A piston group is a piston and a group of sealing rings. It also includes a piston pin and mounting parts. It is worth considering the purpose of this mechanism.
Due to it, the
gas pressure is perceived and transmitted through the connecting rod to the crankshaft. Also, thanks to such a mechanism as a piston group, the piston cavity of the cylinder is compacted. Thus, it will be protected from excessive ingress of lubricating oil and gases into the crankcase. This feature is essential for good engine performance. About what technical condition it is in is judged by its sealing ability. For example, in machine engines it is not allowed that the oil consumption is more than three percent of the fuel consumption.
The piston group also carries out its work in severe climatic conditions. That is why the details of this mechanism have high thermal tension, and this is taken into account when the material and structure are selected for them. Manufacturers usually develop their elements, taking into account the type of engines and the purpose (transport, stationary, diesel, formed, etc.). However, the overall device still remains the same. So, you should consider what the piston group comes from.
Tronkovaya part (guide) is also called a piston skirt. It has tides inside, holes for a piston pin are drilled in them. The lower edge of the skirt is often used as a technological base for processing the piston. It is equipped with a boring shoulder for this. In addition, the walls of the skirt still absorb lateral pressure forces, and this increases their friction against the cylinder walls and increases the heating of the cylinder and piston.
The piston head carries piston rings and has a bottom. The lower groove has drainage holes, lubricating oil leaves through them so that it does not accidentally enter the combustion chamber. Its bottom is one of the chamber walls. She perceives significant gas pressure. The bottom itself can be flat, concave, convex or curly. Again, its shape is selected when considering the type of engine, as well as the combustion chamber.
We cannot but mention such a mechanism as a cylinder-piston group. The main defects of the cylinder blocks are cracks, chips and wear. These malfunctions are established after a thorough inspection, pressure testing and measurement of the cylinder. In this process, a head or a cast-iron plate must be installed on the block (a rubber gasket is required). In general, this group is distinguished by heat-resistant steel and oil cooling, which is carried out due to the circulating general lubrication system of the main diesel engine. If you provide good care to the mechanism and high-quality oil, then you can easily increase the life of the pistons and cylinders.
And one more mechanism - a connecting rod and piston group. The piston is cast and aluminum. The outer surface has a very complex shape. The piston pin is hollow and steel, it rotates freely in the connecting rod sleeve and piston bosses. And the piston rings are made of cast iron. And, of course, the connecting rod - forged and steel. In its upper head there is a sleeve made of a mixture of steel and bronze, which positively affects the work of the entire group.