【正文】 e side of the block. To check the oil lever in the open pan, the dipstick can be pulled out and the height of the oil on the stick noted. Oil can then be added if the oil lever is too low for adequate engine protection.In general, the lubrication system of an automotive engine apart from the lubricating passages also contains a reservoir (called the oil pan, sump, or crankcase) to hold the oil supply, a pump to develop pressure, and the valves for controlling flow and pressure etc.The oil pumps are of the positive displacement type in several designs. Vanes, plungers, rotors and gears are all used to build up the necessary pressure. The pumps of gear and rotor types are always positively driven, usually from the camshaft either by means of gears or cams.The oil pump in tractor engine is driven from a gear on the nose of the crankshaft。 while in automobile engines, it is driven from a gear made integral with the camshaft.To remove mechanical impurities from the oil circulating through the engine lubrication system, the oil filter is used. The oil filter can filter dirt and solids out of the oil in lubrication system. As these particles of foreign matter are prevented from entering the engine by oil filter, the rate of wear of engine parts is reduced. Engines of more recent designs use a fullflow centrifugal oil filter. That is, all oil passes through the filter before it reaches the bearings. This is a reactiontype centrifugal filter with which all oil delivered by the oil pump is cleaned in the filter rotor. This filter has an oil outlet pipe fitted inside the hollow spindle of the filter rotor and connected to the oil line that distributes the oil to the various parts of the lubrication system.In centrifugal oil filters the rotor consists of a body and a bowl. The surface area of the rotor top is greater than that of the bottom, because the diameter of the upper journal of the spindle is greater than that of the lower journal. The total oil pressure force acting on the top from below is greater than the force acting on the bottom. Therefore, when the engine is running。 the rotor is lifted and its bearing end face is thus relived. The higher the pressure in the rotor, the greater the distance the rotor is lifted through.The thrust washer keeps the maximum lift of the rotor within to mm. However, in the event the filter gets clogged or obstructed, a bypass valve is provided so that oil will continue to reach the bearings.The oil pressure relief valve is mainly to act both as a pressure regulator and as a safety device in lubrication system. As a pressure regulator, the valve prevents the oil pump from building up excessive pressure. When the oil passages of the rise too high, the relief valve will drain the excess filtered oil into the engine crankcase. As a safety device, the valve is set by the adjusting screw to secure the oil circulation through engine parts under proper pressure.發(fā)動機潤滑系統(tǒng) 如果不借助于摩擦，汽車就不能自動行駛，然而過度的摩擦就意味著迅速損毀。當(dāng)然，我們不可能消除摩擦，但可以使用潤滑油來大幅度減少摩擦，從而使汽車能夠利用適當(dāng)?shù)哪Σ疗椒€(wěn)行駛。 發(fā)動機的潤滑主要是通過潤滑油的流動實現(xiàn)的，在潤滑系統(tǒng)中潤滑油的作用是：首先，在金屬表面形成保護油膜以防止金屬與金屬直接接觸，從而減少摩擦、降低磨損。其次，當(dāng)潤滑油到達發(fā)動機各運動零部件時，吸收并帶走零部件的熱量。第三，潤滑油經(jīng)過發(fā)動機運動部件循環(huán)流動，會沖刷機件表面的污物。最后，發(fā)動機內(nèi)軸承和其他機件間的潤滑油還吸收運動產(chǎn)生的沖擊，而缸壁和活塞環(huán)之間的潤滑油則加強了密封。 發(fā)動機潤滑系統(tǒng)分為兩種形式:飛濺和壓力潤滑。在飛濺潤滑系統(tǒng)中，連桿蓋下部有一油勺，曲軸每轉(zhuǎn)圈。油勺插入淺盤式油底殼一次。油勺運動將機油甩向發(fā)動機上方的部件，這樣給配氣機構(gòu)、汽缸壁、活塞環(huán)和軸承提供足夠的潤滑。 飛濺潤滑是一種簡單的潤滑萬式，只有當(dāng)油底殼的機油平面保持一定高度，不能過高或過低，且發(fā)動機保持水平時才能保證潤滑。 除了簡單潤滑和飛濺潤滑外，發(fā)動機大都采用壓力潤滑，壓力潤滑的特點是機油在機油泵的壓力作用下被送到發(fā)動機主要部件，特別是主軸承和連桿軸承。 現(xiàn)代發(fā)動機通常結(jié)合飛濺和壓力潤滑兩種方式。機油泵產(chǎn)生壓力，把機油送到濾清器實現(xiàn)清潔，然后被送到發(fā)動機上部的凸輪軸和氣門組件。其他零部件通過飛濺和油路網(wǎng)實現(xiàn)潤滑。 無論何種類型的潤滑系統(tǒng)，都要向所有運動零部件提供足夠的機油，而機油具有各種作用。在大負荷發(fā)動機中，機油工作 (條件)更苛刻，溫度更高，因此潤滑系統(tǒng)中包括機油散熱器。機油散熱器的結(jié)構(gòu)與冷卻系的散熱器相似，流經(jīng)機油散熱器后機油得到了冷卻。所有發(fā)動機都有某種類型的指示機油液面的裝置，通常為從缸體側(cè)面伸進曲軸箱的機油標(biāo)尺。檢查機油液面高度時，取出機油標(biāo)尺，(從機油標(biāo)尺上)可以看到油液面高度。若液面過低，必須添加機油，以保證發(fā)動機的潤滑。 總之，汽車發(fā)動機潤滑系除油道外，還包括儲存機油的油底殼、產(chǎn)生壓力的機油泵和控制油路和油壓的閥類等。 容積式機油泵一般有幾種不同的類型，采用葉輪、柱塞、轉(zhuǎn)子或齒輪來建立所需要的壓力。齒輪泵和轉(zhuǎn)子泵要通過齒輪或凸輪，由凸輪軸強制驅(qū)動。 拖拉機的發(fā)動機機油泵由曲軸前端的齒輪驅(qū)動，而在汽車上，機油泵由與凸輪軸一體的齒輪帶動。 采用機油濾清器來過濾掉機油中的機械雜質(zhì)。機油濾清器可以去除機油中的污物及固體顆粒。這樣機油濾清器就阻止了有害雜質(zhì)進入發(fā)動機，發(fā)動機零部件的磨損率就下降了。新型發(fā)動機大多采用全流式離心濾清器。也就是說，在進入發(fā)動機軸承前機油先要經(jīng)過濾清器。在反力式離心濾清器中，機油泵壓送的所有機油在轉(zhuǎn)子中被濾清。濾清器的出油口在空心轉(zhuǎn)子軸內(nèi)并與油路相通，從而把機油分配到不同的零部件。 離心式濾清器的轉(zhuǎn)子由轉(zhuǎn)子體和轉(zhuǎn)子碗形容器組成。因為轉(zhuǎn)子軸的軸頸上面要比下面大，所以轉(zhuǎn)子蓋的上表面比下表面大，作用于上萬的機油壓力大于下方。因此發(fā)動機工作時，轉(zhuǎn)子被提升，轉(zhuǎn)子軸承端面的壓力減小。轉(zhuǎn)子內(nèi)壓力越高，轉(zhuǎn)子被提升所經(jīng)過的距離越長。 ～。當(dāng)濾清器堵塞時，旁通閥會起作用，使機油仍然到達軸承。 卸壓閥就是既作為機油壓力調(diào)節(jié)器又作為潤滑系統(tǒng)的安全裝置。作為機油壓力調(diào)節(jié)器，它防止機油泵產(chǎn)生過大的壓力。當(dāng)油路中機油壓力過大時，卸壓閥打開，多余的經(jīng)過濾清的機油流回曲軸箱。作為安全裝置，可以通過調(diào)整螺釘來設(shè)定卸壓閥，從而保證潤滑系統(tǒng)在一定壓力下正常工作。14 / 14