Filter for solenoid operated fluid metering devices

That portion of the body of a bottom-feed solenoid operated fuel injector which is placed in communication with pressurized liquid fuel when the injector is mounted in an injector-receiving socket of a fuel rail contains a circumferentially continuous stepped groove in a radially outer portion of which a frameless circular fine mesh filter screen is disposed to cover a radially inner portion and through-holes via which liquid fuel enters the fuel injector. In one embodiment, the margins of the screen are welded to shoulders of the groove against which they are disposed. In another, they are crimped into slots adjacent the groove. In still another, at least one shoulder has a taper so that the corresponding screen margin wedges onto the shoulder. In yet another, a retaining ring is used.

FIELD OF THE INVENTION 
This invention relates to solenoid operated fluid metering devices such as 
solenoid operated fuel injector valves for internal combustion engines, 
and in particular to the organization and arrangement of a filter on such 
a device for filtering certain particulate material from fluid entering 
the device. 
BACKGROUND AND SUMMARY OF THE INVENTION 
It is known to make filter screens for certain solenoid operated fluid 
metering devices from plastic mesh screen supported by an overmolded 
frame. Certain plastic materials are not universally capable of 
maintaining compliance with relevant filtering specifications when 
subjected to certain fuel blends, such as certain gasoline/alcohol (i.e., 
flex fuel) mixtures. In order to provide adequate support for a plastic 
mesh screen, an overmolded frame may have to be of such a size and/or 
shape that it limits the ability to miniaturize the package size of a 
filter-equipped fuel injector. 
The inventor has further observed that a stainless steel mesh screen can 
possess sufficient rigidity to be self-supporting so that in accordance 
with principles of the invention it becomes possible to provide a solenoid 
operated fluid metering device with a frameless filter screen that 
attaches directly to the body of the device. The use of stainless steel 
for the mesh material will solve the problem of compatibility with flex 
fuels, and a frameless filter will be more compact than one which includes 
a peripheral frame for supporting the screen. 
Further features, advantages, and benefits of the invention, along with 
those just mentioned, will be seen in the ensuing description and claims 
which should be considered in conjunction with the accompanying drawings. 
The drawings disclose a presently preferred embodiment of the invention 
according to the best mode presently contemplated for carrying out the 
invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIGS. 1-4 illustrate a fuel injector 10 embodying principles of the 
invention. The fuel injector is of the type commonly known as a 
bottom-feed type. It comprises a solenoid 12 at the top axial end of a 
generally tubular body 14. Body 14 comprises an outlet port 16 and an 
inlet port 18. Outlet port 16 is in the form of a nozzle at the axial end 
of body 14 opposite solenoid 12. Inlet port 18 is disposed in the sidewall 
of body 14 in axially spaced relation to outlet port 16. Inlet port 18 is 
bounded by a circumferentially continuous, circular, radially outwardly 
open groove 20 in body 14. Groove 20 is shown (in FIG. 1 only) stepped so 
as to comprise a radially outer portion that is defined by sides 21a, 21b 
and shoulders 32, 34 and a radially inner portion that is defined by sides 
(unnumbered) and a bottom (unnumbered). One or more circular through-holes 
22 extend radially inwardly from the groove bottom to the interior of body 
14. 
The interior of body 14 contains a valve mechanism 24 that is operated by 
solenoid 12. Valve mechanism 24 is normally closed so that when solenoid 
12 is de-energized, liquid fuel that is supplied to inlet port 18 does not 
flow through a flow path through the fuel injector to outlet port 16, and 
when solenoid 12 is energized, valve mechanism 24 opens to allow fuel flow 
with the result that fuel is injected at the nozzle. 
In use, fuel injector 10 is typically assembled into a corresponding socket 
in a fuel rail (not shown). The socket transversely intersects a 
longitudinal fuel passage in the fuel rail. The fuel injector contains two 
axially spaced apart 0-rings 26, 28 around its outside, and they serve to 
seal the fuel injector in the socket so that fuel will not leak from the 
axial region between them which is communicated to the pressurized liquid 
fuel that is within the longitudinal fuel passage of the fuel rail. 
A circular cylindrical fine mesh filter screen 30 is assembled onto body 
14. Filter screen 30 is disposed within the radially outer portion of 
groove 20 against shoulders 32, 34 so as to be in covering relation to the 
radially inner groove portion and hole(s) 22. Filter screen 30 is 
fabricated from a suitable length of screen material of a width 
corresponding to the axial dimension of the completed filter screen. The 
length of screen material is formed to a circular shape having lengthwise 
end margins overlapped and seam welded together to form a seam 36 that 
does not compromise the integrity of the screen's mesh because it does not 
allow fuel-entrained particulates greater than the screen's mesh to 
intrude through the seam. 
For the embodiment of FIG. 1, the filter screen is fabricated by laying the 
screen material lengthwise into the radially outer portion of groove 20, 
tacking it to the shoulders 32, 34, wrapping it tightly around shoulders 
32, 34, and then welding the overlapped lengthwise ends of the strip 
together to create seam 36. Alternately, the final step could consist of 
tacking the overlapped ends and then seaming them together To insure 
integrity of the assembly, cylindrical margins 38, 40 of the filter screen 
that axially bound a central filtering zone 42 of the filter screen and 
that are in direct and circumferentially continuous contact with shoulders 
32, 34 of body 14 are welded directly to the body to create respective 
joints that are effective to preclude fuel-entrained particulates of a 
size that would be filtered by zone 42 from reaching the radially inner 
portion of the groove and hole(s) 22 by intruding between shoulders 32, 34 
and margins 38, 40. Welding can be conducted by conventional procedures 
such as laser or resistance welding. It is preferable for the seam 36 to 
be located other than over a hole 22. The radially inner portion of groove 
20 serves to distribute filtered fuel around the full circumference of the 
fuel injector and thereby avoid restricting the flow to the individual 
hole(s) 22. 
FIG. 5 illustrates another embodiment in which the radially outer portion 
of groove 20 extends axially all the way to an axially facing shoulder 
designated by numeral 44 in FIG. 1 so that as a result side 21b is 
eliminated. In addition, body 14 comprises two narrow circumferentially 
continuous, circular, radially outwardly open slots 46, 48 that are 
disposed in shoulders 32, 34 to opposite axial sides of the radially inner 
portion of the groove. Thus after having been formed to circular shape and 
provided with seam 36, the screen is slid axially over the nozzle end of 
body 14 to a final position covering the radially inner portion of the 
groove and hole(s) 22. The edges of margins 38, 40 are mechanically 
crimped, or pressed, into slots 46, 48 to complete the assembly. The crimp 
joints prevent intrusion of particulate material between the screen 
margins and the outside of body 14, and do not necessarily require 
welding. 
FIG. 6 illustrates still another embodiment which embodies certain features 
of the previously described embodiments. As in the FIG. 5 embodiment, 
groove 20 is fully open to shoulder 44 to allow the filter screen which 
has already been formed to circular shape to be slid axially over the 
nozzle end of the fuel injector to place margin 38 over shoulder 32. A 
single slot 48 is provided for allowing the edge of the other margin 40 to 
be crimped into it. The margin 38 is joined to the injector body by 
welding. 
While it may be deemed preferable to weld margin 38 to shoulder 32 as 
described in preceding embodiments, such a step may be optionally 
dispensed with by making shoulder 32 to have a slight taper as shown on a 
somewhat enlarged scale by the still further embodiment of FIG. 7. Such a 
tapered shoulder will exert a wedging action on the upper margin 38 as the 
circular screen is being axially slid to final position on body 14. This 
will serve to circumferentially tension the upper screen margin on the 
body and offers the possibility of a joint that will allow for the welding 
step to be dispensed with. The lower margin 40 is joined to body 14 by 
welding, but could alternatively be joined by crimping in the manner of 
FIGS. 5 or 6. 
The embodiment of FIG. 8 is like that of FIG. 7 except insofar as the 
joining of margin 40 to body 14 is concerned. The assembly of the screen 
to the injector proceeds in the same manner as in the case of FIG. 7 until 
the step of securing the lower margin 40 to the body. Such securement is 
obtained, not by welding, but rather by sliding a retention ring 50 over 
the nozzle end of the body. Ring 50 has a circular body engaging portion 
52 that is pressed onto body 14 and a circular filter engaging portion 54 
that girdles the lower margin 40. Portion 54 is shaped to have a suitable 
lead for fitting over the lower margin 40 as ring 50 is brought to its 
final position of assembly as shown in FIG. 8. Portion 54 serves to retain 
the lower margin 40 against the underlying shoulder surface so that the 
integrity of the joint is assured. Thus ring 50 axially overlaps both the 
filter screen mesh margin and the valve body. It is to be understood that 
the steps of assembling filter screen 30 and ring 50 onto the fuel 
injector occur prior to the step of assembling O-ring 28, as would also be 
true for assembling the filter screens to the bodies in the embodiments of 
FIGS. 5, 6, and 7. 
A preferred screen material for filter screen 30 is 304-L stainless steel 
woven wire having a single or multiple layers. A sintered Dutch weave, or 
equivalent, will provide appropriate filtration (44 microns or less) and 
rigidity. A two-layer screen may comprise a fine filtration cloth layer on 
the outside and a reinforcing cloth layer on the inside that are sintered 
together to produce a single laminate which is equivalent to the sintered 
Dutch weave. Thus, such a two-layer screen may be substituted for the 
sintered Dutch weave in any of the drawing FIGS., and it may also be used 
in any injector which does not have a step in the groove. In this latter 
case, the reinforcing cloth layer serves as a drainage cloth which 
performs a function equivalent to that of the stepped radially inner 
portion of groove 20 in the embodiments illustrated in the drawing 
FIGURES. 
While a principal intent of this invention is to provide a filter that will 
be resistant to flex fuels, certain principles may be applied to 
non-stainless-steel (such as plastic) mesh screens that are used in 
non-flex fuel applications. 
Although it is not expressly illustrated in the drawing, the embodiment of 
FIG. 1 could have both its shoulders 32, 34 tapered in the same manner as 
the single tapered shoulder 32 of FIG. 7. In such a case, the lower 
shoulder's 34 taper will be the mirror image of the upper shoulder's 32 
about a transverse plane bisecting groove 20. 
In all embodiments the entire circumferential area of filtering zone 42 is 
open to hole(s) 32 on account of the stepped nature of the groove, and the 
filter screen itself is radially recessed although for drawing convenience 
only FIG. 1 shows such a stepped groove. 
While a presently preferred embodiment of the invention has been 
illustrated and described, it should be appreciated that principles of the 
invention are applicable to other embodiments.