ8により駆動される可変速形のモータである。なお、ピニオンギヤ6,7及びブルギヤ5はギヤケーシング3に収容されている。ギヤケーシングの下部は各圧縮機本体1,2の軸受やブルギヤ5、ピニオン6,7を潤滑する潤滑油の油溜りになっている。   The two pinion gears 6 and 7 mesh with a bull gear 5 attached to a bull shaft coupled to the rotating shaft 4A of the motor 4. The motor 4 is a variable speed motor driven by an inverter 8. The pinion gears 6 and 7 and the bull gear 5 are accommodated in the gear casing 3. The lower part of the gear casing is a reservoir for lubricating oil for lubricating the bearings of the compressor bodies 1 and 2, the bull gear 5, and the pinions 6 and 7.

低圧段圧縮機本体1の吸込み流路には、周囲空気を濾過して低圧段圧縮機本体1に供給するためのフィルタ14が取付けられており、このフィルタの下流側には吸込み口14Aが形成されている。低圧段圧縮機本体1の吐出側と高圧段圧縮機本体2の吸込み側との間には、インタークーラ10が設けられており、このインタークーラ10は低圧段圧縮機本体1とは空気配管9で、高圧段圧縮機本体2とは空気配管9Aで配管接続されている。高圧段圧縮機本体2の下流には、逆止弁12を介してアフタークーラ13が空気配管11で配管接続されている。   A filter 14 for filtering the ambient air and supplying it to the low-pressure stage compressor body 1 is attached to the suction flow path of the low-pressure stage compressor body 1, and a suction port 14A is formed on the downstream side of the filter. Has been. An intercooler 10 is provided between the discharge side of the low-pressure stage compressor body 1 and the suction side of the high-pressure stage compressor body 2, and the intercooler 10 is connected to the low-pressure stage compressor body 1 by an air pipe 9. Thus, the high pressure stage compressor body 2 is connected by air piping 9A. An aftercooler 13 is connected to the downstream side of the high-pressure stage compressor body 2 by an air pipe 11 via a check valve 12.

低圧段圧縮機本体1とインタークーラを接続する空気配管9の途中から、低圧段放気配管20が分岐している。そして、この低圧段放気配管20には、低圧段放気二方弁20が設けられている。同様に、高圧段圧縮機本体2とアフタークーラ13とを接続する空気配管11の途中であって逆止弁12の上流側から、高圧段放気配管15が分岐している。この高圧段放気配管15には、高圧段放気二方弁16が設けられている。アフタークーラ13で冷却された圧縮空気を利用側に供給するため、吐出空気配管23がアフタクーラ13の下流に設けられている。   A low-pressure stage discharge pipe 20 is branched from the middle of the air pipe 9 that connects the low-pressure stage compressor body 1 and the intercooler. The low-pressure stage exhaust pipe 20 is provided with a low-pressure stage exhaust two-way valve 20. Similarly, a high-pressure stage discharge pipe 15 is branched from the upstream side of the check valve 12 in the middle of the air pipe 11 connecting the high-pressure stage compressor body 2 and the aftercooler 13. The high-pressure stage vent pipe 15 is provided with a high-pressure stage vent two-way valve 16. In order to supply the compressed air cooled by the aftercooler 13 to the use side, a discharge air pipe 23 is provided downstream of the aftercooler 13.

この吐出空気配管23の途中には、オイルフリースクリュー圧縮機100から吐出される圧縮空気の圧力を計測する圧力検出器17が取付けられている。圧力検出器17が検出した圧力は、制御装置18に入力される。   A pressure detector 17 for measuring the pressure of the compressed air discharged from the oil-free screw compressor 100 is attached in the middle of the discharge air pipe 23. The pressure detected by the pressure detector 17 is input to the control device 18.

このように構成した本実施例の作用を以下に説明する。モータ4が運転されると、モータ4の回転力がブルギヤ5およびピニオンギヤ6,7を介して低圧段圧縮機本体1および高圧段圧縮機本体2に伝達される。これにより、低圧段圧縮機本体1および高圧段圧縮機本体2が備える各々一対のロータが同期回転し、作動ガスである空気を圧縮する。吸込み口14Aから吸込まれた圧縮用の周囲空気は、低圧段圧縮機本体1で圧縮されて圧力が上昇するとともに温度上昇する。この高温の圧縮ガスは空気配管9を経てインタークーラ10に導かれ、インタークーラ10で冷却される。インタークーラ10で冷却された圧縮空気は、空気配管9Aを経て高圧段圧縮機本体2に導かれ、さらに所定の吐出圧力まで昇圧されるとともに温度上昇する。温度上昇した圧縮空気は、空気配管11を経てアフタークーラ13に導かれ、アフタークーラ13で冷却された後、吐出空気配管23から利用側に供給される。   The operation of this embodiment configured as described above will be described below. When the motor 4 is operated, the rotational force of the motor 4 is transmitted to the low pressure stage compressor body 1 and the high pressure stage compressor body 2 through the bull gear 5 and the pinion gears 6 and 7. As a result, the pair of rotors provided in the low-pressure stage compressor main body 1 and the high-pressure stage compressor main body 2 rotate synchronously to compress the air that is the working gas. The ambient air for compression sucked from the suction port 14A is compressed by the low-pressure stage compressor body 1, and the temperature rises as the pressure rises. This high-temperature compressed gas is guided to the intercooler 10 through the air pipe 9 and cooled by the intercooler 10. The compressed air cooled by the intercooler 10 is guided to the high-pressure compressor main body 2 through the air pipe 9A, and is further pressurized to a predetermined discharge pressure and rises in temperature. The compressed air whose temperature has risen is guided to the aftercooler 13 through the air pipe 11, cooled by the aftercooler 13, and then supplied from the discharge air pipe 23 to the use side.

利用側の消費空気量が減少すると、圧力検出器17で検出される吐出圧力は上昇する。この検出された吐出圧力は、制御装置18に入力される。吐出圧力が上昇すると、制御装置18はモータ4の回転速度を低下させる指令信号を、インバータ8に出力する。モータ4の回転速度が低下すると、低圧段圧縮機本体1および高圧段圧縮機本体2が備えるロータの回転速度が低下し、オイルフリースクリュー圧縮機100の吐出空気量が低下する。   When the amount of consumed air on the use side decreases, the discharge pressure detected by the pressure detector 17 increases. The detected discharge pressure is input to the control device 18. When the discharge pressure increases, the control device 18 outputs a command signal for decreasing the rotation speed of the motor 4 to the inverter 8. When the rotational speed of the motor 4 is reduced, the rotational speed of the rotor provided in the low-pressure stage compressor body 1 and the high-pressure stage compressor body 2 is reduced, and the amount of air discharged from the oil-free screw compressor 100 is reduced.

つまり、消費空気量が減少して、オイルフリースクリュー圧縮機から吐出される空気量が仕様吐出空気量の100%から約50%で良いときには、制御装置18は吐出圧力を一定にするため、モータ4の回転数を図2(運転範囲D)に示すように吐出空気量比に比例して制御する。これに対して、吐出空気量が仕様吐出空気量の約50%以下でよいときには、制御装置18は放気減圧運転を指令する。具体的には、圧力検出器17が検出した吐出圧力が制御装置18に予め設定された設定上限圧力を超えていれば、制御装置18は設定下限回転速度を維持するようにインバータに指令する。それとともに、高圧段放気二方弁16を開くためにこの高圧段放気二方弁16に開指令する。高圧段放気二方弁16が開いたことにより、高圧段圧縮機本体2で圧縮された圧縮空気は、アフタークーラ13に導かれることなく大気開放される。   That is, when the amount of air consumed decreases and the amount of air discharged from the oil-free screw compressor may be about 100% to about 50% of the specified amount of discharge air, the control device 18 keeps the discharge pressure constant. 4 is controlled in proportion to the discharge air amount ratio as shown in FIG. 2 (operation range D). On the other hand, when the discharge air amount may be about 50% or less of the specification discharge air amount, the control device 18 commands the discharge air decompression operation. Specifically, if the discharge pressure detected by the pressure detector 17 exceeds the set upper limit pressure preset in the control device 18, the control device 18 instructs the inverter to maintain the set lower limit rotation speed. At the same time, in order to open the high-pressure stage air release two-way valve 16, an opening command is given to the high-pressure stage air release two-way valve 16. By opening the high-pressure stage discharge two-way valve 16, the compressed air compressed by the high-pressure stage compressor body 2 is released to the atmosphere without being guided to the aftercooler 13.

ところで本実施例では、低圧段圧縮機本体1の吐出側の空気配管9の途中から分岐して空気配管20を設けている。そしてこの配管20に低圧段放気二方弁21を介在させている。それは以下の理由による。オイルフリースクリュー圧縮機から吐出される空気量が、仕様吐出空気量の100%から約50%の範囲は、負荷運転の領域である。この負荷運転領域では、圧縮空気の全量を利用側に供給したいので、低圧段放気二方弁21を閉じるように制御装置18が低圧段放気二方弁21に指令する。これにより、低圧段圧縮機本体1が圧縮した圧縮空気の全量が高圧段圧縮機本体2に供給される。   By the way, in this embodiment, the air pipe 20 is branched from the middle of the air pipe 9 on the discharge side of the low-pressure stage compressor body 1. A low pressure stage two-way valve 21 is interposed in the pipe 20. The reason is as follows. The range in which the amount of air discharged from the oil-free screw compressor is from 100% to about 50% of the specified discharge air amount is a region of load operation. In this load operation region, since it is desired to supply the entire amount of compressed air to the use side, the control device 18 instructs the low pressure stage discharge two-way valve 21 to close the low pressure stage discharge two way valve 21. As a result, the entire amount of compressed air compressed by the low-pressure stage compressor body 1 is supplied to the high-pressure stage compressor body 2.

利用側の圧縮空気消費が減少し、利用側へ圧縮空気を供給する必要がなくなった無負荷運転時には、低圧段圧縮機本体1および高圧段圧縮機本体2の回転速度が設定下限値になるように、制御装置18はインバータ8に指令する。それとともに低圧段放気二方弁21に開指令を出力し、低圧段圧縮機本体1で圧縮された圧縮空気の一部を大気に開放する。   During no-load operation when compressed air consumption on the use side is reduced and it is no longer necessary to supply compressed air to the use side, the rotational speeds of the low-pressure stage compressor body 1 and the high-pressure stage compressor body 2 are set to the set lower limit values. In addition, the control device 18 commands the inverter 8. At the same time, an open command is output to the low pressure stage discharge two-way valve 21 to release a part of the compressed air compressed by the low pressure stage compressor body 1 to the atmosphere.

利用側への圧縮空気の供給量が少ないとき、すなわち、吐出空気量が仕様吐出空気量の約50%以下である低負荷運転のときには、低圧段圧縮機本体1と高圧段圧縮機本体2の双方の回転速度が設定下限値となるように制御装置18がインバータ8に指令する。そして制御装置18は、上記した無負荷運転と負荷運転を繰り返すように、低圧段放気二方弁21と高圧段放気二方弁16を制御する。なお、上記いずれの運転においても、圧縮空気の消費量は吐出空気配管23中に設けた圧力検出器17が検出した圧力に基づいて求めている。   When the supply amount of compressed air to the user side is small, that is, during low load operation where the discharge air amount is about 50% or less of the specified discharge air amount, the low pressure stage compressor body 1 and the high pressure stage compressor body 2 The control device 18 commands the inverter 8 so that both rotation speeds become the set lower limit values. Then, the control device 18 controls the low-pressure stage exhaust two-way valve 21 and the high-pressure stage exhaust two-way valve 16 so as to repeat the above-described no-load operation and load operation. In any of the above operations, the amount of compressed air consumed is determined based on the pressure detected by the pressure detector 17 provided in the discharge air pipe 23.

このように制御装置18がインバータ8および低圧段放気二方弁21と高圧段放気二方弁16を制御したときの、オイルフリースクリュー圧縮機の消費動力の変化を図3に示す。図3において、横軸はオイルフリースクリュー圧縮機の吐出空気量を仕様吐出空気量で割った値であり、縦軸は仕様吐出空気量に吐出空気量がなったときの消費動力を100%としたときのオイルフリースクリュー圧縮機の消費動力である。図中F線は比較のために記載したものであり、低圧段圧縮機本体1の吸込側に負荷に応じて開閉する吸込み絞り弁を用いた、従来の容量制御法を用いた場合の消費動力の変化である。この制御法においては、低圧段圧縮機本体および高圧段圧縮機本体の双方を回転速度一定のまま運転し、無負荷運転時には圧縮空気を放気している。なお、点fはこの従来型の容量制御法を適用したときの無負荷運転時の消費動力である。   FIG. 3 shows changes in the power consumption of the oil-free screw compressor when the control device 18 controls the inverter 8 and the low-pressure stage discharge two-way valve 21 and the high-pressure stage discharge two-way valve 16 in this way. In FIG. 3, the horizontal axis is the value obtained by dividing the discharge air amount of the oil-free screw compressor by the specified discharge air amount, and the vertical axis is the power consumption when the discharge air amount becomes 100%. This is the power consumption of the oil-free screw compressor. The F line in the figure is shown for comparison, and the power consumption when the conventional capacity control method using a suction throttle valve that opens and closes according to the load on the suction side of the low-pressure stage compressor body 1 is used. Is a change. In this control method, both the low-pressure stage compressor body and the high-pressure stage compressor body are operated at a constant rotational speed, and compressed air is discharged during no-load operation. The point f is the power consumption during no-load operation when this conventional capacity control method is applied.

また、図3中のG線も本発明との比較のために記載したものであり、低圧段放気二方弁を有せず、高圧段放気二方弁16のみを有する可変速型のオイルフリースクリュー圧縮機の消費動力の変化である。この従来のオイルフリースクリュー圧縮機は、低圧段圧縮機本体および高圧段圧縮機本体を備えており、各圧縮機本体はインバータ駆動のモータで運転されている。そして点gは、この従来型の回転速度制御法を適用したときの無負荷運転時の消費動力である。   The G line in FIG. 3 is also shown for comparison with the present invention, and is a variable speed type that does not have the low-pressure stage two-way valve 16 but has only the high-pressure stage two-way valve 16. This is a change in power consumption of an oil-free screw compressor. This conventional oil-free screw compressor includes a low-pressure stage compressor body and a high-pressure stage compressor body, and each compressor body is operated by an inverter-driven motor. Point g is the power consumption during no-load operation when this conventional rotational speed control method is applied.

図3中のH線は、上述した本発明に係る制御方法を適用した場合のオイルフリースクリュー圧縮機の消費動力特性である。吐出空気量比が100%〜50%までは、消費動力は吐出空気量比に比例して変化する。吐出空気量比が50%以下では、その変化は大流量時(100%〜50%)に比べて緩やかになるが、従来技術であるF線やG線よりも消費動力は少ない。しかも無負荷運転時の消費動力を示すh点は、明らかにf点やg点を下回っている。   The H line in FIG. 3 is the power consumption characteristic of the oil-free screw compressor when the control method according to the present invention described above is applied. When the discharge air amount ratio is 100% to 50%, the power consumption changes in proportion to the discharge air amount ratio. When the discharge air amount ratio is 50% or less, the change becomes milder than that at the time of a large flow rate (100% to 50%), but less power is consumed than the conventional F-line and G-line. Moreover, the point h indicating the power consumption during no-load operation is clearly below the points f and g.

ところで、オイルフリースクリュー圧縮機の消費動力は、空気を圧縮する動力と軸受等で発生する機械損失との和である。無負荷運転時においては、圧縮機本体の回転速度が全負荷運転時の約半分の回転速度に制御されているから、機械損失の割合が小さく、空気圧縮に必要な動力が大半である。本実施例では、無負荷運転時に低圧段圧縮機本体で圧縮された圧縮空気の一部を大気に放出しているので、高圧段圧縮機本体に供給される圧縮空気量が放気空気量だけ減少する。空気圧縮による消費動力は圧縮機本体が吸込む空気量にほぼ比例するから、低圧段圧縮機本体で圧縮された圧縮空気の50%を放出したとすると、高圧段圧縮機本体における空気圧縮による消費動力はほぼ半分となる。したがって、全負荷運転における空気圧縮による消費動力が低圧段圧縮機本体と高圧段圧縮機本体とでほぼ等しいときには、低圧段圧縮機本体で圧縮された圧縮空気の50%を放気すれば、低圧段圧縮機本体および高圧段圧縮機本体における空気圧縮による消費動力を25%低減することができることになる。   Incidentally, the power consumption of the oil-free screw compressor is the sum of the power for compressing air and the mechanical loss generated in the bearings. During no-load operation, the rotational speed of the compressor body is controlled to about half the rotational speed during full-load operation, so the percentage of mechanical loss is small and most of the power required for air compression. In this embodiment, part of the compressed air compressed by the low-pressure stage compressor body during no-load operation is released to the atmosphere, so the amount of compressed air supplied to the high-pressure stage compressor body is only the amount of discharged air. Decrease. The power consumed by air compression is approximately proportional to the amount of air that the compressor body inhales. Therefore, if 50% of the compressed air compressed by the low-pressure compressor body is released, the power consumed by air compression in the high-pressure compressor body Is almost halved. Therefore, when the power consumed by air compression in the full load operation is approximately equal between the low pressure stage compressor body and the high pressure stage compressor body, if 50% of the compressed air compressed by the low pressure stage compressor body is discharged, the low pressure stage The power consumed by air compression in the stage compressor body and the high pressure stage compressor body can be reduced by 25%.

アンロード効率は2段圧縮機の方が一般的に高いので、2段圧縮機の無負荷時の消費動力は、単段圧縮機よりも相対的に小さくなる。そのため、従来の容量制御法における無負荷時の消費動力(f点)と回転速度制御法における無負荷時の消費動力(g点)とでは差が非常に少なくなる。一方、本実施例によれば、図3に示したように吐出空気量が少ないところでは、低圧段圧縮機で圧縮した圧縮空気を大気に放気して高圧段圧縮機の圧縮仕事を減らしているので、消費動力が低減される。なお、回転速度一定の低圧段圧縮機本体と高圧段圧縮機本体を有する2段オイルフリースクリュー圧縮機を吸い込み絞り弁を用いて容量制御すると、低圧段圧縮機本体から吐出される圧縮空気の圧力は負圧となるので、低圧段圧縮機本体で圧縮された圧縮空気を大気に放気することは困難である。   Since the unload efficiency is generally higher in the two-stage compressor, the power consumption when the two-stage compressor is unloaded is relatively smaller than that in the single-stage compressor. Therefore, the difference between the power consumption during no load (point f) in the conventional capacity control method and the power consumption during no load (point g) in the rotational speed control method is very small. On the other hand, according to this embodiment, when the amount of discharged air is small as shown in FIG. 3, the compressed air compressed by the low-pressure stage compressor is discharged to the atmosphere to reduce the compression work of the high-pressure stage compressor. Therefore, power consumption is reduced. When the capacity of a two-stage oil-free screw compressor having a low-pressure stage compressor body having a constant rotational speed and a high-pressure stage compressor body is controlled using a suction throttle valve, the pressure of the compressed air discharged from the low-pressure stage compressor body Therefore, it is difficult to release the compressed air compressed by the low-pressure compressor main body to the atmosphere.

本発明の他の実施例を、図4および図5を用いて説明する。図4は本実施例に係るインバータ駆動オイルフリースクリュー圧縮機の全体構成図であり、図5は図4に示したオイルフリースクリュー圧縮機を回転速度を変えて運転したときの吐出圧力の変化を示す図である。本実施例が図1に示した実施例と異なる点は、低圧段圧縮機本体1の吸込口に吸込絞り弁31を設けたこと、高圧段放気二方弁16の代りに吸込絞り弁31の開閉に連動する放気弁32を設けたこと、および放気弁32の2次側に放気サイレンサ33を設けたことにある。   Another embodiment of the present invention will be described with reference to FIGS. FIG. 4 is an overall configuration diagram of the inverter-driven oil-free screw compressor according to the present embodiment, and FIG. 5 shows changes in discharge pressure when the oil-free screw compressor shown in FIG. 4 is operated at different rotational speeds. FIG. This embodiment is different from the embodiment shown in FIG. 1 in that a suction throttle valve 31 is provided at the suction port of the low-pressure stage compressor body 1 and that the suction throttle valve 31 is used instead of the high-pressure stage discharge two-way valve 16. The air release valve 32 interlocked with the opening / closing of the air release valve 32 is provided, and the air release silencer 33 is provided on the secondary side of the air release valve 32.

このように構成した本実施例では、利用側へ圧縮空気を供給する負荷運転時に制御装置18は、圧力検出器17が検出した吐出圧に基づいて得られた利用側の必要空気量をオイルフリー圧縮機が供給できるように、モータ4の回転速度をインバータ8に指令する。それとともに、吸込絞り弁31を開けるように指示する。   In this embodiment configured as described above, the control device 18 at the time of a load operation for supplying compressed air to the use side uses the oil-free required amount of air on the use side obtained based on the discharge pressure detected by the pressure detector 17. The inverter 8 is commanded to rotate the motor 4 so that the compressor can supply it. At the same time, an instruction is given to open the suction throttle valve 31.

利用側へ圧縮空気を供給しない無負荷運転時には、制御装置18は吸込絞り弁31を閉じるように指令するとともに、モータ4の回転速度が設定下限回転速度となるようにインバータ8に指令する。さらに、制御装置18は放気弁32を開けることも指令する。この無負荷運転時には、低圧段圧縮機本体1の回転速度は設定下限回転速度であるから低圧段圧縮機本体1が吸込む空気量が減少すると、吸込絞り弁31の二次側である低圧段圧縮機本体1の吸込圧力が低下する。ところが、この吸込み絞り弁31を共用化するため大形のもの、例えば22kWの2段圧縮機では100kW用のものを使用しているので、吸込み絞り弁31を絞っても吸込み側圧力は極端には低下しない。その結果、吸込圧力に圧力比を乗じた値である低圧段圧縮機本体1の吐出圧力を、正圧にすることができる。そこで、低圧段放気二方弁21を開けば、低圧段圧縮機本体1で圧縮された圧縮空気を大気に放気することができる。これにより、高圧段圧縮機本体2に供給する圧縮空気量を低減できる。なお、吸込み絞り弁31を定格動力に応じたものとしたときには、低圧段圧縮機の吐出圧が負圧にならないように吸込み絞り弁を制御する。   At the time of no-load operation in which compressed air is not supplied to the use side, the control device 18 instructs the inverter 8 to close the suction throttle valve 31, and instructs the inverter 8 so that the rotational speed of the motor 4 becomes the set lower limit rotational speed. Furthermore, the control device 18 also commands opening the air release valve 32. During this no-load operation, the rotational speed of the low-pressure stage compressor body 1 is the set lower limit rotational speed, so if the amount of air sucked into the low-pressure stage compressor body 1 decreases, the low-pressure stage compression that is the secondary side of the suction throttle valve 31 The suction pressure of the machine body 1 decreases. However, in order to share this suction throttle valve 31, a large type, for example, a 22 kW two-stage compressor, is used for 100 kW. Therefore, even if the suction throttle valve 31 is throttled, the suction side pressure is extremely low. Will not drop. As a result, the discharge pressure of the low-pressure stage compressor body 1 that is a value obtained by multiplying the suction pressure by the pressure ratio can be made positive. Therefore, if the low-pressure stage discharge two-way valve 21 is opened, the compressed air compressed by the low-pressure stage compressor body 1 can be discharged to the atmosphere. Thereby, the amount of compressed air supplied to the high-pressure stage compressor body 2 can be reduced. When the suction throttle valve 31 is adapted to the rated power, the suction throttle valve is controlled so that the discharge pressure of the low-pressure compressor does not become negative.

利用側へ圧縮空気を少量だけ供給する低負荷時には、制御装置18は、低圧段圧縮機本体1と高圧段圧縮機本体2の回転速度が下限値となるようにインバータ8に指令する。そして、上記の無負荷運転と負荷運転を繰り返すように、吸込み絞り弁31と放気二方弁21,32とを制御装置18が制御する。   At the time of low load in which only a small amount of compressed air is supplied to the use side, the control device 18 commands the inverter 8 so that the rotation speeds of the low-pressure stage compressor body 1 and the high-pressure stage compressor body 2 become lower limit values. Then, the control device 18 controls the suction throttle valve 31 and the exhaust two-way valves 21 and 32 so as to repeat the above-described no-load operation and load operation.

図5に、本実施例におけるオイルフリースクリュー圧縮機の各部の圧力を示す。この図5では無負荷運転時を示している。横軸は定格回転速度に対する比である。低圧段圧縮機本体1の回転速度が定格のほぼ60%以下になると、低圧段圧縮機本体1から吐出される圧縮空気の圧力が大気圧を越えることがわかる。したがって、定格速度の50%に設定する無負荷運転では、低圧段圧縮機本体1で圧縮された圧縮空気を大気に放気できることがわかる。   In FIG. 5, the pressure of each part of the oil-free screw compressor in a present Example is shown. FIG. 5 shows a no-load operation. The horizontal axis is the ratio to the rated rotational speed. It can be seen that the pressure of the compressed air discharged from the low-pressure stage compressor body 1 exceeds the atmospheric pressure when the rotational speed of the low-pressure stage compressor body 1 is approximately 60% or less of the rated value. Therefore, it can be seen that in the no-load operation set to 50% of the rated speed, the compressed air compressed by the low-pressure stage compressor body 1 can be discharged to the atmosphere.

1…低圧段圧縮機本体、2…高圧段圧縮機本体、4…モータ、8…インバータ、9…空気配管、11…空気配管、12…逆止弁、16…高圧段放気二方弁、17…圧力検出器、18…制御装置、21…低圧段放気二方弁、31…吸込絞り弁、32…放気弁。   DESCRIPTION OF SYMBOLS 1 ... Low pressure stage compressor main body, 2 ... High pressure stage compressor main body, 4 ... Motor, 8 ... Inverter, 9 ... Air piping, 11 ... Air piping, 12 ... Check valve, 16 ... High pressure stage air-release two-way valve, DESCRIPTION OF SYMBOLS 17 ... Pressure detector, 18 ... Control apparatus, 21 ... Low-pressure stage release two-way valve, 31 ... Suction throttle valve, 32 ... Release valve

Claims (7)

低圧段圧縮機本体と高圧段圧縮機本体の回転速度とを変化させて利用側の消費空気量に応じた運転を行う圧縮機において、
前記低圧段圧縮機本体を回転駆動するための電動機と、
前記電動機の回転速度を変化させるためのインバータと、
前記高圧段圧縮機本体の吐出側に設けられた第1放気手段と、
前記インバータと前記第1放気手段を制御するための制御手段とを備え、
前記制御手段は、
消費空気量が最大空気量から予め定めた設定空気量の範囲では、前記低圧段圧縮機本体及び高圧段圧縮機本体の回転速度を変化させる負荷運転を行わせ、
前記消費空気量がゼロの無負荷運転では低圧段圧縮機本体と高圧段圧縮機本体をそれぞれの圧縮機本体毎に予め定められた設定下限設定速度で運転させると共に前記第1放気手段から吐出側の圧縮空気を放気させ、
消費空気量が設定空気量以下では、前記負荷運転と前記無負荷運転とを繰り返すように制御する
ことを特徴とする回転速度可変形圧縮機。
In a compressor that operates according to the amount of air consumed on the use side by changing the rotation speed of the low-pressure stage compressor body and the high-pressure stage compressor body,
An electric motor for rotationally driving the low-pressure stage compressor body;
An inverter for changing the rotational speed of the electric motor;
First aeration means provided on the discharge side of the high-pressure compressor body;
A control means for controlling the inverter and the first air release means;
The control means includes
In a range of air consumption from the maximum air amount to a preset air amount, a load operation is performed to change the rotation speed of the low-pressure stage compressor body and the high-pressure stage compressor body,
In the no-load operation in which the consumption air amount is zero, the low-pressure stage compressor body and the high-pressure stage compressor body are operated at a preset lower limit setting speed for each compressor body and discharged from the first air discharge means. The compressed air on the side is vented,
When the consumed air amount is equal to or less than the set air amount, control is performed so that the load operation and the no-load operation are repeated.
請求項1に記載の圧縮機であって、
前記低圧段圧縮機本体の吸い込み側には、吸い込み絞り込み弁が設けられ、
前記制御手段が、
前記無負荷運転で、前記吸い込み絞り弁を絞る制御を更に行う圧縮機。
The compressor according to claim 1,
A suction throttle valve is provided on the suction side of the low-pressure stage compressor body,
The control means is
A compressor that further controls to throttle the suction throttle valve during the no-load operation.
請求項1又は2に記載の圧縮機であって、
前記低圧段圧縮機本体と、前記高圧段圧縮機本体とを接続する配管の途中に、圧縮空気を放気するための第2放気手段を更に備え、
前記制御手段が、
前記無負荷運転で、前記第2放気手段から圧縮空気を更に放気する制御を行う圧縮機。
The compressor according to claim 1 or 2,
In the middle of a pipe connecting the low-pressure stage compressor body and the high-pressure stage compressor body, further comprising a second air release means for discharging compressed air,
The control means is
A compressor that performs control to further discharge compressed air from the second discharge means in the no-load operation.
請求項1〜3の何れか一項に記載の圧縮機であって、
前記高圧段圧縮機本体の吐出し側に、圧縮空気を冷却するアフタークーラと、
前記低圧段圧縮機本体の吐出し側と前記高圧段圧縮機本体の吸い込み側の間に、圧縮空気を冷却するインタークーラとを更に備える圧縮機。
The compressor according to any one of claims 1 to 3,
An after cooler for cooling the compressed air on the discharge side of the high-pressure stage compressor body;
A compressor further comprising an intercooler that cools compressed air between a discharge side of the low-pressure stage main body and a suction side of the high-pressure stage main body.
請求項1〜4の何れか一項に記載の圧縮機であって、
前記低圧段縮機本体及び前記高圧段圧縮機本体がスクリュー圧縮機である圧縮機。
The compressor according to any one of claims 1 to 4,
The compressor in which the low-pressure stage compressor body and the high-pressure stage compressor body are screw compressors.
請求項1〜5の何れか一項に記載の圧縮機であって、
前記低圧段圧縮機本体及び前記高圧段圧縮機本体がオイルフリー圧縮機である圧縮機。
A compressor according to any one of claims 1 to 5,
A compressor in which the low-pressure stage compressor body and the high-pressure stage compressor body are oil-free compressors.
請求項1〜6の何れか一項に記載の空気圧縮機であって、
前記高圧段圧縮機の吐出側に、前記消費空気量を検出する圧力検出器を備え、前記制御手段が、前記圧力検出器の検出信号を受信する圧縮機。
It is an air compressor as described in any one of Claims 1-6,
A compressor comprising a pressure detector for detecting the amount of consumed air on a discharge side of the high-pressure stage compressor, wherein the control means receives a detection signal of the pressure detector.
JP2013151259A 2013-07-22 2013-07-22 air compressor Expired - Lifetime JP5526267B2 (en)

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