JP2004251167A

JP2004251167A - Variable valve system for ohv type internal combustion engine

Info

Publication number: JP2004251167A
Application number: JP2003041276A
Authority: JP
Inventors: Koji Masuda; 宏司増田; Takeshi Asai; 豪朝井
Original assignee: Petroleum Energy Center PEC; Yanmar Co Ltd
Current assignee: Yanmar Co Ltd; Japan Petroleum Energy Center JPEC
Priority date: 2003-02-19
Filing date: 2003-02-19
Publication date: 2004-09-09
Anticipated expiration: 2023-02-19
Also published as: JP4157395B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact variable valve system for an OHV type internal combustion engine switched by a connecting mechanism having simple structure, while restricting the height of the engine. <P>SOLUTION: In this variable valve system for an OHV type internal combustion engine, in which a valve driving cam is arranged on a cylinder side, a first cam 32 and a second cam 33 having different cam shapes are arranged on the same axis in a cam for driving one of the exhaust valve and the intake valve such as a cam for the exhaust valve, and a first and a second swing-arm type cam followers 37 and 38 abut on the cam surface of the first and the second cams 32 and 33. Both the cam followers 37 and 38 can be switched by a releasable connecting mechanism between a connection state that both the cam followers 37 and 38 integrally swing with each other and a release state that each of the cam followers 37 and 38 separately swings. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、弁駆動用のカムをシリンダ側方に配設したＯＨＶ型内燃機関において、運転状況に応じて排気弁や吸気弁の開閉時期及び弁リフト量を変更できる内燃機関の可変動弁装置に関する。
【０００２】
【従来の技術】
内燃機関に備えられた吸気弁及び排気弁は、通常、吸気カム及び排気カムによって開閉駆動されるようになっており、各弁の開閉時期、開放期間及び弁リフト量は、カム形状及びカムの回転位相によって決定される。
【０００３】
カムをシリンダ側方に配置したＯＨＶ型内燃機関又はカムをシリンダヘッド上に配置したＯＨＣ型内燃機関のいずれにも適用できる可変動弁装置としては、従来、カム駆動軸とカムの間に揺動プレート（又は偏心円形プレート）を介在させてなる揺動プレート式可変動弁装置がある。この揺動プレート式可変動弁装置は、揺動プレートによってカム駆動軸とカムとの間に回転位相差を生じさせることにより、弁の開閉時期及び開放期間を変更できるようになっている（たとえば特許文献１参照）。しかし、この可変動弁装置はカムの回転角速度を増減させることにより、弁の開閉時期及び開放期間を変更することは可能であるが、カム形状自体（カムプロフィール）は変化しないので弁リフト量を変更することはできない。
【０００４】
弁開閉時期及び弁開放期間と共に、弁リフト量も変更できる可変動弁装置としては、同一の弁に対して、異なるカム形状を有する二つのカム部を備え、各カム部を、切換機構を介してそれぞれ弁に連動連結し、切換機構により各カム部と弁との間の動力伝達経路を切り換える可変動弁装置がある（たとえば特許文献２等参照）。
【０００５】
また、弁リフト量も変更可能な別の可変動弁装置として、弁腕の回動支点を偏心可能とした可変動弁装置もあり、弁腕の回動支点を変更することにより弁腕のレバー比を変更し、それにより弁リフト量を変更できるようになっている。
【０００６】
【特許文献１】
米国特許３，６３３，５５５号明細書。
【特許文献２】
特開２００２−２７６３１５号公報。
【０００７】
【発明が解決しようとする課題】
弁開閉時期等と共に弁リフト量も変更可能とする場合に、上記弁腕の回動支点を変更する方式では、シリンダヘッド上の弁腕及び弁腕軸の構造並びに支点変更操作機構が複雑化すると共に、弁腕室にそれらを収納しなければならず、弁腕室が大型化すると共に機関高さが高くなる。
【０００８】
同一の弁に対してカム形状の異なる２つのカム部を備え、切換機構により切換える可変動弁装置の場合でも、ＯＨＣ型内燃機関では弁腕室に切換機構を収納しなければならず、上記弁腕の改良構造と同様に、弁腕室が大型化すると共に機関高さが高くなる。
【０００９】
また、シリンダー側方にカムを配置したＯＨＶ型では、機関高さを抑えることはできるが、各カム部にそれぞれプッシュロッドを係合し、各プッシュロッドを、切換機構を介して弁腕に切換可能に連結する方式であるので、弁駆動用伝達経路並びに切換機構が複雑化し、弁駆動力の伝達ロスが増加する。
【００１０】
さらに、２つの異なるカム形状のカム部を切換えて利用する従来の可変動弁装置では、一方のカムリフト部に切り換えて運転する場合には、他方のカムリフト部は完全に無効状態となる構造であり、したがって、各カム部は、カムの全回転角範囲において、所望のリフト特性にそれぞれ完全に対応するカム形状としなければならず、各カム形状が複雑化し、カムの製造に手間がかかる。
【００１１】
【発明の目的】
本発明の目的は、異なるカム形状を有する２つのカム部を利用して弁開閉時期及び開放期間並びに弁リフト量を変更可能とする可変動弁装置であって、機関高さを抑えつつ、コンパクトで簡単な構造の切換機構（連結機構）により切り換えることができるＯＨＶ型内燃機関の可変動弁装置を提供することである。
【００１２】
【課題を解決するための手段】
上記課題を解決するため、本願請求項１記載の発明は、弁駆動用のカムをシリンダ側方に配設したＯＨＶ型内燃機関の可変動弁装置において、排気弁又は吸気弁の一方の弁を駆動するカムに、カム形状の異なる第１カム部と第２カム部を同軸心上に並設し、上記第１、第２カム部のカム面にそれぞれスイングアーム式の第１、第２カムフォロワーを当接し、両カムフォロワーは、切断可能な連結機構により、両カムフォロワーが一体的に揺動する連結状態と各カムフォロワーが独立に揺動する切断状態とに切換自在となっている。
【００１３】
これにより、シリンダヘッド上の弁腕部分に可変動弁装置を備える構造に比べて、機関高さを低く抑えることができると共に、可変動弁装置及びその操作機構を簡単な構造でコンパクトに製作し、機関に組み付けることができる。
【００１４】
請求項２記載の発明は、請求項１記載のＯＨＶ型内燃機関の可変動弁装置において、スイングアーム式の第１カムフォロワーには、シリンダヘッド側の弁腕に連結するプッシュロッドが係合し、第２カムフォロワーには、該第２カムフォロワーを第２カム部に押し付ける付勢手段を設けてあることを特徴としている。
【００１５】
これにより、カムから弁腕までの弁駆動力伝達経路を簡素化できると共に、両カムフォロワー間を切断した状態でも、無効状態の第２カム部を、がたつかずに安定した状態に維持でき、騒音の発生を防ぐことができる。
【００１６】
請求項３記載の発明は、請求項１記載のＯＨＶ型内燃機関の可変動弁装置において、第１カム部と第２カム部の各カム形状は、両カムが一体回転時に、いずれのカム部もそれぞれ単独で作用し得る区間を有するように形成していることを特徴としている。
【００１７】
これにより両カムフォロワーの一体回転時において、弁リフト特性は両カム部のカム形状の組み合せとなり、各カム部それぞれを複雑なカム形状に形成することなく、多種の複雑な弁リフト特性を得ることができる。
【００１８】
請求項４記載の発明は、請求項１乃至３のいずれかに記載のＯＨＶ型内燃機関の可変動弁装置において、クランク軸により回転駆動されるカム駆動軸と同一軸上にカムを配置し、カムとカム駆動軸との軸芯方向間に、カム軸心から偏心する揺動プレートを配置し、揺動プレートによりカム駆動軸とカムとの間に回転位相差を生じさせるようにしてあることを特徴としている。
【００１９】
このように、一対のカム部及びスイングアーム式カムフォロワーを利用した可変動弁装置に、揺動プレートを利用した可変機構、すなわちカム駆動軸とカムとの間に生じる回転位相差を利用した可変機構を付加していると、弁リフト特性の可変範囲を、より広くかつ運転状況に応じて多種に設定することができる。
【００２０】
【発明の実施の形態】
［吸排気弁及び弁駆動用カム機構］
図１〜図７は、ＯＨＶ型ツインバルブ式内燃機関に本発明の可変動弁装置を適用した例である。図１は内燃機関を吸気弁部分で切断して示す縦断面略図であり、シリンダ１内に嵌合するピストン２はコンロッド３を介してクランク軸４のクランクピン５に連結している。一対の吸気弁８はシリンダヘッド（仮想線）７に装着され、シリンダヘッド７の上側には吸気弁腕１０が配置され、吸気弁腕１０の先端部は両吸気弁８の上端部にＴ字形の弁押え１１を介して当接している。弁駆動用のカム機構はシリンダ側方のカム室１３内に配置されており、同一のカム軸心Ｏ０上に吸気カム２１と排気カム２２とカム駆動軸２０を並列に配置してある。吸気カム２１にはスイングアーム式の吸気用カムフォロワー２３の先端ローラ２４が当接し、吸気用カムフォロワー２３の先端部の上面は、吸気用プッシュロッド２７を介して吸気弁腕１０の他端に連結している。吸気用カムフォロワー２３の基端部は水平な支軸１５に回動可能に支持されている。
【００２１】
カム駆動軸２０にはカムギヤ２９が結合されており、該カムギヤ２９は中間伝達ギヤ３０を介してクランク軸４のカム駆動ギヤ３１に連動連結している。クランク軸４の回転は中間伝達ギヤ３０等により１／２の回転角速度に減速されてカム駆動軸２０に伝達される。
【００２２】
図２は図１と同じ内燃機関を、排気弁部分で切断して示す縦断面略図であり、一対の排気弁９は前記吸気弁同様にシリンダヘッド７に装着されており、シリンダヘッド７の上側には排気弁腕１４が配置され、排気弁腕１４の先端部は両排気弁９の上端部にＴ字形の弁押え１２を介して当接している。排気弁腕１４の他端部は排気用プッシュロッド２８の上端部に連結し、排気用プッシュロッド２８は下方に延び、後述する排気用第１カムフォロワー３７の先端部上面に連結している。第１カムフォロワー３７の先端に設けられた排気用第１ローラ２５は、後述する排気カム２２の第１カム部３２のカム面に当接している。
【００２３】
［２つのカム部を利用した排気弁用可変動弁装置］
図４は可変動弁装置を備えたカム機構の平面略図であり、カム駆動軸２０は、一端部がクランクケースカバー等のカバー部材３４に軸受を介して回転可能に支持され、他端部はカム室１３に突出し、軸受ハウジング１６により回転可能に支持されている。カム駆動軸２０側から順に吸気カム２１と排気カム２２が軸方向に並んで配置され、両カム２１，２２は、それぞれ軸受ハウジング１７，１７によりカム駆動軸２０と同一軸心Ｏ０上に回転可能に支持されている。
【００２４】
排気カム２２はカム形状の異なる排気用第１、第２カム部３２，３３を一体に備えており、両排気用カム部３２，３３は軸心方向に並んで配設されている。各カム部３２，３３には排気用第１、第２カムフォロワー３７，３８の先端部がそれぞれ排気用第１、第２ローラ２５，２６を介して当接している。各排気用カムフォロワー３７，３８はスイングアーム式となっており、基端部が前記吸気用カムフォロワー２３と同様に支軸１５に揺動可能に支持されている。排気用第１カムフォロワー３７の先端部の上面には前述のように排気用プッシュロッド２８の下端部が連結し、排気用第２カムフォロワー３８の先端部の上面には、付勢ばね８５が当接し、該付勢ばね８５により、排気用第２カムフォロワー３８の先端ローラ２６を第２カム部３３のカム面に押し付けている。
【００２５】
排気用第１カムフォロワー３７と第２カムフォロワー３８は軸心方向に隣接配置されており、摺動可能な連結ピン７８を利用した連結機構により、両排気用カムフォロワー３７，３８が一体に揺動する連結状態と、両カムフォロワー３７，３８が個々独立に揺動する切断状態とに、切換自在となっている。
【００２６】
排気用第１カムフォロワー３７内にはカム軸心Ｏ０と平行なピン支持孔（作動油室）７７が形成されており、該ピン支持孔７７は第２カムフォロワー３８側の端面が開口すると共に前記連結ピン７８が軸心方向摺動可能に嵌合し、該連結ピン７８はピン支持孔７７から第２カムフォロワー３８側へ突出可能となっている。ピン支持孔（作動油室）７７は第１カムフォロワー３７内の油路８２及び支軸１５内の油路８３を介して油圧切換弁等を有する油圧装置８６に連通しており、油圧制御操作により、ピン支持孔７７内へ作動油を圧入する作用と、ピン支持孔７７内から作動油を排出する作用とを、切換自在に行なえるようになっている。
【００２７】
図６は排気用第１、第２カムフォロワー３７，３８の図２のＶＩ−ＶＩ断面拡大図であり、第２カムフォロワー３８には、第１カムフォロワー３７の連結ピン７８に対応する位置に段付きのピン受孔７９が形成されており、該ピン受孔７９内に前記連結ピン７８が嵌入可能となっている。
【００２８】
ピン受孔７９内には、つば付有底筒形（ハット形）のピン受８１がカム軸心方向と平行移動可能に嵌合すると共に、ばね８０により第１カムフォロワー３７側に付勢されており、ピン受８１のつば部８１ａがピン受孔７９の環状段部に当接することにより、停止している。ピン受孔７９の第１カムフォロワー３７側とは反対側の端部には閉塞蓋８４が螺着され、該閉塞蓋８４とピン受８１の間に上記ばね８０が縮設されている。
【００２９】
すなわち、ピン支持孔７７に作動油を圧入して連結ピン７８を第２カムフォロワー３８側へ突出させることにより、図６のように連結ピン７８をピン受孔７９内に嵌入し、これにより両カムフォロワー３７，３８を一体揺動可能に連結する。反対に、図７のようにピン支持孔７７から作動油を排出することにより、連結ピン７８をピン受孔７９から抜き、両カムフォロワー３７，３８間を切断して、個々に揺動可能な状態とする。
【００３０】
図２は排気用第１カム部３２のカム形状の具体化例に示しており、通常運転時に使用するために、排気行程に対応する位置に、ノーマルな排気弁開用のカム山３２ａを形成し、残りはベースサークルとしてある。
【００３１】
図３は排気用第２カム部３３のカム形状の具体化例を示しており、吸気行程初期に対応する位置に、排気弁再啓開用の小さなカム山３３ａを形成し、残りはベースサークルとしてある。
【００３２】
［揺動プレートを利用した吸排気弁用可変動弁機構］
前述のように２つの排気用カム部３２，３３を用いた可変動弁装置に加え、該実施の形態では、図５のように２枚の揺動プレート３５，３６を利用した吸排気弁用可変動弁機構を備えている。
【００３３】
カム駆動軸２０と吸気カム２１の軸心方向間には、吸気用不等速継手機構を構成する部材として吸気用揺動プレート３５が偏心位置変更可能に配置され、吸気カム２１と排気カム２２の軸心方向間には、排気用不等速継手機構を構成する部材として上記吸気用揺動プレート３５とは別に、排気用揺動プレート３６が偏心位置変更可能に配置されている。
【００３４】
吸気用揺動プレート３５の偏心方向及び偏心量を任意にかつ独立に変更可能とするために、カム駆動軸２０内には、吸気用外側偏心軸４０と、該吸気用外側偏心軸４０の内側に嵌合する吸気用内側偏心軸４１とを備えている。
【００３５】
カム駆動軸２０にはカム軸心Ｏ０と同軸心の嵌合孔４３が形成されており、該嵌合孔４３内に上記吸気用外側偏心軸４０が回動可能に嵌合している。吸気用外側偏心軸４０は、偏心部として、カム軸心Ｏ０に対して一定量だけ偏心する偏心孔４４を有しており、該偏心孔（偏心部）４４内に吸気用内側偏心軸４１が回動可能に嵌合している。吸気用内側偏心軸４１の先端には、円柱状のプレート支持部４５が一体に形成されており、該プレート支持部４５は、吸気用揺動プレート３５を支持すると共に、吸気用内側偏心軸４１の軸心（偏心孔４４の中心）Ｏａ１に対して一定量だけ偏心している。
【００３６】
排気用揺動プレート３６の偏心方向及び偏心量を任意にかつ独立に変更可能とするために、排気カム２２内には、排気用外側偏心軸５０と、該排気用外側偏心軸５０の内側に嵌合する吸気用内側偏心軸５１とを備えている。
【００３７】
両排気用偏心軸５０，５１は、基本的には吸気用の偏心軸４０、４１と同様の構造となっている。すなわち、排気カム２２にはカム軸心Ｏ０と同軸心の嵌合孔５３が形成されており、該嵌合孔５３内に排気用外側偏心軸５０が回動可能に嵌合している。排気用外側偏心軸５０は、偏心部としてカム軸心Ｏ０に対して一定量だけ偏心した偏心孔５４を有しており、該偏心孔（偏心部）５４内に排気用内側偏心軸５１が回動可能に嵌合している。排気用内側偏心軸５１の先端には、プレート支持部５５が形成されており、該プレート支持部５５は排気用揺動プレート３６を支持すると共に排気用内側偏心軸５１の軸心（偏心孔５４の中心）Ｏｂ１に対して一定量だけ偏心している。
【００３８】
吸気用揺動プレート３５は円盤状に形成されると共に、中央部に前記プレート支持部４５に嵌合する中央孔３５ａが形成されており、外周端部には吸気用揺動プレート３５の中心Ｏａ２に対して対称な位置に一対の駆動ピン６０，６１が固着されている。各駆動ピン６０，６１は互いに軸心方向の反対方向に突出し、各突出部分に長方体形状のスライダー６２，６３がそれぞれ駆動ピン回り回動可能に嵌合している。すなわち、吸気用の両スライダー６２，６３は、吸気用揺動プレート３５の表裏両面に、揺動プレート中心Ｏａ２に対して対称位置に配置されている。
【００３９】
排気用揺動プレート３６も基本的には前記吸気用揺動プレート３５と同様な構造となっており、表裏両面に一対の駆動ピン７０，７１とそれらに嵌合するスライダー７２，７３をそれぞれプレート中心に対して対称に備え、中央部には排気用内側偏心軸５１のプレート支持部５５に嵌合する中央孔３６ａが形成されている。
【００４０】
カム駆動軸２０と吸気カム２１の間に配置される吸気用揺動プレート３５に対して、カム駆動軸２０の端面には径方向に延びる駆動溝６４が形成され、該駆動溝６４には吸気用揺動プレート３５の一方のスライダー６２が径方向スライド可能に係合し、吸気カム２２の端面には上記カム駆動軸２０の駆動溝６４と対称な位置に、径方向に延びる駆動溝６５が形成され、該駆動溝６５には吸気用揺動プレート３５の他方のスライダー６３が径方向スライド可能に係合する。
【００４１】
吸気カム２１と排気カム２２の間に配置される排気用揺動プレート３６に対して、吸気カム２１の端面には径方向に延びる駆動溝７４が形成され、該駆動溝７４に排気用揺動プレート３６の一方のスライダー７２が径方向スライド可能に係合している。排気カム２２の端面には上記吸気カム２１の駆動溝７４とカム軸心Ｏ０に対して対称な位置に、径方向に延びる駆動溝７５が形成され、該駆動溝７５には排気用揺動プレート３６の他方のスライダー７３が径方向スライド可能に係合する。
【００４２】
上記吸気カム２１の軸方向両端面に形成された両駆動溝６５，７４は、カム軸心Ｏ０に対して対称な位置に形成されている。
【００４３】
吸気用外側偏心軸４０及び吸気用内側偏心軸４１の吸気用揺動プレート３５側とは反対側の端部には、それぞれフランジ部４０ａ，４１ａが一体に形成されており、各フランジ部４０ａ，４１ａはそれぞれ電動ステップモータ等の駆動装置あるいは手動式駆動装置に連動連結しており、両吸気用偏心軸４０，４１をそれぞれ独立して所定の回転角度だけ回動させることができるようになっている。
【００４４】
また、排気用外側偏心軸５０及び排気用内側偏心軸５１の排気用揺動プレート３６側とは反対側の端部には、それぞれフランジ部５０ａ，５１ａが一体に形成されており、各フランジ部５０ａ，５１ａはそれぞれ電動ステップモータ等の駆動装置あるいは手動式駆動装置に連動連結しており、両排気用偏心軸５０，５１をそれぞれ独立して所定の回転角度だけ回動させることができるようになっている。
【００４５】
吸気用内側偏心軸４１の軸心Ｏａ１に対して、吸気用プレート支持部４５の軸心Ｏａ２の偏心量は、吸気用外側偏心軸４０におけるカム軸心Ｏ０に対する偏心孔４４の中心Ｏａ１の偏心量と同じ値に設定されている。これにより、カム軸心Ｏ０に対して外側偏心軸４０の偏心孔４４の中心Ｏａ１を溝６４の長さ方向の一方側に偏心させ、上記偏心孔４４の中心Ｏａ１に対してプレート支持部４５の軸心Ｏａ２を上記一方側とは反対側に偏心させることにより、上記プレート支持部４５の軸心（吸気用揺動プレート３５の中心）Ｏａ２をカム軸心Ｏ０に一致させることができ、これにより揺動プレート３５の偏心量を０とすることができる。
【００４６】
また、カム軸心Ｏ０に対して外側偏心軸４０の偏心孔４４の中心Ｏａ１を溝６４の長さ方向の一方側に偏心させ、上記偏心孔４４の中心Ｏａ１に対してプレート支持ピン４５の軸心Ｏａ２を上記一方側と同じ側に偏心させると、吸気用揺動プレート３５の偏心量を最大に設定することができる。
【００４７】
【作用】
［クランク軸回転力の伝達経路］
図１において、クランク軸４の回転力は、カム軸駆動用ギヤ３１、中間伝達ギヤ３０及びカムギヤ２９を介し、回転角速度を１／２に減速してカム駆動軸２０に伝達される。
【００４８】
カム駆動軸２０から各カム２１，２２への伝達経路は、図５において、カム駆動軸２０→駆動溝６４→スライダー６２→駆動ピン６０→吸気用揺動プレート３５→駆動ピン６１→スライダー６３→駆動溝６５→吸気カム２１→駆動溝７４→スライダー７２→駆動ピン７０→排気用揺動プレート３６→駆動ピン７１→スライダー７３→駆動溝７５→排気カム２２となっている。すなわち、カム駆動軸２０から、吸気用揺動プレート３５及びその駆動ピン６０，６１及びスライダー６２，６３を介してまず吸気カム２１へ伝達され、そして吸気カム２１から排気用揺動プレート３６及びその駆動ピン７０，７１及びスライダー７２，７３を介して排気カム２２に伝達される。
【００４９】
［２つのカム部による排気弁のリフト特性の変更］
通常運転を行なう場合には、図７のように連結ピン７８をピン支持孔７７内に後退させ、両排気用カムフォロワー３７，３８間の連結を切り離し、それぞれ独立に揺動できる状態とする。これにより、常時、図２に示す第１カム部３２による弁駆動力のみが、排気用プッシュロッド２８を介して排気弁腕１４に伝達され、排気弁９を開閉する。このように第１カム部３２の弁駆動力のみが作用する場合には、排気弁９のリフト特性は、カム回転角の全範囲に亘って、図８に実線で示す曲線Ｘ１のようになり、排気行程の所定期間においてのみ排気弁９を開く。
【００５０】
有効圧縮比を小さくして運転する場合には、図６のようにピン支持孔７７内に作動油を圧入し、連結ピン７８を第２カムフォロワー３８側へ突出させてピン受孔７９に嵌入させ、両排気用カムフォロワー３７，３８を一体化させる。両排気用カムフォロワー３７，３８は一体に揺動し、両カム部３２，３３による弁駆動力が排気用プッシュロッド２８を介して排気弁腕１４に伝達され、両カム部３２，３３のカム形状の組み合せによる弁リフト特性で排気弁９を開閉する。
【００５１】
両排気用カムフォロワー３７，３８が一体に連結された状態での排気弁９のリフト特性は、図８に実線で示す曲線Ｘ１と二点鎖線で示す曲線Ｘ２を組み合せた形状となり、排気行程では、第１カム部３２によるカム駆動力が作用して排気弁９を開き、吸気行程初期では、第２カム部３３によるカム駆動力が作用して排気弁９を再啓開する。
【００５２】
なお、図７において、運転中に上記連結ピン７８を突出させた場合には、両カムフォロワー３７，３８が共に各カム部３２，３３のベースサークル面上に当接する期間に、連結ピン７８がピン受孔７９に嵌入し、図６の状態になる。
【００５３】
［揺動プレートによる吸排気弁のリフト特性の変更］
（１）吸気用揺動プレートによる吸気弁開閉時期等の変更
図５の吸気用外側偏心軸４０の回動位置と吸気用内側偏心軸４１の回動位置との組み合せにより、吸気用揺動プレート３５の中心Ｏａ２をカム軸心Ｏ０に一致させ、吸気用揺動プレート３５の偏心量を０とした場合には、カム駆動軸２０の回転は等速で吸気カム２１に伝達される。したがって、カム駆動軸２０と吸気カム２１の間で回転位相差は生じず、等速で同期回転する。
【００５４】
吸気用外側偏心軸４０の回動位置と吸気用内側偏心軸４１の回動位置との組み合せにより、カム軸心Ｏ０に対する吸気用揺動プレート３５の中心Ｏａ２を、所望の偏心方向に、所望の偏心量だけ偏心させた場合には、カム駆動軸２０が１回転する間に、たとえば一方の吸気用スライダー６２が中心Ｏａ２に近づくと同時に他方のスライダー６３が離れ、続いて一方のスライダー６２が中心Ｏａ２から離れると同時に他方のスライダー６３が中心Ｏａ２に近づく動作を行ない、カム駆動軸２０の回転は不等速で吸気カム２１に伝達され、カム駆動軸２０に対する吸気カム２１の回転角速度が増減し、カム駆動軸２０と吸気カム２１の間で回転位相差が生じる。この回転位相差により、吸気弁開閉時期が所望の値に変更される。
【００５５】
上記のように吸気揺動プレート３５の偏心方向及び偏心量を、吸気用外側偏心軸４０の回動調節と、吸気用内側偏心軸４１の回動調節を組み合せて変更することにより、広い範囲に亘り吸気弁の開時期、閉時期及び開放期間を変更調節できる。
【００５６】
（２）排気揺動プレートによる排気弁の開閉時期等の変更。
図５の吸気カム２１に対する排気カム２２の基本的な回転位相差の調節は、カム駆動軸２０に対する吸気カム２１の回転位相差の調節と同様である。排気用揺動プレート３６の中心Ｏｂ２とカム軸心Ｏ０を一致させた場合には、排気カム２２は吸気カム２１と等速で同期回転する。この場合、吸気カム２１がカム駆動軸２０と等速で回転している時には、当然排気カム２２はカム駆動軸２０とも等速で同期回転する。しかし、吸気用揺動プレート３５が任意の方向及び量だけ偏心していることにより、吸気カム２１とカム駆動軸２０との間に回転位相差が生じている時には、排気カム２２はカム駆動軸２０に対して吸気カム２１と同じ位相差で回転することになる。
【００５７】
また、吸気用揺動プレート３５が最大量まで偏心し、吸気カム２１がカム駆動軸２０に対して不等速で回転している場合において、排気カム２２をカム駆動軸２０に対して等速で同期回転させたい時には、排気用揺動プレート３６を吸気用揺動プレート３５の偏心方向と反対方向に、かつ、同じ偏心量だけ偏心させる。この場合、吸気カム２１の軸方向両端に形成された吸気用の駆動溝６４と排気用の駆動溝７４が、カム軸心Ｏ０に対して対称位置に形成してあることにより、排気用揺動プレート３６を、カム軸心Ｏ０に対して簡単に吸気用揺動プレート３５と対称な位置に変更調節することができる。
【００５８】
排気用揺動プレート３６は、カム駆動軸２０から吸気用揺動プレート３６及び吸気カム２１を経て回転力が伝達されるので、カム駆動軸２０に対する排気カム２２の回転位相差は、吸気用揺動プレート３５による回転位相差と、吸気カム２１に対する排気カム２２の回転位相差を加えた位相差になる。したがって、排気用揺動プレート３６の偏心位置を調節する場合には、前記吸気用揺動プレート３５の偏心方向及び偏心量を加味して、排気用揺動プレート３６の偏心方向及び偏心量を設定することになる。
【００５９】
【発明の別の実施の形態】
（１）第１カム部と第２カム部とのカム形状の組み合せは、前述の実施の形態では、図３及び図８に示すように、排気用第１カム部には通常の排気行程に対応するカム山を形成し、排気用第２カム部には吸気行程初期に排気弁を再啓開させるためのカム山を形成しているが、このような組み合せの他に、たとえば図９の排気弁リフト特性に示すように、排気用第２カム部の形状（二点鎖線の曲線Ｘ２）を、排気行程において第１カム部（実線の曲線Ｘ１）より大きなリフト量及び排気弁開放期間となるように形成し、両カムフォロワーが一体揺動する連結状態の場合に、第２カム部の弁駆動力のみが作用する構成とすることも可能である。
【００６０】
（２）２つのカム部よりなる排気弁の可変動弁装置を吸気弁に適用することも可能である。たとえば、図４の排気用可変動弁装置と同様に、吸気カムとして、カム形状（カムプロフィル）の異なる二つの吸気用第１、第２カム部を配置し、各吸気用カム部には互いに隣接配置されたスイングアーム式の吸気用第１，第２カムフォロワーをそれぞれ当接し、連結ピンを利用した連結切離し可能な連結切換機構により、両吸気用第１、第２カムフォロワーを一体揺動する状態と、独立に揺動する状態とに切換自在とする。
【００６１】
図１０は吸気弁のリフト特性を変更する場合の一例を示しており、たとえば吸気用第１カム部による吸気弁リフト特性（破線の曲線Ｙ１）に対して、吸気用第２カム部による吸気弁リフト特性（一点鎖線の曲線Ｙ２）をカム回転角方向に一定量ずらしてある。
【００６２】
かかる構成によると、両吸気用カムフォロワーを切り離して吸気用第１カム部のみが作用している時には、破線の曲線Ｙ１のように吸気弁が作動し、一方、両吸気用カムフォロワーを一体化している時には、吸気用第１カム部と吸気用第２カム部との組み合せとなり、吸気行程前半においては、第２カム部による弁駆動力が作用し、吸気行程後半においては吸気用第１カム部による弁駆動力が作用し、総合的には、吸気弁開時期を早めると共に吸気弁開放期間を長くしている。
【００６３】
（３）上記図８〜図１０で説明した組み合せの他に、第１カム部のカム形状と第２カム部のカム形状に組み合せは、各種エンジンの要求に応じて多種多様に設計できる。
【００６４】
（４）両カムフォロワー間の連結機構として、図６及び図７のように油圧で作動する連結ピンと、該連結ピンが嵌入するピン受孔よりなる機構を採用すると、簡単かつコンパクトで、連結状態も安定する。しかし，本発明はこのような連結ピン式の機構には限定はされず、たとえばロック用ボールと、該ロック用ボールを付勢するばねと、ロック用ボールが嵌合する係合孔との組み合せ構造等、各種連結切換機構を採用することが可能である。
【００６５】
【発明の効果】
以上説明したように本発明は、（１）シリンダ側方に配設した弁駆動用のカム２２に、カム形状の異なる第１カム部３２と第２カム部３３を同軸心上に並設し、これら第１、第２カム部３２，３３にそれぞれ当接するスイングアーム式の第１、第２カムフォロワー３７，３８を、両者３７，３８が一体的に揺動する連結状態と個々独立に揺動する切断状態とに切換自在としているので、シリンダヘッド上の弁腕部分に可変動弁装置を備える構造に比べて、機関高さを低く抑えることができると共に、可変動弁装置及びその連結機構等を簡単な構造でコンパクトに製作し、機関に組み付けることができる。
【００６６】
（２）両カムフォロワー３７，３８を切断可能に連結する構造において、第１カムフォロワー３７にプッシュロッド２８を係合し、第２カムフォロワー３８に該第２カムフォロワー３８を第２カム部３３に押し付けるばね８５等の付勢手段を設けてあると、カム２２から弁腕１４までの弁駆動力伝達経路を簡素化できると共に、両カムフォロワー３７，３８間を切断した状態でも、第２カム部３３を、がたつかずに安定した状態に維持でき、騒音の発生を防ぐことができる。
【００６７】
（３）第１カム部３２と第２カム部３３の各カム形状を、両カムフォロワー３７，３８が一体回転する場合に、いずれのカム部３２，３３もそれぞれ作用し得る区間を有するように形成していると、一体回転時における弁リフト特性は、両カム部３２，３３のカム形状の組み合せとなる。したがって、各カム部３２，３３それぞれを複雑なカム形状に形成することなく、両カム部の組み合せにより多種の複雑な弁リフト特性を得ることができる。
【００６８】
（４）上記一対のカム部３２，３３及びスイングアーム式カムフォロワー３７，３８を利用した可変動弁装置に、揺動プレートを利用した可変機構、すなわひカム駆動軸とカムとの間に生じる回転位相差によるを利用した可変機構を加えていると、弁リフト特性の可変範囲を、より広くかつ運転状況に応じて多種に設定することができる。
【図面の簡単な説明】
【図１】本発明による可変動弁装置を備えた内燃機関であって、吸気弁及び吸気カム部分を通る縦断面略図である。
【図２】本発明による可変動弁装置を備えた内燃機関であって、排気弁及び排気弁の第１カム部分を通る縦断面略図である。
【図３】本発明による可変動弁装置を備えた内燃機関であって、排気カムの第２カム部を通る縦断面略図である。
【図４】カム機構及び可変動弁装置の平面図である。
【図５】図４のカム機構及び可変動弁装置の縦断面分解斜視図である。
【図６】連結状態のカムフォロワーの図２のＶＩ−ＶＩ断面図である。
【図７】切断状態のカムフォロワーの図２のＶＩ−ＶＩ断面図である。
【図８】本発明を適用した場合の弁リフト特性の一例を示す図である。
【図９】本発明を適用した場合の弁リフト特性の一例を示す図である。
【図１０】本発明を適用した場合の弁リフト特性の一例を示す図である。
【符号の説明】
１５カムフォロワー用の支軸
２０カム駆動軸
２１吸気カム
２２排気カム
２８排気用プッシュロッド
３２排気用第１カム部
３３排気用第２カム部
３５吸気用揺動プレート
３６排気用揺動プレート
３７スイングアーム式排気用第１カムフォロワー
３８スイングアーム式排気用第２カムフォロワー
７８、７９連結ピン、ピン受孔（連結切断機構）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an OHV type internal combustion engine in which a valve driving cam is disposed on a side of a cylinder, and a variable valve actuation device for the internal combustion engine capable of changing the opening / closing timing and valve lift of an exhaust valve or an intake valve according to an operating condition. About.
[0002]
[Prior art]
An intake valve and an exhaust valve provided in an internal combustion engine are normally opened and closed by an intake cam and an exhaust cam, and the opening / closing timing, opening period and valve lift of each valve are determined by the cam shape and cam lift. It is determined by the rotation phase.
[0003]
Conventionally, a variable valve apparatus applicable to either an OHV type internal combustion engine in which a cam is disposed on a side of a cylinder or an OHC type internal combustion engine in which a cam is disposed on a cylinder head is a conventional type of a variable valve apparatus which swings between a cam drive shaft and a cam. There is an oscillating plate type variable valve operating device in which a plate (or an eccentric circular plate) is interposed. This oscillating plate type variable valve device can change the opening / closing timing and opening period of the valve by causing a rotational phase difference between the cam drive shaft and the cam by the oscillating plate (for example, Patent Document 1). However, this variable valve apparatus can change the opening / closing timing and the opening period of the valve by increasing or decreasing the rotational angular velocity of the cam. However, since the cam shape itself (cam profile) does not change, the valve lift amount is reduced. It cannot be changed.
[0004]
As a variable valve operating device capable of changing the valve lift amount together with the valve opening / closing timing and the valve opening period, the same valve is provided with two cam portions having different cam shapes, and each cam portion is connected via a switching mechanism. There is a variable valve operating device that is interlocked with each valve and switches a power transmission path between each cam portion and the valve by a switching mechanism (for example, see Patent Document 2).
[0005]
Further, as another variable valve operating device that can also change the valve lift amount, there is a variable valve operating device that allows the rotation fulcrum of the valve arm to be eccentric, and the lever of the valve arm is changed by changing the rotation fulcrum of the valve arm. The ratio can be changed, thereby changing the valve lift.
[0006]
[Patent Document 1]
U.S. Pat. No. 3,633,555.
[Patent Document 2]
JP-A-2002-276315.
[0007]
[Problems to be solved by the invention]
In the case where the valve lift amount can be changed together with the valve opening / closing timing, the method of changing the rotation fulcrum of the valve arm complicates the structure of the valve arm and the valve arm shaft on the cylinder head and the fulcrum changing operation mechanism. At the same time, they must be stored in the valve arm chamber, which increases the size of the valve arm chamber and the height of the engine.
[0008]
Even in the case of a variable valve apparatus that is provided with two cam portions having different cam shapes for the same valve and that is switched by a switching mechanism, the switching mechanism must be housed in the valve arm chamber in the OHC type internal combustion engine. As with the improved arm structure, the valve arm chamber becomes larger and the engine height becomes higher.
[0009]
In the OHV type with a cam arranged on the side of the cylinder, the height of the engine can be suppressed. However, each cam is engaged with a push rod, and each push rod is switched to a valve arm via a switching mechanism. Since the connection is made possible, the valve drive transmission path and the switching mechanism become complicated, and the transmission loss of the valve drive force increases.
[0010]
Further, in a conventional variable valve apparatus that switches and uses two different cam shapes, when switching to one cam lift and operating the other, the other cam lift is completely disabled. Therefore, each cam portion must have a cam shape completely corresponding to a desired lift characteristic in the entire rotation angle range of the cam, and each cam shape becomes complicated, and it takes time to manufacture the cam.
[0011]
[Object of the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a variable valve operating device capable of changing a valve opening / closing timing, an opening period, and a valve lift amount by using two cam portions having different cam shapes. To provide a variable valve train for an OHV internal combustion engine that can be switched by a switching mechanism (connection mechanism) having a simple structure.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 of the present application is directed to a variable valve apparatus for an OHV internal combustion engine in which a valve driving cam is disposed on a side of a cylinder, wherein one of an exhaust valve and an intake valve is used. A first cam portion and a second cam portion having different cam shapes are coaxially juxtaposed on a driving cam, and the first and second cams of a swing arm type are respectively provided on the cam surfaces of the first and second cam portions. By contacting the followers, the two cam followers can be switched between a connected state in which the two cam followers swing together and a disconnected state in which the respective cam followers swing independently by a disconnectable connecting mechanism.
[0013]
As a result, the height of the engine can be kept low as compared with a structure in which the valve arm portion on the cylinder head is provided with a variable valve operating device, and the variable valve operating device and its operating mechanism are made compact with a simple structure. , Can be assembled to the institution.
[0014]
According to a second aspect of the present invention, in the variable valve train of the OHV type internal combustion engine according to the first aspect, a push rod connected to a valve arm on a cylinder head side is engaged with the first cam follower of the swing arm type. The second cam follower is provided with a biasing means for pressing the second cam follower against the second cam portion.
[0015]
Thus, the valve driving force transmission path from the cam to the valve arm can be simplified, and even in a state where both cam followers are disconnected, the invalid second cam portion can be maintained in a stable state without play. Generation of noise can be prevented.
[0016]
According to a third aspect of the present invention, in the variable valve apparatus of the OHV type internal combustion engine according to the first aspect, each of the first and second cam portions has a different cam shape when both cams rotate integrally. Are formed so as to have sections that can act independently.
[0017]
As a result, when the two cam followers rotate integrally, the valve lift characteristics are a combination of the cam shapes of the two cam portions, so that various complicated valve lift characteristics can be obtained without forming each cam portion in a complicated cam shape. Can be.
[0018]
According to a fourth aspect of the present invention, in the variable valve apparatus for an OHV type internal combustion engine according to any one of the first to third aspects, a cam is arranged on the same axis as a cam drive shaft that is rotationally driven by a crankshaft. An oscillating plate that is eccentric from the cam shaft center is arranged between the cam and the cam drive shaft in the axial direction, and a rotational phase difference is generated between the cam drive shaft and the cam by the oscillating plate. It is characterized by.
[0019]
As described above, a variable mechanism using a swing plate, that is, a variable mechanism using a rotation phase difference generated between a cam drive shaft and a cam, is used for a variable valve apparatus using a pair of cam portions and a swing arm type cam follower. When the mechanism is added, the variable range of the valve lift characteristic can be set wider and various types according to the operating conditions.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
[Intake / exhaust valve and valve drive cam mechanism]
1 to 7 show an example in which the variable valve train of the present invention is applied to an OHV twin-valve internal combustion engine. FIG. 1 is a schematic longitudinal sectional view showing the internal combustion engine cut at an intake valve portion. A piston 2 fitted in a cylinder 1 is connected to a crankpin 5 of a crankshaft 4 via a connecting rod 3. A pair of intake valves 8 are mounted on a cylinder head (virtual line) 7, and an intake valve arm 10 is disposed above the cylinder head 7. Abuts through the valve presser 11 of the first embodiment. The cam mechanism for driving the valve is arranged in the cam chamber 13 on the side of the cylinder, and the intake cam 21, the exhaust cam 22, and the cam drive shaft 20 are arranged in parallel on the same cam shaft center O0. A tip roller 24 of a swing arm type intake cam follower 23 abuts on the intake cam 21, and an upper surface of a distal end of the intake cam follower 23 is connected to the other end of the intake valve arm 10 via an intake push rod 27. Connected. The base end of the intake cam follower 23 is rotatably supported by a horizontal support shaft 15.
[0021]
A cam gear 29 is connected to the cam drive shaft 20, and the cam gear 29 is linked to a cam drive gear 31 of the crankshaft 4 via an intermediate transmission gear 30. The rotation of the crankshaft 4 is reduced to half the rotational angular speed by the intermediate transmission gear 30 and the like and transmitted to the cam drive shaft 20.
[0022]
FIG. 2 is a schematic longitudinal sectional view showing the same internal combustion engine as that of FIG. 1 at an exhaust valve portion. A pair of exhaust valves 9 is mounted on the cylinder head 7 similarly to the intake valve. The exhaust valve arm 14 is disposed at the front end of the exhaust valve arm 14. The distal end of the exhaust valve arm 14 is in contact with the upper ends of the exhaust valves 9 via the T-shaped valve retainer 12. The other end of the exhaust valve arm 14 is connected to the upper end of the exhaust push rod 28, and the exhaust push rod 28 extends downward and is connected to the upper surface of the distal end of a first exhaust cam follower 37 described later. The first exhaust roller 25 provided at the end of the first cam follower 37 is in contact with a cam surface of a first cam portion 32 of the exhaust cam 22 described later.
[0023]
[Variable valve gear for exhaust valve using two cams]
FIG. 4 is a schematic plan view of a cam mechanism provided with a variable valve operating device. The cam drive shaft 20 has one end rotatably supported by a cover member 34 such as a crankcase cover via a bearing, and the other end thereof. It projects into the cam chamber 13 and is rotatably supported by the bearing housing 16. An intake cam 21 and an exhaust cam 22 are arranged side by side in the axial direction from the cam drive shaft 20 side, and both the cams 21 and 22 can rotate on the same axis O0 as the cam drive shaft 20 by the bearing housings 17 and 17, respectively. It is supported by.
[0024]
The exhaust cam 22 integrally includes first and second exhaust cam sections 32 and 33 having different cam shapes, and the exhaust cam sections 32 and 33 are arranged side by side in the axial direction. The distal ends of the first and second exhaust cam followers 37 and 38 are in contact with the cam portions 32 and 33 via the first and second exhaust rollers 25 and 26, respectively. Each of the exhaust cam followers 37 and 38 is of a swing arm type, and its base end is swingably supported by the support shaft 15 similarly to the intake cam follower 23. The lower end of the exhaust push rod 28 is connected to the upper surface of the distal end of the first exhaust cam follower 37 as described above, and the urging spring 85 is mounted on the upper surface of the distal end of the second exhaust cam follower 38. The abutting spring 85 presses the tip roller 26 of the second exhaust cam follower 38 against the cam surface of the second cam portion 33.
[0025]
The first exhaust cam follower 37 and the second exhaust cam follower 38 are arranged adjacent to each other in the axial direction, and the exhaust cam followers 37 and 38 are integrally swung by a connection mechanism using a slidable connection pin 78. It can be switched between a connected state in which it moves and a disconnected state in which both cam followers 37 and 38 swing independently.
[0026]
A pin support hole (hydraulic oil chamber) 77 parallel to the cam axis O0 is formed in the first exhaust cam follower 37. The pin support hole 77 has an open end face on the second cam follower 38 side. The connecting pin 78 is fitted so as to be slidable in the axial direction, and the connecting pin 78 can protrude from the pin support hole 77 toward the second cam follower 38. The pin support hole (hydraulic oil chamber) 77 communicates with a hydraulic device 86 having a hydraulic switching valve and the like via an oil passage 82 in the first cam follower 37 and an oil passage 83 in the support shaft 15, and a hydraulic control operation is performed. Accordingly, the operation of press-fitting the hydraulic oil into the pin support hole 77 and the operation of discharging the hydraulic oil from the pin support hole 77 can be switched.
[0027]
FIG. 6 is an enlarged cross-sectional view of the first and second exhaust cam followers 37 and 38 taken along the line VI-VI in FIG. 2. The second cam follower 38 has a position corresponding to the connecting pin 78 of the first cam follower 37. A stepped pin receiving hole 79 is formed, and the connecting pin 78 can be fitted into the pin receiving hole 79.
[0028]
In the pin receiving hole 79, a bottomed cylindrical (hat-shaped) pin receiver 81 with a flange is fitted so as to be movable in parallel with the cam axis direction, and is urged by the spring 80 toward the first cam follower 37. The pin holder 81 is stopped when the collar portion 81a of the pin receiver 81 comes into contact with the annular step portion of the pin receiving hole 79. A closing cover 84 is screwed into an end of the pin receiving hole 79 opposite to the first cam follower 37 side, and the spring 80 is contracted between the closing cover 84 and the pin receiver 81.
[0029]
In other words, the operating oil is press-fitted into the pin support hole 77 to project the connecting pin 78 toward the second cam follower 38, thereby fitting the connecting pin 78 into the pin receiving hole 79 as shown in FIG. The cam followers 37 and 38 are connected so as to be integrally swingable. On the contrary, by discharging the hydraulic oil from the pin support hole 77 as shown in FIG. 7, the connecting pin 78 is pulled out from the pin receiving hole 79, and the two cam followers 37 and 38 are cut off to be able to swing individually. State.
[0030]
FIG. 2 shows a specific example of the cam shape of the first exhaust cam portion 32. In order to use the cam during normal operation, a cam ridge 32a for opening a normal exhaust valve is formed at a position corresponding to the exhaust stroke. And the rest as base circles.
[0031]
FIG. 3 shows a concrete example of the cam shape of the second exhaust cam portion 33. A small cam ridge 33a for reopening the exhaust valve is formed at a position corresponding to the initial stage of the intake stroke, and the rest is a base circle. There is.
[0032]
[Variable valve mechanism for intake and exhaust valves using swing plate]
As described above, in addition to the variable valve operating device using the two exhaust cam portions 32, 33, in this embodiment, as shown in FIG. It has a variable valve mechanism.
[0033]
Between the cam drive shaft 20 and the intake cam 21 in the axial direction, an intake swinging plate 35 is disposed so as to be capable of changing its eccentric position as a member constituting an intake variable speed joint mechanism. Aside from the above-mentioned intake swing plate 35, an exhaust swing plate 36 is disposed between the axial directions of the above as a member constituting the exhaust non-uniform velocity joint mechanism so that the eccentric position can be changed.
[0034]
In order to be able to arbitrarily and independently change the eccentric direction and the amount of eccentricity of the swinging plate 35 for intake, the cam drive shaft 20 includes an outer eccentric shaft 40 for intake and an inner eccentric shaft 40 for the outer eccentric shaft 40 for intake. And an intake inner eccentric shaft 41 that fits into the intake eccentric shaft.
[0035]
The cam drive shaft 20 is formed with a fitting hole 43 coaxial with the cam shaft center O0, and the intake outer eccentric shaft 40 is rotatably fitted in the fitting hole 43. The intake outer eccentric shaft 40 has, as an eccentric portion, an eccentric hole 44 that is eccentric by a fixed amount with respect to the cam shaft center O0, and the intake inner eccentric shaft 41 is provided in the eccentric hole (eccentric portion) 44. It is fitted rotatably. At the tip of the intake inner eccentric shaft 41, a columnar plate support portion 45 is integrally formed. The plate support portion 45 supports the intake swing plate 35, and at the same time, supports the intake inner eccentric shaft 41. (Center of the eccentric hole 44) Oa1 by a certain amount.
[0036]
In order to be able to arbitrarily and independently change the eccentric direction and the amount of eccentricity of the exhaust rocking plate 36, the exhaust cam 22 includes an exhaust outer eccentric shaft 50 and an inner side of the exhaust outer eccentric shaft 50. And a suction inner eccentric shaft 51 to be fitted.
[0037]
The exhaust eccentric shafts 50 and 51 have basically the same structure as the intake eccentric shafts 40 and 41. That is, the exhaust cam 22 is formed with a fitting hole 53 coaxial with the cam shaft O0, and the exhaust outer eccentric shaft 50 is rotatably fitted in the fitting hole 53. The outer eccentric shaft for exhaust 50 has an eccentric hole 54 as an eccentric portion which is eccentric with respect to the cam shaft center O0 by a fixed amount, and the inner eccentric shaft 51 for exhaust is turned in the eccentric hole (eccentric portion) 54. It is movably fitted. A plate support portion 55 is formed at the end of the exhaust inner eccentric shaft 51, and the plate support portion 55 supports the exhaust swing plate 36 and also has the axial center (the eccentric hole 54) of the exhaust inner eccentric shaft 51. (Center of the center) Ob1 is decentered by a certain amount.
[0038]
The suction swing plate 35 is formed in a disk shape, and has a center hole 35a formed at the center thereof so as to be fitted to the plate support portion 45. The center Oa2 of the suction swing plate 35 is formed at the outer peripheral end. A pair of drive pins 60 and 61 are fixed at symmetrical positions with respect to. Each of the drive pins 60 and 61 protrudes in a direction opposite to the axial center direction, and rectangular sliders 62 and 63 are fitted to the respective protruding portions so as to be rotatable around the drive pins. That is, the intake sliders 62 and 63 are arranged on both front and back surfaces of the intake swing plate 35 at symmetrical positions with respect to the swing plate center Oa2.
[0039]
The exhaust swing plate 36 has basically the same structure as the intake swing plate 35, and a pair of drive pins 70, 71 and sliders 72, 73 fitted thereto are provided on both front and rear surfaces, respectively. A central hole 36a is formed symmetrically with respect to the center, and is fitted at the center to the plate supporting portion 55 of the exhaust inner eccentric shaft 51.
[0040]
A drive groove 64 extending in the radial direction is formed on the end face of the cam drive shaft 20 with respect to the intake swing plate 35 disposed between the cam drive shaft 20 and the intake cam 21. One of the sliders 62 of the swinging plate 35 is slidably engaged in the radial direction, and a drive groove 65 extending in the radial direction is provided on the end face of the intake cam 22 at a position symmetrical to the drive groove 64 of the cam drive shaft 20. The other slider 63 of the intake swing plate 35 is slidably engaged with the drive groove 65 in the radial direction.
[0041]
A drive groove 74 extending in the radial direction is formed on the end face of the intake cam 21 with respect to the exhaust swing plate 36 disposed between the intake cam 21 and the exhaust cam 22. One slider 72 of the plate 36 is slidably engaged in the radial direction. A drive groove 75 extending in the radial direction is formed on the end face of the exhaust cam 22 at a position symmetrical with respect to the drive groove 74 of the intake cam 21 and the cam axis O0. The other slider 73 of 36 is slidably engaged in the radial direction.
[0042]
Both drive grooves 65 and 74 formed on both axial end surfaces of the intake cam 21 are formed at positions symmetrical with respect to the cam shaft center O0.
[0043]
Flanges 40a, 41a are integrally formed at the ends of the intake outer eccentric shaft 40 and the intake inner eccentric shaft 41 on the side opposite to the intake swing plate 35 side, respectively. Reference numeral 41a is interlockingly connected to a driving device such as an electric step motor or a manual driving device so that the intake eccentric shafts 40 and 41 can be independently rotated by a predetermined rotation angle. I have.
[0044]
Further, flange portions 50a and 51a are integrally formed at the ends of the exhaust outer eccentric shaft 50 and the exhaust inner eccentric shaft 51 on the side opposite to the exhaust swing plate 36 side, respectively. Reference numerals 50a and 51a are respectively linked to a driving device such as an electric step motor or a manual driving device so that the two eccentric shafts 50 and 51 can be independently rotated by a predetermined rotation angle. Has become.
[0045]
The amount of eccentricity of the axis Oa2 of the plate supporting portion 45 for intake with respect to the axis Oa1 of the inner eccentric shaft 41 for intake is the amount of eccentricity of the center Oa1 of the eccentric hole 44 with respect to the cam axis O0 of the outer eccentric shaft 40 for intake. Is set to the same value as Thereby, the center Oa1 of the eccentric hole 44 of the outer eccentric shaft 40 is eccentric to one side in the longitudinal direction of the groove 64 with respect to the cam shaft center O0, and the plate supporting portion 45 is By eccentricizing the axis Oa2 to the opposite side to the one side, the axis Oa2 of the plate supporting portion 45 (the center of the swinging plate 35 for intake) can coincide with the cam axis O0. The eccentric amount of the swing plate 35 can be set to zero.
[0046]
Further, the center Oa1 of the eccentric hole 44 of the outer eccentric shaft 40 is eccentric to one side in the length direction of the groove 64 with respect to the cam shaft O0, and the axis of the plate support pin 45 is aligned with respect to the center Oa1 of the eccentric hole 44. When the center Oa2 is eccentric to the same side as the one side, the eccentric amount of the suction swing plate 35 can be set to the maximum.
[0047]
[Action]
[Transmission path of crankshaft torque]
In FIG. 1, the rotational force of the crankshaft 4 is transmitted to the cam drive shaft 20 via the camshaft drive gear 31, the intermediate transmission gear 30 and the cam gear 29 while reducing the rotational angular speed to に.
[0048]
The transmission path from the cam drive shaft 20 to each of the cams 21 and 22 is, as shown in FIG. 5, a cam drive shaft 20 → a drive groove 64 → a slider 62 → a drive pin 60 → a suction swing plate 35 → a drive pin 61 → a slider 63 → The driving groove 65 → the intake cam 21 → the driving groove 74 → the slider 72 → the driving pin 70 → the exhaust swing plate 36 → the driving pin 71 → the slider 73 → the driving groove 75 → the exhaust cam 22. That is, first, it is transmitted from the cam drive shaft 20 to the intake cam 21 via the intake swing plate 35 and the drive pins 60, 61 and the sliders 62, 63, and then transmitted from the intake cam 21 to the exhaust swing plate 36 and the exhaust swing plate 36. The driving force is transmitted to the exhaust cam 22 via the driving pins 70 and 71 and the sliders 72 and 73.
[0049]
[Change of lift characteristics of exhaust valve by two cams]
When the normal operation is performed, as shown in FIG. 7, the connecting pin 78 is retracted into the pin support hole 77, and the connection between the exhaust cam followers 37 and 38 is cut off so that the exhaust cam followers 37 and 38 can swing independently. Thus, only the valve driving force of the first cam portion 32 shown in FIG. 2 is constantly transmitted to the exhaust valve arm 14 via the exhaust push rod 28, and the exhaust valve 9 is opened and closed. When only the valve driving force of the first cam portion 32 acts as described above, the lift characteristics of the exhaust valve 9 are as shown by a solid line curve X1 in FIG. 8 over the entire range of the cam rotation angle. The exhaust valve 9 is opened only during a predetermined period of the exhaust stroke.
[0050]
When operating with a small effective compression ratio, as shown in FIG. 6, hydraulic oil is press-fitted into the pin support hole 77, and the connecting pin 78 is protruded toward the second cam follower 38 to fit into the pin receiving hole 79. Then, both exhaust cam followers 37 and 38 are integrated. The two exhaust cam followers 37 and 38 swing together, and the valve driving force of the two cam parts 32 and 33 is transmitted to the exhaust valve arm 14 via the exhaust push rod 28, and the cams of the two cam parts 32 and 33 are moved. The exhaust valve 9 is opened and closed by the valve lift characteristics based on the combination of shapes.
[0051]
The lift characteristic of the exhaust valve 9 in a state where the two exhaust cam followers 37 and 38 are integrally connected has a shape obtained by combining a curve X1 shown by a solid line and a curve X2 shown by a two-dot chain line in FIG. Then, the cam driving force of the first cam portion 32 acts to open the exhaust valve 9, and at the beginning of the intake stroke, the cam driving force of the second cam portion 33 acts to reopen the exhaust valve 9.
[0052]
In FIG. 7, when the connecting pin 78 is protruded during operation, the connecting pin 78 is moved during a period in which both the cam followers 37 and 38 abut on the base circle surfaces of the cam portions 32 and 33. It fits into the pin receiving hole 79 and becomes the state of FIG.
[0053]
[Change in lift characteristics of intake and exhaust valves by swing plate]
(1) Change of intake valve opening / closing timing etc. by the intake swing plate
The center Oa2 of the intake swing plate 35 coincides with the cam shaft center O0 by the combination of the rotational position of the intake outer eccentric shaft 40 and the rotational position of the intake inner eccentric shaft 41 in FIG. When the eccentric amount of the moving plate 35 is set to 0, the rotation of the cam drive shaft 20 is transmitted to the intake cam 21 at a constant speed. Therefore, there is no rotational phase difference between the cam drive shaft 20 and the intake cam 21, and they rotate synchronously at a constant speed.
[0054]
By the combination of the rotational position of the intake outer eccentric shaft 40 and the rotational position of the intake inner eccentric shaft 41, the center Oa2 of the intake rocking plate 35 with respect to the cam shaft center O0 is moved in a desired eccentric direction. When the cam drive shaft 20 makes one rotation, when the cam drive shaft 20 makes one rotation, for example, one intake slider 62 approaches the center Oa2 and the other slider 63 separates at the same time. At the same time as moving away from Oa2, the other slider 63 moves closer to the center Oa2, and the rotation of the cam drive shaft 20 is transmitted to the intake cam 21 at an unequal speed, and the rotational angular velocity of the intake cam 21 with respect to the cam drive shaft 20 increases and decreases. , A rotational phase difference occurs between the cam drive shaft 20 and the intake cam 21. Due to this rotation phase difference, the intake valve opening / closing timing is changed to a desired value.
[0055]
As described above, the eccentric direction and the amount of eccentricity of the intake rocking plate 35 are changed over a wide range by changing the rotational adjustment of the intake outer eccentric shaft 40 and the rotational adjustment of the intake inner eccentric shaft 41 in combination. The opening timing, closing timing, and opening period of the intake valve can be changed and adjusted over the entire period.
[0056]
(2) Changing the opening / closing timing of the exhaust valve by the exhaust swing plate.
The basic adjustment of the rotational phase difference of the exhaust cam 22 with respect to the intake cam 21 in FIG. 5 is the same as the adjustment of the rotational phase difference of the intake cam 21 with respect to the cam drive shaft 20. When the center Ob2 of the exhaust swing plate 36 and the cam shaft center O0 coincide with each other, the exhaust cam 22 rotates synchronously with the intake cam 21 at a constant speed. In this case, when the intake cam 21 is rotating at a constant speed with the cam drive shaft 20, the exhaust cam 22 is also synchronously rotated with the cam drive shaft 20 at the same speed. However, when a rotational phase difference occurs between the intake cam 21 and the cam drive shaft 20 due to the eccentricity of the intake swing plate 35 by an arbitrary direction and an amount, the exhaust cam 22 Rotates with the same phase difference as the intake cam 21.
[0057]
Further, when the intake swing plate 35 is eccentric to the maximum amount and the intake cam 21 is rotating at an irregular speed with respect to the cam drive shaft 20, the exhaust cam 22 is moved at a constant speed with respect to the cam drive shaft 20. When it is desired to rotate synchronously, the exhaust swing plate 36 is eccentric in the direction opposite to the eccentric direction of the intake swing plate 35 and by the same eccentric amount. In this case, since the drive groove 64 for intake and the drive groove 74 for exhaust formed at both ends in the axial direction of the intake cam 21 are formed at symmetrical positions with respect to the cam axis O0, the swing for exhaust is performed. The plate 36 can be easily changed and adjusted to a position symmetrical to the swinging plate 35 for intake with respect to the cam axis O0.
[0058]
Since rotational force is transmitted from the cam drive shaft 20 to the exhaust swing plate 36 via the intake swing plate 36 and the intake cam 21, the rotational phase difference of the exhaust cam 22 with respect to the cam drive shaft 20 is determined by the intake swing The phase difference is obtained by adding the rotation phase difference of the moving plate 35 and the rotation phase difference of the exhaust cam 22 with respect to the intake cam 21. Therefore, when adjusting the eccentric position of the exhaust swing plate 36, the eccentric direction and the eccentric amount of the exhaust swing plate 36 are set in consideration of the eccentric direction and the eccentric amount of the intake swing plate 35. Will be.
[0059]
Another Embodiment of the Invention
(1) In the above-described embodiment, the combination of the cam shapes of the first cam portion and the second cam portion is such that the first cam portion for exhaust has a normal exhaust stroke as shown in FIGS. Corresponding cam ridges are formed, and a cam ridge for reopening the exhaust valve at the beginning of the intake stroke is formed in the second exhaust cam portion. In addition to such a combination, for example, FIG. As shown in the exhaust valve lift characteristics, the shape of the second exhaust cam portion (the dashed double-dotted line curve X2) is set to a larger lift amount and the exhaust valve open period than the first cam portion (solid line curve X1) in the exhaust stroke. It is also possible to adopt a configuration in which only the valve driving force of the second cam portion acts in a connection state in which both cam followers swing together.
[0060]
(2) It is also possible to apply an exhaust valve variable valve device including two cam portions to an intake valve. For example, similarly to the exhaust variable valve device of FIG. 4, two intake first and second cam portions having different cam shapes (cam profiles) are arranged as intake cams, and each intake cam portion has The first and second cam followers for intake are swinging together by a connection switching mechanism that abuts the adjacently arranged swing arm type intake first and second cam followers and that can be disconnected using a connection pin. And a state in which it swings independently.
[0061]
FIG. 10 shows an example in which the lift characteristic of the intake valve is changed. For example, the intake valve lift characteristic (broken line Y1) of the intake first cam portion is changed by the intake valve of the intake second cam portion. The lift characteristic (dashed-dotted line curve Y2) is shifted by a certain amount in the cam rotation angle direction.
[0062]
According to such a configuration, when only the first intake cam portion is acting while the two intake cam followers are separated, the intake valve operates as shown by a dashed curve Y1, while the two intake cam followers are integrated. In this case, the first cam portion for intake and the second cam portion for intake are combined. In the first half of the intake stroke, the valve driving force by the second cam portion acts. The valve driving force by the section acts, and overall, the opening timing of the intake valve is advanced and the opening period of the intake valve is extended.
[0063]
(3) In addition to the combinations described with reference to FIGS. 8 to 10, various combinations of the cam shapes of the first cam portion and the cam shape of the second cam portion can be designed according to the requirements of various engines.
[0064]
(4) As a connecting mechanism between the two cam followers, a mechanism comprising a hydraulically operated connecting pin and a pin receiving hole into which the connecting pin is fitted as shown in FIGS. Is also stable. However, the present invention is not limited to such a connecting pin type mechanism. For example, a combination of a locking ball, a spring for urging the locking ball, and an engaging hole into which the locking ball fits. Various connection switching mechanisms, such as a structure, can be adopted.
[0065]
【The invention's effect】
As described above, according to the present invention, (1) the first cam portion 32 and the second cam portion 33 having different cam shapes are arranged coaxially on the valve driving cam 22 disposed on the side of the cylinder. The swing arm type first and second cam followers 37 and 38 that respectively contact the first and second cam portions 32 and 33 are individually and independently swung in a connected state in which the two 37 and 38 swing integrally. Since the switchable state can be switched between a movable state and a movable state, the height of the engine can be kept low as compared with a structure in which the variable arm device is provided in the valve arm on the cylinder head, and the variable valve system and its coupling mechanism. Can be manufactured compactly with a simple structure and assembled to the engine.
[0066]
(2) In the structure in which the two cam followers 37 and 38 are cutably connected, the push rod 28 is engaged with the first cam follower 37, and the second cam follower 38 is connected to the second cam follower 38 by the second cam portion 33. If a biasing means such as a spring 85 is provided, the path for transmitting the valve driving force from the cam 22 to the valve arm 14 can be simplified, and even if the cam followers 37 and 38 are cut off, The portion 33 can be maintained in a stable state without rattling, and generation of noise can be prevented.
[0067]
(3) Each cam shape of the first cam portion 32 and the second cam portion 33 has a section in which each of the cam portions 32 and 33 can act when the two cam followers 37 and 38 rotate integrally. When formed, the valve lift characteristics at the time of integral rotation are a combination of the cam shapes of the cam portions 32 and 33. Therefore, various complicated valve lift characteristics can be obtained by combining the two cam portions without forming each of the cam portions 32 and 33 in a complicated cam shape.
[0068]
(4) A variable valve operating device using the pair of cam portions 32 and 33 and the swing arm type cam followers 37 and 38 includes a variable mechanism using a swinging plate, and a mechanism between a cam drive shaft and a cam. By adding a variable mechanism utilizing the generated rotational phase difference, the variable range of the valve lift characteristic can be set to be wider and various types according to the operating conditions.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view of an internal combustion engine provided with a variable valve operating device according to the present invention, which passes through an intake valve and an intake cam portion.
FIG. 2 is a schematic longitudinal sectional view of an internal combustion engine provided with the variable valve operating device according to the present invention, which passes through an exhaust valve and a first cam portion of the exhaust valve.
FIG. 3 is a schematic longitudinal sectional view of an internal combustion engine provided with a variable valve operating device according to the present invention, which passes through a second cam portion of an exhaust cam.
FIG. 4 is a plan view of a cam mechanism and a variable valve operating device.
5 is an exploded perspective view in vertical section of the cam mechanism and the variable valve apparatus of FIG. 4;
FIG. 6 is a sectional view of the cam follower taken along the line VI-VI in FIG. 2 in a connected state;
7 is a sectional view of the cam follower taken along the line VI-VI in FIG. 2 in a cut state;
FIG. 8 is a diagram illustrating an example of a valve lift characteristic when the present invention is applied.
FIG. 9 is a diagram illustrating an example of a valve lift characteristic when the present invention is applied.
FIG. 10 is a diagram illustrating an example of a valve lift characteristic when the present invention is applied.
[Explanation of symbols]
15 Support shaft for cam follower
20 cam drive shaft
21 intake cam
22 Exhaust cam
28 Exhaust push rod
32 Exhaust first cam
33 Second exhaust cam section
35 Swing plate for intake
36 Swing plate for exhaust
37 Swing arm type first cam follower for exhaust
38 Swing arm type second cam follower for exhaust
78, 79 Connecting pin, pin receiving hole (connection cutting mechanism)

Claims

In a variable valve train of an OHV internal combustion engine in which a cam for driving a valve is arranged on a side of a cylinder,
A first cam portion and a second cam portion having different cam shapes are coaxially arranged side by side on a cam for driving one of the exhaust valve and the intake valve,
Swing arm type first and second cam followers abut against the cam surfaces of the first and second cam portions, respectively.
The OHV is characterized in that both cam followers can be switched between a connected state in which both cam followers swing together and a cut state in which each cam follower swings independently by a disconnectable connecting mechanism. Variable valve train for internal combustion engines.

A push rod connected to the valve arm on the cylinder head side is engaged with the swing arm type first cam follower. The variable valve train for an OHV internal combustion engine according to claim 1, wherein the variable valve train is provided.

The cam shape of the first cam portion and the cam shape of the second cam portion are characterized in that when both cams are in an integrally rotating state, each of the cam portions has a section that can act independently. 3. The variable valve train for an OHV internal combustion engine according to claim 2, wherein

The variable valve gear of an OHV type internal combustion engine according to any one of claims 1 to 3,
A cam is arranged on the same axis as a cam drive shaft that is rotationally driven by a crankshaft. A variable valve train for an OHV internal combustion engine, wherein a rotational phase difference is generated between a cam drive shaft and a cam.