Pondering high-power internal combustion engine cylinder liner

The diesel engine cylinder liner is an important part of the diesel engine. The quality of the honing mesh on the inner wall directly affects the engine power, oil consumption level and emission index. The evaluation of the quality of honing is mainly determined by the following three parameters: the simple peak height Rpk, which is the initial wear height of the piston ring; the surface roughness core contour depth Rk; the simple valley depth Rvk, which is within the normal wear range, The maximum depth of the groove portion that is well lubricated. The quality requirements for diesel engine cylinder liner honing are shown in Figure 1.

Platform honing

Platform honing is a more advanced honing process than ordinary honing. It has a smooth flat top (not a sharp peak) on the surface of the cylinder bore, and a relatively deep trough (deeper than the ordinary honing). Interval distribution, short running-in period of the engine, good lubrication conditions and high production efficiency. The platform trowel formed on the inner surface of the cylinder liner improves the cylinder mass of the engine, prolongs the service life of the engine and improves the economy of the engine. And dynamics are important, especially in overcoming the early engine wear and reducing engine fuel consumption. Therefore, the design requirements are: Rpk < 0.5 μm, Rk = 1.2 to 2.7 μm, and Rvk = 3.0 to 5.8 μm. In order to meet the design requirements, our company introduced platform honing technology when developing diesel engines. The platform honing is a new process for our company. The cylinder liner that has just been processed has a honing texture quality of 70% to 80% that does not meet the design requirements, and most of them are Rpk values ​​and Rvk values ​​exceeding the standard. Looking at the relevant information, we found that most of these materials are small cylinder liners, and there is not much information on the honing processing of cylinder liners in high-power diesel locomotives. Therefore, after a lot of experimental production, we have determined the honing allowance and honing. Process parameters such as speed and honing working pressure of oil stone.

Fig.1 Quality requirements for boring of inner bore of diesel engine cylinder liner

2. Implementation process

(1) Roughing process of platform honing process: rough inner hole, mainly to form a cylindrical hole with correct geometric shape, suitable for basic surface roughness and uniform cross-mesh of subsequent processing, forming a netting for the platform honing process basic structure. Fine boring process: forming a uniform cross-web. Platform honing process: forming a platform section.

(2) The determination of the honing machining allowance is small, the inherent error of the cylinder bore cannot be fully eliminated, the accuracy is re-established; the margin is large, the honing time is long, the machining efficiency is low, the stone wear is fast, the processing cost is high and the machining precision is poor, the quality Unstable. After repeated tests, considering the processing quality, machining accuracy and processing cost, the rough machining allowance is determined to be 0.03 to 0.07 mm, and the fine machining allowance is 0.03 to 0.05 mm.

(3) Determination of coarse and fine honing angle In honing processing, the cutting cross angle has a great influence on the amount of cutting and the amount of honing stone wear and surface roughness. Increasing the cutting cross angle increases with the reduction of the grindstone. Of course, the surface roughness value of the surface to be processed also becomes larger. This is because the sharpness of maintaining the honing stone during the honing cutting process is trimmed by the surface roughness of the machined surface. Only a sharp honing stone can increase the amount of cutting, and if the oil stone is sharp, it must wear. When the cutting cross angle is 0°, the cutting efficiency is low; when the cutting cross angle is 90°, the honing oilstone wears large, and the processing surface roughness value is large, which in turn makes the cutting amount small. Through the test, the cutting amount is the largest when the cutting cross angle is about 45°. Therefore, in the roughing process, a cutting cross angle of about 45° is used, and a cutting cross angle of 40° is used in the platform processing.

(4) Selection of working pressure of honing oilstone Working pressure of honing oilstone has great influence on honing cutting performance, which directly affects cutting efficiency, honing oilstone wear and workpiece precision and surface roughness. When the honing work pressure is high, the honing cutting amount and the honing stone wear amount are large, and the machining precision and the surface roughness are also poor. When the working pressure is small, the amount of cutting and the wear of the honing stone are small, and the machining accuracy and surface roughness are good.

When selecting the working pressure of honing stone, in addition to the above considerations, according to the size of the machine tool used, the rigidity of the honing head and the honing jig, the strength of the honing stone, the actual contact surface of the honing stone and the machined surface, and the workpiece Factors such as material, size and shape are fully considered.

Based on the above factors, the working pressure of honing oilstone is 28~29MPa when rough, and the working pressure of honing oilstone is 23MPa when boring.

(5) Selection of honing speed The honing angle is determined by the combination of the rotational speed and the reciprocating speed. The honing angle is determined, and the ratio of the two speeds is determined. The reciprocating motion should have sufficient acceleration and the commutation should be fast, otherwise the arc shape will appear at the intersection of the netting. The speed and reciprocating speed also affect the efficiency of the honing. The higher the speed, the higher the efficiency, but the excessive speed will adversely affect the quality of the reticle.

Finally, we determined that the speed was 40r/min when rough. The speed of the platform honing is 52r/min. As shown in Fig. 2, the traverse angle of the honing is θ, the reciprocating speed of the honing head is vy, the rotation speed is n, and the cylinder hole diameter is D, according to the formula of the crepe crossing angle

figure 2

Tan(θ/2)=fy/vx=vy/(πDn)

It is concluded that the reciprocating speed of the honing head is

Fy=πDn tan(θ/2)

When the rough boring is obtained, the reciprocating speed of the honing head is 216.77 mm/s, and the reciprocating speed of the honing head during the honing of the platform is 247.62 mm/s.

3. Conclusion

Through the improvement of the honing process parameters and the continuous trial processing, the author gradually mastered this new process, and the surface quality of the processed cylinder liners has been continuously improved and stabilized. At present, the processed cylinder liner is controlled to be within 0.5 μm by the Rpk value, and the Rvk value is controlled within 3.0 to 5.8 μm, which improves the service life and emission index of the diesel engine.

British Fittings are manufactured using British threads such as British Standard Pipe Parallel (BSPP) and British Standard Pipe Tapered (BSPT). These fittings and adapters are commonly found on equipment manufactured in the United Kingdom as well as from some OEM's in Europe.                                                     

The BSPT (tapered) male will mate with a BSPT (tapered) female and the BSPP female swivel. The BSPT male has tapered threads and a 30-degree inverted seat.