Fuel injector equipped with a metering servovalve for an internal combustion engine

Patent metadata

Field	Value
Publication number	US-9464613-B2
Application number	US-201213708963-A
Country	US
Kind code	B2
Filing date	Dec 8, 2012
Priority date	Jun 27, 2008
Publication date	Oct 11, 2016
Grant date	Oct 11, 2016

Abstract

A fuel injector has an injector body and a control rod, which is movable in the injector body along an axis to control the opening/closing of a nozzle that injects fuel into a cylinder of the engine; the injector body houses a metering servovalve having a control chamber, which is axially delimited by the control rod and communicates with an inlet and with a discharge channel; the metering servovalve is provided with a shutter, which slides axially on an axial guide, from which the discharge channel exits, to open and close the discharge channel and, in consequence, vary the pressure in the control chamber; the discharge channel has three restrictions having calibrated passage sections and arranged in series with each other to divide the pressure drop along the discharge channel.

First claim

The invention claimed is:

1. A fuel injector for an internal combustion engine, the injector ending with a nozzle to inject fuel into an associated engine cylinder and comprising:
a hollow injector body extending along an axial direction;
a metering servovalve housed in said injector body and comprising:
an electro-actuator;
a control chamber communicating with a fuel inlet and with a fuel discharge channel, the pressure in said control chamber controlling the opening/closing of said nozzle;
a shutter axially movable in response to the action of said electro-actuator between a closed position, in which an outlet of said discharge channel is closed, and an open position, in which the discharge channel is open, to vary the pressure in said control chamber;

wherein said discharge channel comprises three restrictions having calibrated passage sections and arranged in series with each other so as to cause respective pressure drops when said discharge channel is open, said calibrated passage sections of each of the three calibrated restrictions restricting fuel flow in both directions, said restrictions spaced apart from one another by enlarged intermediate segments of the discharge channel that extend between adjacent ones of the restrictions, each of said enlarged intermediate segments having a cross-sectional area that is larger than a cross-sectional area of the restrictions that it extends between;
wherein said restrictions are defined by respective bodies that are distinct from each other.

2. The injector according to claim 1 , wherein two of said calibrated restrictions are arranged along said axial direction.

3. The injector according to claim 1 , wherein said discharge channel is in a fixed position with respect to the injector body.

4. The injector according to claim 1 , wherein a first body is housed in a second body.

5. The injector according to claim 4 , wherein the first body is defined by an insert coupled to the second body by interference fitting.

6. The injector according to claim 5 , wherein said insert is arranged along said axial direction.

7. The injector according to claim 1 , wherein the first body is defined by a plate arranged in axial contact against the second body and axially delimiting said control chamber on one side.

8. The injector according to claim 3 , further comprising a stem located in a fixed position with respect to said injector body and having a lateral surface which guides said shutter between said open and closed positions; said discharge channel defining an outlet opening located onto said lateral surface in a position so as to cause a substantially null axial force resultant due to the fuel when said shutter is located in its closed position.

9. The injector according to claim 8 , wherein said stem is defined by a substantially cylindrical protrusion, and said shutter is defined by a sleeve.

10. The injector according to claim 8 , wherein, considering the direction of the flow exiting from said control chamber into said discharge channel, the last of said restrictions is made in said stem.

11. The injector according to claim 2 , further comprising: a tubular portion of the hollow injector body radially delimiting said control chamber; wherein a stem defines part of a piece distinct from said tubular portion of the hollow injector body; and wherein said three calibrated restrictions are made, respectively: in said piece; in an insert housed in said piece; and in a disc arranged in axial contact against said piece on one side and, on the other side, against said tubular portion of the hollow injector body.

12. The injector according to claim 10 , wherein the last of said restrictions is obtained in at least one straight outlet segment that exits through said lateral surface.

13. The injector according to claim 12 , wherein said straight outlet segment is inclined with respect to said axis by an angle other than 90°.

14. The injector according to claim 13 , wherein the angle of inclination of said straight outlet segment with respect to said axis is between 30° and 45°.

15. The injector according claim 1 , wherein, considering the direction of the flow exiting from said control chamber into said discharge channel, the first of said restrictions is associated with a pressure drop greater than the pressure drops to which the successive restrictions are associated.

Assignees

• Fiat Ricerche

Inventors

• Ricco Mario
• Ricco Raffaele
• Stucchi Sergio
• De Michele Onofrio

Classifications

• F02M63/0031 Primary

  characterized by the type of valves, e.g. special valve member details, valve seat details, valve housing details · CPC title

• F02M2200/28

  Details of throttles in fuel-injection apparatus · CPC title

• F02M63/0042

  combined with valve seats of the lift valve type · CPC title

• F02M63/008 Primary

  Hollow valve members, e.g. members internally guided · CPC title

• F02M47/027

  Electrically actuated valves draining the chamber to release the closing pressure · CPC title