A ring-shaped stop face (63c) of a sector (63) impacts the seat (32) when the valve sector (63) seats to give an annular gap (65) between stop face and seat to form the opening for the raised position of the valve. In this, (B) is greater than (Ao), (B) denoting the sectional area of the gap and (Ao) that of the injection orifice (33). Otherwise, an annular gap (66) forms between the edge surround of the inner end of the orifice and the valve sector (63) surface to give a formulated expression (B) is greater than (A1), here using (B) for the sectional area of the orifice and (A1) that of the annular gap (76). Valve sector (63) has first and second conical surfaces (63a and 63b) directed away from the orifice entry to give larger and smaller cone angles (THETA1) and (THETAo). Thus the cone angle (THETA2) of surface (63b) is smaller than that of the seat (32).
