Fuel injector having valve stack with vented back-up plate for check seal retention

Patent metadata

Field	Value
Publication number	US-10473073-B2
Application number	US-201815915721-A
Country	US
Kind code	B2
Filing date	Mar 8, 2018
Priority date	Mar 8, 2018
Publication date	Nov 12, 2019
Grant date	Nov 12, 2019

Abstract

A fuel injector includes a valve stack forming a seal cavity, and an outlet check extending through the seal cavity. A check seal is positioned within the seal cavity and seals about the outlet check. The valve stack also includes a back-up plate trapping the check seal within the seal cavity, such that a crevice is formed within the seal cavity between the check seal and the back-up plate. The back-up plate has a vent formed therein that fluidly connects the crevice to a drain.

First claim

What is claimed is:

1. A fuel injector comprising:
an injector body defining a longitudinal center axis extending between a first injector body end and a second injector body end including a nozzle with a plurality of spray orifices formed therein;
a valve stack positioned within the injector body and forming a check guide, a seal cavity in fluid communication with the check guide, and a drain;
an outlet check extending through the check guide and the seal cavity, the outlet check being guided within the valve stack by way of the check guide between an advanced position where the outlet check blocks the plurality of spray orifices, and a retracted position;
a check seal positioned within the seal cavity and in sealing contact with the outlet check;
the valve stack further including a back-up plate trapping the check seal within the seal cavity, such that a crevice is formed within the seal cavity between the check seal and the back-up plate; and
the back-up plate having a vent formed therein that fluidly connects the crevice to the drain.

2. The fuel injector of claim 1 wherein the outlet check extends through the back-up plate, and wherein a guide clearance is formed between the outlet check and the check guide and an enlarged clearance is formed between the outlet check and the back-up plate.

3. The fuel injector of claim 2 wherein the crevice is annular and extends circumferentially around the longitudinal center axis, and the vent includes a plurality of vent holes distributed circumferentially around the longitudinal center axis.

4. The fuel injector of claim 3 wherein the plurality of vent holes are arranged in a circular pattern.

5. The fuel injector of claim 4 wherein the back-up plate has formed therein a plurality of dowel holes and a plurality of fuel holes, and the plurality of dowel holes and the plurality of fuel holes are arranged in a trapezoidal pattern that overlaps the circular pattern.

6. The fuel injector of claim 3 wherein the valve stack further includes a piston guide piece forming a piston guide, and a check guide piece forming the check guide, and the back-up plate is sandwiched between the piston guide piece and the check guide piece and the seal cavity is formed in part by each of the check guide piece and the back-up plate.

7. The fuel injector of claim 6 wherein the seal includes a sealing sleeve providing the sealing contact with the outlet check, and a seal energizer compressed between the sealing sleeve and the check guide piece, and wherein the crevice is defined in part by each of the check guide piece, the back-up plate, and the seal energizer.

8. The fuel injector of claim 6 further comprising a check piston within the piston guide piece and having an axial footprint, and wherein the plurality of vent holes are arranged within the axial footprint.

9. The fuel injector of claim 2 wherein the back-up plate includes a chamfer adjoining the central aperture and facing an axial direction of the first injector body end.

10. A valve stack assembly for a fuel injector comprising:
a plurality of coaxially arranged valve stack pieces positionable within a fuel injector body and including a check guide piece, a piston guide piece, and a back-up plate positioned axially between the check guide piece and the piston guide piece;
an outlet check movable within the valve stack between an advanced position and a retracted position, for opening and closing a plurality of spray orifices formed in the fuel injector body;
a check seal positioned in sealing contact with the outlet check;
the check guide piece forming a check guide that guides the outlet check between the advanced position and the retracted position, and the piston guide piece forming a drain for draining fluid displaced during movement of the outlet check within the valve stack between an advanced position and a retracted position;
the check guide piece and the back-up plate together defining a seal cavity receiving the check seal, and the valve stack further including a back-up plate trapping the check seal within the seal cavity, such that a crevice is formed within the seal cavity between the check seal and the back-up plate; and
the back-up plate having a vent formed therein that fluidly connects the crevice to the drain.

11. The valve stack assembly of claim 10 wherein the valve stack assembly defines a longitudinal center axis, and wherein the crevice is annular and extends circumferentially around the longitudinal center axis, and the vent includes a plurality of vent holes distributed circumferentially around the longitudinal center axis.

12. The valve stack assembly of claim 11 wherein the plurality of vent holes are arranged in a circular pattern defining a common circle centered on the longitudinal center axis.

13. The valve stack assembly of claim 12 wherein the outlet check extends through the back-up plate, and wherein a guide clearance is formed between the outlet check and the check guide and an enlarged clearance is formed between the outlet check and the back-up plate.

14. The valve stack assembly of claim 13 wherein the back-up plate has a central aperture forming the enlarged clearance, and a chamfer adjoining the central aperture.

15. The valve stack assembly of claim 13 wherein the central aperture has an aperture diameter from about 3.0 millimeters to about 3.7 millimeters, and the enlarged clearance is from about 0.4 millimeters to about 0.7 millimeters.

16. The valve stack assembly of claim 15 wherein the back-up plate has a plate diameter from about 15 millimeters to about 17 millimeters, and wherein the common circle has a circle diameter from about 6 millimeters to about 7 millimeters and the chamfer has a chamfer angle from about 45 degrees to about 55 degrees.

17. The valve stack assembly of claim 15 wherein:
the check seal includes a sealing sleeve providing the sealing contact with the outlet check, and a seal energizer compressed between the sealing sleeve and the check guide piece;
the crevice has an annular shape and is defined in part by each of the check guide piece, the back-up plate, and the seal energizer.

18. A back-up plate for trapping a check seal in a valve stack assembly of a fuel injector comprising:
a disc-shaped plate body having an outer perimetric edge, and an inner perimetric edge, the inner perimetric edge defining a central aperture structured for receiving an outlet check in the fuel injector and defining a longitudinal center axis extending between a first plate body side and a second plate body side;
the disc-shaped plate body further having formed therein a plurality of dowel holes and a plurality of fuel holes, and the plurality of dowel holes and the plurality of fuel holes are arranged in a trapezoidal pattern;
the disc-shaped plate body further having a chamfer located on the first plate body side and extending radially and axially outward from the inner perimetric edge, and a vent extending between the first plate body side and the second plate body side; and
the vent including a plurality of vent holes, at least a majority of which are positioned within the trapezoidal pattern, structured for venting a fluid pressure from a crevice formed between the check seal and the back-up plate in the valve stack assembly.

19. The back-up plate of claim 18 wherein the plurality of vent holes are circular and define center axes arranged on a common circle centered on the longitudinal center axis and located radially between the central aperture and each of the plurality of dowel

Assignees

• Caterpillar Inc

Inventors

• Warne Derik S
• Long Michael Craig

Classifications

• F02M55/008

  Arrangement of fuel passages inside of injectors · CPC title

• F02M61/12

  characterised by the provision of guiding or centring means for valve bodies · CPC title

• F02M47/027 Primary

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

• F02M2200/16

  Sealing of fuel injection apparatus not otherwise provided for · CPC title

• F02M55/002 Primary

  Arrangement of leakage or drain conduits in or from injectors · CPC title