Airtight structure of main shaft

The utility model relates to an airtight structure of a main shaft. The airtight structure comprises a shaft core, an outer sealing sleeve and an inner sealing sleeve, wherein an air inlet passage communicated with an outside high-pressure air source is formed in the outer sealing sleeve, a first annular air groove communicated with the air inlet passage is formed between the external sidewall of the inner sealing sleeve and the outer sealing sleeve, a second annular air groove is formed between the top end face of the inner sealing sleeve and the outer sealing sleeve, a plurality of shunting holes are uniformly distributed in the inner sealing sleeve, one end of each shunting hole is communicated with the first annular air groove, and the other end of each shunting hole is communicated with the second annular air groove; a plurality of air holes are uniformly distributed in the inner sealing sleeve, the air holes downwards extend to the lower end face of the inner sealing sleeve from the second annular air groove, and an annular groove which is used for communicating the lower end parts of the air holes in a penetrating manner is formed in the lower end face of the inner sealing sleeve. According to the airtight structure of the main shaft, high-pressure gas can be uniformly distributed at the periphery of the shaft core so as to form a uniformly-distributed high-pressure sealing gas ring, and thus, the sealing effect of the main shaft is improved.