201139906 六、發明說明： 【發明所屬之技術領域】 本發明係關於一種引擎減壓機構，尤指一種利用# ^ 齒條運動原理致動之引擎減壓機構》 【先前技術】 當引擎熄火時，由於曲軸受旋轉運動的慣性作用，使 得引擎會繼續旋轉若干轉數，在此過程之中有許多阻抗會 導致旋轉逐漸緩慢下來，最後停止。其中最大的阻抗是壓 縮行程的壓縮壓力，因此常使引擎受該壓縮壓力之作用而 導致正常旋轉停止後反轉，然後停下來。 當内燃機要重新啟動時，汽缸内之活塞係向燃燒室移 動’此時’因進氣閥門連桿之進氣閥與排氣閥門連桿之排 氣閥係皆處於關閉狀態，故活塞於移動時，必須克服燃燒 室内受擠壓的氣體壓力以完成剩餘部分的移動。亦即，不 論是以電動馬達啟動或是人工施力啟動，皆必須提供足以 克服前述燃燒室内之氣體壓力，否則若是以電動馬達啟動 而言’則電動馬達必須設計成馬力較大而無法小型化；又 若是以人工施力啟動，例如在需踩踏以發動機車引擎之場 合’則會導致踩踏不易而增加使用者之負擔。 為了針對上述壓力問題，目前某些内燃機會裝設所謂 之減壓裝置，其係可減少内燃機於啟動之壓力，以避免上 述問題之產生。 眾所周知，為了降低上述壓縮壓力問題，某些引擎會 201139906 裝設離合式減壓裝置，藉由凸輪軸轉動時離心配重塊所產 生的離心力大小以在特定轉速内時控制減壓裝置為有減壓 作用’而在此特定轉速以上則失去減壓效果。 習知之減壓裝置大多是以多連桿設計者，例如有習知 技術是採用連桿機構來驅動減壓凸輪以達到引擎減壓目 的°上述習知之減壓裝置可見於日本公開特許公報特開 2006-144627號所揭露之減壓裝置’該減壓裝置機構複雜、 傳動支點過多故而定位性不佳，且因設置於凸輪軸末端， 需使用較長之軸構件，不利於整體尺寸小型化。 【發明内容】 本發明之引擎減壓機構包括一凸輪軸、一本體、一離 心配重塊、一彈性件、以及一減壓桿。上述凸輪轴固設有 一閥動凸輪’本體是固設於凸輪軸。 上述離心配重塊滑設於本體，包括有一第一齒部。彈 性件一端抵頂於離心配重塊而沿平行於離心配重塊滑動之 方向施予一預力。 上述減壓桿包括有一凸輪部、及一第二齒部，其中第 一齒部喃合於第一齒部，且凸輪部伴隨離心配重塊之滑動 而轉動’以選擇式發揮減壓功能。 藉由上述機構設計，減壓機構之離心配重塊除了以新 穎而有別於習知轉動之方式驅動減壓桿，即滑動運動’齒 輪傳動機構之運用亦較習知連桿傳動機構具有設計簡單之 優點’同時可藉由齒輪傳動機構的尺寸配置關係達成離心 201139906 配重塊移動小距離即能使減壓桿轉動所需要的角度，輕易 達成縮小機構整體尺寸及裝置空㈣目的。此外，利用本 發明更可貫現更少零件數、組件配置不受限之目的。 上述本體可軸向貫設有—穿孔，減壓桿穿過穿孔以避 免任意移位。上述彈性件可為-彈簧。本體可軸向突伸有 一谷置座以收容彈性件。上述容置座可具有一 L型側壁，且 離心配重塊可更包括有一滑動部係抵靠滑行於L型側壁。 上述凸輪軸可於末端包括有一驅動輪’凸輪軸上可更 包括有一第一轴承係介於驅動輪與本體之間。凸輪軸上可 更包括有一第二軸承係位於與驅動輪相反之另一末端。 引擎減壓機構可更包括有一蓋板係與本體共同軸向拘 束離心配重塊。 【實施方式】 參考圖1〜3 ’分別為一實施例之機車引擎剖視圖、減壓 機構分解圖、及減壓機構剖視圖。圖丨示出一機車之引擎結 構，機車引擎主要包括依序連結之一汽缸頭u、一汽缸體 12、及一曲軸箱13。一汽缸頭上蓋14結合於汽缸頭丨丨頂部， 一汽缸頭側蓋15結合於汽缸頭n側旁。一減壓機構（包含凸 輪軸2 1 ) ax置於 > 飞缸頭1 1内部，一活塞連桿組1 6設置於汽缸 體12内部，一曲柄機構17設置於曲軸箱13内部，曲柄機構 17並連結於一傳動機構18以將旋轉動力傳遞出去。 減壓機構除上述凸輪軸21外，更包括有一本體24、一 離心配重塊25、一彈性件26、一減壓桿27、以及一蓋板28。 201139906 凸輪轴21上一體地形成有二閥動凸輪22,23，負貴頂推對庳 之搖臂32,33 ’進而使排氣閥門與進氣閥門（圖未示）產生位 移。凸輪軸21於末端固設有一驅動輪31，透過一傳動件34 如鍊條接收來自曲柄機構17之動力，令凸輪轴21同步轉動。 本體24於約略中央位置挖設有一固定孔245，本體24 即疋以固定孔245套固於凸輪轴21。此外，本體24還包括有 一軸向凸起之容置座241、一平直之第一抵靠部244、及— 穿孔246 ’其中容置座241塑形成具有凹槽242之結構以收容 前述彈性件26，容置座241並具有一L型側壁作為一第二抵 靠部243。本例中彈性件26係一彈簧。 離心配重塊25包括有一第一齒部25 1、一第一滑動部 252、及一L型第二滑動部253，其中第一滑動部252可對應 抵靠滑行於本體24之第一抵靠部244，第二滑動部253可對 應抵靠滑行於本體24之第二抵靠部243。第二滑動部253上 更形成有一受力端254係延伸入凹槽242而與彈性件26 —端 相接’彈性件26另一端則抵頂於本體24。 減壓桿27前端呈圓柱狀且環周設有一第二齒部272與 離心配重塊25之第一齒部251相嚙合，其後端則塑形成一凸 輪部271 ’例如一半月形截面結構。減壓桿27並以凸輪部271 穿過本體24之穿孔246。透過相嚙合之二齒部251，272,減壓 桿27可受離心配重塊25驅動。 蓋板28組設於離心配重塊25旁，與本體24 —起將離心 配重塊25夾於中間’具有防止離心配重塊25及彈性件26軸 向脫離之功能。 201139906 此外’於蓋板28旁再組設有一第一轴承29，於最外側 之閥動凸輪23旁組設有一第二軸承30，第二軸承3〇與驅動 輪31分別位於凸輪軸相反之兩末端。 參考圖4與圖5。當機車引擎低於特定轉速或停止運轉 時，離心配重塊25因彈性件26之施力而致受力端254朝凹槽 242外部移動。此時藉由相嚙合之二齒部251，272，減壓桿” 樞轉至一第一位置，亦即凸輪部271高於閥動凸輪22基圓之 狀態，如圖中標示之高度差Η，因此可將搖臂32上頂，發揮 引擎減壓作用。另一方面，經適當形體設計可使離心配重 塊25於此階段卡抵於本體24，不須擔心徑向脫出之情形。 圖中箭頭所示為離心配重塊25之移動方向。 參考圖6與圖7。當機車引擎運轉至一特定轉速以上 時，離心配重塊25所受離心力使其足以抵抗彈性件％之施 力而致受力端254朝凹槽242内部移動。此時藉由相嚙合之 一齒部251，272，減壓桿27樞轉至一第二位置，亦即凸輪部 27他於閥動凸輪22基圓之狀態，並未將搖臂32上頂，無引 籲$減壓作用。同樣地，離心配重塊25於此階段亦設計為卡 抵於本體24而不會徑向脫出。圖中箭頭所示為離心配重塊 25之移動方向。 上述可知，本發明之機構設計使得離心配重塊以苴 滑動部抵靠滑行於本體之抵靠部，進而透過齒輪齒條運動 之原理控制減壓桿轉動，以選擇式發揮引擎減壓作用。 構整優點在於可縮短轴件所需長度，有效縮小機 尺寸’並且所用零件較習知少、也因此組裝步驟減 201139906 少 ο ’本發明所 而非僅限 上述實施例僅係為了方便說明而舉例而已 主張之權利範圍自應以申請專利範圍所述為準 於上述實施例。 【圖式簡單說明】 圖1係本發明一較佳實施例之機車引擎剖視圖。 圖2係本發明一較佳實施例之減壓機構分解圖。 圖3係本發明一較佳實施例之減壓機構剖視圖。 圖4係引擎減壓作用下減壓機構前視圖。 圖5係引擎減壓作用下減壓機構後視圖。 圖6係引擎無減壓作用下減壓機構前視圖。 圖7係引擎無減壓作用下減壓機構後視圖。 汽缸體12 汽缸頭上蓋14 活塞連桿組16 傳動機構18 閥動凸輪22,23 容置座241 第二抵靠部243 固定孔245 離心配重塊25 【主要元件符號說明】 汽缸頭11 曲軸箱13 汽缸頭側蓋15 曲柄機構17 凸輪軸21 本體24 凹槽242 第一抵靠部244 穿孔246 201139906 第一齒部251 第二滑動部253 彈性件26 凸輪部271 蓋板28 第二軸承30 搖臂32,33 第一滑動部252 受力端254 減壓桿27 第二齒部272 第一軸承29 驅動輪31 傳動件34201139906 VI. Description of the Invention: [Technical Field] The present invention relates to an engine decompression mechanism, and more particularly to an engine decompression mechanism actuated by the #^ rack motion principle. [Prior Art] When the engine is turned off, Because the crankshaft is subjected to the inertia of the rotating motion, the engine will continue to rotate a number of revolutions. During this process, there are many impedances that cause the rotation to gradually slow down and finally stop. The largest impedance is the compression pressure of the compression stroke, so the engine is often subjected to the compression pressure to cause the normal rotation to stop and then reverse, and then stop. When the internal combustion engine is to be restarted, the piston in the cylinder moves toward the combustion chamber. [At this time, the intake valve of the intake valve connecting rod and the exhaust valve of the exhaust valve connecting rod are both closed, so the piston moves. At this time, the pressure of the compressed gas in the combustion chamber must be overcome to complete the movement of the remaining portion. That is, whether it is started by an electric motor or manually applied, it must provide sufficient gas pressure to overcome the pressure in the combustion chamber. Otherwise, if the electric motor is started, the electric motor must be designed to have a large horsepower and cannot be miniaturized. If it is started by manual force, for example, when it is necessary to step on the engine of the engine car, it will cause the pedaling to be difficult and increase the burden on the user. In order to address the aforementioned pressure problems, some internal combustion engines are currently equipped with a so-called pressure reducing device which reduces the pressure of the internal combustion engine at the start to avoid the above problems. As we all know, in order to reduce the above compression pressure problem, some engines will install a clutch type decompression device in 201139906. By controlling the centrifugal force generated by the centrifugal weight when the camshaft rotates, the pressure reducing device is controlled at a certain speed. The pressure action 'has lost the pressure reduction effect above this specific speed. Conventionally, the pressure reducing device is mostly a multi-link designer. For example, it is a conventional technique that uses a link mechanism to drive a pressure reducing cam to achieve engine decompression. The above-mentioned conventional pressure reducing device can be found in the Japanese public notice. The pressure reducing device disclosed in No. 2006-144627 has a complicated mechanism and a large number of transmission fulcrums, and the positioning property is poor, and since it is disposed at the end of the cam shaft, a long shaft member is required, which is disadvantageous for miniaturization of the overall size. SUMMARY OF THE INVENTION The engine pressure reducing mechanism of the present invention includes a cam shaft, a body, a centrifugal weight, an elastic member, and a pressure reducing rod. The cam shaft is fixedly provided with a valve cam. The body is fixed to the cam shaft. The centrifugal weight is slidably disposed on the body and includes a first tooth portion. One end of the elastic member abuts against the centrifugal weight and applies a preload in a direction parallel to the sliding of the centrifugal weight. The pressure reducing lever includes a cam portion and a second tooth portion, wherein the first tooth portion is coupled to the first tooth portion, and the cam portion is rotated by sliding of the centrifugal weight to perform a pressure reducing function in a selective manner. According to the above mechanism design, the centrifugal weight of the pressure reducing mechanism drives the pressure reducing rod in a novel and different manner from the conventional rotation, that is, the sliding motion 'gear transmission mechanism is also designed according to the conventional linkage transmission mechanism. The advantage of simplicity is that the centrifugation can be achieved by the size configuration of the gear transmission mechanism. 201139906 The distance required for the weight to move the weight can be easily reduced to reduce the overall size of the mechanism and the device (4). In addition, with the present invention, it is possible to achieve a smaller number of parts and an unrestricted component configuration. The body may be axially provided with a perforation, and the pressure reducing rod passes through the perforations to avoid any displacement. The above elastic member may be a spring. The body can axially project with a valley seat to receive the elastic member. The accommodating seat may have an L-shaped side wall, and the centrifugal weight may further include a sliding portion that abuts against the L-shaped side wall. The camshaft may include a drive wheel at the end. The camshaft may further include a first bearing between the drive wheel and the body. The camshaft may further include a second bearing system at the other end opposite the drive wheel. The engine decompression mechanism may further include a cover system that axially constrains the centrifugal weight together with the body. [Embodiment] Referring to Figs. 1 to 3', respectively, a cross-sectional view of a locomotive engine, an exploded view of a decompression mechanism, and a cross-sectional view of a pressure reducing mechanism of an embodiment are shown. The figure shows the engine structure of a locomotive. The locomotive engine mainly includes a cylinder head u, a cylinder block 12, and a crankcase 13 in sequence. A cylinder head upper cover 14 is coupled to the top of the cylinder head cymbal, and a cylinder head side cover 15 is coupled to the cylinder head n side. A pressure reducing mechanism (including the cam shaft 2 1 ) ax is placed inside the flying cylinder head 1 1 , a piston connecting rod set 16 is disposed inside the cylinder block 12 , and a crank mechanism 17 is disposed inside the crankcase 13 , and the crank mechanism 17 is coupled to a transmission mechanism 18 to transmit rotational power. The pressure reducing mechanism further includes a body 24, a centrifugal weight 25, an elastic member 26, a pressure reducing lever 27, and a cover plate 28 in addition to the cam shaft 21. 201139906 The camshaft 21 is integrally formed with two valve cams 22, 23, and the rocker arms 32, 33' of the counter-pushing pair aligning the exhaust valve with the intake valve (not shown). The cam shaft 21 is fixed at the end with a driving wheel 31, and receives power from the crank mechanism 17 through a transmission member 34 such as a chain, so that the cam shaft 21 rotates synchronously. The body 24 is dug with a fixing hole 245 at a substantially central position, and the body 24 is fastened to the cam shaft 21 by a fixing hole 245. In addition, the body 24 further includes an axially convex receiving seat 241, a straight first abutting portion 244, and a through hole 246'. The receiving seat 241 is shaped to have a recess 242 to accommodate the aforementioned elasticity. The member 26 has a receiving seat 241 and has an L-shaped side wall as a second abutting portion 243. In this example, the elastic member 26 is a spring. The centrifugal weight 25 includes a first tooth portion 25 1 , a first sliding portion 252 , and an L-shaped second sliding portion 253 , wherein the first sliding portion 252 can abut against the first abutting of the body 24 . The second sliding portion 253 can correspond to the second abutting portion 243 that slides on the body 24 . The second sliding portion 253 is further formed with a receiving end 254 extending into the recess 242 to be in contact with the end of the elastic member 26. The other end of the elastic member 26 abuts against the body 24. The front end of the pressure reducing rod 27 has a cylindrical shape and a second tooth portion 272 is circumferentially engaged with the first tooth portion 251 of the centrifugal weight block 25, and a rear end portion thereof is molded with a cam portion 271' such as a half moon-shaped cross-sectional structure. . The pressure reducing lever 27 passes through the through hole 246 of the body 24 with the cam portion 271. The pressure reducing lever 27 is driven by the centrifugal weight 25 through the meshing teeth 251, 272. The cover plate 28 is disposed beside the centrifugal weights 25, and sandwiches the centrifugal weights 25 together with the body 24 to have a function of preventing the centrifugal weights 25 and the elastic members 26 from being axially disengaged. 201139906 In addition, a first bearing 29 is further disposed beside the cover plate 28, and a second bearing 30 is disposed beside the outermost valve cam 23, and the second bearing 3〇 and the driving wheel 31 are respectively located opposite to the cam shaft. End. Refer to Figures 4 and 5. When the locomotive engine is below a certain rotational speed or is stopped, the centrifugal weight 25 is moved toward the outside of the recess 242 by the biasing force of the elastic member 26. At this time, by the meshing two tooth portions 251, 272, the pressure reducing lever" is pivoted to a first position, that is, the cam portion 271 is higher than the base circle of the valve cam 22, as indicated by the height difference in the figure Η Therefore, the rocker arm 32 can be topped to exert the engine decompression effect. On the other hand, the appropriate weight design can cause the centrifugal weight 25 to be stuck to the body 24 at this stage without worrying about the radial escape. The arrows in the figure show the direction of movement of the centrifugal weight 25. Referring to Figures 6 and 7, when the locomotive engine is operated above a certain speed, the centrifugal weight 25 is subjected to centrifugal force sufficient to resist the elastic member. The force receiving end 254 moves toward the inside of the recess 242. At this time, by the one tooth portion 251, 272 that is engaged, the pressure reducing lever 27 is pivoted to a second position, that is, the cam portion 27 is on the valve cam In the state of 22 base circles, the rocker arm 32 is not topped, and no decompression is applied. Similarly, the centrifugal weight 25 is also designed to be stuck against the body 24 at this stage without radially coming off. The arrows in the figure show the direction of movement of the centrifugal weights 25. As can be seen from the above, the mechanism of the present invention is designed to The weight of the weight is controlled by the sliding portion of the sliding portion against the abutting portion of the body, and then the rotation of the reducing rod is controlled by the principle of the movement of the rack and pinion to selectively decompress the engine. The advantage of the structure is that the shaft member can be shortened. Length, effectively reducing the size of the machine' and using fewer parts, and therefore the assembly steps are less than 201139906. The present invention is not limited to the above-described embodiments, but the scope of the claims has been claimed for the sake of convenience of description. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a locomotive engine according to a preferred embodiment of the present invention. FIG. 2 is an exploded view of a pressure reducing mechanism according to a preferred embodiment of the present invention. 3 is a cross-sectional view of a pressure reducing mechanism according to a preferred embodiment of the present invention. Fig. 4 is a front view of the pressure reducing mechanism under decompression of the engine. Fig. 5 is a rear view of the pressure reducing mechanism under decompression of the engine. Front view of the decompression mechanism under action. Figure 7 is a rear view of the decompression mechanism under no pressure reduction of the engine. Cylinder block 12 Cylinder head cover 14 Piston rod set 16 Transmission mechanism 18 Valve cam 22, 23 241 second abutment 243 fixing hole 245 centrifugal weight 25 [main component symbol description] cylinder head 11 crankcase 13 cylinder head side cover 15 crank mechanism 17 camshaft 21 body 24 groove 242 first abutment portion 244 perforation 246 201139906 First tooth portion 251 Second sliding portion 253 Elastic member 26 Cam portion 271 Cover plate 28 Second bearing 30 Rocker arm 32, 33 First sliding portion 252 Force end 254 Reducing rod 27 Second tooth portion 272 First Bearing 29 drive wheel 31 transmission member 34