Design Method, Simulation Analysis And Experimental Study Of Automotive Timing Silent Chain System

In recent years, with the invention of new engines and development of design and manufacture technology, silent chain is widely used in the timing drive, pump drive, high-pressure pump drive, common rail pump drive and balancing draft drive of the automotive engines because of significant characteristics such as compact structure, high transmission power, high reliability and wear-ability and low noise. The percentage of the silent chain drive users is 53% in 2006 and increase to 55% in 2011. While the percentage of belt-drive users is 38% in 2006 and decrease to 34% in 2011. At present, only a few industrial countries overseas can produce new silent chain for high-speed automobile engines, and their own most of the patented and interior design tips, the key design methods and results are not published in journals, thus dominating and monopolizing the market and technology in this field. This phenomena causes the technical barrier of new high-quality silent chain production and silent chain system for domestic companies.This paper is sponsored by the National Nature Science Foundation of China (50275062)"Meshing mechanism and design method of new high-speed silent chain"and National Middle and little Company Technology Innovation Foundation (08C26213711011)"Manufacture technology and products of high-performance silent chain of automotive engine", based on intensive analysis of the meshing traces of different meshing mechanisms silent chains, and puts forward the design method of auto engine timing silent chain system, and design method, simulation and experiment on one automotive engine timing silent chain system are studied.The mathematical models of inner-meshing silent chain and inner-outer compound meshing silent chain meshing with the sprocket at different meshing stages are respectively built based on the theory of differential geometry and coordinate transformation. The models are based on the study of the meshing mechanism of inner-meshing and inner-outer compound meshing. Meshing traces of two different meshing mechanism silent chains are solved. From the meshing traces of inner-meshing and inner–outer compound silent chain, it can be seen that the engagement process of inner-meshing silent chain is divided into the meshing process of plateⅢwith the teethⅢand the locating of plateⅡ, and the engagement process of inner-outer compound meshing silent chain is divided into inner meshing, inner-outer compound meshing and locating of outer meshing. The trace on inner meshing stage is the longest. The polygon effect of new silent chain according to the fluctuating quantity of the centerline of the silent chain's tight side is studied, and the results of the traces of the chain's pin center show that, the fluctuating quantity of the tight side's centerline in inner-meshing is only 64.6% of which in outer-meshing, and the fluctuating quantity in inner-outer compound meshing is only 28% of which in outer meshing, it can be concluded that the polygon effect in inner-meshing and inner-outer compound meshing is better than that in outer-meshing obviously.Situations of study on auto engine timing chain system in domestic and international are summarized in this paper, and the importance of silent chain system in auto engine is described. Auto engine timing system's intake and exhaust stroke and related phases are studied deeply. The design method of auto engine timing silent chain system is raised, and the key calculation of the tensioner and the guider are described, and designs and calculates the timing silent chain system of the engine according to the layout plan and performance requirements of the auto engine are get, and it lays an important foundation for the formation of independent intellectual property rights in silent chain system design theory and methods.The mechanism-control virtual digital prototype model of the auto silent chain system based on the multi-body dynamics theory of recursive algorithm and modern contact dynamics are built in this paper. The dynamic characteristics of the timing silent chain system in the multiple constraints boundary conditions under different speeds are studied. The trajectory, chain tension force, drive ratio of crankshaft sprocket and camshaft sprocket and contact force of the tensioner plunger and tension plate are obtained. Dynamic harmonic amplitudes of the chain tension and normal contact force at different speeds and different engine orders are also obtained. The result not only provides scientific methods for the simulation of the auto timing chain system's dynamic characters, but also provides effective methods for the changes of contact force between different components and FFT spectrum analysis. Compared with the previous results by scholars in mass-spring-damper element simulation, the research results have more scientific and reliable for its physical access method which is more close to the actual conditions.The paper is studied on the first automatic loading, automatic transmission multi-axis drive system auto engine timing chain system test bed which is in independent research and development. With the real-time noise analyzer AWA6290A, the timing silent chain system's noise characteristics are researched under a variety of conditions. By analyzing the load torque of the camshaft and noise, the result show that the noise increases with the increase of camshaft's load torque. By analyzing the speed of the crankshaft sprocket and the noise of the timing chain system, the result show that weighted noise level increases along with the increase of speed of the crankshaft sprocket. According to the spectrum analysis at three different speeds, the result show that the peak frequency is related to the meshing frequency and the inherent frequency of the silent chain. By the engine spectrum analysis, the result show that the peak of the noise is the 9.5th, 19th, and 38th, and the noise value is the maximum at the meshing frequency (19th) of the chain plate and the sprocket (z1=19), which verifies the correctness of the simulation. According to the research of the oil pressure of the tensioner and the noise, the result show that the noise is relatively low when the pressure is high, but thus leading to the wear between silent chain and the guider, silent chain and the tensioner, silent chain and the sprocket, so suggested that the oil pressure takes 5bar. The mechanism of noise is researched in this paper, and method of control noise is proposed.Takes real-time temperature measurement of the timing silent chain system at low speed using PhotoTemp MX digital photography infrared thermometer when the oil pressure is 5bar and 3bar, the results shows that the temperature in the two pin showing the location changes at two peaks, this is because of the friction between the pin and the plate; the working oil temperature, the tank oil temperature and the returning oil temperature are tested under different oil pressures, at the pressure of 5bar and 3bar, though the temperatures are all under the limited 120℃, the working oil temperature, the tank oil temperature and the returning oil temperature at the pressure of 3bar are all higher than that of 5bar, so the oiling plays an important role in the reliable of the timing silent chain system.The research results play an important role in the formation of independent intellectual property rights in China in design theory and method of the auto engine timing silent chain, according to the dynamic simulation and the experiments of the auto timing silent chain, the design theory and method mentioned in this paper are scientific and reliable. The research results accelerate the domestic process of the auto engine timing silent chain system, and they have very important significance in improving the ability of independent research and design in related industries and enterprises.