Hypoid Gears Loaded Tooth Contact Analysis And Studies Of Lubrication And Wear

Hypoid gears are widely employed in a variety of industries such as vehicles,aircrafts and instruments,due mainly to its capability of conducting heavy duties as well as enabling long-term stable operation.Scientists of hypoid gears in early studies used to pay their great attention to machining accuracy on the manufacturing side.However,this would be insufficient,and an obvious trend has seen modern industry increasing demand for high-performance and noise-free drivetrain of hypoid gears.In consideration of such trend,the “conjugate approach” is introduced as core contact theory of this doctorial dissertation,of which the loaded tooth contact analysis(LTCA)model of hypoid gears is developed to carry out series of key studies,including: tooth contact performance;dynamic behaviors;frictional loss,mesh stiffness,damping and load sharing in multi-contact;and tooth surface wear.The most unique feature of this dissertation is that key performances are investigated with full consideration of tooth contact condition.For such purpose,same design hypoid gears are subject to different curvature correction on tooth surface,and its influence on key performances is investigated.The face-milling(FM)hypoid gears is chosen as research target of this dissertation for reason that Gleason has led hypoid gears design and manufacturing for more than ten decades.Gleason has successfully developed “partial conjugate” theory for spiral bevel gears to promote its performance by method of exerting certain degree of curvature correction on tooth surface from “reference point” in tooth profile and lead directions.Model of loaded tooth contact analysis(LTCA)is often used as the tool to investigate the tooth contact performance of hypoid gears,and tooth contact theory is the most essential part of this dissertation which facilitates the aforementioned key studies that requires LTCA involved.Till now,gear scientists have developed analytical,finite element,numerical simulation methods for hypoid gears LTCA.Disadvantage of analytical method for hypoid gears is that the method is only applicable to reference point which is the only point of tooth surface in full conjugate contact,and there is no accurate solution to a point which is far away from reference point.Disadvantag of finite element method is that precise 3D-CAD solid model and extremely high mesh refinement are needed.Moreover,the finite element model is inefficient to represent machining settings variation which would lead to tooth surface curvature correction.Numerical LTCA,as a preference,is applied for easy combination with other key studies,since this dissertation involves different research target and computation module.By aid of tooth surface discretization,numerical LTCA is also possible to give precise solution to any tooth surface point of hypoid gears.Kubo-Wang “conjugate approach” is introduced in this dissertation as contact theory of hypoid gears,in which reference surface is built from pinion parameters and expressed in gear coordinate system to provide convenience to contact search operation in one coordinate system with high computation accuracy and convergence speed in return.The conjugate approach LTCA model is utilized in this dissertation as base module which combines with other key studies aforementioned.The main contents and originality highlights of this dissertation are:1)Conjugate approach LTCA model is developed applicable for theoretic tooth surface from machining settings but also worn tooth surface.The conjugate approach LTCA algorithms are developed in many aspects to give fast computation speed and good convergence.Particularly,conjugate approach is applicable to worn tooth surface contact analysis with capability of transmission error generation.2)Micro gullies tooth surface roughness pattern construction is developed linking to milling method and its surface friction calculation under mixed EHL.The gully-shape roughness pattern of hypoid gears tooth surface is constructed linking to the milling method.Surface frictions are therefore compared between the gully-shape roughness pattern and the generally assumed isotropic roughness pattern in most cases.3)Surface wear prediction model of hypoid gears is developed and calibrated by transmission error.The wear model combines with conjugate approach LTCA model with an additional function to yield transmission error from the predicted surface wear pattern.A particular mechanism is designed that surface wear geometry update and progress is adjustable to transmission error by modifying wear factor of wear equation to keep surface wear in same progress with real solid hypoid gears.