Combined piston with built-in piston pin

The invention discloses a combined piston with a built-in piston pin. A piston head (1), an upper pin seat (2), a bushing (3), a piston pin (4) and a lower pin seat (5) are connected in sequence through four squarely and uniformly arranged tightening bolts (11); the upper pin seat (2), the bushing (3), the piston pin (4), the lower pin seat (5) and a bolt (6) are arranged from top to bottom in sequence and are positioned in a piston skirt (7) in a built-in manner; no pin holes are formed in the piston skirt (7); the outer circle of the skirt part forms a complete drum shape; and the piston skirt (7) is connected with the lower pin seat (5) through the bolt (6). The piston pin is attached to the piston in the entire length, so that the stress and the specific pressure of the piston are reduced; the volume of a cooling oil cavity formed by the upper pin seat and the piston head is extremely large, so that the cooling effect of the piston is enhanced; the connecting rod is connected with the piston pin by using the bolt, so that a friction pair is reduced; and the deflection size of the piston is increased, the attachment area of the connecting rod and the piston pin is increased, and the stress of the connecting rod is reduced.