DE102020130684A1 - Exhaust system and method for exhaust gas recirculation in a motor vehicle and motor vehicle - Google Patents

Abstract

The invention relates to an exhaust system, comprising a control unit, an exhaust line along which an exhaust gas turbine, an exhaust gas aftertreatment device and an exhaust gas flap are arranged, an exhaust gas storage area, a compressor for conveying and compressing exhaust gas from a branch point arranged behind the exhaust gas aftertreatment device in the direction of flow into the exhaust gas storage area and an exhaust gas recirculation line for conducting exhaust gas from the exhaust gas storage area to a feed point located in front of the exhaust gas turbine. The control unit is set up to keep the exhaust pipe closed by means of the exhaust gas flap during a heating-up phase of the exhaust gas aftertreatment device and to convey any exhaust gas that occurs by means of the compressor into the exhaust gas storage area and the exhaust gas storage area even after a specified operating temperature of the exhaust gas aftertreatment device has been reached by actuating the compressor when the exhaust gas flap is then open to keep filled with exhaust gas and deliver exhaust gas from the exhaust gas storage area through the feed point in each case with an increased power requirement of the internal combustion engine. The invention also relates to a corresponding method and a motor vehicle.

Description

The present invention relates to an exhaust system for a motor vehicle, a motor vehicle equipped therewith and a corresponding operating method in which exhaust gas recirculation is provided during operation of the internal combustion engine or motor vehicle.

Although motor vehicles have been known for a long time, the improvement and further development, in particular for reducing harmful emissions and for improving efficiency and power density, is still or even increasingly important.

For example, from the EP 3 121 408 B1 a method for controlling an internal combustion engine is known. In this case, an increase in a target torque to be provided by the internal combustion engine is detected. A gas densified by a compressor is fed into a combustor and exhaust gas discharged therefrom is recirculated into the combustor at an increased exhaust gas recirculation rate over a reference rate used in steady-state operation. This recirculation of the exhaust gas takes place during a time interval between the beginning of the increase in the setpoint torque and an end of this increase, the time interval being between 0.1 s and 5 s. The exhaust gas recirculation rate is characterized by a time profile in which the exhaust gas recirculation rate initially increases and after a maximum falls to the reference rate. The exhaust gas recirculation is carried out synchronously with a filling quantity of the gas fed into the combustion chamber. This is intended to reliably enable transient operation of the internal combustion engine in such a way that pollutant emissions are limited or reduced, but at the same time rapid and reliable response behavior is ensured.

As another example, the DE 10 2017 201 399 A1 with an exhaust aftertreatment system. For this purpose, an arrangement of an internal combustion engine with an exhaust tract is provided, from which an exhaust gas recirculation line of a low-pressure exhaust gas recirculation system branches off, and in which an exhaust gas aftertreatment system is arranged. The latter comprises a first nitrogen oxide storage catalytic converter, a second catalytic device arranged downstream thereof and a particle filter, which is also arranged downstream from the first nitrogen oxide storage catalytic converter. The exhaust gas recirculation line branches off downstream from the first nitrogen oxide storage catalytic converter and upstream from the second catalytic device. The exhaust gas aftertreatment system includes a valve for controlling the mass of the recirculated exhaust gas and a temperature sensor in the area of the first nitrogen oxide storage catalytic converter. This is intended to optimize exhaust aftertreatment.

The object of the present invention is to enable improved use of an exhaust system in a motor vehicle with an internal combustion engine.

According to the invention, this object is achieved by the subject matter of the present patent claims. Possible refinements and developments of the present invention are specified in the dependent patent claims, in the description and in the drawing.

The exhaust system according to the invention for a motor vehicle comprises a control unit and an exhaust pipe intended for discharging an exhaust gas flow from an internal combustion engine of the motor vehicle. An intended flow direction is provided for the exhaust pipe, for example from an exhaust valve or exhaust manifold of the internal combustion engine in the direction of an exhaust pipe of the motor vehicle, ie an end of the exhaust pipe facing away from the internal combustion engine. An exhaust gas turbine that can be driven by the exhaust gas flow, for example for driving or as part of a turbocharger, an exhaust gas aftertreatment device for reducing emissions and an exhaust gas flap that can be controlled by the control unit to close and open the exhaust gas line are arranged along the exhaust gas line in this direction of flow. The exhaust gas aftertreatment device can be, for example, a catalytic converter or include one. Likewise, the exhaust aftertreatment device can include a particle filter, for example.

The exhaust system according to the invention further comprises an exhaust gas storage area, a compressor for conveying and compressing exhaust gas from the exhaust gas flow from a branch point arranged behind the exhaust gas aftertreatment device in the intended flow direction into the exhaust gas storage area. In the exhaust gas storage area, the exhaust gas can therefore be received or temporarily stored at a pressure that is higher than the respective ambient pressure.

Furthermore, the exhaust system according to the invention comprises an exhaust gas recirculation line for guiding or recirculating exhaust gas from the exhaust gas storage area to a feed point located in front of the exhaust gas turbine with respect to the intended flow direction.

According to the invention, the control unit is set up to keep the exhaust pipe closed by means of the exhaust flap during operation of the exhaust system or the internal combustion engine connected to it in a heating-up phase during which the exhaust gas aftertreatment device is heated to a predetermined operating temperature. Furthermore, the control unit is set up to convey exhaust gas occurring during operation of the exhaust system or the internal combustion engine to the exhaust gas storage area by means of the compressor and to keep the exhaust gas storage area filled with exhaust gas or .refill. The control unit is also set up to emit exhaust gas from the exhaust gas storage area through the feed point in each case when the power requirement of the internal combustion engine increases, in particular abruptly, compared to previous operation, ie when there is a load step requirement.

The present invention thus provides that exhaust gas generated by the internal combustion engine during the heating-up phase is not discharged or ejected directly into a respective environment. Rather, this exhaust gas occurring during the heating-up phase is temporarily stored in the exhaust gas storage area. Once the exhaust gas aftertreatment device, in particular its catalytic converter, has reached the specified operating temperature, the exhaust gas that was temporarily stored, i.e. collected in the exhaust gas storage area during the heating phase, can then be passed through the exhaust gas aftertreatment device again, since the feed point is arranged upstream of the exhaust gas aftertreatment device. Due to the operating temperature then reached, an improved cleaning or after-treatment of the exhaust gas can be achieved and thus the emission of harmful emissions or pollutants can be reduced.

However, instead of automatically releasing the exhaust gas collected in the exhaust gas storage area immediately after the operating temperature has been reached and passing it through the exhaust gas aftertreatment device, this only takes place when there is an increased power requirement. The invention is therefore based on the finding that an exhaust gas storage device as described here can not only be used to reduce harmful emissions, but can also contribute to boosting performance or improving the response behavior of the internal combustion engine. Since the exhaust gas can be kept under increased pressure in the exhaust gas storage area by the compressor, the intermediately stored exhaust gas is always directly available with a correspondingly increased pressure, which means that the exhaust gas can be fed in particularly quickly and thus a particularly quick reaction to the respective power requirement or its Increase or increase allowed.

This is not only made possible here once with the exhaust gas collected during the heating-up phase, i.e. not only once per or after each cold start of the internal combustion engine, but regularly or permanently during the entire respective operating time of the internal combustion engine, since even with a heated exhaust gas aftertreatment device and a correspondingly open exhaust gas flap the compressor continuously or regularly exhaust gas is fed into the exhaust gas storage area - at least as long as the exhaust gas storage area has not been completely filled, i.e. still has free intake or storage capacity.

The compressor can be set up or controlled or regulated to set or maintain a predetermined pressure of the exhaust gas in the exhaust gas storage area. The compressor can also be activated as required when the exhaust gas storage area has been completely or partially emptied or when a pressure within the exhaust gas storage area has fallen below a predetermined threshold value, in particular at least as long as the internal combustion engine is in operation.

A dual or multiple functionality of the exhaust system can thus be realized by the present invention, for which purpose the same parts or components can be used at least for the most part. Overall, improved use of the exhaust system or the exhaust gas is therefore possible in a particularly simple and efficient manner.

During operation of the exhaust system or the internal combustion engine or after each cold start of the internal combustion engine, exhaust gas can be released for the first time, i.e. fed back from the exhaust gas storage area through the feed point, after the operating temperature of the exhaust gas aftertreatment device has been reached, i.e. at the first corresponding increased load request after the operating temperature of the exhaust gas aftertreatment device has been reached take place. In order to control this, a corresponding timer circuit can be provided, for example, which only allows the exhaust gas to be fed back from the exhaust gas storage area after a predetermined minimum operating time of the internal combustion engine. This minimum operating time can also depend on an operating time according to a predetermined model be, for example, a speed and / or a load of the internal combustion engine during the heating phase or be dynamically adjusted.

However, actual temperature control can also be provided. For this purpose, for example, a temperature sensor can be arranged in the exhaust gas flow or on the exhaust gas line, in particular in or on the exhaust gas aftertreatment device, which is connected to the control unit. The control unit can then permit or enable the recirculation of exhaust gas from the exhaust gas storage area as soon as the temperature sensor or a measurement or sensor signal provided by it indicates or indicates that the specified operating temperature of the exhaust gas aftertreatment device has been reached.

In one possible embodiment of the present invention, the exhaust system includes a rear silencer arranged in the intended flow direction between the exhaust gas aftertreatment device and the exhaust gas flap. The branch is then arranged in or on this rear silencer. In other words, the exhaust gas to be returned is sucked in or sucked out by the compressor in the rear silencer or out of the rear silencer, in order then to be compressed or conveyed into the exhaust gas storage area. Due to the arrangement of the branching point proposed here, excessive volume or noise emissions from the exhaust system can also be avoided in a particularly simple and reliable manner if the exhaust gas recirculation line is not soundproofed.

In a further possible embodiment of the present invention, a valve, which can be controlled by the control unit, for setting an outflow or an outflow rate of the exhaust gas from the exhaust gas storage area is arranged on a side of the exhaust gas storage area that faces the feed point—and thus in particular also on a side of the compressor that faces the feed point . The control unit is then set up to keep the valve closed during stationary operation of the internal combustion engine. Depending on the duration of the heating phase and the size or capacity of the dedicated exhaust gas storage area, the valve can be kept closed in stationary operation at least until the specified operating temperature of the exhaust gas aftertreatment device is reached and/or the dedicated exhaust gas storage area is not yet filled to the maximum. With the valve proposed here, the feedback of the exhaust gas through the feed point can be controlled or metered according to the situation and needs. In addition, a particularly high pressure of the temporarily stored exhaust gas can be maintained in the exhaust gas storage area without affecting the functionality of the rest of the exhaust system and/or the internal combustion engine. As a result, a particularly large amount of exhaust gas can be temporarily stored with a particularly small installation space requirement, and the exhaust gas can be discharged or fed in particularly quickly and effectively from the exhaust gas storage area. In addition, the feed point can be easily arranged in or on an area of the exhaust system or the internal combustion engine or a component connected to the internal combustion engine in which an increased pressure also prevails, without impeding the feeding of the exhaust gas. In other words, high-pressure exhaust gas recirculation (HP-EGR) can thus be implemented in a particularly simple manner.

In a further possible embodiment of the present invention, the exhaust gas storage area includes a dedicated pressure tank. In other words, a pressure tank is provided in which the temporarily stored exhaust gas can be kept under a particularly high overpressure relative to the environment. The exhaust gas storage area can correspond to the pressure tank, that is to say it can be completely formed by it. The exhaust gas storage area can also include other parts or areas, for example a line leading from the branch point or from the compressor to the pressure tank and/or a line leading from the pressure tank to the feed point or to the valve mentioned elsewhere. A lower pressure than in the dedicated pressure tank can then possibly prevail in these lines at least temporarily. The use of a pressure tank integrated into the exhaust system can be used in a particularly space-saving manner to provide sufficient storage capacity for the exhaust gas occurring during the entire heating-up phase. The pressure tank can have a volume of about 30 liters, for example. The pressure tank can, for example, be designed to be stable or robust against an internal pressure or overpressure of several bars or several tens of bars.

In a further possible embodiment of the present invention, the feed point is arranged in a part of the exhaust gas line that leads directly to the exhaust gas turbine. In other words, no other component or part with which the exhaust gas can come into contact is arranged between the feed point and the exhaust gas turbine—apart from the corresponding part of the exhaust gas line. In the intended installation position of the exhaust system, the feed point is therefore arranged between a cylinder outlet or an outlet manifold of the internal combustion engine and an inlet of the exhaust gas turbine. In this way, through the exhaust gas exhaust gas fed back into the storage area, i.e. increase a mass flow or a pressure drop across the exhaust gas turbine. As a result, for example, the exhaust gas turbine or a turbocharger compressor driven by it can be brought to a target speed particularly quickly. This represents a particularly simple and effective way of improving the use of the exhaust system, since in this way, for example, the response behavior of the internal combustion engine can be improved or accelerated

In a further possible embodiment of the present invention, the feed point or a second feed point is in the intended installation position of the exhaust system, i.e. when it is connected to the internal combustion engine or installed in the motor vehicle ready for operation, in an air supply line leading to a cylinder inlet of the internal combustion engine arranged. In other words, the corresponding feed point is then arranged upstream of the internal combustion engine. In particular, the corresponding feed point can be arranged in front of the cylinder inlet or an inlet valve or in front of an inlet manifold of the internal combustion engine, but downstream of an inlet compressor of the internal combustion engine or of the motor vehicle. The described devices or components of the exhaust system according to the invention can therefore not only be used to reduce harmful emissions during the heating-up phase of the exhaust gas aftertreatment device, but also for high-pressure exhaust gas recirculation during further operation of the internal combustion engine.

In order to enable particularly flexible use of the exhaust system, one branch of the exhaust gas recirculation line can be routed from the exhaust gas storage area to a first feed point directly in front of the exhaust gas turbine and a second branch of the exhaust gas recirculation line to a second feed point in front of the cylinder inlets or the inlet manifold of the internal combustion engine. A valve device or a flap or the like can then be used to switch between these branches, for example by the control unit.

In one possible development of the present invention, the control unit is set up to feed at least part of the exhaust gas conveyed by the compressor into the air supply line leading to the cylinder inlet of the internal combustion engine during the heating-up phase, ie when the exhaust gas flap is then closed. A circulation or circulatory conveyance of the exhaust gas within the combination of exhaust system and internal combustion engine, ie within the motor vehicle, then takes place possibly already during the heating-up phase. Due to the fact that exhaust gas is already fed back in this operating phase, that is to say it is routed through the cylinders or combustion chambers of the internal combustion engine, raw emissions from the combustion chambers can ultimately be reduced. This is possible by means of a corresponding control that is particularly easy to implement, that is to say with particularly little effort and does not require any additional components or devices, for example. In addition, a load on the exhaust gas aftertreatment device can be reduced if necessary.

In a further possible embodiment of the present invention, the control device is set up to recirculate the occurring exhaust gas by means of the compressor in a circuit during the heating-up phase, ie when the exhaust gas valve is then closed. In other words, the exhaust gas is then actively circulated or pumped around in the circuit, so that the exhaust gas effectively flows within the exhaust system or the combination of exhaust system and internal combustion engine, i.e. ultimately within the motor vehicle, in a circle, so to speak, until the specified operating temperature of the exhaust gas aftertreatment device is reached is. The circuit in which the exhaust gas is recirculated, ie circulates, comprises at least the exhaust gas recirculation line and the exhaust gas line, which then in turn form at least part of the exhaust gas storage area. In other words, the entire exhaust system or a large part of the exhaust system can then form the exhaust gas storage area, so that a dedicated pressure tank that can be sealed off from the rest of the exhaust system, for example, does not necessarily have to be provided as the exhaust gas storage area. Nevertheless, such a pressure tank or additional tank can still be provided, in which case it can optionally be correspondingly smaller or designed for lower pressures.

In the embodiment proposed here, the feed is possible, as described, immediately before the exhaust gas turbine or before the intake valves of the internal combustion engine. In the latter case, the circuit can then also include, for example, the internal combustion engine, its intake manifold, its exhaust manifold and/or the like. The proposed circular conveyance of the exhaust gas within the exhaust system with the exhaust flap closed can be used in particular when using high-pressure exhaust gas recirculation. Even with the configurations proposed here, a particularly effective reduction in raw emissions from the internal combustion engine and ultimately a special efficient use of the exhaust system can be achieved.

Regardless of the other configuration of the present invention, the exhaust system according to the invention can include an exhaust gas cooler. This can be arranged, for example, in the flow or conveying direction downstream of the compressor, in particular upstream of the exhaust gas storage area or pressure tank. As a result, on the one hand a particularly effective cooling of the exhaust gas in the cooler can be achieved and on the other hand a predetermined quantity of exhaust gas can be temporarily stored in the exhaust gas storage area with a particularly small installation space requirement and at the same time particularly low pressure.

A further aspect of the present invention is a method for operating a motor vehicle which has an internal combustion engine and an exhaust system according to the invention connected to it. In the method according to the invention, the exhaust gas flap is closed after a cold start of the internal combustion engine, i.e. when the exhaust gas aftertreatment device has not yet reached its intended operating temperature - at least after an initial flushing of the exhaust gas system - and when the intended operating temperature of the exhaust gas aftertreatment device is reached and/or after a predetermined time opened again. During flushing, the residual air contained in the exhaust system can be replaced by the first exhaust gas produced after the respective cold start, i.e. it can be pushed out of the exhaust system through the exhaust flap, which is then still open. The exhaust flap can then be closed during the heating-up phase as soon as the exhaust system or the exhaust line from the exhaust gas turbine to the exhaust flap is at least largely or essentially filled with exhaust gas. Furthermore, in the method according to the invention, when the exhaust gas flap is closed, exhaust gas occurring is conveyed into the exhaust gas storage area by means of the compressor. Furthermore, in the method according to the invention, after opening the exhaust gas flap - which takes place automatically in particular when or after the specified operating temperature of the exhaust gas aftertreatment device has been reached - the exhaust gas stored in the exhaust gas storage area with excess pressure is released from the exhaust gas storage area via the feed point in response to an increased power requirement of the internal combustion engine, i.e returned or fed back.

Further measures, sequences, control processes and/or the like mentioned in connection with the exhaust system according to the invention can represent further, optionally optional, method steps of the method according to the invention.

The method according to the invention can in particular be carried out automatically. For this purpose, the control device can have, for example, a computer-readable data memory and a processor device connected thereto, for example a microchip, microprocessor or microcontroller. A program code or operating or computer program can then be stored in this data memory, which represents the processes or method steps of the method according to the invention, i.e. encodes or implements them, and can be automatically executed by the processor device in order to cause or cause the corresponding method to be carried out.

A further aspect of the present invention is a motor vehicle which has an exhaust system according to the invention and/or is set up for automatically carrying out or using the method according to the invention. The motor vehicle according to the invention can in particular be the motor vehicle mentioned in connection with the exhaust system according to the invention and/or the method according to the invention. Accordingly, the motor vehicle according to the invention can have some or all of the properties and/or features mentioned in connection with the exhaust system according to the invention and/or the method according to the invention.

Further features of the invention can result from the claims, the figures and the description of the figures. The features and feature combinations mentioned above in the description and the features and feature combinations shown below in the description of the figures and/or in the figures alone can be used not only in the combination specified in each case, but also in other combinations or on their own, without going beyond the scope of the invention to leave.

• 1 eine schematische Darstellung eines Kraftfahrzeugs mit einer Verbrennungskraftmaschine und einer zur Abgasrückführung eingerichteten Abgasanlage;
• 2 eine Detailansicht zur Veranschaulichung einer ersten Variante der Abgasrückführung; und
• 3 eine Detailansicht zur Veranschaulichung einer zweiten Variante der Abgasrückführung.

The drawing shows in:

• 1 a schematic representation of a motor vehicle with an internal combustion engine and an exhaust system set up for exhaust gas recirculation;
• 2 a detailed view illustrating a first variant of the exhaust gas recirculation; and
• 3 a detailed view to illustrate a second variant of the exhaust gas recirculation.

In the figures, identical and functionally identical elements are provided with the same reference symbols.

For example, in order to meet future specifications or emission regulations for vehicles operated by internal combustion engines, exhaust gas recirculation, in particular with intermediate exhaust gas storage, can be provided during a heating-up phase. This enables full conversion, that is to say particularly effective or thorough cleaning of all the exhaust gas that occurs, which is only possible, for example, above a specific minimum temperature of a corresponding catalytic converter. At the same time, this results in further possible uses of the system components or parts required for this.

1 shows a schematic representation of a motor vehicle 10 with an internal combustion engine 12 to which an exhaust system 14 for discharging exhaust gas is connected. The exhaust system 14 connects to an outlet manifold 16 of the internal combustion engine 12 . However, this outlet manifold 16 can also be part of the exhaust system 14 . Viewed from the internal combustion engine 12 , an exhaust gas turbine 18 is arranged downstream of the exhaust manifold 16 in or with respect to an intended flow direction of the exhaust system 14 . An exhaust gas aftertreatment device 20 is in turn arranged downstream of the exhaust gas turbine 18. This exhaust gas aftertreatment device 20 can, for example, comprise one or more catalytic converter blocks and a particle filter.

At least one section of an exhaust gas line 22 leads from the exhaust gas aftertreatment device 20 downstream to a rear silencer 24. The rear silencer 24 has an outlet which leads, for example, to an exhaust pipe of the motor vehicle 10. Downstream of the rear muffler 24 is an exhaust gas valve 26, which can be used to block or release exhaust gas from the rear muffler 24 into an area surrounding the motor vehicle 10, depending on the position or switching state.

In addition, a branch point 28 is provided in or on the rear silencer 24 . A line is connected to this, through which exhaust gas can be conveyed from the rear silencer 24 to a compressor 30 . The compressor 30 can be, for example, a screw, piston or centrifugal compressor or the like.

In particular, the compressor 30 can be driven by an electric compressor drive 32 . Exhaust gas can be conveyed from the rear silencer 24 by the compressor 30 under compression or with an increase in pressure. Downstream of the compressor 30, this conveyed exhaust gas then reaches an exhaust gas cooler 34.

After the exhaust gas has passed through the exhaust gas cooler 34, it arrives in an exhaust gas storage area 36, which in the present case comprises in particular a dedicated pressure tank 38 for temporarily storing the exhaust gas. A metering valve, referred to here as valve 40 for short, is arranged downstream of the exhaust gas storage area 36 or of the pressure tank 38 . Appropriate activation, ie a controlled opening and closing of the valve 40, allows the exhaust gas to flow out of the exhaust gas storage area 36 through or into an exhaust gas recirculation line 42 automatically, ie regulated or metered.

Exhaust gas originating from the internal combustion engine 12 and which has already flowed through the exhaust gas line 22 can be returned to the exhaust system 14 upstream of the exhaust gas turbine 18 through the exhaust gas recirculation line 42 . For this purpose, the exhaust gas recirculation line 42 can be routed differently depending on the configuration. For example, a first branch 44 of the exhaust gas recirculation line 42 can lead to a first feed point 46 . This first feed point 46 is arranged here between the outlet manifold 16 and an inlet of the exhaust gas turbine 18 . Additionally or alternatively, a second branch 48 of the exhaust gas recirculation line 42 can lead to a second feed point 50 . This second feed point 50 is arranged upstream here, that is to say on the inlet side of the internal combustion engine 12 .

The control of the components described or the intermediate storage and recirculation or refeeding of the exhaust gas can be carried out automatically here by a correspondingly set up control unit 52 . For this purpose, control unit 52 is connected to exhaust gas flap 26 , compressor drive 32 and valve 40 , for example. However, control unit 52 can also be connected to other components or devices and/or, for example via an on-board electrical system of motor vehicle 10, can record and/or output corresponding and/or other data or signals, for example with regard to an operating state of internal combustion engine 12, exhaust gas turbine 18, the Exhaust aftertreatment device 20, the pressure tank 38 and / or the like more.

For further illustration shows 2 a schematic detailed view of a variant in which the exhaust gas recirculation line 42 is led to the first feed point 46. An exhaust gas flow 54 is schematically indicated here by corresponding arrows, which exits from the internal combustion engine 12 through the exhaust manifold 16 , passes through the exhaust gas turbine 18 and then enters the exhaust gas aftertreatment device 20 . After reclaim, the exhaust stream 54 is then through the exhaust gas recirculation line 42 to the first feed point 46 so that it can pass through the exhaust gas turbine 18 again.

3 12 shows a schematic detail view of an alternative embodiment in which the exhaust gas recirculation line 42 is routed to an intake side of the internal combustion engine 12 . In the present case, the exhaust gas recirculation line 42 is routed to an intake manifold 56, which here forms the second infeed point 50 mentioned. The recirculated exhaust gas stream 54 can thus pass through the internal combustion engine 12 or its combustion chambers again before it reaches the exhaust gas turbine 18 through the exhaust manifold 16 .

The examples described expand a possible use of an exhaust gas storage system by the function of exhaust gas recirculation with in particular at least partially cleaned and possibly cooled exhaust gas. Provision can also be made for the exhaust gas cooler 34 to be bypassed - for example by a bypass line - and/or to be separated from a cooling circuit, so that optionally uncooled exhaust gas that is nevertheless compressed by the compressor 30 can be returned to the feed upstream of the exhaust gas turbine 18.

Appropriate control of the exhaust gas storage system can, on the one hand, achieve a reduction in emissions and, on the other hand, respond to dynamic demands on internal combustion engine 12 by increasing a mass flow flowing through exhaust gas turbine 18, for example to bring exhaust gas turbine 18 more quickly to a respective target speed.

Reference List

10

motor vehicle

12

internal combustion engine

14

exhaust system

16

exhaust manifold

18

exhaust turbine

20

exhaust aftertreatment device

22

exhaust pipe

24

rear silencer

26

exhaust flap

28

junction

30

compressor

32

compressor drive

34

exhaust gas cooler

36

storage area

38

pressure tank

40

Valve

42

exhaust gas recirculation line

44

first branch

46

first feed point

48

second branch

50

second feed point

52

control unit

54

exhaust flow

56

intake manifold

QUOTES INCLUDED IN DESCRIPTION

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

Patent Literature Cited

• EP 3121408 B1 [0003]
• DE 102017201399 A1 [0004]

Claims (10)

Exhaust system (14) for a motor vehicle (10), comprising a control unit (52), an exhaust line (22) intended for discharging an exhaust gas flow (54) from an internal combustion engine (12), along which, in the intended flow direction, a drivable exhaust gas turbine (18), an exhaust gas after-treatment device (20) for reducing emissions and an exhaust gas valve (26) which can be controlled by the control unit (52) to close and open the exhaust pipe (22), an exhaust gas storage area (36), a compressor (30) for Conveying and compressing exhaust gas from a branch point (28) arranged behind the exhaust gas aftertreatment device (20) in the direction of flow into the exhaust gas storage area (36), an exhaust gas recirculation line (42) for conducting exhaust gas from the exhaust gas storage area (36) to a point in front of the exhaust gas storage area (36) in terms of the direction of flow Exhaust gas turbine (18) lying feed point (46, 50), wherein the control unit (52) set up is to keep the exhaust pipe (22) closed by means of the exhaust flap (26) during operation of the exhaust system (14) in a heating-up phase for heating up the exhaust gas after-treatment device (20) to a predetermined operating temperature and accumulating exhaust gas to be fed into the exhaust gas storage area ( 36) and to keep the exhaust gas storage area (36) filled with exhaust gas even after the operating temperature has been reached by appropriate activation of the compressor (30) with the exhaust gas valve (26) then open and exhaust gas from the exhaust gas storage area in each case when there is an increased power requirement from the internal combustion engine (12). (36) to deliver through the feed point (46, 50). Exhaust system (14) after claim 1 , characterized in that the exhaust system (14) comprises a rear silencer (24) arranged in the intended flow direction between the exhaust gas after-treatment device (20) and the exhaust gas flap (26) and the branching point (28) is arranged on the rear silencer (24). Exhaust system (14) according to one of the preceding claims, characterized in that on a side of the exhaust gas storage area (36) facing the feed point (46, 50) there is a valve (40) controllable by the control unit (52) for adjusting the outflow of the exhaust gas from the The exhaust gas storage area (36) is arranged and the control unit (52) is set up to keep the valve (40) closed during stationary operation of the internal combustion engine (12). Exhaust system (14) according to one of the preceding claims, characterized in that the exhaust gas storage area (36) comprises a pressure tank (38). Exhaust system (14) according to one of the preceding claims, characterized in that the feed point (46) is arranged in a part of the exhaust gas line (22) leading directly to the exhaust gas turbine (18). Exhaust system (14) according to one of the preceding claims, characterized in that the feed point (46) or a second feed point (50) is arranged in the intended installation position of the exhaust system (14) in an air supply line (56) leading to a cylinder inlet of the internal combustion engine (12). is. Exhaust system (14) after claim 6 , characterized in that the control unit (52) is set up to feed at least part of the exhaust gas conveyed by the compressor (30) into the air supply line (56) leading to the cylinder inlet of the internal combustion engine (12) during the heating-up phase. Exhaust system (14) according to one of the preceding claims, characterized in that the control unit (52) is set up to recirculate the exhaust gas occurring during the heating-up phase by means of the compressor (30) in a circuit which comprises at least the exhaust gas recirculation line (42) and the exhaust gas line (22), which in turn form at least part of the exhaust gas storage area (36). Method for operating a motor vehicle (10), which has an internal combustion engine (12) and an exhaust system (14) connected thereto according to one of the preceding claims, in which - the exhaust flap (26) is closed after a cold start of the internal combustion engine (12) and opened again when the specified operating temperature is reached and/or after a specified time, - when the exhaust gas flap (26) is closed, exhaust gas occurring is conveyed by means of the compressor (30) into the exhaust gas storage area (36), and - after opening the exhaust gas valve (26), the exhaust gas stored with overpressure in the exhaust gas storage area (36) is discharged from the exhaust gas storage area (36) via the feed point in response to an increased power requirement of the internal combustion engine (12). Motor vehicle (10) having an exhaust system (14) according to one of Claims 1 until 8th having and/or for the automatic implementation of the method claim 9 is set up.

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