WO2011163110A1

WO2011163110A1 - Two phase flex spring fuel injector spacer

Info

Publication number: WO2011163110A1
Application number: PCT/US2011/041038
Authority: WO
Inventors: Robert R. Schaser; Jason D. Holt; Jeremy R.D. Tuttle
Original assignee: Illinois Tool Works Inc.
Priority date: 2010-06-21
Filing date: 2011-06-20
Publication date: 2011-12-29

Abstract

A spacer (10) in the form of an annular two-phase flex spring of unitary construction including an outer wall (30) and an inwardly projecting circumferential ledge (34) of flexible, resilient character extending radially inwardly from the outer wall (30). The circumferential ledge terminates at a free edge (36) extending circumferentially about a pass -through opening for receipt of an element to be centered. The outer wall (30) and the circumferential ledge (34) form a dogleg cross - sectional profile. The two-phase flex spring (10) is characterized by a first phase stiffness upon application of a first compressive force and by a greater, second phase stiffness upon application of a second greater compressive force.

Description

TWO PHASE FLEX SPRING FUEL INJECTOR SPACER

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This non-provisional application claims the benefit of, and priority from, prior US provisional application 61/356,758 filed June 21, 2010. The contents of such prior application are incorporated by reference in their entirety as if fully set forth herein.

TECHNICAL FIELD

[0002] The present invention relates generally to a resilient spacer element providing alignment and vibration supression, and more particularly to a vibration damping two phase flex spring spacer adapted for use in supporting and aligning a fuel injector in an engine injection bore.

BACKGROUND OF THE INVENTION

[0003] In internal combustion engines it is known to use fuel injectors to introduce atomized fuel streams into cylinder combustion chambers for compression and ignition during a combustion cycle. The fuel injectors are typically seated in injector bores in the engine head. Current known fuel injector systems use a c-clip or helical spring as a spacer disposed below an alignment ring. The c-clip or spring provides height control to set the location of the injector tip relative to the associated combustion chamber.

[0004] By way of example only, in one known prior embodiment, a spring element is positioned below a separate alignment ring on a circumferential shoulder at the interior of the injector bore. The fuel injector body rests on the alignment ring, which in turn is supported by the underlying spring to provide height control and a degree of vibration dampening. While the prior system is believed to function quite adequately, the use of two separate structures to provide alignment and height control may increase the potential for error during assembly. Moreover, close tolerances are required for both the spring element and the alignment ring to fit properly on the supporting ledge. [0005] Consequently, there is a continuing need for a simplified system that can provide both height control and vertical alignment for a fuel injector system and which also provides effective control of noise and vibration over a range of engine operating conditions.

SUMMARY OF THE INVENTION

[0006] The present invention provides advantages and alternatives over the prior art by providing a vibration dampening fuel injector spacer in the form of a two phase flex spring adapted to control both the height and vertical alignment of a fuel injector in an injector bore. The two phase flex spring spacer further provides suppression of vibration and noise over a broad range of load conditions including low loads corresponding to engine idle conditions and high loads corresponding to high rpm values.

[0007] In accordance with one exemplary aspect, the present invention provides a fuel injector spacer adapted to support a fuel injector at a predefined orientation within an engine injector bore. The fuel injector spacer is in the form of an annular two-phase flex spring of unitary construction including an outer wall and an inwardly projecting circumferential ledge of flexible, resilient character extending radially inwardly from the outer wall. The circumferential ledge terminates at a free edge extending circumferentially about a pass-through opening for receipt of a reduced diameter portion of the fuel injector. The outer wall and the circumferential ledge form a dogleg cross-sectional profile with the circumferential ledge projecting away from the outer wall in an upwardly angled orientation. The outer wall includes a convex curved inner surface extending away from the circumferential ledge. The two-phase flex spring defines a supporting seat for an enhanced diameter body portion of the fuel injector with the

circumferential ledge defining a resilient biasing structure disposed in underlying supporting relation to the enhanced diameter body portion. The two-phase flex spring is characterized by a first phase stiffness upon application of a first compressive force by the fuel injector as the circumferential ledge flexes in the direction of the first compressive force and by a greater, second phase stiffness upon application of a second greater compressive force by the fuel injector. Under low load conditions, the fuel injector body contacts only the inner distal portion of the inwardly projecting ledge. Upon the application of compressive force, the inwardly projecting ledge is flexed downwardly with the inwardly projecting ledge defining a leaf spring providing a biasing resistance at a first resistance level. With increased deflection, the fuel injector body eventually contacts the inner surface of the outer wall. Further deflection is thereafter resisted by the combined biasing forces of the outer wall and the inwardly projecting ledge thereby providing the substantially enhanced second resistance level. The spacer further acts to hold the fuel injector body in a substantially vertical orientation within the injector bore.

[0008] In accordance with another exemplary aspect, the present invention provides a fuel injector system for an engine. The fuel injector system includes a fuel injector adapted for acceptance within an engine injector bore wherein the fuel injector includes an enhanced diameter body portion including a chamfered perimeter surface and a reduced diameter portion extending away from the body portion. The fuel injector system further includes a fuel injector spacer supported within the engine injector bore. The fuel injector spacer is in the form of an annular two-phase flex spring of unitary construction including an outer wall and an inwardly projecting circumferential ledge of flexible, resilient character extending radially inwardly from the outer wall. The circumferential ledge terminates at a free edge extending circumferentially about a pass-through opening for receipt of the reduced diameter portion of the fuel injector. The outer wall and the circumferential ledge form a dogleg cross-sectional profile with the circumferential ledge projecting away from the outer wall in an upwardly angled orientation. The outer wall includes a convex curved inner surface extending away from the circumferential ledge. The two-phase flex spring defines a supporting seat for the enhanced diameter body portion of the fuel injector with the circumferential ledge defining a resilient biasing structure disposed in underlying supporting relation to the enhanced diameter body portion. The two- phase flex spring is characterized by a first phase stiffness upon application of a first compressive force by the fuel injector as the circumferential ledge flexes in the direction of the first compressive force. The two-phase flex spring is characterized by a substantially greater second phase stiffness upon application of a second greater compressive force by the fuel injector. [0009] In accordance with another exemplary aspect, the present invention provides a method for supporting a fuel injector at a predefined orientation within an engine injector bore, the method includes the steps of providing an engine injector bore and a fuel injector having an enhanced diameter body portion and a reduced diameter portion extending away from the body portion. The method further includes supporting the fuel injector within the engine injector bore using a fuel injector spacer supported within the engine injector bore. The fuel injector spacer is in the form of an annular two-phase flex spring of unitary construction including an outer wall and an inwardly projecting circumferential ledge of flexible, resilient character extending radially inwardly from the outer wall. The circumferential ledge terminates at a free edge extending circumferentially about a pass-through opening for receipt of the reduced diameter portion of the fuel injector. The outer wall and the circumferential ledge form a dogleg cross- sectional profile with the circumferential ledge projecting away from the outer wall in an upwardly angled orientation. The outer wall includes a convex curved inner surface extending away from the circumferential ledge. The two-phase flex spring defines a supporting seat for the enhanced diameter body portion of the fuel injector with the circumferential ledge defining a resilient biasing structure disposed in underlying supporting relation to the enhanced diameter body portion. The two-phase flex spring is characterized by a first phase stiffness upon application of a first compressive force by the fuel injector as the circumferential ledge flexes in the direction of the first compressive force and by a substantially greater second phase stiffness upon application of a second greater compressive force by the fuel injector.

[0010] Other objects and advantages of the present invention will become apparent from a description of certain present preferred embodiments thereof which are shown in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a schematic view illustrating a fuel injector held in an injector bore with a two phase flex spring spacer according to the present invention in place in supporting relation to the fuel injector body; [0012] FIG. 2 is a top isometric view of an exemplary two phase flex spring spacer according to the present invention;

[0013] FIG. 3 is a schematic sectional view taken generally along line 3-3 in FIG. 2 illustrating an exemplary arrangement for the outer wall and inwardly projecting ledge in an exemplary two phase flex spring spacer according to the present invention;

[0014] FIG. 4 is a schematic view taken generally along line 4-4 in FIG.2 illustrating orientation of a fuel injector body relative to a two phase flex spring spacer according to the present invention at low compressive load conditions corresponding to engine idling;

[0015] FIG. 5 is a schematic view similar to FIG. 4 illustrating orientation of a fuel injector body relative to a two phase flex spring spacer according to the present invention at high compressive load conditions corresponding to high rpm levels; and

[0016] FIG. 6 is a graph illustrating the results of a sample noise and vibration test in an engine environment comparing the use of an exemplary two phase flex spring spacer according to the present invention to a prior known rigid design.

[0017] Before exemplary embodiments of the invention are explained in detail, it is to be understood that the invention is in no way limited in its application or construction to the details and the arrangements of the components set forth in the following description or illustrated in the drawings. Rather, the invention is capable of other embodiments and being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for purposes of description only and should not be regarded as limiting. The use herein of terms such as "including" and "comprising" and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0018] Reference will now be made to the drawings, wherein to the extent possible, like elements are designated by like reference numerals in the various views. FIG. 1 illustrates an exemplary environment of use wherein a two phase flex spring spacer 10 is positioned in supporting relation to a fuel injector 12 having a body portion 14 and a coaxial tip portion 16. As will be readily appreciated by those of skill in the art, in the illustrated environment of use the fuel injector 12 is disposed within an injector bore 18 at the interior of an engine head 20.

[0019] As shown, the injector bore 18 typically has a stepped reduction in diameter extending from a relatively wide proximal segment adapted to retain the enhanced diameter fuel injector body portion 14 to a relatively narrow distal channel which conforms closely to the outer diameter of the fuel injector tip portion 16. As will be appreciated, in view of the relatively close tolerances between the fuel injector tip portion 16 and the distal channel of the injector bore 18, it is desirable to maintain a substantially centered orientation of the fuel injector 12 within the injector bore 18. In addition, in order to maintain proper operation, the fuel injector 12 must be maintained with a range of prescribed heights within the injector bore 18 to facilitate proper fuel discharge. It is also necessary to maintain sufficient spacing between the fuel injector body portion 14 and the surrounding walls of the injector bore 18 to permit sliding insertion and removal of the fuel injector 12 during assembly and maintenance.

[0020] In operation, the two phase flex spring spacer 10 provides the dual functions of maintaining proper injector tip height relative to an opposing combustion chamber (not shown) while also maintaining centered alignment of the fuel injector 12 within the injector bore 18. As shown, in the exemplary environment of use the two phase flex spring spacer 10 is configured to rest on a circumferential shoulder 24 at the interior of the injector bore 18 so as to nest with an inwardly angled chamfered perimeter surface 26 at the bottom of the body portion 14. The two phase flex spring spacer 10 thus acts as a vertical spacer between the circumferential shoulder 24 and the body portion 14 thereby controlling the final height of the injector tip 16.

[0021] As best seen through joint reference to FIGS. 2-5, the exemplary two phase flex spring spacer 10 has an annular configuration with a dogleg cross-sectional profile. In the exemplary configuration, the two phase flex spring spacer 10 includes an upwardly angled outer wall 30 having a convex curved inner surface 32. The outer wall 30 also includes a substantially vertical outboard face 33 (FIGS. 2 and 3). In the illustrated exemplary construction a

circumferential ledge 34 projects radially inwardly away from a lower portion of the outer wall 30. As best seen in FIGS. 4 and 5, the inwardly projecting circumferential ledge 34 normally extends away from the outer wall 30 in an upwardly angled orientation such that the inner free edge 36 is slightly raised in the absence of applied downward force.

[0022] The two phase flex spring spacer 10 may be formed from stamped metal or other suitable material as desired. By way of example only, one suitable material may be 17-7 stainless steel or the like to aid in corrosion prevention. Of course, other suitable materials including carbon steel with a coating to prevent corrosion as well as other metallic or

nonmetallic materials may be used if desired.

[0023] As best seen through joint reference to FIGS. 1, 4 and 5, in operation the body portion 14 of the fuel injector 12 is disposed with the chamfered perimeter surface 26 in nested, opposing relation to the curved inner surface 32 of the outer wall 30. Of course, the body portion 14 may also be free of a chamfered surface if desired. Regardless of the construction of the fuel injector, under conditions corresponding to low loading such as when the engine is idling, the fuel injector body portion contacts only the upper distal portion of the circumferential ledge 34 (FIG. 4). As shown, in this condition the circumferential ledge is disposed in underlying supporting relation to the fuel injector body portion 14 with a gap 40 being present between the fuel injector body portion 14 and the opposing curved inner surface 32 of the outer wall 30.

[0024] Upon the application of axial force by the fuel injector 12, such as when the rpm level of the engine is increased, the fuel injector body portion 14 and the two phase flex spring spacer 10 are pressed together. As the fuel injector body portion 14 and the two phase flex spring spacer 10 are pressed together, the inwardly projecting circumferential ledge 34 is initially caused to flex downwardly. As will be appreciated, during the flexing operation the inwardly projecting circumferential ledge 34 is moved from its upwardly angled condition to a more horizontal condition. Due to the resilient character of the circumferential ledge 34, it acts as a leaf spring which applies a continuous resistance force urging the components back towards the original unstressed condition.

[0025] During the initial phase of spring compression corresponding to relatively low applied loads, the flexing resistance of the circumferential ledge 34 provides isolation and vibration damping. As will be appreciated, due to the normally occurring gap 40 between the fuel injector body portion 14 and the opposing curved inner surface 32 at low load levels, the outer wall 30 is not involved during the initial phase of loading.

[0026] In the event that the compressive force applied by the fuel injector body portion 14 is raised to a sufficient level, the inwardly projecting circumferential ledge 34 will eventually flex enough to permit the fuel injector body portion 14 to contact the convex curved inner surface 32 of the outer wall 30. By way of example, such high applied force levels may be present at relatively high rpm conditions in an engine. Once the surface of the fuel injector body portion 14 contacts the inner surface 32 of the outer wall 30, any further axial displacement is resisted by both the inwardly projecting circumferential ledge 34 and by the outer wall 30. Thus, the resistance to displacement during a second phase is greatly increased and the flex spring spacer 10 is substantially stiffer. In operation, the substantial second phase spring resistance provided by the flex spring spacer 10 may be adequate to prevent any further displacement of the injector tip 16 even at high applied force levels corresponding to high rpm values. In this regard, it has been shown that there is a well defined transition from deflection to stiffness when the outer wall 30 is engaged thereby providing very little deflection even at high applied load values.

However, when the engine returns to the idle condition corresponding to a relatively low applied compressive load, the flex spring spacer 10 will relax back to the initial low load state.

[0027] It has been found that a two phase flex spring spacer 10 in accordance with the present invention provides a first, relatively light spring rate which is effective to mitigate low deflection forces while dampening vibration in combination with a second stiffer spring rate which is effective for higher deflection forces. In this regard, a two phase flex spring spacer 10 according to the present invention displays a dramatic transition in stiffness from light to stiff at the time the outer wall 30 becomes engaged. This may be contrasted to prior c-clip designs which tend to be very stiff across all deflections. Thus, the flex spring spacer according to the present invention provides high stiffness at high deflection loads in combination with low stiffness at low loading conditions.

[0028] A unitary two phase flex spring spacer 10 according to the present invention may be used over a range of applied forces to provide limited deflection and vibration dampening while nonetheless preventing excessive displacement of the injector tips even at high applied loads corresponding to high rpm values. At the same time, the convex curved inner surface provides a boundary to maintain vertical alignment of the fuel injector body so that it does not become tilted.

[0029] It has been found that a two phase flex spring spacer 10 consistent with the present invention provides substantial benefits in terms of vibration dampening and noise reduction while also centering the fuel injector. FIG. 6 is a graph illustrating the results of a sample noise and vibration test comparing a two phase flex spring spacer of annular construction as described to a prior known rigid c-clip design. On this graph, the reported data for mobility is a vibration measurement that corresponds to radiated noise. Accordingly, a lower value on the graph means that less energy is being transferred to the engine head. As can be appreciated, noise and vibration are generally considered to be undesirable from a vehicle user's point of view.

Generally speaking, lower mobility corresponds to quieter results.

[0030] As seen in FIG. 6, at frequencies above about 4000 Hz, the mobility values achieved using a two phase flex spring spacer as presently described are much lower than those of the hard mount design. In this regard, although the two phase flex spring spacer displays slightly higher mobility levels at frequencies below about 4000 Hz, such low frequency peaks are relatively easy to cover up with known sound treatments. Conversely, peaks at higher frequencies are much more difficult to mask. Thus, the shifting of the mobility peak to lower frequencies is beneficial. Moreover, shifting of the mobility peak also causes the isolation zone (i.e the transition to low mobility) to begin sooner which is also beneficial. Accordingly, at frequencies above about 4000 Hz, the two phase flex spring spacer as presently described provides substantially improved isolation and noise reduction. Considering the entire frequency range, the two phase flex spring spacer has a significantly lower average mobility thereby providing noise reduction over a wide range of frequencies.

[0031] Of course, it is to be understood that the invention is not limited in its application to the details of construction and/or to the arrangements of the components set forth herein. Rather, the invention is capable of other embodiments and of being practiced or carried out in various ways. Thus, variations and modifications of the foregoing are within the scope of the present invention. Moreover, it is to be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention.

[0032] Various features of the invention are set forth in the following claims.

Claims

CLAIMS WHAT IS CLAIMED IS:

1. A fuel injector spacer adapted to support and center a fuel injector at a predefined orientation within an engine injector bore, the fuel injector spacer comprising:

an annular two-phase flex spring of unitary construction including an outer wall and an inwardly projecting circumferential ledge of flexible, resilient character extending radially inwardly from the outer wall, the circumferential ledge terminating at a free edge extending circumferentially about a pass-through opening for receipt of a reduced diameter portion of the fuel injector, the outer wall and the circumferential ledge forming a dogleg cross-sectional profile with the circumferential ledge projecting away from the outer wall in an upwardly angled orientation, and wherein the outer wall includes a convex curved inner surface extending away from the circumferential ledge, the two-phase flex spring defining a supporting seat for an enhanced diameter body portion of the fuel injector with the circumferential ledge defining a resilient biasing structure disposed in underlying supporting relation to the enhanced diameter body portion, wherein the two-phase flex spring is characterized by a first phase stiffness upon application of a first compressive force by the fuel injector as the circumferential ledge flexes in the direction of the first compressive force and by a greater second phase stiffness upon application of a second greater compressive force by the fuel injector.

2. The fuel injector spacer as recited in Claim 1, wherein the convex curved inner surface of the outer wall is angled to be normally disposed in spaced apart relation from the enhanced diameter body portion during application of the first compressive force but is operatively contacted upon application of the second greater compressive force.

3. The fuel injector spacer as recited in Claim 2, wherein the two-phase flex spring is formed from metal.

4. The fuel injector spacer as recited in Claim 3, wherein the two-phase flex spring is formed from stamped stainless steel.

5. The fuel injector spacer as recited in Claim 2, wherein the two-phase flex spring is characterized by the first phase stiffness during an engine idling condition and is characterized by the second phase stiffness at a higher engine rpm value.

6. The fuel injector spacer as recited in Claim 2, wherein the stiffness of the two- phase flex spring spacer returns to the first phase stiffness upon a reduction in compressive loading from the second greater compressive force to the first compressive force.

7. The fuel injector spacer as recited in Claim 2, characterized by a mobility peak in an engine environment of not greater than about 4000 Hz.

8. A fuel injector system for an engine comprising:

a fuel injector adapted for acceptance within an engine injector bore, the fuel injector having an enhanced diameter body portion including a chamfered perimeter surface and a reduced diameter portion extending away from the body portion; and

a fuel injector spacer supported within the engine injector bore, the fuel injector spacer comprising an annular two-phase flex spring of unitary construction including an outer wall and an inwardly projecting circumferential ledge of flexible, resilient character extending radially inwardly from the outer wall, the circumferential ledge terminating at a free edge extending circumferentially about a pass-through opening for receipt of the reduced diameter portion of the fuel injector, the outer wall and the circumferential ledge forming a dogleg cross-sectional profile with the circumferential ledge projecting away from the outer wall in an upwardly angled orientation, and wherein the outer wall includes a convex curved inner surface extending away from the circumferential ledge, the two-phase flex spring defining a supporting seat for the enhanced diameter body portion of the fuel injector with the circumferential ledge defining a resilient biasing structure disposed in underlying supporting relation to the enhanced diameter body portion, wherein the two-phase flex spring is characterized by a first phase stiffness upon application of a first compressive force by the fuel injector as the circumferential ledge flexes in the direction of the first compressive force and wherein the two-phase flex spring is

characterized by a greater second phase stiffness upon application of a second greater compressive force by the fuel injector.

9. The fuel injector system as recited in Claim 8, wherein the convex curved inner surface of the outer wall is angled to be disposed in opposing spaced apart relation from the chamfered perimeter surface during application of the first compressive force but is operatively contacted by the chamfered perimeter surface upon application of the second greater

compressive force.

10. The fuel injector system as recited in Claim 9, wherein the two-phase flex spring is formed from metal.

11. The fuel injector system as recited in Claim 10, wherein the two-phase flex spring is formed from stamped stainless steel.

12. The fuel injector system as recited in Claim 8, wherein the two-phase flex spring is characterized by the first phase stiffness during an engine idling condition and is characterized by the second phase stiffness at a higher engine rpm value.

13. The fuel injector system as recited in Claim 8, wherein the stiffness of the two- phase flex spring spacer returns to the first phase stiffness upon a reduction in compressive loading from the second greater compressive force to the first compressive force.

14. The fuel injector system as recited in Claim 8, characterized by a mobility peak of not greater than about 4000 Hz in an engine environment.

15. A method for supporting and centering a fuel injector at a predefined orientation within an engine injector bore, the method comprising the steps of:

providing an engine injector bore;

providing a fuel injector having an enhanced diameter body portion with a chamfered perimeter surface and a reduced diameter portion extending away from the body portion; and supporting the fuel injector within the engine injector bore using a fuel injector spacer supported within the engine injector bore, the fuel injector spacer comprising an annular two- phase flex spring of unitary construction including an outer wall and an inwardly projecting circumferential ledge of flexible, resilient character extending radially inwardly from the outer wall, the circumferential ledge terminating at a free edge extending circumferentially about a pass-through opening for receipt of the reduced diameter portion of the fuel injector, the outer wall and the circumferential ledge forming a dogleg cross-sectional profile with the

circumferential ledge projecting away from the outer wall in an upwardly angled orientation, and wherein the outer wall includes a convex curved inner surface extending away from the circumferential ledge, the two-phase flex spring defining a supporting seat for the enhanced diameter body portion of the fuel injector with the circumferential ledge defining a resilient biasing structure disposed in underlying supporting relation to the enhanced diameter body portion, wherein the two-phase flex spring is characterized by a first phase stiffness upon application of a first compressive force by the fuel injector as the circumferential ledge flexes in the direction of the first compressive force and by a greater second phase stiffness upon application of a second greater compressive force by the fuel injector.

16. The method as recited in Claim 15, wherein the convex curved inner surface of the outer wall is angled to be normally disposed in opposing spaced apart relation from the chamfered perimeter surface during application of the first compressive force but is operatively contacted upon application of the second greater compressive force.

17. The method as recited in Claim 16, wherein the two-phase flex spring is formed from metal.

18. The method as recited in Claim 17, wherein the two-phase flex spring is characterized by the first phase stiffness during an engine idling condition and is characterized by the second phase stiffness at a higher engine rpm value.

19. The method as recited in Claim 18, wherein the stiffness of the two-phase flex spring spacer returns to the first phase stiffness upon a reduction in compressive loading from the second greater compressive force to the first compressive force.

20. The method as recited in Claim 19, wherein the fuel injector is characterized by a mobility peak of not greater than about 4000 Hz in an engine environment.