Mixer assembly unit

A mixer assembly unit, especially for an exhaust system of an internal combustion engine of a vehicle, includes a mixer body (48) with an incoming flow side (58) and with an outgoing flow side (60); and a carrier element (24) with a carrier element body (44) enclosing the mixer body (48) radially on an outside in relation to a mixer longitudinal axis. The mixer body (48) includes a plurality of flow deflection elements (62) and at least one holding area (70). The carrier element (24) includes a counter holding area (46) in association with a holding area (70). The counter holding area (46) is connected in substance to the holding area (70). The counter holding area (46) overlaps the holding area (70) at least partly radially on a side oriented in a direction of the outgoing flow side (60) of the mixer body (48).

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119 of German Applications 10 2016 119 294.5, filed Oct. 11, 2016, and 10 2016 120 171.5, filed Oct. 24, 2016, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention pertains to a mixer assembly unit that can be used, for example, in an exhaust system of an internal combustion engine of a vehicle for mixing a reactant, which was injected into the exhaust gas emitted from an internal combustion engine, with the exhaust gas.

BACKGROUND OF THE INVENTION

To reduce the emission of harmful substances especially from diesel internal combustion engines in motor vehicles, it is known to inject a reactant, for example, a urea/water solution, into the exhaust gas emitted from the internal combustion engine in order to carry out a selective catalytic reduction in a catalytic converter device integrated into the exhaust system for reducing the nitrogen oxide content in the exhaust gas. In order thereby to achieve an efficient mixing of the exhaust gas with the reactant injected into same, a mixer, which brings about a swirling of the exhaust gas flowing in the exhaust system with a plurality of blade-like (blade-shaped or partially blade-shaped) flow deflection elements and thus a mixing with the injected reactant, is integrated into the exhaust system downstream of the reactant injection and upstream of the catalytic converter device. Such mixers are generally configured such that they are, in principle, mounted in the interior of tubular exhaust gas-carrying elements of the exhaust system and are carried thereon in their radially outer area.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a mixer assembly unit guaranteeing an efficient mixing of exhaust gas and reactant and secured against detachment from the exhaust system.

According to the present invention, this object is accomplished by a mixer assembly unit, especially for an exhaust system of an internal combustion engine of a vehicle, comprising a mixer body with an incoming flow side and with an outgoing flow side; and a carrier element with a carrier element body enclosing the mixer body radially on the outside in relation to a mixer longitudinal axis, wherein the mixer body comprises a plurality of flow deflection elements and at least one holding area, wherein the carrier element comprises a counter holding area in association with at least one holding area, wherein at least one counter holding area is connected in substance to a holding area, and wherein at least one counter holding area overlaps a holding area at least partly radially on a side oriented in the direction of the outgoing flow side of the mixer body.

The mixer assembly unit configured according to the present invention is, in principle, divided into two functional areas. On the one hand, the mixer body is provided, which can be configured in an optimized manner in relation to the requirements placed on it in case of the mixing of reactant and exhaust gas. On the other hand, the carrier element is provided, which is provided, in principle, as a component configured separately from the mixer body and can thus be configured in an optimized manner in relation to the existing requirements on securing and stably carrying the mixer body at an exhaust system. These two system areas, the mixer body and the carrier element, are permanently connected to one another in substance, preferably by welding, in the area of at least one counter holding area and an associated holding area. In addition, there is a positive-locking connection in the area of at least one counter holding area and of the holding area interacting with it due to the radial overlap, which prevents the motion of the mixer body in the downwards direction and thus in the direction towards the catalytic converter device positioned downstream, in the event of a failure of the connection in substance. Also in case the connection in substance between the carrier element and the mixer body is no longer effective, a reliable holding of the mixer body at the site of installation is thus provided, so that such a mixer assembly unit that is damaged due to the failure of the connection in substance can be replaced with a new mixer assembly unit without the risk that there will be damages to other system areas of an exhaust system.

In order to be able to achieve an essentially uniform holding interaction between the carrier element and the mixer body over the entire circumference in case of the mixer assembly unit according to the present invention, it is proposed that the carrier element body have a ring-like (ring shape) configuration, or/and that a plurality of counter holding areas, which extend radially inwards and are spaced circumferentially apart from one another, be provided at the carrier element body.

To obtain a configuration that can be produced in a simple and cost-effective manner and meets the thermal requirements in an exhaust system, the carrier element may have a plate-like (plate-shape) configuration and preferably be configured as a shaped sheet metal part.

It is proposed that at least one counter holding area at least partly axially overlap an associated holding area for a more improved holding interaction between the carrier element and the mixer body.

In order to thereby secure the mixer body against excessive radial motion, provisions may be made for at least one counter holding area to axially overlap the associated holding area radially on the inside.

In case of a configuration guaranteeing a stable and secure hold and at the same time also permitting a tolerance compensation, at least one counter holding area may comprise an essentially U-shaped holding section with two U-legs and a connection area connecting these legs, wherein the U-legs and the connection area define a holding area mounting space, which is essentially open in the direction towards the incoming flow side of the mixer body. Since the holding area mounting space is open in the direction towards the incoming flow side, it is not open in the direction towards the outgoing flow side against an outlet of the holding area of the mixer body mounted therein, so that a motion of the mixer body out of the holding area mounting space in the downstream direction is not possible even in case of failure of the connection in substance.

In order to be able to guarantee a stable connection over a long operating life, especially taking into account various thermal expansions of the mixer body, on the one hand, and of the carrier element, on the other hand, it is further proposed that one of the U-legs be arranged radially on the outside in relation to a holding area which is arranged in the holding area mounting space; that one of the U-legs be arranged radially on the inside in relation to the holding area arranged in the holding area mounting space; and that the holding area be connected to the U-leg, which is arranged radially on the inside in relation to this holding area; or/and an intermediate space be provided between the holding area and the U-leg which is arranged radially on the outside in relation to this holding area.

When the mixer body is connected in substance to the carrier element in the area of at least one, and preferably of each counter holding area radially overlapping a holding area, both the connection in substance and the positive-locking connection can be established in these holding areas and counter holding areas interacting with one another, and thus an efficient utilization of the holding areas and counter holding areas provided can be guaranteed.

In order to be able to obtain a configuration which is stable and essentially does not compromise the flow guiding in the area of the mixer body, it is proposed that at least one holding area be adjacent to a radially outer area of at least one flow deflection element. Provisions may especially be made in this case for at least one holding area to comprise a holding web connecting two flow deflection elements to one another.

For a symmetrical configuration which is especially advantageous with respect to flow guiding, it is proposed that at least some of the flow deflection elements and preferably all flow deflection elements be arranged following one another in the circumferential direction, and that a ring-like connection area connecting these flow deflection elements to one another and providing at least one holding web be provided at a radially outer area of at least some of the flow deflection elements and preferably of all flow deflection elements. In this connection, when the mixer body is configured, for example, as a cast metal component, the connection area may be configured as being integral with the flow deflection elements connected by this area.

The present invention further pertains to an exhaust system, especially for an internal combustion engine of a vehicle, comprising at least one mixer assembly unit configured according to the present invention.

For integration of at least one mixer assembly unit into the exhaust system, provisions may be made for this mixer assembly unit to be arranged in an area of two tubular exhaust gas-carrying elements bordering one another, wherein each of the exhaust gas-carrying elements in the border area comprises a preferably flange-like (flange-shape) coupling section for coupling with the coupling section of the respective other exhaust gas-carrying element, and wherein the carrier element body of a mixer assembly unit is arranged between the coupling sections of the exhaust gas-carrying elements.

In an embodiment especially advantageous for a simplified configuration of an exhaust system, provisions may be made for at least one, preferably a plurality of fixing straps extending behind the coupling section of one of the exhaust gas-carrying elements to be provided at the carrier element body. By means of such fixing straps, the mixer assembly unit can be preassembled with one of the exhaust gas-carrying elements and can then be assembled in a simple manner with the other of the two exhaust gas-carrying elements due to the fixing straps held rigidly thereon.

In order to be able to provide a simple configuration especially in the area of the exhaust gas-carrying elements, on the one hand, and to be able to guarantee that exhaust gas can flow entirely about the mixer body, on the other hand, it is proposed that an outer dimension, preferably outer diameter, of the mixer body of the mixer assembly unit not be greater than an inner dimension, preferably inner diameter, of a downstream exhaust gas-carrying element of the two exhaust gas-carrying elements. In such a configuration, the securing of the mixer body against motion in the downstream direction in case of failure of the connection in substance has an especially distinct effect, since the mixer body could move unhindered towards the catalytic converter device in the interior of the downstream exhaust gas-carrying element in case of the absence of securing because of the dimensioning in the case of failure of the connection in substance.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, an exhaust system for an internal combustion engine of a vehicle is generally designated by10inFIG. 1. The exhaust system10has two tubular exhaust gas-carrying elements14,16adjacent to one another in an upstream area12. These exhaust gas-carrying elements14,16have each a flange-like coupling section20and22, respectively, in a border area18, in which these exhaust gas-carrying elements are permanently connected to one another, for example, by bolts passing through the flange-like coupling sections20,22. A carrier element24of a mixer assembly unit generally designated by26, which carrier element24will be described in even more detail below, is positioned between the two flange-like coupling areas20,22and is thus fixed to the exhaust system10by means of the bolts, which are, e.g., also passing through this carrier element24, with the two exhaust gas-carrying elements14,16and their flange-like coupling sections20,22in the border area18.

The border area18is located downstream of a reactant injection device, by means of which a reactant, for example, a urea/water solution, can be injected into the exhaust gas stream. A catalytic converter device, which is generally designated by28, in which the mixture of exhaust gas and reactant is subjected to a selective catalytic reduction in order to thus lower the nitrogen oxide content in the exhaust gas, is provided downstream of the border area18, bordering on the exhaust gas-carrying element16. Via another exhaust gas-carrying element30, the exhaust gas reaches an exhaust gas muffler32, from which this exhaust gas is discharged to the outside, for example, via two tail pipes34,36.

It should be pointed out that the exhaust system shown inFIG. 1represents only one example of a plurality of different configurations of such an exhaust system. Thus, a plurality of mufflers could be integrated into the exhaust system10. A plurality of catalytic converter devices could also be provided in order to further lower the harmful substance content in the exhaust gas in this manner.

The mixer assembly unit26, which is positioned in the border area18of the two exhaust gas-carrying elements14,16downstream of the reactant injection device and upstream of the catalytic converter device28for carrying out a selective catalytic reduction, is described in detail below with reference toFIGS. 2 through 5.

FIG. 2shows the mixer assembly unit26in a perspective view. The mixer assembly unit26comprises the already mentioned carrier element24, which preferably has a plate-like configuration and whose circumferential contour may correspond, for example, essentially to the circumferential contour of the flange-like coupling section22. Just as the flange-like coupling section22, the carrier element24, which is preferably provided as a shaped sheet metal part and has a plate-like configuration, is configured with a ring-like structure and has radial expansions on two circumferential areas located opposite one another with openings38,40, through which the bolts connecting the two flange-like coupling sections20,22and thus the exhaust gas-carrying elements14,16can be passed.

To be able to combine the carrier element24and the mixer assembly unit26as a preassembled assembly unit with the exhaust gas-carrying element16, the carrier element24has, for example, in the two above-mentioned circumferential areas, fixing straps42, which are bent or are bent at the exhaust gas-carrying element16after positioning the mixer unit26, such that they extend behind the flange-like coupling section22and thus fix the mixer assembly unit26to this section22. The thus assembled assembly unit can then be assembled with the exhaust gas-carrying element14in a simple manner by the flange-like coupling section thereof being fixed to the flange-like coupling section22or the carrier element24and being connected therewith by screw connection.

Four counter holding areas46, to which a mixer body, generally designated by48, of the mixer assembly unit26is secured, are provided at preferably uniform circumferential distances to one another in the exemplary embodiment shown at an inner circumferential area of a carrier element body, generally designated by44, of the carrier element24, from which carrier element body44the fixing straps42also extend. Each of the counter holding areas46comprises a strap-like holding section50projecting inwards, which can be clearly seen inFIG. 5. Each strap-like holding section50has an essentially U-shaped configuration and has an outer U-leg52, an inner U-leg54as well as a connection area56connecting these legs. The U-shaped holding sections52are shaped such that the holding sections50are open in the direction towards an incoming flow side58of the mixer body48, which can be seen inFIG. 3, i.e., in the upstream direction, and are closed, especially by the connection area56, towards an outgoing flow side60of the mixer body48, which is obscured inFIG. 2, i.e., in the downstream direction. Each of the holding sections50has an essentially hook-like shape and thus makes possible a stable hold of the mixer body48at the carrier element24. In this connection, the U-leg52extends, starting from the carrier element body44, essentially in the direction of a mixer longitudinal axis L and in the direction towards the outgoing flow side60of the mixer body48, while the U-leg54extends, starting from the connection area56, essentially parallel to the U-leg52in the direction towards the incoming flow side58of the mixer body48.

The mixer body48comprises a plurality of blade-like flow deflection elements62following one another in the circumferential direction and extending, for example, essentially radially in relation to the mixer longitudinal axis L. These flow deflection elements62start from a central body area64of the mixer body48and extend radially to the outside up to a ring-like connection area66, which is preferably connected to the flow deflection elements62on the incoming flow side58. The mixer body48may be provided as an integral component, for example, as a cast metal component with the central body area64, the blade-like flow deflection elements62and the ring-like connection area66.

In its areas extending between the flow deflection elements62directly following one another in the circumferential directions and connecting these elements to one another, the ring-like connection area66provides holding areas70, each of which is configured in the form of a holding web68, for each interacting with a counter holding area46of the carrier element24. These holding areas70, which are configured as holding webs68, may, as shown inFIG. 5, be inserted into a holding area mounting space72provided by the U-shaped holding sections50of the counter holding areas46, so that the holding sections50, on the one hand, overlap the holding areas70interacting with same in relation to the mixer longitudinal axis L from radially outwards to radially inwards and overlap the holding areas70axially with the inner U-legs54also in the direction of the mixer longitudinal axis L. The holding webs68, which are thus located in at least some areas within the holding area mounting spaces72, cannot thus move out of the holding sections50in the direction towards the outgoing flow side60of the mixer body48, i.e., they are secured against excessive axial motion, and are also essentially centered radially due to interaction with the inner U-legs54. Thus, a defined positioning of the mixer body48in relation to the carrier element24is provided, wherein a compensation of manufacturing tolerances is made possible because of the configuration of the holding sections50as straps, which can be brought into their desired shape by shaping sheet metal material and which also have a certain flexibility.

The mixer body48is permanently connected in substance, especially by welding74, to the carrier element24in the area of the holding webs68and of the holding sections50. This welding preferably establishes a connection between the holding webs68and the inner U-legs54, wherein the mixer body48is more preferably connected in substance by welding with the carrier element24for a uniform stable fixing over the circumference in each of the four counter holding areas46. Counter holding areas46could nevertheless be provided, which are used only for securing against excessive axial motion, but not for establishing a connection in substance. Further, counter holding areas and holding areas may be provided, which are used only for establishing the connection in substance and in which the counter holding areas do not necessarily have to overlap the holding areas radially.

It is further seen inFIG. 5that an intermediate space76is formed between the outer U-leg52and the holding web68. The mixer assembly unit26is heated in the exhaust gas stream, wherein the mixer body48, which is manufactured, for example, from cast metal material, is more intensely thermally expanded than the carrier element24, which is generally provided as a shaped sheet metal part. By providing the intermediate space76, sufficient space is created for the thermal expansion of the mixer body48, especially of the ring-like connection area66of same, in which intermediate space76this connection area66can expand radially without coming into contact with the outer U-leg52. In case of this radial expansion, the ring-like connection area66can pull the inner U-leg54or the inner U-legs54connected therewith by the weldings74radially outwards, which is possible because of the circumstance that the carrier element24is configured with comparatively greater flexibility in the area of its U-shaped counter holding areas46and because of the circumstance that the inner U-legs54have a greater axial extension than the outer U-legs52, without generating tensions excessively stressing the weldings74.

During operation, the mixer assembly unit26is exposed to a comparatively high mechanical stress, especially due to vibrations occurring in a vehicle and the high temperatures in the exhaust system10. Under unfavorable circumstances, this may lead to damage to the connection in substance, so that in the extreme case the mixer body48could detach from the carrier element24. Since the mixer body48is held against a detachment from the carrier element24in the downstream direction, i.e., in the direction towards the flow-carrying element16and the catalytic converter unit28due to the interaction of the holding areas70with the counter holding areas46, there is no risk that in such a state the mixer body48, whose outer dimension, for example, outer diameter, will generally at least not be greater than the inner dimension, i.e., for example, the inner diameter, of the exhaust gas-carrying element16, can move into this exhaust gas-carrying element16and towards the catalytic converter device28. After the detachment of the mixer body48from the carrier element24occurring in case of a failure of the connection in substance, rattling noises may occur, but damage to the downstream system areas is avoided. Thus, after uncoupling the two exhaust gas-carrying elements14,16from one another, the mixer assembly unit26can be removed and be replaced with a new one.

It should be pointed out that a great variety of variations may also be made in the area of the mixer assembly unit26within the scope of the present invention. Thus, for example, more or fewer than the four counter holding areas46shown could also be provided. For example, the mixer body48could also be configured such that holding areas, i.e., for example, a holding web68connecting two adjacent flow deflection elements62, are provided only where a holding interaction is to be provided with counter holding areas46. The mixer body48itself could also be provided with another configuration. Another ring-like connection area could, for example, be provided on the outgoing flow side in order to increase the stability of the mixer body48. The geometry of the blade-like deflection elements62could be selected differently than shown inFIG. 2.

Further, the holding areas could be configured with recesses essentially open in the radial direction, into which counter holding areas, which are meshing with holding areas from radially outwards, can be positioned, so that a radial overlap likewise forms and the mixer body is held against moving in the and optionally against the gas flow direction. In this case as well, a respective holding area is overlapped radially at an area oriented in the direction of the outgoing flow side or downstream in the sense of the present invention.