Device and method for influencing the acoustic behavior of an exhaust system of an internal combustion engine, as well as a corresponding exhaust system

Abstract

Device for influencing the acoustic behavior of an exhaust system (10) of an internal combustion engine (12), comprising: - an exhaust duct (20) through which exhaust gas flows, - a field generation arrangement (21) positioned in the exhaust duct (20) for generating an electric field, wherein the field generation arrangement (21) comprises an anode unit (22) around which exhaust gas flows in the exhaust duct (20) and a cathode unit (24) arranged at least partially downstream of the anode unit (22) with respect to a main exhaust gas flow direction (H) in the exhaust duct (20) and around which exhaust gas flows, as well as a high voltage generator (34) for applying a high voltage between the anode unit (22) and the cathode unit (24).

Description

[0001] The invention relates to a device for influencing the acoustic behavior of an exhaust system of an internal combustion engine and to a method by which the acoustic behavior of an exhaust system of an internal combustion engine can be influenced using such a device.

[0002] Various measures are known to influence the acoustic behavior of exhaust systems from internal combustion engines used in vehicles. For example, it is known to use silencers that, due to the flow direction of the exhaust gas, can dampen sound transported in the exhaust stream by means of chambers lined with sound-absorbing material and / or by using so-called Helmholtz resonators. It is also known to actively influence the exhaust gas flow to affect the acoustic behavior. For example, the acoustic behavior can be switched by changing the flow direction using flaps.The use of sound-generating elements can produce superimposed noises on the sound transported in the exhaust gas stream, which can contribute to a reduction in the sound level through destructive superposition and / or can particularly emphasize certain frequencies or frequency ranges through constructive superposition.

[0003] The object of the present invention is to provide a device and a method for influencing the acoustic behavior of an exhaust system of an internal combustion engine, with which, in a structurally simple design, a reliable, preferably variable, influence on the acoustic behavior of an exhaust system can be achieved.

[0004] According to a first aspect of the present invention, this problem is solved by a device for influencing the acoustic behavior of an exhaust system of an internal combustion engine, comprising: - an exhaust duct through which exhaust gases flow - a field generation arrangement positioned in the exhaust duct for generating an electric field, wherein the field generation arrangement comprises an anode unit around which exhaust gas flows in the exhaust duct and a cathode unit around which exhaust gas flows in the exhaust duct at least partially downstream of the anode unit with respect to a main exhaust gas flow direction, as well as a high voltage generator for applying a high voltage between the anode unit and the cathode unit.

[0005] The present invention utilizes the effect of ionizing the exhaust gas flowing in an exhaust system and influencing the flow behavior of the ionized exhaust gas through an electric field. This influence on the flow behavior makes it possible, for example, to smooth out turbulence or eddies in the exhaust gas stream or to generate a more uniform exhaust gas flow, which also contributes to a lower noise level. Furthermore, the influence on the movement of the exhaust gas stream made possible by the interaction with the electric field allows it to be set into vibration, for example, taking into account the sound carried within it, in order to minimize or eliminate, or emphasize, certain frequencies or frequency ranges through destructive or constructive superposition.Generating and modifying an electric field does not require the use of, for example, movable system components located in the exhaust stream, which could be subject to wear and / or corrosion and thus malfunction.

[0006] The anode unit can comprise an anode body with an anode tip region arranged in a downstream end region of the same. In this anode tip region, a particularly high field strength of the electric field to be generated will be present, so that an ionization volume is also formed in this region in which the exhaust gas flowing around the anode unit is ionized.

[0007] The cathode unit can comprise a cathode body with a cathode surface, arranged at least partially downstream of the anode unit. An electric field is established between the cardboard surface and the anode tip region, such that the field lines are directed essentially downstream from the anode tip region towards the cathode body. This results in the electric field and the electrostatic interaction established between it and the ionized exhaust gas accelerating the exhaust gas and its ionized molecules in the flow direction, thus contributing to a more uniform flow behavior.

[0008] For this purpose, the cathode body is preferably arranged completely downstream of the anode body.

[0009] To prevent the cathode body from interfering with the exhaust gas flow as much as possible, it is proposed that the cathode surface have a surface normal oriented essentially orthogonal to the main exhaust gas flow direction. Such an orientation of the surface normal results in the main exhaust gas flow direction being essentially parallel to the surface of the cathode body.

[0010] The least possible influence on the vibration behavior by the cathode body arranged in the exhaust gas can be achieved by making the cathode body essentially cylindrical and having a cylinder longitudinal axis oriented essentially in the main exhaust gas flow direction.

[0011] For a particularly uniform and therefore efficient effect, the anode tip area can be arranged essentially concentrically to the longitudinal axis of the cylinder.

[0012] The cathode body can, for example, be designed in a tube-like shape, whereby, to allow exhaust gas to pass through, the cathode body is open at its upstream end for the inlet of exhaust gas and at its downstream end for the outlet of exhaust gas.

[0013] In order to influence the acoustic behavior in an area where a uniform exhaust gas flow is supported, the exhaust gas channel can be provided in an exhaust gas pipe that is preferably elongated in the direction of a longitudinal pipe axis.

[0014] It is particularly advantageous if the longitudinal axis of the cylindrically constructed cathode body essentially corresponds to the longitudinal axis of the pipe, so that the cathode body extends essentially along the exhaust pipe or parallel and / or concentric to it.

[0015] For stable and defined positioning in the exhaust duct, a support arrangement can be provided to carry the anode unit and the cathode unit in the exhaust duct.

[0016] For example, the support arrangement for the anode unit can comprise a plurality of anode supports arranged circumferentially around the longitudinal axis of the pipe at intervals and electrically insulated from the exhaust pipe. This also ensures that the anode unit can be exposed to exhaust gas flow.

[0017] Furthermore, the support arrangement associated with the cathode unit can comprise a plurality of cathode supports arranged circumferentially around the longitudinal axis of the pipe at intervals and electrically insulating the cathode unit from the exhaust pipe. This ensures that the exhaust gas flow can also flow along the outside of the cathode unit. If such flow around the outside is not necessary or desired, the support arrangement associated with the cathode unit can, for a simple yet stable mounting, comprise a bearing material arrangement, preferably a fiber mat arrangement, that essentially completely surrounds the cathode unit and electrically insulates it from the exhaust pipe.Such bearing material arrangements, particularly those provided as fiber mat arrangements, are used, for example, in exhaust systems to hold catalyst blocks in a defined manner within tubular housings.

[0018] The device according to the invention can include a control arrangement, wherein the control arrangement can control the high-voltage generator to apply a high voltage between the anode unit and the cathode unit.

[0019] To provide information about the exhaust gas flow in the exhaust system, a current sensing arrangement can be provided to detect the electric current flowing between the anode unit and the cathode unit, wherein the control arrangement for controlling the high-voltage generator is designed based on the electric current detected by the current sensing arrangement. This utilizes the effect that there is a close relationship between the amount of exhaust gas flowing in the exhaust system, and thus also the amount of ionized exhaust gas, and the electric current generated during the ionization process between the anode unit and the cathode unit.

[0020] The present invention further relates to an exhaust system for an internal combustion engine with a device according to the invention.

[0021] The problem stated at the outset is further solved by a method for operating a device according to the invention for influencing the acoustic behavior of an exhaust system of an internal combustion engine, comprising the following measures: a) Operating the internal combustion engine to generate an exhaust gas flow through the exhaust system, b) Applying a high voltage between the anode unit and the cathode unit.

[0022] In order to provide information about the exhaust gas flow rate and the sound transported in the exhaust gas in these processes, it is further proposed that a measure c) be provided to record the electric current flowing between the anode unit and the cathode unit.

[0023] If, in measure b), a high voltage of at least 1.5 kV is applied between the anode unit and the cathode unit, it is ensured that a comparatively large quantity of the exhaust gas flowing around the anode unit is ionized.

[0024] To achieve the most uniform flow possible, in measure b) a substantially constant high voltage can be applied at least temporarily, preferably permanently.

[0025] If the method according to the invention is intended to actively influence the sound spectrum, a varying high voltage can be applied at least temporarily, preferably permanently, in measure b).

[0026] In order to provide a defined interaction with the periodic movements of the exhaust gas column in the exhaust system caused by the transported sound, the high voltage can be applied periodically in measure b).

[0027] Since information about the exhaust gas flow or the sound transported therein can be provided by measuring the electric current between the anode unit and the cathode unit, it is further proposed that the frequency and / or the phase angle and / or the amplitude of the periodically varying component of the high voltage be adjusted depending on the electric current measured in measure c) between the anode unit and the cathode unit.

[0028] The present invention is described in detail below with reference to the accompanying figures. These show: Fig. 1 a basic representation of a device for influencing the acoustic behavior of an exhaust system; Fig. 2 a basic representation of a vehicle's drive system with an internal combustion engine and an exhaust system.

[0029] In the Fig. 1 and Fig. 2 is a device for influencing the acoustic behavior of a Fig. 2 exhaust system shown 10 an internal combustion engine 12 generally with 14 designated. The device 14 includes, for example, an exhaust pipe that is preferably elongated in a straight line along a longitudinal axis A. 16 , the part of an upstream and downstream section of the device 14 running exhaust pipe 18 the exhaust system 10 It can be or be integrated into it. Inside the exhaust pipe 16 is an exhaust gas channel through which exhaust gas flows in a main flow direction H 20 formed. It should be noted that the main exhaust gas flow direction H essentially corresponds to the direction of extension of the exhaust pipe. 16along its longitudinal pipe axis A, and that, depending on turbulence or eddies occurring in the exhaust gas, there may be local flow directions of the exhaust gas flow that deviate from this main exhaust gas flow direction H.

[0030] In the exhaust pipe 16 is a field generation arrangement 21 provided for, which in the direction of flow are successive an anode unit 22 and a cathode unit 24 includes the anode unit. 22 comprises an anode body constructed with electrically conductive material, for example, solid metal material 26 , which can be streamlined in its upstream end region to generate as little turbulence as possible in the exhaust gas flow, and which has an anode tip region in its downstream end region 28 can form.

[0031] The anode unit is positioned downstream of the main exhaust gas flow direction H and preferably at a distance in the direction of the longitudinal axis of the pipe A. 22 arranged cathode unit 24 comprises a cathode body that, in the example shown, is tubular and cylindrical, the longitudinal axis of which of the cylinder essentially corresponds to the longitudinal axis of the tube A, so that the tubular cathode body 30 to the exhaust pipe 16 are essentially arranged concentrically. The cathode body 30 Its inner surface, in particular, constitutes a cathode surface. 32 ready. The cathode body, too. 30It is constructed of electrically conductive material, for example, metal, and its cathode surface, or its inner and outer surfaces, are oriented such that the surface normals present on essentially all surface areas are orthogonal to the main exhaust gas flow direction H. This means that the exhaust gas, flowing essentially in the main exhaust gas flow direction H, passes over the cathode body. 30 the flow around its outer and inner surfaces is essentially parallel to these surfaces, so that the cathode body is also affected 30 Due to its physical presence, it does not significantly affect the exhaust gas flow.

[0032] A high-voltage generator 34 is designed and equipped to connect the anode unit 22 and the cathode unit 24 to apply a high voltage of at least 1.5 kV. With such a voltage between the anode unit...22 and the cathode unit 24 The applied high voltage creates a voltage between the anode body. 26 , especially the anode tip area 28 the same and the cathode body 30 , especially the cathode surface 32 , an electric field which is located in the area of ​​the anode tip 28 exhibits a particularly high field strength. Due to this high field strength, in the area downstream of the anode tip region... 28 an ionization volume 36 formed, in which the exhaust duct 20 The flowing exhaust gas molecules are ionized. Due to the electric field, the positively charged ions transported in the exhaust gas stream move between the anode unit. 22 and the cathode unit 24 approximately along the field lines of the electric field onto the cathode surface 32as indicated by flow arrows P. As a result, the positively charged ions transported in the exhaust gas stream experience an acceleration acting in the direction of the electric field, and in particular also an acceleration in the main exhaust gas flow direction H.

[0033] This accelerating effect on the ions present in the exhaust gas stream leads to a smoothing of the exhaust gas flow and a reduction or elimination of turbulence and eddies. The presence of the tubular cathode body can also contribute to this. 30 two separately flowable volume areas of the exhaust duct 20 are present, so that in each of these volume regions, the flow stabilization can occur in a decoupled and enhanced manner from the other volume region. This is due to the movement towards the cathode surface. 32The positively charged ions take up electrons again upon contact with this, resulting in an essentially uncharged exhaust gas stream downstream of the cathode body. 30 will be available.

[0034] This process involves ionization and the uptake of electrons through interaction with the cathode body. 30 A connection is made between the anode unit 22 and the cathode unit 24 A current-sensing arrangement generates a flowing electric current. 38 can detect this current and send a signal corresponding to the strength of the electric current to a control arrangement. 40 feed in. The control arrangement 40 can then the high-voltage generator 34 to control the area between the anode unit 22 and the cathode unit 24 electric field to be generated or the field strength as a function of the area between the anode unit 22and the cathode unit 24 to control flowing electric current.

[0035] In principle, the high-voltage generator can be used for the previously described comparative moderation of the exhaust gas flow. 34 It is operated in such a way that it maintains an essentially constant high voltage between the anode unit. 22 and the cathode unit 24 The strength of the electric field, or the level of this high voltage, can be adjusted, for example, depending on the current detection arrangement. 38 The detected electrical current can be adjusted. The strength of this electrical current depends in particular on the temperature in the exhaust duct. 20 the flowing exhaust gas volume. The more exhaust gas in the exhaust duct 20 The more exhaust gas flows, the more it is contained within the ionization volume. 36 are ionized and interact with the cathode body 30absorb electrons again. This means that a larger exhaust gas mass flow also results in a larger electrical current between the anode unit. 22 and the cathode unit 24 will cause. The strength of the electric field or the voltage level can be chosen, for example, so that with increasing exhaust gas flow and correspondingly increasing electric current between the anode unit 22 and the cathode unit 24 A higher voltage is also applied to contribute to a correspondingly greater degree to the smoothing of the flow. However, it must be taken into account that a higher voltage between the anode unit also 22 and the cathode unit 24 This will lead to stronger ionization and thus a greater electric current. This effect occurs when controlling the high-voltage generator. 34to take into account, for example by ensuring that short-term changes in the electric current, especially those caused by a change in the applied high voltage, do not lead to a change in the applied high voltage.

[0036] The sound transported in the exhaust stream causes a vibration in the exhaust duct. 20 existing exhaust gas column. Although this oscillation is fundamentally omnidirectional, it will exhibit a directional component in the direction of the main exhaust gas flow H. Such an oscillation in the main exhaust gas flow direction H results in an oscillation of the exhaust gas flow rate, corresponding to the frequency of this oscillation and thus the frequency of the transmitted sound, for example, through a fictitious plane orthogonal to the main exhaust gas flow direction H. This oscillation in the exhaust gas flow rate also forms in the anode unit when high voltage is applied. 22and the cathode unit 24 flowing electric current. This oscillation, reflected in the electric current, can be detected in the control unit. 40 The vibration frequency, amplitude, and phase are evaluated. Depending on at least one of these parameters—frequency, amplitude, and phase—the control arrangement can be adjusted. 40 the high-voltage generator 34 control to increase the high voltage between the cathode unit 22 and the anode unit 24to provide a corresponding oscillating component or to superimpose such an oscillating component on a fundamentally constant high voltage. The oscillating component of the high voltage and a corresponding oscillating component in the field strength of the electric field can then influence the exhaust gas flow or the ions transported in the exhaust gas flow in such a way that an oscillation opposing the fundamental oscillation in the exhaust gas flow is generated. In other words, an attempt is made to reduce or eliminate such oscillation of the exhaust gas flow through destructive superposition. This can be achieved, for example, within a control loop by measuring the electric current between the cathode unit. 22 and the anode unit 24 by varying at least one of the previously specified parameters to minimize the vibration component in the area between the anode unit 22and the cathode unit 24 The flowing electric current can be influenced. However, it would also be possible to emphasize certain frequencies to provide a specific acoustic characteristic, i.e., to create a vibration in the exhaust gas column in the exhaust duct through an oscillation superimposed on the high voltage. 20 and thus create a corresponding soundscape.

[0037] The Fig. Figure 1 also illustrates different ways to design the anode unit 22 or the cathode unit 24 in the exhaust pipe 16 to be held. A carrier arrangement provided for this purpose. 42 can be assigned to the anode unit 22 a plurality of rib-like anode supports arranged at intervals around the longitudinal axis A of the tube 44 These can be attached to the anode body. 26 and the exhaust pipe 16They are connected by material interlocking or / and form interlocking and are preferably constructed at least partially of electrically insulating material in order to also provide electrical insulation of the anode unit. 22 regarding the exhaust pipe 16 to ensure this. Between the anode carriers arranged circumferentially at a distance from each other. 44 The exhaust gas can flow through it.

[0038] The carrier arrangement 42 can also be assigned to the cathode unit 24 a plurality of such cathode supports arranged circumferentially at a distance from each other 46 include. This is in the upper half of the Fig. Figure 1 illustrates this. These cathode supports are also shown. 46 are at least partially constructed with electrically insulating material to insulate the cathode body 30 electrically with regard to the exhaust pipe 16 to isolate. Due to the axial expansion of the cathode body. 30It may be advantageous to also offset such cathode supports in the direction of the longitudinal axis A of the pipe. 46 to be provided. It should be noted that the exhaust pipe 16 It can be constructed from electrically insulating material, for example thermally resistant plastic material, so that an electrically insulated design of the support arrangement is possible. 42 for the anode unit 22 or the cathode unit 24 is not necessary.

[0039] In the lower part of the Fig. 1 is an alternative design of the carrier arrangement 42 This is shown. In the example shown, this includes a tubular cathode body. 30 storage material arrangement surrounding its entire circumference 48 This can, for example, be constructed with fiber material and surround the outer circumference of the cathode body. 30be wrapped. To prevent this from happening when, in such a storage material arrangement, 48 Moisture accumulates, electrical insulation of the cathode body 30 Since the storage material arrangement can no longer be guaranteed, the storage material arrangement may be affected. 48 at least one layer 50 Made of electrically insulating material, for example, thermally resistant plastic. This can be sandwiched between several layers or plies of the bearing material assembly. 48 be embedded. By means of the storage material arrangement 48 , which are located between the cathode body 30 and the inner surface of the exhaust pipe 16 A stable and defined mounting of the cathode body is necessary to keep it compressed. 30 This is ensured by the storage material arrangement. 48preferably extend over its entire axial length. Other materials can also be used for the bearing material arrangement. 48 can be used. For example, this can be achieved by filling the space between the cathode body with foam. 30 and the exhaust pipe 16 The resulting space is provided with thermally resistant and electrically insulating foam. Providing such a space protects the cathode body. 30 the structure of the support arrangement surrounding its entire circumference 42 This results in the entire exhaust gas flow passing through the internal volume of the cathode body. 30 is forced through, which can improve the interaction for ionization.

[0040] The device constructed according to the invention 14 Will it be possible to influence the acoustic behavior of the exhaust system? 10to actively influence the device without requiring any moving components. The system areas of the device 14 Components that are to be arranged in the exhaust gas stream and interact with it can be designed in such a way that they generally influence the exhaust gas stream as little as possible or in a defined manner. This naturally includes both the anode unit and the components themselves. 22 , as well as the cathode unit 24 It will be provided in a different form than described above.

Claims

[1] Device for influencing the acoustic behavior of an exhaust system of an internal combustion engine, comprising: - an exhaust duct (20) through which exhaust gas flows - a field generation arrangement (21) positioned in the exhaust duct (20) for generating an electric field, wherein the field generation arrangement (21) comprises an anode unit (22) around which exhaust gas flows in the exhaust duct (20) and a cathode unit (24) arranged at least partially downstream of the anode unit (22) with respect to a main exhaust gas flow direction (H) in the exhaust duct (20) and around which exhaust gas flows, as well as a high voltage generator (34) for applying a high voltage between the anode unit (22) and the cathode unit (24). [2] Device according to claim 1, characterized by , that the anode unit (22) comprises an anode body (26) with an anode tip area (28) arranged in a downstream end region of the same. [3] Device according to claim 1 or 2, characterized by , that the cathode unit (24) comprises a cathode body (30) arranged at least partially downstream of the anode unit (22) with a cathode surface (32). [4] Device according to claim 2 and claim 3, characterized by , that the cathode body (30) is arranged completely downstream of the anode body (26). [5] Device according to claim 3 or 4, characterized by , that the cathode surface (32) has a surface normal oriented substantially orthogonal to the main exhaust gas flow direction (H). [6] Device according to one of claims 3-5, characterized by , that the cathode body (30) is essentially cylindrical and has a cylinder longitudinal axis oriented essentially in the main exhaust gas flow direction (H). [7] Device according to claim 2 and claim 6, characterized by, that the anode tip region (28) is arranged essentially concentrically to the longitudinal axis of the cylinder. [8] Device according to one of claims 3-7, characterized by , that the cathode body (30) is tubular in shape, wherein the cathode body (30) is open at its upstream end for the inlet of exhaust gas and at its downstream end for the outlet of exhaust gas. [9] Device according to any of the preceding claims, characterized by , that the exhaust duct (20) is provided in an exhaust pipe (16) which is preferably elongated in the direction of a longitudinal pipe axis (A). [10] Device according to claim 6 and claim 9, characterized by , that the longitudinal axis of the cylinder essentially corresponds to the longitudinal axis of the tube (A). [11] Device according to any of the preceding claims, characterized by , that a support arrangement (42) is provided for supporting the anode unit (22) and the cathode unit (24) in the exhaust duct (20). [12] Device according to claim 9 and claim 11, characterized by , that the support arrangement (42) in relation to the anode unit (22) comprises a plurality of anode supports (44) arranged circumferentially around the longitudinal axis of the tube (A) at a distance from each other and electrically insulating the anode unit (22) with respect to the exhaust pipe (16). [13] Device according to claim 9 and claim 11 or 12 characterized by, that the support arrangement (42) in association with the cathode unit (24) comprises a plurality of cathode supports (46) arranged circumferentially around the longitudinal axis (A) of the tube and electrically insulated from each other and supporting the cathode unit (24) with respect to the exhaust pipe (16), or that the support arrangement (42) in association with the cathode unit (24) comprises a bearing material arrangement (48), preferably a fiber mat arrangement, which substantially completely surrounds the cathode unit (24) and electrically insulates the cathode unit (24) with respect to the exhaust pipe (16). [14] Device according to any of the preceding claims, characterized by , that a control arrangement (40) is provided, wherein the control arrangement (40) controls the high voltage generator (34) to apply a high voltage between the anode unit (22) and the cathode unit (24). [15] Device according to claim 14, characterized by, that a current sensing arrangement (38) is provided for sensing the electric current flowing between the anode unit (22) and the cathode unit (24), wherein the control arrangement (40) is designed to control the high voltage generator (34) on the basis of the electric current detected by the current sensing arrangement (38). [16] Exhaust system for an internal combustion engine, comprising a device (14) according to any of the preceding claims. [17] Method for operating a device (14) according to one of claims 1-15 for influencing the acoustic behavior of an exhaust system (10) of an internal combustion engine (12), comprising the measures: a) Operating the internal combustion engine (12) to generate an exhaust gas flow through the exhaust system (10), b) Applying a high voltage between the anode unit (22) and the cathode unit (24). [18] Method according to claim 17, characterized by, that a measure c) is provided for recording the electric current flowing between the anode unit (22) and the cathode unit (24). [19] Method according to claim 17 or 18, characterized by , that in measure b) a high voltage of at least 1.5 kV is applied between the anode unit (22) and the cathode unit (24). [20] Method according to any one of claims 17-19, characterized by , that in measure b) a substantially constant high voltage is applied at least temporarily. [21] Method according to any one of claims 17-20, characterized by , that in measure b) a varying high voltage is applied at least temporarily. [22] Method according to claim 21, characterized by , that in measure b) the high voltage is applied with periodic variations. [23] Method according to claim 18 and claim 22, characterized by, that the frequency and / or the phase angle and / or the amplitude of the periodically varying component of the high voltage is set as a function of the electric current detected in measure c) between the anode unit (22) and the cathode unit (24).

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