Exhaust gas burner and exhaust gas aftertreatment system

Abstract

The invention relates to an exhaust gas burner (10) for an exhaust gas aftertreatment system (1) of an internal combustion engine (2), comprising a combustion chamber (11) in which a mixture of an oxygen-containing gas and fuel can be combusted, wherein the combustion chamber (11) has an outlet (15) that can be connected to the exhaust gas aftertreatment system (2), and wherein at least one injection valve (12) for injecting the fuel into the combustion chamber (11) is arranged on the combustion chamber (11), and wherein a guide device (13) is arranged on the combustion chamber (11) through which the gas can be introduced into the combustion chamber, wherein the injection valve (12) is enclosed by the guide device (13) in a longitudinal section facing the combustion chamber (11), so that fuel and gas can be introduced coaxially into the combustion chamber (11). It is intended that the guide device (13) together with a cover (28) arranged on the guide device (13) completely encloses the injection valve (12).

Description

[0001] The invention relates to an exhaust gas burner for an exhaust gas aftertreatment system of an internal combustion engine, having a combustion chamber in which a mixture of an oxygen-containing gas and fuel can be combusted, wherein the combustion chamber has an outlet connectable to the exhaust gas aftertreatment system, and wherein at least one injection valve for injecting the fuel into the combustion chamber is arranged on the combustion chamber, and wherein a guide device is assigned to the combustion chamber through which the gas can be introduced into the combustion chamber, wherein the injection valve is enclosed by the guide device in a longitudinal section facing the combustion chamber, so that fuel and gas can be introduced coaxially into the combustion chamber.

[0002] Furthermore, the invention relates to an exhaust gas aftertreatment system for an internal combustion engine of a motor vehicle, which has at least one exhaust gas aftertreatment device, in particular a catalyst and / or particulate filter, wherein an exhaust gas burner is fluidically connected upstream of the at least one exhaust gas aftertreatment device. State of the art

[0003] Exhaust gas burners of the type mentioned above are already known from the prior art. For example, the published patent application DE 19 504 208 A1 discloses an exhaust gas burner that is fluidically arranged upstream of a catalyst of an exhaust gas aftertreatment system. The exhaust gas burner has a combustion chamber to which air and fuel are supplied and combusted in the combustion chamber with the aid of an ignition device, and are subsequently added or mixed into the exhaust gas flow upstream of the catalyst. This ensures that the catalyst is heated particularly quickly to a favorable operating temperature. A similar solution is also proposed in the published patent application DE 10 2009 053 379 A1. It is also provided that the fuel and the oxygen-containing gas are introduced coaxially into the combustion chamber.For this purpose, a guide device is assigned to the combustion chamber, which surrounds the injection valve at its end facing the combustion chamber along an axial section of the injection valve and thereby forms an air flow channel coaxial with the injection valve, the annular opening of which opens into the combustion chamber coaxial with the injection opening of the injection valve.

[0004] Further exhaust gas burners are known from the published patent applications EP 0 306 743 A2 and US 2006 / 0 218 902 A1. Disclosure of the invention

[0005] The invention is based on the object of providing an exhaust gas burner which, compared to known exhaust gas burners, has the advantage of increasing protection of the exhaust gas burner against unwanted failure and also offering improved acoustic decoupling. The object underlying the invention is achieved by an exhaust gas burner having the features of claim 1. According to the invention, this is achieved in that the guide device, together with a cover arranged on the guide device, completely encloses the injection valve, wherein at least one first through-opening for a fuel channel connectable to the injection valve and a second through-opening for a control cable for the injection valve are preferably formed in the cover.According to the invention, the injection valve is completely encased, providing advantageous protection against external influences, particularly against contamination and / or moisture, thus increasing the service life of the exhaust burner. Furthermore, this offers the advantage that the exhaust burner is also wading or submersible. Encapsulation in the valve housing, which consists of the cover and guide device, also significantly improves the acoustic behavior of the exhaust burner, as noise from the injection valve, in particular, is reduced by encapsulation outside the exhaust burner. Damage caused by stone chips is also prevented by the advantageous housing.

[0006] According to a preferred embodiment of the invention, at least one elastically deformable sealing element is arranged between the cover and the guide device. The sealing element ensures, in particular, a fluid-tight connection between the cover and the guide device, thereby preventing the penetration of liquid or moisture into the valve chamber or the valve housing. Furthermore, the sealing element decouples the oscillations or vibrations originating from the injection valve. Furthermore, the sealing element offers the advantage of contributing to noise dampening, since the sound waves guided through the guide device are then transmitted to the cover only in a dampened manner by the sealing element. In this respect, the sealing element is preferably used or designed as an acoustic dampening element.

[0007] Furthermore, it is preferably provided that the sealing element is designed as a sealing ring that extends along an outer edge of the cover and, along its length, forms a sealing contact with both the cover and the guide device. This ensures that the acoustic insulation and the seal extend over the entire circumference of the cover, thereby further optimizing the aforementioned advantages.

[0008] Preferably, the guide device has a sleeve-shaped receiving section that completely or almost completely accommodates the injection valve, thus largely forming the valve chamber. The cover rests on a free end face of the receiving section facing away from the combustion chamber. As a result, the injection valve is advantageously protected from damage by the receiving section, for example, even after assembly. Furthermore, the cover can be easily and securely attached to the end face.

[0009] Furthermore, it is preferably provided that the end face has a recess extending in a ring shape along the end face, in particular in the manner of a circumferential groove or annular groove, and that the sealing element has a web-shaped projection designed to correspond to the recess and which is pressed into the recess at least in part. As a result, a labyrinth seal is formed between the sealing element and the end face, by means of which the degree of sealing of the connection is improved. Furthermore, the recess and projection allow an advantageous alignment of the sealing element and guide device with respect to one another, by means of which assembly is facilitated. According to an alternative embodiment, the web-shaped projection is formed directly in the cover, so that the projection, together with the end face, forms the seal, in which case the additional sealing element can be and is preferably dispensed with.According to a further alternative embodiment of the invention, the projection is formed on the end face and the recess is formed in the sealing element. According to a further embodiment, compression is provided without an annular groove.

[0010] According to an advantageous development of the invention, the cover has a first connection piece protruding in the direction of the receiving section, into which connection piece the injection valve can be pressed or is pressed with its end having a fuel inlet opening. As a result, the injection valve on the exhaust gas burner is additionally held and guided by the cover, resulting in a particularly robust and stable design of the exhaust gas burner. Furthermore, by pressing the injection valve into the connection piece, it is ensured that a fluidic connection between the cover and the injection valve is reliably maintained, whereby the fuel channel is formed in particular directly in the cover by at least the first connection piece, and no additional fuel line needs to be routed through the cover.

[0011] Furthermore, it is preferably provided that a retaining clip which engages behind the first connection piece is arranged on the injection valve and limits any axial displacement of the injection valve relative to the cover and / or any rotation of the injection valve relative to the cover. In particular, any rotational movement and / or the axial displacement of the valve is limited to a predetermined and permissible value in order to improve the robustness of the exhaust gas burner. In particular, in an application where fuel pressure acts on the injection valve, forcing the injection valve out of the first connection piece, the retaining clip ensures in a form-fitting manner that the injection valve cannot become detached from the cover or the cover cannot become detached from the injection valve.

[0012] According to a first preferred embodiment, the cover is formed in one piece, with the sealing element then preferably being arranged on the inner side of the cover facing the guide device. According to an alternative embodiment of the invention, the cover is preferably formed in multiple parts and has at least one inner part containing the connection piece and an annular outer part radially surrounding the inner part and associated with the end face of the combustion chamber, wherein the central part and the outer part are connected to one another by an elastically deformable ring element. As a result, the connection piece or the fuel channel is further decoupled from the rest of the cover, resulting in further acoustic improvements.Furthermore, the elastically deformable ring element advantageously dampens the mounting of the injection valve in the cover, which advantageously compensates for manufacturing or assembly tolerances during assembly. The second through-opening for the injection valve control cable is preferably formed in the outer part. Regardless of whether the cover is constructed in one piece or in multiple pieces, the second through-opening is particularly designed to guide the control cable hermetically through the cover, so that no contaminants or moisture can enter the valve chamber through the second through-opening.

[0013] Particularly preferably, the ring element is formed integrally with the sealing element. Furthermore, the ring element and sealing element are made of the same material or are manufactured using the same process. Preferably, the ring element and the sealing element are connected to one another by one or more connecting webs.

[0014] Particularly preferably, the ring element is positively connected to both the inner part and the outer part, thereby advantageously permanently connecting the inner part and the outer part. For this purpose, the ring element preferably engages behind the inner part and the outer part, respectively, both on the side of the cover facing the valve chamber and on the side facing away from the valve chamber.

[0015] Particularly preferably, at least one screw opening is formed in the outer part and / or in the inner part for a fastening screw fastening the cover to the guide device or the combustion chamber, wherein a sleeve-shaped sealing and damping element is inserted in the screw opening. One or more fastening screws are thus provided for fastening the cover to the combustion chamber or the guide device. The respective fastening screw is guided through a screw opening in the cover, wherein the damping element is also assigned to the screw opening, so that the damping element is interposed between the outer surface of the fastening screw and the inside of the screw opening in the cover, thereby ensuring advantageous acoustic decoupling of the combustion chamber or the guide device from the cover.

[0016] Furthermore, it is preferably provided that the cover has, in particular as an extension of the first connection piece on the side of the cover facing away from the combustion chamber, a second connection piece protruding from the cover for connection to a fuel line, wherein the first and the second connection pieces are fluidically connected to one another by the cover. In particular, the cover itself forms the aforementioned fuel channel through which the fuel line is or can be connected to the injection valve. By providing the second connection piece, a simple, fluidically tight connection to the fuel line is ensured, in particular by the fuel line being able to be pushed onto the connection piece. For this purpose, the connection piece preferably has a radially protruding sealing bead that can be pressed into the fuel line.Preferably, the first connection piece and the second connection piece are aligned with each other so that a straight fuel channel is created.

[0017] Furthermore, it is preferably provided that the cover and / or the guide device have at least one cooling line connection, in particular a coolant inlet opening and / or a coolant outlet opening, through which the exhaust gas burner can be connected to a cooling device. The cooling line connection ensures advantageous cooling of the injection valve in the valve chamber. Optionally, the cooling line connection is designed such that coolant can flow around the injection valve in the valve chamber. This can increase the efficiency of the injection valve and its service life.

[0018] The exhaust gas aftertreatment system according to the invention with the features of claim 15 is characterized by the inventive design of the exhaust gas burner. This results in the advantages already mentioned above. If the exhaust gas aftertreatment system has more than one exhaust gas aftertreatment device, for example, two catalysts or a catalyst and a particulate filter arranged downstream of the first catalyst, or a second catalyst arranged downstream of the first catalyst, the exhaust gas burner is preferably connected to the exhaust gas aftertreatment system upstream of the first or second catalyst.

[0019] Further advantages and preferred features and combinations of features emerge in particular from the above description and from the claims. The invention will be explained in more detail below with reference to the drawings. Fig. 1 an advantageous exhaust gas aftertreatment system with an exhaust gas burner in a simplified representation, Fig. 2 the exhaust gas burner in a schematic detailed view, Fig. 3A to C further embodiments of the exhaust gas burner, Fig. 4A to D show another embodiment of the exhaust gas burner in different representations.

[0020] Fig. 1 shows a simplified representation of an advantageous exhaust gas aftertreatment system 1 for an internal combustion engine 2 of a motor vehicle, which in this case is designed as a reciprocating piston engine. The internal combustion engine 2 is assigned a fresh air tract 3 and an exhaust tract 4. From the exhaust valves of the internal combustion engine 2, an exhaust pipe 5 of the exhaust tract 4 leads to several exhaust gas aftertreatment devices 6, 7, and 8 of the exhaust gas aftertreatment system 1. In this case, viewed in the direction of flow, the first exhaust gas aftertreatment device 6 is a three-way catalytic converter, the second exhaust gas aftertreatment device 7 is a second three-way catalytic converter, and the third exhaust gas aftertreatment device 8 is a particulate filter. The exhaust gas from the internal combustion engine flows through the exhaust gas aftertreatment devices 6, 7, and 8 one after the other and serves to reduce pollutant emissions and particles in the exhaust gas.To ensure that the exhaust gas aftertreatment devices 6, 7, 8 reach their optimal operating temperature as quickly as possible, particularly after a cold start of the internal combustion engine 2, a heating device 9 with an exhaust gas burner 10 of the exhaust gas aftertreatment system 1 is also assigned to the exhaust tract 4. The exhaust gas burner 10 has a combustion chamber 11 to which fuel can be supplied through an injection valve 12 and oxygen-containing gas, in this case air, can be supplied through a guide device 13 in order to be ignited and combusted in the combustion chamber with the aid of an ignition device 14. The combusted fuel / air mixture is supplied through an outlet opening 15 of the exhaust gas burner 10 to the exhaust tract 4 upstream of the first catalytic converter 6, so that the heated gas mixture increases the operating temperature of the exhaust gas aftertreatment devices 6, 7, 8 even before the internal combustion engine 2 itself has reached its necessary operating temperature.

[0021] A controllable valve device 16 is connected upstream of the exhaust gas burner 10, by means of which the supplied air flow can be adjusted. An air pump or air conveying device 17 is advantageously arranged upstream of the valve device 16, by means of which fresh air can be drawn in and conveyed toward the valve device 16. An air mass meter 18 and an air filter 19 are also connected upstream of the air conveying device 17.

[0022] A control unit 20 of the heating system controls or operates the air mass meter 18, the air pump 17, the valve device 16, and the exhaust gas burner 10 to generate the desired amount of hot gas as a result of the combustion of the air-fuel mixture, which is fed to the exhaust tract 4 to heat the exhaust gas aftertreatment devices 6, 7, 8. The control unit 20 is in particular in communication with a control unit 21 of the internal combustion engine.

[0023] Fig. Figure 2 shows a schematic longitudinal sectional view of the exhaust gas burner 10. The combustion chamber 11 is sleeve-shaped or can-shaped and has the guide device 13 and the injection valve 12 on one end face 22 and the outlet opening 15 connectable to the exhaust pipe 5 on the opposite end face 23. The ignition device 14, for example in the form of a glow plug or spark plug, is arranged in the jacket wall of the combustion chamber 11 in order to ignite the mixture of air and fuel in the combustion chamber 11.

[0024] The guide device 13 is designed to introduce the air flow released by the valve device 16 through the end face 22 into the combustion chamber 11 centrally or centrally. For this purpose, the guide device 13 has a swirl chamber 24 into which the fresh air flow is introduced in such a way that the air flow is set into a swirling or rotational movement. For this purpose, the air flow is introduced centrally or off-center into the swirl chamber 24, in particular tangentially. The guide device 13, together with the swirl chamber 24, surrounds a longitudinal section of the injection valve 12 that is assigned to the combustion chamber 11. The guide device 13 has an air outlet opening 25 that is annular and to which a swirl grille 26 is assigned, by means of which the outflow behavior of the fresh air into the combustion chamber 11 is optimized.The injection valve 12 ends with an injection opening 27 centrally or coaxially with the annular inlet opening 25 of the guide device 13, so that fuel and air are introduced coaxially into the combustion chamber 11. According to the present embodiment, the guide device 13 is designed asymmetrically, so that its end side facing away from the end face 22 is inclined toward the end face 22.

[0025] With a second longitudinal section, the injection valve 12 thus protrudes axially at least from the swirl chamber 24 of the guide device 13. This longitudinal section of the injection valve 12 is advantageously assigned a cover 28 which, together with the guide device 13, completely encloses the further longitudinal section of the injection valve 12. As a result, the injection valve 12 is completely enclosed by the guide device 13 and the cover 28 and protected from external influences. For this purpose, the cover 28 is provided to tightly seal the injection valve 12, bear sealingly against the guide device 13, and a cable feedthrough of a control cable of the injection valve 12 is hermetically sealed by the cover 28. For this purpose, a sealing element 29 is arranged between the cover 28 and the guide device 13, which sealing element 29 is in particular elastically deformable and is preferably made of an elastomer material.The cover 28 further comprises a connecting piece 30 projecting toward the injection valve 12, into which the injection valve 12 is pressed with its inlet end to create a tight connection. The connecting piece 30 itself forms a first through-opening 31 through which fuel can be supplied to the injection valve 12.

[0026] A connecting cable 32, which is connected to the injection valve 12 for its control, has a connector plug 32' at its end facing away from the injection valve 12 for connection to the control unit 20. Furthermore, the connecting cable 32 is guided through a second through-opening 33 of the cover 28 to the injection valve 12.

[0027] The cover 28 and the guide device 13 thus form a valve chamber in which the injection valve 12 is arranged in a protected manner. The passage through the through-opening 33 is hermetically sealed, in particular by the presence of appropriate sealing material 33' in the flow opening.

[0028] By enclosing the injection valve 12, it is advantageously protected against contamination, moisture, liquids, and damage caused, for example, by stone chips. Furthermore, the exhaust burner 10 in this form is also suitable for surviving diving or wading without damage. Encapsulating the injection valve 12 also significantly reduces its acoustic impact on the rest of the motor vehicle, which includes the exhaust aftertreatment system 1. This allows, for example, NVH requirements (NVH = noise, vibration, harshness), i.e., in particular, requirements regarding noise behavior, to be met, and the operation of the exhaust burner 10 is either unnoticeable or less noticeable to the user of the motor vehicle.

[0029] Fig. 3A to C show further embodiments of the exhaust gas burner 10 in simplified sectional views.

[0030] According to the embodiment of Fig. 3A, the connecting cable 32 is provided at its end facing the injection valve 12 with an adapter plug 34, by means of which the control cable 32 is or can be connected hermetically sealed directly to the injection valve 12. This further optimizes the electrical connection of the injection valve 12 with regard to its water or moisture protection. The connecting cable 32 itself is preferably also tightly routed through the second flow opening 33, so that the valve chamber is advantageously sealed from the outside.

[0031] According to the embodiment of Fig. 3B, the exhaust gas burner 10 is designed such that the adapter plug 34 is not located entirely within the valve chamber, but rather directly in the second through-opening 33, so that the sealing of the valve chamber to the outside is also ensured in the area of ​​the adapter plug 34. For this purpose, the cover 28, in particular, is provided with a wall profile that guides the through-opening 33 into the area of ​​the connection adapter 34.

[0032] According to the embodiment of Fig. 3C it is provided that the cable feedthrough and the fuel feedthrough are as in the embodiment of Fig. 2 are solved, whereby the solutions from the Fig. 3A and Fig. 3B. In contrast to the embodiment of Fig. 2, it is provided that the guide device 13 has a symmetrical swirl chamber 24, so that the front side of the guide device 13 facing away from the front side 22 is aligned parallel to the front side 22 and the swirl chamber is thus at least substantially rotationally symmetrical.

[0033] Fig. 4A to D show a further embodiment of the exhaust gas burner 10, wherein Fig. 4A the exhaust gas burner in a perspective view, Fig. 4B the exhaust gas burner in a partial sectional view, Fig. 4C the cover of the exhaust gas burner 10 in a perspective front view and Fig. 4D shows the cover 28 in a perspective rear view.

[0034] As previously described, the cover 28 is sealingly mounted on the end face 22 of the guide device 13, in particular on the end face 22 of the swirl chamber 24. In the present case, the cover 28 is secured to the guide device 13 and / or to the combustion chamber 11 by two fastening screws 35. The cover 28 has a first cover surface aligned parallel to the end face 22 and a second cover surface aligned obliquely thereto, wherein the first through-opening is formed in the parallel cover surface and the second through-opening is formed in the oblique cover surface, thus enabling advantageous cable passage without stressing the cable.

[0035] The cover 28 has a further second connecting piece 36 pointing away from the combustion chamber 11, which has a sealing bead 36' extending radially over its circumference. A fuel line can be pushed onto the connecting piece 36 and over the sealing bead 36', which is connected, for example, to the pressure side of a fuel pump, wherein the sealing bead 36' is preferably pressed into the fuel line, thus ensuring a sealed connection. Alternatively, according to a further exemplary embodiment, not shown here, a screw connection is provided instead of this plug connection. Preferably, and as also in Fig. 2 and Fig. 3, the connecting piece 36 extends in extension or in alignment with the first connecting piece 30 and forms together with these a fuel channel 37 which leads from the fuel line to the injection valve 12, which is provided with an inlet opening, such as in Fig. 4B, is pressed into the connecting piece 30.

[0036] According to the embodiment of Fig. 4, the cover 28 is formed in two parts, with an inner part 38 and an outer part 39 arranged coaxially with each other. The inner part 38 has the two connecting pieces 36 and 30. The outer part 39 has the passage opening 33 for the connecting cable of the injection valve 12.

[0037] The outer part 39 and the inner part 38 are connected to each other by an elastically deformable ring element 40. As shown in the sectional views of Fig. 4B, the ring element 40 is substantially H-shaped, at least in sections, in order to axially engage behind both the outer part 39 and the inner part 38 on both sides, thereby holding the two parts together. The elastic deformability of the ring element 40 ensures that the fuel channel 37 is movable relative to the outer part 39, which, on the one hand, advantageously compensates for manufacturing and assembly tolerances during assembly, and on the other hand, ensures that sound waves from the injection valve 12 are not transmitted to the outer part 39 or are transmitted only in a dampened manner during operation.

[0038] The injector 12 is further assigned a retaining clip 41 which, on the one hand, engages in a retaining groove 42 extending over part of the circumference of the injector 12 and, on the other hand, engages behind a radial projection 43 of the connecting piece 30, viewed axially and in the circumferential direction, such that the axial displacement path of the injector 12 relative to the fuel channel 37 is positively limited by the retaining clip 41, and such that an anti-twist device is realized between the valve element 12 and the connecting piece 30 or inner part 38. When fuel is supplied to the injector 12 at high pressure during operation, the retaining clip 41 ensures that the injector 12 cannot become detached from the connecting piece 30. This allows high fuel pressures to be used safely.

[0039] Fig. Figure 4C shows a perspective front view of the cover 28. In the present case, screw openings 44 are formed in the outer part 39, through which the fastening screws 35 are guided. A sealing and damping sleeve 45 is inserted into each of the screw openings 44. These sealing and damping sleeves are made, in particular, of an elastomer material and also have an acoustic damping effect.

[0040] When mounted, the sealing and damping sleeve 45 thus ensures reduced sound wave transmission through the fastening screws 35 into the cover 28, whereby the noise generation of the exhaust gas burner 10 during operation is further optimized or reduced.

[0041] The ring element 40 is advantageously formed in one piece or integrally with the aforementioned sealing element 29, which lies between the cover 28 and the guide device 13.

[0042] Fig. 4D shows a perspective view of the rear side of the cover 28. The ring element 40 is integrally connected to the sealing element 29 by at least one transverse or radial web 46.

[0043] Advantageously, the sealing element 29 has on its side facing the guide device 13 a web-shaped projection 47, which can be pressed or is pressed into a groove-shaped recess 48 extending over the end face 22, as in Fig. 4B to form a labyrinth seal between sealing element 29 and guide device 13.

[0044] This advantageously seals the valve chamber hermetically from the external environment. Optionally and as described in the Fig.As shown in Figure 4, the guide device 13 has a sleeve-shaped receiving projection 49 that protrudes from the side facing away from the combustion chamber and completely or almost completely accommodates the injection valve 12. Together with the cover 28, the receiving projection 49 forms the valve chamber. Optionally, a coolant inlet opening 50 and a coolant outlet opening 51 are formed in the cover 28 and / or in the receiving projection 49, for example in the form of connecting pieces that can be integrated into a coolant system of the motor vehicle or the internal combustion engine 2, so that coolant can be guided through the valve chamber, whereby the injection valve 12 can be advantageously cooled during operation. List of reference symbols 1 exhaust aftertreatment system 2 internal combustion engine 3 Fresh air wing 4 Exhaust system 5 exhaust pipe 6 Exhaust aftertreatment system 7 Exhaust aftertreatment system 8 Exhaust aftertreatment system 9 Heating device 10 exhaust gas burners 11 Combustion chamber 12 Injector 13 Guidance device 14 Ignition device 15 Outlet opening 16 Valve device 17 Air conveyor 18 air mass meter 19 Air filter 20 Control unit 21 Control unit 22 front side 23 Front side 24 swirl chamber 25 Air outlet opening 26 swirl grilles 27 Injection opening 28 lids 29 Sealing element 30 connecting pieces 31 first passage opening 32 connection cables 32' connector plug 33 second passage opening 33' sealing material 34 adapter plugs 35 fixing screw 36 connecting pieces 36' sealing bead 37 Fuel channel 38 inside part 39 Outer part 40 ring element 41 retaining clip 42 Retaining groove 43 Radial projection 44 screw opening 45 Sealing and damping sleeve 46 Transverse or radial web 47 lead 48 Deepening 49 Recording projection 50 Coolant inlet opening 51 Coolant outlet opening

Claims

[1] Exhaust gas burner (10) for an exhaust gas aftertreatment system (1) of an internal combustion engine (2), having a combustion chamber (11) in which a mixture of an oxygen-containing gas and fuel can be combusted, wherein the combustion chamber (11) has an outlet (15) connectable to the exhaust gas aftertreatment system (2), and wherein at least one injection valve (12) for injecting the fuel into the combustion chamber (11) is arranged on the combustion chamber (11), and wherein a guide device (13) is arranged on the combustion chamber (11), through which the gas can be introduced into the combustion chamber (11), wherein the injection valve (12) is surrounded by the guide device (13) in a longitudinal section facing the combustion chamber (11), so that fuel and gas can be introduced coaxially into the combustion chamber (11), characterized by that the guide device (13) together with a cover (28) arranged on the guide device (13) completely encloses the injection valve (12). [2] Exhaust gas burner (10) according to claim 1, characterized by that at least one first through-opening (31) for a fuel channel (37) connectable to the injection valve (12) and / or a second through-opening (33) for a connecting cable (32) for the injection valve (12) are formed in the cover (28). [3] Exhaust gas burner (10) according to one of the preceding claims, characterized by that at least one elastically deformable sealing element (29) is arranged between the cover (28) and the guide device (13). [4] Exhaust gas burner (10) according to claim 3, characterized by that the sealing element (29) is designed as a sealing ring which extends along an outer edge of the cover (28) and lies sealingly along its extent both on the cover (28) and on the guide device (13). [5] Exhaust gas burner (10) according to one of the preceding claims, characterized byin that the guide device (13) has a sleeve-shaped receiving section (49) which receives the injection valve (12) completely or almost completely, wherein the cover (28) rests on a free end face (22) of the receiving section (49) facing away from the combustion chamber (11). [6] Exhaust gas burner (10) according to claim 5, characterized by that the end face (22) has a recess (48) extending in an annular manner along the end face (22), and that the sealing element (29) has a web-shaped projection (47) formed corresponding to the recess (48) and which is pressed into the recess (48) at least in some areas. [7] Exhaust gas burner (10) according to claim 5 or 6, characterized by that the cover (28) has a first connecting piece (30) projecting in the direction of the receiving section (49), into which the injection valve (12) can be pressed or is pressed with its end having a fuel inlet opening. [8] Exhaust gas burner (10) according to claim 7, characterized by that a retaining clip (41) which engages behind the connecting piece (30) is arranged on the injection valve (12), which clip limits an axial displacement of the injection valve (12) relative to the cover (28) and / or forms a rotation lock of the injection valve (12) relative to the cover (28). [9] Exhaust gas burner (10) according to claim 7 or 8, characterized by that the cover (28) has an inner part (38) having the connecting piece (30) and an annular outer part (39) radially surrounding the inner part (38) and assigned to the end face (22), wherein the inner part (38) and the outer part (39) are connected to one another by an elastically deformable ring element (40), wherein the ring element (40) is preferably formed integrally with the sealing element (29). [10] Exhaust gas burner (10) according to claim 9, characterized bythat the ring element (40) is connected to the sealing element (29) by at least one radially extending connecting web (46). [11] Exhaust gas burner (10) according to claim 9 or 10, characterized by that the ring element (40) is positively connected to the inner part (38) and the outer part (39). [12] Exhaust gas burner (10) according to one of claims 9 to 11, characterized by that in the outer part (39) and / or in the inner part (38) at least one screw opening (44) is formed for a fastening screw (35) fastening the cover (28) to the guide device (13) or the combustion chamber (11), wherein a sleeve-shaped sealing and damping sleeve (45) is inserted in the respective screw opening (44). [13] Exhaust gas burner (10) according to one of claims 7 to 12, characterized bythat the cover (28) has, in extension of the first connecting piece (30), on the side facing away from the combustion chamber (11), a second, projecting connecting piece (36) for connection to a fuel line, wherein the first and the second connecting pieces (30, 36) are fluidically connected to one another by the cover (28), in particular for forming a fuel channel (37). [14] Exhaust gas burner (10) according to one of claims 5 to 13, characterized by that the cover (28) and / or the guide device (13), in particular the receiving section (49) have a coolant inlet opening (50) and / or a coolant outlet opening (51). [15] Exhaust gas aftertreatment system (1) for an internal combustion engine (2), with at least one exhaust gas aftertreatment device (6, 7, 8), which is fluidically upstream of an exhaust gas burner (10) according to one of claims 1 to 14.

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