JP2004308473A

JP2004308473A - Air intake device for internal combustion engine

Info

Publication number: JP2004308473A
Application number: JP2003100201A
Authority: JP
Inventors: Taro Sakai; 太朗酒井; Yusuke Hosokawa; 裕介細川
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 2003-04-03
Filing date: 2003-04-03
Publication date: 2004-11-04
Anticipated expiration: 2023-04-03
Also published as: JP3861838B2

Abstract

PROBLEM TO BE SOLVED: To reinforce tumble in a cylinder 2 without reducing opening rate of an intake port 5 excessively. SOLUTION: A bulkhead 11 is provided along the longitudinal direction in the intake port 5 and is divided into a first flow passage 5A on an upper side and a second flow passage 5B on a lower side. An intake control valve 31 is arranged on the upstream side of the bulkhead 11, and a clearance 12 is formed between the bulkhead 11 and a valve element 33. A central part of the bulkhead 11 is recessed on a second flow passage 5B side as a channel part 11A, and the clearance 12 at a close position of the valve element 33 is relatively large in a central part. When the intake control valve 31 is closed, suction air stream is restricted in only the first flow passage 5A on the upper side, and a low pressure region occurs on the downstream side of the valve element 33 simultaneously. Suction air is taken in from a downstream side end of the second flow passage 5B due to difference in pressure and is refluxed into the first flow passage 5A from the clearance 12. For this reason, flow rate of stream passing through the valve clearance on the lower side of an intake valve 7 is reduced and flow rate of stream passing through the valve clearance on the upper side is increased to reinforce tumble. COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
この発明は、シリンダに接続された吸気ポートを含む内燃機関の吸気装置、特に、シリンダ内のタンブルやスワール等のガス流動の強化を図った吸気装置の改良に関する。
【０００２】
【従来の技術】
例えば、火花点火式内燃機関における安定した燃焼の実現のためには、タンブルもしくはスワールといったシリンダ内のガス流動が非常に重要であり、より広い運転領域でガス流動を強化できることが必要である。
【０００３】
従来から知られているシリンダ内のガス流動を強化する方法の一つは、特許文献１に見られるように、吸気ポートの通路断面の一部を遮蔽する吸気制御弁を用い、吸気ポート内を流れる吸気流を吸気ポートの一方の側に片寄らせる方法である。例えば、タンブル生成のためには、吸気ポートの下側に吸気制御弁が配置され、吸気ポートの上側に片寄って吸気が流れることで、シリンダ内のタンブルが強化されることになる。
【０００４】
また、ガス流動を強化する他の方法として、特許文献２あるいは特許文献３に見られるように、吸気ポート内に、その長手方向に沿った隔壁を設けるとともに、この隔壁により区画された一方の流路を開閉弁により開閉するようにした構成が知られている。例えば、タンブル生成のためには、吸気ポート内を上下に仕切るように隔壁が設けられ、その下側の流路が開閉弁によって閉じられることになる。これにより、上側の流路のみを通してシリンダ内に吸気が流入するため、前述した例に比べて流速や指向性が高く得られ、一般に、タンブル比はより向上する。
【０００５】
特に、特許文献３は、開閉弁が閉じたときに吸気が流れる隔壁の一方の面に、隔壁長手方向に沿った一対の溝部を設け、吸気弁の弁軸部の側方を通る一対の細い流れを形成するようにした構成を開示している。
【０００６】
【特許文献１】
特開２００２−５４５３５号公報
【０００７】
【特許文献２】
特開平６−１５９０７９号公報
【０００８】
【特許文献３】
特開２００１−１９３４６９号公報
【０００９】
【発明が解決しようとする課題】
上記のような公知の方法は、いずれも、ガス流動強化時に、吸気ポートの通路断面積を、吸気制御弁等によって実質的に減少させることになり、ベースとなる吸気ポート断面積に対する有効な通路断面積の割合を「開口率」として定義すると、一般に、開口率が小さいほどガス流動が高く得られる。しかしながら、開口率を小とすると、通気抵抗は増大し、シリンダ内に吸入可能な吸気量が減少するので、吸気制御弁等を閉じてガス流動を強化することができる運転条件は、比較的狭い範囲に制限されてしまう。
【００１０】
この発明は、開口率を過度に小さくすることなくシリンダ内のガス流動を強化することができる内燃機関の吸気装置を提供することを目的とする。
【００１１】
【課題を解決するための手段】
この発明は、内燃機関のシリンダに吸気ポートが接続され、かつこの吸気ポートの下流側の先端を吸気弁が開閉する内燃機関の吸気装置を前提としており、上記吸気ポートをその断面で２つの領域に区画するように、吸気ポートの長手方向に沿って設けられた隔壁と、上記隔壁により区画された一方の流路を開閉する吸気制御弁と、を備えている。上記吸気制御弁は、回転軸を中心に回動可能な板状の弁体からなり、上記隔壁の上流端に近接して位置している。そして、本発明では、上記隔壁の幅方向の中央部に、吸気ポートの長手方向に沿って延びるとともに上記の一方の流路の側に凹んだ凹溝部を有し、上記吸気制御弁が一方の流路を遮蔽した閉位置において、上記凹溝部の端縁に沿った形状の間隙が形成されるようになっている。
【００１２】
本発明では、上記吸気制御弁が一方の流路を遮蔽した閉位置にあるときに、他方の流路のみを通して吸気がシリンダ側へ流れることになり、吸気弁の周囲の一方に片寄った位置から相対的に多くの吸気がシリンダ内に流れ込む。これと同時に、吸気制御弁が吸気流を絞ることによって該吸気制御弁の下流側に局部的な圧力低下が生じ、これが、連通路となる間隙の出口側（他方の流路に面する側）に作用する。従って、吸気制御弁で遮蔽された一方の流路の下流側の端部と上記間隙との間で圧力差が発生し、上記端部から吸気が吸い込まれるとともに、吸気ポートの上流側へ向かって逆に流れ、かつ上記間隙を通して他方の流路へと合流する。つまり、遮蔽した流路を介して吸気の一部が上流側へと還流する。そのため、吸気弁の周囲を通る吸気流の流量ないしは流速の不均衡が一層拡大し、シリンダ内のガス流動が効果的に強化される。
【００１３】
ここで、上記の局部的な圧力低下は、他方の流路を流れる吸気流の流速に依存するので、吸気ポートの中心付近つまり隔壁の幅方向の中央部では大きな圧力低下が生じるのに対し、吸気ポートの壁面付近つまり隔壁の幅方向の両側部では圧力低下は小さい。本発明では、隔壁の中央部が凹溝部として一方の流路の側に凹んでいるので、閉位置においては、両側部に比べて相対的に大きな間隙が確保される。そのため、吸気ポートの中心付近の流れを有効に利用して上述の還流作用を得ることができる。また、隔壁の上流端の位置および弁体の下流端の位置を変えずに、閉位置において、実質的な間隙をより大きく得ることができる。
【００１４】
なお、本件の請求項における「吸気ポート」という用語は、必ずしもシリンダヘッド内部の部分のみを意味するのではなく、態様によっては、その上流側の一部が、シリンダヘッド外部の他の部材、例えば吸気マニホルドの一部として構成される場合も含む。例えば、後述する実施例では、シリンダヘッド内に形成された吸気ポート部分と吸気マニホルドブランチ部内の通路の先端部分とを含めた範囲が請求項の「吸気ポート」に相当する。
【００１５】
【発明の効果】
この発明に係る内燃機関の吸気装置によれば、吸気制御弁が遮蔽した流路を介して一部の吸気が還流することによってシリンダ内のガス流動を効果的に向上させることができ、特に、吸気制御弁による開口率を小さくせずにより強いガス流動を得ることができる。従って、通気抵抗の増加に伴うポンピングロスの増加が抑制され、またシリンダ内に流入する吸気量を多く確保できることから広範な運転領域でガス流動の強化が図れる。
【００１６】
特に、本発明によれば、流速が高い吸気ポート中心付近の流れを利用して、吸気の還流作用をより確実に得ることができる。
【００１７】
【発明の実施の形態】
以下、この発明の好ましい実施の形態を図面に基づいて詳細に説明する。
【００１８】
図１および図２は、この発明をポート噴射型火花点火式内燃機関の吸気装置に適用した第１実施例を示しており、これは、ガス流動としてタンブルの強化を図った例である。シリンダブロック１に円筒状のシリンダ２が複数形成されているとともに、その頂部を覆うシリンダヘッド３に、ペントルーフ型の燃焼室４が凹設されている。この燃焼室４の２つの傾斜面にそれぞれ開口するように、吸気ポート５および排気ポート６が形成されており、吸気ポート５の先端を吸気弁７が開閉し、かつ排気ポート６の先端を排気弁８が開閉している。ここで、吸気ポート５は、先端部が中央壁部１５を介して二股状に分岐しており、各気筒に一対設けられた吸気弁７がそれぞれの先端を開閉している。同様に、排気弁８も各気筒に一対設けられている。そして、これらの４つの弁に囲まれた燃焼室４中心部に、点火栓９が配置されている。なお、シリンダ２内に配置されたピストン１０は、本発明の要部ではないので、頂面が平坦な単純形状として図示してあるが、必要に応じてタンブルを用いた燃焼に適した所望の形状に構成される場合もある。
【００１９】
そして、図１に示すように、本実施例では、吸気ポート５をその断面で上下２つの領域に区画するように、吸気ポート５の長手方向に沿った隔壁１１が設けられている。この隔壁１１は、例えばアルミニウム合金にてシリンダヘッド３を鋳造する際に別体の金属板（例えば鋼板）を鋳込むことによって構成されており、その下流端１１ａができるだけ下流側つまり吸気弁７に近い位置となるように配置されている。より詳しくは、吸気ポート５が二股状に分岐する中央壁部１５上流の分岐点１５ａの直前まで、上記下流端１１ａが延びている。ここで、図示例では、クランクシャフト（図示せず）と直交する平面に沿った断面（図１）において、隔壁１１が存在する長手方向の部分で吸気ポート５がほぼ直線状をなし、これに対応して隔壁１１もほぼ直線状の断面形状をなしているが、必ずしもこれに限定されるものではなく、吸気ポート５が湾曲している場合には、これに沿うように湾曲した隔壁１１が設けられる。また、隔壁１１の上流端１１ｂは、吸気マニホルド２１が取り付けられるシリンダヘッド３の吸気マニホルド取付座面２２付近にまで延びている。なお、吸気マニホルド取付座面２２の機械加工の際に、鋼板等からなる隔壁１１に工具が接触することのないように、隔壁１１の上流端１１ｂを、吸気マニホルド取付座面２２から内側（吸気ポート５下流側）に極僅かだけ後退させるようにしてもよい。
【００２０】
上記のように隔壁１１が設けられていることにより、吸気ポート５内は、その下流側部分を除き、上側の通路状部分つまり第１流路５Ａと下側の通路状部分つまり第２流路５Ｂとに分割される。
【００２１】
なお、当業者には明らかなように、本明細書において吸気ポート５や吸気流等についての「上」「下」とは、シリンダ２の上下を基準とするものであり、空間上の絶対的な上下の意味ではない。
【００２２】
上記隔壁１１は、所定の板厚の金属板から構成されているが、本実施例では、その幅方向（機関前後方向に沿った方向）の中央部を下方つまり第２流路５Ｂ側に凹ませることで、吸気ポート５の長手方向に沿って延びる凹溝部１１Ａが形成されている。この凹溝部１１Ａは、隔壁１１の全長（下流端１１ａから上流端１１ｂまで）に亘って一定の断面形状に形成されており、下流端１１ａ付近の断面である図３および図２に示すように、広い溝幅を有するとともに、この溝幅に比して浅い深さを有する偏平な溝形状をなし、かつ底部両側が適宜なＲ形状をなしている。また、上記隔壁１１において上記凹溝部１１Ａの両側部に残る一対のフランジ部１１Ｂは、図３に示すように、互いに同じ面に沿って形成されており、その側縁が上述のようにシリンダヘッド３の母材に鋳込まれている。
【００２３】
また上記吸気ポート５は、上記吸気マニホルド２１の各気筒毎のブランチ部２３におけるブランチ部通路２４に連続しており、これによって、上流側の図示せぬコレクタ部から各シリンダ２に至る気筒毎の吸気通路が構成されている。上記ブランチ部通路２４は、吸気ポート５に近い下流側部分では、吸気ポート５の形状に沿った直線状をなし、かつこれよりも上流側の部分では、上方に位置するコレクタ部へ向かって上方へ湾曲している。
【００２４】
そして、上記ブランチ部通路２４の下流側の端部に、上記隔壁１１により区画されてなる下側の第２流路５Ｂを入口側つまり上流端で遮蔽するように、各気筒毎に吸気制御弁３１が設けられている。この吸気制御弁３１は、回転軸３２を中心に回動可能な板状の弁体３３を備えたもので、上記回転軸３２が、上記隔壁１１の両側部つまりフランジ部１１Ｂを上流側へ延長した延長線上、特に、吸気マニホルド２１のブランチ部２３側に位置し、この回転軸３２に、板状をなす弁体３３の一端が固定されている。詳しくは、上記弁体３３は、上記の第２流路５Ｂを開閉するために回転軸３２から一方へ延びた主弁部３３ａを有するとともに、これとは反対側へ相対的に短く延びた延長部３３ｂを有している。上記主弁部３３ａは、ブランチ部通路２４の下側の断面形状に応じて、楕円を２分したような形状（図２参照）をなしている。これに対し、上記延長部３３ｂの先端つまり下流端３３ｃは、本実施例では、図２に示すように、吸気マニホルド取付座面２２および回転軸３２と平行な直線状をなしている。また、上記回転軸３２は、上記隔壁１１の上流端１１ｂに近接しているものの、少なくとも上記延長部３３ｂが干渉しない程度に、上記上流端１１ｂから離れている。本実施例では、上記延長部３３ｂの先端つまり下流端３３ｃが、ブランチ部２３の先端フランジ面（吸気マニホルド取付座面２２と実質的に同じ面）よりも僅かに上流側に後退して位置している。
【００２５】
上記回転軸３２は、図示せぬアクチュエータに連係しており、タンブルを強化すべき運転条件では、弁体３３が図示の姿勢のような閉位置に制御され、下側の第２流路５Ｂを、その入口側で遮蔽する。このとき、主弁部３３ａは回転軸３２より上流側にあり、吸気制御弁３１上流側から流れてきた吸気流を上側の第１流路５Ａへ案内する方向に、弁体３３が傾斜した状態となる。換言すれば、このような所定の傾斜位置で回転軸３２より下側の領域を完全に塞ぐように、上記主弁部３３ａの外形状が設定されている。上記の閉位置における弁体３３の傾斜角θ（隔壁１１を上流側へ延長した線ｍと弁体３３とのなす角）は、３０°〜４０°程度である。また、このような閉位置に回動すると、主弁部３３ａの反対側に位置する下流側の延長部３３ｂは、隔壁１１（詳しくはフランジ部１１Ｂ）よりも上方つまり第１流路５Ａ側に突出した状態となる。そして、隔壁１１の上流端１１ｂと弁体３３の延長部下流端３３ｃとの間には、第１流路５Ａ上流端と第２流路５Ｂ上流端とを連通させる連通路となる適宜な大きさの間隙１２が生じる。
【００２６】
ここで、本実施例では、前述したように隔壁１１が凹溝部１１Ａを備えているので、上記隔壁１１の上流端１１ｂの端縁は、立体的に見て単純な直線ではなく、中央部が下方へ凹んだ形となる。なお、隔壁１１の上流端１１ｂの端面は、吸気マニホルド取付座面２２と平行な面に沿っており、実質的に、フランジ部１１Ｂに対し垂直な平面に沿ったものとなっている。
【００２７】
従って、上記のように吸気制御弁３１が閉位置にあるときに、直線状をなす弁体下流端３３ｃとの間に生じる間隙１２は、図４に弁体３３の傾斜角θに沿った矢印β方向から見た図を示すように、両側部のフランジ部１１Ｂ部分において相対的に小さく、かつ中央部の凹溝部１１Ａ部分において相対的に大きい。換言すれば、吸気ポート５の中心付近に十分に大きな間隙１２が確保され、吸気ポート５の壁面に近い位置での間隙１２は小さい。
【００２８】
一方、吸気量が大となる運転条件、例えば高速高負荷域では、上記吸気制御弁３１は、吸気ポート５の長手方向に沿った開位置に制御され、第２流路５Ｂを開放することとなる。この開位置では、上記弁体３３が隔壁１１のフランジ部１１Ｂと直線状に連続した姿勢となり、吸気流と平行となる。そして、延長部３３ｂも上記隔壁１１のフランジ部１１Ｂと直線状に整列し、延長部３３ｂの先端（下流端３３ｃ）と隔壁１１の上流端１１ｂとが互いに隣接した状態となる。
【００２９】
また、各気筒の吸気ポート５へ向けて燃料を噴射する燃料噴射弁４１が、シリンダヘッド３の吸気ポート５上方に配置されている。この燃料噴射弁４１は、一対の吸気弁７に対応して略Ｖ字形に分岐した一対の噴霧を形成し得る形式のもので、図１に示すように、吸気弁７の弁頭部を指向した噴霧Ｆが隔壁１１と干渉することのないように、比較的下流側つまり吸気弁７寄りに配置されている。例えば、その噴口部つまり先端部が、隔壁１１の中間部の上方に位置している。そして、この燃料噴射弁４１の噴霧Ｆが通過する凹部４２が、吸気ポート５の上壁面に形成されている。
【００３０】
ここで、上記噴霧Ｆは、図３に示すように、隔壁１１の下流端１１ａにおいては、凹溝部１１Ａ内側の凹んだ領域を通過する。換言すれば、この凹溝部１１Ａの下側に凹んだ形状を利用して、隔壁１１と一対の噴霧Ｆとの干渉を避けつつ、隔壁１１をできるだけ下流側まで延ばした構成となっている（図１参照）。従って、上記凹溝部１１Ａの溝幅や深さは、上流端１１ｂで形成される間隙１２の大きさと併せて、下流端１１ａでの噴霧Ｆとの位置関係を最大限に考慮したものとなっている。図３の例では、Ｖ字形に拡がる一対の噴霧Ｆを包含するように、凹溝部１１Ａの溝幅が設定され、かつそれぞれの噴霧Ｆの下方の一部が凹溝部１１Ａ内を通過する。
【００３１】
なお、図示しないが、この内燃機関は、排気系から吸気系に排気の一部を還流させるために、排気還流制御弁などを含む公知の排気還流装置を備えており、特に、シリンダ２内のタンブルを積極的に利用して高い排気還流率の下での安定した燃焼を実現することにより、部分負荷域での燃費低減を図った構成となっている。還流排気は、吸気マニホルド２１の図示せぬコレクタ部などにまとめて導入してもよく、あるいは、各気筒のブランチ部通路２４にそれぞれ分配して導入することも可能である。
【００３２】
次に、図５の説明図を用いて、上記実施例の構成における基本的な作用について説明する。吸気行程において、吸気弁７が開き、かつピストン１０が下降すると、吸気は、吸気弁７周囲の弁隙間を通して、シリンダ２内に流入する。このとき、吸気制御弁３１が開位置にあれば、第１流路５Ａおよび第２流路５Ｂの双方を通して吸気が流れ、吸気弁７の周囲の各部からほぼ均等に吸気が流れ込むので、シリンダ２内に発生するガス流動は比較的弱い。
【００３３】
これに対し、吸気制御弁３１が図５に示すように閉位置に制御されると、下側の第２流路５Ｂが遮蔽され、上側の第１流路５Ａのみを通して吸気がシリンダ２側へ流れることになる。特に、図５に示すように吸気ポート５の上側の内壁面５ａ（以下、上側内壁面５ａと記す）に沿って吸気流が偏在し、吸気ポート５の下側の内壁面５ｂ（以下、下側内壁面５ｂと記す）に沿う流れは非常に少ない。そのため、吸気弁７の周囲について見たときに、吸気弁７の下側つまりシリンダ２外周に近い側の弁隙間２０ａでは、吸気の流量が少ないとともに、流速も低く、また吸気弁７の上側つまり点火栓９に近い側の弁隙間２０ｂでは、吸気の流量が多いとともに、流速も高くなる。この結果、シリンダ２内には、矢印で示すように、吸気弁７側から排気弁８側を経てピストン１０頂面へと向かうタンブル（いわゆる順タンブル）が生じる。そして、本実施例では、吸気制御弁３１が図示のように閉位置にあると、この部分が絞り部となって吸気流が第１流路５Ａのみを流れるように絞られるので、第１流路５Ａにおいて、隔壁１１の上流端１１ｂ付近で、局部的な圧力低下が生じ、破線１３で示すような低圧領域が発生する。第１流路５Ａと第２流路５Ｂとの間の連通路となる間隙１２は、この低圧領域１３に向かって開口する形となるので、第２流路５Ｂの下流側の開口端１４との間で圧力差が生じる。そのため、上記開口端１４が吸気取り入れ口となり、上記圧力差によって、上記開口端１４から吸気が取り込まれるとともに、吸気ポート５の上流側へ向かって逆に流れ、かつ間隙１２から第１流路５Ａへと合流する。つまり、第１流路５Ａ通過後に吸気ポート５の下側の領域へと拡がろうとした吸気が第２流路５Ｂを通して上流側へ還流し、上側の第１流路５Ａへと戻されることになる。そのため、吸気弁７の下側の弁隙間２０ａを通る吸気流がより少なくなると同時に、上側の弁隙間２０ｂを通る吸気流がより多くなり、シリンダ２内のタンブルがより強く得られる。特に、下側の弁隙間２０ａを通る吸気流は、シリンダ２内のタンブルを弱めるように作用するのであるが、上記実施例では、上側の弁隙間２０ｂを通る流れによりタンブルが強められるのみならず、このタンブルを弱めるように作用する下側の弁隙間２０ａを通る流れが抑制されることから、非常に効果的にタンブルが強化される。
【００３４】
このようにシリンダ２内に形成される強いタンブルは、燃費向上のために大量に排気還流を行う上で非常に有用であり、部分負荷域において、高排気還流率となる大量の排気還流を与えつつ吸気制御弁３１を閉じて強いタンブルを生成することによって、安定した燃焼を実現でき、燃費向上を達成できる。
【００３５】
特に、上記の実施例では、図示の閉位置において、弁体３３の延長部３３ｂが隔壁１１よりも上方つまり第１流路５Ａ側に突出しているので、その背面側でより効果的に低圧領域が発達し、間隙１２を通した吸気の還流が確実に行われる。
【００３６】
そして、高速高負荷域などで吸気制御弁３１が開位置となったときには、前述のように弁体３３が隔壁１１（フランジ部１１Ｂ）と直線状に整列することで吸気抵抗の増加が回避されるとともに、延長部３３ｂによって間隙１２が狭められるため、吸気流の乱れが抑制される。なお、本実施例では、図１に示すように、弁体３３が一定厚の板状ではなく、主弁部３３ａおよび延長部３３ｂの双方で、先端へ向かって徐々に薄くなるテーパ状の断面形状を有しているので、吸気流が円滑に流れ、吸気抵抗がより低減する。
【００３７】
図６は、上記実施例の吸気装置における実際の吸気の流れを解析したものであり、各部の流れの速さおよび方向を、微細なベクトルつまり矢印でもって示している。矢印の粗密は、流量を示し、矢印が密に集まっている部位は、流量が大であることを意味する。また、図７は、比較例として、連通路となる間隙１２を閉塞したものの吸気の流れを同様に示している。つまり、図７の構成は、単に隔壁１１と吸気制御弁３１とで吸気流を偏在させるようにした従来技術に相当する。なお、両者とも吸気制御弁３１の開口率は同一（約２０％）である。
【００３８】
これらの図を対比すれば明らかなように、比較例である図７のものでは、上側の第１流路５Ａを通過した吸気流は、隔壁１１の下流端１１ａよりも下流で下方へも拡散していくので、吸気弁７の下側の弁隙間２０ａを通る吸気流が少なからず存在する。なお、隔壁１１の下側の第２流路５Ｂでは殆ど流れが見られず、淀んだ状態となる。これに対し、本発明の基本的構成を示す図６では、吸気弁７寄りの下側領域から下側の第２流路５Ｂを通して吸気が還流し、この結果、吸気弁７の下側の弁隙間２０ａを通る吸気流が極端に減少する。また、これに伴って上側の弁隙間２０ｂを通る吸気流が増加する。従って、効果的にタンブルを強化できる。
【００３９】
図８は、図６もしくは図７のように隔壁１１と吸気制御弁３１とを用いた吸気装置におけるタンブルの強さと吸入空気量との関係を示している。なお、ここでは、タンブルの強さを、吸気行程中のタンブル比の最大値でもって表している。一般に、タンブルが弱いと燃焼が遅く不安定となる傾向があり、タンブルが強いと燃焼が速く安定となる。図の実線で示す特性は、図７の比較例の場合の関係を示しており、開口率を小さく設定するほどタンブルが強くなるものの吸入空気量が少なくなり、逆に、開口率を大きく設定するほど吸入空気量が多く得られるもののタンブルが弱くなる、という相関関係がある。吸入空気量が少なくなることは、タンブルの生成が可能な運転領域（つまり吸気制御弁３１を閉じることができる運転領域）が狭いことを意味し、吸入空気量が多いことは、逆にその運転領域が広いことを意味する。間隙１２を通した還流を利用した本発明によれば、破線で示すような領域に、タンブル強さと吸入空気量との相関を得ることができる。つまり、同一のタンブル強さであれば、吸入空気量をより大きく確保でき、また同一の吸入空気量（開口率）であれば、タンブルをより強く得ることができる。
【００４０】
従って、燃費向上手段として前述したように大量排気還流と強いタンブルとを組み合わせた運転を、より広い運転領域において行うことができ、内燃機関全体として、大幅な燃費向上が図れる。そして、同じ運転領域で比較すると、タンブルがより強く生成されることから、より大量の排気還流が可能となり、一層の燃費向上が可能である。
【００４１】
また、さらに、上記実施例では、隔壁１１の中央部に凹溝部１１Ａを設けることで、吸気ポート５の壁面に近い両側部に比べて吸気ポート５の中心付近に十分に大きな間隙１２を確保するようにしたので、上述の還流作用をより一層効果的に得ることができる。つまり、吸気制御弁３１下流での負圧発生は、吸気流の流速に依存しており、この流速は、吸気ポート５の壁面に近い位置よりも吸気ポート５の中心付近で高くなるので、吸気ポート５の中心付近で相対的に強い負圧が発生する。そのため、吸気ポート５の中心付近に十分に大きな間隙１２を確保することで、吸気ポート５の中心付近での高い流速を有効に利用して、還流作用を一層効果的に得ることができる。しかも、吸気制御弁３１が閉じた状態で第１流路５Ａ側を流れる吸気流は、上記凹溝部１１Ａによって案内かつ整流され、凹溝部１１Ａにより生じた大きな間隙１２の上を通って、より円滑に流れるため、還流作用がより強化される。
【００４２】
また、上記のような還流作用を十分に得るためには、それに見合った間隙１２の大きさ（流路面積）が必要であるが、隔壁１１の上流端１１ｂの位置と弁体３３の下流端３３ｃの位置とが同じであれば、凹溝部１１Ａを形成することによって、吸気制御弁３１の閉位置での間隙１２の流路面積が増加する。換言すれば、同一の流路面積を確保しようとする場合に、吸気制御弁３１の位置を相対的に下流側に配置することが可能であり、例えばブランチ部２３の下流側の直線状部分が短いような場合に、吸気制御弁３１開位置での吸気抵抗増加を抑制できる。
【００４３】
さらに、上記凹溝部１１Ａの存在によって、上述のように燃料噴霧Ｆと隔壁１１との干渉を回避しつつ、より下流側まで隔壁１１を延ばすことができる。そのため、タンブル強化の上で一層有利となる。
【００４４】
なお、図６に例示するように吸気制御弁３１の弁体３３が隔壁１１に対しほぼ垂直であると、隔壁１１の中央部（凹溝部１１Ａ部分）と両側部（フランジ部１１Ｂ）とで、間隙１２の幅は一定となるが、このような場合でも、隔壁１１の上流端１１ｂが直線である（つまり凹溝部１１Ａを具備しない場合）よりも、両者間の流路面積は大となる。そして、図１のように弁体３３の傾斜角θが９０°よりも小さければ、隔壁１１の中央部での間隙１２が相対的に大きなものとなる。
【００４５】
次に、図９〜図１２は、この発明の第２実施例を示している。この実施例では、隔壁１１の中央部に、一対の凹溝部１１Ａが平行に形成されており、両者間に、両側のフランジ部１１Ｂと同一面上に位置するランド部１１Ｃが設けられている。上記の一対の凹溝部１１Ａは、互いに同一の断面形状を有し、かつ、隔壁１１の上流端１１ｂから下流端１１ａに亘って一定断面形状に形成されている。具体的には、図１１に示すように、楕円を長軸に沿って２分したような断面形状にそれぞれ凹んでいる。そして、特に、この実施例では、図１１に示すように、燃料噴射弁４１から噴射された一対の噴霧Ｆの一部が、ちょうど隔壁１１の下流端１１ａにおいて各凹溝部１１Ａの内側の領域を通過するように、各凹溝部１１Ａの位置や大きさが設定されている。
【００４６】
この実施例においても、凹溝部１１Ａの形成によって、図１２に示すように十分に大きな間隙１２が確保され、また隔壁１１の長さをより長くできることから、前述した第１実施例と同様の作用効果を得ることができる。また、特に、図９から明らかなように、一対の凹溝部１１Ａによって整流かつ案内された一対の吸気流が、それぞれ各吸気弁７を指向して直線的に流れるようになるので、一対の吸気弁７の間に位置する吸気ポート５内の中央壁部１５に衝突する流れが少なくなる、という利点がある。
【図面の簡単な説明】
【図１】この発明に係る吸気装置の第１実施例を示す断面図。
【図２】この第１実施例の吸気装置を上方から見た平面図。
【図３】図１のα−α線に沿った要部の断面図。
【図４】図１の矢印β方向から見た矢視図。
【図５】第１実施例の構成を模式的に示した構成説明図。
【図６】この吸気装置における吸気の流れを示す説明図。
【図７】比較例の吸気装置における吸気の流れを示す説明図。
【図８】タンブルの強さと吸入空気量との関係を示す特性図。
【図９】この発明に係る吸気装置の第２実施例を示す断面図。
【図１０】この第２実施例の吸気装置を上方から見た平面図。
【図１１】図９のα−α線に沿った要部の断面図。
【図１２】図９の矢印β方向から見た矢視図。
【符号の説明】
３…シリンダヘッド
５…吸気ポート
７…吸気弁
１１…隔壁
１１Ａ…凹溝部
１２…間隙
２１…吸気マニホルド
３１…吸気制御弁[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an intake device for an internal combustion engine including an intake port connected to a cylinder, and more particularly, to an improvement of an intake device for enhancing gas flow such as tumble and swirl in a cylinder.
[0002]
[Prior art]
For example, in order to achieve stable combustion in a spark ignition type internal combustion engine, gas flow in a cylinder such as a tumble or swirl is very important, and it is necessary to be able to enhance gas flow in a wider operation range.
[0003]
One of the conventionally known methods of enhancing gas flow in a cylinder is to use an intake control valve that blocks a part of a passage cross section of an intake port, as disclosed in Patent Literature 1, to reduce the inside of the intake port. This is a method in which the flowing intake air flow is biased to one side of the intake port. For example, in order to generate a tumble, an intake control valve is disposed below the intake port, and intake air is biased above the intake port, so that the tumble in the cylinder is strengthened.
[0004]
Further, as another method for enhancing the gas flow, as shown in Patent Literature 2 or Patent Literature 3, a partition wall is provided in the intake port along the longitudinal direction, and one of the flow paths partitioned by the partition wall is provided. There is known a configuration in which a path is opened and closed by an on-off valve. For example, in order to generate a tumble, a partition is provided so as to partition the inside of the intake port up and down, and the lower flow path is closed by an on-off valve. As a result, the intake air flows into the cylinder only through the upper flow path, so that the flow velocity and the directivity are higher than those in the above-described example, and the tumble ratio generally improves.
[0005]
In particular, Patent Literature 3 discloses that, on one surface of a partition wall through which intake air flows when the on-off valve is closed, a pair of grooves is provided along the partition wall longitudinal direction, and a pair of narrow holes passing sideways of a valve shaft of the intake valve. Disclosed is an arrangement for forming a flow.
[0006]
[Patent Document 1]
JP-A-2002-54535
[Patent Document 2]
JP-A-6-159079
[Patent Document 3]
JP 2001-193469 A
[Problems to be solved by the invention]
In any of the known methods as described above, when the gas flow is enhanced, the passage cross-sectional area of the intake port is substantially reduced by an intake control valve or the like. When the ratio of the cross-sectional area is defined as “opening ratio”, generally, the smaller the opening ratio, the higher the gas flow. However, when the opening ratio is reduced, the ventilation resistance increases, and the amount of intake air that can be taken into the cylinder decreases. Therefore, the operating conditions under which the intake control valve and the like can be closed to enhance the gas flow are relatively narrow. It is limited to the range.
[0010]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an intake device for an internal combustion engine that can enhance gas flow in a cylinder without excessively reducing an opening ratio.
[0011]
[Means for Solving the Problems]
The present invention presupposes an intake device for an internal combustion engine in which an intake port is connected to a cylinder of the internal combustion engine and an intake valve opens and closes a downstream end of the intake port. A partition provided along the longitudinal direction of the intake port so as to define the intake port; and an intake control valve for opening and closing one of the flow paths partitioned by the partition. The intake control valve is formed of a plate-shaped valve element that can rotate around a rotation axis, and is located near the upstream end of the partition. In the present invention, the partition wall has a groove extending in the longitudinal direction of the intake port and recessed on the side of the one flow path at a central portion in the width direction of the partition wall, and the intake control valve is provided with one of the two grooves. At the closed position where the flow path is shielded, a gap having a shape along the edge of the concave groove is formed.
[0012]
In the present invention, when the intake control valve is in the closed position where one of the flow paths is shielded, the intake air flows to the cylinder side only through the other flow path, and the intake air flows from one side around the intake valve toward the cylinder. A relatively large amount of intake air flows into the cylinder. At the same time, the intake control valve throttles the intake air flow, causing a local pressure drop downstream of the intake control valve, which is caused by the outlet side of the gap that becomes the communication path (the side facing the other flow path). Act on. Therefore, a pressure difference is generated between the downstream end of one of the flow passages shielded by the intake control valve and the gap, and the intake air is sucked from the end and toward the upstream side of the intake port. It flows in the opposite direction and merges into the other flow path through the gap. That is, a part of the intake air returns to the upstream side through the shielded flow path. Therefore, the imbalance in the flow rate or the flow velocity of the intake air flowing around the intake valve is further increased, and the gas flow in the cylinder is effectively enhanced.
[0013]
Here, since the local pressure drop depends on the flow rate of the intake air flowing through the other flow path, a large pressure drop occurs near the center of the intake port, that is, at the center in the width direction of the partition wall. The pressure drop is small near the wall surface of the intake port, that is, on both sides in the width direction of the partition wall. In the present invention, since the central portion of the partition wall is recessed toward one of the flow paths as a concave groove portion, a relatively large gap is secured in the closed position as compared with both side portions. Therefore, the above-described recirculation effect can be obtained by effectively utilizing the flow near the center of the intake port. In addition, a substantial gap can be obtained in the closed position without changing the position of the upstream end of the partition and the position of the downstream end of the valve element.
[0014]
In addition, the term "intake port" in the claims of the present invention does not necessarily mean only a portion inside the cylinder head, and in some embodiments, a part on the upstream side is another member outside the cylinder head, for example, This includes the case where it is configured as part of the intake manifold. For example, in an embodiment described later, a range including an intake port portion formed in a cylinder head and a front end portion of a passage in an intake manifold branch portion corresponds to an “intake port” in the claims.
[0015]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the intake device of the internal combustion engine which concerns on this invention, the gas flow in a cylinder can be improved effectively by recirculating a part of intake air through the flow path blocked by the intake control valve, A stronger gas flow can be obtained without reducing the opening ratio by the intake control valve. Therefore, an increase in pumping loss due to an increase in ventilation resistance is suppressed, and a large amount of intake air flowing into the cylinder can be secured, so that gas flow can be enhanced in a wide operating range.
[0016]
In particular, according to the present invention, it is possible to more reliably obtain the intake air recirculation effect by utilizing the flow near the center of the intake port where the flow velocity is high.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
[0018]
1 and 2 show a first embodiment in which the present invention is applied to an intake device of a port injection type spark ignition type internal combustion engine. This is an example in which a tumble is strengthened as a gas flow. A plurality of cylindrical cylinders 2 are formed in a cylinder block 1, and a pent roof type combustion chamber 4 is formed in a cylinder head 3 that covers the top of the cylinder 2. An intake port 5 and an exhaust port 6 are formed so as to open on the two inclined surfaces of the combustion chamber 4, respectively. An intake valve 7 opens and closes the tip of the intake port 5, and exhausts the tip of the exhaust port 6. Valve 8 opens and closes. Here, the front end of the intake port 5 is bifurcated through a central wall portion 15, and a pair of intake valves 7 provided in each cylinder open and close the respective front ends. Similarly, a pair of exhaust valves 8 are provided for each cylinder. An ignition plug 9 is arranged at the center of the combustion chamber 4 surrounded by these four valves. Note that the piston 10 arranged in the cylinder 2 is not a main part of the present invention, and is illustrated as a simple shape having a flat top surface. However, if necessary, a desired shape suitable for combustion using a tumble It may be configured in a shape.
[0019]
As shown in FIG. 1, in the present embodiment, a partition wall 11 is provided along the longitudinal direction of the intake port 5 so as to partition the intake port 5 into two upper and lower regions in a cross section thereof. The partition wall 11 is formed by casting a separate metal plate (for example, a steel plate) when casting the cylinder head 3 with, for example, an aluminum alloy. They are arranged to be close to each other. More specifically, the downstream end 11a extends to just before a branch point 15a upstream of the central wall portion 15 where the intake port 5 branches in a forked shape. Here, in the illustrated example, in a cross section (FIG. 1) along a plane orthogonal to the crankshaft (not shown), the intake port 5 has a substantially linear shape at a longitudinal portion where the partition wall 11 exists. Correspondingly, the partition wall 11 also has a substantially straight cross-sectional shape, but is not necessarily limited to this. If the intake port 5 is curved, the partition wall 11 curved along this shape is formed. Provided. The upstream end 11b of the partition 11 extends to near the intake manifold mounting seat surface 22 of the cylinder head 3 to which the intake manifold 21 is mounted. During machining of the intake manifold mounting seat surface 22, the upstream end 11b of the partition wall 11 is placed inside (intake air) The port (downstream side of the port 5) may be slightly retreated.
[0020]
By providing the partition wall 11 as described above, the inside of the intake port 5 except for the downstream side portion thereof has an upper passage-like portion, that is, the first flow passage 5A, and a lower passage-like portion, that is, the second flow passage. 5B.
[0021]
As will be apparent to those skilled in the art, the terms “upper” and “lower” with respect to the intake port 5 and the intake flow in this specification are based on the upper and lower sides of the cylinder 2 and are absolute It doesn't mean up and down.
[0022]
The partition 11 is made of a metal plate having a predetermined thickness. In the present embodiment, the center in the width direction (direction along the engine front-rear direction) is recessed downward, that is, toward the second flow path 5B. By doing so, a concave groove portion 11A extending along the longitudinal direction of the intake port 5 is formed. This concave groove portion 11A is formed in a constant cross-sectional shape over the entire length of the partition wall 11 (from the downstream end 11a to the upstream end 11b), and as shown in FIGS. 3 and 2, which are cross sections near the downstream end 11a. It has a wide groove width, a flat groove shape having a shallow depth as compared with the groove width, and an appropriate R shape on both sides at the bottom. Further, a pair of flange portions 11B remaining on both sides of the concave groove portion 11A in the partition wall 11 are formed along the same plane as shown in FIG. No. 3 is cast in the base material.
[0023]
Further, the intake port 5 is continuous with a branch passage 24 in a branch 23 of each cylinder of the intake manifold 21, whereby each cylinder from an unillustrated collector portion to each cylinder 2 from an upstream not-shown portion is provided. An intake passage is configured. The branch portion passage 24 has a linear shape in accordance with the shape of the intake port 5 in a downstream portion near the intake port 5, and has an upward portion toward an upper collector portion in an upstream portion thereof. It is curved to
[0024]
An intake control valve is provided for each cylinder at the downstream end of the branch passage 24 so as to block the lower second flow path 5B defined by the partition wall 11 at the inlet side, that is, at the upstream end. 31 are provided. The intake control valve 31 is provided with a plate-shaped valve element 33 rotatable about a rotation shaft 32. The rotation shaft 32 extends both sides of the partition wall 11, that is, the flange portion 11B to the upstream side. One end of a plate-shaped valve body 33 is fixed to the rotating shaft 32 on the side of the extended line, in particular, on the branch portion 23 side of the intake manifold 21. Specifically, the valve body 33 has a main valve portion 33a extending to one side from the rotating shaft 32 to open and close the second flow path 5B, and an extension relatively shortly extending to the opposite side. It has a portion 33b. The main valve portion 33a has a shape obtained by dividing an ellipse into two parts (see FIG. 2) according to the cross-sectional shape of the lower side of the branch portion passage 24. On the other hand, the tip of the extension portion 33b, that is, the downstream end 33c, in this embodiment, has a linear shape parallel to the intake manifold mounting seat surface 22 and the rotation shaft 32, as shown in FIG. The rotating shaft 32 is close to the upstream end 11b of the partition 11, but is separated from the upstream end 11b at least so as not to interfere with the extension 33b. In this embodiment, the distal end of the extension portion 33b, that is, the downstream end 33c, is located slightly retreating upstream from the distal end flange surface of the branch portion 23 (substantially the same surface as the intake manifold mounting seat surface 22). ing.
[0025]
The rotating shaft 32 is linked to an actuator (not shown). Under operating conditions for strengthening the tumble, the valve element 33 is controlled to the closed position as shown in the figure, and the lower second flow path 5B is closed. , Shielding at the entrance side. At this time, the main valve portion 33a is on the upstream side of the rotary shaft 32, and the valve body 33 is inclined in a direction to guide the intake air flowing from the upstream of the intake control valve 31 to the upper first flow path 5A. It becomes. In other words, the outer shape of the main valve portion 33a is set such that the region below the rotation shaft 32 is completely closed at such a predetermined inclined position. The inclination angle θ of the valve body 33 at the above-mentioned closed position (the angle formed by the line m extending the partition 11 to the upstream side and the valve body 33) is about 30 ° to 40 °. Further, when pivoted to such a closed position, the downstream extension portion 33b located on the opposite side of the main valve portion 33a is located above the partition wall 11 (specifically, the flange portion 11B), that is, toward the first flow path 5A side. It will be in a protruding state. An appropriate size between the upstream end 11b of the partition wall 11 and the downstream end 33c of the extended portion of the valve body 33 is a communication path for communicating the upstream end of the first flow path 5A and the upstream end of the second flow path 5B. A gap 12 is formed.
[0026]
Here, in this embodiment, since the partition 11 has the concave groove 11A as described above, the edge of the upstream end 11b of the partition 11 is not a three-dimensionally simple straight line, The shape is concave downward. The end face of the upstream end 11b of the partition wall 11 extends along a plane parallel to the intake manifold mounting seat surface 22, and substantially along a plane perpendicular to the flange portion 11B.
[0027]
Therefore, when the intake control valve 31 is in the closed position as described above, the gap 12 generated between the valve body downstream end 33c and the linear valve body 33 is indicated by an arrow along the inclination angle θ of the valve body 33 in FIG. As shown in the view seen from the β direction, it is relatively small in the flange portions 11B on both sides and relatively large in the central groove portion 11A. In other words, a sufficiently large gap 12 is secured near the center of the intake port 5, and the gap 12 near the wall surface of the intake port 5 is small.
[0028]
On the other hand, under operating conditions where the amount of intake air is large, for example, in a high-speed high-load region, the intake control valve 31 is controlled to an open position along the longitudinal direction of the intake port 5 to open the second flow path 5B. Become. In this open position, the valve body 33 is in a posture linearly continuous with the flange portion 11B of the partition wall 11, and is parallel to the intake air flow. The extension 33b is also linearly aligned with the flange 11B of the partition 11, so that the tip (downstream end 33c) of the extension 33b and the upstream end 11b of the partition 11 are adjacent to each other.
[0029]
A fuel injection valve 41 for injecting fuel toward the intake port 5 of each cylinder is disposed above the intake port 5 of the cylinder head 3. The fuel injection valve 41 is of a type capable of forming a pair of sprays branched in a substantially V-shape corresponding to the pair of intake valves 7, and directs the valve head of the intake valve 7 as shown in FIG. The spray F is disposed relatively downstream, that is, near the intake valve 7 so that the spray F does not interfere with the partition 11. For example, the nozzle orifice, that is, the tip, is located above the middle part of the partition 11. A recess 42 through which the spray F of the fuel injection valve 41 passes is formed on the upper wall surface of the intake port 5.
[0030]
Here, as shown in FIG. 3, the spray F passes through a concave area inside the concave groove 11A at the downstream end 11a of the partition wall 11. In other words, the configuration in which the partition 11 is extended to the downstream side as much as possible while avoiding interference between the partition 11 and the pair of sprays F by utilizing the shape recessed below the concave groove 11A (FIG. 1). Therefore, the groove width and the depth of the concave groove portion 11A take into account the positional relationship with the spray F at the downstream end 11a as well as the size of the gap 12 formed at the upstream end 11b. I have. In the example of FIG. 3, the groove width of the concave grooves 11A is set so as to include a pair of sprays F spreading in a V-shape, and a part below each of the sprays F passes through the concave grooves 11A.
[0031]
Although not shown, the internal combustion engine is provided with a known exhaust gas recirculation device including an exhaust gas recirculation control valve and the like in order to recirculate a part of exhaust gas from the exhaust system to the intake system. By using tumble positively to achieve stable combustion under a high exhaust gas recirculation rate, the fuel consumption is reduced in the partial load range. The recirculated exhaust gas may be collectively introduced into a collector section (not shown) of the intake manifold 21 or may be distributed and introduced into the branch passages 24 of each cylinder.
[0032]
Next, the basic operation of the configuration of the above embodiment will be described with reference to the explanatory diagram of FIG. In the intake stroke, when the intake valve 7 opens and the piston 10 descends, the intake air flows into the cylinder 2 through a valve gap around the intake valve 7. At this time, if the intake control valve 31 is at the open position, the intake air flows through both the first flow path 5A and the second flow path 5B, and the intake air flows from each part around the intake valve 7 almost uniformly. The gas flow generated within is relatively weak.
[0033]
On the other hand, when the intake control valve 31 is controlled to the closed position as shown in FIG. 5, the lower second flow path 5B is blocked, and the intake air flows to the cylinder 2 side only through the upper first flow path 5A. It will flow. In particular, as shown in FIG. 5, the intake air flow is unevenly distributed along the upper inner wall surface 5 a of the intake port 5 (hereinafter, referred to as the upper inner wall surface 5 a), and the lower inner wall surface 5 b (hereinafter, referred to as the lower The flow along the inner side wall surface 5b) is very small. Therefore, when viewed around the intake valve 7, in the valve gap 20 a below the intake valve 7, that is, near the outer periphery of the cylinder 2, the flow rate of the intake air is small, the flow rate is low, and the upper side of the intake valve 7, In the valve gap 20b close to the ignition plug 9, the flow rate of the intake air is high and the flow velocity is high. As a result, a tumble (so-called forward tumble) from the intake valve 7 side to the top surface of the piston 10 through the exhaust valve 8 side is generated in the cylinder 2 as shown by an arrow. In the present embodiment, when the intake control valve 31 is in the closed position as shown in the figure, this portion serves as a throttle, and the intake air is throttled so as to flow only through the first flow path 5A. In the road 5 A, a local pressure drop occurs near the upstream end 11 b of the partition 11, and a low pressure region as shown by a broken line 13 occurs. Since the gap 12 serving as a communication path between the first flow path 5A and the second flow path 5B has a shape that opens toward the low-pressure area 13, the gap 12 between the downstream side open end 14 of the second flow path 5B and Between the pressure differences. Therefore, the open end 14 serves as an intake air intake port, the intake air is taken in from the open end 14 by the pressure difference, the air flows backward toward the upstream side of the intake port 5, and the first flow path 5 A To join. That is, after passing through the first flow path 5A, the intake air that is going to expand to the lower area of the intake port 5 is returned to the upstream side through the second flow path 5B and returned to the upper first flow path 5A. Become. Therefore, the amount of intake air flowing through the lower valve clearance 20a of the intake valve 7 is reduced, and at the same time, the amount of intake air flowing through the upper valve clearance 20b is increased, so that a stronger tumble in the cylinder 2 is obtained. In particular, the intake air flow passing through the lower valve gap 20a acts to weaken the tumble in the cylinder 2, but in the above embodiment, not only the flow through the upper valve gap 20b increases the tumble, but also Since the flow through the lower valve gap 20a acting to weaken the tumble is suppressed, the tumble is very effectively strengthened.
[0034]
The strong tumble formed in the cylinder 2 as described above is very useful in performing a large amount of exhaust gas recirculation for improving fuel efficiency, and provides a large amount of exhaust gas recirculation with a high exhaust gas recirculation rate in a partial load region. By closing the intake control valve 31 while generating a strong tumble, stable combustion can be realized, and improvement in fuel efficiency can be achieved.
[0035]
In particular, in the above embodiment, in the illustrated closed position, the extension 33b of the valve body 33 projects above the partition wall 11, that is, toward the first flow path 5A side, so that the low pressure region is more effectively provided on the back side thereof. Is developed, and the recirculation of the intake air through the gap 12 is reliably performed.
[0036]
When the intake control valve 31 is in the open position in a high-speed, high-load region or the like, the valve body 33 is linearly aligned with the partition wall 11 (flange portion 11B) as described above, thereby preventing an increase in intake resistance. In addition, since the gap 12 is narrowed by the extension 33b, the turbulence of the intake air flow is suppressed. In this embodiment, as shown in FIG. 1, the valve body 33 is not a plate having a constant thickness, but has a tapered cross section that gradually becomes thinner toward the distal end in both the main valve portion 33 a and the extension portion 33 b. Since it has a shape, the intake flow smoothly flows, and the intake resistance is further reduced.
[0037]
FIG. 6 shows an analysis of the actual flow of intake air in the intake device of the above embodiment, and shows the speed and direction of the flow of each part by minute vectors, that is, arrows. The density of the arrows indicates the flow rate, and a portion where the arrows are densely gathered means that the flow rate is large. FIG. 7 similarly shows, as a comparative example, the flow of intake air with the gap 12 serving as a communication passage closed. That is, the configuration shown in FIG. 7 corresponds to a conventional technique in which the intake air flow is unevenly distributed between the partition wall 11 and the intake control valve 31. In both cases, the opening ratio of the intake control valve 31 is the same (about 20%).
[0038]
7, which is a comparative example, the intake air flow passing through the upper first flow path 5 A is diffused downward below the downstream end 11 a of the partition 11. Therefore, there is not a small amount of intake air flowing through the valve gap 20a below the intake valve 7. It should be noted that almost no flow is seen in the second flow path 5B below the partition 11, and the second flow path 5B is in a stagnant state. On the other hand, in FIG. 6 showing the basic configuration of the present invention, the intake air recirculates from the lower region near the intake valve 7 through the lower second flow path 5B, and as a result, the lower valve of the intake valve 7 The intake air flow passing through the gap 20a is extremely reduced. In addition, the intake airflow passing through the upper valve gap 20b increases accordingly. Therefore, the tumble can be effectively strengthened.
[0039]
FIG. 8 shows the relationship between the intensity of tumble and the amount of intake air in an intake device using the partition wall 11 and the intake control valve 31 as in FIG. 6 or FIG. Here, the strength of the tumble is represented by the maximum value of the tumble ratio during the intake stroke. Generally, if the tumble is weak, the combustion tends to be slow and unstable, and if the tumble is strong, the combustion is fast and stable. The characteristic shown by the solid line in the figure shows the relationship in the case of the comparative example in FIG. 7, and the smaller the opening ratio, the stronger the tumble, but the smaller the intake air amount, and conversely, the larger the opening ratio. There is a correlation that the larger the intake air amount is, the weaker the tumble is. A decrease in the amount of intake air means that an operation region in which tumble can be generated (that is, an operation region in which the intake control valve 31 can be closed) is narrow. It means that the area is large. According to the present invention using the recirculation through the gap 12, a correlation between the tumble strength and the intake air amount can be obtained in a region indicated by a broken line. In other words, if the tumble strength is the same, a larger intake air amount can be secured, and if the same intake air amount (opening ratio), the tumble can be obtained more strongly.
[0040]
Therefore, as described above, the combined operation of the large amount of exhaust gas recirculation and the strong tumble can be performed in a wider operation range as a fuel efficiency improving means, and the fuel efficiency of the entire internal combustion engine can be significantly improved. Then, when compared in the same operation region, the tumble is generated more strongly, so that a larger amount of exhaust gas recirculation is possible, and further improvement in fuel efficiency is possible.
[0041]
Further, in the above embodiment, by providing the concave groove portion 11A at the center of the partition wall 11, a sufficiently large gap 12 is secured near the center of the intake port 5 as compared with both side portions near the wall surface of the intake port 5. As a result, the above-described reflux action can be more effectively obtained. That is, the generation of the negative pressure downstream of the intake control valve 31 depends on the flow velocity of the intake flow, and this flow velocity becomes higher near the center of the intake port 5 than at a position near the wall surface of the intake port 5. A relatively strong negative pressure is generated near the center of the port 5. Therefore, by securing a sufficiently large gap 12 near the center of the intake port 5, a high flow velocity near the center of the intake port 5 can be effectively used, and the recirculation action can be more effectively obtained. In addition, the intake airflow flowing in the first flow path 5A side with the intake control valve 31 closed is guided and straightened by the concave groove 11A, passes over the large gap 12 created by the concave groove 11A, and becomes more smooth. , The reflux effect is further enhanced.
[0042]
Further, in order to sufficiently obtain the above-mentioned reflux effect, the size of the gap 12 (flow area) is necessary, but the position of the upstream end 11b of the partition 11 and the downstream end of the valve body 33 are required. If the position of 33c is the same, the flow channel area of the gap 12 at the closed position of the intake control valve 31 increases by forming the concave groove portion 11A. In other words, when trying to ensure the same flow passage area, it is possible to arrange the position of the intake control valve 31 relatively on the downstream side. In the case where the intake control valve 31 is short, an increase in intake resistance at the open position of the intake control valve 31 can be suppressed.
[0043]
Further, the presence of the concave groove 11A makes it possible to extend the partition 11 further downstream while avoiding interference between the fuel spray F and the partition 11 as described above. Therefore, it is more advantageous in strengthening the tumble.
[0044]
When the valve body 33 of the intake control valve 31 is substantially perpendicular to the partition 11 as illustrated in FIG. 6, the central portion (the concave groove portion 11A) and both side portions (the flange portion 11B) of the partition 11 are Although the width of the gap 12 is constant, even in such a case, the flow path area between the partition 11 and the upstream end 11b is larger than that of the case where the upstream end 11b is linear (that is, the groove 11A is not provided). If the inclination angle θ of the valve body 33 is smaller than 90 ° as shown in FIG. 1, the gap 12 at the center of the partition 11 becomes relatively large.
[0045]
9 to 12 show a second embodiment of the present invention. In this embodiment, a pair of concave grooves 11A are formed in the center of the partition wall 11 in parallel, and land portions 11C located on the same plane as the flange portions 11B on both sides are provided between the two. The pair of concave grooves 11A have the same cross-sectional shape, and are formed to have a constant cross-sectional shape from the upstream end 11b to the downstream end 11a of the partition wall 11. Specifically, as shown in FIG. 11, the ellipse is depressed to have a sectional shape as if it were bisected along the long axis. In particular, in this embodiment, as shown in FIG. 11, a part of the pair of sprays F injected from the fuel injection valve 41 is located at the downstream end 11 a of the partition wall 11 at the area inside each groove 11 A. The position and size of each groove 11A are set so as to pass through.
[0046]
Also in this embodiment, the formation of the concave groove portion 11A secures a sufficiently large gap 12 as shown in FIG. 12 and can make the length of the partition wall 11 longer, so that the same operation as in the first embodiment described above. The effect can be obtained. In particular, as apparent from FIG. 9, the pair of intake air flows rectified and guided by the pair of concave grooves 11 A linearly flow toward the respective intake valves 7. There is an advantage that the flow colliding with the central wall portion 15 in the intake port 5 located between the valves 7 is reduced.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a first embodiment of an intake device according to the present invention.
FIG. 2 is a plan view of the intake device of the first embodiment as viewed from above.
FIG. 3 is a sectional view of a main part taken along line α-α in FIG. 1;
FIG. 4 is a view as seen from an arrow β direction in FIG. 1;
FIG. 5 is a configuration explanatory view schematically showing the configuration of the first embodiment.
FIG. 6 is an explanatory diagram showing a flow of intake air in the intake device.
FIG. 7 is an explanatory diagram showing a flow of intake air in an intake device of a comparative example.
FIG. 8 is a characteristic diagram showing a relationship between tumble strength and intake air amount.
FIG. 9 is a sectional view showing a second embodiment of the intake device according to the present invention.
FIG. 10 is a plan view of the intake device of the second embodiment as viewed from above.
11 is a cross-sectional view of a main part along the line α-α in FIG. 9;
FIG. 12 is a view as viewed in the direction of the arrow β in FIG. 9;
[Explanation of symbols]
3 ... Cylinder head 5 ... Intake port 7 ... Intake valve 11 ... Partition wall 11A ... Concave groove 12 ... Gap 21 ... Intake manifold 31 ... Intake control valve

Claims

In an intake device of an internal combustion engine, an intake port is connected to a cylinder of the internal combustion engine, and an intake valve opens and closes a downstream end of the intake port.
A partition wall provided along the longitudinal direction of the intake port so as to partition the intake port into two regions in its cross section;
An intake control valve comprising a rotatable plate-shaped valve element located close to the upstream end of the partition, and opening and closing one of the flow paths defined by the partition,
With
A central groove portion in the width direction of the partition wall extends along the longitudinal direction of the intake port, and has a concave groove portion that is concave on the side of the one flow path,
In the closed position in which the intake control valve blocks one flow path, a gap having a shape along the edge of the concave groove portion is formed between the upstream end of the partition and the valve body. Of the internal combustion engine.

The rotation axis of the intake control valve is located on an extension line extending both sides in the width direction of the partition to the downstream side, and in the open position, the valve body is linearly continuous with the both sides of the partition. The intake device for an internal combustion engine according to claim 1, wherein:

3. The intake system according to claim 1, wherein when the intake control valve is in the closed position, the valve body is inclined in a direction to guide the intake air flow to the other flow path. apparatus.

4. The valve according to claim 1, wherein when the intake control valve is in the closed position, a part of the valve body projects toward the other flow path from an extension of the both sides of the partition. An intake device for an internal combustion engine according to any one of the above.

The valve body has a main valve portion extending from the rotation axis to one side so as to block one flow path at the closed position, and has an extension portion extending from the rotation axis to the opposite side to the main valve portion. 5. The internal combustion engine according to claim 4, wherein, in the closed position, the extension protrudes toward the other flow path, and in the open position, the extension portion is close to the upstream end of the partition so as to narrow the gap. Engine intake device.

The intake device for an internal combustion engine according to any one of claims 1 to 5, wherein the concave groove portion is formed to have a constant cross-sectional shape from an upstream end to a downstream end of the partition.

The intake device for an internal combustion engine according to any one of claims 1 to 6, wherein a plurality of the concave grooves are formed.

8. The air conditioner according to claim 1, wherein the partition wall is provided so as to partition an intake port up and down with reference to a vertical direction of the cylinder, and a lower flow path is blocked by the intake control valve. An intake device for an internal combustion engine according to any one of the above.

A fuel injection valve for injecting fuel toward the intake valve is disposed above the partition, and the concave groove portion is formed at a downstream end of the partition so as to avoid interference between the partition and fuel spray. The intake device for an internal combustion engine according to any one of claims 1 to 8, wherein:

The intake device for an internal combustion engine according to claim 9, wherein a fuel spray passes through a region inside the concave groove at a downstream end of the partition.

Each cylinder is provided with a pair of intake valves, the fuel injection valve is configured to form a pair of sprays toward each intake valve, and interference between the partition and each fuel spray at the downstream end of the partition. 11. The intake device for an internal combustion engine according to claim 9, wherein a pair of concave grooves are formed so as to be avoided.