Engine exhaust valve

The exhaust valve is a timing element, when opened which is removed (output) відпрацьованих газів з камери згоряння двигуна.

The release of gases occurs then, when the piston in the engine cylinder is directed from the bottom dead center (NMT) to the top dead center (TDC). During engine operation, the exhaust valves are subjected to significant thermal loads, as constantly in contact with hot exhaust gases. The valve head during engine operation can be heated within 600-800 degrees.

After the end of the intake and compression stroke, the main requirement at the time of fuel ignition in the combustion chamber is the maximum tightness. The inlet and outlet valves are closed. When the piston has taken on the energy of the expanding gases after the ignition of the fuel-air mixture, these exhaust gases must be removed from the combustion chamber. Sealing the chamber is no longer required at this stage. Exhaust plate valve is responsible for the removal of exhaust gases in the design of the valve train, which is located in the cylinder head (GBC).

A discharge is created at the inlet stroke, and at the stroke of the release in the working combustion chamber of the engine, high pressure is formed. After combustion of the mixture of fuel and air, the exhaust gases leave the combustion chamber through which the exhaust valve opens at the right time.. The force of the pressure allows the gases to easily leave the working chamber. This explains the smaller size of the exhaust valve plate compared to the intake valve plate. At the inlet stroke, the vacuum is less in force than the outlet pressure. Exhaust gases are practically pushed out through the open exhaust valve.

Effective sealing of the combustion chamber became possible due to the use of plate valves in the design of the timing belt of modern internal combustion engines. The valve device is simple, the element has a plate and a rod. The chamfer smoothly passes into the rod, which makes the valve quite strong. The conical shape of the transition significantly reduces the resistance of the exhaust gases when leaving the chamber, and further improves sealing.

The opening of the exhaust valve is due to the force received from the camshaft. Rod (stock) the valve is located in the guide sleeve of the valve, which is pressed into the cylinder head. The camshaft cam presses directly on the valve stem or on the rocker, from which the force is transmitted to the rod. The cylinder head seat is also located in the cylinder head. The valve seat is recessed, which in its shape corresponds to the upper part of the valve plate. The valve plate and the valve seat press against each other with filigree precision. This solution allows you to ensure maximum tightness at that time, when the inlet and outlet valves are closed. The main task is to prevent the breakthrough of gases from the combustion chamber.

On the upper part of the valve stem is a special turn. This turning is the place of installation of "breadcrumbs". This "zero" is a conical ring, which is cut into two equal parts. The solution is needed to mount the valve spring plate. If the valve is opened by a "push" from the camshaft, then the closing of the valve is realized by the force of the valve spring. The specified spring closes the valve, firmly pressing the plate to the saddle. Additionally, there is a mechanism, which turns the valve. This is necessary for even valve wear and cleaning of the valve from soot.

The exhaust valve operates in very difficult conditions. Exhaust gases cause severe corrosion of the exhaust valves. If the fuel burns in the chamber in full, then this may cause the valve to burn out. Adjusting the valve mechanism is an important procedure in the operation of the internal combustion engine. Closing the exhaust valve early can cause it to burn out quickly.