DE112017006739T5 - POST - TREATMENT TEMPERATURE CONTROL DEVICE AND METHOD - Google Patents

Abstract

The present disclosure relates to a system (1) for a vehicle (V). The vehicle (V) may include an internal combustion engine (2) having a diesel engine. The system (1) comprises a compressor (10) having an inlet (12) and an outlet (13) for supplying compressed air to the internal combustion engine (2). An exhaust pipe (3) for conveying exhaust gas from the internal combustion engine (2) is provided. A particulate filter (25) and a selective catalytic reduction (SCR) device are arranged in the exhaust pipe (3). An injection conduit (33) is provided for diverting a portion of the compressed air from the compressor (10) to the exhaust conduit (3) to control an operating temperature of the SCR apparatus (26). The present disclosure also relates to a control unit (37) and to a method.

Description

TECHNICAL PART

The present disclosure relates to an apparatus and method for controlling the post-treatment temperature. More particularly, but not exclusively, the present disclosure relates to a vehicle configured to control the supply of compressed air to an aftertreatment system for controlling the operating temperature of a selective catalytic reduction (SCR) device. The present disclosure also relates to a method of controlling the operating temperature of the SCR device and to a controller configured to control the operating temperature of the SCR device.

BACKGROUND

The reduction of particulate and NOx emissions from vehicles is becoming increasingly important. Selective catalytic reduction (SCR) catalysts are widely used to control NOx (NOx) emissions from diesel engines and have an effective operating window between 150 ° C and 550 ° C. Above 550 ° C, the ammonia required as a reductant in the SCR reaction can be oxidized and is therefore not available to reduce NOx emissions. The capacity of the SCR catalyst for storage of ammonia also decreases with increasing temperature, and at high temperatures some ammonia can not be oxidized, but desorbed from the bearing points on the catalyst and discharged as ammonia gas from the tailpipe.

Diesel Particulate Filters (DPFs) are also commonly used in diesel vehicles to collect particulates. When the DPF reaches its maximum carbon black capacity, it will be regenerated on a regular basis. The regeneration involves changing the operation of the engine (and DOC) to raise the temperature of the gas entering the DPF to above 550 ° C and up to 700 ° C, whereby the soot stored on the DPF is oxidized and stored as carbon dioxide ( CO2) is emitted. During the DPF regeneration event, the inlet gas to the SCR catalyst may exceed 550 ° C, resulting in ammonia oxidation and desorption. The oxidized and desorbed ammonia is no longer available for NOx reduction and reduces the effectiveness of the NOx reduction catalyst both during and after the completion of the regeneration event.

Against this background, the present invention was conceived. In at least certain embodiments, the present invention aims to overcome or ameliorate the shortcomings of prior art devices or at least to overcome some of the deficiencies.

SUMMARY OF THE INVENTION

Aspects of the present invention relate to a system, to a vehicle, to a method of controlling an operating temperature of a selective catalytic reduction (SCR) device, and to a controller for controlling the temperature of an SCR device as claimed in the appended claims.

• einen Kompressor (Verdichter) zum Zuführen von verdichteter Luft zu einem Verbrennungsmotor, wobei der Kompressor einen Einlass und einen Auslass aufweist;
• eine Abgasleitung zum Fördern von Abgasen aus dem Verbrennungsmotor;
• einen Partikelfilter und eine Vorrichtung zur selektiven katalytischen Reduktion (SCR), die in der Abgasleitung angeordnet ist;
• eine Einspritzleitung zum Umleiten eines Teils der verdichteten Luft vom Kompressor zur Abgasleitung, um eine Betriebstemperatur der SCR-Vorrichtung zu steuern. Die verdichtete Luft aus dem Kompressor kann in die Abgasleitung vor der SCR-Vorrichtung eingeleitet werden. Zumindest in bestimmten Ausführungsformen kann die Temperatur der in die SCR-Vorrichtung eingeleiteten Einlassgase gesteuert werden, wodurch die Betriebstemperatur der SCR-Vorrichtung gesteuert werden kann.

According to another aspect of the present invention, there is provided a system for a vehicle, the system comprising:

• a compressor for supplying compressed air to an internal combustion engine, the compressor having an inlet and an outlet;
• an exhaust pipe for conveying exhaust gases from the internal combustion engine;
• a particulate filter and a selective catalytic reduction (SCR) device disposed in the exhaust passage;
• an injection conduit for diverting a portion of the compressed air from the compressor to the exhaust conduit to control an operating temperature of the SCR apparatus. The compressed air from the compressor may be introduced into the exhaust pipe in front of the SCR device. At least in certain embodiments, the temperature of the inlet gases introduced into the SCR device may be controlled, whereby the operating temperature of the SCR device may be controlled.

The system may include a first valve means for controlling the supply of the compressed air from the injection line to the exhaust line. The system may include a control unit configured to control the first valve means. The control unit may be configured to control the first valve means for supplying compressed air from the compressor to the exhaust passage during regeneration of the particulate filter.

The injection line may be used to direct a portion of the compressed air from the compressor to the SCR device. The proportion of the compressed air supplied from the compressor to the exhaust pipe may be fixed or variable. The air can be injected into the exhaust pipe in front of the SCR device. Thereby, the operating temperature of the SCR device can be controlled. This is especially true for the regeneration of Aftertreatment systems, such as a particulate filter, that can be performed at elevated temperatures. The injection line can thereby facilitate the transport of the gas from a venting point of the post-compressor to the SCR device. The system includes a low pressure exhaust gas recirculation (LP-EGR) line for recirculating exhaust gas from the exhaust line to the inlet of the compressor. The injection line is arranged so that a part of the compressed air is passed from the compressor into the exhaust pipe. The injection line selectively serves to supply air to the SCR device via the LP EGR line. The injection line connects the output of the compressor to the LP EGR line.

A first heat exchanger may be provided for cooling the compressed air from the compressor. The first heat exchanger may be disposed between the compressor and the engine. The injection line can be connected to the outlet of the compressor before or after the first heat exchanger. The first heat exchanger may be a charge air cooler.

A second heat exchanger can be provided. The second heat exchanger can be arranged, for example, in the LP EGR line between the injection line and the exhaust pipe.

The first valve means may be adapted to control the compressed air supply from the injection line to the LP EGR line. The first valve means may be arranged in the injection line, for example at an inlet to the injection line or at an outlet of the injection line. The first valve means may comprise a first valve. The first valve may be a first two-way valve.

A second valve means may be provided to control the compressed air supply from the LP EGR passage to the inlet of the compressor. The second valve means may be located in the LP EGR line or at an output of the LP EGR line. The second valve means may comprise a second valve. The second valve may be a second two-way valve.

The first valve means and the second valve means may be independently controlled, e.g. for exhaust gas recirculation through the LP EGR line or for introduction of compressed air into the LP EGR line. In order to control the operating temperature of the SCR device, the first valve means can be opened and the second valve means closed. By opening the first valve means, compressed air from the compressor can be fed into the LP EGR line. Closing the second valve means prevents the compressed air from returning from the LP EGR line to the compressor. Rather, the compressed air is supplied to the SCR device via the LP EGR line.

The first and second valve means can be combined. For example, the first and second valves may include a three-way valve located at the junction of the LP EGR line and the injection line. For example, the three-way valve could be configured to operate in one or more of the following states: close both the LP EGR line and the injection line; connect the LP-EGR line to the input of the compressor and close the injection line; and connect the LP EGR line to the injection line and close the connection to the input of the compressor.

The injection pipe may be connected to the LP-EGR pipe between the second valve means and the exhaust pipe.

A control unit may be provided to control the first valve means (valve means) and / or the second valve means. The controller may be configured to open the first valve means and close the second valve means to supply compressed air to the SCR device.

The controller may be configured to control the first valve means and / or the second valve means to direct compressed air from the compressor to the LP EGR passage during regeneration of the particulate filter. Alternatively or additionally, the control unit may be configured to control the first and second valve means in response to an operating temperature of the SCR device. The operating temperature of the SCR device may be modeled, for example, based on operating parameters of the internal combustion engine. Alternatively, the operating temperature of the SCR device may also be measured, e.g. a temperature sensor associated with the SCR device. Another alternative is to control the compressed air supplied to a fixed portion of the exhaust stream, thereby controlling the temperature of the mixture without temperature modeling or measurement, albeit with larger variations. Additionally, with short term high engine power demand, the valve means may be controlled to preferentially supply air to the engine for combustion. This would allow the SCR to warm up during this transient condition, with the valve returning to provide cooling after the transient power demand.

An injector may be provided to introduce a liquid reductant, such as urea or other ammonia precursor, into the exhaust conduit upstream of the SCR apparatus. The LP EGR line can be connected before or after the injector.

The system may include a second heat exchanger. The second heat exchanger may be disposed in the LP EGR passage between the injection pipe and the exhaust pipe. The second heat exchanger may be used to cool the compressed air prior to introduction into the SCR device. By cooling the air from the compressor in the LP-EGR, the amount of air needed to achieve sufficient cooling of the SCR device can be reduced.

A particulate filter can be arranged in the exhaust pipe. The internal combustion engine may be a diesel engine and the particulate filter may be a diesel particulate filter. The SCR device may be disposed in the exhaust pipe downstream of the particulate filter. The LP EGR conduit may be connected to the exhaust conduit between the particulate filter and the SCR apparatus.

The compressor can be part of a turbocharger. The turbocharger may include a turbine for driving the compressor. The turbine can be arranged in the exhaust pipe.

Alternatively, the compressor may also be an electric compressor (also known as an e-compressor). The electric compressor may include an electric machine for driving the compressor. The electric compressor may be used in combination with a turbocharger to achieve, for example, first and second stage compression. The electric compressor can be provided in front of the turbocharger. The injection line may be connected between the electric compressor and the turbocharger; or it may be connected downstream of the turbocharger.

• mindestens einen Prozessor zum Steuern einer Zufuhr verdichteter Luft von einem Kompressor zur Abgasleitung; und
• eine Speichervorrichtung, die mit dem mindestens einen Prozessor gekoppelt ist;
• wobei der mindestens eine Prozessor konfiguriert ist, um ein erstes Ventilmittelöffnungssignal auszugeben, um ein erstes Ventilmittel zu öffnen, um verdichtete Luft vom Ausgang des Kompressors über eine Niederdruck-Abgasrückführleitung (LP-EGR) zur Abgasleitung zu liefern, um die Betriebstemperatur der SCR-Vorrichtung zu reduzieren.

According to one aspect of the invention, there is provided a control unit for controlling an operating temperature of a selective catalytic reduction (SCR) apparatus disposed in an exhaust pipe connected to an internal combustion engine; wherein the control unit comprises:

• at least one processor for controlling a supply of compressed air from a compressor to the exhaust pipe; and
• a memory device coupled to the at least one processor;
• wherein the at least one processor is configured to output a first valve-means opening signal to open a first valve means for supplying compressed air from the outlet of the compressor via a low-pressure exhaust gas recirculation (LP-EGR) line to the exhaust pipe to the operating temperature of the SCR device to reduce.

• Mittel zum Empfangen eines Signals, das die Betriebstemperatur der SCR-Vorrichtung anzeigt; und
• Mittel zum Steuern einer Betriebstemperatur der Vorrichtung zur selektiven katalytischen Reduktion (SCR) durch Steuern eines ersten Ventilmittels zum Zuführen von verdichteter Luft vom Ausgang des Kompressors über eine Niederdruck-Abgasrückführungsleitung (LP-EGR) zur Abgasleitung.

According to one aspect of the invention, a vehicle system controller is provided to control an operating temperature of a selective catalytic reduction (SCR) device disposed in an exhaust pipe connected to an internal combustion engine, the controller comprising:

• Means for receiving a signal indicative of the operating temperature of the SCR device; and
• Means for controlling an operating temperature of the selective catalytic reduction (SCR) apparatus by controlling a first valve means for supplying compressed air from the outlet of the compressor via a low pressure exhaust gas recirculation (LP-EGR) conduit to the exhaust conduit.

• die Mittel zum Empfangen eines Signals, das die Betriebstemperatur der SCR-Vorrichtung anzeigt, einen elektronischen Prozessor mit einem elektrischen Eingang zum Empfangen des Signals, das die Betriebstemperatur der SCR-Vorrichtung anzeigt, umfassen; und
• eine elektronische Speichervorrichtung, die elektrisch mit dem elektronischen Prozessor gekoppelt ist und darin gespeicherte Anweisungen aufweist,
• das Mittel zum Steuern einer Betriebstemperatur der Vorrichtung zur selektiven katalytischen Reduktion (SCR) durch Steuern eines ersten Ventilmittels zum Zuführen von verdichteter Luft vom Kompressor zur Abgasleitung, das konfiguriert ist, um: auf die Speichervorrichtung zuzugreifen und die darin gespeicherten Anweisungen auszuführen, so dass es betreibbar ist, ein erstes Ventilmittel zum Zuführen von verdichteter Luft vom Kompressor zur Abgasleitung zu steuern.

Control panel as described above, wherein:

• the means for receiving a signal indicative of the operating temperature of the SCR device comprises an electronic processor having an electrical input for receiving the signal indicative of the operating temperature of the SCR device; and
• an electronic storage device electrically coupled to the electronic processor and having instructions stored therein;
• the means for controlling an operating temperature of the selective catalytic reduction (SCR) apparatus by controlling a first valve means for supplying compressed air from the compressor to the exhaust conduit configured to: access the storage device and execute the instructions stored therein such that it is operable to control a first valve means for supplying compressed air from the compressor to the exhaust pipe.

In accordance with another aspect of the present invention, a vehicle is provided that includes a system as described herein. The vehicle may include an internal combustion engine, such as a diesel engine.

• Betreiben eines Kompressors zum Zuführen von verdichteter Luft zum Verbrennungsmotor; und
• Umleiten eines Teils der verdichteten Luft vom Ausgang des Kompressors durch eine Niederdruck-Abgasrückführungsleitung (LP-EGR) zu einer Abgasleitung, um die Betriebstemperatur der SCR-Vorrichtung zu steuern.

According to another aspect of the present invention, there is provided a method for controlling an operating temperature of a selective catalytic reduction (SCR) apparatus disclosed in US Pat an exhaust pipe of an internal combustion engine, the method comprising:

• Operating a compressor for supplying compressed air to the internal combustion engine; and
• Diverting a portion of the compressed air from the exit of the compressor through a low pressure exhaust gas recirculation (LP-EGR) conduit to an exhaust conduit to control the operating temperature of the SCR apparatus.

The method may include cooling the compressed air from the compressor prior to introduction into the exhaust conduit.

The method may include cooling the compressor-derived compressed air prior to introduction into the SCR device.

A particulate filter may be arranged in the exhaust pipe. The method may include supplying the compressed air into the exhaust passage during regeneration of the particulate filter. The method may include isolating the inlet of the compressor from the exhaust conduit during regeneration of the particulate filter.

The method may include controlling the compressed air supply or supply of compressed air to the exhaust pipe in response to an operating temperature of the SCR device.

• mindestens einen Prozessor zum Steuern einer Zufuhr verdichteter Luft von einem Kompressor zur Abgasleitung; und
• eine Speichervorrichtung, die mit dem mindestens einen Prozessor gekoppelt ist;
• wobei der mindestens eine Prozessor konfiguriert ist, um ein erstes Ventilmittelöffnungssignal auszugeben, um ein erstes Ventilmittel zu öffnen, um verdichtete Luft vom Kompressor zur Abgasleitung zu liefern, um die Betriebstemperatur der SCR-Vorrichtung während einer Regeneration des Partikelfilters zu reduzieren.

According to another aspect of the present invention, there is provided a control unit for controlling an operating temperature of a selective catalytic reduction (SCR) apparatus disposed in an exhaust pipe connected to an internal combustion engine; wherein the control unit comprises:

• at least one processor for controlling a supply of compressed air from a compressor to the exhaust pipe; and
• a memory device coupled to the at least one processor;
• wherein the at least one processor is configured to output a first valve-means opening signal to open a first valve means to provide compressed air from the compressor to the exhaust conduit to reduce the operating temperature of the SCR apparatus during regeneration of the particulate filter.

Particulate filter, which is arranged in the exhaust pipe. The at least one processor may be configured to receive a regeneration signal from a motor controller. The at least one processor may be configured to output the first valve means opening signal in response to the regeneration signal. The at least one processor may open first valve means during regeneration of the particulate filter.

The at least one processor may be configured to receive a temperature signal from a temperature sensor associated with the SCR device. The at least one processor may be configured to output the first valve means opening signal in response to a temperature of the SCR device. The at least one processor may be configured to output the first valve means open signal when the temperature of the SCR device is greater than or equal to a predetermined temperature threshold.

The at least one processor may be configured to control the supply of compressed air from the compressor to a low pressure exhaust gas recirculation (LP-EGR) line connected to the exhaust passage.

The at least one processor may also be adapted to output a second valve means closing signal for closing a second valve means to prevent communication between the LP EGR passage and an inlet of the compressor. The second valve means closing signal can be output simultaneously with the opening signal of the first valve.

As used herein, the term "processor" includes both a single processor and a plurality of processors that work in concert to provide any control functionality. To configure a processor, an appropriate set of instructions may be provided that, when executed, cause the processor to implement the control techniques described herein. The instruction set may be suitably embedded in the one or more processors. Alternatively, the instruction set may also be provided as software stored in one or more memories associated with the processor and executed on the processor. The instructions may be provided on a non-transitory, computer-readable medium.

It is expressly intended in the context of this application that the various aspects, embodiments, examples and alternatives set forth in the preceding paragraphs, in the claims and / or in the following descriptions and drawings, and in particular the individual features thereof, be made independently or in part any combination can be accepted. That is, all embodiments and / or features of one embodiment may be combined in any manner and / or combination unless, these features are not compatible. The Applicant reserves the right to change a claim originally filed or to submit a new claim accordingly, including the right to change a claim originally filed in order to be dependent on another claim and / or to accept a property of another claim, although it was not initially claimed in this way.

list of figures

• 1 zeigt eine schematische Darstellung eines Fahrzeugs mit einem Steuergerät gemäß einer Ausführungsform der vorliegenden Erfindung; und
• 2 zeigt eine schematische Darstellung eines Verbrennungsmotors und einer funktionsfähig gesteuerten Abgasleitung gemäß einer Ausführungsform der vorliegenden Erfindung.

One or more embodiments of the present invention will now be described by way of example only with reference to the accompanying persons, in which:

• 1 shows a schematic representation of a vehicle with a control unit according to an embodiment of the present invention; and
• 2 shows a schematic representation of an internal combustion engine and a functionally controlled exhaust pipe according to an embodiment of the present invention.

DETAILED DESCRIPTION

A system 1 according to one aspect of the present invention is in 1 shown schematically. The system 1 is in a vehicle V with an internal combustion engine 2 and an exhaust pipe 3 Installed. The internal combustion engine 2 is a compression ignition engine, such as a diesel engine. In alternative embodiments, the internal combustion engine 2 a spark ignition engine, such as a gasoline engine. The vehicle V in the present embodiment is an automobile, but the present invention can be applied to other types of vehicles.

With reference to 2 points the internal combustion engine 2 an inlet pipe 4 and an exhaust outlet 5 on. In operation, air is supplied via the inlet pipe 4 for fuel combustion in the combustion chambers of the internal combustion engine 2 fed. In the inlet pipe 4 is a first heat exchanger 6 for cooling the air prior to introduction into the internal combustion engine 2 arranged. The first heat exchanger 6 is a charge air cooler. The exhaust gas is from the exhaust outlet 5 in the exhaust pipe 3 pushed out. The exhaust outlet 5 can be designed for example in the form of an exhaust manifold. A turbocharger 9 is for compacting the internal combustion engine 2 supplied air. The turbocharger 9 includes a compressor 10 and a turbine 11 , The compressor includes a compressor inlet 12 , a compressor outlet 13 and an impeller 14 , The turbine 11 includes a turbine inlet 15 , a turbine outlet 16 and a turbine wheel 17 , The impeller 14 and the turbine wheel 17 are mechanically interconnected. The turbine 11 is in the exhaust pipe 3 arranged and in operation the turbine wheel 17 through the engine 2 ejected exhaust gas turned. The rotation of the turbine wheel 17 turns the wheel 14 driving, causing air through the compressor inlet 12 in the turbocharger 9 is sucked. The air gets through the impeller 14 compressed and through the compressor outlet 13 pushed out. The compressed air is the internal combustion engine 2 over the inlet pipe 4 supplied and thus increases the mass of the combustion in the combustion chambers of the internal combustion engine 2 available air.

It is known that the exhaust gas by the internal combustion engine 2 is recycled to reduce emissions such as nitrogen oxides (NOx). A high-pressure exhaust gas recirculation line (HP-EGR) 18 is provided to high-pressure exhaust gas from the exhaust pipe 3 recirculate. As in shown, has the HP EGR line 18 an HP EGR inlet 19 and an HP EGR outlet 20 , The HP EGR inlet 19 is in the exhaust pipe 3 between the exhaust outlet 5 and the turbine inlet 15 arranged. The HP EGR outlet 20 is in the inlet line 4 between the first heat exchanger 6 and the internal combustion engine 2 arranged. A second heat exchanger 21 is in the HP EGR line 18 arranged to remove the heat from the recirculated exhaust gas before reintroducing it into the internal combustion engine 2 derive. An HP EGR valve 22 controls the recirculation of the high-pressure exhaust gas. In particular, the HP-EGR valve 22 be selectively opened and closed to control the recirculation of the exhaust gas. The HP EGR line 18 Can be opened so that a part of the high-pressure exhaust gas selectively through the internal combustion engine 2 can be returned.

In the exhaust pipe 3 downstream of the turbocharger 9 is an aftertreatment system 23 intended. The aftertreatment system 23 is configured to control the exhaust gases of the internal combustion engine 2 For example, to reduce carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) emissions. The aftertreatment system 23 includes a diesel oxidation catalyst (DOC) 24 , a particle filter 25 and a selective catalytic reduction (SCR) device 26 , The particle filter 25 in the present embodiment, a diesel particulate filter (DPF) 25 , The DPF 25 is regenerated periodically. A regeneration event includes controlling the internal combustion engine 2 to the temperature of the DPF 25 entering exhaust gas to over 550 ° C and up to 700 ° C increase. At these elevated temperatures, the soot stored in the DPF is oxidized and released as carbon dioxide (CO2). An injection valve 27 is intended to be a liquid reducing agent, also called Diesel exhaust fluid (DEF), into the exhaust gas upstream of the SCR device 26 inject. The DEF may be, for example, urea or another ammonia precursor. The injection of the DEF promotes reactions within the SCR device 26 to reduce nitrogen oxides (NOx) in the exhaust gas. It is understood that the DOC 24 can be replaced by a Lean NOx Trap (LNT) and also the DPF by a Selective Catalytic Reduction Filter (SCRF) (RTM).

A low pressure exhaust gas recirculation (LP-EGR) line 28 is provided to low pressure exhaust gas from the exhaust pipe 3 recirculate. As in shows the LP EGR line 28 an LP EGR inlet 29 and an LP-EGR outlet 30 on. In the present embodiment, the LP EGR inlet is 29 in front of the injector 27 arranged. The LP EGR inlet 29 is between the DPF 25 and the SCR device 26 arranged. The LP EGR output 30 is upstream of the compressor outlet 13 arranged. The recirculated exhaust gas is before compression by the compressor 10 mixed with air. A third heat exchanger 31 is in the LP EGR line 28 arranged. The third heat exchanger 31 dissipates heat from the exhaust gas before entering the compressor 10 is introduced. An LP EGR valve means that 32 in the LP EGR line 28 is provided. The LP EGR valve means 32 controls the return of low-pressure exhaust gas to the turbocharger 9 , The LP EGR valve means that 32 can be executed in the form of a valve. In the present embodiment, the LP-EGR valve means comprises 32 a two-way valve. It is understood that opening the LP EGR valve means that 32 it allows a part of the low-pressure exhaust gas from the internal combustion engine 2 selectively through the LP EGR line 28 recirculate.

It is an injection pipe 33 provided a portion of the compressed air from the compressor outlet 13 of the turbocharger 9 selectively into the exhaust pipe 3 redirect. In the present embodiment, the injection pipe is 33 with the LP EGR line 28 connected. The injection line 33 has an injection line inlet 34 and an injection line outlet 35 on. The injection line inlet 34 is in the inlet line 4 between the compressor outlet 13 and the internal combustion engine 2 arranged. In the present embodiment, the injection pipe inlet 34 upstream of the first heat exchanger 6 arranged, but this arrangement can be modified so that the injection line inlet 34 downstream of the first heat exchanger 6 (ie between the first heat exchanger 6 and the internal combustion engine 2 ) lies. The injection line outlet 35 is in the injection line 33 between the LP-EGR valve device 32 and the third heat exchanger 31 arranged. An injection line valve 36 is selective for opening and closing the injection pipe 33 intended. The injection line valve means 36 can be designed in the form of a valve. In the present embodiment, the injection line valve comprises means 36 a two-way valve. It is understood that the opening of the injection line valve means 36 It allows a portion of the compressed air from the internal compressor 10 into the LP EGR line 28 contribute. The injection line valve means 36 can inside the injection line 33 (as in 2 shown), at the injection line inlet 34 or at the injection line outlet 35 be arranged. In alternative embodiments, the injection line valve 36 comprise a three-way valve, for example, at the connection between the injection line 33 and the LP EGR line 28 is arranged. In use, the injection line valve becomes 36 open to allow some of the compressed air from the compressor 10 into the LP EGR line 28 can be directed. The compressed air is passed through the LP EGR line 28 pumped and in front of the SCR device 26 initiated. By controlling the supply of compressed air via the LP EGR line 28 may be the operating temperature of the SCR device 26 be managed. As described herein, this has particular importance in the regeneration of the DPF 25 at elevated temperature.

A control unit 37 is for controlling the operating temperature of the SCR device 26 intended. In particular, the control unit 37 configured to control the supply of compressed air from the compressor 10 to the LP-EGR line 28 to control the temperature of the SCR device 26 to lower. The control unit 37 includes a processor 38 that with a storage device 39 connected is. A set of non-volatile calculation instructions is placed on the storage device 39 saved. When the calculation instructions are executed, they cause the processor 38 to carry out the methods described herein. The processor 38 is configured to receive a first valve means control signal S1 to the LP-EGR valve means 32 to spend; and a second valve means control signal S2 to the injection line valve 36 , In the present embodiment, the control unit is 37 configured to control the operation of the injection line valve, ie 36 to the SCR device 26 during the regeneration of the DPF 25 supply compressed air. The control unit 37 receives a regeneration signal S3 For example, from an engine control unit 40 is output to a communication channel. Depending on the regeneration signal S3 gives the control unit 37 a first valve means control signal S1 to close the LP-EGR valve means 32 out; and a second valve means control signal S2 for opening the injection line valve means 36 , Closing the LP-EGR valve means 32 isolates the LP EGR line 28 from the compressor inlet 12 ; and opening the injection line valve means 36 connects the compressor outlet 13 with the LP EGR line 28 , Part of the compressor 10 discharged compressed air is doing to the LP-EGR line 28 diverted and into the exhaust pipe 3 in front of the SCR device 26 initiated. The air supply from the LP EGR pipe 28 Can help to improve the operating temperature of the LP EGR pipe 28 to lower. The exhaust pipe 3 fed compressed air is through the third heat exchanger 31 before the introduction into the SCR device 26 cooled.

The control unit described herein 37 is configured to control the air supply to the SCR device 26 depending on the regeneration signal S3 to control. In a modified arrangement, the control unit 37 be configured to control the air supply to the SCR device 26 depending on one of a temperature sensor 41 received temperature signal S4 to control. The temperature sensor 41 For example, at an input to the SCR device 26 or within the SCR device 26 be arranged. The control unit 37 For example, depending on the temperature signal S4 via the LP EGR line 28 the SCR device 26 supply with air. For example, if the temperature signal S4 indicates that the measured inlet temperature of the SCR device 26 is greater than a predefined temperature threshold, the control unit may 37 be configured to control the signals S1 . S2 of the first and second valve means to the LP-EGR valve means 32 close and the injection line valve 36 to open.

The LP EGR inlet 29 in the present embodiment is in front of the injector 27 arranged. Thus, the air from the LP-EGR line 28 in the exhaust pipe 3 in front of the injector 27 initiated. This arrangement can provide the additional advantage of cooling the exhaust gas prior to urea injection. This can reduce or minimize the oxidation of ammonia and the operation of the SCR device 26 improve by reducing the Leidenfrost effect (where liquid droplets bounce off of hot surfaces, rather than breaking up into smaller droplets or spreading to a thin film on the surface). In alternative arrangements, the LP EGR may be downstream of the injector 27 to be ordered.

It should be understood that various changes and modifications may be made to the embodiments described herein without departing from the scope of the present invention.

Claims (22)

A system for a vehicle, the system comprising: a compressor for supplying compressed air to an internal combustion engine, the compressor having an inlet and an outlet; an exhaust pipe for conveying exhaust gases from the internal combustion engine; a particulate filter and a selective catalytic reduction (SCR) device disposed in the exhaust passage; a low-pressure exhaust gas recirculation line (LP-EGR) for returning exhaust gas from the exhaust passage to the inlet of the compressor, and an injection conduit for directing a portion of the compressed air from the outlet of the compressor to the exhaust conduit through the LP EGR conduit to control an operating temperature of the SCR apparatus. System after Claim 1 comprising a first valve means for controlling the supply of compressed air from the injection pipe to the exhaust pipe. System after Claim 2 comprising a control unit configured to control the first valve means. System after Claim 3 wherein the control unit is configured to control the first valve means to direct compressed air from the compressor to the exhaust passage during regeneration of the particulate filter. System according to one of Claims 1 to 4 comprising a first heat exchanger for cooling the compressed air from the compressor, the injection line being connected to the outlet of the compressor downstream of the first heat exchanger. A system as claimed in any preceding claim, comprising a second heat exchanger, wherein the second heat exchanger is disposed in the LP EGR passage between the injection pipe and the exhaust pipe. A system as claimed in any preceding claim comprising a second valve means for controlling the supply of compressed air from the LP EGR passage to the inlet of the compressor. System after Claim 7 wherein the injection line is connected to the LP EGR passage between the second valve means and the exhaust passage. System after Claim 7 or Claim 8 if it is directly or indirectly from Claim 3 dependent, wherein the control unit is configured to control the second valve means. System according to one of Claims 3 . 4 or 9 wherein the control unit is configured to control the first valve means and / or the second valve means in dependence on an operating temperature of the SCR device. A system as claimed in any one of the preceding claims, wherein the compressor is part of a turbocharger. System according to one of Claims 1 to 10 wherein the compressor is an electric compressor. A vehicle comprising a system as claimed in any one of the preceding claims. A method of controlling an operating temperature of a selective catalytic reduction (SCR) device disposed in an exhaust passage of an internal combustion engine, the method comprising: Operating a compressor for supplying compressed air to the internal combustion engine; and Diverting a portion of the compressed air from the exit of the compressor through a low pressure exhaust gas recirculation (LP-EGR) conduit to an exhaust conduit to control the operating temperature of the SCR apparatus. Method according to Claim 14 comprising cooling the compressed air from the compressor prior to introduction into the exhaust pipe. Method according to Claim 14 or Claim 15 wherein a particulate filter is disposed in the exhaust conduit, the method comprising supplying the compressed air into the exhaust conduit during regeneration of the particulate filter. Method according to one of Claims 14 . 15 or 16 comprising isolating the inlet of the compressor from the LP EGR conduit during regeneration of the particulate filter. Method according to one of Claims 14 to 17 comprising controlling the supply of compressed air into the exhaust conduit in response to an operating temperature of the SCR apparatus. A control unit for controlling an operating temperature of a selective catalytic reduction (SCR) device disposed in an exhaust pipe connected to an internal combustion engine, the control unit comprising: at least one processor for controlling a supply of compressed air from a compressor to the exhaust pipe; and a memory device coupled to the at least one processor; wherein the at least one processor is configured to output a first valve-means opening signal to open a first valve means for supplying compressed air from the outlet of the compressor via a low-pressure exhaust gas recirculation (LP-EGR) line to the exhaust pipe to the operating temperature of the SCR device to reduce. Control unit after Claim 19 wherein the at least one processor is configured to receive a regeneration signal and to output the first valve-means-opening signal in response to the regeneration signal. Control unit after Claim 19 or Claim 20 wherein the at least one processor is configured to receive a temperature signal and to output the first valve-means-opening signal in response to the temperature signal. Control unit according to one of Claims 19 . 20 or 21 wherein the at least one processor is also adapted to output a second valve means closing signal to close a second valve means to prevent communication between the LP EGR passage and an inlet of the compressor.

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