1251637 (1) 玖、發明說明 【發明所屬之技術領域】 本發明是關於將凸輪軸設置在汽缸蓋上的OHC型內 燃機，特別是關於用來可自由旋轉地支承凸輪軸的構造。 【先前技術】 以往的凸輪軸支承構造，是在汽缸蓋罩與汽缸蓋的接 合面之間形成上下對開狀的軸承保持部，經由滾動軸承而 可自由旋轉地支承著凸輪軸（例如，參照專利文獻1)。 做爲其他凸輪軸支承構造，設置有與汽缸蓋罩爲不同 個體構件的凸輪軸上部支承體，在同凸輪軸上部支承體與 汽缸蓋的接合面之間形成上下對開狀的軸承保持部，是經 由浪動軸承而可自由旋轉地支承著凸輪軸。汽缸蓋罩，在 安裝了包含凸輪軸的閥門機構之後，再被安裝在汽缸蓋來 將其覆蓋（例如，參照專利文獻2)。 [專利文獻1] 曰本實公平2— 16002號公報（第1圖） 【專利文獻2】 日本實公昭5 7 — 45 3 87號公報（第1圖） 在傳統技術中，在汽缸蓋罩與汽缸蓋的接合面之間， 或是在凸輪軸上部保持體與汽缸蓋的接合面之間，是形成 了上下對開狀的軸承保持部。爲了在分別製作的構件的接 合面形成軸承保持部，要先將接合面對準來組裝，然後穿 設軸承保持部，再將其分解，需要耗費這樣的過程的製程 -5- (2) 1251637 ，在要組裝的情況，是先在形成爲對開狀的其中一方的構 件經由軸承安裝凸輪軸之後，再次組裝另一邊的構件，需 要這樣的製程。 【發明內容】 [發明欲解決的課題] 本發明爲了解決上述先前技術的缺點，而取消了在分 別製作的構件的接合面形成對開狀軸承保持部的方式，而 作成藉由與汽缸蓋罩或汽缸蓋獨立的凸輪軸座來支承軸承 ’讓軸承保持部的製作以及凸輪軸安裝作業更容易進行。 [用來解決課題的手段及效果] 本發明是要解決上述課題，第1發明，是在汽缸蓋上 設置有與曲軸連動旋轉的凸輪軸之OHC型內燃機，其特 徵爲：將用來可自由旋轉地支承上述凸輪軸的凸輪軸座作 成’與上述汽缸蓋爲不同個體的構件，以貫穿汽缸的雙頭 螺栓來將其鎖裝在一起來加以固定。 本發明如上述的方式，由於是將凸輪軸座作成與汽缸 蓋不同個體的構件，所以不需要像傳統的方式，形成會耗 費製造程序的上下對開狀的軸承保持部，而可以做成容易 製作的形狀的軸承保持部。而能夠以貫穿汽缸的雙頭螺栓 來將凸輪軸座鎖裝在一起加以固定，而可堅固地加以固定 〇 第2發明，是第1發明的OHC型內燃機，在上述凸 1251637 (3) 輪軸座是一體地形成有搖臂軸支承部，上述凸輪軸座的鎖 裝位置是在較上述搖臂軸支承部的更上面部。 由於在凸輪軸座是一體地形成有搖臂軸支承部，所以 能夠以連續的製程來進行凸輪軸的安裝與搖臂軸的安裝。 而以錦合金製作的凸輪軸座會熱膨脹變大，所以在固定在 較搖臂軸支承部更下方的情況，由於熱膨脹會讓凸輪軸與 搖臂軸的間隔改變，搖臂的位置會出錯，會產生推桿的餘 隙會變大這樣的缺失，可是由於是將凸輪軸座的鎖裝位置 作在搖臂軸支承部的更上面部，所以不會產生這種缺失。 【實施方式】 第1圖是從後方來看本發明的一實施方式的機車用 OHC型單汽缸內燃機的主要部分的橫剖面的視圖。在圖 中，該內燃機的外殼，是由：左曲軸箱1、右曲軸箱2、 左曲軸箱蓋3、右曲軸箱蓋4、汽缸體5、汽缸蓋6、以及 汽缸蓋罩7所構成。曲軸8是由左右的部分所構成，藉由 曲軸銷9而被一體化。曲軸8，是分別經由滾動軸承1 0、 1 1而可旋轉地被支承在左曲軸箱1與右曲軸箱2。在曲軸 銷9是經由連桿1 2連接著活塞1 3，同活塞是在汽缸體5 中進行上下運動。在汽缸蓋6的下面部形成有燃燒室1 4 。在汽缸蓋6安裝著火星塞1 5，其前端是面對於上述燃 燒室14。 在汽缸蓋6與汽缸蓋罩7之間的閥門室2 0所設置的 凸輪軸座2 1是可旋轉地支承著閥門機構的凸輪軸22。在 -7 - 1251637 (4) 內燃機的左側部，設置有從凸輪軸22的左端部空間貫穿 到左曲軸箱1的內部的凸輪鏈條室2 3。在曲軸8的左側 部分是嵌裝著傳動鏈輪24，在凸輪軸22的左端部是固定 著從動鏈輪25，在該兩鏈輪，是繞掛著凸輪鏈條26。藉 此，將曲軸8的旋轉驅動力傳達到凸輪軸2 2，而能夠以 預定的時序來驅動配置在汽缸蓋6的後述的進排氣閥。 第2圖是從右側來看設置在上述內燃機的上部的進排 氣閥與閥門機構的縱剖面的視圖，箭頭F是指出前方。在 圖中，在汽缸蓋6形成了聯繋於燃燒室14的排氣口 27與 進氣口 29。在排氣口 27的內側端設置有用來開閉該通路 的排氣閥28。在排氣口 27的外側端是連接著省略圖示的 排氣管。在進氣口 29的內側端是設置有用來開閉其通路 的進氣閥30。在進氣口 29的外側端是連接著省略圖示的 化油器。 排氣閥2 8是讓其軸部2 8 a前傾而設置在靠近汽缸蓋 6前側，在軸部2 8 a的上部突出部安裝有將排氣閥2 8朝 向關閉方向彈壓的閥彈簧31。進氣閥30是讓其軸部30a 前傾而設置在靠近汽缸蓋6後側’在軸部3 0a的上部突出 部安裝有將進氣閥30朝向關閉方向彈壓的閥彈簧32。 第3圖是從上面來看閥門室2 0的內部的水平剖面圖 ，箭頭F是指出前方。以下的說明，是參照第2圖與第3 圖來敘述。藉由汽缸蓋6與汽缸蓋罩7形成了閥門室20 ，在這裡收容有凸輪軸22與用來開閉上述排氣閥28與進 氣閥30的閥門機構。在以排氣閥28與進氣閥30所形成 (5) 1251637 的V字型的空間，是將相對於內燃機的前後方向垂直相 交的凸輪軸2 2可旋轉地支承在凸輪軸座2 1。凸輪軸座2 1 ，如後述，是具備有：左側部分2 1 a、右側部分2丨b、前 部連接部2 1 c、以及後部連接部2 1 d的一體的構件。第3 圖是看到凸輪軸座2 1的左側部分2 1 a與右側部分2 1 b。 在凸輪軸座2 1所支承的凸輪軸2 2，是形成有：用來開閉 驅動排氣閥2 8的排氣用凸輪3 4、以及用來開閉驅動進氣 閥3 0的進氣用凸輪3 5。 在排氣閥2 8的上方，是將排氣用搖臂3 6可擺動地支 承於排氣用搖臂軸3 7，其中一端是經由推桿3 8連接於排 氣閥的軸部2 8 a的上端2 8 b，另一端是經由支承於滾子軸 39的排氣用滾子40而連接於排氣用凸輪34。在進氣閥 3 〇的上方，是將進氣用搖臂4 1可擺動地支承於進氣用搖 臂軸4 2，其中一端是經由推桿4 3連接於進氣閥的軸部 3〇a的上端30b，另一端是經由支承於滾子軸44的進氣用 滾子45而連接於進氣用凸輪3 5。閥門機構是如上述的構 造，所以可以因應凸輪軸22的旋轉以預定的時序來開閉 進排氣閥。在第3圖中，排氣用搖臂軸3 7、滾子軸3 9、 進氣用搖臂軸42、滾子軸44僅圖示中心線，將圖號附加 在中心線。 第4圖是凸輪軸座21的平面圖，第5圖是第4圖的 V — V剖面圖，第6圖是第4圖的VI — VI剖面圖，第7 圖是第4圖的VII— VII剖面圖。凸輪軸座21，是由：左 側部分2 1 a、右側部分2 1 b、前部連接部2 1 c、以及後部 1251637 (6) 連接部2 1 d所構成的一體的構件。在左側部分2 1 a與右側 部分2 1 b，是分別設置有：貫穿於一直線上的凸輪軸支承 孔46、排氣用搖臂軸支承孔47、以及進氣用搖臂軸支承 孔4 8。顯示孔部的位置的圖號，是附加在孔部的中心線 。藉此，支承著各軸部。凸輪軸2 2是經由滾動軸承而被 支承在上述凸輪軸支承孔4 6。搖臂軸3 7、4 2是固定軸， 搖臂3 6、4 1是於該固定軸周圍擺動。該凸輪軸座2 1的軸 支承孔，由於不是傳統的對開式構造，是從凸輪軸座的其 中一側插入於車體框架。而再該構件的角落的四個位置， 設置有長蓋形螺帽插通孔49。 第8圖是顯示凸輪軸座2 1的安裝構造的從右側來看 內燃機的縱剖面的視圖，凸輪軸座2 1，是顯示左側部分 2 1 a的剖面。箭頭F是指向前方。在上述凸輪軸座的左側 部分21a，是顯示有：凸輪軸支承孔46、排氣用搖臂軸支 承孔47、以及進氣用搖臂軸支承孔48。 在左曲軸箱1上植入有兩支雙頭螺栓5 0，雙頭螺栓 5 0的上部，是被插通在汽缸體側部的雙頭螺栓插通孔5 3 與汽缸蓋側部的雙頭螺栓插通孔5 4。雖然省略圖示，可 是與第8圖同樣的，在內燃機右側的右曲軸箱也植設有兩 支雙頭螺栓5 0，是被插通在汽缸體5與汽缸蓋6的右側 的雙頭螺栓插通孔。 凸輪軸座2 1被設置在上述狀態的汽缸蓋上，將插通 於四個位置的長蓋形螺帽插通孔49的長蓋形螺帽5 1分別 螺合於上述四支雙頭螺栓5 0的頭部的公螺紋部來加以鎖 -10- 1251637 (7) 裝。鎖裝面是在凸輪軸座的上面部，也就是搖臂軸支承部 - 的更上側。在凸輪軸座2 1的上面部與長蓋形螺帽5 1的頭 部之間是安裝著墊片5 2。汽缸蓋罩7，在閥門機構的安裝 動作結束之後，會被安裝在汽缸蓋6。1251637 (1) Field of the Invention The present invention relates to an OHC type internal combustion engine in which a camshaft is provided on a cylinder head, and more particularly to a structure for rotatably supporting a camshaft. [Prior Art] The conventional camshaft support structure is a bearing holding portion that is vertically opposed to the joint surface between the cylinder head cover and the cylinder head, and the cam shaft is rotatably supported via a rolling bearing (for example, refer to the patent literature) 1). As another camshaft support structure, a camshaft upper support body that is different from the cylinder head cover is provided, and a bearing holding portion that is vertically opposed to the joint surface between the camshaft upper support body and the cylinder head is formed. The camshaft is rotatably supported via a wave bearing. The cylinder head cover is attached to the cylinder head to cover it after mounting the valve mechanism including the cam shaft (for example, refer to Patent Document 2). [Patent Document 1] 曰本实公平2—16002 (1) [Patent Document 2] Japan Shigongzhao 5 7 — 45 3 87 (1) In the conventional technology, in the cylinder head cover Between the joint faces of the cylinder heads or between the joint faces of the upper portion of the camshaft and the cylinder head, a bearing holding portion that is formed in an up-and-down shape is formed. In order to form the bearing holding portion on the joint surface of the separately produced member, the joint surface is first aligned to be assembled, and then the bearing holding portion is pierced and then decomposed, and a process that requires such a process is required -5 - (2) 1251637 In the case of assembly, the other member is assembled again after the cam member is mounted via a bearing after one of the members formed in the split shape, and such a process is required. SUMMARY OF THE INVENTION [Problems to be Solved by the Invention] In order to solve the above-described problems of the prior art, the present invention eliminates the manner in which the split bearing holding portion is formed on the joint surface of the separately fabricated member, and is formed by the cylinder head cover or A separate camshaft seat for the cylinder head supports the bearing 'making the bearing retaining portion and camshaft mounting work easier. [Means and Effects for Solving the Problems] The present invention has been made to solve the above problems. The first invention is an OHC type internal combustion engine in which a cylinder head is provided with a cam shaft that rotates in conjunction with a crankshaft, and is characterized in that it is freely available. The cam shaft seat that rotatably supports the cam shaft is formed as a member different from the above-described cylinder head, and is fixed by locking together through the stud bolts of the cylinder. According to the above aspect of the present invention, since the cam shaft base is made of a member different from the cylinder head, it is not necessary to form a bearing holding portion that can be used for the upper and lower sides of the manufacturing process as in the conventional manner, and can be easily manufactured. The shape of the bearing retaining portion. Further, the camshaft seat can be locked and fixed together by a stud bolt penetrating through the cylinder, and can be firmly fixed. According to the second invention, the OHC type internal combustion engine of the first invention is in the above-mentioned convex 1251637 (3) wheel axle seat. A rocker arm support portion is integrally formed, and the lock position of the cam shaft base is an upper surface portion of the rocker arm support portion. Since the rocker arm support portion is integrally formed in the cam shaft seat, the cam shaft can be attached and the rocker shaft can be mounted in a continuous process. However, the camshaft seat made of the brocade alloy has a large thermal expansion, so that when it is fixed below the rocker arm shaft support portion, the position of the rocker arm may be wrong due to the thermal expansion which causes the interval between the camshaft and the rocker arm shaft to change. There is such a loss that the clearance of the push rod becomes large, but since the locking position of the cam shaft seat is made on the upper surface of the rocker shaft support portion, such a loss does not occur. [Embodiment] FIG. 1 is a cross-sectional view of a main portion of an OHC type single cylinder internal combustion engine for a locomotive according to an embodiment of the present invention. In the figure, the outer casing of the internal combustion engine is composed of a left crankcase 1, a right crankcase 2, a left crankcase cover 3, a right crankcase cover 4, a cylinder block 5, a cylinder head 6, and a cylinder head cover 7. The crankshaft 8 is composed of left and right portions, and is integrated by the crank pin 9. The crankshaft 8 is rotatably supported by the left crankcase 1 and the right crankcase 2 via rolling bearings 10 and 11. The crank pin 9 is connected to the piston 13 via the connecting rod 12, and the piston is moved up and down in the cylinder block 5. A combustion chamber 14 is formed in a lower portion of the cylinder head 6. A Mars plug 15 is attached to the cylinder head 6, and its front end faces the above-described combustion chamber 14. The cam shaft seat 21 provided in the valve chamber 20 between the cylinder head 6 and the cylinder head cover 7 is a cam shaft 22 that rotatably supports the valve mechanism. In the left side portion of the internal combustion engine of -7 - 1251637 (4), a cam chain chamber 23 that penetrates the space from the left end portion of the cam shaft 22 to the inside of the left crankcase 1 is provided. A drive sprocket 24 is fitted to the left side of the crankshaft 8, and a driven sprocket 25 is fixed to the left end of the camshaft 22, and the cam chain 26 is wound around the sprocket. As a result, the rotational driving force of the crankshaft 8 is transmitted to the camshaft 22, and the intake and exhaust valves, which will be described later, disposed on the cylinder head 6 can be driven at a predetermined timing. Fig. 2 is a longitudinal sectional view of the intake and exhaust valve and the valve mechanism provided at the upper portion of the internal combustion engine as seen from the right side, and arrow F indicates the front. In the figure, an exhaust port 27 and an intake port 29 which are in contact with the combustion chamber 14 are formed in the cylinder head 6. An exhaust valve 28 for opening and closing the passage is provided at the inner end of the exhaust port 27. An exhaust pipe (not shown) is connected to the outer end of the exhaust port 27. An intake valve 30 for opening and closing the passage is provided at the inner end of the intake port 29. A carburetor (not shown) is connected to the outer end of the intake port 29. The exhaust valve 28 is disposed on the front side of the cylinder head 6 with its shaft portion 28 8 forward, and a valve spring 31 that biases the exhaust valve 28 toward the closing direction is attached to the upper projection of the shaft portion 28 8 a. . The intake valve 30 is provided with a valve spring 32 that biases the intake valve 30 toward the closing direction by attaching the shaft portion 30a forward and close to the rear side of the cylinder head 6 at the upper protruding portion of the shaft portion 30a. Fig. 3 is a horizontal sectional view of the inside of the valve chamber 20 from the above, and an arrow F indicates the front. The following description is described with reference to Figs. 2 and 3. The valve chamber 20 is formed by the cylinder head 6 and the cylinder head cover 7, and a cam shaft 22 and a valve mechanism for opening and closing the exhaust valve 28 and the intake valve 30 are housed therein. The V-shaped space in which (5) 1251637 is formed by the exhaust valve 28 and the intake valve 30 is rotatably supported by the cam shaft holder 2 1 with the cam shaft 2 2 perpendicularly intersecting with the longitudinal direction of the internal combustion engine. The camshaft base 2 1 is an integral member including a left side portion 2 1 a, a right side portion 2丨b, a front connecting portion 2 1 c, and a rear connecting portion 2 1 d as will be described later. Figure 3 is a view showing the left side portion 2 1 a and the right side portion 2 1 b of the camshaft seat 2 1 . The cam shaft 22 supported by the camshaft base 21 is formed with an exhaust cam 3 4 for opening and closing the exhaust valve 28, and an intake cam for opening and closing the intake valve 30. 3 5. Above the exhaust valve 28, the exhaust rocker arm 36 is swingably supported by the exhaust rocker shaft 3, 7 and one end thereof is connected to the shaft portion 28 of the exhaust valve via the push rod 38. The upper end 2 8 b of a is connected to the exhaust cam 34 via the exhaust roller 40 supported by the roller shaft 39. Above the intake valve 3 ,, the intake rocker arm 4 is swingably supported by the intake rocker shaft 42, and one end thereof is connected to the shaft portion 3 of the intake valve via the push rod 43. The upper end 30b of a is connected to the intake cam 35 via the intake roller 45 supported by the roller shaft 44 at the other end. Since the valve mechanism has the above configuration, the intake and exhaust valves can be opened and closed at a predetermined timing in response to the rotation of the cam shaft 22. In Fig. 3, the exhaust rocker shaft 37, the roller shaft 39, the intake rocker shaft 42, and the roller shaft 44 are only shown with a center line, and the figure is attached to the center line. 4 is a plan view of the camshaft seat 21, FIG. 5 is a V-V sectional view of FIG. 4, FIG. 6 is a VI-VI sectional view of FIG. 4, and FIG. 7 is a VII-VII of FIG. Sectional view. The camshaft base 21 is an integral member composed of a left side portion 2 1 a, a right side portion 2 1 b, a front connecting portion 2 1 c, and a rear portion 1251637 (6) connecting portion 2 1 d. The left side portion 2 1 a and the right side portion 2 1 b are provided with a cam shaft support hole 46 penetrating the straight line, a rocker arm shaft support hole 47 for exhaust, and a rocker arm shaft support hole for the intake air, respectively. . The figure number showing the position of the hole portion is the center line attached to the hole portion. Thereby, each shaft portion is supported. The cam shaft 22 is supported by the cam shaft support hole 46 via a rolling bearing. The rocker shafts 3 7 and 4 2 are fixed shafts, and the rocker arms 36, 4 1 are swung around the fixed shaft. The shaft support hole of the cam shaft base 2 1 is inserted into the vehicle body frame from one side of the cam shaft seat because it is not a conventional split type configuration. Further, at four positions of the corners of the member, a cap-shaped nut insertion hole 49 is provided. Fig. 8 is a view showing a longitudinal section of the internal combustion engine as seen from the right side of the mounting structure of the camshaft housing 21, and the camshaft housing 21 is a cross section showing the left side portion 2 1 a. The arrow F is pointing to the front. The left side portion 21a of the cam shaft base is provided with a cam shaft support hole 46, an exhaust rocker shaft support hole 47, and an intake rocker shaft support hole 48. Two stud bolts 50 are implanted on the left crankcase 1. The upper part of the stud bolts 50 is a pair of stud insertion holes 5 3 and side portions of the cylinder head that are inserted into the side of the cylinder block. The head bolt is inserted through the hole 5 4 . Although not shown in the drawings, similar to Fig. 8, the right crankcase on the right side of the internal combustion engine is also provided with two stud bolts 50, which are stud bolts inserted into the right side of the cylinder block 5 and the cylinder head 6. Insert the through hole. The camshaft seat 2 1 is disposed on the cylinder head in the above state, and the long cap nut 51 of the long cap nut insertion hole 49 inserted through the four positions is screwed to the four stud bolts respectively. The male thread of the head of the 50 is locked -10- 1251637 (7). The lock surface is on the upper surface of the camshaft seat, that is, the upper side of the rocker shaft support portion. A spacer 52 is attached between the upper surface portion of the camshaft seat 2 1 and the head of the cap-shaped nut 51. The cylinder head cover 7 is mounted to the cylinder head 6 after the installation of the valve mechanism is completed.
如以上詳述，在本實施方式的氣冷室內燃機中，是使 用與汽缸蓋不同個體構造的凸輪軸座，並不採用對開式構 造，是作成單純的圓孔的凸輪軸支承方式，所以容易進行 軸部支承部的製作，也容易進行軸部的安裝作業。 I 由於在凸輪軸座，是一體地形成有搖臂軸支承部，所 以能夠以連續的流程來簡單地進行凸輪軸的安裝與搖臂軸 的安裝動作。 並且，由於是將凸輪軸座的鎖裝位置作在搖臂軸支承 部的更上側，所以不會產生由於熱膨脹來改變搖臂的位置 或是造成推桿餘隙變化等的不好的情形。 【圖式簡單說明】 · 第1圖是從後方來看本發明的一實施方式的機車用 OHC型單汽缸內燃機的主要部分的橫剖面的視圖。 第2圖是從右側來看設置在上述內燃機的上部的進排 氣閥與閥門機構的縱剖面的視圖。 第3圖是從上面來看上述內燃機的閥門室的內部的水 平剖面圖。 第4圖是凸輪軸座的平面圖。 第5圖是第4圖的V— V剖面圖。 -11 - 1251637 (8) 第6圖是第4圖的VI— VI剖面圖。 第7圖是第4圖的VII — VII剖面圖。 第8圖是從右側來看凸輪軸座的安裝部的縱剖面的視 圖。 [圖號說明] 1 :左曲軸箱 2 :右曲軸箱 3 :左曲軸箱蓋 4 :右曲軸箱蓋 5 :汽缸體 6 :汽缸蓋 7 :汽缸蓋罩 8 :曲軸 9 ·曲軸銷 1 0 :滾動軸承 1 1 :滾動軸承 1 2 :連桿 13 :活塞 1 4 :燃燒室 15 :火星塞 2 0 :閥門室 2 1 :凸輪軸座 2 1 a :左側部分 -12- 1251637 (9) 2 1 b :右側部分 2 1 c :前側連接部 2 1 d :後側連接部 2 2 :凸輪軸 2 3 :凸輪鏈條室 24 :傳動鏈輪 2 5 :從動鏈輪 2 6 :凸輪鏈條 27 :排氣口 28 :排氣閥 28a :排氣閥的軸部 29 :進氣閥 3 〇 :進氣閥 3 0a :進氣閥的軸部 3 1 :閥彈簧 3 2 :閥彈簧 3 4 :排氣用凸輪 3 5 :進氣用凸輪 3 6 :排氣用搖臂 3 7 :排氣用搖臂軸 3 8 :推桿 3 9 :滾子軸 40 :排氣用滾子 4 1 :進氣用搖臂 -13- 1251637 (10) 42 :進氣用搖臂軸 - 43 :推桿 . 44 :滾子軸 4 5 :進氣用滾子 4 6 :凸輪軸支承孔 47 :排氣用搖臂軸支承孔 48 :進氣用搖臂軸支承孔 49 :長蓋形螺帽插通孔 β 5 〇 :雙頭螺栓 5 1 :長蓋形螺帽 52 :墊片 5 3 :雙頭螺栓插通孔 54 :雙頭螺栓插通孔 -14-As described in detail above, in the air-cooling chamber internal combustion engine of the present embodiment, a cam shaft seat having a different structure from that of the cylinder head is used, and the split shaft structure is not used, and the cam shaft support method of forming a simple circular hole is easy. It is also easy to perform the mounting work of the shaft portion by making the shaft portion support portion. I Since the rocker arm support portion is integrally formed in the cam shaft seat, the cam shaft can be easily attached and the rocker shaft can be attached in a continuous flow. Further, since the lock position of the cam shaft base is made higher on the rocker shaft support portion, there is no possibility that the position of the rocker arm is changed due to thermal expansion or the change in the clearance of the push rod is caused. [Brief Description of the Drawings] Fig. 1 is a cross-sectional view of a main portion of an OHC type single cylinder internal combustion engine for a locomotive according to an embodiment of the present invention. Fig. 2 is a longitudinal sectional view of the intake and exhaust valve and the valve mechanism provided in the upper portion of the internal combustion engine as seen from the right side. Fig. 3 is a horizontal sectional view showing the inside of the valve chamber of the above internal combustion engine as seen from above. Figure 4 is a plan view of the camshaft seat. Fig. 5 is a V-V sectional view of Fig. 4. -11 - 1251637 (8) Figure 6 is a cross-sectional view of VI-VI in Figure 4. Fig. 7 is a sectional view taken along line VII-VII of Fig. 4. Fig. 8 is a perspective view showing a longitudinal section of a mounting portion of a camshaft seat as seen from the right side. [Description of the figure] 1 : Left crankcase 2 : Right crankcase 3 : Left crankcase cover 4 : Right crankcase cover 5 : Cylinder block 6 : Cylinder head 7 : Cylinder head cover 8 : Crankshaft 9 · Crank pin 1 0 : Rolling bearing 1 1 : Rolling bearing 1 2 : Connecting rod 13 : Piston 1 4 : Combustion chamber 15 : Mars plug 2 0 : Valve chamber 2 1 : Camshaft seat 2 1 a : Left part -12- 1251637 (9) 2 1 b : Right side part 2 1 c : Front side connecting part 2 1 d : Rear side connecting part 2 2 : Camshaft 2 3 : Cam chain chamber 24 : Drive sprocket 2 5 : Driven sprocket 2 6 : Cam chain 27 : Exhaust port 28: Exhaust valve 28a: Shaft portion 29 of exhaust valve: Intake valve 3 〇: Intake valve 3 0a: Shaft portion 3 of intake valve: Valve spring 3 2 : Valve spring 3 4 : Exhaust cam 3 5 : intake cam 3 6 : exhaust rocker 3 7 : exhaust rocker shaft 3 8 : push rod 3 9 : roller shaft 40 : exhaust roller 4 1 : intake rocker -13- 1251637 (10) 42 : Rocker shaft for intake air - 43 : Push rod. 44 : Roller shaft 4 5 : Intake roller 4 6 : Camshaft support hole 47 : Exhaust rocker shaft support Hole 48: Rocker shaft support hole for intake air 49: Long cap nut insertion hole β 5 〇: Stud bolt 5 1 : Long cover Nut 52: spacer 53: stud bolt insertion hole 54: stud bolt insertion holes -14-