JP2749909B2 - Engine valve gear - Google Patents

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明は例えば３本の吸気弁及び２本の排気弁を有す
るSOHC 5バルブエンジンに好適の動弁装置に関し、特に
ロッカアームのアジャストスクリューと弁棒との当接面
における滑り速度を抑制しながら動弁機構の高さ、ひい
てはエンジン高さを低くできるようにした構造に関す
る。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve train suitable for a SOHC 5-valve engine having, for example, three intake valves and two exhaust valves, and more particularly to an adjusting screw and a valve for a rocker arm. The present invention relates to a structure in which the height of a valve mechanism and, consequently, the height of an engine can be reduced while suppressing a sliding speed at a contact surface with a rod.

〔従来の技術〕[Conventional technology]

最近、シリンダヘッドの剛性を確保しながら吸気弁開
口面積をより増大するために吸気弁を３本，排気弁２本
備えた５バルブエンジンが注目されている。このような
エンジンの動弁装置としては、上記中央の吸気弁及びこ
れの両側を位置する左，右吸気弁をシリンダ軸方向に見
て（平面視）カム軸と直角に配置する構造が一般に採用
されている。このような動弁装置としては、従来、例え
ば中央吸気弁を両側の吸気弁より起立させ、かつ該中央
吸気弁の上端が両側吸気弁の上端より高所に位置するよ
うに配置する。そして各吸気弁とアジャストスクリュー
との接点とロッカアームの揺動軸とを結ぶ作動直線と、
弁棒の軸線とのなす作動角度が90度になる基準揺動位置
を中心に上，下に同一角度だけ、つまり上，下に振り分
けてロッカアームを揺動させるのが一般的である。この
ように上，下に振り分けることにより、アジャストスク
リューと弁棒との接点応力のピーク値を下げることがで
きる。Recently, a five-valve engine provided with three intake valves and two exhaust valves has been attracting attention in order to further increase the opening area of the intake valve while securing the rigidity of the cylinder head. Such a valve train for an engine generally employs a structure in which the central intake valve and the left and right intake valves located on both sides of the central intake valve are arranged at right angles to the cam shaft when viewed in the cylinder axis direction (in plan view). Have been. Conventionally, as such a valve operating device, for example, a central intake valve is erected from the intake valves on both sides, and the central intake valve is disposed so that the upper end thereof is located higher than the upper ends of the intake valves on both sides. And an operating straight line connecting the contact point between each intake valve and the adjusting screw and the rocking axis of the rocker arm,
In general, the rocker arm is rocked up and down by the same angle, that is, up and down, around a reference rocking position at which the operating angle formed with the axis of the valve stem is 90 degrees. As described above, by distributing the pressure upward and downward, the peak value of the contact stress between the adjusting screw and the valve stem can be reduced.

〔発明が解決しようとする問題点〕[Problems to be solved by the invention]

上記従来の動弁装置では、中央吸気弁の上端を左，右
吸気弁の上端より高所に位置させ、しかも基準揺動位置
を中心に上，下に振り分けて揺動させるようにしている
ので、特にこの中央吸気弁用アジャストスクリュー部分
の位置が高くなり、従ってそれだけ動弁機構の高さが高
くなり、ひいてはエンジン高さが高くなる問題がある。In the above conventional valve train, the upper end of the central intake valve is positioned higher than the upper ends of the left and right intake valves, and the upper and lower swings are centered on the reference swing position. In particular, there is a problem that the position of the adjusting screw for the central intake valve is increased, and accordingly, the height of the valve operating mechanism is increased and the height of the engine is increased accordingly.

ここで上記作動角度が90度をなす位置（基準揺動位
置）より下方領域で揺動させるようにすればそれだけア
ジャストスクリューの揺動高さを低くすることができ
る。しかしこのようにすると、アジャストスクリューと
弁棒との当接部における滑り速度が高くなるとともに、
上記接点応力が大きくなり、耐久性の低下が懸念され
る。即ち、上記滑り速度，接点応力は上記基準揺動位置
においても最も低速，最小となり、これより外方に行く
ほど増大するから、上記下方領域を使用するほど耐久性
上不利となる。Here, the swing height of the adjusting screw can be reduced accordingly by swinging in the region below the position where the operating angle forms 90 degrees (reference swing position). However, in this case, the sliding speed at the contact portion between the adjusting screw and the valve stem increases,
The contact stress increases, and there is a concern that the durability may decrease. That is, the sliding speed and the contact stress are the lowest and the lowest even at the reference swing position, and increase further outward. Therefore, the use of the lower region is disadvantageous in durability.

本発明は上記従来の問題点に鑑みてなされたもので、
耐久性に支障をきたすことなくエンジン高さを低くでき
るエンジンの動弁装置を提供することを目的としてい
る。The present invention has been made in view of the above conventional problems,
It is an object of the present invention to provide an engine valve train that can lower the engine height without impairing durability.

〔問題点を解決するための手段〕[Means for solving the problem]

本発明の構成を、後述の実施例を示す図に沿って説明
すれば、請求項１の発明は、１本のカム軸の一側に３本
の吸気弁を、他側に排気弁を配置し、カム軸と吸気弁と
の間に吸気揺動部材を軸支する吸気揺動軸を、カム軸と
排気弁との間に排気揺動部材を軸支する排気揺動軸を、
それぞれカム軸と平行にかつカム軸より上方に配置し、
上記揺動部材をシーソータイプのものとし、上記各弁を
上記カム軸により上記揺動部材を介して駆動するように
したエンジンの動弁装置において、上記吸気弁をシリン
ダ軸線Ｆと第１傾斜角θｓをなすように配置された第１
弁34,36と、上記第１傾斜角θｓより小さい第２傾斜角
θｃをなすように配置された第２弁35とで構成し、上記
吸気揺動部材を上記第1,第２弁を押圧する第1,第２押圧
部材を備えたものとするとともに、上記各吸気弁と上記
各押圧部材との接点と上記揺動軸45とを結ぶ作動直線
が、該作動直線と上記各吸気弁の軸線とのなす作動角度
が90度をなす基準揺動位置を弁移動行程の途中で通過す
るように上記各吸気弁の傾斜角度及び上記揺動軸の位置
を設定し、上記第２弁35の上端を第１弁34,36の上端よ
りカム軸直角方向外方に位置させ、かつ該第１弁34,3
6、第２弁35の上端を上記揺動軸45を含む略同一平面内
に位置させ、上記基準揺動位置における作動直線ｃ又ｂ
と全閉位置における作動直線ａとで構成される閉側揺動
角度θ１又はθ３と、上記基準揺動位置における作動直
線ｃ又はｂと全閉位置における作動曲線ｄとで構成され
る開側揺動角度θ２又はθ４とに関して、上記第１弁3
4,36については閉側揺動角度θ１を開側揺動角度θ２よ
り大きく設定し、かつ上記第２弁35については閉側揺動
角度θ３を開側揺動角度θ４より小さく設定したことを
特徴としている。The structure of the present invention will be described with reference to the drawings showing the embodiments described later. According to the invention of claim 1, three intake valves are arranged on one side of one camshaft and exhaust valves are arranged on the other side. An intake swing shaft that supports the intake swing member between the camshaft and the intake valve, an exhaust swing shaft that supports the exhaust swing member between the camshaft and the exhaust valve,
Each is arranged parallel to the camshaft and above the camshaft,
In the valve operating apparatus for an engine, wherein the swing member is a seesaw type, and each of the valves is driven by the cam shaft through the swing member, the intake valve is formed by a cylinder axis F and a first inclination angle. θs
Valves 34 and 36, and a second valve 35 disposed so as to form a second inclination angle θc smaller than the first inclination angle θs, and the intake swinging member presses the first and second valves. And an operating straight line connecting the contact point between each of the intake valves and each of the pressing members and the oscillating shaft 45 is formed by the operating straight line and each of the intake valves. The inclination angle of each of the intake valves and the position of the oscillating shaft are set so as to pass through a reference oscillating position having an operating angle of 90 degrees with the axis in the middle of the valve movement stroke. The upper end is located outward of the upper ends of the first valves 34, 36 in the direction perpendicular to the camshaft, and the first valves 34, 3
6. The upper end of the second valve 35 is positioned in substantially the same plane including the swing shaft 45, and the operating straight line c or b at the reference swing position is set.
And a closing swing angle θ1 or θ3 composed of an operating straight line a at the fully closed position, an open swinging angle d at the reference swing position, and an operating curve d at the fully closed position. With respect to the moving angle θ2 or θ4, the first valve 3
The closing side swing angle θ1 is set to be larger than the opening side swing angle θ2 for 4, 36, and the closing side swing angle θ3 is set to be smaller than the opening side swing angle θ4 for the second valve 35. Features.

また、請求項２の発明は、シリンダ軸線Ｆと第１傾斜
角θｓをなすように配置された第１弁34,36と、上記第
１傾斜角θｓより小さい第２傾斜角θｃをなすように配
置された第２弁35と、揺動軸45回りに揺動して上記第1,
第２弁を移動させる揺動部材と、該揺動部材に設けられ
上記第１弁，第２弁の上端を押圧する第1,第２押圧部材
とを備えたエンジンの動弁装置において、上記第２弁35
の上端を第１弁34,36の上端よりカム軸直角方向外方に
位置させ、かつ該第１弁34,36、第２弁35の上端を上記
揺動軸45を含む略同一平面内に位置させ、上記各弁と各
押圧部材との接点と上記揺動軸45とを結ぶ作動直線が、
該作動直線と上記各弁の軸線とのなす作動角度が90度を
なす基準揺動位置を弁移動行程の途中で通過するように
上記各弁の傾斜角度及び上記揺動軸の位置を設定し、上
記基準揺動位置における上記作動直線ｃ又はｂと全閉位
置における作動直線ａとで構成される閉側揺動角度θ１
又はθ３と、上記基準揺動位置における上記作動直線ｃ
又はｂと全開位置における作動曲線ｄとで構成される開
側揺動角度θ２又はθ４とに関して、上記第１弁34,36
については閉側揺動角度θ１を開側揺動角度θ２より大
きく設定し、かつ上記第２弁35については閉側揺動角度
θ３を開側揺動角度θ４より小さく設定し、上記押圧部
材を上記揺動部材に進退可能に装着するとともに、該押
圧部材53,54の軸線D,Eと上記各弁の軸線B,Aとが平行と
なる押圧部材平行状態が上記弁移動行程の途中で存在す
るように上記各弁の傾斜角度及び上記押圧部材の装着角
度を設定し、上記押圧部材平行状態における平行時作動
直線ｃ′又はｂ′と全閉位置における作動直線ａとで構
成される閉側揺動角度θ１′又はθ３′と、上記平行時
作動直線ｃ′又はｂ′と全閉位置における作動曲線ｄと
で構成される開側揺動角度θ２′又はθ４′とに関し
て、上記第１弁34,36については閉側揺動角度θ１′を
開側揺動角度θ２′より大きく設定し、かつ上記第２弁
35については閉側揺動角度θ３′を開側揺動角度θ４′
より小さく設定したことを特徴としている。Further, according to the invention of claim 2, the first valves 34 and 36 arranged so as to form the first inclination angle θs with the cylinder axis F and the second inclination angle θc smaller than the first inclination angle θs. The second valve 35 is arranged, and the first valve 35 is swung about a swing shaft 45 so that
An engine valve operating apparatus comprising: a swing member for moving a second valve; and first and second pressing members provided on the swing member for pressing upper ends of the first valve and the second valve. Second valve 35
The upper ends of the first and second valves 34, 36 are located in a direction substantially perpendicular to the camshaft from the upper ends of the first valves 34, 36, and the upper ends of the first and second valves 34, 36, Position, an operating straight line connecting the contact point between each valve and each pressing member and the swing shaft 45,
The tilt angle of each valve and the position of the swing shaft are set so that the operating angle between the operating straight line and the axis of each valve passes through a reference swing position at 90 degrees in the middle of the valve movement stroke. A closing-side swing angle θ1 composed of the operating line c or b at the reference swing position and the operating line a at the fully closed position.
Or θ3 and the operating line c at the reference swing position.
Or the open-side swing angle θ2 or θ4 composed of b and the operation curve d at the fully open position.
For the second valve 35, the closing side swing angle θ3 is set smaller than the opening side swing angle θ4 for the second valve 35, and the pressing member is Attached to the swing member so as to be able to advance and retreat, and a pressing member parallel state in which the axes D and E of the pressing members 53 and 54 and the axes B and A of the valves are parallel exists in the middle of the valve moving stroke. The inclination angle of each of the valves and the mounting angle of the pressing member are set such that the operating line c 'or b' in the parallel state of the pressing member and the operating line a in the fully closed position are set. With respect to the swing angle θ1 ′ or θ3 ′, and the open-side swing angle θ2 ′ or θ4 ′ composed of the operating line c ′ or b ′ in the parallel state and the operating curve d in the fully closed position, the first valve For 34 and 36, the closing side swing angle θ1 'is set larger than the open side swing angle θ2' And the second valve
For 35, the closed swing angle θ3 'is changed to the open swing angle θ4'.
It is characterized by being set smaller.

なお、上記請求項２の発明における上記θ１とθ１′
と、θ２とθ２′、θ３とθ３′、θ４とθ４′はそれ
ぞれ実施例で示すように同じ値に設定することができ
る。Note that the θ1 and θ1 ′ in the second aspect of the present invention.
, Θ2 and θ2 ', θ3 and θ3', and θ4 and θ4 'can be set to the same value as shown in the embodiment.

ここで本発明において、上記接点を揺動軸を含む「略
同一平面上」に位置させるとは、以下の意味である。即
ち、一般に上記押圧部材の先端は球状に形成されている
から、本発明のように上記傾斜角度に差がある場合は、
仮に全閉状態で上記接点を完全な同一平面上にセットし
ても揺動部材の揺動に伴って上記接点は完全な同一平面
上からは若干ずれることとなるが、本発明はこのような
ずれが生じる場合も含むとの意味である。Here, in the present invention, the fact that the contact point is located “substantially on the same plane” including the swing axis has the following meaning. That is, since the tip of the pressing member is generally formed in a spherical shape, when there is a difference in the inclination angle as in the present invention,
Even if the contacts are completely set on the same plane in the fully closed state, the contacts slightly deviate from the completely same plane with the swing of the swinging member. This means that a shift may occur.

〔作用〕[Action]

本発明に係るエンジンの動弁装置によれば、各弁の上
端高さを各接点が揺動軸ｆを含む略同一平面内に位置す
るように設定したので、揺動部材52の揺動に伴って、第
1,第２弁が同時に移動する。この場合、まず第1,第２弁
とも全閉の状態（作動直線ａの位置）から第２弁に関す
る作動角度が90度の状態（作動直線ｂで示す基準揺動位
置），第１弁に関する作動角度が90度の状態（作動直線
ｃで示す基準揺動位置）を通って全開（作動直線ｄの位
置）に至る。According to the valve train of the engine according to the present invention, the height of the upper end of each valve is set so that each contact is located in substantially the same plane including the swing axis f. Accompanying
1. The second valve moves simultaneously. In this case, first, the first and second valves are fully closed (the position of the operation straight line a) and the operation angle of the second valve is 90 degrees (the reference swing position indicated by the operation straight line b). Through the state where the operation angle is 90 degrees (the reference swing position indicated by the operation line c), it reaches the fully opened position (the position of the operation line d).

そして本発明では、傾斜角の小さい、つまりより起立
している第２弁については、閉側揺動角度θ３を開側揺
動角度θ４より小さく設定したので、上述の公報記載の
従来装置に比較して該第２弁の押圧部材54の上方への移
動量が少なくて済み、従ってそれだけ該動弁機構が低く
なり、エンジン高さの増加を抑制できる。In the present invention, the closing angle θ3 is set to be smaller than the opening angle θ4 for the second valve having a small inclination angle, that is, a more upright valve. Therefore, the amount of upward movement of the pressing member 54 of the second valve can be reduced, and accordingly, the valve operating mechanism is reduced accordingly, and an increase in the engine height can be suppressed.

ここで、上述のように上記押圧部材と弁棒との接点に
おける滑り速度は、上記作動角度が90度をなす基準揺動
位置で最も低速であり、該位置から離れる程高速とな
り、あまり高速になると耐久性の点で不利となる。これ
に対して本発明では、揺動角度を上述のように設定しな
がら基準揺動位置を挟んでこれの上，下に揺動させるよ
うにしているので、この滑り速度がそれほど増加するこ
とはなく、耐久性の問題が生じることもない。Here, as described above, the sliding speed at the contact point between the pressing member and the valve rod is the lowest at the reference swing position where the operating angle is 90 degrees, becomes higher as the operating angle becomes farther from the position, and becomes extremely high. This is disadvantageous in terms of durability. On the other hand, in the present invention, since the swing angle is set as described above, the swing is made to swing upward and downward with the reference swing position interposed therebetween. There is no durable problem.

また、請求項２の発明では、押圧部材平行状態に関し
て、傾斜角の大きい第１弁34,36側の閉側揺動角度θ
１′を大きくし、傾斜角の小さい第２弁35側の閉側揺動
角度θ３′を小さく設定したので、第１押圧部材53,第
２押圧部材54の軸線D,Eをなす角度を平行に設定するこ
とが可能となり、例えば二股状の押圧部材に第1,第２押
圧部材53,54を装着する場合に両方の孔を同時に開ける
ことができる等、孔明け加工が容易となる。According to the second aspect of the present invention, with respect to the parallel state of the pressing member, the closing-side swing angle θ of the first valve 34, 36 having a large inclination angle.
1 ′ is increased and the closing-side swing angle θ3 ′ of the second valve 35 having a small inclination angle is set small, so that the angles between the axes D and E of the first pressing member 53 and the second pressing member 54 are parallel. In the case where the first and second pressing members 53 and 54 are attached to the forked pressing member, for example, both holes can be opened at the same time.

〔実施例〕〔Example〕

以下、本発明の実施例を図について説明する。 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

第１図ないし第８図は本発明の一実施例によるSOHCエ
ンジンの動弁装置を説明するための図であり、第１図の
ロッカアームと弁棒との関係を模式的に示す拡大図、第
２図、第３図はアジャストスクリューと弁棒との当接状
態を模式的に示す拡大図、第４図，第５図は第６図のIV
-IV線断面図、第Ｖ−Ｖ線断面図、第６図は該装置の平
面図、第７図は吸，排気通路付近の断面平面図、第８図
は本実施例エンジンを搭載した自動二輪車の右側面図で
ある。なお、平面図，側面図では図示右側が車両前方で
あり、以下、特記なき場合は車両後側から前方を見た状
態で説明する。1 to 8 are views for explaining a valve operating device of an SOHC engine according to one embodiment of the present invention, and are enlarged views schematically showing a relationship between a rocker arm and a valve rod in FIG. 2 and 3 are enlarged views schematically showing a contact state between the adjusting screw and the valve stem, and FIGS. 4 and 5 are IV in FIG.
-IV line sectional view, VV line sectional view, Fig. 6 is a plan view of the device, Fig. 7 is a sectional plan view near the intake and exhaust passages, and Fig. 8 is an automatic system equipped with the engine of the present embodiment. FIG. 2 is a right side view of the motorcycle. In the plan view and the side view, the right side in the drawing is the front of the vehicle. Hereinafter, unless otherwise specified, the description will be made in a state where the front is viewed from the rear side of the vehicle.

図において、１は本実施例エンジンが搭載された自動
二輪車であり、該自動二輪車１の車体フレーム２は、ヘ
ッドパイプ2aの上部，下部に１本のメインパイプ2b,ダ
ウンチューブ2cの前端を溶接接続し、メインパイプ2bの
後端にシートピラー2dの上端を溶接接続したいわゆるダ
イヤモンド型のものである。なお2gはクランクケースを
保護するアンダーガード、2eはメインパイプ2bとダウン
チューブ2cの途中に架け渡されたエンジン懸架用の支持
パイプ、2fはシートレールである。In the drawing, reference numeral 1 denotes a motorcycle on which the engine of this embodiment is mounted, and a body frame 2 of the motorcycle 1 has a main pipe 2b and a front end of a down tube 2c welded to an upper part and a lower part of a head pipe 2a. It is a so-called diamond type in which the upper end of the sheet pillar 2d is connected to the rear end of the main pipe 2b by welding. In addition, 2g is an underguard for protecting the crankcase, 2e is a support pipe for the engine suspension bridged in the middle of the main pipe 2b and the down tube 2c, and 2f is a seat rail.

上記ヘッドパイプ2aには下端で前輪を軸支する前フォ
ーク３が左右に操向自在に軸支されており、上記リヤパ
イプ2dには後端で後輪４を軸支するリヤアーム５が上下
に揺動自在に軸支されている。またこのリヤアーム５は
図示しないリンク機構及び１本のショックアブソーバ８
を介して上記メインパイプ2bの後端付近に連結されてい
る。なお、６は燃料タンク、７はシート、9aはタンク側
面を覆うエアスクープ、9bはシート下方を覆うサイドカ
バー、9cは車両後部を覆うリヤカバーである。A front fork 3 that pivotally supports the front wheel at the lower end is pivotally supported on the head pipe 2a at the lower end, and a rear arm 5 that pivotally supports the rear wheel 4 at the rear end is swinging up and down on the rear pipe 2d. It is pivotally supported. The rear arm 5 includes a link mechanism (not shown) and a single shock absorber 8.
Is connected near the rear end of the main pipe 2b. Reference numeral 6 denotes a fuel tank, 7 denotes a seat, 9a denotes an air scoop that covers a side surface of the tank, 9b denotes a side cover that covers a lower portion of the seat, and 9c denotes a rear cover that covers a rear portion of the vehicle.

上記車体フレーム２内にエンジンユニット10が懸架支
持されている。このエンジンユニット10は水冷式４サイ
クル単気筒５バルブエンジンであり、クランクケース11
の前部上面にシリンダボディ12,シリンダヘッド13及び
ヘッドカバー14を僅かに前傾させて積層した構造のもの
である。上記シリンダヘッド13の下面の略中央には１つ
の燃焼室壁面13aが凹設されている。該壁面13aは上記シ
リンダボディ12のシリンダライナ12a内に摺動自在に挿
入されたピストン（図示せず）の頭部とで燃焼室15を構
成する。上記燃焼室壁面13aの略中央にはプラグねじ孔1
3bが形成されており、該プラグねじ孔13bは該シリンダ
ヘッド13,ヘッドカバー14に形成されたプラグ挿入孔13
c,14aによってシリンダ軸線に対して排気側（前側）に
傾斜するように外方に導出されている。また上記プラグ
ねじ孔13bには点火プラグ16が螺挿されている。An engine unit 10 is suspended and supported in the vehicle body frame 2. This engine unit 10 is a water-cooled 4-cycle single-cylinder 5-valve engine, and a crankcase 11
The cylinder body 12, the cylinder head 13, and the head cover 14 are slightly tilted forward and stacked on the upper surface of the front part. One combustion chamber wall surface 13a is recessed substantially in the center of the lower surface of the cylinder head 13. The wall 13a forms a combustion chamber 15 with the head of a piston (not shown) slidably inserted into the cylinder liner 12a of the cylinder body 12. A plug screw hole 1 is provided substantially at the center of the combustion chamber wall 13a.
3b are formed, and the plug screw holes 13b are formed in the plug insertion holes 13 formed in the cylinder head 13 and the head cover 14.
It is led outward by c and 14a so as to be inclined toward the exhaust side (front side) with respect to the cylinder axis. An ignition plug 16 is screwed into the plug screw hole 13b.

上記シリンダヘッド13の燃焼室壁面13aの上記プラグ
ねじ孔13bを挟んだ一側の周縁には、左，中央，右吸気
弁開口17,18,19が、他側の周縁には左，右排気弁開口2
0,21が形成されており上記プラグ挿入孔13cは上記左，
右排気弁開口20,21間を上方に延びている。また上記左
吸気弁開口17は、後述するカム軸42の軸線と平面視で略
直交するように車両後方に延びる左吸気通路22でシリン
ダヘッド後壁に導出されており、上記中央，右吸気弁開
口18,19は上記カム軸42に対して車幅方向右方に延びる
中吸気通路23a及び略直角に延びる右吸気通路23bによっ
て後方に導出され、該両吸気通路23a,23bの合流通路23
は全体として車幅方向右方に延びている。上記左吸気通
路22,及び合流通路23の後端開口には左，右キャブジョ
イント24,25を介して左，右気化器26,27が接続されてい
る。Left, center, and right intake valve openings 17, 18, and 19 are provided on one side of the combustion chamber wall 13a of the cylinder head 13 across the plug screw hole 13b, and left and right exhaust valves are provided on the other side. Valve opening 2
0,21 are formed, and the plug insertion hole 13c is
It extends upward between the right exhaust valve openings 20,21. The left intake valve opening 17 is led to the rear wall of the cylinder head by a left intake passage 22 extending rearward of the vehicle so as to be substantially orthogonal to an axis of a cam shaft 42 described later in a plan view. The openings 18 and 19 are led out rearward by a middle intake passage 23a extending rightward in the vehicle width direction with respect to the camshaft 42 and a right intake passage 23b extending substantially perpendicular to the camshaft 42, and a merging passage 23 of the two intake passages 23a and 23b is provided.
Extends rightward in the vehicle width direction as a whole. Left and right carburetors 26 and 27 are connected to the rear end openings of the left intake passage 22 and the merging passage 23 via left and right cab joints 24 and 25, respectively.

また上記左，右排気弁開口20,21は、ハの字状に拡が
りながら車両前方に延びる左，右排気通路28,29によっ
てシリンダヘッド前壁に導出され、該角通路の前端開口
には排気装置30の左，右の排気管31,32が接続されてい
る。この両排気管31,32は上述のダウンチューブ2cの
左，右側方を通った後右側に屈曲され、ここで合流した
後車両後方に延びており、該延長端にはバックステーを
兼ねる消音器33が接続されている。The left and right exhaust valve openings 20, 21 are led to the front wall of the cylinder head by left and right exhaust passages 28, 29 extending in the shape of a letter C and extending forward of the vehicle. The left and right exhaust pipes 31, 32 of the device 30 are connected. The two exhaust pipes 31 and 32 are bent rightward after passing through the left and right sides of the down tube 2c, and merged here and extend to the rear of the vehicle, and a muffler serving as a back stay is provided at the extended end. 33 is connected.

そして上記左，中央，右吸気弁開口17,18,19にはこれ
を開閉する左，中央，右吸気弁34,35,36の弁板34a,35a,
36aが、上記左，右排気弁開口20,21にはこれを開閉する
左，右排気弁37,38の弁板37a,38aがそれぞれ配置されて
いる。上記角弁34〜38の弁棒34b〜38bは上記各吸気，排
気通路23,23a,23b,28,29の天井壁を貫通して該シリンダ
ヘッド13の合面より上方に突出している。The left, center, and right intake valve openings 17, 18, and 19 have valve plates 34a, 35a, which open and close the left, center, and right intake valves 34, 35, 36, respectively.
In the left and right exhaust valve openings 20 and 21, valve plates 37a and 38a of left and right exhaust valves 37 and 38 for opening and closing the same are disposed, respectively. The valve rods 34b to 38b of the square valves 34 to 38 penetrate through the ceiling walls of the intake and exhaust passages 23, 23a, 23b, 28, and 29 and protrude above the mating surface of the cylinder head 13.

ここで上記排気弁37,38の弁棒37b,38bは平面から見る
とカム軸42と直角に、つまり相互に平行になっており、
カム軸42方向に見ると前方に同一角度で傾斜して相互に
重なっている。そして該各排気弁37,38は、これの上端
に固着された上ストッパ39とシリンダボディ13のばね座
に配設された下ストッパ40との間に介設された付勢ばね
41によって上記開口20,21を閉じるよう付勢されてい
る。Here, the valve rods 37b, 38b of the exhaust valves 37, 38 are perpendicular to the cam shaft 42 when viewed from a plane, that is, parallel to each other,
When viewed in the direction of the camshaft 42, they are inclined forward at the same angle and overlap each other. Each of the exhaust valves 37 and 38 has an urging spring interposed between an upper stopper 39 fixed to an upper end thereof and a lower stopper 40 disposed on a spring seat of the cylinder body 13.
The opening 41 is urged to close the openings 20 and 21 by 41.

また上記各吸気弁34〜36の弁棒34b〜36bも平面視でカ
ム軸42と直角をなしており、カム軸方向に見ると左，右
吸気弁34,36はシリンダ軸線Ｆと傾斜角θｓをなすよう
後方に傾斜して相互に重なっている。なお、この傾斜角
θｓは左，右排気弁37,37と略同一である。また中央吸
気弁35の弁棒35bは上記傾斜角θｓより小さい傾斜角θ
ｃをなすよう後方に傾斜しており、つまり左，右吸気弁
34,36に比べてより起立した状態に配置されている。そ
して上記左，右吸気弁34,36の弁棒34b,36bの上端と中吸
気弁35の弁棒35bの上端とは後述する接点が同一平面上
に位置するようにその高さが設定されており、かつこれ
らの軸線A,Bの交点Ｃはこれらの弁棒の上端より高所に
位置している。またシリンダ軸方向に見ると、中央吸気
弁35の弁棒35bの上端は左，右の弁棒34b,36bの上端より
後方に位置している。また上記各吸気弁34〜36は上，下
ストッパ39,40間に介設された付勢ばね41で閉方向に付
勢されている。The valve rods 34b to 36b of the intake valves 34 to 36 also form a right angle with the camshaft 42 in a plan view, and when viewed in the camshaft direction, the left and right intake valves 34 and 36 have a cylinder axis F and an inclination angle θs. They are inclined backward and overlap each other. The inclination angle θs is substantially the same as the left and right exhaust valves 37, 37. The valve rod 35b of the central intake valve 35 has an inclination angle θ smaller than the inclination angle θs.
c, that is, the left and right intake valves
It is arranged in a more upright state compared to 34 and 36. The heights of the upper ends of the valve rods 34b, 36b of the left and right intake valves 34, 36 and the upper end of the valve rod 35b of the middle intake valve 35 are set so that a contact point described later is located on the same plane. And the intersection C of these axes A and B is located higher than the upper ends of these valve stems. When viewed in the cylinder axis direction, the upper end of the valve stem 35b of the central intake valve 35 is located behind the upper ends of the left and right valve stems 34b, 36b. The intake valves 34 to 36 are urged in the closing direction by an urging spring 41 provided between the upper and lower stoppers 39 and 40.

また上記カム軸42は、上記吸気，排気弁間で、かつシ
リンダ軸線Ｄより吸気弁側にL1だけ偏位した位置を横切
るように配設されている。このカム軸42はその左，右端
部及び中央部がカム軸受で軸支されており、左，右カム
軸受はシリンダヘッド13の合面部に形成された左，右下
軸受13d,13fとヘッドカバー14の合面部に形成された
左，右上軸受（図示せず）とから構成されている。また
上記中央部のカム軸受はシリンダヘッド13の中央に形成
された中央下軸受13eとヘッドカバー14の中央に形成さ
れた中央上軸受14bとから構成されており、この中央上
軸受14bは後述する右吸気ロッカアーム52のボス部52fと
の干渉を避けるためにシリンダ軸線Ｄから左吸気カム42
b側に距離L2だけ偏位している。なお43は該カム軸42の
左端に固着された駆動スプロケット、44はエンジン始動
時に左排気弁37から圧縮圧力を少し逃がすことによって
始動トルクを軽減するためのデコンプ装置である。The camshaft 42 is disposed between the intake and exhaust valves and across a position deviated by L1 from the cylinder axis D toward the intake valve. The left, right and center portions of the camshaft 42 are supported by cam bearings. The left and right cam bearings are formed by the left and right lower bearings 13d, 13f formed on the mating surface of the cylinder head 13 and the head cover 14. And left and right upper bearings (not shown) formed on the mating surface of the upper and lower surfaces. The cam bearing at the center is composed of a lower center bearing 13e formed at the center of the cylinder head 13 and an upper center bearing 14b formed at the center of the head cover 14. In order to avoid interference with the boss 52f of the intake rocker arm 52, the left intake cam 42
It is deviated to the b side by a distance L2. Reference numeral 43 denotes a driving sprocket fixed to the left end of the camshaft 42, and reference numeral 44 denotes a decompression device for reducing the starting torque by slightly releasing the compression pressure from the left exhaust valve 37 when starting the engine.

ここで上記左，右，中央カム軸受は２分割型のもので
あり、ヘッドカバー14をシリンダヘッド13に固定するこ
とによって構成されるわけであるが、このヘッドカバー
14とシリンダヘッド13とは、その開口周縁部（合面
部），上記各カム軸受部，及び上記プラグ挿入口13cの
両縁部が固定ボルトで固定されている（第６図にハッチ
ングを付して示す）。この開口周縁部のうち、排気側部
分については後述するキャップ56,56間の外側に形成さ
れたフランジ部14gが固定ボルト50aで固定されているの
に対し、吸気側については上記各吸気弁間２ヵ所の内側
に形成されたフランジ部14hが固定ボルト50bで固定され
ている。なお、この固定ボルト50bは上記キャップ57を
外すと外方に臨むようになっている。また上記固定ボル
トのうち50は上記シリンダヘッドとヘッドカバーとの固
定と後述のロッカ軸回り止めとに兼用されている。但し
50cは回り止め専用ボルトである。Here, the left, right, and center cam bearings are of a two-part type, and are constituted by fixing the head cover 14 to the cylinder head 13.
14 and the cylinder head 13 are fixed with fixing bolts at the peripheral edge of the opening (joint face), each of the cam bearings, and both edges of the plug insertion port 13c (hatched in FIG. 6). Shown). Of the opening peripheral portion, a flange 14g formed on the outer side between caps 56, which will be described later, is fixed with fixing bolts 50a on the exhaust side, while the intake valve is connected between the intake valves on the intake side. Flanges 14h formed inside two places are fixed with fixing bolts 50b. The fixing bolt 50b faces outward when the cap 57 is removed. 50 of the fixing bolts are also used for fixing the cylinder head to the head cover and for locking the rocker shaft, which will be described later. However
50c is a non-rotating bolt.

そして上記カム軸42と左，右吸気弁37,38との間には
左，右排気ロッカ軸46a,46bがカム軸42と平行に配置さ
れており、上記ヘッドカバー14の内面に一体形成された
軸受部14eで支持され、かつ上記ヘッドカバー固定用ボ
ルト50で回り止めされている。この左，右排気ロッカ軸
46a,46bによって左，右排気ロッカアーム47,48が揺動自
在に軸支されている。該各ロッカアーム47,48の後端に
形成された摺動部47a,48aは上記カム軸42の左，右排気
カム42a,42dに摺接しており、また前端47b,48bに螺挿さ
れたアジャストスクリュー49の球面状に形成された下端
部が上記左，右排気弁棒37b,38bの上端に当接してい
る。Left and right exhaust rocker shafts 46a and 46b are disposed between the cam shaft 42 and the left and right intake valves 37 and 38 in parallel with the cam shaft 42, and are integrally formed on the inner surface of the head cover 14. It is supported by the bearing portion 14e and is prevented from rotating by the head cover fixing bolt 50. Left and right exhaust rocker shafts
Left and right exhaust rocker arms 47 and 48 are pivotally supported by 46a and 46b. The sliding portions 47a, 48a formed at the rear ends of the rocker arms 47, 48 are in sliding contact with the left and right exhaust cams 42a, 42d of the cam shaft 42, and are adjusted by being screwed into the front ends 47b, 48b. The spherical lower end of the screw 49 is in contact with the upper ends of the left and right exhaust valve rods 37b, 38b.

また上記カム軸42と吸気弁34〜36との間には上記左，
右カム軸受に渡る長さの吸気ロッカ軸45がカム軸42と平
行に配置されており、該ロッカ軸45はその両端部及び中
央部がヘッドカバー14に一体形成された軸受部14fで支
持され、かつヘッドカバー固定用ボルト50で回り止めさ
れている。そして該ロッカ軸45の上記中央カム軸受より
左側部分に左吸気ロッカアーム51が、右側部分に右吸気
ロッカアーム52が揺動自在に軸支されている。上記左吸
気ロッカアーム51の前端に形成された摺動部51aは上記
カム軸42の中央カム軸受の左隣に形成された左吸気カム
42bに摺接しており、後端51bに螺挿されたアジャストス
クリュー53の下端は上記左吸気弁棒34bの上端に当接し
ている。また上記右吸気ロッカアーム52の前端に形成さ
れた摺動部52cは上記カム軸42の中央カム軸受の右隣に
形成された右吸気カム42cに摺接している。この右吸気
ロッカアーム52の後半部は中央アーム部52aと右アーム
部52bとに分岐されており、それぞれの後端部52d,52eに
螺挿されたアジャストスクリュー54,53の球面状に形成
された下端は中央，右吸気弁棒35b,36bの上端に当接し
ている。ここで上述のようにカム軸方向に見ると上記中
央吸気弁棒35bの上端は左，右吸気弁棒34b,35bの上端と
ロッカ軸ｆを含む同一平面上に位置し、かつシリンダ軸
方向に見ると後方に位置している。そのためロッカ軸45
から中央吸気弁35用アジャストスクリュー54の上端まで
の平面投影距離l2′は左，右吸気弁34,36用アジャスト
スクリュー53までの平面投影距離１′より長くなって
いる。その結果中央吸気弁35のアーム長（ロッカ軸から
軸線Ａまでの垂直距離）l2も左，右吸気弁34,36のアー
ム長１より長くなっている。Further, between the camshaft 42 and the intake valves 34 to 36, the left,
An intake rocker shaft 45 having a length extending over the right cam bearing is arranged in parallel with the cam shaft 42, and the rocker shaft 45 is supported at both ends and a central portion by bearings 14f formed integrally with the head cover 14, And it is prevented from rotating by a head cover fixing bolt 50. A left intake rocker arm 51 is pivotally supported on a left portion of the rocker shaft 45 from the center cam bearing, and a right intake rocker arm 52 is pivotally supported on a right portion of the rocker shaft 45. A sliding portion 51a formed at the front end of the left intake rocker arm 51 is a left intake cam formed to the left of the center cam bearing of the camshaft 42.
The lower end of the adjustment screw 53 screwed into the rear end 51b is in contact with the upper end of the left intake valve rod 34b. A sliding portion 52c formed at the front end of the right intake rocker arm 52 is in sliding contact with a right intake cam 42c formed on the cam shaft 42 on the right of the center cam bearing. The rear half of the right intake rocker arm 52 is branched into a central arm 52a and a right arm 52b, and is formed in a spherical shape with adjusting screws 54, 53 screwed into the rear ends 52d, 52e, respectively. The lower end is in contact with the upper end of the center, right intake valve rod 35b, 36b. Here, when viewed in the cam axis direction as described above, the upper end of the central intake valve rod 35b is located on the same plane including the upper ends of the left and right intake valve rods 34b and 35b and the rocker shaft f, and in the cylinder axial direction. Looking backward, it is located behind. Rocker shaft 45
The plane projection distance l2 'from the top to the upper end of the adjustment screw 54 for the central intake valve 35 is longer than the plane projection distance 1' to the adjustment screw 53 for the left and right intake valves 34, 36. As a result, the arm length (vertical distance from the rocker shaft to the axis A) l2 of the central intake valve 35 is also longer than the arm length 1 of the left and right intake valves 34, 36.

また上記ヘッドカバー14の排気弁側には上記左，右排
気弁37,38のアジャストスクリュー49を調整するための
２つの調整口14cが形成されており、これは別途のキャ
ップ56で開閉可能となっている。また吸気弁側には上記
各吸気弁34〜36のアジャストスクリュー53,54を調整す
るための１つの調整口14dが形成されており、これは１
つのキャップ57で開閉可能となっている。On the exhaust valve side of the head cover 14, two adjusting ports 14c for adjusting the adjusting screws 49 of the left and right exhaust valves 37 and 38 are formed, which can be opened and closed by a separate cap 56. ing. One adjustment port 14d for adjusting the adjustment screws 53 and 54 of the intake valves 34 to 36 is formed on the intake valve side.
It can be opened and closed with two caps 57.

ここで本実施例のアジャストスクリューと吸気弁との
配置関係について第１図〜第３図に沿って詳述する。な
お、弁棒の上端のアジャストスクリューとの当接面は、
一般にアジャストスクリューの球状当接面より大きい曲
率の球状の凹設されているが、理解を容易化するため上
記当接面が平面である状態で説明する。Here, the positional relationship between the adjustment screw and the intake valve of the present embodiment will be described in detail with reference to FIGS. The contact surface of the upper end of the valve stem with the adjustment screw is
Generally, a spherical concave portion having a curvature larger than that of the spherical contact surface of the adjusting screw is provided.

第１図において、θはロッカアーム51,52の全揺動角
度、ａ〜ｄはロッカ軸ｆと、アジャストスクリューと弁
軸との後述する接点とを結ぶ作動直線であり、a,dはそ
れぞれ吸気弁全閉時，全開時の作動直線を示し、ｂは作
動直線と中央吸気弁の弁軸Ａとがなす作動角度θ′が90
度をなす時点での作動直線を、ｃは左，右吸気弁の弁軸
Ｂとの作動角度θ′が90度をなす時点での作動直線を示
す。同図からも明らかなように、本実施例では、左，中
央，右吸気弁34〜36の各接点は上記揺動軸ｆを含む同一
平面上に位置しており、また各弁34〜36の何れにおいて
も、上記作動角度θ′が90度の位置（基準揺動位置）を
通って揺動するように設定されており、かつ左，右吸気
弁34,36については上記基準揺動位置（作動直線ｃ）よ
り閉側の揺動角度θ１が開側揺動角度θ２より大きく設
定されており、また中央吸気弁35については閉側揺動角
度θ３が開側揺動角度θ４より小さく設定されている。In FIG. 1, θ is the total swing angle of the rocker arms 51 and 52, a to d are operation straight lines connecting the rocker shaft f and a contact point between the adjust screw and the valve shaft, and a and d are intake air, respectively. B indicates an operating straight line when the valve is fully closed and fully opened, and b indicates that the operating angle θ ′ formed by the operating straight line and the valve axis A of the central intake valve is 90 °.
And c indicates an operation straight line when the operation angle θ ′ of the left and right intake valves with the valve shaft B is 90 degrees. As can be seen from the figure, in the present embodiment, the respective contacts of the left, center, and right intake valves 34 to 36 are located on the same plane including the swing axis f. In either case, the operating angle θ 'is set so as to swing through a position (reference swing position) of 90 degrees, and the left and right intake valves 34 and 36 have the reference swing position. The swing angle θ1 on the closing side from (operating straight line c) is set larger than the opening side swing angle θ2, and the closing side swing angle θ3 of the central intake valve 35 is set smaller than the opening side swing angle θ4. Have been.

また上記ロッカアームの揺動に伴ってアジャストスク
リュー53,54の軸線D,Eもθだけ揺動する。そのため第３
図に示すように、アジャストスクリュー53と左，右吸気
弁34,36との接点は、Ts1（全閉時）〜Ts2（アジャスト
スクリューとの弁棒の上端面とが垂直に当接する基準揺
動位置）〜Ts3（全開時）と変化し、Ts1,Ts3はTs2に対
してそれぞれDs1,Ds2だけ偏位することとなる。この場
合、閉側揺動角度θ１が開側揺動角度θ２より大きく設
定されていることから、Ds1＞Ds2となっており、この偏
位量を吸気弁の軸線Ｂに対して対称に振り分けるため、
左，右吸気弁用アジャストスクリュー53は上記基準揺動
位置において軸線Ｄが左，右吸気弁34,36の軸線Ｂに対
してDsだけカム軸直角方向後方（第１図左方）に偏位す
るように設定されている。The axes D and E of the adjusting screws 53 and 54 also swing by θ with the swing of the rocker arm. Therefore the third
As shown in the figure, the contact point between the adjusting screw 53 and the left and right intake valves 34 and 36 is from Ts1 (when fully closed) to Ts2 (the reference oscillation when the upper end surface of the valve stem with the adjusting screw is in vertical contact). Position) to Ts3 (when fully opened), and Ts1 and Ts3 are deviated from Ts2 by Ds1 and Ds2, respectively. In this case, since the closing-side swing angle θ1 is set to be larger than the open-side swing angle θ2, Ds1> Ds2, and this deviation amount is symmetrically distributed with respect to the axis B of the intake valve. ,
In the reference swing position, the axis D of the left and right intake valve adjust screw 53 is displaced rearward in the direction perpendicular to the cam shaft by Ds with respect to the axis B of the left and right intake valves 34 and 36 (leftward in FIG. 1). Is set to

同様にアジャストスクリュー54と中央吸気弁35との接
点は、第２図に示すように、Tc1〜Tc2〜Tc3と変化し、
閉側揺動角度θ３が開側揺動角度θ４より小さく設定さ
れていることから偏位量はDc1＜Dc2となり、これを対称
に振り分けるため、上記アジャストスクリュー54はカム
軸直角方向前方にDcだけ偏位するように設定されてい
る。Similarly, the contact point between the adjusting screw 54 and the central intake valve 35 changes from Tc1 to Tc2 to Tc3 as shown in FIG.
Since the closing-side swing angle θ3 is set to be smaller than the open-side swing angle θ4, the amount of deviation is Dc1 <Dc2. In order to distribute the deviation symmetrically, the adjusting screw 54 is only Dc forward in the direction perpendicular to the cam shaft. It is set to deviate.

次に本実施例の作用効果について説明する。 Next, the operation and effect of this embodiment will be described.

本実施例の動弁装置では、カム軸42の回転に伴って、
ロッカアーム51,52が揺動し、これのアジャストスクリ
ュー53,54が左，右吸気弁34,36,中央吸気弁35を同時
に、かつ上記作動角度θ′が鋭角〜直角〜鈍角をなすよ
うに移動させる。まず全閉状態からθ３だけ揺動した時
点で中央吸気弁35の作動角度θ′が直ちに90度となり、
θ１揺動した時点で上記交差角θｓとθｃとの差角だけ
中央吸気弁に遅れて左，右吸気弁34,36の作動角度θ′
が90度となり、これからさらにθ２だけ揺動した時点で
全開となる。In the valve gear of this embodiment, with the rotation of the cam shaft 42,
The rocker arms 51 and 52 swing, and the adjusting screws 53 and 54 thereof move the left and right intake valves 34 and 36 and the central intake valve 35 at the same time, and the operating angle θ 'forms an acute angle to a right angle to an obtuse angle. Let it. First, at the time of swinging by θ3 from the fully closed state, the operating angle θ ′ of the central intake valve 35 immediately becomes 90 degrees,
When θ1 swings, the operating angles θ ′ of the left and right intake valves 34 and 36 are delayed by the difference between the crossing angles θs and θc behind the central intake valve.
Becomes 90 degrees, and when it further swings by θ2, it is fully opened.

このように本実施例では、角吸気弁の接点を揺動軸ｆ
を含む同一平面上に位置させるとともに、より起立して
いる中央吸気弁35の閉側揺動角θ３を開側揺動角θ４よ
り小さく設定したので、上記従来の基準揺動位置を中心
に上，下に振り分けた場合に比較して、該中央吸気弁35
の基準揺動位置より上方への揺動高さが低くなり、それ
だけ動弁機構の高さ、ひいてはエンジン高さが低くな
る。As described above, in the present embodiment, the contact point of the square intake valve is changed to the swing axis f.
And the closed-side swing angle θ3 of the more upright central intake valve 35 is set smaller than the open-side swing angle θ4. , The central intake valve 35
The swing height upward from the reference swing position becomes lower, and accordingly, the height of the valve mechanism and, consequently, the engine height becomes lower.

また何れの吸気弁においても、作動角度θ′が90度を
なす揺動基準位置を通るように揺動角度を設定したか
ら、上記接点における滑り速度，接点応力の増大を抑制
でき、耐久性が低下することもない。Further, in any of the intake valves, the swing angle is set so that the operating angle θ 'passes through the swing reference position at 90 degrees, so that the increase in the sliding speed and the contact stress at the contact point can be suppressed, and the durability is improved. It does not drop.

さらにまた本実施例では、閉側揺動角度θ１が開側揺
動角度θ２より大きく設定された左，右アジャストスク
リュー53については、カム軸直角方向後方に偏位させた
ので、その全閉時の接点Ts1と全開時の接点Ts3とが弁軸
Ｂを中心に対称に振り分けられ、弁棒の当接面を有効に
使用することができる。また閉側揺動角度θ３が開側揺
動角度θ４より小さく設定された中央アジャストスクリ
ュー54については、カム軸直角方向前方に偏位させたの
で、接点の変化量が上記左，右吸気弁の場合と同様に弁
軸Ａを中心に対称に振り分けられ、当接面を全体に平均
的に使用することができる。Furthermore, in the present embodiment, the left and right adjustment screws 53 in which the closing-side swing angle θ1 is set to be larger than the open-side swing angle θ2 are displaced rearward in the direction perpendicular to the camshaft. The contact Ts1 and the contact Ts3 when fully opened are distributed symmetrically about the valve axis B, so that the contact surface of the valve stem can be used effectively. Further, since the center adjusting screw 54 in which the closing-side swing angle θ3 is set smaller than the open-side swing angle θ4 is displaced forward in the direction perpendicular to the camshaft, the amount of change in the contact point is smaller than that of the left and right intake valves. In the same way as in the case described above, the contact is distributed symmetrically around the valve axis A, and the contact surface can be used on average as a whole.

なお上記実施例では吸気弁が３本の場合を説明した
が、本発明は異なる傾斜角で持って配設された複数の弁
を有するエンジンであれば、吸気弁が４本以上の場合に
も、また排気弁の場合にも勿論適用できるものである。In the above embodiment, the case where the number of intake valves is three has been described. However, the present invention is applicable to an engine having a plurality of valves arranged with different inclination angles even when the number of intake valves is four or more. Of course, the present invention can be applied to the case of an exhaust valve.

本発明は、単気筒エンジンに限らず複数気筒エンジン
にも勿論適用できる。The present invention is applicable not only to a single cylinder engine but also to a multiple cylinder engine.

〔発明の効果〕〔The invention's effect〕

以上のように本発明に係るエンジンの動弁装置によれ
ば、押圧部材と弁棒との各接点を同一平面上に位置させ
るとともに、傾斜角の小さい第２弁に関する閉側揺動角
度を開側揺動角度より小さく設定したので、該第２弁の
基準揺動位置より上方への揺動量が小さくなり、その分
だけ動弁機構、ひいてはエンジン高さを低減できる効果
がある。またこの場合、何れの弁についても作動角度が
90度をなす基準揺動位置を通るように移動するので、接
点における滑り速度，接点応力の増加を抑制でき、耐久
性に支障をきたすこともない。As described above, according to the valve train of the engine according to the present invention, each contact point between the pressing member and the valve stem is located on the same plane, and the closing-side swing angle of the second valve having a small inclination angle is opened. Since the swing angle is set to be smaller than the side swing angle, the swing amount of the second valve upward from the reference swing position is reduced, and the valve operating mechanism and the engine height can be reduced accordingly. In this case, the operating angle of each valve is
Since it moves so as to pass through the 90-degree reference swing position, it is possible to suppress an increase in the sliding speed and the contact stress at the contact, and there is no hindrance to durability.

また、請求項２の発明では、押圧部材平行状態に関し
て、傾斜角の大きい第１弁側の閉側揺動角度を大きく
し、傾斜角の小さい第２弁側の閉側揺動角度を小さく設
定したので、第１押圧部材及び第２押圧部材の軸線のな
す角度を平行に設定することが可能となり、例えば二股
状の押圧部材に第1,第２押圧部材を装着する場合に両方
の装着孔を同時に開けることができる等、孔明け加工が
容易となる効果がある。According to the second aspect of the present invention, with respect to the pressing member parallel state, the closing-side swing angle of the first valve having a large inclination angle is set to be large, and the closing-side swing angle of the second valve having a small inclination angle is set to be small. Therefore, it is possible to set the angle between the axes of the first pressing member and the second pressing member to be parallel, and for example, when mounting the first and second pressing members on the forked pressing member, both mounting holes are used. Can be opened at the same time.

【図面の簡単な説明】[Brief description of the drawings]

第１図ないし第８図は本発明の一実施例によるSOHCエン
ジンの動弁装置を説明するための図であり、第１図はア
ジャストスクリューと弁棒との関係を模式的に示す拡大
図、第２図，第３図はその接点部分を模式的に示す拡大
図、第４図，第５図はそれぞれ第６図のIV-IV線断面図,
V−Ｖ線断面図、第６図は該装置の平面図、第７図は吸
気，排気通路部分を示す断面平面図、第８図は該実施例
エンジンが搭載された自動二輪車の右側面図である。 図において、10はSOHCエンジン、34,36は左，右吸気弁
（第１弁）、35は中央吸気弁（第２弁）、51,52は左，
右ロッカアーム（揺動部材）53,54はアジャストスクリ
ュー（第1,第２押圧部材）、A,Bは第2,第１弁の軸線、
ａ〜ｄは作動直線、Ｆはシリンダ軸線、ｆは揺動軸、Ts
1〜TS3,Tc1〜Tc3は接点、θｓは第１傾斜角、θｃは第
２傾斜角、θ′は作動角度、θ1,θ３は閉側揺動角度、
θ2,θ４は開側揺動角度である。1 to 8 are views for explaining a valve operating device of an SOHC engine according to one embodiment of the present invention, and FIG. 1 is an enlarged view schematically showing a relationship between an adjusting screw and a valve stem; 2 and 3 are enlarged views schematically showing the contact portion, and FIGS. 4 and 5 are sectional views taken along the line IV-IV of FIG. 6, respectively.
6 is a plan view of the device, FIG. 7 is a sectional plan view showing intake and exhaust passages, and FIG. 8 is a right side view of a motorcycle equipped with the engine of the embodiment. It is. In the figure, 10 is a SOHC engine, 34 and 36 are left and right intake valves (first valve), 35 is a central intake valve (second valve), 51 and 52 are left and
Right rocker arms (swing members) 53 and 54 are adjusting screws (first and second pressing members), A and B are axes of the second and first valves,
a to d are operating straight lines, F is a cylinder axis, f is a swing axis, Ts
1 to TS3, Tc1 to Tc3 are contact points, θs is a first inclination angle, θc is a second inclination angle, θ ′ is an operating angle, θ1 and θ3 are closing swing angles,
θ2 and θ4 are open side swing angles.

Claims (2)

(57)【特許請求の範囲】(57) [Claims] 【請求項１】１本のカム軸の一側に３本の吸気弁を、他
側に排気弁を配置し、カム軸と吸気弁との間に吸気揺動
部材を軸支する吸気揺動軸を、カム軸と排気弁との間に
排気揺動部材を軸支する排気揺動軸を、それぞれカム軸
と平行にかつカム軸より上方に配置し、上記揺動部材を
シーソータイプのものとし、上記各弁を上記カム軸によ
り上記各揺動部材を介して駆動するようにしたエンジン
の動弁装置において、上記吸気弁をシリンダ軸線Ｆと第
１傾斜角θｓをなすように配置された第１弁34,36と、
上記第１傾斜角θｓより小さい第２傾斜角θｃをなすよ
うに配置された第２弁35とで構成し、上記吸気揺動部材
を上記第1,第２弁を押圧する第1,第２押圧部材を備えた
ものとするとともに、上記各吸気弁と上記各押圧部材と
の接点と上記揺動軸45とを結ぶ作動直線が、該作動直線
と上記各吸気弁の軸線とのなす作動角度が90度をなす基
準揺動位置を弁移動行程の途中で通過するように上記各
吸気弁の傾斜角度及び上記揺動軸の位置を設定し、上記
第２弁35の上端を第１弁34,36の上端よりカム軸直角方
向外方に位置させ、かつ該第１弁34,36、第２弁35の上
端を上記揺動軸45を含む略同一平面内に位置させ、上記
基準揺動位置における作動直線ｃ又ｂと全閉位置におけ
る作動直線ａとで構成される閉側揺動角度θ１又はθ３
と、上記基準揺動位置における作動直線ｃ又はｂと全閉
位置における作動曲線ｄとで構成される開側揺動角度θ
２又はθ４とに関して、上記第１弁34,36については閉
側揺動角度θ１を開側揺動角度θ２より大きく設定し、
かつ上記第２弁35については閉側揺動角度θ３を開側揺
動角度θ４より小さく設定したことを特徴とするエンジ
ンの動弁装置。An intake oscillating member which has three intake valves on one side of a camshaft and exhaust valves on the other side, and supports an intake oscillating member between the camshaft and the intake valve. The shaft is disposed between the camshaft and the exhaust valve, the exhaust swinging shaft supporting the exhaust swinging member is arranged in parallel with the camshaft and above the camshaft, and the swinging member is of a seesaw type. In the valve operating device for an engine in which each of the valves is driven by each of the camshafts through each of the swing members, the intake valve is disposed so as to form a first inclination angle θs with the cylinder axis F. The first valves 34, 36,
A second valve 35 disposed so as to form a second inclination angle θc smaller than the first inclination angle θs, and the first and second valves which press the first and second valves by pressing the intake swinging member. A pressing member is provided, and an operating straight line connecting the contact point between each of the intake valves and each of the pressing members and the swing shaft 45 is an operating angle formed by the operating straight line and the axis of each of the intake valves. The inclination angle of each of the intake valves and the position of the oscillating shaft are set so that the traversing position passes through a reference oscillating position of 90 degrees in the middle of the valve movement stroke. , 36, and the upper ends of the first valves 34, 36, and the second valve 35 are located in substantially the same plane including the oscillating shaft 45. The closing swing angle θ1 or θ3 composed of the operating line c or b at the position and the operating line a at the fully closed position.
And an open side swing angle θ composed of an operating line c or b at the reference swing position and an operating curve d at the fully closed position.
2 or θ4, for the first valves 34 and 36, the closing-side swing angle θ1 is set to be larger than the open-side swing angle θ2,
The valve operating device for an engine, wherein the second valve 35 is set such that the closing-side swing angle θ3 is smaller than the open-side swing angle θ4. 【請求項２】シリンダ軸線Ｆと第１傾斜角θｓをなすよ
うに配置された第１弁34,36と、上記第１傾斜角θｓよ
り小さい第２傾斜角θｃをなすように配置された第２弁
35と、揺動軸回りに揺動して上記第1,第２弁を移動させ
る揺動部材と、該揺動部材に設けられ上記第１弁，第２
弁の上端を押圧する第1,第２押圧部材とを備えたエンジ
ンの動弁装置において、上記第２弁35の上端を第１弁3
4,36の上端よりカム軸直角方向外方に位置させ、かつ該
第１弁34,36第２弁35の上端を上記揺動軸45を含む略同
一平面内に位置させ、上記各弁と各押圧部材との接点と
上記揺動軸45とを結ぶ作動直線が、該作動直線と上記各
弁の軸線とのなす作動角度が90度をなす基準揺動位置を
弁移動行程の途中で通過するように上記各弁の傾斜角度
及び上記揺動軸の位置を設定し、上記基準揺動位置にお
ける上記作動直線ｃ又はｂと全閉位置における作動直線
ａとで構成される閉側揺動角度θ１又はθ３と、上記基
準揺動位置における上記作動直線ｃ又はｂと全開位置に
おける作動曲線ｄとで構成される開側揺動角度θ２又は
θ４とに関して、上記第１弁34,36については閉側揺動
角度θ１を開側揺動角度θ２より大きく設定し、かつ上
記第２弁35については閉側揺動角度θ３を開側揺動角度
θ４より小さく設定し、上記押圧部材を上記揺動部材に
進退可能に装着するとともに、該押圧部材53,54の軸線
D,Eと上記各弁の軸線B,Aとが平行となる押圧部材平行状
態が上記弁移動行程の途中で存在するように上記各弁の
傾斜角度及び上記押圧部材の装着角度を設定し、上記押
圧部材平行状態における平行時作動直線ｃ′又はｂ′と
全閉位置における作動直線ａとで構成される閉側揺動角
度θ１′又はθ３′と、上記平行時作動直線ｃ′又は
ｂ′と全閉位置における作動曲線ｄとで構成される開側
揺動角度θ２′又はθ４′とに関して、上記第１弁34,3
6については閉側揺動角度θ１′を開側揺動角度θ２′
より大きく設定し、かつ上記第２弁35については閉側揺
動角度θ３′を開側揺動角度θ４′より小さく設定した
ことを特徴とするエンジンの動弁装置。2. The first valves 34, 36 arranged to form a first inclination angle θs with the cylinder axis F, and the second valves 34, 36 arranged to form a second inclination angle θc smaller than the first inclination angle θs. 2 valves
35, a swing member that swings around the swing axis to move the first and second valves, and the first valve and the second valve that are provided on the swing member.
In a valve operating device for an engine having first and second pressing members for pressing an upper end of a valve, an upper end of the second valve 35 is connected to a first valve 3.
The upper ends of the first valve 34 and the second valve 35 are positioned substantially in the same plane including the oscillating shaft 45, and the upper and lower ends of the first and second valves 34 and 36 are positioned in the direction perpendicular to the camshaft. An operating straight line connecting the contact point with each pressing member and the swing shaft 45 passes a reference swing position in which the operating angle between the operating straight line and the axis of each valve forms 90 degrees in the middle of the valve moving stroke. The tilt angle of each of the valves and the position of the swing axis are set so that the operating straight line c or b at the reference swing position and the operating straight line a at the fully closed position are set. Regarding θ1 or θ3, and the open-side swing angle θ2 or θ4 composed of the operating line c or b at the reference swing position and the operating curve d at the fully open position, the first valves 34 and 36 are closed. The side swing angle θ1 is set larger than the open side swing angle θ2, and the second valve 35 is closed side swing angle. θ3 smaller set than the open-side swing angle θ4 and the pressing member while retractably mounted on the swing member, the axis of the pressing member 53 and 54
D, E and the axis of each of the valves B, A parallel to the pressing member parallel state is set in the middle of the valve movement stroke, the inclination angle of each valve and the mounting angle of the pressing member are set, A closing side swing angle θ1 ′ or θ3 ′ composed of the operating line c ′ or b ′ in the parallel state of the pressing member and the operating line a in the fully closed position, and the operating line c ′ or b ′ of the parallel state With respect to the open-side swing angle θ2 ′ or θ4 ′ formed by the first valve 34, 3 and the operation curve d at the fully closed position.
For 6, the closed side swing angle θ1 'is changed to the open side swing angle θ2'.
An engine valve operating device characterized in that the valve is set to be larger and the second valve 35 is set so that the closing side swing angle θ3 ′ is smaller than the open side swing angle θ4 ′.