Research On Meshing Mechanism And Experimentation Of Double-pitch And Variable-pitch Silent Chain For Conveyor

As the development of automobile industry, the performance of traditional chainconveyor for automobile assembly line has been unable to meet requires of automobile’sassembling speed and quality. In the automobile assembly line, the chain conveyors almostall adopt double-pitch roller conveyor chain as the traction and carrying components.Because of the constraints of the structure, as the increase of assembly speed, the highernoise, severe abrasion, the conveyor was locked since the dimensions of parts was smallerthan the width of inner-link and other problems appeared in succession, which affectsautomobile assembly line’s assembly speed and assembly quality. Traditional silent chainhas a lot of advantages such as high-speed, low noise, low wear, high stability, and so on,and has been widely used in various transmission fields. But when it is used in theconveyor chain, since its heavy self-weight, there will result in great impact, large noiseand severe vibration which seriously affect chain conveyor’s delivery performance. So, ithas important theoretical value and engineering application significance that research howto reduce traditional silent chain’s self-weight and make it can be applied in the chainconveyor to meet the chain conveyor’s new requirements about delivery speed, reliabilityand environmental friendliness.Firstly, this paper described application and research status of chain transmission andchain conveyor in various fields, emphasized the important role the conveyor chain playedin chain conveyor and the important role the chain conveyor played in the nationaleconomy, which reflects the academic value and practical significance of the research ofdouble-pitch variable-pitch silent conveyor chain (short for double-pitch silent chainbelow). By analyzing the cause of why silent chain can’t be applied in chain conveyor andbased on the research achievements home and aboard, this project proposed the structure ofdouble-pitch variable-pitch silent conveyor chain which is suitable for chain conveyor.A new type of double-pitch silent conveyor chain with inner-outer compound meshingmechanism and rocker-pin joint was proposed for the first time in this paper. The chainplate has three teeth, teeth on both sides are work teeth and middle tooth is used to decreasethe wear between the top toe of chain plate and the track. The main technical parametersand its calculation method were given. And a new type of silent chain connector wasdesigned for being easily assembled. Based on the meshing theory and generating method,the meshing design system of double-pitch silent chain—traditional silent chain—hob—involutes tooth profile sprocket was established, and studied on the coupling relationsbetween the main design parameters of double-pitch silent chain and involutes profilesprocket. Take the double-pitch silent chain system for an example whose pitch is25.4 millimeter and number of sprocket is38, the blueprints had been drawn using CAD soft,and found that the system mesh good. Though weighing test and pull off test, it was foundthat under the condition of equal tensile strength, compared with the traditional silent chain,the self-weight of double-pitch silent chain reduced more than30%. Thus, it verified thecorrect of the design method of double-pitch silent chain and sprocket.The inner-outer compound meshing mechanism was firstly introduced into thestructure of double-pitch silent chain. And then the meshing process of double-pitch silentchain and involutes tooth profile sprocket was deeply analyzed. The analysis results showthat the meshing cycle time was4z, and could be divided into five stages: the innermeshing stage of current chain link→the outer meshing and position stage of previouschain link→the floating stage of current chain link→the inner meshing stage of next chainlink→the outer meshing and position stage of current chain link. Using the planecoordinate transformation principle, the mathematical meshing model of double-pitchsilent chain and involutes tooth profile sprocket was created. And by calculating, the Initialmeshing position equation, the final location equation and the inner and outer meshingalternating position equation were all determined.Based on the research of meshing mechanism of double-pitch silent chain, Theoreticalanalysis and simulation studies on the structural feature, the motion unevenness andmeshing impact feature were implemented. The results showed that the double-pitch silentchain has variable pitch feature and variable pitch cycle feature, which make the Polygoneffect, motion unevenness and impact force significantly reduced. Under the samesimulation conditions, compared with double-pitch roller conveyor chain, the double-pitchsilent chain’s tension side lateral fluctuates reduced24.18%, the unevenness of horizontalvelocity reduced45.61%, the unevenness of driven sprocket’s angular velocity reduced23.13%and meshing impact force reduced52.06%. According to the results, it can bededuced that the double-pitch silent chain play a better conveying performance thandouble-pitch roller conveyor chain.Because of the chain conveyor in automobile assembly line is horizontal, the forcemathematical model of horizontal double-pitch silent chain system was build, and thentheoretical analysis about static load and dynamic load during movement were carried out.The analysis results show that the static load of double-pitch silent conveyor chain containsfriction between the chain and the guide rail besides centrifugal force、chain tension and soon; the additional dynamic load caused by motion unevenness is significantly lower thandouble-pitch roller conveyor chain’s. So it can be seen that the forces situation ofdouble-pitch silent conveyor chain is better than double-pitch roller conveyor chain.Compare tests were carried out to compare the noise feature and wear resistance feature between double-pitch silent conveyor chain system and double-pitch rollerconveyor chain system by closed power flow chain test bench. The test results show thatwhen the rotating speed is equal to200rpm, load is equal to2kN, compared todouble-pitch roller conveyor chain system, the noise of double-pitch silent conveyor chainsystem reduced3.5dB, and with the increase of rotating speed, the noise reduction amountincrease significantly, when the two system under the same rotating speed, and thedouble-pitch silent conveyor chain system’s noise fluctuations is only about double-pitchroller conveyor chain system’s33%; After250hours wear test, Wear elongation rate ofdouble-pitch silent chain is only0.182%, which is only54.5%of that of double-pitch rollerconveyor chain’s. therefore, it can be concluded that compared to double-pitch rollerconveyor chain, the double-pitch silent chain has the advantages of lower noise, higherwere resistance, better reliability and environmental friendliness.The double-pitch silent chain was assembly in the chain conveyor, which is used inthe automobile assembly line, and the40weeks filed wear test was made. The test resultshow that after40weeks filed wear test, the double-pitch silent chian weared slightly, wearelongation rate is only0.13%and the chain conveyor rans well. That can prove thereasonableness of its structure and the feasibility it is used in chain conveyors.In summary, the double-pitch silent chain proposed in this paper, compared withtraditional silent chain, has a lighter self-weight, compared with double-pitch rollerconveyor chain, and has more accuracy delivery position, better reliability andenvironmental friendliness. It is more suitable for application in chain conveyor.This project is supported by national general equipment department project “CDX01Project the noises reduce of chain drive system”.