The present invention relates to fuel injection systems of internal combustion engines; more particularly, to fuel injectors; and most particularly, to an internal lower filter of a fuel injector.
Fuel injected internal combustion engines are well known. Fuel injection is a way of metering fuel into an internal combustion engine. Fuel injection arrangements may be divided generally into multi-port fuel injection (MPFI), wherein fuel is injected into a runner of an intake manifold ahead of a cylinder intake valve, and direct injection (DI), wherein fuel is injected directly into the combustion chamber of an engine cylinder, typically during or at the end of the compression stroke of the piston.
A typical fuel injector includes an internal valve assembly that may include a reciprocably actuated ball that seals against a beveled circular seat in a circular sealing line. A guide that assists in positioning the ball relative to the seat may further be included in the internal valve assembly.
It is most desirable, in a modern internal combustion engine, to precisely control the flow of fuel to the combustion chamber in order to meet performance requirements as well as emission regulations. Therefore, it is desirable to ensure that the ball completely seals against the seat when the valve assembly is in a closed position to avoid fuel passage when not needed. It is known to position an upper filter proximate to a fuel inlet of the injector. While the upper filter may capture contaminants generated upstream of the fuel injector, it cannot capture contaminants that may be generated during the assembly and/or operation of the fuel injector. It is important to prevent contamination of the area between the ball and the seat. Contamination between the ball and seat may be caused by internally generated particles which may lead to a malfunction of the injector. Malfunction of the injector due to contamination could result in a stuck open condition of one or multiple injectors. With the injector stuck open, uncontrolled amounts of fuel may enter the engine's combustion chamber, which may cause a hydraulic lock of the engine. Contaminants may be generated within the fuel injector, for example during injector assembly operations, due to insufficient cleaning of the fuel injector parts prior to assembly, or during operation of the fuel injector, for example, due to friction and wear of the contacting surfaces. It is currently not possible to completely eliminate such internal contamination of a fuel injector.
A stuck open condition can lead to a severe failure mode for the injector and, therefore, injector manufacturing companies try, from both a design and a process stand point, to prevent such a failure mode by eliminating contamination as much as possible. In order to further reduce contamination of the fuel flowing through the injector with particles of internal origin, filters have been disposed internally of the fuel injector between the fuel inlet and the fuel outlet in the prior art. While such internal filters may prevent internally generated contaminants from reaching the internal valve assembly and from getting stuck between the ball and the seat, such prior art internal filters are typically supported by the valve guide, which may interfere with the accurate positioning of the ball relative to the seat.
What is needed in the art is an internal filter for a fuel injector that is positioned in close proximity to the fuel outlet and that does not interfere with the accurate positioning of the ball relative to the seat.
It is a principal object of the present invention to provide a self-supporting internal lower filter for a fuel injector that is assembled in the seat above a ball guide of an internal valve assembly of the fuel injector.
Briefly described, a lower fuel filter is assembled internally of a fuel injector downstream of a fuel inlet and upstream of a valve guide. The lower filter may be, for example, a stainless steel filter with photo chemically etched holes. By positioning the lower filter upstream of the guide, contrary to the known prior art, contact of the filter with the guide is eliminated. Thus, interference with the positioning function of the guide is avoided while, at the same time, particulates that may be generated internally in the injector are captured before reaching the valve guide area and the sealing area between the seat and the ball.
In one aspect of the invention, the lower filter is a self-supporting annular disk that may be welded, for example by laser welding or by resistance welding, to a shoulder integral with the seat. The shoulder is integrated into the seat such that the annular disk is positioned in close proximity to the guide without contacting the guide.
In another aspect of the invention, the lower filter is attached to a retaining ring that is then assembled in the seat either by a press fit into the inner diameter of the seat or by a snap fit into a groove integrated into the inner diameter of the seat. It may further be possible to capture the retaining ring with the attached filter between the body of the fuel injector and the seat during injector assembly. The retaining ring, with the filter attached, may be assembled in the seat upstream of the guide to avoid interference with the guidance of the ball.
In still another aspect of the invention, the filter is attached to an annular support ring containing fuel flow holes. The annular support ring and filter assembly is then assembled into the inner diameter of the seat with a close tolerance fit to the valve shaft outer diameter to prevent built in contaminants from flowing down to the ball and seat interface. The annular support ring and filter subassembly are assembled in the seat either by a press fit into the inner diameter of the seat or by a snap fit into a groove integrated into the inner diameter of the seat. It may further be possible to capture the annular support ring and filter subassembly between the body of the fuel injector and the seat during injector assembly.
The lower filter in accordance with the invention may be used preferably in multi-port fuel injection (MPFI) injectors, but may be applicable in direct injection (DI) fuel injectors as well. Integration of a lower internal filter into MPFI injectors is desirable, since due to the lower fuel pressure compared to DI, there is a higher possibility for contaminants getting trapped between the ball seat and the ball. Thus, without interfering with the guidance of the valve, the application of the lower filter above a valve guide in accordance with the invention in fuel injectors may reduce the occurrence of injector failure.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
a is an isometric view of a lower filter, in accordance with the invention;
b is an enlarged partial view of a filter area enclosed by circle 1b in
c is a partial cross-sectional view along line 1c-1c in
d is a partial cross-sectional view of a dimpled lower filter, in accordance with the invention;
a is an isometric top view of an annular support ring, in accordance with the invention;
b is an isometric bottom view of the annular support ring, in accordance with the invention; and
c is an isometric cross-sectional view of the annular support ring, in accordance with the invention.
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates preferred embodiments of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.
Referring to
Filter hole area 116 shown in detail in
To maximize fuel flow through a fuel injector and the filter efficiency of lower filter 100, as many filter holes 140 as desired without reducing the stability of disk 110 may be formed in reduced thickness area 128. Filter holes 140 have a diameter 142 that may be the same for each of the filter holes 140 or that may not be the same for each of the filter holes 140. The diameter 142 of filter holes 140 is preferably smaller than the largest possible distance between a ball, such as ball 214, 314, or 414, and a seat, such as seat 212, 312, or 412, when a valve assembly, such as valve assembly 210, 310, or 410 (shown in
Referring to
A body 224 of fuel injector 200 houses internal valve assembly 210. Internal valve assembly 210 includes a valve seat, such as beveled circular seat 212, a reciprocably actuated valve, such as ball 214, that seals against seat 212, for example, in a circular sealing area 216, and a shaft 218 extending axially from ball 214. Shaft 218 may be hollow. Internal valve assembly 210 regulates the fuel flow through fuel outlet end 204. A guide 230 that directs ball 214 is positioned in close proximity to and upstream of sealing area 216 within seat 212. Lower filter 100, as shown in detail in
Referring to
Fuel flowing from fuel inlet end 202 to fuel outlet end 204 through fuel injector 200 (all shown in
Lower filter 100 may be retained in seat 212, for example, by welding, such as spot welding, area 126 of disk 110 to shoulder 222. This could be done, for example by laser welding or resistance welding. In the case of laser welding, disk 110 could be spot welded to shoulder 222, for example, in three spots positioned in area 126 and spaced apart by 120 degrees. In the case of resistance welding, disk 110 need to include dimples 132 as shown in
While lower filter 100 is shown in
Referring to
Lower filter 100 is attached to an annular retaining ring 350 that is assembled into seat 312. Lower Filter 100 is preferably attached to retaining ring 350 prior to assembly of retaining ring 350 in seat 312 forming a sub-assembly. Retaining ring 350 may be formed, for example, of a stainless steel. Retaining ring 350 is attached to area 126 of disk 110 of lower filter 100 such that an outer circumferential contour of disk 110 overlaps with an inner circumferential contour of retaining ring 350. For example, an outer diameter 352 of retaining ring 350 extends beyond outer diameter 114 of disk 110 and an inner diameter 354 of retaining ring 350 does not extend beyond area 126. Accordingly, retaining ring 350 does not cover filter hole area 116 of lower filter 100.
Retaining ring 350 is assembled in seat 312 preferably such that lower filter 100 is positioned upstream of ball 314 such that inner diameter 112 of disk 110 surrounds shaft 318 of valve assembly 310. Outer diameter 114 of disk 110 is adapted to loosely fit into an inner circumferential contour of seat 312. Inner diameter 112 of lower filter 100 is designed to closely fit around an outer diameter of shaft 318 without interfering with the reciprocating movement of shaft 318, precluding particles or internal contaminants from entering valve guide area 332 and sealing area 316. Seat 312 may include a shoulder 322 integrated into the inner circumferential contour that may assist in positioning retaining ring 350. Retaining ring 350 with lower filter 100 attached is inserted into seat 312 until it makes contact with shoulder 322. Shoulder 322 may have a smaller width than shoulder 222 shown in
Retaining ring 350 may be retained within seat 312 by either a press fit into an inner circumferential contour of seat 312 as shown in
Referring to
Lower filter 100 is attached to an annular support ring 450 that includes a plurality of flow through holes 456. Lower filter 100 is preferably attached to support ring 450 prior to assembly of support ring 450 in seat 412 thereby forming a sub-assembly. The support ring 450 and lower filter 100 sub-assembly is then installed into seat 412 eliminating the need to handle multiple parts during assembly.
Annular support ring 450, shown in detail in
Seat 412 may include a shoulder 422 integrated into the inner circumferential contour that may assist in positioning support ring 450. Support ring 450 with lower filter 100 attached is inserted into seat 412 until it makes contact with shoulder 422. Shoulder 422 may have a smaller width than shoulder 222 shown in
Support ring 450 may be retained within seat 412 by either a press fit into an inner circumferential contour of seat 412 as shown in
By capturing particles or contaminants generated within a fuel injector, for example fuel injector 200, with lower filter 100 in accordance with a preferred embodiment of the invention, failure modes of the injector, such as a stuck open condition that may lead to a hydraulic lock of the engine, can be reduced compared to prior art fuel injectors that are operated without an internal lower filter. By installing lower filter 100 upstream of a ball guide, such as guide 230, 330, or 430, and without contact to the ball guide, internally generated contaminants are captured before reaching the ball and guide interface and the ball and seat interface while avoiding interference with the guidance and reciprocal movement of the ball, such as ball 214, 314, and 414.
While the lower filter 100 in accordance with the invention may be especially useful for applications in fuel injectors for multi-port fuel injection as described above, lower filter 100 may also be utilized in fuel injectors for direct injection.
While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.