Sealing structure

Abstract

A sealing structure includes an O-ring (11) and a back-up ring (21). An outer diameter of the back-up ring is smaller than an inner diameter of a mounting portion (81) of a delivery pipe. An inner diameter of the back-up ring is gradually increased from a pressure-receiving surface (23) toward a seating surface (22), and is greater than an outer diameter of a fuel introducing portion (93) of a fuel injection valve. In a section of the backup ring, an edge angle (?1) defined between the pressure-receiving surface and an inner circumferential surface (28) is smaller than a gap angle (?2) defined between the pressure-receiving surface and a tapered outer surface (97) of a tapered portion (96) in the fuel introducing portion. A dimension (RW1) of the seating surface in the back-up ring is shorter than a dimension (PW1) in an end surface (92).