Patent Application
20130305690
The present invention relates to an exhaust gas system having an exhaust-gas purification component, an exhaust line, a connection device and a fastening element. The present invention also relates to a motor vehicle having an exhaust system and a method for operating the motor vehicle.
Exhaust-gas purification components in exhaust systems of internal combustion engines may have different functions. The exhaust-gas purification components are used, for example, as catalyst carrier bodies, as adsorbers, as filters, as flow mixers and/or as particle separators. The exhaust-gas purification components typically have passages or channels through which a fluid can flow and which are, if appropriate, at least partially (catalytically) coated and/or formed with a filter material. The exhaust gas which flows into a channel may also, by using diverting structures, be caused to partially pass through the channel walls, in such a way that, for example, filter materials or separation surfaces for particles and/or intimate contact with a catalytically active surface are realized. The deposited soot particles, ash and/or carbon particles can be at least intermittently converted by using high exhaust-gas temperatures, in the presence of NO2 (nitrogen dioxide) and/or by using a catalytically active coating.
However, situations arise in which the deposited soot particles and/or carbon particles or the ash are not completely converted. If such unconverted residues collect in the filter material and/or on the channel walls, in particular at the transition points between the adjacent channels, an exhaust-gas purification component can become at least partially blocked. That leads to an increased pressure drop of the exhaust gas across the exhaust-gas purification component and thus to a decrease in efficiency of the internal combustion engine. Furthermore, the catalytically active surface can be at least partially covered and thus reduced in that way, which is likewise undesirable.
It is accordingly an object of the invention to provide an exhaust system, a motor vehicle having an exhaust system and a method for operating a motor vehicle, which overcome the hereinafore-mentioned disadvantages and at least partially solve the highlighted problems of the heretofore-known systems, vehicles and methods of this general type and, in particular, to specify an exhaust system with which particles (such as, for example, ash) that cannot be converted into gaseous substances can be eliminated from critical regions of the exhaust system.
With the foregoing and other objects in view there is provided, in accordance with the invention, an exhaust system, comprising at least one exhaust-gas purification component, at least one exhaust line, at least one connector or connection device for connecting the exhaust system to an internal combustion engine of a motor vehicle, and at least one fastener or fastening element for additionally fastening the exhaust system to the motor vehicle. The at least one exhaust-gas purification component can, in a fastened state, be stimulated to perform oscillations with a first resonance frequency range of lower than 300 Hz [1/sec], preferably lower than 150 Hz and the exhaust-gas purification component can, in a fastened state, preferably be stimulated to perform oscillations with a first resonance frequency range of at least 50 Hz.
An exhaust-gas purification component is to be understood, in particular, to mean at least one of the following components: honeycomb body, filter, separator, catalyst carrier body, adsorber or flow mixer. The exhaust-gas purification components are disposed in the exhaust line or in an exhaust-gas recirculation line of the exhaust system assigned to an internal combustion engine, and are thus exposed to the exhaust gas. For this purpose, the exhaust-gas purification component is, for example, connected in a force-locking and/or form-locking and/or cohesive fashion, or is in contact, with the exhaust line. A force-locking connection is one which connects two elements together by force external to the elements, as opposed to a form-locking connection which is provided by the shapes of the elements themselves.
A connector or connection device is to be understood to mean elements by which the exhaust system is directly connected to, or placed in contact with, the internal combustion engine. The connection device may be in the form of a flange which is screwed to the internal combustion engine. The connection device may, however, also be realized by using a welded connection of the exhaust system to the internal combustion engine. The connection device is normally adjoined by the exhaust line through which the exhaust gas is conducted and in which the at least one exhaust-gas purification component is disposed. The exhaust system is connected to the motor vehicle by at least one further fastener or fastening element. The at least one fastening element can produce a rigid or elastic connection of the exhaust system to the motor vehicle. The at least one fastening element is, in particular, provided on the underside of the motor vehicle and includes, for example, at least one bracket which, at a distance from the internal combustion engine, fixes the exhaust system in the desired position.
A fastened state is to be understood, in particular, to mean that the exhaust system is clamped at the connection device and at the at least one fastening element corresponding to the intended use situation. In order to determine the resonance frequency, the exhaust system is thus either mounted as intended in a motor vehicle or else is clamped in a test stand in the same way as in the intended use situation.
The resonance frequencies of the at least one exhaust-gas purification component of the exhaust system may, on one hand, be determined by using numerical methods in simulations. Furthermore, experimental determination of the resonance frequencies of the exhaust-gas purification components disposed in the exhaust system is also possible. For this purpose, the exhaust system, clamped in the same way as during operation of the internal combustion engine is, for example, stimulated in up to three (3) mutually orthogonal directions in succession, with an amplitude of at least 1 mm [millimeter] in the spatial direction, by an oscillation source. The oscillation source passes through a stimulation frequency of, for example, 1 Hz up to 16,000 Hz. In order to determine the resonance frequency, an oscillation amplitude is recorded at different points of the exhaust system, in particular at the exhaust-gas purification components, as a function of the stimulation frequency. The frequency at which the maximum amplitudes are determined is referred to as the resonance frequency.
A resonance frequency range refers to a frequency interval with a width of 10 Hz, preferably 5 Hz, particularly preferably 2 Hz, which centrally surrounds the resonance frequency. Alternatively, the resonance frequency range may be determined by using the half width of the resonance frequency in a plot of the oscillation amplitude versus stimulating frequency, wherein the resonance frequency range corresponds to at most 10 times, preferably at most 5 times and particularly preferably at most 3 times the half width.
The exhaust system can be stimulated to perform oscillations by vibrations. The oscillations may be distinguished, at a predefined location of the exhaust system, by an amplitude and a frequency. In this case, the amplitude and the frequency need not correspond at all locations of the exhaust system. Oscillations with frequencies in a first resonance frequency range are, in particular, oscillations which are performed by an exhaust-gas purification component as a whole, that is to say in particular oscillations with which a housing of the exhaust-gas purification component oscillates out of its rest position. All of the parts of the exhaust-gas purification component also oscillate together with the oscillations of the housing out of its rest position. Parts mounted in the housing in a damped manner may oscillate with a smaller amplitude than the housing itself. It is, however, preferable for oscillations with a frequency in the first resonance frequency range to be transmitted in an undamped manner to all of the parts. It is, however, also conceivable for rigid structures of the exhaust-gas purification system, such as for example the housing, to oscillate with a relatively small amplitude, whereas flexible elements of the exhaust-gas purification component, such as for example the filter material, oscillate with a larger amplitude. The oscillations of the exhaust-gas purification component thus also stimulate the ash particles and/or soot particles deposited in the exhaust-gas purification component to perform oscillations. Due to the mass inertia of the particles which differs from that of the accumulation site, the deposited particles can detach from the accumulation site and pass, for example, back into the exhaust-gas flow.
As a result of a stimulation of the exhaust-gas purification component with a frequency in the first resonance frequency range, the exhaust-gas purification component performs oscillations with a large amplitude, whereby the particles are detached from their accumulation sites.
In accordance with another feature of the invention, a first resonance frequency range of lower than 300 Hz and, in particular, of lower than 150 Hz is selected in such a way that at least one exhaust-gas purification component can be stimulated to perform oscillations by vibrations of the internal combustion engine at least during starting or shut-down of the internal combustion engine. Since, during starting, the internal combustion engine passes through frequencies of 0 Hz up to frequencies of 300 Hz, which can be assigned to the idle rotational speed, the exhaust-gas purification component is cleaned by the vibrations at least once during the operation of the internal combustion engine. If the resonance frequency range is higher than 50 Hz, a stimulation of oscillations of the exhaust-gas purification component by oscillations caused by uneven road surfaces during a trip is prevented.
In accordance with a further feature of the invention, frequencies from the first resonance frequency range are preferably attained by way of the construction of at least two of the following components:
In particular, the mechanical properties of the above-mentioned components are coordinated (with one another) in such a way that a first resonance frequency range of lower than 300 Hz or even lower than 150 Hz is realized. The mechanical properties refer, in particular, to the mass, the bending stiffness, the modulus of elasticity of the components and/or the connecting points thereof.
The at least one exhaust-gas purification component preferably has channels, through which a fluid can flow and which have walls formed at least partially with filter material, and a multiplicity of structures which project into the channels. By using an exhaust-gas purification component constructed in this way, the fluid flowing in a channel can flow to an adjacent channel through a filter material which captures the particle and/or the ash. In a preferred embodiment, the channels are disposed in a layered fashion. The exhaust gas can thus be diverted in two mutually orthogonal directions. It is advantageous in this case for the at least one exhaust-gas purification component to oscillate in at least one of the diverting directions. It is thus possible for the soot particles and/or carbon particles deposited in the filter material to be accelerated in both directions from the rest position toward a channel. The “open” embodiment of a particle separator of that type has the advantage that the ash can also be removed by virtue of its being conveyed to the open outlet by vibration and exiting the particle separator. Reference is made to known patent publications of the Applicant of the instant application for a more detailed description of the so-called open partial-flow filter. In this regard, reference is made, in particular, to International Publication No. WO 02/00326 A2, corresponding to U.S. Pat. No. 6,712,884 or to International Publication No. WO 2005/099867 A1, corresponding to U.S. Pat. No. 7,959,868, the content of which can be taken into consideration for the characterization of the open partial-flow filter.
In accordance with an added feature of the exhaust system of the invention, the at least one exhaust-gas purification component has at least one part which has a second resonance frequency range of higher than 500 Hz, preferably of higher than 800 Hz, particularly preferably of higher than 1000 Hz. In contrast to the first resonance frequency range, which distinguishes the behavior of the fastened exhaust-gas purification component in the exhaust system, the second resonance frequency range distinguishes a part of the exhaust-gas purification component itself. The parts of the at least one exhaust-gas purification component are, in particular, the structures and/or the walls of the channels, in particular the filter material. The second resonance frequency range thus lies outside the vibration frequencies normally generated by an internal combustion engine. The parts of the exhaust-gas purification component therefore cannot be stimulated to perform oscillations by the internal combustion engine alone (that is to say, in particular, without a corresponding resonance oscillation of the exhaust line in that range), so that an undesired stimulation of the parts to perform oscillations during a trip is avoided.
The second resonance frequency range is, in particular, determined by virtue of the clamped exhaust-gas purification component being stimulated with vibrations, wherein the oscillations of the individual parts are recorded as a function of the frequency of the stimulating oscillations.
In accordance with an additional advantageous feature of the invention, the at least one exhaust-gas purification component is assigned a vibration element which can stimulate the exhaust-gas purification component to perform oscillations with a frequency in the second resonance frequency range. As a result of the oscillations, the particles deposited in the exhaust-gas purification component are detached from the accumulation sites. Additionally to the vibrations generated by the internal combustion engine during starting or shut-down, the exhaust-gas purification component can be cleaned in a targeted manner during the operation of the internal combustion engine by using the vibration element.
With the objects of the invention in view, there is also provided a motor vehicle, comprising an exhaust system according to the invention.
With the objects of the invention in view, there is concomitantly provided a method for operating a motor vehicle having an internal combustion engine and an exhaust system. The method comprises, during a starting process, operating the internal combustion engine in such a way that vibrations of the internal combustion engine are stimulated for such a length of time that the vibrations are transmitted to an exhaust-gas purification component which is stimulated to perform oscillations in a resonance frequency range of lower than 150 Hz, so that it is freed from particles. Such a method is realized, in particular, by virtue of the injection time and the injection duration being selected correspondingly during the starting of the engine.
Other features which are considered as characteristic for the invention are set forth in the appended claims, noting that the features specified individually in the dependent claims may be combined with one another in any desired technologically meaningful way and define further embodiments of the invention. Furthermore, the features specified in the claims are rendered more precisely and explained in more detail in the description, with further preferred refinements of the invention being presented.
Although the invention is illustrated and described herein as embodied in an exhaust system, a motor vehicle having an exhaust system and a method for operating a motor vehicle, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
Referring now to the figures of the drawings in detail and first, particularly, to
The mechanical properties of the exhaust-gas purification component 2, of the exhaust line 3, of the connection device 4 and of the fastening element 7, are coordinated with one another in such a way that at least one exhaust-gas purification component 2 has a first resonance frequency range of below 300 Hz or even below 150 Hz, but above 50 Hz. It is ensured in this way that, during the starting of the internal combustion engine 5, as a result of transmitting the vibrations of the internal combustion engine 5 to the exhaust system 1, the at least one exhaust-gas purification component 2 is stimulated to perform oscillations or excited to oscillate, in such a way that particles deposited in the exhaust-gas purification component 2 are detached. A stimulation of oscillations as a result of uneven road surfaces during a journey is, however, prevented. A stimulation of the exhaust-gas purification component 2 to perform oscillations while the internal combustion engine 5 is at idle and/or under load can thus likewise practically be prevented (if desired). During the starting of the internal combustion engine 5, the control unit 19 controls injection processes in such a way that preferably oscillations with frequencies from a first resonance frequency range are stimulated.
The detectors 17 determine parameters of the exhaust gas, such as pressure, temperature and/or exhaust-gas composition, in the exhaust line 3 and transmit these to the control unit 19. The control unit 19 can, after predefined intervals and/or in the presence of predefinable parameters of the internal combustion engine 5 and/or in the presence of predefinable parameters of the exhaust gas, transmit a signal for performing vibrations to the vibration element 9. The vibration element 9 performs, in particular, oscillations with frequencies higher than 500 Hz [1/sec]. The frequency of the stimulating oscillation can thus be set in such a way that the exhaust-gas purification component 2 is stimulated with a frequency in a second resonance frequency range of parts 8 of the exhaust-gas purification component 2 shown in
The present invention permits, in particular, the removal of ash residues from an exhaust-gas purification component 2 during the starting of the motor vehicle 6, in such a way that the maintenance expenditure for such an exhaust-gas purification component is reduced and long-term effective operation of the exhaust-gas purification component 2 is possible.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102010047275.1 | Oct 2010 | DE | national |
This application is a continuation, under 35 U.S.C. §120, of copending International Application No. PCT/EP2011/067142, filed Sep. 30, 2011, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German Patent Application DE 10 2010 047 275.1, filed Oct. 1, 2010; the prior applications are herewith incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2011/067142 | Sep 2011 | US |
| Child | 13854355 | US |
