JP3600649B2

JP3600649B2 - Pressure control valve

Info

Publication number: JP3600649B2
Application number: JP03623195A
Authority: JP
Inventors: 高橋　　清
Original assignee: Toyooki Kogyo Co Ltd
Current assignee: Toyooki Kogyo Co Ltd
Priority date: 1995-01-31
Filing date: 1995-01-31
Publication date: 2004-12-15
Anticipated expiration: 2019-12-15
Also published as: JPH08210537A

Description

【０００１】
【産業上の利用分野】
本発明は、密閉した油タンク内部を常時一定の圧力範囲内に維持するのに好適な圧力制御弁に関する。
【０００２】
【従来の技術】
この種の圧力制御弁を適用するものとして、本出願人の出願に係る特願平６−１０６０３６号の如き図５に示すものがある。このものは、塵埃が多い環境下に設置して良好に使用し得るよう作動油を貯蔵する油タンク２５内部を密閉して設け、密閉した内部の貯蔵作動油上の空間Ｃ１に圧縮空気が流通する流路２９を連通して内部を常時圧縮空気により予圧を付与して設け、内部の予圧を圧力検出センサ３０で検出し、制御器３１で設定した一定範囲の設定圧力と比較して設け、流路２９に配設した電磁方向切換弁３２を制御器３１からの通電信号により切換操作し、予圧が設定圧力の下限より低い場合には油タンク２５の内部に圧縮空気を供給したり予圧が設定圧力の上限より高い場合には内部の圧縮空気を排気したり予圧が設定圧力の範囲内にある場合には内部を遮断したりして、油圧ポンプ３３の吸入吐出や外部負荷より戻り流路３４を流れての作動油の還流による貯蔵作動油量の急激な増減にかかわりなく油タンク２５内部を常時一定の圧力範囲内に維持して設けている。
【０００３】
【発明が解決しようとする課題】
ところが、かかる構成では、貯蔵作動油量の急激な増減にかかわりなく油タンク２５内部を常時一定の圧力範囲内に維持するよう電磁切換弁３２を切換操作するのに、圧力検出センサ３０、制御器３１を必要とし、高価になってしまう問題点があった。
本発明は、かかる問題点を解決するもので、圧縮空気の圧力により直接作動して密閉した油タンクの内部を貯蔵作動油量の急激な変動にかかわりなく常時一定の圧力範囲内に維持し得る低コストな圧力制御弁を提供するものである。
【０００４】
【課題を解決するための手段】
このため本発明は、弁本体の嵌合孔へ軸方向に間隙を有して供給ポートと負荷ポートと排気ポートとを開口して設け、供給ポートは圧縮空気源に接続し、負荷ポートは作動油を貯蔵する内部を密閉して貯蔵作動油を油圧ポンプで吸入吐出して外部負荷に供給したり外部負荷より作動油が還流したりして貯蔵作動油量が変動する油タンクの貯蔵作動油上の空間に接続し、排気ポートは外気に開放して設け、弁本体の嵌合孔には負荷ポートを供給ポートと排気ポートとに切換連通する弁体を軸方向へ摺動自在に嵌合して設け、弁体にはその軸方向に自重に基づき設定した設定圧力に負荷ポート側の圧力を対向作用して設け、負荷ポート側の圧力が設定圧力より低い場合には弁体が負荷ポートを供給ポートに連通して排気ポートを遮断する第１位置と、負荷ポート側の圧力が設定圧力より高い場合には弁体が負荷ポートを排気ポートに連通して供給ポートを遮断する第２位置と、負荷ポート側の圧力と設定圧力とが圧力平衡する場合には弁体が各ポート間を遮断する中立位置とを有して成る。
また、弁本体の嵌合孔に軸方向へ摺動自在に嵌合した弁体にはその軸方向に大きなばね力と小さなばね力を対向作用して設け、このばね力差に基づき設定した設定圧力に負荷ポート側の圧力を対向作用して設け、圧縮空気源より圧縮空気を供給していない場合及び負荷ポート側の圧力が設定圧力より低い場合には弁体が負荷ポートを供給ポートに連通して排気ポートを遮断する第１位置と、負荷ポート側の圧力が設定圧力より高い場合には弁体が負荷ポートを排気ポートに連通して供給ポートを遮断する第２位置と、負荷ポート側の圧力と設定圧力とが圧力平衡する場合には弁体が各ポート間を遮断する中立位置とを有しても良い。
【０００５】
【作用】
かかる本発明の構成において、設定圧力を維持したい一定の圧力範囲の上限より低く下限より高く弁体の自重若しくは弁体の軸方向に対向作用する大きなばね力と小さなばね力とのばね力差により設定し、圧縮空気を供給していない状態では弁体が自重若しくは前記ばね力差に基づく設定圧力で第１位置に位置しており、この状態で圧縮空気源より圧縮空気を供給すると、圧縮空気は供給ポートより負荷ポートを流れて油タンク内部の貯蔵作動油上の空間に導入されて内部に予圧を付与し、圧縮空気を供給し続けることで内部に予圧を付与する負荷ポート側の圧力が上昇して設定圧力と圧力平衡すると、弁体が第１位置から中立位置に切換操作されて各ポート間を遮断し、内部に付与する予圧は設定圧力に制御される。そして、油タンクの内部に貯蔵した作動油が油圧ポンプにより吸入吐出され貯蔵作動油量が減少して内部の予圧が低下し負荷ポート側の圧力が設定圧力より低くなると、弁体が中立位置から第１位置に切換操作されて圧縮空気が供給ポートより負荷ポートを流れて油タンク内部の空間に導入して予圧を上昇し、予圧の上昇により負荷ポート側の圧力が上昇して設定圧力と圧力平衡すると、弁体が第１位置から中立位置に切換操作されて各ポート間を遮断する。また、外部負荷より作動油が油タンクの内部に還流され貯蔵作動油量が増加して内部の予圧が上昇し負荷ポート側の圧力が設定圧力より高くなると、弁体が中立位置から第２位置に切換操作されて油タンク内部の貯蔵作動油上の空間にある圧縮空気が負荷ポートより排気ポートを流れて外気に排気して予圧を下降し、予圧の下降により負荷ポート側の圧力が下降して設定圧力と圧力平衡すると、弁体が第２位置から中立位置に切換操作されて各ポート間を遮断する。このため、油タンクの内部に付与する予圧の上昇下降に応じる負荷ポート側の圧力で弁体を中立位置から各位置に切換操作して、密閉した油タンクの内部を貯蔵作動油量の急激な変動にかかわりなく常時一定の圧力範囲内に維持することができるから、従来の如き圧力検出センサ、制御器を不要にできて低コストにすることができる。
【０００６】
【実施例】
以下、本発明の一実施例を図面に基づいて説明する。
図１（Ａ）において、１は油タンクで、内部に作動油を貯蔵して貯蔵作動油上に空間Ｃを設け、この内部を密閉して設けている。２は油圧ポンプで、電動機３により回転駆動されて油タンク１内部に貯蔵の作動油を一端にストレーナ４を有した吸入流路５を介して吸入し吐出流路６へ吐出して図示しない外部負荷に供給するよう設けている。７は戻り流路で、外部負荷より排出された作動油を油タンク１内部に還流するよう設けている。８は圧力制御弁で、供給ポートＰと負荷ポートＡと排気ポートＥとを有し、供給ポートＰは供給流路９により圧縮空気源Ｐ１に接続し、負荷ポートＡは負荷流路１０により油タンク１の貯蔵作動油上の空間Ｃに接続し、排気ポートＥは一端にサイレンサ１１を有した排気流路１２により外気に開放して設けている。１３は供給流路９に配設したドレン排出器付きエアフイルタ、１４は供給流路９にドレン排出器付きエアフイルタ１３の後側に配設したリリーフ付き減圧弁で、二次側圧力を０．０５ＭＰａ（メガパスカル）に減圧制御するよう設定圧力を設定して設けている。１５は吸気弁１５Ａと排気弁１５Ｂとを備えた吸排気安全弁で、負荷流路１０に分岐接続した分岐流路１０Ａに配設し、吸気弁１５Ａの設定圧力を油タンク１内部の維持したい一定の圧力範囲の下限（０．０００５ＭＰａ）より低い−０．００２ＭＰａに設定すると共に、排気弁１５Ｂの設定圧力を維持したい一定の圧力範囲の上限（０．００２５ＭＰａ）より高い０．００３ＭＰａに設定して設けている。
【０００７】
以下、圧力制御弁８の構成を図１（Ｂ）において説明する。
１６は弁本体で、図１（Ｂ）の縦方向に配置し、内部に嵌合孔１７を貫設したスリーブ部材１８を装着して有している。１９、２０は弁本体１６の軸方向両端に固定して設けた蓋部材で、嵌合孔１７の両端開口を閉塞している。弁本体１６の嵌合孔１７にはその下方より順次軸方向に間隙を有して供給ポートＰと負荷ポートＡと排気ポートＥとを開口して設けている。２１は嵌合孔１７に軸方向へ摺動自在に嵌合した弁体で、負荷ポートＡを供給ポートＰと排気ポートＥとに切換連通するようランド部２１Ａ、２１Ｂを軸方向に間隙を有して設けている。そして、弁本体２１はその自重に基づき設定圧力（０．００１５ＭＰａ）を設定して設けると共に、その下方端に負荷ポートＡ側の圧力を流路２２を介して導入し設定圧力に対向作用して設けている。また、弁体２１の上方端は流路２３を介して排気ポートＥに接続している。圧力制御弁８は負荷ポートＡ側の圧力が設定圧力より低い場合には弁体２１が負荷ポートＡを供給ポートＰに連通して排気ポートＥを遮断する第１位置Ｘ（図１（Ａ）に示す。）と、負荷ポートＡ側の圧力が設定圧力より高い場合には弁体２１が負荷ポートＡを排気ポートＥに連通して供給ポートＰを遮断する第２位置Ｙ（図１（Ａ）に示す。）と、負荷ポートＡ側の圧力と設定圧力とが圧力平衡する場合には弁体２１が各ポートＰ、Ａ、Ｅ間を遮断する中立位置Ｚ（図１に（Ａ）に示す。）とを有している。
【０００８】
次にかかる構成の作動を説明する。
図１（Ａ）（Ｂ）は圧縮空気源Ｐ１より圧縮空気を供給していない状態を示し、圧力制御弁８は弁体２１の自重に基づく設定圧力で第１位置Ｘに位置し、弁体２１のランド部２１Ａが供給ポートＰの嵌合孔１７への開口個所より下方にあると共に、ランド部２１Ｂが負荷ポートＡの開口個所と排気ポートＥの開口個所間にあり、負荷ポートＡを供給ポートＰに連通して排気ポートＥを遮断している。
【０００９】
この状態で、圧縮空気源Ｐ１より圧縮空気を供給すると、圧縮空気は供給ポートＰより負荷ポートＡを流れて油タンク１内部の貯蔵作動油上の空間Ｃに導入されて内部に予圧を付与する。そして、圧縮空気を供給し続けることで内部に予圧を付与する負荷ポートＡ側の圧力が上昇して設定圧力（０．００１５ＭＰａ）と圧力平衡すると、圧力制御弁８は弁体２１が第１位置Ｘから中立位置Ｚに切換操作されて上昇した負荷ポートＡ側の圧力に基づく作用力で上方向へ摺動して図２に示す如きに成り、ランド部２１Ａが供給ポートＰの開口個所を閉塞すると共に、ランド部２１Ｂが排気ポートＥの開口個所を閉塞し、各ポートＰ、Ａ、Ｅ間を遮断する。これにより、油タンク１の内部に付与する予圧は設定圧力に制御される。
【００１０】
この油タンク１内部の予圧が設定圧力に制御された状態で、電動機３により油圧ポンプ２を回転駆動して油タンク１内部の貯蔵作動油を吸入吐出して外部負荷に供給すると、貯蔵作動油量が急激に減少して内部の予圧が低下する。そして、予圧の低下により負荷ポートＡ側の圧力が設定圧力より低くなると、圧力制御弁８は弁体２１が中立位置Ｚから第１位置Ｘに切換操作されて図１の状態に復帰し、圧縮空気が供給ポートＰより負荷ポートＡを流れて油タンク１内部の空間Ｃに導入して予圧を上昇し、予圧の上昇により負荷ポートＡ側の圧力が上昇して設定圧力と圧力平衡すると、弁体２１が第１位置Ｘから中立位置Ｚに切換操作されて図２に示す如きに成り、各ポートＰ、Ａ、Ｅ間を遮断する。
【００１１】
また、油タンク１内部の予圧が設定圧力に制御された状態で、外部負荷より排出した作動油が戻り流路７を流れて油タンク１内部に還流すると、貯蔵作動油量が急激に増加して内部の予圧が上昇する。そして、予圧の上昇により負荷ポートＡ側の圧力が設定圧力より高くなると、圧力制御弁８は弁体２１が中立位置Ｚから第２位置Ｙに切換操作されて上昇した負荷ポートＡ側の圧力に基づく作用力で上方向へ摺動して図３に示す如きに成り、ランド部２１Ａが供給ポートＰの開口個所と負荷ポートＡの開口個所間に摺動すると共に、ランド部２１Ｂが排気ポートＥの開口個所より上方に摺動し、負荷ポートＡを排気ポートＥに連通して供給ポートＰを遮断する。そして、油タンク１内部の空間Ｃにある圧縮空気が負荷ポートＡより排気ポートＥを流れて外気に排気して予圧を下降し、予圧の下降により負荷ポートＡ側の圧力が下降して設定圧力と圧力平衡すると、圧力制御弁８は弁体２１が第２位置Ｙから中立位置Ｚに切換操作されて設定圧力を設定する自重で下方向へ摺動して図２に示す如きに成り、各ポートＰ、Ａ、Ｅ間を遮断する。
【００１２】
かかる作動で、圧力制御弁８は、油タンク１内部の貯蔵作動油量の増減に伴う予圧の上昇下降に応じる負荷ポートＡ側の圧力で弁体２１を中立位置Ｚから各位置Ｘ、Ｙに切換操作して、密閉した油タンク１の内部を油圧ポンプ２による貯蔵作動油の吸入吐出や戻り流路７を流れての作動油の還流による貯蔵作動油量の急激な変動にかかわりなく常時一定の圧力範囲（０．０００５ＭＰａから０．００２５ＭＰａ）内に維持することができるから、従来の如き圧力検出センサ、制御器を不要にできて低コストにすることができる。また、設定圧力を弁体２１の自重に基づいて設定しているため、設定圧力をばね力、パイロツト圧力、電磁力等により設定するものに比べ、格別の部材を必要とせず部品点数を削減でき、より低コストにすることができる。
【００１３】
図４は本発明の他実施例を示し、一実施例と同一個所については同符号を付して説明を省略し、異なる個所についてのみ説明する。
圧力制御弁８Ａは弁本体１６を図４の横方向に配置し、弁体２１の軸方向両端に大きなばね力のばね２４Ａと小さなばね力のばね２４Ｂとを収装し、弁体にばね２４Ａ、２４Ｂ力を対向作用して設け、このばね２４Ａ、２４Ｂ力差に基づき設定圧力（０．００１５ＭＰａ）を設定して設けている。
【００１４】
作動は、図４は圧縮空気を供給していない状態を示し、弁体２１はばね２４Ａ、２４Ｂ力差に基づく設定圧力で左方端にあり負荷ポートＡを供給ポートＰに連通して排気ポートＥを遮断する第１位置Ｘ（図１（Ａ）に示す。）に位置している。そして、圧縮空気の供給で油タンク内部に予圧を付与する負荷ポートＡ側の圧力が上昇して設定圧力と圧力平衡すると、弁体２１が図４の右方向へ摺動して第１位置Ｘから中立位置Ｚに切換操作され、一実施例と同様に、油タンク内部の貯蔵作動油量の増減に伴う予圧の上昇下降に応じる負荷ポートＡ側の圧力で弁体２１を中立位置Ｚから各位置Ｘ、Ｙに切換操作して、油タンク１の内部を貯蔵作動油量の急激な変動にかかわりなく常時一定の圧力範囲（０．０００５ＭＰａから０．００２５ＭＰａ）内に維持することができ、従来の如き圧力検出センサ、制御器を不要にできて低コストにすることができる。また、設定圧力を弁体２１の軸方向に対向作用したばね２４Ａ、２４Ｂ力差に基づいて設定しているため、弁体に負荷ポート側の圧力に軸方向へ対向作用するばね力に基づいて設定圧力を設定して設ける場合と比べ、０．００１５ＭＰａと言う非常に低い設定圧力を設定するのに各ばね２４Ａ、２４Ｂ自体はばね力を低くすることなく線径を十分なものにでき、長期間にわたる弁体２１の軸方向への摺動で各ばね２４Ａ、２４Ｂに繰り返し作用するせん断力に対応できて耐久性を向上することができる。さらにまた、ばね２４Ａ、２４Ｂ力差に基づいて設定圧力を設定しているため、弁体２１を摺動自在に嵌合した弁本体１６の配置方向にとらわれることなくできる。
【００１５】
【発明の効果】
このように本発明は、弁本体の嵌合孔へ軸方向に間隙を有して供給ポートと負荷ポートと排気ポートとを開口して設け、供給ポートは圧縮空気源に接続し、負荷ポートは作動油を貯蔵する内部を密閉して貯蔵作動油を油圧ポンプで吸入吐出して外部負荷に供給したり外部負荷より作動油が還流したりして貯蔵作動油量が変動する油タンクの貯蔵作動油上の空間に接続し、排気ポートは外気に開放して設け、弁本体の嵌合孔には負荷ポートを供給ポートと排気ポートとに切換連通する弁体を軸方向へ摺動自在に嵌合して設け、弁体にはその軸方向に自重若しくは対向作用する大きなばね力と小さなばね力とのばね力差に基づき設定した設定圧力に負荷ポート側の圧力を対向作用して設け、負荷ポート側の圧力が設定圧力より低い場合には弁体が負荷ポートを供給ポートに連通して排気ポートを遮断する第１位置と、負荷ポート側の圧力が設定圧力より高い場合には弁体が負荷ポートを排気ポートに連通して供給ポートを遮断する第２位置と、負荷ポート側の圧力と設定圧力とが圧力平衡する場合には弁体が各ポート間を遮断する中立位置とを有しているため、従来の如き圧力検出センサ、制御器を不要にできて低コストにすることができる。
また、請求項１のものでは、設定圧力を弁体の自重に基づいて設定しているため、設定圧力を設定する格別の部材を必要とせず部品点数を削減でき、より低コストにすることができる効果を有する。
また、請求項２のものでは、設定圧力を弁体の軸方向に対向作用した大きなばね力と小さなばね力とのばね力差に基づいて設定しているため、低い設定圧力を設定する場合であっても各ばね自体はばね力を低くすることなく線径を十分なものにでき、長期間にわたる弁体の軸方向への摺動で各ばねに繰り返し作用するせん断力に対応できて耐久性を向上することができる。さらにまた、弁体を摺動自在に嵌合した弁本体の配置方向にとらわれることなくできる効果を有する。
【図面の簡単な説明】
【図１】本発明の一実施例を示し、（Ａ）は回路図、（Ｂ）は圧力制御弁の縦断面図である。
【図２】図１（Ｂ）の圧力制御弁の作動状態を示す縦断面図である。
【図３】図２とは異なる作動状態を示す圧力制御弁の縦断面図である。
【図４】本発明の他実施例を示した圧力制御弁の縦断面図である。
【図５】従来例を示した回路図である。
【符号の説明】
１油タンク
２油圧ポンプ
８、８Ａ圧力制御弁
１６弁本体
１７嵌合孔
２１弁体
２４Ａ、２４Ｂばね
Ｃ空間
Ｐ供給ポート
Ａ負荷ポート
Ｅ排気ポート
Ｘ第１位置
Ｙ第２位置
Ｚ中立位置[0001]
[Industrial applications]
TECHNICAL FIELD The present invention relates to a pressure control valve suitable for always keeping the inside of a closed oil tank within a constant pressure range.
[0002]
[Prior art]
As an application of this type of pressure control valve, there is one shown in FIG. 5 as disclosed in Japanese Patent Application No. 6-106036 filed by the present applicant. In this case, the inside of an oil tank 25 for storing hydraulic oil is provided in a hermetically sealed state so that it can be installed and used in an environment with a lot of dust, and compressed air flows through a space C1 on the stored hydraulic oil inside the hermetically sealed interior. The internal pressure is always provided by compressed air, and the internal pressure is detected by a pressure detection sensor 30 and provided by comparing with a set pressure in a certain range set by a controller 31, When the preload is lower than the lower limit of the set pressure, compressed air is supplied to the inside of the oil tank 25 or the preload is controlled by switching the electromagnetic directional control valve 32 disposed in the flow passage 29 by an energization signal from the controller 31. When the pressure is higher than the upper limit of the set pressure, the internal compressed air is exhausted, and when the preload is within the set pressure range, the inside is shut off, and the return flow from the suction / discharge of the hydraulic pump 33 or the external load is returned. Reflux of hydraulic oil flowing through 34 The internal oil tank 25 regardless of the rapid increase and decrease of the storage amount of hydraulic oil is provided to maintain at all times within a predetermined pressure range with.
[0003]
[Problems to be solved by the invention]
However, in this configuration, the pressure detection sensor 30 and the controller are used to switch the electromagnetic switching valve 32 so as to always maintain the inside of the oil tank 25 within a constant pressure range regardless of a sudden increase or decrease of the stored hydraulic oil amount. 31 is required, and there is a problem that it becomes expensive.
The present invention solves such a problem, and can directly operate by the pressure of compressed air to maintain the inside of a sealed oil tank within a constant pressure range at all times regardless of a sudden change in the amount of stored hydraulic oil. It is intended to provide a low-cost pressure control valve.
[0004]
[Means for Solving the Problems]
Therefore, according to the present invention, the supply port, the load port, and the exhaust port are provided with an opening in the fitting hole of the valve body with an axial gap, the supply port is connected to the compressed air source, and the load port is operated. A storage hydraulic oil in an oil tank in which the amount of stored hydraulic oil fluctuates due to the fact that the inside of the oil storage is closed and the storage hydraulic oil is sucked and discharged by a hydraulic pump and supplied to an external load, or the hydraulic oil recirculates from the external load. Connected to the upper space, the exhaust port is provided open to the outside air, and the valve body that switches the load port between the supply port and the exhaust port is slidably fitted in the fitting hole of the valve body in the axial direction. The pressure on the load port side is provided in the valve body in the axial direction so as to oppose the set pressure set based on its own weight. When the pressure on the load port side is lower than the set pressure, the valve body is connected to the load port. 1st position which communicates with the supply port and shuts off the exhaust port When the pressure on the load port side is higher than the set pressure, the valve body communicates the load port with the exhaust port to shut off the supply port, and when the pressure on the load port side is equal to the set pressure. Has a neutral position in which the valve element blocks between the ports.
A large spring force and a small spring force are provided in the valve body slidably fitted in the fitting hole of the valve body in the axial direction so as to oppose each other in the axial direction. The valve connects the load port to the supply port when the compressed air source is not supplying compressed air or when the load port side pressure is lower than the set pressure. A first position for shutting off the exhaust port and a second position for shutting off the supply port by connecting the load port to the exhaust port when the pressure on the load port side is higher than the set pressure; When the pressure and the set pressure are balanced with each other, the valve body may have a neutral position that blocks between the ports .
[0005]
[Action]
In such a configuration of the present invention, the spring force difference between a large spring force and a small spring force acting opposite to the own weight of the valve body or the axial direction of the valve body higher than the lower limit and higher than the lower limit of the predetermined pressure range in which the set pressure is desired to be maintained. set, the valve body is in a state of not supplying compressed air is positioned at the first position setting pressure based on the own weight or the spring force difference, when supplying compressed air from the compressed air source in this state, compressed air Flows through the load port from the supply port, is introduced into the space above the storage hydraulic oil inside the oil tank, applies preload inside, and continues to supply compressed air, so that the pressure on the load port side that applies preload inside is increased. When the pressure rises and the pressure equalizes with the set pressure, the valve body is switched from the first position to the neutral position to shut off between the ports, and the preload applied inside is controlled to the set pressure. When the hydraulic oil stored in the oil tank is sucked and discharged by the hydraulic pump and the amount of the stored hydraulic oil decreases, the internal preload decreases, and the pressure on the load port side becomes lower than the set pressure, the valve body moves from the neutral position. Switching to the first position causes the compressed air to flow from the supply port to the load port and to be introduced into the space inside the oil tank to increase the preload. When equilibrated, the valve element is switched from the first position to the neutral position to shut off between the ports. When the hydraulic oil is recirculated from the external load into the oil tank and the amount of the stored hydraulic oil increases, the internal preload increases, and the pressure on the load port side becomes higher than the set pressure, the valve body moves from the neutral position to the second position. Compressed air in the space above the stored hydraulic oil inside the oil tank flows from the load port to the exhaust port, exhausts to the outside air, and lowers the preload. When the pressure equalizes with the set pressure, the valve body is switched from the second position to the neutral position to shut off between the ports. For this reason, the valve body is switched from the neutral position to each position with the pressure on the load port side according to the rise and fall of the preload applied to the inside of the oil tank, and the inside of the sealed oil tank is suddenly increased in the amount of stored hydraulic oil. Since the pressure can always be maintained within a constant pressure range irrespective of the fluctuation, the conventional pressure detecting sensor and controller can be dispensed with and the cost can be reduced.
[0006]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In FIG. 1 (A), reference numeral 1 denotes an oil tank, which stores hydraulic oil therein to provide a space C on the stored hydraulic oil and hermetically seals the inside. Reference numeral 2 denotes a hydraulic pump, which is rotated by an electric motor 3 and sucks hydraulic oil stored in the oil tank 1 through a suction flow path 5 having a strainer 4 at one end, discharges the hydraulic oil to a discharge flow path 6, and discharges the hydraulic oil to a discharge flow path 6 (not shown). It is provided to supply to the load. Reference numeral 7 denotes a return flow passage which is provided so that hydraulic oil discharged from an external load is returned to the inside of the oil tank 1. Reference numeral 8 denotes a pressure control valve having a supply port P, a load port A, and an exhaust port E. The supply port P is connected to a compressed air source P1 through a supply flow path 9, and the load port A is connected to an oil source through a load flow path 10. The exhaust port E is connected to a space C on the storage hydraulic oil in the tank 1 and is opened to the outside air through an exhaust passage 12 having a silencer 11 at one end. Reference numeral 13 denotes an air filter with a drain discharger disposed in the supply flow path 9, and 14 denotes a pressure reducing valve with a relief disposed behind the air filter 13 with a drain discharger in the supply flow path 9. The secondary pressure is 0.05 MPa. (Mega Pascal) The set pressure is set so as to control the pressure reduction. Reference numeral 15 denotes an intake / exhaust safety valve having an intake valve 15A and an exhaust valve 15B. The intake / exhaust safety valve is disposed in a branch flow path 10A branched and connected to the load flow path 10, and a predetermined pressure to maintain the set pressure of the intake valve 15A inside the oil tank 1. Is set to -0.002 MPa, which is lower than the lower limit (0.0005 MPa) of the pressure range, and set to 0.003 MPa, which is higher than the upper limit (0.0025 MPa) of the constant pressure range in which the set pressure of the exhaust valve 15B is desired to be maintained. Provided.
[0007]
Hereinafter, the configuration of the pressure control valve 8 will be described with reference to FIG.
Reference numeral 16 denotes a valve body, which is disposed in the vertical direction in FIG. 1B, and has a sleeve member 18 having a fitting hole 17 provided therein. Reference numerals 19 and 20 denote lid members fixedly provided at both ends in the axial direction of the valve body 16, and close both end openings of the fitting hole 17. A supply port P, a load port A, and an exhaust port E are provided in the fitting hole 17 of the valve body 16 so as to be opened sequentially from the lower side thereof with a gap in the axial direction. Numeral 21 is a valve body which is slidably fitted in the fitting hole 17 in the axial direction, and has a gap in the axial direction between the land portions 21A and 21B so as to switch the load port A between the supply port P and the exhaust port E. It is provided. The valve body 21 is provided with a set pressure (0.0015 MPa) set based on its own weight, and a pressure on the load port A side is introduced into the lower end of the valve body 21 through the flow path 22 to oppose the set pressure. Provided. The upper end of the valve body 21 is connected to an exhaust port E via a flow path 23. When the pressure on the load port A side is lower than the set pressure, the pressure control valve 8 is in a first position X where the valve element 21 connects the load port A to the supply port P and shuts off the exhaust port E (FIG. 1A). When the pressure on the load port A side is higher than the set pressure, the valve element 21 communicates the load port A with the exhaust port E to shut off the supply port P (FIG. 1A). ), And when the pressure on the load port A side and the set pressure are pressure-balanced, the valve body 21 shuts off between the ports P, A, and E at the neutral position Z (in FIG. Shown).
[0008]
Next, the operation of this configuration will be described.
1A and 1B show a state in which compressed air is not supplied from the compressed air source P1, the pressure control valve 8 is located at the first position X at a set pressure based on the weight of the valve body 21, and The land 21A is located below the opening of the supply port P to the fitting hole 17, and the land 21B is between the opening of the load port A and the opening of the exhaust port E to supply the load port A. The exhaust port E is shut off by communicating with the port P.
[0009]
When compressed air is supplied from the compressed air source P1 in this state, the compressed air flows through the load port A from the supply port P, is introduced into the space C on the storage hydraulic oil inside the oil tank 1, and applies a preload therein. . When the pressure on the load port A side for applying a preload to the inside increases by continuing to supply the compressed air and the pressure equalizes with the set pressure (0.0015 MPa), the pressure control valve 8 moves the valve body 21 to the first position. The operation is switched from X to the neutral position Z and slides upward by the acting force based on the pressure on the load port A side that has risen, as shown in FIG. 2, and the land portion 21A closes the opening of the supply port P. At the same time, the land 21B closes the opening of the exhaust port E, and blocks the ports P, A, and E. Thus, the pre-pressure applied to the inside of the oil tank 1 is controlled to the set pressure.
[0010]
In a state where the preload in the oil tank 1 is controlled to the set pressure, the hydraulic pump 2 is driven to rotate by the electric motor 3 to suck and discharge the storage hydraulic oil in the oil tank 1 and supply it to the external load. The amount decreases rapidly and the internal preload decreases. Then, when the pressure on the load port A side becomes lower than the set pressure due to a decrease in the preload, the pressure control valve 8 is switched from the neutral position Z to the first position X so that the pressure control valve 8 returns to the state of FIG. When air flows through the load port A from the supply port P and is introduced into the space C inside the oil tank 1 to increase the preload, the pressure on the load port A side increases due to the increase in the preload, and the pressure is balanced with the set pressure. The body 21 is switched from the first position X to the neutral position Z, as shown in FIG. 2, and the ports P, A, and E are shut off.
[0011]
In addition, when the hydraulic oil discharged from the external load flows through the return flow path 7 and returns to the inside of the oil tank 1 in a state where the pre-pressure inside the oil tank 1 is controlled to the set pressure, the amount of the stored hydraulic oil rapidly increases. The internal preload rises. Then, when the pressure on the load port A side becomes higher than the set pressure due to the increase in the preload, the pressure control valve 8 switches the valve body 21 from the neutral position Z to the second position Y to increase the pressure on the load port A side. As shown in FIG. 3, the land portion 21A slides between the opening portion of the supply port P and the opening portion of the load port A, and the land portion 21B slides in the exhaust port E. , The load port A communicates with the exhaust port E to shut off the supply port P. Then, the compressed air in the space C inside the oil tank 1 flows from the load port A to the exhaust port E and is exhausted to the outside air to lower the preload. When the pressure is balanced with the pressure control valve 8, the valve body 21 is switched from the second position Y to the neutral position Z and slides downward with its own weight to set the set pressure, as shown in FIG. The ports P, A, and E are shut off.
[0012]
With this operation, the pressure control valve 8 moves the valve body 21 from the neutral position Z to each of the positions X and Y with the pressure on the load port A side according to the rise and fall of the preload in accordance with the increase and decrease of the stored working oil amount inside the oil tank 1. By switching, the inside of the sealed oil tank 1 is always constant regardless of the sudden change in the amount of stored hydraulic oil due to the suction and discharge of stored hydraulic oil by the hydraulic pump 2 and the return of hydraulic oil flowing through the return flow path 7. Can be maintained within the pressure range (0.0005 MPa to 0.0025 MPa), so that the conventional pressure detection sensor and controller can be eliminated and the cost can be reduced. Further, since the set pressure is set based on the own weight of the valve element 21, the number of parts can be reduced without requiring special members, as compared with the case where the set pressure is set by a spring force, a pilot pressure, an electromagnetic force, or the like. , Can be lower cost.
[0013]
FIG. 4 shows another embodiment of the present invention. The same parts as those in one embodiment are denoted by the same reference numerals, and description thereof will be omitted. Only different parts will be described.
In the pressure control valve 8A, the valve main body 16 is disposed in the lateral direction in FIG. 4, and a spring 24A having a large spring force and a spring 24B having a small spring force are accommodated at both axial ends of the valve body 21. , 24B are provided in opposition to each other, and a set pressure (0.0015 MPa) is set based on the difference between the springs 24A, 24B.
[0014]
In operation, FIG. 4 shows a state in which compressed air is not supplied, and the valve body 21 is at the left end at a set pressure based on the force difference between the springs 24A and 24B, and connects the load port A to the supply port P to connect to the exhaust port. It is located at a first position X (shown in FIG. 1A) that blocks E. Then, when the pressure on the load port A side for applying a preload to the inside of the oil tank by the supply of the compressed air rises and becomes equal to the set pressure, the valve body 21 slides rightward in FIG. From the neutral position Z to the neutral position Z with the pressure on the load port A side corresponding to the rise and fall of the preload accompanying the increase and decrease of the amount of stored working oil inside the oil tank, as in the embodiment. By switching between the positions X and Y, the inside of the oil tank 1 can be constantly maintained within a constant pressure range (0.0005 MPa to 0.0025 MPa) regardless of a sudden change in the amount of stored hydraulic oil. The pressure detection sensor and controller as described above can be eliminated, and the cost can be reduced. Further, since the set pressure is set based on the force difference between the springs 24A and 24B acting in the axial direction of the valve body 21, the set pressure is set based on the spring force acting in the axial direction on the pressure on the load port side of the valve body. As compared with the case where the set pressure is set and provided, the springs 24A and 24B themselves can have a sufficient wire diameter without reducing the spring force to set a very low set pressure of 0.0015 MPa. By sliding the valve body 21 in the axial direction over the period, it is possible to cope with the shearing force repeatedly acting on each of the springs 24A and 24B, and the durability can be improved. Further, since the set pressure is set based on the force difference between the springs 24A and 24B, the set pressure can be set regardless of the arrangement direction of the valve body 16 in which the valve body 21 is slidably fitted.
[0015]
【The invention's effect】
As described above, according to the present invention, the supply port, the load port, and the exhaust port are provided with an opening in the fitting hole of the valve body with an axial gap, the supply port is connected to the compressed air source, and the load port is connected to the load port. The operation of storing an oil tank in which the amount of stored hydraulic oil fluctuates due to the fact that the inside of storing hydraulic oil is sealed and the stored hydraulic oil is sucked and discharged by a hydraulic pump and supplied to an external load, or the hydraulic oil is recirculated from the external load. Connected to the space above the oil, the exhaust port is provided open to the outside air, and the valve body that switches the load port between the supply port and the exhaust port is slidably fitted in the fitting hole of the valve body in the axial direction. The pressure on the load port side is provided on the valve body to oppose the set pressure set based on the spring force difference between the large and small spring forces acting on its own weight or facing each other in the axial direction. If the pressure on the port side is lower than the set pressure, A first position in which the load port communicates with the supply port to shut off the exhaust port, and a first position in which the valve element communicates the load port with the exhaust port to shut off the supply port when the pressure on the load port side is higher than the set pressure. Since the valve has two positions and a neutral position where the valve element shuts off between the ports when the pressure on the load port side and the set pressure are in equilibrium, there is no need for a conventional pressure detection sensor and controller. And lower costs.
According to the first aspect of the present invention, since the set pressure is set based on the weight of the valve body, no special member for setting the set pressure is required, so that the number of parts can be reduced and the cost can be reduced. Has an effect that can be.
According to the second aspect, since the set pressure is set based on the spring force difference between the large spring force and the small spring force that are opposed to each other in the axial direction of the valve element, the low set pressure is set. Even if there is a spring, the wire diameter of each spring itself can be made sufficient without lowering the spring force, and it can cope with the shearing force that repeatedly acts on each spring by sliding the valve body in the axial direction for a long period of time, and it is durable Can be improved. Furthermore, there is an effect that the valve body can be slidably fitted without being restricted by the arrangement direction of the valve body.
[Brief description of the drawings]
FIG. 1 shows an embodiment of the present invention, in which (A) is a circuit diagram and (B) is a longitudinal sectional view of a pressure control valve.
FIG. 2 is a longitudinal sectional view showing an operation state of the pressure control valve of FIG. 1 (B).
FIG. 3 is a longitudinal sectional view of the pressure control valve showing an operation state different from that of FIG. 2;
FIG. 4 is a longitudinal sectional view of a pressure control valve showing another embodiment of the present invention.
FIG. 5 is a circuit diagram showing a conventional example.
[Explanation of symbols]
1 oil tank 2 hydraulic pump 8, 8A pressure control valve 16 valve body 17 fitting hole 21 valve body 24A, 24B spring C space P supply port A load port E exhaust port X first position Y second position Z neutral position

Claims

A supply port, a load port, and an exhaust port are provided in the fitting hole of the valve body with an opening in the axial direction with a gap therebetween, the supply port is connected to a compressed air source, and the load port is configured to store the inside of the working oil. Closed and connected to the space above the storage oil in the oil tank where the amount of storage hydraulic oil fluctuates by sucking and discharging the stored hydraulic oil with a hydraulic pump and supplying it to an external load, or the hydraulic oil is recirculated from the external load. The exhaust port is provided to be open to the outside air, and a valve body for switching the load port between the supply port and the exhaust port is fitted in the fitting hole of the valve body so as to be slidable in the axial direction. The pressure on the load port side is provided opposite to the set pressure set based on its own weight in the axial direction, and when the pressure on the load port side is lower than the set pressure, the valve communicates the load port with the supply port. Between the first position where the exhaust port is shut off When the force is higher than the set pressure, the valve body connects the load port to the exhaust port to shut off the supply port, and when the load port side pressure and the set pressure are balanced, the valve body is closed. A pressure control valve having a neutral position for shutting off between the ports.

A supply port, a load port, and an exhaust port are opened and provided with a gap in the axial direction to the fitting hole of the valve body, the supply port is connected to a compressed air source, and the load port is an interior for storing hydraulic oil. Closed and connected to the space above the storage oil in the oil tank where the amount of storage hydraulic oil fluctuates due to supply and discharge of the storage hydraulic oil to the external load by suctioning and discharging the storage hydraulic oil with the hydraulic pump The exhaust port is provided to be open to the outside air, and a valve body for switching and connecting the load port to the supply port and the exhaust port is provided in the fitting hole of the valve body so as to be slidable in the axial direction. In the axial direction, a large spring force and a small spring force are provided to oppose each other, and the pressure on the load port side is provided to oppose the set pressure set based on this spring force difference, and compressed air is supplied from the compressed air source. If not supplying and pressure set pressure of the load port side When the pressure is lower, the valve element connects the load port to the supply port to shut off the exhaust port, and when the pressure on the load port side is higher than the set pressure, the valve element connects the load port to the exhaust port. A pressure control valve having a second position for shutting off the supply port and a neutral position for shutting off between the ports when the pressure on the load port side and the set pressure are pressure-balanced.