汽车专业英语3 Chapter 2.4-2.5
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2.4.1 New Words and Phrases bearing journal throw attach ['bεəriŋ] ['ʤə:nəl] [θrou] [ə'tæt∫] n.轴承 n.轴颈 n.& v.投掷，扔；n.投掷距离，偏心 距离，摆幅；（pl.）曲柄 v.附着，连接，固定（to）
Fig.2-5 Pistons, connecting rods and crankshaft
Chapter 2 Internal Combustion Engine 2.4 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 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 drop-forged to shape and then machined.
复习
提问（教师说发动机汉语部件名称，同学回 答英文名称） 用英语说明内燃机分类方式和类别
What are four strokes in a four-strokecycle engine?
本次课学习内容、目标和重点难点
学习内容
2.4 Pistons, Connecting Rods and Crankshaft 2.5 Valve System
学习目标
1.掌握曲柄连杆机构主要组成、零件英文名 称； 2.了解VVT系统的主要功能 1.重点为记忆曲柄连杆机构主要组成、零件 英文专业术语 2.难点需要记忆的生词偏多 3.汉译准确表达也是难点
难点重点
Chapter 2 Internal Combustion Engine
2.4 Pistons, Connecting Rods and Crankshaft
Fig.2-6 Connecting rod
Chapter 2 Internal Combustion Engine 2.4 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 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. It may have fewer main bearings than cylinders.
reciprocating [ri'siprəkeit a.往复的 iŋ]
Chapter 2 Internal Combustion Engine 2.4 PLeabharlann Baidustons, Connecting Rods and Crankshaft
2.4.2 Text 2.4.1 Piston and connecting rod The 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 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 exhausts 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 excellent wear characteristics and will provide good performance.
Fig.2-5 Pistons, connecting rods and crankshaft
Chapter 2 Internal Combustion Engine 2.4 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 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 drop-forged to shape and then machined.
复习
提问（教师说发动机汉语部件名称，同学回 答英文名称） 用英语说明内燃机分类方式和类别
What are four strokes in a four-strokecycle engine?
本次课学习内容、目标和重点难点
学习内容
2.4 Pistons, Connecting Rods and Crankshaft 2.5 Valve System
学习目标
1.掌握曲柄连杆机构主要组成、零件英文名 称； 2.了解VVT系统的主要功能 1.重点为记忆曲柄连杆机构主要组成、零件 英文专业术语 2.难点需要记忆的生词偏多 3.汉译准确表达也是难点
难点重点
Chapter 2 Internal Combustion Engine
2.4 Pistons, Connecting Rods and Crankshaft
Fig.2-6 Connecting rod
Chapter 2 Internal Combustion Engine 2.4 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 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. It may have fewer main bearings than cylinders.
reciprocating [ri'siprəkeit a.往复的 iŋ]
Chapter 2 Internal Combustion Engine 2.4 PLeabharlann Baidustons, Connecting Rods and Crankshaft
2.4.2 Text 2.4.1 Piston and connecting rod The 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 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 exhausts 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 excellent wear characteristics and will provide good performance.