Automotive piston conversion knowledge a few simple modification

Engine is like a car's "heart", while the piston can be understood as a "hub" of the engine, in addition to living in harsh working environment, it is the busiest one of the engine, constantly carried from bottom to top Stop, reciprocating motion from top dead center to bottom dead center, aspirating, compressing, working, exhausting ... The interior of the piston is hollowed out, more like a cap, the holes at both ends connect the piston Pin, piston pin connecting rod small head, connecting rod bulk is connected with the crankshaft, the piston reciprocating motion into the crankshaft circular motion.

Piston introduction

Pistons are the "heart" of a car engine, withstand alternating mechanical and thermal loads, and are one of the most critical components in the engine. The function of the piston is to withstand the gas pressure and to the connecting rod through the piston pin to drive the crankshaft to rotate. The top of the piston is also part of the combustion chamber.

Piston types are generally divided into: diesel piston, gasoline engine piston, universal piston.

The function of the piston is to withstand the gas pressure and to the connecting rod through the piston pin to drive the crankshaft to rotate. The top of the piston is also part of the combustion chamber. Working conditions Pistons in high temperature, high pressure, high speed, poor lubrication conditions work. Pistons directly contact with hot gas, the instantaneous temperature up to 2500K or more, so serious heating, and cooling conditions are poor, so the piston work temperature is high, the top up to 600 ~ 700K, and the temperature distribution is uneven; piston top to withstand The gas pressure is great, especially the maximum work pressure, gasoline up to 3 ~ 5MPa, diesel up to 6 ~ 9MPa, which makes the piston impact and endure the role of side pressure; piston in the cylinder at a very high speed (8 ~ 12m / s) reciprocating motion, and the speed is constantly changing, which produced a lot of inertia force, the piston subjected to a large additional load. Pistons work under such harsh conditions, will produce deformation and accelerated wear and tear, but also generate additional load and thermal stress, at the same time by gas chemical corrosion.

Working conditions

Pistons in high temperature, high pressure, high speed, poor lubrication conditions. Pistons directly contact with hot gas, the instantaneous temperature up to 2500K or more, so serious heating, and cooling conditions are poor, so the piston work temperature is high, the top up to 600 ~ 700K, and the temperature distribution is uneven; piston top to withstand The gas pressure is great, especially the maximum work pressure, gasoline up to 3 ~ 5MPa, diesel up to 6 ~ 9MPa, which makes the piston impact and endure the role of side pressure; piston in the cylinder at a very high speed (8 ~ 12m / s) reciprocating motion, and the speed is constantly changing, which produced a lot of inertia force, the piston subjected to a large additional load. Pistons work under such harsh conditions, will produce deformation and accelerated wear and tear, but also generate additional load and thermal stress, at the same time by gas chemical corrosion.

Piston inspection is mainly skirt diameter, piston ring groove height and piston pin hole size measurements, the piston should be selected according to the size of the cylinder repair to determine the size of the general increase in size marked on top of the piston.

In the same series to send fish, the piston structure is not necessarily the same, so the choice of piston, you must select the type of piston according to the type of engine on the same engine, you should use the same label, the same group or the same Pistons with the same product code, Pistons with the same product code must be used to ensure that the difference in piston diameter and mass difference does not exceed the original specified range, otherwise, the engine may cause poor combustion, rough work, economic and dynamic decline. Therefore, when matching the piston, the type of piston must be selected according to the type of engine.

Piston structure

Pistons are generally cylindrical body, according to different engine working conditions and requirements, the piston itself has a variety of different structures, the piston is generally divided into the small things the head, skirt and piston pin seat three parts.

Head refers to the piston top and ring groove part. Piston top completely depends on the requirements of the combustion chamber, the top flat or near flat-top design is conducive to the piston to reduce contact with high-temperature gas area, the stress distribution. Most gasoline engines use flat-top pistons, and some engines, such as direct-injection diesel engines and new in-cylinder injection gasoline engines, are required for mixture formation to increase combustion efficiency and minimize knocking, requiring more complex shapes at the piston tip , With a depth of pits as part of the combustion chamber. The groove of the piston is called a ring groove for mounting the piston ring. The role of the piston ring is sealed to prevent air leakage and prevent oil from entering the combustion chamber.

Piston skirt refers to the lower part of the piston, its role is to try to maintain the reciprocating piston in a vertical position, which is the guide part of the piston.

Piston skirt shape very particular attention, especially as a passenger car such as light passenger cars, designers from the structure and performance of the engine, often on the skirt skirt to use their brains to try to make the engine structure is compact and smooth operation.

Piston pin seat is the piston through the piston pin connecting rod connecting part, located above the piston skirt. High speed engine piston pedestal is peculiar in that the pin pedestal does not have to be on the same centerline plane as the piston and can be offset a little to one side, that is, offset to the side where the piston contacts the cylinder wall during the power stroke When the piston to the top dead center change direction after the piston knock cylinder wall degree will be reduced, thus reducing the engine noise.

Piston type

As the internal combustion engine piston in high temperature and high pressure conditions, the requirements of the piston is relatively high, so the main classification of internal combustion engine piston.

1, according to the use of fuel to points, can be divided into gasoline engine piston, diesel piston, natural gas piston.

2, according to the manufacture of piston material to points, can be divided into cast iron piston, steel piston, aluminum piston and piston combination.

3, according to the process of manufacturing piston blank, can be divided into gravity casting piston, squeeze casting piston, forging piston.

4, according to the working conditions of the piston can be divided into non-pressurized piston and pressurized piston two categories.

5, according to the use of pistons to points, can be divided into car piston, truck piston, motorcycle piston, marine piston, tank piston, tractor piston, lawn mower piston.