KR20250091669A - Dual SCR application exhaust purification system and method for vehicle - Google Patents

Abstract

A dual SCR application exhaust purification system for a vehicle and a method therefor are disclosed.
According to an embodiment of the present invention, a dual SCR-applied exhaust gas purification system for a vehicle includes an engine that emits exhaust gas combusted when the vehicle is driven, a first SCR and a second SCR that purify nitrogen oxides (NOx) emitted through an exhaust line of the engine and are installed in a sequence close to the engine, a first injector and a second injector that inject urea corresponding to the first SCR and the second SCR, respectively, and a controller that monitors an SCR temperature over time and a difference in absorption amount between a target absorption amount and an actual absorption amount in order to improve the purification efficiency of the NOx, and changes an absorption amount speed according to an absorption amount difference condition by temperature area set in an absorption amount injection decision map (MAP).

Description

{Dual SCR application exhaust purification system and method for vehicle}

The present invention relates to a dual SCR application exhaust purification system for a vehicle and a method therefor, and more particularly, to a dual SCR application exhaust purification system for a vehicle and a method therefor for efficiently reducing NOx through an improved absorption amount logic of a first SCR which is close to an engine and thus has a large temperature change amount.

In the automotive industry, vehicle fuel efficiency and environmental regulations are major concerns, and to address these, vehicle manufacturers are accelerating research to simultaneously improve fuel efficiency and satisfy strengthened emission regulations (Euro 7).

Typically, exhaust systems of vehicles use exhaust gas aftertreatment devices such as DOC (Diesel Oxidation Catalyst), DPF (Diesel Particulate Matter Filter), and SCR (Selective Catalyst Reduction) to reduce pollutants such as nitrogen oxides (NOx) contained in exhaust gas. Among these, SCR stands for selective reduction in the sense that it allows reducing agents such as urea (Urea), ammonia (NH3), carbon monoxide, and hydrocarbons (HC) to react better with nitrogen oxides than with oxygen and nitrogen oxides.

Figure 1 schematically illustrates the configuration of a conventional dual SCR application exhaust gas purification system.

Figure 2 shows the conventional urea injection amount determination logic.

Referring to FIGS. 1 and 2, the exhaust purification system of a vehicle to respond to recently strengthened emission regulations is equipped with two independent SCRs: a cc (Closed coupled)-SCR and a uf (Under floor)-SCR.

The urea injection amount is determined by utilizing the urea injection amount determination logic that considers the nitrogen oxide (NOx) concentration of the exhaust purification system, exhaust flow rate, ammonia and nitrogen oxide (NH3-NOx) ratio, and NOx purification efficiency. The urea injection amount determined in this way is to reduce cc-SCR injection and purify NOX in uf-SCR when the difference in absorption between the target absorption amount and the actual absorption amount of cc-SCR increases due to exposure of the SCR carrier to high temperature.

The above urea injection amount is determined by the sum of the NOx removal required injection amount (A) (which has only positive (+) values) calculated by the exhaust flow rate and the NOx concentration and the absorption target injection amount (B) (which has positive (+) and negative (-) values) required to absorb NH3 in the SCR carrier, and urea injection is performed by the urea injection amount determined in this way.

In the conventional urea injection amount determination logic, the mapping of the target injection amount (B) is determined by one variable (the difference in the amount of absorption) that determines the urea injection amount according to the target absorption amount. At this time, if the target absorption amount is greater than the actual absorption amount, the urea injection amount increases (+), and if the target absorption amount is less than the actual absorption amount, the urea injection amount decreases (-).

However, cc-SCR has a disadvantage in that the temperature change is very large because it is located close to the engine, and the control error accumulates due to the difference (deviation) between the target absorption amount and the actual absorption amount caused by the influence of this. In addition, the conventional absorption amount logic determines the urea injection amount only by one variable, the absorption amount difference, so it cannot control the NH3 absorption amount according to the large temperature change, which has a problem in that the NOx purification efficiency is reduced.

The information contained in this background section has been prepared to promote understanding of the background of the invention and may include matters that are not prior art and are already known to those skilled in the art.

An embodiment of the present invention is to provide an exhaust purification system for a vehicle and a method thereof, which monitors the difference between the target absorption amount of a first SCR and the actual absorption amount and variably controls the absorption amount speed according to conditions of each set temperature range in order to improve the NOx purification efficiency of an exhaust purification system to which a dual SCR is applied.

According to one aspect of the present invention, an exhaust purification system for a vehicle includes: an engine that emits exhaust gas combusted when the vehicle is driven; a first SCR (Selective Catalyst Reduction) and a second SCR that purify nitrogen oxides (NOx) emitted through an exhaust line of the engine and are installed in a sequence close to the engine; a first injector and a second injector that inject urea in response to the first SCR and the second SCR, respectively; and a controller that monitors an SCR temperature over time and a difference in absorption between a target absorption amount and an actual absorption amount in order to improve the purification efficiency of the NOx, and changes an absorption amount speed according to an absorption amount difference condition for each temperature area set in an absorption amount injection decision map (MAP).

In addition, the exhaust purification system of the vehicle may further include sensors that measure at least one status information among the NOx concentration, SCR temperature, NH3 concentration, and exhaust flow rate required for determining the absorption rate at positions corresponding to the first SCR and the second SCR, respectively.

Additionally, the controller can variably control the urea injection amount of at least one of the first injector and the second injector according to the absorption rate determined through the absorption amount injection decision map (MAP).

In addition, the second SCR can be modularized to include an SCR catalyst installed in the exhaust line (L); a DOC (Diesel Oxidation Catalyst) and a DPF (Diesel Particulate Matter Filter) installed in front of the SCR catalyst to purify carbon monoxide (CO), hydrocarbons (HC), and soot in the exhaust gas; and an AOC (Ammonia Oxidation Catalyst) installed in the rear of the SCR catalyst to convert ammonia (NH3) emitted into harmless nitrogen (N2).

Additionally, the controller can change the absorption rate so that the actual absorption amount slowly follows the target absorption amount according to the absorption amount injection decision map (MAP) in the case of a low temperature region (T1) where the first SCR satisfies a negative (-) difference condition.

In addition, the controller can change the absorption rate so that the actual absorption rate quickly follows the target absorption rate according to the absorption amount injection decision map (MAP) in the case of a high temperature region (T2) where the first SCR satisfies a negative (-) difference condition.

Meanwhile, a method for exhaust gas purification using dual SCR of a vehicle according to one aspect of the present invention comprises: a) a step of collecting real-time status information through sensors of a first SCR (Close Coupled-SCR) and a second SCR (Under Floor-SCR) sequentially installed in an exhaust line (L) of an engine; b) a step of monitoring a difference in the amount of absorption between a target absorption amount and an actual absorption amount and an average temperature of the first SCR over time based on the status information; and c) a step of inputting the difference in the amount of absorption and the average temperature of the first SCR into a set absorption amount logic and changing a absorption amount speed according to a set temperature range and an absorption amount difference condition according to a absorption amount injection decision map (MAP) to determine a absorption target injection amount (B).

In addition, the step c) may include a step of checking whether the input difference in absorption satisfies a negative difference condition; if the negative difference condition is satisfied, a step of determining whether the average temperature satisfies a low temperature region (T1) below a certain temperature or a high temperature region (T2) above the certain temperature; a step of changing the absorption rate according to the determined information and an absorption rate injection decision map (MAP); and a step of determining the absorption target injection amount (B) according to the absorption rate.

In addition, the step of changing the absorption rate may include a step of controlling the absorption rate so that the actual absorption rate quickly follows the target absorption rate according to the absorption rate injection decision map (MAP) when the average temperature satisfies the high temperature region (T2).

In addition, the step of changing the absorption rate may include a step of controlling the absorption rate so that the actual absorption rate slowly follows the target absorption rate according to the absorption rate injection decision map (MAP) when the average temperature satisfies the low temperature region (T1).

In addition, after the step c), the step d) may further include a step of controlling the first injector to operate the first SCR with a urea injection amount calculated by adding the NOx removal required injection amount (A) calculated by the exhaust flow rate and NOx concentration collected by the status information and the absorption target injection amount (B).

In addition, after the step of checking whether the above negative (-) difference condition is satisfied, if the input absorption amount difference does not satisfy the negative (-) difference condition, a step of determining the absorption target injection amount (B) using logic that applies one variable of the absorption amount difference regardless of the temperature condition may be further included.

According to an embodiment of the present invention, by changing the absorption rate through improved absorption logic considering variables of the SCR temperature and absorption difference, there is an effect of reducing the control error of the first SCR having a very large temperature change amount.

In addition, there is an effect of quickly reducing the difference in absorption amount and reducing the amount of urea injection by quickly following the target absorption amount in a high temperature range where the actual absorption amount satisfies the condition of a negative (-) difference between the target absorption amount and the target absorption amount.

Furthermore, by rapidly reducing the difference in adsorption amount through the first SCR in the high-temperature region and reducing residual NOx through the second SCR in the low-temperature region with high NOx purification efficiency, it is possible to reduce the amount of urea injected throughout the entire exhaust purification system with dual SCR application while securing NOx purification efficiency.

Figure 1 schematically illustrates the configuration of a conventional dual SCR application exhaust purification system.
Figure 2 shows the conventional urea injection amount determination logic.
FIG. 3 schematically illustrates the configuration of a dual SCR application exhaust purification system of a vehicle according to an embodiment of the present invention.
FIG. 4 shows a first SCR monitoring graph for explaining the concept of improved storage logic according to an embodiment of the present invention.
Figure 5 shows an improved absorption logic according to an embodiment of the present invention.
FIG. 6 illustrates a storage amount determination map (MAP) structure applied to the storage amount logic according to an embodiment of the present invention.
Figure 7 is a flow chart schematically illustrating a method for applying dual SCR to exhaust gas purification of a vehicle according to an embodiment of the present invention.

Below, with reference to the attached drawings, an embodiment of the present invention is described in detail so that a person having ordinary skill in the art to which the present invention pertains can easily implement the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the terms "comprises" and/or "comprising," when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any one or all combinations of the associated listed items.

Throughout the specification, terms such as first, second, A, B, (a), (b), etc. may be used to describe various components, but the components should not be limited by these terms. These terms are only used to distinguish the components from other components, and the nature, order, or sequence of the components is not limited by these terms.

Throughout the specification, when a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components in between. Conversely, when a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

Throughout the specification, the terminology used is only used to describe specific embodiments and is not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

Additionally, it is understood that one or more of the methods or aspects thereof below may be executed by at least one controller. The term "controller" may refer to a hardware device including a memory and a processor. The memory is configured to store program instructions, and the processor is specifically programmed to execute the program instructions to perform one or more processes described in more detail below. The controller may control the operation of units, modules, components, devices, or the like, as described herein. It is also understood that the methods below may be executed by a device including the controller in conjunction with one or more other components, as will be appreciated by those skilled in the art.

Now, a dual SCR application exhaust purification system and method thereof for a vehicle according to an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 3 schematically illustrates the configuration of a dual SCR application exhaust purification system of a vehicle according to an embodiment of the present invention.

Referring to FIG. 3, the dual SCR application exhaust purification system (100) of a vehicle according to an embodiment of the present invention includes an engine (110) that discharges exhaust gas combusted during driving of the vehicle;

The system comprises: a first SCR (Selective Catalyst Reduction) (120) and a second SCR (130) installed in the order of proximity to the engine (110) to purify nitrogen oxides (NOx) discharged through an exhaust line (L); a first injector (121) and a second injector (131) respectively injecting urea corresponding to the first SCR (120) and the second SCR (130); and a controller (140) that monitors the SCR temperature over time and the difference in absorption between the target absorption amount and the actual absorption amount in order to improve the purification efficiency of the nitrogen oxides (NOx), and changes the absorption amount speed according to the absorption amount difference condition by temperature range set based on the improved absorption amount logic (141).

Throughout the specification of the present invention, the first SCR (120) and the second SCR (130) are collectively defined as a dual SCR.

The dual SCR application exhaust purification system (100) further includes sensors (S1, S2, S3, S4) that measure at least one status information among NOx concentration, SCR temperature, NH3 concentration, and exhaust flow rate required for determining the absorption rate at positions corresponding to the first SCR (120) and the second SCR (130), respectively.

The controller (140) can variably control the urea injection amount of at least one of the first injector (121) and the second injector (131) according to the absorption rate determined through the improved absorption amount logic.

The first SCR (120) is also called a direct-coupled selective reduction catalyst and is located at the uppermost part of the exhaust line (L) close to the engine (110) to rapidly purify nitrogen oxides (NOx) under high temperature conditions compared to the second SCR (130).

The second SCR (130) is also called a downstream selective reduction catalyst and can purify residual NOx remaining in exhaust gas purified through the first SCR (120).

The second SCR (130) is configured as a modular structure by housing in a box an SCR catalyst (132) installed in an exhaust line (L), a DOC (133) and a DPF (134) installed in front of the SCR catalyst (132) to purify carbon monoxide (CO), hydrocarbons (HC), soot, etc. in the exhaust gas, and an AOC (Ammonia Oxidation Catalyst) (135) installed in the rear of the SCR catalyst (132) to convert ammonia (NH3) that is discharged without reacting in the SCR catalyst (132) into harmless nitrogen (N2).

The first injector (121) is mounted in the exhaust line (L) between the engine (110) and the first SCR (120) and injects urea into the exhaust gas just before it flows into the catalyst of the first SCR (120).

The second injector (131) is mounted in the exhaust pipe (110) between the DPF (134) and the SCR catalyst (132) and injects urea into the exhaust gas just before it flows into the SCR catalyst (132).

These first injector (121) and second injector (131) can control the urea injection amount according to the control signal of the controller (140). Here, urea injected into the exhaust gas is decomposed into ammonia (NH3), and the decomposed ammonia (NH3) is used as a reducing agent for purifying the nitrogen oxides (NOx). Therefore, throughout this specification, the fact that the first and second injectors (121, 132) inject urea can be interpreted to mean substantially the same as injecting a reducing agent.

The controller (140) may be implemented as a Dosing Control Unit (DCU) or an electronic control unit (ECU) above it that controls the overall operation of the dual SCR application exhaust purification system (100) of a vehicle including the first SCR (120) and the second SCR (130) according to an embodiment of the present invention.

The controller (140) collects status information of at least one of NOx concentration, SCR temperature, NH3 concentration, and exhaust flow rate from sensors (S1, S2, S3, S4) installed to control exhaust purification of the first SCR (120) and the second SCR (130) while the vehicle is running.

The controller (140) monitors the SCR temperature, target absorption amount, actual absorption amount, and NOx absorption amount over time based on the collected status information.

At this time, in the vehicle's dual SCR application exhaust purification system (100), the first SCR (120) is installed at the closest position to the engine (110) on the exhaust line (L), and reacts quickly to the exhaust gas temperature of the engine (110) and has a large temperature change, so the absorption amount control in the first SCR (120) is more important than that in the second SCR (130).

Therefore, the concept of the improved storage logic according to the embodiment of the present invention will be explained mainly with reference to the first SCR (120).

FIG. 4 shows a first SCR monitoring graph for explaining the concept of improved storage logic according to an embodiment of the present invention.

Figure 5 shows an improved absorption logic according to an embodiment of the present invention.

FIG. 6 illustrates a storage amount determination map (MAP) structure applied to the storage amount logic according to an embodiment of the present invention.

Referring to FIGS. 4 to 6, the monitoring graph of the first SCR (120) according to the embodiment of the present invention shows changes in the average temperature, target absorption amount, actual absorption amount, and NOx absorption amount (Tail NOx/ppm) of the first SCR over time, respectively.

As mentioned in the background technology of the invention, the first SCR is located close to the engine, so that a large temperature change occurs, and there is a disadvantage in that control errors accumulate due to the difference (deviation) between the target absorption amount and the actual absorption amount caused by the influence of the temperature change. Since the conventional absorption amount logic determines the urea injection amount only by one variable of the absorption amount difference, it is impossible to control the NH3 absorption amount according to the large temperature change, so there is a problem that the NOx purification efficiency is reduced.

Meanwhile, let's look at the analysis characteristics referring to the above first SCR monitoring graph.

Looking at the monitoring graph above, in the positive (+) difference section where the target absorption amount is greater than the actual absorption amount, the urea injection amount increases, and in the negative (-) difference section where the target absorption amount is less than the actual absorption amount, the urea injection amount decreases. Therefore, the negative (-) difference section where urea injection consumption is less is advantageous for absorption amount control.

In addition, since the first SCR (120) has a smaller difference in the absorption amount in a high temperature section above a certain temperature (ex: 400°C) than in the SCR average temperature rise section (ex: 200°C to less than 400°C), the actual absorption amount in the high temperature section can quickly follow the target absorption amount, and since the absorption amount tracking is faster, the amount of urea injection (consumption) is reduced, so it can be seen that the high temperature section is advantageous for absorption amount control.

In addition, when the average physical SCR temperature is at a high temperature condition (400°C or higher), there is no NH3 absorption inside the SCR, so the actual absorption calculated by the controller (140) must quickly follow (follow) the target absorption to increase the NOx purification efficiency in the next cycle.

By synthesizing these analysis characteristics, the controller (140) according to the embodiment of the present invention applies an improved absorption logic (141) that determines the absorption target injection amount (B) by considering a negative difference condition in which the target absorption amount is less than the actual absorption amount and a low temperature area (T1) below a certain temperature (ex: 400°C) and a high temperature area (T2) above the certain temperature. Here, the T1 and T2 areas indicated in the graph are one example for the convenience of explanation, and the embodiment of the present invention is not limited thereto.

The controller (140) subtracts the actual storage amount from the target storage amount based on real-time monitoring information to determine the storage amount difference. Then, the storage amount difference and the SCR average temperature are input into the storage amount logic (141).

The absorption logic (141) inputs the absorption difference and the SCR average temperature into the absorption injection decision map (MAP), and determines (derives) the absorption target injection amount (B) changed to different absorption rates by distinguishing between the low temperature area (T1) and the high temperature area (T2) while satisfying the negative (-) difference condition.

For example, the absorption logic (141) gradually changes the absorption speed according to the absorption injection determination map (MAP) so that the actual absorption slowly follows the target absorption in the case of the low temperature region (T1) where the first SCR (120) satisfies the negative (-) difference condition. According to the mapping of the negative (-) difference and the low temperature region (T1) condition, the absorption difference can be slowly reduced, and ultimately, the urea injection of the first SCR (120) can be increased to increase the NOx purification efficiency.

In particular, the absorption logic (141) rapidly changes the absorption speed according to the absorption injection decision map (MAP) so that the actual absorption quickly follows the target absorption in the case of the high temperature region (T2) where the first SCR (120) satisfies the negative (-) difference condition. According to this absorption injection decision map (MAP), the absorption difference can be quickly reduced, and finally, in the high temperature region (T2) of the first SCR (120), the NOx purification efficiency of the first SCR (120) becomes a low temperature condition (T1), so that NOx can be reduced by complementing each other.

In other words, the target injection amount (B) determined according to the injection amount logic (141) according to the embodiment of the present invention can reduce the total urea injection amount due to urea injection under temperature conditions with a small negative (-) difference, and even if the total urea injection amount is reduced, there is no change in the NOx purification efficiency through the interaction of the first SCR (120) and the second SCR (130). Therefore, there is an effect of securing the NOx purification efficiency while reducing the urea injection amount.

Meanwhile, if the input difference in absorption amount does not satisfy the negative (-) difference condition, the absorption amount logic (141) determines the absorption target injection amount (B) according to one variable of the absorption amount difference regardless of the temperature condition with the same mapping as the existing logic. At this time, the basic logic for controlling the absorption amount target operates with the concept of time, and for example, if there is a difference of -2g, the target absorption amount can be controlled for 25 seconds.

In addition, the absorption logic (141) can control the first injector (121) with a urea injection amount calculated by adding the NOx removal required injection amount (A) calculated by the exhaust flow rate and the NOx concentration and the absorption target injection amount (B).

The controller (140) may be implemented as one or more processors operating according to a set program, and the set program may be programmed to perform each step of the vehicle dual SCR application exhaust gas purification method using the improved absorption amount logic (141) according to an embodiment of the present invention.

The dual SCR application exhaust purification method of these vehicles will be described in more detail with reference to the drawings below.

Figure 7 is a flow chart schematically illustrating a method for applying dual SCR to exhaust gas purification of a vehicle according to an embodiment of the present invention.

Referring to Fig. 7, the controller (140) of the dual SCR application exhaust purification system (100) of the vehicle collects real-time status information necessary for determining the absorption rate through sensors (S1, S2, S3, S4) of the first SCR (120) and the second SCR (130) sequentially installed in the exhaust line (L) of the engine (110) while the vehicle is running (S10). The status information may include the NOx concentration, SCR temperature, NH3 concentration, and exhaust flow rate corresponding to each position of the first SCR (120) and the second SCR (130).

The controller (140) monitors the first SCR temperature, target absorption amount, actual absorption amount, and NOx absorption amount over time based on the collected status information, and calculates the absorption amount difference and average temperature between the target absorption amount and the actual absorption amount of the first SCR (120) (S20). At this time, the controller (140) can further calculate the absorption amount difference and average temperature for the second SCR (130).

And, the controller (140) inputs the difference in the absorption amount and the average temperature of the first SCR (120) into the improved absorption amount logic (141) and changes the absorption amount speed according to the temperature range set according to the absorption amount injection decision map (MAP) and the absorption amount difference condition (S30), thereby determining the absorption target injection amount (B) (S40).

For example, the step (S30) of changing the absorption speed is as follows.

The controller (140) checks whether the input storage amount difference satisfies the negative (-) difference condition (S31), and if the negative (-) difference condition is satisfied (S31; example), it determines whether the average temperature satisfies a low temperature area (T1) below a certain temperature (ex: 400°C) or a high temperature area (T2) above the certain temperature (S32), and maps the determined information (T1 or T2) to a storage amount injection decision map (MAP) to change the storage amount speed (S33 or s34).

At this time, the controller (140) controls the absorption rate so that the actual absorption rate slowly (gently) follows the target absorption rate according to the absorption rate injection determination map (MAP) when the average temperature satisfies the low temperature region (T1) (S4; T1) (S34). The absorption target injection amount (B) determined by this absorption rate change can slowly reduce the absorption rate difference according to the mapping of the negative (-) difference and the low temperature region (T1) condition, and finally, the urea injection of the first SCR (120) can be increased to increase the NOx purification efficiency.

On the other hand, if the average temperature satisfies the high temperature region (T2) (S4; T2), the controller (140) controls the absorption rate according to the absorption rate injection determination map (MAP) so that the actual absorption rate quickly (abruptly) follows the target absorption rate (S33). The absorption target injection amount (B) determined by this absorption rate change can reduce the total urea injection amount due to urea injection under temperature conditions with a small negative (-) difference.

Meanwhile, in the step S31, if the input difference in absorption amount does not satisfy the condition of a negative (-) difference (S31; No), the controller (140) can determine the absorption target injection amount (B) by applying one variable of the absorption amount difference (S35) regardless of the temperature condition with the same mapping as the existing logic (S40).

Thereafter, the controller (140) operates the first injector (121) by calculating the urea injection amount by adding the NOx removal required injection amount (A) and the absorption target injection amount (B) calculated by the exhaust flow rate and NOx concentration collected as status information (S50).

In addition, the controller (140) can operate the second injector (131) of the first SCR (120) with the urea injection amount calculated by applying the same method as the first SCR (120) above to the second SCR (130). Accordingly, the residual NOx remaining in the exhaust gas purified while passing through the first SCR (120) can be purified.

In this way, according to an embodiment of the present invention, by changing the absorption rate through improved absorption logic considering the variables of the SCR temperature and absorption difference, there is an effect of reducing the control error of the first SCR having a very large temperature change amount.

In addition, there is an effect of quickly reducing the difference in absorption amount and reducing the amount of urea injection by quickly following the target absorption amount in a high temperature range where the actual absorption amount satisfies the condition of a negative (-) difference between the target absorption amount and the target absorption amount.

Furthermore, by rapidly reducing the difference in adsorption amount through the first SCR in the high-temperature region and reducing residual NOx through the second SCR in the low-temperature region with high NOx purification efficiency, it is possible to reduce the amount of urea injected throughout the entire exhaust purification system with dual SCR application while securing NOx purification efficiency.

The embodiments of the present invention are not implemented only through the devices and/or methods described above, and may also be implemented through a program for realizing a function corresponding to the configuration of the embodiments of the present invention, a recording medium on which the program is recorded, etc., and such implementation can be easily implemented by an expert in the technical field to which the present invention belongs, based on the description of the embodiments described above.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

100: Dual SCR applied exhaust purification system
110: Engine
120: 1st SCR
121: 1st injector
130: 2nd SCR
131: 2nd injector
132: SCR catalyst
133: DOC
134: DPF
135: AOC
140: Controller
141: Adsorption logic
L: Exhaust line
S1: NOx sensor
S2: Temperature sensor
S3: NH3 sensor
S4: Exhaust flow sensor

Claims (12)

An engine that emits exhaust gases combusted while driving a vehicle;
The first SCR (Selective Catalyst Reduction) and the second SCR, which are installed in the order closest to the engine, purify nitrogen oxides (NOx) emitted through the exhaust line of the engine;
A first injector and a second injector that inject urea corresponding to the first SCR and the second SCR, respectively; and
A controller that monitors the SCR temperature over time, the difference in absorption between the target absorption amount and the actual absorption amount, and changes the absorption rate according to the absorption amount difference condition by temperature area set in the absorption amount injection decision map (MAP) to improve the purification efficiency of the above NOx;
An exhaust purification system for a vehicle including: In the first paragraph,
An exhaust gas purification system for a vehicle further comprising sensors for measuring at least one of NOx concentration, SCR temperature, NH3 concentration, and exhaust flow rate required for determining an absorption rate at positions corresponding to the first SCR and the second SCR, respectively. In the first paragraph,
The above controller,
An exhaust gas purification system for a vehicle that variably controls the urea injection amount of at least one of the first injector and the second injector according to the absorption rate determined through the absorption amount injection determination map (MAP). In the first paragraph,
The above second SCR is,
SCR catalyst installed in the above exhaust line;
A DOC (Diesel Oxidation Catalyst) and a DPF (Diesel Particulate Matter Filter) installed in front of the SCR catalyst to purify carbon monoxide (CO), hydrocarbons (HC), and soot in the exhaust gas, and
AOC (Ammonia Oxidation Catalyst) installed at the rear end of the above SCR catalyst to convert the emitted ammonia (NH3) into harmless nitrogen (N2);
An exhaust purification system for a vehicle that is modularized. In the third paragraph,
The above controller,
An exhaust gas purification system for a vehicle that changes the absorption rate so that the actual absorption amount slowly follows the target absorption amount according to the absorption amount injection decision map (MAP) in a low temperature region (T1) where the above first SCR satisfies a negative (-) difference condition. In paragraph 5,
The above controller,
An exhaust gas purification system for a vehicle that changes the absorption rate according to the absorption amount injection decision map (MAP) so that the actual absorption amount quickly follows the target absorption amount in a high temperature region (T2) where the above first SCR satisfies a negative (-) difference condition. a) A step of collecting real-time status information through sensors of the first SCR (Close Coupled-SCR) and the second SCR (Under Floor-SCR) sequentially installed in the exhaust line (L) of the engine;
b) a step of monitoring the difference in absorption amount between the target absorption amount and the actual absorption amount of the first SCR over time and the average temperature based on the above status information; and
c) a step of inputting the absorption amount difference and average temperature of the above first SCR into the set absorption amount logic, and changing the absorption amount speed according to the set temperature range and absorption amount difference condition according to the absorption amount injection decision map (MAP) to determine the absorption target injection amount (B);
A method for exhaust gas purification using dual SCR of a vehicle including a. In Article 7,
Step c) above,
A step for checking whether the input absorption difference satisfies the negative (-) difference condition;
If the above negative (-) difference condition is satisfied, a step of determining whether the average temperature satisfies a low temperature region (T1) below a certain temperature or a high temperature region (T2) above the certain temperature;
A step of changing the absorption rate according to the above-described information and the absorption injection decision map (MAP); and
A step of determining the target injection amount (B) based on the above absorption rate;
A method for exhaust gas purification using dual SCR of a vehicle including a. In Article 8,
The step of changing the above absorption speed is:
A method for exhaust gas purification using dual SCR for a vehicle, comprising the step of controlling the absorption rate so that the actual absorption amount quickly follows the target absorption amount according to the absorption amount injection decision map (MAP) when the above average temperature satisfies the high temperature region (T2). In Article 9,
The step of changing the above absorption speed is:
A method for exhaust gas purification using dual SCR for a vehicle, comprising the step of controlling the absorption rate so that the actual absorption amount slowly follows the target absorption amount according to the absorption amount injection decision map (MAP) when the above average temperature satisfies the low temperature region (T1). In Article 7,
After step c) above,
d) A method for exhaust purification using dual SCR for a vehicle, further comprising the step of controlling the first injector to operate the first SCR with a urea injection amount calculated by adding the NOx removal required injection amount (A) calculated by the exhaust flow rate and NOx concentration collected using the above status information and the absorption target injection amount (B). In Article 8,
After the step of checking whether the above negative (-) difference condition is satisfied,
A method for exhaust gas purification using dual SCR for a vehicle, further comprising the step of determining the target injection amount (B) of the absorption amount by using a logic that applies one variable of the absorption amount difference regardless of the temperature condition, if the input absorption amount difference does not satisfy the negative (-) difference condition.

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