Carburation device in particular for internal combustion engines

Abstract: In order to obviate the drawbacks of fluid-dynamic character which affect the traditional carburettors equipped with control valves of throttle or of guillotine type, the carburation device (1, 1A, 1B, 1C) provides for the feed duct (6, 6A-6C) to be a tubular portion made of an elastic material constrained at its ends and that at least one pair of relatively movable blades (10) act on said elastic feed duct (6, 6A-6C) on its outer surface, squeezing it in a perpendicular direction relatively to its axis (8). The surface area of the cross-section of the inner bore of said duct (6, 6A-6C) varies taking (relatively to the fuel stream flowing through it) a gradually convergent-divergent shape, i.e., without sharp changes in said inner bore cross-section surface area, and the fuel stream has hence a fluid-dynamically optimal motion independently from the actual revolution speed of the engine.

Description: The present invention relates to a carburation device in particular for internal combustion engines. One known carburation device, disclosed for example in FR 1596218, substantially comprises the following elements: means for delivering the fuel at a metered rate relatively to combustion-supporting air according to the desired stoichiometric ratio, a supply duct for at least one from the following fluids: combustion-supporting air and combustible mixture obtained by mixing combustion-supporting air with fuel, suitable means for varying the surface area of the internal bore of said feed duct in order to change the revolution speed of the engine with which said carburation device can be associated. The feed duct can be co-axially constrained to the intake duct of the engine it is destined for. The suitable means for varying the surface area of the inner bore of the feed duct are presently constituted by throttle valves or guillotine valves which, by acting inside said feed duct choke it as a function of the instantaneous performance required from the engine. Unfortunately, some time ago it was discovered that said throttle or guillotine valves considerably disturb the fuel stream which consequently, by displaying irregularities from fluid-dynamic point of view, generates drawbacks. Said drawbacks are well-known for those skilled in the art and therefore only the main ones of them are generally mentioned: lower torque at low revolution speed values, smaller power at high values of revolution speed values, higher actual specific consumption than theoretical. At present, in order to at least partially obviate the above said drawbacks, the valve manufacturers give such throttle or guillotine valves such shapes as to limit as far as possible the fluid-dynamic disturbance caused by said valves and design such valves for use in several engines based on target engine characteristics and envisaged usage. The purpose of the present invention is of obviating the above said drawbacks, i.e., providing a carburation device which is capable of choking the stream of combustible mixture supplied without substantially altering the fluid-dynamic character of its flow, i.e., always keeping the fluid-dynamic flow under best conditions in order that the subsequent combustion inside the engine may take place with the maximal conversion of heat energy liberated by the combustion of the fuel mix, into mechanical energy, independently of the instantaneous engine revolution speed. Such purposes are achieved by a carburation device according to Claim 1, to which reference is made here for the sake of brevity. By positioning the suitable means for varying the surface area of the cross-section of the internal bore of the feed duct outside of said duct, such means are no longer having any effects on the flow of combustion-supporting air or combustible streams, which therefore flow according to the best fluid-dynamic conditions. The absence of valves inside the interior of said feed duct makes it furthermore possible any hindrances to be removed from the interior of said feed duct, which might be generated by the necessary devices for constraining and actuating said valves, with further advantages being gained as regards the regularity of flow of combustion-supporting air or combustible streams. Choking said feed duct by transversely squeezing it relatively to its axis (preferably by perpendicular squeezing) always causes, independently on the size of the cross-section, a convergent-divergent portion to be formed which, from the fluid-dynamic viewpoint, is an optimal structure for stream flow through it. The sub-claims related to some of further embodiments of the invention which are expressly referred to owing to the further advantages they offer or technical problems they address. The feed duct is preferably made from an elastic material. The elasticity of the material can be therefore used in order to cause said feed duct to automatically return back to its original conditions after being deformed. In such a case, the suitable means for varying the surface area of the cross-section of the internal bore can be simplified in their structure, because it is not necessary that they are capable of acting on said duct also when said duct must be returned back to its original conditions of maximal inner bore cross-section surface area. Preferably, the suitable means for varying the surface area of the cross-section of the internal bore comprise at least one pair of mutually movable blades. This means that: in a first case, a first blade is movable relatively to the second blade, which is stationary and therefore acts as a fixed shoulder for the first one. In the second case, both blades are movable in synchronism until they completely shut the feed duct; said shutting preferably takes place at the middle of the internal bore. In all above mentioned cases, the feed duct gets deformed with its interior bore taking a convergent-divergent shape. The experience will allow those skilled in the art to understand when a device according to the invention should be used with either one, or both blades being movable. According to the available room and the structure of the actuator means used to drive said blades, said actuator means can be electrical, hydraulic, pneumatic or even of manual type, by means of a Bowden cable. According to a possible embodiment, at least one of said blades is hinged at one of its ends, so as to act as if it was a pressing cam urging on the feed duct, whilst the other blade, which is stationary, simply acts as a shoulder. According to further possible embodiments, at least one of said blades slides along guides, so as to act as a guillotine blade pressing on said feed duct, whereas the other blade acts as a stationary or movable shoulder. The selection of the movement type and of the type of actuation device for the blades is usually carried out as a function of the structure and of the usage the engine is designed for. The possibility of individually actuating the blades enables the operator to act on combustible mixture feed in the best way relatively to the usage conditions. The blades are actuated by the operator by means of the gas pedal together with the means for delivering metered amounts of fuel, relatively to the combustion-supporting air according to the desired stoichiometric ratio; however, the selection of the modality of actuation of said blades can be committed to a central electronic control unit. In order to increase the fluid-dynamic effects, the feed duct is, under fully opened condition, preferably of convergent type and is provided with end flanges in order to allow it to be fastened. The invention is illustrated for merely exemplifying, non limitative purposes in the Figure of the accompanying drawing tables which display some of possible embodiments. Figure 1 is a sectional view of a device according to the present invention as applied to an internal combustion engine. In the illustrated device, the means for metered delivery of fuel comprise an injector means. Figure 2 is a sectional view of a device according to the invention, which can be applied to internal combustion engines. In the illustrated device, the means for metered fuel delivery are those which are usually present in a traditional carburettor. Figures 3 and 4 show sectional views of a device according to the present invention in its maximal delivery rate and minimal delivery rate positions, respectively, as applied in lieu of the intake fitting on a racing engine. The means for metered fuel delivery are not illustrated for the sake of simplicity, however they preferably comprise an injection device provided with at least one injector means. Figure 5 schematically illustrates, in sectional view, a device according to the present invention in which there are two sets of suitable means for varying the surface area of the cross-section of the internal bore of said feed duct. For the sake of simplicity, the means for metered fuel delivery are not illustrated, however they preferably comprise an injection device provided with at least one injector means. Figures 6-8 schematically illustrate the device shown in Figure 5, in those configurations it takes when the suitable means for varying the surface area of the cross-section of the internal bore of the feed duct are variously actuated. Figure 9 shows a sectional view along the section line IX-IX of Figure 6. Referring in particular to Figure 1, the device according to the invention, generally indicated with (1), is installed between an intake fitting (2) and the relevant filter (3) and an intake duct (4) of an internal combustion engine (5). The device (1) comprises a body (9), a feed duct (6) [the axis of which is indicated with (8)], one pair of mutually opposite blades (10), and an injection unit (7). The body (9) is a rigid support structure which houses and constrains the feed duct (6) at its ends, and internally supports the pair of blades (10). The feed duct (6) has a convergent shape and is made from an elastic material capable of withstanding heat while keeping practically unchanged its elasticity characteristics. The preferably used materials for producting the feed duct (6) are fluoro-silicone rubbers, or a material marketed under the trade name "Viton". The blades (10) are keyed on the pivots (11) which are driven to revolve by actuator means, not illustrated in the figure, which can be of mechanical, electrical or pneumatic type. The actuator means are controlled by the gas pedal in synchronism with the injection unit (7). The device (1) furthermore comprises a compensation duct (12) which connects the internal chamber of the body (9) with the intake duct (4). In such a way, the pressure existing inside the interior of body (9) [or, better, between the inner surface of said body (9) and the external surface of the feed duct (6)] and the internal pressure inside the intake duct are always the same. In such a way, phenomena of prolonged squeezing of feed duct (6) are avoided, which may follow sudden actuations of blades (10) (duct opening and shutting, arrows "F" and "G", respectively), above all when the engine operates under release conditions, at a high revolution speed. Referring in particular to Figure 2, the device (1A) illustrated in this figure is different from the preceding one mainly owing to the structure of the feed duct (6A) and the structure of the means for metered fuel supply relatively to combustion-supporting air. The feed duct (6A) is of convergent-divergent type. Instead of being constituted by the injection unit (7), the means for metered fuel supply relatively to combustion-supporting air are those of a traditional carburettor. Therefore, they essentially comprise a slow-running (idling) mixture delivery nozzle (not visible in figure) and a maximal-speed running mixture delivery nozzle (14), operatively associated with a cup (15)-float (16) assembly. The surface area of the cross-section of the calibrated bore of the maximal speed running mixture delivery nozzle (14) is determined by the vertical position inside said bore of a calibrated pin (13) the sliding of which is synchronized with the motion of the blades (10) which are the suitable means for varying the surface area of the cross-section of the internal bore of said feed duct (6A). The residual elements of the device (1A) of Figure 2 have been identified with the same reference numeral as used for the device (1) of Figure 1. Referring in particular to Figures 3 and 4, the device (1B) illustrated in these figures mainly differs from the preceding devices because the blades (10) are actuated in this case by respective cams (17) hinged in (19) and equipped with an end bearing (18) which allows them to be actuated more smoothly and reduces the wear of the implied parts. It should be observed that in the illustrated case, the feed duct (6B) also acts as the intake fitting. The residual elements have been indicated with the same reference numerals. For the sake of simplicity, the means for metered fuel delivery relatively to combustion-supporting air according to the desired stoichiometric ratio are not illustrated; however, they are constituted by an injection unit comprising at least one nozzle which can be indifferently installed upstream or downstream from the line (20) along which the feed duct (6B) gets choked/shut. In the case when said nozzle is installed upstream, through the feed duct (6B) the combustion-supporting air and the fuel mixture obtained from combustion-supporting air mixing with fuel (i.e., the "combustible mixture") will flow. In the case when said nozzle is installed downstream, through said feed duct (6B) only combustion-supporting air will flow. Referring now in particular to Figure 5, the carburation device (1C) illustrated in this figure mainly differs from the preceding one in that two sets of the suitable means for varying the surface area of the cross-section of the inner bore of said feed duct are present. In order to fully understand the considerable advantages offered by such an embodiment,it should be reminded here that the characteristic of an internal combustion engine is strongly conditioned by the size of its intake duct. Summarizing, an engine provided with a slim (i.e., narrow and long) intake duct displays tendentially flat power and torque curves, i.e.: power and torque only change slightly as the revolution speed (revolutions per minute) of engine changes. An engine equipped with a squat intake duct shows high-slope power and torque curves, i.e.: power and torque considerably vary with varying revolution speed (revolutions per minute). By doubling the suitable means for varying the surface area of the cross-section of the internal bore of said feed duct [i.e., by providing two pairs of blades (10) respectively arranged at both ends of feed duct (6C)], also the shape of said feed duct (6C) can be changed, which can take a slimmer or less slim shape (Figure 8) and therefore a squatter or less squat shape (Figure 5), thus influencing the characteristic of the engine. Furthermore, by actuating only one of both blade (10) pairs, the feed duct (6C) can be given a convergent shape (Figure 6) or a divergent shape (Figure 7). It is important to observe that in an internal combustion engine provided with the device (1C) the feed duct (6C), or the intake duct of the engine it is associated with, can be given an as large as possible size, then letting to the device (1C) the task of shaping, and/or decreasing the cross-section of the feed duct as a function of engine running requirements, with the engine resulting capable of both supplying a high specific power and a high specific torque also at those values of revolution speed which are commonly regarded as being slow. In other terms, it is possible to obtain that, according to the requirements, an engine of the same type can have the same performances of a high-specific-power-engine or of a high-specific torque-engine. This performance was unknown until nowadays because the values of the geometric parameters of the intake (4)- feed (6) ducts have always been selected based on the best balance between power and torque requirements.

Claims: Carburaticn device (1, 1A-1C) in particular for internal combustion engines, comprising: means (7, 13-16) for delivering metered amounts of fuel relatively to combustion-supporting air according to the desired stoichiometric ratio; a body (9) having a rigid support structure which houses and contains a feed duct (6, 6A-6C) for combustible mixture obtained by mixing the combustion-supporting air with the fuel in which said body (9) and said feed duct (6, 6A-6C) can be coaxially constrained (8) to an intake duct (4) of the engine (5) it is designed for use in; suitable means (10) for varying the surface area of the cross-section of the internal bore of said feed duct (6, 6A-6C) in order to vary the revolution speed at which the engine (5) runs with which said device (1, 1A-1C), can be associated; said feed duct (6, 6A-6C) comprising at least one portion of tubular shape made of a deformable material which can be constrained at its ends co-axially (8) to said intake duct (4) of the engine (5) it is designed for use in; said suitable means (10) for varying the surface area of the cross-section of the internal bore of said duct (6, 6A-6C) acting on said at least one portion of deformable material of the feed duct (6, 6A-6C) from the outside, squeezing it transversely to its axis (8) in such a way that the surface area of the cross-section of the internal bore of said feed duct varies taking a gradually convergent-divergent shape, i.e. without sharp changes in inner bore cross-section surface area relatively to the fuel mixture which must flow through it characterised in that the device furthermore comprises a compensation duct (12) which connects an internal chamber of the body (9) with the intake duct (4) in such a way that the pressure existing inside the interior of body (9) and the internal pressure inside the intake duct are always the same and in that the suitable means (10) are able to shut completely said feed duct (6, 6A-6C). Device according to claim 1, characterized in that said feed duct (6, 6A-6C) is totally made of an elastic material. Device according to one or more of the preceding claims, characterised in that said suitable means for varying the surface area of the cross-section of its internal bore comprises at least one pair of relatively movable blades (10), i.e., a first blade movable relatively to the second blade, or vice-versa, or both of them are synchronously movable. Device according to claim 1, characterized in that at least one of said blades (10) is hinged at an end thereof so that it can act as a cam pressing on the feed duct (6, 6A-6C), whereas the other blade acts as stationary shoulder. Device according to claim 3, characterized in that at least one of said blades slides along guides, so as to act in a guillotine fashion pressing on the feed duct (6, 6A-6C), whereas the other blades acts as a stationary shoulder. Device according to one or more of the preceding claims, characterized in that the feed duct (6, 6A-6C) is of convergent type. Device according to one or more of the preceding claims, characterized in that the feed duct (6, 6A-6C) is of convergent-divergent type. Device according to claim 3, characterized in that the suitable means for varying the internal bore of said feed duct (6, 6A-6C) comprise, on a same feed duct, at least two pairs of mutually opposite blades (10) which can be also simultaneously actuatable, so as to deform the feed duct (6, 6A-6C) in such a way that its interior bore takes a convergent-constant-divergent shape, with the width of the constant-diameter portion being established as a function of the desired engine operating parameters. Device according to claim 3, characterized in that the means for fuel feed comprises calibrated nozzles for minimal and maximal operating speed rates (14), the cross section of the calibrated bore of the latter being determined by position taken inside its calibrated bore by a calibrated pin (13) the sliding of which is synchronised with the suitable means (10) for varying the surface area of said feed duct. Device according to claim 3, characterized in that the fuel feed means comprise an injection unit (7) in which fuel delivery is synchronised with the suitable means (10) for varying the surface area of said feed duct.

Inventors: PICCININI GIUSEPPE RAOUL, PICCININI, GIUSEPPE RAOUL
Applicants: PICCININI GIUSEPPE RAOUL, PICCININI, GIUSEPPE RAOUL
Application year: 1995
Main classification: F02M9
IPC codes: F02M9