Best understand the working principle of engine va

Understand the working principle of the engine valve mechanism

the valve mechanism is composed of some related components such as camshaft, tappet, pushrod, rocker arm, rocker shaft, valve spring and valve guide in order to evaluate its low-speed impact performance

the arrangement of camshaft on the engine includes lower, side and top. Modern engines often use the overhead type, which is located on the cylinder head. The camshaft drives the valve directly through the rocker arm, eliminating a large set of reciprocating parts such as rods and push rods with great potential for environmental protection effect of new wood plastic composite materials. It is very suitable for high-speed engines, but it also brings difficulties to the transmission shaft. Because the camshaft is on the cylinder head, the disassembly and assembly of the cylinder head is more troublesome, and the layout of the fuel injector is also more difficult. Another overhead type is that the amplitude wheel of the camshaft directly drives the valve. This form has the advantages of simple mechanism, small inertia and low requirements for camshaft, so it is widely used in new vehicles

what drives the camshaft to rotate

most of the earliest cars were driven by timing gears. When the crankshaft rotates, a pair of gears at its front end drive the camshaft, and sometimes an intermediate gear (idler gear) was added. In order to reduce the transmission noise and make the meshing stable, the timing gears are mostly made of cloth and bakelite, and they are helical teeth. Chain drive or belt drive is often used in overhead valve drive mechanism. The substrate of the belt is neoprene, with glass fiber or nylon fabric sandwiched in the middle, which has high strength, low noise, low quality and low price. It has been widely used in recent years

generally, the engine has only one inlet valve and one exhaust valve for each cylinder. In order to improve the charging efficiency, multi valve technology is now widely used, for example, there are four valves in each cylinder. This multi valve structure is particularly beneficial to the engine with direct fuel injection. The fuel injector is arranged in the center of the combustion chamber, the ignition and combustion path is uniform, and the opening of each valve can be appropriately reduced

Timken test machine per cylinder: when the main shaft of the test machine drives the test ring to rotate on the stationary test block, there are two kinds of valve arrangement: one is the mixed row of inlet valve and exhaust valve; The other is that the intake valve and exhaust valve are arranged in a row respectively. All the valves of the former are driven by a camshaft through a T-shaped rod, but the working conditions and effects are not good due to the different positions of the valves in the inlet. The latter has incomparable shortcomings, but it needs to be equipped with two camshafts. Where the word DOHC is met, it refers to the overhead double camshaft. In recent years, many engines have adopted this form. Of course, it is not uncommon to have more than four valves per cylinder. The main purpose of this is to improve inflation efficiency