What is the piston?

1. Introduction

of the piston “piston” The word was originally “Bei Gou” is a translation of early Western incoming steam engine piston, once widely used. Through literature research, that is Mr. Xu Shou first Piston translated as “Bei Gou.” However, with modern technology terminology translation norms of implementation, “Gou Bei” inevitably be replaced by popular usage of “plug.”
automotive piston engine is the “heart”, subjected to mechanical and thermal loads alternating, is one of the key components of the engine operating condition is the worst.

is a function of the piston to withstand the gas pressure, and driven by a piston rod to pass pin crankshaft rotation, the top part of the piston or combustion chamber. Working conditions of the piston at high temperatures, high pressure, high speed, poor lubrication conditions. Hot gas in direct contact with the piston, the instantaneous temperature of up to 2500K or more, and therefore, severe heat, and cooling conditions is very poor, so that when the piston working temperature is high, up to the top 600 ~ 700K, and the temperature distribution is not uniform; top of the piston to withstand large gas pressure, in particular, the maximum pressure power stroke, gasoline up to 3 ~ 5MPa, diesel up to 6 ~ 9MPa, which makes an impact piston, and a pressure receiving side effect; the piston in the cylinder at high speed (8 ~ 12m / s) to reciprocate, and the speed is constantly changing, which had a great inertia force by the piston significant additional load. Piston working in such harsh conditions, will produce distortion and accelerated wear, but also have additional loads and thermal stress, while the chemical etching action by the gas.

2. Structure

of the piston are generally cylindrical piston body, and according to the requirements of different operating conditions of the engine, there are various configuration of the piston itself, the piston will generally small items divided into three parts of the head, the skirt portion and the piston pin boss. It refers to the top of the piston head portion and the annular groove portion. Depends entirely on the requirements of the piston to the top of the combustion chamber, or near the top of using flattened flattened piston design facilitates reducing the contact area with the high temperature gas, so that uniform stress distribution. Most gasoline engineUsing flat-top piston, some engines (e.g., direct injection diesel engine and a new cylinder injection gasoline engine) required to mixture formation, combustion efficiency is improved, to reduce the knock to a minimum, require the piston tip has a more complicated shape, provided there is a certain depth of the pit as part of the combustion chamber.

is referred to as the groove of the piston ring groove for mounting piston rings. The role of the piston ring is sealed to prevent leakage and prevent the oil from entering the combustion chamber. Refers to a portion of the skirt portion of the piston, its role is to keep the posture of the piston reciprocating motion in the vertical, i.e. the guide portion of the piston. Shape of the piston skirt very particular, especially as a light passenger car type, the designer from the structure and performance of the engine, the piston skirt often brains, to try to make the engine compact structure running smoothly.

support pin boss portion is connected to the piston through a piston pin and the connecting rod, located above the piston skirt. High-speed engine piston pin boss is unique in that the piston pin bore is not necessarily the center line in the same plane, may be shifted a little to one side, namely the side during the power stroke of the piston in contact with the cylinder wall offset so when the piston top dead center to the direction of extent of conversion percussion piston of the cylinder wall will decrease, thereby reducing engine noise.

3, the impact

of the piston

With increasingly stringent automotive vehicle power, economy, environmental protection and reliability requirements of the engine, the piston has become a high-tech new set of high-strength lightweight materials, composite shaped outer profile, shaped pin holes and a number of new technologies in one product, in order to ensure the heat resistance of the piston, wear resistance, smooth oriented and a good sealing function, to reduce the friction loss of the engine power, reduced fuel consumption, noise and emissions.

To meet these functional requirements, generally cylindrical shaped piston is designed as a cylindrical (elliptical convex change), i.e., perpendicular to the axis of the piston cross-section is elliptical or oval correction, and an axial ovality the direction of a certain variation (FIG. 1), the degree of accuracy of 0.005mm oval; longitudinal sectional outer contour of the piston is a function of higher order curve fitting, contour accuracy of 0.005 ~ 0.01mm; to improve the bearing pistonCarrying capacity, or power of the engine to increase, generally a high load of the piston pin bore is designed to be conical or positive stress micro-curved (shaped pin hole), the pin hole size accuracy of IT4 level, contour accuracy of 0.003mm.

of the piston as a typical key auto parts, has a strong characteristic in the processing of the cutting process. At present, the domestic piston manufacturing industry usually by the general machine and technological characteristics of the piston special equipment components machining line, therefore, special equipment has become the key equipment piston cutting its functionality and accuracy will directly affect the key features of the final product Quality Index.

4, Category

of the piston 1, engine piston
2, diesel engine piston
3, automotive piston pump piston
4, automobile air-conditioning piston
5 lawnmower piston
6, farm piston
7, generator pistons, etc.

5, the difference between

there is no difference between the

the main structure, the biggest difference between gasoline and diesel engines in that the ignition and the intake: gasoline into the cylinder oil and gas mixing combustible gas, diesel pure air; gasoline engine is by spark ignition, the wood is in the compressed air after reaching the diesel autoignition temperature from the spray hole diesel injected, At this time, since the in-cylinder temperature, the diesel combustion.

say the difference may be up to the skirt of the piston, the piston stroke because most diesel engines than gasoline captain, may have special style with flywheel movement of the skirt, but not all diesel engines are the same.

acquire the piston 2 valve gasoline and diesel engines relative ratio of: the difference between the top of the piston of a gasoline engine the piston is flat, the top of the diesel engine piston with a combustion chamber which is the maximum difference between a chance to multi-valve gasoline engine pistons and diesel… piston comparison: the top of the combustion chamber are relatively simple but the gasoline engine is a large diesel engine piston ring groove separation distance than gasoline and diesel oil ring groove…Machine with a hole. Gasoline is not. In summary, there is no difference.

6, the piston rings

piston PVD, the TIN surface treatment of the piston is one of the major automobile engine parts in the engine, which piston ring, piston pins group component parts of the piston, and a cylinder head together form a combustion chamber, the gas subjected to a force by a piston pin and a connecting rod and the power to the crankshaft, in order to complete the work of the internal combustion engine. Since the piston in the hostile environment of a high-speed working, high pressure and temperature, but also taking into account the durability and the smooth operation of the engine, thus requiring the piston must also have sufficient strength and rigidity, good thermal conductivity, high heat resistance, small coefficient of expansion (change in shape and size is smaller), the relative density (light weight), wear resistance and corrosion resistance, even lower cost. Because the requirements are many and high, and some conflicting requirements, the piston is difficult to find a material able to fully meet the requirements. Modern engine piston generally made of aluminum alloy, since the aluminum alloy has low density, highlight the advantages of good thermal conductivity but being relatively large coefficient of expansion, the relatively poor high-temperature strength drawbacks only through rational design in order to meet the requirements. Therefore, the quality of the merits of a car engine, not only depends on the materials used, but also depends on the rationality of the design.

The piston is generally cylindrical body, and according to the requirements of different operating conditions of the engine, there are various configuration of the piston itself, the piston of the small things generally divided into three parts of the head, the skirt portion and the piston pin boss .

refers to the top of the head portion of the piston ring groove. Depends entirely on the requirements of the piston to the top of the combustion chamber, or near the top of using flattened flattened piston design facilitates reducing the contact area with the high temperature gas, so that uniform stress distribution. Most flat-top piston using gasoline, some engines (e.g., direct injection diesel engine and a new cylinder injection gasoline engine) required to mixture formation, combustion efficiency, the deflagration as to minimize the required piston top having more complex shapes , with a certain depth of the pit as a part of the combustion chamber. The groove of the piston ring groove is referred to for mounting piston rings. The role of the piston ring is sealed to prevent leakage and prevent the oil from entering the combustion chamber.

refers to a portion of the skirt portion of the piston, its role is to keep the posture of the piston reciprocating motion in the vertical, i.e. the guide portion of the piston. Shape of the piston skirt very particular, especially as a light passenger car type, the designer from the structure and performance of the engine, the piston skirt often brains, to try to make the engine compact structure running smoothly.

support pin boss portion is connected to the piston through a piston pin and the connecting rod, located above the piston skirt. High-speed engine piston pin boss is unique in that the piston pin bore is not necessarily the center line in the same plane, may be shifted a little to one side, namely the side during the power stroke of the piston in contact with the cylinder wall offset so when the piston top dead center to the direction of extent of conversion percussion piston of the cylinder wall will decrease, thereby reducing engine noise.

piston There are tens of thousands of automobile parts, such as large as the crankshaft, gearbox, small spring washers, bolts, nuts. Each part has its role, such as piston rings “little”, from the seemingly simple shapes, very light weight, the price is very cheap, but the effect is no small matter. The lack of it of course, the car could not move, even it just a little small problems, the car will not normal, either big fuel consumption, or lack of motivation. In the group with the entire piston cylinder, the piston and cylinder set real contact the cylinder wall is a piston ring, it fills the voids of the piston and the cylinder walls, to close the combustion chamber, it is most likely to wear engine parts .

generally made from cast iron piston rings, have a certain elasticity, a variety of cross-sectional shapes, surface coating to increase the running-in behavior. When the engine is running will be the thermal expansion of the piston, thus opening gap piston ring, when installed in order to maintain the sealing, the opening of each piston ring gap position To offset. A piston rings often three to four, according to their different functions, gas ring and oil ring into two categories. Gas ring mounted on the upper piston ring groove of the head, to prevent leakage, transferring heat to the cylinder wall of the piston head, the piston heat evacuation. Effect is to prevent lubricant oil ring fleeing the combustion chamber, the cylinder wall scraping excess oil back to the oil pan, which is installed below the gas ring of the ring groove. As long as the requirements of sealing function, the number of rings is much less than the number of good, the number of rings less friction while maintaining the minimum area, reduces the power consumption, but also shorten the height of the piston, and accordingly also reduces the high engineDegree, the current high-speed gasoline engines generally two gas rings and an oil ring.