4D94 4D94-2 Engine Cylinder Head d6144-11-1112 6144-11-1010 6144-11-1011 6144-11-1100 6144-11-1101

The piston top is a component of the combustion chamber, and is often made into different shapes. Gasoline engines often use a flat or concave top to make the combustion chamber structure compact, with a small heat dissipation area, and a simple manufacturing process. The convex piston is commonly used in two-stroke gasoline engines. The piston crown of diesel engines is often made into various pits.

The piston head is the part above the piston pin seat. The piston head is equipped with a piston ring to prevent high-temperature and high-pressure gas from entering the crankcase and oil from entering the combustion chamber; Most of the heat absorbed by the top of the piston is also transmitted to the cylinder through the piston head, and then through the cooling medium.

The piston head is machined with several ring grooves for installing piston ring. The number of piston ring depends on the sealing requirements and is related to the engine speed and cylinder pressure. High speed engines have fewer rings than low speed engines, and gasoline engines have fewer rings than diesel engines. Generally, gasoline engines use two gas rings and one oil ring; The diesel engine has three gas rings and one oil ring; Low speed diesel engines use 3-4 valve rings. To reduce friction loss, the height of the ring should be minimized as much as possible, and efforts should be made to reduce the number of rings while ensuring sealing.

All parts below the piston ring groove are called skirt. Its function is to guide the piston to move back and forth in the cylinder and withstand lateral pressure. When the engine is working, due to the pressure of the gas in the cylinder, the piston will bend and deform. After the piston is heated, due to the large amount of metal at the piston pin, its expansion is greater than that of other parts. In addition, the piston will also experience compression deformation under lateral pressure. The comprehensive result of the above deformation causes the cross-section of the piston skirt to become an ellipse with the long axis perpendicular to the direction of the piston pin. In addition, due to the uneven distribution of temperature and mass along the axis direction of the piston, the thermal expansion of each section is large in the upper part and small in the lower part.

Assembly of piston connecting rod group

The key points of piston connecting rod assembly of diesel generator are as follows:

1, Press fit the connecting rod copper sleeve. When installing the copper sleeve of the connecting rod, it is best to use a press or a vise, and do not use a hammer to strike fiercely; The oil holes or grooves on the copper sleeve should be aligned with the oil holes on the connecting rod to ensure lubrication.

2, Assemble the piston and connecting rod. When assembling pistons and connecting rods, attention should be paid to their relative positions and directions.

3, Install the piston pin skillfully. The piston pin and the pin hole are interference fit. When installing, the piston should be evenly heated to 90 ℃~100 ℃ in water or engine oil. After removal, the pull rod should be placed in a suitable position between the piston pin seat holes, and then the piston pin coated with engine oil should be installed into the piston pin hole and connecting rod copper sleeve in the predetermined direction.

4, Installation of piston ring. When installing the piston ring, pay attention to the position and order of each ring.

5, Install the connecting rod assembly. [1]