Internal combustion engine with variable-capacity intake system for a vehicle

Abstract: A variable-capacity intake system (1) for a vehicle internal combustion engine, and of the type presenting: a first (3) and second (4) reservoir connected to common air supply means; at least a first intake conduit (5) connecting the first reservoir (3) to a respective cylinder of a corresponding first block (6); at least a second intake conduit (7) connecting the second reservoir (4) to a respective cylinder of a corresponding second block (8); respective branches (17, 18) connecting the first intake conduit (5) to the second reservoir (4) and the second intake conduit (7) to the first reservoir (3); and valve means (19, 20) for selectively connecting each reservoir (3, 4) to one of the intake conduits (5, 7).

Description: The present invention relates to a variable-capacity intake system for an internal combustion engine, in particular a high-performance GT car engine. As is known, it is possible to enhance the volumetric efficiency of an internal combustion engine using a system, which provides for varying intake conditions and optimizing engine filling by determining resonance conditions in the system at different engine speeds. Increasing the volumetric efficiency of the engine provides to a certain extent for increasing power output for a given engine speed, reducing fuel consumption by burning the fuel better, and hence reducing the amount of pollutant exhaust gas produced. The state of the art is familiar with intake systems for internal combustion engines, especially those of high-performance, e.g. GT, cars, in which the air intake conduits comprise so-called "trumpet" elements designed to vary their length to diameter ratio and so vary the intake conditions of the engine. Such elements are substantially of two types: a first presents a telescopic end conduit portion defined by two coaxial elements sliding one inside the other and which, by varying their axial position in relation to each other, provide for varying the length to diameter ratio (the length increasing or decreasing, and the diameter remaining constant); and a second presents an inlet portion comprising a pair of semicylindrical lobes hinged to each other and laterally superimposed to define a continuous-section conduit portion variable in diameter according to the extent to which the two lobes are parted. In the case of engines with no trumpet elements, use is made, for each cylinder, of two parallel intake conduits of appropriate length and diameter and end-connected by a manifold fitted inside with a throttle valve. By controlling the throttle valve, it is possible to use either one or both of the conduits, thus changing the "equivalent diameter" of the resulting intake conduit, and so achieve resonance conditions for a given number of different engine speeds. A relevant example of this kind of intake systems is disclosed in EP-A-370 515. The above systems present the drawback of being relatively bulky and expensive; and the first, featuring telescopic trumpet elements, is also relatively delicate in terms of mechanical control. It is an object of the present invention to provide an engine including a variable-capacity intake system for optimizing engine filling by determining resonance conditions in the system at predetermined engine speeds, and which at the same time is of straightforward, robust design, and ensures a high degree of reliability. According to the present invention, there is provided an internal combustion engine for a vehicle as claimed in claim 1. Being straightforward in design, the above engine with variable-capacity intake system is therefore highly reliable, inexpensive and compact, and also provides for optimizing engine filling by determining resonance conditions in the system at predetermined engine speeds. Two non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows a schematic top plan view of a variable-capacity intake system for a vehicle internal combustion engine in accordance with the present invention; Figure 2 shows a section along line II-II in Figure 1; Figure 3 shows a section of a variation of the embodiment of Figure 1, in which valves at the inlet of each branch are not illustrated for sake of simplicity; Figure 4 shows a schematic top plan view, with parts removed for clarity, of the intake system in Figure 3. Number 1 in Figures 1 and 2 indicates a variable-capacity intake system for an otherwise known internal combustion engine (not shown) of any known type of vehicle (not shown), e.g. a GT car. Intake system 1 is fitted to the cylinder head 2 of the engine, and comprises a first and second reservoir 3 and 4 located facing each other on either side of cylinder head 2. Intake system 1 also comprises one or more first intake conduits 5, each connecting reservoir 3 to a respective cylinder of a corresponding first block 6; and one or more second intake conduits 7, each connecting second reservoir 4 to a respective cylinder of a corresponding second block 8. Blocks 6 and 8, which present in-line cylinders of which only one cylinder per block is shown in the accompanying drawings, are located parallel to and beneath reservoirs 3 and 4, and may be arranged in a V or power separate drive shafts. Reservoirs 3, 4 are also connected in known manner to respective air manifolds 9, 10 communicating with conduits 11, 12, for connection to an air filter 13, via throttled bodies 14, 15 opened and closed continuously by a known electromechanical system 16 controlled by the accelerator pedal of the vehicle. According to the present invention, intake conduits 5, 7 are Y-shaped, and comprise respective opposite branches 17, 18 comprising respective curved branches of conduits 5, 7 and connecting each first conduit 5 to second reservoir 4 and each second conduit 7 to first reservoir 3; branches 17, 18 are oppositely oriented to cross-over one another (Figure 2); and the inlet of each intake conduit 5, 7 connected to the respective reservoir 3, 4 presents ON/Off valve means 19, 20 comprising a throttle valve in the preferred embodiment shown. In the example shown in Figures 1 and 2, each intake conduit 5, 7 also comprises a substantially straight branch 21, 22 connecting the relative reservoir 3, 4 to the relative block 6, 8, and which is connected to respective branch 17, 18 and presents an axis inclined in relation to the axis of respective branch 17, 18 at the connecting point; and the inlet sections of branches 17, 18 connected to respective reservoirs 4, 3 are substantially inclined in relation to the axes of relative manifolds 10, 9. Finally, reservoirs 3, 4, branches 17, 18 and conduits 5, 7 are defined by respective cavities in cylinder head 2; and valves 19, 20 are all controlled together by a single shaft (not shown). In actual use, when valves 19, 20 are closed (as shown), conduits 5 of block 6 are cut off from reservoir 3 and communicate with reservoir 4 via branches 17 (Figure 2). The same also applies to reservoir 4. For block 6, therefore, the volume of intake system 1 involved in the intake stroke equals the volume of reservoir 4 plus the volume of the whole formed by branch 21 of respective intake conduit 5, which is closed, and by respective branch 17, and vice versa for block 8. At the design stage, therefore, reservoirs 3, 4, intake conduits 5, 7 and branches 17, 18 may be so sized as to determine resonance conditions in system 1 at a predetermined engine speed and so optimize the efficiency of the engine at that speed. When valves 19, 20 are opened (simultaneously or separately), the total volume of system 1 communicating with each block 6, 8 increases by an amount equal to the volume of reservoir 3, 4 over the respective block, thus varying the resonance conditions; and the volumes of reservoirs 3, 4 may of course be so calculated as to determine resonance conditions, this time, at a different engine speed, thus achieving optimum intake conditions at two different engine speeds by simply opening/closing valves 19, 20 as a function of the engine speed. According to the invention valve means 19, 20 are fitted to the intake conduits 5,7 connected to respective reservoirs 4, 3 and to the inlets of each branch 17,18 in order to change, in use, the resonance conditions desired during intake. Accordingly, in addition to valve means 19, 20 inside intake conduits 5, 7 as described above, a further pair of ON/OFF valve means 23, 24 (shown by the dotted line in Figure 2) are fitted to the inlets of branches 17, 18 connected to respective reservoirs 4, 3, so as to achieve optimum resonance conditions for at least three different predetermined engine speeds: a first adjustment with valves 19, 20, 23, 24 all open; a second adjustment by closing valves 19, 20 so that blocks 6, 8 are supplied exclusively by branches 17, 18, i.e. along paths with a high length to diameter ratio; and a third adjustment by closing valves 23, 24 and opening valves 19, 20, so that blocks 6, 8 are supplied along "short" paths defined by conduits 5, 7 with a smaller length to diameter ratio. Figures 3 and 4 show a further embodiment of a variable-capacity intake system for an internal combustion engine in accordance with the present invention and indicated as a whole by 1'. Wherever possible, the component parts of system 1' are indicated using the same reference numbers as for the corresponding parts of system 1. System 1' differs from system 1 by comprising a further conduit 25 connecting reservoirs 3 and 4; and ON/OFF valve means 26 housed inside conduit 25 and comprising a throttle valve in the preferred embodiment shown. Moreover, each intake conduit 5, 7 comprises a substantially straight branch 27, 28, which differs from branch 21, 22 by presenting an axis substantially perpendicular to the axis of respective branch 17, 18 at the point of connection to branch 27, 28; and the inlet sections of branches 17, 18 connected to respective reservoirs 4, 3 are substantially parallel to the axes of respective branches 28, 27. In actual use, when valve means 26 are opened, the total volume of system 1' communicating with each block 6, 8 increases by an amount equal to the volume of reservoir 4, 3 over the adjacent block 8, 6, thus varying the resonance conditions; and the volumes of reservoirs 3, 4 may of course be so calculated as to determine resonance conditions at an engine speed other than those of system 1. Clearly, changes may be made to intake systems 1 and 1' as described and illustrated herein without, however, departing from the present invention as defined in the appended claims.

Claims: An internal combustion engine for a vehicle comprising a first (6) and a second (8) cylinder block and a variable-capacity intake system (1), this latter comprising: a first (3) and second (4) reservoir connected to common air supply means; at least a first intake conduit (5) connecting the first reservoir (3) to a respective cylinder of the corresponding first block (6); at least a second intake conduit (7) connecting the second reservoir (4) to a respective cylinder of the corresponding second block (8); respective branches (17, 18) connecting each said first conduit (5) to the second reservoir (4), and each said second conduit (7) to the first reservoir (3); and valve means (19, 20, 23, 24) for selectively connecting each said reservoir (3, 4) to said first and second intake conduits (5, 7);; characterized in that said valve means (19, 20, 23, 24) are fitted both to the inlet of each intake conduit (5, 7) connected to the corresponding reservoir (3, 4) and to the inlet of each branch (17, 18) connected to the corresponding reservoir (4, 3). An engine as claimed in Claim 1, characterized in that the reservoirs (3, 4) are located on either side of a cylinder head (2), each at and over a respective said block (6, 8); and in that the intake conduits (5, 7) are Y-shaped, said branches (17, 18) comprise respective curved branches of said Y-shaped intake conduits (5, 7), and said curved branches are oppositely oriented to connect each reservoir (4, 3) to the cylinders of the opposite block (6, 8). An engine as claimed in Claim 1 or 2, characterized in that said valve means (19, 20, 23, 24) are ON/OFF types. An engine as claimed in any one of the foregoing Claims, characterized in that said valve means (19, 20) are throttle valves fitted to the inlets of said intake conduits (5, 7) connected to the corresponding reservoirs (3, 4). An engine as claimed in any one of the foregoing Claims from 1 to 3, characterized in that said valve means (23, 24) are throttle valves fitted to the inlets of said branches (17, 18) connected to the corresponding reservoirs (4, 3). An engine as claimed in any one of the foregoing Claims, characterized in that said reservoirs (3, 4), said intake conduits (5, 7) and said branches (17, 18) are defined by respective cavities delimited in said cylinder head (2). An engine as claimed in any one of the foregoing Claims, characterized by comprising a conduit (25) connecting said first and second reservoirs (3, 4); and interception valve means (26) in series with said conduit (25). An engine as claimed in Claim 7, characterized in that said valve means (26) are of the ON/OFF type. An engine as claimed in Claim 7, characterized in that said valve means (26) comprise a throttle valve housed inside said connecting conduit (25).

Inventors: MARTINELLI PAOLO, MARTINELLI, PAOLO
Applicants: FERRARI SPA, FERRARI S.P.A.
Application year: 1996
Main classification: F02B27
IPC codes: F02M35, F02B27