Timing chain of double VVT overhead camshaft engine for SUV and fabrication method

Abstract

The invention relates to a timing chain of a double VVT (variable valve timing) overhead camshaft engine for an SUV (sports utility vehicle) and a fabrication method. When the maximum output power of the engine is 103kW, the maximum torque of the engine is 180N.m, the maximum crankshaft sprocket speed is 6000rpm, and the compacting moment of a camshaft is 28N.m, (1) the tensile strength of the timing chain is greater than or equal to 10kN and the circumferential tension is less than or equal to 1650N; (2) arc diameters of two ends of outer and inner chain plates of outer and inner chain links in a transmission chain of a timing system is 7.6max; two chain pin shaft holes with 8mm of a pitch are formed on each of the chain plates of the outer and inner chain links; the distance between every two holes is 8mm; and the internal distance between the two chain plates of the inner chain link is 4.6min. The method has the advantages that: firstly, the requirements that the tensile strength of the timing chain is greater than or equal to 10kN and the circumferential tension is less than or equal to 1650N are met; secondly, the pin shafts adopt 75 material and the surfaces of the pin shafts are strengthened by chroming; the tensile strength reaches 11-12kN; the requirements of the high-power and high-torque SUV and double VVT vehicle engine are met; thirdly, rollers are subjected to cold heading, thermal pretreatment ,quenching and tempering; the stress concentration of circumferential cracks is eliminated effectively; and the impact resistance is improved.

Description

technical field [0001] The invention relates to a seamless sleeve outcropping assembly, the pin shaft tensile strength reaches 11-12KN, and the roller adopts the method of cold heading + preheating + quenching and tempering, which can effectively eliminate the stress concentration of annular cracks and improve the impact resistance of the chain The invention discloses a double VVT ​​overhead camshaft engine timing chain and a manufacturing method for a high-performance SUV automobile, belonging to the field of auto parts manufacturing. Background technique [0002] CN102312690A, title "Design method of V-type automobile engine timing chain system", the calculation of the concave sag value of the timing chain is based on the following formula: hn=rn[1-cos(αn / 2)], where: h corresponds to The concave sag value of the timing chain; r the radius of curvature of the side arc in contact with the corresponding guide rail; α the radian of the side arc in contact with the timing chain...

AI Technical Summary

Problems solved by technology

Its shortcomings: first, the rolling sleeve and the inner chain plate are flattened, and the pin shaft is carburized with 30CrMnTi material, and the tensile strength is low, only 7.9-8.2KN; second, the rolling roller is round at the seam Poor precision, the impact force increases when it meshes with the sprocket in a free state, and it is prone to fragmentation; the third is that the punch is chamfered and transitioned, which is easy to scratch the workpiece (the deep one may turn into a crack source) and the symmetry Not good, the roller has obvious annular steps; the fourth is that after perforation, it is easy to produce a stress concentration area when it is torn with the part itself, and it is deformed and broken after heat treatment; Larger ones may turn into crack sources) and the symmetry is not good, and the rollers have obvious annular steps; fifth, after perforation, the part itself is torn and easily produces a stress concentration area, and after heat treatment, it is deformed and then cracked; sixth, due to cold heading At the same time, the coaxiality of the upper and lower punch rods is not well controlled, and the end of the punch rod is a straight chamfer transition. The cold heading roller has a ring of steps on the bottom surface of the punch, which can also be said to be the source of cracks. Concentration, reduced fatigue strength, unable to withstand the complex working conditions of high-speed variable load and multiple impacts of automobile engine chain rollers

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