JP3846919B2

JP3846919B2 - Hydraulic control valve

Info

Publication number: JP3846919B2
Application number: JP18308495A
Authority: JP
Inventors: 正典小林; 善之斎藤; 貴史大畑
Original assignee: JTEKT Corp
Current assignee: JTEKT Corp
Priority date: 1995-07-19
Filing date: 1995-07-19
Publication date: 2006-11-15
Anticipated expiration: 2015-07-19
Also published as: JPH0930436A

Description

【０００１】
【発明の属する技術分野】
本発明は、バルブボディーとバルブスプールとの同軸上での相対角変位により油圧の制御動作をなす回転式の油圧制御弁に関し、特に、油圧式の動力舵取装置において、操舵補助用のパワーシリンダへの送給油圧を舵輪操作に応じて制御すべく用いられる油圧制御弁に関する。
【０００２】
【従来の技術】
油圧式の動力舵取装置は、舵取機構中に配した複動式の油圧シリンダ（パワーシリンダ）が発生する油圧力により舵取りを補助し、舵輪（ステアリングホィール）の操作に要する労力負担を軽減して、快適な操舵感覚を得ようとするものであり、前記パワーシリンダの両シリンダ室（送油先）と、エンジンにて駆動される油圧ポンプ（油圧源）及び作動油を収納する油タンク（排油先）との間に、舵輪に加わる操舵トルクの方向及び大きさに応じて油圧の給排制御を行う油圧制御弁を介装してなる。
【０００３】
前記油圧制御弁としては、一般的に、舵輪の回転を直接的に利用する回転式の油圧制御弁が用いられている。これは、舵輪に連なる入力軸と舵取機構に連なる出力軸とをトーションバーを介して同軸的に連結し、一方の連結端に係合された筒形のバルブボディーの内側に、他方の連結端に一体的に形成したバルブスプールを同軸上での相対回転自在に嵌め合わせてなり、舵輪に操舵トルクが加えられたとき、前記トーションバーの捩れに伴ってバルブボディーとバルブスプールとの間に相対角変位を生ぜしめる構成となっている。
【０００４】
バルブボディーとバルブスプールとの嵌合周上（前者の内周と後者の外周）には、軸長方向に延びる各複数の油溝が周方向に並設してあり、バルブボディーとバルブスプールとは、夫々の油溝が周方向に千鳥配置され、両側に相隣するもの同士が相互に連通するように位置決めされており、これらの油溝の夫々は、油圧源及び排油先に夫々連なる給油室及び排油室と、給油室の両側にて排油室との間に夫々位置し、送油先となるパワーシリンダの両シリンダ室に各別に連なる一対の送油室とを構成している。
【０００５】
図10は、この種の油圧制御弁の動作説明図である。本図は、バルブボディー１及びバルブスプール２の嵌合部を直線展開したものであり、バルブボディー１の内周に並ぶ油溝４，４…は、パワーシリンダの両シリンダ室Ｓ_R，Ｓ_Lに各別の送油孔を介して接続され、一対の送油室12，13を交互に構成しており、またバルブスプール２の外周に並ぶ油溝５，５…は、油圧源たる油圧ポンプＰに導油孔を介して接続された給油室10と、排油先たる油タンクＴに排油孔を介して接続された排油室11とを交互に構成している。なお、図とは逆の構成、即ち、バルブボディー１側の油溝４，４…を給油室10及び排油室11とし、バルブスプール２側の油溝５，５…を送油室12，13とした構成もまた可能である。
【０００６】
バルブボディー１側の油溝４，４…と、バルブスプール２側の油溝５，５…とは、夫々の両側にて等しい面積を有して連通しており、これらの連通部が前記相対角変位に応じて絞り面積を変える絞り部６，６…として作用し、この絞り面積の変化により、前記送油室12，13を経てシリンダ室Ｓ_R，Ｓ_Lに送給される油圧が制御される。
【０００７】
図10（ａ）は、バルブボディー１とバルブスプール２との間に相対角変位が生じていない状態を示している。このとき、油圧ポンプＰから給油室10に供給される油圧は、該給油室10の両側の絞り部６，６が等面積を有することから、相隣する送油室12，13に均等に振り分けられ、他側の絞り部６，６を経て排油室11，11に導かれて、これらに連なる油タンクＴに還流する経路を辿ることになり、給油室10への供給油圧は、前記シリンダ室Ｓ_R，Ｓ_Lのいずれにも送給されず、パワーシリンダは何らの力も発生しない。
【０００８】
図10（ｂ）は、舵輪に操舵トルクが加わり、バルブボディー１とバルブスプール２との間に相対角変位が生じた状態を示している。このとき、給油室10の両側の絞り部６，６の内、一方（送油室12側）の絞り面積が増大し、他方（送油室13側）の絞り面積が減少する結果、前記給油室10への供給油圧は、絞り面積を増した絞り部６を経て、主として送油室12に導入されるようになり、該送油室12と他方の送油室13との間、及びこれら夫々に連なるシリンダ室Ｓ_R，Ｓ_L間に圧力差が生じ、前記パワーシリンダは、この圧力差に相当する油圧力（操舵補助力）を発生する。
【０００９】
この際に生じる圧力差は、他側（送油室13側）の絞り部６での絞り面積の減少程度に依存し、この減少程度は前記相対角変位の大きさ、即ち、舵輪に加わる操舵トルクの大きさに対応する。従って、前記パワーシリンダが発生する操舵補助力は、舵輪に加わる操舵トルクに対応する向きと大きさとを有することになり、舵取りを補助することができる。なお、パワーシリンダの動作に伴って他方のシリンダ室Ｓ_Lから押し出される油は、他方の送油室13に還流し、該送油室13の一側（排油室11側）にて絞り面積を増した絞り部６を経て相隣する排油室11に導入され、該排油室11に接続された油タンクＴに排出される。
【００１０】
各絞り部６を臨むバルブスプール２側の角部には、周方向に所定の幅を有して面取り部（チャンファ７）が形成してある。このチャンファ７は、バルブスプール２側の油溝５の側面と油溝５，５間のランドの周面とが交叉する角部を、ランドの周面に対して所定の傾斜角度を有して斜めに切欠き、周方向に所定の幅を有して形成されており、バルブボディー１とバルブスプール２との相対角変位に対し、各絞り部６の絞り面積を緩やかに変化せしめる調整作用をなす。動力舵取装置における操舵補助力の望ましい増加特性は、舵輪に加わる操舵トルクに対して比例的に増加する特性ではなく、前記操舵トルクが小さい範囲では漸増し、所定の限界を超えると共に急増する特性であり、このような特性は、前記チャンファ７，７…の作用により達成される。
【００１１】
【発明が解決しようとする課題】
さて、以上の如き動作をなす油圧制御弁においては、特に、バルブボディー１とバルブスプール２との相対角変位が大きい場合、絞り面積を減じた絞り部６を作動油が通流する際に耳障りな流動音を伴ってキャビテーションが発生する問題があった。この流動音は、車室の内部が比較的静かな停止又は低速走行中に舵輪が大きく操作された場合に発生し、車室内部の静粛性を阻害するのみならず、運転者に無用な不安を与える不都合を招来することから、動力舵取装置用の油圧制御弁においては、前記流動音の低減が重要な課題となっている。
【００１２】
前述した如く、絞り部６の絞り面積の増減は、給油室10の両側と排油室11の両側とにおいて、送油室12，13に対して逆に生じる。即ち、図10（ｂ）に示す動作状態にあるとき、給油室10の両側においては、送油室12側の絞り部６の絞り面積が増加し、送油室13側の絞り部６の絞り面積が減少するのに対し、排油室11の両側においては、逆に送油室13側の絞り部６の絞り面積が増加し、送油室12側の絞り部６の絞り面積が減少する。
【００１３】
このとき、前記流動音の原因となる作動油の流れは、絞り面積を減じた側の絞り部６，６、即ち、給油室10と送油室13との間の絞り部６、及び排油室11と送油室12との間の絞り部６において夫々生じるが、これらの流れにおけるキャビテーションの発生挙動には差異があるとされており、このような知見に従って流動音の低減を図った油圧制御弁が従来から種々提案されている。
【００１６】
また特開平6-206555号公報には、作動油のキャビテーションによる流動音が、給油室10の両側の絞り部６，６よりも排油室11の両側の絞り部６，６に顕著に発生するとされ、後者に前者と同様の流れ形態を得るべく、図12に示す如く、排油室11の両側の絞り部６，６には、バルブスプール２側ではなく、バルブボディー１側の角部にチャンファ７，７を形成することにより流動音の低減を図った油圧制御弁が開示されている。
【００１７】
同様の構成とした油圧制御弁は、特開平6-156292号公報にも開示されている。但し、この油圧制御弁は、特開平6-206555号公報におけるとは逆に、給油室10の両側の絞り部６，６がキャビテーションに対して不利であるとされ、これらの絞り部６，６において、バルブボディー１側の角部にチャンファ７，７を形成した構成となっている。
【００１８】
また一方、特開昭60−203580号公報、及び米国特許3022772 号には、図10、図11及び図12に示す油圧制御弁と逆の構成、即ち、バルブボディー１側の油溝４，４…を給油室10及び排油室11とし、バルブスプール２側の油溝５，５…を送油室12，13とした構成において、作動油のキャビテーションに伴う流動音が、給油室10の両側の絞り部６，６よりも排油室11の両側の絞り部６，６に顕著に発生するとされ、図13に示す如く、給油室10の両側の絞り部６，６に対してのみチャンファ７，７を形成することにより流動音の低減を図った油圧制御弁が開示されている。
【００１９】
この構成によれば、図13（ｂ）に示す如く、バルブボディー１に対してバルブスプール２の相対角変位が生じたとき、排油室11の一側（送油室12側）のチャンファ７を有さない絞り部６は、早期に締切り状態となるのに対し、給油室10の同側（送油室13側）のチャンファ７を有する絞り部６は、所定の絞り面積を維持していることから、流動音の原因となる作動油の流れは、キャビテーションに対して好条件であるとされた給油室10と送油室13との間の絞り部６に集中し、流動音を低減し得ることとなっている。
【００２０】
この油圧制御弁は、前記特開平6-206555号公報及び前記特開平6-156292号公報に開示されているように流れの形態に着目すると、特開平6-156292号公報と同じ、即ち、特開平6-206555号公報とは逆の流れ形態が得られることになる。
【００２１】
このように、給油室10の両側と排油室11の両側とにおけるキャビテーションの発生挙動の差異に着目して流動音の低減を図った従来の提案は、キャビテーションの発生挙動に関する考え方が種々に異なるものとなっている。キャビテーションの発生挙動を明確にすべく本発明者等は、給油室10と排油室11との間を直線展開した模擬油路を外部からの観察可能に構成し、給油室10側の絞り面積を減じた場合と、排油室11側の絞り面積を減じた場合とにおけるキャビテーションの発生挙動を、流動音の測定データと目視での観察とにより比較する実験を行った。
【００２２】
図14及び図15は、この実験の結果を示す図表であり、図14には、図10，図11及び図12に示す如く、給油室10及び排油室11をバルブスプール２側に設けた場合の結果が、また図15には、図13に示す如く、給油室10及び排油室11をバルブボディー１側に設けた場合の結果が夫々示されている。流動音の測定結果は、絞り面積の減少に伴って増加する絞り部の上流側油圧（kgf/cm²）を横軸とし、測定された流動音の音圧レベル（dB）を縦軸として示してあり、またキャビテーションの観察結果は、目視での観察による相対評価となっている。
【００２３】
図14においては、給油室10側の絞り面積を減じた場合の結果が（ａ）に、排油室11側の絞り面積を減じた場合の結果が（ｂ）に夫々示されている。両者を比較した場合、流動音の測定データには、絞り部の上流側油圧が60kgf/cm²以下の領域において顕著な差異が現れており、特に、（ａ）の場合に、上流側油圧が40kgf/cm²以下での流動音の音圧レベルが20dB程度の低レベルに保たれるのに対し、（ｂ）の場合には、上流側油圧が20kgf/cm²を超える領域において、高圧域と同等の音圧レベル（40dB前後）を有する流動音が発生している。
【００２４】
また目視での観察においても、（ａ）の場合、絞り部の絞り面積が十分に小さく、上流側油圧が高圧となるまでキャビテーションの発生が観察されないのに対し、（ｂ）の場合、絞り部の絞り面積が比較的大きい段階にてキャビテーションの発生が観察された。これらのことから、図14に示す構成、即ち、給油室10及び排油室11をバルブスプール２側に設けた構成においては、給油室10側の絞り部での流れがキャビテーションの発生に対して有利であることがわかる。
【００２５】
一方図15においては、図14とは逆に、排油室11側の絞り面積を減じた場合の結果が（ａ）に、給油室10側の絞り面積を減じた場合の結果が（ｂ）に夫々示されている。両者の流動音の測定データを比較した場合、図14の場合ほど顕著ではないが、上流側油圧が30kgf/cm²以下の領域において差異があり、（ａ）の場合の流動音が低レベルである。また、目視での観察においても、（ａ）の場合のキャビテーションの発生程度は、（ｂ）の場合のそれよりも良好であった。これらのことから、図15に示す構成、即ち、給油室10及び排油室11をバルブボディー１側に設けた構成においては、排油室11側の絞り部での流れがキャビテーションの発生に対して有利であることがわかる。
【００２６】
流動音の低減を図った従来の油圧制御弁をこの実験結果と比較した場合、特開平6-206555号公報に開示された油圧制御弁は、前記実験結果に対応するのに対し、特開昭60−203580号公報、米国特許3022772 号及び前記特開平6-156292号公報に開示された油圧制御弁は、前記実験結果と相反し、流動音の低減に対し有害なものとなっている。
【００２７】
また、絞り部６における前記チャンファ７は、バルブスプール２側の角部に形成されるのが一般的であるが、バルブボディー１側の角部に形成される場合もある。このような場合のキャビテーションの発生挙動は、図14及び図15に示された絞りの状態の図を天地を逆にして見た場合に相当し、給油室10及び排油室11をバルブスプール２側に設けた構成においては、図15の結果から、排油室11側の絞り部がキャビテーションの発生に対して有利となり、給油室10及び排油室11をバルブボディー１側に設けた構成においては、図14の結果から、給油室10側の絞り部がキャビテーションの発生に対して有利となる結果が得られている。従って、バルブボディー１側にチャンファ７を形成した場合には、特開平6-206555号公報に開示された構成は、キャビテーションの発生に対して不利なものとなる。
【００２８】
このように、流動音の低減のために従来からなされている提案は、夫々に固有の構成、具体的には、油圧源、排油先及び送油先とバルブボディー１及びバルブスプール２の嵌合周上に並ぶ油溝との連通態様と、各油溝間の絞り部におけるチャンファの形成態様との所定の組み合わせに対してのみ通用するに過ぎず、種々の構成の油圧制御弁全体に適用し得るものではない。
【００２９】
更に、従来の提案は、絞り部６に設けられるチャンファ７の寸法（幅、傾斜角度）の変更を強いるものであるが、実際に必要となる寸法差はわずかなものであり、このような差を有する二種類のチャンファ７，７を交互に形成するために、多大の工数と高度の加工技術とを要する難点があった。
【００３０】
本発明は斯かる事情に鑑みてなされたものであり、バルブボディーとバルブスプールとの嵌合周上に並ぶ絞り部におけるキャビテーションを有効に抑制でき、流動音の大幅な低減を図れる油圧制御弁を、構成の如何に拘わらず、また加工の困難さを伴うことなく提供することを目的とする。
【００３１】
【課題を解決するための手段】
本発明の第１発明に係る油圧制御弁は、筒形をなすバルブボディーの内側に同軸上での相対角変位可能にバルブスプールを嵌め合わせ、両者の嵌合周上に並設された各複数の油溝を千鳥配置し、バルブスプール側の油溝を油圧源と排油先とに交互に連通させる一方、これらの間のバルブボディー側の油溝を相異なる送油先に交互に連通させ、周方向に相隣する夫々の油溝間に前記相対角変位に応じて絞り面積を変える絞り部を構成してなり、各絞り部を臨むバルブスプール側の角部に絞り面積調整用の面取り部を備える油圧制御弁において、前記油圧源に連なる油溝の両側の絞り部が前記排油先に連なる油溝の両側の絞り部よりも大なる絞り面積を有するように、前記バルブスプール側の各油溝間のランドを周方向にオフセット配置してなることを特徴とする。
【００３２】
この発明は、バルブスプール側の油溝を給油室及び排油室とし、各絞り部における絞り面積調整用の面取り部（チャンファ）をバルブスプール側に設けた構成を対象とし、バルブスプール側のランドを周方向にオフセット配置して、給油室の両側の絞り部が排油室の両側の絞り部よりも大なる絞り面積を有するようになし、バルブボディーとバルブスプールとの相対角変位が生じたとき、図14に示す実験結果からキャビテーションに対して有利とされる給油室の両側の絞り部に作動油の流れを集中させて流動音を低減する。
【００３３】
本発明の第２発明に係る油圧制御弁は、筒形をなすバルブボディーの内側に同軸上での相対角変位可能にバルブスプールを嵌め合わせ、両者の嵌合周上に並設された各複数の油溝を千鳥配置し、バルブスプール側の油溝を油圧源と排油先とに交互に連通させる一方、これらの間のバルブボディー側の油溝を相異なる送油先に交互に連通させ、周方向に相隣する夫々の油溝間に前記相対角変位に応じて絞り面積を変える絞り部を構成してなり、各絞り部を臨むバルブボディー側の角部に絞り面積調整用の面取り部を備える油圧制御弁において、前記排油先に連なる油溝の両側の絞り部が前記油圧源に連なる油溝の両側の絞り部よりも大なる絞り面積を有するように、前記バルブボディー側の油溝、又は前記バルブスプール側の各油溝間のランドを周方向にオフセット配置してなることを特徴とする。
【００３４】
この発明は、バルブスプール側の油溝を給油室及び排油室とし、各絞り部のチャンファをバルブボディー側に設けた構成を対象とし、バルブボディー側の油溝又はバルブスプール側のランドのオフセット配置により、排油室の両側の絞り部が給油室の両側の絞り部よりも大なる絞り面積を有するようになし、バルブボディーとバルブスプールとの相対角変位が生じたとき、図15に示す実験結果からキャビテーションに対して有利とされる排油室の両側の絞り部に作動油の流れを集中させて流動音を低減する。
【００３５】
本発明の第３発明に係る油圧制御弁は、筒形をなすバルブボディーの内側に同軸上での相対角変位可能にバルブスプールを嵌め合わせ、両者の嵌合周上に並設された各複数の油溝を千鳥配置し、バルブボディー側の油溝を油圧源と排油先とに交互に連通させる一方、これらの間のバルブスプール側の油溝を相異なる送油先に交互に連通させ、周方向に相隣する夫々の油溝間に前記相対角変位に応じて絞り面積を変える絞り部を構成してなり、各絞り部を臨むバルブスプール側の角部に絞り面積調整用の面取り部を備える油圧制御弁において、前記排油先に連なる油溝の両側の絞り部が前記油圧源に連なる油溝の両側の絞り部よりも大なる絞り面積を有するように、前記バルブボディー側の各油溝間のランド、又は前記バルブスプール側の油溝を周方向にオフセット配置してなることを特徴とする。
【００３６】
この発明は、バルブボディー側の油溝を給油室及び排油室とし、各絞り部のチャンファをバルブスプール側に設けた構成を対象とし、バルブボディー側のランド又はバルブスプール側の油溝のオフセット配置により、排油室の両側の絞り部が給油室の両側の絞り部よりも大なる絞り面積を有するようになし、バルブボディーとバルブスプールとの相対角変位が生じたとき、図15に示す実験結果からキャビテーションに対して有利とされる排油室の両側の絞り部に作動油の流れを集中させて流動音を低減する。
【００３７】
本発明の第４発明に係る油圧制御弁は、筒形をなすバルブボディーの内側に同軸上での相対角変位可能にバルブスプールを嵌め合わせ、両者の嵌合周上に並設された各複数の油溝を千鳥配置し、バルブボディー側の油溝を油圧源と排油先とに交互に連通させる一方、これらの間のバルブスプール側の油溝を相異なる送油先に交互に連通させ、周方向に相隣する夫々の油溝間に前記相対角変位に応じて絞り面積を変える絞り部を構成してなり、各絞り部を臨むバルブボディー側の角部に絞り面積調整用の面取り部を備える油圧制御弁において、前記油圧源に連なる油溝の両側の絞り部が前記排油先に連なる油溝の両側の絞り部よりも大なる絞り面積を有するように、前記バルブボディー側の各油溝間のランド、又は前記バルブスプール側の油溝を周方向にオフセット配置してなることを特徴とする。
【００３８】
この発明は、バルブボディー側の油溝を給油室及び排油室とし、各絞り部のチャンファをバルブボディー側に設けた構成を対象とし、バルブボディー側のランド又はバルブスプール側の油溝のオフセット配置により、給油室の両側の絞り部が排油室の両側の絞り部よりも大なる絞り面積を有するようになし、バルブボディーとバルブスプールとの相対角変位が生じたとき、図14に示す実験結果からキャビテーションに対して有利とされる給油室の両側の絞り部に作動油の流れを集中させて流動音を低減する。
【００３９】
【発明の実施の形態】
以下本発明をその実施の形態を示す図面に基づいて詳述する。図１は、動力舵取装置の油圧回路と共に示す本発明の第１発明に係る油圧制御弁の横断面図である。
【００４０】
図中１はバルブボディー、２はバルブスプールである。円筒形をなすバルブボディー１の内周面には、８本の油溝４，４…が周方向に等配をなして並設され、また、バルブボディー１の内径と略等しい外径を有する厚肉円筒形のバルブスプール２の外周面には、同様に、８本の油溝５，５…が周方向に等配をなして並設されている。
【００４１】
バルブボディー１側の８本の油溝４，４…は、夫々等しい幅を有しているが、バルブスプール２側の８本の油溝５，５…は、図に明らかな如く、夫々の間のランドを周方向にオフセット配置することにより、１つおきに位置する４本の幅を拡げ、残りの４つの幅を逆に狭めて形成されている。なお、バルブスプール２における前記ランドのオフセット量は、バルブスプール２の中心角に直して数分〜十数分前後のわずかなものである。
【００４２】
第１発明に係る油圧制御弁は、以上の如く構成されたバルブボディー１とバルブスプール２とを用い、バルブボディー１の内側にバルブスプール２を同軸上での相対回転自在に嵌め合わせ、これら両者を、バルブスプール２の内側に挿通されたトーションバー３により相互に連結して構成されている。バルブボディー１側の油溝４，４…とバルブスプール２側の油溝５，５…とは、前記トーションバー３に捩れが生じていない中立状態において、図示の如く周方向に千鳥配置され、夫々の両側に相隣するものと連通するように位置決めされている。
【００４３】
以上の構成により、バルブボディー１側の油溝４，４…の夫々は、バルブスプール２側の油溝５，５…間のランドに対向し、また、バルブスプール２側の油溝５，５…の夫々は、バルブボディー１側の油溝４，４…間のランドに対向して、バルブボディー１とバルブスプール２との嵌合周上には、油溝４，４…の内側の８つの油室と、油溝５，５…の外側の８つの油室とが、夫々の間に連通部を有して交互に並んだ状態となる。
【００４４】
バルブボディー１とバルブスプール２とは、これらを連結するトーションバー３の捩れの範囲内での相対角変位が可能であり、前記各油室間の連通部は、この相対角変位に応じて夫々の連通面積（絞り面積）を増減する絞り部として作用する。本発明に係る油圧制御弁においては、バルブスプール２側のランドが前述の如くオフセット配置され、広幅の４本の油溝５，５…と狭幅の４本の油溝５，５…とが形成されている。従って、バルブボディー１との嵌合周上に並ぶ前記絞り部の絞り面積は均等ではなく、広幅の油溝５，５…により形成された４つの油室の両側に位置する８か所の絞り部6a，6a…は、狭幅の油溝５，５…の外側の４つの油室の両側に位置する８か所の絞り部6b，6b…よりも大なる絞り面積を有することになる。
【００４５】
このようにバルブスプール２側の油溝５，５…の外側に形成された８つの油室の内、１つおきに位置し、両側に広幅の絞り部6a，6aを有する４つの油室は、バルブボディー１の周壁を貫通する各別の導油孔を介して油圧源たる油圧ポンプＰの吐出側に接続され、該油圧ポンプＰの発生油圧が供給される給油室10，10…を構成している。これに対し、両側に狭幅の絞り部6b，6bを有する残りの４つの油室は、バルブスプール２を半径方向に貫通する各別の排油孔及びバルブスプール２内側の中空部を介して排油先となる油タンクＴに接続され、該油タンクＴへの排出油の通路となる排油室11，11…を構成している。
【００４６】
一方、バルブボディー１側の油溝４，４…の内側に形成された８つの油室は、一側に広幅の絞り部6aを、他側に狭幅の絞り部6bを夫々有することになり、これらの内、前記給油室10，10…に周方向の同側にて相隣する４つの油室は、バルブボディー１の周壁を貫通する各別の導油孔を介して、油圧の送給先であるパワーシリンダＳの一方のシリンダ室Ｓ_Rに接続され、このシリンダ室Ｓ_Rへの送油室12，12…を構成しており、残りの４つは、前記パワーシリンダＳの他方のシリンダ室Ｓ_Lに接続され、該シリンダ室Ｓ_Lへの送油室13，13…を構成している。
【００４７】
図２は、バルブボディー１とバルブスプール２との嵌合周上に並ぶ各室を直線展開して示す動作説明図である。前述した構成により、図の中央に示す給油室10の両側には、送油室12又は送油室13を経て排油室11に至る油路が夫々形成され、給油室10と送油室12，13とは広幅の絞り部6a，6aを介して連通し、また、送油室12，13と排油室11，11とは狭幅の絞り部6b，6bを介して連通する。
【００４８】
図２（ａ）は、バルブボディー１とバルブスプール２との間に相対角変位が生じていない状態（中立状態）を示している。このとき、給油室10の両側の絞り部6a，6aは、相互に等しい絞り面積を有し、これらの絞り部6a，6aを介して連通する送油室12，13の他側の絞り部6b，6bもまた、相互に等しい絞り面積を有している。従って、油圧ポンプＰから給油室10に供給される作動油は、両側の油路に均等に配分され、送油室12又は13を経て排油室11に達し、これら夫々に開口する排油孔を経てバルブスプール２内側の中空部に流れ込み、該中空部内にて合流して油タンクＴに還流する。
【００４９】
このとき、前記送油室12，13間、及びこれら夫々に接続されたパワーシリンダＳの両シリンダ室Ｓ_R，Ｓ_L間に圧力差は発生せず、該パワーシリンダＳはなんらの力も発生しない。またこのとき、前記油路の中途に介在する絞り部6a，6bは大なる絞り面積を保っており、油圧ポンプＰと油タンクＴとの間に大なる通流抵抗を有する部分が存在しないことから、前記油圧ポンプＰの駆動負荷は小さく保たれる。
【００５０】
これに対し、図示しない舵輪に操舵トルクが加えられた場合、バルブボディー１とバルブスプール２との間にトーションバー３の捩れを伴って相対角変位が生じ、給油室10と送油室12，13との間の絞り部6a，6a、及び送油室12，13と排油室11との間の絞り部6b，6bの絞り面積が変化する。
【００５１】
この変化は、送油室12，13の両側において互いに逆向きに生じる。例えば、バルブボディー１に対するバルブスプール２の相対回転が図１における時計回りに生じた場合、バルブスプール２は、図２（ｂ）中に白抜矢符にて示す向きに相対移動し、一方の送油室12の両側においては、給油室10側の絞り部6aの絞り面積が増大し、排油室11側の絞り部6bの絞り面積が減少するのに対し、他方の送油室13の両側においては、逆に、給油室10側の絞り部6aの絞り面積が減少し、排油室11側の絞り部6bの絞り面積が増大する。
【００５２】
従って、給油室10に供給された作動油の大部分は、絞り面積を増した絞り部6aを経て送油室12に導入されて、該送油室12に連通するシリンダ室Ｓ_Rに送給されることとなり、送油室12への導入油の一部は、他側において絞り面積を減じた絞り部6bを経て排油室11に流出する。また、給油室10への供給油の一部は、絞り面積を減じた絞り部6aを経て送油室13に流出し、この流出油は、送油室13の他側において絞り面積を増した絞り部6bを経て排油室11に導入される。
【００５３】
以上の如き動作状態においては、送油室12の内圧は給油室10と略等圧に保たれるのに対し、送油室13の内圧は、給油室10との間にて絞り面積を減じた絞り部6aの通流に伴う減圧分だけ低下することになり、送油室12，13間、及びこれら夫々に連通されたシリンダ室Ｓ_R，Ｓ_L間に圧力差が生じ、パワーシリンダＳは、シリンダ室Ｓ_RからＳ_Lに向かう油圧力（操舵補助力）を発生する。パワーシリンダＳのこの動作に伴って、シリンダ室Ｓ_L内の封入油は押し出され、この押出し油は、該シリンダ室Ｓ_Lに接続された送油室13に還流し、前記給油室10からの流入油と合流して、送油室13の他側において絞り面積を増した絞り部6bを経て排油室11に導入され、バルブスプール２の中空部を経て油タンクＴに排出される。
【００５４】
以上の動作によりパワーシリンダＳが発生する操舵補助力は、給油室10と送油室13との間の絞り部6a、及び排油室11と送油室12との間の絞り部6bにおける絞り面積の減少程度に依存する。この絞り面積の減少は、バルブボディー１とバルブスプール２との間の相対角変位に応じて生じ、この相対角変位は、バルブボディー１とバルブスプール２とを連結するトーションバー３に捩れを生ぜしめるべく舵輪に加わられた操舵トルクの大きさに対応する。
【００５５】
一方、バルブボディー１に対するバルブスプール２の相対回転が図１における反時計回りに生じた場合、給油室10の両側の絞り部6a，6aと、排油室11の両側の絞り部6b，6bとに前述の場合と逆の面積変化が生じ、パワーシリンダＳは、シリンダ室Ｓ_LからＳ_Rに向かう操舵補助力を発生し、この大きさもまた舵輪に加わる操舵トルクの大きさに対応する。このようにして、舵輪に加わる操舵トルクの方向及び大きさに応じた操舵補助力が得られる。
【００５６】
絞り部6a又は絞り部6bを臨むバルブスプール２側の角部には、チャンファ７，７…が形成してある。これらのチャンファ７，７…は、図２に示す如く、バルブスプール２側の油溝５の側面と油溝５，５間のランドの周面とが交叉する角部を、ランドの周面に対して所定の傾斜角度を有して斜めに切欠き、周方向に所定の幅を有して形成されており、バルブボディー１とバルブスプール２との相対角変位に対し、各絞り部６の絞り面積を緩やかに変化せしめるべく設けてあり、動力舵取装置における操舵補助力の望ましい増加特性、即ち、舵輪に加わる操舵トルクが小さい範囲においては操舵補助力が漸増し、操舵トルクが所定値を超えると共に急増する特性を実現する作用をなす。
【００５７】
さて、図２（ｂ）に示す動作状態において、給油室10に供給される作動油は、該給油室10の一側において絞り面積を減じた絞り部6aを経て一方の送油室13に流出し、また、他方の送油室12の他側にて絞り面積を減じた絞り部6bを経て排油室11に流出することになり、前述した如く、これらの流れにおいてキャビテーションが発生し、耳障りな流動音を伴う。
【００５８】
図１及び図２に示す油圧制御弁は、バルブボディー１側の油溝４，４…を送油室12，13とし、またバルブスプール２側の油溝５，５…を給油室10及び排油室11とする一方、絞り部6a又は絞り部6bを臨むバルブスプール２側の角部にチャンファ７，７…を備えた構成となっており、この構成におけるキャビテーションの発生挙動は、前記図14に示す如くであり、油圧源たる油圧ポンプＰに連なる給油室10の両側の絞り部6a，6a…での流れが、排油先たる油タンクＴに連なる排油室11の両側の絞り部6b，6bでの流れよりもキャビテーションの発生に対して有利である。
【００５９】
そして、図１及び図２に示す油圧制御弁においては、バルブスプール２側の各油溝５，５…間のランドが前述した如くオフセット配置され、給油室10の両側の絞り部6a，6aが排油室11の両側の絞り部6b，6bよりも大なる絞り面積を有するようになしてあり、この大小関係は、図２（ｂ）に示す動作状態においても維持され、給油室10と送油室13との間の絞り部6aは、送油室12と排油室11との間の絞り部6bよりも大なる絞り面積を有する。従って、給油室10から排油室11への作動油の流れは、キャビテーションに対して好条件となる給油室10と送油室13との間の絞り部6aに集中することになり、キャビテーションの発生が有効に抑制され、該キャビテーションに伴う流動音を大幅に低減することができる。
【００６０】
図３及び図４は、本発明の第２発明に係る油圧制御弁の動作説明図であり、図２におけると同様に、バルブボディー１とバルブスプール２との嵌合周上に並ぶ各室を直線展開して示してある。
【００６１】
これらの図に示す油圧制御弁は、バルブボディー１側の油溝４，４…を送油室12，13とし、またバルブスプール２側の油溝５，５…を給油室10及び排油室11とする一方、絞り部6a及び絞り部6bの絞り面積調整用のチャンファ７，７…をバルブボディー１側の角部に備えた構成となっており、各絞り部6a，6bでの流れの形態は、前記図15に示す絞り部の状態を天地を逆として見た場合に対応し、キャビテーションの発生挙動は、図15に示す結果に相当するものとなり、排油先たる油タンクＴに連なる排油室11の両側の絞り部6b，6bでの流れが、油圧源たる油圧ポンプＰに連なる給油室10の両側の絞り部6a，6a…での流れよりもキャビテーションの発生に対して有利である。
【００６２】
図３においては、バルブボディー１側の油溝４，４…が周方向にオフセット配置され、また図４においては、バルブスプール２側の各油溝５，５…間のランドが周方向にオフセット配置されており、いずれにおいても、排油室11の両側の絞り部6b，6bが給油室10の両側の絞り部6a，6aよりも大なる絞り面積を有するようになしてある。
【００６３】
この大小関係は、図３（ｂ）及び図４（ｂ）に示す如く、バルブボディー１とバルブスプール２との間に相対角変位が生じた動作状態においても維持され、送油室12と排油室11との間の絞り部6bは、給油室10と送油室13との間の絞り部6aよりも大なる絞り面積を有する。従って、この動作状態において給油室10から排油室11への油流は、キャビテーションに対して好条件となる送油室12と排油室11との間の絞り部6bに集中することになり、キャビテーションの発生が有効に抑制され、該キャビテーションに伴う流動音を低減することができる。
【００６４】
なお、図４におけるランドのオフセットは、図２におけるそれと逆方向になされており、オフセット方向のこの相違は、バルブボディー１とバルブスプール２とのいずれの側に前記チャンファ７，７…が形成されているかにより生じるものである。従って、チャンファ７，７…をバルブスプール２側に備える第１発明に係る油圧制御弁においても、図３におけると逆方向にバルブボディー１側の油溝４，４…をオフセットすることにより、バルブスプール２側のランドを前述の如くオフセットした図２の場合と同等の効果が得られるが、このような油溝４，４…のオフセットにより流動音の低減を図った構成は、本願出願人により先に提案されており（特願平6-323144号及びその国内優先出願である特願平7-176464号）、本発明の範囲には含まれない。
【００６５】
図５及び図６は、本発明の第３発明に係る油圧制御弁の動作説明図であり、前記図２ないし図４と同様に、バルブボディー１とバルブスプール２との嵌合周上に並ぶ各室を直線展開して示してある。
【００６６】
これらの図に示す油圧制御弁は、図１〜図４に示す油圧制御弁とは異なり、バルブボディー１側の油溝４，４…を給油室10及び排油室11とし、またバルブスプール２側の油溝５，５…を送油室12，13とした構成となっており、絞り面積調整用のチャンファ７，７…は、バルブスプール２側の角部に形成されている。この構成におけるキャビテーションの発生挙動は、前記図15に示す如くであり、排油室11の両側の絞り部6b，6bでの流れが、給油室10の両側の絞り部6a，6a…での流れよりもキャビテーションの発生に対して有利となる。
【００６７】
図５においては、バルブボディー１側の各油溝４，４…間のランドが周方向にオフセット配置され、また図６においては、バルブスプール２側の油溝５，５…が周方向にオフセット配置されており、いずれにおいても、排油室11の両側の絞り部6b，6bが給油室10の両側の絞り部6a，6aよりも大なる絞り面積を有するようになしてある。
【００６８】
この大小関係は、図５（ｂ）及び図６（ｂ）に示す如く、バルブボディー１とバルブスプール２との間に相対角変位が生じた動作状態においても維持され、送油室12と排油室11との間の絞り部6bは、給油室10と送油室13との間の絞り部6aよりも大なる絞り面積を有する。従って、この動作状態において給油室10から排油室11への油流は、キャビテーションに対して好条件となる送油室12と排油室11との間の絞り部6bに集中することになり、キャビテーションの発生が有効に抑制され、該キャビテーションに伴う流動音を低減することができる。
【００６９】
図７及び図８は、本発明の第４発明に係る油圧制御弁の動作説明図であり、前記図２ないし図６と同様に、バルブボディー１とバルブスプール２との嵌合周上に並ぶ各室を直線展開して示してある。
【００７０】
これらの図に示す油圧制御弁は、図５及び図６に示す油圧制御弁と同様、バルブボディー１側の油溝４，４…を給油室10及び排油室11とし、またバルブスプール２側の油溝５，５…を送油室12，13とした構成となっており、絞り面積調整用のチャンファ７，７…は、図５及び図６とは異なり、各絞り部6a，6bを臨むバルブボディー１側の角部に形成されている。この構成における各絞り部6a，6bでの流れの形態は、前記図14に示す絞り部の状態を天地を逆として見た場合に対応し、キャビテーションの発生挙動は、図14に示す結果に相当するものとなり、給油室10の両側の絞り部6a，6a…での流れが、排油室11の両側の絞り部6b，6bでの流れよりもキャビテーションの発生に対して有利となる。
【００７１】
図７においては、バルブボディー１側の各油溝４，４…間のランドが周方向にオフセット配置され、また図８においては、バルブスプール２側の油溝５，５…が周方向にオフセット配置されており、いずれにおいても、給油室10の両側の絞り部6a，6aが排油室11の両側の絞り部6b，6bよりも大なる絞り面積を有するようになしてある。即ち、これらにおけるランド又は油溝のオフセットは、図５及び図６における夫々のオフセットと逆方向になされている。
【００７２】
以上のオフセット配置により得られた絞り部6a，6bの大小関係は、図７（ｂ）及び図８（ｂ）に示す如く、バルブボディー１とバルブスプール２との間に相対角変位が生じた動作状態においても維持され、給油室10と送油室13との間の絞り部6aは、送油室12と排油室11との間の絞り部6bよりも大なる絞り面積を有する。従って、この動作状態において給油室10から排油室11への油流は、キャビテーションに対して好条件となる給油室10と送油室13との間の絞り部6aに集中することになり、キャビテーションの発生が有効に抑制され、該キャビテーションに伴う流動音を低減することができる。
【００７３】
以上の如く本発明に係る油圧制御弁は、バルブボディー１側の油溝４，４…若しくは各油溝４，４…間のランド、又はバルブスプール２側の油溝５，５…若しくは各油溝５，５…間のランドのオフセット配置により、給油室10，10…の両側の絞り部6a，6a…の絞り面積と排油室11，11…の両側の絞り部6b，6b…の絞り面積との間に差異を生ぜしめ、流動音の低減効果を得ようとしたものであり、チャンファ７，７…の寸法調整を必要とする従来の油圧制御弁に比較した場合、加工の困難さが大幅に改善される。
【００７４】
ところが、実際に必要となるオフセット量は、バルブボディー１の中心角に直して数分〜十数分程度のわずかな量であり、バルブボディー１又はバルブスプール２の加工時における芯出し誤差の影響を受ける。従って、バルブボディー１とバルブスプール２との嵌合部の全周に亘って見た場合、給油室10，10…の両側の絞り部6a，6a…の一部が、排油室11，11…の両側の絞り部6b，6b…の一部よりも小さい面積となる場合があり得る。逆に、バルブボディー１側の油溝４，４…とランド、及びバルブスプール２側の油溝５，５…とランドが等配をなして形成されている油圧制御弁においては、前述した芯出し誤差の影響により、意識的なオフセット配置がなされているかの如くなり、給油室10，10…の両側の絞り部６，６…の一部が排油室11，11…の両側の絞り部６，６…の一部よりも大きい面積となる場合があり得る。
【００７５】
本発明に係る油圧制御弁は、以上の如き芯出し誤差の影響が生じている場合においても、従来の油圧制御弁との差別化が可能である。図９は、両者の相違点の説明図である。これらの図は、横軸に展開されたバルブボディー１とバルブスプール２との嵌合周上に並ぶ絞り部の絞り面積を図示するものであり、図中の○印は、オフセット配置がなされていない従来の油圧制御弁における絞り面積を、△印及び□印は、本発明に係る油圧制御弁の絞り面積を夫々示している。
【００７６】
図９（ａ）は、芯出し誤差が存在しない理想的なバルブの場合を示しており、このとき、従来の油圧制御弁においては、前記嵌合周上に並ぶ絞り部が等しい絞り面積を有するのに対し、本発明に係る油圧制御弁においては、大きい絞り面積を有する絞り部（△印）と、同じく小さい絞り面積を有する絞り部（□印）とが交互に並ぶことになる。
【００７７】
図９（ｂ）及び（ｃ）は、芯出し誤差が存在する場合を示している。芯出し誤差が存在する場合、バルブスプール２と嵌合するバルブボディー１の内周は、図中に破線にて示す如く、各一か所の小径部及び大径部を有する周期的な変化を示し、従来の油圧制御弁における絞り面積は、内径の変化線に沿って大小に変化する分布を示す。
【００７８】
一方本発明の油圧制御弁における絞り面積は、図９（ａ）におけると同様に、オフセット配置がなされていない場合の絞り面積を大小両側に交互に偏倚させた分布となり、図９（ｃ）に示す如く芯出し誤差が大きい場合には、△印にて示す絞り部の一部が、□印にて示す絞り部の一部よりも小さい絞り面積を有することがあるが、この場合においても、相隣する絞り部間の絞り面積に着目すると、交互に大小となる大小関係が嵌合周の全周に亘って周期的に現出しており、従来の油圧制御弁における絞り面積の分布とは明らかに異なる。このように本発明に係る油圧制御弁は、相隣する絞り部の絞り面積が交互に大小となる分布を示し、オフセット配置がなされていない構成において芯出し誤差の影響により現出する絞り面積の大小関係との区別が可能となる。
【００７９】
なお以上の実施の形態においては、動力舵取装置のパワーシリンダへの送給油圧を制御する油圧制御弁としての使用例について述べたが、本発明の適用範囲はこれに限るものではなく、各種の油圧回路において油圧制御のために用いられる回転式の油圧制御弁全般への適用が可能である。
【００８０】
【発明の効果】
以上詳述した如く本発明に係る油圧制御弁においては、バルブボディーとバルブスプールとの嵌合周上に並ぶ複数の油溝により、油圧源に連なる給油室、排油先に連なる排油室、及びこれらの間にて送油先に連なる送油室を形成し、バルブボディー側又はバルブスプール側の油溝若しくは各油溝間のランドをオフセット配置し、給油室の両側の絞り部と排油室の両側の絞り部との間に絞り面積の差異を生ぜしめ、給油室から排油室に向かう作動油の流れがキャビテーションの発生に対して有利な絞り部に集中するようにしたから、煩雑な加工を要することなくキャビテーションの発生に伴う流動音を大幅に低減することができる等、本発明は優れた効果を奏する。
【図面の簡単な説明】
【図１】本発明の第１発明に係る油圧制御弁の模式的横断面図である。
【図２】第１発明に係る油圧制御弁の動作説明図である。
【図３】第２発明に係る油圧制御弁の動作説明図である。
【図４】第２発明に係る油圧制御弁の動作説明図である。
【図５】第３発明に係る油圧制御弁の動作説明図である。
【図６】第３発明に係る油圧制御弁の動作説明図である。
【図７】第４発明に係る油圧制御弁の動作説明図である。
【図８】第４発明に係る油圧制御弁の動作説明図である。
【図９】本発明に係る油圧制御弁と従来の油圧制御弁とにおける絞り面積の分布状態の説明図である。
【図１０】従来の一般的な油圧制御弁の動作説明図である。
【図１１】流動音の低減を図った従来の油圧制御弁の動作説明図である。
【図１２】流動音の低減を図った従来の油圧制御弁の動作説明図である。
【図１３】流動音の低減を図った従来の油圧制御弁の動作説明図である。
【図１４】キャビテーションの発生挙動を調べた実験の結果を示す図表である。
【図１５】キャビテーションの発生挙動を調べた実験の結果を示す図表である。
【符号の説明】
１バルブボディー
２バルブスプール
４油溝
５油溝
6a 絞り部
6b 絞り部
７チャンファ
10 給油室
11 排油室
12 送油室
13 送油室
Ｐ油圧ポンプ
Ｓパワーシリンダ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotary hydraulic control valve that performs a hydraulic control operation by a relative angular displacement on the same axis between a valve body and a valve spool, and in particular, a power cylinder for steering assistance in a hydraulic power steering apparatus. The present invention relates to a hydraulic control valve used to control the hydraulic pressure supplied to the vehicle according to the steering wheel operation.
[0002]
[Prior art]
The hydraulic power steering device assists steering by the hydraulic pressure generated by a double-acting hydraulic cylinder (power cylinder) arranged in the steering mechanism, reducing the labor burden required to operate the steering wheel (steering wheel) In order to obtain a comfortable steering sensation, both cylinder chambers (oil feed destination) of the power cylinder, a hydraulic pump (hydraulic power source) driven by the engine, and an oil tank that stores hydraulic oil are stored. A hydraulic control valve that performs hydraulic pressure supply / discharge control in accordance with the direction and magnitude of the steering torque applied to the steered wheels is interposed between the oil discharge destination and the oil discharge destination.
[0003]
As the hydraulic control valve, a rotary hydraulic control valve that directly uses the rotation of the steering wheel is generally used. This is because the input shaft connected to the steering wheel and the output shaft connected to the steering mechanism are connected coaxially via a torsion bar, and the other connection is made inside the cylindrical valve body engaged with one connection end. A valve spool formed integrally with the end is fitted so as to be relatively rotatable on the same axis, and when a steering torque is applied to the steering wheel, the valve body and the valve spool are twisted together with the twist of the torsion bar. It has a configuration that causes relative angular displacement.
[0004]
On the fitting circumference of the valve body and the valve spool (the inner circumference of the former and the outer circumference of the latter), a plurality of oil grooves extending in the axial length direction are juxtaposed in the circumferential direction. The oil grooves are arranged in a zigzag manner in the circumferential direction, and are positioned so that the adjacent ones on both sides communicate with each other, and each of these oil grooves is connected to the hydraulic source and the oil discharge destination, respectively. A pair of oil supply chambers, which are located between the oil supply chamber and the oil discharge chamber, and the oil discharge chambers on both sides of the oil supply chamber, respectively, are connected to both cylinder chambers of the power cylinder that is the oil supply destination. Yes.
[0005]
FIG. 10 is an explanatory view of the operation of this type of hydraulic control valve. In this figure, the fitting part of the valve body 1 and the valve spool 2 is linearly developed, and the oil grooves 4, 4... Arranged along the inner periphery of the valve body 1 are formed in both cylinder chambers S of the power cylinder. _R , S _L Are connected to each other through separate oil feeding holes, and alternately constitute a pair of oil feeding chambers 12, 13, and oil grooves 5, 5 ... arranged on the outer periphery of the valve spool 2 are hydraulic pumps serving as hydraulic pressure sources. An oil supply chamber 10 connected to P via an oil introduction hole and an oil discharge chamber 11 connected to an oil tank T, which is an oil discharge destination, via an oil discharge hole are alternately configured. The oil grooves 4, 4 ... on the valve body 1 side are the oil supply chamber 10 and the oil discharge chamber 11, and the oil grooves 5, 5 ... on the valve spool 2 side are the oil feed chamber 12, A configuration of 13 is also possible.
[0006]
The oil grooves 4, 4... On the valve body 1 side and the oil grooves 5, 5... On the valve spool 2 side communicate with each other with an equal area. Acts as throttles 6, 6... That change the throttle area in accordance with the angular displacement. _R , S _L The hydraulic pressure supplied to the is controlled.
[0007]
FIG. 10A shows a state where no relative angular displacement occurs between the valve body 1 and the valve spool 2. At this time, the hydraulic pressure supplied from the hydraulic pump P to the oil supply chamber 10 is equally distributed to the adjacent oil supply chambers 12 and 13 because the throttle portions 6 and 6 on both sides of the oil supply chamber 10 have the same area. Then, the oil is supplied to the oil discharge chambers 11 and 11 through the other throttle portions 6 and 6 and recirculates to the oil tank T connected to them, and the oil pressure supplied to the oil supply chamber 10 is Room S _R , S _L The power cylinder does not generate any force.
[0008]
FIG. 10B shows a state in which a steering torque is applied to the steered wheel, and a relative angular displacement is generated between the valve body 1 and the valve spool 2. At this time, the throttle area of one (oil feeding chamber 12 side) of the throttle portions 6 and 6 on both sides of the oil feeding chamber 10 is increased, and the throttle area of the other (oil feeding chamber 13 side) is decreased. The hydraulic pressure supplied to the chamber 10 is mainly introduced into the oil feeding chamber 12 through the throttle section 6 having an increased throttle area, and between these oil feeding chamber 12 and the other oil feeding chamber 13 and these Cylinder chamber S connected to each other _R , S _L A pressure difference is generated between them, and the power cylinder generates an oil pressure (steering assisting force) corresponding to the pressure difference.
[0009]
The pressure difference generated at this time depends on the degree of reduction of the throttle area at the throttle part 6 on the other side (oil feeding chamber 13 side), and this degree of reduction is the magnitude of the relative angular displacement, that is, the steering applied to the steered wheels. Corresponds to the magnitude of the torque. Therefore, the steering assist force generated by the power cylinder has a direction and a magnitude corresponding to the steering torque applied to the steered wheels, and can assist steering. The other cylinder chamber S is operated with the operation of the power cylinder. _L The oil pushed out from the oil flows back to the other oil feeding chamber 13 and is adjacent to the oil exhausting chambers 11 through the constricted portion 6 having an increased throttle area on one side of the oil feeding chamber 13 (oil discharging chamber 11 side). And discharged to an oil tank T connected to the oil discharge chamber 11.
[0010]
A chamfered portion (chamfer 7) having a predetermined width in the circumferential direction is formed at a corner on the valve spool 2 side facing each throttle portion 6. The chamfer 7 has a corner portion where the side surface of the oil groove 5 on the valve spool 2 side intersects with the peripheral surface of the land between the oil grooves 5 and 5 with a predetermined inclination angle with respect to the peripheral surface of the land. It is formed with a notch obliquely and with a predetermined width in the circumferential direction, and has an adjustment function that gently changes the throttle area of each throttle portion 6 with respect to the relative angular displacement between the valve body 1 and the valve spool 2. Eggplant. The desirable increase characteristic of the steering assist force in the power steering apparatus is not a characteristic that increases proportionally with respect to the steering torque applied to the steered wheels, but a characteristic that gradually increases when the steering torque is small, exceeds a predetermined limit, and increases rapidly. These characteristics are achieved by the action of the chamfers 7, 7.
[0011]
[Problems to be solved by the invention]
Now, in the hydraulic control valve that performs the operation as described above, particularly when the relative angular displacement between the valve body 1 and the valve spool 2 is large, it is annoying when hydraulic fluid flows through the throttle portion 6 with a reduced throttle area. There is a problem that cavitation is generated with a flowing sound. This flow noise occurs when the interior of the passenger compartment is relatively quietly stopped or when the steering wheel is operated greatly during low-speed driving, not only disturbing the quietness of the interior of the passenger compartment, but also unnecessarily disturbing the driver. Therefore, in the hydraulic control valve for a power steering apparatus, the reduction of the flow noise is an important issue.
[0012]
As described above, the increase / decrease of the throttle area of the throttle portion 6 occurs oppositely to the oil feeding chambers 12 and 13 on both sides of the oil supply chamber 10 and on both sides of the oil discharge chamber 11. That is, in the operating state shown in FIG. 10 (b), the throttle area of the throttle section 6 on the oil feed chamber 12 side increases on both sides of the oil supply chamber 10, and the throttle section 6 on the oil feed chamber 13 side throttles. Whereas the area decreases, on both sides of the oil discharge chamber 11, the throttle area of the throttle section 6 on the oil feed chamber 13 side increases, and the throttle area of the throttle section 6 on the oil feed chamber 12 side decreases. .
[0013]
At this time, the flow of the hydraulic oil causing the flow noise is caused by the throttle parts 6 and 6 on the side where the throttle area is reduced, that is, the throttle part 6 between the oil supply chamber 10 and the oil feed chamber 13, and the drained oil. It occurs in the throttle section 6 between the chamber 11 and the oil feeding chamber 12, respectively, but it is said that there is a difference in the cavitation generation behavior in these flows, and hydraulic pressure that aims to reduce the flow noise according to such knowledge Various control valves have been conventionally proposed.
[0016]
Japanese Patent Application Laid-Open No. 6-206555 , Product It is said that the flow noise caused by the cavitation of fluid oil is more prominently generated in the throttle parts 6 and 6 on both sides of the oil discharge chamber 11 than in the throttle parts 6 and 6 on both sides of the oil supply chamber 10. As shown in FIG. 12, the narrowing portions 6 and 6 on both sides of the oil discharge chamber 11 are formed with chamfers 7 and 7 at the corners on the valve body 1 side, not on the valve spool 2 side. A hydraulic control valve that reduces this is disclosed.
[0017]
A hydraulic control valve having the same configuration is also disclosed in Japanese Patent Laid-Open No. 6-156292. However, this hydraulic control valve is disclosed in JP-A-6-206555. In the news On the contrary, the throttle parts 6 and 6 on both sides of the oil supply chamber 10 are considered disadvantageous to cavitation. In these throttle parts 6 and 6, chamfers 7 and 7 are provided at the corners on the valve body 1 side. It has a formed configuration.
[0018]
On the other hand, Japanese Patent Laid-Open No. 60-203580 and US Pat. No. 3022772 disclose a configuration opposite to the hydraulic control valve shown in FIGS. 10, 11 and 12, that is, oil grooves 4 and 4 on the valve body 1 side. In the configuration in which the oil supply chamber 10 and the oil discharge chamber 11 are used and the oil grooves 5, 5 on the valve spool 2 side are the oil supply chambers 12 and 13, the flow noise caused by cavitation of hydraulic oil is generated on both sides of the oil supply chamber 10. It is assumed that the oil is generated more significantly in the throttle parts 6 and 6 on both sides of the oil discharge chamber 11 than in the throttle parts 6 and 6, and as shown in FIG. , 7 is disclosed to reduce the flow noise.
[0019]
According to this configuration, as shown in FIG. 13B, when the relative angular displacement of the valve spool 2 with respect to the valve body 1 occurs, the chamfer 7 on one side of the oil discharge chamber 11 (oil feed chamber 12 side). The throttle portion 6 that does not have a clog is quickly closed, whereas the throttle portion 6 having the chamfer 7 on the same side (oil feed chamber 13 side) of the oil supply chamber 10 maintains a predetermined throttle area. Therefore, the flow of hydraulic oil that causes flow noise is concentrated in the throttle section 6 between the oil supply chamber 10 and the oil supply chamber 13, which are considered to be favorable conditions for cavitation, and the flow noise is reduced. It is supposed to be possible.
[0020]
This hydraulic control valve ,in front Focusing on the flow form as disclosed in JP-A-6-206555 and JP-A-6-156292, the same as JP-A-6-156292, that is, JP-A-6-206555 News and Would give the opposite flow form.
[0021]
As described above, the conventional proposal for reducing the flow noise by paying attention to the difference in cavitation generation behavior on both sides of the oil supply chamber 10 and on both sides of the oil discharge chamber 11 has various ways of thinking about the cavitation generation behavior. It has become a thing. In order to clarify the occurrence behavior of cavitation, the present inventors configured a simulated oil passage that is linearly developed between the oil supply chamber 10 and the oil discharge chamber 11 so that it can be observed from the outside. An experiment was conducted to compare the behavior of cavitation in the case of reducing the amount of squeezed water and the case of reducing the throttle area on the side of the oil discharge chamber 11 based on the flow sound measurement data and visual observation.
[0022]
14 and 15 are diagrams showing the results of this experiment. In FIG. 14, as shown in FIGS. 10, 11 and 12, an oil supply chamber 10 and an oil discharge chamber 11 are provided on the valve spool 2 side. FIG. 15 shows the results when the oil supply chamber 10 and the oil discharge chamber 11 are provided on the valve body 1 side, as shown in FIG. The flow noise measurement result shows that the upstream side hydraulic pressure (kgf / cm) increases as the throttle area decreases. ² ) Is shown on the horizontal axis, and the sound pressure level (dB) of the measured flow sound is shown on the vertical axis. The observation result of cavitation is a relative evaluation by visual observation.
[0023]
In FIG. 14, the result when the throttle area on the oil supply chamber 10 side is reduced is shown in (a), and the result when the throttle area on the oil discharge chamber 11 side is reduced is shown in (b). When comparing the two, the flow pressure measurement data shows that the upstream hydraulic pressure of the throttle is 60 kgf / cm. ² Significant differences appear in the following areas, especially in the case of (a), the upstream hydraulic pressure is 40 kgf / cm. ² In the case of (b), the upstream side hydraulic pressure is 20 kgf / cm, while the sound pressure level of the flowing sound is kept at a low level of about 20 dB. ² In a region exceeding 1, a flowing sound having a sound pressure level (around 40 dB) equivalent to that in the high pressure region is generated.
[0024]
Also in visual observation, in the case of (a), the throttle area of the throttle part is sufficiently small, and the occurrence of cavitation is not observed until the upstream hydraulic pressure becomes high, whereas in the case of (b), the throttle part. Occurrence of cavitation was observed at a relatively large stage of the aperture area. Accordingly, in the configuration shown in FIG. 14, that is, in the configuration in which the oil supply chamber 10 and the oil discharge chamber 11 are provided on the valve spool 2 side, the flow at the throttle portion on the oil supply chamber 10 side is affected by the occurrence of cavitation. It turns out to be advantageous.
[0025]
On the other hand, in FIG. 15, contrary to FIG. 14, the result when the throttle area on the oil discharge chamber 11 side is reduced is (a), and the result when the throttle area on the oil supply chamber 10 side is reduced is (b). Respectively. When the measurement data of both flow noises are compared, the upstream hydraulic pressure is 30 kgf / cm, although not as remarkable as in the case of FIG. ² There is a difference in the following areas, and the flowing sound in the case of (a) is at a low level. Further, in the visual observation, the degree of occurrence of cavitation in the case of (a) was better than that in the case of (b). Accordingly, in the configuration shown in FIG. 15, that is, the configuration in which the oil supply chamber 10 and the oil discharge chamber 11 are provided on the valve body 1 side, the flow at the throttle portion on the oil discharge chamber 11 side is affected by the occurrence of cavitation. It turns out that it is advantageous.
[0026]
Comparison of the conventional hydraulic control valve that reduces flow noise with the results of this experiment , Special The hydraulic control valve disclosed in Kaihei 6-206555 corresponds to the above experimental results, whereas it is disclosed in JP-A-60-203580, US Pat. No. 3022772, and JP-A-6-156292. The hydraulic control valve is contrary to the experimental result and is harmful to the reduction of the flow noise.
[0027]
Further, the chamfer 7 in the throttle portion 6 is generally formed at a corner portion on the valve spool 2 side, but may be formed at a corner portion on the valve body 1 side. The occurrence behavior of cavitation in such a case corresponds to the state of the throttle shown in FIGS. 14 and 15 when the top and bottom are reversed, and the oil supply chamber 10 and the oil discharge chamber 11 are connected to the valve spool 2. In the configuration provided on the side, from the result of FIG. 15, the throttle portion on the oil discharge chamber 11 side is advantageous for the occurrence of cavitation, and in the configuration in which the oil supply chamber 10 and the oil discharge chamber 11 are provided on the valve body 1 side. FIG. 14 shows that the throttle portion on the oil supply chamber 10 side is advantageous for the occurrence of cavitation. Therefore, when the chamfer 7 is formed on the valve body 1 side, , Special The configuration disclosed in Kaihei 6-206555 is disadvantageous to the occurrence of cavitation.
[0028]
As described above, the proposals conventionally made for reducing the flow noise have their own configurations, specifically, fitting of the hydraulic source, the oil discharge destination and the oil supply destination, and the valve body 1 and the valve spool 2. This is only applicable to a predetermined combination of the mode of communication with the oil grooves arranged on the circumference and the mode of formation of the chamfers at the throttle portions between the oil grooves, and is applied to the entire hydraulic control valve having various configurations. It is not possible.
[0029]
In addition, the conventional proposal is to change the dimensions (width, inclination angle) of the chamfer 7 provided in the throttle unit 6, but the actual required dimensional difference is slight. In order to alternately form the two types of chamfers 7 and 7 having the above, there is a difficulty that requires a great number of man-hours and advanced processing techniques.
[0030]
The present invention has been made in view of such circumstances, and a hydraulic control valve capable of effectively suppressing cavitation in the throttle portion arranged on the fitting periphery of the valve body and the valve spool and capable of greatly reducing the flow noise is provided. It is an object of the present invention to provide an image without any difficulty in processing regardless of the configuration.
[0031]
[Means for Solving the Problems]
The hydraulic control valve according to the first aspect of the present invention is configured such that a valve spool is fitted on the inner side of a cylindrical valve body so as to be capable of relative angular displacement on the same axis, and each of a plurality of them arranged in parallel on the fitting circumference of both. The oil grooves on the valve spool side are alternately communicated with the hydraulic pressure source and the oil discharge destination, while the oil grooves on the valve body side between them are alternately communicated with different oil supply destinations. A throttle part that changes the throttle area according to the relative angular displacement is formed between the oil grooves adjacent to each other in the circumferential direction, and a chamfer for adjusting the throttle area is formed at the corner on the valve spool side facing each throttle part. In the hydraulic control valve having a portion, the throttle portions on the valve spool side are arranged such that the throttle portions on both sides of the oil groove connected to the hydraulic power source have a throttle area larger than the throttle portions on both sides of the oil groove connected to the oil discharge destination. The land between each oil groove is offset in the circumferential direction. And wherein the door.
[0032]
The present invention is directed to a configuration in which an oil groove on the valve spool side is used as an oil supply chamber and an oil discharge chamber, and a chamfered portion (chamfer) for adjusting a throttle area in each throttle portion is provided on the valve spool side. Was placed offset in the circumferential direction so that the throttle parts on both sides of the oil supply chamber had a larger throttle area than the throttle parts on both sides of the oil discharge chamber, resulting in relative angular displacement between the valve body and the valve spool. At this time, the flow of hydraulic oil is concentrated on the throttle portions on both sides of the oil supply chamber, which is advantageous for cavitation from the experimental results shown in FIG.
[0033]
The hydraulic control valve according to the second aspect of the present invention is configured such that a valve spool is fitted on the inner side of a cylindrical valve body so as to be capable of relative angular displacement on the same axis, and each of the plurality is arranged in parallel on both fitting circumferences. The oil grooves on the valve spool side are alternately communicated with the hydraulic pressure source and the oil discharge destination, while the oil grooves on the valve body side between them are alternately communicated with different oil supply destinations. A throttle part that changes the throttle area according to the relative angular displacement is formed between the oil grooves adjacent to each other in the circumferential direction, and a chamfer for adjusting the throttle area is formed at the corner of the valve body facing each throttle part. In the hydraulic control valve having a portion, the throttle portions on both sides of the oil groove connected to the oil drain destination have a throttle area larger than the throttle portions on both sides of the oil groove connected to the hydraulic power source. Oil groove or land between each oil groove on the valve spool side In the circumferential direction characterized by being arranged offset.
[0034]
The present invention is directed to a configuration in which an oil groove on the valve spool side is used as an oil supply chamber and an oil discharge chamber, and a chamfer for each throttle portion is provided on the valve body side, and an oil groove on the valve body side or an offset of a land on the valve spool side FIG. 15 shows the arrangement in which the throttle portions on both sides of the oil discharge chamber have a larger throttle area than the throttle portions on both sides of the oil supply chamber, and relative angular displacement between the valve body and the valve spool occurs. From the experimental results, the flow of hydraulic oil is concentrated on the throttle parts on both sides of the oil discharge chamber, which is advantageous for cavitation, and the flow noise is reduced.
[0035]
A hydraulic control valve according to a third aspect of the present invention is configured such that a valve spool is fitted on the inner side of a cylindrical valve body so as to be capable of relative angular displacement on the same axis, and each of a plurality of them arranged in parallel on the fitting circumference of both. The oil grooves on the valve body side are alternately connected to the hydraulic pressure source and the oil discharge destination, while the oil grooves on the valve spool side between these are alternately connected to different oil supply destinations. A throttle part that changes the throttle area according to the relative angular displacement is formed between the oil grooves adjacent to each other in the circumferential direction, and a chamfer for adjusting the throttle area is formed at the corner on the valve spool side facing each throttle part. In the hydraulic control valve having a portion, the throttle portions on both sides of the oil groove connected to the oil drain destination have a throttle area larger than the throttle portions on both sides of the oil groove connected to the hydraulic power source. Land between each oil groove, or oil groove on the valve spool side In the circumferential direction characterized by being arranged offset.
[0036]
The present invention is directed to a configuration in which an oil groove on the valve body side is used as an oil supply chamber and an oil discharge chamber, and a chamfer of each throttle portion is provided on the valve spool side, and an offset of a land on the valve body side or an oil groove on the valve spool side FIG. 15 shows the arrangement in which the throttle portions on both sides of the oil discharge chamber have a larger throttle area than the throttle portions on both sides of the oil supply chamber, and relative angular displacement between the valve body and the valve spool occurs. From the experimental results, the flow of hydraulic oil is concentrated on the throttle parts on both sides of the oil discharge chamber, which is advantageous for cavitation, and the flow noise is reduced.
[0037]
A hydraulic control valve according to a fourth aspect of the present invention is configured such that a valve spool is fitted on the inner side of a cylindrical valve body so as to be capable of relative angular displacement on the same axis, and a plurality of valves are arranged in parallel on the fitting circumference of both. The oil grooves on the valve body side are alternately connected to the hydraulic pressure source and the oil discharge destination, while the oil grooves on the valve spool side between these are alternately connected to different oil supply destinations. A throttle part that changes the throttle area according to the relative angular displacement is formed between the oil grooves adjacent to each other in the circumferential direction, and a chamfer for adjusting the throttle area is formed at the corner of the valve body facing each throttle part. In the hydraulic control valve provided with a portion, the throttle body on the valve body side is arranged such that the throttle portions on both sides of the oil groove connected to the hydraulic power source have a throttle area larger than the throttle portions on both sides of the oil groove connected to the oil discharge destination. Land between each oil groove, or oil groove on the valve spool side In the circumferential direction characterized by being arranged offset.
[0038]
The present invention is directed to a configuration in which an oil groove on the valve body side is used as an oil supply chamber and an oil discharge chamber, and a chamfer for each throttle portion is provided on the valve body side, and an offset of an oil groove on the valve body side or an oil groove on the valve spool side FIG. 14 shows the arrangement in which the throttle portions on both sides of the oil supply chamber have a larger throttle area than the throttle portions on both sides of the oil discharge chamber, resulting in relative angular displacement between the valve body and the valve spool. From the experimental results, the flow of hydraulic oil is concentrated on the throttle portions on both sides of the oil supply chamber, which is advantageous for cavitation, and the flow noise is reduced.
[0039]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. FIG. 1 is a cross-sectional view of a hydraulic control valve according to a first aspect of the present invention, shown together with a hydraulic circuit of a power steering apparatus.
[0040]
In the figure, 1 is a valve body and 2 is a valve spool. Eight oil grooves 4, 4... Are arranged in parallel in the circumferential direction on the inner peripheral surface of the cylindrical valve body 1, and have an outer diameter substantially equal to the inner diameter of the valve body 1. Similarly, eight oil grooves 5, 5... Are arranged in parallel on the outer peripheral surface of the thick cylindrical valve spool 2 in the circumferential direction.
[0041]
The eight oil grooves 4, 4... On the valve body 1 side have the same width, but the eight oil grooves 5, 5. By arranging the lands between them offset in the circumferential direction, the width of every other four is increased, and the remaining four widths are conversely narrowed. The offset amount of the land in the valve spool 2 is a slight one that is around several minutes to ten and several minutes in relation to the central angle of the valve spool 2.
[0042]
The hydraulic control valve according to the first aspect of the present invention uses the valve body 1 and the valve spool 2 configured as described above, and the valve spool 2 is fitted inside the valve body 1 so as to be relatively rotatable on the same axis. Are connected to each other by a torsion bar 3 inserted inside the valve spool 2. The oil grooves 4, 4 ... on the valve body 1 side and the oil grooves 5, 5 ... on the valve spool 2 side are staggered in the circumferential direction as shown in the figure in a neutral state where the torsion bar 3 is not twisted. Positioned to communicate with adjacent ones on both sides of each.
[0043]
With the above configuration, each of the oil grooves 4 on the valve body 1 side faces the land between the oil grooves 5 on the valve spool 2 side, and the oil grooves 5 on the valve spool 2 side 5 Are opposed to the lands between the oil grooves 4 on the valve body 1 side, and 8 on the inner side of the oil grooves 4, 4. The two oil chambers and the eight oil chambers outside the oil grooves 5, 5... Are alternately arranged with communication portions therebetween.
[0044]
The valve body 1 and the valve spool 2 are capable of relative angular displacement within the torsional range of the torsion bar 3 that connects them, and the communicating portions between the oil chambers are respectively corresponding to the relative angular displacement. It functions as a diaphragm for increasing or decreasing the communication area (diaphragm area). In the hydraulic control valve according to the present invention, the land on the valve spool 2 side is offset as described above, and the four wide oil grooves 5, 5,... And the four narrow oil grooves 5, 5,. Is formed. Therefore, the throttling areas of the throttling portions arranged on the periphery of the fitting with the valve body 1 are not uniform, and eight throttling positions located on both sides of the four oil chambers formed by the wide oil grooves 5, 5. The sections 6a, 6a,... Have a larger area than the eight throttle sections 6b, 6b, located on both sides of the four oil chambers outside the narrow oil grooves 5, 5,.
[0045]
In this way, among the eight oil chambers formed on the outer side of the oil grooves 5, 5... On the valve spool 2 side, four oil chambers which are located every other and have wide throttle portions 6a and 6a on both sides are provided. The oil supply chambers 10 are connected to the discharge side of a hydraulic pump P, which is a hydraulic power source, through different oil guide holes penetrating the peripheral wall of the valve body 1 and supplied with the hydraulic pressure generated by the hydraulic pump P. is doing. On the other hand, the remaining four oil chambers having narrowed narrow portions 6b, 6b on both sides are connected via respective oil drain holes that penetrate the valve spool 2 in the radial direction and hollow portions inside the valve spool 2. .. Are connected to an oil tank T serving as an oil discharge destination, and constitute oil discharge chambers 11, 11,... Serving as a passage of discharged oil to the oil tank T.
[0046]
On the other hand, the eight oil chambers formed inside the oil grooves 4, 4... On the valve body 1 side have a wide throttle portion 6a on one side and a narrow throttle portion 6b on the other side. Among these, the four oil chambers adjacent to the oil supply chambers 10, 10... On the same side in the circumferential direction are supplied with hydraulic pressure via different oil guide holes penetrating the peripheral wall of the valve body 1. One cylinder chamber S of the power cylinder S that is the supplier _R Connected to the cylinder chamber S _R The remaining four chambers are the other cylinder chamber S of the power cylinder S. _L Connected to the cylinder chamber S _L The oil feeding chambers 13, 13.
[0047]
FIG. 2 is an operation explanatory view showing the chambers lined up on the fitting circumference of the valve body 1 and the valve spool 2 in a straight line. With the above-described configuration, oil passages that reach the oil discharge chamber 11 through the oil supply chamber 12 or the oil supply chamber 13 are formed on both sides of the oil supply chamber 10 shown in the center of the drawing. , 13 communicate with each other through wide throttle parts 6a, 6a, and the oil feeding chambers 12, 13 and the oil discharge chambers 11, 11 communicate with each other through narrow throttle parts 6b, 6b.
[0048]
FIG. 2A shows a state (neutral state) in which no relative angular displacement occurs between the valve body 1 and the valve spool 2. At this time, the throttle portions 6a and 6a on both sides of the oil supply chamber 10 have the same throttle area, and the throttle portions 6b on the other side of the oil feeding chambers 12 and 13 communicating with each other through these throttle portions 6a and 6a. , 6b also have equal aperture areas. Accordingly, the hydraulic oil supplied from the hydraulic pump P to the oil supply chamber 10 is evenly distributed to the oil passages on both sides, reaches the oil discharge chamber 11 via the oil supply chamber 12 or 13, and the oil discharge holes that open to these respectively. Then, it flows into the hollow portion inside the valve spool 2, joins in the hollow portion, and returns to the oil tank T.
[0049]
At this time, both cylinder chambers S of the power cylinder S connected between the oil feeding chambers 12 and 13 and these respectively. _R , S _L No pressure difference occurs between them, and the power cylinder S does not generate any force. At this time, the throttle portions 6a and 6b interposed in the middle of the oil passage maintain a large throttle area, and there is no portion having a large flow resistance between the hydraulic pump P and the oil tank T. Therefore, the driving load of the hydraulic pump P is kept small.
[0050]
On the other hand, when a steering torque is applied to a steered wheel (not shown), a relative angular displacement is generated between the valve body 1 and the valve spool 2 with the twist of the torsion bar 3, and the oil supply chamber 10, the oil supply chamber 12, The throttling areas of the throttling portions 6a and 6a between the throttling portions 13 and the throttling portions 6b and 6b between the oil feeding chambers 12 and 13 and the oil discharge chamber 11 change.
[0051]
This change occurs in opposite directions on both sides of the oil feeding chambers 12 and 13. For example, when the relative rotation of the valve spool 2 with respect to the valve body 1 occurs in the clockwise direction in FIG. 1, the valve spool 2 moves relative to the direction indicated by the white arrow in FIG. On both sides of the oil feed chamber 12, the throttle area of the throttle portion 6a on the oil supply chamber 10 side increases and the throttle area of the throttle portion 6b on the oil discharge chamber 11 side decreases, whereas the other oil feed chamber 13 On both sides, conversely, the throttle area of the throttle portion 6a on the oil supply chamber 10 side decreases, and the throttle area of the throttle portion 6b on the oil discharge chamber 11 side increases.
[0052]
Accordingly, most of the hydraulic oil supplied to the oil supply chamber 10 is introduced into the oil supply chamber 12 through the throttle portion 6a having an increased throttle area, and is connected to the oil supply chamber 12. _R Accordingly, a part of the oil introduced into the oil feeding chamber 12 flows out into the oil discharge chamber 11 through the throttle portion 6b having a reduced throttle area on the other side. In addition, a part of the oil supplied to the oil supply chamber 10 flows out to the oil feeding chamber 13 through the throttle portion 6a having a reduced throttle area, and this spilled oil increases the throttle area on the other side of the oil feeding chamber 13. The oil is introduced into the oil discharge chamber 11 through the throttle portion 6b.
[0053]
In the operation state as described above, the internal pressure of the oil feeding chamber 12 is kept substantially equal to that of the oil supply chamber 10, whereas the internal pressure of the oil feeding chamber 13 reduces the throttle area with the oil supply chamber 10. Therefore, the pressure is reduced by the reduced pressure accompanying the flow of the throttle portion 6a, and the cylinder chamber S communicated between the oil feeding chambers 12 and 13 and each of them. _R , S _L A pressure difference occurs between the power cylinder S and the cylinder chamber S. _R To S _L The oil pressure (steering assisting force) toward is generated. Along with this operation of the power cylinder S, the cylinder chamber S _L The enclosed oil inside is extruded, and this extruded oil is sent to the cylinder chamber S. _L Is recirculated to the oil feeding chamber 13 connected to the oil feeding chamber, merged with the inflow oil from the oil feeding chamber 10, and introduced into the oil discharging chamber 11 through the throttle portion 6b having an increased throttle area on the other side of the oil feeding chamber 13. The oil is discharged into the oil tank T through the hollow portion of the valve spool 2.
[0054]
The steering assist force generated by the power cylinder S as a result of the above operation is restricted by the throttle portion 6a between the oil supply chamber 10 and the oil feed chamber 13 and the throttle portion 6b between the oil discharge chamber 11 and the oil feed chamber 12. Depends on the area reduction. The reduction in the throttle area occurs in response to the relative angular displacement between the valve body 1 and the valve spool 2, and this relative angular displacement causes the torsion bar 3 connecting the valve body 1 and the valve spool 2 to be twisted. Corresponds to the magnitude of the steering torque applied to the steering wheel to tighten.
[0055]
On the other hand, when the relative rotation of the valve spool 2 with respect to the valve body 1 occurs counterclockwise in FIG. 1, the throttle portions 6 a and 6 a on both sides of the oil supply chamber 10 and the throttle portions 6 b and 6 b on both sides of the oil discharge chamber 11 The area change opposite to that described above occurs in the power cylinder S, and the power cylinder S _L To S _R A steering assist force toward the vehicle is generated, and this magnitude also corresponds to the magnitude of the steering torque applied to the steering wheel. In this way, a steering assist force corresponding to the direction and magnitude of the steering torque applied to the steered wheels is obtained.
[0056]
Chamfers 7, 7... Are formed at the corners on the valve spool 2 side facing the throttle portion 6a or the throttle portion 6b. As shown in FIG. 2, these chamfers 7, 7... Have corners where the side surface of the oil groove 5 on the valve spool 2 side intersects with the peripheral surface of the land between the oil grooves 5, 5 on the peripheral surface of the land. It is formed with a predetermined inclination angle and a notch obliquely and with a predetermined width in the circumferential direction. Each of the throttle portions 6 has a relative angular displacement between the valve body 1 and the valve spool 2. It is provided to gradually change the aperture area, and the desired increase characteristic of the steering assist force in the power steering device, i.e., in a range where the steering torque applied to the steered wheel is small, the steering assist force gradually increases and the steering torque becomes a predetermined value. It has the effect of realizing characteristics that increase rapidly as it exceeds.
[0057]
In the operating state shown in FIG. 2B, the hydraulic oil supplied to the oil supply chamber 10 flows out into one oil supply chamber 13 through a throttle portion 6a having a reduced throttle area on one side of the oil supply chamber 10. In addition, on the other side of the other oil feeding chamber 12, it flows out to the oil discharge chamber 11 through the throttle portion 6b having a reduced throttle area, and as described above, cavitation occurs in these flows, which is annoying. Accompanied by a flowing sound.
[0058]
The hydraulic control valve shown in FIGS. 1 and 2 has oil grooves 4, 4... On the valve body 1 side as oil feed chambers 12, 13, and oil grooves 5, 5. The oil chamber 11 is provided with chamfers 7, 7... At the corners on the valve spool 2 side facing the throttle portion 6a or the throttle portion 6b. The behavior of cavitation in this configuration is shown in FIG. The flow in the throttle portions 6a, 6a,... On both sides of the oil supply chamber 10 connected to the hydraulic pump P, which is a hydraulic power source, is shown in FIG. , 6b is more advantageous for the occurrence of cavitation than the flow in 6b.
[0059]
In the hydraulic control valve shown in FIGS. 1 and 2, the lands between the oil grooves 5, 5... On the valve spool 2 side are offset as described above, and the throttle portions 6a, 6a on both sides of the oil supply chamber 10 are provided. The throttle areas 6b, 6b on both sides of the oil discharge chamber 11 have a larger throttle area. This magnitude relationship is maintained even in the operating state shown in FIG. The throttle part 6 a between the oil chamber 13 has a larger throttle area than the throttle part 6 b between the oil feeding chamber 12 and the oil discharge chamber 11. Accordingly, the flow of the hydraulic oil from the oil supply chamber 10 to the oil discharge chamber 11 is concentrated on the throttle portion 6a between the oil supply chamber 10 and the oil supply chamber 13 which are favorable conditions for cavitation. Generation | occurrence | production is suppressed effectively and the flow sound accompanying this cavitation can be reduced significantly.
[0060]
3 and 4 are explanatory views of the operation of the hydraulic control valve according to the second aspect of the present invention. As in FIG. 2, the chambers arranged on the fitting periphery of the valve body 1 and the valve spool 2 are arranged. It is shown as a straight line.
[0061]
In the hydraulic control valves shown in these drawings, the oil grooves 4, 4... On the valve body 1 side are oil supply chambers 12, 13, and the oil grooves 5, 5 on the valve spool 2 side are oil supply chambers 10 and oil discharge chambers. On the other hand, the chamfers 7, 7... For adjusting the throttle area of the throttle part 6a and the throttle part 6b are provided at the corners on the valve body 1 side, and the flow of each throttle part 6a, 6b is controlled. The form corresponds to the case where the state of the throttle portion shown in FIG. 15 is viewed upside down, and the cavitation generation behavior corresponds to the result shown in FIG. The flow in the throttle portions 6b, 6b on both sides of the oil discharge chamber 11 is more advantageous for the occurrence of cavitation than the flow in the throttle portions 6a, 6a ... on both sides of the oil supply chamber 10 connected to the hydraulic pump P as a hydraulic source. is there.
[0062]
3, the oil grooves 4, 4... On the valve body 1 side are offset in the circumferential direction, and in FIG. 4, the lands between the oil grooves 5, 5. In any case, the throttle parts 6b, 6b on both sides of the oil discharge chamber 11 have a larger throttle area than the throttle parts 6a, 6a on both sides of the oil supply chamber 10.
[0063]
This magnitude relationship is maintained even in an operating state in which a relative angular displacement has occurred between the valve body 1 and the valve spool 2 as shown in FIGS. 3 (b) and 4 (b). The throttle portion 6b between the oil chamber 11 has a larger throttle area than the throttle portion 6a between the oil supply chamber 10 and the oil feeding chamber 13. Therefore, in this operating state, the oil flow from the oil supply chamber 10 to the oil discharge chamber 11 is concentrated in the throttle portion 6b between the oil supply chamber 12 and the oil discharge chamber 11 which is favorable for cavitation. The occurrence of cavitation is effectively suppressed, and the flow noise accompanying the cavitation can be reduced.
[0064]
The land offset in FIG. 4 is in the opposite direction to that in FIG. 2, and this difference in the offset direction is that the chamfers 7, 7... Are formed on either side of the valve body 1 and the valve spool 2. It depends on what you are doing. Accordingly, even in the hydraulic control valve according to the first aspect of the present invention having the chamfers 7, 7 ... on the valve spool 2 side, the oil grooves 4, 4 ... on the valve body 1 side are offset in the opposite direction to that in FIG. The same effect as in the case of FIG. 2 in which the land on the spool 2 side is offset as described above can be obtained. However, the configuration in which the flow noise is reduced by the offset of the oil grooves 4, 4. Previously proposed (Japanese Patent Application No. 6-323144 and Japanese Patent Application No. 7-176464, which is a domestic priority application), it is not included in the scope of the present invention.
[0065]
5 and 6 are explanatory views of the operation of the hydraulic control valve according to the third aspect of the present invention, and are arranged on the fitting circumference of the valve body 1 and the valve spool 2 in the same manner as in FIGS. Each chamber is shown in a straight line.
[0066]
Unlike the hydraulic control valves shown in FIGS. 1 to 4, the hydraulic control valves shown in these drawings are provided with oil grooves 4, 4... On the valve body 1 side as an oil supply chamber 10 and an oil discharge chamber 11, and a valve spool 2. The oil grooves 5, 5... On the side are oil feeding chambers 12, 13, and the chamfers 7, 7... For adjusting the throttle area are formed at the corners on the valve spool 2 side. The cavitation generation behavior in this configuration is as shown in FIG. 15, and the flow at the throttle portions 6b, 6b on both sides of the oil discharge chamber 11 is the flow at the throttle portions 6a, 6a ... on both sides of the oil supply chamber 10. This is more advantageous for the occurrence of cavitation.
[0067]
5, the lands between the oil grooves 4, 4... On the valve body 1 side are offset in the circumferential direction, and in FIG. 6, the oil grooves 5, 5. In any case, the throttle parts 6b, 6b on both sides of the oil discharge chamber 11 have a larger throttle area than the throttle parts 6a, 6a on both sides of the oil supply chamber 10.
[0068]
This magnitude relationship is maintained even in an operating state in which a relative angular displacement has occurred between the valve body 1 and the valve spool 2 as shown in FIGS. 5 (b) and 6 (b). The throttle portion 6b between the oil chamber 11 has a larger throttle area than the throttle portion 6a between the oil supply chamber 10 and the oil feeding chamber 13. Therefore, in this operating state, the oil flow from the oil supply chamber 10 to the oil discharge chamber 11 is concentrated in the throttle portion 6b between the oil supply chamber 12 and the oil discharge chamber 11 which is favorable for cavitation. The occurrence of cavitation is effectively suppressed, and the flow noise accompanying the cavitation can be reduced.
[0069]
7 and 8 are explanatory views of the operation of the hydraulic control valve according to the fourth aspect of the present invention, and are arranged on the fitting periphery of the valve body 1 and the valve spool 2 in the same manner as in FIGS. Each chamber is shown in a straight line.
[0070]
The hydraulic control valve shown in these drawings is similar to the hydraulic control valve shown in FIGS. 5 and 6, the oil grooves 4, 4... On the valve body 1 side are used as the oil supply chamber 10 and the oil discharge chamber 11, and the valve spool 2 side. The oil grooves 5, 5 ... are oil feed chambers 12, 13, and the chamfers 7, 7 ... for adjusting the throttle area are different from those shown in FIGS. It is formed in the corner | angular part by the side of the valve body 1 which faces. The form of the flow in each throttle part 6a, 6b in this configuration corresponds to the case where the state of the throttle part shown in FIG. 14 is viewed upside down, and the cavitation generation behavior corresponds to the result shown in FIG. Therefore, the flow at the throttle portions 6a, 6a... On both sides of the oil supply chamber 10 is more advantageous for the occurrence of cavitation than the flow at the throttle portions 6b, 6b on both sides of the oil discharge chamber 11.
[0071]
In FIG. 7, the land between the oil grooves 4, 4... On the valve body 1 side is offset in the circumferential direction, and in FIG. 8, the oil grooves 5, 5. In any case, the throttle parts 6a, 6a on both sides of the oil supply chamber 10 have a larger throttle area than the throttle parts 6b, 6b on both sides of the oil discharge chamber 11. That is, the offset of the land or the oil groove in these directions is opposite to the respective offsets in FIGS.
[0072]
As shown in FIGS. 7 (b) and 8 (b), a relative angular displacement occurs between the valve body 1 and the valve spool 2 in the magnitude relationship between the throttle portions 6a and 6b obtained by the offset arrangement described above. The throttle portion 6a between the oil supply chamber 10 and the oil feeding chamber 13 has a throttle area larger than that of the throttle portion 6b between the oil feeding chamber 12 and the oil discharge chamber 11, which is maintained even in the operating state. Therefore, in this operating state, the oil flow from the oil supply chamber 10 to the oil discharge chamber 11 is concentrated on the throttle portion 6a between the oil supply chamber 10 and the oil supply chamber 13 which are favorable conditions for cavitation, The generation of cavitation is effectively suppressed, and the flow sound accompanying the cavitation can be reduced.
[0073]
As described above, the hydraulic control valve according to the present invention includes the oil grooves 4, 4... On the valve body 1 side or the land between the oil grooves 4, 4. By the land offset arrangement between the grooves 5, 5 ..., the throttle areas of the throttle portions 6a, 6a ... on both sides of the oil supply chambers 10, 10 ... and the throttles 6b, 6b ... on both sides of the oil discharge chambers 11, 11 ... This is intended to obtain a reduction effect of the flow noise by making a difference with the area, and it is difficult to process as compared with the conventional hydraulic control valve that requires the dimension adjustment of the chamfers 7, 7. Is greatly improved.
[0074]
However, the amount of offset actually required is a slight amount of several minutes to tens of minutes or more, which is corrected by the central angle of the valve body 1, and the influence of the centering error when the valve body 1 or the valve spool 2 is processed. Receive. Accordingly, when viewed over the entire circumference of the fitting portion between the valve body 1 and the valve spool 2, a part of the throttle portions 6a, 6a... On both sides of the oil supply chambers 10, 10. There may be a case where the area is smaller than a part of the narrowed portions 6b, 6b,. On the other hand, in the hydraulic control valve in which the oil grooves 4, 4... On the valve body 1 side and the lands and the oil grooves 5, 5. It is as if a conscious offset arrangement has been made due to the influence of the extraction error, and part of the throttle parts 6, 6 ... on both sides of the oil supply chambers 10, 10 ... are part of the throttle parts on both sides of the oil discharge chambers 11, 11 ... The area may be larger than a part of 6, 6.
[0075]
The hydraulic control valve according to the present invention can be differentiated from the conventional hydraulic control valve even when the influence of the centering error as described above occurs. FIG. 9 is an explanatory diagram of the difference between the two. These drawings illustrate the throttle areas of the throttle portions arranged on the fitting circumference of the valve body 1 and the valve spool 2 developed on the horizontal axis, and the circles in the figure are offset. The throttle area in the conventional hydraulic control valve which is not present, and the Δ mark and the square mark indicate the throttle area of the hydraulic control valve according to the present invention, respectively.
[0076]
FIG. 9A shows an ideal valve having no centering error. At this time, in the conventional hydraulic control valve, the throttle portions arranged on the fitting circumference have the same throttle area. On the other hand, in the hydraulic control valve according to the present invention, throttle portions (Δ mark) having a large throttle area and throttle portions (□ symbol) having a small throttle area are alternately arranged.
[0077]
FIGS. 9B and 9C show a case where a centering error exists. When there is a centering error, the inner circumference of the valve body 1 fitted to the valve spool 2 undergoes a periodic change having a small diameter portion and a large diameter portion at one location as indicated by a broken line in the figure. The throttle area in the conventional hydraulic control valve shows a distribution that changes in magnitude along the change line of the inner diameter.
[0078]
On the other hand, the throttle area in the hydraulic control valve of the present invention has a distribution in which the throttle area in the case where the offset arrangement is not arranged is biased alternately on both sides, as in FIG. 9A. As shown in the figure, when the centering error is large, a part of the diaphragm part indicated by △ may have a smaller diaphragm area than a part of the diaphragm part indicated by □. Paying attention to the throttle area between adjacent throttle parts, the magnitude relationship that alternately becomes larger and smaller appears periodically over the entire circumference of the fitting circumference, and the distribution of the throttle area in the conventional hydraulic control valve is Obviously different. As described above, the hydraulic control valve according to the present invention shows a distribution in which the throttle areas of adjacent throttle portions alternately increase and decrease, and the throttle area that appears due to the influence of the centering error in the configuration in which the offset arrangement is not made. It is possible to distinguish between large and small relationships.
[0079]
In the above embodiment, the example of use as a hydraulic control valve for controlling the hydraulic pressure supplied to the power cylinder of the power steering apparatus has been described, but the scope of application of the present invention is not limited to this, The present invention can be applied to all types of rotary hydraulic control valves used for hydraulic control in hydraulic circuits.
[0080]
【The invention's effect】
As described in detail above, in the hydraulic control valve according to the present invention, a plurality of oil grooves arranged on the fitting circumference of the valve body and the valve spool, an oil supply chamber connected to the hydraulic source, an oil discharge chamber connected to the oil discharge destination, In addition, an oil feed chamber connected to the oil feed destination is formed between them, the oil groove on the valve body side or the valve spool side or the land between each oil groove is arranged offset, and the throttle part and the oil drainage on both sides of the oil supply chamber Since there is a difference in throttle area between the throttle parts on both sides of the chamber, the flow of hydraulic oil from the oil supply chamber to the oil discharge chamber is concentrated in the throttle part that is advantageous for the occurrence of cavitation. The present invention has an excellent effect, for example, it is possible to greatly reduce the flow noise caused by the occurrence of cavitation without requiring special processing.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a hydraulic control valve according to a first invention of the present invention.
FIG. 2 is an operation explanatory view of a hydraulic control valve according to the first invention.
FIG. 3 is an operation explanatory view of a hydraulic control valve according to a second invention.
FIG. 4 is an operation explanatory diagram of a hydraulic control valve according to a second invention.
FIG. 5 is an operation explanatory view of a hydraulic control valve according to a third invention.
FIG. 6 is an operation explanatory view of a hydraulic control valve according to a third invention.
FIG. 7 is an operation explanatory view of a hydraulic control valve according to a fourth invention.
FIG. 8 is an operation explanatory view of a hydraulic control valve according to a fourth invention.
FIG. 9 is an explanatory diagram of a distribution state of throttle areas in a hydraulic control valve according to the present invention and a conventional hydraulic control valve.
FIG. 10 is an operation explanatory diagram of a conventional general hydraulic control valve.
FIG. 11 is an operation explanatory diagram of a conventional hydraulic control valve for reducing flow noise.
FIG. 12 is an operation explanatory diagram of a conventional hydraulic control valve for reducing flow noise.
FIG. 13 is an operation explanatory diagram of a conventional hydraulic control valve that aims to reduce flow noise.
FIG. 14 is a chart showing the results of an experiment examining the occurrence behavior of cavitation.
FIG. 15 is a chart showing the results of an experiment examining the occurrence behavior of cavitation.
[Explanation of symbols]
1 Valve body
2 Valve spool
4 Oil groove
5 Oil groove
6a Aperture
6b Aperture
7 Chanfa
10 Refueling chamber
11 Oil discharge chamber
12 Oil transfer chamber
13 Oil transfer chamber
P Hydraulic pump
S Power cylinder

Claims

The valve spool is fitted inside the cylindrical valve body so that it can be displaced relative to the coaxial axis, and a plurality of oil grooves arranged in parallel on the fitting circumference of both are arranged in a staggered manner. While the groove is alternately communicated with the hydraulic power source and the oil discharge destination, the oil groove on the valve body side between them is alternately communicated with different oil supply destinations, and between the oil grooves adjacent to each other in the circumferential direction. A hydraulic control valve comprising a throttle portion that changes a throttle area in accordance with the relative angular displacement, and having a chamfered portion for adjusting the throttle area at a corner on the valve spool side facing each throttle portion. The lands between the respective oil grooves on the valve spool side are offset in the circumferential direction so that the throttle parts on both sides of the oil groove have a larger throttle area than the throttle parts on both sides of the oil groove connected to the oil drain destination. A hydraulic control valve characterized by comprising:

The valve spool is fitted inside the cylindrical valve body so that it can be displaced relative to the coaxial axis, and a plurality of oil grooves arranged in parallel on the fitting circumference of both are arranged in a staggered manner. While the groove is alternately communicated with the hydraulic power source and the oil discharge destination, the oil groove on the valve body side between them is alternately communicated with different oil supply destinations, and between the oil grooves adjacent to each other in the circumferential direction. In a hydraulic control valve comprising a throttle portion that changes a throttle area according to the relative angular displacement, and having a chamfered portion for adjusting the throttle area at a corner portion of the valve body facing each throttle portion, Between the oil grooves on the valve body side or between the oil grooves on the valve spool side so that the throttle parts on both sides of the continuous oil grooves have a larger throttle area than the throttle parts on both sides of the oil groove connected to the hydraulic power source. The land is offset in the circumferential direction. Hydraulic control valve according to claim.

The valve spool is fitted inside the cylindrical valve body so that it can be displaced relative to the same axis coaxially, and a plurality of oil grooves arranged in parallel on the fitting circumference of both are arranged in a staggered manner. While the groove is alternately communicated with the hydraulic power source and the oil discharge destination, the oil groove on the valve spool side between them is alternately communicated with different oil supply destinations, and between the oil grooves adjacent to each other in the circumferential direction. A hydraulic control valve comprising a throttle portion that changes a throttle area in accordance with the relative angular displacement, and having a chamfered portion for adjusting the throttle area at a corner portion on the valve spool side facing each throttle portion. The land between the oil grooves on the valve body side or the valve spool side so that the throttle parts on both sides of the continuous oil groove have a larger throttle area than the throttle parts on both sides of the oil groove connected to the hydraulic power source. The oil groove is offset in the circumferential direction. Hydraulic control valve according to claim.

The valve spool is fitted inside the cylindrical valve body so that it can be displaced relative to the same axis coaxially, and a plurality of oil grooves arranged in parallel on the fitting circumference of both are arranged in a staggered manner. While the groove is alternately communicated with the hydraulic power source and the oil discharge destination, the oil groove on the valve spool side between them is alternately communicated with different oil supply destinations, and between the oil grooves adjacent to each other in the circumferential direction. A hydraulic control valve comprising a throttle portion that changes a throttle area in accordance with the relative angular displacement, and having a chamfered portion for adjusting the throttle area at a corner of the valve body facing each throttle portion. Lands between the oil grooves on the valve body side or the valve spool side so that the throttle parts on both sides of the oil groove have a larger throttle area than the throttle parts on both sides of the oil groove connected to the oil drain destination. The oil groove is offset in the circumferential direction. Hydraulic control valve according to claim.