KR100857338B1 - Device and method for variable injection in post injection of lean nox trap - Google Patents

Abstract

A device and a method of the variable injection for NOx(Nitrogen Oxides) adsorber are provided to prevent fuel efficiency from being deteriorated and to improve exhaust gas purification efficiency by installing developed fuel injection patterns to an injector controller and varying fuel injection patterns based on the condition of engine operation. A device and a method of the variable injection having a CPF(Catalyst Particle Filter,200) and a NOx adsorber catalyst system containing NOx adsorber catalyst(500) have an injector controller(120) which controls the fuel injection timing based on the calculated amount of NOx generation under a specific operational condition of an engine and the NOx concentration of the exhaust gas and changes fuel injection pattern based on the operational condition and engine status such as increment of NOx emission and hydrocarbon slip amount, an oxygen sensor(410) which measures oxygen concentration of the exhaust gas, an injector(300) injecting fuel for post-injection, a NOx sensor(400) located at least a place before or after the NOx adsorber catalyst system to measure NOx concentration or discharged amount, a hydrocarbon slip prevention catalyst(560) at rear end of the NOx adsorber catalyst, and a HC(Hydro-Carbon) sensor(420) at downstream of the NOx adsorber catalyst to measure the amount of slipped hydrocarbon after passing through the hydrocarbon slip prevention catalyst.

Description

Device and Method for variable injection in post injection of lean NOx trap

1 is a structural diagram showing the structure of a secondary injection system variable injection device of a conventional NOx catalyst.

2 is a graph illustrating a spray pattern of a post injection injector of the related art.

Figure 3 is a structural diagram showing the structure of the secondary injection system variable injection device of the storage type NOx catalyst of the present invention.

4A is a flowchart illustrating a step of determining a fuel injection pattern of a post-injection injector according to a regeneration time of an occlusion type NOx catalyst of the present invention and a concentration of NOx.

FIG. 4B is a flowchart illustrating a step of changing a fuel injection pattern of a post-injection injector when an operating condition of an engine is changed during regeneration of an occlusion type NOx catalyst of the present invention.

5 is a graph showing the definition of the injection pattern of the post injection injector.

FIG. 6 is a graph showing various cases of gun-hollow injection patterns of the after injection injector of the present invention. FIG.

7 is a graph showing an example of deformation of the injection pattern according to the NOx regeneration condition of the present invention.

8 is a graph illustrating a NOx low emission map according to engine conditions.

<Explanation of symbols for the main parts of the drawings>

100: ECU 120: after injection injector control unit

200: diesel particulate catalyst filtration filter (CPF) 300: after injection injector

400: NOx sensor 410: oxygen sensor

420: HC sensor 500: occluded NOx catalyst system

520: Reducing agent generation role catalyst additional coating unit

540: occluded NOx catalyst 560: HC anti slip catalyst

600: fuel decomposition catalyst (DFC)

The present invention relates to exhaust gas purification of diesel vehicles. More particularly, the present invention relates to a method and apparatus for controlling injection in a variable injection period by adjusting the injection pattern of a post injection injector according to engine operating conditions when the stored NOx catalyst is regenerated.

The main air pollutants in diesel vehicles are nitrogen oxides (NOx) and particulate matter. Therefore, they have become a major target of diesel vehicle exhaust gas regulation.

Techniques for responding to the regulation of diesel vehicle emissions can be largely divided into engine improvement and aftertreatment technology. In particular, post-treatment techniques to reduce diesel main exhaust gases include oxidation catalysts to purify high boiling point hydrocarbons (HC) in particulate matter and NOx under an excess oxygen atmosphere. An occlusion type NOx catalyst that decomposes or reduces, and a diesel particulate filter (DPF) system that filters particulate matter.

1 is a structural diagram showing the structure of a secondary injection system variable injection device of a conventional NOx catalyst.

A CCC type CPF (20) of a type in which an exhaust pipe direct type (CCC type) diesel oxidation catalyst (DOC) and a diesel particulate catalyst filter (CPF) are added to the rear of the turbocharger of the engine exhaust pipe. At the rear, a diesel fuel cracking (DFC) 60 and an occlusion type NOx catalyst system 50 are installed in series. The occlusion type NOx catalyst system 50 has a structure in which a catalyst additional coating portion 52 is coated on a reducing agent generating role in the front portion.

In addition, a post injection injector 30 for injecting diesel fuel between the DFCs 60 behind the CPF 20 is installed, and a NOx sensor capable of measuring the concentration of NOx in front of the occlusion type NOx catalyst system 50. 40 is installed.

When the ECU (Electronic control unit) 10 determines the regeneration time of the storage type NOx catalyst 54 from the NOx concentration measured by the NOx sensor 40, the after injection injector 30 is operated to inject fuel.

2 is a graph illustrating a spray pattern of a post injection injector of the related art.

In order to reduce the NOx catalyst 54 and the NOx reduction, the engine exhaust gas is controlled to be close to the air-fuel ratio condition, and fuel is injected using the after injection injector 30. In the apparatus and method for reducing NOx occluded in the occlusion type NOx catalyst 54 with the effect of a reducing agent, fuel injection of the post injection injector 30 having a great influence on the NOx purification performance of the occlusion type NOx catalyst 54. The pattern was developed from the continuous injection method during the initial injection period to the injection method with a constant injection pattern of a single injection.

However, this method is limited in the change of the engine's instantaneous and various operating conditions. When the fuel of a certain injection pattern is injected for various conditions such as the exhaust gas temperature and the oxygen concentration in the exhaust gas according to the operating conditions of the various engines, even more fuel is required to be injected even if the fuel injection amount is to be reduced, so that the DFC 60 is occluded. Promote deterioration and sulfur poisoning of the type NOx catalyst 54.

Therefore, the present invention has been invented to solve such a problem, by determining the operating conditions at the time of regeneration of the occlusion type NOx catalyst, and determining the injection pattern suitable for various operating conditions of the engine and developing the post-injection of the occlusion type NOx catalyst. Its purpose is to provide a variable injection method and apparatus.

In order to achieve the above object, the present invention provides a variable injection device for a post-injection type NOx catalyst including a diesel particulate catalyst filtration filter (CPF) and a storage type NOx catalyst system incorporating the storage type NOx catalyst. Post injection variable injection of the occlusion type NOx catalyst including a post injection injector control unit controlling the fuel injection timing according to the calculated NOx generation amount and the NOx concentration of the exhaust gas and changing the fuel injection pattern according to the engine operating condition and engine condition. An apparatus and method are provided.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

Figure 3 is a structural diagram showing the structure of the secondary injection system variable injection device of the storage type NOx catalyst of the present invention.

The conventional ECU 10 used the NOx concentration in the conventional NOx sensor 40 to determine the regeneration time of the occlusion type NOx catalyst 54 to operate the post injection injector 30. 100 serves to provide only the engine operation information such as the intake air amount, fuel injection amount, engine speed, EGR, torque to the after injection injector control unit 120, the after injection injector control unit 120 provides the engine operation information and the like. The regeneration time of the occlusion type NOx catalyst 540 is determined, and the injection pattern of the post injection fuel suitable for the engine operating condition is determined to control the injection of the post injection injector 300.

Fuel injected from the after injection injector 300 is decomposed so as to easily react in the occlusion type NOx catalyst 540 while passing through the DFC 600, and is evenly introduced into the occlusion type NOx catalyst 540 through the outlet of the diffusion tube structure. do. HC is generated from the fuel passing through the DFC 600, and NO is removed from the occluded NOx catalyst 540.

The exhaust pipe is directly connected to the rear of the turbocharger (CCC type) in the CPF (20) consisting of the conventional DOC and CPF, the catalyst is concentrated on the inlet metal in the inlet to play the DOC role to remove the DOC and CCC-type CPF (200 only CPF) ) Is installed. At the rear, a DFC 600 and an occlusion type NOx catalyst system 500 are installed in series. The occlusion type NOx catalyst system 500 has a reductant generation catalyst additional coating part 520 coated on the front part of the occlusion type NOx catalyst 540 to supplement the role of the DFC 600, and the occlusion type NOx catalyst ( 540), the rear portion is coated with a HC slip prevention catalyst 560 to prevent HC slip. The HC slip prevention catalyst 560 is installed to prevent the HC from slipping because the fuel injection amount and the injection condition do not match when the engine operation is suddenly reduced.

A NOx sensor is installed between the CPF 200 and the DFC 600, and the after injection injector 300 is installed to measure the NOx concentration in the front or rear of the occlusion type NOx catalyst system 500, or both front and rear. 400 is installed. In addition, an oxygen sensor 410 is installed at the rear end of the CPF 200 to measure the oxygen concentration of the exhaust gas, and an HC slip sensor 420 capable of measuring HC slip at the rear of the NOx sensor 400 is provided. Is installed.

4 is a flowchart illustrating a step of variably controlling the injection during the injection period by adjusting the injection pattern of the after injection injector according to the engine operating conditions when the occlusion type nitrogen oxide (NOx) catalyst of the present invention is regenerated, FIG. 6 is a graph showing various cases of gun-hollow injection patterns of the after injection injector of the present invention. FIG. 8 is a graph illustrating a NOx low emission map according to engine conditions.

After-injector injector control unit receives the engine operating conditions such as the intake air amount, fuel injection amount, rotation speed, exhaust gas recirculation (EGR), torque provided by the ECU (S402) and using the graph of FIG. A generation amount of NOx is predicted (S406). It is determined whether the predicted value is equal to or greater than a set ratio based on the occlusion amount of the occlusion type NOx catalyst, and receiving the measurement of the concentration of the NOx by the NOx sensor (S404) to determine whether the concentration of the NOx is greater than or equal to the set value (S408). .

The post-injection injector control unit determines the fuel injection pattern of the post-injection injector based on the predicted NOx generation amount and the measured NOx concentration and determines the fuel injection pattern of the post-injection injector (S450). As a result, the occlusion type NOx catalyst is regenerated.

Between the step of predicting the amount of NOx generation and measuring the NOx concentration (S410) and the step of determining the fuel injection pattern of the after-use injector (S450) whether the temperature of the exhaust gas to the temperature sensor is 200 ℃ or more, and the exhaust gas If it is determined that the oxygen concentration is 3% or less (S432) and this condition is not satisfied, the operating conditions of the engine are changed to increase the temperature of the exhaust gas to 200 ° C, and the oxygen concentration of the exhaust gas is adjusted to 3% or less. In step S434, the process goes through step S430. When the temperature of the exhaust gas is 200 ° C. or more and the oxygen concentration of the exhaust gas satisfies a condition of 3% or less, the process proceeds to a step S450 of determining a fuel injection pattern of the post injection injector.

The fuel injection pattern of the after injection injector is determined based on the concentration of NOx (S454). When the NOx concentration is 43 ppm or less, the fuel is injected with a uniform injection pattern in the after injection injector illustrated in FIG. 6A. In the case where the concentration of NOx is 43 ppm or more and 290 ppm or less, the fuel is injected with an initially rich injection pattern in the post injection injector shown in FIG. 6 (b) (S458). When the concentration of NOx is 290 ppm or more, the fuel is injected (S460) in the latter thick injection pattern in the post injection injector shown in FIG. 6E.

6 (c) is a graph showing a pattern to be thickly sprayed in the middle of the post-injection injector, Figure 6 (d) is a graph showing a pattern of a thick injection in the early and second half in the post-injection injector.

As the engine operating condition is changed while the occlusion type NOx catalyst is regenerated (S462), the injection pattern of the fuel injected from the post-injection injector is changed (S464). When the engine is decelerated, the oxygen increase in the oxygen sensor is increased. If the oxygen content of the exhaust gas increases by more than 5%, the fuel injection is stopped by the after-injector (S474). When the oxygen content of the exhaust gas does not increase by more than 5%, HC slip sensor is used. The amount of slips is measured (S476). When the slip amount of the HC increases by more than a predetermined concentration, the flow returns to the step of changing the fuel injection pattern of the post injection injector (S450), and the fuel injection pattern of the post injection injector is changed (S454), and the slip amount of HC is increased. If it does not increase above a certain concentration, the process returns to step S462 of maintaining the regenerated state of the stored NOx catalyst at present (S470).

In addition, when the engine is accelerated, the NOx sensor and the engine operation information are received during regeneration of the occlusion type NOx catalyst, and it is determined whether the standard emission amount of NOx is increased (S492). When the standard emission amount of NOx is increased, the fuel injection of the post injection injector is increased. Returning to the step of changing the pattern (S450) to change the fuel injection pattern of the after injection injector, and if the reference emission of the NOx does not increase, returning to the step (S462) of maintaining the regeneration state of the stored Nox catalyst at present. It passes through (S490).

In addition, when the operation information of the engine does not change, the NOx sensor receives the measurement of the concentration of NOx (S482) and determines whether it is below a certain concentration (S484). If it is below a certain concentration, the regeneration of the occlusion type NOx catalyst is terminated and the NOx If the concentration is not below a predetermined concentration, the process returns to step S462 of maintaining the regenerated state of the current occlusion type NOx catalyst (S480).

5 is a graph showing the definition of the injection pattern of the post injection injector.

When defining the injection pattern of the post injection injector, the injection period and one injection period are measured, and the one injection period is divided into the injection periods and defined as the ratio.

7 is a graph showing an example of deformation of the injection pattern according to the NOx regeneration condition of the present invention.

Depending on the oxygen concentration of the exhaust gas, there is a certain threshold level of post-injection concentration for the reduction of NOx, so that the post-injection below a certain level does not reduce the NOx and only makes the table. Therefore, spraying at a concentration above a certain level (Threshold level) can reduce the hernia NOx. However, post-injection to higher concentrations above a certain threshold level causes excessive total hydrocarbon (THC) slip.

In addition, the reducible post injection concentration (NOx) of the NOx decreases as the oxygen concentration is low. As the exhaust flow rate increases, the post injection concentration and the injection amount should be increased to improve the NOx purification rate. In addition, since the increase in after injection concentration increases the slip amount of the total hydrocarbon (THC), it is preferable to increase the injection amount according to the engine conditions.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

As described above, according to the present invention, the fuel injection pattern of the after injection injector is developed and installed in the after injection injector control unit to organically change the injection pattern according to the engine operating conditions, thereby preventing fuel economy from deteriorating and It is effective to improve the purification efficiency.

Claims (12)

In a post injection variable injection device for a stored NOx catalyst comprising a diesel particulate catalyst filtration filter (CPF) and a stored NOx catalyst system incorporating the stored NOx catalyst, Post injection injector control to control the fuel injection time according to the NOx concentration calculated by engine operating condition and NOx concentration of exhaust gas and to change the fuel injection pattern according to engine operating condition and engine condition The engine state includes an increase state of the amount of NOx emissions, HC slip amount and the injector An oxygen sensor for measuring the oxygen concentration of the exhaust gas; After injection injectors for injecting fuel; A NOx sensor installed in at least one of front and rear of the occlusion type NOx catalyst system to measure the concentration and the emission amount of the NOx; An HC slip prevention catalyst installed at a rear end of the occlusion type NOx catalyst to prevent slippage of HC; HC sensor installed at the rear of the storage type NOx catalyst system to measure the HC slip amount of the exhaust gas which has passed the HC slip prevention catalyst After injection variable injection device of the storage type NOx catalyst further comprising. delete The method of claim 1, A post injection variable injection apparatus for the occlusion type NOx catalyst further comprising a catalyst additional coating part installed at a front end of the occlusion type NOx catalyst to generate a reducing agent. The method of claim 3, And a fuel decomposition catalyst (DFC) installed in the storage type NOx catalyst system and installed at a front end of the catalyst additional coating portion for reducing the generation agent, and further comprising a fuel decomposition catalyst (DFC). The method of claim 1, And a engine control ECU for providing engine operation conditions such as intake air amount, fuel injection amount, engine speed, engine load, and the like to the after injection injector control unit. The fuel injection pattern of claim 1, wherein the fuel injection pattern is stored in the post-injection injector control unit, and the uniform injection pattern, the initially rich injection pattern, the intermediate rich injection pattern, and the early and second rich in accordance with the operating conditions of the engine. A post injection variable injector for an occlusion type NOx catalyst comprising one spray pattern, a thick spray pattern in the latter half, and the like. A post injection variable injection method for regeneration control of an occlusion type NOx catalyst which removes nitrogen oxide (NOx) discharged from an engine, Determining a regeneration time based on the amount of NOx generated by the engine operation information and the concentration of NOx measured by the NOx sensor; Determining a fuel injection pattern of a post injection injector according to the concentration of NOx; When the engine is decelerated during the regeneration of the occlusion type NOx catalyst, if the increase in oxygen concentration of the exhaust gas is greater than or equal to the set value, the injection of the after-injector is stopped. Changing the spray pattern of the post-injection injector if the predetermined value is higher than the predetermined value, and maintaining the regeneration state if the HC slip amount is lower than the predetermined value; Determining the fuel injection pattern according to whether the emission of the NOx increases when the engine accelerates during the regeneration of the occlusion type NOx catalyst; Determining whether to end the regeneration according to the exhaust concentration of the NOx when there is no condition change of the engine during regeneration of the occlusion type NOx catalyst; After injection variable injection method of the occlusion type NOx catalyst comprising a. The method of claim 7, wherein the determining of the reproduction time point, A post injection variable injection method of an occlusion type NOx catalyst further comprising the step of adjusting the temperature of the exhaust gas to 200 ° C. or more and the exhaust gas oxygen concentration to 3% or less. The method of claim 7, wherein the determining the fuel injection pattern, Uniform fuel injection in the post injection injector when the concentration of NOx is about 43 ppm or less; When the concentration of the NOx is about 43ppm or more and 290ppm or less, a step of fuel injection is carried out in the early stage in the post injection injector; If the concentration of the NOx is more than 290ppm, the fuel injection is made rich in the latter part of the post injection injector; After injection variable injection method of the occlusion type NOx catalyst comprising a. 8. The variable injection method of post-injection type NOx catalyst according to claim 7, wherein the set value of the amount of exhaust oxygen increased in the step of decelerating the engine is 5%. The method of claim 7, wherein the step of accelerating the engine, The injection method of the post-injection variable injection method of the occlusion type NOx catalyst which changes the injection pattern of the after-injection injector when the reference amount of NOx increases, and maintains the regeneration state when the reference amount of the NOx does not increase. The method of claim 7, wherein the step of changing the engine condition, After the injection of the post injection injector is terminated when the concentration of NOx is below a certain concentration, regeneration is terminated, and when the concentration is above a predetermined concentration, the post injection variable injection method of the stored NOx catalyst is maintained.

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