Design Theory Research Of Coplanar Axes Spatial Helix Gear With Equal Diameter Of Tines

Micro-electro mechanical systems (MEMS) have advantages of structure miniaturization,functional diversities, intelligent, low energy consumption, high sensitivity and efficiency.The most important characteristics of MEMS products are small size and light weight, whichare mostly using for low-power motion transmission and dividing movement. Theconventional power transmission is no longer applicable for MEMS. Therefore, theinnovative research of work principle, performance characteristics and the design andmanufacture of small devices or microdevices has become one of the hot and importantresearch fields of mechanical transmission.The domestic and foreign research results of microdevices are analyzed systematically inthis dissertation. On the basis of space-curve meshing-wheel (SCMW) transmissionmechanism used for orthogonal shaft drive, the coplanar axes spatial helix gear with equaldiameter of tines is researched. The generalized mesh theory is founded firstly, which suits fortransmission between arbitrary angle intersected axes and parallel axes in one plane. The keypoints of industrialized application are researched, which will lay the foundation ofindependent and complete design theory of coplanar axes spatial helix gear with equaldiameter of tines. Lots of analysis and experimental study indicate that the proposed coplanaraxes spatial helix gear with equal diameter of tines has guidance and feasibility forindustrialized application. The detailed work accomplished in this dissertation is as follows.First of all, the generalized space curve mesh theory is established for transmissionmotion between arbitrary intersected axes and parallel axes in one plane. Based on the spacemesh coordinate systems, constraint conditions of space mesh are indicated and the vectorrelationships between the driving and driven tines are analyzed. Then the equations of thecontact curves and the central curves of the driving and driven tines of coplanar axes spatialhelix gear are deduced.Secondly, the design formula of contact ratio is deduced based on the generalized meshequation of coplanar axes spatial helix gear. Impacting factors of the contact ratio areanalyzed, and different design methods for contact ratio are discussed. The least tooth numberof the driving wheel is studied, according to the impacting factors. Then material samples aremanufactured for kinematics simulation and experiments. Numerical examples illustrate thedesign formula of contact ratio and the kinematics performance of the coplanar axes spatialhelix gear mechanism. Thirdly, the standardized parameters design for spatial helix gear with equal diameter oftines is worked out. The tooth profile structure parameters for the spatial helix gear with equaldiameter of tines are studied, including tooth number, helical angle, helical pitch, diameter oftines, height of teeth etc., and the central distance of the coordinate systems is determined.Then the basic design parameter and basic design size of spatial helix gear with equaldiameter of tines are determined. The parameters value scope of central curve of the drivingand driven tines are corrected to avoid interference between the bodies of the wheels.Fourthly, a design criterion of bending fatigue infinite lifetime for spatial helix gear withequal diameter of tines is presented. Applied forces and the maximum localized stressesbetween the meshing tines of spatial helix gear with equal diameter of tines are analyzed.Analytic formula for the maximum nominal stress at the end of the tine is deduced, combinedwith ANSYS simulation. The equation of theoretical stress concentration factor is fittednumerically, which suits for the general application situation. According to fatigue theory, thedesign criterion of bending fatigue infinite lifetime for spatial helix gear with equal diameterof tines is presented, combined with safety factor method. Then a numerical exampleillustrates the design criterion.Fifthly, optimization design for driving tine’s structure of spatial helix gear with equaldiameter of tines is presented. The variation between the skew parameters and the stress anddeformation of the driving tine is analyzed, and the optimum value scope of the skewparameters including helix angle with equal diameter of tines are determined, which willhighly improve the carrying capacity and anti-distortion capacity of the spatial helix gearmechanism.