The present invention relates to fuel injection systems of internal combustion engines; more particularly to fuel rail assemblies for supplying highly pressurized fuel to fuel injectors for direct injection into engine cylinders; and most particularly, to an apparatus and method for coupling a fuel injector for gasoline direct injection to a fuel rail.
Fuel rails for supplying fuel to fuel injectors of internal combustion engines are well known. A fuel rail assembly, also referred to herein simply as a fuel rail, is essentially an elongated tubular fuel manifold connected at an inlet end to a fuel supply system and having a plurality of ports for mating in any of various arrangements with a plurality of fuel injectors to be supplied. Typically, a fuel rail assembly includes a plurality of fuel injector sockets in communication with a manifold supply tube, the injectors being inserted into the sockets at the injectors' fuel inlet ends.
Fuel injection systems may be divided generally into Multi-Port Fuel Injection (MPFI), wherein fuel is injected from the fuel outlet end of the injector into a runner of an air intake manifold ahead of a cylinder intake valve, and Direct Injection (DI), wherein fuel is injected directly into the combustion chamber of an engine cylinder, typically during or at the end of the compression stroke of the piston. DI is designed to allow greater control and precision of the fuel charge to the combustion chamber, resulting in better fuel economy and lower emissions. DI is also designed to allow higher compression ratios, delivering higher performance with lower fuel consumption compared to other fuel injection systems.
A Gasoline DI (GDI) fuel rail assembly must sustain much higher fuel pressures than a gasoline MPFI fuel rail assembly to assure precise metering of injected fuel into a cylinder during the compression stroke. GDI fuel rail assemblies may be pressurized to about 100 atmospheres or more, for example, whereas MPFI fuel rail assemblies may sustain pressures in the magnitude of about 4 atmospheres.
To withstand higher pressures, fuel injectors of GDI fuel systems are typically supported rigidly on the engine's cylinder head and are, therefore, regarded as “non-hanging” injectors. On the other hand, a hanging injector system typically used on MPFI injectors suspends the injectors from the fuel rail via a mechanical coupling at the fuel rail. Since no hard connection exists between the injector and the cylinder head, hanging injectors are preferred for reducing acoustic noise. However, since a hanging injector is not rigidly supported at the cylinder head, if used in a GDI fuel system, it may not be capable of mechanically supporting loads originating from higher fuel pressures and from opposing combustion pressure imposed on the fuel injector.
What is needed in the art is a GDI fuel injector to fuel rail connection of the hanging injector type that is able to withstand the higher fuel and opposing combustion pressures.
It is a principal object of the present invention to provide a hanging fuel injector coupling for a GDI fuel injector that is able to manage relatively high fuel and combustion pressures.
Briefly described, a fuel injector coupling includes a coupling member such as a threaded nut to mechanically connect a fuel injector assembly to an injector socket of a fuel rail assembly, such that the fuel injector is in fluid communication with the interior of a fuel conduit. The threaded nut may be contained as part of the fuel injector assembly. Utilizing a threaded nut to connect the fuel injector with a fuel rail provides a simple and reliable fuel injector-to-fuel rail connection that is able to withstand separating loads originating from the pressures of a DI fuel system.
In one aspect of the invention, an outward extending spherical collar is integrated into the upper housing of a fuel injector. The spherical collar mates with a conical seat integrated into an inner circumferential contour of the threaded nut, thereby providing a seal against fuel leakage, even while the injector may be skewed or tilted because of a dimensional mis-alignment between the fuel rail and engine cylinder head.
In another aspect of the invention, a biasing member, positioned between the injector and the injector socket, provides a force that keeps the spherical collar of the fuel injector in sealable contact with the conical seat of the threaded nut against the force of the opposing combustion chamber pressures.
In still another aspect of the invention, a means for rotationally orienting the fuel injector assembly relative to the fuel rail assembly may be integrated into the hanging injector fuel system to properly position the injector tip in the combustion chamber. For example, a tab and receiving notch may be formed in the socket and fuel injector assembly to fix the proper alignment of the fuel injector assembly.
The fuel injector coupling in accordance with the invention adapts a hanging injector system to a GDI fuel system thereby eliminating hard contact between the injector and the cylinder head. The coupling compensates for any dimensional mis-alignment among the components while supporting the opposing high pressures inherent with a GDI system.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.
Referring to
Injector socket 114 may have a generally cylindrical geometric shape, may be closed at a first end 116 and open at an opposite second end 118 for receiving a fuel inlet end 132 of fuel injector assembly 130. Accordingly, injector socket 114 may have, but is not limited to, the shape of a cup. Injector socket 114 includes a threaded area 122 positioned proximate to the open second end 118. A continuous helical thread 124 is formed in an outer circumferential contour of injector socket within area 122, as shown in
As shown in detail in
Upper housing 134 includes a spherical collar 146 having an outward extending circular edge, integrated into the outer circumferential contour. Threaded nut 144 has a generally cylindrical geometric shape, is threaded at the inner circumferential contour for engagement with helical thread 124, and includes a conical seat 148 (shown in
After nut 144 is tightened so that nut face 145 is in contact with surface 126 of socket 114, a vertical clearance area 156 is also formed between second end 116 of injector socket 114 and spherical collar 146 of fuel injector assembly 130. Vertical clearance area 156 is provided to allow some movement of the components to also compensate for dimensional mis-alignment among the components.
Conical seat 148 and spherical collar 146 include mating surfaces 152. Mating surfaces 152 are configured so that sealing against fuel leakage is provided even while injector assembly 130 may be skewed or tilted with respect to fuel rail assembly 110 because of dimensional mis-alignment.
A biasing member 150, such as the spring-clip shown in
An orientation feature 160 may also be employed to assure proper rotational alignment of fuel injector assembly 130 with its mating socket 114, about the injector assembly's longitudinal axis. Feature 160 includes tab 162 extending below end 164 of injector socket 114 for only a small angular portion of the circumference of end 164. Spherical collar 146 of injector assembly 130 has a notch 166 disposed in a complementary small angular portion of circumferential shoulder 168 of collar 146 to receive tab 162 to fix the rotational alignment of the injector assembly.
Referring to
Biasing member 250 may be, for example, a disc spring stack as shown in
By providing a threaded nut 144 or 244 having a conical seat 148 or 248 to mechanically couple a fuel injector assembly 130 or 230 to a fuel rail assembly 110 or 120 and by mating the conical seat 148 or 248 with a spherical collar 146 or 246 integral with the fuel injector assembly 130 or 230, respectively, an injector coupling is provided that mechanically supports loads from relatively high fuel pressure and combustion pressure while allowing the injector assembly 130 or 230 to pivot relative to the fuel rail assembly 110 or 210, respectively. By providing a spring preload via biasing members 150, 250, sealing between the injector assembly and socket can be maintained.
While fuel injector systems 100 and 200 are shown as fuel injector systems for direct injection, applications of the features in accordance with the invention in MPFI systems may be possible.
While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.