As a result of the inadequate carrying capacity and poor meshing performance of gears with a few teeth, the reasonable and optimal choice of parameters is a key step in design. Aiming at this problem, the stress equation for gear pairs with a few teeth was derived and it is discovered that the main failure mode of gears with a few teeth is pitting on contacting surface. At the same time, the results of theoretic analysis were also verified by strength test. A new optimization method of parameters which aimed at minimizing the contact stress was presented based on equal bending fatigue life at the tooth root of pinion and gear. The equation was solved by the genetic algorithm and reasonable design parameters are obtained. Tooth contact analysis based on finite element method is carried out and the results demonstrated that the method presented was an effective way to enhance the carrying capacity and meshing performance of gear pair with a few teeth. The study in this article laid a solid foundation for the further promotion of gear transmission with a few teeth.

A novel generation method of tooth profile curve is presented in this paper. It introduces the concept of a variable involute whose curve is generated by the generating line rolling and slipping on the base circle simultaneously. The generation principle of variable involute is described and the equation of variable involute is deduced. Then, equations are established to synthesize a conjugate profile for the gear teeth, which include some restrictions to keep the involute meshing properties. With a selectable and arbitrary relative slippage which is defined as a slipping function, the variable involute has desirable properties of controllability and flexibility. By constructing different slipping functions, involute, cycloid and circular-arc gears can be expressed into one unified form. The freedom and unified form of variable involute suggests the possibility of optimal conjugation design. An application example of gear pair with a few teeth is presented, aiming at overcoming the shortcomings of involute gear pair in load-carrying capacity and meshing performance, and its simulation analysis is conducted. Through comparative analysis with the involute gear, the results demonstrate that the variable involute gear pair with a few teeth has larger contact ratio as well as load-carrying capacity, and engagement performance has been effectively improved.

There are two basic types of EPB shield cutter: panel type and spoke type. The efficiency and process of the driving work will be directly related to the chose of the cutter type. Torque model of the shield cutter can be established by analyzing the load under working conditions. Methods to analyze the efficiency of two different types of cutters under working conditions can be explored, through analysis with specific examples of projects in this paper. Thus, theoretical basis can be provided for analyzing and studying the efficiency of shield cutter.

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