Fuel pump for a direct injection system

Patent metadata

Field	Value
Publication number	US-9822751-B2
Application number	US-201514847286-A
Country	US
Kind code	B2
Filing date	Sep 8, 2015
Priority date	Sep 8, 2014
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

Abstract

Fuel pump for a direct injection system provided with a common rail. The fuel pump has a pumping chamber defined in a main body; a piston which is mounted in a sliding manner inside the pumping chamber to cyclically vary the volume of the pumping chamber; an intake channel which originates from a wall of the pumping chamber; an intake valve which is coupled to the intake channel; a delivery channel which originates from a wall of the pumping chamber; a delivery valve which is coupled to the delivery channel; and an actuating spring which has a plurality of turns having a pitch that varies between the turns and that is coupled to the piston so as to push the piston towards a maximum volume or minimum volume position of the pumping chamber.

First claim

The invention claimed is:

1. A fuel pump for a direct injection system provided with a common rail; the fuel pump comprises:
a pumping chamber defined in a main body;
a piston which is mounted in a sliding manner inside the pumping chamber to cyclically vary the volume of the pumping chamber;
an intake channel, which originates from a wall of the pumping chamber;
an intake valve which is coupled to the intake channel;
a delivery channel which originates from a wall of the pumping chamber;
a delivery valve which is coupled to the delivery channel; and
an actuating spring, which comprises a plurality of turns and is coupled to the piston so as to push the piston towards a maximum volume or minimum volume position of the pumping chamber;
wherein the actuating spring has, along its length, a pitch (P) that is variable between the turns so that at each cycle of the piston a predetermined portion of the turns that is less than all of the turns pack—tighten together so as to change an application direction of a lateral load generated by the actuating spring for limiting a maximum value of lateral load;
wherein at both ends of the actuating spring, the pitch (P) between the turns is smaller than the pitch (P) between the turns at a central portion.

2. The fuel pump as set forth in claim 1 , wherein the pitch (P) between the turns is identical at both ends of the actuating spring.

3. The fuel pump as set forth in claim 1 , wherein, at a central portion, the pitch (P) between the turns ranges from 1.2 and 2.2 times the pitch (P) between the turns at least at one end of the actuating spring.

4. The fuel pump as set forth in claim 1 , wherein at a central portion, the pitch (P) between the turns ranges from 1.4 and 2.0 times the pitch (P) between the turns at least at one end of the actuating spring.

5. The fuel pump as set forth in claim 1 , wherein the actuating spring comprises two dead turns at the opposite ends of the actuating spring.

6. The fuel pump as set forth in claim 1 , wherein the actuating spring comprises, as a whole, a number of turns ranging from 4.5 to 7.5.

7. The fuel pump as set forth in claim 1 , wherein the actuating spring is manufactured in a mirror-like manner relative to a transverse symmetry plane arranged at the center.

8. The fuel pump as set forth in claim 1 , wherein, when the pitch (P) between the turns is variable along the length of the actuating spring, during the cyclical compression and expansion, only some of the turns pack-tighten together; in this condition, the overall load of the actuating spring varies its inclination also decreasing the lateral load as the axial load increases.

Assignees

• Magneti Marelli Spa

Inventors

• Vezzani Enrico
• Petrone Michele
• Mancini Luca

Classifications

• F02M63/0265 Primary

  Pumps feeding common rails · CPC title

• F04B53/1002

  Ball valves · CPC title

• F02M59/06

  with cylinders arranged radially to driving shaft, e.g. in V or star arrangement · CPC title

• F04B1/0452

  Distribution members, e.g. valves (machines or pumps with cam-actuated distribution members at the outer ends of the cylinders F04B1/0472; machines or pumps with cam-actuated distribution members at the inner ends of the cylinders F04B1/0531; the piston-driving cams being provided with inlets and outlets F04B1/0535) · CPC title

• F02M2200/02

  Fuel-injection apparatus having means for reducing wear · CPC title