EP0787253B1

EP0787253B1 - Fuel injector having reduced stream dispersion, especially of an off-axis injected stream

Info

Publication number: EP0787253B1
Application number: EP95936333A
Authority: EP
Inventors: Ross W. Woods; Henry C. Dozier
Original assignee: Siemens Automotive Corp
Current assignee: Siemens Automotive Corp
Priority date: 1994-10-17
Filing date: 1995-10-16
Publication date: 2000-08-16
Anticipated expiration: 2015-10-16
Also published as: DE69518432D1; JP3625834B2; KR970707382A; WO1996012104A1; DE69518432T2; EP0787253A1; JPH10507507A; KR100386218B1; CN1168712A

Description

Field of the Invention

This invention relates to fuel injectors of the type that inject fuel into an internal combustion engine, and in particular to a novel cooperation between the needle and the valve seat that reduces the dispersion of fuel injected from the fuel injector through a thin disk orifice at the injector nozzle, especially in an off-axis direction. The invention offers rather dramatically reduced dispersion for various multiple split stream configuration although inventive principles can be useful with other injected stream configurations.

Background and Summary of the Invention

In order to improve the combustion process within combustion chamber space of an internal combustion engine for meeting certain objective criteria, especially those related to tail-pipe emissions, it has been recognized that control of the pattern of fuel injected from the nozzle of a fuel injector is a significant factor.

A fuel injection valve is discussed in patent application WO-A-87/07334. The valve has a valve needle which is drawn against a core when a magnetic coil is exited. The valve needle is caused to rise together with a sealing seating formed on it, from a valve seating surface formed on the nozzle. The sealing seating formed on the needle has a rounded profile and as a result the tendency of the needle to adhere to the valve seating on the nozzle is reduced.

In patent application DE 4123692A1, a fuel injector is discussed having a body including an orifice in which is seated a ball valve which can be caused to rise to let fuel pass through the body, or fall to prevent the passage of fuel. Fuel which passes through the body is passed out of the fuel injector valve via a disk having a raised portion. The raised portion has metering orifices through which the fuel passes into an engine for combustion.

One aspect of control involves the extent to which an injected fuel stream disperses, or spreads out, as it leaves a metering orifice in the nozzle, and for certain engine configurations, it is important to limit the extent to which an injected fuel stream disperses. The present invention relates to reducing the dispersion of injected fuel, especially in off-axis directions from multiple metering orifices although certain principles of the invention have application to other orifice configurations.

The invention arises not from any modification to a metering orifice or to a thin disk that contains one or more such metering orifices, but rather to a modification to the shape of the tip end of the needle valve and its cooperation with the associated valve seat. While the geometry of a needle tip end and its associated valve seat is apt to bear some relation to controlling the nature of the injected fuel stream leaving a metering orifice, it has been discovered that a particular shaping of the needle tip end in relation to the valve seat produces significantly less dispersion of injected fuel streams in comparison to a prior needle tip end that is spherically contoured throughout.

According to the present invention there is provided a fuel injector for injecting fuel into an internal combustion engine wherein the injector has a body, a fuel passageway through the body leading to a nozzle comprising a valve seat member disposed internally of the body within the passageway, the valve seat member having a hole from which fuel is ejected, a frustoconical valve seat, a valve having a compound valve needle surface at the tip end that is operated relative to the valve seat to close and open the passageway to flow by seating and unseating a tip end of the valve on and from the valve seat to disallow and allow flow to said hole, an orifice disk which is disposed against the valve seat member in covering relation to said hole, and through one or more metering orifices of which, fuel is injected, the tip end of said valve comprising a proximal tip portion having a spherical surface that seats on and unseats from said valve seat as said valve is operated, and a distal tip portion having a frustoconical surface extending tangentially from said spherical surface of said proximal tip portion, characterised in that said distal tip portion terminates in substantially a cone tip so that the entirety of the distal tip portion is substantially a full cone for directing the flow of fuel to the orifices.

More specific aspects relate to the rather dramatically reduced dispersion obtained with various multiple split stream configurations.

The foregoing, along with further features, advantages, and benefits of the invention, will be seen as the description of a presently preferred exemplary embodiment, accompanied by drawings, proceeds.

Brief Description of the Drawings

Fig. 1 is a longitudinal view, partly in cross section, of a fuel injector embodying principles of the invention.

Fig. 2 is a fragmentary longitudinal cross section view-proximate the nozzle of the fuel injector.

Fig. 3 is a longitudinal view of the needle tip end.

Figs. 4-10 are graphical plots diagrams useful in illustrating representative improvements obtained with the invention.

Detailed Description of the Preferred Embodiment

Fig. 1 shows a fuel injector 10 to comprise: a housing 12 of magnetically permeable material; a fuel inlet tube 14 also of magnetically permeable material; an adjusting tube 16; a helical coil spring 18; an armature 20 having a needle valve element 21 joined thereto; a solenoid coil assembly 22, including electrical terminals 23 extending therefrom via which the fuel injector is connected with an electrical operating circuit (not shown) for selectively energizing the solenoid coil; a non-metallic end cap 24; and a valve body assembly 26.

The relative organization and arrangement of these various parts are essentially the same as in the fuel injector of commonly assigned U.S. patent No. 4,610,080. The injector is the type which is commonly referred to as a top-feed type wherein fuel is introduced through inlet tube 14 and emitted as injections from the axially opposite nozzle, or tip, end. Principles of the invention are equally applicable to "side-" and "bottom-" feed injectors.

Inlet tube 14 is disposed within solenoid coil assembly 22, and in addition to conveying pressurized liquid fuel into the interior of the fuel injector, it functions as a stator of the magnetic circuit that operates armature 20. The lower end of tube 14 and the upper end of armature 20 cooperatively define a working gap 28. Because the axial dimension of the working gap is small, it appears in Fig. 1 simply as a line thickness. When the solenoid coil assembly is not energized, spring 18 pushes armature 20 away from tube 14 to cause the tip end of valve element 21 to be seated on a valve seat member 30 (to be described shortly) so that fuel is prevented from flowing through the fuel injector's internal passageway from the inlet to the nozzle. When the solenoid coil assembly is energized, it pulls armature 20 toward tube 14 to unseat valve element 21 so that fuel is allowed to flow and be injected into an engine (not shown) from the fuel injector nozzle.

Valve seat member 30 is disposed in the nozzle end of housing 12 and comprises a frustoconical seat 32. Figs. 2 and 3 show more detail. A needle guide member 36 is affixed to the upstream rim of seat member 30 for guiding the motion of the needle proximate the tip end; and it also contains several holes 36a allowing fuel to pass through. Seat 32 funnels to a circular hole 38 that is covered by a thin orifice disk 40. A back-up washer 42 holds disk 40 against member 30 and the

parts

42, 40, and 30 are axially secured within the nozzle end of the fuel injector by being axially captured between an internal shoulder 44, and a crimp 46.

Disk 40 contains a central dimple 48 that has two orifices 48a, 48b diametrically opposite each other for injecting fuel in a dual split stream pattern. As each stream leaves an orifice, it has a tendency to disperse, or spread out. In certain applications where targeting of a stream is especially important, it is desirable to minimize the dispersion of the stream. According to principles of the invention, this is accomplished by modifying the shape of the needle tip end so that instead of being completely spherically contoured, it comprises a proximal tip portion and a distal tip portion, wherein the proximal tip portion comprises a surface 52 in the form of a segment of an imaginary sphere that is geometrically defined by imaginary spaced-apart, parallel planes passing through such imaginary sphere, said surface of said proximal tip portion being that portion of said tip end that seats on and unseats from seat 32 as valve element 21 is reciprocated, and the distal tip portion comprises a frustoconical surface 54 extending tangentially from surface 52 of the proximal tip portion. The frustoconical surface 54 preferably terminates in substantially a cone tip 56 so that the entirety of the distal tip portion may be deemed substantially a full cone extending tangentially from surface 52. A substantially full cone includes a cone whose tip comes to a point that is slightly blunted, or flattened, so as to be substantially, but not perfectly, a sharp point.

In the disclosed example, surface 52 has a spherical radius of 1.18 mm and the included cone angle is 110 degrees. Seat 32 has an included angle of 90 degrees.

The improvement that is obtained is seen by comparing Figs. 4-6 against Figs. 7-10. Figs. 4-6 represent "topographical plots" of spray dispersion patterns of three substantially identical fuel injectors embodying principles of the invention while Figs. 7-10 represent "topographical plots" of spray dispersion patterns of four fuel injectors substantially identical to those three, but embodying a prior needle tip that was fully spherically contoured. These tests were conducted under like conditions with the target fixture disposed in a plane 143 mm from the injector nozzle. The invention retains a spherically contoured proximal segment of the needle tip end for seating purposes, but has a frustoconical surface - preferably substantially a full cone - extending from that spherically contoured segment. Since the tested fuel injectors were essentially the same except for the needle tip, it seems conclusive that the combination of these

surfaces

52, 54 in the manner disclosed herein results in significant constriction of the dispersion of fuel injected from each metering orifice.

While, these orifice disk members produced dual split streams diverging in opposite directions non-parallel to the injector axis 56, it is believed that principles of the invention for obtaining less dispersion of an individual stream are applicable to other metering orifice configurations, and hence the scope of the invention is limited only by the following claims.

Claims

A fuel injector (10) for injecting fuel into an internal combustion engine wherein the injector has a body (26), a fuel passageway through the body (26) leading to a nozzle comprising a valve seat member (30) disposed internally of the body (26) within the passageway, the valve seat member (30) having a hole from which fuel is ejected, a frustoconical valve seat (32), a valve (21) having a compound valve needle surface at the tip end that is operated relative to the valve seat (30) to close and open the passageway to flow by seating and unseating a tip end of the valve (21) on and from the valve seat (32) to disallow and allow flow to said hole, an orifice disk (40) which is disposed against the valve seat member (30) in covering relation to said hole, and through one or more metering orifices (48a, 48b) of which, fuel is injected, the tip end of said valve (21) comprising a proximal tip portion (52) having a spherical surface that seats on and unseats from said valve seat (34) as said valve (21) is operated, and a distal tip portion (54) having a frustoconical surface extending tangentially from said spherical surface of said proximal tip portion (52), characterised in that said distal tip portion (54) terminates in substantially a cone tip (56) so that the entirety of the distal tip portion is substantially a full cone for directing the flow of fuel to the orifices (48a, 48b).
A fuel injector as claimed in Claim 1, wherein the metering orifices (48a, 48b) comprises two orifices diametrically opposite each other about a main longitudinal axis of the fuel injector.
A fuel injector as claimed in Claim 2, wherein the orifices (48a, 48b) are disposed in a dimple (48).
A fuel injector as claimed in Claim 2 or Claim 3, wherein said metering orifices (48a, 48b) and dimple (48) are contained in a separate orifice disk member (40) that is disposed against said valve seat (30).