JP5493677B2 - Variable valve gear - Google Patents

Variable valve gear Download PDF

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JP5493677B2
JP5493677B2 JP2009237455A JP2009237455A JP5493677B2 JP 5493677 B2 JP5493677 B2 JP 5493677B2 JP 2009237455 A JP2009237455 A JP 2009237455A JP 2009237455 A JP2009237455 A JP 2009237455A JP 5493677 B2 JP5493677 B2 JP 5493677B2
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cam
surface portion
valve
flat surface
intake
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JP2011085049A (en
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幸作 山内
勇人 滝
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Suzuki Motor Co Ltd
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Description

本発明は、自動二輪車または自動車などのエンジンの運転状況（例えばエンジン回転数など）に応じてバルブリフト特性を変更可能な可変動弁装置に関する。   The present invention relates to a variable valve gear that can change valve lift characteristics in accordance with the operating conditions (for example, engine speed) of an engine such as a motorcycle or an automobile.

自動二輪車または自動車のエンジンでは、以前より燃焼効率の向上を図るべく、種々の工夫あるいは提案等がなされている。バルブの開閉タイミングをずらして行なう可変位相方式に始まり、カムの切換によるバルブリフトの可変制御等が採用されてきた。尚、このカム切換方式は、低速用と高速用の２つのカムを用意し、エンジンの出力に応じて作用角の小さなカムから大きなカムに切り換えるものである。   Various ideas or proposals have been made for motorcycles or automobile engines in order to improve combustion efficiency. Beginning with a variable phase system in which the valve opening and closing timing is shifted, variable control of the valve lift by switching the cam has been adopted. In this cam switching system, two cams for low speed and high speed are prepared, and a cam with a small operating angle is switched to a large cam according to the output of the engine.

更に、近年では可変位相とカム切換を組み合せたものが提案され、その後、作用角及びバルブリフト量を連続可変する３次元カム（立体形状カム）を使用する方式が提案されている。例えば、特許文献１に記載の動弁装置のように、３次元カムを軸方向にスライドさせることにより、バルブリフト量及び作用角を無段階に変化させて、燃費及びトルクの向上、並びに有害排ガスの低減を図ったものが提案されている。   Further, in recent years, a combination of variable phase and cam switching has been proposed, and thereafter a method using a three-dimensional cam (three-dimensional cam) that continuously varies the operating angle and valve lift amount has been proposed. For example, as in the valve operating device described in Patent Document 1, by sliding the three-dimensional cam in the axial direction, the valve lift amount and the operating angle are changed steplessly, thereby improving fuel consumption and torque, and harmful exhaust gas. The thing which aimed at reduction of this is proposed.

特開２００３−３８１１号公報JP 2003-3811 A

ところが、上記公報記載の動弁装置では、カムとタペット（バルブリフタ）とが点接触するものであるため、耐久性を向上させるためにはタペットを大径化させる必要がある。この結果、タペットの重量が増大して、エンジンの高速回転化（例えば１５０００ｒｐｍ）に好適に対応することができない恐れがある。   However, in the valve gear described in the above publication, since the cam and tappet (valve lifter) are in point contact, it is necessary to increase the diameter of the tappet in order to improve durability. As a result, the weight of the tappet increases, and there is a possibility that it is not possible to appropriately cope with the high speed rotation of the engine (for example, 15000 rpm).

本発明の目的は、上述の事情を考慮してなされたものであり、カムのカムプロフィルに追従してバルブを進退動作させるバルブリフタの重量を低減して、エンジンの高速回転化に好適に対応できる可変動弁装置を提供することにある。   The object of the present invention has been made in consideration of the above-mentioned circumstances, and can reduce the weight of the valve lifter that moves the valve forward and backward following the cam profile of the cam, and can suitably cope with high-speed engine rotation. The object is to provide a variable valve gear.

本発明は、シリンダヘッドに回転自在に軸支されたカムシャフトと、このカムシャフトに回転一体で且つ軸方向に移動可能に設けられたカムと、このカムのカムプロフィルに追従してバルブを進退動作させるバルブリフタと、を備えた可変動弁装置であって、前記カムは、軸方向一定区間に亘りカムプロフィルが変化しない平坦面部と、軸方向一定区間に亘りカムプロフィルが連続的に無段階に変化する傾斜面部とが交互に形成された立体形状カムであり、前記平坦面部は少なくとも２箇所に設けられ、それぞれが互いに異なるバルブリフト特性を有するカムプロフィルに形成され、前記バルブリフタは、前記カムの平坦面部に摺接して転動する円筒面状部と、前記カムの傾斜面部に摺接して転動する球面状部とを設けたローラ部を備えるとともに、このローラ部を含むバルブリフタは、前記バルブの軸方向にのみ移動可能にバルブリフタホルダによって浮動保持され、このローラ部の前記円筒面状部は、前記カムの前記平坦面部の任意の一の平坦面部と線接触することでその平坦面部のバルブリフト特性に従って前記バルブリフタを作動させる一方、前記カムが回転しつつ軸方向に移動することで、前記ローラ部の前記円筒面状部が前記カムの前記平坦面部の任意の一の平坦面部と線接触した状態から、前記ローラ部の前記球面状部が、前記カムの平坦面部と平坦面部との間に形成した前記傾斜面部に点接触した状態に移行し、前記カムの任意の一の平坦面部から隣接する他の平坦面部に切り換えて前記カムの前記バルブリフト特性を変更するように構成したことを特徴とするものである。 The present invention includes a camshaft rotatably supported by a cylinder head, a cam that is rotatably integrated with the camshaft and movable in the axial direction, and a valve that moves forward and backward following the cam profile of the cam. A variable valve device having a valve lifter to be operated, wherein the cam has a flat surface portion where the cam profile does not change over a constant axial direction, and the cam profile continuously and steplessly over a constant axial direction. The three-dimensionally shaped cams alternately formed with the changing inclined surface portions, the flat surface portions are provided in at least two locations, each formed in a cam profile having different valve lift characteristics, and the valve lifter a cylindrical surface portion that rolls in sliding contact with the flat surface portion and in sliding contact with the inclined surface of the cam Ru provided with a roller portion provided with a spherical portion that rolls Moni, valve lifter including the roller portion, the movable valve lifter holder only in the axial direction of the valve is floatingly retained, the cylindrical surface portion of the roller portion, any one of the flat surface portion of the cam The valve lifter is operated according to the valve lift characteristic of the flat surface portion by making line contact with the flat surface portion, while the cylindrical surface portion of the roller portion is moved in the axial direction while the cam rotates. From the state in which the flat surface portion is in line contact with any one flat surface portion, the spherical portion of the roller portion is in point contact with the inclined surface portion formed between the flat surface portion and the flat surface portion of the cam. migration was also characterized in that switching to the other flat surface portion adjacent from any one of a flat surface portion of the cam is configured so as to change the valve lift characteristics of the cam It is.

本発明によれば、カムの平坦面部とバルブリフタのローラ部の円筒面状部とが線接触するので、バルブリフタのローラ部の耐久性が向上し、このローラ部を小型化できる。このため、このローラ部を含むバルブリフタの重量が低減して、エンジンの高速回転化に好適に対応できる。   According to the present invention, since the flat surface portion of the cam and the cylindrical surface portion of the roller portion of the valve lifter are in line contact, the durability of the roller portion of the valve lifter is improved and the roller portion can be reduced in size. For this reason, the weight of the valve lifter including this roller portion is reduced, and it is possible to suitably cope with the high speed rotation of the engine.

本発明に係る可変動弁装置の一実施形態が適用されたエンジンを搭載する自動二輪車を示す左側面図。1 is a left side view showing a motorcycle equipped with an engine to which an embodiment of a variable valve operating apparatus according to the present invention is applied. 図１のエンジンのシリンダヘッド内に装備された可変動弁装置を示す断面図。Sectional drawing which shows the variable valve gear equipped in the cylinder head of the engine of FIG. 図２のＩＩＩ−ＩＩＩ線に沿う断面図。Sectional drawing which follows the III-III line | wire of FIG. 図２の一部（吸気バルブ及びバルブリフタ周り）を拡大して示す断面図。Sectional drawing which expands and shows a part of FIG. 2 (intake valve and valve lifter periphery). 図４のＶ矢視図。The V arrow line view of FIG. 図２及び図３の吸気カム及び排気カムを示す正面図。The front view which shows the intake cam and exhaust cam of FIG.2 and FIG.3. 図６の吸気カムのバルブリフト特性を示すグラフ。The graph which shows the valve lift characteristic of the intake cam of FIG. 図４の吸気カムの一部を拡大して示す拡大図。The enlarged view which expands and shows a part of intake cam of FIG. 吸気カムの軸方向移動量とバルブリフタのリフト量との関係を示すグラフ。The graph which shows the relationship between the axial direction movement amount of an intake cam, and the lift amount of a valve lifter. バルブリフト特性変更時におけるバルブリフトカーブの変化を示すグラフ。The graph which shows the change of the valve lift curve at the time of valve lift characteristic change. 圧縮自着火を生じさせる場合の吸気カムと排気カムのバルブリフト特性を示すグラフ。The graph which shows the valve lift characteristic of the intake cam in the case of producing compression self-ignition, and an exhaust cam.

以下、本発明を実施するための最良の形態を、図面に基づき説明する。   The best mode for carrying out the present invention will be described below with reference to the drawings.

図１は、本発明に係る可変動弁装置の一実施形態が適用されたエンジンを搭載する自動二輪車を示す左側面図である。尚、本発明は、自動二輪車あるいは四輪自動車に搭載される各種のガソリンエンジンに対して有効に適用可能であり、この実施形態では、図１に示す自動二輪車のエンジンに適用された例を示す。   FIG. 1 is a left side view showing a motorcycle equipped with an engine to which an embodiment of a variable valve operating apparatus according to the present invention is applied. The present invention can be effectively applied to various gasoline engines mounted on a motorcycle or a four-wheeled vehicle, and in this embodiment, an example applied to the motorcycle engine shown in FIG. 1 is shown. .

まず、自動二輪車１０の全体構成を説明する。図１において、鋼製あるいはアルミニウム合金材でなる車体フレーム１１は前部にヘッドパイプ１２を備え、このヘッドパイプ１２にフロントフォーク１３が左右に旋回可能に支持される。フロントフォーク１３の上端にはハンドルバー１４が固定され、このハンドルバー１４の両端にグリップ１５（後述のアクセルグリップを含む）が設けられる。フロントフォーク１３の下部には、前輪１６が回転可能に支持されると共に、前輪１６の上部を覆うようにフロントフェンダ１７が固定される。前輪１６は、前輪１６と一体回転するブレーキディスク１８を備える。   First, the overall configuration of the motorcycle 10 will be described. In FIG. 1, a vehicle body frame 11 made of steel or aluminum alloy is provided with a head pipe 12 at the front portion, and a front fork 13 is supported on the head pipe 12 so as to be able to turn left and right. A handle bar 14 is fixed to the upper end of the front fork 13, and grips 15 (including an accelerator grip described later) are provided at both ends of the handle bar 14. A front fender 17 is fixed to the lower portion of the front fork 13 so as to rotatably support the front wheel 16 and cover the upper portion of the front wheel 16. The front wheel 16 includes a brake disk 18 that rotates integrally with the front wheel 16.

車体フレーム１１の後部には、スイングアーム１９が揺動可能に設けられると共に、車体フレーム１１とスイングアーム１９の間にリヤショックアブソーバ２０が装架される。スイングアーム１９の後端には後輪２１が回転可能に支持され、この後輪２１は、チェーン２２が巻回されたドリブンスプロケット２３により回転駆動される。   A swing arm 19 is swingably provided at the rear of the body frame 11, and a rear shock absorber 20 is mounted between the body frame 11 and the swing arm 19. A rear wheel 21 is rotatably supported at the rear end of the swing arm 19, and the rear wheel 21 is rotationally driven by a driven sprocket 23 around which a chain 22 is wound.

車体フレーム１１に搭載されたエンジン２４（実線部）には、エアクリーナ２５に結合する吸気管２６及びスロットルボディ（不図示）を経て混合気が供給されると共に、燃焼後の排気が排気管２７を通って排出される。また、エンジン２４の上方には燃料タンク２８が搭載され、この燃料タンク２８の後方にシート２９及びシートカウル３０が連設される。   The engine 24 (solid line portion) mounted on the vehicle body frame 11 is supplied with an air-fuel mixture via an intake pipe 26 and a throttle body (not shown) coupled to an air cleaner 25, and exhaust gas after combustion passes through an exhaust pipe 27. Discharged through. A fuel tank 28 is mounted above the engine 24, and a seat 29 and a seat cowl 30 are connected to the rear of the fuel tank 28.

図１において、符号３１はヘッドランプ、符号３２はスピードメータ、タコメータあるいは各種インジケータランプ等を含むメータユニット、符号３３は、ステー３４を介してハンドルバー１４に支持されるバックミラーである。また、車体フレーム１１の下部にはメインスタンド３５が揺動自在に取付けられる。   In FIG. 1, reference numeral 31 denotes a headlamp, reference numeral 32 denotes a meter unit including a speedometer, tachometer, or various indicator lamps, and reference numeral 33 denotes a rearview mirror supported by the handlebar 14 via a stay 34. A main stand 35 is swingably attached to the lower part of the body frame 11.

ここで、車体フレーム１１は、前部に設けられたヘッドパイプ１２から後斜め下方へ向けて延設され、エンジン２４の下方を包むように湾曲した後、スイングアーム１９の軸支部であるピボット３８を形成し、更に燃料タンク２８及びシート２９を支持する。この車体フレーム１１には、フロントフェンダ１７との干渉を避けるべく車体フレーム１１と平行にラジエータ３６が設けられる。また、ラジエータ３６から車体フレーム１１に沿って冷却水ホース３７が配設され、この冷却水ホース３７は排気管２７と干渉することなくエンジン２４に連通している。   Here, the vehicle body frame 11 extends obliquely downward and rearward from the head pipe 12 provided at the front part, and after bending so as to wrap the lower part of the engine 24, a pivot 38 which is a shaft support part of the swing arm 19 is provided. Further, the fuel tank 28 and the seat 29 are supported. The vehicle body frame 11 is provided with a radiator 36 in parallel with the vehicle body frame 11 to avoid interference with the front fender 17. A cooling water hose 37 is disposed from the radiator 36 along the vehicle body frame 11, and the cooling water hose 37 communicates with the engine 24 without interfering with the exhaust pipe 27.

前記エンジン２４は、本実施の形態では単気筒エンジンであり、吸気側（ＩＮ）及び排気側（ＥＸ）にそれぞれ２つのバルブ（つまり４バルブ）を有している。シリンダ１内にはピストン（不図示）が上下方向に往復運動し、このシリンダ１の上部にシリンダヘッド２が配置される。図２及び図３に示すように、このシリンダヘッド２及びヘッドカバー３内に可変動弁装置４０が収容される。   The engine 24 is a single cylinder engine in the present embodiment, and has two valves (that is, four valves) on the intake side (IN) and the exhaust side (EX). A piston (not shown) reciprocates in the cylinder 1 in the vertical direction, and a cylinder head 2 is disposed above the cylinder 1. As shown in FIGS. 2 and 3, the variable valve gear 40 is accommodated in the cylinder head 2 and the head cover 3.

可変動弁装置４０は、水平方向に配置される吸気側カム・カムシャフトユニット４１、排気側カム・カムシャフトユニット４２と、吸気側カム・カムシャフトユニット４１、排気側カム・カムシャフトユニット４２のそれぞれの下方に配置される吸気側バルブリフタユニット４３、排気側バルブリフタユニット（不図示）と、吸気、排気をそれぞれ制御する吸気バルブユニット４５、排気バルブユニット（不図示）と、アクセル開度に応じて吸気カム４８及び排気カム４９を変位（軸方向移動）させるアクセルシャフトユニット４７と、を有して構成される。   The variable valve device 40 includes an intake side cam / camshaft unit 41, an exhaust side cam / camshaft unit 42, an intake side cam / camshaft unit 41, and an exhaust side cam / camshaft unit 42 arranged in the horizontal direction. An intake side valve lifter unit 43, an exhaust side valve lifter unit (not shown), an intake valve unit 45, an exhaust valve unit (not shown) for controlling intake and exhaust, respectively, and an accelerator opening degree And an accelerator shaft unit 47 that displaces (moves in the axial direction) the intake cam 48 and the exhaust cam 49.

吸気側カム・カムシャフトユニット４１は、シリンダヘッド２に軸受５０を介して回転自在に軸支された吸気側カムシャフト５１に、吸気カム４８がキー５２やスプライン等を用いて、回転一体で且つ軸方向に移動（スライド）可能に設けられたものであり、吸気側カムシャフト５１の一端に吸気側ドリブンスプロケット５３が回転一体に取り付けられている。また、排気側カム・カムシャフトユニット４２も、吸気側カム・カムシャフトユニット４１と同様に構成され、シリンダヘッド２に軸受５０を介して回転自在に軸支された排気側カムシャフト５４に、排気カム４９がキー５２やスプライン等を用いて、回転一体で且つ軸方向に移動（スライド）可能に設けられたものであり、排気側カムシャフト５４の一端に排気側ドリブンスプロケット５５が回転一体に取り付けられている。   The intake side cam / camshaft unit 41 is integrated with an intake side camshaft 51 rotatably supported by a cylinder head 2 via a bearing 50, and an intake cam 48 is integrally rotated using a key 52, a spline, and the like. An intake side driven sprocket 53 is rotatably attached to one end of the intake side camshaft 51 so as to be movable (slidable) in the axial direction. Further, the exhaust side cam / camshaft unit 42 is also configured in the same manner as the intake side cam / camshaft unit 41, and the exhaust side camshaft 54 rotatably supported by the cylinder head 2 via a bearing 50 is connected to the exhaust side camshaft 54. A cam 49 is provided so as to be rotatable and axially movable (slidable) using a key 52 or a spline, and an exhaust-side driven sprocket 55 is attached to one end of an exhaust-side camshaft 54 so as to be integrally rotated. It has been.

吸気側ドリブンスプロケット５３と、排気側ドリブンスプロケット５５と、図示しないクランクシャフトに回転一体に取り付けられたカムドライブスプロケット（不図示）とにカムチェーン５６が巻き掛けられる。このカムチェーン５６等を介して、吸気側カムシャフト５１及び排気側カムシャフト５４は、クランクシャフトにより回転駆動され、それぞれ吸気カム４８、排気カム４９を回転駆動させる。尚、図２及び図３中の符号６１は、吸気側カムシャフト５１、排気側カムシャフト５４にそれぞれ形成された潤滑油路を示す。   A cam chain 56 is wound around an intake-side driven sprocket 53, an exhaust-side driven sprocket 55, and a cam drive sprocket (not shown) that is rotatably attached to a crankshaft (not shown). The intake side camshaft 51 and the exhaust side camshaft 54 are rotationally driven by the crankshaft via the cam chain 56 and the like, and the intake cam 48 and the exhaust cam 49 are rotationally driven, respectively. 2 and 3 indicate the lubricating oil passages formed in the intake side camshaft 51 and the exhaust side camshaft 54, respectively.

ここで、吸気カム４８は、後に詳説するが、図３に示すように、軸方向一定区間に亘りカムプロフィルが変化しない平坦面部５７と、軸方向一定区間に亘りカムプロフィルが連続的に無段階に変化する傾斜面部５８とが交互に形成された立体形状カムである。平坦面部５７は、少なくとも２個（本実施の形態では３個）設けられ、それぞれが互いに異なるバルブリフト特性を有するカムプロフィルに形成される。平坦面部５７は、本実施の形態では低リフト平坦面部５７Ａ、中リフト平坦面部５７Ｂ、高リフト平坦面部５７Ｃであり、傾斜面部５８は、本実施の形態では第１傾斜面部５８Ａ、第２傾斜面部５８Ｂである。   Here, the intake cam 48 will be described in detail later. As shown in FIG. 3, the flat surface portion 57 in which the cam profile does not change over the constant axial direction and the cam profile continuously stepless over the constant axial direction. It is a three-dimensional cam in which the inclined surface portions 58 that change into the shape are alternately formed. At least two flat surface portions 57 (three in the present embodiment) are provided, and each of the flat surface portions 57 is formed into a cam profile having different valve lift characteristics. The flat surface portion 57 is a low lift flat surface portion 57A, a middle lift flat surface portion 57B, and a high lift flat surface portion 57C in the present embodiment, and the inclined surface portion 58 is a first inclined surface portion 58A and a second inclined surface portion in the present embodiment. 58B.

また、排気カム４９も後に詳説するが、軸方向一定区間に亘りカムプロフィルが変化しない平坦面部５９と、軸方向一定区間に亘りカムプロフィルが連続的に無段階に変化する傾斜面部６０とが交互に形成された立体形状カムである。平坦面部５９は、少なくとも２個（本実施の形態では３個）設けられ、それぞれが互いに異なるバルブリフト特性を有するカムプロフィルに形成される。平坦面部５９は、本実施の形態では低リフト平坦面部５９Ａ、中リフト平坦面部５９Ｂ、高リフト平坦面部５９Ｃであり、傾斜面部６０は、本実施の形態では第１傾斜面部６０Ａ、第２傾斜面部６０Ｂである。   The exhaust cam 49 will also be described in detail later, but a flat surface portion 59 where the cam profile does not change over a constant axial direction and an inclined surface portion 60 where the cam profile changes continuously and continuously over a constant axial direction are alternated. It is the three-dimensional shape cam formed in this. At least two flat surface portions 59 (three in the present embodiment) are provided, and each is formed into a cam profile having different valve lift characteristics. The flat surface portion 59 is a low lift flat surface portion 59A, a middle lift flat surface portion 59B, and a high lift flat surface portion 59C in the present embodiment, and the inclined surface portion 60 is a first inclined surface portion 60A and a second inclined surface portion in the present embodiment. 60B.

前記吸気側バルブリフタユニット４３は、図２に示すように、吸気カム４８のカムプロフィルに追従して吸気バルブ６２を進退動作させるバルブリフタ６４と、このバルブリフタ６４を収容して保持するバルブリフタホルダ６５とを有してなる。バルブリフタ６４は、ローラ部６６と、このローラ部６６を回転自在に支持する芯材６７とを備える。また、図示しない排気バルブリフタユニットは、バルブリフタ、バルブリフタホルダ、ローラ部及び芯材を有して吸気バルブリフタユニット４３と同様に構成され、このうちのバルブリフタが、排気カム４９のカムプロフィルに追従して排気バルブ（不図示）を進退動作させる。従って、以下、吸気バルブリフタユニット４３について説明する。 As shown in FIG. 2, the intake valve lifter unit 43 includes a valve lifter 64 that moves the intake valve 62 forward and backward following the cam profile of the intake cam 48, and a valve lifter holder 65 that houses and holds the valve lifter 64. Have. The valve lifter 64 includes a roller portion 66 and a core member 67 that rotatably supports the roller portion 66. An exhaust valve lifter unit (not shown) includes a valve lifter , a valve lifter holder , a roller portion, and a core member , and is configured in the same manner as the intake valve lifter unit 43. Among these, the valve lifter follows the cam profile of the exhaust cam 49 and exhausts. A valve (not shown) is moved back and forth. Accordingly, the intake valve lifter unit 43 will be described below.

図４及び図５に示すように、バルブリフタ６４のローラ部６６は、ドーナツ形状に形成され、内周面と芯材６７の基部６７Ａとの間に、針状コロなどのベアリング６８が介在されることで、芯材６７に対し回転自在に支持される。このため、ローラ部６６は、吸気カム４８（排気カム４９）のカムプロフィルに摺接して転動する。このローラ部６６の摺接面である外周面には、吸気カム４８の平坦面部５７（排気カム４９の平坦面部５９）に線接触可能な円筒面状部６９と、吸気カム４８の傾斜面部５８（排気カム４９の傾斜面部６０）に点接触可能な球面状部７０とを備える。   As shown in FIGS. 4 and 5, the roller portion 66 of the valve lifter 64 is formed in a donut shape, and a bearing 68 such as a needle roller is interposed between the inner peripheral surface and the base portion 67 </ b> A of the core material 67. As a result, the core material 67 is supported rotatably. For this reason, the roller part 66 rolls in sliding contact with the cam profile of the intake cam 48 (exhaust cam 49). On the outer peripheral surface, which is a sliding contact surface of the roller portion 66, a cylindrical surface portion 69 that can come into line contact with the flat surface portion 57 of the intake cam 48 (the flat surface portion 59 of the exhaust cam 49), and an inclined surface portion 58 of the intake cam 48. And a spherical portion 70 that can be brought into point contact with the inclined surface portion 60 of the exhaust cam 49.

バルブリフタ６４の芯材６７は、長手方向中央に位置する前記基部６７Ａと、この基部６７Ａの両側から延びるアーム部６７Ｂと、各アーム部６７Ｂの端部に設けられ、吸気バルブ６２（排気バルブ）のバルブステム７５のステム頂面に当接する押圧ねじ部６７Ｃとを備えてなる。押圧ねじ部６７Ｃと吸気バルブ６２（排気バルブ）の前記ステム頂面とのクリアランス調整は、押圧ねじ部６７Ｃの進退移動によってなされ、ロックナット７１が押圧ねじ部６７Ｃの位置を規制する。ローラ部６６及び芯材６７を備えるバルブリフタ６４では、１個のローラ部６６によって押圧ねじ部６７Ｃを介し、２本の吸気バルブ６２（排気バルブ）を同時に進退動作させることが可能になる。   The core 67 of the valve lifter 64 is provided at the base 67A located at the center in the longitudinal direction, the arm 67B extending from both sides of the base 67A, and the end of each arm 67B, and the intake valve 62 (exhaust valve). And a pressing screw portion 67 </ b> C that comes into contact with the stem top surface of the valve stem 75. The clearance between the pressing screw portion 67C and the stem top surface of the intake valve 62 (exhaust valve) is adjusted by the forward and backward movement of the pressing screw portion 67C, and the lock nut 71 regulates the position of the pressing screw portion 67C. In the valve lifter 64 including the roller portion 66 and the core member 67, the two intake valves 62 (exhaust valves) can be simultaneously advanced and retracted by the single roller portion 66 via the pressing screw portion 67C.

バルブリフタホルダ６５は、シリンダヘッド２の適所にボルト７２を用いて固定され、内側空間に前記バルブリフタ６４が収容される。このバルブリフタホルダ６５の内側には、ローラ規制面７３及びアーム規制面７４が形成される。ローラ規制面７３は、バルブリフタ６４のローラ部６６の側面に当接して、このローラ部６６を位置規制する。また、アーム規制面７４は、バルブリフタ６４の芯材６７におけるアーム部６７Ｂに当接して、このアーム部６７Ｂを位置規制する。これにより、ローラ部６６を含むバルブリフタ６４は、吸気バルブ６２（排気バルブ）の軸方向にのみ移動可能にバルブリフタホルダ６５によって浮動保持される。   The valve lifter holder 65 is fixed at an appropriate position of the cylinder head 2 with a bolt 72, and the valve lifter 64 is accommodated in the inner space. A roller restricting surface 73 and an arm restricting surface 74 are formed inside the valve lifter holder 65. The roller restricting surface 73 is in contact with the side surface of the roller portion 66 of the valve lifter 64 and restricts the position of the roller portion 66. The arm restricting surface 74 abuts on the arm portion 67B of the core member 67 of the valve lifter 64 to restrict the position of the arm portion 67B. Thus, the valve lifter 64 including the roller portion 66 is floated and held by the valve lifter holder 65 so as to be movable only in the axial direction of the intake valve 62 (exhaust valve).

前記吸気バルブユニット４５は、図２に示すように、それぞれのバルブステム７５が、シリンダヘッド２に設けられたバルブガイド７６によってガイドされる２本の吸気バルブ６２を備える。各吸気バルブ６２は、バルブステム７５の端部に設けられたバルブリテーナ７７と、シリンダヘッド２に設けられたスプリングシート７８との間にバルブスプリング７９が装着される。前記排気バルブユニットは、吸気バルブ６２が排気バルブに置き換えられた点を除き、吸気バルブユニット４５と同様に構成される。   As shown in FIG. 2, the intake valve unit 45 includes two intake valves 62 in which each valve stem 75 is guided by a valve guide 76 provided in the cylinder head 2. Each intake valve 62 is provided with a valve spring 79 between a valve retainer 77 provided at the end of the valve stem 75 and a spring seat 78 provided on the cylinder head 2. The exhaust valve unit is configured in the same manner as the intake valve unit 45 except that the intake valve 62 is replaced with an exhaust valve.

前記アクセルシャフトユニット４７は、図３に示すように、吸気側カムシャフト５１と排気側カムシャフト５４との間に、これらのカムシャフト５１及び５４に平行に配置されたアクセルシャフト８０と、このアクセルシャフト８０に固着されると共に吸気カム４８に連結される吸気側アクセルフォーク８１と、アクセルシャフト８０に固着されると共に排気カム４９に連結される排気側アクセルフォーク８２と、を備えて構成される。アクセルシャフト８０は、その軸方向に移動可能にシリンダヘッド２に支持される。このアクセルシャフト８０の一端側には、例えば台形ねじ８３や捩りスプライン等を介してドリブンギア８４が係合される。このドリブンギア８４は、複数の軸受８５によって回転自在にシリンダヘッド２に支持され、図示しない減速ギアを介してアクセルモータ（不図示）に連結される。   As shown in FIG. 3, the accelerator shaft unit 47 includes an accelerator shaft 80 disposed between the intake side camshaft 51 and the exhaust side camshaft 54 in parallel with the camshafts 51 and 54, and the accelerator shaft. An intake-side accelerator fork 81 fixed to the shaft 80 and connected to the intake cam 48 and an exhaust-side accelerator fork 82 fixed to the accelerator shaft 80 and connected to the exhaust cam 49 are configured. The accelerator shaft 80 is supported by the cylinder head 2 so as to be movable in the axial direction. A driven gear 84 is engaged with one end of the accelerator shaft 80 via, for example, a trapezoidal screw 83 or a torsion spline. The driven gear 84 is rotatably supported by the cylinder head 2 by a plurality of bearings 85 and is connected to an accelerator motor (not shown) via a reduction gear (not shown).

アクセルモータは例えばヘッドカバー３に設置され、アクセル変化（アクセル開度や加速・減速方向など）に対応してその出力軸が回転するものである。アクセルモータの出力軸の回転は、減速ギア、ドリブンギア８４及び台形ねじ８３を介してアクセルシャフト８０の軸方向移動に変換される。尚、本実施の形態の自動二輪車では、アクセルグリップの回転操作量をアクセルモータの出力軸の回転量に対応させてもよく、より詳細には、アクセルグリップの回転操作量(開度)の他に、変速段、車両速度、気圧、気温及びアクセルグリップ開速度等によりアクセルシャフト８０の軸方向移動量を決定してもよい。   The accelerator motor is installed on the head cover 3, for example, and its output shaft rotates in response to accelerator changes (accelerator opening, acceleration / deceleration direction, etc.). The rotation of the output shaft of the accelerator motor is converted into the axial movement of the accelerator shaft 80 via the reduction gear, the driven gear 84 and the trapezoidal screw 83. In the motorcycle according to the present embodiment, the amount of rotation of the accelerator grip may correspond to the amount of rotation of the output shaft of the accelerator motor. More specifically, in addition to the amount of rotation operation (opening) of the accelerator grip. Further, the axial movement amount of the accelerator shaft 80 may be determined based on the gear position, the vehicle speed, the atmospheric pressure, the air temperature, the accelerator grip opening speed, and the like.

吸気側アクセルフォーク８１は、ベアリング８６を介して吸気カム４８の端部に回転自在に装着されたフォークガイド８７に係合される。また、排気側アクセルフォーク８２は、ベアリング８６を介して排気カム４９の端部に回転自在に装着されたフォークガイド８７に係合される。これにより、吸気側アクセルフォーク８１の軸方向移動に連動または同期して、吸気カム４８が吸気側カムシャフト５１に沿って軸方向に移動し、且つ、排気カム４９が排気側カムシャフト５４に沿って軸方向に移動する。   The intake side accelerator fork 81 is engaged via a bearing 86 with a fork guide 87 that is rotatably attached to the end of the intake cam 48. Further, the exhaust-side accelerator fork 82 is engaged with a fork guide 87 that is rotatably attached to an end portion of the exhaust cam 49 via a bearing 86. As a result, the intake cam 48 moves in the axial direction along the intake side camshaft 51 in conjunction with or in synchronization with the axial movement of the intake side accelerator fork 81, and the exhaust cam 49 moves along the exhaust side camshaft 54. To move in the axial direction.

ところで、図３及び図６に示すように、前記吸気カム４８は、前述の如く低リフト平坦面部５７Ａ、第１傾斜面部５８Ａ、中リフト平坦面部５７Ｂ、第２傾斜面部５８Ｂ、高リフト平坦面部５７Ｃが順次形成された立体形状カムである。また、前記排気カム４９は、低リフト平坦面部５９Ａ、第１傾斜面部６０Ａ、中リフト平坦面部５９Ｂ、第２傾斜面部６０Ｂ、高リフト平坦面部５９Ｃが順次形成された立体形状カムである。低リフト平坦面部５７Ａ及び５９Ａは、エンジン低速回転時に使用され、燃費及び有害排ガス低減に優れた特性を有する。中リフト平坦面部５７Ｂ及び５９Ｂは、エンジン中速回転時に使用され、最高トルクの発生に優れた特性を有する。高リフト平坦面部５７Ｃ及び５９Ｃは、エンジン高速回転時に使用され、最高出力の発生に優れた特性を有する。   As shown in FIGS. 3 and 6, the intake cam 48 includes the low lift flat surface portion 57A, the first inclined surface portion 58A, the middle lift flat surface portion 57B, the second inclined surface portion 58B, and the high lift flat surface portion 57C as described above. Are three-dimensionally shaped cams formed sequentially. The exhaust cam 49 is a three-dimensional cam in which a low lift flat surface portion 59A, a first inclined surface portion 60A, a middle lift flat surface portion 59B, a second inclined surface portion 60B, and a high lift flat surface portion 59C are sequentially formed. The low lift flat surface portions 57A and 59A are used at the time of engine low speed rotation, and have excellent characteristics in fuel consumption and reduction of harmful exhaust gas. The middle lift flat surface portions 57B and 59B are used during medium-speed rotation of the engine and have excellent characteristics for generating the maximum torque. The high lift flat surface portions 57C and 59C are used during high-speed rotation of the engine, and have excellent characteristics for generating the maximum output.

また、吸気カム４８において、低リフト平坦面部５７Ａのカムプロフィルは中リフト平坦面部５７Ｂのカムプロフィル内に収まり、この中リフト平坦面部５７Ｂのカムプロフィルは、高リフト平坦面部５７Ｃのカムプロフィル内に収まるよう形成されることが好ましい。また、排気カム４９において、低リフト平坦面部５９Ａのカムプロフィルは中リフト平坦面部５９Ｂ内に収まり、この中リフト平坦面部５９Ｂのカムプロフィルは、高リフト平坦面部５９Ｃのカムプロフィル内に収まるよう形成されることが好ましい。ここで、排気カム４９は、後述のバルブリフト特性が吸気カム４８と若干異なるものの、その他の点では吸気カム４８と同様に構成されるため、以下、主に吸気カム４８について説明する。   Further, in the intake cam 48, the cam profile of the low lift flat surface portion 57A is accommodated in the cam profile of the medium lift flat surface portion 57B, and the cam profile of the medium lift flat surface portion 57B is accommodated in the cam profile of the high lift flat surface portion 57C. It is preferable to be formed as described above. Further, in the exhaust cam 49, the cam profile of the low lift flat surface portion 59A is accommodated in the middle lift flat surface portion 59B, and the cam profile of the intermediate lift flat surface portion 59B is formed to be accommodated in the cam profile of the high lift flat surface portion 59C. It is preferable. Here, although the exhaust cam 49 has a valve lift characteristic that will be described later slightly different from that of the intake cam 48, the exhaust cam 49 is configured in the same manner as the intake cam 48 in other points. Therefore, the intake cam 48 will be mainly described below.

吸気カム４８の低リフト平坦面部５７Ａ、中リフト平坦面部５７Ｂ、高リフト平坦面部５７Ｃのバルブリフト特性（バルブリフト量、作用角、バルブタイミング）を図７に曲線（バルブリフトカーブ）Ａ、曲線（バルブリフトカーブ）Ｂ、曲線（バルブリフトカーブ）Ｃでそれぞれ示す。例えば、バルブリフト量は、低リフト平坦面部５７Ａが３．５ｍｍ、中リフト平坦面部５７Ｂが５．５ｍｍ、高リフト平坦面部５７Ｃが７．５ｍｍである。また、低リフト平坦面部５７Ａのバルブリフト量、作用角は、高リフト平坦面部５７Ｃのバルブリフト量、作用角のそれぞれの１／２程度に設定される。更に、使用頻度が高い低リフト平坦面部５７Ａによる最大加速度は、使用頻度の低い高リフト平坦面部５７Ｃによる最大加速度よりも低く設定されて、吸気カム４８の耐久性の向上が図られている。   The valve lift characteristics (valve lift amount, operating angle, valve timing) of the low lift flat surface portion 57A, the middle lift flat surface portion 57B, and the high lift flat surface portion 57C of the intake cam 48 are shown in FIG. A valve lift curve (B) and a curve (valve lift curve) C are shown respectively. For example, the valve lift amount is 3.5 mm for the low lift flat surface portion 57A, 5.5 mm for the medium lift flat surface portion 57B, and 7.5 mm for the high lift flat surface portion 57C. Further, the valve lift amount and working angle of the low lift flat surface portion 57A are set to about ½ of the valve lift amount and working angle of the high lift flat surface portion 57C. Furthermore, the maximum acceleration by the low lift flat surface portion 57A with high use frequency is set lower than the maximum acceleration by the high lift flat surface portion 57C with low use frequency, so that the durability of the intake cam 48 is improved.

図２、図４及び図８に示すように、吸気カム４８の低リフト平坦面部５７Ａ、中リフト平坦面部５７Ｂ、高リフト平坦面部５７Ｃのそれぞれが、バルブリフタ６４のローラ部６６における円筒面状部６９と線接触することで、各平坦面部５７Ａ、５７Ｂ、５７Ｃのバルブリフト特性に従ってバルブリフタ６４を介し吸気バルブ６２が進退動作される。このとき、吸気カム４８の低リフト平坦面部５７Ａ、中リフト平坦面部５７Ｂ、高リフト平坦面部５７Ｃのそれぞれの軸方向長さＬは、上記バルブリフタ６４のローラ部６６における円筒面状部６９の軸方向長さＬ０よりも長さΔＬだけ長く形成されている。例えば、軸方向長さＬ０が４．５ｍｍのとき、長さΔＬが０．２ｍｍに設定されて、平坦面部５７Ａ、５７Ｂ、５７Ｃの軸方向長さＬは４．７ｍｍに設定される。   As shown in FIGS. 2, 4, and 8, each of the low lift flat surface portion 57 </ b> A, the middle lift flat surface portion 57 </ b> B, and the high lift flat surface portion 57 </ b> C of the intake cam 48 is a cylindrical surface portion 69 in the roller portion 66 of the valve lifter 64. , The intake valve 62 is moved back and forth through the valve lifter 64 in accordance with the valve lift characteristics of the flat surface portions 57A, 57B, and 57C. At this time, the axial length L of each of the low lift flat surface portion 57A, the middle lift flat surface portion 57B and the high lift flat surface portion 57C of the intake cam 48 is the axial direction of the cylindrical surface portion 69 of the roller portion 66 of the valve lifter 64. The length ΔL is longer than the length L0. For example, when the axial length L0 is 4.5 mm, the length ΔL is set to 0.2 mm, and the axial length L of the flat surface portions 57A, 57B, and 57C is set to 4.7 mm.

図４及び図６に示すように、吸気カム４８には、高リフト平坦面部５７Ｃに隣接して、
少なくとも最高リフト付近に最高リフト部８８が形成されてもよい。この最高リフト部８８は、高リフト平坦面部５７Ｃを挟んで中リフト平坦面部５７Ｂと反対側に形成され、バルブリフタ６４におけるローラ部６６の球面状部７０に点接触する形状を呈し、高リフト平坦面部５７Ｃよりも高いリフト部とするのがよい。同様にして、排気カム４９には、高リフト平坦面部５９Ｃに隣接して、少なくとも最高リフト付近に最高リフト部９１（図６）が形成されてもよい。 As shown in FIGS. 4 and 6, the intake cam 48 is adjacent to the high lift flat surface portion 57C.
The highest lift portion 88 may be formed at least near the highest lift. The highest lift portion 88 is formed on the opposite side of the middle lift flat surface portion 57B across the high lift flat surface portion 57C, and has a shape that makes point contact with the spherical surface portion 70 of the roller portion 66 in the valve lifter 64. A lift part higher than 57C is preferable. Similarly, a maximum lift portion 91 (FIG. 6) may be formed in the exhaust cam 49 adjacent to the high lift flat surface portion 59C at least near the maximum lift.

図８に示すように、吸気カム４８のバルブリフト特性の変更は、吸気カム４８が軸方向へ移動することにより、バルブリフタ６４のローラ部６６の円筒面状部６９が吸気カム４８の任意の一の平坦面部５７（例えば低リフト平坦面部５７Ａ）への摺接から他の平坦面部５７（例えば中リフト平坦面部５７Ｂ）への摺接に切り換わることによってなされる。このバルブリフト特性を変更する際には、バルブリフタ６４のローラ部６６の球面状部７０が、吸気カム４８における上記両平坦面部５７間の傾斜面部５８（例えば第１傾斜面部５８Ａ）に点接触状態で摺接することで、吸気カム４８の軸方向移動がスムーズになされる。 As shown in FIG. 8, the valve lift characteristic of the intake cam 48 is changed by moving the intake cam 48 in the axial direction so that the cylindrical surface portion 69 of the roller portion 66 of the valve lifter 64 is in any one of the intake cams 48. This is done by switching from sliding contact to the flat surface portion 57 (for example, the low lift flat surface portion 57A) to sliding contact to another flat surface portion 57 (for example, the middle lift flat surface portion 57B). When changing the valve lift characteristic, the spherical surface portion 70 of the roller portion 66 of the valve lifter 64 is in point contact with the inclined surface portion 58 (for example, the first inclined surface portion 58A) between the two flat surface portions 57 of the intake cam 48. As a result, the intake cam 48 moves smoothly in the axial direction.

吸気カム４８の上記傾斜面部５８（図８では第１傾斜面部５８Ａ）は、前述の如くカムプロフィルが連続して無段階に変化するが、隣接する平坦面部５７との境界部分Ｍ１、Ｍ２に、傾斜面部５８の主要部分Ｍ０の軸方向勾配よりも緩やかな勾配を有する緩斜面部８９、９０を備える。図８には、緩斜面部８９及び９０を形成しない場合の傾斜面部５８（例えば第１傾斜面部５８Ａ）のカムプロフィルを破線で示す。   The inclined surface portion 58 (the first inclined surface portion 58A in FIG. 8) of the intake cam 48 has a cam profile continuously changing as described above, but at the boundary portions M1 and M2 with the adjacent flat surface portion 57, Slowly inclined surface portions 89 and 90 having a gentler gradient than the axial gradient of the main portion M0 of the inclined surface portion 58 are provided. In FIG. 8, the cam profile of the inclined surface portion 58 (for example, the first inclined surface portion 58A) when the gentle inclined surfaces 89 and 90 are not formed is indicated by a broken line.

バルブリフト特性を変更させるときの吸気カム４８の軸方向移動量とバルブリフタ６４のリフト量との関係を図９に示す。緩斜面部８９及び９０を形成しない場合の傾斜面部５８（例えば第１傾斜面部５８Ａ）では、図９の破線に示すように、吸気カム４８の軸方向移動開始と同時にバルブリフタ６４のリフト量（つまりバルブリフト量）が増大し始め、移動終了と同時にバルブリフタ６４のリフト量の増大も終了する。これに対し、緩斜面部８９及び９０が形成された傾斜面部５８（第１傾斜面部５８Ａ）では、図９の実線に示すように、バルブリフタ６４のリフト量（つまりバルブリフト量）は、吸気カム４８の軸方向移動開始時に直ちに増大せず、吸気カム４８の移動量の増加と共に徐々に増大し、また、吸気カム４８の軸方向移動終了前から増大量が徐々に減少する。   FIG. 9 shows the relationship between the axial movement amount of the intake cam 48 and the lift amount of the valve lifter 64 when changing the valve lift characteristic. In the inclined surface portion 58 (for example, the first inclined surface portion 58A) when the gentle inclined surface portions 89 and 90 are not formed, the lift amount of the valve lifter 64 (that is, as the intake cam 48 starts moving in the axial direction, as shown by the broken line in FIG. 9) The valve lift amount) starts to increase, and the lift amount of the valve lifter 64 also ends at the same time as the movement ends. On the other hand, in the inclined surface portion 58 (first inclined surface portion 58A) in which the gentle inclined surface portions 89 and 90 are formed, the lift amount (that is, the valve lift amount) of the valve lifter 64 is the intake cam as shown by the solid line in FIG. 48 does not increase immediately when the axial movement starts, but gradually increases as the amount of movement of the intake cam 48 increases, and the amount of increase gradually decreases before the end of the axial movement of the intake cam 48.

つまり、吸気カム４８の傾斜面部５８（例えば第１傾斜面部５８Ａ）に緩斜面部８９が形成されることで、傾斜面部５８におけるバルブリフタ６４のリフト方向の加速度が抑制
されて、吸気カム４８の傾斜面部５８とバルブリフタ６４のローラ部６６の球面状部７０との接触点における面圧を低減することができる。更に、吸気カム４８の傾斜面部５８（例えば第１傾斜面部５８Ａ）に緩斜面部９０が形成されることで、吸気カム４８の軸方向移動が終了に近づいた際のバルブリフタ６４のジャンプやバウンスを防止することができ、且つ、傾斜面部５８と球面状部７０との接触点における面圧を低減することができる。 That is, by forming the gentle slope portion 89 on the slope surface portion 58 (for example, the first slope surface portion 58A) of the intake cam 48, acceleration in the lift direction of the valve lifter 64 on the slope surface portion 58 is suppressed, and the slope of the intake cam 48 is inclined. The surface pressure at the contact point between the surface portion 58 and the spherical portion 70 of the roller portion 66 of the valve lifter 64 can be reduced. Furthermore, the inclined surface portion 58 (for example, the first inclined surface portion 58A) of the intake cam 48 is formed with a gentle inclined surface portion 90, so that the valve lifter 64 jumps or bounces when the axial movement of the intake cam 48 approaches the end. This can be prevented, and the surface pressure at the contact point between the inclined surface portion 58 and the spherical portion 70 can be reduced.

ここで、バルブリフタ６４のリフト方向の最大加速度は、吸気カム４８の傾斜面部５８においては、全体として吸気カム４８の低リフト平坦面部５７Ａによる場合よりも低く設定される。これにより、吸気カム４８の傾斜面部５８とバルブリフタ６４のローラ部６６の球面状部７０との接触点における応力が、吸気カム４８の低リフト平坦面部５７Ａとローラ部６６の円筒面状部６９との接触箇所の応力よりも低減される。これは、傾斜面部５８においては点接触となり、平坦面部５７における線接触に比べてヘルツ応力（面圧）が大きくなることから、点接触でのヘルツ応力を低減させるために傾斜面部５８における最大加速度を相対的に低くする必要があるからである。   Here, the maximum acceleration in the lift direction of the valve lifter 64 is set lower in the inclined surface portion 58 of the intake cam 48 than in the case of the low lift flat surface portion 57A of the intake cam 48 as a whole. As a result, the stress at the contact point between the inclined surface portion 58 of the intake cam 48 and the spherical portion 70 of the roller portion 66 of the valve lifter 64 causes the low lift flat surface portion 57A of the intake cam 48 and the cylindrical surface portion 69 of the roller portion 66 to This is less than the stress at the contact point. This is point contact at the inclined surface portion 58, and hertz stress (surface pressure) is larger than line contact at the flat surface portion 57. Therefore, the maximum acceleration at the inclined surface portion 58 is reduced in order to reduce the Hertz stress at the point contact. This is because it is necessary to relatively lower the value.

図４に示すように、バルブリフタ６４のローラ部６６の円筒面状部６９が吸気カム４８の任意の一の平坦面部５７（例えば低リフト平坦面部５７Ａ）に摺接した状態から、この吸気カム４８のバルブリフト特性を変更する際には、ローラ部６６の球面状部７０が吸気カム４８の傾斜面部５８（例えば第１傾斜面部５８Ａ）を少なくとも１回転摺接した後に、ローラ部５６の円筒面状部６９が吸気カム４８の他の平坦面部５７（例えば中リフト平坦面部５７Ｂ）に摺接するよう構成される。上述の少なくとも１回転の摺接は、１回転を含まず、１回転を超えた回転での摺接が好ましい。図４では、ローラ部６６の球面状部７０が吸気カム４８の第１傾斜面部５９Ａを３回転摺接してバルブリフト特性を変更する状況を２点鎖線の矢印で示し、ローラ部６６の球面状部７０が吸気カム４８の第１傾斜面部５８Ａを通過しているときのバルブリフトカーブを、図７に２点鎖線で示している。   As shown in FIG. 4, from the state in which the cylindrical surface portion 69 of the roller portion 66 of the valve lifter 64 is in sliding contact with any one flat surface portion 57 (for example, the low lift flat surface portion 57A) of the intake cam 48, the intake cam 48 When the valve lift characteristic of the roller portion 66 is changed, the spherical surface portion 70 of the roller portion 66 comes into sliding contact with the inclined surface portion 58 (for example, the first inclined surface portion 58A) of the intake cam 48 at least once, and then the cylindrical surface of the roller portion 56 The shaped portion 69 is configured to be in sliding contact with another flat surface portion 57 (for example, the middle lift flat surface portion 57B) of the intake cam 48. The sliding contact of at least one rotation described above does not include one rotation, and sliding contact with a rotation exceeding one rotation is preferable. In FIG. 4, a situation in which the spherical portion 70 of the roller portion 66 is in sliding contact with the first inclined surface portion 59 </ b> A of the intake cam 48 for three rotations to change the valve lift characteristics is indicated by a two-dot chain line arrow. A valve lift curve when the portion 70 passes through the first inclined surface portion 58A of the intake cam 48 is shown by a two-dot chain line in FIG.

図１０は、吸気カム４８及び排気カム４９のバルブリフト特性変更時におけるバルブリフトカーブの変化を示すグラフである。この図１０において、吸気カム４８のバルブリフトカーブ（後述のＡ、α、Ｂ）を実線で示し、排気カム４９のバルブリフトカーブ（後述のＤ、β、Ｅ）を破線で示す。図３に示すアクセルシャフトユニット４７を用いて吸気カム４８及び排気カム４９を同時に軸方向に移動させて、これら吸気カム４８及び排気カム４９のバルブリフト特性を変更する際には、吸気カム４８のバルブリフトカーブによって開閉動作する吸気バルブ６２の閉じ終る付近（図１０の時点Ｐ）から吸気カム４８及び排気カム４９の軸方向移動を開始させる。   FIG. 10 is a graph showing changes in the valve lift curve when the valve lift characteristics of the intake cam 48 and the exhaust cam 49 are changed. In FIG. 10, the valve lift curves (A, α, B described later) of the intake cam 48 are indicated by solid lines, and the valve lift curves (D, β, E described later) of the exhaust cam 49 are indicated by broken lines. When changing the valve lift characteristics of the intake cam 48 and the exhaust cam 49 by simultaneously moving the intake cam 48 and the exhaust cam 49 in the axial direction using the accelerator shaft unit 47 shown in FIG. The intake cam 48 and the exhaust cam 49 are started to move in the axial direction from the vicinity of the end of closing of the intake valve 62 that opens and closes by the valve lift curve (time point P in FIG. 10).

この吸気バルブ６２の閉じ終る付近は、具体的には、吸気バルブ６２が閉じ終ると同時、または吸気バルブ６２が閉じ終る直前もしくは直後である。また、吸気カム４８のバルブリフトカーブに基づく吸気バルブ６２の開閉動作は、排気カム４９のバルブリフトカーブに基づく排気バルブの開閉動作後になされる。   Specifically, the vicinity of the end of closing of the intake valve 62 is at the same time as the end of the intake valve 62, or immediately before or after the end of closing of the intake valve 62. The opening / closing operation of the intake valve 62 based on the valve lift curve of the intake cam 48 is performed after the opening / closing operation of the exhaust valve based on the valve lift curve of the exhaust cam 49.

この図１０では、排気カム４９が低リフト平坦面部５９Ａのバルブリフト特性（バルブリフトカーブＤ）で排気バルブを進退動作させ、また吸気カム４８が低リフト平坦面部５７Ａのバルブリフト特性（バルブリフトカーブＡ）で吸気バルブ６２を進退動作させた状態から、吸気カム４８及び排気カム４９が軸方向に移動されて、排気バルブ４９が中リフト平坦面部５９Ｂのバルブリフト特性（バルブリフトカーブＥ）で排気バルブを進退動作させ、また吸気カム４８が中リフト平坦面部５７Ｂのバルブリフト特性（バルブリフトカーブＢ）で吸気バルブ６２を進退動作させる例を示している。これらのバルブリフトカーブＤとＥの間のバルブリフトカーブβは、排気カム４９の第１傾斜面部６０Ａにおけるものであり、また、バルブリフトカーブＡとＢの間のバルブリフトカーブαは、吸気カム４８の第１傾斜面部５８Ａにおけるものである。   In FIG. 10, the exhaust cam 49 moves the exhaust valve back and forth with the valve lift characteristic (valve lift curve D) of the low lift flat surface portion 59A, and the intake cam 48 moves the valve lift characteristic (valve lift curve) of the low lift flat surface portion 57A. From the state in which the intake valve 62 is moved back and forth in A), the intake cam 48 and the exhaust cam 49 are moved in the axial direction, and the exhaust valve 49 is exhausted by the valve lift characteristic (valve lift curve E) of the middle lift flat surface portion 59B. An example is shown in which the valve is advanced and retracted, and the intake cam 48 causes the intake valve 62 to advance and retract with the valve lift characteristic (valve lift curve B) of the intermediate lift flat surface portion 57B. A valve lift curve β between the valve lift curves D and E is at the first inclined surface portion 60A of the exhaust cam 49, and a valve lift curve α between the valve lift curves A and B is an intake cam. 48 in the first inclined surface portion 58A.

以上のように構成されたことから、本実施の形態によれば、次の効果（１）〜（６）を奏する。   With the configuration as described above, the following effects (1) to (6) are achieved according to the present embodiment.

（１）吸気カム４８の平坦面部５７、排気カム４９の平坦面部５９とバルブリフタ６４のローラ部６６の円筒状面部６９とが線接触するので、バルブリフタ６４のローラ部６６の耐久性が向上し、このローラ部６６を小型化できる。このため、このローラ部６６を含むバルブリフタ６４の重量が低減して、エンジン２４の高速回転化（例えば１５０００ｒｐｍ）に好適に対応した可変動弁装置４０を実現できる。   (1) Since the flat surface portion 57 of the intake cam 48 and the flat surface portion 59 of the exhaust cam 49 and the cylindrical surface portion 69 of the roller portion 66 of the valve lifter 64 are in line contact, the durability of the roller portion 66 of the valve lifter 64 is improved. The roller portion 66 can be reduced in size. For this reason, the weight of the valve lifter 64 including the roller portion 66 is reduced, and the variable valve operating apparatus 40 that can suitably cope with high speed rotation (for example, 15000 rpm) of the engine 24 can be realized.

（２）吸気カム４８の傾斜面部５８は、隣接する平坦面部５７との境界部分Ｍ１、Ｍ２（図８）に、傾斜面部５８の主要部分Ｍ０の軸方向勾配よりも緩やかな勾配の緩斜面部８９、９０を備えている。同様に、排気カム４９の傾斜面部６０にも、隣接する平坦面部５９との境界部分に、傾斜面部６０の主要部分の軸方向勾配よりも緩やかな勾配の緩斜面部（不図示）を備えている。このため、吸気カム４８、排気カム４９のバルブリフト特性の変更時に、バルブリフタ６４のローラ部６６の球面状部７０が吸気カム４８の傾斜面部５８、排気カム４９の傾斜面部６０に接触するときの衝撃を緩和できるので、バルブリフト特性変更時の騒音を低減できると共に、吸気カム４８、排気カム４９及びバルブリフタ６４の耐久性を向上させることができる。更に、バルブリフト特性の変更時に、バルブリフタ６４の球面状部７０が吸気カム４８、排気カム４９のそれぞれの傾斜面部５８、６０から平坦面部５７、５９に移行する際のジャンプやバウンスを防止することができる。   (2) The inclined surface portion 58 of the intake cam 48 is a gentle inclined surface portion having a gentler gradient than the axial gradient of the main portion M0 of the inclined surface portion 58 at the boundary portions M1 and M2 (FIG. 8) with the adjacent flat surface portion 57. 89 and 90 are provided. Similarly, the inclined surface portion 60 of the exhaust cam 49 also includes a gentle slope portion (not shown) having a gentler slope than the axial gradient of the main portion of the inclined surface portion 60 at the boundary portion with the adjacent flat surface portion 59. Yes. Therefore, when the valve lift characteristics of the intake cam 48 and the exhaust cam 49 are changed, the spherical surface portion 70 of the roller portion 66 of the valve lifter 64 comes into contact with the inclined surface portion 58 of the intake cam 48 and the inclined surface portion 60 of the exhaust cam 49. Since the impact can be mitigated, noise at the time of changing the valve lift characteristics can be reduced, and durability of the intake cam 48, the exhaust cam 49, and the valve lifter 64 can be improved. Further, when changing the valve lift characteristics, the spherical portion 70 of the valve lifter 64 is prevented from jumping or bouncing when moving from the inclined surface portions 58, 60 of the intake cam 48 and the exhaust cam 49 to the flat surface portions 57, 59, respectively. Can do.

（３）吸気カム４８の低リフト平坦面部５７Ａ、中リフト平坦面部５７Ｂ、高リフト平坦面部５７Ｃのそれぞれの軸方向長さＬ（図４）が、バルブリフタ６４のローラ部６６における円筒面状部６９の軸方向長さＬ０よりも長さΔＬだけ長く形成される。また、排気カム４９の低リフト平坦面部５９Ａ、中リフト平坦部５９Ｂ、高リフト平坦面部５９Ｃのそれぞれの軸方向長さが、バルブリフタ６４のローラ部６６における円筒面状部６９の軸方向長さＬ０よりも長く形成されている。このため、吸気カム４８、排気カム４９のバルブリフト特性を変更するために吸気カム４８、排気カム４９を軸方向に移動させたとき、停止位置の誤差やオーバーシュート（過剰な移動）が生じた場合にも、吸気カム４８の平坦面部５７、排気カム４９の平坦面部５９とローラ部６６の円筒面状部６９との線接触状態が確保される。この結果、吸気カム４８の平坦面部５７、排気カム４９の平坦面部５９によるバルブリフト特性を良好に維持できる。   (3) The axial length L (FIG. 4) of each of the low lift flat surface portion 57A, the middle lift flat surface portion 57B and the high lift flat surface portion 57C of the intake cam 48 is the cylindrical surface portion 69 in the roller portion 66 of the valve lifter 64. Is longer than the axial length L0 by a length ΔL. Further, the axial lengths of the low lift flat surface portion 59A, the middle lift flat surface portion 59B, and the high lift flat surface portion 59C of the exhaust cam 49 are equal to the axial length L0 of the cylindrical surface portion 69 in the roller portion 66 of the valve lifter 64. It is formed longer than. For this reason, when the intake cam 48 and the exhaust cam 49 are moved in the axial direction in order to change the valve lift characteristics of the intake cam 48 and the exhaust cam 49, stop position errors and overshoot (excessive movement) occur. Even in this case, a line contact state between the flat surface portion 57 of the intake cam 48 and the flat surface portion 59 of the exhaust cam 49 and the cylindrical surface portion 69 of the roller portion 66 is ensured. As a result, the valve lift characteristics of the flat surface portion 57 of the intake cam 48 and the flat surface portion 59 of the exhaust cam 49 can be maintained well.

（４）吸気カム４８、排気カム４９のバルブリフト特性の変更途中におけるバルブ開閉を吸気カム４８の傾斜面部５８、排気カム４９の傾斜面部６０で生じさせることができ、バルブリフト特性が瞬時に変更されることを防止して、エンジン出力の急激な変化を伴なうことを抑制できる。   (4) Valve opening / closing during the change of the valve lift characteristics of the intake cam 48 and the exhaust cam 49 can be caused by the inclined surface portion 58 of the intake cam 48 and the inclined surface portion 60 of the exhaust cam 49, and the valve lift characteristics can be changed instantaneously. It is possible to prevent the engine output from being suddenly changed.

（５）吸気カム４８及び排気カム４９のバルブリフト特性を変更する際には、吸気バルブ６２の閉じ終る付近（図１０の時点Ｐ）から吸気カム４８及び排気カム４９の軸方向移動を開始させるので、吸気バルブ６２及び排気バルブの作動中に吸気カム４８、排気カム４９のバルブリフト特性を変化させることを極力抑制することができる。   (5) When changing the valve lift characteristics of the intake cam 48 and the exhaust cam 49, the axial movement of the intake cam 48 and the exhaust cam 49 is started from near the end of closing of the intake valve 62 (time point P in FIG. 10). Therefore, it is possible to suppress as much as possible that the valve lift characteristics of the intake cam 48 and the exhaust cam 49 are changed during the operation of the intake valve 62 and the exhaust valve.

（６）吸気カム４８において、高リフト平坦面部５７Ｃに隣接して、少なくとも最高リフト付近に最高リフト部８８（図４）が形成され、また、排気カム４９において、高リフト平坦面部５９Ｃに隣接して、少なくとも最高リフト付近に最高リフト部９１（図６）が形成されてもよい。この場合には、吸気カム４８の高リフト平坦面部５７Ｃ、排気カム４９の高リフト平坦面部５９Ｃによるバルブリフト特性に比べて、エンジン２４の最高出力をさらに向上させることができる。   (6) In the intake cam 48, the highest lift portion 88 (FIG. 4) is formed at least near the highest lift adjacent to the high lift flat surface portion 57C, and the exhaust cam 49 is adjacent to the high lift flat surface portion 59C. Thus, the highest lift portion 91 (FIG. 6) may be formed at least near the highest lift. In this case, the maximum output of the engine 24 can be further improved as compared with the valve lift characteristics of the high lift flat surface portion 57C of the intake cam 48 and the high lift flat surface portion 59C of the exhaust cam 49.

以上、本発明を上記実施の形態に基づいて説明したが、本発明はこれに限定されるものではない。   As mentioned above, although this invention was demonstrated based on the said embodiment, this invention is not limited to this.

例えば、図１１に示すように、吸気カム４８の低リフト平坦面部５７Ａ、中リフト平坦面部５７Ｂ、高リフト平坦面部５７Ｃのバルブリフト特性をそれぞれ表すバルブリフトカーブＡ、Ｂ、Ｃと、排気カム４９の低リフト平坦面部５９Ａ、中リフト平坦面部５９Ｂ、高リフト平坦面部５９Ｃのバルブリフト特性をそれぞれ表すバルブリフトカーブＤ、Ｅ、Ｆとのうちで、バルブリフトカーブＡとＤがオーバーラップしないように設定することも可能である。この場合には、エンジン２４の低速回転時に吸気バルブ６２がバルブリフトカーブＡに基づいて、排気バルブがバルブリフトカーブＤに基づいてそれぞれ進退動作することで、バルブオーバーラップによりＥＧＲ（Ｅｘｈａｕｓｔ Ｇａｓ Ｒｅｃｉｒｃｕｌａｔｉｏｎ）量が増大し、圧縮自着火燃焼を実現できる。   For example, as shown in FIG. 11, valve lift curves A, B, and C representing the valve lift characteristics of the low lift flat surface portion 57A, middle lift flat surface portion 57B, and high lift flat surface portion 57C of the intake cam 48, and the exhaust cam 49, respectively. Among the valve lift curves D, E, and F representing the valve lift characteristics of the low lift flat surface portion 59A, middle lift flat surface portion 59B, and high lift flat surface portion 59C, respectively, the valve lift curves A and D should not overlap. It is also possible to set. In this case, when the engine 24 rotates at a low speed, the intake valve 62 moves forward and backward based on the valve lift curve A and the exhaust valve moves forward and backward based on the valve lift curve D, so that EGR (Exhaust Gas Recirculation) is caused by valve overlap. The amount increases and compression autoignition combustion can be realized.

また、吸気カム４８には平坦面部５７が３段（低リフト平坦面部５７Ａ、中リフト平坦面部５７Ｂ、高リフト平坦面部５７Ｃ）形成され、排気カム４９には平坦面部５９が３段（低リフト平坦面部５９Ａ、中リフト平坦面部５９Ｂ、高リフト平坦面部５９Ｃ）形成されるものを述べた。これに対し、吸気カム４８の平坦面部５７と排気カム４９の平坦面部５９とが、それぞれ２段または４段以上形成されてもよい。   The intake cam 48 has three flat surface portions 57 (low lift flat surface portion 57A, medium lift flat surface portion 57B, and high lift flat surface portion 57C), and the exhaust cam 49 has three flat surface portions 59 (low lift flat surface). The surface portion 59A, the middle lift flat surface portion 59B, and the high lift flat surface portion 59C) are described. On the other hand, the flat surface portion 57 of the intake cam 48 and the flat surface portion 59 of the exhaust cam 49 may be formed in two steps or four or more steps, respectively.

更に、本実施の形態では、排気カム４９が、平坦面部５９と傾斜面部６０とが交互に形成された立体形状カムに構成されて、この排気カム４９のバルブリフト特性が変更されるものを述べた。これに対し、この排気カム４９は、バルブリフト特性が変更されない平カム形状に構成され、吸気カム４８のみが、平坦面部５７と傾斜面部５８とが交互に形成された立体形状カムに構成されて、吸気カム４８のみのバルブリフト特性が変更されるものでもよい。   Furthermore, in the present embodiment, the exhaust cam 49 is configured as a three-dimensional cam in which the flat surface portion 59 and the inclined surface portion 60 are alternately formed, and the valve lift characteristic of the exhaust cam 49 is changed. It was. On the other hand, the exhaust cam 49 is configured in a flat cam shape in which the valve lift characteristics are not changed, and only the intake cam 48 is configured in a three-dimensional cam in which flat surface portions 57 and inclined surface portions 58 are alternately formed. The valve lift characteristic of only the intake cam 48 may be changed.

２ シリンダヘッド
２４ エンジン
４０ 可変動弁装置
４８ 吸気カム
４９ 排気カム
５１ 吸気側カムシャフト
５４ 排気側カムシャフト
５７ 平坦面部
５７Ａ 低リフト平坦面部
５７Ｂ 中リフト平坦面部
５７Ｃ 高リフト平坦面部
５８ 傾斜面部
５８Ａ 第１傾斜面部
５８Ｂ 第２傾斜面部
５９ 平坦面部
５９Ａ 低リフト平坦面部
５９Ｂ 中リフト平坦面部
５９Ｃ 高リフト平坦面部
６０ 傾斜面部
６０Ａ 第１傾斜面部
６０Ｂ 第２傾斜面部
６２ 吸気バルブ
６４ バルブリフタ
６６ ローラ部
６９ 円筒面状部
７０ 球面状部
Ｍ０ 傾斜面部の主要部分
Ｍ１、Ｍ２ 境界部分
Ｐ 時点（吸気バルブの閉じ終わる付近） 2 Cylinder head 24 Engine 40 Variable valve system 48 Intake cam 49 Exhaust cam 51 Intake side camshaft 54 Exhaust side camshaft 57 Flat surface portion 57A Low lift flat surface portion 57B Middle lift flat surface portion 57C High lift flat surface portion 58 Inclined surface portion 58A First Inclined surface portion 58B Second inclined surface portion 59 Flat surface portion 59A Low lift flat surface portion 59B Middle lift flat surface portion 59C High lift flat surface portion 60 Inclined surface portion 60A First inclined surface portion 60B Second inclined surface portion 62 Intake valve 64 Valve lifter 66 Roller portion 69 Cylindrical surface Portion 70 Spherical surface portion M0 Major portion M1, M2 boundary portion P of inclined surface portion Time point (near end of closing of intake valve)

Claims (5)

シリンダヘッドに回転自在に軸支されたカムシャフトと、このカムシャフトに回転一体で且つ軸方向に移動可能に設けられたカムと、このカムのカムプロフィルに追従してバルブを進退動作させるバルブリフタと、を備えた可変動弁装置であって、
前記カムは、軸方向一定区間に亘りカムプロフィルが変化しない平坦面部と、軸方向一定区間に亘りカムプロフィルが連続的に無段階に変化する傾斜面部とが交互に形成された立体形状カムであり、前記平坦面部は少なくとも２箇所に設けられ、それぞれが互いに異なるバルブリフト特性を有するカムプロフィルに形成され、
前記バルブリフタは、前記カムの平坦面部に摺接して転動する円筒面状部と、前記カムの傾斜面部に摺接して転動する球面状部とを設けたローラ部を備えるとともに、このローラ部を含むバルブリフタは、前記バルブの軸方向にのみ移動可能にバルブリフタホルダによって浮動保持され、
このローラ部の前記円筒面状部は、前記カムの前記平坦面部の任意の一の平坦面部と線接触することでその平坦面部のバルブリフト特性に従って前記バルブリフタを作動させる一方、
前記カムが回転しつつ軸方向に移動することで、前記ローラ部の前記円筒面状部が前記カムの前記平坦面部の任意の一の平坦面部と線接触した状態から、前記ローラ部の前記球面状部が、前記カムの平坦面部と平坦面部との間に形成した前記傾斜面部に点接触した状態に移行し、前記カムの任意の一の平坦面部から隣接する他の平坦面部に切り換えて前記カムの前記バルブリフト特性を変更するように構成したことを特徴とする可変動弁装置。 A camshaft rotatably supported by the cylinder head, a cam provided integrally with the camshaft so as to be movable in the axial direction, and a valve lifter for moving the valve forward and backward following the cam profile of the cam; A variable valve operating apparatus comprising:
The cam is a three-dimensional cam in which a flat surface portion where the cam profile does not change over a constant axial direction and an inclined surface portion where the cam profile changes continuously and continuously over a constant axial direction are alternately formed. The flat surface portion is provided in at least two places, each formed in a cam profile having different valve lift characteristics,
The valve lifter is Rutotomoni comprises a cylindrical surface-shaped portion that rolls in sliding contact with the flat surface portion of said cam, a roller portion provided with a spherical portion that rolls in sliding contact with the inclined surface of the cam, this roller The valve lifter including the portion is floated and held by the valve lifter holder so as to be movable only in the axial direction of the valve ,
While the cylindrical surface portion of the roller portion is in line contact with any one flat surface portion of the flat surface portion of the cam, the valve lifter is operated according to the valve lift characteristic of the flat surface portion,
When the cam rotates and moves in the axial direction, the cylindrical surface portion of the roller portion comes into line contact with any one flat surface portion of the flat surface portion of the cam from the spherical surface of the roller portion. The shape portion is in a point contact state with the inclined surface portion formed between the flat surface portions of the cam, and is switched from any one flat surface portion of the cam to another adjacent flat surface portion. A variable valve operating apparatus configured to change the valve lift characteristic of a cam. 前記カムの傾斜面部には、前記カムの平坦面部との境界付近に、この傾斜面部の主要部分の軸方向勾配よりも緩やかな勾配を有する緩斜面部が形成されたことを特徴とする請求項１に記載の可変動弁装置。 The inclined surface portion of the cam is formed with a gentle slope portion having a gentler slope than an axial gradient of a main portion of the inclined surface portion in the vicinity of a boundary with the flat surface portion of the cam. The variable valve operating apparatus according to 1. 前記バルブリフタのローラ部の円筒面状部がカムの任意の一の平坦面部への摺接から他の平坦面部への摺接に切り換わることでバルブリフト特性が変更され、このバルブリフト特性の変更時には、前記ローラ部の球面状部が、前記カムにおける前記両平坦面部間の傾斜面部に少なくとも１回転摺接するよう構成された特徴とする請求項１に記載の可変動弁装置。 The valve lift characteristics are changed by switching the cylindrical surface portion of the roller portion of the valve lifter from sliding contact to any one flat surface portion of the cam to sliding contact to another flat surface portion. 2. The variable valve operating apparatus according to claim 1, wherein the spherical portion of the roller portion is configured to be in sliding contact with the inclined surface portion between the two flat surface portions of the cam at least once. 前記カムは、バルブリフト特性を変更する際に、排気バルブの開閉動作後に開閉動作する吸気バルブが閉じ終わる付近から軸方向への移動を開始するよう構成されたことを特徴とする請求項１に記載の可変動弁装置。 The said cam is comprised so that the movement to an axial direction may be started from the vicinity which the intake valve which opens and closes after the opening / closing operation | movement of an exhaust valve closes, when changing a valve lift characteristic. The variable valve operating device described. 前記カムは、吸気バルブを吸気側バルブリフタを介して進退動作させる吸気カムと、排気バルブを排気側バルブリフタを介して進退動作させる排気カムとのうち、少なくとも吸気カムであることを特徴とする請求項１乃至４のいずれか１項に記載の可変動弁装置。 The cam is at least an intake cam among an intake cam that causes the intake valve to advance and retract through an intake side valve lifter and an exhaust cam that causes an exhaust valve to advance and retract via an exhaust side valve lifter. The variable valve operating apparatus according to any one of 1 to 4.
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