Automobile provided with an exhaust system having a pneumatic effect

Abstract

The present invention relates to a vehicle equipped with an exhaust system having a pneumatic effect, comprising: two front wheels (2); two rear wheels (3); a floor wall defining a lower surface facing the road surface and being blown by an airflow flowing beneath the vehicle (1) during use; an internal combustion engine (4); and an exhaust system (6) coupled to the internal combustion engine (4) and provided with an exhaust pipe (7) originating from the internal combustion engine (4) and having an end chamber (9) having an outlet opening (10) at its end through which exhaust gases are released into the atmosphere. The end chamber (9) of the exhaust pipe (7) has at least one movable baffle (23) that can be moved to different positions to change the width of the outlet opening (10). The movable baffle (23) defines the lower surface of the end chamber (9) facing the road surface and being blown by an airflow flowing beneath the vehicle (1) during use.

Description

[0001] Cross-reference to related applications

[0002] This patent application claims priority to Italian Patent Application No. 102020000032849, filed on December 30, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This invention relates to a vehicle equipped with an internal combustion engine and an exhaust system. Background Technology

[0004] Vehicle type approval regulations mandate that manufacturers limit acoustic emission levels, especially when the vehicle is traveling at medium speeds (i.e., when it is driving through a city center). Therefore, exhaust systems (which fulfill the function of releasing combustion gases into the atmosphere and limiting noise and pollutant levels) are always equipped with at least one muffler, which is located downstream of the pollutant reduction device along the exhaust pipe.

[0005] In general, a muffler comprises a tubular body, typically having an elliptical cross-section and an inlet opening and an outlet opening. A labyrinth section is defined within the tubular body, defining the path of exhaust gas from the inlet opening to the outlet opening; the labyrinth section typically includes: diaphragms (or baffles) arranged laterally (i.e., perpendicular to the longitudinal axis of the tubular body) to define chambers within the tubular body; and conduits connecting the chambers to each other. In a conventional muffler that ensures significant reduction in noise at low engine speeds, the exhaust back pressure generated by the muffler (i.e., the pressure loss in the exhaust gas as it flows through the muffler) increases exponentially with increasing engine speed (i.e., with increasing average exhaust gas velocity). Therefore, to avoid excessive exhaust back pressure at high engine speeds (and thus excessively impair performance at high engine speeds), a bypass pipe is provided, which is set to run parallel to the muffler (i.e., designed to bypass the muffler) and regulated by a bypass valve that remains closed at low engine speeds (thus maximizing the muffler's effectiveness at the expense of performance, although performance is not important at low engine speeds) and opens at high engine speeds (thus reducing exhaust back pressure to an acceptable level).

[0006] Furthermore, an important aspect of judging a high-performance sports car is the "quality" of the sound emitted by its exhaust system, which is a crucial perceptual feedback during extreme driving conditions. However, known exhaust systems with variable geometry (i.e., equipped with one or more electrically or pneumatically controlled valves that can alter the path of exhaust gases and thus change the sound along the exhaust system) do not always guarantee that the exhaust sound will correspond to the user's needs.

[0007] In general, turbocharged engines are disadvantageous because the presence of the turbine along the exhaust pipe and the compressor along the intake pipe adds filtering and reduction to the sound levels of both the exhaust and intake systems.

[0008] Furthermore, recent emission standards have made the use of exhaust gas treatment devices severely compromise sound performance, because even in gasoline engines, a second catalytic converter or particulate filter (also known as GPF, or "Gasoline Particulate Filter") must be installed in parallel with the catalytic converter.

[0009] Patent documents US1483354A, KR20160108625A, and GB2274681A describe an exhaust system for an internal combustion engine, wherein an exhaust pipe originating from the internal combustion engine has an end chamber with an outlet opening at its end through which exhaust gases are released into the atmosphere; the end chamber of the exhaust pipe has at least one movable baffle that can be moved to different positions to change the width of the outlet opening. Specifically, the movement of the movable baffle can be performed manually (as described in US1483354A) or automatically due to the pressure of the exhaust gases and the elastic thrust generated against a spring that tends to minimize the width of the outlet opening (as described in KR20160108625A and GB2274681A).

[0010] Patent application US2008282688A1 describes an exhaust system for an internal combustion engine, which includes an exhaust pipe with multiple ventilation valves that automatically open as the exhaust gas temperature rises. Summary of the Invention

[0011] The object of the present invention is to provide a car equipped with an internal combustion engine and an exhaust system that complies with type approval requirements and maximizes performance by ensuring natural exhaust noise suitable for the racing application of the car.

[0012] According to the present invention, an automobile is provided, comprising: two front wheels; two rear wheels; a floor wall defining a lower surface facing the road surface and blown by an airflow flowing beneath the automobile during use; an internal combustion engine; and an exhaust system coupled to the internal combustion engine and including an exhaust pipe originating from the internal combustion engine and having an end chamber having an outlet opening at its end through which exhaust gases are released into the atmosphere, wherein the end chamber of the exhaust pipe has at least one movable baffle that can be moved to different positions to change the width of the outlet opening; the automobile is characterized in that the movable baffle defines the road-facing side of the end chamber. Furthermore, the lower surface, which is blown by the airflow flowing beneath the vehicle during use, increases the width of the extractor channel defined between the road surface and the lower movable partition by moving the lower movable partition away from the road surface, thereby increasing the aerodynamic load generated by the extractor channel; the vehicle is also equipped with a motor-driven actuator configured to actively move the movable partition and capable of electronic control; and the vehicle is also equipped with a control unit configured to change the position of the movable partition by controlling the actuator, and configured to move the movable partition away from the road surface when a larger aerodynamic load is required.

[0013] The end chamber includes a first fixed wall that terminates in the region at the end of the movable partition and defines the lower surface of the end chamber facing the road surface and being blown by airflow flowing beneath the vehicle during use.

[0014] The distance between the first fixed wall and the road surface gradually increases as it faces the outlet opening.

[0015] The end chamber includes a second fixed wall that terminates in the region at the end of the movable partition, is configured to be higher than the first fixed wall, and defines a space at the bottom for the flow of exhaust gas.

[0016] The end chamber is located behind the corresponding rear wheel.

[0017] The exhaust system includes: a muffler leading to the end chamber; a bypass pipe starting at the exhaust pipe and terminating at the inlet of the muffler in the region of the bifurcation; and a regulating valve that is electronically controllable, located downstream of the bifurcation at the start of the bypass pipe along the exhaust pipe, and designed to regulate the exhaust flow toward the end chamber.

[0018] The silencing device is connected to the end chamber, thereby forming a single unit with the end chamber.

[0019] The end chamber includes a tubular body and has an inlet opening connected to the exhaust pipe and an outlet opening opposite to the inlet opening; and the muffler is disposed above the tubular body on the side opposite to the movable partition.

[0020] The movable baffle is movable between a maximum expansion position and a minimum expansion position. In the maximum expansion position, the movable baffle causes the end chamber of the exhaust pipe to have a diffuse shape in which the cross-sectional area gradually increases as the outlet opening approaches. In the minimum expansion position, the movable baffle causes the end chamber of the exhaust pipe to have a converging shape in which the cross-sectional area gradually decreases as the outlet opening approaches.

[0021] The end chamber of the exhaust pipe has two opposing movable baffles, only one of which defines the lower surface of the end chamber facing the road surface and being blown by the airflow flowing under the vehicle during use.

[0022] The control unit is configured to create the position of the movable partition based solely on noise reduction requirements at low and medium speeds, and based on aerodynamic requirements that help generate load at high speeds. Attached Figure Description

[0023] The invention will now be described with reference to the accompanying drawings, which illustrate some non-limiting embodiments of the invention, wherein:

[0024] Figure 1 It is a schematic plan view of a car that is driven by an internal combustion engine equipped with an exhaust system according to the invention;

[0025] Figure 2 yes Figure 1 A side view of the car;

[0026] Figure 3 yes Figure 1 A perspective view of the end chamber of the exhaust pipe of the exhaust system (which is not manufactured according to the present invention and is provided with two movable baffles);

[0027] Figure 4 yes Figure 3 A front view of the end chamber;

[0028] Figure 5 yes Figure 3 A longitudinal sectional view of a portion of the end chamber;

[0029] Figures 6-9 The movable partitions are in different positions. Figure 3 A schematic diagram of the end chamber;

[0030] Figure 10 , Figure 11 and Figure 12 The movable partitions are positioned in different locations, highlighting the airflow beneath the vehicle. Figure 3 Schematic diagrams of different embodiments of the end chamber (manufactured according to the present invention); and

[0031] Figure 13 yes Figure 1 A schematic plan view of a car, in which the exhaust system is designed according to different implementation methods.

[0032] List of reference numerals

[0033] 1-Automobile; 2-Front wheel; 3-Rear wheel; 4-Internal combustion engine; 5-Passenger compartment; 6-Exhaust system; 7-Exhaust pipe; 8-Treatment device; 9-End chamber; 10-Outlet opening; 11-Silencer; 12-Bypass pipe; 13-Bifurcation; 14-Regulating valve; 15-Tube body; 16-Inlet opening; 17-Outlet opening; 18-Tube body; 19-Inlet opening; 20-Base wall; 21-Base wall; 22-Side wall; 23-Modible partition; 24-Actuator; 25-Rotating shaft; 26-Inlet opening; 27-Control unit; 28-Fixed wall. Detailed Implementation

[0034] exist Figure 1 In the figure, reference numeral 1 generally represents a car equipped with two front wheels 2 and two rear wheels 3 that receive torque from an internal combustion engine 4, which is boosted by a turbocharger and located at the front.

[0035] The vehicle 1 is equipped with a passenger compartment 5 designed to accommodate the driver and possible passengers.

[0036] According to a feasible but non-limiting embodiment, the internal combustion engine 4 is a "V8" engine and has two (double) cylinder banks comprising four cylinders arranged at an angle relative to each other to form a "V" shape. In each cylinder bank, the four cylinders are connected to an intake manifold (not shown) via two intake valves and to an exhaust manifold (not shown) via two exhaust valves; each exhaust manifold collects the gases produced by combustion, which flow out periodically through the exhaust valves.

[0037] The internal combustion engine 4 is equipped with an exhaust system 6, which functions to release the combustion-produced gases into the atmosphere and to limit noise and pollutant levels. The exhaust system 6 includes two pairs of exhaust pipes 7, each originating from a corresponding exhaust manifold, receiving combustion-produced gases from the exhaust manifold itself, and terminating in the area at the rear of the vehicle 1. Along each exhaust pipe 7 is a known exhaust treatment device 8: always having at least one catalytic converter and particulate filter or another catalytic element (thus complying with the EURO6D emission standard).

[0038] Each exhaust pipe 7 (starting from the internal combustion engine 4) has an end chamber (component) 9, which has an outlet opening 10 at the end for releasing exhaust gases into the atmosphere.

[0039] according to Figure 2 The vehicle 1 includes a bottom wall that defines a lower surface facing the road surface and blown by airflow flowing beneath the vehicle 1 during use.

[0040] according to Figure 3 , 4 And 5, the exhaust system 6 (which is not manufactured according to the invention) includes a muffler 11 for each exhaust pipe 7, which leads to the corresponding end chamber 9 (i.e., it sends the exhaust gas flowing therethrough into the corresponding end chamber 9). In addition, the exhaust system 6 includes a bypass pipe 12 for each exhaust pipe 7, which starts at the exhaust pipe 7 in the region of the bifurcation 13 and terminates at the inlet of the corresponding muffler 11; in other words, each bypass pipe 12 replaces the last section of the corresponding exhaust pipe 7.

[0041] Finally, the exhaust system 6 includes a regulating valve 14 for each exhaust pipe 7, which is electronically controlled, located downstream of the bifurcation 13 at the beginning of the corresponding bypass pipe 12 along the exhaust pipe 7 (i.e., located between the bifurcation 13 and the end chamber 9), and designed to regulate the exhaust flow toward the end chamber 9. Preferably, each regulating chamber 14 has the possibility of being partially open evenly between a fully closed position and a fully open position; that is, each regulating valve 14 is not a switch valve, but can present a certain range of intermediate positions between the fully closed position and the fully open position.

[0042] Each silencer 11 is a conventional silencer and includes, for example, a tubular body 15 with an inlet opening 16 (where a corresponding bypass pipe 12 is installed), an outlet opening 17 leading to the end chamber 9, and an internal labyrinth section (not shown) that defines the path of exhaust gas from the inlet opening 16 to the outlet opening 17.

[0043] When each regulating valve 14 is open, exhaust gases tend to flow directly into the end chamber 9, bypassing the bypass pipe 12 and the muffler 11 (due to the greater load loss when flowing through the muffler 11). However, when each regulating valve 14 is closed, exhaust gases are forced to flow through the bypass pipe 12 to reach the end chamber 9. In other words, the regulating valves 14 move toward the fully closed position to prevent exhaust gases from flowing in the last section of the exhaust pipe 7, thus forcing them to flow through the bypass pipe 12 terminating at the muffler 11 in order to reach the end chamber 9, thereby greatly reducing noise and having a greater back pressure; conversely, the regulating valves 14 move toward the fully open position to guide exhaust gases toward the last section of the exhaust pipe 7 (without needing to close the bypass pipe 12, because the greater back pressure determined by the muffler 11 causes minimal exhaust gas to flow along the bypass pipe 12 when an alternative, less congested path is available).

[0044] Each end chamber 9 includes a tubular body 18 and has an inlet opening 19 connected to an exhaust pipe 7 and an outlet opening 10 opposite to the inlet opening 19. Exhaust gas from the exhaust pipe 7 flows into the end chamber 9 (i.e., into the tubular body 18) through the inlet opening 19 and flows out of the end chamber 9 (i.e., out of the tubular body 18) through the outlet opening 10. Each end chamber 9 (i.e., each tubular body 18) is shaped as a trumpet with a rectangular cross-section, increasing in size toward the outlet opening 10, and is defined by two fixed base walls 20 and 21 (lower wall and upper wall, respectively) that are opposite each other and diffuse toward the outlet opening 10, and two fixed side walls 22 that are opposite each other and parallel to each other.

[0045] Each exhaust pipe 7 has two movable baffles 23 facing each other, which can be moved to different positions (e.g., Figures 6-9 As explicitly shown in the diagram. Each end chamber 9 has a motor-driven actuator 24 (i.e., preferably equipped with an electric or pneumatic motor designed to actively generate motion), configured to move the movable partition 23; preferably (but not necessarily), each actuator 24 is configured to move both movable partitions 23 independently. In other words, each motor-driven actuator 24 is active and electronically (electrically) controlled to generate the force (torque) that determines the movement of the movable partition 23; thus, in each end chamber 9, the position of the movable partition 23 can be adjusted (by controlling the corresponding actuator 24) completely independently of the pressure and velocity of the exhaust gas flowing through the end chamber 9 (e.g., the movable partition 23 can be moved to have a very large outlet opening 10 when the exhaust gas pressure and velocity are moderate, and can be moved to have a very small outlet opening 10 when the exhaust gas pressure and velocity are high).

[0046] According to a preferred embodiment, each movable partition 23 is hinged to rotate about a rotation axis 25 (which is horizontally arranged); that is, each movable partition 23 is hinged to the tubular body 25 in the region of the fixed base wall 20 or 21, thereby rotating about the rotation axis 25. Therefore, each actuating device 24 is configured to rotate the two movable partitions 23 about the corresponding rotation axis 25 (in this way, movement of the two movable partitions 23 can cause the two movable partitions 23 to move away from each other or can cause the two movable partitions 23 to move closer to each other).

[0047] In the end chamber 9 of each exhaust pipe 7, two movable baffles 23 can be in the maximum expansion position (e.g., at... Figure 6 (as shown in) and the minimum expansion position (e.g. in) Figure 9 The outlet opening 10 moves between the two movable partitions 23 (as shown in the diagram); clearly, the outlet opening 10 is in its maximum expansion position when the two movable partitions 23 are in the maximum expansion position (e.g., in the diagram). Figure 6 The area shown in the figure is (significantly) larger than that of the outlet opening 10 when the two movable partitions 23 are in the minimum expansion position (e.g., in the case of...). Figure 9 The area shown in the image is larger.

[0048] In the position of maximum expansion (e.g., at) Figure 5 (as shown in the image), or in other expansion locations (e.g., in...). Figure 7 As shown in the figure, the two movable baffles 23 cause the end chamber 9 of the exhaust pipe 7 to acquire a diffusion shape in which the cross-sectional area gradually increases as the outlet opening 10 approaches.

[0049] According to a preferred embodiment, in the minimum expansion position (in Figure 9 As shown in the figure, the two movable baffles 23 cause the end chamber 9 of the exhaust pipe 7 to acquire a converging shape in which the cross-sectional area gradually decreases as the outlet opening 10 approaches.

[0050] At the position of minimum expansion (e.g., in) Figure 9 (as shown in the diagram) and the location of maximum expansion (e.g., in...) Figure 5 The intermediate position between (as shown in) Figure 8 (As shown in the image) is also feasible.

[0051] That is, each actuating device 24 is capable of placing and holding the two movable partitions 23 in the maximum expanded position (in Figure 6 (shown in) and the minimum expansion position (in Figure 9 (shown in the image) The middle position between them.

[0052] according to Figure 3 , 4In one possible embodiment shown in Figure 5, the fixed base wall 20 or 21 each extends beyond the rotation axis 25 of the corresponding movable partition 23 (i.e., the fixed base wall 20 or 21 does not terminate in the region of the corresponding movable partition 23), so that in the maximum expanded position, the corresponding movable partition 23 abuts 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), so that they slide against the fixed sidewall 22 as they rotate about the corresponding rotation axis 25.

[0053] according to Figure 3 , 4 In one feasible embodiment shown in Figure 5, each silencing device 11 is disposed below the corresponding end chamber 9 (i.e., the tubular body 15 of each silencing device 11 is disposed below the end chamber 9, i.e., below the tubular body 18). Therefore, the lower base wall 20 of each end chamber 9 (i.e., each tubular body 18) includes at least one inlet opening 26 through which the silencing device 11 opens (i.e., overlapping with the outlet opening 17 of the silencing device 11). Preferably, in each end chamber 9, the inlet opening 26 is disposed upstream of the movable baffle 23 relative to the exhaust gas flow.

[0054] In other words, each end chamber 9 has separate and independent inlet openings 19 and 26, and an outlet opening 10 for releasing exhaust gases into the atmosphere. The exhaust pipe 7 originates from the internal combustion engine 4 and leads to the inlet opening 19 of the end chamber 9, while the muffler 11 has an outlet opening 17 that leads directly to the inlet opening 26 of the end chamber 9. A bypass pipe 12 originates from the exhaust pipe 7 in the region of the bifurcation 13 and terminates at the inlet opening 16 of the muffler 11; furthermore, a regulating valve 14 is disposed downstream of the bifurcation 13 (i.e., between the bifurcation 13 and the inlet opening 19) along the exhaust pipe 7 and is designed to regulate the exhaust gas flow toward the inlet opening 19 of the end chamber 9.

[0055] According to a preferred embodiment, each silencing device 11 is connected to an end chamber 9, thereby forming a single integral unit with the end chamber 9; that is, the tubular body 15 of the silencing device 11 (typically by means of welding) is stably and firmly connected to the end chamber 9 (i.e., connected to the tubular body 18), 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) is shaped into a horn shape with its dimensions increasing toward the outlet opening 10; the silencing device 11 has a shape complementary to the shape of the end chamber 9 (i.e., the tubular body 18), and thus its dimensions decrease toward the outlet opening 10. In this way, the single unit consisting of the tubular body 15 of the silencing device 11 and the end chamber 9 (i.e., the tubular body 18) has a construction with an approximately parallelepiped shape.

[0056] There is also a control unit 27 (illustratively located in...) Figure 1 As shown in the figure, it is configured (by controlling the corresponding actuation device 24) to change the position of the movable partition 23 of each end chamber 9 according to the following factors: the rotational speed of the internal combustion engine 4, the engine load of the internal combustion engine 4, the gear engaged in 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.

[0057] That is, the control unit 27 is configured to detect the following (e.g., read from the vehicle’s BUS network): the rotational speed of the internal combustion engine 4, the engine load of the internal combustion engine 4, the gear engaged in the transmission, the longitudinal speed of the vehicle, and the longitudinal acceleration of the vehicle 1; by acquiring this information (which has been read in advance), the control unit 27 can create the position of the movable partition 23 of each end chamber 9 based on the information.

[0058] The control unit 27 may also be configured to change the position of the movable partition 23 of each end chamber 9 according to the driving mode selected by the driver (i.e., which may be a sport driving mode, racing driving mode, city driving mode, highway driving mode, wet driving mode, etc., which is usually selected by the driver operating a selector called a "grid").

[0059] Control unit 27 must control the position of the movable partition 23 of each end chamber 9 to achieve three objectives: to meet type approval requirements regarding the intensity of the exhaust system's sound (a mandatory requirement that must always be met), to obtain a high-quality sound from the exhaust system (i.e., a sound that is considered pleasing to the driver and thus meets their expectations), and to maximize the performance of the internal combustion engine 4. While control unit 27 is configured to always meet type approval requirements regarding the intensity of the exhaust system's sound, in some cases control unit 27 may improve the "quality" of the exhaust system's sound rather than the performance of the internal combustion engine 4; however, in other cases control unit 27 may improve the performance of the internal combustion engine 4 rather than the "quality" of the exhaust system's sound.

[0060] In general, the control unit 27 is configured to hold the movable partition 23 of each end chamber 9 in the minimum expansion position when the internal combustion engine 4 has a low revolutions per minute and a low load, and to move the movable partition 23 of each end chamber 9 toward the maximum expansion position when the internal combustion engine 4 has a high revolutions per minute and a high load. Furthermore, the control unit 27 is configured to move the movable partition 23 of each end chamber 9 toward the minimum expansion position in a low gear position, and to move the movable partition 23 of each end chamber 9 toward the maximum expansion position in a high gear position.

[0061] According to a preferred embodiment, different mapping tables (each corresponding to one or more drive modes) are stored in the control unit 27. These tables provide the desired (ideal) position of the movable partition 23 of each end chamber 9 as output, based on data provided as inputs, including the revolutions per minute (RPM) and engine load of the internal combustion engine 4, and the gear engaged in the transmission coupled to the internal combustion engine 4. Clearly, each mapping table stored in the control unit 27 includes a finite number of points, so the control unit 27 can perform interpolation between the closest points in the mapping tables to determine the desired (ideal) position of the movable partition 23 of each end chamber 9.

[0062] In the position of maximum expansion (e.g., at) Figure 5 As shown in the diagram, the "open," i.e., "diffusion" position of the movable partition 23 of each end chamber 9 provides the exhaust pipe 7 with minimal exhaust back pressure and also provides the exhaust pipe 7 with minimal exhaust noise reduction capability; on the other hand, in the minimum expansion position (e.g., in...) Figure 9 As shown in the figure, the “closed” or “converging” position of the movable partition 23 of each end chamber 9 gives the exhaust pipe 7 the maximum exhaust noise reduction capability.

[0063] Control unit 27 is configured to orient the movable partition 23 of each end chamber 9 toward the position of minimum expansion (e.g., in) when improvement in noise reduction is needed rather than performance. Figure 9 (as shown in the diagram) move, and when improved performance is needed rather than noise reduction, the movable partition 23 of each end chamber 9 is oriented toward the position of maximum expansion (e.g., in...). Figure 5 (As shown in the image) movement.

[0064] exist Figure 10 , Figure 11 and Figure 12 In the alternative embodiment shown (which is part of the invention), in each exhaust pipe 7, the muffler 11 is disposed above the end chamber 9 (on the side opposite to the fixed base wall 20) rather than below the end chamber 9; furthermore, the (lower) fixed base wall 20 terminates in the region of the rotation axis 25 of the corresponding movable partition 23 (i.e., in the region of the end of the corresponding movable partition 23), so the lower movable partition 23 defines the lower surface of the end chamber 9 facing the road surface and blown by the airflow flowing below the vehicle 1 during use.

[0065] According to a preferred (but not limiting) embodiment, there is also a fixed wall 28 that is connected to the end chamber 9 (i.e., connected to the tubular body 18), covers the end chamber 9 at the bottom, is lower than the (lower) fixed base wall 20, terminates in the region of the rotation axis 25, defines the lower surface of the end chamber 9 (i.e., the tubular body 18) facing the road surface, and gradually increases the distance between the end chamber 9 and the road surface toward the outlet opening 10.

[0066] In this embodiment, the control unit 27 is configured to change the position of each lower movable partition 23 (i.e., the movable partition connected to the lower fixed base wall 20) by controlling the actuator 24 and also based on the required pneumatic load, so that the control unit 27 is configured to move each lower movable partition 23 away from the road surface when a larger pneumatic load is required.

[0067] In fact, by moving the lower movable partition 23 away from the road surface, the width of the "extractor channel" limited between the road surface and the lower movable partition 23 is increased, thereby increasing the pneumatic load generated by the "extractor channel".

[0068] Specifically, at low and medium speeds (indicatively, below 150-180 km / h), the control unit 27 creates the position of the partition 23 of each end chamber 9 solely based on silencing requirements, while at high speeds (indicatively, above 150-180 km / h), the control unit 27 additionally and especially based on aerodynamic requirements that help generate load at high speeds.

[0069] In the embodiment shown in the accompanying drawings, each exhaust pipe 7 has two movable baffles 23 facing each other; according to different embodiments not shown here, each exhaust pipe 7 has a single movable baffle 23 or more than three movable baffles 23. In other words, it is not necessary to have two opposing movable baffles 23; there may only be a single movable baffle 23.

[0070] exist Figure 13 In the variant shown, there is no bypass pipe 12 (and therefore no associated muffler 11) or regulating valve 14; thus, the overall management of the sound reduction strategy is entirely assigned to the variable geometry of the end chamber 9 of the exhaust pipe 7. In this embodiment, the lower movable baffles 23 preferably also have a pneumatic function, as they define the lower surface of the end chamber 9 facing the road surface and being blown by the airflow flowing below the vehicle 1 during use.

[0071] According to a preferred embodiment, each end chamber 9 is located behind the corresponding rear wheel 3, thereby leaving a larger space between the two rear wheels 3 for the pneumatic extractor.

[0072] In the embodiment shown in the accompanying drawings, the internal combustion engine 4 has eight cylinders 6 arranged in a V-shape. Clearly, the internal combustion engine can have different numbers of cylinders and / or different cylinder arrangements; in the case of an internal combustion engine with inline cylinders (and therefore a single cylinder bank), there is typically a single exhaust pipe 7, and thus an end chamber 9.

[0073] In the embodiment shown in the accompanying drawings, the internal combustion engine 4 is supercharged; according to other embodiments not shown here, the internal combustion engine 4 is not supercharged, i.e., it is an air-breathing engine.

[0074] The embodiments described herein can be combined with each other without exceeding the scope of protection of this invention.

[0075] The exhaust system 6 described above has several advantages.

[0076] First, the aforementioned exhaust system 6 allows for ideal silencing at low engine speeds while simultaneously allowing for minimal exhaust back pressure at high engine speeds.

[0077] In particular, the exhaust system 6 described above allows for optimization of the frequency response of each variable geometry end chamber 9 under any possible operating conditions by appropriately adjusting the width and / or shape of each outlet opening 10 (i.e., by appropriately adjusting the sound amplification / attenuation capability of each variable geometry end chamber 9) and the position of each regulating valve 14.

[0078] exist Figure 11 , 12 In the embodiments shown in 13, the exhaust system 6 also has an aerodynamic effect that can be used on demand, i.e., at higher vehicle speeds, so aerodynamic characteristics are more important than noise reduction (i.e., at vehicle speeds exceeding 150-180 km / h).

[0079] The exhaust system 6 described above is particularly lightweight and compact because the mufflers 11 have a very small size (so that they can operate in combination with the corresponding variable geometry of the end chamber 9); that is, the overall silencing effect is not produced by the mufflers 11 alone, but by the assembly consisting of the mufflers 11 and the variable geometry of the end chamber 9 (therefore, the mufflers 11 can be much smaller than before).

[0080] Finally, the exhaust system 6 described above is simpler and more economical to manufacture than similar conventional exhaust systems 6, requiring only the addition of some small parts that can be easily manufactured.

Claims

1. A car (1), comprising: Two front wheels (2); Two rear wheels (3); The bottom wall defines the lower surface facing the road surface and being blown by the airflow flowing below the vehicle (1) during use; Internal combustion engine (4); and An exhaust system (6) coupled to the internal combustion engine (4) and including an exhaust pipe (7) originating from the internal combustion engine (4) and including an end chamber (9) having an outlet opening (10) at its end through which exhaust gases are released into the atmosphere. The end chamber (9) of the exhaust pipe (7) has at least one movable baffle (23) that can be moved to different positions to change the width of the outlet opening (10). The movable partition (23) defines the lower surface of the end chamber (9) facing the road surface and blown by the airflow flowing below the vehicle (1) during use, thereby increasing the width of the extractor channel defined between the road surface and the lower movable partition (23) by moving the lower movable partition (23) away from the road surface, thereby increasing the aerodynamic load generated by the extractor channel. The vehicle is also equipped with a motor-driven actuation device (24), which is configured to actively move the movable partition (23) and is electronically controllable; and The vehicle is also provided with a control unit (27) configured to change the position of the movable partition (23) by controlling the actuation device (24), and configured to move the movable partition (23) away from the road surface when a large aerodynamic load is required.

2. The automobile (1) according to claim 1, characterized in that, The end chamber (9) includes a first fixed wall (28) that terminates in the region at the end of the movable partition (23) and defines the lower surface of the end chamber (9) facing the road surface and being blown by the airflow flowing below the vehicle (1) during use.

3. The automobile (1) according to claim 2, characterized in that, The distance between the first fixed wall (28) and the road surface gradually increases as it moves toward the outlet opening (10).

4. The automobile (1) according to claim 2, characterized in that, The end chamber (9) includes a second fixed wall (20) which terminates in the region at the end of the movable partition (23), is configured to be higher than the first fixed wall (28), and defines a space at the bottom for the flow of exhaust gas.

5. The automobile (1) according to claim 1, characterized in that, The end chamber (9) is located behind the corresponding rear wheel (3).

6. The automobile (1) according to claim 1, characterized in that, The exhaust system (6) includes: Silencing device (11) leading to the end chamber (9); A bypass pipe (12), which begins in the region of the bifurcation (13) at the exhaust pipe (7) and terminates at the inlet of the muffler (11); and A regulating valve (14), which is electronically controlled, is located downstream of the bifurcation (13) at the beginning of the bypass pipe (12) along the exhaust pipe (7) and is designed to regulate the exhaust gas flow toward the end chamber (9).

7. The automobile (1) according to claim 6, characterized in that, The silencing device (11) is connected to the end chamber (9) and thus forms a single unit with the end chamber (9).

8. The automobile (1) according to claim 6, characterized in that, The end chamber (9) includes a tubular body (18) and has an inlet opening (19) connected to the exhaust pipe and an outlet opening (10) opposite to the inlet opening (19); and the muffler (11) is disposed above the tubular body (18) on the side opposite to the movable partition (23).

9. The automobile (1) according to claim 1, characterized in that, The movable baffle (23) is movable between a maximum expansion position and a minimum expansion position. In the maximum expansion position, the movable baffle (23) causes the end chamber (9) of the exhaust pipe (7) to have a diffuse shape in which the cross-sectional area gradually increases as the outlet opening (10) approaches. In the minimum expansion position, the movable baffle (23) causes the end chamber (9) of the exhaust pipe (7) to have a converging shape in which the cross-sectional area gradually decreases as the outlet opening (10) approaches.

10. The automobile (1) according to claim 1, characterized in that, The end chamber (9) of the exhaust pipe (7) has two opposing movable baffles (23), only one of which defines the lower surface of the end chamber (9) facing the road surface and being blown by the airflow flowing below the vehicle (1) during use.

11. The automobile (1) according to claim 1, wherein, The control unit (27) is configured to create the position of the movable partition (23) based solely on noise reduction requirements at low and medium speeds, and to create the position of the movable partition (23) based on aerodynamic requirements that help generate load at high speeds.

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