Abstract: A piston bearing structure for a fluid pressure cylinder includes one seal ring which is housed in a housing groove of a piston and is held in sliding contact with a cylinder tube and two backup wear rings which is housed in a housing groove of a piston, is held in sliding contact with a cylinder tube and sandwiches the seal ring. The backup wear ring includes a pressure relief groove which faces the housing groove and extends over the backup ring portion and the wear ring portion, and the pressure relief groove allows opposite sides of the backup wear ring to communicate between the piston and the cylinder tube.

Abstract: A piston bearing structure for a fluid pressure cylinder includes one seal ring which is housed in a housing groove of a piston and is held in sliding contact with a cylinder tube and two backup wear rings which is housed in a housing groove of a piston, is held in sliding contact with a cylinder tube and sandwiches the seal ring. The backup wear ring includes a pressure relief groove which faces the housing groove and extends over the backup ring portion and the wear ring portion, and the pressure relief groove allows opposite sides of the backup wear ring to communicate between the piston and the cylinder tube.

Abstract: A seal structure for a sliding part including a shaft (11) and a member (10) having a shaft hole (10a) into which the shaft (11) is inserted in a freely and relatively sliding manner, and a first packing (P1) and a second packing (P2) arranged sequentially in series from a direction in which a high pressure is applied between the shaft (11) and the shaft hole (10a). The first packing (P1) includes a sealing member (22) for sealing a space between the shaft (11) and the shaft hole (10), and a backup ring (25) disposed on a part of the side of the sealing member (22) which is in contact with a sliding surface of the shaft (11) or the shaft hole (10a), and the sealing member (22) and backup ring (25) are inseparably integrated.