Investigations On Design Theory And Cutting Process Of Conjugate-curve Gears

As an important basic part in the manufacturing equipment industry and national defense industry, the gear is considered to be the symbol of industries. The development of science and technology has put forward higher and higher requirements to the performance of gears, such as high efficiency, high reliability, high load capacity, and high transmission accuracy. The study on the principle of gear meshing is the theoretical basis to improve the gear performance. The principle of conjugate curves studies the meshing of spacial smooth curves and provides a theory foundation for the new gear transmissions. The conjugate curve gears are proposed based on the principle of conjugate curves. Due to the small sliding ratio and the convex-to-concave contact pattern, the conjugate curve gears are good lubricating and have a large load capacity and long service life. In the design of conjugate curve gears, the number of teeth of pinion can be very small and the module can be very large. So the conjugate curve gears have extensive applications in the mining and transport machinery where there is a need on the high load capacity, and the aerospace and shipping marine where there are restraints on the weight and volume due to the large load capacity, compact structure, and lighter and smaller volume. Aiming at the study of the conjugate curve gears, the meshing geometry is developed; the meshing performance, the profile characteristics, the tooth surface manufacturing and measuring are studied; the prototype is assembled and performance test is carried out. The prime content of the paper may summarize as follows:(1) The meshing theory of conjugate curve gears are studied based on the differential geometry. The equations of meshing, action line and the conjugate curves are derived. The equidistance-envelope method is proposed to establish the meshing surfaces of the conjugate curve gears. And the equations of equidistance curves and enveloping surfaces are derived. A general method of a normal profile having helical motion to generate the meshing surfaces of conjugate curve gear drive is also proposed and the related equations are derived. The meshing surfaces generated by two rack cutters are proposed. And the derivation of the generated meshing surface and the idea meshing surface are derived.(2) The tooth profile design and the method of establishing exactitude solid model of the conjugate curve gears are studied. The basic tooth profile parameters and the design principle are present. The method to establish the exactitude solid model is proposed based on the equations of tooth surfaces of conjugate-curve gears, and 3D models of five conjugate curve gear drives are established based on the proposed method.(3) The finite element analysis of conjugate curve gears are developed to investigate the contact stress, bending stress, and contact deformation. Five conjugate curve gear drives with the only difference of normal profiles are present to demonstrate the influence of the profile design parameters and the contact positions on the stress distribution.(4) The investigations on cutting process and measurement of the conjugate curve gears are carried out. The hobs to manufacture the gears are designed based on the basic tooth profile and design principle. The processing technique of hobbing the conjugate curve gears are proposed. And the measuring method of field detection of the conjugate curve gears is investigated.(5) The performance test of the conjugate curve gears are carried out. The testing principle of the test rig are determined. The craft equipment, the support and connection device are designed. Installation and adjustment of the test rig are carried out and to investigate the transmission performance such as transmission efficiency and load capacity of the conjugate curve gearbox, UMA involute gearbox and FLENDER involute gearbox with the same center distance and transmission ratio. The results show that the conjugate-curve gearbox with soft teeth has larger load capacity compared to the involute gearbox with hardened teeth. Two conjugate curve gearboxs are designed and manufacutured for their engineering applications on the crown block and slag truck.