JP4371384B2 - Cylinder block of multi-cylinder engine - Google Patents

Description

【００５７】
【表２】

【００５８】
【表３】

上記表１〜表３に示したように、母材のアルミニウム合金はＳｉを５〜２０％（重量％）含有し、スリーブ２７のアルミニウム合金としては、（スリーブ２７のＳｉ重量含有率／母材の重量含有率）×１００をαとすると、
５０＜α＜１５０
となるようなＳｉ含有量のアルミニウム合金を用いる。このような構成のアルミニウム合金を用いて母材およびスリーブをそれぞれ形成することにより、母材とスリーブの熱膨張率の差が小さくなり、母材とスリーブ間でのヒートスポットの発生やスリーブ内周面の熱変形が軽減して、スリーブ内周面に施しためっき皮膜ａの剥がれが抑制される。
【００５９】
なお、表２のＡＣ４Ｃによりシリンダブロック母材を形成する場合には、母材のＳｉ重量含有率は６．５〜７．５％となるので、表３の合金１あるいは合金２において、Ｓｉ含有量を例えば３．７５〜９．７５重量％に変更した合金を使用し、上記スリーブのＳｉ重量含有率／母材のＳｉ重量含有率の条件を満足させるようにする。同様に、ＡＤＣ１０によりシリンダブロック母材６０を形成する場合には、母材６０のＳｉ重量含有率は７．５〜９．５％となるので、表３の合金１あるいは合金２において、Ｓｉ含有量を例えば４．７５〜１５重量％に変更した合金を使用し、上記スリーブのＳｉ重量含有率／母材のＳｉ重量含有率の条件を満足させるようにする。
【００６０】
さらに、表３に示すようにスリーブのアルミニウム合金は各々少なくとも０．２以上１０以下のＣｕとＭｇの両方を含有する。これにより、下記するようにＴ６処理をして容易に硬度をＨＢ７０以上とすることができる。なお、ＣｕとＭｇの内一方のみ含有する場合でもＴ６処理をして容易に硬度をＨＢ７０以上とすることができる。また、表１及び表２に示すように母材のアルミニウム合金はＣｕとＭｇの一方あるいは両方を含有する。これにより、下記するようにスリーブとともに母材にＴ６処理をして容易に硬度を上げることができ、スリーブのめっき層支持部のめっき保持能力の向上を図りつつ、シリンダブロック全体の剛性を上昇させることができ、エンジンの耐久性を向上させることができる。
【００６１】
図１３は、上記スリーブ２７の鋳込みによるシリンダブロック２２の製造工程を説明するためのフローチャートである。このフローにおいて、Ｔ６処理（ステップＳ２、Ｓ４、Ｓ６）は、スリーブのめっき皮膜支持部となる内周面の表面硬度を高めるために、ＪＩＳ規格Ｈ５２０２に基づき、スリーブ単体またはスリーブを鋳込んだシリンダブロック全体を所定の温度で溶体化後時効硬化するものであり、ステップＳ２、Ｓ４、Ｓ６のいずれか１回行えばよく、或いは省略してもよい。このようなＴ６処理によりスリーブ表面硬度をＨＢ７０以上（７０〜１５０）とすることが望ましい。なお、スリーブの押出し又は引き抜き成形により、内周面の表面硬度をＨＢ７０以上とした場合には、その後のＴ６処理により表面硬化処理を省略することもできる。
【００６２】
なお、ステップＳ２、Ｓ４のいずれかのＴ６処理によれば、スリーブのみ硬度上昇を図ることができる。鋳込み時、溶湯状態の母材側の熱によりスリーブの硬度が若干低下するが、鋳造時間そのものはＴ６処理に相対して短く、スリーブの内周側の硬度をＨＢ７０以上に保つことができる。また、ステップＳ６のＴ６処理によれば、スリーブの硬度上昇に加えシリンダブロックの母材の硬度も上昇することができ、シリンダブロック全体の剛性を上昇させることができ、エンジン振動により各部の摺動部のクリアランス等が小さくなって摺動摩耗が増加する等に起因する、エンジンの耐久性の低下を防止することができる。
【００６３】
外周ショットブラスト（ステップＳ３）は、スリーブ外周面に細かい凹凸を形成し、母材との接合性を高めるためのものである。このようにスリーブの鋳込み前にスリーブ外周面に凹凸を形成することにより、運転中の母材とスリーブの熱膨張率の違いにより緊迫力が低下しても、スリーブの抜けを確実に防止できる。このようなスリーブ外周面の凹凸は、ショットブラスト以外にも他の機械加工あるいはスリーブ全体の酸洗い（エッチング）等により形成することができる。なお、このショットブラスト処理（ステップＳ３）は省略してもよい。また、ショットブラスト等によりスリーブ外周に凹凸を形成して母材との接合性を高める方法に代えて、低融点半田を用いてスリーブと母材とを接合しスリーブの抜け防止を図ってもよい。
【００６４】
なお、ここでショットブラストとは、粒径が５０〜１５０μｍの鋼球、超硬ビーズ、ステンレス鋼球、亜鉛ビーズ、ガラスビーズや、粒径はもう少し大きい石英を多く含む川砂等を、投射機で、例えば４０〜８０ｍ／ｓの投射速度でワークを投射するものを言う。
【００６５】
図１４は上記めっき処理工程（ステップＳ８）の詳細なフローチャートであり、図２０，図２１はこのめっき処理を行うめっき処理装置の構成図である。図１４のフローチャートにおいて、スリーブ内面のめっき処理は、基本的には、脱脂処理（ステップＳ１１）、アルカリエッチング処理（ステップＳ１３）、混酸エッチング処理（ステップＳ１５）、アルマイト処理（ステップＳ１７）および複合めっき処理（ステップＳ１９）の５つの工程からなり、各工程の後に水洗処理（ステップＳ１２、１４、１６、１８、２０）が施される。
【００６６】
上記水洗処理は各工程ごとに別々の２つの水槽（合計１０個）を用いて、シリンダブロック全体を順番に２つの水槽内に浸漬し上下に動かして前工程の処理液を除去するものである。水槽内の水は定期的に新しい清浄な水と交換される。各水洗処理終了後に次の工程への移動はできるだけ速やかに行い、表面に水膜がついている状態で次の処理を行うことが望ましい。これにより、処理部への塵埃等の付着や空気中の酸素が直接触れることを防止して酸化膜の形成等を防止し、後の工程での処理の信頼性を高めることができる。これは特にメッキ処理の場合有効である。
【００６７】
図２０，図２１に示すように、スリーブ２７を母材に鋳込んだシリンダブロック２２は、スリーブ２７の内周面に各処理を施すために、シリンダ本体部２２ｃの合面を下側にして、各工程において専用の装置本体１００ａ，１００ｂ上にシール用ガスケット１０１ａ，１０１ｂを介して搭載される。各工程でそれぞれ専用の処理液糟１０２ａ，１０２ｂ内の処理液１０５ａ，１０５ｂが専用のポンプ１０６ａ，１０６ｂにより装置本体１００ａ，１００ｂの内部に供給され、スリーブ２７の内側を上昇して内筒１０７ａ，１０７ｂを通って処理液糟１０２ａ，１０２ｂに戻る。
【００６８】
図２０はアルカリエッチング，混酸エッチング処理状態を示す。このエッチング処理の範囲は、上記めっき皮膜の形成範囲に対して余裕を持たせる必要があることから、上記スリーブ２７の上記逃げ部２７ａのクランク軸側端部付近までとされる。そしてこの場合の処理範囲の管理は、上記内筒１０７ａの上端面１０７ａ´の高さ位置によって処理液１０５ａの液面を管理することによって行われるが、この方法では精度良く行うには限界がある。仮に上記エッチンク処理液１０５ａがミッションケース２６側等に溢れ出た場合、図６左端の気筒についてはミッションケース２６側の加工済み面を荒らす恐れがある。
【００６９】
そこで本実施形態では、上記左端の気筒については、上述のようにミッションケース２６側部分にリブ状の堰部２５ｄ′を形成したものであり、これによりエッチング処理液がミッションケース側に溢れ出るのを防止できる。
【００７０】
上記ガスケット１０１ａ，１０１ｂは、各処理工程における処理液の漏れを防止するためのシール材であるとともにアルマイト処理工程（ステップＳ１７）および複合めっき工程（ステップＳ１９）においては電解作用の絶縁材として機能する。このアルマイト処理工程と複合めっき工程においては、図２１に示すように、それぞれ、例えば交流電源１０８から整流器１０９および制御回路１１０を介してシリンダ本体部２２ｃと内筒１０７間に直流電圧を印加して電解液中に直流電流を流す。なお、その他の工程においては処理液中に直流電流は流さない。
【００７１】
上記複合めっき処理は高速メッキ処理であり、所定のめっき条件で、専用の処理液糟１０２ｂ内のメッキ液１０５ｂをポンプ１０６ｂにより装置本体１００ｂ内に供給し、内筒１０７ｂを通して処理液糟１０２ｂに戻すといった経路を高速で循環させながらスリーブ２７の内面にめっき皮膜を形成する。この高速めっき工程においては、内筒１０７ｂを電源回路の（＋）側に、シリンダ本体部２２ｃを（−）側に接続し、直流電流をめっき液中に流す。これにより、後述の組成のめっき液中のＮｉ⁺ およびＰ⁺ がスリーブ内周面に付着し、これに伴って分散剤であるＳｉＣ粒子がめっき層中に巻き込まれる。このようにして、スリーブ内周面に、ＳｉＣを含み耐摩耗性および潤滑性に優れためっき皮膜ａが５０〜１５０μｍの厚さに形成される。
【００７２】
また上記ステップＳ１９の高速めっき処理ではスリーブ２７の上端部にカバー１１１が装着される。このカバー１１１は、高速で循環するめっき液１０５ｂの飛散噴出を防止するとともに、スリーブ２７の内面のめっき範囲を規制する。めっき範囲は、スリーブ２７の内周面のうち、シリンダヘッドとの境界部になるガスケット１０１ｂからカバー１１１のＯリング１１２までの範囲に規制される。従って上記Ｏリング１１２の位置を上記逃げ部２７ａの途中に設定することにより上述のようにめっき皮膜ａの下端縁ａ′にピストン３１の外周面下端部が接触しないようにできる。
【００７３】
上記ステップＳ１９の複合めっき処理の後、再びステップＳ２０の水洗処理が実施されてめっき液が除去され、ステップＳ２１のエアーブローによりシリンダブロック２２に付着する水分が除去される。そして以上のめっき処理ステップＳ８の後、貫通孔５２の加工を経た後にホーニングステップＳ９でスリーブ２７内周面のめっき層にホーニング仕上げを施し、めっき皮膜の厚みを望ましくは約５０μｍ、場合によっては２０μｍ〜１００μｍとするとともに、めっき層の面粗さを１．０μｍＲｚ以下にする。これにより、確実にめっき層表面を滑らかにすることができてピストン３１およびピストンリング３１ｄの摺動時の摩擦係数を小さくすることができるとともに、エンジンオイルの保持性が向上し潤滑性を向上させることができる。なお、ＲｚとはＪＩＳ規格のＢ０６０１に定められたものである。
【００７４】
次に本実施形態の作用効果について説明する。
本実施形態では、シリンダ本体部２２ｃと上クランクケース部２５ａ及び上ミッションケース部２６ａをアルミ合金のダイカスト鋳造により一体形成したので、部品点数を削減できるとともに各部の薄肉化が可能となり軽量化を図ることができる。
【００７５】
また上記シリンダ本体部２２ｃ内にアルミ合金の引き抜きパイプ材からなるスリーブ２７を鋳込み、これの内表面にめっき皮膜ａを形成するようにしたので、該スリーブ２７の内表面には、ダイカスト鋳造面にめっき皮膜を直接形成する場合のような巣がないことから、めっきの付着性が良好であり、生産不良率を低減できる。
【００７６】
また上記めっき皮膜ａの形成に当たって、めっき液をスリーブ２７の内面と処理液層との間で高速で循環させようにした高速めっき法を採用したので、静止浴内にワーク全体を浸漬してめっきする方法に比較して生産性を向上できる。
【００７７】
また変速装置を収容する上ミッションケース部２６ａの上縁部２６ｃを上記シリンダ本体部２２ｃのシリンダヘッド側合面より下方に位置させたので、図２０，２１に示すように、上記めっき処理工程においてシリンダヘッド側合面を下側に向けてめっき処理用装置本体１００ａ，１００ｂ上に搭載した場合に、上ミッションケース部２６ａの上縁部２６ｃが装置本体１００ａ，１００ｂに干渉しにくくなり、それだけめっき処理作業におけるワークの支持が容易でありめっき処理作業性を向上できる。
【００７８】
さらにまた図２に示すように、クランク軸２１，メイン軸７２，及びドライブ軸７４を、クランク軸・メイン軸直線Ａと気筒軸線２０とのなす第１軸角度θ１、及び上記軸直線Ａとメイン軸・ドライブ軸直線Ｂとのなす第２軸角度θ２がそれぞれ鋭角をなすように配置したので、クランク軸２１とドライブ軸７４との軸間距離を縮小でき、エンジン前後長を短くでき、従ってミッションケース部２６のシリンダ本体部２２ｃからのオーバーハング量を小さくでき、この点からもワークの支持が容易でありめっき処理作業性を向上できる。
【００７９】
また上記メイン軸７２をクランク軸２１を通る直角直線Ｃよりシリンダヘッド２３側に寄せて配置したので、メイン軸７２はシリンダブロック２２の背面に背負うように配置されることとなり、エンジンユニット１５の前後長さをさらに縮小できる。さらにクラッチ機構８１をこれの最大外周面８１ａが下死点のピストン頂面を通る直角直線Ｄよりシリンダヘッド２３側に位置するように配置したので、この点からもエンジンユニット１５を小型化できる。
【００８０】
上記クラッチ機構８１の最大径部分の軸方向投影面内にメイン軸７２，シフトドラム９０，各フォーク軸９１，９２及びドライブ軸７４を配置したので、各軸の配置がコンパクトとなり、ユニットケース２５の出っ張りを小さくでき、この点からもエンジンを小型できる。
【００８１】
またシリンダ本体部２２ｃのピストン摺動面２２ａを構成するスリーブ２７（シリンダ内壁）の下端でかつミッションケース部２６側の部位に反ミッションケース部側に比べてクランク軸２１側に突出するリブ状の堰部２５ｄ′を設けたので、上述のめっき処理行程において、特にエッチッグ液等の処理液がミッションケース２６側に溢れるのを、スリーブ２７を必要以上にクランク軸２１側に延長することなく回避でき、既に加工済みの面がエッチング液等で荒らされるのを防止できる。
【００８２】
また上記堰部２５ｄ′を設けるに当たり、クランク軸軸受ボス部２９間に出力取出部を有する気筒のミッションケース側の部位にのみ該堰部２５ｄ′を設け、他の気筒についてはクランク室とミッション室との間に両者を仕切り、かつ上記ピストン摺動面２２ａ（スリーブ２７）の下端よりシリンダ軸２１方向高さの高い隔壁２５ｄを設けたので、該隔壁２５ｄを上記堰部２５ｄ′に兼用できる。なお、上記隔壁２５ｄの本来の目的はケース剛性を向上させる点にある。
【００８３】
さらにまたスリーブ２７（シリンダ内壁）のクラン軸側端部にピストン摺動面２２ａより大径の逃げ部２７ａを形成し、めっき皮膜ａをこの逃げ部２７ａの途中部位（ｈ２）まで渡るように形成し、ピストン３１が下死点位置に下降したとき、該ピストン３１の下端部３１ｅと上記めっき皮膜の下端縁ａ′との間に隙間ｃが形成されるようにしたので、めっき皮膜ａの縁部ａ′がホーニング処理Ｓ９の際の刃具及びピストン３１の外周面に接することがなく、該めっき皮膜ａの端縁からの剥離，脱落の問題を回避できる。
【００８４】
またピストン３１が下死点に下降したとき、該ピストン３１の下端部３１ｅが上記逃げ部２７ａに重なるようにしたので、同じピストンストロークを備えながらエンジン高さを低くできる。即ち、上記逃げ部を設けない場合において、ピストン下端部がめっき皮膜の端縁に当接するのを回避するにはスリーブ長さを長くする必要があり、それだけエンジン高さ寸法が大きくなるが、本実施形態ではこの問題を回避できる。
【００８５】
例えば、図１２において、ｈ２までめっき皮膜を設ける場合は、ホーニング加工領域は刃具がメッキ皮膜の下縁ａ´に当たらないよう余裕をもってｈ３に設定する必要があり、そうなるとピストンの摺動領域はホーニング加工領域から余裕を取る必要があることからｈ４となり、本発明に比べると（ｈ４´−ｈ４）だけエンジン高さが高くなる。
【００８６】
シリンダ本体部２２ｃに挿入されたスリーブ２７とクランクケース部２５との境界部に各気筒用クランク室１９同士を連通する横断面円形の連通孔５２をドリルにより形成する場合に、該ドリルの加工中心点ｂを上記スリーブ２７とクランクケース部２５との境界よりスリーブ２７側に偏位させたので、上記連通孔５２を所定の位置に容易確実に形成できる。ちなみに低硬度の上ランクケース部２５ａ側に加工中心点ｂを偏位させた場合にはドリル加工中心がスリーブから遠ざかるようにずれていく恐れがある。
【００８７】
また上記連通孔５２をスリーブ２７のピストン摺動面２２ａに渡るように貫通形成する場合に、該ピストン摺動面２２ａの上記連通孔上縁５２ａから下死点位置にあるピストン３１の下端のオイルリング３１ａまでの寸法を３mm以上に設定したので、ピストン摺動面２２ａのホーニング加工によりその面粗さ等が許容範囲にある部分のみでピストンリングを摺動させることができ、ピストンリングとピストン摺動面２２ａとの隙間が許容寸法以下に狭くなってしまうといった問題を解消できる。
【００８８】
さらにまた上記連通孔５２を、クランク軸方向に見たときシリンダブロック２２の外側壁２２ｂに設けられたカム軸駆動機構の組付け用開口５０内に位置するように形成したので、該組付け開口５０を利用して機械加工することにより連通孔５２を穿設することができ、機械加工用の開口を別個に形成する、或いは加工によって開いた孔に埋栓を施す等の余分な加工をする必要がなく、従って該加工用開口の専用蓋部材での閉塞を不要にでき、製造コストを低減できる。
【００８９】
また、潤滑油通路５３を上ケース２６の各ボス部２９に連通孔５２の内周面に開口するよう形成し、該通路５３を通して潤滑油をピストン裏面に噴射するように構成する場合に、上記連通孔５２の上部の幅Ｗ１を下部の幅Ｗ２より狭くしたので、噴射された潤滑油は連通孔５２の上縁によって遮断されることなく確実にピストン裏面に供給されることとなり、従来のようにクランク室壁に噴射通路を切り欠き形成する必要がなく、コスト上昇を招くことなくピストン３１を効率良く冷却できる。
【００９０】
さらにまた本実施形態では、ピストンスカート３１ａに切り欠き凹部３１ｃを形成してなるスリッパ型ピストン３１を採用し、上記潤滑油通路５３の噴射口５４ａを下死点に位置するピストン３１の切り欠き凹部３１ｃを通してピストン裏面に指向させたので、ピストンスカート３１ａにより潤滑油の噴射流が遮断されることがなく、この点からも冷却効率を向上できる。また上記切欠き凹部３１ｃを設けたのでピストンスカート３１ａにより連通孔５２の有効面積が狭められるという問題も回避できる。あるいは、スカートによる面積減少を避けるためにコンロッドを長くするといったことも不要となる。
【００９１】
アルミ合金製シリンダブロック本体部２２ｃ内にピストン摺動面を構成するスリーブ２７を鋳込んでなるシリンダブロック２２とアルミ合金製シリンダヘッド２３との間にガスケット９１を介在させる場合に、上記シリンダブロック本体部２２ｃとシリンダヘッド２３とを線膨張係数の略等しい材料で形成するとともに、上記ガスケット９１のビード部９１ａのシリンダブロック側のシール点ｐ，ｐを上記スリーブ２７に渡ることなくシリンダ本体部２２ａ側の合面２２ｆのみに当接させたので、シール性を確保できるとともに、ガスケットの寿命を確保できる。
【００９２】
即ち、スリーブ２７はピストン摺動面２２ａを形成する必要があることから、上記シリンダ本体部２２ｃと線膨張係数が異なるものとなる場合が多く、そのため熱間運転状態では、シリンダ部本体２２ｃとスリーブ２７の合面間にシリンダ軸方向の段差が生じる可能性がある。仮に上記ビード部９１のシリンダブロック側シール点ｐ，ｐがシリンダ本体部２２ｃとスリーブ２７との両方に渡って当接している場合には、上記段差によりガスケット９１のビード部９１ａ部分に剪断方向の力が作用し、その寿命が短縮したりあるいはシール性が低下する懸念がある。
【００９３】
また本実施形態では、ガスケット９１のシリンダ内周側部分９１ｄをスリーブ２７のシリンダヘッド側の端面（合面２７ｆ）に対面させたので、該部分９１ｄがスリーブ２７とシリンダヘッド２３と間の空間を埋めることとなり、それだけ圧縮比を高めることができ、また燃焼室表面形状に不要の凹部を生じさせることがなく、燃焼を良好にできる。
【００９４】
また、ガスケット９１の上記シリンダ内周側部分９１ｄがスリーブ２７の合面２７ｆに対面する場合でもビード部９１ａはシリンダ本体部２２ｃの合面２２ｆのみに当接しているのでシール性，ガスケットと寿命に影響が生じることはない。さらにまた、めっき皮膜形成時にいわゆる花咲がスリーブ端面に形成された場合でもシール性に支障が生じることはない。
【図面の簡単な説明】
【図１】本発明の一実施形態によるエンジンが搭載された自動二輪車の左側面図である。
【図２】上記エンジンの右側面図である。
【図３】上記エンジンのチェーン配置室回りの構造を示す右側面図である。
【図４】上記エンジンの断面背面展開図である。
【図５】上記エンジンの連通孔部分を示す断面図である。
【図６】上記エンジンのシリンダブロックのクランク軸側から見た底面図である。
【図７】上記シリンダブロックの右端気筒部分の断面側面図である。
【図８】上記シリンダブロックの右端から２番目の気筒部分の断面側面図である。
【図９】上記シリンダブロックの平面図である。
【図１０】上記シリンダブロックとシリンダヘッドとの間のガスケットの平面図である。
【図１１】上記シリンダブロックのシリンダヘッドとの間のシール構造を示す拡大断面図である。
【図１２】上記シリンダブロックのスリーブ下端部を示す拡大断面図である。
【図１３】上記シリンダブロックの製造工程を示すフローチャートである。
【図１４】上記製造工程におけるめっき処理工程の詳細を示すフローチャートである。
【図１５】上記シリンダブロックの連通孔形成実験の結果を示す図である。
【図１６】上記シリンダブロックの連通孔形成実験の結果を示す図である。
【図１７】上記シリンダブロックの連通孔形成実験の結果を示す図である。
【図１８】上記シリンダブロックの連通孔形成実験の結果を示す図である。
【図１９】上記シリンダブロックの連通孔形成実験におけるホーニング後状態を示す図である。
【図２０】上記めっき処理工程におけるエッチング処理装置を示す模式図である。
【図２１】上記めっき処理工程における高速めっき処理装置を示す模式図である。
【符号の説明】
１５ エンジン
１９ クランク室
２１ クランク軸
２２ シリンダブロック
２２ａ ピストン摺動面
２２ｃ シリンダ本体部
２５ クランクケース部
２７ スリーブ
５２ 連通孔
ｂ 連通孔の中心[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cylinder block of a multi-cylinder engine suitable for a motorcycle.
[0002]
[Prior art]
In some engines used in motorcycles, etc., the cylinder block is formed separately from the crankcase. In this structure, the parts for connecting the cylinder block to the crankcase and the connecting surface (joint surface) Machining is necessary to ensure sealing performance, and there is a problem that the number of parts, processing man-hours, and assembly man-hours increase. Therefore, it is conceivable to reduce the number of parts and the number of assembly steps by integrally forming the cylinder block and the crankcase.
[0003]
Further, in this type of engine, as a structure for forming a piston sliding surface in the cylinder block, a separate sleeve having the piston sliding surface is disposed in the cylinder block by press-fitting or casting, or the cylinder block body. It is conceivable to directly apply plating or the like.
[0004]
In the case of a four-cycle engine, a structure is known in which crank chambers of adjacent cylinders communicate with each other through a communication hole in order to reduce a pumping loss caused by compression of air in the crank chamber during a piston lowering stroke.
[0005]
[Problems to be solved by the invention]
However, when the communication hole is formed to reduce the pumping loss in the cylinder block in which the cylinder main body and the crankcase are integrally formed, and a sleeve is disposed in the cylinder, for example, In some cases, it is difficult to accurately form the communication hole at a predetermined position.
[0006]
That is, in the cylinder block having the above structure, the sleeve has a high hardness so as to ensure the wear resistance necessary as a piston sliding surface, while the cylinder body and the crankcase are in view of ensuring castability. Since the material is set, the hardness is generally lower than that of the sleeve. For this reason, when the communication hole is drilled using a drill, the machining center line may shift to the low hardness side as the machining progresses depending on the setting of the drill center.
[0007]
An object of the present invention is to provide a cylinder block of a multi-cylinder engine in which the communication hole can be accurately formed at a predetermined position with a simple structure.
[0008]
[Means for Solving the Problems]
  According to a first aspect of the present invention, in a cylinder block of a multiple cylinder engine having a cylinder body portion having a piston sliding surface, the cylinder body portion and at least an upper half portion of a crankcase portion accommodating the crankshaft are made of an aluminum alloy. The piston sliding surface is made harder than the cylinder body portion and the crankcase portion, and a circular communication hole having a circular cross section for communicating the crank chambers of the cylinders is formed in the piston sliding surface and the crankcase. The center of the drill for forming the communication hole is positioned on the piston sliding surface side from the boundary between the piston sliding surface and the crankcase portion,The hole width becomes narrower toward the crankcase part side than the center of the communication hole in the outer peripheral part of the communication hole on the piston sliding surface,An overhang portion that prevents movement of the drill toward the crankcase portion is formed.
  According to a second aspect of the present invention, in the first aspect, the cylinder main body portion includes a sleeve having the piston sliding surface, and a relief portion having a larger diameter than the cylinder head side portion is provided at the crankshaft side end portion of the sleeve. Is formed, and the center of the communication hole is located in the escape portion.
[0009]
[Effects of the invention]
According to the first aspect of the present invention, the circular communication hole having a circular cross section for communicating the crank chambers for each cylinder is formed by a drill at the boundary between the high hardness piston sliding surface of the cylinder main body and the low hardness crankcase. In forming the drill, since the machining center point of the drill is displaced to the piston sliding surface side from the boundary between the piston sliding surface and the crankcase portion, the escape of the drill can be avoided, and the communication hole is formed in a predetermined manner. It can be easily and reliably formed at a precise position.
[0010]
  The above escape avoidance effect is due to the high hardness of the drill centerThe piston sliding surfaceBecause it is located on the side,Prevents the drill from moving to the low hardness side of the piston sliding surfaceOverhang part (area 52b part of FIG. 7)FormationIt is thought that it is obtained by doing.As a result, the communication hole can be easily and accurately formed at a predetermined position.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIGS. 1 to 21 are views for explaining a cylinder block of a motorcycle engine according to an embodiment of the present invention. FIG. 1 is a left side view of a motorcycle on which the engine is mounted, and FIG. FIG. 3 is a right side view of the cylinder block, cylinder head, and head cover portion of the engine, FIG. 4 is a developed cross-sectional rear view of the engine, and FIG. 5 is a cross-sectional view showing a communication hole portion of the cylinder block. 6 is a bottom view of the cylinder block as viewed from the crankshaft side, FIG. 7 is a sectional side view of the rightmost cylinder portion of the cylinder block, FIG. 8 is a sectional side view of the second cylinder portion from the right of the cylinder block, and FIG. FIG. 10 is a plan view of the cylinder gasket, FIG. 10 is a plan view of the head gasket, and FIG. 11 is an enlarged view showing the sealing state of the head side mating surface of the cylinder block 2 is an enlarged view showing a rib-like weir of a cylinder block, FIGS. 13 and 14 are views showing a manufacturing process, FIGS. 15 to 18 are views showing drilling test results of communication holes, and FIG. 19 is a honing process of FIG. FIG. 20 and FIG. 21 are schematic views showing a plating apparatus. Note that front and rear and left and right in the present embodiment mean front and rear and left and right when viewed in a seated state.
[0012]
In FIG. 1, reference numeral 1 denotes a motorcycle, and a body frame 2 of the motorcycle has a structure in which a seat rail 4 extending rearward of the vehicle body is connected to the rear ends of a pair of left and right main frames 3 having a substantially inverted L shape in a side view. The fuel tank 5 is mounted on the upper portion of the main frame 3, and the main seat 6 and the tandem seat 7 are mounted on the upper portion of the seat rail 4.
[0013]
A front fork 9 is pivotally supported at the front end of the main frame 3 by a head pipe 8, and a front wheel 10 is pivotally supported at the lower end of the front fork 9. A rear arm 11 is pivotally supported by a pivot shaft 12 on a rear arm bracket 3a below the rear end of the main frame 3, and a rear wheel 13 is pivotally supported on the rear end of the rear arm 11. .
[0014]
A rear cushion 14 is interposed between the rear arm 11 and the vehicle body frame 2. The lower end of the rear cushion 14 is erected on the rear side of the rear cushion 14 and connected to the lower end of the first link 14a pivotally supported by the rear arm 11, and the upper end is pivotally supported by the vehicle body frame. The upper end of the first link 14a is connected to the vehicle body frame via a second link 14b that is erected on the rear side of the rear cushion 14, and the second link 14b and the first link 14a are connected to the rear cushion 14. A triangle. As described above, the lower end of the rear cushion 14 is supported by the first and second links 14a and 14b which are arranged upright upward, so that a large space is secured below the rear cushion 14 while ensuring so-called progressive characteristics. ing.
[0015]
An engine unit 15 is suspended below the main frame 3, and a radiator 16 is disposed on the front side of the engine unit 15. The exhaust unit of the engine unit 15 is disposed between the exhaust pipe 141 connected to each exhaust port opened in the front wall of the cylinder head 23, the engine unit 15 and the rear wheel 13 and below the rear cushion 14. The first muffler 142 and the second muffler 143 disposed on the upper right side of the rear wheel 13 are configured.
[0016]
The engine unit 15 is a water-cooled four-cycle parallel four-cylinder five-valve engine, and is mounted with the cylinder axis 20 inclined forward and the crankshaft 21 directed in the vehicle width direction. As shown in FIG. 2, the engine unit 15 is formed by laminating an aluminum alloy cylinder head 23 on the upper joint surface of the aluminum alloy cylinder block 22 and fastening it with a head bolt. An aluminum alloy head cover 24 is attached, and an aluminum alloy oil pan 28 is connected to the lower portion of the cylinder block 22.
[0017]
The cylinder block 22 includes a cylinder body 22a and a unit case 27 that are integrally formed by die casting using an aluminum alloy. The unit case 27 includes a crankcase portion 25 that accommodates and supports the crankshaft 21, and a transmission case portion 26 that accommodates the transmission, and the crankcase portion 25 and the transmission case portion 26 are arranged on the upper side. The lower crankcase portions 25a and 25b are divided into upper and lower mission case portions 26a and 26b.
[0018]
The crankshaft 21 is pivotally supported via a bearing 30 by a plurality of bearing boss portions 29 formed on the split surfaces of the upper and lower crankcase portions 25a and 25b. Further, the crank chambers 19, 19,... For each cylinder are partitioned into independent chambers by the boss portion 29, and communicate with each other through a communication hole 52 described later.
[0019]
In the cylinder bore wall 22d of the cylinder main body 22c of the cylinder block 22, sleeves 27 made of four aluminum alloy drawn pipe members are cast in parallel and at the same interval. An inner surface of the lower end of the sleeve 27 is formed with a relief portion 27a that is a diameter of the cutter when the honing process is performed. The outer surface is a surface that prevents the sleeve 27 from coming off toward the crankshaft. A take part 27b is formed. Further, a chamfered portion 27c is formed on the inner surface of the upper end of the sleeve 27 so as to escape when the piston is inserted and assembled, and a latching step portion (preventing the retaining of the sleeve 27 to prevent the sleeve 27 from coming off to the cylinder head side). (Thin wall portion) 27d is formed to have a smaller diameter than other portions. By providing this stepped portion 27d, the cylinder head mating surface 22f portion on the cylinder body portion 22c side is thick, and as a result, a contact space of a bead portion 91a of a gasket 91a described later can be easily secured.
[0020]
The sleeve 27 has a piston sliding surface 22a formed by forming a plating film a on the inner surface. The piston sliding surface 22a is formed by casting the sleeve 27 into the cylinder body 22c, performing a boring process for removing thermal distortion during the casting, and performing an etching process on the processed surface by a method described later. This is formed by forming a plating film a later and honing the plating film a.
[0021]
Here, as shown in FIG. 12, the etching process is applied to a region h1 from the upper end to the lower end of the sleeve 27, and the plating film a is a region h2 from the upper end of the sleeve 27 to the middle of the escape portion 27a. It is formed over. A small end portion of a connecting rod 32 is connected to a piston 31 slidably inserted in the piston sliding surface 22a through a piston pin 31b. The lower end portion 31e of the piston 31 is plated. It slides in a region h4 ′ overlapping the lower end portion a ′ of the coating a. The honing process is performed over a region h3 ′ from the upper end of the sleeve 27 to the corner portion of the escape portion 27a.
[0022]
The large end of the connecting rod 32 is an upper and lower split type of the main body portion and the cap member. The main body portion is covered on the upper side of the crankpin 21a of the crankshaft 21, and the cap member is covered on the lower side. Then, it is connected to the crankshaft 21 by bolting and fixing. In assembling the piston 31, the main body portion of the connecting rod 32 is assembled to the piston 31, the main body portion and the piston 31 are inserted into the sleeve 27 from the cylinder head side, and the main body portion is inserted into the sleeve by the cap member. It will be connected to the crankpin 21a.
[0023]
The piston 31 is of a so-called slipper type in which a notch recess 31c is formed in the piston pin 31b shaft end portion of the piston skirt 31a. When the piston 31 is lowered to its bottom dead center position, the lower end 31e of the piston skirt 31a faces the escape portion 27a of the sleeve 27 with a gap c. That is, the provision of the gap c prevents the piston 31 from contacting the lower end edge a ′ of the plating film a.
[0024]
In FIG. 6 showing the cylinder block 22 as viewed from the crankshaft side, the crankshaft side openings of the sleeves 27, 27, 27 of the three cylinders from the right end are the front side wall 25c of the upper crankcase portion 25a, The periphery is surrounded by the partition wall 25d that defines the chamber and the mission chamber, and the crankshaft bearing boss portion 29. Therefore, as will be described later, in the plating film forming step, an etching solution or the like overflows to the outside. Inflow to the 26d side can be prevented.
[0025]
On the other hand, the sleeve 27 of the left end cylinder in FIG. 6 has a portion corresponding to the partition wall 25d in order to secure an arrangement space for the reduction small gear 82 and the reduction large gear 82 that connect the crankshaft 21 and the main shaft 72. Not. Therefore, in the left end cylinder, the effect of preventing the etching solution or the like from flowing into the mission chamber by the partition wall 25d in the plating film forming step cannot be obtained.
[0026]
Therefore, in the present embodiment, in the sleeve casting step, the left end cylinder is covered with the aluminum chamfered portion 27b formed on the outer surface of the lower end portion of the sleeve 27 with the aluminum alloy and on the crankshaft side than the other portions. A rib-like weir portion 25d 'protruding slightly is integrally formed. This weir 25d 'prevents the etchant from overflowing to the mission case 26d side in the plating process.
[0027]
Three intake ports and two exhaust ports that open to each combustion recess 23 a of the cylinder head 23 can be opened and closed by an intake valve 35 and an exhaust valve 36. The valves 35 and 36 are driven to open and close by an intake camshaft 40 and an exhaust camshaft 41 through bottomed cylindrical valve lifters 37 and 37 attached to the upper ends. Cam sprockets 40 a, 41 a attached to the right end of each camshaft 40, 41 in the axial direction and crank sprocket 21 b formed integrally with the right end of the crankshaft 21 are connected by a timing chain 42.
[0028]
The cam sprockets 40a and 41a, the timing chain 42, and the crank sprocket 21b of the cam shaft drive mechanism configured as described above are accommodated in a chain arrangement chamber 43 that is integrally formed on the right outer end surface of the cylinder block 22 and the cylinder head 23. Has been. A rotor 44 having outer peripheral teeth is mounted on the inside of the crank sprocket 21b of the crankshaft 21, and a pickup 45 for detecting a crank rotation angle is opposed to the rotor 44. Reference numeral 46 denotes an auto tensioner that automatically adjusts the tension of the timing chain 42, and reference numeral 47 denotes a chain guide.
[0029]
An opening 50 for assembling the camshaft drive mechanism is formed in a portion of the outer wall 22b of the cylinder block 22 constituting the chain arrangement chamber 43 that faces the shaft end of the crankshaft 21. The lid member 51 is bolted so as to be detachable. The communication holes 52 for reducing the pumping loss due to the reciprocating motion of the piston by connecting the adjacent crank chambers 19, 19 are positioned in the assembly opening 50 when viewed in the crankshaft direction. In addition, it is formed so as to penetrate the same axis parallel to the crankshaft 21.
[0030]
Here, the communication hole 52 has a circular cross section that is drilled by inserting a long drill through the assembly opening 50 in the process between the plating process and the honing process. The processing center point b of the communication hole 52 is set at a position displaced from the crankshaft side end 27e of the sleeve 27 toward the cylinder head. The sleeve 27 has higher hardness than the upper crankcase portion 25a.
[0031]
As described above, in this embodiment, when a circular hole is formed by drilling so as to extend over both the upper crankcase portion 25a and the sleeve 27 having different hardnesses, the center of the drill is displaced toward the sleeve 27 having a high hardness. Since it is set, the escape of the drill can be avoided and the workability can be improved. This escape avoidance effect is due to the fact that the drill center is located on the side of the high hardness member, and therefore there is an overhang portion (region 52b portion in FIG. 7) that prevents the drill from moving on the side of the high hardness member. It is considered to be obtained. Incidentally, if the machining center point b is displaced toward the low crank upper crankcase portion 25a side, the drill machining center may be displaced away from the high hardness sleeve.
[0032]
Further, the communication hole 52 is disposed so as to face the notch 31c and the piston pin 31b when the piston 31 is lowered to the bottom dead center, and the upper end edge 52a is moved to the bottom dead center. The center position b and the hole diameter are set so that the distance from the lower end of the piston 31 positioned to the lower edge of the oil ring 31d is 3 mm or more, preferably 7 mm or more.
[0033]
The reason why the center position of the communication hole 52 is set as described above is as follows. That is, when the communication hole 52 is formed, the peripheral edge of the communication hole 52 is unacceptably burred or deformed as a piston sliding surface. This burr or the like is removed by a subsequent honing process. However, in the range of about 3 mm from the periphery of the communication hole 52, it may not be sufficiently removed to an extent acceptable as a piston sliding surface. It was because it became clear.
[0034]
15 to 19 show the results of experiments conducted to investigate the occurrence of burrs and the like when the through-hole 52 is formed and the surface finishing state by honing. In each figure, the actual dimensions are shown in the vertical direction (cylinder axis direction), while the horizontal direction is enlarged 1000 times.
[0035]
15 to 18 show the state of occurrence of burrs or the like in the first to fourth cylinders when a through-hole is formed by inserting a drill in the direction of the arrow after forming a plating film on each sleeve of the experimental cylinder block. . In each figure, the right part shows the situation when the drill penetrates the plating film and enters the sleeve, and the left part shows the situation when the drill penetrates the plating film from the sleeve and enters the cylinder body. It can be seen that the burrs and the like are about 5 to 30 μm in any cylinder.
[0036]
FIG. 19 shows the state of the piston sliding surface after the honing process. As is apparent from the figure, the above-described burrs and the like are removed by honing, and α μm (for example, a dimension acceptable as a piston sliding surface is provided above the point 3 mm above the upper edge 52a of the through hole 52 (for example, It is smaller than 5 μm). Therefore, when the piston 31 is located at the bottom dead center, the dimension between the lower edge of the oil ring 31d disposed on the lowermost side and the upper edge 52a of the through hole 52 is set to be larger than 3 mm. Thus, the gap between the oil ring 31d and the piston sliding surface can be set within an allowable range, and output loss due to an increase in sliding resistance can be prevented.
[0037]
Further, as shown in FIG. 5, each bearing boss portion 29 of the upper crankcase portion 25 a is formed with a lubricating oil passage 53 that connects the bearing 30 of the crankshaft 21 and the inner peripheral surface of the communication hole 52. Yes. A cooling nozzle 54 is inserted into the lubricating oil passage 53, and an injection port 54a of the nozzle 54 is directed so as to eject the lubricating oil from the notch 31c of the piston 31 located at the bottom dead center to the piston back surface. is doing. Further, the thickness in the crankshaft direction of the communication hole 52 portion of the bearing boss portion 29 is W2 on the crankshaft side and narrower on the piston side with W1. Therefore, the lubricating oil injected from the injection port 54a is reliably supplied to the piston back surface without being obstructed by the peripheral edge of the communication hole 52 or the piston skirt, so that the piston 31 can be reliably cooled.
[0038]
A water cooling jacket 90 is formed in the cylinder block 22 so as to surround the sleeve 27, and the inside of the water cooling jacket 90 is a cylinder bore wall 22d. The depth of the portion of the water cooling jacket 90 excluding the chain arrangement chamber 43 side is set to coincide with the upper end surface of the piston 31 at a position lowered by 116 ° from the top dead center at a crank angle. On the other hand, the depth of the chain arrangement chamber 43 side portion 90a of the water cooling jacket 90 is set to coincide with the vicinity of the upper end surface of the piston 31 located at the bottom dead center, and the bottom wall 90b of the water cooling jacket portion 90a. The cylinder axial direction height is set to be slightly lower than the height of the upper edge 50a of the assembly opening 50. The water-cooling jacket 90 is opened over the entire circumference on the head-side mating surface, and is closed by a gasket 91 described later.
[0039]
Thus, since the chain arrangement chamber 43 side portion 90a of the water cooling jacket 90 is formed deeper than the other portions, the provision of the chain arrangement chamber 43 reduces the cooling performance of the arrangement chamber 43 portion of the cylinder block. Can be compensated. That is, the portion surrounding the sleeve 27 of the cylinder block 22 is also cooled by direct contact with traveling wind, but the right end portion of the cylinder block 22 in FIG. Is difficult to hit, and there is a concern that the cooling performance is lowered. In this embodiment, since the chain arrangement chamber side portion 90a of the cooling jacket 90 is formed deeper, it is possible to compensate for a decrease in cooling performance due to the fact that the traveling wind does not hit.
[0040]
Further, the height in the cylinder axial direction of the bottom wall 90b of the water cooling jacket portion 90a of the cylinder block 22 is set to be slightly lower than the height of the upper edge 50a of the assembly opening 50 (see FIG. 4). The part casting mold can be simplified. That is, when the bottom wall 90b is higher than the upper edge 50a, a slide mold is required. In the present embodiment, the bottom wall 90b is also formed by a mold that moves in the crankshaft direction for forming the opening 50. Therefore, the above slide mold is unnecessary.
[0041]
A gasket 91 is interposed between the mating surfaces of the cylinder block 22 and the cylinder head 23. The gasket 91 is formed by stacking three thin plates 92, 93, 94 cut in accordance with the shape of the mating surface of the cylinder block 22 with substantially the same gap as the thin plate, and surrounding the sour rib 27. A concentric bore bead portion 91a having a larger diameter is formed, and a peripheral bead portion 91b having a shape along the peripheral edge of the mating surface, a chain chamber bead portion 91c having a shape along the opening edge of the chain arrangement chamber 43, and the like are press-molded. Etc. are formed. In each of the bead portions 91a to 91c, the central thin plate 93 remains flat, and the upper and lower thin plates 92 and 94 are bent so as to contact the central thin plate 93, and the portions other than the bead portion are caulked or the like. It is fixed and formed. FIG. 11 is schematically shown to emphasize the bead portion and the gap.
[0042]
When the gasket 91 is interposed between the mating surfaces of the cylinder block 22 and the cylinder head 23 and tightened with head bolts, the bend points p of the bead portions 91a and 91b are press-fitted to the mating surface. At the same time, the upper and lower thin plates 92, 94 are pressed against the central thin plate 93, thereby sealing between the cylinder block 22 and the cylinder head 23. The cylinder inner peripheral portion 91d of the gasket 91 faces the cylinder head side mating surface 22f of the sleeve 27.
[0043]
2 and 4, reference numeral 70 designates a transmission mainly disposed in the upper transmission case 26a, which has a main shaft (input shaft) 72 having an input gear group 71 mounted on the rear part of the crankshaft 21. In addition, drive shafts (output shafts) 74 mounted with an output gear group 73 meshing with the input gear group 71 below the main shaft 72 are arranged in parallel with the crankshaft 21.
[0044]
The drive shaft 74 is formed between the split surfaces of the upper and lower mission case portions 26a and 26b in the same manner as the crankshaft 21 is disposed between the split surfaces of the upper and lower crankcase portions 25a and 25b. The boss portion is supported via a bearing 75. The main shaft 72 is disposed in the upper mission case portion 26a, and the left end portion of the main shaft 72 is supported by a boss portion of the upper mission case portion 26a via a bearing 76. The right side portion is supported by the right side wall 26g of the upper mission case portion 26a via a bearing 77 and a flange 78, and the flange 78 is fixed to the right side wall 26g by bolting.
[0045]
The left end portion of the drive shaft 74 protrudes outward from the mission case portion 26, and a drive sprocket 79 attached to the protrusion is connected to the rear wheel sprocket 13a of the rear wheel 13 via a chain 80. . A clutch mechanism 81 is attached to the right end portion of the main shaft 72. The clutch mechanism 81 meshes with a reduction gear 82 of the crankshaft 21 and is splined to the main shaft 72 and an outer drum 84 that is connected to a reduction gear 83 supported by the main shaft 72 via a damper. In this structure, a large number of clutch plates 86 are interposed between the inner drum 85 and the inner drum 85. The clutch mechanism 81 connects and disconnects engine power by rotating a push lever 87 connected to the inner drum 85.
[0046]
A shift drum 90, an input-side fork shaft 91, and an output-side fork shaft 92 are disposed in parallel with the rear side of the main shaft 72 and the drive shaft 74, and the shift drum 90 and each fork shaft 91 are arranged. , 92 are supported by right and left boss portions formed integrally with the upper mission case portion 26a.
[0047]
One input-side shift fork 93 is mounted on the input-side fork shaft 91, and two output-side shift forks 94, 94 are mounted on the output-side fork shaft 92 so as to be movable in the axial direction. The bifurcated claw portions of the shift forks 93 and 94 are slidably engaged with sliding grooves 71b and 73b formed in the gears of the input gear group 71 and the output gear group 73, and the shift forks 93 and 94 are slidably engaged. The engaging pin formed integrally with the base of the shift drum 90 is slidably engaged with a guide groove formed on the outer peripheral surface of the shift drum 90. By rotating the shift drum 90 by a change mechanism (not shown), the shift forks 93 and 94 slide in the axial direction to move the gears of the input gear group 71 and the output gear group 73. Switching is performed between the lowest speed stage and the highest speed stage.
[0048]
Next, the positional relationship among the crankshaft 21, the main shaft 72, and the drive shaft 74 will be described mainly with reference to FIG. The main shaft 72 has a sharp first axis angle θ1 formed by the crankshaft / main shaft straight line A connecting the shaft core and the shaft shaft of the crankshaft 21 and the cylinder axis 20 on the cylinder head side and the main shaft side. In other words, it is disposed at a position closer to the cylinder head 23 than a straight line C passing through the axis of the crankshaft 21 and perpendicular to the cylinder axis 20.
[0049]
The drive shaft 74 includes a main shaft / drive shaft straight line B connecting the shaft core of the main shaft 72 and the crank shaft / main shaft straight line A on the drive shaft side and the crank shaft side. It arrange | positions so that 2nd axial angle (theta) 2 may become an acute angle. Thus, the main shaft 72 and the drive shaft 74 are arranged so as to be carried on the back surface of the cylinder block 22.
[0050]
The maximum outer peripheral surface (the outer peripheral surface of the large reduction gear) 81a of the clutch mechanism 81 is located closer to the cylinder head 23 than the straight line D passing through the top surface of the piston 31 'located at the bottom dead center and perpendicular to the cylinder axis 20. is doing. The main shaft 72, the shift drum 90, the fork shafts 91 and 92, and the drive shaft 74 are located in the axial projection surface of the reduction gear 83 of the clutch mechanism 81.
[0051]
As shown mainly in FIG. 2, both the cooling water pump 100 and the lubricating oil pump of this embodiment are accommodated in the lower mission case part 26b, and the pump shaft 102 common to both pumps is the crankshaft 21, The drive shaft 74 is disposed below and parallel to the drive shaft 74. A driven sprocket 108 attached to the right end of the pump shaft 102 is connected via a chain 109 to a drive sprocket 110 mounted on the outer side of the flange 78 of the main shaft 72. The cooling water discharged from the cooling water pump 100 is supplied to the cooling jacket 90 through the cooling water passages 119, 123a, 123b.
[0052]
The lubrication pump sucks the lubricating oil in the oil pan 28 through the oil strainer 120 and cranks the lubricating oil from the oil filter 121 attached to the front wall of the lower crankcase portion 25b through the main gallery 122. The engine 21 is supplied to each engine lubrication section such as the shaft 21, the main shaft 72, the drive shaft 74, and the cam shafts 40 and 41.
[0053]
Here, as shown in FIG. 3, the lubricating oil for the valve mechanism moves along the intake side camshaft 40 from the oil passage 126 that opens between the first cylinder intake side of the cylinder head 23 and the chain arrangement chamber 43. Is supplied to an oil passage 127 that extends along the exhaust side camshaft 41 by an oil passage 128. The lubricating oil that has lubricated each camshaft bearing portion is collected in the oil pan 28 through an oil return passage formed between the exhaust sides of the third and fourth cylinders of the cylinder head 23.
[0054]
In FIG. 2, reference numeral 135 denotes a starting motor, which is disposed in parallel with the crankshaft 21 on the back surface of the cylinder body 22c of the upper mission case 26a. The output of the starting motor 135 is transmitted to the crankshaft 21 through an intermediate gear 138, a starting gear 139, a one-way clutch 140, and a reduction large gear 83.
.
[0055]
Next, the manufacturing process of this embodiment cylinder block 22 is demonstrated.
Examples of the die casting aluminum alloy for the cylinder main body 22c, the upper crankcase portion 25a, and the upper mission case portion 26a (hereinafter also referred to as cylinder block base material) constituting the cylinder block 22 of the present embodiment are as follows. As the aluminum alloy for the cylinder head 23, the alloy shown in Table 2 can be used, and as the aluminum alloy for the sleeve 27, the alloy shown in Table 3 can be used.
[0056]
[Table 1]

[0057]
[Table 2]

[0058]
[Table 3]

As shown in Tables 1 to 3 above, the aluminum alloy of the base material contains 5 to 20% (wt%) of Si, and the aluminum alloy of the sleeve 27 includes (Si weight content of the sleeve 27 / base material). Weight content) × 100 is α,
50 <α <150
An aluminum alloy having a Si content such that By forming the base material and the sleeve using the aluminum alloy having such a configuration, the difference in the coefficient of thermal expansion between the base material and the sleeve is reduced, the generation of heat spots between the base material and the sleeve, and the inner circumference of the sleeve. Thermal deformation of the surface is reduced, and peeling of the plating film a applied to the inner peripheral surface of the sleeve is suppressed.
[0059]
When the cylinder block base material is formed from AC4C in Table 2, the Si weight content of the base material is 6.5 to 7.5%. Therefore, in Alloy 1 or Alloy 2 in Table 3, Si content is included. An alloy whose amount is changed to, for example, 3.75 to 9.75% by weight is used so that the condition of the Si weight content of the sleeve / the Si weight content of the base material is satisfied. Similarly, when the cylinder block base material 60 is formed by the ADC 10, the Si weight content of the base material 60 is 7.5 to 9.5%. Therefore, in the alloy 1 or the alloy 2 in Table 3, Si content is included. An alloy whose amount is changed to, for example, 4.75 to 15% by weight is used so that the condition of Si weight content of the sleeve / Si weight content of the base material is satisfied.
[0060]
Furthermore, as shown in Table 3, each aluminum alloy of the sleeve contains at least 0.2 and 10 or less of both Cu and Mg. As a result, the hardness can be easily increased to HB70 or higher by performing T6 treatment as described below. Even when only one of Cu and Mg is contained, the hardness can be easily increased to HB70 or more by T6 treatment. In addition, as shown in Tables 1 and 2, the base aluminum alloy contains one or both of Cu and Mg. This makes it possible to easily increase the hardness by performing T6 treatment on the base material together with the sleeve, as described below, and increase the rigidity of the entire cylinder block while improving the plating holding ability of the plating layer support portion of the sleeve. And the durability of the engine can be improved.
[0061]
FIG. 13 is a flowchart for explaining a manufacturing process of the cylinder block 22 by casting the sleeve 27. In this flow, the T6 process (steps S2, S4, S6) is a cylinder in which a sleeve alone or a sleeve is cast in accordance with JIS standard H5202 in order to increase the surface hardness of the inner peripheral surface that serves as a plating film support portion of the sleeve. The entire block is subjected to age hardening after solution treatment at a predetermined temperature, and may be performed once in steps S2, S4, and S6, or may be omitted. It is desirable that the sleeve surface hardness be HB70 or more (70 to 150) by such T6 treatment. In addition, when the surface hardness of the inner peripheral surface is set to HB70 or more by extrusion or pultrusion of the sleeve, the surface hardening process can be omitted by the subsequent T6 process.
[0062]
In addition, according to the T6 process in either step S2 or S4, only the sleeve can increase the hardness. At the time of casting, the hardness of the sleeve slightly decreases due to the heat on the base metal side in the molten state, but the casting time itself is short relative to the T6 treatment, and the hardness on the inner peripheral side of the sleeve can be kept at HB70 or higher. In addition, according to the T6 process of step S6, the hardness of the base material of the cylinder block can be increased in addition to the increase in the hardness of the sleeve, the rigidity of the entire cylinder block can be increased, and the sliding of each part can be caused by engine vibration. It is possible to prevent a decrease in engine durability caused by a decrease in the clearance of the portion and the increase in sliding wear.
[0063]
The outer peripheral shot blasting (step S3) is for forming fine irregularities on the outer peripheral surface of the sleeve and enhancing the bondability with the base material. By forming irregularities on the outer peripheral surface of the sleeve before casting the sleeve in this way, the sleeve can be reliably prevented from coming off even if the tightening force is reduced due to the difference in thermal expansion coefficient between the base material and the sleeve during operation. Such irregularities on the outer peripheral surface of the sleeve can be formed by machining other than shot blasting or pickling (etching) of the entire sleeve. This shot blasting process (step S3) may be omitted. Further, instead of a method of forming irregularities on the outer periphery of the sleeve by shot blasting or the like to improve the bondability with the base material, the sleeve and the base material may be joined using a low melting point solder to prevent the sleeve from coming off. .
[0064]
Here, shot blasting refers to steel balls, cemented carbide beads, stainless steel balls, zinc beads, glass beads with a particle size of 50 to 150 μm, river sand containing a lot of quartz with a slightly larger particle size, etc. with a projector. For example, what projects a workpiece | work with the projection speed of 40-80 m / s is said.
[0065]
FIG. 14 is a detailed flowchart of the plating process (step S8), and FIGS. 20 and 21 are configuration diagrams of a plating apparatus for performing the plating process. In the flowchart of FIG. 14, the inner surface of the sleeve is basically degreased (step S11), alkaline etching (step S13), mixed acid etching (step S15), anodized (step S17), and composite plating. The process consists of five processes (step S19), and a water washing process (steps S12, 14, 16, 18, 20) is performed after each process.
[0066]
The above water washing treatment uses two separate water tanks (10 in total) for each process, so that the entire cylinder block is immersed in the two water tanks in order and moved up and down to remove the processing liquid from the previous process. . The water in the aquarium is regularly replaced with new clean water. It is desirable to move to the next step as soon as possible after completion of each water washing treatment, and to carry out the next treatment with a water film on the surface. As a result, it is possible to prevent adhesion of dust or the like to the processing unit or direct contact with oxygen in the air, thereby preventing formation of an oxide film and the like, and improving the reliability of processing in a later process. This is particularly effective in the case of plating.
[0067]
As shown in FIGS. 20 and 21, the cylinder block 22 in which the sleeve 27 is cast into the base material has the cylinder body portion 22 c on the lower side so that the inner peripheral surface of the sleeve 27 is subjected to various treatments. In each process, they are mounted on dedicated apparatus main bodies 100a and 100b via sealing gaskets 101a and 101b. In each process, the processing liquids 105a and 105b in the dedicated processing liquid tanks 102a and 102b are supplied to the inside of the apparatus main bodies 100a and 100b by the dedicated pumps 106a and 106b, and ascend inside the sleeve 27 to move the inner cylinders 107a, It returns to the processing liquid tanks 102a and 102b through 107b.
[0068]
FIG. 20 shows the state of alkali etching and mixed acid etching. The range of this etching process is limited to the vicinity of the crankshaft side end portion of the escape portion 27a of the sleeve 27 because it is necessary to have a margin with respect to the formation range of the plating film. The management of the processing range in this case is performed by managing the liquid level of the processing liquid 105a according to the height position of the upper end surface 107a ′ of the inner cylinder 107a. . If the etchant 105a overflows to the mission case 26 side or the like, the processed surface on the mission case 26 side may be roughened for the leftmost cylinder in FIG.
[0069]
Therefore, in the present embodiment, the leftmost cylinder is formed with the rib-like weir 25d ′ on the mission case 26 side portion as described above, and this causes the etching solution to overflow to the mission case side. Can be prevented.
[0070]
The gaskets 101a and 101b are sealing materials for preventing leakage of the processing liquid in each processing step, and function as an insulating material for electrolytic action in the alumite processing step (step S17) and the composite plating step (step S19). . In the anodizing process and the composite plating process, as shown in FIG. 21, for example, a DC voltage is applied between the cylinder body 22c and the inner cylinder 107 from the AC power source 108 via the rectifier 109 and the control circuit 110, respectively. A direct current is passed through the electrolyte. In other steps, no direct current is passed through the processing solution.
[0071]
The composite plating process is a high-speed plating process. Under predetermined plating conditions, the plating liquid 105b in the dedicated processing liquid tank 102b is supplied into the apparatus main body 100b by the pump 106b and returned to the processing liquid tank 102b through the inner cylinder 107b. A plating film is formed on the inner surface of the sleeve 27 while circulating such a path at a high speed. In this high-speed plating process, the inner cylinder 107b is connected to the (+) side of the power supply circuit, and the cylinder body 22c is connected to the (−) side, and a direct current is passed through the plating solution. Thereby, Ni in the plating solution having the composition described later⁺And P⁺Adheres to the inner peripheral surface of the sleeve, and accordingly, SiC particles as a dispersant are wound into the plating layer. In this way, a plating film a containing SiC and having excellent wear resistance and lubricity is formed on the inner peripheral surface of the sleeve to a thickness of 50 to 150 μm.
[0072]
In the high-speed plating process in step S19, the cover 111 is attached to the upper end portion of the sleeve 27. The cover 111 prevents the plating solution 105 b circulating at high speed from being scattered and restricts the plating range on the inner surface of the sleeve 27. The plating range is restricted to a range from the gasket 101 b that is a boundary portion with the cylinder head to the O-ring 112 of the cover 111 on the inner peripheral surface of the sleeve 27. Accordingly, by setting the position of the O-ring 112 in the middle of the escape portion 27a, it is possible to prevent the lower end portion of the outer peripheral surface of the piston 31 from contacting the lower end edge a 'of the plating film a as described above.
[0073]
After the composite plating process in step S19, the water washing process in step S20 is performed again to remove the plating solution, and the moisture attached to the cylinder block 22 is removed by air blowing in step S21. After the above plating step S8, the through hole 52 is processed, and then the honing step S9 is applied to the plating layer on the inner peripheral surface of the sleeve 27, so that the thickness of the plating film is preferably about 50 μm, and in some cases 20 μm. The surface roughness of the plating layer is set to 1.0 μm Rz or less. As a result, the plating layer surface can be surely smoothed, the friction coefficient during sliding of the piston 31 and the piston ring 31d can be reduced, and the retention of the engine oil is improved and the lubricity is improved. be able to. Rz is defined in JIS standard B0601.
[0074]
Next, the effect of this embodiment is demonstrated.
In the present embodiment, the cylinder body 22c, the upper crankcase portion 25a, and the upper mission case portion 26a are integrally formed by die casting of an aluminum alloy, so that the number of parts can be reduced and the thickness of each portion can be reduced, thereby reducing the weight. be able to.
[0075]
In addition, since the sleeve 27 made of an aluminum alloy drawn pipe material is cast into the cylinder body 22c and the plating film a is formed on the inner surface thereof, the inner surface of the sleeve 27 has a die-cast casting surface. Since there is no nest as in the case of directly forming the plating film, the adhesion of plating is good and the production failure rate can be reduced.
[0076]
In forming the plating film a, a high-speed plating method in which the plating solution is circulated at high speed between the inner surface of the sleeve 27 and the treatment solution layer is employed. Productivity can be improved compared to the method of doing.
[0077]
Further, since the upper edge portion 26c of the upper mission case portion 26a that accommodates the transmission is positioned below the cylinder head side mating surface of the cylinder body portion 22c, as shown in FIGS. When mounted on the plating processing apparatus main bodies 100a and 100b with the cylinder head side facing surface facing downward, the upper edge portion 26c of the upper mission case section 26a is less likely to interfere with the apparatus main bodies 100a and 100b, and plating is performed accordingly. It is easy to support the workpiece in the processing operation, and the plating processing workability can be improved.
[0078]
Further, as shown in FIG. 2, the crankshaft 21, the main shaft 72, and the drive shaft 74 are connected to the first shaft angle θ1 formed by the crankshaft / main shaft straight line A and the cylinder shaft line 20, and the shaft straight line A to the main shaft. Since the second shaft angle θ2 formed between the shaft and the drive shaft straight line B is an acute angle, the distance between the crankshaft 21 and the drive shaft 74 can be reduced, and the longitudinal length of the engine can be shortened. The amount of overhang from the cylinder body portion 22c of the case portion 26 can be reduced. From this point, the workpiece can be easily supported and the plating process workability can be improved.
[0079]
Further, since the main shaft 72 is disposed closer to the cylinder head 23 than the right-angled straight line C passing through the crankshaft 21, the main shaft 72 is disposed so as to be supported by the back of the cylinder block 22. The length can be further reduced. Further, since the clutch mechanism 81 is disposed such that the maximum outer peripheral surface 81a thereof is located on the cylinder head 23 side with respect to the straight line D passing through the top surface of the piston at the bottom dead center, the engine unit 15 can also be reduced in size from this point.
[0080]
Since the main shaft 72, the shift drum 90, the fork shafts 91 and 92, and the drive shaft 74 are arranged in the axial projection surface of the maximum diameter portion of the clutch mechanism 81, the arrangement of the shafts becomes compact, and the unit case 25 The protrusion can be made smaller, and the engine can be made smaller in this respect as well.
[0081]
Also, a rib-like shape that protrudes to the crankshaft 21 side at the lower end of the sleeve 27 (cylinder inner wall) constituting the piston sliding surface 22a of the cylinder body portion 22c and to the site on the mission case portion 26 side compared to the side opposite the mission case portion. Since the weir portion 25d 'is provided, it is possible to avoid the processing liquid such as the etch solution from overflowing to the mission case 26 side without extending the sleeve 27 to the crankshaft 21 side more than necessary in the above-described plating process. The surface that has already been processed can be prevented from being damaged by an etching solution or the like.
[0082]
Further, in providing the dam portion 25d ', the dam portion 25d' is provided only at a portion on the mission case side of the cylinder having the output extraction portion between the crankshaft bearing boss portions 29, and the crank chamber and the mission chamber are provided for the other cylinders. Since the partition wall 25d is provided between the lower end of the piston sliding surface 22a (sleeve 27) and higher in the cylinder shaft 21 direction than the lower end of the piston sliding surface 22a (sleeve 27), the partition wall 25d can also be used as the dam portion 25d '. The original purpose of the partition wall 25d is to improve the case rigidity.
[0083]
Furthermore, an escape portion 27a having a diameter larger than that of the piston sliding surface 22a is formed at the end of the sleeve 27 (cylinder inner wall) on the clan shaft side, and the plating film a is formed so as to extend to the middle portion (h2) of the escape portion 27a. When the piston 31 is lowered to the bottom dead center position, a gap c is formed between the lower end portion 31e of the piston 31 and the lower end edge a 'of the plating film. The part a ′ does not come into contact with the cutting tool and the outer peripheral surface of the piston 31 during the honing process S9, and the problem of peeling and dropping from the edge of the plating film a can be avoided.
[0084]
Further, when the piston 31 is lowered to the bottom dead center, the lower end portion 31e of the piston 31 is overlapped with the escape portion 27a, so that the engine height can be lowered while providing the same piston stroke. That is, in the case where the relief portion is not provided, the sleeve length needs to be increased in order to avoid the lower end of the piston coming into contact with the edge of the plating film, and the engine height dimension increases accordingly. In the embodiment, this problem can be avoided.
[0085]
For example, in FIG. 12, when the plating film is provided up to h2, it is necessary to set the honing area to h3 with a margin so that the cutting tool does not hit the lower edge a ′ of the plating film. Since it is necessary to take a margin from the machining area, it becomes h4, and the engine height becomes higher by (h4′−h4) than in the present invention.
[0086]
When a drilling hole 52 having a circular cross section that communicates between the crank chambers 19 for each cylinder is formed at the boundary between the sleeve 27 inserted into the cylinder body 22c and the crankcase 25, the processing center of the drill Since the point b is displaced to the sleeve 27 side from the boundary between the sleeve 27 and the crankcase portion 25, the communication hole 52 can be easily and reliably formed at a predetermined position. Incidentally, when the machining center point b is displaced to the upper rank case portion 25a side of the low hardness, there is a possibility that the drill machining center may be shifted away from the sleeve.
[0087]
Further, when the communication hole 52 is formed so as to extend over the piston sliding surface 22a of the sleeve 27, the oil at the lower end of the piston 31 at the bottom dead center position from the communication hole upper edge 52a of the piston sliding surface 22a. Since the dimension up to the ring 31a is set to 3 mm or more, the piston ring can be slid only in a portion whose surface roughness is within an allowable range by honing the piston sliding surface 22a. The problem that the gap with the moving surface 22a becomes narrower than the allowable dimension can be solved.
[0088]
Furthermore, the communication hole 52 is formed so as to be positioned in the assembly opening 50 of the camshaft drive mechanism provided in the outer wall 22b of the cylinder block 22 when viewed in the crankshaft direction. The communication hole 52 can be drilled by machining using the machine 50, and an extra machining such as forming a machining opening separately or plugging the hole opened by machining is performed. Therefore, it is not necessary to block the processing opening with a dedicated lid member, and the manufacturing cost can be reduced.
[0089]
Further, when the lubricating oil passage 53 is formed in each boss portion 29 of the upper case 26 so as to open to the inner peripheral surface of the communication hole 52, and the lubricating oil is injected to the back surface of the piston through the passage 53, Since the upper width W1 of the communication hole 52 is narrower than the lower width W2, the injected lubricating oil is reliably supplied to the back surface of the piston without being blocked by the upper edge of the communication hole 52. In addition, it is not necessary to cut out the injection passage in the crank chamber wall, and the piston 31 can be efficiently cooled without increasing the cost.
[0090]
Furthermore, in the present embodiment, a slipper type piston 31 formed by forming a notch recess 31c in the piston skirt 31a is adopted, and the notch recess of the piston 31 located at the bottom dead center of the injection port 54a of the lubricating oil passage 53. Since the piston is directed to the back surface of the piston through 31c, the injection flow of the lubricating oil is not blocked by the piston skirt 31a, and the cooling efficiency can be improved from this point. Further, since the notch recess 31c is provided, the problem that the effective area of the communication hole 52 is narrowed by the piston skirt 31a can be avoided. Alternatively, it is not necessary to lengthen the connecting rod in order to avoid the area reduction due to the skirt.
[0091]
When the gasket 91 is interposed between the cylinder block 22 formed by casting the sleeve 27 constituting the piston sliding surface in the aluminum alloy cylinder block main body portion 22c and the aluminum alloy cylinder head 23, the cylinder block main body described above is used. The portion 22c and the cylinder head 23 are formed of a material having substantially the same linear expansion coefficient, and the cylinder main body portion 22a side without passing the seal points p and p on the cylinder block side of the bead portion 91a of the gasket 91 to the sleeve 27. Therefore, the sealing performance can be ensured and the life of the gasket can be ensured.
[0092]
That is, since it is necessary to form the piston sliding surface 22a, the sleeve 27 often has a linear expansion coefficient different from that of the cylinder body 22c. Therefore, in the hot operation state, the cylinder body 22c and the sleeve are often different. There is a possibility that a step in the cylinder axial direction may occur between the 27 mating surfaces. If the cylinder block-side seal points p, p of the bead portion 91 are in contact with both the cylinder body 22c and the sleeve 27, the bead portion 91a portion of the gasket 91 is sheared in the shearing direction due to the step. There is a concern that the force acts to shorten the service life or reduce the sealing performance.
[0093]
Further, in the present embodiment, the cylinder inner peripheral portion 91d of the gasket 91 faces the cylinder head side end surface (fitting surface 27f) of the sleeve 27, so that the portion 91d provides a space between the sleeve 27 and the cylinder head 23. Therefore, the compression ratio can be increased accordingly, and the combustion chamber surface shape can be improved without causing unnecessary recesses.
[0094]
Further, even when the cylinder inner peripheral portion 91d of the gasket 91 faces the mating surface 27f of the sleeve 27, the bead portion 91a is in contact with only the mating surface 22f of the cylinder body 22c. There is no impact. Furthermore, even when so-called Hanasaki is formed on the sleeve end surface during the formation of the plating film, there is no problem in sealing performance.
[Brief description of the drawings]
FIG. 1 is a left side view of a motorcycle equipped with an engine according to an embodiment of the present invention.
FIG. 2 is a right side view of the engine.
FIG. 3 is a right side view showing a structure around a chain arrangement chamber of the engine.
FIG. 4 is a developed sectional rear view of the engine.
FIG. 5 is a cross-sectional view showing a communication hole portion of the engine.
FIG. 6 is a bottom view of the cylinder block of the engine as viewed from the crankshaft side.
FIG. 7 is a cross-sectional side view of a right end cylinder portion of the cylinder block.
FIG. 8 is a cross-sectional side view of the second cylinder portion from the right end of the cylinder block.
FIG. 9 is a plan view of the cylinder block.
FIG. 10 is a plan view of a gasket between the cylinder block and the cylinder head.
FIG. 11 is an enlarged cross-sectional view showing a seal structure between the cylinder block and the cylinder head.
FIG. 12 is an enlarged sectional view showing a lower end portion of a sleeve of the cylinder block.
FIG. 13 is a flowchart showing manufacturing steps of the cylinder block.
FIG. 14 is a flowchart showing details of a plating process in the manufacturing process.
FIG. 15 is a view showing a result of a communication hole formation experiment of the cylinder block.
FIG. 16 is a view showing a result of a communication hole formation experiment of the cylinder block.
FIG. 17 is a view showing a result of a communication hole formation experiment of the cylinder block.
FIG. 18 is a view showing a result of a communication hole formation experiment of the cylinder block.
FIG. 19 is a diagram illustrating a state after honing in the communication hole forming experiment of the cylinder block.
FIG. 20 is a schematic view showing an etching apparatus in the plating process.
FIG. 21 is a schematic view showing a high-speed plating apparatus in the plating process.
[Explanation of symbols]
15 engine
19 Crank chamber
21 Crankshaft
22 Cylinder block
22a Piston sliding surface
22c Cylinder body
25 Crankcase section
27 sleeve
52 communication hole
b Center of communication hole

Claims (2)

In a cylinder block of a multi-cylinder engine having a cylinder body having a piston sliding surface, the cylinder body and at least an upper half of a crankcase housing a crankshaft are integrally formed of an aluminum alloy, and the cylinder The piston sliding surface is harder than the main body and the crankcase portion, and the circular communication hole that communicates the crank chambers of the cylinders extends over both the piston sliding surface and the crankcase portion. And the center of the drill for forming the communication hole is positioned closer to the piston sliding surface than the boundary between the piston sliding surface and the crankcase portion, thereby forming the communication hole of the piston sliding surface . The hole width becomes narrower toward the crankcase part side than the center of the communication hole in the outer peripheral part as it goes to the crankcase part side. Ri, a cylinder block of plural cylinder engine, characterized in that the formation of the overhanging portion to prevent movement of the crank case side of the drill.   In claim 1, the cylinder body portion includes a sleeve having the piston sliding surface, and a relief portion having a larger diameter than the cylinder head side portion is formed at the crankshaft side end portion of the sleeve, A cylinder block of a multi-cylinder engine, characterized in that the center of the communication hole is located in the escape portion.

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