汽车专业英语课件3chapter2425.ppt
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1、复习o 提问(教师说发动机汉语部件名称,同学回答英文名称)o 用英语说明内燃机分类方式和类别o What are four strokes in a four-stroke-cycle engine?学习内容学习内容本次课学习内容、目标和重点难点本次课学习内容、目标和重点难点学习目标学习目标难点重点难点重点2.4 Pistons,Connecting Rods and 2.4 Pistons,Connecting Rods and CrankshaftCrankshaft2.5 Valve System2.5 Valve System1.1.掌握曲柄连杆机构主要组成、零件英文名掌握曲柄连杆机构
2、主要组成、零件英文名称;称;2.2.了解了解VVTVVT系统的主要功能系统的主要功能1.1.重点为记忆曲柄连杆机构主要组成、零件重点为记忆曲柄连杆机构主要组成、零件英文专业术语英文专业术语2.2.难点需要记忆的生词偏多难点需要记忆的生词偏多3.3.汉译准确表达也是难点汉译准确表达也是难点Chapter 2 Internal Combustion Engine2.4 Pistons,Connecting Rods and Crankshaft bearingbrin.轴承轴承journal:nln.轴颈轴颈throwroun.&v.投掷,扔;投掷,扔;n.投掷距离,偏心投掷距离,偏心距离,摆幅;
3、(距离,摆幅;(pl.)曲柄)曲柄attachttv.附着,连接,固定(附着,连接,固定(to)reciprocatingrisiprkeitia.往复的往复的2.4.1 New Words and Phrases 2.4.1 Piston and connecting rodThe piston must move down through the cylinder to produce a vacuum to draw a fuel charge into the cylinder.It then travels up in the cylinder and compresses the
4、mixture.When the mixture is fired,the pressure of the expanding gas is transmitted to the top of the piston.This drives the piston back down through the cylinder with great force,transmitting the energy of the expanding gas to the crankshaft.The piston then travels up through the cylinder and exhaus
5、ts the burned fuel charge.Pistons are usually made of aluminum.Often,aluminum pistons are tin-plated to allow proper break-in when the engine is started.Aluminum pistons can be forged,but they are more commonly cast.Cast iron is a good material for pistons used in a slow-speed engine.It has excellen
6、t wear characteristics and will provide good performance.Chapter 2 Internal Combustion Engine2.4 Pistons,Connecting Rods and Crankshaft 2.4.2 TextFig.2-5 Pistons,connecting rods and crankshaft As the name implies,connecting rods are used to connect pistons to the crankshaft(Fig.2-5).The upper end of
7、 the rod has a hole through it for the piston pin.The bottom of the large end of the connecting rod(Fig.2-6)must be removed so the rod can be installed on the crankshaft journal.The section that is removed is called the connecting rod cap.Connecting rods are normally made of alloy steel.They are dro
8、p-forged to shape and then machined.Fig.2-6 Connecting rodChapter 2 Internal Combustion Engine2.4 Pistons,Connecting Rods and Crankshaft 2.4.2 Crankshaft The engine crankshaft(Fig.2-7)provides a constant turning force to the wheels.It has throws to which connecting rods are attached,and its function
9、 is to change the reciprocating motion of the piston to a rotary motion to drive the wheels.Crankshafts are made of alloy steel or cast iron.The crankshaft is held in position by a series of main bearings.The maximum number of main bearings for a crankshaft is one more than the number of cylinders.I
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