Abstract:On the basis of three-axis coordinate (crankshaft coordinate, intake and exhaust camshaft coordinate) of valve timing mechanism, the geometric layout of timing chain, design calculation method of trajectory and constraint boundary are studied. By using the method of piecewise arc or straight line approximation, the length calculation formula is presented according to the curve’s camber of tension edge and guiding edge. Using the cylinder head of anti drag system test bench, the change rules of transverse vibration displacement of tension plate and noise characteristics at different rotating speeds is studied under the condition of simulating real time chain system alternating load and working environment. With this timing chain system walking trajectory calculation method, under the premise of keeping the system proper tensioning, between the timing chain elongation and the amount of plunger out of tension device has better harmonic relationship. At the same time, the timing chain system is at the normal speed of engine, the transverse displacement of tension edge and noise characteristic of timing chain system can meet the requirements of automotive engine’s power performance. The results provide a new method and approach for the design and evaluation of timing chain system of automotive engine. It has important significance to the wide application of the chain transmission in the automobile and other high technology fields.