KR20120036008A - Vehicle emission purification system - Google Patents

Abstract

PURPOSE: An emission reduction system of a car is provided to simplify an engine control work by arranging a rich mixer require for regenerating a NOx absorber on a burner. CONSTITUTION: An emission reduction system of a car comprises a burner(300), an oxidation catalyst(400), a NOx absorber(500), a DPF(Diesel Particulate Filter)(600), and an electronic control module(800). The burner burns fuel. The oxidation catalyst oxidizes unburned hydrocarbon and carbon monoxide generated from an engine(100). The NOx absorber absorbs NOx from exhaust gas and purifies the absorbed NOx. The DPF collects particulate matter from the exhaust gas. The electronic control module controls the operation of the burner using values measured from sensors(710,720,730,740,750,760).

Description

Vehicle Emission Reduction Device {Vehicle Emission Purification System}

The vehicle exhaust gas reducing device of the present invention includes a burner in front of an exhaust aftertreatment device composed of an oxidation catalyst, a nitrogen oxide storage reduction catalyst, and a soot filtration filter to remove harmful emissions emitted from a vehicle. The present invention relates to a vehicle exhaust gas reducing device which facilitates the control of the engine by improving the efficiency, facilitates the reduction agent to the nitrogen oxide storage reduction catalyst, and regenerates the soot filtration filter using a burner.

Recently, many countries around the world, including Korea, are tightening regulations in consideration of the human hazards of soot, nitrogen oxides, unburned hydrocarbons, and carbon monoxide emitted from automobiles. As a countermeasure to satisfy the emission regulations of internal combustion engines, pretreatment technologies aimed at reducing the generation of pollutants, such as fuel improvement, combustion methods, and engine improvement, and exhaust gas exhaust pipes It is divided into post-treatment technology to purify exhaust gas by installing catalyst. Constant research and development is being conducted in each field, but at present, the post-treatment technology is considered to be more favorable for commercialization in consideration of emission reduction performance.

Such post-treatment techniques include (1) an oxidation catalyst for purifying carbon monoxide (CO) and unburned hydrocarbon (HC), (2) a diesel particulate filter that filters particulate matter (PM) through a filter, ( 3) DeNOx catalyst system that decomposes or reduces NOx in a reducing atmosphere, such as NOx adsober and Selective Catalytic Reduction. Combined systems are widely used.

Carbon monoxide and unburned hydrocarbons emitted from an automobile engine are usually purged using a catalyst, but as the exhaust gas temperature is about 250 ° C. or higher as shown in FIG. However, when the start-up or low-speed urban operation, the emission temperature is low, the catalyst has a disadvantage of reducing the ability to reduce these harmful emissions.

Nitrogen oxide storage reduction catalyst is a device in which a ceramic honeycomb is simultaneously coated with a catalyst which absorbs nitrogen oxide in a lean air fuel mixer condition and a catalyst for reducing nitrogen oxide in a rich air fuel mixer condition. You should drive heavily and regularly. However, this technology has a disadvantage in that the engine control is complicated and the combustion noise control is difficult because the engine operating conditions must be changed frequently.

The soot filtration filter requires a lot of back pressure due to the accumulation of smoke in the filter when the vehicle is operated for a long time, and thus it is necessary to periodically remove the filtration material accumulated in the filter. This is called a filter regeneration technology. As one of such filter regeneration techniques, a fuel post-injection technique for regenerating a soot filtration filter has been developed and used to inject fuel into the latter part of the engine's combustion stroke to raise the temperature of the exhaust gas to about 600 ° C. at which the soot is combusted. This technique has the disadvantages of diluting or contaminating the engine oil due to the post-injected fuel and complicated engine control.

The present invention has been made to solve the problems of the prior art as described above, an object of the present invention is to oxidize the burner in front of the exhaust gas reducing device consisting of an oxidation catalyst, a nitrogen oxide storage reduction catalyst, a soot filtration filter Improve the efficiency of catalyst reduction, supply the rich mixer for nitrogen oxide storage reduction catalyst without affecting the engine, and supply the soot filtration filter regeneration heat source by using the burner It is to provide a vehicle emission reduction device that solves the difficulty of engine control.

The automobile exhaust gas reducing device of the present invention for achieving the above object is a vehicle exhaust gas reducing device installed in the exhaust pipe 200 of the engine 100, the burner for burning the fuel supplied from the vehicle fuel tank ( 300); An oxidation catalyst 400 positioned at a rear end of the burner 300 to oxidize unburned hydrocarbons and carbon monoxide generated from the engine 100 or the burner 300; A nitrogen oxide storage and reduction catalyst (500) positioned at a rear end of the oxidation catalyst (400) to occlude and purify nitrogen oxide in the exhaust gas; A soot filtration filter 600 positioned at a rear end of the oxidation catalyst 400 to collect particulate soot in exhaust gas; A filter before and after differential pressure sensor 730 for monitoring the amount of soot collected in the soot filtration filter 600; An air fuel ratio sensor 740 positioned at a rear end of the burner 300 to measure an air fuel ratio of the exhaust gas; An exhaust gas temperature sensor 750 positioned at a rear end of the oxidation catalyst 400 to monitor a temperature of the exhaust gas introduced into the nitrogen oxide storage reduction catalyst 500 and the soot filtration filter 600; A nitrogen oxide concentration sensor 760 positioned at a rear end of the nitrogen oxide storage catalyst 700 to measure a concentration of nitrogen oxide in the exhaust gas; In the sensors provided in the vehicle exhaust gas reducing device including the filter before and after the differential pressure sensor 730, the air fuel ratio sensor 740, the exhaust gas temperature sensor 750, the nitrogen oxide concentration sensor 760. An electronic control module 800 for controlling the operation of the burner 300 using the measured value; And a control unit.

At this time, the burner 300 is operated when the exhaust gas temperature is lower than a predetermined reference so as to efficiently purify the unburned hydrocarbon and carbon monoxide in the oxidation catalyst 400, characterized in that for heating the oxidation catalyst 400. . At this time, the predetermined reference is characterized in that the value within the range of 200 ℃ to 250 ℃.

In addition, the burner 300 periodically supplies fuel as a reducing agent by a predetermined reference amount to purify the nitrogen oxides stored when the nitrogen oxide storage reduction catalyst 500 exceeds the nitrogen oxide storage capacity. . At this time, the predetermined reference amount is characterized in that the excess air ratio measured by the air fuel ratio sensor 740 is 0.7 to 1.0.

In addition, the amount of soot collected in the soot filtration filter 600 is predicted based on the value measured by the differential pressure sensor 730 before and after the filter, and the particulate soot collected per filter volume in the soot filtration filter 500. When the amount is more than a predetermined reference, the burner 300 is operated to regenerate the soot filtration filter 600. At this time, the predetermined reference is characterized in that the value within the range of 5g / L to 8g / L.

In addition, the burner 300 uses the value measured by the intake air flow rate sensor 710 or the engine speed sensor 720 installed in the engine 100 to reach a predetermined target value of the exhaust gas. The fuel injection amount supplied to the 300 is determined, and the value measured by the exhaust gas temperature sensor 750 is used to additionally control the fuel injection amount supplied to the burner 300. At this time, the predetermined target value is characterized in that 500 ℃ to 600 ℃.

In addition, the nitrogen oxide storage reduction catalyst 500 is characterized in that the catalyst is coated on a separate carrier located in front of the soot filtration filter 600 or the catalyst is coated on the soot filtration filter 600 surface.

In addition, the electronic control module 800 determines whether the nitrogen oxide storage capacity of the nitrogen oxide storage reduction catalyst 700 is exceeded based on a value measured by the nitrogen oxide concentration sensor 750, and at the burner 300. It is characterized by determining when to inject fuel with a reducing agent.

According to the present invention, since the burner is disposed in front of the oxidation catalyst, the exhaust gas temperature is increased by using the burner even when the exhaust gas temperature is low, such as at the start of the start-up and the vehicle at low speed, thereby improving the carbon monoxide and unburned hydrocarbon reduction ability of the oxidation catalyst. It works.

In addition, by providing a rich mixer necessary for the regeneration of the nitrogen oxide storage and reduction catalyst in the burner, engine control is simplified, and engine combustion noise control is easily performed.

In addition, by regenerating the soot filtration filter using a burner, it is possible to solve the problem of oil contamination and engine control complicated by the technology of re-injecting the fuel during the expansion process to regenerate the soot filtration filter.

1 is a car exhaust gas reduction device embodiment of the present invention.
2 is a purification efficiency according to the exhaust gas temperature of the oxidation catalyst.
Figure 3 is another example of the implementation of the vehicle emissions reduction apparatus of the present invention.
4 is an enlarged view of the nitrogen oxide storage reduction catalyst and the soot filtration filter of FIG.

Hereinafter, with reference to the accompanying drawings, a vehicle exhaust gas reducing device according to the present invention having the configuration as described above will be described in detail.

FIG. 1 illustrates an embodiment of a vehicle exhaust gas reducing apparatus using a burner of the present invention, and will be described in detail with reference to FIG. 1. The exhaust gas reducing device of the present invention is installed in the exhaust pipe 200 of the engine 100, the burner 300, the oxidation catalyst 400, the nitrogen oxide storage reduction catalyst 500, the soot filtration filter 600, various sensors Fields 730, 740, 750, and 760 and an electronic control module 800. Hereinafter, each part will be described in more detail.

The burner 300 serves to increase the temperature of the exhaust gas by burning the fuel supplied from the vehicle fuel tank. When the fuel is burned in the burner 300, combustion gas having a very high temperature is generated, and the combustion gas of this high temperature is mixed with the exhaust gas circulating around the burner 300 to transfer heat to the exhaust gas. Therefore, the temperature of the exhaust gas is increased. In addition, the fuel can be used as a reducing agent in the nitrogen oxide storage reduction catalyst 500 to be described below, the burner 300 also serves to periodically supply the reducing agent required for nitrogen oxide reduction.

The oxidation catalyst 400 is located at the rear end of the burner 300 and serves to oxidize the unburned hydrocarbon and carbon monoxide generated from the engine 100 or the burner 300. It is well known that incomplete combustion occurs when fuel is combusted, resulting in unburned hydrocarbons and carbon monoxide, and these materials have a significant adverse effect on the environment. At this time, the automobile exhaust gas and the combustion gas burned by the burner 300 passes through the oxidation catalyst 400, thereby preventing and removing the unburned hydrocarbons and carbon monoxide generated during incomplete combustion.

The nitrogen oxide storage reduction catalyst 500 is coated on the surface of the ceramic honeycomb carrier positioned at the rear end of the oxidation catalyst 400 to occlude nitrogen oxides in the exhaust gas under a lean air fuel mixer condition in which the engine is normally operated. It serves to reduce nitrogen oxide to nitrogen which is harmless to human body in the condition of rich air fuel mixer.

The soot filtration filter 600 is located at the rear end of the nitrogen oxide storage and reduction catalyst 500 to collect particulate soot in the exhaust gas. In general, the soot filtration filter 600 is made of a heat resistant material, such as ceramic or metal, and is made of a porous material that can pass the exhaust gas while filtering particulate soot.

Various devices as described above are operated according to various conditions, and these conditions are obtained through values measured by various sensors provided between the devices.

The differential pressure sensor 730 before and after the filter monitors the amount of soot collected in the soot filtration filter 600. As described above, the soot filtration filter 600 has a porous shape to filter particulate soot and allow exhaust gas to pass therethrough. Therefore, the longer the collection time, the more the flow resistance is increased by the particulate smoke accumulated in the soot filtration filter 600, the passage through which the exhaust gas can be reduced, and thus the exhaust gas passing through the soot filtration filter 600 The pressure drop of the gas rises. Therefore, by the pressure value measured by the differential pressure sensor 730 before and after the filter, it is possible to determine the soot collection degree.

The air fuel ratio sensor 740 is located at the rear of the burner 300 to monitor the air fuel ratio in the exhaust gas, and is used as an input value for controlling the air fuel ratio of the exhaust gas during the regeneration of the nitrogen oxide storage reduction catalyst.

The exhaust gas temperature sensor 750 is positioned at the rear end of the oxidation catalyst 400 to monitor the exhaust gas flowing into the soot filtration filter 600 and the nitrogen oxide storage catalyst 700.

The nitrogen oxide concentration sensor 760 is positioned after the nitrogen oxide storage catalyst 500 or after the soot filtration filter 600 to measure the concentration of nitrogen oxide in the exhaust gas.

Lastly, the electronic control module 800 includes the filter before and after the differential pressure sensor 730, the air fuel ratio sensor 740, the exhaust gas temperature sensor 750, the nitrogen oxide concentration sensor 760. The operation of the burner 300 is controlled using values measured by sensors provided in the vehicle exhaust gas reducing device.

The operation of each unit by the sensors will be described in detail as follows.

First, the burner 300 is operated when the exhaust gas temperature is lower than a predetermined standard so that the unburned hydrocarbon and carbon monoxide purification in the oxidation catalyst 400 is efficiently performed, thereby heating the oxidation catalyst. Figure 2 shows the purification efficiency according to the exhaust gas temperature of the oxidation catalyst, unburned hydrocarbons and carbon monoxide shows a higher purification efficiency as the temperature is higher, but should be heated to more than 250 ℃ to obtain the required purification efficiency in the vehicle. Therefore, it is preferable that the predetermined criterion is a value within the range of 200 ° C to 250 ° C.

In addition, the burner 300 burns by periodically supplying a fuel as a reducing agent by a predetermined reference amount to purify the nitrogen oxides stored when the nitrogen oxide storage reduction catalyst 500 exceeds the nitrogen oxide storage capacity. It is done. At this time, the predetermined reference amount is characterized in that it is determined so that the excess air ratio measured by the air fuel ratio sensor 740 is 0.7 to 1.0. Where the excess air ratio is the actual air volume divided by the amount of air needed to burn the fuel in theory. In other words, in connection with the operation of supplying fuel as a reducing agent to the nitrogen oxide storage reduction catalyst 500, the injection timing of the reducing agent is determined based on the nitrogen oxide concentration measurement value, and the injection amount of the reducing agent is determined by measuring the air fuel ratio measurement value. It is calculated based on that.

As described above, when the burner 300 is operated to increase the exhaust gas temperature, the intake air flow sensor 710 or the engine rotation speed installed in the engine 100 is sensed to reach a predetermined target value of the exhaust gas. The fuel injection amount supplied to the burner 300 is determined by using the value measured by the sensor 720, and the fuel injection amount supplied to the burner 300 by using the value measured by the exhaust gas temperature sensor 750. This additional feedback is to be controlled. At this time, the predetermined target value is characterized in that 500 ℃ to 600 ℃. In the burner 300, heat is supplied by burning the injected fuel, and as the amount of fuel injected increases, the temperature of the exhaust gas may rise quickly. Therefore, as described above, an appropriate fuel injection amount is determined through a value specified by the intake air flow rate sensor 710 or the engine speed detection sensor 720 provided in the engine 100, and is also stepwise by feedback control. By determining the fuel injection amount, it is possible to reduce the waste of fuel and to reach the appropriate exhaust gas temperature as quickly as possible.

As described above, the electronic control module 800 controls the operation of the burner 300 by using values measured by various sensors, but may further control the following operations. First, the electronic control module 800 predicts the amount of soot collected in the soot filtration filter 600 based on the value measured by the differential pressure sensor 730 before and after the filter, and (the particulate soot collected per filter volume. Since there is a constant correlation between the amount and the pressure, the pressure value can be easily calculated.) When the amount of particulate particulates collected per filter volume in the particulate filter 600 is greater than a predetermined standard, the filter is regenerated. will be. At this time, the predetermined reference is preferably a value within the range of 5g / L to 8g / L.

As described above, as the collection amount of particulate soot increases, the flow resistance in the exhaust gas passing through the soot filtration filter 600 increases, so that the pressure drop increases, through the filter before and after the differential pressure sensor 730. The regeneration point of the soot filtration filter 600 is determined using the measured pressure value. In addition, the electronic control module 800 determines whether the storage capacity of the nitrogen oxide storage reduction catalyst 600 is exceeded based on a value measured by the nitrogen oxide concentration sensor 760, and determines when to inject fuel with a reducing agent. Make a decision.

Figure 3 shows another embodiment of the vehicle exhaust gas reducing device of the present invention, as shown in Figure 4 so that the catalyst is coated on the surface of the soot filtration filter 600, consequently the nitrogen oxide storage reduction catalyst ( 500 and the soot filtration filter 600 is to be integrated. By configuring as in the embodiment of Figures 3 and 4, it is possible to further reduce the size of the exhaust gas reducing device and further reduce the cost.

The present invention is not limited to the above-described embodiments, and the scope of application of the present invention is not limited to those of ordinary skill in the art to which the present invention pertains without departing from the gist of the present invention as claimed in the claims. Of course, various modifications can be made.

100: engine
200: exhaust pipe
300: burner
400: oxidation catalyst
500: nitrogen oxide storage catalyst
600: soot filtration filter
710: intake air flow rate sensor 720: engine speed detection sensor
730: differential pressure sensor before and after the filter 740: air fuel ratio sensor
750: exhaust gas temperature sensor 760: nitrogen oxide concentration sensor
800: electronic control module

Claims (11)

In the vehicle exhaust gas reduction device installed in the engine 100, exhaust pipe 200,
A burner 300 for burning fuel supplied from an automobile fuel tank;
An oxidation catalyst 400 positioned at a rear end of the burner 300 to oxidize unburned hydrocarbons and carbon monoxide generated from the engine 100 or the burner 300;
A nitrogen oxide storage and reduction catalyst (500) positioned at a rear end of the oxidation catalyst (400) to occlude and purify nitrogen oxide in the exhaust gas;
A soot filtration filter 600 positioned at a rear end of the oxidation catalyst 400 to collect particulate soot in exhaust gas;
A filter before and after differential pressure sensor 730 for monitoring the amount of soot collected in the soot filtration filter 600;
An air fuel ratio sensor 740 positioned at a rear end of the burner 300 to measure an air fuel ratio of the exhaust gas;
An exhaust gas temperature sensor 750 positioned at a rear end of the oxidation catalyst 400 to monitor a temperature of the exhaust gas introduced into the nitrogen oxide storage reduction catalyst 500 and the soot filtration filter 600;
A nitrogen oxide concentration sensor 760 positioned at a rear end of the nitrogen oxide storage catalyst 700 to measure a concentration of nitrogen oxide in the exhaust gas;
In the sensors provided in the vehicle exhaust gas reducing device including the filter before and after the differential pressure sensor 730, the air fuel ratio sensor 740, the exhaust gas temperature sensor 750, the nitrogen oxide concentration sensor 760. An electronic control module 800 for controlling the operation of the burner 300 using the measured value;
Vehicle emission reduction device, characterized in that comprises a.
The method of claim 1, wherein the burner 300
In order to purify unburned hydrocarbons and carbon monoxide in the oxidation catalyst (400) efficiently, it is operated when the exhaust gas temperature is below a predetermined criterion to heat the oxidation catalyst 400, characterized in that for heating the oxidation catalyst (400).
The method of claim 2, wherein the predetermined criterion is
Vehicle emission reduction device, characterized in that the value in the range of 200 ℃ to 250 ℃.
The method of claim 1, wherein the burner 300
An apparatus for reducing vehicle emissions, wherein the nitrogen oxide storage / reduction catalyst (500) periodically supplies fuel as a reducing agent by a predetermined reference amount to purify the nitrogen oxides stored when the nitrogen oxide storage / reduction catalyst (500) exceeds the nitrogen oxide storage capacity.
The method of claim 4, wherein the predetermined reference amount is
The apparatus for reducing vehicle emissions, characterized in that the excess air ratio measured by the air fuel ratio sensor 740 is determined to be 0.7 to 1.0.
The method of claim 1, wherein the burner 300
The amount of soot collected in the soot filtration filter 600 is predicted by the value measured by the differential pressure sensor 730 before and after the filter, and the amount of particulate soot collected per filter volume in the soot filtration filter 600 is determined. The exhaust gas reducing device characterized in that for burning the soot trapped in the soot filtration filter (600) when more than a predetermined criterion.
The method of claim 6, wherein the predetermined criterion is
Vehicle emission reduction device, characterized in that the value in the range of 5g / L to 8g / L.
The method of claim 1, wherein the burner 300
Fuel injection amount supplied to the burner 300 by using the value measured by the intake air flow rate sensor 710 or the engine speed detection sensor 720 installed in the engine 100 to reach a predetermined target value of the exhaust gas Is determined, and the value measured by the exhaust gas temperature sensor (750) is used to further feedback control the fuel injection amount supplied to the burner (300).
The method of claim 8, wherein the predetermined target value
Vehicle emission reduction device, characterized in that 500 ℃ to 600 ℃.
The method of claim 1, wherein the nitrogen oxide storage and reduction catalyst 500
The catalyst is coated on a separate carrier positioned in front of the soot filtration filter 600 or the exhaust gas reducing device, characterized in that the catalyst is coated on the surface of the soot filtration filter 600.
The method of claim 1, wherein the electronic control module 800
Determining whether or not the nitrogen oxide storage capacity of the nitrogen oxide storage reduction catalyst 700 is exceeded based on the value measured by the nitrogen oxide concentration sensor 750, and determines when to inject fuel into the reducing agent in the burner 300 Automobile emission gas reduction device, characterized in that.

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