There are many reasons that lead to the engine cylinder. For the average user or even many technicians engaged in related work, it is not easy to analyze and judge the cause of the failure quickly and accurately. Xiaobian today to pull the tank for several major reasons to be analyzed, hoping to help the majority of users and maintenance staff.

Engine at work, the piston and piston rings in the cylinder to do high-speed reciprocating motion. Due to the huge expansion thrust generated by the combustion of the mixture, the oil film formed by the piston and the piston ring through the oil is in close contact with the inner wall of the cylinder. Under normal circumstances, the piston and piston ring are not in direct contact with the cylinder due to the isolation and cushioning effect of the oil film. However, under certain conditions, the two will directly contact with each other to generate sliding friction and produce large amounts of heat. If the cooling conditions can not be effectively improved, it may melt the piston, piston ring or cylinder wall metal surface, the sliding friction surface together, resulting in longitudinal movement of the piston longitudinal pull marks, both serious locking, that is, The so-called pull cylinder phenomenon.

The main reason for the following aspects:

1, the initial lack of running the engine, high-speed operation caused by the pull cylinder

For the new engine just assembled, the seemingly smooth inner surface of the cylinder and piston, the outer peripheral surface of the piston ring, in fact, is composed of rugged protrusions of countless micrometers. Before the engine can run at will, The surface of the initial run-in, cut off the peak spikes, so that the surface smooth, uniform force, sliding does not bite each other, smooth operation. Therefore, the new engine must be assembled to some degree of running-in. Otherwise, the piston, piston ring and cylinder with the higher surface of the protuberance, will be subject to concentrated load, the pressure per unit area is very large, the temperature rise after friction, the protrusions soften, melt, so that cylinder.

2, caused by overheating piston cylinder

Local abnormal expansion occurs when the piston overheats. Due to the deformation of the piston, the piston ring groove twisted into wavy, piston ring and piston ring groove briefly or even a long time bite together, resulting in the piston ring does not work. At this time, the edge of the piston ring with very high unit surface pressure and direct contact with the cylinder wall friction, the piston ring not only failed to seal the combustion gas function, and destroyed the engine oil film on the inner wall, causing the cylinder.

The main causes of piston overheating are:

① petrol poor quality, resulting in abnormal combustion of the mixture to produce high temperature;

② oil supply system, the ignition setting or adjustment is poor, resulting in abnormal combustion of the mixture to produce high temperature;

③ poor design of the piston body or poor piston aluminum density, so that from the piston to the cylinder heat transfer caused by insufficient heat overheating;

④ engine external cooling caused by inadequate and overheating.

3, piston ring clearance caused by improper pull cylinder

When the engine is running, its combustion chamber will inevitably produce carbon deposition. Although the oil and piston rings have the function of removing carbon deposit, it is very difficult to clean the carbon accumulated in the piston ring groove, especially in the first gas ring groove. When the piston ring groove carbon deposition is gradually increased, it will give the piston ring to bring improper backlash and backlash, hinder the activity of the piston ring, the piston ring to exert abnormal pressure, the piston ring and the cylinder wall direct contact friction , Resulting in pulling cylinder.

There are several reasons for the carbon deposition in the combustion chamber:

① poor gasoline used in gasoline;

② mixed gas abnormal combustion;

③ mixture of oil supply system too thick;

④ ignition system, especially spark plug ignition failure;

⑤ too much residual oil on the cylinder wall;

⑥ leakage from the cylinder head to the combustion chamber oil.

4, piston and cylinder gap caused by improper pull cylinder

Due to the cylinder bore and piston, piston ring diameter and poor precision machining dimensions and other reasons, making the gap between the piston and cylinder caused improper pull cylinder. When the clearance is too small, the contact pressure between the piston and the cylinder increases and even locks. When the clearance is too large, the swing amount of the piston head increases, the piston head and skirt contact with the cylinder portion, or the edge of the piston ring contacts with the cylinder portion , The pressure per unit area is very high, thus causing pull cylinder.

5, piston and cylinder surface caused by the poor shape of the cylinder

When the engine is working, the ideal shape of the contact surface between the piston and the cylinder should be cylindrical, so that the two are in uniform contact with each other to prevent the occurrence of a large surface pressure. Due to the effect of thermal expansion and contraction, at normal temperature, the shape of the skirt portion of the piston is barrel-shaped in the longitudinal direction and elliptical in the transverse direction. This complex geometry has high accuracy requirements. However, due to design, manufacturing, processing, or materials, it may cause the cylinder to have an undesirable shape.

The main reasons are:

① piston skirt processing accuracy caused by the deformation of the shape;

② poor shape of the cylinder surface processing (roundness, cylindrical degree of tolerance);

③ piston pin diameter or piston pin hole diameter machining accuracy is insufficient, resulting in the gap between the two is too small, or between the two caught foreign objects, making the engine piston pin after the expansion and locking pin lock, hinder the piston skirt Department in the pin hole direction of expansion, resulting in the skirt can not reach the desired shape;

④ When the poor design of the skirt structure of the piston leads to the lack of rigidity, the deformation of the front and rear stress surface of the skirt is concave and concave so that the local stress increases in the direction of 45 ° on the side of the skirt and draws the cylinder.

⑤ Cylinder liner design poor or bad material caused cylinder deformation, making the piston and cylinder near the top dead center with tight, friction increases, causing the cylinder.

6, surface treatment caused by the pull cylinder

From the material point of view, the piston, piston ring in the cylinder high-speed movement, friction heat, the metal surface will melt serious adhesion together, therefore, the general piston, piston rings and even the cylinder surface of a variety of surfaces Treatment, such as chrome plating, nickel plating, molybdenum spray, nitriding, phosphating, PVD (physical vapor deposition), so that the surface covered with a layer of high melting point material, so as not to produce the purpose of high temperature fusion. However, if the surface treatment is poor, such as coating thickness is not enough, poor adhesion, the piston and the ring and the cylinder at high temperature fusion, it is inevitable.

7, caused by the failure of oil lubrication cylinder

Engine work, the oil in the cylinder and piston, piston ring form a layer of oil film, which can effectively avoid the direct contact between the two friction. However, the following conditions will make the oil can not give full play to its lubricating effect, resulting in pull cylinder:

① lack of oil. Obviously, when the lack of access to the amount of oil, the engine oil consumption in the course of continuous consumption can not be replenished, it can not build a sufficient thickness of the film and pull the cylinder.

② oil emulsification. Especially in winter, when the temperature of the engine drops off after the engine is turned off, the moisture in the air in the lower part of the cylinder bore and in the crankcase (drawn in from the breather pipe) condenses into water and mixes in the oil, which gradually causes the emulsification of the engine oil. At the same time, the mixture leaking from the combustion chamber is also continuously incorporated into the oil to promote the emulsification of the oil. Oil concentration after emulsification thinning, so deterioration of oil, not easy to cylinder and piston, piston ring to establish an effective oil film.

③ improper selection of oil grades. Depending on the region, the season should choose the appropriate brand of oil, if improper selection, in the winter oil sticky, poor liquidity, in the summer oil too thin, can lead to poor lubrication.

8, foreign body, impurities caused by the pull cylinder

When the cylinder and the piston, the piston ring between the hard foreign body, the foreign material play the role of research materials, so that the two accelerated wear and tear, serious pull cylinder.

The main sources of foreign objects are the following aspects:

① engine parts cleaning is not clean and bring in dust and other foreign matter;

② engine parts on the residual burr;

③ engine iron grinding process down, aluminum scrap;

④ air filter filter with poor air into the dust;

⑤ oil, mixed gas combustion caused by insufficient carbon deposition;

⑥ muffler Sand blasting process remained in the muffler iron sand was sucked into the combustion chamber.