Patent Application
20140261330
a. Technical Field
The instant disclosure relates to a fuel rail assembly.
b. Background Art
This background description is set forth below for the purpose of providing context only. Therefore, any aspects of this background description, to the extent that it does not otherwise qualify as prior art, is neither expressly nor impliedly admitted as prior art against the instant disclosure.
It is known to provide a fuel delivery system for use with an internal combustion engine. Such a system may include one or more fluid conduits that allow for the delivery of pressurized fuel to multiple fuel injectors. The fluid conduit (i.e., a fuel rail) may include an inlet that is connected to an outlet of a fuel source, for example, in some systems, a high-pressure fuel pump. The fluid conduit also typically includes a plurality of outlets that are configured for mating with a corresponding fuel injector. An ongoing challenge involves controlling and/or reducing the amount of pressure variation within the fuel rail itself. Such pressure variation can have an adverse impact on the performance of the engine to which the fuel delivery system is connected.
For example, pressure variation (e.g., pressure waves) may cause inaccurate metering of fuel by the fuel injectors associated with the fuel rail. This degrades the performance of the engine to which the fuel injectors supply fuel because the desired amount of metered fuel may vary with the amount of pressure within the fuel rail. In addition, the pressure waves may cause undesirable noise in the fuel rail. There are different causes of such pressure variation.
One cause of pressure fluctuation applies to fuel delivery systems that employ a high-pressure fuel pump directly connected to the fuel rail(s). It is typical to drive such pumps directly (or indirectly) off of a camshaft and typically has 3 or 4 lobes. Because of this low number of lobes and a high volume per pumping event, the pressure swings of the pump output can be quite high. For example, the pressure levels at the output of such a high-pressure pump can be as low as substantially zero pressure on the low end to as high as 20-21 MPa (e.g., ˜2900 psi) on the high end. Such pressure variations have been challenging to accommodate in conventional fuel delivery systems.
One approach taken to address the above-described problem involves enlarging the size of fuel rails (i.e., increasing the volume of each rail). While effective, this approach (i) increases the material cost of the fuel rail assembly (i.e., increases the amount of materials needed for the rails), and (ii) increases the physical size of the overall fuel rail assembly (i.e., increases the footprint of the package). Some applications cannot accommodate the larger-size package, nor tolerate the lower performance of conventional configurations that can be provided in a smaller-sized package.
The foregoing discussion is intended only to illustrate the present field and should not be taken as a disavowal of claim scope.
One advantage of embodiments consistent with the present teachings involves improved performance (i.e., reduced pressure fluctuations) as compared to conventional configurations with the same or similar sized fuel rails. Another advantage involves a reduced material cost as compared to conventional, similarly performing but larger-sized fuel rails. A still further advantage involves the ability to meet predetermined performance requirements in a reduced-size package, where conventional approaches, based on enlarged fuel rail configurations, cannot be used. Embodiments consistent with the teachings of the instant disclosure decouple the rail volumes—which feed the injectors—from the pressure swings of the pump, by providing multiple flow restrictors that in turn define multiple pulsation control volumes, as more fully described herein.
In an embodiment, a fuel rail assembly, configured for connection to an internal combustion engine, includes a first fuel rail, a second fuel rail, and a crossover hose. The first fuel rail includes a first interior and an inlet configured to be coupled to a high-pressure fuel pump using a supply hose. A first flow restrictor is located between the pump and the first interior of the first fuel rail. The first fuel rail further includes a second flow restrictor disposed in the first interior (i.e., internal) to divide the first interior into a first rail volume (which feed the injectors) and a remainder volume. The first fuel rail also includes a first crossover port, which is coupled to the crossover hose. The second fuel rail includes a second interior with a second rail volume. The second fuel rail has a second crossover port, which is coupled to the crossover hose. The crossover hose is configured to communicate fuel between the first and second fuel rails. A third flow restrictor is located near to the second crossover port of the second fuel rail (e.g., in an embodiment, it is disposed in the crossover hose).
In an embodiment, a first pulsation control volume is defined between the high-pressure pump and the first flow restrictor (e.g., which may be formed in the inlet, in an embodiment). A second pulsation control volume is also defined, and which includes the remainder volume of the first rail, in addition to the volume of the crossover hose (i.e., the total volume between the second, internal flow restrictor and the third flow restrictor). The first and second pulsation control volumes serve to reduce the pressure fluctuations in the first rail volume and the second rail volume, by decoupling the rail volumes from the pump. In this regard, the fuel rail assembly provides two flow restrictors between the high-pressure pump and each of the first and second rail volumes. In addition, the fuel rail assembly provides two flow restrictors between the first and second fuel rail volumes, thereby decoupling pressure variations induced by injector activity occurring in one rail from affecting the other rail. In addition, the second pulsation control volume in enlarged (and thus more effective) by the incremental volume contributed by the remainder volume of the first fuel rail.
In another aspect, a method of making a fuel rail is described.
The foregoing and other aspects, features, details, utilities, and advantages of the present disclosure will be apparent from reading the following description and claims, and from reviewing the accompanying drawings.
Referring now to Figures wherein like reference numerals identify identical or similar components in the various views,
The fuel delivery system 10 includes a high-pressure fuel pump 12, a fuel rail assembly 14, and a supply hose or conduit 16 fluidly coupling the pump to the fuel rail assembly 14. The fuel delivery system 10 may be configured for use with a multiple-cylinder internal combustion engine, for example, a six-cylinder engine in the illustrative embodiment. The high-pressure fuel pump 12 is configured with an inlet (shown—but unconnected) for connection to a source of fuel, for example, a low-pressure fuel pump coupled to a fuel tank. As described in the Background, the high-pressure pump 12 may be driven off of an engine camshaft, resulting in large variations in pump output pressure. The high-pressure fuel pump 12 may comprise conventional components known in the art. The outlet of the high-pressure fuel pump 12 is coupled through the supply hose 16 to the fuel rail assembly 14, and may be attached at each end using conventional fluid attachment means (e.g., including nuts 18, 20).
The fuel rail assembly 14 is configured for connection to a plurality of fuel injectors (shown) used in an internal combustion engine (not shown). The fuel rail assembly 14 includes a first fuel rail 22, a second fuel rail 24, and a crossover hose or conduit 26 configured to provide fuel communication between the first and second fuel rails 22, 24.
The first fuel rail 22 includes a fuel inlet 28 that is configured to be coupled to the outlet of the high-pressure pump 12 via the supply hose 16, and a first plurality of output ports 30, including fuel injector receptor cups 32 configured to receive corresponding fuel injectors 34. As also shown, the injectors 34 may be of the electrically-controlled type, and therefore each may include a respective electrical connector 36 configured for connection to an electronic engine controller or the like (not shown). In addition, the first fuel rail 22 may include a plurality of mounts or brackets 38, which can be used in combination with corresponding fasteners 40 or the like to secure the fuel rail assembly 14 within an engine compartment.
The second fuel rail 24 also includes the above-described output ports 30, fuel injector cups 32 for the fuel injectors 34 (and connectors 36), mounting brackets 38, and fasteners 40, and thus a duplicate description will not be set forth again. Only one of port 30, cup 32, injector 34, connector 36, mounting 38 and fastener 40 has been labeled in
Each of the fuel rails 22, 24 and components thereof may be formed of numerous types of materials, such as, for exemplary purposes only, aluminum, various grades of stainless steel, low carbon steel, other metals, and/or various types of plastics. In an embodiment, the fuel rails may be formed of a metal or other materials that can be brazed, and thus can withstand furnace brazing temperatures on the order of 2050° F. (1121° C.)). The fuel rails 22, 24 may further have different thicknesses in various portions. Additionally, although the fuel rails 22, 24 may each have a generally circular cross-sectional shape in the illustrated embodiment, it should be understood that each may alternatively have any number of different cross-sectional shapes, and may be a one-piece fuel rail or have a number of constituent pieces.
The first flow restrictor 52 is disposed between the outlet of the high-pressure pump 12 and the interior of the first fuel rail 22, which defines a first pulsation control volume 58. In an embodiment, the first flow restrictor 52 may be integral with the inlet 28, as best shown in
The above-described placement of flow restrictors forms a second pulsation control volume 60 between the second flow restrictor 54 and the third flow restrictor 56. In this regard, a part of the first fuel rail 22, namely, the remainder volume 68, is added to the volume of the crossover hose 26 in order to form an enlarged second pulsation control volume 60. In light of the placement of the flow restrictors, the fuel rail assembly 14 includes (i) a first rail volume 66 in the first fuel rail 22 that is in fluid communication with a first plurality of injector outlets, and (ii) a second rail volume 64 in the second fuel rail 24 that is in fluid communication with a second plurality of fuel injector outlets.
The first and second pulsation control volumes 58, 60 are configured to reduce the magnitude of the pressure fluctuations experienced in either of the first or second rail volumes 66, 64. In other words, the first and second pulsation control volumes 58, 60 act as damping volumes with respect to the rail volumes 66, 64. The configuration of the fuel rail assembly 14 places two flow restrictors between the first rail volume 66 and the high-pressure pump 12, and the second rail volume 64 and the high-pressure pump 12. This de-couples the rail volumes 66, 64 from the adverse effects of the pump output fluctuations. In addition, the fuel rail assembly 14 places two flow restrictors between the first rail volume 66 and the second rail volume 66, which serve to reduce pressure differentials between the rail volumes 66, 64.
The relative sizing of the pulsation control volumes, relative to the rail volumes, can provide further improvements in performance. In an embodiment, a first ratio between the second pulsation control volume 60 to the first pulsation control volume may be between about 2 and 5, and may be between about 4 and 5. In an embodiment, a second ratio between the first rail volume 66 and the second pulsation control volume 60 may be between about 3 and 6, and may be between about 3 and 5. Likewise, a third ratio between the second rail volume 64 and the second pulsation control volume 60 may be between about 3 and 6, and may be between about 3 and 5. It should be understood that these ratio ranges are exemplary only and not limiting in nature.
Each of the flow restrictors 52, 54, and 56 may comprise conventional components known in the art, for example only, a small diameter orifice of conventional construction. In an embodiment, each of the flow restrictors 52, 54, and 56 may comprise a small orifice having a diameter of between about 0.70 mm and 2.00 mm, and may be about 1.10 and 1.16 mm in one embodiment.
With continued reference to
In one embodiment, the hole 80 itself is sized, for example as described above, to act as a flow restrictor. However, in another embodiment, the hole 80 is enlarged sufficiently to accept an insert 82, which includes an orifice 84 that is sized to operate as a flow restrictor, again, for example only, as described above. In the latter embodiment, the larger hole 80 has the advantage of allowing for adequate venting during manufacturing, for example, during a brazing process, to allow heated gases to more easily exit from the fuel rail. In addition, insertion of the insert 82 (with orifice 84) after manufacturing (i.e., after brazing) allows for improved brazing and further permits keeping the orifice clear and clean from brazing materials (e.g., copper braze flash) that could otherwise clog the orifice.
With continued reference to
The third flow restrictor 56 may be disposed in the crossover hose 26, or alternatively as part of the crossover connector of the second fuel rail 24. In an embodiment, the third flow restrictor 56 may be an insert that reduces the diameter of the crossover hose 26, for example, as seen by reference to U.S. application Ser. No. 10/721,943, filed 25 Nov. 2003 (the '943 application), now U.S. Pat. No. 7,021,290, which is hereby incorporated by reference as though fully set forth herein.
In step 104, the method involves providing a fluid conduit (e.g., item 46) that includes an inlet, one or more outlets (e.g., for coupling to an injector cup), and an end cap or the like to close one end opening of fluid conduit 46, while retaining the other, opposing end opening clear and open. Generally, the fluid conduit 46 may include the features already described above. The method then proceeds to step 106.
In step 106, the method further involves introducing a cup—top opening first—through the uncapped end opening of the fluid conduit 46, with continued insertion, in an embodiment, until the cup engages the transition region 90 (i.e., mechanical stop). The cup may be the cup described above, e.g., cup 70, which includes a through-hole 80 in its base 74. The method proceeds to step 108.
In step 108, the method further involves introducing a crossover connector—shank end first—into the uncapped end opening of the fluid conduit 46. The crossover connector may be the connector 91 described herein. The foregoing steps form a sub-assembly the fuel rail 22. The method proceeds to step 110.
In step 110, the method further involves performing a brazing operation on the sub-assembly that was formed in step 108. In an embodiment, this brazing operation may involve a furnace brazing process. To perform this step, brazing material may be placed at the locations where components are to be affixed together, e.g., around the outside surface of the cup 70, where the endcap 46 engages the distal end of the fluid conduit 46, where the outside surface of the shank 94 of the crossover connector 91 contacts the first inside diameter portion 86, etc.
The brazing material may be characterized as having a melting point such that it will change from a solid to a liquid when exposed to the level of heat being applied during the brazing operation (e.g., on the order of 2050° F. (1121° C.)), and which will then return to a solid once cooled. Examples of materials that can be used include without limitation, for exemplary purposes only, pre-formed copper pieces, copper paste, various blends of copper and nickel and various blends of silver and nickel, all of which have melting points on the order of approximately 1200-2050° F. (650-1121° C.). As the heating and cooling steps of the brazing operation are performed, the brazing material melts and is pulled into the joint(s)/contact surfaces described above. Once sufficiently cooled, the brazing material returns to a solid state, to thereby fix together the components of the sub-assembly. The method then proceeds to step 112.
In step 112, the method further involves securing an insert, e.g., insert 82, having an orifice, e.g., orifice 84, in the cup hole 80. In an embodiment, this step is performed using the insertion tool 98. In particular, the insert 82 is first loaded onto the end of the insertion tool 98, and is introduced into the interior of the fluid conduit 46 through the crossover port 96, moving in a generally longitudinal direction. When the insert 82 has been introduced far enough to reach the hole 80, the insert 82 can then be secured in the hole 80. In one embodiment, the insert can be threaded into a like-threaded hole 80. In another embodiment, the insert 82 can be press-fit into hole 80. In a still further embodiment, the insert 82 can be spin welded into the hole 80. Other conventional affixation methods may be used to secure the insert 82 in the hole 80.
It should be understood that variations are possible, as seen by reference to
In one single-rail embodiment (not shown) the inlet 28 includes the first flow restrictor and the first fuel rail 22 includes the second flow restrictor 54, but does not include the crossover connector 91, the crossover hose 26, or the second fuel rail 24. The end opening of the fluid conduit 46 previously occupied by the crossover connector 91 in the above-described embodiment may be replaced by a further end-cap or the like to close the end opening. The first pulsation control volume 58 remains as described in connection with the fuel rail assembly 14. A second pulsation control volume 60 is modified, and now corresponds to the remainder volume 68 described above (i.e., without the additional volume of the crossover hose 26).
In a second single-rail embodiment, shown in
Embodiments consistent with the present teachings have the advantage of improved performance (i.e., reduced pressure fluctuations) as compared to conventional configurations with the same or similar sized fuel rails. Another advantage involves a reduced material cost as compared to conventional, similarly performing but larger-sized fuel rails. A still further advantage involves the ability to meet predetermined performance requirements in a reduced-size package, where conventional approaches, based on enlarged fuel rail configurations, cannot be used. Embodiments consistent with the teachings of the instant disclosure decouple the rail volumes—which feed the injectors—from the pressure swings of the pump, by providing multiple flow restrictors that in turn define multiple pulsation control volumes.
It should be understood that the terms “top”, “bottom”, “up”, “down”, and the like are for convenience of description only and are not intended to be limiting in nature.
While one or more particular embodiments have been shown and described, it will be understood by those of skill in the art that various changes and modifications can be made without departing from the spirit and scope of the present teachings.
This application claims the benefit of U.S. provisional application No. 61/792,928 filed 15 Mar. 2013, which is hereby incorporated by reference as though fully set forth herein.
| Number | Date | Country | |
|---|---|---|---|
| 61792928 | Mar 2013 | US |
