Field of the Invention

This invention relates generally to fuel injectors of the type that are use to inject liquid fuel into the air induction system of an internal combustio engine and particularly to an atomizer that fits over the nozzle of such a fu injector and serves to convey assist air to promote the atomization of th injected liquid fuel that has just left the nozzle.

Background and Summary of the Invention

Air assist atomization of the liquid fuel injected from the nozzle of a fu injector is a known technique that is used to promote better preparation of th combustible air/fuel mixture that is introduced into the combustion chambers an internal combustion engine. A better mixture preparation promotes both cleaner and a more efficient combustion process, a desirable goal from th standpoint of both exhaust emissions and fuel economy.

The state of the art contains a substantial number of patents relating t air assist atomization technology. The technology recognizes the benefits tha can be gained by the inclusion of special assist air passages that direct th assist air into interaction with the injected liquid fuel. Certain air assist fu injection systems use pressurized air, from either a pump or some other sourc of pressurization, as the assist air. Other systems rely on the pressur differential that exists between the atmosphere and the engine's inductio system during certain conditions of engine operation. It is a common techniqu to mount the fuel injectors in an engine manifold or fuel rail which is constructe to include assist air passages for delivering the assist air to the individua injectors.

It is known from commonly assigned U.S. Ser. No. 07/652,166 t construct an air assist atomizer in which the definition of the final length of th assist air passage to each fuel injector tip is provided by the cooperativ organization and arrangement of two additional parts which form an atomize assembly disposed between the nozzle of an injector and the wall of a socke that receives the injector. One advantage of that invention is that it adapts a otherwise conventional electrically-operated fuel injector for use in an air assis

system without the need to make modifications to the basic injector, and with the need to make special accommodations in the injector-receiving socket ot than suitably dimensioning the socket to accept the air assist atomizer.

The air assist atomizer of the present invention is similar to that of U Ser. No. 07/652,166 in that it comprises the cooperative organization a arrangement of two individual parts; in other respects, as will become appar from the ensuing description, drawings, and claims, it is distinguished from t air assist atomizer of U.S. Ser. No. 07/652,166.

From Patentschrift DE 40 04 897 C1 it is known to construct a one-pie atomizer with a series of short, circumferentially spaced apart risers on t interior of the atomizer's end wall which abut the end of the nozzle so as thereby cooperatively define a number of circumferentially spaced apart assist openings through which assist air passes radially to act upon the inject fuel just after it has left the nozzle. In order to create and to closely control t axial dimension of these air assist openings, it would seem essential to condu precision machining operations on the interior of the end wall, and since t dimensions involved are small, it may be forecast that such machini operations will be difficult to conduct in a cost-effective manner for ma production of the atomizer. The present invention is similar to the atomizer disclosed in Patentschr

DE 40 04 897 C1 and other earlier prior art in that it comprises a number of assist openings that are circumferentially spaced apart and that convey assi air radially inwardly toward the injected fuel; it is distinguished however in th instead of risers, a separate disk is inserted into the interior of a surroundin shroud that is fitted over the nozzle. The disk is disposed axially sandwiche between, and in mutual abutment with, the nozzle and the end wall of th shroud to thereby create the air assist openings through which assist air i radially inwardly directed to the injected fuel that has just left the nozzle. Th disk can be advantageously fabricated by conventional stamping technolog and the interior of the shroud can be finished without the ostensibly elaborat measures that may be expected in the case of the atomizer described in th referenced Patentschrift.

Further features, advantages, and benefits of the present invention wi be seen in the ensuing description and claims which are accompanied b drawings. These drawings disclose a presently preferred embodiment of th

invention according to the best mode contemplated at this time for carrying o the invention.

Brief Description of the Drawings Fig. 1 is a longitudinal cross sectional view through a fuel inject containing an air assist atomizer in accordance with principles of the prese invention.

Fig. 2 is an enlarged view of the nozzle end of the fuel injector of Fig. 1.

Fig. 3 is a full end view in the direction of arrows 3-3 in Fig. 2. Fig. 4 is a side view in the radial direction of a disk that is used in the assist atomizer.

Fig. 5 is a plan view of the disk of Fig. 4.

Fig. 6 is a plan view of a second embodiment of disk.

Fig. 7 is a plan view of a third embodiment of disk. Fig. 8 is a plan view of a fourth embodiment of disk.

Description of the Preferred Embodiment

Figs. 1-3 illustrate an electrically operated fuel injector 10 containing a air assist atomizer 12 embodying principles of the invention. Fuel injector 1 has a main longitudinal axis 14 and is a top-feed type device comprising a inlet 16 and a nozzle 18 at its opposite axial ends. The passage of liquid fu through the fuel injector between inlet 16 and nozzle 18 is controlled by th seating and unseating of the rounded tip end of a metal needle 20 on and fro a valve seat 22 located just interior of nozzle 18. Needle 20 is resiliently biase by a spring 24 to seat on seat 22 thereby closing the passage to flow. Whe the valve is electrically energized by the delivery of electric energizing current t its solenoid coil 26, the needle unseats to allow fuel flow. Figs. 1 and 2 sho the fuel injector closed.

The construction in the vicinity of nozzle 18 is shown in greater detail i Fig. 2. The fuel injector comprises a generally tubular metal housing 28 whic contains in order of assembly at the nozzle end, a metal needle guide memb 30, a metal valve seat member 32, a thin disk orifice member 34 made metal, and a metal retainer member 36. An O-ring seal 40 is disposed betwee member 32 and the inside wall of housing 28. Thin disk orifice member 3 contains a central conical dimple 42 having exactly two orifices 44, 4

diametrically opposite each other equidistant from axis 14. When the fu injector is operated open, the pressurized fuel that is supplied to the injector inlet 16 is injected from nozzle 18 in two distinctly divergent directio represented generally by the respective numerals 48, 50 in Fig. 2. T construction of the injector and its nozzle end which has thus far be described is generally like that disclosed in certain commonly assigned issu patents, and therefore will not be described further at this time so that attenti can be focused on the inventive features residing in air assist atomizer 12 a its association with fuel injector 10. The air assist atomizer comprises two parts in assembly relation with th fuel injector: one part being a shroud 52 and the other being an insert 5 Shroud 52 possesses a general cap shape having a side wall 56 and an en wall 58. Side wall 56 has a circular cylindrical inside diameter including shoulder 60 that divides it into a larger diameter portion 62 and a small diameter portion 64. Portion 64 extends from immediate contiguousness wit end wall 58 to shoulder 60 while portion 62 extends from shoulder 60 to the en of shroud 52 that is opposite end wall 58.

A portion of housing 28 has a nominally circular outside diameter 66 tha is dimensioned to allow portion 62 of shroud 52 to snuggly fit onto it. Howeve that nominally circular outside diameter 66 is provided with one or mor interruptions, such as an axial flat or slot 68, so as to thereby cooperativel define with the shroud's side wall the entrance portion of axially extendin passage means 70 for assist air to flow axially along the outside of housing 2 toward nozzle 18. The small arrows in Fig. 2 represent the assist air flow. End wall 58 extends radially inwardly from side wall 56 to provide a axially frusto-conically expanding aperture 72 which is coaxial with axis 14 an through which fuel that has just been injected from nozzle 18 passes. A raise circular annular ledge 74 is fashioned on the inside of end wall 58 in circumscription of aperture 72. Insert 54 is disposed axially between nozzle 18 and end wall 58 and is in fact held between ledge 74 and the exterior axial end face of member 36.

Figs. 5-8 disclose four different embodiments of insert 54, and for convenience each of them is uniquely identified by including a particular literal suffix after the base numeral 54 such that the respective disks are 54a, 54b, 54c, and 54d for each of Figs. 5-8 respectively. The view of Fig. 4 is equally

applicable to all four embodiments and is designated by only the base numer 54. While it is possible for any given insert to be used with a fuel inject having almost any type of thin disk orifice member, or equivalent, it is intend that either insert 54b or 54d be used in a fuel injector containing the particul thin disk orifice member 34 that has been described above; inserts 54a and 5 are intended to be used with thin disk orifice members that have a single orifi at the center and no dimple.

Each insert 54 is in the form of a disk that is flat and of uniform thickne throughout. It comprises a central circular void 76 that is surrounded by circular annulus 78 which contains at least one circumferential discontinuity 8 Annulus 78 is bounded in radially outwardly spaced relationship by a secon circular annulus 82 which, as shown, is preferably circumferentially continuou A third circular annulus 84 joins annuli 78 and 82 and comprises one or mor circumferential discontinuities 86, each of which is contiguous with corresponding discontinuity 80 of annulus 78 and has a circumferential exte greater than that of the corresponding discontinuity 80.

Insert 54a has a single discontinuity 80 and a single discontinuity 8 insert 54b has two and two; insert 54c has three and three; and insert 54d ha four and four. Each discontinuity 80 is circumferentially centered with respe to its contiguous discontinuity 86, and in the case of inserts 54b, 54c, and 54 the discontinuities 80 are of equal circumferential dimensions and are arrange in a uniform pattern such that each discontinuity 80 is equally circumferentiall spaced from immediately adjacent ones.

The outside diameter (O.D.) of an insert 54 is dimensioned just slightl less than the inside diameter (I.D.) of side wall portion 64 to allow the insert t pass axially through the shroud so that it can be disposed against the inside end wall 58 preparatory to assembling the atomizer to the fuel injector. In thi way, annulus 82 functions as a locator to properly center, i.e. radially locate, th insert within the shroud. Such placement serves to dispose annulus 78 o ledge 74 so that when the insert-containing shroud is thereafter assemble onto the nozzle by advancing the shroud over the end of housing 28, annulu 78 will be sandwiched between and in mutual abutment with ledge 74 and th annular end surface of member 36, as appears in Figs. 1 and 2.

Thus after assembly of the atomizer to the fuel injector, the sandwiche annulus 78 will in cooperation with the end surface of member 36 and ledge 7

define a number of air assist openings 88 (see Fig. 2) through which assist passes radially inwardly toward fuel just injected from the nozzle. The ax dimension of each opening 88 is equal to the thickness of insert 54, and circumferential extent is equal to the circumferential dimension of t corresponding discontinuity 80 in the insert. Assist air enters each opening from the corresponding discontinuity 86 which is in communication with t inner downstream end of passage means 70.

The illustrated inserts 54 are advantageous in that they can fabricated by stamping from sheet material. Because they are flat and uniform thickness throughout, the inserts have an overall axial dimension that equal to their thickness. While the illustrated inserts do not have expre provision for securing circumferential registry with the corresponding shroud, a express means therefor could be incorporated if desired. Likewise, it i possible to secure proper circumferential registry without an express mean therefor. In such case, the insert is properly circumferentially oriented on th shroud prior to assembling the shroud over the end of the nozzle. Suc circumferential registry is important in the case of a fuel injector which has thin disk orifice member like that illustrated in Figs. 1 and 2. This is because is deemed preferable to align diametrically opposite openings 88 on th common diameter between orifices 44 and 46.

The insert and shroud are fabricated from suitable materials, such a stainless steels. It is preferred that the covers between void 76 an discontinuities 80 be kept sharp while those between discontinuities 80 and 8 be radiused. The several parts of the fuel injector are fabricated fro conventional parts and materials in known manner.

The atomizer-equipped fuel injector 10 is adapted to be installed i manifold (not shown) that delivers assist air to the open upstream end o passage means 70. Axially spaced apart O-rings 90, 92 on the outside o housing 28 and the outside of shroud 52 provide for sealing of th atomizer-equipped fuel injector to a socket in the manifold for receiving the injector.

In use, the air atomizer promotes the atomization of fuel being injected. In the case of the illustrated fuel injector, the injections along the directions 48, 50 will be nebulized by the atomizer into the shape of respective clouds, as distinguished from narrower streams. Of course, it should be understood that

principles of the invention may be practiced in other than only the specifical disclosed examples.