| Tamping machine is a kind of special engineering equipment which is used for railway construction. Tamping device being used to compact ballast is the key part of tamping machine, with which two main tamping processes, clamping and vibrating, could be carried out Clamping squeezes the stones to flow under the sleeper and vibrating compresses ballast The development of tamping device is briefly introduced, and then the current status of tamping device and the exciting technology are discussed in detail. Combining with project practice, the problems concerning excitation technology of tamping device, control of electro-hydraulic vibration in high frequency and adjustable amplitude are analyzed, and the new electro-hydraulic excitation for tamping device is proposed. The novel electro-hydraulic exciter can increase the export force, realize high amplitude during certain frequency range and solve the problem of bias impact to the cylinder. Its key technology is realizing the control of excitation frequency and amplitude through the rotation valve spool which is driven by step motor and the hydraulic cylinder changing direction lead by the high frequent oil flow direction. This work developed a novel electro-hydraulic exciter comprising of high speed rotation valve with four-way commutation and auto-limitation micro-displacement double-rod cylinder. It can overcome the limitation of flow quantity under the condition of high frequent changing direction to meet the needs of different operating work of the tamping unit The main research works are as follows.1. Based on working principle of tamping device, mathematical models of the exciting part and tamping arm were built According to the technical parameters of the existing tamping unit and the mechanism analysis of tamping arm, the new tamping unit mechanical design and structure modeling were completed. Then, the size of the device’s main structure and the work performance parameters of electro-hydraulic exciter were determined. Taking advantage of virtual prototyping technology and simulation software platform Pro/E, a virtual prototype of the new tamping unit was created and kinematics simulation was carried out 2. The mathematical model of the electro-hydraulic exciter and rotary valve were built in order to study the characteristics of electro-hydraulic exciter and rotary valve respectively. According to the exciting performance requirements of tamping unit, the main structure principles and parameters of the electro-hydraulic exciter were determined, the valve port based on the required vibration waveform was solved. The different parameters (spool speed, the width of the valve port in axial direction, damping and oil pressure) working on the dynamic performance of the electro-hydraulic exciter were studied.3. Through stress analysis of the rotary valve spool, the formation mechanism and calculation methods of hydrodynamic torque and viscous friction torque were studied. The impact of structural parameters (the Spool diameter, spool and radial sleeve clearance, the axial length of the valve port, damping ratio and rotational inertia) on the operating characteristics of high speed rotation valve was discussed. Based on different types of rectangular valve port structures, and considering the valve port flow area change caused by the pressure drop, the corresponding valve port flow area model and the average load flow model to spool with ring groove and without ring groove were built separately. Numerical calculation and analysis for vibration waveform of the new electro-hydraulic exciter were conducted.4. Electro-hydraulic vibration test system used in tamping unit was established. The work flow, motion parameter values and exciting force of vibration cylinder within the range of20to60Hz are measured through flow meter, ICP acceleration and pressure sensors to verify the theoretical research. |
PDF Full Text Request