Study Of Meshing Design And Transmission Performance Of Rotundity-Datum-Aperture Hy-Vo Silent Chain

The movement and power of the silent chain transmission are transmitted by the meshing between the teeth of the sprocket and the silent chain plates. According to the structure shape of the pin, there exist two types of silent chains: round-pin silent chain and rocker-pin silent chain. The rocker-pin silent chain can be also called Hy-Vo silent chain. Having the characteristics of variable pitch and variable equivalent side-heart distance, Hy-Vo silent chain may reduce the chordal action, impact and noise when meshing with the sprocket. Therefore, Hy-Vo silent chain is frequently used as transmitting device in the case of high velocity and heavy load, large center distance, exact transmission rate, especially used for gear box and transfer box of new type sedans. However, the Hy-Vo silent chain is the flexible structure with sectional rigidity, which determines that the reduction of the chordal action is only to a limited extent, i.e., the speed fluctuation of the driven sprocket is reduced to a limited extent. Generally speaking, the meshing transmission of Hy-Vo silent chain and sprocket is quasi-conjugating meshing transmission.With the support and funding from the two projects of the National Natural Science Foundation of China-New Hy-Vo Silent Chain Meshing Mechanism and Design Method (50575089), Meshing and Design Theories Based on the Multi-variant and New Hy-Vo Silent Chain(50975117), and national high technological and developmental plan project (863) titled"Digital Method Research and Platform Development Based on the Sophisticated and Divesified Hy-Vo Silent Chain (2009AA04Z109), this paper conducts an in-depth study on the meshing mechnism of rotundity-datum-aperture Hy-Vo silent chain and its theoratical basis– the meshing mechanism of rack and gear. Also in this paper, an example is given of rotundity-datum-aperture Hy-Vo silent chain composed of outer meshing mechanism and inner-outer meshing mechanism in an ordered arrangement. The meshing design system, the correct meshing condition, the transmission characteristic, the simulation technology of dynamics and the laboratory test methods are analyzed in this example.The research of the meshing mechanism is the key aspect as well as the more difficult one of the rotundity-datum-aperture Hy-Vo silent chain transmission research. The investigation about the meshing mechanism of rotundity-datum-aperture Hy-Vo silent chain can rarely be found in literatures both home and abroad. The related literature indicates that the meshing between the silent chain and the sprocket can be seen as the meshing between the rack and gear. Actually, the sprocket is a gear with large negative modified coefficient and large pressure angle. The study of the meshing mechanism and correct meshing condition of rack and gear is the premise and foundation of studying silent chain meshing mechanism and correct conditions. The paper studies and discusses the meshing mechanism and correct meshing conditions between the rack and standard gear, the rack and modified gear, the rack and standard gear with unequal module and pressure angle. The resolved expressions of the correct meshing conditions and the modification coefficients of the modified gears are put forward. It can be found that the meshing between the rack and gear is actually the meshing between the standard rack and modified gear when the so-called gear and rack module and pressure angle are not equal, but still meet the proper meshing conditions, the module and pressure angle of the rack and gear being still equal with each other. When the rack engages with the modified gear, changing of the module and pressure angle of the gear under the correct meshing condition has in essence changed the modified coefficient of the gear, and it is still the rack meshing with the gear with different modified coefficient, in which the module and pressure angle of the rack and gear are still equal with each other. For an engagement between standard rack and gear, under correct meshing condition, to increase pressure angle is to increase corresponding module, which is equivalent to positive modification; whereas to decrease the pressure angle will decrease module, which is equivalent to negative modification;Based on the study of the meshing mechanism and correct meshing condition of involute spur rack and gear, the basic terms, symbols and definitions are given of the rotundity-datum-aperture Hy-Vo silent chain. Discussions centers round the relationships and differences among the basic pitch, measured pitch and round-chain pitch of silent chain and their separate applications. The author studies the meshing design mechanisms of the rotundity-datum-aperture Hy-Vo silent chain from several different aspects such as the meshing theoretical basis of silent chain and sprocket, the correct meshing condition between silent chain and sprocket, and the incremental calculation of correct meshing round-chain pitch. The design system of the rotundity-datum-aperture Hy-Vo silent chain is also given, with discussions focusing on the attributes of the latter one's variable pitch and variable equivalent side-heart distance. An application in the real-life engineering case is provided in this paper which uses the serial products of rotundity-datum-aperture Hy-Vo silent chain HV6 and HV8.In this paper, the force of each structural parts of rotundity-datum-aperture Hy-Vo silent chain in the process of silent chain drive is analyzed. The finite element analysis to the inner-outer meshing silent chain plate and the outer meshing silent chain plate are done with the working load. The result indicates that the stress distribution and the weak point in intensity of the chain plate can be known easily, which may provide the reliable theoretical basis for the topology design of the chain plate.The virtual prototype simulation is conducted after this paper elaborates the simplifying method of the rotundity-datum-aperture Hy-Vo silent chain transmission system, separately establishes three dimensional models for the pure outer meshing, inner-outer meshing and outer plus inner-outer meshing sequential arrangement rotundity-datum-aperture Hy-Vo silent chain transmission system, and establishes their corresponding virtual prototype models. The method of segmentation refinement is proposed to deal with the mating surfaces involved in the virtual prototype of rotundity-datum-aperture Hy-Vo silent chain. The problem that the simulation result affected by the real contour curves cannot be simulated in the Adams software is also resolved. The chordal actions produced in the three silent chain transmission systems are gained respectively from the two aspects of the tight side chain plate and the sprocket center distance and then compared with each other. The contact forces of typical hinge are gained and its rule of changing is analyzed. The force flow distribution of the whole silent chain is gained and analyzed. The rule of changing of the contact forces between the typical chain plate and sprocket in the silent chain transmission system is then studied.The index and effective testing methods to test the transmission performance of the rotundity-datum-aperture Hy-Vo silent chain are also put forward, and then tested for various index with these methods. The basic theory about noise is analyzed, the test equipment and test methods are introduced, with the test data given and analyzed. The result obtained under the premise that without affecting the silent chain and sprocket meshing indicates that, it is more beneficial to reduce noise with the smaller silent chain sag. The result has certain significance for the practical application of engineering. The test principle and method of chordal action of rotundity-datum- aperture Hy-Vo silent chain is put forward, the chordal action is tested, and the test data is gained and analyzed. It can be known from the test result that the chordal action of the rotundity-datum- aperture Hy-Vo silent chain is small.Proposed first in this paper, the correct meshing design method of the rotundity-datum-aperture Hy-Vo silent chain has national independent intellectual property right. It not only has academic value but also has practical significance. Part of the research achievements have already been applied in Hangzhou Donghua Chain Co. Ltd. and has assisted the company in developing rotundity-datum-aperture Hy-Vo silent chain products with three specifications, among which HV6 and HV8 has passed the official check by Shanghai Steam Turbine Works and Dongfang Steam Turbine Works. They are now being manufactured in bulk package and have replaced the similar products once imported from Morse Company. It has been proved that their performance is better than their counterparts from abroad. HV6 product has won the First Prize of the General Machinery Parts and Components for its outstanding performance. The engine assembly test and the host machine operating test combined show that the meshing design method raised in this paper is both scientific and feasible.The achievement of this paper will promote the progress of related industry, enhance the innovation capacities of enterprises and produce significant economic and social benefits and its practical application and prospects are bright.The most innovative achievements of this study are listed as follows:(1) It is the first study which explores the meshing mechanism and correct meshing condition of the rotundity- datum-aperture Hy-Vo silent chain based on the meshing mechanism and correct meshing condition between rack and gear. The meshing design system of the rotundity-datum-aperture Hy-Vo silent chain is further perfected.(2)Based on the meshing design method of rotundity-datum-aperture Hy-Vo silent chain proposed by this paper, the designed HV6 silent chain got the first prize of Chinese general mechanical parts design.(3) It is the first study which elaborates the transmitting process of the chain force stream in the rotundity-datum-aperture Hy-Vo silent chain transmission and conducts the finite element analysis on the main structural parts. The study thus provides a strong theoretical basis for the topological design for the main structure.(4) The whole virtual prototype of meshing transmission system which includes driving sprocket, driven sprocket and the rotundity-datum-aperture Hy-Vo silent chain is established based on the multi-body dynamics theory; the meshing process of rotundity-datum-aperture Hy-Vo silent chain is simulated on the multi-contact dynamics simulation technology; the research provides the effective analysis method to the study of the chordal action, the contact force between link plate and sprocket, link plate and pins, pin and pin.(5) It is the first study to put forward the laboratory measurement method to measure the chordal action of the rotundity-datum-aperture Hy-Vo silent chain and conduct the measurement test in laboratory. Compared with the dynamic simulation results, the simulation results indicate that the method is reliable and effective. (6) This study also conducts the bench noise test on the rotundity-datum-aperture Hy-Vo Silent chain products with different sags and rotational speeds, whose result helps to put forward the recommendation value of the allowed sag for engineering practice.(7) The meshing design method of the rotundity-datum-aperture Hy-Vo silent chain proposed by this paper has already been successfully applied in Hangzhou Donghua Chains Group Co. Ltd and has assisted the company in developing rotundity-datum-aperture Hy-Vo silent chain products with three specifications, among which HV6 and HV8 has passed the official check by Shanghai Steam Turbine Works and Dongfang Steam Turbine Works. They are now being manufactured in bulk package and have replaced the similar products once imported from Morse Company. It has been proved that their performance is better than their counterparts from abroad.