1, the function of the valve mechanism:
Valve means is an engine intake and exhaust control apparatus which functions according to the working order of the engine and each cylinder operating cycle requirements, opening and closing timing of intake and exhaust valves, so that the stroke is performed as many combustible mixture into the cylinder, the rapid discharge of the exhaust stroke the exhaust gas cylinder.
2, the main components
the valve assembly. a valve assembly comprising a valve, valve guides, valve seat and a valve spring and other parts.
Function of the valve assembly is to ensure reliable sealing of the cylinder, for which the valve head and the valve seat requires fit tight valve guide catheter well to reciprocate the valve stem, the valve spring ends valve stem centerline perpendicular to each other, to ensure that the elastic force of the valve spring is pressed against the valve seat when the valve is closed.
The valve train assembly. a valve drive assembly including a camshaft and its drive mechanism, tappet push rod and a rocker arm mechanism and other components.
camshaft valve train camshaft is the main component of the group, whose role is to control the variation of the valve opening and closing lift.
Usually a camshaft made by forging quality steel, and high-frequency induction hardening (carbon steel) or carburizing and quenching (low carbon steel) and the journal of the cam working surface treated.
tappet
lifter role is generated when the driving force transmitted to the plunger or valve camshaft rotates, lifter generally with good wear resistance alloy steel or alloy cast iron and other materials.
The rocker arm assembly
The main rocker arm, the rocker shaft supporting base lash adjusting screw and other parts. The intermediate rocker is a shaft hole as the fulcrum of the lever arms, with one side of the short arm of the valve clearance adjusting screw, one end of a long arm for urging the valve arcuate face.
3, a valve arrangement
Formula valve side valve mechanism . This form of valve train mechanism having a simple structure, low cost, and easy maintenance. But because of its side opposite the valve structure cause less compact combustion chamber, resulting in the engine power and high speed poor economy is not high. At present, this valve train has become obsolete.
overhead valve type valve mechanism. valvetrain overhead valve structure
a valve mounted in the cylinder head, at the top of the cylinder, using a hemispherical, bowl-shaped or wedge-shaped combustion chamber, the combustion chamber compact structure, high compression ratio, improvement the combustion process, the combustion process is reduced, reducing heat losses, improves thermal efficiency.
of the camshaft arrangement
Depending on the arrangement of the camshaft in a camshaft mounting position in the body, mounted partitioned into, and mounted in an overhead three.
divided by the camshaft drive mode
with a gear drive, a toothed belt drive and chain drive valve mechanism.
divided by the number of valve
has two valves per cylinder, three-valve type, four or five-valve-type valve Formula (two camshafts, one for the intake camshaft, the exhaust camshaft to the other ) gas distribution mechanism or the like.
4, the transmission process
When the engine crankshaft through a timing gear driving rotation of the camshaft, when the convex portion of the cam from the top of the tappet, the tappet push rod pushed together the uplink, the driving force acting on the driven rocker about the rocker arm shaft, the rocker arm and the other end of the compression spring in the valve downstream valve, opens the valve, with the continued rotation of the camshaft, when the convex portion of the cam away from tappet , then under the action of the valve spring tension upstream valve to close the valve.
5 lash
The size of the gap is determined by the engine valve is generally the manufacturer according to the experiment. In general, cold state, the intake valve gap, 0.25 ~ 0.30mm, rowThe valve clearance of 0.30 ~ 0.35mm. gap is too small, the engine gas leakage may occur in the hot state, resulting in the power drop, or even burn the valve; gap is too large, the impact generated between the valve and valve seat and between the transmission components, with the whole resulting gas means is not running smoothly, the noise increases, and the valve opened duration decreases, the intake and exhaust insufficient.
The hydraulic tappet engine by automatically adjusting hydraulic tappet axial length tappet functional changes at any time to compensate thermal expansion valve, it is required to reserve a lash.