DE102017219938B4 - Exhaust system for a motor vehicle, motor vehicle with such an exhaust system and method for conditioning an exhaust system - Google Patents

Abstract

Exhaust system for a motor vehicle, with a particle filter (4), wherein an ash particle storage device (6) is arranged upstream of the particle filter (4) on an inner wall of a pipe section (5), accessible from the exhaust gas flow, in which ash particles are enclosed, wherein the ash particle storage device (6) encloses the ash particles at least at temperatures below 30°C and releases at least a portion of the ash particles at least at temperatures above 120°C, wherein the majority of the ash particles have a maximum diameter of less than 80 nm.

Description

The invention relates to an exhaust system for a motor vehicle, a motor vehicle with such an exhaust system and a method for conditioning an exhaust system.

Exhaust systems for discharging and cleaning exhaust gases from an internal combustion engine can have a particle filter. A particle filter filters out ash and soot particles in particular from the exhaust gas, which then settle in the filter material. With some particle filters for gasoline engines, the effect described below can occur. Large particles are filtered relatively well because, due to their size, they are very likely to hit the filter material and stick to it. With very small particles, it can be observed with some particle filters that, starting with a brand-new particle filter, an increase in filtration efficiency can be observed in the initial phase of use of the particle filter. This is because very small particles are more likely to stick to particles that have already settled in the filter material than to the clean filter material of a brand-new particle filter.

EN 10 2009 049 624 A1 relates to a method for operating a particle filter for filtering out particles contained in the exhaust gas of motor vehicle internal combustion engines. According to the invention, a conditioning step is carried out when the particle filter is in a new state, the conditioning step being carried out in such a way that the separation performance of the particle filter is increased compared to the value that exists in the new state.

EN 10 2016 110 166 A1 describes a method for a vehicle. The method includes, in response to installation of a new exhaust particulate filter, doping the fuel with an ash-producing additive and burning the doped fuel to produce ash, wherein the ash is deposited as an ash coating on the new exhaust particulate filter. In this way, a filtration efficiency of an exhaust particulate filter can be rapidly increased compared to a filter without a deposited ash layer, cost-effectively compared to conventional methods using membranes, and with a lower drop in back pressure compared to conventional methods.

EN 10 2017 107 893 A1 relates to a method for producing an exhaust system of a gasoline engine having a particle filter, with the following features:- positioning of at least two components intended for the passage of exhaust gas, wherein at least one of the components is provided in the exhaust system between an exhaust valve of the gasoline engine and the particle filter, with at least one spacer element arranged between the components and positioning them, wherein the spacer element contains ash-forming components,- permanently connecting the components,- burning the spacer element when the exhaust system is first heated up with the ash-forming components being released and deposited on the particle filter.

From the EN 10 2016 103 735 A1 A method for artificially incinerating a particle filter is known. In this method, a layer of ash is applied to a particle filter as a filter cake in a new state. A first method is described in which a special fuel is used as the initial filling of the vehicle, a second method in which a special ash-forming oil is fed to the vehicle. In a third method, the channel surface of the particle filter is directly coated with an ash-forming agent, which is burned off in a downstream process.

It is therefore an object of the present invention to provide an exhaust system which has an increased filtration efficiency, in particular in an initial life cycle of a particle filter. This object is achieved by an exhaust system according to claim 1 and a method according to claim 6. Advantageous developments of the invention are the subject of the dependent claims.

According to one embodiment of the invention, an exhaust system for a motor vehicle is provided, with a particle filter, wherein an ash particle storage device is arranged upstream of the particle filter on an inner wall of a pipe section, accessible from the exhaust gas flow, in which ash particles are enclosed, wherein the ash particle storage device encloses the ash particles at least at temperatures below 30°C and releases at least some of the ash particles at least at temperatures above 120°C. The advantage of this embodiment is that ash particles are already in the filter material when the exhaust system is put into operation or are carried into the filter material by the commissioning and the associated exhaust gas flow. As a result, very small particles which are created by combustion in the combustion engine can be filtered out of the exhaust gas flow right from the start with a brand new particle filter with higher filtration efficiency. In comparison to the prior art described at the beginning, ash is not first formed by combustion, which is associated with a certain time delay, but rather existing ash, which is enclosed in the ash storage, is released. This has the advantage that the ash can be released more quickly than in the prior art, thus enabling a faster increase in filtration efficiency. In addition, it is not the inner wall of the particle filter that is coated, as in the prior art, but the piping upstream of the particle filter, which is more cost-effective. The majority of ash particles have a maximum diameter of less than 80 nm. The inventor of this invention found that this particle size is suitable for forming an adhesion base for the very small particles in the exhaust gas mentioned at the beginning.

According to a further embodiment of the invention, the exhaust system is designed such that the ash particle storage device is in a non-flowable state at temperatures below 30°C, for example in the form of a solid or a paste, and encloses the ash particles and is in a liquid and/or gaseous state at least at temperatures above 120°C and releases at least a portion of the ash particles.

According to a further embodiment of the invention, the ash particle storage is a substrate material in which the ash particles are embedded.

Preferably, this substrate material is a spreadable paste at 25°C.

According to a further embodiment of the invention, the substrate material comprises paraffin or consists of paraffin. The advantage of paraffin is that it can be provided inexpensively and can be burned essentially without residue.

In addition, the invention provides a method for conditioning an exhaust system of a motor vehicle with an internal combustion engine. The method comprises the step of introducing an ash particle storage device, before a first start-up of the internal combustion engine, at a location upstream of a particle filter on an inner wall of a pipe section such that the ash particle storage device, in which ash particles are enclosed, is arranged so as to be accessible from the exhaust gas flow, enclosing the ash particles by the ash particle storage device at least at temperatures below 30°C, and
Releasing at least some of the ash particles at least at temperatures above 120°C. The majority of the ash particles have a maximum diameter of less than 80 nm. The inventor of this invention found that this particle size is suitable for forming an adhesion base for the very small particles in the exhaust gas mentioned at the beginning.

According to a further embodiment of the invention, the method is developed such that the ash particle storage device is in a non-flowable state at temperatures below 30°C, for example in the form of a solid or a paste, and encloses the ash particles and is in a liquid and/or gaseous state at least at temperatures above 120°C and releases at least a portion of the ash particles.

According to a further embodiment of the invention, the method is developed such that the ash particle storage device comprises a substrate material in which the ash particles are embedded.

According to a further embodiment of the exhaust system and/or the method, the ash particle storage device releases at least a portion of the ash particles at least at temperatures above 100°C. Preferably, the ash particle storage device is in a liquid and/or gaseous state at least at temperatures above 100°C.

According to a further embodiment of the exhaust system and/or the method, the ash particle storage device releases at least a portion of the ash particles at least at temperatures above 80°C. Preferably, the ash particle storage device is in a liquid and/or gaseous state at least at temperatures above 80°C.

Furthermore, the present invention provides a motor vehicle with such an exhaust system.

• Die Figur zeigt schematisch eine Abgasanlage für ein Kraftfahrzeug mit einem Verbrennungsmotor 1, einer Abgasrohrleitung 2, die Verbrennungsabgase aus dem Verbrennungsmotor abführt und an eine Umgebung abgibt. Der Verbrennungsmotor 1 kann ein Dieselmotor oder ein Ottomotor sein, vorzugsweise handelt es sich jedoch um einen Ottomotor, da bei diesem die in der Beschreibungseinleitung beschriebene Effizienzsteigerung stärker ausgeprägt ist. In der Abgasrohrleitung 2 sind ein Katalysator 3 und ein Partikelfilter 4 so angeordnet, dass diese von dem in der Abgasrohrleitung 2 geführten Abgas durchströmt werden. Der Katalysator 3 und der Partikelfilter 4 sind als baulich getrennte Einheiten ausgebildet, wobei der Katalysator 3 abgasstromaufwärts des Partikelfilters 4 angeordnet ist. Dazwischen ist ein Rohrleitungsabschnitt 5 der Rohrleitung 2 angeordnet. In dem Partikelfilter 4 ist Filtermaterial aufgenommen, wie dies aus dem Stand der Technik bekannt ist. Insbesondere ist der Partikelfilter 4 ein von dem Rohrleitungsabschnitt 5 separates Bauteil, welche als vorzugsweise lösbar miteinander verbundene Bauteile miteinander verbindbar sind.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings, in which:

• The figure shows a schematic of an exhaust system for a motor vehicle with an internal combustion engine 1, an exhaust pipe 2, which removes combustion exhaust gases from the internal combustion engine and releases them into the environment. The internal combustion engine 1 can be a diesel engine or a gasoline engine, but it is preferably a gasoline engine, since the increase in efficiency described in the introduction to the description is more pronounced in this case. A catalyst 3 and a particle filter 4 are arranged in the exhaust pipe 2 in such a way that the exhaust gas guided in the exhaust pipe 2 flows through them. The catalyst 3 and the particle filter 4 are designed as structurally separate units, with the catalyst 3 being arranged upstream of the exhaust gas flow of the particle filter 4. A pipe section 5 of the pipe 2 is arranged between them. Filter material is accommodated in the particle filter 4, as is known from the prior art. In particular, the particle filter 4 is a component separate from the pipe section 5, which can be connected to one another as components that are preferably detachably connected to one another.

In order to increase the filtration efficiency of the particle filter 4, according to the invention ash particles are introduced into the exhaust system before exhaust gases from the internal combustion engine 1 flow through it for the first time. The ash particles are introduced upstream of the particle filter 4. “Upstream of the particle filter” is to be understood in particular as a plane that extends perpendicular to the longitudinal direction of the particle filter (where the longitudinal direction extends essentially along its flow direction) at a point that is located at the upstream end of the filter material of the particle filter. Of course, the present invention does not rule out the possibility of ash particles also being introduced into the exhaust system downstream of this plane. In particular, the ash particles are introduced into the interior of the pipe section 5. As already mentioned, this pipe section 5 is preferably designed as a component separate from the particle filter 4, which has the advantage that the ash particles can be introduced more cost-effectively into the structurally simpler pipe section 5 (compared to the particle filter 4).

If the ash particles are introduced upstream of the particle filter 4, then the ash particles are carried downstream by the exhaust gas flow into the particle filter 4 during initial start-up, when the exhaust system is flowed through by exhaust gases from the internal combustion engine 1, and at least some of them settle there. The ash particles are advantageously introduced downstream of the catalyst 3 in order to avoid contamination of the catalyst 3 with these ash particles.

Ash is a solid residue from the combustion of organic material and consists mainly of oxides and (bi)carbonates of various metals. Ash can, for example, contain one or more of the following substances: CaO, Fe ₂ O ₃ , MgO, MnO, P ₂ O ₅ , K ₂ O, SiO ₂ , Na ₂ CO ₃ , NaHCO ₃ .

The ash particles can be introduced into this part, for example, after the production of the part of the exhaust system into which the ash particles are to be introduced, before this part is installed on the motor vehicle or after installation and before the first commissioning, i.e. the first exposure to exhaust gases from the internal combustion engine. Preferably, the ash particles predominantly have a maximum diameter of less than 80 nm. Since the ash particles are usually not perfectly spherical, but have an irregular outer contour, the maximum diameter is determined in such a way that, regardless of the measurement direction on the ash particle, the measured ash particle does not have a dimension larger than this maximum diameter in any direction. Preferably, the majority of the ash particles according to the invention, i.e. more than 50% of the ash particles introduced into the exhaust system according to the invention, are smaller than this maximum diameter. Even more preferably, more than 60% of the ash particles introduced into the exhaust system according to the invention are smaller than this maximum diameter. Even more preferably, more than 70% of the ash particles introduced into the exhaust system according to the invention are smaller than this maximum diameter. Even more preferably, more than 80% of the ash particles introduced into the exhaust system according to the invention are smaller than this maximum diameter. The ash particles can be produced, for example, by means of spark erosion.

• Beispielsweise können die Aschepartikel in einem Aschepartikelspeicher 6 eingeschlossen sein, welcher bei Umgebungstemperatur die Aschepartikel einschließt und nach der Inbetriebnahme der Abgasanlage die Aschepartikel freigibt.

There are various ways to introduce the ash particles into the exhaust system, which are explained below:

• For example, the ash particles can be enclosed in an ash particle storage device 6, which encloses the ash particles at ambient temperature and releases the ash particles after the exhaust system is put into operation.

A vessel or a bag in which the ash particles are held is suitable as an ash particle storage device 6. The material from which the vessel or bag is made is in a non-flowable state at ambient temperature, preferably in a solid state, so that the ash particles are enclosed, and changes to a liquid and/or gaseous state after the exhaust system is put into operation, so that at least some, preferably all, of the ash particles are released.

A substrate material in which the ash particles are embedded is also preferably suitable as the ash particle storage device 6. The substrate material is in a non-flowable state at ambient temperature, for example in the form of a solid or a paste, so that the ash particles are enclosed, and after commissioning entering the exhaust system into a liquid and/or gaseous state, so that at least some of the ash particles are released. In particular, a material is suitable for the ash particle storage (a substrate material or a material for the vessel/bag) which is in a non-flowable state at least at temperatures below 30°C (the substrate material can therefore also be in a non-flowable state at temperatures above 30°C), so that it encloses the ash particles, and is in a liquid and/or gaseous state at least at temperatures above 120°C (the substrate material can therefore already be liquid and/or gaseous at temperatures below 120°C), so that it releases at least some of the ash particles. For example, paraffin doped with ash particles is suitable as a substrate material. The paraffin applied, for example, to the pipe section 5, in particular to its inner wall, is not flowable at ambient temperature and encloses the doped ash particles. When the exhaust system is started up, the paraffin is initially converted into a liquid and then possibly a gaseous state by the hot exhaust gases and, from the liquid state, releases at least some of the ash particles, which are then carried by the exhaust gas flow downstream into the particle filter, more precisely into the filter material of the particle filter, and at least partially settle there. The paraffin is evaporated or burned by the hot exhaust gases, so that the paraffin mainly produces CO ₂ and H ₂ O. A particle size distribution and/or a mass of ash particles can be varied by appropriate dosing in the substrate material. The more ash particles are embedded or enclosed in the substrate material, the more ash particles can be deposited in the particle filter 4.

While the invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description is to be considered as illustrative or exemplary and not restrictive, and it is not intended to limit the invention to the embodiment disclosed. The mere fact that certain features are recited in various dependent claims is not to suggest that a combination of these features could not also be used to advantage.

Claims (9)

Exhaust system for a motor vehicle, with a particle filter (4), wherein an ash particle storage device (6) is arranged upstream of the particle filter (4) on an inner wall of a pipe section (5) accessible from the exhaust gas flow, in which ash particles are enclosed, wherein the ash particle storage device (6) encloses the ash particles at least at temperatures below 30°C and releases at least some of the ash particles at least at temperatures above 120°C, wherein the majority of the ash particles have a maximum diameter of less than 80 nm. Exhaust system according to Claim 1 , wherein the ash particle storage device (6) is in a non-flowable state at temperatures below 30°C and encloses the ash particles and is in a liquid and/or gaseous state at least at temperatures above 120°C and releases at least a portion of the ash particles. Exhaust system according to one of the preceding claims, wherein the ash particle storage (6) is a substrate material in which the ash particles are embedded. Exhaust system according to Claim 3 , wherein the substrate material is a spreadable paste at 25°C. Exhaust system according to Claim 3 or 4 , wherein the substrate material comprises or consists of paraffin. Method for conditioning an exhaust system of a motor vehicle with an internal combustion engine (1), comprising the step: Introducing an ash particle storage device (6), before the internal combustion engine is first started up, at a location upstream of the exhaust gas flow of a particle filter (4) on an inner wall of a pipe section (5) such that the ash particle storage device (6), in which ash particles are enclosed, is arranged so that it can be reached by the exhaust gas flow, Enclosing the ash particles by the ash particle storage device (6) at least at temperatures below 30°C, and Releasing at least some of the ash particles at least at temperatures above 120°C, whereby the majority of the ash particles have a maximum diameter of less than 80nm. Procedure according to Claim 6 , wherein the ash particle storage device (6) is in a non-flowable state at temperatures below 30°C and encloses the ash particles and is in a liquid and/or gaseous state at least at temperatures above 120°C and releases at least some of the ash particles. Procedure according to Claim 6 or 7 , wherein the ash particle storage (6) is a substrate material in which the ash particles are embedded. Motor vehicle with an exhaust system in accordance with one of the Claims 1 until 5 .

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