Dosing device, exhaust system and motor vehicle

Abstract

The invention relates to a metering device (12) for introducing a fluidic secondary mass flow (13) into a fluidic primary mass flow (14), - with a flow channel (15) through which the primary mass flow (14) can flow, - with a dosing unit (18) through which the secondary mass flow (13) can flow, which has a secondary inlet (19) arranged outside the flow channel (15) through which the secondary mass flow (13) can flow into the dosing unit (18), and a secondary outlet (20) arranged inside the flow channel (15) through which the secondary mass flow (13) can flow out of the dosing unit (18) and into the flow channel (15). A compact design can be achieved by - that the dosing unit (18) has a dosing body (22) arranged in the flow channel (15), which has a plurality of passage openings (23) through which the primary mass flow (14) can flow in parallel and a plurality of outlet openings (24) through which the secondary mass flow (13) can flow in parallel, each of which is arranged at one of the passage openings (23), and - that the dosing body (22) is hollow, is fluidically connected to the secondary inlet (19) and fluidically connects the secondary inlet (19) to the outlet openings (24).

Description

[0001] The present invention relates to a metering device for introducing a fluidic secondary mass flow into a fluidic primary mass flow, according to the preamble of claim 1. The invention also relates to an exhaust system equipped with such a metering device and to a motor vehicle having such an exhaust system.

[0002] A generic dosing device is known from DE 22 21 793 B2 and comprises a flow channel through which the primary mass flow can flow, as well as a dosing unit through which the secondary mass flow can flow, which has a secondary inlet arranged outside the flow channel, through which the secondary mass flow can flow into the dosing unit, and a secondary outlet arranged inside the flow channel, through which the secondary mass flow can flow out of the dosing unit and into the flow channel. In the known dosing device, the dosing body of the dosing unit is designed as a tubular lance having several outlet openings through which the secondary mass flow can flow in parallel. As a result, the secondary mass flow is fed to the primary mass flow in a quasi-linear manner along the lance.For mixing with the primary mass flow, the known dosing device requires a mixing chamber, which requires a comparatively large amount of installation space in the flow direction of the primary mass flow.

[0003] EP 0 697 505 A1 discloses another metering device which also operates with a metering body configured as a lance, but which only has a single outlet opening at the end of the lance. In this metering device, the lance is used to feed the secondary mass flow downstream of a catalyst body through which the primary mass flow flows to a central channel formed centrally in this catalyst body. In this way, the secondary mass flow can pass through the central channel to the upstream side of the catalyst body and be mixed there with the primary mass flow. Alternatively, the lance can also be arranged on the upstream side of the catalyst body and there feed the secondary mass flow to the central channel on the upstream side.

[0004] Dosing devices are known from DE 11 2011 104 763 B4 in which the flow channel through which the primary mass flow flows is enclosed by a feed chamber through which the secondary mass flow can flow. Within the feed chamber, the flow channel has radial openings distributed circumferentially through which the secondary mass flow can flow parallel to the primary mass flow.

[0005] The known metering devices require a comparatively large amount of installation space in the flow direction of the primary mass flow in order to ensure sufficient mixing of the secondary mass flow with the primary mass flow. Good mixing is desirable for many applications. For example, in an exhaust system for an internal combustion engine, it may be necessary to add air to the exhaust gas flow upstream of a catalyst in order to carry out a desired oxidation process in the catalyst. This requires the most homogeneous mixing possible between the exhaust gas flow and the air flow. However, for many applications, only comparatively little installation space is available to create a comparatively large mixing chamber for mixing the primary mass flow with the secondary mass flow.

[0006] To achieve good mixing, it is generally possible to arrange a mixing structure in the flow channel downstream of the dosing unit, while requiring comparatively little space in the direction of flow of the primary mass flow. This ensures the desired mixing as the fluid flows through it. However, flow through such a mixing structure is accompanied by flow resistance and causes an increase in backpressure in an exhaust system, which impairs the performance of the combustion engine.

[0007] The present invention addresses the problem of providing an improved or at least a different embodiment for a metering device of the type described above or for an exhaust system equipped therewith or for a motor vehicle equipped therewith, which is characterized in particular by a small installation space requirement in the flow direction of the primary mass flow and by a low back pressure.

[0008] This problem is solved according to the invention by the subject matter of the independent claim. Advantageous embodiments are the subject matter of the dependent claims.

[0009] The invention is based on the general idea of ​​configuring the dosing unit such that it has a plurality of through-openings and a plurality of outlet openings, wherein the outlet openings are each arranged in the region of one of the through-openings. The through-openings and the outlet openings are arranged in the flow channel, wherein the primary mass flow can flow through the through-openings in parallel, while the secondary mass flow can flow through the outlet openings in parallel, so that the primary mass flow flows through the outlet openings into the flow channel and mixes there with the primary mass flow. The large number of such through-openings and outlet openings, through which flow is carried out in parallel, allows a quasi-area introduction of the secondary mass flow into the primary mass flow, so that mixing can already take place in the region where the secondary mass flow is introduced into the primary mass flow.The large number of through-holes divides the primary mass flow into several small sub-flows that flow parallel through the through-holes. Likewise, the large number of outlets divides the secondary mass flow into several small sub-flows that flow parallel through the outlets. These many small sub-flows each require comparatively little installation space in the flow direction of the primary mass flow to achieve the required mixing. The parallel arrangement of the large number of through-holes and outlets results in a flat introduction of the secondary mass flow into the primary mass flow, which requires extremely little installation space in the flow direction of the primary mass flow to achieve the desired mixing between the primary and secondary mass flows downstream of the dosing unit.Since the primary mass flow can freely flow through the passage openings, the dosing body only generates a comparatively low back pressure in the primary mass flow.

[0010] In the present context, a ‘configuration’ corresponds to a ‘design’ and / or a ‘facility’, so that the phrase ‘configured so that’ is synonymous with the phrase ‘designed so that’ and / or ‘arranged so that’.

[0011] Specifically, the invention proposes that the dosing unit comprise a dosing body arranged in the flow channel, which body comprises a plurality of passage openings through which the primary mass flow can flow in parallel, and a plurality of outlet openings through which the secondary mass flow can flow in parallel, each of which is arranged at one of the passage openings. The dosing body is hollow and fluidically connected to the secondary inlet and further configured to fluidically connect the secondary inlet to the outlet openings. As a result, the secondary mass flow can flow within the dosing body to the outlet openings and flow into the primary mass flow there. Accordingly, the outlet openings together form the secondary outlet of the dosing unit. Expediently, each passage opening is assigned exactly one outlet opening. Advantageously, the number of passage openings is the same size as the number of outlet openings.In principle, however, an embodiment is also conceivable in which at least one further or different outlet opening is provided that is not associated with a passage opening. Additionally or alternatively, it may also be provided that at least one other or further passage opening is provided that is not associated with an outlet opening.

[0012] The fluidic primary mass flow is preferably a gaseous primary mass flow, but can also be a liquid primary mass flow. The fluidic secondary mass flow is preferably a gaseous secondary mass flow, but can also be a liquid secondary mass flow.

[0013] The channeling of the primary mass flow in the passage openings leads to a uniform alignment of the primary mass flow. Since the passage openings have a smaller overall flow cross-section than the flow channel, the primary mass flow is accelerated in the passage openings. Downstream of the dosing unit, this creates a hydrodynamic vacuum in the primary mass flow, which draws the secondary mass flow out of the hollow dosing body via the outlet openings. In other words, a Venturi effect or a Venturi nozzle occurs at the passage openings and outlet openings during operation of the dosing device, whereby the primary mass flow flowing through the respective passage opening draws in the secondary mass flow from the respective outlet opening. At the same time, the Venturi effect results in intensive mixing between the primary mass flow and the drawn-in secondary mass flow.Since the dosing body has several such passage openings and several such outlet openings, several parallel acting Venturi nozzles are generated on the dosing body, whereby intensive mixing can be achieved over virtually the entire cross section of the flow channel with an extremely short design in the flow direction of the primary mass flow.

[0014] According to an advantageous embodiment, it can be provided that the respective outlet opening encloses the respective passage opening in a ring-shaped manner, in particular in a circular ring. This results in the most homogeneous mixing possible in the region of the respective passage opening.

[0015] According to an advantageous embodiment, the dosing body can have a first sheet metal body which has a plurality of first holes and forms an outflow side of the dosing body in the flow channel with respect to the primary mass flow. Furthermore, the dosing body can have a second sheet metal body which has a plurality of second holes and forms an inflow side of the dosing body in the flow channel with respect to the primary mass flow. In addition, the second holes can each be enclosed by a collar which projects from the second sheet metal body towards the first sheet metal body and ends there in or at one of the first holes. These collars form the passage openings. The first holes can each be enclosed by an opening edge which encloses the respective collar, forming a gap. These gaps now form the outlet openings.

[0016] This makes the dosing body particularly easy to implement. In particular, only two components are required: the two sheet metal bodies. Furthermore, such sheet metal bodies can be manufactured easily and inexpensively. By using sheet metal bodies, the dosing body, and thus the dosing device, can be realized particularly compactly, even in the direction of flow of the primary mass flow.

[0017] The first holes and / or the second holes can be non-circular, in particular polygonal, in their configuration. Likewise, the first holes and / or the two holes can be round, in particular circular, elliptical, or oval.

[0018] According to an advantageous embodiment, the collars can be configured cylindrically, in particular circularly cylindrical. Additionally or alternatively, the gaps can be configured annularly, in particular annularly. The cylindrical or annular configuration promotes low flow resistance.

[0019] According to an advantageous embodiment, a web enclosing the respective first hole can be formed on the respective opening edge and protrudes from the first sheet metal body on the downstream and / or upstream side. In other words, the respective web can be configured such that it protrudes from the first sheet metal body only on the downstream side, only on the upstream side, or both on the upstream and downstream sides. The web improves the flow guidance for the secondary mass flow. Furthermore, the respective collar can protrude into the respective web. This transforms the gap into a channel, which improves flow guidance and reduces flow resistance.

[0020] The respective collar can be dimensioned such that it ends essentially flush with the first sheet metal body in the respective first hole. Likewise, the respective collar can be dimensioned such that it protrudes beyond the first sheet metal body on the downstream side in the flow direction of the primary mass flow. In this respect, the respective collar penetrates the respective associated first hole.

[0021] According to an advantageous embodiment, the secondary inlet can have at least one inlet connection formed on the first sheet metal body. The secondary mass flow is supplied to the metering body via the respective inlet connection and then distributed to the outlet openings in the metering body. With two or more inlet connections, these can be formed on the first sheet metal body, distributed, in particular, in the circumferential direction of the channel body. Forming the respective inlet connection on the first sheet metal body simplifies the manufacture of the metering body.

[0022] The respective sheet metal body can in particular be a formed sheet metal part, which is produced for example by deep drawing. The sheet metal bodies can also be configured as primary formed parts, for example they can be sintered parts or cast parts. Additionally or alternatively, the sheet metal bodies can be tightly and firmly connected to one another radially on the outside, in particular welded to one another. Furthermore, the sheet metal bodies or the dosing body can be tightly and firmly connected, in particular welded, to a tubular body with which the flow channel is formed. For example, the flow channel can have two tubular bodies which are axially adjacent at the end, with the dosing body being inserted axially between the two tubular bodies. The dosing body can then be tightly and firmly connected, in particular welded, to one of these tubular bodies or to both tubular bodies.

[0023] In another advantageous embodiment, the metering body can be configured such that it fills a flowable cross-section of the flow channel. Consequently, the entire primary mass flow must flow through the passage openings. This allows the metering device to operate particularly efficiently. Furthermore, the metering body can be configured flat and plate-shaped. Furthermore, the metering body can optionally extend in a plane oriented transversely to the flow direction of the primary mass flow in the flow channel. These measures make the metering device extremely short in the flow direction of the primary mass flow.

[0024] In an advantageous embodiment, the passage openings can be provided to converge in the flow direction of the primary mass flow. In this way, the respective passage opening is configured as a nozzle. This allows the acceleration of the primary mass flow to be increased as it flows through the passage openings. At the same time, the pressure drop at the outlet side of the metering body can also be increased. In particular, these measures lead to an intensification of the Venturi effect.

[0025] Although the use of the dosing device presented here in an exhaust system is preferred, other uses and applications are also conceivable and should not be excluded.

[0026] An exhaust system according to the invention is provided for an internal combustion engine and has at least one exhaust aftertreatment device through which an exhaust gas flow can flow. The exhaust aftertreatment device can be, in particular, a catalytic converter. Furthermore, the exhaust system has a secondary air supply device for supplying a secondary air flow to the exhaust gas flow. The secondary air supply device can then be equipped with a metering device of the type described above. Within the exhaust system, the exhaust gas flow then forms the primary mass flow for the metering device, while the secondary air flow forms the secondary mass flow for the metering device. Furthermore, such a secondary air supply device can have an air pump for driving the secondary air flow.Within the exhaust system, the flow channel of the metering device can be formed by another component of the exhaust system, such as a housing of a catalytic converter or by a piece of pipe that serves to deflect and / or calm and / or mix the exhaust gas flow.

[0027] A motor vehicle according to the invention, which may in particular be a passenger car, is equipped with an internal combustion engine and an exhaust system of the type described above. The exhaust system is connected to the internal combustion engine in such a way that combustion exhaust gases generated during operation of the internal combustion engine are fed to the exhaust system as an exhaust stream.

[0028] Furthermore, all passage openings can be configured identically or identically with regard to their flow-through cross-section. An embodiment is also conceivable in which the passage openings can have different flow-through cross-sections. In particular, at least one passage opening can have a different flow-through cross-section than at least one other passage opening. All outlet openings expediently have the same opening cross-section. It is also conceivable for the outlet openings to have different opening cross-sections. In particular, at least one outlet opening can have a different opening cross-section than at least one other outlet opening.

[0029] Further important features and advantages of the invention emerge from the subclaims, from the drawings and from the associated description of the figures based on the drawings.

[0030] It is understood that the features mentioned above and those to be explained below can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention. Components mentioned above and those to be mentioned below of a higher-level unit, such as a device, a device, or an arrangement, which are designated separately, may form separate parts or components of this unit or be integral areas or sections of this unit, even if this is shown differently in the drawings.

[0031] Preferred embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description, wherein the same reference numerals refer to the same or similar or functionally identical components.

[0032] They show, schematically, Fig. 1 a circuit diagram-like schematic representation of a motor vehicle with an exhaust system, Fig. 2 a view of a section of the exhaust system with a metering device, Fig. 3 an enlarged detail III from Fig. 2 in the area of ​​the dosing device, Fig. 4 a highly simplified, basic longitudinal section of the dosing device, Fig. 5 a view of a dosing unit of the dosing device, Fig. 6 a view in Fig. 5, but with a different embodiment.

[0033] Accordingly Fig. 1 includes a motor vehicle 1 which is Fig. 1 is symbolized by a rectangular frame and can preferably be a passenger car, an internal combustion engine 2 and an exhaust system 3 for discharging combustion exhaust gases generated by the internal combustion engine 2 during its operation. According to the Fig. 1 and Fig. 2, the exhaust system 3 has in a section 4 at least one exhaust gas aftertreatment device 5 through which an exhaust gas flow 6 can flow. In the example of Fig. 2, the exhaust system 3 has, in section 4, an upstream secondary catalyst 7 and a downstream main catalyst 8, which is arranged downstream of the secondary catalyst 7 with respect to the exhaust gas flow 6. Furthermore, the exhaust system 3 is equipped in the section 4 shown with a secondary air supply device 9, which is configured to supply a secondary air flow 10 to the exhaust gas flow 6. To generate the secondary air flow 10, the secondary air supply device 9 can be equipped with an air pump 11. The secondary air supply device 9 is equipped with a metering device 12, which is generally configured to introduce a fluidic secondary mass flow 13 into a fluidic primary mass flow 14. Within the secondary air supply device 9, the exhaust gas flow 6 forms the primary mass flow 14, while the secondary air flow 10 forms the secondary mass flow 13.

[0034] According to the Fig. 3 and Fig. 4, the metering device 12 has a flow channel 15 through which the primary mass flow 14 can flow. Within the exhaust system 3, this flow channel 15 can be formed by other components of the exhaust system 3. For example, the flow channel 15 can be formed in part by a housing 16 of the secondary catalyst 7, while another part of the flow channel 15 is formed by a pipe section 17 that connects the secondary catalyst 7 to the main catalyst 8.

[0035] The dosing device 12 is also equipped with a dosing unit 18 through which the secondary mass flow 13 can flow. The dosing unit 18 has at least one secondary inlet 19 arranged outside the flow channel 15, through which the secondary mass flow 13 can flow into the dosing unit 18. Furthermore, the dosing unit 18 has a secondary outlet 20 arranged within the flow channel 15, through which the secondary mass flow 13 can flow out of the dosing unit 18 and into the flow channel 15. In the flow channel 15, the secondary mass flow 13 then mixes with the primary mass flow 14. By admixing the secondary mass flow 13 to the primary mass flow 14, a flow mixture or a mixture mass flow 21 is created, which flows out of the dosing unit 18.

[0036] At least in Fig. 3, section 4 of the exhaust system 3 is shown transparent in the area of ​​the metering device 12. Furthermore, at least the metering unit 18 is shown in section. The metering unit 18 has, according to the Fig. 3 and Fig. 4 comprises a dosing body 22 arranged in the flow channel 15 and having a plurality of passage openings 23 through which the primary mass flow 14 can flow in parallel, and a plurality of outlet openings 24 through which the secondary mass flow 13 can flow in parallel. The outlet openings 24 are each assigned to one of the passage openings 23 and are arranged at the respective passage opening 23. The outlet openings 24 collectively form the secondary outlet 20 of the dosing device 12. The dosing body 22 is hollow, so that the secondary mass flow 13 can flow inside the dosing body 22. The hollow dosing body 22 is fluidically connected to the secondary inlet 19 and ensures a fluidic connection of the secondary inlet 19 with the outlet openings 24. This allows the secondary mass flow 13 to flow within the dosing body 22 to the outlet openings 24.

[0037] According to the Fig. 5 and Fig. 6, it is expediently provided that the same number of outlet openings 24 as passage openings 23 are formed on the metering body 22. The outlet openings 24 can expediently enclose the respective passage opening 23 in a ring-shaped manner, preferably in a circular ring-shaped manner. In the example of Fig. 5, all outlet openings 24 are configured the same. In addition, all passage openings 23 are configured the same. In the example of Fig. 6, however, several outlet openings 24' are different, namely smaller in size than all other outlet openings 24. The same applies to the associated passage openings 23, so that several passage openings 23' are smaller in size than all other passage openings 23.

[0038] According to Fig. 4, the metering body 22 may comprise a first sheet metal body 25 which contains a plurality of first holes 26 and forms an outflow side 37 of the metering body 22 in the flow channel 15 with respect to the primary mass flow 14. In the example of Fig. 4, the primary mass flow 14 flows from right to left. Accordingly, the outflow side 37 of the metering body 22 is located on the left side of the metering body 22. Consequently, the first sheet metal body 25 is also located on the left side of the metering body 22. The metering body 22 also has a second sheet metal body 27, which has a plurality of second holes 28 and forms an inflow side 38 of the metering body 22 in the flow channel 15 with respect to the primary mass flow 14. Accordingly, the inflow side 38 of the metering body 22 is located in Fig. 4 right. Accordingly, the second sheet metal body 27 is in Fig. 4 on the right. The second holes 28 are each enclosed by a collar 29, which projects from the second sheet metal body 27 to the first sheet metal body 25 and ends there at or in one of the first holes 26. In Fig. 4, the collars 29 protrude from the second sheet metal body 27 arranged on the right to the left in the direction of the first sheet metal body 25 and there end essentially flush with the first sheet metal body 25 in one of the first holes 26. The collars 29 form the through-openings 23 with the first holes 28. The first holes 26 are each bordered by an opening edge 30. At the respective first hole 26, the respective opening edge 30 encloses the collar 29 protruding into the first hole 26 at a distance, whereby a gap 31 is formed there. The respective gap 31 forms the respective outlet opening 24. The first holes 26 and the second holes 28 are each circular in the examples shown here. Consequently, the collars 29 are cylindrical or circular-cylindrical in configuration. In addition, the gaps 31 are configured as annular gaps and are accordingly annular or circular-ring-shaped.

[0039] In a special embodiment, according to a Fig. 4, a web 32 enclosing the respective first hole 26 may be formed on the respective opening edge 30, which web 32 protrudes, for example, on the downstream side from the first sheet metal body 25. The associated collar 29 may be dimensioned such that it protrudes into the respective web 32. In Fig. 4, representative of all first holes 26, only in detail 39 at the first hole 26 is the corresponding opening edge 30 equipped with such a web 32. As can be seen, the corresponding collar 29 is correspondingly extended in the flow direction of the primary mass flow 14, so that the collar 29 is flush with the web 32.

[0040] The secondary inlet 19 may have at least one inlet port 33 which, according to Fig. 4 is formed on the first sheet metal body 25. In the example of Fig. 3, two such inlet connections 33 are provided, which together form the secondary inlet 19.

[0041] The first sheet metal body 25 and the second sheet metal body 27 can be formed sheet metal parts or primary formed parts. The dosing body 22 can be in a connecting area 34, which is Fig.4 is marked by curly brackets, be integrated into the flow channel 15. For example, the flow channel 15 can be formed for this purpose with two tubular bodies 35, 36, which form a first tubular body 35 on the upstream side and a second tubular body 36 on the downstream side. The two tubular bodies 35, 36 are connected to one another in the connecting region 34, in particular plugged in, so that the connecting region 34 represents a plug-in connection. In the connecting region 34, the two tubular bodies 35 can be welded to the dosing body 22. At the same time, the two sheet metal bodies 25, 27 can also be welded to one another in the connecting region 34. A common, complete circumferential weld seam is conceivable.

[0042] The metering body 22 is expediently configured such that it fills a flowable cross-section of the flow channel 15. As a result, the primary mass flow 14 is forced to flow completely through the passage openings 23. Furthermore, it is provided here that the metering body 22 is configured flat and plate-shaped and, moreover, is oriented transversely to the flow direction of the primary mass flow 14 in the flow channel 15 with respect to a plane in which it extends.

[0043] According to a particularly advantageous embodiment, the passage openings 23 can converge in the flow direction of the primary mass flow 14. For example, the collars 29 can have a flow-through cross-section that decreases in the flow direction of the primary mass flow 14. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 22 21 793 B2

[0002] EP 0 697 505 A1

[0003] DE 11 2011 104 763 B4

[0004]

Claims

[1] Dosing device (12) for introducing a fluidic secondary mass flow (13) into a fluidic primary mass flow (14), - with a flow channel (15) through which the primary mass flow (14) can flow, - with a dosing unit (18) through which the secondary mass flow (13) can flow, which has at least one secondary inlet (19) arranged outside the flow channel (15) through which the secondary mass flow (13) can flow into the dosing unit (18), and a secondary outlet (20) arranged inside the flow channel (15) through which the secondary mass flow (13) can flow out of the dosing unit (18) and into the flow channel (15), characterized by , - that the dosing unit (18) has a dosing body (22) arranged in the flow channel (15), which has a plurality of passage openings (23) through which the primary mass flow (14) can flow in parallel and a plurality of outlet openings (24) through which the secondary mass flow (13) can flow in parallel, each of which is arranged at one of the passage openings (23), - that the dosing body (22) is hollow, is fluidically connected to the secondary inlet (19) and fluidically connects the secondary inlet (19) to the outlet openings (24). [2] Dosing device (12) according to claim 1, characterized by , - that the respective outlet opening (24) encloses the respective passage opening (23) in a ring shape. [3] Dosing device (12) according to claim 1 or 2, characterized by , - that the metering body (22) has a first sheet metal body (25) which has a plurality of first holes (26) and forms an outflow side (37) of the metering body (22) in the flow channel (15) with respect to the primary mass flow (14), - that the metering body (22) has a second sheet metal body (27) which has a plurality of second holes (28) and forms an inflow side (38) of the metering body (22) in the flow channel (15) with respect to the primary mass flow (14), - that the second holes (28) are each enclosed by a collar (29) which projects from the second sheet metal body (27) to the first sheet metal body (25) and ends there in or at one of the first holes (26), - that the collars (29) form the passage openings (23), - that the first holes (26) are each enclosed by an opening edge (30) which encloses the respective collar (29) to form a gap (31), - that the gaps (31) form the outlet openings (24). [4] Dosing device (12) according to claim 3, characterized by , - that the collars (29) are cylindrically configured, - that the gaps (31) are configured in a ring shape. [5] Dosing device (12) according to claim 3 or 4, characterized by , - that a web (32) enclosing the respective first hole (26) is formed on the respective opening edge (30) and projects from the first sheet metal body (25) on the downstream side, - that the respective collar (29) projects into the respective web (32). [6] Dosing device (12) according to one of claims 3 to 5, characterized by , - that the secondary inlet (19) has at least one inlet connection (33) which is formed on the first sheet metal body (25). [7] Dosing device (12) according to one of the preceding claims, characterized by , - that the dosing body (22) fills a flow-through cross-section of the flow channel (15) so that the entire primary mass flow (14) flows through the passage openings (23). [8] Dosing device (12) according to one of the preceding claims, characterized by , - that the passage openings (23) converge in the flow direction of the primary mass flow (14). [9] Exhaust system (3) for an internal combustion engine (2), - with at least one exhaust gas aftertreatment device (5) through which an exhaust gas stream (6) can flow, - with a secondary air supply device (9) for supplying a secondary air flow (10) to the exhaust gas flow (6), - wherein the secondary air supply device (9) comprises a metering device (12) according to one of the preceding claims, - wherein the exhaust gas flow (6) forms the primary mass flow (14), while the secondary air flow (10) forms the secondary mass flow (13). [10] Motor vehicle (1), in particular passenger car, - with an internal combustion engine (2), - with an exhaust system (3) according to claim 9.

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