The Research And Design Of Gear Mechanism Of The Noncircular Planetary-gear Mud Motor

The major existing down-hole motors types are the turbine motor, the screw motor, the electric motor and the blade motor. The non-circular gears are special in terms of kinematics and geometry that they can meet the transmission requirements of any variable gear ratio, so they are more and more widely applied to all kinds of machines. After 1980s, another kind of low-speed high torque hydraulic motor mechanism employing the theory of the positive displacement motor has been developed: the non-circular planetary-gear motor. The performance of this kind of motor has been greatly improved compared with the other hydraulic motors.This thesis studies the gear mechanism of the non-circular planetary-gear hydraulic motors(hydraulic motor 4-6). Its planetary gear is the cylindrical spur gear, and the pitch curves of its external gears and internal gears are the 4 cycles and 6 cycles plane curves.This thesis analyzes the feasibility of the application of motor mechanism principle to the manufacturing research of petroleum down-hole hydraulic motor, and concludes the equation of non-circular gear curve on the basis of analyzing the basic movement relationship of the non-circular planetary gear train with changing center-distance. Through research, the thesis summarizes three practical design methods of the pitch curve. It adopts the Matlab language to calculate, and generates or draws the graphics of the pitch curves of the non-circular gear, and simplifies the solving calculation process of the pitch curves. Based on this method, it gives a brief description of the designing methods of the non-circular planetary gear mechanism with double-circular pitch-curve, and focuses on the Principles of Gear Connection under the condition that the known planetary gear is the in-volute cylindrical gear, and concludes that the point coordinates on the tooth profile of the meshed non-circular gear. It uses these coordinates to build models in the three-dimensional software Pro / Engineer, providing the basis for the further study on the other performances of the down-hole motors with non-circular planetary gears.