EP0013842A1 - Device for controlling the air-fuel ratio of a carburettor mixture during transition from idle to normal running - Google Patents

Abstract

The invention relates to a device for admitting additional air or gas into the idling well 20 of a carburettor when the throttle 14 is in the vicinity of the progression 24 and idling 25 ports in the partial opening position. A circuit parallel to the air calibrator 21 and terminating, for example, at a hollow adjusting screw 30 is controlled by an adjusting member 50, such as a valve, the movable shutter of which is actuated, for example, by a linkage 55 coupled to a throttle on the one hand and to a differential pressure gauge on the other hand or by means of a stepping motor 58 coupled to a pulse generator 59 controlled by a microprocessor receiving information from various sensors C1 to Cn. This device makes it possible positively to control the relative vacuum in the idling well and consequently the airflow through the calibrator and thus the flow of fuel sucked up by the nozzle, in order to keep substantially constant the richness of the mixture supplied to the engine during transitions between idling and normal running. <IMAGE>

Description

The invention relates to a device for regulating the richness of the fuel mixture produced by the supply carburetor of an internal combustion engine and controlled ignition during the transitions between the idle speed and normal running, and in particular when the butterfly masks or unmasks a port of progressiveness connecting the carburetor chamber to the idle well.

It is known that when the engine rotates at a speed below a certain limit, the vacuum prevailing in the nozzle is insufficient to prime the main jet of the carburetor, even if the throttle valve is ajar or wide open. We also know that at low depressions, the mixture tends to be too rich, due to the very different specific masses of air and gasoline.

To overcome the first drawback, all modern carburetors are provided with an auxiliary device ensuring the supply of the engine at low rotational speeds, and in particular at idle when the throttle is closed (cf. for example the book "The engines" by Messrs. Ménardon & Jolivet, Editeurs Chotard & Associés, new edition 1977) This idling device comprises a well made in the body of the carburetor, at the top of which open a nozzle of air called calibrator and an idling jet, generally supplied with main jet bypass; the bottom of the idle well communicates with the carburetor chamber through a hole opening below the butterfly valve formed and the passage section of which is controlled by a screw-point at the adjustment of the mixing flow, and in corollary manner of its richness. This vi3 is regulated so that the engine receives a mixture of medium richness at idle.

At the start of the throttle opening from idle speed, the debris on the one hand is relatively low since the engine rotates slowly, and on the other hand is mainly located at the throttle level. The main jet of the carburetor cannot therefore come into play and the engine must be supplied by the idling device alone. As the mixing flow allowed by the adjusting screw is insufficient under these conditions, there is provided between the idle well and the carburetion chamber a free communication established by one or more orifices called progressivity or bypass which come into play as soon as the throttle discovers them, thereby providing the engine with additional mixing flow.

The opening of the throttle continues and the engine accelerating as a result, the vacuum on the one hand increases in absolute value and on the other hand is gradually transferred to the nozzle and initiates the main jet, which can therefore take the motor supply relay.

During this transition between idle speed and normal operation, the auxiliary device is therefore subjected to a vacuum which increases firstly to a maximum value, obtained when the progressiveness produces its full effect, then decreases until '' to a negligible value as soon as the throttle is wide open and the pressure drop in the gas stream occurs mainly at the nozzle.

These variations in the relative vacuum prevailing in the idle well on the one hand correspond to those of the vacuum in the intake manifold of the engine, but on the other hand are accentuated by the fact that the overall passage section of the orifices of idle and progressiveness varies depending on the angular position of the throttle, while that of the air calibrator is invariable by construction. This fact introduces a first cause of non-linearity in the operation of the device.

In addition, since the air calibrator is therefore the site of very variable pressure losses, the speed of the air flow passing through it and consequently the flow of fuel sucked into the idle jet vary considerably and not proportional, not only because of the large difference in the specific masses of the two fluids concerned, but also because of the intrinsic properties of the calibrator-nozzle assembly. This results in additional causes of non-linearity of operation of the device.

In total, it follows that the richness of the mixture supplied to the engine is in practice excessive throughout the transition phase, and in proportions varying according to a complex law depending on the many parameters involved, relating to the engine - for example its speed of rotation and its temperature -, to the carburetor - for example the angular position and the direction of movement of the butterfly - and to the operating conditions - for example the pressure and the temperature of the ambient air, even its hygrometric level.

In order to at least partially compensate for the overall excess of the richness of the mixture during the transition phase concerned, it is certainly known - for example by French Patent No. 2,384.11B of which the Applicant is the Holder - to dilute it by admission an additional air flow depending on the depressions prevailing in the idle well and / or in the intake manifold. The air thus injected - indifferently into one or the other of these circuits - acts as additional oxidizer to correct the excessive richness in fuel of the mixture produced by the calibrator-idle jet assembly, whose nonlinear behavior does not is that incidentally modified in certain embodiments envisaged, as demonstrated by the comparison of FIGS. 2 and 3. On the contrary, it will be noted that in the case of FIG. 2, if the air were replaced by any gas devoid of oxygen - for example taken from the exhaust - the richness of the mixture would remain unchanged.

It has also been known for a long time - for example by French Patent N ° 1,026,466 requested on October 24, 1950 - to neutralize the auxiliary idling device by free admission of additional air as soon as the engine speed exceeds a predetermined value . In this case, the admitted air acts by dynamic effect by suppressing any suction of fuel by the idle jet. However, such an action can only take place after the ignition of the main carburetor jet, otherwise the engine would be exposed to a supply "hole".

The present invention aims to achieve a regulating device capable of ensuring a near-perfect correction of the richness of the mixture supplied to the engine during the entire transition phase between the idle speed and normal running, taking into account all the desirable operating parameters, by selective and controlled admission of an air flow or other additional gas acting by dynamic effect to correct the non-linear behavior of the calibrator-nozzle assembly of the idling circuit at partial loads.

The regulating device according to the invention is essentially characterized in that it comprises a semi-parallel circuit for admitting air or other gas, which opens into the idle well downstream of the associated calibrator and nozzle but upstream of the idle and progressive openings connecting it to the carburetor chamber, this circuit comprising a raglage member whose passage section is controlled by at least one of the engine operating parameters in order to positively modulate the relative depression prevailing in the idle well, and consequently the air flow passing through the calibrator and therefore the flow of fuel sucked in by the nozzle, thus maintaining the richness of the mixture supplied to the engine substantially equal to its optimum value during the aforementioned transitions.

In other words, the air or gas flow admitted into the idle well through this device essentially serves as an agent or tool for dynamically controlling the behavior of the calibrator-nozzle assembly by acting on the vacuum in the idle shaft. Indeed, when the butterfly opens and unmasks the openings of progressiveness, the strong depression prevailing in the intake manifold is freely transmitted inside the idle well. The mixing flow rate, originally limited by the section of the idle orifice controlled by the wealth screw, then suddenly increases to increase the engine speed until the main carburetion system is started. However, the idling system designed to operate under a low depression in the well (a few tens of grams) reacts in a non-linear manner when it is subjected to high depressions (a few hundred grams), the air calibrator being faster saturated than the idle jet, whose fuel flow then increases faster than the air flow from the calibrator. It is therefore during this transitional phase that the richness of the mixture is highest, as shown by the analyzes of the pollutants emitted during a standardized operating cycle.

The device according to the invention makes it possible to effectively control the richness of the mixture supplied during this phase, thanks to the choice of the air or gas injection point (a parallel circuit with the calibrator but in series with the idle orifices and progressiveness) and to the controlled modulation of the additional flow injected, which make it possible to reduce the relative vacuum in the idle well and thus subject the calibrator-nozzle assembly to operating conditions such that the flow of fuel sucked is less for a unchanged final mixing flow.

The admission of air or gas provided for this purpose by the device of the invention can be carried out by materially different but topologically equivalent routes, depending on whether this device constitutes an adaptation to an existing carburetor or else is integrated into a new one. carburetor during its conception. In the first case, the injection can conveniently be done through the wealth screw specially arranged for this purpose, or even by passages provided for example in an isolation flange separating the main body of the carburetor from its foot including the butterfly , or else under a judiciously fitted one-piece calibrator-nozzle assembly.

Of course and in all cases, it is important that the injection of air or gas into the idle well takes place as indicated, downstream of the system for preparing the primary mixture, which is generally too rich to correct operation without disturb it by plug effect or by dynamic oscillation.

For this particular purpose, it is necessary that the gas flow injected by the device is effectively and precisely controlled. For this purpose, it is obviously preferable that the passage section of the circuit is at any point at least equal to that of its adjusting member at full opening. It is above all essential that the effective passage section of this member be modifiable according to a predetermined law as a function of the combination of the operating parameters of the engine taken into account.

To do this, the adjusting member can be provided with a movable or deformable shutter member - for example and respectively a valve or a diaphragm, a needle shaped to a flattened sleeve - whose displacement or deformation is effected by the action of mechanical, pneumatic and / or electromechanical control means coupled to mobile members, fluid circuits and / or sensors translating the parameters to be taken into account. These parameters can be combined by any appropriate internal means - for example the regulation law specific to the regulating member - or external, such as a simple linkage or a differential cylinder, and in particular using a microprocessor programmable according to the characteristics of the vehicle and / or its traffic conditions.

• La Figure 1 montre en coupe partielle schématique un carburateur équipé d'un dispositif régulateur à commande intrinsèque, dont le fonctionnement est illustré par les schémas de la Figure 2;
• La Figure 3 montre ce même carburateur équipé d'un autre dispositif régulateur à commandes extrinsèques combinées, dont le fonctionnement est illustré par les schémas de la Figure 4;
• Les Figures 5 et 6 montrent deux autres agencements possibles pour l'injection d'air dans le puits de ralenti; et
• Les Figures 7 et 8 représentent deux organes de règlage du débit d'air injecté.

In the latter case in particular, the control of the regulating member can be done by means of electrical pulses causing either the moving step by step of a movable shutter, or its alternating opening and closing, for example at constant recurrence frequency and variable duty cycle, respectively applied to a reversible stepping motor or to a simple electromagnet, from a generator controlled directly by the sensors or else controlled by the microprocessor processing the information coming from these sensors. Other characteristics and advantages of the invention will appear more clearly on reading the detailed description which follows of the various nonlimiting examples of implementation illustrated by the appended drawings, in which:

• Figure 1 shows in schematic partial section a carburetor equipped with an intrinsically controlled regulating device, the operation of which is illustrated by the diagrams of Figure 2;
• Figure 3 shows this same carburetor fitted with another regulating device with combined extrinsic controls, the operation of which is illustrated by the diagrams in Figure 4;
• Figures 5 and 6 show two other possible arrangements for injecting air into the idle shaft; and
• Figures 7 and 8 show two regulating members of the injected air flow.

The inverted carburetor with single body shown schematically in Figures 1 and 3 (in particular, the relative proportions of its organs are not respected for better readability of the drawing) essentially comprises a tubular body of light alloy delimiting a vertical carburation chamber 10 , in which are arranged from upstream to downstream (or from top to bottom in the drawing) a nozzle 11 forming a venturi around an axial assembly 12 for suction and spraying of fuel coming from a conduit 13 of the main nozzle and the constant-level tank (name shown), then a butterfly 14 carried by a transverse axis 15 coupled to the accelerator pedal.

In a lateral dependency of the body of the carburetor, an idle well 20 is arranged, comprising from top to bottom an air nozzle or calibrator 21, an idle jet 22 supplied by a channel 23 connected in bypass to the conduit 13 (said carburetor monojet), and finally a progressive opening 24 and an idle opening 25 which both open into the carburetor chamber 10, respectively on either side of the butterfly 14 in the closed position. The passage section of the idle orifice 25 is controlled by an adjusting screw 30.

The arrangement of the carburetor described and illustrated is conventional, and its operation well known: the rotation of the engine creates a depression in its intake manifold 16, at the end of which the carburetor is mounted. When the butterfly 14 is widely open, this depression induces a high flow of air sucked into the atmosphere - and therefore at normal pressure - through a filter (not shown) for example mounted directly on the nozzle 18 of the carburetor. As it passes through the nozzle 11 the air speed increases, creating a local depression which ensures the suction and the spraying by the main supply assembly 12 of a fuel flow rate substantially proportional to the flow rate of air. The engine consequently receives a combustible mixture of substantially constant richness.

Under these normal engine operating conditions, the vacuum prevailing in its intake manifold 16 and in the downstream portion of the carburetion chamber 10 is low, since the widely open throttle valve 14 hardly hinders the flow of the air-mixture. fuel. This vacuum is also low when the engine is idling, the butterfly 14 then being closed, as shown. In these two cases of normal running and idling speed, the auxiliary supply assembly 21-22 subjected to this low vacuum transmitted to the idling well 20 through the orifices 24 and / or 25 as the case may be, can provide a fuel mixture suitably dosed, the flow rate and richness of which are determined by adjusting the life-needle 30 at idle.

On the other hand, when the throttle valve 14 is only half-open and therefore forms a constriction in the carburetion chamber 10 while the engine in the course of acceleration or deceleration is already running or is still relatively fast, most of the pressure drop at the crossing of the carburetor is deferred to the level of the throttle valve 14, which has the double effect of defusing the main supply assembly 12 and subjecting the auxiliary assembly 21-22 to a strong vacuum involving the production of a mixture of excessive wealth, for the reasons indicated.

The regulating device which is the subject of the invention has the function of correcting this excess wealth by admitting air or any gas. - for example taken from the engine exhaust - in the idle well 20, so as to control the relative depression which prevails there and consequently the operation of the calibrator 21 - nozzle 22 assembly.

To this end, as shown in Figures 1 and 3, the regulating device can be connected to a special adjusting screw 30 - substituted for the original screw visible in Figure 5 and retaining the partial sealing function of the idle orifice 25. This special screw is provided at the end with a transverse passage 31 into which opens an axial passage 32 which extends to the outer end of the screw, shaped as a tip or cannula 33 for connection sealed from a conduit 34 coming from the regulating device. As the latter does not intervene at idling speed and as shown in Figure 1, the duct 34 could possibly include a bypass symbolized at 35 for the supply of an auxiliary idling carburetor 3 ₆ gasifying the mixture produced by the together 21-22 before returning it to the intake manifold 16 via a conduit 37, as described in French patent application No. EN 76 / 33.619 of 08.11.76 of which the Applicant is co-holder. In this case, the screw 30 should completely close the orifice 25, which clearly shows that the regulating device which is the subject of the present invention only intervenes during transitions, when the butterfly 14 masks or unmasks the progressiveness orifice 24 respectively. in deceleration or acceleration.

The regulating device 40 shown in FIG. 1 essentially comprises a cover 41 of stamped sheet metal and a bottom 42 of molded light alloy between which is tightly enclosed the periphery of a flexible membrane 43 of elastomeric material, impregnated fabric or metal, which separates a closed upper chamber called "control" and an annular lower chamber called "working" that a duct 44 leading for example to the air filter maintains permanently at ambient atmospheric pressure. This duct constitutes the additional air inlet.

Dnas the axis of the bottom 42 of the device is trapped by molding a piece 45 of soft magnetic material such as low-grade steel made of carbon, the outer end of which forms a nozzle or cannula 46 for connecting the duct 34, and the inner end of which forms an annular sealing seat 47 surrounded by the working chamber and engaged by the membrane 43 acting as a valve closing when it is in the rest position shown. On the central portion of the opposite face of the membrane 43, and therefore in the control chamber, is attached a permanent magnet 48 of cylindrical shape, for example made of ferrite or a cobalt / rare earth alloy, capable of generating a high magnetic induction for a low weight and having a large coercive field despite its shape. This magnet and the membrane are secured - with the interposition of washers and cups if necessary - by means of a tubular axial rivet 49, which constitutes a throttle with a very small passage section connecting the upper control chamber with the seat d seal 45 and therefore with the idle well 20 of the carburetor.

The operation of the regulating device 40 which has just been described will be better understood by referring to the sketches of FIG. 2, which show very schematically and respectively in the "Closed" and "Open" positions an equivalent device, in which the membrane 43 is replaced by a piston 143 sliding in a cylinder 141, the bottom 142 of which is crossed by an axial duct 145 forming an annular sealing seat 147, and by a radial duct 144 opening out under the piston. The latter is crossed by an axial passage 149 of very small section and returned to the closed or rest position shown on the left by the action of return means shown by a spring 148 for convenience, but which it is understood that the force of reminder - like that of magnet 48 - decreases rapidly when the piston moves away from the seal seat. The conduit 144 is in relation to the atmosphere and therefore maintained at ambient pressure Po, while the conduit 145 connected to the idle well of the carburetor is subjected to the pressure prevailing in the latter, namely P0-Δp, where Δp represents the relative depression.

For the closed or rest position shown in the sketch on the left, this relative depression is established in the control chamber of the device, with a delay conditioned in particular by its variations by volume and by the section of the passage 149, this delay being counted from the moment when the sealing seat 147 is engaged by the piston 143, which then undergoes a restoring force R.

The piston remains in this position, as long as the sum of the ascending forces which it undergoes, either: Po (ss) + s (P0- Δp) is less than the sum of the descending forces, ie: R + S (Po- Δp), if S and s represent respectively the active surface of the piston and the area enclosed by the sealing seat. The simplification of this inequality shows that the piston remains in the rest position for: Δp (S - s) <R. The value of this restoring resting force R is chosen or adjusted so that the piston is not detached from its sealing seat only when the relative vacuum in the idle well exceeds its value corresponding to the operation of the engine at idle speed, the throttle valve of the carburetor being closed.

As soon as the throttle opens, this vacuum limit value is exceeded, and the pressure in the control chamber of the device drops with some delay. As soon as the inequality Δ p (S - s) <R is no longer satisfied, the piston is lifted and thereby detached from the sealing seat 147. The atmospheric pressure Po therefore acts on the entire lower face of the piston and the return force R decreases as it is raised. This double positive reaction ensures instantaneous "switching" of the piston towards its open position shown in the right sketch of Figure 2.

The piston being in this open position, on the one hand the restoring force is reduced to a value r "R, and on the other hand the relative depression in the control chamber is gradually canceled out since the passage 149 is then in relation to the atmosphere. It follows that the piston remains in this position as long as the ascending force Po, S remains greater than the sum of the descending forces r + S (Po - Δp), and therefore, after simplification, as long as the inequality Δp .S> r is satisfied. Then, the piston is suddenly switched to the closed position, since the restoring force which it undergoes increases when it approaches the sealing seat. Meanwhile, while the piston is raised, the additional air flow admitted by the device is of course modulated by the vacuum prevailing in the idle well, which itself is modulated by this flow in proportions fixed by the ratio of pressure losses across the assembly 21-22 and the device 40 in parallel, on the one hand, and on the other hand through the orifices 24-25, the effective overall section of which depends on the angular position of the butterfly 14 with small openings. In this way, for a judicious choice of the elements and forces in question, the richness of the mixture supplied to the engine during the transitions between the idling speed and normal running can be kept substantially constant, without "hole" or excess, as the have demonstrated the approval tests of the device described. In addition, during a sharp acceleration or a sudden deceleration, the intervention then superfluous of the device is avoided by the time constant inherent in its operation.

The regulating device 40 shown in Figure 1 could of course be the subject of multiple alternative embodiments and many detailed improvements. Thus and for example, the magnet could be incorporated into the sealing seat, the membrane itself being made of soft magnetic material or carrying a simple washer of such material. Washers of non-magnetic material could be interposed on either side of the air gap to modify the width, and consequently the value of the initial restoring force. The law of variation of this force could be adjusted as necessary by adding to the device at least one spring such as R1 and / or R2 or else direct or indirect abutment means on the cover 41 limiting the lifting of the pressure gauge member, and moreover the variations in volume of the control chamber and therefore the time constant of the device, which could as well be adjusted by acting on the passage section of the rivet 49, for example extended by a tube opening through a restriction orifice. R3.

It will be noted that in all cases, the regulating device 40 is directly controlled by the vacuum in the idle well 20, namely by the very magnitude that it has the function of correcting. Therefore, the device 40 can be considered to be intrinsically controlled and unique.

We will now describe with reference to Figure 3 another regulating device according to the invention, which unlike the previous one is of an extrinsic and multiple control type, but acts basically in the same way on the idle circuit of the carburetor .

This device symbolically represented in FIG. 3 and designated by 50 as a whole essentially comprises an adjusting member - for example a ball valve 51 and rotating 52 - constituting a throttle with adjustable passage section interposed between a conduit 53 of intake d additional air or gas, connected for example to the filter or to an outlet on the exhaust, and a conduit 54 leading to the idle well 20 of the carburetor, in the example represented by means of the conduit 34 and the screw special 30, and in any case in any upoint but necessarily located on the one hand, downstream of the calibrator-nozzle assembly 21-22 but on the other hand, upstream of the openings of progressiveness 24 and of idle speed 25, this with reference to the circulation of the mixture in the well 20. In this way and as before, the regulating device 50 is in parallel with the calibrator 21 but in series with the orifices 24-25.

Under these conditions, the relative vacuum prevailing in the idle well 20 can be reduced at will by modulating the additional air flow admitted by the device 50, which has the effect of reducing the pressure drop and therefore the flow of air through calibrator 21, and consequently correct the richness of the fuel mixture supplied to the engine during the transitions between idling and normal running.

This process will be better understood by referring to the diagrams in Figure 4, the first of which represents a pneumatic equivalent of the device, while the second constitutes an electrical analogy. These two diagrams would also apply equally well to the device 40 of FIG. 1 with the addition of a reaction loop.

The first diagram in FIG. 4 shows that the calibrator 21 with an invariable passage section and the orifices 24-25 with overall effective section varying according to the position of the half-opened butterfly are always in series and therefore share the pressure drop ΔP se producing at the level of the throttle valve to absorb the difference between the ambient pressure PA at the inlet to the carburetor and the slightest pressure PT prevailing in the intake manifold of the engine.

In the absence of a regulating device, the same air flow or mixture of value ⌀ passes through the calibrator 21 and the orifices 24-25, the variations in effective section of which modify the law for sharing losses. Of charge δP / Δp, and consequently the relative depression PR existing in the idle well for the same depression PT in the intake manifold. The pressure drop δp through the calibrator 21, and consequently the air speed and therefore the flow of fuel sucked into the nozzle 22, hence finally the richness of the mixture supplied to the engine, correspond in these conditions to complex function of many parameters involved, ^t they input intrinsically linked and not linear.

The regulating device 50 mounted in parallel with the calibrator 21 allows the admission into the idle well 20 of an adjustable flow ϕ 'of additional air or gas which - for the same overall flow g through the orifices 24-25 is subtracts from the flux initially passing through the calibrator and reduces it to a value ϕ-⌀-ϕ '. and thereby decreases the relative depression PR in the idle well. In other words, the device 50 makes it possible to control the flow rate and the speed of the residual air flow ϕ passing through the calibrator 21 then the nozzle 22. The richness of the mixture produced by these elements can therefore be maintained at its optimum value - if necessary, taking into account its dilution by additional air - during the transitions between idling and normal running, by judiciously controlling the device 50 to any suitable combination of parameters conditioning the operation of the engine and its carburetor and / or reflecting their operating conditions. Such slaving to multiple parameters is in fact made possible by the extrinsic control mode of the device 50, as several application examples will show below.

The electrical diagram in Figure 4 shows that the vacuum in the intake manifold can be compared to a source of variable voltage E which feeds a network comprising a variable resistance potentiometer P representing the orifices 24-25 in series with a fixed resistance R appearing the calibrator 21 and, in parallel on the latter, an adjustable resistance S appearing the regulating device 50. A simple calculation shows that the voltage drop e at the terminals of R and consequently the intensity of the current i passing through it can be regulated by action on S and maintained appreciably constant in spite of the variations of E and P. This analogy is only approximate, since the applicable laws are linear, but has the advantage of facilitating the understanding of the mode of action of the device according to the invention.

• Sur la Figure 3, deux exemples distincts de réalisation du dispositif régulateur 50 sont symboliquement représentés, respectivement à gauche et à droite du conduit 53-54 d'admission d'air additionnel :

Referring again to FIG. 3, it will be noted that the addition of this regulating device does not imply any modification of the structure of the carburetor, except the arrangement of an additional air or gas inlet in the idle well 20 - for example and as represented by substitution of the special hollow screw 30 for the original adjusting screw - and the installation of means for controlling the operation of this device to that of the engine and / or its carburetor. The choice of servo parameters and their combination mode is obviously very wide. This means that the few examples which will now be described have only an indicative value:

• In FIG. 3, two distinct embodiments of the regulating device 50 are symbolically represented, respectively to the left and to the right of the duct 53-54 for additional air intake:

In the first example, the adjusting member of the device is assumed to be constituted by a valve 51, the movable shutter of which is a drawer 52 coupled to a lifting beam 55 with double action, one of its ends being connected by a rod 56 to a crank 1? wedged on the axis 15 of the butterfly 14, while its opposite end is articulated at the end of the rod 57 of a piston subjected on the one hand to the vacuum PT in the intake manifold and on the other hand to the vacuum CS in idle well. The displacements of the slide valve 52 of the valve are therefore dark tion of the combination of the opening of the butterfly and the ratio of depressions. The choice of lever arms, active surfaces of the piston and its return force allows the relative importance of each of the parameters in question to be determined at will.

In the second example, the movable shutter 51 of the valve 52 is assumed to be rotating and actuated by an electric motor 58 of the reversible and step-by-step type, powered by a pulse generator 59 of one or the other. polarity or relative phase, itself controlled by a microprocessor µP ensuring according to a programmed law the adequate combination in each circumstance of many parameters measured by respective sensors C1, C2 ... Cn. These sensors can for example comprise a magnetic rev counter coupled to the shaft of the engine or of the gearbox, an encoder coupled to the accelerator and clutch control pedals, to the gear shift lever, to the choke. .. accelerometers, thermometers, manometers and other bodies for measuring operating conditions. Of course, the microprocessor and these various sensors could be used in parallel for other purposes, for example to optimize the driving of the vehicle.

The embodiments of the invention hitherto described are in no way limiting, but on the contrary show that the regulating device could be the subject of numerous variant embodiments and / or arrangements of the various elements which constitute it. . Thus and for example, Figures 5 and 6 illustrating two different arrangements of the injection of air, or additional gas A 'in the idle well 20 of the carburetor, which in these two cases remains equipped with its richness adjustment screw of origin:

Figure 5 shows that the additional air injection A 'can be carried out conveniently by a channel formed in a flange B interposed between the two superimposed elements C1, C2 of the body of a carburetor otherwise similar to that of Figures 1 and 3, the upper element C1 containing the main supply device 12 surrounded by its venturi and moreover the calibrator 21 and the nozzle 22 mounted at the head of the idling well, while the lower element or foot C2 contains the throttle valve and the bottom of the idle well, connected to the carburetor chamber 10 by the openings of progressiveness 24 and of idle 25, the latter controlled by the original adjustment screw. This arrangement therefore ensures the injection of additional air under the conditions desired by the invention, without the need to make any modification to the carburetor.

Figure 6 shows that the injection of additional air could also be done in certain carburetors by taking advantage of the presence of a monobloc assembly 60 bringing together the calibrator and the idle jet. The body of such a monobloc sprinkler is tubular and has, beyond a threaded surface 61, an external extension forming a connecting piece 62. Below the penetration of the sprinkler into the idle well 20, its axial passage 63 is closed by a plug 64, while its outer cylindrical surface has a wide peripheral groove 65 framed by two seals 66,67. The axial passage 63 communicates by a radial bore 6B with this groove, to the right of which opens a passage 69 obliquely pierced in the body of the carburetor, so as to also open into the idle well below the nozzle. Thus, at the cost of a simple arrangement of this monobloc nozzle and a simple drilling of the carburetor body, the injection of air or additional gas A ′ can be ensured under the conditions recommended by the invention.

• L'organe de règlage 70 représenté en coupe sur la Figure 7 est un dispositif d'étranglement variable comportant un corps 71 de forme générale tubulaire dont une extrémité porte un moteur pas à pas MPP (5E sur la Figure 3) entraînant un obturateur mobile 72 à la fois tournant et coulissant, qui se termine par une pointe 73 profilée selon les besoins de la régulation pour contrôler le débouché d'un embout d'admission d'air ou gaz 74 dans une chambre 75 d'où est issu le conduit aboutissant au puits de ralenti du carburateur.

The regulating member of the regulating device can itself be the subject of very numerous variant embodiments, especially since it can be indifferently controlled by mechanical, pneumatic and / or electrical means in particular. An example of mixed mechanical and pneumatic control has already been briefly described in relation to Figure 3, and a purely pneumatic example is the device of Figure 1. Also will now be described two adjustment members electrically controlled by stepping motor or by pulse generator, as suggested in Figure 3 and respectively illustrated by Figures 7 and 8:

• The adjusting member 70 shown in section in Figure 7 is a variable throttling device comprising a body 71 of general shape tubular one end of which carries an MPP stepping motor (5E in FIG. 3) driving a movable shutter 72 both rotating and sliding, which ends in a tip 73 profiled according to the needs of the regulation to control the outlet of an air or gas inlet nozzle 74 into a chamber 75 from which the conduit leading to the idle well of the carburetor originates.

The bore of the body 71 adjacent to the MPP engine has a long thread 76 into which a threaded surface 77 of the shutter 72 is screwed, which has a square axial hole 78 in which slides a rod 79 of the same section secured to the axis of the motor. The latter receives from a generator not shown positive or negative pulses ensuring its rotation step by step in one or the other direction, and consequently the advance or the retraction of the shutter 72 relative to the outlet of the '74 air intake nozzle. It is understood that a judicious combination of the sequence of pulses and the profile of the tip 73 makes it possible to obtain any desired regulation law, with excellent precision.

The regulating member 80 illustrated in FIG. 8 essentially comprises a normally closed valve 81 and an electromagnet 82 actuating it periodically upon opening on command of recurrent pulses supplied by a GI generator (59 in FIG. 3). The valve 81 comprises an air or gas inlet connection 83 and a sealing seat 84 for the outlet of the additional air or gas A ', normally prevented by a valve E5 returned to the closed position by a spring 86 The valve rod 87 passes tightly through the end wall of the electromagnet mandrel 82, made of a non-magnetic material, and carries at the end a permanent magnet 88 which slides with gentle friction in the mandrel and is polarized by as indicated. The coil 89 is located so as to surround the magnet in the rest position, and arranged to have the indicated polarity - in the same direction as that of the magnet - when it receives a control pulse, so that the play of attractive and repulsive magnetic forces bring the magnet into the working position shown, and consequently the valve 85 at full opening. If the recurrence period T of the pulses is constant and if these pulses are modulated in duration, as shown in the attached diagram, depending on the variations of the parameters taken into account, everything happens as if the valve lift was modulated in average value by these same parameters.

In the course of the foregoing description, mention has been made repeatedly of the possibility of substituting any additional gas, taken from the engine exhaust or supplied by any other source, for the additional air. Such a gas can in fact be devoid of oxygen, and therefore not modify the richness of the mixture coming from the idle-calibrator-jet assembly, while increasing the volume supplied to the engine. This results in particular in better filling of the cylinders and a lower end-of-combustion temperature, circumstances favorable to the reduction of emissions of pollutants and particularly of nitrogen oxides.

Of course, the invention is in no way limited to the various examples of implementation described and illustrated, but on the contrary comprises all the means by constituting, separately or in combination, technical equivalents and coming within the scope of the claims which follow.

Claims (10)

1. Device for regulating the richness of the fuel mixture produced by the supply carburetor of an internal combustion engine and controlled ignition during the transitions between the idle speed and normal operation, and in particular when the butterfly (14) masks or unmasks a progressive opening (24) connecting the idling well (20) to the carburetion chamber (10), by selective admission of an additional air or gas flow, characterized in that it comprises a semi-parallel circuit (34 + 44.53 + 54) for admitting air or other gas, which opens into the idle well downstream of the calibrator (21) and the nozzle (22 ) associated but upstream of the progressive and idle orifices (24,25) leading to the carburetion chamber, this circuit comprising an adjusting member (40,50,70,80) whose passage section is slaved to at least l '' one of the operating parameters of the engine in order to positively modulate the relative depression prevailing in the idle well, and consequently the air flow passing through the calibrator and therefore the flow of fuel sucked by the nozzle, thus maintaining substantially equal to its optimal value the richness of the mixture supplied to the engine during the aforementioned transitions. 2. Device according to claim 1, characterized in that the above-mentioned circuit opens into the idle well (20) through a special hollow screw (30) substituted for the original richness adjustment screw. j. Device according to claim 1, characterized in that the aforesaid circuit opens into the idle well (20) through a channel formed in a flange (e) interposed between the main body (C1) of the carburetor and its foot (C2) containing the butterfly (14). 4. Device according to claim 1, characterized in that the aforementioned circuit opens into the idle well (20) through a one-piece calibrator-nozzle assembly (60) arranged for this purpose, then through an oblique passage (69) pierced under the latter in the carburetor body. 5. Device according to any one of claims 1 to 4, characterized in that the aforementioned adjustment member is a valve (40,50,70,80) comprising a movable shutter (43,52,72,85) whose the movements are controlled pneumatically, mechanically and / or electrically at least one of the aforementioned parameters. 6. Device according to claim 5, characterized in that the movable shutter of the valve (40) is constituted or actuated by a pressure gauge member (43) normally maintained in a rest position, for which it closes a sealing seat (47) interposed between the idling well (20) and an additional air or gas inlet (44), by a permanent magnet (48) or other return means whose force decreases when said member is moved away from said seat by the vacuum prevailing in the idle shaft, applied to its opposite face through a capillary throttle (49). 7. Device according to Claim 6, characterized in that the pressure gauge member (43) is a flexible membrane separating two chambers, one of which surrounds the sealing seat (47) and communicates freely with the air inlet or gas (44), and the other of which is closed and connected to the idle well (20) through the throttle (49), arranged through a magnet (48) mounted on the membrane to the right of the seat, made of a soft magnetic material. 8. Device according to claim 5, characterized in that the movable shutter of the valve (50) is a rotary drawer or valve (52) directly actuated by a wheelhouse (55-57) coupled to at least one control mechanism of the motor and / or mechanical transducer of pressure, temperature, speed or other quantity. 9. Device according to claim 5, characterized in that the movable shutter of the valve (70,80) is a drawer, rotating or valve (72, E5) actuated by an electric transducer such as a stepping motor ( 58) or an electromagnet (82) coupled to a pulse generator (59) whose sequence, polarity and / or modulation is representative of several parameters combined 10. Device according to claim 9, characterized in that the pulse generator (59) is controlled by a microprocessor ensuring the programmed combination of information provided by several sensors (C1, C2 ... Cn).

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