EP0424821B1 - Verfahren und Gerät zur Kraftstoffmessung - Google Patents

Verfahren und Gerät zur Kraftstoffmessung Download PDF

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Publication number
EP0424821B1
EP0424821B1 EP90120109A EP90120109A EP0424821B1 EP 0424821 B1 EP0424821 B1 EP 0424821B1 EP 90120109 A EP90120109 A EP 90120109A EP 90120109 A EP90120109 A EP 90120109A EP 0424821 B1 EP0424821 B1 EP 0424821B1
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EP
European Patent Office
Prior art keywords
fuel
venturi
chamber
carburetor
nozzle
Prior art date
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Expired - Lifetime
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EP90120109A
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English (en)
French (fr)
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EP0424821A1 (de
Inventor
John Clark Woody
Mark Steven Swanson
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Walbro Corp
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Walbro Corp
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Publication date
Priority claimed from US07/594,021 external-priority patent/US5133905A/en
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Publication of EP0424821A1 publication Critical patent/EP0424821A1/de
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M17/00—Carburettors having pertinent characteristics not provided for in, or of interest apart from, the apparatus of preceding main groups F02M1/00 - F02M15/00
    • F02M17/02—Floatless carburettors
    • F02M17/04—Floatless carburettors having fuel inlet valve controlled by diaphragm
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M7/00—Carburettors with means for influencing, e.g. enriching or keeping constant, fuel/air ratio of charge under varying conditions
    • F02M7/10—Other installations, without moving parts, for influencing fuel/air ratio, e.g. electrical means
    • F02M7/11—Altering float-chamber pressure

Definitions

  • the present invention relates to fuel metering for engines using carburetors, and more particularly to a small diaphragm-type or float-bowl-type carburetor for small internal combustion engines such as used in portable tools such as chain saws, in lawn mowers and other power lawn and garden equipment and in small off-road sport vehicles, etc.
  • a diaphragm-type carburetor generally comprises a mixture conduit in which fuel is mixed with air for delivery to the intake manifold of an engine, a fuel chamber closed by a diaphragm and communicating through a nozzle with the mixture conduit for delivery of fuel thereto, and valve means controlled by the diaphragm for controlling delivery of fuel from a fuel tank to the fuel chamber.
  • An air filter is provided for cleaning air entering the mixture conduit.
  • the mixture conduit is formed with a restriction, e.g., a venturi.
  • the effect of the moving pressure wave forms on the fuel delivered from the nozzle of the carburetor has long been a source of problems for the carburetor design engineer.
  • the wave effect is superimposed on the normal vacuum caused by the engine intake air stream flow through the venturi. This in turn causes the nozzle to deliver fuel in a manner which is not fully responsive to the vacuum caused by the air flow.
  • the tuning waves are superimposed on the venturi pressure drop and adversely effect fuel metering otherwise designed to follow this relationship. More particularly, this tuning wave is imposed on the fuel delivery side of the main jet and adversely affects the desired design value of the pressure drop ⁇ P, across the main nozzle-fuel controlling restriction.
  • tuning waves i.e., air pressure waves generated in the carburetor mixture conduit by the sudden opening and closing of the engine intake port, are responsible for such well known problems as fuel "spit back" under certain engine operating conditions as well as certain abnormal and less well recognized deviations in the desired engine-carburetor performance curves plotting fuel-air ratio against engine speed, (e.g., undesirable "rich or lean spots” in the performance curves) and related plots of such parameters as specific fuel consumption, engine power output, exhaust constituents, etc.
  • vent passageway comprises a pair of passages opening into the mixture conduit so as to sense static pressure therein.
  • One of said passages extends from the mixture conduit adjacent to its upstream end and upstream of a choke valve to the air chamber, while the other passage extends from the mixture conduit adjacent the main fuel nozzle in the conduit restricted portion (venturi).
  • Both passages include restrictions to dampen the effect of engine pulsations in the mixture conduit. While these passages are intended to maintain a predetermined air and fuel ratio regardless of air filter clogging they are not suited to cancel the adverse effect of the aforementioned moving pressure tuning wave forms.
  • US-A-3,065,957 discloses a fuel metering apparatus comprising a diaphragm type carburator.
  • the carburator includes an air entrance Pitot tube projecting into the mixture conduit and having an inlet opening facing upstream relative to the air flow direction in the mixture conduit.
  • the air entrance tube is disposed adjacent the upstream end of the mixture conduit upstream of a choke valve and is connected via a restriction to a pair of air chambers arranged between a pair of diaphragms for operating an inlet valve.
  • the purpose of such air entrance tube is to equalize the pressures in the two chambers defined by said pair of diaphragms.
  • Another object is to provide an improved carburetor incorporating the aforementioned system which is also operable as a vent system for the "dry" side of the diaphragm chamber which functions effectively to prevent or reduce adverse effects of air filter clogging relative to the maintenance of a predetermined air and fuel ratio.
  • a still further object is to provide a fuel metering system method and apparatus of the aforementioned character which may also be applied to float feed carburetors in a manner similar to the application thereof to diaphragm carburetors.
  • Yet another object of the present invention is to provide a fuel metering system and method of the aforementioned character in which the effect of the aforementioned tuning waves is utilized to advantage to modulate the fuel metering system in a favorable manner to produce varying effects such as a lean mixture for an economy range and/or a rich mixture for a power range.
  • the objects of the invention are accomplished by providing a diaphragm carburetor with a vent passageway system operable to sense dynamic as well as static components of the engine tuning pressure wave imposed on the air stream in the carburetor venturi and to route the same to the underside ("dry side") of the diaphragm in such a manner that the pressure wave will be better imposed on both sides of the diaphragm, thus essentially canceling the adverse effect of the pressure wave and leaving only the desired ⁇ P pressure drop operable between the diaphragm fuel chamber and venturi main nozzle.
  • vent passageway pitot tube and the main fuel nozzle opening are offset slightly from one another in the venturi passage by a predetermined leading or lagging amount in the direction of wave propagation in the carburetor throttle bore to thereby introduce a leading or lagging wave impingement relationship between these two venturi openings.
  • the aforementioned one end of the vent passageway communicates with the head space of the fuel sump or well in the float bowl, the surface of the fuel and the float therein being considered the equivalent of the diaphragm, and the bowl headspace being treated as the "dry side" chamber.
  • FIG. 1 is a side elevational view of a small, compact diaphragm carburetor designed for a chain saw engine application incorporating the improved fuel metering system in a first embodiment of the present invention, the intended direction of engine intake air flow through the carburetor being indicated by the arrow A/F.
  • FIG. 2 is a cross sectional view taken on the line 2-2 of FIG. 1.
  • FIG. 3 is a bottom view of the carburetor of FIG. 1 and rotated 90° from the orientation in FIG. 1.
  • FIG. 4 is a fragmentary cross-sectional view taken on the line 4-4 of FIG. 3, and is an inverted view relative to FIGS. 1, 2 and 5.
  • FIG. 5 is a elevational view of the carburetor of FIG. 1 looking into the choke end of the mixing passage and having a portion broken away and shown in cross section to better illustrate detail.
  • FIG. 6 is a fragmentary cross-sectional view taken on the lines 6-6 of FIG. 5.
  • FIG. 7 is a view taken on the line 7-7 of FIG. 5 illustrating the bottom of the carburetor body with the bottom plate removed.
  • FIG. 8 is a fragmentary cross-sectional view taken on the line 8-8 of FIG. 7.
  • FIG. 9 is a fragmentary bottom plan view of the bottom cover assembly of the carburetor shown by itself.
  • FIG. 10 is a fragmentary cross-sectional view taken on the line 10-10 of FIG. 9.
  • FIG. 11 is a fragmentary top plan view of a portion of a sealing gasket of the bottom cover assembly taken on the line 11-11 of FIG. 10.
  • FIG. 12 is a side elevational view of a small, compact float bowl carburetor designed for a twelve horsepower lawn and garden appliance engine application incorporating the improved fuel metering system in a second embodiment of the present invention, the intended direction of engine intake air flow through the carburetor being indicated by the arrow A/F.
  • FIG. 13 is a cross-sectional view taken on the line 13-13 of FIG. 12 but enlarged double size thereover.
  • FIG. 14 is a cross-sectional view taken on the line 14-14 of FIG. 12 but enlarged double size thereover.
  • FIG. 15 is an end elevational view of the carburetor of FIG. 12 looking into the choke end of the mixing passage.
  • FIG. 16 is a cross-sectional view taken on the line 16-16 of FIG. 15 but enlarged double size thereover.
  • FIG. 17 is a side elevational view of the carburetor of FIG. 12, showing the side opposite that of FIG. 12.
  • FIG. 18 is an end elevational view of the carburetor of FIG. 12, looking into the throttle end of the mixing passage.
  • FIGS. 19, 20 and 21 are fragmentary cross-sectional views taken on the line 19-19 of FIG. 17 but enlarged four times thereover and respectively illustrating the orientation of the choke plate, choke shaft and modified shunt or bypass passageway relative to one another with the choke fully closed (FIG. 19), with the choke positioned 15° before full closure (FIG. 20) and with the choke positioned in fully opened condition (FIG. 21) respectively.
  • FIG. 22 is a top plan view of the carburetor of FIG. 12 rotated 90° about the carburetor axis from the illustration of FIG. 17.
  • FIG. 23 is a cross-sectional view taken on the line 23-23 of FIG. 22 but enlarged double sized thereover.
  • FIG. 24 is a cross-sectional view taken on the line 24-24 of FIG. 22 but enlarged double size thereover.
  • FIG. 1 illustrates by way of example a diaphragm carburetor 20 designed for use with a chain saw engine and incorporating the best mode presently known for carrying out the fuel metering system of the invention. Except where indicated hereinafter, carburetor 20 is of known design embodying conventional but state of the art constructional features.
  • Carburetor 20 has a main body 22 with a top cover or cap plate 24 secured to its upper surface and a bottom cover assembly 26 secured to its under surface. From the side view of FIG. 1, the upper ends of the choke shaft 28 and throttle shaft 30 may be seen, as may the throttle stop arm 32, throttle stop adjustment screw 34, high speed needle valve 36 and low speed needle valve 38.
  • carburetor 20 has a mixture conduit or bore 40 and a venturi constriction 42 disposed within bore 40.
  • a choke valve 44 is mounted on choke shaft 28 and disposed in the entrance (in the choke bore) to bore 40 upstream of venturi 42, while a throttle valve (not shown) is provided on throttle shaft 30 so as to be disposed in bore 40 (in the throttle bore) downstream of venturi 42.
  • Fuel may be supplied to the carburetor by a pump (not shown) which may be formed by components disposed in and between cover 24 and body 22, as will be understood by those skilled in the art.
  • the fuel pump discharge is connected through a passage 50 and filter screen 52 with a passage 54 leading to the metering chamber 56 of the carburetor.
  • a needle valve 58 in passage 54 is controlled by a diaphragm 60 disposed between the metering or "wet" chamber 56 and a vent or “dry” chamber 62.
  • Diaphragm 60 is connected with valve 58 by a lever 64 which is biased by a spring 66 in a direction to move valve 58 toward closed position.
  • the main fuel nozzle outlet 70 opens into venturi 42 of the carburetor and, in accordance with conventional practice, has its axis oriented perpendicular to the axis of venturi 42 and direction of engine intake air flow in bore 40. Hence primarily or only static pressure of the air flow is sensed by nozzle 70.
  • Nozzle 70 is connected via the main fuel metering system, to metering chamber 56 through a fuel passageway network, including the adjustable high speed needle valve 36 which controls flow through a passageway 72 leading, via such network, to the fuel well 74 feeding, via capillary seal screen 75, nozzle outlet 70.
  • high speed needle valve 36 is a temperature compensating needle valve which serves as the main fuel metering restriction, and is constructed in accordance with the disclosure and claims of the Woody and Swanson United States Patent No. 4,759,883, issued July 26, 1988 and assigned to the assignee of record herein, the same being incorporated herein by reference.
  • carburetor 20 is provided with a vent passageway system operable to modify and/or cancel the effects of tuning pressure waves transiting venturi 42 which otherwise would adversely affect the metering function of needle valve 36 and associated passageway 72.
  • This vent passageway interconnects a specially constructed pressure sensing port in venturi 42 with the dry side chamber 62.
  • a pitot tube protruberance 80 is cast integrally with the body 22 so as to project from venturi 42 into the air flow stream drawn through bore 40 by engine intake suction.
  • Projection 80 has a flared mouth 82 defined by an integral hood 84 leading to a short entrance passage 86.
  • the axis of passage 86 is parallel to the axis of bore 40, and thus, mouth 82 faces directly upstream relative to the air flow through bore 40. Mouth 82 defines the end of the vent passageway system communicating with the carburetor throat.
  • Passage 86 constitutes a blind bore which is connected near its blind end to a passage 88, the axis of which is disposed perpendicular to the axis of bore 86.
  • Passage 88 merges with a coaxial counterbore 90 closed at its outer end by a press fit ball 91.
  • Passage 90 is intersected by a short passage 92 (shown schematically in phantom by dash lines in FIG. 5) which in turn opens to the bottom face 94 of body 22, as best seen in FIG. 7.
  • Passage 92 communicates with a passage 96 formed in bottom cover 26 (FIGS. 9, 10 and 11), and passage 96 is connected by a passage 98 and 100 to the dry side chamber 62.
  • Passage 100 constitutes the opposite end of the vent passageway system communicating with the dry side of the diaphragm metering chamber 62.
  • the entrance 82 of the vent passageway communicating with bore 40 should be located in the plane of the circle defined by venturi 42, which plane also includes the outlet of nozzle 70. It has also been found that this entrance to the vent passageway is preferably configured as a pitot tube, as shown in FIGS. 5 and 6, having the flared mouth 82 and hood 84. Moreover, the axis of the entrance passage 86 should preferably be located within a zone in the aforementioned venturi plane where the air stream velocity in bore 40 and passing through venturi 42 is at a maximum under engine operating conditions when choke valve 44 is fully opened.
  • opening 86 is located generally in the center of the chordal segment defined by the lower edge of shaft 28 and the portion of venturi 42 disposed between shaft 28 and nozzle 70.
  • the diametrically opposed chordal segment in this plane, located on the other side of shaft 28, could likewise be chosen for locating pitot tube projection 80, but the head of the mounting stud 102 for choke plate 44 offers a slight obstruction to this side of the choke shaft 28 and hence the aforementioned chordal zone closer to nozzle 70 is chosen as preferred in this particular arrangement.
  • the axis of entrance 86 of the pitot tube 80 preferably would be disposed coincident with the axis of venturi 42 (and bore 40), inasmuch as air stream velocity would be greatest at the center of an unobstructed venturi.
  • the total axial length of interconnected passages 86, 88, 90, 92, 96, 98 and 100 is 8,53 mm (.336 inches) and the diameter of these passages ranges from about 1,24 to about 1,57 mm (about .049 to about .062 inches) respectively, the diameter of venturi 42 is 13,87 mm (.546 inches), the diameter of shaft 28 is 0,89 mm (.186 inches), and the axis of passage 86 is located 2,41 mm (.095 inches) from the nearest point on the surface of venturi 42.
  • a shunt passageway system is provided for producing a bypassing "shut-off" of the effect of the vent passageway 82-100 when initiating choke valve closure, i.e., after the first 5° of rotation of choke shaft 28 from its fully opened position on FIG. 5 toward its closed position.
  • This "shut-off" shunt passageway comprises a slot or flat 104 formed in shaft 28 (FIG.
  • Passage 106 opens at the bottom face 94 of body 22 (FIGS. 4 and 7 and 8), and is connected to passage 96 by a cross passageway 110 formed in bottom cover 26 as well as in a sealing gasket 112 (FIGS. 4 and 11) which may be formed integrally with diaphragm 60.
  • Cover 26 may be provided with a raised rib 114 (FIG. 10) to help seal this cross passageway 110 when gasket 112 is pressed against the upper face 116 of cover assembly 26.
  • a depressed or recessed ledge 118 may be formed in gasket 112 to cooperate with the rib 114 to further define a sealing connection for cross passageway 110.
  • slot 104 in choke shaft 28 faces upstream relative to air flow in bore 40 in the closed condition of choke shaft 28.
  • shunt passageway 104-110 is gradually closed off by the deregistration of slot 104 with passage 106 by the corresponding rotation of shaft 28 in bore 108.
  • vent passageway 82-100 is operable to route the tuning pressure wave to the dry side chamber 62 of the carburetor in such a manner that the pressure wave will be imposed on both sides of diaphragm 60 to thereby counter-modulate or cancel the adverse effect of the pressure wave communicated by nozzle 70 to the wet side chamber 56 of the carburetor, thereby leaving only the desired static pressure drop P as established by the predetermined design parameters engineered for the particular carburetor and engine application.
  • venturi-communicating opening 82 of vent passageway 82-100 in the plane of venturi 42, co-planar with nozzle 70, and preferably located in the zone of maximum air flow velocity when choke valve 44 is open.
  • this orientation and location relationship, as well as the pitot tube configuration of protuberance 80, have been found to be critical to the ability of the vent passageway 82-100 to counter-modulate or cancel the tuning waves, or to at least cancel or substantially reduce the adverse effect of such tuning waves on the predetermined fuel metering parameters desired for the carburetor.
  • vent passageway 82-100 has been found to also perform a second function, namely, it prevents the fuel/air mixture from going over rich as the air filter located upstream of the entrance to the carburetor bore becomes clogged with dirt particles.
  • Vent passageway 82-100 of the present invention thus provides the further advantages of the full inside vent as disclosed in the United States Brown patent 3,174,732 but is believed to be operable in an improved manner thereover to thereby better maintain a predetermined air/fuel ratio regardless of air filter clogging.
  • the system of the invention is also believed to reduce or eliminate undesirable carburetor performance characteristics resulting from phase shifts between engine suction pulses and tuning wave pulses otherwise occurring with changes in engine speed.
  • the present invention may be applied to a float bowl carburetor.
  • a carburetor the surface of the fuel in the bowl is treated as equivalent to the diaphragm 60, and the vent passageway system in accordance with the invention is operable in a manner similar to that described in conjunction with the hereinabove disclosed diaphragm carburetor 20.
  • phase shift can thus be established in accordance with an empirically predetermined dimensional relationship relative to the fuel metering effect of diaphragm 60 so as to produce a lean mixture for an economy range or a rich mixture for a power range, as will now be understood by those skilled in the art in view of the foregoing disclosure.
  • vent passageway 82-100 of the present invention may be modified or modulated by venting the dry side chamber 62 to atmosphere in a controlled manner.
  • bottom cover assembly 26 may be provided with a well 130 containing filter media 132, and an annular row of slots 134 may be provided in the bottom of the well 130 to communicate filter media 132 with atmosphere.
  • a cover 136 is seated over well 130 and is provided with spaced ribs 137 to press down the filter media 132 so the same is held spaced from the underside of cover 136.
  • a restricted orifice 138 is provided in cover 136 communicating with the head space above filter media 132.
  • Orifice 138 is shown enlarged (not to scale) but preferably has a diameter of 0,635 mm (.025 inches) in a working embodiment of carburetor 20 as determined by emperical testing. Atmospheric bleed orifice 138 on the dry side chamber 62 can thus be employed to modulate the effect of pressure wave cancellation provided by vent passageway 82-100, as may be found desirable for certain engine applications or for particular operating conditions found desirable for given applications.
  • vent passageway system 82-100 of the present invention because of the pitot tube arrangement of the venturi end of the vent passageway system, better measures or senses both dynamic and static pressure conditions in venturi 42 of bore 40, rather than primiarly static pressure conditions as is the case with prior art vent passageway systems such as that disclosed in the aforementioned Brown '732 patent as well as in the United States Patents to Phillips 3,065,957; Brown et al 3,181,843 and Yagi et al 4,494,504 (FIGS. 19 and 20).
  • the communication of the sensed pressure wave via the vent passageway system to the dry side chamber 62 has been found to be effectively transmitted to the wet chamber 56 via the diaphragm 60 without thereby adversely affecting the diaphragm in performing its principal function of controlling, via its associated lever linkage 64, the fuel inlet valve 58.
  • the invention also may be applied to a float bowl carburetor.
  • a prior art commercially available float bowl carburetor 20' manufactured and sold by Walbro Corporation of Cass City, Michigan, assignee of the inventors herein, under Part No. LMK1 for use on a Kohler C.V. 12 engine is illustrated in FIGS. 12 through 24, wherein the same has been modified to incorporate the vent passageway system in accordance with the invention so as to be operable in a manner similar to that described in conjunction with the hereinabove disclosed diaphragm carburetor 20.
  • the float bowl carburetor 20' as shown in FIGS. 12 through 24 is described in association with reference numerals raised by a prime suffix applied to those elements corresponding in structure and function to that described previously in conjunction with carburetor 20, and their description is not repeated inasmuch as the construction of the float bowl carburetor 20' will be well understood by those skilled in the art when viewing the illustrations of FIGS. 12 through 24.
  • float carburetor 20' is provided with a vent passageway system of the present invention operable to modify and/or cancel the effects of tuning pressure waves transisting venturi 42' which otherwise would adversely affect the metering function of fixed high speed jet 36', well 74' and main nozzle 70'.
  • This vent passageway interconnects a specially constructed pressure sensing port in venturi 42' with the head space 62' of the float bowl 63.
  • bowl 63 contains liquid fuel in the sump or well thereof in which an annular hollow float 60' is partially submerged, and float bouyancy is operable via lever 64' to control inlet valve 58' in response to fuel sump surface level variations.
  • a pitot tube 80' is provided so as to project from venturi 42' into the air flow stream drawn through bore 40' by engine intake suction.
  • Pitot tube 80' in the embodiment illustrated in FIGS. 12-24 may be cast integrally with carburetor body as in the carburetor 20.
  • pitot tube 80' in the embodiment illustrated in FIGS. 12-24 is fabricated from separate parts including a cylindrical brass plug 140 having a blind bore 142 drilled therein so that the open end of bore 142 forms a mouth 82' of the pitot tube 80'.
  • a tube 144 is inserted at one end into a side opening drilled in plug 140, and is press fit into a drilled passage 146 which extends perpendicularly to the carburetor axis and which in turn is sealed at its outer end by a press fit ball 148.
  • Passage 146 intersects a larger diameter drilled passage 150 already provided in carburetor 20', and which extends downwardly into a larger diameter counter bore 152 (FIG. 13) and which may, if desired, be at its lower end closed by a welch plug which seats at 154 in accordance with conventional practice.
  • a notch 156 in the sidewall intended to receive the welch plug communicates passage 150 with the head space 62' of bowl 63.
  • a large diameter passage 158 extends parallel to the carburetor axis and has its mouth 160 located adjacent the choke end of the carburetor just downstream from the air filter (not shown) normally provided upstream of the entrance to carburetor mixing passage 40'.
  • the downstream end of passage 158 perpendicularly intersects passage 150 and together therewith provides the main air pressure venting system for the float bowl head space 62' in accordance with the conventional practice.
  • passage 158 is sealed by a plug 162 and not utilized.
  • these pre-existing passages 158 and 150 would be eliminated in favor of a simplier passageway from tube 144 to headspace 62'.
  • mouth 82' of pitot tube 80' would be designed to be flush with the mid-plane of venturi 42' and the centerline of nozzle 70', unless a phase shift offset relationship as described previously, was desired.
  • pitot tube 80' is oriented and located in a manner quite similar to pitot tube 80 of carburetor 20.
  • the mouth 82' of the entrance bore 142 of pitot tube 80' is disposed a very short distance upstream of the plane of the minor diameter of venturi 42' and just slightly upstream from coplanar relationship with main nozzle 70' in order to accomodate the physical limitations imposed by this pre-existing carburetor design.
  • Passage 142 like passage 86, extends parallel to the main axis A of bore 40' and venturi 42'.
  • carburetor 20' is provided with a choke plate 44' mounted on choke shaft 28', similar to diaphragm carburetor 20, pitot tube 80' is offset from axis A toward the side wall of venturi 42' so as to be disposed of about halfway between axis A and the associated side wall of venturi 42'. However, taken vertically in the carburetor as seen in FIGS. 13 and 15, pitot tube 80' is centered in horizontal alignment with axis A.
  • the entrance mouth 82' of pitot tube 80' is located in the chordal space just downstream of choke plate 44' wherein engine induced air flow velocity is maximized, taken into consideration the presence of choke plate 44' and choke shaft 28' and their obstructing effect relative to air flow through carburetor bore 40' and venturi 42'.
  • carburetor 20' is also provided with a shunt passageway system for producing a by-passing "shut-off" of the effect of the vent passageway 142, 144, 150, 156 when initiating choke valve closure.
  • This "shut-off" shunt passageway comprises, as best seen in FIGS. 19-21 and 24, a drilled passage 170 extending from the front face of carburetor 20' parallel to axis A and diametrically intersecting the bore 29 (FIG. 24) which receives choke shaft 28' above choke plate 44'.
  • passage 170 terminates at an intersection with an angled drilled passage 172 which in turn intersects the upper end of passage 150.
  • the outer end of passage 170 is sealed by press fit ball 174, and likewise the outer end of passage 172 is sealed by a press fit ball 176.
  • Another angled drilled passage 178 is provided upstream of choke plate 44', near its upper edge, and which opens into carburetor bore 40'. Passage 178 intersects passage 170 where both passages meet choke shaft bore 29.
  • Choke shaft 28' is provided with a drilled cross passage 180 extending diametrically of shaft 28' so as to be rotatable, in response to choke shaft rotation, into and out of registry at its opposite ends with passages 170 and 178.
  • vent passageway 142, 144, 146 is rendered inoperable when the choke valve is closed as in FIG. 19, and hence the high vacuum conditions immediately behind choke plate 44' in the vicinity of pitot tube 80' cannot be communicated to the air chamber 62' of the float bowl 63' because of the shunting effect of the shunt passageway 178, 180, 170.
  • shunt passageway 180 is gradually closed off by the deregistration of passage 180 with passage 178 and 170 by the corresponding rotation of shaft 28'.
  • vent passageway 142, 144, 150 may be modified or modulated in carburetor 20' by venting the bowl headspace 62' to atmosphere in a controlled manner.
  • a restricted orifice 138' is provided in the body of carburetor 20' communicating passage 150 with atmosphere, in the manner of orifice 138 as described previously in conjunction with carburetor 20.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of The Air-Fuel Ratio Of Carburetors (AREA)

Claims (8)

  1. Kraftstoffzumeßvorrichtung mit, in Kombination, einem Gehäuse (22), einem Kraftstoff-Luft-Gemischkanal (40; 40') durch das Gehäuse, wobei das Gehäuse (22) mit einer Kraftstoffkammer (56; 56') versehen ist, der Gemischkanal (40; 40') einen Einlaß und einen Auslaß sowie einen VenturiDrosselabschnitt (42; 42') zwischen dem Einlaß und Auslaß aufweist, einem Kraftstoffeinlaß und einem Kraftstoffkanal (50, 54; 50', 54'), der von dem Kraftstoffeinlaß zu der Kraftstoffkammer (56, 56') verläuft, einem Einlaßventil (58; 58') in dem Kraftstoffkanal zwischen dem Kraftstoffeinlaß und der Kraftstoffkammer (56, 56'), einer Hauptkraftstoffdüse (70; 70') mit einer Auslaßöffnung innerhalb des Drosselabschnittes (42; 42'), wobei die Hauptkraftstoffdüsen-Auslaßöffnung relativ zu dem Gemischkanal (40; 40') so gerichtet ist, daß sie allein den darin herrschenden statischen Druck erfaßt, wobei das Gehäuse (22; 22') eine Kraftstoffverbindung (72, 74; 72', 74') von der Kraftstoffkammer (56; 56') zu der Hauptkraftstoffdüse (70; 70') aufweist und Hauptkraftstoffsteuermittel (36; 36') enthält, Membranmittel (60) oder Schwimmermittel (60') zum Betätigen des Einlaßventils (58; 58'), einer einzigen Luftkammer (62; 62'), die mit den Membranmitteln (60) oder Schwimmermitteln (60') zusammenwirkt, um deren Betätigung relativ zu dem Einlaßventil (58; 58') zu regeln, wobei das Gehäuse einen Entlüftungskanal (86-100; 142-156) aufweist, der den Gemischkanal (40; 40') mit der Luftkammer (62; 62') verbindet, um einen Druckzustand in dem Drosselabschnitt (42; 42') des Gemischkanals zu erfassen und ein entsprechendes Drucksignal an die Luftkammer (62; 62') zu übertragen, dadurch gekennzeichnet, daß das Gehäuse (22; 22') ein Pitot-Rohr (80; 80') mit einer Einlaßöffnung (82; 82') besitzt, die stromauf relativ zu der Luftstromrichtung im Gemischkanal (40; 40') gerichtet und in dem Drosselabschnitt (42; 42') in einem Bereich maximaler Luftgeschwindigkeit angeordnet ist, um motoreinlaßinduzierte Gesamtdruckwellen an die Trockenkammer zu übertragen, so daß die Gesamtdruckwellen den Membranmitteln (60) oder Schwimmermitteln (60') aufgeprägt werden.
  2. Kraftstoffzumeßvorrichtung nach Anspruch 1, bei der die Hauptdüse (70, 70'), die in den Venturi-Abschnitt (42; 42') mündet, und der Pitot-Rohreinlaß (82; 82') beide im wesentlichen in einer gemeinsamen Ebene angeordnet sind, die senkrecht zu der Achse des Venturi-Abschnittes verläuft.
  3. Kraftstoffzumeßvorrichtung nach Anspruch 1, bei der die Hauptdüse (70, 70'), die in den Venturi-Abschnitt (42; 42') mündet, und der Pitot-Rohreinlaß (82; 82') versetzt zueinander relativ zu der Richtung des motoreinlaßinduzierten Luftstromes durch den Venturi-Abschnitt (42; 42') einen solchen Abstand zueinander haben, daß durch den Abstand eine vorgegebene Phasenverschiebung in der Wirkung einer Einlaßresonanzdruckwelle erzeugt wird, die abwechselnd auf den Pitot-Rohreinlaß (82; 82') und die Hauptdüsenöffnung (70; 70') auftrifft.
  4. Kraftstromzumeßvorrichtung nach einem der Ansprüche 1 bis 3, bei der die Auslaßöffnung der Hauptkraftstoffdüse (70;. 70') so angeordnet ist, daß ihre Achse im wesentlichen senkrecht zur Richtung des motorinduzierten Luftstromes durch den Venturi-Drosselabschnitt (42; 42') verläuft und die Ebene der Auslaßöffnung der Düse (70; 70') im wesentlichen parallel zu dieser Luftstromrichtung verläuft, und die Pitot-Rohr-Einlaßöffnung (82; 82') so angeordnet ist, daß ihre Achse parallel zu der besagten Luftstromrichtung verläuft und die Ebene der Pitot-Rohr-Einlaßöffnung (82; 82') im wesentlichen senkrecht zu der besagten Luftstromrichtung verläuft.
  5. Kraftstoffzumeßvorrichtung nach einem der Ansprüche 1 bis 4, mit einem in dem Gemischkanal (40; 40') angeordneten Choke-Ventil (44; 44'), das aus einer offenen Choke-Position in eine geschlossene Choke-Postion bewegbar ist, Ventilmitteln (104-110; 78-180), die auf die Bewegung des Choke-Ventils (44; 44') ansprechen, um den Entlüftungskanal (86-100; 142-156) in Betrieb zu setzen und somit die Wellenwirkungen auf die Luftkammer (62; 62') zu übertragen, wenn das Choke-Ventil (44; 44') in eine Öffnungsposition bewegt wird, und um den Entlüftungskanal (86-100; 142-156) außer Betrieb zu setzen und somit die Wellenwirkungen auf die Luftkammer (62; 62') zu übertragen, wenn das Choke-Ventil (44; 44') geschlossen ist.
  6. Kraftstoffzumeßvorrichtung nach einem der Ansprüche 1 bis 5 in Verbindung mit einem Zweitakt-Verbrennungsmotor mit einem Zylinder, einem Kolben, der im Zylinder hin- und herbewegbar ist, und einem Kurbelgehäuse, wobei die Kraftstoffzumeßvorrichtung vom Membrantyp ist und eine Zumeßmembran (60) umfaßt, die einen Raum im Gehäuse (22) in eine die Kraftstoffkammer bildende Zumeßkammer (56) und eine die Luftkammer bildende Trockenkammer (62) unterteilt, wobei das Einlaßventil durch die Membran (60) betätigbare zumeßventilmittel (58) aufweist und die Hauptkraftstoffsteuermittel ein Hochgeschwindigkeits-Nadelventil (36) aufweisen.
  7. Kraftstoffzumeßvorrichtung nach Anspruch 6, mit einem Luftablaßkanal (104, 106), der atmosphärische Luft von einem zum Venturi-Drosselabschnitt (42) des Gemischkanals (40) beabstandeten Punkt mit der Trockenkammer (62) verbindet, um die Auswirkung des Entlüftungskanals (86-100) auf die Trockenkammer (62) zu modulieren.
  8. Verfahren zum Zumessen von Kraftstoff zu einem Verbrennungsmotor mit einem Zylinder, einem Kolben, der im Zylinder hin- und herbewegbar ist, und einem Kurbelgehäuse, einem Vergaser mit einem Gehäuse (22), der einen Venturi-Abschnitt (42; 42') bildet, Kraftstoffzuführmittel zum Zuführen von Kraftstoff zu dem Venturiabschnitt (42; 42') einschließlich Zumeßeinlaßventilmitteln (58; 58'), die durch zugehörige Membranmittel (60) oder Schwimmermittel (60') betätigbar sind, einem Raum in dem Gehäuse (22), einer in dem Raum vorgesehenen einzigen Luftkammer (62; 62'), die mit den Membranmitteln (60) oder Schwimmermitteln (60') zusammenwirkt, um ihre Betätigung relativ zu den Einlaßventilmitteln (58; 58') zu regeln, Hauptkraftstoffsteuermitteln (36; 36') und einer Hauptkraftstoffdüse (70; 70'), die in dem Venturi-Abschnitt (42; 42') so angeordnet ist, daß ihre Auslaßöffnung mit ihrer Achse im wesentlichen senkrecht zur Richtung des motoreinlaßinduzierten Luftstromes durch den Venturi-Abschnitt verläuft, wobei die Düse (70; 70') mit den Kraftstoffzuführmitteln durch eine kraftstoffsteuernde Drosselstelle (36; 36') verbunden ist, wobei das Verfahren die Schritte umfaßt,
    (1) daß die motoreinlaßinduzierten Druckwellen, die durch den Venturi-Abschnitt (42; 42') verlaufen, abgefühlt werden, um ein Druckwellensignal zu erzeugen,
    (2) daß das abgefühlte Druckwellensignal an die Luftkammer (62; 62') übertragen wird, und
    (3) eine vorgegebene Phasenbeziehung zwischen dem Auftreffen der Wellen auf die Auslaßöffnung der Hauptkraftstoffdüse (70; 70') und dem abgefühlten Druckwellensignal entwickelt wird, um dadurch die Auswirkung des Wellenauftreffens auf den Abfall des statischen Drucks an den Hauptkraftstoffdrosselmitteln (36; 36') in Abhängigkeit von dem Motoreinlaßluftstrom durch den Venturi-Abschnitt (42, 42') zu modulieren,
       dadurch gekennzeichnet, daß das Abfühlen mit einem Pitot-Rohr (80; 80') durchgeführt wird, dessen Einlaßöffnung stromauf weist, um den Gesamtdruck zu erfassen, und in einer gemeinsamen Ebene angeordnet ist, die senkrecht zu der genannten Luftstromrichtung verläuft und die Auslaßöffnung der Hauptdüse (70; 70') schneidet.
EP90120109A 1989-10-26 1990-10-19 Verfahren und Gerät zur Kraftstoffmessung Expired - Lifetime EP0424821B1 (de)

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US42667289A 1989-10-26 1989-10-26
US594021 1990-10-09
US07/594,021 US5133905A (en) 1989-10-26 1990-10-09 Fuel metering method and apparatus
US426672 1999-10-25

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EP0424821A1 EP0424821A1 (de) 1991-05-02
EP0424821B1 true EP0424821B1 (de) 1993-11-24

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US1779803A (en) * 1921-02-28 1930-10-28 Drogo Aurelien Carburetor for internal-combustion engines
US2212258A (en) * 1936-01-15 1940-08-20 Beck Ludwig Carburetor
GB459095A (en) * 1936-03-30 1937-01-01 Bernard Granville Improvements relating to carbureters for internal combustion engines
US3174732A (en) * 1962-09-28 1965-03-23 Acf Ind Inc Carburetor
US4020859A (en) * 1972-05-29 1977-05-03 Regie Nationale Des Usines Renault System for controlling pressure by acoustic means
JPS6427459U (de) * 1987-08-11 1989-02-16

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EP0424821A1 (de) 1991-05-02
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JP2549199B2 (ja) 1996-10-30
CA2028577A1 (en) 1991-04-27
CA2028577C (en) 1997-12-30
JPH03151557A (ja) 1991-06-27
IE903709A1 (en) 1991-05-08
DE69004779T2 (de) 1994-03-17

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