WO2011107122A1

WO2011107122A1 - Reductant metering and injecting module for exhaust purification for internal combustion engines

Info

Publication number: WO2011107122A1
Application number: PCT/EP2010/001400
Authority: WO
Inventors: Achim Bleutge; Wilhelm Kullen; Jochen Schöllhammer
Original assignee: Elringklinger Ag
Priority date: 2010-03-05
Filing date: 2010-03-05
Publication date: 2011-09-09
Also published as: DE112010005351A5

Abstract

The invention relates to a reductant metering and injecting module for installing on an exhaust gas line for hot exhaust gases of an internal combustion engine operated in particular under varying load, said exhaust gas line containing a reduction catalyst, wherein the module has a metering device and an injection nozzle downstream thereof for a liquid reductant; in order to keep the input of heat into temperature-sensitive elements of the module as low as possible in such a module during engine operation, the module is designed in such a way that the injection nozzle is arranged in a nozzle retaining pipe and is connected to the metering device by means of a feed pipe containing at least one flow channel for the reductant, wherein (a) the length L of the flow channel is at least 20 mm, (b) the ratio V₁ of L and the total cross-sectional area of the feed pipe is at least 3 mm^-1, and (c) the ratio V₂ of the material cross-sectional area and the flow channel cross-sectional area of the feed pipe is at least 2.5 and at most 50.

Description

REDUCER DOSING AND INJECTION MODULE

FOR EMISSION CONTROL IN INTERNAL COMBUSTION ENGINES

The invention relates to a reducing agent metering and injection module for mounting to a reduction catalyst containing exhaust pipe for hot exhaust gases of an internal combustion engine, wherein the module for a liquid reducing agent, a metering device and downstream thereof has an injection nozzle.

In particular, the invention is concerned with such a module for the purification of the exhaust gases of a variable load combustion engine.

In the following, the invention is explained and discussed with reference to a module of the type defined above, which serves to inject an aqueous urea solution into an exhaust pipe of a diesel engine, which contains a reduction catalyst to which or in which the atomized urea solution mixed with the exhaust gases is applied In order to reduce nitrogen oxides contained in the exhaust gases to nitrogen and H ₂ 0 (selective catalytic reduction - abbreviated to SCR), but in principle the invention is also suitable for the injection of other, present in liquid form reducing agent for the selective catalytic reduction of others Exhaust components of internal combustion engines. In the catalytic reduction of nitrogen oxides by means of urea, this decomposes in the hot exhaust gases to ammonia (NH ₃ ), which reacts with the nitrogen oxides (NO _x ), so that the reaction products nitrogen and H ₂ 0 result. Devices for the metered injection of a liquid exhaust aftertreatment agent are described for example in WO 2008151908 AI and in EP 2 132 420 AI. Since a module of the type defined above must be attached to an exhaust pipe so that its injection nozzle is located in or in the immediate vicinity of an opening in a wall of the exhaust pipe, are in machine operation without special measures except the injector and other elements of the module due to heat conduction and / or thermal radiation exposed to high temperatures, by which in particular the metering device can be damaged or rendered completely inoperative.

This is where the invention is based, which was based on the object of keeping the heat input in temperature-sensitive elements of such a metering and injection module that is basically unavoidable in machine operation as small as possible in a module of the type defined at the outset. In this connection, it should be noted that the metering devices of the present metering and injection modules usually contain valves, which are actuated by an electromagnet or other electrically controlled actuators.

Since it can not be avoided that the injection nozzle is more or less exposed to the hot exhaust gases in operation, the heat input in relation to the reducing agent injected upstream of the injection nozzle, temperature-sensitive elements of the module is mainly reduced by the fact that the injection nozzle arranged in a nozzle support tube is connected to the metering device via a supply tube containing at least one flow channel for the reducing agent, the material cross-sectional area which determines the heat conduction in relation to its length between the injection nozzle and the upstream of the temperature-sensitive element of the latter Module, that is usually the metering device, is as small as possible (without endangering the mechanical stability of the supply tube), including for the dimensioning of the Zuluungsungs tube According to the invention, the following is suggested: (a) the aforesaid length L of the flow channel formed by the supply tube is at least 20 mm,

(b) the ratio Vi between L and the total cross sectional area of the

Supply tube is at least 3 mm ^"1 , and

(c) the ratio V ₂ between the material cross-sectional area and the flow channel cross-sectional area of the feeder tube (or the sum of the cross-sectional areas of the flow channels formed by the feeder tube) is at least 2.5 and at most 50, preferably 9.

In preferred embodiments of the module according to the invention said length L is at least 30 mm, more preferably at least 40 mm, but at most 50 mm, Vi is greater than 10 and smaller than 30 mm ^"1 , even better at least 18 mm ^{" 1} and still better at least 22 mm ^"1 , wherein it has proved to be extremely advantageous if Vi is 22 to 23 mm ^"1; finally, it is recommended for V ₂ that this ratio be at least 2.8, more preferably greater than 4, and most preferably greater than 6, with V _{2 being found to be} 8 to 10 most advantageously.

In one embodiment, which has proven to be extremely favorable, L is about 45 mm, the outer diameter of the supply tube about 1.6 mm and the inner diameter, that is, the diameter of its flow channel, about 0.5 mm.

In preferred embodiments of the module according to the invention, the average wall thickness of the supply tube for stability reasons is at least 0.2 mm and preferably about 0.5 mm. Since in preferred embodiments of the module according to the invention, the injection quantity (at a predetermined pressure on the metering device side facing the Zuleitungsröhrchens) by the flow cross-section of the outlet opening of the injection nozzle, that is, the narrowest point of this outlet opening should be determined, it is recommended that the smallest Cross-sectional area of the inlet to the injection nozzle forming flow channel of the supply tube is at least as large as the flow cross-sectional area of the outlet opening of the injection nozzle. In principle, the injection nozzle could contain a valve for the liquid reducing agent, in particular a valve which opens at a predetermined feed pressure for the reducing agent, as is the case for example with a valve with a spring-loaded or spring-loaded valve member. However, embodiments of the module according to the invention are preferred, which are characterized by a valveless injection nozzle, so that the flow path formed by the supply tube and the injection nozzle in the flow direction is open. This not only determines the response of the module exclusively by the metering device, but also prevents that at low ambient temperatures and when no reducing agent is injected, standing in the injector and the supply tube reducing agent freezes, thereby expanding and thereby damage these components.

To ensure that the supply tube is shielded as well as possible against high temperatures by the nozzle holder tube, a configuration is recommended in which the total cross-sectional area of the supply tube is only a fraction of the internal cross-sectional area of the nozzle holder tube (along the supply tube), so that the supply tube and the inner wall surface of the nozzle holder tube at a considerable distance from each other. As a result, even better heat protection for the supply tube can be brought about, namely by a gas filled annular chamber between the supply tube and the nozzle holder tube.

In order to provide the best possible shielding of the supply pipe, it is also recommended to design the module so that the nozzle holder pipe extends over more than half the length of the supply pipe and preferably over at least the entire length of the supply pipe between the injection nozzle and the end region of the metering device feed tube.

For an even better shielding of the supply tube, a preferred embodiment of the module according to the invention comprises an outer holding or casing tube enclosing the nozzle holder tube, wherein it is particularly advantageous if the outer holding tube and the nozzle holder tube form a gas-filled annular chamber between them.

In order to ensure that the injection nozzle is protected as well as possible against the high exhaust gas temperatures, it is recommended to design the module according to the invention so that I extend the nozzle holder tube in the longitudinal direction of the supply tube up to an end face of the injection nozzle facing away from the latter. In this sense, it is also advantageous if the end region of the nozzle holder tube facing away from the metering device is closed gas-tight except for a passage opening for the reducing agent to be injected, wherein embodiments are recommended in which the end of the nozzle holder tube and the injection nozzle facing away from the metering device, preferably gas-tight, abut against each other; This makes it possible to prevent the hot exhaust gases from penetrating into the module around the injection nozzle and exposing the end face of the injection nozzle facing the exhaust pipe more than unavoidably to the hot exhaust gases. In embodiments with an outer holding or jacket tube, it is advisable to use the longitudinal extension and the end region of the outer holding tube adjacent to the injection nozzle, whereby embodiments are particularly advantageous in which the end of the outer holding tube facing away from the metering device is in particular gas-tightly connected to a sealing washer which covers the injection nozzle, has an opening which opens the outlet opening and at least covers or even gas-tightly seals the annular chamber between the nozzle holder tube and the outer holding or jacket tube, in particular by means of a sealing bead which is impressed into the sealing disc and elastically deformable perpendicular to the sealing disc plane is sealingly pressed around the outlet opening of the injection nozzle against the end of the nozzle holder tube or the nozzle body. According to the invention, it is recommended to provide a gas-filled insulating gap between the sealing disk and an end face of the injection nozzle facing away from the supply pipe.

To further reduce the heat input in relation to the injected reducing agent upstream of the supply tube elements of the module according to the invention, in particular in the metering device, it is extremely advantageous to divide the module into assemblies which are interconnected by connecting means in the longitudinal direction of the supply tube have the lowest possible thermal conductivity. Therefore, preferred embodiments of the module according to the invention are characterized in that it comprises a first assembly containing the injection nozzle, the supply tube, the nozzle holder tube and the metering device and a second assembly containing the outer support tube, wherein the two assemblies are positively connected to each other by means of a particular releasable connection device since such a connecting device can be obtained by an appropriate selection of the materials used for the latter and / or by a corresponding chende cross-sectional configuration of the connecting device or its parts can be designed so that it introduces as little heat from the first module in the second module. In order to better protect the metering device against overheating, it is also proposed to insert an end portion of the metering device facing the injection nozzle in a receiving sleeve extending in the direction of the injection nozzle, on the outer circumference of which cooling fins are provided; these cooling ribs can be realized in manufacturing technology easiest by being formed by arranged on the receiving sleeve metal discs, which are arranged in the longitudinal direction of the receiving sleeve at intervals from each other.

In embodiments with a receiving sleeve holding at least one end region of the metering device, the connection of the two assemblies by means of a connecting device with the lowest possible (axial) thermal conductivity can be achieved most simply by moving radially on the second assembly with respect to the outer holding tube provided on the outside of the extending annular first retaining flange and the first assembly is provided at one of the injector end portion of the receiving sleeve with a radially outwardly extending therefrom annular second retaining flange and the connecting device comprises a two retaining flanges at least predominantly enclosing strap, which from each other remote flanks of the two retaining flanges at least partially overlaps. Since such a tension band, even if it is formed by a metal band, can be designed with an extremely small cross-section, a small axial thermal conductivity is achieved in this way; In principle, however, the two retaining flanges could also be connected to each other by other suitable connecting means, for example by connecting means in the manner of a union nut, which then has the smallest possible Have cross-section and / or should be made of a material with the lowest possible thermal conductivity.

In terms of the lowest possible (axial) heat transfer, it is advantageous if the first retaining flange is formed by an annular retaining flange piece fastened to the second structural group, in particular on the outer retaining tube, whose cross section lies in a diameter plane of the retaining flange piece through recesses is essentially reduced to the following elements:

(A) two in the axial direction of the Halteflanschstücks spaced from each other, the end faces of the Halteflanschstücks forming edges which are advantageously inclined relative to the axial direction so that they approach each other in the radial direction, and

(B) a radially inner mounting portion of the retaining flange piece for attaching the latter to the second assembly.

If the said flanks of the Halteflanschstücks are inclined in the manner described against each other, it can be achieved that with a corresponding design of the connecting device and thus in particular of the clamping band, the two assemblies are braced against each other in the axial direction, so that the connection between the two assemblies in the axial Direction also makes gas-tight easily.

If the connection device for the two modules has a tensioning strap, it is recommended to use a metal strap with free strap ends which is almost closed to a ring and which can be tightened by reducing the ring diameter by means of a tensioning screw, the annular area of the tensioning strap being in an in one

Diameter level lying cross section has an approximately U-shaped, opening towards the supply tube profile, the two legs are mutually inclined and form an opening in the radial direction inwardly acute angle with each other.

In order to minimize the heat input into the module according to the invention attached to the exhaust pipe, it is further recommended to provide it with a plate-like holding plate which has a peripheral edge region that can be gas-tightly connected to the exhaust gas line, and a passage opening for a jacket tube enclosing the injection nozzle and the supply tube (Nozzle holder tube or outer holding tube), which is gas-tight welded to the edge of the passage opening. Then, this jacket tube does not have to be connected directly to the exhaust pipe, but the wall of the exhaust pipe may have an opening covered by the holding plate whose edge extends a short distance from said jacket tube so as to achieve the narrowest possible gap through which exhaust gases pass can. Embodiments of the retaining plate in which it is stepped along its circumferential edge region to be connected to the exhaust pipe in the direction of the metering device, that is to say when the module is mounted in the direction away from the wall of the exhaust pipe, as well as to the shape of the exhaust pipe, are particularly advantageous Formed with the module mounted between the retaining plate and the wall of the exhaust pipe, a gas-filled, enclosed by the peripheral edge portion of the retaining plate insulating gap.

For even better shielding of temperature-sensitive elements of the module according to the invention compared to the hot exhaust pipe, a shield-like shielding member is recommended with a recess for the passage of the injection nozzle and the supply tube enclosing jacket tube (nozzle holder tube or outer holding tube), said shielding facing the metering of the module Side of the retaining plate at a distance from this is immediately adjacent. Especially when the module according to the invention is intended for use on a motor vehicle, the arrangement of the metering device in a protective and holding sleeve holding the latter is recommended, in which the metering device is also fixed in particular; Such a sleeve can serve not only the even better shielding of the metering device against harmful temperature influences, but also the protection of the metering device from splashing water, falling rocks and the like.

Since an inventive module is often exposed to corrosive influences - except the hot exhaust gases often reducing agent acting corrosive, but also on the streets discharged de-icing salts and the like -, we recommend the use of stainless steel for the metallic parts of the module, especially for the injection nozzle Supply tube, the nozzle holder tube, the outer holding tube, the aforementioned connection device, the cooling fins, the housing of the metering device, the protective sleeve, the mentioned holding plate and / or the aforementioned shield-like shielding.

Further features, advantages and details of the invention will become apparent from the accompanying drawings and the following description of a particularly advantageous embodiment of the invention in its configuration as an SCR injection device. in the drawing show:

1A shows a longitudinal section through the attached to an exhaust pipe SCR injection device.

FIG. 1B shows the portion of the injection device marked in dash-dotted lines in FIG. 1A on a larger scale; FIG. a plan view of a to be welded to the exhaust pipe retaining plate of the injection device; an isometric view of a to be welded to this holding plate shielding of the injection device; an isometric view of a designed as a receiving sleeve first holding member for a metering device of the injection device; a plan view of a Halteflanschteil on which the said receiving sleeve is supported; an isometric view of a said retaining flange portion supporting the sealing washer; a plan view of a disc-shaped end seal of the injection device; an isometric view of a clamping band for connecting two modules of the injection device with each other, and a section through an injection nozzle of the injection device.

1 shows a designated as a whole with 10 injection device according to the invention, the most essential components are a dosing device 12, not shown in detail, a in Fig. 1 only in a side views drawn injector 14 and especially an inventively designed supply tube 16, over which the metering device 12 and the injection nozzle 14 are connected to each other. An inlet port 18 of the metering device 12 shown in section in FIG. 1 is liquid-tightly fitted with a connecting piece 20, via which, as indicated by an arrow F, the metering device 12 from a tank for an aqueous urea solution, not shown, by means of a also not dargstellten pump, as indicated by the arrow F, an aqueous urea solution is supplied.

In the metering device 12, whose operating principle is not the subject of the present invention, there is a known liquid metering device, which in particular contains an electromagnetically actuated metering valve for the urea solution, and Fig. 1 leaves a

Identify connecting piece 22 for the implementation of an only schematically indicated electrical control line 22a. Finally, FIG. 1 also shows, in section, a shielding part 24 which serves the purpose of protecting the parts serving to supply the urea solution to the inlet connection 18 from harmful influences such as high temperatures.

In its lower part according to FIG. 1, the injection device 10 has a metallic outer holding tube 26, in particular of circular cross-section, which projects into an exhaust pipe 28 with its injection unit 10 mounted and thus extends through an opening 28a in the exhaust pipe wall 28b, the axis of the holding tube 26 forms an acute angle with the axis 28c of the exhaust pipe 28. In order to avoid a heat transfer from the exhaust pipe wall 28b to the holding tube 26, the opening 28a is so large that its edge extends at a distance from the holding tube 26.

In Fig. 1 is still a part of a relative to the exhaust stream upstream of a catalyst body arranged mixer 30 for turbulence of the exhaust gases and the injected urea solution shown schematically; this catalyst, in conjunction with the ammonia (NH ₃ ) resulting from the urea solution, reduces nitrogen oxides to nitrogen and H ₂ O.

The mounting of the holding tube 26 on the exhaust pipe 28 is a designed according to the invention and in particular according to FIG. 2 formed holding plate 32, which preferably consists essentially of a shield-like flange area 32a and a collar 32b formed on the latter, which is penetrated by the holding tube 26. As indicated in Fig. 1, is shown in FIG. 1 upper edge portion of the collar 32 b around a gas-tight welded to the holding pipe 26, and the flange portion 32a is inventively designed such that its outer peripheral portion 32a ¹ via a visible in FIG. 1, circumferential step or bend in the radially located within the outer peripheral portion of the flange portion 32a passes, so that after the gas-tight welding of the outer peripheral portion 32a 'with the exhaust pipe wall 28b an approximately annular gas gap 34 between the flange 32a and the exhaust pipe wall 28b remains through the According to the invention, a large-area contact between the retaining plate 32 and the exhaust pipe wall 28b having high temperatures during operation is avoided - the exhaust gases filling the gas gap 34 have a very low heat content and an extremely low thermal conductivity compared to a metal.

In order to improve the shielding of the injection device 10 with respect to the hot during operation exhaust pipe wall 28b, according to the invention shown in Figures 1 and 3 shielding plate 38 is provided by the invention at least the largest part at a considerable distance from the exhaust pipe wall 28b; If the axis of the injection device or holding tube 26 designated 10a in FIG. 1 runs obliquely to the exhaust pipe axis 28c and as a result the right-hand side of the injection device 10 is more or less remote from the exhaust pipe wall 28b as shown in FIG. 1, the shielding plate 38 becomes so according to the invention designed and arranged so that at least its largest part at the acute angle between the exhaust pipe wall 28b and the injection device 10 extends. As shown in FIG. 3, in the preferred embodiment, the shielding plate 38 has an open-edged recess 38a, so that it can be pushed onto the collar 32b of the holding plate 32; Furthermore, the shielding plate 38 is fixed to the holding plate 32, in the illustrated embodiment by spot welding at several points in that area in which the shielding in the Near its recess 38a rests against the retaining plate 32. In place of the shielding plate shown in the drawing, another, in particular roughly disc-shaped shielding element could occur, which has an opening for the passage of the holding tube 26, and instead of a metallic shielding could also be a shield of another, mechanically sufficiently strong and temperature-resistant material be used.

On the upper end of the holding tube 26 shown in FIG. 1, a retaining flange piece 40 is fixed, which is preferably a metallic rotary member, that is, a machined machining member on a lathe; if it is a metal part, it can - as indicated in Fig. 1 - be connected by means of a circumferential, gas-tight weld with the upper end portion of the holding tube 26. According to the invention, the retaining flange piece 40 is provided with a plurality of recesses circulating about the axis 10 a, with three such recesses 40 a, 40 b and 40 c in the embodiment shown in FIG. 1, in order to keep the cross-sectional area of the retaining flange piece 40 as small as possible, so that it is in Direction of the axis 10a as little heat in the direction of the metering device 12 can transmit. Further, it is advantageous if, as shown in Fig. 1, an upper and a lower edge 40d and 40e of the Halteflanschstücks 40 obliquely to the axis 10a and are mutually inclined so that they extend in relation to the axis 10a radial direction to each other - the meaning of these oblique flanks will become apparent from the following. To increase the stability of the connection between the Halteflanschstück 40 and the support tube 26 engages the upper end of the latter fits into a further recess 40 f of the Halteflanschstücks 40, which at its upper in Fig. 1 at the Halteflanschstück an annular shoulder and thus a stop forms when attaching the Halteflanschstücks on the holding tube 26. The lower end portion of the metering device 12 according to FIG. 1 has an outer diameter reduced relative to the adjoining portion of the metering device and is inserted into a receiving sleeve 42 shown in FIG. 4, which at its upper end has a support flange 42a for supporting the metering device 12 and at its lower end End has several, along the sleeve circumference spaced from each other projections 42 b. The receiving sleeve 42 is supported on a Halteflanschteil 44 shown in Figure 5, which has the shape of a circular disk in a plan view, the Halteflanschstück 40 largely covers and has a central opening 44a, which is enclosed by an annular collar 44b; In addition, the Halteflanschteil 44 for each projection 42b of the receiving sleeve 42 has a Einsteckschlitz 44c (see Fig. 5), so that the Halteflanschteil 44 can be plugged onto the receiving sleeve 42, after which the two parts on the bottom of FIG. 1 - Flange member 44 on the projections 42b and the insertion slots 44c gas-tight welded together.

Previously, however, a plurality of (in the embodiment 5 shown in FIG. 1) cooling plates 46 are pushed onto the receiving sleeve 42, which have substantially the shape of preferably perforated discs, each of which is provided with an annular collar 46 a, which serves to the cooling plates 46 fitting on the receiving sleeve 42 on the one hand and on the other to position the cooling plates in the direction of the axis 10a relative to each other and the receiving sleeve 42 - for fixing the axial positions of the cooling plates 46, however, two parts are still required in the illustrated embodiment, which hereinafter be described, but one of these two parts could also be omitted if the collar 46a of FIG. 1 lowest cooling plate 46 would be supported directly on the Halteflanschteil 44. As can be seen from FIG. 1, a nozzle holder tube 50 is arranged within the holding tube 26, the diameter of which has been selected such that an outer, air-filled annular gap 52 is located between the two tubes and an inner gas-filled annular gap 54 between the nozzle holder tube 50 and the supply tube 16 At its lower end according to FIG. 1, the nozzle holder tube 50 has a radially inwardly projecting, flange-like annular shoulder 50a, which has an outer annular region of FIG. 1 engages below the lower end face of the injection nozzle 14, wherein this annular region and the annular shoulder 50a are tightly pressed against each other, in particular gas-tight, and a slight projection 14a of the injection nozzle 14 enclosed by this annular region (see FIG. 9) into a central zone formed by the annular shoulder 50a Opening the nozzle engages the holding tube 50 so that the injection nozzle is centered in the nozzle holder tube. In addition, the inner diameter of the nozzle holder tube 50 and the outer diameter of the injection nozzle 14 are coordinated so that there is a narrow, air-filled and in Fig. 1 recognizable annular gap between these two parts. Thus, the injection nozzle 14 is fixedly positioned in the axial direction in the nozzle holder tube 50, the relatively thin wall of the nozzle holder tube 50 is rolled after insertion of the injector 14 and the Zuleitungsröhrchens 16 in the nozzle holder tube 50 at the upper end of the injector or otherwise deformed so that the wall of the nozzle holder tube 50 forms one or more projections 50b which bear against the top of the injection nozzle 14.

As indicated in FIG. 1B, the retaining flange part 44 and the nozzle holder tube 50 are welded together in a gas-tight manner in accordance with the invention.

Fig. 1 shows a Halteflanschstück 40 enclosing strap 60 from a profiled, relatively thin-walled metal strip, which is designed in the manner of a hose clamp or pipe clamp and of which Fig. 8 shows an isometric view. This strap forms with a ring portion 62 (see Fig. 8) - seen in the direction of the axis 10a - an almost closed annular region, to which two seen in the axial direction approximately rectilinear clamping straps 64 follow, in each of which a hole for the passage of a in FIG 8 together with a clamping nut with 66 designated clamping screw. In the region of the ring section 62, the clamping band 60 has a cross-sectional profile which is recognizable in particular in FIG. 1 and whose cross-sectional shape corresponds approximately to a U with inclined lateral limbs whose inclination is matched to that of the oblique flanks 40d and 40e of the retaining flange piece 40. As long as the clamping screw 66 or its clamping nut is not tightened, the two clamping straps 64 extend at a certain distance from each other.

As can be seen from FIG. 1, between the retaining flange part 44 and the retaining flange piece 40 there is a sealing disk 68 shown in FIG. 6, the shape of which in a plan view corresponds approximately to a circular disk with a central opening 68a; this sealing disc can be fitted onto the collar 44b of the retaining flange part 44 and serves for the axial sealing between the retaining flange piece 40 and the retaining flange part 44.

After the retaining flange portion 44 with its collar 44b attached to the nozzle holder tube 50 and the clamping band 60, which has not yet been provided with the clamping screw 66 has been placed in an expanded state around the retaining flange piece 40, the sealing washer 68 and the retaining flange 44, it is with help the clamping screw 66 contracted and tense, so that it not only holds together with appropriate adaptation to the shape and dimensions of the clamping band 60 parts, but also braced against each other in the direction of the axis 10a. Fig. 1 still shows a spacer ring 70 between the collar 46a of the lowermost cooling plate 46 and the Halteflanschteil 44, but this spacer ring could also be omitted with appropriate dimensional ratios.

At the lower end of the holding tube 26 shown in Fig. 1, a circular disc-shaped metallic end seal 72 shown in Fig. 7 is attached, which, as indicated in Fig. 1, is connected to the lower end of the holding tube 26 by means of a circumferential gas-tight weld. FIG. 7 also shows a central passage opening 72a of the end seal 72, which releases a nozzle opening 14b of the injection nozzle 14. Finally, FIG. 7 also indicates an annular sealing bead 72b embossed in the end seal 72, which is a height-elastic full or half bead projecting in the direction of the injection nozzle 14, the comb of which is lower than that shown in FIG End face of the annular shoulder 50a of the nozzle holder tube 50 is gas-tight and liquid-tight pressed.

According to the invention, a gas-filled insulating gap is provided between the seal 72 and the end face of the injection nozzle 14 facing away from the supply pipe 16.

The protection and attachment of the metering device 12 is shown in Fig. 1, in particular metallic protective sleeve 80 which encloses the metering device 12 and with a according to FIG. 1 lower annular collar 80a the support flange 42a of the receiving sleeve 42 engages below and due to a measure to be described is pressed against the uppermost heat sink 46. For this purpose, but especially for fixing the metering device 12 in the injection device 10 in the peripheral wall of the protective sleeve 80 over the circumference of the latter spaced apart holding tabs 80b are formed, by particular U-shaped die cuts, and these retaining tongues can after insertion of the metering device 12, as shown in FIG. 1, from the peripheral wall of the Protective sleeve 80 are bent out inwardly so that they rest against the bottom according to FIG. 1 edges of recesses 12 b, which are provided on the outer circumference of the metering device 12. With corresponding dimensional ratios, this also makes it possible without further ado that the metering device 12, the support flange 42a of the receiving sleeve 42 and the annular collar 80a of the protective sleeve 80 are pressed against each other in a sealing manner.

According to the invention, the supply pipe 16 is formed by a relatively long metal tube, the total cross-sectional area in relation to its length between the injector 14 and the metering device 12 is extremely small and the wall thickness is only so large that the supply tube has the required mechanical stability, even to the fluid pressure of the fluid delivered by the aforementioned pump through the tube. In this connection, it should be mentioned that the length of the supply pipe is to be understood as meaning the length of its flow channel 16a, irrespective of whether the latter and the holding pipes 50 and 26 have a straight course or a different course, as illustrated in FIG , In addition, for reasons of stability, the cross-sectional area of the tube wall 16b should be larger than the cross-sectional area of the flow channel 16a, for the sake of the lowest possible

Heat input from the injection nozzle 14 in the metering device 12, however, preferably at most about eight to ten times the cross-sectional area of the flow channel 16a amount. In this context, for the sake of completeness, it should also be mentioned that the supply tube 16 can also contain more than one flow channel, in particular two flow channels, in which case the sum of the cross-sectional areas of these flow channels replaces the cross-sectional area of the one flow channel 16a. As indicated in FIG. 1, the supply tube 16 terminates inside the metering device 12 where it is to be connected to an outlet of a metering or control valve of the metering device 12. For a tight introduction tion of the feed tube 16 in the metering device 12 provides a penetrated by the supply tube seal, in particular a in Fig. 1 shown so-called O-ring 86. As already revealed from the foregoing description, the Invention ^¬ proper injection device according to the invention in several areas designed that as little heat as possible is introduced into the dosing device and that there is a strong drop in temperature between the injection nozzle and the dosing device. The following designs contribute in particular, both in their entirety and individually:

The thin supply tube 16 with a small cross-sectional area of its wall in relation to the length of its flow channel or its flow channels.

The greatest possible reduction in the material cross-sections between the area of the injection device containing the metering device and the area of the injection device containing the injection nozzle, wherein the following design features are important:

the cross-sectional reduction of the retaining flange piece 40;

- The connection of said two areas using the thin-walled strap 60th

(3) Reduction of the material cross-section of the injection device between the air-cooled region formed in particular by the cooling plates 46 and the connecting region formed in particular by the retaining flange part 44. (4) At least one gas-filled and therefore heat-insulating annular region between the supply tube 16 and the tubular receiving portion for the injection nozzle 14 and most of the length of the supply tube.

(5) Gas-filled gap between the exhaust pipe and the holder designed in particular as a holding plate 32 for said tubular receiving area for the injection nozzle and the supply pipe. (6) Most extensive shielding of the injector and said tubular holding portion by the end seal 72.

(7) Gas-filled gap between the end seal and an end face of the injection nozzle 14 facing away from the supply pipe 16.

(8) At least substantially prevent the entry of hot exhaust gases into the injection device directly at that point of the injection device at which the liquid to be injected into the exhaust pipe exits the injection device, in particular through the end seal 72.

(9) Shielding of the air-cooled area between the metering device 12 and said tubular receiving area relative to the hot exhaust pipe 28 by a shielding member, which in particular has the shape of the shielding plate 38.

In Fig. 9, the interior of the injection nozzle 14 is shown only schematically, since the interior of the injection nozzle can be designed in different ways The shown in Fig. 9 lower portion of the supply tube 16 is liquid-tightly connected to the injection nozzle 14 around, in particular welded, and the Flow channel 16a of the supply tube 16 merges into a flow channel 14c of the injection nozzle 14, which at the nozzle Opening 14b ends. As indicated in FIG. 9, the nozzle opening 14b may be tapered in cross-section.

Preferably, the injection nozzle 14 is formed so that it can produce a cone-shaped spray 100 shown in Fig. 1, which is directed to the mixer 30.

According to the invention, the holding plate 32 is designed and adapted to the exhaust pipe 28 and attached to the holding tube 26 so that at least one of the following features and preferably all of the following features results:

The remote from the metering device 12 free end of the injection device 10 terminates in the opening 28a of the exhaust pipe wall 28b or passes through this opening only slightly.

The axis 10 a of the injection nozzle 14 forms an acute angle with the exhaust pipe axis 28 c, which is directed in the direction of the mixer 30. The axis of the spray jet 100 generated by the injection nozzle 14 forms an acute angle with the exhaust pipe axis 28c.

The side facing away from the metering device 12 front side of the injection device 10 is oriented with respect to the in Fig. 1 indicated by an arrow G flow direction of the exhaust gases so that the exhaust stream is not directed against this end face of the injection device 10 but the axis of the nozzle opening of the injection nozzle 14th forms an acute angle with the flow direction of the exhaust gases or is approximately rectified with this flow direction.

Claims

PATE NTAN SP RICK

1. reducing agent metering and injection module for attachment to a reduction catalyst containing exhaust pipe for hot exhaust gases of a particular operating with changing load internal combustion engine, wherein the module for a liquid reducing agent a metering device and downstream of the same has an injection nozzle, dad u rch geke nzeich net in that the injection nozzle is arranged in a nozzle holding tube and connected to the metering device via a supply tube containing at least one flow channel for the reducing agent, wherein

(a) the length L of the flow channel is at least 20 mm,

(b) the ratio Vi between L and the total cross-sectional area of the feed tube is at least 3 mm ^-1 , and

(c) the ratio V ₂ between the material cross-sectional area and the flow channel cross-sectional area of the delivery tube is at least 2.5 and at most 50.

2. Module according to claim 1, characterized in that L is at least 30 mm.

3. Module according to claim 1, characterized in that L is at least 40 mm.

4. Module according to claim 1, characterized in that L at most

50 mm.

5. Module according to claim 1, characterized in that Vi is at least 7 mm ^"1 .

6. Module according to one of claims 1 to 5, characterized in that Vi is greater than 10 and smaller than 30 mm ^"1 .

7. Module according to claim 6, characterized in that i is at least 18 mm ^"1 .

8. Module according to claim 7, characterized in that Vi at least

22 mm ^"1 is.

9. Module according to one of claims 1 to 8, characterized in that Vi is smaller than 27 mm ^"1 .

10. Module according to claim 9, characterized in that Vi 22 bis

23 mm ^"1 .

11. Module according to one of claims 1 to 10, characterized in that V _{2 is} at least 3.

12. Module according to one of claims 1 to 11, characterized in that V _{2 is} at most 20.

13. Module according to claim 12, characterized in that V _{2 is} at most 10.

14. Module according to claim 11, characterized in that V _{2 is} greater than 4.

15. Module according to claim 14, characterized in that V _{2 is} greater than 6.

16. Module according to one of claims 1 to 15, characterized in that V _{2 is} 7 to less than 10.

17. Module according to claim 16, characterized in that V ₂ 8 to 9

is.

18. Module according to one of claims 1 to 17, characterized in that the flow channel cross-sectional area is at least equal to the flow cross-sectional area of the outlet opening of the injection nozzle.

19. Module according to one of claims 1 to 18, characterized by a valveless injection nozzle.

20. Module according to one of claims 1 to 19, characterized in that the total cross-sectional area of the supply tube is only a fraction of the inner cross-sectional area of the nozzle holder tube along the supply tube.

21. Module according to claim 20, characterized by a gas-filled annular chamber between the supply tube and the nozzle holder tube.

22. Module according to one of claims 1 to 21, characterized in that the nozzle holder tube extends over more than half the length of the supply tube.

23. Module according to one of claims 1 to 22, characterized by a nozzle holding tube enclosing the outer holding tube.

24. Module according to claim 23, characterized in that the outer

Holding tube and the nozzle holder tube form a gas-filled annular chamber between them.

25. Module according to one of claims 1 to 24, characterized in that the nozzle holder tube extends in the longitudinal direction of Zuieitungsröhrchens to a side facing away from the latter end face of the injection nozzle.

26. Module according to one of claims 1 to 25, characterized in that the end region of the nozzle holding tube facing away from the metering device is closed gas-tight except for a passage opening for the reducing agent to be injected.

27. Module according to claim 26, characterized in that the end facing away from the metering device of the nozzle holder tube and the injection nozzle all around tightly against each other.

28. Module according to claim 23, characterized in that the outer holding tube extends in the longitudinal direction of Zuieitungsröhrchens up to the end facing away from the metering device of the nozzle holder tube.

29. Module according to claims 24 and 28, characterized in that the side facing away from the metering end of the outer holding tube is gas-tight in particular all around a gasket, which covers the injector, having an outlet opening releasing and the annular chamber between the nozzle holder tube and the outer holding tube closes gas-tight in particular.

30. Module according to claim 29, characterized by a gas-filled

Insulating gap between the sealing washer and an end face of the injection nozzle facing away from the supply tube. Module according to Claim 23, characterized in that the module has a first assembly containing the injection nozzle, the supply pipe, the nozzle holder tube and the metering device, and a second assembly containing the outer holding tube, and in that the two assemblies are positively connected to one another by means of a detachable connection device.

Module according to one of claims 1 to 31, characterized in that an injection nozzle facing the end portion of the metering device is inserted into a extending in the direction of the injector receiving sleeve, on the outer circumference of which cooling fins are provided.

33. Module according to claim 32, characterized in that the cooling ribs are formed by arranged on the receiving sleeve metal discs, which are arranged in the longitudinal direction of the receiving sleeve at intervals from each other.

34. Module according to claims 31 and 32, characterized in that on the second assembly is provided with respect to the outer holding tube in the radially outwardly extending annular first holding flange, that the first assembly on one of the injection nozzle facing end portion of the receiving sleeve has an annular second retaining flange extending outwardly therefrom in the radial direction, and in that the connecting device has a tension band which at least predominantly encloses the two retaining flanges and engages over the mutually remote flanks of the two retaining flanges at least in regions.

35. Module according to claim 34, characterized in that the first holding flange is formed by an annular holding flange piece fastened to the outer holding tube, the cross section of which lying in a diameter plane of the holding flange piece being reduced by recesses substantially to the following elements:

(A) two in the axial direction of the Halteflanschstücks spaced from each other, the end faces of the Halteflanschstücks forming flanks, which are inclined relative to the axial direction so that they approach each other in the radially outward direction, and

(B) a radially inner mounting portion for attaching the Halteflanschstücks on the outer holding tube.

36. Module according to claim 35, characterized in that the tensioning band is a metal band with free band ends almost closed to a ring, which can be tightened by reducing the ring diameter by means of a tightening screw, and in that the annular portion of the tension band lies in a plane lying in a diameter plane Cross section has an approximately U-shaped, towards the Zuleitungsröhr- Chen opening profile, the two legs are inclined to each other and form a radially inwardly opening acute angle with each other.

37. Module according to one of claims 1 to 36, characterized by a shield-like retaining plate with a gas-tight connectable to the exhaust pipe peripheral edge region and a passage opening for the injection nozzle and the supply tube enclosing the jacket tube, which is welded gas-tight around with the edge of the passage opening.

38. Module according to claim 37, characterized in that the passage opening of the holding plate is formed by a pipe socket-like collar of the holding plate.

39. Module according to claim 37, characterized in that the holding plate is stepped along its peripheral edge region in the direction of the metering device and adapted to the exhaust pipe to form a gas-filled, surrounded by the peripheral edge region insulating gap between the retaining plate and the wall of the exhaust pipe.

40. Module according to claims 23 and 37, characterized in that the jacket tube is formed by the outer holding tube.

41. Module according to claim 37, characterized by a shield-like

Shielding element with a recess for the passage of the injection nozzle and the supply tube enclosing the jacket tube, said shielding of the metering device facing side of the holding plate at a distance from this is immediately adjacent.

42. Module according to one of claims 1 to 41, characterized in that the average wall thickness of the supply tube is at least 0.2 mm.

43. Module according to one of claims 1 to 42, characterized in that a remote from the injection nozzle end portion of the supply pipe engages in a receiving channel of the metering device and is sealingly enclosed therein by a sealing ring made of a soft elastic material.

44. Module according to one of claims 1 to 43, characterized in that the metering device is arranged in a latter holding the protective and holding sleeve and fixed in this.

45. Module according to one of claims 1 to 44, characterized in that the metallic parts of the module consist of a stainless steel.

46. Module according to one of claims 1 to 45, characterized in that the metering device includes an electrically controlled metering valve.

47. Module according to one of claims 1 to 46, characterized in that the module is designed for injecting an aqueous urea solution into nitrogen oxide-containing exhaust gases.