JP4219227B2 - Internal combustion engine with cam holder - Google Patents

Internal combustion engine with cam holder Download PDF

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Publication number
JP4219227B2
JP4219227B2 JP2003196750A JP2003196750A JP4219227B2 JP 4219227 B2 JP4219227 B2 JP 4219227B2 JP 2003196750 A JP2003196750 A JP 2003196750A JP 2003196750 A JP2003196750 A JP 2003196750A JP 4219227 B2 JP4219227 B2 JP 4219227B2
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intake
exhaust
thrust
bearing portion
specific
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JP2005030310A (en
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和明 下山
有利 今里
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Honda Motor Co Ltd
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Honda Motor Co Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
    • F01L1/02—Valve drive
    • F01L1/04—Valve drive by means of cams, camshafts, cam discs, eccentrics or the like
    • F01L1/047—Camshafts
    • F01L2001/0476—Camshaft bearings

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  • Valve-Gear Or Valve Arrangements (AREA)
  • Cylinder Crankcases Of Internal Combustion Engines (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は、動弁装置の吸気カム軸および排気カム軸を回転可能に支持するジャーナル軸受部と、各カム軸の軸方向の移動を規制するスラスト受け部とが設けられるカムホルダを備える内燃機関に関する。
【０００２】
【従来の技術】
この種のカムホルダを備える内燃機関として、特許文献１に開示されたものがある。この内燃機関では、吸気用カム軸および排気用カム軸に相互に噛合するヘリカルギヤからなる１対のタイミングギヤが設けられ、各カム軸のジャーナル部は、シリンダヘッドと軸受キャップとで構成される軸受部に支持される。軸受部には、ジャーナル部に形成されたスラスト規制部が内嵌係合するスラスト溝が形成され、各カム軸に作用するスラスト荷重が、スラスト規制部を介してスラスト溝で受け止められる。
【０００３】
【特許文献１】
実用新案登録第２５２８２６１号公報
【０００４】
【発明が解決しようとする課題】
ところで、前記従来技術では、両カム軸について、軸受部の内周面を軸方向で分断して形成されたスラスト溝は、スラスト溝に対して、前記内周面の、反タイミングギヤ側での軸方向幅が、タイミングギヤ側での軸方向幅よりも大きくなる位置に形成される。一方、両タイミングギヤがヘリカルギヤから構成されることに起因して、両カム軸には互いに反対方向のスラスト荷重が作用する。このため、スラスト荷重が反タイミングギヤ側からタイミングギヤ側に作用する軸受部においては、タイミングギヤ側の前記軸方向幅が小さいことから、軸受部の軸方向での肉厚も小さく、スラスト荷重を受けるタイミングギヤ側の部分の剛性が反タイミングギヤ側の部分の剛性よりも小さくなって、剛性が不足する虞がある。
【０００５】
また、両カム軸について、スラスト溝は、スラスト溝に対して、軸受部の軸受キャップを締結する締結ボルトが反タイミングギヤ側に位置する位置に形成される。このため、両カム軸には、両タイミングギヤがヘリカルギヤであることに起因して互いに反対方向のスラスト荷重が作用し、スラスト荷重が反タイミングギヤ側からタイミングギヤ側に作用する軸受部においては、スラスト荷重を受けるタイミングギヤ側の部分の剛性が、締結ボルトがあることにより剛性が高められている反タイミングギヤ側の部分の剛性よりも小さくなって、剛性が不足する虞がある。
【０００６】
そこで、この剛性不足を解消するために、軸受部において剛性が不足する部分の軸方向幅を大きくすると、軸受部が軸方向で大型化すると共に重量が増加し、ひいてはカムホルダもしくはシリンダヘッドの軸方向での大型化および重量増を招来する。
【０００７】
本発明は、このような事情に鑑みてなされたものであり、請求項１〜６記載の発明は、カムホルダの軸方向での大型化および重量増を抑制したうえで、スラスト受け部の剛性を高めることを目的とする。そして、請求項４記載の発明は、さらに、吸気スラスト当接部および排気スラスト当接部の潤滑を良好にすると共に吸気カム軸および排気カム軸のシリンダヘッドへの組付け性の向上を図ることを目的とする。
【０００８】
【課題を解決するための手段および発明の効果】
請求項１記載の発明は、動弁装置の吸気カム軸および排気カム軸をそれぞれ回転可能に支持する複数の吸気ジャーナル軸受部および複数の排気ジャーナル軸受部と、前記吸気カム軸および前記排気カム軸の軸方向への移動をそれぞれ規制する吸気スラスト受け部および排気スラスト受け部とが設けられたカムホルダを備え、前記吸気カム軸および前記排気カム軸に設けられて相互に噛合する１対のヘリカルギヤにより前記吸気カム軸および前記排気カム軸が駆動連結される内燃機関において、前記吸気スラスト受け部は、前記複数の吸気ジャーナル軸受部のうちの特定吸気ジャーナル軸受部と一体成形され、前記吸気スラスト受け部の吸気受け面は、前記特定吸気ジャーナル軸受部の吸気軸受面の、前記吸気カム軸に作用する吸気スラスト力の作用方向で前記吸気受け面よりも前方の軸方向幅が前記吸気軸受面全体の軸方向幅の１／２を越える位置に形成され、前記排気スラスト受け部は、前記複数の排気ジャーナル軸受部のうちの特定排気ジャーナル軸受部と一体成形され、前記排気スラスト受け部の排気受け面は、前記特定排気ジャーナル軸受部の排気軸受面の、前記排気カム軸に作用する排気スラスト力の作用方向で前記排気受け面よりも前方の軸方向幅が前記排気軸受面全体の軸方向幅の１／２を越える位置に形成される内燃機関である。
【０００９】
これによれば、スラスト力の作用方向で吸気および排気受け面の前方には、吸気および排気ジャーナル軸受部の軸受面のうちの、１／２を越える軸方向幅の軸受面が存在することから、吸気および排気ジャーナル軸受部の、軸方向での肉厚が大きい部分からなる高剛性部分が存在する。そして、１対のヘリカルギヤの噛合により吸気および排気カム軸に作用する互いに反対方向のスラスト力は、吸気および排気スラスト受け部のそれぞれにおいて、吸気および排気ジャーナル軸受部の前記高剛性部分の剛性を利用して受け止められる。
【００１０】
この結果、請求項１記載の発明によれば、次の効果が奏される。すなわち、吸気および排気スラスト受け部の受け面が、特定ジャーナル軸受部の軸受面の、スラスト力の作用方向で受け面よりも前方の軸方向幅が軸受面全体の軸方向幅の１／２を越える位置に形成されることにより、吸気および排気カム軸に作用するスラスト力の作用方向に合わせて、吸気および排気スラスト受け部に作用するスラスト力がジャーナル軸受部の前記高剛性部分の剛性を利用して受け止められるので、スラスト受け部の軸方向での大型化および重量増が抑制されたうえで、スラスト受け部の剛性が高められる。
【００１１】
請求項２記載の発明は、動弁装置の吸気カム軸および排気カム軸をそれぞれ回転可能に支持する複数の吸気ジャーナル軸受部および複数の排気ジャーナル軸受部と、前記吸気カム軸および前記排気カム軸の軸方向への移動をそれぞれ規制する吸気スラスト受け部および排気スラスト受け部とが設けられたカムホルダを備え、前記吸気カム軸および前記排気カム軸に設けられて相互に噛合する１対のヘリカルギヤにより前記吸気カム軸および前記排気カム軸が駆動連結される内燃機関において、前記吸気スラスト受け部は、前記複数の吸気ジャーナル軸受部のうちの特定吸気ジャーナル軸受部と一体成形され、前記特定吸気ジャーナル軸受部を締結する吸気締結ボルトが、前記吸気カム軸に作用する吸気スラスト力の作用方向で前記吸気スラスト受け部の吸気受け面よりも前方に位置し、前記排気スラスト受け部は、前記複数の排気ジャーナル軸受部のうちの特定排気ジャーナル軸受部と一体成形され、前記特定排気ジャーナル軸受部を締結する排気締結ボルトが、前記排気カム軸に作用する排気スラスト力の作用方向で前記排気スラスト受け部の排気受け面よりも前方に位置する内燃機関である。
【００１２】
これによれば、スラスト力の作用方向で吸気および排気受け面の前方には、吸気および排気ジャーナル軸受部において、締結ボルトの剛性により剛性が高められた高剛性部分が存在する。そして、１対のヘリカルギヤの噛合により吸気および排気カム軸に作用する互いに反対方向のスラスト力は、吸気および排気スラスト受け部において、それぞれ吸気および排気ジャーナル軸受部の前記高剛性部分の剛性を利用して受け止められる。
【００１３】
この結果、請求項２記載の発明によれば、吸気および排気スラスト受け部の受け面が、特定ジャーナル軸受部を締結する締結ボルトの位置がスラスト力の作用方向で受け面よりも前方になる位置に形成されることにより、請求項１記載の発明と同様の効果が奏される。
【００１４】
請求項３記載の発明は、請求項１または請求項２記載の内燃機関において、前記特定吸気ジャーナル軸受部の、前記吸気スラスト力の作用方向で前記吸気受け面よりも前方に位置する部位と、前記特定排気ジャーナル軸受部の、前記排気スラスト力の作用方向で前記排気受け面よりも前方に位置する部位とが、連結部により連結されるものである。
【００１５】
これによれば、連結部により、特定吸気および特定排気ジャーナル軸受部において、スラスト力の作用方向で受け面よりも前方に位置する前記高剛性部分の剛性が高められる。
【００１６】
この結果、請求項３記載の発明によれば、引用された請求項記載の発明の効果に加えて、次の効果が奏される。すなわち、特定吸気ジャーナル軸受部の、吸気受け面よりも前方に位置する部位と、特定排気ジャーナル軸受部の、排気受け面よりも前方に位置する部位とが連結部により連結されることにより、前記高剛性部分剛性が高められるので、スラスト受け部の剛性を一層高めることができる。
【００１７】
請求項４記載の発明は、請求項１ないし請求項３のいずれか１項記載の内燃機関において、前記各ジャーナル軸受部は、前記内燃機関のシリンダヘッドに着脱可能に結合されるロア軸受部と、前記ロア軸受部に着脱可能に結合されるアッパ軸受部とからなり、前記吸気スラスト受け部は前記特定吸気ジャーナル軸受部の特定吸気アッパ軸受部と一体成形され、前記特定吸気ジャーナル軸受部の特定吸気ロア軸受部には前記吸気スラスト受け部に対向する位置に前記吸気カム軸に設けられた吸気スラスト当接部のための潤滑用油溜が形成され、前記排気スラスト受け部は前記特定排気ジャーナル軸受部の特定排気アッパ軸受部と一体成形され、特定排気ロア軸受部の前記排気スラスト受け部に対向する位置には前記排気カム軸に設けられた排気スラスト当接部のための潤滑用油溜が形成され、前記特定吸気アッパ軸受部は、前記吸気カム軸を前記カムホルダに組み付けるための吸気予備締結ボルトにより前記特定吸気ロア軸受部と締結され、前記特定排気アッパ軸受部は、前記排気カム軸を前記カムホルダに組み付けるための排気予備締結ボルトにより前記特定排気ロア軸受部と締結されるものである。
【００１８】
これによれば、特定吸気および特定排気ロア軸受部に形成された潤滑用油溜には、動弁装置の潤滑のために供給された潤滑油の一部が、例えば特定吸気および特定排気ジャーナル軸受部から流下して、または飛沫となってが落下して、油溜に貯留され、その貯留された潤滑油が吸気および排気スラスト当接部のための潤滑に使用される。また、吸気および排気カム軸が、スラスト受け部により軸方向の移動が規制された状態でカムホルダに予備的に組み付けられるので、動弁装置の他の構成要素、例えばロッカアームがシリンダヘッドに組み付けられた状態でも、ロア軸受部と共に、吸気および排気カム軸をシリンダヘッドに組み付けることが容易になる。さらに、スラスト受け部はアッパ軸受部のみに形成されるので、スラスト受け部が軽量化される。
【００１９】
この結果、請求項４記載の発明によれば、引用された請求項記載の発明の効果に加えて、次の効果が奏される。すなわち、特定吸気および特定排気ジャーナル軸受部の特定ロア軸受部には、それぞれ吸気および排気スラスト受け部に対向する位置に吸気および排気スラスト当接部のための潤滑用油溜が形成されることにより、油溜に貯留された潤滑油が吸気および排気スラスト当接部のための潤滑に使用されるので、吸気および排気スラスト当接部の潤滑が良好になる。また、特定吸気および特定排気アッパ軸受部は、それぞれ吸気および排気カム軸をカムホルダに組み付けるための吸気および排気予備締結ボルトにより特定吸気および特定排気ロア軸受部と締結されることにより、特定ロア軸受部と共に、吸気および排気カム軸をシリンダヘッドに組み付けることが容易になるので、吸気および排気カム軸のシリンダヘッドへの組付け性が向上する。さらに、吸気および排気スラスト受け部は、それぞれ、特定吸気および特定排気アッパ軸受部と一体成形されることにより、吸気および排気スラスト受け部が軽量化される。
【００２０】
請求項５記載の発明は、請求項４記載の内燃機関において、前記吸気予備締結ボルトは、前記吸気スラスト受け部の直交方向での端部に位置し、前記排気予備締結ボルトは、前記排気スラスト受け部の直交方向での端部に位置するものである。
【００２１】
これによれば、予備締結ボルトの剛性によりスラスト受け部の剛性が高められる。また、予備締結ボルトは直交方向での端部に位置するので、スラスト受け部の軸方向での大型化が抑制される。
【００２２】
この結果、請求項５記載の発明によれば、引用された請求項記載の発明の効果に加えて、次の効果が奏される。すなわち、吸気および排気予備締結ボルトは、それぞれ吸気および排気スラスト受け部の直交方向での端部に位置することにより、吸気および排気スラスト受け部の軸方向での大型化が抑制されたうえで、吸気および排気スラスト受け部の剛性が高められるので、吸気および排気スラスト受け部の剛性が一層高められる。
【００２３】
請求項６記載の発明は、請求項１ないし請求項５のいずれか１項記載の内燃機関において、前記特定吸気ジャーナル軸受部および前記排気スラスト受け部は、軸方向において相互に重なる領域を有するように配置され、前記特定排気ジャーナル軸受部および前記吸気スラスト受け部は、軸方向において相互いに重なる領域を有するように配置されているものである。
【００２４】
これによれば、カムホルダにおいて、特定吸気ジャーナル軸受部と排気スラスト受け部とが、そして特定排気ジャーナル軸受部と吸気スラスト受け部とが、軸方向でオーバラップするように配置されるので、特定吸気および特定排気ジャーナル軸受部に対して軸方向で互いに反対側にスラスト受け部が設けられるカムホルダの軸方向での長さが、スラスト受け部が設けられるジャーナル軸受部が軸方向で同じ位置に設けられるものに比べて短くなる。
【００２５】
この結果、請求項５記載の発明によれば、引用された請求項記載の発明の効果に加えて、次の効果が奏される。すなわち、特定吸気ジャーナル軸受部および排気スラスト受け部が、そして特定排気ジャーナル軸受部および吸気スラスト受け部が、軸方向において相互いに重なる領域を有するように配置されていることにより、特定ジャーナル軸受部に対して軸方向で互いに反対側にスラスト受け部が設けられるカムホルダの軸方向での長さが短くなるので、カムホルダが軸方向でコンパクト化される。
【００２６】
なお、この明細書において、「軸方向」とは、カム軸の回転中心線に平行な方向を意味し、「直交方向」とは、平面視で前記回転中心線と直交する方向を意味する。
【００２７】
【発明の実施の形態】
以下、本発明の実施例を図１ないし図９を参照して説明する。
図１，図２を参照すると、本発明が適用された内燃機関Ｅは圧縮点火式のＤＯＨＣ型直列４気筒内燃機関である。内燃機関Ｅは、頂面に形成された凹部からなる燃焼室を有するピストン（図示されず）が往復動可能に嵌合する４つのシリンダ１が一列に配列されたシリンダブロック（図示されず）と、該シリンダブロックの上端面にヘッドボルトＢ１（図４参照）により締結されるシリンダヘッド２と、シリンダヘッド２の上端面に締結されたヘッドカバー３とを備える。この明細書において、上下方向は、各シリンダ１のシリンダ軸線に平行な方向Ａ１（以下、シリンダ軸線方向Ａ１という。）であるとする。
【００２８】
シリンダヘッド２には、シリンダ１毎に、シリンダ１の前記ピストンが嵌合するシリンダ孔に開口する吸気口４１ａ，４２ａを有する１対の独立した第１，第２吸気ポート４１，４２および前記シリンダ孔に開口する１対の排気口５ａを有する排気ポート５が形成され、前記燃焼室内に燃料を噴射する燃料噴射弁（図示されず）がシリンダ軸線にほぼ平行な軸線を有するように装着される。
【００２９】
各シリンダ１において、１対の吸気口４１ａ，４２ａをそれぞれ開閉する１対の吸気弁６および１対の排気口５ａをそれぞれ開閉する１対の排気弁７は、シリンダヘッド２にシリンダ軸線方向Ａ１に摺動可能に支持され、弁バネ８により常時閉弁方向に付勢されており、シリンダヘッド２とヘッドカバー３とにより形成される動弁室９内に収納される動弁装置10により開閉作動される。
【００３０】
動弁装置10は、シリンダヘッド２に設けられるカムホルダＨに回転可能に支持される１対の動弁カム軸である吸気カム軸11および排気カム軸12と、吸気および排気カム軸11，12にそれぞれ設けられる吸気カム11ａおよび排気カム12ａと、シリンダヘッド２に揺動可能に支持される吸気ロッカアーム13および排気ロッカアーム14とを備える。
【００３１】
吸気カム軸11は、そのジャーナル部11ｂ（図４，図７参照）において、カムホルダＨに設けられる複数の吸気ジャーナル軸受部である吸気軸受部Ｊi1〜Ｊi5に回転可能に支持され、排気カム軸12は、そのジャーナル部12ｂ（図４，図８参照）において、カムホルダＨに設けられる複数の排気ジャーナル軸受部である排気軸受部Ｊe1〜Ｊe5に回転可能に支持される。吸気および排気軸受部Ｊi1〜Ｊi5，Ｊe1〜Ｊe5のうち、吸気および排気カム軸11，12の一端部側の端部軸受部Ｊi1，Ｊe1は、軸方向Ａ２で前記シリンダ列の一端部に対応する位置に配置され、吸気および排気カム軸11，12の他端部側の端部軸受部Ｊi5，Ｊe5は、軸方向Ａ２で前記シリンダ列の他端部に対応する位置に配置され、両端部軸受部Ｊi1，Ｊi5；Ｊe1，Ｊe5の間に位置する中間軸受部Ｊi2〜Ｊi4；Ｊe2〜Ｊe4は、前記シリンダ列において軸方向Ａ２で隣接するシリンダ１の間に対応する位置に配置される。
【００３２】
図１を参照すると、吸気および排気カム軸11，12は、内燃機関Ｅのクランク軸の回転中心線と平行な回転中心線を有し、カム駆動機構を介して伝達されるクランク軸の動力により回転駆動される。前記カム駆動機構は、クランク軸と両動弁カム軸の一方である排気カム軸12との間で動力を伝達する第１駆動機構Ｄ１と、排気カム軸12と両動弁カム軸の他方である吸気カム軸11との間で動力の伝達を行う第２駆動機構Ｄ２とからなる。
【００３３】
第１駆動機構Ｄ１は、クランク軸に設けられる駆動スプロケットと、排気カム軸12の、カムホルダＨの外側に位置する一端部に設けられるカムスプロケット15と、前記駆動スプロケットとカムスプロケット15とに巻き掛けられる無端チェーン16とから構成される。吸気および排気カム軸11，12を駆動連結するカム軸間駆動機構を構成する第２駆動機構Ｄ２は、排気カム軸12の一端部において、カムスプロケット15に隣接して配置されるヘリカルギヤからなるカム駆動ギヤ17と、吸気カム軸11の、カムホルダＨの外側に位置する一端部に設けられてカム駆動ギヤ17と噛合するヘリカルギヤからなるカム被動ギヤ18とから構成される。カム駆動ギヤ17は、バックラッシによるギヤ音の発生を抑制するためのシザーズギヤ機構を構成する主ギヤ17ａと副ギヤ17ｂとから構成される。
【００３４】
そして、排気カム軸12は、第１駆動機構Ｄ１を介して伝達されるクランク軸の動力により、クランク軸の１／２の回転速度で回転駆動され、吸気カム軸11は、第１，第２駆動機構Ｄ１，Ｄ２を介して伝達されるクランク軸の動力により排気カム軸12と等速で回転駆動される。それゆえ、クランク軸の動力により回転駆動される吸気および排気カム軸11，12と一体に回転する吸気および排気カム11ａ，12ａは、それぞれ、シリンダヘッド２に保持されたラッシュアジャスタ19（図２参照）に球面支持されて揺動可能な吸気および排気ロッカアーム13，14のローラ13ａ，14ａ（図２参照）に摺接して、吸気および排気ロッカアーム13，14を揺動させ、吸気および排気ロッカアーム13，14を介して各吸気弁６および各排気弁７を所定のタイミングで開閉作動させる。
【００３５】
また、カム駆動ギヤ17とカム被動ギヤ18との噛合により、吸気および排気カム軸11，12には互いに反対方向のスラスト力が作用する。この実施例では、排気カム軸12には、その他端部から一端部に向かう向きの排気スラスト力Ｆｅが作用し、吸気カム軸11には、その一端部から他端部に向かう向きの吸気スラスト力Ｆｉが作用する。これら排気および吸気スラスト力Ｆｅ，Ｆｉは、カム駆動ギヤ17がカム被動ギヤ18を駆動するときに、排気および吸気カム軸12，11にそれぞれ作用するスラスト力である。そして、排気および吸気カム軸12，11には、それぞれ排気および吸気スラスト力Ｆｅ，Ｆｉの作用方向に、最大のスラスト力を含め、平均的に大きなスラスト力が作用する。
【００３６】
また、シリンダヘッド２の他端部には、内燃機関Ｅの補機としての高圧燃料ポンプ20をクランク軸の動力により駆動するための補機駆動機構Ｄ３が配置される。補機駆動機構Ｄ３は、排気カム軸12の、カムホルダＨの外側に位置する他端部に設けられるヘリカルギヤからなる補機駆動ギヤ21と、補機駆動ギヤ21と噛合するヘリカルギヤからなる補機被動ギヤ22とから構成される。
【００３７】
補機駆動ギヤ21は、シザーズギヤ機構を構成する主ギヤ21ａと副ギヤ21ｂとから構成される。補機被動ギヤ22は、シリンダヘッド２に取り付けられた高圧燃料ポンプ20の回転軸20ａにオルダム継手23を介して結合される。そして、補機駆動ギヤ21と補機被動ギヤ22との噛合により、排気カム軸12には排気スラスト力Ｆｅと同じ向きのスラスト力が作用する。
【００３８】
図１〜図４を参照すると、動弁室９内に配置されてシリンダヘッド２に着脱可能に結合されるカムホルダＨは、吸気および排気軸受部Ｊi1〜Ｊi5，Ｊe1〜Ｊe5の下半分である吸気および排気ロア軸受部41〜45，51〜55が形成されたロアカムホルダ30と、吸気および排気軸受部Ｊi1〜Ｊi5，Ｊe1〜Ｊe5の上半分である吸気および排気アッパ軸受部71〜75，81〜85が形成されたアッパカムホルダ60とからなる。アッパカムホルダ60は、ロアカムホルダ30と共に、複数の締結ボルトＢ２（図４参照）によりシリンダヘッド２に締結されることにより、カムホルダＨがシリンダヘッド２に固定される。
【００３９】
図３によく示されるように、シリンダヘッド２に着脱可能に結合されるロアカムホルダ30は、一体成形された枠構造を有するカムホルダであり、軸方向Ａ２に互いに平行に延びると共に直交方向Ａ３に間隔をおいて配置される１対の外側縦枠31，32と、外側縦枠31，32に対して、中心面Ｐ寄りの１対の内側縦枠33，34と、各縦枠31〜34の一端部同士および他端部同士を連結すると共に直交方向Ａ３に延びる１対の横枠35，36とを有する。ここで、直交方向Ａ３は平面視で軸方向Ａ２に直交する方向であり、中心面Ｐは各シリンダ軸線を含む平面である。
【００４０】
さらに、ロアカムホルダ30は、吸気側の外側縦枠31と内側縦枠33との間に、直交方向Ａ３に互いに平行に延びると共に軸方向Ａ２に間隔をおいて設けられる各軸受部Ｊi1〜Ｊi5のロア軸受部41〜45を有する。端部吸気軸受部Ｊi1の端部吸気ロア軸受部41および端部吸気軸受部Ｊi5の端部吸気ロア軸受部45は、横枠35および横枠36にそれぞれ設けられ、１対のロア軸受部41，45の間に、３つの中間吸気軸受部Ｊi2〜Ｊi4の中間吸気ロア軸受部42〜44が設けられる。
【００４１】
同様に、ロアカムホルダ30は、排気側の外側縦枠32と内側縦枠34との間に、直交方向Ａ３に互いに平行に延びると共に軸方向Ａ２に間隔をおいて設けられる各軸受部Ｊe1〜Ｊe5のロア軸受部51〜55を有する。端部排気軸受部Ｊe1の端部排気ロア軸受部51および端部排気軸受部Ｊe5の端部排気ロア軸受部55は、横枠35および横枠36にそれぞれ設けられ、１対のロア軸受部41，45の間に、３つの中間排気軸受部Ｊe2〜Ｊe4の中間排気ロア軸受部52〜54が設けられる。
【００４２】
各ロア軸受部41〜45；51〜55は、吸気カム軸11または排気カム軸12のジャーナル部11ｂ;12ｂが摺接すると共に軸方向Ａ２での幅である所定長さの軸方向幅（図７に軸受面44ａの軸方向幅Ｗｉが、図８に軸受面54ａの軸方向幅Ｗｅが示されている。）の吸気軸受面41ａ〜45ａまたは排気軸受面51ａ〜55ａと、軸受面41ａ〜45ａ；51ａ〜55ａを挟んでその両側の外側および内側縦枠31，33；32，34との連結部に設けられて締結ボルトＢ２が挿通される貫通孔37が形成された締結部を構成する外側および内側の１対のボス部41ｂ〜45ｂ，41ｃ〜45ｃ；51ｂ〜55ｂ，51ｃ〜55ｃとを有する。そして、貫通孔37に挿通された締結ボルトＢ２が、シリンダヘッド２に形成されたネジ孔24（図４参照）に螺合することにより、カムホルダＨがシリンダヘッド２に締結される。
【００４３】
また、シリンダヘッド２に形成された油路から供給された潤滑油は、両外側縦枠31，32に形成された孔からなる油路48ａ，58ａを経て、それぞれ、一端で油路48ａ，58ａに連通すると共に他端で吸気軸受面41ａ〜45ａおよび排気軸受面52ａ〜55ａに開口する孔からなる油路48ｂ，58ｂを通じて、吸気および排気軸受部Ｊi1〜Ｊi5，Ｊe2〜Ｊe5に供給される。なお、軸受部Ｊe1には、後述する端部アッパカムホルダ61に形成された油路に連通する溝からなる油路58ｃを通じて潤滑油が供給される。
【００４４】
図１を参照すると、アッパカムホルダ60は、分割型のカムホルダであり、端部吸気アッパ軸受部71および端部排気アッパ軸受部81が、両アッパ軸受部71，81を連結する架設された連結部68と共に一体成形された端部アッパカムホルダ61と、端部吸気アッパ軸受部75および端部排気アッパ軸受部85が、両アッパ軸受部75，85を連結する架設された連結部69と共に一体成形された端部アッパカムホルダ62と、３つの中間吸気アッパ軸受部72〜74と、３つの中間排気アッパ軸受部82〜84とからなる。
【００４５】
各アッパ軸受部71〜75；81〜85は、吸気カム軸11または排気カム軸12のジャーナル部11ａ；12ａが摺接すると共に対応するロア軸受部41〜45；51〜55とほぼ同じ幅の軸方向幅の吸気軸受面または排気軸受面と（図７に吸気軸受面74ａの軸方向幅Ｗｉが、図８に排気軸受面84ａの軸方向幅Ｗｅが示されている。）、それら軸受面を挟んで、対応するロア軸受部41〜45；51〜55の１対のボス部41ｂ〜45ｂ，41ｃ〜45ｃ；51ｂ〜55ｂ，51ｃ〜55ｃに対応して、締結ボルトＢ２が挿通される貫通孔67が形成された締結部を構成する外側および内側の１対のボス部71ｂ〜75ｂ，71ｃ〜75ｃ；81ｂ〜85ｂ，81ｃ〜85ｃを有する。両端部アッパカムホルダ61；62の連結部68；69は、アッパ軸受部71；75およびアッパ軸受部81；85の両内側のボス部71ｃ，81ｃ；75ｃ，85ｃを連結する。
【００４６】
そして、各アッパ軸受部71〜75，81〜85が各ロア軸受部41〜45，51〜55に対応して締結ボルトＢ２で締結されることにより、各軸受部Ｊi1〜Ｊi5，Ｊe1〜Ｊe5が形成される。さらに、カムホルダＨにおいて、その吸気側では、軸方向Ａ２で隣接する軸受部Ｊi1，Ｊi2；Ｊi2，Ｊi3；Ｊi3，Ｊi4；Ｊi4，Ｊi5の間に、シリンダ１毎に、２つの吸気カム11ａおよび２つの吸気ロッカアーム13のそれぞれの一部を収容する収容空間25が形成され、その排気側では、軸方向Ａ２で隣接する軸受部Ｊe1，Ｊe2；Ｊe2，Ｊe3；Ｊe3，Ｊe4；Ｊe4，Ｊe5の間に、シリンダ１毎に、２つの排気カム12ａおよび２つの排気ロッカアーム14のそれぞれの一部を収容する収容空間26が形成される。
【００４７】
また、図１，図４〜図８を参照すると、カムホルダＨには、吸気カム軸11に一体成形により設けられる吸気スラスト当接部としての鍔状の吸気スラストプレート11ｃと当接して、吸気カム軸11の軸方向Ａ２での移動を規制する吸気スラスト受け部Ｔｉと、排気カム軸12に一体成形により設けられる排気スラスト当接部としての鍔状の排気スラストプレート12ｃと当接して、排気カム軸12の軸方向Ａ２での移動を規制する排気スラスト受け部Ｔeとが設けられる。
【００４８】
吸気および排気スラスト受け部Ｔｉ，Ｔeは、それぞれ、複数の軸受部Ｊi1〜Ｊi5のうちの１つの特定吸気軸受部としての軸受部Ｊi4および複数の軸受部Ｊe1〜Ｊe5のうちの１つの特定排気軸受部としての軸受部Ｊe4と一体成形されて設けられ、それら軸受部Ｊi4，Ｊe4は、それぞれ端部軸受部Ｊi5，Ｊe5に隣接する軸受部である。
【００４９】
図１，図４，図５，図７を参照すると、吸気スラスト力Ｆｉの作用方向で、軸受部Ｊi4よりも後方に位置する吸気スラスト受け部Ｔｉは、アッパ軸受部74と一体成形されて、アッパ軸受部74から吸気スラスト力Ｆｉの向きとは反対向きに突出する突出部から構成される。吸気スラスト受け部Ｔｉは、吸気スラストプレート11ｃの一部が収容される半円環状溝の収容溝76と、吸気スラストプレート11ｃが当接する吸気受け面77とを有する。また、吸気スラスト受け部Ｔｉおよび排気軸受部Ｊe4は、軸方向Ａ２において相互いに重なる領域Ｒｉを有するように配置されている（図１参照）。
【００５０】
受け面77は、軸受部Ｊi4において、吸気スラスト受け部Ｔｉが形成されたアッパ軸受部74の軸受面74ａの、吸気スラスト力Ｆｉの作用方向で受け面77よりも前方の軸方向幅が、軸受面74ａ全体の軸方向幅Ｗｉの１／２を越える位置に形成される。このとき、受け面77は、軸受面74aにおける吸気スラスト力Ｆｉの作用方向で受け面77よりも前方の軸方向幅が後方の軸方向幅に対して大きくなる位置に形成されることになる。また、この受け面77は、軸受面74ａの、軸方向Ａ２での両端74a1，74a2の位置により規定される軸受面74aの間隔を二等分する位置Ｃｉよりも、吸気スラスト力Ｆｉの作用方向で後方に位置する。このため、吸気スラスト力Ｆｉの作用方向で受け面77よりも前方でのアッパ軸受部74の軸方向Ａ２での肉厚が、受け面77よりも後方でのアッパ軸受部74の軸方向Ａ２での肉厚に比べて大きくなる。
【００５１】
そして、この実施例では、軸受面74aの、吸気スラスト力Ｆｉの作用方向で受け面77よりも後方の軸方向幅が０（ゼロ）になる場合として、受け面77は、吸気スラスト力Ｆｉの作用方向で受け面77よりも前方の軸方向幅が軸受面74ａ全体の軸方向幅Ｗｉとなる位置、すなわち軸受面74ａが吸気スラスト力Ｆｉの作用方向で受け面77よりも前方のみに位置するような位置に形成される。さらに、受け面77は、貫通孔67，37に挿通されてアッパ軸受部74を締結する吸気締結ボルトとしての１対の締結ボルトＢ２（図４参照）の全体の位置が吸気スラスト力Ｆｉの作用方向で受け面77よりも前方になる位置に形成される。すなわち、１対の締結ボルトＢ２の全体が、吸気スラスト力Ｆｉの作用方向で受け面 77 よりも前方に位置する。
【００５２】
図５，図７を参照すると、軸受部Ｊi4のロア軸受部44には、吸気カム軸11を挟んで上下方向で吸気スラスト受け部Ｔｉと対向する位置に、ロア軸受部44から軸方向Ａ２で吸気スラスト受け部Ｔｉと同じ向きに突出する突出部から構成される油溜形成部46が、ロア軸受部44と一体成形される。油溜形成部46には、吸気スラストプレート11ｃの一部が入り込む凹部からなる油溜47（図２も参照）が形成される。吸気スラストプレート11ｃのための潤滑用油溜である油溜47には、動弁装置10の摺動部などの潤滑箇所に供給された潤滑油の一部が、軸受部Ｊi4から流下して、または動弁室９内で飛沫となって落下して、貯留される。そして、吸気スラストプレート11ｃが油溜47で潤滑油に浸漬することで、吸気スラストプレート11ｃに付着した潤滑油により、吸気スラストプレート11ｃと受け面77との摺動部の潤滑が行われる。
【００５３】
同様に、図１，図４，図６，図８を参照すると、排気スラスト力Ｆｅの作用方向で、軸受部Ｊe4よりも後方に位置する排気スラスト受け部Ｔeは、アッパ軸受部84と一体成形されて、アッパ軸受部84から排気スラスト力Ｆｅの向きとは反対向きに突出する突出部から構成される。排気スラスト受け部Ｔeは、排気スラストプレート12ｃの一部が収容される半円環状溝の収容溝86と、排気スラストプレート12ｃが当接する排気受け面87とを有する。また、排気スラスト受け部Ｔｅおよび吸気軸受部Ｊi4は、軸方向Ａ２において相互いに重なる領域Ｒｅを有するように配置されている（図１参照）。
【００５４】
受け面87は、軸受部Ｊe4において、排気スラスト受け部Ｔｅが形成されたアッパ軸受部84の軸受面84ａの、排気スラスト力Ｆｅの作用方向で受け面87よりも前方の軸方向幅が、軸受面84ａ全体の軸方向幅Ｗｅの１／２を越える位置に形成される。このとき、受け面87は、軸受面84aにおける排気スラスト力Ｆｅの作用方向で受け面87よりも前方の軸方向幅が後方の軸方向幅に対して大きくなる位置に形成されることになる。また、この受け面87は、軸受面84ａの、軸方向Ａ２での両端84a1，84a2の位置により規定される軸受面84aの間隔を二等分する位置Ｃｅよりも、排気スラスト力Ｆｅの作用方向で後方に位置する。このため、排気スラスト力Ｆｅの作用方向で受け面87よりも前方でのアッパ軸受部84の軸方向Ａ２での肉厚が、受け面87よりも後方でのアッパ軸受部84の軸方向Ａ２での肉厚に比べて大きくなる。
【００５５】
そして、この実施例では、軸受面84aの、排気スラスト力Ｆｅの作用方向で受け面87よりも後方の軸方向幅が０（ゼロ）になる場合として、受け面87は、排気スラスト力Ｆｅの作用方向で受け面87よりも前方の軸方向幅が軸受面84ａ全体の軸方向幅Ｗｅとなる位置、すなわち軸受面84ａが排気スラスト力Ｆｅの作用方向で受け面87よりも前方のみに位置するような位置に形成される。さらに、受け面87は、貫通孔67，37に挿通されてアッパ軸受部84を締結する排気締結ボルトとしての１対の締結ボルトＢ２（図４参照）の全体の位置が排気スラスト力Ｆｅの作用方向で受け面87よりも前方になる位置に形成される。すなわち、１対の締結ボルトＢ２の全体が、排気スラスト力Ｆｅの作用方向で受け面 87 よりも前方に位置する。
【００５６】
図６，図８を参照すると、軸受部Ｊe4のロア軸受部54には、排気カム軸12を挟んで上下方向で排気スラスト受け部Ｔｅと対向する位置に、ロア軸受部54から軸方向Ａ２で排気スラスト受け部Ｔeと同じ向きに突出する突出部から構成される油溜形成部56が、ロア軸受部54と一体成形される。油溜形成部56には、排気スラストプレート12ｃの一部が入り込む凹部からなる油溜57（図２も参照）が形成され、排気スラストプレート12ｃのための潤滑用油溜である油溜57には、油溜47と同様にして潤滑油が貯留される。そして、排気スラストプレート12ｃが油溜57で潤滑油に浸漬することで、排気スラストプレート12ｃに付着した潤滑油により、排気スラストプレート12ｃと受け面87との摺動部の潤滑が行われる。
【００５７】
なお、図７，図８を参照すると、内燃機関Ｅのトルク変動や両カム軸11，12の回転変動等に起因して、吸気スラスト力Ｆｉとは反対向きに吸気カム軸11に作用することがある小さなスラスト力、および排気スラスト力Ｆｅとは反対向きに排気カム軸12に作用することがある小さなスラスト力は、それぞれ、吸気および排気スラストプレート11ｃ，12ｃが吸気および排気受け面77，87と軸方向Ａ２で対向する受け面Ｔia，Ｔeaに当接することにより受け止められる。
【００５８】
図１，図３，図５，図６を参照すると、吸気および排気スラスト受け部Ｔｉ，Ｔeには、各スラスト受け部Ｔｉ，Ｔeの直交方向Ａ３での端部に、好ましくは収容溝76，86の直交方向Ａ３での端部76ａ，86ａに近接した位置であってスラスト受け部Ｔｉ，Ｔeに対するスラスト力Ｆｉ，Ｆｅの作用により応力集中が発生し易い端部Ｔib，Ｔebに、吸気および排気予備締結ボルトとしての予備締結ボルトＢ３が挿通される貫通孔79，89が形成された締結部であるボス部78，88が形成される。これらボス部78，88は、アッパ軸受部74，84のそれぞれの内側ボス部74ｃ，84ｃに連結されると共に、吸気および排気スラスト受け部Ｔｉ，Ｔeの互いに近接した位置にある端部Ｔib，Ｔebに形成される。
【００５９】
そして、ロア軸受部44，54においては、各ボス部78，88に対応して締結ボルトＢ３がそれぞれねじ込まれるネジ孔92，93を有する締結部であるボス部90，91が、図３に示されるように、ボス部44ｃ，54ｃに連結されて油溜形成部46，56に形成される。
【００６０】
予備締結ボルトＢ３は、締結ボルトＢ２によりカムホルダＨがシリンダヘッド２に結合される前に、スラスト受け部Ｔｉ，Ｔeが一体成形されたアッパ軸受部74，84を利用して、カムホルダＨに吸気および排気カム軸11，12を予備的に組み付けるためのものである。
【００６１】
そして、図１，図２を参照すると、カムホルダＨに吸気および排気カム軸11，12を安定した状態で組み付けるために、両予備締結ボルトＢ３から軸方向Ａ２で複数の軸受部Ｊi2，Ｊi3；Ｊe2，Ｊe3を挟んで位置し、しかも単一部材により吸気および排気カム軸11，12を組み付けることができる端部アッパカムホルダ61が予備締結ボルトＢ３でロアカムホルダ30の横枠35に締結される。具体的には、端部アッパカムホルダ61の連結部68に、予備締結ボルトＢ３が挿通される貫通孔95を有する締結部であるボス部94が形成され、該ボス部94に対応して、ロアカムホルダ30の横枠35に予備締結ボルトＢ３がねじ込まれるネジ孔97を有する締結部としてのボス部96が形成される。
【００６２】
このように、カムホルダＨがシリンダヘッド２に締結ボルトＢ２により固定される前に、吸気および排気カム軸11，12が、それぞれ吸気および排気スラスト受け部Ｔｉ，Ｔeにより、ロアカムホルダ30に対して軸方向Ａ２に移動することが規制された状態でカムホルダＨに組み付けられているため、シリンダヘッド２に組み付けられた吸気および排気ロッカアーム13，14の上方から両カム軸11，12が組み付けられるときの組付けが容易になる。
【００６３】
さらに、ロアカムホルダ30は、図１，図３，図５を参照すると、吸気軸受部Ｊi1，Ｊi5および排気軸受部Ｊe1，Ｊe5に、それぞれ軸方向Ａ２で隣接する１対の軸受部Ｊi2，Ｊi4および１対の軸受部Ｊe2，Ｊe4において、ロア軸受部42，44の内側ボス部42ｃ，44ｃとロア軸受部52，54の内側ボス52ｃ，54ｃとを連結すべく、両内側ボス部42ｃ，52ｃ；44ｃ，54ｃの間に架設された壁状の連結部38，39を有する。そして、１対の連結部38，39により、１対の内側縦枠33，34が直交方向Ａ３で連結されるので、ロアカムホルダ30の剛性が高められる。
【００６４】
そして、ロア軸受部44，54を連結する連結部39は、吸気軸受部Ｊi4の、吸気スラスト力Ｆｉの作用方向で受け面77よりも前方に位置する部位である内側ボス部44ｃと、排気軸受部Ｊe4の、排気スラスト力Ｆｅの作用方向で受け面87よりも前方に位置する部位である内側ボス54ｃとを連結する。このため、連結部39により、ロア軸受部44およびロア軸受部54の剛性が高められ、ひいてはそれらロア軸受部44，54に締結ボルトにより結合されるアッパ軸受部74，84の剛性が高められる。
【００６５】
次に、前述のように構成された実施例の作用および効果について説明する。
カムホルダＨに設けられる吸気および排気軸受部Ｊi4，Ｊe4のアッパ軸受部74，84とそれぞれ一体成形された吸気および排気スラスト受け部Ｔｉ，Ｔeにおいて、その受け面77，87が、アッパ軸受部74，84の軸受面74ａ，84ａの、吸気および排気スラスト力Ｆｉ，Ｆｅの作用方向で受け面77，87よりも前方の軸方向幅が軸受面74ａ，84ａ全体の軸方向幅Ｗｉ，Ｗｅの１／２を越える位置に形成されることにより、吸気および排気スラスト力Ｆｉ，Ｆｅの作用方向で吸気および排気受け面77，87の前方には、ぞれぞれ、軸受面74ａ，84ａのうちの、１／２を越える軸方向幅の軸受面74ａ，84ａが存在することから、アッパ軸受部74，84の、軸方向Ａ２での肉厚が大きい部分からなる１つの高剛性部分が存在する。そして、１対のヘリカルギヤからなるカム駆動ギヤ17およびカム被動ギヤ18の噛合により吸気および排気カム軸11，12に作用する互いに反対方向の排気および吸気スラスト力Ｆｉ，Ｆｅは、吸気および排気スラスト受け部Ｔｉ，Ｔeのそれぞれにおいて、吸気および排気カム軸11，12に作用する吸気および排気スラスト力Ｆｉ，Ｆｅの作用方向に合わせて、吸気および排気スラスト受け部Ｔｉ，Ｔeに作用する吸気および排気スラスト力Ｆｉ，Ｆｅがアッパ軸受部74，84の前記高剛性部分の剛性を利用して受け止められるので、スラスト受け部Ｔｉ，Ｔeの軸方向Ａ２での大型化および重量増が抑制されたうえで、吸気および排気スラスト受け部Ｔｉ，Ｔeの剛性が高められる。
【００６６】
さらに、吸気および排気スラスト受け部Ｔｉ，Ｔeの受け面77，87が、それぞれ軸受部Ｊi4，Ｊe4を締結する締結ボルトＢ２の位置が吸気および排気スラスト力Ｆｉ，Ｆｅの作用方向で受け面77，87よりも前方になる位置に形成されることにより、吸気および排気スラスト力Ｆｉ，Ｆｅの作用方向で受け面77，87の前方には、吸気および排気軸受部Ｊi4，Ｊe4において、締結ボルトＢ２の剛性により剛性が高められた別の高剛性部分が存在するので、該別の高剛性部分および前記高剛性部分の剛性により、吸気および排気スラスト受け部Ｔｉ，Ｔeの剛性が一層高められる。
【００６７】
吸気軸受部Ｊi4のロア軸受部44の、吸気スラスト力Ｆｉの作用方向で受け面77よりも前方に位置する内側ボス部44ｃと、軸受部Ｊe4のロア軸受部54の、排気スラスト力Ｆｅの作用方向で受け面87よりも前方に位置する内側ボス54ｃとが連結部39で連結されることにより、連結部39により、両軸受部Ｊi4，Ｊe4において、それぞれ吸気および排気スラスト力Ｆｉ，Ｆｅの作用方向で受け面77，87よりも前方に位置する前記別の高剛性部分および前記高剛性部分の剛性が高められるので、スラスト受け部Ｔｉ，Ｔeの剛性を一層高めることができる。
【００６８】
吸気および排気軸受部Ｊi4，Ｊe4のロア軸受部44，54には、それぞれ吸気および排気スラスト受け部Ｔｉ，Ｔeに対向する位置に、吸気および排気スラストプレート11ｃ，12ｃのための油溜47，57が形成されることにより、動弁装置10の潤滑のために供給された潤滑油の一部が、軸受部Ｊi4，Ｊe4から流下して、または動弁室９内で飛沫となって落下して、油溜47，57に貯留され、その貯留された潤滑油が吸気および排気スラストプレート11ｃ，12ｃのための潤滑に使用されるので、吸気および排気スラストプレート11ｃ，12ｃの潤滑が良好になる。
【００６９】
アッパ軸受部74，84は、それぞれ吸気および排気カム軸11，12をカムホルダＨに組み付けるための予備締結ボルトＢ３によりロア軸受部44，54と締結されることにより、吸気および排気カム軸11，12が、スラスト受け部Ｔｉ，Ｔeにより軸方向Ａ２の移動が規制された状態でカムホルダＨに予備的に組み付けられるので、動弁装置10の他の構成要素である吸気および排気ロッカアーム13，14がシリンダヘッド２に組み付けられた状態で、ロア軸受部44，54と共に、吸気および排気カム軸11，12をシリンダヘッド２に組み付けることが容易になるので、吸気および排気カム軸11，12のシリンダヘッド２への組付け性が向上する。また、吸気および排気スラスト受け部Ｔｉ，Ｔeは、それぞれ両アッパ軸受部74，84と一体成形されることにより、スラスト受け部Ｔｉ，Ｔeはアッパ軸受部74，84のみに形成されるので、吸気および排気スラスト受け部Ｔｉ，Ｔeが軽量化される。
【００７０】
予備締結ボルトＢ３は、それぞれ吸気および排気スラスト受け部Ｔｉ，Ｔeの直交方向Ａ３での端部Ｔib，Ｔebに位置することにより、吸気および排気スラスト受け部Ｔｉ，Ｔeの軸方向Ａ２での大型化が抑制されたうえで、両スラスト受け部Ｔｉ，Ｔeの剛性が高められるので、吸気および排気スラスト受け部Ｔｉ，Ｔeの剛性が一層高められる。そして、これら端部Ｔib，Ｔebは、それぞれ吸気および排気スラスト受け部Ｔｉ，Ｔeへの吸気および排気スラスト力Ｆｉ，Ｆｅの作用により応力集中が発生し易い収容溝76，86の端部76ａ，86ａに近接して位置するので、端部Ｔib，Ｔebで発生する応力が低減される。
【００７１】
軸受部Ｊi4および排気スラスト受け部Ｔｅが、そして軸受部Ｊe4および吸気スラスト受け部Ｔｉが、それぞれ軸方向Ａ２において相互いに重なる領域Ｒｉ，Ｒｅを有するように配置されていることにより、特定ジャーナル軸受部Ｊi4，Ｊe4に対して軸方向Ａ２で互いに反対側にスラスト受け部Ｔｉ，Ｔｅが設けられるカムホルダＨの軸方向Ａ２での長さが、スラスト受け部が設けられるジャーナル軸受部が軸方向Ａ２で同じ位置に設けられるものに比べて短くなるので、カムホルダＨが軸方向Ａ２でコンパクト化される。
【００７２】
以下、前述した実施例の一部の構成を変更した実施例について、変更した構成に関して説明する。
前記実施例では、ヘリカルギヤからなる補機駆動ギヤ21は、排気カム軸12に対して、カム駆動ギヤ17およびカム被動ギヤ18の噛合により排気カム軸12に作用する排気スラスト力Ｆｅとは反対向きのスラスト力を作用させるものでもよい。さらに、補機駆動ギヤ21を捩れ角の異なるヘリカルギヤから構成して排気カム軸12に作用するスラスト力を調整することにより、吸気および排気スラスト力Ｆｉ，Ｆｅの大きさを調整することができるので、補機駆動ギヤ21は吸気および排気スラスト力Ｆｉ，Ｆｅの調整手段としても機能する。
【００７３】
前記カム駆動機構の第１駆動機構Ｄ１は、クランク軸と吸気カム軸11との間に設けられてもよい。ロアカムホルダは、アッパカムホルダ60と同様に分割型のカムホルダであってもよい。前記各実施例では、各シリンダ１は、１対の吸気弁６および１対の排気弁７を有するものであったが、吸気弁６および排気弁７の少なくともいずれか一方は、各シリンダ１に１つであってもよい。
【００７４】
吸気および排気スラスト受け部Ｔｉ，Ｔeは、ロア軸受部およびアッパ軸受部の少なくともいずれか一方のみに設けられていればよい。さらに、吸気スラスト受け部Ｔｉは、複数の吸気軸受部Ｊi1〜Ｊi5のいずれか１つの軸受部である特定吸気気軸受部と、また排気スラスト受け部Ｔｅは、複数の排気軸受部Ｊe1〜Ｊe5のいずれか１つの軸受部である特定排気軸受部と、それぞれ一体成形されて設けられていればよい。
【００７５】
また、図９（Ａ），（Ｂ）に示されるように、１つの特定吸気ジャーナル軸受部Ｊ′ｉおよび１つの特定排気ジャーナル軸受部Ｊ′ｅにおいて、吸気および排気スラスト受け部Ｔ′ｉ，Ｔ′ｅの受け面104 ，114 は、それぞれ、吸気および排気軸受面101a，102a；111a，112aを軸方向Ａ２で分断する位置に設けられて、特定吸気および特定排気ジャーナル軸受部Ｊ′ｉ，Ｊ′ｅを分断する形態で吸気および排気スラスト受け部Ｔ′ｉ，Ｔ′ｅが形成されてもよい。この場合、吸気スラスト受け部Ｔ′ｉが設けられた吸気ロア軸受部101 および吸気アッパ軸受部102 と、排気スラスト受け部Ｔ′ｅが設けられた排気ロア軸受部111 および排気アッパ軸受部112 とにおいて、それぞれ、吸気および排気カム軸11，12のジャーナル部11ａ、12ａが摺接する吸気軸受面101a，102a全体および排気軸受面111a，112a全体の軸方向幅Ｗｉ，Ｗｅは、吸気および排気スラストプレート11ｃ，12ｃが収容される収容溝103 ，113 の軸方向Ａ２での幅を除いたものとなり、収容溝103 ，113 よりも吸気および排気スラスト力Ｆｉ，Ｆｅの作用方向で前方の軸方向幅ＷiF，ＷeFと収容溝103 ，113 よりも後方の軸方向幅ＷiR，ＷeRとの和に等しい。
【００７６】
そして、吸気受け面104は、軸受面101a，102aにおける吸気スラスト力Ｆｉの作用方向で吸気受け面104よりも前方の軸方向幅ＷiFが後方の軸方向幅ＷiRに対して大きくなる位置に形成され、排気受け面114は、軸受面111a，112aにおける排気スラスト力Ｆｅの作用方向で排気受け面114よりも前方の軸方向幅ＷeFが後方の軸方向幅ＷeRに対して大きくなる位置に形成される。このとき、吸気および排気受け面104 ，114 は、それぞれ、吸気軸受面101a；102aの、軸方向Ａ２での両端101a1 ，101a2 ；102a1 ，102a2の位置により規定される軸受面101a，102aの間隔を二等分する位置Ｃｉ、および排気軸受面111a；112aの、軸方向Ａ２での両端111a1 ，111a2 ；112a1 ，112a2の位置により規定される軸受面101a；102aの間隔を二等分する位置Ｃｅよりも、吸気および排気スラスト力Ｆｉ，Ｆｅの作用方向で後方に位置する。
【００７７】
内燃機関は、圧縮点火式のものであったが、火花点火式の内燃機関であってもよい。また、内燃機関は、鉛直方向を指向するクランク軸を備える船外機等の船舶推進装置に使用されてもよい。
【図面の簡単な説明】
【図１】本発明の実施例である内燃機関において、吸気カム軸および排気カム軸が組み付けられたカムホルダの上平面図である。
【図２】図１のＩＩ−ＩＩ矢視に相当する、シリンダヘッドおよびカムホルダ等の断面図である。
【図３】図１のカムホルダのロアカムホルダの上平面図である。
【図４】図１のＩＶ−ＩＶ矢視に相当する、シリンダヘッドおよびカムホルダ等の断面図である。
【図５】図１のＶ−Ｖ矢視での断面図である。
【図６】図１のＶＩ−ＶＩ矢視での断面図である。
【図７】図５のＶＩＩ−ＶＩＩ矢視での断面図である。
【図８】図６のＶＩＩＩ−ＶＩＩＩ矢視での断面図である。
【図９】本発明の別の実施例を示し、（Ａ）は、図７に対応する断面図であり、（Ｂ）は、図８に対応する断面図である。
【符号の説明】
１…シリンダ、２…シリンダヘッド、３…ヘッドカバー、４１，４２…吸気ポート、５…排気ポート、６…吸気弁、７…排気弁、８…弁バネ、９…動弁室、10…動弁装置、11，12…カム軸、11ｃ，12ｃ…スラストプレート、13，14…ロッカアーム、15…カムスプロケット、16…無端チェーン、17…駆動ギヤ、18…被動ギヤ、19…ラッシュアジャスタ、20…高圧燃料ポンプ、21…駆動ギヤ、22…被動ギヤ、23…オルダム継手、24…ネジ孔、25，26…収容空間、
30…ロアカムホルダ、31〜34…縦枠、35，36…横枠、37…貫通孔、38，39…連結部、41〜45，51〜55，101 ，111 …ロア軸受部、101a，111a…軸受面、46，56…油溜形成部、47，57…油溜、48ａ，48ｂ，58ａ，58ｂ，58ｃ…油路、
60…アッパカムホルダ、61，62…端部アッパカムホルダ、67…貫通孔、68，69…連結部、71〜75，81〜85，102 ，112 …アッパ軸受部、74ａ，84ａ，102a，112a…軸受面、76，86，103 ，113 …収容溝、77，87，104 ，114 …受け面、78，88，90，91，94，96…ボス部、79，89，95…貫通孔、92，93，97…ネジ孔、
Ｅ…内燃機関、Ｂ１…ヘッドボルト、Ｂ２…締結ボルト、Ｂ３…予備締結ボルト、Ａ１…シリンダ軸線方向、Ａ２…軸方向、Ａ３…直交方向、Ｊi1〜Ｊi5，Ｊe1〜Ｊe5，Ｊ′ｉ，Ｊ′e…軸受部、Ｄ１〜Ｄ３…駆動機構、Ｆｉ，Ｆｅ…スラスト力、Ｐ…中心面、Ｔｉ，Ｔe，Ｔ′ｉ，Ｔ′e…スラスト受け部、Ｒｉ，Ｒｅ…領域、Ｗｉ，Ｗｅ…軸方向幅、Ｃｉ，Ｃｅ…位置。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine including a cam holder provided with a journal bearing portion that rotatably supports an intake cam shaft and an exhaust cam shaft of a valve operating device, and a thrust receiving portion that restricts axial movement of each cam shaft. .
[0002]
[Prior art]
An internal combustion engine provided with this type of cam holder is disclosed in Patent Document 1. In this internal combustion engine, a pair of timing gears including helical gears meshing with an intake camshaft and an exhaust camshaft are provided, and a journal portion of each camshaft is a bearing composed of a cylinder head and a bearing cap. Supported by the part. A thrust groove in which a thrust restricting portion formed in the journal portion is fitted and engaged is formed in the bearing portion, and a thrust load acting on each cam shaft is received by the thrust groove via the thrust restricting portion.
[0003]
[Patent Document 1]
Utility Model Registration No. 2528261
[0004]
[Problems to be solved by the invention]
By the way, in the prior art, the thrust groove formed by dividing the inner peripheral surface of the bearing portion in the axial direction with respect to both camshafts is opposite to the thrust groove on the side opposite to the timing gear. It is formed at a position where the axial width is larger than the axial width on the timing gear side. On the other hand, due to the fact that both timing gears are composed of helical gears, thrust loads in opposite directions act on both camshafts. For this reason, in the bearing portion where the thrust load acts from the anti-timing gear side to the timing gear side, since the axial width on the timing gear side is small, the axial thickness of the bearing portion is small, and the thrust load is reduced. The rigidity of the portion on the timing gear side to be received becomes smaller than the rigidity of the portion on the anti-timing gear side, and there is a possibility that the rigidity is insufficient.
[0005]
For both camshafts, the thrust groove is formed at a position where the fastening bolt for fastening the bearing cap of the bearing portion is located on the counter-timing gear side with respect to the thrust groove. For this reason, on both camshafts, thrust loads in opposite directions act due to the fact that both timing gears are helical gears, and in the bearing portion where the thrust load acts on the timing gear side from the counter-timing gear side, The rigidity of the portion on the timing gear side that receives the thrust load is smaller than the rigidity of the portion on the counter-timing gear side where the rigidity is increased by the presence of the fastening bolt, and the rigidity may be insufficient.
[0006]
Therefore, in order to resolve this lack of rigidity, if the axial width of the portion where the rigidity is insufficient in the bearing portion is increased, the bearing portion increases in size in the axial direction and increases in weight, and consequently the axial direction of the cam holder or cylinder head. Will lead to an increase in size and weight.
[0007]
This invention is made | formed in view of such a situation, and the invention of Claims 1-6 is the rigidity of a thrust receiving part, after suppressing the enlargement and weight increase in the axial direction of a cam holder. The purpose is to increase. The invention according to claim 4 further improves the lubricity of the intake thrust contact portion and the exhaust thrust contact portion and improves the assembling property of the intake cam shaft and the exhaust cam shaft to the cylinder head. With the goal.
[0008]
[Means for Solving the Problems and Effects of the Invention]
According to the first aspect of the present invention, there are provided a plurality of intake journal bearing portions and a plurality of exhaust journal bearing portions that rotatably support the intake cam shaft and the exhaust cam shaft of the valve gear, respectively, the intake cam shaft and the exhaust cam shaft. A pair of helical gears provided on the intake camshaft and the exhaust camshaft and meshing with each other. In the internal combustion engine in which the intake cam shaft and the exhaust cam shaft are drivingly connected, the intake thrust receiving portion is integrally formed with a specific intake journal bearing portion of the plurality of intake journal bearing portions, and the intake thrust receiving portion The intake receiving surface of the intake intake thrust force acting on the intake camshaft of the intake bearing surface of the specific intake journal bearing portion An axial width in front of the intake receiving surface in the acting direction is formed at a position exceeding 1/2 of the axial width of the entire intake bearing surface, and the exhaust thrust receiving portion is formed of the plurality of exhaust journal bearing portions. The exhaust thrust bearing portion of the exhaust thrust receiving portion is integrally formed with the specific exhaust journal bearing portion, and the exhaust thrust receiving surface of the specific exhaust journal bearing portion is the same as the exhaust thrust force acting on the exhaust camshaft. The internal combustion engine is formed at a position where the axial width in front of the exhaust receiving surface exceeds 1/2 of the axial width of the entire exhaust bearing surface.
[0009]
According to this, a bearing surface with an axial width exceeding 1/2 of the bearing surface of the intake and exhaust journal bearing portion exists in front of the intake and exhaust receiving surfaces in the direction of the thrust force. In addition, there is a high-rigidity portion including a portion having a large thickness in the axial direction of the intake and exhaust journal bearing portions. The thrust forces in opposite directions that act on the intake and exhaust camshafts by meshing the pair of helical gears use the rigidity of the high-rigidity portions of the intake and exhaust journal bearing portions in the intake and exhaust thrust receiving portions, respectively. And be accepted.
[0010]
As a result, according to the first aspect of the present invention, the following effects can be obtained. That is, the receiving surface of the intake and exhaust thrust receiving portions has a bearing surface of the specific journal bearing portion whose axial direction width in front of the receiving surface in the acting direction of the thrust force is ½ of the axial width of the entire bearing surface. The thrust force acting on the intake and exhaust thrust receiving parts uses the rigidity of the high rigidity part of the journal bearing part according to the direction of the thrust force acting on the intake and exhaust camshafts. Thus, the thrust receiving portion is prevented from being increased in size and weight in the axial direction, and the rigidity of the thrust receiving portion is increased.
[0011]
  According to a second aspect of the present invention, there are provided a plurality of intake journal bearing portions and a plurality of exhaust journal bearing portions that rotatably support the intake cam shaft and the exhaust cam shaft of the valve gear, respectively, the intake cam shaft and the exhaust cam shaft. A pair of helical gears provided on the intake camshaft and the exhaust camshaft and meshing with each other. In the internal combustion engine in which the intake camshaft and the exhaust camshaft are drivingly connected, the intake thrust receiving portion is integrally formed with a specific intake journal bearing portion of the plurality of intake journal bearing portions.,in frontThe intake fastening bolt that fastens the specified intake journal bearingGIn the direction of action of the intake thrust force acting on the intake camshaft, theOf the intake thrust receiverForward of the intake receiving surfacePositionPlaceShiThe exhaust thrust receiving portion is integrally formed with a specific exhaust journal bearing portion of the plurality of exhaust journal bearing portions.,in frontExhaust fastening bolt for fastening the specified exhaust journal bearingGIn the direction of the action of the exhaust thrust force acting on the exhaust camshaft, theOf the exhaust thrust receiverFront of exhaust receiving surfacePositionPlaceDoIt is an internal combustion engine.
[0012]
According to this, in the forward direction of the intake and exhaust receiving surfaces in the acting direction of the thrust force, there is a highly rigid portion whose rigidity is enhanced by the rigidity of the fastening bolt in the intake and exhaust journal bearing portion. The thrust forces in opposite directions that act on the intake and exhaust camshafts due to the meshing of the pair of helical gears utilize the rigidity of the high-rigidity portions of the intake and exhaust journal bearing portions at the intake and exhaust thrust receiving portions, respectively. Can be accepted.
[0013]
As a result, according to the second aspect of the present invention, the receiving surface of the intake and exhaust thrust receiving portion is a position where the position of the fastening bolt that fastens the specific journal bearing portion is ahead of the receiving surface in the acting direction of the thrust force. As a result, the same effects as those of the first aspect of the invention can be achieved.
[0014]
A third aspect of the present invention is the internal combustion engine according to the first or second aspect, wherein the specific intake journal bearing portion is positioned in front of the intake receiving surface in the direction of action of the intake thrust force. A portion of the specific exhaust journal bearing portion that is located in front of the exhaust receiving surface in the direction of action of the exhaust thrust force is connected by a connecting portion.
[0015]
According to this, in the specific intake and specific exhaust journal bearing portions, the rigidity of the high-rigidity portion positioned in front of the receiving surface in the acting direction of the thrust force is enhanced by the connecting portion.
[0016]
As a result, according to the invention described in claim 3, in addition to the effect of the invention described in the cited claim, the following effect is produced. That is, the portion of the specific intake journal bearing portion that is positioned in front of the intake receiving surface and the portion of the specific exhaust journal bearing portion that is positioned in front of the exhaust receiving surface are connected by the connecting portion, thereby Since the high rigidity partial rigidity is increased, the rigidity of the thrust receiving section can be further increased.
[0017]
According to a fourth aspect of the present invention, in the internal combustion engine according to any one of the first to third aspects, each journal bearing portion includes a lower bearing portion that is detachably coupled to a cylinder head of the internal combustion engine. An upper bearing portion that is detachably coupled to the lower bearing portion, and the intake thrust receiving portion is integrally formed with a specific intake upper bearing portion of the specific intake journal bearing portion, and the specific intake journal bearing portion is specified. A lubricating oil reservoir for an intake thrust abutting portion provided on the intake camshaft is formed at a position facing the intake thrust receiving portion in the intake lower bearing portion, and the exhaust thrust receiving portion is the specific exhaust journal An exhaust that is integrally formed with the specific exhaust upper bearing portion of the bearing portion and that is provided on the exhaust camshaft at a position facing the exhaust thrust receiving portion of the specific exhaust lower bearing portion. A lubricating oil reservoir for a last contact portion is formed, and the specific intake upper bearing portion is fastened to the specific intake lower bearing portion by an intake preliminary fastening bolt for assembling the intake camshaft to the cam holder, The specific exhaust upper bearing portion is fastened to the specific exhaust lower bearing portion by an exhaust preliminary fastening bolt for assembling the exhaust cam shaft to the cam holder.
[0018]
According to this, in the lubricating oil reservoir formed in the specific intake and specific exhaust lower bearing portion, a part of the lubricating oil supplied for lubrication of the valve operating device is, for example, the specific intake and specific exhaust journal bearing. The oil flows down from the section or drops as a droplet and falls and is stored in the oil reservoir, and the stored lubricating oil is used for lubrication for the intake and exhaust thrust abutting portions. Further, since the intake and exhaust camshafts are preliminarily assembled to the cam holder in a state where the axial movement is restricted by the thrust receiving portion, other components of the valve gear, for example, the rocker arm are assembled to the cylinder head. Even in this state, the intake and exhaust camshafts can be easily assembled to the cylinder head together with the lower bearing portion. Furthermore, since the thrust receiving portion is formed only in the upper bearing portion, the weight of the thrust receiving portion is reduced.
[0019]
As a result, according to the invention described in claim 4, in addition to the effects of the invention described in the cited claims, the following effects are produced. That is, the specific lower bearing portion of the specific intake and specific exhaust journal bearing portion is formed with a lubricating oil reservoir for the intake and exhaust thrust abutting portions at positions facing the intake and exhaust thrust receiving portions, respectively. Since the lubricating oil stored in the oil reservoir is used for lubrication for the intake and exhaust thrust abutting portions, the lubrication of the intake and exhaust thrust abutting portions is improved. In addition, the specific intake and specific exhaust upper bearing portions are respectively connected to the specific intake and specific exhaust lower bearing portions by intake and exhaust preliminary fastening bolts for assembling the intake and exhaust camshafts to the cam holder. At the same time, since the intake and exhaust camshafts can be easily assembled to the cylinder head, the ease of assembling the intake and exhaust camshafts to the cylinder head is improved. Further, the intake and exhaust thrust receiving portions are integrally formed with the specific intake and specific exhaust upper bearing portions, respectively, thereby reducing the weight of the intake and exhaust thrust receiving portions.
[0020]
According to a fifth aspect of the present invention, in the internal combustion engine according to the fourth aspect, the intake preliminary fastening bolt is located at an end of the intake thrust receiving portion in an orthogonal direction, and the exhaust preliminary fastening bolt is the exhaust thrust It is located at the end of the receiving part in the orthogonal direction.
[0021]
According to this, the rigidity of the thrust receiving portion is enhanced by the rigidity of the preliminary fastening bolt. Further, since the preliminary fastening bolt is located at the end portion in the orthogonal direction, an increase in size of the thrust receiving portion in the axial direction is suppressed.
[0022]
As a result, according to the invention described in claim 5, in addition to the effects of the invention described in the cited claims, the following effects can be obtained. That is, the intake and exhaust preliminary fastening bolts are positioned at the end portions in the orthogonal direction of the intake and exhaust thrust receiving portions, respectively, and the increase in size in the axial direction of the intake and exhaust thrust receiving portions is suppressed. Since the rigidity of the intake and exhaust thrust receiving parts is increased, the rigidity of the intake and exhaust thrust receiving parts is further increased.
[0023]
According to a sixth aspect of the present invention, in the internal combustion engine according to any one of the first to fifth aspects, the specific intake journal bearing portion and the exhaust thrust receiving portion have regions that overlap each other in the axial direction. The specific exhaust journal bearing portion and the intake thrust receiving portion are disposed so as to have regions overlapping each other in the axial direction.
[0024]
According to this, in the cam holder, the specific intake journal bearing portion and the exhaust thrust receiving portion, and the specific exhaust journal bearing portion and the intake thrust receiving portion are arranged so as to overlap in the axial direction. Further, the axial length of the cam holder in which the thrust receiving portion is provided on the opposite side in the axial direction with respect to the specific exhaust journal bearing portion is the same as the journal bearing portion in which the thrust receiving portion is provided in the axial direction. Shorter than things.
[0025]
As a result, according to the invention described in claim 5, in addition to the effects of the invention described in the cited claims, the following effects can be obtained. That is, the specific intake journal bearing portion and the exhaust thrust receiving portion, and the specific exhaust journal bearing portion and the intake thrust receiving portion are arranged so as to have regions that overlap each other in the axial direction, so that the specific journal bearing portion On the other hand, since the axial length of the cam holder in which the thrust receiving portions are provided on the opposite sides in the axial direction is reduced, the cam holder is made compact in the axial direction.
[0026]
In this specification, “axial direction” means a direction parallel to the rotation center line of the cam shaft, and “orthogonal direction” means a direction orthogonal to the rotation center line in plan view.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to FIGS.
1 and 2, an internal combustion engine E to which the present invention is applied is a compression ignition type DOHC type in-line four-cylinder internal combustion engine. The internal combustion engine E includes a cylinder block (not shown) in which four cylinders 1 in which pistons (not shown) having a combustion chamber formed of a recess formed on the top surface are reciprocally fitted are arranged in a line. The cylinder head 2 is fastened to the upper end surface of the cylinder block by a head bolt B1 (see FIG. 4), and the head cover 3 is fastened to the upper end surface of the cylinder head 2. In this specification, the vertical direction is assumed to be a direction A1 parallel to the cylinder axis of each cylinder 1 (hereinafter referred to as cylinder axis direction A1).
[0028]
The cylinder head 2 has, for each cylinder 1, an intake port 4 that opens into a cylinder hole into which the piston of the cylinder 1 is fitted.1a, 42a pair of independent first and second intake ports 4 having a1, 42An exhaust port 5 having a pair of exhaust ports 5a opened in the cylinder hole is formed, and a fuel injection valve (not shown) for injecting fuel into the combustion chamber has an axis substantially parallel to the cylinder axis. Installed.
[0029]
In each cylinder 1, a pair of intake ports 41a, 42A pair of intake valves 6 that respectively open and close a and a pair of exhaust valves 7 that open and close a pair of exhaust ports 5a are supported by the cylinder head 2 so as to be slidable in the cylinder axial direction A1, and by valve springs 8 respectively. The valve is normally urged in the valve closing direction, and is opened and closed by a valve operating device 10 housed in a valve operating chamber 9 formed by the cylinder head 2 and the head cover 3.
[0030]
The valve operating device 10 includes a pair of valve operating cam shafts that are rotatably supported by a cam holder H provided in the cylinder head 2, an intake cam shaft 11 and an exhaust cam shaft 12, and intake and exhaust cam shafts 11 and 12. An intake cam 11a and an exhaust cam 12a provided respectively, and an intake rocker arm 13 and an exhaust rocker arm 14 that are swingably supported by the cylinder head 2 are provided.
[0031]
The intake cam shaft 11 is rotatably supported by intake bearing portions Ji1 to Ji5 which are a plurality of intake journal bearing portions provided in the cam holder H in its journal portion 11b (see FIGS. 4 and 7). The journal portion 12b (see FIGS. 4 and 8) is rotatably supported by exhaust bearing portions Je1 to Je5 which are a plurality of exhaust journal bearing portions provided in the cam holder H. Of the intake and exhaust bearing portions Ji1 to Ji5 and Je1 to Je5, the end bearing portions Ji1 and Je1 on one end side of the intake and exhaust camshafts 11 and 12 correspond to one end portion of the cylinder row in the axial direction A2. The end bearing portions Ji5, Je5 on the other end side of the intake and exhaust camshafts 11, 12 are disposed at positions corresponding to the other end portions of the cylinder row in the axial direction A2, and both end bearings The intermediate bearing portions Ji2 to Ji4; Je2 to Je4 located between the portions Ji1 and Ji5; Je1 and Je5 are disposed at corresponding positions between the cylinders 1 adjacent in the axial direction A2 in the cylinder row.
[0032]
Referring to FIG. 1, the intake and exhaust camshafts 11 and 12 have a rotation center line parallel to the rotation center line of the crankshaft of the internal combustion engine E, and are driven by the power of the crankshaft transmitted through the cam drive mechanism. Driven by rotation. The cam drive mechanism includes a first drive mechanism D1 that transmits power between the crankshaft and the exhaust camshaft 12 that is one of the double-acting camshafts, and the other of the exhaust camshaft 12 and the double-acting camshafts. It comprises a second drive mechanism D2 that transmits power to and from a certain intake camshaft 11.
[0033]
The first drive mechanism D1 is wound around a drive sprocket provided on the crankshaft, a cam sprocket 15 provided at one end of the exhaust camshaft 12 located outside the cam holder H, and the drive sprocket and the cam sprocket 15 The endless chain 16 is made up of. The second drive mechanism D2 constituting the inter-cam shaft drive mechanism for drivingly connecting the intake and exhaust cam shafts 11 and 12 is a cam composed of a helical gear arranged adjacent to the cam sprocket 15 at one end of the exhaust cam shaft 12. The driving gear 17 and a cam driven gear 18 formed of a helical gear that is provided at one end of the intake cam shaft 11 located outside the cam holder H and meshes with the cam driving gear 17 are configured. The cam drive gear 17 is composed of a main gear 17a and a sub gear 17b that constitute a scissors gear mechanism for suppressing the generation of gear noise due to backlash.
[0034]
The exhaust camshaft 12 is rotationally driven at a rotational speed half that of the crankshaft by the power of the crankshaft transmitted through the first drive mechanism D1, and the intake camshaft 11 The crankshaft power transmitted via the drive mechanisms D1 and D2 is rotated at a constant speed with the exhaust camshaft 12. Therefore, the intake and exhaust cams 11a and 12a that rotate integrally with the intake and exhaust camshafts 11 and 12 that are rotationally driven by the power of the crankshaft are respectively lash adjusters 19 (see FIG. 2) held by the cylinder head 2. ) Is slidably brought into contact with rollers 13a and 14a (see FIG. 2) of the intake and exhaust rocker arms 13 and 14 that are supported by the spherical surface and swings, and the intake and exhaust rocker arms 13 and 14 are oscillated. The intake valves 6 and the exhaust valves 7 are opened / closed at predetermined timings via 14.
[0035]
Further, due to the engagement of the cam drive gear 17 and the cam driven gear 18, thrust forces in opposite directions act on the intake and exhaust cam shafts 11 and 12, respectively. In this embodiment, the exhaust camshaft 12 is subjected to an exhaust thrust force Fe directed from the other end toward one end, and the intake camshaft 11 is directed toward the intake thrust directed from the other end toward the other end. A force Fi acts. These exhaust and intake thrust forces Fe and Fi are thrust forces acting on the exhaust and intake camshafts 12 and 11 respectively when the cam drive gear 17 drives the cam driven gear 18. On the exhaust and intake camshafts 12 and 11, an average large thrust force including the maximum thrust force acts on the exhaust and intake thrust forces Fe and Fi in the acting direction, respectively.
[0036]
Also, at the other end of the cylinder head 2, an auxiliary machine drive mechanism D3 for driving the high-pressure fuel pump 20 as an auxiliary machine of the internal combustion engine E by the power of the crankshaft is disposed. The accessory drive mechanism D3 includes an accessory drive gear 21 comprising a helical gear provided at the other end of the exhaust camshaft 12 located outside the cam holder H, and an accessory driven comprising a helical gear meshing with the accessory drive gear 21. And a gear 22.
[0037]
The accessory drive gear 21 is composed of a main gear 21a and a sub gear 21b that constitute a scissor gear mechanism. The accessory driven gear 22 is coupled to the rotary shaft 20a of the high-pressure fuel pump 20 attached to the cylinder head 2 via an Oldham joint 23. Due to the meshing of the accessory drive gear 21 and the accessory driven gear 22, a thrust force in the same direction as the exhaust thrust force Fe acts on the exhaust camshaft 12.
[0038]
Referring to FIGS. 1 to 4, the cam holder H that is disposed in the valve operating chamber 9 and is detachably coupled to the cylinder head 2 is the lower half of the intake and exhaust bearing portions Ji1 to Ji5, Je1 to Je5. The lower cam holder 30 in which the exhaust lower bearing portions 41 to 45 and 51 to 55 are formed, and the intake and exhaust upper bearing portions 71 to 75 and 81 to 85 which are the upper half of the intake and exhaust bearing portions Ji1 to Ji5 and Je1 to Je5 The upper cam holder 60 is formed. The upper cam holder 60, together with the lower cam holder 30, is fastened to the cylinder head 2 by a plurality of fastening bolts B2 (see FIG. 4), whereby the cam holder H is fixed to the cylinder head 2.
[0039]
As shown well in FIG. 3, the lower cam holder 30 detachably coupled to the cylinder head 2 is a cam holder having an integrally formed frame structure, and extends parallel to each other in the axial direction A2 and spaced apart in the orthogonal direction A3. A pair of outer vertical frames 31, 32, a pair of inner vertical frames 33, 34 near the center plane P with respect to the outer vertical frames 31, 32, and one end of each vertical frame 31-34. It has a pair of horizontal frames 35 and 36 which connect the parts and the other end parts and extend in the orthogonal direction A3. Here, the orthogonal direction A3 is a direction orthogonal to the axial direction A2 in plan view, and the center plane P is a plane including each cylinder axis.
[0040]
Further, the lower cam holder 30 extends between the outer vertical frame 31 and the inner vertical frame 33 on the intake side in parallel to each other in the orthogonal direction A3 and is provided at lower intervals of the bearing portions Ji1 to Ji5 provided at intervals in the axial direction A2. It has bearing parts 41-45. The end intake lower bearing portion 41 of the end intake bearing portion Ji1 and the end intake lower bearing portion 45 of the end intake bearing portion Ji5 are provided on the horizontal frame 35 and the horizontal frame 36, respectively, and are a pair of lower bearing portions 41. , 45, intermediate intake lower bearing portions 42 to 44 of three intermediate intake bearing portions Ji2 to Ji4 are provided.
[0041]
Similarly, the lower cam holder 30 extends between the exhaust-side outer vertical frame 32 and the inner vertical frame 34, and extends in parallel to each other in the orthogonal direction A3 and is spaced from each other in the axial direction A2. Lower bearing portions 51 to 55 are provided. An end exhaust lower bearing portion 51 of the end exhaust bearing portion Je1 and an end exhaust lower bearing portion 55 of the end exhaust bearing portion Je5 are provided in the horizontal frame 35 and the horizontal frame 36, respectively, and a pair of lower bearing portions 41. , 45, intermediate exhaust lower bearing portions 52 to 54 of three intermediate exhaust bearing portions Je2 to Je4 are provided.
[0042]
Each of the lower bearing portions 41 to 45; 51 to 55 is in contact with the journal portion 11b; 12b of the intake cam shaft 11 or the exhaust cam shaft 12, and has an axial width of a predetermined length that is the width in the axial direction A2 (FIG. 7). 8 shows the axial width Wi of the bearing surface 44a and FIG. 8 shows the axial width We of the bearing surface 54a.) The intake bearing surfaces 41a to 45a or the exhaust bearing surfaces 51a to 55a and the bearing surfaces 41a to 45a. ; 51a-55a sandwiching the outer and inner vertical frames 31, 33; 32, 34 on the both sides, and the outer part constituting the fastening part formed with the through hole 37 through which the fastening bolt B2 is inserted And a pair of inner boss portions 41b to 45b, 41c to 45c; 51b to 55b, 51c to 55c. Then, the fastening bolt B <b> 2 inserted through the through hole 37 is screwed into a screw hole 24 (see FIG. 4) formed in the cylinder head 2, whereby the cam holder H is fastened to the cylinder head 2.
[0043]
Further, the lubricating oil supplied from the oil passage formed in the cylinder head 2 passes through the oil passages 48a and 58a formed of holes formed in both the outer vertical frames 31 and 32, respectively, and the oil passages 48a and 58a at one end, respectively. Are connected to the intake and exhaust bearing surfaces Ji1 to Ji5 and Je2 to Je5 through oil passages 48b and 58b having holes opened to the intake bearing surfaces 41a to 45a and the exhaust bearing surfaces 52a to 55a at the other end. Lubricating oil is supplied to the bearing portion Je1 through an oil passage 58c including a groove communicating with an oil passage formed in an end upper cam holder 61 described later.
[0044]
Referring to FIG. 1, the upper cam holder 60 is a split cam holder, and an end intake upper bearing portion 71 and an end exhaust upper bearing portion 81 are installed to connect the upper bearing portions 71, 81. The end upper cam holder 61 integrally formed with the portion 68, the end intake upper bearing portion 75, and the end exhaust upper bearing portion 85 are integrally formed with an overhanging connecting portion 69 that connects both the upper bearing portions 75 and 85. The formed end upper cam holder 62 includes three intermediate intake upper bearing portions 72 to 74 and three intermediate exhaust upper bearing portions 82 to 84.
[0045]
Each of the upper bearing portions 71 to 75; 81 to 85 is a shaft having a journal shaft 11a; 12a of the intake cam shaft 11 or the exhaust cam shaft 12 that is in sliding contact with the corresponding lower bearing portions 41 to 45; 51-55. The intake bearing surface or the exhaust bearing surface having a directional width (the axial width Wi of the intake bearing surface 74a is shown in FIG. 7 and the axial width We of the exhaust bearing surface 84a is shown in FIG. 8). A through-hole through which the fastening bolt B2 is inserted so as to correspond to the pair of boss portions 41b to 45b, 41c to 45c; 51b to 55b and 51c to 55c of the corresponding lower bearing portions 41 to 45; A pair of outer and inner boss portions 71b to 75b and 71c to 75c; 81b to 85b and 81c to 85c constituting a fastening portion in which 67 is formed. The connecting portions 68; 69 of the upper cam holders 61; 62 at both ends connect the boss portions 71c, 81c; 75c, 85c on both inner sides of the upper bearing portions 71; 75 and the upper bearing portions 81;
[0046]
And each upper bearing part 71-75, 81-85 is fastened by fastening bolt B2 corresponding to each lower bearing part 41-45, 51-55, and thereby each bearing part Ji1-Ji5, Je1-Je5 It is formed. Further, on the intake side of the cam holder H, two intake cams 11a and 2 are provided for each cylinder 1 between the bearing portions Ji1, Ji2; Ji2, Ji3; Ji3, Ji4; Ji4, Ji5 adjacent in the axial direction A2. A housing space 25 is formed for housing a part of each of the two intake rocker arms 13, and on the exhaust side thereof, adjacent bearing portions Je1, Je2; Je2, Je3; Je3, Je4; Je4, Je5 in the axial direction A2 For each cylinder 1, a housing space 26 for housing a part of each of the two exhaust cams 12 a and the two exhaust rocker arms 14 is formed.
[0047]
1 and 4 to 8, the cam holder H is in contact with a hook-shaped intake thrust plate 11c as an intake thrust contact portion provided integrally with the intake cam shaft 11 so as to be in the intake cam. The exhaust cam is in contact with an intake thrust receiving portion Ti for restricting the movement of the shaft 11 in the axial direction A2 and a bowl-shaped exhaust thrust plate 12c as an exhaust thrust contact portion provided by integral molding on the exhaust cam shaft 12. An exhaust thrust receiving portion Te that restricts the movement of the shaft 12 in the axial direction A2 is provided.
[0048]
The intake and exhaust thrust receiving portions Ti and Te are respectively a bearing portion Ji4 as one specific intake bearing portion of the plurality of bearing portions Ji1 to Ji5 and one specific exhaust bearing of the plurality of bearing portions Je1 to Je5. The bearing portions Ji4 and Je4 are formed integrally with the bearing portion Je4 as a portion, and are adjacent to the end bearing portions Ji5 and Je5, respectively.
[0049]
Referring to FIGS. 1, 4, 5, and 7, the intake thrust receiving portion Ti positioned behind the bearing portion Ji <b> 4 in the acting direction of the intake thrust force Fi is integrally formed with the upper bearing portion 74. The upper bearing portion 74 includes a protruding portion that protrudes in the direction opposite to the direction of the intake thrust force Fi. The intake thrust receiving portion Ti includes a semicircular groove accommodating groove 76 in which a part of the intake thrust plate 11c is accommodated, and an intake receiving surface 77 on which the intake thrust plate 11c abuts. Further, the intake thrust receiving portion Ti and the exhaust bearing portion Je4 are arranged so as to have a region Ri that overlaps each other in the axial direction A2 (see FIG. 1).
[0050]
The bearing surface 77 is configured such that, in the bearing portion Ji4, the bearing surface 74a of the upper bearing portion 74 in which the intake thrust receiving portion Ti is formed has an axial width ahead of the receiving surface 77 in the acting direction of the intake thrust force Fi. The surface 74a is formed at a position exceeding 1/2 of the axial width Wi. At this time, the receiving surface 77 is formed at a position where the axial width in front of the receiving surface 77 is larger than the axial width in the rear in the acting direction of the intake thrust force Fi on the bearing surface 74a. In addition, the receiving surface 77 has a direction in which the intake thrust force Fi acts, rather than a position Ci that bisects the interval between the bearing surfaces 74a defined by the positions of both ends 74a1 and 74a2 in the axial direction A2 of the bearing surface 74a. At the rear. For this reason, the wall thickness in the axial direction A2 of the upper bearing portion 74 in front of the receiving surface 77 in the acting direction of the intake thrust force Fi is in the axial direction A2 of the upper bearing portion 74 in the rear of the receiving surface 77. It becomes larger than the wall thickness.
[0051]
  In this embodiment, assuming that the axial width of the bearing surface 74a behind the receiving surface 77 in the acting direction of the intake thrust force Fi becomes 0 (zero), the receiving surface 77 has the intake thrust force Fi. A position where the axial width in front of the receiving surface 77 in the acting direction becomes the axial width Wi of the entire bearing surface 74a, that is, the bearing surface 74a is located only in front of the receiving surface 77 in the acting direction of the intake thrust force Fi. It is formed in such a position. Further, the receiving surface 77 is inserted into the through holes 67 and 37 and the entire position of a pair of fastening bolts B2 (see FIG. 4) as the fastening bolts for fastening the upper bearing portion 74 is affected by the intake thrust force Fi. It is formed at a position in front of the receiving surface 77 in the direction.In other words, the whole of the pair of fastening bolts B2 is the receiving surface in the direction in which the intake thrust force Fi acts. 77 Located ahead of.
[0052]
Referring to FIGS. 5 and 7, the lower bearing portion 44 of the bearing portion Ji4 has an axial direction A2 from the lower bearing portion 44 at a position facing the intake thrust receiving portion Ti in the vertical direction across the intake camshaft 11. An oil reservoir forming portion 46 constituted by a protruding portion protruding in the same direction as the intake thrust receiving portion Ti is integrally formed with the lower bearing portion 44. The oil reservoir forming portion 46 is formed with an oil reservoir 47 (see also FIG. 2) that is a recess into which a part of the intake thrust plate 11c enters. In the oil reservoir 47, which is a lubricating oil reservoir for the intake thrust plate 11c, a part of the lubricating oil supplied to the lubricating portion such as the sliding portion of the valve gear 10 flows down from the bearing portion Ji4, Or it falls in the valve operating chamber 9 as a droplet and is stored. The intake thrust plate 11c is immersed in the lubricating oil in the oil reservoir 47, so that the sliding portion between the intake thrust plate 11c and the receiving surface 77 is lubricated by the lubricating oil adhering to the intake thrust plate 11c.
[0053]
Similarly, referring to FIGS. 1, 4, 6 and 8, the exhaust thrust receiving portion Te located behind the bearing portion Je <b> 4 in the acting direction of the exhaust thrust force Fe is integrally formed with the upper bearing portion 84. Thus, the upper bearing portion 84 is constituted by a protruding portion that protrudes in the direction opposite to the direction of the exhaust thrust force Fe. The exhaust thrust receiving portion Te has a semicircular groove accommodating groove 86 in which a part of the exhaust thrust plate 12c is accommodated, and an exhaust receiving surface 87 with which the exhaust thrust plate 12c abuts. Further, the exhaust thrust receiving portion Te and the intake bearing portion Ji4 are arranged so as to have regions Re that overlap each other in the axial direction A2 (see FIG. 1).
[0054]
The bearing surface 87 is configured such that, in the bearing portion Je4, the bearing surface 84a of the upper bearing portion 84 in which the exhaust thrust receiving portion Te is formed has an axial width ahead of the receiving surface 87 in the acting direction of the exhaust thrust force Fe. The surface 84a is formed at a position exceeding 1/2 of the axial width We. At this time, the receiving surface 87 is formed at a position where the axial width in front of the receiving surface 87 becomes larger than the axial width in the rear in the acting direction of the exhaust thrust force Fe on the bearing surface 84a. In addition, the receiving surface 87 has a direction in which the exhaust thrust force Fe acts more than a position Ce that bisects the interval between the bearing surfaces 84a defined by the positions of both ends 84a1 and 84a2 in the axial direction A2 of the bearing surface 84a. At the rear. For this reason, the wall thickness in the axial direction A2 of the upper bearing portion 84 in front of the receiving surface 87 in the acting direction of the exhaust thrust force Fe is in the axial direction A2 of the upper bearing portion 84 in the rear of the receiving surface 87. It becomes larger than the wall thickness.
[0055]
  In this embodiment, assuming that the axial width of the bearing surface 84a behind the receiving surface 87 in the acting direction of the exhaust thrust force Fe becomes 0 (zero), the receiving surface 87 has the exhaust thrust force Fe. A position where the axial width in front of the receiving surface 87 in the acting direction becomes the axial width We of the entire bearing surface 84a, that is, the bearing surface 84a is located only in front of the receiving surface 87 in the acting direction of the exhaust thrust force Fe. It is formed in such a position. Further, the receiving surface 87 is inserted into the through holes 67 and 37, and the entire position of a pair of fastening bolts B2 (see FIG. 4) as the exhaust fastening bolts that fasten the upper bearing portion 84 is affected by the exhaust thrust force Fe. It is formed at a position in front of the receiving surface 87 in the direction.That is, the whole of the pair of fastening bolts B2 is the receiving surface in the direction in which the exhaust thrust force Fe acts. 87 Located ahead of.
[0056]
6 and 8, the lower bearing portion 54 of the bearing portion Je4 has an axial direction A2 from the lower bearing portion 54 at a position facing the exhaust thrust receiving portion Te in the vertical direction across the exhaust camshaft 12. An oil reservoir forming portion 56 constituted by a protruding portion protruding in the same direction as the exhaust thrust receiving portion Te is integrally formed with the lower bearing portion 54. The oil reservoir forming portion 56 is formed with an oil reservoir 57 (see also FIG. 2) that is a recess into which a part of the exhaust thrust plate 12c enters. The oil reservoir 57 is a lubricating oil reservoir for the exhaust thrust plate 12c. In the same manner as the oil reservoir 47, the lubricating oil is stored. Then, the exhaust thrust plate 12c is immersed in the lubricating oil in the oil reservoir 57, whereby the sliding portion between the exhaust thrust plate 12c and the receiving surface 87 is lubricated by the lubricating oil adhering to the exhaust thrust plate 12c.
[0057]
7 and 8, the intake camshaft 11 acts on the intake camshaft 11 in the opposite direction to the intake thrust force Fi due to torque fluctuations of the internal combustion engine E, rotation fluctuations of both camshafts 11 and 12, and the like. The small thrust force that acts on the exhaust camshaft 12 in the direction opposite to that of the exhaust thrust force Fe, and the intake and exhaust thrust plates 11c and 12c are the intake and exhaust receiving surfaces 77 and 87, respectively. Are received by contacting the receiving surfaces Tia and Tea facing each other in the axial direction A2.
[0058]
Referring to FIGS. 1, 3, 5, and 6, the intake and exhaust thrust receiving portions Ti and Te are preferably provided at the end portions of the thrust receiving portions Ti and Te in the orthogonal direction A <b> 3, Intake and exhaust are provided at the ends Tib and Teb, which are close to the ends 76a and 86a in the orthogonal direction A3 of 86, and where stress concentration is likely to occur due to the action of the thrust forces Fi and Fe on the thrust receiving portions Ti and Te. Boss portions 78 and 88, which are fastening portions in which through holes 79 and 89 into which a preliminary fastening bolt B3 as a preliminary fastening bolt is inserted, are formed. These boss portions 78 and 88 are connected to the respective inner boss portions 74c and 84c of the upper bearing portions 74 and 84, and end portions Tib and Teb at positions close to each other of the intake and exhaust thrust receiving portions Ti and Te. Formed.
[0059]
In the lower bearing portions 44 and 54, boss portions 90 and 91, which are fastening portions having screw holes 92 and 93 into which the fastening bolts B3 are respectively screwed corresponding to the boss portions 78 and 88, are shown in FIG. The oil reservoir forming portions 46 and 56 are connected to the boss portions 44c and 54c.
[0060]
The preliminary fastening bolt B3 uses the upper bearing portions 74 and 84 in which the thrust receiving portions Ti and Te are integrally formed before the cam holder H is coupled to the cylinder head 2 by the fastening bolt B2, and the intake and This is for preparatory assembly of the exhaust camshafts 11 and 12.
[0061]
1 and 2, in order to assemble the intake and exhaust camshafts 11 and 12 to the cam holder H in a stable state, a plurality of bearing portions Ji2, Ji3; Je2 in the axial direction A2 from both preliminary fastening bolts B3. , Je3 and an end upper cam holder 61 to which the intake and exhaust camshafts 11 and 12 can be assembled by a single member is fastened to the horizontal frame 35 of the lower cam holder 30 by a preliminary fastening bolt B3. Specifically, a boss portion 94 which is a fastening portion having a through hole 95 through which the preliminary fastening bolt B3 is inserted is formed in the connecting portion 68 of the end upper cam holder 61, and corresponding to the boss portion 94, A boss portion 96 as a fastening portion having a screw hole 97 into which the preliminary fastening bolt B3 is screwed is formed in the horizontal frame 35 of the lower cam holder 30.
[0062]
Thus, before the cam holder H is fixed to the cylinder head 2 by the fastening bolt B2, the intake and exhaust cam shafts 11 and 12 are axially moved relative to the lower cam holder 30 by the intake and exhaust thrust receiving portions Ti and Te, respectively. Since it is assembled to the cam holder H in a state where movement to A2 is restricted, the assembly when the cam shafts 11 and 12 are assembled from above the intake and exhaust rocker arms 13 and 14 assembled to the cylinder head 2 Becomes easier.
[0063]
Further, referring to FIGS. 1, 3 and 5, the lower cam holder 30 has a pair of bearing portions Ji2, Ji4 and 1 adjacent to the intake bearing portions Ji1, Ji5 and the exhaust bearing portions Je1, Je5 in the axial direction A2, respectively. In the pair of bearing portions Je2 and Je4, both inner boss portions 42c and 52c; 44c are used to connect the inner boss portions 42c and 44c of the lower bearing portions 42 and 44 to the inner bosses 52c and 54c of the lower bearing portions 52 and 54. , 54c are provided with wall-like connecting portions 38, 39. Since the pair of inner vertical frames 33 and 34 are coupled in the orthogonal direction A3 by the pair of coupling portions 38 and 39, the rigidity of the lower cam holder 30 is enhanced.
[0064]
A connecting portion 39 that connects the lower bearing portions 44 and 54 includes an inner boss portion 44c that is a portion of the intake bearing portion Ji4 that is located in front of the receiving surface 77 in the direction of action of the intake thrust force Fi, and an exhaust bearing. The portion Je4 is connected to the inner boss 54c, which is a portion located in front of the receiving surface 87 in the acting direction of the exhaust thrust force Fe. For this reason, the rigidity of the lower bearing portion 44 and the lower bearing portion 54 is increased by the connecting portion 39, and consequently the rigidity of the upper bearing portions 74 and 84 coupled to the lower bearing portions 44 and 54 by the fastening bolts is increased.
[0065]
Next, operations and effects of the embodiment configured as described above will be described.
In the intake and exhaust thrust receiving portions Ti and Te integrally formed with the intake and exhaust bearing portions Ji4 and Je4 of the intake and exhaust bearing portions Ji4 and Je4 provided in the cam holder H, the receiving surfaces 77 and 87 are respectively provided with the upper bearing portion 74 and The axial widths of the bearing surfaces 74a and 84a of the 84 in front of the receiving surfaces 77 and 87 in the acting direction of the intake and exhaust thrust forces Fi and Fe are 1 / of the axial widths Wi and We of the entire bearing surfaces 74a and 84a. By being formed at a position exceeding 2, in front of the intake and exhaust receiving surfaces 77 and 87 in the acting direction of the intake and exhaust thrust forces Fi and Fe, respectively, of the bearing surfaces 74a and 84a, Since there are bearing surfaces 74a and 84a having an axial width exceeding 1/2, there is one high-rigidity portion consisting of a portion having a large thickness in the axial direction A2 of the upper bearing portions 74 and 84. The exhaust and intake thrust forces Fi and Fe acting in opposite directions acting on the intake and exhaust camshafts 11 and 12 due to the engagement of the cam drive gear 17 and the cam driven gear 18 formed of a pair of helical gears are received by the intake and exhaust thrust receivers. In each of the portions Ti and Te, the intake and exhaust thrust acting on the intake and exhaust thrust receiving portions Ti and Te in accordance with the acting direction of the intake and exhaust thrust forces Fi and Fe acting on the intake and exhaust camshafts 11 and 12, respectively. Since the forces Fi and Fe are received using the rigidity of the high-rigidity portions of the upper bearing portions 74 and 84, the thrust receiving portions Ti and Te are restrained from increasing in size and weight in the axial direction A2, The rigidity of the intake and exhaust thrust receiving portions Ti and Te is increased.
[0066]
Further, the receiving surfaces 77 and 87 of the intake and exhaust thrust receiving portions Ti and Te are respectively connected to the receiving surfaces 77 and 87 in the acting direction of the intake and exhaust thrust forces Fi and Fe. By being formed at a position ahead of 87, in the direction of the action of the intake and exhaust thrust forces Fi, Fe, in front of the receiving surfaces 77, 87, the fastening bolts B2 of the intake and exhaust bearing portions Ji4, Je4 Since there is another high-rigidity portion whose rigidity is increased by the rigidity, the rigidity of the intake and exhaust thrust receiving portions Ti and Te is further enhanced by the rigidity of the other high-rigidity portion and the high-rigidity portion.
[0067]
The action of the exhaust thrust force Fe of the inner boss part 44c positioned in front of the receiving surface 77 in the acting direction of the intake thrust force Fi of the lower bearing part 44 of the intake bearing part Ji4 and the lower bearing part 54 of the bearing part Je4. The inner boss 54c positioned in front of the receiving surface 87 in the direction is connected by the connecting portion 39, so that the connecting portion 39 causes the intake and exhaust thrust forces Fi and Fe to act on the bearing portions Ji4 and Je4, respectively. Since the rigidity of the other high-rigidity part and the high-rigidity part positioned in front of the receiving surfaces 77 and 87 in the direction is increased, the rigidity of the thrust receiving parts Ti and Te can be further increased.
[0068]
In the lower bearing portions 44 and 54 of the intake and exhaust bearing portions Ji4 and Je4, oil reservoirs 47 and 57 for the intake and exhaust thrust plates 11c and 12c are provided at positions facing the intake and exhaust thrust receiving portions Ti and Te, respectively. As a result, a part of the lubricating oil supplied for lubrication of the valve gear 10 flows down from the bearing portions Ji4 and Je4 or drops in the valve train chamber 9 as droplets. Since the stored lubricating oil is used for lubricating the intake and exhaust thrust plates 11c and 12c, the intake and exhaust thrust plates 11c and 12c are lubricated well.
[0069]
The upper bearing portions 74 and 84 are fastened to the lower bearing portions 44 and 54 by preliminary fastening bolts B3 for assembling the intake and exhaust camshafts 11 and 12 to the cam holder H, respectively. However, since it is preliminarily assembled to the cam holder H in a state where the movement in the axial direction A2 is restricted by the thrust receiving portions Ti and Te, the intake and exhaust rocker arms 13 and 14 as other components of the valve gear 10 are cylinders. Since it becomes easy to assemble the intake and exhaust camshafts 11 and 12 together with the lower bearing portions 44 and 54 to the cylinder head 2 in the state of being assembled to the head 2, the cylinder head 2 of the intake and exhaust camshafts 11 and 12 Improves assembly. Further, the intake and exhaust thrust receiving portions Ti and Te are integrally formed with the upper bearing portions 74 and 84, respectively, so that the thrust receiving portions Ti and Te are formed only in the upper bearing portions 74 and 84. And the exhaust thrust receiving portions Ti and Te are reduced in weight.
[0070]
Preliminary fastening bolts B3 are positioned at ends Tib and Teb in the orthogonal direction A3 of the intake and exhaust thrust receiving portions Ti and Te, respectively, so that the intake and exhaust thrust receiving portions Ti and Te are enlarged in the axial direction A2. Since the rigidity of both thrust receiving portions Ti and Te is increased, the rigidity of the intake and exhaust thrust receiving portions Ti and Te is further increased. These end portions Tib and Teb are end portions 76a and 86a of the housing grooves 76 and 86 where stress concentration easily occurs due to the action of the intake and exhaust thrust forces Fi and Fe to the intake and exhaust thrust receiving portions Ti and Te, respectively. Therefore, the stress generated at the ends Tib and Teb is reduced.
[0071]
The specific journal bearing portion is formed by arranging the bearing portion Ji4 and the exhaust thrust receiving portion Te, and the bearing portion Je4 and the intake thrust receiving portion Ti so as to have regions Ri and Re that overlap each other in the axial direction A2. The length in the axial direction A2 of the cam holder H in which thrust receiving portions Ti and Te are provided on opposite sides in the axial direction A2 with respect to Ji4 and Je4 is the same in the axial direction A2 as the journal bearing portion in which the thrust receiving portion is provided. Since it is shorter than that provided at the position, the cam holder H is made compact in the axial direction A2.
[0072]
Hereinafter, an example in which a part of the configuration of the above-described embodiment is changed will be described with respect to the changed configuration.
In the above-described embodiment, the accessory drive gear 21 formed of a helical gear is opposite to the exhaust thrust force Fe acting on the exhaust camshaft 12 due to the engagement of the cam drive gear 17 and the cam driven gear 18 with respect to the exhaust camshaft 12. It is also possible to apply a thrust force of. Further, the magnitude of the intake and exhaust thrust forces Fi and Fe can be adjusted by adjusting the thrust force acting on the exhaust camshaft 12 by configuring the accessory drive gear 21 from helical gears having different torsion angles. The accessory drive gear 21 also functions as a means for adjusting the intake and exhaust thrust forces Fi and Fe.
[0073]
The first drive mechanism D1 of the cam drive mechanism may be provided between the crankshaft and the intake camshaft 11. Similarly to the upper cam holder 60, the lower cam holder may be a split cam holder. In each of the above embodiments, each cylinder 1 has a pair of intake valves 6 and a pair of exhaust valves 7. However, at least one of the intake valves 6 and the exhaust valves 7 is connected to each cylinder 1. There may be one.
[0074]
The intake and exhaust thrust receiving portions Ti and Te may be provided only in at least one of the lower bearing portion and the upper bearing portion. Further, the intake thrust receiving portion Ti is a specific intake air bearing portion which is any one of a plurality of intake bearing portions Ji1 to Ji5, and the exhaust thrust receiving portion Te is a plurality of exhaust bearing portions Je1 to Je5. The specific exhaust bearing part which is any one of the bearing parts may be integrally formed and provided.
[0075]
Further, as shown in FIGS. 9A and 9B, in one specific intake journal bearing portion J′i and one specific exhaust journal bearing portion J′e, intake and exhaust thrust receiving portions T′i, The receiving surfaces 104 and 114 of T′e are provided at positions where the intake and exhaust bearing surfaces 101a and 102a; 111a and 112a are divided in the axial direction A2, respectively, and the specific intake and specific exhaust journal bearing portions J′i, The intake and exhaust thrust receiving portions T′i and T′e may be formed in a form that divides J′e. In this case, the intake lower bearing portion 101 and the intake upper bearing portion 102 provided with the intake thrust receiving portion T′i, the exhaust lower bearing portion 111 and the exhaust upper bearing portion 112 provided with the exhaust thrust receiving portion T′e, , The axial widths Wi and We of the entire intake bearing surfaces 101a and 102a and the entire exhaust bearing surfaces 111a and 112a with which the journal portions 11a and 12a of the intake and exhaust camshafts 11 and 12 are slidably contacted respectively are the intake and exhaust thrust plates. 11c and 12c are accommodated by removing the width in the axial direction A2 of the housing grooves 103 and 113, and the axial width WiF ahead of the housing grooves 103 and 113 in the acting direction of the intake and exhaust thrust forces Fi and Fe. , WeF and the axial widths WiR, WeR behind the receiving grooves 103, 113 are equal to the sum.
[0076]
The intake receiving surface 104 is formed at a position where an axial width WiF in front of the intake receiving surface 104 is larger than an axial width WiR in the rear in the acting direction of the intake thrust force Fi on the bearing surfaces 101a and 102a. The exhaust receiving surface 114 is formed at a position where the axial width WeF in front of the exhaust receiving surface 114 is larger than the rear axial width WeR in the acting direction of the exhaust thrust force Fe on the bearing surfaces 111a and 112a. . At this time, the intake and exhaust receiving surfaces 104 1 and 114 respectively have intervals between the bearing surfaces 101a and 102a defined by the positions of both ends 101a1 and 101a2; 102a1 and 102a2 in the axial direction A2 of the intake bearing surfaces 101a and 102a. From the position Ci that bisects the interval of the bearing surface 101a; 102a defined by the position of the two ends 111a1, 111a2; 112a1, 112a2 of the exhaust bearing surface 111a; 112a in the axial direction A2 Are also located rearward in the direction of action of the intake and exhaust thrust forces Fi, Fe.
[0077]
The internal combustion engine is of a compression ignition type, but may be a spark ignition type of internal combustion engine. Further, the internal combustion engine may be used in a marine vessel propulsion apparatus such as an outboard motor having a crankshaft oriented in the vertical direction.
[Brief description of the drawings]
FIG. 1 is an upper plan view of a cam holder in which an intake cam shaft and an exhaust cam shaft are assembled in an internal combustion engine that is an embodiment of the present invention.
2 is a cross-sectional view of a cylinder head, a cam holder, and the like corresponding to the view taken along the line II-II in FIG.
3 is a top plan view of the lower cam holder of the cam holder of FIG. 1. FIG.
4 is a cross-sectional view of a cylinder head, a cam holder, and the like corresponding to the view taken along arrows IV-IV in FIG.
5 is a cross-sectional view taken along the arrow VV in FIG. 1. FIG.
6 is a cross-sectional view taken along arrow VI-VI in FIG. 1;
7 is a cross-sectional view taken along arrow VII-VII in FIG.
8 is a cross-sectional view taken along arrow VIII-VIII in FIG. 6;
9A and 9B show another embodiment of the present invention, in which FIG. 9A is a cross-sectional view corresponding to FIG. 7, and FIG. 9B is a cross-sectional view corresponding to FIG.
[Explanation of symbols]
1 ... Cylinder, 2 ... Cylinder head, 3 ... Head cover, 41, 42Intake port, 5 ... Exhaust port, 6 ... Intake valve, 7 ... Exhaust valve, 8 ... Valve spring, 9 ... Valve operating chamber, 10 ... Valve operating device, 11, 12 ... Cam shaft, 11c, 12c ... Thrust plate, 13, 14 ... Rocker arm, 15 ... Cam sprocket, 16 ... Endless chain, 17 ... Drive gear, 18 ... Drive gear, 19 ... Rush adjuster, 20 ... High pressure fuel pump, 21 ... Drive gear, 22 ... Drive gear, 23 ... Oldham Joint, 24 ... screw hole, 25, 26 ... accommodation space,
30 ... Lower cam holder, 31-34 ... Vertical frame, 35, 36 ... Horizontal frame, 37 ... Through hole, 38, 39 ... Connection part, 41-45, 51-55, 101, 111 ... Lower bearing part, 101a, 111a ... Bearing surface, 46, 56 ... oil reservoir forming portion, 47, 57 ... oil reservoir, 48a, 48b, 58a, 58b, 58c ... oil passage,
60 ... upper cam holder, 61, 62 ... end upper cam holder, 67 ... through hole, 68, 69 ... connecting part, 71 to 75, 81 to 85, 102, 112 ... upper bearing part, 74a, 84a, 102a, 112a ... bearing surface, 76, 86, 103, 113 ... receiving groove, 77, 87, 104, 114 ... receiving surface, 78, 88, 90, 91, 94, 96 ... boss, 79, 89, 95 ... through hole , 92, 93, 97 ... screw holes,
E ... Internal combustion engine, B1 ... Head bolt, B2 ... Fastening bolt, B3 ... Preliminary fastening bolt, A1 ... Cylinder axial direction, A2 ... Axial direction, A3 ... Orthogonal direction, Ji1-Ji5, Je1-Je5, J'i, J 'E ... bearing portion, D1-D3 ... drive mechanism, Fi, Fe ... thrust force, P ... center plane, Ti, Te, T'i, T'e ... thrust receiving portion, Ri, Re ... area, Wi, We ... Axial width, Ci, Ce ... position.

Claims (6)

動弁装置の吸気カム軸および排気カム軸をそれぞれ回転可能に支持する複数の吸気ジャーナル軸受部および複数の排気ジャーナル軸受部と、前記吸気カム軸および前記排気カム軸の軸方向への移動をそれぞれ規制する吸気スラスト受け部および排気スラスト受け部とが設けられたカムホルダを備え、前記吸気カム軸および前記排気カム軸に設けられて相互に噛合する１対のヘリカルギヤにより前記吸気カム軸および前記排気カム軸が駆動連結される内燃機関において、
前記吸気スラスト受け部は、前記複数の吸気ジャーナル軸受部のうちの特定吸気ジャーナル軸受部と一体成形され、前記吸気スラスト受け部の吸気受け面は、前記特定吸気ジャーナル軸受部の吸気軸受面の、前記吸気カム軸に作用する吸気スラスト力の作用方向で前記吸気受け面よりも前方の軸方向幅が前記吸気軸受面全体の軸方向幅の１／２を越える位置に形成され、前記排気スラスト受け部は、前記複数の排気ジャーナル軸受部のうちの特定排気ジャーナル軸受部と一体成形され、前記排気スラスト受け部の排気受け面は、前記特定排気ジャーナル軸受部の排気軸受面の、前記排気カム軸に作用する排気スラスト力の作用方向で前記排気受け面よりも前方の軸方向幅が前記排気軸受面全体の軸方向幅の１／２を越える位置に形成されることを特徴とする内燃機関。A plurality of intake journal bearing portions and a plurality of exhaust journal bearing portions that rotatably support the intake cam shaft and the exhaust cam shaft of the valve gear, respectively, and the movement of the intake cam shaft and the exhaust cam shaft in the axial direction, respectively The intake camshaft and the exhaust cam are provided by a pair of helical gears that are provided on the intake camshaft and the exhaust camshaft and mesh with each other, each of which includes a cam holder having an intake thrust receiver and an exhaust thrust receiver to be regulated. In an internal combustion engine whose shaft is drivingly connected,
The intake thrust receiving portion is integrally formed with a specific intake journal bearing portion of the plurality of intake journal bearing portions, and an intake receiving surface of the intake thrust receiving portion is an intake bearing surface of the specific intake journal bearing portion, An exhaust thrust force acting on the intake camshaft is formed at a position where an axial width in front of the intake receiving surface exceeds a half of an axial width of the entire intake bearing surface in the acting direction of the intake thrust force; And a specific exhaust journal bearing portion of the plurality of exhaust journal bearing portions, and an exhaust receiving surface of the exhaust thrust receiving portion is the exhaust camshaft of the exhaust bearing surface of the specific exhaust journal bearing portion. The axial direction width ahead of the exhaust receiving surface in the acting direction of the exhaust thrust force acting on the exhaust bearing surface is formed at a position exceeding 1/2 of the axial width of the entire exhaust bearing surface. Internal combustion engine according to claim. 動弁装置の吸気カム軸および排気カム軸をそれぞれ回転可能に支持する複数の吸気ジャーナル軸受部および複数の排気ジャーナル軸受部と、前記吸気カム軸および前記排気カム軸の軸方向への移動をそれぞれ規制する吸気スラスト受け部および排気スラスト受け部とが設けられたカムホルダを備え、前記吸気カム軸および前記排気カム軸に設けられて相互に噛合する１対のヘリカルギヤにより前記吸気カム軸および前記排気カム軸が駆動連結される内燃機関において、
前記吸気スラスト受け部は、前記複数の吸気ジャーナル軸受部のうちの特定吸気ジャーナル軸受部と一体成形され、前記特定吸気ジャーナル軸受部を締結する吸気締結ボルトが、前記吸気カム軸に作用する吸気スラスト力の作用方向で前記吸気スラスト受け部の吸気受け面よりも前方に位置し、前記排気スラスト受け部は、前記複数の排気ジャーナル軸受部のうちの特定排気ジャーナル軸受部と一体成形され、前記特定排気ジャーナル軸受部を締結する排気締結ボルトが、前記排気カム軸に作用する排気スラスト力の作用方向で前記排気スラスト受け部の排気受け面よりも前方に位置することを特徴とする内燃機関。A plurality of intake journal bearing portions and a plurality of exhaust journal bearing portions that rotatably support the intake cam shaft and the exhaust cam shaft of the valve gear, respectively, and the movement of the intake cam shaft and the exhaust cam shaft in the axial direction, respectively The intake camshaft and the exhaust cam are provided by a pair of helical gears that are provided on the intake camshaft and the exhaust camshaft and mesh with each other, each of which includes a cam holder having an intake thrust receiver and an exhaust thrust receiver to be regulated. In an internal combustion engine whose shaft is drivingly connected,
The intake thrust receiving portion is integrally molded with the intake-journal bearing portion of the plurality of intake journal bearing part, the intake fastening bolts for fastening the front Symbol intake-journal bearing part, acts on the intake camshaft wherein in the direction of action of the intake thrust force to position further forward than the intake receiving surface of the intake thrust receiving portion, the exhaust thrust receiving portion is integrally molded with a particular exhaust journal bearing portion of the plurality of exhaust journal bearing part , characterized in that the exhaust fastening bolts for fastening the front Symbol particular exhaust journal bearing part, to position more forward than the exhaust receiving surface of the exhaust thrust receiving portion in the direction of action of the exhaust thrust force acting on the exhaust camshaft An internal combustion engine. 前記特定吸気ジャーナル軸受部の、前記吸気スラスト力の作用方向で前記吸気受け面よりも前方に位置する部位と、前記特定排気ジャーナル軸受部の、前記排気スラスト力の作用方向で前記排気受け面よりも前方に位置する部位とが、連結部により連結されることを特徴とする請求項１または請求項２記載の内燃機関。A portion of the specific intake journal bearing portion that is positioned in front of the intake receiving surface in the direction of action of the intake thrust force, and a direction of action of the exhaust thrust force of the specific exhaust journal bearing portion from the exhaust receiving surface. The internal combustion engine according to claim 1, wherein a portion positioned forward is also connected by a connecting portion. 前記各ジャーナル軸受部は、前記内燃機関のシリンダヘッドに着脱可能に結合されるロア軸受部と、前記ロア軸受部に着脱可能に結合されるアッパ軸受部とからなり、前記吸気スラスト受け部は前記特定吸気ジャーナル軸受部の特定吸気アッパ軸受部と一体成形され、前記特定吸気ジャーナル軸受部の特定吸気ロア軸受部には前記吸気スラスト受け部に対向する位置に前記吸気カム軸に設けられた吸気スラスト当接部のための潤滑用油溜が形成され、前記排気スラスト受け部は前記特定排気ジャーナル軸受部の特定排気アッパ軸受部と一体成形され、特定排気ロア軸受部の前記排気スラスト受け部に対向する位置には前記排気カム軸に設けられた排気スラスト当接部のための潤滑用油溜が形成され、前記特定吸気アッパ軸受部は、前記吸気カム軸を前記カムホルダに組み付けるための吸気予備締結ボルトにより前記特定吸気ロア軸受部と締結され、前記特定排気アッパ軸受部は、前記排気カム軸を前記カムホルダに組み付けるための排気予備締結ボルトにより前記特定排気ロア軸受部と締結されることを特徴とする請求項１ないし請求項３のいずれか１項記載の内燃機関。Each journal bearing portion includes a lower bearing portion that is detachably coupled to a cylinder head of the internal combustion engine, and an upper bearing portion that is detachably coupled to the lower bearing portion, and the intake thrust receiving portion is An intake thrust which is integrally formed with a specific intake upper bearing portion of the specific intake journal bearing portion and is provided on the intake camshaft at a position facing the intake thrust receiving portion in the specific intake lower bearing portion of the specific intake journal bearing portion A lubricating oil reservoir is formed for the abutment portion, and the exhaust thrust receiving portion is integrally formed with the specific exhaust upper bearing portion of the specific exhaust journal bearing portion and faces the exhaust thrust receiving portion of the specific exhaust lower bearing portion A lubricating oil sump for an exhaust thrust abutting portion provided on the exhaust camshaft is formed at a position where the specific intake upper bearing portion is provided. The specific intake lower bearing portion is fastened to the specific intake lower bearing portion by an intake preliminary fastening bolt for assembling the shaft to the cam holder, and the specific exhaust upper bearing portion is connected to the specific exhaust by an exhaust preliminary fastening bolt for assembling the exhaust cam shaft to the cam holder. The internal combustion engine according to any one of claims 1 to 3, wherein the internal combustion engine is fastened to a lower bearing portion. 前記吸気予備締結ボルトは、前記吸気スラスト受け部の直交方向での端部に位置し、前記排気予備締結ボルトは、前記排気スラスト受け部の直交方向での端部に位置することを特徴とする請求項４記載の内燃機関。The intake preliminary fastening bolt is positioned at an end portion of the intake thrust receiving portion in the orthogonal direction, and the exhaust preliminary fastening bolt is positioned at an end portion of the exhaust thrust receiving portion in the orthogonal direction. The internal combustion engine according to claim 4. 前記特定吸気ジャーナル軸受部および前記排気スラスト受け部は、軸方向において相互に重なる領域を有するように配置され、前記特定排気ジャーナル軸受部および前記吸気スラスト受け部は、軸方向において相互いに重なる領域を有するように配置されていることを特徴とする請求項１ないし請求項５のいずれか１項記載の内燃機関。The specific intake journal bearing portion and the exhaust thrust receiving portion are arranged so as to have a region overlapping each other in the axial direction, and the specific exhaust journal bearing portion and the intake thrust receiving portion have a region overlapping each other in the axial direction. The internal combustion engine according to any one of claims 1 to 5, wherein the internal combustion engine is arranged so as to have.
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