Main shaft mechanism of full-automatic sheet polishing machine

The utility model provides a main shaft mechanism of a full-automatic sheet polishing machine. The main shaft mechanism comprises a main shaft support arranged on a polishing machine rack, a grinding head lower pressure compensation assembly is arranged on the main shaft support, a main shaft fixing plate is arranged at the bottom end of the grinding head lower pressure compensation assembly, and a main lifting driving device is arranged on the main shaft support. The grinding head lower pressure compensation assembly comprises an upper fixing plate, more than one liftable main shaft assembly is arranged between the main shaft fixing plate and the upper fixing plate, a lower pressure compensation driving device for driving the main shaft assembly to ascend and descend is arranged on the upper fixing plate, and an electric proportional valve is arranged on the main shaft support. The pressure of the combined grinding head on the sheet is reduced, at the moment, the electric proportional valve controls compress