Patent Application
20050258277
This invention relates generally to electrically operated fuel injectors of the type that inject volatile liquid fuel into an automotive vehicle internal combustion engine, and in particular the invention relates to a novel thin disc orifice member for such a fuel injector.
It is believed that contemporary fuel injectors must be designed to accommodate a particular engine. The ability to meet stringent tailpipe emission standards for mass-produced automotive vehicles is at least in part attributable to the ability to assure consistency in both shaping and aiming the injection spray or stream, e.g., toward intake valve(s) or into a combustion cylinder. Wall wetting should be avoided.
Because of the large number of different engine models that use multi-point fuel injectors, a large number of unique injectors are needed to provide the desired shaping and aiming of the injection spray or stream for each cylinder of an engine. To accommodate these demands, fuel injectors have heretofore been designed to produce straight streams, bent streams, split streams, and split/bent streams. In fuel injectors utilizing thin disc orifice members, such injection patterns can be created solely by the specific design of the thin disc orifice member. This capability offers the opportunity for meaningful manufacturing economies since other components of the fuel injector are not necessarily required to have a unique design for a particular application, i.e. many other components can be of common design.
The present invention provides a fuel injector for spray targeting fuel. The fuel injector includes a seat, a movable member cooperating with the seat, and an orifice plate. The seat includes a passage that extends along a longitudinal axis, and the movable member cooperates with the seat to permit and prevent a flow of fuel through the passage. The orifice disc includes a member having first and second generally parallel surfaces, and an orifice extending through the member between first and second generally planar surfaces of the member. The first surface generally confronts the seat, and the second surface faces opposite the first surface. The orifice is defined by a wall that couples the first and second surfaces. And the wall includes first and second portions. The first wall portion is spaced from the first surface and extends substantially perpendicular to the first and second generally planar surfaces. The second wall portion couples the first wall portion to the first surface to define a inlet perimeter on the first surface. The inlet perimeter includes a plurality of curved surfaces connecting the inlet perimeter and the transition perimeter. Each of the plurality of curved surfaces is separated by adjacent curved surfaces by a line connecting the inlet and transition perimeters in a helical orientation with respect to the orifice axis.
The present invention also provides a method of forming an orifice disc for a fuel injector. The orifice disc includes a member that has first and second generally parallel surfaces. The orifice is defined by a wall that couples the first and second surfaces, and the orifice extends along an orifice axis that is generally perpendicular to the first and second generally parallel surfaces. The method can be achieved by forming an orifice extending through the member between first and second generally planar surfaces of the member and deforming the orifice proximate the first surface; and deforming the orifice proximate the first surface into a plurality of segmented surfaces extending helically from the first surface to the orifice.
The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate presently preferred embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain features of the invention.
Seat 138 can include a frustoconical seating surface 138a that leads from guide member 136 to a central passage 138b of the seat 138 that, in turn, leads to a central portion 140B of orifice disc 140. Guide member 136 includes a central guide opening 136A for guiding the axial reciprocation of a sealing end 122a of a closure member assembly 122 and several through-openings 136B distributed around opening 136A to provide for fuel to flow through sealing end 122a to the space around seat 138.
The orifice disc 140 can have a generally circular shape with a circular outer peripheral portion 140A that circumferentially bounds the central portion 140B that is located axially in the fuel injector. The central portion 140B of orifice disc 140 is imperforate except for the presence of one or more asymmetric orifices 32 via which fuel passes through orifice disc 140. Any number of asymmetric orifices 32 can be configured in a suitable array about the longitudinal axis A-A so that the orifice disc 140 can be used for its intended purpose in metering, atomizing, and targeting fuel spray of a fuel injector. The preferred embodiments include four such through-asymmetric orifices 32 (although only two are shown in the Figures) arranged about the longitudinal axis A-A through the orifice disc 140.
Referencing
The symmetrical through opening or orifice 30 is further penetrated by a suitable technique to form an asymmetrical through-opening or orifice 32. Thereafter, the work piece can be processed into an orifice disc 140 by a suitable material finishing technique such as, for example, stamping, grinding, deburring, skiving, or polishing the work piece into a desired configuration.
In a preferred embodiment, the asymmetric orifice 32 is formed by a punch tool 50 having a conic surface defining an apex 52 with at least two leading edges disposed about the tool axis Y-Y such that the resulting cross-section of the punch tool 50 is asymmetric about the orifice axis 200 (
Referring to
Furthermore, the working surface of the tool 50 can be provided with a plurality of raised helical surfaces 58A, 58B, 58C . . . Upon impact with the cylindrical pilot orifice 30, the helical surfaces 58A-58C can form corresponding segmented surfaces 35A-35F that extend helically towards a transition perimeter 42 so that the segmented surfaces 35A-35F define an asymmetric orifice 32. As shown in
The benefits of the asymmetrical geometry of the orifice 32 are believed to be many. The orifice 32 can be formed by two tools moving in a direction perpendicular to the work piece to generate an orifice that emulates an angled orifice without requiring a tool to be oriented oblique to the perpendicular direction. Furthermore, the asymmetrical geometry of the orifice 32 tends to angle the fuel flow 34 from and about the axis 200 to provide a spiraling fuel flow 36, which feature is believed to permit more of the fuel to be atomized. Moreover, the spiral segmented surfaces 35A-35F formed by the tool 50 are believed to induce the spiral fuel flow path 36 such that increased fuel atomization can be achieved.
While the present invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the sphere and scope of the present invention, as defined in the appended claims. Accordingly, it is intended that the present invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims, and equivalents thereof.
