Dynamic/static pressure bearing electric main shaft

The utility model relates to an electric main shaft of a dynamic and a static-pressure bearings, wherein the main shaft is directly driven by a motor between two bearings and the main shaft and a rotor shaft of the motor are combined into the integration. The main shaft is arranged on a casing through the support of a front and a back bearings, and a motor stator is arranged in the casing. The front and the back bearings are both sliding bearings with annular bearing shells, and the surface of an outer circle of each of the bearings is provided with a current regulator and an oil passage. The sliding bearings are formed by that two annular oil grooves which surround the surface of the outer circle of each of the bearings are communicated by a plurality of longitudinal oil grooves. The circumference of the surface of bearing inner holes are symmetrically distributed with 4 longitudinal static-pressure oil cavities and 4 longitudinal dynamic-pressure oil cavities, the static-pressure oil cavities in cross section form a falcate shape, and the dynamic-pressure oil cavities form a wedge shape. The back part on the bearing casing is provided with an oil-feeding passage, the lower bottom part is provided with an oil-returning passage, the oil-feeding passage and the oil-returning passage are respectively communicated with oil-feeding passages and oil-returning passages of the front and the back bearings to form a pressure-oil circulation oil circuit, and the outer circle of each of the bearings forms a cylindrical shape. The utility model has the characteristics of good bearing rigidity, high rotating precision, stable work and long service life and is suitable for various large and precise numerical control machines and other devices.