The present disclosure relates to an internal combustion engine having fuel injectors mounted within a cylinder head and spraying fuel into the engine's combustion chambers.
Most spark-ignited internal combustion engines used in automotive vehicles have employed fuel systems with either a carburetor, or more recently, multiple fuel injectors mounted in an intake manifold or within individual intake ports. Each of these systems provides fuel to the engine via the intake manifold. Although manifold/port mounted fuel injectors have generally been satisfactory, and indeed, a great improvement as compared with carburetor systems, automotive designers are increasingly moving to the use of direct fuel injection with spark-ignited engines. With a direct injection system, fuel injectors are typically mounted through the fire deck of the engine's cylinder head and provide fuel directly into each of the engine's combustion chambers.
In spark ignition engines, direct injection has been found to be beneficial in terms of improved fuel economy, coupled with reduced exhaust emissions. Although direct injection has been used in many types of diesel engines for years, this new application of direct injection, particularly in gasoline engines intended for use in automotive vehicles, has created a problem because the higher pressures utilized with direct injection have caused unwanted noise or “tick” while the engine is idling; under certain cases the tick may become more pronounced at high speeds and loads. This tick noise, resulting from injector needle impact, has not generally been a problem with most diesel engines, but has definitely proved to be an issue with direct-injected spark ignited engines used in automobiles, as well as with some diesel engines.
It would be desirable to provide a system allowing a low noise signature for gasoline and diesel direct injection fuel systems at lower loads, including idle, while at the same time preserving the durability of fuel injectors by preventing unwanted injector movement during higher load operation. This presents a challenge, because if, without anything more, the injector's mounting is softened to the point where ticking noise is attenuated at idle, the corresponding axial movement of the injector within the cylinder head's injector pocket at high loads may cause adverse durability affects upon injector tip seals.
According to an aspect of the present disclosure, a fuel injection system for an internal combustion engine includes a cylinder head having an injector pocket extending through the cylinder head to a combustion chamber, with the pocket having a conical lower wall. A fuel injector is mounted within the injector pocket and extends to the combustion chamber. The injector has a conical mounting surface for engaging the conical lower wall of the injector pocket. An isolator mounted between the conical mounting surface of the injector and the lower wall of the injector pocket includes a conical ring having an outer surface and an inner surface. The isolator is configured so that at lower injection loads, only an upper contact portion of the outer surface of the conical ring contacts said conical lower wall of said injector pocket. Also at lower injection loads, only a lower contact portion of said inner surface of the conical ring contacts the conical mounting surface of the injector. However, at higher injection loads, the portion of the conical ring extending between the ring's upper contact portion and lower contact portion is clamped between the conical mounting surface of the injector and the conical lower wall of the injector pocket.
According to another aspect of this disclosure, the isolator is configured as a conical ring having a single, radially oriented spring rate and an included conic angle which is greater than the included conic angles corresponding to the conicity of said conical mounting surface of said injector and said conical lower wall of said injector pocket.
According to another aspect of the present disclosure, substantially the entire portion of the conical ring extending between the ring's upper contact portion and lower contact portion is clamped solidly between the conical mounting surface of the injector and the conical lower wall of the injector pocket during operation of the injector at higher loads, whereby axial movement of the injector will be restricted at higher injector loads.
According to another aspect of the present disclosure, the isolator reacts elastically to radial loading during operation of the injector at idle and stacks solidly between the conical mounting surface of the injector and the conical lower wall of the injector pocket at higher injection loads.
It is an advantage of a fuel injection system according to the present disclosure that objectionable ticking noise which is particularly prevalent in engines having direct cylinder injectors, will be avoided, while at the same time protecting injector tip seals from harm which could otherwise occur as a result of a compliant mounting system.
It is another advantage of a system according to the present disclosure that a single rate load deflection curve is established for an initial elastic response of the injector mount to the forces imposed upon the injector while the injector is operating at lower loads, with the elasticity being supplanted by stacked solid operation at and above moderate injector loads.
It is yet another advantage of a fuel injection system according to the present disclosure that the isolator used in the present system is readily tunable to accommodate changes in engine operating parameters.
Other advantages, as well as features of the present isolator system, will become apparent to the reader of this specification.
As shown in
As with
As before, the portion of conical ring 100 extending between upper contact portion 100a and lower contact portion 100bd is displaced radially outward by injector 10 and clamped solidly between conical mounting surface 44 and conical lower wall 50 of injector pocket 30, but only during higher load operation; at idle and other lower load operation, isolator 100 acts as a spring suspension to prevent the ticking noise discussed above.
The foregoing system has been described in accordance with the relevant legal standards, thus the description is exemplary rather than limiting in nature. Variations and modifications to the disclosed embodiments may become apparent to those skilled in the art and fall within the scope of the disclosure. Accordingly, the scope of legal protection can only be determined by studying the following claims.
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