JP3894704B2

JP3894704B2 - Hydraulic power steering device

Info

Publication number: JP3894704B2
Application number: JP2000116673A
Authority: JP
Inventors: 晃久梅谷; 眞悟吉永
Original assignee: JTEKT Corp
Current assignee: JTEKT Corp
Priority date: 2000-04-18
Filing date: 2000-04-18
Publication date: 2007-03-22
Anticipated expiration: 2020-04-18
Also published as: JP2001301634A

Description

【０００１】
【発明の属する技術分野】
本発明は、操舵補助力発生用油圧アクチュエータに作用する油圧をロータリータイプ制御弁によって制御する油圧パワーステアリング装置に関する。
【０００２】
【従来の技術】
油圧パワーステアリング装置においては、油圧アクチュエータに作用する油圧を制御弁により制御することで操舵補助力を発生している。その制御弁として、バルブハウジングと、このバルブハウジングに相対回転可能に挿入される筒状の第１バルブ部材と、この第１バルブ部材に操舵抵抗に応じて相対回転可能に挿入される第２バルブ部材とを有するロータリータイプのものが用いられている。
【０００３】
そのロータリータイプの制御弁において、車両の高速走行時における安定性と低速走行時における旋回性を向上するため、高速走行時において操舵補助力を低減し、低速走行時において操舵補助力を増大する構成を有するものがある。そのため、その第１バルブ部材の外周に、複数の周溝が軸方向の間隔をおいて並列するように形成され、その第１バルブ部材の内周と第２バルブ部材の外周とに、複数の軸方向溝が互いに周方向の間隔をおいて形成される。その第１バルブ部材の軸方向溝の軸方向に沿う縁と、第２バルブ部材の軸方向溝の軸方向に沿う縁との間が、両バルブ部材の相対回転角度に応じて開度が変化する複数の絞り部とされる。各絞り部の開度変化に応じた操舵補助力を付与できるように、その制御弁を介して前記アクチュエータがポンプとタンクに接続される。その周溝として、そのアクチュエータの右操舵補助力発生用油室に接続される右操舵用周溝と、そのアクチュエータの左操舵補助力発生用油室に接続される左操舵用周溝と、そのポンプに接続される圧油供給用周溝と、そのタンクに運転条件に応じて開度が変化する可変絞り部を介して接続される圧油排出用周溝とを有する。その軸方向溝として、その右操舵用周溝に通じる右操舵用軸方向溝と、その左操舵用周溝に通じる左操舵用軸方向溝と、その圧油供給用周溝に通じる圧油供給用軸方向溝と、そのタンクに接続される第１圧油排出用軸方向溝と、その圧油排出用周溝に通じる第２圧油排出用軸方向溝とを有する。
【０００４】
右操舵時においては、そのポンブから吐出された圧油は、制御弁の圧油供給用周溝、圧油供給用軸方向溝、右操舵用軸方向溝、右操舵用周溝を介して油圧アクチュエータの右操舵補助力発生用油室に供給され、左操舵補助力発生用油室の油は、左操舵用軸方向溝から一部が制御弁の第１圧油排出用軸方向溝からタンクに至り、残部が第２圧油排出用軸方向溝および圧油排出用周溝から可変絞り部を介してタンクに至る。
また、左操舵時においては、そのポンブから吐出された圧油は、制御弁の圧油供給用周溝、圧油供給用軸方向溝、左操舵用軸方向溝、左操舵用周溝を介して油圧アクチュエータの左操舵補助力発生用油室に供給され、右操舵補助力発生用油室の油は、右操舵用軸方向溝から一部が制御弁の第１圧油排出用軸方向溝からタンクに至り、残部が第２圧油排出用軸方向溝および圧油排出用周溝から可変絞り部を介してタンクに至る。
【０００５】
その可変絞り部の開度は、高速走行時に大きくされ、低速走行時に小さくされる。これにより、高速走行時においては、操舵抵抗が小さい間は操舵補助力発生用油圧の増加は小さく走行安定性が向上し、低速走行時においては、操舵抵抗が小さくても操舵補助力発生用油圧の増加が大きく旋回性能が向上する。
【０００６】
【発明が解決しようとする課題】
従来の油圧パワーステアリング装置においては、右操舵時と左操舵時とで操舵フィーリングに差を感じたり、左操舵時に発生する音が大きくなる場合があり、操舵フィーリングと静粛性の一層の向上が要望されている。
【０００７】
本発明は、上記問題を解決することのできる油圧パワーステアリング装置を提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明は、操舵補助力発生用油圧アクチュエータと、そのアクチュエータに作用する油圧の制御弁とを有し、その制御弁は、バルブハウジングと、このバルブハウジングに相対回転可能に挿入される筒状の第１バルブ部材と、この第１バルブ部材に操舵抵抗に応じて相対回転可能に挿入される第２バルブ部材とを有し、その第１バルブ部材の外周に、複数の周溝が互いに軸方向の間隔をおいて並列するように形成され、その第１バルブ部材の内周と第２バルブ部材の外周とに、複数の軸方向溝が互いに周方向の間隔をおいて形成され、その第１バルブ部材の軸方向溝の軸方向に沿う縁と、第２バルブ部材の軸方向溝の軸方向に沿う縁との間が、両バルブ部材の相対回転角度に応じて開度が変化する複数の絞り部とされ、各絞り部の開度変化に応じた操舵補助力を付与できるように、その制御弁を介して前記アクチュエータがポンプとタンクに接続され、その周溝として、そのアクチュエータの右操舵補助力発生用油室に接続される右操舵用周溝と、そのアクチュエータの左操舵補助力発生用油室に接続される左操舵用周溝と、そのポンプに接続される圧油供給用周溝と、そのタンクに運転条件に応じて開度が変化する可変絞り部を介して接続される圧油排出用周溝とを有し、その軸方向溝として、その右操舵用周溝に通じる右操舵用軸方向溝と、その左操舵用周溝に通じる左操舵用軸方向溝と、その圧油供給用周溝に通じる圧油供給用軸方向溝と、そのタンクに接続される第１圧油排出用軸方向溝と、その圧油排出用周溝に通じる第２圧油排出用軸方向溝とを有する油圧パワーステアリング装置において、その右操舵用周溝と左操舵用周溝との間に、その圧油供給用周溝と圧油排出用周溝とが配置されていることを特徴とする。
【０００９】
上記従来の油圧パワーステアリング装置において、右操舵時と左操舵時とで操舵フィーリングに差がある原因を探究したところ、図１１の（１）に示すように、第１バルブ部材１０１の外周における圧油排出用周溝１０１Ｔと左操舵用周溝１０１Ｌとの間に、右操舵用周溝１０１Ｒと圧油供給用周溝１０１Ｐとが配置されていることが原因であることが究明された。すなわち、右操舵時においては、右操舵用周溝１０１Ｒと圧油供給用周溝１０１Ｐと圧油排出用周溝１０１Ｔとにおいて油圧が上昇すると共に左操舵用周溝１０１Ｌでは油圧が背圧まで低下し、左操舵時においては、左操舵用周溝１０１Ｌと圧油供給用周溝１０１Ｐと圧油排出用周溝１０１Ｔとにおいて油圧が上昇すると共に右操舵用周溝１０１Ｒでは油圧が背圧まで低下する。そうすると、各周溝における油圧の作用による第１バルブ部材１０１の変形量が、右操舵時と左操舵時とで大きく相異する。すなわち、図１１の（２）は右操舵時、図１１の（３）は左操舵時において、第１バルブ部材１０１の中心Ｏ上の各位置から外周までの距離の、その油圧の作用による直進状態からの変形方向と変形量を示し、右操舵時よりも左操舵時の方が油圧による変形が大きくなる。これは、右操舵時は油圧上昇が生じる３つの周溝１０１Ｒ、１０１Ｐ、１０１Ｔは互いの中の何れかと隣接するのに対して、左操舵時は油圧上昇が生じる二つの周溝１０１Ｌ、１０１Ｐと一つの周溝１０１Ｔとの間に油圧低下が生じる周溝１０１Ｒが位置することから、右操舵時と左操舵時とで油圧の分布態様が相異するためである。
【００１０】
また、上記従来の油圧パワーステアリング装置においては、互いに隣接する周溝相互の間と、圧油排出用周溝１０１Ｔよりも軸方向外方位置と、左操舵用周溝１０１Ｌよりも軸方向外方位置とに、バルブハウジング１０２と第１バルブ部材１０１との間に介在する第１〜第５シールリング１０３ａ、１０３ｂ、１０３ｃ、１０３ｄ、１０３ｅが配置されている。その圧油排出用周溝１０１Ｔよりも軸方向外方位置の第１シールリング１０３ａは、第１バルブ部材１０１の軸方向外方位置においてタンクに通じる油流路１０４と圧油排出用周溝１０１Ｔとの間をシールし、その左操舵用周溝１０１Ｌよりも軸方向外方位置の第５シールリング１０３ｅは、第１バルブ部材１０１の軸方向外方位置においてタンクに通じる油流路１０５と左操舵用周溝１０１Ｌとの間をシールする。各シールリング１０３ａ、１０３ｂ、１０３ｃ、１０３ｄ、１０３ｅにより隔てられる隣接領域間に油圧差が生じる時、その油圧差の作用で各シールリング１０３ａ、１０３ｂ、１０３ｃ、１０３ｄ、１０３ｅはバルブハウジング１０２の内周に押し付けられる。従来の構成では、シールリング１０３ａ、１０３ｂ、１０３ｃ、１０３ｄ、１０３ｅの中で油圧差の作用を受けるものの数が左操舵時では右操舵時よりも多くなる。すなわち図１０の（２）は、操舵がなされていない直進時（図中Ｎ）と、右操舵時（図中Ｒ）と、左操舵時（図中Ｌ）とにおいて、各シールリング１０３ａ、１０３ｂ、１０３ｃ、１０３ｄ、１０３ｅが油圧差を受ける場合を〇、受けない場合を×で示す。直進時は、圧油供給用周溝１０３Ｐは圧油供給により高圧状態となり、圧油排出用周溝１０１Ｔの圧油は可変絞り部により絞られることで高圧状態となり、左右操舵用周溝１０１Ｌ、１０１Ｒは第１バルブ部材１０１の軸方向外方位置においてタンクに通じる油流路１０４、１０５と同様に背圧が作用する低圧状態となる。よって、第１〜第４シールリング１０３ａ、１０３ｂ、１０３ｃ、１０３ｄが油圧差を受け、第５シールリング１０３ｅは油圧差を受けない。右操舵時は、圧油供給用周溝１０３Ｐ、右操舵用周溝１０１Ｒは高圧状態となり、圧油排出用周溝１０１Ｔの圧油は可変絞り部により絞られることで高圧状態となり、左操舵用周溝１０１Ｌは背圧が作用する低圧状態となる。よって、第１、第４シールリング１０３ａ、１０３ｄが油圧差を受け、第２、第３、第５シールリング１０３ｂ、１０３ｃ、１０３ｅは油圧差を受けない。左操舵時は、圧油供給用周溝１０３Ｐ、左操舵用周溝１０１Ｌは高圧状態となり、圧油排出用周溝１０１Ｔの圧油は可変絞り部により絞られることで高圧状態となり、右操舵用周溝１０１Ｒは背圧が作用する低圧状態となる。よって、第１〜第３シールリング１０３ａ、１０３ｂ、１０３ｃと第５シールリング１０３ｅが油圧差を受け、第４シールリング１０３ｄは油圧差を受けない。
【００１１】
上記のように、右操舵時と左操舵とにおいて第１バルブ部材１０１の変形状態や油圧差を受けるシールリングの数が相異することで、第１バルブ部材１０１とバルブハウジング１０２との接触状態も相異し、操舵フィーリングの相異や発生音の増大を生じていた。
【００１２】
本発明の構成によれば、右操舵用周溝と左操舵用周溝との間に、その圧油供給用周溝と圧油排出用周溝とが配置されているので、右操舵時と左操舵時の何れの場合にも、油圧上昇が生じる３つの周溝は互いの中の何れかと隣接する。これにより、右操舵時と左操舵時とで、各周溝における油圧の作用による第１バルブ部材の変形量の差を低減し、第１バルブ部材とバルブハウジングとの接触状態の相異を低減できる。
【００１３】
さらに本発明においては、互いに隣接する周溝相互の間と、前記右操舵用周溝よりも軸方向外方位置と、前記左操舵用周溝よりも軸方向外方位置とに、前記バルブハウジングと前記第１バルブ部材との間に介在する第１〜第５シールリングが配置され、前記右操舵用周溝よりも軸方向外方位置の前記第１シールリングにより、前記第１バルブ部材の一端の軸方向外方位置において前記タンクに通じる油流路と前記右操舵用周溝との間がシールされ、前記左操舵用周溝よりも軸方向外方位置の前記第５シールリングにより、前記第１バルブ部材の他端の軸方向外方位置において前記タンクに通じる油流路と前記左操舵用周溝との間がシールされ、直進時は、前記圧油供給用周溝と前記圧油排出用周溝が高圧状態となると共に前記左右操舵用周溝が低圧状態となることで、前記右操舵用周溝と前記圧油排出用周溝との間の前記第２シールリングと、前記左操舵用周溝と前記圧油供給用周溝との間の前記第４シールリングが各シールリングにより隔てられる隣接領域間の油圧差を受けると共に、前記第１シールリング、前記圧油排出用周溝と前記圧油供給用周溝との間の前記第３シールリング、および前記第５シールリングが前記油圧差を受けることがないものとされ、右操舵時は、前記圧油供給用周溝、前記右操舵用周溝、前記圧油排出用周溝が高圧状態となると共に前記左操舵用周溝が低圧状態となることで、前記第１、第４シールリングが前記油圧差を受けると共に前記第２、第３、第５シールリングが前記油圧差を受けることがないものとされ、左操舵時は、前記圧油供給用周溝、前記左操舵用周溝、前記圧油排出用周溝が高圧状態となると共に前記右操舵用周溝が低圧状態となることで、前記第２、第５シールリングが前記油圧差を受けると共に前記第１、第３、第４シールリングが前記油圧差を受けることがないものとされている。
この構成によれば、各シールリングにより隔てられる隣接領域間の油圧差の作用で、バルブハウジングの内周に押し付けられるシールリングの数は、右操舵時と左操舵と直進時とで等しくなり、また、左操舵時と直進時にバルブハウジングの内周に押し付けられるシールリングの数は従来よりも少なくなる。
【００１４】
その圧油供給用軸方向溝の数は少なくとも２つとされ、その軸方向溝として少なくとも２つの連絡用軸方向溝を含み、その右操舵用軸方向溝と左操舵用軸方向溝の間に第１圧油排出用軸方向溝が配置され、その連絡用軸方向溝の間に第２圧油排出用軸方向溝が配置され、右操舵用軸方向溝と連絡用軸方向溝との間および左操舵用軸方向溝と連絡用軸方向溝との間に圧油供給用軸方向溝が配置され、その左右操舵用軸方向溝と第１圧油排出用軸方向溝との間の絞り部と左右操舵用軸方向溝と圧油供給用軸方向溝との間の絞り部とは第１の組に属し、圧油供給用軸方向溝と連絡用軸方向溝との間の絞り部と連絡用軸方向溝と第２圧油排出用軸方向溝との間の絞り部とは第２の組に属するものとされ、その第２の組に属する絞り部の閉鎖角度は第１の組に属する絞り部の閉鎖角度よりも大きくされ、その第２の組に、互いに閉鎖角度が異なる２種類の絞り部が属し、その第２の組に属する絞り部とタンクとの間の油路に前記可変絞り部が設けられているのが好ましい。これにより、操舵補助力を操舵抵抗に応じ制御できない領域を小さくでき、より操舵フィーリングの向上を図ることができる。
【００１５】
【発明の実施の形態】
図１に示す本発明の実施形態の車両のラックピニオン式油圧パワーステアリング装置１は、ステアリングホイール（図示省略）に連結される入力シャフト２と、この入力シャフト２にトーションバー６を介し連結される出力シャフト３を備えている。そのトーションバー６は、ピン４により入力シャフト２に連結され、セレーション５により出力シャフト３に連結されている。その入力シャフト２は、ベアリング８を介しバルブハウジング７により支持され、また、ブッシュ１２を介し出力シャフト３により支持されている。その出力シャフト３はベアリング１０、１１を介しラックハウジング９により支持されている。その出力シャフト３にピニオン１５が形成され、このピニオン１５に噛み合うラック１６に操舵用車輪（図示省略）が連結される。これにより、操舵による入力シャフト２の回転は、トーションバー６を介してピニオン１５に伝達され、このピニオン１５の回転によりラック１６は車両幅方向に移動し、このラック１６の移動により車両の操舵がなされる。なお、入出力シャフト２、３とハウジング７との間にはオイルシール４２、４３が介在する。また、ラック１６を支持するサポートヨーク４０がバネ４１の弾力によりラック１６に押し付けられている。
【００１６】
操舵補助力発生用油圧アクチュエータとして油圧シリンダ２０が設けられている。この油圧シリンダ２０は、ラックハウジング９により構成されるシリンダチューブと、ラック１６に一体化されるピストン２１を備えている。そのピストン２１により仕切られる油室２２、２３に操舵抵抗に応じて圧油を供給することで、その油圧シリンダ２０に作用する油圧を制御するロータリー式油圧制御弁３０が設けられている。
【００１７】
その制御弁３０は、バルブハウジング７に相対回転可能に挿入される筒状の第１バルブ部材３１と、この第１バルブ部材３１に同軸中心に相対回転可能に挿入される第２バルブ部材３２とを備える。その第１バルブ部材３１は出力シャフト３にピン２９により同行回転するよう連結されている。その第２バルブ部材３２は入力シャフト２と一体的に成形され、入力シャフト２の外周部により第２バルブ部材３２が構成され、第２バルブ部材３２は入力シャフト２と同行回転する。よって、第１バルブ部材３１と第２バルブ部材３２は、操舵抵抗に応じ前記トーションバー６がねじれることで同軸中心に弾性的に相対回転する。
【００１８】
そのバルブハウジング７に、ポンプ７０に接続される入口ポート３４と、前記油圧シリンダ２０の右操舵補助力発生用油室２２に接続される第１ポート３７と、左操舵補助力発生用油室２３に接続される第２ポート３８と、直接にタンク７１に接続される第１出口ポート３６と、後述の運転条件に応じて開度が変化する可変絞り弁６０の可変絞り部６７を介しタンク７１に接続される第２出口ポート６１とが設けられている。各ポート３４、３６、３７、３８、６１は、その第１バルブ部材３１と第２バルブ部材３２との内外周間の流路を介し互いに接続されている。
【００１９】
すなわち、図９の（１）に示すように、その第１バルブ部材３１の外周に、複数の周溝３１Ｒ、３１Ｌ、３１Ｐ、３１Ｔが互いに軸方向の等間隔をおいて並列するように形成されている。その周溝３１Ｒ、３１Ｌ、３１Ｐ、３１Ｔは、上記右操舵補助力発生用油室２２に上記第１ポート３７を介して接続される右操舵用周溝３１Ｒと、上記左操舵補助力発生用油室２３に上記第２ポート３８を介して接続される左操舵用周溝３１Ｌと、上記ポンプ７０に上記入口ポート３４を介して接続される圧油供給用周溝３１Ｐと、上記タンク７１に第２出口ポート６１と上記可変絞り弁６０を介して接続される圧油排出用周溝３１Ｔとから構成される。そして、その右操舵用周溝３１Ｒと左操舵用周溝３１Ｌとの間に、その圧油供給用周溝３１Ｐと圧油排出用周溝３１Ｔとが配置されている。本実施形態では、その右操舵用周溝３１Ｒは圧油排出用周溝３１Ｔに隣接し、左操舵用周溝３１Ｌは圧油供給用周溝３１Ｐに隣接するように配置されているが、右操舵用周溝３１Ｒが圧油供給用周溝３１Ｐに隣接し、左操舵用周溝３１Ｌが圧油排出用周溝３１Ｔに隣接するように配置されてもよい。
【００２０】
互いに隣接する上記周溝３１Ｒ、３１Ｌ、３１Ｐ、３１Ｔ相互の間と、右操舵用周溝３１Ｒよりも軸方向外方位置と、左操舵用周溝３１Ｌよりも軸方向外方位置とに、バルブハウジング７と第１バルブ部材３１との間に介在する第１〜第５シールリング３９ａ、３９ｂ、３９ｃ、３９ｄ、３９ｅが配置されている。その右操舵用周溝３１Ｒよりも軸方向外方位置の第１シールリング３９ａは、第１バルブ部材３１の一端の軸方向外方位置においてタンク７１に通じる油流路８１と右操舵用周溝３１Ｒとの間をシールし、その左操舵用周溝３１Ｌよりも軸方向外方位置の第５シールリング３９ｅは、第１バルブ部材３１の他端の軸方向外方位置においてタンク７１に通じる油流路８２と左操舵用周溝３１Ｌとの間をシールする。各シールリング３９ａ、３９ｂ、３９ｃ、３９ｄ、３９ｅにより隔てられる隣接領域間に油圧差が生じる時、その油圧差の作用で各シールリング３９ａ、３９ｂ、３９ｃ、３９ｄ、３９ｅはバルブハウジング７の内周に押し付けられる。
【００２１】
図３、図４に示すように、第１バルブ部材３１の内周に軸方向溝５０ａ、５０ｂ、５０ｃが、周方向に等間隔をおいた１２箇所に形成されている。第２バルブ部材３２の外周に軸方向溝５１ａ、５１ｂ、５１ｃが、周方向に等間隔をおいた１２箇所に形成されている。図４は実線により第２バルブ部材３２の展開図を示し、鎖線により第１バルブ部材３１に形成された軸方向溝５０ａ、５０ｂ、５０ｃを示す。第１バルブ部材３１に形成された軸方向溝５０ａ、５０ｂ、５０ｃの間に第２バルブ部材３２に形成された軸方向溝５１ａ、５１ｂ、５１ｃが位置する。
【００２２】
その第１バルブ部材３１の軸方向溝は、３つの右操舵用軸方向溝５０ａと、３つの左操舵用軸方向溝５０ｂと、６つの連絡用軸方向溝５０ｃとを構成する。その右操舵用軸方向溝５０ａは、第１バルブ部材３１に形成された流路５３を介して右操舵用周溝３１Ｒに通じることで、第１ポート３７から右操舵補助力発生用油室２２に接続され、互いに周方向に１２０°離れて配置される。その左操舵用軸方向溝５０ｂは、第１バルブ部材３１に形成された流路５４を介して左操舵用周溝３１Ｌに通じることで、第２ポート３８から左操舵補助力発生用油室２３に接続され、互いに周方向に１２０°離れて配置される。
【００２３】
その第２バルブ部材３２の軸方向溝は、６つの圧油供給用軸方向溝５１ａと、３つの第１圧油排出用軸方向溝５１ｂと、３つの第２圧油排出用軸方向溝５１ｃとを構成する。その圧油供給用軸方向溝５１ａは、第１バルブ部材３１に形成された圧油供給路５５を介して圧油供給用周溝３１Ｐに通じることで、入口ポート３４からポンプ７０に接続され、互いに周方向に６０°離れて配置される。その第１圧油排出用軸方向溝５１ｂは、入力シャフト２に形成された流路５２ａから入力シャフト２とトーションバー６との間を通り、入力シャフト２に形成された流路５２ｂ（図１参照）と第１出口ポート３６とから直接にタンク７１に接続され、互いに周方向に１２０°離れて配置される。その第２圧油排出用軸方向溝５１ｃは、第１バルブ部材３１に形成された流路５９を介して圧油排出用周溝３１Ｔに通じることで、第２出口ポート６１から可変絞り弁６０に接続され、互いに周方向に１２０°離れて配置される。
【００２４】
各第１圧油排出用軸方向溝５１ｂは右操舵用軸方向溝５０ａと左操舵用軸方向溝５０ｂの間に配置され、各第２圧油排出用軸方向溝５１ｃは連絡用軸方向溝５０ｃの間に配置され、右操舵用軸方向溝５０ａと連絡用軸方向溝５０ｃとの間および左操舵用軸方向溝５０ｂと連絡用軸方向溝５０ｃとの間に圧油供給用軸方向溝５１ａは配置される。
【００２５】
その第１バルブ部材３１に形成された軸方向溝５０ａ、５０ｂ、５０ｃの軸方向に沿う縁と第２バルブ部材３２に形成された軸方向溝５１ａ、５１ｂ、５１ｃの軸方向に沿う縁との間が、両バルブ部材３１、３２の相対回転角度に応じて開度が変化する絞り部Ａ、Ａ′、Ｂ、Ｂ′、Ｃ、Ｃ′、Ｄ、Ｄ′を構成する。これにより、各絞り部Ａ、Ａ′、Ｂ、Ｂ′、Ｃ、Ｃ′、Ｄ、Ｄ′はポンプ７０とタンク７１と油圧シリンダ２０とを接続する油路２７に配置されている。
【００２６】
図５に示すように、その第２バルブ部材３２に形成された軸方向溝５１ａ、５１ｂ、５１ｃの軸方向に沿う縁は面取り部とされている。各面取り部の周方向幅は、各絞り部Ａ、Ａ′、Ｂ、Ｂ′、Ｃ、Ｃ′、Ｄ、Ｄ′を全閉するのに要する両バルブ部材の相対回転角度である閉鎖角度に応じて定められている。すなわち、その圧油供給用軸方向溝５１ａと連絡用軸方向溝５０ｃとの間の絞り部Ａ′、Ｃ′における圧油供給用軸方向溝５１ａの軸方向に沿う縁（図３において□で囲む）の面取り部の周方向幅をＷ、連絡用軸方向溝５０ｃと第２圧油排出用軸方向溝５１ｃとの間の絞り部Ｂ′、Ｄ′における第２圧油排出用軸方向溝５１ｃの軸方向に沿う縁（図３において△で囲む）の面取り部の周方向幅をＷ′、その他の絞り部Ａ、Ｂ、Ｃ、Ｄにおける第２バルブ部材３２に形成された軸方向溝の軸方向に沿う縁（図３において○で囲む）の面取り部の周方向幅をＷ″として、図４、図５に示すように、Ｗ＞Ｗ′＞Ｗ″とされている。操舵抵抗のない状態（図４、図５の状態）から各絞り部Ａ、Ａ′、Ｂ、Ｂ′、Ｃ、Ｃ′、Ｄ、Ｄ′を全閉するのに要する両バルブ部材３１、３２の相対回転角度（すなわち閉鎖角度）を互いに比較すると、絞り部Ａ′、Ｃ′の閉鎖角度θｒは絞り部Ｂ′、Ｄ′の閉鎖角度θｓよりも大きく、両閉鎖角度θｒ、θｓは、他の各絞り部Ａ、Ｂ、Ｃ、Ｄの閉鎖角度θｔよりも大きい。これにより、第１バルブ部材３１と第２バルブ部材３２との間の各絞り部は、複数の絞り部Ａ、Ｂ、Ｃ、Ｄからなる第１の組と、第１の組に属する絞り部Ａ、Ｂ、Ｃ、Ｄよりも閉鎖角度の大きな複数の絞り部Ａ′、Ｂ′、Ｃ′、Ｄ′からなる第２の組とに組分けされる。また、第２の組に属する絞り部は、絞り部Ｂ′、Ｄ′と、この絞り部Ｂ′、Ｄ′よりも閉鎖角度の大きな絞り部Ａ′、Ｃ′の２種類とされる。
【００２７】
その入力シャフト２と出力シャフト３は、路面から操舵用車輪を介し伝達される操舵抵抗によるトーションバー６のねじれによって相対回転する。その相対回転により第１バルブ部材３１と第２バルブ部材３２とが相対回転することで、各絞り部Ａ、Ｂ、Ｃ、Ｄ、Ａ′、Ｂ′、Ｃ′、Ｄ′の流路面積すなわち開度が変化する。各絞り部Ａ、Ｂ、Ｃ、Ｄ、Ａ′、Ｂ′、Ｃ′、Ｄ′の開度変化に応じた操舵補助力を付与できるように、制御弁３０を介して油圧シリンダ２０がポンプ７０とタンク７１に接続され、油圧シリンダ２０が操舵抵抗に応じた操舵補助力を発生する。
【００２８】
すなわち、図４は操舵が行なわれていない状態を示し、両バルブ部材３１、３２の間の絞り部Ａ、Ｂ、Ｃ、Ｄ、Ａ′、Ｂ′、Ｃ′、Ｄ′は全て開かれ、入口ポート３４と各出口ポート３６、６１とは弁間流路２７を介し連通し、ポンプ７０から制御バルブ３０に流入する油はタンク７１に還流し、操舵補助力は発生しない。
【００２９】
この状態から右方へ操舵することによって生じる操舵抵抗により両バルブ部材３１、３２が相対回転すると、図３に示すように、絞り部Ａ、Ａ′の開度が大きくなり、絞り部Ｂ、Ｂ′の開度が小さくなり、絞り部Ｃ、Ｃ′の開度が小さくなり、絞り部Ｄ、Ｄ′の開度が大きくなる。これにより、図中矢印で示す圧油の流れにより油圧シリンダ２０の右操舵補助力発生用油室２２に操舵抵抗に応じた圧力の圧油が供給され、また、左操舵補助力発生用油室２３からタンク７１に油が還流し、車両の右方への操向補助力が油圧シリンダ２０からラック１６に作用する。
【００３０】
左方へ操舵すると第１バルブ部材３１と第２バルブ部材３２とが右方に操舵した場合と逆方向に相対回転し、絞り部Ａ、Ａ′の開度が小さくなり、絞り部Ｂ、Ｂ′の開度が大きくなり、絞り部Ｃ、Ｃ′の開度が大きくなり、絞り部Ｄ、Ｄ′の開度が小さくなるので、車両の左方への操舵補助力が油圧シリンダ２０からラック１６に作用する。
【００３１】
図１、図６に示すように、その第２出口ポート６１に連通する可変絞り弁６０は、バルブハウジング７に接続される第２バルブハウジング７′と、この第２バルブハウジング７′に形成された挿入孔６６に軸方向（図１、図６において上下方向）に移動可能に挿入されたスプール６２と、そのスプール６２にねじ合わされるネジ部材６４とを有する。その挿入孔６６の一端はプラグ６８により閉鎖され、他端はカバー９４′により閉鎖されている。そのスプール６２とプラグ６８との間に圧縮コイルバネ９０が配置されている。そのネジ部材６４にステッピングモータ８０が接続され、そのステッピングモータ８０にコントローラ（図示省略）が接続される。そのコントローラは車速センサ（図示省略）に接続され、そのステッピングモータ８０を車速に応じ制御する。すなわち、高速になるとネジ部材６４は一方向に回転してスプール６２は図中上方に変位し、低速になるとネジ部材６４は他方向に回転してスプール６２は図中下方に変位する。
【００３２】
そのスプール６２の外周に周溝６２ａが形成され、その挿入孔６６の内周に周溝６６ａが形成され、両周溝６２ａ、６６ａの間が可変絞り部６７とされている。すなわち、その可変絞り部６７は、第２の組に属する絞り部Ａ′、Ｂ′、Ｃ′、Ｄ′とタンク７１との間の油路に設けられている。その可変絞り部６７の開度は、高速になってスプール６２が図中上方に変位すると大きくなり、低速になってスプール６２が下方に変位すると小さくなる。
【００３３】
その挿入孔６６の内周の周溝６６ａと第２出口ポート６１とを連通する連絡流路５８が、スプール６２の径方向外方において第２バルブハウジング７′に形成されている。そのスプール６２の外周の周溝６２ａとスプール６２の通孔６２ｄとを連通する径方向孔６２ｃがスプール６２に形成されている。そのスプール６２の通孔６２ｄは、その挿入孔６６におけるスプール６２の下方空間に連絡する。そのスプール６２の下方空間と第１出口ポート３６とを連通する連絡流路７６が、スプール６２の径方向外方においてバルブハウジング７と第２バルブハウジング７′とに亘り形成されている。
【００３４】
これにより、ポンプ７０から供給される圧油は、前記圧油供給用周溝３１Ｐ、弁間流路２７、圧油排出用周溝３１Ｔおよび第２出口ポート６１から連絡流路５８に導かれ、この連絡流路５８から可変絞り部６７に至り、この可変絞り部６７から連絡流路７６、第１出口ポート３６を介しタンク７１に至る。なお、スプール６２には通孔６２ｄと平行にドレン流路６２ｈが形成され、スプール６２の上方空間と下方空間とを接続する。
【００３５】
その可変絞り部６７の開度に対応する流路面積の最大値は、第２の組に属する絞り部Ａ′、Ｂ′、Ｃ′、Ｄ′の開度に対応する流路面積の最大値（両バルブ部材３１、３２の相対回転角が大きくなる程に流路面積が小さくなる特性における最大値である。すなわち、右操舵時は絞り部Ｂ′、Ｃ′の合計流路面積の最大値をいい、左操舵時は絞り部Ａ′、Ｄ′の合計流路面積の最大値をいう。以下「流路面積の最大値」という場合は同旨）以上、若しくは絞り機能を奏さなくなるまで大きくされている。その可変絞り部６７の流路面積の最小値は、第２の組に属する絞り部Ａ′、Ｂ′、Ｃ′、Ｄ′の流路面積の最小値（両バルブ部材３１、３２の相対回転角が大きくなる程に流路面積が小さくなる特性における最小値である。すなわち、右操舵時は絞り部Ｂ′、Ｃ′の合計流路面積の最小値をいい、左操舵時は絞り部Ａ′、Ｄ′の合計流路面積の最小値をいい、全閉状態を含む。以下「流路面積の最小値」という場合は同旨）以下とされる。
【００３６】
これにより、図２に示す油圧回路が構成され、第２の組に属する絞り部Ａ′、Ｂ′、Ｃ′、Ｄ′とタンク７１との間の油路に、車速に応じて開度が変化する可変絞り部６７が可変絞り弁６０により設けられる。
【００３７】
図７において、実線Ｘは両バルブ部材３１、３２の相対回転角に対する第１の組に属する絞り部Ａ、Ｂ、Ｃ、Ｄの開度に対応する流路面積の変化特性（その相対回転角が大きくなる程に流路面積が小さくなる特性である。この場合、右操舵時は絞り部Ｂ、Ｃの合計流路面積の変化特性をいい、左操舵時は絞り部Ａ、Ｄの合計流路面積の変化特性をいう。以下「流路面積の変化特性」という場合は同旨）を示す。１点鎖線Ｕは、その相対回転角に対する第２の組に属する絞り部Ａ′、Ｃ′の流路面積の変化特性を示す。１点鎖線Ｖは、その相対回転角に対する第２の組に属する絞り部Ｂ′、Ｄ′の流路面積の変化特性を示す。実線Ｙは、その絞り部Ａ′、Ｃ′の流路面積の変化特性と絞り部Ｂ′、Ｄ′の流路面積の変化特性を合成した特性を示す。破線Ｒは可変絞り部６７の中速走行時における流路面積を示す。
【００３８】
低速走行時においては、スプール６２は図１、図６において下方に変位し、このスプール６２の変位により可変絞り部６７は全閉状態になる。よって、油圧シリンダ２０に作用する油圧は、第１の組の絞り部Ａ、Ｂ、Ｃ、Ｄの流路面積の変化特性線Ｘに応じ制御される。この場合、図８において実線αで示すように、操舵抵抗に対応する操舵トルクが小さく、両バルブ部材３１、３２の相対回転角が小さくても、第１の組に属する絞り部Ａ、Ｂ、Ｃ、Ｄの開度は小さいので、操舵トルクの変化に対して油圧変化が少ない領域を小さくし、操舵の高応答性を満足させて旋回性能を向上できる。
【００３９】
高速走行時においては、スプール６２は図１、図６において上方に変位し、このスプール６２の変位によって可変絞り部６７の流路面積は、第２の組に属する絞り部Ａ′、Ｂ′、Ｃ′、Ｄ′の流路面積の最大値以上になる。よって、油圧シリンダ２０に作用する油圧は、第２の組の絞り部Ａ′、Ｂ′、Ｃ′、Ｄ′の流路面積の変化特性線Ｙ及び第１の組の絞り部Ａ、Ｂ、Ｃ、Ｄの流路面積の変化特性線Ｘの合成特性に応じ制御される。この場合、図８において実線βで示すように、操舵トルクが大きく、両バルブ部材３１、３２の相対回転角が大きくても、第２の組に属する絞り部Ａ′、Ｂ′、Ｃ′、Ｄ′の開度は大きいので、操舵トルクの変化に対して油圧変化が少ない領域を大きくし、高速走行時における走行安定性を満足させることができる。
【００４０】
中速走行時においては、スプール６２の変位により可変絞り部６７の流路面積は、第２の組に属する絞り部Ａ′、Ｂ′、Ｃ′、Ｄ′の流路面積の最小値よりも大きく最大値よりも小さくなる。これにより、図７に示すように、第１の組に属する絞り部Ａ、Ｂ、Ｃ、Ｄの流路面積が最小値（本実施形態では全閉状態）になるまでの間（図７において両バルブ部材の相対回転角がθａになるまでの間）は、その第１の組に属する絞り部Ａ、Ｂ、Ｃ、Ｄの流路面積の変化特性線Ｘに可変絞り部６７の流路面積の特性線Ｒを合成した特性に応じて、油圧シリンダ２０に作用する油圧が制御される。第１の組に属する絞り部Ａ、Ｂ、Ｃ、Ｄが全閉状態になった時点から、第２の組に属する絞り部Ａ′、Ｂ′、Ｃ′、Ｄ′の流路面積が可変絞り部６７の流路面積よりも小さくなるまでの間（図７において両バルブ部材の相対回転角がθａとθｂとの間）では、可変絞り部６７の流路面積により定まる一定値になり、油圧シリンダ２０に作用する油圧は操舵抵抗に応じて制御できない。しかる後に、第２の組に属する絞り部Ａ′、Ｂ′、Ｃ′、Ｄ′の流路面積が可変絞り部６７の流路面積よりも小さくなると、第２の組に属する絞り部Ａ′、Ｂ′、Ｃ′、Ｄ′の流路面積の変化特性線Ｙに応じた操舵補助力が付与される。この場合、図８において実線γで示すように、操舵トルクの変化に対する油圧変化は、低速走行時と高速走行時の中間の特性を示す。
【００４１】
その第１の組に属する絞り部Ａ、Ｂ、Ｃ、Ｄが全閉状態になった後に、第２の組に属する絞り部Ａ′、Ｂ′、Ｃ′、Ｄ′の流路面積が可変絞り部６７の流路面積よりも小さくなるまでの間（θａ〜θｂの間）は、その第２の組に属する絞り部Ａ′、Ｂ′、Ｃ′、Ｄ′が全閉状態になる点と、第１の組に属する絞り部Ａ、Ｂ、Ｃ、Ｄが全閉状態になる点との差（θｃ−θａ）を小さくすることなく、小さくされている。すなわち、絞り部Ｂ′、Ｄ′が絞り部Ａ′、Ｃ′と同様に図中１点鎖線Ｕで示す相対回転角に対する流路面積変化特性を有すると仮定すると、相対回転角に対する第２の組に属する絞り部Ａ′、Ｂ′、Ｃ′、Ｄ′の流路面積の変化特性は、図７において２点鎖線Ｍで示すものになる。そうすると、第２の組に属する絞り部Ａ′、Ｂ′、Ｃ′、Ｄ′の流路面積が可変絞り部６７の流路面積よりも小さくなるまでの間（両バルブ部材の相対回転角がθａとθｄとの間）は大きくなるので、操舵補助力を操舵抵抗に応じ制御できない領域が大きくなる。これに対し、上記実施形態では、絞り部Ｂ′、Ｄ′の閉鎖角度θｓは絞り部Ａ′、Ｃ′の閉鎖角度θｒよりも小さいので、中速走行時において操舵補助力を操舵抵抗に応じ制御できない領域を小さくできる。しかも、絞り部Ｂ′、Ｄ′が全閉状態になる点（図７において両バルブ部材の相対回転角がθｅの点）では、絞り部Ａ′、Ｃ′は未だ閉じていないので、操舵補助力を操舵抵抗に応じ制御できる領域は小さくなることはない。
【００４２】
上記構成によれば、第１バルブ部材３１の外周において右操舵用周溝３１Ｒと左操舵用周溝３１Ｌとの間に圧油供給用周溝３１Ｐと圧油排出用周溝３１Ｔが配置されている。また、右操舵時においては、右操舵用周溝３１Ｒと圧油供給用周溝３１Ｐと圧油排出用周溝３１Ｔとにおいて油圧が上昇すると共に左操舵用周溝３１Ｌでは油圧が背圧まで低下し、左操舵時においては、左操舵用周溝３１Ｌと圧油供給用周溝３１Ｐと圧油排出用周溝３１Ｔとにおいて油圧が上昇すると共に右操舵用周溝３１Ｒでは油圧が背圧まで低下する。これにより、各周溝３１Ｒ、３１Ｌ、３１Ｐ、３１Ｔにおける油圧の作用による第１バルブ部材３１の変形量が、右操舵時と左操舵時とで大きく相異するのを防止できる。すなわち、図９の（２）は右操舵時、図９の（３）は左操舵時において、第１バルブ部材３１の中心Ｏ上の各位置から外周までの距離の、その油圧の作用による直進状態からの変形方向と変形量を示し、右操舵時と左操舵時とで変形量に差が生じるのを防止できる。これは、右操舵時に油圧上昇が生じる３つの周溝３１Ｒ、３１Ｐ、３１Ｔは互いの中の何れかと隣接し、左操舵時に油圧上昇が生じる周溝３１Ｌ、３１Ｐ、３１Ｔも互いの中の何れかと隣接することから、右操舵時と左操舵時とで油圧の分布態様を等しくできるためである。右操舵時と左操舵時とで、各周溝３１Ｒ、３１Ｌ、３１Ｐ、３１Ｔにおける油圧の作用による第１バルブ部材３１の変形量の差を低減することで、第１バルブ部材３１とバルブハウジング７との接触状態の相異を低減できる。
【００４３】
また、上記構成においては、シールリング３９ａ、３９ｂ、３９ｃ、３９ｄ、３９ｅの中で油圧差の作用を受けるものの数が、左操舵時と右操舵時と直進時とで等しくなる。すなわち図１０の（１）は、操舵がなされていない直進時（図中Ｎ）と、右操舵時（図中Ｒ）と、左操舵時（図中Ｌ）とにおいて、各シールリング３９ａ、３９ｂ、３９ｃ、３９ｄ、３９ｅが油圧差を受ける場合を〇、受けない場合を×で示す。直進時は、圧油供給用周溝３１Ｐは圧油供給により高圧状態となり、圧油排出用周溝３１Ｔの圧油は可変絞り弁６０により絞られることで高圧状態となり、左右操舵用周溝３１Ｌ、３１Ｒは第１バルブ部材３１の軸方向外方位置においてタンク７１に通じる油流路８１、８２と同様に背圧が作用する低圧状態となる。よって、第２、第４シールリング３９ｂ、３９ｄが油圧差を受け、第１、第３、第５シールリング３９ａ、３９ｃ、３９ｅは油圧差を受けない。右操舵時は、圧油供給用周溝３１Ｐ、右操舵用周溝３１Ｒは高圧状態となり、圧油排出用周溝３１Ｔの圧油は可変絞り弁６０により絞られることで高圧状態となり、左操舵用周溝３１Ｌは背圧が作用する低圧状態となる。よって、第１、第４シールリング３９ａ、３９ｄが油圧差を受け、第２、第３、第５シールリング３９ｂ、３９ｃ、３９ｅは油圧差を受けない。左操舵時は、圧油供給用周溝３１Ｐ、左操舵用周溝３１Ｌは高圧状態となり、圧油排出用周溝３１Ｔの圧油は可変絞り弁６０により絞られることで高圧状態となり、右操舵用周溝３１Ｒは背圧が作用する低圧状態となる。よって、第２、第５シールリング３９ｂ、３９ｅが油圧差を受け、第１、第３、第４シールリング３９ａ、３９ｃ、３９ｄは油圧差を受けない。これにより、各シールリング３９ａ、３９ｂ、３９ｃ、３９ｄ、３９ｅにより隔てられる隣接領域間の油圧差の作用で、バルブハウジング７の内周に押し付けられるシールリング３９ａ、３９ｂ、３９ｃ、３９ｄ、３９ｅの数は、右操舵時と左操舵と直進時とで等しくなり、また、左操舵時と直進時にバルブハウジング７の内周に押し付けられるシールリングの数は従来よりも少なくなる。これにより、右操舵時と左操舵時とにおいて操舵フィーリングに差が生じることがなく、操舵補助力を操舵抵抗に応じ制御できない領域を小さくできることと相まって良好な操舵フィーリングと静粛性を得ることができ、さらにシールリングの寿命向上を図ることができる。
【００４４】
本発明は上記実施形態に限定されない。例えば、各バルブ部材における軸方向溝の数は限定されない。
【００４５】
【発明の効果】
本発明によれば、右操舵時と左操舵時とにおいて操舵フィーリングに差が生じることがなく良好な操舵フィーリングと静粛性を得ることができ、さらにシールリングの寿命向上を図ることができる油圧パワーステアリング装置を提供できる。
【図面の簡単な説明】
【図１】本発明の実施形態の油圧パワーステアリング装置の縦断面図
【図２】本発明の実施形態の油圧パワーステアリング装置の油圧回路を示す図
【図３】本発明の実施形態の油圧パワーステアリング装置における制御弁の横断面構造の説明図
【図４】本発明の実施形態の油圧パワーステアリング装置の制御弁の展開図
【図５】本発明の実施形態の油圧パワーステアリング装置の制御弁の部分拡大図
【図６】本発明の実施形態の油圧パワーステアリング装置の可変絞り弁の縦断面図
【図７】本発明の実施形態の油圧パワーステアリング装置における制御弁の絞り部の開度とバルブ部材の相対回転角との関係を示す図
【図８】油圧パワーステアリング装置における操舵トルクと油圧との関係を示す図
【図９】本発明の実施形態の第１バルブ部材の（１）は正面図、（２）は右操舵時における油圧の作用による変形方向と変形量を示す図、（３）は左操舵時における油圧の作用による変形方向と変形量を示す図
【図１０】（１）は本発明の実施形態の第１バルブ部材におけるシールリングの配置と油圧差の作用状態を示す図、（２）は従来の第１バルブ部材におけるシールリングの配置と油圧差の作用状態を示す図
【図１１】従来の油圧パワーステアリング装置における第１バルブ部材の（１）は正面図、（２）は右操舵時における油圧の作用による変形方向と変形量を示す図、（３）は左操舵時における油圧の作用による変形方向と変形量を示す図
【符号の説明】
７バルブハウジング
２０油圧シリンダ
３０制御弁
３１第１バルブ部材
３１Ｒ右操舵用周溝
３１Ｌ左操舵用周溝
３１Ｐ圧油供給用周溝
３１Ｔ圧油排出用周溝
３２第２バルブ部材
３９ａ、３９ｂ、３９ｃ、３９ｄ、３９ｅシールリング
５０ａ、５０ｂ、５０ｃ、５１ａ、５１ｂ、５１ｃ軸方向溝
６７可変絞り部
７０ポンプ
７１タンク
Ａ、Ｂ、Ｃ、Ｄ第１の組に属する絞り部
Ａ′、Ｂ′、Ｃ′、Ｄ′ 第２の組に属する絞り部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic power steering apparatus that controls a hydraulic pressure acting on a hydraulic actuator for generating a steering assist force by using a rotary type control valve.
[0002]
[Prior art]
In the hydraulic power steering apparatus, the steering assist force is generated by controlling the hydraulic pressure acting on the hydraulic actuator with a control valve. As the control valve, a valve housing, a cylindrical first valve member inserted into the valve housing so as to be relatively rotatable, and a second valve inserted into the first valve member so as to be relatively rotatable according to a steering resistance. A rotary type having a member is used.
[0003]
The rotary type control valve is configured to reduce the steering assist force at high speeds and increase the steering assist force at low speeds in order to improve the stability of the vehicle at high speeds and the turning performance at low speeds. Some have. Therefore, a plurality of circumferential grooves are formed on the outer periphery of the first valve member so as to be parallel to each other at an axial interval, and a plurality of circumferential grooves are formed on the inner periphery of the first valve member and the outer periphery of the second valve member. Axial grooves are formed at circumferential intervals. The opening degree changes between the edge along the axial direction of the axial groove of the first valve member and the edge along the axial direction of the axial groove of the second valve member according to the relative rotation angle of both valve members. A plurality of apertures. The actuator is connected to the pump and the tank through the control valve so that a steering assist force can be applied according to the opening degree change of each throttle part. As the circumferential groove, a right steering circumferential groove connected to the right steering assist force generating oil chamber of the actuator, a left steering circumferential groove connected to the left steering assist force generating oil chamber of the actuator, It has a pressure oil supply circumferential groove connected to the pump, and a pressure oil discharge circumferential groove connected to the tank via a variable throttle portion whose opening degree changes according to operating conditions. As the axial groove, the right steering axial groove that leads to the right steering circumferential groove, the left steering axial groove that leads to the left steering circumferential groove, and the pressure oil supply that leads to the pressure oil supply circumferential groove And a first pressure oil discharging axial groove connected to the tank, and a second pressure oil discharging axial groove communicating with the pressure oil discharging circumferential groove.
[0004]
At the time of right steering, the pressure oil discharged from the pump is hydraulically supplied via the pressure oil supply circumferential groove, pressure oil supply axial groove, right steering axial groove, and right steering circumferential groove of the control valve. The oil in the left steering assist force generating oil chamber is supplied to the right steering assist force generating oil chamber of the actuator, and a part of the oil in the left steering assist force generating oil chamber is tanked from the first pressure oil discharging axial groove of the control valve. Thus, the remaining part reaches the tank from the second pressure oil discharging axial groove and the pressure oil discharging circumferential groove through the variable restrictor.
During left steering, the pressure oil discharged from the pump passes through the pressure oil supply circumferential groove, the pressure oil supply axial groove, the left steering axial groove, and the left steering circumferential groove of the control valve. Is supplied to the oil chamber for generating the left steering assist force of the hydraulic actuator, and the oil in the oil chamber for generating the right steering assist force is partially fed from the right steering axial groove to the first pressure oil discharge axial groove of the control valve. From the second axial groove for discharging pressure oil and the peripheral groove for discharging pressure oil to the tank through the variable restrictor.
[0005]
The opening of the variable throttle is increased during high-speed travel and decreased during low-speed travel. As a result, during high speed running, the steering assist force generating hydraulic pressure is small and the driving stability is improved while the steering resistance is small. When driving at low speed, the steering assist force generating hydraulic pressure is increased even when the steering resistance is small. Is greatly increased, and the turning performance is improved.
[0006]
[Problems to be solved by the invention]
In the conventional hydraulic power steering system, there may be a difference in steering feeling between right steering and left steering, or the noise generated during left steering may increase, which further improves steering feeling and quietness. Is desired.
[0007]
An object of the present invention is to provide a hydraulic power steering device that can solve the above-described problems.
[0008]
[Means for Solving the Problems]
The present invention has a steering assist force generating hydraulic actuator and a hydraulic control valve acting on the actuator, and the control valve is a tubular housing inserted into the valve housing so as to be relatively rotatable. A first valve member, and a second valve member inserted into the first valve member so as to be relatively rotatable in accordance with a steering resistance, and a plurality of circumferential grooves are axially arranged on an outer periphery of the first valve member. A plurality of axial grooves are formed on the inner circumference of the first valve member and the outer circumference of the second valve member at intervals in the circumferential direction. Between the edge along the axial direction of the axial groove of the valve member and the edge along the axial direction of the axial groove of the second valve member, a plurality of opening degrees change according to the relative rotation angle of both valve members. It is a throttle part, and it is The steering actuator is connected to the pump and the tank through the control valve so that the steering assist force can be applied, and the peripheral groove is connected to the oil chamber for generating the right steering assist force of the actuator. A circumferential groove, a left steering circumferential groove connected to the oil chamber for generating the left steering assist force of the actuator, a pressure oil supply circumferential groove connected to the pump, and an opening degree in the tank according to operating conditions A pressure oil discharge circumferential groove connected via a variable throttle portion that changes, and as its axial groove, a right steering axial groove that leads to the right steering circumferential groove, and a left steering circumference A left steering axial groove that communicates with the groove, a pressure oil supply axial groove that communicates with the pressure oil supply circumferential groove, a first pressure oil discharge axial groove that is connected to the tank, and a pressure oil discharge Hydraulic power steering having a second pressure oil discharging axial groove communicating with the circumferential groove In the ring system, between its right steering circumferential groove and a left steering circumferential groove, characterized in that the pressure oil supply circumferential groove and the pressure oil discharge circumferential grooves are disposed.
[0009]
In the above-described conventional hydraulic power steering device, the cause of the difference in steering feeling between the right steering and the left steering was investigated. As shown in FIG. 11 (1), in the outer periphery of the first valve member 101, It was investigated that the cause is that the right steering circumferential groove 101R and the pressure oil supply circumferential groove 101P are arranged between the pressure oil discharge circumferential groove 101T and the left steering circumferential groove 101L. That is, at the time of right steering, the hydraulic pressure increases in the right steering circumferential groove 101R, the pressure oil supply circumferential groove 101P, and the pressure oil discharge circumferential groove 101T, and the hydraulic pressure decreases to the back pressure in the left steering circumferential groove 101L. During left steering, the hydraulic pressure increases in the left steering circumferential groove 101L, the pressure oil supply circumferential groove 101P, and the pressure oil discharge circumferential groove 101T, and in the right steering circumferential groove 101R, the hydraulic pressure decreases to the back pressure. To do. Then, the amount of deformation of the first valve member 101 due to the action of hydraulic pressure in each circumferential groove is greatly different between right steering and left steering. That is, (2) in FIG. 11 is during right steering, and (3) in FIG. 11 is during left steering, the distance from each position on the center O of the first valve member 101 to the outer periphery is linearly driven by the action of the hydraulic pressure. The deformation direction and amount of deformation from the state are shown, and the deformation due to hydraulic pressure is greater during left steering than during right steering. This is because the three circumferential grooves 101R, 101P, 101T in which the hydraulic pressure rises during right steering are adjacent to one of the other, whereas the two circumferential grooves 101L, 101P in which the hydraulic pressure rises during left steering are This is because the circumferential groove 101R in which the hydraulic pressure is reduced is positioned between the one circumferential groove 101T, and the distribution mode of the hydraulic pressure is different between the right steering and the left steering.
[0010]
Further, in the conventional hydraulic power steering apparatus described above, between the adjacent circumferential grooves, an axially outward position from the circumferential groove 101T for discharging the hydraulic oil, and an axially outward position from the circumferential groove 101L for the left steering. The first to fifth seal rings 103a, 103b, 103c, 103d, and 103e interposed between the valve housing 102 and the first valve member 101 are disposed at the positions. The first seal ring 103a axially outward from the pressure oil discharge circumferential groove 101T has an oil passage 104 and a pressure oil discharge peripheral groove 101T communicating with the tank at the axially outer position of the first valve member 101. The fifth seal ring 103e at a position axially outward from the left steering circumferential groove 101L is connected to the oil flow path 105 communicating with the tank at the axially outward position of the first valve member 101 and the left. The space between the circumferential groove 101L for steering is sealed. When a hydraulic pressure difference occurs between adjacent regions separated by the seal rings 103a, 103b, 103c, 103d, and 103e, the seal rings 103a, 103b, 103c, 103d, and 103e are caused to move to the inner periphery of the valve housing 102 by the action of the hydraulic pressure difference. Pressed against. In the conventional configuration, the number of the seal rings 103a, 103b, 103c, 103d, and 103e that are affected by the hydraulic pressure difference is greater during left steering than during right steering. That is, (2) in FIG. 10 shows the seal rings 103a and 103b when the vehicle is traveling straight (N in the figure), right steered (R in the figure), and left steered (L in the figure). , 103c, 103d, and 103e are indicated by O, and when not received by x. During straight travel, the pressure oil supply circumferential groove 103P is in a high pressure state by the pressure oil supply, and the pressure oil in the pressure oil discharge circumferential groove 101T is in a high pressure state by being squeezed by the variable restrictor, and the left and right steering circumferential grooves 101L, 101R is in a low pressure state in which back pressure is applied in the same manner as the oil flow paths 104 and 105 communicating with the tank at the axially outer position of the first valve member 101. Therefore, the first to fourth seal rings 103a, 103b, 103c, and 103d receive a hydraulic pressure difference, and the fifth seal ring 103e does not receive a hydraulic pressure difference. During right steering, the pressure oil supply circumferential groove 103P and the right steering circumferential groove 101R are in a high pressure state, and the pressure oil in the pressure oil discharge circumferential groove 101T is in a high pressure state by being squeezed by a variable restrictor. The circumferential groove 101L is in a low pressure state where the back pressure acts. Therefore, the first and fourth seal rings 103a and 103d receive a hydraulic pressure difference, and the second, third, and fifth seal rings 103b, 103c, and 103e do not receive the hydraulic pressure difference. During left steering, the pressure oil supply circumferential groove 103P and the left steering circumferential groove 101L are in a high pressure state, and the pressure oil in the pressure oil discharge circumferential groove 101T is in a high pressure state by being squeezed by the variable restrictor. The circumferential groove 101R is in a low pressure state where the back pressure acts. Therefore, the first to third seal rings 103a, 103b, 103c and the fifth seal ring 103e receive a hydraulic pressure difference, and the fourth seal ring 103d does not receive the hydraulic pressure difference.
[0011]
As described above, the deformation state of the first valve member 101 and the number of seal rings receiving the hydraulic pressure difference are different between the right steering and the left steering, so that the contact state between the first valve member 101 and the valve housing 102 is different. However, there was a difference in steering feeling and an increase in generated sound.
[0012]
According to the configuration of the present invention, the pressure oil supply circumferential groove and the pressure oil discharge circumferential groove are disposed between the right steering circumferential groove and the left steering circumferential groove. In any case during left steering, the three circumferential grooves in which the hydraulic pressure rises are adjacent to one another. This reduces the difference in deformation amount of the first valve member due to the action of hydraulic pressure in each circumferential groove between right steering and left steering, and reduces the difference in the contact state between the first valve member and the valve housing. it can.
[0013]
Furthermore, in the present invention,Between adjacent circumferential grooves,SaidAn axially outer position than the right steering circumferential groove,SaidIn the axially outer position than the left steering circumferential groove,SaidWith valve housingSaidIntervening between the first valve member1st to 5thA seal ring is placed,SaidThe axially outer position than the right steering circumferential grooveThe firstWith seal ring,SaidAt the axially outward position of one end of the first valve memberSaidThe oil flow path leading to the tankSaidThe space between the right steering circumferential groove is sealed,SaidAn axially outward position from the left steering grooveThe fifthWith seal ring,SaidAt the axially outward position of the other end of the first valve memberSaidThe oil flow path leading to the tankSaidThe space between the left steering groove is sealedDuring straight travel, the pressure oil supply circumferential groove and the pressure oil discharge circumferential groove are in a high pressure state and the left and right steering circumferential grooves are in a low pressure state, so that the right steering circumferential groove and the pressure oil are Hydraulic pressure between adjacent regions in which the second seal ring between the discharge circumferential groove and the fourth seal ring between the left steering circumferential groove and the pressure oil supply circumferential groove are separated by each seal ring. The first seal ring, the third seal ring between the pressure oil discharge circumferential groove and the pressure oil supply circumferential groove, and the fifth seal ring are subjected to the hydraulic pressure difference. During right steering, the pressure oil supply circumferential groove, the right steering circumferential groove, and the pressure oil discharge circumferential groove are in a high pressure state, and the left steering circumferential groove is in a low pressure state. The first and fourth seal rings receive the hydraulic pressure difference and the second and third The fifth seal ring is not subjected to the hydraulic pressure difference, and during left steering, the pressure oil supply circumferential groove, the left steering circumferential groove, and the pressure oil discharge circumferential groove are in a high pressure state. When the right steering circumferential groove is in a low pressure state, the second and fifth seal rings receive the hydraulic pressure difference and the first, third, and fourth seal rings do not receive the hydraulic pressure difference. AndHaveThe
According to this configuration, the number of seal rings pressed against the inner periphery of the valve housing by the action of the hydraulic pressure difference between adjacent regions separated by each seal ring becomes equal between right steering, left steering, and straight traveling, In addition, the number of seal rings pressed against the inner periphery of the valve housing during left steering and straight traveling is smaller than in the prior art.
[0014]
The number of the axial grooves for supplying pressure oil is at least two, including at least two connecting axial grooves as the axial grooves, and between the right steering axial groove and the left steering axial groove. A pressure oil discharge axial groove is disposed, a second pressure oil discharge axial groove is disposed between the communication axial grooves, and between the right steering axial groove and the communication axial groove; A pressure oil supply axial groove is disposed between the left steering axial groove and the communication axial groove, and a throttle portion between the left and right steering axial grooves and the first pressure oil discharge axial groove. And the throttle part between the left and right steering axial grooves and the pressure oil supply axial groove belong to the first set, and the throttle part between the pressure oil supply axial groove and the communication axial groove The throttle part between the communication axial groove and the second pressure oil discharging axial groove belongs to the second group, and the closing angle of the throttle part belonging to the second group is the first angle. An oil passage between the throttle part and the tank belonging to the second group, the two kinds of throttle parts having different closure angles belong to the second group. It is preferable that the variable throttle portion is provided in the main body. As a result, the region in which the steering assist force cannot be controlled according to the steering resistance can be reduced, and the steering feeling can be further improved.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
A vehicle rack and pinion type hydraulic power steering apparatus 1 according to an embodiment of the present invention shown in FIG. 1 is connected to an input shaft 2 connected to a steering wheel (not shown), and connected to the input shaft 2 via a torsion bar 6. An output shaft 3 is provided. The torsion bar 6 is connected to the input shaft 2 by a pin 4 and connected to the output shaft 3 by a serration 5. The input shaft 2 is supported by the valve housing 7 via a bearing 8 and is supported by the output shaft 3 via a bush 12. The output shaft 3 is supported by the rack housing 9 via bearings 10 and 11. A pinion 15 is formed on the output shaft 3, and a steering wheel (not shown) is connected to a rack 16 that meshes with the pinion 15. Thereby, the rotation of the input shaft 2 by the steering is transmitted to the pinion 15 through the torsion bar 6, and the rack 16 moves in the vehicle width direction by the rotation of the pinion 15, and the steering of the vehicle is performed by the movement of the rack 16. Made. Oil seals 42 and 43 are interposed between the input / output shafts 2 and 3 and the housing 7. A support yoke 40 that supports the rack 16 is pressed against the rack 16 by the elasticity of the spring 41.
[0016]
A hydraulic cylinder 20 is provided as a steering assist force generating hydraulic actuator. The hydraulic cylinder 20 includes a cylinder tube constituted by the rack housing 9 and a piston 21 integrated with the rack 16. A rotary hydraulic control valve 30 is provided to control the hydraulic pressure acting on the hydraulic cylinder 20 by supplying pressure oil to the oil chambers 22 and 23 partitioned by the piston 21 according to the steering resistance.
[0017]
The control valve 30 includes a cylindrical first valve member 31 that is inserted into the valve housing 7 so as to be relatively rotatable, and a second valve member 32 that is inserted into the first valve member 31 so as to be relatively rotatable about a coaxial center. Is provided. The first valve member 31 is connected to the output shaft 3 by a pin 29 so as to rotate together. The second valve member 32 is formed integrally with the input shaft 2, and the second valve member 32 is constituted by the outer peripheral portion of the input shaft 2, and the second valve member 32 rotates along with the input shaft 2. Therefore, the first valve member 31 and the second valve member 32 are elastically rotated relative to each other about the coaxial center by twisting the torsion bar 6 according to the steering resistance.
[0018]
The valve housing 7 has an inlet port 34 connected to the pump 70, a first port 37 connected to the right steering assist force generating oil chamber 22 of the hydraulic cylinder 20, and a left steering assist force generating oil chamber 23. The tank 71 via a second port 38 connected to the first outlet port 36, a first outlet port 36 directly connected to the tank 71, and a variable throttle 67 of the variable throttle valve 60 whose opening degree changes according to operating conditions described later. And a second outlet port 61 connected to the. Each port 34, 36, 37, 38, 61 is connected to each other via a flow path between the inner and outer circumferences of the first valve member 31 and the second valve member 32.
[0019]
That is, as shown in (1) of FIG. 9, a plurality of circumferential grooves 31R, 31L, 31P, and 31T are formed on the outer periphery of the first valve member 31 so as to be parallel to each other at equal intervals in the axial direction. ing. The circumferential grooves 31R, 31L, 31P, 31T are connected to the right steering assist force generating oil chamber 22 via the first port 37 and the right steering assist groove 31R. The left steering circumferential groove 31L connected to the chamber 23 via the second port 38, the pressure oil supply circumferential groove 31P connected to the pump 70 via the inlet port 34, and the tank 71 It is comprised from the 2 outlet port 61 and the peripheral groove | channel 31T for pressure oil discharge connected via the said variable throttle valve 60. FIG. The pressure oil supply circumferential groove 31P and the pressure oil discharge circumferential groove 31T are arranged between the right steering circumferential groove 31R and the left steering circumferential groove 31L. In this embodiment, the right steering circumferential groove 31R is disposed adjacent to the pressure oil discharge circumferential groove 31T, and the left steering circumferential groove 31L is disposed adjacent to the pressure oil supply circumferential groove 31P. The steering circumferential groove 31R may be disposed adjacent to the pressure oil supply circumferential groove 31P, and the left steering circumferential groove 31L may be disposed adjacent to the pressure oil discharge circumferential groove 31T.
[0020]
Valves between the circumferential grooves 31R, 31L, 31P, 31T adjacent to each other, at an axially outer position than the right steering circumferential groove 31R, and at an axially outer position than the left steering circumferential groove 31L First to fifth seal rings 39a, 39b, 39c, 39d, 39e interposed between the housing 7 and the first valve member 31 are arranged. The first seal ring 39a at the axially outward position from the right steering circumferential groove 31R has an oil passage 81 communicating with the tank 71 at the axially outward position at one end of the first valve member 31 and the right steering circumferential groove. The fifth seal ring 39e is sealed between the first steering valve 31R and axially outward from the left steering circumferential groove 31L. The fifth seal ring 39e communicates with the tank 71 at the axially outward position at the other end of the first valve member 31. The space between the flow path 82 and the left steering circumferential groove 31L is sealed. When a hydraulic pressure difference occurs between adjacent regions separated by the seal rings 39a, 39b, 39c, 39d, and 39e, the seal rings 39a, 39b, 39c, 39d, and 39e are moved to the inner periphery of the valve housing 7 by the action of the hydraulic pressure difference. Pressed against.
[0021]
As shown in FIGS. 3 and 4, axial grooves 50 a, 50 b, and 50 c are formed on the inner periphery of the first valve member 31 at twelve locations that are equally spaced in the circumferential direction. On the outer periphery of the second valve member 32, axial grooves 51a, 51b, and 51c are formed at twelve locations at equal intervals in the circumferential direction. FIG. 4 shows a developed view of the second valve member 32 by a solid line, and shows axial grooves 50a, 50b, 50c formed in the first valve member 31 by a chain line. Between the axial grooves 50a, 50b, 50c formed in the first valve member 31, the axial grooves 51a, 51b, 51c formed in the second valve member 32 are located.
[0022]
The axial grooves of the first valve member 31 constitute three right steering axial grooves 50a, three left steering axial grooves 50b, and six connecting axial grooves 50c. The right steering axial groove 50a communicates with the right steering circumferential groove 31R through a flow path 53 formed in the first valve member 31, so that the right steering assist force generating oil chamber 22 is supplied from the first port 37. And 120 ° apart from each other in the circumferential direction. The left steering axial groove 50b communicates with the left steering circumferential groove 31L via a flow path 54 formed in the first valve member 31, so that the left steering assist force generating oil chamber 23 is supplied from the second port 38. And 120 ° apart from each other in the circumferential direction.
[0023]
The axial grooves of the second valve member 32 include six pressure oil supply axial grooves 51a, three first pressure oil discharge axial grooves 51b, and three second pressure oil discharge axial grooves 51c. And configure. The axial groove 51a for pressure oil supply is connected to the pump 70 from the inlet port 34 by communicating with the circumferential groove 31P for pressure oil supply via the pressure oil supply passage 55 formed in the first valve member 31. They are arranged 60 ° apart from each other in the circumferential direction. The first pressure oil discharging axial groove 51b passes between the input shaft 2 and the torsion bar 6 from the flow path 52a formed in the input shaft 2, and the flow path 52b formed in the input shaft 2 (FIG. 1). And the first outlet port 36 are directly connected to the tank 71 and are spaced apart from each other by 120 ° in the circumferential direction. The second pressure oil discharging axial groove 51c is connected to the pressure oil discharging circumferential groove 31T through a flow path 59 formed in the first valve member 31, and thereby the variable throttle valve 60 is connected to the second outlet port 61. And 120 ° apart from each other in the circumferential direction.
[0024]
Each first pressure oil discharging axial groove 51b is disposed between the right steering axial groove 50a and the left steering axial groove 50b, and each second pressure oil discharging axial groove 51c is a connecting axial groove. 50c between the right steering axial groove 50a and the connecting axial groove 50c and between the left steering axial groove 50b and the connecting axial groove 50c. 51a is arranged.
[0025]
The edge along the axial direction of the axial grooves 50a, 50b, 50c formed in the first valve member 31 and the edge along the axial direction of the axial grooves 51a, 51b, 51c formed in the second valve member 32. The gaps constitute throttle portions A, A ′, B, B ′, C, C ′, D, D ′ whose opening degree changes according to the relative rotation angle of both valve members 31, 32. Accordingly, the throttle portions A, A ′, B, B ′, C, C ′, D, and D ′ are arranged in the oil passage 27 that connects the pump 70, the tank 71, and the hydraulic cylinder 20.
[0026]
As shown in FIG. 5, the edges along the axial direction of the axial grooves 51a, 51b, 51c formed in the second valve member 32 are chamfered portions. The circumferential width of each chamfered portion is a closing angle that is a relative rotation angle of both valve members required to fully close each throttle portion A, A ′, B, B ′, C, C ′, D, D ′. It is determined accordingly. That is, the edge along the axial direction of the axial groove 51a for pressure oil supply at the throttle portions A 'and C' between the axial groove 51a for pressure oil supply and the connecting axial groove 50c (in FIG. The circumferential width of the chamfered portion is W, and the second pressure oil discharging axial groove at the throttle portions B ′ and D ′ between the connecting axial groove 50c and the second pressure oil discharging axial groove 51c. The circumferential width of the chamfered portion of the edge (enclosed by Δ in FIG. 3) along the axial direction of 51c is W ′, and the axial groove formed in the second valve member 32 in the other throttle portions A, B, C, D W> W ′> W ″, as shown in FIGS. 4 and 5, where W ″ is the circumferential width of the chamfered portion of the edge (circled in FIG. 3) along the axial direction. Both valve members 31, 32 required to fully close the throttle portions A, A ', B, B', C, C ', D, D' from the state without steering resistance (the state shown in FIGS. 4 and 5). Are compared with each other, the closing angle θr of the throttle parts A ′ and C ′ is larger than the closing angle θs of the throttle parts B ′ and D ′, and both the closing angles θr and θs are different from each other. Is larger than the closing angle θt of each of the aperture portions A, B, C, and D. Thereby, each throttle part between the 1st valve member 31 and the 2nd valve member 32 is the 1st group which consists of a plurality of throttle parts A, B, C, and D, and the throttle part which belongs to the 1st group. They are grouped into a second group consisting of a plurality of apertures A ′, B ′, C ′, D ′ having a larger closing angle than A, B, C, D. Further, there are two types of apertures belonging to the second group: apertures B ′ and D ′ and apertures A ′ and C ′ having a closing angle larger than that of the apertures B ′ and D ′.
[0027]
The input shaft 2 and the output shaft 3 rotate relative to each other by the torsion of the torsion bar 6 due to the steering resistance transmitted from the road surface via the steering wheel. By the relative rotation of the first valve member 31 and the second valve member 32 due to the relative rotation, the flow passage areas of the throttle portions A, B, C, D, A ′, B ′, C ′, D ′, that is, The opening changes. The hydraulic cylinder 20 is connected to the pump 70 via the control valve 30 so that a steering assist force can be applied according to the opening degree change of each of the throttle portions A, B, C, D, A ′, B ′, C ′, D ′. The hydraulic cylinder 20 generates a steering assist force corresponding to the steering resistance.
[0028]
That is, FIG. 4 shows a state in which steering is not performed, and the throttle portions A, B, C, D, A ′, B ′, C ′, D ′ between the valve members 31, 32 are all opened, The inlet port 34 and each of the outlet ports 36 and 61 communicate with each other via the inter-valve flow path 27, and oil flowing into the control valve 30 from the pump 70 returns to the tank 71, and no steering assist force is generated.
[0029]
When the valve members 31 and 32 are rotated relative to each other by the steering resistance generated by steering to the right from this state, as shown in FIG. 3, the opening degree of the throttle portions A and A ′ increases, and the throttle portions B and B The opening of 'is reduced, the opening of the throttles C and C' is reduced, and the opening of the throttles D and D 'is increased. As a result, the pressure oil having a pressure corresponding to the steering resistance is supplied to the right steering assist force generating oil chamber 22 of the hydraulic cylinder 20 by the flow of the pressure oil indicated by the arrow in the drawing, and the left steering assist force generating oil chamber is provided. The oil flows back from 23 to the tank 71, and the steering assist force to the right of the vehicle acts on the rack 16 from the hydraulic cylinder 20.
[0030]
When steered to the left, the first valve member 31 and the second valve member 32 rotate relative to each other in the opposite direction to that when steered to the right, and the apertures of the throttle parts A and A ′ become smaller, so that the throttle parts B and B 'Is increased, the apertures of the throttles C and C' are increased, and the apertures of the throttles D and D 'are decreased, so that the steering assist force to the left of the vehicle is generated from the hydraulic cylinder 20 to the rack. 16 acts.
[0031]
As shown in FIGS. 1 and 6, the variable throttle valve 60 communicating with the second outlet port 61 is formed in the second valve housing 7 ′ connected to the valve housing 7 and the second valve housing 7 ′. The spool 62 is inserted into the insertion hole 66 so as to be movable in the axial direction (vertical direction in FIGS. 1 and 6), and the screw member 64 is screwed into the spool 62. One end of the insertion hole 66 is closed by a plug 68, and the other end is closed by a cover 94 '. A compression coil spring 90 is disposed between the spool 62 and the plug 68. A stepping motor 80 is connected to the screw member 64, and a controller (not shown) is connected to the stepping motor 80. The controller is connected to a vehicle speed sensor (not shown) and controls the stepping motor 80 according to the vehicle speed. That is, when the speed is high, the screw member 64 rotates in one direction and the spool 62 is displaced upward in the figure, and when the speed is low, the screw member 64 is rotated in the other direction and the spool 62 is displaced downward in the figure.
[0032]
A circumferential groove 62 a is formed on the outer periphery of the spool 62, a circumferential groove 66 a is formed on the inner periphery of the insertion hole 66, and a variable throttle portion 67 is formed between both the circumferential grooves 62 a and 66 a. That is, the variable throttle portion 67 is provided in the oil passage between the throttle portions A ′, B ′, C ′, D ′ belonging to the second group and the tank 71. The opening degree of the variable throttle 67 increases when the spool 62 is displaced upward in the drawing at a high speed, and decreases when the spool 62 is displaced downward at a low speed.
[0033]
A communication flow path 58 that communicates the inner circumferential groove 66 a of the insertion hole 66 with the second outlet port 61 is formed in the second valve housing 7 ′ on the radially outer side of the spool 62. A radial hole 62 c is formed in the spool 62 to communicate the circumferential groove 62 a on the outer periphery of the spool 62 and the through hole 62 d of the spool 62. The through hole 62 d of the spool 62 communicates with the space below the spool 62 in the insertion hole 66. A communication flow path 76 that communicates the space below the spool 62 and the first outlet port 36 is formed across the valve housing 7 and the second valve housing 7 ′ on the radially outer side of the spool 62.
[0034]
Thus, the pressure oil supplied from the pump 70 is guided to the communication flow path 58 from the pressure oil supply circumferential groove 31P, the inter-valve flow path 27, the pressure oil discharge circumferential groove 31T, and the second outlet port 61, The communication flow path 58 leads to the variable throttle section 67, and the variable throttle section 67 reaches the tank 71 via the communication flow path 76 and the first outlet port 36. The spool 62 is formed with a drain passage 62h parallel to the through hole 62d, and connects the upper space and the lower space of the spool 62.
[0035]
The maximum value of the channel area corresponding to the opening of the variable throttle 67 is the maximum of the channel area corresponding to the openings of the throttles A ′, B ′, C ′, D ′ belonging to the second group. (This is the maximum value in the characteristic that the flow path area decreases as the relative rotation angle of both valve members 31 and 32 increases. That is, the maximum value of the total flow path area of the throttle portions B 'and C' during right steering. During left steering, it refers to the maximum value of the total flow area of the throttles A 'and D' (hereinafter referred to as "maximum value of the flow area"), or increased until the throttle function is not achieved. ing. The minimum value of the flow passage area of the variable restricting portion 67 is the minimum value of the flow passage areas of the restricting portions A ′, B ′, C ′, D ′ belonging to the second group (relative rotation of both valve members 31, 32). The minimum value in the characteristic that the flow path area decreases as the angle increases, that is, the minimum value of the total flow path area of the throttle parts B ′ and C ′ during right steering, and the throttle part A during left steering. The minimum value of the total flow area of ′ and D ′, including the fully closed state (hereinafter referred to as “minimum value of the flow area” is the same).
[0036]
Accordingly, the hydraulic circuit shown in FIG. 2 is configured, and the opening degree is set in the oil passage between the throttle portions A ′, B ′, C ′, D ′ belonging to the second group and the tank 71 according to the vehicle speed. A variable throttle portion 67 that changes is provided by the variable throttle valve 60.
[0037]
In FIG. 7, a solid line X represents a change characteristic of the flow path area corresponding to the opening degree of the throttle portions A, B, C, and D belonging to the first group with respect to the relative rotation angle of both valve members 31 and 32 (its relative rotation angle). In this case, the change characteristic of the total flow area of the throttle parts B and C during the right steering, and the total flow of the throttle parts A and D during the left steering. This means the change characteristic of the road area (hereinafter referred to as “change characteristic of the flow path area”). A one-dot chain line U indicates a change characteristic of the flow path area of the throttle portions A ′ and C ′ belonging to the second group with respect to the relative rotation angle. An alternate long and short dash line V indicates a change characteristic of the flow path area of the throttle portions B ′ and D ′ belonging to the second group with respect to the relative rotation angle. A solid line Y indicates a characteristic obtained by synthesizing the change characteristics of the flow passage areas of the throttle portions A ′ and C ′ and the change characteristics of the flow passage areas of the throttle portions B ′ and D ′. A broken line R indicates the flow path area during the medium speed travel of the variable throttle portion 67.
[0038]
During low-speed travel, the spool 62 is displaced downward in FIGS. 1 and 6, and the variable restrictor 67 is fully closed by the displacement of the spool 62. Therefore, the hydraulic pressure acting on the hydraulic cylinder 20 is controlled according to the change characteristic line X of the flow path area of the first set of throttle portions A, B, C, and D. In this case, as shown by a solid line α in FIG. 8, even if the steering torque corresponding to the steering resistance is small and the relative rotation angles of both the valve members 31 and 32 are small, the throttle portions A, B, Since the opening degree of C and D is small, the region where the hydraulic pressure change is small with respect to the change of the steering torque can be reduced, and the turning performance can be improved by satisfying the high response of the steering.
[0039]
During high-speed travel, the spool 62 is displaced upward in FIGS. 1 and 6, and the displacement of the spool 62 causes the flow area of the variable restrictor 67 to be the restrictors A ′, B ′, It becomes more than the maximum value of the channel area of C 'and D'. Therefore, the hydraulic pressure acting on the hydraulic cylinder 20 is the change characteristic line Y of the flow path area of the second set of throttle portions A ′, B ′, C ′, D ′ and the first set of throttle portions A, B, Control is performed according to the composite characteristic of the change characteristic line X of the flow path areas of C and D. In this case, as indicated by the solid line β in FIG. 8, even if the steering torque is large and the relative rotational angles of both valve members 31 and 32 are large, the throttle portions A ′, B ′, C ′, Since the opening degree of D ′ is large, the region where the hydraulic pressure change is small with respect to the change of the steering torque can be increased to satisfy the running stability during high speed running.
[0040]
During medium speed running, the flow path area of the variable throttle 67 is smaller than the minimum value of the flow areas of the throttles A ′, B ′, C ′, D ′ belonging to the second group due to the displacement of the spool 62. Greatly smaller than the maximum value. As a result, as shown in FIG. 7, the flow passage areas of the throttle portions A, B, C, and D belonging to the first group become the minimum value (in the present embodiment, the fully closed state) (in FIG. 7, Until the relative rotation angle of the two valve members reaches θa), the flow path of the variable throttle 67 is shown in the change characteristic line X of the flow areas of the throttles A, B, C, D belonging to the first group. The hydraulic pressure acting on the hydraulic cylinder 20 is controlled according to the characteristic obtained by combining the characteristic lines R of the area. The flow passage areas of the throttle parts A ′, B ′, C ′, D ′ belonging to the second group are variable from the time when the throttle parts A, B, C, D belonging to the first group are fully closed. Until it becomes smaller than the flow path area of the throttle part 67 (in FIG. 7, the relative rotation angles of both valve members are between θa and θb), it becomes a constant value determined by the flow path area of the variable throttle part 67, The hydraulic pressure acting on the hydraulic cylinder 20 cannot be controlled according to the steering resistance. Thereafter, when the flow passage areas of the throttle portions A ′, B ′, C ′, D ′ belonging to the second group become smaller than the flow passage area of the variable throttle portion 67, the throttle portions A ′ belonging to the second group. , B ′, C ′, and D ′ are applied with a steering assist force corresponding to the change characteristic line Y of the flow path area. In this case, as indicated by a solid line γ in FIG. 8, the change in hydraulic pressure with respect to the change in steering torque shows an intermediate characteristic between low speed running and high speed running.
[0041]
After the throttle portions A, B, C, and D belonging to the first group are fully closed, the flow passage areas of the throttle portions A ′, B ′, C ′, and D ′ belonging to the second group are variable. The throttle portions A ′, B ′, C ′, and D ′ belonging to the second set are fully closed until the flow passage area of the throttle portion 67 becomes smaller (between θa and θb). And the difference (θc−θa) from the point where the aperture portions A, B, C, and D belonging to the first group are in the fully closed state are made small. That is, if it is assumed that the throttle portions B ′ and D ′ have the flow path area change characteristic with respect to the relative rotation angle indicated by the one-dot chain line U in the drawing similarly to the throttle portions A ′ and C ′, The change characteristics of the flow path areas of the throttle portions A ′, B ′, C ′, and D ′ belonging to the set are shown by a two-dot chain line M in FIG. Then, until the flow passage area of the throttle portions A ′, B ′, C ′, D ′ belonging to the second group becomes smaller than the flow passage area of the variable throttle portion 67 (the relative rotation angle of both valve members is Since (between θa and θd) increases, the region in which the steering assist force cannot be controlled according to the steering resistance increases. On the other hand, in the above embodiment, the closing angle θs of the throttle parts B ′ and D ′ is smaller than the closing angle θr of the throttle parts A ′ and C ′, so that the steering assist force depends on the steering resistance during medium speed traveling. The area that cannot be controlled can be reduced. Moreover, at the point where the throttle parts B ′ and D ′ are fully closed (the relative rotation angle of both valve members in FIG. 7 is the point of θe), the throttle parts A ′ and C ′ are not yet closed. The region in which the force can be controlled according to the steering resistance is never reduced.
[0042]
According to the above configuration, the pressure oil supply circumferential groove 31P and the pressure oil discharge circumferential groove 31T are arranged on the outer periphery of the first valve member 31 between the right steering circumferential groove 31R and the left steering circumferential groove 31L. Yes. Further, at the time of right steering, the hydraulic pressure increases in the right steering circumferential groove 31R, the pressure oil supply circumferential groove 31P, and the pressure oil discharge circumferential groove 31T, and the hydraulic pressure decreases to the back pressure in the left steering circumferential groove 31L. During left steering, the hydraulic pressure increases in the left steering circumferential groove 31L, the pressure oil supply circumferential groove 31P, and the pressure oil discharge circumferential groove 31T, and in the right steering circumferential groove 31R, the hydraulic pressure decreases to the back pressure. To do. Thereby, it is possible to prevent the deformation amount of the first valve member 31 due to the action of the hydraulic pressure in each of the circumferential grooves 31R, 31L, 31P, 31T from greatly differing between right steering and left steering. That is, in FIG. 9 (2) during right steering and in FIG. 9 (3) during left steering, the distance from each position on the center O of the first valve member 31 to the outer periphery is linearly driven by the action of the hydraulic pressure. The deformation direction and deformation amount from the state are shown, and it is possible to prevent the deformation amount from being different between right steering and left steering. This is because the three circumferential grooves 31R, 31P, 31 in which the hydraulic pressure rises during right steering are generated.TAre adjacent to each other, and the circumferential grooves 31L, 31P, 31 in which the hydraulic pressure rises during left steering are generated.TThis is because the hydraulic pressure distribution mode can be made equal during right steering and left steering because they are adjacent to each other. By reducing the difference in deformation amount of the first valve member 31 due to the action of hydraulic pressure in each of the circumferential grooves 31R, 31L, 31P, 31T during right steering and left steering, the first valve member 31 and the valve housing 7 are reduced. The difference in contact state with can be reduced.
[0043]
In the above configuration, the number of seal rings 39a, 39b, 39c, 39d, and 39e that are affected by the hydraulic pressure difference is the same during left steering, right steering, and straight travel. That is, (1) in FIG. 10 shows the seal rings 39a and 39b when the vehicle is traveling straight without steering (N in the drawing), during right steering (R in the drawing), and during left steering (L in the drawing). , 39c, 39d, and 39e are indicated by ◯, and not received by x. When running straight, the circumferential groove 3 for supplying pressure oil1P is in a high pressure state by pressure oil supply, and the pressure oil in the pressure oil discharge circumferential groove 31T is in a high pressure state by being throttled by the variable throttle valve 60. The left and right steering circumferential grooves 31L and 31R are shafts of the first valve member 31. As in the oil flow paths 81 and 82 communicating with the tank 71 at the outward position in the direction, a low pressure state in which back pressure acts is obtained. Therefore, the second and fourth seal rings 39b and 39d receive a hydraulic pressure difference, and the first, third, and fifth seal rings 39a, 39c, and 39e do not receive the hydraulic pressure difference. During right steering, the peripheral groove 3 for pressure oil supply1P, the right steering circumferential groove 31R is in a high pressure state, the pressure oil in the pressure oil discharge circumferential groove 31T is brought into a high pressure state by being throttled by the variable throttle valve 60, and the left steering circumferential groove 31L is a low pressure on which the back pressure acts. It becomes a state. Therefore, the first and fourth seal rings 39a and 39d receive a hydraulic pressure difference, and the second, third, and fifth seal rings 39b, 39c, and 39e do not receive the hydraulic pressure difference. During left steering, pressure oil supply circumferential groove 31P, the left steering circumferential groove 31L is in a high pressure state, the pressure oil in the pressure oil discharge circumferential groove 31T is brought into a high pressure state by being throttled by the variable throttle valve 60, and the right steering circumferential groove 31R is a low pressure on which the back pressure acts. It becomes a state. Therefore, the second and second5The seal rings 39b and 39e receive a hydraulic pressure difference, and the first, third, and fourth seal rings 39a, 39c, and 39d do not receive the hydraulic pressure difference. As a result, the number of seal rings 39a, 39b, 39c, 39d, and 39e pressed against the inner periphery of the valve housing 7 by the action of the hydraulic pressure difference between adjacent regions separated by the seal rings 39a, 39b, 39c, 39d, and 39e. Is equal between right steering, left steering, and straight traveling, and the number of seal rings that are pressed against the inner periphery of the valve housing 7 during left steering and straight traveling is smaller than in the prior art. As a result, there is no difference in steering feeling between right steering and left steering, and it is possible to obtain a good steering feeling and quietness coupled with the fact that the area where the steering assist force cannot be controlled according to the steering resistance can be reduced. In addition, the life of the seal ring can be improved.
[0044]
The present invention is not limited to the above embodiment. For example, the number of axial grooves in each valve member is not limited.
[0045]
【The invention's effect】
According to the present invention, there is no difference in steering feeling between right steering and left steering, good steering feeling and quietness can be obtained, and the life of the seal ring can be improved. A hydraulic power steering device can be provided.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a hydraulic power steering apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing a hydraulic circuit of the hydraulic power steering apparatus according to the embodiment of the present invention.
FIG. 3 is an explanatory diagram of a cross-sectional structure of a control valve in the hydraulic power steering apparatus according to the embodiment of the present invention.
FIG. 4 is an exploded view of a control valve of the hydraulic power steering apparatus according to the embodiment of the present invention.
FIG. 5 is a partially enlarged view of a control valve of the hydraulic power steering apparatus according to the embodiment of the present invention.
FIG. 6 is a longitudinal sectional view of a variable throttle valve of the hydraulic power steering apparatus according to the embodiment of the present invention.
FIG. 7 is a diagram showing the relationship between the opening degree of the throttle portion of the control valve and the relative rotation angle of the valve member in the hydraulic power steering apparatus according to the embodiment of the present invention.
FIG. 8 is a diagram showing a relationship between steering torque and hydraulic pressure in a hydraulic power steering apparatus.
9A is a front view of the first valve member according to the embodiment of the present invention, FIG. 9B is a diagram showing a deformation direction and a deformation amount due to the action of hydraulic pressure during right steering, and FIG. Of deformation direction and amount of deformation due to hydraulic action
FIGS. 10A and 10B are views showing the arrangement of the seal ring in the first valve member and the action state of the hydraulic pressure difference in the first embodiment of the present invention, and FIG. Diagram showing the action state of the difference
11 is a front view of a first valve member in a conventional hydraulic power steering device, FIG. 11 is a diagram showing a deformation direction and a deformation amount due to the action of hydraulic pressure during right steering, and FIG. Of deformation direction and amount of deformation caused by hydraulic action
[Explanation of symbols]
7 Valve housing
20 Hydraulic cylinder
30 Control valve
31 First valve member
31R Circumferential groove for right steering
31L Circumferential groove for left steering
31P Circumferential groove for pressure oil supply
31T Circumferential groove for pressure oil discharge
32 Second valve member
39a, 39b, 39c, 39d, 39e Seal ring
50a, 50b, 50c, 51a, 51b, 51c Axial groove
67 Variable aperture
70 pump
71 tanks
A, B, C, D Apertures belonging to the first group
A ′, B ′, C ′, D ′ Apertures belonging to the second set

Claims

A steering assist force generation hydraulic actuator, and a hydraulic control valve acting on the actuator,
The control valve includes a valve housing, a cylindrical first valve member inserted into the valve housing in a relatively rotatable manner, and a second valve inserted into the first valve member in a relatively rotatable manner in accordance with a steering resistance. And having a member
On the outer periphery of the first valve member, a plurality of circumferential grooves are formed in parallel with each other at an axial interval,
On the inner periphery of the first valve member and the outer periphery of the second valve member, a plurality of axial grooves are formed at intervals in the circumferential direction.
The opening degree changes between the edge along the axial direction of the axial groove of the first valve member and the edge along the axial direction of the axial groove of the second valve member according to the relative rotation angle of both valve members. A plurality of aperture parts to be
The actuator is connected to the pump and the tank via the control valve so that a steering assist force can be applied according to the opening change of each throttle part,
As the circumferential groove, a right steering circumferential groove connected to the right steering assist force generating oil chamber of the actuator, a left steering circumferential groove connected to the left steering assist force generating oil chamber of the actuator, A pressure oil supply circumferential groove connected to the pump, and a pressure oil discharge circumferential groove connected to the tank through a variable throttle that changes in opening according to operating conditions;
As the axial groove, the right steering axial groove that leads to the right steering circumferential groove, the left steering axial groove that leads to the left steering circumferential groove, and the pressure oil supply that leads to the pressure oil supply circumferential groove In the hydraulic power steering apparatus having an axial groove for use, a first pressure oil discharge axial groove connected to the tank, and a second pressure oil discharge axial groove connected to the pressure oil discharge circumferential groove,
Between the right steering circumferential groove and the left steering circumferential groove, the pressure oil supply circumferential groove and the pressure oil discharge circumferential groove are arranged ,
The valve housing and the first valve member are located between adjacent circumferential grooves, at an axially outward position from the right steering circumferential groove, and at an axially outward position from the left steering circumferential groove. The first to fifth seal rings interposed between and are arranged,
An oil flow path communicating with the tank at an axially outer position of one end of the first valve member, and a right steering circumferential groove by the first seal ring at a position axially outward from the right steering circumferential groove. Is sealed
Due to the fifth seal ring in the axially outward position from the left steering circumferential groove, an oil flow path communicating with the tank in the axially outward position at the other end of the first valve member and the left steering circumferential groove Is sealed
When traveling straight, the pressure oil supply circumferential groove and the pressure oil discharge circumferential groove are in a high pressure state and the left and right steering circumferential grooves are in a low pressure state, so that the right steering circumferential groove and the pressure oil discharge are Hydraulic pressure difference between adjacent regions in which the second seal ring between the circumferential grooves and the fourth seal ring between the left steering circumferential groove and the pressure oil supply circumferential groove are separated by the respective seal rings The first seal ring, the third seal ring between the pressure oil discharge circumferential groove and the pressure oil supply circumferential groove, and the fifth seal ring do not receive the hydraulic pressure difference. It is assumed
When the right steering is performed, the pressure oil supply circumferential groove, the right steering circumferential groove, and the pressure oil discharge circumferential groove are in a high pressure state, and the left steering circumferential groove is in a low pressure state. The fourth seal ring receives the hydraulic pressure difference, and the second, third, and fifth seal rings are not subjected to the hydraulic pressure difference.
At the time of left steering, the pressure oil supply circumferential groove, the left steering circumferential groove, and the pressure oil discharge circumferential groove are in a high pressure state, and the right steering circumferential groove is in a low pressure state. A hydraulic power steering device, wherein the fifth seal ring receives the hydraulic pressure difference and the first, third, and fourth seal rings do not receive the hydraulic pressure difference .

The number of axial grooves for supplying pressure oil is at least two,
Including at least two connecting axial grooves as its axial grooves;
A first pressure oil discharging axial groove is disposed between the right steering axial groove and a left steering axial groove, and a second pressure oil discharging axial groove is disposed between the connecting axial grooves. A pressure oil supply axial groove is disposed between the right steering axial groove and the communication axial groove and between the left steering axial groove and the communication axial groove;
The throttle portion between the left and right steering axial grooves and the first pressure oil discharge axial groove and the throttle portion between the left and right steering axial grooves and the pressure oil supply axial groove are the first set. And the throttle part between the pressure oil supply axial groove and the communication axial groove and the throttle part between the communication axial groove and the second pressure oil discharge axial groove are the second set. Belonging to
The closing angle of the throttle part belonging to the second group is made larger than the closing angle of the throttle part belonging to the first group,
In the second set, there are two types of throttles with different closing angles,
The hydraulic power steering apparatus according to claim 1 , wherein the variable throttle portion is provided in an oil passage between the throttle portion and the tank belonging to the second set .