Fuel injection nozzle

Abstract: A fuel injection nozzle (10) for use in an internal combustion engine has a spray tip (40) with a spring biased poppet valve (42) journaled for reciprocable movement therein. The poppet valve has a fuel supply passage (48) extending through the stem (46) thereof for flow communication with fuel spray orifices (52) that are located so as to discharge fuel in a predetermined spray pattern upon outward opening movement of the poppet valve. The nozzle has an integral locating and secondary stop assembly comprising complimentary grooves (62,64) formed in the nozzle body (16) and the stem of the poppet valve which, when aligned, form a cylindrical bore (66) which is adapted to receive a locating ball (68). The ball acts through interference at the nozzle-stem interface to prevent rotation of the poppet valve relative to the nozzle body and additionally acts to limit outward movement of the poppet valve from the nozzle body by an interference with the upper shoulder (72) of the cylindrical bore.

Description: This invention relates to fuel injection nozzles for internal combustion engines and, in particular, to a fuel injection nozzle of the outwardly opening poppet valve type particularly suited for installation in an engine where a predetermined fuel spray pattern is desired. Fuel injection nozzles of the outwardly opening, poppet valve type for use in diesel engines are well known. In this type of fuel injection nozzle there is provided a closure member, in the form of a poppet valve, that is movable to an open position relative to an associated valve seat by fuel pressure pulses from a high pressure fuel pump. The poppet valve is movable to a closed position in seating engagement with the valve seat by a return spring which acts on the valve stem of the poppet valve upon cessation of the high pressure fuel pulse. Examples of fuel injection nozzles having many features of the present nozzle are disclosed, for example, in US Patent Nos. 4,693,424; 4,905,908; 4,909,444. The fuel injector nozzles described in the above references have been limited to cylinder head installations in which the fuel spray pattern is symetric about the fuel injector nozzle. These installations are generally in a near vertical orientation. The poppet valves are free to rotate within the nozzle body with minimal effect on engine performance due to the substantially symmetric fuel spray pattern. Such fuel injector nozzles are not well suited to angled installations or installations where predetermined fuel spray patterns are desired since poppet valve rotation adversely affects the spray pattern and, as a result, engine performance. A fuel injection nozzle which overcomes this problem is disclosed in DE-A-3113475 which is considered as the closest prior art. A fuel injection nozzle in accordance with the present invention is characterised over DE-A-3113475 by the features specified in the characterising portion of claim 1. The improved fuel injection nozzle for use in an internal combustion engine is operable in a manner which allows a predetermined spray pattern to be achieved without regard to fuel injection nozzle orientation. A locator having a locator ball residing in a cylindrical bore formed cooperatively between the valve stem of the poppet valve and the nozzle body inhibits relative rotation therebetween. It is a primary object of the present invention to provide an improved fuel injection nozzle of the outwardly opening poppet valve type wherein the stem of the poppet valve is restrained from movement into the combustion chamber of the engine by action of the locator ball against an upper shoulder of the cylindrical bore. The present invention will now be described, by way of example, with reference to the following description, and the accompanying drawings, in which:- Figure 1 is a plan view, partially in section of a fuel injection nozzle embodying the present invention; Figure 2 is an enlarged sectional view of a portion of the fuel injection nozzle of Figure 1 showing details of the locator assembly; Figure 3 is an enlarged sectional view taken along line 3-3 of Figure 2 showing details of the locator assembly; and Figure 4 is an enlarged sectional view of the spray tip of the fuel injection nozzle of Figure 1. In Figure 1 there is illustrated a preferred embodiment of a fuel injection nozzle, designated generally as 10, constructed in accordance with the present invention. The fuel injection nozzle 10 is of a type that is adapted to be mounted, for example, in a suitable nozzle receiving socket for this purpose in the cylinder head (not shown) of an internal combustion engine with the spray tip end thereof suitably located so as to discharge fuel into an associated combustion chamber of the engine in a predetermined desired spray pattern. The fuel injection nozzle 10, in the construction illustrated, is provided with a multi-piece nozzle housing that comprises a (tubular) inlet fitting 12, a (tubular) nut 14 and a nozzle body 16 suitably secured together in a conventional manner. The inlet fitting 12 is secured to the nut 14 by threaded engagement of the external threads 18 thereof with the internal threads 20 at the upper end of the nut 14. An upper end surface 16a of the nozzle body 16 abuts against the lower face 12a of the inlet fitting 12 and its downwardly facing retaining shoulder 16b abuts against the internal shoulder 14a of nut 14. A dowel pin 22 inserted in pin bores formed in the end surface 12a and lower face 16a prevents rotation of nozzle body 16 in the assembled fuel injection nozzle 10. The inlet fitting 12 is provided with an axially extending stepped bore therethrough forming an inlet passage 24 extending from the upper or free end of the inlet fitting 12 to open at its lower end, as viewed in Figure 1, into a (cylindrical) fuel chamber 26. In addition, the inlet fitting 12 is provided with suitable external connector means such as threads 28 or other suitable connector to which a fuel supply (not shown) can be secured thereto so that the fuel injection nozzle 10 can be intermittently supplied with fuel, for example as by a high pressure fuel pump (not shown) in a conventional manner. An enlarged external diameter portion 29 having opposed flats 29a effect attachment of fuel injection nozzle 10 to a cylinder head as by a clamp or yoke, not shown, in a well known manner. The clamp minimizes movement of the fuel injection nozzle relative to the cylinder head. Nozzle body 16, of stepped external cylindrical configuration, is provided with an axially extending stepped bore therethrough so as to define the lower portion of fuel chamber 26 at its upper, inlet end, and an intermediate fuel passage 30, which at its lower, free end is encircled by a (frusto-conical) valve seat 34 of a predetermined included angle. Fuel chamber 26 and intermediate fuel passage 30 are connected by a flat shoulder 36. The lower outer peripheral end of nozzle body 16 may be stepped to receive shield 38 which may be useful to protect the end of the nozzle body from high temperatures present in the combustion chamber. The shield 38 insulates the nozzle body tip thereby minimizing the tendency for damage due to overheating. Additionally, spray tip 40 of nozzle body 16 is chamfered so as to improve the injection performance of the fuel injector nozzle as is well known. Fuel discharge from the spray tip 40 of the nozzle body 16 is controlled by means of an injection valve in the form of a poppet valve 42, that includes a head 44 with an (elongated) valve stem 46 extending therefrom. The lower portion of the valve stem 46 is of a predetermined external diameter wherein it is reciprocably and sealingly guided within intermediate fuel passage 30. The intermediate portion of valve stem 46 has axially extending flats 47, shown in Figures 2 and 3, which minimize the extent of contact with the wall of intermediate fuel passage 30 and provide for the flow of fuel from fuel chamber 26 to the head 44. The head 44 of the poppet valve 42 is preferably of a predetermined maximum external diameter corresponding to the external diameter of the valve seat 34 of the nozzle body 16 and is provided with an (annular frusto-conical) valve seat surface 50, shown in Figure 4, to effect seating engagement against valve seat 34, shown in phantom in Figure 4. Extending from a position within the intermediate portion of the valve stem 46 to the interior of the head 44 is fuel passage 48 which opens to a plurality of (radially outwardly extending) fuel discharge orifices 52. Although it is common for the fuel discharge orifices to be oriented to produce a fuel spray pattern which is symmetrical about the fuel injection nozzle 10, in particular applications, namely those which require the fuel injection nozzle to be mounted in a non-vertical, non-central position within the cylinder head, a predetermined, nonsymmetrical fuel spray pattern may be desired. The poppet valve 42 is normally biased to a valve closed position relative to the valve seat 34 by means of a valve return spring 54 encircling that portion of the valve stem 46 disposed within the fuel chamber 26. One end of the valve return spring 54 abuts against a retainer shim or washer 56 of predetermined thickness. The opposite or upper end of the valve return spring 54 abuts against the lower surface of spring keeper-primary stop 58 which is suitably fixed to the upper, free end portion of the valve stem 46. The spring keeper 58 is formed so as to be of a cylindrical configuration with an outside diameter suitably less than the internal diameter of that portion of the fuel chamber formed within the tubular inlet fitting in which it is disposed for reciprocable movement, but larger than that portion of the fuel chamber 26 formed within the nozzle body 16. With the above arrangement, since the lower surface 58a of spring keeper-primary stop 58 is positioned so as to abut against the upper end surface 16a of nozzle body 16, opening movement of the poppet valve 42 is limited thereby preventing the poppet valve from entering the combustion chamber beyond a desired predetermined distance. As earlier described, a predetermined fuel discharge pattern requires that the head 44 of the poppet valve 42 remain stationary. That is, in order to achieve the desired pattern, the poppet valve 42 must be prevented from rotating relative to its placement within the cylinder head. As shown in Figures 1, 2, and 3, the nozzle body 16 is provided with an axially extending locating bore 62 extending downwardly a predetermined distance from flat shoulder 36 at the lower end of fuel chamber 26. The locating bore 62 is placed off-centre from the axis of the nozzle body 16 and is of a diameter which partially intersects the intermediate fuel passage 30. A valve positioning slot 64 is formed in the side of the valve stem 46, intermediate the upper free end and the head 44. The valve positioning slot 64 is formed in the valve stem 46 by nose milling or other suitable machining operation. As shown in Figure 3, the radius of the valve positioning slot 64 is chosen to be substantially the same as that of the locating bore 62 so that upon alignment therewith the locating bore 62 and valve positioning slot 64 form a cylindrical bore 66 which receives locating ball 68 therein. The locating ball 68 is inserted within cylindrical bore 66 during the assembly of the valve stem 46 within nozzle body 16 and is retained within cylindrical bore 66 by retainer shim 56. A chamfer 70 extending about the opening of locating bore 62 aides in the insertion of the locating ball 68 within cylindrical bore 66 by guiding it from the edge of the flat shoulder 36 into the cylindrical bore. As is best shown in Figure 1, valve positioning slot 64 has an axial length which is sufficient to facilitate insertion of the locating ball 68 into cylindrical bore 66 and also to allow valve stem 46 to reciprocate freely during operation. The locating ball 68 prevents rotation of the valve stem 46 relative to nozzle body 16 which in turn is positionally fixed by dowel pin 22 with respect to inlet fitting 12 thereby assuring that the head 44 remains positionally fixed relative to the combustion chamber of the engine thereby assuring the desired fuel spray pattern. The outwardly opening design of the fuel injection nozzle 10 requires that the poppet valve 42 be securely restrained within the nozzle body 16 to prevent its incursion into the combustion chamber beyond that required for normal operation. As described above, spring keeper-primary stop 58 acts against the upper end surface 16a of the nozzle body 16 to limit downward, or outward travel of the poppet valve 42. The poppet valve locator assembly described, acts as a secondary valve stop should the spring keeper-primary stop 58 be damaged in a manner that would allow the poppet valve 42 to drop from the nozzle body 16. In such an instance, the poppet valve 42 would be limited in its downward, or outward travel by the locating ball 68 contacting an upper shoulder 72 of valve positioning slot 64 thereby preventing the poppet valve 42 from contacting the piston within the cylinder of the engine. The (poppet covered orifice) fuel injector nozzle of the present invention is suited for installations within the cylinder head of an internal combustion engine which require predetermined fuel spray patterns presenting the engine designer with greater flexibility in combustion chamber and other component designs. The fuel injector nozzle disclosed utilizes a simple, and completely internal poppet valve locator assembly for preventing undesirable rotation of poppet valves having such specific fuel spray patterns. The internal design eliminates leakage concerns inherent with externally inserted positioning dowels. Furthermore, the poppet valve locator assembly functions as a secondary poppet valve stop, preventing incursion of the poppet valve into the combustion chamber should the primary valve travel limiter fail.

Claims: A fuel injection nozzle (10) comprising a nozzle body (16) having a fuel passage (30) extending axially and configured to receive the valve stem (46) of a poppet valve (42) for reciprocable movement therein; a locating bore (62) extending axially into the nozzle body from one end thereof, the locating bore being positioned off-centre from the fuel passage; a valve positioning slot (64) which is axially elongated, formed in the side of the valve stem, having a predetermined length, and a radius substantially equal to the radius of the locating bore, wherein alignment of the locating bore with the valve positioning slot will form a cylindrical bore (66) therebetween; and a locating ball (68) disposed in the cylindrical bore to inhibit rotation of the valve stem relative to the nozzle body while facilitating reciprocable axial movement therebetween; characterised in that the circumference of the locating bore intersects the perimeter of the fuel passage and in that the predetermined length of the valve positioning slot (64) is delimited by a shoulder (72) which limits outward movement of the poppet valve (42) from the nozzle body (16) by interference of the locating ball (68) with the shoulder of the valve positioning slot. A fuel injection nozzle as claimed in claim 1, further comprising means (56) for closing the cylindrical bore (66) to prevent egress of the locating ball (68) therefrom. A fuel injection nozzle as claimed in claim 1 or claim 2, having an inlet (28) for pressurized fuel at one end thereof, a spray tip (40) at the opposite end thereof, the poppet valve (42) including an annular head portion (44) at one end of the valve stem (46) with a valve seat surface positioned for movement between a closed position when in engagement with a valve seat 34 at the spray tip and an outward opened position, the poppet valve having internal passage means (48) in fluid communication at one end with the inlet by way of the fuel passage (30) and terminating at its other end in fuel discharge means (52) that are located so as to discharge fuel in a predetermined spray pattern upon outward opening movement of the head portion.

Inventors: SCZOMAK DAVID PETER, SCZOMAK, DAVID PETER
Applicants: GEN MOTORS CORP, GENERAL MOTORS CORPORATION
Application year: 1992
Main classification: F02M61
IPC codes: F02M61