DE102014207834A1 - Arrangement for the reduction of nitrogen oxides - Google Patents

Abstract

Arrangement for the reduction of nitrogen oxides in the exhaust gas of an internal combustion engine 1, comprising a metering module 8 for introducing a reducing agent into an exhaust gas-carrying exhaust system 3 with an SCR catalytic converter 7, wherein the metering module 8 is connected to a coolant circuit 16 for cooling the metering module 8, and a flow regulator 17 is arranged in the cooling circuit 16. According to the invention, an arrangement for the reduction of nitrogen oxides is specified, which operates reliably in a compact design in all operating states of the arrangement. This is achieved in that the flow regulator 17 is arranged on the dosing module 8 and is installed directly in a coolant circulation outlet 14 of the dosing module 8.

Description

The invention relates to an arrangement for the reduction of nitrogen oxides in the exhaust gas of an internal combustion engine, comprising a metering module for introducing a reducing agent into an exhaust gas-carrying exhaust system with a catalyst, wherein the metering module is connected to a coolant circuit for cooling the metering and a flow regulator is arranged in the cooling circuit. Furthermore, the invention relates to a method for operating such an arrangement.

The invention relates to the technical field of cleaning exhaust gases of an internal combustion engine installed in a vehicle by means of selective catalytic reduction of nitrogen oxides in an SCR catalytic converter. As the reducing agent, a urea water solution is usually used. This urea water solution is removed during operation of the internal combustion engine from a reservoir and introduced by means of a metering module in the exhaust gas-carrying exhaust system before the downstream SCR catalyst.

State of the art

Such an arrangement for the reduction of nitrogen oxides in the exhaust gas of an internal combustion engine is known from DE 10 2012 206 563 A1 known. The arrangement described in this document has an exhaust system with an SCR catalyst, wherein upstream of the SCR catalyst, a metering module for introducing a reducing agent is arranged. This dosing is connected to the cooling of the same to a coolant circuit of an internal combustion engine to which the assembly is installed. For this purpose, the metering module has a coolant inlet and a coolant outlet, which are connected via corresponding lines to the internal combustion engine or its cooling system. In the return line from the metering module to the internal combustion engine, a flow regulator in the form of a thermostat is installed, which regulates the flow of coolant through the metering module. The regulation takes place in such a way that, at a start, in particular a cold start of the internal combustion engine, the flow of cooling liquid through the metering module is throttled or shut off.

The invention is based on the object to provide an arrangement and a method for operating an arrangement for the reduction of nitrogen oxides, which / works reliably in a compact design in all operating conditions of the arrangement.

Disclosure of the invention

This object is achieved in that the flow control is arranged on the metering module. The arrangement of the flow control on the metering initially contributes to a compact design of the entire arrangement by no independent component must be installed in a corresponding connection line and secured accordingly. The attachment of the flow control to the dosing module can be accomplished with an optimal design without an increase in space. Moreover, it is moreover the case that the dosing module is normally arranged and fastened to the exhaust system, so that no additional fastening is necessary for the flow regulator attached to the dosing module. Because the flow regulator is arranged directly on the dosing module, more precise control of the coolant flow through the dosing module can be carried out since, for example, a temperature recorded in the dosing module can be used for direct regulation of the flow regulator.

In a development of the invention, the flow regulator is arranged in a coolant circulation outlet of the metering valve. In principle, the flow regulator can also be installed in the coolant circulation inlet or directly into the coolant-carrying region of the dosing module, but the incorporation into the coolant circulation outlet has the advantage that overheating of the flow regulator is precluded since the flow regulator is designed in this case to be so then opens by itself.

In a further embodiment of the invention, the flow regulator has a cylindrical needle seat guide and the needle seat guide is inserted directly into a coolant circuit outlet port. This embodiment is particularly advantageous, since no additional conversions or additions to the metering module are necessary in order to grow the flow regulator. The flow regulator may be designed to be inserted into an existing coolant circulation outlet or else the coolant circulation outlet is particularly adapted in terms of its diameter so that an existing flow regulator can be installed therein.

In a development of the invention, the opening direction of the flow regulator is aligned in the flow direction of the coolant. This alignment increases the intrinsic safety of the flow regulator, since this can be designed to open automatically, for example, in the event of overheating.

In a further development of the invention, the flow regulator is a thermostatic valve, which in turn has a bimetallic element in a further embodiment. On the one hand, corresponding thermostatic valves are available in a wide variety of designs and, on the other hand, such is one Thermostatic valve reliably self-regulating. By the above-mentioned orientation of the thermostatic valve so that the opening direction is aligned in the flow direction of the coolant, the bimetallic element is arranged on the influence side in the thermostatic valve possibly up to the interior of the dosing. This ensures a very precise detection of the temperature prevailing in the metering module. In addition, overheating of the thermostatic valve is excluded by this configuration, since the thermostatic valve opens in this case without further action by itself. Basically, the thermostatic valve is designed so that this opens when the coolant temperature exceeds a predetermined minimum value and closes when this minimum value is exceeded. Flowing transitions in the opening operation and closing operation can be represented in the form that the valve throttles more or less within a certain temperature range. In this way, the valve-side coolant temperature in the operating range is very reliable and sensitive.

In a development of the invention, the metering module has an electrically actuated metering valve and a valve device of the metering valve is arranged on an outlet side for reducing agent on the metering module. On the one hand, this embodiment enables exact metering of the reducing agent near the inlet point into the exhaust system and, on the other hand, reliable cooling of this thermally loaded area, including the valve device, by means of the coolant guide device provided in the development.

In a development of the invention, the metering module has a coolant guide device which directs the coolant flow to the outlet side for the reducing agent. This embodiment ensures the aforementioned cooling of this thermally stressed area.

In a development of the invention, the coolant guide device has a passage opening having a guide wall. This baffle is disposed within the dosing between a coolant circuit inlet and the coolant circuit outlet and the passage openings are arranged or aligned so that intensive cooling of the valve device takes place when the thermostatic valve is open.

In a development of the invention, a vehicle having an exhaust gas-conducting exhaust system and an arrangement for reducing nitrogen oxides of the exhaust gas carried in an exhaust system in accordance with one of the described embodiments is configured. The vehicle may be, for example, a passenger car or a light commercial vehicle. In this segment, increasingly used arrangements for the reduction of nitrogen oxides, which are equipped with a described liquid cooling. In principle, however, the arrangement according to the invention can also be used on internal combustion engines which are installed in any vehicles or machines.

The method according to the invention provides that the flow regulator arranged on the dosing module sets throttling or blocking of the coolant flow through the flow regulator when the coolant temperature falls below approximately 120 ° C. This coordination or this method has the effect that at a start, in particular a cold start of the internal combustion engine and consequently still cold coolant, a flow through the metering module is throttled or shut off with coolant. As a result, cooling of the valve device is prevented in the start case and a valve clamp of the valve device can be solved at any time by electrical heating of the valve device. This valve clamp is caused by crystals, in particular urea crystals of the dosing agent, which is preferably a urea-water solution, wherein the urea crystals can be melted by electric heating. In the event that below a coolant temperature of 120 ° C, a throttling of the coolant flow is set, this is done so that below a temperature of 80 ° C, a blockage of the coolant flow is set by the flow controller. Alternatively or additionally, a freezing of the valve device during operation can be prevented. This can occur in particular in internal combustion engines installed in vehicles, which have a separate charge air cooling circuit. If the valve device is cooled via this circuit, temperatures of less than -ca. 11 ° C below which the dosing freezes in the form of a urea water solution. For this case, the flow control closes below a temperature of 0 ° C, preferably below -5 ° C. This antifreeze function can also be combined by a corresponding design of the flow regulator with the function of preventing a cooling in the starting case.

Further advantageous embodiments of the invention are described in the drawings, in which an illustrated in the figures embodiment is described in detail.

Show it:

1 a schematic representation of a built-in an internal combustion engine exhaust system with an inventively designed dosing,

2 a sectional view of a dosing with an integrated flow regulator and

3 a detailed view of a built-in a coolant circuit outlet of the metering flow regulator.

The 1 shows a schematic representation of an internal combustion engine 1 , which may be, for example, a four-cylinder auto-ignition internal combustion engine, the fuel is supplied by means of a common-rail injection system. The internal combustion engine 1 has an exhaust manifold 2 on, which merges the discharged from the combustion chambers of the individual cylinder exhaust and into an exhaust system 3 initiates. The exhaust system 3 has a multi-part exhaust pipe 4 on, in which a component or more components for reducing the harmful components of the exhaust gas can be installed or can be. These components are, for example, an output side of the exhaust manifold 2 arranged catalyst 5 , a subsequent soot filter 6 and also a subsequent catalyst, as the SCR catalyst 7 is trained. On the output side of the SCR catalytic converter 7 The exhaust gases cleaned in this way are discharged into the environment.

The SCR catalyst 7 is designed for the selective catalytic reduction of nitrogen oxides in the exhaust gas. To operate the SCR catalyst 7 is in the the SCR catalyst 7 supplied exhaust gas to supply a reducing agent. The supply of the reducing agent via a metering module 8th that is connected to the exhaust pipe 4 between the soot filter 6 and the SCR catalyst 7 is grown. In the event that no catalyst 5 and no soot filter 6 in the exhaust system 3 are present, is the dosing module 8th between the exhaust manifold 2 and the SCR catalyst 7 the exhaust pipe 4 built-in. The dosing module 8th is via a Dosiermittelleitung 9 a dosing agent, which is in particular a urea water solution supplied. The dosing agent is stored in a dosing tank, not shown, and conveyed via a metering medium pump, also not shown in the dosing. The dosing module 8th also has an electrical control line 10 on, which is connected for example to an internal combustion engine control unit and a valve unit explained below 11 (please refer 2 ) of a metering valve 12 of the dosing module 8th controls. Furthermore, the metering module 8th a coolant circulation inlet 13 and a coolant circulation outlet 14 on, both via appropriate lines 15a . 15b with a coolant guide in the internal combustion engine 1 are connected and a coolant circuit 16 form.

2 shows in a sectional view of the dosing 8th with the connections described above. Into the coolant circuit outlet 14 is a flow regulator designed as a thermostatic valve 17 installed, the flow of coolant, which is in particular the cooling water of the internal combustion engine, through the metering module 8th regulates. This regulation will be explained in more detail below. The dosing module 8th further has the aforementioned with the dosing agent line 9 connected metering valve 12 on, in particular the solenoid-operated valve device 11 includes. The valve device 11 has a valve ball 18 on, one on the exit side and in the exhaust pipe 4 opening outlet opening 19 controlled. In the closed state of the metering valve 12 is the outlet opening 19 from the valve ball 18 closed and vice versa in the opened state, dosing agent flows from the dosing medium line 9 through the outlet opening 19 in the exhaust pipe 4 , When energizing a coil 20 becomes a hollow bolt 21 against the force of a spring 22 from the outlet opening 19 moved away, leaving the valve ball 18 from the outlet opening 19 is moved away and a flow connection between the Dosiermittelleitung 9 and the outlet opening 19 consists.

For cooling the valve device 11 of the metering valve 12 becomes the dosing module 8th flows through coolant that through the coolant circulation inlet 13 into the interior of the dosing module 8th is introduced and via the coolant circuit outlet 14 back into the coolant circuit 16 is derived. For the separation in particular of the electrical part of the metering valve 12 is a partition 23 in the dosing module 8th mounted on the top of a Dosiermodulgehäuse 24 and in the area of the valve device 11 on the valve body 25 tight. To a targeted flow of the valve device 11 To ensure in the area of the outlet side of the dosing, is as a guide wall 26 trained Kühlmittelleiteinrichtung in the dosing 8th fitted with the dosing module housing 24 in the area between the coolant circulation inlet 13 and the coolant circulation outlet 14 is firmly connected. Furthermore, the baffle is 26 on the valve body 25 in the area below the connection of the partition 23 attached. The baffle 26 has flow openings 27 in particular in the area of the valve device 11 are arranged and so a targeted cooling of the thermally stressed areas of the valve device 11 to ensure.

3 shows in a detailed view designed as a thermostatic flow regulator 17 entering the coolant circuit outlet 14 is installed. The designed as a thermostat flow controller 17 has a cylindrical needle seat guide 28 on, the immovable in the coolant circuit outlet 14 is used. The needle seat guide 28 has one or more guide bars 29 to Guide a valve disk 30 carrying valve needle 31 on. A seat 32 of the valve disk 30 acts in the closed state of the flow controller 17 with a valve seat 33 the needle seat guide 28 together. In the open state shown is the seat 32 spaced from the valve seat 33 arranged and thus is a flow connection through the flow regulator 17 Approved. The designed as a thermostat flow controller 17 also has a bimetallic element 34 on, with the needle seat guide 28 is connected and on the opposite side with a retaining ring 35 for the valve needle 31 connected is. The valve needle 31 is in the retaining ring 25 mounted and is by a valve spring 36 , which are located at the guide bridge 29 and the valve plate 30 supports in the direction of an opening movement of the flow regulator 17 biased.

The flow regulator 17 is preferably adjusted so that at a start, in particular a cold start of the internal combustion engine and consequently still cold coolant, a flow through the dosing 8th is shut off with coolant. This is the case below a temperature range of 80 ° C to 120 ° C. This will cause the valve device to cool 11 prevented in the start case and a valve clamp of the valve device 11 can by a in 2 not shown electrical heating of the valve device 11 be solved at any time. This valve clamp is caused by urea crystals, which can be melted by electric heating.

Alternatively or additionally, a freezing of the valve device 11 be prevented during operation of the internal combustion engine. This can occur in particular in internal combustion engines installed in vehicles, which have a separate charge air cooling circuit. Will the valve device 11 Cooled through this cycle, temperatures of less than about -11 ° C are possible, from which the urea water solution freezes. In this case, the flow regulator 17 adjusted so that it closes below a temperature of 0 ° C, preferably -5 ° C.

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 102012206563 A1 [0003]

Claims (12)

Arrangement for the reduction of nitrogen oxides in the exhaust gas of an internal combustion engine ( 1 ), comprising a dosing module ( 8th ) for introducing a reducing agent into an exhaust gas-carrying exhaust system ( 3 ) with an SCR catalyst ( 7 ), wherein the dosing module ( 8th ) with a coolant circuit ( 16 ) for cooling the dosing module ( 8th ), and a flow regulator ( 17 ) in the cooling circuit ( 16 ), characterized in that the flow regulator ( 17 ) on the dosing module ( 8th ) is arranged. Arrangement according to claim 1, characterized in that the flow regulator ( 17 ) in a coolant circulation outlet ( 14 ) of the metering valve ( 8th ) is arranged. Arrangement according to claim 2, characterized in that the flow control ( 17 ) a cylindrical needle seat guide ( 28 ), and that the needle seat guide ( 28 ) in the coolant circuit outlet ( 14 ) is used. Arrangement according to one of the preceding claims, characterized in that the opening direction of the flow regulator ( 17 ) is aligned in the flow direction of the coolant. Arrangement according to one of the preceding claims, characterized in that the flow regulator ( 17 ) is a thermostatic valve. Arrangement according to claim 5, characterized in that the thermostatic valve is a bimetallic element ( 34 ) having. Arrangement according to one of the preceding claims, characterized in that the dosing module ( 8th ) an electrically operated metering valve ( 12 ), and the one valve device ( 11 ) of the metering valve ( 12 ) on a discharge side for reducing agent on the dosing module ( 8th ) is arranged. Arrangement according to claim 7, characterized in that the dosing module ( 8th ) has a Kühlmittelleiteinrichtung which the coolant flow to the valve device ( 11 ) on the exit side. Arrangement according to claim 8, characterized in that the Kühlmittelleiteinrichtung a passage openings ( 27 ) having baffle ( 26 ). Vehicle with an exhaust gas carrying exhaust system ( 3 ) and an arrangement for the reduction of nitrogen oxides in the in the exhaust system ( 3 ) guided exhaust gas according to one of the preceding claims. Method for operating an arrangement for the reduction of nitrogen oxides in the exhaust gas of an internal combustion engine ( 1 ), comprising a dosing module ( 8th ) for introducing a reducing agent into an exhaust gas-carrying exhaust system ( 3 ) with an SCR catalyst ( 7 ), wherein the dosing module ( 8th ) with a coolant circuit ( 16 ) for cooling the dosing module ( 8th ), and a flow regulator ( 17 ) in the cooling circuit ( 16 ), characterized in that on the dosing ( 8th ) flow regulators ( 17 ) when the coolant temperature falls below approximately 120 ° C., throttling or blocking of the coolant flow through the flow regulator ( 17 ). A method according to claim 11, characterized in that the coolant flow at a throttling of the coolant flow below a temperature of 120 ° C from a temperature below 80 ° C by the flow regulator ( 17 ) Is blocked.

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