| The rack and pinion drill is a new kind drill which can pressurize actively. Compared to the traditional drill, it possesses a faster drilling speed and remarkable superiority in terms of shallow drilling process. At the same time, it owns drilling capability, which can strengthen those special wells, such as directional well, cluster well, horizontal well and sidetracked well, demonstrating fully its multi-functional characteristic. In the current increasingly fierce competition in the international oil and gas resources development situation, it has been developed as a highly kind efficient drill by each country. As the core part of the drill, rack and pinion transmission mechanism is usually designed as a statically indeterminate structure and worked in a long-term state of time-varying low speed and heavy load in the process of lifting operation, which can result in easily its fatigue, ineffectiveness and even break. Concurrently, due to its hyper-static structural layout, it is difficult to guarantee the uniformity of each gear’s load distribution and stability of motion synchronization under special working conditions, and it overalls the security and performance of drilling rig. Therefore, this paper research on the mechanical characteristics of rack and pinion drill transmission mechanism as the following aspects.According to the working requirement of the drill’s transmission mechanism, the structural design parameter of the gear and rack is given, and the maximum bending stress of the root and the maximum stress of the tooth flank are calculated and obtained by theoretical formula. Though ANSYS finite element numerical method, two contact models of the meshing process between the gear and the rack and instantaneous static state are separately established. The result indicates that the maximum bending stress appears at the position where the gear teeth begins to mesh and the maximum contact stress appears at the meshing position where the gear teeth is to separate; the maximum stress caused by dynamic impact load is more than the maximum stress of instantaneous static state analysis; the result errors of maximum bending stress and the maximum contact stress calculated by the finite element method and theoretical formula, meet the requirement of engineering precision. Hence, the result of finite element calculation can provide references for safety assessment of the transmission mechanism of the gear rack drill.The rack and pinion meshing is regarded as spring-quality-damping system, at the same time considering the effect of time-varying mesh stiffness and backlash error, the model was established based on Newton’s second law of dynamics equation. Also in the paper, the motion characteristics of the meshing process between the gear and the rack in the drill’s transmission mechanism, and the vibration performance of the elastic deformation of flexible drill strings are analyzed:by the use of multi--body dynamics theory, the rigid body dynamic equations of local meshing between the gear and the rack and the integrated transmission mechanism are separately established, and the necessity of the flexibility of the transmission mechanism’s key parts in the practical work is expounded; the rigid-and-flexible coupling dynamic equation of the transmission mechanism after the flexibility handling of the drill pipe is established, and the solving methods of two dynamic equations are provided.According to the integrated application of ADAMS flexible body multi-rigid-body modeling and ANSYS modeling method, based on above-mentioned multi-body dynamic model and rigid-and-flexible coupling model, the research of the dynamic characteristics of each gear when longitudinal vibration and transverse vibration of the drill pipe are separately taken into consideration under the normal working condition and abnormal working condition are carried out. Under the influence imposed by working conditions, including the transverse vibration of the drill pipe, the effectiveness of a single gear, and the effectiveness of two gears which are in the asymmetric position. The comparison analysis research for two kinds of simulation model under the influence law of various factors on the gear mesh force curve is carred out. The results show that different special conditions for transmission mechanism of load distribution uniformity and movement synchronization has obvious difference, at the same time explained this paper established the coupled dynamics model can more accurately reveal the transmission mechanism of the actual dynamic characteristics, for the study of gear and rack drill provides effective basis for drive mechanism and mechanical properties.Based on the original model case, a test bed of the rack and pinion drill model is manufactured according to the geometric similarity ratio 0.1 by the use of similar theoretical method. Corresponding to the relevant elements influencing mechanical properties of the transmission mechanism, such as the lifting state of the drill, terminal load, gear motor flow, the vibration direction of the drill pipe and the effectiveness state of the gear motor, the experimental research of the transmission mechanism’s stress measurement and vibration measurement are carried out by the use of orthogonal test method. The measurement results and the simulation analysis results are compared and the corresponding test error and its cause are analyzed. The results indicated that the stress test and the vibration test have good consistency, which verify the effectiveness of above transmission theory dynamical model and simulation dynamical model. |
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