Exhaust system

Abstract

Exhaust system, comprising: a diesel oxidation catalyst (DOC) device (20) installed on an exhaust pipe (5) for removing hydrocarbon (HC) and carbon monoxide (CO) from the exhaust gas and for discharging the exhaust gas of an internal combustion engine (10); a urea injector (30) downstream of the diesel oxidation catalyst device (20) for injecting an aqueous urea solution into the exhaust pipe (5); a mixer (40) downstream of the urea injector (30) which ensures rapid diffusion of the exhaust gas flowing through the diesel oxidation catalyst device (20); a diesel particulate filter (DPF) (50) downstream of the mixer (40) connected to a non-precious metal catalyst or a hydrolysis catalyst that does not oxidise ammonia and hydrolyses the injected urea to reduce particulate matter in the exhaust gas; a selective catalytic reduction device (SCR) (70) downstream of the diesel particulate filter (50) which reduces the nitrogen oxide of the exhaust gas flowing through the diesel particulate filter (50), and an injection chamber (35) as a part of the exhaust pipe (5), which connects the diesel oxidation catalyst device (20) and the diesel particulate filter (50) and which forms a space into which the reducing agent is injected from the urea injector (30), wherein the mixer (40) is provided in the injection chamber (35).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an exhaust system. More particularly, the present disclosure relates to an exhaust system in which high-temperature urea injection is possible, selective catalytic reduction performance is improved, and exhaust self-diagnosis is facilitated. BACKGROUND

[0002] To reduce carbon monoxide (CO), hydrocarbons (HC), particulate matter (PM), nitrogen oxide (NOx), etc., which are contained in the exhaust gas as pollutants, an exhaust system of an internal combustion engine can generally include an exhaust aftertreatment device such as a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), a selective catalytic reduction (SCR), and a nitrogen oxide storage catalyst (lean NOx trap, LNT catalyst), etc. An exhaust system for internal combustion engines for this purpose is known, for example, from DE 10 2004 036 036 A1.

[0003] As in Fig. As shown in Figure 4, a conventional exhaust system may include an internal combustion engine 10, a diesel oxidation catalyst device 20, a urea injector 30, a mixer 40, a composite catalyst unit 55 (SDPF), and a selective catalytic reduction device 70. The conventional exhaust system may include a composite catalyst unit 55 after the mixer 40, and the composite catalyst unit 55 may be configured such that the selective catalytic reduction device connected to a high pore volume diesel particulate filter may be exposed to a high temperature when the composite catalyst unit 55 is regenerated for soot combustion. Since the selective catalytic reduction is degraded by the high temperature, the maximum soot retention amount must be controlled to a predetermined amount or less before the regenerative soot combustion.That is, in order to prevent deterioration, the soot mass limit (SML) must be lowered so that the regeneration period of the composite catalyst unit 55 is shortened and deterioration of fuel consumption is prevented.

[0004] The composite catalyst unit 55, like the diesel particulate filter with a high pore volume (pore rate of 50% or more), has low heat resistance and numerous pores, resulting in lower retention efficiency compared to the conventional diesel particulate filter, which is disadvantageous in terms of soot absorption. Furthermore, in the structure of the composite catalyst unit 55, a low-pressure exhaust gas generation device and the selective catalytic reduction device 70 may be arranged sequentially, and the partial flow may be recirculated to the combustion chamber through the low-pressure exhaust gas regeneration (LP-EGR) line 60, which is disadvantageous in terms of exhaust gas self-diagnosis (OBD). Furthermore, when the exhaust gas temperature is increased by engine post-injection, no purification function can be performed for the excessively generated hydrocarbon and carbon monoxide to burn the retained soot.

[0005] With a conventional exhaust system of Fig. 5, in the case of the system where the diesel oxidation catalyst device 20 and the diesel particulate filter 55 are arranged in an engine compartment CC, after the diesel oxidation catalyst device 20, the urea injector 30, the mixer 40, and the selective catalytic reduction device 70 are arranged at a lower part of a vehicle, exhaust gas self-diagnosis is possible by the nitrogen oxide sensors 72 and 74 before and after the selective catalytic reduction device 70. However, since the urea injector 30 is installed at the lower part of the vehicle, and the urea is injected at a position with a low exhaust gas temperature, the injection is limited to low temperatures, and the overall purification performance is low.

[0006] In addition, the lower part of the vehicle is designed to ensure a uniform supply of ammonia (NH 3) to the selective catalytic reduction device 70 for urea injection, a predetermined distance is required between the urea injector 30, the mixer 40, and the selective catalytic reduction device 70 at the lower part of the vehicle. That is, a space is required for the thermal decomposition, hydrolysis, and mixing of the urea. If the urea injector and the mixer are all arranged at the lower part of the vehicle, the space may be too cramped to accommodate the volume of the selective catalytic reduction device 70.

[0007] The above information disclosed in this background section is intended only to provide a better understanding of the background of the disclosure and may therefore contain information that is not part of the prior art already known to a person of ordinary skill in the art in this country. OVERVIEW

[0008] It is therefore an object of the present disclosure to provide an exhaust system in which the diesel oxidation catalyst device, the urea injector, the mixer and the diesel particulate filter are arranged in the engine compartment, the catalyst containing no precious metal or a hydrolysis catalyst is connected to the diesel particulate filter, and the selective catalytic reduction device is installed only at the lower part of the vehicle.

[0009] The object is achieved by an exhaust system having the features of claims 1 or 7. Advantageous further developments can be found in the subclaims.

[0010] An exhaust system according to the embodiment of the present disclosure may include a diesel oxidation catalyst (DOC) device installed on an exhaust pipe for removing hydrocarbon (HC) and carbon monoxide (CO) from the exhaust gas and discharging the exhaust gas of an internal combustion engine; a urea injector downstream of the diesel oxidation catalyst device for injecting an aqueous urea solution into the exhaust pipe; a mixer downstream of the urea injector for rapidly diffusing the exhaust gas passing through the diesel oxidation catalyst device; a diesel particulate filter (DPF) downstream of the mixer, connected with a non-precious metal catalyst or a hydrolysis catalyst that does not oxidize ammonia and hydrolyzes the injected urea to reduce particulate matter in the exhaust gas;a selective catalytic reduction (SCR) device downstream of the diesel particulate filter, which reduces the nitrogen oxide of the exhaust gas flowing through the diesel particulate filter; and an injection chamber as a part of the exhaust passage connecting the diesel oxidation catalyst device and the diesel particulate filter, which forms a space into which the reducing agent is injected from the urea injector, wherein the mixer is provided in the injection chamber.

[0011] A low-pressure exhaust gas regeneration (LP-EGR) line may be provided between the diesel particulate filter and the selective catalytic reduction device.

[0012] The exhaust system according to an embodiment of the present disclosure may further include an ammonia oxidation catalyst (AOC) device after the selective catalytic reduction device for oxidizing ammonia (NH 3) and to reduce nitrogen oxide in the exhaust gas passing through the selective catalytic reduction device.

[0013] A nitrogen oxide sensor may be provided before and after the selective catalytic reduction device.

[0014] A nitrogen oxide sensor may be provided between the diesel oxidation catalyst device and the urea injector, and between the diesel particulate filter and the selective catalytic reduction device.

[0015] The diesel oxidation catalyst device, the urea injector, the mixer, and the diesel particulate filter may be installed in the engine compartment CC of the vehicle and the selective catalytic reduction device may be installed at a lower part of the vehicle.

[0016] An exhaust system according to another embodiment of the present disclosure may include a nitrogen oxide storage catalyst device (lean NOx trap; LNT) for absorbing and storing nitrogen oxide generated by lean combustion of an internal combustion engine and reducing the nitrogen oxide to nitrogen to be discharged through reduction; a urea injector downstream of the nitrogen oxide storage catalyst device for injecting an aqueous urea solution into the exhaust line; a mixer downstream of the urea injector for rapidly diffusing the exhaust gas flowing through the nitrogen oxide storage catalyst device; a diesel particulate filter (DPF) downstream of the mixer connected with a non-precious metal catalyst or a hydrolysis catalyst that does not oxidize ammonia and hydrolyzes the injected urea to reduce particulate matter in the exhaust gas;a selective catalytic reduction (SCR) device downstream of the diesel particulate filter for reducing the nitrogen oxide in the exhaust gas flowing through the diesel particulate filter; and an injection chamber as a part of the exhaust line connecting the nitrogen oxide storage catalyst device and the diesel particulate filter and forming a space into which the reducing agent is injected by the urea injector, wherein the mixer is provided in the injection chamber.

[0017] A low-pressure exhaust gas regeneration device line may be connected between the diesel particulate filter and the selective catalytic reduction device.

[0018] The exhaust system according to another embodiment of the present disclosure may further include an ammonia oxidation catalyst device downstream of the selective catalytic reduction device for oxidizing the ammonia and reducing the nitrogen oxide in the exhaust gas flowing through the selective catalytic reduction device.

[0019] A nitrogen oxide sensor may be provided before and after the selective catalytic reduction device.

[0020] A nitrogen oxide sensor may be provided between the nitrogen oxide storage catalyst device and the urea injector, as well as between the diesel particulate filter and the selective catalytic reduction device.

[0021] The nitrogen oxide storage catalyst device, the urea injector, the mixer, and the diesel particulate filter may be installed in the engine compartment of the vehicle and the selective catalytic reduction device may be installed at a lower part of the vehicle.

[0022] According to the present disclosure, high temperature urea injection and uniform mixing of exhaust gas are possible by installing the urea injector and the mixer in the engine compartment.

[0023] In addition, the conventional diesel particulate filter is provided without selective catalytic reduction and the diesel particulate filter is not coated with precious metal, thus preventing the oxidation of ammonia.

[0024] In addition, by injecting the urea in such a way that the ammonia flows very smoothly by mixing the exhaust gas, ammonia is supplied to the selective catalytic reduction device at the lower part of the vehicle, and a larger volume selective catalytic reduction device at the lower part of the vehicle can be ensured.

[0025] In addition, the selective catalytic reduction device or the selective catalytic reduction device and the ammonia oxidation catalyst device are provided at the lower part of the vehicle, and the nitrogen oxide sensor is installed before and after the catalyst device, so that the urea injection control and the exhaust gas self-diagnosis are possible. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic block diagram of an exhaust system according to an embodiment of the present disclosure. Fig. 2 is a schematic block diagram of an exhaust system according to another embodiment of the present disclosure. Fig. Figure 3 is a graph showing the measurement results of exhaust gas temperature versus time for each position of a vehicle. Fig. Figure 4 is a schematic block diagram of a conventional exhaust system. Fig. Figure 5 is a schematic block diagram of another conventional exhaust system. DETAILED DESCRIPTION

[0026] The present disclosure will be described in more detail below with reference to the accompanying drawings, which illustrate embodiments of the disclosure. It will be understood by those skilled in the art that the described embodiments may be modified in various ways without departing from the spirit or scope of the present disclosure.

[0027] Furthermore, since identical reference numerals denote the same elements having the same configuration in the embodiments, only a first embodiment will be representatively described, and of other embodiments, only the configurations different from those of the first embodiment will be described.

[0028] The drawings are schematic and not drawn to a true scale. The relative dimensions and proportions of portions in the drawings may be exaggerated or reduced for clarity or simplicity, and the dimensions are illustrative and not limiting. In addition, the same structures, elements, or components shown in two or more drawings may bear identical reference numerals to indicate similar features. It is to be understood that when an element such as a layer, film, zone, area, or substrate is referred to as being "on, at" another element, it may be provided directly on / at the other element, or there may be intervening elements.

[0029] An embodiment of the present disclosure illustrates an embodiment of the present disclosure in detail. Various modifications to the drawings are possible. Therefore, the embodiment is not limited to a specific aspect of the illustrated range and includes, for example, modifications from a manufacturing aspect.

[0030] An exhaust gas purification device according to an embodiment of the present disclosure is described with reference to Fig. 1 to 3.

[0031] Fig. 1 is a schematic view of an exhaust gas purification device according to an embodiment of the present disclosure.

[0032] As in Fig. 1, the exhaust system may be connected to an internal combustion engine 10 for purifying the exhaust gas of the internal combustion engine 10 and may include a diesel oxidation catalyst device 20, a urea injector 30, a mixer 40, a diesel particulate filter 50, and a selective catalytic reduction device 70.

[0033] The diesel oxidation catalyst device 20 may be installed on an exhaust pipe 5 for discharging the exhaust gas of the internal combustion engine 10. That is, the front side of the diesel oxidation catalyst device 20 may be connected to the internal combustion engine 10 to receive the exhaust gas from the internal combustion engine 10. Herein, the front and rear sides of the components refer to the exhaust flow, and it is defined that the exhaust gas flows from the front to the rear side of the components.

[0034] The diesel oxidation catalyst device 20 is a device in which a carrier is provided in a dedicated housing, and the diesel oxidation catalyst is connected to the carrier. The diesel oxidation catalyst device 20 oxidizes hydrocarbons and carbon monoxide in the exhaust gas flowing through the diesel oxidation catalyst.

[0035] The diesel particulate filter 50 may be configured to absorb the particulate matter contained in the exhaust gas onto the catalyst support, and the particulate matter is purified through a chemical conversion process. That is, the diesel particulate filter 50 is a device for physically trapping the particulate matter in the exhaust gas of the diesel internal combustion engine 10 using the filter and raising the exhaust temperature of the particulate matter above an ignition temperature of 550°C after driving a predetermined distance to burn the particulate matter, thereby reducing pollutants. A pressure sensor or a temperature sensor may be installed in the diesel particulate filter 50 before and after the diesel particulate filter 50, and the sensors may detect pressure and temperature before and after the exhaust gas passes through the diesel particulate filter 50. An electronic control unit (ECU) may control the internal combustion engine 10 and related devices to remove the particulate matter.

[0036] The diesel particulate filter 50 can be connected to a catalyst without precious metal (platinum (Pt), palladium (Pd), rhodium (Rh)). Since it is not coated with precious metal, the oxidation of ammonia in the exhaust gas flowing into the diesel particulate filter 50 can be prevented.

[0037] In addition, the hydrolysis catalyst may be connected to the diesel particulate filter 50 to hydrolyze the urea injected from the urea injector 30. The hydrolysis catalyst does not oxidize nitrogen, but hydrolyzes the injected urea. In the composite catalyst unit (SDPF) used in the conventional exhaust system, the selective catalytic reduction (SCR) device with a high pore volume may be connected to the diesel particulate filter, and this may degrade the selective catalytic reduction at high temperatures.As a result, the regeneration period of the composite catalyst unit is shortened and the fuel consumption of the present embodiment may become less favorable, in contrast to the composite catalyst unit in which the catalyst without precious metal or the filter with the hydrolysis catalyst connected is used to remove the particulate matter, thereby extending the regeneration period and improving the fuel consumption.

[0038] Since the conventional exhaust system of Fig. 4, the selective catalytic reduction (SCR) device includes the composite catalyst unit 55 connected to the high-pore-volume diesel particulate filter, the partial exhaust gas flow is redirected to the combustion chamber through the low-pressure exhaust gas regeneration device line 60, and it can be confirmed that the exhaust gas flow exiting the low-pressure exhaust gas regeneration device complicates exhaust gas self-diagnosis. However, according to embodiments of the present disclosure, instead of the composite catalyst unit, the diesel particulate filter connected to the catalyst without precious metal or the hydrolysis catalyst is provided. Accordingly, the nitrogen oxide sensor arranged upstream and downstream of the selective catalytic reduction device can confirm the exhaust gas flow in such a way that exhaust gas self-diagnosis is possible.

[0039] The selective catalytic reduction device 70 may be arranged downstream of the diesel oxidation catalyst device 20. The selective catalytic reduction device 70 may convert the reducing agent (urea) into ammonia using exhaust heat and reduce nitrogen oxide as the catalyst reaction of nitrogen oxide and ammonia in the exhaust gas through selective catalytic reduction to nitrogen gas and water.

[0040] The nitrogen oxide sensors 72 and 74 may be arranged before and after the selective catalytic reduction device 70 and measure the amount of nitrogen oxide after and before the exhaust gas passes the selective catalytic reduction device 70.

[0041] The urea injector 30 may be arranged downstream of the diesel oxidation catalyst device 20 and injects the aqueous urea solution into the exhaust line 5. The urea injector 30 may directly inject the urea and ammonia. Other reducing agents may be injected along with the ammonia.

[0042] The mixer 40 may be arranged after the urea injector 30 to enable rapid diffusion of the exhaust gas passing through the diesel oxidation catalyst device 20.

[0043] The low-pressure exhaust gas regeneration device line 60 can be connected between the diesel particulate filter 50 and the selective catalytic reduction device 70 such that the exhaust gas flowing through the diesel particulate filter 50 can be recirculated to the internal combustion engine 10 through the exhaust gas regeneration device. The exhaust gas regeneration device recirculates the portion of the exhaust gas discharged after the fuel is burned in the internal combustion engine 10 to an intake device of the internal combustion engine 10, where it is recirculated into the combustion chamber of the internal combustion engine 10. As a result, the density of the air / fuel mixture decreases without changing the air / fuel ratio of the air / fuel mixture, thereby lowering the combustion temperature.

[0044] That is, the exhaust gas regeneration device directs the portion of the exhaust gas to the intake system of the internal combustion engine 10, from where it is directed into the combustion chamber when the amount of exhaust nitrogen oxide needs to be reduced depending on the driving condition of the internal combustion engine 10. In this way, exhaust gases, which are inert gases whose volume remains constant, contribute to reducing the density of the mixture to a lower level and therefore lowering the flame propagation speed during fuel combustion. This prevents an increase in combustion temperature and slows fuel combustion, thereby preventing the generation of nitrogen oxides.

[0045] The diesel oxidation catalyst device 20, the urea injector 30, the mixer 40 and the diesel particulate filter 50 may be arranged in the engine compartment CC of the vehicle, and the selective catalytic reduction device 70 may be arranged at the lower part of the vehicle.

[0046] By installing the urea injector 30 and the mixer 40 in the engine compartment CC, high-temperature urea injection and uniform mixing of the exhaust gas are possible. Furthermore, since the urea is injected from the engine compartment CC, the ammonia is supplied to the selective catalytic reduction device 70 in the lower part of the vehicle. The ammonia flows very smoothly by mixing with the exhaust gas, and a larger volume selective catalytic reduction device 70 in the lower part of the vehicle can be ensured.

[0047] Fig. 2 is a schematic block diagram of an exhaust system according to another embodiment of the present disclosure.

[0048] The nitrogen oxide storage catalyst device 20 can absorb and store the nitrogen oxide produced by lean combustion of the internal combustion engine 10 and reduce the nitrogen oxide to the nitrogen to be discharged by reduction, and the urea injector 30 injecting the aqueous urea solution into the exhaust line 5 is arranged downstream of the nitrogen oxide storage catalyst device 20.

[0049] The mixer 40, which enables the rapid diffusion of the exhaust gas flowing through the nitrogen oxide storage catalyst device 20, may be arranged downstream of the urea injector 30, and the diesel particulate filter 50 for reducing the particulate matter in the exhaust gas and the selective catalytic reduction device 70 for reducing the nitrogen oxide in the exhaust gas flowing through the diesel particulate filter 50 may be arranged downstream of the mixer 40.

[0050] As in the embodiment described above, the diesel particulate filter 50 in the present embodiment can also be connected to the catalyst without precious metal or to a hydrolysis catalyst for hydrolyzing the urea.

[0051] The urea injector 30, the mixer 40, and the selective catalytic reduction device 70 in the exhaust system according to the present embodiment may be identical to those in the above-described embodiment, so repeated description is omitted.

[0052] As in Fig. As shown in Figure 2, nitrogen oxide sensors 72 and 74 may be installed between the nitrogen oxide storage catalyst device 20 and the urea injector 30, as well as between the diesel particulate filter 50 and the selective catalytic reduction device 70. The amount of nitrogen oxide may be measured before and after the exhaust gas flows through the mixer 40 and the diesel particulate filter 50.

[0053] An injection chamber 35 connecting the nitrogen oxide storage catalyst device 20 and the diesel particulate filter 50, which forms the space into which the reducing agent is injected from the urea injector 30, may be further included as part of the exhaust line 5. The reducing agent injected into the injection chamber 35 can be uniformly mixed by the mixer 40 in the injection chamber 35, and the exhaust gas and the reducing agent rapidly diffuse into the diesel particulate filter 50 after the injection chamber 35.

[0054] In the Fig. 2, the injection chamber may also be connected to the diesel oxidation catalyst device 20 and the diesel particulate filter 50, and the reducing agent injected into the injection chamber 35 may be uniformly mixed by the mixer 40 in the injection chamber 35.

[0055] In addition, the low-pressure exhaust gas regeneration device line 60 may be connected between the diesel particulate filter 50 and the selective catalytic reduction device 70. This allows the exhaust gas flowing through the diesel particulate filter 50 to be recirculated to the internal combustion engine 10 through the exhaust gas regeneration device.

[0056] An ammonia oxidation catalyst (AOC) device 80 for oxidizing the ammonia and reducing the nitrogen oxide in the exhaust gas passing through the selective catalytic reduction device 70 may be further included after the selective catalytic reduction device 70.

[0057] The ammonia oxidation catalyst device 80 can prevent ammonia from being directly emitted into the atmosphere. This is to avoid air pollution caused by the ammonia slip phenomenon, in which the reducing agent does not participate in the reaction and is directly discharged into the atmosphere when too much reducing agent is injected, to ensure high selective catalytic reduction efficiency.

[0058] The ammonia oxidation catalyst may be copper-containing, zeolite-impregnated and coated with the noble metal, or iron-containing, zeolite-impregnated and coated with the noble metal, or zeolite-impregnated and coated with the noble metal, or consist of copper impregnated with the noble metal, or of silicon with an alumina catalyst composition.

[0059] The nitrogen oxide storage catalyst device 20, the urea injector 30, the mixer 40 and the diesel particulate filter 50 may be arranged in the engine compartment CC of the vehicle and the selective catalytic reduction device 70 may be arranged at the lower part of the vehicle.

[0060] Fig. Figure 3 is a graph showing the measurement results of exhaust gas temperature versus time for each position of a vehicle.

[0061] As from Fig.3, the exhaust gas temperature for urea injection must reach at least 180°C or more. In this case, the engine compartment CC, where the diesel oxidation catalyst device 20 and the diesel particulate filter 50 are located, reaches the exhaust gas temperature of 180°C or more after approximately 150 seconds or more, so that rapid urea injection is possible. However, in the lower part of the vehicle, where the selective catalytic reduction device 70 is located, the exhaust gas temperature only reaches 180°C after approximately 800 seconds. Therefore, to perform urea injection in the lower part of the vehicle, approximately 800 seconds or more are required. Therefore, it is advantageous if urea injection is performed when the engine compartment reaches the high temperature earlier.

[0062] As described above, according to embodiments of the present disclosure, by disposing the urea injector and the mixer in the engine compartment, high-temperature urea injection and uniform mixing of the exhaust gas are possible.

[0063] In addition, the conventional diesel particulate filter is provided without selective catalytic reduction and the diesel particulate filter is not coated with precious metal, which prevents oxidation of ammonia.

[0064] In addition, since ammonia is supplied to the selective catalytic reduction device at the lower part of the vehicle by injecting the urea into the engine compartment, the ammonia flows very smoothly by mixing with the exhaust gas, and a selective catalytic reduction device with a larger volume at the lower part of the vehicle can be ensured.

[0065] In addition, the selective catalytic reduction device or the selective catalytic reduction device and the ammonia oxidation catalyst device are arranged in the lower part of the vehicle, and the nitrogen oxide sensor is installed before and after the catalyst device so that the urea injection control and the exhaust gas self-diagnosis are possible.

Claims

[1] Exhaust system, comprising: a diesel oxidation catalyst (DOC) device (20) installed on an exhaust pipe (5) for removing hydrocarbon (HC) and carbon monoxide (CO) from the exhaust gas and for discharging the exhaust gas of an internal combustion engine (10); a urea injector (30) downstream of the diesel oxidation catalyst device (20) for injecting an aqueous urea solution into the exhaust pipe (5); a mixer (40) downstream of the urea injector (30) which ensures rapid diffusion of the exhaust gas flowing through the diesel oxidation catalyst device (20); a diesel particulate filter (DPF) (50) downstream of the mixer (40) connected to a non-precious metal catalyst or a hydrolysis catalyst that does not oxidise ammonia and hydrolyses the injected urea to reduce particulate matter in the exhaust gas; a selective catalytic reduction device (SCR) (70) downstream of the diesel particulate filter (50) which reduces the nitrogen oxide of the exhaust gas flowing through the diesel particulate filter (50), and an injection chamber (35) as a part of the exhaust pipe (5), which connects the diesel oxidation catalyst device (20) and the diesel particulate filter (50) and which forms a space into which the reducing agent is injected from the urea injector (30), wherein the mixer (40) is provided in the injection chamber (35). [2] The exhaust system of claim 1, wherein a low-pressure exhaust gas regeneration (LP-EGR) device line (60) is connected between the diesel particulate filter (50) and the selective catalytic reduction device (70). [3] The exhaust system of claim 1, further comprising an ammonia oxidation catalyst device (AOC) (80) downstream of the selective catalytic reduction device (70) for oxidizing the ammonia (NH 3) and for reducing the nitrogen oxide in the exhaust gas flowing through the selective catalytic reduction device (70). [4] The exhaust system of claim 1, wherein a nitrogen oxide sensor (72) is provided before and after the selective catalytic reduction device (70). [5] The exhaust system according to claim 1, wherein a nitrogen oxide sensor (74) is provided between the diesel oxidation catalyst device (20) and the urea injector (30) and between the diesel particulate filter (50) and the selective catalytic reduction device (70). [6] The exhaust system according to claim 1, wherein the diesel oxidation catalyst device (20), the urea injector (30), the mixer (40) and the diesel particulate filter (50) are arranged in the engine compartment CC of the vehicle, and the selective catalytic reduction device (70) is arranged at a lower part of the vehicle. [7] Exhaust system, comprising: a nitrogen oxide storage catalyst device (lean NOx trap; LNT) for absorbing and storing nitrogen oxide generated by lean combustion of an internal combustion engine (10) and for reducing the nitrogen oxide to nitrogen to be discharged by reduction; a urea injector (30) downstream of the nitrogen oxide storage catalyst device for injecting an aqueous urea solution into the exhaust line (5); a mixer (40) downstream of the urea injector (30) which ensures rapid diffusion of the exhaust gas flowing through the nitrogen oxide storage catalyst device; a diesel particulate filter (DPF) (50) downstream of the mixer (40) connected to a non-precious metal catalyst or a hydrolysis catalyst that does not oxidise ammonia and hydrolyses the injected urea to reduce particulate matter in the exhaust gas; a selective catalytic reduction device (SCR) (70) downstream of the diesel particulate filter (50) for reducing the nitrogen oxide in the exhaust gas flowing through the diesel particulate filter (50), and an injection chamber (35) as a part of the exhaust pipe (5) connecting the nitrogen oxide storage catalyst device and the diesel particulate filter (50) and forming a space into which the reducing agent is injected by the urea injector (30), the mixer (40) being provided in the injection chamber (35). [8] The exhaust system of claim 7, wherein a low-pressure exhaust gas regeneration device line (60) is connected between the diesel particulate filter (50) and the selective catalytic reduction device (70). [9] The exhaust system of claim 7, further comprising an ammonia oxidation catalyst device (80) disposed downstream of the selective catalytic reduction device (70) for oxidizing the ammonia and reducing the nitrogen oxide in the exhaust gas flowing through the selective catalytic reduction device (70). [10] An exhaust system according to claim 7, wherein a nitrogen oxide sensor is arranged before and after the selective catalytic reduction device (70). [11] Exhaust system according to claim 7, wherein a nitrogen oxide sensor is arranged between the nitrogen oxide storage catalyst device and the urea injector (30) and between the diesel particulate filter (50) and the selective catalytic reduction device (70). [12] An exhaust system according to claim 7, wherein the nitrogen oxide storage catalyst device, the urea injector (30), the mixer (40) and the diesel particulate filter (50) are arranged in the engine compartment of a vehicle and the selective catalytic reduction device (70) is arranged at a lower part of the vehicle.

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