DE102012218851A1 - reducing agent - Google Patents

Abstract

The present invention relates to a method for operating a reducing agent feed device (5) for an exhaust gas system (1), which introduces an injection quantity of a reducing agent (8) into an exhaust gas flow (9) by means of at least one injector (7). A simplified variation of the injection quantity results when a return quantity of the reducing agent (8) fed back by a delivery device (11) supplying the injector (7) with reducing agent (8) is varied to change and / or change the injection quantity. The invention also relates to such a reducing agent feed device (5) with a control device (15) which is designed or programmed in such a way that it can carry out the method according to the invention. The invention also relates to an exhaust system (1) with such a reducing agent feed device (5).

Description

The present invention relates to a method for operating a reducing agent supply device for an exhaust system and to such a reducing agent supply device. The invention further relates to an exhaust system with such a reducing agent supply device, which is operated in particular according to the inventive method.

A reducing agent supply device is usually part of an exhaust system and serves the purpose of introducing a reducing agent into the exhaust gas originating from an associated internal combustion engine. Said reducing agent can be introduced into the exhaust gas for versatile purposes, for example a corresponding aftertreatment of the exhaust gas. In this case, it is conceivable, in particular, that such aftertreatment of the exhaust gas takes place in the form of a selective catalytic reaction (SCR), in which case the reducing agent may in particular be a urea-containing fluid and the like in order to effect a chemical conversion of nitrogen oxides into nitrogen. In addition to the use in conventional internal combustion engines, which are to be found for example in passenger cars and the like, it is also conceivable to use such Reduktionsmittelzuführeinrichtung in a large engine, for example, has a capacity of 10 liters or more or a power of 600 kW or more.

Such Reduktionsmittelzuführeinrichtung is from the DE 10 2010 002 987 A1 known. Here, the introduction of the reducing agent into the exhaust gas by means of injectors, which are supplied by an associated conveyor with the reducing agent. The disadvantage here is that a variation of the reducing agent quantity of the reducing agent introduced into the exhaust gas leads to an increased load on the conveying device and thus of the reducing agent supply device.

The present invention is concerned with the problem of providing, for a reductant supply device and an associated operating method, an improved or at least other embodiment which is characterized in particular by a reduced load of the reducing agent supply device and / or by an improved variation of the exhaust gas to be supplied Reductant quantity distinguished. In addition, the realization of the Reduktionsmittelzuführeinrichtung or the associated operating method should be carried out as economically as possible.

This problem is solved according to the invention by the subject matters of the independent claims. Advantageous embodiments are the subject of the dependent claims.

The present invention is based on the general idea of providing a conveyor supplying an injector with a reducing agent with a return line which returns a recirculation amount of the reducing agent from the conveyor and the recirculation amount of the reducing agent to and / or in the change of one of the injector in the Flue gas introduced amount of reducing agent to vary. This makes it possible in particular, the conveyor constant, ie with relatively low operating state changes to operate, which on the one hand leads to a reduced load or increased life of the conveyor and thus the associated Reduktionsmittelzuführeinrichtung and on the other hand permits a more accurate variation of the introduced into the exhaust reducing agent quantity , In addition, already existing and produced in large quantities components, in particular conveyors and / or injectors, can be used, resulting in an economic production of Reduktionsmittelzuführeinrichtung or implementation of the method according to the invention. In this case, the reducing agent supply device according to the invention has at least one such injector which serves to introduce the reducing agent into the exhaust gas flow. The introduction of the reducing agent into the exhaust gas flow through the injector is preferably carried out by injecting or injecting the reducing agent into the exhaust gas flow, so that the amount of reducing agent introduced by the injector into the exhaust gas is referred to below as the injection quantity. The reducing agent passes by means of said conveyor to the injector, so that the conveyor supplies the injector with reducing agent, for example by the conveyor drives the reducing agent from a tank or reservoir or a container to the injector and / or pressurizes the injector. The supply of the injector with reducing agent by means of the delivery device is preferably realized via a supply line, which fluidly connects the injector to the associated delivery device. According to the invention, a supply line and a return line are further provided, wherein the feed line for supplying the reducing agent to the conveyor, while the return line is used to return the reducing agent from the conveyor to a tank or reservoir or a container. In this case, a return amount of the reducing agent is returned by the conveyor by means of the return line. Thus, according to the invention, the recirculation quantity returned by the return line through the return line is Reducing agent varies to change the introduced by the injector in the exhaust gas injection quantity of the reducing agent and / or to keep a delivery rate of the conveyor when changing the injection quantity as substantially as possible. In other words, the delivery device delivers a delivery rate of the reducing agent which is divided into the injection quantity introduced into the exhaust gas flow by the injector and the recirculation amount returned by the delivery device. On the one hand, it can be provided that the variation of the return quantity leads to a corresponding change in the injection quantity, wherein the delivery rate can be constant, in particular. On the other hand, it can be provided that the amount of return is varied in the change of the injection quantity, whereby combinations of these variants are conceivable. This is intended, in particular, that the correlation according to the invention between the injection quantity and the return quantity leads to a constant operating state of the conveyor device, for example a constant operating speed or delivery rate and the like.

In particular, the amount of recirculation to and / or in the increase of the injection quantity is reduced. Accordingly, the recirculation amount for and / or in the reduction of the injection amount is increased.

By reducing the amount of return to increase the injection quantity takes place, in particular at a constant operation of the associated injector and the associated conveyor, an increase in the pressure in the reducing agent pressure side of the injector, so that the injection quantity is increased. Accordingly, in the increase of the return amount for reducing the injection quantity, in particular at otherwise constant conditions, the pressure in the reducing agent on the pressure side of the injector decreases, so that the injection quantity is reduced.

Alternatively or additionally, the variation of the return quantity occurs in the case of another change in the injection quantity. In particular, if the injection quantity is otherwise increased, a corresponding reduction of the return quantity takes place in order, for example, to keep the delivery rate of the delivery device substantially constant. Similarly, in a different reduction of the injection quantity, a corresponding increase in the recirculation amount can take place, in order in particular to keep the delivery rate of the delivery device substantially constant.

A further advantage of the solution according to the invention can be seen in the fact that it is possible to provide essentially constant pressure conditions on the pressure side of the injector without varying the conveying capacity of the conveyor or at least achieving this with slight variations of the delivery rate.

In further preferred embodiments, the recirculation amount can be completely reduced, that is set to zero. In addition, the recirculation amount can preferably be increased up to a maximum possible value of the recirculation quantity, that is to say a maximum recirculation quantity, which is given in particular by the size or the flow cross section of the return line and the delivery rate of the delivery device. Thus, the recirculation amount can thus be adjusted preferably between zero and the maximum recirculation amount.

The Reduktionsmittelzuführeinrichtung is preferably used in large engines, which are to be considered below large engines internal combustion engines with a displacement of at least 10 liters and / or a power of at least 600 kW. Such large engines are used for example in combined heat and power plants and locomotives, for driving a ship and for power generation.

The introduced into the exhaust stream reducing agent is suitably selected according to the particular needs. If the exhaust gas originating from the internal combustion engine is to be aftertreated, for example, in a catalytic converter, for example in order to screen out harmful components, appropriate fluids and in particular liquids are used as reducing agents. An example of this is the selective catalytic reaction (SCR) by means of an exhaust gas treatment device, in which nitrogen oxides are converted into nitrogen. Here, the reducing agent may be, for example, a urea-containing or an ammonia-containing fluid.

Preferably, the supply of the reducing agent to the conveyor from a reducing agent tank such as such a tank or reservoir and the like. Here, the return of the reducing agent by means of the return line to said reducing agent tank, so that the recirculated from the conveyor recirculation amount of the reducing agent again reaches the reducing agent tank and can be guided by means of the feed line to the conveyor.

The variation of the return amount to and / or during the change of the injection quantity can be done in principle in any way. In preferred embodiments, a controllable valve device is provided for this purpose, which is arranged in the return line. The valve device may in this case have one or more valves, of which at least one is controllable and therefore can be referred to as a control valve. The control of the valve device is further preferably carried out by means of a control device of the reducing agent supply device, which is programmed or configured such that it can operate the valve device according to the invention.

The injection quantity introduced into the exhaust gas stream is determined, in particular, by the respective requirement of the reducing agent in the exhaust gas stream, for example by a desired aftertreatment of the exhaust gas. Accordingly, the variation of the injection quantity preferably takes place as a function of a reduction agent requirement in the exhaust gas flow.

The variation of the return amount can generally be stepwise. However, preferred are those embodiments in which the recirculation amount is varied continuously. The continuous variation of the return amount to and / or the change in the injection quantity has the consequence that the pressure conditions in the reducing agent, in particular in the supply line or the supply line do not vary suddenly or jerkily, and thus a corresponding load on the components of the reducing agent supply, in particular the conveyor, prevents or at least reduced. These so-called and in particular reduced by the continuous variation of the recirculation pressure pulsations can also lead to damage to the injector and allow a comparatively low precision of the injection quantity.

In principle, the change in the injection quantity can take place on the injector side, that is to say by means of the injector, wherein the change in the injection quantity can take place according to the invention from a combination of the variation of the return quantity and the injector-side changes. Such an injector-side change is realized, for example, by the variation of a flow cross-section of the injector through which the reducing agent flows. That is, the flow area may be reduced, for example, to reduce the injection amount or the flow area may be increased to increase the injection amount. This can be done in particular by a corresponding change in the size of an injector opening of the injector.

Such an injector-side variation of the injection quantity preferably takes place via the change in an opening time of the injector opening of the injector through which the reducing agent flows. In other words, the injector opening is closed and opened, the injection quantity resulting from the respective opening times or opening duration of the injector opening or the associated timing.

This means that the injector opening is opened longer or the opening duration is increased in order to increase the injection quantity or that the injector opening is opened shorter or the opening duration is shortened in order to reduce the injection quantity. The opening and closing of the injector opening preferably takes place by means of a pulse width modulation (PWM), in which the injector opening is opened and / or closed in particular periodically. Further, for opening and closing the injector opening, for example, a throttle or a throttle disk may be provided, which is arranged in the injector or outside the injector, in particular upstream of the injector, in the supply line and is controllable, for example, by said control.

In this way, the method can in particular be realized in such a way that, to increase the injection quantity, the opening time or the opening duration of the injector opening or the associated timing increases and the return quantity is reduced. Similarly, to reduce the injection quantity, the opening time or opening duration can be reduced and the recirculation amount can be increased. This makes it possible in particular to operate the associated conveyor even with varying injection quantities at comparatively low operating state changes, wherein with a corresponding adjustment of the change of the opening times and the return amount of the operating state can be kept substantially constant. In particular, this also makes it possible to provide substantially constant pressure conditions on the pressure side of the injector. Such substantially constant pressure conditions on the pressure side of the injector have the advantage that the opening time of the injector opening or the corresponding timing and the injection quantity have a relatively accurate and calculable dependency, so that a more precise variation of the injection quantity is possible.

Analogously, the change of the flow cross-section of the injector to be adapted to a change in the return amount to vary the injection quantity.

In preferred embodiments, the change in the opening time of the injector or the change in the flow cross-section of the injector also by means of said control unit, which is for this purpose with the injector and / or a the opening time or the flow cross-section varying means, in particular said throttle or throttle plate connected , The controller may also be connected to the conveyor to also control the conveyor to, for example, increase or reduce the capacity of the conveyor.

In further embodiments, it is conceivable that two or more injectors are supplied by such a common conveyor with reducing agent. It is also conceivable that such an injector or several such injectors are supplied jointly by two or more common such conveyors with reducing agent. For this purpose, the feeders / conveyors associated injectors are supplied by means of such a common supply line with reducing agent or are supplied with different such supply lines with reducing agent, embodiments are preferred in which the supply of such a conveyor injectors by means of such a common supply line.

In this case, the change of the opening times of the injectors associated with such a conveyor preferably takes place with a time delay. This means that the change in the opening time of the respective injector openings initially takes place in one or more such injectors and subsequently by one or more such other injectors. This can be realized, for example, in that the injector openings of one or more of such injectors supplied by such a common conveyor are open, while the injector openings of one or more such other injectors supplied by the same conveyor are closed. This has in particular the consequence that the pressure in the common supply line can be kept relatively constant. In the case of a PWM introduction of the injection quantity into the exhaust gas flow, in which a PWM signal is periodic, the opening times of the respective injectors associated with the conveying device / delivery devices can be changed and / or adapted to one another in a time-shifted manner in such a way that comparatively low and low values occur in the common supply line preferably no pressure pulsations arise. If the reducing agent supply device has, for example, two such injectors which are supplied with reducing agent from such a common delivery device by means of a common supply line, the change in the opening times of the respective injector, with identical injectors, preferably with a time delay, which is half the period length of the periodic PWM Signal corresponds.

In preferred embodiments, the time-delayed opening or timing of the such a supply line and / or conveyor associated injectors is such that the opening phases of at least two of the injector openings overlap. Thus, the pressure in the reducing agent resulting from the closing of such an injector opening can be compensated by the other open injector opening, so that substantially constant pressure conditions prevail within the supply line.

Of course, it is also possible to vary a plurality of conveyors or the corresponding recirculation amounts according to the invention, wherein the respective conveyor can serve to supply one or more injectors. Embodiments are also conceivable in which two or more such delivery devices jointly serve to supply such an injector or several such injectors, in particular by means of a common supply line, wherein at least one of the delivery devices or the associated return quantity is varied according to the invention.

The control unit can have a plurality of output stages for supplying the injectors with power, it being possible for a single injector or a plurality of injectors to be connected to the respective output stage. It is also conceivable to supply the conveyor or several such conveyors by means of such a power amplifier of the control unit with power. In addition, it is conceivable to connect said valve device or a plurality of such valve devices to one or more such output stages of the control device in order to supply the respective valve device with power or to control the respective valve device.

In principle, the respective injectors of the reducing agent supply device are identical or of the same type. However, it is also conceivable that the different injectors of the reducing agent supply device are of different types. Thus, it is conceivable that the injectors supplied with reducing agent by such a delivery device have different maximum injection quantities. In particular, it is possible for the reducing agent supply device to have one or more such injectors with a maximum injection quantity of 12 kg / h and other such injectors with a maximum injection quantity of 7.2 kg / h.

Also, in the Reduktionsmittelzuführeinrichtung different conveyors are used. For example, the respective delivery devices can have a maximum flow rate of 21 kg / h. Since the recirculation amount can be reduced and in particular reduced to zero, thus, for example, the entire flow rate can reach the associated injector or the associated injectors. This makes it possible in particular to supply the entire flow rate of such a conveyor to a single such injector, so that the delivery rate corresponds to the injection quantity.

In other preferred embodiments, the reductant supply means is modular. This means that the respective injector is designed as an injector module or forms such an injector module, while the respective conveyor device forms a conveyor module or is designed as such. In addition, the control unit has a plurality of injector output stages for controlling and energizing at least one injector module and / or a plurality of delivery output stages for activating and energizing at least one delivery module. Furthermore, the control unit is preferably configured or programmed such that any number of injector modules and / or conveyor modules can be connected to the control unit. In this case, the number of injector modules is limited by the product of the number of injector output stages and the number of injector modules which can be connected to such an injector output stage, while the number of conveyor modules can be connected by the product to the number of conveyor output stages and the maximum number of such a conveyor output stage Delivery modules is limited.

This makes it possible, in particular, to expand the reducing agent supply device as desired. In addition to the expansion of the Reduktionsmittelzuführeinrichtung by the corresponding modules, it can also be provided that the control unit with one or more other control devices is connectable to expand the Reduktionsmittelzuführeinrichtung. In this case, the respective control devices are preferably cascadable, the control devices preferably communicating with one another in such a way that they function according to the master-slave principle.

In an advantageous development of the reducing agent supply device, at least one sensor device is provided, which is connected in a communicating manner with the control device. Such a sensor device can serve, for example, the measurement of pressure and / or temperature and / or a fluid concentration of at least one fluid, for example the exhaust gas and / or oxygen and of the reducing agent, in particular in the exhaust gas flow. In particular, with the aid of such a sensor device, the reducing agent requirement in the exhaust gas flow and thus the necessary injection quantity of the reducing agent into the exhaust gas flow can be determined. For this purpose, the sensor device can have one or more sensors, wherein the respective sensor can be arranged within the reducing agent device or outside the reducing agent device. Thus, it is conceivable to arrange one or more such sensors in the exhaust gas stream upstream or downstream of the respective injector and downstream and upstream of an associated exhaust gas treatment device, for example an associated catalytic converter, in order to determine said reducing agent requirement. Also, such sensors can be arranged in the supply line, the supply line and the return line.

It is understood that an exhaust system with a reducing agent supply device according to the invention also belongs to the scope of this invention. In this case, the exhaust gas originating from the internal combustion engine flows through at least one exhaust pipe of the exhaust system, wherein the reducing agent supply device introduces the reducing agent upstream of an exhaust gas treatment device of the exhaust system in the exhaust gas flow.

As such an exhaust gas treatment device, for example, a catalyst for exhaust aftertreatment is used, wherein the catalyst may be formed in particular as an SCR catalyst.

Furthermore, the exhaust system may have two or more such exhaust pipes. In this case, a plurality of such injectors may be provided, each of which introduce the reducing agent in the same exhaust pipe or different exhaust pipes. In particular, it is conceivable that the injectors of the reducing agent supplied by a common delivery device with reducing agent introduce into different exhaust gas lines. In addition, embodiments are conceivable in which two or more exhaust pipes open into a common intermediate section, in particular into a common collection section. In this intermediate section, the injection of the reducing agent then takes place through at least one such injector and optionally a corresponding treatment of the exhaust gas. At least one exhaust pipe may be fluidly connected to the intermediate section downstream of the intermediate section in order to discharge the exhaust gas from the intermediate section.

Other important features and advantages of the invention will become apparent from the dependent claims, from the drawing and from the associated description of the figures with reference to the drawing.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Preferred embodiments of the invention are illustrated in the drawings and will be explained in more detail in the following description.

The only 1 shows a greatly simplified schematic diagram of an exhaust system.

According to 1 has an exhaust system 1 an internal combustion engine 2 an exhaust treatment plant 3 on that several exhaust treatment devices 4 includes. Furthermore, the exhaust system points 1 a reducing agent supply device 5 on, wherein the reducing agent supply 5 flues 6 the exhaust system 1 by means of injectors 7 a reducing agent 8th supplies. Here, the reducing agent 8th with the help of the respective injectors 7 in an exhaust gas stream 9 injected, the exhaust gas flow 9 illustrated by arrows, while the reducing agent 8th in the exhaust pipes 6 is shown as spraying. The reducing agent 8th , which may be, for example, a urea-containing liquid, passes through supply lines 10 to the respective injector 7 , The exhaust system shown 1 Here, by way of example, has four such exhaust pipes 6 in which in each case such an exhaust gas treatment device 4 is arranged, wherein the respective exhaust pipe 6 two such injectors 7 are assigned, which the reducing agent 8th in each case upstream of the exhaust gas treatment device 4 in the exhaust stream 9 contribute. Further, the two of such exhaust pipe 6 associated injectors 7 by means of a common supply line 10 with reducing agent 8th provided.

The respective supply line 10 is with a conveyor 11 connected, so that the respective conveyor 11 the injectors 7 such exhaust pipe 6 with reducing agent 8th provided. The respective conveyor 11 , which may be configured for example as a pump, relates the reducing agent 8th by means of a supply line 12 from a reducing agent tank 13 , Further, to the respective conveyor 11 a return line 14 provided, the return of a return amount of the reducing agent 8th from the conveyor 11 to the reducing agent tank 13 serves.

The reducing agent supply device 5 has a controller 15 on that the conveyors 11 and the injectors 7 actuated and controls. These are the conveyors 11 each by means of a control line 16 to the control unit 15 connected. Furthermore, those of such exhaust pipe 6 associated injectors 7 in pairs via a control line 17 with the control unit 15 connected. The connection of the conveyors 11 by means of the control lines 16 with the control unit 15 takes place via power amplifiers 18 of the control unit 15 , wherein the respective conveyor 11 such a power amplifier 18 , hereinafter referred to as the final output stage 18 is called, is realized. Further, the connection of the injectors 7 with the control unit 15 by means of the control lines 17 also by means of power amplifiers 19 of the control unit 15 realized below as injector output stages 19 be designated. Here are the two of such exhaust pipe 6 associated injectors 7 with such a Injektorendstufe 19 connected. The two associated injectors 7 are each further by means of a signal line 20 with the control unit 15 connected to the control unit information about the current operating state of the respective injector 7 to convey.

In the respective return line 14 is a valve device 21 arranged, which by the associated conveyor 11 to the reducing agent tank 13 recycled recirculation amount of the reducing agent 8th can vary. For this purpose, the respective valve device 21 designed controllable and by means of a signal line 22 with an associated power amplifier 23 of the control unit 15 connected, these power amplifiers 23 subsequently as valve output stages 23 be designated. It is also conceivable, the respective valve device 21 by means of a control line to the control unit 15 to connect, for example, information about the current operating state of the respective valve device 21 to the control unit 15 to convey. The control unit 15 further includes a processor 24 in which algorithms and the like for driving the valve means 21 as well as the injectors 7 and the conveyors 11 are deposited. In other words, the controller 15 is programmed to be the injectors 7 as well as the valve devices 21 and the conveyors 11 can drive. Here are the valve devices 21 triggered such that the of the respective conveyor 11 to the reducing agent tank 13 recycled recirculation amount of the reducing agent 8th is reduced to one of the associated injectors 7 in the exhaust stream 9 introduced injection quantity or injection quantity of the reducing agent 8th to increase. Alternatively or additionally, the return amount in the increase of the injection quantity of the reducing agent 8th be reduced. Accordingly, the recirculation amount of the reducing agent becomes 8th enlarged by the associated injectors 7 in the exhaust stream 9 introduced injection quantity of the reducing agent 8th to reduce and / or the recirculation amount is increased in reducing the injection quantity. The respective valve device 21 So it can be closed to the whole of the associated conveyor 11 funded delivery of the reducing agent 8th the associated injectors 7 supply. Analog can be provided that when completely open the valve device 21 the entire delivery of the associated conveyor 11 to the reducing agent tank 13 is returned, so no reducing agent 8th through the associated injectors 7 in the gas stream 9 can get. The change of the return quantity takes place here continuously between these values or states, so that no pressure pulsations can arise due to the variation of the return quantity. All in all This is a substantially constant capacity of the associated conveyor 11 and / or a substantially constant pressure in the reducing agent 8th pressure side of the associated injectors 7 or within the associated supply line 10 guaranteed.

The change in the injection quantity of the respective injector 7 can by an appropriate opening time of an injector 25 the associated injector 7 respectively. That means the injector opening 25 closed and opened, leaving reducing agent 8th is introduced into the exhaust gas flow in appropriate injection cycles. With a corresponding increase in the opening time, therefore, the injection quantity can be increased, at the same time or during the recirculation amount by means of the associated valve device 21 is reduced. Analogously, the injection quantity can be achieved by reducing the opening time of the associated injector opening 25 be reduced, at the same time or while the recirculation amount by means of the associated valve means 21 is increased.

The opening and closing of the respective injector opening 25 takes place by means of pulse width modulation (PWM), wherein a corresponding PWM signal by means of the control unit 15 over the signal line 17 to such an injector 7 the Injektorpaares the respective exhaust pipe 6 is sent. The injector receiving the PWM signal 7 is also by means of a coupling line 26 with the other injector 7 connected to the Injektorpaars, such that at the directly to the control unit 15 over the signal line 17 connected injector 7 Sent PWM signal with time delay at the other injector 7 arrives. The time delay is chosen such that the opening times of the injector openings 25 the associated injectors 7 overlap. This makes it possible to pressure pulsations in the supply line 10 to avoid.

By varying the amount of recirculation during and / or for changing the injection quantity, it is possible, in particular, for the respective conveying device 11 constant, that is to operate at a constant operating state, which is the life of the respective conveyor 11 and thus the life of the associated Reduktionsmittelzuführeinrichtung 5 or exhaust system 1 elevated. It is also possible within the associated supply line 10 and in particular the pressure side of the associated injectors 7 or injector openings 25 , Especially at substantially constant operating conditions of the associated conveyor 11 to provide substantially constant pressure ratios to achieve more accurate injection quantity variation. Here, the injection quantity determined by the in the exhaust stream 9 required amount of reducing agent, which is necessary to a corresponding aftertreatment by the exhaust gas treatment device 4 to ensure. When as SCR catalyst 27 trained exhaust treatment facilities 4 So is the amount of reducing agent and thus the injection quantity of the reducing agent 8th chosen such that this ensures sufficient conversion of nitrogen oxides to nitrogen.

To determine the required amount of reducing agent of the reducing agent 8th and accordingly, the injection amount and, consequently, the amount of recirculation of the reducing agent 8th Here is a sensor device 28 provided the two sensors 29 . 30 which, in each case at an interface 31 of the control unit 15 with the control unit 15 are connected. Here are the sensors 29 . 30 for example, in such an exhaust pipe 6 upstream and / or downstream of the injectors 7 arranged to determine the required amount of reducing agent or injection quantity. It is also conceivable, such sensors 29 . 30 downstream of the exhaust treatment device 4 to arrange. The control device 15 has another such interface 31 on, for example, as a data bus interface 31 can be configured to connect a data bus to the control unit 15 to join.

In preferred embodiments, the reductant delivery device is 5 modular. This means that the reducing agent supply device in particular such injectors 7 can each have an injector module 7 form. Furthermore, the reducing agent supply device 5 such conveyors 11 each having a delivery module 11 the Reduktionsmittelzuführeinrichtung 5 form. Also, the respective valve device 21 a valve module 21 form. This makes it possible in particular, the reducing agent supply 15 through appropriate conveyor modules 11 or injector modules 7 as well as valve modules 21 to expand almost arbitrarily. For this purpose, the control unit 15 a variety of conveyor output stages 18 and / or Injektorendstufen 19 and / or valve output stages 23 on, where to the respective power amplifier 18 . 19 . 23 such a module 7 . 11 . 21 or more such modules 7 . 11 . 21 can be connected. In the example shown are at the respective Injektorendstufe 19 two such injector modules 7 connected to such an exhaust pipe 6 assigned.

Furthermore, two such injector modules 7 from such a delivery module 11 by means of a common supply line 10 with reducing agent 8th supplied, both injectors 7 or injector modules 7 such exhaust pipe 6 assigned. However, it is also conceivable that different injector modules 7 that of a common conveyor module 11 or several common conveyor modules 11 with reducing agent 8th provided be, reducing agents 8th in different exhaust pipes 6 contribute.

If the number of power amplifiers 18 . 19 . 23 of the control unit 15 in particular for a desired extension of the modular reducing agent supply device 15 are not sufficient, so it is also possible, the reducing agent supply 15 by such another control device 15 or more such other control devices 15 to complete. Here are the respective control units 15 , for example through such an interface 31 , communicating with each other, this connection being made such that the control devices 15 form a cascade, the controllers 15 preferably operate according to the master-slave principle.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102010002987 A1 [0003]

Claims (15)

Method for operating a reducing agent supply device ( 5 ) for an exhaust system ( 1 ) an internal combustion engine ( 2 ), in particular a large engine, which preferably has at least 600 kW of power and / or at least 10 liters of displacement, - with at least one injector ( 7 ) for introducing an injection amount of a reducing agent ( 8th ) in an exhaust gas stream ( 9 ), - with a conveyor ( 11 ) for supplying at least one such injector ( 7 ) with reducing agent ( 8th ), - with a supply line ( 12 ) for the supply of the reducing agent ( 8th ) to the conveyor ( 11 ), - with a return line ( 14 ) for returning a recirculation amount of the reducing agent ( 8th ) from the conveyor ( 11 ), - wherein the return amount is varied to and / or when changing the injection quantity. A method according to claim 1, characterized in that - the recirculation amount is reduced to and / or in the increase of the injection quantity, and / or - that the recirculation amount to and / or in the reduction of the injection amount is increased. A method according to claim 1 or 2, characterized in that the return amount is varied continuously. Method according to one of claims 1 to 3, characterized in that - an opening time of one of the reducing agent ( 8th ) through the injector opening ( 25 ) of the injector ( 7 ) is increased to increase the injection amount, and / or - that the opening time of the injector opening ( 25 ) is reduced to reduce the injection quantity. Method according to one of claims 1 to 4, characterized in that the change of the opening times of two or more of the conveyor ( 11 ) with reducing agent ( 8th ) supplied injectors ( 7 ) time offset takes place. Method according to one of claims 1 to 5, characterized in that the return amount of two or more conveyors ( 11 ) is varied. Reducing agent supply device ( 5 ) for an exhaust system ( 1 ) an internal combustion engine ( 2 ), in particular a large engine, which preferably has at least 600 kW of power and / or at least 10 liters of displacement, - with at least one injector ( 7 ) for introducing an injection amount of a reducing agent ( 8th ) in an exhaust gas stream ( 9 ), - with at least one supply line ( 10 ) for supplying at least one such injector ( 7 ) with reducing agent ( 8th ), - with at least one conveyor ( 11 ) for driving the reducing agent ( 8th ) in the at least one supply line ( 10 ), - with at least one supply line ( 12 ) for supplying the reducing agent ( 9 ) to at least one such conveyor ( 11 ), - with a return line ( 14 ) for returning a recirculation amount of the reducing agent ( 8th ) of at least one such conveyor ( 11 ), - with one in the return line ( 14 ) arranged controllable valve device ( 21 ) for varying the recirculation quantity, - with a control unit ( 15 ), to which the at least one valve device ( 21 ) is connected, - wherein the control unit ( 15 ) is configured and / or programmed such that it is the valve device ( 21 ) operated according to the method of any one of the preceding claims. Reducing agent supply device according to claim 7, characterized in that the valve device ( 21 ) associated conveyor ( 11 ) and / or the valve device ( 21 ) associated at least one injector ( 7 ) to the control unit ( 15 ) and the control unit ( 15 ) for actuating the connected injectors ( 7 ) and the connected conveyor ( 11 ) is configured and / or programmed. Reducing agent supply device according to claim 7 or 8, characterized in that the control device ( 15 ) several power amplifiers ( 19 ) for supplying power to the injectors ( 7 ), wherein to the respective output stage ( 19 ) a single injector ( 7 ) or several injectors ( 7 ) is / are connected. Reducing agent supply device according to one of claims 7 to 9, characterized in that the of the conveyor ( 11 ) injectors supplied with reducing agent ( 7 ) of the same type or different design. Reducing agent supply device according to one of claims 7 to 10, characterized in that - the reducing agent supply device ( 5 ) has a modular construction, - in which the respective injector is an injector module ( 7 ), in which the respective conveyor device is a conveyor module ( 11 ), - in which the control unit ( 15 ) several injector output stages ( 19 ) for controlling and energizing at least one injector module ( 7 ) and several Power amplifiers ( 18 ) for controlling and energizing at least one conveyor module ( 11 ), - in which the control unit ( 15 ) is designed and / or programmed so that any number of injector modules ( 7 ) to the control unit ( 15 ), provided that the number of injector modules ( 7 ) not larger than a product of the number of injector output stages ( 19 ) and the maximum number of such an injector output stage ( 19 ) connectable injector modules ( 7 ), - in which the control unit ( 15 ) is designed and / or programmed so that any number of conveyor modules ( 11 ) to the control unit ( 15 ), provided that this number of conveyor modules ( 11 ) not larger than a product of the number of delivery stages ( 18 ) and the maximum number of such a conveyor output stage ( 18 ) connectable conveyor modules ( 11 ). Reducing agent supply device according to one of claims 7 to 11, characterized in that the reducing agent supply device ( 5 ) at least one with the control unit ( 15 ) communicating sensor device ( 28 ) having. Exhaust system ( 1 ) with at least one exhaust stream ( 9 ) leading exhaust pipe ( 6 ) in which an exhaust gas treatment device ( 4 ) and with a reducing agent supply device ( 5 ) according to any one of claims 7 to 12 for introducing the reducing agent ( 8th ) in the exhaust pipe ( 6 ) upstream of the exhaust treatment device ( 4 ). Exhaust system according to claim 13, characterized in that such a conveyor ( 11 ) two or more such injectors ( 7 ) with reducing agent ( 8th ), these injectors ( 7 ) the reducing agent ( 8th ) each in the same exhaust pipe ( 6 ) or in different exhaust pipes ( 6 ). Exhaust system according to claim 13 or 14, characterized in that the exhaust gas treatment device ( 4 ) a catalyst ( 27 ), in particular an SCR catalyst ( 27 ' ), having.

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