As the requirements of power, fuel economy, environmental protection and reliability of the engine become more and more strict, The piston has developed into a high-tech product with many new technologies, such as   lightweight,high strength new materials, special-shaped outer circular compound surfaces, special-shaped pinholes, and so on. In order to ensure the piston heat resistance, wear resistance, smooth steering and good sealing function, reduce the engine friction work loss, reduce fuel consumption, noise and emissions. In order to meet the above functional requirements, the outer circle of the piston is usually designed as a shaped outer circle (medium convex variable ellipse), that is, the cross section perpendicular to the piston axis is an ellipse or a modified ellipse. And the ellipticity changes along the axis (as shown in Fig. 1), the ellipticity precision is 0.005mm, the profile of the longitudinal section of the piston is the fitting curve of higher order function, the contour precision is 0.005mm and 0.01mm, in order to improve the bearing capacity of the piston; In order to increase the power of engine, the pin hole of high load piston is usually designed as micro inner cone or normal stress curved hole (irregular pin hole). The dimension precision of pin hole is up to IT4 class, and the outline precision is 0.003mm.

      As a typical key component of automobile, piston has strong technological characteristics in cutting. In the domestic piston manufacturing industry, the machining production line is usually composed of general machine tools and special equipment which combines the characteristics of piston technology. Therefore, the special equipment has become the key equipment of piston cutting. A quality index whose function and accuracy will directly affect the key characteristics of the final product.

      Piston Distinction.

      The pistons of gasoline engine and diesel engine are very different in the main structure. Generally speaking, the piston

diameter of gasoline engine is smaller, the wall thickness is smaller, and the weight is lighter. But the diesel engine piston

diameter is bigger, the wall thickness is thicker, the weight is heavier. The shape of the piston is quite different.
      The biggest difference between a gasoline engine and a diesel engine lies in the way it ignites and the intake of air:

the gasoline engine enters the cylinder with a mixture of flammable gases and the diesel engine is pure air; the gasoline

engine is ignited by spark plugs. The diesel engine injects the diesel fuel through the injection hole after the compressed

air reaches the self-ignition temperature of the diesel fuel. At this time, the diesel fuel ignites spontaneously because of

the high temperature in the cylinder.
      The most likely difference is in the piston skirt, because most diesel engines have longer piston strokes than gasoline engines,

and there may be a special shape at the skirt to match the motion of the flywheel, but not all diesel engines are like this.

Compare the piston of a 2-valve gasoline engine with that of a diesel engine: at the top of the piston. The piston of the

gasoline engine is flat. A combustion chamber is provided at the top of the piston of a diesel engine. This is the biggest

difference. Compare the piston of a multi-valve gasoline engine with that of a diesel engine: both have combustion

chambers at the top. But gasoline engines are simpler. Distance between piston ring grooves for diesel engines. Bigger

than a gasoline engine. Oil ring grooves have holes in a diesel engine. Gasoline engines do not. On the whole, there is

a big difference.
      The piston of automobile engine is one of the main parts in the engine. It forms piston group with piston ring and piston

pin, combustor with cylinder head and so on. It bears gas force and transmits power to crankshaft through piston pin

and connecting rod. In order to complete the internal combustion engine work process. Because the piston is in a bad

working environment of high speed, high pressure and high temperature, and taking into account the smooth and

durable operation of the engine, the piston must also have sufficient strength and stiffness, good thermal conductivity

and high heat resistance. Small expansion coefficient (size and shape changes to be small), small relative density

(light weight), wear and corrosion resistance, but also low cost. As the requirements are many and high, some

requirements are contradictory, it is difficult to find a piston material that can fully meet the requirements.

      The pistons of modern engines are generally made of aluminum alloy, because aluminum alloy has the outstanding

advantages of low density and good thermal conductivity, but at the same time, it has the disadvantages of large

coefficient of expansion and poor strength at high temperature. These shortcomings can only be met by reasonable

structural design to meet the requirements of the use. Therefore, the quality of the automobile engine, not only

depends on the material used, but also depends on the rationality of the design.
      There are tens of thousands of parts in the car, as large as the crankshaft, gearbox body, as small as spring washers,

bolts and nuts. Every part has its function, such as the piston ring "dot", looks simple from the shape, weight is light,

the price is also very cheap, but the function is not small. Without it, the car will not move, even if it has a little fault,

the car will not normal, or fuel consumption, or lack of power. In the coordination of the whole piston group and the

cylinder, the piston ring which really contacts with the cylinder wall of the cylinder is the piston ring, which fills the gap

between the piston and the cylinder wall to seal the combustion chamber, so it is also the most easily worn part in

the engine. Piston rings are generally made of cast iron, have a certain flexibility, cross section in a variety of shapes,

the surface has a coating to improve the running-in performance. When the engine is running, the piston will be

heated to expand, so the piston ring has an opening gap. In order to maintain the sealing, the position of the

opening gap of each piston ring should be staggered during installation. A piston usually has three to four piston

rings, which are divided into gas ring and oil ring according to their function. The air ring is arranged in the ring

groove of the upper end of the piston head and is used to prevent air leakage, transfer the heat from the piston

head to the cylinder wall, and disperse the heat of the piston. The purpose of the oil ring is to prevent the lubricating

oil from creeping into the combustion chamber and scraping the excess lubricating oil from the cylinder wall back to

the oil pan, which is installed in the ring groove below the air ring. As long as the requirement of sealing function is

ensured, less piston ring is better than more piston ring, which not only keeps the minimum friction area, reduces

power loss, but also shortens the height of piston, and accordingly reduces the height of engine.

If the piston ring is not installed properly or the sealing is not good, it will cause the oil on the cylinder wall to go up

to the combustion chamber and burn with the mixture, which will cause the phenomenon of oil burning. If the

matching gap between piston ring and cylinder wall is too small, or the piston ring is stuck in the ring groove due to

carbon deposition, the piston will probably scratch the cylinder wall when doing the reciprocating motion up and

down, and for a long time, it will form a very deep groove on the cylinder wall. That is often said, "cylinder"

phenomenon. Cylinder wall with a groove, poor sealing, the same will cause the burning of oil. Therefore, the working

condition of the piston should be checked regularly to avoid the occurrence of the above two conditions and ensure

the good running condition of the engine.

      The piston ring stuck in the ring slot was caused by the carbon deposit during the oil combustion. And what you said about the uneven wear of the piston rings. And just changed four matching or a lot of oil burning. Should be the quality problem that belongs to accessory. diesel oil. Even if the machine for four matching also need to measure the piston and cylinder liner clearance. Do not look at the four sets are components. When it leaves the factory, the assembly is not very serious. There will be too many gaps, It might as well be measured. Your condition should be caused by oil burning piston ring stuck. This situation is mainly caused by the problem of accessories. The installation of the four matching techniques is a necessary skill for a repairman. Generally there are no problems. Once there is a problem the situation will be more serious than this. Such as knock on the cylinder. Slit the tile. The piston ring broke. You said the lack of water caused by the cylinder parts supplier will not compensate for the loss of package. As for the repairman, Outsiders are not easy to judge. Unless you stop working in this garage, another repair shop will find the real reason, And tell you the truth. If the new cylinder liner. Piston and Piston Ring Assemblies but the engine still burns oil. Mainly caused by the following reasons: cylinder liner and piston clearance is too large. The opening gap of the piston ring is too large. Rough internal machining of cylinder liner, The cylinder liner has a taper. In addition, the diesel engine crankcase natural ventilation device also need to check whether unimpeded.

Anodic oxidation.
      With the increase of diesel engine output power, the thermal stress and mechanical stress of piston rise

correspondingly, which leads to the crack and ablation of the wall of piston top combustion chamber.

Because the hard oxide film can effectively improve the heat resistance of aluminum piston top surface. It has

extremely good inhibitory effect on hot cracking, especially for the hot cracking tendency of the combustion chamber

side of the direct injection diesel engine. For this reason, high power pistons generally need to be anodized.
      Judgment.
      When the engine is running in the vehicle, part of the piston knocks on the cylinder. The piston knock is located in

the upper part of the cylinder and is a rhythmic "ticking" sound similar to that of hitting cement with a small hammer.

When the engine is running at idle speed, the sound is obvious and clear. Especially when the engine is running at low

temperature, the sound is obvious, and when the temperature rises, the noise decreases or even disappears.
      The judgment method of Piston knocking cylinder:
(1) cut off oil tank by cylinder. Take the method of cylinder by cylinder to determine the location of the knock, if the oil

to a cylinder, the sound significantly reduced or disappeared, and when the resumption of fuel supply can be heard

when the obvious "tap" sound, indicating that the cylinder piston knock cylinder.
(2) in order to further prove that the cylinder piston knocks the cylinder, the injector of the cylinder may be removed,

a small amount of CD class medium pressurized oil (acting as a seal) may be added to the cylinder, and the injector and

engine shall be installed, and the knock shall disappear or abate, Running for a while the sound of knock again, is the

cylinder piston knock cylinder no doubt.
      The main reasons for piston knock cylinder are as follows:
(1) the clearance between piston and cylinder wall is too large. The standard clearance between piston skirt and

cylinder of WD615 series engines is 0.143-0.182, and the maximum wear limit is 0.35-0.40.
(2) after the engine runs for a period of time, the piston of the cylinder is worn, in addition to the bad lubrication,

the fit gap between the piston and the cylinder is increased due to wear, and a more serious step appears at the

slightly lower part of the first air ring, which makes the piston knock the cylinder with abnormal sound.
(3) after the piston skirt and the cylinder run for a period of time, the wear and tear is serious, causes the serious

round and knocks the cylinder.
(4) some connecting rods are deformed due to various reasons, resulting in eccentric wear of the piston, widening

of the clearance and knocking on the cylinder. Piston knock cylinder will lead to excessive fuel consumption, engine oil,

oil consumption, poor economy. When the piston knocks the cylinder seriously, it will also break the piston and break

the cylinder, so that the connecting rod will be broken and the cylinder block will be damaged.
      Processing. 

      Piston knocks can be handled in the following ways:
(1) after the engine starts, the low temperature movement has the knock sound, after the temperature is normal,the sound

 disappears, may suspend the processing, continues to run. 

(2) when the engine temperature is normal, there is obvious knock sound, it should avoid high speed operation as far as possible,

 disassemble and maintain as soon as possible. 

(3) After removing the cylinder head and extracting the piston, it is found that the cylinder is seriously out of roundness or strain,

 or the clearance between the piston and the cylinder is too large, and should be replaced to replace the cylinder liner, piston and

 piston ring. 

(4) if the connecting rod is found to be deformed, it should be replaced as far as possible.
      Piston connecting rod assembly.
      The main points of assembly of piston and connecting rod of diesel generator are as follows:
Press the copper sleeve of connecting rod. It is best to use a press when installing the connecting rod copper sleeve, or by means 

of a vise. Do not use a hammer to strike it; the oil hole or oil groove on the copper sleeve should be aligned with the oil hole on the

connecting rod to ensure lubrication. 

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

      Smart installation of Piston Pins. Piston pin and pin hole for interference fit. When installing, the piston should be

heated uniformly in water or oil to 90 ℃, 100 ℃, and then the pull rod should be placed in the proper position

between the holes of the piston pin seat, and then the oil coated piston pin should be put into the hole of the piston pin and the

 copper sleeve of the connecting rod in the specified direction. 

      The installation of piston ring. When installing piston rings, pay attention to the position and sequence of each ring. Load the

 connecting rod.