What is the composition of a car valve train?

Main parts. 1) Valve assembly. The valve assembly is composed of valves, valve guides, valve seats and valve springs, and the valve distribution mechanism. The function of the valve assembly is to ensure the reliable sealing of the cylinder, for which the valve head and the valve seat are required to fit tightly, the valve guide guide to the reciprocating motion of the valve stem is well guided, the two ends of the valve spring and the valve stem center line are perpendicular to each other, and the elastic force of the valve spring ensures that the valve is tightly pressed on the valve seat when the valve is closed.

2) Valve transmission components. Valve transmission components mainly include camshafts and their transmission mechanisms, tappets, push rods and rocker arm mechanisms and other parts.

Camshaft. The camshaft is the main component in the valve transmission group, and its function is to control the opening and closing of the valve and the change law of its lift.

Camshafts are generally forged from high-quality steel dies, and the cam and journal working surfaces are subjected to high-frequency induction heating and quenching (medium carbon steel) or carburizing and quenching (low carbon steel) treatment.

Tappets The function of tappets is to transfer the driving force generated when the camshaft rotates to the push rod or valve, and the tappets are generally made of alloy steel or alloy cast iron and other materials with good wear resistance.

The rocker arm assembly mainly includes the rocker arm, rocker arm shaft, support seat, valve clearance adjustment screw and other parts. The rocker arm is a double-arm lever with the intermediate shaft hole as the fulcrum, the short arm side is equipped with a valve clearance adjustment screw, and the long arm has an arc working surface at one end to push the valve.

Transmission process. When the engine is working, the crankshaft drives the camshaft to rotate through the timing gear, when the convex part of the cam jacks up the tappet, the tappet pushes the push rod up together, the thrust acting on the rocker arm drives the rocker arm to rotate around the shaft, and the other end of the rocker arm compresses the valve spring to make the valve go down and open the valve. As the camshaft continues to rotate, when the raised part of the cam leaves the tappet, the valve goes up under the action of the valve spring tension, closing the valve.

The function of the valve mechanism is to open and close the intake and exhaust valves of each cylinder regularly in accordance with the requirements of the working cycle and firing sequence in each cylinder of the engine, so that the fresh charge can enter the cylinder in time and the exhaust gas can be discharged from the cylinder in time; During the compression and expansion strokes, the sealing of the combustion chamber is ensured. Fresh charge is a combination of gasoline and air for a gasoline engine, and pure air for a diesel engine.

Side-mounted valve-type valve train. This structural form of the gas distribution mechanism has the advantages of simple structure, low cost and convenient maintenance. However, due to the fact that the combustion chamber structure is not compact due to its valve side-setting, the engine power and high speed are poor, and the economy is not high.

At present, this valve mechanism has tended to be eliminated.

Overhead valve-type valve train. Overhead valve valve train form.

The valve is installed in the cylinder head, at the top of the cylinder, with a hemispherical, wedge-shaped or basin-shaped combustion chamber, which has a compact structure and a high compression ratio, which improves the combustion process, reduces heat loss and improves thermal efficiency.

The valve train is composed of camshafts, tappets, push rods, rocker arms, rocker arm shafts, valve springs and valve guides and other related components. Camshafts are arranged on the engine with bottom, side and overhead. Modern engines are often overhead-mounted, 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 tappets and push rods, which is very suitable for high-speed engines, but also brings the difficulty of the transmission shaft, because the camshaft is on the cylinder head, the cylinder head is more troublesome to disassemble and assemble, and the arrangement of the fuel injector is also more difficult. There is also an overhead type in which the camshaft is directly actuated by the spokes of the valve. The advantages of this form are not only simple mechanism, small inertia, and low requirements for camshafts, so it is widely used in new automobiles.

The valve train is composed of camshaft, rocker arm, rocker arm shaft, tappet, push rod, valve blind lift, valve seat, valve spring chain sail and valve guide.

Hope this helps,!! Grind the old!

Cylinder heads, valve chamber cover camshafts, valve intake manifolds, exhaust manifolds, air filters, mufflers, three-way catalytic superchargers, etc.

1. Function: In accordance with the requirements of the work cycle or the delay in the firing of each cylinder in the engine, open and close the intake and exhaust valves of each cylinder during the fixed volcanic search, so that the fresh combustible mixture or air can be entered into the cylinder in time, and the exhaust gas can be discharged from the cylinder in time.

2. Composition: valve group: valve and its associated parts; Valve train train:

Everything from the timing gear to the propulsion valve action. There is a valve gap between the tail end of the valve stem and the rocker end (the tappet end of the side-mounted valve train) to compensate for the expansion of the valve after heating.

When the engine is started, the valves will inflate in response to the rising temperature. If there is no gap between the valve and its transmission parts in the cold state or the gap is too small, in the hot state, the thermal expansion of the valve and its transmission parts will inevitably cause the valve to close loosely, resulting in the leakage of the engine in the compression and power stroke, so that the power decreases, and it is not even easy to start in serious cases.

In order to eliminate this phenomenon, a certain gap between the valve and its transmission mechanism is usually reserved in the cold assembly of the engine to compensate for the expansion of the valve after heating. This gap is called the valve clearance.

However, if the valve clearance is too large, there will be collisions between the transmission parts and between the valves and the valve seats in the cold state, and the wear will be accelerated, and the duration of valve opening will be reduced, and the cylinder inflation will deteriorate. Therefore, hydraulic tappets are used in high-end cars, and the length of the tappet can be automatically changed to compensate for the thermal expansion of the valve at any time, so there is no need to reserve valve clearance.

Valve train composition: valve train is composed of valve transmission group and valve group, valve transmission group includes crankshaft timing gear, camshaft timing gear, camshaft, tappet, push rod, rocker arm, valve clearance adjustment screw and lock nut, rocker arm shaft, valve group including valve, valve guide, valve spring, valve spring seat, valve oil seal, valve seat, valve seat, etc. The function of the valve mechanism is to open and close the intake and exhaust valves of each cylinder regularly in accordance with the requirements of the working cycle and firing sequence in each gas disturbance lead cylinder of the engine, so that the fresh charge can enter the cylinder in time and the exhaust gas can be discharged from the cylinder in time; During the compression and expansion strokes, the sealing in the combustion chamber is ensured.

Fresh charge is a combination of gasoline and air for a gasoline engine, and pure air for a diesel engine. Working principle of valve mechanism:

When the camshaft rotates, when the base circle part of the cam is in contact with the tappet, the tappet does not rise, the transmission parts above the tappet do not act, and the valve is closed. When the protrusion of the cam comes into contact with the tappet, it starts to jack up the tappet and the valve is opened. When the maximum bulge of the cam comes into contact with the tappet, the valve reaches its maximum opening.

Subsequently, the bulge on the contact surface between the cam and the tappet begins to gradually become smaller, the valve begins to rise and close under the action of the valve spring, and the transmission rod such as the rocker arm is pushed in reverse to keep the tappet in contact with the cam. When the cam bulge leaves the tappet, the valve closes completely.

The role of the gas distribution mechanism is to open and close the inlet and exhaust valves in a timely manner according to the needs of the work, and introduce the combustible gas into the cylinder socks and discharge the exhaust gas in time. At the same time, it drives distributors, gasoline pumps and other parts to work. The main parts of the valve mechanism include:

Intake valves, exhaust valves, camshaft drives, etc.

The function of the automobile valve train is to open or close the intake and exhaust valves according to the actual working condition of each cylinder of the engine.