Car provided with exhaust system with aerodynamic effect

Abstract

To provide a car including an internal combustion engine with an exhaust system capable of maximizing performances while following a type approval regulation and ensuring natural exhaust sound suitable for sport use of the car.SOLUTION: A car has: two front wheels; two rear wheels; a bottom wall delimiting a lower surface which faces a road surface and is brushed by an air flow flowing under the car in use; an internal combustion engine; and an exhaust system coupled to the internal combustion engine and provided with an exhaust duct (7). In the exhaust system, the exhaust duct originates from the internal combustion engine and has an end chamber (9), the end chamber ends at an outlet opening portion (10), through which an exhaust gas is released into the atmosphere. The end chamber of the exhaust duct has at least one movable partition (23), and the movable partition can be moved to a plurality of different positions so as to change a width of the outlet opening portion. The movable partition delimits a lower surface of the end chamber which faces the road surface and is brushed by the air flow flowing under the car in use.SELECTED DRAWING: Figure 3

Description

Cross-reference to related applications

[0001] This patent application claims priority from Italian Patent Application No. 102020000032849 filed on December 30, 2020, the entire disclosure of which is incorporated herein by reference.

Technical field

[0002] The present invention relates to a motor vehicle equipped with an internal combustion engine having an exhaust system.

Background art

[0003] According to the vehicle type approval regulations, the manufacturer has to limit the sound emission level, especially when the vehicle is traveling at medium speed (i.e., when traveling in the city center). As a result, the exhaust system (which performs the function of discharging the gases generated by combustion into the atmosphere and limiting both the noise and the pollutant content) always includes at least one muffler arranged along the exhaust duct downstream of the pollutant reduction device.

[0004] Generally speaking, a muffler typically comprises a tubular body having an elliptical cross-section and an inlet and outlet opening. Inside the tubular body is a defined labyrinth that determines the path of exhaust gases from the inlet to the outlet opening. This labyrinth usually consists of diaphragms (or partitions) positioned intersectingly (i.e., perpendicular to the longitudinal axis of the tubular body) to define chambers within the tubular body, and tubes connecting the chambers to each other. In conventional mufflers that ensure significant noise reduction at low engine speeds, the exhaust back pressure generated by the muffler (i.e., the pressure loss in the exhaust gases as they flow through the muffler) increases exponentially as the revolutions per minute of the internal combustion engine increases (i.e., as the average velocity of the exhaust gases increases). As a result, bypass ducts are provided to avoid excessively high exhaust back pressure values ​​at high engine speeds (and thus unduly jeopardizing performance at high engine speeds). The bypass duct is positioned in parallel with the muffler (i.e., designed to bypass the muffler) and is regulated by a bypass valve. The bypass valve remains closed at low engine speeds (to maximize muffler operation; however, this is not essential at low engine speeds, although performance is sacrificed), and opens at high engine speeds (to reduce exhaust back pressure to an acceptable level).

[0005] Furthermore, a crucial factor in evaluating high-performance sports cars is the "quality" of the sound emitted from the exhaust system. This is a very important sensory feedback when using the car at its limits. However, known exhaust systems with variable shapes (i.e., those equipped with one or more electrically or pneumatically controlled valves that can alter the path of the exhaust gases, and therefore the path of the sound along the exhaust system) do not always guarantee that the sound emitted by the exhaust system will meet the user's needs.

[0006] Generally speaking, turbocharged engines are at a disadvantage because the presence of the turbine along the exhaust duct and the compressor along the intake duct adds filtering and reduction of sound levels in both the exhaust and intake systems.

[0007] Furthermore, recent emission standards require a second catalytic converter or particulate filter (GPF, i.e., "gasoline particulate filter") to be present in series with the catalytic converter, even in gasoline engines, thus establishing the use of exhaust gas treatment devices that significantly compromise sound performance.

[0008] U.S. Patent No. 1,483,354, Korean Patent Application Publication No. 20160108625, and UK Patent Application Publication No. 2274681 describe an exhaust system for an internal combustion engine in which an exhaust duct originating from the engine has an end chamber terminating at an outlet opening through which exhaust gases are released into the atmosphere, and the end chamber of the exhaust duct has at least one movable partition which can be moved to various positions to change the width of the outlet opening. In particular, the movement of the movable partition can be performed manually (as described in U.S. Patent No. 1,483,354) or automatically against an elastic thrust generated by a spring that tends to minimize the width of the outlet opening due to the pressure of the exhaust gases (as described in Korean Patent Application Publication No. 20160108625 and UK Patent Application Publication No. 2274681).

[0009] U.S. Patent Application Publication No. 2008282688 describes an exhaust system for an internal combustion engine, comprising an exhaust pipe with multiple vent flaps that automatically open when the exhaust gas temperature rises. [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] The object of the present invention is to provide an automobile equipped with an internal combustion engine and an exhaust system that can maximize performance while complying with type approval regulations and simultaneously ensuring natural exhaust noise suitable for sporty use of the automobile.

[0011] According to the present invention, an automobile is provided that has an internal combustion engine equipped with an exhaust system as described in the appended claims.

[0012] The attached claims describe preferred embodiments of the present invention and form an integral part of this specification. [Brief explanation of the drawing]

[0013] The present invention will now be described with reference to the accompanying drawings illustrating some non-limiting embodiments thereof. [Figure 1] This is a schematic plan view of an automobile driven by an internal combustion engine equipped with the exhaust system according to the present invention. [Figure 2] Figure 1 is a side view of the automobile. [Figure 3] Figure 1 is a perspective view of the end chamber of the exhaust duct of the exhaust system (not manufactured according to the present invention, and equipped with two movable partitions). [Figure 4] This is a front view of the end chamber shown in Figure 3. [Figure 5] This is a longitudinal cross-sectional view of a portion of the end chamber shown in Figure 3. [Figure 6] This is a schematic diagram of the end chamber in Figure 3, which has a movable partition in one of several different positions. [Figure 7] This is a schematic diagram of the end chamber in Figure 3, which has a movable partition in one of several different positions. [Figure 8] This is a schematic diagram of the end chamber in Figure 3, which has a movable partition in one of several different positions. [Figure 9] This is a schematic diagram of the end chamber in Figure 3, which has a movable partition in one of several different positions. [Figure 10]Schematic view of different embodiments of the end chamber of FIG. 3 (manufactured according to the present invention), where the movable partition is in one of a plurality of different positions, emphasizing the air flow flowing under the vehicle. [Figure 11] Schematic view of different embodiments of the end chamber of FIG. 3 (manufactured according to the present invention), where the movable partition is in one of a plurality of different positions, emphasizing the air flow flowing under the vehicle. [Figure 12] Schematic view of different embodiments of the end chamber of FIG. 3 (manufactured according to the present invention), where the movable partition is in one of a plurality of different positions, emphasizing the air flow flowing under the vehicle. [Figure 13] Schematic plan view of the motor vehicle of FIG. 1, where the exhaust system is designed according to different embodiments.

Mode for Carrying Out the Invention

[0014] In FIG. 1, reference numeral 1 generally indicates a motor vehicle having two front wheels 2 and two rear drive wheels 3. The motor vehicle is supercharged by a turbocharger and receives torque from an internal combustion engine 4 disposed at a front position.

[0015] The motor vehicle 1 includes a passenger compartment 5 designed to accommodate a driver and possible passengers.

[0016] According to a possible but non-binding embodiment, the internal combustion engine 4 is a "V8" engine and has two (twin) banks with four cylinders arranged at an angle to each other so as to form a "V". In each bank, the four cylinders are connected to an intake manifold (not shown) by two intake valves and to an exhaust manifold (not shown) by two exhaust valves. Each exhaust manifold collects the gases generated by combustion, and the gases flow out cyclically from the exhaust valves.

[0017] The internal combustion engine 4 is equipped with an exhaust system 6 that has the function of discharging the gas generated by combustion into the atmosphere, limiting both noise and the content of pollutants. The exhaust system 6 starts from the respective exhaust manifolds, and for this reason, receives the gas generated by combustion from the exhaust manifolds themselves and comprises two twin exhaust ducts 7 that terminate in the region of the rear of the vehicle 1. Along each exhaust duct 7, there are known exhaust gas treatment devices 8, and there is always at least one catalytic converter and a particulate filter or further catalytic elements always present (to comply with the EURO6D standard regarding pollutant emissions).

[0018] Each exhaust duct 7 (starting from the internal combustion engine 4) has an end chamber (end) 9, which is terminated by an outlet opening 10 through which the exhaust gas is discharged into the atmosphere.

[0019] According to FIG. 2, the vehicle 1 comprises a bottom wall that faces the road surface and separates the lower surface that is swept by the air flow flowing under the vehicle 1 during use.

[0020] According to FIGS. 3, 4 and 5, the exhaust system 6 (not manufactured according to the present invention) comprises, for each exhaust duct 7, a silencing device 11 that connects to the corresponding end chamber 9 (i.e., sends the exhaust gas flowing through it to the corresponding end chamber 9). Furthermore, the exhaust system 6 comprises, for each exhaust duct 7, a bypass duct 12 that starts from the exhaust duct 7 in the region of the branch 13 and terminates at the inlet of the corresponding silencing device 11. In other words, each bypass duct 12 is an alternative route to the last segment of the corresponding exhaust duct 7.

[0021] Finally, the exhaust system 6 is equipped with a control valve 14 for each exhaust duct 7, which can be electronically controlled and is located along the exhaust duct 7 downstream of the branch 13 from which the corresponding bypass duct 12 originates (i.e., located between the branch 13 and the end chamber 9), and is designed to regulate the exhaust gas flow toward the end chamber 9. Preferably, each control chamber 14 has the capability to open at least partially between a fully closed position and a fully open position. That is, each control valve 14 is not an on / off valve, but can take an intermediate position within a certain range between the fully closed position and the fully open position.

[0022] Each silencing device 11 is a conventional silencing device and consists of a tubular body 15 having, for example, an inlet opening 16 (to which a corresponding bypass duct 12 is attached), an outlet opening 17 connected to an end chamber 9, and an internal labyrinth (not shown) that determines the path of exhaust gas from the inlet opening 16 to the outlet opening 17.

[0023] When each control valve 14 is open, the exhaust gas tends to flow directly into the end chamber 9, thus bypassing the bypass duct 12 and the silencer 11 (due to the greater load loss experienced when flowing through the silencer 11). Conversely, when each control valve 14 is closed, the exhaust gas is forced to flow through the bypass duct 12 to reach the end chamber 9. In other words, the control valve 14 is moved towards the fully closed position to prevent the exhaust gas from flowing into the last segment of the exhaust duct 7, thus forcing the exhaust gas to flow through the bypass duct 12, which terminates at the silencer 11, to reach the end chamber 9, resulting in greater noise attenuation and greater back pressure. Conversely, the control valve 14 is moved to the fully open position to direct the exhaust gas flow towards the last segment of the exhaust duct 7 (the bypass duct 12 does not need to be closed, as the greater back pressure determined by the silencer 11 minimizes exhaust gas flow along the bypass duct 12 when an alternative, freer path is available).

[0024] Each end chamber 9 comprises a tubular body 18 and has an inlet opening 19 connected to the exhaust duct 7 and an outlet opening 10 opposite the inlet opening 19. Exhaust gas entering from the exhaust duct 7 flows into the end chamber 9 (i.e., the tubular body 18) through the inlet opening 19 and flows out of the end chamber 9 (i.e., the tubular body 18) through the outlet opening 10. Each end chamber 9 (i.e., each tubular body 18) has a trumpet-like shape that increases in size toward the outlet opening 10, has a rectangular cross-section, and is separated by two fixed base walls 20 and 21 (lower wall and upper wall, respectively) that face each other and radiate toward the outlet opening 10, as well as two fixed side walls 22 that face each other and are parallel.

[0025] Each end chamber 9 of the exhaust duct 7 has two movable partitions 23 facing each other, which can move to several different positions (as clearly shown in Figures 6 to 9). Each end chamber 9 has a motor-driven actuator device 24 configured to move the movable partitions 23 (i.e., equipped with an electric or pneumatic motor designed to actively generate motion). Preferably (but not necessarily), each actuator device 24 is configured to move the two movable partitions 23 independently. In other words, each motor-driven actuator device 24 is active and electronically (electrically) controlled to generate a force (torque) that determines the movement of the movable partitions 23. As a result, in each end chamber 9, the position of the movable partition 23 can be adjusted completely independently of the pressure and flow rate of the exhaust gas flowing through the end chamber 9 (by controlling the corresponding actuator device 24) (for example, the movable partition 23 can be moved to have a very large outlet opening 10 when the exhaust gas pressure and flow rate are moderate, and can be moved to have a very small outlet opening 10 when the exhaust gas pressure and flow rate are high).

[0026] In a preferred embodiment, each movable partition 23 is hinged to rotate around a pivot axis 25 (which is positioned horizontally). That is, each movable partition 23 is hinged to the tubular body 25 in the area of ​​the fixed base wall 20 or 21 so as to rotate around the pivot axis 25. As a result, each actuator device 24 is configured to rotate two movable partitions 23 around their respective pivot axes 25 (thus, the movement of the two movable partitions 23 can move them away from each other or move them closer to each other).

[0027] In the end chambers 9 of each exhaust duct 7, the two movable partitions 23 can move between a maximum expansion position (e.g., shown in Figure 6) and a minimum expansion position (e.g., shown in Figure 9). Obviously, when the two movable partitions 23 are in the maximum expansion position (e.g., shown in Figure 6), the area of ​​the outlet opening 10 is (significantly) larger than when the two movable partitions 23 are in the minimum expansion position (e.g., shown in Figure 9).

[0028] At the maximum expansion position (for example, shown in Figure 6), or even at other expansion positions (for example, shown in Figure 7), the two movable partitions 23 cause the end chamber 9 of the exhaust duct 7 to obtain a divergent shape in which the cross-sectional area gradually increases as it approaches the outlet opening 10.

[0029] In a preferred embodiment, at the minimum expanded position (for example, as shown in Figure 9), the two movable partitions 23 cause the end chamber 9 of the exhaust duct 7 to obtain a converging shape in which the cross-sectional area gradually decreases as it approaches the outlet opening 10.

[0030] Intermediate positions (e.g., shown in Figure 8) between the minimum extension position (shown in Figure 9) and the maximum extension position (e.g., shown in Figure 6) are also possible.

[0031] In other words, each actuator device 24 can position and hold the two movable partitions 23 in an intermediate position between the maximum extension position (shown in Figure 6) and the minimum extension position (shown in Figure 9).

[0032] According to possible embodiments shown in Figures 3, 4, and 5, each fixed base wall 20 or 21 also extends beyond the rotation axis 25 of each movable partition 23 (i.e., each fixed base wall 20 or 21 does not terminate in the region of each region movable partition 23), and therefore, in the fully extended position, each movable partition 23 leans against the fixed base wall 20 or 21. Furthermore, both movable partitions 23 are fully inserted into the end chamber 9 (i.e., into the tubular body 18), and therefore, as they rotate around their respective rotation axes 25, they slide against the fixed side walls 22.

[0033] According to possible embodiments shown in Figures 3, 4, and 5, each silencer 11 is positioned below its respective end chamber 9 (i.e., the tubular body 15 of each silencer 11 is positioned below its respective end chamber 9, i.e., below its tubular body 18). As a result, the lower base wall 20 of each end chamber 9 (i.e., each tubular body 18) is provided with at least one inlet opening 26 to which the silencer 11 is connected (i.e., overlapping with the outlet opening 17 of the silencer 11). Preferably, in each end chamber 9, the inlet opening 26 is positioned upstream of the movable partition 23 with respect to the exhaust gas flow.

[0034] In other words, each end chamber 9 has separate and independent inlet openings 19 and 26, and an outlet opening 10 through which exhaust gas is released into the atmosphere. The exhaust duct 7 starts from the internal combustion engine 4 and connects to the inlet openings 19 of the end chambers 9, while the silencer 11 has an outlet opening 17 that connects directly to the inlet openings 26 of the end chambers 9. The bypass duct 12 starts from the exhaust duct 7 within the region of the branch 13 and terminates at the inlet opening 16 of the silencer 11. Furthermore, a control valve 14 is positioned along the exhaust duct 7 downstream of the branch 13 (i.e., between the branch 13 and the inlet openings 19) and is designed to regulate the exhaust gas flow toward the inlet openings 19 of the end chambers 9.

[0035] According to a preferred embodiment, each silencer 11 is connected to the end chamber 9 so as to form a single body with the end chamber 9. That is, the tubular body 15 of the silencer 11 is stably and firmly connected to the end chamber 9 (i.e., the tubular body 18) (typically by welding), so that the tubular body 15 and the tubular body 18 can share the same fixed base wall 20 or 21. As described above, each end chamber 9 (i.e., each tubular body 18) has a trumpet-like shape that increases in size toward the outlet opening 10. The silencer 11 has a shape complementary to the shape of the end chamber 9 (i.e., the tubular body 18), and thus decreases in size toward the outlet opening 10. In this way, the single body (i.e., the tubular body 18) consisting of the tubular body 15 and the end chamber 9 of the silencer 11 has a substantially parallelepiped structure.

[0036] A control unit 27 ( schematically shown in Figure 1) is also present, which is configured to change the position of the movable partitions 23 of each end chamber 9 (by controlling the corresponding actuator devices 24) in response to the rotational speed of the internal combustion engine 4, the engine load of the internal combustion engine 4, the gears engaging with the gearbox coupled to the internal combustion engine 4, the longitudinal speed of the vehicle 1 equipped with the internal combustion engine 4, and the longitudinal acceleration of the vehicle 1 equipped with the internal combustion engine 4.

[0037] In other words, the control unit 27 is configured to detect the rotational speed of the internal combustion engine 4, the engine load of the internal combustion engine 4, the gears engaged with the gearbox coupled to the internal combustion engine 4, the longitudinal speed of the vehicle, and the longitudinal acceleration of the vehicle 1 (for example, by reading them from the vehicle's BUS network). Knowing this information (which is read in advance), the control unit 27 can determine the position of the movable partitions 23 of each end chamber 9 accordingly.

[0038] The control unit 27 can also be configured to change the position of the movable partition 23 in each end compartment 9 in accordance with the driving mode selected by the driver (i.e., sport driving mode, racing driving mode, city driving mode, highway driving mode, wet road driving mode, etc., which is generally selected by the driver by operating a selector called a "hand lever").

[0039] The control unit 27 needs to control the position of the movable partitions 23 in each end chamber 9 in order to pursue three objectives: compliance with type approval regulations regarding the intensity of sound emitted by the exhaust system (an unnegotiable requirement that must always be met), obtaining high "quality" of sound emitted by the exhaust system (i.e., the type of sound emitted by the exhaust system that can be considered pleasant to the driver and therefore meets the driver's expectations), and maximizing the performance of the internal combustion engine 4. Provided that the control unit 27 is configured to always comply with type approval regulations regarding the intensity of sound emitted by the exhaust system, in some situations the control unit 27 may prioritize the "quality" of sound emitted by the exhaust system over the performance of the internal combustion engine 4, while in other situations the control unit 27 may prioritize the performance of the internal combustion engine 4 over the "quality" of sound emitted by the exhaust system.

[0040] Generally speaking, the control unit 27 is configured to hold the movable partitions 23 of each end chamber 9 in the minimum expanded position when the rotational speed per minute is low and the load on the internal combustion engine 4 is low, and to move the movable partitions 23 of each end chamber 9 toward the maximum expanded position when the rotational speed per minute is high and the load on the internal combustion engine 4 is high. Furthermore, the control unit 27 is configured to move the movable partitions 23 of each end chamber 9 toward the minimum expanded position in low-speed gears, and to move the movable partitions 23 of each end chamber 9 toward the maximum expanded position in high-speed gears.

[0041] According to a preferred embodiment, the control unit 27 stores different maps (each corresponding to one or more operating modes) and, based on data provided as inputs relating to revolutions per minute and engine load of the internal combustion engine 4, as well as the gears engaged in the gearbox coupled to the internal combustion engine 4, provides as an output the desired (ideal) position of the movable partition 23 of each end chamber 9. Obviously, each map stored in the control unit 27 contains a limited number of points, and therefore the control unit 27 can perform interpolation between the nearest points of the maps to determine the desired (ideal) position of the movable partition 23 of each end chamber 9.

[0042] At the maximum expansion position (for example, shown in Figure 6), the "open" or "diverging" position of the movable partition 23 of each end chamber 9 provides the exhaust duct 7 with the minimum exhaust back pressure and the minimum exhaust noise attenuation capacity. On the other hand, at the minimum expansion position (for example, shown in Figure 9), the "closed" or "converging" position of the movable partition 23 of each end chamber 9 provides the exhaust duct 7 with the maximum exhaust noise attenuation capacity.

[0043] The control unit 27 is configured to move the movable partitions 23 of each end chamber 9 toward the minimum expanded position (for example, shown in Figure 9) when it is necessary (useful) to prioritize noise reduction over performance, and to move the partitions 23 of each end chamber 9 toward the maximum expanded position (for example, shown in Figure 6) when it is necessary (useful) to prioritize performance over noise reduction.

[0044] In alternative embodiments shown in Figures 10, 11, and 12 (which are not part of the present invention), in each exhaust duct 7, the silencer 11 is located above the end chamber 9 (on the opposite side of the fixed base wall 20) rather than below the end chamber 9, and furthermore, the (lower) fixed base wall 20 terminates in the region of the rotation axis 25 of each movable partition 23 (i.e., terminates in the region of the end of each movable partition 23), and as a result the lower movable partition 23 demarcates the lower surface of the end chamber 9 that faces the road surface and is brushed against by the airflow that flows under the vehicle 1 during use.

[0045] In a preferred, but unrestrictive, embodiment, there is also a fixed wall 28, which is connected to the end chamber 9 (i.e., the tubular body 18), covers the end chamber 9 at its lower end, is lower than the (lower) fixed base wall 20, terminates in the region of the rotation axis 25, demarcates the lower surface of the end chamber 9 (i.e., the tubular body 18) facing the road surface, and progressively increases the distance from the road surface toward the outlet opening 10.

[0046] In this embodiment, the control unit 27 is configured to change the position of each lower movable partition 23 (i.e., partition connected to the lower fixed base wall 20) by controlling the actuator device 24, in accordance with the required aerodynamic load. Therefore, the control unit 27 is configured to move each lower movable partition 23 away from the road surface when a greater aerodynamic load is required.

[0047] In fact, by moving the lower movable partition 23 away from the road surface, the width of the "extraction channel" defined between the road surface and the lower movable partition 23 increases, and therefore the aerodynamic load generated by the "extraction channel" increases.

[0048] In particular, at low and medium speeds (indicated as less than 150-180 km / h), the control unit 27 determines the position of the partitions 23 in each end chamber 9 based solely on the need for noise reduction, while at high speeds (indicated as more than 150-180 km / h), the control unit 27 determines the position of the partitions 23 in each end chamber 9 based on the need to generate load at high speeds, and especially on aerodynamic considerations.

[0049] In the embodiment shown in the attached figure, each end chamber 9 of the exhaust duct 7 has two movable partitions 23 facing each other. According to different embodiments not shown herein, each end chamber 9 of the exhaust duct 7 has a single movable partition 23 or three or more movable partitions 23. In other words, it is not necessary for there to be two opposing movable partitions 23, and a single movable partition 23 may be present.

[0050] In the variation shown in Figure 13, neither the bypass duct 12 (and therefore the relative silencer 11) nor the regulating valve 14 are present. As a result, the overall control of the acoustic attenuation strategy is entirely dependent on the variable shape of the end chamber 9 of the exhaust duct 7. In this embodiment, the lower movable partition 23 also preferably has an aerodynamic function, as it faces the road surface and separates the lower surface of the end chamber 9 from the airflow that passes under the vehicle 1 during use.

[0051] According to a preferred embodiment, each end chamber 9 is positioned behind the corresponding rear wheel 3 so as to leave a large space between the two rear wheels 3 for the aerodynamic extractor.

[0052] In the embodiment shown in the attached figure, the internal combustion engine 4 has eight cylinders 6 arranged in a V-shape. Obviously, the internal combustion engine may have a different number of cylinders and / or different cylinder arrangements, and in the case of an internal combustion engine with inline cylinders (and therefore with a single cylinder bank), there is usually a single exhaust duct 7 and therefore one end chamber 9.

[0053] In the embodiment shown in the attached figure, the internal combustion engine 4 is supercharged. According to other embodiments not shown herein, the internal combustion engine 4 is not supercharged; that is, it is a naturally aspirated engine.

[0054] The embodiments described herein can be combined with each other without exceeding the scope of protection of the present invention for this reason.

[0055] The exhaust system 6 described above has many advantages.

[0056] Firstly, the exhaust system 6 described above enables ideal noise reduction at low engine speeds, while simultaneously minimizing exhaust back pressure at high engine speeds.

[0057] In particular, the exhaust system 6 described above allows for the optimization of the frequency response of each variable-shaped end chamber 9 under any possible operating conditions by appropriately adjusting both the width and / or shape of each outlet opening 10 (i.e., by appropriately adjusting the sound amplification / attenuation capability of each variable-shaped end chamber 9), and by appropriately adjusting the position of each control valve 14.

[0058] In the embodiments shown in Figures 11, 12, and 13, the exhaust system 6 also has aerodynamic effects that can be used when necessary, i.e., when the vehicle speed is high and therefore aerodynamics is more important than noise reduction (i.e., when the vehicle speed exceeds 150-180 km / h).

[0059] The exhaust system 6 described above is particularly lightweight and compact because the silencer 11 has particularly small dimensions (as it operates together with and in combination with each of the variable-shape end components 9). That is, the overall eliminating effect is not produced by the silencer 11 alone, but by the assembly consisting of the silencer 11 and the variable-shape end components 9 (and therefore the silencer 11 can be significantly smaller than usual).

[0060] Finally, the exhaust system 6 described above can be manufactured easily and economically because it requires the addition of several small-sized parts that can be easily manufactured, compared to a similar conventional exhaust system 6. [Explanation of symbols]

[0061] 1. Automobile 2 Front wheels 3 Rear wheels 4. Internal combustion engine 5 guest rooms 6 Exhaust System 7 Exhaust duct 8 Processing Unit 9 End chambers 10 Outlet opening 11 Silencer 12 Bypass duct 13 Branching point 14. Adjustment valve 15 Tubular body 16 Inlet opening 17 Outlet opening 18 Tubular body 19 Inlet opening 20 Base wall 21 Base wall 22 Side wall 23 Movable partition 24 Actuator device 25 Rotation axis 26 Inlet opening 27 Control Unit 28 Fixed wall

Claims

1. A motor vehicle (1), Two front wheels (2), Two rear wheels (3), a bottom wall defining a lower surface facing the road surface and brushed by air currents passing under the vehicle (1) in use; an internal combustion engine (4); an exhaust system (6) coupled to the internal combustion engine (4) and comprising an exhaust duct (7), the exhaust duct starting from the internal combustion engine (4) and having an end chamber (9), the end chamber terminating in an outlet opening (10) through which exhaust gases are discharged into the atmosphere; the end chamber (9) of the exhaust duct (7) has at least one movable partition (23) that can be moved to a number of different positions to vary the width of the outlet opening (10); The automobile (1) the movable partition (23) delimits the underside of the end chamber (9) facing the road surface and which, in use, is brushed by the airflow passing under the vehicle (1), and by moving the movable partition (23) away from the road surface, the width of the extraction channel defined between the road surface and the movable partition (23) increases, and therefore the aerodynamic load generated by the extraction channel increases; a motor-driven actuator device (24) configured to actively move the movable partition (23) and capable of being electronically controlled; a control unit (27) configured to change the position of the movable partition (23) by controlling the motor-driven actuator device (24), and configured to move the movable partition (23) away from the road surface when greater aerodynamic loads are required.

2. 2. The vehicle (1) according to claim 1, wherein the end chamber (9) comprises a first fixed wall (28) which terminates in the region of the end of the movable partition (23) and delimits an underside of the end chamber (9), the underside facing the road surface and which is brushed by the air currents flowing under the vehicle (1) during use.

3. 3. The vehicle (1) according to claim 2, wherein the first fixed wall (28) progressively increases in distance from the road surface towards the exit opening (10).

4. 4. The motor vehicle (1) according to claim 2 or 3, wherein the end chamber (9) comprises a second fixed wall (20) which terminates in the region of the end of the movable partition (23) and is arranged higher than the first fixed wall (28) and which delimits a space in the lower part of the end chamber (9) through which the exhaust gases flow.

5. The motor vehicle (1) according to any one of claims 1 to 4, wherein the end chambers (9) are arranged behind the corresponding rear wheels (3).

6. The exhaust system (6) comprises: a silencer (11) connected to the end chamber (9); a bypass duct (12) that starts from the exhaust duct (7) in the region of a branch (13) and terminates at the inlet of the silencer (11); an electronically controllable regulating valve (14) arranged along the exhaust duct (7) downstream of the branch (13) at which the bypass duct (12) begins, and designed to regulate the exhaust gas flow towards the end chamber (9); A motor vehicle (1) according to any one of claims 1 to 5, comprising:

7. The end chamber (9) comprises a tubular body (18) and has an inlet opening (19) connected to the exhaust duct (7) and an outlet opening (10) opposite the inlet opening (19); 7. The motor vehicle (1) according to claim 6, wherein the silencer (11) is arranged on the tubular body (18) on the opposite side to the movable partition (23).

8. 8. The motor vehicle (1) according to claim 7, wherein the silencer (11) is connected to the end chamber (9) so as to form a single body with the end chamber (9).

9. 9. The vehicle (1) according to any one of claims 1 to 8, wherein the movable partition (23) can be moved between a maximum expansion position, in which the movable partition (23) causes the end chamber (9) of the exhaust duct (7) to assume a diverging shape with a cross-sectional area that gradually increases as the outlet opening (10) is approached, and a minimum expansion position, in which the movable partition (23) causes the end chamber (9) of the exhaust duct (7) to assume a converging shape with a cross-sectional area that gradually decreases as the outlet opening (10) is approached.

10. 10. A vehicle (1) according to any one of claims 1 to 9, wherein the end chamber (9) of the exhaust duct (7) has two opposing movable partitions (23), only one of which delimits an underside of the end chamber (9), the underside facing the road surface and which is brushed by an air flow passing under the vehicle (1) during use.

11. A motor vehicle (1) as described in claim 1, wherein the control unit (27) establishes the position of the movable partition (23) at low and medium speeds based solely on the need for sound damping, and at high speeds establishes the position of the movable partition (23) based on the aerodynamic needs at high speeds, prioritizing load generation.

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