Manufacture of a Compact Ejector System for a Boosted Internal Combustion Engine

Abstract

Vapors in the fuel tank of a vehicle are collected in a carbon canister. An ejector or aspirator is used to purge the carbon canister in a pressure-charged engine in which a positive pressure exists in the intake. A compact ejector includes a substantially planar flange and a venturi tube coupled to the flange with a central axis of the venturi tube substantially parallel to the flange. By manufacturing the ejector in two pieces, dimensions within the ejector: throat, converging section, and diverging section, is more accurate than prior art manufacturing techniques thereby providing better flow characteristics throughout the boost range.

Claims

1. A method to fabricate an ejector, comprising: molding a first piece comprising: a first tube, a second tube, a flange and a first portion of a venturi tube; molding a second piece comprising a second portion of the venturi tube; and affixing the first piece with the second piece.

2. The method of claim 1 wherein the first piece is affixed to the second piece by welding.

3. The method of claim 1 wherein: the first piece is affixed to the second piece by a plurality of snap fit connectors around the periphery of the first piece; a seal between an interface surface of the first piece and an interface surface of the second piece is formed by one of: surface features of the mating first and second pieces that substantially prevent flow between the mating surfaces; a groove in the interface surface of the first piece with an 0-ring disposed therein; a groove in the interface surface of the second piece with an 0-ring disposed therein; and an adhesive applied to at least one of the interface surface of the first piece and the interface surface of the second piece.

4. The method of claim 1 wherein: an interface between the first piece and the second piece is substantially coincident with a centerline of the venturi tube.

5. The method of claim 1, comprising: testing leak rate, flow rate, and vacuum draw in the ejector wherein if any of the leak rate, the flow rate, and the vacuum draw of the ejector is out of range, the ejector is scrapped.

6. The method of claim 1 wherein the venturi tube comprises: a converging section, a throat of a predetermined diameter, and a diverging section.

7. The method of claim 1 wherein: a centerline of the first tube forms an acute angle with the flange; the first tube forms a flow straightening section upstream of the venturi tube: and the venturi tube comprises: a converging section, a throat of a predetermined diameter, and a diverging section.

8. A method to fabricate an ejector on an air intake component of an internal combustion engine, comprising: placing a venturi tube of the ejector into an opening formed in an intake system component; welding the ejector to the intake air component of the engine wherein the ejector is fabricated by: molding a first ejector piece that comprises a first tube, a second tube, a flange, and a first portion of the venturi tube; molding a second ejector piece comprising a second portion of the venturi tube; and affixing the first ejector piece to the second ejector piece.

9. The method of claim 8 wherein the intake air component is an air intake duct.

10. The method of claim 8 wherein the intake air component is an air filter box.

11. The method of claim 8 further comprising: attaching a first line to an inlet of the first tube; and attaching a second line to an inlet of the second tube wherein: the first tube is fluidly coupled to an engine intake; and the second tube is fluidly coupled to a carbon canister.

12. The method of claim 8 wherein the first ejector piece is affixed to the second ejector piece by welding.

13. The method of claim 8 wherein: the first ejector piece is affixed to the second ejector piece by a plurality of snap fit connectors around the periphery of an interface between the first and second ejector pieces; a seal between an interface surface of the first ejector piece and an interface surface of the second ejector piece is formed by one of: a groove in the interface surface of the first ejector piece with an O-ring disposed therein; a groove in the interface surface of the second ejector piece with an O-ring disposed therein; and an adhesive applied to at least one of the interface surface of the first ejector piece and the interface surface of the second ejector piece.

14. The method of claim 8 wherein the venturi tube comprises: a converging section, a throat, and a converging section with a portion of the converging section distal from the throat being an exit of the venturi tube, the method further comprising: tilting an exit of the venturi tube toward the opening in the intake air component before placing the ejector into the opening in the intake system component.

15. A method to install an ejector into an intake air duct of an internal combustion engine wherein: the ejector is fabricated by: molding a first ejector piece that comprises a first tube, a second tube, a flange, and a first portion of a venturi tube; molding a second ejector piece comprising a second portion of the venturi tube; and welding the first ejector piece to the second ejector piece, the method comprising: placing the venturi tube of the ejector into an opening formed in the intake air duct; and welding the ejector to the intake air duct proximate to the opening of the intake air duct.

16. The method of claim 15 wherein: a centerline of the second tube is substantially perpendicular to the flange; and a centerline of the first tube forms an acute angle with a centerline of the second tube.

17. The method of claim 15 wherein: the venturi tube comprises: a converging section, a throat, and a diverging section; and p1 the first tube serves as a flow straightener upstream of the converging section.

18. The method of claim 15 wherein the intake air duct has a flat surface proximate the opening in the air duct; and the flange is welded to the flat surface.

19. The method of claim 15 wherein the venturi tube comprises: a converging section, a throat, and a diverging section with a portion of the diverging section distal from the throat being an exit of the venturi tube, the method further comprising: tilting an exit of the venturi tube toward the opening in the intake air component before placing the ejector into the opening in the intake system component.

20. The method of claim 15 wherein: a centerline of the first tube is substantially perpendicular to the flange; a centerline of the second tube is substantially perpendicular to the flange; and the venturi tube further comprises a flow straightening section upstream of the converging section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIG. 1 is an illustration of a canister purge system which includes an ejector according to the prior art;

[0045] FIG. 2 is a prior art ejector;

[0046] FIG. 3 is the ejector of FIG. 2 in cross section;

[0047] FIG. 4 is the ejector of FIG. 2 shown installed in an air box;

[0048] FIG. 5 is an ejector according to an embodiment of the disclosure;

[0049] FIG. 6 is the ejector of FIG. 5 shown in cross section;

[0050] FIG. 7 is an ejector according to an embodiment of the disclosure shown in cross section;

[0051] FIG. 8 is a cross section of an exit section of a venturi tube according to an embodiment of the disclosure;

[0052] FIG. 9 is a graph of flowrate as a function of boost pressure comparing a prior art ejector and a presently disclosed ejector;

[0053] FIGS. 10 and 11 are cross sections of a portion of ejectors having snap fit connections;

[0054] FIG. 12 is a flowchart illustrating a prior art process by which an ejector can be fabricated;

[0055] FIG. 13 is a flowchart illustrating a process, according to the present disclosure, by which an ejector can be fabricated;

[0056] FIGS. 14 and 15 are flowcharts showing alternative processes to those shown in FIG. 13;

[0057] FIG. 16 is a flowchart showing processes involved in installing the ejector into an engine air component;

[0058] FIG. 17 is an illustration showing an air duct and an ejector prior to assembly;

[0059] FIG. 18 is a cross section of the air duct and the ejector after assembly;

[0060] FIG. 19 is a cross-sectional view of a shortened ejector;

[0061] FIG. 20 is an illustration showing an air duct with the shortened ejector of

[0062] FIG. 19 prior to assembly;

[0063] FIG. 21 is a one-piece embodiment of the ejector that provides tight tolerance for the diverging section, the converging section, and the throat;

[0064] FIG. 22 is a two-piece embodiment of the ejector in which the centerline of the converging section is offset from the centerline of the diverging section;

[0065] FIG. 23 is an expanded, cross-sectional view of a portion of the two pieces of ejector, showing an energy director and a skirt;

[0066] FIG. 24 is an isometric view of an ejector having a divot proximate the exit of the diverging section;

[0067] FIGS. 25 and 26 are two views of the diverging section of the ejector of FIGS. 24; and

[0068] FIG. 27 is an isometric view of an ejector having a squared off divot proximate the exit of the diverging section.

DETAILED DESCRIPTION

[0069] As those of ordinary skill in the art will understand, various features of the embodiments illustrated and described with reference to any one of the Figures may be combined with features illustrated in one or more other Figures to produce alternative embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for particular applications or implementations. Those of ordinary skill in the art may recognize similar applications or implementations whether or not explicitly described or illustrated.

[0070] One embodiment of an ejector 150 according to the disclosure is shown in FIGS. 5 and 6. Ejector 150 has a flange 152 with a surface 154. Surface 154 allows coupling with the periphery of an opening in an intake component. Flange 152 has a first tube 160 having a centerline 164 and a second tube 162 having a centerline 166 extending there through. First tube 160 is coupled to an air inlet (not shown) to bring in fresh air. Second tube 162 is coupled to a carbon canister (also not shown) to purge the carbon canister. A venturi tube 170 is at the bottom of ejector 150. A first end 172 of venturi tube 170 is closed and a second end 174 is open. The fresh air through first tube 160 and the fuel vapor laden gases of second tube 162 that are mixed in venturi tube 170 exits through second end 174. Ejector 150 is made up of two pieces that are welded together at an interfaces of the two parts to form weld joint 176. Weld joint 176 is slightly angled in ejector 150. In other embodiments, weld joint is planar. The first piece includes the elements above weld joint 176, i.e., first tube 160, second tube 162, flange 152 and an upper portion of venturi tube 170. The second piece includes a lower portion of venturi tube 170.

[0071] Weld joint 176 is substantially parallel to flange 152 and is coincident with a diameter of an opening through venturi tube 170. Referring now to FIG. 6, which is a cross-sectional view of FIG. 5, an internal shape of venturi tube is shown. An entrance section 180 receives fresh air from tube 160. The purpose of entrance section 180 is to straighten the flow after traveling through the 90-degree bend between tube 160 and entrance section 180. A converging section 182 is downstream of entrance section 180. Flow is accelerated in converging section 182. Flow from converging 182 is introduced into a throat 184. Throat 184 includes the smallest cross-sectional portion of venturi tube 170. The embodiment of throat 184 shown in FIG. 6 slightly diverges. The downstream end of second tube 162 couples to venturi tube 170 immediately downstream throat 184. As is well known by one skilled in the art, the acceleration of flow in the throat area leads to a drop in pressure, which draws the flow through tube 162. Downstream of throat 184 is diverging section 186. In the embodiment in FIG. 6, a centerline of diverging section 184 dips downward as considered from left to right. This improves flow characteristics. In other embodiments, the centerline of the venturi tube is straight.

[0072] In some embodiment, such as shown in FIG. 6, tube 162 expands near a downstream end, such as the portion 165 of tube 162 shows.

[0073] In some embodiments, the weld between the two pieces of ejector 150 in FIG. 6 is a combination of a butt weld at the interface between the two surfaces and a shear weld. The shear weld comes about by providing a skirt 168 on the lower piece of ejector 150 that extends toward the upper piece. In an alternative embodiment, the skirt can be provided on the upper piece of ejector 150.

[0074] Referring to FIG. 7, an alternative embodiment of an ejector 200 is shown that includes a flange 202 and first and second tubes 210 and 212, respectively, which extend through flange 202. First tube 210 is canted with respect to second tube 212. A centerline 220 of first tube 210 forms an acute angle 230 with respect to flange 202. An advantage of such a configuration is that tube 210 doubles as an entrance section of the venturi tube. A converging section 232 couples directly with first tube 210. A throat 234 is downstream of converging section 232. A diverging section 226 is downstream of throat 234. Ejector 200 is made up of two separately formed pieces that are affixed at a weld joint 226. Alternatively, these can be snap fit, twist locked, mechanically fastened, or coupled with an adhesive.

[0075] One of the advantage of ejector 200 of FIG. 7 is that the length of ejector 200 is shown as 240 compared to length 190 of ejector 150 of FIG. 6 is shorter. Such a configuration requires a smaller opening in an air intake component to accommodate it. In an application where the intake duct has many curves and bends, there may be only a short section that is straight enough to accommodate the ejector. Thus, a short ejector is particularly useful in certain applications.

[0076] As will be discussed below, ejector 200 is coupled to an air intake component. In some embodiments, a surface 240 on the underside of flange 202 interfaces or mates with a surface on the intake air component. As discussed, some of the material is displaced into a place where it is not wanted during the molding process, molding flash. When ejector 200 is welded to the air intake component, welding flash develops. To present welding flash from going into places that would interfere with the function of the ejector, flash traps 242 and 244 are provided on either side of ejector 200.

[0077] Analysis of the design has indicated that it is preferable for exit cross section of the ejector (150, 200, as examples) to be a flattened circle. An exit 190 of an ejector is shown in FIG. 8. The upper portion 192 of exit 190 is flattened. Exit 190 is made up of two pieces that are welded together at interfaces 194.

[0078] Flowrate 850 of a prior art ejector and flowrate 860 of the ejector of FIGS. 7 and 8 have been compared and are shown in FIG. 9. The ejector, according to the present disclosure, has significantly improved flowrate at all boost pressures. The improved flowrate is due to the venturi tube having a distinct converging and diverging sections rather than straight tubes found in the prior art.

[0079] In an alternative embodiment in FIG. 10, an alternative method of affixing the upper piece 502 and lower piece 504 of a cross section of a portion of an ejector 500 is shown. Lower piece 504 is provided with a groove 506 in a face of lower piece 504 that interfaces with lower piece 502. An O-ring 508 is placed into groove 506. Upper piece 502 is provided with a recess 510 along an outer surface. Recess 510 does not extend all the way to the interface with lower piece 502. A lip 514 extends outwardly. Lower piece 512 is molded with a flexible finger 510 that engages with lip 514.

[0080] In another embodiment in FIG. 11, a cross section of a portion of an ejector 520 has an upper piece 522 and a lower piece 524. Upper piece 520 has a wedge 530 that extends outwardly from the surface. Lower piece 524 has a flexible finger 532 that engages with wedge 530. In the embodiment in FIG. 11, an adhesive 526 has been applied to the interface surface of upper part 522 and/or the interface surface of lower part 524. In the discussion of FIGS. 10 and 11, the flexible finger is on the lower part. However, this is simply a non-limiting example. Variations of these examples are also within the scope of the disclosure

[0081] The improved design of the ejector disclosed herein is at least partially due to a new method of manufacturing such ejectors. A prior art process is shown in FIG. 12. In blocks 300 and 302, the resin to provide to the injector molder is of the appropriate specification and that is properly dried, respectively. In block 304, the resin is injected into the three molds to produce: an ejector body, a plug, and an orifice piece that includes at least the throat of the venturi. The orifice part is molded separately because the orifice size at the throat is small. It is possible to integrate the orifice piece into the ejector body. However, a thin pin is required to form the throat. A rule of thumb is that the length of the pin should be no more than 3.5 times the diameter of the pin. Such a pin for an integrated throat would exceed this safe number by at least an order of magnitude. Such a thin pin that much extend into the ejector body at such a distance is likely to lead to failures of the pin. This causes breakage, downtime, increases scrap, and generally increases the cost of the manufacturing process. The more robust method to manufacture, according to the prior art, is to make the orifice piece separately. In block 306, the orifice part is inserted into the ejector body. Each of the ejector bodies is inspected in block 308. If improperly installed, the part is rejected in block 310. If proper installation, the plug is affixed to the ejector body in block 312. In the prior art ejector such as shown in FIGS. 2 and 3, almost the entire ejector is formed in one piece. To form tube 134 of FIG. 3, an opening at one end is provided that is closed off by plug 144.

[0082] Quality assurance measures begin in block 350 in which all of leak, flow and vacuum draw are measured and it is determined whether they are in acceptable ranges. If so, the ejector is ready for assembly into an engine intake component, in block 352. If out of specification in block 350, it is determined whether the flaw was caused by the molding process or molding flash (excess material on the part) in block 360. If that is determined to be the issue, in block 362, the molding process is adjusted or machine maintenance is performed and it is verified that the correction is effective before resuming. If a negative result from block 360, in block 370, it is determined whether the flaw was caused by the welding process. If so, the weld tooling or process is adjusted in block 372. Also, in block 372, it is determined whether the correction is effective. If a negative result in block 370, in block 380, it is determined whether the flaw is caused by excess moisture and/or whether the resin material is out of specification. If the dryness is causing the flaw, the material drying process is adjusted and verified. If the material is out of specification, the proper material is obtained and loaded into the molding machine, in block 382. In any case with an out of specification part, the part is scrapped in block 392. If a negative result in block 390, additional review of the processes is continued until cause of the flaw is determined and rectified.

[0083] A flow chart showing processes undertaken to produce the disclosed ejector is shown in FIG. 13. Blocks 300, 302, 350, 352, etc. are mostly the same for the disclosed process and the prior art process. Thus, they are not separately described here. Starting in block 320, the upper and lower pieces of the ejector are injection molded. In block 322, the two pieces are affixed. In one embodiment, the pieces are affixed by welding: sonic, ultrasonic, thermal, or any suitable type of welding. An alternative embodiment is shown in FIG. 14 in which an O-ring is placed in a groove in an interface of the first or second pieces in block 324. One of the first and second pieces has a flexible finger that engages with a feature on the other piece in block 326. When the pieces are snapped together, the O-ring is pressed into the groove and seals the first piece with the second piece. In another alternative in FIG. 15, the interfaces between the first and second piece is flat. At least one of the interfaces has adhesive applied, block 328, so that when the first and second pieces are snapped together in block 330, the adhesive seals the interface between the first and second pieces.

[0084] In FIG. 16, an ejector is manufactured in block 400, such as by the process in FIGS. 13-16. In block 402, the air intake component is manufactured with an opening to accommodate the ejector. In some embodiments, the flange of the ejector is as short as possible so that the opening in the intake air component is as small as possible. This is particularly useful when the desired location is in an engine duct with lots of turns, i.e., a limited straight run to accommodate the ejector. In such cases with short flanges, the exit portion of the ejector is tilted downward to access the opening in block 410. In some other embodiments, the ejector can be put into the orifice directly without tilting. In block 412, the interface of the flange of the ejector is aligned with the interface of the air intake component, i.e., a raised portion around the opening in the air intake component that is provided for this purpose. The ejector is welded onto the intake air component, in block 414.

[0085] In FIG. 17, an ejector 600 is shown above an air duct 610 prior to assembly. Ejector 600 has a flange 602, first and second tubes 604 and 606, and a venturi tube 608. Air duct 610 has a protuberance 618 that accommodates forming a flat surface 616 onto which a flange 602 mounts. Surface 616 surrounds an opening 614 into which venturi tube 608 be placed. Opening 614 is large enough to allow venturi tube 608 to go into opening 614 straight on, as shown by arrows 630. Ejector 600 is affixed to air duct 610 by friction welding or any other suitable process. A cross section of an ejector-air duct assembly is shown in FIG. 18. The underside of flange 602 is affixed to the periphery of the opening, surface 616 of FIG. 17.

[0086] The duct shown in FIGS. 17 and 18 has a straight section that is long enough to accommodate an opening 614 (shown in FIG. 17) for ejector 610. However, in some applications, air ducts have limited ability to accommodate ejector 610, or even the shorter ejector shown in FIG. 7. A shorter version of ejector 150 of FIG. 6 is shown in FIG. 19. Ejector 188 is nearly identical to ejector 150, of FIG. 6, except that flange 192 couples to diverging section 174 at location 196, which is closer to tube 162 than in FIG. 6. The length of ejector 188 is shown having a length 198 in FIG. 19, which is shorter than ejector 150 of FIG. 6 that has a length 190.

[0087] In FIG. 20, a shortened ejector 640 is shown that has a shortened flange 642 (similar to the shortened flange in FIG. 19) with tubes 604 and 606 extending from flange 642. Air duct 650 has a protuberance 658 that has an opening 654 (also shortened) that has a surrounding surface 656 to which flange 642 is affixed. Because venturi tube 608 sticks out beyond flange 642 compared to venturi tube 608 in relation to flange 602 of FIG. 17, venturi tube 608 cannot be installed into opening 654 directly but must be tipped, as shown in FIG. 20. After venturi tube 608 enters opening 654, ejector 640 can be straightened out so that flange 642 meets with surface 656. This tilting and then straightening is illustrated by arrow 660.

[0088] It is known to manufacture the ejectors by injection molding. In the prior art, such manufacturing technique leads to the difficulty in making diverging and converging sections in the ejector because such sections are formed by cylindrical pins. According to embodiments disclosed above, the two-piece version that is split along venturi tube allows a complicated shape can be formed with a converging section, a diverging section, and a throat, that in some embodiments, slightly diverges. In the prior art, throats are typical straight. However, in some applications, it has been found that the diverging throat yields improved flow efficiency approaching supersonic flow. In some embodiments, the diverging section has a non-uniform shape and in some embodiments, tilts downwardly; such features are easily accomplished with the two-piece ejector disclosed herein. Although it might be less expensive to injection mold the ejector out of two pieces, there are alternative manufacturing techniques that allow the desired shape in one piece. A 3-D printing process is one alternative. The resulting could be like any of FIGS. 5-7, except that the ejector would be of one piece. The difference between a 3-D printed ejector according to an embodiment of the present disclosure compared to the prior art in FIGS. 2-4 is that the ejector in FIGS. 2-4 have straight tube, whereas a 3-D printed ejector can have a converging section, a throat of controlled diameter, and a diverging section. In yet another embodiment shown in FIG. 21, an ejector, according an embodiment of the disclosure, is formed in one piece via a traditional casting method. To remove the core pieces, i.e., that provide the openings within the venturi tube, a plug is provided proximate the upstream end of the venturi tube. Finally, although very costly, the ejector can be machined from a blank.

[0089] In FIG. 22, an ejector 710 has a throat 715 with a converging section to the left (upstream) and a diverging section to the right (downstream). A centerline 712 of the converging section is offset from a centerline 714 of the diverging section. It has been found through modeling that such an offset provides greater flow.

[0090] As described above, some embodiments show a snap fit to affix the two pieces of the ejector. In such embodiments, an O-ring, adhesive, or other sealant can be used. Alternatively, a bump near the periphery of one of the pieces causes an interference with the other piece of the ejector.

[0091] In FIG. 23, a detail of a lower portion 900 of the ejector is shown. A surface 902 has an energy director 904 that is useful in the welding process. Energy director 904 is typically sits proud of the surface by about 0.6 mm. Surface 902 forms a butt weld with respect to a mating surface (not shown). A skirt 908 has two functions: serves as a pilot to locate the mating surface during assembly. Furthermore, the surface 908 forms a shear weld with a portion of the mating part.

[0092] An isometric view of an ejector has a diverging section 1000 in which a divot 1002 is formed. FIGS. 25 is a top view of diverging section 1000 with divot 1002 and FIG. 26 is a side view. Figure shows an isometric view of an ejector 1100 in which a diverging section 1002 is provided with a squared-off divot 1106 that has a short wall 1104. Divots 1002 and 1106 are provided to prevent recirculation, which would diminish flow through the ejector, that occurs at some operating conditions.

[0093] While the best mode has been described in detail with respect to particular embodiments, those familiar with the art will recognize various alternative designs and embodiments within the scope of the following claims. While various embodiments may have been described as providing advantages or being preferred over other embodiments with respect to one or more desired characteristics, as one skilled in the art is aware, one or more characteristics may be compromised to achieve desired system attributes, which depend on the specific application and implementation. These attributes include, but are not limited to: cost, efficiency, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. The embodiments described herein that are characterized as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.