【導(dǎo)讀】發(fā)動(dòng)機(jī)的潤(rùn)滑系統(tǒng)是保證發(fā)動(dòng)機(jī)正常運(yùn)轉(zhuǎn)的依據(jù)。潤(rùn)滑系的基本任務(wù)就是將潤(rùn)滑油不。斷地供給各零件的摩擦表面使其潤(rùn)滑，減少零件的摩擦和磨損。功能轉(zhuǎn)換，卻能保證發(fā)動(dòng)機(jī)正常工作，使其具有較長(zhǎng)的使用壽命。通過對(duì)發(fā)動(dòng)機(jī)潤(rùn)滑系故。見故障現(xiàn)象，故障部位，故障機(jī)理，故障的分析檢測(cè)和維修及故障排除有了一定的認(rèn)識(shí)，明確了分析檢測(cè)和診斷的基本思路。的常見組成和功用及故障檢測(cè)與為維修做了相應(yīng)說明。隨著汽車科技的發(fā)展，汽車的結(jié)構(gòu)。地查找汽車的故障原因，并把故障排除。

　　

【正文】 nd the cylinder wall. Compression rings are used as a gas seal and the oil ring is used to prevent excess oil from finding its way up past the piston into the bustion chamber. The connecting rod has a removable cap and a split bearing at its lower end where it is connected to the crankshaft. Its upper has a piston pin that provides a wristtype of action with the piston. Because of its action, the piston pin is sometimes referred to as a wrist pin. The cylinder head is made of cast aluminum alloy. It is bolted to the top of the cylinder block so that it encloses the cylinders. It has bustion chambers above the cylinders in which the airfuel mixture is burnt. Cylinder heads can be made of cast iron, which is more resistant to corrosion, but aluminum alloy is used for petrol engines because it has advantages of better heat transfer and lighter weight. The cylinder head has intake ports and exhaust ports. The intake valves open the intake ports to admit the fuel charge into the cylinder during the intake stroke. The exhaust valves open the exhaust ports to allow the burnt gases to leave the cylinder following the exhaust stroke. The camshaft and the valve mechanism are used to open and close the valves at the correct time. The camshaft is driven from the crankshaft at half the crankshaft speed. The valve cover, also called the cylinderhead cover, is fitted to the top of the cylinder head. This encloses the valve mechanism. An additional cover on top of the engine covers the ignition coils. This cylinderhead arrangement, for a fourcylinder engine, has two camshafts and sixteen valves. Other fourcylinder engines can have two camshafts and twelve valves, or one camshaft and eight valves. The timing belt and pulleys drive the camshaft at half the crankshaft speed ( engine speed ). A toothed drive belt is often used, but gears and chains are also usedin some instances a belt and chain are both used. On some engines, the timing chain is used to drive the oil pump. On diesel engines, a timing chain or a timing gear is used to drive the injection pump as well as the camshaft. The oil pan, or sump, holds the oil for the engine lubricating system. The oil pan is made of steel that has been pressed to shape. Other oil pans are made of aluminum alloy that has been cast to shape. The oil pan is bolted to the underside of the engine so that it closes off the crankcase. Only the ends of the crankshaft that extend beyond the cylinder block are exposed. 21 Various forms of gaskets and seals are used between the surfaces where the parts are bolted together. Some of these are used to seal against oil, some against coolant and some against heat and pressure. Some provide a seal on flat surfaces, other seal against rotating shafts. As well as the larger parts of an engine, there are numerous small parts. These include bolts, washers, retainers, spring and brackets which go to make up the mechanical ponents of the engine. ３ . Engine Systems The engine systems that enable the engine to start and to continue to operate are as follows: (1) Starting system。 (2) Fuel system。 (3) Ignition system。 (4) Cooling system。 (5) Lubricating system。 (6) Intake system。 (7) Exhaust system。 (8) Charging system。 (9) Engine’s electronic control system. These are the systems for petrol engines. Diesel engines have similar systems except for the fuel and ignition systems. Some parts of the systems are built into the engine, some parts are attached to the engine and other parts are located on the body panels in the engine partment. Starting system The starter is used to rotate the engine during starting. It consists of an electric motor and a drive. The drive has a small pinion that meshes with the ring gear on the flywheel during starting. The battery supplies the electrical energy to operate the starter and rotate the engine until it fires and runs on its own. Fuel system These are four basic types of fuel systems: carburetor systems for petrol engines, fuel injection systems for petrol engines, gas fuel systems ( LPG or NGV ), and diesel injection systems. All these systems operate in different ways, but they all have somewhere to store fuel ( a fuel tank or a cylinder ) and a way of supplying the engine with the fuel. They also have a way of supplying air and fuel mixed in the correct proportion so that it can be effectively burn in the bustion chambers. Ignition system Petrol engines and engines operating on gas require an ignition system. This is needed to provide the sparks that fire the charges in the bustion chambers. For this reason, petrol engines are sometimes referred to as sparkignition engines. This distinguishes them from them diesel engines that do not need a spark because they use pression ignition. Combustion in a diesel occurs when the fuel is sprayed into the bustion chamber. The air in the cylinder is at high temperature from being pressedhigh enough to ignite the fuel 22 that is sprayed from the injector. Cooling system A considerable amount of heat is produced in an engine by the burning airfuel mixture. Some of the heat is used to do useful work, some is transferred to other parts of the engine and some is carried away with exhaust gases. However, there is still enough heat to cause damage unless it is removed. This is still the function of the cooling system, which removes about onethird of the heat that is produced. The cooling system does not just remove heat。 it maintains the engine at a desirable operating temperature. In a liquidcooled engine, this is done by circulating coolant through the waterjackets. In an aircooled engine, cooling is by air over cooling fins. Lubricating system The enginelubricating system consists of an oil pump, a relief valve and a filter。 also pipes, passages and drillings in various p