Fuel injector with tubular lower needle guide

Abstract: A solenoid actuated fuel injector (10) comprises a valve body (14) having a longitudinal axis (A). A valve seat subassembly (20) is mounted in one end (22) of the valve body. The valve seat subassembly (20) includes a valve seat (24) having a seating surface (26) and a circumferential sealing surface (27) surrounding the seating surface. The valve seat subassembly also includes a lower needle guide (44) and swirl disk (50) welded to the valve seat. The lower guide includes a flange portion (47) and a tube portion (48) having an axially disposed tubular bore (46) for guiding the needle in a tight tolerance relationship. The tubular bore provides a longer length interface with the needle and a smoother wear surface than a conventional pierced hole thin lower guide.

Description: Field of the Invention This invention relates to needle type solenoid operated fuel injectors for controlling the injection of fuel into an internal combustion engine and more particularly to a fuel injector for direct injection of fuel into the engine. Background of the Invention It is known in the fuel injection art to utilize a needle within a solenoid operated fuel injector to close a fuel passageway in a valve seat. In such injectors, a pierce hole thin lower guide aligns and supports the needle during movement. The pierced hole typically has a breakout which leaves a very small (thin) guide surface. Also, the needle has occasion to wear due to the sharp thin punched hole. This wear reduces alignment, allows fuel flow around the needle and may initiate or contribute to fuel leakage. Misalignment the cone edge before being guided into the seal position and closing the flow port. Friction between the needle and the cone delays closing and disrupts the uniform spray pattern prior to complete shut off. A similar delay in developing a uniform spray pattern occurs as the needle is lifted out of the seal position. EP 0 781 916 describes a fuel injector having a deep drawn valve guide. Summary of the Invention The present invention provides a solenoid actuated fuel injector having improved axial alignment of a needle with a valve seat, reducing initial and long term leakage, resulting in improved manufacturing yield and extended life durability. According to the invention there is provided a solenoid actuated fuel injector for use with an internal combustion engine comprising: a valve body having a longitudinal axis; said valve body having an end for mounting a valve seat subassembly; said end including a pocket and a shoulder therein; a valve seat subassembly mounted on the end of said valve body; said valve seat subassembly including a valve seat having a seating surface and an annular sealing surface surrounding said seating surface and facing the interior of said valve body; said seating surface including a fuel outlet opening centered on said axis and in communication with means for conducting pressurized fuel into said valve body against said seating surface; a needle having a distal end moveable between a seated position, wherein the distal end is urged against said seating surface to close the outlet opening against fuel flow, and an open position, wherein said distal end is spaced from said seating surface to allow fuel flow through said outlet opening; and biasing means in said valve body and biasing said needle distal end against said seating surface; said valve seat subassembly also including a lower needle guide having a flange portion and a tube portion, characterised by; said tube portion extending into said valve body away from said flange portion and including an axially disposed tubular bore for guiding said needle in a tight tolerance relationship; said flange portion facing said seating surface and having a plurality of apertures annularly disposed for communicating fuel through said lower guide. In an exemplary embodiment, a swirl disk is sandwiched between the valve seat sealing surface and the lower guide flange. The swirl disk receives fuel from the plurality of fuel flow holes in the lower guide flange and distributes the fuel to the valve seat fuel outlet opening. The valve seat subassembly can be assembled on a weld guide that aligns the valve seat, swirl disk, and lower guide against a shoulder in the end of the valve body, and the nose of the valve body is crimped to hold the seat subassembly in the valve body and the valve seat is laser welded in the end of the valve body mounting the subassembly therein. These and other features and advantages of the invention will be more fully understood from the following detailed description of the invention taken together with the accompanying drawings. Brief Description of the Drawings In the drawings: FIG. 1 is a sectional view of a solenoid actuated fuel injector constructed in accordance with the present invention; FIG. 2 is a sectional view of a valve body assembly of the fuel injector of FIG. 1 illustrating a valve seat subassembly mounted at one end of the valve body; FIG. 3 is an enlarged sectional view of the valve seat subassembly illustrating the assembly of a valve seat, swirl disk and lower needle guide; and FIG. 4 is an exploded perspective view of the valve seat subassembly illustrating sealing and seating surfaces and a fuel outlet opening, the lower guide having a tubular bore and annular apertures and the swirl disk having a plurality of flow passages. Detailed Description of the Invention Referring now to the drawings in detail, numeral 10 generally indicates a solenoid actuated fuel injector of the top feed type for use with an internal combustion engine. The fuel injector 10 includes a housing 12 having a longitudinal axis A and a valve body 14 fixed to the housing. The valve body 14 has a cylindrical sidewall 16 coaxial with the longitudinal axis A that laterally bounds the interior of the valve body 14. A valve seat subassembly 20 mounted on one end, or nose, 22 of the valve body 14 includes a valve seat 24 having a seating surface 26 and a sealing surface 27 surrounding the seating surface and a peripheral sidewall 28 having a tapered end 29. The seating and sealing surfaces 26, 27 face the interior of the valve body 14. The seating surface 26 is of a frustoconical or concave shape and includes a fuel outlet opening 30 centered on the axis A and is in communication with an inlet connector or fuel tube 32 for conducting pressurized fuel into the valve body 14 against the seating surface 26. Fuel tube 32 includes a mounting end 34 for mounting the injector in a fuel rail (not shown) as is known. An O-ring 36 is used to seal the mounting end 34 in the fuel rail. An elongated needle 38 having an end 40, of an arcuate or tapered shape, is disposed along the axis A and movable between a seated position, wherein the end is urged against the seating surface 26 to close the outlet opening against fuel flow, and an open position wherein the end is spaced from the seating surface to allow fuel flow through the outlet opening 30. A spring 42 is provided in valve body 14 for biasing the end 40 toward the seated position. The valve seat subassembly 20 also includes a lower needle guide 44 of a diameter smaller than the diameter of the valve seat 24 having an axially disposed tubular bore 46 for guiding the needle 38. In the illustrated embodiment, lower needle guide 44 includes a flange portion 47 and a tube portion 48 which includes the tubular bore 46. The tubular bore 46 has a length at least 1.5 times the diameter of the needle and preferably is in the range of 1.5 to 2.0 times the diameter of the needle. Tubular bore 46 offers a long length interface with the needle 38 and a smooth wear surface. The internal diameter of the tubular bore 46 is controlled to a tight tolerance in relation to the precision ground needle 38 diameter. The increased contact length of the needle 38 and bore 46 combined with the tight tolerance relationship provides improved axial alignment which places the end 40 precisely in the cone of the seating surface 26. This alignment reduces leakage vis-a-vis conventional injectors, allows a desired spray pattern to develop quickly and allows the injector to be closed quickly. Lower needle guide 44 also includes a plurality of apertures 49 annularly disposed for communicating fuel through the guide. Preferably valve seat subassembly 20 also includes a swirl disk 50 of a diameter smaller than the diameter of the valve seat 24 and sandwiched between the valve seat sealing surface 27 and the lower guide 44. The valve seat subassembly 20, which includes the valve seat 24, lower guide 44 and swirl disk 50, may have its components laser welded together before assembly into the pocket 51 in the end 22 of the valve body 14. Swirl disk 50 includes a like plurality of flow passages 52 in communication with the plurality of apertures 49 in lower guide 44 for communicating fuel toward fuel outlet opening 30. The thickness of the flange portion 47 of the lower needle guide 44 is at least as thick as the swirl disk 50 and generally in the range of 1.0 to 2.0 times the thickness of the swirl disk. An armature 54 connected to needle 38 is axially movable in the valve body 14. A solenoid coil 56 is operable to draw the armature 54 away from the valve seat subassembly 20, thereby moving the needle end 40 off the seating surface 26, and allowing fuel to pass through the fuel outlet opening 30. The valve seat subassembly 20 is assembled in the valve body 14 as follows. The lower guide 44, swirl disk 50 and valve seat 24 are stacked in the pocket 51 against shoulder 57 in the end 22 of the valve body 14. The nose 22 of the valve body is crimped to hold the subassembly therein. The seat 24 is laser welded around its tapered end 29 to fasten the seat subassembly 20 in the end 22 of the valve body 14. Although the invention has been described by reference to a specific embodiment, it should be understood that numerous changes may be made within the scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiment, but that it have the full scope defined by the following claims.

Claims: A solenoid actuated fuel injector (10) for use with an internal combustion engine comprising: a valve body (14) having a longitudinal axis (A); said valve body (14) having an end (22) for mounting a valve seat subassembly (20); said end (22) including a pocket and a shoulder therein; a valve seat subassembly (20) mounted on the end (22) of said valve body (14); said valve seat subassembly(20) including a valve seat (24) having a seating surface (26) and an annular sealing surface (27) surrounding said seating surface (26) and facing the interior of said valve body (14); said seating surface (26) including a fuel outlet opening (30) centered on said axis (A) and in communication with means for conducting pressurized fuel into said valve body (14) against said seating surface (27); a needle (38) having a distal end (40) moveable between a seated position, wherein the distal end (40) is urged against said seating surface (26) to close the outlet opening (30) against fuel flow, and an open position, wherein said distal end (40) is spaced from said seating surface (26) to allow fuel flow through said outlet opening (30); and biasing means (42) in said valve body (14) and biasing said needle distal end (40) against said seating surface (26); said valve seat subassembly (20) also including a lower needle guide (44) having a flange portion (47) and a tube portion (48), characterised by ; said tube portion (47) extending into said valve body (14) away from said flange portion (47) and including an axially disposed tubular bore (46) for guiding said needle (38) in a tight tolerance relationship; said flange portion (47) facing said seating surface (26) and having a plurality of apertures (49) annularly disposed for communicating fuel through said lower guide. The fuel injector (10) of claim 1 wherein said tubular bore (46) has a length greater than 1.5 times the diameter of said needle (38). The fuel injector (10) of claim 2, wherein said valve seat subassembly further includes a swirl disk (50) sandwiched between said valve seat sealing surface (27) and said lower guide flange portion (47); said swirl disk (50) including a plurality of flow passages (52) in communication with said apertures (49) in said flange portion (47) for communicating fuel toward said fuel outlet opening (30). The fuel injector (10) of claim 3, wherein said needle guide flange portion (47) has a thickness at least as thick as said swirl disk (50). The fuel injector (10) of claim 3, wherein said tube portion (48) has a length 1.5 to 2.0 times the diameter of said needle. The fuel injector of claim 1 wherein said valve seat (20) has a peripheral sidewall having a tapered end spaced from said seating surface (26). The fuel injector of claim 1 wherein said valve seat subassembly is of laser welded construction.

Inventors: BRINN BENJAMIN F JR, BRINN, BENJAMIN F., JR.
Applicants: SIEMENS VDO AUTOMOTIVE CORP, SIEMENS VDO AUTOMOTIVE CORPORATION
Application year: 2000
Main classification: F02M51
IPC codes: F02M51, F02M61