The engine must be disassembled and repaired during overhaul. Assembly after overhaul is an important work, how to smoothly install the parts into a complete diesel engine, which has high technical requirements. In particular, the quality of assembly directly affects the service life of diesel engine and the frequency of repair. The following describes the assembly process of the main parts of the engine.
Installation of cylinder liner
When the engine is working, the inner surface of the cylinder liner is in direct contact with high temperature gas. Its temperature and pressure are changing frequently, and its instantaneous value is very high, which gives the cylinder a great heat load and mechanical load. The piston does high-speed reciprocating linear motion in the cylinder, and the inner wall of the cylinder plays a guiding role.
The lubrication condition of the inner wall of the cylinder is poor, and the formation of oil film is difficult. Wear faster in use, especially around the top dead center area. In addition, combustion products are also corrosive to the cylinder. Under such harsh working conditions, cylinder wear is unavoidable. Cylinder wear will affect the engine performance, cylinder liner is also vulnerable parts of diesel engine.
The installation points of cylinder liner are as follows:
(1) Put the cylinder liner without water resistance ring into the cylinder block for a test, so that it can rotate flexibly without obvious shaking. At the same time, check whether the size of the cylinder liner step higher than the cylinder block plane is within the specified range.
(2) Whether the cylinder liner is new or old, all the new water rings should be used in the installation of the cylinder liner. The glue of the water resistance ring should be soft and crack free, and the specification and size should meet the requirements of the original engine.
(3) When pressing into the cylinder liner, you can apply some soapy water around the water blocking ring to facilitate lubrication, the cylinder can also be appropriately coated some, and then gently push the cylinder liner into the corresponding cylinder hole according to the designated cylinder hole sequence number, to use special installation tools, slowly completely press the cylinder liner into the cylinder block, so that the shoulder and the cylinder block stop plane closely fit, Hammering is not allowed.
After installation, the diameter dial indicator is used to measure the deformation (size reduction and loss of circle) of the water resistance ring shall not be greater than 0. 02 mm. When the deformation is large, the cylinder liner should be pulled out and the water resistance ring reinstalled. After the cylinder set is in, the shoulder of the cylinder liner should protruding from the cylinder body plane 0.06 ~ 0.12mm. This size should be tested before loading the water resistance ring. When the amount of protrusion is small, the appropriate thickness of copper skin can be padded on the shoulder of the cylinder liner. When the protrusion is too large, the cylinder liner shoulder should be turned.
Installation of piston ring
Piston rings are divided into gas rings and oil rings. The model 195 diesel engine uses a gas ring and an oil ring, and the Z1100 diesel engine uses two gas rings and an oil ring. They are installed in the piston ring groove, and rely on the elastic force to stick to the cylinder wall, and move up and down with the piston. The role of the gas ring has two, one is to seal the cylinder, try to make the gas in the cylinder does not leak into the crankcase; The second is to transfer the heat of the piston head to the cylinder wall.
Once the piston ring leaks, a large number of high temperature gas from the gap between the piston and the cylinder sprang out, not only the heat accepted from the top of the piston can not be passed to the cylinder wall with the piston ring, but also the piston circle surface and the piston ring is strongly heated by the gas, finally leading to the piston and the piston ring burned out. Oil ring mainly plays the role of scraping oil to prevent oil from entering the combustion chamber. Piston ring working environment is bad, but also the diesel engine wear parts.
When replacing the piston ring, pay attention to the following points:
(1) Matching qualified piston ring, set on the piston should use special piston ring pliers to moderately open the piston ring, avoid excessive force.
(2) When assembling the piston ring, attention should be paid to the direction, the chrome-plated ring should be installed in the first ring groove, and the inner notch up; When the piston ring with an external incision is installed, the external incision is downward; The outer edge of the upper end face of the oil ring is generally chamfered, while the outer edge of the lower end face of the lower lip is not chamfered. Attention should be paid to the installation direction and can not be installed wrong.
(3) Before the piston connecting rod assembly is loaded into the cylinder, the position of the ring end gap should be evenly distributed according to the circular direction of the piston, so as to avoid the overlap of the port caused by air leakage, oil channeling and other phenomena.
The position of the end gap of the piston ring, if it is four rings, the end gap of the first and second piston ring and the axis of the piston pin into 45°, and staggered 180°; The end gap of the third and fourth ring is at a right Angle to the first and second ring, and also 45° to the axis of the piston pin, and staggered 180° to each other. For a three-way ring, the end gap of the first ring shall be at an Angle of 30° from the axis of the piston pin, and the remaining rings shall be spaced 120° from each other in turn.
Post time: Feb-20-2023