The function of the general engine valve is to regularly open and close the intake and exhaust valves according to the working sequence of the engine to ensure that the combustible mixture or fresh air enters the cylinder immediately, and the exhaust gas generated after combustion is immediately discharged out of the cylinder. The general engine valve includes a valve unit And valve unit. The valve block includes intake valves, exhaust valves, valve springs and other components to maintain the valve closed. The general-purpose engine valve drive device includes timing sprocket, timing pulley, timing chain, timing belt, intake camshaft, exhaust camshaft and other elements, which can well drive the opening of the valve to ensure that the valve has enough Opening degree and valve opening time, then, let's learn about the structure and principle of the automobile general-purpose engine valve!

Types of general purpose engine valves

General engine valve

General-purpose engine valve mechanisms are classified according to camshaft positions and are divided into camshaft upper, Chinese and lower types. The engine camshaft of a car is usually on the engine cylinder head, which is a camshaft mounted type. The camshaft of the lower camshaft valve mechanism is installed in the crankcase, and the cam timing gear directly meshes with the crankshaft timing gear and is driven by the crankshaft. There are two types on the camshaft: the structure of the camshaft driving the valve through the hydraulic tappet and the structure of the camshaft driving the valve through the rocker arm.

General-purpose engine valves are divided into timing chain drive, timing belt drive and gear drive according to the transmission mode. Cars generally use timing chain or timing belt drive. General engine valves mainly include camshafts, hydraulic tappets, timing sprockets (or timing pulleys), timing chains (or timing belts), chain tensioners, etc.

Camshaft

The car universal engine valve drive device transmits the power of the crankshaft to the crankshaft timing pulley (or timing sprocket), timing belt (or timing chain), camshaft timing pulley (or timing sprocket) The camshaft cover is fixedly supported on the cylinder head, and there is a lubricating oil hole on the camshaft support shaft diameter. Through the lubricating oil hole, the camshaft support shaft diameter and bearing cover can be lubricated. When there are two camshafts on the upper part of the cylinder, it is called double overhead camshaft (DOHC). The camshaft has a special profile, and its rotation controls the valve opening time, duration, and valve opening lift.

hydraulic tappet

When the engine is running, the temperature changes greatly. Due to thermal expansion and cooling contraction, when the engine is cooling, in order to compensate for the expansion of the valve after heating, a gap needs to be left at the end of the valve stem. Therefore, when the engine is assembled at normal temperature, a certain clearance is ensured at the rear end of the valve stem. This gap is called the valve gap. At present, in an automobile engine, a hydraulic lifter or a valve clearance adjuster having an intake port whose length can be automatically changed by pressure oil from an oil pump is generally used to adjust a valve clearance. The valve lash adjuster is used in valve transmissions with roller rocker arms, and the working principle is similar to that of a hydraulic tappet.

The oil enters the plunger of the hydraulic tappet from the oil circuit of the cylinder head. Under the action of the oil pressure, the spring of the one-way valve is compressed, the one-way ball valve opens, and the high-pressure oil chamber under the plunger is immediately filled with oil. The one-way ball valve returns, the plunger rises, and the valve gap disappears. After the movable part of the valve mechanism is worn, the oil pressure remains constant. At this time, the oil pressure opens the one-way ball valve, the high-pressure oil chamber under the plunger is immediately filled with oil, the plunger rises, and the valve gap is automatically compensated.

The above introduction is the structure and principle of the automobile general engine valve. If you need to know more, you can contact Chongqing Yongfeng Jingqi Auto Parts Co., Ltd. at any time!