Research On Tooth-skipped Gear Honing&Its Key Technology

Gears are basic parts in the mechanical systems.Among them,case-hardened gears are widely applied in automobile,aerospace,high speed train,wind power and so on with its advantages,small size,low weight,high load capacity,long lifetime and good transmission precision.The main process to manufacture gears contains gear hobbing,gear shaving,gear shaping,gear skiving,gear grinding and gear honing.As grinding and honing have better precision and surface quality,they are usually used as the last process of gear manufacture.Compared with grinding,honed gears have lower transmission noise and better wear resistance.So it is more suitable for the processing of case-hardened gears.The gear honing technique includes internal gear honing and external gear honing.The internal gear honing machines are complicated and expensive,and our country relies on imports for it.The external gear honing machines are cheap,but they will produce mid-concaved profils and the honing wheels have poor stability of precision.These problems limit the application and promotion of gear honing.Through the theoretical innovation and technological innovation,this paper solves the key problems of meshing principle of tooth-skipped gear honing,grinding mechanism of tooth-skipped gear honing,topology modification profile peocessing based on tooth-skipped gear honing and profile processing error correction technology,which provide strong support for the successful application of the tooth-skipped gear honing to the manufacture of case-hardened gears.The research shows the tooth-skipped gear honing could be used to process case-hardened gears with high precision and coud realize the profile topology modification with any shape.This paper studies on the basic theories and key techniques of this new gear process technology.The main contents of this dissertation are as follows:(1)The external tooth-skipped gear honing technology is proposed.This process uses the characteristic of the principle,that there is only one pair of teeth in contact,to ensure the grinding force doesn't change a lot during the honing,which avoids the mid-concaed profile.The meshing principle of the external tooth-skipped gear honing is studied in two aspects,two-dimension and three-dimension.The different meshing processes are decribed and the models of involute meshing process and tip meshing process are established.The computing method of the demarcation points between each process is given.The trail of the contact points and the relative speed at the contact point are calculated.The speed curve of the processed gear and the gear integrated error unit curve are drawn.These two curves of the 2-D model and 3-D model are compared,which shows that the 2-D model could replace the 3-D model to deduce the angle relationship between the honing wheel and the processed gear when the gear is without modification.(2)The grinding force and grinding burn of the grinding mechanism are studied.Based on the geometry characteristic and motion law,the analog grinding model suitable for external tooth-skipped gear honing is built.According to analyze the analog grinding model,the model of the grinding force are established based on plane grinding model.The grinding speed,equivalent diameter and grinding deep are computed.The grinding power is deduced based on the grinding force model.Referring to the temperature rise model and energy partition model of the processed gear,the temperature of the grinding region after max temperature rise is calculated.The temperature could be used to judge whether the grinding burn will appear.(3)A new kind of topology modification processing method is presented based on the external tooth-skipped gear honing.It uses motion control to process modification instead of copying the modification on the cutting tool.This method makes effective use of the characteristic that there is only one contact point during the honing.The topology modification could be completed because the position of this contact point could be determined by controlling the motion relationship between the honing wheel and the processed gear.The differenc between the new topology modification method and existing methods are explained and the advantages of the new method are shown.Taking the parabola modification as an example,the relationship between the modified profile and the honing wheel are analyzed.For the problems of cutting tool adjusting and angle synchronization,this paper gives the appropriate solve with deep analysis.(4)Gear processing error reverse correction technique is put forward based on the external tooth-skipped gear honing.Same as the topology modification method,this technique also uses the characteristic that there is only one contact point between the honing wheel and the processed gear.By controlling the angle relation of them,the single point correction processing could be conducted precisely.Using the multi-degrees of freedom theory for gear deviation to decompose the profile deviation of the processed gear,the models of each error are built.The undetermined coefficients in the models are calculated based on the measured data.The model with error elimination is given to be the reference to calculate the new angle relationship.(5)A complete set of experiment scheme is provided to verify the research.The machines and instruments used in the experiment are introduced.The hob which is used in rough processing before honing is inspected to guarantee the gear before honing meets the requirement.The 2-D model and 3-D model are used to honing gears to examine validity.It is analyzed that the 2-D model could replace the 3-D model.Gears with sevral kinds of modified parameters design are processed.The results verify the feasibility of the new topology modification method and some its advantages.