Valve: The valve is divided into inlet valve and exhaust valve. It is used to open and close the inlet and exhaust passages. It is composed of head and stem. The head is used to open and close the intake and exhaust passages, and the stem is used to guide the movement of the valve. The inlet valve is made of ordinary alloy steel, and the exhaust valve is made of heat-resistant alloy steel, because the head of the exhaust valve directly contacts with the combustion gas and is seriously heated.
In order to ensure the close fitting and heat conduction between the valve head and the valve seat, the conical joint surface is used between the valve head and the valve seat and is grinded. The included angle between the cone surface and the top plane is called the valve cone angle, and the commonly used valve cone angles are 30 ° and 45 °. The valve stem is the guide part of the valve movement. The tail of the common valve stem is cut with a groove to install the tapered lock.
Valve seat: the valve seat is a round seat hole directly machined on the cylinder block (side mounted valve) or cover (overhead valve), which plays a sealing role in conjunction with the valve. Some valve seats can be machined into seat rings with wear-resistant alloy cast iron and embedded in the cylinder block or cylinder head.
Valve guide: it is used to guide the valve to make correct axial movement, and it also transfers the heat of the valve stem to the water jacket indirectly. To facilitate repair and replacement, the valve guide is made separately and then pressed into the cylinder block (or cylinder head). When the valve guide is pressed into the cylinder block (or cylinder head), there should be a certain amount of interference and pressing depth to ensure good heat transfer.
Valve spring: it is used to ensure the tightness of the valve and valve seat, and to slow down and overcome the inertial force generated by the valve and other transmission parts, so as to prevent damaging the normal operation of the valve train.
Valve tappet: It transmits the lifting motion of cam to the valve (side mounted) or push rod (overhead mounted) to control the opening and closing of the valve.
Valve push rod: In the overhead valve valve mechanism, the movement of the tappet is transmitted to the rocker arm. The push rod is a straight rod made of hollow steel pipe, with ends of different shapes welded at both ends. The upper end is concave spherical, and the ball head of the adjusting screw on the rocker arm is located therein; The lower end is a ball joint to insert the concave ball mount of the tappet.
Valve rocker arm: it is used to transmit the change direction of tappet movement to the valve. It is an unequal double arm lever with a circular hole in the middle. The end of the long arm is provided with an arc shaped working surface which contacts the tail of the valve; The end of the short arm is provided with a screw hole for installing adjusting screws and lock nuts to adjust the valve clearance. The middle part is rocker arm bearing, with bronze bushing inside.
Rocker arm shaft: it is a hollow round shaft, which is installed on the cylinder head with several supports. The rocker arm is sleeved on the rocker arm shaft and can swing in circular arc on the shaft. The inner hole of the shaft is connected with the main oil passage to supply lubricating oil to the valve distribution mechanism.
Camshaft: used to control the closing time and opening change of each cylinder valve. And drive the engine oil pump, gasoline pump, distributor and other accessories. The utility model is composed of an intake cam, an exhaust cam, a journal, a gear which drives the oil pump and a distributor, and an eccentric wheel which drives the rocker arm of the gasoline pump.
Timing gear: The camshaft is usually driven by the crankshaft through a pair of timing gears. The pinion is installed at the front end of the crankshaft and is called the crankshaft timing gear. The big gear is installed at the front end of the camshaft and is called the camshaft timing gear. The ratio of big and small gears is 2:1, which ensures that the crankshaft rotates twice and the camshaft rotates once.
In order to ensure the correct valve timing and ignition time, the corresponding positions of the two gears are marked with engagement marks. In order to limit the axial displacement of camshaft due to the change of engine speed during operation, axial limit devices are installed.
