汽车专业英语课件与汽车专业英语读译教程2版配套3U2TB.ppt

 UNIT 2 ENGINE MECHANICAL TEXT B Valve Systems UNIT 2 ENGINE MECHANICAL TEXT B Valve Systems ? Operation of Valve System ? VVT—Toyotas Continuously Variable Valve Timing  ? VTEC—Honda Variable Valve Timing and Lift Electronic Control ? MIVEC—Mitsubishi Innovative Valve timing Electronic Control  ? Electronic Valve Control System ? Smart Valves 本次课学习目标 掌握可变气门定时机构主要部件的英文名称 掌握可变气门定时机构的基本原理 掌握常用术语（phrases and expressions） 了解相关术语（related terms） NEW WORDS nominal [n?minl] a. 有名无实的；极微小的；标定的，额 定的 bus [b?s] n.总线 innovation [inouvei∫?n] v.改进，革新，创新，新发明[技术，方法] residual [rizidju?l] a.剩余的，残余的 When the camshaft is turn, the lobes will not even touch the valve stem. The lifter is installed between the cam lobe and the valve stem. The upper end rides on the lobe and the lower end almost touches the valve stem. The lifter slides up and down in a hole bored in the head metal that separates the valve stem from the camshaft [2]. You have developed a method of opening and closing the valves. The next problem is how and at what speed to turn the camshafts. Each valve must be open for one stroke. The intake valve is open during the intake stroke and remains closed during the compression, power, and exhaust strokes. This would indicate that the cam lobe must turn fast enough to raise the valve every fourth stroke. You can see that it takes one complete revolution of the cam lobe for every four strokes of the piston. Remember that four strokes of the piston require two revolutions of the crankshaft. You can say that for every two revolutions of the crankshaft, the camshaft must turn once. If you are speaking of the speed of the camshaft, you can say that the camshaft must turn at one-half crankshaft speed. If the crankshaft is turning and the camshaft must turn at one-half crankshaft speed, it seems logical to use the spinning crankshaft to turn the camshaft. One very simple way to driv