1. Valve: The valve is divided into two types: intake valve and exhaust valve. Its function is to open and close the intake and exhaust passages. It consists of a head and a rod. The head is used to open and close the intake and exhaust channels, and the rod is used to guide the movement of the valve. The intake 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 is directly in contact with the combustion gas and is severely heated.
In order to ensure the tight fit and heat conduction between the valve head and the valve seat, a tapered joint surface is used between the valve head and the valve seat, and it is ground. The 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 shaft is the part that guides the movement of the valve. Common valve stems have grooves cut into the end to accommodate tapered cleats.
2. Valve seat: The valve seat is a circular seat hole directly processed on the cylinder block (side-mounted valve) or cover (overhead valve), and it cooperates with the valve to play a sealing role. Some valve seats can be processed into seat rings by wear-resistant alloy cast iron, and inlaid on the cylinder block or cylinder head.
3. Valve guide: Its function is to guide the valve to make the correct axial movement, and at the same time transfer the heat from the valve stem to the water jacket indirectly. To facilitate repair and replacement, the valve guides are made separately and 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.
4. Valve spring: Its function is to ensure the tight fit between the valve and the valve seat, and to slow down and overcome the inertial force generated by the valve and other transmission parts, so as to prevent the normal operation of the valve mechanism from being damaged.
5. Valve lifter: It transmits the pushing motion of the cam to the valve (side type) or push rod (overhead type) to control the opening and closing of the valve.
6. Valve push rod: In the overhead valve type gas distribution 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 in it; the lower end is a ball head for insertion into the jig. Concave ball bearings for rods.
7. Valve rocker arm: Its function is to change the direction of movement of the tappet to the valve. It is a unequal-length double-armed lever with a circular hole in the middle. The end of the long arm has an arc-shaped working surface in contact with the tail of the valve; the end of the short arm has screw holes for installing adjustment screws and lock nuts to adjust the valve clearance. The middle part is the rocker arm bearing, which is equipped with a bronze bushing.
8. Rocker arm shaft: It is a hollow circular shaft, which is installed on the cylinder head with several supports. The rocker arm is set on the rocker arm shaft and can swing in a circular arc on the shaft. The inner hole of the shaft communicates with the main oil passage to supply the lubricating oil for the valve mechanism.
9. Camshaft: used to control the closing time and opening of each cylinder valve. And drive oil pump, gasoline pump, distributor and other accessories. It is made as a whole by the intake cam, exhaust cam, journal, gears driving the oil pump and distributor, and the eccentric wheel driving the rocker arm of the petrol pump.
10. Timing Gears: The camshaft is usually driven by the crankshaft through a pair of timing gears. The pinion gear is installed at the front end of the crankshaft and is called the crankshaft timing gear. The large gear is installed on the front end of the camshaft and is called the camshaft timing gear. The ratio of the large and small gears is 2:1, that is, to ensure that the crankshaft rotates two times and the camshaft rotates one time.
In order to ensure the correct gas timing and ignition timing, the corresponding positions of the two gears are engraved with meshing marks. In order to limit the axial movement of the camshaft as the engine speed changes during operation, an axial limit device is installed in the installation.
