英语翻译VALVE gearIn an internal combustion engine,the valve gea

英语翻译
VALVE gearIn an internal combustion engine,the valve gear provides timely admission of the fresh charge into the cylinders and exhaust of spent gases from them.For this purpose the valves at definite moments open and close the intake and exhaust ports in the cylinder head,through which the cylinders communicate with the intake and exhaust manifold.The valve gear is composed of timing gears,a camshaft,tappets,push rods,rockers,valves,valve seats,spring with fasteners and valve guides.The timing gears in most engines are housed in a special case fitted at the front end of the engine .These are necessary to transmit rotation from the crankshaft to the camshaft,fuel injection pump shaft ,and to oil pump and other mechanisms.The gears are made of steel and use helical teeth to reduce noise.Camshaft's function is to open the engine valves positively and timely,in a definite sequence,and to control their closing against the return action action of the valve springs.The shaft is made integral with its cams and bearing journals.Each cam controls a single valve,either intake or exhaust.In some autombile engines,the camshaft is made integral with fuel pump eccentric wheel and oil pump drive gear.The camshaft bearings are lubricated with oil supplied under pressure from the main gallery in the cylinder block.The tappets serve to transmit the force from the camshaft to the push rods.The tappets are small cylindrical bores receiving the push rods.They are made of cast iron or steel and located in the guides ,which may be made integral with cylinder block or removable as in the engine.When the engines operate,the tappets continuously rotate about their axes for uniform wear.The rotaion is ensured by a convex surface of their bottoms and a slanted surface of the cams.The push rods transmit the force from the tappets to the rocker.They usually have small convex balls inserted on each of their ends.These convex balls fit into the tappet and rocker arm to allow proper movement.Overhead camshafts do not need the push rod.

内燃机阀动齿轮及时提供气缸的新鲜充量,排气和耗气.为此,阀动齿轮在一定时刻打开吸气孔和关闭排气孔,这些气缸连通了吸气和排气总管.阀动机构包括定时齿轮、凸轮轴、挺杆、推杆、摇杆、气阀、阀座、紧固弹簧和气门导杆.多数发动机的定时齿轮服帖地封装在发动机前端的特别的盒内,对从机轴到凸轮轴、到喷油泵轴、到油泵和其它机构的旋转传送来说是必要的.
不锈钢的齿轮采用螺旋齿减少了噪音,凸轮轴按一定顺序及时果断地打开发动机的气门,控制气门弹黄回弹的闭合,整体结构的机轴带凸轮和轴颈,每个凸轮控制一个单阀,既可进气也可排气.
一些汽车的发动机是一体的凸轮轴,有燃油泵偏心轮和油泵驱动齿轮.凸轮轴轴承在受到压力下从气缸座的主轴颈上以润滑油润滑.