In modern motor vehicles having compression-ignition internal combustion
engines due to the increasingly stringent emission limits, among other things,
nitrogen oxides (NOx) must be reduced in the exhaust stream. A method used for this
purpose is catalytic reduction (so called "SCR = Selective Catalytic Reduction") b5 y
means of a NOx reduction catalyst. In the course of this exhaust gas aftertreatment, a
reducing agent is fed using a pump from a reservoir to a dosing module, which is
localized in the range of the exhaust gas line of the internal combustion engine. By
means of the dosing module, a precisely defined amount of the reducing agent is
10 given intermittently into the exhaust stream upstream of the NOx reduction catalyst.
A urea-water solution (so called "AdBlue ®") is generally used as the reducing agent.
In order to position the dosing module as closely as possible to the exhaust
stream, the lower portion of the dosing module is actively cooled with the injection
nozzle located therein for the reducing agent. This ensures that even when a close
15 arrangement of the metering module, a temperature of 120°C is not exceeded in the
area of the injection nozzle. A disadvantage of this embodiment lies in the lack of
cooling of the remaining components of the dosing module, in which normally the
actuating magnet for the injection valve is arranged, and the connection of the dosing
module is performed by means of an electrical plug-connector. Due to the only partial
20 cooling, such a dosing module is not suitable for ambient temperatures exceeding
160°C, otherwise the plug connector and/or the coil of the actuating magnet may
cause permanent damage.
DE 44 36 397 A1 describes a device for after treatment of exhaust gases.
Herein, a reducing agent is injected with the aid of a dosing device connected
25 upstream to a reduction catalyst into an exhaust pipe.
The dosing device comprises, inter alia, a control valve, a dosing valve and a
cooling device. The cooling device is designed as a cooling jacket. This is connected
to the cooling water circuit of the internal combustion engine, and provides an
3
efficient cooling of the dosing device which is exposed to the high temperatures of
the exhaust pipe during the vehicle operation. However, the cooling jacket allows
only a partial cooling, which can lead to lasting damage to the electrical actuating
magnet and/or the plug connection.
EP 2 192 280 A1 relates to a thermal management system for a dosing devic5 e
for urea-water solution in an exhaust system, wherein an injector is cooled. For this
purpose, a cooling liquid is used, which is taken from the engine cooling circuit. The
cooling liquid flows through the injector into coolant channels. Downstream of the
injector, the cooling liquid is returned to the engine cooling circuit.
10 DE 101 29 592 A1 discloses a dispensing assembly for a reducing agent in a
motor vehicle. This includes a housing, in which there is a pump for delivering
reducing agent. The pump generates compressed air during the operation, wherein
guide plates cause the compressed air stream around the pump. Herein a turbulent
swirling of the stream of compressed air takes place. This is done in a region
15 immediately downstream of the air inlet. Thereby, the cooling effect of the
compressed air of the streamed component is increased and also reaches a
temperature of the injected reducing agent. An active water cooling is not provided in
this exhaust arrangement.
The object of the invention is to provide a completely water cooled dosing
20 module, which is able to permanently withstand high temperatures in the range of an
exhaust pipe of a compression-ignition internal combustion engine.
DISCLOSURE OF THE INVENTION
A dosing module is disclosed for injecting a reducing agent, in particular an
25 aqueous urea solution, into an exhaust pipe of an internal combustion engine,
particularly a compression-ignition internal combustion engine, for reducing nitrogen
oxides in the exhaust stream, wherein the dosing module includes a main cooling
element, which flows through a cooling fluid, in particular for cooling an injection
4
valve for the reducing agent. According to the invention, an additional cooling
element bypassed by cooling fluid, in particular for cooling in region of an electrical
plug-connection and an electromagnet to actuate the injection valve, is placed on the
main cooling body, wherein a guide insert for the cooling fluid is arranged in the base
cooling element5 .
By guide insert, an optimized cooling of the direct end portion of the injection
valve comes directly in contact with the exhaust gas stream, in which an outlet
opening is localized for the reducing agent. Hereby a continuous, trouble-free
operation of the dosing module is also guaranteed at ambient temperatures of 160°C
10 or above. In conjunction with the additional cooling element attached to the main
cooling element, an active cooling is given to the cooled assemblies of the dosing
module, in particular of the electromagnet for actuating the injection valve, the
electrical connector and the reducing agent feeder not coming in contact with the
exhaust gas ( top).
15 An embodiment of the dosing module provides that the guide insert causes a
substantially u-shaped flow path of the cooling fluid in the region of an end portion of
the injection valve.
Hereby the hot lower end portion of the injector that comes into direct contact
with the exhaust gas is surrounded by the cooling fluid, while the cooler zones of the
20 dosing module, in particular of an electromagnet, the plug-connector, and the
reducing agent supply flows through only subordinated cooling fluid and thereby
cooled.
In a further embodiment of the dosing module, it is provided that an inlet port
is arranged in the region of the base cooling element and an outlet port is arranged in
25 the region of the additional cooling element for the cooling fluid.
Hereby, the cooling water is fed to the dosing module in a zone of a
particularly high temperature, while the discharge of the heated cooling fluid takes
place in a cooler zone of the dosing module.
5
In accordance with a further embodiment of the dosing module, the inlet port
and the outlet port are connected to a cooling circuit of the internal combustion
engine, and cooling water of the internal combustion engine is used as the cooling
fluid.
Hereby, the existing cooling circuit of the internal combustion engine can b5 e
used in a simple manner to control the temperature of the dosing module.
According to a further advantageous embodiment, the guide insert has a
circumferential flange having a shank, which passes into a first taper portion. The
flange together with the shank allows a simple structural integration in a cooling
10 device, in particular a cooling element, of the dosing module. The shank of the guide
insert is of hollow-cylindrical design, whereas the first taper portion has a slightly
conical shape.
In a further embodiment of the dosing module, a center portion is connected
to the first taper connection portion, which merges into a second taper portion having
15 at least two recesses.
Due to the underlying recesses in the second tapering portion, the cooling
water is guided initially to the hot exhaust gas side end section of the injection valve
and after passing through the same, it enters in the cooler zones in the region of the
additional cooling element. A central portion of the guide insert has an approximately
20 hollow cylindrical shape in order to cause the u-shaped flow of the end portion of the
injection valve radially surrounded by the base cooling element. A different shape of
the central portion is also possible depending on the installation conditions.
In a further embodiment of the dosing module, a lower edge of the guide
insert of the at least two recesses is interspersed in crown-like manner.
25 Thereby, the formation of regions in the cooling element is avoided, in which
only a small flow rate of the cooling fluid is prevailed. Preferably at least six recesses
are disposed in the region of the second (lower) taper portion in each case having a
geometry that is approximately equal to that of a divided oval or a semicircle.
6
A further embodiment provides that at least one drainage opening is provided
between the main cooling element and the additional cooling element.
By this opening, the electromagnet of the injection valve is protected from the
injected water splashed from outside, which cannot be drained in controlled manner.
The opening thereby limits the height to which water seepage - without the risk o5 f
permanent damage to the valve - can no more rise. An embodiment of the dosing
module provides that the guide insert is formed with a metallic material, particularly
with sheet metal.
This enables a simple and suitable mass production using known
10 manufacturing methods and machines. In addition, the metallic material ensures a
sufficient temperature resistance. Optionally, instead of a metallic material, a
thermally sufficient resilient, possibly reinforcing fibers, which are reinforced with
thermosetting or thermoplastic high-performance plastic, are used.
15 BRIEF DESCRIPTION OF DRAWINGS
With reference to the drawing, the invention will be described below in more
detail.
Figure 1 shows a schematic perspective view of a water cooled dosing
module.
20 Figure 2 shows an isometric side view of a guide insert.
Figure 3 shows an isometric view of an inventive guide insert oblique from
above.
Figure 4 shows a simplified cross-sectional view of the exhaust gas
surrounding the (lower) main cooling element of the dosing module along the section
25 line IV-IV in Figure 1.
Figure 5 shows a complete longitudinal section of the water-cooled dosing
module.
Figure 6 shows an enlarged view of the section VI in Figure 5.
7
EMBODIMENTS OF THE INVENTION
Figure 1 shows a schematic view of an inventive water cooled dosing module
for injecting a reducing agent into an exhaust stream of a self-ignited internal
combustion engine5 .
A dosing module 10 includes, among other things, a main cooling element 12,
on which an additional cooling element 14 is placed. The main cooling element 12
has a tubular inlet fitting 16 for feeding a cooling fluid, which is a cooling water of a
cooling circuit of a not shown, self-ignited internal combustion engine. Further, the
10 additional cooling element 14 is provided with an outlet port 18 for discharging the
supplied cooling water. Starting from the inlet port 16, the cooling water flows firstly
through the main cooling element 12, and passes from there in the additional cooling
element 14 and leaves it again through the outlet port 18. The cooling water flows
against the temperature path (temperature gradient) prevailing in the dosing module
15 10 from the hot main cooling element 12 in the additional cooling element 14, which
is relatively colder. The main cooling element 12 and the superimposed additional
cooling element 14 are formed here as at least two part cooling water jacket, through
which cooling water can flow, where the water jacket is made of a formed sheet of
suitable thickness. The inner hollow cooling element 12, 14 with a respective roughly
20 cylindrical outer geometry ensure that the dosing module 10 can be operated
continuously and reliably at ambient temperatures in the range of 160 °C or higher,
which can easily occur in the region of an exhaust stream or in the vicinity of an
exhaust pipe of an internal combustion engine.
In addition, a supply 20 for the reducing agent as well as an electric plug
25 connection 22 is connected on the upper side with an additional cooling element 14.
Via the supply 20, the dosing module 10 is supplied with a suitable reducing agent, in
particular an aqueous urea-water solution (e.g. AdBlue®). The reducing agent is fed,
by means of a pump, from a storage tank into a not shown connection line, which is
8
connected to the supply 20. By means of the dosing module 10, the reducing agent is
injected intermittently temporally in exactly dosed amount into a not illustrated
exhaust pipe of the internal combustion engine in a similar manner. The injection of
the reducing agent with the aid of the dosing module 10 is carried out upstream of a
reduction catalyst suitable for the course of the chemical reaction process durin5 g
SCR-method. Between the main cooling element 12 and the additional cooling
element 14, small drainage holes are present, two of which are visible and are
referred with the reference numerals 24 and 26.
Figures 2 and 3, at the same time refer to the further progress of the
10 specification, illustrate one (cooling water) guide insert according to the invention in
a perspective side view and in an isometric view, which is oblique from above. A
substantially tubular guide insert 30 for the cooling water includes, among other
things, an annular flange 32, which continues downward into a hollow cylindrical
shaft 34. Through the shaft 34, among other thing, a centering of guide insert 30
15 within the lower cooling element is facilitated. The shaft 34 passes into a slightly
conical first taper portion 36, to which a substantially hollow cylindrical central
portion 38 is connected. Deviating from the shown hollow cylindrical shape of the
central portion 38, this, in particular in dependence of the geometric proportions of
the main cooling element has a different spatial form. The central portion 38 adjoins a
20 second tapered portion 40. In the tapered portion 40, in the shown embodiment, a
total of six recesses are placed, of which only three front recesses 42, 44, 46 are
provided with reference numerals. The recesses have a (lower) edge 48 of the guide
insert 30, i.e. the recesses are opened at the bottom. Thus, inter alia, the formation of
spatial regions within the cooling element is avoided, in which a flow velocity of the
25 cooling water drops to a very small value or to zero.
The recesses have a geometric shape, which corresponds to approximately
half of the oval and are preferably introduced over the circumference of the second
tapered section 40 in uniformly distributed manner. An alternative geometric
9
configuration such as semi-circular recesses is also possible. In addition, a different
number of the recesses optionally distributed unevenly around the circumference may
be provided. A number and/or cross-sectional area of the recesses is accessed such
that under all operating conditions of the internal combustion engine, an optimum
cooling water passage is ensured for cooling of the dosing module5 .
During operation of the dosing module, a flow path 50 of the cooling water,
which extends parallel to an outer surface 52 of the guide insert 30, which then passes
through the six recesses and eventually in parallel with an inner surface 54 of the
guide insert 30, extends back through a central opening 56 of the guide insert 30.
10 Figure 4 illustrates a simplified (partial) cross section of the exhaust gas
surrounding the (lower) main cooling element of the dosing module along the section
line IV-IV in Figure 1.
The dosing module 10 is fixed by means of a clamp 60 on a nozzle 62 of the
exhaust pipe of the internal combustion engine that is not shown in detail. The
15 injection valve 64 disposed within the dosing module 10includes, inter alia, a valve
needle 66, which is accommodated in a guide 68in vertically displaceable manner. By
means of the valve needle 66, an outlet opening 70 is opened and closed
intermittently to allow injection of a precisely defined amount of reducing agent. The
vertical displacement of the valve needle 66 is performed by means of an
20 electromagnet, not shown in Figure 4. The guide 68, a non- designated lower tip of
the valve needle 66 and the outlet opening 70 for the reducing agent are located in an
end portion 72 of the injector 64, which comes into direct contact with the exhaust
gas stream of the internal combustion engine and is consequently exposed to very
high temperatures.
25 The cooling water from the cooling circuit of the internal combustion engine
passes through the inlet port 16 in the main cooling element 12 and is led around by
the action of guide insert 30 in the direction of a U-shaped flow pattern 50 indicated
by the dotted line about the hot end portion 72 of the injection nozzle 64. Hereby
10
according to the invention the primary cooling of the end portion 72 of the injector 64
exposed to high temperature is performed in such a manner that the dosing module 10
functions reliably even at ambient temperatures of 160°C or above. The cooling water
flows first along the outer surface 52 of the guide insert 30 through the underlying
recesses 42, 46 of the guide inserts 30 and then passes on the inner surface 54, furthe5 r
the cooling components of the dosing module 10, not shown in Figure 4, are exposed
in the portion of the main cooling element 12, but here not shown additional cooling
element.
Figure 5 illustrates a complete longitudinal section of the water-cooled dosing
10 module.
The dosing module 10 is dragged by means of the inlet port 16 and the outlet
port 18 into the not shown cooling circuit of the internal combustion engine. The inlet
port 16 is attached to the main cooling element 12, while the outlet port 18 is in a
hydraulic connection to the additional cooling element 14. The supply of the reducing
15 agent takes place via the supply 20, while the feeding of the dosing module 10 is
carried out with electric energy via the waterproof plug connector 22. The guide
insert 30 with the recesses 42, 46 is included in the main cooling element 12.
By means of an electromagnet 80, the valve needle 66 in the guide 68 is
vertically moved up and down in order to realize the intermittent opening and closing
20 of the outlet opening 70 of the injection valve 64. The activation of the electromagnet
80 and thus the valve needle 66 is effected by means of an electronic control and/or
regulating device, not shown, depending on the operating state of the self-igniting
internal combustion engine. Through the drain opening 24 that is prevented from
splashing water can permanently remain in the portion of the electromagnet 80
25 encapsulated with an electrical insulation from outside.
Figure 6 shows an enlarged view of the section VI of the figure 5.
The drainage opening 24 is present between the main cooling element 12 with
the guide insert 30 and the attached additional cooling element 14. Through the drain
11
opening 24, inter alia, the dosing spray water 82 ingress to temporarily increase to a
maximum level 84 from outside. When exceeding the maximum level 84, it may
otherwise cause permanent damage to the injection valve 64 and the encapsulated
electromagnet 80 within the dosing module. Statically the spray water 82 may not
exceed a minimum level 865 .
12

Claims:
1. A dosing module (10) for injecting a reduction agent, in particular a ureawater
solution, into an exhaust pipe of an internal combustion engine, in
particular of a self-igniting internal combustion engine, to reduce nitrogen
oxides in the exhaust stream, wherein the dosing module has a main coolin5 g
element (12) through which a cooling liquid flows, in particular for cooling an
injection valve (64) for the reduction agent, characterized in that, an
additional cooling element (14), through which the cooling liquid likewise
flows, in particular for cooling in the region of an electrical plug connection
10 (22) and of an electromagnet (80) for actuating the injection valve (64), is
placed on the main cooling element (12), wherein a guide insert (30) for the
cooling liquid is arranged in the main cooling element (12).
2. The dosing module (10) according to claim 1, wherein the guide insert (30)
causes a substantially u-shaped flow path (50) of the cooling fluid in the
15 region of an end portion (72) of the injection valve (64).
3. The dosing module (10) according to claim 1 or 2, wherein an inlet port (16)
is arranged in the region of the base cooling element (12), and an outlet port
(18) for the cooling fluid is arranged in the region of the additional cooling
element (14).
20 4. The dosing module (10) according to one of the claims 1 to 3, wherein the
inlet port (16) and the outlet port (18) are connected to a cooling circuit of the
internal combustion engine, and cooling water of the internal combustion
engine is used as the cooling fluid.
5. The dosing module (10) according to one of the claims 1 to 4, wherein the
25 guide insert (30) has a circumferential flange (32) with a shank (34), which
bypasses in the first tapered portion (36).
13
6. The dosing module (10) according to claim 5, wherein a central portion (38) is
connected to the first tapered portion (36), which bypasses in a second tapered
portion (40) having at least two recesses (42-46).
7. The dosing module (10) according to claim 6, wherein a lower edge (48) of
the guide insert (30) is interspersed by the at least two recesses (42-46) i5 n
crown like manner.
8. The dosing module (10) according to one of the claims 1 to 7, wherein at least
one drainage opening (24, 26) is provided between the base cooling element
(12) and the additional cooling element (14).
10 9. The dosing module (10) according to one of the claims 1 to 8, wherein the
guide insert (30) is formed with a metallic material, in particular sheet metal.