Abstract: High-speed spindles supported by hydrodynamic and hydrostatic hybrid bearings are widely applied in the field of high-speed precision machine tools due to highrotation accuracy, high dynamic stiffness, high vibration damping and long life. But some technical problems caused by integrated structure and high speed, including temperature rise control and motor performance optimization, are yet to be resolved when the integration of hybrid bearings and motor are developed to meet the requirements of ultra-high speed and ultra-precision machining. Also major scientific problems involved in the dynamic and thermal characteristics of hybrid journal bearings and the mechanism of electromagnetic losses of high-frequency motor are to be further studied. Therefore, it is necessary to review current achievements systematically and intensively. The retrospect of the development history of high-speed hybrid spindle is presented. The effects of critical factors and key technology on the characteristics of bearings for high-speed liquid suspension motorized spindles are analyzed and commented successively from the aspects of oil recess structure, restrictor, journal inclination, bush elastic deformation, bearing surface topography, fluid inertia, thermal effects, fluid compressibility and non-Newtonian behavior, and water-lubricated hybrid bearings. The method of electromagnetic parameter design, the mechanism of electromagnetic loss and its calculating methods , and the fault mechanism of electromagnetic failure and its preventing methods are thoroughly elaborated to fulfill the requirements of the motor in motorized hybrid spindle from the aspects of geometric characteristics, speed-torque characteristics, thermal effects, vibration and noise characteristics. Key technical problems of optimal design of motorized spindles are analyzed in detail. And the future development tendency of motorized hybrid spindle technology is predicted and prospected.*

Key words: High-frequency motor spindle, High-speed spindle, Hydrodynamic and hydrostatic bearing, Ultra-high speed grinding, Ultra-precision grinding