an injection valve (7) comprising an injection jet (3) and provided with a plunger (15), which is mobile in order to control the flow of fuel and ends with a sealing head (22);

an electromagnetic actuator (6) capable of displacing the plunger (15) between a closed position and an open position of the injection valve (7) and comprising a coil (11), a fixed magnetic armature (12), and an armature (9), which is attracted magnetically by the magnetic armature (12) and is mechanically connected to the plunger (15);

a main spring (10) for holding the plunger (15) in the closed position of the injection valve (7) and having one end resting against the armature (9);

a calibration spring (28), which comprises one end that rests against the armature (9) on the opposite side to the main spring (10);

a support body (4) having a tubular shape and comprising a feed channel (5) within which are arranged the plunger (15) and the spring (10); and

a plug body (17), in which is defined a valve seat (16) of the injection valve (7) in which the sealing head (22) engages; the plug body (17) comprises a disk-shaped plug element (18) which tightly seals the feed channel (5) at the bottom, and a guide element (19), which rises from the plug element (18), is tubular in shape, and accommodates within it the plunger (15);

wherein the sealing head (22)is of a frustoconical shape, is arranged externally relative to the guide element (19) and is thrust by the main spring (10) against said guide element (19) in a direction contrary to the direction of feed of the fuel; the valve seat (16) has a frustoconical shape which is a negative reproduction of the frustoconical shape of the sealing head (22) such that, in the open position of the injection valve (7), the sealing head (22) is separated from the valve seat (16), so creating an opening which permits passage of the fuel of a circular, ring-shaped section and a frustoconical shape in order to impart an internally hollow conical shape to the injected fuel;

wherein the armature (9) comprises an annular element (24) and a discoidal element (25) which closes the annular element (24) at the top, has a central through-hole (26) capable of receiving an upper portion of the plunger (15), has a plurality of peripheral through-holes (27) capable of permitting fuel to flow towards the injection jet (3), has an upper wall against which rest one end of the calibration spring (28), and has a lower wall opposite to the upper wall against which rest one end of the main spring (10).