GB2131876A - Carburettor throttle valves - Google Patents

Abstract

A carburettor has a butterfly valve (16) Fig. 1 formed with an internal passage (26) and outlet openings (27), (28) communicating therewith. Fuel is discharged through the butterfly valve into the air stream to form a combustible mixture. The valve may be provided with a flap (247), Fig. 14, which can be pivoted relative to the main body part (246). <IMAGE>

Description

SPECIFICATION Carburettor This invention relates to a carburettor, by which I mean a device which defines respective inlets for air and fuel and a common outletfor a mixture ofthe air and fuel, which device causes mixing ofthe fuel and airwhen in use. The invention is concerned primarily with carburettors for internal combustion engines.

A pressure differential which causes flow of fuel into the carburettorthroughthe fuel inletthereof and into a stream offlowing through the carburettor may be established by a venturi effect on the air stream, by the action of gravity on the fuel, by the action of a pump on the fuel or by a combination ofthese. In a case where the fuel is caused to flow into the carburettor by a pump, the pump may operate continuously. Alternatively, the pump may operate intermittentlyto inject into the air stream at a predetermined time a predetermined volume of fuel orto injectfuel into the air stream for a period of predetermined duration.

The object ofthe invention is to provided a new or im p roved carburettor.

According to one aspect of the invention, there is provide a carburettor comprising a valve member which is movable to regulate the flow ofairfrom the air inlet to the outlet, at least one opening being provided in the valve member and communicating withthefuel inlettodischargefuel into an air stream which flows pastthevalve member in use.

The term "air" as used herein is intended to include atmospheric air, and any other gas containing oxygen which, when mixed with the fuel, provides an explosive mixture.

The arrangement is preferably such that the restriction ofthe path along which fuel flows from the fuel inlet tothe outlet is varied in accordance with movement ofthe valve member. With this arrangement,the valve member may be used to regulate both airflowandthefuel flow. The valve member may act asavalve in the airflow path and in the fuel flow path.

Preferably, the valve member is turnableto regulate theflowofairfromthe airinlettothe outlet.

In this case, thevalve member preferably comprises an element of generally plate-like form which is turnable about an axis transverse to the longitudinal axis a passageway through which airflowsfrom the air inlet to the outlet to vary the effective crosssectional area ofthe passageway and hence the air flow th rough it The passageway may be of substantially cylindrical form and the valve member may be in the form of a disc or butterfly valve.

The valve member preferably has a plurality of said openings.

The openings may be distributed over partoforthe entire surface ofthe valve member. They may be arranged to directfuel into the airflow upstream and/or downstream ofthevalve member or upstream and/or downstream ofthe position occupied by the valve member when it restricts the airflow to a maximum degree.

Preferably, as the valve member is turned to increase or reduce the airflowto the outlet, the rate at which fuel is introduced into the airflow through the opening or openings in the valve member is automatically increased or decreased, respectively, thereby maintaining an appropriatefuel/air mixture.

This may be achieved by providing the valve memberwith a hollow part and with an inner element disposed within the hollow part and movable relative to the valve member to open or cover one or more apertures which form part of the fuel flow path from the fuel inletto the outlet. The inner element may be fixed with respect to a body of the carburettor, the valve memberturning on the inner element. Alternatively, the inner element may be movable along the hollow part ofthe valve member as thevalve member turns.

The apertures may be arranged in various configurations. In one example, the hollow part of the valve member and a fixed innerfeed pipe each has along its length a plurality of apertures arranged so thatturning ofthe hollow part varies the number of apertures brought into registration or/and varies the degree of registration of the apertures. In another example, the hollow part has a circumferentially extending series of apertures and the feed pipe has a single aperture in the end thereof inside the hollow part, this end of the feed pipe being formed so that on turning ofthe pipe it closes a varying number ofthe apertures in the hollow part.

In a preferred embodiment, side faces of the valve member are shaped aerodynamically, so thatthere is a reduction in air pressure adjacent one or both ofthe faces which assiststheflow dffuel from the openings into the airstream. For example, both faces may be convex oroneside face may be convex and the other concave.

There is also provided according to the invention an internal combustion engine having a carburettor according to the first aspect ofthe invention in combination with a poppet valve for controlling flow of mixture from the carburettorthrough said outlet and meansforguiding the poppet valve for reciprocation along a rectilinear path inclines to a main axis of the carburettor wherein the plane containing the main axis of the carburettor and an axis about which the valve member moves is inclined atan acute angle to the plane containing the main axis of the carburettor and a longitudinal centreline of the path along with the poppetvalve is guided.

According to a further aspect of the invention, there is provided a method of mixing a fluid fuel with air wherein the restriction of a path along which the air flows and the restriction of a path along which the fuel flows are both varied by movement of a single valve member.

FIGURE lisa front view, partly in section, of one form of carburettor according to the invention; FIGURE 2 is a side view, also partly in section, corresponding to Figure 1; FIGURE 3 is a detailed plan view of a valve member ofthe carburettor; FIGURE 4 is a section through the valve member; FIGURE 5,6 and 7 show different arrangements of apertures in a fuel feed pipe and the valve member; FIGURE 8 is an enlarged view of a needle adjuster; FIGURE 9 shows a first modification of the carburettor; FIGURE 10 is a view similarto Figure 1 illustrating modifications ofthe carburettor of Figure 1; FIGURE 11 shows isolated and in perspective view certain components shown in Figure 10; FIGURE 12shows a different perspective view of one ofthese components, the component being partly broken away;; FIGURE 13 illustrates diagrammatically a combination of a carburettor in accordance with the invention and a poppet valve; FIGURE 14 is a cross-section of a part of a valve member ofthe combination shown in Figure 13, the section being in a plane perpendicularto an axis of rotation ofthevalve member; FIGURE 15 is a view along a main axis ofthe carburettorofthe parts shown in Figure 13; and FIGURE 16 is a view similarto Figure 13 illustrating an alternative arrangement.

Referring to Figure 1, there is shown a carburettor 10 comprising an elongate cylindrical tube 11 having a flared open end 12 providing an air inlet and a plain open end 13 providing an outletthroughwhich, in use, an air/fuel mixture passes to one or more combustion chambers of an internal combustion engine. The tube 11 provides a passageway containing a butterfly valve 16.

The valve 16 comprises a valve member 17 in the form of a disc having a diametral sleeve 18 extending through it and mounted forturning on fuel feed pipe 26 extending tranversely of the longitudinal axis of the passageway. Thevalve member isturnable by a radially extending tever 25 attached to the valve member and connected via a cable or rigid link, arany other means, to a control such as an accelator pedal (not shown).

Alternatively, the valve member 17 may be formed of a single piece of material into which fuel passages are drilled and which is keyed on the fuel feed pipe 26.

As shown in Figure 2, the side faces 14, 15 ofthe valve member 17 are each of convex form.

The valve member 17 is turned to vary the restriction ofthe airflow path to regulate the airflow from the air inlet 12 to the outlet 13 by varying the effect cross-sectional area ofthe passageway. When the valve member is in its fully closed position, airflow is nottotallyoccluded buta small residual airflow through the passageway is maintained.

Fuel isfed either by gravity or by a pump from a fuel line 29 into a fuel inlet in the feed pipe 26. When the fuel is supplied under pump pressure, i.e. above float pressure, a system incorporating the carburettor functions as an injector system rather than as a simple carburettor. Injection of fuel into the air stream throughthe carburettor may be intermittent or continuous.

Theterm "carburettor" is used herein genericallyto embrace devices which introduce a fluid fuel into an air stream. In a case where fuel is supplied to the carburettor at substantially constant pressure, this pressure may be derived from a float chamberto which fuel is supplied bya low pressure pump,from a headertube or directfrom a low pressure pump, where a return line which by-passes the pump is provided to convey surplus fuel backto a reservoir.

Thevalve member is provided with a plurality of openings arranged to directjets offuel into the air flowing through the passageway. Therearetwo axially extending rows of openings 27 atthe external surface ofthevalve member at opposite sides ofthe sleeve 18 and a number of openings 28 around the side faces 14, of ofthevalve member.

The sleeve 18 has four rows of apertures 40 therein, two ofwhich communicate directly with the openings 27 and two of which communicate with the openings 28 through drilled or moulded bores 30. The feed pipe 26 also has four rows of apertures 311 arranged to register respectively with the four rows of apertures in the sleeve. The arrangement is that on turning ofthe valve member, the number of apertures of each pair of rows brought into registration is varied and/orthe degree of registration of the apertures is varied.

Figure 5 shows an arrangement in which the apertures 40 in the sleeve of the valve member are small circular apertures disposed in a row parallel to the axis ofthe sleeve and the apertures 31 in the feed pipe are slots of progressively increasing length so that as the valve member is turned from its closed position towards its open position, more apertures come into register with one another.

Figure 6 shows a similar arrangement butwith the apertures 40 at different angular positions.

In Figure 7 the rows of apertures 40 and 31 are both parallel to the common axis of the sleeve and feed pipe and the apertures are all in the form of identical slots whereby, on turning ofthevalve memberfrorn its closed position toward its open position, the degree of registration of each pair of corresponding slots increases.

Thus the rate at which fuel is introduced into the air flow varies accordingto the position of the valve member and hence the rate of flow of air through the passageway. As the airflows past the valve member its convex side faces produce a pressure drop which assists the flow of fuel out of the openings 27,28 by providing a suction effect. Thus, a venturi effect is created in the zones A at opposite sides ofthe valve member.

Referring to Figure 1 ,the sleeve 18 of the valve member 17 is mounted in seals 32 which prevent air/fuel mixture escaping from the passageway 11, and the feed pipe 26 has a threaded sleeve 33 which is engaged with a support 34 on the carburettor.

A needle adjustor 35 is located within thefeed pipe 26,the needle having a threaded end 36 engaged in a screw-threaded bore in a supportS7 on tlxecar- burettorwherebythe needle is tu rnahle-fbr adj ust- ment.

The needle adjuster is shown in detail in Figure 8, the needle having a segmental shaped closure part 38 which can be moved around the interior of the fuel feed pipe 26 byturning the needle to open or closeto a selected degree, a pilot hole dritled in the feed pipe 26 thereby to provide a pilotset.

Although thevalve member 17 has been described as being of double sided convex configuration, it will be appreciated that a valve member of any other suitable aerodynamic shape can be used. Further, for different engine requirements, the arrangement of apertures and/orthe configuration ofthe valve mem bey can be changed to provide the required air/fuel mixture over a range of valve member positions.

For example, as shown in Figure 9, the sleeve 18 of the valve member may be provided with a series of apertures41 extending around approximately one halfofthecircumference ofthesleeveandcommuni- cating with the openings in the valve memberthrough which fuel is introduced into the air stream flowing through the tube 11 (which openings may have the same configuration asthe openings 27,28 or a different configuration), and the end 42 of the feed pipe 26 remotefrom the lever 25 may be formed with a single aperture43 communicating through the bore of the pipewiththe fuel inlet and may be ofangled form so that turning of the va[ve member, it closes a varying number ofthe apertures 41 and hence varies the amount of fuel delivered into the air stream according to the position ofthe valve member.

The carburettor illustrated in Figures 10,11 and 12 comprises a tube 111 which defines the airflow path andwhich may be identical with the tube 11 hereinbefore described. In the tube 111, there is disposed a valve member 117 in the form of a disc having convex faces. The disc is carried on a tube 718, opposite end portions of which protrude from the valve member into bearing openings in walls ofthetube 71.

At one of its ends, the tube 118 communicateswith a fuel feed pipe 126 corresponding to the fuel feed pipe 26 hereinbefore described'. An end portion ofthetube 118 is a sliding fit in an end portion ofthefuel feed pipe, so that the tube 118 can rotate relativeto the feed pipe but the joint between the tube and the fuel pipe is substantially fuel-tight Towards its opposite end, the tube 118 is closed by an inner element in the form of a piston 179. The piston can slide alonng the tube to obscure apertures 140 provided in the sleeve and corresponding to the apertures 40 hereinbefore described.

The tube 1 18is mounted in oris integral with a hollow housing 122 which lies outside the tube 111 and is supported by a bracket 123 for rotation about the axis of the tube 118, which is perpendiculartothe axis of the tube 111. The bracket 123 is fixed on the outside ofthetube 111. The housing includes an actuation lever 127 which, when the carburettor is in use, is connected with a control wire or control rod and by means of which the housing, the tube 118 and the valve member 117 can be turned together relative to the tube 111 through a range of 90".

A dog 128 projects from the internal surface ofthe housing 122 into a cam slot 129 formed in the metering piston 11 9.This cam slot extends somewhat morethan 90 around the axis ofthe metering piston and along the piston so that relative rotation of the housing and piston causes relative axial displacement. Rotation ofthe metering piston 119 with the housing 122 is prevented by a pin 130 on the bracket.

123 which projects into an axially extending, rectilinear slot 131 formed in the external surface ofthe metering piston. The dog 130 permits axial sliding of the metering piston relative to the bracket but prevents rotation of the piston relative to the bracket. It will be noted that the portion of the metering piston in which the slots 129 and 131 are formed has a diameter several times that of the part of the metering piston which is disposed inthetube 118.

Different samples of carburettor can have cam slots 129 of respective different forms selected according to the required variation of fuel flow rate with airflow rate.

It will be understood that rotation ofthe valve member 117 in the tube 111 is necessarily accompa- nied by longitudinal movement ofthe metering piston 119 relative to the tube 118 and therefore adjustment ofthe number of apertures 140 which are open. The rate offlowoffuelthroughthe valve member 117 into the tube 111 is adjusted automatically in accordance withthe rate offlow ofairthrough the tube 111 As shown, the tube 111 maycomprisetwo parts, 132 and 133, which cooperate with each otheratajoint situated adjacenttothe bearingsforthetube 118. This joint may be a screwedjoint.

A needle adjustor as hereinbefore described may be provided within the feed pipe 126.

In each embodiment of the invention herein described, the valve member may comprise a hollow, two-part body with at least some of the openings 27 and 28 being defined between the parts, or defined by respective jet elements mounted between the two body parts. In a casewherethe body ofthe valve member supports jet elements through which fuel is discharged into the air stream, the relation between the airflow rate and fuel flow rate through the carburretorcan bevaried by substituting for one or more jet elements alternative jet elements with openings of different size.

In a case where the valve member has a one-piece body provided with bores along which the fuel flows, jet elements may be screwed or otherwise fitted into counter bores atthe outer ends of the bores.

In Figure 13, there is illustrated a carburettor having a poppet valve 240 for controlling the flow of a mixture of air andfuel through an outlet of the carburettor. The general arrangement and construction ofthe carburettor may be as herein before described with reference to Figures 1 to 9 or as hereinbefore described with reference to Figures 10,11 and 12. For convenience of illustration, only the tube 211 which defines the air inlet and the outletofthe carburettor and the valve member 217 are shown in Figure 13. The poppetvalve is guided by a valve guide 241 for reciprocation along a rectilinear path having a centreline 242 defined by the guide.The guide is fixed with respect to the tube 211 and protrudes into the interior ofthattubeata position downstream ofthevalve member 217. Known valve gear (not shown) may be provided for operating the valve. It will be noted that the centreline 242 is inclined at an acute angle to a main axis 243 of the tube 211, which main axis extends through the centre ofthe air inletto the carburettor and through the centre oftheoutletfrom the carburettor.

Figure 15 is a plan view ofthe parts shown in Figure 13. From Figure 15, it can be seen that the plane 244 containing the main axis 243 and the axis about which the valve member 217 can pivot is inclined at an acute angle to the plane 245 containing the main axis 243 and the centreline 242 defined by the valve guide 241.

This inclination improves the distribution ofthe flow through the outletfrom the carburettor and may be as small as a few degrees or as large as 90". The outlet may lead directly into the combustion chamberofan engine.

The valve member 217 comprises a main body 246 and a flap 247 at one edge ofthe main body. The main body and the flap together have a shape similarto that ofthevalve member 17. The structureofthe main body is similarto that ofthe valve member 17. Thus, the main body 246 definesfuel-flow passages (not shown) leading from a central fuel pipe (not shown) to openings at the surface ofthe valve member.De mountable jet elements may be provided in these passages, The flap 247 is connected with the main body 246 for angular movement relative thereto about an axis 248 which extends through the main bodyadjacenttothe flap.As illustrated in Figure 14, the flap can pivot from a position into which it is urged by a spring 249 and in which it is arranged symmetrically with the main body part 246, to a position in which it is offsettowards one majorface of the main body part.

Control means is provided for controlling pivoting oftheflap 247 relative to the main body part 246 in accordance with pivoting of the main body part about the axis ofthe valve member. The valve member is provided with a metering piston 219 corresponding to the metering piston 119 hereinbefore described and illustrated in Figures 10 and 11. However, the metering piston 219 has at a position spaced axiallyfrom the fuel flow passages a circumferential recess 251 which extends a part ofthe way around the axis 250.

Opposite ends ofthe recess are defined by a cam formation 252. The control means for the flap 247 includes a control rod 253 slidably mounted in a rectilinear passage formed in the main body part 246 and having one end which is disposed in the recess 251, when the valve member 217 occupies a closed position in the tube 211. An opposite end of the control rod lies adjacent to an operating lever 254 on the flap.

When the valve member 217 is pivoted aboutthe axis 250 from its closed position to its fully open position, the control rod 253 is engaged by the cam formation 252 and driven out of the recess 251, towards the flap 247. This movement of the control rod is transmittedto the flap atthe lever254to pivot theflap about the axis 248 againstthe action ofthe spring 249.

When the valve member 217 occupies its fully open position, the flap 247 is offsetf rom the main body 246 ofthe valve member somewhat towards the side of the tube 211 atwhich the valve guide 241 is disposed.

Theflapthen deflects the mixture of fuel and air which flows towards the outlet ofthe tube 211 so that the flow is distributed more evenly around the periphery ofthe valve 240 than would be the case iftheflap 247 were omitted.

Figure 16 illustrates an alternative to the pivoted flap 247 which achieves similar results. The valve member317 shown in Figure 16 may be substituted forthe valve member 217 in the arrangement of Figure 13. One marginal portion ofthevalve member 317 is offset relative to the remainder of the valve member somewhat in a direction which, when the valve member is in its fully open position, is towards that side ofthetube 311 atwhich the valve guide is disposed. The profile of the valve member 317 is similarto that presented collectively by the main body portion 246 and flap 247 ofthe valve member 217, when the latter is in itsfullyopen position.When the valve member317 is partly open, the offset marginal portion has a lesser effect on theflow of air and fuel through the tube 311 than is the case when the valve member is in its fully open position.

The offset marginal portion ofthevalve member 317 may have a compound curvature. This valve member and both partsofthe valve member 217 may be formed of polytetrafluorethylene.

The valve member is preferably mounted, as itiustratedrfor pivoting about an axis which intersects the main axis of the carburettor,that is an axis extendingthrough the centre ofthe air inlet and through the centre ofthe outlet. Alternatively, the valve member may be mounted for movement about an axis which lies to one side of the main axis, for example an axis which is nearto a tangentto an internal surface ofthe main tube of the carburettor.

Thattu be may be formed with a recess at one side to acommodate a part of the valve member, when the valve member is in a fully open position. The sleeve of the valve memberfor containingthe fuel feed tube would be disposed near to an edge ofthevalve member. The valve memberwould define passages similar to those hereinbefore described for leading fuel to openings at the surface of the valve member, from which the fuel is discharged info the air stream.

Thevalve memberalso may be provided with a flap for modifying theflow of air. The main tube ofthe carburettor may be formed to define with the valve member, when in the fully open position, aventuri throat adjacent to the valve member.

It will be appreciated that a carburettor in accordance with the invention requires only one control line, in contra distinction to a conventional fuel injection system wherein a first control line is required for controlling a butterflyorotherairvalve and a second control line is required for controlling afuel nozzle.

Claims (15)

1. A carburettor having means defining an air inlet, a fuel inlet and an outletfor a mixture of fuel and airand havingamovablevalvememberforregulating the flow of airfrom the air inlet to the outlet, wherein the valve member has at least one opening which is in communication with thefuel inletfor discharging fuel into an air stream which flows pastthevalve member in use.

2. A carburettor having means defining an air inlet, a fuel inlet and an outletfor a mixture of fuel and air and having a movable valve memberforregulating the flow of airfrom the air inletto the outlet, wherein there is provided control means for controlling the degree of constriction of a fuel flow path from the fuel inlet to the outlet in accordance with the movement of the valve memberto regulate the flow of air.

3. AcarburettoraccordingtoCtaim 1 further comprising means defining a fuel flow path from the fuel inletto the opening in the valve member and control means for controlling the degree ofconstric- tion of said fuel flow path in accordance with movement ofthe valve memberto regulate said flow of air.

4. Acarburettoraccording to Claim 3 having a main axis extending through the air inlet and through the outlet and wherein the valve member is mounted for turning about a further axis transverse to the main axis.

5. A carburettor according to any one of Claims 1, 3 and 4wherein the valve member has a plurality of said openings.

6. Acarburettor according to Claim 5 wherein the openings are distributed over an upstream part and a downstream part of the surface of the valve member.

7 A carburettor according to any preceding claim wherein the valve member has aerodyna-micaiy shapedfaces.

8. A carburettor according to any preceding claim further comprising means defining a pilotjet through which fuel can flow from the fuel inlet towards the outlet, afeed pipe leading from the fuel inletto the pilotjetanda needle adjustor in the feed pipeto control the flow of fuel to the pilot jet.

9. A carburettor according to any preceding claim wherein the valve member comprises a main body, a flap mountedfor limited movement relative to the main body and means for adjusting the angular relation oftheflaptothe main body in accordance with movement ofthe valve member as a whole relative to said means definingthe outlet.

10. The combination comprising a carburettor according to Claim 4, a poppet valve forcontrolling flow of mixture from the carburettorthrough said outlet and means for guiding the poppet valve for reciprocation along a rectilinear path inclined to said main axis and defining a longitudinal centreline of said path, wherein the plane containing the main axis and said further axis is inclined atan acute angleto the plane containing the main axis and said centreline.

11. A method of mixing a fluid fuel with air wherein the restriction of a path along which the air flows andthe restriction of a path along which thefuel flows are both varied by movement of a single valve member.

12. Acarburettorsubstantiallyas hereinbefore described with reference to Figures 1 to 4 ofthe accompanying drawings.

13. Acarburettoraccording to Claim 12 modified as herein described with reference to and as shown in any one of Figures 5,6,7 and 9 of the accompanying drawings.

14. A carburettor substantially as herein described with reference to Figures 10, 11 1 and 12 of the accompanying drawings.

15. Any novel feature or novel combination of featuresdisclosedhereinand/orshown intheaccompanying drawings.