Design Theory And Method Of Non-Hertz Contact Gear And It’s Empirical Research

Gear is widely used in mechanical equipment and plays an important role in mechanical transmission.With the rapid development of industrial production,the requirements for the life and reliability of gear transmissions are also increasing.At present,China’s gear industry basically relies on ISO gear standard design gears,and the evaluation of tooth surface contact strength is based on Hertz contact theory.The Hertz contact theory does not take into account the effects of lubrication,relative motion,roughness,etc.of the contact tooth surface,so the description of the contact state of the tooth surface is too simplified.Although there are some factors determined by experiments to consider the effects of these factors,with the improvement of performance requirements such as high power density and long service life of gears,the design criterion based on Hertz contact theory is difficult to reveal the contact and failure mechanism of tooth surface accurately,which usually leads to unclear failure form and life estimation of gear,these problems highlight the necessity and importance of accurately describing the real contact of tooth surface and establishing a gear design method considering more factors.In this paper,based on the line contact EHL stress fitting formula,the design formula of gear contact fatigue strength based on EHL stress is deduced.After the viscosity of the lubricating oil is segmented according to different working conditions,the EHL stress and Hertz stress of the gear under different conditions are compared and analyzed,and the size between the design results based on the two stresses.The research shows that the EHL center stress and Hertz stress are very close under different conditions,and between the two design results are very close;The central stress of EHL can also be the same as Hertz stress,which can be used as the theoretical basis for the design of contact fatigue strength of gear.Based on Dowson’s EHL oil film theory,the gear lubrication design formula based on EHL oil film thickness is deduced.Combining the strength design of gears based on EHL stress with the lubrication design of gears,the design formula of non-Hertz contact gears fulfill both strength and lubrication is obtained.The design results of non-Hertz contact gears are compared with those based on Hertz theory under different working conditions.Non-Hertz contact gear design results were validated using a number of different gear examples and anti-scuffing checks were performed on all examples.The research analysis shows that the design results of the non-Hertz contact gear is very close to the actual size of the gears,and all of them fulfill the anti-scuffing check of the gear;However,based on the Hertz theory,the design results is smaller than the actual size of the gears,and some are even difficult to fulfill the anti-scuffing check;The design method of non-Hertz contact gear comprehensively considers the double standards of gear strength and lubrication,which is more in line with the actual working conditions,and the design result is satisfactory,which fully meets the engineering requirements,and has important significance for improving the fatigue life and reliability of the gear.Develop application software based on non-Hertz contact gear design theory and method,This thesis uses the Visual Basic development tools on the Windows platform and Access database management system for software development,which provides convenience to use the theory and method of non-Hertz contact gear design in gear design.