1316985 (1) 九、發明說明 【發明所屬之技術領域】 本發明是關於’具備有：用來感測內燃機狀態的感測 器、及包圍內燃機主體而形成冷卻風的通風路的護罩之氣 冷式內燃機，該內燃機例如搭載於車輛。 【先前技術】 g 習知的氣冷式內燃機，是具備有：用來感測作爲內燃 機狀態的內燃機溫度的感測器、及包圍內燃機主體而形成 冷卻風的通風路的護罩（例如參照專利文獻1 )。而又習 知有內燃機’是具備有：用來感測作爲內燃機的狀態的排 出氣體的性質的排出氣體感測器（例如參照專利文獻 2 ) ° 〔專利文獻1〕 • 日本特開2004 — 11436號公報 〔專利文獻2〕 曰本特開2004 - 3 1 6430號公報 【發明內容】 〔發明欲解決的課題〕 當將用來感測內燃機狀態的感測器，安裝於構成內燃 機主體的氣缸、氣缸頭、或氣缸頭罩蓋時，感測器其露出 於內燃機外部的部分、或在該露出部分連接於感測器的電 -4- (2) 1316985 線，例如內燃機爲車輛用的情況，是藉由車體外殼所覆 蓋，保護其免於受到異物（例如在車輛行駛中彈起的小石 頭）的衝撞。而爲了防止因爲來自於內燃機的熱而讓感測 器或電線過熱，需要將其適度地冷卻，所以往往會限制感 測器及電線的配置方式，或相反地來限制在感測器或電線 附近所配置的周邊構件的配置方式。 本發明鑒於這種情形，第1〜3發明，其目的要提供 φ 一種氣冷式內燃機，藉由簡單的構造，能確保感測器及連 接於該感測器的電線的保護機能及冷卻性，並且感測器的 配置自由度很大。第2、4發明，其目的要使在感測器所 連接的電線的冷卻性更提昇，且更提昇感測器的感測精 度，第3發明，其目的爲，除了要將排出氣體感測器及排 出氣體淨化用空氣的空氣通路配置成緊緻化，且使排出氣 體感測器的冷卻性及排出氣體淨化用空氣所達到的排出氣 體淨化性能更提昇。 〔用以解決課題的手段〕 ‘第1發明，是具備有：安裝於內燃機主體而用來感測 * 內燃機狀態的感測器、及藉由覆蓋上述內燃機主體，包圍 上述內燃機主體而形成冷卻風的通風路的護罩之氣冷式內 燃機，上述感測器、及連接於上述感測器的電線，是配置 於上述通風路。 藉此，感測器及電線是配置於護罩內，所以能保護其 免於異物的衝撞或接觸等。而與，藉由在護罩45的外部 -5- (3) 1316985 配置感測I器’而在該感測器與該感測器附近的周邊零件之 間會產生配置限制的技術並不相同，相反地不會限制該構 件的配置。而在通風路內所配置的感測器及電線，在護罩 內會被冷卻I ®所冷卻，所以能防止因爲來自於內燃機的熱 而導致過熱情形。 第2發明’是針對第1發明的氣冷式內燃機，具備 有：被上述護罩所覆蓋，且將冷卻風送到上述通風路的冷 卻風扇’上述電線是配置在較上述內燃機主體更靠近冷卻 風的上流側處。 藉此’在以冷卻風扇所造成的冷卻風來強制氣冷的內 燃機，是藉由冷卻內燃機主體之前的冷卻風，來有效地冷 卻電線’所以能防止：因爲來自於內燃機的熱導致電線溫 度上昇而引起的電阻變化情形。 第3發明’是針對第1或2發明的氣冷式內燃機，在 構成上述內燃機主體的氣缸頭，設置有排氣口，上述感測 器，是安裝於上述氣缸頭，在排氣口用來感測作爲上述內 燃機狀態的排出氣體的性質的排出氣體感測器，上述排出 氣體感測器，是安裝在較上述排氣口更靠近冷卻風的上流 的位置，在較上述排氣口更靠近冷卻風的下流的位置處， 設置有：用來將排出氣體淨化用空氣導引到上述排氣口的 空氣通路。 藉此，則能將排出氣體感測器及空氣通路接近配置於 排氣口。並且，排出氣體感應器，會藉由在被排氣口的排 出氣體所加熱之前的冷卻風，而有效地加以冷卻，針對流 -6- (4) (4)1316985 通於空氣通路的排出氣體淨化用空氣，藉由將其形成該空 氣通路的部分暴露於，將排氣口附近的氣缸頭冷卻之後的 藉由排出氣體所加熱的冷卻風，則能抑制或防止其溫度降 低，所以能促進排出氣體中的未燃成分與排出氣體淨化用 空氣的反應。 第4發明，是針對第1或2發明的氣冷式內燃機，上 述感測器，是用來感測作爲上述內燃機狀態的排出氣體的 性質的排出氣體感測器、與用來感測作爲上述內燃機狀態 的內燃機溫度的溫度感測器；上述排出氣體感測器及上述 溫度感測器，是安裝成：相對於位於上述內燃機主體的內 部的感測部，讓其與上述電線的連接部，是位於，在曲軸 的軸端部所設置的上述冷卻風扇附近。 藉此，在排出氣體感測部及溫度感測部，其個別的連 接部是位於更接近於冷卻風扇的位置，所以連接於各感測 器的電線會被更低溫的冷卻風所冷卻，而能防止：因爲電 線的溫度上昇所導致的電阻的變化。 〔發明效果〕 藉由第1發明，能達到如下的效果。也就是說’在氣 冷式內燃機，藉由利用護罩，利用簡單的構造’則能確 保：感測器及連接於該感測器的電線的保護機能及冷卻 性，並且能增加感測器及電線的配置的自由度。 藉由第2發明，除了所引用的發明的效果之外’還可 達到如下的效果。也就是說，藉由使連接於感測器的電線 -7- (5) 1316985 的冷卻性更增加，能抑制電阻的變化，而提昇了感測器的 感測精度。 藉由第3發明，除了所引用的發明的效果之外，還可 達到如下的效果。也就是說，除了能將排出氣體感測器及 排出氣體淨化用空氣的空氣通路配置成緊緻化之外，還能 提昇排出氣體感測器的冷卻性，並且使排出氣體淨化用空 氣所達到的排出氣體淨化性能提昇。 藉由第4發明，除了所引用的發明的效果之外，還可 達到如下的效果。也就是說，藉由使連接於感測器的電線 的冷卻性更提昇，能抑制電阻的變化，所以提昇了各感測 器的感測精度。 【實施方式】 以下參照第1圖〜第6圖來說明本發明的實施方式。 參照第1圖、第2圖，適用本發明的氣冷式內燃機 E’是具備有V型皮帶式自動變速機Μ的動力傳達裝置， 並且搭載於作爲車輛的機車。 是以讓曲軸7的旋轉中心線L 1朝向左右方向橫向配 置的方式’被支承於車體的內燃機Ε，是單氣缸四行程內 燃機’是具備有內燃機主體，該內燃機主體是由：氣缸 1、在氣缸軸線L2的方向（以下稱作「氣缸軸線方向」） 與氣缸1的曲軸7側結合的曲軸箱2、在氣缸軸線方向與 氣缸1的反曲軸7側所結合的氣缸頭3、及結合於氣缸頭 3的氣缸頭罩蓋4所構成。氣缸1、曲軸箱2、氣缸頭3、 -8 - (6) (6)1316985 及氣缸頭罩蓋4，是藉由作爲熱的良好導體的材料的金 屬，例如藉由鋁合金所形成。 在該實施方式’其上下、前後、及左右，是代表：分 別以當將具備有內燃機E的機器的機車作爲基準時的上 下、前後、及左右，軸方向，是代表與曲軸7的旋轉中心 線平行的方向。當將左方及右方的其中一方當作在軸方向 的其中一方時，左方及右方的另一方，就是軸方向的另— 方。 氣缸1，是以讓氣缸軸線L2朝向前方而朝稍斜上 方，相對於水平面朝稍斜上方傾斜的狀態，被配置於車 體。在氣缸1的氣缸孔la可往復運動地嵌合著活塞5，經 由連桿6而連結著該活塞5的曲軸7，是經由由滾珠軸承 所構成的一對主軸承8，而可旋轉地被支承於曲軸箱2。 形成了用來收容曲軸7的曲軸室9，而左右對切的曲軸箱 2，是由：左箱體半體2a、與右箱體半體2b所構成。 氣缸頭3，是藉由在氣缸1及氣缸頭3所設置的插穿 孔1〇(參照第4圖、第6圖）上所插穿的複數的，這裡是 四個氣缸蓋螺栓11 (參照第6圖），而與氣缸1 一起鎖裝 於曲軸箱2。 在氣缸頭3，形成有：在氣缸軸線方向與活塞5相對 向的燃燒室1 2、及於燃燒室1 2所開口的進氣口 1 3及排氣 口 14;火星塞15是安裝成面對於燃燒室12。在氣缸頭3 所設置的進氣閥I6及排氣閥17，是藉由閥門裝置20所開 閉驅動’該閥門裝置20’具備有：藉由經由閥門用傳動機 -9 - (7) 1316985 構18所傳達的曲軸7的動力所旋轉驅動的凸輪軸22 ;而 與曲軸7的旋轉同步，分別將進氣口 13及排氣口 14進行 開閉。 在藉由氣缸頭3及氣缸頭罩蓋4所形成的閥門室21 所收容的閥門裝置20，是具備有：經由軸承可旋轉地被支 承於氣缸頭3的凸輪軸22、以及藉由設置於凸輪軸22的 進氣凸輪2 2 a及排氣凸輪2 2 b所分別驅動，分別以搖臂軸 23、24爲中心而擺動的進氣搖臂25及排氣搖臂26。傳動 機構18，是由：在貫穿左邊的主軸承8而突出到曲軸室9 的左方的曲軸7的左邊的軸端部7 a所設置的驅動鏈輪 l8a、在凸輪軸22的軸端部所設置的從動鏈輪18b、及繞 掛於兩鏈輪18a、18b的作爲循環式傳動帶的循環式的鏈 條l8c所構成。兩鏈輪l8a、Wb及鏈條18c，是被收容 於：藉由氣缸1、氣缸頭3、氣缸頭罩蓋4、及左箱體半體 2a所形成，並且與閥門室21及曲軸室9連通的作爲傳動 室的鏈條室2 7。 在軸方向（也是左右方向）隔著鏈條室27而在曲軸 室9的左方，形成了：收容著變速機Μ的變速室33，該 變速機Μ，具備有：繞掛著V型皮帶30且藉由離心配重 3la因應於內燃機轉速來變更繞掛半徑的驅動皮帶輪31及 從動皮帶輪（沒有圖示）。形成變速室33的變速箱32 ’ 是由：以左箱體半體2a所構成的箱體主體32a、以及用多 數的螺栓結合於箱體主體32a的左側的外殼321)所構成。 貧穿左箱體半體2a而朝左方突出的軸端部7a’構成了驅 -10- (8) 1316985 動皮帶輪3 1的驅動軸。 內燃機E的進氣裝置，是具備有進氣管35，該進氣 管35是將節氣門體（沒有圖示）與氣缸頭3的進氣口 13 側予以連接’ ^節氣門體’是設置有：用來將來自於空氣 濾清器的吸入空氣的流量予以控制的節流閥。在進氣管 35，是安裝有作爲混合氣形成手段的燃料噴射閥36，該燃 料噴射閥36 ’是將燃料供給到，流通於上述進氣裝置的進 φ 氣通路的吸入空氣來形成混合氣。 從燃料噴射閥3 6朝向進氣口 1 3所噴射的燃料，成爲 混合氣’而當進氣閥16開閥時會經過進氣口 13流入到燃 燒室12’在燃燒室12藉由火星塞15點火而燃燒。而藉由 所產生的燃燒氣體的壓力所驅動而進行往復運動的活塞 5，會經由連桿6將曲軸7旋轉驅動。燃燒氣體，會成爲 排出氣體，當排氣閥1 7開閥時，經過排氣口 14，通過具 備排氣管3 7的排氣裝置，而排出到內燃機E的外部。 % 而曲軸7的動力，在變速機Μ因應於內燃機轉速而自 動變速之後，最後經由減速機構，傳達到作爲驅動輪的後 輪，而將該後輪旋轉驅動。 •參照第1圖、第3圖，在曲軸室9的右方，形成有風 扇室41，該風扇室41收容有：交流發電機39、及吸引外 空氣來產生將上述內燃機主體強制氣冷的冷卻風的冷卻風 扇4〇。風扇室41是藉由：右箱體半體2b、與從右方覆蓋 冷卻風扇40的風扇外殻42所形成。藉由曲軸7所驅動的 交流發電機39及冷卻風扇40，是安裝於：貫穿右箱體半 -11 - (9) 1316985 體2b朝右方突出而在風扇室41內延伸的曲軸7的右邊的 軸端部7b。 參照第1圖、第3圖，在內燃機E所具備而藉由複數 的螺栓43結合於右箱體半體2b的合成樹脂製的風扇外殼 42，具有：在風扇室41形成有讓外空氣流入的吸入口 41a 的圓筒狀的空氣吸入部42a。在空氣吸入部42a的內側配 置有：將所吸引的空氣整流成讓其朝軸方向流動的百葉板 42b。藉由冷卻風扇40所加壓輸送的空氣，是在冷卻風扇 40的直徑方向外側，且在氣缸軸線方向，從開口於氣缸1 側的送風口 41 b，作爲冷卻風，被輸送到後述的通風路 4 6° 合倂參照第2圖、第4圖，具備於內燃機E的護罩 45，藉由將構成上述內燃機主體的氣缸1及氣缸頭3的全 體予以覆蓋，來包圍氣缸1及氣缸頭3，來形成冷卻風的 通風路46。更具體來說，護罩45，是在氣缸軸線L2周 圍，涵蓋整個周圍將氣缸1及氣缸頭3予以覆蓋，且在氣 缸軸線涵蓋氣缸1及氣缸頭3的全長將其覆蓋。在氣缸1 及氣缸頭3的外面部，分別設置有：用來提高冷卻風所造 成的對於氣缸1及氣缸頭3的冷卻效果的多數的冷卻葉片 If、3f ° 合成樹脂製的護罩45，是由··藉由與氣缸軸線L2大 致平行的分割面而被分割爲兩個的作爲第一護罩部分的上 側護罩部分45a、及作爲第二護罩部分的下側護罩部分 45b所構成。而藉由具有爪部47的卡止構造及螺栓48， -12- (10) 1316985 將兩護罩部分45a、45b互相結合，各護罩部分45a、45b 是藉由螺栓49而結合在風扇外殼42，下護罩部分4 5b是 藉由螺栓50而結合在左箱體半體2a，並且有供氣缸頭罩 蓋4從護罩45朝前方突出的開口部51，藉由讓用來限定 開口部51的各護罩部分45a、45b的緣部45al、45bl嵌 合於氣缸頭3的鍔部3a，來將護罩45安裝於上述內燃機 主體。 在護罩45，除了在其前面部涵蓋兩護罩部分45a、 4 5b所設置的開口部51之外，在其右面部具有：涵蓋兩護 罩部分45a、45b所設置，插穿著在火星塞15所安裝的火 星塞蓋19的開口部52;在其上面部具有：設置於上護罩 部分45a，插穿著進氣管35的開口部53 ;在其下面部具 有：設置於下護罩部分45b，插穿著排氣管37及後述的通 路形成部83的開口部54 ;在左面部具有：設置於下護罩 部分45b，朝向右方開放的排風口 55。 來自於冷卻風扇40的冷卻風，是在冷卻風扇40的直 徑方向外側，且具有冷卻風扇4 0的旋轉方向的成分，從 風扇室41的送風口 41b流入到通風路46(在第3圖，是 以虛線的箭頭來顯示冷卻風的大致的流動情形。），在通 風路46內流動於氣缸1及氣缸頭3的周圍來將其冷卻， 然後，從排風口 55排出到護罩45的外部。冷卻風，是朝 向排氣管38而從排風口 55流出，來冷卻排氣管38。 參照第1圖，在軸端部7b，設置有：在右邊的主軸承 8與交流發電機3 9之間用來將構成內燃機e的潤滑系統 -13- (11) 1316985 的油泵浦（沒有圖示）予以驅動的驅動齒輪60。該油泵 浦，經由以包含驅動齒輪60的齒輪組所構成的傳動機 構，藉由所傳達的曲軸7的動力所驅動，從藉由曲軸箱2 的底部所構成的儲油部所汲起的潤滑油，通過多數的油 路，供給到：以曲軸7及閥門裝置20爲主的內燃機E的 潤滑部位。 參照第2圖、第4圖〜第6圖，在設置於氣缸頭3的 閥門裝置20，是將從上述油泵浦所排出的潤滑油，流通於 利用插穿孔1 〇a所形成的油路61，將油路61的一部分的 潤滑油導引到’在氣缸頭罩蓋4所形成的油路62 (參照第 2圖），從油路62的噴口 62a噴出到閥門室21內，並且 油路61的剩餘的潤滑油，是從搖臂軸23內的油路63 (參 照第2圖）通過其與進氣搖臂25的滑動部而噴出到閥門 室21內，供給到閥門裝置2 0等的閥門室21內的潤滑部 位。而將該潤滑部位潤滑之後的潤滑油，會於從閥門室2 1 貫穿氣缸頭3的下側周壁部3b及氣缸1的下側周壁部lb 而由開放於曲軸室9的貫穿孔所構成的回流油路64 (也參 照第4圖）流下，流入到曲軸室9，回到上述儲油部。 參照第1圖〜第6圖’內燃機E，具備有：作爲用來 感測內燃機狀態的感測器，安裝於氣缸頭3，在排氣口 1 4 來感測出排出氣體的性質的排出氣體感測器、例如用來感 測出排出氣體中的氧氣濃度的氧氣濃度感測器70、以及作 爲用來感測出作爲內燃機狀態的內燃機溫度的溫度感測 器，用來感測出潤滑油的溫度的油溫感測器7 5。 -14 - (12) 1316985 氧氣濃度感測器7〇，在氣缸頭3安裝於排氣口 14的 出口 14a附近的下側周壁部3b。大致柱狀且配置成大致平 行於軸方向的氧氣濃度感測器7〇，是具有：螺合入氣缸頭 3來安裝的由螺紋部所構成的安裝部70a、位於氣缸頭3 的內部而面對於排氣口 14內的感測部7〇b、以及連接著用 來將感測訊號傳達到控制裝置的電線7 1的連接部70c。連 接著在電線7 1的前端所設置的作爲連接部的耦合器72的 連接部70c，在以護罩45所覆蓋的狀態，從氣缸1露出而 配置於通風路46。 油溫感應器75，是安裝於：排氣口 14的出口 14a開 口側的氣缸1的下側周壁部1 b。大致柱狀且配置成與軸方 向大致平行的油溫感測器7 5，是具有：螺合入氣缸頭3來 安裝的由螺紋部所構成的安裝部75 a、位於氣缸1的內部 而面對於回流油路64的感測部75b、以及連接著用來將感 測訊號傳達到上述控制裝置的電線76的連接部75c。連接 著在電線76的前端所設置的作爲連接部的耦合器77的連 接部75c，在以護罩45所覆蓋的狀態’從氣缸1露出而配 置於通風路46。 油溫感測器75是配置成：在軸方向從感測部75b朝 向與鏈條室27相反側延伸，並且從與平面H(參照第6 圖）垂直相交的方向來觀察，油溫感測器75的全體與氣 缸1重疊（參照第1圖）。因此，油溫感測器75在軸方 向不會從氣缸1朝軸方向突出，而相對於氣缸1配置成緊 緻化。這裡所謂的平面H，是包含氣缸軸線L2，並且與旋 -15- (13) 1316985 轉中心線L1平行，或包含旋轉中心線L1的平面。 在各感測器70、75，連接部70c、75c，是位於：相 對於感測部7 Ob、7 5b在軸方向在軸端部7b所設置的冷卻 風扇40附近。因此，連接部70c、75c，在各感測器70、 75是位於冷卻風的上流處。 氧氣濃度感測器70及油溫感測器75，在相對於平面 Η而排氣口 14的出口 14a開口側的上述內燃機主體的部 分，在該實施方式是在分別形成於氣缸頭3及氣缸1的下 面部的下側周壁部3b、lb，配置成互相大致平行地並排於 氣缸軸線方向（參照第1圖）。而兩感測器70、75，是位 於從氣缸軸線方向觀察重疊的位置（參照第6圖）。 各電線71、76，是從連接部70c、75c橫越通風路46 而朝接近冷卻風扇40的方向朝軸方向延伸，貫穿於在兩 護罩部分45a、45b的缺口部所嵌合保持的絕緣環79而朝 護罩45的外部延伸，連接於上述控制裝置。而各電線 71、76，是配置在：較氣缸1及氣缸頭3更靠近冷卻風的 上流側處。因此，各電線71、76，是暴露於在到達氣缸1 及氣缸頭3之前的冷卻風。 而以氧氣濃度感測器70所感測的感測値，是爲了將 上述排氣裝置所具備的觸媒裝置所達到的排出氣體的淨化 性能予以提高，而使用於燃料噴射閥3 6的燃料量的控制 中，而以油溫感測器7 5所感測的感測値’是使用於，供 因應於內燃機E的暖機狀態的燃料噴射閥3 6的燃料量的 控制、或暖機時的怠速轉速控制所用的怠速空氣量的控 -16- (14) 1316985 制。 參照第3圖、第4圖’在內燃機e，具備有：用來使 排出氣體中的未燃成分（HC、C0)燃燒來淨化排出氣 體’而將排出氣體淨化用空氣供給到排出氣體中的排氣系 統二次空氣供給裝置。該二次空氣供給裝置，是具備有： 用來將供給到排出氣體的空氣量予以控制的控制閥8 1、以 及將該控制閥8 1與氣缸頭3予以連接，將以控制閥8 1所 控制的排出氣體淨化用空氣導引到排氣口 14的空氣供給 管8 2。控制閥8 1，例如當處於沒有根據氧氣濃度感測器 7 0的感測値來進行燃料量的控制的運轉狀態時，將排出氣 體淨化用空氣供給到排出氣體中。而空氣供給管82，是 由：與控制閥81連接且由橡膠軟管所構成的上流側供給 管82a、及沿著護罩45來配管的金屬製的下流側供給管 82b所構成。下流側供給管82b，是從氣缸頭3的外面部 突出而橫越通風路46，連接到：從護罩45的開口部54延 伸到護覃45的外部而由突出部所構成的通路形成部83。 在與氣缸頭3 —體形成的通路形成部83，設置有：於排氣 口 14所開口的空氣通路84，流通於空氣供給管82的排出 氣體淨化用空氣’會流通於空氣通路8 4而供給到排氣口 14。 通路形成部83，是以讓空氣通路84位於較排氣口 14 在通風路46更靠近冷卻風的下流側處的方式’設置在較 排氣口 1 4及排氣管3 8更靠近冷卻風的下流側的位置。 接著，針對如上述所構成的實施方式的作用及效果來 -17- (15) 1316985 加以說明。 藉由將在氣缸頭3所安裝的氧氣濃度感測器7 〇及在 氣缸1所安裝的油溫感測器7 5所分別連接著的電線7 1、 76’配置在通風路46’由於各感測器70、75及各電線 71、76是配置在護罩45內’所以能保護其免於受到異物 例如在行駛中彈起的小石頭等的衝撞或接觸。與在護罩45 的外部配置感測器而在該感測器與該感測器附近的周邊零 件之間產生配置的限制的技術不相同，不會因爲在護罩4 5 的外部所配置的構件，而限制了感測器70、75及電線 71、76的配置，相反地，感測器70、75或電線71、76也 不會限制該構件的配置。而由於在通風路46所配置的感 測器70、75及電線71、76，是在護罩45內藉由冷卻風所 冷卻，所以能防止因爲來自於內燃機E的熱讓其過熱。結 果，在內燃機E，藉由利用護罩45，利用簡單的構造，則 能確保各感測器70、75及連接於該感測器70、75的電線 71、76的保護機能及冷卻性，並且能增大感測器70、75 及電線71、7 6的配置的自由度。 藉由具備有：被護罩45所覆蓋且用來將冷卻風輸送 到通風路46的冷卻風扇40’且將各電線71、76配置在較 氣缸1及氣缸頭3更靠近冷卻風的上流側處，在以冷卻風 扇40所造成的冷卻風進行強制氣冷的內燃機E’藉由將 氣缸1及氣缸頭3予以冷卻之前的冷卻風’能有效地冷卻 電線71、7 6，所以能抑制’因爲來自於內燃機E的熱造 成電線7 1、7 6的溫度上昇而導致電阻變化的情形。而氧 -18- (16) 1316985 氣濃度感測器70及油溫感測器75，是安裝成：相對於位 於氣缸頭3及氣缸1的內部的感測部7 Ob、7 5b，讓連接部 70c、7 5c，位於，在曲軸7的軸端部7b所設置的冷卻風 扇40附近；在氧氣濃度感測器70及油溫感測器75，其個 別的連接部70c、75c是位於更接近於冷卻風扇40的位 置，所以連接於各感測器70、75的電線71、76會被更低 溫的冷卻風所冷卻，而能防止：因爲電線的溫度上昇所導 致的電阻的變化。結果，能將連接於感測器70、75的電 線7 1、76的冷卻性更提昇，能抑制電阻的變化，所以能 提昇感測器70、75的感測精度。 氧氣濃度感測器70，是安裝在：較排氣口 14更靠近 冷卻風的上流的位置，藉由在較排氣口 14更靠冷卻風的 下流的位置，設置：用來將排出氣體淨化用空氣導引到排 氣口 14的空氣通路84，則能將氧氣濃度感測器70及空氣 通路84接近配置於排氣口 14。並且，氧氣濃度感測器 7 0，會藉由以排氣口 1 4的排出氣體所加熱之前的冷卻風 而有效地加以冷卻，針對流通於空氣通路84的排出氣體 淨化用空氣，是藉由將形成空氣通路84的通路形成部S3 暴露於，將排氣口 1 4附近的氣缸頭3冷卻之後的藉由排 出氣體所加熱的冷卻風’能抑制或防止其溫度降低的情 形，而能促進排出氣體中的未燃成分與排出氣體淨化用空 氣的反應。結果’除了能將氧氣濃度感測器7〇及排出氣 體淨化用空氣的空氣通路84配置成緊緻化之外’還能提 昇氧氣濃度感測器7〇的冷卻性，並且提昇排出氣體淨化 -19- (17) 1316985 用空氣的排出氣體淨化性。 以下，針對變更上述實施方式的一部分的構造的實施 方式，來說明關於變更的構造。 排出氣體感測器，也可以是用來感測排出氣體中的空 燃比的LAF感測器、或用來感測未燃成分的感測器。 內燃機溫度，也可以是上述內燃機主體的溫度或燃燒 溫度，而在並用水冷方式的內燃機，也可以是冷卻水的溫 度。 通路形成部8 3，也可以用與氣缸頭3不同個體的構件 所構成，在這種情況，通路形成部8 3，與鋁合金等的輕合 金製的氣缸頭3同樣地，以金屬製等的熱的良導體材料所 形成。 內燃機，也可以將氣缸與氣缸頭一體成型，也可以是 多氣缸式的內燃機。 【圖式簡單說明】 第1圖是適用本發明的氣冷式內燃機的第2圖的大致 1〜I線剖面圖。 第2圖是第1圖的11 一 11線剖面圖。 第3圖是第1圖的氣冷式內燃機的主要部分右側面 圖。 第4圖是在第1圖的內燃機’將下護罩部分卸下時的 主要部分立體圖。 第5圖是從第3圖的V箭頭方向觀察的氣缸及氣缸頭 -20- (18) (18)1316985 的主要部分的圖面。 第6圖是第5圖的Via — Via線的剖面圖，一部分是 第5圖的VIb — VIb線剖面圖。 【主要元件符號說明】 1 :氣缸 3 :氣缸頭 7 :曲軸 20 :閥門裝置 4 0 :冷卻風扇 45 :護罩 4 6 :通風路 64 :回流油路 70 :氧氣濃度感測器 71、7 6 :電線 75 :油溫感測器 82 :空氣供給管 E :氣冷式內燃機 -21 -1316985 (1) EMBODIMENT OF THE INVENTION [Technical Field of the Invention] The present invention relates to a hood having a sensor for sensing the state of an internal combustion engine and a ventilating path for forming a cooling air surrounding the main body of the internal combustion engine. A cold internal combustion engine that is mounted, for example, on a vehicle. [Prior Art] The conventional air-cooled internal combustion engine is provided with a sensor for sensing the temperature of the internal combustion engine as the state of the internal combustion engine, and a shroud for ventilating the cooling air to surround the main body of the internal combustion engine (for example, refer to the patent) Literature 1). Further, an internal combustion engine is provided with an exhaust gas sensor for sensing the property of the exhaust gas as a state of the internal combustion engine (for example, refer to Patent Document 2) ° [Patent Document 1] • Japanese Patent Laid-Open No. 2004-11436 [Patent Document 2] Japanese Unexamined Patent Application Publication No. JP-A No. 2004-351 a cylinder head or a cylinder head cover, wherein the sensor is exposed to a portion outside the internal combustion engine, or an electric -4-(2) 1316985 line connected to the sensor at the exposed portion, for example, when the internal combustion engine is used for a vehicle, It is covered by the outer casing of the car body to protect it from the collision of foreign objects (such as small stones that bounce off during the running of the vehicle). In order to prevent the sensor or the wire from overheating due to the heat from the internal combustion engine, it needs to be moderately cooled, so the sensor and the wire are often limited in configuration, or conversely, in the vicinity of the sensor or the wire. The configuration of the configured peripheral components. The present invention has been made in view of such circumstances, and it is an object of the first to third inventions to provide an air-cooled internal combustion engine which can ensure the protection function and the cooling performance of the sensor and the electric wires connected to the sensor by a simple structure. And the degree of freedom of configuration of the sensor is large. According to the second and fourth inventions, the object of the invention is to improve the cooling performance of the electric wire connected to the sensor and to improve the sensing accuracy of the sensor, and the third invention has an object of sensing the exhaust gas. The air passage of the air for exhausting the gas and the exhaust gas is arranged to be compacted, and the cooling performance of the exhaust gas sensor and the exhaust gas purification performance by the exhaust gas purifying air are further improved. [Means for Solving the Problem] The first invention includes a sensor attached to the main body of the internal combustion engine for sensing the state of the internal combustion engine, and a cooling air that surrounds the main body of the internal combustion engine by covering the main body of the internal combustion engine The air-cooled internal combustion engine of the shroud of the air passage is configured such that the sensor and the electric wire connected to the sensor are disposed in the air passage. Thereby, the sensor and the electric wire are disposed in the shroud, so that it can be protected from collision or contact of foreign matter. And, by configuring the sensing device 'on the outside of the shield 45-5-(3) 1316985, the technique for creating configuration restrictions between the sensor and the peripheral parts near the sensor is not the same. Conversely, the configuration of the component is not limited. The sensors and wires disposed in the air duct are cooled by the cooling I ® in the shroud, so that overheating due to heat from the internal combustion engine can be prevented. According to a second aspect of the present invention, in the air-cooled internal combustion engine of the first aspect of the present invention, the cooling fan that is covered by the shroud and that sends cooling air to the air passage is provided. The electric wire is disposed closer to the main body than the internal combustion engine. The upper side of the wind. Therefore, the internal combustion engine that is forced to air-cool by the cooling air caused by the cooling fan is to effectively cool the electric wire by cooling the cooling air before the main body of the internal combustion engine, so that it can prevent: the temperature of the electric wire rises due to heat from the internal combustion engine. The resulting change in resistance. According to a third aspect of the invention, in the air-cooled internal combustion engine according to the first or second aspect of the invention, the cylinder head constituting the main body of the internal combustion engine is provided with an exhaust port, and the sensor is attached to the cylinder head, and is used at the exhaust port. An exhaust gas sensor that senses a property of the exhaust gas in the state of the internal combustion engine, wherein the exhaust gas sensor is installed at an upstream position closer to the cooling air than the exhaust port, and is closer to the exhaust port than the exhaust port At a position downstream of the cooling air, an air passage for guiding the exhaust gas purifying air to the exhaust port is provided. Thereby, the exhaust gas sensor and the air passage can be arranged close to the exhaust port. Moreover, the exhaust gas sensor is effectively cooled by the cooling air before being heated by the exhaust gas of the exhaust port, and the exhaust gas passing through the air passage for the flow-6-(4)(4)1316985 The purifying air is exposed to the portion in which the air passage is formed, and the cooling air heated by the exhaust gas after cooling the cylinder head near the exhaust port can suppress or prevent the temperature from being lowered, thereby promoting The reaction of the unburned component in the exhaust gas with the exhaust gas purifying air. According to a fourth aspect of the present invention, in the air-cooled internal combustion engine according to the first or second aspect of the present invention, the sensor is an exhaust gas sensor for sensing a property of an exhaust gas in a state of the internal combustion engine, and is used for sensing a temperature sensor for the temperature of the internal combustion engine in an internal combustion engine state; the exhaust gas sensor and the temperature sensor are mounted to be connected to the electric wire with respect to a sensing portion located inside the main body of the internal combustion engine, It is located near the above-mentioned cooling fan provided at the shaft end of the crankshaft. Thereby, in the exhaust gas sensing portion and the temperature sensing portion, the individual connecting portions are located closer to the cooling fan, so that the wires connected to the respective sensors are cooled by the cooler cooling air. It can prevent: changes in resistance due to the rise in temperature of the wire. [Effect of the Invention] According to the first aspect of the invention, the following effects can be obtained. In other words, in the air-cooled internal combustion engine, by using a shield, the simple structure can ensure the protection function and cooling of the sensor and the wires connected to the sensor, and can increase the sensor. And the degree of freedom in the configuration of the wires. According to the second invention, in addition to the effects of the cited invention, the following effects can be achieved. That is to say, by increasing the cooling of the wire -7-(5) 1316985 connected to the sensor, the change in resistance can be suppressed, and the sensing accuracy of the sensor is improved. According to the third invention, in addition to the effects of the cited invention, the following effects can be obtained. That is to say, in addition to arranging the air passages of the exhaust gas sensor and the exhaust gas purifying air to be compacted, the cooling performance of the exhaust gas sensor can be improved, and the exhaust gas purifying air can be achieved. The exhaust gas purification performance is improved. According to the fourth invention, in addition to the effects of the cited invention, the following effects can be obtained. That is to say, by making the cooling of the electric wires connected to the sensor higher, the change in resistance can be suppressed, so that the sensing accuracy of each sensor is improved. [Embodiment] Hereinafter, embodiments of the present invention will be described with reference to Figs. 1 to 6 . Referring to Fig. 1 and Fig. 2, an air-cooled internal combustion engine E' to which the present invention is applied is a power transmission device including a V-belt type automatic transmission, and is mounted on a locomotive as a vehicle. The internal combustion engine is supported by the vehicle body such that the rotation center line L 1 of the crankshaft 7 is disposed laterally in the left-right direction. The single-cylinder four-stroke internal combustion engine is provided with an internal combustion engine body, and the internal combustion engine body is: a crankcase 2 coupled to the crankshaft 7 side of the cylinder 1 in the direction of the cylinder axis L2 (hereinafter referred to as "cylinder axis direction"), and a cylinder head 3 coupled to the counter crankshaft 7 side of the cylinder 1 in the cylinder axis direction, and combined The cylinder head cover 4 of the cylinder head 3 is constructed. Cylinder 1, crankcase 2, cylinder head 3, -8 - (6) (6) 1316985 and cylinder head cover 4 are formed of a metal which is a material of a good conductor of heat, for example, by an aluminum alloy. In the above-described embodiment, the upper and lower sides, the front and rear, and the left and right sides represent the upper and lower sides, the front and rear, and the left and right sides when the locomotive of the machine including the internal combustion engine E is used as a reference, and the axial direction represents the center of rotation of the crankshaft 7. The direction parallel to the line. When one of the left and right sides is regarded as one of the axial directions, the other of the left and right sides is the other side of the axial direction. The cylinder 1 is disposed in the vehicle body such that the cylinder axis L2 is inclined upward toward the front and is inclined obliquely upward with respect to the horizontal plane. The piston 5 is reciprocally fitted to the cylinder bore 1a of the cylinder 1, and the crankshaft 7 to which the piston 5 is coupled via the link 6 is rotatably coupled via a pair of main bearings 8 composed of ball bearings. Supported by the crankcase 2. A crank chamber 9 for accommodating the crankshaft 7 is formed, and the left and right opposite crankcases 2 are composed of a left case half body 2a and a right case body half 2b. The cylinder head 3 is a plurality of insertion holes 1 (refer to Figs. 4 and 6) provided in the cylinder 1 and the cylinder head 3, and here are four cylinder head bolts 11 (refer to 6)), and locked to the crankcase 2 together with the cylinder 1. The cylinder head 3 is formed with a combustion chamber 1 2 facing the piston 5 in the cylinder axis direction, and an intake port 13 and an exhaust port 14 opened in the combustion chamber 12; the spark plug 15 is mounted in a face. For the combustion chamber 12. The intake valve I6 and the exhaust valve 17 provided in the cylinder head 3 are driven by the opening and closing of the valve device 20. The valve device 20' is provided by: a transmission through a valve -9 - (7) 1316985 The cam shaft 22 that is rotationally driven by the power of the crankshaft 7 is transmitted, and the intake port 13 and the exhaust port 14 are opened and closed in synchronization with the rotation of the crankshaft 7. The valve device 20 housed in the valve chamber 21 formed by the cylinder head 3 and the cylinder head cover 4 is provided with a cam shaft 22 rotatably supported by the cylinder head 3 via a bearing, and The intake cam 2 2 a and the exhaust cam 2 2 b of the camshaft 22 are respectively driven, and the intake rocker arm 25 and the exhaust rocker arm 26 which are swung around the rocker shafts 23 and 24, respectively. The transmission mechanism 18 is a drive sprocket 18a provided at the shaft end portion 7a of the left crankshaft 7 projecting to the left of the crank chamber 9 through the main bearing 8 on the left side, at the shaft end portion of the camshaft 22 The driven sprocket 18b and the circulating chain l8c which is wound around the sprocket wheels 18a and 18b as a circulating belt are formed. The two sprockets l8a, Wb and the chain 18c are housed by the cylinder 1, the cylinder head 3, the cylinder head cover 4, and the left casing half 2a, and are connected to the valve chamber 21 and the crank chamber 9. The chain chamber 2 as a transmission chamber. In the axial direction (also in the left-right direction), on the left side of the crank chamber 9 via the chain chamber 27, a shifting chamber 33 in which a transmission Μ is housed is formed, and the shifting machine 具备 is provided with a V-belt 30 wound around it. The drive pulley 31 and the driven pulley (not shown) of the winding radius are changed by the centrifugal weight 3a in response to the engine speed. The transmission case 32' forming the shifting chamber 33 is composed of a case main body 32a composed of the left case half body 2a and a case 321 which is coupled to the left side of the case main body 32a by a large number of bolts. The shaft end portion 7a' which is poorly worn by the left case half body 2a and protrudes to the left constitutes a drive shaft of the drive 10- (8) 1316985 movable pulley 31. The intake device of the internal combustion engine E is provided with an intake pipe 35 that connects the throttle body (not shown) to the intake port 13 side of the cylinder head 3 ' ^ Throttle body ' is set There are: a throttle valve for controlling the flow rate of the intake air from the air cleaner. In the intake pipe 35, a fuel injection valve 36 as a mixture forming means is provided, and the fuel injection valve 36' supplies fuel to the intake air flowing through the intake air passage of the intake device to form a mixed gas. . The fuel injected from the fuel injection valve 36 toward the intake port 13 becomes a mixture', and when the intake valve 16 is opened, it flows into the combustion chamber 12' through the intake port 13 at the combustion chamber 12 by the spark plug 15 ignition and burning. The piston 5, which is reciprocated by the pressure of the generated combustion gas, rotationally drives the crankshaft 7 via the connecting rod 6. The combustion gas becomes an exhaust gas, and when the exhaust valve 17 is opened, it is discharged to the outside of the internal combustion engine E through the exhaust port 14 through the exhaust device having the exhaust pipe 37. %, the power of the crankshaft 7 is automatically shifted by the speed changer Μ in response to the engine speed, and finally transmitted to the rear wheel as the drive wheel via the speed reduction mechanism, and the rear wheel is rotationally driven. Referring to FIGS. 1 and 3, a fan chamber 41 is formed on the right side of the crank chamber 9, and the fan chamber 41 houses an alternator 39 and attracts outside air to generate air-cooling of the internal combustion engine body. Cooling fan cooling fan 4〇. The fan chamber 41 is formed by a right case half body 2b and a fan case 42 that covers the cooling fan 40 from the right side. The alternator 39 and the cooling fan 40 driven by the crankshaft 7 are attached to the right side of the crankshaft 7 that extends in the fan chamber 41 so as to protrude rightward through the right casing half-11 - (9) 1316985 body 2b. The shaft end 7b. With reference to the first and third figures, the synthetic resin fan casing 42 provided in the internal combustion engine E and coupled to the right casing half 2b by a plurality of bolts 43 has a fan chamber 41 formed to allow outside air to flow in. The cylindrical air suction portion 42a of the suction port 41a. Inside the air intake portion 42a, a louver 42b that rectifies the sucked air so as to flow in the axial direction is disposed. The air that is pressurized and transported by the cooling fan 40 is outside the diameter direction of the cooling fan 40, and is blown to the air supply port 41b that is opened to the cylinder 1 side in the cylinder axis direction, and is sent to the ventilation described later as cooling air. Referring to FIGS. 2 and 4, the cover 46 is incorporated in the shield 45 of the internal combustion engine E, and covers the cylinder 1 and the cylinder head by covering the entire cylinder 1 and the cylinder head 3 constituting the main body of the internal combustion engine. 3, to form a cooling air passage 46. More specifically, the shroud 45 covers the cylinder 1 and the cylinder head 3 around the cylinder axis L2, and covers the entire length of the cylinder 1 and the cylinder head 3 in the cylinder axis. In the outer surface of the cylinder 1 and the cylinder head 3, a plurality of cooling blades If, 3f, a synthetic resin cover 45 for improving the cooling effect on the cylinder 1 and the cylinder head 3 by the cooling air are provided, respectively. The upper shroud portion 45a as the first shroud portion and the lower shroud portion 45b as the second shroud portion are divided into two by the dividing surface substantially parallel to the cylinder axis L2. Composition. The two shroud portions 45a, 45b are joined to each other by a locking structure having claws 47 and bolts 48, -12-(10) 1316985, and the shroud portions 45a, 45b are coupled to the fan casing by bolts 49. 42. The lower shroud portion 45b is coupled to the left case half body 2a by a bolt 50, and has an opening portion 51 for the cylinder head cover 4 to protrude forward from the shroud 45, by which the opening is defined The edge portions 45a1 and 45b1 of the respective shroud portions 45a and 45b of the portion 51 are fitted to the crotch portion 3a of the cylinder head 3, and the shroud 45 is attached to the internal combustion engine body. In the shroud 45, except for the opening portion 51 provided at the front portion thereof covering the two shroud portions 45a, 45b, on the right side thereof, there are provided that the two shroud portions 45a, 45b are provided, and the plug is worn in the spark plug. The opening portion 52 of the installed Mars plug 19; the upper surface portion thereof has: an opening portion 53 that is disposed in the upper shroud portion 45a and that is inserted into the intake pipe 35; and a lower portion of the lower portion that is disposed in the lower shroud portion 45b, the opening portion 54 of the passage forming portion 83 to be described later is inserted into the exhaust pipe 37, and the air outlet 55 provided to the lower cover portion 45b and open to the right is provided on the left surface portion. The cooling air from the cooling fan 40 is outside the radial direction of the cooling fan 40 and has a component in the rotation direction of the cooling fan 40, and flows into the air passage 46 from the air blowing port 41b of the fan chamber 41 (in FIG. 3, The approximate flow of the cooling air is indicated by a broken line arrow.), it flows around the cylinder 1 and the cylinder head 3 in the air passage 46 to cool it, and then is discharged from the air outlet 55 to the outside of the shroud 45. . The cooling air flows out of the exhaust port 55 toward the exhaust pipe 38 to cool the exhaust pipe 38. Referring to Fig. 1, at the shaft end portion 7b, there is disposed between the main bearing 8 on the right side and the alternator 39 for pumping the oil of the lubricating system-13-(11) 1316985 constituting the internal combustion engine e (no The drive gear 60 is driven as shown. The oil pump is driven by the power transmission portion formed by the bottom portion of the crankcase 2, driven by the transmitted power of the crankshaft 7 via a transmission mechanism including a gear train including the drive gear 60. The lubricating oil is supplied to the lubricating portion of the internal combustion engine E mainly including the crankshaft 7 and the valve device 20 through a plurality of oil passages. Referring to Fig. 2 and Fig. 4 to Fig. 6, in the valve device 20 provided in the cylinder head 3, the lubricating oil discharged from the oil pump flows through the oil passage formed by the insertion hole 1 〇a. 61. The lubricating oil of a part of the oil passage 61 is guided to the oil passage 62 formed in the cylinder head cover 4 (see FIG. 2), and is discharged from the nozzle 62a of the oil passage 62 into the valve chamber 21, and the oil The remaining lubricating oil of the path 61 is ejected into the valve chamber 21 from the sliding portion of the intake rocker 25 through the oil passage 63 (see FIG. 2) in the rocker shaft 23, and is supplied to the valve device 20. The lubrication part in the valve chamber 21, etc. The lubricating oil after the lubricating portion is lubricated is formed by the through hole which is opened to the crank chamber 9 from the valve chamber 2 1 through the lower peripheral wall portion 3b of the cylinder head 3 and the lower peripheral wall portion 1b of the cylinder 1. The return oil passage 64 (see also Fig. 4) flows down, flows into the crank chamber 9, and returns to the above-described oil reservoir. Referring to Figs. 1 to 6, the internal combustion engine E is provided with a sensor for sensing the state of the internal combustion engine, an exhaust gas attached to the cylinder head 3, and sensing the nature of the exhaust gas at the exhaust port 14 a sensor, for example, an oxygen concentration sensor 70 for sensing the concentration of oxygen in the exhaust gas, and a temperature sensor for sensing the temperature of the internal combustion engine as the state of the internal combustion engine for sensing the lubricating oil The temperature of the oil temperature sensor 7 5. -14 - (12) 1316985 The oxygen concentration sensor 7 is attached to the lower peripheral wall portion 3b near the outlet 14a of the exhaust port 14 at the cylinder head 3. The oxygen concentration sensor 7A having a substantially columnar shape and arranged substantially parallel to the axial direction has a mounting portion 70a formed of a screw portion that is screwed into the cylinder head 3 and is mounted inside the cylinder head 3 A sensing portion 7bb in the exhaust port 14 and a connecting portion 70c for connecting the sensing signal to the electric wire 71 of the control device are connected. The connecting portion 70c of the coupler 72 as the connecting portion provided next to the tip end of the electric wire 7 1 is exposed from the cylinder 1 in a state covered by the shroud 45, and is disposed in the air passage 46. The oil temperature sensor 75 is attached to the lower peripheral wall portion 1b of the cylinder 1 on the opening side of the outlet 14a of the exhaust port 14. The oil temperature sensor 75 that is substantially columnar and arranged substantially parallel to the axial direction has a mounting portion 75a formed of a screw portion that is screwed into the cylinder head 3 and is mounted inside the cylinder 1. The sensing portion 75b of the return oil passage 64 and the connecting portion 75c to which the sensing signal is transmitted to the electric wire 76 of the control device are connected. The connecting portion 75c, which is a coupler 77 as a connecting portion provided at the tip end of the electric wire 76, is exposed from the cylinder 1 in a state of being covered by the shroud 45, and is disposed in the air passage 46. The oil temperature sensor 75 is disposed so as to extend from the sensing portion 75b toward the opposite side of the chain chamber 27 in the axial direction, and is viewed from a direction perpendicular to the plane H (refer to FIG. 6), and the oil temperature sensor The whole of 75 overlaps with the cylinder 1 (refer to Fig. 1). Therefore, the oil temperature sensor 75 does not protrude from the cylinder 1 in the axial direction in the axial direction, but is configured to be compacted with respect to the cylinder 1. The plane H here is a plane containing the cylinder axis L2 and parallel to the rotation -15-(13) 1316985 rotation center line L1 or containing the rotation center line L1. In each of the sensors 70, 75, the connecting portions 70c, 75c are located in the vicinity of the cooling fan 40 provided at the shaft end portion 7b in the axial direction with respect to the sensing portions 7 Ob and 75b. Therefore, the connecting portions 70c and 75c are located at the upstream of the cooling air in the respective sensors 70 and 75. The oxygen concentration sensor 70 and the oil temperature sensor 75 are the portions of the internal combustion engine body on the opening side of the outlet 14a of the exhaust port 14 with respect to the plane ,, and are formed in the cylinder head 3 and the cylinder, respectively, in this embodiment. The lower peripheral wall portions 3b and 1b of the lower portion of the first portion are arranged in parallel with each other in the cylinder axis direction (see Fig. 1). The two sensors 70 and 75 are located at positions overlapping from the cylinder axis direction (see Fig. 6). Each of the electric wires 71 and 76 extends in the axial direction from the connection portion 70c and 75c across the air passage 46 toward the cooling fan 40, and penetrates the insulation that is fitted in the notch portion of the cover portions 45a and 45b. The ring 79 extends toward the outside of the shroud 45 and is connected to the above control device. Each of the electric wires 71, 76 is disposed closer to the upstream side of the cooling air than the cylinder 1 and the cylinder head 3. Therefore, each of the electric wires 71, 76 is exposed to the cooling air before reaching the cylinder 1 and the cylinder head 3. The sensing enthalpy sensed by the oxygen concentration sensor 70 is for improving the purification performance of the exhaust gas achieved by the catalyst device provided in the exhaust device, and the amount of fuel used for the fuel injection valve 36. In the control, the sensing 値' sensed by the oil temperature sensor 75 is used for controlling the fuel amount of the fuel injection valve 36 in response to the warm-up state of the internal combustion engine E, or during warm-up The control of the idle air volume used for idle speed control is -16- (14) 1316985. Referring to Fig. 3 and Fig. 4', in the internal combustion engine e, the exhaust gas purification air is supplied to the exhaust gas by burning the unburned components (HC, C0) in the exhaust gas to purify the exhaust gas. Exhaust system secondary air supply device. The secondary air supply device includes a control valve 8 1 for controlling the amount of air supplied to the exhaust gas, and a control valve 8 1 connected to the cylinder head 3 to be controlled by the control valve 8 1 The controlled exhaust gas purifying air is guided to the air supply pipe 82 of the exhaust port 14. The control valve 8 1 supplies the exhaust gas for purification to the exhaust gas, for example, when it is in an operating state in which the control of the amount of fuel is not performed based on the sense of the oxygen concentration sensor 70. The air supply pipe 82 is composed of an upstream side supply pipe 82a connected to the control valve 81 and a rubber hose, and a metal downstream side supply pipe 82b piped along the shroud 45. The downstream side supply pipe 82b protrudes from the outer surface of the cylinder head 3 and traverses the air passage 46, and is connected to a passage forming portion that is formed by the protruding portion that extends from the opening portion 54 of the shroud 45 to the outside of the shin guard 45. 83. The passage forming portion 83 formed integrally with the cylinder head 3 is provided with an air passage 84 that is opened to the exhaust port 14, and the exhaust gas purifying air ' flowing through the air supply pipe 82 flows through the air passage 84. It is supplied to the exhaust port 14. The passage forming portion 83 is disposed such that the air passage 84 is located closer to the downstream side of the cooling air than the exhaust port 46 in the air passage 46. The cooling passage is disposed closer to the exhaust port 14 and the exhaust pipe 38. The position of the downstream side. Next, the action and effect of the embodiment constructed as described above will be described in -17-(15) 1316985. The electric wires 7 1 and 76' respectively connected to the oxygen concentration sensor 7 attached to the cylinder head 3 and the oil temperature sensor 75 mounted in the cylinder 1 are disposed in the air passage 46'. The sensors 70 and 75 and the respective electric wires 71 and 76 are disposed in the shroud 45 so that they can be protected from collision or contact with foreign objects such as small stones that bounce during traveling. The technique of arranging the sensor outside the shroud 45 to create a configuration restriction between the sensor and the peripheral part near the sensor is not the same as that disposed outside the shroud 45. The components, while limiting the configuration of the sensors 70, 75 and the wires 71, 76, conversely, the sensors 70, 75 or wires 71, 76 also do not limit the configuration of the members. Further, since the sensors 70, 75 and the electric wires 71, 76 disposed in the air passage 46 are cooled by the cooling air in the shroud 45, it is possible to prevent the heat from the internal combustion engine E from being overheated. As a result, in the internal combustion engine E, the protective function and the cooling performance of the respective sensors 70, 75 and the electric wires 71, 76 connected to the sensors 70, 75 can be ensured by the use of the shield 45 by a simple structure. Further, the degree of freedom in the arrangement of the sensors 70, 75 and the electric wires 71, 76 can be increased. The cooling fan 40' covered by the shroud 45 and used to convey the cooling air to the air passage 46 is provided and the electric wires 71, 76 are disposed closer to the upstream side of the cooling air than the cylinder 1 and the cylinder head 3. In the internal combustion engine E' that is forced air-cooled by the cooling air caused by the cooling fan 40, the cooling air 'before cooling the cylinder 1 and the cylinder head 3 can effectively cool the electric wires 71 and 76, so that it can be suppressed' The heat from the internal combustion engine E causes the temperature of the electric wires 7 1 and 76 to rise to cause a change in electrical resistance. The oxygen-18-(16) 1316985 gas concentration sensor 70 and the oil temperature sensor 75 are mounted so as to be connected with respect to the sensing portions 7 Ob and 75b located inside the cylinder head 3 and the cylinder 1. The portions 70c and 75c are located in the vicinity of the cooling fan 40 provided at the shaft end portion 7b of the crankshaft 7; in the oxygen concentration sensor 70 and the oil temperature sensor 75, the individual connecting portions 70c, 75c are located at Close to the position of the cooling fan 40, the electric wires 71, 76 connected to the respective sensors 70, 75 are cooled by the cooler air of a lower temperature, and it is possible to prevent a change in electric resistance due to an increase in the temperature of the electric wire. As a result, the cooling performance of the wires 7 1 and 76 connected to the sensors 70 and 75 can be further improved, and the change in resistance can be suppressed, so that the sensing accuracy of the sensors 70 and 75 can be improved. The oxygen concentration sensor 70 is installed at a position closer to the upstream of the cooling air than the exhaust port 14, and is disposed at a position lower than the cooling air of the exhaust port 14 to clean the exhaust gas. When the air is guided to the air passage 84 of the exhaust port 14, the oxygen concentration sensor 70 and the air passage 84 can be disposed close to the exhaust port 14. Further, the oxygen concentration sensor 70 is effectively cooled by the cooling air before being heated by the exhaust gas of the exhaust port 14, and the exhaust gas for the exhaust gas flowing through the air passage 84 is caused by The passage forming portion S3 forming the air passage 84 is exposed to a situation in which the cooling air heated by the exhaust gas after the cylinder head 3 in the vicinity of the exhaust port 14 is cooled can suppress or prevent the temperature from being lowered, thereby promoting The reaction of the unburned component in the exhaust gas with the exhaust gas purifying air. As a result, in addition to the fact that the oxygen concentration sensor 7 and the air passage 84 for exhausting the air for purifying air can be configured to be compacted, the cooling of the oxygen concentration sensor 7 can be improved, and the exhaust gas purification can be improved. 19- (17) 1316985 Purified by the exhaust gas of air. Hereinafter, the configuration of the change will be described with respect to an embodiment in which the structure of a part of the above embodiment is changed. The exhaust gas sensor may also be a LAF sensor for sensing an air-fuel ratio in the exhaust gas, or a sensor for sensing an unburned component. The temperature of the internal combustion engine may be the temperature of the main body of the internal combustion engine or the combustion temperature, and the internal combustion engine of the water-cooling type may be the temperature of the cooling water. The passage forming portion 83 may be formed of a member different from the cylinder head 3. In this case, the passage forming portion 83 is made of metal or the like in the same manner as the light alloy cylinder head 3 made of an aluminum alloy or the like. The formation of a good, good conductor material. In the internal combustion engine, the cylinder and the cylinder head may be integrally formed, or a multi-cylinder internal combustion engine may be used. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view taken along line 1 to line I of Fig. 2 of an air-cooled internal combustion engine to which the present invention is applied. Fig. 2 is a sectional view taken along line 11-11 of Fig. 1. Fig. 3 is a right side view showing the main part of the air-cooled internal combustion engine of Fig. 1. Fig. 4 is a perspective view of a main portion of the internal combustion engine of Fig. 1 with the lower shroud portion removed. Fig. 5 is a view showing a main portion of the cylinder and the cylinder head -20-(18) (18) 1316985 as seen from the direction of the V arrow in Fig. 3. Figure 6 is a cross-sectional view of the Via - Via line of Figure 5, and a portion is a cross-sectional view of the VIb - VIb line of Figure 5. [Main component symbol description] 1 : Cylinder 3 : Cylinder head 7 : Crankshaft 20 : Valve device 4 0 : Cooling fan 45 : Shield 4 6 : Ventilation path 64 : Return oil path 70 : Oxygen concentration sensor 71 , 7 6 : Wire 75: Oil Temperature Sensor 82: Air Supply Tube E: Air-Cooled Internal Combustion Engine-21 -