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A valve train or valvetrain is a mechanical system that controls operation of the valves in an internal combustion engine, in which a sequence of components transmits motion throughout the assembly. A traditional reciprocating internal combustion engine uses valves to control air and fuel flow into and out of the cylinders, facilitating combustion.〔(【引用サイトリンク】title=Sci-Tech Dictionary: "valve train" )〕 ==Layout== The valve train consists of valves, rocker arms, pushrods, lifters, and camshaft(s).〔(【引用サイトリンク】title=The Valve Train )〕 Valve train opening/closing and duration, as well as the geometry of the valve train, controls the amount of air and fuel entering the combustion chamber at any given point in time. Timing for open/close/duration is controlled by the camshaft that is synchronized to the crankshaft by a chain, belt, or gear. Valve trains are built in several configurations, each of which varies slightly in layout but still performs the task of opening and closing the valves at the time necessary for proper operation of the engine. These layouts are differentiated by the location of the camshaft within the engine: ; Overhead camshaft : The camshaft (or camshafts, depending on the design employed) is located above the valves within the cylinder head, and operates either indirectly or directly on the valves. ; Cam-in-block : The camshaft is located within the engine block, and operates directly on the valves, or indirectly via pushrods and rocker arms. Because they often require pushrods they are often called ''pushrod'' engines. ; Camless : This layout uses no camshafts at all. Technologies such as solenoids are used to individually actuate the valves. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Valvetrain」の詳細全文を読む スポンサード リンク
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