EP0361600B1 - Atomiser for the carburettor of a combustion engine - Google Patents

Description

The present invention relates to a sprayer for the carburetor of an internal combustion carburetion engine, comprising means for the automatic correction of the composition (dosage) of the mixture delivered according to the different operating conditions of the engine.

It is known that an elementary carburetor, comprising a Venturi tube diffuser through which the air sucked in by the engine passes, a gasoline sprayer arranged in the restricted section of the diffuser, a constant level tank supplying gasoline to the sprayer, and a calibrated nozzle (fuel nozzle) arranged between the tank and the sprayer, delivers to the engine a mixture of air and gasoline whose composition is not constant but is enriched when the flow of l the air drawn in by the engine increases. Various devices have been proposed to automatically correct this change in the composition of the mixture delivered. Among these proposed devices, a so-called air brake device has often been used, which comprises, between the fuel nozzle and the sprayer, a small well in which is immersed a blind tube having perforated walls, which at its upper end communicates with the atmosphere through a second calibrated nozzle (air jet). By this arrangement, the sprayer sucks, with the gasoline which passes through the gasoline nozzle, air which is sucked in by the air jet and leaves through the perforations of the tube. This air opposes the passage of petrol through the small well, a resistance which increases when the flow rate increases, so that, at least within certain limits, the desired correction is obtained during operation under stationary conditions. However, this device has drawbacks. It carries a considerable complication to the structure of the carburetor and it is quite expensive in its construction; its adjustment is difficult and does not allow a complete correction to be obtained; it is difficult to access its parts even simply for cleaning. The device mentioned also has a favorable action under transient operating conditions, namely during accelerations, because the tube immersed in the small well has a reserve of gasoline which can be sucked up quite easily, not being braked by the fuel nozzle but only through the perforations in the tube. However, this effect is not sufficient in practice, so that in most cases it is also necessary to provide an acceleration or recovery pump.

An improvement to this state of the art has been carried by document US-A-2,346,711, which describes a device which corresponds substantially to the classification part of claim 1, according to which a sprayer comprises a flow nozzle, a first dip tube in a tank with constant fuel level and provided with a fuel nozzle, and a second tube plunging into the tank with constant fuel level, surrounding the first pipe and determining a gap therefrom, second tube being closed at its lower end by a bottom traversed by a calibrated hole, and being provided with openings which pass through it at a level higher than the constant level of filling of the tank.

By these characteristics, the level of petrol which is established, in operation under stationary conditions, in the gap between the two tubes, is reduced when the petrol flow increases and, like the load applied to the fuel nozzle depends on this level, an antagonistic effect is obtained with the tendency to enrich the mixture supplied to the engine, when the latter's speed increases. However, no means is provided to promote the mixing between air and petrol and the vaporization of petrol.

The main object of the present invention is to provide a sprayer in which the automatic correction of the composition of the mixture cut must be carried out in a particularly rational and efficient manner, while allowing a very simple structure, any part of which must be easy to access, both for adjustment and for cleaning, particular means being provided to promote as much as possible the mixture between air and petrol and the vaporization of the latter.

This main object is achieved, according to the invention, in that said first tube comprises an atmospheric air intake provided with an air jet, and it has inside a dividing wall defining a section which communicates with said air jet and which extends downwards into said first tube, and a section (9) which communicates with said flow nozzle (1).

By this characteristic, air is sucked with the gasoline and it is led by said dividing wall to bubble in the sucked gasoline, thus favoring as much as possible the mixture between air and gasoline and the vaporization of the gasoline.

Preferably, in addition, said first tube also comprises at its upper end a second atmospheric air intake provided with an air jet, which communicates with said section (9) of the first tube (4). This nozzle presents itself as another element that can be adjusted for adjusting the dosage.

Yet another object of the invention is to improve a sprayer as defined above, so as to give it in operation in transient conditions indeed so favorable to make unnecessary the installation of an acceleration pump.

This further object of the invention is achieved in that said dividing wall extends downwards over more than half of the extension of the first tube.

By this characteristic, the section delimited in the first tube and communicating with the air jet forms a reserve of fuel which can be sucked up without appreciable resistance when the shutter of the diffuser is opened to pass from an operation at minimum speed to normal operation, so that it temporarily enriches the mixture supplied to the engine during the acceleration phase, by replacing the function normally entrusted to a recovery pump.

• Fig. 1 montre en section verticale et à une échelle quelque peu agrandie le pulvérisateur suivant l'invention, immergé en une cuve à niveau constant représentée seulement en partie, et s'ouvrant dans la section restreinte d'un diffuseur à tube de Venturi;
• Fig. 2 montre une vue en plan du diffuseur représenté dans la figure 1; et
• Fig. 3 montre le même diffuseur décomposé dans ses parties constituantes.

These characteristics and others and the advantages of the subject of the invention will emerge more clearly from the following description of a complete embodiment of the invention, and which is shown diagrammatically in the appended drawing, in which:

• Fig. 1 shows in vertical section and on a somewhat enlarged scale the sprayer according to the invention, immersed in a constant level tank shown only in part, and opening in the restricted section of a Venturi tube diffuser;
• Fig. 2 shows a plan view of the diffuser shown in Figure 1; and
• Fig. 3 shows the same diffuser broken down into its constituent parts.

Referring to Figure 1, the letter V denotes a tank, closed above by a cover C, in which, by arrangements well known per se and which are neither described nor shown here, a constant level L of gasoline is maintained . The letter D designates a diffuser intended to be connected to the suction manifold of a carburetion engine to be traversed by the aspirated air, flowing in the direction shown by the arrow F. The diffuser D is shaped like a tube of Venturi and it has a restricted section R. In this restricted section R is arranged the flow nozzle 1 of the sprayer. In the embodiment shown, this nozzle is curved by 90 ° and it is connected to a coupling sleeve 2 which passes through a corresponding hole in the wall of the diffuser D to connect to the other parts of the sprayer. However, this arrangement, which is advantageous from the point of view of construction, is not necessary, and the flow nozzle 1 could also be manufactured in one piece with other parts of the sprayer.

Outside the diffuser D, the sprayer has a first tube 4 which passes through the cover C of the tank V and plunges into the latter. The tube 4 has a lateral connection 5 to which is joined the coupling sleeve 2 of the flow spout 1. At its lower end, the tube 4 carries a calibrated nozzle 13 constituting the fuel nozzle of the sprayer. In the form shown, the vertical tube 4 also extends upwards by a section 6 which opens into the atmosphere and carries at its upper end a calibrated nozzle 14 constituting an air jet. In addition, the tube 4 has a connector 7, opposite the connector 5, which opens to the atmosphere and carries a calibrated nozzle 15 constituting an air nozzle. The vertical tube 4 is subdivided inside by a dividing wall 8 which extends over part of its height, dividing the tube 4 into a section 9 communicating with the flow nozzle 1 and with the air jet 14, and a section 10 communicating with the air jet 15. The tube 4 finally carries, on the outside, a pair of flanges 11 and 12. It has been specified that the parts 6, and 14 relate to the particular shape shown, because they are not necessary to achieve the main object of the invention, so it can also be assumed that they are lacking in simplified embodiments. In these simplified forms the tube 4 should be blind in correspondence with the lacking nozzle.

The sprayer finally comprises a second tube 16 plunging into the tank V, the upper end of which is joined to the flanges 11 and 12 and communicates with the atmosphere of the tank V, above the filling level L, through openings 17 The lower end of the tube 16 is closed by a bottom 18 in which a calibrated hole has been formed 19. The internal diameter of the tube 16 is somewhat larger than the external diameter of the fuel nozzle 13 mounted on the end bottom of tube 4. Between tubes 4 and 16 there is a gap 20.

To clarify the essential operation of the device, it will first be assumed that the air nozzles 14 and 15 are closed, which corresponds to the absence of the parts 6, 7 and 8 of the tube 4 which, in this case, would be blinded above .

When the diffuser D is not traversed by a flow F of aspirated air (i.e., when the engine is stopped, or else in operation at minimum speed, with the suction shutter closed), none suction is not exerted on the flow nozzle 1, and the sprayer does not deliver gasoline. In this condition, in the gap 20 between the tubes 4 and 16, which communicates with the tank V, below through the calibrated hole 19 and above through the openings 17, a fuel level is established which (unlike the level M which is represented in FIG. 1) corresponds to the level L of filling of the tank V.

When, on the contrary, a flow of aspirated air F passes through the diffuser D, a suction is exerted on the flow nozzle 1, which is located in the restricted section R of the diffuser D, and by the action of this suction a certain fuel flow is sucked from the tank V, through the calibrated hole 19, the fuel nozzle 13 and the tube 4, and it is sprayed into the diffuser D through the flow nozzle 1. This fuel flow being subjected to a pressure drop due to the constriction represented by the calibrated hole 19, in the gap 20 a level of petrol M is now established which (precisely as shown in FIG. 1) is lower than the filling level L of the tank V, and more precisely it is all the lower the greater the flow of gasoline through the calibrated hole 19. Consequently, the fuel nozzle 13 of the sprayer (which determines the flow rate of fuel aspirated, as a function of the vacuum existing in the restricted section R of the diffuser D and as a function of the hydraulic load to which it is subjected) no more subject, as in known carburetors, to a constant load corresponding to the level L of filling of the tank V, but to a variable load corresponding to the level M of the petrol in the gap 20, which level decreases with the increased air flow drawn in by the engine. This effect is antagonistic to the tendency of the flowed mixture to get richer when the flow of the aspirated air increases, and therefore, as we includes, an appropriate proportioning of the different parts of the sprayer, and in particular of the fuel nozzle 13 and of the calibrated hole 19, makes it possible to achieve the course considered most suitable for the composition of the mixture delivered, according to the engine speed.

In addition, the content of the gap 20 also introduces a favorable effect in the operation at a transient regime, be it acceleration or deceleration. Indeed, during an acceleration the level M in the gap 20 must be reduced from the higher level corresponding to the initial speed of the engine to the reduced level corresponding to the higher final speed, and all the quantity of petrol which corresponds to this level variation is debited to the motor in addition during the acceleration phase. On the contrary, during a deceleration, the level M in the gap 20 must rise from the level corresponding to the initial speed of the engine to the higher level corresponding to the reduced final speed, and all the quantity of petrol which corresponds this level variation is subtracted from the motor supply during the deceleration phase. This behavior is favorable both in terms of performance and in terms of economy, and its intensity can be adjusted by appropriately choosing the capacity of the gap 20.

Now taking into consideration the presence of the secondary air jet 15, communicating with the section 10 of the tube 4 divided by the wall 8, it is noted that, by the effect of the depression which is established in the tube 4, a certain amount of air is sucked by the nozzle 15, descends in section 10 of the tube 4 and goes back in section 9 with the gasoline, bubbling in the latter and promoting its vaporization. In this way the spout 1 flows into the diffuser D of the gasoline already partly mixed with air and vaporized, to the advantage of the homogeneity of the mixture which finally forms. In addition, the presence of the air jet 15 introduces an additional element which can be adjusted to obtain the metering conditions considered most suitable. This effect can also be achieved with an extension relatively reduced towards the bottom of the dividing wall 8. When there is the air jet 14, air is sucked through it too, and this air mixes in the flow nozzle 1 with the mixture already formed by gasoline and air; this introduces yet another element for adjusting the dosage.

A significant effect can be obtained by the structure described if the dividing wall 8 extends downwards over a substantial length in the tube 4, say more than half of the extension of the tube. When the engine is running at minimum speed, and therefore there is no suction through the sprayer, the two sections 9 and 10 of the tube 4 are both filled with petrol up to level L filling the tank V. When, then, the engine is accelerated, and the flow of gasoline through the nozzle 1 begins, all the gasoline contained in section 10 is sucked up without encountering any resistance, because it does not must cross no nozzle, hole or restricted section, before the suction of air by the nozzle 15 begins. In this way a significant additional quantity of petrol is positively supplied to the engine during the acceleration phase, making the installation of an acceleration pump superfluous. The importance of this effect can be proportional to the actual needs by appropriately dimensioning the capacity of the section 10 of the tube 4. In addition, the delivery to the engine of said additional quantity of petrol is more efficient than the injection of '' an equal amount of gasoline carried out by a usual recovery pump, because this latter injects the fuel under a very reduced pressure, and therefore without it being able to spray and vaporize in an effective way, so that it cannot be used in the best way. On the contrary, the additional quantity of gasoline delivered by the sprayer according to the invention is sucked through the flow nozzle 1 located in the restricted section of the diffuser D, and therefore in the best mixing conditions.

As can be seen, even in its most complete embodiments, such as the mode which has been described and which is represented in the drawing, the sprayer according to the invention is compact and simple in construction, and all of its parts can be easily accessed for adjustment and for cleaning.

Of course, various modifications, in addition to those which have already been explained in the course of the description, can be brought to the device described and illustrated. The fuel nozzle, which it is advantageous to apply to the lower end of the first tube, could nevertheless be applied in any other place of this tube or of the flow nozzle. The bottom of the second tube, provided with a calibrated hole, could be replaced by a real nozzle. The first tube with dividing wall, which represents a suitable embodiment, could be replaced, with the same function, by a U-tube having a lower opening for the entry of gasoline. The characteristics of the invention, exposed in their application to a sprayer intended to feed the feed in the normal operation of the engine, can also, all or part of them, find application in a sprayer intended to provide the power supply in operation at minimum speed or in the start-up period (choke).

Claims (6)

1. A jet for the carburetor of a gasoline internal combustion engine, including means for automatically correcting the composition of the mixture which is delivered in the different operation conditions of the engine, comprising a delivery spout (1), a first tube (4) which plunges in a bowl (V) having a constant fuel level (L) and is provided with a fuel nozzle, (13), and a second tube (16) which plunges into the constant level fuel bowl (V), surrounds the first tube (4) and forms a gap (20) with respect to the same, this second tube (16) being closed at the lower end thereof by a bottom (18) traversed by a calibrated hole (19), and being provided with through apertures (17) located at a level higher than the constant level (L) of the fuel bowl (V), characterized in that said first tube (4) has an air intake (7) provided with an air nozzle (15) and it is generally provided with a dividing wall (8) which delimites a section (10) communicating with said air nozzle (15) and extending downwards within said first tube (4), and a section (9) communicating with said delivery spout (1).

2. A jet as set forth in Claim 1, characterized in that said first tube (4) plunging in the bowl further has at its top end a second air intake (6) provided with an air nozzle (14), which communicates with said section (9) of the first tube (4).

3. A jet as set forth in Claim 1, characterized in that said dividing wall (8) extends downwards for more than a half of the length of the first tube (4).

4. A jet as set forth in the foregoing Claims, constructively characterized in that it comprises a first body (4-8) including the first tube (4) with the inner dividing wall (8), the air intakes (6 and 7) and a delivery union (5), a second body formed by the second tube (16), and the calibrated nozzles (13-15) mounted on said two bodies (4-8 and 16).

5. A jet as set forth in Claim 4, characterized in that said delivery union (5) carries a separately manufactured delivery spout (1), intended to be placed within the restricted cross section (R) of the choke of a carburetor (D).

6. A jet as set forth in Claim 4, characterized in that said first body (4-8) also has a pair of outer flanges (11,12) intended to connect the second body (16) to the first body (4-8).

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