Fuel pump
A GDi fuel pump comprising an inlet valve assembly arranged in an inlet passage of the pump housing. The inlet valve assembly comprises a check valve comprising a seat member cooperating with a valve member; and an actuator assembly having a needle assembly reciprocally moveable by means of a magnetic field to actuated the valve member. The needle assembly includes an actuating needle, an armature, a washer with a plurality of through holes and an obturating member. The obturating member comprises a plurality of flexible blades, each blade comprising an obturating pad configured to be moveable between a rest position, wherein the obturating pad rests on the washer and closes a respective through hole thereof, and a raised position, raised from the washer when the needle moves away from the check valve. Each obturating pad comprises a plurality of openings, the cumulative cross-sections of the openings in a respective pad representing a fraction of the flow cross-section through the respective hole in the washer.
1. A fuel pump for a gasoline direct injection fuel equipment of an internal combustion engine, comprising:
a housing provided with a pumping bore extending along a pumping axis and defining, at an end, a compression chamber which volume is cyclically varied by a piston reciprocating in said pumping bore;
an inlet passage in said housing in communication with a fuel supply passage;
an outlet passage in said housing, in which an outlet valve assembly is arranged and selectively discharges high pressure fuel;
an inlet valve assembly arranged in said inlet passage and configured to selectively allow low-pressure fuel to enter said compression chamber;
wherein said inlet valve assembly comprises:
a check valve comprising a seat member with at least one outlet passage therethrough cooperating with a valve member moveable between a seated position preventing flow through said at least one outlet passage and an unseated position permitting flow through the latter;
an actuator assembly comprising an actuating needle reciprocally moveable by means of a magnetic field to actuated said valve member between said seated and unseated positions, wherein said actuating needle is part of a needle assembly including an armature, a washer with a plurality of through holes and an obturating member,
wherein said obturating member comprises a plurality of flexible blades, each blade comprising an obturating pad configured to be moveable between a rest position, wherein said obturating pad rests on said washer and closes a respective through hole thereof, and a raised position, raised from said washer when said needle moves away from said check valve,
wherein each obturating pad comprises a plurality of openings, the cumulative cross-sections of the openings in a respective pad representing a fraction of the flow cross-section through the respective hole in the washer.
2. The fuel pump according to claim 1 , wherein the cumulative cross-section of the openings in a respective pad represents less than 70% of the flow cross-section through the respective hole.
3. The fuel pump according to claim 1 , wherein each opening in the pad is dimensioned to block passage of particles with a diameter from 280 μm and greater.
4. The fuel pump according to claim 1 , wherein the openings in the pad have a diameter of less than 320 μm.
5. The fuel pump according to claim 1 , wherein the openings in said pad have a diameter in the range of 170 to 300 μm.
6. The fuel pump according to claim 1 , wherein each pad comprises three openings with a diameter of about 250 to 270 μm.
7. The fuel pump according to claim 1 , wherein each pad comprises four openings with a diameter of about 220 to 230 μm.
8. The fuel pump according to claim 1 , wherein each pad comprises five openings with a diameter of about 190 to 210 μm.
9. The fuel pump according to claim 1 , wherein the pads comprise a number of slit-shaped openings distributed on the pad.
10. The fuel pump according to claim 9 , wherein the slit-shaped openings are disposed in a parallel manner, or in a square or cross.
11. The fuel pump according to claim 9 , wherein the slit-shaped openings are straight or curved and present a width of less than 50 μm.
12. The fuel pump according to claim 1 , wherein the obturating member comprises a base portion fixed to the washer, wherein each pad is attached to the base portion by a flexible stem.
13. The fuel pump according to claim 12 , wherein the base portion is annular and extends peripherally on the washer, surrounding the holes therein.
14. The fuel pump according to claim 1 , wherein the obturating member is attached to the washer on the side thereof facing check valve.
15. The fuel pump according to claim 1 , comprising
a spring biasing said needle assembly towards said valve seat in order to maintain said valve member in unseated position; and
a solenoid assembly with a coil surrounding a pole piece, configured to selectively generate a magnetic field adapted to attract the armature and hence pull the needle assembly away from the seat member to bring the valve member in seated position.