Key Processes in Automotive Engine Cylinder Block without Cylinder Liner Technology | Coating Honing
Release time:
2020-09-14
Automobile engine liner-less technology originated in Europe. It utilizes thermal spray technology to apply a wear-resistant coating to the inner wall of aluminum engine cylinders, replacing traditional cast iron cylinder liners. This not only reduces engine weight and fuel consumption but also significantly lowers engine friction and improves engine performance.
Engine technology without cylinder liners originates from Europe. It utilizes thermal spraying technology to spray a wear-resistant coating onto the inner wall of the aluminum engine cylinder, replacing the traditional cast iron cylinder liner. This not only reduces engine weight and fuel consumption but also significantly reduces engine friction and improves engine performance.
After cylinder spraying, the final machining of the coating is crucial. The coating must be honed to ensure the cylinder achieves the correct diameter, roundness, and surface roughness. A well-known European thermal spraying company, based on the measured results of oil and fuel consumption reduction from engine tests, has made fine adjustments to the recommended technical specifications for the honed coating surface, as shown in the table below. To ensure that pores do not retain potentially mixed debris, it is crucial to properly clean the coating surface after honing. Burr removal is needed at the edges of the pores, and the honed surface should be free of deposits.
Table 1: Recommended Roughness Specifications After Coating Honing
Recommended Roughness Specifications After Coating Honing
After rough and fine honing, the inner surface of the cylinder bore achieves a mirror-like finish, as shown in Figure 2. Compared to the honing of traditional cast iron cylinder liners, the honed coating surface exhibits a porous structure rather than a network structure. Figure 3a shows the microscopic structure of a traditionally honed cast iron cylinder liner, and Figure 3b shows the microscopic structure of a honed coating.
Mirror-like state after coating honing
Figure 2: Mirror-like state after coating honing Figure 3: Microscopic morphology of traditional cylinder liner honing and coating honing
It is precisely because the coating surface has a porous structure that the smoothness of the coating surface is reduced by 25%, which is one of the reasons why this technology can significantly save engine oil. The gentle, rounded pores also reduce the area of oil exposed to the combustion chamber and piston rings, reducing the tangential force of the oil scraper ring, allowing the piston ring to enter the hydrodynamic state faster, significantly reducing friction, as shown in the work diagram in Figure 4. Less engine friction means lower frictional heat energy consumption, reduced engine blow-by and oil consumption, and ensures maximum operational reliability. (Blow-by refers to the combustion gas "blowing" from the piston ring gap into the crankcase due to wear or deformation of the cylinder and piston, affecting engine power and fuel consumption.) Due to the inherent porosity of the final coating, the oil storage structure will not be worn away like a network structure, but will open new pores as wear progresses into the coating, thus significantly improving its service life efficiency.
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