JP3881842B2

JP3881842B2 - Variable displacement pump

Info

Publication number: JP3881842B2
Application number: JP2000370384A
Authority: JP
Inventors: 義治稲熊; 豪哉加藤; 強池田
Original assignee: JTEKT Corp
Current assignee: JTEKT Corp
Priority date: 2000-12-05
Filing date: 2000-12-05
Publication date: 2007-02-14
Anticipated expiration: 2020-12-05
Also published as: JP2002174185A

Description

本発明は、車両用動力舵取装置などに使用するのに適した可変容量形ポンプ、特にポンプの負荷圧に応じてポンプ吐出流量特性を制御するようにした可変容量形ポンプに関する。
【０００１】
【従来の技術】
このようなポンプの負荷圧に応じてポンプ吐出流量特性を制御するようにした可変容量形ポンプとしては、特公平２−６１６３８号公報に開示された技術がある。これは、ベーンポンプのロータ中心に対する偏心量が可変となるようにボデーに支持したカムリングをスプリングにより偏心方向に付勢するとともに、吐出通路に設けたオリフィス前後の差圧により作動するピストンのロッドをスプリングに抗してカムリングを移動させる向きに当接させ、また、吐出通路に設けたオリフィス前側の内圧に応動する切換弁により高圧（内圧）または低圧が選択的に導入される油圧ピストンにより、カムリングを直接付勢している前記スプリングの初期荷重を変化させている。この技術によれば、ポンプ回転速度が増大してポンプ吐出流量がある限度値に達すればポンプ回転速度がそれより増大してもポンプ吐出流量はそれより増大しないようにポンプの回転数に応じたポンプ吐出流量特性の制御を行い、また、このポンプ吐出流量の限度値が負荷圧の増大に応じて増大するように負荷圧に応じたポンプ吐出流量特性の制御を行うことができる。動力舵取装置に使用する場合は、負荷圧の増減に応じてこの吐出流量の限度値が増減するようにポンプ吐出流量特性を制御すれば、直進走行などの動力舵取装置が作動しておらず従ってポンプからの吐出流量が不要な状態におけるポンプ吐出流量の最大値が減少するので、動力舵取装置の作動に影響を与えることなく省エネルギ効果を得ることができる。
【０００２】
【発明が解決しようとする課題】
しかしながら、上述したような特公平２−６１６３８号公報の技術では、負荷圧が所定値を越えると、先ずバルブのスプールがスプリングの付勢力に抗して摺動されて油路が切替えられ、これにより油圧ピストンを収納したシリンダに圧油が導入されて油圧ピストンが摺動され、その結果カムリングに作用するスプリングの初期荷重を変化させるようにしている。
【０００３】
従って、スプリング力の変化がカムリングに直接及ぼされるので、カムリングの作動が不安定になる問題があり、しかも、負荷圧の上昇に対してポンプ吐出流量を増加させる応答性を高くできない問題があった。
【０００４】
本発明は、差圧制御バルブに作用するスプリングによる押付力を負荷圧の上昇に応じて増大させるようにしてこのような問題を解決することを目的とする。
【０００５】
【課題を解決するための手段】
請求項１の発明による可変容量形ポンプは、ハウジング内に径方向移動可能に設けられたカムリングと、このカムリング内でハウジングに回転可能に支持され同カムリングの内面と摺動可能に当接する複数のベーンを放射方向に移動可能に保持するロータと、ハウジングまたはこれに固定された部材に形成された吸入ポートおよび吐出ポートと、吐出ポートを吐出口に連通する吐出通路の途中に設けたオリフィスを有し、カムリングの外周に同カムリングの移動方向において互いに対向する第１作用室と第２作用室を形成し、カムリングをロータに対する偏心量が最大となる第１作用室側に弾性的に付勢してなる可変容量形ポンプにおいて、ハウジングに形成した弁孔内に第１および第２作用室に作用する各圧力を制御する差圧制御バルブと負荷圧感応スプールを同軸上にそれぞれ軸線方向移動可能に嵌合して同差圧制御バルブと負荷圧感応スプールの間にバルブ押付用スプリングを介装し、負荷圧感応スプールは負荷圧の上昇に応じて摺動されてバルブ押付用スプリングの初期荷重を増大させるよう構成してなるものである。
【０００６】
この発明では、差圧制御バルブを付勢するバルブ押付用スプリングの初期荷重は負荷圧の上昇に応じて増大されるので、差圧制御バルブがこの押付力に抗して移動されるようになるときの差圧も増大し、従ってカムリング両側の各作用室にこの差圧が導入されてカムリングの偏心量が減少し始めるときのポンプ回転速度も増大するので吐出流量がそれ以上増大しなくなるときの吐出流量の限度値も負荷圧の上昇に応じて増大する。
【０００７】
請求項２の発明は、請求項１の発明において、差圧制御バルブの両端とハウジングの間にそれぞれ内圧作用室と負荷圧作用室を形成して負荷圧感応スプールおよびバルブ押付用スプリングは負荷圧作用室内に配置し、差圧制御バルブが内圧作用室側に押し付けられているときは第１作用室に低い圧力を導入するとともに負荷圧作用室側に移動すれば同第１作用室に内圧を導入し、第２作用室には負荷圧を導入するよう構成したものである。
【０００８】
請求項３の発明は、請求項２の発明において、負荷圧作用室となる弁孔を差圧制御バルブ側が小径で反対側が大径となる段付き孔に形成し、負荷圧感応スプールはこの小径と大径の両部分に摺動可能に嵌合し、負荷圧は負荷圧感応スプールの軸線方向両側に導入したものである。
【０００９】
請求項４の発明による可変容量形ポンプは、ハウジング内に径方向移動可能に設けられたカムリングと、このカムリング内で前記ハウジングに回転可能に支持され同カムリングの内面と摺動可能に当接する複数のベーンを放射方向に移動可能に保持するロータと、前記ハウジングまたはこれに固定された部材に形成された吸入ポートおよび吐出ポートと、前記吐出ポートを吐出口に連通する吐出通路の途中に設けたオリフィスを有し、前記カムリングの外周に同カムリングの移動方向において互いに対向する第１作用室と第２作用室を形成し、前記カムリングを前記ロータに対する偏心量が最大となる前記第１作用室側に弾性的に付勢してなる可変容量形ポンプにおいて、前記ハウジングに形成した弁孔内に設けられて前記第１および第２作用室に作用する各圧力を制御する差圧制御バルブは、軸線方向摺動可能に前記弁孔に嵌合された筒状部と、この筒状部の内孔内に軸線方向摺動可能に嵌合されて一端部に前記内孔より大径のスプリング受けが固着された負荷圧感応部よりなり、また前記スプリング受けと前記ハウジングの間にバルブ押付用スプリングを介装し、前記負荷圧感応部は負荷圧の上昇に応じて筒状部に対し前記一端部方向に摺動されて前記バルブ押付用スプリングの初期荷重を増大させるよう構成してなるものである。
【００１０】
この発明でも、差圧制御バルブを付勢するバルブ押付用スプリングの初期荷重は負荷圧の上昇に応じて増大されるので、差圧制御バルブがこの押付力に抗して移動されるようになるときの差圧も増大し、従ってカムリング両側の各作用室にこの差圧が導入されてカムリングの偏心量が減少し始めるときのポンプ回転速度も増大するので吐出流量がそれ以上増大しなくなるときの吐出流量の限度値も負荷圧の上昇に応じて増大する。
【００１１】
請求項５の発明は、請求項４の発明において、差圧制御バルブの両端とハウジングの間にそれぞれ内圧作用室と負荷圧作用室を形成してバルブ押付用スプリングは負荷圧作用室内に配置し、差圧制御バルブは内圧作用室側に押し付けられているときは第１作用室に低い圧力を導入するとともに負荷圧作用室側に移動すれば同第１作用室に内圧を導入し、第２作用室には負荷圧を導入するよう構成したものである。
【００１２】
また請求項６の発明は、請求項４または請求項５の発明において、筒状部の内孔はスプリング受け側が小径で反対側が大径となる段付き孔に形成し、負荷圧感応部はこの小径と大径の両部分に摺動可能に嵌合し、筒状部と負荷圧感応部の間には自由状態ではスプリング受けを筒状部の一端に当接させるバルブスプリングを介装し、筒状部の他端部は自由状態ではハウジングまたはこれに固定された部材に当接し、負荷圧が増大すればその増大に応じて負荷圧感応部に固着されたスプリング受けが筒状部から離れる向きに移動するよう構成したものである。
【００１３】
請求項７の発明は、請求項１〜請求項６の発明において、オリフィスをカムリングが第２作用室側に移動するにつれて開口面積が減少する可変オリフィスとしたものである。
【００１４】
【発明の実施の形態】
先ず図１〜図４に示す第１の実施の形態の説明をする。この実施の形態の可変容量形ポンプは動力舵取装置の作動流体供給源として使用するものであり、エンドカバー１１により液密に覆われたハウジング１０と、ハウジング１０内に設けられてポンプ軸２６により回転駆動されるロータ２２および径方向に移動可能なカムリング２１を有するベーンポンプ部２０と、カムリング２１の移動を制御する差圧制御バルブ３１と、ベーンポンプ部２０の吐出通路５３ａ，５３ｂ，５３ｃの途中に設けられた可変オリフィス５４を主な構成部材としている。
【００１５】
図１および図２に示すように、ハウジング１０とこれにねじ止め固定されたエンドカバー１１には、ポンプ軸２６の中間部および後端部がそれぞれ軸受を介して回転自在に支持されている。ポンプ軸２６と同軸的にハウジング１０に形成された円筒状の内面１０ａには、奥側に円盤状のサイドプレート１２が、また手前側に筒状のアダプタ１３が、何れも回転しないように嵌合支持され、これらエンドカバー１１とサイドプレート１２とアダプタ１３の間には次に述べるベーンポンプ部２０が設けられている。ハウジング１０から突出するポンプ軸２６の先端にはエンジンからの動力が伝達されるＶプーリ２９が固定されている。
【００１６】
ベーンポンプ部２０は、アダプタ１３内に設けられたカムリング２１と、ポンプ軸２６の中間部に同軸的にスプライン結合されたロータ２２と、ロータ２２に形成された複数の半径方向スリットに摺動自在に保持されてカムリング２１の円筒状の内面に常に当接されているベーン２３よりなり、これら各部材２１〜２３の側面はエンドカバー１１およびサイドプレート１２の端面に摺動可能に当接されている。ベーンポンプ部２０の吸入ポート２４はエンドカバー１１の端面に形成され、吸入通路１４および吸入口１５を介してリザーバ６１からの作動流体が供給されている。また吐出ポート２５はサイドプレート１２の端面に形成され、裏側に位置する圧力室１６から、後述する可変オリフィス５４を途中に設けた吐出通路５３ａ，５３ｂ，５３ｃを通って、ハウジング１０に形成された吐出口５５に導かれている。
【００１７】
ポンプ軸２６と平行に設けられて両端がエンドカバー１１およびサイドプレート１２に支持されたピン１７は、中間部の外周の一部がアダプタ１３の内面と係合されている。カムリング２１は、外周面の一部に形成した凹部２１ａがピン１７に係合されてピン１７を中心として揺動することによりカムリング２１の径方向に移動可能であり、カムリング２１の外周面の凹部２１ａと反対側となる部分は、アダプタ１３の内面に形成した溝内に設けられてゴムによりバックアップされたテフロンのシール部材５０により摺動自在にシールされている。アダプタ１３とカムリング２１の間には、このピン１７とシール部材５０により、カムリング２１の移動方向において互いに対向する第１作用室５１ａと第２作用室５１ｂが形成されている。
【００１８】
カムリング２１の移動方向で第２作用室５１ｂ側となるハウジング１０には、ポンプ軸２６方向に向かう円筒孔１０ｂが形成され、この円筒孔１０ｂに摺動自在に嵌合支持されたカム押付ピストン２７は、円筒孔１０ｂの開口端に液密にねじ込み固定されたプラグ１８Ａとの間に介装されたカム押付用スプリング２８によりポンプ軸２６方向に付勢されている。このカム押付ピストン２７の先端の突起部２７ａはアダプタ１３を隙間をおいて通り抜けてカムリング２１の外周面に当接し、カムリング２１をロータ２２に対する偏心量が最大となる第１作用室５１ａ側に弾性的に付勢している。
【００１９】
可変オリフィス５４は、カム押付ピストン２７の環状溝２７ｃの縁部と吐出通路５３ｂ一端の開口部により形成され、カムリング２１が第２作用室５１ｂ側に移動してカム押付ピストン２７がカム押付用スプリング２８に抗して後退するにつれて吐出通路５３ｂがカム押付ピストン２７の環状溝２７ｃの縁部により次第に塞がれて開口面積が減少するようになっている。ベーンポンプ部２０からの作動流体は吐出通路５３ａ，５３ｂから可変オリフィス５４を通り、吐出通路５３ｃを通って吐出口５５から吐出される。この可変容量形ポンプが作動して作動流体が流れている状態では、可変オリフィス５４の前後で圧力が降下して差圧が生じ、可変オリフィス５４の後側の吐出通路５３ｃおよび吐出口５５内の圧力は作動流体供給先の機器の作動状態により与えられる負荷圧であり、可変オリフィス５４の前側の吐出通路５３ａ，５３ｂおよび圧力室１６内の圧力はポンプの内圧である。この内圧は可変オリフィス５４による差圧の分だけ負荷圧より大であり、従って負荷圧が変動すれば内圧もそれと同じように変動する。通常の作動状態では、この差圧は内圧または負荷圧に比してかなり小さい値である。
【００２０】
主として図１に示すように、ポンプ軸２６と立体的に直交するようにハウジング１０に形成されて右側が開口された弁孔３０には、奥側に差圧制御バルブ３１が、開口側に負荷圧感応スプール４５が同軸上にそれぞれ軸線方向移動自在に嵌合支持され、弁孔３０の開口端はプラグ１９Ａをねじ込んで液密に閉じられ、差圧制御バルブ３１と負荷圧感応スプール４５の間にはバルブ押付用スプリング３３Ａが介装されている。差圧制御バルブ３１の両端とハウジング１０の間にそれぞれ形成される各作用室５２ａ，５２ｂは、プラグ１９Ａ側となる作用室５２ｂが連通孔５９Ａを介して吐出口５５から負荷圧が導入される負荷圧作用室であり、反対側の作用室５２ａがポンプ内圧導入路５６を介して圧力室１６から内圧が導入される内圧作用室である。
【００２１】
負荷圧感応スプール４５とバルブ押付用スプリング３３Ａは負荷圧作用室５２ｂ内に位置しており、負荷圧感応スプール４５にはその両端面を連通する中心孔が形成されている。弁孔３０の負荷圧作用室５２ｂとなる部分は、差圧制御バルブ３１側が小径で、プラグ１９Ａ側となる反対側が大径となる段付き孔に形成され、負荷圧感応スプール４５はこの小径と大径の両部分に摺動可能に嵌合されている。弁孔３０と負荷圧感応スプール４５の間で段付き部となる位置に形成される環状の空間は連通管路６０を介して常にリザーバ６１に連通されている。
【００２２】
内圧作用室５２ａ側となるハウジング１０の一部に形成した導入路５７ａは、差圧制御バルブ３１の移動により、せ１２リザーバ６１と内圧作用室５２ａに選択的に連通されるものである。この導入路５７ａは、差圧制御バルブ３１がバルブ押付用スプリング３３Ａにより内圧作用室５２ａ側の末端位置まで押し付けられた不作動状態では内圧作用室５２ａと連通されないが、差圧制御バルブ３１がバルブ押付用スプリング３３Ａに抗して負荷圧作用室５２ｂ側に移動し始めればすぐに内圧作用室５２ａと連通される位置において弁孔３０に開口され、この導入路５７ａはアダプタ１３に形成したダンピングオリフィス５８ａを介してカムリング２１の外周一側の第１作用室５１ａに連通されている。また差圧制御バルブ３１に形成された連通路３２Ａは、導入路５７ａが内圧作用室５２ａと連通されていない状態では導入路５７ａと連通されるが、差圧制御バルブ３１が負荷圧作用室５２ｂ側に移動し始めて導入路５７ａが内圧作用室５２ａと連通されるようになればすぐに導入路５７ａと連通されなくなるものである。この連通路３２Ａは連通管路６０を介して常にリザーバ６１に連通されている。
【００２３】
負荷圧作用室５２ｂ側となるハウジング１０の一部に形成した負荷圧導入路５７ｂは、常に負荷圧作用室５２ｂ内に開口する位置において弁孔３０に開口され、この負荷圧導入路５７ｂはアダプタ１３に形成したオリフィス５８ｂを介してカムリング２１の外周他側の第２作用室５１ｂに連通されている。また差圧制御バルブ３１内には、負荷圧が過度に増大した場合に負荷圧作用室５２ｂ内の圧力をリザーバ６１にレリーフし、差圧制御バルブ３１を負荷圧作用室５２ｂ側に移動させてポンプ吐出流量を最小にするパイロットレリーフ弁６５が設けられている。
【００２４】
弁孔３０と嵌合される段付きの負荷圧感応スプール４５は、バルブ押付用スプリング３３Ａ側の断面積よりもプラグ１９Ａ側の断面積の方が大であるので、負荷圧作用室５２ｂ内の負荷圧が０または低い状態では、図１および図４(a) に示すようにプラグ１９Ａに当接されているが、負荷圧が所定値より増大すれば図４(b) に示すように差圧制御バルブ３１側に移動し、バルブ押付用スプリング３３Ａを圧縮してその初期荷重を増大させる。これにより、両端の各作用室５２ａ，５２ｂに作用する内圧と負荷圧の差圧により差圧制御バルブ３１に与えられる右向きの力に抗して差圧制御バルブ３１を内圧作用室５２ａ側に向けて付勢するバルブ押付用スプリング３３Ａの押付力は、負荷圧の増大による負荷圧感応スプール４５の移動により増大する。
【００２５】
Ｖプーリ２９に掛けた駆動ベルトを介して車両のエンジンの回転がポンプ軸２６に伝達されてベーンポンプ２０のロータ２２が回転されれば、リザーバ６１内の作動流体は吸入口１５および吸入通路１４から吸入ポート２４を介してベーンポンプ部２０の各ベーン２３の間に吸入され、吐出ポート２５から圧力室１６内に吐出され、可変オリフィス５４を設けた吐出通路５３ａ，５３ｂ，５３ｃを通って吐出口５５から動力舵取装置などの機器に供給される。
【００２６】
ポンプ回転速度が小さいときは吐出通路５３ａ，５３ｂ，５３ｃを通る流量が少なく、従って可変オリフィス５４前後の差圧が小さいので、差圧制御バルブ３１は、図１に示すように、バルブ押付用スプリング３３Ａにより内圧作用室５２ａ側末端位置に押し付けられており、第１作用室５１ａは導入路５７ａおよび連通路３２Ａを介してリザーバ６１側に連通され、カムリング２１はカム押付用スプリング２８により吐出流量が最大となる第１作用室５１ａ側に押し付けられている。この状態では、吐出通路５３ａ，５３ｂ，５３ｃを介して吐出口５５から吐出される作動流体の吐出流量は、図３の特性Ａに示すように、ポンプ回転速度の増大にともない急激に増大する。
【００２７】
ポンプ回転速度の増大により吐出流量が増大して可変オリフィス５４前後の差圧が増大すれば、内圧作用室５２ａ内の内圧と負荷圧作用室５２ｂ内の内圧の差圧により差圧制御バルブ３１を負荷圧作用室５２ｂ側に移動させようとする力も増大する。負荷圧が低い状態（ハンドルが操作されていない状態）においては、図４(a) に示すように、バルブ押付用スプリング３３Ａの付勢力により差圧制御バルブ３１と負荷圧感応スプール４５がそれぞれの摺動端に保持され、バルブ押付用スプリング３３Ａは最大に伸びた状態にある。
【００２８】
従って、比較的小さいポンプ吐出流量によって発生する可変オリフィス５４前後の差圧によって差圧制御バルブ３１が作動し始め、第１作用室５１ａはリザーバ６１側から内圧作用室５２ａ側に連通されるようになる。これにより、それまでは吐出流量が最大となる第１作用室５１ａ側に当接されていたカムリング２１は、ポンプ回転速度の上昇に応じて可変オリフィス５４前後の差圧を一定に維持すべく偏心量が減少されるようになり、吐出流量特性は、図３の特性Ｂに示すように、低流量に保持され、省エネルギを達成する。
【００２９】
なおカムリング２１の偏心量の減少にともない、可変オリフィス５４の絞り面積が縮小されるため、ポンプ回転速度の増大に応じてポンプ吐出流量が減少される。
【００３０】
しかる状態において、ハンドル操作によって負荷圧が上昇すると、図４(b) に示すように、受圧面積差を持つ負荷圧感応スプール４５がバルブ押付用スプリング３３Ａの付勢力に抗して摺動される。これにより差圧制御バルブ３１に作用するバルブ押付用スプリング３３Ａによるばね加重が増大され、可変オリフィス５４前後の差圧が大きくならないと、すなわち、ポンプ吐出流量が増大しないと、第１作用室５１ａがリザーバ６１側より内圧作用室５２ａ側に切り替えられない。従って、吐出流量は、図３の特性Ｃに示すように、ハンドル操作をアシストするに必要な流量に保持される。
【００３１】
ここにおいて、負荷圧の増減による差圧制御バルブ３１に作用するバルブ押付用スプリング３３Ａの変化がカムリング２１に直接及ぼされることがないので、カムリング２１の作動の安定性は高いものとなる。また負荷圧の増減に対する吐出流量特性の増減は、負荷圧の上昇に応じてバルブ押付用スプリング３３Ａによる押付力が増大して作動状態が変化する差圧制御バルブ３１により第１および第２作用室５１ａ，５１ｂに作用する各圧力を直接制御することによりカムリング２１の偏心量を変化させて行っているので、負荷圧の増減に対する吐出流量特性の増減の応答性も向上する。
【００３２】
なおこの第１の実施の形態では、負荷圧感応スプール４５に中心孔を設けて負荷圧感応スプール４５両側に導入される負荷圧が同一となるようにしたが、ハウジング１０内に連通路を形成して負荷圧感応スプール４５両側の負荷圧が同一となるようにしてもよい。
【００３３】
次に図５により、第２の実施の形態の説明をする。この第２の実施の形態の可変容量形ポンプは、各作用室５２ａ，５２ｂに作用する内圧と負荷圧の差圧により差圧制御バルブ３５に与えられる右向きの力に抗して差圧制御バルブ３５を内圧作用室５２ａ側に向けて付勢する押付力を発生させるための構造が、バルブ押付用スプリング３３Ｂとその初期荷重を変化させる差圧制御バルブ３５の負荷圧感応部３７よりなっている点が第１の実施の形態と相違しており、その他の構成は同一であるので、主としてこの相違点につき説明する。
【００３４】
図５に示すように、左側が開口側となるようにハウジング１０に形成された弁孔３０には、複数の部分よりなる差圧制御バルブ３５が挿入され、弁孔３０の開口端はプラグ１９Ｂをねじ込んで液密に閉じられている。差圧制御バルブ３５の両端とハウジング１０の間にそれぞれ形成される各作用室５２ａ，５２ｂは、プラグ１９Ｂ側となる作用室５２ａがポンプ内圧導入路５６を介して圧力室１６から内圧が導入される内圧作用室であり、反対側となる作用室５２ｂが連通孔５９Ｂを介して吐出口５５から負荷圧が導入される負荷圧作用室である。
【００３５】
差圧制御バルブ３５は、軸線方向摺動可能に弁孔３０に嵌合された筒状部３６と、この筒状部３６の内孔内に軸線方向摺動可能に嵌合されて負荷圧作用室５２ｂ側となる端部に内孔より大径のスプリング受け３７ａが固着された負荷圧感応部３７と、筒状部３６とスプリング受け３７ａの対向する端面が互いに当接される向きに両部材３６，３７を付勢するバルブスプリング３８により構成されている。筒状部３６の内孔はスプリング受け３７ａ側が小径で反対側が大径となる段付き孔に形成され、これにより、筒状部３６は、図５に示すように、ポンプ内圧作用室５２ａ側の断面積よりも負荷圧作用室５２ｂ側の断面積の方が大であるように構成されており、一方、負荷圧感応部３７はこの小径と大径の両部分に摺動可能に嵌合され、これにより、負荷圧感応部３７は、図５に示すように、負荷圧作用室５２ｂ側の断面積よりもポンプ内圧作用室５２ａ側の断面積の方が大であるように構成されており、バルブスプリング３８はこの両部材３７，３８の間に形成される環状の空間内に位置して、各部材３７，３８に形成され段部の間に介装されている。この環状の空間は連通管路６０を介して常にリザーバ６１に連通されている。
【００３６】
差圧制御バルブ３５は、負荷圧作用室５２ｂ側となる弁孔３０の内端部とスプリング受け３７ａの間に介装したバルブ押付用スプリング３３Ｂにより、内圧作用室５２ａ側に向けて付勢されており、自由状態では図５(a) に示すように、筒状部３６と負荷圧感応部３７の対向する端面は互いに当接され、筒状部３６と負荷圧感応部３７の内圧作用室５２ａ側となる端面はそれぞれプラグ１９Ｂの円筒部の先端面と内底面にほゞ同時に当接されるようになっている。プラグ１９Ｂの円筒部の先端部には、筒状部３６が当接した状態でもこの円筒部の内外を連通する小孔１９ａが形成されている。なお負荷圧感応部３７の端面は、自由状態においてプラグ１９Ｂの内底面から浮き上がっていても差し支えない。
【００３７】
第１の実施の形態と同様、差圧制御バルブ３５の筒状部３６には前述した環状の空間および連通管路６０を介して常にリザーバ６１に連通される連通路３２Ｂが設けられ、これにより第１作用室５１ａに連通される導入路５７ａは、差圧制御バルブ３５の筒状部３６の移動によりリザーバ６１と内圧作用室５２ａに選択的に連通される。第２作用室５１ｂに連通される負荷圧導入路５７ｂは常に負荷圧作用室５２ｂに連通され、またスプリング受け３７ａにはパイロットレリーフ弁６５が設けられている。
【００３８】
差圧制御バルブ３５の負荷圧感応部３７は、小径部と大径部よりなる筒状部３６の内孔に嵌合されているので、負荷圧および内圧が０から上昇して所定値を越えれば、図５(b) に示すように、バルブスプリング３８が圧縮されて筒状部３６とスプリング受け３７ａの対向する端面は離れるが、筒状部３６は、前記したようにポンプ内圧作用室５２ａ側の断面積よりも負荷圧作用室５２ｂ側の断面積の方が大であるため、筒状部３６には図５において左向きの力が与えられ、筒状部３６の内圧作用室５２ａ側となる端面はプラグ１９Ｂの円筒部の先端面に当接されており、負荷圧感応部３７は、前記したように負荷圧作用室５２ｂ側の断面積よりもポンプ内圧作用室５２ａ側の断面積の方が大であるため、負荷圧感応部３７が負荷圧作用室５２ｂ側に移動し、これによりスプリング受け３７ａとハウジング１０の間に介装されたバルブ押付用スプリング３３Ｂを圧縮してその初期荷重を増大させる。これにより、両端の各作用室５２ａ，５２ｂに作用する内圧と負荷圧の差圧により差圧制御バルブ３５に与えられる右向きの力に抗して差圧制御バルブ３５を内圧作用室５２ａ側に向けて付勢するバルブ押付用スプリング３３Ｂの押付力は、負荷圧および内圧が増大するにつれて次第に増大する。
【００３９】
この第２の実施の形態でも、ポンプ回転速度が低い状態では可変オリフィス５４（図５に記載のない符号は全て図１と同じ）前後の差圧が小さいので、差圧制御バルブ３５は、図５(a) に示すように、バルブ押付用スプリング３３Ｂにより内圧作用室５２ａ側末端位置に押し付けられ、筒状部３６とスプリング受け３７ａはバルブスプリング３８により当接されており、第１作用室５１ａにはリザーバ６１からの低圧が導入され、カムリング２１はカム押付用スプリング２８により吐出流量が最大となる第１作用室５１ａ側に押し付けられている。従って、図３の特性Ａに示すように、ポンプ吐出流量はポンプ回転速度の増大にともない急激に増大する。
【００４０】
ポンプ回転速度の増大により吐出流量が増大して可変オリフィス５４前後の内圧と負荷圧の差圧が増大すれば、差圧制御バルブ３５を負荷圧作用室５２ｂ側に移動させようとする力も増大し、バルブ押付用スプリング３３Ｂにより与えられる押付力を越えれば差圧制御バルブ３５は負荷圧作用室５２ｂ側に向かって移動し始める。そして導入路５７ａが連通路３２Ｂから遮断されて第１作用室５１ａに連通されるようになれば、第１作用室５１ａには可変オリフィス５４より前側の内圧が導入されるので、第１の実施の形態と同様、そのときの負荷圧に応じて、図３の特性Ｂ，Ｃに示すように、ポンプ回転速度が増大しても吐出流量はある限度値以上には増大しないようになる。これにより、ポンプの回転数に応じたポンプ吐出流量特性の制御は行われる。なお、この第２の実施の形態でも、ポンプ吐出流量の減少に応じて、可変オリフィス５４の開口面積は減少するので、ポンプ回転速度が増大するにつれてポンプ吐出流量が減少するという、動力舵取装置に適した特性の可変容量形ポンプが得られる。
【００４１】
また負荷圧および内圧が増大すれば、前述のように、差圧制御バルブ３５を内圧作用室５２ａ側に向けて付勢するバルブ押付用スプリング３３Ｂの押付力も増大する。従って第１の実施の形態と同様、図３の特性Ａに示ように可変容量形ポンプが作動している状態において、負荷圧および内圧が低ければ、ポンプ回転速度が、従ってポンプ吐出流量が比較的少ないうちに差圧制御バルブ３５は負荷圧作用室５２ｂ側に移動し始め、導入路５７ａが内圧作用室５２ａに連通されてカムリング２１の偏心量が減少し始めるので、図３の特性Ｂに示ようにポンプ吐出流量がそれ以上とならない限度値は低くなる。これに対し負荷圧および内圧が高くなれば、ポンプ回転速度が、従ってポンプ吐出流量が多くなってから差圧制御バルブ３５は負荷圧作用室５２ｂ側に移動し始め、導入路５７ａが内圧作用室５２ａに連通されてカムリング２１の偏心量が減少し始めるようになるので、ポンプ吐出流量がそれ以上とならない限度値は高くなる。吐出圧および内圧が上昇するにつれてこの限度値は上昇して、負荷圧感応部３７が筒状部３６に対するストロークエンドに達すれば特性Ｃに示すように吐出流量の限度値は最大となり、それ以上ポンプ吐出流量の限度値が大きくなることはなくなる。これにより、負荷圧に応じたポンプ吐出流量特性の制御は行われる。
【００４２】
この第２の実施の形態でも、負荷圧の増減による差圧制御バルブ３１に作用するバルブ押付用スプリング３３Ｂの変化がカムリング２１に直接及ぼされることがないので、カムリング２１の作動の安定性は高いものとなる。また負荷圧の増減に対する吐出流量特性の増減は、負荷圧の上昇に応じてバルブ押付用スプリング３３Ｂによる押付力が増大して作動状態が変化する差圧制御バルブ３１により第１および第２作用室５１ａ，５１ｂに作用する各圧力を直接制御することによりカムリング２１の偏心量を変化させて行っているので、負荷圧の増減に対する吐出流量特性の増減の応答性も向上する。
【００４３】
なお上記各実施の形態では、カムリング２１の径方向移動をピン１７を中心とする揺動により行っているが、本発明はこれに限らず、ピン１７とシール部材５０に相当する位置においてカムリング２１をアダプタ１３の内面に液密かつ径方向摺動可能に案内支持するようにして実施することも可能である。
【００４４】
【発明の効果】
本発明によれば、カムリングの外周に対向して形成した第１および第２作用室に作用する各圧力を制御する差圧制御バルブに作用するバルブ押付用スプリングの初期荷重を負荷圧の上昇に応じて増大させることにより負荷圧に応じたカムリングの偏心量の調整を行っているので、カムリングの作動の安定性を高めることができ、また負荷圧の増減に対する吐出流量特性の増減の応答性を向上させることができる。
【図面の簡単な説明】
【図１】本発明による可変容量形ポンプの第１の実施形態の全体構造を示す横断面図である。
【図２】図１の２−２断面図である。
【図３】本発明による可変容量形ポンプのポンプ吐出流量特性を示す図である。
【図４】図１に示す第１の実施形態の作動状態を説明する部分断面図である。
【図５】本発明による可変容量形ポンプの第３の実施形態の要部および作動状態を示す部分断面図である。
【符号の説明】
１０…ハウジング、２１……カムリング、２２…ロータ、２３…ベーン、２４…吸入ポート、２５…吐出ポート、３０…弁孔、３１，３５…差圧制御バルブ、３３Ａ，３３Ｂ…バルブ押付用スプリング、３６…筒状部、３７…負荷圧感応部、３７ａ…スプリング受け、３８…バルブスプリング、４５…負荷圧感応スプール、５１ａ…第１作用室、５１ｂ…第２作用室、５２ａ…内圧作用室、５２ｂ…負荷圧作用室、５３ａ，５３ｂ，５３ｃ…吐出通路、５４…オリフィス（可変オリフィス）、５５…吐出口。The present invention relates to a variable displacement pump suitable for use in a power steering apparatus for vehicles, and more particularly to a variable displacement pump configured to control a pump discharge flow rate characteristic according to a load pressure of the pump.
[0001]
[Prior art]
As a variable displacement pump configured to control the pump discharge flow rate characteristic according to the load pressure of such a pump, there is a technique disclosed in Japanese Patent Publication No. 2-61638. This is because the cam ring supported by the body is urged in the eccentric direction by the spring so that the amount of eccentricity with respect to the rotor center of the vane pump is variable, and the piston rod operated by the differential pressure across the orifice provided in the discharge passage is spring-loaded. The cam ring is brought into contact with the direction in which the cam ring is moved against the pressure, and the hydraulic ring is selectively introduced with high pressure (internal pressure) or low pressure by a switching valve that responds to the internal pressure in front of the orifice provided in the discharge passage. The initial load of the spring that is directly biased is changed. According to this technique, if the pump rotation speed increases and the pump discharge flow rate reaches a certain limit value, the pump discharge flow rate does not increase even if the pump rotation speed increases beyond that. The pump discharge flow rate characteristic can be controlled, and the pump discharge flow rate characteristic can be controlled according to the load pressure so that the limit value of the pump discharge flow rate increases as the load pressure increases. When used in a power steering device, if the pump discharge flow rate characteristic is controlled so that the limit value of the discharge flow rate increases / decreases according to the increase / decrease of the load pressure, the power steering device such as straight running will not operate. Therefore, since the maximum value of the pump discharge flow rate in a state where the discharge flow rate from the pump is unnecessary is reduced, an energy saving effect can be obtained without affecting the operation of the power steering apparatus.
[0002]
[Problems to be solved by the invention]
However, in the technique disclosed in Japanese Patent Publication No. 2-61638 as described above, when the load pressure exceeds a predetermined value, the valve spool is first slid against the urging force of the spring to switch the oil passage. As a result, pressure oil is introduced into the cylinder containing the hydraulic piston and the hydraulic piston is slid, and as a result, the initial load of the spring acting on the cam ring is changed.
[0003]
Therefore, since the change of the spring force is directly applied to the cam ring, there is a problem that the operation of the cam ring becomes unstable, and there is a problem that the responsiveness to increase the pump discharge flow rate cannot be increased with respect to the increase of the load pressure. .
[0004]
An object of the present invention is to solve such a problem by increasing a pressing force by a spring acting on a differential pressure control valve in accordance with an increase in load pressure.
[0005]
[Means for Solving the Problems]
A variable displacement pump according to a first aspect of the present invention includes a cam ring provided in a housing so as to be movable in a radial direction, and a plurality of cam rings rotatably supported by the housing within the cam ring and slidably in contact with an inner surface of the cam ring. There is a rotor that holds the vane movably in the radial direction, a suction port and a discharge port formed in the housing or a member fixed to the housing, and an orifice provided in the middle of the discharge passage that communicates the discharge port with the discharge port. Then, a first working chamber and a second working chamber that are opposed to each other in the moving direction of the cam ring are formed on the outer periphery of the cam ring, and the cam ring is elastically biased toward the first working chamber where the amount of eccentricity with respect to the rotor is maximized. And a differential pressure control valve for controlling each pressure acting on the first and second working chambers in a valve hole formed in the housing. The load pressure-sensitive spools are fitted coaxially so that they can move in the axial direction, and a valve pressing spring is interposed between the differential pressure control valve and the load pressure-sensitive spool. The load pressure-sensitive spool increases the load pressure. Accordingly, it is configured to increase the initial load of the valve pressing spring by being slid accordingly.
[0006]
In the present invention, the initial load of the valve pressing spring that urges the differential pressure control valve is increased as the load pressure increases, so that the differential pressure control valve is moved against this pressing force. The pressure difference at the time also increases, so the pump rotation speed when the differential pressure is introduced into the working chambers on both sides of the cam ring and the eccentric amount of the cam ring starts to decrease also increases, so the discharge flow rate does not increase any more. The limit value of the discharge flow rate also increases as the load pressure increases.
[0007]
According to a second aspect of the present invention, in the first aspect of the present invention, an internal pressure acting chamber and a load pressure acting chamber are formed between both ends of the differential pressure control valve and the housing, respectively, and the load pressure sensitive spool and the valve pressing spring are loaded pressure When the differential pressure control valve is placed on the inner pressure working chamber side when it is placed in the working chamber, a low pressure is introduced into the first working chamber and the inner pressure is applied to the first working chamber by moving to the load pressure working chamber side. Introduced and configured to introduce a load pressure into the second working chamber.
[0008]
According to a third aspect of the present invention, in the second aspect of the invention, the valve hole serving as the load pressure working chamber is formed as a stepped hole having a small diameter on the differential pressure control valve side and a large diameter on the opposite side, and the load pressure sensitive spool has a small diameter. The load pressure is introduced on both sides in the axial direction of the load pressure-sensitive spool.
[0009]
A variable displacement pump according to a fourth aspect of the present invention is a cam ring provided in a housing so as to be movable in a radial direction, and a plurality of cam rings rotatably supported by the housing within the cam ring and slidably in contact with the inner surface of the cam ring. A rotor that holds the vane in a radially movable manner, a suction port and a discharge port formed in the housing or a member fixed to the housing, and a discharge passage that connects the discharge port to a discharge port. The first working chamber side that has an orifice, forms a first working chamber and a second working chamber facing each other in the moving direction of the cam ring on an outer periphery of the cam ring, and the cam ring has a maximum amount of eccentricity with respect to the rotor In the variable displacement pump that is elastically biased to the valve, the first and second operations are provided in a valve hole formed in the housing. Differential pressure control valve for controlling the respective pressures acting on the chamber, axially slidably said valve Hole And a cylindrical portion fitted into the cylindrical portion, and fitted in the inner hole of the cylindrical portion so as to be slidable in the axial direction. one A load pressure sensitive part having a spring receiver having a diameter larger than the inner hole fixed to the end, and a valve pressing spring interposed between the spring receiver and the housing, the load pressure sensitive part being a load pressure sensitive part. Against the cylindrical part according to the rise of In the direction of the one end The sliding load increases the initial load of the valve pressing spring.
[0010]
Also in this invention, since the initial load of the valve pressing spring that urges the differential pressure control valve is increased as the load pressure increases, the differential pressure control valve is moved against this pressing force. The pressure difference at the time also increases, so the pump rotation speed when the differential pressure is introduced into the working chambers on both sides of the cam ring and the eccentric amount of the cam ring starts to decrease also increases, so the discharge flow rate does not increase any more. The limit value of the discharge flow rate also increases as the load pressure increases.
[0011]
According to a fifth aspect of the present invention, in the fourth aspect of the present invention, an internal pressure acting chamber and a load pressure acting chamber are formed between both ends of the differential pressure control valve and the housing, respectively, and the valve pressing spring is disposed in the load pressure acting chamber. When the differential pressure control valve is pressed against the inner pressure working chamber side, a low pressure is introduced into the first working chamber, and when the differential pressure control valve moves to the load pressure acting chamber side, the inner pressure is introduced into the first working chamber. The working chamber is configured to introduce a load pressure.
[0012]
According to a sixth aspect of the present invention, in the invention of the fourth or fifth aspect, the inner hole of the cylindrical portion is formed as a stepped hole having a small diameter on the spring receiving side and a large diameter on the opposite side. A slidably fitted into both the small diameter and large diameter parts, and a valve spring that abuts the spring receiver against one end of the cylindrical part in a free state is interposed between the cylindrical part and the load pressure sensitive part. In the free state, the other end portion of the cylindrical portion abuts against the housing or a member fixed thereto, and when the load pressure increases, the spring receiver fixed to the load pressure sensitive portion is separated from the cylindrical portion according to the increase. It is configured to move in the direction.
[0013]
According to a seventh aspect of the present invention, in the first to sixth aspects of the invention, the orifice is a variable orifice whose opening area decreases as the cam ring moves toward the second working chamber.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
First, the first embodiment shown in FIGS. 1 to 4 will be described. The variable displacement pump according to this embodiment is used as a working fluid supply source of a power steering apparatus. The housing 10 is liquid-tightly covered by an end cover 11, and the pump shaft 26 is provided in the housing 10. The rotor 22 that is rotationally driven by the vane and the vane pump part 20 having the cam ring 21 that is movable in the radial direction, the differential pressure control valve 31 that controls the movement of the cam ring 21, and the discharge passages 53a, 53b, and 53c of the vane pump part 20 The variable orifice 54 provided in is used as a main constituent member.
[0015]
As shown in FIGS. 1 and 2, the housing 10 and the end cover 11 fixed to the housing 10 by screws are rotatably supported by the intermediate portion and the rear end portion of the pump shaft 26 via bearings. The cylindrical inner surface 10a formed coaxially with the pump shaft 26 in the housing 10 is fitted with a disk-shaped side plate 12 on the back side and a cylindrical adapter 13 on the front side so as not to rotate. A vane pump unit 20 described below is provided between the end cover 11, the side plate 12, and the adapter 13. A V pulley 29 to which power from the engine is transmitted is fixed to the tip of the pump shaft 26 protruding from the housing 10.
[0016]
The vane pump unit 20 is slidable in a cam ring 21 provided in the adapter 13, a rotor 22 coaxially splined to an intermediate part of the pump shaft 26, and a plurality of radial slits formed in the rotor 22. The vane 23 is held and is always in contact with the cylindrical inner surface of the cam ring 21, and the side surfaces of these members 21 to 23 are slidably in contact with the end surfaces of the end cover 11 and the side plate 12. . The suction port 24 of the vane pump unit 20 is formed on the end face of the end cover 11, and the working fluid is supplied from the reservoir 61 through the suction passage 14 and the suction port 15. The discharge port 25 is formed on the end surface of the side plate 12 and is formed in the housing 10 from the pressure chamber 16 located on the back side through discharge passages 53a, 53b, and 53c provided with variable orifices 54 to be described later. It is guided to the discharge port 55.
[0017]
The pin 17 provided in parallel with the pump shaft 26 and supported at both ends by the end cover 11 and the side plate 12 has a part of the outer periphery of the intermediate portion engaged with the inner surface of the adapter 13. The cam ring 21 is movable in the radial direction of the cam ring 21 by a recess 21 a formed on a part of the outer peripheral surface being engaged with the pin 17 and swinging about the pin 17. The portion opposite to 21a is slidably sealed by a Teflon sealing member 50 provided in a groove formed on the inner surface of the adapter 13 and backed up by rubber. A first working chamber 51 a and a second working chamber 51 b that are opposed to each other in the moving direction of the cam ring 21 are formed between the adapter 13 and the cam ring 21 by the pin 17 and the seal member 50.
[0018]
A cylindrical hole 10b directed toward the pump shaft 26 is formed in the housing 10 on the second working chamber 51b side in the moving direction of the cam ring 21, and a cam pressing piston 27 slidably fitted and supported in the cylindrical hole 10b. Is urged in the direction of the pump shaft 26 by a cam pressing spring 28 interposed between a plug 18A screwed and fixed in a liquid-tight manner to the opening end of the cylindrical hole 10b. The protrusion 27 a at the tip of the cam pressing piston 27 passes through the adapter 13 with a gap and comes into contact with the outer peripheral surface of the cam ring 21, and the cam ring 21 is elastic toward the first working chamber 51 a side where the amount of eccentricity with respect to the rotor 22 is maximized. Is energized.
[0019]
The variable orifice 54 is formed by an edge of the annular groove 27c of the cam pressing piston 27 and an opening at one end of the discharge passage 53b. The cam ring 21 moves to the second working chamber 51b side, and the cam pressing piston 27 is a cam pressing spring. 28, the discharge passage 53b is gradually closed by the edge of the annular groove 27c of the cam pressing piston 27 so that the opening area is reduced. The working fluid from the vane pump unit 20 passes through the variable orifice 54 from the discharge passages 53a and 53b, and is discharged from the discharge port 55 through the discharge passage 53c. In a state where the variable displacement pump is operated and the working fluid flows, the pressure drops before and after the variable orifice 54 to generate a differential pressure, and the discharge passage 53c on the rear side of the variable orifice 54 and the discharge port 55 The pressure is a load pressure given by the operating state of the device to which the working fluid is supplied, and the pressure in the discharge passages 53a and 53b and the pressure chamber 16 on the front side of the variable orifice 54 is the internal pressure of the pump. This internal pressure is larger than the load pressure by the amount of the differential pressure due to the variable orifice 54. Therefore, if the load pressure changes, the internal pressure changes in the same way. Under normal operating conditions, this differential pressure is much smaller than the internal pressure or load pressure.
[0020]
As shown mainly in FIG. 1, a differential pressure control valve 31 is provided on the back side and a differential pressure control valve 31 is provided on the opening side of the valve hole 30 formed in the housing 10 so as to be three-dimensionally orthogonal to the pump shaft 26 and opened on the right side. The pressure sensitive spool 45 is fitted and supported on the same axis so as to be movable in the axial direction, and the opening end of the valve hole 30 is closed with a liquid tightly closed by screwing the plug 19 </ b> A between the differential pressure control valve 31 and the load pressure sensitive spool 45. A valve pressing spring 33 </ b> A is interposed in this. In each of the working chambers 52a and 52b formed between both ends of the differential pressure control valve 31 and the housing 10, the working pressure 52 is introduced into the working chamber 52b on the plug 19A side from the discharge port 55 through the communication hole 59A. It is a load pressure working chamber, and the opposite working chamber 52 a is an internal pressure working chamber into which the internal pressure is introduced from the pressure chamber 16 via the pump internal pressure introducing passage 56.
[0021]
The load pressure sensitive spool 45 and the valve pressing spring 33A are located in the load pressure acting chamber 52b, and the load pressure sensitive spool 45 is formed with a center hole communicating with both end faces. The portion of the valve hole 30 which becomes the load pressure working chamber 52b is formed in a stepped hole having a small diameter on the differential pressure control valve 31 side and a large diameter on the opposite side which is the plug 19A side, and the load pressure sensitive spool 45 has a small diameter. It is slidably fitted to both large diameter parts. An annular space formed at a position that becomes a stepped portion between the valve hole 30 and the load pressure sensitive spool 45 is always in communication with the reservoir 61 via the communication pipe 60.
[0022]
An introduction passage 57a formed in a part of the housing 10 on the internal pressure working chamber 52a side is selectively communicated with the sage 12 reservoir 61 and the internal pressure working chamber 52a by the movement of the differential pressure control valve 31. The introduction path 57a does not communicate with the internal pressure working chamber 52a in the non-operating state in which the differential pressure control valve 31 is pressed to the end position on the internal pressure working chamber 52a side by the valve pressing spring 33A. As soon as it begins to move toward the load pressure acting chamber 52b against the pressing spring 33A, it opens into the valve hole 30 at a position communicating with the inner pressure acting chamber 52a, and this introduction path 57a is a damping orifice formed in the adapter 13. The first working chamber 51a on one side of the outer periphery of the cam ring 21 is communicated with the cam ring 21 through 58a. The communication passage 32A formed in the differential pressure control valve 31 is communicated with the introduction passage 57a in a state where the introduction passage 57a is not communicated with the internal pressure working chamber 52a, but the differential pressure control valve 31 is connected to the load pressure working chamber 52b. If the introduction path 57a starts to move to the side and communicates with the internal pressure working chamber 52a, the introduction path 57a is not communicated immediately. The communication path 32 </ b> A is always in communication with the reservoir 61 through the communication pipe 60.
[0023]
A load pressure introducing passage 57b formed in a part of the housing 10 on the load pressure acting chamber 52b side is always opened to the valve hole 30 at a position where it opens into the load pressure acting chamber 52b. The load pressure introducing passage 57b is an adapter. 13 is communicated with the second working chamber 51 b on the other outer periphery of the cam ring 21 through an orifice 58 b formed in the nozzle 13. In the differential pressure control valve 31, when the load pressure increases excessively, the pressure in the load pressure working chamber 52b is relieved to the reservoir 61, and the differential pressure control valve 31 is moved to the load pressure working chamber 52b side. A pilot relief valve 65 is provided to minimize the pump discharge flow rate.
[0024]
The stepped load pressure sensitive spool 45 fitted to the valve hole 30 has a larger cross-sectional area on the plug 19A side than a cross-sectional area on the valve pressing spring 33A side. When the load pressure is 0 or low, it is in contact with the plug 19A as shown in FIGS. 1 and 4 (a). However, if the load pressure increases beyond a predetermined value, the difference as shown in FIG. It moves to the pressure control valve 31 side and compresses the valve pressing spring 33A to increase its initial load. As a result, the differential pressure control valve 31 is directed toward the internal pressure working chamber 52a against the rightward force applied to the differential pressure control valve 31 due to the differential pressure between the internal pressure acting on the working chambers 52a and 52b at both ends and the load pressure. The pressing force of the valve pressing spring 33 </ b> A that is biased increases due to the movement of the load pressure sensitive spool 45 due to an increase in the load pressure.
[0025]
When the rotation of the engine of the vehicle is transmitted to the pump shaft 26 via the drive belt hung on the V pulley 29 and the rotor 22 of the vane pump 20 is rotated, the working fluid in the reservoir 61 flows from the suction port 15 and the suction passage 14. The air is sucked into the vanes 23 of the vane pump unit 20 through the suction port 24, discharged into the pressure chamber 16 from the discharge port 25, and discharged through the discharge passages 53a, 53b, 53c provided with the variable orifice 54. Is supplied to equipment such as a power steering device.
[0026]
When the pump rotational speed is low, the flow rate through the discharge passages 53a, 53b, 53c is small, and therefore the differential pressure before and after the variable orifice 54 is small. Therefore, the differential pressure control valve 31 is a valve pressing spring as shown in FIG. The first working chamber 51a is communicated to the reservoir 61 side via the introduction path 57a and the communication path 32A, and the cam ring 21 has a discharge flow rate by the cam pressing spring 28. It is pressed to the first working chamber 51a side that is the largest. In this state, the discharge flow rate of the working fluid discharged from the discharge port 55 via the discharge passages 53a, 53b, and 53c increases rapidly as the pump rotation speed increases as shown by the characteristic A in FIG.
[0027]
If the discharge flow rate increases due to the increase in the pump rotation speed and the differential pressure before and after the variable orifice 54 increases, the differential pressure control valve 31 is controlled by the differential pressure between the internal pressure in the internal pressure working chamber 52a and the internal pressure in the load pressure working chamber 52b. The force to move to the load pressure acting chamber 52b side also increases. When the load pressure is low (the handle is not operated), as shown in FIG. 4 (a), the differential pressure control valve 31 and the load pressure sensitive spool 45 are respectively moved by the urging force of the valve pressing spring 33A. The valve pressing spring 33A is held at the sliding end and is in a state of being extended to the maximum.
[0028]
Accordingly, the differential pressure control valve 31 starts to operate due to the differential pressure across the variable orifice 54 generated by a relatively small pump discharge flow rate, so that the first working chamber 51a communicates from the reservoir 61 side to the internal pressure working chamber 52a side. Become. As a result, the cam ring 21 that has been in contact with the first working chamber 51a where the discharge flow rate is maximum until then is eccentric so as to maintain a constant differential pressure across the variable orifice 54 as the pump rotational speed increases. The amount is decreased, and the discharge flow rate characteristic is maintained at a low flow rate as shown in the characteristic B of FIG. 3 to achieve energy saving.
[0029]
As the eccentric amount of the cam ring 21 decreases, the throttle area of the variable orifice 54 is reduced, so that the pump discharge flow rate is reduced as the pump rotational speed increases.
[0030]
In this state, when the load pressure is increased by operating the handle, the load pressure sensitive spool 45 having a pressure receiving area difference is slid against the urging force of the valve pressing spring 33A as shown in FIG. 4 (b). . As a result, the spring load by the valve pressing spring 33A acting on the differential pressure control valve 31 is increased, and the differential pressure across the variable orifice 54 does not increase, that is, unless the pump discharge flow rate increases, the first working chamber 51a Switching from the reservoir 61 side to the internal pressure working chamber 52a side is not possible. Therefore, the discharge flow rate is maintained at a flow rate necessary to assist the steering operation, as indicated by characteristic C in FIG.
[0031]
Here, since the change of the valve pressing spring 33A acting on the differential pressure control valve 31 due to increase or decrease of the load pressure is not directly applied to the cam ring 21, the operation stability of the cam ring 21 is high. Further, the discharge flow rate characteristic is increased or decreased with respect to the increase or decrease of the load pressure. The first and second working chambers are controlled by the differential pressure control valve 31 in which the pressing force by the valve pressing spring 33A increases as the load pressure increases and the operating state changes. Since the amount of eccentricity of the cam ring 21 is changed by directly controlling the pressures acting on the 51a and 51b, the response of the increase and decrease of the discharge flow rate characteristic to the increase and decrease of the load pressure is also improved.
[0032]
In the first embodiment, a central hole is provided in the load pressure sensitive spool 45 so that the load pressure introduced to both sides of the load pressure sensitive spool 45 is the same. However, a communication path is formed in the housing 10. Thus, the load pressure on both sides of the load pressure sensitive spool 45 may be the same.
[0033]
Next, the second embodiment will be described with reference to FIG. The variable displacement pump according to the second embodiment has a differential pressure control valve that resists the rightward force applied to the differential pressure control valve 35 due to the differential pressure between the internal pressure and the load pressure acting on the working chambers 52a and 52b. The structure for generating a pressing force that urges 35 toward the inner pressure acting chamber 52a side includes a valve pressing spring 33B and a load pressure sensitive portion 37 of the differential pressure control valve 35 that changes its initial load. Since the points differ from the first embodiment and the other configurations are the same, this difference will be mainly described.
[0034]
As shown in FIG. 5, a differential pressure control valve 35 composed of a plurality of portions is inserted into the valve hole 30 formed in the housing 10 so that the left side is the opening side, and the opening end of the valve hole 30 is plug 19B. The screw is closed in a liquid-tight manner. In each of the working chambers 52a and 52b formed between both ends of the differential pressure control valve 35 and the housing 10, the working chamber 52a on the plug 19B side receives the internal pressure from the pressure chamber 16 via the pump internal pressure introduction passage 56. The opposite working chamber 52b is a load pressure working chamber into which a load pressure is introduced from the discharge port 55 through the communication hole 59B.
[0035]
The differential pressure control valve 35 has a cylindrical portion 36 fitted in the valve hole 30 so as to be slidable in the axial direction, and is fitted in the inner hole of the cylindrical portion 36 so as to be slidable in the axial direction so as to apply a load pressure. The load pressure sensitive portion 37 having a spring receiver 37a having a diameter larger than the inner hole fixed to the end on the chamber 52b side, and both members in such a direction that the opposite end surfaces of the tubular portion 36 and the spring receiver 37a are in contact with each other. A valve spring 38 for urging 36 and 37 is constituted. The inner hole of the cylindrical portion 36 is formed as a stepped hole having a small diameter on the spring receiver 37a side and a large diameter on the opposite side, Thereby, as shown in FIG. 5, the cylindrical portion 36 is configured such that the cross-sectional area on the load pressure working chamber 52 b side is larger than the cross-sectional area on the pump internal pressure working chamber 52 a side, , The load pressure sensitive portion 37 is slidably fitted to both the small diameter portion and the large diameter portion, Thereby, as shown in FIG. 5, the load pressure sensitive portion 37 is configured such that the cross-sectional area on the pump internal pressure acting chamber 52 a side is larger than the cross-sectional area on the load pressure acting chamber 52 b side, The valve spring 38 is located in an annular space formed between the members 37 and 38 and is formed between the members 37 and 38 and interposed between the step portions. This annular space is always in communication with the reservoir 61 through the communication pipe 60.
[0036]
The differential pressure control valve 35 is urged toward the internal pressure working chamber 52a by a valve pressing spring 33B interposed between the inner end of the valve hole 30 on the load pressure working chamber 52b side and the spring receiver 37a. In the free state, as shown in FIG. 5A, the opposite end surfaces of the cylindrical portion 36 and the load pressure sensitive portion 37 are in contact with each other, and the internal pressure working chamber of the cylindrical portion 36 and the load pressure sensitive portion 37 The end surfaces on the 52a side are in contact with the front end surface and the inner bottom surface of the cylindrical portion of the plug 19B almost simultaneously. A small hole 19a is formed at the tip of the cylindrical portion of the plug 19B so as to communicate the inside and outside of the cylindrical portion even when the cylindrical portion 36 is in contact therewith. Note that the end surface of the load pressure sensitive portion 37 may be lifted from the inner bottom surface of the plug 19B in a free state.
[0037]
As in the first embodiment, the tubular portion 36 of the differential pressure control valve 35 is provided with a communication path 32B that is always in communication with the reservoir 61 via the annular space and the communication conduit 60 described above. The introduction path 57a communicated with the first working chamber 51a is selectively communicated with the reservoir 61 and the internal pressure working chamber 52a by the movement of the cylindrical portion 36 of the differential pressure control valve 35. The load pressure introduction passage 57b communicated with the second working chamber 51b is always communicated with the load pressure working chamber 52b, and a pilot relief valve 65 is provided in the spring receiver 37a.
[0038]
Since the load pressure sensitive portion 37 of the differential pressure control valve 35 is fitted in the inner hole of the cylindrical portion 36 having a small diameter portion and a large diameter portion, the load pressure and the internal pressure rise from 0 and exceed a predetermined value. For example, as shown in FIG. 5 (b), the valve spring 38 is compressed to form the cylindrical portion 36. Spring receiver 37a The opposite end face of As described above, the cylindrical portion 36 has a larger cross-sectional area on the load pressure acting chamber 52b side than a sectional area on the pump internal pressure acting chamber 52a side. Is given, The end surface of the cylindrical portion 36 on the side of the internal pressure acting chamber 52a is in contact with the distal end surface of the cylindrical portion of the plug 19B. Since the load pressure sensing portion 37 has a larger cross-sectional area on the pump internal pressure working chamber 52a side than a cross-sectional area on the load pressure working chamber 52b side as described above, The load pressure sensitive portion 37 moves to the load pressure acting chamber 52b side, thereby compressing the valve pressing spring 33B interposed between the spring receiver 37a and the housing 10 to increase its initial load. As a result, the differential pressure control valve 35 is directed toward the internal pressure working chamber 52a against the rightward force applied to the differential pressure control valve 35 due to the differential pressure between the internal pressure acting on the working chambers 52a and 52b at both ends and the load pressure. The pressing force of the valve pressing spring 33B that is biased increases gradually as the load pressure and the internal pressure increase.
[0039]
Also in the second embodiment, since the differential pressure before and after the variable orifice 54 (all reference numerals not shown in FIG. 5 are the same as those in FIG. 1) is small when the pump rotational speed is low, the differential pressure control valve 35 is As shown in FIG. 5 (a), it is pressed against the inner pressure action chamber 52a side end position by the valve pressing spring 33B, and the tubular portion 36 and the spring receiver 37a are in contact with each other by the valve spring 38, and the first action chamber 51a. The low pressure from the reservoir 61 is introduced, and the cam ring 21 is pressed against the first working chamber 51a side where the discharge flow rate is maximized by the cam pressing spring 28. Therefore, as shown by characteristic A in FIG. 3, the pump discharge flow rate increases rapidly as the pump rotational speed increases.
[0040]
If the discharge flow rate increases due to the increase in the pump rotation speed and the differential pressure between the internal pressure around the variable orifice 54 and the load pressure increases, the force to move the differential pressure control valve 35 toward the load pressure working chamber 52b also increases. If the pressing force applied by the valve pressing spring 33B is exceeded, the differential pressure control valve 35 starts to move toward the load pressure acting chamber 52b. When the introduction path 57a is cut off from the communication path 32B and communicates with the first working chamber 51a, the internal pressure on the front side of the variable orifice 54 is introduced into the first working chamber 51a. In the same manner as in, the discharge flow rate does not increase beyond a certain limit value even if the pump rotational speed increases, as shown in the characteristics B and C of FIG. 3, according to the load pressure at that time. Thereby, control of the pump discharge flow rate characteristic according to the rotation speed of the pump is performed. In the second embodiment, the opening area of the variable orifice 54 decreases as the pump discharge flow rate decreases, so that the pump discharge flow rate decreases as the pump rotation speed increases. A variable displacement pump having characteristics suitable for the above is obtained.
[0041]
As the load pressure and the internal pressure increase, as described above, the pressing force of the valve pressing spring 33B that biases the differential pressure control valve 35 toward the internal pressure acting chamber 52a also increases. Therefore, as in the first embodiment, when the variable pressure pump is operating as shown in the characteristic A of FIG. 3, if the load pressure and the internal pressure are low, the pump rotation speed and therefore the pump discharge flow rate are compared. The differential pressure control valve 35 begins to move toward the load pressure acting chamber 52b and the introduction path 57a communicates with the inner pressure acting chamber 52a and the amount of eccentricity of the cam ring 21 begins to decrease. As shown in the figure, the limit value at which the pump discharge flow rate does not become higher is lower. On the other hand, if the load pressure and the internal pressure are increased, the differential pressure control valve 35 starts to move toward the load pressure action chamber 52b after the pump rotation speed, and hence the pump discharge flow rate, increases, and the introduction path 57a becomes the inner pressure action chamber. Since the amount of eccentricity of the cam ring 21 starts to decrease as communicated with the valve 52a, the limit value at which the pump discharge flow rate does not become higher becomes higher. This limit value increases as the discharge pressure and the internal pressure rise. When the load pressure sensitive portion 37 reaches the stroke end with respect to the cylindrical portion 36, the limit value of the discharge flow rate becomes the maximum as shown in the characteristic C, and the pump is exceeded. The limit value of the discharge flow rate does not increase. Thereby, control of the pump discharge flow rate characteristic according to the load pressure is performed.
[0042]
Even in the second embodiment, since the change of the valve pressing spring 33B acting on the differential pressure control valve 31 due to the increase or decrease of the load pressure is not directly applied to the cam ring 21, the operation stability of the cam ring 21 is high. It will be a thing. Further, the discharge flow rate characteristic is increased or decreased with respect to the load pressure. The first and second working chambers are controlled by the differential pressure control valve 31 in which the pressing force by the valve pressing spring 33B increases and the operating state changes according to the increase in the load pressure. Since the amount of eccentricity of the cam ring 21 is changed by directly controlling the pressures acting on the 51a and 51b, the response of the increase and decrease of the discharge flow rate characteristic to the increase and decrease of the load pressure is also improved.
[0043]
In each of the above embodiments, the cam ring 21 is moved in the radial direction by swinging around the pin 17. However, the present invention is not limited to this, and the cam ring 21 is located at a position corresponding to the pin 17 and the seal member 50. It is also possible to carry out by guiding and supporting the adapter 13 on the inner surface of the adapter 13 so as to be liquid-tight and slidable in the radial direction.
[0044]
【The invention's effect】
According to the present invention, the initial load of the valve pressing spring acting on the differential pressure control valve that controls each pressure acting on the first and second working chambers formed opposite to the outer periphery of the cam ring is used to increase the load pressure. Since the cam ring eccentricity is adjusted according to the load pressure by increasing it accordingly, the stability of the cam ring operation can be improved, and the response of the discharge flow rate characteristic to the increase and decrease of the load pressure can be increased. Can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing the overall structure of a first embodiment of a variable displacement pump according to the present invention.
2 is a cross-sectional view taken along the line 2-2 in FIG.
FIG. 3 is a graph showing pump discharge flow characteristics of a variable displacement pump according to the present invention.
FIG. 4 is a partial cross-sectional view for explaining an operating state of the first embodiment shown in FIG.
FIG. 5 is a partial cross-sectional view showing a main part and an operating state of a third embodiment of a variable displacement pump according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Housing, 21 ... Cam ring, 22 ... Rotor, 23 ... Vane, 24 ... Intake port, 25 ... Discharge port, 30 ... Valve hole, 31, 35 ... Differential pressure control valve, 33A, 33B ... Spring for valve pressing, 36 ... Cylindrical part, 37 ... Load pressure sensitive part, 37a ... Spring receiver, 38 ... Valve spring, 45 ... Load pressure sensitive spool, 51a ... First working chamber, 51b ... Second working chamber, 52a ... Internal pressure working chamber, 52b ... Load pressure working chamber, 53a, 53b, 53c ... Discharge passage, 54 ... Orifice (variable orifice), 55 ... Discharge port.

Claims

A cam ring provided in the housing so as to be movable in the radial direction, and a rotor that rotatably supports the housing within the cam ring and that slidably contacts the inner surface of the cam ring so as to be movable in the radial direction. A suction port and a discharge port formed in the housing or a member fixed thereto, and an orifice provided in the middle of a discharge passage communicating the discharge port with a discharge port. A variable capacity type in which a first working chamber and a second working chamber are formed opposite to each other in the moving direction, and the cam ring is elastically urged toward the first working chamber where the amount of eccentricity with respect to the rotor is maximized. In the pump, a differential pressure control valve and a load for controlling each pressure acting on the first and second working chambers in a valve hole formed in the housing The sensitive spools are fitted coaxially so as to be movable in the axial direction, and a valve pressing spring is interposed between the differential pressure control valve and the load pressure sensitive spool. The load pressure sensitive spool responds to an increase in load pressure. And a variable displacement pump configured to increase an initial load of the valve pressing spring.

2. The variable displacement pump according to claim 1, wherein an internal pressure acting chamber and a load pressure acting chamber are formed between both ends of the differential pressure control valve and the housing, respectively, and the load pressure sensitive spool and the valve pressing spring are the When the differential pressure control valve is pressed against the internal pressure working chamber side, a low pressure is introduced into the first working chamber and moved to the load pressure working chamber side. A variable displacement pump characterized in that the internal pressure is introduced into one working chamber and a load pressure is introduced into the second working chamber.

3. The variable displacement pump according to claim 2, wherein the valve hole serving as the load pressure working chamber is formed as a stepped hole having a small diameter on the differential pressure control valve side and a large diameter on the opposite side, and the load pressure sensitive spool A variable displacement pump characterized in that it is slidably fitted into both a small diameter portion and a large diameter portion, and load pressure is introduced on both sides in the axial direction of the load pressure sensitive spool.

A cam ring provided in the housing so as to be movable in the radial direction, and a rotor that rotatably supports the housing within the cam ring and that slidably contacts the inner surface of the cam ring so as to be movable in the radial direction. A suction port and a discharge port formed in the housing or a member fixed thereto, and an orifice provided in the middle of a discharge passage communicating the discharge port with a discharge port. A variable capacity type in which a first working chamber and a second working chamber are formed opposite to each other in the moving direction, and the cam ring is elastically urged toward the first working chamber where the amount of eccentricity with respect to the rotor is maximized. In the pump, a differential pressure control bar that is provided in a valve hole formed in the housing and controls each pressure acting on the first and second working chambers. Bed includes axially slidably the valve hole in the fitted cylindrical portion, from said bore to an end fitted so as to be axially slidable in the bore of the tubular portion large A load pressure sensitive portion to which a spring receiver having a diameter is fixed, and a valve pressing spring is interposed between the spring receiver and the housing, and the load pressure sensitive portion is formed in the cylindrical shape according to an increase in load pressure. A variable displacement pump configured to increase an initial load of the valve pressing spring by sliding in the direction of the one end with respect to a portion .

5. The variable displacement pump according to claim 4, wherein an internal pressure working chamber and a load pressure working chamber are formed between both ends of the differential pressure control valve and the housing, respectively, and the valve pressing spring is located in the load pressure working chamber. When the differential pressure control valve is pressed against the internal pressure working chamber side, a low pressure is introduced into the first working chamber and when the differential pressure control valve moves to the load pressure working chamber side, the first working chamber is moved to the first working chamber. A variable displacement pump characterized in that an internal pressure is introduced and a load pressure is introduced into the second working chamber.

6. The variable displacement pump according to claim 4 or 5, wherein the inner hole of the cylindrical part is formed as a stepped hole having a small diameter on the spring receiving side and a large diameter on the opposite side, and the load pressure sensitive part is formed of the stepped hole. A valve spring is slidably fitted to both the small diameter portion and the large diameter portion, and a valve spring is provided between the tubular portion and the load pressure sensitive portion so that the spring receiver abuts on one end of the tubular portion in a free state. And the other end of the cylindrical portion is in contact with the housing or a member fixed thereto in a free state, and if the load pressure increases, the spring fixed to the load pressure sensitive portion according to the increase A variable displacement pump characterized in that the receiver moves in a direction away from the tubular portion.

7. The variable displacement pump according to claim 1, wherein the orifice is a variable orifice whose opening area decreases as the cam ring moves toward the second working chamber.