Fuel injector

Abstract: An electromagnetic fuel injector (10) for the discharge of discrete spray streams (16,18) of fuel to separate intake valves of an internal combustion engine is disclosed. The injector has a valve member (50) moveable between open and closed positions with respect to a valve seat (52) and includes a fuel director plate (20) having fuel injector orifices (19) extending through said director plate which are aligned so that discrete streams (16,18) of fuel depart from the injector plate when said valve is open. The fuel injector also includes an air director plate (90) for discharging pressurized, atomization air. The director plate has a central opening (120) for the passage of the discrete fuel streams and a first group of associated atomizing air orifices (116), at predetermined locations, and oriented to direct atomizing air towards the fuel streams to impinge thereon and produce a finely atomized fuel spray. A second group of associated atomizing air orifices (118) directs atomizing air between the fuel streams to maintain separation thereof.

Description: The invention relates to an electromagnetic fuel injector for an internal combustion engine. Electromagnetic fuel injectors used in internal combustion engines are capable of effectively delivering metered quantities of fuel per unit time to the engine. Proper atomization of the injected fuel results in a homogeneous fuel/air mixture with a resultant reduction of fuel deposition, or wetting of the manifold walls. Such improved atomization and reduced manifold wall wetting should aid in achieving a reduction in the emission of regulated exhaust constituents, improved combustion stability, and better cold engine operation. Air assisted injection systems are known which deliver a continuous flow of atomization air through the injectors without regard for the timing of the injection event or other engine operating parameters. The continuous flow of air may, in certain instances, result in less than optimum transient fuel control affecting the operation of the engine across its operating range. Fuel injection systems may rely on the throttle plate position to vary the quantity of atomization air passing through the injector for a given set of engine parameters. In such cases, air flow is initiated by the differential pressure between the intake manifold and atmospheric pressure. Although many of the difficulties encountered with continuous flow, air assist systems may be addressed through the application of means for varying air flow through the injector, based on engine operating parameters, injector tip wetting may be encountered when atomization air flow is reduced and fuel spray impinges on the inoperative air assist mechanism downstream of the fuel outlets. Internal combustion engines having multiple intake valves per cylinder present an additional challenge for the delivery of fuel. It is desirable, with such an engine system, to individually fuel each of the intake valves for optimum fuel-air homogeneity entering the engine cylinder. Without resort to multiple injectors per cylinder, individual injectors must deliver a multiple spray pattern. Dual spray injectors are known to use a flow divider which directs fuel through two orifices within which atomizing air is introduced to improve atomization of the fuel. These designs have been known to drip fuel excessively when atomizing air is not present and, in addition, excessive pressure differentials may result in the downstream merging of the dual sprays thereby increasing manifold wall wetting and resulting in reduced engine performance. DE-A-4 129 834 discloses a fuel injector in accordance with the preamble of claim 1. The present invention relates to an electromagnetic fuel injector for use with an internal combustion engine. In a preferred embodiment, an injector delivers metered fuel through an outlet in a fuel director plate, used to divide the fuel into a desired spray pattern. Atomizing air may be introduced to the fuel stream downstream of the fuel outlet through an air director plate surrounding the injector fuel outlet. Such an atomizing air director configuration allows a precisely targeted series of air jets to impinge upon the fuel spray stream for the purpose of enhancing spray configuration. In the absence of atomizing air, fuel sprays pass through the annular air director plate without disruption of the flow thereby limiting fuel wetting and resultant engine performance degradation. The injector of the present invention may include an annular air director plate, downstream of the fuel outlet of the fuel injector having a series of atomizing air outlets positioned to preferentially target separate fuel streams exiting the fuel director plate outlets of a multiple fuel stream injector. Preferential targeting of the individual fuel streams by atomizing air outlets allows a portion of the atomizing air to impact the fuel stream for greater fuel atomization while a portion of the air is utilized to jacket and separate the fuel streams, thereby preserving defined fuel sprays. An embodiment of the present invention is described below, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic view of an engine intake system embodying the fuel injection system of the present invention; Figure 2 is a sectional view of a fuel injection embodying features of the present invention; Figure 3 is an enlarged, partial section of the fuel injector of Figure 2; Figure 4 is a view, partially in section, of an atomizing air director plate embodying features of the present invention; Figure 5 is an installation view, of the fuel injector of Figure 2, in an engine intake manifold; and Figure 6 is an installation view, of an alternative embodiment of the fuel injector of the present invention, in an engine intake manifold. Referring to Figure 1, there is illustrated a fuel injector, designated generally as 10, operatively mounted in an intake manifold 12 of an internal combustion engine 14. The injector 10 is operative to inject a pair of discreet spray cones of fuel 16 and 18 through orifices 19 in a fuel director plate 20, operatively mounted within the lower end of the injector 10, as viewed in Figures 2 and 3. The spray cones 16,18 are accurately targeted to project, with minimal manifold wall wetting, through discrete passages 22,24 of intake port 26 partitioned by a septum 28 onto separate intake valves 30 and 32 of a cylinder 34 of the engine 14. A preferred form of the fuel injector has a solenoid assembly 36 with a generally cylindrical and stepped diameter shell 38 having a skirt portion 40 at the lower end thereof, as viewed in Figure 2, that receives the upper end of a fuel nozzle assembly 42 which has a cylindrical, stepped diameter main casing 44. The annular end of the skirt portion 40 of the shell 38 is crimped inwardly to grip the enlarged head portion 46 of the fuel nozzle assembly 42 to the lower end of the injector shell to rigidly secure the two assemblies together. Operatively mounted for linear movement within the nozzle assembly 42 is a reciprocably movable and elongated valve element 48 having at its lower end a semi-spherical core ball 50 which is adapted to be moved from a seated and fuel sealing engagement position with a cooperating valve seat 52 of valve body 54 to define a flow passage through nozzle assembly 42. The valve element 48 is controlled in its movement by the electromagnetic force of a periodically energizable coil 56 of solenoid assembly 36 operatively mounted in the injector shell 38 and opposing the return force of a helical return spring 58. The upper end of the valve element 48 is fixed within an armature 60 which strokes with radial clearance within the spacer ring 62 which operates as an outer pole piece in the magnetic circuit of the solenoid assembly 36. Valve lift occurs on energization of the coil 56, which is wound about a hollow, elongate solenoid stator that forms the center pole piece 64 of the solenoid assembly 36. The lower end of the center pole piece 64 terminates at working surface 66 which contacts, and limits the upward lift of, the armature 60 and attached valve element 48. The center pole piece 64 accommodates the flow of fuel through the injector 10 by a centralized fuel flow passage 68 leading from injector fuel inlet 70 at its upper end to radial, intermediate flow passages 72. Fuel flows from the radial passages 72 through the annular passage 74 surrounding the lower portion of the center pole piece 64 and through the axial passages 76 in the spacer ring 62 to the fuel chamber 78 where it passes through the open valve seat 52 for distribution across the upper surface 53 of fuel director plate 20 and discharge through orifices 19. The shell 38 is encased within an insulated polymer material 80 which is formed with an elongated side socket 82 having electrical leads 84, one of which is shown in Figure 2, that operatively connect the coil 56 to a control source of electrical power (not shown). Electrical pulses from the control are fed through leads 84 to the coil 56 to thereby affect the electromagnetic operation of the injector. The fuel inlet end of the injector is configured for leak-free attachment to a source of fuel, in a conventional manner. The fuel director plate 20 is supported in a fixed position between the lower end of the valve body 54 and an annular land 86 depending from the upper surface 88 of an atomizing air director plate 90. The atomizing air director plate 90 is positioned below the fuel director plate 20 by cylindrical nozzle insert 92 which is adjustably threaded into an inner diameter 94 of stepped main casing 44 of fuel nozzle assembly 42. The upper end 96 of the cylindrical nozzle insert 92 includes an annular shoulder 98 in which the atomizing air director plate 90 is seated and which is operable to position the air director plate, relative to the fuel director plate 20. The annular land 86 defines annular space 100 between the fuel director plate 20 and the atomizing air director plate 90. The space 100 communicates with atomizing air inlets 102, formed in main casing 44 of the fuel nozzle assembly 42, through openings 91. The air inlets 102 in casing 44 communicate with a source of pressurized air such that an annular air chamber 104 which, as is illustrated in Figures 2 and 5, may be defined between the outer surface of main casing 44, the intake manifold 12, and resilient sealing members 106 and 108 seated in annular grooves 110 and 112 in the casing 44. The annular air chamber 104 may be supplied with atomization air through the air supply passage 114 in intake manifold 12. Pressurized air from passage 114 enters the injector 10 through the openings 102 in casing 44 and 91 in atomizing air director plate 90 and is distributed through space 100 for discharge through atomizing air orifices in air director plate 90. The discharge of atomizing air is through orifices 116 which are located so as to impinge upon one of the fuel streams 16,18 departing the injector 10 through the fuel director plate 20. Impingement of the atomizing air from orifices 116 with a fuel stream will assist in atomization of the fuel. In the alternative, air exiting the orifices 116 may be targeted so as to jacket the fuel sprays 16,18 to further define the fuel spray pattern exiting injector 10. In addition to the discharge of atomization air through orifices 116, additional air may be discharged through orifices 118 in the air director plate 90. The orifices 118 are configured to discharge pressurized air streams in a pattern which bisects the fuel streams 16,18 to thereby improve the separation of the streams at high flow rates. Assuring separation of the fuel streams 16,18 is desirable for minimizing fuel wetting of the walls in intake passages 22 and 24. The number of orifices 116 and 118, discharging air through director plate 90, will depend on the desired level of fuel spray atomization and control of targeting and fuel spray configuration. The atomizing air director plate 90, with a central fuel passage 120 defined by annular land 86, allows unimpeded fuel flow from injector 10 at all air flow rates. Fuel exiting injector 10 through fuel outlets 19 in fuel director plate 20, in instances of little or no atomizing air flow, passes through the central passage 120 in the atomizing air plate 90 without further contact with the injector body. As a result, wetting of the injector tip and subsequent dripping of the injector, a problem in prior art air assist injector designs used in multi-valve engines, is eliminated. Alternately fuel exiting the injector 10 through director plate 20 in the presence of high atomizing air flow, passes through central fuel passage 120 in the atomizing air plate 90 where it is further atomized and configured by the air streams exiting the orifices 116 and 118. As a consequence of the unique air director plate 90 of the present invention, fuel delivery to the engine 14 is optimized at all atomizing air flow rates and, as such, across the entire engine operating range. Figure 6 illustrates an additional embodiment of the present invention which is useful in engines having intake manifolds which lack the capability for internal air distribution. In this embodiment, fuel injector 10A includes an outer, air supply housing 130 which is received over the lower end, as viewed in Figure 6, of the injector 10A to define an annular air distribution chamber 132. An inlet 134 is connected to a supply of atomization air, such as hose 136. The inlet 134 conducts atomization air from hose 136 into annular air distribution chamber 132 where it is distributed to the air inlet openings 102A in the injector casing 44A. The present invention discloses a fuel injector useful for supplying highly atomized and targeted fuel to the intake system of an internal combustion engine. A preferred embodiment of the fuel injector utilizes a nonintrusive, atomizing air director plate which is operable to direct variously targeted air streams which enhance both the atomization and the configuration of the fuel departing the injector. Additionally, the director plate may be configured to allow injector operation at all rates of atomizing air flow by allowing fuel flow through a central opening to prevent wetting of the injector tip and by injecting atomization air, when present, through a series of perimeter orifices.

Claims: A fuel injector (10) having an atomizing air director plate (90) for discharging pressurized air into the intake system of an internal combustion engine, said director plate having an upper (88) and a lower surface, a central opening (120) for the passage of discrete fuel streams, and a first atomizing air orifice (116) extending through said director plate, said orifice oriented to direct atomizing air towards said fuel streams (16,18) to impinge thereon and produce a finely atomized fuel spray, characterised by a second atomizing air orifice (118) extending through said director plate, said second orifice oriented to direct atomizing air between said fuel streams to maintain separation of said streams. A fuel injector having an atomizing air director plate, as defined in claim 1, said first atomizing air orifice (116) comprising a first group of associated atomizing air orifices at predetermined locations and extending through said director plate (90), each of said associated orifices oriented to direct atomizing air towards said fuel streams (16,18) to impinge thereon and produce a finely atomized spray and said second atomizing air orifice (118) comprising a second group of associated atomizing air orifices at predetermined locations and extending through said director plate, each of said second group of associated orifices oriented to direct atomizing air between said fuel streams to maintain separation of said streams. A fuel injector having an atomizing air director plate, as defined in claims 1 or 2 said director plate (90) further comprising an annular land (86) extending about said central opening (120) defining a fuel passage on the inner side of said land and defining an atomizing air passage, in communication with said atomizing air orifices on the outer side of said land. A fuel injector having an atomizing air director plate as claimed in claims 1 through 3, including a valve member (50) moveable between open and closed positions with respect to a valve seat (52), a fuel director plate (20) upstream of said atomizing air director plate (90) having opposed upper and lower surfaces and a plurality of fuel injection orifices (19) extending therethrough and aligned so that discrete streams of fuel (16,18) depart from said director plate when said valve member is in said open position relative to said valve seat for passage through said central opening (120) in said atomizing air director plate. A fuel injector, as defined in claim 4, wherein said annular land (86) extending about said central opening (120) of said atomizing air director plate (90) contacts said lower surface of said fuel director plate (20) to define a fuel passage on the inner said of said land extending from said fuel director plate to said atomizing air director plate and to define an atomizing air passage, in communication with said first and second groups of associate orifices, on the outer side of said land between said lower surface of said fuel director plate and said upper surface (88) of said atomizing air director plate.

Inventors: LAVAN MICHAEL BRIAN, LAVAN, MICHAEL BRIAN
Applicants: GEN MOTORS CORP, GENERAL MOTORS CORPORATION
Application year: 1995
Main classification: F02M69
IPC codes: F02M51, F02M69