Fuel pump for a direct injection system

A valve assembly (7) for a fuel pump (1) comprising:

• a one-way outlet closing valve (8), which only allows fuel to flow out;
• a one-way pressure relief valve (9), which only allows fuel to flow in;
• a connector (11), which has a housing (13);
• a valve disc (14), which engages the housing (13) of the connector (11) and has a plurality of through outlet holes (18), which are part of the outlet closing valve (8) and are each provided with a first valve seat (19) obtained in an area of a first wall (16) of the valve disc (14), and a through relief hole (20), which is part of the pressure relief valve (9) and is provided with a second valve seat (21) obtained in an area of a second wall (15) of the valve disc (14) parallel to and opposite the first wall (16);
• an annular body (33), which is arranged in the housing (13) of the connector (11), engages the housing (13) without clearance and has a central through hole (34) with a cylindrical shape, which allows fuel to axially flow towards the valve disc (14);
• a spring (30), which is part of the pressure relief valve (9), is arranged in the central hole (34) of the annular body (33) and pushes a first shutter (29) of the pressure relief valve (9) against the second valve seat (21);
• a striker body (41), which is cup-shaped so as to contain, on the inside, one end of the spring (30), has a centrally perforated base wall, against which the spring (30) rests, is arranged in the central hole (34) of the annular body (33) and is fixed inside the annular body (33);
• and
• a connection element (31), which is interposed between the first shutter (29) of the pressure relief valve (9) and the spring (30);
• wherein the central hole (34) of the annular body (33) has an annular protuberance (40), which projects from a wall of the central hole (34) and constitutes a limit stop that limits travel of the connection element (31);
• wherein the outlet closing valve (8) comprises a second shutter, which engages the first valve seat (19) of the outlet hole (18) and is movable so as to detach from the first valve seat (19), when the fuel pressure downstream of the valve disc (14) is smaller than the fuel pressure upstream of the valve disc (14);
• wherein the pressure relief valve (9) comprises the first shutter (29), which engages the second valve seat (21) of the relief hole (20) and is movable so as to detach from the second valve seat (21), when the difference between the fuel pressure downstream of the valve disc (14) and the fuel pressure upstream of the valve disc (14) exceeds a predetermined intervention threshold;
• wherein the second shutter consists of a flexible sheet (22), which is fixed to the valve disc (14) and comprises a plurality of shutting portions (23), each having a circular shape, being arranged in the area of a first valve seat (19) of a corresponding outlet hole (18) and being configured to prevent fuel from flowing through the corresponding outlet hole (18), when the outlet closing valve (8) is closed;
• a peripheral mounting portion (25) with an annular shape, which is arranged along the outer edge of the valve disc (14);
• and a plurality of outer connection portions (26), each connecting the peripheral mounting portion (25) to a corresponding shutting portion (23) of the plurality of shutting portions (23);
• wherein the sheet (22) comprises a corresponding outer connection portion (26) for each shutting portion (23) so that each shutting portion (23) is always connected to one and only one outer connection portion (26), and vice versa, that is, each outer connection portion (26) is always connected to one and only one shutting portion (23);
• wherein the sheet (22) comprises a central mounting portion (24) which is arranged at the center of the plurality of shutting portions (23);
• wherein the sheet (22) comprises a plurality of inner connection portions (27), each connecting the central mounting portion (24) to a corresponding shutting portion (23) so that each shutting portion (23) is connected to one and only one inner connection portion (27), and vice versa, that is, each inner connection portion (27) is always connected to one and only one shutting portion (23);
• wherein each shutting portion (23) is supported exclusively by a single outer connection portion (26) and a single inner connection portion (27) and has no other connection than the corresponding outer connection portion (26) and the corresponding inner connection portion (27);
• and
• wherein each shutting portion (23) is in no way directly connected to another shutting portion (23).