Fuel injection nozzle

Abstract: An accumulator type fuel injection nozzle (11) having a relief valve (53) for the control chamber (43) that is controlled by an electromagnet construction (58) in such a way so as to reduce flux losses to the outer housing (12) of the injection nozzle. In addition, the inlet (35) and return (57) ports of the nozzle are formed in the outer end of the nozzle and extend axially so that the mounting position of the nozzle will not be critical to the fuel connections to the pump and return lines.

Description: BACKGROUND OF THE INVENTION This invention relates to a high pressure fuel injection device for an engine and more particularly to an improved electromagnet assembly and general overall configuration for such a fuel injection device. One popular form of fuel injection device for engines is the so-called "accumulator type". This type of injection nozzle includes an accumulator chamber that is charged with fuel under pressure and which communicates with a nozzle port. An injection valve is supported within the accumulator chamber and controls the discharge through the nozzle port. An actuating device is associated with the injection valve and is moveable within a control chamber that is also pressurized with fuel. A relief valve is associated with the control chamber and is opened so as to reduce thc pressure and cause the pressure in the accumulator chamber to unseat the injection valve and initiate fuel injection. Normally the relief valve is operated by an electromagnet assembly that is contained within the housing of the fuel injection nozzle. Although this type of injection system is quite effective, the positioning of the electromagnet within the housing can give rise to stray flux paths which will adversely effect the operation of the device and its responsiveness. For example, when the supporting yoke of the electromagnet is disposed adjacent and in close contact with the outer housing, this stray flux path can significantly reduce the responsiveness of the relief valve and, accordingly, the Operation of the System. With the type of injection nozzle described, it is, of course, necessary to provide a supply conduit for supplying the pressurized fuel to both the accumulator chamber and the control chamber. In addition, a return line must also be incorporated so as to provide a path for return flow of fuel from the control chamber back to the fuel tank. With conventional types of injection nozzles, these passages or at least one of them have been disposed at an angular relationship to the nozzle housing. As a result, when the nozzle is screwed in place into the engine, the passage may not be appropriately located and, accordingly, shimming or adjustment is required. An accumulator type of injection nozzle as indicated in the precharacterizing portion of claim 1 is known from EP-A-0234314. With regard to said most pertinent state of the art, it is the object of the present invention to provide an electromagnetic assembly for a fuel injection nozzle wherein stray flux paths are substantially eliminated and wherein the fuel supply and return ports are located in such a position that the insertion of the injection nozzle into an engine is facilitated. The above object is achieved by the subject matter of claim 1. Preferred embodiments and further improvements of the inventive injection nozzle of the accumulator type are defined in the subclaims. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of a fuel injection nozzle constructed in accordance with an embodiment of the invention and shown in a fuel system which is depicated schematically. Figure 2 is a top plan view of the fuel injection nozzle. Figure 3 is an enlarged cross-sectional view showing the relief valve. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION Referring to the drawings, a fuel injection nozzle constructed in accordance with an embodiment of the invention is identified generally by the reference numeral 11. The injection nozzle 11 is comprised of an outer housing assembly, indicated generally by the reference numeral 12 that is adapted to be mounted, in a manner to be described, in the cylinder head of an internal combustion engine with a nozzle port 13 communicating with the combustion chamber for delivering fuel to it in a manner to be described. Rather than direct cylinder injection, the invention may be utilized in conjunction with manifold injection systems but the invention has particular utility with direct injection, for example as used with high speed diesel engines. Fuel is supplied to the injection nozzle 11 from a remotely positioned fuel tank 14 by means of a high pressure pump 15. Excess fuel is returned back to the reservoir 14 through a return line 16. The fuel delivery and return systems per se form no part of the invention and, for that reason, they have been illustrated only schematically. The outer housing 12 is comprised of a first housing unit that has a threaded lower end 18 that is adapted to be threaded into a suitable aperture in the cylinder head of the associated engine (not shown) in a known manner. The nozzle port 13 is defined by a tip 19 that has a threaded portion 21 that is received in a threaded bore 22 formed at the lower end of the first housing unit 17. An adjusting shim 23 is interposed between the nozzle piece 19 and housing unit 17 for length adjustment. An injection valve 24 is slidably supported within a bore 25 of the nozzle piece 19 and has a reduced diameter portion 26 and a flow controlling tip 27 which, in the closed position, closes the injection nozzle port 13. The valve portion 26 has interrupted enlargements for slidably support in the injection valve 24 in the bore 26 in a known manner. An accumulator chamber 28 is formed above the bore 25 by the housing unit 17. The accumulator chamber 28 is closed at its upper end by means of a closure plate 29 that is held against a shoulder in the housing unit 17 by a second housing unit 31 which comprises said closure plate 29. The second housing unit 29,31 has a threaded portion 32 that is received within a threaded bore 33 of the first housing unit 17 so as to hold the closure plate 29 in position and maintain the chamber 28 in a sealed condition, except as in hereinafter noted. Externally of the threaded opening 33, the first housing unit 17 is formed with a hexagonal portion 34 so as to facilitate its insertion into the threaded bore of the cylinder head. The second housing unit 29,31 is formed with an inlet conduit 35 that has a threaded external portion 36 so as to receive a fitting for connecting a supply line 37 extending from the pressure pump 15 to the inlet conduit 35. The inlet conduit 35, which is generally a drilled opening, is intersected by a further drilled passageway 38 that extends axially along the second housing unit (29 + 31 at one side thereof and which communicates at its lower end with a corresponding circumferential groove 39 formed in the upper face of the closure plate 29. The groove 39 is intersected by a radially extending bore 41 which, in turn, has tapped into it a metering jet 42 for delivering fuel under pressure to the accumultaor chamber 28. A control chamber 43 is formed in the closure plate 29 by means of a bore 44 that opens through the lower end of the closure plate. The injection valve 24 has a generally cylindrical actuator portion 45 that is slidably supported within the bore 44 and which closes the lower end of the control chamber 43. A restricted orifice 46 fixed in the end of the actuator portion 45 communicates an axial passage 47 of the portion 45 and radial port 48 with the passage 41. The control chamber 43 communicates with the orifice to receive the pressurized fluid and normally urge the injection valve 24 towards its downward or closed position. A coil compression spring 49 encircles the injection valve 24 and bears against the closure plate 29 at its upper end. The lower end of the spring 49 engages a cup shaped retainer 51 that is held axially in position against a shoulder formed by an enlargement 52 on the injection valve 24 so as to further assist in maintaining the injection valve 24 in the closed position as shown in the drawings. A relief valve 53 is supported within the upper end of the closure plate 29 and controls the opening of a relief valve seat 54 fixed in the upper end of the closure plate 29 and communicating with the control chamber 43. The relief valve 53 comprises a headed portion that is received within a corresponding recess 54 formed in an enlarged disk like armature plate 55. The relief valve 53 is held in this recess 54 by upsetting a portion of the armature plate 55 around the valve 53 as shown at 56 in figure 3. The relief valve 53 is biased towards its closed position with the valve seat 54 in a manner to be described. The relief valve 53 when opened will permit the fuel in the control chamber 43 to return to the tank 14 through a return fitting 57 that extends axially through the end of the housing piece 31 parallel to the inlet passageway 35. The return passageway 57 communicates with the conduit 16. Fuel can flow from the relief valve seat 54 to the return passageway 57 through suitable internal passageways or clearances to permit this return flow, which is relatively small in volume. The relief valve 53 is opened and closed so as to control the discharge of fuel from the nozzle port 13 by means of an electromagnet assembly, indicated generally by the reference numeral 58. This electromagnetic assembly 58 includes a generally cylinderical yoke 59 that has a threaded opening at an enlarged diameter lower end portion 61 which is received on a threaed portion of the closure plate 29 so as to secure the electromagnetic assembly 58 in position. The electromagnetic assembly 58 is comprised of solenoid coil or winding 62 that is disposed at the lower end of the housing or yoke 59 and which encircles an armature 63. The armature 63 is formed with a bore which slidably supports an extension 64 of the relief valve. An enlarged portion 65 is affixed to the upper end of the relief valve extension 64 and is received within a counter bore 60 formed in the upper end of the armature 63. A coil compression spring 66 is received in this counter bore and is preloaded by means of an adjustable screw 67 so as to apply a preset closing biasing force on the relief valve 53 so as to hold it in the closed position as aforenoted. The yoke 59 of the electromagnet 58 has an upper portion 68 which is also cylindrical in shape but which is reduced in diameter from the mounting portion 61 and is of substantially lesser diameter than the bore of the housing piece 31 in which it is received. This provides a clearance 71 which, as will be noted, will prevent the transmission of stray flux paths to the housing 12. The yoke parts 68 and 61 are connected to each other by means of an intermediate part 72 that extends radially inwardly in proximity to the lower end of the winding 62 and immediately above the armature 55 of the relief valve 53. This provides a concentrated flux path between the armature 63 of the electromagnet 58 and the armature 55 of the relief vlave 53. In order to reduce the transmission of flux to the housing piece 31, the intermediate portion 72 is provided with weakened or reduced portions 73 and 74 that interconnect it to the remaining components so as to provide the aforenoted result. The lack of transmission of flux path can also be accomplished by other methods so long as the area of contact between the intermediate portion 72 and portion 68 to the mounting portion 61 is reduced A circuit is provided for energizing the coil 62 of the electromagnet assembly 58 for opening and closing the relief valve 53. This circuit includes a pair of terminal posts 75 that extend through the upper end of the housing piece 31 with an insulating sleeve 76 being interposed between the housing piece 31 and the terminal posts 75. Electrical tab connectors 77 are held on the posts 75 in electrical contact with them between a respective pair of nuts 78 so as to afford attachment to an appropriate lead of a circuit (not shown). A wire (not shown) is connected by a nut 79 to the post 75 to complete the connection to the winding 62. The condition shown in figure 1 is that which occurs when the winding 62 is deenergized. When the winding 62 is deenergized the relief valve 51 will be held in its closed position by the spring 66 so that the accumulator chamber 28 and control chamber 43 may be pressurized. At the appropriate instant for fuel injection to begin, which may be controlled in any suitable strategy, the winding 62 is energized. When this happens, the relief valve armature 55 will be attracted upwardly by the flux in the armature 63 so as to urge the valve portion 64 upwardly and open the relief valve 53 against the action of the spring 66. The pressure in the control chamber 43 will then be rapidly depleted and the higher pressure of the fuel acting in the accumulator chamber 28 Will urge the injection valve 24 upwardly and permit fuel to issue from the nozzle port 13. When the fuel pressure in the accumulator chamber 28 has been depleted, the spring 66 will move the injection valve 24 to its closed position and the fuel pressure can then build up in the accumulator chamber 28. This action is initiated by discontinuing the energization of the winding 62 so as to close the relief valve 51 and permit pressure in the control chamber 43 to again build up. It should be readily apparent from the foregoing description that the described fuel injection nozzle is particularly adapted in insuring against stray flux leakage and, furthermore, one that permits ease of installation into the engine and the associated fuel supply and return system. It is to be understood, however, that the foregoing description is only that of a preferred embodiment of the invention and that various changes and modifications may be made.

Claims: An accumulator type of injection nozzle comprised of an outer housing (12) having a part (18) for attachment to an engine and defining an accumulator chamber (28) adapted to be supplied with high pressure fuel, a nozzle port (13) communicated to said accumulator chamber (28), an injector valve (24) moveable between a closed position and an opened position for controlling the discharge of fuel from said accumulator chamber (28) through said nozzle port (13), a control chamber (43) for receiving a pressurized fuel, an actuating member (45) supported for movement within said control chamber (43) and associated with said injector valve for retaining said injector valve (24) in its closed position when said control chamber (43) is pressurized and for movement of said injector valve (24) to its opened position when pressure is relieved in said control chamber (43), relief valve means (53) moveable between a closed position for maintaining pressure in said control chamber (43) and an opened positon for relieving said control chamber (43) for effecting fuel discharge through said nozzle port (13), a fuel inlet port (35) formed in the end of the outer housing (12) remote from the nozzle port (13) and disposed radially offset from the centre of the housing (12), is provided for admitting fuel to said accumulator chamber (28) and to said control chamber (43) from a source, and a return port (57) for returning fuel to the source (14) from the control chamber (43) when said relief valve (53) is opened, said inlet port (35) extending axially relative to said attachment part (18), said outer housing (12) comprising a first housing unit (17) adjacent said nozzle port (13) and a second housing unit (29,31) arranged at the end of said first housing unit (17) remote from said nozzle port (13), characterized in that a) the attachment part (18) is a threaded part, b) the injection nozzle comprises only one fuel inlet port (35) and one return port (57) and no further fuel port is formed in the radial side portion of the outer housing (12), c) electrical terminal posts (75) of the electromagnetically operated relief valve means (53) are formed in the axial end face of the outer housing (12) remote from the nozzle port (13), d) the second housing unit (29 + 31) is provided on the end of the first housing unit (17) for closing said accumulator chamber (28) in said first housing unit (17) e) said second housing unit (29 + 31) houses said control chamber (43), said actuating member (45), a solenoid coil (62) energizing an armature (55) of said relief valve means (53), conduit means connecting the fuel inlet ports (35,37) with said control chamber (43) and means for connecting said electrical terminal posts (75) with said solenoid coil. An injection nozzle as claimed in claim 1, characterized in that, said second housing unit (29,31) houses an electromagnet (58) for moving said relief valve (53) to one of its positions when said electomagnet (58) is energized, said electromagnet (58) comprising an armature (63) surrounded by said solenoid coil (62), a yoke (59) surrounding said solenoid coil (62) and having an intermediate portion (72) in proximity to one end thereof and extending inwardly toward said armature (63), said yoke (59) having a first portion spaced from said second housing unit (29,31) and a mounting portion (61) fixed relative to said second housing unit and connected to said intermediate portion (72) by means of a reduced cross-sectional area (68) interconnecting the intermediate portion (72) to the mounting portion (61) for reducing flux leakage to said outer housing (12). An injection nozzle as claimed in claim 2, characterized in that, the relief valve (53) has an annular armature (55) that is juxtaposed to the yoke intermediate portion (72). An injection nozzle as claimed in claims 2 or 3, characterized in that, the reduced portion (68) is formed by at least one groove (73,74) on one side of the intermediate portion (72). An injection nozzle as claimed in claim 4, characterized in that, the reduced portion (68) is formed by a further groove (73,74) on the other side of the intermediate portion (72). An injection nozzle as claimed in at least one of preceding claims 2 to 5, characterized in that, the first yoke portion is a first cylindrical portion (68) and the mounting portion (61) is a second cylindrical portion having a greater diameter than the first portion (68) and wherein the first and second portions are joined to each other at the intermediate portion (72) through the reduced area portion (23,24). An injection nozzle as claimed in claim 6, characterized in that, both of the fuel ports (35,57) extend axially at the end of the outer housing (12) remote from the nozzle port (13). An injection nozzle as claimed in at least one of the preceding claims 1 to 7, characterized in that, the accumulator chamber (28) is closed at its upper end by means of a closure plate (29) forming part of said second housing unit (29,31), said control chamber (43) being formed in said closure plate (29). An injection nozzle as claimed in claims 7 and 8 characterized in that, the fuel ports (35,37,57) are formed at least in part in the second housing unit (29,31).

Inventors: TAUE JUN, YOSHIDA TAKEO, TAUE, JUN, YOSHIDA, TAKEO
Applicants: YAMAHA MOTOR CO LTD, YAMAHA MOTOR CO., LTD.
Application year: 1989
Main classification: F02M47
IPC codes: F02M47