DE102010032269A1 - Dosing system for injecting reducing agent into exhaust stream for selective catalytic reduction of nitrogen oxide emitted from diesel engine of commercial vehicle, has flow channel sensors measuring fluid state quantities - Google Patents

Abstract

The system has a metering pump (1) conveying reducing agent from a reducing agent tank. A compressed air feed circuit is provided with a nozzle (3) connected with a pressure side of the metering pump. The metering pump is mounted on a component carrier (2). Pressurized air channels (4, 5) and reducing agent channels (6, 7) are provided in the component carrier. The pressurized air channels and the reducing agent channels are integrated by terminal portions. Flow channel sensors (8, 9) measure fluid state quantities.

Description

The invention relates to a Reduktionsmitteldosiersystem for injection of a reducing agent in the exhaust stream of an internal combustion engine for selective catalytic reduction, wherein the metering system with a reducing agent tank is connected / connected, removed from the reducing agent and conveyed by a metering pump, wherein a compressed air supply and arranged at least one nozzle is, which is connected to the pressure side of the metering pump and via which the reducing agent is injected into the exhaust stream and atomized by means of compressed air.

Dosing systems for introducing a reducing agent into the exhaust gas stream for the selective catalytic reduction of nitrogen oxides (English: Selective Catalytic Reduction, abbreviated SCR) are known. For this purpose, a reducing agent is injected into the exhaust system with a metering device. The reducing agent used is, for example, ammonia. Under reducing agent or urea solution in this sense, both ammonia and urea solution or another reducing agent and in particular the so-called AdBlue, ie a urea solution according to DIN 70070 be understood. So-called SCR catalysts are used to reduce the nitrogen oxide emissions of diesel engines.

Since the entrainment of ammonia in vehicles is safety-critical, urea is used in aqueous solution with usually 32.5% urea content. In the exhaust gas, the urea decomposes at temperatures above 150 ° Celsius into gaseous ammonia and CO ₂ . Parameters for the decomposition of the urea are essentially time (evaporation and reaction time), temperature and droplet size of the injected urea solution. In these SCR catalysts, selective catalytic reduction (SCR) reduces nitrogen oxide emissions by about 90%.

Various systems for the injection of urea as a reducing agent are known. The injection of urea can be assisted by compressed air. The compressed air serves as an energy supplier. This is beneficial for achieving small droplets. The urea solution is metered by means of a metering system, injected into the exhaust gas stream and ensures the desired chemical reaction in the SCR catalyst. Here, the nitrogen oxides are converted into nitrogen and water vapor.

A disadvantage of the known systems is the complex structure of a variety of items that are to be mounted and connected, such as compressed air hoses, reducing agent lines, valves and the like. Another disadvantage is the required installation space of the known systems due to the complexity and the many individual components.

The object of the invention is to overcome these disadvantages and to develop a generic metering device such that the entire metering forms a compact unit that requires only a small installation space, the overall arrangement having a simplified structure and should allow easy installation.

This object is achieved by a metering system according to claim 1. Advantageous embodiments of the invention are specified in the dependent claims.

Particularly advantageous in the Reduktionsmitteldosiersystem for injecting a reducing agent in the exhaust stream of an internal combustion engine for selective catalytic reduction, wherein the metering system with a reducing agent tank is connected / connected, removed from the reducing agent and conveyed by a metering pump, wherein a compressed air supply and arranged at least one nozzle is that is connected to the pressure side of the metering pump and via which the reducing agent is injected into the exhaust stream and atomized by means of compressed air, wherein at least the metering pump of the metering system is mounted on a component carrier, it is that in the component carrier a plurality of flow channels are integrated form at least one compressed air channel and a reducing agent channel and having at the exits from the component carrier connection areas, wherein integrated in the flow channels sensors for measuring fluid state variables are.

The fact that the flow channels for the compressed air and the reducing agent are integrated into the component carrier, results in an overall very compact arrangement, since the metering pump of the metering system is mounted on this same component carrier itself. The component carrier can accommodate other components of the dosing system, such as valves and the like.

The compressed air supply can be done by a compressed air system of the vehicle, in the exhaust system, the dosing system is integrated. In commercial vehicles regular compressed air systems are provided, which can be used for this purpose.

Alternatively or cumulatively, charge air of a supercharger, in particular a compressor and / or turbocharger in supercharged engines for the Distributed compressed air supply of the dosing and fed to this.

If the vehicle in whose exhaust system the metering system is integrated, does not have a charged engine or an on-board compressed air system or because of capacity reasons no sufficient compressed air supply of the metering system can be ensured, an air compressor can be provided to the required compressed air for atomizing the reducing agent provide.

Such an optionally arranged air compressor can also be arranged on the component carrier and flanged to it. Furthermore, in this case, pockets can be introduced into the component carrier which form the suction nozzle and / or the discharge nozzle of the air compressor.

In this case, the suction line and / or the pressure line of the air compressor may have at least one check valve. This ensures that a backflow of the fluid within the suction line and / or pressure line of the air compressor is prevented and the check valve opens automatically only with a corresponding delivery pressure in the conveying direction.

It is therefore possible that at least part of the compressed air is taken from a supercharger of the internal combustion engine and / or on-board compressed air system, and that the compressed air supply parallel to the air compressor has a further channel or a bypass, so that via the bypass the charge air of the supercharger the compressor can flow over or the output from the loader opens into the suction nozzle of the compressor. A supercharged engine is thus an engine with a supercharger group, which may be an exhaust gas turbocharger and / or a compressor.

For this purpose, in a preferred embodiment, at least one further channel may be introduced into the mounting plate, into which the pressure line of the air compressor opens via at least one check valve and which is fed by compressed air from a supercharger of the internal combustion engine.

In the operating points of the engine, in which a sufficient charge pressure of the supercharger, so for example a turbocharger or a compressor, is available, the charge air, d. H. a part of the charge air removed therefrom is used to atomize the reducing agent solution, the air compressor provided in the compressed air supply operating only in the low load or low speed in order to provide the compressed air required for the metering system.

By evaluating the signal of a pressure sensor in the pressure line of the compressed air supply, the compressed air supply can thus be obtained from a supercharger of the supercharged internal combustion engine and optionally alternatively or cumulatively by a switchable electric air compressor as required in the metering system. As a result, a compressed air supply of the Reduktionsmitteldosiersystems is guaranteed in all operating points of the engine.

Thus, in the dosing system according to the invention, a plurality of components of the system can thus be jointly arranged on the component carrier and fastened thereto, in particular screwed on.

As a result, an overall very compact arrangement of several components of the metering is possible, so that the entire system takes up little space. The component carrier itself may be attached to or on the reducing agent tank or attached to another preferred location in or on the vehicle.

It is particularly advantageous that in particular a very simple and inexpensive installation of the metering pump and thus integration into the metering system is possible. Characterized in that in the same time serving as a mounting plate component carrier channels are integrated, which form the flow channels for compressed air or reducing agent and having at the exits from the mounting plate connection areas, a number of hoses and their complex assembly can be omitted. Instead, only the dosing pump and optionally an air compressor on the component carrier need to be placed and flanged. Furthermore, pockets may be formed in the component carrier which form the suction nozzle and / or the discharge nozzle of the metering pump. It is thus a pre-assembly possible, so that only the complete assembly of component carrier and metering pump is to be mounted. The simultaneously acting as a mounting plate component carrier has for mounting preferably corresponding mounting areas, holes or the like to mount the entire assembly. Preferably, the assembly is mounted directly on the reducing agent tank itself.

The metering pump may be a diaphragm pump or a piston pump or another type of pump. If an air compressor is additionally arranged, this may be a membrane compressor or a piston compressor and another type of compressor.

The fact that sensors for measuring fluid state variables are integrated into the flow channels, on the one hand a compact arrangement given and further monitoring of one or more state variables of the flowing in the respective channel fluid, ie the compressed air or the reducing agent solution possible.

In a preferred embodiment, the sensors are located in recesses in the component carrier. As a result, a pre-assembly and particularly compact design can be realized.

Preferably, a pressure sensor and / or a temperature sensor or a combined pressure and temperature sensor is integrated in the compressed air channel. By evaluating and monitoring the sensor signal, monitoring of the compressed air supply of the dosing system is ensured. In particular, an optionally arranged compressor can be switched on / off or regulated as a function of the measured pressure.

Preferably, a pressure sensor and / or a temperature sensor or a combined pressure and temperature sensor is integrated in the reducing agent channel. Particularly preferred is the arrangement of a combined pressure and temperature sensor in the reducing agent channel, which thus allows simultaneous detection and monitoring of the two fluid state variables pressure and temperature of the subsidized reducing agent. This makes it possible to monitor at any time the operating parameters of the reducing agent promotion such as pressure and temperature of the reducing agent. Furthermore, in particular a monitoring and control of the metering system is possible, in particular a control of the metering pump. By a corresponding control of the pump, this can not only only the promotion of the reducing agent, but also the dosage, d. H. controlling the flow rate, serve.

Preferably, a switchable air valve is arranged in the compressed air channel, in particular, an integrated valve assembly may be arranged with a controllable proportional valve and a check valve in the compressed air channel.

The arrangement of a controllable proportional valve is an adjustment of the desired air pressure applied to the atomizer, possible. This pressure applied behind the switchable air valve, in particular the controllable proportional valve, is preferably measured and monitored by means of a pressure sensor integrated into the compressed air channel. The arrangement of the check valve counteracts unwanted backflow within the compressed air channel.

The air valve may be extended by a further outlet channel, in which the check valve is inserted. The check valve is then inserted as a kind of connecting piece between air valve and component carrier and is only to be sealed with an O-ring. As a result, an assembly of a few parts and with little effort is possible.

The proportional valve on the component carrier bridges the compressed air channel in such a way that a first portion of the integrated in the component carrier compressed air channel opens at the top of the component carrier in the valve assembly and a second portion of integrated in the component carrier compressed air channel is fed from the valve assembly, so also a terminal portion in the region of the top of the component carrier, in which the valve assembly is mounted with the air valve on the component carrier.

Preferably, the metering pump is arranged on the component carrier and flanged to the reducing agent channel, wherein the reducing agent channel in the component carrier upstream of the metering pump forms the suction line and downstream of the metering pump, the pressure line of the metering pump. The pump is thus arranged in this preferred embodiment such that a first portion of the integrated in the component carrier reducing agent channel opens at the top of the component carrier in the suction mouth of the metering pump. The discharge nozzle of the metering pump in turn sets at the top of the component carrier to a beginning here second portion of the integrated in the component carrier reducing agent channel, so that the arranged on the component carrier pump forms the bridge of the reducing agent channel formed from two sections.

Particularly preferably, a sensor for measuring at least one substance property of the conveyed reducing agent is arranged in the reducing agent channel, in particular for measuring the electrical conductivity and / or for measuring the speed of sound of the conveyed reducing agent. As a result, a permanent quality control of the reducing agent solution used is possible.

Preferably, a connecting channel is arranged between the compressed air channel and the reducing agent channel in the component carrier, wherein the connecting line has a valve, in particular a check valve and / or a switching valve, in particular a solenoid valve.

In order to completely interrupt the air supply in metering pauses, it is necessary that the Remove reducing agents such as urea from the hot areas to prevent deposits from forming. However, urea is only mentioned as an example for every other reducing agent. The urea would decompose at high temperatures and lead to deposits and thus to blockages. By arranging a compressed air line, ie a connecting line between the reducing agent line, ie the urea line, and a line of compressed air supply, such deposits can be prevented by the reducing agent line is blown free in dosing intervals by means of compressed air. In this connection line, a check valve or a switching valve such as a solenoid valve is used, which is opened to blow the urea line at an existing air pressure in the air line, so preferably when the air pump.

In dosing mode, this valve is closed. To blow the urea line with compressed air, the urea flow through the metering pump is turned off and the switching valve is opened. This results in a pressure gradient in the dosing and the compressed air drives the urea in the exhaust system. The line is thus cleaned by means of compressed air. After a brief puff of air, the urea is blown out of the dosing nozzle and the air supply can be completely switched off.

If an onboard compressed air system is present, can be cleaned by means of compressed air from this system, which has a higher pressure, the urea-promoting area. For this purpose, a provided in the compressed air supply proportional control valve is opened briefly, so that arranged in the connecting line check valve opens automatically and the urea-promoting area is flushed by means of compressed air.

The dosing system particularly preferably has a sensor for measuring the exhaust gas temperature. From the exhaust gas temperature, it is possible to control via a corresponding control electronics of the dosing system, the pressure and / or the amount of air and / or the metered amount of reducing agent and / or valve opening times, since the exhaust gas temperature is a parameter for the selective catalytic reduction.

Preferably, the connections of a fresh air line and / or a compressed air line and / or a reducing agent line for connection to the reducing agent tank and / or a reducing agent line for connection to the nozzle form-fit and / or non-positively in the connection areas of the component carrier, in particular, these connections in the corresponding Be pressed connection areas.

Preferably, the mounting plate of the air compressor and / or the metering pump is composed of two superimposed plates, wherein in one or both plates recesses, in particular channels are introduced, pressed or milled, wherein the recesses are closed by the other plate.

As a result, a particularly advantageous and simple production of the mounting plate / s is possible because formed by in one or both plates recesses the required channels and pockets are formed.

Already during assembly of the component carrier composed of two plates, lines for air and / or reducing agent can be inserted or pressed in the area of the connection areas.

Preferably, the component carrier is composed of two superimposed plates, which are produced as diecasting / e or injection molded part / s and welded together and / or glued and / or screwed.

In a preferred embodiment, the component carrier has at least one recess or groove, in which a coolant line of the internal combustion engine rests, so that the component carrier forms a heat sink of the coolant circuit of the internal combustion engine.

Preferably, a groove or a plurality of grooves on the outside along the longitudinal edge of the component carrier is arranged so that the largest possible thermal contact surface between the inserted in the groove coolant line of the cooling circuit of the engine as a heat source and the component carrier is created as a heat sink.

By inserting a coolant line of the cooling circuit of the internal combustion engine in heat-conducting contact in the recess or groove of the component carrier thus takes place via the waste heat of the engine, heating of the component carrier and thus simultaneously arranged on the component carrier components and integrated in the component carrier flow channels. As a result, the reducing agent solution flowing through the reducing agent channel is heated at the same time, so that it does not freeze. This will prevent any frost damage effectively and easily.

Optionally, the coolant line can also be integrated directly as a flow channel in the plate segments of the component carrier. Optionally, the control valve for the Coolant line can be integrated on the component carrier. The complete system is thus very compact. The necessary connections for the individual cables can either be screwed in, welded in, pressed in or molded on. The type of fasteners depends on the requirements of the customer.

Preferably, in the flow channel, which forms a portion of a cooling circuit of the internal combustion engine, a control valve for the coolant line is integrated. In this case, however, the coolant channel integrated in the component carrier forms a bypass to the cooling circuit of the internal combustion engine so as not to interrupt it by closing the control valve. By the control valve, it is advantageously possible to direct coolant as required by the component carrier, which then forms a heat sink of the cooling circuit and thereby heating of the component carrier itself and all incorporated in the component carrier flow channels and all standing with the component carrier in thermal contact components he follows.

Preferably, an external air pump for generating the necessary compressed air is mounted on the component carrier. As a result, a compressed air supply is always guaranteed, even in cases where an onboard compressed air system is not available or due to operating point does not provide sufficient compressed air supply.

In a preferred embodiment, an air connection to a charge air circuit of the internal combustion engine is present.

Preferably, both a connection to a charge air circuit of the internal combustion engine and an external air pump mounted on the component carrier.

Preferably, a connection to an external air pump is present on the component carrier.

In operation, the dosing system is coupled to a control unit, by means of which the dosing pump and the valves as well as the optional air compressor are controlled depending on the motor data and the sensor data. The control can also take place via the usually existing central control unit of the vehicle, which is set up for this purpose.

By the arrangement of such a control device, which one or more components of the metering system in dependence of the sensor measured values, d. H. depending on the current operating parameters, is an optimization of the operation of the dosing system, d. H. in particular an air optimization in a particularly advantageous manner feasible. It is thus possible by means of such a control device, the reducing agent flow rate and the air flow rate to optimally adapt to the current operating parameters of the internal combustion engine and the catalyst for selective catalytic reduction and thus to regulate.

In the figures, three different embodiments of the invention are shown, which are explained in more detail below. Show it:

1 : the connection and wiring diagram of a dosing system with on-board compressed air supply;

2 : the component carrier of the dosing system according to 1 in three views;

3 : the connection and wiring diagram of a dosing system without on-board compressed air supply;

4 : the component carrier of the dosing system according to 3 in three views

5 : the connection and wiring diagram of a dosing system with on-board compressed air supply and integrated cooling water channels;

6 : the component carrier of the dosing system according to 5 in three views

In the 1 to 6 identical components and assemblies are provided with identical reference numerals.

The 1 shows a connection and wiring diagram of a first embodiment of a metering system according to the invention for the injection of a reducing agent in the exhaust stream of an internal combustion engine for selective catalytic reduction, wherein an on-board compressed air supply is present.

To promote the reducing agent from a reducing agent tank, not shown, is an electric pump and metering pump 1 intended. The reducing agent is passed over the line 6 aspirated and by means of the metering pump 1 continue via the pressure line 7 promoted.

The atomization of the reducing agent is carried out by means of compressed air, via the lines 4 . 5 is provided by an on-board compressed air supply of the vehicle, not shown. Into the compressed air line 4 . 5 is an air pressure sensor 8th integrated, by means of which in the pressure line 4 . 5 applied air pressure is measured and monitored.

The dosing pump 1 is on the component carrier 2 attached and flanged to this. The component carrier 2 at the same time forms the mounting plate for the components of the dosing system mounted thereon. In the component carrier 2 are introduced the corresponding flow channels 4 . 5 to guide the air. Also the flow channels 6 . 7 from and to the metering pump 1 are in the component carrier 2 brought in, so the pump 1 only on the carrier 2 must be flanged. The entire assembly can then be made very compact, for example, be arranged directly on the reducing agent tank, not shown.

About the line 6 Reducing agent, such as a urea solution, is removed from a reducing agent tank and by means of the metering pump 1 via the pressure line 7 to the nozzle 3 promoted. In the pressure line 7 is a pressure and temperature sensor 9 provided for detecting the pressure and the temperature of the reducing agent solution.

The atomization of the reducing agent through the nozzle 3 takes place by means of compressed air, which via the compressed air channel 4 . 5 is fed, which also to the nozzle 3 runs. From a first outlet of the nozzle 3 Reducing agent is injected into the exhaust port of the engine, not shown, and outside the nozzle 3 by means of compressed air, which emerges from a second nozzle opening, atomized. At the nozzle 3 Thus, in the illustrated embodiment, it is an externally mixing nozzle, in which the aerosol formation takes place outside of the nozzle body. Alternatively, however, a compressed air-assisted aerosol formation can also take place in a mixing chamber upstream of the nozzle outlet. In the air pressure line 4 . 5 is arranged a pressure sensor 8th for recording the applied air pressure.

The compressed air supply takes place by means of an onboard compressed air system. Since such on-board compressed air systems provide compressed air at a relatively high pressure, but the metering system itself requires only a very small air pressure to atomize the reducing agent, is in the air pressure line 4 a proportional control valve 11 provided by means of which the pressure is lowered to the desired level. The monitoring of the applied pressure by means of the pressure sensor 8th ,

When the internal combustion engine is switched off, the reducing agent line must 7 between dosing pump 1 and nozzle 3 as well as the nozzle 3 even be rinsed with air. This is a connection line 10 between the compressed air duct 5 and the reducing agent line 7 provided a check valve 28 contains. To the dosing medium line 7 to purge by air, is the control valve 11 open for a short time. Here is the metering pump 1 off. Due to the now applied increased pressure opens the check valve 28 and compressed air flows into the reducing agent line 7 over the connection channel 10 , By means of compressed air, the reducing agent line 7 to the nozzle 3 blown free and cleaned.

During normal operation, reductant is transferred via the line 6 from the tank, not shown, by means of the metering pump 1 sucked in and over the pressure side of the metering pump 1 arranged pressure line 7 to the nozzle 3 promoted. Compressed air passes through the compressed air channel 4 . 5 also to the nozzle 3 and atomizes the reducing agent solution. In normal operation, the check valve 28 in the connection line 10 between air pressure channel 5 and reductant channel 7 closed because the air pressure in the pressure line 4 by means of the proportional control valve 11 down regulated and set to a lower level than the applied pressure in the compressed air system. For venting the reducing agent line 7 will this valve 11 briefly open, whereby by the pressure jump, the check valve 28 opens and the line section 7 between dosing pump 1 and nozzle 3 as well as the nozzle 3 itself is cleaned of urea solution by means of compressed air.

The component carrier 2 is in 2 in three views, with one view the section AA according to the other two views as in 2 indicated.

The component carrier 2 is composed of two superimposed plates 20 . 21 , The top left view shows the section AA and thus the view of the plate 21 without the cover plate 20 is mounted.

In the plates 20 . 21 are introduced the flow channels 4 . 5 . 6 . 7 . 10 forming recesses. At their respective end points of the flow channels 4 . 5 . 6 . 7 are outlet openings through the cover plate 20 arranged to the surface to connect at these outlet openings, the corresponding reducing agent line or the compressed air line. The outlet openings thus simultaneously form the connection areas of the flow channels.

The compressed air channel is formed by a first section 4 and a second section 5 , At the entrance 12 the first section is connected to a compressed air line, not shown, and the system compressed air supplied thereto. The first paragraph 4 of the compressed air channel 4 . 5 flows through the outlet 13 in the end of the first section 4 in one on the component carrier 2 mounted proportional valve. The proportional valve is not shown and is used to set the desired air pressure in the dosing system. The proportional valve bridges the interruption of the compressed air channel 4 . 5 and flows at its exit into the inlet 14 of the second section 5 of the compressed air channel 4 . 5 , The sealing of the proportional valve against the component carrier 2 takes place easily by means of a simple O-ring.

At the exit of the second section 5 the compressed air channel is an in 2 unillustrated pressure sensor 8th attached. By means of the pressure sensor 8th there is a detection and monitoring of the voltage applied behind the proportional valve air pressure in the system. The sensor 8th is inserted from above into the outlet opening of the conon carrier and sealed by means of an O-ring.

Furthermore, in the plates 20 . 21 Recesses introduced, which form the reducing agent channel. The reductant channel is formed by two sections 6 . 7 , Both sections 6 . 7 flow into their respective ends 16 . 17 . 18 . 19 in outlet openings. These also form the connection areas of the reducing agent channel. About the entrance 16 to the first section 6 of the reducing agent channel is sucked reducing agent, which is removed from a tank, not shown, The first paragraph 6 the reducing agent channel opens via the outlet opening 17 in the suction mouth of the metering pump, not shown in this view 1 , The discharge nozzle of the dosing pump 1 is placed on the inlet 18 of the second section 7 of the reducing agent channel. The on the component carrier 2 mounted and flanged on this pump 1 thus bridges the interruption of the two sections 6 . 7 formed reducing agent channel.

At the exit of the second section 7 of the reducing agent channel is a combination sensor 9 attached. The combination sensor 9 is inserted from above into the outlet opening of the conon carrier and sealed by means of an O-ring.

In the combination sensor 9 it is a combined pressure and temperature sensor 9 , By means of the combination sensor 9 there is a simultaneous detection and monitoring of the delivery pressure of the reducing agent behind the metering pump 1 in the system and at the same time the reducing agent temperature, since this is an important parameter for the quality of the selective catalytic reduction and thus for the dosage of the reducing agent.

The measured values of the sensors 8th . 9 are evaluated by an unillustrated control unit, by means of which, depending on the operating parameters and the measured values, the control of the proportional valve, ie the adjustment of the air pressure, as well as the control of the metering pump is performed.

Between the second section 5 of the compressed air duct and the second section 7 of the reducing agent channel is a connecting channel 10 with a switching valve 11 arranged. At the switching valve 11 it is a solenoid valve 11 , The activation of the solenoid valve 11 also takes place via the control unit. In metering pauses, the switching valve 11 opened and the second section 7 the reducing agent channel cleaned by means of compressed air of reducing agent residues to prevent deposits. In normal operation, ie in dosing is the switching valve 11 closed.

Via the outlet connection 15 of the compressed air channel 5 or the outlet connection 19 of the reducing agent channel 7 the connection to the nozzle takes place 3 ,

On the long sides, the component carrier points 2 longest running grooves 22 . 23 on. When installed in these grooves 22 . 23 Inserted or clipped coolant lines of the internal combustion engine, so that the component carrier 2 forms a heat sink of the coolant circuit of the internal combustion engine. This is followed by a heat transfer to the component carrier 2 and accordingly heating the on the component carrier 2 arranged components, whereby a freezing of the reducing agent within the pump 1 as well as within the flow channels 6 . 7 in the component carrier 2 are introduced, is prevented. It is thus reliably prevented by the use of engine waste heat freezing of the reducing agent.

The following is the description of the second embodiment according to FIGS 3 and 4 , which refers to a dosing system without on-board compressed air system.

To promote the reducing agent from a reducing agent tank, not shown, is an electric pump and metering pump 1 intended. The reducing agent is passed over the line 6 aspirated and by means of the metering pump 1 continue via the pressure line 7 promoted.

The atomization of the reducing agent is carried out by means of compressed air, via the lines 4 . 5 is diverted from the charge air of the turbocharger. The engine is in an operating condition in which the boost pressure is insufficient, the required compressed air is provided via an air pump, not shown. Into the compressed air line 4 . 5 is an air pressure sensor 8th integrated, by means of which in the pressure line 4 . 5 applied air pressure is measured and monitored.

The dosing pump 1 is on the component carrier 2 attached and flanged to this. The component carrier 2 at the same time forms the mounting plate for the components of the dosing system mounted thereon. In the component carrier 2 are introduced the corresponding flow channels 4 . 5 to guide the air. Also the flow channels 6 . 7 from and to the metering pump 1 are in the component carrier 2 brought in, so the pump 1 only on the carrier 2 must be flanged. The entire assembly can then be made very compact, for example, be arranged directly on the reducing agent tank, not shown.

About the line 6 Reducing agent, such as a urea solution, is removed from a reducing agent tank and by means of the metering pump 1 via the pressure line 7 to the nozzle 3 promoted. In the pressure line 7 is a pressure and temperature sensor 9 provided for detecting the pressure and the temperature of the reducing agent solution.

The atomization of the reducing agent through the nozzle 3 takes place by means of compressed air, which via the compressed air channel 4 . 5 is fed, which also to the nozzle 3 runs. From a first outlet of the nozzle 3 Reducing agent is injected into the exhaust port of the engine, not shown, and outside the nozzle 3 by means of compressed air, which emerges from a second nozzle opening, atomized. At the nozzle 3 Thus, in the illustrated embodiment, it is an externally mixing nozzle, in which the aerosol formation takes place outside of the nozzle body. Alternatively, however, a compressed air-assisted aerosol formation can also take place in a mixing chamber upstream of the nozzle outlet. In the air pressure line 4 . 5 is arranged a pressure sensor 8th for recording the applied air pressure. If the internal combustion engine is too low boost pressure, this is the air pressure sensor 8th determined and switched by the control unit, not shown, the air pump, not shown.

When the internal combustion engine is switched off, the reducing agent line must 7 between dosing pump 1 and nozzle 3 as well as the nozzle 3 even be rinsed with air. This is a connection line 10 between the compressed air duct 5 and the reducing agent line 7 provided, which is a switching valve 29 contains. At the switching valve 29 is it in the illustrated embodiment is a solenoid valve. To the dosing medium line 7 to purge with air, the solenoid valve 29 open. Here is the metering pump 1 off. It flows compressed air into the reducing agent line 7 over the connection channel 10 , By means of compressed air, the reducing agent line 7 to the nozzle 3 blown free and cleaned.

During normal operation, reductant is transferred via the line 6 from the tank, not shown, by means of the metering pump 1 sucked in and over the pressure side of the metering pump 1 arranged pressure line 7 to the nozzle 3 promoted. Compressed air passes through the compressed air channel 4 . 5 also to the nozzle 3 and atomizes the reducing agent solution. In normal operation is the valve 29 in the connection line 10 between air pressure channel 5 and reductant channel 7 closed. For venting the reducing agent line 7 will this valve 29 opened and the line section 7 between dosing pump 1 and nozzle 3 as well as the nozzle 3 even cleaned of urea solution by means of compressed air.

The component carrier 2 according to 3 is in 4 shown in three views, with one view the section AA according to the other two views as in 4 indicated.

The component carrier 2 is composed of two superimposed plates 20 . 21 , The top left view shows the section AA and thus the view of the plate 21 without the cover plate 20 is mounted.

In the plates 20 . 21 are introduced the flow channels 4 . 6 . 7 forming recesses. At their respective end points of the flow channels 4 . 6 . 7 are outlet openings through the cover plate 20 arranged to the surface to connect at these outlet openings, the corresponding reducing agent line or the compressed air line. The outlet openings thus simultaneously form the connection areas of the flow channels.

At the entrance 12 the compressed air channel is connected to a compressed air line, not shown, and the system compressed air supplied thereto, which is taken from the charge air of a turbocharger of the supercharged internal combustion engine. The compressed air channel 4 flows through the outlet 30 a branch of the canal 4 in one on the component carrier 2 attached switching valve. The switching valve is not shown and serves to bridge an interruption of the branch of the compressed air channel 4 , The branch forms the flushing line for flushing the reducing agent channel 7 by means of compressed air up to the nozzle 3 in metering pauses and / or shutdown of the dosing system. The sealing of the switching valve against the component carrier 2 takes place easily by means of a simple O-ring.

In the compressed air channel 4 a recess is provided in which a pressure sensor 8th rests. By means of the pressure sensor 8th there is a detection and monitoring of the voltage applied behind the proportional valve air pressure in the system.

Furthermore, in the plates 20 . 21 Recesses introduced, which form the reducing agent channel. The reductant channel is formed by two sections 6 . 7 , Both sections 6 . 7 flow into their respective ends 16 . 17 . 18 . 19 in outlet openings. These also form the connection areas of the reducing agent channel. About the entrance 16 to the first section 6 the reducing agent channel is sucked reducing agent, which is removed from a tank, not shown. The first paragraph 6 the reducing agent channel opens via the outlet opening 17 in the suction mouth of the metering pump, not shown in this view 1 , The discharge nozzle of the dosing pump 1 is placed on the inlet 18 of the second section 7 of the reducing agent channel. The on the component carrier 2 mounted and flanged on this pump 1 thus bridges the interruption of the two sections 6 . 7 formed reducing agent channel.

In the second section 7 the reducing agent channel is provided a recess in which a combination sensor 9 rests. In the combination sensor 9 it is a combined pressure and temperature sensor 9 , By means of the combination sensor 9 there is a simultaneous detection and monitoring of the delivery pressure of the reducing agent behind the metering pump 1 in the system and at the same time the reducing agent temperature, since this is an important parameter for the quality of the selective catalytic reduction and thus for the dosage of the reducing agent.

The measured values of the sensors 8th . 9 are evaluated by an unillustrated control unit, by means of which, depending on the operating parameters and the measured values, the control of the proportional valve, ie the adjustment of the air pressure, as well as the control of the metering pump is performed.

Via the outlet connection 15 of the compressed air channel 4 or the outlet connection 19 of the reducing agent channel 7 the connection to the nozzle takes place 3 ,

On the long sides, the component carrier points 2 longitudinal grooves 22 . 23 on. When installed in these grooves 22 . 23 Inserted or clipped coolant lines of the internal combustion engine, so that the component carrier 2 forms a heat sink of the coolant circuit of the internal combustion engine. This is followed by a heat transfer to the component carrier 2 and accordingly heating the on the component carrier 2 arranged components, whereby a freezing of the reducing agent within the pump 1 as well as within the flow channels 6 . 7 in the component carrier 2 are introduced, is prevented. It is thus reliably prevented by the use of engine waste heat freezing of the reducing agent.

In the 5 and 6 a third embodiment is shown, which refers to a metering system with on-board compressed air supply and integrated cooling water channels. The metering system itself corresponds schematically and in line with the first embodiment according to FIGS 1 and 2 so reference is made to the above description.

In addition, the component carrier points 2 this third embodiment, another integrated in the component carrier flow channel 26 on, which forms a portion of the coolant circuit of the internal combustion engine, so that the component carrier 2 a forms a heat sink of the coolant circuit of the internal combustion engine. This is followed by a heat transfer to the component carrier 2 and accordingly heating the on the component carrier 2 arranged components, whereby a freezing of the reducing agent within the pump 1 as well as within the flow channels 6 . 7 in the component carrier 2 are introduced, is prevented. It is thus reliably prevented by the use of engine waste heat freezing of the reducing agent.

For this purpose, corresponding connection areas are provided 24 . 25 in which coolant lines or coolant hoses of the coolant circuit of the internal combustion engine to the component carrier 2 be flanged. Further, in the component carrier 2 integrated cooling circuit section 26 a control valve 27 integrated for the coolant line.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited non-patent literature

• DIN 70070 [0002]

Claims (18)

Reduktionsmitteldosiersystem for injecting a reducing agent in the exhaust stream of an internal combustion engine for selective catalytic reduction, wherein the metering system with a reducing agent tank is connected / connected, taken from the reducing agent and by means of a metering pump ( 1 ), wherein there is a compressed air supply and at least one nozzle ( 3 ) is arranged, which with the pressure side ( 7 ) of the dosing pump ( 1 ) is injected and via which the reducing agent is injected into the exhaust stream and atomized by means of compressed air, wherein at least the metering pump ( 1 ) of the dosing system on a component carrier ( 2 ) is mounted, characterized in that in the component carrier ( 2 ) several flow channels ( 4 . 5 . 6 . 7 ) are integrated, the at least one compressed air channel ( 4 . 5 ) and a reductant channel ( 6 . 7 ) and at the exits from the component carrier ( 2 ) Connection areas ( 12 . 13 . 14 . 15 . 16 . 17 . 18 . 19 ), wherein in the flow channels sensors ( 8th . 9 ) are integrated to measure fluid state variables. Dosing system according to claim 1, characterized in that the sensors ( 8th . 9 ) in recesses in the component carrier ( 2 ) einliegen. Dosing system according to claim 1 or 2, characterized in that in the compressed air channel ( 5 ) a pressure sensor ( 8th ) and / or a temperature sensor or a combined pressure and temperature sensor is integrated. Dosing system according to one of the preceding claims, characterized in that in the reducing agent channel ( 7 ) a pressure sensor and / or a temperature sensor or a combined pressure and temperature sensor ( 9 ) is integrated. Dosing system according to one of the preceding claims, characterized in that in the compressed air channel ( 4 . 5 ) a switchable air valve is arranged, in particular that an integrated valve assembly with a controllable proportional valve and a check valve in the compressed air channel ( 4 . 5 ) is arranged. Dosing system according to one of the preceding claims, characterized in that the metering pump ( 1 ) on the component carrier ( 2 ) and to the reducing agent channel ( 6 . 7 ) is flanged, wherein the reducing agent channel ( 6 . 7 ) in the component carrier ( 2 ) upstream of the metering pump ( 1 ) the suction line ( 6 ) and downstream of the dosing pump ( 1 ) the pressure line ( 7 ) of the dosing pump ( 1 ). Dosing system according to one of the preceding claims, characterized in that in the reducing agent channel ( 6 . 7 ) a sensor for measuring at least one substance property of the conveyed reducing agent is arranged, in particular for measuring the electrical conductivity and / or for measuring the speed of sound of the subsidized reducing agent. Dosing system according to one of the preceding claims, characterized in that between the compressed air channel ( 4 . 5 ) and the reducing agent channel ( 7 ) in the component carrier ( 2 ) a connection channel ( 10 ), wherein the connecting line ( 10 ) has a valve, in particular a check valve ( 28 ) and / or a switching valve ( 29 ), in particular a solenoid valve. Dosing system according to one of the preceding claims, characterized in that the connections of a fresh air line and / or a compressed air line and / or a reducing agent line for connection to the reducing agent tank and / or a reducing agent line for connection to the nozzle positively and / or non-positively in the connection areas ( 12 . 13 . 14 . 15 . 16 . 17 . 18 . 19 ) of the component carrier ( 2 ) einliegen, in particular are pressed. Dosing system according to one of the preceding claims, characterized in that the component carrier ( 2 ) of two superimposed plates ( 20 . 21 ), in one or both plates ( 20 . 21 ) Recesses are introduced, in particular milled, which are closed by the other plate and the channels ( 4 . 5 . 6 . 7 . 10 ) form. Dosing system according to one of the preceding claims, characterized in that the component carrier ( 2 ) of two superimposed plates ( 20 . 21 ), which are manufactured as a diecast part / s or injection molded part / s and welded together and / or glued and / or screwed together. Dosing system according to one of the preceding claims, characterized in that the component carrier ( 2 ) at least one recess or groove ( 22 . 23 ), in which a coolant line of the internal combustion engine rests, so that the component carrier ( 2 ) forms a heat sink of the coolant circuit of the internal combustion engine. Dosing system according to one of the preceding claims, characterized in that in the component carrier ( 2 ) at least one further flow channel ( 26 ), which forms a section of a cooling circuit of the internal combustion engine, so that the component carrier ( 2 ) one Heat sink of the coolant circuit of the internal combustion engine forms. Dosing system according to claim 13, characterized in that in the flow channel ( 26 ), which forms a portion of a cooling circuit of the internal combustion engine, a control valve ( 27 ) is integrated for the coolant line. Dosing system according to one of the preceding claims, characterized in that on the component carrier an external air pump for the generation of the necessary compressed air is mounted. Dosing system according to one of the preceding claims, characterized in that an air connection to a charge air circuit of the internal combustion engine is present. Dosing system according to one of the preceding claims, characterized in that both a connection to a charge air circuit of the internal combustion engine and an external air pump is mounted on the component carrier. Dosing system according to one of the preceding claims, characterized in that on the component carrier ( 2 ) a connection to an external air pump is present.

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