Investigation On The Optimization Design And Static Charateristics Of Precision And Heavyload Hydrodynamic Bearings

Hydrodynamic journal bearing is widely used in machine tool spindle system, and plays a role of positioning and supporting the spindle. Compared with rolling bearing, hydrodynamic journal bearing presents many characteristics such as high load capacity, small overall dimensions low power dissipation, impact resistance, high anti-shaking, high rotary precision and so on. As demand of higher speed and precision, hydrodynamic journal bearing need to meet more demand. In the condition of ensuring the journal bearing’s load capacity, the journal bearing bush temperature need to control within the rational range, and the oil flow need to reduce as possible for saving. But there are a lot of factors which can affect the working performance of bearings, and the factors interact with each other. The working process is complex. So it is necessary and meaningful to analyze the influence of every factor. This dissertation could provide the theory base for journal bearing optimization design.Based on the fluid dynamics equations, this dissertation set up the theory simulation model of hydrodynamic journal bearing, which chooses RNG k-ε model as the turbulence model, for that k-ε model is suitable for the simulation of moving machines. In finite volume method, the fluid dynamics equations and turbulence equations are transformed to discretization equations. And solve the equations with the coupled method of SIMOLE. Considered of the precision and heavy load working conditions, this paper carry out simulations of hydrodynamic journal bearing with different bush. From the contrast of the simulation results, choice the best form considered of both carrying capacity and lubrication effect. According to the before simulation model, establish the three dimensional model of journal bearing oil film. After meshing the oil film model and setting appropriate boundary conditions, calculate with the computational fluid software, fluent. The action rules of factors are obtained, including radius clearance, spindle speed, the oil supply pressure, the oil supply temperature, oil viscosity and so on. The experiments were made on ZDY-1 sliding bearing work bench, which is independently developed by Harbin Institute of Technology. Applying same load, the oil film pressure distribution of bearings under different rotational speed is gotten. Compared with the simulation in the same conditions, the simulation model is proved.In the steady working condition, the bearing oil film can rupture in the divergence region, and film cavitation appear. The reason of film cavitation is discussed and the effects of the factors on the cavitation area is studied. The half Sommerfeld boundary condition is selected to solve the cavitation problem. Heat transfer process in journal bearing in the steady working condition is analysis. Frictional heat, side leakage flow, thermal radiation, viscosity-temperature characteristics of oil effect with each other to get heat Balance. The most suitable viscosity-temperature model is selected from the existing model. Compared with the steady model, the effect of the viscosity-temperature characteristics of oil is studied. On the basis of the action rules of factors, journal bearing optimization design is carried out to get the best case.