FR2920487A1 - Air distributor for supercharged internal combustion engine, has plenum provided with air inlet and opening in conduits, where two conduits having different geometries such that distances separating inlet from outlets of conduits are equal - Google Patents

Abstract

The distributor (40) has a plenum (40A) provided with a fresh air inlet (45), and opening in inlet conduits (41-44), where outlets of the conduits are connected to distinct cylinders (11-14) of an internal combustion engine (1). The conduits (41, 42) have different geometries such that acoustical distances (L1-L4) separating the inlet of the plenum from the outlets of the conduits are equal. The conduit (41) extends along a curves mean line, and the conduit (41) extends along a rectilinear mean line.

Description

TECHNICAL FIELD TO WHICH THE INVENTION RELATES The present invention relates generally to the distribution of fresh air in the cylinders of an internal combustion engine. It relates more particularly to an air distributor of an internal combustion engine internally defining a plenum provided with a single inlet of fresh air and opening into at least three intake ducts, the outlets of which are capable of being connected to separate cylinders of the internal combustion engine. The invention finds a particularly advantageous application in the production of air distributors of supercharged internal combustion engines, the plenums of which have reduced volumes. The invention also relates to an internal combustion engine provided with such an air distributor. It also relates to a fresh air intake line of an internal combustion engine, comprising at least three fresh air supply ducts connected to separate cylinders of the internal combustion engine, and an air distributor defining internally a plenum having a single inlet of fresh air and opening into intake ducts connected to said at least three supply ducts.

BACKGROUND OF THE INVENTION Internal combustion engines use, for combustion of the fuel, a mixture of fresh air and flue gas, or only fresh air. This fresh air is generally taken by an air intake of an intake line, then led by an air line of the intake line to an air distributor of the aforementioned type which distributes the fresh air in each of the cylinders. The intake ducts of this air distributor generally have all identical geometries and are connected to fresh air supply ducts which are hollowed into the cylinder head and which open into the cylinders. The regulation of fresh air in each of these cylinders is achieved by means of intake valves mounted in these fresh air supply ducts. In operation, pressure fluctuations are generated in the intake line by the movements of the pistons, modulated by those of the intake valves. These pressure fluctuations form acoustic waves which can improve or, on the contrary, hinder the fresh air admission of the cylinders, according to the geometry of the air distributor and the intake line. It is then known to optimize this geometry, to improve the average fresh air filling of the various cylinders. However, when the engine is operating at high speeds, a difference in the filling of fresh air between the different cylinders of the engine is observed.

This difference in filling induces differences in wealth in the cylinders of the engine, since the volume of fuel injected into all cylinders is identical while the amount of fresh air admitted into these cylinders differs. These differences in wealth generate temperature differences between the cylinders, resulting in premature wear of some parts of the engine. They also cause a rejection of unburned fuel by some of the cylinders in the atmosphere. To reduce the differences in cylinder filling, a known solution is to increase the volume of the plenum, so that it creates an obstacle to the rise of acoustic waves from the cylinders to the air intake. Thus, the intake ducts are all identical, the fresh air filling of the cylinders is homogeneous. However, this increase in the volume of the plenum is detrimental to the performance of supercharged engines at low speeds.

OBJECT OF THE INVENTION In order to overcome the aforementioned drawbacks of the state of the art, the present invention proposes an air distributor allowing a uniform filling of the engine cylinders, without however reducing at low speeds the performance of this engine.

More particularly, it is proposed according to the invention an air distributor as defined in the introduction, wherein at least a first and a second of said intake ducts have different geometries, so that the acoustic distances separating the single inlet of the plenum of the outlets of the intake ducts are all equal.

By acoustic distance is meant the length of a reference tube whose first resonance is identical to that of the duct considered. The Applicant has noted, as part of its research, that the difference in filling between the cylinders was due to the fact that the acoustic distances between each of the cylinders and the air intake of the intake line were different. Indeed, the intake ducts generally have identical geometries but are connected to the plenum at variable distances 3 from the air inlet thereof. These variations in distances then cause differences in the behavior of the acoustic waves in the intake ducts, which causes the differences in the filling of the cylinders. Here, thanks to the invention, the inlet ducts have appropriate shapes that allow to equalize the acoustic distances between the air intake and each of the cylinders, so that the filling of fresh air is done in a homogeneous manner, In this way, the volume of fuel injected into the cylinders can be controlled precisely, so that the combustion of fresh air and fuel is done identically from one cylinder to another. Other advantageous and non-limiting characteristics of the air distributor according to the invention are as follows: the geometrical distances of the path of the fresh air between the single inlet of the plenum and the outlets of the intake ducts are all equal; said first and second intake ducts have different lengths and identical sections; the geometrical distances of the fresh air path between the single inlet of the plenum and the outlets of the first and second intake ducts are different; said first and second intake ducts have identical lengths and different sections; the first inlet duct extends along a curved mean line and the second intake duct extends along a straight rectilinear line; - The inlet ducts have lengths depending on their distance to the single entry of the plenum; at least one of the intake ducts has a conical shape; at least one of the intake ducts is provided with an enlargement of section; the plenum having an elongate shape, the single plenum inlet is located at one end of said plenum and the geometries of the inlet ducts are all different; or - the plenum having an elongated shape, the single entry of the plenum is located midway length of said plenum and the geometries of the inlet ducts are symmetrical two by two, on either side of said single inlet.

The invention also relates to an internal combustion engine provided with such an air distributor. The invention also relates to a fresh air intake line such as 4 defined in the introduction, wherein at least a first and a second of said supply ducts have different geometries, so that the acoustic distances separating the single Plenum inlet of the outlets of the supply ducts are all equal.

The aforementioned supply ducts are hollowed out in the cylinder head and are located in the extension of the intake ducts of the air distributor. Here, thanks to the invention, the geometries of the fresh air supply ducts participate in the equalization of the acoustic distances between the air intake and each of the cylinders. DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT The following description, with reference to the appended drawings, given by way of non-limiting example, will make it clear what the invention consists of and how it can be achieved. In the accompanying drawings: - Figure 1 is a schematic view of an internal combustion engine 15 comprising an air distributor according to a first embodiment of the invention; FIG. 2 is a schematic view of the internal combustion engine of FIG. 1, comprising an air distributor according to a second embodiment of the invention; FIG. 3 is a schematic view of the internal combustion engine of FIG. 1, comprising an air distributor according to a third embodiment of the invention; and FIG. 4 is a schematic view of the internal combustion engine of FIG. 1, comprising an air distributor according to a fourth embodiment of the invention. In the description, the terms upstream and downstream will be used in the direction of the gas flow, from the point of sampling fresh gases in the atmosphere to the exit of the flue gas by a catalytic converter 34. In the figures 1 to 4, various embodiments of an air distributor 40, 50, 60, 70 of an internal combustion engine 1 are diagrammatically represented. This internal combustion engine 1 conventionally comprises an engine block 10 comprising a cylinder block, here provided with four cylinders 11, 12, 13, 14 in line, and a cylinder head (not shown) which covers the cylinder block. At the outlet of the cylinders 11, 12, 13, 14, the internal combustion engine 1 comprises a burnt gas exhaust line 30 which extends from an exhaust manifold 31 to exhaust gas treatment means , here formed by an auxiliary oxidation catalyst 33 and the catalytic converter 34 mentioned above. The exhaust line 30 further comprises, downstream of the exhaust manifold 31, a turbine 32 which actuates a compressor 22. Upstream of the cylinders 11, 12, 13, 14, the internal combustion engine 1 5 comprises a line intake 20 provided with an air filter 21 which filters fresh gases taken from the atmosphere. This intake line 20 is further provided with the compressor 22 which compresses the fresh gases filtered by the air filter 21, as well as a main air cooler 23 which cools these compressed fresh gases. The intake line 20 also comprises an air distributor 40; 50; 60; 70 adapted to distribute the fresh air cooled by the main air cooler 23 to each of the four cylinders 11, 12, 13, 14 of the engine block. It is for this purpose fixed against a side face of the cylinder head of the engine block. Whatever the embodiment of the air distributor 40; 50 60; 70, the latter internally defines a plenum 40A; 50A; 60A; 70A, that is to say a volume of air, provided with a single inlet 45, 55, 65, 75 of fresh air and one or two outlets 46; 56; 66; 76 fresh air per cylinder. Here, the plenum has a cylinder shape and has four fresh air outlets 46; 56; 66; 76 regularly distributed along this cylinder. This air distributor further internally defines intake ducts 41, 42, 43, 44; 51, 52, 53, 54; 61, 62, 63, 64; 71, 72, 73, 74 whose inputs are respectively connected to the fresh air outlets 46; 56; 66; 76 of the plenum and whose outputs are connected to the cylinders 11, 12, 13, 14 via supply ducts 11A, 12A, 13A, 14A of fresh air dug in the cylinder head. Four of these four intake ducts are then defined as two central intake ducts 42, 43; 52, 53; 62, 63; 72, 73 which are connected to the two central cylinders 12, 13 of the cylinder block and two end intake ducts 41, 44; 51, 54; 61, 64; 71, 74 which are connected to the two cylinders 11, 14 located at the ends of the cylinder block. These four intake ducts here have sections of average sizes substantially equal to the size of a section of the plenum. The supply ducts 11A, 12A, 13A, 14A fresh air dug in the cylinder head originate on said side face of the cylinder head, facing the intake ducts of the air distributor 40; 50; 60; 70, and open into the four cylinders 11, 12, 13, 14 of the internal combustion engine 1. Here, as shown in Figures 1 to 4, the ends of the supply ducts which are connected to the cylinders are subdivided into two parts. pipes opening through two openings in the cylinders. Optionally, the internal combustion engine 1 may also include a recirculation line (not shown) of the flue gas from the exhaust line 30 to the intake line 20. This recirculation line can then indifferently lead into the line of combustion. inlet 20 upstream of the air distributor 40; 50; 60; 70 or directly in it. Given the architecture of the internal combustion engine 1, we will call primary acoustic distance L1, L2, L3, L4 associated with a cylinder 11, 12, 13, 14, the acoustic distance between the inlet 45; 55; 65; 75 of the plenum 40A; 50A; 60A; 70A of the outlet of the intake duct 41, 42, 43, 44; 51, 52, 53, 54; 61, 62, 63, 64; 71, 72, 73, 74 opening into this cylinder. In addition, secondary acoustic distance L5, L6, L7, L8 associated with a cylinder 11, 12, 13, 14 will be called the acoustic distance separating the inlet 45; 55; 65; 75 of the plenum 40A; 50A; 60A; 70A of the output of the supply duct 11A, 12A, 13A, 14A of fresh air corresponding to this cylinder.

According to a particularly advantageous characteristic of the invention, at least a first 41; 51; 61; 71 and a second 42; 52; 62; 72 of said inlet ducts of the air distributor have different geometries, so that the primary acoustic distances L1, L2, L3, L4 associated with all the cylinders 11, 12, 13, 14 are all equal.

Preferably, as shown in FIGS. 1, 3 and 4, the inlet 45; 65; 75 of the plenum 40A; 60A; 70A is central, that is to say situated halfway up the cylinder formed by the plenum. In this case, the central intake ducts 42, 43; 62, 63; 72, 73 have different geometries than the end inlet ducts 41, 44; 61, 64; 71, 74. In contrast, the two central intake ducts 42, 43; 62, 63; 72, 73 are, like the two end inlet ducts 41, 44; 151, 64; 71, 74, symmetrical with respect to each other. Alternatively, as shown in Figure 2, the inlet 55 of the plenum 50A may be located at one end of the cylinder formed by the plenum. In this case, the intake ducts 51, 52, 53, 54 all have different geometries. According to a first and a second embodiment of the invention, more particularly shown in FIGS. 1 and 2, the geometrical distances of the path of the fresh air between the single inlet 45; Plenum 40A; 50A and the outlets of the intake ducts 41, 42, 43, 44; 51, 52, 53, 54 are all equal.

In the first embodiment of the air distributor 40 shown in Figure 1 (in which the inlet 45 of the plenum 40A is central), the four intake ducts 41, 42, 43, 44 of the air distributor 40 have identical sections 7, but the end intake ducts 41, 44 have lengths different from those of the central intake ducts 42, 43. More specifically, the two end intake ducts 41, 44 have shapes of straight tubes, axes orthogonal to the longitudinal axis of the plenum 40A. In contrast, the two central intake ducts 42, 43 have curved tube shapes, here according to circular arcs. The tubes formed by these four intake ducts 41, 42, 43, 44 have constant and identical diameters. The circular arcs formed by the two central intake ducts 42, 43 extend here around the same axis which is parallel to the longitudinal axis of the plenum. In a variant, the central intake ducts could have different shapes, for example S. Anyway, the lengths of the central intake ducts 42, 43 are then greater than those of the intake ducts. end 41, 44, so that the geometric distances separating the inlet 45 of the plenum 40A from the outlets of the intake ducts 41, 42, 43, 44 are all equal (the aforementioned geometric distances of course correspond to the distances that the air fresh must travel from the entrance of the plenum to the outlets of the intake ducts). Thus, since, on the one hand, these geometric distances are equal, and on the other hand, the four intake ducts 41, 42, 43, 44 have identical sections, the primary acoustic distances L1, L2, L3, L4 associated with the four cylinders 11, 12, 13, 14 are also equal. Therefore, the acoustic waves propagate uniformly in all the intake ducts 41, 42, 43, 44 and in the plenum 40A, so that the fresh air filling of the four cylinders 11, 12, 13, 14 is homogeneous. The air distributor 40 is then said to be acoustically tuned. In the second embodiment of the air distributor 50 shown in FIG. 2 (in which the inlet 55 of the plenum 50A is situated at one of its ends), the intake ducts 51, 52, 53, 54 have all different lengths and identical sections. Here, all the inlet ducts 51, 52, 53, 54 have straight tube shapes of constant and identical diameters and axes parallel and orthogonal to the longitudinal axis of the plenum. On the other hand, they have decreasing lengths as a function of their distance from the inlet 55 of the plenum 50A, so that the geometrical distances separating the inlet 55 from the plenum 50A from the outlets of the intake ducts 51, 52, 53, 54 are all equal. Thus, since, on the one hand, these geometric distances are equal, and on the other hand, the four intake ducts 51, 52, 53, 54 have identical sections. the primary acoustic distances L1, L2, L3, L4 associated with the four cylinders 11, 12, 13, 14 are equal.

Therefore, the acoustic waves propagate uniformly in all the intake ducts 51, 52, 53, 54 and in the plenum 50A, so that the fresh air filling of the cylinders 11, 12, 13, 15 is carried out in a controlled manner. homogeneous. In order that the intake ducts 51, 52, 53, 54 may have different lengths, the plenum 50A of the air distributor 50 extends in length along a longitudinal axis inclined with respect to the longitudinal axis of the cylinder block (axis perpendicular to the axes of the four cylinders). As shown in FIG. 2, the longitudinal axis of the air distributor 50 is situated in a plane normal to the axes of the four cylinders 11, 12, 13, 14.

Of course alternatively, the longitudinal axis of the air distributor 50 could be located in a plane parallel to the axes of the four cylinders 11, 12, 13, 14, so that the air distributor is glued to the engine block 10 According to a third and a fourth embodiment of the invention, more particularly shown in FIGS. 3 and 4, the geometrical distances of the path of the fresh air between the single inlet 65; 75 of the plenum 60A; 70A and the outlets of at least two of the intake ducts 61, 62; 71, 72 are different. In the third embodiment of the air distributor 60 shown in FIG. 3, the four intake ducts 61, 62, 63, 64 have identical lengths, but the end intake ducts 61, 64 have sections other than those of the central intake ducts 62, 63. More specifically, the end intake ducts 61, 64 have strictly cylindrical tube shapes, axes orthogonal to the longitudinal axis of the plenum 60A. In contrast, the central intake ducts 62, 63 have tube shapes each provided with a sectional enlargement.

These sectional enlargements here form cylindrical chambers located midway along the central inlet ducts 62, 63. Of course, alternatively, these sectional enlargements could have different shapes, such as divergent cone shapes whose vertices are turned to the plenum.

Since the four intake ducts have identical lengths, it is understood that the geometric distances separating the inlet 65 of the plenum 60A from the outlets of the central intake ducts 62 and 63 are different from the geometrical distances separating the inlet 65 from the plenum. However, the sections of the end and central intake ducts are different, so that their own resonant frequencies (and therefore their acoustic lengths) are identical. The sizes of the section enlargements are then provided so that the primary acoustic distances L1, L2, L3, L4 are all equal, so that the fresh air filling of the four cylinders is done homogeneously. In the fourth embodiment of the air distributor 70 shown in FIG. 4, the four intake ducts 71, 72, 73, 74 have identical lengths, but the end intake ducts 71, 74 have sections other than those of the central intake ducts 72, 73. More specifically, the end intake ducts 71, 74 have cone shapes of axes orthogonal to the longitudinal axis of the plenum 70A, the vertices of which are turned to the breech. In contrast, the central intake ducts 72, 73 have cylindrical tube shapes. Since the four intake ducts 71, 72, 73, 74 have identical lengths, it is understood that the geometric distances separating the inlet 75 of the plenum 70A from the outlets of the central intake ducts 72, 73 are different from the geometric distances separating the inlet 75 of the plenum 70A of the outlets of the end inlet ducts 71, 74. However, the sections of the end and central inlet ducts are different, so that their resonance frequencies are clean (and therefore their lengths acoustic) are identical.

The cone geometries are then provided so that the primary acoustic distances L1, L2, L3, L4 are all equal, so that the fresh air filling of the four cylinders is done homogeneously. The present invention is not limited to the embodiments described and shown, but the skilled person will be able to make any variant within his mind. In particular, the equalization of the primary acoustic distances associated with the cylinders can be achieved by combining length differences and section differences between the intake ducts. For example, the end inlet ducts may have rectilinear tube shapes while the central intake ducts have curved tube shapes with sectional enlargements. According to another embodiment of the air distributor, the equalization 10 of the primary acoustic distances associated with the cylinders can be achieved by modifying the shape of the plenum. For example, if the entry of the plenum is central, it can be bent so that its ends are positioned at a distance from the yoke lower than its central portion. According to another embodiment of the invention, the supply ducts and the intake ducts may have shapes such that the primary acoustic distances L1, L2, L3, L4 are different but that the secondary acoustic distances L5, L6 , L7, L8 are equal.

In this mode, the intake ducts of the plenum have lengths and / or different sections from each other. However, these differences in geometries are not sufficient to equalize the primary acoustic distances L1, L2, L3, L4 associated with the four cylinders. Consequently, the supply ducts 11A, 12A, 13A, 14A are designed to have lengths and / or different sections from each other, so as to participate in the equalization of the secondary acoustic distances L5, L6, L7, L8. In this way, the fresh air filling of the cylinders is homogeneous.

Claims (14)

An air distributor (40; 50; 60; 70) of an internal combustion engine (1) internally defining a plenum (40A; 50A; 60A; 70A) having a single inlet (45; 55; 65); 75) of fresh air and opening into at least three intake ducts (41, 42, 43, 44, 51, 52, 53, 54, 61, 62, 63, 64, 71, 72, 73, 74); whose outlets are capable of being connected to cylinders (11, 12, 13, 14) separate from the internal combustion engine (1), characterized in that at least one first (41; 51; 61; 71) and one second (42; 52; 62; 72) of said intake ducts have different geometries, so that the acoustic distances (L1, L2, L3, L4) separating the single inlet (45; 55; 65; 75) plenum (40A; 50A; 60A; 70A) outlets of the intake ducts (41, 42, 43, 44; 51, 52, 53, 54; 61, 62, 63, 64; 71, 72, 73, 74); are all equal. 2. Air distributor (40; 50) according to the preceding claim, wherein the geometrical distances of the fresh air path between the single inlet (45; 55) of the plenum (40A; 50A) and the duct outlets. (41, 42, 43, 44, 51, 52, 53, 54) are all equal. 3. Air distributor (40; 50) according to the preceding claim, wherein said first (41; 51) and second (42; 52) intake ducts have different lengths and identical sections. The air distributor (60; 70) according to claim 1, wherein the geometric distances of the fresh air path between the single inlet (65; 75) of the plenum (60A; 70A) and the outlets of the first and second intake ducts (61, 62; 71, 72) are different. 25 5. Air distributor (60; 70) according to the preceding claim, wherein said first and second intake ducts (61, 62; 71, 72) have identical lengths and different sections. 6. air distributor (40) according to one of the preceding claims, wherein the first intake duct (41) extends along a curved mean line and the second intake duct (42) extends along a straight line. 7. Air distributor (40; 50) according to one of the preceding claims, wherein the intake ducts (41, 42, 43, 44; 51, 52, 53, 54) have lengths depending on their distance. at the single entrance of the plenum (40A; 50A). 35 8. air distributor (70) according to one of the preceding claims, wherein at least one of the inlet ducts (71, 74) has a conical shape. 12 9. Air distributor (60) according to one of the preceding claims, wherein at least one of the inlet ducts (62, 63) is provided with a sectional enlargement. 10. air distributor (50) according to one of the preceding claims, wherein, the plenum (50A) having an elongated shape, the single inlet (55) of the plenum (50A) is located at one end of said plenum ( 50A) and the geometries of the intake ducts (51, 52, 53, 54) are all different. 11. Air distributor (40; 60; 70) according to one of claims 1 to 9, wherein the plenum (40A; 60A; 70A) having an elongate shape, the single inlet (45; 65; 75) plenum (40A; 60A; 70A) is located midway along said plenum (40A; 60A; 70A) and the geometries of the inlet ducts (41,42,43,44; 61,62,63,64; , 72, 73, 74) are symmetrical in pairs, on either side of said single input (45; 65; 75). 12. Internal combustion engine (1) having at least three cylinders (11, 12, 13, 14) and an intake line (20) of fresh air provided with an air distributor (40; 50; 60 70) according to one of the preceding claims, wherein the intake ducts open into each of said cylinders (11, 12, 13, 14). 13. Intake line (20) for fresh air of an internal combustion engine (1), comprising: - at least three fresh air intake ducts (11A, 12A, 13A, 14A) connected to cylinders (11, 12, 13, 14) separate from the internal combustion engine (1), and - an air distributor (40; 50; 60; 70) internally defining a plenum (40A; 50A; 60A; 70A) having a single inlet (45; 55; 65; 75) of fresh air and opening into branch lines (41, 42, 43, 44; 51, 52, 53, 54; 61, 62, 63, 64; 71, 72, 73, 74) connected on said at least three supply ducts (11A, 12A, 13A, 14A), characterized in that at least a first (11A) and a second (12A) of said supply ducts have different geometries, so that the acoustic distances (L5, L6, L7, L8) separating the single inlet (45; 55; 65; 75) from the plenum (40A; 50A; 60A; 70A) from the outlets of the supply ducts (11A, 12A, 13A); , 14A) are all equal.