| Hydrostatic thrust bearing is critical component in heavy type numerical control processes equipment, the capability of which directly impact the quality and operational efficiency of the processes equipment. With the development of advanced manufacturing technology, especially the appearance of quick-cutting technology, the requirement of the main shaft rotation speed is much higher. The problem, which is existed in the domestic heavy numerical control process equipment at present, is that the rotation speed of the working table is lower than that of abroad and it has low efficiency and precision. How to improve the rotation speed, running accuracy, equipment efficiency and process precision of the working table of heavy type numerical control process equipment, and how to enhance its competition in international market is one of the most urgent missions at present. The rotation speed and precision of working table are determined by many factors of thrust bearing, such as theoretical arithmetic, design, process and assembly, etc. hydrostatic thrust bearing is mostly adopts analogy design without systematical and accurate calculation. It doesn't have integral optimization and key technology of independent intellectual property right. Due to the low precision of large scale parts, the gap between friction joints is asymmetric when thrust bearing is working. The temperature of the bearings will rise locally and the oil film will be damaged because of friction or the border lubrication under high speed and heavy-duty conditions, and then the local deformation will occurred, the oil pads will deflect the theoretical design models, and the rotation speed will be restricted.In order to discover the mechanics property, pressure state and flow state of large scale constant current multi-pad open static pressure support pan bearing, under the support of two fund items, one of which is Key R&D Project of Heilongjiang Province (GC05A512)" Research on Hydrostatic Support Bearing of Heavy Vertical Numerical Lathe Working Label, the other is Ministry of Education doctor station fund item(20050214001)" Research on Self-adapting Thrust Bearing of Heavy Numerical Machine", this paper, aiming at the large scale bearing(diameter D＞10m), based on the computational hydrodynamics and lubrication theory, presents the hypothesis for the research of the sector cavity that the model is simplified for the annular plane gap and the rectangular plane flat flow, which can make theory calculation result accord with actual flow condition and diminish the error of theory calculation result. For the research of circular oil cavity, the concept of homalographic equivalent radius is proposed, which can simplify the mechanical property parameter derivation with making use of the homalographic circle area to replace the area of oil pad big sector. By using the hydromechanics calculation software FLUENT, the three-dimensional synthetic numerical value simulation analysis on the pressure state, flow state and the temperature field of the oil film is carried out. It reveals the influence law of friction joint mechanical property, oil film pressure state, flow state and the temperature field, which is caused by the cavity area and deep of the circular cavity and sector cavity under constant current and rotational speed condition. The oil film pressure, oil film thickness and the temperature distribution are measured on 10 meter vertical numerical control lathe, and the correctness of the result made by theory calculation and numerical simulation is verified by experiments. Then, the tribology action and failure mechanism of the support is explored by combining theory with experiment. And one of the feasible methods is provided for predicting, simulating, designing and calculating the model of the support.
|
PDF Full Text Request