KR102394582B1 - Exhaust system and the control method thereof - Google Patents

Abstract

An exhaust system control method according to an embodiment of the present invention is an engine that produces power by burning a mixture of air and fuel in a combustion chamber, and discharges exhaust gas generated in the combustion process to the outside through the exhaust pipe, and is mounted on the exhaust pipe In addition, an injection module that injects a reducing agent into the exhaust gas flowing through the exhaust pipe, and a selective reduction catalyst coated with a selective reduction catalyst for reducing nitrogen oxides contained in exhaust gas using the reducing agent injected from the injection module (Selective Catalytic Reduction on Diesel) Particulate Filter), and a controller for removing nitrogen oxides contained in the exhaust gas passing through the SDPF by controlling the injection amount of the reducing agent injected from the injection module to a set injection amount according to the operation information of the engine, wherein the controller calculates the internal temperature (T) of the SDPF according to the operation information of the engine, calculates the slope value (dT/dt) for time (t) from the calculated internal temperature, the slope value is the slope setting If greater than the value, it is possible to perform a control logic to correct the injection amount of the reducing agent injected from the injection module to increase or decrease based on the injection amount set value.

Description

EXHAUST SYSTEM AND THE CONTROL METHOD THEREOF

The present invention relates to an exhaust system having a selective catalytic reduction catalyst on diesel particulate filter (SDPF) coated thereon, and a method for controlling the same.

In general, the exhaust gas discharged from the engine through the exhaust manifold is guided to a catalytic converter installed in the exhaust pipe to be purified, and the noise is attenuated while passing through the muffler, and then discharged to the atmosphere through the tail pipe.

The catalytic converter purifies pollutants contained in the exhaust gas. In addition, a soot filter for collecting particulate matter (PM) contained in the exhaust gas is mounted on the exhaust pipe.

A Selective Catalytic Reduction (SCR) catalyst is a type of catalytic converter that purifies nitrogen oxides (NOx) contained in exhaust gas. When a reducing agent such as urea, ammonia, carbon monoxide and hydrocarbon (HC) is provided to the exhaust gas, the SCR catalyst reduces nitrogen oxides contained in the exhaust gas through an oxidation/reduction reaction with the reducing agent. do.

Recently, Lean NOx Trap (LNT) is used together with an SCR catalyst in order to respond to stricter exhaust gas regulations. LNT adsorbs nitrogen oxides contained in exhaust gas when the engine is operated in an atmosphere with a lean air-fuel ratio, and desorbs adsorbed nitrogen oxides when the engine is operated in an atmosphere with a rich air-fuel ratio. It reduces oxides and nitrogen oxides contained in exhaust gas.

However, when the LNT and the SCR catalyst are used together, the SCR catalyst may be coated on the diesel soot filter due to space constraints. A selective catalytic reduction catalyst on diesel particulate filter (SDPF) collects particulate matter contained in exhaust gas and uses a reducing agent to remove nitrogen oxides contained in the exhaust gas.

Here, if the particulate matter collected in the SDPF is equal to or greater than the set amount, the temperature of the exhaust gas is raised to burn the particulate matter collected in the SDPF to remove it. This is called SDPF regeneration.

Matters described in this background section are prepared to improve understanding of the background of the invention, and may include matters that are not already known to those of ordinary skill in the art to which this technology belongs.

Korean patent application 10??2015??0044458

It is an object of the present invention to provide an exhaust system capable of reducing ammonia slipping and being discharged to the outside by optimizing the injection of urea, and efficiently removing nitrogen oxides from exhaust gas, and a control method thereof.

An exhaust system control method according to an embodiment of the present invention is an engine that produces power by burning a mixture of air and fuel in a combustion chamber, and discharges exhaust gas generated in the combustion process to the outside through the exhaust pipe, and is mounted on the exhaust pipe In addition, an injection module that injects a reducing agent into the exhaust gas flowing through the exhaust pipe, and a selective reduction catalyst coated with a selective reduction catalyst for reducing nitrogen oxides contained in exhaust gas using the reducing agent injected from the injection module (Selective Catalytic Reduction on Diesel) Particulate Filter), and a controller for removing nitrogen oxides contained in the exhaust gas passing through the SDPF by controlling the injection amount of the reducing agent injected from the injection module to a set injection amount according to the operation information of the engine, wherein the controller calculates the internal temperature (T) of the SDPF according to the operation information of the engine, calculates the slope value (dT/dt) for time (t) from the calculated internal temperature, the slope value is the slope setting If greater than the value, it is possible to perform a control logic to correct the injection amount of the reducing agent injected from the injection module to increase or decrease based on the injection amount set value.

When the slope value is less than the slope setting value, a control logic for correcting a preset NOx purification rate for the SDPF may be performed.

It may further include first and second Knox sensors for detecting nitrogen oxides entering the inlet side of the SDPF and detecting nitrogen oxides discharged from the outlet side of the SDPF.

The controller calculates an actual flow rate of nitrogen oxide discharged from the rear end of the SDPF from a second Knox sensor, selects a model flow rate according to operation information, and sets a first difference value by subtracting the actual flow rate from the model flow rate If it is greater than or equal to the value, it is possible to perform a control logic for reducing the injection amount of the reducing agent injected from the injection module to a set ratio.

When the difference value obtained by subtracting the actual flow rate from the model flow rate is less than a second set value, a control logic for increasing the injection amount of the reducing agent injected from the injection module at a set ratio may be performed.

a temperature sensor for sensing a temperature of exhaust gas passing through the exhaust pipe; Including, the controller may perform a control logic for calculating the internal temperature of the SDPF using the temperature signal sensed by the temperature sensor.

It may further include an injector controlled by the controller and arranged to inject diesel or gasoline into the combustion chamber.

An exhaust gas recirculation device for recirculating exhaust gas flowing through the exhaust pipe to the intake manifold of the engine may be further included.

The exhaust gas occludes nitrogen oxides (NOx) contained in the exhaust gas in a lean atmosphere, desorbs the nitrogen oxides stored in the rich atmosphere, and removes nitrogen oxides or desorbed nitrogen oxides contained in the exhaust gas. It may further include reducing LNT.

It may further include a mixer arranged to mix the reducing agent injected from the injection module.

The control method of an exhaust system according to an embodiment of the present invention comprises the steps of calculating the internal temperature (T) of the SDPF according to the operation information of the engine, and a slope value (dT/dt) for time (t) from the calculated internal temperature Calculating , if the slope value is greater than the slope set value, it is possible to perform the step of correcting the injection amount of the reducing agent injected from the injection module to increase or decrease based on the injection amount set value.

When the slope value is less than the slope setting value, a preset NOx purification rate for the SDPF may be corrected.

calculating the actual flow rate of nitrogen oxide discharged from the rear end of the SDPF, selecting a model flow rate according to operation information, and if the difference value obtained by subtracting the actual flow rate from the model flow rate is equal to or greater than a first set value, the injection module It is possible to perform the step of reducing the injection amount of the reducing agent injected in the set ratio.

If the difference value obtained by subtracting the actual flow rate from the model flow rate is less than the second set value, the step of increasing the injection amount of the reducing agent injected from the injection module to a set ratio may be performed.

Calculating the internal temperature of the SDPF may be performed using the temperature signal sensed by the temperature sensor.

According to an embodiment of the present invention, it is possible to reduce the consumption of urea injected from the injection module, or to improve the purification performance of nitrogen oxides.

Further, it is possible to improve the deterioration of the purification performance caused by the deterioration of the SDPF, and it is possible to reduce the error of the purification rate with respect to the preset model value.

1 is a schematic diagram of an exhaust system according to an embodiment of the present invention;
2 is a block diagram of an exhaust system according to an embodiment of the present invention.
3 is a flowchart illustrating a method for controlling an exhaust gas stem according to an embodiment of the present invention.
4 is a flowchart illustrating a method of correcting an injection amount of urea in an exhaust gas system according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

However, since the size and thickness of each component shown in the drawings are arbitrarily indicated for convenience of explanation, the present invention is not necessarily limited to the bar shown in the drawings, and the thickness is enlarged to clearly express various parts and regions. it was

However, in order to clearly explain the embodiment of the present invention, parts irrelevant to the description are omitted, and the same or similar components are given the same reference numerals throughout the specification.

In the following description, the names of the components are divided into the first, the second, and the like to distinguish them because the names of the components are the same, and the order is not necessarily limited thereto.

1 is a schematic diagram showing an exhaust gas purification apparatus according to an embodiment of the present invention.

1, the exhaust device of the internal combustion engine includes an engine 10, an exhaust pipe 20, an exhaust gas recirculation (EGR) device 30, and a Lean NOx Trap (LNT) ( 40 ), an injection module 50 , a particulate filter 60 , and a controller 70 .

The engine 10 converts chemical energy into mechanical energy by burning a mixture of fuel and air. The engine 10 is connected to the intake manifold 16 to receive air into the combustion chamber 12 , and exhaust gas generated in the combustion process is collected in the exhaust manifold 18 and then discharged out of the engine. An injector 14 is mounted in the combustion chamber 12 to inject fuel into the combustion chamber 12 .

A diesel engine is exemplified here, but a lean burn gasoline engine may be used. When a gasoline engine is used, the mixture is introduced into the combustion chamber 12 through the intake manifold 16 , and a spark plug (not shown) for ignition is mounted on the combustion chamber 12 . In addition, when using a gasoline direct injection (GDI) engine, the injector 14 is mounted on the upper portion of the combustion chamber 12 like a diesel engine.

The exhaust pipe 20 is connected to the exhaust manifold 18 to discharge exhaust gas to the outside of the vehicle. The LNT 40 , the injection module 50 , and the soot filter 60 are mounted on the exhaust pipe 20 to remove hydrocarbons, carbon monoxide, particulate matter, nitrogen oxides, etc. contained in the exhaust gas.

The exhaust gas recirculation device 30 is mounted on the exhaust pipe 20 to re-supply a portion of the exhaust gas discharged from the engine 10 to the engine 10 through the exhaust gas recirculation device 30. In addition, the exhaust gas recirculation device 30 is connected to the intake manifold 16 to control the combustion temperature by mixing a part of the exhaust gas with air. This control of the combustion temperature is performed by adjusting the amount of exhaust gas supplied to the intake manifold 16 under the control of the controller 70 . thus,

A recirculation valve (not shown) controlled by the controller 70 may be mounted on a line connecting the exhaust gas recirculation device 30 and the intake manifold 16 .

A first oxygen sensor 72 is mounted on the rear exhaust pipe 20 of the exhaust gas recirculation device 30 to detect the amount of oxygen in the exhaust gas that has passed through the exhaust gas recirculation device 30 and transmit it to the controller 70 . By doing so, it is possible to assist the controller 70 in performing lean/rich control of exhaust gas. In the present specification, the measured value of the first oxygen sensor 72 will be referred to as an air-fuel ratio (lambda) of the LNT front end.

In addition, a first temperature sensor 74 is mounted on the rear exhaust pipe 20 of the exhaust gas recirculation device 30 to detect the temperature of the exhaust gas that has passed through the exhaust gas recirculation device 30 .

The LNT 40 is mounted on the rear exhaust pipe 20 of the exhaust gas recirculation device 30 . The LNT 40 occludes nitrogen oxides (NOx) contained in exhaust gas in a lean atmosphere, desorbs nitrogen oxides stored in a rich atmosphere, and nitrogen oxides or desorbed nitrogen oxides contained in exhaust gas. reduce nitrogen oxides. In addition, the LNT 40 oxidizes carbon monoxide (CO) and hydrocarbons (HC) contained in the exhaust gas.

Here, it should be understood that the hydrocarbon refers to both a compound composed of carbon and hydrogen contained in exhaust gas and fuel.

A second oxygen sensor 76 , a second temperature sensor 78 , and a first Knox sensor 80 are mounted on the rear exhaust pipe 20 of the LNT 40 .

The second oxygen sensor 76 measures the amount of oxygen included in the exhaust gas flowing into the soot filter 60 and transmits the signal to the controller 70 . Based on the detection values of the first oxygen sensor 72 and the second oxygen sensor 76 , the controller 70 may perform lean/rich control of the exhaust gas. In this specification, the measured value of the second oxygen sensor 76 will be referred to as an air-fuel ratio (lambda) of the front end of the filter.

The second temperature sensor 78 measures the temperature of the exhaust gas flowing into the soot filter 60 and transmits a signal corresponding thereto to the controller 70 . Here, a third temperature sensor 90 that detects the temperature of the exhaust gas discharged from the soot filter 60 and transmits it to the controller 70 may be further disposed.

The first Knox sensor 80 measures the amount of NOx included in the exhaust gas flowing into the soot filter 60 and transmits a signal corresponding thereto to the controller 70 . The amount of NOx measured by the first Knox sensor 80 may be used to determine the amount of the reducing agent to be sprayed by the injection module 50 .

The injection module 50 is mounted on the exhaust pipe 20 at the front end of the soot filter 60 and is controlled by the controller 70 to inject the reducing agent into the exhaust gas. Typically, the injection module 50 injects urea, and the injected urea is converted into ammonia by hydrolysis.

However, the reducing agent is not limited to ammonia. Hereinafter, for convenience of explanation, it is exemplified that ammonia is used as a reducing agent and that urea is injected from the injection module 50 . However, it should be understood that the use of a reducing agent other than ammonia within the spirit of the present invention is also included in the scope of the present invention.

A mixer 55 is mounted on the exhaust pipe 20 at the rear end of the injection module 50 to evenly mix the reducing agent with the exhaust gas.

The soot filter 60 is mounted on the exhaust pipe 20 at the rear end of the mixer 55, collects particulate matter included in the exhaust gas, and uses the reducing agent injected from the injection module 50 to be included in the exhaust gas reduce nitrogen oxides. For this purpose, the soot filter 60 is a diesel soot filter coated with a selective reduction catalyst (Selective Catalytic).

Reduction on Diesel Particulate Filter; SDPF) 62 and an additional selective reduction (SCR) catalyst 64 .

On the other hand, the name of the SCR catalyst in the present specification and claims should be interpreted as including both the SCR catalyst itself or SDPF.

In the SDPF 62, the SCR catalyst is coated on the partition walls constituting the channel of the DPF. Typically, the DPF includes a plurality of inlet channels and outlet channels. One end of the inlet channel is opened and the other end is closed, so that exhaust gas is introduced from the front end of the DPF.

In addition, one end of the outlet channel is blocked and the other end is opened to discharge the exhaust gas inside the DPF. The exhaust gas flowing into the DPF through the inlet channel enters the outlet channel through the porous partition wall dividing the inlet channel and the outlet channel, and then is discharged from the DPF through the outlet channel.

As the exhaust gas passes through the porous partition wall, particulate matter contained in the exhaust gas is collected. In addition, the SCR catalyst coated on the SDPF 62 reduces nitrogen oxides contained in the exhaust gas using the reducing agent injected from the injection module 50 .

An additional SCR catalyst 64 is mounted at the rear end of the SDPF 62 . The additional SCR catalyst 64 may additionally reduce nitrogen oxides when nitrogen oxides are not completely purified in the SDPF 62 . The additional SCR catalyst 64 may be mounted to be physically separated from the SDPF 62 .

Meanwhile, a differential pressure sensor 66 is mounted on the exhaust pipe 20 . The differential pressure sensor 66 measures the pressure difference between the front end and the rear end of the soot filter 60 and transmits the signal to the controller 70 . The controller 70 may control the soot filter 60 to be regenerated when the pressure difference measured by the differential pressure sensor 66 is equal to or greater than a set pressure.

In this case, the particulate matter collected in the soot filter 60 may be burned by post-injecting fuel from the injector 14 .

In addition, a second Knox sensor 82 is mounted on the exhaust pipe 20 at the rear end of the soot filter 60 . The second Knox sensor 82 detects the amount of nitrogen oxide contained in the exhaust gas discharged from the soot filter 60 , and transmits the signal to the controller 70 . The controller 70 may monitor whether the soot filter 60 normally removes nitrogen oxides included in the exhaust gas based on the detection value of the second Knox sensor 82 . That is, the second Knox sensor 82 may be used to evaluate the performance of the soot filter 60 .

The controller 70 determines the operating conditions of the engine based on the signals detected by the respective sensors, and controls the amount of the reducing agent injected from the lean/rich control and injection module 50 based on the operating conditions of the engine. .

As an example, the controller 70 controls the air-fuel ratio to a rich atmosphere to remove nitrogen oxides from the LNT 40 (referred to as 'regeneration of LNTs' in this specification), and nitrogen from the SDPF 60 through reducing agent injection. Oxides can be removed. The lean/rich control may be performed by adjusting the injection timing and the amount of fuel injected from the injector 14 .

On the other hand, the controller 70 calculates the internal temperature of the SDPF 62, the amount of ammonia stored in the SDPF 62, the NOx amount at the rear end of the LNT 40, etc. based on the engine operating conditions, and based on these, the SDPF 62 ) to predict the NOx purification rate.

For this purpose, the controller 70 includes ammonia occlusion/oxidation characteristics according to the internal temperature of the soot filter 60, ammonia desorption characteristics according to the internal temperature of the soot filter 60, and NOx slip of the LNT 40 in a rich atmosphere. properties are stored.

Ammonia occlusion/oxidation characteristics according to the internal temperature of the soot filter 60, ammonia desorption characteristics according to the internal temperature of the soot filter 60, NOx slip characteristics of the LNT 40 in a rich atmosphere, etc. were determined as maps by numerous experiments. can be done In addition, the controller 70 performs regeneration of the soot filter 60 and desulfurization of the LNT 40 .

For this purpose, the controller 70 may be implemented as one or more processors operating by a set program, and the set program performs each step of the control method of the exhaust gas purification apparatus according to an embodiment of the present invention. It may be programmed.

2 is a block diagram illustrating an input and output relationship in a controller used in an exhaust gas purification method according to an embodiment of the present invention.

As shown in FIG. 2 , a first oxygen sensor 72 , a first temperature sensor 74 , a second oxygen sensor 76 , a second temperature sensor 78 , a first Knox sensor 80 , a second The Knox sensor 82 , the third temperature sensor 90 , and the differential pressure sensor 66 are electrically connected to the controller 70 , and transmit detected values to the controller 70 .

The first oxygen sensor 72 detects the amount of oxygen in the exhaust gas that has passed through the exhaust gas recirculation device 30 and transmits a signal corresponding thereto to the controller 70 . The controller 70 may assist in performing lean/rich control of the exhaust gas based on the amount of oxygen in the exhaust gas detected by the first oxygen sensor 72 . The value detected by the first oxygen sensor 72 may be expressed as lambda (λ). Lambda indicates the ratio of the actual air-fuel ratio to the stoichiometric air-fuel ratio. If lambda exceeds 1, it is considered a lean atmosphere, and if lambda is less than 1, it is considered a rich atmosphere.

The first temperature sensor 74 detects the temperature of the exhaust gas that has passed through the exhaust gas recirculation device 30 and transmits a signal thereto to the controller 70.

The second oxygen sensor 76 measures the amount of oxygen included in the exhaust gas flowing into the soot filter 60 and transmits the signal to the controller 70 .

The second temperature sensor 78 measures the temperature of the exhaust gas flowing into the soot filter 60 and transmits a signal corresponding thereto to the controller 70 .

The first Knox sensor 80 measures the amount of NOx included in the exhaust gas flowing into the soot filter 60 and transmits a signal corresponding thereto to the controller 70 .

The second Knox sensor 82 detects the amount of nitrogen oxide contained in the exhaust gas discharged from the soot filter 60 , and transmits the signal to the controller 70 .

The differential pressure sensor 66 measures the pressure difference between the front end and the rear end of the soot filter 60 and transmits the signal to the controller 70, and the third temperature sensor 90 is the soot filter 60 The temperature of the exhaust gas discharged from the is measured and a signal for this is transmitted to the controller 70 .

The controller 70 determines engine operating conditions, fuel injection amount, fuel injection timing, fuel injection pattern, reducing agent injection amount, regeneration timing of the soot filter 60, and regeneration/desulfurization timing of the LNT 40 based on the transmitted values and outputs a signal for controlling the injector 14 and the injection module 50 to the injector 14 and the injection module 50 .

Meanwhile, the exhaust gas purification apparatus according to the embodiment of the present invention may be equipped with a plurality of sensors in addition to the sensors illustrated in FIG. 2 , but will be omitted for convenience of description.

3 is a flowchart illustrating a method for controlling an exhaust gas stem according to an embodiment of the present invention.

Referring to FIG. 3 , when the engine 10 is started, the controller 70 starts control in S300 .

In S310, the controller 70 detects the temperature of the front or rear end of the SDPF 62, and in S315, the controller 70 calculates the internal temperature of the SDPF (62).

In an embodiment of the present invention, the controller 70 may calculate the internal temperature of the SDPF 62 according to the operation information. Here, the operation information may include RPM of the engine 10 , fuel injection amount, outside temperature, or coolant temperature.

In S320, the controller 70 calculates a temperature change gradient (temperature gradient: dT/dt) according to the internal temperature change of the SDPF 62 .

In S325, the controller 70 determines whether the calculated slope value (temperature gradient) is greater than the slope set value. Then, if the condition of S325 is satisfied, S340 is performed. If the condition of S325 is not satisfied, S330 is performed.

In S340 , the controller 70 corrects the injection amount of urea injected from the injection module 50 , and in S330 , the controller corrects and resets the NOx purification rate of the SDPF 62 . Then, when the engine 10 is turned off, the controller 70 ends the control in S350 .

With reference to FIG. 4 , the control flow of S340 will be described in detail.

4 is a flowchart illustrating a method of correcting an injection amount of urea in an exhaust gas system according to an embodiment of the present invention.

Referring to FIG. 4 , in S400 , the controller 70 detects an actual flow rate of nitrogen oxide from the second Knox sensor 82 at the rear end of the SDPF 62 . Here, the Knox flow rate refers to the flow amount of nitrogen oxides, and may be replaced by the density of nitrogen oxides.

In S410, the controller 70 selects a model flow rate of nitrogen oxide discharged to the rear end of the SDPF 62 from the operation information. Then, in S420, the controller 70 calculates a difference value obtained by subtracting the model flow rate from the actual flow rate.

In S430, the controller 70 determines whether the difference value is greater than a first set value. If the condition of S430 is satisfied, the controller 70 performs S450. If the condition of S430 is not satisfied, the controller 70 performs S440.

In S450, the controller 70 reduces the injection amount set value of the urea injected from the injection module 50 by a set ratio.

Then, in S440, the controller 70 determines whether the difference value is less than the second set value, and if the condition in S440 is satisfied, the controller 70 in S460 sets the injection amount of urea injected from the injection module 50. is increased by the set ratio. Also, if the condition of S440 is not satisfied, S400 or S310 may be performed again.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and can be easily changed by those of ordinary skill in the art to which the present invention pertains from the embodiments of the present invention and equivalent. Including all changes to the extent recognized as

10: engine 70: controller
62: SDPF 50: spray module

Claims (15)

an engine that produces power by burning a mixture of air and fuel in a combustion chamber, and discharges exhaust gas generated in the combustion process to the outside through an exhaust pipe;
an injection module mounted on the exhaust pipe and injecting a reducing agent into the exhaust gas flowing through the exhaust pipe;
Selective Catalytic Reduction on Diesel Particulate Filter (SDPF) coated with a selective reduction catalyst for reducing nitrogen oxides contained in exhaust gas using the reducing agent injected from the injection module; and
a controller controlling the injection amount of the reducing agent injected from the injection module to a set injection amount according to the operation information of the engine to remove nitrogen oxides contained in the exhaust gas passing through the SDPF; includes,
The controller is
Calculates the internal temperature (T) of the SDPF according to the operation information of the engine, calculates the slope value (dT/dt) for time (t) from the calculated internal temperature, the slope value is higher than the slope set value If it is large, the exhaust system performs a control logic to correct the injection amount of the reducing agent injected from the injection module to increase or decrease based on the injection amount set value. According to claim 1,
When the slope value is less than the slope set value, the exhaust system performs a control logic for correcting a preset NOx purification rate with respect to the SDPF. According to claim 1,
first and second Knox sensors for detecting nitrogen oxides entering the inlet side of the SDPF and detecting nitrogen oxides discharged from the outlet side of the SDPF; An exhaust system further comprising a. 4. The method of claim 3,
The controller is
Calculate the actual flow rate of nitrogen oxide discharged from the second Nox sensor at the rear end of the SDPF,
Select the model flow rate according to the operation information,
When the difference value obtained by subtracting the actual flow rate from the model flow rate is equal to or greater than a first set value, the exhaust system performs a control logic for reducing the injection amount of the reducing agent injected from the injection module by a set ratio. 5. The method of claim 4,
When the difference value obtained by subtracting the actual flow rate from the model flow rate is less than a second set value, the exhaust system performs a control logic to increase the injection amount of the reducing agent injected from the injection module at a set ratio. According to claim 1,
a temperature sensor for sensing a temperature of exhaust gas passing through the exhaust pipe; including,
and the controller executes a control logic for calculating the internal temperature of the SDPF by using a temperature signal sensed by the temperature sensor. According to claim 1,
an injector controlled by the controller and arranged to inject diesel or gasoline into the combustion chamber; An exhaust system further comprising a. According to claim 1,
an exhaust gas recirculation device for recirculating exhaust gas flowing through the exhaust pipe toward an intake manifold of the engine; An exhaust system further comprising a. According to claim 1,
The exhaust gas occludes nitrogen oxides (NOx) contained in the exhaust gas in a lean atmosphere, desorbs the nitrogen oxides stored in the rich atmosphere, and removes nitrogen oxides or desorbed nitrogen oxides contained in the exhaust gas. reducing LNT; An exhaust system further comprising a. According to claim 1,
a mixer arranged to mix the reducing agent injected from the injection module; An exhaust system further comprising a. calculating an internal temperature (T) of the SDPF according to the operation information of the engine;
calculating a slope value (dT/dt) with respect to time (t) from the calculated internal temperature;
If the slope value is greater than the slope setting value, correcting the injection amount of the reducing agent injected from the injection module to increase or decrease based on the injection amount set value;
A control method of an exhaust system that performs 12. The method of claim 11,
When the slope value is less than the slope set value, the control method of the exhaust system for correcting a preset NOx purification rate for the SDPF. 12. The method of claim 11,
calculating an actual flow rate of nitrogen oxide discharged from the rear end of the SDPF and selecting a model flow rate according to operation information; and
If the difference value obtained by subtracting the actual flow rate from the model flow rate is equal to or greater than a first set value, reducing the injection amount of the reducing agent injected from the injection module to a set ratio; A control method of an exhaust system that performs 14. The method of claim 13,
If the difference value obtained by subtracting the actual flow rate from the model flow rate is less than a second set value, increasing the injection amount of the reducing agent injected from the injection module to a set ratio; A control method of an exhaust system that performs 12. The method of claim 11,
A control method of an exhaust system comprising the step of calculating the internal temperature of the SDPF by using a temperature signal detected by a temperature sensor.

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