Diesel engine valve mechanism disassembly and assembly steps.
First, the function of the gas distribution mechanism.
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. After the fresh air is filtered out of dust by the air filter, it enters the intake main pipe through the air filter duct and enters the cylinders through the intake valve. The exhaust gas is discharged into the atmosphere through the exhaust valve and exhaust pipe. The function of the valve mechanism is to open and close the intake and exhaust valves regularly according to the working process and sequence of each cylinder of the engine, so that fresh air can enter each cylinder and exhaust the exhaust gas will be discharged.
Second, the classification of gas distribution mechanism.
The valve mechanism can be divided into three types: mechanical, semi-automatic and fully automatic according to its transmission mode.
1.Mechanical valve mechanism.
This valve mechanism is simple and reliable, but it requires high-precision manufacturing to ensure the mating clearance between parts, and it is more cumbersome to adjust and is suitable for smaller bore. Its advantages are that the structure is more compact, the weight is lighter, the transmission power consumption is smaller, and there is no gas distribution phase problem of "early opening before top dead center" and "delayed closing after top dead center".
2.Semi-automatic valve mechanism.
Although this valve mechanism is easy to use, it is not as reliable as the mechanical valve mechanism, and the maintenance and adjustment are more complicated, and it is mainly used for diesel engines with large cylinder bore and poor working conditions. This valve mechanism has two structural forms: the side valve type where the intake and exhaust valves are arranged in the same straight line and the overhead valve type where the intake and exhaust valves are arranged on the cylinder head.
3.Fully automatic valve mechanism.
This valve mechanism has the advantages of few transmission parts, compact structure, light weight and easy operation, and is widely used in small and medium-sized vehicle diesel engines. However, the parts of this valve mechanism have high machining accuracy, high cost and inconvenient maintenance and adjustment. There are two types of common automatic gas distribution mechanisms: oscillating tappet type and hydraulic tappet type.
3. Disassembly steps.
1.Remove the camshaft timing gear and half-circle key.
2.Remove the camshaft bearing cover in the order of removing the bearing cover of the first channel, then the bearing cover of the first channel, and finally the bearing cover of the fourth channel, and put it in order.
3.Gently take the camshaft out of the cylinder head.
4.Use a screwdriver to pry the tappet body assembly off the camshaft.
5.Use a screwdriver to pry the tappet assembly off the tappet.
6.Clean the oil duct hole of the cylinder head.
7.Loosen the cylinder head by tapping the cylinder head around it with a hammer (without damaging the cylinder edge).
8.Remove the cylinder head and head gasket. In order to better disassemble and assemble, the cylinder head and the cylinder head gasket to be disassembled can be placed on the same plane. The installation of the head gasket is reversed, i.e. the reverse side is facing up.
9.Wash the removed parts and put them away.
10.Replace all parts except the cylinder block in reverse order: tappet assembly, tappet, timing gear, camshaft, bearing cover (note: in this case, use the sequence number to make it correspond one by one) and put the first bearing cover fixing bolt back and tighten it. Finally, the head gasket and cylinder head are attached.