TECHNICAL FIELD
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.
BACKGROUND
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.
SUMMARY
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.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representation of a portion of an engine having a fuel injection system according to the present disclosure.
FIG. 2 is a partially schematic representation of an injector mounted in a cylinder head according to an aspect of the present disclosure.
FIG. 3 shows a portion of the injector of FIG. 2, specifically an isolator portion of the injector mounting system.
FIG. 4 is a perspective enlargement of a portion of FIG. 3, showing a ring isolator system in greater detail.
FIG. 5 shows the isolator of FIG. 4 in an elastic state corresponding to lower load operation.
FIG. 6 shows the isolator of FIG. 4 in a compressed state corresponding to higher load operation.
FIG. 7 is a partially schematic representation of an injector mounted in a cylinder with a modified isolator according to another aspect of the present disclosure.
FIG. 8 shows a portion of the injector of FIG. 7, specifically an isolator portion of the injector mounting system.
FIG. 9 is a perspective enlargement of a portion of FIG. 8, showing a ring isolator system in greater detail.
FIG. 10 shows the isolator of FIG. 9 in an elastic state corresponding to lower load operation.
FIG. 11 shows the isolator of FIG. 9 in a compressed state corresponding to higher load operation.
FIG. 12 shows a reversed conicity isolator in an elastic state corresponding to lower load operation.
FIG. 13 shows the isolator of FIG. 12 in a compressed state corresponding to higher load operation.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 illustrates an engine, 2, having a crankshaft, 8, with a piston, 4, and a connecting rod, 6, attached thereto, for reciprocating motion within a cylinder, 5, formed in a cylinder block, 16. A cylinder head, 26, is mounted at the top of engine 2. A fuel injector, 10, is mounted through cylinder head 26 so as to supply fuel directly to a combustion chamber, 13, defined by cylinder head 26 and piston 4.
FIG. 2 is a partially schematic representation of a fuel injection system having an injector isolator according to an aspect of the present disclosure. Fuel injector 10 receives fuel through a supply system including a fuel rail cap, 12, which is mounted to the top of injector 10. Injector 10 has a generally cylindrical outer body, 14, which is mounted within an injector pocket, 30, formed in cylinder head, 26. Injector 10 has a tip, 18, with a tip seal, 22, which is preferably formed from a plastics material such as polytetrafluoroethylene. Injector tip 18 extends through fire deck 34 of cylinder head 26. Because fire deck 34 and the upper surface of piston 4 configure combustion chamber 13, injector 10 is deemed to be a direct injector. Tip seal integrity is important because tip seal 22 prevents high pressure gases from leaking from combustion chamber 13 past injector tip 18. Those skilled in the art will appreciate in view of this disclosure that the present injector mounting system could be employed with either top or side feed, or yet other types of injectors.
As shown in FIG. 3, injector pocket 30 has an outer wall, 30a, which is generally cylindrical, and a conical lower wall, 34. Injector 10 is mounted within injector pocket 30, including surfaces 30a and 34, with an isolator, 40, being mounted between conical mounting surface 44 of injector 10 and conical lower wall 34 of injector pocket 30. Conical lower wall 34 of the injector pocket is incorporated within a base ring, 38, inserted into injector pocket 30.
FIG. 4 shows ring isolator 40, which is formed as a high-strength, resilient annulus, preferably formed from a metal such as stainless steel. Isolator 40 has an outer surface, 40a, and an inner surface, 40b. Ring 40 has a single internal radially directed spring rate which enables ring 40 to function as both a resilient or spring mounting system, and a solid shim.
FIGS. 5 and 6 detail the employment of isolator 40. In FIG. 5, which applies to lower load operation, upper contact portion 40c of outer surface 40a is in contact with conical lower wall 34 of base ring 38. Lower contact portion 40d, which is provided on inner surface 40b, is in contact with conical mounting surface 44 of injector 10. In essence, when injector 10 is operating at lower loads, such as during idle operation, isolator 40 suspends injector 10 elastically between conical mounting surface 44 and conical lower wall 34. This resilient, or spring, mounting helps to prevent ticking noises which arise within injector 10 from being transmitted to cylinder head 16, thereby reducing objectionable noise. Isolator 40 is able to function as a suspension spring for injector 10 because conical ring 40 has an included conic angle which is greater than the included conic angles corresponding to the conicity of both conical mounting surface 44 of injector 10 and conical lower wall 34 of injector pocket 30.
FIG. 6 illustrates injector 10 during higher load operation in which injector 10 is forced downwardly into injector pocket 30. Downward displacement of injector 10 drives isolator ring 40 outward radially, clamping ring 40, particularly the span between upper contact portion 40c and lower contact portion 40d, solidly between surfaces 44 and 34. In effect, injector 10 is stacked solid with cylinder head 26. This solid stacking provides a very high measure of resistance to further axial displacement of injector 10, protecting tip seal 22 from damage.
FIGS. 7-11 illustrate another embodiment of the present isolator in which, as shown in FIG. 9, a conical upper ring section, 60a and 60b, is joined with an annular plate, 64 extending from a lower portion of the conical ring, with annular plate 64 and the conical ring being one piece. Annular plate 64, which increases the stiffness of isolator 60, may be employed to tune the operation of isolator 60 to the needs of a particular engine.
FIGS. 8, 10, and 11 also show conical lower wall 50 as being one-piece with the parent metal of cylinder head 26. Head liner 52, which is preferably formed from a high strength material such as steel, is employed to protect head 26 from the wear effects of isolator 60. Head liner 52, which is not intended to be a resilient element, merely follows the contour of conical lower wall 50. Those skilled in the art will appreciate in view of this disclosure that, depending upon the alloy chosen for cylinder head 26, head liner 52 may not be required. It will further be appreciated that either of the isolators disclosed herein may be employed with an integral, one-piece conical lower wall 50.
As with FIG. 5, FIG. 10 shows the present system during lower load operation in which surfaces 60c and 60d are in contact with head liner 52, and injector mounting surface 44, respectively. Resilient, elastic flexing of isolator 60 provides a spring suspension for injector 10.
FIG. 11 shows isolator 60 clamped between surface 44 of injector 10 and headliner 52, as supported by conical lower wall 50. As before, the portion of conical ring 60 extending between upper contact portion 60c and lower contact portion 60d is displaced radially outward by injector 10 and clamped solidly between conical mounting surface 44 and conical lower wall 50 of injector pocket 30.
FIGS. 12 and 13 show a reverse conicity isolator, 100 mounted between surface 44 of injector 10 and headliner 52, as supported by conical lower wall 50. Isolator 100 is said to have reverse conicity because its conical structure opens downwardly. Said another way, isolator 100 has an included conic angle which is less than the included conic angles corresponding to the conicity of said conical mounting surface 44 of injector 10/14 and conical lower wall 34 of the injector pocket. The first and second conic angles corresponding to surface 44 and lower wall 34 are preferably generally equal.
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.
Patent Application
20120138013
