DE102011088549A1 - Dosing module for introducing reducing agent into exhaust gas treatment system of internal combustion engine, has passive valve for controlling flow of cooling medium through channels based on dosing module temperature - Google Patents

Abstract

The dosing module (18) has a cooling structure provided with the channels (36) for flow of cooling medium such as cooling water. The cooling structure is provided with a passive valve for controlling the flow rate of the cooling medium through the channels based on dosing module temperature. The passive valve is arranged in an inlet (32) and outlet (34) of the cooling medium.

Description

State of the art

DE 44 36 397 B4 refers to a device for post-treatment of exhaust gases. The device comprises an exhaust gas collection system in which a reduction catalyst for reducing NO _x components of the exhaust gas of the internal combustion engine is arranged. The device further comprises a metering device, comprising an electrically controlled metering valve for the metered introduction of a reducing agent into the flow of exhaust gas supplied to the catalytic converter as a function of values of the NO _x content in the exhaust gas stored in a map in the case of various operating parameters of the internal combustion engine and of the catalytic converter. The valve for controlling the air supply is an electrically controlled control valve which is arranged downstream of the outlet opening of the metering valve and whose outlet opening opens directly into the exhaust gas of the internal combustion engine. The control valve is received by a body, which can be flowed around by a cooling medium, so that the control valve is cooled.

DE 10 2007 003 120 A1 refers to a device for introducing a liquid into the exhaust gas of an internal combustion engine. A cooling device is provided, which cools a holding device holding the injection device, an intermediate section being arranged between the holding device and the injection device and influencing the heat flow between injection device and holding device at least in regions. A cooling device preferably comprises a cooling channel, which is arranged in the holding device and is flowed through by a cooling medium. As a cooling medium, reducing agent, cooling water or fuel can be used. Such a cooling device is very effective, robust and at the same time inexpensive to produce.

DE 10 2009 047 375 A1 refers to a dosing module with liquid cooling. A device for cooling a metering module, in particular for metering in a reducing agent into the exhaust gas tract of an internal combustion engine, is disclosed, wherein the metering module is assigned a cooling device through which a cooling liquid flows. A lateral surface of the metering module is enclosed by a heat sink, through which the cooling liquid flows. The cooling fluid may be fuel or cooling fluid circulating in the internal combustion engine or the reducing agent itself.

US 2010/0242439 A1 relates to a control unit and a control method for an exhaust gas purification system. By injecting a urea solution in the exhaust gas tract of an internal combustion engine, nitrogen oxides contained in the exhaust gas are reduced. The cooling of the device takes place at least partially by cooling water, which circulates within the internal combustion engine.

The dosing modules in exhaust aftertreatment systems have injectors, which must ensure that the injector tips are exposed to a continuous temperature of 120 ° C, and this temperature must not be exceeded. For this reason metering modules are cooled, for example by the cooling water of the internal combustion engines. Cooling the metering modules at the injector tip to ensure a permanent temperature level of 120 ° C leads to a reduction of the temperature load of this component and thus to an increase in the life of the metering, in particular an improvement of its robustness. Cool areas in the vicinity of the metering module, however, are ideal areas for crystallization of the operating / auxiliary substance, in particular the reducing agent. At cool ambient temperatures and cold exhaust gas, there is a risk of urea deposits in the area of the dosing module. Therefore, it is desirable to cool the metering module locally very efficiently, but on the other hand to ensure a temperature level at which no deposits occur, in particular at the metering module. These requirements run counter to each other, remedy is however necessary.

Presentation of the invention

According to the invention it is proposed to implement a cooling water flow control in the heat sink of a dosing in an exhaust aftertreatment system, wherein a temperature-dependent change in the cooling water flow rate, so that the temperature of the Dosiermodules, in particular the temperature of the temperature-sensitive injector tip can be permanently ensured at the required maximum allowable temperature level.

In a particularly advantageous embodiment of the invention underlying idea is at a dosing, in particular in the heat sink of the cooling water flow at the cooling water inlet in front of a ring surrounding the injector tip channel influenced by a passive valve, in particular by means of a bimetallic strip. Depending on the temperature setting in the heat sink traversed by the cooling medium channels, the cooling water flow is completely blocked, throttled or released by a corresponding deformation of the passive valve designed as a bimetal strip.

If the temperature in the heat sink, in which the channels for the cooling medium extend too high, opens the passive valve, which is designed in particular as a deformable bimetallic strip, the inflow of the cooling medium, so that an increase in the flow rate of the cooling medium enters through the heat sink and increases its cooling becomes. The passive valve in the form of a bimetallic strip can be installed during installation of the heat sink, the channel system, in particular on the injector tip of the heat sink.

A particularly easy to produce embodiment is to attach the passive valve performing bimetallic strip to a corresponding connection to the heat sink cohesively, so that can be achieved by the channel system of the heat sink a very easy to achieve influencing the cooling water flow. Since the heat sink is generally made of several components, there is access to the channel system, so that in particular designed as a bimetallic strip passive valve is directly mountable.

In particular, the passive valve can be attached in the form of a bimetallic strip at the entrance of a cooling ring or in the region of the connection of the inlet channel.

Advantages of the invention

The proposed solution according to the invention avoids the installation of a valve to be controlled. The inventively proposed passive valve in the supply line of the cooling medium are flow cross-sections depending on the temperature that prevails in the heat sink automatically without external actuators free or changed them. In the closed position, ie at a prevailing in the heat sink relatively low temperature level only a minimum flow cross-section (throttle area) is released from the inlet of the cooling medium, while at an elevated temperature, even below the critical temperature of 120 ° C, at the injector tip may occur, a maximum flow cross-section in the inlet for the cooling medium released, so that the heat sink is subjected to maximum flow rate of the cooling medium. The cooling medium may be both the cooling water of the internal combustion engine. The cooling medium could just as well be an operating / auxiliary substance such as fuel or AdBlue ^® .

Brief description of the drawings

With reference to the drawings, the invention will be described in more detail below.

It shows:

1 a dosing module,

2 the components of an exhaust aftertreatment system for the reduction of NO _x components in the exhaust gas of internal combustion engines in a schematic representation,

3 a first embodiment of the invention proposed improved cooling of the dosing,

4 a further, second possible embodiment of the solution proposed according to the invention,

5 in a schematic representation of the passive valve in the form of a bimetallic strip in its throttle position, and

6 the passive valve on the cooling medium inlet in the heat sink of the dosing module at elevated temperature and maximum flow cross-section for the cooling medium.

variants

The representation according to 1 is a dosing module 18 for an exhaust aftertreatment system, as will be explained in more detail below.

From the illustration according to 1 this results in that in the dosing module 18 which is in a holder 41 is included, a flange 30 is attached. The flange 30 includes a cooling medium inlet 32 and a cooling medium drain 34 , Inside the Dosiermodulkörpers runs a channel 36 , on the one hand with the cooling medium inlet 32 and on the other hand with a cooling medium drain 34 connected is. A branch point is by reference numerals 38 characterized. Laterally on the dosing module 18 is an electrical contact 44 provided over which the dosing via an in 1 not shown control unit is controlled. Above the dosing module 18 there is a connection for supplying an operating / auxiliary substance, in particular a reducing agent, such as urea or a urea water solution for after-treatment of the exhaust gas of the internal combustion engine.

1 shows that in this embodiment, the channel 36 within the housing of the dosing module 18 runs.

The representation according to 2 are to be taken in a schematic representation of the components of an exhaust aftertreatment system.

2 shows that an operating / auxiliary substance in a storage tank 12 an exhaust aftertreatment system 10 is stored. From the storage tank 12 for storing the operating / auxiliary substance, in particular a reducing agent such as urea or a urea water solution, a suction line extends 14 to a delivery unit 15 , which is generally designed as a pump. On the pressure side of the delivery unit 15 is a pressure line 16 connected, via which the reducing agent to the dosing 18 is directed. The dosing module 18 is at the exhaust tract 20 arranged, the of an elevated temperature level having exhaust gas flow 22 - as in 2 indicated - is flowed through. In the dosing module 18 becomes a spray 24 produced from air and the excipient, as in 2 shown. The spray 24 gets into the exhaust tract 20 introduced and into the exhaust gas flow 22 introduced before this into an SCR chamber 26 , downstream of the dosing module 18 is provided, enters. In the SCR chamber 26 the reduction of NO _x components in the exhaust gas, in particular of self-igniting internal combustion engines, to N ₂ and H ₂ O.

The delivery unit 15 as well as the dosing module 18 be over in 2 schematically illustrated control unit 28 controlled by suitable control lines.

3 shows a first embodiment of the inventively proposed provided with an improved cooling dosing.

As shown in the illustration 3 indicates are on the flange 30 the cooling medium inlet 32 and cooling medium drain 34 connected. At the in 3 illustrated embodiment extends from the cooling medium inlet 32 for the realization of a ring cooling 48 a first channel section 50 on the inlet side through a heat sink 56 with internal channels. To the first channel section 50 the ring cooling 48 closes a second, curved channel section 52 on which the injector tip 42 inside the heat sink 56 of the dosing module 18 encloses. The wrap angle of the second, curved channel section 52 is at least 180 ° around the injector tip 42 around. To the second, curved channel section 52 closes a third channel section 54 on the drain side, leading to the cooling medium drain 34 extends. In the illustration according to 3 are the material of the heat sink for better representation of the channel 56 with only implied in this inwardly extending channels, so that the interior of the heat sink 56 can be shown better. In the embodiment according to 3 is an optimal installation position 99 of the passive valve 60 at the beginning of the canal section 52 , Of course, there is also the option of the passive valve 60 elsewhere in the channel section 52 to arrange.

4 shows a further embodiment of the invention proposed dosing with improved cooling.

4 shows that above the holder 41 in which the heat sink 56 of the dosing module 18 is included, the flange 30 is arranged. Analogous to the representation according to 3 includes the flange 30 the cooling medium inlet 32 and the cooling medium drain 34 , A channel formed by a first channel section 50 a second annular section 53 and a third channel section 54 connects the cooling medium inlet 32 with the cooling medium drain 34 In contrast to the representation according to 3 where a continuous channel path with channel sections 50 . 52 and 54 for the representation of a ring cooling 48 is shown in the heat sink 56 according to the embodiment according to 4 the branch point 38 contain. The two sections 50 and 54 of the channel run like the channels 36 the in 1 variant shown at a junction 38 together. In the in 4 illustrated embodiment is the junction point 38 blocked, so no cooling medium from the cooling medium inlet 32 in the cooling medium drain 34 can get without the annular channel section 53 to have happened.

As shown in the illustration 4 can be further removed, takes place in this embodiment, a ring cooling 48 the injector tip 42 through the second annular channel section 53 .. in the in 4 illustrated embodiment is a passive valve 60 in the third channel section 54 at the with the reference numeral 99 characterized position, which opens or closes depending on the temperature, so that the flow rate of the cooling medium, via the second annular channel section 53 around the injector tip 42 can be routed to the temperature level to which the dosing 18 each exposed, can be adjusted. At high temperature at the dosing module 18 opens the passive valve 60 and the cooling medium can be the channel 36 flow through unhindered. When the temperature is low, the passive valve closes 60 and the flow of cooling medium through the channel 36 is throttled. Analogous to the representation according to 3 , is the upstream part of the channel 36 with reference number 50 referred to and the downstream part of the channel 36 with reference number 54 identified. Analogous to the representation according to 3 is in 4 the material of the heat sink 56 for a better representation of the internally extending channels 50 . 53 . 54 , omitted. The optimal installation positions of the passive valve 60 are in the embodiment according to 4 by reference numerals 99 indicated; In addition, of course, there is also the possibility of the passive valve 60 in the first channel section 50 or elsewhere in the circumference of the annular channel section 53 to arrange.

In other embodiments, instead of a permanent blockade at the junction 38 also a passive valve 60 be used. Is the passive valve 60 closed, a cooling medium short circuit is avoided, and the cooling medium must the annular channel section 53 at the injector tip 42 run through. Opens the passive valve 60 creates a cooling medium short circuit and parts of the coolant bypass the annular channel section 53 ,

The representations according to the 5 and 6 are switching states of the passive valve in the cooling medium body 56 refer to.

The passive valve 60 or its temperature-dependent functions are described below with reference to 5 and 6 described.

In 5 is shown that the passive valve 60 , which preferably by an at least two layers executed bimetallic strip 70 is formed, to a connection 74 on a front side 62 of the here indicated only schematically heat sink 56 is attached. In the heat sink 56 there is a channel that is above the cooling medium inlet 32 is charged. About this flows the cooling medium be it fuel, be it the operating / auxiliary material, be it cooling water in the flow direction 58 the valve 60 to. In the illustration according to 5 is shown that the bimetallic strip 70 , the passive valve here 60 represents, only a throttle cross-section 72 releases, over which the cooling medium from the cooling medium inlet 32 exiting, for example in the first channel section 50 can emerge on the inlet side. Due to the throttle position 64 of the passive valve 60 according to 5 is the heat sink 56 , in which the channels are designed for the circulation of a cooling medium, relatively cold, so that still no temperature-dependent deformation of the passive valve 60 represented by the bimetallic strip 70 occurs.

In the embodiment according to 6 has the heatsink 56 heated. The heating of the heat sink 56 goes over the connection 74 to the through the bimetallic strip 70 illustrated passive valve 60 over, so this from the in 5 illustrated throttle position 64 in his open position 66 passes. The bimetallic strip 70 deforms and goes into its open position 66 over, so that a maximum flow cross-section 68 between the heat sink 56 and the bimetallic strip 70 is released by the above the cooling medium inlet 32 Pending cooling medium in the flow direction 58 For example, in the first channel section 50 as in 3 represented or in the according to 4 directly into the second curved channel section 52 can flow. Because the respective channel sections are the temperature sensitive injector tip 42 of the dosing module 18 is at opening of the passive valve 60 the maximum coolant flow rate ensures effective cooling of the injector tip 42 and whose temperature limitation to a temperature level of well below 120 ° C can be achieved.

Depending on the dimensions of the channels 50 . 52 . 54 in the heat sink 56 and depending on the dimensioning and design of the passive valve 60 forming bimetallic strip 70 can at high temperatures of the heat sink 56 a corresponding flow rate can be realized, but this is limited locally to the area in which the injector tip 42 of the dosing module 18 lies. Since this is the temperature-critical component, their cooling is locally limited, so that the temperature level, the dosing 18 apart from the injector tip 42 remains relatively high in order to avoid unwanted deposits of reducing agent in the form of urea or a urea water solution unconditionally. These opposing requirements, ie a relatively high temperature level on the dosing 18 to avoid unwanted deposits on the one hand and effective cooling of the injector tip 42 on the dosing module 18 to a temperature level of about 120 ° C on the other hand, can be achieved by the solution proposed by the invention in its entirety.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4436397 B4 [0001]
• DE 102007003120 A1 [0002]
• DE 102009047375 A1 [0003]
• US 2010/0242439 A1 [0004]

Claims (10)

Dosing module ( 18 ) for an exhaust aftertreatment system ( 10 ) for NO _x reduction in an exhaust gas flow ( 22 ) by introducing an operating / auxiliary substance ( 24 ) in the exhaust gas flow ( 22 ) with a channel ( 36 . 50 . 52 . 53 . 54 ) for a cooling medium comprising heat sink ( 56 ), characterized in that the heat sink ( 56 ) a passive valve ( 60 ), the temperature-dependent the flow rate of a cooling medium through the channels ( 36 . 50 . 52 . 53 . 54 ). Dosing module ( 18 ) according to claim 1, characterized in that the passive valve ( 60 ) in the inflow ( 32 . 50 ) is arranged for the cooling medium. Dosing module ( 18 ) according to claim 1, characterized in that the passive valve ( 60 ) in the process ( 34 . 54 ) is arranged for the cooling medium. Dosing module ( 18 ) according to claim 1, characterized in that the passive valve ( 60 ) at a meeting point ( 38 ) is arranged, on which a channel ( 36 ) from the coolant inlet ( 32 . 50 ) in the coolant outlet ( 34 . 54 ) passes over. Dosing module ( 18 ) according to one of the preceding claims, characterized in that the heat sink ( 56 ) a ring cooling ( 48 ) for an injector tip ( 42 ) of the dosing module ( 18 ). Dosing module according to the preceding claim, characterized in that the annular cooling ( 48 ) a first channel section ( 50 ), an annular second channel section ( 52 . 53 ) and a third channel section ( 54 ) has drainage side. Dosing module ( 18 ) according to the preceding claim, characterized in that the curved, annular second channel section ( 52 . 53 ) the injector tip ( 42 ) of the dosing module ( 18 ) encloses at least 180 °. Dosing module ( 18 ) according to one of the preceding claims, characterized in that the passive valve ( 60 ) a temperature-dependent deformable bimetallic strip ( 70 ). Dosing module ( 18 ) according to one of the preceding claims, characterized in that the passive valve ( 60 ) in a throttle position ( 64 ) a throttle cross-section ( 72 ) from the cooling medium inlet ( 32 ) releases. Dosing module ( 18 ) according to one of the preceding claims, characterized in that passive valve ( 60 ) in its open position ( 66 ) a maximum cross section ( 68 ) of the cooling medium inlet ( 32 ) releases.

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